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## Bagasse Boilers Should be Regulated in a Separate S ubcategory
under the Boiler MACT Rules Because they are a Unique Class of Boilers

Submitted by the Florida Sugar Industry 1

May 14, 2009



### I. Introduction

The U. S. Environmental Protection Agency (EPA) is currently developing new Boiler MACT rules that will regulate many types of industrial boilers, inc luding the bagasse boilers operated by the Florida Sugar Industry. Accordingly, the Florida Sugar Industry is providing this white paper to EPA to explain why (a) bagasse boilers constitute a unique class of in dustrial boilers, and (b) bagasse boilers should be placed in a separate subcategory under the new Boiler MACT ru les.

Bagasse boilers exhibit several distinctive design, operating, and emissions characteristics when burn ing bagasse. These characterisitcs can be summarized a s follows: (a) Bagasse is a unique fuel, with high moisture conten t and low density; (b) Bagasse boilers are uniquely designed and operated to burn bagasse; and (c) Bagasse boilers are fully integrated with sugar mil l and the other boilers at the mill.

When these characteristics are considered together, it is clear that bagasse boilers constitute a uniq ue class of industrial boilers. Consequently, bagasse boile rs should be regulated in a separate subcategory un der the new Boiler MACT rules. This subcategory should not include other types or classes of boilers (e.g., b oilers that burn other types of biomass or fossil fuel).

Bagasse is produced when a sugar mill is extracting sugar from sugarcane. Bagasse is the wet fibrous material remaining after the sugarcane has been cut , ground, and repeatedly washed and pressed to reco ver as much sucrose as possible. Since the very beginn ing of its operations in the United States, the sug ar producing industry has used bagasse as the primary fuel for its boilers. Bagasse boilers are specific ally designed to dry and burn the bagasse in one unit, a nd the boilers are wholly integrated into the opera tions of the sugar mills. As bagasse is produced in the mil ling process, it is fed directly into the boilers, where the bagasse is dried and burned. In a typical integrat ed sugar mill, the burning of the bagasse generates enough heat to produce the steam and electricity needed to power the operation of the sugar mills.

Many times in the past, EPA has created various sub categories in rulemaking under the Clean Air Act (CAA) because EPA has recognized that a facility’s emissions can be significantly affected by the facility’s fuel, design, size, age, and use. When establishing the upcoming Boiler MACT rules, EPA ha s the statutory authority pursuant to Section 112 of the CAA to create subcategories based on “classes, types, or sizes” of industrial boilers.

1 The Florida Sugar Industry is comprised of sugarcan e processors located in south Florida. These proce ssors harvest sugarcane to produce raw and/or refined sug ar. The FSI operates industrial boilers fired prim arily by bagasse, which is a co-product of the sugarcane pro cessing operations. Wood and other agricultural ma terials, as well as very limited amounts of fossil fuel, may al so be burned in the FSI’s boilers. The FSI also is coordinating the submittal of this paper with a sugarcane processor located in Hawaii.May 2009 0838-7513

Reports/Boiler MACT 2/Separate Class of Bagasse Boi lers 05-14-09.doc 2 EPA should create a subcategory for bagasse boilers because these boilers constitute a distinct class. Their design and operation sets them apart from oth er solid fuel boilers. Their unique characteristic s significantly affect the boilers’ emissions. Bagas se also has distinctive characteristics that affect the boilers’ emissions. Creating a subcategory for bag asse boilers, based on the class of boilers or fuel type, will help ensure that the MACT emissions standards for bagasse boilers are based on the performance of “similar sources,” as required by the CAA. Convers ely, EPA would not be able to establish an appropriate MACT floor for bagasse-fired boilers if bagasse boilers were regulated in a MACT category that includes other types or classes of solid fuel- fired or biomass boilers.



### II. Background Information on Sugarcane and Sugarc ane Processing

The following discussion summarizes some basic info rmation about sugarcane, sugarcane processing, bagasse, and bagasse boilers. Sugarcane is a membe r of the grass family, and is grown in numerous countries around the world, including the United St ates, China, India, Cuba, Venezuela, Indonesia, Australia, and many more. The cane grows year roun d, but typically the harvesting and milling operations occur over just a few months. In the U. S., the sugar mills typically run 24 hours per day during the milling season. The milling operations usually are completed in 3 to 4 months in Louisiana

, 4 to 6 months in Florida, and 9 months in Hawaii.

The tops of the sugarcane plants and most of the le aves are removed in the field and then the cane is brought to the mills in large trailers by truck or railcar. The typical composition of the sugarcane is presented in Table 1, below.

Table 1. Typical Sugarcane Composition (from vario us literature sources)

Water 75% Sugars 12% (mostly sucrose, with some glucose & fructose) Fiber/Pith 12% (mostly cellulose, with some li gnins) Other 1 to 2% (mostly salts and soil minerals , with some organic compounds)

In the sugar mill, the cane is first cut into small er pieces. 2 Next the sugarcane is subjected to grinding and washing, which may occur 4 to 8 times in a suga r mill “tandem.” This process extracts as much of the sugarcane juices (primarily sucrose) as possibl e from the cane. This process also removes some, b ut not all, of the soil that may be clinging to the ca ne (carried in from the fields). The sugarcane juices are then clarified and evaporated to produce raw sugar crystals.

Bagasse is the traditional name given to the cellul osic fiber and pith that remain after the sucrose j uice has been extracted from a sugarcane stalk during the mi lling process. The composition of the biomass is changed in this process of producing bagasse from s ugarcane. The typical composition of bagasses is
shown in Table 2.

Table 2. Typical Bagasse Composition

Water 48 to 55% Sugars 1 to 2%
Fiber/Pith 44 to 50%
Other 1 to 4%

2 In Hawaii, but not Florida, the cane is washed in a cane “cleaner” prior to cutting. The cleaner is used to remove
some of the extraneous soil that adheres to the can e when it is brought in from the fields.May 2009 0838-7513

Reports/Boiler MACT 2/Separate Class of Bagasse Boi lers 05-14-09.doc 3 The heat needed to operate the evaporators in the s ugar production process, and the power needed to operate the mill equipment, are obtained by burning the bagasse in boilers that are specifically desig ned for the simultaneous drying and combustion of bagas se. The design of a sugar mill always includes the complete integration of the bagasse-burning boilers with the rest of the mill. The bagasse generated in the mill is normally sent directly to the boilers a s fuel. The boilers produce steam, which in turn i s used
in the mill. The steam also is used in steam turbi ne generators to produce electricity for the mill’s internal consumption. In some locations, excess el ectricity is fed back into the local power grid.



### III. Design and Operation of Bagasse Boilers

The design and operation of bagasse boilers differs significantly from other solid fuel boilers (even other biomass boilers). First, because bagasse contains about 50% moisture, it must be dried before it can be burned. This is accomplished in boilers specifical ly designed for this task. The bagasse typically i s conveyed directly from the mill to the boiler and t hen is dropped into chutes and fed into the boilers by means of fuel distributors. The distributors injec t air at the point where the bagasse is introduced into the boiler in order to spread the baggase over the boil er width. The drying (and much of the combustion) occurs while the material is suspended in air. Hen ce, they are often called “suspension” boilers. However, some of the bagasse is not burned complete ly and falls to the grate or floor below, where the combustion continues. Accordingly, many bagasse bo ilers have grates of various types, which allow
additional air to mix with the fuel and thus enhan ce the combustion. For this reason, many bagasse
boilers can also be called “stoker” boilers. In re ality, bagasse boilers utilize a combination of sus pension firing and grate firing, and that affects the perfo rmance of the boilers.

