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Alternative Technologies for the Destruction of Chemical Agents and Munitions 8 Application of Alternative Technologies to the Destruction of the U.S. Chemical Weapons Stockpile This final chapter discusses the use of alternative destruction and decontamination technologies to manage the components of the U.S. chemical weapons stockpile, namely, chemical agents, energetics, and contaminated metal parts and containers. Several major issues are addressed: possible improvements in the composition of the waste streams produced, principal destruction options for achieving demilitarization goals, and substitution of alternative processes for elements of the baseline process. The discussion draws on the preceding chapters, summarizing the characteristics of different technologies and providing perspective on their use in the Army Chemical Stockpile Disposal Program. DESTRUCTION TECHNOLOGIES The destruction technologies investigated by the committee include those under development for disposal of other types of toxic wastes (especially chlorinated hydrocarbons) as well as those specifically for chemical warfare munitions destruction Other alternative technologies, such as high-temperature ovens, are more widely available components that have been developed and used by private industry. Technologies are sorted here by unit processes. Unit process groups include all technologies that appear useful for accomplishing a distinct step in the destruction process. Major categories of these processes are the following: low-temperature, low-pressure, liquid-phase detoxification; low-temperature, low-pressure, liquid-phase oxidation (including biological oxidation); moderate-temperature, high-pressure oxidation; high-temperature, low-pressure pyrolysis; high-temperature, low-pressure oxidation; and other technologies.
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Alternative Technologies for the Destruction of Chemical Agents and Munitions The first two types of technologies are discussed in more detail in Chapter 6, the remainder in Chapter 7. Table 8-1 provides summary information on the applicability and status of all these destruction technologies. Comments on them follow. Low-Temperature, Low-Pressure, Liquid-Phase Detoxification Reaction in high Ph (alkaline or basic) solution offers the potential to convert all three agents in the U.S. chemical stockpile to products of much lower toxicity, that is, such reactions can be used for detoxification: The agent GB has been detoxified by using sodium hydroxide (NaOH) in the United States and worldwide. Limited laboratory studies suggest that the agent VX can be detoxified if hydrogen peroxide (H2O2) is added to the NaOH. Agent HD has been successfully detoxified by calcium hydroxide (Ca(OH)2) at a higher temperature (90° to 100°C). When an alcohol or ethanolamine is used as solvent instead of water it is believed that all three agents will be detoxified. Reactions in low pH (acidic) solutions make use of oxidizing agents (Cl2, peracids, or hypochlorite). All three agents should be treatable in this manner, but little information was found except for VX. Application to HD was ineffective under the conditions used because of poor contact between reacting chemical species. At ambient temperatures HD solubility is very low. Its high viscosity, when it contains thickeners, makes adequate contact with aqueous solutions difficult. Yet HD is quite reactive, and with an adequate extent of HD-aqueous phase interface, many of the reactions useful for GB are likely to be effective with HD. High interfacial surface area can be obtained by high-energy physical dispersion or use of emulsifying agents. The latter approach, for microemulsions, requires about equal quantities of agent and emulsifier, which will increase the amount of organic waste. Operations at 70° to 100°C may alleviate the phase interface problem, as illustrated by the success of the Ca(OH)2 treatment discussed in Chapter 6. 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 of the reaction products could be converted back to the original agent. They would not, therefore, meet the treaty demilitarization requirements of irreversibility while stored. However, they would be more suitable as a feed
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Alternative Technologies for the Destruction of Chemical Agents and Munitions TABLE 8-1 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 HCl 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 supercritical 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 are 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 to subsequent processing steps that accomplish irreversible conversion by oxidation. Low-Temperature, Low-Pressure, Liquid-Phase Oxidation Although demilitarization goals can be met by detoxification, oxidation of all carbon to carbon dioxide (CO2) is highly desirable for final disposal. 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 contaminated groundwater by low-temperature oxidation is an active field of investigation that provides some leads on treating wastes from agent detoxification. At temperatures below the boiling point of water, very active oxidizing agents (with catalysis) are required for oxidation. Peroxydisulfate salts are capable of oxidizing most organic compounds to CO2 but would produce a very large solids waste stream. It has been proposed that to optimize the process, spent reagent be recycled to electrolytic regeneration and catalyzed H2O2 be used to convert the more reactive components (Cooper, 1992). Ultraviolet light can activate mixtures of ozone (O2) and H2O2 and is an option in treating contaminated groundwater. However, the large electricity requirements of this process for treating large reaction product streams are disadvantageous compared with other options. Biological oxidation is commonly applied for industrial and municipal waste streams. Although applications to the waste stream from demilitarization have not been developed, research on such processes might well prove successful. Moderate-Temperature, High-Pressure Oxidation Both wet air oxidation (WAO) and supercritical water oxidation (SCWO) processes can detoxify and convert residual organic materials to CO2. WAO is carried out at lower temperatures then SCWO, and requires residence times greater than 1 hour. Even then, more refractory organic compounds remain. However, these residuals are judged by the committee to be suitable for biological degradation. SCWO, at higher temperatures and pressures, can achieve a greater conversion of all organics in about 10 minutes. Because pure oxygen is used in this process, waste gas is primarily CO2, which can, if necessary, be removed as solid calcium carbonate (CaCO3) or limestone). Adaptation of WAO to use pure oxygen would require a pilot plant program.
