Combustion behaviour of coal blends

The combustion behaviour of several coals, different in rank and maceral composition, and of their blends was studied by thermogravimetric analysis and kinetic tests. Combustion profiles of the blends reflect those of the individual components. In particular, the curves representing the weight loss of the blends are located in between those pertaining to the individual coals. A flow reactor was employed to perform kinetic tests that allowed the determination of the dependence of the reaction rate on the temperature in the range 723-873 K. The selectivity of the carbon combustion reaction to carbon monoxide and carbon dioxide formation was also evaluated. Results of combustion tests of single coals and of blends in the flow reactor confirmed the findings of thermogravimetric tests since the time profiles of reactivity of the blends were predictable from the reactivity profiles of individual coals. The role of macerals in determining the reactivity of coals and related blends was then studied and a relationship between coal reactivity and vitrinite random reflectance clearly identified. Experimental findings were discussed and the key parameters determining the combustion behaviour and the reactivity of the blends were indicated.