Low Temperature Thermal Deactivation for Remediation of Energetic Materials in Soil

摘要

Low temperature thermal desorption (LTTD) has traditionally been used to remediate soils contaminated with petroleum based fuels, non-fuel hydrocarbons and chlorinated solvents. A relatively new area for application of the technology is remediation of soil impacted by energetic materials. This paper covers the operation of a large-scale transportable LTTD system, operated in 2006 at an ongoing manufacturing facility for energetic materials in Utah. The system processed approximately 91,000 tons of soils containing nitrated compounds that were successfully remediated with the LTTD, with no incidents related to the energetic material processed. Soils containing residual levels of the constituents RDX, PETN, TNT, and HMX, ranging from 100 ppb to pure component as excavated were processed, with a 100% success rate in achieving the risk-based processed soil cleanup criteria. About 90% of the processed soils were below detection limits for residual concentrations. In addition to the soil, 55 cubic yards of nitrostarch product (an energetic material) present at the remediation site was introduced to the LTTD unit during the project, and that too was processed successfully. The nitrostarch was metered into the system, according to a specific protocol, at a maximum rate of 5 lb every 15 seconds. Deactivation of the energetic constituents occurs in the primary treatment unit, also known as the dryer or desorber, at an average hourly temperature of about 680 degrees F and a processing rate of not more than 40 tons per hour. Stack testing demonstrated that energetic constituent concentrations in the stack discharge were below detection limits. While the oxidizer was operated at 1,500 degrees F, this treatment step is probably unnecessary for the energetic constituents which are effectively deactivated in the dryer. This paper includes information on: techniques employed to remediate the nitrostarch product and the energetic compounds in soil; the technical data gathered during the project; and, a discussion of risk assessment associated with the work.