BART DETERMINATION FOR ALCOA INTALCO WORKS 

FERNDALE, WASHINGTON 

Prepared for: 

Alcoa Intalco Works 

Ferndale, Washington 

Prepared by: 

ENVIRON Corporation 

6001 Shellmound Street, Suite 700 

Emeryville, California 94608 

November 2007 

Contract Number 03-8979C 
Intalco BART Determination FINAL.doc - i - 

TABLE OF CONTENTS 

1.0 INTRODUCTION.......................................................................................................... 1-1

2.0 IDENTIFICATION OF BART-ELIGIBLE UNITS AT INTALCO ........................ 2-1

3.0 BART-ELIGIBLE EMISSION UNIT GROUP DESCRIPTION ............................. 3-1

3.1 PRIMARY ALUMINUM REDUCTION PROCESS DESCRIPTION........................................ 3-1 

3.1.1 EXISTING POTLINE EMISSIONS CONTROL......................................................... 3-2 

3.1.2 ANODE BAKE FURNACE EMISSIONS CONTROL................................................. 3-2 

3.1.3 ALUMINUM HOLDING FURNACE EMISSIONS CONTROL .................................... 3-3 

4.0 BASELINE CONDITIONS AND VISIBILITY IMPACTS FOR BART-ELIGIBLE 

UNITS ............................................................................................................................. 4-1

4.1 CALPUFF MODEL AND BASELINE EMISSION INPUTS ............................................... 4-1 

4.2 SCREENING-LEVEL MODELING ANALYSIS................................................................. 4-1 

4.3 REFINED MODELING ANALYSIS................................................................................. 4-2 

5.0 BART ANALYSIS FOR BART-ELIGIBLE EMISSION UNITS ............................ 5-1

5.1 AVAILABLE AND TECHNICALLY FEASIBLE EMISSION CONTROL OPTIONS ................. 5-1 

5.1.1 POTLINE EMISSIONS AND EXISTING CONTROLS ............................................... 5-1 

5.1.2 ANODE BAKE FURNACE EMISSIONS AND EXISTING CONTROLS ....................... 5-1 

5.1.3 POTENTIALLY APPLICABLE BART CONTROL OPTIONS FOR SO2 ..................... 5-2 

5.1.4 POTENTIALLY APPLICABLE BART CONTROL OPTIONS FOR PM.................... 5-12 

5.1.5 POTENTIALLY APPLICABLE BART CONTROL OPTIONS FOR NOX .................. 5-13 

5.1.6 SUMMARY OF TECHNICALLY FEASIBLE BART CONTROL OPTIONS ............... 5-15 

5.2 CONTROL EFFECTIVENESS OF FEASIBLE OPTIONS ................................................... 5-17 

5.2.1 SO2 WET SCRUBBING .................................................................................... 5-17 

5.2.2 SO2 POLLUTION PREVENTION ........................................................................ 5-18 

5.2.3 ANODE BAKE FURNACE ADVANCED FIRING SYSTEM .................................... 5-18 

5.2.4 ANODE BAKE FURNACE LOTOXTM SYSTEM .................................................. 5-18 

5.3 EVALUATION OF COSTS AND OTHER IMPACTS......................................................... 5-18 

5.3.1 COST IMPACTS FOR FEASIBLE CONTROLS ...................................................... 5-18 

5.3.2 ENERGY IMPACTS........................................................................................... 5-21 

5.3.3 GREENHOUSE GAS GENERATION ................................................................... 5-21 

5.3.4 NON-AIR QUALITY ENVIRONMENTAL IMPACTS............................................. 5-21 

5.3.5 REMAINING USEFUL LIFE............................................................................... 5-22 

5.4 EVALUATE VISIBILITY IMPACTS .............................................................................. 5-22 

6.0 DETERMINATION OF BART.................................................................................... 6-1

6.1 ALUMINUM POTLINES................................................................................................ 6-1 

6.2 ANODE BAKE FURNACE............................................................................................. 6-1 

6.3 ALUMINUM HOLDING FURNACES .............................................................................. 6-2 

6.4 MATERIAL HANDLING AND TRANSFER OPERATIONS................................................. 6-2 
Intalco BART Determination FINAL.doc - ii - 

TABLES 

3-1 Primary Aluminum Reduction Emission Units 

4-1 Source Input Data for Baseline Modeling – Point Sources 

4-2 Source Input Data for Baseline Modeling – Line Sources 

4-3 Source Input Data for Baseline Modeling – Area Sources 

4-4 Source Input Data for Baseline Modeling – Volume Sources 

4-5 Screening Baseline Visibility Modeling Results 

4-6 Refined Baseline Visibility Modeling Results 

4-7 Culpability Analysis for Refined Baseline Visibility Modeling Results in Olympic 

National Park 

5-1 RBLC Database Search Results for Primary Aluminum Facilities 

5-2 Post Control SO2 Emission Rates 

5-3 Summary of Impacts Analysis for SO2 Control Scenarios 

5-4 Source Input Data for Post Control SO2 Modeling 

5-5 Post Control SO2 Visibility Modeling Results 

FIGURES 

5-1 Wet Scrubber Process Flow Diagram 

APPENDICES 

A BART Modeling Results 

B Business Confidential Information 

C Pre-Feasibility Report 

D Wet Scrubber Economic and Energy Impact 

E Greenhouse Gas Emission Calculations 
Intalco BART Determination FINAL.doc - iii - 

ACRONYMS 

acfm actual cubic feet per minute 

AWMA Air and Waste Management Association 

BACT Best Available Control Technology 

BART Best Available Retrofit Technology 

CAA Clean Air Act 

CFR Code of Federal Regulations 

DNR Department of Natural Resources 

dv deciview 

ELG Effluent Limitations Guidelines 

ESP Electrostatic Precipitator 

FGD Flue Gas Desulfurization 

Intalco Alcoa Intalco Works 

LAER Lowest Achievable Emissions Rate 

lb/day pounds per day 

LSFO Limestone Slurry Forced Oxidation 

LSNO Limestone Slurry Natural Oxidation 

MW Megawatt 

NESHAP National Emission Standards for Hazardous Air Pollutants 

NOx Nitrogen Oxides 

PAH Polycyclic Aromatic Hydrocarbons 

PM Particulate Matter 

PM2.5 Particulate Matter less than 2.5 micrometers in diameter 

PM10 Particulate Matter less than 10 micrometers in diameter 

ppm parts per million 

ppmv parts per million by volume 

RACT Reasonably Available Control Technology 

RBLC RACT/BACT/LAER Clearinghouse 

SCR Selective Catalytic Reduction 

SEPA State Environmental Protection Act 

SNCR Selective Non-Catalytic Reduction 

SO2 Sulfur Dioxide 

USEPA United States Environmental Protection Agency 
Intalco BART Determination FINAL.doc - ES-1 - 

EXECUTIVE SUMMARY 

The Clean Air Act (CAA) requires the protection of visibility in 156 scenic areas across the 

United States. Under CAA Section 169A(b)(2)(A), states must require certain existing stationary 

sources to install Best Available Retrofit Technology (BART). Alcoa, Inc. – Intalco Works 

(Intalco) is a “BART-eligible” source. A BART determination is required because Intalco emits 

air pollutants that may reasonably be anticipated to contribute to impairment of visibility in a 

Class I area. 

The BART analysis contained herein lists the individual BART-eligible emission units and 

evaluates visibility impacts, control option feasibility, cost effectiveness and visibility 

improvement. The BART evaluation was completed according to guidance provided in 40 Code 

of Federal Regulations (CFR) 51, Appendix Y and the Washington, Oregon, and Idaho BART 

modeling protocol1

. 

A baseline Class I area visibility impact analysis was performed on 100 BART-eligible emission 

units at Intalco using the CALPUFF model as recommended by the modeling protocol. These 

sources include three potlines, the anode bake furnace, 12 aluminum holding furnaces, various 

material handling and transfer operations, natural gas, diesel and propane combustion sources, 

and other small miscellaneous sources. 

The modeled or projected 98th percentile visibility impacts for the entire facility exceed the 0.5 

deciview (dv) contribution threshold in five Class I areas: Alpine Lakes Wilderness Area, 

Glacier Peak Wilderness Area, Mount Rainier National Park, North Cascades National Park, and 

Olympic National Park. The highest modeled facility-wide impact is 1.527 deciviews (dv) in the 

Olympic National Park (ONP). The modeled visibility impacts are primarily from the potlines, 

with a small amount from the anode bake furnace. Other sources contribute negligible amounts 

to the total as described further below. 

The highest modeled or projected 98th percentile visibility impact of the potlines is 

approximately 1.44 dv in the ONP. The projected impacts in the other, more distant, Class I 

areas are lower. More than 98% of the projected impact from the potlines is attributable to 

emissions from the potroom primary control devices, with the remainder from the existing 

potroom roof scrubbers. More than 96% of the potroom primary control device impact is from 

emissions of sulfur dioxide (SO2). 

 

1 Modeling Protocol for Washington, Oregon, and Idaho: Protocol for the Application of the CALPUFF Modeling 

System Pursuant to the Best Available Retrofit Technology (BART) Regulation.

www.deq.state.or.us/aq/haze/docs/bartprotocol. October 11, 2006. 
Intalco BART Determination FINAL.doc - ES-2 - 

Results from the BART analysis for potroom emissions determined that BART for potline SO2

emissions is a pollution prevention limit of 3% sulfur in the calcined petroleum coke used to 

manufacture anodes (i.e., coke). BART for other pollutants emitted from the potlines 

[particulate matter (PM) and nitrogen oxides (NOx)] was determined to be the existing level of 

emission control. 

The highest modeled or projected 98th percentile visibility impact from the anode bake furnace is 

approximately 0.053 dv in ONP, with lower projected impacts in other Class I areas. More than 

40% of the anode bake furnace impact (0.02 dv) is from SO2 emissions and 55% of the impact 

(0.03 dv) is from NOx. The analysis of control options for the anode bake furnace determined 

that BART for bake furnace SO2 emissions is a pollution prevention limit of 3% sulfur in the 

coke. BART for other pollutants emitted from the anode bake furnace (NOx and PM) was 

determined to be the existing level of emission control. 

Additional BART-eligible emission units at the Intalco facility include aluminum holding 

furnaces, various material handling and transfer operations, natural gas, diesel, and propane 

combustion, and other small miscellaneous sources that support the primary aluminum ore 

reduction process. The combined projected impacts from all remaining BART-eligible emission 

units (sources other than the potlines and anode bake furnace) are less than 0.05 dv in ONP, with 

lower projected impacts in other Class I areas. Considering the minimal contribution to visibility 

impairment (less than 0.05 dv) and the existing level of emissions control, these emission sources 

were excluded from further engineering analysis and BART was determined to be no further 

emissions control for these sources. 
Intalco BART Determination FINAL.doc 1-1

1.0 INTRODUCTION 

The Clean Air Act (CAA) requires the protection of visibility in 156 scenic areas across the 

United States. Under CAA Section 169A(b)(2)(A), states must require certain existing stationary 

sources to install Best Available Retrofit Technology (BART). A “BART-eligible” source is one 

that is contained in the 26 identified source categories that has the potential to emit greater than 

or equal to 250 tons per year of any air pollutant and was put in place during the 15-year interval 

between August 7, 1962, and August 7, 1977. BART is required when any source meeting this 

definition emits any air pollutant that may reasonably be anticipated to cause or contribute to any 

impairment of visibility in any Class I area. 

 
Intalco BART Determination FINAL.doc 2-1

2.0 IDENTIFICATION OF BART-ELIGIBLE UNITS AT INTALCO 

Alcoa, Inc. – Intalco Works (Intalco) operates emission units that fall within the categories of 

primary aluminum ore reduction plants, one of the 26 identified source categories to which 

BART is applicable. The Intalco facility was originally constructed in 1965, and began 

operation in 1966. Therefore, the facility’s emission units were in existence on August 7, 1977, 

but were not in operation before August 7, 1962. The facility has the potential to emit greater 

than or equal to 250 tons/year of sulfur dioxide (SO2), nitrogen oxides (NOx), and particulate 

matter (PM), all of which have been classified as visibility impairing pollutants. As such, the 

Intalco facility is defined as a BART-eligible source. All emission units at Intalco, with the 

exception of one remelt furnace, were constructed between August 7, 1962 and August 7, 1977 

and are, therefore, BART-eligible. 
Intalco BART Determination FINAL.doc 3-1

3.0 BART-ELIGIBLE EMISSION UNIT GROUP DESCRIPTION 

3.1 PRIMARY ALUMINUM REDUCTION PROCESS DESCRIPTION

Intalco’s primary aluminum reduction operations include three potlines, an electrode 

manufacturing operation, consisting of a paste production operation and a green anode baking 

furnace, and miscellaneous material handling operations. 

The potline operation manufactures metallic aluminum by the electrolytic reduction of alumina 

in side-worked prebake cells. Direct electrical current, passing between anodes and the cathode, 

electrolytically reduces the alumina to metallic aluminum and oxygen. Molten aluminum is 

deposited and accumulates over time at the cathode beneath a layer of molten cryolite bath. 

Periodically the molten aluminum is siphoned from beneath the cryolite bath and processed to 

achieve specific metal properties or is retained as pure aluminum. The produced aluminum is 

solidified into intermediate or final products. 

Anodes are manufactured in an ancillary on-site paste production plant. Calcined petroleum 

coke used to manufacture anodes (i.e., coke) is crushed and sized, anode butt material is crushed 

and sized, and both are mixed together with pitch and formed into self-supporting carbonaceous 

blocks called “green anodes.” The green anodes are then cured and baked in furnaces before 

being used in the side-worked prebake aluminum reduction process. 

Table 3-1 presents the individual emission units that are included in the primary aluminum 

reduction emission unit group and that were identified as BART-eligible emission units. Potlines 

A, B, and C emit SO2 and PM, and the anode bake furnace emits lesser amounts of SO2, NOx, 

and PM. These emission units are already equipped with sophisticated emission control 

equipment for PM, so the BART determination for these emission units focuses primarily on 

potential reductions for SO2 and NOx. 

The remaining emission units identified in Table 3-1 include aluminum holding furnaces, various 

material handling and transfer operations, natural gas, diesel, and propane combustion, and other 

small miscellaneous sources that support the potlines and anode bake furnace. Aside from the 

natural gas combustion products, emissions from most of the support operations consist of 

relatively small amounts of PM that are controlled by fabric filter type control devices. Fabric 

filters effectively remove more than 99% of particulate emissions and, based on the control 

technology review, represent the best available control for these types of material handling and 

transfer operations. The natural-gas fired units at Intalco emit very little PM. Given the 

relatively low level of emissions, the fact that fabric filters represent the best available control, 

and the minimal impacts of these sources on visibility, these emission units were excluded from 
Intalco BART Determination FINAL.doc 3-2

further BART engineering analysis. BART for these support operations was determined to be 

the existing level of control. 

3.1.1 Existing Potline Emissions Control 

The potlines at Intalco consist of six potroom groups [i.e., “...a group of potroom segments 

ducted to a common control system” (40 Code of Federal Regulations 60.191)] of electrolytic 

reduction cells connected in series that produce molten aluminum. There are two potroom 

groups per potline. Each potroom is comprised of 120 reduction cells (or pots) with 18 anodes 

per cell. All pots at Intalco are hooded to control emissions. Emissions captured by the hoods 

are drawn through primary control systems, which consist of dry alumina injection systems with 

baghouses for the control of PM and fluoride emissions. A small fraction of the pot emissions 

escape capture by the hoods and are released inside the potrooms. These secondary emissions 

are drawn through a secondary control system which consists of wet roof scrubbers that control 

PM and fluoride emissions. 

Each of Intalco’s primary control system centers consists of multi-compartment baghouse cells. 

Either reverse pulse or reverse flow is used in cleaning the fabric filters of the baghouse cells. 

The multiple compartment design allows for maintenance and troubleshooting of individual cells 

while the baghouse center is still operating. The PM control efficiency of the primary control 

system is estimated to be 97.7% based on measured emissions. 

Fugitive potroom emissions from primary aluminum smelters are typically not controlled. 

However, Intalco operates a secondary pollution control system on each of its potlines to abate 

fugitive emissions. The secondary control system consists of 159 wet roof scrubbers for the 

three potlines. Each wet roof scrubber treats approximately 10,000 actual cubic feet per minute 

(acfm) of potroom air. The wet roof scrubbers become inoperable and must be shutdown during 

any sustained periods of below-freezing temperatures in order to avoid permanent damage from 

freezing. These shutdowns occur only in the winter months, and occur infrequently. For the last 

four operating years, shutdowns due to cold temperatures have averaged less than six or seven 

days per year. The PM control efficiency of the secondary control system is estimated to be 

approximately 82%. 

3.1.2 Anode Bake Furnace Emissions Control 

Products of natural gas combustion, products of combustion from volatiles liberated during the 

baking of green anodes, and other emissions typically associated with anode baking are 

exhausted to a dry alumina scrubbing system. The baking furnace emission control equipment 

conditions the exhaust gases prior to alumina being injected. Fabric filtration modules located 

downstream of the alumina injection reduce PM emissions by as much as 99%. 
Intalco BART Determination FINAL.doc 3-3

3.1.3 Aluminum Holding Furnace Emissions Control 

The 12 holding furnaces at Intalco vary in size. The largest of these furnaces has a natural gas 

rated burner capacity of 22 MMBtu/hr. There are no emission controls associated with the 

aluminum furnaces at Intalco. 
Intalco BART Determination FINAL.doc 4-1

4.0 BASELINE CONDITIONS AND VISIBILITY IMPACTS FOR BARTELIGIBLE UNITS 

CALPUFF modeling was performed to evaluate the cumulative visibility impacts of BARTeligible emission units at Intalco, and to compare the relative contribution of individual emission 

units to the total visibility impact. All modeling performed in association with this BART 

determination was done by TRC Environmental Corporation following the WDOE’s BART 

modeling protocol2. The complete Intalco BART modeling report is contained in Appendix A. 

