### EAB CONTROL COST MANUAL (Third Edition)

EPA 450/5-87-001A

U.S. Environmental Protection Agency Office ofAir.and Radiation Office ofAir**Qu~lity** 

### Planning and Standards Economic Analysis Branch Research Triangle Park, North Carolina 27711

February 1987

REPROOUCEDBY U.S.DEPARTMENTOFCOMMERCE NATIONALTECHNICAl INFORMATIONSERVICE SPRINGFIELD,VA22161 PB8?·166583 11111111111111111111111111111111111111. REPORT NO. EPA-450/5-87-001A TECHNICAL REPORTDATA (PleasereadInstructionsonthereversebeforecompleting) 3. RECIPIENT'S ACCESSION NO. p:s87-166583/AS 4. TITLE AND SUBTITLE EAB Control Cost Manual (Third Edition) 5. REPORT DATE February 1987 6. PERFORMING ORGANIZATION CODE

11. CONTRACT/GRANT NO. 8. PERFORMING ORGANIZATION REPORT NO. 

# I 7,AUTHOR(S)W.M. Vatavuk (principal), R.E. Jenkins, V.S. Katari','cW.L.·Kloti,**J.D~ McKenna~**  R.L.·,Stallings JH;f.

### ~~~~g~~fuJ**bRgi~TI~1 ~N**  NAM'E AN0ADDRESS . -

### ----~· .......

### -1-:1-=-O.-;:P:-::R:-::O:-::G"=R~A-:-:M;-;E:-:-L-=E-:-:M:-:=E-:-:N':;'T'7N:-::O,.....------1

Office ofAir and Radiation Office ofAir Quality Planning and Standards Strategies and Air Standards Division Economic Analysis Branch
UI"\ ," " .,...., n .1. 

## ..f'**"~~11** 13. TYPE OF REPORT AND PERIOD COVERED

14. SPONSORING AGENCY CODE Same as box 

### 9.



## .. 15. 5,l..!PP.LEMENT./'R,¥ NqTES t prlnClpal**~OntaC** : William M. Vatavuk (Comm'l #: 919-541-5309; FTS # 629-5309)

16. ABSTap..CT •• d d d f 1 d InlS report provldes deslgn proce ures an current cost ata or common y use "add-on" air pollution control devices and auxiliary equipment. It supercedes two EPA reports, both entitled Capital and Operatinq Costs of Selected Air Pollution Control Systems: EPA-450/3-76-U14 tMay 1976) and ltS revlslon, EPA-450/5-8U-UU, (December 1978). This issuance ofthe Manual contains five sections. Sections 1 ("Introduction") and 2 ("Manual Estimating Methodology") present, respectively, introductorymaterial and a**compr~hensive,** general procedure for developing "study". (+ 30% accurate) control cost estimates. Sections 3 to 5discuss the applications, design, and cost estimating procedures and data for thermal and catalytic incinerators, carbon adsorbers, and fabric filters, respectively. This issuance of the Manual will be followed by others as more sections are completed.

17. KEY WORDS AND DOCUMENT ANALYSIS a. DESCRIPTORS

Costs Manual Fabric filters Thermal incinerators Catalytic incinerators Carbon adsorbers b.IDENTIFIERS/OPEN ENDED TERMS c. COSATI Field/Group Cost estimation**technique~** Capital costs Annual costs Control device design and operation Air pollution control systems

18. DISTRIBUTION STATEMENT Un1imited 19. SECURITY CLASS (This Report) Unclassified 20. SECURITY CLASS(Thispage) Unclassified 21. NO. OF PAGES 184 22. PRICE

EPA Form 2220-1 (Rev. 4-77) PREVIOUS EDITION IS OBSOLETENOTE:

o Apreliminary draft ofthis Manual was distributed in November 1986. Since then, extensive revisions have been made to Section 5 ("Fabric Filters") and minor changes to Sections 3 ("Thermal and Catalytic Incinerators") and 4 ("Carbon Adsorbers"). No revisions weremade to Sections 1 and 2, however.

o The pages in this Manual have been fastened together. Ifdesired, they may be unfastened, hole-punched, and reassembled in athree-ring binder. This will facilitate the addition of updates when they become available.

### OVERVIEW OF THE MANUAL*
Section Completion Date Date To Be Completed 1 2 3 4 5 6 7 

### 8 9 

### 10 11 

### 12 13 14 

### 15 16 17 18 19 20 21 INTRODUCTION MANUAL ESTIMATING METHODOLOGY THERMAL AND CATALYTIC INCINERATORS CARBON ADSORBERS FABRIC FILTERS ELECTROSTATIC PRECIPITATORS DUCTWORK FANS FLARES REFRIGERATION UNITS STACKS PUMPS GAS ABSORBERS VENTURI SCRUBBERS WASTEWATER TREATMENT FACILITIES** CAPTURE HOODS MECHANICAL COLLECTORS PRECOOLERS (SPRAY CHAMBERS AND QUENCHERS) SCREW CONVEYORS COMPREHENSIVE SAMPLE COST-ESTIMATING PROBLEMS ESCALATING COSTS 1/86 1/86 7/86 7/86 9/86 FY 87 FY 87 FY 87 FY 87 FY 87 FY 88 FY 88 FY 88 FY 88 FY 88 Not Established Not Established Not Established Not Established Not Established Not Established APPENDIX A COMPOUND INTEREST FACTORS APPENDIX B EQUIPMENT COST INDICIES APPENDIX C CONTROL EQUIPMENT VENDORS Not Established Not Established Not Established
*For more information about the Manual, contact Albert Wehe, Robert PahelShort, or WilliamVatavuk (at FTS:629-5610). **These are facilities that would be required to treat only the wastewater generated by venturi scrubbers, quenchers, spray chambers, and gas absorbers.TABLE OF CONTENTS

Section

1 INTRODUCTION 1.1 Role ofCost in the Setting ofRegulations 1.2 Purpose ofManual 1.3 Organization ofthe Manual 1.4 "Uniqueness" ofthe Manual References for Section 1 1-1 1-2 1-2 .1-5 1-7 2 MANUAL ESTIMATING METHODOLOGY 2.1 Types ofCost Estimates 2-1 2.2 Cost Categories Defined 2-3 2.2.1 Elements ofTotal Capital Investment 2-3 2.2.2 Elements ofTotal Annual Cost 2-7 2.3 Engineering Economy Concepts 2-9 2.3.1 Time Value ofMoney 2-9 2.3.2 Cash Flow 2-9 2.3.3 Annualization Methods 2-14 2.4 Estimating Procedure 2-15 2.4.1 Facility Parameters and Regulatory Options 2-15 2.4.2 Control SystemDesign 2-17 2.4.3 Sizing the Control System 2-18 2.4.4 Estimating Total Capital Investment 2-20TABLE OF CONTENTS

Section

2.4.5 Retrofit Cost Considerations 2.4.6 Estimating Annual Costs References for Section 2
3 THERMAL AND CATALYIC INCINERATORS 3.1 Process Description 3.1.1 Elements ofCombustion 3.1.2 Types ofIncinerators 3.2 Design Procedure 3.2.1 Design and Operating Features 3.2.2 Design Calculations 3.3 Estimating Total Capital Investment 3.3.1 Thermal IncineratorEquipment Costs 3.3.2 Catalytic IncineratorEquipment Costs 2-23 2-25 2-33

3-1 3-1 3-6 3-8 3-8 3-10 3-23 3-24 3-27 3.3.3 Total Capital Investment for Incinerators 3-29 3.4 Estimating Total Annual Cost 3.4.1 Direct Annual Costs 3.4.2 Indirect Annual Costs References for Section 3 Appendix3A Appendix3B

< , v 3-30 3-30 3-34 3-35TABLE OF CONTENTS

Section Page

4 CARBON ADSORBERS 4.1 Process Description 4-1 4.1.1 Introduction 4-1 4.1.2 Types ofAdsorbers 4-2 4.1.3 Adsorption Theory 4-6 4.2 Design Procedure 4-11 4.2.1 Sizing Parameters 4-11 4.2.2 Determining Adsorption and DesorptionTimes 4-13 4.2.3 Estimating Carbon Requirement 4-15 4.3 Estimating Total Capital Investment 4-20 4.3.1 Fixed-Bed Systems 4-21 4.3.2 CannisterSystems 4-26 4.4 Estimating Total Annual Cost 4-28 4.4.1 Direct Annual Costs 4-28 4.4.2 Indirect Annual Costs 4-34 4.4.3 Recovery Credits 4-35 4.4.4 Total Annual Cost 4-36 References for Section 4 4-37TABLE OF CONTENTS
Section 5 FABRIC FILTERS 5.1 Process Description 5.1.1 Introduction 5.1.2 Types ofFabric Filters 5.1.3 Auxiliary Equipment 5.1.4 Fabric Filtration Theory 5.2 Design Procedures 5.2.1 Gas-to-Cloth Ratio 5.2.2 Pressure Drop 5.2.3 Particle Characteristics 5.2.4 Gas Stream Characteristics 5.2.5 Pressure or Suction Housings 5.2.6 Standard or Custom Construction 5.2.7 FilterMedia 5.3 Estimating Total Capital Investment 5.3.1 Equipment Cost 5.3.2 Total Purchased Cost 5.3.3 Total Capital Investment 5.4 Estimating Total Annual Costs 5.4.1 Direct Annual Cost 5.4.2 Indirect Annual Cost 5.4.3 Recovery Credits 5.4.4 Total Annual Cost 5.4.5 Example Problem References for Section 5 5-1 5-1 5-2 5-5 5-7 5-15 5-15 5-23 5-24 5-25 5-27 5-28 5-29 5-30 5-30 5-40 5-41 5-41 5-41 5-46 5-47 5-47 5-48 5-54i-)
Section 1 INTRODUCTION WilliamM. Vatavuk Economic Analysis Branch, OAQPS
1.1 Role of Cost in the Setting ofRegulations Cost has an important role in setting many state and federal air pollution control regulations. The extent of this role varies with the type of regulation. For some types of regulations, cost is explicitly used in determining their stringency. This use may involve a balancing of costs and environmental impacts. costs and dollar valuation of benefits, or environmental impacts and economic consequences of control costs. For othertypes of regulations cost analysis is used to choose among alternative regulations with the same level of stringency. Forthese regulations. the environmental goal is determined by some set of criteria which do not include costs. However, cost-effectiveness analysis is employed to determine the minimum cost way of achieving the goal. For some regulations. cost influences enforcement procedures or requirements for demonstration of progress towards compliance with an air quality standard. For example. the size of any monetary penalty assessed for noncompliance as part of an enforcement action needs to be set with
awareness of the magnitude of the control costs being postponed by the noncomplying facility. For regulations without a fixed compliance schedule, demonstration of reasonable progress towards the goal is sometimes tied to the cost of attaining the goal on different schedules. Cost is a vital input into two other types of analyses that also sometimes have a role in standard setting. Cost is needed for a benefit-cost analysis that addresses the economic efficiency of alternative regulations.1-2 Cost is also an input into any analysis of the economic impact of each regulatory alternative. An economic impact analysis deals with the consequences ofthe regulation for small businesses, employment, prices, and industry structure. 1.2 Purpose ofManual The purpose of this Manual is two-fold: (l) to compile up-to-date capital costs, operating and maintenance expenses, and other costs for "add-on" air pollution control systems and (2) to provide a comprehensive, concise, consistent, and easy-to-use procedure for estimating and (where appropriate) escalating these costs. (IlAdd-on" systems are those installed downstream of an air pollution source to control its emissions.) The Manual estimating procedure rests on the notion of the "factored" or "study" estimate, nominally accurate to within +30%. This type ofestimate is well suited to estimating control system costs intended for use in regulatory development. Study estimates are sufficiently accurate, yet do not require the detailed, site-specific data inputs needed to make "definit iveil

or othermore accurate types of estimates. 1.3 Organization ofthe Manual This Manual is a major revision of the 1978 edition of the EAB Control Cost Manual,(1) which, in turn, was a revision of the original edition, completed in 1976. This third edition of the Manual includes amore thorough discussion of estimating methodology and more detailed design procedures for an enlarged set of equipment types. The appendices have been revised to delete some infrequently used material, and to include certain new and
more useful material. The format of the Manual has been changed to one which will permit more flexibility in its updating and expansion. To achieve this flexibility1-3

this edition will be issued in self-contained sections. Each section will address a logically separate topic, which can be either of a general nature (e.g., this introduction) or of amore specific, equipment-oriented nature (e.g., fabric filters). The sections which comprise this portion of the Manual are listed in Table 1-1, alongside the sections in the 1978 Manual they wi11 replace. Two changes in the 1978 Manual are indicated byTable 1-1. First, the numbering scheme is different. In the third edition, each type of equipment, background topic, etc., is given its own number, for ease of identification and to reinforce the intent that each section should "stand alonell
• Second, the auxiliary equipment items (e.g., ductwork), which were collected into a single chapter in the previous Manuals, are now also standalone sections. This was mainly done to eliminate the confusion that arises when classifying auxiliaries like mechanical collectors which can either support aprimary control device or be control devices in their own right. The notion of a stand alone section is also new. Wherein the 1976 and 1978 Manuals, the various capital and annual cost factors were collected in an introductory section (old Section 3), now they are dispersed among the sections covering the equipment types. Each of these sections contains a:
o Process description, where the types, uses, and operating modes of the equipment item and (if applicable) its auxiliaries are discussed;

o Design procedure, which enables one to use the parameters ofthe pollution source (e.g., gas volumetric flowrate) to size the equipment item(s) in question;

o**~apital** and annual costs for the equipment and suggested factors to
use in estimating these costs from equipment design and operationalTable 1-1 Format of the EAB Control Cost Manual (Third Edition)

New Section ! Old Section(s) Replaced Number 1

2

3

4

5 Title IIIntroduction li
IIManual Estimating Methodologyll
IIThermal and Catalytic Incineratorsll

IICarbon Adsorbersll

IIFabric Filtersll

(Other sections to be developed) Number(s) 1 2,3
5.4
5.5
5.3 Title IIIntroductionll
IIApplication to Industryll; IICost Estimating

ProceduresII IIThermal and Catalytic IncineratorSystemsll

IIAdsorbers li
IIFabric Filtersll I-' I ..j::>o1-5 (e.g., operating hours) parameters. These costs are presented in both graphical and equational forms wherever possible. 1.4 "Uniqueness" ofthe Manual TheManual presents adifferent perspective on estimating air pollution control system costs than other cost-oriented reports, such as:
o The Cost Digest: Cost Summaries of Selected Environmental Control Technologies(2) o AStandard Procedure for Cost Analysis ofPollution Control Operations(3)
o Evaluation ofControl Technologies for Hazardous AirPollutants(4) Although these reports (as well as many ofthe NSPS Background Information Documents) contain costs for add-on control systems, they do not duplicate the Manual for one ormore ofthe following reasons: (1) their costs have been based eitherwholly or partly on data in the previous Manuals; (2) they apply to specific source categories only, whereas the Manual data may be applied generally; (3) their estimating procedures and costs are of less than study estimate quality; or (4) they are not intended for estimating costs used in regulatory development. Reason (3) applies to the Cost Digest, for example, as this report, designed for use by non-technical personnel, contains procedures for making "order-of-magnitude" estimates (! 30% accuracy orworse). AStandard Procedure, conversely, was primarily intended for estimating costs forR&D cases (e.g., demonstration projects), where some site-specific data are available. Further, although the latter report contains athorough list of equipment installation factors, it contains few equipment costs. The report, Evaluation ofControl Technologies, used data and estimating procedures from the 1978 Manual to provide sound generalized procedures for estimating thermal and catalytic1-6 incinerator costs. The third edition ofthe Manual updates and expands this information. Finally, the second edition ofthe Manual (published December 1978),

was one of the earliest of its kind. It has been extensively used in Agency regulatory development efforts. Accordingly, the Manual's role in the speciality of air pollution control system cost estimating is both unique and secure.1-7
References for Section 1:
1. Neveril, R. B. (GARO, Inc.) Capital and Operating Costs for Selected AirPollution Control Systems, EPA, Office ofAirQuality Planning and Standaros, Economic Analysis Branch, December 1978 (EPA450/5- 80-002). 2. DeWolf, Glenn, et al. (Radian, Inc.) The Cost Digest: Cost Summaries ofSelected Environmental Control Technologies. EPA, ORO, Office of Environmental Engineering and Technology, October 1984 (EPA-600/884-010). 3. Vhl, Vincent W. Standaro Procedure for Cost Analysis ofPollution Control Operations, Volumes I and II. EPA, ORO, Industrial Environmental Research Laboratory, June 1979 (EPA-600/8-79-018a). 4. Katari, Vishnu (Pacific Environmental Services) Evaluation ofControl Technologies for Hazaroous AirPollutants. EPA, Air and Energy Engineering Research Laboratory, ORO, October 1985.Section 2 MANUAL ESTIMATING METHODOLOGY WilliamM. Vatavuk Economic Analysis Branch. OAQPS This section presents a methodology that will enable the user. having knowledge of the source being controlled. to produce study-level cost estimates for a control system to control that source. The methodology. which applies to each of the control systems included in this Manual. is general enough to be used with other "add-on" systems as well. Further. the methodology may also be applicable to estimating costs of fugitive emission controls and of other nonstack abatement methods. Before presenting this methodology in detail. we should first discuss the various kinds of cost estimates and then define the cost categories and engineering economy concepts employed in making the estimates. 2.1 Types of Cost Estimates As noted above. the costs and estimating methodology in this Manual
are directed toward the "study" estimate. of.:!:. 30% accuracy. According to Perry's Chemical Engineer's Handbook. a study estimate is "•••• used to estimate the economic feasibility of aproject before expending significant funds for piloting. marketing. land surveys, and acquisition ••• [However] it can be prepared at relatively low cost with minimumdata."(1) Specifically, to make a study estimate. the following must be known:
o Location of the source within the plant;
o Rough sketch ofthe process flow sheet (i.e., the relative locations of the equipment in the system);
o Preliminary sizes of. and material specifications for, the system equipment items;2

..2

o Approximate sizes and types of construction of any buildings required to house the control system;
o Rough estimates of utility requirements**(e.g.~** electricity);

o Preliminary flow sheet and specifications for ducting and piping;
o Approximate sizes ofmotors required.(l) In**addition~** an estimate of the labor hours required for engineering and drafting is needed. as the accuracy of an estimate (study or otherwise) is highlydependent on the amount of engineering work expended on the project. There are. however, four other types of estimates, three ofwhich
are more accurate than the study estimate. These are:(l)

o 1I0rder-of-magnitudellu"a rule of-thumb procedure applied only to repetitive types of plant installations for which there exists good cost historyll. Its accuracy is >.:!:.30%. (However. according to Perry's. 1I•••no limits of accuracy can safely be applied to it. lI ) The sole input required for making this level of estimate is the control system's capacity (often measured by the maximum volumetric flowrate of the gas passing through the system). So-called IIsixtenths factorll estimates (not to be confused with factored estimates) are examples of this type.
o IlScopell/IlBudget authorizationll;UPreliminari' • This estimate. nominally of+ 20% accuracy. requires more detailed knowledge than the study estimate regarding the site, flow sheet. equipment. buildings. etc. In addition. rough specifications for the insulation and instrumentation are also needed.2-3

o "Project controllll"Definitive" estimates. accurate to within2:. 10%. require yet more information than the scope estimates. especially concerning the site. equipment. and electrical requirements.

o "FirmIlI"Contractor'sIlI"Detailed li
• This is the most accurate (..:!::. 5%) of the estimate types. requiring complete drawings. specifications. and site surveys. Further. II[t]ime seldom permits the preparation of such estimates prior to an approval to proceed with the project. II(1) For the purposes of regulatory development. study estimates have been found to be acceptable. as tney represent a compromise between the less accurate 1I0rder-of-magnitudeli and the more accurate estimate types. The former are too imprecise to be of much value. while the latter are not only very expensive to make. but require detailed site and process-specific knowledge that most Manual users will not have available to them. 2.2 Cost Categories Defined The names given certain IIcategoriesll of costs and what they contain vary considerably throughout the 1iterature. Certain words 1ike IIcapital costll can have vastly different meanings. which can often lead to confusion.
even among cost estimators. To avoid this confusion and. at the same time. provide uniformity in the Manual. basic terms are defined in this Section and will be used throughout. The terminology used is adapted from that of the American Association ofCost Engineers(2). Although it has been developed for general use. it is readily adaptable to air pollution control system costing. 2.2.1 Elements ofTotal Capital Investment First. two general kinds of costs are estimated. total capital investment (TCI) and total annual cost (TAC). The total capital investment includes2-4
all costs required to purchase equipment needed for the control system (termed IIpurchased equipmentll costs), the costs of labor and materials for installing that equipment (termed lidirect installation ll costs), site preparation, building costs, and certain other costs which are termed lIindirect installationll costs. Direct installation costs include costs for foundations and supports, erecting and handling the equipment, electrical work, piping, insulation, and painting. Indirect installation costs include such costs as engineering costs; construction and field expenses (i.e., costs for construction supervisory personnel, office personnel, rental of temporary offices, etc.); contractor fees (for construction and engineering firms involved in the project); start-up and performance test costs (to get the control system running and to verify that it meets performance guarantees); and contingencies. Contingencies is a catch-all category that covers unforeseen costs that may arise, including (but certainly not limited to) II••• possible redesign and modification of equipment, escalation increases in cost of equipment, increases in field labor costs, and delays encountered in start-up.II(2) These elements of total capital investment are displayed in Figure 2-1. Note that the sum ofthe purchased equipment cost, direct and indirect installation costs, site preparation, and buildings costs comprise the battery limits estimate. Bydefinition, this is the total estimate II••• for a specific job without regard to required supporting facilities which are assumed to already exist••• 1I(2) at the plant. This would mainly apply to control systems installed in existing plants, though it could also apply to those systems installed in new plants when no special facilities for supporting the control system would be required.oPrimary Control Device oAuxiliary Equipment (including ductwork) oInstrumentationa oSales Taxesa oFreighta Figure 2-1

Purchased I Equipment Cost Elements ofTotal Capital Investment

Lande ] Working Capitale Total Nondeprec1ab1e Investment

oFoundations and Supports oHandling and Erection oElectrical oPiping oInsulation oPainting Direct I Installation Costb SitePreparationc,d Buildingsd Total Direct Cost
"Battery Limits" Cost Total Capital Investment N I U1 oEngineering oConstruction and Field Expenses oContractorFees oStart-up oPerformanceTest oContingencies Indirect Installation Costb Total 

## = Indirect Cost Off-Site facilitese Total Depreciable Investment

a These costs are factored from the sum ofthe control device and auxiliary equipment costs. b

.These costs are factored from the purchased equipment cost. c Usually required only at "grass roots" installations. d Unlike the other direct and indirect costs, costs for these items are not factored from the purchased equipment cost. Rather, they are sized and costed separately.

--- e Normally not required with add-on control systems.2-6
Where required, these supporting facilities would encompass units to produce steam, electricity, and treated water; laboratory buildings, railroad spurs, roads, and the like. It is unusual, however, for a control system to have one of these units (e.g., a power plant) dedicated to it. The system needs are rarely that great. However, it may be necessary--especially in the case of control systems installed in new or IIgrass roots ll plants-- for extra capacity to be built into the site generating plant to service the system. (A venturi scrubber, which often requires large amounts of electricity, is a good example of this.) It is customary for the utility costs to be charged to the project as operating costs at a rate which covers both the investment and operating costs for the utility. As Figure 2-1 shows, there are two other costs which may be included in the total capital investment for a control system. These are IIworking capital ll

, and IIlandll
• The first ofthese, working capital, is a fund set aside to coverthe initial costs of fuel, chemicals, and other materials,

as well as labor and maintenance. It usually does not apply to control systems, for the quantities of utilities, materials, labor, etc., they require are usually small. (An exception might be an oil-fired thermal incinerator, where a small supply (e.g., 30-day) ofdistillate fuel would have to be available during its initial period of operation.) Land may also be required. But, since most add-on control systems take up very little space (a quarter-acre or less) this cost would be relatively small. (Certain control systems, such as those used for flue gas desulfurization, require largerquantities of land for the process equipment, chemicals storage, and waste disposal.)2-7
Note also in Figure 2-1 that the working capital and land are IInondepreciablell expenses. I n otherwords, these costs are IIrecoveredII when the control system reaches the end of its useful life (generally in 10 to 20 years). Conversely, the other capital costs are IIdepreciablell
, in that they cannot be recovered and are included in the calculation ofthe income tax credit and depreciation allowance, whenever such taxes are considered in a cost analysis. (In the Manual methodology. however, income taxes are not considered. See Section 2.3.) Notice that when 100% of the system costs are depreciated, no salvage value is taken for the system equipment at the conclusion of its useful life. This is a reasonable assumption for add-on control systems, as most ofthe equipment. which is designed for a specific source, cannot be used elsewhere without modifications. Even if it were reusable, the cost of disassembling the system into its components could be as high (or higher) than the salvage value. 2.2.2 Elements ofTotal Annual Cost TheTotal Annual Cost (TAC) for control systems is comprised of three elements: IIdirectll costs, (DC) lIindirectll costs, (IC) and IIrecovery creditsll (RC), which are related by the following equation:
TAC 

### =DC + IC

- RC (2-1) Clearly, the basis of these costs is one year, as this period allows for seasonal variations in production (and emissions generation) and is directly usable in profitability analyses. (See Section 2.3.) Direct costs are those which tend to be proportional or partially proportional to the quantity of exhaust gas processed by the control system per unit time. These include costs for raw materials, utilities (steam.2-8 electricity, process and cooling water, etc.), waste treatment and disposal, maintenance materials, replacement parts, and operating, supervisory, and maintenance labor. Of these direct costs, costs for raw materials, utilities, and waste treatment and disposal are variable, in that they tend to be a direct function of the exhaust flowrate. That is, when the flowrate is at its maximum rate, these costs are highest. Conversely, when the flowrate is zero, so are the costs. Semivariable direct costs are only partly dependent upon the exhaust flowrate. These include all kinds oflabor, maintenance materials, and replacement parts. Although these costs are a function of the gas flowrate, they are not linear functions. Even while the control system is not operating, some of the semivariable costs continue to be incurred. Indirect, or "fixed", annual costs are those whose values are totally independent of the exhaust flowrate and, in fact, would be incurred even if the control system were shut down. They include such categories as overhead, property taxes, insurance, and capital recovery. Finally, the direct and indirect annual costs are offset by recovery credits, taken for materials or energy recovered by the control system, which may be sold, recycled to the process, or reused elsewhere at the site. These credits, in turn, must be offset by the costs necessary for their purification, storage, transportation, and any other costs required to make them reusable or resalable. Great care and judgement must be exercised in assigning values to recovery credits since materials recovered may be of small quantity or ofdoubtful purity, resulting in their having less value than virgin material.2-9 The various annual costs and their interrelationships are displayed in Figure 2-2. Amore thorough description ofthese costs and how they may be estimated is given in Section 2.4. 2.3 Engineering Economy Concepts As mentioned previously, the estimating methodology presented in Section 2.4 rests upon the notion ofthe IIfactoredli or study estimate. However, there are other concepts central to the cost analyses which must be understood. These are (1) the time value ofmoney, (2) cash flow, and (3) annualization. 2.3.1 Time Value ofMoney The IItime value ofmoneyll is based on the truism that 1I •••adollar now is worth more than the prospect of adollar••• at some later date.II(3) Ameasure ofthis value is the interest rate which 1I •••may be thought of as the return obtainable by the productive investment ofcapital.II(3) 2.3.2 Cash Flow During the lifetime of a project, various kinds ofcash expenditures
are made and various incomes are received. The amounts and timing ofthese expenditures and incomes constitute the cash flows for the project. In control system costing it is normal to considerexpenditures (negative cash flows) and unusual to consider income (positive cash flows), except for product or energy recovery income. Bythe simplifying convention recommended byGrant, Ireson, and Leavenworth(4), each annual expenditure (orpayment) is considered to be incurred at the end ofthe year, even though the payment will probably be made sometime during the year in question. (The error introduced by this assumption is minimal, however.) Figure 2-3, which shows three hypothetical cash flow IIdiagramsll
, illustrates these end-ofyear payments. In these diagrams, IIpli represents the capital investment,o Raw materials o Utilities

- Electricity

- Steam

- Water

- Others Figure 2-2 Elements ofTotal Annual Cost

Variable

o Labor

- Operating

- Supervisory

- Maintenance 1---Semivariable o Maintenance materials o Replacement parts Oirect Annual Costs

+

o Overhead o Property Taxes o Insurance o Capital Recovery Indirect "-Annua1 Costs 

### = Total Annual Cost

o Materials o Energy Recovery 1------CreditsFigure 2-3 Hypothetical Cash Flow Diagrams

1. All Values Are Constant Year (Real) Dollars 

## o 1 2 3 4 5 6 7 8 9 10 Year 

# p1 

# Al A2t

# A3~ A4{ 

# Asl 

# Atil All Ag

# t Ag

# t AlO

# t

N( j I

.

......
...... 10 Year 9 8 7 6 5 4 3 2 1

- - - A A A A, A A , A A A , A 

# , o II. P

III. 

