| With the development of economy and increased energy using,primary energy gradually reduced and environmental problems increased.In our country,the proportion of thermal power generation is larger,while energy-saving emission reduction putting forward,the power industry began to try to use other renewable energy.In the short term,the power plant would carry out the equipment transformation.The optimization of the cold end system has attracted more and more attention,and the condenser vacuum system is one of the cold end systems.When the external environment temperature is high,the performance of the air ejector decreased,which leads to the increase of steam turbine exhaust pressure and the consumption of coal.The condenser vacuum system optimization is to solve this problem,to save coal consumption and to increase power generation.This paper introduces the classification,structure and working principle of condenser and air extractor respectively.Condenser pressure factors are cooling water inlet temperature,temperature rise,condenser end difference and the performance of the vacuum system.Under the good condition of the ejector performance,with the lower the inlet water temperature,the smaller the temperature rise,the smaller terminal difference within condenser,the condenser vacuum is higher.Considering the problem of circulating water pump power,so the condenser vacuum is not as high as possible,there is an optimal vacuum value.There are three kinds of air ejector,steam jet ejector,water jet ejector and water-ring pump.The water-ring pump has the best performance among them.Because of its working fluid-water,when the internal pressure below its ultimate pressure,the water ring pump will produce cavitation phenomenon,this paper put forward preventive measures on this phenomenon.The presence of air in the condenser can hinder the heat transfer of the steam,increase the heat transfer end difference,reduce the condenser vacuum,but also make the condensate water subcooled.It needs the exhaust to extract the air in time,so as not to accumulate air.In this paper,the amount of air leakage is calculated.The variable condition and the characteristics and regularity of water ring vacuum pump were is analyzed by using EES to simulate vacuum system.The following conclusions are that:The suction capacity of the vacuum pump decreases with the temperature of the working fluid.With the increase of the suction pressure,the effect of the working water temperature on the water ring pump is weakened.In a certain range with the suction pressure increasing,the suction flow increases.More than the critical pressure,the suction flow is reduced.The higher the inspiratory temperature,the worse the suction performance.Factly,the greatest impact on the performance of the water ring pump is the working fluid temperature.So,in the summer case,when the vacuum pump working fluid temperature exceeds a certain value,the vacuum pump output will be significantly reduced,resulting in condenser vacuum smaller,affecting the safety of the unit operation.This paper analyzes the condenser pressure corresponding to the temperature of different working fluid under different load of the unit,and makes the user interface.Two methods of evaluating back pressure change on unit efficiency is introduced,steam turbine final stage calculation and equivalent enthalpy drop method.To improve the performance of the condenser in summer and improve the safety and efficiency of the whole generating unit,the vacuum of the condenser can be improved by adding air-conditioning chilled water in the system.The data is acquired in the 600MW units of Shandong power plant,to establish the relationship between income and investment.The program can improve the vacuum about 0.6kpa,resulting in a total benefit of 1.85 million,recovering the cost one year.This article presents a new type of vacuum system,that chilled water directly into the water ring pump for sealing fluid.Comparing with the previous transformation system,it reduces the loss of the pipeline,and the vacuum can be increased by about 0.8kpa,resulting in considerable economic benefits. |
