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The gas released from the hp is rich in hydrogen

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Unformatted text preview: 100°C) from which the liquid phase is further transferred to a low-pressure (LP) gas liquid separator (P = 1 atm, T = 20°C). The gas released from the HP is rich in hydrogen, while the LP separator produces a CO2-rich gas. H 2 -rich gas Heat Exchanger CO2-rich fuel gas Feed Pump Water & Minerals Fig. 1 Simplified scheme of the PDU at Twente University (the Netherlands) for biomass gasification in supercritical water[9]. Figure 2 shows that, according to thermodynamics, there is a strong shift from methane towards hydrogen and carbon monoxide while increasing the temperature. Methane-rich gas can be produced up to temperatures of about 500oC, higher temperatures favour the production of hydrogen. At relatively low temperatures of about 350oC (just below the critical temperature), methane-rich gases can be produced by using a catalyst. Fig. 2 Equilibrium concentrations H2, CH4, CO, and CO2 as function of the temperature (Pressure = 300 bar; feedstock: 90 wt.% water, 10 wt.% glycerol)[11]. ECN-RX--04-085 7 Based on an expected market and technology development, the first commercial products of supercritical gasification of biomass would be electricity (>2008) and SNG (>2010). Later on (>2015), mixtures of CH4 / H2 could be added to the natural gas grid. Finally, in long term (>2020), pure H2 could be produced (requiring infrastructure for storage and distribution of pure H2), contributing to a potential future hydrogen economy[9][10]. CO-PRODUCTION OF FISCHER-TROPSCH-SNG FROM BIOMASS In the co-production FT-SNG concept the off-gases from FT synthesis are used for SNG production through methanation (figure 3a). This concept can be considered as an alternative route to stand-alone FT synthesis, in which large amounts of off-gases would be recycled to the gasification step (figure 3b), requiring a large amount of auxiliary power. FT liquids Biomass Gasification FT synthesis off-gas Methanation SNG (a) FT liquids Biomass Gasification FT synthesis off-gas (b)...
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