Chlorobenzene formation from fly ash: effect of moisture, chlorine gas, cupric chloride, urea, ammonia and ammonium sulfate

Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) are formed jointly with numerous products of incomplete combustion during waste incineration. Chlorobenzenes (CBz) are often cited as surrogates or precursors of PCDD/Fs. Experiments were conducted to investigate the effect of some key parameters on CBz formation, including moisture (H2O), chlorine gas (Cl2), cupric chloride (CuCl2), urea [(NH2)2CO], ammonia (NH3), and ammonium sulfate [(NH4)2SO4]. Cl2 and CuCl2 promoted CBz formation from fly ash, increasing the chlorination degree. In addition, Cl in cupric compound was more active than chlorine atom of Cl2, and chlorine type significantly affected the chlorination process. Less CBz yield was detected after S- and N-containing compounds [(NH2)2CO, NH3, and (NH4)2SO4] were added into reactive ash. High content of moisture in gas prevented CBz synthesis and reduced chlorination. These experimental results are useful to optimize CBz emission control and realize the mechanism of the correlation between CBz and PCDD/Fs.