Temperature of freely moving burning carbonaceous particles in fluidized beds

In fluidized bed combustion (FBC), relatively few large and lighter coal particles are fluidized with more dense and smaller sulpher-sorbent bed particles. The need to burn poor quality feed materials in an environmentally acceptable fashion is one of the main motives behind the development of FBC. Low rank coals contain significant amounts of organically bound inorganics compounds and sodium chloride which, when the coal is burnt, are released and react to form compounds in the ash matrix around the particles. These compounds, due to their physical and chemical nature, lead to operational problems such as particle agglomeration, segregation and defluidization. The nature of the problems are closely related to the temperature history of the coal particles since it is known that the viscosity of the ash is highly temperature dependent in the typical FBC temperature regimes. Because of this, the need to understand the temperature history of the coal particles is of importance in trying to determine the fate of the ash layer. With this in mind, the single particle receding core model studied in Linjewile and Agarwal (1990) is extended here to include the effects of the interphase movement that the particle would see under normal FBC conditions (Nienow et al., 1978; Agarwal, 1987). The results show that the particle's temperature will undergo oscillations which are expected to be significant in determination of the ash fate.