Thermodynamic analysis of biomass and liquefied natural gas complementary CCHP system with liquid air energy storage

Abstract

Biomass gasification, as a green energy, can be integrated with natural gas combined cooling, heating and power system to realize energy cascade utilization and reduce carbon emissions. This paper proposes a biomass gasification and liquefied natural gas complementary system, including biomass gasifier, gas turbine combined cycle, liquid air energy storage, and absorption chiller, to use more biomass efficiently. The system uses a liquid air energy storage system to absorb excess exhaust from the compressor and solves the compressor's surge when using low calorific value gas. This integration can raise mixed burning ratio of gas to 0.9 without modifying GT. The thermodynamic model of the system is established, and the evaluation indicators are proposed. Based on the rated power of a 270 MW gas turbine, the thermodynamic performances of the system under design conditions are simulated by Aspen Plus. The exergy flow diagrams of the three seasons are obtained. When the ambient temperature changes, the exergy destruction of gas turbine changes the most, and its exergy destruction in winter is 8.3% of the rated power lower than in summer. Besides, the heating exergy destruction of syngas reaches 76.8% for preheating feed water. The performances of the system under off-design conditions are discussed. When the mixed burning ratio of syngas and natural gas increases to 0.9, the input power of liquid air energy storage is 92 MW, and the output power is 53 MW. The electric efficiency of the system with liquid air energy storage increases by 5.6% compared to the system without liquid air energy storage. By selecting the design pressure of liquid air energy storage, the exergy efficiency can be increased by 6.5% when the mixed burning ratio is 0.9.