Simulation and optimization of a combined cycle power plant with low heating value fuel gas

Abstract

Combined cycle power plant (CCPP) usually plays an important role in balancing byproduct gas generation and consumption in integrated iron and steel plant. The low heat value fuel gases, such as blast furnace gas (BFG) or mixed gas with Coke oven gas (COG) and BFG, are preferred to be used in high-efficient CCPP for power generation. In practice, the general heat value of mixed gas can be set in the range of 3500–4400[Formula: see text]kJ/Nm3. This paper presents a methodology to simulate operating parameters of CCPP with BFG. A generic model of gas turbine with open loop stage cooling employing air is used to simulate the performance of gas turbines cycle under different compressor pressure ratios and turbine inlet temperatures (TIT). The isentropic efficiencies for gas compressor and gas turbine are supposed to be constants and set corresponding to published industrial experience. The steam cycle is composed of classical double-pressure heat recovery steam generator (HRSG) and steam turbines according to gas turbine outlet temperature. Specific work, gas turbine cycle efficiency, cogeneration thermal efficiency and coolant air flow requirements are evaluated to find the optimal compressor pressure ratio and TIT. The research results are useful to select the optimum operating parameters of CCPP with BFG. Performance features were estimated with the help of compression ratios 12.5–20 and combustor exit temperature 1150–1350[Formula: see text]C.