Thermal desorption soil decontamination

The effectiveness of thermal desorption to decontaminate soil containing HO and of UV photolysis to destroy HO toxic constituents has been demonstrated in bench- and pilot-scale tests. Some additional technical information is needed for a complete evaluation of the process and to provide the basis for design of a full-scale system for on-site remedial action. This project illustrates the requirements for developing and implementing new process technology for solving contaminated-soil environmental problems. Only through such demonstration efforts can more cost-effective and environmentally sound remedial action alternatives be made available. 

Thermal processes like pyrolysis use heat to increase the volatility (separation) to burn, decompose, or detonate (destruction) or to melt (immobilization) contaminants in soil. Separation technologies include thermal desorption and hot gas decontamination. Destruction technologies include incineration, open bum/open detonation, and pyrolysis. Vitrification is used to immobilize inorganic compounds and to destroy some organic materials. In contrast, pyrolysis transforms... 

Decontamination of soils using supercritical fluids is an attractive process compared to extraction with liquid solvents because no toxic residue is left in the remediated soil and, in contrast to thermal desorption, the soils are not burned. In particular, typical industrial wastes such as PAHs, PCBs, and fuels can be removed easily [7 to 21]. The main applications are in preparation for analytical purposes, where supercritical fluid extraction acts as a concentration step which is much faster and cheaper than solvent-extraction. The main parameters for successful extraction are the water content of the soil, the type of soil, and the contaminating substances, the available particle-size distribution, and the content of plant material, which can act as adsorbent material and therefore prolong the extraction time. For industrial regeneration, further the amount of soil to be treated has to taken into account, because there exists, so far, no possibility of continuous input and output of solid material for high pressure extraction plants, so that the process has to be run discontinuously. 

Technolt Demonstration of a Thermal Desorption-UV Photolysis Process for Decontaminating Soils Containing Herbicide Orange... 

Laboratory and field testing determined the effectiveness of a new decontamination process for soils containing 2,4-D/2,4,5-T and traces of dioxin. The process employs three primary operations - thermal desorption to volatilize the contaminants, condensation and absorption of the contaminants in a solvent, and photochemical decomposition of the contaminants. Bench-scale experiments established the relationship between desorption conditions (time and temperature) and treatment efficiency. Laboratory tests using a batch photochemical reactor defined the kinetics of 2,3,7,8-TCDD disappearance. A pilot-scale system was assembled to process up to 100 pounds per hour of soil. Tests were conducted at two sites to evaluate treatment performance and develop scale-up information. Soil was successfully decontaminated to less than 1 ng/g... 

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