BASIS AND PURPOSE DOCUMENT FOR

THE DEVELOPMENT OF PROPOSED STANDARDS FOR

THE PRIMARY ALUMINUM INDUSTRY

U.S. ENVIRONMENTAL PROTECTION AGENCY Office of Air and Radiation Office of Air Quality Planning and Standards Research Triangle Park, North Carolina 27711

July 19, 1996ii

TABLE OF CONTENTS Section Page

1.0 BACKGROUND..................................... ....... 1

1.1 NATIONAL EMISSION STANDARDS FOR HAZARDOUS AIR POLLUTANTS FOR SOURCE CATEGORIES............. 2

1.2 SELECTION OF SOURCE CATEGORY.................. ... 3

1.3 PRIMARY ALUMINUM PLANTS....................... ... 4

2.0 RATIONALE FOR THE PROPOSED STANDARDS........... ....... 7

2.1 SOURCE CATEGORY TO BE REGULATED............... ... 7

2.2 AFFECTED SOURCES.............................. ... 7

2.2.1 Selection of Affected Sources............. 7 2.2.2 HAPs from Affected Sources................ 9

2.3 POLLUTANTS FOR REGULATION..................... ... 11

2.3.1 Health Effects............................ 11 2.3.2 Measurement............................... 14 2.3.3 Other Pollutants.......................... 16

2.4 SELECTION OF MACT............................. ... 17

2.4.1 Background................................ 17 2.4.2 Subcategorization......................... 18 2.4.3 MACT Floor Technologies................... 22 2.4.4 Beyond MACT Floor Evaluation.............. 23

3.0 PROPOSED STANDARDS............................. ....... 25

3.1 EMISSION LIMITS............................... ... 25

3.2 MONITORING AND COMPLIANCE REQUIREMENTS........ ... 31

3.2.1 Potlines.................................. 34 3.2.2 Anode Bake Furnaces....................... 37 3.2.3 Paste Production.......................... 37 3.2.4 Emission Averaging........................ 37 3.2.5 Reduced Sampling Frequency................ 40

3.3 RECORDKEEPING AND REPORTING REQUIREMENTS..... .... 41

3.4 DELEGATION OF AUTHORITY...................... .... 41iii

4.0SUMMARY OF ENVIRONMENTAL, COST, ENERGY, AND ECONOMIC IMPACTS.................................. .... 49

4.1 AIR QUALITY IMPACTS........................... ... 49

4.2 SOLID WASTE IMPACTS........................... ... 49

4.3 COST IMPACTS.................................. ... 49

4.4 ECONOMIC IMPACTS............................. .... 51

4.5 NON-AIR QUALITY HEALTH AND ENVIRONMENTAL IMPAC TS. 51

4.5.1 Deposition................................ 51 4.5.2 Water..................................... 51 4.5.3 Solid Waste............................... 52

4.6 ENERGY IMPACTS................................ ... 52

APPENDIX A: Rationale for Subcategorization of Sour ces for the Primary Aluminum Industry

APPENDIX B: Determination of MACT Floor Performance Levels

APPENDIX C: Beyond-the-Floor Analysis

APPENDIX D: Complete Listing of MACT Floor Dataiv

LIST OF TABLES

Table Page

1 SUMMARY OF PROPOSED EMISSION LIMITS FOR EXISTING SOURCES.26

2 SUMMARY OF PROPOSED EMISSION LIMITS FOR NEW SOURC ES......30

3 PROPOSED MONITORING AND COMPLIANCE REQUIREMENTS.. ........32

4 POTLINE EMISSION LIMITS FOR EMISSIONS AVERAGING.. ........39

5 BAKE FURNACE EMISSION LIMITS FOR EMISSIONS AVERAG ING.....40

6 APPLICABILITY OF GENERAL PROVISIONS TO SUBPART LL ........421.0 BACKGROUND

The EPA developed this proposed air emissions rule through a rulemaking process known as the Share-A-MACT Prog ram. Participants in the pilot program include State reg ulators, tribal governments, industry representatives, and a ssociated groups including the Aluminum Association and STAPP A/ALAPCO (State and Territorial Air Pollution Program Admini strators Association/Association of Local Air Pollution Cont rol Officials). The partnership process included a coo perative effort in identifying data needs; collecting availa ble data; conducting emission testing with shared funding fro m the EPA, Washington Department of Ecology, and the industry; and meeting with these representatives to share technical infor mation.

The proposed MACT standard for primary aluminum pl ants limits emissions of hazardous air pollutants (HAPs) , primarily hydrogen fluoride (HF) and polycyclic organic matte r (POM), from aluminum production, paste production, and anode ba ke furnaces. The overall effect of the proposed rule would be to raise the control performance of nearly half of the industry to the level of control achieved by the best performing plants. Currently, over 11,000 tons per year (tpy) of total fluoride ( TF) and POM and emitted nationwide; these emissions would be re duced by more than 50 percent. In addition, emissions of total p articulate matter would be reduced by 16,000 tpy. The benefit s of these reductions will be lower ambient air concentrations of these pollutants, and consequently, lower levels of expos ure. The deposition of fluorides and POM on waters, such as the Great Lakes, would also be reduced. These benefits will be achieved with no plant closures predicted and without any si gnificant adverse economic impacts on the industry.

The proposed standard is based on a combination of control techniques that either prevent the escape of emissi ons in the first place or that capture the pollutants and retu rn them to the process. Over the past 20 years, many plants have already implemented these control techniques both to reduce emissions and to recover valuable fluorides, which reduces the op erating costs of the emission control systems.

For the control of fugitive emissions, enhanced wo rk practices and operating procedures are used to prev ent the escape of emissions. Emissions that are collected by prim ary control systems are routed to dry alumina scrubbers (for po tlines or bake furnaces) or dry coke scrubbers (for paste producti on) where the pollutants are captured and returned to the product ion process. Several plants will achieve emission reductions wel l beyond the nationwide average of 50 percent by replacing less efficient wet scrubbers with more efficient dry scrubbers and by installing emission controls on those anode bake furnaces and paste production operations that currently have no emissi on controls.2

The proposed rule also provides flexibility in its requirements for monitoring the performance of the control techniques while ensuring the MACT level of control is achieved on a continuing basis. It contains provisions for reducing the frequency of sampling at those plants that show con sistent performance below the level of the standard, which reduces the cost of monitoring. Provisions are also included t o allow the use of innovative continuous emission monitors (CEM s) for hydrogen fluoride (HF) as an alternative measuremen t method for TF emissions. These new CEMs have shown promise fo r monitoring emission control and can also be used as a process tool to reduce operating costs by improving work practices and ope rating procedures. The rule also contains provisions for emission averaging, which provides owners or operators an op portunity to find the most cost-effective way to meet the limits at their particular plant.

The proposed rule has negligible adverse effects o n energy consumption and secondary environmental impacts. W hen one plant replaces wet scrubbers with the highly-efficient dr y scrubbers, the generation of sludge (solid waste) that require s disposal and the discharge of contaminated water will be elimina ted.

The MACT level for new sources will have the effec t of either discouraging the construction of Soderberg p otlines, which emit much more of the carcinogenic POMs than do pre bake potlines, or encouraging process changes for Soderberg potlin es that will reduce POM and fluoride emissions to levels achieve d by the best controlled prebake potlines.

The following sections of this report provide addi tional information on the standards development process fo r MACT standards; the industry and its regulatory history; the rationale for selection of the source category, emission sour ces, emission limits, and monitoring and compliance requirements; and the impacts of the proposed requirements.

1.1 National Emission Standards for Hazardous Air Pollutants (NESHAP) for Source Categories

Section 112 of the Clean Air Act as amended requir es the development of NESHAP for the control of emissions of HAPs from both new and existing major or area sources. The s tatute requires the standard to reflect the maximum degree of reduction in emissions of HAP's that is achievable taking int o consideration the cost of achieving the emission re duction, any nonair quality health and environmental reduction, and energy requirements. This level of control is commonly re ferred to as the maximum achievable control technology (MACT).3

Emission reductions may be accomplished through ap plication of measures, processes, methods, systems or techniq ues including, but not limited to: (1) Reducing the volume of, or eliminating emissions of, such pollutants through process chang es, substitution of materials, or other modifications, (2) enclosing systems or processes to eliminate emissions, (3) co llecting, capturing, or treating such pollutants when release d from a process, stack, storage or fugitive emissions point , (4) design, equipment, work practice, or operational standards (including requirements for operator training or certification ) as provided in subsection (h), or (5) a combination of the abov e [section 112(d)(2)].

1.2 Selection of Source Category

Section 112 specifically directs the EPA to develo p a list of all categories of all major and area sources as appropriate emitting one or more of the 189 HAP's listed in sec tion 112(b). The EPA published an initial list of source categor ies on July 16, 1992 (57 FR 31,576) and may amend the list at a ny time. A schedule for promulgation of standards for each sou rce category was published on December 3, 1993 (58 FR 63941). P rimary aluminum production is one of the 174 categories of sources listed. As defined in the EPA report documenting t he selection of the source categories, this category consists of plants engaged in producing primary aluminum by electrolyt ically reducing alumina, including but not limited to, the following process units: (1) carbon mix plants, (2) reductio n plants, (3) anode bake plants, (4) holding furnaces in the cast ing area, (5) casting processes, and (6) refining processes. 1 The listing was based on the Administrator's determination that pri mary aluminum plants may reasonably be anticipated to emit severa l of the 189 listed HAP's in sufficient quantity to be designate d as major sources. The EPA subsequently decided to include c arbon mix plants, reduction plants, and anode bake furnaces i n the primary aluminum source category and placed the other sourc es in a separate source category for secondary aluminum pro duction.

1 Documentation for Developing the Initial Source Ca tegory List: Final Report. U.S. Environmental Protection Agency. Office of Air Quality Planning and Standards. EPA- 450/3091-030. July 1992. Pages 3-4 and A-6.4

1.3 Primary Aluminum Plants

Primary aluminum plants produce aluminum metal thr ough the electrolytic reduction of aluminum oxide (alumina) by direct current voltage in an electrolyte (called "cryolite ") of sodium aluminum fluoride. A total of 23 primary aluminum plants are currently located in 14 States. A majority of thes e plants are concentrated in the Northwest in close proximity to hydroelectric
power sources.

New source performance standards (NSPS) for primary aluminum reduction plants (40 CFR part 60, Subpart S) were o riginally promulgated in 1976 (41 FR 3826, January 26, 1976) and amended in 1980 and 1989 (45 FR 44202, June 30, 1980; 54 FR 66 69, February 14, 1989). The NSPS limits emissions of gaseous an d particulate fluorides, measured as total fluorides (TF), from a ll potroom groups and anode bake furnaces constructed, modifie d, or reconstructed after October 23, 1974. Emissions ar e limited to 1.0 kg/Mg (2.0 lb/ton) of aluminum produced for pot room groups at Soderberg plants, 0.95 kg/Mg (1.9 lb/ton) of alumin um produced for potroom groups at prebake plants, and 0.05 kg/M g (0.1 lb/ton) of aluminum equivalent for anode bake plants. High er, never-tobe-exceeded limits, are allowed for potrooms at pre bake plants (2.5 lb/ton) and Soderberg plants (2.6 lb/ton) if t he owner or operator can establish that a proper control system was installed and operated and maintained in an exemplary manner.

Monthly performance tests are required by the NSPS to verify compliance; less frequent testing of the anode bake plant or the primary control system for the potroom may be permi tted if the owner/operator can demonstrate low emissions variab ility. A monitoring device to determine the daily weight of aluminum and anode produced also is required to provide informat ion used to compute the emission rate of TF based on the weight of metal tapped during a 30-day period. Visible emissions e xiting potroom roof monitors, determined by Method 9 observations, are limited to 10 percent opacity for potroom groups and 20 per cent opacity for any anode bake plant. A total of five potlines at four plants are subject to the NSPS.

Existing facilities are subject to varying State emission regulations for TF developed pursuant to section 11 1(d) of the Act. A limited number of States also impose limits specific to sulfur dioxide (SO 2 ) and particulate matter (PM). In some States, more stringent TF limits (in addition to li mits for SO 2 and PM) are applicable to new or modified facilitie s subject to requirements for the prevention of significant dete rioration (PSD). Additional information on State regulations is included in the Technical Support Document.5

As a result of Federal and State regulations, emis sion controls are in place at all plants for the reducti on cells and at many plants for materials handling, paste produc tion, and anode bake furnaces. Emissions from materials hand ling are typically controlled by hoods and closed systems du cted to baghouses as a result of the NSPS for metallic mine ral processing plants (40 CFR part 60, Subpart LL) or State rules. Emissions from reduction cells, paste production, and bake fu rnaces are captured by hooding and enclosure systems evacuated to a control device (or series of control devices) for removal o f gaseous and particulate emissions using dry scrubbers with bagh ouses, wet scrubbers, or wet scrubbers with electrostatic prec ipitators. Thus the majority of emissions are secondary emissi ons from the reduction cells that escape capture by primary cont rol systems.

The aluminum industry also is subject to effluent guidelines and standards set pursuant to the Clean Water Act . The EPA's effluent limitations for primary aluminum productio n (40 CFR part 421, Subpart B) apply to fluorides and other metals , toxic organics, and other pollutants in wastewater genera ted from wet air pollution control systems for paste production plants, anode bake plants, and potlines or potrooms; as well as f rom anode contact cooling, cathode reprocessing, and aluminum casting operations. The discharge rules require either lim e treatment of a bleed stream off the scrubber loop or cryolite re covery with lime treatment of the cryolite bleed stream if wet control technology is used.

Under the Resource Conservation and Recovery Act (RCRA) regulations, spent potliner from primary aluminum r eduction is a listed hazardous waste (K088) under 40 CFR 261.32, Hazardous Wastes from Specific Sources, due to the presence o f iron cyanide complexes and must meet applicable RCRA requirement s. Treatment standards for newly-listed spent aluminum potliner were proposed on March 2, 1995 (60 FR 11704). Hydrogen fluoride (HF) and spent potliner are designated as hazardous substances und er section 102(a) of the Comprehensive Environmental Response, Compensation, and Liability Act and under section 311(b) of the Clean Water Act . In general, any unallowable release or discharge exceeding 100 pounds of HF (or one pound of spent potliner) i s subject to notification requirements under 40 CFR Parts 302 an d 355. If more than 500 pounds of HF are present at the facil ity, EPA rules in 40 CFR Part 370 and 40 CFR 372 implementing the Emergency Planning and Right-to-Know-Act also may require companies to prepare material data safety sheets and submit annu al toxic chemical release reports.

The Occupational Safety and Health Administration limits the concentration of fluoride dust in air to a time-wei ghted average (TWA) of 2.5 milligrams per cubic meter of air (mg/ m 3 ) for an 8-6

hour work day, 40 hour week; the concentration of H F is limited to 3.0 ppm. The concentration of coal tar pitch vo latiles (benzene soluble fraction), including anthracene, b enzo(a)pyrene, phenanthrene, acridine, chrysene, and pyrene (all P OM components) is limited to 0.2 mg/m 3 . Particulates not otherwise regulated (including all inert or nuisance dusts whether mine ral, inorganic, or organic not listed specifically by su bstance name) are limited to 15 million particles per cubic foot of air (mppcfa) and 15 mg/m 3 for the respirable fraction and 50 mppcfa and 15 mg/m 3 for total dust (58 FR 35338, June 30, 1993).7

2.0 RATIONALE FOR THE PROPOSED STANDARDS

2.1 Source Category to be Regulated

Typically, primary aluminum plants are components of larger facilities that prepare a variety of finished produ cts. Under the proposed standard, the primary aluminum source category excludes holding furnaces, casting, and refining pr ocesses because emissions from these sources are being regu lated within the secondary aluminum source category. The EPA sc hedule for promulgation of the MACT standards (58 FR 63941, De cember 3, 1993), requires rules for both the primary and seco ndary aluminum source category to be promulgated by November 15, 1 997. If MACT standards for this source category are not promulga ted by May 15, 1999 (18 months following the promulgation deadline ), Section 112(j) of the Act requires States or local agencies with approved permit programs to issue permits or revise existing permits containing either an equivalent emission limitation or an alternate emission limitation for HAP control. (Se e Guidelines for MACT Determinations under Section 112(j) , EPA 453/R-94-026, May 1994). For additional information on the secon dary aluminum source category, contact Juan Santiago, Metals Grou p, Emission Standards Division, U.S. Environmental Protection A gency, Research Triangle Park, North Carolina 27711, tele phone number (919) 541-1084.

2.2 Affected Sources

2.2.1 Selection of Affected Sources. The proposed standard defines the affected sources as each individual pot line, each individual anode bake furnace, and each paste produ ction plant. Several factors were considered in the selection of the affected sources, such as ensuring that: (1) MACT is determ ined appropriately with respect to the MACT control tech nology and its performance, (2) the proposed MACT standard is impl emented in a manner consistent with the way it was derived from the data base, (3) it is consistent with the development of subcat egories, (4) it permits a clear distinction between new and existing sources and is appropriately related to the General Provisions, and (5) it provides adequate flexibility for implem entation (e.g., emissions averaging).

For the aluminum reduction process, the EPA consid ered several options for defining the affected source, i ncluding groups of similar potlines at a plant, all potlines at a given plant, and each individual potline. For bake furna ces, the options included all bake furnaces and each bake fu rnace individually. For paste plants, the only option co nsidered was for each paste production plant because no facility has more than one paste production operation. The options under consideration8

for potlines and bake furnaces were important becau se they affect how the MACT floor and MACT are determined from the available data, the applicability of the new source MACT stan dard (what constitutes a new or reconstructed source), and imp lementation of emissions averaging.

The selection of each potline, bake furnace, and p aste plant as the affected sources ensures that the MACT contr ol technologies, which are different for each of the a ffected sources, are implemented. This approach is consist ent with the way measurements were made and the type of data tha t were submitted, i.e., to characterize the emission contr ol performance of each individual potline, each bake furnace, and each paste plant. The subcategories for aluminum production w ere based most reasonably on types and characteristics of individu al potlines rather than groups of potlines. This permitted the MACT floor to be determined based on the average (median) perform ance of the top five potlines in each subcategory. The MACT de termination would have been more difficult and less effective i f it had been based on the entire group of potlines at each of th e plants. This approach also ensures that if a new potline, b ake furnace, or paste plant is built, it would be subject to MAC T for new sources, which is consistent with the way the new s ource limit was derived. This approach does not limit the flex ibility in implementing emissions averaging, which has been in cluded as a provision of the rule.

There was concern that the selection of the affect ed source as an individual potline could subject an existing potline that is rebuilt to the new source MACT, even if it were infeasible for the rebuilt potline to meet the standard. However, the General Provisions address this by stating that a source is not considered reconstructed and subject to new source MACT unless "it is technologically and economically feasible fo r the reconstructed source to meet the relevant standard. " Consequently, if the owner or operator of an existi ng potline that is rebuilt shows that it is technologically or economically infeasible to met the new source MACT, the potline would not be considered to be reconstructed and would not be sub ject to the new source limit.

If a new potline (or bake furnace) is built, it wo uld reasonably be expected to have no technical or econ omical problem with achieving new source MACT. Consequently, the definition of each individual potline (or bake furnace) as the af fected source ensures that new potlines (or bake furnaces) must m eet the more stringent limits for new sources. If the affected source had been defined as the group of potlines at a plant, a potline of entirely new construction would not necessarily hav e to meet new source limits.9

After considering all of these factors, the indivi dual potline, bake furnace and paste plant were selected as the affected sources. The major considerations were co nsistency with the available data, data analysis, and subcategoriz ation (by potline); a clear and reasonable distinction betwee n existing and new or reconstructed sources, and no loss of flexib ility in implementing the rule.

2.2.2 HAPs from Affected Sources. Potlines of reduction cells comprise the largest source of HAP emissions in the primary aluminum category. HF, one of the major HAPs of co ncern, is generated from the fluoride compounds used in alumi num production. Emissions that are not collected by th e primary system are released in the potroom where they mix w ith the ventilation air and escape through the roof monitor at most plants. The basic process operations that create s econdary emissions include charging alumina to the bath, per iodically removing the molten aluminum ("tapping"), replacing the anode, and correcting "anode effects", usually by adding m ore alumina and mixing the bath. Approximately 6,400 tpy of TF are emitted from potlines. POM and other organic compounds are introduced into the process primarily by the use of coal tar p itch in the anodes. POM emissions (measured as methylene chlor ide extractables) are estimated at 3,300 tpy.

During the MACT test program, additional analyses were made to quantify 20 individual POM compounds. Tests at two Soderberg plants showed these compounds were emitted at a rat e of 0.5 to 0.6 pound per ton (lb/t) compared to levels less th an 0.01 lb/t from tests at two prebake plants. 2 Additional emission tests also were performed by the industry and provided to the Agency for analysis.

The anode paste plant (also known as the "green mi ll") produces anode paste or briquettes for Soderberg ce lls, cathode paste, or green pressed anodes (baked in the anode furnace) for prebake cells. In prebake plants, multiple anodes are formed and baked prior to use and the anodes are consumed in t he reduction process. In the Soderberg process, a single mass o f paste or briquettes of coke and pitch forms the anode. Beca use the anode is baked in place, plants using the Soderberg proce ss do not have anode bake furnaces.