## o 1 2 3 4 5 6 . 7 8 9 10 Year 

# Al

# I All All Al

# I All· All At All All Al

# t2-12
while the A's denote the end-of-year annual payments. Note that in all diagrams, the cash flows are in "constant" ("real") dollars, meaning that they do not reflect the effects of inflation. Also note that in the top diagram (I), the annual payments are different for each year. {These represent the control system annual costs (exclusive of capital recovery) described in Section 2.2.) In reality, these payments would be different,
as labor and maintenance requirements, labor and utility costs, etc., would vary from yearto year. Agenerally upward trend in annual costs would be seen, however. In diagram II, these fluctuating annual payments have been converted to equal payments. This can be done by calculating the sum of the present values of each of the annual payments shown in diagram I and annualizing the total net present value to equivalent equal annual payments via a capital recovery factor. (See discussion in the following paragraphs and in Section 2.3.3.) Alternatively, it is adequate to choose a value of Aequal to the

sum ofthe direct and indirect annual costs estimated for the first year. This assumption is in keeping with the overall accuracy of study estimates and allows for easier calculations. Finally, notice diagram III. Here, the annual costs (AI) are again equal, while the capital investment (P) is missing. Put simply, Phas been incorporated into Al so that Al reflects not only the various annual costs but the investment as well. This was done by introducing another term, the capital recovery factor (CRF), defined as follows: "w hen multiplied by a present debt or investment, [the CRF] gives the uniform end-of-year payment necessary to repay the debt or investment in nyears with interest rate i."(5) The product ofthe CRF and the investment (P) is the capital recovery cost (CRC): CRC

### =CRF x P (2-2)2-13
where: CRF 

### =i(1 + i)n (l + i) 11_1 Therefore, Al is the sum ofAand the CRC, or: Al 

### =A+CRF x P (2-3)



### (2-4) In this context, "n" is the control system economic life, which,
as stated above, typically varies from 10 to 20 years. The interest rate ("i") used in this Manual is a real rate of 10% (annual). This value is used in most oftheOAQPS cost analyses and is in keeping with current EAB guidelines(6) and the Office ofManagement and Budget recommendation for use in regulatory analyses.(7) It may be helpful to illustrate the difference between IIreal II and

"nominal" interest rates. The mathematical relationship between them is straightforward:(6) (l +in) 

### =(1 + i)(1 + r) where: in i 

### =the annual nominal and real interest rates, respectively 

### ,r

## =the annual inflation rate (2-5)

Clearly, the IIreal II rate does not consider inflation and is in keeping with the expression of annual costs in constant (i.e., real) dollars. EAB guidelines also recommend the exclusion of income tax considerations from cost analyses.(6) Not onlydoes this simplify the analysis, but it also allows for the calculation ofthe "economic" costs of air pollution control--i.e., the true cost to society. Income taxes generally represent transfer payments from one segment of society to another and as such are not properly part ofthe economic costs.2-14
2.3.3 Annualization Methods The above method of "smoothing out" the investment into equal end-ofyear payments, is termed the "equivalent uniform annual cash flow" (EUAC) method.(8) In addition to its inherent simplicity, this method is very useful when comparing the costs oftwo or more alternative control systems (i.e., those which are designed to control the same source to an equivalent degree). In fact, the EUAC's--or simply the total annual costs--of two competing systems'may be compared even ifboth the systems have different economic lives, say 10 and 20 years. We recommend that the EUAC method be used for control cost work unless particular circumstances preclude its

use. Comparisons of systems with differing economic lives cannot be made, however, using the other two annualization (i.e., profitability analysis) methods--"present worth" and "internal rate of return"• The lipresent worth" (or "discounted cash flow") method involves the "discounting" of all cash flows occuring afteryear "0" (i.e., the system startup date) back to year "0". These cash flows are discounted by multiplying each by a "discount factor", 1 , where "mil is the number ofyears from year

## ato the year (1 + i)m in which the cash flow is incurred. The sum of these discounted cash flows is then added to the capital investment to yield the "present worth" of the project. The alternative having the highest present worth would be selected (in control system costing this is usually a negative number). But when comparing the present worths of alternative systems, the system lifetimes must be equal for the comparison to be valid.(9)2-15
The third annualization method, "internal rate of return" (IRR). is similarto the present worth method, in that it involves the discounting of
a series ofunequal cash flows. However, where with the PW method the interest rate, "i", is set beforehand, in the IRR method the interest rate is solved for (usually via trial-and-error) after arbitrarily setting the PW to zero. When comparing alternative systems, the one with the highest IRR is selected.(10) But again, the alternative systems compared must have equal economic lives. 2.4 Estimating Procedure The estimating procedure used in the Manual consists of five steps: (1) obtaining the IIfacility parameters" and "regulatory options" for a given facility; (2) "roughing out" the control systemdesign; (3) sizing the control system components; (4) estimating the costs ofthese individual components; and (5) estimating the costs (capital and annualized) ofthe entire system. 2.4.1 Facility Parameters and Regulatory Options Obtaining the facility parameters and regulatory options involves not only assembling the parameters ofthe air pollution source (i.e., the quantity, temperature, and composition ofthe emission stream(s)), but also compiling data for the facility's operation. (Table 2-1 lists examples ofthese.) Note that two kinds of facility parameters are identified

-- "intensivell and lIextensive". The former are simply those variables whose values are independent ofquantity ordimensions

-- i.e., the "extent" ofthe system. Conversely, "extensivell parameters encompass all size-dependent variables, such as the gas volumetric flowrate.2-16
Table 2-1 Facility Parameters and Regulatory Options (11)
FACILITY PARAMETERS

o Intensive

- Facility status (new or existing, location)

- Gas characteristics (temperature, pressure, moisture content)

- Pollutant concentration(s) and/or particle size distribution
o Extensive Facility capacity

- Faci1ity 1ife

- Gas flow rate Pollutant emission rate(s)
REGULATORY OPTIONS

o No control
o "Add-on" devices Emission 1imits

- Opacity 

### "
o Process modifications

- Raw material changes

- Fuel substitution
o Others

- Coal desulfurization2-17
Like the facility parameters, the IIregulatory optionsll are usually specified by others. These options are ways to achieve apredetermined emission limit. They range from IIno controlII to maximum control technically achievable. The option provided will depend, firstly, on whether the emission source is a stack (point source), aprocess leak (llprocess fugitivesll source) or an unenclosed (orpartly closed) area, such as a storage pile (llarea fugitivesll source). Stacks are normally controlled by lIa dd-onll devices. As discussed above, this Manual will deal primarily with these add-on devices. (However, some ofthese devices can be used to control process fugitives in certain cases, such as a fabric filter used in conjunction with abuilding evacuation system.) Add-ons are normally used to meet a specified emission level, although in the case of particulate emissions, they may also be required to meet an opacity level. 2.4.2 Control SystemDesign Step 2

-- roughing out the control systemdesign

-- first involves deciding what kinds of systems will be priced (a decision that will depend
on the pollutants to be controlled, gas stream conditions, and other factors), and what auxiliary equipment will be needed. When specifying the auxiliary equipment, several questions need to be answered:
o What type of hood (if any) will be needed to capture the emissions at the source?
o Will a fan be needed to convey the exhaust through the system?
o Is a cyclone or another pre-cleaner needed to condition the exhaust before it enters the control device?
o Will the captured pollutants be disposed of or recycled? How will this be done?2-18

o Can the on-site utility capacity (e.g., electricity) accomodate the added requirements ofthe control system? The kinds of auxiliary equipment selected will depend on the answers to these and other site-specific questions. However, regardless of the
source being controlled, each systemwill likely contain, along with the control device itself, the following auxiliaries:
o Hood, or othermeans for capturing the exhaust;
o Ductwork, to convey the exhaust from the source, to, through, and from the control system;
o Fan system (fan, motor, starter, inlet/outlet dampers, etc.), to
move the exhaust through the system;
o Stack, for dispersing the cleaned gas into the atmosphere. 2.4.3 Sizing the Control System Once the system components have been selected, they must be sized. Sizing is probably the most critical step, because the assumptions made in this step will more heavily influence the capital investment than any other. Before discussing how to size equipment, we need to define the term. For the purposes ofthis Manual, "sizing" is the calculation (or estimation) of certain "critical" design parameters for a control device against which the purchased cost of that device is most accurately correlated. For instance, the purchased cost of an electrostatic precipitator (ESP) is most often correlated with its collecting area. This, in turn, is a function ofthe exhaust volumetric flowrate, the overall collection efficiency and the empirically-determined drift velocity, the ESP "critical" parameter. (Table 2-2 lists examples ofthese parameters.)2-19

Table 2-2 Examples of Typical Control Device Parameters(11)

GENERAL

- Material of construction: e.g., carbon steel Insulated? Yes Economic life: 20 yr

- Redundancya: none
DEVICE-SPECIFIC

- Air-to-cloth ratio (llcritical parameterll): 7.5 to 1

- Pressure drop: 6.0 in w.g. (inches water gauge)

- Construction: suction (vs. pressurized)

- Duty: continuous (vs. intennittent)

- Other features: dilution air port (for exhaust temperature regulation)

a Refers to whether there are any extra equipment items installed (e.g., fans) to function in case the basic item becomes inoperative, so as to avoid shutting down the entire system.2-20
Also listed in Table 2-2 are "general" parameters which must also be specified before the purchased cost of the system equipment can be estimated. Note that, unlike the control device parameters, these may apply to kind of control system. These include materials of construction (which may range from carbon steel to various stainless steels to fiberglass-reinforced polyester), presence or absence of insulation, and the economic or "useful" life of the system. As indicated in Section 2.3.2, this last parameter is required for estimating the annual capital recovery costs. The lifetime not only varies according to the**ty~e** of the control system, but with the severity ofthe environment in which it is installed. (Representative values for this and the other control device parameters will be presented in those Sections of the Manual covering them.) 2.4.4 Estimating Total Capital Investment The fourth step is estimating the total purchased cost of the control system equipment. These costs are available from this Manual for the most commonly used add-on control devices and auxiliary equipment. Each type of equipment is covered in a separate section. (See Table of Contents.) Most ofthese costs, in turn, have been based on data obtained from control equipment vendors. There are over one hundred of these firms, many ofwhom fabricate and erect a variety of control systems.(12) They have readily available, current price lists oftheir equipment, usually indexed by model designation. Ifthe items for which costs are requested are fabricated, "off-the-shelf" equipment, then the vendor can provide a written quotation listing their costs, model designations, date ofquotation, estimated shipment date, and other information. (See Figure 2-4 for a sample quotation.) Moreover, the quote is usually "F.O.B. II ("free-on-board")·2-·21

.. 

### Figure 2-4 Typical Vendor Quotation 

### .QUOTATION

xessEQuipmentPlant 

### (NOTE: Company name and address ha,.vebeen deleted.)


# r MAIL DROP 1# 

### 12 

# -, 85S23382 QUOTATION NO. 

### U.S. EPA' RESEARCHTRIANGLE PARK DATE 

### 9-23-85 DURHAM, NC 27711 REFERENCE 

### VERBAL

- BUDGET ATTN: MR. BILLVATAVUK L 

### .-J Thankyou foryourinQuiry.WearepleasedtosubmitourQuotationasfollows:
QUANTITY
1

1 DESCRIPTION 

### ITEM I#l 

### PREHEATER

. MODEL 191-19 SIZE 1#9 

### IMPERVITE SHELL

### &TUBE HEATEXCHANGERWITH' 55.8 SQ. FT. OFHEATTRANSFERAREAAND CODE STAMPED ITEM 1#2

### CONDENS£R MODEL 191-19 SIZE#12 IMPERVITE SHELL

### &TUBE HEATEXCHANGERWITH 74.5 SQ. FT. OF HEATTRANSFERAREAANDCODESTAMPED' APPROVALDWG'S 2 - 3WEEKS AFTER RECEIPTOFORDER. THIS QUOTATION IS INCONFIRMATION OFOUR PHONECONVERSATIONOF 9/18/85. PRICE
$ 7,147.00 EA.

7,430.00 EAo

ESTIMATEDSHIPMENT 6 to 8 WEEKSAFTER 

# o RECEIPTOFORDER 

# o RECEIPTOFDRAWING APPROVAl. Pricesare F.O.B. >. Net30 Days. ' • Unlessotherwisestatedthesepricesaresubjecttoacceptancewithin30daysfromdate.

By_ lilYPURCHASE01160RESULnNGFROMTHISQUOTATIONWILLIESUBJECTTOTHECONTRACTTERMSANDCONIlITlONSPIIINTEDONTHEREVERSESIDEOFTHISPAGE.2-22
the vendor, meaning that no taxes, freight, or other charges are included. However, ifthe items are not off-the-shelf, they must be custom fabricated or, in the case of very large systems, constructed on-site. In such cases, the vendor can still give quotations--but will likely take much longer to do so and may even charge for this service, to recoup the labor and overhead expenses ofhis estimating department. As discussed in Section 2.2 in this Manual, the total capital investment is Ufactored ll from the IIpurchased equipment costll

, which in turn, is the

sum of the base equipment cost (control device plus auxiliaries), freight, instrumentation, and sales tax. The values of these installation factors depend on the type ofthe control system installed and are, therefore, listed in the individual Manual sections dedicated to them. The costs of freight, instrumentation, and sales tax are calculated differently from the direct and indirect installation costs. These items

are IIfactored ll also, but from the base equipment cost (F.O.B. the vendor(s)). But unlike the installation factors, these factors are essentially equal for all control systems. Values for these are as follows: Cost Range Typical Freight 0.01

- 0.10 0.05 Sales tax 0 - 0.08 0.03 Instrumentation 0.05

- 0.30 0.10
The range in freight costs reflects the distance between the vendor and the site. The lower end is typical ofmajorU.S. metropolitan areas, while the latterwould reflect freight charges to remote locations such as Alaska and Hawaii.(ll) The sales tax factors simply reflect the range of local and state tax rates currently in effect in the U.S.(13)2-23
The range of instrumentation factors is a1so quite 1arge. For systems requiring only simple continuous or manual control, the lower factor would apply. However, if the control is intermittent and/or requires safety backup instrumentation, the higher end of the range would be applicab1e.(ll) Finally, some "package" control systems (e.g., incinerators covered in Section 3) have built-in controls, whose cost is included in the base equipment cost. In those cases, the factor to use would, of course, be zero. 2.4.5 Retrofit Cost Considerations The installation factors listed elsewhere in the Manual apply primarily to systems installed in new facilities. These factors must be adjusted whenever a control system is sized for, and installed in (i.e, IIretrofitted")

an existing facility. However, because the size and number of auxiliaries
are usually the same in a retrofit situation, the total purchased cost of the control systemwould probably not be different from the new plant purchased cost. An exception is the ductwork cost, for in many retrofit situations exceptionally long duct runs are required to tie the control system into the existing process. Each retrofit installation is unique; therefore, no general factors
can be developed. Nonetheless, some general information can be given concerning the kinds of system modifications one might expect in a retrofit: 1. Auxiliaries. Again, the most important component to consider is the ductwork cost. In addition, to requiring very long duct runs,
some retrofits require extra tees, elbows, dampers, and other fittings. 2. Handling and Erection. Because of a IItight fit", special care may need to be taken when unloading, transporting, and placing the2-24 equipment. This cost could increase significantly if special

means (i.e., helicopters) are needed to get the equipment on roofs
orto other inaccessible places. 3. Piping, Insulation, and Painting. Like ductwork, large amounts of piping may be needed to tie in the control device to sources of process and cooling water, steam, etc. Of course, the more piping and ductwork required, the more insulation and painting will be needed. 4. Site Preparation. Unlike the other categories, this cost may actuallydecrease, for most of this work would have been done when the original facility was built. 5. Facilities. Conceivably, retrofit costs for this category could be the largest. For example, ifthe control system requires large amounts of electricity (e.g., a venturi scrubber), the facility's power plant may not be able to service it. In such cases, the facility would have to purchase the additional power from a public utility, expand its power plant, or build another one. In any case, the cost of electricity supplied to that control system would likely be higher than ifthe systemwere installed in
a new facility where adequate provision for its electrical needs would have been made. 6. Engineering. Designing a control system to fit into an existing plant normally requires extra engineering, especially when the system is exceptionally large, heavy, or utility-consumptive. For the same reasons, extra supervision may be needed when the installation work is being done.2-25
7. Lost Production. This cost is incurred whenever a retrofit control system cannot be tied into the process during normally scheduled maintenance periods. Then, part or all ofthe process may have to be temporarily shut down. The revenue lost during this shutdown period is a bonafide retrofit expense. 8. Contingency. Due to the uncertain nature of retrofit estimates, the contingency (i.e., uncertainty) factor in the estimate should be increased. Fromthe above points, it is apparent that some ormost of these installation costs would increase in a retrofit situation. However, there may be other cases where the retrofitted installation cost would be less than the cost of installing the system in a new plant. This could occurwhen one control device, sayan ESP, is being replaced by amore efficient unit--a baghouse, for example. The ductwork, stack, and other auxiliaries for the ESP may be adequate for the new system, as perhaps would the support facilities (power plant, etc.). 2.4.6 Estimating Annual Costs Determining the total annual cost is the last step in the estimating procedure. As mentioned in Section 2.2 theTAC is comprised ofthree components

-- direct and indirect annual costs and recovery credits. Unlike the installation costs, which are "factored" from the purchased equipment cost, annual cost items are usually computed from known data on the system size and operating mode, as well as from the facility and control device parameters. Following is amore detailed discussion ofthe items comprising the total annual cost. (Values/factors for these costs are also given in the sections for the individual devices.)2-26
2.4.6.1 Raw Materials Raw materials are generally not required with control systems. Exceptions would be chemicals used in absorbers or venturi scrubbers as absorbents or to neutralize acidic exhaust gases (e.g., hydrochloric acid). Chemicals may also be required to treat wastewaterdischarged by scrubbers or absorbers before releasing it to surface waters. But, these costs are only considered when awastewatertreatment system is exclusively dedicated to the control system. In most cases, a pro-rata waste treatment charge is applied. (See section 2.4.6.5.) Quantities of chemicals required are calculated via material balancies, with an extra 10 to 20% added for miscellaneous losses. Costs for chemicals
are available from the Chemical Marketing Reporter and similar publications. 2.4.6.2 Operating Labor The amount of labor required for a systemdepends on its size, complexity, level of automation, and operating mode (i.e., batch or continuous). The labor is usually figured on an hours-per-shift basis. As a rule, though, data showing explicit correlations between the labor requirement and capacity
are hard to obtain. Atypical correlation is logarithmic: (2-6)
where: ll' L2 

## =labor requirements for systems 1 and 2 Vl, V2 

## =capacities of systems 1 and 2 (as measured by the gas flow rate, for instance) y

## =0.2 to 0.25 (typically)(14) The exponent in equation (2-6) can vary considerably, however. Conversely, in many cases, the amount of operator labor required for a systemwill be approximately the same regardless of its size.2-27


### Acertain amount must be added to operating labor to cover supervisory requirements. Fifteen per cent ofthe operating labor requirement is representative. (15) To obtain the annual labor cost, multiply the operating and supervisory labor requirements by the respective wage rates (in $/hr) and the system operating factor (number of hours peryear the system is in operation). The wage rates also vary widely, depending upon the source category, geographical location, etc. These data are tabulated and periodically updated by the U.S. Department ofLabor, Bureau ofLabor Statistics, in its Monthly Labor Review and in other publications. Finally, note that these
are base labor rates, which do not include payroll and plant overhead. (See overhead discussion below.) 2.4.6.3 Maintenance Maintenance labor is calculated in the same way as operating labor and is influenced by the same variables. The maintenance labor rate, however, is normally higherthan the operating labor rate, mainly because
more skilled personnel are required. A10% wage rate premium is typical.(15) Further, there are expenses for maintenance materials

-- oil, other lubricants, duct tape, etc., and ahost of small tools. Costs for these items can be figured individually, but since they are normally so small, they are typically factored from the maintenance labor. Reference 15 suggests a factor of 100% ofthe maintenance labor. 2.4.6.4 Utilities This cost category covers many different items, ranging from electricity to compressed air. Ofthese, only electricity is common to all control devices, where fuel oil and natural**~as** are generally used only by2-28 incinerators; water and watertreatment, by venturi scrubbers, quenchers, and spray chambers; steam, by carbon adsorbers; and compressed air, by pulse-jet fabric filters. Techniques and factors for estimating utility costs for specific devices
are presented in their respective sections. However, because nearly every system requires a fan to convey the exhaust gases to and through it, a general expression for computing the fan electricity cost (Ce) is given here:{ll) 

### C

e

### =0.746 

### Q**~P** s

## eP e 6356 where: 

### Q= gas flowrate (actual ft3/min)**~P** = pressure drop through system (inches ofwater, gauge) (2-7)

(Values for are given in the sections covering the equipment

items.)
s

### =specific gravity of gas relative to air (1.000, for all practical purposes) 

## e=operating factor (hr/yr)

= combined fan and motor efficiency (usually 0.60 to 0.70) P

e

### =electricity cost ($/kwhr). Asimilar expression can be developed for calculating motor electricity requirements. 2.4.6.5 WaterTreatment and Disposal Though often overlooked, there can be a significant cost associated with treating and/ordisposing ofwaste material captured by a control system that neither can be sold nor recycled to the process. Liquid waste streams, such as the effluent from a venturi scrubber,
are usually processed before being released to surface waters. The type2-29
and extent of this processing will, of course, depend on the characteristics of the effluent. For example, the waste can first be sent to one (or more) clarifiers, for coagulation and removal of suspended solids. The precipitate from the clarifier is then conveyed to a rotary filter, where most of the liquid is removed. The resulting filter cake is then disposed of, via land filling, for example. The annual cost of this treatment is relatively high--$1.00 to $2.00/thousand gallons treated ormore.(16) The solid waste disposal costs (via land filling, for example) typically would add another$20 to $30/ton disposed of-(lJ) This, however, would .not include transportation to the disposal site. More information on these technologies and their costs is found in References (16) and (17). 2.4.6.6 Replacement Parts This cost is computed separately from maintenance, because it is a large expenditure, incurred one ormore times during the useful life of a control system. This category includes such items as carbon (for carbon adsorbers), bags (for fabric filters) and catalyst (for catalytic incinerators), along with the labor for their installation. The annual cost ofthe replacement materials is a function ofthe initial parts cost, the parts replacement labor cost, the life of the parts, and the interest rate, as follows: CRCp

### =(Cp+Cpl)CRFp (2-8) where: CRCp = capital recovery cost of replacement parts ($/yr) C

p

### =initial cost of replacement parts, including taxes and freight ($) Cpl 

### =cost of parts replacement 1abor ($) CRFp

### =capital recovery factor (defined in Section 2.3).2-30
In the Manual methodology, replacement parts are treated the same as any other investment, in that they are also considered an expenditure that must be amortized over a certain period. Also, the useful life of the parts (typically 2to 5 years) is generally less than the useful life ofthe rest ofthe control system. Replacement part laborwill vary, depending upon the amount of the material, its workability, accessibility ofthe control device, and other factors. 2.4.6.7 Overhead This cost is easy to calculate, but often difficult to comprehend. Much of the confusion surrounding overhead is due to the many different ways it is computed and to the several costs it includes, some ofwhich may appearto be duplicative. There are, generally, two categories of overhead, payroll and plant. Payroll overhead includes expenses directly associated with operating, supervisory, and maintenance labor, such as: workmen's compensation, Social Security and pension fund contributions, vacations, group insurance, and other fringe benefits. Some of these are fixed costs (i.e., they must be paid regardless of how many hours peryear an employee works). Payroll overhead is traditionally computed as a percentage of the total annual labor cost (operating, supervisory, and maintenance). Conversely, plant (or IIfactoryll) overhead account for expenses not necessarily tied to the operation and maintenance ofthe control system, including: plant protection, control laboratories, employee amenities, plant lighting, parking areas, and landscaping. Some estimators compute2-31 plant overhead by taking apercentage of all labor plus maintenance**materials(18)~** while others factor it from the total labor costs alone.(19) For "study" estimates, it is sufficiently accurate to combine payroll and plant overhead into a single indirect cost. This is done in this Manual. Also, overhead will be factored from the sum of all labor (operating, supervisory, and maintenance) maintenance materials, the approach recommended in reference 18. The factors recommended therein range from 50 to 70% (18) An average value of60% is used in this Manual. 2.4.6.8 PropertyTaxes, Insurance, and Administrative Charges These three indirect**o~erating** costs are factored from the system total" capital investment, and typically comprise 1,1, and 2% of it, respectively. Taxes and insurance are self-explanatory. "Administrative charges" covers sales, research and development, accounting, and other home office expenses. (It should not be confused with plant overhead, however.) For simplicity, the three items are usually combined into a single, 4% factor. This value, incidentally, is standard in all OAQPS cost analyses. 2.4.6.9 Capital Recovery As discussed in Section 2.3, the annualization method used in the Manual is the equivalent uniform annualized cost method. Recall that the cornerstone ofthis method is the capital recovery factor which, when multiplied by the total capital investment, yields the capital recovery cost. (See equation 2-2.) However, wheneverthere are parts in the control system that must be replaced before the end of its useful life, equation 2-2 must be adjusted, to avoid double-counting.(2-9) 2-32
That is:
CRCs 

### =CRFs [TCI

- (Cp+Cpl)] where: CRCs 

### =capital recovery cost for control system ($/yr)

TCI 

### =total capital investment for entire system 

### ($). CRFs 

### =capital recovery factor for control system The term (Cp+Cpl) accounts for the cost of those parts that would be replaced during the useful life ofthe control system and the labor for replacing them. Clearly, CRFs and CRFpwill not be equal unless the control system and replacement part lives are equal.2-33

References for Section 2: 1. Perry, Robert H., and Chilton, Cecil H., Perry's Chemical Engineer's Handbook (Fifth Edition). New York: McGraw-Hill, 1973, pp. 25-12 to 25-16. 2. Humphries, K. K. and Katell, S., Basic Cost Engineering, New York: Marcel Dekker, 1981, pp. 17-33. 3. Grant, EeL., Ireson, W.G., Leavenworth, R.S., Principles of**~ngineering** Economy,**~ixth** Edition. New York: John Wiley 

### &Sons, 1976, p.25. 4. Ibid., p. 35. 5. Ibid., p. 36. 6. EAB Guideline Memo: "Interest Rates for Regulatory Impact Analyses (RIA)", May 27, 1982. 7. "lnterim Regulatory Impact Analysis Guidance," Office of Management and Budget, June 5, 1981. 8. Grant, et al., Cit., p. 67. 9. rEid., p. 91. 10. Ibid., pp. 107-131. 11. Vatavuk, W. M. and Neveril, R. B., "Estimating Costs of Air-Pollution Control Systems--Part I: Parameters for Sizing Systems," Chemical Engineering, October 6, 1980, pp. 165-168. 12. Pollution Equipment News, Pittsburgh: Rimbach Publishing, 1982, pp. 71-72. 13. Internal Revenue Service, Form 1040, 1985. 14. Peters, M. S. and Timmerhaus, K. D., Plant Design and Economics for Chemical Engineers (Third Edition). New York: McGraw-Hill, 1980, p. 195. 15. Vatavuk, W. M. and Neveril, R. B., "Estimating Costs of Air-Pollution Control Systems--Part II: Factors for Estimating Capital and Operating Costs," Chemical Engineering, November 3, 1980, pp. 157-162. 16. Ibid., "Part XVII: Particle Emissions Control," Chemical Engineering, April 2, 1984, pp. 97-99. 17. The RCRA Risk-Cost Analysis Model: U.S. Environmental Protection Agency, Office of Solid Waste, January 13, 1984. 18. Peters and Timmerhaus, Cit., p. 203. 19. Humphries and Katell, Cit., pp. 64-68.Section 3 THERMAL AND CATALYTIC INCINERATORS Vishnu S. Katari Pacific Environmental Services (Durham, NC 27707) William M. Vatavuk Economic Analysis Branch, OAQPS

. 3.1 Process Description 3.1.1 Elements ofCombustion Fume incineration, a controlled oxidation process, is atechnique used for destruction of vaporous volatile organic compound (VOG) emissions from industrial waste gases. In the process, the VOC content of waste gases reacts at high temperatures with oxygen to form carbon dioxide and water, while liberating heat. Three parameters: temperature, residence time (also referred to as IIretention timell or IIdwell timell ) and turbulence (the IIthreeTsII) have an interrelated effect upon the final combustion performance. To achieve good oxidation rates and obtain release of the full heat content of the combustion products, emission effluents must be held for sufficient residence times at combustion temperatures**100~** ormore above reported ignition temperatures. Further, turbulent flow conditions must be maintained in the incinerator for good mixing of the fuel combustion products with incoming effluents, so that athorough homogeneity of combustion elements (VaG and oxygen) may be achieved. The ignition temperature of a given VaG is the minimumtemperature at which the VaG reacts instantaneously with oxygen. Below this temperature (ifthe supply of heat were interrupted) combustion would slow down and gradually stop. Typically, the rudimentary combustion parameters for an incinerator design are established empirically and no calculations are involved in their estimation. Ofthe 3Ts, time and turbulence are fixed by3-2 incineratordesign and air flow rate, and only temperature can be significantly controlled. The type ofVOGs present in the waste gas usually dictates the combustion temperature for a required VaG destruction rate. Lower or higher combustion temperatures can be used to a limited extent, with corresponding variations in the residence time (e.g., an incinerator can be designed for a lower residence time but must operate at a correspondingly higher combustion temperature). The possibilities of varying these parameters are limited, because the combustion temperature must always be above the ignition temperature. Moreover, the cost savings realized from reducing the residence time (and, in turn, the incinerator size) generally are not large enough to offset the additional expenses (e.g., fuel) resulting from compensating increases in the combustion temperature. In general, the design of an incinerator system is based on providing the required amounts of: (1) heat to bring the waste gas to the oxidation temperature and (2) oxygen for complete combustion. The waste gas heat and oxygen contents determine, respectively, the auxiliary heat and oxygen requirements (i.e., the lowerthe waste gas heat and oxygen contents, the higher are the auxiliary requirements). Either natural gas or fuel oil can be used as an auxiliary heat source while ambient air is the usual source of oxygen. Natural gas is preferred and used in most incinerators. Oil-fired burners have limited turndown capabilities and require high maintenance. Depending upon the fuel availability and geographic location, some incinerators are designed for adual fuel-burning capability (natural gas with standby oii). In practice, a flue gas oxygen content of at least 3 percent (by volume) is used empirically to insure that a sufficient amount of oxygen is available for combustion.3-3
The waste gas heat content measures the potential heat ofVOG that would be released as heat of combustion upon the oxidation ofthe VOG. The heat and VOG contents of awaste gas are proportional to, and can provide

a measure of. each other. They are also inherently related to, and can be expressed empirically, in terms of the VOG property "flammability." Flammability is characterized by two limits: the lower explosive limit (LEL) and the upper explosive limit (UEL). These limits represent, respectively, the smallest and largest amounts ofVOGs which, when mixed with air, will burn without a continuous application of external heat. Major reference books present VOG flammability (LEL and UEL) data. Table 3A-1 in Appendix 3A presents the flammability data for several VOGs commonly encountered in industrial waste gases. To avoid potential explosions, the VOG content of industrial waste gases released to the atmosphere is normally outsidethe flammability limits. The majority ofwaste gases contain low concentrations ofVQGs. For safety reasons, their composition is typically limited to below 25 percent and will seldom exceed 50 percent ofthe LEL level. It has been empirically determined that, upon combustion, most VOCs release approximately 50 Btu/scf ofwaste gas, iftheir concentration is at 100 percent of the LEL. Therefore, the VOC content of awaste gas at less than 25 percent LEL, the safe upper limit for incineration, will have a potential heat content of less than 13 BTU/scf. TheLEL and heat content values of a given waste gas can also be related empirically to the temperature rise ofthe combustion flue gases. Upon combustion, each one percent ofLEL of the VaG (i.e., a potential heat content of0.50 BTU/scf ofwaste gas) can raise the temperature of one ft3 ofthe waste gas by 27°F based on a heat capacity3-4
of0.018 BTU/ft3°F for dry air. These empirical relations can sometimes be used in making qualitative observations to determine if a given waste gas can be incinerated. They can also be used to make quick and approximate estimates of the auxiliary fuel requirement. Most industrial waste gases incinerated are dilute mixtures of VaGs, air, and inert gas. TheirVaG content is very low, and their oxygen content exceeds that required for combustion of both the VaG and the auxiliary fuel. If awaste gas with aVOG content over25 percent LEL is encountered, it is diluted to below 25 percent LEL priorto incineration by adding outside air (thus increasing the waste gas volume flow rate to be treated). However, awaste gas with aVaG content from 25 to 50 percent LEL can be incinerated without adding dilution air, provided the waste gas VaG levels in the system are continuously monitored viaLEL monitors, to satisfy fire protection regulations. Alow-oxygen content waste gas mixture ofVaG, air, and inert gases could disrupt the burner flame stability. Therefore, when awaste gas with less than 13 to 16 percent oxygen content is incinerated, the portion of such waste gas used for fuel combustion is augmented with ambient air. In afew applications, the waste gas is an inert gas with a low VaG content and negligible or zero oxygen content. In such cases ambient air is provided for burning of both the waste gas VaG and aUXiliary fuel. In

rare cases, the waste gas is a rich VaG streamthat can support combustion without auxiliary fuel. Such a rich VaG waste gas is treated as a fuel and burned, either premixed or oxygen free. This process is sometimes referred to as "direct flame incineration." Figure 3-1 provides a flow chart for categorizing awaste gas to determine its suitability for incinerati.on. (Formore information on waste gas characterization,

see Appendix 38.)3-5

Hazardous, should**~----,** notbeancounterad. Formajorrtyof IIOCs, wastegas is OUlSidethe llammabilitylimitsif 0, < 10% No InappropriB1efor incineration, "-----'-="---' Dillpolliliondapends oncomposition. (NOIcoveredintllia lae:tion.)

