Characteristics of Air-blown Gasification for Woods in a Fixed-bed Downdraft Gasifier

Abstract

An experimental investigation of a fixed-bed, downdraft air-blown gasifier has been carried out using wooden cubes 15 mm3 made of Lauan wood. The reactor is a cylinder with an internal diameter of 200 mm and a height of 1000 mm. The effect of airflow rate, air preheating temperature, and moisture content of wood cubes on producer gas composition and heating value were presented. The conversion rate of wooden cubes increases linearly with the cold airflow rate within the range from 6 to 18 Nm3 · h−1. The producer gas heating value and efficiency of gasifier increase with increasing rate of cold air up to 15 Nm3 · h−1 then drop down due to the dilution effect of cold air. Preheated air temperature up to 573 K was found to have marginal effect on producer gas heating value. Moisture content of wood can significantly lower the wood cubes conversion rate and producer gas heating value. The optimum mean higher heating value of producer gas obtained in this work, using woods with 18% of moisture content and cold air, is ∼ 5.2 MJ · Nm−3. A one-dimensional steady model was developed for biomass gasification to predict the axial profiles of temperature and gas composition in a downdraft reactor. Agreement between experimental and predicted producer gas heating value is acceptable.