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 EP A 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 M ercury 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

- spec ific processes:



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

- bound mercury (Hg) and for vapor phase Hg

. T he amount of particulate

- bound Hg is probably much lower in brick kilns than in coal

- fired boilers due to t he 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, t h e white paper discus ses the necessary temperature

range with in which the oxidation of elemental Hg and subsequent homogeneous HgCl 2 reaction
is most active. The transformation to HgCl 2 is necessary for capture by the carbon injection. The evolution of Hg from brick body mate rials 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 HgCl 2 reaction necessary to support the oxidized Hg collection scenari os. 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. Envir onmental Protection Agency. February 18. 2005.a dditional 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 HgCl 2 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 cak e” 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 HgCl 2 . Also EPA has suggested a n in

- s eries 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 HgCl 2 formation and thus the Hg removal efficiency in the ACI control. 

### 5. Reviewing the few case hi stori es 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 c ould 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 s orbent 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 co ntent 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 generall y depicted as “unproven”. The paper identifies data/science gaps and associated recommendations and goes into great detail on various reduction scenarios with the bottomline being that there is little actual longer term history. Transfer of unproven tech nology 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 metho dologies 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, q uantity 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 numeric al 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 memorandu m.