Development of a reactivity test for coal-blend combustion: the laboratory-scale suspension-firing reactor

Abstract

A laboratory-scale technique has been developed for assessing changes in the combustion reactivity of coal blends with blend composition. The test consists of the incomplete combustion of a batch of coal particles in a novel suspension-firing reactor. Residual chars are analyzed for composition and reactivity by nonisothermal thermogravimetry. Results from the bench-scale combustor were compared with observations from a full-sized power station and a single-burner pilot installation. Using the same sets of coals, the suspension-firing reactor gave the same order of reactivities as that observed in larger-scale equipment. Systematic preferential combustion of the higher-reactivity coal in blends has been identified; the extent of preferential combustion has been quantified from the thermogravimetric profiles of the residual chars. Our findings indicate that the reactivity of residual coal-blend chars is determined by the extent of enrichment of the lower-reactivity component in the blend. The coupled use of the new suspension-firing reactor and nonisothermal thermogravimetric analysis provides a powerful tool in comparing the combustion performance of different coal blends. Initial indications are that this simple system can be used as a predictive tool.