Pressure energy recovery of LNG integrated with multi-stage feedwater fuel preheaters in a combined cycle power plant

Abstract

Liquefied natural gas and combined cycle power plants have emerged as solutions to the intermittency of renewable energy sources, but they require innovative approaches for efficiency improvement. This study proposes a novel pressure recovery system, integrated with multi-stage feedwater fuel preheaters, to improve the efficiency of combined cycle power plants connected to natural gas supply stations. The research demonstrates that preheating the fuel to 350 °C reduces fuel consumption by 2.06% while maintaining the gas turbine inlet temperature. Additionally, heating the fuel gas to 210 °C using feedwater, then expanding it to 30 bar in the turbine, leads to a 193% increase in pressure recovery net power output compared to using seawater alone. By combining these two effects, the proposed system improves the overall efficiency of the combined cycle power plant by 1.08%p compared to the basic system without fuel preheating and pressure recovery. Furthermore, implementing pressure recovery and fuel preheating concurrently, rather than sequentially, increases the efficiency by an additional 0.163%p. These findings highlight the potential for this innovative system to maximize the efficiency of combined cycle power plants, and pave the way for further exploration of new approaches to enhance the performance of liquefied natural gas power plants.