Date: October 15, 2014

To: Susan Fairchild

OAQPS/SPPD/NRG (D243-02)

U.S. Environmental Protection Agency

Research Triangle Park, NC 27711

From: Dave Reeves, RTI International

Subject: Control Cost Evaluation for Glass-Melting Furnaces

Final Wool Fiberglass Manufacturing NESHAP - Residual Risk and 

Technology Review (RTR) Amendments 

Wool Fiberglass Manufacturing RTR

RTI Project No. 0213199.003.009

The purpose of this memorandum is to present the information used for the potential control cost 

evaluation for gas-fired glass-melting furnaces used in the wool fiberglass manufacturing 

industry to comply with the final RTR amendments.

I. OVERVIEW

In order to comply with the chromium compound emission limit proposed for gas-fired glassmelting furnaces, several control options were evaluated for comparison purposes and included:

1) Caustic scrubber;

2) Venturi scrubber;

3) HEPA filter;

4) 3-Stage filter;

5) 3-Stage filter with water clean; 

6) Membrane baghouse;

7) Reduced furnace life cycle (i.e., net present value approach); and 

8) Replacing cullet.

Much of the following information related to options 2 through 5 listed above was provided by 

NAIMA in their comments to the April 15, 2013 supplemental proposal (78 FR 22370). The 

NAIMA information and cost calculations were reviewed and is being included here for 

clarification and comparison. Table 1 provides a summary of potential control options and the 

associated costs.
2

Table 1. Cost Evaluation Summary - Wool Fiberglass Glass-Melting Furnace Control Options

Potential Control Option (in addition to current DEP or fabric filter)

Option 1 Option 2 Option 3 Option 4 Option 5 Option 6 Option 7 Option 8

Capital Costs

Caustic 

Scrubber

Venturi 

Scrubber

HEPA 

Filter

3-Stage 

Filter

3-Stage 

w/H2O Clean

Membrane 

Baghouse1

Furnace Life 

Cycle2

Replace 

Cullet3

A = Total Eqmt 699K 699K 266K 354K 1,180K 262K --- ---

B = Direct Install 391K 391K 149K 198K 188K --- ---

C =Indirect Install 245K 245K 93K 124K 47K 112K --- ---

TCI = A + B + C 1,335K 1,335K 507K 676K 1,227K 568K 10,000K ---

Operating Costs

Direct Annual 249K 449K 264K 264K 291K 264K --- ---

Indirect Annual 247K 247K 139K 161K 233K 170K 212K ---

Total Annual Cost 

(per furnace)

496K 695K 403K 425K 524K 434K 212K 358K

Cost Effectiveness 

per lb Cr4

1.1 – 55K

3.2K (avg)

1.6 – 77K

4.5K (avg)

0.9 – 45K

2.6K (avg)

1.0 – 47K

2.7K (avg)

1.2 – 58K

3.4K (avg)

1.0 – 48K

2.8K (avg)

0.5 – 24K

1.4K (avg)

Unknown

1 Based on cost spreadsheet used for Portland Cement rule changes (2010) and amendments (2012); membrane bags added to existing baghouse.

2 Based on “net present value” approach using the following assumptions: 1) furnace rebuild cost = $10M; 2) normal furnace life cycle = 10 years; 3) Cr complaint life cycle = 

7 years; and 4) industry interest rate = 5%. Example – the company initially considers the cost of replacing the furnace lining (Cr refractories) in the 10th year (at a cost of $10 

million). The present value (today) of the capital cost 10 years in the future is $10M / (1+r)^10 where r is the interest rate. If the lining would instead be replaced in 7th year, the 

present value (today) of the same capital cost is $10M / (1+r)^7.

The incremental cost today would be computed as ($10M / (1+r)^7 - $10M] / [(1+r)^10]. This approximates the value to the company (today) of waiting to install the lining 

additional 3 years. [$10M / (1.0 + 0.07)7 - $10M] / [(1.0 + 0.7)10] = [$10M / 1.6058 - $10M / 1.967151] = $1,144,005. Annualized cost = $1,144,005 x 0.18555 (OAQPS 

capital recovery factor) = $212K 

3

Incremental cost based on a price difference of $6.81 per ton between batch raw materials with and without cullet; assumed 150 tons/day; 350 days/yr.

