Gasification of woody biomass in a novel indirectly heated bubbling fluidized bed steam reformer

Abstract

Within this work, a novel 50 kW_th indirectly heated bubbling fluidized bed steam reformer (IHBFBSR) is presented, along with its commissioning experiments. In the IHBFBSR, heat is provided through two radiant tube natural gas burners in the bed and the freeboard area. The aim of this innovative design is sufficient heat provision for biomass steam reforming and cracking reactions and heat loss reduction, thus allowing the possibility of scaling-up to an industrial level. Experiments were performed with two woody biomass feedstocks and two bed material particle sizes under different operating conditions (steam to biomass ratio, lambda, temperature), in order to identify the setup's main characteristics. Product gas composition and quality, as well as the cold gas efficiency of the IHBFBSR were in reasonable agreement to similar systems, however carbon conversion prediction needs further improvement. H₂ production and tar removal are favoured by small bed material particle sizes as well as by char accumulation in the bed area. Furthermore, air injection above the bed led to improved H₂/CO ratios and lower tar yields compared to when air is used as a fluidization agent. Overall, it was shown that the IHBFBSR technology constitutes a promising development in the field of biomass allothermal gasification.