Process simulation and energetic analysis of different supercritical water gasification systems for the valorisation of biomass

The energetic efficiency for the supercritical gasification of biomass is studied for three cases: hydrogen and methane production, heat and electricity cogeneration. Experimental results from the gasification of glucose are used to represent the gasifier. The other unit operations are simulated using the software ProsimPlus through thermodynamic equilibrium calculations. Simulations are conducted at different pressure, temperature and initial biomass concentration. The energetic and exergetic yields are calculated, as well as the minimum heat requirement estimated from a pinch analysis. All the results are then exploited to determine optimal conditions for two systems: adiabatic and isothermal. The optimal temperature ranges from 584 to 626 degrees C, whereas the optimal initial concentration ranges from 51 to 87 gL(-1). The system giving the best result in term of global energetic optimisation is methane production in isothermal conditions, followed by methane production in adiabatic conditions. The optimal energy efficiencies are 94% and 91% respectively.