Modeling Performance of High-Temperature Biomass Gasification Process

Abstract

Biomass utilization is becoming a subject of increasing interest as an alternative to clean fuel. A novel gasification process using highly preheated air gasifier using agricultural residue such as sugar bagasse, rice husks, and palm stem widely available in Tanzania is presented. The study examines, irreversibilities making the gasifier the least efficient unit in the gasification process employing a thermodynamic equilibrium model allowing predicting the main product gas composition CO, CO 2 , H 2 , and CH 4 . The derived model equations are computed using the MAPLE process simulation code in MATLAB. The gasification regime is investigated at temperatures ranging from 800 K to 1400 K and at equivalence ratio (ER) values between 0.3 and 0.4. The results obtained conform to the second law efficiency based on chemical exergy yielding maximum values for the types of biomass materials used. These results indicate that the application of preheated air has an effect on the increase of the chemical exergy efficiency of the product gas, hence reducing the level of irreversibility. Similarly, these results show that the combined efficiency based on physical and chemical exergy is low, suggesting that higher irreversibilities are encountered, since the exergy present in the form of physical exergy is utilized to heat the reactants. Such exergy losses can be minimized by altering the ratio of physical and chemical exergy in the syngas production.