Sandia Lab News
December 5, 1997

Sandia method to destroy old munitions is scaled up for pilot plant at Army's Pine Bluff Arsenal

Supercritical water oxidation will be used for demilitarization

Nancy Garcia

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Technologies developed in the laboratory to destroy wastes without hazardous emissions are being applied in a pilot-scale plant under construction at the Army's Pine Bluff Arsenal in Arkansas.
ON-SITE OVERSIGHT- Sandia's M.C. Stoddard (8119), the project manager, displays equipment at McAbee Construction in Tuskaloosa, Ala., where the skids were built for the pilot plant demilitarization system.

There, up to 80 pounds per hour of obsolete munitions, slurried in water, will be destroyed in a supercritical water oxidation (SCWO) system. The SCWO system pressurizes and heats the slurry, which fuels an oxidation reaction. The wastes are destroyed within seconds, producing such innocuous end products as carbon dioxide, water, and salts.

The Army is responsible for demilitarization of obsolete munitions from all services. Open burn/open detonation is the mainstay operation, favored due to its low cost, simplicity, and effectiveness. However, some munitions, such as colored smokes and dyes, are sufficiently hazardous that they have been barred from disposal by this method.

Incineration, also widely used, has proven challenging for the smokes and dyes due to their high emissions of soot, ash, and corrosive gases. These smoke and dye munitions, some of which date from World War II, are therefore ideal candidates for SCWO.

At the heart of the new system is a novel reactor design intended to overcome a potential complication. Treating smoke and dye munitions can create effluent of up to 35 percent salt. The salt is insoluble under these conditions (700C and 4,000 psi) and can plug the reactor.

Sandia demonstrated a design that inhibits salt deposits by injecting pure water through small pores in an inner liner to form a protective boundary.

Known as the transpiring wall reactor, this design was developed by Aerojet GenCorp for cooling and fluid management in missile and rocket applications. Brent Haroldsen (8118) led design testing in Sandia's Engineering Evaluation SCWO Reactor, which has the only transpiring wall reactor in operation. Brent was supported by Bert Brown (also 8118). Bernice Mills (8713) provided surface chemistry expertise for diagnostics consultation and data interpretation.

Delivered last month

Sandia's laboratory reactor testing focused on developing operating parameters and evaluating design issues for the transpiring wall concept and led to the reactor design for the Pine Bluff Arsenal pilot plant. Destruction kinetics of the Army materials were developed in Steve Rice's (8361) Supercritical Flow Reactor, and the conceptual design for the plant was developed by Tony LaJeunesse (8118). Results from Sandia's laboratory reactors were critical in the Army's decision to commit this technology to a pilot plant.

Last month, construction reached a milestone when the SCWO system was delivered on skids to the arsenal.

"The leverage achieved from our numerous SCWO sponsors has been exceptional," says M.C. Stoddard (8119), project manager of the Pine Bluff Arsenal pilot plant.

The laboratory work providing the foundation for this plant was funded by the Army and the DOE-DP/DoD Office of Munitions Memorandum of Understanding.

In addition, significant benefit has been realized from complementary work sponsored by other federal agencies. The DOE Office of Technology Development (EM-50) cosponsored Sandia's procurement of the first transpiring wall reactor and its testing. The Office of Naval Research/Defense Advanced Research Projects Agency sponsored validation testing of the feed injector, a key feature of the transpiring wall reactor. Steve's chemical kinetics studies, funded by the Strategic Environmental Research and Development Program, determined the auxiliary fuel selected to initiate the waste destruction reaction.

The plant is being built by Foster Wheeler Development Corp. of Livingston, N.J., under contract to Sandia. Dennis Ariizumi (8118), who led the design and construction of Sandia's Engineering Evaluation Reactor, provides the technical interface between Foster Wheeler and Pine Bluff Arsenal. M.C. provides technical, contract, and programmatic direction to both Foster Wheeler and the Army sponsor, the US Army Armament Research, Development, and Engineering Center (ARDEC) in Picatinny Arsenal, N. J., and the Demilitarization Technology Office at Savanna Army Depot, Ill.

Pine Bluff Arsenal was selected as the site for the SCWO plant because it is both an existing demilitarization site and the center of government expertise in colored smokes and dyes, having originally produced many of these materials.

Pine Bluff Arsenal is currently a production, storage, and demiliterization facility for conventional munitions - operating several incinerators. The arsenal also manages storage and destruction of the second-largest chemical agent stockpile in the United States.

Expecting the unexpected

Under ARDEC, Pine Bluff Arsenal is responsible for preparing the site and supporting facility design and installation. Site preparation includes developing a waste handling and feed system as a front end for the SCWO unit. Pine Bluff Arsenal will participate in the demonstration and validation testing along with Sandia and Foster Wheeler. Once testing is complete, the SCWO unit will be transitioned to normal operations for destruction of the smoke and dye inventory. The Army also plans to use the plant as a test bed to evaluate treating other military wastes. This project is a showcase for alternative technology development there.

The Pine Bluff Arsenal pilot plant is a team effort requiring close communication and coordination among the key participants: Sandia, ARDEC, Pine Bluff Arsenal, Foster Wheeler, and Koch Process Industries.

"Especially as we transition into field installation and testing, each participant owns important task elements that are interconnected with everyone else's," says M.C. "It's a dynamic time for the project - the most exciting time for engineers, who are energized as hardware finally comes together and start-up draws near."

"We expect the unexpected in starting up a pilot unit like this," says Dennis. "Our computer control system will allow remote access to plant operational data, so hopefully we won't need to rent an apartment in Pine Bluff," he adds.

Recently, the construction site at Pine Bluff was toured by about 150 attendees from the 6th Annual Demil User's Meeting. The meeting is an international forum for people responsible for implementing demilitarization of obsolete munitions.

This work was initiated at Sandia in FY92 as a simple feasibility study involving only a few laboratory tests. The early work was developed under the direction of Sheridan Johnston (4527), Jack Swearengen (former Sandian), and Ken Tschritter (8118). From there it grew to a SCWO plant that will be used to dispose the DoD's smoke and dye inventory. Testing is scheduled to begin in March 1998.

"This project is a fine example of unique Sandia contributions in all aspects of research to development to application," says Howard Hirano, Manager of Technology Applications Dept. 8119.

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