MACT Task Force

MEMORANDUM

Date: December 5, 2013

To: Jeff Telander, EPA/SSPD

From: Terry Schimmel

Subject: Review of Activated Carbon Injection and the Applicability to the Brick Industry

A key factor in the accuracy of EPA’s estimate of the nationwide economic impacts of controlling 

mercury emissions from the brick industry is the validity of the assumption that technology can be easily 

transferred from a non-related industry, such as coal-fired electric utility boilers. However, the EPA has

provided no information that demonstrates that this technology relates in any way to brick 

manufacturing. BIA is unaware of any data that exists to support the assumptions equating these two 

processes. A review of the white paper entitled, “Control of Mercury Emissions from Coal Fired Electric 

Utility Boilers: An Update”1, revealed the following issues with simply scaling the costs of these 

technologies without consideration of additional equipment and operating costs to adapt the controls 

for brick-specific processes:

1. A direct scaling of costs assumes similar efficiencies can be achieved for particulate-bound 

mercury (Hg) and for vapor phase Hg. The amount of particulate-bound Hg is probably much 

lower in brick kilns than in coal-fired boilers due to the absence of fly ash and/or unburned 

carbon. As such any efficiency with the collection of Hg via particulate removal can be assumed 

to be significantly less than that achieved in boilers.

2. For the collection of the vapor phase Hg, the white paper discusses the necessary temperature 

range within which the oxidation of elemental Hg and subsequent homogeneous HgCl2 reaction 

is most active. The transformation to HgCl2 is necessary for capture by the carbon injection. The 

evolution of Hg from brick body materials in a brick kiln may occur at temperatures that are 

lower than in a boiler because the temperature rise in a brick kiln is very different than what 

happens when fuel is injected into a coal fired combustion chamber. This will, in turn, hamper 

the HgCl2 reaction necessary to support the oxidized Hg collection scenarios. At a minimum, 

 

1

Control of Mercury Emissions from Coal Fired Electric Utility Boilers: An Update. Air Pollution Prevention and 

Control Division. Office of Research and Development. U.S. Environmental Protection Agency. February 18. 2005.
additional equipment costs for optimizing the exhaust gas temperature would likely need to be 

considered.

3. If the majority of Hg from firing brick is emitted as elemental mercury, this article suggests that 

collection efficiencies may be minimal or at least greatly reduced as compared to the oxidized 

Hg collection scenarios discussed in this white paper. Again the assumption of similar 

efficiencies comes into question if the control of HgCl2 is assumed the same as for elemental Hg 

possibly emitted from a brick kiln. To our knowledge, EPA nor BIA has any speciated data for 

brick kiln emissions.

4. In a fabric filter, the amount of HCl available at the ‘filter cake” may play a big role in collection 

efficiencies of elemental Hg. It could be logical to anticipate that DIFFs on sites with low HCl 

materials could see minimal Hg collection efficiencies because of the reduced formation of 

HgCl2. Also EPA has suggested an in-series post DLA/DIFF ACI scenario as one compliance option 

for Hg. control. It would be logical to think that stripping out the HCl first will reduce HgCl2 

formation and thus the Hg removal efficiency in the ACI control.

5. Reviewing the few case histories on coal fired boiler Hg reductions where flue gas 

concentrations are cited, it appears that most inlet concentrations were in a range of 5 times 

higher than that of brick best performers. As such outlet results may still be comparable but 

efficiencies could be expected to be proportionately lower. “Efficiencies” due to lower inlet 

concentrations and cost/benefit analysis could be expected to be lower in a brick kiln scenario. 

Cited outlet concentrations in ug/dNm3 vs. sorbent injection rates were as follows: 4.7 at 11 

pounds, <5.4 at 10 pounds, COHPAC 1.0 at 1.5 pounds, E3 .6 at 3 pounds. The COPAC and E3 

tests utilized a proprietary designer sorbent formulation. Most coal boiler inlet concentrations 

tested were in the 17ug/dNm3 range. Bricks appear to be between .5 and 3. This would seem to 

either dictate higher injection rates to be necessary for given efficiencies, more elaborate gas 

mixing arrangements, longer retention times and etc. Consideration of a sound engineering 

approach to determining the sorbent injection rates as it would be applied to the low inlet 

concentrations from a brick kiln exhaust needs to integrated into the costing model.

6. Additional sorbent injection comparison problems cited in this paper that further support the 

need for more accurate cost estimates include:

a. Waste combustor collection history of Hg is generally at an order of magnitude higher inlet 

concentration.

b. Waste combustors generally have much higher levels of Cl to support the HgCl2 reaction 

due to high plastics content of feed stock etc.

c. Air volumes are much lower in waste combustors and those scrubber systems generally 

have elaborate systems to mix sorbents into the flue gas.

7. Powdered Activated Carbon (PAC) Injection Systems at the date of this paper were generally 

depicted as “unproven”. The paper identifies data/science gaps and associated 

recommendations and goes into great detail on various reduction scenarios with the bottom 
line being that there is little actual longer term history. Transfer of unproven technology is 

unsound engineering practice and undermines the foundation of the economic analysis.

Mercury emissions from brick manufacturing are not well understood at this time. Not only is there lack 

of knowledge regarding the form of mercury that is emitted, there is confusion regarding the amount of 

mercury emitted. Stack tests resulting from EPA’s Information Collection Request revealed that the 

testing and analytical methodologies are inconsistent across testing firms and laboratories. These 

inconsistencies lead to discrepancies in the reporting of values that are in many cases below detection 

levels. Regulation without understanding basic information, such as the form, quantity and 

controllability of mercury is not sound policy. No true estimate of the costs can be developed by the 

EPA when there is no basis for asserting that these controls would work.

Based on these findings, BIA requests that EPA delay setting numerical mercury limits for the brick and 

structural clay products category until a time when EPA can fully understand both the generation and 

evolution of the mercury compounds emitted from brick kilns and can address the key issues identified 

in this memorandum.