Life Cycle Assessment Research Of Ultra-Clean Flue Gas Emission System In Coal-fired Power Plant

Air pollution represented by haze are frequently occurred in recent years,which affecting people's daily life seriously and threatening people's health.As a pillar of China's power industry,coal-fired power plants emit a large amount of soot,sulfur dioxide and nitrogen oxides.The state has issued "Comprehensive implementation of ultra-clean emission and energy saving reform work plan" and "Action plan for upgrading and reforming of energy saving and emission reduction for coal generated electricity ",which requires that the emission concentration of flue dust,sulfur dioxide and nitrogen oxides of coal-fired power plants can not exceed 10 Mg/m3,35 mg/m3 and 50 mg/m3.The transformation of ultra-clean emission of flue gas has become the compulsory requirement of the coal-fired power industry.Using life cycle assessment,life cycle cost and social life cycle assessment and in the system boundary of“factory gate to factory gate",this paper studies the environmental,economic and social impact of the four processes,i.e.selective catalytic reduction technology,electrostatic precipitator,limestone gypsum wet desulphurization and wet electrostatic precipitator,of the flue gas purification system before and after the ultra-clean emission transformation in a 315MW unit of a coal-fired power plant.It analyzes the impact of the process on the environment and society,and puts forward some relevant advices.It is of great significance for the ultra-clean emission transformation of coal-fired power plants.The results show that the environmental load and economic cost of the desulfurization stage of the flue gas purification system account for a large proportion of the overall environmental impact and economic cost.After the transformation,the environmental load in the desulfurization stage accounts for 42.64%of the overall environmental load,and the economic cost accounts for about 70.32%of the overall economic cost.The environmental impact of desulfurization power consumption in the desulfurization stage accounted for 31.14%and 39.14%of the overall system before and after the transformation.Secondly,as for the residual pollutant,the environmental load of residual emissions account for 55.16%and 37.03%of the overall environmental load of the system before and after the transformation.Although the amount of mercury in the residual pollutants is not large,the environmental impact of the residual pollutants accounted for 80.82%of the overall environmental impact of the residual pollutants.Therefore,desulfurization stage and pollutant emission stage are the key processes of this study,and the desulfurization power consumption and the mercury are identified as key substances in the key process.Before and after the transformation,the total economic cost of each functional unit increased from 16.59 RMB to 20.45 RMB.Before and after the transformation,the economic cost of denitrification and electrostatic precipitator has no obvious change.The economic cost of the desulfurization system before the transformation accounts for about 76.07%of the total economic cost,and the economic cost of the desulfurization system increases obviously after the transformation,accounting for about 70.32%of the total economic cost,and the cost of the new wet electrostatic precipitator can not be ignored,accounting for 9.39%of the total economic cost.The economic cost of desulphurization is the main part of the total cost of economic cost.The economical cost of desulfurization stage is the largest before and after the transformation of ultra-clean emission.The desulfurization process needs to be further optimized and modified.This will be of great significance to the operation and development of the whole coal-fired power plant to control and reduce the power consumption,especially under the current national ultra-clean emission standards.In addition,this study uses the social willingness to pay to link the environmental impact with the social impact,and combines the analytic hierarchy process(AHP)to evaluate the social impact.The paper calculates the potential social impact of each process.The results show that the social impact of SCR and wet electrostatic precipitator is small,which accounting for 4.7%and 5.7%of the total social impact.The electricity consumption in electrostatic precipitator is large.There are a large amount of fly ash to be treated.Therefore,it will have a great social impact,and the social impact latent value accounts for 46.8%of the total.In addition,the desulfurization stage will produce greater social impact besides the environmental impact,and the social impact latent value will account for 42.7%of the total.The paper make contribution to the database of the flue gas purification system in China.It can provide theoretical reference for further optimization of flue gas purification system in coal-fired power plants.