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Recommendations for the Disposal of Chemical Agents and Munitions 6 Comparison of the Baseline System and Alternative Technologies INTRODUCTION This chapter compares candidate alternative technologies to the baseline for the purpose of identifying those that can reduce the total cumulative risk to the public and the environment from stockpile storage and disposal operations. As a basis for comparison, the screening and selection criteria mentioned in Chapter 4 are expanded in the next section. A large number of potential alternatives were considered, which are presented later in the chapter, and have been taken directly from the report Alternative Technologies for the Destruction of Chemical Agents and Munitions (Alternatives report, NRC, 1993a). In that report and here, alternatives are conveniently grouped in six categories: low-temperature, low-pressure detoxification; low-temperature, low-pressure oxidation; moderate-temperature, high-pressure oxidation; high-temperature, low-pressure pyrolysis; high-temperature, low-pressure oxidation; and other technologies. Many of these technologies are, or can be, developed for safe disposal of a variety of hazardous materials in general. However, it was necessary for the committee to use engineering judgment in developing its recommendations for promising alternatives for the very special requirements of this disposal program. In addition to the necessary fundamental process capabilities, and in keeping with the committee's desire to minimize cumulative total risk, technology readiness becomes an important selection criterion. Promising technologies that require extensive research and development programs are unlikely to be of use to this program. The section on agent destruction processes examines the candidate alternatives at two levels. A first screening is used to eliminate unattractive candidates, with brief comments in this report. For more detailed discussion of these technologies, the reader is directed to the Alternatives report. The second-level examination discusses in greater detail those alternatives that are considered attractive. Appendixes D, E, and F are provided for background on these technologies.
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Recommendations for the Disposal of Chemical Agents and Munitions No single technology, including incineration, can meet all criteria with a single process. The committee recommends further study of four alternative technology combinations for agent destruction, all based upon neutralization of the agent as a first step. In addition, an "enhanced" baseline system is discussed. The issues involving handling of gelled agent as an impediment to all technologies that are designed to transfer or treat liquid materials are discussed after the alternative technologies have been presented. The section on metals, energetics, and dunnage disposal describes why the committee could not identify feasible alternatives to baseline system for disposal of metal parts, energetics, or dunnage. Consequently, the remainder of the chapter focuses largely on alternative technologies for agent destruction, as have virtually all calls for alternative technologies. Successful alternatives will thus impact disposal operations only as replacement for the liquid incinerator. All neutralization processes must be followed by secondary treatment to meet both environmental and treaty disposal requirements. This raises the option of transporting the relatively nontoxic neutralized material to another site for secondary treatment. This option may offer economic as well as safety advantages. The chapter concludes with a section that estimates the time necessary to implement the recommended options. BASES FOR SELECTING ALTERNATIVE TECHNOLOGIES In Chapter 4, five criteria are listed as the bases for selecting disposal technologies. The first of these, safety, in the form of minimum cumulative total risk to workers, the public, and the environment is the principal criterion. The other four criteria all relate to the technical capabilities of the candidate technologies. Safety In the absence of detailed quantitative risk assessments of the alternative technologies it is necessary to consider the safety information that is available in some systematic and orderly form. In particular, the following safety factors were considered in reducing the number of potential technologies to those four on which specific findings and recommendations are made.
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Recommendations for the Disposal of Chemical Agents and Munitions Inherent Safety Features Obviously the objective in the design of any system is a facility that is inherently safe. Conditions that contribute to inherently safe systems are low temperature and pressure; simplicity in design; nontoxic effluents (gases, liquids, solids); and simple operations and maintenance. Requirements for Engineered Safeguards Facilities for processing and handling hazardous materials require engineered systems to ensure safety of operation. Such safeguards might be containment systems, effluent cleanup systems, fire suppression systems, emergency power sources, and specially designed systems for the control and mitigation of accidents. Risk Potential The two types of risk that were considered in the technology screening process included (1) the risk from accidents and operational upsets, and (2) the risk from normal facility operations in terms of the health and safety impact of waste streams. Process Readiness Process readiness involves time for process development, engineering and construction requirements, and startup and early operations. As discussed in Chapter 4, time is an important safety issue because disposal delays can adversely affect the cumulative total risk. Process readiness and time are also economic issues, in terms of research and development costs and extended storage costs, but these are of lesser concern than safety. Typical industrial development components are preliminary process design, bench scale testing, and pilot plant testing. The pilot plant phase can include design specifications, facility design modifications, procurement of equipment, and permits. The engineering and construction phase includes design specifications, final process design, and preliminary and final facility design, while obtaining permits and gaining public acceptance. Startup and operations include training; systems integration, testing, and checkout; and operational verification testing.
