## p. 1 of 1

From: Lane, Sean [ mailto:SLane@CenturyKY.com ]

Sent: Thursday, February 13, 2014 2:51 PM

To: Putney, David

Cc: Lane, Sean Subject: Comment Regarding Bake Furnaces



## David,

Per our conversation early last week, be find the attached
letter containing our comments and request to modify the
PMACT standard to accommodate the averaging of emissions
from new and existing baking furnaces ducted to a common

control device.

Please contact me if you have questions.

Thank you.

Sean T. Lane, CSP, CHMM Environmental Manager 

## Century

ALUMINUM 

## of Kentucky

1627 State Route 3543

P.O. Box 500 Hawesville, KY 42348 P - (270) 852-2880 F - (270) 852-2887Century Aluminum of Kentucky ◊ 1627 State Route 3543 ◊ Hawesville, KY 42348 ◊ P - (270) 852-2880 ◊ F - (270) 852-2883

1 F ebruary 13, 2014

Mr. David Putney Environmental Engineer U.S. Environmental Protection Agency Office of Air Quality Planning and Standards Sector Policies and Programs Division

109 T.W. Alexander Drive Research Triangle Park, NC 27711 Mail Drop D243-02

RE: Comments to Primary Aluminum MACT concerning Carbon Bake Furnaces

Dear Mr. Putney:

Century Aluminum of Kentucky (Century), in conjunction with the seven (7) year review of the National Emission Standards for Hazardous Air Pollutants for Primary Aluminum Reduction Plants (PMACT) at 40 CFR Part 63 Subpart LL, formally requests that EPA amend PMACT to establish an alternate emission limit for the unique carbon baking units at Century’s Hawesville smelter that have a single common control device serving existing and new carbon baking sources.

Background

Prior to promulgation of the final PMACT on October 7, 1997, Century’s predecessor, NSA, a Division of Southwire Company, planned and applied for a Prevention of Significant Deterioration (PSD) Permit for a new potline at the Hawesville primary aluminum smelter facility. 1 The original PSD application was submitted to the Kentucky Division for Air Quality (KDAQ) in December 1995. Ultimately, a revised PSD application was submitted by NSA that included construction of a new carbon bake unit to supplement anode production from the two existing anode bake furnaces. The planning and design of the new potline and associated support facilities was initiated prior to issuance of the final PMACT, although construction pursuant to the PSD Permit was initiated in 1998.

As a result of the timing of the application for the new potline, NSA did not have an opportunity to provide input to EPA on the proposed PMACT standard in 1996 relative to the carbon bake furnace configuration at the Hawesville facility or the appropriate emissions standards or compliance monitoring that was deemed appropriate for the unique circumstances at the facility. Because the two existing carbon bake furnaces were uncontrolled, NSA opted to design a single dry scrubber to control emissions from the two existing carbon bake furnaces and the new carbon bake furnace that was authorized by the April 1998 PSD Permit issued by KDAQ. In essence, by designing a single dry scrubber for all three carbon bake furnaces, NSA significantly over-controlled HAP emissions from the two existing carbon bake furnaces as compared to the existing source PMACT standard at 40 CFR 63.843(c).

During development of PMACT, it was never considered or anticipated that there were situations where a new carbon baking furnace and existing furnace would be ducted to a common control device. Primary Aluminum Industry: Technical Support Document for Proposed MACT Standards (July 1996) (hereinafter

1 Century purchased the smelter from NSA in April 2001.



### Attachment 1. p.1 of 6Century Aluminum of Kentucky ◊ 1627 State Route 3543 ◊ Hawesville, KY 42348 ◊ P - (270) 852-2880 ◊ F - (270) 852-2883

2 “TSD”). It was certainly a unique circumstance that as MACT was being promulgated, NSA was in the process of designing a new carbon baking unit and a control device sized and intended to also control HAPs from its existing carbon baking sources. This allowed NSA to build only one control device that provided, on aggregate, more control than required under the final PMACT for each unit separately. In fact, the rulemaking record demonstrates that EPA d etermined emission reductions achieved by a single dry alumina scrubber would represent MACT for multi ple anode bake furnaces at existing source and for new sources. TSD at pp. 4-12, 4-13, App. B, Table B-5; Basis and Purpose Document for the Development of Proposed Standards for the Primary A luminum Industry (July 19, 1996) (hereinafter “BPD”) at App. B, pp. 3-6; see also 61 Fed. Reg. 50588 (Sept. 26, 1996).

