Environmental Impact Research Of Natural Draft Cooling Towers With Flue Gas Injection For Southeast Coastal Power Plant

At present, the flue gas is treated by the wet limestone/gypsum FGD in most coal-fired power plants.The temperature of the flue gas after desulfurization is about 50 ?.The flue gas must be reheated to 80? by gas-gas heater and then discharged into the atmosphere via the chimney to increase the lifting height of the flue gas. Natural Draft Cooling Towers (NDCT) with flue gas injection direct discharge the desulfurization flue gas via the cooling tower.The flue gas discharged by cooling tower has a significant amount of the heat. It can increase the lifting height of the flue gas and reduce the ground concentration of pollutants. The investment of chimney and gas gas heater will be eliminated, the desulfurization system will be simplified and the efficiency of energy utilization will be improved by the use of Natural Draft Cooling Towers with flue gas injection technology.A coal-fired power plant in Zhejiang was taken as an example.The S/P model and the German guidelines were used to calculate the lifting height of flue gas on different conditions. The relationship among the lifting height of flue gas, the atmospheric stability, the ambient wind speed, the outlet velocity of mixed gas, the outlet temperature of mixed gas, the ambient humidity and the ambient temperature was analyzed. The results show that the more unstable the atmospheric condition is, the smaller the ambient wind speed is, the higher the flue gas rise; The lifting height of flue gas which is calculated by fully mixed method is greater than that of the involvement method; The lifting height of cooling tower is better than that of chimney;The greater the mixed gas outlet velocity is, the higher the ambient humidity is, the higher the difference between mixed gas outlet temperature and ambient temperature,the higher the flue gas rise.The ground concentration of pollutants under different conditions in Natural Draft Cooling Towers with flue gas injection scheme and chimney scheme was predicted by the model of atmospheric pollutant dispersion in Austal2000. The analysis results show that there is little difference between the terrain factors and flat factors; When terrain factors are not considered, the influence of involvement method on environment is greater than that of fully mixed method; The contribution of the cooling tower in one technology to the regional air quality is smaller than that of the chimney;Under the same conditions, high winds and high humidity are favorable to the diffusion of pollutants; The higher the difference between mixed gas outlet temperature and ambient temperature is, the higher the maximum hourly ground concentration is; When the froude number is less than 0.35, the ground concentration of pollutants is larger than usual.