Evaluation of supply boiler repowering of an existing natural gas-fired steam power plant

Using supply boiler to repower existing steam power plants (also known as parallel repowering) is one of the awesome repowering methods for almost all types of steam power plants. In this way, the capacity of the gas turbine and heat recovery steam generator (HRSG) can be designed in different ranges. Choosing the best number of HRSG pressure levels and the appropriate way to integrate the generated steam in the HRSG with the existing cycle are important steps during the cycle design. In this paper, we analyse the effects of HRSG pressure levels on the performance of existing boiler and turbines for Montazeri Steam Power Plant in Iran. To do this, we present three separate HRSG configurations and a multi-parameter analysis is provided. For each case, the effects on existing boiler, steam turbines and the condenser are examined. The results show that using HRSG with higher pressure levels (2 or 3) are caused an imbalance in mass flow rate of steam in steam turbines and different parts of the existing boiler. Therefore, using a single-pressure level HRSG with a reheat is recommended for this aim. If we use one HRSG and a gas turbine model Mitsubishi-701G2, net energy and exergy efficiencies and produced power will increases %52.19, %50.9 and 485.8 MW, respectively.