Effect of gasification operating parameters on quality of syngas produced using sawdust feedstock

Thesis Abstract

This research work investigates the effect of gasification operating parameters, namely equivalence ratio (ER), gasification agent, reaction zone temperature, and residence time on quality of syngas produced using sawdust.The research experiments were conducted using a pilot scale downdraft gasifier with constricted throat and a rotating grate. Temperatures at reaction zone of the gasifier were monitored directly using a digital thermometer whereas an online gas analyzer capable of detecting percentage composition and calorific value was employed to monitor quality of the syngas.Two sets of experiments were carried out separately; one using air and the other using oxygen-enriched air as gasifying agents. With air, flow rates at 6.4, 1.9 and 0.7 litre per minute (LPM) were used for the study. The results obtained shows that the higher air flow level favours better quality of syngas. Air flow rate at 0.64LPM generated the best quality of syngas containing 13.55 and 2.59% of CO and H2, respectively. Syngas maximum caloric value of nearly 3MJ/Nm3 at a temperature of 550°C was observed. Using oxygen enriched-air on the other hand, flow rate was maintained at 10LPM while varying the percentage oxygen at 21, 30, 40, 50, 60 and 80%.It was found that 40% oxygen enrichment generated the best quality of syngas containing29.57 and 14.29% of CO and H2 respectively.Syngas calorific value was observed to rise consistently from 2.08 to a maximum of 6.69MJ/Nm3 as percentage oxygen in the gasifying agent was increased from 21 to 40%. Gasification performance shows that both cold gas efficiency (CGE) and carbon conversion efficiency(CCE) reaches peak value of 46.81 and 82.04% respectively at ER value of 0.2953 which also corresponds to the 40% oxygen level in gasifying agent.