4.1 CALPUFF MODEL AND BASELINE EMISSION INPUTS

CALPUFF and its meteorological model CALMET are designed to handle the complexities 

posed by complex terrain, long source receptor distances, chemical transformation and 

deposition, and other issues related to Class I impacts. The USEPA adopted the CALPUFF 

modeling system as a guideline model for source-receptor distances greater than 50 km and for 

use on a case-by-case basis in complex flow situations for shorter distances (Federal Register, 

April 15, 2003). CALPUFF was recommended for Class I impact assessments by the Federal 

Land Managers Workgroup in 2000 and the Interagency Workgroup on Air Quality Modeling in 

1998. CALPUFF is recommended by USEPA (Federal Register, July 6, 2005) and the State of 

Washington3

 for BART analyses. 

Tables 4-1, 4-2, 4-3, and 4-4 present the baseline modeling source input data for point sources, 

line sources, area sources, and volume sources, respectively, that were used in the CALPUFF 

model to forecast the visibility impacts. In accordance with Section IV of 40 CFR 51 Appendix 

Y and the BART modeling protocol for Washington, Oregon, and Idaho, baseline emission rates 

used in the model were based on 24-hour average actual emissions from the highest emitting day. 

4.2 SCREENING-LEVEL MODELING ANALYSIS

Screening runs were performed for 2003 through 2005 using the 4-km resolution CALMET 

meteorological data set prepared by Geomatrix for Washington, Oregon, and Idaho. Eight Class 

I areas (Mount Adams Wilderness Area, North Cascades National Park, Goat Rock Wilderness 

Area, Pasayten Wilderness Area, Glacier Peak National Park, Alpine Lakes Wilderness Area, 

Olympic National Park, and Mount Rainier National Park) were included in the screening level 

visibility modeling. 

 

2 Modeling Protocol for Washington, Oregon, and Idaho: Protocol for the Application of the CALPUFF Modeling 

System Pursuant to the Best Available Retrofit Technology (BART) Regulation.

www.deq.state.or.us/aq/haze/docs/bartprotocol.pdf. October 11, 2006. 3

 Ibid. 
Intalco BART Determination FINAL.doc 4-2

The screening level analysis results are presented in Table 4-5. These results project visibility 

impacts within Mount Adams Wilderness Area of less than 0.5 dv, indicating that Intalco does 

not contribute to visibility impairment in the Mount Adams Wilderness Area. A refined, 1-km 

visibility impact analysis was subsequently performed on the remaining seven Class I areas. 

4.3 REFINED MODELING ANALYSIS

Table 4-6 presents the modeled 98th percentile total source visibility impacts (reported as 

deciviews) for 2003, 2004, and 2005 in the seven Class I areas identified in the screening 

modeling analysis as having visibility impacts greater than 0.5 dv. Refined modeled visibility 

impacts exceed the contribution threshold limit of 0.5 dv at Alpine Lakes Wilderness Area, 

Glacier Peak Wilderness Area, Mount Rainier National Park, North Cascades National Park, and 

Olympic National Park. Refined modeled visibility impacts at the Goat Rock and Pasayten 

Wilderness Areas were below the 0.5 dv contribution threshold. The highest predicted visibility 

impacts were in Olympic National Park. 

Table 4-7 presents a culpability analysis for Olympic National Park. Individual emission unit 

visibility impacts in Olympic National Park were used to identify which emission units were 

forecasted to have the most impact on visibility impairment. The modeled or projected 98th

percentile visibility impact from the combined potline emissions for the maximum year is 

approximately 1.44 dv in Olympic National Park. More than 98% of this projected impact from 

the potlines is attributable to emissions from the potroom primary control devices, with the 

remainder from the potroom wet roof scrubbers. More than 96% of the potroom primary control 

device impact is from emissions of SO2. The modeled or projected 98th percentile visibility 

impact for the maximum year from the anode bake furnace was 0.053 dv in Olympic National 

Park. More than 40% of the anode bake furnace impact is attributable to SO2 emissions and 

approximately 55% of the impact is from NOx emissions. The total projected impacts from the 

remainder of the facility’s BART-eligible sources for the maximum year are 0.049 dv in 

Olympic National Park. 

For all emission units other than the potlines and anode bake furnace, the refined modeling 

results in Table 4-7 show a combined total visibility impact that is less than 0.05 dv. The 

combined impact of these emission units is less than 10% of the facility-wide contribution 

threshold level of 0.5 dv for BART applicability established for Washington4

. Reduction in 

emissions from these units would not result in significant visibility improvement in any of the 

Class I areas. For example, the modeled visibility impact from all 12 aluminum holding furnaces 

(casthouse stacks in Table 4-7) was 0.004 dv at ONP. The use of added controls for these 

 

4 Modeling Protocol for Washington, Oregon, and Idaho: Protocol for the Application of the CALPUFF Modeling 

System Pursuant to the Best Available Retrofit Technology (BART) Regulation. October 11, 2006. 

www.deq.state.or.us/aq/haze/docs/bartprotocol.pdf 
Intalco BART Determination FINAL.doc 4-3

furnaces would provide a negligible visibility improvement at ONP, as well as the other Class I 

areas. 

Based on results from the baseline modeling, the scope of the BART control analysis and 

engineering cost calculations were focused on the potlines and anode bake furnace. 
Intalco BART Determination FINAL.doc 5-1 

5.0 BART ANALYSIS FOR BART-ELIGIBLE EMISSION UNITS 

The results of the refined CALPUFF modeling show that Intalco’s potline reactors and anode 

bake furnace contribute to visibility impairment in five Class I areas. The BART analysis 

completed for these emission sources is described in this section. The analysis included a review 

of available and technically feasible retrofit technologies (Steps 1 and 2), determination of 

control effectiveness for feasible options (Step 3), evaluation of cost and secondary impacts for 

feasible alternatives (Step 4), and analysis of impacts and visibility improvements (Step 5). 

5.1 AVAILABLE AND TECHNICALLY FEASIBLE EMISSION CONTROL OPTIONS

Steps 1 and 2 of the BART analysis are to identify available emission control options and to 

evaluate the technical feasibility of these control technologies. Control options for the potline 

reactors and anode bake furnace are described separately in the following sections. 

5.1.1 Potline Emissions and Existing Controls 

Aluminum is manufactured in large electrolytic reduction cells called pots. Aluminum is 

produced from alumina in the pot as current is passed from a carbon anode to carbon blocks on 

the pot wall, which serve as the cathode. The anodes are made from pitch and coke. The major 

pollutants emitted from the cells are PM, hydrogen fluoride, SO2, and carbon monoxide. PM 

includes particulate fluoride, carbon dust, and alumina. SO2 comes from the sulfur in the 

components used to make the anodes. NOx emissions are minimal since there is no external fuel 

or combustion zone and there are no large sources of nitrogen in the raw materials. 

Emissions from the pots are collected by close capture hoods over each pot. The hoods enclose 

the pot as tightly as possible to collect off-gases, but sections may be removed to allow anodes to 

be changed. The off-gases are collected into manifolds that combine the gases from the 

individual pots. The temperature of the exhaust gases entering the control equipment is typically 

150 to 300°F5

. The combined gases are routed to a dry alumina scrubber. The potline primary 

control systems for Intalco's three potlines consist of dry scrubbers using alumina injection with 

fabric filtration for PM control. The system at Intalco is large, treating approximately 1,815,000 

acfm of 180°F exhaust gases. 

5.1.2 Anode Bake Furnace Emissions and Existing Controls 

The anode bake furnace structure is a series of interconnected refractory flues connected to side 

main exhaust manifolds. The furnace is fueled with natural gas. Exhaust gases are routed so that 

 

5

 Air and Waste Management Association (AWMA). 2000. Air Pollution Engineering Manual, Second Edition. 
Intalco BART Determination FINAL.doc 5-2 

flue gases preheat the next section to be fired. Flue gases from the anode bake furnace contain 

PM, hydrogen fluoride, SO2, carbon monoxide, and hydrocarbons. 

The bake furnace control device used at Intalco is similar to the potline primary control system, 

consisting of dry alumina injection with fabric filtration. The bake oven gas stream is 

conditioned by a water spray to reduce the inlet temperature before it enters the scrubber. Fresh 

and recycled alumina are injected into the gas stream, gaseous fluoride and POM are adsorbed 

onto the alumina surface, and fabric filters on top of the reactor compartments collect entrained 

particulate matter present in the gas stream. The system at Intalco treats approximately 216,000 

acfm of 205°F exhaust gases. 

5.1.3 Potentially Applicable BART Control Options for SO2

Sulfur in the anodes is oxidized, releasing SO2 from the potlines as the anodes are consumed. 

SO2 is also released from the anode bake furnace as pitch used to help form the anodes is 

oxidized during the baking process. Options for controlling SO2 include both add-on controls 

and pollution prevention. 

5.1.3.1 Add-on Emission Controls 

Absorption and adsorption have been used for the control of SO2 emissions from 

numerous power utility and industrial processes. As a result many commercialized 

control technologies have been used for SO2 control. However, the practical application 

of these controls systems to the potline reactors and anode bake furnace is limited by the 

very low inlet SO2 levels, in the range of 100 parts per million by volume (ppmv), and 

the expected range of gas conditions, including temperature, oxygen content, humidity, 

SO2/O2 ratio, and gas impurities. 

Eight different SO2 control options were considered as having potential practical 

application as part of the BART analysis. Two of these technologies have been applied 

to the control of SO2 emissions at aluminum smelters. Six of the control options use wet 

scrubbing and two use dry scrubbing technology. The eight potentially applicable control 

options are: 

• Limestone slurry scrubbing with forced oxidation 

• Limestone slurry scrubbing with natural oxidation 

• Conventional lime wet scrubbing 

• Seawater scrubbing 

• Dual alkali sodium/lime scrubbing (dilute mode) 

• Conventional sodium scrubbing 
Intalco BART Determination FINAL.doc 5-3 

• Dry injection 

• Semi-dry scrubbing 

5.1.3.1.1 Wet Scrubbing 

The primary development of SO2 control technology occurred because of the need to 

control emissions from the coal-fired, electric utility power industry6. The large 

volumetric size of the potroom exhaust (approximately 1,815,000 acfm) would 

require a system similar to those used in the electric utility power industry. 

The typical temperature range for wet scrubbers is 300 to 700°F. For utility 

combustion units, wet scrubbing systems have been installed on systems as large as 

1,500 megawatts (MW). Sodium compounds, lime, or limestone can be used. 

However, the high solubility of sodium complicates disposal of waste and 

wastewater. The typical sorbent material is lime or limestone. Lime is generally 

easier to manage on-site but is significantly more costly. Wet limestone scrubbing 

has a high capital and operating cost due to the handling of liquid reagent and waste, 

but is the preferred process for coal-fired utility power plants due to the low cost of 

limestone and high removal efficiencies. Typical removal efficiencies for wet 

scrubbers are between 80 and 95%. Approximately 85% of the flue gas 

desulfurization (FGD) systems installed in the United States are wet scrubber 

systems7. 

In wet scrubbers, the waste gas enters a large vessel (spray tower or absorber), where 

it is sprayed with water slurry. The calcium in the slurry reacts with SO2 to form 

CaSO3. A portion of the slurry from the reaction tank is pumped into the thickener, 

where the solids settle before going to a filter for final dewatering to about 50% 

solids. Figure 5-1 is a simplified process flow diagram of a conventional wet 

scrubber. 

 

6

 AWMA. 2000. Air Pollution Engineering Manual, Second Edition. 7

 USEPA. 2003. “Air Pollution Control Technology Fact Sheet – Flue Gas Desulfurization.” EPA-452/F-03-034. 

August 8. 
Intalco BART Determination FINAL.doc 5-4 

Figure 5-1. Wet scrubber process flow diagram 

Inlet

Gas

Particulate Control

Clean gas out

Spray tower/absorber

Fly Ash

Lime (stone)

and Water

Reaction

Tank

Calcium-based

sorbent spray

Thickener

Filter

Solids

Stabilized Waste

Lime

Blending

Pugmill

Reagent

Supply

Liquid Waste

Stream

In the utility industry, the CaSO3 waste product is usually mixed with fly ash 

(approximately 1:1) and fixative lime (approximately 5%) and typically disposed of 

in landfills. Alternately, the forced oxidation process oxidizes the spent slurry to 

gypsum. Gypsum crystals dewater more efficiently and reduce the size of waste 

handling equipment. Depending on quality and demand, the gypsum may be 

commercially sold, eliminating the need for landfilling the waste product. 

“Mist eliminators” installed at the spray tower outlet or downstream ductwork 

remove droplets from the gas. In some power plant installations, the gas is reheated 

to avoid corrosion downstream. Many scrubbers have gas bypassing capability, 

which can be used for gas reheating. If the wet scrubber is downstream of a highefficiency particulate removal device [fabric filter or electrostatic precipitator (ESP)], 

the particulate concentration may be higher leaving the scrubber than entering due to 

the solids in mist droplets that are carried out of the scrubber. 
Intalco BART Determination FINAL.doc 5-5 

Some disadvantages of using wet scrubbing techniques in many applications are the 

requirement to treat wastewater, the need to construct components from expensive 

alloys to resist corrosion, and much higher energy usage. A practical issue associated 

with a wet scrubber system is the complexity of the system. The space required for a 

wet system is substantial (i.e., large footprint), the systems require more maintenance 

due to their complexity, and more personnel are required for their operation. 

5.1.3.1.1.1 Limestone Slurry Forced Oxidation 

Limestone slurry forced oxidation (LSFO) is used extensively in the utility FGD 

market. The raw material is finely ground limestone. There are a number of 

suppliers of LSFO technology. The most commonly used equipment is an open, 

multi-level, countercurrent spray tower scrubber equipped with spray nozzles to 

inject the limestone slurry droplets into the gas stream. Liquor is collected at the 

bottom of the tower and sparged with air to oxidize the calcium sulfite to calcium 

sulfate to enhance the settling properties of the calcium sulfate. Recirculation 

pumps circulate the scrubbing liquor to the spray nozzles. SO2 removal 

efficiencies of 90% have been achieved. The bleed from the scrubber is sent to a 

dewatering system to remove excess moisture. For an aluminum smelter, the 

process will produce either solid gypsum waste or commercial-grade gypsum 

suitable for reuse as a cement additive if a cement production facility is available 

and willing to accept the material. Only a very small purge or blowdown stream 

is required. 

LSFO was determined to be a technically feasible retrofit control option for the 

potroom reactor and the anode baking exhausts even though it is not ideally suited 

for scrubbing SO2 concentrations that are less than or equal to 105 ppm. 

5.1.3.1.1.2 Limestone Slurry Natural Oxidation 

Limestone slurry natural oxidation (LSNO) is very similar to LSFO. The major 

difference is the absence of an oxidation stage. The gypsum/calcium sulfite 

product is essentially a waste product with limited possibilities of use for 

agricultural purposes. 

5.1.3.1.1.3 Conventional Lime Wet Scrubbing 

Conventional lime wet scrubbing is also similar to LSFO except that the raw 

material is hydrated lime or quick lime that is either slaked on-site or purchased in 

the slaked form. The system typically uses forced oxidation, although natural 

oxidation is possible. The process will produce either solid gypsum waste or 
Intalco BART Determination FINAL.doc 5-6 

commercial-grade gypsum suitable for reuse as a cement additive if a cement 

production facility is available and willing to accept the material. 

5.1.3.1.1.4 Seawater Scrubbing 

Seawater scrubbing is a method for controlling SO2 emissions in which seawater 

is used to absorb SO2 in exhaust gases. Seawater is slightly alkaline (with a pH of 

approximately 8). SO2 has a high solubility in seawater. Absorbed SO2 is 

subsequently oxidized to sulfates by the use of aeration and the pH is adjusted by 

the addition of additional seawater. 

There are three main steps in this process: absorption, oxidation, and 

neutralization. Seawater is passed countercurrent through the gaseous exhaust 

stream, typically using a spray column in the aluminum industry. SO2

preferentially dissolves in the seawater. Removal efficiencies of 85% to 95% 

have been measured in practice. The clean exhaust gas is de-misted prior to 

release to the atmosphere. The acidified seawater is then passed to an oxidation 

basin in which air is blown through the effluent. The additional oxygen ensures 

that the dissolved SO2 is converted to sulfates. Finally, additional fresh seawater 

is added to adjust the pH back up to neutral (or slightly alkaline) and the seawater 

is discharged back into the ocean. 

The effluent from this process will typically have a temperature increase of about 

1°C and will have a change in sulfate concentration of approximately 2-5% above 

background8,9. Scrubbing of the potline emissions also adds fluoride and trace 

amounts of polycyclic aromatic hydrocarbons (PAHs) to the effluent seawater. 

No additional chemicals are required and there is normally no solid waste 

generated for disposal as the effluent is typically discharged directly to the sea. 

The pH of the effluent can be adjusted to within the original range in the 

neutralization step of the process. 

The volume of seawater required varies with exhaust flowrate and SO2 loading in 

the gaseous exhaust stream. Based on a review of specifications for existing 

potline seawater scrubbing systems, the volumetric flowrate of seawater needed 

for proper operation of a seawater scrubber at Intalco would be approximately 2.2 

million gallons of seawater per hour. 

 

8

 Information from the ALSTOM Seawater FGD – Environmental Impact website 

(www.environment.power.alstom.com/home/power/seawater_fgd/environmental_impact.htm) 9

 Kwawaji, Akili D., et. al. 2005. “Seawater Scrubbing for the Removal of Sulfur Dioxide in a Steam Turbine 

Power Plant”. Proceeding of the PWR2005 ASME Power Conference. April 5-7. Chicago, IL. 
Intalco BART Determination FINAL.doc 5-7 

A global review of feasible control technologies identified seawater scrubbing as 

having been installed at seven aluminum smelters, none of which are in the 

United States10. Even though this technology has been identified as a control 

technology in operation at six primary aluminum ore reduction plants in Norway 

and one primary aluminum ore reduction plant in Sweden11, there are two reasons 

why this technology is not feasible at Intalco. 

