Component-based equilibrium modeling of biomass fixed-bed gasifier

In this paper, the process of gasification of rice husk directly with air in a fixed-bed gasifier was modeled using Aspen Plus. Unlike traditional models based on the elemental balance method, this study modeled the decomposition of rice husk into cellulose, lignin, and hemicellulose based on experimental data from the pyrolysis equipment, and the product yields were fitted to obtain the distribution of product yields in the pyrolysis stage of rice husk. In the redox stage, the thermodynamic equilibrium calculation model and the kinetic calculation model were used for the simulation, respectively, and compared and analyzed with the actual plant operation data. In the simulation of the thermodynamic equilibrium calculation model, the error of gas yield was about 5%. While in the kinetic calculation model, the errors of gas production rates of N2, H2 and CH4 were within 5%, the errors of CO and CO2 were larger, which were 13.73% and 17.09%, respectively. The error of the yield of Bio-char, an additional product of gasification, is about 2% in both models, which is close to the actual working conditions. Based on the model, the effects of gasification temperature, air equivalent ratio (ER) and air preheating temperature on the gasification reaction were discussed in this paper. The results concluded that the gasification temperature should be maintained at about 800 °C, the air equivalent ratio at about 0.3, and the air preheating temperature should be increased appropriately when performing rice husk gasification.