Systematic Mass and Energy Evaluation of Biomass Staged Gasification System Based on Thermodynamic and Kinetic Equilibrium Approaches

Abstract

In this work, a typical three-staged gasification system was studied using Aspen Plus. Two models, namely thermodynamic and kinetic equilibrium models were built and compared. Results show that the kinetic equilibrium model could predict the syngas yield quite accurately than thermodynamic equilibrium model. Pyrolysis stage and reduction stage were endothermic, while the partial oxidation stage was exothermic. The heat load of pyrolysis and reduction stage was -17.632kW and -14.368kW. The oxidation of volatiles released large amount of heat and formed high temperature zone around 1100°C. The hot flue gas contained large amount of sensible heat that provide the heat for pyrolsis and reduction stage. Based on the energy balance calcualtion, autothermal operation could be achieved for this three-staged gasification. And extra heat in hot flue gas could be used for household heat supply. Based on the model, the influence of operation parameters, including reduction temperature, air equivalence ratio, steam flow rate and oxygen concentration on gasification performance was investigated.