2 Primary Aluminum Industry - Draft Technical Suppor t Document for Proposed MACT Standards (Preliminary R eview Draft). U.S. Environmental Protection Agency. Office of A ir Quality Planning and Standards. February 1995.10

To make the paste, solid raw materials (calcined p etroleum coke, anthracite coal, and pitch, as required for t he various types of pastes) are received in bulk and transport ed to carbon plant storage. Dry solids are drawn from the sized mix bins in controlled proportions either in weighed batches fo r batch mixers or continuously for continuous mixers. Mixers are jacketed and heated with either steam or oil. For baked anode p astes, the mixer feed contains either solid crushed coal tar p itch or hot liquid pitch as a binder. The prebake paste is the n transferred to the anode molds for forming by hydraulic or vibr atory compaction. For Soderberg paste, a liquid pitch is metered to the mixers and the hot paste is discharged to trans fer cars for transfer to the potrooms or cooled and formed into briquettes. POM is the major HAP emitted from paste production with nationwide emissions (measured as methylene chlorid e extractables) estimated at 230 tpy. Testing at two paste plants showed that uncontrolled emissions of the 20 target ed POM compounds were about 0.07 lb/t of paste.

Paste production and bake furnaces may be together in the same building, in separate buildings or series of s eparate buildings, or off-site. Under the proposed rule, a n independent manufacturer of anodes with a paste production or a n anode bake furnace located off-site may be subject to the requ irements of the rule if HAPs are emitted at level constituting a major

source.

Nearly all of the anodes produced for prebake plan ts are baked in open-top ring furnaces. Each ring furnace consists of a number of indirectly fired sunken ovens or open-top ped, brick pits arranged in rows. Some of the spaces in the b rickwork are mortared while others are left open intentionally. A large pipe or duct circles the furnace and leads to an exhaust fan. Doublesealed manholes (at least one per furnace section) are spaced along the top of the duct. The pits are filled wit h green anodes and petroleum coke or other insulating material is placed over the anodes from an overhead hopper to cover and ins ulate the anodes. After firing and cooling, the packing coke is removed from the pits by vacuuming or other means and reuse d.

HF and POM are the major HAPs emitted from the ano de bake furnace stack. HF emissions originate from the rec ycling of anode butts when fluorides not removed during clean ing of the butts are volatilized in the furnace and removed wi th the flue gas stream. The amount of HF emitted depends on th e quantity of anode butts recycled, the cleanliness of the butts, and the efficiency of the emission control device (if prese nt). The amount of particulate matter emitted can vary widel y, dependent on the type of furnace, fuel (gas or liquid), the a ge of the brickwork, packing material, and firing conditions. Particulate11

matter released consists mainly of condensed tar at tached to dust released through openings in the brick work or from the placement and removal of packing coke. POM emissions origina te from the coal tar pitch used as the binder and evolve as the green anode is baked in the furnace. Anode bake furnaces emit about 700 tpy of TF (the vast majority of which is gaseous or hyd rogen fluoride from uncontrolled bake furnaces) and 550 tpy of POM measured as methylene chloride extractables. Tests at two bake furnaces showed that the 20 targeted POM compounds were gene rated at a rate of 0.3 to 0.9 lb/t of anode prior to control b y dry alumina scrubbers.

2.3 Pollutants for Regulation

2.3.1 Health Effects. Hydrogen fluoride is a very corrosive and toxic inorganic acid that can be in g as or liquid in anhydrous form or in aqueous solution (with wate r). Liquid HF can severely burn the skin and eyes. Skin contact with anhydrous HF (liquid or gaseous) or solutions above 50 percen t produce immediate pain and tissue damage as the fluoride io n can penetrate the skin and attack underlying tissues an d bone. Inhalation is particularly hazardous because HF rea dily dissolves in the mucous membranes of the upper respiratory tr act, nose, and throat. Hydrogen fluoride also is highly reactive, and in many cases, the reaction products also are hazardous. 3

While the human health effects of inhaling moderat e amounts or the very low concentrations of HF that are typic al at modern, well-controlled primary aluminum plants are not wel l known, animal tests have shown that exposure through inhal ation for several months can result in damage to kidneys and nervous system changes such as learning problems. Inhalation of H F or fluoridecontaining dusts for longer periods (e.g. several y ears) can also result in bone disease, known as skeletal fluorosis . Inhalation of large amounts can be harmful to the heart and lu ngs or fatal. 4

The Agency for Toxic Substances and Disease Regist ry (ASTDR) reports in their 1993 toxicological profile that ac ute inhalation in combination with dermal exposure has resulted in pulmonary edema, pulmonary hemorrhagic edema, and tracheobron chitis.

3 Hydrogen Fluoride Study: Report to Congress under section 112(n)(6) of the Clean Air Act as amended. EPA 550 -R-93-001. September 1993.

4 Toxicological Profile for Fluorides, Hydrogen Fluo ride, and Fluorine. U.S. Department of Health and Human Serv ices. Public Health Service. TP-91/17. April 1993.12

In one study cited, a significant population (about 20 percent) exposed to airborne HF near an aluminum plant repor ted nausea and diarrhea. The ASTDR has not established a minimal risk level (MRL) for inhalation or oral exposure to HF for any exposure duration or system category because exposure data i n humans is not well quantified. However, existing data indica te that subsets of the population may be unusually suscepti ble to the toxic effects of fluoride and its compounds, includ ing the elderly, persons with deficiencies of calcium, magn esium, or vitamin C, and people with cardiovascular and kidne y problems. 5

The EPA oral reference dose (RfD) assessment and i nhalation reference concentration (RfC) assessment for HF are currently undergoing Agency review 6 . Additional information on the health effects of HF and related gases can be found in the literature review contained in the EPA report, "Summary Review of Health Effects Associated with Hydrogen Fluoride and Relat ed Compounds." 7

In the 1974 NSPS background information document, EPA reported documented evidence showing that fluorides emitted from industrial plants are responsible for damage to com mercially grown flowers, fruits, and vegetables. However, ev en at the reduced levels emitted today, fluorides in low conc entrations can be absorbed by grasses and plants and by animals th at feed on the forage. Hydrogen fluoride also is a corrosive gas capable of property damage. For these reasons, several States require plants to monitor for fluoride damage in areas surr ounding the plants. Additional information on the damage to ve getation, soil, wildlife, and livestock (and the critical loa d limit needed to prevent new damage) is available in the recent " Effects Study" conducted by Norwegian aluminum plants and the Norw egian Research Council. 8

5 Reference 4.

6 Integrated Risk Management System (IRIS). Hydroge n Fluoride and Fluorine. U.S. Environmental Protecti on Agency. Printout dated March 8, 1995.

7 Summary Review of Health Effects Associated with H ydrogen Fluoride and Related Compounds: Health Issue Asses sment. U.S. Environmental Protection Agency. Environmental Cri teria and Assessment Office. EPA-600/8-89-002F. December 19 88.

8 The Norwegian Aluminum Industry and the Local Envi ronment: Summary Report on the Project to Study the Effects of Industrial Emissions from Primary Aluminum Plants in Norway. Hydro Aluminum, Elkem Aluminum, and Sor-Norge Aluminum in cooperation with the Norwegian Research Council. ISBN 82-99330 5-0-5.13

Deposition of POM on waters such as the Great Lake s and Chesapeake Bay from aluminum plants also is of conc ern as discussed in the Great Waters Report to Congress. 9 In the report, major aluminum plants are identified as sig nificant sources of polycyclic aromatic hydrocarbons (PAH), including those aluminum plants located adjacent to or near t he Great Lakes and those at long distances from the waterbody. Pr imary aluminum plants also are identified as one of the MACT sourc e categories potentially emitting Great Waters pollutants of con cern.

The term "coal tar pitch volatiles" denotes the co mplete class of fused polycyclic hydrocarbons that volatil ize from pitch. These compounds are high molecular weight p olycyclic aromatic compounds (four, five, and six benzene rin gs) whose normal state is particulate rather than gaseous. A s such they are part of a larger class of compounds called POM (defined in the Act as including organic compounds with more th an one benzene ring and which have a boiling point greater than or equal to 100 ° C.) Emission test results reveal that POM compound s may include a combination of known HAPs such as anthrac ene, benzo(a)pyrene, and naphthalene, among others. POM is introduced into the process primarily by coal tar pitch. The pitch is produced from the refining of coal tar and is recov ered as a 40- to 60-percent bottoms fraction of heavy organics wi th very high boiling points.

Many of the compounds found in POM also are known (and sometimes measured as) PAH. PAHs are a group of ch emicals that are formed during the incomplete burning of coal, o il and gas, garbage, and other organic substances. However, al l 15 compounds considered to be PAH in the 1990 ASTDR toxicologica l profile 10 were found in the analytical results of POM emissio n tests for potlines, bake furnaces, and paste production. The ASTDR study confirms the presence of PAH at aluminum production plants and states:

November 1994.

9 Deposition of Air Pollutants to the Great Waters: First Report to Congress. U.S. Environmental Protection Agency. Office of Air Quality Planning and Standards. EPA-453/R-93-055. May 1994.

10 Toxicological Profile for Polycyclic Aromatic Hydr ocarbons. U.S. Department of Health & Human Services. Publi c Health Service. Agency for Toxic Substances and Disease R egistry. TP90-20. December 1990. Pages 3, 15, 58, 96.14 ... Several of the PAHs, including benzo(a)anthracene, benzo(a)pyrene, benzo(b)fluoranthene, benzo(k)fluoranthene, chrysene, dibenzo(a,h)anthracene, and indeno(1,2,3-cd)pyrene, have caused tumors in laboratory animals when they ate them, when they were applied to their skin, or when they breathed them in the air for long periods of time. Reports on humans show that individuals exposed by breathing or skin contact for long periods of time to mixtures of other compounds and PAH can also develop cancer. 11

And,

Evidence exists to indicate that certain PAHs are carcinogenic in humans and animals. The evidence in humans comes primarily from occupational studies where workers involved in such processes as coke production, roofing, oil refining, or coal gasification are exposed to mixtures containing PAHs... Cancer associated with exposure to PAH containing mixtures in humans occurs predominately in the lung and skin following inhalation and dermal exposure, respectively.... 12

The report also discusses the presence of respirat ory tract tumors observed in rats that inhaled a combination of benzo(a)pyrene (a component of POM) and SO 2 . The study results indicated that benzo(a)pyrene is carcinogenic to an imals when inhaled and that "the carcinogenicity can be enhanc ed with concurrent exposure to gases and particulates commo nly found in the environment." 13

Specific populations that may be susceptible to t he toxic effects produced by exposure to PAHs include: the unborn, people with nutritional deficiencies, genetic diseases, im munodeficiency due to age or disease, people who smoke, those with a history of excessive sun exposure, people with liver and skin disease, and women, especially of child-bearing age. There may be an increased risk of developing lung cancer following prolonged inhalation of PAH-contaminated air and skin cancer following

11 Reference 10. Pages 3, 15, 58, 96.

12 Reference 10. Pages 3, 15, 58, 96.

13 Reference 10. Pages 3, 15, 58, 96.15

concurrent dermal exposure to PAHs and sunlight. 14 The EPA is currently in the process of reviewing a carcinogeni city assessment for POM. 15

2.3.2 Measurement. Historically, the combination of gaseous and particulate fluorides emitted from alum inum plants have been measured and regulated as emissions of to tal fluoride or "TF". Methods 13A and 13B, originally promulgat ed in 1975, have been used for TF sampling and analyses, along with Method 14 which specifies the equipment and sampling procedur es for emission testing of potroom roof monitors.

Traditionally, fluoride captured by the front-half filter has been called "particulate fluoride," and fluorid e captured in the back-half impingers has been called "gaseous fl uoride" (GF). However, the method has been validated only as a me asure of TF expressed as the sum of the front-half and back-hal f catches. Thus, TF has been used for many years as a surrogat e to represent this mixture of gaseous and particulate fluorides, and most emissions data currently available result from samp ling and analysis for TF.

During the development of the proposed standards, EPA discussed with State and industry representatives v arious options for measuring gaseous HF, the listed HAP, and the u se of GF or TF as surrogate measures for HF. Several factors were considered in these discussions that led to the choice of TF as a measure of emission control performance. A major consideratio n was the absence of a validated, accurate method for the mea surement of HF or GF. EPA studies in the development of Method 13 identified problems in attempts to obtain an accurate split be tween particulate and gaseous fluoride. Hydrogen fluorid e is highly reactive and reacts with glass in the sampling prob e to form silicon tetrafluoride. The reactivity of HF has al so been a problem in developing an analytical standard; curre ntly, there is no EPA analytical standard that can be used to dete rmine the accuracy of attempts to measure HF. During samplin g, particulate matter in the front half of the train adsorbs GF, w here it is then measured as particulate fluoride. Fine partic ulate matter that passes through the filter is measured as GF in the back half of the train. These factors produce confounding ef fects in attempts to measure HF or GF with biases in differe nt directions.

14 Reference 10. Pages 3, 15, 58, 96.

15 Integrated Risk Management System (IRIS). Polycyc lic Organic Matter. U.S. Environmental Protection Agen cy. March 10, 1995.16

In addition, the quantity of HF or GF that is form ed is affected by humidity and the water content of raw materials.

A large historical data base for TF was available to characterize the emission control performance of th e industry, to identify the best controlled potlines, and to devel op the MACT floor and MACT level of control. There was a discu ssion among many different parties as to whether the MACT perfo rmance standard should be based on TF or GF, and EPA concl uded that TF provides the most defensible basis to ensure that t he MACT level of control is achieved. However, EPA recognizes th e importance of identifying the contribution of gaseous HF to ad verse health effects when exposure modeling is performed in the future. Consequently, the split between particulate and gas eous fluoride from Methods 13A and 13B will continue to be report ed, and an attempt will be made to improve the accuracy and co nsistency of this determination. In addition, EPA is encouragin g the development and application of HF CEMs as an improv ed monitoring tool for HF emissions.

The choices for measuring POM included expensive s ampling and analysis to identify and quantify each of the n umerous individual compounds that might be present or to de velop a reasonable surrogate measure for POM. During the M ACT test program jointly funded by the EPA, the State of Was hington Department of Ecology, and the industry, sampling a nd analysis were performed for both individual species and for a surrogate measure. The surrogate approach uses methylene chl oride extractables from both the front and back halves of a modified Method 5 procedure. The testing program indicated that methylene chloride extractables provided an adequate surrogat e measure of the total POM species at a fraction of the cost ass ociated with speciation. Consequently, the MACT level of POM co ntrol was defined from data for methylene chloride extractabl es, and the method developed during the test program is being p roposed for POM compliance determinations.

2.3.3 Other Pollutants. Primary aluminum plants also discharge significant quantities of nonHAP pollutan ts such as SO 2 , PM, and greenhouse gases (such as tetrafluorometh ane, hexafluoroethane, and carbon dioxide).

Sulfur is introduced into the aluminum production process primarily by the coke and pitch used to produce ano des; consequently, most plants limit SO 2 emissions by specifying the maximum sulfur content they will accept in these ra w materials. Two plants use SO 2 scrubbers following the dry alumina scrubbers of the primary control system to obtain additional SO 2 control, and four plants use wet roof scrubbers that provide some control of SO 2 in secondary (fugitive) emissions. These plants a nd17

control devices for SO 2 would not be affected by the proposed standard. Four plants use wet systems for their pr imary control device to limit emissions of fluorides, POM, other particulate matter, and SO 2 . If these plants install dry alumina scrubbers to meet the MACT standard and do not keep a wet scr ubber following the alumina scrubber, an increase in SO 2 emissions would be expected. However, this analysis assumes that current SO 2 requirements will remain in place even if dry alum ina scrubbers were installed at these four plants.

The greenhouse gases tetrafluoroethane and hexaflu oroethane are generated during anode effects in the reduction cell. Reducing the frequency and duration of anode effect s will decrease fluoride emissions as well as emissions of these greenhouse gases. The EPA's Global Change Division in the Office of Atmospheric Programs has a voluntary program und erway and is working with the aluminum industry to reduce emissi ons of these greenhouse gases.

2.4 Selection of MACT

2.4.1 Background. After EPA has identified the specific source categories or subcategories of major sources to regulate under section 112, it must set MACT standards for e ach category or subcategory. Section 112 establishes a minimum baseline or "floor" for standards. For new sources, the standa rds for a source category or subcategory cannot be less strin gent than the emission control that is achieved in practice by th e bestcontrolled similar source. [Section 112(d)(3)]. T he standards for existing sources can be less stringent than sta ndards for new sources, but they cannot be less stringent than the average emission limitation achieved by the best-performing 12 percent of existing sources for categories and subcategories w ith 30 or more sources, or the best-performing 5 sources for categ ories or subcategories with fewer than 30 sources.

After the floor has been determined for a new or e xisting source in a source category or subcategory, the Adm inistrator must set MACT standards that are no less stringent than the floor. Such standards must then be met by all sour ces within the category or subcategory.

In establishing the standards, EPA may distinguish among classes, types, and sizes of sources within a categ ory or subcategory [section 112(d)(1)]. For example, the Agency could establish two classes of sources within a category or subcategory based on size and establish a different emissions s tandard for each class, provided both standards are at least as stringent as the MACT floor for that class of sources.18

The next step in establishing MACT standards is traditionally the investigation of regulatory alter natives. With MACT standards, only alternatives at least as strin gent as the floor may be selected. Information about the indus try is analyzed to develop model plant populations for pro jecting national impacts, including HAP emission reduction levels, costs, energy, and secondary impacts. Several regulatory alternative levels (which may be different levels of emissions control, different levels of applicability, or both) are the n evaluated to select the regulatory alternative that best reflect s the appropriate MACT level.

The selected alternative may be more stringent tha n the MACT floor, but the control level selected must be techn ically achievable. In selecting a regulatory alternative that represents MACT, EPA considers the achievable emiss ion reductions of HAP's (and possibly other pollutants that are co -controlled), cost and economic impacts, energy impacts, and othe r environmental impacts. The objective is to achieve the maximum degree of emissions reduction without unreasonable economic or other impacts [section 112(d)(2)]. The regulatory alternatives selected for new and existing sources may be differ ent because of different MACT floors, and separate regulatory deci sions may be made for new and existing sources.

Under the Share-A-MACT approach applied during the development of the proposed standards, EPA met with representatives from State agencies, tribal governm ents, and industry groups to discuss the regulatory alternati ves and associated issues. This approach to standards deve lopment allows EPA to select an alternative based on consensus wit h State partners and the sharing of technical data and anal yses with other partners. For this pilot project, EPA met on several occasions with different groups in different locati ons to seek their views and selected an alternative using a mix ture of analytical and consensus-based decisions.

2.4.2 Subcategorization. Primary aluminum operations are differentiated by the type of anode used and the me thod by which the anode is introduced into the reduction cell. I n the prebake process, used by 17 plants, pots are classified as center-worked prebake (CWPB) or side-worked prebake (SWPB), depen ding on where the pot working (crust breaking and alumina additio n) takes place. Soderberg pots are differentiated by the po sition of the current carrying studs in the anodes, which may be inserted vertically (VSS) or horizontally (HSS). Emission d ata reveal there is a clear difference in the level of POM emi ssions from prebake and Soderberg plants.19

Section 112(d) of the Act requires EPA to establis h emission standards for each category or subcategory of major and area sources. Section 112(d)(1) of the Act states that "the Administrator may distinguish among classes, types, and sizes of sources within a category...in establishing such st andards...." In establishing subcategories, EPA has considered f actors such as air pollution control engineering differences, proc ess operations (including differences between batch and continuous operations), emission characteristics, control device applicabil ity, and opportunities for pollution prevention. For the su bcategories of potlines, the distinctions are based primarily on d ifferences in the process operation, process equipment, emissions , and the applicability of control devices.

The EPA's analysis of existing aluminum production process and operations resulted in the designation of seven subcategories for potlines. These are: (1) CWPB1 potlines; (2) C WPB2 potlines; (3) CWPB3 potlines; (4) SWPB potlines; (5) VSS1 pot lines; (6) VSS2 potlines, and (7) HSS potlines. Additiona l information on the subcategorization is included in Appendix A to this document.

Prebake and Soderberg are two distinctly different processes for aluminum reduction that present different chall enges for capturing emissions from the aluminum reduction cel ls. These two processes also have different characteristics, espe cially with respect to POM emissions. A major difference betwe en the two processes is that the anodes used in the prebake pr ocess have been formed and baked in a separate process operati on (i.e., the anode bake furnace), whereas the Soderberg process bakes the anode in the reduction cell as part of the producti on operation. This difference directly affects emissions and res ults in larger quantities of organic compounds such as POM being e mitted from the Soderberg process.