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Alternative Technologies for the Destruction of Chemical Agents and Munitions Both these oxidation processes can treat all three agents. 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 as in the baseline system. SCWO could also oxidize gaseous products from pyrolysis or other processes and is an alternative to the combustion variations discussed later. It has the disadvantage of requiring gas compression to 3,000 psi; however, it offers a high conversion efficiency. .Application of these processes to chemical agents would still require a problem-solving pilot plant stage. The high operating pressure will call for appropriate confinement, as in industrial operations. Current baseline facilities are remotely operated and designed for energetics explosions and capture of agent released inadvertently. The high-pressure oxidation process might call for some extension of these safeguards. High-Temperature, Low-Pressure Pyrolysis As shown in Table 8-1, many high-temperature pyrolysis and oxidation processes are capable of treating all major stockpile components (agent, energetics, and metal). High temperatures are required to decontaminate metal parts and ignite and destroy energetics (see Chapter 5). These temperatures should be sufficient to ignite energetics and 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. This approach has the advantage of reducing total flue gas volume. However, air (or oxygen) must be supplied to oxidize unburned pyrolysis products, a step that 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 ton containers as well as energetics and small metal parts. Plasma arc and molten metal processes use electrical heat and operate at higher temperatures 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, fragmented energetics, and metal parts. The molten metal system would be expected to handle a larger range of material sizes than do the plasma arc systems.
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Alternative Technologies for the Destruction of Chemical Agents and Munitions In steam-reforming 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 Cl) require oxidation and removal. The gas formed, after purification, can be a generally useful fuel; however, destroying it may be more practical, as is proposed for the products from pyrolysis. Steam reforming is more limited than pyrolysis because it does not appear directly useful for metal decontamination. However, combined pyrolysis and steam gasification is under private development for possible 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 than are the fast-response gaseous system of conventional combustion. These alternative methods also provide good contact between air and fuel. There would be some tendency for bubble formation to result in bypassing of agent through the combustion zone; thus, 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. They can also manage 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, and it would probably be possible to proceed directly to design and construction of a demonstration unit for demilitarization applications. Molten salt designs might also be used as afterburners and for acid gas removal from gaseous waste streams. 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 an agent destruction process. The familiar automobile catalytic converter is an example of this application. The presence of halogens, phosphorus, and sulfur in the agent and the presence of products from energetics destruction 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 heat (electrical) will minimize the need for internal firing to generate heat in the catalytic oxidation unit, thus reducing the 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 (or almost eliminated for some
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Alternative Technologies for the Destruction of Chemical Agents and Munitions processes) by substituting oxygen for air. Although technology is available to shift from air to oxygen, demonstration of operation with oxygen would be required. Combinations of the unit processes in Table 8-1 into systems for use in the stockpile disposal program are considered later. WASTE STREAM HANDLING PROCESSES The waste streams of conversion processes for agent, energetics, and metal parts will require additional processing to meet standards for release to the environment. In all cases, monitoring via chemical analysis is an integral step. Ideally, each waste stream should be stored until chemical analysis is completed and the waste stream can be certified for compliance with the required standards for environmental release (i.e., the process can be operated as a closed system). Discussion of solid, gas, and liquid waste streams follows. Solid Waste Waste metal. In the baseline process, all metal is heat-treated to qualify for the 5X decontamination rating (1000°F for 15 minutes) and can be released to the public and recycled for other uses. The metal parts (traveling-grate) furnace is designed to perform this function for drained ton containers and artillery shells. 5X heat treatment is believed to make monitoring by chemical analysis unnecessary. Treatment to a decontamination level of 3X, to allow transport and disposal as toxic waste, would permit eliminating the traveling grate-kiln, but monitoring would then be necessary. Waste salts. Salts of H2CO3, HF, HCl, H3PO4, and H2SO4 are formed by neutralization of these acidic products of agent and by energetics oxidation and are a major waste stream. They can be formed directly in the destruction process (as in NaOH hydrolysis) or in the gas pollution abatement system. If CO2 is discarded as a gas, oxidation of GB forms 2.3 pounds of calcium salts for each pound of GB destroyed; if the CO2 from oxidation is discarded as CaCO3, an additional 2.8 pounds of salts per pound of GB must be discarded. Excess base, as used in the baseline pollution abatement system, will increase this amount to a total of about 10 pounds of dry salts per pound of GB. If agent destruction involves additional organic solvents or reagents or if flue gas from fuel combustion is treated, additional CO2 will be generated. Although methods for chemical analysis are available, the inherent problem of obtaining a representative sample of a heterogeneous solid for
