Munitions Processing Flowsheet for the Pueblo Chemical Agent
Destruction Pilot Plant (PCAPP)
Craig A. Myler, Chief Engineer, Process, Bechtel National, Inc.
August Benz, Bechtel Fellow, Bechtel National, Inc.
Scott Susman, Project Engineer, U.S. Department of Defense Assembled Chemical
Weapons Alternatives (ACWA) Program
Gary Anderson, U.S. Department of Defense ACWA Site Project Manager, PCAPP
The Pueblo Chemical Agent-Destruction Pilot Plant, or PCAPP, will be built to destroy—safely
and efficiently—the stockpile of chemical weapons stored at the U.S. Army Pueblo Chemical Depot since the 1950s. The PCAPP is designed to destroy more than 2,600 tons of mustard agent in over 780,000 munitions to eliminate the risk from continued storage.
The process involves five steps:
1. Removal and treatment of the energetic items
2. Removing the mustard agent
3. Neutralizing the mustard agent
4. Post treatment of neutralized mustard agent (hydrolysate)
5. Treatment of the metal parts
This paper will discuss the flowsheet and expectations for the above 5 steps. Full scale testing results will be presented for the Projectile Mortar Disassembly (PMD) machine, the Munitions Washout Station (MWS) and the Munitions Treatment Unit (MTU).
recommend that the technology known as 1. Background.
neutralization followed by biotreatment be
used to destroy the chemical weapons. The U.S. Army Pueblo Chemical Depot,
located near Pueblo, Colo., was originally
Neutralization followed by biotreatment constructed as the Pueblo Ordnance Depot
uses hot water to neutralize the chemical in 1942. Through many years and changing
agent, effectively destroying the mustard missions, the depot is currently responsible
agent molecules. The follow-on process, for safe and secure storage of 2600 tons of
biotreatment, utilizes microbes to digest mustard agent in projectiles and mortars.
and break down the neutralization byproduct, The weapons have been stored at the
which is called hydrolysate. 23,000-acre depot since the 1950s. The
In 2002, Bechtel was selected as the Department of Defense Assembled
systems contractor to design, construct, Chemical Weapons Alternatives (ACWA)
systemize, pilot test, operate and close the Program, the depot and the community
Pueblo Chemical Agent-Destruction Pilot worked in partnership to
Plant. The Bechtel Pueblo Team is made up treatment of the chemical agent, the PCAPP of Bechtel National, Inc., and its partners, process flowsheet was established. including Washington Demilitarization
Company, Parsons, Battelle Memorial 2. Process Flowsheet.
Institute, General Atomics and General 1Physics. The overall process flowsheet for the
PCAPP is shown in Figure 2. The main
process operations described in this paper
are highlighted in Figure 3.
2.1 Removing Energetics
The munitions in the Pueblo Stockpile
contain energetic materials including
propellants and explosives. Only a portion
of the 105 mm and all of the 4.2 inch
mortars contain propelling energetics.
These propellents will be safely removed
manually, using procedures proven
previously at other stockpile locations. The
explosive components, which include fuses,
boosters, and bursting charges will be removed using a robotic machine called the Linear Projectile Mortar Disassembly Figure 1: Chemical Weapons in machine (LPMD). Existing U.S. baseline Storage plants use a turntable-based PMD machine to move projectiles and mortars from station to station for reverse assembly and The Pueblo stockpile consists entirely of energetics removal. Using advanced robotic projectiles and mortars, all of which contain technology, the LPMD moves projectiles either distilled mustard (HD) or agent HT. and mortars between individual reverse The total number of munitions is over assembly stations in a linear array, allowing 780,000. for greater flexibility in both control and configuration. A significant improvement is It is apparent from the number of munitions the ability to easily replace individual to be destroyed at the PCAPP that the LPMD component assemblies, thereby processing flowsheet must consider plant reducing maintenance, changeover, and throughput as a critical design requirement. closure complexity. After removal, all As the agent make-up of the munition items uncontaminated propellants and explosives in the Pueblo Stockpile are all blister agent, are shipped off-site for commercial disposal. retooling of the plant for each munition type The LPMD is shown in Figure 4. (called change-over) requires only minor
