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This paper describes the steps involved in the design, construction, and testing of a gasifier-specific solid oxide fuel cell (SOFC) system. The design choices are based on reported thermodynamic simulation results for the entire gasifier- gas cleanup-SOFC system. The constructed SOFC system is tested and the measured parameters are compared with those given by a system simulation. Furthermore, a detailed exergy analysis is performed to determine the components responsible for poor efficiency. It is concluded that the SOFC system demonstrates reasonable agreement with the simulated results. Furthermore, based on the exergy results, the components causing major irreversible performance losses are identified.

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Despite many research works concerning the decomposition and/or gasification reaction pathways for the biomass constituent compounds and on developing lumped reaction mechanisms for real biomass samples, a complete and detailed reaction network for a real biomass has not been proposed to date. Based on the published literature data, this study aims to develop an integrated decomposition and gasification kinetic model using Aspen Plus software for cellulose, hemicellulose, lignin, and protein model compounds in sub-and supercritical water to model the supercritical water gasification of wet biomass feedstocks regarding the carbon gasification efficiency and gas yields. The model involves 55 reactions in the subcritical region and 74 reactions in the supercritical region. The validation of the model by comparing the experimental results of others has been performed, and the results of the model were found to be in an agreement. The model is capable of predicting reliable results for temperatures up to 650°C, at pressures between 25−30 MPa, and at dry matter concentrations up to 10 wt % in the feedstock. In addition, case studies for microalgae, pig−cow manure mixture, and paper pulp gasification in supercritical water have also been performed.

Nowadays, there is worldwide interest in diversifying energy supply. In this regard, biomass is the best possible renewable organic substitute for fossil fuels. In particular, the energy content of very wet biomass, recovered with appropriate technology, could potentially be used for power generation. In addition to power generation, this technology would represent a sanitary option to improve the quality of public health and the environment. Supercritical water gasification (SCWG) is a technology applied for the conversion of wet biomass into gas. It uses the specific physical properties of water at supercritical conditions to decompose the organic matter. However, near 100% conversion, close to thermodynamic equilibrium, of real biomass into gas is not yet demonstrated. The conversion is higher at dry biomass concentrations below 10 wt.%, but at these conditions, the system is not energetically sustainable. The conversion depends on the SCWG operating conditions and the properties of the catalyst. Because of present-day technical limitations, the conversion efficiency in SCWG is low when fed with real biomass. The net electrical efficiency of a combined system SCWG-solid oxide fuel cell (SOFC), fed with fecal sludge at 15 wt.% dry biomass, reaches between 50 and 70% (thermodynamically calculated values), whereas utilizing an SCWG designed with present-day engineering gives 29-40%. The SOFC fuel utilization influences the system efficiency significantly, as the processed heat available for the heat integration depends on fuel utilization. The extreme operating conditions of an SCWG-based system cause technical limitations toward reaching complete conversion during gasification. An efficient and stable catalyst is not yet available at competitive costs for low-temperature SCWG of real biomass. Intensive research in different gasification-SOFC system configurations that include the integration of complementary processes, such as the electrochemical oxidation of higher hydrocarbons or the electrochemical reduction of CO 2 and H 2 O, will increase the potential of the gasification-SOFC system for commercialization in medium scale in the future and become a technology that provides economic, environmental, and health benefits.