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THE NATIONAL ACADEMIES Advisers to the Nation on Science, Engineering, and Medicine Board on Army Science and Technology Mailing Address: 500 Fifth Street, NW Washington, DC 20001 www.nationalacademies.org August 25, 2010 Mr. Conrad F. Whyne Director Chemical Materials Agency 5183 Blackhawk Road Edgewood Area Aberdeen Proving Ground, MD 21010-5424 Re: Review of the Design of the Dynasafe Static Detonation Chamber (SDC) System for the Anniston Chemical Agent Disposal Facility Dear Mr. Whyne: At your request, the National Research Council of the National Academies established the Committee on Review of the Design of the Dynasafe Static Detonation Chamber (SDC) System for the Anniston Chemical Agent Disposal Facility. The purpose of the committee was to review the SDC design as stated below and in the statement of task, given in Appendix A. The committee was provided with information on the Anniston SDC1200 system that was undergoing testing in Europe. This SDC system is being acquired as an efficient means to destroy mustard agent projectiles and mortar rounds at Anniston Army Depot that could present problems for processing through the existing Anniston Chemical Agent Disposal Facility. The committee’s general findings and recommendations are given below. Specific findings and recommendations are given in the attached report. All of these findings and recommendations are based on the presentations, drawings, and design documents provided to the committee on March 30, 2010, and April 1, 2010, by the Army and its contractors—URS Corporation and UXB International, Inc.—and on the committee’s subsequent information-gathering activities.1 Together with Mr. Douglas Medville, another committee member, I visited the workshop in Kristinehamn, Sweden, where the unit was being assembled and tested. Before, during, and after the visit, our questions on construction and operation details were answered by the Army and its contractors. It is noteworthy that significant changes to the planned mode of operation of the pollution abatement system (PAS) were being made or contemplated as this report was being prepared, and that only information received as of June 27, 2010, has been considered by the committee. However, no changes in the overall design of the SDC system to be installed at Anniston from what is described in this report are anticipated. 1 UXB International, Inc., represents Dynasafe in the United States.
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The SDC system being readied for installation at Anniston is the eleventh to be manufactured and operated around the world and will be among four used to destroy chemical weapons. However, the Anniston unit will be the first to process chemical munitions in the United States. The committee was also provided with information on the performance of the Dynasafe SDC2000 installed at Gesellschaft für Entsorgung von Chemischen Kampstoffen und Rüstungs-Altlasten (GEKA), which has been in operation at Munster, Germany, since April 2006. By April 2008, this SDC system had destroyed 28,000 World War I and World War II chemical munitions, and since then has primarily been destroying conventional munitions. 2 It is similar in design to the SDC1200 to be installed at Anniston Army Depot. The GEKA system has demonstrated a destruction and removal efficiency of greater than nine nines (99.9999999 percent) for mustard agent while meeting German environmental regulation requirements (NRC, 2009a).3 Because the GEKA system has operated effectively and safely for a number of years and information on its design and operation was available, the committee focused on any impacts that might be expected from differences between the GEKA and Anniston systems. The review examined the system for feeding the munitions to the detonation chamber, the detonation chamber itself, the metal scrap discharge system, and the PAS (the latter must reduce emissions below U.S. environmental regulatory limits). This letter report provides the technical information necessary to support the general and specific findings and recommendations of the committee. The analysis satisfies the tasks delineated in the following extract from the committee’s complete statement of task, given in Attachment A: …Obtain detailed information on the design of the Anniston Dynasafe SDC1200 CM system and review and comment on the design of the system with emphasis on the pollution abatement system (PAS). Determine the design basis for each unit operation and review materials of construction. Compare the design of the PAS being designed for Anniston with that currently in use at the GEKA facility in Munster, Germany and identify all differences. Evaluate any potential impacts of these differences. Obtain requirements for agent destruction within the Static Detonation Chamber (SDC) system and for emissions from the PAS. Evaluate and comment on the ability of the planned SDC system to meet these requirements. The committee’s general findings and recommendations are the following: 2 Personal communication between Holger Weigel, Vice President, Dynasafe International, and Managing Director, Dynasafe Germany; Richard Ayen, committee chair; and Douglas Medville, committee member, May 5, 2010. 3 The cited reference refers to the NRC report, Assessment of Explosive Destruction Technologies for Specific Munitions at the Blue Grass and Pueblo Chemical Agent Destruction Pilot Plants (NRC, 2009a). This report examined and rated various types of explosive destruction technologies, including the Dynasafe SDC, for their applicability to meet the requirements for several destruction campaign scenarios that were being considered for implementation at the two pilot plants being constructed under the Assembled Chemical Weapons Alternatives program.
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General Finding 1. The SDC1200 system to be used at Anniston Army Depot offers a safe and effective method for destroying reject mustard agent munitions that could otherwise be difficult to disassemble safely through the machinery at the Anniston Chemical Agent Disposal Facility. Note, however, the concerns to be addressed by the Army regarding operation of the spray dryer and management of dioxin-and furan-containing waste as described in the following General Findings and Recommendations. General Recommendation 1. The Army should use the Dynasafe system to destroy the reject mustard agent munitions from the Anniston Chemical Agent Disposal Facility, provided that the factory acceptance testing at Kristinehamn and the preoperational testing at Anniston are satisfactorily completed and the system receives a Resource Conservation and Recovery Act permit modification from the Alabama Department of Environmental Management for operation at Anniston Army Depot and Department of Defense Explosives Safety Board approvals. General Finding 2. The committee was not convinced the thermal oxidizer in the pollution abatement system for the Dynasafe SDC1200 for Anniston will sufficiently oxidize all the organics, including dioxin and furan precursor compounds, to minimize formation of dioxins and furans in the downstream spray dryer. General Finding 3. The committee did not find a precedent for using a spray dryer as a rapid quench to control formation of dioxins and furans (polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans) as proposed by Dynasafe. The hot gas from the Dynasafe SDC1200 at Anniston in the spray dryer of the pollution abatement system must be quenched to below 200ºC rapidly to minimize dioxin and furan formation. Dynasafe has no previous experience in using a spray dryer for this purpose. However, the activated carbon beds in the pollution abatement system should adequately control dioxin and furan emissions from the stack. General Recommendation 2. Computational fluid dynamics modeling should be performed to verify satisfactory performance of the spray dryer in the pollution abatement system of the Dynasafe SDC1200 at Anniston. Modeling of this complicated three-phase system might be difficult, but the modeling should attempt to verify uniform gas flow entering the spray section, proper dispersion of the scrubber liquid in the gas, rapid quenching, minimal buildup on the spray dryer walls, and the formation of dry, flowable solids. General Recommendation 3. The Army and its contractors should develop backup plans in the event that the spray dryer for the Dynasafe SDC1200 system to be installed at Anniston Army Depot does not adequately minimize dioxin and furan formation. Options include installing a conventional rapid quench similar to the one used at GEKA and investigating how to dispose of activated carbon containing these compounds. The Army and its contractors should have a means of disposing of activated carbon and other secondary wastes that are produced in the pollution abatement system and may be contaminated with dioxins and furans.