No

No

OO'EGORV4 Noauxiliaryfuel is llIquirad for**~----,** incineration, DonOl use incineration.

........._--' Useasfuel or premixwith ; addrtionalfuel. CATEGORY5

NoauxUiaryairia llIqUirad OOEGORY 1· 'OO'EGORV3 Incinerale,but mulluseLEL ,COnlfOISand monilDrs

Auxiliaryairis llIquirad CATEGORV2

Auxiliaryfuel ia llIquinldlor incineration. OO'EOORY8

"The IllIjoriIyof -..

_ g.- "" inc_ran inlll C8ISQarY 1. CaIculatJonl !DrC8togory 1 "'"

__ in 1IIe

_ and _lions !Dr

.. calIgOries(i.e. caIIgClries 1 tIlfoug/l61"'"

_ in Appendi. 38.

Reproduced from bestavailable copy. Figure3-1. Flowchartforcategorization ofawaste gastodetermine itssuitabilityfor incineration and needforauxiliaries.3-6
3.1.2 Types of Incinerators Two types of incinerators are in use: thermal and catalytic. The combustion process, as well as equipment, design concept, and calculations,
are essentially the same with both incineratortypes. The only exception is that catalytic incineration is essentially a flameless combustion process, wherein a catalyst bed is used to initiate the combustion reaction at much lower temperatures. HistoMcally, the greatest reason for using a catalytic incinerator has been to reduce fuel consumption. However, because the application of either athermal or a catalytic incinerator systemwithout aheat exchanger (for recovery of flue gas heat) is now rare, the savings associated with catalytic incinerators are less significant. Also, this fuel economy for catalytic incinerators is partially offset by increased operating costs for maintenance (i.e., periodic cleaning and replacement of catalyst). Catalysts undergo a gradual loss of activity through thermal aging, fouling, and erosion of their surfaces. Certain poisonous contaminants, such as phosphorus, arsenic, antimony, lead, and zinc, also cause catalyst deactivation. Catalytic incineration is not recommended for waste gases containing significant concentrations of particulate matter (either organic or inorganic) that cannot be vaporized. The catalysts used in catalytic incinerator systems for gaseous VOC control are usually precious or base metals ortheir salts, either supported on inert carriers, such as alumina or porcelain, or unsupported. Precious metal oxide catalysts are less brittle and more expensive than base metal types, and are used in lesser amounts per unit ofwaste gas volume. Of the precious metal oxide catalysts, platinum/palladium oxides are preferred. Others include rhodium, nickel, and gold.3-7 Manganese dioxide is the most commonly used base metal oxide catalyst. The types ofVOCs present in the waste gas determine the operating temperature required in a catalytic unit. The more stable VOCs are generally the least reactive and require higher inlet catalytic operating temperatures. Methane is an example of a stable, low molecularweight compound that requires a relatively high catalytic conversion temperature, about 1,000°F. Hydrogen, on the other hand, is extremely reactive, having a conversion temperature of about 200°F. To achieve aVOC destruction efficiency of at least 90 percent, the catalytic ignition temperature for most hydrocarbons must be between 400 and 500°F. Highertemperatures are required to obtain higherVOC destruction efficiencies. When methane is present along with other less stable VOCs in awaste gas, preheat temperatures lowerthan 1,000°F can be used, because the less stableVOCs burn first and generate heat. The auxiliary fuel requirement is the most significant operating expense of an incinerator. Further, the temperature rise ofthe combustion products due to the VOC heat release can be substantial. Therefore, to minimize auxiliary fuel expenses, a part of the heat from the incinerator flue gases is recovered. This heat is usually recovered in recuperative heat exchangers, in which the heat from the flue gases is exchanged with the waste gas. Both countercurrent and cross-flow types of heat exchangers are used for this purpose. When feasible, heat may be recovered indirectly, by producing low-pressure steam in a waste heat boiler. Further, heat recovery from the flue gases after primary heat recovery (PHR) can be achieved by employing secondary heat recovery (SHR) units. Of course, SHR can be economical, only ifthe secondary heat can be consumed on-site and cheaper heat sources3-8

are unavailable. The PHR and SHR combinations are most suitable for large installations where recovered secondary heat may be used on-site for waterheating, air heating, and other purposes. In general, a typical incinerator systemmay include the following components: (1) a fan to move the waste gas; (2) a fan to supply ambient air, if required; (3) a combustion unit (i.e., a refractory chamber with burner for thermal units, and a preheat chamberwith burner and catalyst bed for catalytic units); (4) heat recovery equipment (optional, but almost always used); (5) controls, instrumentation, and control panel; (6) a stack; and (7) in the case of catalytic units, a filter/mixer to assure flow distribution, protect the catdlyst bed from flame impingement, and remove noncombustible particulate matter. In addition, auxiliary equipment. such as ductwork, may be required in the system. 3.2 Design Procedure 3.2.1 Design and Operating Features The minimum waste gas characteristics data needed to perform incineratordesign calculations are the waste volume flow rate and temperature, and the

### VaG composition. The waste gas flow rate primarily determines the quantity of combustion flue gases generated which, in turn, dictates the size of an incinerator system. As discussed in Section 3.1, the waste gas composition determines the combustion air requirements. The waste gas and combustion temperatures, along with the waste gas volume flow rate and 

### VaG content, determine the auxiliary heat requirement and the heat exchanger size. Finally, the types of 

### VaG present in the waste gas determine the combustion temperature required in the incinerator for optimum oxidation.3-9
In the incineration process, awaste gas is introduced to the combustion chamber, (or "preheat chamber," in the case of a catalytic incinerator), where the waste gas temperature is raised to the appropriate combustion temperature by burning auxiliary fuel. Because of the high combustion temperatures maintained, refractory chambers are used in thermal incinerators, while stainless steel or carbon steel chambers are used in catalytic incinerators. In thermal incinerators, the waste gas is heated and retained for 0.3 to 1.0 seconds in the combustion chamber at 100°F ormore above the ignition temperature, which ranges from 1,000 to l,400°F for most VOCs. At these temperatures, 95 to 99 percent of the VOCs in the waste gas are combusted. As discussed in Section 3.1, the resulting flue gases are exhausted via a stack to the atmosphere, after apart oftheir sensible heat is recovered via direct exchange with the incoming waste gas. In catalytic incinerators, the waste gas temperature is typically raised in the preheat chamber to 500 to 600°F. This is above the catalytic ignition temperature of400 to 550°F theoretically required for 90 percent destruction ofmost VOCs. (Thermal and catalytic ignition temperature data forVOCs are well documented in the literature. Table 3A-2 in Appendix Apresents catalytic ignition temperatures for several
common VOCs.) The thoroughlymixed gaseous effluents from the preheat chamber (where partial oxidation may occur) are subsequently passed through specially designed units containing catalyst elements, on the surface ofwhich oxidation occurs at an accelerated rate at temperatures of700-900°F--much lower than typical thermal incineration combustion chamber temperatures. As the linear velocity through the catalyst bed is high (600 to 1,200 ft/min.), the residence time is negligible.3-10
Forthis reason residence time is rarely an important factor in the design of catalytic incinerators. The heat of reaction from the oxidation ofthe VOCs in the catalyst bed causes the gas temperature to increase as it passes across the catalyst bed. The amount ofVOCs present in the waste gas determines the temperature increase in the catalyst bed. The desired catalyst bed outlet temperature is typically 700 to 900°F. The maximum temperature to which the catalyst bed can be exposed continuously is limited to about 1,200°F. Therefore, the heat released from the combustion reaction and, accordingly, the vac content ofthe waste gas are limited to about 20 percent LEL. (See Section 3.2.2. for

more details.) Depending upon the catalyst bed temperature swings (i.e., the frequency at which it is subjected to extreme temperature excursions), the operating and maintenance practices, and the particulate matter and specific catalyst poisons encountered, the catalyst would have an effective life of2 to 10 years. The amount of catalyst required (measured by the standard hourly flue gas volume flow rate per unit volume of catalyst orthe "space velocity, II hr-1), depends on the type of catalyst used, but increases with the required vac destruction efficiency. The space velocity, incinerator gas velocity, and pressure drop used in the system design are determined experimentally. Finally, as in thermal incinerators, the flue gases exiting the catalyst bed are exhausted to a stack, usually after heat exchange with the incoming waste gas. 3.2.2 Design Calculations This section presents calculations for designing an incineration systemto the level ofdetail required by a study cost estimate. Further, these calculations only apply to dilute mixtures ofvacs, air, and inert gas.3-11
These mixtures are typical ofmost industrial waste gases (i.e., those

cases which require no outside air for dilution or for combustion of fuel and waste gas VaC--Category 1 in Figure 3-1 and Table 3B-l, Appendix 3B). Appendix 3B presents a general procedure applicable to all types ofwaste gas compositions, including those requiring the
use of outside air for combustion ordilution purposes (i.e., Categories 1 through 6 in Figure 3-1 and Table 3B-l, Appendix 3B). Figure 3-2 is a simplified schematic of an incinerator system. A thermocouple in a thermal incinerator combustion chambermeasures temperature, and appropriate control circuitry alters the rate of auxiliary fuel entering the incinerator to maintain the desired combustion temperature. In catalytic incinerators, thermocouples installed in the preheat chamber and catalytic bed perform the same function. The incineratordesign calculations for the waste gas cases where
no outside air is added for either combustion ordilution and where the
vac content is low (i.e., Category 1) can be summarized by the following step-wise approach. The items that must be calculated or estimated in the design of any emission control system are those which determine the system size, performance, and capital and operating costs. In the

case of incinerators, these items are: (1) the auxiliary fuel requirement and flue gas flow rate; (2) for catalytic incinerators, the amount of catalyst required; and (3) the pressure drop across the system. Item 1. Calculate Auxiliary Fuel Requirement and Flue Gas Flow Rate. The calculations of the auxiliary fuel requirement and the flue gas flow rate constitute an important incineratordesign item. The flue gas flow rate determines**th~** incinerator system size and, consequently, its capital cost. The auxiliary fuel can be amajor operating cost for an incinerator system.W I**~,** I-' ,"N Flue Gas to Vent/Stack! Ambient (7) Waste gas from the process (0) 

# f-------DII." ••AIr' (0) HeatLoss (Hal



# -

t-- Combustion Catalyst Heat Exchanger ry Chamberb Flue Bedc (6) (Optional) (3) Gas (5) 

# j. (2) Auxflia

Fuel Combustion

Air. (4)

Ca) When required. Cb) Referred to as PreheatChamber in the case ofcatalytic incinerators. Cc) Includedonly incatalytic incinerators.

Figure 3-2. Schematic diagram ofan incinerator system.3-13

Identify the waste gas composition data. These include: the volume flow rate (Ql), scfm; temperature (Tl), of; VOC content, 

### %LEL; and heat content (hI), BTU/scf ofwaste gas. The heat content ofthe waste gas is a function ofthe VOC content. (The waste gas pressure is not adesign consideration, because the majority ofwaste gases enter the incinerator at atmospheric pressure.) Forthermal incinerators, determine the combustion temperature (T5) based on the desired VOC destruction efficiency. Suggested combustion temperature (T5) values for waste gases containing nonhalogenated VOCs
are 1,600°F and 1,800°F. respectively, for 98 and 99 percent VOC destruction efficiencies. These temperatures correspond to aO.75-second residence time in the incinerator. Highertemperatures of about 2,OOO°F (and I-second residence time) are required for the destruction ofhalogenated VOCs by 98 percent or Step 2. Calculations of the auxiliary fuel requirement and flue gas flow rate are considered as one item, because they are interrelated. The specified flue gas conditions determine the amount of auxiliary fuel consumed which, in turn, becomes a part ofthe flue gas. The necessary waste gas and combustion information to be compiled and the calculations to be performed are presented in the following steps: Step 1.

more.3-14
For catalytic incinerators, select the preheat temperature (Ts) considering the amount and type of vacs present in the waste gas. Upon oxidation in the catalyst bed, the heat content ofthe waste gas vacs is released in the bed. Consequently, the temperature of the bed and waste gas increase, as explained in Section 3.1.1, by about 27°F per each one percent ofvac LEL. For most
vacs oxidized on precious metal catalysts, the suggested preheat temperature (T5) is 60aoF. For awaste gas content of4to 10 percent LEL, this results in an average catalyst operating temperature of 7UU to 9UO°F (i.e., 60UoF + [4 to 10J% LEL x27°F/%LEL

## =70U to 9UO°F). Less stable VOCs, such as monohydric alcohols, aromatic hydrocarbons or propylene, can use lower catalyst operating temperatures, on the order of500°F. In rare cases, where the vac content in the waste gases is less than 2percent LEL, higher preheat temperatures (7aa-75aOF), or more catalyst than typically required, may have to be used to obtain equivalent 700° to 900°F catalyst operating temperature and VOC destruction. However, to avoid this increase in fuel/catalyst costs, the vac content ofthe waste gas is increased when possible by repeated recycling ofwaste gases within the process being controlled, before introducing them to the incinerator. Waste gases with vac contents higher than 20 percent LEL are not suitable for catalytic incineration, because3-15
the vac heat content released increases the catalyst bed temperature to beyond 1,200°F. the maximum permissible temperature to which the catalyst bed can be exposed continuously. Conversely, for the destruction ofmore stable vacs. such as methane, higher preheat temperatures (900-1.000°F)

are used. This, however, requires a lower maximum allowable
vac content--i.e., 7to 11%. Step 3. (Applies to only catalytic incinerators.) Calculate the catalyst bed outlet temperature (T6). As indicated in Step 2, T6 should not exceed 1,200°F. Further, as explained in Section 3.1.1, the heat of combustion released by the
vac in the waste gas increases the waste gas temperature by 27°F for each one percent ofLEL. Because the average heat capacity of air is approximately 0.018 BTU/scf-oF, the waste gas heat content required to increase the waste gas temperature by 27°F would be equivalent to 0.5 BTU/set. (0.018 x27). It follows that awaste gas vac heat content of 1 BTU/scfwould, when released through combustion, increase the waste gas temperature by about 55°F upon release (2 x27°F). Therefore, we can write: (3-1) where T5 

### =Preheat temperature, of, determined from Step 2 hI 

### =Waste gas heat content, (BTU/scf ofwaste gas) Q1/Q5 

## =Ratio of the waste gas flow rate at the incinerator inlet to the flue gas flow rate at the preheat chamberexit. Fordilute waste gases consider the ratio to be equal to 1, by neglecting the increase in flue gas volume due to the fuel addition. T6 <1200°F3-16 Step 4. Determine the waste gas temperature at the incinerator inlet (T2) 

### =the temperature at the heat exchanger outlet. With thermal incineration, T2 must be no higher than 1,000 to 1,100°F, to avoid preignition of the waste gas before it reaches the combustion chamber. T2 is also limited by the heat VOC content of the inlet waste gas. As eq. 3-1 indicates, the temperature rise realized in the combustion chamber is proportional to this heat content. For example, if a20 percent LEL streamwere incinerated, the temperature rise would be about S40°F (20 x270 ). Subtracting this from a combustion temperature of IS00°F yields amaximumT2 of about 9S0°F. For catalytic incinerators, the waste gas temperature (T2) entering the preheat chamber can be as high as the preferred preheat temperature (TS), 600°F. Broadly speaking, as T2 increases, the auxiliary fuel requirement (and cost) decreases. But at the same time, the size and cost of the recuperative heat exchanger increases, driving up the total capital investment of the system. Thus, there is a trade-off between capital and operating costs, the extent ofwhich depends upon the value ofT2 selected. However, as this selection depends
on the results of aprocess optimization analysis, no firm guidance can be given for selecting T2--except that it should not exceed the design limits noted above. The discussion that follows may guide one in performing such an optimization.3-17

First of all, the waste gas temperature entering the combustion chamber/preheat chamber is determined by the heat exchanger heat transfer performance (denoted by

orHE) and the waste gas inlet temperature (T1). For incinerator systems with heat exchangers T2 

### =Tl (the temperature of the entering waste gas). For incinerator systems with primary (recuperative) heat exchangers, T2 is calculated from the known value of the system1s heat exchanger heat transfer performance**(~)** and the following expressions: T2 

### =Tl + (TS Tl) for thermal incinerators T2 

### =Tl + (T6 Tl) for catalytic incinerators (Note: Use of a secondary heat exchanger has no affect on the T2 value.) Theoretically, a heat exchanger heat transfer performance 

### (0) approaching 100 percent is possible. However, as the heat exchanger performance increases the required heat transfer area, the heat exchanger cost increases enormously, approaching infinity as approaches 100 percent. Therefore, heat exchanger is selected based on economic considerations, as well as the waste gas and flue gas data. Included among the waste gas and flue gas data which impose limitations on are: (1) the flue gas temperature at3-18
the heat exchanger outlet (T7) in the case of eithertype ofincinerator and (2)**t~e** waste gas vac content in the
case ofthermal incinerators. Depending upon the flue gas constituents, mainly moisture and corrosive elements, T7 should be about**5aO~,** due to possible equipment corrosion"and condensation that may occur if it falls below this temperature. The value ofT7 is related to by the following equation:


### = QsCps Q2C P2



### = Q6C P6 Q2CP2 TZ

- Tl [1

- T5

_T1 ] for thermal incinerators (3-4) [1

- Tz

- Tl] for catalytic incinerator (3-5) T

6 - T1
where Q1, Q5, and Q6 =waste gas flow rate and flue gas flow rates at the exit of combustion chamber and catalyst bed respectively (scfm) CP2, CP5, and CP6 

## =Mean heat capacities ofwaste gas and of flue gas at the exit of the combustion chamber3and catalyst bed, respectively (Btu/ft OF) It is evident from the above equation that maximum possible increases with the value ofTl. However, Tl can
never equal or exceed T7. The following heat transferperformance**(~)** capabilities are commonly reported for typical modular heat exchangers: 35 to 40 percent for I-pass, 45 to 50 percent for 2-pass, and 65 to 70 percent for 3-pass units. Step 5. Calculatethe amount of auxiliary fuel required (Q3) based
on the following energy balance around the combustion chamber/ preheat chamber (see Figure 3-2):Amount of sensible heat 1eaving 3-19

Amount of sensible heat 

### = entering Amount of heat ofVOCs

released from

.combustion Amount of + heat of fuel released from combustion

where (H5 + HL)

- (H2 + H3) 

### =Q1 hI + Q3 h3 (forthermal incinerators) (3-6) (H5 + HL)

- (H2 + H3) 

### =Q3 h3' (for catalytic incine- (3-7) rators, because VOC heat content is not released in the preheat chamber). H5 

### =Sensible heat of flue gas at the combustion chamber/preheat chamber exit (BTU/min) HL = Heat loss = 10% H5 (assumed) H2 

### =Sensible heat ofwaste gas at the incinerator/ preheat chamber inlet (BTU/min) H3 

### =Sensible heat of fuel used (BTU/min)

=

## a(for fuel entering at ambient conditions) Q1 

### =Waste gas flow rate (scfm) Q3 

### =Auxiliary fuel flow rate (scfm) hI 

### =Waste gas heat content (BTU/scf ofwaste gas) h3 

### =Lower heating value (LHV) of fuel (BTU/scf). By substituting Hi 

### =Qi CPi DoTi, where CPlrepresents the
mean heat capacity for the temperature difference of DoTi (Ti-Tr, the reference temperature) the sensible heat values of the gas streams leaving and entering the chamber can be expressed by the following equations:(3-8) where 

### =Mean heat capacity of the flue gas for the temperature interval of DoT5) from the reference temperature (70°F) to the combustion temperature (in the case of thermal incinerators) orto the preheat temperature (in the case of catalytic incinerators)3 CP5 

## =0.0194, 0.0196, and 0.0198 BTU/ft of for thermal incinerator combustion temperatures of 1,600, 1j800, 2,000°F, respect- ively, and 0.0183 BTU/ft of for a catalytic incinerator preheat temperature of600°F (3-9)where 3-20
CP2 

### =Mean heat capacity ofthe waste gas for the temperature interval &2 from the reference temperature (70°F) to the temperature at the inlet of the incinerat0

# 3 / preheat chamber (T2). CP2 

### =0.0181 BTU/ft of forwaste gas temperatures (Tl) up to 300°F

(3-10) Substituting the above enthalpy values forH2 and HS and Ql +Q3 

### =Q2 +Q3 for QS in eq. (3-6) or (3-7), rearranging the resulting equation, and accounting for the heat loss yields the following (see Appendix 3B for details):

=Fuel used, ft3/std.ft3 ofwaste gas



### =1.1 Cps LlTS - C P2 LlT2 - h1 h

3 - 1.1 C 

## s LlTS Step 6. Calculate the gas flow rate leaving the combustion chamber/preheat chamber (QS). In the case of athermal incinerator, because the combustion takes place primarily in the combustion chamber, the resulting flue gas consists ofthe products of combustion ofthe waste gas VOCs and the auxiliary fuel. In the case of catalytic incinerators, because fuel is added in the preheating chamberto raise the waste gas temperature for subsequent combustion in the catalyst bed, the gases exiting the preheat chamber consist of the waste gas and the products of fuel combustion. In the incineration ofdilute VOC waste gases the flue gas flow rate is approximately equal to the total of the waste gas flow rate and fuel flow rate used for3-21 combustion, because no outside combustion air is used (i.e., Q4 

### =0). (This is because, in the case of thermal incinerators, the increase in flow rate due to combustion ofthe waste gas VOCs and fuel is negligible.) Therefore,
as indicated above:

where Q5 = Q2 +Q3 Q5 

## =Flue gas flow rate (scfm) Q2 

## =Waste gas flow rate (scfm) Q3 

### =Auxiliary fuel burned (scfm) Item 2. Establish the Amount ofCatalyst Required. (3-11)

The cost of catalyst consumed or replaced represents a significant catalytic incinerator operating cost item. Therefore, the amount of catalyst used and its expected life must be accurately determined in the initial design of a catalytic incinerator system. The amount of catalyst required usually depends upon the type and age of catalyst used, types and amounts ofVOCs encountered, the destruction efficiency required, and the amounts of potential reactants present that impairthe catalyst activity, which is usually highest when the catalyst is fresh. Because in most cases only limited information is available about the potential reactants and noncombustible particulate matterthat may be present in the waste gas, most catalytic incinerator systems are overdesigned to compensate for the unexpected. The amounts of catalyst required for the destruction of various types ofVOCs are usually established by laboratory tests by catalyst manufacturers. The amounts ofprecious metal catalysts commonly used are 1.5 and 2 ft3 per 1,000 scfm waste gas (equivalent to space velocities of 40,000 and 30,000 hr-1) for 90 and 95 percent VOC destruction efficiencies, respectively.(l) The corresponding amounts of base metal3-22
catalysts used are 4 to 6 ft3j1,000 scfm (i.e., space velocities of 15,000 to 10,000 hr-1).(2) Item 3. Determine the Pressure Drop Required Across the System. The total pressure drop required across an incinerator system determines the waste gas fan size and horsepower requirements, which, in turn, determine the fan capital cost and electricity consumption. The total pressure drop across an incinerator system depends on the number and types of equipment included in the system and on design considerations. The estimation of actual pressure drop requirements involves complex calculations based on the specific system's waste gas and flue gas conditions and equipment used. For the purposes of this section, however, the following approximate values can be used:**Pressu~e** drop**(~p,** in. H20) across Thermal incinerators 

### = 4 Catalytic incinerators 

### = 6 Heat exchangers: 35% 

### = 4 50% 

### = 8 70% 

### =15 Once the total pressure drop required is estimated (as a summation ofthe pressure drops across all pieces of equipment in the incinerator system), the blower electricity requirements can be estimated from the basic fan horsepower requirement equation. Forexample, at a combined fan-motor efficiency of62 percent, the fan horsepower equation dictates that 0.19 kWh of electricity per hour is required for moving 1,000 acfm of flow rate at a I-in. water pressure drop. Therefore. the fan power requirement is estimated by multiplying the total pressure drop (inches ofwater) by the total flue gas flow rate (thousand acfm) and the 0.19 kWhjhr factor. Forthe cases where an additional fan is3-24 carbon steel units at costs of60 to 70 percent of that for stainless steel units. Of course, the 1ife of such equipment will be lower-- approximately 10 years. Catalytic incinerators will tolerate lower grade material (e.g., carbon steel) better than thermal units because of their lower operating temperatures. However, catalyst bed enclosures are mostly fabricated of stainless steel. 3.3.1 Thermal IncineratorEquipment Costs Figure 3-3 presents thermal incinerator equipment costs (April 1986 dollars) as a function ofthe waste gas volume flow rate at standard conditions of70°F and 0 psig. This figure was developed from cost information received from three incinerator manufacturers for three volume flow rates each.(3,4,5) Analytical equations for these equipment cost curves are presented in Table 3-1. (The table also presents analytical equations for catalytic incinerators, the cost curves for which are discussed in Section 3.3.2.) The equipment costs listed represent all the equipment in an incinerator system including a combustion chamberwith burner, waste gas fan, inlet and outlet plenums, prepiping and prewiring, instrumentation and controls, a 10-ft stack, and in the case of heat recovery, a primary heat exchanger. The cost data apply to the cases ofdilute vac content waste gases (to which no outside air is added) containing up to 25 percent LEL vac and incinerated at a 150aoF combustion temperature. The Figure 3-3 (orTable 3-1) cost data can be applied to other cases ofwaste gas compositions including those requiring slightly different combustion temperatures without introducing significant errors to the costs. When these data are applied to different combustion temperatures,3-25



### lOa 50 20 5**50~iiiiiii** 3

# l'OOO~~



# - 500 \0 co en 

# - 400 

# - -sa. < 

### 300 0 Q 0• 

# - ...

• 

### 200
en Q

, , .j.,) )' c I;;i 0- 

## .... ., , , ; 

### 100 c- , I.! ';'i I t ,

### .. I.LJ



### Volume Flow Rate, 1,000 scfm

Figure 3-3. 

### Thermal incinerator equipment; 

### cost estimatesTABLE 3-1. EQUATIONS FOR INCINERATOR EQUIPMENT COSTSa (APRIL 1986 DOLLARS)**~-=-=--==............,..** = .....**~.=** -::z .z=.=.::zo=.=:**:C=Z:::=-':E-=-==~ ~-'--=--r**  ':=--='=-=:-:=:**·=_-=·=-=:a·~-_=-=_a:===-~~~=--.=·=..;:-~~..:--'_=.:~_==-~=~~-=-=:"==- -~=--==_=**  :;;.;:.,:**~;;:.:=** Extent of heat Equipment cost equation for Equipment cost equation for exchange thermal incineratorsb catalytic incinerators

None 1n Eq 

### = [14,402

- 992(lnQ)+ 70 (In Q)2] (10-3) In Eq 

### = [24,086

- 3,252(ln Q)+ 205 (lnQ)2](10-3 35% 1 n Eq 

### = [16,175

- 1,262(1nQ)+ 85 (1n Q)2] (10-3) 1n Eq 

### = [27,170

- 3,789(1n Q)+ 231 (1nQ)2](10-3 50% 1n Eq 

### = [15,784

- 1,165(1nQ)+ 81 (1n Q)2] (10-3) In Eq 

### = [26,497

- 3,650(1n Q)+ 225 (lnQ)2](10-3 70% 1n Eq 

### = [20,608

- 2,119(1nQ)+ 131 (1n Q)2](l0-3) In Eq 

### = [21,685

- 2,643(ln Q)+ 174 (lnQ)2](10-3

=,=,":z::

..**==-~~** ........... .=-_..:=:==: =-**~~='=~=~._::=C::.:-:_-:-~** - aThese equations should not be extrapolated outside the flowrate range of 5,000 to 50,000 scfm.

b Eq

- Equipment cost in April 1986 dollars, Q - Volume flow rate in scfm. W I N O'l3-27 it is assumed that the systemwill tolerate minor adjustments to the incinerator face velocity and residence time values resulting from these temperatures. Even ifthe system size were adjusted to compensate for these different temperatures,the resulting changes in the equipment cost would be minor. For example, if a combustion chamber
were sized for a combustion temperature of 1,700°F instead of 1,500°F the cost increase due to the increase in combustion chamber size would be less than 5 percent. The Figure 3-3 and Table 3-1 cost data can also be applied to
cases ofwaste gas compositions to which outside ambient air is added for combustion. In these cases, the flue gas flow rate at standard conditions must be substituted for the waste gas flow rate in the figure. 3.3.2 Catalytic Incinerator Equipment Costs Figure 3-4 presents catalytic incineratorequipment costs (April 1986 dollars) as a function ofthe waste gas volume flow rate at standard conditions (70°F and 0 psig), developed from cost information received from five equipment manufacturers.(6-10) Analytical equations representing these cost data are presented in Table 3-1. The equipment cost data represent all the equipment in an incinerator system, including the burner, fan, housing, skid mounting, instrumentation and controls,
a lO-ft stack, catalyst, and where heat recovery is used, a primary heat exchanger. The cost data apply to dilute vac waste gases requiring
a temperature of60aoF at the preheat chamber exit/catalytic bed inlet. The cost data can be applied to waste gases to which outside air is added by substituting the fiue flow rate at standard conditions for the waste gas flow rate in Figure 3-4.3-28



### 100 .,. 

### Exchange

50 20 ,,,' :' 

### 0 No HE"

I' , ' , '. 

### 0 35% 

### HE
,, " I I , II I I , I II I " I:, " .**50~** 

### HE I I , :,:"." 

### 0**70~** 

### HE

5 

### 5-. 100 LLJ 

## ....

3 700

500

# 11 400 

# - 

# - s. Q, 300 Q

0.



