MEMORANDUM

To:		Rochelle Boyd, U.S. Environmental Protection Agency, OAQPS

From:		Mark Bahner and David Green, RTI  

Date:		January 4, 2012

Subject:	Draft Technology Review for the Secondary Aluminum Production
Source Category

Background

Requirements of Section 112(d)(6) of the CAA

Section 112 of the CAA requires EPA to establish technology-based
standards for sources of HAP. These standards are often referred to as
maximum achievable control technology, or MACT standards. Section 112
also contains provisions requiring EPA to periodically revisit these
standards. Specifically, paragraph 112(d)(6) states:

(6) REVIEW AND REVISION. – The Administrator shall review, and revise
as necessary (taking into account developments in practices, processes,
and control technologies), emissions standards promulgated under this
section no less often than every 8 years.

Description of the Secondary Aluminum Production Source Category and
Requirements of the Current NESHAP

The current National Emissions Standards for Hazardous Air Pollutants
(NESHAP) for the Secondary Aluminum Production source category was
promulgated on March 23, 2000  (65 FR 1690) as 40 CFR part 63, subpart
RRR. The rule was amended at 67 FR 79814, December, 30, 2002; 69 FR
18803, April 9, 2004; 69 FR 53984, September 3, 2004; 70 FR 75346,
October 3, 2005; and 70 FR 57517, December 19, 2005. The NESHAP applies
to affected sources of HAP emissions at secondary aluminum production
facilities. A secondary aluminum production facility is defined as any
establishment using clean charge, aluminum scrap, or dross from aluminum
production, as the raw material and performing one or more of the
following processes: scrap shredding, scrap
drying/delacquering/decoating, thermal chip drying, furnace operations
(i.e., melting, holding, sweating, refining, fluxing, or alloying),
recovery of aluminum from dross, in-line fluxing or dross cooling. A
secondary aluminum production facility may be independent or part of a
primary aluminum production facility. For purposes of the NESHAP,
aluminum die casting facilities, foundries and extrusion facilities are
not considered to be secondary aluminum production facilities if the
only materials they melt are clean charge, customer returns, or internal
scrap, and if they do not operate sweat furnaces, thermal chip dryers,
or scrap dryers/delacquering kilns/decoating kilns.

There are 161 secondary aluminum production facilities that are subject
to the NESHAP. Emission limits have been promulgated for particulate
matter (PM) as a surrogate for metal HAP, total hydrocarbons (THC) as a
surrogate for organic HAP other than dioxins and furans (D/F), dioxins
and furans are expressed as toxicity equivalents, and hydrogen chloride
(HCl) as a surrogate for acid gases, including hydrogen fluoride. HAP
are emitted from the following affected sources: aluminum scrap
shredders (regulated for PM), thermal chip dryers (THC and D/F), scrap
dryers/delacquering kilns/decoating kilns (PM, D/F, HCl and THC), sweat
furnaces (D/F), dross-only furnaces (PM), rotary dross coolers (PM),
group 1 furnaces (PM, HCl and D/F), and in-line fluxers (PM and HCl).
Group 2 furnaces and certain in-line fluxers are regulated by work
practices.  

Control devices currently in use to reduce emissions from affected
sources subject to the NESHAP include, fabric filters for control of PM
from aluminum scrap shredders; afterburners for control of THC and D/F
from thermal chip dryers; afterburners plus lime-injected fabric filters
for control of PM, HCl, THC and D/F from scrap dryers/delacquering
kilns/decoating kilns; afterburners for control of D/F from sweat
furnaces; fabric filters for control of PM from dross-only furnaces and
rotary dross coolers; lime-injected fabric filters for control of PM and
HCl from in-line fluxers; and lime-injected fabric filters for control
of PM, HCl and D/F from group 1 furnaces. All affected sources with
add-on controls are also subject to design requirements and operating
limits to minimize fugitive emissions.  

Developments in Practices, Processes, and Control Technologies

For the purposes of this technology review, a “development” was
considered to be a (n): 

add-on control technology that was not identified during the development
of the current NESHAP for the source category; 

improvement to an existing add-on control technology that could result
in significant additional HAP emissions reductions; 

work practice or operational procedure that was not identified during
development of the current NESHAP for the source category; or 

applicable process change or pollution prevention alternative that was
not identified and considered during the development of the current
NESHAP for the source category. 

We investigated developments in practices, processes and control
technologies through a literature review and discussions with industry
representatives, and included questions in a Section 114 information
collection request (ICR) that was sent to all companies thought to be
subject to the NESHAP. The results of these analyses are presented in
the following sections.

