Cold End Parameters Optimization Of1000MW Ultra-Supercritical Unit Wlth Direct Air Cooling System

It is imperative to develop ultra-supercritical unit with direct air cooling system in coal-rich and water scarce regions. Direct air cooling systems reduced the turbine exhaust steam temperature of the last stage by exchanging heat with ambient air directly. But the air cooled condensers is arranged close to the main machine hall outside, so it is influenced easily by external environment in the cooling process. Therefore, cold side operation parameter of direct air cooling system is often in great change, and it has important influence on the safe and stable operation of the direct air cooling unit. It has important practical value to get the best unit operation state by optimizing cold side operation parameter.The main cold-end parameters of air cooling units and the features of air cooling condensers are introduced with the example of1000MW supercritical direct air cooling units in Lingwu power plants in Ningxia province. The relationship between the exhaust steam pressure and the other main parameters is obtained by analyzing the characteristics of alternated working condition of the air cooling condensers, and the safe pressure range of the unit is also determined. It is decided to optimize for initial temperature of condenser due to the two factors of initial investment and operation cost. The function has been set up by years minimum total cost which is the target, and face velocity and initial temperature which are design variables. It is calculated that investment costs of air cold heat dissipation area, costs of air cooler, costs of fan group years power consumption and costs of years coal consumption under the given design temperature. The cooling unit optimal value that is the years minimum total cost is determined by face velocity and initial temperature difference value. And then design variables and electricity prices, coal prices have been analyzed to prove that the choice of design variables is reasonable. Finally it is got that the optimization results have been influenced by the price of electricity changes greatly. The optimization results have practical significance for the operation unit, which can be directly applied to cooling units in operation.