### Volume Flow Rate, 1,000 scfm



### . Figure 3-4. Catalytic incinerator equipment 

### cost estimates3-29 3.3.3 Total Capital Investment for Incinerators The total incinerator capital investment as a percentage of equipment cost varies with the type of installation. i.e., whether custom or package. The type of incinerator installation is an important consideration. Formost nonchemical industry operations, such as drying ovens, painting facilities, printing and coating operations and other processes where incinerators are commonly used forVOC control, waste gas flow rates generated are small. Modular incinerator units, prefabricated and preassembled, are most suitable for such flow rates. The size of skid-mounted modular units is limited to handling flows up to about 20,000 cfm,.mainly because of limitations to the sizes oftrucks carrying them and access doors at the plant sites. Of course, larger units, prefabricated and partially assembled, are possible for outdoor installations. Some incinerators handling up to 100,000 cfm, which are partly field-fabricated and field-assembled, can be found in chemical plant applications. Typically, heat exchangers can accommodate gas flows from 3,000 to 20,000 cfm. Forlarger flowrates, multiple heat exchangers units are usually installed in parallel in a single incinerator system. For incinerators, the total capital investment varies from a small percentage (about 110 percent) to more than 200 percent of the total equipment purchased cost. The custom installation charges of an incinerator system, including incinerator and heat exchanger units, ductwork, fans, and atall stack if required, may amount to 300 to 400 percent ofthe total equipment purchased cost, depending upon the installation. The skid-mounted units ready to be placed on a concrete pad at a prepared site incur the lowest installation expenses. Roof top installations will require higher costs, field-assembled units even higher,3-30
and field-fabricated and assembled units the highest costs. For estimating purposes, the total capital investment (TCI) of a skid-mounted modular unit can be calculated at.125 percent of the total purchased equipment cost. Conversely, Table 3-2 presents typical estimated capital cost factors applicable to custom installations of both thermal and catalytic incinerator systems. No cost factor is included for estimating ductwork cost in the table because the ductwork size and length and, consequently, its cost will vary with the installation and the waste gas flowrate. For both packaged and custom incinerator units, the ductwork capital cost must be estimated separately. Alternatively, in the case of custom units, the purchased cost of the ductwork and other auxiliary equipment can be added to the total incinerator equipment cost priorto applying the Table 3-2 factors for estimating the total capital investment. (Note: As Section 2 of the Manual indicates, the TCI also includes costs for land, working capital, and off-site facilities, which are not included in the direct/indirect installation factor. However, as these items are rarely required with incinerator systems, they will not be considered here. Further, no factor has been provided for site preparation (S.P.), or buildings (Bldg.) since these site-specific costs depend very little on the purchased equipment cost. Lastly, for the incinerator cases in which outside air is added for combustion ordilution, the cost ofthe fan used for this purpose also must be estimated separately.) 3.4 Estimating Total Annual Cost 3.4.1 Direct Annual Costs For incinerator systems with no heat exchanger, the cost of auxiliary fuel is the majordirect annual cost. Fuel costs are considerably3-31
TABLE 3-2. CAPITAL COST FACTORS FOR CUSTOM THERMAL AND CATALYTIC INCINERATORSa
Cost Item Cost Factor (Fraction of Indicated Cost)
DIRECT COSTS 1) Purchased eguipment cost Incinerator Auxi1iary equipmentb Instruments and controlSC Taxes Freight As required 

### L As required }1\ 0.1 A 0.03 A 0.05 A Total Purchased Equipment cost 2) Direct installation costs B(=1.18A)

Foundations and supports Erection and handlin9 Electrical Piping Insulation Painting Site preparation (S.P) Buildings (Bldg.) Total Installation Direct Costs Total Direct Cost 0.08 B 0.14 

### B 0.04 

### B 0.02 B 0.01 B 0.01 

### B As reguired 0.30 B +S.P. + Bldg. 1.30 B + S.P. + Bldg. INDIRECT COSTS

0.31 B 0.10 B 0.05 B 0.10 B 0.02 

### B 0.01 

### B 0.03 

### B Engineering and supervlslon Construction and field expenses Construction fee Start-up Perfonnance test Contingency Total Indirect Costs Total Direct and Indirect costs =Total Capital Investment ]1.61 B+ S.P. + Bldg.

## L I**~=-- -=o=o~**  __..".",=--

__**:...-.z=o=o~** ,""""",**===-==_==o=o~~.~** -= aReferenc"e 11. bIncludes ductwork and any other equipment normally not included with unit furnished

by incinerator vendor. cCost of instrumentation and controls often furnished by vendor.(3-12) 3-32
lower for catalytic incinerators than for thermal units because of the lower operating temperature. Besides the fuel, the utility requirements for an incinerator include electricity for the waste gas fan and, if used, the ambient air fan. Operating labor is usually small for both types of incinerators--0.5 hr/shift.(ll) Maintenance costs ofwell-designed and maintained thermal or catalytic incinerators of either type are low, with a substantial portion required for the heat exchanger maintenance. (Well-designed and fabricated heat exchangers, i.e., stainless heat exchangers, usually have lowermaintenance expenses.) The incinerator unit maintenance requirements may include repairs to the refractory lining and blowers, maintenance of control instruments, and cleaning of flame rods, if used. Maintenance labor may be estimated at 0.5 hr/shift. The maintenance materials may be assumed to equal the maintenance labor cost.(ll) Depending upon the incinerator and how it is operated, the life of a given load of catalyst may be 2 to 10 years. Aconservative estimate of catalyst replacement cost can be based on the lower life time--2 years. The initial costs of precious metal and base metal (manganese dioxide) catalysts are $3,000/ft3(1) and $600/ft3 (2), respectively. Item 2of Section 3.2.2 showed how to estimate the catalyst requirement (ft3). Finally, the catalyst replacement labor is minimal compared to the catalyst cost. Based on these values and the estimating procedure shown in Section 2, the catalyst replacement cost (CRCcat) would be: CRCcat 

### = Ccat x 1.08 xCRFcat3-33 TABLE 3-3. SUGGESTED FACTORS FOR ESTIMATING INCINERATOR ANNUAL COSTS
Item
Direct OperatingCosts Operating labora Supervisory 1abora Maintenance labor Maintenance materialsa Replacement parts Utilities: Fuel

£1ectricityb,c Suggested Factor

0.5 hr/shift 15% of operating labor 0.5 hr/shift 100% ofmaintenance labor Thermal incinerators: None Catalytic incinerators: (See eq. 3-12)
The amount of fuel required is calculated from Step 5 (Q3) ofSection 3.2. Use the following Pvalues in estimating electricity requirements: Thermal incinerators 

### = 4 in. water Catalytic incinerators 

### = 6in. water Heat exchange of 35% 50% 70% Ductwork and stack = 4 in. water 

## = 8 in. water

= 15 in. water



### = As required Indirect Operating Costs Overhead Administrative charges Property tax Insurance**Capit~** recovery coste 60% of sum of operating, supervisory, and maintenance labor and maintenance materials 2% XTCId 1%XTCId 1%XTCI CRFs X[TCI

-**1.0~** x C cat] aReference 11. b

Thetotal Pof an incinerator system is the sum ofbase (i.e., incinerator) P+ heat exchanger P. CAn equation to calculate electricity requirements (kWh per hour) is given

in Item 3 ofSection 3.2.2. dTCI 

## =Total capital investment. €!TheCRFs (system capital recovery factor) is afunction ofthe equipment life

(10years, typically) and the opportunity cost ofthe capital (i.e., interest rate). For instance, for a 10-year 1ife and a 10% interest rate, CRFs =0.1628.3-34
where: Ccat 

### =initial catalyst cost ($) 1.08 

### =factor accounting for taxes and freight CRFcat 

### =capital recovery factor for catalyst (e.g., for a 2-year life and a 10% interest rate, the factor would be 0.5762). 3.4.2 Indirect Annual Costs As Table 3-3 shows, the indirect (fixed) annual operating costs include capital recovery; overhead; and property taxes, insurance, and administrative charges. The last three costs can be estimated at 1 percent, 1 percent, and 2percent ofthe total capital investment, respectively. The system capital recovery cost is based on an estimated 10-year equipment life. (The incinerator system life varies from 5to 15 years depending on thematerial of construction used and thedurability ofthe design.) However, as Section 2indicates, the system capital recovery cost is the product of the system capital recovery factor (CRFs) and the total capital investment (TCI) less the purchased cost ofthe catalyst (IICcat x 1.0811 ), This offset is necessary to avoid double-counting. Finally, overhead may be estimated at 60% of the sum of operating, supervisory, and maintenance labor and maintenance materials. (See Section 2of theManual for adetailed discussion of the items comprising the total annual cost.)3-35 References for Section 3 1. Telephone conversation: Robert M. Yarrington (Engelhard Corporation, Union, NJ) with Vishnu S. Katari (Pacific Environmental Services, Inc., Durham, N C), J une 2, 1986• 2. Telephone conversation: Bob Campbell (Pillar Technologies, Inc., Hartland, WI) with Tom Rhoads (Pacific Environmental Services, Inc., Durham, NC), February 28, 1986. 3. Correspondence: Ralph N. Stettenbenz (C-E Air Preheater, Combustion Engineering, Inc., Wellsville, NY), to Vishnu S. Katari, April 3,1986. 4. Correspondence: Ronald J. Baschiere (Hirt Combustion Engineers, Montebello, CA) to Vishnu S. Katari, April 7,1986. 5. Correspondence: C.le Bumford (Peabody Engineering, Stamford, CT) to Michael K. Sink (Pacific Environmental Services, Inc., Durham, NC), March 24, 1986. 6. Correspondence: Robert M. Yarrington (Engelhard Corporation, Union, NJ) to Vishnu S. Katari, April 30, 1986. 7. Correspondence: Kent Lewis (C-E Air Preheater, Combustion Engineering, Inc., Wellsville, NY) and Vishnu S. Katari, June 16, 1986. 8. Correspondence: Robert Hablewitze (Pillar Technologies, Inc., Hartland, WI) to Vishnu S. Katari, March 3,1986. 9. Correspondence: Thomas Schmidt (Energy DevelopmentAssociates, Itascon, IL) to Michael K. Sink, March 7, 1986. 10. Correspondence: Richard J. Ihde (TEC Systems, DePere, WI) to Michael K. Sink, March 11, 1986. 11. Vatavuk, William M. and Neveril, Robert. IIEstimating Costs of AirPollution Control Systems, Part II: Factors for Estimating Capital and Operating Costs. 1I Chemical Engineering, November 3. 1980, pp. 157-162.

### APPENDIX 3A. LOWER AND UPPER EXPLOSIVE LIMITS FOR VOCs3A-2
TABLE 3A-1. FLAMMABILITY CHARACTERISTICS OF COMBUSTIBLE ORGANIC COMPOUNDS IN AIRa,b
Mol. LEL,c UEL,d

wt. %vol. %vol.
Methane 16.04 5.0 15.0 Ethane 30.07 3.0 12.4 Propane 44.09 2.1 9.5 n-Butane 58.12 1.8 8.4 n-Pentane 72.15 1.4 7.8 n-Hexane 86.17 1.2 7.4 n-Heptane 100.20 1.05 6.7 n-Octane 114.23 0.95 3.2 n-Nonane 128.25 0.85 2.9 n-Decane 142.28 0.75 5.6 n-Undecane 156.30 0.68 n-Dodecane 170.33 0.60 n-Tridecane 184.36 0.55 n-Tetradecane 108.38 0.50 n-Pentadecane 212.41 0.46 n-Hexadecane 226.44 0.43 Ethylene 28.05 2.7 36 Propylene 42.08 2.4 11 Butene-1 56.10 1.7 9.7 cis-Butene-2 56.10 1.8 9.7 Isobutylene 56.10 1.8 9.6 3-Methyl-Butene-1 70.13 1.5 9.1 Propadiene 40.06 2.6 1,3-Butadiene 54.09 2.0 12 Acetylene 2.5 100 Methylacetylene 1.7 Benzene 78.11 1.3 7.0 Toluene 92.13 1.2 7.1 Ethylbenzene 106.16 1.0 6.7 o-Xylene 106.16 1.1 6.4 m-Xylene 106.16 1.1 6.4 p-Xylene 106.16 1.1 6.6 Cumene 120.19 0.88 6.5 p-Cymene 134.21 0.85 6.5 Cyclopropane 42.08 2.4 10.4 Cyclobutane 56.10 1.8 Cyclopentane 70.13 1.5 Cyclohexane 84.16 1.3 7.8 Ethylcyclobutane 84.16 1.2 7.73A-3
TABLE 3A-l. FLAMMABILITY CHARACTERISTICS OF COMBUSTIBLE ORGANIC COMPOUNDS IN AIRa,b (concluded)**===-===:~.:a:===.:....::..:a** .:::z....:=**=~~==.:.~-::z:** Mol. LEL, UEL, wt. %vol. %vol. Cycloheptane 98.18 1.1 6.7 Methylcyclohexane 98.18 1.1 6.7 Ethylcyclopentane 98.18 1.1 6.7 Ethylcyclohexane 112.21 0.95 6.6 Methyl alcohol 32.04 6.7 36 Ethyl alcohol 46.07 3.3 19 n-Propyl alcohol 60.09 2.2 14 n-Butyl alcohol 74.12 1.7 12 n-Amyl alcohol 88.15 1.4 10 n-Hexyl alcohol 102.17 1.2 7.9 Dimethyl ether 46.07 3.4 27 Diethyl ether 74.12 1.9 36 Ethyl propyl ether 88.15 1.7 9 Diisopropyl ether 102.17 1.4 7.9 Acetaldehyde 44.05 4.0 36 Propionaldehyde 58.08 2.9 14 Acetone 58.08 2.6 13 Methyl ethyl ketone 72.10 1.9 10 Methyl propyl ketone 86.13 1.6 8.2 Diethyl ketone 86.13 1.6 Methyl butyl ketone 100.16 1.4 8.0**~-~~~~===** aReference 1. bMost common handbooks (e.g., Reference 2) provide

flammability information forVOCs. cLEL

- lower explosive limit dUEL

- upper explosive limit3A-4
TABLE 3A-2. CATALYTIC IGNITION TEMPERATURE FOR 90% CONVERSIONa Component Temperature, of Hydrogen Acetylene Carbon monoxide Propyne Propadiene Propylene Ethylene .Q.-Heptane Benzene Toluene Xylene Ethanol Methyl ethyl ketone Methyl isobutyl ketone Propane Ethyl acetate Dimethyl formamide Ethane Cyclopropane Methane aReference 3. 220 395 425 460 480 500 550 575 575 575 575 600 700 700 770 775 800 810 850 9203A-5 References for Appendix 3A 1. Hilado, Carlos J., IIHow to Predict if Materials Burn," Chemical Engineering, December 14, 1970, pp. 174-178. 2. Handbook

## QfChemistry and Physics, 54th Edition. Cleveland: The Chemical Rubber Co., 1973-1974, pp. D85-D92. 3. Organic Chemical Manufacturin Volume!: Combustion Control Devices, \EPA-450/3-80-026 • Research Triangle Park: U.S. Environmental Protection Agency, Emissions Standards and Engineering Division. December 1980. Report 3, p. 1-2.APPENDIX 3B This appendix presents equations to estimate flue gas and fuel requirements of incineration systems combusting all types ofwaste gas compositions. These equations have been derived from energy and material balances around the incinerator system. Figure 3B-1, a reproduction ofFigure 3-2, Section 3.2, is a schematic of an incinerator system. {All streams shown in Figure 3B-1 are also identified by the
same subscripts in the energy and material balances}

lIe.t lou

(1\) lIast. gas fr_ t'" proceu (0) 

## """u",.,OJ

lIast. Gil (I)
CoIIbustion

Afr' (4) ----.4

Auxnfary ---+f

Fu.l (3) CoIIbustfon Chuberb Flue Gn (5) (6) Heat Exch.nger (Optfonal) Flu. GiS to Vent/Stackl AIIbfent (7)

(.) IIhen required. (b) Referred to as Pr

.....t Chub.r hi the c.se ofc.t.lytfc fncfner.tors. (c) Included only fn c.talytic IncfnerAtors. Reproduced from best available copy. Figure 3B-1. Schematic diagram of an incinerator system. Energy Balance The basic energy balance equation around the combustion chamber is:

## sensib~e heat] rSensibl: heatl

_ [Heat released] [Heat released 

# J leavlng

- 

# Lenterlng 

# J - from the + from the combustion , combustion of of fuel VOCs FromFigure 3B-1, (HS +HL)

- (H2 +H3 +H4) 

## =Q1h l +Q3h 3 where: H

## =Sensible heat ofthe stream identified by the subscript, Btu/min Q

### =Flow rate ofthe stream identified by the subscript, scfm3B-2 hI 

### =Waste gas heat content released upon combustion, BTU/scf ofwaste gas h3 

### =Lower heating value (LHV) of fuel (BTU/scf) Assume

Therefore, H3 

### =

# °for fuel at ambient temperature H4 

## =

# °for ambient air HL 

### =10% ofH5 1.1 HS

- H2 

### =Q1 hI + Q3 h3 Substituting the sensible heat expression H

### =QCp**~T** in the above equation yields: (3B-1) where Q

### =Flow rate (scfm) C

p

### =Mean heat cap9city for the temperature interval of**~T,** BTU/ft3 of**~T** = Temperature interval fromTR (70°F) to Tidentified by the subscript hI 

### =Waste gas heat content (BTU/scf ofwaste gas) h3 

### =Lower heating value (LHV) of natural gas BTU/ft3 Material Balance (see Figure 3B-1) An (approximate) material balance around the combustion chamberyields:* (3B-2) where Q5 

### =Flue gas flow rate (scfm) Q2 

### =Waste gas flow rate entering the system (scfm) Q3 

### =Auxiliary fuel burned (scfm) Q4 

### =Ambient air used for combustion (scfm) The quantities ofQ2' Q3' and Q4 are estimated as follows: 1) Waste gas entering the combustion chamber (Q2)



### =QO For cases ofwaste gases to which no dilution air is added (i.e., Cases I, 2, and 4 through 6 in Table 3B-1)



## =QO (he/hd) For cases ofwaste gases to which dilution air is added (i.e., Case 3 in Table 3B-1) (3B-3) where he 

### =Waste gas heat content before dilution, BTU/scf hd 

### =Waste gas heat content afterdilution. *Strictly speaking, equation 3B-2 is amole balance, not amaterial balance.

However, because the moles (or volumesr-orthe reactants (Vac, fuel, air, etc.) entering the combustion chamber/catalyst bed approximately equal the moles ofproducts leaving (H20, C02, N2' etc.), equation 36-2 is accurate-- at least for purposes of this Manual.3B-3 2) Ambient air used (Q4) Q4 

### =0FordiluteVOC waste gases (category 1 in Table3B-1) Q4 

### =Q4,VOC +Q4,Fuel (3B-4) where Q4.VOC 

### =Ambient air used for the combustion ofthe VOC


### =Q2 [Lmi (X +Y/4

- Z/2)i

-

### rna ] 4.79 2 where mi = Volume content of ith VOC component in the waste gas X, Y, Z

### =Atoms ofC. H2, and 02 in the VOC 

### rna 

## =Volume content ofoxygen in the waste gas 2 Q4,Fuel 

### =Ambient air used for the combustion ofthe fuel 

### =9.58 (base amount of fuel burned)(l +E) where

where E

### =Excess air used, %oftotal stoichiometric air requirement for fuel 

### .Q!!.l.l

K

### =Excess amount used, %of base amount The value ofKcan be determined as follows: (Additional fuel used)



### = [9.58 (base amount of fuel) E+Additional fuel] CPS llTS

... h3* Therefore. Additional fuel used K

### =Base amount offuel



### =9.S8E/[(h3/CPS llT5)

- 1] (3B-5)



### =Constant for a given fuel and known values ofEand TS



### =

## afor dilute VOC waste gases. *In otherwords, the "additional fuel" must heat both the excess air used

in combustion ofthe base fuel and itself, from the ambient (reference) temperature to the combustion temperature (T5)'38-4
Estimation ofCombustion Flue Gases Generated Substituting the values of Q2, Q3, and Q4 into the basic material balance equation (Equation 38-2) yields the following expression: Qs 

## =Q2 +Q3 +Q2 [Imi (X + Y/4

- Z/2)i

-**m~** ] 4.79

+ 9.S8 (base amount of fuel)(l +E) (3B-6)

so that: Z/2)i

- ma ] 4.79 2 However, the base amount of fuel 

### =Q3/(1 +

### K), Qs 

### =Q2 +Q3 +Q2 [Imi (X + Y/4

-
+ 9.S8 Q3 (1 +

### E)/(l + K)



### =Q2 +Q3 (fordilute

### vac waste gases) (3B-7)

The above equation applies to thewaste gases to which ambient air is added for combustion purposes. However, in many cases, the waste gas contains air sufficient to provide partial or complete combustion air

(38-8) ] requirements. Table 38-1 identifies various waste gas types and their ambient air and auxiliary fuel requirements. Table 3B-2 presents the equations for estimating the flue gas (QS) flow rate from the combustion of each type ofwaste gas. Estimation ofActual Amount ofAuxiliary Fuel Burned (Q3) Substituting the material balance equation (Equation 3B-2) into the energy balance equation (Equation 38-1) and solving for Q3/Q2 (i.e., the amount of fuel required per unit ofwaste gas flow rate) yields the following expression:

Q

3 1.1 [1 + Q2 

### =

_1.1 CPS flTS

- CP2 flT2

- hI

- h3

- 1.1 CPS flTS (fordilutewaste gases) The values of all items in the above equation are specific to the waste gas composition and fuel type. Therefore, the equation can be further3B-5
TABLE 3B-l. CATEGORIZATION OF WASTE GAS STREAMS

Category

1

2

3

4

5

6 Waste gas Composition
Mixture ofVOC, air, and inert gas with >16% 02 and aVOC content <25% LEL (i.e., heat content <13 Btu/ft3) Mixture ofVOC, air, and inert gas with >16% 02 and aVOC content between 25 and 50% LEL (i.e., heat content between 13 to 26 Btu/ft3) Mixture ofVOC, air, and inert gas with <16% 02

Mixture ofVOC and inert gas with zero to negligible amount of02 (air) and <100 Btu/scf heat content**Mixtu~e** ofVOC and inert gas with zero to negligible amount of02 (air) and >100 Btu/scf heat Mixture ofVOC and inert gas with zero to negligible amount of02 and heat content insufficient to raise the waste gas to the combustion temperature Auxiliaries and other requirements Auxiliary fuel is required. No auxiliary air is required.
Dilution air is required to lowerthe heat content to <13 Btu/ft3• (Alternative to dilution air is installation ofLEL monitors.) Treat this waste stream the same as categories 1 and 2, except augment the portions of the waste gas used for fuel burning with outside air to bring its 02 content to above 16 percent. Oxidize it directly with a sufficient amount of air.
Premix and use it as a fuel.
Auxiliary fuel and combustion air for both the waste gas VOC and fuel are required.Waste gas category

1 2 3

4

5 6 3B-6
TABLE 3B-2. EQUATIONS FOR ESTIMATING FLUE GAS QUANTITIES
Equations for flue gas flow rate (Q5). scfm Q5 = Q2 +Q3. where Q2 = Qo Q5 =Q2 +Q3. where Q2 =QO (he/hd) Q5 

### =Q2 +Q3 +Q4.Fuel•where Q4,Fuel 

### =9.58 (l+E) (Base amount of fuel used)



## =9.58 Q3 (l+E)/(l+K) Q5 

### =Q2 +Q2 [Dni (X + Y /4

- Z/2)i

- 

### rna ] 4.79 (l+E) 2 Assumes no auxiliary fuel except for pilot is needed Premix and use it as afuel. Q5 

### =Q2 +Q3 +9.58 Q3 (l+E)/(l+K) +Q2 [Dni (X + Y /4

- Z/2)i

- mO ] 4.79 23B-7 simplified by substituting known values ofthese items. The values ofC p and Kare established based on the waste gas temperature, flue gas combustion temperature, and the type of fuel used. The overall C pvalue ofthe flue gas is calculated more accurately from the C pvalues of the flue gas components, which include C02, H20, 02, and N2. Alternatively, as an approximation, the C pvalue of air can be substituted for C pvalues of the flue gas and the waste gas. The mean heat capacity values for air are 0.0194,0.0196, and 0.0198 BTU/ft3°F for combustion temperatures of 1,600, 1,800, and 2,OOO°F, respectively. The mean heat capacity value of air, to use with awaste gas at 100°F, is 0.018 BTU/ft3°F. At a combustion temperature ofl,600°F, K

### =0.033 for aLHV of900 BTU/ft3 for natural gas, an excess air of 10 percent, and a reference temperature of70°F. When this value ofKand the values ofCps' and**~Ts'** are substituted into equation 3B-8, assuming the waste gas temperature to be 100°F, we obtain:

Table 3B-3 presents equations for estimating fuel requirements of all types ofwaste gases.3B-8
TABLE 3B-3. EQUATIONS FOR ESTIMATING FUEL REQUIREMENTS
Waste gas category**Gener~l e~uation**  for fuel, ft /ft ofwaste gas

1 1.1 C pSD.T5 - C P2D.T2 - h) h3

- 1.1 C P5D.T5 1.1 CPSD.t

## s- CP2D.Tr

- hI h3

- 1.1 CP5D. 5 3b,c 1.1 CPSD.TS- CPZD.TZ- hI (h3

- 1.1 CP5D.T5)

- 10.54 CP5 D.T5 (l+El/(l+K) 4 ld.CpsD.Ts + 1.1 [l:mj (X +Y/4

- Z/2)jJ 4.79 (HE) CPSD.Ts

- CP2t:.T2

- h) h3 5 6 Waste gas is premixed and used as fuel. Q3 = 1.1 [l + (l:mi (X +Y/4

- Z/2)i

-**mo~)** 4.79J CPjt:.T

### s- [CPZt:.T2+hIJ Q2 (h3 - 1.1 CP5t:.T5)

- 10.54 ( +E) CP5t:.T5 (l+K)
aThe waste gas for this category must be adjusted for dilution (See Table 38-2). bE

- Excess air used cK

- Constant

### =9.58E/[(h3/CP5t:.T5)

- 1J.-i Section 4 CARBON ADSORBERS WilliamM. Vatavuk Economic Analysis Branch. OAQPS William L. Klotz and Robert L. Stallings Research Triangle Institute (Research Triangle Park, NC 27709)
4.1 Process Description 4.1.1 Introduction In air pollution control, adsorption is employed to remove volatile organic compounds (VOC's) from low to medium concentration gas streams, when a stringent outlet concentration must be met and/or recovery of the VOC is desired. Adsorption itself is a phenomenon where gas molecules passing through a bed of solid particles are selectively held there by attractive forces which are weaker and less specific than those of chemical bonds. During adsorption, a gas molecule migrates to the surface of the solid where it is held by physical atttraction releasing energy-- the "heat of adsorption", which approximately equals the heat of condensation. Adsorptive capacity of the solid for the gas tends to increase with the gas phase concentration. Some gases form actual chemical bonds with the adsorbent surface groups. This phenomenon is termed "chemisorption". Most gases ("adsorbates") can be removed ("desorbed") from the adsorbent by heating to a sufficiently high temperature, usually via steam, or by reducing the pressure to a sufficiently low value (vacuum desorption). The physically adsorbed species in the smallest pores of the solid and the chemisorbed species may require rather high temperatures to be removed, and for all practical purposes cannot be desorbed during regeneration. For example, approximately 3 to 5 percent of organics adsorbed on virgin activated carbon is either chemisorbed or very4-2 strongly physically adsorbed and, for all intents, cannot be desorbed during regeneration.(1) Adsorbents in large scale use include activated carbon, silica gel, activated alumina, synthetic zeolites, fuller's earth, and other clays. This Section is oriented toward the use of activated carbon, a commonly used adsorbent for vacs. 4.1.2 Types ofAdsorbers Five types of adsorption equipment are used in collecting gases: (1) fixed regenerable beds; (2) disposable/rechargable cannisters; (3) traveling bed adsorbers; (4) fluid bed adsorbers; and (5) chromatographic baghouses.(2) Ofthese, the most commonly used in air pollution control are the fixed bed and cannister types. 4.1.2.1 Fixed-bed Units Fixed-bed units are normally used for controlling continuous, VOCcontaining streams over a wide range of flowrates, ranging from several thousand to several hundred thousand cubic feet/minute (cfm). The VOC concentration of streams treated by fixed-bed adsorbers can be as low as several parts per billion (ppbv) by volume in the case of some toxic chemicals or as high as 25% ofthe VOCs' lower explosive limit (LEL). For most VOCs, this ranges from 25UO to 1U,UOU ppmv.(3) Fixed-bed adsorbers may be operated in either intermittent or continuous modes. In intermittent operation, the adsorber removes vac for a specified time (the "adsorption time"), which corresponds to the time during which the controlled source is emitting VOC. After the adsorber and the source are shut down (e.g., overnight), the unit begins the desorption cycle during which the captured VOC is removed from the carbon. This cycle, in turn, consists of three4-3 steps: (1) regeneration of the carbon by blowing steam through the bed in the direction opposite to the gas flow; (2) drying ofthe bed, with compressed air or a fan; and (3) cooling the bed to its operating temperature via a fan. (In some designs, the same fan can be used both for bed drying and cooling.) At the end of the desorption cycle (which usually lasts 1 to 1 1/2 hours), the unit sits idle until the source starts up again. In continuous operation a regenerated carbon bed is always available for adsorption, so that the controlled source can operate continuously without shut down. For example, two carbon beds can be provided: while

one is adsorbing, the second is desorbing/idled. As each bed must be large enough to handle the entire gas flowrate while adsorbing, twice as much carbon must be provided than an intermittent system handling the
same flowrate. Ifthe desorption cycle is significantly shorter than the adsorption cycle, it may be more economical to have three, four, or even
more beds operating in the system. This can reduce the amount of extra carbon capacity needed or provide some additional benefits, relative to maintaining a low vae content in the effluent. (See Section 4.2 for a more thorough discussion of this.) Atypical two-bed, continuously operated adsorber system is shown in Figure 4-1. One bed is adsorbing at all times, while the second is desorbing/idled. As shown here, the VaC-laden gas enters vessel #1 through valve A, passes through the carbon bed (shown by the shading) and exits through valve B, from whence it passes to the stack. Meanwhile, vessel #2 is in the desorption cycle. Steam enters through valve C, passes up through the bed and exits through D. The steam-VQe vaporI



### Decanter Out In



# ,

Coo11ng

Water
Total Condenser

'Water (To Treatmentl Sewer) VOC Condensate 

# I (To Storage, • Processing)SteamVOC Vapor I



### Outlet

Gas D



### , ..' • (To Stack) Vessel 11 (Drying/Cooling Air)

Steam Waste Gas (From Source)
SystemFan (Dryingl CoolingAir)**~~I** '