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Recommendations for the Disposal of Chemical Agents and Munitions Technical Capabilities Principal considerations in assessing a candidate technology's capabilities are the treatment of process materials, environmental impacts, and treaty compliance. Multiple materials must be processed, including agent (three types), energetics, metal parts, and dunnage. Successful technologies, or combinations of technologies, must produce environmentally acceptable waste products (gaseous, liquid, and solid) suitable for final disposal. Treaty compliance issues are the irreversibility of the agent destruction process and the schedule for completion of disposal operations. LISTING OF ALTERNATIVES The Committee on Alternative Chemical Demilitarization Technologies' Alternatives report presented a structured listing of potential alternative technologies and a detailed discussion of each. That listing (slightly amended by the Stockpile Committee) is repeated here as Table 6-1. Each of these technologies is then discussed briefly for preliminary selection, followed by a more detailed discussion of those technologies to be recommended for further development. INITIAL SCREENING OF AGENT DESTRUCTION PROCESSES Evaluations of Destruction Processes All of the technologies of listed in Table 6-1 were evaluated, based on the preceding selection considerations. The evaluations are summarized below. Many of these technologies have been developed and will find application for ordinary industrial wastes. However, most were ruled out for the very special materials of interest here, (i.e., chemical agents or munitions). Only four are recommended for development. Low-Temperature, Low-Pressure Detoxification Several processes have been suggested for chemically altering the agents to render them nontoxic. The products in all cases would not be acceptable for immediate disposal, but would require further treatment. These processes therefore represent the first step of a multistep destruction system.
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Recommendations for the Disposal of Chemical Agents and Munitions TABLE 6-1 Summary of Process Capabilities and Status Stream Treated Agent Metal and Energetics Process Initial Agent Detoxification Complete Organic Oxidization Afterburner Needed Energetics Metal Afterburner Needed Next Step Comments Low-temperature, Low-pressure detoxification Base hydrolysis (NaOH) GB, VX 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 100ºC) 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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Recommendations for the Disposal of Chemical Agents and Munitions Stream Treated Agent Metal and Energetics Process Initial Agent Detoxification Complete Organic Oxidization Afterburner Needed Energetics Metal Afterburner Needed Next Step Comments Low-temperature, low-pressure oxidation Peroxydisulfate, CIO2, H2O2, O3 All Yes Yes No No N.A. Lab Catalysts generally needed for complete conversion; spent peroxydisulfate can he electrochemically regenerated UV light with O3 or 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 Enzyme-catalyzed hydrolysisa GB Possibly VX; not mustard No Yes No No N.A. Lab Moderate-temperature, high-pressure oxidation Wet air and supercritical water oxidation (SCWO) All Partially Yes Yes? No Yes PP Residual organic components can be low for SCWO; residual materials are believed suitable for biodegradation
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Recommendations for the Disposal of Chemical Agents and Munitions Stream Treated Agent Metal and Energetics Process Initial Agent Detoxification Complete Organic Oxidization Afterburner Needed 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 trait 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. SOURCE: NRC, 1993a. a The Committee on Review and Evaluation of the Army Chemical Stockpile Disposal Program added this information to the original Table, found in the 1993 report, Alternative Technologies for the Destruction of Agents and Munitions, NRC, 1993a.
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Recommendations for the Disposal of Chemical Agents and Munitions The mild operating conditions—low temperature and pressure—are an attractive feature of these processes. There is little likelihood of large accidental release, and the formation of toxic gases is usually not a problem. The processes do generate a large volume of liquid solution, and in some cases this is a major handicap. Chemical ''neutralization'' (or hydrolysis) is possible with any of several reagents. The most commonly used have been bases, such as sodium hydroxide, potassium hydroxide, calcium hydroxide, and ethanolamine (hydrolysis or solvolysis), and oxidizers such as sodium hypochlorite. See Appendix E for details. Neutralization of GB has been carried out on a large scale. Its application to VX and to HD has been held up by problems: both materials have limited water solubility; reaction rates have generally been slow; and some products of VX can themselves be highly toxic. However, a recent research program of very limited scope has already shown promising results for both VX and mustard, using hot (75-90º) alkaline hydrolysis. This work is described in detail in Appendix F. Much remains to be done to prove a full scale system capable of treating field-grade materials, including gelled mustard. Given proper support, this approach may well provide an effective alternative within a schedule compatible with minimum overall cumulative risk. An advantage of neutralization with bases (exception—ethanolamine) is that no "additional" chemical material is added to the overall system; the bases are ultimately required to form salts with the acidic products of agent oxidation (i.e., NaCl, NaF, Na3PO4) that are acceptable for disposal. Hydrolysis is also possible by use of acids, such as hydrogen chloride. The acidic solution has two disadvantages: (1) it is corrosive, and (2) the acid must ultimately be neutralized to form additional salts, which add to the solid waste from the process. Acidic hydrolysis appears unattractive compared with basic hydrolysis. Low Temperature, Low Pressure Oxidation Several reagents have been proposed for both hydrolysis and either partial or complete oxidation: hypochlorite, peracids such as oxone (KHSO5), potassium persulfate (K2S2O8), and other oxidizing agents such as hydrogen peroxide or chlorine oxide. Little experimental work with agents or surrogates has been done. Potassium persulfate, a very strong oxidizing agent, is believed capable of completely mineralizing the agent. A very large amount is required however, leading to a large increase in the waste material to be handled—sulfuric acid or potassium sulfate solution diluted with the acidic products of the oxidation (HCl, H3PO4, etc.; see Appendix E). Recycle of the sulfuric acid