1) The Administrator of USEPA has issued environmental regulations 

establishing effluent limitations guidelines (ELGs) pursuant to section 304(b) of 

the Clean Water Act for facilities producing primary metals from ore concentrates 

and recovering secondary metals from recycled wastes. The ELGs are for 

facilities that discharge or may discharge pollutants to waters of the United States 

or which introduce or may introduce pollutants into a publicly owned treatment 

works. Seawater scrubbers installed to abate SO2 and other visibility impairing 

pollutants from the Intalco’s BART eligible potline emission units would be 

subject to the ELGs for “Potline SO2 Emissions Wet Air Pollution Control.”12 A 

seawater scrubber installed downstream of the alumina dry scrubbers at Intalco 

would remove both fluoride and SO2 from the dry scrubber exhaust. The amount 

of fluoride absorbed into the seawater would exceed the ELG, requiring treatment 

of the seawater to remove fluoride before it could be discharged back into the sea. 

For example with three potlines operational, approximately 159 lb/day of fluoride 

would be absorbed by the seawater and the applicable ELG would be 59.5 lb/day 

(monthly average). Removal of potline fluoride from the seawater scrubber 

effluent may be feasible, but would also require precipitation of many other 

naturally occurring salts in the seawater (chlorides, sulfates, other fluorides, etc.), 

resulting in the unnecessary generation of large amounts of sludge for land 

disposal. Seawater scrubbing is, therefore, not a viable alternative for smelters in 

the United States, especially when compared with other scrubbing technologies 

that use fresh water and require treatment/disposal for only those salts present in 

the potline exhaust. 

2) In addition to the regulatory restrictions and economic viability issues 

discussed above, a seawater scrubber is infeasible for BART compliance due to 

permitting obstacles. The Washington State Environmental Policy Act (SEPA), 

Chapter 43.21C RCW was enacted in 1971, and it provides the framework for 

agencies to consider the environmental consequences of a proposal before taking 

 

10 The HATCH Group. 2006. “Analysis of Options for BART Compliance”. April 18. Page 4. 11 Ibid. Page 9. 

12 40 CFR 421.23(n) 
Intalco BART Determination FINAL.doc 5-8 

action. It also gives agencies the ability to condition or deny proposals due to 

adverse impacts identified as likely to occur as a result of a proposal. The portion 

of Puget Sound where seawater would be withdrawn and discharged for an Intalco 

seawater scrubber has been included as part of the Cherry Point Aquatic Reserve 

that was established in 2000. The Aquatic Reserves Program is part of the 

Washington Department of Natural Resources (DNR) efforts to promote 

preservation, restoration, and enhancement of state-owned aquatic sites that 

benefit the health of native aquatic habitat and species in the state. The aquatic 

reserves established by DNR are aquatic lands of special educational or scientific 

interest, or lands of special environmental importance. The construction of intake 

and/or discharge structures within the Cherry Point Aquatic Reserve would 

require an impact analysis, assessment, and DNR authorization of any 

environmental impacts associated with a seawater scrubbing system. Since seven 

years have already passed since Cherry Point was designated as an aquatic reserve 

and the initial SEPA evaluation has yet to be completed, the time required to 

complete an analysis of the environmental impacts associated with a seawater 

scrubbing system and obtain the requisite authorizations for a system that 

withdraws seawater from and discharges scrubber liquor into the Cherry Point 

Aquatic Reserve would render this technology infeasible for BART compliance. 

5.1.3.1.1.5 Dual Alkali Sodium/Lime Scrubbing (Dilute Mode) 

Dual alkali sodium/lime scrubbing (dilute mode) uses a caustic sodium solution in 

the scrubber tower. A portion of the scrubbing liquid is discharged to a 

neutralization stage where lime slurry is used to regenerate the caustic, which is 

returned to the scrubber. The bleed from the scrubber is sent to a dewatering 

system to produce a gypsum byproduct. The process will produce either solid 

gypsum waste or commercial-grade gypsum suitable for reuse as a cement 

additive. It should be noted, however, that dual alkali sodium/lime scrubbing 

(dilute mode) is not currently marketed by major FGD vendors because the 

system is too complicated and expensive. 

5.1.3.1.1.6 Conventional Sodium Scrubbing 

Globally, conventional sodium scrubbing has been installed in at least 12 

aluminum smelters. An alkaline solution of either soda ash or sodium hydroxide 

is pumped into the scrubbing tower and recirculated through a network of spray 

nozzles. Atomized droplets contact the up-flowing gas containing SO2. Where 

this technology has been deployed, the liquid effluent containing dissolved salts, 

including sodium and fluorides, has been discharged into a large receiving stream 

or an open body of water without treatment. 
Intalco BART Determination FINAL.doc 5-9 

5.1.3.1.2 Dry Scrubbing 

5.1.3.1.2.1 Dry Injection 

In dry injection, a reactive alkaline powder is injected into a furnace, ductwork, or 

a dry reactor. Typical removal efficiencies with calcium adsorbents are 50 to 

60% and up to 80% with sodium base adsorbents. However, as with wet 

scrubbing, disposal of waste using sodium adsorbents must consider their high 

solubility in water compared to those from calcium adsorbents. The temperature 

range over which scrubbing has been used is 300 to 1,800°F; the minimum 

temperature is 300 to 350°F. Dry systems are rarely used and according to 

USEPA only 3% of FGD systems installed in the United States are dry systems13. 

The dry waste material is removed using particulate control devices such a fabric 

filter or an ESP. 

Dry scrubbing downstream of the potline reactors and anode bake furnace fabric 

filters is not technically feasible because of the low temperatures (less than or 

equal to 205°F) and low SO2 concentrations (less than or equal to 105 ppm). 

5.1.3.1.2.2 Semi-Dry Scrubbing (Spray Dryer) 

Semi-dry scrubbing is more commonly referred to as spray drying. Calcium 

hydroxide slurry (lime mixed with water) is introduced into a spray dryer tower. 

Sodium compounds can be used, but as with the dry scrubber, the high solubility 

of the sodium-based waste products in water complicates disposal of the waste. 

The slurry is atomized and injected into a reactor with the exhaust gases, where 

droplets react with SO2 as the liquid evaporates. This system is categorized as a 

semi-dry system because the end product of the SO2 conversion reaction is a dry 

material. The dry waste product is collected in the bottom of the spray dryer 

reactor and a fabric filter or ESP downstream of the spray dryer removes the 

CaSO3, CaSO4, and unreacted lime. This air pollution control system uses water 

for evaporative cooling and for the SO2 reaction. It operates in a temperature 

range of 300 to 350°F because the temperature of the gases must be high enough 

to evaporate the water portion of the slurry. Approximately 12% of the FGD 

systems installed in the United States are spray dry systems14 with typical SO2

removal efficiencies in the range of 80 to 90%. Unlike a wet scrubbing system 

there is no liquid blow-down stream from the dry system and the collected solids 

are typically landfilled. 

 

13 USEPA. 2003. “Air Pollution Control Technology Fact Sheet – Flue Gas Desulfurization.” EPA-452/F-03-034. 

August 8. 14 Ibid. 
Intalco BART Determination FINAL.doc 5-10 

Spray dry scrubbing downstream of the potline reactors and anode bake furnace 

fabric filters is not technically feasible because of the low temperatures (less than 

or equal to 205°F) and low SO2 concentrations (less than or equal to 105 ppm). 

5.1.3.2 Pollution Prevention 

The guidelines for BART determinations under the Regional Haze Rule recommend 

consideration of pollution prevention options in addition to add-on controls. The primary 

opportunity for pollution prevention in the smelting process to minimize SO2 emissions is 

through limitations on the sulfur content in the incoming coke. Coke is a major raw 

material used in the manufacture of green anodes. Green anodes are subsequently baked 

in a furnace prior to their use in the smelting process. 

Intalco’s Title V operating permit currently has a number of operational limits that cap 

allowable emissions of SO2 from the facility, including: a net potline aluminum 

production limit of 307,000 ton/yr; a daily potline SO2 limit of 37,780 pounds per day 

(lb/day); limits on sulfur in coke and pitch at 3.0% and 0.6%, respectively; and a carbon 

consumption limit of 0.425 pounds of carbon per pound of aluminum produced. 

During the BART process, Intalco evaluated the current levels of sulfur in coke used by 

other aluminum smelters to determine whether a pollution prevention option using lower 

sulfur content coke would be a feasible BART option. This analysis indicated that 

certain smelters currently utilize coke with sulfur contents as low as 2%. Given that 

sulfur contents lower than the current Intalco specification are utilized, Intalco undertook 

a low sulfur coke availability analysis to determine whether coke at levels below 3% 

would be available beyond 2013 when BART controls requirements are anticipated. 

Confidential research information belonging to the market analysts assisting with the 

coke availability analysis is included in Appendix B. The primary conclusions from this 

analysis indicate that: 

• Coke is a byproduct of the oil refining process. The sulfur content of the world’s 

crude oil supply has been and will continue increasing in sulfur content. Those 

refiners with coking capacity are minimizing their raw material costs by 

maximizing use of high sulfur crude oils and oil sands to the optimal extent for 

their overall refinery design. The result will be a continuing increase in the sulfur 

content of available coke. 

• Coke is a relatively small, low revenue component of the refinery’s product 

profile. As such, the aluminum industry has little influence in controlling the 

quantity, quality, and price of the coke produced by refineries. 
Intalco BART Determination FINAL.doc 5-11 

• Anode grade (or anode quality) coke is a small subset of the total coke produced 

world-wide. Growth in the aluminum industry has increased the demand for the 

limited quantities of anode grade coke and has driven prices for coke to 

unprecedented levels. Refining higher sulfur crude oils and oil sands further 

shrinks this small subset of anode grade coke. 

• Prices for coke nearly doubled from 1994 to 2006. 

• The increased global growth in aluminum production will continue to outpace the 

production of coke. 

• Primary aluminum production is expected to grow at the rate of 3 to 4% annually, 

resulting in a commensurate growth in demand for anode grade coke. 

• Coke providers are blending imported, high cost, lower sulfur coke with 

domestically sourced coke in attempts to meet the current specification 

requirements for coke. 

• Removal or reduction of the sulfur content of the coke once it has been received is 

not feasible. 

• Aluminum smelters are experimenting with alternative cokes and technologies 

that are outside of the traditional specifications to ensure continued aluminum 

production in the face of the changing characteristics of this key raw material. 

• The deterioration in coke quality and the tightness of supply is expected to 

continue for the foreseeable future. 

• The increased demand for coke will force the aluminum industry to accept lower 

quality coke with higher sulfur contents. 

Based on the market and availability analysis of the future coke supply, Intalco 

determined that it is infeasible to consider coke at sulfur contents below 3% as a BART 

pollution prevention option because a supply of coke with sulfur contents below 3% 

cannot be ensured beyond 2013 when BART control requirements are anticipated. These 

same market pressures are expected to force facilities currently using coke with sulfur 

contents below 3% to begin using higher sulfur content coke in the future. Although 

coke at sulfur contents below 3% is considered infeasible due to availability concerns, a 

pollution prevention option that maintains Intalco’s current sulfur in coke limit of 3% is 

considered technically viable or feasible, assuming that sufficient imported lower sulfur 

coke remains available to allow blending to 3% sulfur content beyond 2013. 
Intalco BART Determination FINAL.doc 5-12 

5.1.3.3 Feasible Control Options from RBLC Database 

A review of USEPA’s RACT/BACT/LAER Clearinghouse (RBLC) database was also 

completed to determine which control technologies or techniques have been utilized by 

primary aluminum ore reduction plants. The results from the RBLC database search are 

summarized in Table 5-1. 

The data in the RBLC database support the approach of limiting raw material sulfur 

content as a control option for the potlines and the anode bake furnace. Many facilities 

have limited sulfur content in coke to limit SO2 emissions. Two facilities have limits of 

3% sulfur content in coke and one has a 2.95% sulfur content limit. One facility is shown 

in the RBLC to have a wet scrubber to control SO2 emissions; however, an investigation 

revealed that the wet scrubber was not required as part of a best available control 

technology (BACT) determination and that the facility currently does not operate a wet 

scrubber to control SO2 emissions. That facility’s current Title V permit for “Potline 5” 

simply limits coke sulfur content to 3% and coal tar pitch sulfur to 0.8%. 

Dry alumina scrubbers (with fabric filters) are the controls that have been considered 

BACT for PM.

5.1.4 Potentially Applicable BART Control Options for PM 

Potentially applicable PM emission controls are discussed in the following sections. 

5.1.4.1 Fabric Filters 

Fabric filters generally provide high collection efficiencies for both coarse and fine 

(submicron) particles. They are relatively insensitive to fluctuations in gas stream 

conditions. Efficiency is relatively unaffected by large changes in inlet dust loadings. Filter 

outlet air is very clean15. Collected material is dry, which usually simplifies processing or 

disposal. Fabric filters are currently applied for controlling PM emissions from the 

potrooms and the anode bake furnace at Intalco. 

5.1.4.2 Electrostatic Precipitators 

ESPs are capable of very high removal efficiencies for large and small particles16. They 

offer control efficiencies that are comparable to fabric filters. Because of their modular 

design, ESPs, like fabric filters, can be applied to a wide range of system sizes. The 

operating parameters that influence ESP performance include fly ash mass loading, 

particle size distribution, fly ash electrical resistivity, and precipitator voltage and current. 

 

15 USEPA. 2003. “Air Pollution Control Technology Fact Sheet – Fabric Filter.” EPA-452/F-03-025. August 7. 16 USEPA. 2003. “Air Pollution Control Technology Fact Sheet – Dry Electrostatic Precipitator.” EPA-452/F-03-

028. August 7. 
Intalco BART Determination FINAL.doc 5-13 

Dusts with high resistivities are not well-suited for collection in dry ESPs because the 

particles are not easily charged. This also affects the ash layers on the collecting 

electrodes. An ESP is technically feasible for control of PM from the potrooms and the 

anode bake furnace at Intalco. 

5.1.4.3 Cyclones, Inertial Separators, and Wet Scrubbers 

Cyclones and inertial separators are used for collection of medium-sized and coarse 

particles. Wet scrubbers generally remove large particles but can remove small particles 

with the use of high pressure drops. However, none of these devices are as effective at 

removing small and submicron particles as fabric filters and ESPs17. 

5.1.5 Potentially Applicable BART Control Options for NOx

Potentially applicable NOx emission controls include combustion controls and post-combustion 

controls. 

5.1.5.1 Combustion Controls 

The concentration of NOx in the potroom reactor exhaust is extremely low (less than 1 

ppm) because there is no external fuel or combustion zone and there are no large sources 

of nitrogen in the raw materials. Traditional methods of preventing NOx formation using 

staged combustion or low NOx burners are not applicable to the potlines at Intalco. 

NOx emissions from anode baking depend on operating practices and burner controls. 

The traditional methods of preventing NOx formation using staged combustion or low 

NOx burners are not applicable because of the unique configuration of an anode baking 

ring furnace, with fuel injected at several points in narrow flues. However, advanced 

firing systems that measure and regulate fuel flow precisely using a computerized control 

system may reduce NOx emissions by reducing total fuel usage. Prevention of NOx

formation using advanced firing control is technically feasible for the anode bake furnace 

at Intalco. 

5.1.5.2 Post-Combustion Controls 

Selective non-catalytic reduction (SNCR), selective catalytic reduction (SCR), and low 

temperature oxidation (LoTOx) controls are discussed in this section. 

5.1.5.2.1 Selective Non-Catalytic Reduction 

SNCR is an add-on technique that involves injecting ammonia or urea into a specific 

temperature zone in a furnace or boiler. The ammonia or urea reacts with NOx in the gas 

to produce nitrogen and water. SNCR typically provides a NOx reduction of 30 to 50%. 
Intalco BART Determination FINAL.doc 5-14 

The effectiveness of SNCR depends on the temperature where reagents are injected, 

mixing of the reagent in the gas, residence time of the reagent within the required 

temperature window, and the ratio of reagent to NOx. The required temperature window 

is 1,600 to 2,100°F. Typical uncontrolled NOx levels where this technology has been 

applied vary from 200 to 400 ppm. SNCR is less effective at lower levels of uncontrolled 

NOx

18. 

The temperature (approximately 200°F) and NOx concentration (less than 1 ppm) of the 

potroom emission exhaust are outside the levels where SNCR could be used. Thus, 

SNCR is not technically feasible for the potlines at Intalco. 

The temperature of the anode baking emission exhaust (300 to 450°F) is below the 

temperature where SNCR could be used. Downstream of the reactor where tar vapors are 

removed, the temperature is approximately 200°F, which is also below the appropriate 

range. In addition, the NOx concentration (less than 20 ppm) is below the level where 

SNCR could be used. Thus, SNCR is not technically feasible for the anode bake furnace 

at Intalco. 

5.1.5.2.2 Selective Catalytic Reduction 

SCR is an add-on technique similar to SNCR that involves injecting ammonia into flue 

gas in the presence of a metal-based catalyst to convert NOx emissions to elemental 

nitrogen and water. The catalyst allows SCR systems to operate at much lower 

temperatures than SNCR; typical temperatures for SCR are 500 to 800°F, compared with 

1,600 to 2,100°F for SNCR. The optimum temperature range is 700 to 750°F19. SCR is 

capable of NOx reduction efficiencies in the range of 70 to 90% and can be used with 

NOx concentrations as low as 20 ppm. However, higher NOx levels result in increased 

performance20. 

The temperature of the potroom emission exhaust (approximately 200°F) and NOx

concentration (less than 1 ppm) of the potroom emission exhaust are outside the levels 

where SCR could be used. Thus, SCR is not technically feasible for the potlines at 

Intalco. 

The temperature of the anode baking emission exhaust (300 to 450°F) is below the 

temperature where SCR could be used. Downstream of the reactor where tar vapors are 

 17 AWMA. 2000. Air Pollution Engineering Manual, Second Edition. 18 USEPA. 2003. “Air Pollution Control Technology Fact Sheet – Selective Non-Catalytic Reduction.” EPA452/F-03-031. August 8. 

