Performance evaluation of small size externally fired gas turbine (EFGT) power plants integrated with direct biomass dryers

This paper concerns a performance evaluation of a small scale (about 100 kWe), externally fired gas turbine (EFGT) fuelled by residual biomass and integrated with a biomass dryer. In biomass fuelled EFGT power plants, compressed air is heated in the high temperature heat exchanger by using the hot gases produced by the biomass combustion process. The hot air expands in the turbine and then feeds the biomass furnace. The exhaust waste heat is recovered by drying the raw biomass in a rotary dryer and, in case, in a low temperature heat exchanger for hot water production. In the paper, a parametric analysis of EFGT performance has been carried in order to evaluate the influence of the most important operating parameters, as the pressure ratio, the turbine inlet temperature, the temperature difference in the heat exchanger and the biomass moisture content. In particular, the use of dry biomass allows efficiency values of about 22–33% to be obtained, depending on the turbine inlet temperature here assumed for the different EFGT configurations. Moreover, since the rotary dryer is able to dry more biomass (about 3.5–4.0 times) than they need, the integration of the EFGT power plant with the biomass dryer allows a very flexible operation to be achieved, particularly in the presence of a seasonal heat power demand and/or other external biomass uses