Following construction of the new carbon bake furna ce and fifth potline, NSA contacted EPA Research Triangle Park to determine how the recent PMACT com pliance standards would apply to the two existing

and one new carbon bake furnaces that were ducted t o a common control device, since emission limitations for this configuration were not directl y addressed in the proposed and final PMACT preambl es or the rule development documents. At that time, t he informal EPA response was that the issue could n ot be addressed in the short-term through a PMACT rule making, but that the issue should be raised with th e state regulatory authority to explore a compliance demonstration approach based upon use of a formula similar to that specified in 40 CFR 63.845(b) for n ew potroom groups that are added to an existing pot line. (See Attachment 1).

After working with KDAQ to develop a compliance dem onstration plan for POM for the three carbon bake furnaces, KDAQ ultimately approved a compliance dem onstration approach as part of the Title V Permit that was issued to the facility in 2003. KDAQ appr oved permit language that established a combined permit limit at the outlet of the control device fo r two (2) existing sources and one (1) new source. These

limits were established as 0.14 lbs POM / ton Green Anode and 0.14 lbs TF / ton Green Anode. (See Attachment 2, 2003 Title V Permit). The Title V per mit was reviewed by EPA Region IV without objection

.

It was not until EPA Region IV did a compliance aud it in 2008 that Title V Permit language became an issue for EPA. Region IV’s contention was that sin ce a combined weighted average emission formula was not specifically provided for in PMACT, the lim it was not permissible. Century ultimately settled upon a solution with Region IV that determined complianc e with the respective new and existing source limit s for the three furnaces separately, but this methodo logy has proven to be overly burdensome to the faci lity and actually penalizes the facility for efficient f urnace and control device operation.

Concerns with Current Testing Approach

The current testing scenario utilizes the sum of th e mass of pollutant loadings in the inlets to the c ommon control device along with the mass of pollutants in the outlet of the common control device to obtain an overall control system pollutant removal efficiency . This overall efficiency is then applied to the

uncontrolled emissions from each source to determin e a controlled pounds per hour for each furnace. The controlled pounds per green ton of emissions is then calculated from the calculated controlled pounds per hour. The respective calculated emissio n rates for the new and existing furnaces are then compared to the new and existing source PMACT stand ards to determine compliance. (See Attachment 3, excerpt from current Title V Permit.)

Since implementing this approved compliance demonst ration approach, Century has had difficulty on occasion in demonstrating compliance with the new s ource emission limitation of (0.05 # POM/GT) through the calculated emissions rate for the new u nit. However, on a combined emissions basis, the d ry scrubber comes close to meeting the new source limi t of 0.05 # POM/GT with the long term average of 0.059 # POM/GT since the year 2000 for all three un its. Moreover, on a combined control basis of the new and two existing units, emissions of POM and ga seous fluoride are an average 95.7% (POM) andCentury Aluminum of Kentucky ◊ 1627 State Route 3543 ◊ Hawesville, KY 42348 ◊ P - (270) 852-2880 ◊ F - (270) 852-2883

3 57.9% (TF) lower on an equivalent production basis than the cumulative allowable for the three units under PMACT. If Century operated the three furnaces (1 new, 2 existing) with separate control devices and at its permitted production capacity (233,000 green tons), the allowable hourly emissions per the

PMACT would be as follows:

Furnace POM Limitation

(@ 233,000 TPY Production) TF Limitation (@ 233,000 TPY Production)

lbs/GT lbs/hr lbs/GT lbs/hr

New 0.05 0.44 0.02 0.18 Existing 1 0.18 1.60 0.20 1.77 Existing 2 0.18 1.60 0.20 1.77

Combined NA 3.64 NA 3.72

A s previously stated, the three furnaces (1 new, 2 existing) were ducted to a common control device that was designed at the time of permit issuance for all three units. The testing since 2000 shows that the

actual emissions to the environment were as follows:

Furnace POM Total Fluoride *

AVG.

Emissions Max

Emissions AVG.

Emissions Max Emissions

lbs/GT lbs/hr lbs/GT lbs/hr lbs/GT lbs/hr lbs/GT lbs/hr

Common

Exhaust Stack 0.059 1.200 0.133 2.870 0.006 0.239 0.029 0.730

*lbs/hr emissions only reflect 2011-2013, but are representative of highest emission rate.

