Study on Optimization of Reheat Pressure after Retrofit of Coal-fired Power Plants for Heat Supply

Abstract

After the retrofit of condensing power unit for heat supply, the reheat pressure of the unit deviates from the optimal value. When the heat supply and flow path of the turbine are retrofitted synchronously, or the retrofit of flow path is carried on the units witch heat supply retrofit had been done, the reheat pressure should be redetermined during the design phase of the flow path retrofit and the thermal economy of off-rated load should be taken into account to ensure the best operation efficiency of the unit. Taking 660MW supercritical single reheat unit as an example, the reheat pressure optimization analysis was carried out for the heat supply from the cold end piping of reheat system or the connection pipe between IP and LP in the wide load range. The results show that the optimization of the reheat pressure after the retrofit of heat supply can obtain significant gains of heat rate in the wide load range.