19 USEPA. 2002. EPA Air Pollution Control Cost Manual, Sixth Edition. EPA/452/B-02-001. January. 20 USEPA. 2003. “Air Pollution Control Technology Fact Sheet – Selective Catalytic Reduction.” EPA-452/F-03-

032. August 8. 
Intalco BART Determination FINAL.doc 5-15 

removed, the temperature is approximately 200°F, which is also below the appropriate 

range. In addition, the NOx concentration (less than 20 ppm) is below the level where 

SCR could be used. Thus, SCR is not technically feasible for the anode bake furnace at 

Intalco. 

5.1.5.2.3 Low-temperature Oxidation Technology (LoTOxTM) 

The LoTOxTM system is the patented technology of BOC Gases. In this NOx removal 

system, ozone is injected into the exhaust gas stream in order to oxidize insoluble NOx to 

soluble nitrogen compounds, including N2O5. N2O5 is highly soluble and reacts with 

moisture in the gas stream to form nitric acid. A scrubber is required downstream of the 

LoTOxTM system to remove the nitric acid formed by the reaction of N2O5 and moisture 

in the gas stream. The ozone is typically generated on site and on demand. Since 

LoTOxTM is a low temperature system it does not require heat input and the low operating 

temperature (150 to 250°F) allows for stable and consistent control even with variations 

in flow, load, and NOx concentrations21. 

Use of the LoTOxTM system has not been demonstrated at an aluminum plant. Research 

indicates that application of the LoTOxTM technology has been limited to a sulfuric acid 

regeneration plant, a lead smelting reverbatory furnace, a stainless steel plant, a coal-fired 

electric generation unit, and two fluidized-bed catalytic cracking units (FCCU) at 

refineries22,23. Reported NOx removal efficiencies for the LoTOxTM system are on the 

order of 90% to 95%. 

The temperature of the anode baking emission exhaust (approximately 200°F) is within 

the temperature range where LoTOxTM could be used. Although this technology has not 

been demonstrated on an anode bake furnace, low-temperature oxidation technology may 

be technically feasible for reducing anode bake furnace NOx emissions. 

5.1.6 Summary of Technically Feasible BART Control Options 

5.1.6.1 Feasible BART Control Options for SO2

Two technically feasible options were identified for controlling SO2 emissions from the 

potlines and anode bake furnace: 

• Adding a wet scrubber to the potline and/or anode bake furnace exhausts, and 

 

21 BOC Process Gas Solutions. 2001. Low Temperature Oxidation System Demonstration at RSR Quemetco, Inc., 

City of Industry, California. June 28. (www.arb.ca.gov/research/icat/projects/boc.pdf) 22 USEPA. 2005. “Using Non-Thermal Plasma to Control Air Pollutants”. EPA-456/R-05-001. February. 

www.epa.gov/ttn/catc/dir1/fnonthrm.pdf, 23 USEPA RACT/BACT/LAER Clearinghouse (RBLC) database. 
Intalco BART Determination FINAL.doc 5-16 

• A pollution prevention option limiting the sulfur content in the coke used to 

produce anodes to 3.0%. 

These two options were evaluated further as part of the BART determination analysis. 

5.1.6.2 Feasible BART Control Options for PM 

Cyclones, inertial separators, wet scrubbers, ESPs, and fabric filters are all technically 

feasible for controlling potroom PM emissions. However, ESPs and fabric filters are 

superior devices for controlling fine PM. 

Fabric filtration with dry alumina scrubbing has been widely used in the primary 

aluminum industry. Most smelters constructed within the past 20 years have used dry 

alumina scrubbing with fabric filters to control emissions from potlines. A few plants use 

control systems consisting of ESPs to collect PM followed by spray towers to scrub 

gaseous fluoride. Wet systems have many disadvantages, such as corrosion by 

hydrofluoric acid, scaling, and the requirement to treat wastewater. ESPs and wet 

systems are no longer installed on new smelters24. 

Dry scrubbers are widely used on anode bake furnaces because they provide effective 

removal of hydrocarbons, fluorides, and PM. Wet systems have the same disadvantages 

for anode bake furnaces as for potlines: corrosion by hydrofluoric acid, scaling, and the 

requirement to treat wastewater. Dry scrubbers with fabric filters are a superior choice 

for anode bake furnaces. 

Given that fabric filters are already used for PM control and that these high-efficiency 

devices are superior or equal to other feasible control options, no further analysis of PM 

controls was performed. 

5.1.6.3 Feasible BART Control Options for NOx

Since there is no external fuel or combustion zone in the smelting cells, there are no 

technically feasible pre-combustion NOx controls. Likewise, there are no technically 

feasible add-on controls because of the temperature of the potroom exhaust 

(approximately 200°F) and low NOx concentration (less than 1 ppm). 

Advanced firing systems may prevent NOx formation by reducing natural gas usage and 

are technically feasible for the anode bake furnace. Add-on SCR and SNCR controls are 

not feasible at the furnace exhaust because of the temperature (less than 450°F) and 

presence of tar vapor. SCR and SNCR are not feasible downstream of the reactor 

because of the temperature (approximately 200°F) and low NOx concentration (less than 

 

24 Air and Waste Management Association (AWMA). 2000. Air Pollution Engineering Manual, Second Edition. 
Intalco BART Determination FINAL.doc 5-17 

20 ppm). The use of low temperature oxidation (LoTOxTM) may be a viable option for 

reducing NOx emissions if a wet scrubber were installed on the bake furnace for SO2

control. 

The option for reducing NOx formation through advanced firing systems for the anode 

bake furnace was evaluated further as part of the BART determination analysis. Further 

consideration was also given to the potential use of low temperature oxidation 

(LoTOxTM). 

5.2 CONTROL EFFECTIVENESS OF FEASIBLE OPTIONS

Step 3 of the BART analysis is to evaluate the control effectiveness of the technically feasible 

control technologies. 

5.2.1 SO2 Wet Scrubbing 

A wet scrubber was identified as a technically feasible add-on pollution control option to 

reduce SO2 from the potline reactors. Typical removal efficiencies are 80 to 95%. 

Capital cost estimates and control efficiencies for wet scrubbers at Intalco were 

developed by scaling costs from two vendor quotes obtained for the installation of LSFO 

scrubbing technology at Alcoa’s facility in Alcoa, Tennessee. Each of the vendors that 

provided proposals for the Tennessee facility indicated that a 95% SO2 removal was 

technically feasible. Accordingly, an SO2 removal efficiency of 95% was used in the 

Intalco BART analysis for the wet scrubber control option. 

Mist droplets will be a component of the gas stream emitted from the scrubber. Solids in 

the droplets will become airborne PM when the water in the droplets evaporates. The PM 

concentration in the outlet of the wet scrubber was predicted to be 20 mg/Nm3 by one of 

the vendors. This compares to a concentration of 10 mg/Nm3

 currently emitted from the 

existing potline control system. Consequently, the wet scrubber option would cause a 

collateral increase in PM from the potlines. 

A wet scrubber was also identified as a technically feasible add-on pollution control 

option for the anode bake furnace since it has an SO2 concentration and a temperature 

similar to the potline reactor exhaust. However, the anode bake furnace is a smaller 

source than the potlines because of the lower exhaust gas flow rate (1,950,000 acfm 

versus 202,500 acfm). A separate vendor cost proposal was not obtained for the anode 

bake furnace, but an SO2 removal efficiency of 95% is assumed to be feasible. Wet 

scrubber costs for the anode bake furnace were also scaled from the LSFO potline wet 

scrubber vendor quotes. 
Intalco BART Determination FINAL.doc 5-18 

Table 5-2 summarizes the SO2, NOx, and PM emission levels under the control scenarios 

considered for BART. The emissions represent the combined total emissions from the 

primary and secondary potline control systems and the anode bake furnace for each 

scenario. Control scenario #1 is the addition of a wet scrubber to the potline reactors. 

Control scenario #2 is the addition of a wet scrubber to the anode bake furnace. The 

current potential emissions with 3.0% sulfur coke are also listed. The emissions 

reductions achievable for each of the scenarios were compared to current potential 

emissions. 

5.2.2 SO2 Pollution Prevention 

The pollution prevention option represents a 3.0% sulfur limit in the coke used to produce 

anodes. This option reflects the current sulfur limit in Intalco’s Title V operating permit. 

5.2.3 Anode Bake Furnace Advanced Firing System 

NOx emissions from the anode bake furnace could be reduced by incorporating an advanced 

firing system. Total gas usage is projected to be reduced by 20%, which would result in a 

corresponding 20% reduction in NOx emissions, or approximately 27 tons/year. 

5.2.4 Anode Bake Furnace LoTOxTM System 

NOx emissions from the anode bake furnace could potentially be reduced by using the LoTOxTM

system for post-combustion control. This technology has a control efficiency of 90% for NOx

emissions when combined with wet scrubbing, resulting in a potential reduction in NOx

emissions of approximately 122 tons/year. 

5.3 EVALUATION OF COSTS AND OTHER IMPACTS

Step 4 of the BART analysis involves evaluation of cost and other impacts, including energy 

impacts, greenhouse gas generation, non-air quality environmental impacts, and remaining useful 

life. Costs of control, energy impacts, greenhouse gas generation impacts, non-air quality 

environmental impacts, and remaining useful life are evaluated in this section. 

5.3.1 Cost Impacts for Feasible Controls 

5.3.1.1 Wet Scrubbers 

The exhaust gases from each potline are routed to dry alumina reactors. Potline gases 

currently exhaust to atmosphere from stacks above the fabric filters in each of the six 

baghouse scrubbing centers, which are located in courtyards between the potrooms. 

Wet scrubber costs for Intalco were estimated based on cost quotes received by Alcoa 

from two flue gas desulphurization equipment vendors. The cost quotes were originally 

provided as part of the BART analysis for Alcoa’s Tennessee Operations in Alcoa, TN. 
Intalco BART Determination FINAL.doc 5-19 

Both vendors provided cost proposals for wet scrubbing systems based on limestone 

forced oxidation (LSFO) SO2 scrubbers. Lime- or sodium-based scrubbers could also be 

used for potlines, but lime and sodium are less desirable reagents considering that these 

reagents are much more expensive. An advantage of the limestone forced oxidation 

process is that the spent slurry is oxidized to gypsum, which dewaters more efficiently, 

resulting in less waste materials requiring disposal. Thus, an LFSO scrubber was 

determined to be the most appropriate control device for the cost analysis. The vendor 

proposals are provided in Appendix B. These proposals contain confidential business 

information and are, therefore, labeled as confidential. 

Neither of the two vendors provided a comprehensive installed cost estimate. Both 

preliminary designs were based on a central scrubbing center as the least cost approach, 

where exhaust from all dry scrubbing systems would be ducted to a centralized scrubbing 

system. Both design estimates were based on systems that would provide 100% 

availability of emissions control on each day of the year, given that potlines cannot be 

easily shutdown and restarted for control system outages. 

One vendor provided an estimate of the scrubber equipment only. The other provided an 

“indicative price,” with an installed cost assumed equal to the equipment cost. Important 

retrofit considerations for installing a potline wet scrubbing system include: (1) that gases 

must be collected from multiple individual baghouse stacks, (2) the system must 

simultaneously maintain balanced flow from multiple potline control devices, and (3) the 

system installation would require transport of new components through narrow passages 

in the existing potline. Coordination of the equipment delivery and the daily work 

schedule of the potline operation would also affect the control system installation. One 

of the vendors recognized the complexity of this project, pointing out in their proposal 

that an extensive engineering effort was needed because of space limitations, access 

limitations, uncertainty as to laydown areas, and uncertainty of ductwork and supports. 

These retrofit issues would apply equally to both the Alcoa, TN facility and Intalco. 

The vendor cost proposals for the Tennessee facility were based on a total scrubber exit 

gas volume of approximately 1,580,000 acfm at 101o

F compared to a design exit gas 

volume of approximately 1,950,000 acfm at 98o

F for Intalco. Vendor equipment cost 

proposals for the Alcoa, TN facility therefore had to be adjusted to account for 

differences in exhaust gas volume and other design parameters. 

Hatch, an engineering firm contracted by Alcoa, prepared a pre-feasibility report for 

Intalco in which equipment costs provided by one of the vendors for the Alcoa, TN 

facility were scaled or adjusted to estimate LSFO equipment costs for Intalco. The 

procedure used by Hatch adjusted equipment cost estimates using appropriate exponential 
Intalco BART Determination FINAL.doc 5-20 

factors for equipment type (reagent feed, SO2 removal, gas handling, etc.), along with 

differences in system exhaust gas volume, limestone consumption, and gypsum byproduct generation. ENVIRON used the cost adjustment approach developed by Hatch 

to prepare an average equipment cost based on both vendor quotations. The equipment 

cost scaling procedures are outlined in the Hatch report in Appendix C and ENVIRON’s 

parallel calculations based on the average of the two vendor quotes are provided in 

Appendix D. 

The average scrubber equipment cost was used with factors from the EPA Air Pollution 

Cost Control Manual25 to determine installation costs and total capital costs. Operating 

costs were calculated based on utility and raw material requirements provided by Hatch, 

along with unit cost information provided by Intalco and other cost assumptions from the 

EPA Air Pollution Cost Control Manual. Complete cost calculations and assumptions 

are provided in Appendix D. 

Separate vendor cost quotes were not obtained for installing a wet SO2 scrubbing system 

on the anode bake furnace. Instead, the potline SO2 scrubber equipment costs were 

scaled to estimate Intalco anode bake control equipment costs using the same approach 

discussed above for the potlines. The anode bake wet scrubber design was based on a 

scrubber exhaust gas volume of 202,500 acfm at 98oF. The vendor equipment costs were 

adjusted using exponential factors that account for differences in exhaust gas volume, 

limestone consumption, and gypsum by-product generation. 

Table 5-3 summarizes the cost of installing and operating an LSFO wet scrubber on the 

Intalco potlines and anode bake furnace to remove 95% of the SO2. The capital and total 

annualized costs for a potline wet scrubber are high at approximately $234.5 million and 

$46.8 million per year, respectively. The wet scrubber cost effectiveness is also high at 

$7,500 per ton of SO2 removed. 

The estimated installed capital cost to add a wet scrubber to remove 95% of the SO2 from 

the anode bake furnace exhaust would be approximately $29.5 million with an annualized 

cost of $6.3 million per year. The wet scrubber cost effectiveness is also high at $36,400 

per ton of SO2 removed. 

5.3.1.2 Coke Sulfur Limit 

Intalco is currently able to obtain coke with 3.0% sulfur without incurring significant additional 

cost. However, as low sulfur coke becomes more difficult to procure, the cost will increase. 

Additional information regarding low sulfur coke availability is included in Appendix B. 

 

25 USEPA. 2000. EPA Air Pollution Cost Control Manual, Sixth Edition. EPA-452/B-02-001. January 2002 (and 

updates). 
Intalco BART Determination FINAL.doc 5-21 

5.3.1.3 Anode Bake Furnace LoTOxTM System 

Cost data for the LoTOxTM system is not readily available. However, as demonstrated above for 

the control of SO2 emissions from the anode bake furnace, the cost of the downstream scrubber 

required for the use of the LoTOxTM system would make this option cost prohibitive. NOx

emissions are lower than SO2 emissions for the anode bake furnace, so the cost per ton values for 

NOx would be even higher than for SO2. 

5.3.2 Energy Impacts 

A wet scrubber removes SO2 by forcing the exhaust gas through a spray tower or absorber where 

it contacts water droplets that contain the unreacted lime or limestone. Energy is required to 

overcome the resistance of the scrubber components as well as falling water droplets. A 

substantial amount of energy would be associated with fans to move the potline and anode bake 

furnace exhaust streams through scrubbers. Other energy is required for the slurry pumps, 

instrumentation, and miscellaneous items (e.g., lighting). The total energy required26 would be 

approximately 7,400 kilowatt-hours (kWh)/hr for the potline scrubber and 750 kWh/hr for the 

anode bake furnace scrubber. As listed in Table 5-3, this is equivalent to 64,824,000 kWh of 

electricity per year for the potline scrubber. A wet scrubber on the anode bake furnace would 

add 6,570,000 kWh per year. 

5.3.3 Greenhouse Gas Generation 

Greenhouse gases (GHGs) are gaseous compounds that are known to provide a warming effect to 

the atmosphere. The predominant GHG is carbon dioxide (CO2). Other GHGs include nitrous 

oxide and methane. The proposed SO2 control devices will increase overall emissions of GHGs 

via three mechanisms: (1) as a byproduct of the reaction chemistry in the scrubbers, (2) as 

indirect emissions from the generation of electricity required to power the scrubbing systems, 

and (3) as direct emissions from vehicle travel for the additional personnel that will be required 

at the facility to maintain and operate the scrubbing systems. The details of the GHG emission 

calculations for each of these mechanisms are presented in the Appendix E. 

The total GHGs (in carbon dioxide equivalents) generated by the implementation of the proposed 

scrubbing system for the potline fumes was estimated to be 96,441 pounds per day, or 17,597 

tons per year. The total GHGs (in carbon dioxide equivalents) generated by the implementation 

of the proposed scrubbing system for the anode baking furnace was estimated to be 7,298 pounds 

per day, or 1,330 tons per year. 

5.3.4 Non-Air Quality Environmental Impacts 

Both of the wet scrubber proposals were based on the LSFO process. This process oxidizes the 

spent slurry to gypsum, which may be landfilled or commercially sold. There is no way to know 
Intalco BART Determination FINAL.doc 5-22 

at this time whether the gypsum would have commercial value or whether there would be any 

demand for it. Therefore, it must be assumed that 27,130 tons of waste from a potline wet 

scrubber and 639.5 tons of waste from an anode bake furnace wet scrubber would be landfilled 

each year. 