Bagasse boilers almost universally are designed to have high heat release rates ([all except one above 22,800 British thermal units per hour per cubic foo t (Btu/hr-ft 3 )]. These high heat release rates are needed to quickly dry the wet bagasse as it is blow n into the boilers. Despite the high heat release rates, the combustion temperatures are considerably lower than in other classes of boilers, due mainly to the wet nature of the fuel. The high heat release rate s means shorter residence times for flue gases. Consequently, even though bagasse is a very clean f uel with respect to metals, sulfur and chlorine, th e wet bagasse and the shorter residence times in the boiler result in an incomplete burn out of carbon monoxide (CO). As a result of these factors, the c oncentrations of CO in the furnace gases can be ver y high in comparison with the CO emissions from other classes of boilers. Conversely, the lower temperature in the furnace results in significantly lower NO

x emissions compared with other classes of
boilers.

Normally, bagasse generated in the mill is fed dire ctly to the boilers, without any intermediate stora ge. No blending or further processing of the bagasse ta kes place prior to combustion in the boilers. This characteristic of bagasse boilers differs from othe r biomass-fired boilers. Because the boilers recei ve the bagasse as it is produced, the performance of the b oilers can be adversely affected when there is variability in the moisture content or other charac teristics of the bagasse being produced by the suga r mill. Since the moisture content of the bagasse of ten fluctuates significantly, there often is consid erable variability (minute-to-minute and hour-to-hour) in the CO concentrations and emissions from bagasse
boilers.

All of the mill’s boilers are tied into a single st eam header, which provides high-pressure steam to t he sugar mill tandems that grind the sugarcane. The i ntegrated operations of the boilers and the sugar m ill tandems is a unique feature of sugar mills. High-p ressure steam is also provided to steam turbine electrical generators, and low pressure steam is pr ovided to the raw sugar manufacturing process. Because all of the operations are integrated (i.e., linked together), the boilers’ emission rates are affectedMay 2009 0838-7513

Reports/Boiler MACT 2/Separate Class of Bagasse Boi lers 05-14-09.doc 4 by mill steam demand, mill upsets, startups/shutdow ns, and other events occurring in the mills which affect steam consumption affect the steam load on t he boilers. Operating conditions in one boiler can also adversely affect the other boilers, again due to the effect on steam demand.

Appendix A contains additional technical informatio n concerning the unique design features of bagasse boilers. Appendix A also contains additional techn ical information comparing bagasse boilers to woodfired boilers.



### IV. EPA’s Statutory Authority to Create Subcategori es

Section 112 of the CAA contains the statutory requi rements for establishing emission standards for
industrial boilers based on the use of maximum achi evable control technology (MACT). Section 112(d)(1) of the CAA expressly authorizes E PA to establish subcategories:

The [EPA] Administrator shall promulgate regulation s establishing emission standards for each category or subcategory of major sources...T he Administrator may distinguish among classes, types, and sizes of sources within a category or subcategory in establishing such standards...

Section 129 of the CAA also authorizes EPA to disti nguish between classes, types, and sizes of units when setting MACT standards for incinerators. When construing Section 129, the U.S. Court of Appeals
noted that EPA has “broad discretion to differentia te among units in a category” while setting MACT standards. Northeast Maryland Waste Disposal Autho rity v. EPA , 358 F.3d 936, 946 (D.C. Cir. 2004).
The court concluded that the term “class” is “not d efined in the Clean Air Act, and the dictionary definition –‘a group, set, or kind marked by common attributes’- could hardly be more flexible.” Id . The court’s analysis implies that EPA may reasonably es tablish subcategories based on a “class” whenever EPA finds that there is a “group, set, or kind” of unit (boiler, incinerator, etc.) marked by common
attributes.

EPA has exercised its discretionary authority to cr eate subcategories in many prior MACT rulemaking proceedings. For example, EPA previously created s ubcategories when EPA set the MACT emissions standards for industrial boilers, electric utility steam generating units, and municipal waste combust ors. EPA created these subcategories because EPA wanted to account for the differences between source types, the types of fuel used, the size of the regu lated units, and other factors. In EPA’s “Notice o f Regulatory Finding on the Emissions of Hazardous Ai r Pollutants from Electric Utility Steam Generating Units” [Federal Register (FR), December 20, 2000], EPA stated:

In developing standards under Section 112(d) to dat e, the EPA has based subcategorization on considerations such as: the si ze of the facility, the type of fuel used at the facility, and the plant type. The EPA may a lso consider other relevant factors such as geographic conditions in establishing subca tegories.

In EPA’s 2004 MACT proposal for electric utility st eam generating units (Utility MACT) (FR, January 30, 2004), EPA stated that it has broad discretion to create subcategories based on these same criteri a (i.e., size of the facility, type of fuel used, and plant type). [pg. 4664] In addition, “EPA also is free to consider other relevant factors, such as geographic factors, process design or operation, variations i n emission profiles, or differences in the feasibilit y of application of control.” [pg. 4664] In the Ut ility MACT, EPA exercised its discretion by proposing to create five separate subcategories for coal-fired electric utility boilers. [pg. 4666]. Four of the proposed subcategories were based on the type of co alMay 2009 0838-7513

Reports/Boiler MACT 2/Separate Class of Bagasse Boi lers 05-14-09.doc 5 burned (i.e., bituminous/anthracite, sub-bituminous , lignite, and coal refuse). The fifth subcategory was based on the type of process used by the utility to convert coal into electricity (i.e., integrated ga sification combined cycle technology).

In EPA’s 2008 MACT proposal for mercury cell chlor- alkali plants (73 FR 33258; June 11, 2008), EPA noted that “EPA’s broad authority to establish cate gories and subcategories of industry sources is fir mly established, and has been recognized as entitled to substantial deference by the U.S. Court of Appeals for the D.C. Circuit and the U.S. Supreme Court.” [page 33273]. In defense of its decision to create a subcategory for mercury cell chlor-alkali plants, E PA stated that “we have a long history of using subcategorization . . . Subcategories, or subsets o f similar emission sources within a source category, may
be defined if technical differences in emissions ch aracteristics, processes, control device applicabil ity, or opportunities for pollution prevention exist within the source category. This policy is supported by section 112(d)(1), the legislative history, our pri or rulemakings, and judicial precedent.” (emphasis added) [Id .]

