Experimental study of a biomass gasifier

Thumbnail Image
Journal Title
Journal ISSN
Volume Title
The availability of biomass materials and development in technologies to use them with low levels of emission make biomass an attractive renewable source of energy. Gasilication of biomass into a combustible gas brings with it a number of advantages over the direct method of burning the biomass materials, mainly: Ease of distribution in pipelines to consumers in whole cities or to each point of use e.g. gas stove, lamp or cylinder in an engine. If the gas is of the right quality, it can be used in spark, compression, turbine and Stirling engines for efficient power generation in compact units. The study was in two parts; one part dealt with the gasification of three classes of biomass residues from industrial activities to determine their suitability for use in energy conversion by the gasification route using a locally constructed downdraft gasifier. The other part was a study of the influence of the variation in the gasifier inlet air valve opening on the characteristics of the producer gas and the gasifier performance characteristics. Among the characteristics studied are the producer gas composition, the gas heating value, the gas flow rate, temperature, gasification efficiency and heat loss along the cooling/delivery pipe for the following hiomass feedstock: redwood, 0/ram, teakwood shear butter cakes and sawdust. 1he above characteristics were determined tor each gasitier feedstock and four settings of the inlet air valve opening namely 25%, 50%, 75% and 100%. By a graphical method, the percentage inlet air valve opening that yielded the maximum gasification efficiency as well as the maximum value of this efficiency was determined. This study revealed a number of facts relating to the type of inputs (both biotnass type or the inlet air valve opening) that produce maximum or minimum output: Although the lower heating value of the gas produced had a maximum value of 4.1628 ± 0.063MJm3 for redwood feedstock at full inlet air valve setting, the maximum gasification efficiency of 66% was obtained at 62% inlet air valve setting. An amount of 156.17± 12.33MJ, the highest value of heat energy was lost along the cooling pipe at 25% inlet air valve setting.
A thesis presented to the School of Engineering, Kwamc Nkrumah University of Science and Technology, Kumasi, in fulfilment of the requirement for a Master of Science Degree in Mechanical Engineering, 2004