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General Finding 4. Although Dynasafe has some experience in spray drying spent scrubber brines, its ability to effectively reduce this particular brine to dry, flowable solids has not yet been demonstrated. General Recommendation 4. The Army and its contractors should test the spray dryer during preoperational testing at Anniston to develop suitable conditions for reducing scrubber brine to dry, flowable solids. General Finding 5. The materials of construction for the Dynasafe SDC1200 are the same or very similar to the materials that have been used for the SDC2000 at GEKA, which has been in operation since 2006. The committee found no cause for concern regarding the anticipated performance of the materials of construction for the Anniston installation. More specific findings and recommendations are provided in the detailed analysis that follows. Sincerely, Richard J. Ayen, Chair Committee to Review the Design of the Dynasafe Static Detonation Chamber (SDC) System for the Anniston Chemical Agent Disposal Facility Attachments A Statement of Task B Abbreviations and Acronyms C Committee on Review of the Design of the Dynasafe Static Detonation Chamber (SDC) System for the Anniston Chemical Agent Disposal Facility D Acknowledgement of Reviewers
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Detailed Analysis of the Design of the Anniston Static Detonation Chamber INTRODUCTION The Army is in the process of destroying projectiles and mortars that contain the chemical agent mustard at the Anniston Chemical Agent Disposal Facility (ANCDF) located on the Anniston Army Depot (ANAD) in Anniston, Alabama. It has already collected 246 leaking and 61 rejected projectiles and mortars from among the munitions that have been processed, and based on statistics, anticipates that more rejects will be collected before the operations are completed. The “leakers” are sealed in overpacks and returned to storage. The “rejects” are munitions that could not be disassembled robotically in the linear projectile-mortar disassembly machine because the nose plug, burster, or burster well could not be removed. In some cases, the burster has broken and part of the burster remains in the well. As reject munitions become apparent, they are returned to a dedicated storage igloo to await future disposal. Were the leakers and rejects to eventually be processed through the ANCDF, it would require that they be disassembled manually by workers wearing personnel protective equipment known as demilitarization protective ensemble suits. This operation nonetheless would expose the operators to a high safety risk. Rather than exposing the workers to this additional risk, the Army will use an explosive detonation technology (EDT) to destroy the munitions without disassembling them. The particular EDT system that the Army plans to use is a static detonation chamber (SDC) system manufactured by the Swedish company, Dynasafe AB. The detonation chamber is conceptually illustrated in Figure 1. It shows the munitions dropped into the heated, thick-walled detonation chamber and resting on a scrap bed of hot metal fragments from previously processed munitions. The heating of the explosives in the munitions and/or the pressure generated from the heated liquid agent contents eventually cause the munitions to rupture and add to the scrap bed, which is periodically reduced by a chamber tipping procedure. The complete SDC system contains a munitions handling and loading system and a detonation chamber with a pollution abatement system (PAS) and a metal scrap disposal system. This SDC system was fabricated in Germany and, as this report was being prepared, was being assembled and tested in Kristinehamn, Sweden. When testing was completed, the system was to be shipped to ANAD. The various units are housed in between 20 and 25 ISO (International Organization for Standardization) shipping containers. They will remain in these containers and they will be abutted, stacked, and connected to form a complete system. These containers also will serve as secondary containment for the system. This system could be disassembled after operations are completed at ANCDF and moved to another site or used to destroy conventional munitions. As mentioned in the cover letter, Dynasafe has produced ten similar systems that have been used throughout the world. The system for Anniston will be the eleventh. As of April 2010, two of the eleven systems had been used to destroy chemical weapons. With the ongoing installations in Japan and at Anniston, the number put to this use increases to four. However, no two of these systems are identical, because specific
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FIGURE 1 SDC cutaway showing basic detonation chamber construction and concept of operation. SOURCE: Tim Garrett, Site Project Manager, ANCDF and Charles Wood, ANCDF Deputy Operations Manager, URS, “Static detonation chamber (SDC),” presentation to the committee, March 30, 2010. customer requirements have been implemented in each project.4 Also, the Army has two Dynasafe chambers—not complete explosive destruction technology systems—installed at its Munitions Assessment and Processing System facility at the Aberdeen Proving Ground in Maryland (NRC, 2009a), which processes chemical munitions recovered from burial sites, and which makes the Army familiar with, and comfortable with, Dynasafe detonation chambers. The Army has requested the National Research Council through the auspices of the Board on Army Science and Technology to assemble a committee to …Obtain detailed information on the design of the Anniston Dynasafe SDC1200 CM system and review and comment on the design of the system with emphasis on the pollution abatement system (PAS). Determine the design basis for each unit operation and review materials of construction. Compare the design of the PAS being designed for Anniston with that currently in use at the GEKA facility in Munster, Germany and identify all differences. Evaluate any potential impacts of these differences. 4 Personal communication between Harley Heaton, Vice President, Research, UXB International, Inc., and Harrison Pannella, NRC, study director, April 28, 2010.
