EXPERIMENTAL TESTS OF THE GASIFICATION CHAMBER OF A WOOD-BURNING BOILER

Abstract

On the European market, biomass boilers accounted for 36% of the total number of boilers sold in 2021. Among them, there are three constructions used for burning wood: the typical upward flow design and constructions with co-current and cross-current gasification. The latter two constructions are characterized by multi-stage combustion: first, gasification is carried out in a separate chamber, and then the combustible gas is burned in the combustion chamber. Refractory inserts are used between the mentioned chambers to enable the combustion of combustible gas and the large amounts of particles it carries, as well as to improve heat transfer in the combustion chamber. When designing the refractory part and the combustion chamber, it is necessary to know the temperature and velocity fields, as well as the composition of the combustible gas. The aim of the study is to: (i) present experimental tests of the gasification chamber and (ii) provide guidelines for its design. The tests were carried out on an 18 kW wood gasification boiler, and were conducted intermittently by first entering the nominal operating mode, which was then interrupted by closing the secondary air inlet. Under such conditions, the combustible gas was sampled, and its composition was most affected by the distance between the primary air inlets and the gasification chamber outlet, the size, shape, and moisture content of the wood, the characteristics of the gasified layer (voids, zones of different temperatures), heat loss, and the shape and geometry of the outlet of the chamber.