The externally-fired gas-turbine (EFGT-Cycle) for decentralized use of biomass

The externally-fired gas turbine unites two advantages. On the one hand, the utilisation of the waste heat from the turbine in a recuperative process and, on the other, the possibility of burning “dirty” fuel. In particular, the EFGT opens a new option to utilise biomass for combined-heat-and-power and contributes to reduce greenhouse-gas emissions. A micro-gas turbine with 100 kW electric-output is chosen as an example to study the effects of temperature difference and pressure loss in the gas-to-air heat exchanger on cycle efficiency and power. The simulation calculations are performed with the code AspenPlus. In addition to cycle optimisation, the effect of low-calorific biogas on the combustion air ratio and the possibility of solar energy as a heat source for the EFGT are studied. For combusting biomass in an EFGT-Cycle, two alternatives are possible: First, a special, well-designed combustor for solid biomass, with a cyclone to reduce particles in the exhaust gas. Secondly, a gasifier with gas cleaning and a standard gas-burner. Waste heat from the process can be used for the gasification process, especially for drying and preheating the biomass. The detailed results are presented in the [Kautz M. Auslegung von extern gefeuerten Gasturbinen für dezentrale Energieanlagen im kleinen Leistungsbereich. Dissertation, Universität Rostock, Fakultät für Maschinenbau und Schiffstechnik; 4.11.2005.].