It is estimated that 182.5 million gallons of water will be required annually to operate the potline 

wet scrubber at a cost of approximately $97,000. This will significantly impact the community 

infrastructure in that this will increase Intalco’s daily water demand by approximately 9%27. 

It is also estimated that a total of approximately 71.4 million kWh would be needed to operate 

the potline and anode bake furnace scrubbers annually. This would impact power demand in the 

community and would also have an environmental impact due to power production equivalent to 

adding approximately 6,700 new households in the community28. 

5.3.5 Remaining Useful Life 

The Intalco smelter has been in operation since 1966 and remains a critical component of 

Alcoa’s aluminum production in the United States. The facility intends to be in operation 

throughout the period of the Regional Haze Program. 

5.4 EVALUATE VISIBILITY IMPACTS

Step 5 of the BART analysis involves evaluation of visibility impacts. More specifically, this is 

an evaluation of the potential improvement in visibility resulting from application of feasible 

pollution prevention/add-on control options. Refined CALPUFF modeling was performed for 

two control scenarios: one with wet SO2 scrubbing applied to the potline and one with wet SO2

scrubbing applied to the anode bake furnace. This modeling was accomplished according to 

State of Washington’s BART modeling protocol29. In general, this modeling was the same as the 

baseline modeling except stack data and emission data associated with the application of the 

feasible add-on controls were used as model inputs. Table 5-4 presents the post-control 

modeling source input data that were used in the CALPUFF model to forecast visibility impacts 

for the two control options. 

Table 5-5 presents the results of modeling with the two scrubber SO2 control scenarios along 

with baseline impacts. As shown in Table 5-5, the addition of a potline wet scrubber reduced 

 26 Hatch. 2007. SO2 Scrubbing for the INTALCO Primary Aluminum Smelter: Pre-Feasibility Report. July 26. 27 Based on average facility incoming water flow rates for 1998 through 2000, the three most recent years the 

facility was at full production. 28 Calculated based on 2001 average energy usage per household for the United States as reported by the 

Department of Energy (http://www.eia.doe.gov/emeu/reps/enduse/er01_us_tab1.html). 

29 Modeling Protocol for Washington, Oregon, and Idaho: Protocol for the Application of the CALPUFF Modeling 

System Pursuant to the Best Available Retrofit Technology (BART) Regulation. October 11, 2006. 

www.deq.state.or.us/aq/haze/docs/bartprotocol.pdf 
Intalco BART Determination FINAL.doc 5-23 

modeled visibility impacts in all five Class I areas to between approximately 0.1 and 0.35 dv for 

the three years modeled. For example, the baseline modeling results indicate that the highest 98th

percentile visibility impact from Intalco’s BART-eligible sources at Olympic National Park with 

3% sulfur in the coke was 1.527 dv. The post-control modeling results indicate that the highest 

98th percentile visibility impact from Intalco’s BART-eligible sources at Olympic National Park 

with wet scrubbers installed on the potlines was 0.355 dv in 2003. This represents a 1.17 dv 

reduction in total facility visibility impacts at Olympic National Park with the addition of wet 

scrubbers on the potlines. 

The modeled visibility improvements shown in Table 5-5 from adding a wet scrubber at the 

anode bake furnace are minimal, with improvements ranging from approximately 0.004 to 0.024 

dv compared to the baseline conditions. For example, the post-control modeling results for the 

anode bake furnace indicate a highest 98th percentile visibility impact of 1.503 dv compared to 

the baseline value of 1.527 dv in 2003. This represents less than a 2% reduction in total facility 

visibility impacts at Olympic National Park with the addition of wet scrubbers on the anode bake 

furnace. 

For NOx, the use of an advanced firing system or LoTOxTM technology for the anode bake 

furnace would also result in minimal improvements in visibility. The baseline visibility 

modeling indicated that the highest 98th percentile visibility impact due to anode bake furnace 

NOx emissions was approximately 0.03 dv (55% of 0.053 dv). Therefore, a 20% reduction in 

NOx emissions from the anode bake furnace with the use of an advanced firing system would 

reduce Intalco’s total visibility impacts by approximately 0.006 dv and a 90% reduction with the 

use of LoTOxTM would reduce the impacts by approximately 0.027 dv. Based on the minimal 

change in visibility forecast resulting from the installation of an advanced firing system or use of 

LoTOxTM, it was determined that neither of these technologies represents reasonably effective 

BART control technologies for the anode bake furnace. 
 

Intalco BART Determination FINAL.doc 6-1

6.0 DETERMINATION OF BART 

6.1 ALUMINUM POTLINES

For potline SO2 emissions, BART was determined to be the current level of control, which is a 

pollution prevention limit of 3% sulfur in the coke used to manufacture anodes. A pollution 

prevention limit based on coke sulfur contents below 3% was determined by Intalco to be 

infeasible as BART for 2013 and beyond based on a market and availability analysis for future 

coke supply. Use of wet scrubbing technology to reduce potline SO2 emissions was rejected as 

BART due to excessive costs: total cost effectiveness of $7,500 per ton of SO2 removed and 

capital and total annualized costs of $234.5 million and $46.8 million per year, respectively. A 

potline wet scrubber would also have substantial secondary impacts, including increased energy 

usage of 64,824,000 kWh of electricity per year, added water consumption of 183 million 

gallons per year, and solid waste generation of 27,000 tons per year. 

For PM emissions, BART was determined to be the current level of control, which is the use of 

baghouses to control PM emissions from the alumina dry scrubbers and wet roof scrubbers to 

control secondary PM emissions from the potroom roofs. 

There are no feasible technologies for control of NOx from the potlines; thus, BART for NOx

was determined to be no controls. 

6.2 ANODE BAKE FURNACE

A pollution prevention limit of 3% sulfur in the coke was also determined to be BART for anode 

bake furnace SO2 emissions. The cost of wet scrubbing to reduce SO2 emissions would be 

excessive at $36,400 per ton of SO2 removed while providing minimal visibility improvement. 

The existing level of control (based on baghouses on the alumina dry scrubbers) was determined 

to be BART for PM emissions. 

BART for anode bake furnace NOx emissions was determined to be no controls. The use of an 

advanced firing system for reduced energy use was rejected as BART because the technology 

would result in negligible visibility improvement. Similarly, the use of LoTOxTM was rejected as 

BART because the cost of the technology would be excessive and result in negligible visibility 

improvement. 
 

Intalco BART Determination FINAL.doc 6-2

6.3 ALUMINUM HOLDING FURNACES

BART for the aluminum holding furnaces was determined to be no controls. The use of 

additional controls was rejected as BART because any visibility improvement would be 

negligible. 

6.4 MATERIAL HANDLING AND TRANSFER OPERATIONS

PM emissions from the BART-eligible material handling and transfer operations are all 

controlled using fabric filter technology. This existing level of emissions control was determined 

to be BART for these material handling and transfer operations. 
TABLES 
Process 

Number

Emission Unit 

ID Emission Unit Description

Visibility 

Impairing 

Pollutants

Existing 

Pollution 

Controls

Modeling Source 

Type

5 181-186 Potline primary emission control system stacks PM, SOx

Reactor/ 

Fabric Filter Point

5 22-180 Potline secondary emission control system stacks PM, SOx

Roof Water 

Scrubbers Line

3 187 Anode bake furnace PM, SOx, NOx

Reactor/ 

Fabric Filter Point

6 4, 5, 7, 8, 10, 11, 

13, 14, 16-19 Aluminum holding furnaces PM Fabric Filter Point

2 188 Paste plant baghouse stack PM Fabric Filter Point

2 189 Phase A ball mill baghouse stack PM Fabric Filter Point

2 191 Phase B ball mill baghouse stack PM Fabric Filter Point

7 195 Primary WTP kiln wet scrubber PM Wet Scrubber Point

4 198 Rod shop (west) baghouse stack PM Fabric Filter Point

4 199 Rod shop (east) baghouse stack PM Fabric Filter Point

7 208 Ladle cleaning baghouse stack PM Fabric Filter Point

7 209 Autogenous mill baghouse stack PM Fabric Filter Point

7 210 TAC station baghouse stack PM Fabric Filter Point

6 217 Remelt furnace stack PM Point

2 232 Butts baghouse stack PM Fabric Filter Point

4 260 Aluminum spray cyclone stack PM Point

4 312 Rod shop induction furnace (east) stack PM Point

4 313 Rod shop induction furnace (west) stack PM Point

2 316 Pitch fume treatment system PM Point

3 251 Anode bake building monitor roof PM Volume

3 252 Anode block hole blower PM Volume

4 257A Rod shop crust recovery discharge to trucks from bins #1 and #2 PM Volume

4 257B Rod shop crust recovery discharge to trucks from bins #1 and #2 PM Volume

4 259A Rod shop carbon recovery discharge to trucks from bins #1 and #2 PM Volume

4 259B Rod shop carbon recovery discharge to trucks from bins #1 and #2 PM Volume

7 280 Annex cathode assembly area roof vents PM Volume

7 282 Annex ramming paste area roof vents PM Volume

1 239 Paved road vehicle dust emissions PM Area

1 241 Facility-wide natural gas combustion PM, SOx, NOx Area

7 273 Alumina ore handling fugitive dust PM Area

1 233 General welding PM Volume (combined)

1 240 Fugitive dust from loading and dumping waste PM Volume (combined)

1 242 Plant-wide propane combustion emissions PM, SOx, NOx Volume (combined)

2 190 Phase "A" mixer fugitives PM Volume (combined)

2 192 Phase "B" mixer fugitives PM Volume (combined)

2 193 KVS ball mill baghouse stack PM Fabric Filter Volume (combined)

2 194 Pet coke baghouse stack PM Fabric Filter Volume (combined)

2 243 Paste plant roof vents PM, SOx, NOx Volume (combined)

2 244 Phase "A" paste cooling conveyor fugitives PM Volume (combined)

2 245 Phase "B" paste cooling conveyor fugitives PM Volume (combined)

2 248 Scrap paste storage bins PM Volume (combined)

2 249 Paste plant vacuum system baghouse stack PM Fabric Filter Volume (combined)

3 250 Packing coke silo vent PM Volume (combined)

4 253 Rod shop roof vents (north) PM Volume (combined)

4 254 Rod shop roof vents (south) PM Volume (combined)

4 255 Hot anode butts transport PM Volume (combined)

4 256A,B Rod shop crust recovery discharge to storage bins #1 and #2 PM Volume (combined)

4 258A,B Rod shop carbon recovery discharge to storage bins #1 and #2 PM Volume (combined)

4 263 Cooling of cast iron dross sows outside rod shop PM Volume (combined)

Table 3-1

Primary Aluminum Reduction Emission Units

Alcoa Intalco Works

Ferndale, Washington
Process 

Number

Emission Unit 

ID Emission Unit Description

Visibility 

Impairing 

Pollutants

Existing 

Pollution 

Controls

Modeling Source 

Type

Table 3-1

Primary Aluminum Reduction Emission Units

Alcoa Intalco Works

Ferndale, Washington

5 238 Auxiliary diesel generators PM, SOx, NOx Volume (combined)

6 3, 6, 9, 12, 15 Casting pit steam exhaust stacks PM Volume (combined)

6 21 Pigger cooling conveyor exhaust stack PM Volume (combined)

6 220a, 220b, 

221a, 221b MHD holding furnaces PM Volume (combined)

6 266 Casthouse monitor roof PM Volume (combined)

6 269 Pigger aluminum furnace door exhaust hood PM Volume (combined)

6 315 Dross/silicon storage baghouse PM Fabric Filter Volume (combined)

7 196 Primary WTP reclaimed storage silo baghouse stack PM Fabric Filter Volume (combined)

7 206 Pangborn baghouse stack PM Fabric Filter Volume (combined)

7 207 Annex paste plant baghouse stack PM Fabric Filter Volume (combined)

7 211 Alumina ore silo #1 baghouse stack PM Fabric Filter Volume (combined)

7 212 Alumina ore silo #2 baghouse stack PM Fabric Filter Volume (combined)

7 213 Alumina ore silo #3 baghouse stack PM Fabric Filter Volume (combined)

7 214 Alumina ore silo #4 railcar unloader baghouse stack PM Fabric Filter Volume (combined)

7 215 Alumina ore pier-head transfer point baghouse stack PM Fabric Filter Volume (combined)

7 216 Alumina ore ship unloading baghouse stack PM Fabric Filter Volume (combined)

7 226 Aluminum fluoride silo baghouse stack PM Fabric Filter Volume (combined)

7 228 Covered annex bunkers for crust and digout PM Volume (combined)

7 229 Brick crushing facility baghouse stack PM Fabric Filter Volume (combined)

7 274 Alumina silo #4 truck loader baghouse stack PM Fabric Filter Volume (combined)

7 275 Aluminum fluoride/anthracite railcar unloading fugitive dust PM Volume (combined)

7 276 Coke unloading and transfer fugitive dust PM Volume (combined)

7 281 Annex ramming paste area roof vents PM Volume (combined)

7 284 Annex west pitch melter stack PM Volume (combined)

7 285 Annex east pitch melter stack PM Volume (combined)

7 286 Annex ramming paste mixer stack PM Volume (combined)

7 287 Autogenous mill silo baghouse stack PM Fabric Filter Volume (combined)

7 293 Baghouse hopper unloading PM Volume (combined)

7 295 Landfill - solid waste PM Volume (combined)

7 296 Landfill - RCRA waste PM Volume (combined)

7 306 Alumina ore ship unloader clamshell PM Volume (combined)

8 222 Paint shop shot blaster baghouse stack PM Fabric Filter Volume (combined)
LCC 

Coordinate 

X

LCC 

Coordinate 

Y

Stack 

Height

Base 

Elevation

Effective 

Stack 

Diameter

Exit 

Velocity

Flow 

Rate

Exit 

Temperature

PM10 

Emission 

Rate

Filterable 

PM2.5 

Emission 

Rate

Conde

PM

Emi

R

(km) (km) (m) (m) (m) (m/s) (m3/s) (°K) (g/s) (g/s) (g

DSA1 -120.536 -14.914 19.8 65.4 3.733 12.98 142.1 363.7 1.81 0.097 1.DSA2 -120.466 -15.150 19.8 63.9 3.733 13.05 142.8 363.7 1.81 0.097 1.

DSB3 -120.691 -14.958 17.9 62.2 5.957 5.17 144.1 353.1 1.81 0.097 1.DSB4 -120.621 -15.195 17.9 61.4 5.957 5.17 144.1 353.1 1.81 0.097 1.DSC5 -120.840 -15.000 17.9 59.7 5.723 4.90 126.0 355.1 1.81 0.097 1.DSC6 -120.770 -15.238 17.9 59.0 5.723 4.79 123.2 355.1 1.81 0.097 1.

BAKEOVEN -121.011 -15.391 25.5 57.5 2.129 12.98 46.2 369.4 0.35 0.15 0.

CAST1-6 -120.392 -15.061 26.9 66.1 2.365 5.69 25.0 433.0 0.33 0.079 0.CAST7-8 -120.415 -14.965 23.2 66.1 1.365 5.69 8.3 433.0 0.11 0.026 0.0

CAST9-10 -120.422 -14.960 18.4 66.1 1.365 5.69 8.3 433.0 0.11 0.026 0.0

CAST11-12 -120.433 -14.922 23.2 66.1 1.365 5.69 8.3 433.0 0.11 0.026 0.0

188 -120.933 -15.393 36.1 58.5 1.462 5.34 9.0 Ambient 0.010 0.010189 -120.919 -15.088 36.1 58.5 1.287 3.63 4.7 Ambient 0.090 0.090191 -120.940 -15.395 36.1 58.5 1.287 3.63 4.7 Ambient 0.090 0.090195 -120.553 -15.394 17.7 63.1 0.61 4.29 1.3 343.0 0.080 0.080198 -120.957 -15.122 13.3 58.5 1.219 20.23 23.6 Ambient 0.24 0.24199 -120.953 -15.121 13.3 58.5 1.219 20.23 23.6 Ambient 0.24 0.24208 -121.006 -15.002 5.0 58.5 1.828 2.53 6.6 Ambient 0.076 0.076209 -121.095 -14.985 15.7 74.4 0.914 36.19 23.7 Ambient 0.43 0.43210 -120.400 -15.282 9.4 65.2 0.762 3.11 1.4 395.0 0.00018 0.00018217 -120.360 -15.210 23.2 77 1.365 5.69 8.3 433.0 0.026 0.0035 0.0232 -120.931 -15.423 6.6 58.2 0.61 29.12 8.5 Ambient 0.097 0.097260 -120.925 -15.134 11 59.1 0.26 1.46 0.08 Ambient 0.025 0.025312 -120.922 -15.099 13.7 58.5 0.49 1.59 0.30 370.0 0.11 0.11313 -120.941 -15.104 13.7 58.5 0.49 1.59 0.30 370.0 0.11 0.11316 -120.858 -15.400 22.86 57.96 1.372 15.9 23.5 302.9 0.30 0.30

Source 

Description

Table 4-1

Source Input Data for Baseline Modeling - Point Sources

Alcoa Intalco Works

Ferndale, Washington
Roof Scrubber Water On Conditions

LCC 

Coordinate 

Begin X

LCC 

Coordinate 

Begin Y

LCC 

Coordinate 

End X

LCC 

Coordinate 

End Y

Release 

Height

Base 

Elevation

Line 

Source 

Width

Exit 

Velocity

Flow 

Rate

Buoyancy 

Parameter

PM10 

Emission 

Rate

Filterable 

PM2.5 

Emission 

Rate

C

(km) (km) (km) (km) (m) (m) (m) (m/s) (m3/s) (m4/s3) (g/s) (g/s) 

WSLINEA1 -120.532 -14.845 -120.422 -15.219 16.40 65.4 4.24 3.920 55.32 410.22 2.30 0.87 WSLINEA2 -120.606 -14.867 -120.496 -15.241 16.40 64.1 4.24 3.920 55.32 410.22 2.30 0.87 

