Mathematical Model Of Thermal Economic Analysis Of Power Plant Boiler Low Pressure Economizer System

In nowadays, because of the aging of boilers and other reasons, there are many boilers whose temperature of exhaust gas is very high, we can't use this amount of heat, which cause the waste of energy source. Along with increasing amount used of energy source in our country and energy source is finite, so that's very important to save energy and reduce consumption. In our country, there are so many boilers whose temperature of exhaust gas is very high, so reducing the temperature of exhaust gas is a very important way to solve the problem of saving energy.There are many ways to reduce the temperature of exhaust gas. To sum up, there are three aspects:(1).Optimize .design structure of heating surface in tail flue.(2).Improve the capacity of heat exchange of heat exchanger.(3).Add new heating surface, reduce the temperature of exhaust gas of boiler.These aspects above all can reduce the temperature of exhaust gas, achieve the goal of saving energy and reducing consumption, but all of them have their merits and demerits.In this text, we mainly use the third aspect to reduce the temperature of exhaust gas, the way is to install low pressure economizer in tail flue of boiler. This way has been proved that it's a very effective way to reduce the temperature of exhaust gas and standard coal consumption. In this text, we mainly calculate how these thermal parameters of a thermodynamic system influence economic performance. We can input original parameter, and then calculate the increment of equivalent enthalpy drop of every amount of water and the maximal increment of equivalent enthalpy drop. Calculating how these parameters influence the drop of exhaust gas temperature and without regard to economic performance, only with the goal of reduce exhaust gas temperature. In this text, we separate two cases. One is that outlet parameters of low pressure heater change after being installed low pressure economizer, the other one is that outlet parameters of low pressure heater don't change after that. In these two cases, we calculate economic performance separately. The result indicates that the tendency of economic performance because of the change of any parameter is the same. So if the goal of calculating is to know how parameters influence economic performance without regarding to accuracy, we can calculate outlet parameters of low pressure heater with no change, and reduce the amount of calculation greatly in this way.In the calculation of this text, we can get conclusions below in the aspect of economic performance:(1).With the increase of water flow in low pressure economizer, economic performance first increase and then decrease, so there is an optimum water flow which corresponds a optimum economic performance.(2).Compare economic performances of different entrance of low pressure economizer, if the entrance is at the outlet of low pressure heater ahead, the maximal increment of equivalent enthalpy drop is higher.(3).Compare economic performances of different outlet of low pressure economizer, if the outlet is at the inlet of low pressure heater behind, the maximal increment of equivalent enthalpy drop is higher.(4).With the increase of exhaust gas temperature of boiler and KF, the maximal increment of equivalent enthalpy drop is higher and higher.(5).With the reducing of boiler load, the maximal increment of equivalent enthalpy drop is lower and lower.If only regarding to the amount of exhaust gas temperature drop, we can get conclusions below:(1).With the increase of exhaust gas temperature, the maximal amount of exhaust gas temperature drop becomes higher and higher.(2).With the increase of low pressure economizer inlet water temperature, the maximal amount of exhaust gas temperature drop becomes lower and lower.(3).With the increase of KF, the amount of exhaust gas temperature drop becomes higher and higher.It can guide design and operation of this thermodynamic system which is installed low pressure economizer through comparing the influence of economic performance and exhaust gas temperature drop which is caused by the change of many parameters.