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Evaluation of Demonstration Test Results of Alternative Technologies for Demilitarization of Assembled Chemical Weapons: A Supplemental Review 2 Burns and Roe Plasma Arc Process The plasma arc process proposed by the Burns and Roe team uses modified baseline disassembly for munitions access. Agent, energetics, metal parts, and shredded dunnage are all treated in plasma waste converters (PWCs). The PWCs use plasma arc technology—electrically driven torches with various gases that produce an intense field of radiant energy and high temperature ions and electrons that cause the dissociation of chemical compounds. Materials are processed with steam in the absence of air to produce a plasma converted gas (PCG) that could be used as a synthetic fuel after cleanup and testing. The integrated PWC system used for the demonstration tests consisted of a PWC—a 300-kW unit capable of operating with a variety of gases (Ar, N2, CO2, etc.) in either of two modes: a nontransferred mode (arcing from electrode to electrode on the torch) and a transferred mode (arcing from torch electrode to the melt) (DOD, 1999b). A steam injection system was used for feeding liquids, and a box feed module with a horizontal ram feed was used for feeding solids via a conveyor to the PWC. The gas polishing system, a pollution abatement system, consisted of a quench, a venturi scrubber, a caustic (NaOH) scrubber, a demister, and a high-efficiency particulate air (HEPA) filter. The PWC system was the only unit operation that was tested. Other components used in the demonstration but not intended to demonstrate a specific unit operation are listed below (DOD, 1999b): a liquid feed module thermal oxidizers to characterize the effluent from burning PCG an energetics deactivation chamber (EDC) for generating and supplying the expected energetics off-gas feed to the PWC PLASMA WASTE CONVERTER Demonstration test campaigns of the PWC were planned for treatment of (1) energetics, (2) dunnage and secondary waste, (3) agent, and (4) projectile agent heels. Energetics Campaign The energetics campaign was required to validate that the PWC can destroy off-gas from a proposed EDC, which is used for thermal initiation of high explosive components (bursters and fuzes). The following test objectives were established for this campaign (DOD, 1999b): Demonstrate the feasibility of the proposed energetics destruction strategy using the integrated EDC demonstration unit and PWC system for high explosives and the PWC system for M28 propellant. Validate that the integrated EDC and PWC unit operations can achieve a destruction and removal efficiency (DRE) of 99.999 percent for energetics Comp B and tetrytol. Validate that the PWC unit operations can achieve a DRE of 99.999 percent for M28 propellant. Characterize the detonation gases and residues from Comp B and tetrytol from the EDC demonstration unit for suitability for processing in the PWC. Characterize the deflagration gases from the M28 propellant feed to the PWC system. Compare the detonation gases from the EDC demonstration unit to the deflagration gases from the M28 propellant in the PWC system. The energetics campaign was only designed to show that the PWC could destroy off-gas from the EDC. During the
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Evaluation of Demonstration Test Results of Alternative Technologies for Demilitarization of Assembled Chemical Weapons: A Supplemental Review demonstration, 16 grams each of tetrytol and Comp B were detonated in four test runs. Because the design of the detonation chamber was not the one intended for full-scale use, no attempt was made to evaluate its efficacy. Detonation gases were fed to the PWC. (Detonation usually efficiently destroys materials such as tetryl, TNT, and RDX.) The off-gases generated from the EDC were shown to be suitable for feeding to the PWC. In the opinion of the committee, the use of the EDC would be a poor solution for the destruction of a large volume of energetic materials. During the demonstration tests, M28 propellant was not completely ignited, which was attributed to poor propagation from the initiator. The technology provider explains that initiation at full scale will be accomplished by heating the energetic to 1,100°F. Although a small amount of M28 propellant was introduced directly into the PWC during the demonstration tests, the committee concluded that the test results did not demonstrate conclusively that the direct introduction of propellants would be safe. Dunnage and Secondary Waste Campaign The dunnage and secondary waste campaign was required to validate the destruction of solid and liquid secondary wastes and the decontamination of dunnage to a 5X level. 