Chlorine removal from incinerator bottom ash by superheated steam

Abstract

In this study, the dechlorination of two kinds of incineration bottom ashes containing NaCl, CaCl2 and MgCl2 was investigated under various superheated steam temperatures between 408 and 693K and a steam flow rate of 10kg/h. The mechanism of chlorine removal from three kinds of simulated ash samples shaped into cuboid was discussed on the basis of chlorine removal rate data involving one kind of inorganic chloride. The chlorine removal amount from the incineration ashes increased with increasing superheated steam temperature, however the amount of chlorine removal depended on the composition of the incineration ashes. The amount of chlorine removal from the incineration ash containing NaCl and CaCl2 was smaller than that from the ash containing NaCl and MgCl2 at the same superheated steam temperature. The chlorine removal amount from the simulated ash samples with different chlorides was increased in the following order: CaCl2, NaCl and MgCl2. The dechlorination rate was analyzed by an unreacted core model newly applied for cuboid. It is suggested that the chlorine removal rates from the simulated samples containing SiO2, Al2O3 and one of the inorganic chlorides (NaCl, CaCl2 or MgCl2) were controlled by the diffusion of gas in the solid sample.