WSLINEB1 -120.681 -14.892 -120.571 -15.266 16.40 62.9 4.24 3.990 56.30 417.52 2.30 0.87 WSLINEB2 -120.755 -14.914 -120.645 -15.288 16.40 61.7 4.24 3.990 56.30 417.52 2.30 0.87 WSLINEC1 -120.828 -14.936 -120.719 -15.309 16.40 60.5 4.24 3.904 55.08 408.49 2.30 0.87 WSLINEC2 -120.903 -14.958 -120.793 -15.332 16.40 59.3 4.24 3.904 55.08 408.49 2.30 0.87 

Roof Scrubber Water Off Conditions

LCC 

Coordinate 

Begin X

LCC 

Coordinate 

Begin Y

LCC 

Coordinate 

End X

LCC 

Coordinate 

End Y

Release 

Height

Base 

Elevation

Line 

Source 

Width

Exit 

Velocity

Flow 

Rate

Buoyancy 

Parameter

PM10 

Emission 

Rate

Filterable 

PM2.5 

Emission 

Rate

C

(km) (km) (km) (km) (m) (m) (m) (m/s) (m3/s) (m4/s3) (g/s) (g/s) 

WSLINEA1 -120.532 -14.845 -120.422 -15.219 16.40 65.4 4.24 3.920 55.32 860.33 11.94 4.48 WSLINEA2 -120.606 -14.867 -120.496 -15.241 16.40 64.1 4.24 3.920 55.32 860.33 11.94 4.48 

WSLINEB1 -120.681 -14.892 -120.571 -15.266 16.40 62.9 4.24 3.990 56.30 875.62 11.94 4.48 WSLINEB2 -120.755 -14.914 -120.645 -15.288 16.40 61.7 4.24 3.990 56.30 875.62 11.94 4.48 WSLINEC1 -120.828 -14.936 -120.719 -15.309 16.40 60.5 4.24 3.904 55.08 856.70 11.94 4.48 WSLINEC2 -120.903 -14.958 -120.793 -15.332 16.40 59.3 4.24 3.904 55.08 856.70 11.94 4.48 

Source 

Description

Source 

Description

Table 4-2

Source Input Data for Baseline Modeling - Line Sources

Alcoa Intalco Works

Ferndale, Washington
Southwest 

Corner LCC 

Coordinate X

Southwest 

Corner LCC 

Coordinate Y

Release 

Height

Initial 

σz

Base 

Elevation

Total 

Area

PM10 

Emission 

Rate

Filterable 

PM2.5 

Emission 

Rate

Cond

P

Em

R

(km) (km) (m) (m) (m) (m2) (g/s/m2) (g/s/m2) (g/

239 Fugitive dust from vehicle travel on paved roads -120.536 -14.914 5 10 60 720,000 0.00000040 0.000000059 241 Facility-wide natural gas combustion (fugitive) -120.466 -15.150 15 15 60 720,000 0.00000022 0.00000022 273 Alumina ore handling fugitive dust -120.691 -14.958 15 15 60 720,000 0.000000053 0.0000000080 

Source 

ID Source Description

Table 4-3

Source Input Data for Baseline Modeling - Area Sources

Alcoa Intalco Works

Ferndale, Washington
Reference 

LCC 

Coordinate 

X

Reference 

LCC 

Coordinate 

Y

Release 

Height

Initial 

σy

Initial 

σz

Base 

Elevation

PM10 

Emission 

Rate

Filterable 

PM2.5 

Emission 

Rate

(km) (km) (m) (m) (m) (m) (g/s) (g/s) 

251 Anode bake building monitor roof -120.982 -15.242 22 33.7 10.2 58.7 0.13 0.13 252 Anode block hole blower -120.982 -14.242 22 33.7 10.2 58.7 0.12 0.12 

257A Rod shop crust recovery discharge to trucks from bins #1 and #2 -120.948 -15.123 4.6 1.07 1.07 58.5 0.0021 0.00032 

257B Rod shop crust recovery discharge to trucks from bins #1 and #2 -120.906 -15.112 4.6 1.07 1.07 58.5 0.0021 0.00032 

259A Rod shop carbon recovery discharge to trucks from bins #1 and #2 -120.948 -15.123 4.6 1.07 1.07 58.5 0.0030 0.00046 

259B Rod shop carbon recovery discharge to trucks from bins #1 and #2 -120.906 -15.112 4.6 1.07 1.07 58.5 0.0030 0.00046 

280 Annex cathode assembly area roof vent -120.983 -15.013 18.3 8.97 8.51 58.5 0.054 0.054 282 Annex ladle rebuild area rood vents -120.952 -14.99 18.3 8.97 8.51 58.5 0.38 0.38 

Others1 Other sources smaller than 0.1 g/s, combined (no SOx or NOx) -120.665 -15.076 4.6 1.07 1.07 62.0 0.358 0.307 

Others2 Other sources greater than 0.1 g/s, combined (no SOx or NOx) -120.665 -15.076 4.6 1.07 1.07 62.0 0.849 0.7414 

Others3 Other sources, combined (with SOx or NOx emissions) -120.665 -15.076 4.6 1.07 1.07 62.0 0.1722 0.1676 

Source 

ID Source Description

Table 4-4

Source Input Data for Baseline Modeling - Volume Sources

Alcoa Intalco Works

Ferndale, Washington
Modeled 

98th 

Percentile

Modeled 

98th 

Percentile

Modeled 

98th 

Percentile

(deciview) (deciview) (deciview)

Alpine Lakes Wilderness Area 1.244 36 0.965 37 0.881 23

Goat Rock Wilderness Area 0.500 8 0.579 10 0.317 3

Glacier Peak Wilderness Area 1.161 37 1.156 38 0.736 23

Mount Adams Wilderness Area 0.456 7 0.472 6 0.357 2

Mount Rainier National Park 0.843 22 1.052 26 0.629 15

North Cascades National Park 1.376 65 1.395 56 1.138 32

Olympic National Park 2.363 59 1.858 53 2.136 45

Pasayten Wilderness Area 0.866 30 0.871 33 0.659 13

Note:

2003

Number of 

Days 

Exceeding 

0.5 dv

2004

Number of 

Days 

Exceeding 

0.5 dv

Modeled visibility impacts that exceed the 0.5 dv contribution threshold are presented in bold in this table.

Table 4-5

Screening Baseline Visibility Modeling Results

Alcoa Intalco Works

Ferndale, Washington

Class I Area

2005

Number of 

Days 

Exceeding 

0.5 dv
Modeled 

98th 

Percentile

Modeled 

98th 

Percentile

Modeled 

98th 

Percentile

(deciview) (deciview) (deciview)

Alpine Lakes Wilderness Area 0.738 24 0.742 18 0.632 9

Goat Rock Wilderness Area 0.332 4 0.287 5 0.194 0

Glacier Peak Wilderness Area 0.916 24 0.769 25 0.552 10

Mount Rainier National Park 0.660 11 0.574 9 0.414 3

North Cascades National Park 0.936 36 0.986 35 0.693 14

Olympic National Park 1.527 41 1.369 37 1.225 34

Pasayten Wilderness Area 0.448 6 0.469 6 0.412 2

Note:

Table 4-6

Refined Baseline Visibility Modeling Results

Alcoa Intalco Works

Ferndale, Washington

Modeled visibility impacts that exceed the 0.5 dv contribution threshold are presented in bold in this table.

Class I Area

2005

Number of 

Days 

Exceeding 

0.5 dv

2003

Number of 

Days 

Exceeding 

0.5 dv

2004

Number of 

Days 

Exceeding 

0.5 dv
Modeled 98th 

Percentile

(deciview) SO4 NO3 Filterable PM2.5 Coarse PM Co

Total of all sources 1.527 92.5% 3.0% 0.5% 0.5% Potline primary emission controls 1.414 96.6% 0% 0.05% 0.3% 

Potline secondary emission controls 0.026 67.6% 0% 5% 5.4% Anode bake furnace 0.048 59.4% 39.1% 0% 0% 

Casthouse stacks 0.002 0% 0% 0% 0% All other stacks 0.003 0% 0% 80.0% 20.0% All volume sources 0.022 6.3% 75.0% 12.5% 6.3% All area sources 0.011 0% 93.8% 0% 0% Total of all sources 1.369 80.8% 4.4% 1.7% 2.4% Potline primary emission controls 1.142 90.6% 0% 0.12% 1.1% 

Potline secondary emission controls 0.124 40.4% 0% 10.1% 11.8% Anode bake furnace 0.053 40.8% 55.3% 1.3% 1.3% Casthouse stacks 0.004 0% 0% 16.7% 16.7% All other stacks 0.006 0% 0% 66.7% 33.3% All volume sources 0.025 2.8% 69.4% 16.7% 11.1% All area sources 0.014 0% 95.0% 5.0% 5.0% Total of all sources 1.225 90.3% 2.5% 0.95% 0.89% Potline primary emission controls 1.080 95.7% 0% 0% 0% 

Potline secondary emission controls 0.079 61.5% 0% 7.3% 5.5% Anode bake furnace 0.039 62.3% 34.0% 0% 0% Casthouse stacks 0.001 0% 0% 0% 0% All other stacks 0.003 0% 0% 75.0% 25.0% All volume sources 0.016 4.5% 68.2% 13.6% 9.1% All area sources 0.007 0% 90.0% 0% 0% 

200320042005

Year Source Group

Percentage of Species Contribution

Table 4-7

Culpability Analysis for Refined Baseline Visibility Modeling Results in Olympic National Park

Alcoa Intalco Works

Ferndale, Washington
RBLC ID Facility Last Update Process Pollutant Control Option Percent Efficiency E

KY-0070 NSA - A Division of Southwire Company 03/02/2004 Potline 5 SO2 Wet scrubber1 93% 

SC-0037 Alumax of South Carolina 09/17/2002 Potroom Groups (4) PM Existing dry alumina scrubbers (fabric filter) SC-0037 Alumax of South Carolina 09/17/2002 Potroom Groups (4) SO2 Limit maximum % sulfur of anode coke to 2.95%; limit maximum % sulfur of anode pitch to 1.2% 

SC-0037 Alumax of South Carolina 09/17/2002 Anode Bake Plant SO2

No upgrade; limit maximum % sulfur of anode coke to 2.95%; limit maximum % sulfur of anode pitch to 1.2%

SC-0037 Alumax of South Carolina 09/17/2002 Anode Bake Plant PM No upgrade; limit sulfur content of raw materials SC-0037 Alumax of South Carolina 09/17/2002 Anode Bake Plant NOx No upgrade; limit sulfur content of raw materials 

KY-0041 Arco Metals Co. 12/18/2001 Primary Aluminum Reduction Potline PM Baghouse, hooding for raw material handling 98% 

KY-0041 Arco Metals Co. 12/18/2001 Primary Aluminum Reduction Potline SO2 Fuel spec: low sulfur coke and pitch (calc. 3% sulfur) 

OR-0002 Alumax Pacific Corp. 12/18/2001 Entire Plant PM Baghouse 5.4 lb

5.0 lb

OR-0002 Alumax Pacific Corp. 12/18/2001 Anode Coke SO2 Fuel spec: sulfur limit in coke 

WA-0003 Alcoa 12/18/2001 Potlines 1, 2, and 3 SO2 Fuel spec: limit S content in coke, raw 

NC-0003 Alcoa 01/28/2002 Potline 3 PM Fabric filter NC-0003 Alcoa 01/28/2002 Potline 3 SO2 

NC-0003 Alcoa 01/28/2002 Anode Production SO2 

NC-0003 Alcoa 01/28/2002 Anode Production PM 

MO-0036 Noranda Aluminum, Inc. 05/09/2006 Carbon Baking Furnace for Potline 3 PM10 

MO-0036 Noranda Aluminum, Inc. 05/09/2006 Potline 1 PM10 Coated filter dry scrubber 

MO-0036 Noranda Aluminum, Inc. 05/09/2006 Potline 3 PM10 Coated filter dry scrubber 

Note:

1 This wet scrubber is not actually used or required by permit.

Table 5-1

RBLC Database Search Results for Primary Aluminum Facilities

Alcoa Intalco Works

Ferndale, Washington
Emissions Emissions Emissions Emission

(tons/yr) (tons/yr) (tons/yr) (tons/yr

1 LSFO Scrubber for Potlines 854 88 136 0 984 (42) 1,113 2 LSFO Scrubber for Anode Bake Furnace 6,904 2 136 0 747 (8) 921 

Current 

Allowable 

Emissions

Operating Limit of 3% Sulfur in Coke 7,076 136 693 869

Notes:

SO2 NOx

Table 5-2

Post Control Emission Rates1

Alcoa Intalco Works

Ferndale, Washington

% Reduction 

(Increase)2

1 Emission rates include the potline primary control system, the potline secondary control system emissions, and the anode ba

emissions.

2 Compared with current potential emissions.

PM2.5 

% Reduction 

(Increase)2

% Reduction 

(Increase)2

Control 

Scenario

SO2 Control 

Technology
Control 

Scenario

Control 

Technology 

Evaluated

Controlled 

SO2 Emission 

Rate1

(tons/year)

SO2 

Emission 

Reductions2

(tons/year)

Installed 

Capital Cost

Total 

Annualized 

Control 

Costs

Cost 

Effectiveness

(per ton SO2 

removed)

Energy 

Impact

(kW-hr/yr)

291 tons/yr PM2.5 27,130 to

243 tons/yr PM10 182.5 m

17,597 tons/yr GHG3

54 tons/yr PM2.5 639.5 to

52 tons/yr PM2.5 12.8 m

1,330 tons/yr GHG3

Current 

Allowable 

Emissions

Operating Limit of 3% Sulfur in Coke

7,076

Notes:

3 Greenhouse gas (GHG) emissions are presented as CO2 equivalent emissions. The GHG emission calculations are presented in Appendix E.

Non-A

Table 5-3

Summary of the Impacts Analysis for SO2 Control Scenarios

Alcoa Intalco Works

Ferndale, Washington

Collateral Increase 

in Other Pollutants

1 Emission rates include the potline primary control system, the potline secondary control system emissions, and the anode bake furnace emissions.2 Compared with current potential emissions.

12

LSFO Scrubber for PotlinesLSFO Scrubber for Anode Bake Furnace

854

6,904

6,223

172 $29,482,194

$234,531,049

6,570,000

$46,820,000 64,824,000

$6,277,000

$7,500

$36,400
LCC 

Coordinate 

X

LCC 

Coordinate 

Y

Stack 

Height

Base 

Elevation

Effective 

Stack 

Diameter

Exit 

Velocity

Exit 

Temperature

PM10 

Emission 

Rate

Filterable 

PM2.5 

Emission 

Rate

C

(km) (km) (m) (m) (m) (m/s) (°K) (g/s) (g/s) 

1 LSFO Scrubber for Potlines Potline Wet Scrubber2 -120.425 -15.316 38.1 59.0 8.1 18.3 310 0.00 17.8 

2 LSFO Scrubber for Anode Bake Furnace Anode Bake Furnace Wet Scrubber3 -121.018 -15.614 30.5 57.5 2.6 18.3 336 0.00 1.70 

Notes:

1 Source input data for all other sources are the same as listed in Table 4-1 through 4-4 for the baseline modeling.2 Potline wet scrubber source replaces sources DSA1, DSA2, DSB3, DSB4, DSC5, and DSC6 in Table 4-1 from the baseline modeling.3 Anode bake oven wet scrubber source replaces source BAKEOVEN in Table 4-1 from the baseline modeling.

Control 

Scenario

SO2 Control 

Technology Source Description

Table 5-4

Source Input Data for Post Control SO2 Modeling1

Alcoa Intalco Works

Ferndale, Washington
Modeled 

98th 

Percentile

Modeled 

98th 

Percentile

Mode

98th 

Percen

(deciview) (deciview) (decivi

Alpine Lakes Wilderness Area 0.158 0 0.147 0 0.12Glacier Peak Wilderness Area 0.190 0 0.163 0 0.12Mount Rainier National Park 0.108 0 0.107 0 0.08North Cascades National Park 0.198 0 0.212 0 0.17Olympic National Park 0.355 2 0.303 1 0.32Alpine Lakes Wilderness Area 0.723 22 0.729 18 0.62

Glacier Peak Wilderness Area 0.901 24 0.752 23 0.54

Mount Rainier National Park 0.648 11 0.565 9 0.41

North Cascades National Park 0.921 36 0.974 34 0.68

Olympic National Park 1.503 41 1.348 37 1.20

Alpine Lakes Wilderness Area 0.738 24 0.742 18 0.63

Glacier Peak Wilderness Area 0.916 24 0.769 25 0.55

Mount Rainier National Park 0.660 11 0.574 9 0.41

North Cascades National Park 0.936 36 0.986 35 0.69

Olympic National Park 1.527 41 1.369 37 1.22

Note:

Table 5-5

SO2 Post Control Visibility Modeling Results

Alcoa Intalco Works

Ferndale, Washington

Control 

Scenario

SO2 Control 

Technology 

Evaluated

Class I Area

2003

Number of 

Days 

Exceeding 

0.5 dv

2004

Number of 

Days 

Exceeding 

0.5 dv

Current 

Allowable 

Emissions

Operating Limit of 3% Sulfur in Coke

Modeled visibility impacts that exceed the 0.5 dv contribution threshold are presented in bold in this table.

