Thermodynamic Analysis of a Cycle Integrating a Solid-Oxide Fuel Cell and Micro Gas Turbine with Biomass Gasification

An integrated solid-oxide fuel cell-micro gas turbine system with biomass gasification is investigated based on energy and exergy. The system consists of a biomass gasification system, a solid-oxide fuel cell (SOFC), a micro gas turbine (MGT), and a heat recovery steam generator (HRSG). Various parameters are determined for the integrated system, including syngas molar fraction, and heat input to the gasifier. Moreover, exergy flows and exergy destruction rates of major components of the system are calculated. The maximum energy and exergy efficiencies of the gasification system are 65.7% and 84.8%, respectively. These values for the SOFC-MGT cycle with biomass gasification are reported as 58.3% and 69.6%. The variations of syngas molar fraction and mass flow rate, gasifier exergy destruction, and CO2 emissions with the steam to carbon (SC) ratio are investigated. The results show that there is an optimum value for the SC ratio at which the syngas mass flow rates and the gasification energy efficiency reach a maximum. The CO2 emission, which is an important factor for the sustainability of the system, increases by 19.4% as the value of the SC ratio increases. Increasing the gasification temperature, from 800 to 1000 °C, reduces the energy and exergy efficiencies of the total integrated system by 7.90%, mainly by increasing the required heat input to the gasifier.