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 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 the 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/metals 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/metals 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 

particulate/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 of 
2

fluoride, 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 

generation, 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 

for 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 studies 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 or 
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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 approved 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 "particulate 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 (cassettes) 

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 obviously 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 total 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,

Mike
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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 morning. 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 perhaps 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 from 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);
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 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 metal 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