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Alternative Technologies for the Destruction of Chemical Agents and Munitions Executive Summary The U.S. Department of Defense, through its executive agent the U.S. Army, is embarked on a Chemical Stockpile Disposal Program (CSDP) to destroy the nation's unitary chemical weapons.1 There are about 25,000 tons of chemical warfare agents in the U.S. stockpile, primarily the nerve agents GB and VX and the blister, or mustard, agents H, HD, and HT. These agents are contained in a variety of munitions and in bulk containers that are distributed among eight continental U.S. sites and Johnston Island in the Pacific Ocean. The baseline incineration technology, developed by the Army, has undergone Operational Verification Testing at Johnston Island, to demonstrate that it can be used to destroy agent and weapons safely and meet all environmental standards. The baseline technology entails the transport of weapons from storage to destruction areas, manual unpacking, and automated disassembly. This approach results in four primary process streams requiring treatment: agent, energetics, metals parts, and dunnage (packing materials and other miscellaneous solid wastes).2 Agent is destroyed in one incinerator, energetics (explosives and propellants) are destroyed in a second, and metal parts are 1 The U.S. chemical weapons stockpile contains unitary and binary chemical weapons. Unitary chemical weapons contain agents that, by virtue of their molecular composition and structure, are highly toxic or lethal. By comparison, binary chemical agents consist of two nonlethal chemicals that, upon mixing, form a lethal chemical agent. Although slated for destruction in the same time frame as unitary weapons, binary weapons are not included in the CSDP and are not addressed in this report. These weapons will be destroyed as part of a separate Army program. 2 The critical materials to be destroyed are the agent (including that on metal parts and dunnage) and energetics. Agents are large molecules containing carbon, chlorine, hydrogen, phosphorus, fluorine, sulfur, nitrogen, and oxygen. To detoxify these agents, the molecular bonds need to be broken and the components reacted to produce less hazardous materials. Complete oxidation (mineralization) of molecules produces carbon dioxide, water, and nitrogen (N2), and fluorides, phosphates, and sulfates that can be removed as salts. Combustion is the most common oxidation process.
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Alternative Technologies for the Destruction of Chemical Agents and Munitions detoxified in a third. A fourth incinerator, designed for dunnage, has not yet been used for hazardous waste disposal at Johnston Island.3 Afterburners that use fuel combustion are then used to destroy any further contaminants emitted by the incinerator and to achieve a high degree of oxidation. Exhaust from the afterburners is treated in a pollution abatement system. The Army has proposed a program plan to build similar plants at the eight continental storage sites. This plan must be approved by Congress. Concerns have been raised about the baseline incineration approach. Some groups and individuals have claimed that the Army's baseline technology poses risks to surrounding populations and the environment, risks that could be reduced by using alternative disposal technologies. Congress has also shown interest in the use of alternative technologies for disposal of the chemical stockpile. It has directed the Army to submit a report on the subject by December 31, 1993, based in part on the present study by the National Research Council (NRC) Committee on Alternative Chemical Demilitarization Technologies. The present report addresses the possible use of alternative destruction technologies to replace partly or wholly or to be used in addition to the current baseline technology. The report considers the principal technologies that might be applied to the CSDP, strategies that might be used to manage the stockpile, and combinations of technologies that might be used. However, no specific recommendations are made here about the use of these technologies in the Army's disposal program. Another NRC Committee, the Committee on Review and Evaluation of the Army Chemical Stockpile Disposal Program, which provides continuing technical advice to the Army, will issue a report later this year that, based partly on the present report, may offer specific findings and recommendations for the use of alternative technologies in the CSDP. The present report is summarized here in sections on the requirements and other considerations for alternative technologies, the characteristics of proposed alternative technologies, options for gas and other waste stream handling to manage risks of special concern, strategies and system issues regarding the use of alternative technologies in the disposal program, and concluding observations. In its study, the committee examined a variety of technologies and processes, in part through a workshop at which developers made presentations on their technologies. Companies also provided information in writing. Although the committee has used such information provided by individual developers, it has not compared one company's technology with another's 3 Dunnage (packing materials, used protective suits, etc.) must be either destroyed or sent to a disposal site. Although incineration is one option, shipment to a hazardous waste landfill is an alternative.