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Recommendations for the Disposal of Chemical Agents and Munitions is complicated by the presence of these other acidic materials. The persulfuric acid reagent is made electrolytically. The amount required would represent a large power consumption for the agent destruction (see discussion of electrochemical oxidation, below) The persulfate oxidation has been considered unattractive for this application. The other oxidants are not strong enough to perform complete mineralization; a follow-on oxidation process would be required. At the same time, some of them complicate the process by adding to the final volume of solid waste. They are not considered sufficiently attractive to pursue. One oxidant, hydrogen peroxide, is under investigation as an aid to caustic neutralization (of VX). Ultraviolet light with ozone or hydrogen peroxide and a catalyst (TiO2) is another oxidizing system evaluated by the Alternatives Committee. However, it appears best suited for removal of trace quantities of contaminants. Bulk destruction on a large scale has not been attempted and appears to have severe limitations, including a large photon requirement and the low penetration of ultraviolet light into the reaction mixture. Ionizing radiation has been suggested, but it is believed to be at an early research phase, with many problems anticipated. Electrochemical oxidation has been proposed for many chemical reactions. Complete oxidation requires a very active catalyst; Ag(II) has been proposed. It also has a large power requirement—estimated at close to 1 megawatt for 24 hours, to mineralize 1 ton of GB. The process has serious disadvantages for agents because of their heteroatom content (Cl, F, P, and S), which greatly complicates recycle of the electrochemical agents (as in the sulfate/persulfate cycle). The committee believes that this process is not ready to handle agents; a substantial research and development effort would be required. The committee considers biological oxidation to be an unlikely candidate for neat agents. No biological material has been found that is resistant to mustard, for example. A more likely application of biological oxidation is as a second step following initial detoxification of the agent. The committee has considered it for oxidation of the products of caustic neutralization or the products of wet air oxidation (see Appendix F for a more detailed discussion). Finally, enzyme-catalyzed biological hydrolysis of nerve agents may be possible. Proof of concept has been demonstrated for GB on a laboratory scale. Hydrolysis of VX has been observed but currently at reaction rates too slow for practical application. The time required for development of enzymes with increased activity for VX is not predictable because of the nature of the basic research required. Similar enzyme-based processes for both GB and VX would have to be available for practical application to the stockpile configuration. Therefore, engineering development appears premature. Traditional biological oxidation processes (analogous to wastewater treatment
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Recommendations for the Disposal of Chemical Agents and Munitions processes) would not be appropriate for direct detoxification of GB or VX because of the extremely high destruction efficiencies required. No biological process has been found that is directly applicable to mustard. Discovery of such a process for mustard is extremely unlikely because of its general xenobiotic characteristics. Moderate-Temperature, High-Pressure Oxidation Two related processes are listed in Table 6-1: wet air oxidation and supercritical water oxidation. Both processes are capable of destroying neat agent. They are both, however, high-pressure processes, operating at 2,000 to 4,000 psi (pounds per square inch). The committee questions the safety of handling toxic agent at this pressure. Both processes are subject to severe corrosion problems because of the release of strong acids in the oxidation process, such as hydrogen fluoride (HF) and hydrogen chloride (HCl). Corrosion might be handled by very special materials of construction. Alternatively, it could be controlled by addition of caustic to neutralize the acids formed. If the latter approach is taken, the processes appear particularly suitable for cleanup of the products from caustic neutralization (discussed above). The neutralized material is in dilute aqueous solution and already contains excess caustic, conditions that would avoid the acids that cause corrosion. More detailed reviews of these two processes are provided in Appendix D. High-Temperature, Low-Pressure Pyrolysis Several pyrolysis processes developed for other applications have been suggested for chemical agents. All produce combustible gases at high temperature, which would then require the same kind of gas clean-up used in the baseline system. That is, they would be burned in an afterburner and then scrubbed of acidic material before release. These new processes would therefore replace only the first stage, the liquid agent incinerator, in the baseline system. The molten metal furnace not only pyrolysis the agent but also should react some of the heteroatom materials in the metal or slag. There seems little question that the destruction process should be rapid and complete. However, it does not appear to offer a significant advantage over the current process, since a similar afterburner and gas scrubber will be required. As a consequence, the committee does not recommend a development program to demonstrate the process on agent.
