PSA design for stoichiometric adjustment of bio-syngas for methanol production and co-capture of carbon dioxide

The use of synthesis gas obtained from biomass gasification as a feed stream to methanol production appears to be an environmental attractive alternative. However, the composition of the bio-syngas is deficient in hydrogen and therefore not suitable for direct methanol synthesis. A process to adjust the syngas composition to the required stoichiometric ratio (H2–CO2)/(CO + CO2) of 2.1 is needed. In this study a pressure swing adsorption process used to adjust the stoichiometric ratio of a bio-syngas and co-capture carbon dioxide was designed. The results show that the separation and concentration of carbon dioxide to a stream ready for capture, purity above 95%, can be accomplished at high recovery of both products – 99.7% for CO2 and 99.5% for H2, with a power consumption of 0.841 MW (1.83 kWh kmolCO2−1)(1.83 kWh kmolCO2−1). An optimized operation of the process reduces the power consumption over 30% to 0.584 MW (1.27 kWh kmolCO2−1)(1.27 kWh kmolCO2−1), but with a slight decrease in products recovery – 99.6% for CO2 and 98.6% for H2.