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Alternative Technologies for the Destruction of Chemical Agents and Munitions but instead has assessed generic approaches to chemical weapons destruction. The committee did not have access to proprietary information in this study. REQUIREMENTS AND CONSIDERATIONS Destruction of the chemical stockpile is a complex undertaking. Determining the appropriate technologies to perform this task must include cognizance of a number of requirements and considerations. A number of process streams must be treated. Destruction technologies must be able to treat liquid nerve and mustard agents and the products of their aging, such as gels and reaction products. Because agent is stored both in bulk in metal containers and in weapons containing explosives and propellants, destruction technologies must also be able to manage solids contaminated with agent, both with and without explosives and propellants. The committee focused on these process streams, recognizing that dunnage, ventilation air, and spent decontamination fluids must also be treated and disposed of. An integrated system of unit processes will be required. As the name of this committee suggests, the word ''technology'' is usually applied to processes that are or might be used to destroy the chemical stockpile, such as baseline technology or plasma arc technology. However, many unit processes are entailed in any technology. The baseline technology, for example, encompasses transport and dismantling of weapons, separation of agent from explosives, agent combustion, combustion of by-products in an afterburner, and cleanup of waste gas streams. Alternative approaches to these processes may be useful, but alone they are often unable to demilitarize the chemical stockpile. For example, chemical hydrolysis might be used to detoxify the chemical agent drained from munitions. The products of this process might then be oxidized by a biological process, a wet air oxidation, or a supercritical water oxidation to further destroy organic materials. The effluents of this step might require yet further treatment, for example, in a catalytic oxidizer, before release to the environment. Such a sequence of processes might be viewed as one technology for the destruction of a given agent. Other processes would still be required to destroy or detoxify agent on metal parts, dunnage, and energetics. These system considerations must be taken into account when assessing the likely potential value of alternative technologies and unit processes. International treaty deadlines should be met. The international treaty on chemical weapons, the Chemical Weapons Convention (signed by the United States and a number of other nations January 13-15, 1993), specifies that chemical agents should be converted essentially irreversibly (to
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Alternative Technologies for the Destruction of Chemical Agents and Munitions a form unsuitable for the production of chemical weapons) and that munitions and other devices should be rendered unusable as such. The convention, when ratified, will require destruction of all chemical weapons within a 10-year period, with provision for a one-time extension. For the deadline to be met, technologies must be developed and demonstrated in a timely fashion, and they must be able to process weapons at an acceptable rate. Hence, the development stage of a technology and the time likely required to demonstrate its effectiveness become important considerations. Although treaty deadlines may change, there also remains the risk of agent release from any continued storage of weapons, which should be balanced against the risks of demilitarization. Waste streams must meet environmental standards. All technologies used to destroy chemical weapons will produce liquid, solid, and gas waste streams in proportions depending on the technology. All systems, including the baseline technology, must meet regulatory standards for effluents. This requirement implies that liquid wastes, such as salt solutions, spent decontamination fluid, and contaminated water, must be converted to dry solids and water and that the water be treated to allow recycling. Solid wastes consist mainly of salts and decontaminated metal parts. For solid wastes, the Army has developed a classification of degrees of decontamination achieved. Level 3X, established primarily for worker safety, applies to once-contaminated or potentially contaminated material that has since been decontaminated to show zero residual contamination as indicated by air monitoring above the material. Worker contact is allowed with such materials, but they cannot be released to the public. A level 5X rating is applied to a fully decontaminated solid that can be released to the public for uncontrolled use; this