EPA has previously used criteria such as furnace he at release rate in developing NSPS subcategories fo r boilers. For example, 40 CFR 60 Subpart Db contain s separate NO

x limits for low heat release rates boilers and high heat release rate boilers burning fuel oil. For purposes of Subpart Db, a high heat release rate is defined as greater than 70,000 Btu/ hr-ft 3 and a low heat release rate is less than or equal to 70,000 Btu/hr-ft 3

Another example of EPA using subcategories to set e mission standards involved the NSPS for municipal waste combustors (MWCs) in 40 CFR 60, Subpart Ea. In this rulemaking, EPA set new standards for two categories of MWC combustor types. In the 1995 emission guidelines, EPA identified three distinct types of MWC units that burn refuse-derived fuel (R DF), as follows: (1) RDF stoker, (2) pulverized coal/RDF mixed fuel-fired combustor, and (3) spread er stoker coal/RDF mixed fuel-fired combustor. Recently, EPA identified two additional types of RD F-fired MWC designs that do not fit within the thre e types of RDF combustors defined in the regulations. Since none of the three previous subcategories of RDF municipal waste combustors correctly describe t he design or operation of these particular units, EPA recognized a need to add combustor types that w ould adequately describe and set CO emission
limits for these combustors. The EPA therefore add ed definitions for ‘‘spreader stoker RDF-fired combustor/100 percent coal capable’’ and ‘‘semi-sus pension RDF-fired combustor/wet RDF process conversion.’’ This latter subcategory was defined a s follows:

Semi-suspension refuse-derived fuel-fired combustor /wet refuse-derived fuel process
conversion means a combustion unit that was converted from a w et refuse-derived fuel process to a dry refuse-derived fuel process, and b ecause of constraints in the design of the system, includes a low furnace height (less tha n 60 feet between the grate and the roof) and a high waste capacity-to-undergrate air z one ratio (greater than 300 tons of waste per day (tpd) fuel per each undergrate air zo ne).

For these additional MWC technology types, EPA crea sted CO emission limits based on the use of good combustion practices. A spreader/stoker RDF-fired combustor/100-percent coal-capable combustor feeds RDF into the combustion zone by a mechanism t hat throws the fuel onto the grate from above. Combustion takes place both in suspension and on th e grate. Such a unit is capable of firing 100-perc ent coal as a replacement for RDF. A semi-suspension R DF-fired combustor/wet RDF process conversion
means a combustion unit that was converted from wet RDF processing to dry RDF processing. For both of these technologies, CO emission limits were prom ulgated by EPA based on the CO levels achievable with good combustion practices.May 2009 0838-7513

Reports/Boiler MACT 2/Separate Class of Bagasse Boi lers 05-14-09.doc 6 Section 112(d)(3) of the CAA indicates that the MAC T floor for new sources shall be established by determining “the maximum degree of reduction in emi ssions that is deemed achievable for new sources in a category or subcategory”. The MACT floor for new sources must be based on the emissions achieved by “the best controlled similar source, as determined by the Administrator” [Section 112(d)(3 )]. The EPA’s regulations define the term “similar sour ces” to mean:

“ a stationary source or process that has comparable emissions and is structurally similar in design and capacity to a constructed or reconstructed major source such that the source could be controlled using the same contr ol technology .” [40 CFR 63.41]

When the definition of “similar source” is read in conjunction with the mandate in Section 112(d)(3), which requires EPA to evaluate similar sources when setting MACT standards, it is clear that EPA has
the discretion to establish MACT standards and MAC T categories that account for the differences in design and capacity between sources. Indeed, the u se of subcategories is necessary to ensure that EPA ’s MACT standards are only applied to groups or classe s of sources that have similar design, operational, and performance characteristics for controlling HAP emissions.

Therefore, when setting MACT standards for industri al boilers, it appears that EPA is authorized to distinguish between: (a) General classes or types of fuels (e.g., solid , liquid, and gaseous fuel); (b) Specific classes or types of solid fuels (e.g. , coal, wood, bagasse, and other biomass); (c) Types of boilers (e.g., spreader stoker, fuel cell, fluidized bed, bagasse); (d) Sizes of boilers; and (e) Geographical locations of the boilers.

Determining the appropriate source categories and s ubcategories is a critical first step when EPA sets the MACT floor for biomass-fired boilers, because there are a wide range of combustion processes, control technologies, unit sizes, and fuels used by biomass -fired boilers. These factors can have major impac ts on a boiler’s performance and emissions profile.

Based on the analysis set forth in the preceding pa ragraphs, the Florida Sugar Industry believes the
MACT standards for industrial boilers should includ e a category for biomass boilers, and a separate subcategory for bagasse boilers. These categories and subcategories are necessary to ensure that EPA only compares the performance of “similar sources” when EPA sets the emissions standards for bagassefired boilers. As explained below, boilers that bu rn bagasse constitute a separate class of boilers t hat are
different than other solid fuel and biomass boilers . Technical support data is provided in Appendix A

. Given the differences between bagasse boilers and o ther types and classes of boilers, EPA should creat e a separate subcategory for bagasse boilers, and thi s subcategory should not include boilers that burn wood or other types of biomass.



### V. Characteristics of Bagasse and Bagasse Boilers

Bagasse and bagasse boilers have many distinctive c haracteristics. When all of these characteristics are considered together, it is apparent that bagasse bo ilers are a unique class of boilers. These boilers must contend with the chemical and physical nature of th e fuel, the drying and combustion of the fuel in th e boiler, and other factors that affect the design an d operation of the bagasse boilers. These combined characteristics warrant the creation of a separate class and subcategory in the new Boiler MACT rules. Refer to Appendix A for additional technical inform ation concerning the unique design features of bagasse boilers.May 2009 0838-7513

Reports/Boiler MACT 2/Separate Class of Bagasse Boi lers 05-14-09.doc 7 A. Key Characteristics of Bagasse Fuel

Bagasse has the following key characteristics, whic h collectively make bagasse unique and much different than other types of biomass fuel:

• Bagasse is a co-product of an industrial process, w herein sugarcane is crushed and washed, and water displaces sucrose within the sugarcane fiber;

• The industrial process alters the composition of th e biomass;

• The bagasse goes directly from the process (mill) t o the boilers for fuel;

• The geographic area in which sugarcane is grown, an d the variety of sugarcane that is grown, affects the composition of the bagas se;

• Bagasse is about 3 times less dense than wood.

• Bagasse boilers must be designed specifically and u niquely to burn this fuel:

• Bagasse absorbs moisture while stored;

• Harvesting conditions and harvesting methods affect the composition, including the moisture content of the bagasse;

• Bagasse as produced and burned has a high moisture content (48 to 55 percent);

• It is very low in heavy metals;

• It is typically only 2 percent ash;

• The heating value [British thermal units per pound (Btu/lb)] as-fired is ample, but it is relatively low by comparison to the heati ng value of wood and other types of biomass;

• Its use eliminates the need to import and use milli ons of gallons of fuel oil 3 or other types of fossil fuel each year in Florida and Hawaii, and thus its use greatly reduces the emissions of greenhouse gases in Florid a and Hawaii; and

• It is a renewable resource, which is produced annua lly without disturbing new
land.