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Obtain requirements for agent destruction within the Static Detonation Chamber (SDC) system and for emissions from the PAS. Evaluate and comment on the ability of the planned SDC system to meet these requirements. The complete statement of task is presented in Attachment A. This report contains the committee’s detailed findings and recommendations. The general findings and recommendations are presented in the cover letter. REGULATORY AND PERMITTING BACKGROUND, EMISSIONS LIMITS, AND OTHER PERFORMANCE REQUIREMENTS The ANCDF is designed to dispose of chemical nerve agents, mustard agents, agent-containing munitions, contaminated refuse, ton containers, liquid wastes, and explosive and propellant components. From a regulatory perspective, the facility is considered a hazardous waste disposal facility. The ANCDF operates under a Resource Conservation and Recovery Act (RCRA) permit, AL3 210 020 027, issued pursuant to the Code of Alabama 1975 §§ 22–30–1 et seq. ANCDF must also comply with any ANAD Clean Air Act Permit. On March 19, 2010, ANAD filed an application with the Alabama Department of Environmental Management (ADEM) to modify its RCRA permit to allow the addition of one permitted miscellaneous (RCRA Subpart X) unit—an SDC, which will enable the thermal treatment of both chemical and conventional waste munitions.5 Due to the varied nature of these units, requirements for construction and operation of Subpart X miscellaneous units are generally established in the permit. However, ADEM regulations require that miscellaneous units do not release materials that may adversely affect human health or the environment if waste constituents migrate in the groundwater or subsurface environment, surface water or wetlands or on the soil surface, or in the air. In addition, the terms and conditions for a miscellaneous unit permit must include the requirements for other types of treatment units, as appropriate for the miscellaneous unit being permitted.6 As set forth in the application and accompanying regulatory filings, this miscellaneous unit will need to meet the requirements for a hazardous waste incinerator. Under the regulations, RCRA regulations concerning hazardous air emissions do not apply to hazardous waste incinerators that demonstrate compliance with the Hazardous Waste Combustor Maximum Achievable Control Technology (MACT) requirements by conducting a comprehensive performance test, submitting to the ADEM a notification of compliance, and documenting compliance under the ADEM air quality regulations.7 As stated in the application for modification, ANAD will comply with National Emission Standards for Hazardous Pollutants Hazardous Waste Combustor MACT 5 Public Notice-424, Alabama Department of Environmental Management, Notice of Request for Comments and Announcement of Public Hearing for Modification of the Operating Permit under the Alabama Hazardous Wastes Management and Minimization Act (AHWMMA) and Notice of Proposed Air Permit. 6 ADEM Administrative Code (ACC) 335–14–5-.24(2), March 30, 2010. 7 ACC 335–14–5-.15(1)(b), March 30, 2010.
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requirements.8,9 This rule stipulates emission standards based on the performance of maximum achievable control technology, commonly referred to as MACT standards, because the EPA used the MACT concept to determine the levels of emission control.10 In essence, MACT standards ensure that all major sources of air hazardous air pollutant emissions are controlled to a level achieved by the best controlled and lowest emission sources in each category. The EPA found that this approach assures citizens that each major source of toxic air pollution is being effectively controlled.11 The MACT standards limit emissions of chlorinated dioxins and furans,12 carbon monoxide and hydrocarbons, toxic metals (including mercury and arsenic), hydrogen chloride and chlorine gas, and particulate matter. The ANAD application for RCRA permit modification states that performance standards to be met are as follows: Destruction and removal efficiency (DRE) of 99.9999 percent for mustard agent (HD/HT); Emissions from products of incomplete combustion from the stack such that the CO level in the stack, corrected to 7 percent O2, are not to exceed 100 ppm, dry volume, over a rolling hourly average; Emission levels for mustard agent, measured by an automatic continuous air monitoring system (ACAMS) installed at the stack, are not to exceed a maximum stack emission (mg/m3) of 0.006 rolling hourly average and 0.03 instantaneous; and Particulate matter emissions from the common stack, corrected to 7 percent O2, are not to exceed 0.013 grains per dry standard cubic foot (dscf).13 The final permit will establish the emissions limits for the following parameters in terms of grams per second (g/s): HCl emissions; Metal emission rates for antimony, arsenic, barium, beryllium, boron, cadmium, chromium, cobalt, copper, lead, manganese, mercury, nickel, phosphorus, selenium, silver, thallium, tin, vanadium, and zinc; Volatile, semivolatile, and total organic compound emissions; Dioxin/furan emissions; and Energetic emissions.14 8 The ADEM has incorporated by reference the federal Environmental Protection Agency (EPA) National Emission Standards for Hazardous Air Pollutants for Source Categories (ACC 335–3-11-.01, March 30, 2010). 9 Tim Garrett, Site Project Manager, ANCDF, and Charles Wood, ANCDF Deputy Operations Manager, URS, “Static detonation chamber (SDC)," presentation to the committee, March 30, 2010. 10 The MACT standards reflect the “maximum degree of reduction in emissions of … hazardous air pollutants” that the Administrator determines is achievable, taking into account the cost of achieving such emission reduction and any non-air-quality health and environmental impacts and energy requirements [Section 112(d)(2)]. 11 64 FR 53038, September 30, 1999, as amended, at 65 FR 42297, July 10, 2000; 67 FR 6986, February 14, 2002; 70 FR 59540, October 12, 2005. 12 Polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans. 13 A grain is defined as 1/7000th of a pound.
