Optimal Operation Analysis On 600MW Combined Dry And Wet Cooling Unit Cool End

Air-cooled units,especially direct air-cooled units,are widely used in the three north areas of China's rich coal and water shortage due to their remarkable water-saving characteristics.However,the air-cooling unit in the high temperature and high load period in summer is much higher than the design pressure,the exhaust steam temperature is high,the condensate temperature is high,the safe operation reliability of the unit is poor,and the economy is much lower than the wet cooling unit.With the gradual improvement of national energy conservation and emission reduction policies,many air-cooled units have undergone a peak system transformation,and the addition of wet condensers is one of the main methods.After the air-cooling unit is added with a wet condenser,the steam exhaust of the steam turbine will be condensed in the air condenser and the wet condenser respectively,and the steam condensation process is more complicated.The air-cooling fan,the circulating water pump and the cooling tower have their own operating characteristics.Dry-wet combined cooling is a new steam turbine exhaust cooling method in recent years.There are few studies on the optimization of its operation mode at home and abroad.In this paper,the 2×600MW direct air cooling unit of Hebei Jiantou Shahe Power Plant is taken as the research object,and the optimal operation mode of the combined wet and dry cooling system is analyzed.Firstly,the thermal calculation model of the direct air cooling system and the peak wet cooling system is established respectively,and the influences of the parameters such as unit load,ambient temperature,air cooling fan output,circulating water pump output and cooling tower working conditions on the condenser back pressure are analyzed,and the values are determined.Relationship,analyze the impact of various factors on the economics of unit operation.The analysis shows that after the addition of the peak condenser,the cooling capacity of the steam exhaust of the steam turbine is enhanced,and the safety and economic efficiency of the unit are significantly improved.Based on the operation of the air-cooled wet-cold parallel system,the cooling efficiency of the unit equipment of the dry-wet combined cooling system is analyzed.The results show that the summer working condition and the peak cooling system work more efficiently than the air-cooling system,and the peak cooling system should be kept running.It not only increases the cooling capacity of the cold end,but also ensures the full capacity of the unit,and also saves electricity and reduces coal consumption.In the spring and autumn,the air cooling system and the peak cooling system can be deployed to keep the cold end of the unit in optimal operating conditions.In winter,the ambient temperature is low,the unit load is low,and the heat exchange capacity of the air-cooling system is greatly improved.The cooling capacity is significantly better than that of the wet cooling system under the same power consumption,and the peak cooling system should be exited.The air cooling,peak cooling alone and its joint operation characteristics test in different seasons and different unit load conditions verify that the analysis results are accurate and effective.According to the analysis results,the theoretical back pressure during the operation of the peak cooling system is modified,and the peak system is further optimized and modified.The cold-end automatic optimization system of the steam turbine is designed,which is operated with the unit design back pressure curve or the operating personnel.Compared with the experience adjustment method,the system can analyze the external parameters such as ambient temperature and unit load in real time,and automatically optimize the cold end operation mode of the unit through the DCS system configuration function,which effectively improves the economic and safety of the unit.