Bagasse consistently contains from 48- to about 55- percent moisture as produced, and about 2-percent ash. The solids portion is composed mostly of cell ulose fiber and pith, but it also contains some minerals, ash, and a small amount of sugars. It is bagasse’s high moisture content in combination wit h its processed state (highly fibrous with high porosity) that renders it unique compared with other forms o f biomass. This high moisture content has a direct ef fect upon its combustion characteristics, as has be en recognized by researchers. 4

Bagasse is also distinctive in that it is “spongy,” like peat moss. Consequently, the bagasse absorbs moisture more easily than woody biomass. Moisture is absorbed and contained in tiny pores throughout the bagasse material, as opposed to woody biomass, where the moisture is primarily surface moisture.
This difference affects the combustion characterist ics of bagasse and emissions of organics (especiall y CO).

Both the high moisture content and the low ash cont ent of bagasse is a result of the thorough washing of the sugarcane during the processing to extract the sugars. In this process, water displaces sucrose w ithin

3 The Florida Sugar Industry estimates that the use o f bagasse in Florida’s sugar mills offsets or displ aces the use of approximately 150 million gallons of fuel oil each year.

4 Shanmukharadhya, K.S. and Sudhakar, K. G., “Effect of Fuel Moisture on Combustion in a Bagasse Fired Furnace,” Transactions of the ASME, Vol. 129, Septe mber 2007.May 2009 0838-7513

Reports/Boiler MACT 2/Separate Class of Bagasse Boi lers 05-14-09.doc 8 the fiber of the sugarcane. The washing removes so me, but not all, of the soil material that comes in to the mill with the sugarcane.

As noted above, the mill-run bagasse has a moisture content ranging from 48 to 55 percent, but it also has a heat content of about 3,600 to 4,200 Btu/lb as-fi red. Consequently, bagasse can be readily used as a valuable fuel. Indeed, bagasse has been the main f uel of the sugar industry for the past 200 years.

When bagasse is burned, small amounts of ash remain , most of which either falls out as bottom ash or i s collected by air pollution control devices. Most o f the sugar industry uses wet scrubbers and/or mult iclones to capture the ash. Two bagasse boilers at one sugar mill in Florida have an ESP control devic e.

Bagasse bottom ash and fly ash contain some unburne d carbon and some of the non-combustible minerals that entered the mill (some from the soil clinging to the cane, but also some minerals in the cane itself). Some of the soluble minerals are extracte d during the washing of the bagasse and are later precipitated from the sugarcane juices. These “cla rifier muds” are not combusted, but are returned to
farm fields to reduce the need to add fertilizers o r other necessary soil amendments.

As noted earlier, bagasse is a very clean fuel with respect to heavy metals and, as a result, the ash particles emitted from bagasse-fired boilers contai n extremely low concentrations of such metals. Bagasse boilers are equipped with either wet scrubb ers or ESPs and, consequently, the boilers emit relatively small amounts of particulate matter (PM) and even smaller amounts of metal HAPs.

PM is a good surrogate for metals emissions from ba gasse boilers, but given the low metals content of bagasse ash, an appropriate PM emissions limit for bagasse boilers could likely be higher than the PM
emissions limit for other solid fuel boilers. Addi tionally, the wet scrubbers used at most sugar mill s will
remove almost all of the small amounts of HCl that might be formed in the boilers from the combustion of bagasse.

B. Key Combustion Characteristics of Bagasse

Bagasse fuel is a light-weight, fibrous, high-moist ure content fuel. Given these characteristics, bag asse is combusted differently than wood, wood chips and bar k, which are heavier and have a lower moisture content and a higher heating value than bagasse. I f EPA contemplates setting emission limits for orga nic HAPs, or for CO as a surrogate for organic HAPs, EP A should recognize that the combustion characteristics of bagasse are different than the c ombustion characteristics of other types of biomass , and these characteristics strongly influence emissions. The key combustion characteristics of bagasse, wh ich collectively make bagasse burn differently than oth er types of biomass, are as follows:

• It has a low combustion temperature because it has a high moisture content;

• It is dried and burned in boilers with relatively h igh heat release rates and high excess air rates;

• It has relatively low NO

x emissions and very low SO 2 emissions;

• It is carbon neutral;

• It is burned for combined heat and power production (i.e., steam and electricity);
and

• It is combusted on a seasonal basis.

These characteristics of bagasse, combined with the distinctive design and operation of bagasse boiler s, strongly influence the emissions from bagasse boile rs. The high moisture content (48 to 55 percent) o fMay 2009 0838-7513

Reports/Boiler MACT 2/Separate Class of Bagasse Boi lers 05-14-09.doc 9 bagasse (and especially the moisture absorbed in th e fiber) results in a relatively low combustion temperature in bagasse-fired boilers. The low temp erature occurs because a significant amount of heat is consumed in the furnace by the process of evaporati ng the water from the bagasse, and the moisture suppresses the combustion temperatures.

These factors, combined with the furnace design, an d in particular the amount of heat input per unit o f furnace volume (Btu/hr-ft 3 ), cause significant effects on the combustion proc ess and the subsequent emissions of CO. Higher heat release rates produce shorter residence times for combustion gases within the furnace, allowing less time to completel y burn out the CO in the gases. Existing Florida a nd Hawaii bagasse boilers, except for one newer boiler , have furnace heat release rates ranging from 23,0 00 to 51,000 Btu/hr-ft 3

.

Additionally, it must be remembered that sugarcane processing is a seasonal operation; in some cases, the season is only a few months. Given similar emission factors, seasonal operations produce lower total annual emissions than year-round operations. It als o means that many of these boilers are older compar ed to non-seasonal industries because (being used only part of a year each year) they are typically opera ted for more years to achieve the same operating life. This seasonality is another factor in requesting a separate sub-category for bagasse boilers.

Refer to Appendix A for further information regardi ng the combustion characterisitics of bagasse.

C. Key Design and Operating Characteristics of Bag asse Boilers

Bagasse boilers are designed and operated different ly than other solid fuel boilers:

• The boilers are designed to dry and burn bagasse;

• The boilers operate primarily with suspension firin g, with some grate firing;

• The boilers operate at relatively low temperatures;

• The boilers have relatively high heat release rates ;

• The boilers have relatively high excess air rates;

• The boilers are fully integrated into the milling o peration; and

• The boilers experience considerable variability in operation during a typical day.

As described previously, moisture in bagasse is bot h surface moisture and moisture contained throughou t the fiber. As a result, this moisture is more diff icult to remove compared to surface moisture, such as that present with wood. The combustion of bagasse in a bagasse boiler is carried out in a three-step process within the furnace. The first step is dryi ng of the bagasse, which occurs mainly in suspensio n but also on the grate or fuel pile. The second step is the driving off of the volatile constituents. The third and final step is combustion of the bagasse (carbon burning). The high moisture content (48 to 55 percent) of bagasse coupled with the porous fibe rs results in a relatively low combustion temperatu re in bagasse-fired boilers. This factor, combined wi th the furnace design, and in particular the heat r elease rate (amount of heat input per unit of furnace volu me) and higher excess air amounts, causes significa nt effects on the combustion process and the subsequen t emissions of CO compared with fossil fuels or woody biomass. Existing bagasse boilers were desig ned with smaller furnace volumes and higher heat release rates than the newest bagasse boilers. Non etheless, even the newest bagasse boilers with low heat release rates experience variable and transient CO emissions due to bagasse variability and their integration with mill operations, as described belo w.May 2009 0838-7513

Reports/Boiler MACT 2/Separate Class of Bagasse Boi lers 05-14-09.doc 10 Using bagasse as a fuel also produces lower emissio ns of NO

x and SO 2 compared with fossil fuels. Bagasse, like most biomass, has a significant oxyge n content within its molecular structure. The inte rnal oxygen and internal moisture content of bagasse con tribute to bagasse burning at a lower temperature than fossil fuels. In turn, the lower combustion t emperature reduces the formation of combustion-rela ted
NO

x (mostly NO and NO 2 ), in comparison to the levels associated with the combustion of fossil fuel. This reduction is important because NO

x is one of the main pollutants responsible for urba n smog and ozone, and SO 2 and NO

x are the largest contributors to acid rain.

