Comparison of strategies for H2 production by biomass fast pyrolysis and in line conventional steam reforming or sorption enhanced steam reforming

Abstract

H₂ is expected to play a crucial role in the energy transition as fuel, energy vector and building block. Therefore, different routes for producing renewable H₂ are currently under study. In this context, biomass thermochemical conversion is encouraging, with the two-step pyrolysis and in line steam reforming (PY-SR) being an outstanding alternative. The aim of this study is to further develop this alternative by coupling the steam reforming with in situ CO₂ capture, i.e., pyrolysis and in line sorption enhanced steam reforming (PY-SESR). A commercial Ni-based material and dolomite were used as catalyst and sorbent, respectively. PY-SR and PY-SESR were compared in terms of their performance when varying the reforming temperature (450–750 °C) and the Steam to Biomass (S/B) ratio (0.5–3). PY-SR led to best results in terms of H₂ production (0.1086 g_H2 g⁻¹_biomass) and H₂ purity (65.2 mol %) at a temperature of 600 °C and a S/B ratio of 3. PY-SESR yielded optimal results concerning H₂ production (0.1180 g_H2 g⁻¹_biomass) and H₂ purity (99.8 mol %) at temperatures in the 525–600 °C range and S/B ratios between 1 and 3. Therefore, PY-SESR approach allowed lowering the reforming temperature and S/B ratio, as well as widening the range of optimal conditions and improving the performance of PY-SR. In short, PY-SESR process led to the maximization of biomass conversion to H₂ by producing a highly pure H₂ stream with lower energy requirements. Additionally, negative emissions are attained by integrating CO₂ capture in the processing of a carbon-neutral feedstock, such as biomass.