Exergy-based parallel between steam- and combined-cycle power plant configurations burning blast furnace gas

Abstract

This manuscript provides an exergy-based parallel between combined- and steam-cycle power plant configurations burning blast furnace gas (BFG). The combined cycle (CC) was based on a currently operational power plant located in Rio de Janeiro, Brazil. The steam cycle (SC) was created by replacing the gas turbines (GTs) for steam generators (SGs) that handled the same amount of fuel. The results show that the combined cycle achieved 21.25% higher exergy efficiency, although emitting twice as much nitrogen oxide. The combined cycle generated 52.08% less steam while wasting 78.86% less exergy, which indicated that steam generators benefit from a higher amount of excess air. The gas turbine combustion chamber high exergy efficiency indicates that burning low-grade fuels is beneficial for reducing the intrinsic waste of chemical reactions. However, the compression process required prior to combustion undermines this benefit. Ultimately, this manuscript provides a comparison between two options to avail blast furnace gas.