Influence of coal briquette size on the combustion kinetics

In this study, the effects of one of the most important parameters in coal briquetting process, the briquette size, on the combustion behaviour of coal briquettes were determined from the view of combustion kinetics, i.e. their liability to ignite and combust. Effect of size on the combustion kinetics was treated by two different approaches. The first one consists of combustion kinetics experiments with briquettes of increasing sizes, thus of expanding volumes. In the second phase, briquette dimensions were alternated by keeping the briquette volume fixed. The influences of the concerned parameters were investigated through effluent gas analysis method and interpreted by an Arrhenius kinetic model relying on the changes in the amounts of evolved carbon oxides and consumed O2 gas as a function of temperature and time at three different pressure levels, 25, 50 and 75 psig. At the end of experiments, the activation energy and Arrhenius constant for each run were calculated and the distinct variations in the activation energy values showed that the liability of the coal briquettes to ignite and the efficiency and effectiveness of the combustion reaction were considerably affected both by the size enlargement and dimension variation on a constant volume basis.