changes to the mechanical systems. With
this in mind, and the overall requirement for
neutralization followed by biological
1 Taken from ACWA Program Fact Sheet on Chemical Weapons Destruction at U.S. Army Pueblo Chemical Depot, http://www.pmacwa.army.mil/co/ip/dl/acwa_pueblo_overview.pdf
DUNNAGE/METAL OFF-SITE MUNITIONS MUNITIONS MUNITIONS PARTS SHIPMENT STORAGE SERVICE (G-BLOCK) MAGAZINE ENERGETICS STORAGE ENERGETICS/ SERVICE IGLOO HVAPROPELLANTS MAGAZINE (H-BLOCK) C VENBASELINE AND T OFF-SITE ENHANCED VENT TO SHIPMENT ENHANCED ATMOSPHERE EXPLOSIVE RECONFIGURATION CONTAMINATED RECONFIGURED DESTRUCTION ENERGETICS, CLEAN MUNITIONS TECHNOLOGY (EDT) LEAKERS, AND WASTE REJECTS DEMIN 25% NaOH WATER OFF-GAS VENT AGENT VENTREATMENT SYSTEM FILTER VENT T AREA VENT FROM (OTS) SDU/AUTOCLAVE MUNITIONS MUNITIONS BUFFER EMPTY CLEAN MUNITIONS TREATMENT WASHOUT SYSTEM OFF-SITE MUNITIONS STORAGE (MWS) SHIPMENT UNIT (MTU) VENT TO ATMOSPHERE VENT 25% NaOH WASHED BTA OTS 25% NaOH 5% NaOH STEAM AGENT VENT VENT TO ATMOS. SOLID SPENT BIO- AGENT COLLECTION WATER RECOVERY HYDROLYSATRESIDUE DECON DECON E TREATMENT & SYSTEM (WRS) 25% NaOH SYSTEM NEUTRALIZATION BRS OTS 93% HSO24 STEAM HOT PROCESS WATER VENT RECOVERED PROCESS BRINE REDUCTION CONDENSATOFF-SITE WATER TO WATER SYSTEM SYSTEM (BRS) E SOLID SHIPMENT USERS RESIDUE
CLEAN DUNNAGE/ OFF-SITE SECONDARY WASTE SHIPMENT VENT TO OTS COOLING TOWER MAKEUP CONTAMINATED DUNNAGE/ SDU/AUTOCLAVE SECONDARY WASTE
RAW TREATED SANITARY SANITARY SANITARY WASTE 25% NaOH 25% NaOH BULK CHEM WASTE WASTE TREATMENT TO USERS STORAGE
Figure 2: PCAPP Process Flowsheet
DUNNAGE/METAL OFF-SITE MUNITIONS MUNITIONS MUNITIONS PARTS SHIPMENT STORAGE SERVICE (G-BLOCK) MAGAZINE ENERGETICS STORAGE ENERGETICS/ SERVICE IGLOO HVAPROPELLANTS MAGAZINE (H-BLOCK) C VENBASELINE AND T OFF-SITE ENHANCED VENT TO SHIPMENT ENHANCED ATMOSPHERE EXPLOSIVE RECONFIGURATION CONTAMINATED RECONFIGURED DESTRUCTION ENERGETICS, CLEAN MUNITIONS TECHNOLOGY (EDT) LEAKERS, AND WASTE REJECTS DEMIN 25% NaOH WATER OFF-GAS VENT AGENT VENTREATMENT SYSTEM FILTER VENT T AREA VENT FROM (OTS) SDU/AUTOCLAVE MUNITIONS MUNITIONS BUFFER EMPTY CLEAN MUNITIONS TREATMENT WASHOUT SYSTEM OFF-SITE MUNITIONS STORAGE (MWS) SHIPMENT UNIT (MTU) VENT TO ATMOSPHERE VENT 25% NaOH WASHED BTA OTS 5% NaOH 25% NaOH STEAM AGENT VENT VENT TO ATMOS. SOLID SPENT BIO- AGENT COLLECTION WATER RECOVERY HYDROLYSATRESIDUE DECON DECON TREATMENT E & SYSTEM (WRS) 25% NaOH SYSTEM NEUTRALIZATION 93% HSOBRS OTS 24 STEAM HOT PROCESS WATER VENT RECOVERED PROCESS BRINE REDUCTION CONDENSATOFF-SITE WATER TO WATER SYSTEM SYSTEM (BRS) E SOLID SHIPMENT USERS RESIDUE
CLEAN DUNNAGE/ OFF-SITE SECONDARY WASTE SHIPMENT VENT TO OTS COOLING TOWER MAKEUP CONTAMINATED DUNNAGE/ SDU/AUTOCLAVE SECONDARY WASTE
RAW TREATED SANITARY SANITARY SANITARY WASTE 25% NaOH 25% NaOH BULK CHEM WASTE WASTE TREATMENT STORAGE TO USERS
Figure 3: PCAPP Process Flowsheet Highlighting Main Process Operations
agent to drain from the munition. This operation is conducted with the projectile oriented vertically, ojive down. Once the adapter is fractured and the burster well crushed, agent drains into a receiving cup. Once drained, the projectile is rinsed with high pressure water to remove residual agent material. A schematic of the MWS is shown in Figure 5. The agent and rinse water from the MWS is recovered in tanks for
