Techno-economic Analysis Of A Lignite-fired Oxy-combustion Power Plant With Integrated Drying

The oxy-fuel combustion technology is a kind of effective methodused in coal-fired power plant to reduce CO2emission. It is now recognized asimportant technology for carbon capture, which can basically achieve zero CO2emission and obtain high concentrations of CO2products. The lignite will play animportant role in primary energy supply in China for its abundant reserve. Its highmoisture content will result in decreasing the combustion efficiency of power stationand increasing CO2emission. The technology used in a lignite-fired oxy-combustionpower plant with integrated drying is an effective method to reduce the carbonemission.The simulation of lignite drying process was carried out with Aspen Plussoftware. The effect on lignite drying characteristics for different drying medium, fluegas temperature and the content of CO2and H2O in the flue gas were performedcomparison and analysis. The results show that, comparing with air and conventionalflue gas, the cost will be reduced in oxy-combustion power plants using the exhaustgas to dry the lignite. The drying temperature is lower and the lignite will be easier tomeet drying requirements for CO2as a main component in the flue gas. Withincreasing the drying requirements, the drying temperature increased. The increasingof dried lignite calorific value and decreasing of the coal consumption cost will bebeneficial to improve the economy of power plant.Through the establishment of a600MW oxy-fuel power plant model, thecombustion system and power generation system were simulated and the effect of airleakage coefficient, circulation ratio and oxygen concentration on the system wereanalyzed respectively. It is showed that, comparing with the conventional aircombustion power plant, the furnace exit temperature of oxy-fuel combustion systemincrease55℃and the steam output increase70t/h. The obviously decreasing for NOXand increasing for SOXin the flue gas will be benefit for pollutant removing. The CO2concentration in the exhaust up to87%will be helpful for CO2capture and reducingcapture costs.The comparative results of energy consumption and power generation cost forthree power systems show that the total energy consumption of a lignite-firedoxy-combustion power plant is slightly lower than a bituminous-fired one because ofits lower oxygen consumption and the oxygen producing energy. The characteristics of lower lignite price and oxygen consumption will be conductive to improve theeconomic benefit of the whole oxy-fuel power plant.