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Recommendations for the Disposal of Chemical Agents and Munitions The plasma arc furnace appears to be in the same category with molten metal. That is, it produces a combustible gas, which will then require the same follow-on equipment as the baseline system. As a result, it does not offer a significant advantage over the current incinerator design. Several steam reforming gasification processes were reviewed: a synthetic process for waste destruction and several steam gasification processes for production of a synthesis gas. All can be expected to have trouble with the larger heteroatom content of the chemical agents. All will require follow-on steps resembling the baseline system (afterburner, gas scrubber). As a consequence, the committee judged them not to offer significant advantages over the baseline system. High-Temperature, Low-Pressure Oxidation The committee evaluated three alternative combustion processes. Catalytic fixed-bed oxidation is applicable only to low concentrations of agent in air, well outside the normal flammable range, where a catalyst is needed. The process does not appear suitable as a result. Fluidized-bed combustion, uncatalyzed or catalyzed to aid nitrogen oxides (NOx) destruction, is a reasonably established process. As with other processes, it could replace the liquid incinerator but would require the rest of the baseline system. The committee judged it as not offering a significant advantage over the baseline. Molten salt is a promising technology that can combine combustion with acid gas removal in one unit. Combustion reactions in molten salt have been demonstrated to produce high rates of conversion from feed material to oxidation products. However, the long-term mechanical operability of the process appears difficult: a considerable development effort would be required. In addition, the committee judged that to apply this technology to highly toxic materials, an afterburner and gas scrubber would still be required. It thus does not appear to offer sufficient advantage over the baseline incinerator to justify the development time required. Ordinary high-temperature, low-pressure combustion, as in incineration, also fits in this category, but not as an "alternative" in the present sense. It is capable of mineralizing dunnage, agents, and energetics, but must be followed by an afterburner and proper pollution abatement systems to meet environmental requirements.
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Recommendations for the Disposal of Chemical Agents and Munitions Other Technologies The committee evaluated two technologies that did not fit the categories listed above. Hydrogenation has been recommended by its proponents as a process for recovering useful chemicals, primarily fuels, from wastes. This process depends on suitable catalysts. Chemical agents, with their large content of heteroatoms would require a long-term development effort. As a consequence, the committee did not consider this alternative further. An entirely different approach is the reaction of waste material with sulfur. The process has many interesting aspects. For instance, the major product is a hard, black solid, consisting primarily of carbon and sulfur, with uncertain composition. The process appears to be in an early research and development stage, with uncertain chemistry and possible mechanical problems, such as fine dust formation. The committee judged it not sufficiently mature to be recommended for agent destruction. Alternative Processes Recommended for Further Research and Development Although no single process, including incineration, can do the entire job of agent destruction and waste treatment, several combinations of processes deserve further study as alternatives to the liquid incinerator and follow-up components of the baseline system. The four most promising alternatives to destroy liquid agent are based on neutralization as an initial step. Neutralization is an attractive approach because it operates at low temperature and atmospheric pressure in conventional chemical reactors (Appendix E). However, it is a limited technology that merely converts agents to less toxic products, rather than "mineralizing" them or destroying them as required by the 1993 Chemical Weapons Convention. To replace a liquid incinerator completely, it is necessary to follow neutralization with a process such as wet air, supercritical water, or biological oxidation that irreversibly destroys the products of neutralization. Although these combined processes offer no advantage in destroying energetics or in decontaminating agent-bearing metal parts, neutralization-based systems, with suitable posttreatment, can replace the liquid incinerator. They are, therefore, of particular interest where agent is stored only in bulk. There are several neutralization-based combinations of processes that are potentially useful for destroying blister and nerve agents. The most promising integrated systems, in the committee's judgment, are described below.
