The Research Of Auxiliary Cooling Evaporative Condenser Used In The Direct Air Cooling System Of Power Plant

Rich in coal resources in northwest China, but the lack of water resources, direct air cooling system in power plant has been widely used because of its water saving characteristic.By means of several plants of the actual monitoring found that direct air cooling system in power plant is not perfect, the high temperature in summer time and dirt on the surface of heat exchanger and the wind, the cooling efficiency reduce is widespread, the unit back pressure rise and load reduce, affect the safe operation of power plants, and bring huge economic loss.Aiming at the existing problem of direct air cooling system in power plant,Direct air cooling system of a certain power plant in Ning Xia with evaporative condenser auxiliary condensing steam turbine steam exhaust, 16 sets of evaporative condenser were set up, the shunt 320 t/h steam exhaust. Evaporative condenser,relying on the latent heat of vaporization of water take away heat, its ability to remove heat is nearly 2500 times than air-cooled, nearly 1/600 of water cooled. Through the system test, found that the condition of evaporative condenser is suitable for open as follows: the environment temperature is higher than 25 ℃, the unit running at full capacity, at this point should try to reduce the frequency of the direct air cooling system fan. The whole system in the environmental wet bulb temperature of 15 ℃,the back pressure value up to 20 k Pa, and design value of environmental wet temperature of 21 ℃, back pressure value of 18 k Pa, actual operation does not meet the design conditions. key Parameters of evaporative condenser were tested,evaporative condenser air volume and drench water volume is small, right against the face wind speed is larger, leading to the condensation efficiency reduce, condensing coil pipe arrangement in the form of lower also affect the cooling efficiency.Evaporative condenser is mainly affected by the environment air wet-bulb temperature, condensation efficiency is limited, and the direct air cooling system,every 1 k Pa, below the back pressure can save 1 g/k W.h power supply coal consumption, so it is necessary to transform of evaporative condenser.Dry climate in northwest China, very suitable for economic and environmental protection of evaporative cooling, so put forward a type of compound evaporativecondenser consists of indirect evaporative cooler, direct evaporative cooler and the cooling coil. By indirect evaporative cooler to reduce the ambient air wet bulb temperature, fill direct evaporative arrangement between the cooling coil, increase the heat exchange of air, water and coil, thus improve the cooling efficiency.Lie on tubular indirect evaporative cooler, the different length of vertical tube type indirect evaporative cooler of the actual test, found the vertical tube type indirect evaporative cooler’s cooling efficiency is better than lie tubular, 1.7 m long vertical tube type indirect evaporative cooler’s cooling efficiency with 1.4 m long tubular indirect evaporative cooler are basically same, but when handling the same airflow length is 1.7 m of vertical tube type indirect evaporative cooler is more energy-saving.Considering the factors of the energy consumption, investment and operation covers,Compound evaporative condenser select length of 1.7 m vertical tube type indirect evaporative cooler, in order to enhance heat transfer effect, Using finned tube heat exchange tube.Through theoretical analysis of heat and mass and actual testing experience of evaporative condenser, design and calculate the vertical tube type indirect eavporative cooler, direct eavporative cooler and cooling coil, Finished Parts structure design unit.Compound evaporative condenser condensing steam exhaust quantity is 1 t/h, steam exhaust temperature is 65 ℃, condensing temperature of 40 ℃.According to the practical operation of a certain power plant in Ning Xia, Direct air cooling system uses compound evaporative condenser auxiliary condensing steam turbine steam exhaust, condensing steam exhaust quantity also is 320 t/h. Discovered by theoretical analysis In environmental wet bulb temperature of 22 ℃, the unit back pressure reached 21 k Pa, Direct air cooling system using evaporative condenser auxiliary, environment of wet bulb temperature of 15 ℃, the unit back to 20 k Pa pressure drop. Proving the condensation efficiency of compound evaporative condenser is higher than the evaporative condenser. The use of compound evaporative condenser, Power plants can be obtained income is 10.538 million yuan in a year, at the same time reduce 2043 tons of coal cinder emissions, reduce soot emissions by557.1 tons, reduce sulfur dioxide emissions 16.7 tons, reduce nitrogen oxide emissions by 42.5 tons, greatly reduce the im Pact on the surrounding environment,bring huge social benefits.