Experimental Study On Combined Wet And Dry Cooling Of Direct Air Cooling Unit

Air cooling unit, especially direct air cooling unit has been widely used in the rich coal and shortage water region because of using little water. With climate temperature got higher and higher, exhaust pressure often goes higher than the design pressure at high temperature in summer.This paper take the 2×600MW direct air cooling unit of Shangan Plant as research object to better analysis the wet and dry cooling system. Firstly, a thermodynamic calculation model of direct air cooling system has been developed. Ambient temperature, face velocity and exhaust steam flow rate influence on condenser pressure were studyed. The results show that, the condenser pressure rises with ambient temperature and exhaust steam flow rate, while reduces with face velocity. Secondly, a thermodynamic model of wet and dry cooling system was established in order to study ambient temperature, face velocity, exhaust steam flow rate and circulating cooling water flow influence on condenser pressure. Direct air cooling system and the wet and dry cooling system at single pump, double pump and non-pump states were tested. The performance of wet and dry cooling system and direct air cooling system are being compared. The results showe that the adoption of wet and dry cooling systems can increase vacuum at least 2~3k Pa, save coal consumption about 2.5~3.75g/(k W·h). Finally, the optimum vacuum at different ambient temperatures was calculated based on variable characteristics of wet and dry cooling system inorder to optimizing the operation of wet and dry cooling system.Research shows that wet and dry cooling can effectively solve the problem of high backpressure of air cooling unit at summer. The results can provide a theoretical reference for optimizing the operation of the wet and dry cooling systems.