The integrated operation of sugar mills and sugar m ill boilers is unique, to our knowledge, and has a direct impact on emissions from the boilers. The bagasse for the boilers comes directly from the mill. When the quality of cane coming into the mill changes (e.g., due to wet, muddy field conditions), the performan ce of the mills can be adversely affected. Any change in the output of the mills will have an immediate imp act on the quality of bagasse being fed to the boilers. B agasse moisture, for example, can swing widely in a very short period of time. These fluctuations in the qu ality of the bagasse necessitate constant adjustmen ts by boiler operators (e.g., adjustments to combustion a ir) to optimize combustion as the fuel quality vari es, and may also require the use of supplemental fuels (e.g ., fossil fuels) to stabilize combustion.

All of these adjustments contribute to transient co nditions in CO emissions (and therefore higher aver age CO emissions) than would be observed in a boiler op erating on fuel of consistent quality. Even the bu rning of supplemental fossil fuels cannot always resolve these transient CO conditions. As a result, even n ewer bagasse boilers can experience higher CO emissions than wood or other biomass-fired boilers.

Fluctuating steam loads are typical of sugar mill o perations and they contribute to emissions transien ts. This phenomenon can be witnessed in the control roo m of any sugar mill and it is documented by the ste am charts for the boilers. Unlike utility boilers and many industrial boilers which operate at a relativ ely steady load, steam loads at a sugar mill can vary widely o ver short periods of time. Field conditions or a l ack of cane can result in the sudden starting and stopping of the mills, which are a major steam load for the boilers. The rapid change in steam load has a dual impact on the boilers because (1) it causes emissions transi ents and (2) it also adversely impacts the bagasse moist ure when the mill restarts because the hydraulic pr essure exerted by the mills is dependent on adequate steam load. As a result, unstable regimes of combustion often occur in bagasse boilers. 5

Similarly, conditions in the boiling house can caus e increases and decreases in steam demand. For uni ts that supply power to electric utilities, fluctuations on the transmission line grid can result in a sudden increase in electricity demand, which again results in an incre ase in steam demand. These operational considerati ons significantly affect the emissions from bagasse-fir ed boilers and thus they are important factors to c onsider when determining the emissions standards that are a chievable for sugar mill boilers.

Representative steam charts from actual bagasse boi ler operations are provided in Appendix B. These steam charts demonstrate the typical variability i n steam production rates experienced by bagasse boi lers.



### VI

. Other Considerations

Given the unique characteristics of bagasse, it wou ld be appropriate to create a subcategory in the Bo iler MACT rules for bagasse boilers, based on the type o f fuel used and the design of these boilers. The information contained in this document provides a r ationale basis for such a subcategory. Although th e bulk

5 Woodfield, P., Kent, J., Novozhilov, V., and Dixon , T., “Prediction of unstable regimes in the operat ion of bagasse fired furnaces,” Second Internation Conference on C FD in the Minerals and Process Industries, CSIRO, M elbourne, Australia, December 6-8, 1999.May 2009 0838-7513

Reports/Boiler MACT 2/Separate Class of Bagasse Boi lers 05-14-09.doc 11 of this document advocates the creation of a subcat egory based on the class of boilers used by the sug ar industry, a strong argument can be made that the su bcategory should be based on the type of fuel used by the sugar industry’s boilers.

A subcategory for bagasse fuel is not inconsistent with the concept that fuel switching may be a suita ble emissions control technique in certain industries. In some industries, there may be several fuels (e. g., fuel oil and natural gas) that can be used in a cost-eff ective manner and thus it may be possible for those industries to switch to a cleaner fuel. In the sug ar industry, however, fuel switching is not a feasi ble option. Bagasse is the only fuel that is produced by the su gar industry. Bagasse is a co-product of the sugar cane harvest and it is essentially a free fuel. There i s no other fuel that could be substituted for bagas se and used by the sugar industry in an economically viable fas hion.

Creating a subcategory for bagasse boilers is consi stent with the national goal of using locally-produ ced renewable energy sources to meet our national energ y needs. Bagasse is truly a “green” resource—it is produced during the sugarcane harvest each year and it displaces the use of fossil fuels. Bagasse als o is carbon neutral (or a carbon sink) and, therefore, i ts use as an energy source helps reduce the creatio n of greenhouse gases.

For these reasons, EPA should encourage the continu ed use of bagasse as a renewable fuel. Conversely, EPA should not adopt Boiler MACT rules that would h inder or preclude the use of this valuable resource

. The unique characteristics of this fuel warrant the creation of a separate subcategory for bagasse boi lers, based on the type of fuel they use.



### VII

. Conclusions

In summary, bagasse is a valuable fuel that is uniq ue to the sugar industry. Bagasse results from and is a co-product of the cane sugar production process, wh ich alters the characteristics of this biomass fuel

. Bagasse boilers constitute a separate and unique cl ass of boilers, which are are uniquely designed and operated to dry and burn bagasse in a fully integra ted process within the sugar mills. This combinati on of factors results in a unique emissions profile (l ow metals, low NO

x , low-sulfur oxides, low HCl, but high CO). For all the reasons discussed above, we are convinced that the emissions data from other solid-fuel boilers are not representative of bagass e boilers. Including bagasse boilers with other so lidfuel or biomass boilers will result in an inappropr iate MACT floor for bagasse boilers.

Given the design and operation of sugar mill boiler s, as well as nature of bagasse, the FSI believes t hat it is appropriate for EPA to place bagasse boilers in a separate subcategory (containing only the class o f boilers designed to burn bagasse) under Section 112 of the CAA when EPA establishes MACT standards
for industrial boilers.

## APPENDIX AMay 2009 - 1 - 0838-7513

Appendix A to FSI White Paper 5-14-09.docx APPENDIX A

TECHNICAL DATA CONCERNING THE DESIGN AND OPERATION OF BAGASSE BOILERS

This document contains technical data concerni ng the design and operation of bagasse boilers. The following data demonstrate that bagasse boilers s hould be placed in a separate subcategory under the Boiler MACT rules being promulgated by the U. S. Environmental Protection Agency (EPA).

