Hydrogen-rich syngas production and insight into morphology-kinetics correlation for furfural residue steam gasification in a bubbling fluidized bed

Abstract

Biomass steam gasification technology has attracted considerable interest for its potential of low-cost and high-efficiency in hydrogen production. However, there is still a large knowledge gap regarding morphology-kinetic correlation. To avoid the technical difficulties of thermogravimetric analysis and fixed bed studying steam gasification kinetics, this work pursues the design and building of a visualized bubbling fluidized bed with an online analysis system. According to the morphology evolution of biomass real-time observed by a high-speed camera, the shrinkage ratio during high-temperature gasification in a fluidized bed has been first deduced. Moreover, based on accurate monitoring of the gas products releasing behavior, multiple kinetic models were applied to evolve the activation energy at different carbon conversion efficiencies (CCE). The results showed that the synergistic regulation of steam concentration and temperature achieved a high H2/CO ratio (2.46) and H2 yield (869.5 L/kg). A comparative analysis of the coupling relationship between shrinkage ratio, activation energy and CCE successfully separated the volatile precipitation and char gasification processes. It was also revealed that the shrinkage rate peaked at the transition from pyrolysis to char gasification (20 % CCE). At CCE below 20 %, the reaction mechanism tended towards a nucleation and growth mechanism. As CCE reached 20 %, the reaction form shifted. Subsequently, the chemical reaction mechanism controlled the main reaction, and the average apparent activation energies of H2, CO2 and CO were 86.76, 31.27 and 39.90 kJ/mol, respectively. This work provides new insights and a theoretical basis for understanding and modeling the biomass steam gasification process in fluidized beds.