level is achieved by a thermal treatment of at least 1000°F for at least 15 minutes. To achieve 5X solids decontamination with technologies that do not operate at such temperatures would require treatment equivalent to this thermal treatment. Agent release must be avoided. For gas waste streams, the highly toxic nature of chemical warfare agents requires that any demilitarization system encompass safety systems to prevent agent release to the environment. In addition, discharge of other toxic materials in air generated by the destruction process must be below regulatory requirements for both design operation and operation in the case of equipment or operational failure. Alternative demilitarization technologies must be able to meet these criteria. Time for development must be weighed. All alternative technologies will require some time for development dependent on their stage of development. Although there is a treaty deadline, the committee did not eliminate from consideration any technology because of the development time it would require; development time is one factor that must be weighed by the
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Alternative Technologies for the Destruction of Chemical Agents and Munitions political process when determining a technology's acceptability. Precise estimates of development times are also hard to make, because these times will depend on the quality and level of development effort. The committee estimated that about 12 years are typically required for a technology to progress from concept through demonstration. Once a technology is demonstrated, time for construction and startup of a production facility would probably be similar to that for the existing program, in which design, construction, and systematization of a facility require about 5 years. Costs must ultimately be considered. The committee decided that cost estimates were premature until the number of options is narrowed and more detail about them is known. Thus, no cost projections are made here. However, the committee believes that the selection of any alternative technology would likely incur additional program costs, largely because of technical development requirements and program delays. CHARACTERISTICS OF ALTERNATIVE DESTRUCTION TECHNOLOGIES In characterizing alternative processes and technologies for chemical weapons destruction, the committee focused on the following: Functional performance. The capability of the technology to treat or process the different agents, solid parts, explosives, propellants, dunnage, and air streams; the liquid, solid, and gas waste streams generated; and any requirements for further treatment of solid parts or waste streams. Engineering factors. The degree and manner in which engineering factors (e.g., explosion potential or extreme conditions such as very high pressures or corrosivity) may affect a technology's effectiveness, its potential for successful development, and its safety and hazard potential during operation. Development status. The development and demonstration stage of the technology (whether laboratory, conceptual design, pilot plant, in commercial use for similar operations, or used previously to destroy one or more chemical warfare agents). Development status is an indicator of the time required for full development. As discussed above, this time is difficult to estimate because it is determined by many factors, such as the level of development effort. Typically, to progress through the end of demonstration from the laboratory stage takes 9 to 12 years; from the conceptual design stage, 10 to 11 years; from the pilot plant stage, 7.5 to 9 years; and from the beginning of demonstration itself, 3 years (see Table 4-2).
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Alternative Technologies for the Destruction of Chemical Agents and Munitions The committee investigated a variety of alternative destruction processes (see Chapters 6 and 7). Table E-1 summarizes their status and applicability. For convenience, the technologies and processes are grouped in the following categories: (1) low-temperature, low-pressure, liquid-phase detoxification processes that convert agent to less toxic compounds; (2) low-temperature, low-pressure, liquid-phase oxidation processes, including biological oxidation, which react agent with oxygen to form carbon dioxide, water, and salts (for complete oxidation, or mineralization); (3) moderate-temperature, high-pressure oxidation; (4) high-temperature, low-pressure pyrolysis, which uses heat to destroy molecular bonds; (5) high-temperature, low-pressure oxidation; and (6) other technologies. Destruction technologies investigated by the committee include those under development for disposal of other types of toxic wastes (especially chlorinated hydrocarbons) and those being developed