4 Cr reduction based on 3 potentially impacted furnaces: 435 lbs (K2) + 9 lbs (K1) + 20 lbs (DM1) = 464 lbs total. Average = 464 / 3 = 155 lb Cr/yr.
3

II. BACKGROUND 

Glass-melting furnaces at wool fiberglass manufacturing facilities are equipped with add-on 

control technologies, including, but not limited to, electrostatic precipitators (ESPs) and fabric 

filters that effectively control PM and most metal hazardous air pollutant (HAP) emissions. 

However, chromium emissions can vary significantly between furnace types, furnace designs 

and over time. All of the control options evaluated for this project would be in addition to the 

current ESP or fabric filter.

As was noted in the NAIMA comments, some of the control options that were evaluated may or 

may not be effective in achieving the chromium compound emission limit and would have to be 

optimized with specific furnace parameters and operating conditions. This is particularly true for 

those furnaces with chromium emissions that increase over time with the degradation of the 

chromium refractory materials above and/or below the glass melt line.

In setting standards, EPA does not typically specify how sources will comply with the 

promulgated standard or in other words how the emission limit will be met. Consistent with that 

approach, the proposed rule does not specify or mention any specific control equipment for 

glass-melting furnaces to meet the chromium emission limit. The information being presented 

here is not meant to suggest that each of the control options evaluated would work on any given 

glass-melting furnace but is intended to show several potential options that can be considered 

when developing a compliance strategy to meet the chromium compound emission limit.

III. Control Options 1 and 2 – Wet Scrubbers 

Costs for installation and operation of the following wet scrubbing designs were developed:

 Caustic scrubber train (Option 1)

 Venturi scrubber train (Option 2)

The total equipment cost was estimated to be $592,200 for both types of scrubbers. Using the 

EPA Cost Manual, the total equipment purchase cost = $592,200 x 1.18 = $698,800. Total direct 

installation costs for both scrubbers were calculated to be $391,326 and the total indirect costs 

were $244,579 for both types of scrubbers. Therefore, the total capital investment (TCI) was 

calculated to be $1,344,700 for both types of scrubbers.

Operating costs are similar for the scrubbers except for electricity costs: Venturri scrubber -

$245,400/yr versus caustic scrubbers - $45,779/yr. The total annual costs (TAC) were $464,000.

For the three furnace-specific applications identified at proposal, the cost of controlling 

chromium with wet scrubbing is estimated at between $1,100 – $77,000 per pound of chromium 

removed, depending on the device selected. The average cost effectiveness for the caustic 

scrubber (Option 1), was estimated to be in the range of $3,200 per pound. The average cost 

effectiveness for a Venturri scrubber application (Option 2), was estimated to be in the range of 

$4,500 per pound. 

As noted by NAIMA, “these high costs are largely due to the initial capital cost of not only the 

control device but also the related infrastructure and installation cost. In addition to similar 
4

requirements as dry filtration, a new hazardous waste stream is generated that must be treated 

and disposed of (i.e., wastewater). Unlike particulate collected from the DEP, the wet material 

collected from this system will be treated with chemicals and will be unsuitable for reuse in the 

furnace. There would also be significantly higher energy and environmental impacts resultant 

from the use of these systems. The detailed cost calculations are provided as Attachment 1 of this 

document.”

IV. Control Options 3, 4, and 5 - Dry/Physical Filtration 

As noted in the NAIMA comments, dust collectors, baghouses, ESPs, and similar devices are a 

form of dry/physical filtration already used in the wool fiberglass manufacturing industry 

extensively. Emissions from the existing furnaces are already being reduced using these proven 

controls. Other potential controls that were analyzed are listed below: 

 3‐Stage filter consisting of a quench tower, coalescing pad and fiber bed filters. This 

custom design has the option of utilizing a water system to clean the filter media; 

otherwise, the filter media would need replacement on a more frequent basis.

 Series of inline high efficiency particulate air (HEPA) filters with water quench. This 

custom design would require changeouts at an unknown frequency.

Costs for installation and operation of the following dry/physical filtration designs were 

developed:

 HEPA filters (Option 3) 

 3-Stage filter (Option 4)

 3-Stage filter with water cleaning (Option 5)

For the three furnace-specific applications identified at proposal, the cost of controlling 

chromium with additional dry filtration is estimated at between $900 - $58,000 per pound of 

chromium removed, depending on the device selected. The average cost effectiveness for a 

furnace using HEPA filters to meet the proposed chromium emission limit is estimated to be in 

the range of $2,600 per pound. The average cost effectiveness for a furnace using 3-stage filter is

estimated in the range of $2,700 per pound. Finally, the average cost effectiveness for a furnace 

using a 3-stage filter with water cleaning is estimated in the range of $3,400 per pound.

