Chlorine removal from incinerator bottom ash by superheated steam

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 693 K and a steam flow rate of 10 kg/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.