1 Characterization of gaseous, liquid, and solid effluents was required, as was verification of operating parameters. The demonstration tests had the following objectives (DOD, 1999b): Demonstrate that the PWC unit operation can process carbon filter media, demilitarization protective ensembles (DPEs), wooden pallets spiked with 4,000 parts per million pentachlorophenol, decontamination solution with carbon filter media, and M55 rocket shipping and firing containers. Characterize the process gases, liquids, and solids. Validate the ability of the PWC unit operation to meet a 5X condition for solid residues from these feeds. The demonstration test runs were designed to evaluate the treatment of a variety of dunnage materials, including oak pallets, activated charcoal, fiberglass shipping and firing containers, and DPE materials. Although the test plan originally called for separate testing with each material, the plan was subsequently modified to using a mix of materials. The tests demonstrated the PWC could treat these materials as a mixture, could achieve 5X temperature conditions, and could destroy the pentachlorophenol that had been spiked into the pallets. The mixed dunnage tests were the only demonstration runs in which sufficient carbon, oxygen, and hydrogen were available in the feed to generate synfuel with appreciable fuel value. The average fuel value of the PCG exceeded 100 Btu/scf in only one of the six mixed dunnage test runs. In several runs, the measurement technique for fuel value failed; in others, the measured average fuel value was very low. In all runs, the oxygen content of the PCG ranged from 5 to 7 percent. This was attributed either to air leakage into the PWC or downstream components or to a lack of control of the oxygen content in the feed materials and gases. The presence of a combustible gas premixed with oxygen clearly represents an unsafe condition susceptible to ignition. Fullscale operation would require design features and/or procedures that would preclude these conditions. The process did not produce PCG with an acceptable synfuel quality when a steady feed of carbon/hydrogen-containing material was used. Thus, the committee is concerned about the appropriateness, reliability, and robustness of the measurement and control systems. In addition, unless careful control of the steam-to-carbon ratio is maintained, excessive soot may form. Because the system does not include on-line monitoring of the carbon and hydrogen in the feed, the monitoring and control system must reliably measure fuel value and adjust parameters, such as steam flow, to achieve acceptable fuel quality. Such monitoring and control systems were not demonstrated during the test runs, and, therefore, must be developed to ensure the reliable operation of the system with variable feedstocks. Agent Campaign The agent campaign was required to validate the destruction of chemical agents. Characterization of gaseous, liquid, and solid effluents was required, as was verification of operating parameters. The test objectives for this campaign are listed below (DOD, 1999b): Validate that the PWC process can achieve a DRE of 99.9999 percent for chemical agents HD, GB, and VX. Characterize the process gases, liquids, and solids. Balance the elemental carbon and heteroatoms from each agent, to the extent possible. For various reasons, the equipment was not deemed ready for agent tests during the demonstration tests. Therefore, there was no direct demonstration of the ability of the proposed plasma technology to destroy chemical agents. The committee concluded that the variety of equipment problems encountered in the demonstration were due to the immaturity of the proposed integrated process and the particular demonstration equipment, and not due to a fundamental inability of plasma-based technologies to achieve acceptable 1 Treatment of solids to a 5X decontamination level is accomplished by holding the material at 1,000°F for 15 minutes. This treatment results in completely decontaminated material that can be released for general use or sold to the general public in accordance with applicable federal, state, and local regulations.
