Indirectly biomass fired gas turbine

The IFGT cycle uses clean air as working fluid and is based on small turbo-equipment with inherently long service intervals and high reliability. The aim was to develop a cost-effective system with an overall electric efficiency of more than 20 %. Most components for the proposed system were available but required some modification and development work. However, there was especially a need for development of a combustion system that could reduce the potential fouling of the heat exchanger (HEX); a higher temperature HEX and the hot parts of available turbocharger components. Laboratory test were carried out on high temperature HEX materials. A rather cheap materials SS-310 shower promising. However additional tests over a prolonger period will have to be carried out to investigate the corrosion behaviour in more details. A Two Stage Combustion furnace was chosen after promising experiments. A dynamic model was also developed to simulate different operational cases including emergency trips. Different cycles including the Humid Air Turbine (HAT) cycle were evaluated. Due to simplicity and reliability the simple cycle was chosen. With this cycle 20% electric efficiency can be obtained at investment costs at 2850 ECU/kWel. (21.000 DKK/kWel). Four application studies were conducted. The most promising cycle is a small scale sewage sludge based cycle, mainly due to lower tax on sewage sludge for power production. A demonstration programme will be needed in order to demonstrate the viability under different conditions