Thermodynamic Analysis Of Circulating Fluidized Bed Power Generation System With Oxy-Fuel Combustion Of Low Heating Value Waste

Clean,efficient and low calorific value coal utilization is a major strategic demand for sustainable energy development in China.With the increase of high ash coal mining and coal washing,the accumulated coal gangue piles up over the years,and the harmful gas produced by its spontaneous combustion brings a series of problems.Resourcezation of low calorific value waste,like coal gangue,waste coal and coal washery reject in a low-carbon and economic way can preventing environmental pollution,carbon emission and wasting of resources.In this paper,a low heating value waste oxy-fuel combustion circulating fluidized bed power generation system using coal gangue as fuel is designed and studied.The sensitive analysis are performed to present the possibility of the proposed system scheme.The thermodynamic analysis of the design system is carried out by using Ebsilon simulation software.The system flowchart relating the steam heating surface design and selection of the extraction position of the circulating flue gas are performed.Key parameters including circulating air volume,exhaust gas temperature,combustion pressure and O2 concentration are analyzed and optimized by thermodynamic simulation.The optimized net power generation efficiency with the subcritical parameters is 29.67%.Based on the low calorific value coal oxy fuel combustion circulating fluidized bed power generation system,a hot air power cycle with ventilation of mine as fuel and its coupling are designed.Two coupling modes are proposed,and the energy consumption analysis and sensitivity analysis are made for the two coupling systems.The economic analysis shows that the net efficiency of supercritical parameters is 1.58 percentage points higher than that of critical parameters,and the generation cost of supercritical parameters is 2.93%lower than that of critical parameters.The results show that the supercritical circulating fluidized bed power generation system is suitable for low calorific value coal power generation.In the economic evaluation of CO2 capture,the power generation costs of oxy-fuel combustion circulating fluidized bed power generation system and coupled system under subcritical and supercritical parameters are calculated respectively.The results show that the economic cost of supercritical is lower,and the power generation costs of coupled system and single power generation system are not significantly different.The comprehensive evaluation of CO2 capture is preliminarily summarized from three aspects of thermodynamic evaluation index,economic evaluation index and emission intensity,and the comprehensive evaluation index system of CO2 capture is constructed.The comprehensive evaluation results of oxy-fuel combustion circulating fluidized bed power generation system are summarized in the CO2 emission reduction evaluation table.In this paper,through the design of low calorific value coal oxy-fuel combustion system,and its sensitivity,economic analysis,the resource utilization of coal gangue and oxy-fuel combustion technology are preliminarily explored,which has a certain reference significance for the development and application of related technologies.