Other differences between the two processes also a ffect emissions and their control. In the prebake proces s, spent anodes are periodically removed and replaced, and t his operation directly affects secondary (fugitive) emissions. C onversely, "green" paste (a mixture of unbaked coke and pitch) is added in a semi-continuous manner to the Soderberg reduction c ell to allow it to be baked in place and to replace the anode as it is consumed. In addition, there are differences in th e type and efficiency of hooding used for the two processes. In general, the hoods used for the Soderberg process have lower capture efficiencies because the gases evolving from the So derberg cell are more difficult to capture.

Within the prebake process, center-worked (CWPB) a nd sideworked (SWPB) units have significant differences in design of the20

equipment, its operation, and applicable emission c ontrols, especially in the capture of primary emissions. Th e process and operational differences include the placement of th e anodes, the type of side shields, the method of alumina additio n, and how the reduction cells are worked.

In the SWPB process, alumina is added along the si des of the reduction cell and the anodes are set close togethe r near the center line. In the CWPB process, alumina is added down the center of the pot and the anodes are closer to the side. Consequently, the covers and hoods for the primary collection system are different for these two types of units b ecause of the design, placement of anodes, and working the bath f rom the center versus from the side. In addition, the newer CWPB units can be equipped with computer-controlled crust breakers an d point feeders, which often allow them to be worked withou t removing the side shields.

The design and operational differences between SWP B and CWPB result in different design considerations for the p rimary system. In general, emissions from the CWPB reduction cell s can be captured with a higher efficiency than those from S WPB cells.

The investigation of the CWPB process indicates th at there are two different designs that directly affect the ability of the operator to control emissions. One group is compos ed of CWPB reduction cells that are larger, generally newer, a nd operate at higher amperages (called CWPB1) than the older and smaller CWPB units (labeled CWPB2). The major factor affecting the difference in emissions and controls for the two types of unit s is the number of anode changes required.

Data were obtained from industry surveys on the fr equency of changing anodes. 16 These data indicate that the older and smaller CWPB2 cells have more frequent anode changes per to n of aluminum than do the newer and larger CWPB1 cells. More fre quent anode changes result in greater quantities of secondary ( fugitive) emissions that are difficult to capture and control

. There are two other differences between the large and small CWPB units that affect emissions and their capture. Access is required more often to the smaller units because th ey are generally more unstable and are less likely to have computer controls. More frequent access means the shields o f the primary collection system are opened more frequently and pe rhaps for

16 K. Ours, Research Triangle Institute, to Docket. Memorandum on Summary of Information for ICR-1 and ICR-2. September 30, 1993.21

longer periods, which results in poorer emission ca pture and higher emissions. Another factor is the smaller un its generally have more anodes per reduction cell, which affects the design and capture efficiency of the hooding. These combinati ons of factors indicate that the larger CWPB units have lower emis sions per ton of aluminum produced and that less emissions escape capture by the primary collection system.

Four center-worked prebake potlines with wet prima ry control systems were assigned a separate subcategory (CWPB3 ). These potlines produce a high purity aluminum for a speci alized market, and they can do so only because metal impurities ar e removed with the sludge from the wet scrubbers. If these potlin es were required to install dry alumina scrubbers, the cont aminants would be returned to the reduction cell and contaminate t he aluminum. The company claims that if they must meet MACT for the prebake subcategory of modern potlines with dry alumina scr ubbers, they could lose their market for high purity aluminum. The EPA is requesting comments on the issue of a separate subc ategory for plants that produce high purity aluminum.

There are two distinct designs used in the Soderbe rg process: horizontal (HSS) and vertical stud (VSS). The VSS design has steel studs that carry electrical curren t vertically through the unbaked paste and into the baked portio n of the anode. In the HSS design, the studs project horizo ntally. The differences in design and operation result in diffe rent types of hooding and evaluation rates, both of which affect emissions and controls. In the VSS cells, the stationary anode c asing and vertical projection of the studs through the anode allow the installation of a gas collection skirt between the anode casing and bath. The collected gases are ducted to burner s where carbon monoxide, tars, and other hydrocarbons are burned p rior to the primary control device.

The design of the HSS cell prevents the installati on of an integral gas collection device because the anode ca sing is formed by removable channels that support the studs, and t hese channels must be periodically changed as the anode moves dow nward. Consequently, the hooding for the HSS cell is restr icted to a canopy suspension, which results in air infiltratio n and dilution. The collected gases from the HSS cell ar e too dilute to support combustion in burners. For comparison, a typical VSS cell has an evacuation rate on the order of 500 ft 3 /min compared to a range of 3,500 of 5,000 ft 3 /min for an HSS cell.

Two VSS plants with five potlines use wet roof scr ubbers to control secondary emissions, and the third plant al so with five potlines uses work practices for secondary emission control. Consequently, EPA investigated the use of wet roof scrubbers as22

the MACT floor technology for all VSS plants. Howe ver, data obtained from one plant with wet roof scrubbers ind icated that their scrubbers were shut down in periods of cold w eather to avoid damage to the scrubbers and water treatment p lant. The data indicated that the scrubbers were shut down du e to cold weather an average of 36 days per year (a range of 19 to 48 days per year from 1986 to 1993). This represents a dow n time of 10 percent, i.e., they operated about 90 percent of th e year. The procedure is to shut the scrubbers down when the te mperature reaches 27 ° F and the temperature is predicted to drop further.

The VSS plant without wet roof scrubbers is locate d in northern Montana where the weather is much colder. Data obtained from the National Weather Service indicated that th e normal daily average temperature was below 27 ° F about 21 percent of the time and the normal daily low temperature was below 27 ° F about 40 percent of the year. Consequently, the use of wet roof scrubbers based on the other plant's experience suggests that scrubbers installed in northern Montana could be shut down on the order of 20 to 40 percent of the time. Consequently, EPA de termined that wet roof scrubber technology has not been adequatel y demonstrated for very cold climates.

The EPA believes that the technical feasibility of emission controls is an important consideration when evaluat ing the need to develop subcategories. For this case, EPA concl uded that wet roof scrubbers were not applicable or feasible as t he MACT floor technology for the VSS plant in Montana. Consequen tly, a separate subcategory (VSS2) was created for the fiv e potlines at the plant in Montana, and the MACT floor for this s ubcategory would be determined by the average emission limitat ion achieved by these five potlines.

Because of the air pollution control engineering differences, including consideration of the variati ons in process operation, emission characteristics, and control de vice applicability, EPA developed separate MACT floors f or each of these subcategories of potlines.

The vast majority of anode bake furnaces are simil ar in emissions potential and the applicability of emissi on control devices. One exception that exists is an anode bak e furnace that is not located on the same site as the primary alum inum production facility. This facility does not have a ccess to alumina for use in the dry alumina scrubber, and it does not have potlines that can use the reacted alumina generated by a dry alumina scrubber. On the other hand, bake furnaces co-located with the primary aluminum potlines have access to a lumina, the basic raw material used for aluminum production, an d can transfer the reacted alumina from the dry scrubber to the re duction cells.23

Consequently, a separate subcategory was created f or this offsite bake furnace because the emission control tech nology (dry alumina scrubbers) would not be applicable.

2.4.3 MACT Floor Technologies. In general, the control option for primary emissions is the installation of highlyefficient dry alumina scrubbers at those plants tha t do not have them. Dry alumina scrubbers use alumina ore to ads orb gaseous pollutants and a baghouse to remove particulate pol lutants and the alumina. This system controls 99.5+ percent of the fluoride emissions and 90 to 99 percent of the POM emissions at the best controlled plants. Consequently, this control devi ce represents the MACT floor technology and the best control for primary emissions.

The MACT floor technology associated with the cont rol of secondary emissions includes the use of wet roof sc rubbers for SWPB and VSS1 potlines and, for all subcategories, adherence to specific work practices such as high draft on open pots, operating conditions, equipment inspection, mainten ance, and repair.

Several control devices are currently in use for the control of emissions from paste production. Dry co ke scrubbers are used at five plants to control POM emissions, a nd the other plants use various types of controls for specific e mission points in paste production. The dry coke scrubber is the most effective of these control devices (shown to achieve up to 99 .8 percent control of POM emissions) because the coke (carbon) provides a condensation point for the organic vapors generated during paste production, and a baghouse is used to control fine particulate matter and to remove coke fines. The coke can be r eturned directly to the paste production operation. Given that there are less than 30 plants, EPA examined the top five best performing plants. Based on the top five plants, the dry coke scrubber was identified as the MACT floor technology for paste p roduction.

The most common and effective control device curre ntly used for anode bake furnaces located at primary aluminum plants is the dry alumina scrubber, used by 12 of the 17 plants w ith anode bake furnaces. Two plants use an electrostatic precipit ator (ESP) and three plants do not use a control device. The dry alumina scrubber is the most effective of these control dev ices because the alumina is an adsorbent for the HF gas generate d during the baking process and provides a condensation point fo r tars (POM); a baghouse is used to control fine particulate matt er containing fluorides and POM. The dry alumina scrubber has be en shown to achieve 99 to 99.6 percent control of TF emissions and 94 to 98 percent control of POM emissions. For the bake fur nace that is24

not located at a primary aluminum plant, the MACT f loor technology is an electrostatic precipitator.

2.4.4 Beyond MACT Floor Evaluation. The EPA's analysis of control options for new and existing sources reveal ed that the control technologies chosen to represent the MACT f loor (described above) were the most efficient for the c ontrol of HAP's among the various control devices used in the industry. No additional control options were identified that had been demonstrated to be more effective than the MACT flo or technologies at a reasonable cost or that would ach ieve significant additional reductions in HAP emissions. Consequently, the technologies associated with the MACT floor were also determined to represent the MACT technolo gy.

For example, the retrofit of wet roof scrubbers wa s considered as a control option to reduce further th e secondary emissions from the potlines. The analysis (see App endix C) indicated that only a nominal additional emission r eduction would be achieved on a nationwide basis by wet roof scrub bers at a very high additional cost. Consequently, wet roof scrub bers were determined not to represent the MACT control techno logy for potlines that do not have them based on considerati on of nationwide impacts (such as the high cost relative to nominal reductions in emissions). The "beyond-the-floor" a nalysis focuses on the technology basis for determining MAC T; it does not consider the potential effects on risk or other hea lth considerations for a specific plant. Consequently, this analysis does not conclude that wet roof scrubbers are not a pplicable or reasonable for a specific plant if site-specific he alth considerations can be determined and are factored i nto the decision. However, an analysis of residual risk an d the need to reduce it will be evaluated later (within 8 years o f promulgation of the MACT standard). At that time, a considerati on of health effects and potential reductions for a specific pla nt could indicate the wet roof scrubbers are warranted.25

3.0 PROPOSED STANDARDS

3.1 Emission Limits

Emission data from primary aluminum plants were so licited through two series of EPA information collection re quests (ICR), from the industry trade association, from State age ncies, and from individual plants. In addition, several prima ry aluminum plants were surveyed to collect additional detailed information on sources and processes. Emission tests also were conducted at seven plants as part of the MACT Test Program, whic h was funded jointly by EPA, the State of Washington Department of Ecology, and the industry. Additional emission test data al so were submitted by individual plants.

The available data were evaluated to identify the "MACT" potrooms, anode bake furnaces, and paste production operations. The sampling and analytical procedures used histori cally by the plants were investigated and any differences from E PA procedures were evaluated. For each subcategory, the median p otline was identified from the top 5 performing potlines to re present the performance associated with the MACT floor technolo gy (i.e., the average emission limitation achieved by the top 5). Additional emission testing was performed for these potlines a s needed to supplement the historical data, to characterize the emission control performance, and to obtain data on POM emis sions.

Analysis of these available data leads EPA to conc lude that the emission levels shown in Table 1 represent exis ting source MACT. These emission limits for potlines are in th e same format as the NSPS (kg/Mg or lb/ton of aluminum). The pro posed standard retains this format for anode bake furnaces, but us es lb/ton of anode rather than lb/ton aluminum equivalent as in the NSPS.

The limits for bake furnaces in Table 1 apply to b ake furnaces located on the same site as the primary al uminum plant. For the one bake furnace not located with a primar y aluminum plant, the limits do not apply because the MACT con trol technology determined for the other bake furnaces ( dry alumina scrubber) does not apply. However, the Louisiana D epartment of Environmental Quality has developed MACT standards for this plant under an approved State program. For this particul ar anode bake furnace plant, EPA is adopting the State's MACT det ermination. This approach is consistent with EPA's approach of working with the States, adopting MACT determinations from State programs when appropriate, and avoiding regulatory duplication.

For paste plants, the EPA concluded that it was no t feasible to prescribe or enforce an emission standard; conse quently, an26

equipment standard was developed for this source [s ection 112(h)]. The evaluation of the POM data for paste plants27

TABLE 1. SUMMARY OF PROPOSED EMISSION LIMITS FOR EXISTING SOURCES

Source Emission Limit

Potlines TF Emission Limits

0.95 kg/Mg (1.9 lb/ton) of aluminum produced for CWPB1 a potlines

1.5 kg/Mg (3.0 lb/ton) of aluminum produced for CWPB2 a potlines

1.25 kg/Mg (2.5 lb/ton) of aluminum produced for CWPB3 a potlines

0.80 kg/Mg (1.6 lb/ton) of aluminum produced for SWPB a potlines

1.1 kg/Mg (2.2 lb/ton) of aluminum produced for VSS1 a potlines

1.35 kg/Mg (2.7 lb/ton) of aluminum produced for VSS2 a potlines

1.35 kg/Mg (2.7 lb/ton) of aluminum produced for HSS a potlines

POM Emission Limits

2.35 kg/Mg (4.7 lb/ton) of aluminum produced for HSS potlines

1.2 kg/Mg (2.4 lb/ton) of aluminum produced for VSS1 potlines

1.85 kg/Mg (3.7 lb/ton) of aluminum produced for VSS2 potlines28

Paste Production POM Emission Limit

Install, operate, and maintain equipment for capture of emissions and vent emissions to a dry coke scrubber.

Anode Bake Furnace (located with a primary aluminum plant) TF Emission Limit

0.10 kg/Mg (0.20 lb/ton) of anode

POM Emission Limit

0.09 kg/Mg (0.18 lb/ton) of anode

a Abbreviations defined:

CWPB1 =Center-worked prebake potline with the most modern

reduction cells; includes all center-worked prebake potlines not specifically identified as CWPB2 or CW PB3 CWPB2 =Center-worked prebake potlines located at A lcoa in

Rockdale, Texas; Kaiser Aluminum in Mead, Washingto n; Ormet Corporation in Hannibal, Ohio; Ravenswood Aluminum in Ravenswood, West Virginia; Reynolds Met als in Troutdale, Oregon; and Vanalco Aluminum in Vancouver, Washington CWPB3 =Center-worked prebake potline that produces very high

purity aluminum, has wet scrubbers as the primary control system, and is located at the primary alumi num plant operated by NSA in Hawesville, Kentucky HSS =Horizontal stud Soderberg potline SWPB = Side-worked prebake potline VSS1 = Vertical stud Soderberg potline at Northwe st Aluminum in

The Dalles, Oregon, or at Columbia Aluminum in Goldendale, Washington VSS2 = Vertical stud Soderberg potlines at Columb ia Falls

Aluminum in Columbia Falls, Montana29

concluded that it was not practical to set an emiss ion limit because there were too few data to characterize the control performance that could be achieved by the various t ypes of paste plants and because of uncertainty in the limited ex isting data. The high level of uncertainty would cause EPA to se t a standard that could be impractical on a technological basis. The EPA considered drafting a standard that would require e ach owner or operator to conduct measurements to set limits on a case-by-case basis; however, the cost of this approach was not c onsidered to be reasonable, especially given the reasonableness and effectiveness of specifying a design and equipment standard. Consequently, the proposed rule requires the instal lation of a capture system that collects and vents emissions to a dry coke scrubber (or equivalent alternative control device) for all paste production plants. If the owner or operator prefer s to develop an applicable emission limit rather than comply wit h the equipment and design standard, this option is avail able under provisions for an alternative standard in section 1 12(h)(3).

In developing the emission limits, EPA considered different statistical approaches and different upper percenti les of performance. The industry generally recommended a level at least as high as the 99th percentile, and State represent atives recommended using the 95th percentile. The EPA ana lyzed the data and considered the statistical approaches as well a s examining the levels that had been achieved by the MACT floor plants. An important consideration in developing the proposed emission limits was that the monthly averages of the MACT fl oor potline must show that the limit has been achieved.

For cases with adequate historical data to determi ne the limit that had been achieved (e.g., TF from potline s), the MACT floor limits were determined from the highest month ly averages in the data base. In cases with no historical data (e .g., POM limits for all sources), the EPA used a statistical approach to estimate the MACT floor levels that had been achiev ed. Additional details on the data analysis are given i n Appendix B, and a complete listing of the data is given in Appe ndix D.

Based on data submitted by the affected plant, EPA determined that the CWPB3 potlines could have their wet primary control systems upgraded and improve control of sec ondary emissions to achieve a limit of 2.5 lb TF/ton as th e MACT level of control, which has been the historic NSPS level for prebake potlines. Information supplied by NSA indicated th at upgrading their wet scrubber system enabled them to meet a li mit of 2.5 lb TF/ton. 17

17 Memorandum from W. Hill, Southwire Company, to M. McKeever, EPA:ESD, May 23, 1995. Docket Item II-D-85.30

The POM limits for HSS potlines were determined fr om the data collected during the MACT Test Program. The 9 5th percentile was used to determine the POM limit for the HSS sub category for both the primary control system and secondary emiss ions. The POM limits for VSS1 are based on the limited test data available from one potline at Columbia-Goldendale and one potline at Northwest Aluminum. The results from these two potlines were combined to provide enough data to assess performance and to re present the MACT floor. These two potlines achieved a level of 2.4 lb/ton. There were no validated POM data available for the VSS2 subcategory; however, POM data for the VSS1 subcate gory before the wet roof scrubbers represent the same process c onfiguration as that for VSS2. Consequently, the VSS1 POM data were used to derive limits for VSS2. The POM emissions at the i nlet to the wet roof scrubbers did not exceed 3.7 lb/ton. Addi tional details are provided in Appendix B and Appendix D.

For anode bake furnaces located at primary aluminu m plants, POM limits were developed from the two best perform ing furnaces in the industry with the MACT technology (dry alumi na scrubbers), which were the only ones for which EPA had adequate data to determine the MACT level of control. The emission limit for TF from anode bake furnaces was based on data from Nor anda's bake furnace, which supported a level equal to the NSPS level of control. Eight bake furnaces currently are subject to the NSPS, and the NSPS level has been achieved by an older ba ke furnace that is not subject to the NSPS.

Emission limits are also proposed for new and reco nstructed potlines and anode bake furnaces. [See Table 2.] These emission limits are based on data from the best controlled p otline and bake furnace. An equipment standard (dry coke scru bber) is proposed for new paste plants. MACT for new source s applies to all new and reconstructed potlines, and no distinct ion is made for the different subcategories that were developed for existing potlines. As provided in the definition of "recons truction" in the proposed rule, two criteria must be met for a s ource to be considered reconstructed and subject to new source MACT: (1) all of the major components of the source must be repla ced (for example, the major components of a potline include the raw material handling system, reduction cells, superstr ucture, hooding, ductwork, etc.), and (2) it must be techni cally and economically feasible for the reconstructed source to meet new source MACT.

The EPA believes that it is unlikely that an exist ing potline could be reconstructed in such a manner tha t it would be technically feasible for the potline to meet new so urce MACT unless the criteria described above are met. For e xample, the conversion of a Soderberg potline to a prebake potl ine, while31

retaining some of the major components of the origi nal potline, is expected to subject the source to emission limit s for existing prebake potlines rather than triggering new source MACT. Similarly, if an existing potline is modified to in crease capacity (e.g., by adding more reduction cells), th e modified potline would continue to be subject to MACT for ex isting

sources.

Another example is the conversion of a SWPB potlin e to a CWPB potline, which is not expected to be a reconst ruction if some of the major components of the original potlin e are retained. However, when an existing potline is cha nged in such a manner that the applicable subcategory changes, the changed potline must meet the applicable limit for the orig inal subcategory or the applicable limit for the new sub category, whichever is more stringent. In other words, an ex isting potline cannot qualify for less stringent emission limits a ssociated with another subcategory as a result of changes to its o peration.

TABLE 2. SUMMARY OF PROPOSED EMISSION LIMITS FOR NEW SOURCES

Source Emission Limit

Potlines TF Emission Limit

0.6 kg/Mg (1.2 lb/ton) of aluminum produced

POM Emission Limit

0.32 kg/Mg (0.63 lb/ton) of aluminum produced

Paste Production POM Emission Limit

Install and operate equipment for the capture of emissions and vent emissions to a dry coke scrubber

Anode Bake Furnace TF Emission Limit

0.01 kg/Mg (0.02 lb/ton) of anode

POM Emission Limit

0.025 kg/Mg (0.05 lb/ton) of anode32

3.2 Monitoring and Compliance Requirements

The EPA identified and analyzed several different options for enhanced monitoring of primary and secondary em issions from new and existing plants. The major HAPs of interes t from the primary aluminum industry include HF and POM. Curr ently, there is no known continuous emission monitor (CEM) for P OM; however, devices are available for the continuous monitoring of HF emissions. These devices can be used to monitor bo th primary and secondary HF emissions from the potlines and for HF emissions from the anode bake furnace. A continuous opacity monitor also could be used for visible emission observations to ensure proper operation of the control system.

