6
Use and Disposal of Sulfur-Impregnated Carbon for Mercury Adsorption

As noted in Chapter 2, the pollution abatement system (PAS) filtration systems (PFSs) for the process gas streams from the liquid incinerators (LICs), metal parts furnace (MPF), and deactivation furnace system (DFS) at the Anniston, Pine Bluff, and Umatilla Chemical Agent Disposal Facilities (ANCDF, PBCDF, and UMCDF) were added to reassure the public that residual agent would not escape from the incineration pollution abatement systems. A PFS was not included at the Johnston Atoll Chemical Agent Disposal System, but one was being added at the Tooele Chemical Agent Disposal Facility (TOCDF) to control mercury as this report was being prepared.

When mercury was discovered in the mustard agent HD/HT ton containers at TOCDF, PBCDF, and UMCDF, the U.S. Army’s Chemical Materials Agency (CMA) was required to develop a strategy to control the emission of mercury during the incineration of HD/HT. Unlike the agent, mercury is not destroyed in the LIC, MPF, or DFS or their associated PAS units but persists in one form or another throughout these processes. CMA has concluded that using sulfur-impregnated activated carbon in the PFS during HD/HT processing is an effective method of controlling mercury emissions during the processing of mercury-contaminated HD/HT. Mercury adsorption by sulfur-impregnated carbon has been studied extensively (Liu et al., 1998; Hsi et al., 1998; Karatz et al., 2000; Dsi et al., 2001; Jurng et al., 2002; Kilgroe and Senior, 2003; Feng et al., 2006; Uddin et al., 2008). Tests of mercury adsorption from simulated coal combustion flue gases indicate that sulfur-impregnated carbon is able to capture about 2.5 mg metallic mercury per gram carbon and about 1.5 mg of HgCl2 per gram carbon (Hsi et al., 1998).

At UMCDF, ANCDF, and PBCDF, the existing activated carbon beds in the PFS units will be replaced with sulfur-impregnated carbon before HD/HT processing. At TOCDF, a PFS with sulfur-impregnated carbon is being installed before the remaining mustard ton containers and munitions are destroyed. The configuration of the PFS units at UMCDF, ANCDF, and PBCDF is identical. The TOCDF PFS is different from a design perspective.

The expected presence of mercury in the sulfur-impregnated carbon beds poses a new issue for disposal of activated carbon from chemical agent disposal facilities.

KNOWN CHARACTERISTICS OF MUSTARD AGENT STOCKPILES

The HD/HT stockpiles contain bulk storage ton containers and munitions; all of the HD ton containers have been found to contain some mercury, although the amount varies. The semisolid heels of mustard agent at TOCDF are the largest sources of mercury-contaminated mustard agent.

All 6,398 HD/HT ton containers at TOCDF have now been sampled, and some sampling has also been conducted at PBCDF. At TOCDF, 906 (13.5 percent) of the containers registered mercury concentrations in the liquid agent that were above the practical quantification



The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement



Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.

OCR for page 49
6 Use and Disposal of Sulfur-Impregnated Carbon for Mercury Adsorption As noted in Chapter 2, the pollution abatement fur-impregnated carbon is able to capture about 2.5 mg system (PAS) filtration systems (PFSs) for the process metallic mercury per gram carbon and about 1.5 mg of gas streams from the liquid incinerators (LICs), metal �gCl2 per gram carbon (�si et al., 1998). parts furnace (MPF), and deactivation furnace sys- At UMCDF, ANCDF, and PBCDF, the existing acti- tem (DFS) at the Anniston, Pine Bluff, and Umatilla vated carbon beds in the PFS units will be replaced with Chemical Agent Disposal Facilities (ANCDF, PBCDF, sulfur-impregnated carbon before �D/�T processing. and UMCDF) were added to reassure the public that At TOCDF, a PFS with sulfur-impregnated carbon is residual agent would not escape from the incineration being installed before the remaining mustard ton con- pollution abatement systems. A PFS was not included tainers and munitions are destroyed. The configuration at the Johnston Atoll Chemical Agent Disposal System, of the PFS units at UMCDF, ANCDF, and PBCDF is but one was being added at the Tooele Chemical Agent identical. The TOCDF PFS is different from a design Disposal Facility (TOCDF) to control mercury as this perspective. report was being prepared. The expected presence of mercury in the sulfur- When mercury was discovered in the mustard impregnated carbon beds poses a new issue for dis- agent �D/�T ton containers at TOCDF, PBCDF, and posal of activated carbon from chemical agent disposal UMCDF, the U.S. Army’s Chemical Materials Agency facilities. (CMA) was required to develop a strategy to control the emission of mercury during the incineration of �D/�T. kNOWN CHARACTERISTICS OF Unlike the agent, mercury is not destroyed in the LIC, MUSTARD AGENT STOCkPILES MPF, or DFS or their associated PAS units but persists in one form or another throughout these processes. The �D/�T stockpiles contain bulk storage ton CMA has concluded that using sulfur-impregnated containers and munitions; all of the �D ton containers activated carbon in the PFS during �D/�T processing have been found to contain some mercury, although is an effective method of controlling mercury emissions the amount varies. The semisolid heels of mustard during the processing of mercury-contaminated �D/ agent at TOCDF are the largest sources of mercury- �T. Mercury adsorption by sulfur-impregnated carbon contaminated mustard agent. has been studied extensively (Liu et al., 1998; �si et al., All 6,398 �D/�T ton containers at TOCDF have 1998; Karatz et al., 2000; Dsi et al., 2001; Jurng et al., now been sampled, and some sampling has also been 2002; Kilgroe and Senior, 2003; Feng et al., 2006; conducted at PBCDF. At TOCDF, 906 (13.5 percent) of Uddin et al., 2008). Tests of mercury adsorption from the containers registered mercury concentrations in the simulated coal combustion flue gases indicate that sul- liquid agent that were above the practical quantification 