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These emission limits will be established after emission testing is completed and the results are compared with the Human Health Risk Assessment. During normal operations, the established emissions limits must be met by limiting the overall feed rate into the SDC. ANAD will submit a request to modify the permit to include numerically specified data for the above parameters not later than 90 days following the emissions test.15 As part of the application for a RCRA permit modification, ANAD filed a proposed emissions test plan. The test plan defines operating conditions and munitions feed rates that will be used to determine SDC performance in accordance with ADEM hazardous waste incinerator standards. ANCDF is proposing two emissions tests for the SDC system, one using worst-case mustard-agent-filled munitions and the other using conventional munitions. These tests must be done at Anniston after the system is installed there. The mustard-agent-filled munitions emissions test was developed to establish an agent feed limitation and to demonstrate a DRE of ≥99.9999 percent while processing 4.2-in. mortars fed up to 12 mortars per hour, which is equivalent to 72 pounds per hour (lb/hr) of mustard agent and/or 1.7 lb/hr of energetics. The emissions test should also demonstrate an allowable rolling average stack concentration for mustard agent of <0.006 mg/m3 and an allowable instantaneous stack concentration for mustard agent of <0.03 mg/m3. As described in Section 1.0 of the emissions test plan (Westinghouse Anniston, 2010), the overall goals of the emission tests are to demonstrate that emissions are less than the screening levels established in the Human Health Risk Assessment for the site and to verify that the SDC system does not pose an unacceptable risk to public health and the environment when operating at normal conditions. In addition to complying with any Clean Air Act permit requirements, the generation, storage, treatment, and disposal of secondary wastes (i.e., wastes generated during the preparation and treatment of waste munitions in the SDC) must also comply with all applicable RCRA characterization and management regulations, including compliance with any waste control limits for mustard agent and standards for all other hazardous constituents, as established in the RCRA permit modification. Finding 1. As detailed in documentation provided to the committee, the Army appears to be complying with all required procedures for obtaining permits for the planned static detonation chamber facility. 14 The term “energetic emissions” is permit terminology. For clarity, this refers to undestroyed explosive material that would more accurately be termed “emissions of energetics (explosives)” and not to emissions emitted at a high energy level. 15 ANAD permit EPA ID Al3 210 020 027, Module V (ModR6).
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DESIGN OF THE DYNASAFE SDC SYSTEM FOR ANNISTON Overall Process This section provides a brief overall description of the SDC system. The various operations are described in greater detail in subsequent sections. The SDC system is being fabricated by Dynasafe with most components installed in ISO containers and as such delivered to Anniston. It will be installed on a concrete foundation near the existing ANCDF and housed in a Sprung structure. Most of the system will remain within the ISO containers, which will serve as secondary containment. The system will be operated 10 hours per day 5 days a week. The flow of materials through the process is shown in Figures 2a and 2b. The munitions scheduled to be destroyed each day will be delivered at the beginning of each morning. First, each munition is strapped into a preformed polyethylene tray and then manually placed on the input conveyor (Dynasafe, 2010).16 Each tray will contain from one to four munitions depending on the physical size of the munitions and the nature and quantity of the contained energetics.17 After loading the munitions onto the conveyor, personnel will vacate the Sprung structure and move to the control facility. The remainder of the process is controlled remotely from the control room. Each loaded tray is conveyed to the munition lift and raised to the top of the SDC (Dynasafe, 2010). The first blast door is opened and the tray is pushed into loading chamber 1. This door is closed and the second blast door is opened. The tray is pushed from loading chamber 1 onto a cradle in loading chamber 2 above the detonation chamber. In this position, the cradle assembly blocks the opening into the detonation chamber below. The cradle is rotated 90 degrees and the munition tray drops into the chamber. Loading chambers 1 and 2 are shown in Figure 2a, with loading chamber 2 shown in both its horizontal (loading mode) and vertical (discharging) positions. The detonation chamber is double-walled with an air space between the two walls. It is split into upper and lower parts. When in operation, the two parts are sealed together with a hydraulically operated locking ring. The inner wall, which receives damaging impacts from fragments, can be replaced. The chamber is heated electrically at the bottom, as indicated in the cutaway view shown in Figure 3, and maintained at an operating temperature of 1022ºF (550ºC), although the temperature will spike briefly above this value when a munition detonates or deflagrates. Agent contained within a munition cannot survive as agent when exposed to this temperature for more than 15 minutes.18 The burster charge in the projectile or mortar will either deflagrate or detonate as the munition heats up and will burst the munition open. Also upon heating, the liquid agent in the munition evaporates, generating enough 16 Personal communication between Gene Wells, SDC Area Supervisor, ANCDF, Richard Ayen; committee chair; and Douglas Medville, committee member, May 4, 2010. 17 Personal communication between Gene Wells, SDC Area Supervisor, ANCDF; Richard Ayen, committee chair; and Douglas Medville, committee member, May 4, 2010. 18 According to Department of the Army Pamphlet 385–61, Toxic Chemical Agent Safety Standards, Section 5–6, agent is destroyed and materials contaminated by agent are considered clean and may be released for unrestricted use to the public if heated to an internal temperature of 538ºC (1000ºF) for at least 15 minutes (U.S. Army, 2008). Materials decontaminated in this manner were formerly (and still sometimes are) denoted as being decontaminated to a 5X condition.
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FIGURE 2a Process flow diagram for front components of Dynasafe SDC1200 installation for Anniston Army Depot. SOURCE: Adapted from personal communication between Holger Weigel, Vice President, Dynasafe International, and Managing Director, Dynasafe Germany, and Richard Ayen, committee chair, May 12, 2010.
