Characteristics Research Of Boiler Flue Gas Purification System Based On ELCA

In our country, the possession of coal-fired power plants is nearly 90% in thermal power industry. The SO2, NOx, and dusts emission resulted from coal combustion are one kind of main pollution source to the environment which has serious harm to human health. In order to reduce the coal-fired power plant emissions, the SCR denitration technology, the electrostatic dust removal technology and the limestone/gypsum wet desulfuration technology have been widely used.The above pollution control technology will consume a large amount of energy in the process of construction and operation and maybe produce new environmental problems. This paper use exergy life cycle assessment as a method to analysis and evaluate a 600 MW coal-fired boiler flue gas purification system. The lists of material production, material transportation and equipment operation are analyzed, and the pollutant emissions, energy consumption and environmental impact of different processes are calculated. Take one year of power plant’s operation as a functional unit, the greenhouse effect, acidification, eutrophication, photochemical ozone synthesis, toxicity of the human body, smoke and dust on the environmental effect are calculated by the three pollution control technologies, as well as the energy consumption of unit mass pollution removal.This paper compares with the difference between flue gas directly into the atmosphere and different pollution control technologies on the total load of environment impact. Besides, sensitivity analysis of SCR denitration system at different ammonia escape rate and different boiler load; electrostatic precipitator system at different boiler load; alao limestone/gypsum desulphurization system at different boiler load are performed. The results are as follows:Compared to the flue gas directly emitted into the atmosphere, the SCR denitration technology can significantly reduce the environmental impact load of coal fired boiler, nearly 80%. The energy consumption in the operation process of SCR equipment accounts for 41.84% in full life cycle. The total load of the environmental impact in 100% boiler load has increased 22.51% compared to 75% boiler load. Besides, the SCR exergy consumption rate is 14.28 MJ/kg.The quality of dust removed by electrostatic precipitator can be reached 75948.02 t, and the exergy of energy consumption is 31815307.18 MJ, and exergy consumption rate of unit mass pollution removal.is 0.42MJ/kg. After installing the electrostatic precipitator, the environmental impact load can be reduced by 99.89%. Besides, the boiler load which increased from 75% to 100% has little effect on the total environment load.The limestone/gypsum desulphurization system can remove 6696.92 t SO2 per year and the exergy consumption rate is 71.94 MJ/kg. The desulfurization process is the main energy consumption in this process which accounts for 90% in gross caloric value consumption, resulting to more contribution rate of environmental impact. After installing FGD, the acidizing impact load can be reduced by 96.25% and the total environmental impact load can be reduced by 88.76%.