Research On Chlorine Evolution And Transformation Mechanism For Co-processing Of Hazardous Waste In Cement Kiln

Co-processing of hazardous waste in cement kiln is a new hazardous waste incineration technology,which has the benefits including high incineration temperature,long retention time,higher destruction and removal efficiency and lower improvement cost.However,while co-processing of hazardous waste in cement kiln,as hazardous waste always contain chlorine,and excessive existence of chlorine will affect not only operation of cement kiln but also quality of cement products.Therefore,it is necessary to study the evolution and transformation mechanism of chlorine during co-processing of hazardous waste in cement kiln.Firstly,the rectification residue and pure reagent were mixed with raw meal,and the influence of different atmosphere,heating rate,chlorine content and chlorine sources on HCl release were studied by using TG-FTIR.The results showed that the increase of chlorine content and the acceleration of heating rate promoted the release of HCl.In addition,under the same conditions,the mixture of rectification residue and raw meal produced the most HCl,followed by the mixture of PVC and raw meal,and the mixture of CaCl2 and raw meal produced almost no HCl.Next,the partition of Cl in flue gas,fly ash and clinker under different experiment conditions was obtained by using tubular furnace to incinerate mixtures of hazardous waste and raw meal.The results showed that chlorine mainly existed in flue gas and clinker,and only less than 3.5% of chlorine existed in fly ash.The incineration temperature had a significant effect on the distribution of chlorine in each part.The higher the incinerating temperature,the greater the proportion of chlorine in flue gas and fly ash.While temperatures were higher than 1300℃,the proportion of chlorine in all parts remained basically unchanged.With the increase of the retention time,the proportion of chlorine in the flue gas increased gradually.The distribution ratio of chlorine in each part remained unchanged after about 30 min.In addition,the chlorine content of the sample and the chlorine source had a relatively slight effect on the partition of chlorine.Then,the dioxins production and homologous distribution during co-combustion of rectification residue and raw meal were studied.The results showed that the mixed sample with 3% chlorine content produced the least amount of dioxins and the lowest toxicity equivalent.With the increase of chlorine content in mixed samples,the proportion of low chlorinated dioxins increased and the proportion of high chlorinated dioxins decreased.Finally,PVC powder and rectification residue were selected as experimental objects,mixed with raw cement and calcined in a tubular furnace to study the influence of chlorine-containing hazardous waste on mineral composition of cement clinker.The results showed that the main components of cement clinker did not change significantly after adding rectification residues.And the calcination temperature is an important factor for qualified cement clinker.After adding PVC,the calcination temperature of cement clinker is between 1300℃ and 1500℃.