1

From: "Palazzolo, Michael A."
<Michael.Palazzolo@alcoa.com>

To: David Putney/RTP/USEPA/US@EPA

Date: 08 /22/2011 09:44 AM

Subject: RE: Metal HAP info

David,

I have considered t he options raised by our discussion Thursday and in your email. Below are my thoughts regarding the use of TF as a predictor of metals emissions and the potential for establishing standards based on particulate fluoride to represent metals emissions.

TF

I firmly believe that TF can be used as an accurate predictor of metals emissions from a potline because of factors that affect metals emissions and the way that TF emissions from a potline are controlled. There are three primary sources of particulate/m etals emissions from the potline:

* Fugitive (roof) particulate/metals emissions from electrolytic bath in the smelting pots;

* Fugitive particulate/metals emissions from materials handling (e.g., pot feeding) in the potroom; and

* Particulate/metal s emissions from the dry scrubber baghouse.

Fugitive (roof) particulate/metals emissions from the electrolytic bath are minimized by the hooding system (covers) on the smelting pots. The hooding system captures both particulates and gaseous fluoride and there is no way to bias the hooding capture to improve capture of only the gaseous fraction. Electrolyte particulates that contain metals also contain fluorides. So, TF is an accurate predictor of fugitive particulat e/metals emissions from the smelting pot electrolytic

bath.

The remaining fugitive particulate/metals emissions come from materials handling and equipment movement in the potroom. The fugitive dusts from potroom activities all contain some level of2

fluor ide, but these activities do not generate HF emissions. So, TF is a direct and accurate indicator of fugitive particulate/metals emissions from materials handling and equipment activities.

Proper operation of the dry alumina scrubber system minimizes HF emission by continuous injection and contacting with fresh
alumina and minimizes particulate/metals emissions using a baghouse. TF is

an accurate indicator of both HF control and particulate/metals control for this system because poor operation of either the alumina injection system or the baghouse would lead to higher TF emissions. Intentionally operating the system to gain better control of HF and thus allow higher particulate fluoride (or metals) emissions is not technically feasible because all fresh alumina is already fed through dry scrubber to capture HF. Proper particulate control is further monitored under the existing rule through daily visual monitoring of the baghouse

stack.

So, for all three mechanisms of particulate/metals emission
generat ion, TF provides an accurate predictor of particulate/metals emissions. An increase in particulate/metals emissions will directly increase TF because particulate from all three sources (electrolyte, materials handling and dry scrubber)
contains fluoride. And, it is not possible to preferentially reduce only HF emissions from either the smelting pots or the control device to allow higher particulate/metals emissions.

Particulate Fluoride

Aluminum smelters use three different EPA Reference Test Methods

fo r measuring total fluoride: Method 13A/B, Alcoa Method 4075A and Method 14A (cassettes). All of these are equivalent Reference Test Methods for total fluoride. However, none have been validated, or even evaluated, for measurement of "particulate fluoride " as particulate fluoride is currently not a regulated air pollutant (except in North Carolina). So, it's not known whether all three methods would provide the same result for "particulate fluoride", although it has been shown through method evaluation st udies that all three methods give
the same result for total fluoride.

Determining particulate fluoride with Method 13A would require a modification to the sample recovery procedure and modifications to the analytical procedure. This method uses a paper o r3

organic membrane filter, which can absorb HF and potentially bias reported "particulate fluoride" high.

Method 14A has been validated for total fluoride against Method 13. The cassettes use a cellulose filter to collect particulate
and this fraction of the sample is analyzed separately according

to the method. But once again, cellulose will absorb HF and potentially bias the value reported as "particulate fluoride". Also, only a few smelters use cassettes for PAL compliance testing.

Alcoa Method 4075A

- TF was developed specifically to provide an accurate split between particulate and gaseous fluoride. The method uses a Teflon filter, which is inert to HF absorption, so that HF does not adsorb on the particulate filter. However, Method 4075A was only ap proved by EPA as alternate method for total fluoride because it was validated against Method 13. So, despite our intent to provide an accurate split, 4075A is also not a Reference method for particulate fluoride.

Establishing emission standards for "part iculate fluoride" would therefore require EPA to define (and promulgate) a method for determining "particulate fluoride". This could be a modification to Method 13A for particulate fluoride, but there would also need to be a comparison with Method 14A (ca ssettes) to determine if smelters could continue using cassettes to show compliance with both the total fluoride limit and a new particulate fluoride limit. (Otherwise, they would have to install a Method 14 downcomer at considerable expense.) There
is o bviously no time to complete this type of method development
before the RTR needs be finalized.

As we discussed earlier, the methods used for determining total
fluoride also would need to be rewritten and validated to allow comparative determinations of t otal particulate matter. These methods do not include procedures for particulate determination and it is not clear that the different filter types used with each method (13A, cassettes and 4075A

- TF) would provide equivalent particulate matter collection.

I am in the office this week if you would like to discuss further. Just give me a call or let me know when might be a good time to call you.

Thank you,

Mike4

Michael Palazzolo Alcoa, Inc.
201 Isabella Street Pittsburgh, PA 15212

- 5858
Ph: 412

- 553

- 4832

----- Original Message

----- From: Putney.David@epamail.epa.gov [mailto:Putney.David@epamail.epa.gov]

Sent: Thursday, August 18, 2011 9:18 AM To: Palazzolo, Michael A. Subject: Metal HAP info

Mike,

Thanks for your call and input this m orning. I want to make sure we are on the same page on the metal HAP monitoring/control approach. As I mentioned on the phone, I believe we can make a good (i.e., compelling and legal) argument that particulate fluoride emissions are a surrogate for (or pe rhaps more accurately, a predictor of) metal HAP emissions. That is, although metal HAP is not a subset of particulate fluoride, any actions taken to limit/control particulate fluoride emissions will also limit/control metal HAP emissions.

Note that this argument does not hold true for TF. That is, a source could limit/control the HF emissions portion of TF without also limiting/controlling the particulate fluoride portion of TF (this is the analogous situation to the previous legal decision I referred to in our conversation). Therefore, I do not believe management (specifically, OGC) would accept the argument that TF emissions are a surrogate or predictor of metal HAP emissions.

So, if we can either:

Get good data on particulate fluoride emissions fro m both the

stacks and the roof vents (so as to use particulate fluoride as the surrogate or predictor of metal HAP emissions from both the

stacks and roof vents);5

Get good data on PM from the stacks and particulate fluoride

from the roof vents (so as to use PM as the surrogate for metal HAP
emissions from the stacks and use particulate fluoride as the surrogate

or predictor of metal HAP from the roof vents); or

Get good data on PM emissions from both the stacks and the

roof vents (so as to use PM as the surrogate for metal HAP emissions

from both

the stacks and roof vents

- I realize we already ruled this

out for some facilities during our phone conversation)

Then we may have a viable approach to addressing the meta l HAP
issue.

I look forward to your input.

Thanks,

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.gov