Open-cycle Indirectly Fired Gas Turbine for Wet Biomass Fuels

摘要

The Open Cycle Indirectly Fired Gas Turbine (IFGT) allowsa wide range of fuels, solid, liquid or gaseous, to be used. The present study concerns the utilization of biomass fuels. In an IFGT the exhaust from the turbine is used as combustion air. The internal combustion chamber is replaced by a heat exchanger heating the air from the compressor, thus eliminating the flow of flue gas through the turbine. A wood fired IFGT was chosen as reference case. It was found that for this reference, only a low efficiency (below 30% for TIT = 1100°C) may be obtained. The main reasons for this is that the exhaust temperature to the stack is high and that the fuel has a high water content (50% on wet basis). This suggests that the performance could be improved, by adding a fuel dryer driven by the flue gas. This study shows that this does improve the efficiency of the cycle dramatically. However, the flue gas enthalpy still is not fully utilized. This suggests that this system could be used for disposal of still cheaper waste fuels with even higher water content, such as sewer sludge. Calculations show that fuels with a water content of up to 80% may be used. At this point the efficiency on lower heating value basis increases to 50.5%. Equally interesting is, that the efficiency on higher heating value basis is close to 25% for all water contents of the fuel.