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Alternative Technologies for the Destruction of Chemical Agents and Munitions analysis and the need to establish the absence of even very small amounts of residual agent and other toxic organic materials may still require that the waste salts be heated to the 5X criterion. Equipment for drying and heating waste salts would be required. Even so, the presence of fluoride and small amounts of heavy metals will generally result in this waste stream being classified as hazardous. Gas Waste Streams Because of their relatively large volumes, gas waste streams from common industrial oxidation processes are generally not stored before release. Instead, reliance is generally placed, as in the baseline technology, on chemical analysis of the leaving gas stream and on process control to verify that it meets all health-related requirements. However, the high toxicity of chemical warfare agents calls for special care in avoiding small transient emissions (puffs). Even with the careful design and operation of destruction processes, off-design conditions can occur. The current baseline system uses an afterburner to guard against agent puffs that might emerge from the primary combustion system. An additional precaution that could be used by the baseline system is the capture of gas emissions resulting from off-design operation until chemical analyses have been completed and needed corrective measures taken. There are three major options for managing such potential off-design agent emissions in chemical demilitarization: capture of transient puffs by activated-carbon adsorption; gas storage for time sufficient to allow chemical analysis and certification before release (gas of unsatisfactory purity would be recycled to an afterburner); and drastic reduction of waste gas stream volume by using oxygen and capturing CO2 with lime to form CaCO3 (a small amount of nitrogen from air leakage into the system and from the nitrogen in energetics and in VX will require treatment and discharge to the atmosphere). Any remaining waste gas stream could be stored and tested or purified by activated-carbon adsorption. Activated-carbon adsorption. Activated-carbon (charcoal) adsorption can remove extremely low concentrations of organic compounds. Activated carbon is the adsorbent used in gas masks. Because the organic compounds are stored on the charcoal, a series of charcoal beds is used and performance is monitored by analysis of the gas between beds. When the first bed is saturated, unadsorbed organic materials break through and are captured on the next bed. The saturated activated carbon must be removed and discarded
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Alternative Technologies for the Destruction of Chemical Agents and Munitions or detoxified (probably in the facilities used for metal detoxification), and discarded. This approach is best used for removing very small mounts of organic compounds, as for protection from transient puffs. Carbon adsorption beds are part of current Army designs to treat potentially contaminated ventilation air. In May 1992, the NRC sponsored a workshop that led to a recommendation that the Army consider using activated-carbon adsorption for chemical disposal facilities located in populated areas (NRC, 1993). Its use in treating waste gas from agent destruction is currently under study by the Army as is the use of the gas storage facilities discussed below. Gas storage and certification. For large-scale combustion operations, storage of waste gas before analysis and release generally requires a storage volume too large for gas holders to be economically viable. However, the smaller scale of chemical stockpile disposal facilities makes the gas holder a potentially practical option for ensuring that the waste gas meets environmental and health-related standards. A system of four gas holders could be used to store the gaseous effluents of any disposal process, including the current baseline technology. As one gas holder is filled, a second could be analyzed, a third could be emptied, and a fourth could be linked in as a spare at any juncture. Required gas holder volume varies over a wide range depending on cycle time and gas flow rate. The example presented in Chapter 5 estimates needed gas holder volume at 92,000 cubic feet for 8 hours storage, using air for internal firing, for oxidation of 100 pounds of GB per hour. The diameter of such a gas holder would be about 35 feet. Industrial atmospheric pressure gas holders that have been used for many years have storage volumes of several million cubic feet. Use of oxygen instead of air for oxidation would reduce needed storage volume to one-seventh the volume required for air. Capture of CO2 as solid carbonate could further reduce waste gas volume to that of air leakage and unused oxygen. Flue gas from fuel combustion (for internal firing) would increase gas volume. Either a gas storage system or a system of charcoal scrubbers can be designed to capture and hold pulses of agent that might be released by an accident or malfunction during disassembly of a munition or destruction of agent. Either approach can also handle lower amounts of contamination that might result from off-design operation. Facilities for storage, chemical analysis, and certification of the quality of the waste gas stream can convert all technologies for treating agent and weapon parts to a closed-loop system so that gases are not released to the environment until chemical analysis has demonstrated their satisfactory composition.
