Supercritical water gasification of biomass for H2 production: Process design

The supercritical water gasification (SCWG) of biomass for H-2 production is analyzed in terms of process development and energetic self-sustainability. The conceptual design of a plant is proposed and the SCWG process involving several substrates (glycerol, microalgae. sewage sludge, grape marc, phenol) is simulated by means of AspenPlus (TM). The influence of various parameters - biomass concentration and typology, reaction pressure and temperature - is analyzed. The process accounts for the possibility of exploiting the mechanical energy of compressed syngas (later burned to sustain the SCWG reaction) through expansion in turbines, while purified H-2 is fed to fuel cells. Results show that the SCWG reaction can be energetically self-sustained if minimum feed biomass concentrations of 15-25% are adopted. Interestingly, the H-2 yields are found to be maximal at similar feed concentrations. Finally, an energy balance is performed showing that the whole process could provide a net power of about 150 kW(e)/(1000 kg(feed)/h). (C) 2012 Elsevier Ltd. All rights reserved.