specifically for chemical warfare munitions destruction. Other technologies reviewed, such as high-temperature ovens, are commercially available components that have been more widely used. Low-Temperature, Low-Pressure, Liquid-Phase Detoxification Chemical treatment of agents can reduce their toxicity. Such treatment, with relatively low temperatures and pressures, has been used for the agent GB, and a large number of other chemical processes have been proposed. Various results suggest that chemical reaction in basic (high pH) solutions offers the potential to convert all three agents to products of much lower toxicity by what is called detoxification: GB has been detoxified by sodium hydroxide in water solution in the United States and worldwide. Limited laboratory studies suggest that VX can be detoxified by sodium hydroxide and hydrogen peroxide in water solution. HD has been successfully detoxified by calcium hydroxide in water solution at higher temperatures (90° to 100°C). Using an alcohol or ethanolamine in place of water increases agents' solubility and is also believed capable of converting all three agents. Chemical reactions in acidic (low pH) solutions can use oxidizing agents (Cl2, peracids, hypochlorites, or hydrogen peroxide), a method by which all three agents should be treatable; however, except for VX, little information on this approach was found. At ambient temperatures, HD solubility in water is very low, and its high viscosity, when it contains thickeners, makes adequate contact with
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Alternative Technologies for the Destruction of Chemical Agents and Munitions TABLE E-1 Summary of Process Capabilities and Status Stream Treated Agent Metal and Energetics Process Initial Agent Detox Complete Organic Oxidization Need Gas Afterburner Energetics Metal Afterburner Needed Next Step Comments Low-temperature, Low-pressure detoxification Base hydrolysis (NaOH) GB No ? No No N.A. pp Has been used in field; for HD, limited by contacting problems NaOH + H2O2 VX No Yes No No N.A. Lab New finding Ca(OH)2(at 100°C) HD No ? No No N.A. Lab/pp Limited use in England KOH + ethanol HD, GB, VX No ? No No N.A. Lab Hypochlorite ion HD No Yes No No N.A. Lab Difficult contacting problem with HD Organic base (ethanolamine) GB, HD, possibly VX No ? No No N.A. Lab/pp Limited use in Russia; increase in organic waste Acidic systems HCI hydrolysis GB No ? No No N.A. Lab/pp Peracid salts (OXONE, others) VX, perhaps GB and HD No Yes No No N.A. Lab/pp Increased waste Chlorine VX, perhaps GB and HD No Yes No No N.A. Lab/pp Increased inorganic waste Ionizing radiation All No ? Yes? Yes? ? Lab High conversion not yet established
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Alternative Technologies for the Destruction of Chemical Agents and Munitions Stream Treated Agent Metal and Energetics Process Initial Agent Detox Complete Organic Oxidization Need Gas Afterburner Energetics Metal Afterburner Needed Next Step Comments Low-temperature, low-pressure oxidation Peroxydisulfate, ClO2, H2O2, O3 All Yes Yes No No N.A. Lab Catalysts generally needed for complete complete conversion; spent peroxydisulfate can be electrochemically regenerated UV light with O3 and H2O2 N.A. Yes Yes No No N.A. pp Very large power requirement; applications have been for very dilute solutions Electrochemical oxidation All Yes Yes No No N.A. Lab Biological oxidation N.A. Yes Yes No No N.A. Lab Moderate-temperature, high-pressure oxidation Wet air and super-critical water oxidation All Partially Yes Yes? No Yes pp Residual organic components can be low for supercritical; residual materials are believed suitable for biodegradation
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Alternative Technologies for the Destruction of Chemical Agents and Munitions Stream Treated Agent Metal and Energetics Process Initial Agent Detox Complete Organic Oxidization Need Gas Afterburner Energetics Metal Afterburner Needed Next Step Comments High-temperature, low-pressure pyrolysis Kiln (external heat) All Partially Yes Yes Yes Yes Demo May need more than one unit to deal with all streams Molten metal All No Yes Yes? Yes Yes pp Plasma arc All No Yes Yes? Yes Yes Lab/pp Steam reforming All Yes Yes No? No Yes Lab/pp High-temperature, low-pressure oxidation Catalytic, fixed bed N.A. N.A. N.A. No No No Lab/pp Useful for afterburner Catalytic, fluidized bed All Yes Yes Yes No Yes pp Molten salt All Yes Yes Yes? No Yes pp Possible use for afterburner and acid gas removal Combustion All Yes Yes Yes Yes Yes — Baseline technology Other technologies Hydrogenation All No Yes No No No Lab Reactions with sulfur All Yes Yes No No No Lab NOTE: Question mark (?) indicates uncertainty about the noted application. N.A., not applicable; pp, pilot plant; demo, demonstration; lab, laboratory.