### Figure 4-1. Typical Two-Bed, ContinuouslyOperated Fixed-Bed CarbonAdsorber**Syst~**4-5
mixture passes to a condenser, where cooling water condenses the entire mixture. The condensate next passes to a decanter, where the VOC and water layers are separated. The VOC layer is conveyed to storage. If impure, it may receive additional processing, such as distillation. Depending on its quality (i.e., quantity of dissolved organics), the water layer is discharged either to a wastewater treatment facility or to the sewer. Once steaming is completed, valves Cand Dare closed and valve Eis opened, to**allo~** air to enter to dry and cool the bed. After this is done, the bed is placed on standby until vessel #1 reaches the end of its adsorption cycle. At this time, the VQC-laden gas is valved to vessel #2, while vessel #1 begins its desorption cycle, and the above process is repeated. In Figure 4-1, the system fan is shown installed ahead of the vessels, though it could also be placed after them. Further, this figure does not showthe pumps needed to bring cooling water to the condenser. Nor does it depict the solvent pump which conveys the VOC condensate to storage. Also missing are preconditioning equipment used to cool, dehumidify, or
remove particulate from the inlet gases. Such equipment mayor may not be needed, depending on the condition ofthe inlet gas. In any case, preconditioning equipment will not be covered in this Section. 4.1.2.2 Cannister Units Cannister-type adsorbers differ from fixed-bed units, in that they are normally limited to controlling low-volume, (typically 100 ft3/min, maximum) intermittent gas streams, such as those emitted by storage tank vents, where process economics dictate that toll regeneration or throw-away cannisters4-6

are appropriate. The carbon cannisters may not be desorbed. Alternatively, the carbon may be regenerated at a central facility. Once the carbon reaches a certain VOC content, the unit is shut down, replaced with another, and disposed ofor regenerated by the central facility. Each cannister unit consists of a vessel, activated carbon, inlet connection and distributer leading to the carbon bed, and an outlet connection for the purified gas stream.(4) In one design (Calgon1s Ventsorb®), 150 lbs of carbon are installed on an 8-inch gravel bed, in a 55-gallon drum. The type of carbon used depends on the nature ofthe VOC to be treated. In theory, a cannister unit would remain in service no longer than a regenerable unit would stay in its adsorption cycle. Doing so would prevent the allowable outlet concentration from being exceeded. In reality, however, poor operating practice may result in the cannister remaining connected until the carbon is near saturation. This is because: (1) the carbon (and often the vessel) will probably be disposed of, so there is the temptation to operate it until the carbon is saturated; and (2) unlike fixed-bed units, whose outlet VOC concentrations are monitored continuously (via flame ionization detectors, typically), cannisters are usually not monitored. Thus, the user can only guess at the outlet loadiny,and could tend to leave a unit in place longer. 4.1.3 Adsorption Theory At equilibrium, the quantity ofgas that is adsorbed on activated carbon is afunction ofthe adsorption temperature and pressure, the chemical species being adsorbed, and the carbon characteristics, such as carbon particle size and pore structure. For a given adsorbent-VOC combination at a given temperature, an adsorption isotherm can be constructed4-7
which relates the mass of adsorbate per unit weight of adsorbent ("equilibrium adsorptivity") to the partial pressure ofthe VOG in the gas stream. The adsorptivity increases with increasing VaG partial pressure and decreases with increasing temperature. Afamily of adsorption isotherms having the shape typical of adsorption
on activated carbon is plotted in Figure 4-2. This and other isotherms whose shapes are convex upward throughout, are designated "Type I" isotherms. The Freundlich isotherm can be fit to aType I curve; and it is commonly used in industrial design.(2)

where: p 

### =



## =

= (4-1) equilibrium adsorptivity (lb adsorbate/lb adsorbent) partial pressure of VaG in gas stream (psia) k,m 

## = empirical parameters The treatment of adsorption from gas mixtures is complex and beyond the scope of this Section. Except where the VaG in these mixtures have nearly identical adsorption isotherms, one VaG in amixture will tend displace another on the carbon surface. Ge.nerally, VOGs with lower vapor pressures will displace those with higher vapor pressures, resulting in the former displacing the latter previously adsorbed. Thus, during the
course ofthe adsorption cycle the carbon's capacity for ahigher vapor pressure constituent decreases. This phenomonen should be considered when sizing the adsorber. To be conservative, one would normally base the adsorption cycle requirements on the least adsorbable component in a mixture and the desorption cycle on the most adsorbable component.(1) The equilibrium adsorptivity is the maximum amount of adsorbate the carbon can hold at a given temperature and VaG partial pressure. In

## .... >


## .... +d c:L, '-, o lit 

### §



## .... '- .,g



## .... 

# -
.... =' a'



### Adsorbate Partial Pressure (psia)



### Figure 4-2. Freundlich (Type I) Adsorption Isotherms For Hypothetical Adsorbate4-9
actual control systems, however, the carbon bed is never allowed to reach equilibrium. Instead, once the outlet concentration reaches apreset 1imit (the IIbreakthrough concentration ll ), the adsorber is shut down for desorption or (in the case of cannister units) replacement and disposal. At the point where the vessel is shut down, the bed vac concentration may only be 50% or less ofthe equilibrium concentration. As equation 4-1 indicates, the Freundlich isotherm is apower function that plots as a straight line on log-log paper. Conveniently, for the concentrations/partial pressures normally encountered in carbon adsorber operation, most vac - activated carbon adsorption conforms to equation 4-1. At very low concentrations, typical ofbreakthrough concentrations,
alinear approximation to the Freundlich isotherm is adequate. However, the Freundlich isotherm does not accurately represent the isotherm at high gas concentrations and thus should be used with care as such concentrations are approached. Adsorptivity data for several vacs were obtained from an activated carbon vendor and fitted to the Freundlich equation.(S) These VOCs are listed in Table 4-1. The adsorbates listed include aromatics (e.g., benzene, toluene), chlorinated aliphatics (dichloroethane), and one ketone (acetone). However, the list is far from all-inclusive. Additional isotherm data are available from the activated carbon vendors, handbooks (such as Perry's Chemical Engineer's Handbook), and the literature. Notice that arange ofpartial pressures is listed with each set of parameters, IIkll and IIm ll. (Note: In one case (m-xylene) the isotherm was
so curvilinear that it had to be split into two parts, each with adifferent set ofparameters.) This is the range to which the parameters apply.4-10
Table 4-1 Parameters for Selected Adsorption Isothermsa,b

Isotherm Range of Adsorption Parameters isothermc Adsorbate Temp. (OF) k m (psia) (1) Benzene 77 0.597 0.176 0.0001-0.05 (2) Ch1orobenzene 77 1.05 0.188 0.0001-0.01 (3) Cyc1ohexane 100 0.508 0.210 0.0001-0.05 (4) Dich1oroethane 77 0.976 0.281 0.0001-0.04 (5) Phenol 104 0.855 0.153 0.0001-0.03 (6) Trichloroethane 77 1.U6 0.161 0.0001-0.04 (7) Vinyl Chloride IOU 2.00 0.477**U.0001-0.0~** (8) m-Xy1ene 77 0.708 0.113 0.0001-0.Ll01 77 0.527 0.0703 O.LlOl -0.05 (9) Acry1onitrile 100 0.935 0.424 0.0001-0.015 (10) Acetone 100 0.412 0.389 0.0001-0.05 (11) Toluene 77 0.551 0.110 0.0001-0.05

a Reference 5. b Each isotherm is ofthe form: w

## =kpm. (Set text for definition of terms) Data are for adsorption on Ca1gon type IIBPLII carbon (4 x 10 mesh).
c Equations should not be extrapolated outside these ranges.4-11 Extrapolation beyond this range--especially at the high end--can introduce inaccuracyto the calculated adsorptivity. But high-end extrapolation may not be necessary, as the following will show. In most air pollution control applications, the system pressure is approximately one atmosphere (14.696 psia). The upper end of the partial pressure ranges in Table 4-1 goes from 0.04 to 0.05 psia. According to Oalton1s Law, at atotal system pressure ofone atmosphere this corresponds to an adsorbate concentration in the waste gas of 2,720 to 3,400 ppmv. However, as discussed in Section 4.1.2, the adsorbate concentration is usually kept at 25% ofthe lower explosive limit (LEL). For many VOCs, the LEL ranges from 1to 1.5 volume %, so that 25% ofthe LEL would be 0.25 to 0.375% or 2,500 to 3,750 ppmv, which approximates the high end ofthe partial pressure**range~** in Table 4-1. Finally, each set of parameters applies to afixed adsorption temperature, ranging from 77° to 104° F. These temperatures reflect typical operating conditions, although adsorption can take place as low
as 32°F and even higher than 104°F. As the adsorption temperature increases to much higher levels, however, the equilibrium adsorptivity decreases to such an extent that VOC recovery by carbon adsorption may become economically impractica1• 4.2 Design Procedure 4.2.1 Sizing Parameters Data received from adsorber vendors indicate that the size and purchase cost of afixed-bed or cannister carbon adsorber system primarily depend on four parameters:4-12
(1) The volumetric flowrate of the

## vae laden gas passing**throu~h** the carbon bed(s); (2) The inlet and outlet

## voe mass loadings ofthe gas stream; (3) The adsorption time (i.e., the time a carbon bed remains on-line to adsorb

## voe before being taken off-line for desorption of the bed); (4) The working capacity ofthe activated carbon. In addition, the cost could also be affected by other stream conditions, such as the presence/absence of excessive amounts of**particula~e,** moisture,
or other substances which would require the use ofextensive pretreatment and/or corrosive-resistant construction materials. The purchased cost depends to a large extent on the volumetric flowrate (usually measured in actual ft3/min). The flowrate, in turn, determines the size ofthe vessels housing the carbon, the capacities of ttle fan and motor needed to convey the waste gas through the system, and the diameter ofthe internal ducting. Also important are the

## vue inlet and outlet gas stream loadings, the adsorption time, and the working capacity ofthe carbon. These variables determine the amount and cost of carbon charged to the system initially and, in turn, the cost ofreplacing that carbon after it is exhausted (typically, five years after startup). Moreover, the amount of the carbon charge affects the size and cost ofthe auxiliary equipment (condenser, decanter, bed drying/cooling fan), because the sizes ofthese items are tied to the amount of

## voe removed by the bed. The amount of carbon also has abearing on the size and cost ofthe vessels. To illustrate this effect, for each of arange of flowrates, the

## vae inlet concentration was increased ten-fold from 500 to 5000 ppm, while4-13 the respective flowrates and adsorption times were held constant. The resultiny purchased costs obtained from a vendor increased by an averaye of 27%.(6) Part of these increases was needed to pay for the additional carbon required. However, some was also needed for enlarging the adsorber vessels to accomodate the added carbon and for the additional structural steel needed to support the larger vessels. Also, larger condensers, decanters, cooling water pumps, etc., were necessary to treat the more concentrated

## voe streams. (See Section 4.3.) The

## vae inlet loading is set by the source parameters, while the outlet loading is set by the

## voe emission limit. (For example, in many states, the average

## vae outlet concentration from adsorbers may not exceed 25 ppm.) 4.2.2 Determining Adsorption and Desorption Times The relative times for adsorption and desorption and the adsorber bed configuration (i.e., whether single or multiple and series or parallel adsorption beds are used) establish the adsorption/desorption cycle profile. The cycle profile is important in determining carbon and vessel requirements and in establishing desorption auxiliary equipment and utility requirements. An example will illustrate. In the simplest case, an adsorber would be controlling aprocess which emits arelatively small amount of

## voe intermittently--say, during one 8-hour shift per day. During the remaining 16 hours the system would either be desorbing or on stand-by. Such a system would only require a single bed, which would contain enough carbon to treat eight hours worth of gas flow at the specified inlet concentration, temperature, and pressure. Multiple beds, operating in parallel, would be needed to treat large gas flows (>100,00U std. ft3/min, generally)(6), as there are practical limits to the sizes4-14 to which adsorber vessels can be built. But, regardless of whether a single bed or multiple beds were used, the system would only be on-line for part ofthe day. However, ifthe process were operating continuously, extra carbon capacity would have to be built into the system. The amount of this extra capacity would depend on the number of carbon beds that would be adsorbing at anyone time, the length ofthe adsorption period relative to the desorption period, and whether the beds were operating in parallel
or in series. Ifone bed were adsorbing, a second would be needed to
come on-line when the first was shut down for desorption. In this case, 100% extra capacity would be needed. Similarly, if five beds in parallel
were adsorbing at any given time, again only one extra bed would be needed and the extra capacity would be 20% (i.e.,**1/~)--provided,** of course, that the adsorption time were at least five times as long as the desorption time. The relationship between adsorption time, regeneration time, and the required extra capacity can be generalized. 

### M

c

## =McI x f (4-2) where: M c' McI 

## =amounts of carbon required for continuous or intermittent control of a given source, respectively (lbs) f

## =extra capacity factor (dimensionless) The factor, f, is related to the number ofbeds adsorbing 

### (NA) and desorbing (NO) in a continuous system as follows: NO f= 

### 1 + 

### INA (4-3) (Note: 

### NA is also the number ofbeds in an intermittent system that would be adsorbing at any given time. The total number ofbeds in the system would be 

### NA +NO.)4-15 It can be shown that the number ofdesorbing beds required in a continuous system (NO) is related to the desorption time (00), adsorption time (OA), and; the number of adsorbing beds, as follows: (4-4) (Note: 00 is the total time needed for bed regeneration, drying, and cooling.) For instance, for an eight-hour adsorption time, in a continuously operated system of seven beds (six adsorbing, one desorbing) 0 0 would have to be 1 1/3 hrs or 1ess (8 hrs/6 beds). Otherwise, additiona1 beds wou1d have to be added to provide sufficient extra capacity. during desorption. 4.2.3 Estimating Carbon Requirement 4.2.3.1 Carbon Estimation Procedures Developed Obtaining the carbon requirement (Mc orM c ) is not as straightforward as

I determining the other adsorber design parameters. When estimating the carbon charge, the depth of the approach used depends on the data and calculational tools available. In preparing this Section of the Manual, we have developed
two procedures for estimating the carbon requirement. The first procedure, described in more detai1 below, is based to a 1arge extent on ru1es-of-thumb. This procedure, sometimes employed by adsorber vendors, is relatively simple and easy to use, though it normally yields results incorporating a 1arge safety margin. The second procedureyields a more accurate estimate of the carbon requirement but requires additional input data. In addition, the procedure is of such mathematical complexity that a microcomputer is needed to use it. This procedure is centered on the IIBED-.?IZEII model, developed by William LKlotz of Research Triangle Institute. The program 1I •••uses a detailed mathematical description of the adsorption process to predict the bed size needed to maintain the effluent [outlet] concentration below a4-16
defined allowable maximumwhen the inlet concentration is constant over the time period for operation.II{7} Inputs needed to run the program include the inlet and desired outlet (llbreakthroughll) vac concentrations, gas streamtemperature, and the IIbreakthrough time,1I which is usually equal to the adsorption time. Other inputs needed are the carbon particle size and bed void fraction and the gas superficial velocity through the bed. (Superficial velocity is discussed in Section 4.3.1.) As outputs, the program provides the carbon equilibrium capacity, working capacity (see below), the requiTed bed size (as measured by the bed depth) and pressure drop, and the bed efficiency--lIthe percent removal of all adsorbate entering the bed up to the breakthrough time. 1I This efficiency is calculated by integrating the ratio ofvac removed to the vac inlet rate over the entire adsorption cycle. (See Section 4.4.3. for more on this.) These BED_SIZE outputs, along with the bed superficial velocity and other parameters, are input to a second model (IICARADSII), developed by the Economic Analysis Branch. This model is'used to determine the carbon requirement, size the adsorber vessels. and estimate the system capital and annual costs in amanner similarto the rule-of-thumb procedure detailed in the next sections. However, where the rule-of-thumb procedure may be done by hand, amicrocomputer is needed to utilize the CARADS model. 4.2.3.2. Carbon Estimation Procedure Used in Manual The rule-of-thumb carbon esimation procedure is based on the IIworking capacityll (wc, lb VaC/lb carbon). This is the difference per unit mass of carbon between the amount ofvac on the carbon at the end of the4-17 adsorption cycle and the amount remaining on the carbon at the end of the desorption cycle. It should not be confused with the lIequilibrium capacityll (we) defined above in Section 4.1.3. Recall that the equilibrium capacity
measures the capacity of virgin activated carbon when the VaG has been in contact with it (at a constant temperature and partial pressure) long enough to reach equilibrium. In adsorber design, it would not be feasible to allow the bed to reach equilibrium. If it were, the outlet concentration would rapidly increase beyond the allowable outlet (or IIbreakthrough ll ) concentration until the outlet concentration reached the inlet concentration. During this period the adsorber would be violating the emission limit. The working capacity is some fraction ofthe equilibrium capacity. Table 4-2**com~iles** working capacities for selected VOGs. These data were obtained from an adsorber manufacturer.(8)

.For comparison, Table 4-2 also shows the equilibrium capacities for some ofthese VOGs, which were computed from the parameters given above in Table 4-1 in Section 4.1. Note that the working capacities range from 24 to 100% ofthe respective capacities at equilibrium, with an average value of 48%. This average approximates the rule-of-thumb used by adsorber vendors--that is, working capacity equals 5a% of equilibrium capacity. Further, like the equilibrium adsorptivity, the working capacity depends upon the temperature, the VaG partial pressure, and the vac composition. The working capacity also depends on the flow rate and the carbon bed parameters. The working capacity, along with the adsorption time and VOC inlet loading, is used to compute the carbon requirement for a cannister adsorber
or for an intermittently operated fixed-bed adsorber as follows:4-18
Table 4-2. Equilibrium vs. Working Carbon Capacity for Selected VOCs(8)
Adsorption Partial Carbon CapacitiesC Compound Temp. (OF)a Press. (psia)b Equilibrium(We) Working(Wc) wc/we Ratio (1) Acetone 100 0.0147 0.0798 0.08 1.0 (2) Benzene 77 0.000147 0.126 0.06 0.48 (3) Cyclohexane 100 0.00441 0.163 0.06 0.37 (4) Toluene 77 0.00294 0.290 U.U7 0.24 (5) m-Xylened 77 0.00147 0.333 0.10 0.3U Averaye 0.48
aTemperature at which equilibrium capacity was measured. bOirectly proportional to the VOC concentration in the influent (ppmv). Calculated as follows: Partial pressure 

## =Cone. (ppmv) x 14.696 psia x 10-6

cMeasured as lb of VOC/lb. of carbon. Equilibrium capacities were calculated using parameters in Table 4-1; working capacities were obtained from Reference 8. dActually, the compound listed in Reference 8was "xylene." The precise structure

-- i.e., ortho, meta, or para -- was not given. However, as the molecular weight of all three is the same, we have assumed that the working capacity data would apply to m-xylene, as well as to the other two isomers.4-19 (4-5)
where: mVOC 

### =vac inlet loading (lb/hr) Combining this with equations (4-2) and (4-3) yields the general equation for estimating the systemtotal carbon charge: M

c

## =mVOC 0A(1 + NO/NA ) Wc 

### (4-6)
Values for W cmay be obtained from Table 4-2 or similar data sources. If
no value for Wc is available for the VOC (or VOC mixture) in question, the working capacity may be estimated at 5U% ofthe equilibrium capacity, as follows: (4-7) where: we(max) 

### =the equnibrium capacity (lb VOC/lb carbon) taken at the adsorber inlet (i.e., the point ofmaximum 

### voe concentration). (Note: To be conservative, this 50% figure should be lowered if short desorption cycles, very high vapor pressure consituents, or difficultto-desorb VOCs are involved.)



### * * * Example: Asource emitting 100 1b/hr toluene is to be collected in a carbon adsorberc The system operates continuously, with two beds adsorbing at all times. For convenience, adsorption and desorption times of 12 and 1.5 hours, respectively, have been chosen. The total gas flowrate is 35,000 ft3/min at 77°F and 1 atmosphere (or approximately 200 ppmv of VUC). Assume negligible quantities of particulate and moisture. Calculate the system carbon requirement. Solution: From Table 4-2, we find the working capacity oftoluene to be 0.07 lb/lb carbon. Since the regeneration time4-20 (1.5 hrs) is less than 1/2 the adsorption time (see eq. 4-4), one extra bed will be adequate. Substituting these values into equation 4-6 yields the carbon requirement: M

c

## =(100 lb VOC/hr)(12 hr) (1 + 1/2) 0.07 lb VOC/lb carbon



## =approximately 25,700 lbs.



### * * * As equation 4-6 shows, the carbon requirement is directly proportional to the adsorption time. This would tend to indicate that a system could be designed with a shorter adsorption time to minimize the carbon requirement (and purchased cost). There is atrade-off here not readily apparent from equation 4-6, however. Certainly, a shorter adsorption time would require less carbon. But, it would also mean that a carbon bed would have to be desorbed more frequently. This would mean that the regeneration steam would have to be supplied to the bed(s) more frequently to remove (in the long run) the same amount of VOC. Further, each time the bed is regenerated the steam supplied must heat the vessel and carbon, as well as drive off the adsorbed VOC. And the bed must be dried and cooled after each desorption, regardless ofthe amount of VOC removed. Thus, ifthe bed is regenerated too frequently, the bed drying/cooling fan must operate more often, increasing its power consumption. Also, more frequent regeneration tends to shorten the carbon life. As arule-of-thumb, the optimum regeneration frequency for fixed-bed adsorbers treating streams with moderate to high VUC inlet loadings is once every 8to 12 hours.(l) 4.3 Estimating Total Capital Investment An entirely different procedure should be used in estimating the4-21 purchased costs of fixed-bed and cannister-type adsorbers. Therefore, they will be discussed separately. 4.3.1 Fixed-Bed Systems As indicated in the previous section, the purchased cost is afunction ofthe volumetric flowrate, VOC inlet and outlet loadings, the adsorption time, and the working capacity ofthe activated carbon. As Figure 4-1 shows, the adsorber system is made up of several different items. Of these, the adsorber vessels and the carbon comprise nearly 3/4 of the purchased cost. There is also auxiliary equipment, such as fans, pumps, condensers, decanters, and internal piping. But because these usually comprise a small part ofthe total purchased cost, they may be "factored" from the costs ofthe two major items without introducing significant
error. The costs ofthese major items will be considered separately. 4.3.1.1 Carbon Cost This cost (Cc,$) is simply the product ofthe initial carbon requirement (Mc) and the current price of carbon. As adsorber vendors bUy carbon in very large quantities (million-pound lots or larger), their cost is somewhat lower than the list price. Current vendor costs typically range from $1.60 to $2.00/lb (spring 1986 dollars). Taking the midpoint ofthis range, we have: C

c

## =1.S0 M c (4-8) 4.3.1.2 Vessel Cost The cost of an adsorber vessel is primarily determined by its dimensions which, in turn, depend upon the amount of carbon it must hold and the superficial gas velocity through the bed that must be maintained for optimum adsorption. The desired superficial velocity is used to calculate4-22
the cross-sectional area ofthe bed perpendicular to the gas flow. An acceptable superficial velocity is established empirically, considering desired removal efficiency, the carbon particle size and bed porosity, and other factors. For example, one adsorber vendor recommends a superficial bed velocity of 85 ft/min(6), while an activated carbon manufacturer cautions against exceeding 60 ft/min in systems operating at one atmosphere.(5) Another vendor uses a 65 ft/min. superficial face velocity in sizing its adsorber vessels.(9) Lastly, there are practical limits to vessel dimensions which also influence their sizing. That is, due to shipping restrictions, vessel diameters rarely exceed 12 feet, while their length is generally limited to 50 feet.(9) The cost of a vessel is usually correlated with its weight. However,
as the weight is often difficult to obtain or calculate, the cost may be determined from the external surface area. This is true because the vessel material cost

-- and the cost of fabricating that material

-- is directly proportional to its surface area. The surface area (5, ft2) of a vessel is afunction of its length (L) and diameter 

### (D), which in turn, depend upon the superficial bed face velocity, the 

### L/D ratio, and other factors. Most commonly, adsorber vessels are cylindrical in shape and erected horizontally (as in Figure 4-1). In these cases, it can be shown that:

and:
where: I 

## o

## =**O.127~c** vb Q 

### L

## =**~(Q'/Vb)2** Me vb 

## =bed superficial velocity (ft/min)

I M

c 

## =carbon requirement vessel (lbs) 

### (4-9) (4-10)4-23 QI 

### =volumetric flowrate per adsorbing vessel (ft3/min) Equations (4-9) and (4-10) also assume that the carbon occupies 1/3 of the vessel volume(6,9) and that the carbon's bulk density is 30 lb/ft3• Finally, for a cylinder:
S 

### = 'If 

### D(L +

### D/2) (4-11)

(4-12) Similar equations can be developed for other vessel shapes, configurations, etc. Based on vendor data, we developed a correlation between adsorber vessel cost and surface area:(9) C

v

### =exp [18.827

- 3.3945 lnS +0.3090 (lnS)2] where: C v

### =vessel cost (spring 1986 $), F.U.B. vendor and: 228**~S~** 2,111 ft2 These units would be made of 304 stainless steel, which is the most
common material used in fabricating adsorber vessels.(6,9) However, to obtain the cost of a vessel fabricated of another material, multiply C vby an adjustment factor (Fm )• Afew ofthese factors are listed below:
Material Fro Factor Reference(s) Stainless steel, 316 1.3 6, 9, 10 Carpenter 20 CB-3 1.9 10 Monel-400 2.3 6, 10 Nickel-200 3.2 10 Titanium 4.5 10
4.3.1.3. Total Purchased Cost As stated earlier, the costs of such items as the fans, pumps, condenser, decanter, instrumentation, and internal piping can be factored from the sum of the costs for the carbon and vessels. Based on four data4-24 points derived from costs supplied by an equipment vendor (9), we found that, depending on the total gas flowrate 

### (Q), the cost ofthe carbon and vessels together comprised from 50% to 85% ofthe total adsorber equipment cost. These data points spanned agas flowrate range of 4,000 to 500,000 scfm. The average ofthese points was 72%, with a standard deviation of 16%. Taking the reciprocal ofthis average (i.e., 1/0.72

## =1.39), we can write: CA = 1.39[Cc +CvJ (4-13) where: Cc = cost of carbon C

v = cost of vessel(s) CA = cost of adsorber equipment 4.3.1.4. Total Capital Investment As discussed in Section 2, in the methodology used in this Manual, the total capital investment (TCl) is estimated from the total purchased cost via
an overall direct/indirect installation cost factor. Abreakdown ofthat factor for carbon adsorbers is shown in Table 4-3. As Section 2indicates, the TCl also includes costs for land, working capital, and off-site facilities, which are not included in the direct/indirect installation factor. However,
as these items are rarely required with adsorber systems, they will not be considered here. Further, no factors have been provided for site preparation (S.P.) and buildings (l3ldg.), as these site-specific costs depend very little on the purchased equipment cost. Note that the installation factor is applied to the total purchased equipment cost, which includes the cost of the stack and external ductwork and such costs as freight and sales taxes (if applicable). ("External ductworkiti is that ducting needed to convey the exhaust gas from the source to the adsorber system, and then from the adsorber to the stack. Costs for ductwork4-25
Table 4-3. Direct and Indirect Installation Factors for Carbon Adsorbersa
Cost Item
DIRECT COSTS

1) Purchased equipment cost Adsorber Auxi1i ary equipmentb Instruments and controlsc Taxes F

reight Cost Factor (Fraction ofIndicated Cost)

As required) As requiredTA 0.1 A 0.03 A 0.05 A Total Purchased Equipment cost 2) Installation direct costs B(=1.18A)

Foundations and supports Erection and handling Electrical Piping Insulation Painting Site preparation (S.P.), Buildings (Bldg.) Total Installation Direct Costs Total Direct Cost INDIRECT COSTS Engineering and supervision Construction and field expenses Construct;on fee Start-up Performance test Contingency 0.08 

### B 0.14 

### B 0.04 

### B 0.02 B 0.01 B 0.01 B As required 0.30 B+ S.P. + Bldg. 1.30B + S.P. + Bldg.

0.10 B 0.05 B 0.10 

### B 0.02 B 0.01 B 0.03 B Total Indirect Cost Total Direct and Indirect Costs 

### =Total Capital Investment 0.31B [[.61B +S.P. +Bldg.l

aReference 11. b Includes external ductwork, stack, and any otherequipment normally not included with unit furnished by adsorber vendor.
CInstrumentation cost usually included in cost of vendor-supplied adsorber unit.4-26
and stacks are shown elsewhere in this Manual.) Normally, the adjustment would also cover the instrumentation cost, but this cost is usually included with the adsorber purchased cost. Finally, note that these factors reflect "average" installation conditions and could vary considerably, depending upon the installation circumstances. 4.3.2 Cannister Systems Once the carbon requirement is estimated using the above**~rocedure,** the number of cannisters is determined. This is done simply by dividing the total carbon requirement (Mc) by the amount of carbon contained by each cannister (typically, 150 lbs.). This quotient, rounded to the next highest digit, yields the required number of cannisters to control the vent in question. Costs for atypical cannister (Calgon's Ventsorb®) are listed in Table 4-4. These costs include the vessel, carbon, and connections, but do not include freight or installation charges. Note that the cost per unit decreases as the quantity purchased increases. Each cannister contains Calgon's "BPL" carbon (4 x 10 mesh), which is commonly used in industrial adsorption. However, to treat certain VOCs, more expensive speciality carbons (e.g., "FCA 4 x 10") are needed. These carbons can increase the equipment cost by 60% or more.(4) As fewer installation materials and labor are required to install a cannister unit than a fixed-bed system, the composite installation factor is consequently lower. The only costs required are those needed to place the cannisters at, and connect themto, the source. This involves a small amount of piping only; little or no electrical work, painting, foundations, or the like would be needed. Twenty percent ofthe sum of4-27
Table 4-4 Equipment Costs (Spring 1986 $) for aTypical CannisterAdsorbera Quantity
1-3 4-9 10-29 >30 Equipment Cost (each)b $687

659 622 579

aReference 4. bThese costs are F.O.B., Pittsburgh, PA. They do not include taxes and freight charges.4-28
the cannister(s) cost, freight charges, and applicable sales taxes would
cover this installation cost. 404. Estimating Total Annual Cost As Section 2ofthis Manual explains, the annual operating cost is comprised ofthree components: direct costs, indirect costs, and recovery credits. These will be considered separately. 4.4.1 Direct Annual Costs These include the following expenditures: steam, cooling water, electricity, carbon replacement, operating and supervisory labor, and maintenance labor and materials. Ofthese, only electricity and solid waste disposal would apply to the cannister-type adsorbers. 4.4.1.1 Steam: As explained in**Se~ion** 4.1, steam is used during the desorption cycle. The quantity of steam required will depend on the amount of carbon in the vessel, the vessel dimensions, the type and amount of vac adsorbed, and other variables. Experience has shown that the steam requirement ranges from approximately

