1 From: Palazzolo, Michael A. [Michael.Palazzolo@alcoa.com] Sent: Thursday, April 07, 2011 8:02 AM To: Putney.David@epamail.epa.gov Cc: Boyd.Rochelle@epamail.epa.gov; Bahner, Mark A.; Green, David A.; Charles D. Johnson Subject: Surrogate justification Attachments: TF Limit as Surrogate.docx

David,

Please find attached a justification or rationale for using total fluoride as a surrogate for regulation of metals and POM from prebake potlines. The bottom line is that by regulating total fluoride at the MACT floor level, EPA is already limiting metals and POM. This justification is not applicable to POM for Soderberg potlines, but the Soderberg category already has a POM emissions standard.

P lease let me know if you have any questions.

Mike

Michael Palazzolo Alcoa, Inc. 201 Isabella Street Pittsburgh, PA 15212- 5858 Ph: 412

- 553

- 48322 From: Putney.David@epamail.epa.gov [mailto:Putney.David@epamail.epa.gov] Sent: Tuesday, April 05, 2011 1:28 PM
To: Palazzolo, Michael A. Cc: Boyd.Rochelle@epamail.epa.gov; bahner@rti.org; green@rti.org Subject: Surrogate justifications/arguments; COS reductions

Mike,

During the EPA/PAL RTR conference call last month (on 03/2 2/11 I believe) we discussed the possibility of using PM as a surrogate for not only HAP metals but also for other HAP (POM and TF as I recall). Have you made any progress on a document presenting your justifications and supporting arguments for this appro ach? Do you have a time frame for when I could expect that document?

Also, as a not

- so

- subtle reminder, please be thinking about approaches (e.g. work practice standards, raw material specifications, controls, etc.) that could be used to reduce the COS e missions from the potlines at PAL facilities. Also, any rationale from the industry perspective for why potlines should or should not be sub

- categorized for purposes of COS (i.e. as they are for POM and TF) would be helpful. That is, are you aware of any r easons why COS emissions would vary between the various prebake and Soderberg potline types. Rochelle and I are attempting to spread the word about the COS issue to the PAL facilities (we discussed this with the folks at Century Aluminum in KY, Rio

- Tinto A lcan in KY, and Noranda Aluminum in MO during our recent plant tours) and would appreciate any help/information we can get that would assist in addressing COS emissions.

Thanks so much,

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, RTP, NC 27711 Mail Drop D243

- 02 Ph: (919) 541

- 2016 Fax: (919) 541

- 3207 Email: putney.david@epa.govT otal F luoride as a S urrogate for POM and Metals from P re - bake Anode P otline s

For pre

- baked anode potlines, the P rimary Aluminum MACT regulates emissions of total fluoride (TF), requiring:

 M onthly secondary (potroom roof) emission testing for total fluoride ;

 A nnual primary control device emissio ns testing for total fluoride ;

 D aily primary control device visible emission checks ; and

 P rimary control device operation within parametric limits for air flow and ore flow.

Total fluoride consists of approximately 50% particulate fluorides (PF) and 50% gaseous fluoride (HF). These particulate

- and gas

- phase pollutants are controlled using a pot hood
capture system (typically 98% + efficiency) followed by dry alumina injection and a baghouse (dry alumina scrubber)

.

On

- going compliance with the total fl uoride limit, in conjunction with the associated control device monitoring

, ensures that the pot hood capture and dry alumina scrubber systems are operated and maintained at the MACT floor level established by EPA for the various center

work prebake categories.

Metals

- In addition to particulate fluoride ( i.e., fluoride salts), the particulate matter released
from a n aluminum smelting pot also contain s trace amounts of HAP metals . Control of these HAP metals is achieved using the exact same equipment that is used to control the particulate component of total fluoride : the pot hood capture system and dry alumina scrubber baghouse

. So, the MACT floor te chnology for HAP metals is identical to that for total fluoride and control of total fluorides can thus be considered a surrogate for the control of HAP metals.

POM

– POM emissions from an aluminum smelting pot are present as both particulate

- and gas

phas e pollutants. Control of POM emissions is achieved using the exact same equipment that is used to control fluorides: the pot hood capture system and dry alumina scrubber system. Particulate POM are collected by the baghouse and gas

- phase POM are absorbed or condensed on the injected alumina and then collected by the baghouse . A portion of the gas

- phase POM is not removed and passes through the baghouse as does some fraction of gaseous fluoride (HF). So, the MACT floor control technology for POM is ident ical to that for total fluoride and control of total fluorides (PF and GF) and can thus be considered a surrogate for the control of POM
emissions. (Control of POM emissions at the anode bake furnaces is similarly accomplished using a dry alumina scrubber system .)