A lso, under the methodology that Century must now use to demonstrate compliance, there have actually been test events where the combined emissions from the stack were measured as being below the

allowable new source limit , but the new source (Building #3) was calculated as out of compliance with the new source limit due to over control of the emissions from the two existing sources. 2 This is illustrated by the stack test data from May 23, 2011, below.

Date Stack

(lbs POM/GT) Building#1

- Existing

(lbs POM/GT) Building #2

- Existi ng (lbs POM/GT) Building #3

- New (lbs POM/GT)

2/17/2011 0.05 0.06 0.03 0.054

5/23/2011 0.04 0.02 0.04 0.071

8/25/2011 0.04 0.06 0.06 0.003

6/21/2012 0.13 0.13 0.09 0.172

11/13/2012 0.04 0.05 0.03 0.015

5/31/2013 0.10 0.11 0.12 0.078

8/20/2013 0.06 0.04 0.03 0.091

11/15/2013 0.03 0.05 0.03 0.018

I n all stack tests to date, Century’s control system reduces HAP emissions on a combined mass basis beyond that required by PMACT had each unit been controlled separately. For example, the allowable

2 This may be caused by variability in one or more of the tested parameters or due to the dry scrubber receiving variable loading from the existing units and the new furnace.Century Aluminum of Kentucky ◊ 1627 State Route 3543 ◊ Hawesville, KY 42348 ◊ P - (270) 852-2880 ◊ F - (270) 852-2883

4 emissions of POM of three separate furnaces as show n above would be 3.64 lbs/hr at the permitted maximum production rate. Century’s actual worst-ca se emission rate performance since the beginning of

the PMACT for the three sources ducted to the same control device was 2.87 lbs/hr of POM, and the average emissions of POM have been 1.20 lbs/hr.

Regulatory Support for Proposed Amendments

As aluminum plants in the United States age, they m ay rebuild their carbon bake sources and subsequently may meet the definition of “modified” or “reconstructed”. These modified or reconstructe d sources can potentially be ducted to a control devi ce that also controls “existing” sources.

Century believes that there is precedent in the ori ginal NESHAP language in 40 CFR Part 63 Subpart LL to support its requested amendments. 40 CFR 63.845 was written to allow additional cells to be added to an existing potline. 40 CFR 63.845 allows recalcul ation of the permit limit for potlines based on the fraction of the potlines total aluminum production capacity that is contained within all modified, reconstructed, or new potroom groups and, of course , ducted to a common control device. In the final PMACT rule preamble, EPA noted that because there w ere “many variations in the configuration of potrooms and potlines in the industry” establishing limits for both an NSPS and NESHAP could result in the confusing situation of duplicative emission lim its and unnecessary monitoring obligations for potl ines. As explained in the final rule preamble,

To resolve this issue a method was devised in the N ESHAP to combine the limit for the NSPS potroom group with that for the NESHAP potline based on the production capacity of the reduction cells that wou ld be subject to each set of limits. The result is a single TF emission limit f or the entire potline that maintains equivalent stringency, and it has the additional ad vantage of allowing the use of the NESHAP potline requirements for monitoring, rep orting and recordkeeping to avoid unnecessary duplication.

62 Fed. Reg. 52384, 52394 (Oct. 7, 1997).

Accordingly, the unique circumstances of the design and operation of the three carbon bake furnaces at Century’s Hawesville facility justify amending the regulation to create an emission limit for the comm on stack that represents an emission limitation of “eq uivalent stringency” to PMACT standards as applied on a common control basis for a new and existing furna ces.

As EPA noted in the TSD, several design factors for carbon bake furnaces, such as combustion conditions in the flues (temperature, oxygen conten t, residence time, mixing) affect the quantity of hydrocarbons in the flue entering the control devic e. That in turn can affect the overall control eff iciency and certainly the ultimate emission rate of POM. A ccordingly, the differing flue combustion condition s among existing and new anode furnaces result in flu e conditions to a common control device that are no t
reflective of a new carbon bake furnace. EPA’s new source MACT determination for POM was based upon very limited testing at a single facility with low POM inlet concentrations as compared to other facilities. TSD at App. B, B-7. Century is the on ly primary aluminum facility that is subject to a n ew source MACT standard for an anode bake furnace. Th erefore, it is appropriate to allow facilities with existing and new carbon bake furnaces controlled by a common dry alumina scrubber to determine compliance with new source POM standards through a weighted average equivalent emission limit. As EPA noted in the proposed PMACT with respect to emi ssions averaging for existing sources:

Consistent with EPA policy on regulatory flexibilit y . . . , the use of emissions averaging under this rule should reduce pollution a s well as benefit regulatedCentury Aluminum of Kentucky ◊ 1627 State Route 3543 ◊ Hawesville, KY 42348 ◊ P - (270) 852-2880 ◊ F - (270) 852-2883

5 entities. Compliance through averaging is expected to achieve somewhat greater emissions reductions than would occur witho ut averaging.

The same rationale applies equally here.

Establishing an amended emissions standard for the common stack on the three carbon bake furnaces at Century's Hawesville facility is further justified by the small universe of primary reduction plants i n the United States that are subject to PMACT and the con siderable variation in the configuration of units a t

those sources. 3 Specifically, Section 112(d)(1) of the Clean Air Act provides that EPA may distinguish among classes, types, and sizes of sources within a n industrial category in establishing MACT standard s. That includes such factors as differences in air po llution control technologies and configurations and opportunities for further pollution prevention.

Accordingly, Century proposes that the PMACT be mod ified to include the following language:

63.844(e) Equivalent Emission Limit for new anode b ake furnaces sharing a common control device with existing anode bake furnaces.

(1) This provision applies to new anode bake furnac es ducted to a common control device that is

shared with one or more anode bake furnaces that el ect to be subject to an equivalent emission limit established pursuant to this section in lieu of the separate limits under 63.843(c) and 63.844(c).

(2) On each anniversary date of the start-up of the new source, the following production weighted calculations shall be performed:

EL (TF) = ((EL 1 x P 1 ) + (EL 2 x P 2 ))/(P 1 + P 2 )

EL (POM) = ((EL 1 x P 1 ) + (EL 2 x P 2 ))/(P 1 + P 2 )

Where:

EL (TF) = Combined emission limit for Total Fluorid e EL (POM) = Combined emission limit for Polycyclic O rganic Matter

EL 1 = New source emission limit

EL 2 = Existing source emission limit

P 1 = Monthly average new source production

P 2 = Monthly average existing source production

(3) The owner or operator of a new anode bake furna ce that is controlled by a dry scrubber that

also controls emissions of TF and POM from one or m ore existing anode bake furnaces shall not discharge or cause to be discharged into the atmosp here any emissions of TF or POM in excess of the limits established pursuant to paragraph (e)(2) of this section.

3 The 1996 proposed rule states that, at that time, there were 23 primary aluminum plants in 14 states.

61 Fed. Reg. 50586, 50587 (Sept. 26, 1996). Of those, 17 used pre-bake technology. Dev. Doc. At pp. 2-5, 3-20, 3-21. Of the 17, five plants used dry a lumina scrubbers (injection type) for control of an ode

bake furnaces. Id. at 3-21. Today there are 8 primary aluminum plant s in operation in 5 states. None of the remaining plants have bake furnaces that are subject to the new source MACT.Century Aluminum of Kentucky ◊ 1627 State Route 3543 ◊ Hawesville, KY 42348 ◊ P - (270) 852-2880 ◊ F - (270) 852-2883

6 

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In conclusion, Century believes the unique circumstances of the design and construction of the common control device on its new source anode bake furnace at its Hawesville facility justifies amendment of the PMACT as part of the seven year review to establish an equivalent common stack control standard. Such a standard would be protective of the environment because it would provide for over control of HAPs, as compared to the application of individual emission limits to each of the three furnaces. Establishment of an equivalent common stack standard would also eliminate the complications of the currently approved testing and compliance demonstration method.

EPA’s favorable consideration of this proposal would be greatly appreciated. Please feel free to contact me directly if you have questions or need further information regarding this proposal.

Sincerely,

Sean T. Lane, CSP, CHMM Environmental Manager

CC: Danny Carroll, Century Aluminum – Sebree Works Jason Young, Century Aluminum – Sebree Works Sean Byrne, Century Aluminum – Hawesville Jamie Coomes, Century Aluminum – Hawesville John Hoerner, Century Aluminum Michael Serafini, Century Aluminum Chuck Johnson, Aluminum Association Sean Alteri, KY Division for Air Quality