Most plants currently perform emission tests as of ten as once to three times per month for pollutants such a s particulate matter (PM) and TF. Currently, very little samplin g and testing is performed for POM emissions. Methods 13 and 14 can be used to determine the quantity of TF from aluminum producti on. The analysis adds particulate and gaseous fluoride (GF) captured in the front half filter to GF from the back-half impi ngers to determine total fluoride. In addition, a method ha s been developed to provide a surrogate measure of POM emi ssions (Method 315). This method uses a gravimetric deter mination of methylene chloride extractables from both the front and back halves of the sampling train. Methylene chloride e xtracts that portion of the particulate matter that is POM; howe ver, it is a surrogate because it also extracts some material th at is not POM. Options for manual sampling include sampling at di fferent frequencies; manual sampling for each potline; or s ampling one potline to represent a group of similar potlines.

Parametric monitoring also is an option and includ es monitoring of certain parameters associated with th e production process, the control device, or both to ensure prop er operation of the control system. These parameters may be mon itored on a more frequent basis than periodic manual sampling t o supplement the manual sampling. Examples of possible monitori ng parameters for a dry alumina scrubber include the alumina flow rate, air flow rate, pressure drop, and inlet gas temperature . For a wet scrubber and secondary emissions, parameters could include the scrubbing liquor flow rate, the pressure drop acros s the scrubber, and air flow. Parameters for secondary e missions also could include inspections to observe work practices ; the condition of the hoods and shields; the number of s hields removed; the frequency of removal, and the duration . Visual observations of opacity, a bag break detection syst em, and periodic inspection of fabric filters for tears or gaps also could be made.33

The EPA considered the various options for monitor ing and concluded that the provisions selected for proposal (see Table 3)34

TABLE 3. PROPOSED MONITORING AND COMPLIANCE REQUI REMENTS

Source Requirement

Potlines 1.Monthly sampling for TF secondary emissi ons from each potline plus quarterly POM sampling for Soderberg potlines. May sample one potline to represent a similar potline(s).

2.If one potline represents one or more similar potlines, the owner or operator must monitor the similar potline(s) with an HF CEM or an Alcan cassette sampler. These devices must meet certain Method 14 criteria, and an enforceable limit for these devices must be established based on simultaneous performance testing using Methods 13 and 14.

3.An HF CEM or Alcan cassette sampler can be used instead of manual sampling if the owner or operator correlates or demonstrates them to be equivalent to Methods 13 and 14 to the satisfaction of the regulatory authority.

4.Annual sampling of TF and POM (for Soderberg potlines only) from each primary control system.

5.Monitor control device parameters.

6.Install monitoring device to measure weight of aluminum produced.

7.Compute a monthly average from at least 3 runs for secondary emissions and the 12-month average of tests of the primary control system (at least 3 runs per year). Using the monthly average and 30-day average production rate, compute TF emissions in lb/ton to determine compliance. POM emissions are determined in a similar manner (for Soderbergs only) on a quarterly basis from at least one run for secondary emissions per month and 3 runs annually for emissions from the primary control system.35

Source Requirement

Paste Production 1.Install required equipment.

2.Monitor process parameters for control device.

Anode Bake Furnace 1.Monitor process parameters for control device.

2.Install monitoring device for weight of green anodes placed in the bake furnace.

3.Annual sampling for TF and POM from furnace stack. Compute average of at least 3 runs and weight of anodes to determine compliance.36

represented a cost-effective approach to determine emission control performance. Periodic manual sampling was chosen to measure emissions instead of an HF CEM because CEMs have not been adequately demonstrated and validated. However, th e EPA encourages the development and future use of HF CEM s for secondary emissions because they show promise for i mproved measurement of HF emissions and as a tool for impro ved process control. In addition to periodic manual sampling, monitoring of control device parameters is proposed to ensure tha t the control device is operated properly on a continuous basis. Additional details on the monitoring requirements are given in the following sections; highlights are given in Table 3.

3.2.1 Potlines. The proposed rule would require compliance monitoring for each new and existing potline (or si milar potline). For secondary emissions of TF from each p otline (or group of similar potlines) exiting the roof monitor , the proposed rule would require the owner or operator to perform at least three runs each month by Methods 13 and 14. If wet roof scrubbers are used, the owner or operator would mea sure emissions using methods approved by the regulatory authority. For POM emissions from Soderberg potlines, the owner or ope rator would perform one run per month (three runs per quarter) using a Method 14 sampling manifold and procedures and Method 315 (proposed as part of this rulemaking) for POM analyses.

Plants may sample secondary emissions from one pot line to represent similar potlines rather than perform manu al sampling on each potline. To show that a potline is similar, t he owner or operator must demonstrate (to the satisfaction of t he regulatory authority) that the level of emission control is th e same for all of the potlines in the group. An HF CEM or Alcan c assette sampler may be used to demonstrate compliance by si milar potlines that are not manually sampled. An emission limit f or the device must be established based on a minimum of 9 simulta neous runs using Methods 13/14 and the alternative monitoring device. The alternative limit may be based on a mathematical co rrelation of the results and the applicable TF limit or it may b e based on the highest reading of the alternative device that corr esponds to a Method 13/14 result that is in compliance with the applicable TF limit. The similar potline must be monitored with the HF CEM or Alcan cassette on the same frequency as that requir ed for manual sampling. Exceeding the emission limit established for the alternative device would be a violation. Procedure s are also included to develop alternative methods for POM det erminations.

The industry has requested and EPA is considering work practice inspections as a monitoring alternative to show similar levels of control for similar potlines. This appro ach may be feasible. However, this issue is unresolved becaus e every37

specific work practice and its corresponding effect on emissions are difficult to identify and quantify, and there i s no evidence that a work practice "score" is relatable to emissi on rates. Consequently, there have been difficulties in devel oping work practice inspections as an acceptable alternative c ompliance approach.

Methods other than manual sampling using Methods 1 3 and 14 may be approved on a case-by-case basis by the regu latory authority. The EPA is encouraging the development and use of HF CEMs to monitor secondary emissions because they sh ow promise for improved monitoring, lower costs, and better proces s control of fluoride losses. Alternative methods must be corre lated with Method 13 and 14 results to the satisfaction of the regulatory authority. Alternative methods must account for or include gaseous fluoride and cannot be based on measurement of particulate matter or particulate fluoride alone be cause HF, the HAP of interest, is in gaseous form. For example, the use of the Alcan cassette has been approved for TF measurement s at one plant in the CWPB1 subcategory based on a demonstrated co rrelation to the results from Method 14. Demonstrations would b e required to obtain approval to use the Alcan cassette for potli nes in other subcategories (such as the Soderberg subcategories) because of potential differences in emission characteristics, including the effects of higher levels of particulate matter.

For the primary control system, the proposed rule would require the owner or operator to sample each primar y control device on an annual basis (at minimum) for TF emiss ions using Method 13 and for POM (from Soderberg potlines only ) using Method 315. For both the TF and the POM tests, at least three runs are required. If there are multiple primary c ontrol devices or stacks, the owner or operator must rotate sampli ng or sample representative stacks to ensure that each primary c ontrol device is sampled during the year (i.e., at least one run per control device). If the primary control system is tested m ore than once during the previous 12-month period, the average of all runs for the 12-month period is used to determine the contri bution from the primary control device.

The owner or operator also would install, operate, and maintain a device for the monitoring and recording of process parameters to ensure proper operation of the contro l system. For dry alumina scrubbers, the devices must monitor and record the alumina flow and the air flow of the device. For w et scrubbers used as primary control devices, the device must mo nitor and record the water flow rate to the scrubber and the air flow rate. Plants using electrostatic precipitators must inst all devices to monitor voltage and secondary current. In addition , the stacks of all primary control systems must be visually ins pected each38

day for indication of abnormal operation. Plants w ith wet roof scrubbers that control secondary emissions must mon itor total water flow and inspect each scrubber each day to en sure each one is operating properly. If an emission control devi ce other than one of those described above is used, the owner or operator must include recommended monitoring parameters in the pa rt 70 permit application.

Using data from the initial performance test and h istorical performance tests, the owner or operator would use these monitoring devices to determine the upper and/or lo wer operating limits, as appropriate, for each parameter. The ow ner or operator may redetermine the upper and/or lower ope rating limits, as appropriate, based on historical data or other i nformation and submit an application to the regulatory authority t o change the applicable limits.

The monitoring parameter limit(s) would be used as the baseline against which subsequent readings would be compared to ensure normal operation of the control device. A c orrective action program would be triggered if the control de vice is operating outside of the acceptable range for the s pecified parameters. Failure to initiate corrective actions within one hour after exceeding the limit is a violation. A v iolation also occurs if the operating limit for a parameter is ex ceeded more than 6 times in any semiannual reporting period. F or the purpose of determining the number of exceedances, no more t han one exceedance would be attributed in any given 24-hour period. The EPA limited the number of times the monitoring para meter(s) could be exceeded without a violation (no more than 6 tim es in a semiannual period) to ensure that the control equip ment is properly repaired under the corrective action progr am. The semiannual period also provides the owner or operat or adequate time to submit a request to redetermine the limit(s ) as described earlier if historical data or other information sho ws that the original monitoring parameter limits are no longer appropriate.

To determine compliance with the single emission l imit for primary and secondary emissions from the potline, t he plant owner or operator would compute the monthly average (mini mum of three runs per month) for secondary emissions of TF and q uarterly emissions of POM (from a minimum of one run per mon th for Soderberg potlines) from each potline. Using the e mission test results (the average of at least 3 runs for seconda ry emissions and the most recent annual test or 12-month average of the primary control system) and the 30-day average prod uction rate for aluminum production, the owner or operator woul d calculate the emissions in a kg/Mg (lb/ton) format to compare to the emission limits in the rule. The results of the se condary emission tests and the most recent compliance test for the primary control system are added together and compa red to the39

emission limit. If the average value is less than the applicable emission limit, the potline (or group of similar po tlines) is in compliance.

Compliance with the standard must be demonstrated at startup for new sources and within 2 to 3 years of the effe ctive date of the final rule for existing sources, depending on t he changes needed at a given plant to meet the standards. All plants have at least 2 years to comply. Plants that demonstrat e that more time is needed to install control equipment for a s pecific source will be given three years to comply for that source . The owner or operator must submit semiannual reports of exces s emissions and semiannual reports of startups, shutdowns, and malfunctions (if applicable).

3.2.2 Anode Bake Furnaces . The proposed rule would require the owner or operator to sample TF emissions from n ew and existing anode bake furnaces using Method 13 and to sample POM emissions using Method 315. Both pollutants must b e sampled annually; at least three runs must be performed. T he provisions for establishing monitoring parameter limits, monit oring of control device parameters, corrective actions, etc. are the same as those described earlier for potlines.

3.2.3 Paste Production. The proposed rule would require the owner or operator to install and operate a capt ure system vented to a dry coke scrubber (or equivalent altern ative control device) for new and existing paste plants. There w ere only limited data 18,19 available to characterize the performance of dry coke scrubbers, and after review of the data, the E PA determined that a control efficiency of 90 percent was achieva ble for batch mixers and 95 percent was achievable for continuous mixers. Consequently, if a control device other than a dry coke scrubber is used, the proposed rule requires that the altern ative control achieve a POM reduction efficiency of at least 95 percent for continuous paste mixing operations and at least 90 percent for batch operations. In addition, the owner or operat or must install, calibrate, maintain, and operate a monitor ing device to measure and record the coke flow rate and the air f low rate to the scrubber (or other parameters for an approved a lternative device). If other control devices are used, the ow ner or operator must include recommended monitoring parame ters in the part 70 permit application. The provisions for mon itoring of

18 Emissions Measurements Test Report - Northwest Alu minum Company. Prepared by Entropy, Inc. June 1994. 77 p.

19 Kaiser Aluminum and Chemical Corporation Method 5/ POM and 13B Testing - Mead, Washington - March 15-24, 1994. Prepared by AmTest Air Quality, Inc. November 9, 1994. pp. 1 to 99.40

control device parameters, corrective actions, etc. are the same as those described earlier for potlines.

3.2.4 Emission Averaging. The proposed rule contains provisions for the averaging of TF emissions from p otlines and anode bake furnaces. Emission sources not located on the plant site or not within the same State or permitting jur isdiction would not be eligible for emissions averaging and a veraging would be limited to TF emissions from like sources. For example, TF emissions from one potline can be averaged with the TF emissions from another potline at the same plant. Each emiss ion point used in emission averaging must be sampled to ensure an accurate accounting of emissions. Averaging would not be al lowed between two different pollutants (e.g., TF and POM). Emiss ions averaging would not be allowed in any State that selects to e xclude this option from their operating permits program under t he provisions of the proposed rule. To conduct the emissions ave raging, the owner or operator would include an Averaging Plan i n their part 70 permit application identifying each potline or g roup of potlines in the average, and the assigned TF emissi on limit for each potline or similar potline.

The option that was developed for emission averagi ng is a monthly average for TF and a quarterly average for POM for the group of sources that ensures emissions are less th an the level achieved by the limit for individual sources. The limit for averaging is lower than the limit for individual so urces and was calculated by estimating the decrease in standard d eviation (variability) when multiple potlines are included i n the average. The applicable emission limits for emissions avera ging for the possible combinations of sources at existing plants are given in Table 4. The emission limits decrease as the numbe r of sources included in the average increases because of the lo wer variability when more sources are included. Additi onal details on the derivation of emission limits for emissions averaging are given in Appendix B.

For plants choosing to use emission averaging, at least three runs must be made each month for TF for secon dary emissions from each potline to determine the average emission s from each potline. The sum of emissions from each potline (i ncluding both the primary system and secondary emissions) for the month is divided by the total aluminum production from all o f the potlines for the month to determine the monthly emissions in lb/ton for comparison to the limit. The approach is the same for POM from Soderberg potlines except that three runs are made each quarter (one run per month) instead of three runs each mont h.

Options were also developed for emissions averagin g for POM using the same basic procedure described for TF. T he proposed limits for POM for emissions averaging are also giv en in Table 4.41

Emissions averaging limits were also developed for bake furnaces for plants with multiple furnaces that mus t be sampled annually and are presented in Table 5. The limits for TF were based on the results for Noranda's bake furnace and the limits for POM were developed from the tests of the Kaiser -Mead bake furnace. The same procedures used for developing l imits for potlines were used for bake furnaces and are descri bed in Appendix B.42

TABLE 4. POTLINE TF AND POM LIMITS FOR EMISSIONS AVERAGING

Type Monthly TF limit (lb/ton) for given number of potli nes

2 lines 3 lines 4 lines 5 lines 6 lines 7 lines 8 lines

CWPB1 1.7 1.6 1.5 1.5 1.4 1.4 1.4

CWPB2 2.9 2.8 2.7 2.7 2.6 2.6 2.6

CWPB3 2.3 2.2 2.2 2.1 2.1 2.1 2.1

VSS1 2.0 1.9 1.8 1.7 1.7 1.7 1.7

VSS2 2.6 2.5 2.5 2.4 2.4 2.4 2.4

HSS 2.5 2.4 2.4 2.3 2.3 2.3 2.3

SWPB 1.4 1.3 1.3 1.2 1.2 1.2 1.2

Quarterly POM limit (lb/ton) for number of potline s

HSS 4.1 3.8 3.7 3.5 3.5 3.4 3.3

VSS1 2.1 2.0 1.9 1.9 1.8 1.8 1.8

VSS2 3.4 3.2 3.2 3.1 3.1 3.0 3.043

TABLE 5. BAKE FURNACE EMISSION LIMITS FOR EMISSIO NS AVERAGING

Number of furnaces Limit (lb/ton of anode)

TF POM

2 0.11 0.17

3 0.090 0.17

4 0.077 0.17

5 0.070 0.17

The owner or operator may submit an application to the regulatory authority to revise their averaging plan . In addition, owners or operators who do not choose to use emission averaging for initial compliance may submit a reque st to implement averaging after the initial compliance da te.

3.2.5 Reduced Sampling Frequency. The proposed rule also contains provisions for reduced sampling frequency for both TF and POM. The owner or operator may petition the re gulatory authority to establish an alternative testing requi rement that requires less frequent testing for secondary emissi ons, the primary control system, or the anode bake plant. I f the owner or operator shows that the emissions from these source s have low variability during normal operations, the regulator y authority may establish an alternative testing requirement. The alternative testing requirement must include a test ing schedule and the method to be used to measure emissions for the purpose of performance tests.

Guidance is provided to the owner or operator and the regulatory authority for evaluating alternative sam pling frequencies in the EPA report, Primary Aluminum: Statistical Analysis of Potline Fluoride Emissions and Alternat e Sampling Frequency

(EPA-450/3-86-012, October 1986). Plants that hav e received approval for an alternate sampling frequen cy under the NSPS may continue this alternate frequency under th e proposed NESHAP.44

3.3 Recordkeeping and Reporting Requirements

The proposed standards would incorporate nearly al l notification, recordkeeping, and reporting requirem ents in the General Provisions to Part 63. These include: (1) initial notifications, notification of performance test, no tification of compliance status, and (2) a report of performance test results, semiannual report of startup, shutdown, and malfunc tions (if applicable), and semiannual reports of excess emiss ions. The General Provisions also require the owner or operat or to develop a startup, shutdown, and malfunction plan. Table 6 shows the recordkeeping and reporting requirements in the Gen eral Provisions and the applicability of these requireme nts to the requirements in the proposed rule.

In addition to the records required by the Genera l Provisions to part 63, the proposed rule would requ ire new and existing aluminum plants to maintain records of dai ly production rates for aluminum and anodes. This information is needed to document the 30-day average production rate used in compliance equations. The proposed standard also would requir e the owner or operator choosing to use emission averaging as a me ans of compliance to develop and submit an Averaging Plan to the applicable regulatory authority, who would review a nd approve or disapprove the plan based on specified criteria wit hin a specified time frame.