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Alternative Technologies for the Destruction of Chemical Agents and Munitions aqueous solutions difficult. HD is quite reactive; with an adequate area of HD-liquid interface, many of the reactions useful for GB are likely to be effective for HD. Greater surface area of the interface can be obtained by high-energy physical dispersion or use of emulsifying agents. The latter approach, for microemulsions, requires about equal quantifies of agent and emulsifier, which increases the amount of organic waste. Operations at 70° to 100°C may alleviate the interface problem, as illustrated by the successful treatment of GB with calcium hydroxide at such temperatures. Physical dispersion may still be required for the gelled HD found in the stockpile. Although the above reactions convert agent to less toxic compounds, some reaction products could be converted back to the original agent and would not meet the treaty demilitarization requirement of irreversibility of agent products under storage. However, these reaction products would be more suitable feed for subsequent processing steps that accomplish further conversion by oxidation. The development and demonstration of such detoxification processes will require substantial laboratory and pilot plant work for all three agents. Low-Temperature, Low-Pressure, Liquid-Phase Oxidation Demilitarization treaty requirements can be met by detoxification, but further conversion, possibly by oxidation, may be needed for general environmental, storage, safety, and other reasons. There has been little investigation of the use of low-temperature oxidation processes for waste streams resulting from low-and medium-temperature detoxification processes. However, treatment of industrial waste and contaminated groundwater by low-temperature oxidation is being actively investigated and provides some leads on the use of chemical and biological processes for treating agent waste streams. At temperatures below the boiling point of water, very active oxidizing agents (with catalysis) are required for oxidation. Peroxydisulfate salts can oxidize most organic compounds to carbon dioxide but would produce a very large waste stream. It has been proposed that to optimize the process the spent reagent be recycled by electrolytic regeneration; use of catalyzed hydrogen peroxide might reduce the regeneration requirements. Ultraviolet light can activate aqueous solutions of ozone and hydrogen peroxide and is an option for treating contaminated groundwater. However, the large electricity requirements of this process when treating large reaction product streams place it at a disadvantage with alternatives. Biological oxidation is commonly applied to industrial and municipal waste streams. Although its application to the liquid waste streams from
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Alternative Technologies for the Destruction of Chemical Agents and Munitions demilitarization processes has not been developed, with research this approach might well be successful. All the above low-temperature, low-pressure, liquid-phase processes might be used to treat liquid waste streams but not be directly applicable to contaminated metal parts or energetics. Moderate-Temperature, High-Pressure Oxidation In wet air oxidation, organic materials in a dilute aqueous mixture axe oxidized at elevated temperatures and pressures. Supercritical water oxidation operates at still higher temperatures and pressures (above the critical point of water at which hydrocarbons, for example, are highly soluble). Both wet air and supercritical water oxidation processes can detoxify and convert residual organics to carbon dioxide. Wet air oxidation requires residence times of greater than 1 hour. Even then, more refractory organic compounds remain; however, these compounds are judged to be suitable for subsequent biological degradation. Supercritical water oxidation can achieve a greater conversion of all organics in less than 10 minutes. Because pure oxygen is used in this process, waste gas is primarily carbon dioxide, which can, if necessary, be removed as solid calcium carbonate (limestone). Adaptation of wet air oxidation to use pure oxygen would require a pilot plant program. Both processes can treat all three principal agents in the U.S. stockpile (GB, VX, and the mustard compounds). Both are expected to be capable of treating a slurry of finely divided energetics if care is exercised in the control of feed rates. Some mechanical addition to the disassembly process would be required to remove and make a slurry of the energetics. Their removal from containers is not expected to be complete, so some energetics residues would still need to be destroyed in a metal deactivation process involving high-temperature treatment, as in the baseline system. Supercritical water oxidation could also be used as an afterburner to oxidize gas products of pyrolysis or other processes. This approach is an alternative to the combustion variations discussed later. It has the disadvantage of requiring gas compression to 3,000 psi or higher. However, it also offers high conversion efficiency. Application of these processes to chemical agents would still require a problem-solving stage and would require pilot plant studies. The high operating pressure would require appropriate confinement, as in industrial practice. Currently, baseline facilities are remotely operated and designed for energetics explosions and capture of agent release. The high-pressure oxidation process would call for some extension of these safeguards.
