Performance and Optimisation of Externally Fired Gas Turbines Fuelled with

Biomass Biomass based fuels are attracting much interest recently due to their plentiful supply and their environmentally friendly characteristics if properly managed. The difficulties of burning low grade fuels such as biomass in gas turbines is that they contain some particulate matter which causes corrosion and erosion problems in the turbine blades; this can be overcome by indirectly firing the gas turbine. The work in this paper has been focused on Externally Fired Gas Turbine (EFGT) cycles fuelled with Bagasse, residue of sugar cane milling process, which is especially abundant in Brazil. In a first part, in order to assess the combined cycle performance, the analysis of the simple gas turbine cycle has been carried out. A sensitivity analysis has permitted the determination of an optimal gas turbine in terms of pressure ratio and turbine inlet temperature. Off-ambient and part load performances are also presented within this work. Then in a second part, the influence on the externally fired combined cycle has been determined, and the cycle optimised at design. The simulations have been carried out with the commercial code GateCycle, and the results compared with a conventional configuration of gas turbine and combined cycle fuelled with natural gas. The EFGT cycle presents some disadvantages in terms of gas turbine performance. However, due to its regenerative aspect, the externally fired cycle offers good steam cycle performance. The externally fired combined cycle (EFCC) promises to be competitive with other cycles, even when fuelled with low heating value fuels.

Magali Roquette, Sandro Barros Ferreira, Anthony J.B. Jackson, Pericles Pilidis