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Evaluation of Demonstration Test Results of Alternative Technologies for Demilitarization of Assembled Chemical Weapons: A Supplemental Review results. The history of plasma-based systems for waste treatment indicates that they can destroy chemical agents. Nevertheless, the operability, reliability, and repeatability of the integrated plasma system have not been demonstrated due to equipment failures, system redesigns, and operational modifications. Also, the committee was concerned that some of the agent could bypass the reaction zone (see the discussion below of Finding BR-1 under Review of Previous Committee Findings). Tests were conducted on the agent-surrogate, dimethyl methyl phosphonate (DMMP), and hydrolysates of HD and VX. In these tests, high DREs of both DMMP and hydrolysate compounds were achieved, increasing the confidence level that the proposed plasma-based process would be capable of destroying chemical agents. However, demonstration tests with neat chemical agents will be required to determine specific operational conditions, such as proper control of oxygen and steam, before pilot-scale evaluations can proceed. These tests will be particularly important for determining the formation of by-products, which is dictated by the materials processed, the stoichiometry for oxygen, steam, and carbon, and temperature conditions. The data on the by-products generated in the demonstration tests are of limited value because the tests were not run with agents. Projectile Heel Campaign The projectile heel campaign was required to validate the destruction of chemical agent that had adhered to metal parts and to demonstrate removal of the melt from the PWC. Characterization of gaseous, liquid, and solid effluents was required, as was verification of operating parameters. The test objectives for this campaign are listed below (DOD, 1999b): Validate that the PWC process can achieve a DRE of 99.9999 percent for chemical agent GB heels in simulated projectile shells. Demonstrate that the PWC can process simulated projectile shell heels using chemical agent in pipe nipples. Demonstrate melting of uncontaminated 4.2-inch mortar shells. Validate that the PWC unit operation can meet a 5X condition for solid residues from this feed. Characterize the gases, liquids, and solids. Demonstrate that the melt from the PWC can be removed. The first five objectives were not met because agent was not injected into the PWC. In addition, the sixth objective was not met because samples were manually removed. REVIEW OF PREVIOUS COMMITTEE FINDINGS The committee’s earlier findings concerning the Burns and Roe PWC technology package are quoted below and their status following demonstration tests is examined (NRC, 1999): Finding BR-1. No tests have been done involving actual chemical agent or propellant destruction in a PWC. Tests with agent and M28 propellant were planned for the demonstrations being conducted between February and May of 1999, but no data were available to the committee at the time of this writing. The demonstration tests conducted on the agent surrogate DMMP (a GB simulant), HD hydrolysate, and VX hydrolysate provided only limited data. The DMMP was 99.99997 percent destroyed; trace levels of thiodiglycol were detected in two of the six HD hydrolysate tests; and the levels of ethyl methyl phosphonic acid and methyl phosphonic acid in the VX hydrolysate tests were very low. Energetic materials (Comp B and tetrytol) were reported to be 99.9998 percent destroyed, but trace levels of RDX and TNT were detected. Components of M28 propellant were 99.97 percent destroyed (nitrocellulose) and 99.99998 percent destroyed (nitroglycerin). The detection of RDX and TNT in the PWC effluents is indicative that feed-stocks can bypass the reaction zone and exit without complete reaction. Thus, if chemical agents were fed to the PWC, they could potentially also bypass the reaction zone and be found in the effluents. Solving this problem will require ensuring thorough mixing in the PWC. Finding BR-2 Scale-up from the small PWC units in existence to the very large units proposed is likely to present significant scientific and engineering challenges. The numerous problems encountered in the demonstration described above confirmed this finding. Finding BR-3. Tests performed with one plasma feed gas may not be indicative of PWC performance with a different gas. Because different plasma feed gases have different thermodynamic and chemical properties, the choice of the plasma feed gas could have a significant impact on the performance of the system. For example, the electrical power requirements will be determined, in part, by the plasma feed gas. Electrode wear may also depend on the type of gas, and product gas composition will vary. Initially, the technology package proposal indicated that argon would be used as the plasma feed gas. This would distinguish the PWC from an incinerator because the inert gas is not an oxidizing agent. Citing the expense of argon, the technology provider subsequently shifted to carbon dioxide (CO2), which is cheaper, but introduces a source of oxygen. Computer calculations for various chemical agents introduced into a CO2 plasma at ~ 3,000 K predicted that agents would undoubtedly be destroyed but also indicated that large amounts of carbon soot would be formed as the hot gaseous mixture cooled. The presence of particulates of high surface area (that are probably pyrophoric) in the product creates a new problem. Also, electrical power requirements for CO2-plasma operation would be greater than for argonplasma operation.
