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From: Charles D. Johnson [mailto:cdjohnson@aluminum.org] 

Sent: Wednesday, July 09, 2014 10:50 AM 

To: Putney, David; Curt Wells; 'Palazzolo, Michael A.'

Subject: Secondary potline emissions from primary aluminum 

production facilities 

David – 

Mike, Curt and I put our heads together earlier this week 

on your questions below and Mike briefed us on the

information that he had already shared with you via

phone. That information plus our additional thoughts are 

recapped below in italics as responses to your bullet list 

of questions.

Please feel free to contact me if you have questions 

regarding this information.

Chuck

1. Is it possible or feasible to install wet roof scrubbers (such as those currently installed at the Intalco 

facility) on the existing prebake potlines? That is, are there constraints at the existing prebake facilities 

that would make it impossible to install similar wet roof scrubbers? 

 

Inquiries within the industry indicated that this would 

generally be infeasible or impracticable due to the limits 

of additional weight loads that would be required on 

existing potline buildings. While new potline buildings 

could be designed for these loads, existing buildings 

would need to be structurally modified, or separate 

structures would need to be constructed over the existing 

buildings to support the weight of the wet roof scrubbers. 

 

2. If wet roof scrubbers could be installed on the existing prebake potlines, what capital and annualized costs 

would you expect for such retrofits (perhaps quick calculations based on historical costs at the Intalco 

facility could provide a rough estimate)? 

 

Cost estimates were formulated for wet SO2 scrubbing (not 

for PM) of primary potline emissions in the design phase of 

an international aluminum smelter project. Scaling that 

information based on design potroom roof airflows and 
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infrastructure costs yielded a per potline capital cost 

estimate of $200-$300 million. 

 

3. Does industry have any information as to what fraction of potline secondary particulate matter (PM) 

emissions are expected to be PM2.5 as opposed to PM? If so, what is the source of the estimate (e.g., 

testing, engineering judgement, etc.)? 

 

Limited test data available indicates that approximately 

50% of potline roof vent PM emissions were PM 2.5. This 

data was collected using the previous version of Method 202 

for condensable PM. With the revised Method 202, we 

expect that the percentage of PM measured as PM2.5 would 

be lower. 

 

4. Does industry have any information as to what fraction of potline secondary metals emissions are 

expected to be PM2.5 as opposed to PM? That is, do you have any reason to believe that the metals 

(especially nickel) would be distributed any differently than the “other” particulate matter? Again, if so, 

what is the source of the estimate (e.g., testing, engineering judgement, literature review, etc.)? 

 

We have no reason to believe that nickel would be 

distributed differently than “other” particulate matter in 

general.

 

5. Does industry have any information (perhaps from historical testing at Intalco) as to the control efficiency, 

both for PM2.5 and for PM, expected from such wet roof scrubbers? 

 

The scrubbers at Intalco were installed and optimized for 

Fluoride control, rather than PM. As a rough estimate, PM 

control efficiency is estimated to be on the order of 15% 

to 30%. However, we have requested Intalco to determine 

whether any measurement data are available to confirm this 

estimate. 

From: Putney, David [mailto:putney.david@epa.gov] 

Sent: Friday, June 20, 2014 9:45 AM 

To: Charles D. Johnson; Curt Wells; Michael A. Palazzolo 

Subject: Secondary potline emissions from primary aluminum production facilities

 

Hello Chuck/Curt/Mike, 

 

Again I am reaching out to The Aluminum Association and the 

technical subcommittee for input and information on primary 
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aluminum production facilities. That is, I am soliciting 

information regarding potline secondary emissions and 

possible controls thereof – especially in prebake type 

facilities. Specifically, I have the following questions 

for you: 

 

• Is it possible or feasible to install wet roof scrubbers (such as those currently installed at the Intalco 

facility) on the existing prebake potlines? That is, are there constraints at the existing prebake facilities 

that would make it impossible to install similar wet roof scrubbers? 

 

• If wet roof scrubbers could be installed on the existing prebake potlines, what capital and annualized

costs would you expect for such retrofits (perhaps quick calculations based on historical costs at the

Intalco facility could provide a rough estimate)? 

 

• Does industry have any information as to what fraction of potline secondary particulate matter (PM) 

emissions are expected to be PM2.5 as opposed to PM? If so, what is the source of the estimate (e.g., 

testing, engineering judgement, etc.)? 

 

• Does industry have any information as to what fraction of potline secondary metals emissions are 

expected to be PM2.5 as opposed to PM? That is, do you have any reason to believe that the metals 

(especially nickel) would be distributed any differently than the “other” particulate matter? Again, if 

so, what is the source of the estimate (e.g., testing, engineering judgement, literature review, etc.)? 

 

• Does industry have any information (perhaps from historical testing at Intalco) as to the control 

efficiency, both for PM2.5 and for PM, expected from such wet roof scrubbers? 

 

Sorry to impose on you (again), but I’m hoping that you may 

have information that I do not have at this point. As 

always, please feel free to contact me if you need 

clarification of my information request or if you have any 

questions or comments. 

 

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