INTEGRATION OF BOILERS WITH MILL

The most significant difference between bagasse boilers and other biomass-fired bo ilers is the integration of bagasse boilers directly with the sugar mill. The two primary aspects of boiler and mill integration which can affect bagasse boiler emissions are:

 Integration of the fuel supply from the mill to the boilers; and

 Integration of the steam supply from the boilers to the mill.

The attached flow diagram shows the integrated na ture of these operations. Actual mills are more complicated than shown, since they typically have two grinding mills (tandems) and from three to six boilers, all integrated together.

Bagasse is a fuel that is delivered to the boilers di rectly from the juice extraction process. Therefore, the quality of the bagasse is dependent on the stability and consistency of the juice extraction process. However, this process is variable due to changing va rieties of sugar cane, changing field conditions which affect the quality of the incoming cane, mill stops/starts, etc. These factors also affect the steam demands of the mills, which in turn affects the boiler operatio ns because all the boilers ar e tied into a single steam header system.

Any problems or excursions occurring in the extracti on process normally result in an increased bagasse moisture content of the bagasse delivered to the boile rs. This combined with the lower adiabatic flame temperatures and the lack of thermal inertia on th e grate leads to increased concentrations of unburned

volatiles and carbon monoxide.

These fundamental differences mean that a bagasse bo iler experiences continuous fuel quality changes,

which are far more difficult to control or to accommod ate compared to operations in a typical wood-fired

boiler

In contrast, wood-fired boilers are normally fed from a stockpile of fuel that has known characteristics and a more consistent quality. The wood fuel supply is not tied to the process it is serving, nor is the fuel subject to relatively frequent and signif icant variations due to the process.

At a sugar mill, all the boilers are tied into a single steam header. The steam header supplies steam to multiple grinding/extraction mills, steam turbine electr ical generators, and to the raw sugar manufacturing process. Because of this integration, the operation of a single boiler affects the operation of the other boilers at the mill. If one boiler experiences probl ems due to changing bagasse quality or to mill fluctuations, its steam production can drop quickly, a nd this affects the other boilers (i.e., they mustMay 2009 - 2 - 0838-7513

Appendix A to FSI White Paper 5-14-09.docx attempt to increase their steam production to compen sate), because they are all tied into one steam
system.

To demonstrate the variability of steam production ra tes associated with bag asse boilers, typical steam charts from two representative boilers are attached. These charts clearly show the continuing variability in steam production rates resulting from the integration of the boilers with the mills. Indeed, the steam production and CO data (attached) from the sugar indus try’s newest boiler (U. S. Sugar Boiler No. 8)

demonstrates that even the newest bagasse boilers experience this va riability. The variability experienced with this boiler is much less than the variability ex perienced with most of the other sugar mill boilers, because the new boiler is designed with newer tec hnology that can better handle these fluctuations. Accordingly, this boiler would be representative of a new boiler, not an existing boiler.

In contrast, wood-fired boilers are normally tied into a much more stable process where steam demand is relatively stable, and where the process has much less affect on the boiler operation and no affect on fuel quality.

BOILER DESIGN

Furnace Heat Release Rate

The second most significant difference between wood -fired/other biomass boilers and bagasse-fired

boilers is in furnace heat release ra tes. The furnace heat release rate is the measure of how much energy is released from burning the fuel per cubic foot of furnace volume. This directly relates to the residence time of the combustion gases in the furnace, which in turn affects carbon burnout and emissions of particulate matter, volatile organi cs, and carbon monoxide.

ABB Combustion Engineering Systems (ABB) performed a survey of biomass boilers and presented the results in Technical Paper TIS 8496 (copy attached). A total of nine boilers were field surveyed. Although the type of biomass was not specified for each boiler, it is appears that these were wood-fired boilers. Given ABB’s description of the boilers, it is clear that they were not bagasse boilers located in Florida. All of the boilers, except one, had tangentia l overfire air systems. Excess air ranged from 22 to 58 percent on the units (although one unit operated with 108 percent exce ss air). Furnace heat release rates ranged from 8,900 to 17,900 British therma l units per hour per cubic foot (Btu/hr-ft 3 ), except for one unit that had a heat release rate of 23,200 Btu/hr-ft 3 . Grate heat release rates ranged from 530,000 to 1,019,000 British thermal units pe r hour per square foot (Btu/hr-ft 2 ), except for one unit with a grate heat release rate of 1,324,000 Btu/hr-ft 2

.
Typical design parameters for biomass boilers are also provided in Combustion Fossil Power , 4 th Edition ( Combustion Engineering , 1991). The typical furnace heat release rate for wood-fired boilers ranges from 15,000 to 20,000 Btu/hr-ft 3 , while the typical grate heat release ranges from 900,000 to 1,200,000 But/hr-ft 2

.
In contrast, bagasse boilers have furnace heat release rates ra nging from 18,700 to 51,600 Btu/hr-ft 3

, with only one new boiler and one middle-aged boile r having furnace heat release rates less than 25,000 Btu/hr-ft 3 . Grate heat release rates for bagasse boile rs range from 855,000 to 1,667,000 Btu/hr-ft 2

. Table 1 (attached) contains a compilation of bagasse boile r furnace heat release rates. Typical values for

wood-fired boilers are also shown at the bottom of Table 1. As shown, furnace heat release rates for bagasse boilers are significantly higher than for wood -fired boilers, while grate heat release rates areMay 2009 - 3 - 0838-7513

Appendix A to FSI White Paper 5-14-09.docx slightly higher for bagasse boilers. The furnace heat release rates for bagasse boilers have a significant effect upon the emissions from the bagasse boilers, a nd they cause the emissions from bagasse boilers to be significantly different than the emissions from wood boilers.

EPA has previously used criteria su ch as furnace heat rele ase rate in developing NSPS subcategories for boilers. For example, 40 CFR 60 Subpart Db contains separate NO
x limits for low heat release rates boilers and high heat release rate boilers burning fuel oil. For purposes of Subpart Db, a high heat release rate is defined as greater than 70,000 Btu/hr-ft 3 and a low heat release rate is less than or equal to 70,000 Btu/hr-ft 3 . The FSI is requesting a similar determination for bagasse boilers.

A bagasse boiler must be designed differently than other solid-fueled boilers. For example, when an existing coal-fired boiler at a power plant was purch ased by a sugar mill, the boiler had to be converted before it could be used to burn bagasse at the mill. The coal-fired boiler originally was designed for a 300,000-pound-per-hour (lb/hr) steam rate. It had a furnace volume of 17,200 cubic feet (ft 3 ) and a grate area of 506 square feet (ft 2 ). This design resulted in a furnac e heat release rate of 23,400 Btu/hr-ft 3 , a grate heat release rate of 938,700 Btu/hr-ft 2 , and a grate fuel loading rate of 0.0375 ton per hour per square foot (ton/hr-ft 2 ).

