Linbo Yan

Characterization of a dual fluidized bed gasifier with blended biomass/coal as feedstock

A one-dimensional model is built based on the commercial Aspen Plus software to kinetically simulate the biomass/coal co-gasification process in a dual fluidized bed gasifier. The synergistic effect on the co-gasification kinetics is allowed for, and is coupled with the gas-solid flow hydrodynamics. With the developed model, the effects of different key operating parameters including the biomass blending ratio (Rb), the initial bed temperature (Tg), the feedstock mass flow rate (Ffs), the bed material flux (Fbm) and the steam to carbon ratio (Rsc) on the resultant syngas composition and the supplemental fuel mass flow rate (Fsf) are investigated, and the operation parameters are optimized. It is found that increasing Rb and Tg can enhance the gasification, while increasing Ffs and Rsc restricts the gasification. Increasing Fbm has slight effect on the gasification results but can reduce Fsf. The cold gas efficiency is up to 78.9% under the proposed optimum condition.

Investigation on biomass steam gasification in a dual fluidized bed reactor with the granular kinetic theory

The dual fluidized bed (DFB) reactor is promising to convert biomass into high-quality syngas efficiently. In this work, a three-dimensional model is built based on the granular kinetic theory to predict the biomass steam gasification in dual fluidized bed reactors. The model is firstly validated against a series of experimental results. Then, the effects of some essential operation parameters including the biomass flow rate (Fb), the steam to fuel ratio (Rsf) and the gasification temperature (Tg) on the biomass steam gasification properties in a DFB reactor are comprehensively analyzed with the orthogonal method. In the concerned ranges of the operation parameters, the cold gas efficiency is found to be the most sensitive to Fb and least sensitive to Tg. The optimal cold gas efficiency of the DFB gasifier is 82.9% when Fb, Rsf and Tg are 15 kg/h, 1.5 and 900 °C, respectively, and the H2 mole fraction is 46.62%.

Chemical Equilibrium Model and Prediction for Coal Hydrogasification

Abstract Researches on coal hydrogasification (CHG) which is the core component of the zero emission coal (ZEC) system are rarely reported and the characteristics of CHG have not been well understood. A chemical equilibrium model (CEM) for coal hydrogasification is proposed in this work to study the effects of different reaction conditions on the CHG characteristics. The results from the model are then validated against literature available experimental data and the model is proved reliable. After the validation, sensitivity analysis on the CHG process is done and meaningful results are obtained. Increasing the reaction pressure (p) and H2/coal mass ratio (R) or decreasing the reaction temperature (T) can enhance the hydrogasification reactions. The carbon conversion rate begins to decrease at 800 K and 1,250 K for operation pressures of 0.1 MPa and 7 MPa, respectively. Remarkable effects on the gasification characteristics are found when p is lower than 1 MPa. At 7 MPa and 1,000 K, carbon is entirely converted when R is 0.25 and the maximum CH4 mole fraction is reached. In the case that T is variable, carbon will be all converted at 7 MPa when R is about 0.5. Carbon will never be all converted at 0.1 MPa no matter how high R is. Mole fraction of CH4 will decrease with R both at the pressures of 7 MPa and 0.1 MPa.