Steps to understand the role played by the main operating conditions in the oxidative steam reforming of biomass fast pyrolysis volatiles

Abstract

Biomass pyrolysis and in-line catalytic oxidative steam reforming of the volatiles (P-OSR) has been analyzed in a two-step reaction system made up of a conical spouted bed reactor (CSBR) and a fluidized bed reactor (FBR). A novel O2 multi-point injection system has been designed in order to ensure suitable O2 distribution in the FBR, and hence avoid the formation of hot spots that may lead to irreversible catalyst deactivation by metal sintering. Optimization of the main process parameters has been approached in order to maximize H2 production and overcome the high energy requirements of the endothermic reforming reaction. The study has been conducted in the following ranges of the operating conditions: Reforming temperature, 550–700 °C; space time, 5–20 gcat min gvolatiles−1; steam/biomass (S/B) ratio, 2.5–5; and equivalence ratio (ER) from 0 to 0.19. Moderate reforming temperatures (600–650 °C), a S/B value of 3 and a space time of 15 gcat min gvolatiles−1 are the optimum conditions for the process. Furthermore, when low space time values are used, O2 feeding rates into the reforming step of up to an ER value of 0.12 (corresponding to autothermal operation (ATR)) revealed a synergistic effect promoting reforming reactions. Thus, an improvement in H2 production from 6.81 wt% to 8.26 wt% was observed by changing ER from 0 to 0.12, which means H2 production increases by 21.4% compared to the conventional pyrolysis-reforming (P-SR) process. Therefore, the promising results obtained in this study prove the suitability of the continuous P-OSR strategy for H2 production from biomass and involve a step forward towards the scaling up of the process.