Chemical Equilibrium Model for Fixed-Bed Gasification to Assess Biomass Energy Content

A chemical equilibrium model for fixed-bed gasification is developed, which allows the prediction of the syngas composition, the amount of residual coal or ash, as well as the amount of tars as a function of the gasification temperature and the elemental composition of the biomass and the tars. Moreover, the combustion heat of the gas fuel is calculated, as well as the conversion and process efficiency, in order to perform further analyses which allow the determination of energy potential for different types of biomass under several conditions of moisture and equivalence ratio of gasifying agent. Performance of the proposed model is compared to prediction of some models which were found to be relevant in the literature review. An assessment to the model is also carried out. For this purpose, a case-study is performed for African palm (Elaeis guineensis) shells using a commercial gasifier. Experimental data obtained from the biomass used in the case-study are used to feed the model and perform the assessment. Actual results and model predictions (results) are compared varying the equivalent relation between 0.05 and 0.65, and the moisture content form biomass between 0 and 20%. This case is proposed as a benchmark case for further applications.