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Alternative Technologies for the Destruction of Chemical Agents and Munitions FIGURE 8-1 Unit processes in demilitarization Strategy 1: disassembly and agent detoxification, with storage or transportation of residue. risk of agent release from continued storage. It has the disadvantage of requiring additional time (5 to 12 years) for the research, development, and demonstration of new technologies. It would also delay final disposal of energetics and contaminated metal. It is assumed here that the small amounts of waste gas could be treated along with ventilation air by the activated-carbon adsorption beds that are part of the baseline design. Strategy 2. Conversion of agent and disassembled weapons to salts, CO2 water, and decontaminated metal (mineralization). In Strategy 2, mineralization is completed without long-term storage of agent, energetics, or metal parts and containers. This strategy meets all stated goals by oxidation and heat treatment to produce the waste streams noted. Strategy 2 is illustrated in Figure 8-2.
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Alternative Technologies for the Destruction of Chemical Agents and Munitions FIGURE 8-2 Unit processes for demilitarization Strategy 2: mineralization. For agent, detoxification (as in Strategy 1) can precede the final mineralization processes, or agent can be directly mineralized, as in the baseline technology. The two-step procedure of detoxification by hydrolysis followed by incineration to complete oxidation has been used in the United States and worldwide. It is apparently of some continuing interest for the Russian stockpile disposal program. In this approach, primary oxidation products are treated with an afterburner to destroy any remaining trace organic components, and acid gases (HF, HCl, P2O5, and SO2) are neutralized and removed in the gas cleanup system.2 2 The mineralized oxidation products from halogens, phosphorus, and sulfur are all acidic and readily removed from gas streams by alkaline scrubbers, leaving CO2 and water vapor as the principal gaseous wastes. However, the gas scrubber effluents must be monitored and disposed of as hazardous wastes. All of these can be reacted with lime at high temperatures to avoid liquid wastes.
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Alternative Technologies for the Destruction of Chemical Agents and Munitions Energetics, as well as metal parts and containers, are heated to a high temperature. The vapors from the decomposition and vaporization of these materials are then oxidized and cleaned before release. Metals are detoxified to the 5X level to allow recycling, and salts are rendered suitable for landfill disposal. All waste streams are tested to ensure their suitability for release. System Considerations As Figures 8-1 and 8-2 show, unit processes and technologies must be combined to form a system that meets all demilitarization requirements. The two demilitarization strategies provide a framework for examining the potential roles of alternative technologies. Strategy 1, which delays or avoids local disposal, is discussed first. Alternative processes for Strategy 1 (disassembly and agent detoxification). The only major agent conversion process required for Strategy 1 is detoxification (Figure 8-1). However, decontamination of the disassembled weapon parts and containers will probably be necessary as well for achieving agent demilitarization and acceptable agent emissions during storage or transportation. Table 8-2 shows the alternative processes that might be used in this strategy. Because high-temperature processes to mineralize agent are similar in effect to the baseline incineration technology, these processes are considered as part of Strategy 2 (mineralization). The low-temperature, liquid-phase chemical detoxification processes are particularly suited for Strategy 1. It is assumed that the same process equipment can be used for all three agents and, taken as a whole, this approach is at the laboratory data-gathering stage of development. Because each agent may require different reagents, three separate laboratory and pilot plant programs would be required. Although each of these programs might normally require 12 years to progress through demonstration, they could be run in parallel and use common equipment. One of the processes (NaOH hydrolysis of GB) could form the basis for early demonstration. With skilled management and adequate talent and resources, the time to application of these processes probably could be significantly shortened. An attractive feature of the low-pressure, liquid-phase detoxification processes is their production of little or no gas. The high-pressure oxidation processes, however, produce a waste gas stream, which could be largely eliminated by capture of CO2 by lime. There would probably be few significant differences in the equipment requirements for the three agents for these high-pressure processes, apart from those related to corrosivity.