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Recommendations for the Disposal of Chemical Agents and Munitions Neutralization can be followed by incineration of the hydrolysis products, either on site or after being transported to another site equipped with a liquid incinerator. If the neutralization products are to be transported to another site, a high hydrolysis efficiency will be required. Neutralization can be followed by wet air oxidation. This approach is attractive because wet air oxidation is a well-developed technology and can utilize a feed stream that is less completely hydrolyzed than would be needed for transportation. Because the wet air oxidation products would be water streams containing much organic matter (but little or no agent), a subsequent treatment for water-borne organics, such as conventional biological oxidation, would be required. Neutralization followed by supercritical water oxidation resembles the preceding option. However, as a consequence of the severe reaction conditions of supercritical water oxidation, it may yield a completely mineralized water stream without follow-up oxidation. In contrast to wet air oxidation, however, supercritical water oxidation is not a proven commercial technology. The utility of an agent destruction system based on supercritical water oxidation depends on successful outcomes of current research programs. Neutralization followed by biological treatment would operate under mild process conditions throughout the system and might yield products directly suitable for disposal. Development would require modified neutralization processes and identification of organisms or enzymes adapted to the hydrolysis reaction products from each type of neutralized chemical agent. These integrated systems are discussed in more detail below. Although many other combinations of processes could yield useful integrated technologies, the four systems listed offer the greatest prospects for success. The Stockpile Committee urges aggressive research and development to evaluate the applicability of these integrated systems. Neutralization—Incineration Systems For the two arsenals that store only bulk agent, a system based on neutralization followed by incineration may be uniquely advantageous. In principle, the liquid agent (HD or VX) drained from ton containers can be detoxified by chemical hydrolysis. Treatment of mustard with aqueous sodium hydroxide at 90ºC produces a water solution of thiodiethanol, sodium chloride, and a mixture of thioethers. Early laboratory results indicate that treatment of VX with sodium hydroxide and hydrogen peroxide converts the agent to phosphonic and sulfuric acid derivatives of greatly reduced toxicity. Neither the HD nor the VX products, however, meet the irreversibility requirement
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Recommendations for the Disposal of Chemical Agents and Munitions of the Chemical Weapons Convention. This problem can be addressed by feeding the products to a liquid incinerator much as is done with decontamination fluids in the baseline system. Incineration achieves complete mineralization of the organic products. A potentially attractive application of this approach might avoid incineration facilities at Aberdeen and Newport. To accomplish this goal, it will be necessary to achieve a high degree of hydrolytic destruction of agent in the neutralization step; obtain permission from other states to transport, store, and burn the neutralization products; and develop methods to decontaminate the drained ton containers to the extent that the metal can also be transported for thermal treatment at another site or deposited in a hazardous waste landfill. If these requirements can be met, the neutralization-incineration system has the potential to be implemented rapidly at the two sites, probably with less capital investment than the baseline system would require. It will offer little advantage elsewhere except as a way to reduce the hazard of bulk agent storage prior to incineration. On-Site Treatment of Products of Neutralization As detailed previously, the "neutralization" process yields reasonably nontoxic products, which, however, are complex organic materials unsuitable for immediate disposal. Further oxidation is required, particularly for complete mineralization. Three processes have been recommended for further development: wet air oxidation, supercritical water oxidation, and biological oxidation. The operating characteristics, capabilities, and limitations of wet air oxidation and supercritical water oxidation are reviewed in Appendix D. Both are capable of oxidizing neat agent. Because both are high-pressure processes (1,000-2,000 psi for wet air oxidation; more than 3,200 psi for supercritical water oxidation), it is the committee's judgment that a neutralized-agent feed to either process is much preferred to the agents themselves as the process feed.
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Recommendations for the Disposal of Chemical Agents and Munitions The combination of neutralization followed by one of these three alternatives is synergistic: The product from neutralization is a fairly dilute aqueous solution of organic material; it is the form required as feed to any of these processes. Corrosion is expected to be a problem with wet air oxidation and supercritical water oxidation (see Appendix D for details). This problem is minimized by the addition of caustics to neutralize the acids (HCl, HF, etc.) produced by oxidation. The excess caustic required for corrosion control can be added during neutralization to drive that process. Biological processing of neat agent may be impractical for nerve agents (GB, VX) and impossible for mustard agents (H, HD, HT). No process for mustard is known, but enzymatic hydrolysis has been demonstrated for the nerve agents (see Appendix F for details). Bioprocessing of the neutralized agents, however, appears more promising. Research and development will be needed for each of these processes. Some important problems have been identified that require engineering solutions, for example: Materials of construction for wet air oxidation and supercritical water oxidation, capable of handling the corrosion problems, require further work (Appendix D). The salts formed by caustic addition are insoluble in the fluid phase in supercritical water oxidation: "plugging" problems caused by these salts have been a concern. Operating requirements will have to be determined to ensure that the products meet environmental standards. Other problems will arise as the technologies—neutralization followed by an oxidation step—are integrated into an operating system. Wet air oxidation is the most developed of the three oxidation processes. However, although it is capable of breaking down the chemical agents, it produces intermediate products that are refractory and persist in the product stream. The intermediates, partially oxygenated materials such as acetic acid or methylphosphonic acid, can represent 2040 percent of the carbon in the feed. As a consequence, the product solution from wet air oxidation will need further processing. This final treatment is usually done in commercial wet air oxidation processing by biodegradation. The agent destruction will then require a three-step process: neutralization, wet air oxidation, and bioprocessing. The three oxidation processes offer other advantages in addition to their natural synergism with neutralization:
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Recommendations for the Disposal of Chemical Agents and Munitions They can all be operated with oxygen (or air highly enriched in oxygen) instead of air. They thus have the potential of being operated as "closed-cycle" systems. That is, the gaseous product can be reduced to a small enough volume that it can be conveniently stored for analysis before release to the atmosphere. The carbon dioxide normally produced can be largely collected as additional salt (sodium carbonate) by excess caustic. This has a further benefit for a closed-cycle system (as defined above), but results in a large solid waste stream. Gelled Agent Occurrence of gelled HD is common, as discussed in Chapter 3. Gelling has also been observed in GB. The gel and other solids do not drain completely. Containers with a major "heel" of undrained material will be very difficult, if not impossible, to decontaminate by nonthermal processes. A process for gel removal will be needed if metal parts, decontaminated to 3X, are to be shipped to another location. Some possibilities are chemical treatment to depolymerize the gel; use of high-pressure water jets to wash out gel; and moderate heating (˜300ºF) plus steam purging to distill agent, which can be recondensed in a closed system for routine processing with liquid agent. METALS, ENERGETICS, AND DUNNAGE DISPOSAL Energetics Treatment Energetic materials cannot be safety disposed of in their existing state. They must be "deactivated" as are explosives and propellants from ordinary, nonchemical munitions. This has normally been done by burning the materials. Propellants and explosives are formulated to burn spontaneously, though not completely. They are fuelrich: additional oxidant (air) is needed to complete their combustion. Furthermore, care must be exercised to ensure that they burn rather than detonate, principally by avoiding confinement of the burning materials. The baseline components for disposing of these materials—slicing or punching containers to avoid confinement, and burning in a rotary kiln followed by an afterburner and gas scrubber—has been effective. Indeed, the baseline deactivation furnace system is a scaleup of the
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Recommendations for the Disposal of Chemical Agents and Munitions Ammunition Peculiar Equipment (APE) rotary kiln in successful use for many years to dispose of conventional munitions. Many of the technologies listed in Table 6-1 are capable, in terms of chemical reactions, of destroying (mineralizing) the energetics in the chemical stockpile. However, physical extraction of cast-in-place bursters and propellants from their metal housings and conversion to finely divided slurries that could be fed to these processes would be difficult and perhaps hazardous. A Joint Services Large Rocket Motor Disposal Program has been undertaken to explore environmentally acceptable alternative means for large rocket motor demilitarization to replace open burning and detonation (DOD, 1993). The program includes two research goals: removal of the propellant from its containers, and disposal or reclamation of the propellant. Propellant removal options were mechanical excavation, and high-pressure liquid jet excavation using water or liquid nitrogen (the latter, in a conceptual stage, for subsequent reclamation of the propellant and to avoid a liquid waste stream). Although feasible for large containers, all options were judged by program researchers to be unlikely means to excavate explosives from a long, small-diameter cavity such as a burster tube. Reclamation techniques are of no interest for propellants and explosives contaminated with agent. Disposal techniques ranged from conventional two-stage combustion followed by exhaust gas cleanup (including an enhanced version of the APE kiln) to biodegradation. The latter, having shown some experimental promise in treating highly diluted "pink water" propellant solutions, is in an early experimental stage and would require even further research to treat agent-contaminated solutions. Wet air oxidation and supercritical water oxidation are under consideration in that program and could destroy the energetics effectively if the materials are properly prepared for a slurry feed (see Appendix D regarding limitations of these technologies). Development work would be needed to demonstrate extraction and preparation systems for chemical munitions, as well as the subsequent oxidation process. Because effluent treatment and waste products are similar to those for the baseline system, there would appear to be no safety advantage over baseline system (and possibly a disadvantage in view of the more complex preparation processes). All of the high-temperature pyrolysis processes and most of the high-temperature oxidation processes are capable of destroying the energetics. None appears to offer any significant advantage over the baseline system, however. All would require an afterburner to complete oxidation, followed by a gas cleanup system. Waste production would be the same as baseline, with no apparent increase in safety. Molten salt is claimed to perform a very complete oxidation so that secondary combustion is not needed. Although this may be generally true, the