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Evaluation of Demonstration Test Results of Alternative Technologies for Demilitarization of Assembled Chemical Weapons: A Supplemental Review In the actual demonstration tests, nitrogen (N2) was used as the plasma gas. Although N2 is a nonoxidizing species, reaction products of environmental concern (C2N2, HCN, metal cyanides, etc.) were predicted and were detected in the demonstration tests. The power requirements for N2-plasmas are acceptable. In summary, the technology provider has explored a few alternatives for plasma gases but may not have found the best choice. Also, the problem of torch failure could be minimized by a better choice of metals or by alternative designs. For water-cooled plasma torches, the metals must not react with the plasma gases and must still have high melting points to prevent a sudden release of water into the PWC (see the discussion following Finding BR-5). Finding BR-4. The technology provider’s proposal for recycling the liquid-scrubber effluent through the PWC to vitrify the salts may not be practical. If scrubber liquor is fed to a PWC, some of the contaminants may simply revolatilize. In addition, NaC1 and NaF salts could react with SiO2 at high temperatures to form gaseous SiCl4 and SiF4, respectively (both hazardous materials). The demonstration tests did not address the ability of the PWC to vitrify salts from recycled scrubber liquor. Finding BR-4 remains unchanged. Finding BR-5. The maintenance of negative pressure within the PWC has not been demonstrated under munition-processing conditions. Pressure excursions that produce positive pressure in the PWC vessel could release product gas to the surrounding room. Some upsets that could result in moderate to severe pressure excursions included: A leak in the torch-cooling system to release water into the PWC, and rapid steam formation could pressurize the vessel. Energetic material that remained in a mortar or projectile introduced into a PWC could detonate upon heating, which would generate a pressure pulse. An improper cut of the rocket motor could allow a larger-than-design piece of propellant to be introduced into the PWC. If the gas production rate from the propellant exceeds the capacity of the downstream PAS, the vessel could overpressurize. The primary safety problem apparent from the demonstration tests is an inability to maintain negative pressure. Overpressurization occurred several times during the tests due both to plasma torch failure and poor engineering system design (e.g., ram feeder blow-back and leaks in the gas polishing system). The failure of the plasma torch caused cooling water to be released into the PWC, which could have resulted in catastrophic overpressure that could have released agent, if any had been present. Thus, substantial further engineering development will be necessary, along with design and administrative controls to ensure the safe use of this plasma torch technology. According to the technology provider’s proposal, rocket propellant would be sent directly to the PWC, whereas explosives would be sent first to the EDC. Although a small amount of the propellant was tested in the PWC, the committee was concerned that larger amounts of propellant might detonate rather than deflagrate. The resolution of this issue has not been successfully demonstrated. Finding BR-6. Combustion of plasma-converted gas in a boiler faces three major hurdles: (1) to avoid being permitted under RCRA as a boiler burning hazardous wastes, the gas may have to be delisted; (2) the gas may require significant scrubbing to remove compounds that are unsuitable as boiler feedstock; and (3) the boiler will have to be configured to burn gas that has a low heating value efficiently in order to avoid generating unacceptable emissions. The Environmental Protection Agency (EPA) has recently established an exemption for synfuel produced from hazardous waste. Under the Comparable/Syngas Fuel Exclusion (40 CFR 261.38), synfuels that meet certain specifications are not classified as hazardous wastes and, therefore, could be burned without Resource Conservation and Recovery Act (RCRA) permits in boilers and industrial furnaces (a Clean Air Act [CAA] permit would still be necessary). The synthesis gas fuel specification has the following criteria: a minimum Btu value of 100 Btu/scf less than 1 ppmv of total halogen less than 300 ppmv of total nitrogen other than diatomic nitrogen (N2) less than 200 ppmv of hydrogen sulfide less than 1 ppmv of each hazardous constituent on a target list of 40 CFR 261 Appendix VIII constituents These stringent requirements were not met in any of the demonstration tests. It was not clear that the tests were designed to evaluate this specification, even though it would be critical to the development of an alternative disposal technology using PCG. Without this exemption, the PCG synfuel could not be used in boilers without a RCRA/CAA hazardous waste combustor permit subject to boiler and industrial furnace rules (the so-called “BIF rules”). The demonstration tests revealed several potential problems with PCG meeting the Comparable/Syngas Fuel Exclusion. Only one material tested in the demonstration (mixed dunnage) was converted to synfuel with an appreciable fuel value. Even for this material, the minimum Btu value (> 100 Btu/scf) was only demonstrated in one test (out of six). For all other tested materials, the Btu value of the synfuel was very low (generally close to zero). Furthermore, both the generation of hazardous air emissions and the conversion of carbon are strongly affected by carbon/oxygen stoichiometry. The generation of synfuel of insignificant Btu value in nearly all of the demonstration test runs casts doubt on the relevance of the emissions data to full-scale operation for most of the materials tested in the demonstration. The Comparable/Syngas Fuel Exclusion