### l to

## i lbs of steam/lb of adsorbed VQC.(6,9) Using the midpoint ofthis range, we can develop the following expression for the annual steam cost: C

s 

## =3.5axla-3mvac as ps (4-14) where: C s 

### =steam cost ($/yr)
as 

## =system operating hours (hr/yr)
mvac 

## =vac inlet loading (lbs/hr) ps 

## =steam price ($/thous. lbs) If steam price data are unavailable, one can estimate its cost at 120% ofthe fuel cost. For example, ifthe local price of natural gas4-29

were $5.00/mi11ion BTU, the estimated steam price would be $6.00/mi11ion BTU • $6.00/thousand 1bs. (The 20% factor covers the capital and annual costs of producing the steam.) 4.4.1.2 Cooling Water: Cooling water is consumed by the condenser in which the steam-VOC mixture leaving the desorbed carbon bed is totally condensed. Most of the condenser duty is comprised of the latent heat of vaporization**(~Hv)** of the steam and VOC. As the VOC**~Hv** are usually small compared to the steam**~Hv** (about 1000 BTU/1b), the VOC 6Hvmay be ignored. So Inay the sensible heat of cooling the water-VOC condensate from the condenser inlet temperature (about 212°F) to the outlet temperature. Therefore, the coo1in9 water requirement is essentially a function ofthe steam usage and the allowable temperature rise in the coolant, which is typically 30° to 40°F(6). Using the average temperature rise (35°F), we can write: C

cw

## =3.43Cs Pcw where: C cw 

### =cooling water cost ($/yr) Pcw 

### =cooling water price ($/thous. gal.) (4-15)

Ifthe cooling water price is unavailable, use $0.15 to $0.30/thousand gallons. 4.4.1.3 Electricity: In fixed-bed adsorbers, electricity is consumed by the system fan, bed drying/cooling fan, cooling water pump, and solvent pump(s). Both the system and bed fans must be sized to overcome the pressure drop through the carbon beds. But, while the system fan must continuously convey the(4-17) 4-30
total gas flow through the system, the bed cooling fan is only used during
a part ofthe desorption cycle (one-half hour or less). For both fans, the horsepower needed depends both on the gas f10wrate and the pressure drop through the carbon bed. The pressure drop through the bed (A Pb) depends on several variables, such as the adsorption temperature, bed velocity, bed characteristics (e.g., void fraction), and thickness. But, for agiven temperature and carbon, the pressure drop per unit thickness depends solely on the gas velocity. For instance, for Ca1gon 1s "PCB" carbon (4 x 10 mesh), the following relationship ho1ds:(5) -4 2 APb/tb=0.03679 vb + 1.107 x 10 vb (4-16) where: APb/tb =pressure drop through bed (inches of water/foot of carbon) vb =superficial bed velocity (ft/min) The bed thickness (tb,ft) is the quotient ofthe bed volume (Vb) and the bed cross-sectional area (Ab). For a 30 1b/ft3 carbon bed density, this becomes:

I tb 

### = = 0.0333Mc Ab 

### A b (For instance, for horizontally-erected cylindrical vessels,**Ab~LD.)** Once APb is known, the system fan horsepower requirement (hPsf) can be
ca1culated: hPsf =2.50 x 10-4 

### QAPs where: 

### Q=gas volumetric f10wrate through system (ft3/min) APS 

## =total system pressure drop =APb + 1 (4-18)

(The extra inch accounts for miscellaneous pressure losses through tne external ductwork and other parts ofthe system.(6))4-31
This equation incorporates a fan efficiency of 70% and a motor efficiency of 90%, or 63% overan. The horsepower requirement for the bed drying/cooling fan (hPcf) is computed similarly. While the bed fan pressure drop would still be**~Pb'** the gas flowrate and operating times would be different. (For example, to cool abed from the regeneration temperature to the adsorption temperature, would require from 3to 3.5 SCFM/lb of carbon, based on a 30-minute cooling/drying time.) The cooling water pump horsepower requirement (hpcwp) would be computed
as fonows: (4-19)
where: qcw 

### =cooling water flowrate (gal/min) H

### =required head (normally 100 feet of water)
s 

## =specific gravity of fluid relative to water at 60°F.

n

## =combined pump-motor efficiency Equation 4-18 may also be used to compute the solvent pump horsepower requirement. In the latter case, the flowrate (qs) would be different, of course, although the same head--100 ft. of water--could be used. The specific gravity would depend on the composition and temperature ofthe condensed solvent. For example, the specific gravity oftoluene at 100°F would be approximately 0.86 at 70° F. (However, the solvent pump horsepower is usually very small--usually <0.1 hpo--so its electricity consumption can usually be neglected.) Once the various horsepowers are calculated, the electricity usage (in kWh) is calculated, by multiplying each horsepower value by 0.746 (the factor for converting hp to kilowatts) and the number of hours each fan or4-32
pump operates annually. For the system fan and cooling water pump, the hours would be the annual operating hours for the system 

### (0S). But for the bed drying/cooling fan, the time (Sb) would be much shorter. This is dependent on the time the bed fan is run during a desorption cycle, the number ofdesorption cycles per year, the adsorption time (0A), and other factors. For instance, for athree-bed system, with
a 12-hour adsorption time and a U.5-hour bed cooling/drying time per desorption cycle, the bed fan would operate 8.33 hrs. for every IOU hrs ofon-stream (system) time. To obtain the annual electricity cost, simply multiply kWh by the electricity price (in $/kWh) that applies to the facility being controlled For cannister units, use equation 4-17 to calculate the fan horsepower requirement. However, instead of 6Pb, usethe following to compute the total cannister pressure drop (6PC, inches of water):(4) 6PC

### =0.0471Qc + 9.29 x 10-4Qc2 where: Q c 

### =flowrate through the cannister (ft3/min) 4.4.1.4. Carbon Replacement: (4-20)

As discussed above, the carbon has adifferent economic life than the rest ofthe adsorber system. Therefore, its replacement cost must be calculated separately. Employing the procedure detailed in Section 2,
we have: CRCc

## =CRFc (I.U8Cc +Cel) where: CRFc 

### =capital recovery factor for the carbon
1.08 

### =taxes and freight factor (4-21)

C

e, Ccl 

### =initial cost of carbon and carbon replacement labor cost, respectively ($/yr) (F.O.B. vendor)4-33
The replacement labor cost covers the labor cost for removing spent carbon from vessels and replacing it with virgin or regenerated carbon. The cost would vary with amount of carbon being replaced, the labor rates, and other factors. For example, to remove and replace a50,000

- pound charge would require about 16 person-days, which, at typical wage rates, is equivalent to approximately $0.05/lb replaced.(12) Atypical life for the carbon is five years. However, ifthe inlet contains VOCs that are very difficult to desorb, tend to polymerize, or react with other constituents, a shorter carbon lifetime--perhaps as low as two years--would be likely.(l) For a five-year life and 10% interest rate, CRFc


### =0.2638. 4.4.1.5 Solid Waste disposal: Disposal costs are rarely incurred with fixed-bed adsorbers, because the carbon is almost always regenerated in place, not discarded. In certain cases, the carbon in cannister units is also regenerated, either off-site
or at a central regeneration facility on-site. However, most cannister adsorbers are disposed of once they become saturated. The entire cannister--carbon. drum, connections, etc.--is shipped to a secure landfill. The cost of landfill disposal could vary considerably, depending on the number of cannisters disposed of, the location ofthe landfill, etc. Based on data obtained from two large landfills, for instance, the disposal cost would range from approximately $35 to $65 per cannister excluding transportation costs.(13.14) 4.4.1.6 Operating and Supervisory Labor: The operating labor for adsorbers is relatively low, as most systems
are automated and require little attention. One-half operatorhour per4-34
shift is typical.(ll) Add to this 15% to cover supervisory labor. as Section 2 suggests. The annual labor cost would then be the product of these labor requirements and their respective wage rates ($/hr) which. naturally. would vary according to the facility location, type of industry, etc. 4.4.1.7 Maintenance Labor and Materials: Use 0.5 hours/shift for maintenance labor (11) and the applicable maintenance wage rate. Ifthe latterdata are unavailable, estimate the maintenance wage rate at 110% of the operating labor rate. as Section 2 suggests. Finally, for maintenance materials. add an amount equal to the maintenance labor. also perSection 2. 4.4.2 Indirect Annual Costs These include such costs as capital recovery. property taxes•. insurance. overhead. and administrative costs (IiG&AIi). The capital recovery cost is based on the equipment lifetime and the annual interest rate employed. (See Section 2for athorough discussion ofthe capital recovery cost and the variables that determine it.) For adsorbers. the system lifetime is typically ten years. except for the carbon. which. as stated above. typically needs to be replaced after five years. Therefore. when figuring the system capital recovery cost. one should base it on the installed capital cost less the cost of replacing the carbon (i.e•• the carbon cost plus the cost of labor necessary to replact it). Substituting the initial carbon and replacement labor costs from equation 4-21. we obtain: CRCs 

### = [TCI

- (l.08Cc + Cel)] CRFs where: CRCs 

### =capital recovery cost for adsorber system ($/yr) TCI 

### =total capital investment ($) (4-22)Ccl 4-35
1.08 =taxes and freight factor



### =initial carbon cost (F.O.B. vendor) and carbon**re~acement** cost, respectively ($) CRFs = capital recovery factor for adsorber system (defined ; n Section 2). For aten-year life and a 10% annual interest rate, the CRFs would be 0.1628. As Section 2 suggests, the suggested factor to use for property taxes, insurance, and administrative charges is 4% ofthe TCL Finally, the overhead is calculated as 60% ofthe sum of operating, supervisory, and maintence labor, and maintenance materials.



### * * 

### * The above procedure applies to cannister units as well, except that, in most cases, the carbon is not replaced--the entire unit is. Cannisters

are generally used in specialized applications. The piping and ducting cost can usually be considered a capital investment with auseful life of ten years. However, whetherthe cannister itselfwould be treated as a capital or an operating expense would depend on the particular application and needs to be evaluated on a case-by-case basis. 4.4.3 Recovery Credits These**coul~** apply to the VOC which is adsorbed, then desorbed, condensed, and separated from the steam condensate. However, ifthe

### vac layer contained impurities orwere amixture of compoundS, it would require further treatment, such as distillation. Purification and separation costs are beyond the scope of this Section. Suffice it to say"that the costs ofthese operations could offset and, iflarge enough, obliterate any recovery credits. In any case, the following equation can be used to calculate these credits:4-36
where: pvac 

### =resale value of the captured vac ($/lb) RC = recovery credit ($/yr) E 

### =adsorbervac control efficiency By definition, the efficiency (E) is the difference between the inlet and outlet vac mass loadings, divided by the inlet loading. However, during

an adsorption cycle the outlet vac loading will increase from essentially

zero at the start of the cycle to the breakthrough concentration at the end of the cycle. Because the efficiency is a function of time, it should be calculated via integration over the length of the adsorption cycle. To do this would require knowledge of the temporal variation of the outlet loading during the adsorption cycle. Ifthis knowledge is not available to the Manual user, a conservative approximation ofthe efficiency may be made by setting the outlet loading equal to the breakthrough concentration. 4.4.4 Total Annual Cost Finally, as explained in Section 2, the total annual cost (TAC) is the sum of the direct and indirect annual costs, less any recovery credits,
or: TAC 

### =DC + IC

- RC (4-24)4-37

References for Section 4
1. Correspondence: Robert L. Stallings and William Klotz (Research Triangle Institute, Research Triangle Park, NC) to William M. Vatavuk (U.S. Environmental Protection Agency, Office of Air Quality Planning and Standards, Economic Analysis Branch, Research Triangle Park, NC), June 24, 1986. 2. Calvert, Seymour and Englund, Harold M. (eds.). Handbook of Air Pollution Control Technology. New York: John Wiley &Sons, 1984, pP: 135-192. 3. Handbook of Chemistry and Physics, 54th Edition. Cleveland: The Chemical Rubber Company, 1973-74, pp. 085-092.

. 4. IICalgon Ventsorb@ for Industrial Air Purificationll (Bulletin 23-56a). Pittsburgh: Calgon Corporation, 1986. 5. Adsorption Handbook. Pittsburgh: Calgon Corporation, 1980. 6. Correspondence: Richard Selznick (Baron Blakeslee, Inc., Westfield, NJ) to William M. Vatavuk, April 23, 1986. 7. Klotz, WilliamL., 1I0ocumentation for Program IBed Size'll. Research Triangle Institute (Research Triangle Park, NC), September 3, 1986. 8. Manzone, R.R. et al. IIprofitability of Recycling Solvents from Process Systems.II Pollution Engineering, October 1973. 9. Correspondence: James Jessup (M&W Industries, Inc., Rural Hall, NC) to William M. Vatavuk, May 16, 1986. 10. Matley, Jay (ed.). Modern Cost Engineering. New York: McGraw-Hill Publications Co., 1984, p. 142. 11. Vatavuk, WilliamM. and Neveril, Robert. IIEstimating Costs of Air Pollution Control Systems, Part II: Factors for Estimating Capital and Operating Costs. 1I Chemical Engineering, November 3, 1980, pp. 157- 162. 12. Telephone conversation: Robert L. Stallings (Research Triangle Institute, Research Triangle Park, NC) with William M. Vatavuk, September 11, 1986. 13. Correspondence: William Kitto (Chemwaste, Sulphur, LA) to William M. Vatavuk, July 25, 1986. 14. Correspondence: Jerry Locklear (GSX, Pinewood, SC) to William M. Vatavuk, July 25, 1986.5--/



### Section 5 FABRIC FILTERS James H. Turner Andrew S. Viner Research Triangle Institute (Research Triangle Park, N.C. 22709) John D. McKenna ETS, Inc. Roanoke, VA 24018-4394 Richard E. Jenkins WilliamM. Vatavuk Economic Analysis Branch, OAQPS
5.1 Process Description 5.1.1 Introduction Afabric filter unit consists ofone ormore isolated compartments containing rows of fabric filter bags or tubes. Particle-laden gas passes up (usually) along the surface ofthe bags then radially through the fabric. Particles are retained on the upstream face ofthe bags while the cleaned gas stream is vented to the atmosphere. The filter is operated cyclically alternating between relatively long periods offiltering and short periods of cleaning. During cleaning, dust that has accumulated on the bags is removed from the fabric surface and deposited in ahopper for subsequent disposal. This device will collect particle sizes ranging from submicron to several hundred microns in diameter at efficiencies generally in excess of99 or 99.9 percent. The dust cake collected on the fabric is primarily responsible for such high efficiency. Gas temperatures up to 500 of, 

### with surges to 550 of


### can be accommodated routinely. Most ofthe energy used to operate the system

### 5-2

appears as pressure drop across the bags and associated hardware and ducting. Typical values range from 5 to 20 in. ofwatergauge. Fabric filters are used where high-efficiency particle collection is required. Limitations are imposed by gas characteristics (temperature and corrosivity) and particle characteristics (primarily stickiness) that affect the fabric or its operation and that cannot be accommodated economically. Important process variables include particle characteristics, gas characteristics, and fabric properties. The most important design parameter is the air- orgas-to-cloth ratio (volumetric flow rate divided by fabric area, (ft3/min)/ft2), and the usual operating parameterofinterest is pressure drop across the filter system. The majordistinguishing operating feature offabric filters is the ability to renew the filtering surface periodically by cleaning. 5.1.2 Types of Fabric Filters Fabric filters can be categorized by several means, including type of cleaning (shaker, reverse-air, pulse-jet), direction ofgas flow (from inside the bag towards the outside or vice versa), location ofthe system fan (suction orpressure), or size (low, medium, or high gas flow quantity). Cleaning methods are discussed more fully in this section, and the other categories are described in Section 5.2. 5.1.2.1 Shaker Cleaning For any type ofcleaning, enough energy must be imparted to the fabric to
overcome the adhesion forces holding dust to the bag. In shakercleaning, used with inside to outside gas flow, this is accomplished by suspending the bag from amotor-driven hook or framework that oscillates. Motion may be imparted to the bag in several ways, but the general effect is to create a sine wave along the fabric. As the fabric moves outward, accumulated dust on5-3



### the surface moves with the fabric. When the fabric reaches the limit of its extension, the patches ofdust have enough inertia to tear away from the fabric and descend to the hopper. For small, single-compartment baghouses, a lever attached to the shaker mechanismmay be operated manually at appropriate intervals, typically at the end ofa shift. In multicompartment baghouses, atimer or apressure sensor responding to systempressure drop initiates bag shaking automatically. The compartments operate in sequence so that one compartment at atime is cleaned. Forward gas flow to the compartment is stopped, dust is allowed to settle, residual gas flow stops, and the shakermechanism is switched on for several seconds to aminute ormore. The settling and shaking periods may be repeated, then the compartment is brought back online for filtering. Many large-scale shaker systems employ a small amount ofreverse airduring the shaker cycle to assist cleaning by deflating the bags. Parameters that affect cleaning include the amplitude and frequency of the shaking motion and the tension ofthe mounted bag. The first two parameters are part ofthe baghouse design and generally are not changed easily. Typical values are about 4Hz for frequency and 2to 3 in. for amplitude (half-stroke).(1) The tension is set to about 2lb/in. ofbag circumference when bags are installed. Some installations allow easy adjustment ofbag tension, while others require that the bag be loosened and reclamped to its attaching thimble. The vigorous action of shaker systems tends to stress the bags and requires heavier and more durable fabrics. In the United States, woven fabrics are used almost exclusively(2) for shakercleaning. European practice allows the use offelted fabrics at somewhat higher filtering velocities.5-4

5.1.2.2 

### Reverse-air Cleaning When glass fiber fabrics were introduced, agentlermeans ofcleaning the bags was needed to prevent premature degradation. Reverse-aircleaning was developed as a less intensive way to impart energy to the bags. In this method, gas flow to the bags is stopped in the compartment being cleaned, and
areverse flow of air is directed through the bags. This reversal ofgas flow gently collapses the bags and dust is removed from the fabric surface by shear forces developed between the dust and fabric as the latterchanges its contours. Another difference between reverse-air and shakercleaning is the installation of sewn-in rings to prevent complete collapse ofthe bag, which may be greater than 30 

### ft long, during cleaning. Without these rings, collected dust tends to choke the bag as the fabric collapses in on itself. As with mu1ticompartment shakerbaghouses, the same cycle takes place in reverse-air baghouses of stopping forward gas flow and allowing dust to settle before cleaning action begins. The source ofreverse air is generally a separate fan capable of supplying air for one or two compartments at agas-to-c10th ratio similar to that ofthe forward gas flow. 5.1.2.3 

### Pulse-jet Cleaning This form ofcleaning uses compressed air to force aburst ofairdown through the bag and expand it violently. As with shakerbaghouses, the fabric reaches its extension limit and the dust separates from the bag. In pulse jets, however, gas flows are opposite in direction when compared with shaker
or reverse-airbaghouses. Bags are mounted on wire cages to prevent collapse while the dusty gas flows from outside the bag to the inside.**I~stead** 

### of attaching both ends ofthe bag to the baghouse structure, the bag and cage

### 5-5
assembly generally is attached only at the top. The bottom end ofthe assembly tends to move in the turbulent gas flow and may contact otherbags. which accelerates wear. Although some pulse-jet baghouses are compartmented. most are not. Bags
are cleaned by rows when atimer initiates the burst ofcleaning air through a quick-opening valve. Usually 10% ofthe collector is pulsed at atime by
zones. Apipe across each row ofbags carries the compressed air. The pipe is pierced above each bag so that cleaning airexits directly downward into the bag. Some systems direct the air through a short venturi that is intended to entrain additional cleaning air. The pulse interrupts forward gas flow only for a few tenths ofa second. However. the quick resumption offorward flow redeposits most ofthe dust back on the clean bag or on adjacent bags. An advantage ofonline pulse-jet cleaning is the reduction in baghouse size allowed by not having to build an extra compartment for offline cleaning. Pulsejets normally operate at two ormore times the**gas~to-cloth** 

### ratio of reverse-airbaghouses. 5.1.3 Auxiliary Equipment The typical auxiliary equipment associated with fabric filter systems is shown in Figure 5-1. Along with the fabric filter itself. acontrol system typically includes the following auxiliary equipment: acapture device (i.e•• hood ordirect exhaust connection); ductwork; dust removal equipment (screw conveyor. etc.); fans. motors. and starters; and a stack. In addition. spray chambers. mechanical collectors. and dilution airports may be needed to precondition the gas before it reaches the fabric filter. Capture devices are usually hoods that exhaust pollutants into the ductwork or direct exhaust couplings attached to aprocess vessel. Hoods are more common, yet poorlyFabricFilter

U1 I 0"1 Stack Fan

DustRemoval DilutionAir

SprayCooler DirectExhaust Hood

MechanicalCollector Figure5-10 Typicalalternativeauxiliaryequipmentitemsusedwithfabricfiltercontrolsystems,5-7
designed hoods will allow pollutants to escape. Direct exhaust couplings are less common, requiring sweep air to be drawn through the process vessel, and may not be feasible in some processes. Ductwork provides ameans ofmoving the exhaust stream to the control device. Spray chambers and dilution air ports are used to decrease the temperature ofthe pollutant stream to protect the filter fabric from excessive temperatures. When a substantial portion of the pollutant loading consists ofrelatively large particles, mechanical collectors such as cyclones are used to reduce the load on the fabric filter itself. The fans provide motive power for airmovement and can be mounted before (pressure baghouse) or after (suction baghouse) the filter. Astack, when used, vents the cleaned stream to the atmosphere. Screw conveyors are often used to remove captured dust from the bottom ofthe hoppers. Air conveying systems and direct dumping into containers are also used. 5.1.4 Fabric Filtration Theory The key to designing abaghouse is to determine the face velocity that produces the optimumbalance between pressure drop (operating cost) and baghouse size (capital cost). Major factors that affect design face velocity (or gas-to-cloth ratio), discussed in Section 5.2, include particle and fabric characteristics and gas temperature. Although collection efficiency is another important measure ofbaghouse performance, it is generally assumed that aproperly designed and well run baghouse will be highly efficient. Therefore, the design process focuses on the pressure drop. There are several contributions to the pressure drop across abaghouse including the pressure drop from the flow through the inlet and outlet ducts, from flow through the hopper regions, and from flow through the bags. The pressure drop through the baghouse (excluding the pressure drop across the bags) depends largely on the5-8


### baghouse design and ranges from 1 to 2inches ofH 2

0(3) in conventional designs and up to 3 inches ofH 2

0 in designs having complicated gas flow paths. This loss can be kept to aminimum (i.e., 1 inch ofH 2

0or less) by investing in aflow modeling study ofthe proposed design. Astudy ofthis sort would cost on the orderof$50,000 (in 1986). The pressure drop across the bags (also called the tubesheet pressure drop) can be as high as 10 inches ofH 2

0ormore. The duct and hopper losses are constant and can be minimized effectively through properdesign based on aknowledge ofthe flow through the baghouse. (NQte: Aprocedure for estimating duct pressure losses is given in the "Ductwork" section ofthis Manual.) The tubesheet pressure drop is a complex function ofthe physical properties ofthe dust and fabric and the
manner in which the baghouse is designed and operated. Fabric filtration is inherently abatch process that has been adapted to continuous operation through cleverengineering. One requirement for a continuously operating baghouse is that the dust collected on the bags must be removed periodically. Shaker and reverse-airbaghouses are similar in the
sense that they both normally use woven fabric bags, run at relatively low face velocities, and the filtration mechanism is cake filtration. That is, the fabric merely serves as a substrate for the formation ofadust cake that is the actual filtration medium. Pulse-jet baghouses generally use felt fabrics and run with ahigh face velocity (about double that of shaker or reverse-airbaghouses). Some investigators feel that the felt fabric plays a much more active role in the filtration process. This distinction between cake filtration and fabric filtration has important implications for calculating the rate ofpressure loss across the filter bags. The theoretical description ofcake filtration is quite different from that for fabric filtration, and the design processes are quite different.5-9



### The general equations used to design abaghouse follow beginning with the
reverse air/shake deflate type ofbaghouse. 5.1.4.1 Reverse Air/Shake Deflate Baghouses The construction ofabaghouse begins with a set of specifications including average pressure drop, total gas flow, and**o~her** 

### requirements; a maximum pressure drop is always specified. Given these specifications, the designermust determine the maximum face velocity that can meet these requirements. The standard way to relate baghouse pressure drop to face velocity is given by the relation: AP(8) =

### Ssys(8)Vave where: (5-1)
AP(8) 

### = Ssys(8) 

### = V

ave 

### =the pressure drop across the filter, in. H 2

### 0 (a function oftime, 8) system drag, in. H 2

### 0/(ft/min) (a function oftime) average (i.e., design) face velocity (ft/min) (essentially constant) For amulticompartment baghouse, the systemdrag is determined as the sum of several parallel resistances representative of several compartments. For the typical case where the pressure drop through each compartment is the same, it
can be shown that:

SsYS(8) 

### =

# [~

# i=s.

# lin] -1 

### =

# -M~l_l- = . 1 1 1 t' 1= t.. f:f 

### ;=1 5;(8) where M

### =number ofcompartments ;n the baghouse S;(8) =

### drag across compartment; M 1: 

### ;=1 M (5-2)5-10

The compartment drag is a function of the amount ofdust collected on the bags in that compartment. In general, the dust will be distributed in avery nonuniformmanner. That is, there will be avariation ofdust load from one bag to the next and within a given bag there will also be a variation ofdust load from one area to another. For a suffic1ently small areaj within compartment i, it can be assumed that the drag is a linear function ofdust load:
S. .(9) = S + K 2W.

.(9) 1,J e 1,J where: (5-3)

Se = drag of adust-free (freshly cleaned) filter bag K

2 =dust cake flow resistance, [in. H 2

o/(ft/min)]/(lb/ft2) 

## w. .(9) = dust mass per unit area of areaj in compartment i

1,J If there are Ndifferent areas ofequal size within compartment i , each with a different drag Si,j' then the total drag for compartment i can be computed in
amanner analogous to equation (5-2): Si(9) = N/l:[l/Si,j(9)] (5-4) The constants Se and K 2depend upon the fabric and the nature and size of the dust. The relationships between these constants and the dust and fabric properties are not understood well enough to permit accurate predictions and
so must be determined empirically, either from prior experience with the dust/fabric combination or from laboratory measurements. The dust mass as a function of time is defined as:
(5-5)

### 5-11

where: W r =

### dust mass per unit area remaining on a "clean" bag C

in =

### dust concentration in the inlet gas (gr/ft3) V

i(8) 

### =face velocity in compartment i It is assumed that the inlet dust concentration and the filter area are constant. The face velocity through each compartment changes with time, starting at amaximum valuejust after cleaning and steadily decreasing as dust builds up on the bags. The individual compartment face velocities are related to the average face velocity by the expression: V

ave

## =E{Vi(8)Ai}/E{Ai} (5-6)



## = E{Vi}/M (forMcompartments with equal area) Equations (5-1) through (5-6) reveal that there is no explicit relationship between the design face velocity and the tubesheet pressure drop. On the contrary, the pressure drop that results from agiven design can only be determined by the simultaneous solution ofequations (5-1) through (5-5), with equation (5-6) as aconstraint on that solution. This conclusion has several implications for the design process. The design requires an iterative procedure: one must begin with a known target for the average pressure drop, propose abaghouse design (number ofcompartments, length offiltration period, etc.), assume a face velocity that will yield that pressure drop, and solve the system ofequations (5-1) through (5-6) to verify that the calculated pressure drop equals the target pressure drop. This procedure is repeated until the specified face velocity yields an average pressure drop (and maximumpressure drop, ifapplicable) that is sufficiently close to the design specification.

### 5-12

5.1.4.2 Pulse-Jet Baghouses The distinction between pulse-jet baghouses and reverse-air and shake baghouses is basically the difference between cake filtration and composite dust/fabric filtration (noncake filtration). This distinction is more a matter ofconvenience than physics. In reality, pulse-jet baghouses have been designed to operate in a variety ofmodes. Some pulsejets remain online at all times and are cleaned frequently. Others are taken offline for cleaning at relatively long intervals. Obviously, ifacompartment remains online long enough without being cleaned, then the filtration mechanismbecomes that of cake filtration. Acomplete model ofpulse-jet filtration therefore must account for the depth filtration occurring on arelatively clean pulse-jet filter, the cake filtration that inevitably results from prolonged periods online, and the transition period between the two regimes. Besides the question offiltration mechanism, there is also the question ofcleaning method. Ifacompartment is taken off-line for cleaning, then the dust that is removed from the bags will fall into the dust hopperbefore forward gas flow resumes. Ifacompartment is cleaned while online, then only
a small fraction ofthe dust removed from the bag will fall to the hopper. The remainderofthe dislodged dust will be redeposited (i.e., "recycled") on the bag by the forward gas flow. The redeposited dust layer has different pressure drop characteristics than the freshly deposited dust. The modeling work that has been done to date focuses on the online cleaning method. Dennis and Klemm(4) proposed the following model ofdrag across apulse-jet

### filter~ S = 

### Se + 

### (K2)cW c + 

### K 2

W

o where: S

### =drag across the filter (5-7)5-13

Se 

### =drag of ajust-cleaned filter 

### (KZ)c 

### =specific dust resistance ofthe recycling dust W

c

### =areal density of the recycling dust K

Z

### =specific dust resistance of the freshly deposited dust W

o

### =areal density of the freshly deposited dust This model has the advantage that it can easily account for all three regimes of filtration in a pulse-jet baghouse, i.e., cake filtration, depth filtration, and filtration in the transition region. As in equations (5-1) to (5-6), the drag and areal densities are functions of time (8). However, for a pulse-jet baghouse with online cleaning, the filtration velocity is relatively constant. The pressure drop can thus be expressed as the sum of a relatively constant term and a term that increases due to dust build-up: bP = (PE)bW + KZWoV where: (5-8)

bP = pressure drop (in. HZO)

V

### =filtration velocity (ft/min) (PE)bW

### =[Se + (KZ)cWc] V (5-9) Equation (5-8) describes the pressure drop behavior of an individual bag. To extend this single bag result to amultiple-bag compartment, equation (5-7) would be used to determine the individual bag drag and the total baghouse drag would then be computed as the sum ofthe parallel resistances as in equation (5-2). Pressure drop would then be calculated as in equation (5-1). It seems reasonable to extend this analysis to the case where the dust is distributed unevenly on the bag and then apply equation (5-7) to each area on the bag, followed by an equation analogous to (5-4) to compute the overall bag drag. The difficulty in doing this is that one must assume values for W c for each different area to be modeled.5-14

The disadvantage of the model represented by equations (5-7) and (5-8) is that the constants, Se' K 

### 2, and 

### W c' cannot be predicted at this time. Consequently, correlations of laboratory data must be used to determine the value of (PE)AW. For the fabric-dust combination of Dacron felt and coal fly ash, Dennis and Klemm(4) developed an empirical relationship between (PE)AW' the face velocity, and the cleaning pulse pressure. This relationship (converted from metric to English units) was as follows:
-0.65 (PE)Aw

## =6.08 VPj where: (5-10)



### v = face velocity (ft/min) P

j 

## =pressure of the cleaning pulse (usually 60 to 100 psig; see Section 5.4.1.8) It is not known how well the constants in equation (5-10) would fit the data for a different dust/fabric combination.**~ased** on a limited amount ofdata, it appears that the power law form of equation (5-10) may be a valid model for (PE)Aw. However, equation (5-10) can be used as a first approximation to estimate (PE)Aw for other fabric-dust combinations. Another model that shows promise in the prediction of noncake filtration pressure drop is that of Leith and Ellenbecker(5) as modified by Koehler and Leith.(6) In this model, the tubesheet pressure drop is a function of the clean fabric drag, the system hardware, and the cleaning energy. Specifically:
(5-11) where: P

s = maximum static pressure achieved in the bag during cleaning5-15



### K

1 

### =clean fabric resistance V

f

### =face velocity 

### K

2

### =dust deposit flow resistance 

### K- 

### =bag cleaning efficiency coefficient

3 . K v

### =loss coefficient for the venturi at the inlet to the bag Comparisons of laboratory data with pressure drops computed from equation (5-11)(5,6) are in close agreement for a variety of dust/fabric combinations. The disadvantage of equation (5-11) is that the constants 

### K 1, K 2, and 

### K 3 must be determined from laboratory measurements. The most difficult one to determine is the K 3 value, which can only be found by making measurements in a pilot-scale pulse-jet baghouse. 5.2 Design Procedures 5.2.1 Gas-to-C1oth Ratio The gas-to-c1oth ratio is difficult to estimate from first principles. However, shortcut methods of varying complexity allow rapid estimation. Descriptions of three methods of increasing difficulty follow. For shaker and reverse-air baghouses, the third method is best performed with publicly available computer model programs. 5.2.1.1 Gas-to-Cloth Ratio From Similar Aoplications Net gas-to-c1oth ratio is equal to the total actual volumetric flow rate in cubic feet per minute divided by the net cloth area in square feet. This ratio reduces to units of feet per minute and affects pressure drop and bag life. After a fabric has been selected, the gas-to-c10th ratio can be determined using Table 5-1. Column 1 shows the type of dust; column 2 shows the gas-to-cloth ratios for woven fabric; and column 3 shows gas-to-c1oth ratios for felted fabrics. The net cloth area is determined by dividing the5-16

Table

### ~-1**Gas-~-Cloth** Ratiosa(7) (ft /min)/(ft of cloth area)
Dust Alumina Asbestos Bauxite Carbon Black Coal Cocoa, Chocolate Clay Cement Cosmetics Enamel Frit Feeds, Grain Feldspar

.Fertili zer

Flour Fly Ash Graphite Gypsum

.. Iron Ore Iron Oxide Iron Sulfate Lead Oxide Leather Dust Lime Limestone Mica Paint Pigments Paper Plastics Quartz Rock Dust Sand Sawdust (Wood) Silica Slate Soap, Detergents Spices Starch Sugar Talc Tobacco Zinc Oxide Shaker/Woven Reverse-Air/Woven 2.5 3.0 2.5 1.5 2.5 2.8 2.5 2.0 1.5 2.5 3.5 2.2 3.0 3.0 2.5 2.0 2.0 3.0 2.5 2.0 2.0 3.-5 2.5 2.7 2.7 2.5 3.5 2.5 2.8 3.0 2.5 3.5 2.5 3.5 2.0 2.7 3.0 2.0 2.5 3.5 2.0 Pulse Jet/Felt 8 10

8 5 8 12

9 8 10

9 14

9 8 12

5 5 10 11

7 6 6 12 10

8 9 7 10

7 9 9 10 12

7 12

5 10

8 7 10 13

5 aGenerally safe design values--application requires consideration of particle

size and grain loading.