The sugar mill had to modify the boiler so that the bo ilers could achieve a steam capacity of 275,000 lb/hr while burning bagasse. The drum centers were extende d, new fuel distributors installed, and the furnace volume was increased to 21,245 ft 3 . Since bagasse has a lower hea ting value than coal, much more bagasse than coal was needed to be burned to achieve the desired stea m generation. So the boiler heat input rating was increased from 402 MMBtu/hr (coal) to 633 MMBtu/hr (bagasse). Due to the higher

moisture content and the lower heati ng value of bagasse, the resulting heat release rates were increased to 29,800 Btu/hr-ft 3 for the furnace and 1,251,000 Btu/hr-ft 2 for the grate. The fuel loading rate was

increased to 0.174 ton/hr-ft 2 . All of these parameters are significa ntly higher for the bagasse boiler than

the coal-fired boiler.

Excess Air Levels

Bagasse boilers are also designed for much higher excess air levels than wood-fired or other biomass boilers. Wood-fired boilers typically operate at ap proximately 25 to 50 percent excess air. Bagasse boilers on the other hand ope rate between 50 to 110 percent excess air. Actual excess air levels for the Florida and Hawaii bagasse boilers, based on historic st ack test data, are shown in Table 1 (attached). The major reasons for the high excess air levels are as follows:

 Higher gas upflow and velocities and hence, more excess air, are needed for the higher moisture fuels in order to keep the gas in contact with the fuel particles for the longer period of time needed to dry them ( Cane Sugar Engineering, Chapter 27, Steam

Generation , by N. Magasiner, Thermal Energy Systems, South Africa). The higher excess air levels are also required to maximize combustion in suspension while minimizing combustion on the grate. If excess air is reduced or minimized, piles can form on the grate and inhibit the combusti on process. Higher excess air levels help insure that combustion on the grate is minimized.

 To accommodate anticipated swings in bagasse moisture (higher moisture fuel requiring more excess air). The boilers are operated w ith higher than optimum excess air in orderMay 2009 - 4 - 0838-7513

Appendix A to FSI White Paper 5-14-09.docx to smooth operational swings and minimi ze upset conditions when wetter bagasse (requiring higher excess air) comes from the mill.

Wood boilers generally operate with much more consistent moisture a nd ash levels than bagasse boilers. Consequently, wood boilers can fine-tune their excess air levels to the anticip ated, stable moisture content. The closer excess air levels are to being optimized, the more complete combustion will be. High excess air levels in bagasse boilers further contribu te to the already lower combustion temperatures, which result in higher CO emissions. In addition, more air flow means there is less residence time in the boiler for the combustion gases, which in turn contribut es to higher CO emissions. Even if the bagasse boilers are operated at the optimum excess air for a “typical” moisture content (say, 50 percent), CO

emissions will increase as soon as wett er fuel (which requires more ex cess air) is introduced into the boiler, unless and until air flows can be adjusted.

Bagasse boilers are designed to provide higher excess air levels. This design goal is achieved by employing greater forced draft, induced draft, and ove rfire air capacity. This, design goal also is achieved by using a greater number of overfire air nozzles and by using overfire air nozzles that have a higher capacity. Wood–fired boilers typically employ tang ential overfire air systems, unlike bagasse boilers,

which utilize wall-mounted overfire air nozzles. Th e wall-mounted nozzles are typically located on the front and rear walls of the bagasse boiler, but the nozzles can also be located on the side walls.

Suspension Burning versus Grate Burning

Bagasse and wood are very different fuels on an as-fi red basis, requiring that the firing systems be designed differently. Bagasse is typically between 50- and 55-percent moisture with 2- to 4-percent ash, depending on the type and efficiency of the juice extraction process. Wood fired in spreader stoker boilers typically has a moisture content of 30 to 35 per cent. The typical density of wood fuel is three (3) times that of bagasse. The density of the wood, co mbined with the particle-size distribution resulting from a typical hogger and screening system, means that the bulk of the wood fuel will burn on the grate, and only the fines burn in suspension. In contrast , bagasse has a much finer (smaller) particle size distribution, due to the nature of the cane prepar ation process and the cane grinding process, which both facilitate the extraction of the cane juice. As discussed above, bagasse boilers are also designed and operated with higher excess air levels than wood-fired boilers, in order to promote greater suspension firing as opposed to firing on the grate. Thus, in a ba gasse boiler, the fuel burns primarily in suspension and not on the grate.

Fuel Feed System

Bagasse has a lower bulk density than wood, so a greater volume of fuel must be fired for the same heat input. The need for more fuel is further exacerbated by the higher moisture content of bagasse. Consequently, fuel feed systems for bagasse generally need to be larger than for wood to achieve the same boiler heat input. The use of more fuel and la rger fuel feed systems also negatively affect the boiler’s ability to respond to an incr ease in fuel moisture or changes in boiler loads. When moisture increases in bagasse fuel, a larger volume of fuel must be fed to make up for the higher moisture than

would be the case for the same moistu re increase in wood fuel. Similarly, when the boiler load changes, a larger volume of bagasse fuel must be fed into the boiler to supply the additional heat than would be the

case for a wood boiler. These factors can contribute to a less responsive boiler and therefore larger emissions transients in bagasse bo ilers than in wood boilers.May 20090838-75131-hr SteamCapacityHeat InputCapacityaBagasseFeed RateFurnaceVolumeFurnaceHeatReleaseRateaGrateSurfaceAreaGrate HeatRelease RateFuel LoadingRateAverageExcess AircFurnaceHeightFurnaceWidthbFurnaceDepthCompany(lb/hr) (MMBtu/hr) (TPH) (ft3) (Btu/hr-ft3) (ft2) (Btu/hr-ft2) (tons/hr-ft2) (%) (ft) (ft) (ft)U.S. Sugar Clewiston 1 1968 Riley SS Vibrating 245,000 495 68.8 9,67051,189 297 1,666,667 0.23 104 32 18 17U.S. Sugar Clewiston 2 1968 Riley SS Vibrating 215,000 447 62.1 9,67046,225 297 1,505,051 0.21 106 32 18 17U.S. Sugar Clewiston 4 1984 Foster Wheeler SS Traveling 300,000 633 87.9 21,24529,795 506 1,250,988 0.17 76 44 34 16U.S. Sugar Clewiston 7 1997 Alpha Conal SS Vibrating 385,000 812 112.8 43,47018,680 704 1,153,409 0.16 66 67 34 21U.S. Sugar Clewiston 8 2004 TES/McBurney SS Traveling 633,000 1185 164.6 50,52023,456 986 1,201,826 0.17 52 77 43 23SCGCF 1 1963 Riley SSTraveling; Watercooled Pinhole139,700 267 37.1 8,45031,598 264 1,011,364 0.14 75 36 16 16.5SCGCF 2 1963 Riley SSTraveling; Watercooled Pinhole138,154 269 37.4 8,45031,834 264 1,018,939 0.14 92 36 16 16.5SCGCF 3 1966CombustionEngineeringSSTraveling; Watercooled Pinhole110,000 229 31.8 5,40042,407 224 1,020,267 0.14 86 29 15 15SCGCF 4 1971 Riley SS Traveling 300,000 572 79.4 21,10027,109 540 1,059,259 0.15 65 45 24 22SCGCF 5 1968 Riley SS Traveling 230,000 439 61.0 15,14528,986 390 1,125,641 0.16 71 45.5 20 19SCGCF 8 1982 Riley SS Traveling 264,000 504 70.0 21,10023,886 540 933,333 0.13 71 45 24 22Osceola 2 1965 Bigelow SS Inclined 140,000 280 38.9 9,76828,665 405 691,358 0.10 55 37 24 18Osceola 3 1961 Alpha SS Inclined 150,000 292 40.6 10,10628,894 405 720,988 0.10 51 37 24 18Osceola 4 1965 Bigelow C N/A 140,000 280 38.9 6,40043,750 N/A N/A N/A 77 42 24 18Osceola 5 1978 Alpha C N/A 165,000 330 45.8 6,40051,563 N/A N/A N/A 75 37 24 18Osceola 6 1981 Distral SS Traveling 195,000 379 52.6 11,30033,540 360 1,052,778 0.15 63 36 16 20Puunene- Hawaii 1 1952 Riley SS Traveling 125,000 212 29.4 7,17429,551 235 902,128 0.13 85 33 20.5 17Puunene- Hawaii 2 1952 Riley SS Traveling 125,000 212 29.4 7,17429,551 235 902,128 0.13 85 33 20.5 17Puunene- Hawaii 3 1973 Foster Wheeler SS Traveling 290,000 568 78.9 24,85222,855 570 996,491 0.14 89 53 28 20Typical Wood-Fired Boiler Ref. 1180,000 -550,0008,900 -23,200530,000 -1,324,00022 - 58Typical Wood-Fired Boiler Ref. 215,000 -20,000900,000 -1,200,000Note: SS= spreader stoker.C= fuel cell.aBased on 2008 EPA MACT Combustion Survey.bSide of furnace which includes fuel feeders.cDerived from last 10 years of stack test data.References:1. Biomass Fuel Combuston System Design, Technical Paper TIS 8496. ABB Combuston Engineering Systems.2. Combustion Fossil Fuel, 4th Edition. Combustion Engineering, Inc., 1991.TABLE 1. BAGASSE BOILER FURNACE DATABoiler Year Manufacturer Type Grate TypeFl-HAW Furnace Design Data 5-14-09.XLSGolder Associates

