Review and Assessment of Developmental Issues Concerning the Metal Parts Treater Design for the Blue Grass Chemical Agent Destruction Pilot Plant (2008)

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2 Metal Parts Treater System Overview strate the operation of the MPT concept for the decontami- nation of metal parts and waste. Major equipment in each The Blue Grass Chemical Agent Destruction Pilot Plant first-of-a-kind full-scale MPT system consists of an MPT, a (BGCAPP) design will treat the metal parts and other waste first-of-a-kind bulk oxidizer (BOX) (more accurately called in one of two metal parts treater (MPT) systems. Each of a flameless thermal oxidizer) and cyclone, and an electrically the two MPT systems consists of an MPT and its dedicated heated steam superheater, as shown in the simplified flow off-gas treatment system (OTM), comprising a flameless diagram in Figure 2-1. thermal oxidizer and a cyclone. A venturi scrubber system The first-of-a-kind BOX and cyclone on each MPT are cleans the gases coming from the cyclones. The MPT sys- considered part of the dedicated off-gas treatment system. tems will be used to decontaminate the following: Major process equipment in the remainder of the OTM con- sists of a single venturi scrubber system and off-gas blower, • Washed projectile bodies and associated nose plugs as shown in Figure 2-2. from 8-in. GB (sarin) and 155-mm VX (nerve agent) One MPT is expected to be sufficient for processing and H (Levinstein mustard gas) projectiles, all projectile bodies. The second MPT will serve as a spare • Solid materials (including undissolved fuze parts) or backup and also will be used for the processing of EBH remaining after rocket warhead processing in the residues, secondary waste, and closure waste. BGCAPP energetics batch hydrolyzers (EBHs), and • Agent-contaminated secondary and closure waste. Metal Parts Treater Decontamination will be accomplished by heating all of the materials to 1000oF for at least 15 minutes. For projec- System Description tiles, the bodies and nose plugs are cleared for unrestricted release into the public domain. Solid materials from the Each full-scale MPT consists of four sections: an inlet EBHs and secondary and closure waste can then be released air lock, a main chamber, an outlet air lock, and a cooling to an appropriate disposal site. Superheated steam at 1200oF chamber. Figure 2-3 shows the arrangement of the major serves as a sweep gas to remove gases and particulates gen- elements of the MPT. The air locks, main chamber, and erated by the heating of the metal parts and other materials cooling chamber are provided with separate roller conveyor in the MPT. systems for moving racks containing washed projectiles or The MPTs are designated as first-of-a-kind equipment trays containing EBH solid waste and secondary and closure because they are unique, are being designed for this par- waste through the MPT. The air locks and the cooling cham- ticular application, and have never been used in an actual ber are equipped with doors that are moved up and down in process. A smaller-scale test unit called the Technical Risk structural frames using a screw drive. The main chamber inlet Reduction Program (TRRP) MPT was fabricated to demon- and outlet doors serve as the chamber interface with the inlet and outlet air locks. Inlet and outlet air locks have mechanisms that are The Bechtel Parsons Blue Grass Team uses the acronym “OTM” to used to move trays and projectile racks in and out of each designate the off-gas treatment system attached to the MPT, and reserves the of the four MPT sections. Only the main chamber is heated. acronym “OTS” for other off-gas treatment systems in the design. The inlet and outlet air locks and cooling chamber are not The smaller-scale unit has a 4 ft 8 in. diameter compared with a 6 ft 6 in. diameter for the full-scale MPT. heated but will vary in temperature from ambient to higher 11 

12 Review and Assessment of Developmental Issues Concerning the Metal Parts Treater Design Agent and Nitrogen MPT Off-gas Energetics Access Purge Treatment Munition MPT Bodies and Cyclone Miscellaneous Parts MPT Bulk Off-gas Oxidizer Drummed Nitrogen Particulates Purge Metal Parts Airlock Treater Airlock “5X” Materials Solid Waste (2 units) Handling Nitrogen Purge Steam Process Steam Superheated Superheater Steam FIGURE 2-1 Simplified flow diagram of the metal parts treater system. Source: Samuel Hariri, Process Design Lead, Bechtel Parsons Blue Grass Team, “Overview of the Blue Grass Chemical Agent Destruction Pilot Plant (BGCAPP) Process,” presentation to the committee, September 5, 2007. 2-1 Blower Munition Body Treatment MDB Filters MPT redrawn Filter and MPT Off-Gas Heater Cyclone Ash Raw MPT "Condensate" Bulk Oxidizer Agent Contaminated MPT Neutralization "Condensate" Agent Heated Cleared MPT Hydrolysate Air "Condensate" Storage Natural Gas FIGURE 2-2 Current design of the off-gas treatment system for the metal parts treater. Source: Samuel Hariri, Process Design Lead, Bechtel Parsons Blue Grass Team, “Overview of the Blue Grass Chemical Agent Destruction Pilot Plant (BGCAPP) Process,” presentation to the committee, September 5, 2007. 2-2 