Literature review and industry contacts 

2.1.1.  Multichamber Delacquering Kiln/Melting Furnace

At least one company supplies multichamber furnaces that combine the
functions of a delacquering kiln and a melting furnace. This furnace has
the potential to reduce emissions, because all of the emissions from the
delacquering of used beverage cans and other coated scrap are swept into
another chamber where the delacquered scrap is melted. These emissions
are combusted in the melting chamber, reducing energy requirements;
destroying THC and D/F; and eliminating the need for an afterburner. A
multichamber furnace can therefore be used as a replacement for a
delacquering/decoating kiln (with afterburner) plus a group 1 furnace
handling only clean charge, or the multichamber furnace can be used as a
replacement for group 1 furnace handling other than clean charge.

At least 16 of these furnaces are in operation in Europe, Asia and the
Middle East. One furnace of this type is presently operating in the U.
S. and is permitted as a group 1 furnace handling other than clean
charge.

The emissions test data for the one multichamber furnace operating in
the U.S. indicate that the furnace does not produce lower D/F emissions
(in toxic equivalents, or TEQs) than any other group 1 furnace handling
other than clean charge, or than any delacquering/decoating kiln. Table
1 lists D/F emissions from the one multichamber furnace (operating at
Logan Aluminum). Table 1 also lists D/F emissions from three group 1
furnaces handling other than clean (i.e., “dirty”) charge, and three
delacquering/decoating kilns. The other furnaces and
delacquering/decoating kilns in Table 1 were selected because they had
low reported D/F emissions, and test reports were available to support
those reported emissions. The D/F emissions from these other sources are
lower than the D/F emissions from the multichamber furnace, indicating
that emissions from the multichamber furnace are not lower than any
other group 1 furnace handling other than clean charge, or any
delacquering/decoating kiln. Therefore, based on available information,
it is not clear that the multichamber furnace technology would reduce
HAP emissions relative to technologies that are already used by other
facilities in the U.S.

Table 1. Comparison of D/F Emissions from a Multichamber Furnace with
Other Technologies

RTI ID	Facility Name	Equipment ID	Equipment Type	Test Date
Test-Condition	Average D/F in ug/Mg TEQ(1) 

351	Logan Aluminum	Multichamber Furnace	Grp1 dirty charge	5/13/2008
1-50%Class I/50% Class III	1.061(2)

351	Logan Aluminum	Multichamber Furnace	Grp1 dirty charge	5/13/2008
1-100% Class I	0.461

351	Logan Aluminum	Multichamber Furnace	Grp1 dirty charge	5/14/2008
2-80% UBC’s/20% Class I	0.496

351	Logan Aluminum	Multichamber Furnace	Grp1 dirty charge	8/12/2008
1-50%Class I/50% Class III	0.26

421	Alcan Rolled Products	DC1M	Grp1 dirty charge	1/29-31/2008	1	0.023

335	Jupiter Aluminum	Furnace 2	Grp1 dirty charge	1/25/2010	1	0.027

211	Alumax Texarkana	EPN 011A	Grp1 dirty charge	4/20/2009	1	0.103

198	Novelis	P9A	Delacquering Kiln	10/01-02/2008	1	0.000419

198	Novelis	P9B	Delacquering Kiln	9/30-10/1/2008	1	0.000173

415	JL French	P30-1	Delacquering Kiln	6/22/2009	1	0.02

Average of three test runs, except where noted.

Average of two test runs.

2.1.2. Eddy Current Separators

Sweat furnaces are used in the secondary aluminum industry to separate
aluminum from ferrous metals. Certain types of scrap (primarily
automotive) are composed of individual pieces of metal, which contain
both aluminum and iron or steel. Automobile parts such as aluminum
engine blocks with cast iron cylinders, aluminum transmission cases with
steel gears and inserts and aluminum suspension components with steel
inserts are examples of sweat furnace feed. These materials, often
containing oil and grease, are separated by melting the aluminum from
the ferrous metals with higher melting points. The molten aluminum is
tapped to form ingots or “sows,” and the ferrous residue is raked
from the furnace. Sweat furnace emissions contain D/F, which results
from the combustion of the organic contaminants in the scrap.  

Eddy current separators are used to separate a concentrated aluminum
fraction from a heterogeneous scrap feed. These units operate at ambient
temperature and emit no D/F or other gaseous pollutants. Eddy current
separators are used to separate a concentrated aluminum fraction from a
heterogeneous scrap feed. These units operate at ambient temperature and
emit no D/F or other gaseous pollutants. They are used on the material
output from mechanical shredders that shred automobiles and appliances
(not on the aluminum scrap shredders used in the secondary aluminum
industry). These units can potentially decrease the need for sweat
furnaces. However, the product of eddy current separators is not an
aluminum ingot or sow, as with a sweat furnace. Therefore, the product
of eddy current separators must undergo further processing to produce an
aluminum ingot or sow, and it is not possible to directly compare eddy
current separators with sweat furnaces. 

