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EXECUTIVE SUMMARY 15 Salts Waste salts are formed by neutralization of the acid products of agent and energetics oxidation. The mount of waste salts varies, from around 2 pounds per pound of agent, when no carbon dioxide is captured, to about 10 pounds per pound of agent, when carbon dioxide is captured and excess base is used. These waste salts must be dried, heated, and tested to establish the absence of agent before their disposal as hazardous waste, or they must be given 5X decontamination treatment (1000°F for 15 minutes), which eliminates any residual agent and other organic compounds. Liquid Wastes Water is formed by oxidation of agent, energetics, and fuel. In addition, it is used for cooling, waste gas scrubbing, and decontamination. It can be discarded as vapor in flue gas or as liquid waste. After treatment to remove contaminants, it could also be recycled in the facility to minimize discharge to the environment. Liquid water discharge from the facility must meet applicable standards for purity. Technology is available for water purification and must be integrated into the total operation. STRATEGIES AND SYSTEM IMPLICATIONS FOR DEMILITARIZATION As mentioned above, alternative technologies and processes could be applied in many combinations to achieve demilitarization of chemical weapons. Although this report does not offer recommendations for specific processes that the Army should pursue, it does suggest some general strategies. The committee identified two broad strategies that could be used to achieve demilitarization of agent and weapons, eliminate risks to surrounding communities from continued storage of agent, and dispose of waste streams appropriately and safely. Strategy 1. On-site disassembly and agent detoxification to meet treaty demilitarization requirements and permit transportation to another site or continued local storage of residues. In Strategy 1, liquid-phase processes could be used to decompose agent to meet demilitarization requirements. Final oxidation of all organic residues, energetics destruction, and decontamination of metals could be deferred by
EXECUTIVE SUMMARY 16 continued local storage or conducted at another site to which the materials could be transported for final treatment. Criteria to establish the acceptability of materials for transport to other sites would still need to be determined on the basis of both technical and political considerations. Agent. In Strategy 1, several processes or technologies might be used for agent detoxification: ⢠low-pressure, liquid-phase chemical detoxification; ⢠low-pressure, liquid-phase oxidation with the use of oxidizing compounds; and ⢠high-pressure, wet air or supercritical water oxidation. Again, all the low-temperature, liquid-phase processes are still at the stage of laboratory research. Each type of chemical warfare agent may require a separate chemical destruction process, in which case three new processes would have to be developed. However, it may be possible to use common equipment if the same materials can be used for all three processes. Waste gas production is generally small for such processes. High-pressure, wet air oxidation and high-pressure supercritical water oxidation can detoxify and demilitarize agent; however, some organic compounds remain. The waste gas stream contains organic chemical compounds and may require further treatment. The gas handling problem is reduced if pure oxygen is used, which is normal practice for supercritical water oxidation but would require additional development of wet air oxidation. The waste gas stream from all these processes could be further reduced by capture of carbon dioxide with lime. Energetics and contaminated metal pans and containers. In Strategy 1, energetics and contaminated parts and containers would be treated with decontamination fluid to allow continued storage or transportation to another site. In some cases, drainage of agent from containers is quite incomplete (especially for some batches of mustard agent). Facilities to remove most of the remaining undrained agent would be needed to detoxify the containers with decontamination fluid. Strategy 1 could essentially eliminate local discharge of flue gas, meet the treaty requirements for demilitarization, and eliminate the risk of agent release from continued storage. However, it would require additional time (5 to 12 years) for research, development, and demonstration of new technologies. The medium- temperature, high-pressure, wet air and supercritical water oxidation systems are in the pilot plant stage and would require development and special attention to ensure safety. The process to remove the residual agent from drained weapons and containers would also
EXECUTIVE SUMMARY 17 need to be developed. However, this strategy would allow delaying final disposal of energetics, metal parts contaminated with agent, and residual salts. Strategy 2 Conversion of agent and disassembled weapons to salts, carbon dioxide, water, and decontaminated metal (complete oxidation or mineralization). In Strategy 2, mineralization is completed and there is therefore no requirement for transportation or long- term storage of organic residues from detoxification and treatment of agent, energetics, metal parts, or containers. Demilitarization is achieved by oxidation and heat treatment. Agent. Agent mineralization can be accomplished in two steps: preliminary detoxification followed by additional processing to complete oxidation, as in the treatment of GB by hydrolysis and then incineration (see Chapter 3). Mineralization can also be accomplished in one step as in the baseline process. One-step approaches for complete oxidation of agent include the following: ⢠the current baseline system plus charcoal-filter adsorption of flue gas; ⢠the current baseline system plus storage and certification of flue gas; ⢠low-temperature, liquid-phase oxidation; ⢠medium-temperature, high-pressure, wet air or supercritical water oxidation plus follow-up oxidation (chemical, biological, or with an afterburner); ⢠fluidized-bed or molten salt oxidation with the use of an afterburner; ⢠plasma arc or molten metal pyrolysis with an afterburner; and ⢠steam gasification with an afterburner. For the two-step approach, one of the processes above would be preceded by one of the processes identified under Strategy 1. The alternative system that would entail the least increase in delay and complexity for the Army disposal program would be the baseline technology augmented by the use of activated-carbon beds (charcoal filters) or by storage and certification of gas waste streams. Low-temperature, liquid-phase oxidation with the use of strong oxidizing compounds is attractive because of low emissions of waste gas, but it is only in the research stage. Supercritical water and wet air oxidation with the use of oxygen might also be used for complete oxidation, but a final oxidizing
EXECUTIVE SUMMARY 18 process for residual organic compounds might also be necessary; pilot plant studies of these processes with hazardous compounds are underway. However, several more years of development are probably needed before demonstration. Fluidized-bed combustion and molten salt oxidation operate at lower temperatures than those for conventional combustion. Both have been used for toxic waste disposal, but both would require further development and demonstration for agent destruction. The oxidation efficiency of these operations can be high, but afterburners for the waste gas streams would still be required. The waste gas products from plasma arc and molten metal pyrolysis must be burned, probably in a primary burner combined with an afterburner system. Because electrical energy instead of fuel combustion supplies the heat in these processes, the volume of waste gas would be reduced. Use of oxygen in the follow-up burners can further reduce flue gas, as in other high-temperature systems. Demonstration pilot plants for these processes could probably be designed and built to solve operational problems and demonstrate the performance of the developed systems. High-temperature reaction with steam has most of the features of the high-temperature pyrolysis systems. Energetics and contaminated metal parts and ton containers. In Strategy 2, high-temperature processes are needed to handle the very heterogeneous waste stream of energetics and metal parts and containers. The baseline technology uses two internally fired kilns. There are several alternatives to this approach: ⢠the baseline kilns plus charcoal adsorption or gas storage and certification; ⢠externally heated kilns plus a new afterburner (types of afterburners that would not require internal firing include electrically heated catalytic combustion and supercritical water oxidation); and ⢠molten metal or plasma arc melting furnaces plus a new afterburner. Addition of storage and certification capability or activated-carbon adsorption to the baseline kilns would convert them to closed-loop systems without requiting additional demonstration. The amount of flue gas resulting from internal firing with fuel is large, however, and could be reduced by the use of electrically heated kilns and afterburners. Demonstration and testing would be needed for both these kilns and their afterburners. Modification and testing of the pollution abatement system, which removes acid gases, would also be necessary.
