An unsteady-state two-phase kinetic model for corn stover fluidized bed steam gasification process

• A two-phase kinetic model is developed for the fluidized bed steam gasification.
• Effects of temperature, steam/biomass ratio, and gas velocity are studied.
• Model can predict evolution of a single particle, including size, in the bed.
• Water-gas shift reaction is important in determining gas volumetric fractions.

A complex unsteady-state two-phase kinetic model including reaction kinetics and fluid dynamics was developed for corn stover fluidized bed steam gasification process. The gasification model included an unreacted core shrinking model for char–gas reactions, and a pyrolysis model considering the effect of the particle size on the pyrolysis time and pyrolysis products. In this model, fuel particles stay in the fluidized bed and take part in chemical reactions until their size decreases to a critical size, and then are entrained out of the bed. The kinetic model developed in this study is capable of predicting concentration profiles of gas in the bubble phase and the emulsion phase along the height of the reactor, the evolution of particles in the bed with time, and the particle size distribution in the fluidized bed under different operating conditions (temperature, steam/biomass ratio, and gas superficial velocity). Results show that the water–gas shift reaction and the residence time play important roles in determining the gasification results in terms of the gas volumetric fraction and yields of char and dry tar-free gas.