As noted by NAIMA, “these high costs are largely due to the initial capital cost of not only the 

control device but also the related infrastructure and installation cost. The ongoing cost of 

cleaning the filters and the cost to dispose of a new hazardous waste stream are significant. There 

would also be associated energy and environmental impacts resultant from use of the electricity 

to operate the system, as well as the transfer of this compound into either a wastewater stream or 

a solid waste stream.”

V. Control Option 6 – Membrane Baghouse 

On the recent Portland cement project, the EPA evaluated the performance of fabric filters using 

membrane bag technology, generally considered the most efficient type of fabric filter.
5

Membrane bags have superior performance to the cloth bags that are part of the standard fabric 

filter design. Cloth bags capture PM in the interstices of the woven fabric and form a primary

dust cake. Until the primary dust cake forms, cloth bags are inefficient as filters. Therefore, each 

time the bag is cleaned emissions increase until the primary dust cake reforms. Emissions also 

occur when the pressure drop becomes so high that the PM migrates through the fabric. 

Membrane bags operate differently under the principle of surface filtration, i.e., the PM is 

captured on the bag surface. This results in more consistent performance (no need to build up a 

primary dust cake). In addition, at a constant airflow membrane bags reduce the average pressure 

drop across the fabric filter. However, membrane bags are more expensive than cloth bags.1, 2

The total equipment cost was estimated to be $262,000 for purchasing the membrane filters bags. 

Total direct installation costs for the membrane filers was calculated to be $188,000 and the total 

indirect costs were $112,000. Therefore, the total capital investment (TCI) was calculated to be 

$568,000 for membrane filters installed in an existing baghouse.

Operating costs are $264,000 (direct) and $170,000 (indirect). The total annual costs (TAC) were

$434,000 (per furnace).

For the three furnace-specific applications identified at proposal, the cost of controlling 

chromium with membrane filters is estimated at between $1,000 – $48,000 per pound of 

chromium removed. The average cost effectiveness for the membrane filters (Option 6), was 

estimated to be in the range of $2,800 per pound of chromium removed. 

VI. Control Option 7 – Reduced Furnace Life Cycle 

Costs were estimated for facilities based on the assumption that those furnaces will have a 

shortened operational life cycle and be rebuilt (or replaced) earlier than they might have been 

otherwise. The associated costing of this reduced furnace life cycle scenario is referred to as the 

net present value (NPV) approach which is described in the EPA Air Pollution Control Cost 

Manual (EPA/452/B-02-001), January 2002. 

For this cost analyses, the NPV approach uses the following assumptions: 

1) furnace rebuild cost = $10 million ($10M); 

2) normal furnace life cycle = 10 years; 

3) Cr compliant furnace life cycle = 7 years; and 

4) industry interest rate = 7%.3

The following example is provided to illustrate the net present value approach. A company

expects a furnace to last at least 10 years and they consider the cost of replacing the furnace 

lining (Cr refractories) in the 10th year (at a cost of $10 million). The present value (today) of 

the capital cost 10 years in the future is $10M / (1+r)^10 where r is the interest rate. If the lining 

 

1 Cement Americas ‘‘Optimizing Kiln Operations by Improving Baghouse Performance’’ November 2001, pp. 1–5.

2 Summary of Environmental and Cost Impacts for Final Portland Cement NESHAP and NSPS, August 2010,

Docket item EPA-HQ-OAR-2007-0877-0113.

3 7% interest rate is in accordance with OMB guidance under Circular A-4. 
6

would instead be replaced in 7th year, the present value (today) of the same capital cost is $10M / 

(1+r)^7

The incremental cost today would be computed as: 

NPV Incremental Cost = [

$10M

(1 + r)

7

] − [

$10M

(1 + r)

10]

Assuming an annual interest rate of 7%, the approximate value to the company (today) of 

waiting to install the lining additional 3 years yields the following calculation:

NPV = [$10M / (1.0 + 0.07)7] – [$10M / (1.0 + 0.07)10] = [$10M / 1.6058] – [$10M / 1.967151]

NPV = $1.144M.

