Hydrogen production from woody biomass via fixed-bed gasification at pilot-scale
Veronica Gubin, David Kadlez, Alexander Bartik, L. F. Steiner, J. Zeitlhofer, F. Thelen, Hermann Hofbauer, Stefan Müller
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 th 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 H2 kg −1 BM.db ) and 75.1% (58.9 g H2 kg −1 BM.db ) at adsorption times of 450 and 470 s, respectively, an adsorption pressure of 6.4 bar a and an equalization pressure of 5.0 bar a . The process proves to be technically feasible and offers room for optimization. • High-purity H 2 production via air gasification of wood chips is technically feasible. • > 94% CO conversion by the WGS reaction over a commercial Fe/Cr-based catalyst downstream of the gasifier. • Phenols, cresols, styrene, and indene were converted to a large extent over the Fe/Cr-based catalyst. • The H 2 purity achieved (≥ 99.977 vol.-%) is in-line with the H 2 threshold of the ISO 14687:2019 standard (≥ 99.97 vol.-%). • N 2 and Ar proved to be the impurities with the fastest breakthrough in the PSA unit.