OCR for page 49
0 DISPOSAL OF ACTIVATED CARBON FROM CHEMICAL AGENT DISPOSAL FACILITIES FATE OF MERCURY WITHIN THERMAL limit and 1,602 had high amounts of solids (heels).1 At DESTRUCTION PROCESSES AT CHEMICAL the time this report was prepared, the committee had AGENT DISPOSAL FACILITIES no definitive information on the mercury content in mustard agent munitions. Given the diverse uses of activated carbon at chemi- Fewer samples have been taken of the heels than of cal agent disposal facilities and the focus of this report the liquid-phase agent. In general, despite significant on disposal options for activated carbon from these scatter in the data, high concentrations of mercury facilities, it is important to understand that the adsorp- in liquid-phase agent suggest even higher mercury tion of mercury and the adsorption of agent onto concentrations in the accompanying heel. When the activated carbons occur in physically different carbon amount of the mercury in the heels of 96 ton containers filter units in separate locations during �D/�T thermal was measured, 18 of them averaged mercury levels of destruction. There is virtually no opportunity for both 2,440 mg/kg (2,440 parts per million (ppmw)), while mercury and agent to be adsorbed onto the same car- the average concentration of mercury in liquid-phase bon bed during normal operations at chemical agent agent was 22 ppmw. CMA believes that many muni- disposal facilities. tions and ton containers contain some heel (UDEQ, As shown in Table 2-1, activated carbon is expected 2008). Based on historical documentation, the mercury to be exposed to agent when the latter volatilizes into contamination in ton containers at UMCDF should be the ambient air during disassembly and preprocessing similar to that at TOCDF. Information on the mercury of munitions and ton containers in Level A areas. This content of munitions at UMCDF as well as �D/�T contaminated air flows through the heating, ventilation, stockpiles at ANCDF and PBCDF was not available and air conditioning (��AC) systems of the munitions when this report was being prepared. demilitarization building (MDB) to the ��AC filter Destruction of the heel portion of �D/�T requires units, where the agent is captured. special processing because it is generally too viscous �owever, no mercury is expected in the MDB to be extracted from the containers or munitions by ��AC air. Although the ton containers will be opened simply pumping or draining. Also, early test burns of to the atmosphere in the MDB rooms, the volatilization containers with large heels revealed that boiling over of the contents was a problem.2 TOCDF is permitted of elemental mercury will be negligible. The tendency of a liquid to evaporate at a specified temperature to destroy ton containers holding up to 632 lb heel depends on its vapor pressure at that temperature. The in the MPF, but it has set a more conservative upper vapor pressure of elemental mercury is 2.47 × 10–4 kPa limit of 550 lb per container.3 Also, it has developed at 27°C. Any mercury salts would be insoluble or ion- a special procedure for handling ton containers with ized in solution. Thus, the low vapor pressure of ele- heels exceeding this limit—namely, it mobilizes and mental mercury and the nonvolatility of ionic mercury dissolves the heel by flushing with jets of hot water. salts in solution virtually eliminate the possibility that Then the rinsate is transferred to empty ton containers, the MDB ��AC air would contain mercury in con- which are treated in the MPF. This flushing process centrations of any significance with respect to human completely dissolves the heel. UMCDF is adopting the health and safety, nor would the activated carbon in the same processes to identify and flush ton containers hav- MDB ��AC system filters be exposed to mercury over ing a high content of heel and to transfer the resultant the duration of the mustard agent disposal campaign rinsate into transfer ton containers. to an extent that would be of regulatory concern with respect to mercury. No agent is expected to be found on the PFS carbons because in normal operation, the two-stage design of the LIC, MPF, and DFS provides a more than sufficient 1Personal communication between Gary McCloskey, TOCDF time-temperature history for the constituent elements General Manager, URS Corporation, EG&G Division, and Robert o f mustard agent—hydrogen, carbon, sulfur, and Beaudet, committee chair, March 4, 2009. chlorine—to be fully converted to common gaseous 2Information gathered from committee site visit to TOCDF, combustion products such as �Cl, SOx, NOx, �2O, and September 4, 2008. 3Information gathered from committee site visit to TOCDF, CO2. Because �Cl and SO2 are soluble in aqueous solu- September 4, 2008.

