Optimal process design for the polygeneration of SNG, power and heat by hydrothermal gasification of waste biomass: Thermo-economic process modelling and integration

This paper presents a process model for the polygeneration of Synthetic Natural Gas (SNG), power and heat by catalytic hydrothermal gasification of biomass and biomass wastes in supercritical water. Following a systematic process design methodology, thermodynamic property models and thermo-economic process models for hydrolysis, salt separation, gasification and the separation of CH4, CO2, H-2 and H2O at high pressure are developed and validated with experimental data. Different strategies for an integrated separation of the crude product, heat supply and energy recovery are elaborated and assembled in a general superstructure. The influence of the process design on the performance is discussed for some representative scenarios that highlight the key aspects of the design. Based on this work, a thermo-economic optimisation will allow for determining the most promising options for the polygeneration of fuel and power depending on the available technology, catalyst lifetime, substrate type and plant scale.