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Pressure Equalization Tank Processing at Anniston The pressure equalization tank is a cylindrical reservoir (63 in. diameter × 155.4 in. high) that reduces the pressure and flow rate surges produced in the SDC off-gas during detonation or deflagration of munitions. A 35-mm (1.38-in.) diameter critical orifice at the exit of the pressure equalization tank further restricts pressure and flow rate excursions in the off-gas flow provided to the rest of the PAS equipment, thereby allowing operation that is nearer to optimum design conditions for the PAS unit operations. 40 The pressure equalization tank also acts as a cyclone since it has a tangential gas inlet and a vertical gas outlet, thus allowing larger particulates and small metal pieces to drop out and collect in the conical bottom. This collected particulate matter is periodically and automatically transferred to a holding container through a discharge system using two valves. During detonation or deflagration of munitions, the SDC is operated in an oxygen-starved mode. The pressure equalization tank is designed and constructed to withstand an explosion fueled by the off-gases. No such event has occurred during past SDC operation. The contents of the pressure equalization tank after a detonation or deflagration in the SDC include H2;CO; HCl; sulfur and nitrogen compounds; and, typically, large quantities of carbonaceous particulate matter (soot).41 Both the pressure equalization tank and the 3.94-inch diameter lines connecting it to the SDC are electrically heat traced to maintain wall temperatures above 300ºC (572ºF) at all times, including nights and weekends,42 to prevent internal condensation of liquids or any unburned energetics or chemical agents. However, holding the combination of oxidation products, HCl, oxygen, and carbonaceous particulates near 300ºC approximates conditions like those that are understood to promote dioxin and furan formation (Reimann, 1992; Grandesso et al., 2008). If such compounds did form, they would have to be oxidized in the thermal oxidizer. Finding 5. Conditions in the pressure equalization tank of the pollution abatement system for the Dynasafe SDC1200 system for Anniston are similar to those known to promote formation of dioxins and furans. Processing at GEKA The GEKA system has an expansion tank followed by a separate cyclone (NRC, 2009a). However, according to Dynasafe, the separate cyclone “did not add value,” so a 40 An orifice is considered a critical orifice if it is sized to induce sonic fluid flow (Mach = 1). This prevents pressure fluctuations downstream of the orifice from affecting the flow rate through the orifice. The Dynasafe SDC1200 critical orifice is machined into a replaceable 5-mm-thick stainless steel plate inserted between flanges in a 100-mm (3.94-in.) pipe and is intended to limit pressure and flow rate fluctuations in downstream operations. 41 Harley Heaton, Vice President, Research, UXB International, Inc., “Design features of the SDC 1200 CM installation at ANCDF,” presentation to the committee, March 30, 2010. 42 Personal communication between Harley Heaton, Vice President, Research, UXB International, Inc., and Harrison Pannella, NRC, study director, June 27, 2010.
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change to a combination expansion tank/cyclone was used for the Anniston system.43 The GEKA expansion tank is constructed from carbon steel. Differences Between Processing at GEKA and Anniston As shown in Table 3, GEKA uses a separate pressure equalization tank and cyclone. Finding 6. The use of a combination pressure equalization tank/cyclone at Anniston versus a separate pressure equalization tank and cyclone at GEKA is not expected to adversely affect operations or safety. Thermal Oxidizer Processing at Anniston The internal dimensions of the cylindrical thermal oxidizer are 1.25 m diameter × 3.79 m long.44 It has a steel shell lined with Fibrefrax ceramic fiber in the main body and with other refractory materials at each end. The oxidizer is provided to complete the oxidization of CO, hydrogen, and any trace organic compounds, including any dioxin/furan precursors that may remain in the off-gas from the SDC and the buffer/orifice. Ideally, complete oxidation can be achieved by thorough mixing in the reactor and then allowing a long dwell time in a “plug-flow” (i.e., no recirculation) chamber (Thring, 1962). The mixing and thermal oxidizing design for Anniston could be verified with computational fluid dynamics (CFD) modeling that accounts for chemical reaction equations.45 Such modeling has not been done but is desirable, especially for this oxidizer with its low length to diameter ratio (approx. 3:1).46 The thermal oxidizer must oxidize the CO, hydrogen, trace organics, other gaseous components, and soot. It is designed to be capable of treating all of the products from a detonation within a period of 180 s (Dynasafe, 2010), a relatively short duration in comparison with the approximately 20-minute minimum elapsed time between each munition charging and detonation/deflagration event. 43 Personal communication between Holger Weigel, Vice President, Dynasafe International, and Managing Director, Dynasafe Germany; Richard Ayen, committee chair; and Douglas Medville, committee member, May 5, 2010. 44 Personal communication between Harley Heaton, Vice President, Research, UXB International, Inc., and Harrison Pannella, NRC, study director, May 19, 2010. 45 This modeling is available commercially in the United States and Europe. 46 Personal communication between Holger Weigel, Vice President, Dynasafe International, and Managing Director, Dynasafe Germany; Richard Ayen, committee chair; and Douglas Medville, committee member, May 5, 2010.
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The horizontal gas flow thermal oxidizer is designed for a retention time of at least 2 s (with normal operation at 4 s) and a temperature of >1100ºC (>2012ºF).47 For a design flow of ~500 standard cubic feet per minute, normal operation is at 2100ºF.48 Dynasafe has stated that the thermal oxidizer is oversized even for the design peak flow. It utilizes natural gas as a fuel. Air from the Sprung structure is automatically added to the primary and pilot burners in quantities that ensure an oxidizing environment. An oxygen content of 8 percent is maintained at the outlet of the thermal oxidizer.49 The natural gas burner on the thermal oxidizer for Anniston has a 500 kW capacity and the pilot burner has a capacity of 340 kW.50 The temperature of the thermal oxidizer is kept relatively hot at all times; the operating temperature is reduced to 900ºC overnight and on weekends. Finding 7. The thermal oxidizer in the pollution abatement system for the Dynasafe SDC1200 for Anniston has a relatively low length-to-diameter ratio of approximately 3:1. This low length-to-diameter ratio might adversely affect its oxidization of trace organics, including dioxin and furan precursors. Recommendation 2. Computational fluid dynamics (CFD) modeling should be performed for the thermal oxidizer in the pollution abatement system for the Dynasafe SDC1200 for Anniston to ensure that oxidation of all trace organics, including dioxin and furan precursors, will be sufficiently complete. CFD modeling cases should include conditions to be used during the ramp-up period or during the subsequent emissions testing to obtain the earliest possible experimental confirmation of the CFD modeling results. Processing at GEKA GEKA employs a downward flowing, vertically oriented design and is fired with fuel oil. The gas stream residence time and temperature are the same as those for Anniston. The main body is again lined with a blanket refractory, which is, however, of lower quality than Fiberfrax.51 47 Personal communication between Holger Weigel, Vice President, Dynasafe International, and Managing Director, Dynasafe Germany; Richard Ayen, committee chair; and Douglas Medville, committee member, May 5, 2010. 48 Personal communication between Holger Weigel, Vice President, Dynasafe International, and Managing Director, Dynasafe Germany; Richard Ayen, committee chair; and Douglas Medville, committee member, May 5, 2010. 49 Personal communication between Harley Heaton, Vice President, Research, UXB International, Inc., and Harrison Pannella, NRC, study director, May 19, 2010. 50 Personal communication between Holger Weigel, Vice President, Dynasafe International, and Managing Director, Dynasafe Germany; Richard Ayen, committee chair; and Douglas Medville, committee member, May 5, 2010. 51 Personal communication between Holger Weigel, Vice President, Dynasafe International, and Managing Director, Dynasafe Germany; Richard Ayen, committee chair; and Douglas Medville, committee member, May 5, 2010.