subsequent processing in the Agent
Neutralization System (ANS). Figure 4: Linear Projectile Mortar 2.2.2 Munitions Washout System Disassembly Machine (MWS) for 4.2 inch Mortars As the 4.2 inch mortar has relatively thin 2.2 Removing the Mustard Agent walls and contains an internal baffle, hydraulic crushing of the burster well is not Once the energetic components have been conducted. Instead, the CAM for 4.2 inch removed, the projectile or mortar body mortars incorporates a cutting wheel to containing the mustard agent fill is remove the base of the mortar allowing transferred to a separate building for agent agent to drain. The cutting is done in an processing. The projectiles and mortars are enclosed space within the CAM to reduce at this point essentially heavy walled overall contamination. Following removal containers with a press fit burster well seal. of the mortar base, high pressure water is In U.S. baseline incineration plants, the again used to rinse residual agent material burster well is mechanically pulled out of from the mortar body and the removed the munition body and the chemical agent mortar base. The MWS for 4.2 inch mortar drawn out by vacuum. At the PCAPP, an processing is shown in Figure 6. As in the innovative approach will be used to remove projectile MWS, agent and rinse water from the chemical agent. The approach is the mortar processing is collected in tanks different for the projectiles and the mortars and then fed to the ANS. so they will be discussed separately. 2.3 Neutralizing the Mustard Agent 2.2.1 Munitions Washout System (MWS) for Projectiles. Hot water hydrolysis of distilled mustard was successfully proven out at the Aberdeen A unique system called a Munitions Chemical Agent Destruction Facility Washout System (MWS) will be used to (ABCDF) at an industrial scale. Using remove the agent from projectiles and rinse experience gained at the ABCDF, the residual agent material from the inside of the PCAPP ANS includes two turbine mixer munition body. The system consists of a equipped reactors with recirculation through robotic munitions handling system (using static mixers which are equivalent in the same robot model as used in the LPMD) throughput to the four reactors used at the and a number of Cavity Access Machines ABCDF. As HT has not previously been (CAM). For projectiles (105 and 155 mm), treated using this process, laboratory studies the CAM operates by hydraulically pushing were conducted to confirm the feasibility of the burster well into the munition, fracturing neutralization of HT. These studies the adapter, and creating an opening for the demonstrated that HT reacts very similarly
to HD, and analytical methods have been
developed to confirm the destruction of HT.
Hydraulic RamFigure 6: MWS for 4.2 in Mortar And Spray Processing
2.4 Biotreatment of the Mustard Agent
BursterwellHD mustard hydrolysates contain HydraulicallyProjectileCrushedPlaced inthiodiglycol (a similar diglycol is produced Cupfrom the T in HT), salt, NaOH and water.
The organic diglycols can be effectively
treated biologically. The biotreatment of
mustard hydrolysate was demonstrated at
the ABCDF using a large, off-site,
commercial treatment facility. To treat Step 2Step 1hydrolysates on-site, the PCAPP design includes the use of twenty-four Immobilized
Cell Bioreactors (ICB) segregated into six
modules of four ICBs. Each ICB contains
three treatment cells where air is passed Highthrough a proprietary packing material. PressureAgent WaterDrainBiological treatment occurs at the surface of Spray
the packing and within the liquid in each
ICB cell. Most of the treatment occurs in
the first cell. Treatment in the second cell
effectively completes the treatment with the
third cell acting as a polishing treatment step.
The effluent water from the ICBs is treated Step 4Step 3and returned to the process. Figure 7 shows the design of an ICB module.