Metal Parts Treater System 13 Inlet Main Outlet Airlock Cooling Airlock Chamber Chamber FIGURE 2-3 First-of-a-kind full-scale metal parts treater system. Source: BPBGT, 2007b. 2-3 t ­ emperatures when air lock doors are opened and when uniform heating of the materials. Because of the varying heated trays are present. The air locks are provided with a off-gas generation rates, the feeding of secondary waste, nitrogen purge gas supply. Exhaust gas from the air locks EBH residue, and projectiles into the MPT are controlled by flows to the MPT BOX unit. The main chamber is heated software that, at any one time, allows the MPT main chamber by two 300-kW water-cooled induction coils wrapped on to process only the same type of material in Zones 1 and the outside of the main chamber wall. Each coil heats one 2. A zone is defined as a position within the main chamber of the two zones in the main chamber. Gases generated by where a tray is heated for a set period of time. Interlocks the heating of the projectiles or waste in the main chamber are provided to prevent the mixing of feed materials in the are swept from the chamber using low-pressure, superheated main chamber. 1000 oF–1200oF steam generated by the electrically heated Before a tray is transferred into the MPT inlet air lock, MPT steam superheater. The steam and gases flow out of the the vent valve from the inlet air lock is closed, the air lock main chamber through a header in the top of the chamber nitrogen purge valve remains open, and the main chamber to the BOX unit along with purge gases from the inlet and in-gate remains closed. The MPT main chamber pressure is outlet air locks. Ducting for all gases flowing to the BOX is also lowered before the main chamber inlet gate, or in-gate, insulated and trace heated to prevent a condensation of tars. is opened. These actions minimize the intrusion of main In the BOX, the combustible gases generated in the MPT chamber gases into the air lock. Gas flow generally is from are oxidized and then flow through a cyclone before being the inlet air lock to the main chamber. discharged to the downstream equipment of the OTM. Ad- The inlet air lock in-gate is then opened and a tray is trans- ditional MPT system details are provided in the following ferred into the inlet air lock; then the inlet air lock in-gate is discussion of MPT system operation. closed. The air lock is continuously purged with nitrogen to re- duce its atmosphere to below 3 percent oxygen. The estimated time to purge the inlet air lock is approximately 20 minutes. System Operation Because some air in-leakage from door seals is expected, the All agent-contaminated solid materials are fed to the nitrogen purge is continuous. The inlet air lock is maintained MPTs in trays specifically designed to support the rapid and at a negative atmospheric pressure of –0.25 in. water column 

14 Review and Assessment of Developmental Issues Concerning the Metal Parts Treater Design with respect to the ambient room pressure during purging. At MPT line. During the processing of secondary waste, the the same time, the pressure in the main chamber is maintained temperature of each zone in the main chamber can be con- at –0.5 in. water column with respect to the MPT room by trolled independently to minimize a rapid volatilization of controlling the off-gas treatment system pressure. Thus, gas the waste that would overload the associated BOX and the flow will be from the air lock to the main chamber. rest of the OTM. During secondary-waste processing, if the After completing the purge, the air lock conveyor ad- volatile organic compound (VOC) monitor in the outlet air vances the tray to a latching position. A push-pull mechanism lock indicates that VOCs are still being emitted, the tray engages the tray at the latching position, the main chamber must be backed into the main chamber’s Zone 2. Therefore, inlet gate is opened, and the tray is pushed onto the MPT Zone 2 remains empty until the tray in the MPT outlet air main chamber roller conveyor. The main chamber in-gate is lock/conveyor is cleared. closed after the tray is moved into the main chamber. Then, the inlet air lock is purged with nitrogen gas to remove any Prototype Testing of the