DYNAMIC CHARACTERISTICS OF A SMALL FIXED-BED GASIFIER STOVE

This paper describes work directed at characterizing the dynamic behav iour of a small gasifying fixed-bed biomass stove. The system comprise s a primary gasification chamber, followed by a multi-stage secondary combustor which can allow for the considerable variation in quantity a nd calorific value of fuel gas produced by forming a series of flamele ts which move along the length of the secondary combustor as a functio n of the local mixture ratio. The typical cycle time is about 60 minut es and once warmed up the unit is capable of operating with low emissi ons, providing appropriate guidelines are followed. Correlation of tem perature and gas concentration measurements on the unit with velocity and flow visualization measurements on a perspex model of the secondar y combustor show that improvements can be made to the flow patterns in the bottom of the secondary combustion chamber by reducing the size a nd shape of the recirculation zones formed and revising the location o f the mid-section secondary air inlet. Control of the system is indica ted using a simple measurement of temperature in the secondary combust or to determine appropriate air supply rates.