Study On Life Cycle Assessment Of Cement Kiln Co-processing Of Hazardous Waste

With the rapid development of modern industrial technology,the types and production of industrial waste in many industries are rapidly increasing.The ultimate disposal of hazardous waste is particularly important.Due to environmental protection policies and land restrictions,high-temperature incineration is considered to be one of the most suitable disposal methods of hazardous waste in China.Compared with traditional incinerators and safe landfills,cement kiln co-processing hazardous waste technology shows many advantages:high incineration temperature,harmful substances are thoroughly decomposed,no secondary pollution,low construction investment,and low operating costs,etc.However,the influence of F,Cl,S and other elements after the introduction of hazardous waste on the stable operation of the kiln and the environmental impact of hazardous waste pretreatment and incineration on the resources,energy consumption and pollutant emissions of the cement industry are not clear.In order to explore the environmental impact caused by the introduction of hazardous waste,this paper is limited to carry out the investigation and study of cement kilns co-processing hazardous waste enterprises.Firstly,based on the characteristics of hazardous waste,the kiln waste is defined as three categories:mixed hazardous waste,organic hazardous waste and sludge hazardous waste.Secondly,a life cycle assessment system for the co-processing of hazardous waste in cement kilns was constructed with a 1kg hazardous waste functional unit.The environmental impact was analyzed and evaluated from five potential values:primary energy consumption potential,climate change potential,acidification potential,eutrophication potential and inhalable inorganic matter potential.Finally,sensitivity analysis and economic benefit analysis of LCA calculation results are carried out.The main research content include:(1)The investigation and study on the co-processing hazardous waste enterprises by cement kilns in Shanxi Province was carried out,including the distribution of enterprises,overview,process technology,approved types and scales of hazardous wastes for operation,etc.Mastering the pretreatment process,characteristics and disposal volume of mixed hazardous waste,organic hazardous waste and sludge hazardous waste in the actual disposal process.It also explored the factors affecting the disposal of various types of hazardous waste into the kiln.Among them,the main influencing factor of mixed hazardous waste is the Cl content,which accounts for 74.15%;(2)Combined with the cement kiln co-processing hazardous waste production process,identify related energy consumption and pollutant emissions firstly,the relevant process parameter values are collected,then define the scope of research mainly from the entry of hazardous waste transportation as a start,after hazardous waste pretreatment and high temperature incineration,the clinker output is the end point to clinker output as the end point.The entire life cycle is divided into five parts:direct discharge,raw coal mining,power production,hazardous waste transportation and coal transportation.A life cycle assessment system for the treatment of 1 kg mixed hazardous waste,organic hazardous waste and sludge hazardous waste was established,respectively;(3)The online analysis software eFootprint and CML2002 model were used to characterize the inventory data,and five environmental impact assessment results were calculated,including the primary energy consumption potential,climate change potential,acidification potential,eutrophication potential,and respirable inorganic substances potential.The results show that the types,characteristics and disposal amount of hazardous wastes directly affect energy consumption and air pollutant emissions,resulting in changes in primary energy consumption potential,climate change potential,acidification potential,eutrophication potential and inhalable inorganic substance potential.The impact degree of each type of hazardous waste on the environmental impact potential value is:mixed hazardous waste>sludge hazardous waste>organic hazardous waste.The environmental impact potential value of mixed/sludge hazardous waste is:10.5/4.24 MJ>8.34E-01/3.42E-01 kg CO2 eq>8.26E-03/1.81E-03 kg SO2 eq>9.15E-04/2.55E-04 kg PM2.5 eq>2.96E-04/1.81E-04 kg PO43-eq.The environmental impact potential value of organic hazardous waste is 5.67E-04 kg SO2 eq>7.85E-05 kg PM2.5 eq>3.75E-06 kg PO43-eq>-6.98E-01 kg CO2 eq>-5.28 MJ;(4)The sensitivity of the list data of acidification potential,eutrophication potential and inhalable inorganic substances and economic benefits were analyzed,and some suggestions are put forward according to the results.The results show that the sensitivity of SO2 data and NO,data are relatively high.The sensitivity of SO2 data with mixed acidification potential value of hazardous waste is up to 47.8%,and the sensitivity of NOx data with eutrophication potential value of sludge hazardous waste is up to 54.9%.The total cost of single type hazardous waste treatment is lower than that of mixed hazardous waste treatment,compared with the mixed hazardous waste treatment,the total cost of organic hazardous waste and sludge hazardous waste decreased by 5.14E-01 yuan/kg and 1.3E-01 yuan/kg,respectively,having certain economic benefits.It is suggested that the compatibility research should be strengthened in the process of cement kiln co-processing hazardous wastes,especially mixed hazardous wastes.