Migration And Transformation Of Fusible Minerals In Coal Under O₂/CO₂Atmosphere

As an effective means of CO₂emission reduction Oxy-fuel Combustion has obvioustechnical and economic advantages. A considerable number of basic and applied researchwas carried out In domestic and foreign, but comparatively less research on mineralstransformation in furnace can be found. Minerals transformation is closely related to thecoal combustion process, so the changes in the combustion conditions will affect the lawsof mineral transformation and migration, then affect on the process of fouling and slaggingin furnace. This paper will focus on minerals transformation and the impact on fouling andslagging in furnace.First of all, the minerals transformation in different atmosphere and temperature havebeen carried out. The ash samples got in tube furnace have been analyzed by XRD. Themain conclusions obtained were that under different atmosphere major mineralstransformation was in the same way, but the content of minerals was changed. Hematite andanhydrite transformation process was effected by the atmosphere changes. More anorthite,gehlenite and hedenbergite of low melting point can be generated in O₂/CO₂atmosphere,thus increasing its tendency fouling and slagging tendency.Secondly, the ash got in Muffle furnace in different combustion atmosphere wasdetected about ash melting point in different test atmosphere,then the ash got in Mufflefurnace will be analyzed by XRD. The main conclusions obtained were that in the sameweak reducing test atmosphere the ash melting point of ash got in air was lower than inO₂/CO₂atmosphere; As the ash got in the same atmosphere, the ash melting point inO₂/CO₂test atmosphere was higher than in weak reducing test atmosphere; Whether theburning or testing atmosphere can affect on the final result of ash melting point, henceaffecting the propensities of fouling and slagging.Finally, the evaporation and decomposition process have been studied using TGA andXRF. The ash got in different atmosphere was analyzed by TGA in the correspondingatmosphere. The ash before and after TGA was analyzed by XRF. Elements relativeevaporation rate can be get to find the difference in different atmosphere. The main conclusions obtained were that the anhydrite generation process was improved in O₂/CO₂atmosphere, however the anhydrite decomposition process will be inhibited in O₂/CO₂atmosphere. High CO₂concentration will promote the evaporation of K, Na, which canincreasing the weight loss rate of minerals; The changes in CO/CO₂/O₂proportion caninhibit the evaporation of refractory minerals.