Figure 5: MWS Schematic for Projectile
Another innovation at PCAPP is the
elimination of the heating jacket for the
reactors. The PCAPP reactors will use
direct steam injection for heating. This will
reduce the capital cost of equipment and
provide for shorter heating times in what is
the aqueous reactor system.
is maintained above the capture velocity to assure that no chemical agent can be released from the clean end of the unit. Treated munitions exit the unit to bins outside of the processing facility. The steel from the projectile and mortar bodies will be reclaimed by smelting at an off-site facility. As the muffle contains both the metal parts and the ventilation air, there is never contact by chemical agent outside the muffle of the MTU. A cross-section of the MTU is shown in Figure 8.
Figure 7: Immobilized Cell Bioreactor (ICB) InsulationMuffleModule
2.5 Disposing of the Metal Parts
Another unique element of the PCAPP
which supports the processing of large
numbers of munitions is the method for
treating the projectile and mortar bodies Heating ElementsBeltafter washout in the MWS. After washout, the projectile and mortar bodies (metal parts)
Figure 8: Munitions Treatment Unit (MTU) may contain small yet measurable quantities
Cross-Sectional Diagram of chemical agent. Batch thermal treatment
processes require some form of staging area
2.6 Secondary Waste Treatment before and after the process. Additionally,
batch thermal processes produce a
As chemical weapons are processed through maximum vapor emission load associated
the PCAPP, contamination of miscellaneous with a batch of multiple metal parts
other materials will occur which require thermally desorbing at roughly the same
some form of treatment. These materials time. To avoid these two situations, the
include gloves, protective suits and masks, PCAPP will utilize a continuous thermal
containers, hoses, pallets, and other items processor to treat the metal parts from the
which may come in contact with chemical MWS. The treatment unit operation is
agent. This material is considered called a Muntions Treatment Unit (MTU).
secondary waste. Two novel systems will The unit consists of an electrically heated,
be used to treat secondary wastes at PCAPP. continuous belt muffle oven. Contaminated
The Supplemental Decontamination Unit munitions from the MWS are placed on the
(SDU) is a low temperature oven which chain belt and are conveyed through the
treats waste in mesh trays in circulating hot oven. Six resistance heating zones provide
air (typically 200-400ºF) in order to the positive control to heat the projectile and oovolatilize and/or decompose agent without mortar bodies to at least 1000 F (538 C)
combusting the waste itself. The Autoclave for a minimum of 15 minutes thereby
is the other waste treatment system at destroying any residual chemical agent.
PCAPP, and is a standard commercial Clean air enters the unit at the discharge end
vacuum cycle steam autoclave unit. A and passes through the muffle counter-
version of SDU was successfully utilized at current to the metal parts. The volume of air
the ABCDF. Laboratory data collected on Table 2: Unit Operations of the PCAPP
HD and HT show that with appropriate Process Flowsheet temperature and time, the range of potential
secondary wastes expected at PCAPP can be Unit Operation Number of Parallel effectively treated for disposal in these units. Treatment Systems A list of the items tested is shown in Table 1. Linear Projectile 3
3. Conclusion Munitions Washout 2
The process flowsheet for the Pueblo Agent Neutralization 1 (consisting of 2 Chemical Agent Destruction Pilot Plant has System (ANS) reactors) been developed to safely destroy over Immobilized Cell 24 ICBs in 6 780,000 chemical weapons stored at the Bioreactor (ICB) Modules of 4 Pueblo Chemical Depot. A number of novel Munitions Treatment 2 unit operations have been selected to remove Unit (MTU) energetics from the munitions, access the Supplemental 1 chemical agent contained in the munitions, Decontamination chemically neutralize both HD and HT, Unit (SDU) biologically treat the agent hydrolysate, Autoclave 1 thermally treat the drained and rinsed projectile and mortar bodies, and treat the contaminated secondary wastes from the process. The overall reliability and throughput of the PCAPP has been carefully evaluated in order to establish the number of parallel treatment systems required, as shown in Table 2.
Table 1: Secondary Wastes Tested in SDU and Autoclave for HD and HT Treatment
Material SDU Autoclave
Steel Yes Yes
Leather Yes Yes
PTFE Yes Yes
LDPE Yes Yes
Butyl Rubber Yes Yes
Wood (Oak) Yes Yes
Wood (Pine) Yes Yes
HEPA Filter Yes Yes
Activated Charcoal Yes Yes
Fiber Container Yes Yes
PPE Material Yes Yes
Encapsulated HT Yes No