Metal Parts Treater Technology gases that may have flowed from the main chamber to the in- let air lock when the in-gate was open. Purge gases from the The Bechtel Parsons Blue Grass Team (BPBGT) has air locks and main chamber flow to the MPT system BOX. conducted prototype testing of the MPT technology at the A loaded tray of projectiles or secondary waste is first Parsons fabrication facility in Kennewick, Washington. The heated in Zone 1 of the main chamber. In Zone 1, most com- prototype, referred to as the TRRP MPT, is a three-quarter- bustible material (including agent and paint on projectiles) is scale version of the full-scale MPTs planned for BGCAPP. vaporized and pyrolyzed. Some oxidation is expected owing Figure 2-4 shows the arrangement of major elements of the to the oxygen in the air in-leakage during tray transfers and TRRP MPT. The prototype testing demonstrated that the during operations. In the main chamber, vaporization and MPT can heat projectile bodies and secondary and closure pyrolysis continue at a rate that minimizes major peaks in the waste to a temperature of 1000oF for 15 minutes. However, amount of oxidizable material going to the BOX. The BOX the testing was performed on surrogate materials. is sized to treat up to 252 pounds per hour (lb/h) of products The prototype testing, discussed in Chapter 3, identified from pyrolysis and partial oxidation resulting from the air design changes or improvements that will be incorporated in-leakage. After approximately 1 hour in Zone 1, the tray is into the full-scale MPT. It also provided data to test the advanced to Zone 2. The tray will not be advanced to Zone validity of the computational fluid dynamics (CFD) model 2 until the oxygen content in the chamber indicates that no of heat transfer in the main chamber. The CFD model, dis- further reaction is occurring. The preceding cycle is repeated cussed in Chapter 4, will be used to guide the final design of when each new tray is loaded. the full-scale MPT. At the end of the required time in Zone 1, the main Besides scale-up from three-quarter to full-scale size, chamber in-gate is opened and a new tray in the inlet air lock the other modifications from the prototype TRRP design is inserted into the main chamber by using the inlet air lock that will be implemented in the full-scale design include the mechanism to push the tray in. This in turn pushes the other following: tray from Zone 1 into Zone 2. During normal operation, there will be trays in both Zones 1 and 2. Trays are heated in Zone 1. New designs for gate closure mechanisms and seals 2 for 40 to 60 minutes. At the end of this time period, the on the main chamber and air locks. The closure mechanism oxygen in the outlet air lock atmosphere is reduced below 3 in the TRRP unit abraded the seal material and caused ex- percent by being purged with nitrogen, and the main chamber cessive air in-leakage. The planned design is a cam type pressure is reduced to below the outlet air lock pressure to of closure mechanism in which downward vertical motion minimize intrusion of the main chamber gases into the outlet to the bottom of the gate seat is followed by lateral move- air lock. Then the main chamber outlet door is opened, and ment against the chamber or air lock face. This design is a mechanism in the outlet air lock, which works with the derived from other commercial applications, but it has not powered roller conveyor in the outlet air lock, pulls the tray been tested under operating conditions. It is noted that the into the outlet air lock and the main chamber outlet door is main chamber doors will be larger and heavier than in the closed. prototype. The doors will have approximately a 6-ft-diameter Low-pressure superheated steam at a design flow rate of opening and will weigh approximately 2 tons. 250 lb/h between 1000oF and 1200oF is used as the sweep 2. Improved bearings for conveyor rollers in the main gas to remove the gases and vapors generated in the main chamber and outlet air lock. Bearing failures occurred dur- chamber and for maintaining low oxygen concentrations ing testing. A more robust bearing design has been identified in the main chamber. The superheated steam is fed into the for the full-scale design, as discussed in Chapter 3. It will bottom of the main chamber through a header designed to include the capability for rapid change-out of bearings to provide a uniform distribution of steam in the chamber. accommodate the failure rate in actual operation. Projectiles are normally processed on one MPT line, 3. Improved superheated steam inlet header design to while waste containers are normally processed on the other eliminate the shadowing of projectiles from radiant heat. 