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Recommendations for the Disposal of Chemical Agents and Munitions highly unsteady discharge from energetics reactions, coupled with significant agent contamination, dictates secondary combustion for safety in this case. Other technologies such as hydrogenation of energetics and sulfur oxidation are judged to be at very early research and development stages and are not applicable to this program. Metal Parts Decontamination Virtually all metal parts will be contaminated with agents, and some may contain significant amounts of gelled agent. No alternative to high-temperature treatment (1000ºF for 15 minutes) has been proven to render metal parts safe for release to the public (the 5X condition). The baseline system uses a fuel-fired metal parts furnace to provide this treatment for large metal parts and an electrically heated discharge conveyor for treatment of solids emerging from the deactivation furnace system. Many of the oxidation and pyrolysis processes are capable of detoxifying metal parts to this condition, but they are not suited to metal parts feed, especially large metal parts such as ton containers. Low-pressure processes such as molten metal, plasma arc, and steam reforming could in principle handle intermittent feed, but they offer no improvement in safety or waste products over the baseline system. The use of electrical power, rather than combustion of fuel, to provide heat in the first stage of the metal parts furnace would reduce the flue gas generated by this system. Gases discharged from this first stage would still require an afterburner and gas cleanup system, just as in the present baseline system. Chemical decontamination of metal parts to the 3X level for transport to another facility or for disposal in a hazardous waste landfill remains an attractive alternative if the transport option is available and if gelled agent problems can be overcome. Dunnage Disposal Dunnage includes wood, paper, and other ordinary industrial waste materials. Most dunnage is not contaminated with agent, but some is, and all must be handled as if it is. Disposal of this waste must therefore safely process some agent as well as a mixture of typical industrial materials. Because the dunnage incinerator has not yet been proven at the Johnston Atoll Chemical Agent Disposal System (JACADS), dunnage from that
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Recommendations for the Disposal of Chemical Agents and Munitions operation has been packaged (after being decontaminated to 3X) for disposal at a hazardous waste landfill. Alternatives to acceptable incineration or landfill are not evident. Landfill works, but it may not be a satisfactory solution for the disposal program as a whole. The volume to be processed over a period of years, as well as the mixed nature of this stream, makes a waste reduction process highly desirable. The most efficient of these is reduction by incineration. ENHANCED BASELINE SYSTEM Flue gas emissions from the incinerators of the baseline system are the source of greatest public concern from the deployment of this system. The operations at Johnston Atoll have more than satisfied all requirements for control of agent and toxics discharge concentrations, but accidents or upsets could, in principle, produce unacceptable performance until the problem is detected and corrected (or operations ceased). For agent emissions in the stack gases, the time delay for detection with today's monitoring systems is about 3 to 8 minutes, when detecting at 0.2 of the allowable stack concentration. Detection at this level triggers an automatic shutdown. Confirmation of agent release (versus interfering compounds) requires about 30 minutes. In addition, the public fears unknown emissions of products of incomplete combustion. The following options are available to improve the management of flue gas emissions from the baseline system: capture and temporarily store the entire gas stream until chemical analyses confirm it is safe for release; drastically reduce the volume of waste gas by using electrical power for process heat, using pure oxygen rather than air, condensing all water vapor, and capturing carbon dioxide on lime to produce solid calcium carbonate; and use charcoal scrubbing, as with ventilation air, to remove virtually all residual agent as well as other toxics such as dioxins and other high molecular weight chlorinated compounds. Of these options, which are discussed in more detail in the Alternatives report, only charcoal scrubbing is considered in detail here (and in Appendix C). The first two options are not considered as attractive as charcoal scrubbing due to the complexity and size of the systems required and the more extensive development and testing program that would be necessary for implementation.
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Recommendations for the Disposal of Chemical Agents and Munitions For charcoal scrubbing, gas is typically passed through a stack of six 3-inch-deep beds of high-surface area, activated carbon. High molecular weight, moderately polar molecules, such as agent and dioxins, are adsorbed on the charcoal and drastically reduced in gas concentration. The ventilation air scrubbers at JACADS, for example, were designed to reduce agent concentration by a factor of 10,000 in each 3-inch bed and demonstrated a reduction of 400,000 with fresh beds during the Operational Verification Testing (OVT) VX rocket test. The JACADS ventilation air charcoal beds are monitored after the first, second, and fourth 3-inch beds to detect breakthrough of agent as the first beds become saturated. These saturated beds are replaced when agent is detected beyond bed 2. The lifetime of the first bed was months, even though it was exposed to an appreciable agent content in the ventilation air, providing adequate time for analysis and shutdown before breakthrough in the stack of six beds. Subsequent beds thus remain ''fresh'' for months. Lower molecular weight compounds are also removed by charcoal with an efficiency inversely related to gas temperature. Water vapor must be held to a level that avoids formation of liquid water within the beds.1 The combination of these two factors requires cooling of flue gas upstream of the bed to condense water, followed by some reheat to eliminate further condensation in the charcoal. Drying the stack gases in this way would also avoid formation of a visible plume. By removing most organic compounds, charcoal scrubbing would greatly reduce the number of false alarms from stack gas monitors. The choice of operating temperature is an important compromise, since cooling is expensive, but removal of organic contaminants improves as temperature is reduced. For example, a desirable temperature might be about 100-150ºF, compared to the present stack temperature of approximately 230ºF at JACADS. Advantages of the charcoal system are elimination of agent discharge from the stack, even during system upsets or accidents; long advance warning and simple monitoring for system maintenance; reduction of other industrial pollutant discharges; and elimination of visible stack plume. 1 Activated charcoal can be used to adsorb unwanted materials from gases or from water (as in gas masks or in common filters used in the home to improve drinking water). However, if the charcoal is wet, gaseous contact with the charcoal is blocked and gas cleanup is ineffective.