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Differences Between Processing at GEKA and Anniston The difference in orientation, horizontal for Anniston versus vertical for GEKA, and the fuel used, natural gas for Anniston versus fuel oil for GEKA, are not expected to cause any differences in the performance necessary for thorough destruction of chemical agent. However, the chamber of Anniston’s thermal oxidizer has a low length to diameter ratio, which could result in excessive recirculation. This could adversely affect performance, causing high concentrations of dioxins and furans exiting the spray dryer and, possibly, high levels of dioxins and furans in the secondary waste. The thermal oxidizer at GEKA is followed by a proper quench for dioxin and furan control, so dioxin and furan management in the downstream operations is not an issue. Spray Dryer Processing at Anniston The purpose of the spray dryer is to cool hot gases without generating a liquid discharge by reducing salts in the spent scrubber brine to dry, flowable solids. The goal of avoiding liquid discharges eliminates the need to transport liquid waste from the process offsite.52 The temperature of the gas from the thermal oxidizer at the inlet to the spray dryer is 1100ºC. During cooling, the gases pass through a critical zone for dioxin and furan formation (400ºC to 200ºC) (Reimann, 1992). Dynasafe says that the spray dryer can function as a means to control the formation of such dioxins and furans.53 However, the committee is not aware of information that substantiates this claim under the conditions proposed for the Anniston installation. Even if the thermal oxidizer proves to have a very high destruction efficiency for oxidation of all organic compounds, there would still be a potential for reformation of dioxins and furans if the sprayer dryer does not provide a sufficiently rapid quench through the 400–200ºC temperature regime (Riemann, 1992). The three spray dryer nozzles and the pumps and controls that deliver spent scrubber liquid to the nozzles are supplied by Lechler, a Swiss company.54 The nozzles are located around the top of the dryer and point downwards, cocurrent with the entering gas stream. The body is a 71.3-in.-diameter, 182.4-in.-high carbon steel cylindrical vessel with an extra carbon steel wear layer and a conical top and bottom.55 The gas flow 52 Personal communication between Harley Heaton, Vice President, Research, UXB International, Inc.; Holger Weigel, Vice President, Dynasafe International, and Managing Director, Dynasafe Germany; Richard Ayen, committee chair; and Douglas Medville, committee member, May 4, 2010. 53 Question-and-answer session with Harley Heaton, Vice President, Research, UXB International, Inc., and the committee, April 1, 2010. 54 Personal communication between Harley Heaton, Vice President, Research, UXB International, Inc.; Holger Weigel, Vice President, Dynasafe International, and Managing Director, Dynasafe Germany; Richard Ayen, committee chair; and Douglas Medville, committee member, May 4, 2010. 55 Personal communication between Holger Weigel, Vice President, Dynasafe International, and Managing Director, Dynasafe Germany; Richard Ayen, committee chair; and Douglas Medville, committee member, May 4, 2010.
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entering the spray dryer should be modeled by CFD to ensure uniformity of the gas flow entering the spray section. This mixing section of the spray dryer should also be modeled by CFD to ensure that the gas cools rapidly enough through the 400ºC-200ºC temperature range at which dioxin and furan formation occurs and that little spent scrubber solution impinges on the spray dryer walls, which is a common problem. The dual-fluid nozzles, which are fed spent scrubber solution containing dissolved salts from redundant high-pressure pumps, incorporate compressed air for further atomization. The droplet size distribution from the spray nozzles must be uniform to ensure a “dry” exiting gas. Air from inside the Sprung structure is injected around the nozzles to protect them from acid condensation and thereby avoid corrosion. The hot gas is adiabatically cooled and the flow of the spent scrubber solution is modulated to obtain an exit gas temperature of 356ºF. Dried salts are removed from a 16-in. diameter opening at the bottom of the spray dryer by means of a sealed rotary valve connected to a steel drum. The 16-in. opening can be closed by a manual gate valve during drum change-out operations. In case of power or pump failure, a pressurized emergency water system is provided to continue cooling the gas stream until the system can be shut down. Finding 8. The hot gas from the Dynasafe SDC1200 at Anniston in the spray dryer of the pollution abatement system must be quenched to below 200ºC rapidly to minimize dioxin and furan formation. The committee could not locate information on prior use of a spray dryer for this purpose under the conditions proposed for the Anniston installation. Processing at GEKA The GEKA system does not have a spray dryer; instead, a conventional venturi quench made of lithium carbide is used to minimize the formation of dioxins and furans.56 Differences Between Processing at GEKA and Anniston The difference in the means of controlling dioxins and furans may be very important. Anniston should develop backup plans if the system as now designed does not adequately control formation of dioxins and furans. However, the activated carbon beds in the IONEX unit and, if necessary, the addition of powdered activated carbon upstream of the baghouse are expected to adequately control emissions of dioxins and furans (Pitea et al., 2008). The Army will then be faced with the problem of disposing of activated carbon containing these compounds. Finding 9. The spray dryer to be used in the pollution abatement system for the Dynasafe SDC1200 system to be installed at Anniston Army Depot might not in itself adequately minimize dioxin and furan formation. 56 Personal communication between Holger Weigel, Vice President, Dynasafe International, and Managing Director, Dynasafe Germany; Richard Ayen, committee chair; and Douglas Medville, committee member, May 4, 2010.
