Abstract: On the basis of mass balance, energy balance and chemical reaction equilibrium, the thermodynamic equilibrium model in flaming pyrolysis zone of stratified downdraft gasifier was developed including the consideration of ash as part of the exit products. Then it was solved by Newton method in Matlab. The calculated values were in good agreement with the experimental results and other models' results reported in literature. The model was used to analyze and calculate the flaming behavior in prolysis zone. The results showed that ER, moisture content and heat loss had obvious effect on the temperature and compositions of the product gas. The air preheated temperature and ash content also had obvious impact on the gas temperature, but no obvious impact on the gas compositions. With increment of ER and decreasing of moisture content, the possibility of slagging increased. As the ER value was lower than 0.392, the increasing of air preheated temperature had positive effect on gasification. However, for heat loss>14% and ER<0.32, the biomass cannot be pyrolyzed completely. The contents of H₂O and CO₂ in the product gas of flaming prolysis zone, which had important effect on the reaction of reduction zone, were 20%-25% and 10%-15% for corn stalk gasification. The model provided the initial parameters for development of reduction zone model.

Key words: stratified downdraft gasifier, flaming pyrolysis zone, biomass, pyrolysis, thermodynamic equilibrium model