| Greenhouse gas leads to global warming. About half of CO2emission comes from coal fired plants. Therefore, it is great urgency to control CO2emission from coal-fired power plant. However, capturing CO2from coal-fired power plant will leads to huge energy consumption and investment increase, which is the biggest problem for commercial applications. Thermoeconomic and thermodynamic analyses that evaluate coal fired power plant with CO2capture is the basis of the further technical and economic optimization. There is little research about this topic, although it has important significance in the reality.Two different kinds of CO2capture process, post capture and oxy-fuel technology based on a Chinese typical600MW power plant, were simulated and analyzed in this thesis. Mass and energy balance were calculated. Main energy consumption and detail thermodynamic parameters were obtained. The results showed that the reboiler duty of the regenerator is the biggest energy consumption in the post capture coal fired power plant. The low quality steam could be extracted for this duty to reduce the energy consumption. The air seperation unit takes up18%of the oxy-fuel power plant energy consumption increment. The energy consumption with CO2compress unit was huge whether in post or oxy-fuel coal fired power plant, and the temperature of the exit gas from each stage of the multi-compress system could reach to about120℃. The net efficiency of the oxy-fuel system was higher than the post capture system, but the net efficiency of both above systems were lower than the efficiency of conventional coal fired power plant.Exergy analysis and assessment of the conventional, post and oxy coal fired power plant were carried out based on the second law of thermodynamic. The exergy destruction, exergy efficiency and the situation of the energy utilization were analyzed. The exergy efficiency of the post capture power plant is35.59%, and which of the oxy-fuel power plant is37.75%. All boiler units had the biggest exergy destructions in the conventional, post capture and oxy-fuel coal fired power plant. The steam extracted position would affect the net output, so the low pressure expansion and the heat of the multi-compress intercooler should be considered. to integrate with the water-steam cycle.The termoeconomics of the conventional, post capture and oxy power plant were calculated and analyzed using the matrix model thermoeconomic tool. The forming process of the power generation cost(COE) and the thermoeconomics of the units with this three power plants were obtained. The COE of the conventional coal fired power plant was0.28Y/KWh, which of the post capture power plant was0.53￥/KWh, and the oxy-fuel was0.40￥/KWh. The cost of the CO2reduction could be accurately calculated by the matrix model thermoecnomic the for the power plant. The difference of the "fuel" and "product" in the condenser was the biggest in this three systems, but its exergy destructions were small because of its low fuel exergy. The exergoeconomic parameter of the boier unit in three power plants were all very low, so it should be considered in the optimization. There is huge potential for energy saving because the difference of the "fuel" and "product" in the air seperation unit was also very large.Reducing the energy penalty burdened by integrating the multi-compress unit to the post capture and oxy-fuel power plant was investigated via pinch analysis. The modifications of the heat networks were proposed.42.55%heat energy and70.15%cool energy were saved in the post capture coal fired power plant through pinch analysis.58.15%heat energy and88.93%cool energy were saved for the oxy-fuel coal fired power plant using the same analysis method. The net output of both post and oxy-fuel power plant increased about10.8MW. The net efficiency had been increased by0.78%. |
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