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Operation of spray dryers can be troublesome at times. Liquid feed nozzles can clog and solids can accumulate on walls. Some members of the committee have had direct experience with spray dryers and have encountered these problems. The literature also contains articles on this topic.57 On a brighter note, the managing director of Dynasafe Germany, who was heavily involved in the design of the Anniston system, has had direct experience in designing a spray dryer for evaporating spent scrubber solution to dryness. This was for a refinery in Qatar, where the scrubber solution was similar to the solution to be fed at Anniston. The Qatar system operated well for several years. Thus, while it is likely that the Anniston spray dryer will produce dry, flowable solids, it also likely that operating conditions will need to be adjusted during systemization to accomplish this. Finding 10. Operational problems, such as the adherence of solids to the walls, can occur when using a spray dryer. Adjustments to operating conditions can be expected to solve these problems. Recommendation 3. The Army and its contractors should take full advantage of the pre-operational period at Anniston to optimize conversion of salts in the scrubber solution to dry, flowable solids. Baghouse Filter Processing at Anniston The baghouse that follows the spray dryer operates at 180ºC and captures the portion of the particulate matter precipitated out of the gas by, but not captured in, the spray dryer.58 One or more additives will be injected into the main process gas stream immediately upstream of the baghouse filter. Initially, calcium hydroxide, calcium oxide, or calcium carbonate will be injected.59,60 If necessary, activated carbon will be mixed with whichever calcium compound is used. The mix will be selected after operations are begun to optimize removal of Hg and acid gases (SOx and HCl). If activated carbon is added to the baghouse, it will most likely become contaminated with mercury as well as 57 For example, “Sticky Issues on Spray Drying of Fruit Juices,” the summary of which begins “Spray drying process is the most commonly used method in industries to produce milk powders, fruit juice powders, encapsulated flavour, etc. on a large scale. One of the major problems in spray drying of fruit juices is stickiness of fruit powders on the dryer walls during drying” (Mani et al., 2002). See also “Spray Dryers & the Koshering Process,” which states in part that the particles land on the walls of the dryer, its ductwork, cyclones, baghouse, etc. and the product is actually baked so to speak, on the surface. (Blugrond, undated). 58 Personal communication between Harley Heaton, Vice President, Research, UXB International, Inc., Holger Weigel, Vice President, Dynasafe International, and Managing Director, Dynasafe Germany; Richard Ayen, committee chair; and Douglas Medville, committee member, May 5, 2010. 59 Personal communication between Harley Heaton, Vice President, Research, UXB International, Inc.; Holger Weigel, Vice President, Dynasafe International, and Managing Director, Dynasafe Germany; Richard Ayen, committee chair; and Douglas Medville, committee member, May 5, 2010. 60 Personal communication between Harley Heaton, Vice President, Research, UXB International, Inc., and Harrison Pannella, NRC, study director, May 19, 2010.
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dioxins and furans. The addition of powdered activated carbon upstream of the baghouse might create an explosive dust hazard. This possibility should be explored before carbon is added. Finding 11. The addition of powdered activated carbon upstream of the baghouse might create an explosive dust hazard. Recommendation 4. If it is decided to add powdered activated carbon along with the calcium compound added upstream of the baghouse, the possibility of creating an explosive dust hazard within the process gas ducting and baghouse should be considered before carbon addition is initiated. Processing at GEKA GEKA does not include a baghouse at this location within the stream because it does not have a spray dryer that generates solids. Evaporative Cooler Processing at Anniston An evaporative cooler follows the baghouse and serves only to reduce the temperature of the off-gases and saturate them with water vapor. It lowers the off-gas temperature from 175ºC to 78ºC to match the design operation conditions of the downstream acid and neutral scrubbers. The evaporative cooler has a pressurized water reserve in case of power or pump failure. Processing at GEKA GEKA does not have this evaporative cooling operation. Wet Scrubbers The acid scrubber operates with the scrubbing solution at a pH near 2.61 Upon start-up, this scrubber absorbs HCl, causing the pH to drop. After reaching a pH of 2, pH is maintained by the addition of caustic and the removal of spent scrubber solution. The neutral scrubber is maintained at a pH of 6.7 in the same way.62 Both scrubbers operate at 78ºC and are constructed from fiberglass reinforced polyester. Blowdown of spent scrubber solution from both scrubbers is sent to the same tank, then to the spray dryer for 61 Personal communication between Holger Weigel, Vice President, Dynasafe International, and Managing Director, Dynasafe Germany; Richard Ayen, committee chair; and Douglas Medville, committee member, May 4, 2010. 62 Question-and-answer session with Harley Heaton, Vice President, Research, UXB International, Inc., and the committee, May 19, 2010.
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evaporation to dry solids. The scrubbers are operated at all times, including nights and weekends, and are maintained at the 78ºC operating temperature.63 Processing at GEKA Scrubber operation at GEKA is essentially identical to scrubber operation at Anniston. However, at GEKA, the spent brine is sent to a wastewater treatment plant for disposal. Remaining Operations in Pollution Abatement System Processing at Anniston The balance of equipment at Anniston includes ID fans; a reheater; an IONEX unit (including a prefilter, a HEPA filter, two banks of activated carbon, another HEPA filter, and an ID fan); ductwork designed for emissions testing; and a stack. Following the scrubbers, two ID fans (configured redundantly and sized for a pressure differential of 85 mbar) provide the draft through the remaining components of the PAS. An electric air reheater increases the temperature of the saturated off-gas from 77ºC to 83ºC, reducing relative humidity to improve the performance and operating life of the downstream activated carbon sorbent beds. The IONEX CD2000 includes two activated carbon filter banks to adsorb trace concentrations of species remaining in the off-gas, with the first bank containing sulfur-impregnated activated carbon. Sulfur-impregnated activated carbon is a widely used approach for removing mercury from gaseous combustion streams and has been utilized for this purpose during mustard agent destruction at the Tooele, Utah, chemical agent disposal facility (TOCDF) (NRC, 2009b). The mustard munitions to be destroyed at Anniston, however, are expected to contain much lower concentrations of mercury than the mustard ton containers treated at TOCDF.64 The off-gas passes through a prefilter and a HEPA filter before entering the first bank of sulfur-impregnated carbon. The gas then passes through a second filter bank of activated carbon, another HEPA filter, and through the final ID fan before it is released from the stack. Finding 12. The Dynasafe SDC1200 to be installed at Anniston has redundant induced draft fans before the IONEX CD2000 carbon filter system but only one ID fan after the filter banks. Recommendation 5. The Army should consider installing a spare induced draft fan in the IONEX CD2000 carbon filter system. 63 Personal communication between Harley Heaton, Vice President, Research, UXB International, Inc., and Harrison Pannella, NRC, study director, June 27, 2010. 64 Tim Garrett, Site Project Manager, ANCDF, and Charles Wood, ANCDF Deputy Operations Manager, URS, “Static Detonation Chamber (SDC),” presentation to the committee, March 30, 2010.