The capital recovery cost (CRC) is calculated by multiplying the NPV incremental cost by the 

capital recovery factor (CRF):

CRC = NPV x CRF

Where CRF is defined according to the formula:

 

 

















 





1 1

1

n

n

i

i i

CRF

Using the 7-year furnace life and a 7% interest (discount) rate, CRF = 0.185554; therefore, the 

annualized capital recovery cost was calculated to be:

Annualized CRC = $1,144,005 x 0.18555 = $212K (per furnace)

It should be noted that the calculation using the NPV approach does not include any 

improvements in productivity and energy efficiency, among other factors, resulting from 

rebuilding a furnace, factors that would typically come into play when a wool fiberglass 

company assesses the need for a furnace rebuild using this approach.

IV. Control Option 8 – Eliminate Cullet as Raw Material 

The use of cullet as part of the raw materials going into the glass-melting furnaces may (or may 

not) contribute to the chromium emissions coming out of the furnaces. Industry stakeholders 

stated that they would likely evaluate this as a possible control option because it would not 

 

4 Table A-2: Capital Recovery Factors (from EPA Air Pollution Cost Manual, EPA/452/B-02-001, January 2002).
7

involve any capital equipment costs or significant process changes. To avoid confidentiality 

concerns, NAIMA provided generalized information for the overall industry regarding the cost 

of batch raw materials with and without cullet being included. The incremental cost difference 

was $6.81 per ton between batch raw materials with and without cullet. For this analysis, we 

assumed the furnace capacity to be 150 tons/day and operating 350 days per year.

The total annual cost (per furnace) was calculated to be:

$6.81/ton x 150 tons/day x 350 days/ yr = $357,525.
8

Attachment 1

Table A-1 shows the OAQPS multipliers to use in estimating the total capital investment (TCI) 

for a scrubber installation. 

Table A-1. OAQPS Capital Cost Multipliers for Scrubbers1

Capital Cost OAQPS Notation

Purchased Equipment Costs

Total Equipment Cost A

Instrumentation (e.g., PLC) 0.10 x A

Taxes/Tariffs 0.03 x A

Freight 0.05 x A

Total Purchased Equipment Costs B = 1.18 x A

Direct Installation Costs

Foundations and Supports 0.06 x B

Handling and Erection/Interconnection 0.40 x B

Electrical 0.01 x B

Piping/Ductwork 0.05 x B

Insulation 0.03 x B

Painting 0.01 x B

Total Direct Installation Costs C = 0.56 x B

Indirect Installation Costs

Engineering 0.10 X B

Construction and Field Expense 0.10 x B

Contractor Fees 0.10 x B

Start-up 0.01 X B

Performance Test 0.01 x B

Continegencies 0.03 x B

Total Indirect Installation Costs

D = 0.35 x B

Total Capital Investment $ TCI = B + C + D

1 U.S. EPA OAQPS, EPA Air Pollution Control Cost Manual (6th Edition), January 2002, Section 6,

Chapter 2, page 2-48 (Table 2.8: Direct and Indirect Installation Costs for Venturi Scrubbers).
9

Table A-2 shows the OAQPS multipliers to use in estimating annual operating costs.

Table A-2. OAQPS Operating Cost Multipliers for Scrubbers1

Operating Cost OAQPS Notation

Direct Annual Costs

Operating Labor (2 hr, per 8-hr shift) E

Supervisory Labor F = 0.15 x E

Maintenance Labor (1 hr, per 8-hr shift) G

Maintenance Materials H = 1.00 x G

Water Quench & Other Consumption I

Filter Media Replacement J

Solid Waste Disposal K

Electricity L

Total Direct Annual Costs DAC = E + F + G + H + I + J + K + L

Indirect Annual Costs

Overhead M = 0.60 x (E + F + G + H)

Administrative Charges N = 0.02 x TCI

Property Tax O = 0.01 x TCI

Insurance P = 0.01 x TCI

Capital Recovery Q

Total Indirect Annual Costs IDAC = M + N + O + P + Q

Total Annual Cost $ TAC = (DAC + IDAC)

1 U.S. EPA OAQPS, EPA Air Pollution Control Cost Manual (6th Edition), January 2002, Section 6, Chapter 2,

page 2-51 (Table 2.9: Annual Cost Factors for Scrubbers).