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Alternative Technologies for the Destruction of Chemical Agents and Munitions TABLE 8-2 Low-and Moderate-Temperature Agent Detoxification Processes Process Special Gas Treatment Needed Number of New Processes (Development Status) Low-temperature, liquid-phase detoxification No 3 (laboratory) Wet air or supercritical water oxidation Yes 1 (pilot plant) Removal of agent from metal parts and containers, and agent detoxification with decontamination fluid No 1 (pilot plant) The drainage of agent from weapons and containers is never complete. The amount of agent remaining might normally be between 1 and 5 percent. Thickened or degraded mustards, however, can leave larger residues. In all cases these residues must be removed and detoxified to meet demilitarization requirements and to be suitable for storage or transportation. The baseline technology does not require this step because the residual agent is immediately destroyed in the high-temperature kilns. Using this alternative strategy, additional facilities to clean out the residual agent would need to be added to the current disassembly procedure. Agent removal by water jets, solvent, or decontamination fluids should produce a stream that can be processed in the detoxification step. Such residual agent removal processes could be developed and demonstrated in parallel with development of the detoxification processes. Alternative processes for Strategy 2 (mineralization). As shown in Figures 8-1 and 8-2, drained agent is generally treated separately from the energetics, metals, and other solids resulting from weapons disassembly. Table 8-3 indicates the processes that might be used for agent mineralization and their development status.
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Alternative Technologies for the Destruction of Chemical Agents and Munitions TABLE 8-3 Agent Mineralization Processes Number of New Processes (Development Status) Case/Process Using Air Using Oxygen 1. Baseline incineration 0 (operational) 1 (demonstration) 2. Baseline incineration plus gas storage and certification 0 (operational) 1 (demonstration) 3. Fluidized bed or molten salt combustion 1 (demonstration) 1 (pilot plant) 4. Molten metal or plasma arc plus burner 1 (pilot plant) 1 (pilot plant) 5. Steam gasification plus burner 1 (pilot plant) 1 (pilot plant) 6. Supercritical water oxidation or wet air oxidation 1 (pilot plant) 1 (pilot plant) 1 (pilot plant) 1 (pilot plant) 7. Low-temperature, low-pressure oxidation 1 (laboratory) 1 (laboratory) 8. Biological oxidation 1 (laboratory) 1 (laboratory) For agent treatment, the liquid-phase detoxification processes mentioned under Strategy 1 could be followed by incineration (such as the baseline incineration technology) or by some combination of the pyrolysis and oxidation alternatives to complete the oxidation process. If supercritical water or wet air oxidation is chosen for detoxification, these follow-on processes might be unnecessary; however, some treatment of unoxidized organics might be necessary for wet air oxidation.