LSFO Scrubber for Potlines 1

2 LSFO Scrubber for Anode Bake Furnace
APPENDICES 
APPENDIX A: 

BART MODELING RESULTS
APPENDIX B: 

BUSINESS CONFIDENTIAL INFORMATION
APPENDIX C: 

PRE-FEASIBILITY REPORT
APPENDIX D: 

WET SCRUBBER ECONOMIC AND ENERGY IMPACT
Potlines Anode Bake Furnace Vendor Quote #1 Vendor Quote #2 Average Potli

Reagent feed system 10% 0.33 0.80 $6,500,000 $8,200,000 $7,350,000 $7,894SO2 removal system 35% 0.50 0.80 $22,750,000 $28,700,000 $25,725,000 $28,54

Flue gas system 30% 0.50 0.80 $19,500,000 $24,600,000 $22,050,000 $24,46By-product handling system 10% 0.40 0.80 $6,500,000 $8,200,000 $7,350,000 $8,104General support equipment 15% 0.15 0.80 $9,750,000 $12,300,000 $11,025,000 $11,43

TOTAL $65,000,000 $82,000,000 $73,500,000 $80,44

Scaling of Capital Equipment Costs Based on Vendor Proposals

Intalco Works

Ferndale, Washington

Intalco 

Fraction of 

Total 

Equipment 

Cost

Scrubber Component

Scaling Equation 

Exponent Tennessee Potline Scrubber Equipment Costs

BART cost calculations 110607.xls-Capital equipment costs 
Potlines

Intalco Works

Ferndale, Washington

Value Notes/References

Capital Investment Costs

Direct Capital Costs (DCC)

Purchased Equipment Costs (PEC)

Adsorber vessels with internals $80,445,682 Based on vendor quotations for Tennessee Alcoa smelter, adjusted for 

scrubber exhaust gas flow rate, limestone consumption, and gypsum 

generation per Pre-feasability Report (Hatch 2007)

Pumps Included

Limestone prep Included

Dewatering systems Included

Fans Included

Inlet ductwork Included

Stacks Included

Continuous Emission Monitoring system (2 stacks) $80,000

Subtotal (EC) $80,525,682

Instrumentation $4,026,284 USEPA 2002, Section 5.2, Chapter 1, Table 1.3 (5% of EC; adjusted 

from 10% since basic instrumentation is included in proposal)

Sales tax $5,234,169 State sales tax rate for Washington is 6.5%

Freight $4,026,284 USEPA 2002, Section 5.2, Chapter 1, Table 1.3 (5% of EC)

Total Purchased Equipment Costs (PEC) $93,812,419

Direct Installation Costs (DIC)

Foundations and supports $11,257,490 USEPA 2002, Section 5.2, Chapter 1, Table 1.3 (12% of PEC)

Handling and erection $75,049,936 USEPA 2002, Section 5.2, Chapter 1, Table 1.3 (80% of PEC; adjusted 

from 40% to account for retrofit of existing plant and onsite fabrication)

Electrical $938,124 USEPA 2002, Section 5.2, Chapter 1, Table 1.3 (1% of PEC)

Piping $28,143,726 USEPA 2002, Section 5.2, Chapter 1, Table 1.3 (30% of PEC)

Insulation $938,124 USEPA 2002, Section 5.2, Chapter 1, Table 1.3 (1% of PEC)

Painting $938,124 USEPA 2002, Section 5.2, Chapter 1, Table 1.3 (1% of PEC)

Total Direct Installation Costs (DIC) $117,265,524

Total Direct Capital Costs $211,077,944 Sum of PEC and DIC

Indirect Capital Costs (ICC)

Engineering $4,690,621 USEPA 2002, Section 5.2, Chapter 1, Table 1.3 (5% of PEC; adjusted 

from 10% since vendor proposal includes an allowance for engineering)

Construction and field expenses $9,381,242 USEPA 2002, Section 5.2, Chapter 1, Table 1.3 (10% of PEC)

Contractor fees $4,690,621 USEPA 2002, Section 5.2, Chapter 1, Table 1.3 (5% of PEC; adjusted 

from 10% based on assumption that vendor will oversee scrubber 

installation)

Start-up $938,124 USEPA 2002, Section 5.2, Chapter 1, Table 1.3 (1% of PEC)

Performance test $938,124 USEPA 2002, Section 5.2, Chapter 1, Table 1.3 (1% of PEC)

Contingencies $2,814,373 USEPA 2002, Section 5.2, Chapter 1, Table 1.3 (3% of PEC)

Total Indirect Capital Costs $23,453,105

Total Capital Investment Costs (TCIC) $234,531,049 Sum of DCC and ICC

References:

Hatch. 2007. SO 2 Scrubbing for the INTALCO Primary Aluminum Smelter: Pre-Feasibility Report . July 26.

USEPA. 2002. EPA Air Pollution Control Cost Manual , Sixth Edition. EPA/452/B-02-001. January.

Captial Investment Cost Analysis for SO2 Control Using a Wet Scrubber

BART cost calculations 110607.xls-Capital cost calcs (potlines) E N V I R O N
Potlines

Intalco Works

Ferndale, Washington

Value Units Notes/References

Annual Operation and Maintenance Costs

Direct Annual Costs (DAC)

Operating labor

Operator $324,120 Assumes $37 per hour with one full-time operator, 3 shifts per 

day

Supervisor $48,618 USEPA 2002, Section 5.2, Chapter 1, Table 1.4 (15% of 

operator costs)

Water $96,725

Water usage 500,000 gal/day Pre-feasability Report (Hatch 2007)

Cost of water $0.00053 $/gal Intalco controller

Limestone $470,052

Limestone usage 14,244 tons/yr Pre-feasability Report (Hatch 2007)

Cost of limestone $33 $/ton Assumes $28/ton for 8 mesh size limestone plus $5/ton for 

shipping by barge

Compressed air $18,922

Compressed air usage 150 scfm Pre-feasability Report (Hatch 2007)

Cost of compressed air $0.24 $/1000 scf Average compressed air generation cost for industrial facilities 

(http://www1.eere.energy.gov/industry/bestpractices/pdfs/com

pressed_air1.pdf) 

Gypsum disposal $3,933,809

Gypsum generation rate 6,194 lb/hr Pre-feasability Report (Hatch 2007)

Cost of gypsum disposal $145 $/ton Non-hazardous waste disposal and transportation costs

Maintenance

Labor $673,920 Assumes $45 per hour with 4 full-time maintenance personnel, 

one shift per day, 5 days per week and 1 maintenance 

personnel for all other shifts

Material $1,303,000 Cost for low sulfur boiler system with 1.7 macfm inlet/1.5 

macfm outlet, which is smaller than the potline system with 2.2 

macfm inlet/2.0 macfm outlet (Sargent & Lundy LLC 2003)

Electricity $3,409,742

Electricity usage 7,400 kWh/hr Pre-feasability Report (Hatch 2007)

Electricity cost $0.0526 $/kWh Facility average power rate for 2007 (Intalco controller)

Total Direct Annual Costs $10,278,908

Indirect Annual Costs (IAC)

Overhead $1,409,795 USEPA 2002, Section 5.2, Chapter 1, Table 1.4 (60% of total 

labor and maintenance material costs)

General and administrative costs $4,690,621

USEPA 2002, Section 5.2, Chapter 1, Table 1.4 (2% of TCIC)

Property tax $2,345,310

USEPA 2002, Section 5.2, Chapter 1, Table 1.4 (1% of TCIC)

Insurance $2,345,310

USEPA 2002, Section 5.2, Chapter 1, Table 1.4 (1% of TCIC)

Total Indirect Annual Costs $10,791,037 Sum of PEC and DIC

Total Annual Operating and Maintenance Costs $21,069,945 Sum of DAC and IAC

References:

Hatch. 2007. SO 2 Scrubbing for the INTALCO Primary Aluminum Smelter: Pre-Feasibility Report . July 26.

Sargent & Lundy LLC. 2003. Wet Flue Gas Desulfurization Technology Evaluation . Prepared for National Lime Association. January.

USEPA. 2002. EPA Air Pollution Control Cost Manual , Sixth Edition. EPA/452/B-02-001. January.

Operation and Maintenance Cost Analysis for SO2 Control Using a Wet Scrubber

BART cost calculations 110607.xls-O&M cost calcs (potlines) E N V I R O N
Installation of Wet Scrubber on Potline Exhaust

Reference

Potline hooding capture efficiency 95%Total potline uncontrolled SOx emission rate 37,780 lb/day Total potline SOx emission limit

Primary potline control system uncontrolled SOx emission rate 35,891 lb/day Calculated based on potline hooding capture e

SOx control efficiency 95%

Controlled SOx emission rate 1,795 lb/day

Uncontrolled annual SOx emissions 6,550 tpy

Controlled annual SOx emissions 328 tpy

SOx reduction 6,223 tpy

Direct capital costs (DCC) 211,077,944 $ Indirect capital costs (ICC) 23,453,105 $ Total capital costs 234,531,049 $ Interest rate 7% USEPA 2002, Section 1, Chapter 2.4.2Period of annualization 15 years AssumptionCapital recovery discount factor 0.11 USEPA 2002, Section 1, Chapter 2.4.4.4, EquAnnualized capital cost 25,750,000 $ USEPA 2002, Section 1, Chapter 2.4.4.4, Equ

Operating labor costs 324,120 $ Supervisory labor costs 48,618 $ Maintenance labor costs 673,920 $ Maintenance material costs 1,303,000 $ Electricity costs 3,409,742 $ Water costs 96,725 $ Limestone costs 470,052 $ Compressed air costs 18,922 $ Gypsum disposal costs 3,933,809 $ Overhead 1,409,795 $ Property tax 2,345,310 $ Insurance 2,345,310 $ General and administrative costs 4,690,621 $ Total annual cost estimate 46,820,000 $ Cost of option per ton SO x reduced $ 7,500

BART cost calculations 110607.xls-Potline scrubber cost summary 
Captial Investment Cost Analysis for SO2 Control Using a Wet Scrubber

Anode Bake Furnace

Intalco Works

Ferndale, Washington

Value Notes/References

Capital Investment Costs

Direct Capital Costs (DCC)

Purchased Equipment Costs (PEC)

Adsorber vessels with internals $10,042,642 Based on vendor quotations for Tennessee Alcoa smelter, adjusted for 

exhaust gas flow rate per Pre-feasability Report (Hatch 2007)

Pumps Included

Limestone prep Included

Dewatering systems Included

Fans Included

Inlet ductwork Included

Stacks Included

Continuous Emission Monitoring system (2 stacks) $80,000

Subtotal (EC) $10,122,642

Instrumentation $506,132 USEPA 2002, Section 5.2, Chapter 1, Table 1.3 (5% of EC; adjusted 

from 10% since basic instrumentation is included in proposal)

Sales tax $657,972 State sales tax rate for Washington is 6.5%

Freight $506,132 USEPA 2002, Section 5.2, Chapter 1, Table 1.3 (5% of EC)

Total Purchased Equipment Costs (PEC) $11,792,878

Direct Installation Costs (DIC)

Foundations and supports $1,415,145 USEPA 2002, Section 5.2, Chapter 1, Table 1.3 (12% of PEC)

Handling and erection $9,434,302 USEPA 2002, Section 5.2, Chapter 1, Table 1.3 (80% of PEC; adjusted 

from 40% to account for retrofit of existing plant and onsite fabrication)

Electrical $117,929 USEPA 2002, Section 5.2, Chapter 1, Table 1.3 (1% of PEC)

Piping $3,537,863 USEPA 2002, Section 5.2, Chapter 1, Table 1.3 (30% of PEC)

Insulation $117,929 USEPA 2002, Section 5.2, Chapter 1, Table 1.3 (1% of PEC)

Painting $117,929 USEPA 2002, Section 5.2, Chapter 1, Table 1.3 (1% of PEC)

Total Direct Installation Costs (DIC) $14,741,097

Total Direct Capital Costs $26,533,975 Sum of PEC and DIC

Indirect Capital Costs (ICC)

Engineering $589,644 USEPA 2002, Section 5.2, Chapter 1, Table 1.3 (5% of PEC; adjusted 

from 10% since vendor proposal includes an allowance for engineering)

Construction and field expenses $1,179,288 USEPA 2002, Section 5.2, Chapter 1, Table 1.3 (10% of PEC)

Contractor fees $589,644 USEPA 2002, Section 5.2, Chapter 1, Table 1.3 (5% of PEC; adjusted 

from 10% based on assumption that vendor will oversee scrubber 

installation)

Start-up $117,929 USEPA 2002, Section 5.2, Chapter 1, Table 1.3 (1% of PEC)

Performance test $117,929 USEPA 2002, Section 5.2, Chapter 1, Table 1.3 (1% of PEC)

Contingencies $353,786 USEPA 2002, Section 5.2, Chapter 1, Table 1.3 (3% of PEC)

Total Indirect Capital Costs $2,948,219

Total Capital Investment Costs (TCIC) $29,482,194 Sum of DCC and ICC

References:

Hatch. 2007. SO 2 Scrubbing for the INTALCO Primary Aluminum Smelter: Pre-Feasibility Report . July 26.

USEPA. 2002. EPA Air Pollution Control Cost Manual , Sixth Edition. EPA/452/B-02-001. January.

BART cost calculations 110607.xls-Capital cost calcs (ABF) E N V I R O N
Operation and Maintenance Cost Analysis for SO2 Control Using a Wet Scrubber

Anode Bake Furnace

Intalco Works

Ferndale, Washington

Value Units Notes/References

Annual Operation and Maintenance Costs

Direct Annual Costs (DAC)

Operating labor

Operator $324,120 Assumes $37 per hour with one full-time operator, 3 shifts per 

day

Supervisor $48,618 USEPA 2002, Section 5.2, Chapter 1, Table 1.4 (15% of 

operator costs)

Water $6,771

Water usage 35,000 gal/day Pre-feasability Report (Hatch 2007)

Cost of water $0.00053 $/gal Intalco controller

Limestone $11,286

Limestone usage 342 tons/yr Pre-feasability Report (Hatch 2007)

Cost of limestone $33 $/ton Assumes $28/ton for 8 mesh size limestone plus $5/ton for 

shipping by barge

Compressed air $6,307

Compressed air usage 50 scfm Pre-feasability Report (Hatch 2007)

Cost of compressed air $0.24 $/1000 scf Average compressed air generation cost for industrial facilities 

(http://www1.eere.energy.gov/industry/bestpractices/pdfs/com

pressed_air1.pdf) 

Gypsum disposal $92,725

Gypsum generation rate 146 lb/hr Pre-feasability Report (Hatch 2007)

Cost of gypsum disposal $145 $/ton Non-hazardous waste disposal and transportation costs

Maintenance

Labor $336,960 Assumes $45 per hour with 2 full-time maintenance personnel, 

one shift per day, 5 days per week and a half-time maintenance 

personnel equivalent for all other shifts

Material $163,796 Calculated based on estimated maintenance material costs for 

potline scrubber and ratio of purchased equipment costs for the 

anode bake furnace and potline scrubbers

Electricity $345,582

Electricity usage 750 kWh/hr Pre-feasability Report (Hatch 2007)

Electricity cost $0.0526 $/kWh Facility average power rate for 2007 (Intalco controller)

Total Direct Annual Costs $1,336,165

Indirect Annual Costs (IAC)

Overhead $524,097 USEPA 2002, Section 5.2, Chapter 1, Table 1.4 (60% of total 

labor and maintenance material costs)

General and administrative costs $589,644

USEPA 2002, Section 5.2, Chapter 1, Table 1.4 (2% of TCIC)

Property tax $294,822

USEPA 2002, Section 5.2, Chapter 1, Table 1.4 (1% of TCIC)

Insurance $294,822

USEPA 2002, Section 5.2, Chapter 1, Table 1.4 (1% of TCIC)

Total Indirect Annual Costs $1,703,384 Sum of PEC and DIC

Total Annual Operating and Maintenance Costs $3,039,549 Sum of DAC and IAC

References:

Hatch. 2007. SO 2 Scrubbing for the INTALCO Primary Aluminum Smelter: Pre-Feasibility Report . July 26.

USEPA. 2002. EPA Air Pollution Control Cost Manual , Sixth Edition. EPA/452/B-02-001. January.

BART cost calculations 110607.xls-O&M cost calcs (ABF) E N V I R O N
Installation of Wet Scrubber on Anode Bake Furnace Exhaust

Reference

Uncontrolled SOx emission rate 994 lb/day

SOx control efficiency 95%

Controlled SOx emission rate 50 lb/day

Uncontrolled annual SOx emissions 181 tpy

Controlled annual SOx emissions 9 tpy

SOx reduction 172 tpy

Direct capital costs (DCC) 26,533,975 $ Indirect capital costs (ICC) 2,948,219 $ Total capital costs 29,482,194 $ Interest rate 7% USEPA 2002, Section 1, Chapter 2.4.2Period of annualization 15 years AssumptionCapital recovery discount factor 0.11 USEPA 2002, Section 1, Chapter 2.4.4.4, Equation 2.8aAnnualized capital cost 3,237,000 $ USEPA 2002, Section 1, Chapter 2.4.4.4, Equation 2.8

Operating labor costs 324,120 $ Supervisory labor costs 48,618 $ Maintenance labor costs 336,960 $ Maintenance material costs 163,796 $ Electricity costs 345,582 $ Water costs 6,771 $ Limestone costs 11,286 $ Compressed air costs 6,307 $ Gypsum disposal costs 92,725 $ Overhead 524,097 $ Property tax 294,822 $ Insurance 294,822 $ General and administrative costs 589,644 $ Total annual cost estimate 6,277,000 $ Cost of option per ton SO x reduced $ 36,400

BART cost calculations 110607.xls-Furnace scrubber cost summary 
APPENDIX E: 

GREENHOUSE GAS EMISSION CALCULATIONS
 E-1 

BART Determination 

Alcoa Intalco Works 

Ferndale, Washington 

Greenhouse Gas Emission Calculations 

Greenhouse gases (GHGs) are gaseous compounds that are considered to act as heat trapping 

constituents of the atmosphere. Although there are many gases that may trap heat in the 

atmosphere, there are six GHGs recognized by international and domestic regulations on climate 

change: carbon dioxide (CO2), nitrous oxide (N2O), methane, hydrofluorocarbons (HFCs), 

chlorinated fluorocarbons (CFCs), and sulfur hexafluoride. More than 80% of the global warming 

potential results from CO2 emissions. 

The proposed sulfur dioxide (SO2) control devices will contribute to the facility’s overall emissions 

of GHGs via three mechanisms: (1) as a byproduct of the reaction chemistry in the scrubbers, (2) as 

indirect emissions from the generation of electricity required to power the scrubbing systems, and 

(3) as direct emissions from vehicle travel for the additional personnel that will be required at the 

facility to maintain and operate the scrubbing systems. 