Metal Parts Treater System 15 Inlet Main Outlet Airlock Cooling Airlock Chamber Chamber FIGURE 2-4 Technical Risk Reduction Program metal parts treater system (without staging conveyors, air lock doors, and cooling chamber). SOURCE: BPBGT, 2007b. 2-4 Computerized thermal modeling of heating in the main 5. Improved design of secondary waste trays. The design chamber and instrumentation of prototype test projectiles improvements included increasing tray capacity—for exam- revealed places on the projectiles that were heating more ple, layering with space between the layers—and increasing slowly than other places. The BPBGT believes that the the ease of removing treated waste. These test results were radiative shadowing by the prototype steam header was from a limited test period that involved limited amounts of the primary cause of the slower heating by shadowing the surrogate materials, but they indicate that the tray designs for radiant heat transfer from the main chamber walls. Because secondary waste are adequate. It is noted that the surrogate the prototype projectile trays also may have created some materials did not contain halogenated materials because of shadowing, the design of the trays for the full-scale MPT will restrictions in the TRRP MPT operating permit. The BPBGT be reviewed to minimize or prevent this effect. Both effects noted that there was little char and tar in the off-gas ducting may have contributed to longer heat-up times than those from the main chamber. However, the short test period pro- predicted by the thermal modeling of the prototype tests. vided little chance for a buildup of char and tar deposits. Also, Heat-up time is defined as the time to achieve the 1000oF the presence of air in-leakage may have reduced tar and char for 15 minutes criterion. production by partially oxidizing these materials. The BPBGT 4. Improved induction coil installation, including the design team is providing clean-out access points, added insula- shielding of parts of surrounding structures from stray cur- tion, and trace heating of off-gas ducting to the BOX unit to rent heating and providing improvements to prevent arcing. minimize the chance of depositing tars and chars during actual Currently it is unclear if the induction heating coils will operation. The testing of EBH solid waste treatment was also prevent maintenance from taking place on one MPT if the demonstrated. However, because of permit limitations on other MPT is still in operation. If this is true, some impact on TRRP MPT operations, the EBH surrogate waste materials processing availability may result, although it is not expected did not include energetics, which will be present in the actual that simultaneous operation of both MPTs will be needed for EBH waste. Therefore, possible popping of energetics and much of the processing time. containment of resulting debris were not demonstrated. 

16 Review and Assessment of Developmental Issues Concerning the Metal Parts Treater Design Finding. It is unclear if the induction heating coils, or other Recommendation 2-5. The selection of metal and refractory issues, will prevent maintenance on one MPT if the other materials exposed to the feed gas and off-gas for the BOX metal parts treater is operating. and other equipment in MPT off-gas treatment systems must be carefully assessed to ensure that they will provide reliable Recommendation 2-1. The two MPTs should be positioned long-term operation, with adequate resistance to corrosion and isolated so that one MPT can be operated while the sec- and other effects at operating conditions and under all antici- ond undergoes maintenance. pated transient conditions including shutdown and start-up. These test results and proposed changes to the full-scale Off-gas Treatment System MPT were identified in the BPBGT presentation to the com- mittee on September 6-7, 2007, and in the TRRP draft of the System Description test report (BPBGT, 2007c). While the prototype testing established a “proof of concept,” it also pointed to signifi- The OTM consists of the first-of-a-kind BOX units cant design changes that would improve the operability of and cyclones assigned to each MPT system and the venturi the MPT concept as noted above. These design changes