3.4 Delegation of Authority

Following promulgation, EPA will delegate authorit y to States to implement and enforce the rule. As propo sed, the rule includes provisions allowing States to choose wheth er to include provisions for emission averaging in their program and in permits issued under their program.45

TABLE 6. APPLICABILITY OF GENERAL PROVISIONS (40 CFR Part 63, Subpart A) TO SUBPART LL

General Provisions Citation Requirement Applies to Subpart LL Comment

63.1(a)(1) Applicability Yes

63.1(a)(2) Yes

63.1(a)(3) Yes

63.1(a)(4) Yes

63.1(a)(5) No [Reserved]

63.1(a)(6)-(a)(8) Yes

63.1(a)(9) No [Reserved]

63.1(a)(10) Yes

63.1(a)(11) Yes

63.1(a)(12)-(a)(14) Yes

63.1(b)(1) Yes

63.1(b)(2) Yes

63.1(b)(3) Yes
63.1(c)(1) Applicability After Standard Established Yes

63.1(c)(2) No All are major

sources
63.1(c)(3) No [Reserved]

63.1(c)(4) Yes

63.1(c)(5) Yes

63.1(d) No [Reserved]
63.1(e) Applicability of Permit Program Yes

63.2 Definition of"Reconstruction" No Defined in Subpart LL

63.2 All Other Definitions Yes Additional definitions46

General Provisions Citation Requirement Applies to Subpart LL Comment

in § 63.841

63.3(a)-(c) Units and Abbreviations Yes

63.4(a)(1)-(a)(3) Prohibited Activities Yes

63.4(a)(4) No [Reserved]

63.4(a)(5) Yes

63.4(b)-(c) Yes
63.5(a)(1) Construction/ Reconstruction Yes

63.5(a)(2) Yes
63.5(b)(1) Existing, New, Reconstructed Yes

63.5(b)(2) No [Reserved]

63.5(b)(3) Yes

63.5(b)(4) Yes

63.5(b)(5) Yes

63.5(b)(6) Yes

63.5(c) No [Reserved]
63.5(d)(1) Approval of Construction/ Reconstruction Yes

63.5(d)(2) Yes

63.5(d)(3) Yes

63.5(d)(4) Yes

63.5(e) Yes

63.5(f)(1) Yes

63.5(f)(2) Yes
63.6(a) Compliance for Standards and Maintenance Yes47

General Provisions Citation Requirement Applies to Subpart LL Comment

63.6(b)(1) Yes

63.6(b)(2) Yes

63.6(b)(3) Yes

63.6(b)(4) Yes

63.6(b)(5) Yes

63.6(b)(6) No [Reserved]

63.6(b)(7) Yes
63.6(c)(1) Compliance Date for Existing Sources No Subpart LL specifies compliance date for existing

sources
63.6(c)(2) Yes

63.6(c)(3)-(c)(4) No [Reserved]

63.6(c)(5) Yes

63.6(d) No [Reserved]
63.6(e)(1)-(e)(2) Operation & Maintenance Yes

63.6(e)(3) Startup, Shutdown Malfunction Plan Yes

63.6(f)(1) Compliance with Emission Standards Yes

63.6(f)(2) Yes

63.6(f)(3) Yes
63.6(g)(1)-(g)(3) Alternative Standard Yes

63.6(h) Opacity/VE Standards No Subpart LL does not require COMS,48

General Provisions Citation Requirement Applies to Subpart LL Comment

VE or opacity standards

63.6(i)(1)-(i)(14) Extension of Compliance Yes

63.6(i)(15) No [Reserved]

63.6(i)(16) Yes
63.6(j) Exemption from Compliance Yes

63.7(a)(1)-(a)(3) Performance Testing Requirements Yes

63.7(b) Notification Yes
63.7(c) Quality Assurance/Test Plan Yes

63.7(d) Testing Facilities Yes

63.7(e)(1) Conduct of Tests Yes

63.7(e)(2) Yes

63.7(e)(3) Yes

63.7(e)(4) Yes

63.7(f) Alternative Test Method Yes

63.7(g) Data Analysis Yes

63.7(h) Waiver of Tests Yes

63.8(a)(1) Monitoring Requirements Yes

63.8(a)(2) Yes

63.8(a)(3) No [Reserved]

63.8(a)(4) Yes

63.8(b)(1) Conduct of Yes49

General Provisions Citation Requirement Applies to Subpart LL Comment

Monitoring

63.8(b)(2) Yes

63.8(b)(3) Yes
63.8(c)(1) CMS Operation/ Maintenance Yes

63.8(c)(2) Yes

63.8(c)(3) Yes
63.8(c)(4) - (c)(8) CMS Operation/ Maintenance No Subpart LL does not require COMS/CMS or
CMS performance specification 63.8(d) Quality Control No

63.8(e) Performance Evaluation for CMS No

63.8(f)(1)-(f)(5) Alternative Monitoring Method Yes

63.8(f)(6) Alternative to RATA Test Yes

63.8(g) Data Reduction Yes

63.9(a) Notification Requirements Yes

63.9(b)(1) Initial Notifications Yes

63.9(b)(2) Yes

63.9(b)(3) Yes

63.9(b)(4) Yes

63.9(b)(5) Yes
63.9(c) Request for Compliance Yes50

General Provisions Citation Requirement Applies to Subpart LL Comment

Extension

63.9(d) New Source Notification for Special Compliance Requirements Yes

63.9(e) Notification of Performance Test Yes

63.9(f) Notification of VE/Opacity
Test No

63.9(g) Additional CMS Notifications No Subpart LL does not include VE/opacity standard

63.9(h)(1)-(h)(3) Notification of Compliance Status Yes

63.9(h)(4) No [Reserved]

63.9(h)(5)-(h)(6) Yes
63.9(i) Adjustment of Deadlines Yes

63.9(j) Change in Previous Info. Yes

63.10(a) Recordkeeping/ Reporting Yes

63.10(b) General Requirements Yes

63.10(c)(1) Additional CMS Recordkeeping Yes

63.10(c)(2)-(c)(4) No [Reserved]

63.10(c)(5)-(c)(6) Yes

63.10(c)(7)-(c)(8) Yes51

General Provisions Citation Requirement Applies to Subpart LL Comment

63.10(c)(9) No [Reserved]

63.10(c)(10)-(11) Yes

63.10(c)(12)-(14) Yes

63.10(c)(15) Yes

63.10(d)(1) General Reporting Requirements Yes

63.10(d)(2) Performance Test Results Yes

63.10(d)(3) Opacity or VE Observations No Subpart LL does not require COM or limits for VE/opacity

63.10(d)(4) Yes
63.10(d)(5) Startup, Shutdown, Malfunction Reports Yes

63.10(e)(1) Additional CMS Reports Yes

63.10(e)(2) Reporting Performance Evaluations No Performance evaluation not required

63.10(e)(3) Excess Emissions andCMS Performance Reports Yes Exceedances of parameter limits are

excess emissions

63.10(f) Waiver for Recordkeeping/ Reporting Yes

63.11(a)-(b) Control Device Requirements No Flares not applicable

63.12(a)-(c) State Authority and Delegations Yes52

General Provisions Citation Requirement Applies to Subpart LL Comment

63.13(a)-(c) State/Regional Addresses Yes

63.14(a)-(b) Incorporation by Reference Yes

63.15(a)-(b) Availability of Information Yes

4.0 SUMMARY OF ENVIRONMENTAL, COST, ENERGY, AND ECO NOMIC IMPACTS

Currently, there are 23 primary aluminum plants, o wned by 11 companies, are located in 14 States. The EPA estim ates of the 23 plants, 19 would need to upgrade controls on at lea st one process to reduce emissions. All plants would be subject t o the recordkeeping and reporting requirements.

4.1 Air Quality Impacts

Nationwide emissions from primary aluminum product ion operations are estimated at 6,400 tpy of TF. After implementation of the proposed standards, these emi ssions would decrease by almost 50 percent, to 3,400 tpy. POM e missions would be reduced by about 45 percent, from 3,200 tpy to 1 ,800 tpy. TF emissions from the anode bake furnaces are estimate d at 700 tpy; POM emissions are estimated at 555 tpy. After cont rol of all bake furnaces, TF emissions would be reduced by 97 percent and an 84-percent reduction would be achieved for POM emis sions. POM emissions from paste production plants, estimated a t 147 tpy at baseline, would be reduced by about 130 tpy, to abo ut 16 tpy -- an 89-percent reduction from current levels. Emiss ions of other HAP included in the TF and POM emissions would also be reduced, as would nonHAP pollutants such as PM. For example , PM emissions would be reduced by 16,000 tpy.

4.2 Solid Waste Impacts

Solid waste is generated by wet air emission contr ol devices, such as wet scrubbers and wet ESPs, and th e accompanying wastewater treatment. Dry alumina scrubbing techni ques do not generate any solid wastes because all captured soli ds are returned to the process. Wet scrubbers and wet ESP s generate from 6,000 to 15,000 tpy of solid waste, depending on the size of the plant. When dry scrubbers are used and all the captured solids are returned to the process, solid waste gen eration could be reduced by 6,000 to 15,000 tpy for a typical pla nt. None of the other control options has a significant impact on the generation of solid waste.53

4.3 Cost Impacts

The estimated nationwide capital and annual costs of the proposed standards for all sources is $160 million and $40 million per year, respectively. The major componen ts of the total costs are the control costs for potlines, whi ch are estimated as $104 million in capital with a total a nnual cost of $23 million per year. The major cost impacts expec ted arise from the installation of dry alumina scrubbers for the p rimary control system at one plant and work practices, operating p rocedures, maintenance and repair, and equipment modifications at most plants. A few plants may incur capital costs to up grade wet scrubbers used for primary control, to replace or u pgrade hoods or doors, and to install automated equipment for im proved emission control.

The cost estimates for paste production assume tha t the 18 plants without dry coke scrubbers for the control o f POM emissions will install one. However, some plants m ay be able to meet the proposed performance standard with dry alu mina scrubbers or other control devices, or they may be able to ut ilize many of the components of their existing system. The total capital cost is estimated at $26 million and the estimated total annualized cost is $6.1 million per year.

A dry alumina scrubber system similar to that used for the aluminum production process removes fluoride, POM, and fine particulate from the anode baking furnace exhaust g ases. The system consists of a dry alumina fluidized bed scru bber, a baghouse, and the associated duct work and fans to collect and move the gases from the furnace. The scrubber adso rbs fluorides and POM, which are removed with other particulate m atter in the baghouse. The spent alumina is then recycled to th e potlines and the cleaned gases are released through a stack. Th e total capital cost, estimated at $20.6 million, assumes t hat all plants without a dry alumina scrubber (5 of 17) must insta ll one. The total annualized cost is estimated at $6.2 million per year.

The direct operating costs for paste production an d anode bake furnaces were estimated by averaging the opera ting costs for the dry coke or dry alumina scrubbers that were rep orted by the industry in survey responses. The operating costs reported by the industry were converted into 1994 dollars and r esulted in an annual direct operating cost of $1.16 per ton of pa ste and $4.81 per ton of anode.

The EPA examined several options for enhanced moni toring, ranging from requiring the use of the HF continuous emission monitor to requiring monitoring of process paramete rs with annual54

emission tests. The EPA, in conjunction with State s and industry representatives, selected monthly monitoring of sec ondary TF emissions, quarterly sampling on secondary POM emis sions, and annual sampling of controlled primary emissions, co upled with monitoring of process parameters, as the most reaso nable approach consistent with current State practices.

Currently, about one-third of existing potlines ar e sampled for TF on a regular basis. Because of the flexibil ity provided in the rule, many plants are expected to take advan tage of the use of HF CEMs and Alcan cassettes for similar potl ines, both of which are much less expensive than manual sampling using Methods 13 and 14. The nationwide capital cost est imate of $7 million for monitoring equipment includes new Me thod 14 manifolds, HF CEMs, and Alcan cassettes. The total annualized cost of monitoring is estimated as about $4 million per year once all plants comply with the rule. These costs may b e reduced significantly as plants qualify for reduced samplin g frequency (e.g., quarterly instead of monthly). The CEM will have value as a process monitoring tool, in addition to its use f or monitoring to determine compliance.

4.4 Economic Impacts

The goal of the economic impact analysis was to es timate the market response to the proposed rule and determine whether there would be adverse impacts associated with it. To as sess the industry-wide impacts of control costs, the market price increase resulting from the proposed rule was estimated for the primary aluminum industry. The market price increase estim ate was derived by aggregating the control costs for all ex isting primary aluminum facilities and dividing the sum by industr y revenue. This increase may be thought of as an average price increase required to recover control costs within the indust ry. After estimating the market price increase, the expected reduction in industry output was then calculated, using addition al information regarding price elasticity estimates. The impact o n industrywide employment was also calculated, assuming that employment is proportional to output.

The market price increase calculation indicated th at implementation of the controls will result in a pri mary aluminum market price increase of less than one percent. As a result of the low market price increase and relatively inelas tic demand, the corresponding changes in output, employment, an d total revenue were also low (all less than one percent). Therefore, the economic impact analysis estimates that the pro posed rule will not result in significant economic impacts for the primary aluminum industry.55

4.5 Non-air Quality Health and Environmental Impac ts

4.5.1 Deposition. Fluoride and POM deposition on waters, such as the Great Lakes, is of mounting concern. S everal references to this problem are included in the Repo rt to Congress on the Great Waters Program. Implementation of the program recommendations would reduce emissions at many of t he plants by 50 percent, including plants near the Great Lakes a nd those in the Midwest, which also are contributors due to the long-distance air transport of pollutants.

4.5.2 Water. A wet primary control system generates about 0.1 pound of fluorides per ton of aluminum and 0.2 pounds of total suspended solids per ton of aluminum. Four p lants use scrubbers in their primary control system, and one plant plans to replace the existing wet systems with dry alumina s crubbers. As discussed above, the dry scrubbers do not control S O 2 . Assuming that SO 2 requirements are not changed and these plants cont inue to use wet SO 2 scrubbers following the dry alumina scrubber, no significant decrease is expected in the quantity of wastewater generated by implementation of the proposed standar d. Wastewater quality may be improved because most of the fluorid es and particulates will be recovered by the dry scrubber and returned to the process.

4.5.3 Solid Waste. Solid waste generated from air emissions control in this industry is a direct resu lt of wet air emission control devices and the accompanying waste water treatment. Wet scrubbers and wet ESPs generate 120 to 154 pounds of solid waste per ton of aluminum, which results i n 6,000 to 15,000 tpy for model plants ranging in size from 10 0,000 to 200,000 tpy. Because all the captured solids are r eturned to the process with dry scrubbers, the MACT standard has t he potential to reduce solid waste generation by the same amount

. 4.6 Energy Impacts

The electrical consumption to produce aluminum is estimated at 6 to 7 kwh per ton of aluminum (12,000 to 14,000 kwh/ton). The increase in energy consumption is estimated as an average of 145 kwh/ton for four plants. No significant effect on energy consumption for anode baking and paste production i s expected to occur when control devices are replaced, although c onsumption will increase for those plants that have no control s.APPENDIX ATECHNICAL NOTE: RATIONALE FOR SUBCATEGORIES OF SOU RCES FOR THE PRIMARY ALUMINUM INDUSTRY

1.0Purpose

The purpose of this note is to identify the subcat egories of sources to be used in determinations of maximum ach ievable control technology (MACT) for the primary aluminum industry and to provide the rationale for subcategorization.

2.0 Summary

The analysis of aluminum production processes and their operation resulted in the seven subcategories for t he aluminum smelting operation given in Table 1.

TABLE 1. ALUMINUM SMELTING SUBCATEGORIES

Number of
Subcategory Potlines Plants

Large center-worked prebake - CWPB1 24 8
Small center-worked prebake - CWPB2 36 6
Center-worked prebake (producing high purity aluminum) - CWPB3 4 1

Side-worked prebake- SWPB 5 2
Vertical stud Soderberg (in moderate climates)- VSS1 5 2

Vertical stud Soderberg (in cold climates)- VSS2 5 1

Horizontal stud Soderberg- HSS 12 3

Totals 91 23

The criteria used in developing these subcategorie s are based on air pollution control engineering differen ces and include consideration of the variations in process operation, emission characteristics, and control device applic ability. Details are provided in the following sections.

3.0 Approach

Section 112(d) of the Clean Air Act (as amended on November 15, 1990) requires the Administrator to es tablish emission standards for each category or subcategory of major2

sources and area sources of hazardous air pollutant s listed for regulation. The criteria used to develop subcatego ries are based on air pollution control engineering differences. The criteria include consideration of process operations (includ ing differences between batch and continuous operations ), emission characteristics, control device applicability and c osts, safety, and opportunities for pollution prevention.

The approach used in this analysis is based on characterizing differences among aluminum smelting processes and control device applicability and evaluating these d ifferences with respect to the criteria given above for develo ping subcategories.

4.0 Details

There are significant differences among several al uminum smelting processes that affect control device appli cability, especially the hooding for the primary collection s ystem and its capture efficiency, and emission characteristics. The rationale for the specific subcategories is provided step by step in the following sections, and the approach is illustrated schematically in Figure 1. The criteria and applicability are su mmarized in Table 2.

4.1 Prebake and Soderberg Processes

Prebake and Soderberg are two distinctly different processes for smelting that present different challenges for capturing emissions from the aluminum reduction cells. These two processes also have different emission characteristics, espec ially with respect to polycyclic organic matter (POM). A majo r difference between the two processes is that the anodes used i n the prebake process have been formed and baked in a separate pr ocess operation (i.e., the anode bake furnace), whereas t he Soderberg process bakes the anode in the reduction cell as pa rt of the smelting operation. i This process difference directly affects emissions and results in larger quantities of organ ic compounds such as POM being emitted from the Soderberg proces s during smelting. In the prebake process, significant quan tities of these organics are removed during the separate anod e baking step, which results in lower POM emissions from the reduc tion cell.

Other differences between these two processes also affect emissions and their control. In the prebake proces s, spent anodes are periodically removed and replaced, and t his operation directly affects secondary (fugitive) emissions. C onversely, "green" paste (a mixture of unbaked coke and pitch) is added in a semi-continuous manner to the Soderberg reduction c ell to allow3

it to be baked in place and to replace the anode as it is consumed. In addition, there are differences in th e type and efficiency of hooding used for the two processes. In general,4TABLE 2. SUMMARY OF CRITERIA USED TO DEVELOP SUBCATEGORIESTypes of processes comparedCriteria-differences in the following:aProcessoperationbEmissionsquantityCapture and controlequipmentcPrebake vs. Soderberg yes yes yesCWPB vs. SWPB yes yes yesCWPB1 vs. CWPB2 yes yes yesCWPB1 vs. CWPB3 no yes yesVSS vs. HSSyes yes yesVSS1 vs. VSS2 no yes yesaThese columns indicate if there are differences between the processes with respectto the given criterion. Other criteria (cost, safety, pollution preventionopportunities) were not judged to be significant for the subcategories.bDifferences in process operation that affect emissions or their control.cThe differences are primarily in the type of capture system that can beused and its resulting capture efficiency.CWPB = center-worked prebake HSS = horizontal studSoderbergSWPB = side-worked prebake VSS = vertical stud Soderberg567

the hoods used for the Soderberg process have lower capture efficiencies because the gases evolving from the So derberg cell are more difficult to capture. ii

4.2 Center-Worked and Side-Worked Prebake

Within the prebake process, center-worked (CWPB) a nd side-worked (SWPB) units have significant differenc es in design of the equipment, its operation, and applica ble emission controls, especially in the capture of pri mary emissions. The process and operational differences include the placement of the anodes, the type of side shiel ds used, the method of alumina addition, and how the reducti on cells are worked. iii

In the SWPB process, alumina is added along the si des of the reduction cell and the anodes are set close together near the center line. In the CWPB process, alumina is added down the center of the pot and the anodes are close r to the side. Consequently, the covers and hoods for the p rimary collection system are different for these two types of units because of the design, placement of anodes, and wor king the bath from the center versus from the side. In addi tion, the newer CWPB units can be equipped with computer-cont rolled crust breakers and point feeders, which often allow them to be worked without removing the side shields.

The design and operational differences between SWP B and CWPB result in different design considerations for the primary collection system. In general, emissions f rom the CWPB reduction cells can be captured with a higher efficiency than those from SWPB cells. iv

4.3 Subcategories for Center-Worked Prebake

The investigation of the CWPB process indicates th at there are two different designs that directly affec t the ability of the operator to control emissions. One group is composed of CWPB reduction cells that are larger, g enerally newer, and operate at higher amperages than the old er and smaller CWPB units. The major factor affecting the difference in emissions and controls for the two ty pes of units is the number of anode changes required. Mor e frequent anode changes result in greater quantities of secondary (fugitive) emissions that are difficult t o capture and control.

There are other differences between the large and small CWPB units that affect emissions and their capture. Access8

is required more often to the smaller units because they are generally more unstable and are less likely to have computer controls. More frequent access means the shields o f the primary collection system are opened more frequentl y and perhaps for longer periods, which results in poorer emission capture and higher emissions. Another factor is th e smaller units generally have more anodes per reduction cell , which affects the design and capture efficiency of the ho oding. v These combinations of factors indicate that the lar ger CWPB units have lower emissions per ton of aluminum prod uced and that less emissions escape capture by the primary c ollection system.

A separate subcategory was developed for four cent erworked prebake potlines with wet primary control sy stems (CWPB3). These potlines produce a high purity alum inum for a specialized market, and they can do so only becau se metal impurities are removed with the sludge from the wet scrubbers. If these potlines were required to inst all dry alumina scrubbers, the contaminants would be return ed to the reduction cell and contaminate the aluminum. The c ompany claims that if they must meet MACT for the prebake subcategory of modern potlines with dry alumina scr ubbers, they could lose their market for high purity alumin um. The EPA is requesting comments on the issue of a separa te subcategory for plants that produce high purity alu minum.

4.4 Horizontal and Vertical Stud Soderberg

There are two distinct designs used in the Soderbe rg process: horizontal stud (HSS) and vertical stud ( VSS). As the names imply, in one case the steel studs that c arry current project vertically through the unbaked past e and into the baked portion of the anode, and in the oth er case the studs project horizontally. The differences in design and operation result in different types of hooding and evacuation rates, both of which affect emissions an d controls. In the VSS cell, the stationary anode ca sing and vertical projection of the studs through the anode allow the installation of a gas collection skirt between the anode casing and bath. The collected gases are ducted to burners where carbon monoxide, tars, and other hydr ocarbons are burned prior to the primary control device. vi

The design of the HSS cell prevents the installati on of integral gas collection because the anode casing is formed by removable channels that support the studs, and t hese channels must be periodically changed as the anode moves downward. Consequently, the hooding for the HSS ce ll is9

restricted to a design that results in air infiltra tion and dilution. The gases from the HSS cell are too dilu te to support combustion in burners. vii A typical VSS cell has an evacuation rate on the order of 500 ft 3 /min compared to a range of 3,500 to 5,000 ft 3 /min for an HSS cell. viii

4.5Vertical Stud Soderberg with and without wet roo f scrubbers

Two VSS plants with five potlines use wet roof scrubbers to control secondary emissions, and the t hird plant also with five potlines uses work practices f or secondary emission control. Consequently, the EPA investigated the use of wet roof scrubbers as the M ACT floor technology for all VSS plants. However, data obtai ned from Intalco Aluminum (in Ferndale, WA) on their wet roo f scrubber operation indicated that their scrubbers w ere shut down in periods of cold weather to avoid damage to the scrubbers and water treatment plant.

The data from Intalco indicated that their scrubbe rs were shut down due to cold weather an average of 36 days per year (a range of 19 to 48 days/year from 1986 to 19 93). This represents a down time of 10 percent, i.e., th ey operate about 90 percent of the year. The procedur e used at Intalco is to shut the scrubbers down when the temp erature reaches 27 ° F and the temperature is predicted to drop further.