The estimate of carbon dioxide emissions resulting from the reaction of limestone with the sulfur 

dioxide in the exhaust streams is based on the theoretical reaction chemistry, assuming no other 

byproducts resulting from incomplete reaction. Consistent with the BART analysis, we assumed 

that 95% of the incoming sulfur dioxide reacts with the limestone, and hence is removed from the 

exhaust stream. There are three reactions taking place in the scrubber: 

1) Dissolution of the limestone in the scrubbing water: 

CaCO3 + H2O Æ Ca+2 + HCO3

-

 + OH2) Dissolution of the sulfur dioxide in the scrubbing water: 

SO2 + H2O Æ 2H+

 + SO3

-2

3) Oxidation of the sulfite ions to sulfate ions (and hence, formation of gypsum or calcium sulfate): 

Ca+2 + HCO3

-

 + OH- + 2H+ + SO3

-2 + 1⁄2 O2 Æ CaSO4 + CO2 +2 H2O 

Consistent with the chemical balance shown above, for every mole of SO2 reacted, a mole of 

carbon dioxide is formed. 

The inlet sulfur dioxide molar flowrate was estimated based on design parameters provided by 

Hatch Associates1. Assuming a minimum 95% sulfur dioxide control efficiency (that is, assuming 

that 95% of the sulfur dioxide reacts with the limestone), the mass of carbon dioxide evolved was 

calculated based on the reaction chemistry presented above. 

 

1

 Hatch Associates. 2007. Pre-Feasibility Report – SO2 Scrubbing for the INTALCO Primary Aluminum Smelter. 

November 5. Tables 3 and 6 (potline exhaust and anode baking furnace exhaust, respectively). 
 E-2 

The implementation of the proposed scrubbing systems would also generate GHGs indirectly, as a 

result of consuming electricity. The generation of electricity at some off-site location would 

produce GHGs. The methodology described in the California Climate Action Registry General 

Reporting Protocol (CCARGRP)2

, for estimating indirect emissions of GHGs from electricity use 

was followed. Based on design specifications provided by Hatch Associates3, the daily electricity 

usage of each scrubber (potline fumes scrubber and the anode bake furnace scrubber) were 

multiplied by a state-specific carbon dioxide emission factor. The state-specific emission factor 

was found in the USEPA Emissions and Generation Resource Integrated Database for 2006

(eGrid2006)4 for Washington state. To estimate the emissions of nitrous oxide and methane (two 

minor GHG components from combustion sources), the default emission factors provided in the 

CCARGRP5

 were used. To convert the estimated nitrous oxide and methane emissions to carbon 

dioxide equivalents, the CCARGRP provides an estimate of each compound’s global warming 

potential (GWP)6

. For example, methane has a GWP of 21 times that of carbon dioxide; therefore, 

to convert the methane emission rate to carbon dioxide equivalents, we multiply the methane 

emission rate by its GWP. 

The last potential source of GHGs resulting from the implementation of the proposed scrubbing 

systems is from vehicle travel to and from the facility by additional personnel necessary for the 

operation and maintenance of the scrubbing systems. Based on facility estimates, the potline fumes 

scrubbing system would require nine additional employees per day on weekdays and six additional 

personnel per day on weekends. Similarly, the anode baking furnace scrubbing system would 

require six additional employees per day on weekdays and 4.5 additional personnel equivalents per 

day on weekends. It was assumed that each person would drive a roundtrip distance of 20 miles 

per day. This is approximately the roundtrip distance between the facility and downtown 

Bellingham, Washington. The emission estimates of carbon monoxide, nitrous oxide, and methane 

in the vehicle exhaust were based on assuming an average fuel economy. The fleet average (1988 

to 2007) fuel economy from the USEPA7

 was used. The emission factor for carbon dioxide was 

provided in the CCARGRP for non-California gasoline8. The emission factors for nitrous oxide 

and methane from vehicles were based on the average of the 1988 to present emission factors 

provided in the CCARGRP9

. To convert the nitrous oxide and methane emission rates to carbon 

dioxide equivalents, the GWP for each compound was applied as discussed above. 

 

2

 California Climate Action Registry. 2007. California Climate Action Registry General Reporting Protocol 

(CCARGRP): Reporting Entity-Wide Greenhouse Gas Emissions. Version 2.2. March. Chapter 6. 3

 Hatch Associates. 2007. Pre-Feasibility Report – SO2 Scrubbing for the INTALCO Primary Aluminum Smelter. 

November 5. Tables 5 and 8 (potline fumes scrubbing and anode baking furnace scrubbing, respectively). 4

 United States Environmental Protection Agency (USEPA). 2007. Emissions and Generation Resource Integrated 

Database for 2006 (eGrid2006). Version 2.1. April. Year 2004 summary tables. 

5

 California Climate Action Registry. 2007. California Climate Action Registry General Reporting Protocol 

(CCARGRP): Reporting Entity-Wide Greenhouse Gas Emissions. Version 2.2. March. Table C-2 6

 Ibid. Table III.6-1. 

7

 United States Environmental Protection Agency (USEPA). 2007. Light-Duty Automotive Technology and Fuel 

Economy Trends: 1975 to 2007 (Table 1 – Cars and Trucks). 

8

 California Climate Action Registry. 2007. California Climate Action Registry General Reporting Protocol 

(CCARGRP): Reporting Entity-Wide Greenhouse Gas Emissions. Version 2.2. March. Table C-3. 9

 Ibid. Table C-4 (used weighted average of the factors provided for various spans of model years). 
 E-3 

The GHG emission calculations described above are presented in the attached tables. The total 

GHGs (in carbon dioxide equivalents) generated by the implementation of the proposed scrubbing 

system for the potline fumes was estimated to be 96,441 pounds per day, or 17,598 tons per year. 

The total GHGs (in carbon dioxide equivalents) generated by the implementation of the proposed 

scrubbing system for the anode baking furnace was estimated to be 7,298 pounds per day, or 1,330 

tons per year. 
Greenhouse Gases Emissions

Intalco (Ferndale, WA)

Scope :

Assumptions:

Sources of Greenhouse Gases :

Summary of Potline Wet Scrubber GHG Emission Estimates :

Mass of CO2 evolved from scrubbing potroom emissions 31,969 lb/day

Mass of GHGs (in CO2 equivalents) evolved from electricity production for scrubbing system 64,294 lb/day

Mass of GHGs (in CO2 equivalents) evolved from vehicle travel for additional personnel 177.9 lb/day

96,441 lb/day

17,597 tons/yr

Summary of Anode Bake Furnace Wet Scrubber GHG Emission Estimates :

Mass of CO2 evolved from scrubbing anode bake furnace emissions 663 lb/day

Mass of GHGs (in CO2 equivalents) evolved from electricity production for scrubbing system 6,516 lb/day

Mass of GHGs (in CO2 equivalents) evolved from vehicle travel for additional personnel 118.6 lb/day

7,298 lb/day

1,330 tons/yr

TOTAL GHGs (CO2 equivalents)

TOTAL GHGs (CO2 equivalents)

- The addition of personnel as a result of the operation of the scrubbing systems (vehicle travel)

Calculation of greenhouse gases from the implementation of a flue gas desulfurization system. There will be one 

scrubbing system for the potrooms and one for the anode baking furnace. The scrubbing system consists of a 

limestone-gypsum forced oxidation (LSFO) process.

CO2 is the primary greenhouse gas evolved. Other components, such as methane or nitrous oxide are in de minimus 

quantities. These will be included where there is sufficient information for their estimate.

- Reaction chemistry of the limestone and sulfur dioxide (LSFO)

- Energy consumption of the scrubbing systems
GHG Emissions from Scrubbing Potline Emissions

Scrubbing Reaction Chemistry:1) CaCO3 + H2O ------> Ca+2 + HCO3- + OH2) SO2 + H2O -----------> 2H+ + SO3-23) Ca+2 + HCO3- + OH- + SO3-2 + 2H+ + 1/2 O2 ----------------> CaSO4 + CO2 + 2H2O

So, for every one mole of SO2 (64 grams) removed, one mole of CO2 (44 grams) is evolved.

Based on the final Hatch pre-feasibility report (dated November 5, 2007):

Parameter Reference

SO2 concentration 300 mg/Nm3 Hatch, Table 3

Flowrate 1,814,880 scfm Hatch, Table 3

51,394 m3/min

SO2 at inlet of FGD system 257.0 grams/second Calculated, based on FGD inlet flow characteristics presented in Hatch, Table 

4.02 moles SO2/second Based on molar mass of SO2 of 64 grams/mole

Removal efficiency 95% minimum Hatch, Table 4Moles of SO2 reacted 3.81 moles SO2/second

Moles of CO2 evolved 3.81 moles CO2/second

Mass of CO2 evolved 167.8 grams CO2/second Based on molar mass of CO2 of 44 grams/mole

14,500,691 grams CO2/day

31,969 lb CO2/day

Value
GHG Emissions from Scrubbing Anode Baking Furnace Emissions

Scrubbing Reaction Chemistry:

1) CaCO3 + H2O ------> Ca+2 + HCO3

-

 + OH -

2) SO2 + H2O -----------> 2H+ + SO3

-2

3) Ca+2 + HCO3

-

 + OH - + SO3

-2 + 2H+

 + 1/2 O2 ----------------> CaSO4 + CO2 + 2H2O

So, for every one mole of SO2 (64 grams) removed, one mole of CO2 (48 grams) is evolved.

Based on the final Hatch pre-feasibility report (dated November 5, 2007):

Parameter Reference

SO2 at inlet of FGD system 5.33 grams/second Hatch, Table 6

0.083 moles SO2/second Based on molar mass of SO2 of 64 grams/mole

Removal efficiency 95% minimum Hatch, Table 7

Moles of SO2 reacted 0.079 moles SO2/second

Moles of CO2 evolved 0.079 moles CO2/second

Mass of CO2 evolved 3.5 grams CO2/second Based on molar mass of CO2 of 44 grams/mole

300,772 grams CO2/day

663 lb CO2/day

Value
GHGs resulting from electricity generation associated with potline scrubber system1

Parameters ReferenceElectricity usage for potline wet scrubber 7,400 kWh/h Hatch, Table 5Electricity usage for potline wet scrubber 177,600 kWh/day Assumes continuous operation of wet scrubberN2O global warming potential (GWP) 310 Table III.6.1 - CCARGRP

Methane GWP 21 Table III.6.1 - CCARGRPEmission Factors Reference

CO2 360 lb/MWh Emission factors for Washington state (eGrid 2006 Version 2.1, A

CO2 0.36 lb/kWh

N2O 0.004 lb/MWh Default emission factors for N2O and methane for Washington sta

Methane 0.037 lb/MWh Default emission factors for N2O and methane for Washington staEmission Estimates

CO2 63,936 lb/day

N2O 0.71 lb/day

Methane 6.57 lb/dayConversion of non-CO2 GHGs to CO2 equivalents

CO2 63,936 lb/day

N2O - CO2 equivalents 220 lb/day

Methane - CO2 equivalents 138 lb/day

Total CO2 equivalents 64,294 lb/day

Notes:

1Based on methodology described in the California Climate Action Registry General Reporting Protocol (CCARGRP) (March 2007) and th

Emissions & Generation Resource Integrated Database (eGrid2006).
GHGs resulting from electricity generation associated with anode bake furnace scrubber system1

Parameters ReferenceElectricity usage for anode bake furnace wet scrubber 750 kWh/h Hatch, Table 8Electricity usage for anode bake furnace wet scrubber 18,000 kWh/day Assumes continuous operation of wet scrubberN2O global warming potential (GWP) 310 Table III.6.1 - CCARGRP

Methane GWP 21 Table III.6.1 - CCARGRPEmission Factors Reference

CO2 360 lb/MWh Emission factors for Washington state (eGrid 2006 Version 2.1, A

CO2 0.36 lb/kWh

N2O 0.004 lb/MWh Default emission factors for N2O and methane for Washington st

Methane 0.037 lb/MWh Default emission factors for N2O and methane for Washington stEmission Estimates

CO2 6,480 lb/day

N2O 0.07 lb/day

Methane 0.67 lb/dayConversion of non-CO2 GHGs to CO2 equivalents

CO2 6,480 lb/day

N2O - CO2 equivalents 22 lb/day

Methane - CO2 equivalents 14 lb/day

Total CO2 equivalents 6,516 lb/day

Notes:

1Based on methodology described in the California Climate Action Registry General Reporting Protocol (CCARGRP) (March 2007) and t

Emissions & Generation Resource Integrated Database (eGrid2006).
GHGs resulting from vehicle travel for additional personnel associated with potline scrubber system1

Parameters ReferenceAdditional operating personnel 3 One additional full-time operator per shift, three shifts per day (assumption)Additional maintenance personnel (weekdays) 6 Four additional full-time maintenance personnel, one shift per day, plus one additional fulltime maintenance personnel for off-shifts (assumption)Additional maintenance personnel (weekends) 3 One additional full-time maintenance personnel for off-shifts (assumption)Total additional personnel (weekdays) 9Total additional personnel (weekends) 6Daily round trip distance 20 miles/trip Assumption (distance from plant to downtown Bellingham, WA is approximately 10 miles)Total daily mileage (weekdays) 180 miles/dayTotal daily mileage (weekends) 120 miles/dayAverage fuel economy 20.3 miles/gallon Fleet average (1988 to 2007 model years); USEPA, Light-Duty Automotive Technology 

and Fuel Economy Trends: 1975 to 2007, Table 1 (Cars and Trucks)

N2O global warming potential (GWP) 310 Table III.6.1 - CCARGRPMethane GWP 21 Table III.6.1 - CCARGRPEmission Factors ReferenceCO2 emission factor 8.78 kg/gallon Non-CA gasoline; Table C.3, CCARGRPN2O emission factor 0.050 grams/mile Weighted average of 1988 to present automobile model years; Table C.4, CCARGRPMethane emission factor 0.049 grams/mile Weighted average of 1988 to present automobile model years; Table C.4, CCARGRPEmission EstimatesCO2 (weekdays) 171.4 lb/dayN2O (weekdays) 0.020 lb/dayMethane (weekdays) 0.019 lb/dayCO2 (weekends) 114.3 lb/dayN2O (weekends) 0.013 lb/dayMethane (weekends) 0.013 lb/dayConversion of non-CO2 GHGs to CO2 equivalentsCO2 (weekdays) 171.4 lb/dayN2O - CO2 equivalents (weekdays) 6.2 lb/dayMethane - CO2 equivalents (weekdays) 0.4 lb/day

Total CO2 equivalents (weekdays) 177.9 lb/day

CO2 (weekends) 114.3 lb/day

N2O - CO2 equivalents (weekends) 4.1 lb/dayMethane - CO2 equivalents (weekends) 0.3 lb/day

Total CO2 equivalents (weekends) 118.6 lb/day

CO2 (annual) 28.2 tons/yr

N2O - CO2 equivalents (annual) 1.0 tons/yrMethane - CO2 equivalents (annual) 0.1 tons/yr

Total CO2 equivalents (annual) 29.3 tons/yr

Notes:

1Based on methodology described in the California Climate Action Registry General Reporting Protocol (CCARGRP) (March 2007).
GHGs resulting from vehicle travel for additional personnel associated with anode bake furnace scrubber system1

Parameters ReferenceAdditional operating personnel 3 One additional full-time operator per shift, three shifts per day (assumption)Additional maintenance personnel (weekdays) 3 Two additional full-time maintenance personnel, one shift per day, plus one additional halftime equivalent maintenance personnel for off-shifts (assumption)Additional maintenance personnel (weekends) 1.5 One additional half-time equivalent maintenance personnel for off-shifts (assumption)Total additional personnel (weekdays) 6Total additional personnel (weekends) 4.5Daily round trip distance 20 miles/trip Assumption (distance from plant to downtown Bellingham, WA is approximately 10 miles)Total daily mileage (weekdays) 120 miles/dayTotal daily mileage (weekends) 90 miles/dayAverage fuel economy 20.3 miles/gallon Fleet average (1988 to 2007 model years); USEPA, Light-Duty Automotive Technology 

and Fuel Economy Trends: 1975 to 2007, Table 1 (Cars and Trucks)

N2O global warming potential (GWP) 310 Table III.6.1 - CCARGRPMethane GWP 21 Table III.6.1 - CCARGRPEmission Factors ReferenceCO2 emission factor 8.78 kg/gallon Non-CA gasoline; Table C.3, CCARGRPN2O emission factor 0.050 grams/mile Weighted average of 1988 to present automobile model years; Table C.4, CCARGRPMethane emission factor 0.049 grams/mile Weighted average of 1988 to present automobile model years; Table C.4, CCARGRPEmission EstimatesCO2 (weekdays) 114.3 lb/dayN2O (weekdays) 0.013 lb/dayMethane (weekdays) 0.013 lb/dayCO2 (weekends) 85.7 lb/dayN2O (weekends) 0.0099 lb/dayMethane (weekends) 0.0096 lb/dayConversion of non-CO2 GHGs to CO2 equivalentsCO2 (weekdays) 114.3 lb/dayN2O - CO2 equivalents (weekdays) 4.1 lb/dayMethane - CO2 equivalents (weekdays) 0.3 lb/day

Total CO2 equivalents (weekdays) 118.6 lb/day

CO2 (weekends) 85.7 lb/day

N2O - CO2 equivalents (weekends) 3.1 lb/dayMethane - CO2 equivalents (weekends) 0.2 lb/day

Total CO2 equivalents (weekends) 89.0 lb/day

CO2 (annual) 19.3 tons/yr

N2O - CO2 equivalents (annual) 0.7 tons/yrMethane - CO2 equivalents (annual) 0.05 tons/yr

Total CO2 equivalents (annual) 20.0 tons/yr

Notes:

1Based on methodology described in the California Climate Action Registry General Reporting Protocol (CCARGRP) (March 2007).