are scrubber system that cleans the gases from the cyclones. The being implemented in the full-scale MPT design but will not flow diagram in Figure 2-2 shows the complete OTM; Figure have been successfully demonstrated until completion of ac- 2-5 shows the BOX unit that is connected to the MPT main ceptance testing at the Parsons fabrication facility. chamber and air locks by ducting. The BPBGT has recog- Normal industrial practice would call for each full-scale nized the potential for char and tar deposition in the ducting MPT to undergo, at a minimum, electrical and control system and has provided design features including increased insula- testing and mechanical and thermal functional testing at the tion of the off-gas ducting, trace heating of the ducting, and Parsons fabrication plant and then be disassembled, trans- duct design to allow inspection and cleaning. ported to BGCAPP, and reassembled to undergo systemiza- The gas discharges of the cyclones are combined in a tion and final acceptance testing. common duct and then flow to the OTM venturi scrubber where the hot gases are quenched and then scrubbed in a Finding. The full-scale MPTs, including their associated packed column using a caustic solution. Each of the BOX- off-gas treatment system, will not be tested for complete and-cyclone units is designed to receive and process vent operational performance until systemization. Testing of the gases from other process equipment as well as the MPT prototype TRRP MPT cannot reliably predict these perfor- system. These vapors and gases come primarily from process mance parameters for the full-scale MPTs and their off-gas vessel vapor spaces. Off-gas leaving the scrubber top passes treatment system. through a demister, a cooler, and a reheater, and then to the OTM blower. The blower discharges into the munitions de- Recommendation 2-2. The full-scale MPTs, with the associ- militarization building (MDB) heating, ventilation, and air ated off-gas treatment system, must undergo a complete set conditioning (HVAC) ducting, connected to the BGCAPP of acceptance tests which demonstrate that each unit will op- carbon filters. erate as planned and that the predicted thermal performance The first-of-a-kind BOX units, which are flameless on both projectile and waste streams can be achieved. thermal oxidizers, are designed to oxidize pyrolysis products, hydrocarbons, halogenated organics, carbon monoxide, and Recommendation 2-3. The operating permit should be hydrogen. The resulting products of oxidation consist of changed to allow MPT and off-gas treatment system testing hydrogen halides, chlorine, carbon dioxide, sulfur dioxide, with secondary waste, including halogenated waste, at rates phosphorus pentoxide, and water. Figure 2-5 shows the major expected during BGCAPP operation. This testing should be elements of each BOX. The BOX is to be custom-designed performed at the fabrication facility to provide quick turn- by EPCON Industrial Systems, LP for the BGCAPP MPT around on issues requiring changes in the full-scale MPT. systems and is a first-of-a-kind unit. It incorporates an air inlet with electrical air heater and process gas inlet chamber Recommendation 2-4. If permitting at the fabrication fa- at the bottom where significant oxidation takes place. The cility is not possible or if it would result in extraordinary gases at approximately 1900°F enter a 12-in.-deep structured schedule delays, the BPBGT should be provided time and ceramic matrix section where Epcon assumes that mixing resources to support acceptance testing of the MPT and as- takes place. The gases then enter a plenum section, which sociated off-gas treatment system at BGCAPP before the includes custom-designed natural gas lances. If sufficient start of systemization. heating value is not present in the process gases to heat the gases to 2000°F (or 2200°F for polychlorinated biphenyls), the natural gas lances introduce sufficient fuel to reach the John Ursillo, Pasco Resident Engineer, Bechtel Parsons Blue Grass required operating temperature. Above the natural gas lance Team, “MPT Technical Risk Reduction Program (TRRP) Testing,” presenta- section, the gases flow through a 6-in.-deep random ceramic tion to the committee, September 5, 2007. 