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Alternative Technologies for the Destruction of Chemical Agents and Munitions High-Temperature, Low-Pressure Pyrolysis Some of the high-temperature pyrolysis and oxidation processes are capable of treating all major stockpile components (agent, energetics, and metal; see Table E-1). High temperatures are required to decontaminate metal parts and to ignite and destroy energetics (see Chapter 5). These temperatures must be sufficient to achieve the equivalent of the 5X criterion (treatment at 1000°F for 15 minutes) for metal decontamination. Kilns with electrical heating can meet these requirements and avoid dependence on the internal firing now used, an alternative approach that has the advantage of reducing total flue gas volume. However, air (or oxygen) must be supplied to oxidize unburned pyrolysis products. This step can be achieved within the kiln or in a secondary burner. An afterburner would be needed to ensure complete oxidation. Variations of this system can accept bulk containers as well as energetics and small metal parts. Plasma arc torches, which generate ionized plasmas at temperatures of up to 12,000 K, are being developed to destroy toxic wastes. Molten metal processes are electrically heated melting furnaces adapted for hazardous waste disposal. Both approaches use electrical heat and operate at higher temperatures than ovens or kilns under oxygen-deficient conditions. They generally introduce air to burn the products resulting from the initial pyrolysis but still require an afterburner. In principle both can handle chemical warfare agents and fragmented energetics and metal parts; the molten metal system would likely be able to handle a larger range of material sizes than would the plasma arc systems. In steam gasification processes, steam is reacted with carbon-containing feed at high temperatures to produce a gas containing the combustible components hydrogen, carbon monoxide, soot, and low-molecular-weight hydrocarbons. Other elements (S, P, F, and C1) require oxidation and removal. Steam gasification is more limited than pyrolysis, since it does not appear directly useful for metal decontamination. However, an approach combining pyrolysis and steam gasification is under private development for use in hazardous waste destruction. High-Temperature, Low-Pressure Oxidation High-temperature, low-pressure oxidation is the current workhorse for destroying toxic waste materials. There are several variations of interest. Molten salt and fluidized-bed oxidation, because of the large heat capacity of the molten salt and the pulverized-solids bed, are less likely to suffer flame-out (flame extinction) than is the fast-response gaseous system of conventional combustion. These alternative methods also provide good contact
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Alternative Technologies for the Destruction of Chemical Agents and Munitions between air and fuel. There would be some tendency for bubble formation to result in agent bypassing the combustion zone and afterburners are still needed. These systems can also retain much of the oxidized halogens, sulfur, and phosphorus if appropriate basic acceptors are part of the salt or solids system; and they can also deal with energetics of small particle size, although their ability to handle metal parts seems limited. Both molten salt and fluidized-bed systems are used for toxic waste disposal. To apply either to demilitarization would probably be possible by proceeding directly to design and construction of a demonstration unit. The catalytic fixed bed is of special interest for use as an afterburner for the final oxidation of any unoxidized material in gas effluents from another destruction process. The familiar automobile catalytic converter is an example of this application. The presence of halogens, phosphorus, and sulfur in the destruction products from agents and energetics will probably preclude the use of very active catalysts. However, operation at higher temperatures could allow use of rugged catalysts or even common ceramics. For many situations, external electrical heating will minimize dependence on heat generation in the catalytic oxidation unit and minimize production of waste gas. An important variation on all these high-temperature oxidation systems