2.1.3 Catalytic Filter Bags

Catalytic filtration systems, including catalytic filter bags, are
available to reduce D/F emissions. These bags incorporate an expanded
polytetrafluoroethylene membrane coated with a precious metal catalyst,
which promotes the oxidation of D/F. The manufacturer claims that this
system is installed in over 100 applications around the world, including
at least one secondary aluminum processing plant. To determine the
extent that these bags are in use in the secondary aluminum industry in
the U. S., a question was included in an information collection request
(ICR) sent to all identified secondary aluminum production facilities.
The question “Do you use catalytic filters for dioxin control (e.g.,  
HYPERLINK
"http://www.donaldson.com/en/industrialair/literature/051754.pdf" 
http://www.donaldson.com/en/industrialair/literature/051754.pdf  )?”
was answered no or “not applicable” by 126 of the 159 facilities
that responded. The remaining facilities did not answer this question.
We have insufficient information to conclude that this technology is
generally applicable to secondary aluminum production facilities, or to
estimate the extent of emission reductions that it might achieve. 

Responses to ICR

In an attempt to identify new emission control technologies in use, an
ICR was sent to all identified secondary aluminum production facilities.
To identify new technologies the following questions were asked:

• Please provide details for any alternative control devices (i.e.,
control devices other than fabric filters, lime-coated fabric filters,
or afterburners), monitoring (including particulate matter or HCI
continuous emissions monitors), or operating conditions at this facility
for equipment regulated under 40 CFR 63, subpart RRR. 

• Have you injected activated carbon or other type of sorbent for HAP
control (excluding research efforts)? What barriers do you envision to
adding carbon injection to fabric filters for HAP control?

• Do you have any plans to install any new higher efficiency rated
control devices or have any pending applications to add on any new
controls? 	

2.2.1 Activated Carbon Injection for D/F Control

Three respondents reported using activated carbon injection for control
of dioxin, and one respondent reported using activated carbon injection
previously on a unit that has since been shut down. Activated carbon is
typically added to control D/F, although in one case it was used with a
thermal chip dryer and may also have helped control THC. This technology
was known at the time of the development of the current standard and was
regarded as a possible control alternative for sources that were unable
to demonstrate compliance using lime-injected fabric filters. This
technology is suitable for retrofit to existing fabric filters. In
addition to the cost of the feeder system and carbon supply, all of the
added carbon ultimately adds to the mass of dust requiring disposal.
Carbon injection systems in other industries are typically about 80 to
90% efficient at D/F control.

2.2.2 Ammonia Injection for HCl Control

Four respondents reported injecting ammonia into furnace exhaust gas as
a means of HCl control. This technology was unknown at the time of
development of the current rule. At least one of the four respondents
plans to replace the lime currently used to control HCl emissions with
ammonia. It is not clear from the ICR responses whether the remaining
respondents reporting the use of this technology are replacing lime with
ammonia or adding ammonia in addition to lime. The HAP emission
reductions achieved from using this technology alone or in addition, to
lime injection are also not known. This technology is suitable for
retrofit to existing fabric filters. The applicability of this
technology is unlikely to be influenced by furnace configuration because
the ammonia is added between the furnace and the fabric filter. It has
the potential of decreasing the amount of fabric filter dust requiring
disposal, but would likely result in increased air emissions of ammonia,
which is not a HAP but may be problematic due to nitrogen deposition.

CONCLUSIONS: Recommended Revisions Based on Developments in Practices,
Processes and Control Technologies

     

This review identified several developments in practices, processes or
control technologies that have been implemented in this source category
since promulgation of the current NESHAP. These technologies are not in
use by a substantial number of secondary aluminum production facilities
in the U. S. One possible reason for this is that facilities are able to
meet the current MACT emission limits without using them. In other
industries, such as Portland cement and electric arc steel mills, D/F
emission reductions of 80-90 percent have been achieved with the
addition of activated carbon injection.  

In general, existing technologies can be adapted to achieve lower
emissions. For example, decreased HCl emissions might be achieved by
increasing the lime injection rate.  Decreased THC emissions might be
achieved by increasing afterburner temperature. If more stringent
risk-based standards are justified, it is likely that either
improvements to existing control devices, implementation of new
technologies or pollution prevention techniques will be selected on the
basis of overall cost and reliability. None of the newer technologies
have supporting test data that justify more stringent technology-based
standards. The technologies implemented since the development of the
current NESHAP may provide a means for decreasing HAP emissions from
secondary aluminum production, however there are insufficient data to
justify more stringent technology-based standards for either new or
existing sources.  

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