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Recommendations for the Disposal of Chemical Agents and Munitions Disadvantages are increased requirement for disposal of spent charcoal; and the potential fire hazard presented by the charcoal bed. There is already a requirement for disposal of charcoal from ventilation air scrubbers, so no new risk or technology is added. Adequate fire protection will be necessary. In any case, as with every proposed system change, the decision to install a charcoal scrubber system must be justified by a proper evaluation of advantages and disadvantages. Appendix C contains a more detailed discussion of charcoal bed technology. Charcoal scrubbing is a proven technology for agents (gas masks and JACADS ventilation air experience). It is being increasingly used (in another form) for scrubbing waste gases from European incinerators, but it cannot yet be considered an industrially proven technology at the temperatures considered here. Some development work will be necessary for the proposed charcoal scrubber system and for the associated gas cooling and dewatering system, but the committee foresees no unusual problems. DEVELOPMENT REQUIREMENTS FOR ALTERNATIVE TECHNOLOGIES The potential alternative chemical agent destruction systems identified here have not yet undergone the range of scientific research and engineering development required to certify that they will indeed provide safe, effective, and efficient alternatives to incineration. Key component processes for each of these systems have not progressed past a scientific proof-of-principle stage for at least one, if not more, of the chemical agents to be destroyed. In many cases, even scientific proof of principle has not been demonstrated for individual component processes with agent or agent decomposition products. In order to advance to the status of a viable alternative technology, each potential alternative technology must progress through three levels of research and development: laboratory-scale scientific proof-of-principle demonstration for each system component over the full range of agent chemical and physical compositions and agent decomposition products expected under operational conditions; component process integration into a bench-scale simulation of the alternative technology system and successful demonstration with a full range of agent compositions to provide basic data for further scaleup; and
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Recommendations for the Disposal of Chemical Agents and Munitions engineering, construction, and successful test demonstration (OVT) of an essentially full-scale pilot plant. The time and resources required to progress through each of these research and development levels increase substantially at each step. Time estimates for a slightly more complex alternative technology research, development, and demonstration program were developed in the Alternatives report. That report estimated that 9-to-12 years would be required to move from the laboratory to successful demonstration, if each research and development level is carried to completion before starting the next is started. This time estimate can be reduced by carrying out work on various research and development levels simultaneously. For example, the full-scale demonstration plant could be designed and built while laboratory research and development and small pilot plant work were still under way (at some financial risk, of course). This telescoping of research and development stages is practiced in the chemical industry and is becoming more common, because of the drive for cost reduction and a more competitive market position. A total time of 3-to-5 years after scientific proof of principle is not uncommon. The committee believes that a well-managed and well-funded program, with a strong staff, can develop and demonstrate the alternative(s) of interest in as little as five to seven years. However, this laboratory-through-demonstration schedule assumes that excessive permitting delays (greater than a two-year permitting cycle) for the demonstration and production plants are not encountered. It is significant that permitting for the JACADS and Tooele facilities has required three years each despite the Army's strong efforts to meet permitting requirements expeditiously. Given the increased risk of accidental or chronic exposure from storage imposed by delaying the stockpile destruction, it is important that the most promising of the identified potential alternative technologies be advanced past scientific proof-of-principle as soon as possible. A second reason for moving forward promptly is the fact that the third level of research (pilot plant), described earlier, to be conducted at the Chemical Agent Munitions Disposal System (CAMDS), will require the use of a portion of the stockpile currently stored at Tooele. The Tooele baseline disposal system is scheduled to commence operation soon, and the committee does not recommend that complete destruction of the Tooele stockpile be artificially delayed just to preserve feedstock for an alternative technology demonstration plant at CAMDS.
Representative terms from entire chapter: