Thermogravimetric investigations in prediction of coking behaviour and coke properties derived from inertinite rich coals

Abstract

The coal quality, temperature, pressure, heating rate, various processes and reactor type affect coking behaviour of coal and resulting coke properties. Several petrographic and chemical methods were proposed earlier for prediction of coking behaviour of coals. Inertinite rich coal samples ( I mmf>30 vol%) having different petrographic compositions were selected for thermogravimetric investigations (DTA, DTG and TGA) and their coking behaviour was studied. The petrographic build up, micro-structural properties (porosity and cell wall thickness) and mechanical strength of the resulted cokes were also investigated. Δ H and Δ H max (the main endothermic area of heat absorption and fast absorbing main endothermic area, respectively) were distinguished in DTA curves. Δ A and Δ A max (the main decomposition area and fast disintegrating main decomposition area) under DTG curves were identified. Δ H max/Δ A max shows good correlation with Roga's indices (RI, caking properties) as well as with petrographic caking ratio (PCR). The coarse mosaic content of cokes seem to depend on LΔ T max/Δ T max (ratio of weight loss during fast decomposing main reaction to temperature difference) under DTG. L mΔ T/Δ T (ratio of weight loss during main decomposing reaction to temperature difference) under DTG exhibits correlation with p 1 (mean pore size) and t 1 (mean cell wall thickness) of cokes. Δ A max/( L mΔ T max) also indicates good relationship with mechanical strength of cokes. ( L mΔ T A− T B)/( L mΔ T) (i.e. ratio of weight loss during main endothermic reaction under DTA to weight loss during main decomposing reaction) appears to have relationship with DD (compactness) of cokes. The course of main endothermic reaction/main decomposition reaction under DTA, DTG and TGA seems to govern coking behaviour and the resulting coke strength, which in turn is controlled by microlithotypes.