### 5-17
gas-to-cloth ratio into the actual cubic feet perminute flow ofthe exhaust gas stream. For an intermittent-type baghouse that is shut down for cleaning, this is the total, orgross, cloth area. However, for continuously operated filters, thearea must be increased to allow the shutting down ofone ormore compartments for cleaning. Table 5-2 provides aguide for adjusting the net
area to the gross area, which determines the size ofacontinuously cleaned filter. 5.2.1.2 Gas-to-Cloth Ratio FromManufacturer's Methods Manufacturers have developed nomographs and charts that allow rapid estimation ofthe gas-to-cloth ratio. Two examples are given below, one for shaker-cleaned baghouses and the other for pulse-jet cleaned baghouses. For shakerbaghouses, Table 5-3 gives afactor method for estimating the ratio. Ratios for several materials in different operations are presented, but are modified by factors for particle size and dust load. Directions and
an example are included. Gas-to-cloth ratios for reverse-airbaghouses would be about the same or a little more conservative compared to the Table 5-3 values. Forpulse-jet baghouses, another factor method(9) has been modified with equations to represent temperature, particle size, and dust load:



## v=

### A

### xB

### x2.647T-0.2335 

### x (0.7471 + 

### 0.0853 ln D) 

### x 1.0873 L-0.06021 (5-12) where: V

### =gas-to-cloth ratio, ft/min A

### =material factor, from Table 5-4 

### B

### =application factor, from Table 5-4 T

### =temperature, of 

### (between 50 and 275)5-18

Table 5-2 Approximate Guide to Estimate Gross Cloth Area(8) Net Cloth Area Gross Cloth Area (tt2) (tt2) 1-4,000 Multiply by 2 4,001-12,000 " 1.5 12,001-24,000 " 1.25 24,001-36,000 " 1.17 36,001-48,000 " 1.125 48,001-60,000 " 1.11 60,001-72,000 " 1.10 72,001-84,000 " 1.09 84,001-96,000 " 1.08 96,001-108,000 " 1.07 108,001-132,000 " 1.06 132,001-180,000 " 1.05 above 180,001 " 1.04Table 5-3 Manufacturer's FactorMethod for Estimating Gas-to-Cloth Ratios for Shaker Baghouses

10,II -----2n-RATi<Y------ --Y:511 RATIO

----·-T-·---·-------_.-. -.----------------.--- MATERIAL**~!!AT!~** MATERIAL OPERATION AmmoniumPhos· ActivatedCharcoal 2.4.5.6.7 phatePerl. 2.3,4.5,6,7 Carbon Black II.14 Diatomaceous Detergents 2,4.5,6.7 Earth 4.5,6,7 Metal Fumes, DryPelrochem. 2,3.4,5,6,7,14 Oxidesand D 2 3 4 5 6 7 olherSolid

yes , , , , , Dispersed FlyAsh 10 Producls MetalPowders 2,3,4,5,6,7,14 Plashes 2,3,4,5.6,7.14 Resins 2,3,4,5,6,7,14 Silicales 2,3,4.5,6,7.14 Starch 6,7**~oaps** 3,4,5,6,7 RATlO_:_=--1 2..5/1**RATIO--~** OPERATION MATERIAL OPERATION I Ashestos 1,7.8--- Alumina---

### 2.T4.D 2.3,4,5,6,7 Aluminum Dust I.7.8 CarbonBlack 4,5,6,7 2,3.4,5,6,7 FiblOusMal'l. 1,4.7,8 Cement 3,4,5,6,7 2,3,4,5,6,7 CellulQseMat'!. 1,4.7,8 Coke 2,3,5,6 1,7,8 Gypsum 1,3.5.6.7 CeramicP,gm. 4,5,6,7 1,4,6,7 Lime(Hydrated) 2,4,6.7 Clay&BrickDusl 2,4,6,12 13 Pe,lite 2.4,5.6 Coal 2,3,6,7,12 1,6.7 Rubbe,Chem. 4.5,6,7.8 Kaolin 4,5,7 Sail 2,3.4.5,6,7 Limeslone 2,3,4,5,6,7 Sand• 4,5.6,7.9.15 Rock,OreDust 2,3,4,5,6,7 honScale 1,7.8 Silica 2,3,4,5,6,7 SodaAsh 4,6,7 Suga, 3,4,5,6,7 Talc 3,4,5,6,7 MachiningOperaho 1,8 Cardboard Feeds Flour Grain LeatherDust Tobacco SupplyAll Wood,Dust.Chips

## A[-~~l-:i!!£{X~t{~~a-~=~~~f~RI~~1

This informationconstitutesa guideforcommonly en.countered situations and should not be considereda "hard-and-fast" rule. Air-to-cloth ratiosaredependentondustloading, sizedistribution. particle shapeand "cohesiveness" ofthe deposited dust. These conditions must be evaluated for each application. The longertheinterval between bag cleaning 'the lower the air-to-c1oth ratio must be, Finely-divided, uniformly sized particles generally form more dense filter cakes and requirelowerair-to-clothratiosthanwhenlargerparticles are interspersed with the fines. Sticky, oilyparticles, regardlessofshapeorsize, form dense filler cakes and require lower air-to-cloth ratios. CUTTING

- I CRUSHINr:;

- 2 PUlVERIZING

- 3 B 

# I MIXING

- 4 CONVEYING

- 7

### SCREENI~G - 5 

# I GRINDING

- 8 STORAGE

- 6 SHAKEOUT

- 9 FINENESS FACTOR 'MICRON SIZE FACTOR -->.!QL

### --q 50·100 1.1

10·50' 1.0

- ---- --.



### __.L!L**f----~!..-** I·3 .8 <I .7 FURNACE FUME

- 10 REACTION FUME- II**D~MPING** - 12 INTAKE ClEANING

- 13 PROCESS

- 14 BLASTING

- 15 U1 I

....... 1.0

C DUST LOAD FACTOR LoadingGR. CU.FT. Fodor 1 - 3 1.2 I EXAMPLE: 4- 8 1.0

-- 9 - 17

.95 18

-40

.90

> 40 .85

__ L--.._ Foundry shakeoutunit handling 26000CFM and collecting 3500# / hr. ofsand. The particle distribution shows 90"/. greaterthan 10microns.Theairis toexhaustto room in winter, to atmosphere in summer. 3500 #1 -7- 60MIN.-+-26000f!L!!.: X7000 GIl = 15.7..Q..!..

.IHI liT MIN. 1# cu. FT• ·Chart A = 3/1 ratio, ChartB= Factor 1.0, ChartC "....., .95; 3 x.l x .95=c 2.9 air tocloth ratio. 26000-;-. 2.9= 9,000sq. fl. Reprinted with permission from Buffalo Forge Company Bulletin AHD-29.5-20



### Table 5-4 Factors for Pulse-Jet Gas-to-Cloth Ratios(9) A. Material Factor 

### ISa 

### Cake mix Cardboard dust Cocoa Feeds Flour Grain Leatherdust Sawdust Tobacco 12 

### Asbestos Buffing dust Fibrous and

cellulosic material Foundry shakeout Gypsum Lime (hydrated) Perlite Rubber chemicals Salt Sand Sandblast dust Soda ash Talc 10 

### Alumina Aspirin Carbon black

(finished) Cement Ceramic pigments Clay and

brick dusts Coal Fluorspar Gum, natural Kaolin Limestone Perchlorates Rock dust,

ores and minerals Silica Sorbic acid Sugar 9.0 

### Ammonium

phosphatefertilizer Cake Diatomaceous

earth Dry petro-

chemicals Dyes Fly ash Metal powder Metal oxides Pigments,

meta11ic and synthetic Plastics Resins Silicates Starch Stearates Tannic acid Activated carbon Carbon

black(molecular)Detergents Fumes

and otherdispersed products direct fromreactions Powdered

milk Soaps
B. Application Factor Nuisance Venting Reliefoftransfer points, conveyors, packing stations, etc. Product Collection Air conveying-venting mills flash driers classifiers, etc. Process Gas Filtration Spray driers, kilns, reactors, etc. 

### LO

0.9

0.8



### a1n general physically and chemically stable materials. b

Also includes those solids that are unstable in theirphysical orchemical state due to hygroscopic nature, sublimation, and/orpolymerization.

### 5-21

D

### =mass mean diameter ofparticle, pm (between 3 and 100) L= 

### inlet dust loading, gr/ft3 (between 0.05 and 100) Fortemperatures below 50 of, 

### use T

### =50 but expect decreased accuracy; for temperatures above 275 OF, use T

### =275. Forparticle mass mean diameters less than 3

### pm, the value ofDis 0.8, and for.diameters greater than 100pm, Dis 1.2. For dust loading less than 0.05 gr/ft3
, use L= 

### 0.05; for dust loading above 100 gr/ft3
, use L

### =100. 5.2.1.3 Gas-to-Cloth Ratio FromTheoretical/Empirical Equations 5.2.1.3.1 Shaker and reverse-airbaghouses--The systemdescribed by equations (5-1) through (5-6) is complicated; however, numerical methods can be used to obtain an accurate solution. Acritical weakness in baghouse modeling that has yet to be overcome is the lack ofa fundamental description ofthe bag cleaning process. That is, to solve equations (5-1) through (5-6), the value ofW r (the dust load after cleaning) must be known. Clearly, there must be arelationship between the amount and type ofcleaning energy and the degree ofdust removal from abag. Dennis et al.(10) have developed correlations for the removal ofcoal fly ash from woven fiberglass bags by shakercleaning and by reverse air cleaning. These correlations have been incorporated into acomputerprogramthat generates the solution to the above systemofequations.(10,11,12) Ifone were to apply the correlations developed with coal ash and woven glass fabrics to other dust/fabric combinations, the accuracy ofthe results would depend on how closely that dust/fabric combination mimicked the coal ash/woven glass fabric system. Physical factors that affect the correlation include the particle size distribution, adhesion properties ofthe dust and fabric, and fabric weave, as well as cleaning energy. More research is needed in this area offabric filtration.

### 5-22

The rtgorous design ofabaghouse thus involves several steps. First, the design goal for average pressure drop (and maximum pressure drop, if necessary) must be specified along with total gas flow rate and other parameters, such as Se and K 2 (obtained either from field or laboratory measurements). Second, aface velocity is assumed and the numberof compartments in the baghouse is computed based on the total gas flow, face velocity, bag size, and number ofbags percompartment (typical compartments in the U.S. electric utility industry use bags 1 ft in diameterby 30 ft long with 400 bags per compartment). Standard practice is to design abaghouse to meet the specified pressure drop when one compartment is off-line for maintenance and a second compartment off-line for cleaning. The third step is to specify the operating characteristics ofthe baghouse (i.e., filtration period, cleaning period, and cleaning mechanism). Fourth, the designermust specify the cleaning efficiency so that the residual dust load can be estimated. Finally, the specified baghouse design is used to establish the details for equations (5-1) through (5-6), which are then solved numerically to establish the pressure drop as a function oftime. The average pressure drop is then computed by integrating the instantaneous pressure drop over the filtration cycle and dividing by the cycle time. Ifthe computed average is higher than the design specification, then the face velocity must be reduced and the procedure repeated. Ifthe computed average pressure drop is significantly lowerthan the design specification, then the proposed baghouse
was oversized and should be made smallerby increasing the face velocity and repeating the procedure. When the computed average pressure drop comes sufficiently close to the assumed specified value, then the design has been determined. Acomplete description ofthe modeling process can be found in

### 5-23

the reports by Dennis et al.(10,12) Acritique on the accuracy ofthe.model is presented by Viner et al.(13) 5.2.1.3.2 Pulse-jet baghouses--The overall process ofdesigning apulse jet baghouse is actually simpler than thatrequired for a reverse-air or shakerbaghouse ifthe baghouse remains online for cleaning. The first step is to specify what the desired average tubesheet pressure drop should be. Second, the operating characteristics ofthe baghouse must be established 

### (e.g.! online time, cleaning energy). Third, the designermust obtain values for the coefficients in either equation (5-10) orequation (5-11) from field, pilot plant, or laboratory measurements. Fourth, a value is estimated for the face velocity and the appropriate equation [(8) 

### or (11)] is solved for the pressure drop as a function oftime for the duration ofthe filtration cycle. This information is used to calculate the cycle average pressure drop. Ifthe calculated pressure drop matches the specified pressure drop, then the procedure is finished. Ifnot, then the designermust adjust the face velocity and repeat the procedure. 5.2.2 Pressure Drop Pressure drop for the bags can be calculated rigorously from the equations given in the preceding section ifvalues for the various parameters
are known. Frequently they are not known. Forquick estimation, amaximum pressure drop of5- to 10-in. H 

### 2

0across the baghouse and 10- to 20-in H 

### 2

0


### across the entire system can be assumed if it contains much ductwork. A

### comparable form ofequations (5-1) and (5-3) that may be used for pressure drop across the fabric in a shaker or reverse-airbaghouse is: (5-13)

### 5-24

where: AP

### =pressure drop (in. H 2

0) Se 

### =effective residual drag ofthe fabric [in. H 2

0/(ft/min)] V

### =superficial face ve-locity orgas-to-cloth ratio (ft/min) K

2

### =specific resistance 20efficient ofthe dust [in. H

2

0/(ft/min)]/(lb/ft ) C

i = 

### inlet dust concentration (lb/ft3) 8

### =filtration time, min Although there is much variability, values for Se may range from about 0.2 to 2in. H 2

0/(ft/min) and for K 2from 1 or2to 30 or40 [in. H 20/(ftl 

### min)]/lb/ft. Typical values for coal fly ash are 1to 4. Inlet concentrations vary from less than 0.05 gr/ft3

### to more than 100 gr/ft3
, but amore nearly typical range is from 0.5 to 10 gr/ft3• Filtration times may range from 20 minutes to 8 hours for continuous duty reverse-air and shakerbaghouses, but 30 minutes to 4hours is morefrequently found. Filtration times for pulse-jet baghouses range from 2to 60 minutes, but 5to 20 minutes is typical. Forpulse-jet baghouses, use equations (5-8) and (5-10) to estimate AP, after substituting CiVt for W oand (PE)Aw for Se V. 5.2.3 Particle Characteristics Particle size distribution and adhesiveness are the most important particle properties that affect design procedures. Smallerparticle sizes can form adenser cake, which increases pressure drop. As shown in Table 5-3 and equation (5-12), the effect ofdecreasing average particle size is a lower applicable gas-to-cloth ratio. Sticky particles may require installing equipment that injects a precoating material onto the bag surface, which acts as abuffer that traps5-25



### the particles and prevents them from blinding orpermanently plugging the fabric pores. 5.2.4 

### Gas Stream Characteristics Moisture and corrosives content are the major gas stream characteristics requiring design consideration. The baghouse and associated ductwork should be insulated and possibly heated to avoid condensation. Both the structural and fabric components must be considered, as eithermay be damaged. Where structural corrosion is likely, stainless steel substitution for mild steel may be required, provided that chlorides are not present. (Most austenitic stainless steels are susceptible to chloride corrosion.) 5.2.4.1 

### Temperature The temperature ofthe pollutant streamto be cleaned must be above and remain above the dew point ofany condensables in the stream. Ifthe temperature is high and it can be lowered without approaching the dew point, spray coolers ordilution air can be used to drop the temperature so that temperature limits ofthe fabric will not be exceeded. The additional cost of
aprecoo1erwill have to be weighed against the higher cost ofbags with greatertemperature resistance. The use ofdilution air to cool the stream also constitutes atradeoffbetween a less expensive fabric and a larger filter necessary to accommodate the additional volume ofthe dilution air. Generally, precooling would not be necessary iffabric that will handle the temperature and the chemical action ofthe pollutant stream is available. (Costs for spray chambers, quenchers, and otherprecoo1ers are found in the "Precoo1ers" section ofthe Manual.) Table 5-5 

### lists several ofthe fabrics in current use and provides information on temperature limits and chemical resistance. The column labeled "Flex Abrasion" indicates the fabric's suitability for cleaning by mechanical shakers.5-26 Table 5-5 Properties ofLeading Fabric Materials(14)

Fabric Cotton Creslanb

Dacronc

Fiberglasd Filtrone
Gore-Texf

Polypropylene Teflonc

Wool 180 250
275

160

500 270 Depends on backing

375
200 260

200 450

200 Acid Resistance Poor Good in mineral acids Good in most mineral acids; disolves par- t ially inconcentrated H 2

S04 Little effect even at high concentration Fairto good Good to excellent Depends on backing
Fair
Fair Good to excellent in mineral acids
Excellent Inert except to fluorine

Very good Alkali Resistance Very good Good in weak alkali Good in weak a1ka1i; fair in strong alkali
little effect even in high concentration Fairto good Good Depends on backing
Excellent at low temperature Excellent Fairto good in weak alkali

Excellent Inert except to trifluoride, chlorine, and molten alkaline metals Poor Flex Abrasion Very good Good to very good

Very good

Fairto good
Fair Good to Very good Fair

Excellent
Excellent Good

Excellent Fair

Fair to good aMaximum continuous operating temperatures recommended by the Industrial Gas

Cleaning Institute. bAmerican Cyanamid registered trademark.
cOu Pont registered trademark. dOwens-corning Fiberglas registered trademark.
eW

. W. Criswell Div. of**\~heelabrator-Fry,** Inc., trade name. f

### w . L. Gore and Co., registered trademark.

### 5-27

5.2.4.2 Pressure Standard fabric filters can be used in pressure or vacuum service but only within the range ofabout +25 inches ofwatergauge. Because ofthe sheet metal construction ofthe house, they are not generally suited for more
severe service. However, for special applications, high-pressure shells can be built. 5.2.5 Pressure or Suction Housings The location ofthe baghouse with respect to the fan in the gas stream affects the capital cost. Asuction-type baghouse, with the fan located on the downstream side ofthe unit, must-withstand high negative pressures and therefore must be more heavily constructed and reinforced than abaghouse located downstreamofthe fan (pressure baghouse). The negative pressure in the suction baghouse can result in outside air infiltration, which can result in condensation, corrosion, oreven explosions ifcombustible gases are being handled. In the case oftoxic gases, this inward leakage can have an advantage over the pressure-type baghouse, where leakage is outward. The main advantage ofthe suction baghouse is that the fan handling the process stream is located at the clean-gas side ofthe baghouse. This reduces the wear and abrasion on the fan and permits the use ofmore efficient fans (backwardcurved blade design). However, because for some designs the exhaust gases from each compartment are combined in the outlet manifold to the fan, locating compartments with leaking bags may be difficult and adds to maintenance costs. Pressure-type baghouses are generally less expensive because the housing must only withstand the differential pressure across the fabric. In some designs the baghouse has no external housing. Maintenance also is reduced because the compartments can be entered and leaking bags can be observed while5-28


### the-compartment is in service. With apressure baghouse, the housing acts as the stack to contain the fumes with the subsequent discharge at the roofof the structure, which makes it**ea~er** 

### to locate leaking bags. The main disadvantage ofthe pressure-type baghouse is that the fan is exposed to the dirty gases where abrasion and wearon the fan blades may become aproblem. Also, some applications require a stack for dispersion ofgaseous pollutants, negating some ofthe construction economics. 5.2.6 Standard or Custom Construction The design and construction ofbaghouses are separated into two groups, standard and custom,(8) which are further separated into low, medium, and high capacity. Standard baghouses are predesigned and factory built as complete off-the-shelfunits that are shop-assembled and bagged for low-capacity units (hundreds to thousands ofacfm throughput). Medium-capacity units (thousands to less than 100,000 acfm) have standard designs, are shop-assembled, mayor may not be bagged, and have separate bag compartment and hopper sections. High-capacity baghouses (larger than 50,000 or 100,000 acfm) can be designed
as shippable modules requiring only moderate field assembly. These modules may have bags installed and can be shipped by 

### truck or rail. Upon arrival, they can be operated singly or combined to form units for larger-capacity applications. Because they are preassembled, field labor for installation is less costly. The custombaghouse, also high capacity, is designed for a specific application and is usually built to the specifications prescribed by the customer. Generally, these units are much largerthan standard baghouses. Forexample, many are used on powerplants. The cost ofthe custombaghouse is much higherper square foot offabric because it is not an off-the-shelf

### 5-29

item and requires special setups for manufacture and expensive field labor for. 'assembly upon arrival. The advantages ofthe custombaghouse are many and are

usually directed towards ease ofmaintenance, accessibility, and other customerpreferences. In some very small baghouses, acomplete set ofbags must be replaced in acompartment at one time because ofthe difficulty in locating and replacing single leaking bags, whereas in custombaghouses, single bags are accessible and can be replaced one at atime as leaks develop. 5.2.7 FilterMedia The type offilter material used in baghouses is dependent on the specific application in terms ofchemical composition ofthe gas, operating temperature, dust loading, and the physical and chemical characteristics of the particulate. Avariety offabrics, either felted orwoven, is available and the selection ofa specific material, weave, finish, orweight is based primarily on past experience. The type ofyarn (filament, spun, or staple), the yarn diameter, and twist are also factors in the selection of suitable fabrics for a specific application. For some difficult applications, Gorelex, apolytetrafluoroethylene (PTFE) membrane laminated to a substrate fabric (felt orwoven) or altered-surface fabrics may be used. Because ofthe violent agitation ofmechanical shakers, spun or heavy weight stapleyarn fabrics are commonly used with this type ofcleaning, while lighterweight filament yarn fabrics are used with reverse-air cleaning. The type ofmaterial will limit the maximumoperating gas temperature for the baghouse. Cotton fabric has the least resistance to high temperatures (about 180 OF), while fiberglass has the most (about 500 OF). The temperature ofthe exhaust-gas streammust be well above the dew point ofany of its contained condensables as liquid particles will usually plug the fabric pores

### 5-30
quickly. However, the-temperature must be below the maximum limit ofthe fabric in the bags. These maximum limits are given in Table**5-5~** 

### 5.3 Estimating Total Capital Investment Total capital investment includes costs for the baghouse structure, the initial complement ofbags, auxiliary equipment, and the usual direct and indirect costs associated with installing or erecting new structures. These costs are described below. 5.3.1 Equipment Cost 5.3.1.1 Bare Baghouse Costs Six types ofbaghouses will be considered: Preassembled units
Intermittent Continuous Continuous Continuous Continuous

Continuous Shaker Shaker Pulse-jet**(commo~** 

### housing) Pulse-jet (modular) Reverse-air Field-assembled units Any method Figure 5-2 Figure 5-3 Figure 5-4 Figure 5-5 Figure 5-6
Figure 5-7 Each figure gives costs for the filter without bags and additional costs for stainless steel construction and for insulation. All curves are based on
anumber ofactual quotes. Aleast squares line has been fitted to the quotes and the line's equation is given. However, extrapolation should not be used. The reader should not be surprised ifhe obtains quotes that differ from these
curves by as much as +25%. Significant savings can be obtained by soliciting multiple quotes. All units include inlet and exhaustmanifolds, supports,5-31
platforms, handrails, and hopper discharge devices. The indicated prices are flange to flange. Note that the scales on both axes change from one figure to another to accommodate the differing gas flow ranges over which the various types ofbaghouses operate. The 304 stainless steel add-on cost is used when such construction is necessary to prevent the exhaust gas stream from corroding the interior ofthe baghouse. Stainless steel is substituted for all metal surfaces that are in contact with the exhaust gas stream. Insulation costs are for 3 inches of shop-installed glass fiber encased in ametal skin. One exception is the custom baghouse, which has fieldinstalled insulation. Costs for insulation include only the flange-to-flange baghouse structure on the outside of all areas in contact with the exhaust gas stream. Insulation for ductwork, fan casings, and stacks must be calculated separately as discussed later. The first baghouse type is the intermittent service baghouse cleaned by a mechanical shaker. This baghouse is shut down and cleaned at convenient times, such as the end of the shift or end ofthe day. Although few units are sold, they are applicable for operations that require infrequent cleaning. Figure 5-2 presents the unit cost with price in dollars plotted against the gross square feet ofcloth required.15 Because intermittent service baghouses do not require an extra compartment for cleaning, gross and net fabric areas
are the same. The plot is linearbecause baghouses are made up ofmodular compartments and thus have little economy of scale. Because ofthe modular construction, the price line should not be extrapolated downward. Costs for both types of shakerbaghouse include the.shakermechanism.

### Costwittloutbags: 10- 

### I--

.....

# • I...d",. ...oIi"",. 

## '2.-1-- l.diIIllII'"

## 61~~ \\

## l;i~"

. ....I!!:I-- I--

### ~f.;>~be

## .:;
.... ISI.alnlesssteeladdon I--**~....** 

### T2

....... 

### 06"-- 

# "1 660

# +~ ............ 1-"ldI ldIIIIII J;- 

### $ ::::: ,\"\.

......IJI"" 

# .,... 

## $

# = 1875 

## + 0450

## ft2 

### Insulationaddon-10- ". I 

### II I· Iii
- I 

### . 

### - I I I I n I I I I I I I I I I I I I 1;) 

## 50 o 

## o 

# o 75 

# 8
T"" EI7 

# - <.n i W N



### 18 16 14 

## 6 8 10 12 GrossClothArea (1000

## ft 

## Caution: Donotextrapolate.

42 

## 100 125 150

..... 

## ffi 25 E a. 

## -s .ff 0

# o <0

T"" L- •. (J)
:::1 

## o "E



# --

Source: ETS, Inc. figure5-2. Equipmentcostsforintermittentshakerfilters.5-33
Figure 5-3 presents the same costs for acontinuously operated baghouse cleaned by mechanical shaker.15,16 Again, price is plotted against the gross cloth area in square feet. As in Figure 5-2, the units are modular in construction. Costs for these units, on a square foot basis, are higher because of increased complexity and generallyheavier construction. The third and fourth types are common-housing pulsejets and modular pulsejets. The latter are constructed of separate modules that may be arranged for offline cleaning, and the former have all bags within one housing. The costs for these units are shown in Figures 5-4 and 5-5, respectively.15 The cleaning system compressor is not included. Note that in the single-unit (common-housing) pulsejet, for the range shown, the height and width ofthe unit are constant and the length increases; thus, for a different reason than that for the modular units discussed above, the cost increases linearly with size. Because the common housing is relatively inexpensive, the stainless steel add-on is proportionately higher than for modular units. Added material costs and setup and labor charges associated with the less workable stainless steel account for most of the added expense. Figure 5-6 shows the costs for the reverse-airbaghouses.15 The construction is modular and the reverse-air fan is included. The final type is the custom baghouse which, because of its large size, must be field assembled. It is often used on power plants, steel mills, or other applications too large for the factory-assembled baghouses. Prices for these units are shown in Figure 5_7.15 5.3.1.2 Bag Costs Table 5-6 gives the price per square foot ofbags by type of fabric and by type ofcleaning system used. The prices represent about a 10% range. In calculating the cost, the gross area as determined from Table 5-2 should be

## Caution: Donotextrapolate.



# ! Costwithoutba9s l..<IlIII LdI 

# •

.**i!~**

## 4Jj~~ l1!!

### Stainlesssteeladdon- L.- 

### tz,. 

# .- 10-**'-I---:~P"** 

### 9\\- liiII

# "'"**l~~~~~ be~9**  __... 6c



## 60 1-1- -jijIII 

### 1·l4iIP".l· 

### C50 1**~_** 

### ... >( 

### tz,.be\

.... !Q':>

... .--.-

### ~~~~~~**~~-** . 10- i--**~...** 1...1I

....



## .....

# Ill"~ 2 •**l~** 

### 0.335ft•.

## .1~s~I~~I~nl**a~~ fJ~**  , • i I
-i I" I I co 

### 600 

# m
.,..



## .... 500 

### as :J 

## o 

# :e 400 

# t=.



# - 8 300 

### o 

## .,.. EI:)- 

# - 1ii 

### 200 

## o 

## o



# - c CD 

### 100 

## E a. :J 

# aff 0

# o 10 20 30 40 50 60 GrossClothArea (1000ft2) 

### 70 

## 80 90 U1 • w



### Source: ETS, Inc.; FullerCo. Figure5-3.Equipmentcostsforcontinuousshakerfilters.

### Costwithoutbags= I--

I4lIIld

## .....

.

### ~~--",.,. .- 

### '(l2 .-IIJIIIII"



### .... 

### ,S'f{o2

....

## _-""'IIl -ii!!iI"""



## . ffO

. od8III"'"" 

## 6**~~** 

### Stainlesssteeladdon.

# - $ .;::;9"**:;;a~ ~_,.......**  

## 2- 

# -

...................... 4.54'\\\

..ollIIIIJIIIII" 

### 0489 

### --t; $ .;::; '\ '"1 I I I I I I 

### 2 

# $..: 1.428

## +0.931 ft Insulationaddon: I-- 1 I I I I 1 I 1 I I-- 

### 125

100 

## Caution: Donotextrapolate.

U1 I W U1



### 18 

### 16 14 6 8 10 12 GrossClothArea (1000

### ft

# 4 4 

### 2 1i) 

### 50 

### o 

# o

..... 55 25 

## E a. :J 

### tff 

## 0

# o co 

### 150 

# m ,...

.... 

