Energy Analysis and Heat Integration in the Joint Process of Biomass Fast Pyrolysis and In Line Sorption Enhanced Steam Reforming.

Abstract

Biomass Fast Pyrolysis and in line Steam Reforming (PY-SR) is promising alternative for H2 production. However, there are potential strategies for intensifying the process, such as capturing the CO2 in situ in the reforming step, which is so-called Sorption Enhanced Steam Reforming (SESR). Both PY-SR and PY-SESR were simulated using a thermodynamic approach and empirical correlations, and they were compared based on the energy requirements, H2 production, and H2 purity at different temperatures (500-800 °C) and steam to biomass (S/B) ratios (0-4). Then, the energy requirements for the PY-SESR were analyzed in detail for a reforming temperature of 600 °C and several S/B ratios, and a heat integration scheme was proposed, aiming at making the process thermally autosustained. Although the energy requirement of PY-SESR is always higher than that of PY-SR at the same reforming conditions, it allows the use of milder operating conditions, with the process performance being even better. Thus, PY-SESR outshines PY-SR, as it allows obtaining a higher H2 production (0.124 kgH2 kg-1 biomass vs 0.118 kgH2 kg-1 biomass) and H2 purity (98 mol % vs 67 mol %), with a lower energy requirement, and capturing the CO2 generated, thereby attaining negative emissions. The main energy demands of this process account for water evaporation and sorbent calcination. Nevertheless, a thermally autosustained PY-SESR process may be attained by recovering heat from the product streams, transferring heat from the reforming reactor to the pyrolysis reactor, and burning the char generated in the pyrolysis step.