Abstract
A Plasma Arc Technology (PAT) system treats hazardous wastes in a furnace, at temperatures of 2000° C, or higher, using a plasma torch. The organic components vaporize, decompose or oxidize. The off-gases consist of hydrogen, carbon monoxide, carbon dioxide and nitric oxides. A wet air scrubber is used to remove most of these gases. The scrubber water is treated and recycled. Metal-bearing solids are melted or vaporized. The solids are usually recovered as molten metal, or as non-leachable vitrified slag, suitable for disposal in a landfill.
A Plasma Arc Centrifugal Treatment system was used to evaluate this technology for destruction of the four military hazardous wastes listed below:
1. Sludge from Longhorn Army Ammunition Plant, TX;
2. Blast media from Letterkenny Army Depot, PA;
3. Medical incineration ash from Aberdeen Proving Ground, MD; and
4. Contaminated soil from open burning/open detonation ground at Picatinny Arsenal, NJ.
The evaluation, Phase 1 of a two-phase program, includes determining the process capability of PAT for the ultimate destruction of hazardous components; verifying the suitability of the resulting slag for regular landfill disposal; identifying potential hazards associated with the process emissions; and developing qualified cost estimates for the future utilization of the process on large scale operations.
Process variables such as feed rate, composition of off-gases, run duration, percentage of oxygen used in the secondary chamber, and chamber temperature are controlled. Material balance, destruction and removal efficiency (DRE), air emission quality, wastewater quality, and suitability of slag for landfill are determined. The results from these test runs and analyses are presented in this paper.
In Phase 2, four new candidate waste streams were selected, and are listed below:
1. Waste paint from a U.S. Navy facility;
2. Garnet blast media from a U.S. Air Force Base;
3. Simulated oil-contaminated sorbent, used by Tri-Services and private industry; and
4. Mendocino soil spiked with surrogate chemical warfare materials.
Phase 2 testing begins in May 1996, and the results will be available in July 1996.
The ultimate success of PAT for destroying hazardous wastes depends on achieving a slag that is non-leachable and meets Resource Conservation and Recovery Act (RCRA) requirements, and off-gases and scrubber water that meet Clean Air and Clean Water Act standards.
Preliminary results of Phase 1 show that all slags passed Toxicity Characteristics Leaching Procedure (TCLP) tests, for land disposal requirements; air quality meets California standards, and scrubber water can be treated and recycled.
