| With the expansion of direct air cooling unit application,the relative technology is also improving,but there are still some problems,such as too high back pressure and obvious environmental impact.On the other hand,the system is huge and the pipes are complicate to cause a serious problem which is air leak of the vacuum system.And the air leak is unpredictable and difficult to detect,which will adversely affect the safety and economy of the unit.In this paper,the 2×350MW supercritical direct air cooling unit is studied.The air leakage reasons of the vacuum system are analyzed,and the air leakage diagnosis model is established to study the distribution rules of the air leakage and the influences on the performance parameters of the cold end.On this basis,the performance optimization models of air cooling unit are established,and the optimization analysis of the unit is carried out to find the optimal back pressure and cold end operation parameters,which provides a basis for determining the reasonable operation mode of the unit under variable conditions.Besides,the influence of different air leakage conditions on the optimization parameters of cold end are analyzed,as well as the influence rules of air leakage on coal consumption and power generation before and after optimization.The results of the study show that: The dimensionless factor—air coefficient F can indirectly reflect the air leakage of the system,which can provide basis for on-line monitoring of air leakage in power plants.Variable condition optimization models are suitable for conditions both with air leakage and without air leakage.With the increase of air leakage,the back pressure of system increased,the coal consumption increased,but the power generation power decreased before and after optimization.The research results in this paper can provide guidance for the prevention,diagnosis and operation optimization of the air leakage of the direct air cooling unit. |
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