Development of small-scale downdraft gasifiers for biomass gasification

Abstract

Biomass gasification mainly involves a process whereby agricultural residues or biomass are subjected to partial combustion for the biomass to undergo pyrolysis and reduction, thereby releasing its gaseous component such as hydrogen, carbon-dioxide and methane. Past studies have laid emphasis on the need to study the effect of moisture content and biomass types on the rate of gasification and gasifier efficiency. This study focused on the development of a downdraft gasifier for production of syngas using agricultural wastes as raw materials. The design of the Imbert type downdraft gasifier was based on specific gasification rate, called hearth load Gh, nozzle air blast velocities, throat inclination angle, air inlet diameter and size of reduction zone. The developed gasifier consisted of a reactor, cyclone and filtration unit of 0.006, 0.016, and 0.006 m³ capacities respectively. The testing and evaluation of the designed gasifier showed adequate capacity for biomass treatment by pyrolysis. The fabricated gasifier also showed high efficiency in the pyrolysis of the selected biomasses and the product yields are appreciable. The development and use of such gasifier especially for the treatment of other agricultural wastes is hereby solicited.