A field study of dioxins during co–processing of hazardous waste in multicomponent slurry gasifier

Abstract

A field test was conducted to study the emission and distribution characteristics of dioxins during co–processing of hazardous waste in a multicomponent slurry gasifier (MCSG). The toxicity equivalent concentrations of polychlorinated dibenzo–p–dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) in all exhaust gas, waste water, and solid waste under both blank condition (i.e., feedstock was normal coal–water slurry) and test condition (i.e., feedstock mixed with hazardous waste and labeling reagents) were analyzed. Results showed that organic matter was fully degraded in the MCSG. The dioxin amount in the black water flash steam increased with the addition of hazardous waste and chlorine in the feedstock, and octachlorodibenzo–p–dioxins (OCDD) with the largest increase is the most easily formed monomer in dioxins. The dioxin amount in all samples was far below the standard limit in China and other countries. This indicates the low environmental risk from dioxins during the co–processing process. The dioxin distribution trend in solid, liquid, and gas phase during co–processing did not change: 86.63%–94.18%, 0.02%–0.13%, and 5.8%–13.23% of PCDDs were distributed in the exhaust gas, waste water, and solid waste, respectively, while 6.10%–22.95%, 0.59%–0.80%, and 76.45%–93.10% of PCDFs were distributed in the exhaust gas, waste water, and solid waste, respectively.