is their operation with pure oxygen instead of air. As discussed below, the volume of waste gas can be greatly reduced by substituting oxygen for air. Although technology is available to shift from air to oxygen, demonstration of operation with oxygen would be required. Various combinations of all these systems as they might be used in the stockpile disposal program are considered later. WASTE STREAM HANDLING Chemical demilitarization waste streams that require special treatment are gas effluents, metal parts and containers, salts from the neutralization of acid gases, and liquids. Gas Effluents The risks to surrounding communities from gas effluents of destruction operations can be controlled and reduced by several approaches: use of activated-carbon beds (charcoal filters); temporary storage of gas waste streams, with chemical analysis before release; or approaches that minimize or eliminate the discharge of gas wastes. The techniques involved are generally well-known, but would have to be tailored to address very low
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Alternative Technologies for the Destruction of Chemical Agents and Munitions contaminant concentrations and would require testing and demonstration for use in chemical demilitarization. For stockpiles located in populated areas, activated-carbon filters could be installed on waste gas outlets to remove any remaining agent and other trace organic compounds. These filters would also capture any transient emissions (puffs) of agent that might escape from the destruction system. This approach could greatly reduce the probability of dangerous releases of agent or other toxic materials in air to the atmosphere during both design and off-design operations. Alternatively, a dosed-loop system could store waste streams until chemical analysis established their suitability for disposal. For large combustion facilities (e.g., as for general-purpose hazardous waste incineration), gas storage volume requirements are too large to represent an economically viable option. However, for the stockpile disposal program, the relatively small scale of operations and extremely toxic nature of chemical warfare agents lend interest to this approach. Preliminary calculations by the committee suggest that commercial gas holders may be large enough for this application. The use of gas holders would allow exhaust gases to be retained and analyzed before their release. If unacceptable contaminants were detected, the gas could be recycled through the destruction system. The use of oxygen instead of air would also significantly reduce the size of the gas holders needed. Finally, gas waste streams could be minimized or eliminated. Oxygen could be used instead of air to reduce gas waste streams, but revised designs would be required for those systems now designed to operate with air. Another strategy for eliminating gas waste streams would be to convert them to solid products. The carbon dioxide gas resulting from oxidation, for example, could be converted to solid calcium carbonate. Treated Metal Parts and Containers Metal parts and bulk (ton) containers are heated to the 5X criterion in the baseline approach; they would also be heated to this extent in several high-temperature alternative technologies. Such treatment allows these materials to be recycled as scrap metal. The materials could instead be chemically decontaminated to a level that allows their transportation and disposal as toxic waste, eliminating the need for equipment to heat the larger metal parts, such as drained artillery shells and ton containers.
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Alternative Technologies for the Destruction of Chemical Agents and Munitions 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
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Alternative Technologies for the Destruction of Chemical Agents and Munitions 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
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Alternative Technologies for the Destruction of Chemical Agents and Munitions 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
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Alternative Technologies for the Destruction of Chemical Agents and Munitions 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.