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Evaluation of Demonstration Test Results of Alternative Technologies for Demilitarization of Assembled Chemical Weapons: A Supplemental Review specification for hazardous constituents would have to be demonstrated for the specific conditions that would yield a PCG with acceptable Btu value. In addition, a more complete profile of all 40 CFR 261 Appendix VIII compounds would have to be evaluated. Finally, the demonstration tests did not confirm that predictable control of the PCG heat content could be achieved, even when higher hydrocarbon feedstocks (such as mixed dunnage) are treated. Another challenge to meeting the Comparable/Syngas Fuel Exclusion requirements for PCG is maintaining low levels of nitrogen and halogen compounds. The NOx-level for every PCG material tested in the demonstration unit exceeded the criterion of less than 300 ppmv (~388 mg/m3) of total nitrogen other than diatomic nitrogen (N2). The removal of nitrogen compounds from the PCG synfuel is a critical process capability that was not demonstrated but is necessary for full-scale operation. The PCG synfuel generated from all of the test materials (except tetrytol) exceeded the total halogen requirement of 1 ppmv (~1,500 μg/m3) for chlorine despite the use of an acid scrubber. For example, PCG generated from DMMP in the demonstration tests had 26,980 μg/m 3 (approximately 18 ppmv) of chlorine, which is 18 times the Comparable / Syngas Fuel Exclusion of 1 ppm total halogens. Thus, the demonstration unit also failed to demonstrate that it could generate synfuel that meets these critical synfuel exclusion criteria. Finding BR-7. Although a PWC may not be considered to be an incinerator by permitting authorities, the most likely permitting procedures for a PWC would be similar to those used for incinerators. A key component of the Burns and Roe demonstration tests was to determine the characteristics of the flue gas when the synfuel is burned in the thermal oxidizer. These characteristics can suggest the emissions from a boiler or industrial furnace burning the PCG. In other permitting actions relating to plasma units that generate gas burned in catalytic oxidizers (e.g., the ATG facility in Richland, Washington, EPA Region 10), the EPA and state regulators used appropriate, relevant, and applicable rules (ARARs) based on the hazardous waste combustion rules. A comparison of the thermal oxidizer emission levels with the Hazardous Waste Combustion ARARs indicates that either additional cleanup of the PCG would be required or the emissions of the boiler/industrial furnace would require more rigorous scrubbing. This comparison is complicated by the highly dilute conditions in some of the thermal oxidizer exhaust (i.e., 12 to 20 percent oxygen). It is also worth noting that the thermal oxidizer used would not generally meet the carbon monoxide standard of 100 ppmv. A comparison of the hazardous waste combustion rules with the thermal oxidizer emissions data indicates that the combustion of PCG would not meet some standards, when corrected to the standard 7 percent oxygen, (e.g., the cadmium-plus-lead emission for the system configuration used in the demonstration tests for M28 propellants, mixed dunnage, and VX hydrolysate). Mercury emission could be a problem for M28 propellants, and particulate matter would be a problem for the treatment of mixed dunnage. Chlorinated dioxin/furan was not found to be problematic for the configuration demonstrated when compared to the hazardous waste combustion standard. In summary, the demonstration tests did not show that the PWC system could adequately control emissions for the direct combustion of PCG in a boiler or industrial furnace. SAFETY ISSUES In the earlier report, the committee made the following observation (NRC, 1999): Cooling water is circulated through the plasma torch to keep it from melting at the high plasma temperatures. A leak in the cooling system could spray water into the plasma. If the leak is sudden, rapid vaporization could cause a pressure pulse that might overload the downstream gas-handling equipment. Then, untreated agent could be released into the surrounding room through the torch opening in the top of the PWC. Similar “puffing ” has been observed in combustion equipment when excessive back pressure occurs. If the leak is gradual, the resuiting steam would dissociate in the plasma forming hydrogen and oxygen gas that could recombine and explode if the mixture is in the flammable range above its autoignition temperature. The effect of liquid water introduced into a plasma in the presence of other species present in PWCs must be determined before larger scale experiments