Life Cycle Assessment Of Coal Gangue And Coal Co-combustion In A Circulating Fluidized Bed Power Plant

Coal-fired power generation industry is important to the national economy and society.The environmental hazard of coal gangue solid waste is the key issue of the industry.The government encourages power plants to use coal gangue for power generation.The circulating fluidized bed（CFB）power generation technology can effectively utilize coal gangue.We focus on CFB coal gangue and coal co-combustion power generation.Based on data from investigation of Huainan CFB Power Plant and literature,we establish a life cycle analysis model of circulating fluidized bed power generation.The system boundary includes coal mining,coal washing and coal-fired power generation.The functional unit is 1MWh net power generation.The environmental impacts include global warming potential,acidification potential,human potential toxicity potential,solid waste potential and smoke and dust potential.Based on this model,we firstly evaluated the life cycle environmental impacts and energy utilization efficiency of CFB conventional power generation.Then we use the co-combustion scenario with different weight ratios of coal gangue and coal,and propose a suitable co-combustion ratio to reduce environmental impacts and improve energy efficiency simultaneously.Then we use sensitivity analysis to identify the significant impact factors on the environments and energy efficiency of the co-combustion of coal gangue and coal in the circulating fluidized bed.Finally,we put forward measures and suggestions for the CFB power generation technology.The thesis is summarized as follows:（i）The comprehensive environmental impact potential of CFB conventional coal-fired power generation is 0.42,and the environmental impact degree is in order of solid waste potential,global warming potential,acidification potential,smoke potential and human potential toxicity potential,accounting for 75.9%,21.6%,0.9%,0.7%and0.2%of the total impact after weighting.Of all greenhouse gases,CO₂emissions are the largest,up to 989 kg/MWh.Solid waste discharge mainly comes from coal mining and washing stage,up to 129 kg/MWh.Life cycle energy efficiency is 38.1%.The largest energy consumption comes from fuel consumption,which exceeds 99%of the total energy consumption.（ii）The co-combustion scenario of coal gangue and coal shows that the reduction of the weight ratio of coal gangue reduces the environmental impact potential.The environmental impact potential of the pure coal gangue scenario is the highest,0.91.The 60%coal gangue weight ratio scenario is the lowest with 0.44.In all scenarios,solid waste potential and global warming potential are still the main impacts.Life cycle energy efficiency will increase with the reduction of the weight ratio of coal gangue.The pure coal gangue scenario has the lowest energy efficiency of 34.0%.60%coal gangue scenario has the highest energy efficiency of 35.3%.Considering the actual conditions of CFB power plant and the scenario analysis,the recommended fuel is a mixture of coal gangue and coal,with a coal gangue weight ratio of 70%to 80%.（iii）The sensitivity analysis shows that the sensitivity coefficient of the potential value of the environmental impact on the life cycle in the model is the thermal efficiency of the power plant,the emissions of solid waste and the emissions of flue gas;The sensitivity coefficient of life cycle energy efficiency is thermal efficiency of power plant,auxiliary power consumption rate and other energy consumption.The thermal efficiency of the power plant has a significant impact on the environment and energy efficiency.According to the results,this paper puts forward the following suggestions for this technology:in order to reduce greenhouse gas emissions,CO₂emissions should be controlled in the coal-fired power generation stage and CH₄emissions should be controlled in the coal mining stage.In order to reduce the discharge of solid waste,the solid waste from coal mines should be piled up or recycled.To improve the energy efficiency of the life cycle,it is necessary to further optimize the working performance of CFB boiler,update and upgrade the steam turbine generator unit to improve the thermal efficiency of the power plant,and reduce the auxiliary power rate by adjusting the auxiliary equipment.Figure 13;Table 11;Reference 89...