The objective of this work is to evaluate thermodynamic and economic performance of a small-scale combined cycle plant with microturbine and ORC. The primary source of fuel for the plant is wood. The biomass is converted into a gaseous fuel by means of gasification in a downdraft fixed bed reactor. Size of the plant is limited to 350 kg/h of wet biomass input into the gasifier. Two alternative configurations of the bottoming ORC cycle are taken into account: single stage cycle and cascade cycle. In the first case R123 and n-pentane are analyzed as potential working fluids. In the cascade cycle toluene and n-pentane are selected for top and bottom cycle respectively. Electricity generation efficiency of the proposed small-scale plant is at the level of 23%, that is comparable with direct combustion based systems of much higher electric output. An initial economic evaluation of a sample project gives an outlook on economic effectiveness, that nowadays is strongly dependent on stimulation measures for “green” electricity generation.
Utilizing Downdraft Fixed Bed Reactor for Thermal Upgrading of Sewage Sludge as Fuel by Torrefaction
