Hydrogen production from woody biomass via fixed-bed gasification at pilot-scale

Abstract

Sustainable energy carriers are needed to reduce greenhouse gas emissions and tackle the climate crisis. Low-emissions hydrogen is one of many conceivable energy carriers. In this study, hydrogen production via air gasification of wood chips is experimentally investigated with the aim of achieving a hydrogen purity suitable for proton exchange membrane fuel cells. A 50 kW<inf>th</inf> fixed-bed gasifier is coupled with a pilot-scale process chain for product gas cleaning, conditioning, and hydrogen purification. Test runs are carried out in which the inlet temperatures of the water-gas shift unit and the adsorption time of the pressure swing adsorption unit are varied. Tar compounds are converted in the water-gas shift unit, resulting in a less complex tar composition and potentially simplifying the downstream gas cleaning processes. The obtained hydrogen purity is ≥ 99.977 vol.-% and ≥ 99.964 vol.-% with a hydrogen recovery of 70.3% (55.1 g<inf>H2</inf> kg⁻¹<inf>BM.db</inf>) and 75.1% (58.9 g<inf>H2</inf> kg⁻¹<inf>BM.db</inf>) at adsorption times of 450 and 470 s, respectively, an adsorption pressure of 6.4 bar<inf>a</inf> and an equalization pressure of 5.0 bar<inf>a</inf>. The process proves to be technically feasible and offers room for optimization.