Ethylene production from chlorinated organic hazardous wastes by thermal plasma pyrolysis.

Chlorinated organic hazardous wastes (COHW) from the chemical industry threaten human health and environment due to persistent toxicity and resistance to degradation. Conventional treatments often suffer from incomplete degradation or poor resource recovery. This work proposed an efficient COHW conversion to ethylene (C2H4) for dual COHW treatment and chemical production. Tetrachloroethylene (C2Cl4), a representative of COHW, was selected to develop a hydrogen thermal plasma pyrolysis reaction kinetic model, which was validated through experiments. The particle evolution in the reactor was investigated, and the cascade reaction pathway of C2Cl4 = > acetylene (C2H2) = > C2H4 was unveiled, providing a theoretical foundation for product composition regulation. To address the trade-off between low carbon black (C(B)) formation and high C2H4 selectivity in the pyrolysis with conventional single-stage quenching, a novel two-stage quenching strategy was proposed: rapid quenching (above 1300 K) suppresses C2H2 to C(B) conversion, followed by appropriate slow quenching (below 1300 K) intensifying C2H2 hydrogenation to C2H4. This coupling enhances the C2H4 selectivity and yield. The optimized experiments achieved 100 % chlorine removal, a C(B) yield reduction of 94 %, a C2H4 selectivity of 43.3 %, and a C2H4 yield of 40.2 %, making a 110 % improvement over single-stage quenching and surpassing all reported COHW-derived C2H4 yields.