Energy analysis and techno-economic assessment of a co-gasification of woody biomass and animal manure, solid oxide fuel cells and micro gas turbine hybrid system

Abstract

Co-gasification of woody biomass and animal manure is an effective technology to utilize animal manure. In this work, the thermodynamic and economic analysis of an integration of co-gasification of woody biomass and animal manure with solid oxide fuel cell (SOFC) and micro gas turbine is carried out. The overall thermodynamic performance of this combined heat and power (CHP) system is investigated by a mathematics model consisting of simple zero-dimensional model of SOFC and one-dimensional model of downdraft biomass gasifier. The net present value (NPV) method is adopted to investigate the economic feasible of the CHP system.The gasifier model includes two parts. The pyrolysis-oxidation zone includes pyrolysis zone and combustion zone, and a lumped capacitance method and chemical equilibrium are used to simulate the species in pyrolysis-oxidation zone, while one-dimensional kinetic model is adopted to analyze the performance of reduction zone, which considering geometrical dimensions of downdraft gasifier and actual char conversion process.Effects of three operating parameters such as air flow rate in gasifier, moisture content of blended fuel and mass fraction of woody biomass in blended fuel on overall performance of CHP system are evaluated. The results show that decreased mass fraction of animal manure and increased mass flow rate of gasification air have positive effect on conversion of char owing to higher reaction temperature. Entire conversion of char in gasifier and electrical efficiency of the CHP power system above 45% can be achieved on the condition that mass fraction of animal manure is less than 0.4, moisture content is less than 0.4 and mass flow rate of gasification air is more than 47 kg h−1 as the total mass flow rate of blended fuel equal to 28 kg h−1.Economic analysis shows that more woody biomass rather than animal mature in blend fuel is more economically attractive despite of the low cost of animal mature. The particular high initial capital investment of SOFC is the main part of the whole CHP system. In this work, the payback time is less than eight years. If the target cost less than 3000 €/kW for SOFC in a future year will be reached and the optimized operating parameter is adopted, the investment of a co-gasification of woody biomass and animal manure, SOFC and MGT hybrid system will be more competitive for the user.