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Alternative Technologies for the Destruction of Chemical Agents and Munitions Cases 1 and 2 in Table 8-3 incorporate the baseline technology, which uses air and additional fuel in a two-step burner and afterburner system. This process is operational at Johnston Island without storage and certification of the flue gas stream. It is believed that addition of the storage and certification feature (Case 2) would not require demonstration beyond the normal startup and testing programs for a new installation. About an 85 percent reduction in flue gas volume can be achieved by substituting oxygen for air. Removal of CO2 by reaction with lime would give a large additional reduction in flue gas volume. Such systems could be designed and built based on current experience but would require demonstration. If the current incineration process is not chosen, a number of alternatives could be developed. For these technologies, development could be based on the use of oxygen without adding appreciably to technological risk or development time. In all these cases, at the least a pilot plant program would be needed, and in some cases additional laboratory data would be needed as well. Cases 3 to 5 in Table 8-3 are high-temperature, atmospheric pressure oxidation systems that, combined with appropriate afterburners, may be capable of mineralizing agent. Case 6, high-pressure, supercritical water or wet air oxidation, has the potential, with additional pilot plant work, to oxidize agent at relatively low temperatures. The water streams from both processes may require additional oxidation for complete mineralization. Cases 7 and 8 axe low-temperature, liquid-phase oxidation processes that could potentially be used to complete the oxidation of agent detoxification products. Both axe in a very early laboratory stage. However, they axe similar enough to oxidation processes used for other waste streams for the committee to be optimistic about their chances of success. Gas treatment would be necessary for these processes and, with biological oxidation, a waste sludge stream would be produced. For final disposal of energetics and metal parts and containers, destruction of energetics and heat treatment of metal parts and containers is required to eliminate any residual agent. The alternatives for carrying out these operations, in contrast to those for agent destruction, all require high temperatures. Table 8-4 lists these processes. The baseline system (Case 1 in Table 8-4) makes use of an internally fired rotary kiln to destroy energetics and small metal parts. An internally fired traveling-grate kiln is used for the larger metal parts, such as drained ton containers and drained 155-mm artillery shells. The mixture of pyrolyzed organic compounds and combustion flue gas from these kilns then enters a secondary burner for completion of combustion. As in the agent incinerator, the volume of gas in this system could be reduced by using pure oxygen rather than air. This modification again would require demonstration. Case 2 (Table 8-4)
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Alternative Technologies for the Destruction of Chemical Agents and Munitions TABLE 8-4 Processes for Treatment of Energetics and Metal Parts and Containers Number of New Processes (Development Status) Case/process Using Air Using Oxygen 1. Baseline kilns 0 (operational) 2 (demonstration) 2. Baseline kilns plus gas storage and certification 0 (operational) 2 (demonstration) 3. Electrically heated kilns 2 (demonstration) 2 (demonstration) 4. Molten metal furnace 1-2 (pilot plant) 1-2 (pilot plant) indicates a modification to the baseline that allows certification of gas emissions before release to the environment. The volume of gas can be further reduced by replacing internal firing with electrical heat (Case 3 in Table 8-4). Use of electrical heating and oxygen for oxidation would, after CO2 removal, almost eliminate flue gas. Any air leakage into the system would be discharged after cleanup and analysis. In Case 4 (in Table 8-4), a molten metal furnace could destroy energetics and all metal pieces (ton containers might need to be cut into smaller pieces). Combining the function of the baseline rotary kiln and the traveling-grate furnace could be a useful simplification. Energetics could probably be destroyed in other alternative processes (supercritical water oxidation, molten salt, fluidized-bed combustion, and plasma arc processes) if separated from their metal containers and broken into small particles. Complete removal of energetics from metal containers is expected to be difficult, and high-temperature treatment of metals would still be required. No large advantage is seen for these variations. All the high-temperature systems shown in Table 8-4 require afterburners and similar gas cleanup and handling technologies. The main difference between these systems and the baseline technology is substitution of electrical heating for internal firing. All of these processes also have the potential to destroy bulk agent. Treatment of all streams in one device, as in
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Alternative Technologies for the Destruction of Chemical Agents and Munitions the proposed cryofracture process, offers equipment simplification but with some loss of process control bemuse the several streams are processed together. This approach could lead to uncontrolled production of undesirable gas pollutants, for example. Afterburners are needed to ensure complete oxidation for all systems with waste gas production. The baseline practice is to use internal firing if additional heat is needed. Substituting oxygen for air and external heat for internal firing would minimize waste gas, but the former substitution 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, Cl, and S content of the agents. Molten salt systems might also be used as afterburners and for acid gas removal. Another variation would be to complete gas oxidation by supercritical water oxidation. In this case, it would be necessary to compress the gas to 3,000 psi. With use of afterburners, gas streams from any of the processes can be brought to specified levels of agent and organics destruction, which cart 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 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
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Alternative Technologies for the Destruction of Chemical Agents and Munitions the mount 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 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.
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Alternative Technologies for the Destruction of Chemical Agents and Munitions 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.
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Representative terms from entire chapter: