REACTION KINETICS OF HAZARDOUS METALS IN HIGH-TEMPERATURE PACKED BED OF VARIOUS INORGANIC SORBENTS

摘要

This study investigated the kinetics of the sorption reaction for high-temperature metal capture in the packedrnbed of inorganic sorbents. The investigated sorbents for lead and cadmium capture were bauxite, sand and kaolin.rnThe extensive packed bed experiments were carried out over a temperature range of 700-900℃. The effects of bedrntemperature and metal vapor concentration on the sorption reaction rate were determined by the analysis of experimentalrndata with a developed kinetic model. Detailed information on the metal-sorbent interaction was obtained byrnthe XRD (X-ray diffraction) pattern analysis and microscopic analysis of raw, calcined and metal-sorbed sorbents.rnCalcined kaolin was the most reactive sorbent, and the high-temperature reaction between metal vapor andrnmetakaolinite in calcined kaolin generated stable metal-mineral complexes (PbAl_2Si_2O_6, CdAl_2Si_2O_6 andrnCd_2Al_2Si_2O_7). For both cadmium and lead sorption, an increase in bed temperature results in an increase of capturingrnrates, but it has no effect on maximum uptakes. No significant resistance of pore diffusion was found and thernchemical reaction at the sorbent surface controlled the overall sorption reaction rates. The order of reaction withrnrespect to the gas-phase concentration was determined to be 1.67 and 3.26 for PbCl_2 and CdCl_2, respectively. Thernactivation energy, Ea, was estimated as 10.16 and 5.56 kcal/mol for PbCl_2 and CdCl_2, respectively, according to thernArrhenius relationship.