Thermodynamic analysis of the supercritical water gasification of biomass

Thermodynamic equilibrium modeling is important in order to understand which are the expected yields and the energy needs of the supercritical water gasification (SCWG) process. A thermodynamic equilibrium model allows calculating which is the system composition at equilibrium. Equilibrium composition can allow calculating, with good approximation, the overall process yields, especially when high temperatures and/or catalysts are used. In this Chapter, the current state of the art in the field of thermodynamic equilibrium modeling of SCWG is reviewed. The most common modeling approaches are presented, highlighting their advantages and disadvantages. Then, the practical implementation of a non-stoichiometric thermodynamic equilibrium model, based on Gibbs energy minimization, is performed. Finally, it is shown how thermodynamic modeling can be used to build a process model for SCWG, which is a fundamental tool to evaluate the process energy sustainability and its practical feasibility.