# i :J 

## o "E 

## .- f=.



# .. 

# § 75



## ,... fh 

# -

Source: ETS. Inc.Figure6-4.Equipmentcostsforpulse-jetfilters(commonhousing).I I I I I I I**~.** _l 

# ...,..I!

. . . 

### Costwithoutbags**;i~"""** 

# •**~?,~** r::;;

....11""'" 

### 1· L.dIIII"'" IdIIIIl 

### Stainlesssteeladdon f},.O L4'I I-- I..II8Il! I--

## be1~ .... fl, IilP**~-~,... ~\\**  

# ........**~.** 'tIZ

### ~~~**~,...** .....11II""""**~-:** 

### liiiJII III"'"**Z~O~** 

### ......... fl,be, ' 'III'"

### ~~jj.~ ".. 

### 9ft2 I I 

### 3000

## + 2.01 Insulationaddon- $:::**'--~** I-- 

## Caution: Donotextrapolate.
co 

## co 0)orLa> t:: «1 ::J 

### 0 

## "E 

# .- ..t: I-



# .. 

# - 0 

# 8
or-


# - 1i) 0 

### 0 

# - c: a> 

## E a. 

# .- ::J 0- W



## ... 150

125

100



## 75

50

25



# oo 2 . 4 

### 6 8 10 12 GrossClothArea (1000

### ft 

### 14 16 

### 18 U'l I W m



### Source: ETS, 

### Inc, Figure5-5.Equipmentcostsforpulse-jetfilters(modular).

## Caution: Donotextrapolate.

# R=t:~~tti±£EffR+~~t6II-' II I I .-1 I 

### Costwithoutbagsr-tiWIII",'...dIlf

.. 

### +I-+-W.....I

# ~l~~Ef~~~ft~~~!~~~Ej3jEEI3~~l~~~ti~~EI~3 

# ...IJflII§t;;lii

... jIII1l



### w M-"'-H-I--I-I--J-W,....J**iIJ1~~**



# _ :::t:I-ti-H--Hrl_

...

# ~::J=IClJu.... tJ 

# p:ttttt+H-l+P=ntt'z; 

### Ii

# Ill! """"Iii

.. -

# o:::tt::r-H-H+I~UI. \'2.\\ J-

# ~.-~ ,.....

# ~~L...lf·+-t-H4-l-+::o:::t:l rt-r-H++-il-l--I-U
-

# 19_~..,j~ .....!-On

# at..oll~iIIi'I~:t:~±-8~Ptt:tjjj**c;~ Gi~**  l

# \\~ Will

...

# ~~St I I I

## n~')-'"**~t:;.I~'"** 'n1() "" anesssteeladdon-.....

# ~.(;iIIi 1-1-

# 'E>.~**lildll'tl:t:~~±BlfJR=fR=ii=P:E**

# H-+-~-1-..l-~ 7

# 6-ti~-- \ A' 

## w ........

# ~,.~:tt:t:t:BEI±8::t==t=~tt:t:t:fB3 ...-r-t-+-+-I-L-LL li1IIIIIP"..... n.

# ~~**~1odI~.±r:±:1=H~a:E:aEttf:t=t=HR=S:E:EI** l::ii--

# '\';}\~W~1lI""1c±t3:t+t:l:J:E±Et!ft:1R::t=t:l:EEej3

# H-t--t-I-+,....s~U.l..allilll.J_ ..1-

# ~~**;_~** .....

# 1:=E8j:t:1::f::t:t:lt81:Et!:f:t:1::f::t=SIEe~ H-+--f.....J-W L
-....

# ~all-±t:t:Et~=F~lEEtf!3:f:f:~=FEl:EEt33 ....1ilIIII 1_

...... .....-r+-+-I-lt.::.L...L

## $ = 

### 1,130

# +

# 0.000ft

### 2 Insulationaddon:::

_,. -. I • I I I I • I co 

### 600 

### co m



## ..... L.. 

### 500 as ::l 

## o "E 400 

# .-

.



# - § 300



## ..... (f.)- 

# - 00 200 

## o 

## o

..... c: Q) 

### 100 

## E a. ::l 

# aff 0

# o 10 20 30 40 50 60 

### GrossClothArea (1000ft 

## 70 80 90 U1 

## , W '-l



### Source: ETS, Inc. Figure5-60Equipmentcostsforreverse-aiFfilterso

## Caution: Donotextrapolate.

()1 I W (Xl



### 400 200 300 GrossClothArea (1000ft

# 4 100 0)Ti- 

### 2500 Costwithoutbags I I I I •**m""I~IT1'** :l 1

........... I I 1 II 

# o IIilIIiI!!t • I I --. I:iiiii !. I I I • 

### "E2000

.... 1111111

.... 

## :c 1::1

### iIlIl!!I .,**~,** 

### -.

.... r::;,jjjj'"[liE I I I I I. I I • '/..

.. 11111111111\-' .....::. 1....Oll I • I I. I -. 

# 8 1500

# ~'2-0~ ..- • I 

## o**~. I~"'"**  • I : I I. I. T- I_n.<\

... • I I. I 1--' U'!":I-::l -"".. I 

### 1ii 

### 1000 

# r'tll-b........ I 

### Stainlesssteeladdon 

### o 

# C!IJIIII I 

# o**.~** 

## 2

..... tI"'" 

### 2208

### 1\

. 1_

## ii~ 500$ 1 :::::

### 90,000

## + ., I 1 I I. I 

### E .' .1 I 1 I I' 

### 2 

### a. . 

## $

# =60184

# +0.637

### It I I. I I

._**_,,~** . I 1 I I • I I I :l 1 II 

## aB" 0 J. 1 

### Insulationaddon I I I I I**1~J. J.l~1~J.1J**  IT 

# o

Source: ETS8 

### Inc. figure6-7 Equipmentcostsforcustom-builtfilters,5-39
Table 5-6 Bag**Price~** (3rd quarter 1986 $/ft ) Type ofMateriala Bay Diameter Type ofCleaning inches) PE PP NO HA FG CO TF Pulsejet, TRb 4-1/2 to 5-1/8 0.59 0.61 1.88 0.92 1.29 NA 9.05 6to 8 0.43 0.44 1.56 0.71 1.08 NA 6.80 Pulsejet, BBR 4-1/2 to 5-1/8 0.37 0.40 1.37 0.66 1.24 NA 8.78 6to 8 0.32 0.33 1.18 0.58 0.95 NA 6.71 Shaker Strap top 5 0.45 0.48 1.28 0.75 NA 0.44 NA Loop top 5 0.43 0.45 1.17 0.66 NA 0.39 NA Reverse airwith 8 0.46 NA 

### l.72 NA 0.99 NA NA

rings 11-1/2 0.47 NA 1.69 NA 0.76 NA NA**Re~ers~** airw/o 8 0.32 NA 1.20 NA 0.69 NA NA rlngs 11-1/2 0.32 NA 1.16 NA 0.53 NA NA

but used in low pressure pulse applications. NA =Not applicable. aMaterials: PE = 16-oz polyester PP = 16-oz polypropylene NO

### =14-oz nomex HA = 16-oz homopolymeracrylic bBag removal methods: TR =Top bag removal (snap in) BBR

### =Bottombag removal cldentified as reverse-airbags, FG

### =16-oz fiberglass with 10% Teflon CO

### =9-oz cotton TF =22-oz Teflon felt

NOTE: Forpulse-jet baghouses, all bags are felts except for the fiberglass, which is woven. Forbottom access pulsejets, the cage price for one cage can be calculated from the single-bag fabric area using:

In 50 cage lots In 100 cage lots In 500 cage lots Mild steel cage $ =4.941 +0.163**ft~** $

### =4.441 +0.163 ft2 $ = 3.941 +0.163 ft Stainless steel cage $ _ 2

- 23.335 + 0.280 ft2 $ =21.791 +0.263 ft2 $ =20.564 +0.248 ft These costs apply to 4-1/2-in. or 5-5/8-in diameter, 8-ft and 10-ft cages made of 11 gauge mild steel and having 10 vertical wires and "Roll Band" tops. Forflanged tops, add $1 percage. Ifflow control venturis are used (as they are in about halfofthe pulse-jetmanufacturers' designs), add $5 per cage. For shakers and reverse airbaghouses, all 6ags are woven. All prices are for finished bags, and prices can vary from one supplierto another. ForGore-Tex bag prices, multiply base fabric price by factors of3to 4.5. Source: ETS, Inc.(15)

### 5-40

used. Gore-Tex fabric costs are acombination ofthe base fabric cost and a premium for the PTFE laminate and its application. As fiber market conditions change, the costs offabrics relative to each other also change. The bag prices are based on typical fabric weights, in ounces/squareyard, for the fabric being priced. Sewn-in snap rings are included in the price, but other mounting hardware, such as clamps or cages, is an added cost. 5.3.1.3 Auxiliary Equipment The auxiliary equipment depicted in Figure 5-1 is discussed elsewhere in the Manual. Because hoods, precoolers, cyclones, fans, motors, and stacks are
common to many pollution control systems, they are given extended treatment in the following tentatively numbered separate sections: capture hoods in Section 16, ductwork in Section 7, precoolers (spray chambers and quenchers) in Section 18, cyclones in Section 17, fans and motors in Section 8, and stacks in Section 11. Ifdust-removal equipment is to be considered, Section 19 discusses screw conveyors. 5.3.2 Total Purchased Cost The total purchased cost ofthe fabric filter system is the sumofthe costs ofthe baghouse, bags, auxiliary equipment, instruments and controls; and oftaxes and freight. The last three items generally are taken as percentages ofthe estimated total cost ofthe first three items. Typical values, from Section 2ofthe Manual, are 10% for instruments and controls, 3% for taxes, and 5% for freight. Bag costs can vary from less than 15% to more than 100% ofbare baghouse cost, depending on type offabric required. This situation makes it inadvisable to estimate total purchased cost without considering both costs, and prevents effective use offactors to estimate a single cost for the baghouse and bags.

### 5-41

5.3.3 Total Capital Investment Using the Section 2methodology, the total capital investment (TCI) is estimated from a series offactors applied to the purchased equipment cost to obtain direct and indirect costs for installation. The TCI is the sum of these three costs. The required factors are given in Table 5-7. Because bag costs can have such a large effect on total purchased equipment cost, the factors may cause overestimation oftotal capital investment when expensive bags are used. Using stainless steel components may also cause overestimation. Because baghouses may vary from small units installed within existing buildings to large, separate structures, specific factors for site preparation
or for buildings are not given. However, costs for buildings may be obtained from such references as Means Square Foot Costs 1986.(17) Land, working capital, and offsite facilities are excluded from the table, as they are not normally required. For very large installations, however, they may be needed and would be estimated on an as-needed basis. Note that the factors given in Table 5-7 are for average installation conditions. Considerable variation may be seen with other-than-average installation circumstances. 5.4 Estimating Total Annual Costs 5.4.1 Direct Annual Cost Direct annual costs include operating and supervisory labor, operating materials, replacement bags, maintenance (labor and materials), utilities, and dust disposal. Most ofthese costs are discussed individually below. They vary considerably with location and time, and, for this reason, should be obtained to suit the specific baghouse systembeing costed. Forexample, current labor rates may be found in such publications as the Monthly Labor Review, published by the U.S. Department of Labor, Bureau ofLabor Statistics.5-42

Table 5-7 Capital Cost Factors for Fabric Filters(8) Direct Costs Purchased equipment costs: Fabric fiHer Bags Auxiliary equipment
Instruments 

### &controls Taxes Freight Total purchased equipment cost Installation direct costs Foundations

## &supports Erection 

### &handling Electrical Piping Insulation for ductworka Painting Site preparation (S.P.) Buildings (Bldg.) Total installation direct costs

Total direct costs Factor

As

estimated A= Sum of As estimated As

estimated 0010 A 0.03 A 0.05 A 

### B= 

### 1.18A
0.04 

### B 0.50 B 0.08 B 0.01 B 0.07 B 0.02 B As required As reguired 

### 0.72 + S.P. + Bldg. 1.72 B+ S.P. + Bldg. Indirect costs Engineering 

### &supervlslon Construction and field expense Construction fee Startup fee Performance test Contingencies Total indirect costs Total direct and indirect costs = Total capital investment 0.10 

### B 0020 B 0.10 

### B 0.01 B 0.01 B 0.03 B 

### 0.45 B 2.17 B+ SoP. + Bldg.
aIfductwork dimensions have been established, cost may be estimated based on $10-12/ft2of surface for field application. Fan housings and stacks may also be insulated.15

### 5-43

5.4.1.1 Operating and Supervisory Labor Typical operating labor requirements are 2to 4hours per shift for a wide range offilter sizes.(8) Small orwell-performing units may require less time, while very large or troublesome units may require more. Supervisory labor is taken as 15% ofoperating labor. 5.4.1.2 Operating Materials Operating materials are generally not required for baghouses. An exception is the use ofprecoat materials injected on the inlet side ofthe baghouse to provide aprotective dust layeron the bags when sticky or corrosive particles might harm them. Adsorbents may be similarly injected when the baghouse is used for simultaneous particle and gas removal. Costs for these materials should be included on adollars-per-mass basis (e.g., dollars per ton). 5.4.1.3 Maintenance Maintenance labor varies from 1 to 2hours per shift.(8) As with operating labor, these values may be reduced orexceeded depending on the size and operating difficulty ofaparticular unit. Maintenance materials costs
are assumed to be equal to maintenance labor costs.(8) 5.4.1.4 Replacement Parts The major replacement part items are filter bags, which have anormal operating life of 1 to 5years with about 2years being typical. The following formula is used for computing the bag replacement cost: CRCB= 

### (CB+ 

### C L

) xCRFB where: CRCB

### =bag capital recovery cost ($/year) C

B= 

### initial bag cost including taxes and freight ($) (5-14)

### 5-44

C

l 

### =bag replacment labor ($) CRFB

## =capital recovery factor whose value is afunction ofthe annual interest rate and the useful life ofthe bags. (For instance, for a 10% interest rate and a2-year life, CRFB

## =0.5762.) The bag replacement labor cost (Cl) 

### will depend on such factors as the number, size, and type ofthe bags; their accessibility; how they are connected to the baghouse tubesheet; etc. Forexample, in areverse-air baghouse it would probably take from 10 to 20 man-minutes to change an 8-in. by 24-ft bag that is clamped in place. This bag has a filtering surface area ofapproximately 50 ft2• Ifthe replacement labor rate were $21.12/h (including overhead), C l 

### would be from $0.07 to $0.14/ft2ofbag area. As Table 5-6 shows, for some bags (e.g., cotton), this range ofC l 

### would constitute a significant fraction ofthe purchase cost. Forpulsejets, replacement time would be about 5to 10 man-minutes for a 5-in. by 10-ft bag in atop-access baghouse. These bag replacement times are based on changing a minimum ofan entire module and on having typical baghouse designs. Times would be significantly longer ifonly a few bags were being replaced or ifthe design for bag attachment or access were atypical. This method treats the bags as an investment that is amortized over the useful life ofthe bags, while the rest ofthe control system is amortized
over its useful life (typically 20 years; see Section 5.4.2). Values ofCRFB for bag lives different from 2years can be calculated from equation (2-3) of the Manual. 5.4.1.5 Electricity Power is reqUired to operate system fans and cleaning equipment. Fan power for primary gas movement can be calculated from equation (2-7) ofthe Manual. After substituting into this equation acombined fan-motor efficiency

### 5-45

of0.65 and a specific gravity of 1.000, we obtain:(18) F.P. 

### =0.000181(Q)(AP)(8) where: (5-15)

(5-16) F.P. 

## =fan power requirement (kWh/yr) Q

### =system flow rate (acfm) AP 

### =systempressure drop (in. H 2

0) 8 =

### operating time (h/yr) Cleaning energy for reverse-air systems can be calculated from the number ofcompartments to be cleaned at one time (usually one, sometimes two), and the reverse gas-to-cloth ratio (from about one to two times the forward gasto-cloth ratio). Reverse-airpressure drop varies up to 6or 7in. H 2

0 depending on location ofthe fan pickup (before or after the main system fan).(19) The reverse-air fan generally runs continuously. Typical energy consumption in kWh/yr for a shakercleaning system operated 8,760 h/yr can be calculated from:(2) P= 

### 0.053A where: A

### =gross fabric area (ft2) 5.4.1.6 Fuel Ifthe baghouse or associated ductwork is heated to prevent condensation, fuel costs should be calculated as required. These costs can be significant, but may be difficult to predict. Formethods ofcalculating heat transfer requirements, see Perry.(20) 5;4.1.7 Water Cooling process gases to acceptable temperatures for fabrics being used
can be done by dilution with air, evaporation with water, or heat exchange

### 5-46

with normal equipment. The last two cases require consumption ofplant water, although costs are not usually significant. Section 4.4 ofthe Manual provides information on estimating cooling-watercosts. 5.4.1.8 Compressed Air Pulse-jet filters use compressed air at pressures ofabout 60 to 100 psig. Typical consumption is about 2scfm/1,OOO cfmofgas filtered.(2) Forexample, aunit filtering 20,000 cfmofgas uses about 40 scfof compressed air for each minute the filter is operated. 5.4.1.9 Dust Disposal Ifcollected dust cannot be recycled or sold, it must be landfilled or disposed of in some othermanner. Disposal costs are site-specific, but they may typically run $20 or $30 per ton exclusive oftransportation (see Section 2.4) ofthe Manual. 5.4.2 Indirect Annual Cost These include such costs as capital recovery, property tax, insurance, administrative costs ("G&A"), and overhead. The capital**recove~** 

### cost is based on the equipment lifetime and the annual interest rate employed. (See Section 2for athorough discussion ofthe capital recovery cost and the variables that determine it.) For fabric filters, the system lifetime varies from 5to 40 years, with 20years being typical. However, this does not apply to the bags, which usually have much shorter lives. (See Section 5.4.1.4) Therefore, as Section 2ofthe Manual suggests, when figuring the system capital recovery cost, one should base it on the installed capital cost less the cost ofreplacing the bags (i.e., the purchased cost ofthe bags plus the cost of labor necessary to replace them). In otherwords:

### 5-47

where: CRCs 

### =capital recovery cost for fabric filter system ($/yr)

TCI = 

### total capital investment ($)



### =initial cost ofbags including taxes and freight ($) labor cost for replacing bags ($) capital recovery factor for fabric filter system (defined in Section 2). For example, for a20-year system life and a 10% annual interest rate, the CRFs would be 0.1175. The suggested factor to use for property taxes, insurance, and administrative charges is 4% ofthe TCI. Finally, the overhead is calculated
as 60% ofthe sum ofoperating, supervisory, and maintenance labor, and maintenance materials. 5.4.3 Recovery Credits Forprocesses that can reuse the dust collected in the baghouse orthat
can sell the dust in a local market, such as fly ash sold as an extender for paving mixes, acredit should be taken. As used below, this credit (RC) appears as anegative cost. 5.4.4 Total Annual Cost Total annual cost for owning and operating a fabric filter system is the
sum ofthe components listed in Sections 5.4.1 through 5.4.3, i.e.: TAC 

### =DC + 

### IC

- RC (5-18) where: TAC 

### =total annual cost ($)

DC 

### =direct annual cost ($) IC 

### =indirect annual cost ($) RC 

### =recovery credits (annual) ($)5-48

5.4.5 

### Example Problem Assume abaghouse is required for controlling fly ash emissions from a coal-fired boiler. The flue gas stream is 50,000 

### acfm at 325 of 

### and has an ash loading of4gr/ft3• Analysis ofthe ash shows amass median diameterof 7

### pm. Assume the baghouse operates for 8,640 

### h/yr (360 

### d). Design Gas-to-C10th Ratio The gas-to-c10th ratio (G/C) can be taken from Table 5-1 

### as 2.5, 

### for
woven fabrics in shaker or reverse-airbaghouses, or 5, for felts used in pulse-jet baghouses. Ifafactor method were used for estimating G/C, Table 5-3 

### for shakers wouldyield the following values: A

### =2, B

### =0.9, 

### and C

### =1.0. 

### The gas-to-cloth ratio would be: 2

### x0.9 

### x 1.0

## =1.8. 

### This value could also be used for reverse-aircleaning. For apulse-jet unit, Table 5-4 

### gives a value of 9.0 

### for factor Aand 0.8 

### for factor B. Equation (5-12)**becomes~**


### v=9.0 

### x0.8 

### x 2.647 (275)-0.2335 

### x (0.7471 +0.0853 

### 1n 7)
x 1.0873 (4)-0.06021

= 4.69 (5-19)



### Because this value is so much greater than the shaker/reverse-airG/C, we conclude that the pulse-jet baghousewou1d be the least costly design.*

*This conclusion is based on the inference that amuch higherG/C would yield lower capital and, in turn, annual costs. However, to make amore rigorous selection, we would need to calculate and compare the total annual costs ofall three baghouse designs (assuming all three are technically acceptable). The 

### reader is invited to make this comparison. Further discussion ofthe effects ofG/C increases, and accompanying pressure drop increases, on overall annual costs will be found in Reference 21.

### 5-49

Assume the use ofonline cleaning in a common housing structure and, due to the high operating temperature, the use ofglass filter bags (see Table 5-5). At agas-to-cloth ratio of4.69, the fabric required is: 50,000 acfm/4.69 

### fpm = 

### 10,661 ft2• Baghouse Cost From Figure 5-4, the cost ofthe baghouse ("common housing" design) is: Cost 

### =9,688 + 

### 5.552 (10,661)



### =$68,878 (5-20)

(5-21) Insulation is required. The insulation add-on cost from F.igure 5-4 is: Cost = 

### 1,428 +

### 0.931 (10,661)



### =$11,353 Bag and Cage Cost From Table 5-6, bag costs are $1.24/ft2 

### for 5-1/8-in diameterglass fiber, bottom removal bags. Total bag cost is: 10,661 ft2x$1.24/ft2

### =$13,220. For 10-ft long cages, fabric area per cage = 5-1/8 

### in./12 in.

### 1ft x x 10 ft = 

### 13.42 ft2• The number ofcages 

### =10,661 ft2 /13.42 

### ft2

### =795 cages. From Table 5-6, individual cage cost is: 3.941 + 

### 0.163 (13.42 ft2) = 

### $6.128. Total cage cost is: 795 cages x$6.128/cage = 

### $4,872. Costs ofAuxiliaries Assume the following auxiliary costs have been estimated from data in otherparts ofthe Manual:

### 5-50

Ductwork $16,000 Fan 16,000 Motor 7,500 Starter 4,000 Dampers 7,200 Screw conveyor 4,000 Stack 8,000 $62,700 Total Capital Investment Direct costs for the fabric filter system, based on the factors in Table 5-7, are given in Table 5-8. (Again, we assume site preparation and buildings costs to be negligible.) Total capital investment is $412,315. Annual Costs--Bags Table 5-9 gives the direct and indirect annual costs, as calculated from the factors given in Section 5.4. Forbag replacement labor, assume 10 min perbag for each ofthe 795 bags. At amaintenance labor rate of $21.12 (including overhead), the labor cost is $2,809 for 133 h. The bags are assumed to be replaced every 2yr. The replacement cost is calculated using equation (5-14). Annual Costs--Pressure Drop Pressure drop (for energy costs) can be calculated from equations (5-8) through (5-10), with assumed values of 15 [in. H 2

o/(ft/min)]/(lb/ft2) for K 2, 100 psig for P j , 

### and acleaning interval of 10 min. We further assume that the G/C (4.69 ft/min) is agood estimate ofthe mean face velocity over the duration ofthe filtering cycle.

### 5-51

Table 5-8 Example Costs-for Fabric Filter System

Purchased Equipment Costs Fabric filter (with insulation) Bags and cages Auxiliary equipment
Instruments and controls, O.lA Taxes, 0.03A Freight, 0.05A Total purchased equipment cost Installation Direct Costs Foundation and supports, 0.04B Erection and handling, 0.50B Electrical, 0.08B Piping, O.OlB Insulation for ductwork, 0.07B Painting, 0.02B Site preparation Facilities and buildings Total installation direct costs Total direct costs Indirect Costs Engineering and supervision, 0.10B Construction and field expense, 0.20B Construction fee, 0.10B Startup fee, O.OlB Performance test, O.OlB Contingencies, 0.03B Total indirect costs Total capital investment $80,231 18,092 62,700 $161,023 =

### A 16,102

4,831 8,051 $190,007 = 

### B 7,600 95,004 15,201

1,900 13,300

3,800 $136,805 $326,812 19,001 38,001 19,001

1,900 1,900 5,700 $85,503 $412,315

### $25,920 3,888 5-52

Table 5-9 Example Annual Costs for Fabric Filter Systems Direct Annual Costs Operating labor Operator, 6 h/day x360 d/yr x$12/h = Supervisor, 15% ofoperator

### = Operating materials Maintenance Labor, 3 h/day x360 d/yr x $13.20/h = 14,256 Material, equal to labor costs 14,256 Replacement parts, bags, [2,809 + 

### (13,220 x 1.08*)] x0.5762 = 9,845 Utilities Electricity, 0.000181 x50,000 acfm x 10.3 in. H 20 x8,649 h/yr x $0.06/kWh = 48,323 Compressed air (dried and filtered), 2 scfm/1,OOO acfm



### x50,000 acfm 

### x$0.16/1,000 scfm 

### x60 min/h 

### x8,640 h/yr = 8,294 Waste disposal, at $20/ton onsite for essentially 100%

collection efficiency:

### 4~ ft 3 1 

### lb 50,000 ft 

### x60 min x8,640 h x 1 ton $20

- 8 

### 7,000 gr

### x mln 

### h yr 

### 2,000 16 xton

- 14 ,114

Total direct annual costs Indirect Annual Costs Overhead, 0.6 x (25,920 + 

### 3,888 + 

### 14,256 + 

### 14,256) 

### = Property tax, 0.01 

### x412,315 = Insurance, 0.01 x412,315= Administration, 0.02 x412,315= Capital recovery cost, (412,315

- 2,809

- 13,220 x 1.08)

x0.1175 Total indirect annual costs Total annual cost
*The "1.08" accounts for freight and sales tax on the bags. 

### $272,896 34,992

4,123 4,123 8,246 46,439 97,923 $371,000 (rounded)5-53



### 3 1 lb W

o

### =C iV6 

### =4

### grift x

### 7,000 gr x4.69 

### ft/min x 10 

### min 

### =0.0268 

### lb/ft2 (5-22)
-0.65 

### AP 

### =6.08 

### x4.69 

### ft/min x [100 

### psi9J + 15 

### [in. 

### H 2

### 0/ft/min)]/(lb/ft2)



### x0.0268 

### lb/ft2

### x4.69 

### ft/min 

### =3.32 

### in. 

### H 20 

### across the fabric (when fully loaded). Assume the baghouse structure and the ductwork contribute an additional 3 

### in. H

20 

### and 4

### in. H 20, 

### respectively. The total pressure drop is, therefore, 10.3 

### in. Total Annual Cost The total annual cost is $371,000, 

### nearly halfofwhich is for ash disposal. Ifamarket for the flyash could be found, the total annual cost would be greatly reduced. Forexample, if $2/ton 

### were received for the ash, the total annual cost would drop to $208,000 ($370,819

- $148,114

- $14,811),


### or 56% 

### ofthe cost when no market exists. Clearly, the total annual cost is extremely sensitve to the value chosen for the dust disposal cost in this
case. In this and in similar cases, this value should be selected with care. 5.4.6 

### Acknowledgment We gratefully acknowledge the following companies for contributing data to this section: Aget BACT BHA Dustex Fuller Griff;n W. W. 

### Sly Zurn3. .2. 

### 5-54

References for Section 5 1. Turner, J. H., "Bag Filtration," in Handbook ofMultiphase Systems, ed. by G. Hetsroni, Hemisphere, 1982. 2. Turner, J. H., and J. D. McKenna, "Control of Particles by Filters," in Handbook ofAir Pollution Technology, ed. by S. Calvert and H. Englund, New York: John Wiley

## & Sons, 1984. 3. Donovan, R. P., Fabric Filtration For Combustion Sources, New York: Marcel Dekker, Inc., 1985, p. 201. 4. Dennis, R., and H. A. Klemm, "Modeling Concepts for Pulse Jet Filtration." JAPCA, 30(1), January 1980. 5. Leith, D. and M. J. Ellenbecker, "Theory for Pressure Drop in a Pulse Jet Cleaned Fabric.Filter." Atm. Environment, 14, 1980, pp. 845-852. 6. Koehler, J. L. and D. Leith, "Model Calibration for Pressure Drop in a Pulse-Jet Cleaned Fabric Filter," Atm. Environment, 17(10), 1983, pp. 1909-1913. 7. Northrop Services, Inc. Fabric FilterWorkshop Reference Materials, 1977 Workshop. Air Pollution Tralnlng Institute. 8. Vatavuk, W. M., and R. B. Neveril, "Estimating Costs ofAir-Pollution Control Systems, Part II: Factors for Estimating Capital and Operating Costs," Chemical Engineering, November 3, 1980, pp. 157-162. 9. Frey, R. F., and To 

### V. Reinauer, "New Filter Rate Guide," Air Engineering, 30 April 1964.

--- lO. Dennis, R., et al. Filtration Model for Coal Fly Ash with Glass Fabrics, August 1977 (EPA-600/7-77-084 (NTIS PB 276489]). ll. 

### Owen, M. K. and A. S. Viner, Microcomyuter Programs for Particulate Control, June 1985 (EPA-600/8-85-025a • Dennis, R. and H. A. Klemm. Fabric FilterModel ChaQge: Vol. I Detailed Technical Report. February 1979 (EPA-600/7-79-043a [NTIS PB 293551). Viner, A. S., et al. "Comparison ofBaghouse Test Results with the GCA/EPA Design Model." JAPCA, Vol. 34(8), August 1984•

.4. Reigel, S. A. and R. P. Bundy. "Why the Swing to Baghouses?" Power, 121-1, pp. 68-73, January 1977 (modified)•

.5. ETS, Inc., Suite C-I03, 3140 Chaparral Dr. SW, Roanoke, VA 24018-4394. 6. FullerCompany, P.O. Box 2040, Bethlehem, PA 18001.17. 18.
19.
20.
21. 5-55



### R. S. Means Company, Inc., Means Square Foot Costs 1986, 

### Kingston, MA. Perry, Robert H., et al., perr

# 1's Chemical**En~ineers'** 

### Handbook (Fourth Edition), New York: McGraw-Ai 

### I, 1963, p. 6- 

### O. Personal communication from Gary Greiner, ETS, Inc., to JimTurner, Research Triangle Institute, October 24, 1986. 

### Perry, Robert H., et al., perr

# 1's Chemical Engineers' Handbook (Sixth Edition), New York: McGraw-Ai I, 

### 1984. McKenna, J. 

### D., J. H. Turner, D. Furlong, and D. S. Beachler, Fabric Filters-Baghouses, It Theory, Desi8n and Selection, in preparation, ETS, Inc., Suite C-103, 340 Chaparral r. 

### 5W, Roanoke, VA 24018-4394.