OCR for page 49
 USE AND DISPOSAL OF SULFUR-IMPREGNATED CARBON tions, they are efficiently removed by the wet venturi containing mercury should be disposed of separately and tower scrubbers in the PAS (see Chapter 1, Figure from other activated carbons used at chemical agent 1-1). The PAS does not offer any control of NOx, and disposal facilities. If generator knowledge confirms trial burns to destroy �D/�T in the MPF at TOCDF that mercury-containing carbon has not been exposed have demonstrated NOx concentrations on the order to agent, it should be shipped off-site for disposal of 30 ppm.4 in compliance with existing regulations governing The exposure of activated carbon to mercury is mercury-containing solid wastes. expected to occur exclusively in the PFS units. PFS Recommendation 6-1b. In the unlikely event that an carbon beds at the disposal facilities are situated down- stream of the PAS units for the LIC, MPF, and DFS operational upset were to cause both mercury and agent and will not be exposed to any agent under normal to be deposited on the sulfur-impregnated carbon of operation. Furthermore, because the PFS carbon beds the pollution abatement system filtration system, the are situated downstream of the wet scrubbing processes permit might not allow shipping the carbon off-site for in the PAS, trace concentrations of water-soluble com- disposal, even if sufficient time had elapsed for agent pounds are found in the gas phase; however, no water- on the carbon to degrade. In this case, fresh carbon insoluble products of agent thermal destruction (e.g., should be installed in the pollution abatement system CO2) and contaminant thermal oxidation (e.g., �g0) filtration system. The agent- and mercury-contaminated would be found. carbon should be processed through the metal parts If an upset were to occur (unlikely) and agent were furnace, thereby destroying the agent and transfer- to pass through the incinerator’s PAS, then both agent ring the mercury to the fresh (agent-free) carbon of and mercury would be present on the carbon. This the pollution abatement system filtration system. This would pose a problem, because regulations might not mercury-containing carbon, no longer having agent, allow the carbon to be shipped to a TSDF, and the could then be shipped off-site for disposal. TSDF might not accept waste containing both agent and mercury. Then, the mercury or the agent would REFERENCES have to be separated from the carbon. Dsi, �., M. Rood, M. Rostam-Abadi, S. Chen, and R. Chang. 2001. Ef- fects of sulfur impregnation temperature on the properties and mercury Finding 6-1a. Carbons exposed to agent will not be adsorption capacities of activated carbon fibers (ACFs). Environmental exposed to mercury in the gas streams handled by the Science and Technology 35(13): 2785-2791. heating, ventilation, and air conditioning system of Feng, W., E. Borguet, and R.�idic. 2006. Sulfurization of a carbon surface for vapor phase mercury removal—II: Sulfur forms and mercury uptake. the munitions demilitarization building. No agent will Carbon 44(14): 2998-3004. be present in the gas streams handled by the pollution �si, �., S. Chen, M. Rostam-Abadi, M. Rood, C. Richardson, T. Carey, and abatement system filtration system under normal oper- R. Chang. 1998. Preparation and evaluation of coal-derived activated carbons for removal of mercury vapor from simulated coal combustion ating conditions. flue gases. Energy & Fuels 12(6): 1061-1070. Jurng, J., T. Lee, G. Lee, S. Lee, B. Kim, and J. Seier. 2002. Mercury re- Finding 6-1b. When mercury-containing mustard moval from incineration flue gas by organic and inorganic adsorbents. Chemosphere 47(9): 907-913. agent �D/�T is being destroyed, no agent will be pres- Karatz, D., A. Lancia, D. Musmarra, and C. Zucchini. 2000. Study of ent in the gas streams exiting the pollution abatement mercury adsorption and desorption on sulfur impregnated carbon. Ex - system units for the liquid incinerator, deactivation perimental Thermal and Fluid Science 21(1-3): 150-155. furnace system, and metal parts furnace. �owever, Kilgroe, J., and C. Senior. 2003. Fundamental Science and Engineering of Mercury Control in Coal-Fired Power Plants. Arlington, �a.: Air Qual- mercury will be present, so the Army is installing ity I� Conference. sulfur-impregnated carbon in the pollution abatement Liu, W., R. �idic, and T. Brown. 1998. Optimization of sulfur impregnation system filtration system to capture it. protocol for fixed-bed application of activated carbon-based sorbents for gas-phase mercury removal. Environmental Science and Technology 32(4): 531-538. Recommendation 6-1a. T he pollution abatement UDEQ (Utah Department of Environmental Quality). 2008. TOCDF 2003 system filtration system sulfur-impregnated carbon �D Ton Container �eel Sampling, �igh Mercury Results. Salt Lake City: Utah Department of Environmental Quality. Uddin, A., T. Yamada, R. Ochiai, and E. Sasaoka. 2008. Role of SO2 for 4Information gathered from committee site visit to TOCDF, elemental mercury removal from coal combustion flue gas by activated September 4, 2008. carbon. Energy & Fuels 22(4): 2284-2289.