The VSS plant without roof scrubbers in located in northern Montana where the weather is much colder t han that in Ferndale. Data obtained from the National Weath er Service for Kalispell, MT, which is near the locati on of Columbia Falls' VSS plant, indicated that the norma l daily average temperature was below 27 ° F about 21 percent of the time and the normal daily low temperature was below 27 ° F about 40 percent of the year. Consequently, the us e of wet roof scrubbers based on Intalco's experience sugges ts that scrubbers installed in northern Montana could be sh ut down on the order of 20 to 40 percent of the time.

In assessing the achievability of a technology-bas ed standard, EPA must show that a standard is capable of being met under most adverse conditions that can reasonab ly be expected to occur. The EPA determined that wet roo f scrubber technology has not been adequately demonst rated for very cold climates and is not applicable as the MAC T floor technology for the VSS plant in Montana. Consequen tly, a separate subcategory (VSS2) was created for the fiv e VSS10

potlines in Montana, and the MACT floor for this su bcategory would be determined by the average emission limitat ion achieved by these five potlines.12

5.0 References

i.Primary Aluminum: Guidelines for Control of Fluo ride Emissions from Existing Primary Aluminum Plants. E PA450/2-78-049b. December 1979.

ii.Reference 1.

iii.Reference 1.

iv.Reference 1.

v.Memorandum from Ours, K. D., Research Triangle In stitute, to W. S. Fruh, EPA/ISB. June 10, 1994. Summary of Meeti ng with Aluminum Industry Representatives. 10 pp.

vi.Reference 1.

vii.Reference 1.

viii.Compiled from responses by each plant in the i ndustry to Information Collection Requests issued under Sectio n 114 of the Clean Air Act Amendments.APPENDIX B: MACT FLOOR DETERMINATIONS

I. Purpose:

The purpose of this technical note is to explain h ow emission limits for the MACT floor sources were dev eloped.

II. Approach:

The averages of the top five potlines were used as the basis for determining the MACT floor because there were f ewer than 30 sources in each category or subcategory. For potli nes, the median potline (i.e., the third best performing amo ng the five best performing) was chosen to represent the averag e emission limitation achieved by the top five. Historical da ta for total fluoride for the MACT floor potlines were used and were supplemented by additional data collected during th e MACT test program, especially for polycyclic organic matter ( POM). The data are given in EPA's rulemaking docket for prima ry aluminum and are also listed in Appendix D of this document.

The overall approach included evaluating historica l data when available, identifying any values not represen tative of normal operation, and determining the level of cont rol that had been achieved by the MACT floor potline. When hist orical data were not available (e.g., for POM), a statistical a pproach based on estimation of upper confidence levels was used t o determine the level of control that had been achieved.

III. Results:

A. Total Fluoride from Potlines

The historical data for total fluoride (TF) were r eviewed and discussed with the various companies to identif y and delete "outliers", which are values that are not represent ative of normal operation. The historical data were then an alyzed in the way the rule will be implemented -- as monthly aver ages. The emission limits for the MACT floor for TF were chos en from the review of the data from the highest monthly average s in the data set. This approach ensures that the limits for TF associated with the MACT floor have been achieved by the MACT floor potlines on which they are based. [See Appendix D for the l isting of monthly averages for the MACT floor potlines.]

Adequate historical data for TF were available to characterize the MACT floor for the following subca tegories of potlines as identified in Appendix A: CWPB1, CWPB2 , SWPB, HSS, VSS1, and VSS2. The results (MACT floor limits) ar e summarized in Table 1.2

There were very few historical data available for the CWPB3 subcategory, and the plant that comprises the subca tegory indicated that major improvements had been made or were underway3TABLE 1. SUMMARY OF MACT FLOOR DATA FOR POTLINESlb TF/ton)TABLE 1. SUMMARY OF MACT FLOOR DATA FOR POTLINES (lb TF/ton)lb TF/ton)Plant N MeanaStandarddeviationMACT floorlimitCommentsNoranda Line 3(CWPB1)46 1.13 0.32 1.9 45 monthly averages, 1/89-12/92, plus MACT programresultsKaiser-Mead Line 1(CWPB2)13 2.18 0.49 3.0 12 monthly averages (generally 4 runs per month)8/93-7/94, plus MACT program resultsIntalco Line C (SWPB) 450.970.261.645 monthly averages, 1/90-12/93;Monthly roof and 12-mo average for primaryKaiser-Tacoma Line 2(HSS)23 2.07 0.36 2.7 22 monthly averages, 3/93-12/94, plus MACT programresultsColumbia-GoldendaleLine 1 (VSS1)31 1.31 0.42 2.2 30 monthly averages, 1/92-6/94, plus MACT programresultsColumbia Falls (VSS2) 7 2.22 0.31b2.7 7 averages of 3 runs, 10/94-12/94Mt. Holly A & B 26 0.81 0.14 1.2 26 monthly averages 1/89-12/92aThese mean values also include emissions from theprimary control system.bThe standard deviation was obtained from historical data submitted by the company.4

to reduce both secondary emissions and emissions fr om the wet scrubbers used for the primary control system. The available data and information from the plant indicated that a study of their system showed they had achieved a level of pe rformance that would ensure that they are meeting a monthly limit of 2.5 lb/ton. 20 Consequently, the EPA determined that a TF limit of 2.5 lb/ton represented the MACT floor for CWPB3.

B. POM from Soderberg Potlines

The results of the analysis of POM emissions from HSS potlines are summarized in Table 2. For the HSS su bcategory, the MACT floor was determined from the 95th percentiles for the averages of 3 runs for both primary and secondary P OM emissions. The result was a MACT floor level of 4.7 lb POM/ton from the sum of 2.7 (secondary emissions) and 2.0 lb/ton (primar y system emissions).

The POM limits for VSS1 are based on the limited t est data available from one potline at Columbia-Goldendale a nd one potline at Northwest Aluminum. The results from these two potlines were combined to provide enough data to assess performan ce and to represent the MACT floor. These two potlines achie ved a level of 2.4 lb/ton. There were no validated POM data avail able for the VSS2 subcategory; however, POM data for the VSS1 su bcategory before the wet roof scrubbers represent the same pr ocess configuration as that for VSS2. Consequently, the VSS1 POM data were used to derive limits for VSS2. The POM emiss ions at the inlet to the wet roof scrubbers did not exceed 3.7 lb/ton.

C. POM Limit for New Potlines

A POM limit was derived for new potlines based on the data from sampling at Noranda's Line 3. The average POM from roof sampling was 0.106 lb/ton, and the values from the primary system were 0.426, 0.115, and 0.088. The roof emissions w ere added to the primary system results to obtain three data poi nts with an average of 0.316 and a standard deviation of 0.188. The 95th percentile was chosen as the MACT floor for new pot lines:

95th percentile = 0.316 + 1.645 * 0.188 = 0.63 lb/ton

D. POM and TF Emissions from Anode Bake Furnaces

20 Memorandum from W. Hill, Southwire Company, to M. McKeever, EPA/OAQPS/ESD, dated May 23, 1995.5

Data for anode bake furnaces are given in Table 3 for both TF and POM. The results for anode bake furnaces we re converted6TABLE 2. SUMMARY OF MACT FLOOR POM DATA FOR HSS PTLINES (lb/ton)TABLE 2. SUMMARY OF MACT FLOOR POM DATA FOR HSS POTLINES (lb/ton)TLINES (lb/ton)Plant N Mean StandarddeviationMACT flooraCommentsKaiser-Tacoma Line 2(HSS): secondary (roof)emissions5 1.82 0.52 2.7 Based on averages of 3 runs from MACTprogram resultsKaiser-Tacoma Line 2(HSS): primary systememissions3 0.781 0.756 2.0 Based on averages of 3 runs fromMACTprogram resultsaBased on the 95th percentile from (mean + 1.645 *standard deviation).7

TABLE 3. SUMMARY OF M TABLE 3. SUMMARY OF M TABLE 3. SUMMARY OF MACT FLOOR DATA FOR BAKE FURNA CES (lb/ton of anode) ACT FLOOR DATA FOR BAKE FURNACES (lb/ton of anode) ACT FLOOR DATA FOR BAKE FURNACES (lb/ton of anode)

Plant N Mean Standard deviation Comments

Noranda -- TF 33 0.070 0.118 Averages of 3 runs (96 individual runs 9/83-7/93 plus 4 runs from MACT test program)

Alumax- Mt. Holly -- TF 9 0.0071 0.0065 9 individual runs 1992-1994

3 0.0071 0.0056 Averages of 3 runs

Kaiser-Mead -- TF 3 0.013 0.007 3 individual runs, MACT test program

Noranda -- POM 3 0.025 0.012 3 individual runs, MAC T test program

Kaiser-Mead -- POM 3 0.16 0.011 3 individual runs, MACT test program8

from lb/ton of aluminum to lb/ton of anode by multi plying by 2.

There are eight bake furnaces currently subject to the NSPS level of 0.20 lb/ton anode, and these bake furnaces include the top 5 best performing in the industry. A review of the available data indicated that the NSPS level represented the average limit achieved by the top five, and it also represented a level of control demonstrated by the data as achievable. Co nsequently, the EPA determined that 0.20 lb/ton anode represent ed the MACT floor for TF emissions from bake furnaces.

The MACT floor for POM from bake furnaces was base d on data collected at Kaiser-Mead during the MACT floor test program, which indicated a level of 0.18 lb POM/ton had been achieved. The TF limit for new bake furnaces was based on dat a from Alumax that showed a level of 0.02 lb TF/ton had been achieved (at the 99th percentile). The best-performing bake furnace for which POM data were available was Noranda's furnace that show ed a level of 0.05 lb POM/ton had been achieved (at the 99th percentile).

IV. Emissions Averaging

A. Total fluoride from potlines

An approach is presented here to develop a mechani sm to allow emissions averaging across multiple potlines. The approach attempts to provide a rough estimate of the standar d deviation when averaging across multiple potlines for compari son to a monthly average limit. When averaging is used, the variability (standard deviation) decreases. Consequently, the approach attempts to derive limits that will ensure that emi ssions do not increase above the levels expected if each potline had to comply with the monthly limit for an individual line.

The approach is based on reducing the standard dev iation for the MACT floor potlines by the square root of "N" ( i.e., dividing by the square root of N), where N is the number of potlines that will be used for emission averaging at a specific p lant. The mean and standard deviation used for each subcatego ry are given in Table 4. These values were used in the equation given below to calculate limits for emission averaging for each subcategory for different numbers of potlines that might be use d in the averaging approach. The results are summarized in Table 5.

Averaging limit = mean + z*(sd/N 0.5 )

where:9

"z" is the constant representing the 95th (1.645) o r 99th (2.326) percentile, "sd" is the standard deviation from Table 4, and "N" is the number of potlines used in averaging.

For example, the average for CWPB2 (Kaiser-Mead) wa s 2.18 lb/ton and the standard deviation was 0.49. For the case of averaging across 3 potlines, the limit is calculated as:

Limit (3 lines) = 2.18 + 2.326*(0.49)/3 0.5 = 2.8 lb/ton.

For the CWPB3 category for which there were no use ful historical data, the single potline limit of 2.5 lb /ton was assumed to represent the 99th percentile and the st andard deviation was assumed to be similar to that for CWP B1. The mean that would be needed to achieve a limit of 2.5 lb/t on was then calculated from:

Mean = 2.5 - 2.326*0.32 = 1.8 lb/ton.10

TABLE 4. SUMMARY OF VALUES USED FOR CALCULATING E ISSION

TABLE 4. SUMMARY OF VALUES USED FOR CALCULATING EM

AVERAGING LIMITS FOR TF AVERAGING LIMITS FOR TF

Subcategory Total fluoride (lb/ton) z

Mean Standard deviation

CWPB1 1.13 0.32 2.326

CWPB2 2.18 0.49 2.326

CWPB3 1.80 0.32 2.326

SWPB 0.97 0.26 2.326

HSS 2.07 0.36 1.645*

VSS1 1.31 0.42 2.326

VSS2 2.22 0.31 1.645*

* The constant for the 95th percentile is used for these subcategories to be consistent with the deriv ation of the single line limit and to ensure that emissions do not increase from averaging emissions.

TABLE 5. POTLINE TF AND POM LIMITS FOR EMISSIONS VERAGING

TABLE 5. POTLINE TF AND POM LIMITS FOR EMISSIONS A VERAGING

Type Monthly TF limit (lb/ton) for given number of potlines

2 lines 3 lines 4 lines 5 lines 6 lines 7 lines 8 lines

CWPB1 1.7 1.6 1.5 1.5 1.4 1.4 1.4

CWPB2 2.9 2.8 2.7 2.7 2.6 2.6 2.6

CWPB3 2.3 2.2 2.2 2.1 2.1 2.1 2.1

VSS1 2.0 1.9 1.8 1.7 1.7 1.7 1.7

VSS2 2.6 2.5 2.5 2.4 2.4 2.4 2.4

HSS 2.5 2.4 2.4 2.3 2.3 2.3 2.3

SWPB 1.4 1.3 1.3 1.2 1.2 1.2 1.2

Monthly POM limit (lb/ton) for number of potlines

HSS 4.1 3.8 3.7 3.5 3.5 3.4 3.3

VSS1 2.1 2.0 1.9 1.9 1.8 1.8 1.8

VSS2 3.4 3.2 3.2 3.1 3.1 3.0 3.01112

B. POM from potlines

Emission averaging limits for POM are derived for KaiserTacoma and the HSS subcategory in the same manner d escribed earlier. The mean and standard deviations from Tab le 2 are used in the example calculations given below:

Monthly limit when averaging across 3 potlines:

Primary control system Limit = 0.781 + 1.645 (0.756)/(3) 0.5 = 1.5 lb/t

Secondary emissions Limit = 1.82 + 1.645 (0.52)/(3) 0.5 = 2.3 lb/t

For the VSS1 subcategory, the approach is based on the test results for POM from the wet roof scrubbers with an average of 1.42 lb/ton and a standard deviation of 0.92. The value of "z" was calculated from the mean, standard devation, an d the single line limit of 2.4 lb/ton:

z = (2.4 - 1.42)/0.92 = 1.065.

This value of z was then used to calculate emission averaging limits as in the example when averaging across 3 po tlines:

Limit = 1.42 + 1.065 (0.92)/(3) 0.5 = 2.0 lb/t

For the VSS2 subcategory, the approach is based on the test results for POM at the inlet to the wet roof scrubb ers with an average of 2.63 lb/ton and a standard deviation of 1.04. The value of "z" was calculated from the mean, standard devation, and the single line limit of 3.7 lb/ton:

z = (3.7 - 2.63)/1.04 = 1.029.

This value of z was then used to calculate emission averaging limits as in the example when averaging across 3 po tlines:

Limit = 2.63 + 1.029 (1.04)/(3) 0.5 = 3.2 lb/t

C. Total fluoride from bake furnaces

Emissions averaging limits for fluoride from bake furnaces were derived from the data for Noranda's bake furna ce and are based on a log normal distribution. The log averag e was -3.467 and the standard deviation (log form) was 1.154. A n example calculation is given below for averaging across 3 b ake furnaces:13

Limit = exp [-3.467 + 1.645 (1.154)/(3) 0.5 ]=exp[-2.37] = 0.09 lb/t

Repeating this process for different numbers of bak e furnaces gives the limits listed in Table 6.

D. POM from bake furnaces

POM limits for bake furnaces were derived from the data from the tests at Kaiser-Mead. The very small standard deviation resulted in emissions averaging limits with the sam e value as that for a single bake furnace (0.17 lb/ton). Thes e results are also summarized in Table 6.

TABLE 6. EMISSIONS AVERAGING LIMITS FOR BAKE FURN ACES

Number of furnaces Averaging limits (lb/t of anode)

TF POM

2 0.12 0.17

3 0.09 0.17

4 0.08 0.17

5 0.07 0.17APPENDIX C: EVALUATION OF WET ROOF SCRUBBERS AS A CONTROL OPTION FOR SECONDARY EMISSIONS--BEYOND THE FLOOR

I. Purpose:

The purpose of this note is to estimate the impact s of installing wet roof scrubbers for the control of se condary emissions from aluminum smelting. Wet roof scrubbe rs are being considered as an option for a level of control that is more stringent than the MACT floor (i.e., "beyond the MA CT floor").

II. Approach:

Estimates are provided for three cases: 1) a plan t that already has wet roof scrubbers installed, 2) retrof itting the scrubbers at a vertical stud Soderberg (VSS) plant that has good control of secondary emissions through improved ope ration and maintenance, and 3) installing the scrubbers on a n ew centerworked prebake (CWPB) plant that has good control o f secondary emissions through improved operation and maintenanc e, new hooding, and automated controls. Estimates of impa cts are presented for emission reductions and costs, and th e effects on solid waste generation and wastewater are discussed

.

III. Estimates of Emission Reduction

Northwest Aluminum currently has wet roof scrubber s on their VSS potrooms and was chosen to represent the first case (evaluation of a plant that already has wet roof sc rubbers). Emission testing was conducted at this plant for EP A in August 1993. 1 Table 1 is a summary of the test results for controlled and uncontrolled emission rates and cont rol efficiency for the wet roof scrubbers.

The control efficiencies for the different polluta nts from the tests at Northwest Aluminum are used in this an alysis to estimate the potential for emission reduction if we t roof scrubbers were retrofitted at an existing facility or included in the construction of a new facility. For these two cases, the actual percent emission reduction may be less than that from Northwest Aluminum because these other plants would have lower concentrations of pollutants entering the scrubbers

. Columbia Falls Aluminum Company (CFAC) is a VSS pl ant that controls secondary emissions using improved operati on and maintenance without wet roof scrubbers. This plant will be used to represent the second case of retrofitting wet ro of scrubbers at an existing plant. CFAC reported TF emission ra tes of 2.1 lb/ton and gaseous fluoride rates of 1.0 lb/ton from testing the potrooms using Methods 13 and 14. 2

TABLE 1. TEST RESULTS FOR THE WET ROOF SCRUBBERS A T NORTHWEST ALUMINUM2

Pollutant Inlet (lb/ton) Outlet

(lb/ton) Percent

control Reduction

(lb/ton)

Particulate matter 38.7 17.5 55 21.2
Polycyclic organic matter 3.7 1.8 51 1.9

Gaseous fluoride 3.0 0.39 87 2.6

Total fluoride 10.4 2.0 80 8.4

POM emissions from CFAC are estimated from the rat io of POM:GF entering the scrubbers from the Northwest Al uminum test (1.2). Particulate matter emissions for CFAC are b ased on the ratio of PM:TF measured at Northwest Aluminum (3.7)

. Table 2 presents the TF and GF emission rates repo rted by CFAC and the PM and POM emission rates estimated fr om the ratios. The reduction in emissions that would be achieved b y retrofitting wet roof scrubbers is estimated from the control ef ficiencies measured at Northwest Aluminum. [Note: For this a nalysis, estimates of gaseous fluoride are based on the back -half analysis of fluoride that passes through the front-half filt er.]

TABLE 2. ESTIMATED EMISSION REDUCTIONS FROM RETROF IT OF WET ROOF

SCRUBBERS AT COLUMBIA FALLS ALUMINUM

Pollutant Inlet

(lb/ton) Outlet

(lb/ton) Percent

control Reduction

(lb/ton)

PM 7.8 3.5 55 4.3

POM 1.2 0.6 51 0.6

GF 1.0 0.13 87 0.87

TF 2.1 0.4 80 1.7

Alumax of South Carolina is a relatively new and w ell controlled CWPB plant without wet roof scrubbers. This plant was chosen for the evaluation of wet roof scrubbers on new plants. Alumax reported TF and GF data from their potrooms as shown in Table 3. 3 The POM emissions were estimated as less than 0.3 lb/ton from the test results at Noranda 4 , which is also an NSPS CWPB plant. PM emissions were estimated from the r atio of PM:TF (3.3) measured at another CWPB plant (Kaiser, Mead)

. 53

Table 3 presents the reported TF and GF emission r ates for Alumax and the estimated PM and POM emission rates from the ratios from other tests. The table also gives the estimated the reduction in emissions that might be achieved from wet roof scrubbers (assuming the same control efficiencies a s those reported in the Northwest Aluminum test).

TABLE 3. ESTIMATED EMISSION REDUCTIONS FROM RETROF IT OF WET ROOF SCRUBBERS AT ALUMAX

Pollutant Inlet

(lb/ton) Outlet

(lb/ton) Percent

control Reduction

(lb/ton)

PM 2.4 1.1 55 1.3

POM <0.3 <0.15 51 <0.15

GF 0.37 0.05 87 0.32

TF 0.73 0.15 80 0.58

IV. Cost Estimate:

In 1975, Columbia Falls Aluminum Company estimated the cost of installing SF-type multiventuri wet roof scrubbe rs and a wastewater treatment system to be $20,540,000. The Marshall & Swift Equipment Cost Index published in Chemical En gineering Magazine was used to convert the 1975 cost estimate into 1994 dollars, which is $45,319,000 or $245 per ton of an nual capacity.

In 1970 Northwest Aluminum installed wet roof scru bbers at a total cost of $5,255,000. In 1990, the same plant installed a water treatment pond at a cost of $2,400,000. The total cost in 1994 dollars is approximately $19,556,000 or about $223 per ton of annual capacity.

