The primary evaluation and characterization of obsolete DDT pesticide from precalciner of cement kiln

1,1,1-trichloro-2,2-bi(4-chlorophenyl)ethane (DDT) pesticide was extensively used in agriculture last century in China, and now, has been banned from all purposes. The disposal of obsolete DDT pesticide has been an urgent task for Chinese government. In order to evaluate the feasibility of co-processing DDT in current New Style Dry-process Rotary Kiln with precalciner as feeding point, the destruction efficiency of DDTs (including p,p’-DDT, o,p’-DDT, p,p’-DDE and p,p’-DDD), proportion of DDTs in combustion residue and exhaust gas, and the release of chlorine were studied under different operating conditions of temperature, oxygen content and gas retention time in the lab. The destruction efficiency of DDTs exceeded 99% as the temperature was over 800℃ with enough oxygen. As the temperature rose from 600℃ to 1200℃, the proportion of p,p’-DDD increased and p,p’-DDT decreased but still the main remain in combustion residue. In the exhaust gas, the most dominant phenomenon was the rapid growth of p,p’-DDE concentration as temperature rose. The release of chlorine reached a peak at 800℃～900℃. It was found that the oxygen content had the positive correlation with the process of dechlorination. The proportion of p,p’-DDE increased as the oxygen content elevated in exhaust gas. The gas retention time has almost not influenced the destruction efficiency of DDTs, but effected the degradation extent of DDTs in gas phase. These experiments showed that co-processing of obsolete DDT pesticide in cement kiln precalciners is feasible