Inhibition of chlorobenzenes formation by calcium oxide during solid waste incineration

Solid waste incineration is a major emission source of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs). The injection of N- and S-containing compounds is an effective way to suppress the formation of PCDD/Fs, but this approach is still shortcoming because additional pollutants such as NH₃ and SO_x are emitted. To avoid the secondary pollutions, a de novo synthesis inhibition mechanism in the presence of CaO was postulated to transform CuCl₂ to CuO and deplete Cl₂ and HCl. Chlorobenzenes (CBzs), which are indicators and precursors of PCDD/Fs, were adopted to prove the inhibitory effect of CaO at 400 °C, using both simulated synthetic ash and extracted air pollution control residues. As the molar ratio of CaO to CuCl₂ exceeded 3, the residual carbon increased, and the inhibition efficiency of CBzs exceeded 93 %. This performance is superior to the corresponding performance of NH₄H₂PO₄, which has been proved to be a potential inhibitor. Furthermore, with CaO, chlorides remained in the solid phase and had inactive catalytic performance; and they were the major products rather than HCl, Cl₂ and Cu₂OCl₂. The addition of CaO during waste incineration therefore can facilitate the abatement of PCDD/Fs contamination and reduce the emissions of acid gas simultaneously.