Optiamization Analysis For Thermal System Of The 300MW Turbine Unit Of Qinhuangdao Power Plant

Air is selected as the cooling medium of direct air-cooling unit, the air temperature in summer is higher, which results cooling capacity of the air-cooling unit decreases, and makes vacuum of the unit drops, so the unit is forced to drop load to operate. In this paper, aiming at the existing output delay problem of 1# unit at the Yungang Power Plant during the high temperature period in summer, three types of system improvement projects are proposed to increase the air-cooling unit, increase the ventilation quantity of the air-cooling system and the spraying humidification. By analyzing the technical feasibility, application performance and economy of the three programs, and combining with the actual site, to determine the spraying humidification system as the best rehabilitation program. An optimization of transformation will be done to the main steam pipeline, cooling section and heating section of the reheat heaters, the low pressure bypass system, the shaft seal system, the drainage system and other related systems. Improve the heat pipe and equipment of drainage system and the connection mode will be optimized. Technical measures and advanced mature product will be introduced in to eliminate external leakage points and minimize internal leakage points.Improve the performance of supporting equipment and optimize the cold-end system.Rationally readjusting the performance of supporting equipment and heat recovery systems. According to the optimized equipment and system, complement and perfect the theory about operating strategy and operational measures under various conditions.The thermal and hydraulic calculation results of spraying humidification system show that: when the spraying water volume is 55.52t/h, inlet air temperature of air cooler can be decreased from 34℃to about 30℃during the high temperature period in summer, meanwhile, the unit vacuum can be improved to be over 5kPa, the load capability of unit can be increased by over 10%. Based on the analysis the impact factors of spraying humidification system and the atomization performance, the pressure-type atomizing nozzle is selected, and the spraying humidification system is designed.Numerical simulation shows that atomization performance of the system is good, the industrial test of practical application shows that spraying humidification system reduces the inlet air temperature of air cooler, improves the thermal dissipation efficiency of air cooler and the unit's vacuum.