The average of the two capital costs is $234 per t on of annual capacity. For an estimated life of 30 years , the capital recovery factor is 0.081, which yields an annual co st of capital of $19/ton.

Operating costs provided from responses to informa tion collection requests averaged about $8.57/ton alumin um for those plants that currently have wet roof scrubbers. Add ing the operating cost to the annual cost of capital gives a total annualized cost of about $27.60/ton.

V. Estimate of Cost Effectiveness:4

The estimate of total annualized cost is used in T able 4 along with the annual emission reduction developed earlier to estimate the cost effectiveness for the three cases . Cases 2 and 3 are of primary interest because they represent th e cost effectiveness of retrofitting wet roof scrubbers at an existing plant (Case 2) and incorporating wet roof scrubbers into the construction of a new plant (Case 3). The cost eff ectiveness for HAPs ranges from about $38,000 to over $120,000/ton for these two

cases.

TABLE 4. ESTIMATES OF COST EFFECTIVENESS OF WET RO OF SCRUBBERS

Case 1 (existing VSS) Case 2

(retrofit to VSS) Case 3

(new CWPB)

Capacity (t/yr) 88,000 185,000 200,000
Capital cost ($) 20,600,000 43,000,000 47,000,000
Total annualized cost ($/yr) 2,400,000 5,100,000 5, 500,000
PM reduction (t/yr) 930 400 130
POM* reduction (t/yr) 84 56 <15
GF* reduction (t/yr) 114 80 32
TF reduction (t/yr) 370 157 58
HAP* reduction (t/yr) 198 136 47

Cost effectiveness for PM ($/ton PM) 2,600 13,000 42,000

Cost effectiveness for POM ($/ton POM) 29,000 91,000 >370,000

Cost effectiveness for GF ($/ton GF) 21,000 64,000 170,000

Cost effectiveness for TF ($/ton TF) 6,500 32,000 95,000

Cost effectiveness for HAPs ($/ton GF + POM) 12,000 38,000 120,000

*GF is assumed to be primarily hydrogen fluoride fo r the purpose of estimating emissions of HAPs. POM are represent ed by using methylene chloride extractables as a surrogate.5

VI. Other Impacts:

The use of wet roof scrubbers increases the use of electricity and water, and the scrubbers generate a sludge and wastewater stream. Data from two plants with wet r oof scrubbers indicated that sludge is generated at a rate of 9 t o 26 lb/t aluminum and wastewater is generated at a rate of 1 00 to 600 gal/min. 6 Using a midrange value of 18 lb/t for solid waste generation, the quantity of sludge produced for the three example plants ranges from about 800 to 1,800 t/yr (for cap acities of 88,000 to 200,000 t/yr). Increased electrical usag e is estimated as 300 kwh/t aluminum for the operation of wet roof scrubbers and lime treatment of the water. 7

VII. References:

1.Emissions Measurement Test Report - Northwest Alu minum Company. Prepared by Entropy, Inc. June 1994. 77 p.

2.Data provided by Don Ryan, Columbia Falls Aluminu m, Montana, to Steve Fruh, EPA. January 1995.

3.Data submitted by the Aluminum Association: "Tot al Fluoride Emission Assessment." Covers the period from Janua ry 1989 through December 1992.

4.Noranda Aluminum, Inc. Method 5/POM and 13B Test ing - New Madrid, Missouri - September 14-20, 1994. Prepared by AmTest Air Quality, Inc. January 10, 1994. pp. 1 through 62.

5.Kaiser Aluminum and Chemical Corporation Method 5 /POM and 13B Testing - Mead, Washington - March 15-24, 1994. Pr epared by AmTest Air Quality, Inc. November 9, 1994. pp. 1 through 99.

6.Compiled from responses by each plant in the indu stry to information collection requests.

7.Primary Aluminum: Guidelines for Control of Fluo ride Emissions from Existing Primary Aluminum Plants. U.S. Enviro nmental Protection Agency. Report No. EPA-450/2-78-049b. December 1979. p. 9-33.APPENDIX D. COMPLETE LISTING OF MACT FLOOR DATA1

MACT FLOOR DATA

A brief description of the tables is given below. In general, the analysis focused on the monthly averag es (generally 3 to 4 runs per month) for secondary (roof) emissio ns except for plants with wet roof scrubbers. The monthly averag es for wet roof scrubbers were composed of tests of 3 to 6 fan s per month.

Table 1: The data for Mt. Holly Lines A and B were provide d by the Aluminum Association in a submittal commonly re ferred to as the "blue book" data. 1 Alumax provided corrections for several data points for Line B. 2 Results are for both primary and secondary emissions.

Table 2: The data for Columbia-Goldendale were submitted by the
company 3 and are the monthly averages from sampling four fa ns each month.

Table 3: The data for Noranda were submitted by the company and represent individual runs for secondary emissions. 4 The results of a test conducted for the MACT test program (labe led "Amtest") were also added to the data set. 5

Table 4: The Columbia Falls data (secondary emissions only) were collected by EPA Methods 13/14 and submitted by the company. 6 The original data submitted by the Aluminum Associa tion were based on a method developed by the company (i.e., n ot EPA methods).

Table 5: The data for Kaiser-Tacoma (secondary emissions on ly) were submitted by the company and were collected by EPA Methods 13/14. 7 The results of a test conducted for the MACT test program (labeled "Amtest") were also added to the data set. 8 Data submitted prior to this were not based on EPA methods.

Table 6: The data for Kaiser-Mead (secondary emissions only ) were submitted by the company and were collected by EPA Methods 13/14. 9 The results of a test conducted for the MACT test program (labeled "Amtest") were also added to the data set. 10

Table 7: The data for Intalco were submitted by the compan y 11 and were calculated from kg/day of total fluoride and m onthly aluminum production. The results for both primary and secondary emissions are given for each run. A total of six f ans are sampled each month, along with four runs for the pr imary system. A total of 3 scrubber tests out of 262 total were identified as outliers (2.7 to 3.2 lb/ton in January 1991).2

Table 8: This analysis uses monthly averages for the wet r oof scrubbers and adds a 12-month rolling average for t he primary system to the monthly average of the scrubbers. (T his is the way the rule is expected to be implemented.)

Table 9: This table presents the HSS POM data for secondar y and primary emissions for Kaiser-Tacoma. 12 These data were collected as part of the MACT test program. Data for VSS1 ar e also included from tests conducted under the MACT progra m at ColumbiaGoldendale and Northwest Aluminum. 13, 14, 15

Table 10: The bake furnace data for Noranda were submitted by the company and were analyzed as the average of thr ee runs. 16

Table 11 : Data for the bake furnace at Mt. Holly were subm itted by the company. 17 Results shown for Kaiser-Mead and Noranda were collected under the MACT test program. 18, 193

TABLE 1. ALUMAX MT. HOLLY -- TOTAL FLUORIDE

Line A Line B

MONTH (lb/ton) MONTH (lb/ton)

3/89 0.77 1/89 0.81

7/89 0.77 5/89 0.74

11/89 1.02 9/89 0.96

1/90 0.67 2/90 0.68

4/90 0.63 6/90 0.75

8/90 1.17 10/90 0.78

9/90 0.74 3/91 0.72

12/90 0.84 7/91 0.89

1/91 0.77 11/91 0.87

5/91 0.76 4/92 0.74

9/91 0.87 8/92 0.81

2/92 0.56 12/92 0.63

6/92 1.04

10/92 0.99

Avg. 0.829 0.782

Std dev. 0.172 0.093

N 14 12

Summary of Lines A and B Combined

Avg. 0.807

Std dev. 0.141

N 264

TABLE 2. COLUMBIA-GOLDENDALE LINE 1 ROOF EMISSION S

Date lb/t TF

1 92 2.18

2 92 1.33

3 92 1.55

4 92 1.89

5 92 0.83

6 92 1.33

7 92 0.69

8 92 1.59

9 92 0.66

10 92 1.14

11 92 1.32

12 92 2.00

1 93 0.59

2 93 0.32

3 93 0.90

4 93 1.07

5 93 1.28

6 93 1.43

7 93 1.51

8 93 1.24

9 93 1.31

10 93 1.68

11 93 1.46

12 93 1.48

1 94 1.98

2 94 1.42

3 94 1.43

4 94 1.21

5 94 1.385 6 94 1.30

MACT test 1.05

Avg. 1.31

Std.dev. 0.42

N 31

Add 0.005 to 0.02 lb/t for primary emissions.6

TABLE 3. NORANDA LINE 3 ROOF DATA (lb TF/ton)

Date TF (lb/t)

Single

run Monthly

average

11-Jan-89 1.07 1.22

12-Jan-89 1.40

13-Jan-89 1.17

14-Feb-89 0.89 0.85

15-Feb-89 0.81

16-Feb-89 0.84

07-Mar-89 1.22 0.96

08-Mar-89 0.99

09-Mar-89 0.69
11-Apr-89 1.02 0.80
12-Apr-89 0.59
13-Apr-89 0.79
09-May-89 1.28 1.02
10-May-89 0.79
11-May-89 1.00

06-Jun-89 0.92 1.01

07-Jun-89 1.03

08-Jun-89 1.09

11-Jul-89 0.74 0.82

12-Jul-89 0.70

13-Jul-89 1.01
08-Aug-89 0.80 1.02
09-Aug-89 1.11
10-Aug-89 1.16

18-Dec-89 0.61 0.66

19-Dec-89 0.71

20-Dec-89 0.657 Date TF (lb/t)

Single

run Monthly

average

09-Jan-90 0.59 0.92

10-Jan-90 1.04

11-Jan-90 1.13

06-Feb-90 0.73 0.63

07-Feb-90 0.65

08-Feb-90 0.51

06-Mar-90 1.92 1.81

07-Mar-90 2.41

08-Mar-90 1.09
03-Apr-90 2.03 1.37
04-Apr-90 0.95
05-Apr-90 1.12
08-May-90 0.92 0.87
09-May-90 0.81
10-May-90 0.87

05-Jun-90 1.12 1.19

06-Jun-90 1.24

07-Jun-90 1.20

10-Jul-90 1.37 1.59

11-Jul-90 1.73

12-Jul-90 1.68
08-Aug-90 1.34 1.33
09-Aug-90 1.13
10-Aug-90 1.53
11-Sep-90 1.53 1.46
12-Sep-90 1.73
13-Sep-90 1.12

09-Oct-90 1.18 1.58

10-Oct-90 2.29TABLE 3. NORANDA LINE 3 ROOF DATA (lb TF/ton)

8 11-Oct-90 3.26

23-Oct-90 0.65

24-Oct-90 0.87

25-Oct-90 1.22

06-Nov-90 1.42 1.31

07-Nov-90 1.20

11-Dec-90 1.37 1.75

12-Dec-90 1.53

13-Dec-90 2.34

08-Jan-91 0.59 0.99

09-Jan-91 1.31

10-Jan-91 1.09

05-Feb-91 0.75 0.92

06-Feb-91 0.90

07-Feb-91 1.10

05-Mar-91 1.70 1.54

06-Mar-91 1.20

07-Mar-91 1.71
09-Apr-91 0.78 1.16
10-Apr-91 1.35
11-Apr-91 1.34
08-May-91 1.70 1.82
09-May-91 2.15
10-May-91 1.60

10-Jun-91 1.47 1.56

11-Jun-91 1.57

12-Jun-91 1.63

09-Jul-91 1.08 1.15

10-Jul-91 1.39

11-Jul-91 0.99
12-Aug-91 0.74 0.72TABLE 3. NORANDA LINE 3 ROOF DATA (lb TF/ton)

9 12-Aug-91 0.76
13-Aug-91 0.93
13-Aug-91 0.54
14-Aug-91 0.74
14-Aug-91 0.64
09-Sep-91 0.86 0.69
09-Sep-91 0.54
10-Sep-91 0.76
11-Sep-91 0.70
11-Sep-91 0.50
12-Sep-91 0.92
12-Sep-91 0.58

07-Oct-91 0.89 0.95

07-Oct-91 0.62

08-Oct-91 0.73

08-Oct-91 0.98

09-Oct-91 1.09

09-Oct-91 1.40

05-Nov-91 0.45 0.79

05-Nov-91 0.43

06-Nov-91 0.79

06-Nov-91 1.10

07-Nov-91 0.99

07-Nov-91 1.00

09-Dec-91 0.89 0.80

09-Dec-91 1.07

10-Dec-91 0.94

10-Dec-91 0.76

11-Dec-91 0.57

12-Dec-91 0.61

06-Jan-92 1.04 0.90TABLE 3. NORANDA LINE 3 ROOF DATA (lb TF/ton)

10 07-Jan-92 0.62

07-Jan-92 0.85

08-Jan-92 0.81

08-Jan-92 0.72

09-Jan-92 1.36

10-Feb-92 0.97 0.93

10-Feb-92 0.50

11-Feb-92 0.71

11-Feb-92 1.29

12-Feb-92 1.24

12-Feb-92 0.85

09-Mar-92 1.25 1.34

09-Mar-92 1.56

10-Mar-92 1.52

10-Mar-92 1.04

11-Mar-92 1.96

11-Mar-92 0.73
06-Apr-92 0.86 0.98
06-Apr-92 0.95
07-Apr-92 1.11
07-Apr-92 0.49
08-Apr-92 1.34
08-Apr-92 1.15
04-May-92 0.95 1.20
05-May-92 1.91
05-May-92 0.84
06-May-92 1.18
07-May-92 1.57
07-May-92 0.76

08-Jun-92 1.17 1.12

08-Jun-92 0.95TABLE 3. NORANDA LINE 3 ROOF DATA (lb TF/ton)

11 09-Jun-92 1.55

09-Jun-92 0.94

10-Jun-92 1.33

10-Jun-92 0.78

06-Jul-92 0.85 0.66

06-Jul-92 0.53

07-Jul-92 0.75

07-Jul-92 0.59

08-Jul-92 0.75

08-Jul-92 0.50
12-Aug-92 0.69 1.00
12-Aug-92 0.94
13-Aug-92 1.02
13-Aug-92 1.00
14-Aug-92 1.34
14-Aug-92 0.99
08-Sep-92 0.86 0.87
08-Sep-92 0.71
09-Sep-92 1.04
09-Sep-92 0.90
10-Sep-92 1.00
10-Sep-92 0.72

05-Oct-92 1.03 1.15

05-Oct-92 1.41

06-Oct-92 0.99

06-Oct-92 1.03

07-Oct-92 1.30

07-Oct-92 1.12

09-Nov-92 0.98 0.78

09-Nov-92 0.82

10-Nov-92 0.62TABLE 3. NORANDA LINE 3 ROOF DATA (lb TF/ton)

12 10-Nov-92 0.56

11-Nov-92 0.76

11-Nov-92 0.95

07-Dec-92 0.74 0.77

07-Dec-92 0.58

08-Dec-92 0.72

09-Dec-92 0.59

09-Dec-92 1.03

10-Dec-92 0.96

AMTEST 1.01 0.91

0.83

0.90
Summary:
Avg 1.05 1.08

Std 0.41 0.32

N 192 46
Add 0.06 lb/t for primary system13

TABLE 4. COLUMBIA FALLS ROOF DATA (TF in lb/ton)

SINGLE 3-RUN
Run RUN AVG.

1 2.75 2.40

2 0.86

3 3.58

4 2.69 2.16

5 1.88

6 1.91

7 2.04 1.93

8 1.87

9 1.89

10 1.00 1.60

11 2.24

12 1.57

13 1.29 1.63

14 1.09

15 2.52

16 1.93 2.74

17 2.77

18 3.53

19 2.33 2.34

20 2.34

Avg. 2.12

Std. dev. 0.42

N 7

Add 0.095 lb/ton for primary system emissions.14

TABLE 5. KAISER-TACOMA LINE 2 ROOF DATA (lb/t TF)
Date Single run Monthly avg

Mar-93 2.13 2.12

1.75

2.47
Apr-93 2.83 2.28

1.84

2.18
May-93 1.23 1.56

1.60

1.86

Jun-93 2.09 2.01

2.34

1.61

Jul-93 2.12 1.97

1.56

2.24
Aug-93 1.82 1.90

1.97

1.91
Sep-93 2.03 2.30

2.42

2.45

Oct-93 1.37 1.37

1.38

1.36

Nov-93 1.76 2.11

1.92

2.66

Dec-93 2.13 2.32

2.26

2.5615 Date Single run Monthly avg

Jan-94 0.97 1.39

1.58

1.61

Feb-94 1.43 1.54

1.76

1.44

Mar-94 2.06 1.83

2.00

1.43
Apr-94 2.30 2.13

2.13

1.95
May-94 2.13 2.20

2.07

2.41

Jun-94 2.23 2.02

1.89

1.93

Jul-94 1.61 1.65

1.68
Aug-94 2.06 2.01

2.25

1.72
Sep-94 2.27 2.64

3.00

Oct-94 2.04 2.45

2.86

Nov-94 1.74 2.21

2.40

2.50

Dec-94 2.09 2.46TABLE 5. KAISER- TACOMA LINE 2 ROOF DATA (lb/

16 2.32

2.98

Amtest 1.06 1.24
(Mar-94) 2.12

0.55
Avg 1.98 1.97

Std dev. 0.47 0.36

N 66 23
Add 0.1 lb/t for the primary system17

TABLE 6. KAISER-MEAD LINE 1 ROOF DATA (lb/ton TF)
Date Single run Monthly avg

Aug-93 2.62 2.37

2.60

2.44

1.80
Sep-93 2.98 2.90

2.64

2.56

1.60

4.74

Oct-93 2.14 1.69

1.24

1.68

1.70

Nov-93 1.10 1.38

1.62

1.04

1.76

Dec-93 0.80 1.55

1.56

2.06

1.39

1.96

Jan-94 2.14 2.02

1.78

2.04

2.12

Feb-94 1.70 2.62

1.32

2.80

4.6618 Date Single run Monthly avg

Mar-94 2.73 2.17

2.51

1.62

1.83
Apr-94 1.84 2.04

1.09

2.72

2.51
May-94 2.23 1.78

1.90

1.20

Jun-94 1.91 1.79

1.92

1.60

1.84

1.67

Jul-94 2.05 2.71

3.93

2.53

2.34

Amtest 2.00 1.53

(Mar-94) 1.38

1.20

Avg 2.06 2.04

Std dev. 0.78 0.49

N 53 13
Add 0.14 lb/ton to include primary system19

TABLE 7. INDIVIDUAL RUN DATA FOR INTALCO LINE C ( TF in lb/ton)

Wet roof scrubbers Dry scrubbers

Month/year lb/ton Mon th/year lb/ton

1 1990 0.40 1 1990 0.18

1 1990 0.63 1 1990 0.48

1 1990 0.72 1 1990 0.05

1 1990 0.47 1 1990 0.09

1 1990 0.66 2 1990 0.26

1 1990 0.53 2 1990 0.09

3 1990 0.72 2 1990 0.13

3 1990 0.88 2 1990 0.19

3 1990 0.73 3 1990 0.28

3 1990 0.40 3 1990 0.29

3 1990 0.68 3 1990 0.40

3 1990 0.77 3 1990 0.73

4 1990 0.81 4 1990 0.26

4 1990 0.48 4 1990 0.25

4 1990 0.71 4 1990 0.06

4 1990 0.95 4 1990 0.14

4 1990 0.62 5 1990 0.24

4 1990 0.10 5 1990 0.05

5 1990 0.47 5 1990 0.06

5 1990 0.43 5 1990 0.14

5 1990 0.34 6 1990 0.85

5 1990 0.42 6 1990 0.10

5 1990 0.44 6 1990 0.10

5 1990 0.50 6 1990 0.03

6 1990 0.45 7 1990 0.08

6 1990 0.58 7 1990 0.18

6 1990 0.81 7 1990 0.14

6 1990 1.13 7 1990 0.10

6 1990 0.48 8 1990 0.1020 Wet roof scrubbers Dry scrubbers

Month/year lb/ton Mon th/year lb/ton

6 1990 0.54 8 1990 0.06

7 1990 0.86 8 1990 0.05

7 1990 0.78 8 1990 0.21

7 1990 0.75 9 1990 0.30

7 1990 0.50 9 1990 0.10

7 1990 0.49 9 1990 0.33

7 1990 0.64 9 1990 0.12

8 1990 1.10 10 1990 0.25

8 1990 0.61 10 1990 0.08

8 1990 0.82 10 1990 0.33

8 1990 1.05 10 1990 0.15

8 1990 0.65 11 1990 0.36

8 1990 0.77 11 1990 0.17

9 1990 0.55 11 1990 0.36

9 1990 0.66 11 1990 0.21

9 1990 0.54 12 1990 0.11

9 1990 0.81 12 1990 0.20

9 1990 0.72 12 1990 0.53

9 1990 1.11 12 1990 0.43

10 1990 1.10 1 1991 0.37

10 1990 0.65 1 1991 0.13

10 1990 0.71 1 1991 0.15

10 1990 0.66 1 1991 0.37

10 1990 0.44 2 1991 0.13

10 1990 0.49 2 1991 0.14

11 1990 0.42 2 1991 0.24

11 1990 0.45 2 1991 0.42

11 1990 0.49 3 1991 1.07

11 1990 0.63 3 1991 0.63

11 1990 0.42 3 1991 0.38TABLE 7. INDIVIDUAL RUN DATA FOR INTALCO LINE C (T F in lb/ton)