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Processing at GEKA The remaining unit operations in the PAS at GEKA are an initial ID fan, a wet ionizing scrubber, a DENOX unit for removing nitrogen oxides, a quench, the addition of activated carbon and CaCO3, a baghouse filter, a second ID fan, and a stack. Difference Between Processing at GEKA and Anniston GEKA has a system for removing oxides of nitrogen, which is needed to meet German regulations. Under ADEM regulations, the Dynasafe SDC1200 system for Anniston meets NOx emission standards without additional equipment. At GEKA, the DENOX unit is followed by injection of activated carbon and calcium carbonate into the gas stream immediately upstream of the baghouse. Finding 13. The unit operations downstream of the scrubbers for the Anniston and GEKA installations are specific to meeting the requirements of the applicable environmental regulatory agencies. The unit operations at Anniston are expected to function adequately. MONITORING SYSTEMS Monitoring for the concentrations of agent in real time for personnel protection using ACAMS and depot area air monitoring systems has been perfected over the course of the chemical agent disposal program (NRC, 2005). The plans and procedures for using agent monitors for the Dynasafe SDC1200 installation at Anniston are thorough and may be relied on to protect site personnel and the public at large from harmful exposure to agent. Site personnel will be warned within a few minutes of the presence of mustard agent at levels that approach the permissible short-term exposure limit. The limit for general population exposure is much lower; such exposure is monitored daily by sample collection and laboratory analysis. The exhaust stack of the Anniston SDC1200 is monitored by ACAMS and depot area air monitoring system tubes. Any releases to the environment above the allowable regulatory limits will halt operations. These measures have a proven history of providing good protection for the public and the environment if the SDC were to malfunction. Finding 14. The chemical agent monitoring systems used for the Dynasafe SDC1200 system to be installed at Anniston are similar to the systems that have been in use at all other chemical agent disposal facilities and that have been found to adequately protect personnel and the environment. As discussed earlier in this report in the sections on the spray dryer and the baghouse, the committee cautions that the solids collected from the baghouse (and the solids that precipitate in the spray dryer) may contain dioxins and furans, especially if powdered activated carbon is added to the process gas stream upstream of the baghouse.
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A secondary potential collection point for these materials would be on the carbon in the IONEX filters. Finding 15. Solids collected from the baghouse may contain levels of dioxins and furans that must be managed, especially if powdered activated carbon is added to the process gas stream upstream of the baghouse. Solids collected from the bottom of the spray dryer might also contain dioxins and furans at levels of regulatory interest. Recommendation 6. The Army should be prepared to address the possibility of secondary waste contaminated with dioxins and furans that need to be managed either by design adjustments to avoid the possibility or by having a suitable plan for disposal. ***** REFERENCES Blugrond, R., Spray Dryers & the Koshering Process. Undated. Available online at <http://www.oukosher.org/index.php/common/article/spray_dryers_the_koshering_process>. Accessed July 15, 2010. Dynasafe. 2010. Process Description and Supply Specification of the Static Detonation Chamber (SDC). Karlskoga, Sweden: Dynasafe AB. Grandesso E., S. Ryan, B. Gullett, A. Touati, E. Collina, M. Lasagni, and D. Pitea. 2008. Kinetic modeling of polychlorinated dibenzo-p-dioxin and dibenzofuran formation based on carbon degradation reactions. Environmental Science and Technology 42(19): 7218–7224. Heaton, H. 2010. Typical Day for SDC Operation. Mani, S., S. Jaya, and H. Das. 2002. “Sticky Issues on Spray Drying of Fruit Juices. Paper number MBSK 02–201, presented at the ASAE/CSAE North-Central Intersectional Meeting. Saskatchewan, Canada. NRC (National Research Council). 2005. Monitoring at Chemical Agent Disposal Facilities. Washington, D.C.: The National Academies Press. NRC. 2009a. Assessment of Explosive Destruction Technologies for Specific Munitions at the Blue Grass and Pueblo Chemical Agent Destruction Pilot Plants. Washington, D.C.: The National Academies Press. NRC. 2009b. The Disposal of Activated Carbon from Chemical Agent Disposal Facilities. Washington, D.C.: The National Academies Press. Pitea, D., M. Bortolami, E. Collina, G. Cortili, F. Franzoni, M. Lasagni, and E. Piccinelli. 2008. Prevention of PCDD/F formation and minimization of their emission at the stack of a secondary aluminum casting plant. Environmental Science and Technology 42(19): 7476–7481. Reimann, Dieter. 1992. Dioxin emissions: Possible techniques for maintaining the limit of 0.1 ng TE m−3 (as of 1990/91). Waste Management and Research: The Journal of the International Solid Wastes and Public Cleansing Association 10(1): 37–46.
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Thring, M. 1962. The Science of Flames and Furnaces. Hoboken, N.J.: John Wiley & Sons, Inc. U.S. Army. 2008. Department of the Army Pamphlet 385–61, Toxic Chemical Agent Safety Standards. December 17. Available online at: http://www.apd.army.mil/pdffiles/p385_61.pdf. Last accessed June 29, 2010. Westinghouse Anniston. 2010. Anniston Chemical Agent Disposal Facility Static Detonation Chamber Emissions Test Plan. Anniston, Ala.: Trial Burn Department.