Gasification and Fuel Cell Integration With Bottoming Turbine Cycle: Performances of a Hybrid Plant for Electricity Production

The increasing need of energy resources along with the growing environmental interest promote the creation of new concepts in the field of energy production and management strategies. The development of high temperature fuel cells, suitable for stationary energy production, is one of the most promising aspects, able to bring a significant change in the power generation scenario. One of the most important features for fuel cells is the potential coupling with advanced gasification systems, thus enabling the possibility of energy recovery from waste, RDF (Refuse Derived Fuel) and biomass. The gasification process transfers the energetic value of the original solid fuel to a gaseous product rich in hydrogen, carbon monoxide and dioxide, and other compounds. A post-gasification treatment removes tars, particulates, impurities and makes the gas suitable for power production in a fuel cell unit. In this work an example of an innovative plant for biomass utilization has been considered. The plant includes a gasification section and a Molten Carbonate Fuel Cell unit, coupled with a hot gas cleanup system. For gasification technology, a recent typology was considered involving an indirect heating system such as the Battelle process. Gaseous streams conveyed to the cell after the conditioning processes were considered. In order to achieve higher efficiencies, a bottoming cycle has been added. It comprises a turbine power plant integrated with the gasification and fuel cell lay-out. In the turbine cycle air is compressed in the operating pressure and internally heated by the waste heat of the fuel cell and of the gasification process. The expanded air is then used in the combustion reactor of the gasification system. The proposed plant allows high electric efficiency and high flexibility in choosing for air compression ratio and unit size; sensitivity analyses were performed.