are performed. . . . The technology provider is aware that torch failure is a concern, and the potential for an explosion has been reduced by the torch design and by redundant flow and pressure controls that would actuate fast-closing valves on the water feed as well as the waste feed in the event of a failure. The committee reiterates its earlier observation that appropriate design and administrative controls can ensure the safety of plasma arc technology (NRC, 1999). The technology provider proposes sending rocket propellant directly to the PWC, whereas, explosives will be sent first to the EDC. Although a small amount of the propellant was demonstrated to deflagrate in the PWC, the committee is concerned that larger amounts of propellant may detonate rather than deflagrate. The committee does not believe this issue has been successfully demonstrated. The addition of nickel to the melt to form a conductive bed for the transferred arc operation constitutes another issue regarding worker safety (Burns and Roe, 1999a ). Airborne nickel particulate is very hazardous and should be assessed further with respect to worker exposure during normal operations, anticipated transient conditions, maintenance, and accidents. The recovery of molten metal may require more access
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Evaluation of Demonstration Test Results of Alternative Technologies for Demilitarization of Assembled Chemical Weapons: A Supplemental Review by workers during operations, as well as increased maintenance. Increased access would also increase worker exposure to hazards over predemonstration estimates. REEVALUATION OF STEPS REQUIRED FOR IMPLEMENTATION The committee’s earlier report identified the following five steps required for implementation (NRC, 1999): Determine the effect of sudden water injection into the plasma torch in the presence of argon, nitrogen, carbon dioxide, and other species present in the plasma system. Include an evaluation of the effect of gases present in the PWC on the flammability range of hydrogen gas. Determine the likelihood of the release of untreated agent and other hazardous contaminants from the PWC if the gas generation rate is unexpectedly high (e.g., due to a cooling-water leak, the inadvertent introduction of explosive material into the chamber, or a rapid deflagration of propellant). Conduct a thorough analysis of the product gas generated from each PWC using the plasma feed gas proposed for full-scale operation. This analysis should include the identification of organic intermediates that would be of concern in an HRA [health risk assessment]. Establish the efficacy of pollution-control equipment in removing hazardous compounds (e.g., NOx, SOx, HC1, and metals) from the product gas. Perform a larger-scale demonstration of PWC operation that includes the hold-test-release step. None of these steps was completed in the demonstration tests. Furthermore, the test results do not readily indicate how the concerns raised by the committee could be addressed. Clearly, extensive testing with chemical agents will be necessary if PWCs as currently proposed by the technology provider are to be used. As discussed in Finding BR-5, serious doubts have been raised about the reliability of the torch design and the maintenance of negative pressure in the system, and, hence, about the safety/efficacy of this system. The committee believes a properly configured and operated plasma arc process would be a robust, indiscriminant thermal process capable of destroying chemical agents. However, on the basis of observations during two site visits to plasma arc installations (Ontario Hydro Technologies, Toronto, Ontario, and Aberdeen Providing Ground, Maryland), the results of the demonstration tests, and a review of the available demonstration data, the committee concurs with the Army’s conclusion that the Burns and Roe process is too immature to be considered as a viable solution for the destruction of assembled chemical weapons at this time. SUPPLEMENTAL FINDINGS Finding BR-1. The plasma torch apparatus, as demonstrated by the Burns and Roe team, is not qualified for further consideration for the demilitarization of assembled chemical weapons. The torch design appears to be unreliable for extended use. Furthermore, the design increases the possibility of a catastrophic water leak, which could produce a significant increase in pressure in the PWC, and possibly cause an explosion, which, in turn, could expose personnel to chemical agent. Moreover, the effectiveness of the monitoring and control sensors was not demonstrated. Finding BR-2. Even after more than a year of research and development, the technology provider has not been able to show that its small PWC can adequately destroy agent simulants or that nitrogen is the best gas to use for the plasma feed. If oxygen leaks into the reactor, it could react violently with hydrogen. If air were used for the plasma feed gas, regulatory compliance issues would arise, as well as questions of public acceptance. Finding BR-3. In the absence of any data for processing effluents from agent runs, the committee could not validate the ability of the proposed system to handle and stabilize effluent products from agent processing.
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