Reactivity and kinetics of furfural residue air gasification based on-line gas releasing behaviors in a bubbling fluidized bed

Abstract

Furfural residue (FR), as an industrial by-product, has a huge annual output. The air gasification of FR in fluidized beds is a promising technology to produce high-quality syngas. Understanding the reactivity and kinetics of FR gasification can guide and achieve the directional regulation of target products. The use of a fluidized bed to study air gasification kinetics of FR was proposed to avoid the technical difficulties in thermogravimetric analysis and fixed beds. A bubbling fluidized bed with an on-line analysis system was developed to systematically investigate the synergistic effects of the equivalence ratio (ER) and the temperature on real-time gas releasing behaviors of FR. The shrinking core model (SCM), homogenous model (HM) and modified volume reaction model (MVRM) were used to describe the kinetics characteristics of volatile and char gasification, respectively. The gasification mechanisms were revealed by the reaction model functions. The results showed that the rapid devolatilization of FR led to the maximum rate of volatile gasification at about 1–1.5 min, then the char gasification reaction occurred at about 2 min. In addition, the char gasification time was about 4 times longer than that of the volatile, dominating the whole gasification process. The optimal ER value was 0.3 when the temperature was 800 °C, while it was 0.25 at temperatures above 850 °C, and the volume fraction of CO increased from 47% to 57% with the temperature increase. The SCM performed the best for describing the air gasification kinetics of FR. The activation energies of volatile and char gasification were the largest at the ER of 0.25, being 54 kJ/mol and 112 kJ/mol, respectively. In the fluidized bed gasification, the nucleation and growth mechanism was the most accurate for describing the volatile gasification process, while for the char gasification, the shrinkage geometrical mechanism worked the best.