Metal Parts Treater System 17 Air Heater Ceramic Bed FIGURE 2-5 Bulk oxidizer in the off-gas treatment system for the metal parts treater. Source: Samuel Hariri, Process Design Lead, Bechtel Parsons Blue Grass Team, “Overview of the Blue Grass Chemical Agent Destruc- tion Pilot Plant (BGCAPP) Process,” presentation to the committee, September 5, 2007. 2-5 (saddles) section. The 2000°F or 2200°F gases then enter a when the structured matrix is operating at 1900oF or when residence chamber for 2 seconds, followed by an evapora- these saddles are operating in the 2000°F to 2200°F range. tive cooling section to cool the gases down to 1200°F prior to leaving the BOX. Finding. It is difficult to predict the mixing of preheated Each BOX is followed by a cyclone unit for the re- air with the process gas to obtain uniform flow through the moval of more than 90 percent of particulates smaller than structured matrix and to predict the mixing of the 1900oF 14 microns. These particulates may catalyze the formation gases with natural gas ahead of the saddles to minimize local of dioxins and furans and contaminate the downstream OTM hot spots and to ensure complete oxidation. equipment. These particulates would also increase the rate of sludge accumulation in the scrubber system. The collected Recommendation 2-6. The natural gas lance section should cyclone particulates would be disposed of in an appropriate be modeled by suitable three-dimensional computational treatment, storage, and disposal facility. fluid dynamics modeling and the design modified as required to ensure that good mixing takes place and that a uniform Finding. The bulk oxidizer is considered first-of-a-kind gas temperature profile is achieved before the gases reach equipment because it is custom-designed and its opera- the 6-in.-deep section of saddles. tion has not been demonstrated in any existing facilities. In addition, the ceramic structure matrix and the ceramic Recommendation 2-7. Following the development of a saddles selected for the bulk oxidizer typically are used at three-dimensional model, a pilot test unit at least 6 ft² in cross temperatures between 1600oF and 1800oF. There is little if section should be designed, built, and tested to demonstrate any experience with EPCON Industrial Systems equipment good mixing, uniform temperature profiles, and no dete- 

18 Review and Assessment of Developmental Issues Concerning the Metal Parts Treater Design rioration of structured ceramic media at 1900oF or ceramic these vent gases may also be routed to the MDB HVAC. saddles at 2200oF prior to fabrication of the full-sized bulk ENS off-gas may be diverted (under supervisory control) to oxidizer units. Performance of the air heating and natural gas the off-gas treatment system for the ENS. If both MPTs are system should also be demonstrated before the bulk oxidizer required to process closure waste and the agent collection units are shipped to the BGCAPP. system, agent neutralization system, and ENS are down, the remaining vents from the spent-decontaminant tanks will be sent to the MDB HVAC. System Operation As mentioned above, the MPT BOX uses natural gas As previously discussed, the OTM consists of the two as required during operation for supplemental heating to BOX-and-cyclone unit combinations, each one dedicated maintain an oxidized off-gas temperature of 2000°F or to an MPT, as well as the venturi scrubber system, which 2200°F. The amount of natural gas increases as the amount receives all process gases from the operating BOX-and- of oxidizable material in the process gas decreases. When cyclone units, and a scrubber off-gas blower that discharges vaporizing agent during the initial processing of projectiles scrubbed and suitably dried off-gas to the MDB HVAC or when processing secondary waste or closure waste, a system. Vent gases from other tank and process vessel vapor water mist (using plant air) is provided in the lower oxidiz- spaces are combined with off-gas flowing to the BOX unit ing section in order to maintain its operating temperature at on an operating MPT. These vent gases flow from storage no higher than 1900°F. Fresh air to the BOX is preheated tank or process vessel vapor spaces in the agent neutraliza- to 1550°F by an electrical air heater, which is part of the tion system, agent collection system, spent decontamination BOX unit. The fresh-air flow rate is regulated to achieve a solution, and energetics neutralization system (ENS). They 4.5 to 5.0 percent oxygen concentration, leaving the upper include the following: oxidizing section of the BOX during agent vaporization or during secondary waste processing. Flame arrestors are • Agent hydrolyzers, provided within the BOX package: two (one high-flow •  pent decontamination holding/agent washout treat- S and one low-flow) in the process gas feed line to the BOX ment tanks, and one in the air line to prevent the possibility of flame • An agent holding tank, propagation upstream. A process water mist (using plant • An agent surge tank, air) is provided above the upper oxidizing section to cool • Agent hydrolysate sampling tanks, and the effluent stream to 1200°F before it enters the cyclone. • Energetics neutralization reactors. A plant water line is provided as an emergency backup for the cooling