KINETICS OF HYDROCARBON AND PESTICIDE REMOVAL FROM CLAY SOILS DURING THERMAL-TREATMENT IN A PILOT-SCALE ROTARY KILN

The kinetics of hydrocarbon removal from contaminated clay soils durin g thermal treatment in rotary kilns were studied experimentally, and k inetic parameters were obtained for simple first-order models. Results are given for seven hydrocarbons: toluene, naphthalene, n-hexadecane, lindane (gamma-HCH or 1,2,3,4,5,6-hexachlorocyclohexane), DDT (1,1'-( 2,2,2-trichloroethylidene) bis [4-chlorobenzene]), DDD (1,1'-(2,2-dich loroethylidene) bis [4-chlorobenzene]), and DDE (1,1-dichloro-2,2-bis [p-chlorophenyl] ethylene). The activation energies ranged from 18 kJ/ mol for toluene on wet soil, to 90 kJ/mol for the chlorinated pesticid es. All the kinetic data were obtained in a 130 kW pilot-scale rotary kiln. The wall temperature of the kiln was 700 degrees C for the pesti cides. Three of the hydrocarbons, toluene, naphthalene and n-hexadecan e, were studied on both wet soil (5.0 and 8.5 wt%) and on oven-dried s oil at temperatures ranging from 300 to 650 degrees C in order to unde rstand better the effects of water on desorption rates, Water increase s the rate of desorption of toluene but decreases the rates for the he avier compounds. The pilot-scale data and correlations should be usefu l to those who are operating and/or designing rotary kilns to remediat e soils thermally. A methodology for taking pilot-scale results and us ing them to estimate full-scale performance is given.