Performance Analysis And Optimization Of 600MW Unit Dry And Wet Combined Cooling System

The problem of uneven distribution of resources severely restricts the development of parts of China.In the “rich coal-poor” area,the power plant uses a direct air-cooling system to solve the problem of water shortage,but with the extension of the running time of the unit,the summer running back pressure is increasing year by year,and the economy and safety are declining.To this end,the power plant uses a dry and wet combined cooling system to transform,by increasing the wet and cold subsystem,which can effectively reduce the unit back pressure and improve efficiency.In this paper,a 600 MW unit is taken as an example to establish a mathematical model of the combined wet and dry cooling system,and the performance of the system is analyzed.The details are as follows:When the exhaust steam load is increased from 70% to 100%,the condenser pressure of the wet and dry combined cooling system is increased from 8.5 kPa to 11.2 kPa,and the direct air cooling system condenser pressure is increased from 9 kPa to 13.76 kPa.When the amount of cooling water increased from 4000 t/h to 12,000 t/h,the condenser pressure of the wet and dry combined cooling system decreased from 12.1 kPa to 11.2 kPa.The ambient temperature rose from 17 ° C to 35 ° C,the back pressure of the dry and wet combined cooling system increased from 11.2 kPa to 21 kPa,and the back pressure of the direct air cooling system increased from 13.5 kPa to 31.7 kPa.In high temperature summer,when the ambient temperature rises to 35 ° C,the back pressure of the dry and wet combined cooling system is 10.7 kPa lower than the direct air cooling system.After the transformation of the dry and wet combined cooling system,the annual coal consumption is 11659.5 tons.These fully demonstrate that the dry and wet combined cooling system retrofit can improve the safety and economy of the unit.In winter,the ambient temperature is low and the wet and cold subsystem is idle.In order to meet the local heating demand,this paper proposes a high back pressure heating retrofit scheme.Based on the air-cooling subsystem and the wet-cooling subsystem,the mathematical model of the high back pressure heating system is established.The performance of the variable working condition is analyzed and compared with the adjustment of the extraction heating system.The feasibility and economy of the transformation are proved..Compared with the adjustable extraction heating system,the high back pressure heating system has better energy saving effect when environmental temperature is higher.When the amount of hot water supply is less than 11226t/h,the effect of adjusting the steam extraction is good;when the amount of hot water supply is more than 11226t/h,the high back pressure heating effect is good,and the more heat is supplied,the advantage of high back pressure is the more obvious.