section in the event that the process water These vent gases, which contain VOCs and water va- supply fails. por, are combined in a single pipe or duct that is heated and Particulates are removed in the MPT cyclone. A motor- insulated to prevent condensation before the gases enter the ized rotary valve is included at the cyclone solids discharge MPT ducting feeding a BOX unit. These gases are not sent to allow periodic removal of solids. A BOX and its associated to a BOX if the associated MPT is processing secondary cyclone can be isolated from the venturi scrubber by closing waste. This restriction is intended to prevent the condensa- isolation valves downstream of the cyclone. tion of tars and chars in the MPT-to-BOX ducting. If neither After passing through the cyclones, the off-gas is sent BOX unit is available, that is, if both MPTs are shut down to the venturi scrubber tower system common to both MPT or only secondary waste is being processed, the vent gases systems. The venturi scrubber tower can process gases from flow directly to the venturi scrubber. either one or both cyclones. The venturi scrubber tower As process gases enter a BOX, the gases are combined consists of two major components: a variable throat ven- with air heated by an electrical heater to 1500°F-1600°F. turi quencher and a packed bed scrubber tower. The venturi The combined gas stream then passes through the previously scrubber tower will remove at least 99 percent of the hydro- described ceramic media, and the process gases are oxidized. gen chloride, sulfur dioxide, and other acid gases (except The ceramic media cross section is designed to provide a carbon dioxide). The venturi scrubber is a typical gas-scrub- 2-second residence time, which is sufficient to decompose bing system designed for acid gas streams. any residual agent or VOCs. Gas exits the ceramic media The particulate removal efficiency of the venturi scrub- at 2000°F when the MPT processes projectiles. When pro- ber is 99 percent for particles that are 3.0 μ and larger and 90 cessing gases are generated from contaminated wood and percent for particles from 1.0 to 3.0 μ. The time to quench contaminated shipping and firing tubes in the MPT, the gases the gas to its wet bulb (adiabatic saturation) temperature will leave the ceramic media at 2200°F. A minimum 2-second in the venturi section is designed to not exceed 0.3 second residence time is provided to ensure oxidation of any phency- based on instantaneous maximum flow rate into the venturi. clidines and polychlorinated biphenyls in the off-gas. The rapid quenching minimizes the formation of dioxins and Normally, one of the BOX units is always onstream for furans. The venturi incorporates a variable throat to maintain processing vent gases from other process units. However, a constant pressure differential and achieve high particulate 

Metal Parts Treater System 19 collection efficiency over a wide range of inlet gas flow rates. the scrubber exit gas temperature at 100°F or less. A crinkled The throat of the venturi can be automatically adjusted by Hastelloy C® (or equivalent) wire mesh mist eliminator pad moving a slide gate with a fast-response stepping motor. A is provided above the scrubber liquid distributors for the recycled stream of quench brine from the scrubber bottoms packed bed to remove large mist droplets in the gas leaving quenches the gas in the venturi. A solution of 18 weight per- the scrubber tower. The gases exiting the scrubber are heated cent sodium hydroxide is added to the venturi quench brine in an air reheater to 95°F to prevent condensed liquids from to maintain the condensate stream at a pH of approximately entering the blower and to reduce the relative humidity of 9.0 (8.0 to 9.5) to ensure that the acid gases in the vapor feed the blower discharge as it is fed via the ducting to the MDB are neutralized and to reduce corrosion. HVAC carbon filters. Separated liquid leaving the venturi drains by gravity The scrubber gas discharge blower provides an induced to the scrubber bottom where a sump provides storage and draft for proper operation of the OTM and in turn for re- surge capacity for the recirculation pump. Condensate from moving gases from the MPT main chamber and air locks. the scrubber section above the venturi inlet to the tower is The blower has a variable frequency drive to accommodate added to the sump through the scrubber recirculation pump variable off-gas flows during MPT operations. Key compo- discharge line to make up for the flash evaporation that oc- nents in the OTM, particularly the pumps and blower, will curs in the venturi quencher. Process water can be added be provided with installed spares to give added assurance of as additional makeup. Excess scrubber bottoms are sent high reliability. to the energetics hydrolysate storage tanks or to the spent decontamination-solution storage tank. Finding. Except for the first-of-a-kind bulk oxidizer units, The scrubber tower is based on commercial designs and the off-gas treatment for the MPT uses design concepts found includes a chimney tray, a packed bed, and a mist eliminator in commercial, high-reliability, off-gas cleanup systems. The pad. The recirculated scrubber solution is cooled to maintain venturi scrubber design is a mature technology.