Disposal of Activated Carbon from Chemical Agent Disposal Facilities (2009)

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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 HgCl2 per gram carbon (Hsi 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 HD/HT 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 HD/HT 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 HD/HT. 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 HD/HT stockpiles contain bulk storage ton CMA has concluded that using sulfur-impregnated containers and munitions; all of the HD ton containers activated carbon in the PFS during HD/HT 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 HD/ agent at TOCDF are the largest sources of mercury- HT. Mercury adsorption by sulfur-impregnated carbon contaminated mustard agent. has been studied extensively (Liu et al., 1998; Hsi et al., All 6,398 HD/HT 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 49 

50 DISPOSAL OF ACTIVATED CARBON FROM CHEMICAL AGENT DISPOSAL FACILITIES limit and 1,602 had high amounts of solids (heels). At FATE OF MERCURY WITHIN THERMAL the time this report was prepared, the committee had DESTRUCTION PROCESSES AT CHEMICAL no definitive information on the mercury content in AGENT DISPOSAL FACILITIES mustard agent munitions. Fewer samples have been taken of the heels than of Given the diverse uses of activated carbon at chemi- the liquid-phase agent. In general, despite significant cal agent disposal facilities and the focus of this report scatter in the data, high concentrations of mercury on disposal options for activated carbon from these in liquid-phase agent suggest even higher mercury facilities, it is important to understand that the adsorp- concentrations in the accompanying heel. When the tion of mercury and the adsorption of agent onto amount of the mercury in the heels of 96 ton containers activated carbons occur in physically different carbon was measured, 18 of them averaged mercury levels of filter units in separate locations during HD/HT thermal 2,440 mg/kg (2,440 parts per million (ppmw)), while destruction. There is virtually no opportunity for both the average concentration of mercury in liquid-phase mercury and agent to be adsorbed onto the same car- agent was 22 ppmw. CMA believes that many muni- bon bed during normal operations at chemical agent tions and ton containers contain some heel (UDEQ, disposal facilities. 2008). Based on historical documentation, the mercury As shown in Table 2-1, activated carbon is expected contamination in ton containers at UMCDF should be to be exposed to agent when the latter volatilizes into similar to that at TOCDF. Information on the mercury the ambient air during disassembly and preprocessing content of munitions at UMCDF as well as HD/HT of munitions and ton containers in Level A areas. This stockpiles at ANCDF and PBCDF was not available contaminated air flows through the heating, ventilation, when this report was being prepared. and air conditioning (HVAC) systems of the munitions Destruction of the heel portion of HD/HT requires demilitarization building (MDB) to the HVAC filter special processing because it is generally too viscous units, where the agent is captured. to be extracted from the containers or munitions by However, no mercury is expected in the MDB simply pumping or draining. Also, early test burns of HVAC air. Although the ton containers will be opened containers with large heels revealed that boiling over to the atmosphere in the MDB rooms, the volatilization of the contents was a problem. TOCDF is permitted of elemental mercury will be negligible. The tendency to destroy ton containers holding up to 632 lb heel of a liquid to evaporate at a specified temperature in the MPF, but it has set a more conservative upper depends on its vapor pressure at that temperature. The limit of 550 lb per container. Also, it has developed vapor pressure of elemental mercury is 2.47 × 10–4 kPa a special procedure for handling ton containers with at 27°C. Any mercury salts would be insoluble or ion- heels exceeding this limit—namely, it mobilizes and ized in solution. Thus, the low vapor pressure of ele- dissolves the heel by flushing with jets of hot water. mental mercury and the nonvolatility of ionic mercury Then the rinsate is transferred to empty ton containers, salts in solution virtually eliminate the possibility that which are treated in the MPF. This flushing process the MDB HVAC air would contain mercury in con- completely dissolves the heel. UMCDF is adopting the centrations of any significance with respect to human same processes to identify and flush ton containers hav- health and safety, nor would the activated carbon in the ing a high content of heel and to transfer the resultant MDB HVAC system filters be exposed to mercury over rinsate into transfer ton containers. the duration of the mustard agent disposal campaign 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 Personal communication between Gary McCloskey, TOCDF the LIC, MPF, and DFS provides a more than sufficient time-temperature history for the constituent elements General Manager, URS Corporation, EG&G Division, and Robert Beaudet, committee chair, March 4, 2009. of mustard agent—hydrogen, carbon, sulfur, and Information gathered from committee site visit to TOCDF, chlorine—to be fully converted to common gaseous September 4, 2008. combustion products such as HCl, SOx, NOx, H2O, and Information gathered from committee site visit to TOCDF, CO2. Because HCl and SO2 are soluble in aqueous solu- September 4, 2008. 

USE AND DISPOSAL OF SULFUR-IMPREGNATED CARBON 51 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 HD/HT 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. 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 carbon beds at the disposal facilities are situated down- Recommendation 6-1b.  In the unlikely event that an 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., Hg0) 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, H., 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.Vidic. 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 Hsi, H., 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. agent HD/HT is being destroyed, no agent will be pres- Chemosphere 47(9): 907-913. 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. However, Kilgroe, J., and C. Senior. 2003. Fundamental Science and Engineering of Mercury Control in Coal-Fired Power Plants. Arlington, Va.: Air Qual- mercury will be present, so the Army is installing ity IV Conference. sulfur-impregnated carbon in the pollution abatement Liu, W., R. Vidic, 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.  The pollution abatement UDEQ (Utah Department of Environmental Quality). 2008. TOCDF 2003 system filtration system sulfur-impregnated carbon HD Ton Container Heel Sampling, High Mercury Results. Salt Lake City: Utah Department of Environmental Quality. Uddin, A., T. Yamada, R. Ochiai, and E. Sasaoka. 2008. Role of SO2 for Information 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.