## APPENDIX BMay 2009 0838-7513

Appendix B 5-14-09.docx APPENDIX B

The typical variability in steam flow and CO emissions from bagasse boilers is portrayed in the attached graphs and figures. These data are provided to sh ow the degree of variability that bagasse boilers typically experience due to their full integration wi th the operation of the sugar mill and the variable nature of the bagasse fuel received from the mills. Each set of data are further described below.

Steam Flow- Typical Boiler

These charts display several typical operating days fo r one of the boilers at a sugar mill. Note the

constant fluctuation in steam flow.

USSC - Boiler 8 Steam Flow and Mill Episodes vs. CO

These charts display several typical operating days for the newest boiler in the industry, which began operating in 2005 at U. S. Sugar Corporation (USSC). For each day presented, there is a corresponding chart that provides the hourly average CO emissions from the boiler. The boiler has a limit of 400 parts per million by volume, dry (ppmvd) at 7-percent O 2 , 30-day rolling average, based on the now-vacated

Boiler MACT rule. It is noted that the boiler has b een in compliance with this limit since startup through the present time, despite these normal fluctuations in short-term CO emissions.

USSC – Boiler 8 Steam Flow

This chart displays the hourly steam production rate of Boiler 8 at USSC (the newest boiler in the industry) over the 2008-2009 crop season. The purpose of this chart is to show the continuous variability in steam production, which is normal operation for a s ugar mill boiler, and that even the newest boiler experiences these fluctuations.

## Steam Flow – Typical Boiler250STEAM FLOWFSI - Typical Boiler12/1/2008150200100

Steam Flow (klbs)Steam Flow (klbs)0500:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 0:00250STEAM FLOWFSI - Typical Boiler12/2/2008150200100

Steam Flow (klbs)Steam Flow (klbs)0500:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 0:00250STEAM FLOWFSI - Typical Boiler12/3/2008150200100

Steam Flow (klbs)Steam Flow (klbs)0500:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 0:00250STEAM FLOWFSI - Typical Boiler12/4/2008150200100

Steam Flow (klbs)Steam Flow (klbs)0500:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00

## USSC – Boiler 8 Steam Flow and

Mill Episodes vs. CO80010001200

7 % O2)USSC Boiler 8 - Mill Episodes vs. CO10/08/200802004006000:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 0:00

CO Emissions (ppm @ 7Normal OperationChoked FeedersWet/Poor Fuel400500600USSC - Boiler 8Steam Flow10/08/200801002003000:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 0:00

Steam Flow (klbs)Steam Flow (klbs)500600700

7 % O2)USSC Boiler 8 - Mill Episodes vs. CO10/11/200801002003004000:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 0:00

CO Emissions (ppm @ 7Normal OperationChoked FeedersBagasse Handling StoppedWet Fuel400500600USSC - Boiler 8Steam Flow10/11/200801002003000:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 0:00

Steam Flow (klbs)Steam Flow (klbs)6007008009001000

7 % O2)USSC Boiler 8 - Mill Episodes vs. CO11/03-04/200801002003004005000:00 4:00 8:00 12:00 16:00 20:00 0:00 4:00 8:00 12:00 16:00 20:00 0:00

CO Emissions (ppm @ 7Normal OperationChoked FeedersGap In Bagasse from Mill1762 CaneBoth Mills Up and Down400500600USSC - Boiler 8Steam Flow11/03-04/200801002003000:00 4:00 8:00 12:00 16:00 20:00 0:00 4:00 8:00 12:00 16:00 20:00 0:00

Steam Flow (klbs)Steam Flow (klbs)80010001200

7 % O2)USSC Boiler 8 - Mill Episodes vs. CO11/18/200802004006000:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 0:00

CO Emissions (ppm @ 7Normal OperationChoked FeedersMills bypassed in mill -moisture impacted400500600USSC - Boiler 8Steam Flow11/18/2008010020030021:37 23:37 1:37 3:37 5:37 7:37 9:37 11:37 13:37 15:37 17:37 19:37 21:37 23:37

Steam Flow (klbs)Steam Flow (klbs)500600700

7 % O2)USSC Boiler 8 - Mill Episodes vs. CO02/15/2009Normal OperationCh k d F d01002003004000:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 0:00

CO Emissions (ppm @ 7ChokedFeedersBoilers 1 & 2 offline. Boiler 8compensatesMills bypassed in mill -moisture impacted500600700USSC - Boiler 8Steam Flow02/15/200901002003004000:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 0:00

Steam Flow (klbs)Steam Flow (klbs)500600700USSC - Boiler 8Steam Flow02/15/200901002003004000:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 0:00

Steam Flow (klbs)Steam Flow (klbs)

## USSC – Boiler 8 Steam Flow700USSC - Boiler 8Steam Flow2008-2009 Crop Season500600200300400

Steam Flow (klbs)Steam Flow (klbs)010010/1/08 0:00 10/21/08 0:00 11/10/08 0:00 11/30/08 0:00 12/20/08 0:00 1/9/09 0:00 1/29/09 0:00 2/18/09 0:00 3/10/09 0:00 3/30/09 0:00