21 11 1990 0.50 3 1991 0.37

12 1990 0.72 4 1991 0.29

12 1990 0.47 4 1991 0.31

12 1990 0.55 4 1991 0.07

12 1990 0.79 4 1991 0.56

12 1990 0.88 5 1991 0.29

1 1991 0.80 5 1991 0.11

5 1991 0.14

5 1991 0.20

6 1991 0.24

1 1991 0.53 6 1991 0.10

1 1991 0.88 6 1991 0.26

2 1991 0.63 6 1991 0.08

2 1991 0.53 7 1991 0.32

2 1991 0.94 7 1991 0.13

2 1991 0.63 7 1991 0.32

2 1991 0.85 7 1991 0.09

2 1991 1.33 8 1991 0.16

3 1991 0.26 8 1991 0.45

3 1991 0.47 8 1991 0.54

3 1991 0.71 8 1991 0.33

3 1991 0.56 9 1991 0.76

3 1991 0.48 9 1991 0.29

3 1991 0.42 9 1991 0.40

4 1991 0.49 9 1991 0.29

4 1991 0.56 10 1991 0.56

4 1991 1.00 10 1991 0.23

4 1991 0.69 10 1991 0.50

4 1991 0.64 10 1991 0.12

4 1991 0.63 11 1991 0.14

5 1991 0.51 11 1991 0.21TABLE 7. INDIVIDUAL RUN DATA FOR INTALCO LINE C (T F in lb/ton)

22 5 1991 0.28 11 1991 0.43

5 1991 0.47 11 1991 0.16

5 1991 0.71 12 1991 0.20

5 1991 0.69 12 1991 0.32

5 1991 0.56 12 1991 0.36

6 1991 0.45 12 1991 0.65

6 1991 0.50 1 1992 0.87

6 1991 0.64 1 1992 0.20

6 1991 0.51 1 1992 0.31

6 1991 0.61 1 1992 0.23

6 1991 0.49 2 1992 0.16

7 1991 0.60 2 1992 0.46

7 1991 0.40 2 1992 0.37

7 1991 0.56 2 1992 0.12

7 1991 0.53 3 1992 0.13

7 1991 0.45 3 1992 0.23

7 1991 0.51 3 1992 0.05

8 1991 0.49 3 1992 0.16

8 1991 0.50 4 1992 0.48

8 1991 0.62 4 1992 0.05

8 1991 0.48 4 1992 0.26

8 1991 0.47 4 1992 0.23

8 1991 0.42 5 1992 0.13

9 1991 0.28 5 1992 0.05

9 1991 0.42 5 1992 0.10

9 1991 0.38 5 1992 0.07

9 1991 0.47 6 1992 0.08

9 1991 0.36 6 1992 0.19

9 1991 0.43 6 1992 0.32

10 1991 0.86 6 1992 0.03

10 1991 0.71 7 1992 0.20TABLE 7. INDIVIDUAL RUN DATA FOR INTALCO LINE C (T F in lb/ton)

23 10 1991 0.91 7 1992 0.07

10 1991 0.69 7 1992 0.20

10 1991 0.73 7 1992 0.29

10 1991 0.52 8 1992 0.18

11 1991 0.54 8 1992 0.33

11 1991 0.74 8 1992 0.07

11 1991 0.53 8 1992 0.35

11 1991 0.79 9 1992 0.23

11 1991 0.56 9 1992 0.17

11 1991 0.76 9 1992 0.06

12 1991 0.66 9 1992 0.14

12 1991 1.30 10 1992 0.09

12 1991 1.16 10 1992 0.04

12 1991 0.54 10 1992 0.02

12 1991 0.48 10 1992 0.64

12 1991 0.41 11 1992 0.03

1 1992 0.58 11 1992 0.25

1 1992 1.10 11 1992 0.13

1 1992 0.62 11 1992 0.27

1 1992 0.60 12 1992 0.28

1 1992 0.67 12 1992 0.44

1 1992 0.66 12 1992 0.12

2 1992 0.52 12 1992 0.16

2 1992 0.58 1 1993 0.74

2 1992 0.84 1 1993 0.13

2 1992 0.58 1 1993 0.31

2 1992 0.59 1 1993 0.34

2 1992 0.94 2 1993 0.02

3 1992 0.47 2 1993 0.30

3 1992 0.46 2 1993 0.21

3 1992 0.60 2 1993 0.18TABLE 7. INDIVIDUAL RUN DATA FOR INTALCO LINE C (T F in lb/ton)

24 3 1992 0.41 3 1993 0.29

3 1992 0.66 3 1993 0.47

3 1992 0.60 3 1993 0.36

4 1992 0.86 3 1993 0.78

4 1992 0.34 4 1993 0.07

4 1992 0.65 4 1993 0.17

4 1992 0.49 4 1993 0.17

4 1992 0.84 4 1993 0.12

4 1992 0.62 5 1993 0.21

5 1992 0.51 5 1993 0.31

5 1992 0.84 5 1993 0.09

5 1992 1.05 5 1993 0.20

5 1992 0.56 6 1993 0.16

5 1992 0.69 6 1993 0.66

5 1992 0.14 6 1993 0.67

6 1992 0.39 6 1993 0.78

6 1992 0.46 7 1993 0.36

6 1992 0.67 7 1993 0.15

6 1992 0.38 7 1993 0.15

6 1992 0.37 7 1993 0.15

6 1992 0.47 8 1993 0.18

7 1992 0.57 8 1993 0.32

7 1992 0.46 8 1993 0.20

7 1992 0.76 8 1993 1.24

7 1992 0.62 9 1993 0.16

7 1992 0.49 9 1993 3.44

7 1992 0.77 9 1993 0.40

8 1992 0.64 9 1993 0.31

8 1992 1.84 9 1993 0.31

8 1992 0.98 10 1993 0.14

8 1992 0.43 10 1993 0.11TABLE 7. INDIVIDUAL RUN DATA FOR INTALCO LINE C (T F in lb/ton)

25 8 1992 0.42 10 1993 0.66

8 1992 0.74 10 1993 0.13

9 1992 0.44 11 1993 0.12

9 1992 0.42 11 1993 0.25

9 1992 0.80 11 1993 0.33

9 1992 0.55 11 1993 0.35

9 1992 0.46 12 1993 0.10

9 1992 0.63 12 1993 0.05

10 1992 0.88 12 1993 0.13

10 1992 0.46 12 1993 0.07

10 1992 0.65

10 1992 0.68 Avg. 0.275

10 1992 0.45 Std dev. 0.304

10 1992 0.43 N 193

12 1992 0.50

12 1992 0.57

12 1992 0.67

1 1993 0.41

1 1993 0.51

1 1993 0.67

1 1993 1.02

1 1993 0.89

3 1993 1.09

3 1993 0.86

3 1993 1.09

3 1993 1.28

3 1993 0.69

4 1993 1.35

4 1993 0.46

4 1993 0.38

4 1993 0.72TABLE 7. INDIVIDUAL RUN DATA FOR INTALCO LINE C (T F in lb/ton)

26 4 1993 0.77

4 1993 0.69

5 1993 1.31

5 1993 0.07

5 1993 1.57

5 1993 1.55

5 1993 0.94

5 1993 0.90

6 1993 0.97

6 1993 0.75

6 1993 0.15

6 1993 1.37

6 1993 0.55

6 1993 0.54

7 1993 0.94

7 1993 0.62

7 1993 1.05

7 1993 0.82

7 1993 0.51

7 1993 0.03

8 1993 0.57

8 1993 0.50

8 1993 0.39

8 1993 0.51

8 1993 0.55

8 1993 0.43

9 1993 1.17

9 1993 0.69

9 1993 0.87

9 1993 0.72

9 1993 0.75TABLE 7. INDIVIDUAL RUN DATA FOR INTALCO LINE C (T F in lb/ton)

27 9 1993 0.06

10 1993 0.91

10 1993 0.55

10 1993 0.20

10 1993 0.56

10 1993 0.91

10 1993 0.71

11 1993 0.95

11 1993 0.52

11 1993 2.17

11 1993 0.51

12 1993 0.90

12 1993 0.95

12 1993 1.17

12 1993 0.70

12 1993 1.50

12 1993 0.37

Avg. 0.69

Std dev. 0.37

N 25928

TABLE 8. INTALCO LINE C MONTHLY AVERAGES (Monthly average for wet roof scrubbers plus 12-month average for primary system)

Month/year TF lb/ton

1 1990 0.79

3 1990 0.92

4 1990 0.83

5 1990 0.65

6 1990 0.88

7 1990 0.89

8 1990 1.05

9 1990 0.95

10 1990 0.90

11 1990 0.70

12 1990 0.90

1 1991 0.74

2 1991 1.13

3 1991 0.79

4 1991 0.98

5 1991 0.85

6 1991 0.84

7 1991 0.82

8 1991 0.81

9 1991 0.70

10 1991 1.05

11 1991 0.96

12 1991 1.07

1 1992 0.92

2 1992 0.89

3 1992 0.74

4 1992 0.84

5 1992 0.8429 Month/year TF lb/ton

6 1992 0.67

7 1992 0.82

8 1992 1.05

9 1992 0.76

10 1992 0.80

12 1992 0.79

1 1993 1.13

3 1993 1.36

4 1993 1.09

5 1993 1.42

6 1993 1.08

7 1993 1.02

8 1993 0.85

9 1993 1.07

10 1993 1.00

11 1993 1.40

12 1993 1.29

Avg. 0.97

Std dev. 0.26

N 4530

TABLE 9. SODERBERG POM DATA

TACOMA POM DATA lb/ton

Line 2 Roof Dry scrubber

Single runs Avg 3 runs Single runs Avg 3 runs

lb/ton lb/ton lb/ton lb/ton

March 94 1.76 1.71 2.52 1.60

1.78 1.21

1.58 1.06

Oct 94 1.59 1.63 0.164 0.11

1.51 0.058

1.78 0.093

1.52 1.38 1.72 0.64

1.25 0.105

1.38 0.097

1.42 1.64

1.62

1.88

2.36 2.72

3.72

2.09

Average 1.816 1.816 0.781 0.781

Standard 0.598 0.522 0.899 0.756

deviation31

N 15 5 9 332

TABLE 9. SODERBERG POM DATA (cont'd) POM in lb/ton for roof scrubbers

Plant Fan Inlet POM Avg of 3 Outlet POM Avg of 3

Columbia 9 1.610 0.90 0.365 0.18

Aluminum 0.365 0.029

0.730 0.146

12 2.260 2.07 0.292 0.44

1.460 0.438

2.480 0.584

Northwest 2 3.16 3.68 1.6430 1.42

Aluminum 3.15 1.5730

4.74 1.0420

3 3.13 3.21 1.8800 2.19

3.13 2.0650

3.35 2.6160

2 4.76 3.45 3.0000 2.40

3.48 2.4000

2.12 1.8000

3 3.53 2.47 2.6800 1.88

2.54 1.8800

1.33 1.0800

Avg. 2.63 2.63 1.42 1.42

Std dev. 1.22 1.04 0.95 0.92

N 18 6 18 6

Maximum 4.76 3.68 3.00 2.40

Tests of the primary control system at Northwest Al uminum from 3 runs showed POM emissions averaged on ly 0.0097 lb/ton (range of 0.009 to 0.011 lb/ton).3334

TABLE 10. NORANDA BAKE FURNACE DATA

Total fluoride lb/ton anode

lb/ton Avg of 3 runs

Alum. Anode Ln lb/ton Ln

Sep 1983 0.018 0.036 -3.324 0.035 -3.362

0.017 0.034 -3.381

Nov 1983 0.017 0.034 -3.381

0.011 0.022 -3.817 0.018 -4.017

0.011 0.022 -3.817

Mar 1984 0.005 0.010 -4.605

0.004 0.008 -4.828 0.009 -4.748

0.004 0.008 -4.828

Apr 1984 0.005 0.010 -4.605

0.005 0.010 -4.605 0.010 -4.605

0.005 0.010 -4.605

May 1984 0.005 0.010 -4.605

0.026 0.052 -2.957 0.065 -2.728

0.067 0.134 -2.010

Jun 1984 0.005 0.010 -4.605

0.011 0.022 -3.817 0.014 -4.269

0.004 0.008 -4.828

Jul 1984 0.006 0.012 -4.423

0.026 0.052 -2.957 0.031 -3.463

0.018 0.036 -3.324

Aug 1984 0.003 0.006 -5.116

0.003 0.006 -5.116 0.010 -4.605

0.003 0.006 -5.116

Sep 1984 0.009 0.018 -4.017

0.005 0.010 -4.605 0.011 -4.480

0.007 0.014 -4.269

Oct 1984 0.005 0.010 -4.60535 Total fluoride lb/ton anode

lb/ton Avg of 3 runs

Alum. Anode Ln lb/ton Ln

0.002 0.004 -5.521 0.004 -5.521

0.002 0.004 -5.521

Nov 1984 0.002 0.004 -5.521

0.001 0.002 -6.215 0.006 -5.116

0.004 0.008 -4.828

Dec 1984 0.004 0.008 -4.828

0.015 0.030 -3.507 0.019 -3.981

Jan 1985 0.002 0.004 -5.521

0.011 0.022 -3.817

Apr 1985 0.010 0.020 -3.912 0.011 -4.541

Jun 1985 0.002 0.004 -5.521

0.004 0.008 -4.828

0.006 0.012 -4.423 0.024 -3.730

Jan 1986 0.020 0.040 -3.219

Feb 1986 0.010 0.020 -3.912

Mar 1986 0.007 0.014 -4.269 0.019 -3.981

0.006 0.012 -4.423

0.015 0.030 -3.507

Apr 1987 0.057 0.114 -2.172 0.059 -2.836

May 1987 0.018 0.036 -3.324

Jun 1987 0.013 0.026 -3.650

0.013 0.026 -3.650 0.061 -2.802

0.008 0.016 -4.135

Jun 1988 0.070 0.140 -1.966

Aug 1988 0.026 0.052 -2.957 0.497 -0.698

Sep 1988 0.031 0.062 -2.781

Oct 1988 0.689 1.378 0.321

Nov 1988 0.032 0.064 -2.749 0.160 -1.833TABLE 10. NORANDA BAKE FURNACE DATA

36 0.041 0.082 -2.501

0.167 0.334 -1.097

0.526 1.052 0.051 0.362 -1.016

0.010 0.020 -3.912

0.007 0.014 -4.269

Dec 1988 0.003 0.006 -5.116 0.035 -3.343

Feb 1989 0.031 0.062 -2.781

0.019 0.038 -3.270

Mar 1989 0.022 0.044 -3.124 0.120 -2.120

0.021 0.042 -3.170

0.137 0.274 -1.295

Jul 1989 0.024 0.048 -3.037 0.078 -2.551

Aug 1989 0.005 0.010 -4.605

Jan 1990 0.088 0.176 -1.737

Feb 1990 0.244 0.488 -0.717 0.417 -0.874

0.370 0.740 -0.301

Apr 1990 0.012 0.024 -3.730

0.007 0.014 -4.269 0.013 -4.317

May 1990 0.008 0.016 -4.135

0.005 0.010 -4.605

0.005 0.010 -4.605 0.022 -3.817

Jan 1991 0.013 0.026 -3.650

Aug 1991 0.015 0.030 -3.507

0.018 0.036 -3.324 0.024 -3.730

Sep 1991 0.006 0.012 -4.423

0.012 0.024 -3.730

0.012 0.024 -3.730 0.038 -3.270

Jan 1992 0.007 0.014 -4.269

Feb 1992 0.038 0.076 -2.577

Mar 1992 0.037 0.074 -2.604 0.034 -3.381

Jul 1992 0.005 0.010 -4.605TABLE 10. NORANDA BAKE FURNACE DATA

37 0.009 0.018 -4.017

Aug 1992 0.005 0.010 -4.605 0.014 -4.269

0.007 0.014 -4.269

0.009 0.018 -4.017

May 1993 0.011 0.022 -3.817 0.023 -3.758

Jun 1993 0.011 0.022 -3.817

0.013 0.026 -3.650

Jul 1993 0.031 0.062 -2.781 0.048 -3.037

0.036 0.072 -2.631

0.005 0.010 -4.605

AMTEST 0.054 -2.919 0.027 -3.612

0.016 -4.135

0.024 -3.730

0.014 -4.269

Avg. 0.070 -3.744 0.070 -3.467

Std dev. 0.191 1.199 0.118 1.154

N 100 100 33 3338

TABLE 11. BAKE FURNACE DATA

ALUMAX BAKE FURNACE--TOTAL FLUORIDE

Single runs Avg of 3 runs

lb/ton lb/ton

1992 0.0036 0.0038

0.0042

0.0036

1993 0.0232 0.0136

0.0114

0.0062

1994 0.0040 0.0039

0.0042

0.0036

Avg 0.0071 0.0071

Std dev 0.0065 0.0056

KAISER-MEAD BAKE FURNACE (lb/ton anode)

POM TF

lb/ton lb/ton

0.168 0.006

0.166 0.019

0.148 0.015

Avg. 0.161 0.013

Std dev 0.011 0.007

NORANDA BAKE FURNACE

lb/t POM

0.038

0.020

0.016

Avg. 0.025

Std dev 0.01239

REFERENCES

1.Data submitted by the Aluminum Association: "Tot al Fluoride Emission Assessment." Covers the period from Janua ry 1989 through December 1992. Docket Item II-I-15. 1993.

2.R. Strieter, Aluminum Association, to S. Fruh, EP A:PPSG, May 1, 1995, Enclosing comments on the draft Technical Sup port Document.

3.W. Wooster, Columbia Aluminum Corporation, to T. Mix, Washington Department of Ecology, and S. Fruh, EPA: ISB, August 26, 1994, Enclosing fluoride emission data f or each potline. Docket Item II-D-69 .

4.D. Hart, Noranda Aluminum, to S Fruh, EPA:PPSG, N ovember 8, 1994. Submitting total fluoride data.

5.Emission test report, Method 5/POM and 13B Testin g, Noranda Aluminum, Inc., New Madrid, Missouri, September 14- 20, 1994, vol. I, prepared by Amtest Air Quality, Inc., Janua ry 10, 1995. Docket Item II-I-37.

6.Data provided by D. Ryan, Columbia Falls Aluminum , to S. Fruh, EPA:PPSG. January 1995.

7.B. Leber, Kaiser Aluminum, to S. Fruh, EPA:PPSG, March 1, 1996, Transmitting fluoride data for Kaiser's Tacom a Potline 2.

8.Emission test report, Method 5/POM and 13B Testin g, vol. I, Kaiser Aluminum and Chemical Corporation, Tacoma, Washington, March 1-8, 1994, prepared by AmTest Air Quality, Inc. for Kaiser Aluminum, September 14, 1994. Dock et Item II-I-29.

9.Kaiser Aluminum, Ravenswood Aluminum, and Reynold s Metals Company, to EPA:OAQPS, July 27, 1994, Enclosing "De velopment of Clean Air Act Amendments 112(d) Hazardous Air Po llutant Standards for the Primary Aluminum Industry: Propo sal for Setting Standards for Horizontal Stud Soderberg and Centerwork Prebake - 2 Subcategories." Docket Item II-D-66.

10.Emission test report, Method 5/POM and 13B Testi ng, Kaiser Aluminum and Chemical Corporation, Mead, Washington , March 15-24, 1994, vol. I, prepared by AmTest Air Quality , Inc., November 9, 1994. Docket Item II-I-33.40

11.G. Scott, Intalco Aluminum Corporation, to M. Br anscome, Research Triangle Institute, February 16, 1995, Enc losing computer run of all data from potline dry system an d potline wet scrubber system for 1990-1993. Docket Item II- D-83.

12. Reference 8.

13.Emission test report, Method 5/POM and 13B Testi ng, vol. I, Columbia Aluminum Corporation, Goldendale, Washingt on, November 29 - December 2, 1994, prepared by AmTest Air Quality, Inc., June 9, 1995.

14.G. May, Northwest Aluminum, to S. Fruh, EPA:PPSG , February 4, 1996, Transmitting POM data.

15.Emissions Measurement Test Report: Methylene Ch loride Extractable Organic Sampling, Northwest Aluminum Co mpany, The Dalles, Oregon, prepared by Entropy, Inc. for E PA:EMB, March 1994. Docket Item II-A-16.

16. Reference 4.

17.R. Pulley, Alumax, to M. Branscome, Research Tri angle Institute, February 13, 1995, Transmitting bake ove n scrubber emission sampling results. Docket Item II -D-81.

18.Emission test report, Method 5/POM and 13B Testi ng of Anode Bake Furnace, Kaiser Aluminum and Chemical Corporat ion, Mead, Washington, May 2-5, 1994, prepared by AmTest Air Quality, Inc. for Washington Department of Ecology, December 12, 1994. Docket Item II-I-35.

19.Reference 5.