Thermochemical equilibrium modeling is the basis of the numerical method implemented in this study to predict the performance of a downdraft biomass gasifier. To validate the model, a close agreement is shown between numerical and experimental results. Five different biomass materials of five major families are tested using the model and olive pit is shown to be the most energetic one. The effects of oxygen enrichment and pressure on gasification characteristics are investigated. These characteristics include composition and calorific value of the produced synthetic gas (syngas), as well as cold gas efficiency and temperature of the gasification process. Increasing oxygen enrichment from 21% (as in atmospheric air) to 100%, results in a considerable increase of 118% in syngas calorific value. Gasification under pressure makes a slight increase in calorific value and temperature. Increasing gasification pressure is shown to be economically more feasible than increasing the syngas pressure in downstream equipments.

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