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Alternative Technologies for the Destruction of Chemical Agents and Munitions The molten metal furnace is capable of handling metal parts and energetics, but pilot plant work is required. Plasma arc furnaces might also handle these materials but may not be as useful for large metal parts. Further development of this approach is also required. All of these processes could also be used to destroy bulk agent. Treatment of all streams in one device offers equipment simplification but with some loss of control of the composition of the feed streams and the products resulting from destruction of the several streams. Afterburners For all systems that produce waste gas, afterburners are needed to ensure complete oxidation. The baseline practice is to use internal firing with fuel if additional heat is needed. Substituting oxygen for air and external heating for internal firing would minimize waste gas, but the first option would require demonstration. Catalytic oxidation could reduce the temperatures required, but the use of highly active catalysts is made difficult by the deactivation potential of the P, F, C1, and S content of the agents. Molten salt systems might also serve as afterburners as well as for acid gas removal. Another variation would be to complete gas oxidation by supercritical water oxidation. In this approach, it would be necessary to compress the gas to 3,000 psi. With the use of afterburners, gas streams from any of the processes can be brought to specified levels of agent and destruction of organic material, which can be confirmed by storage and certification. Thus, waste gas purity can be ensured independently of the process used. GENERAL OBSERVATIONS The risk of toxic air emissions can be virtually eliminated for all technologies through waste gas storage and certification or treatment by activated-carbon adsorption. Either of these options can be combined with methods to reduce the volume of gas emissions. Agent releases from accidents in the destruction facility and releases to the atmosphere of residual unreacted agent or toxic products from equipment malfunction can all be avoided for any alternative technology by applying a dosed system concept to all gas streams leaving the facilities. That is, gas streams can be stored until chemical analysis has demonstrated their compliance with regulatory standards. The storage volume needed to handle
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Alternative Technologies for the Destruction of Chemical Agents and Munitions gaseous oxidation products can be made adequate to store any accidental release of vaporized agent from the destruction facility. Large activated-carbon (charcoal) adsorbers can perform much the same function. In this case, agent and products of incomplete combustion are captured and retained on the charcoal. The amount of gas released can be greatly reduced by the use of pure oxygen in destruction processes instead of ordinary nitrogen diluted air. Waste gas can be further reduced by capturing the carbon dioxide it contains with lime, as well as capturing HCl, HF, SO2, and P2O5 , at the cost of increasing the amount of solid waste produced. These techniques can be applied to all technologies. There are many possible destruction processes. A wide variety of processes have been proposed to replace or augment components of the current baseline destruction system. The scope of possible modifications ranges from simply replacing one component, such as the agent combustion process, to replacing all current combustion-based processes. New components would likely require 5 to 12 years for research and demonstration, the lower figure representing the time required for construction and testing of demonstration facilities, the higher figure including research and pilot plant work as well. Initial weapons disassembly and agent detoxification and partial oxidation could meet international treaty demilitarization requirements and eliminate the risk of catastrophic agent releases during continued storage. The strategy of disassembling weapons and applying liquid-phase processes to destroy agent can meet treaty demilitarization requirements. By destroying the stored agent, the risk of catastrophic agent release during storage is avoided. Final disposal of the wastes generated would be delayed until complete oxidation processes are developed. There are a number of promising chemical processes for agent detoxification or oxidation. Chemical techniques could allow agent detoxification in low-temperature, aqueous systems. The reaction products could be confined and tested to determine whether further processing is needed to meet demilitarization requirements and also for suitability for release to a disposal facility or to local storage. The best results with such processes have been
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Alternative Technologies for the Destruction of Chemical Agents and Munitions seen in GB destruction. Although there are laboratory leads for similar VX and mustard treatments, this work is at the early laboratory stage. The combined use of peroxysulfates and hydrogen peroxide shows promise for detoxification of agent and also for complete oxidation of its organic components. Biological and electrochemical processes might be used to further oxidize liquid wastes from detoxification processes, but they are in an early stage of research. Processes used in combination with an afterburner can be used to oxidize agent. Processes proposed for oxidation of agent or of products from its chemical detoxification include wet air and supercritical water oxidation, molten salt oxidation, fluidized-bed combustion, steam gasification, plasma arc (electric arc) furnaces, and molten metal baths. All require an afterburner to complete oxidation, and all are promising but would require development and demonstration. There are technologies to replace the baseline metal parts furnace. Alternative technologies to destroy energetics and reliably detoxify metal parts and containers involve heating to high temperatures. Using electrically heated ovens in place of the baseline internally fired kilns would reduce the amount of flue gas produced. Molten metal or salt baths could also treat these stockpile materials. Like the combustion-fired kilns, all these approaches require the use of afterburners to ensure complete oxidation. Afterburner technologies might be used to control waste gas purity. Alternative afterburner options include external heating, catalytic combustion, molten salt or supercritical water oxidation. Afterburners can be designed to meet requirements for contaminant oxidation for both baseline and alternative processes and are essential in control of waste gas purity.
Representative terms from entire chapter: