Abstract
The swelling behavior of a softening coal particle during carbonization was numerically analyzed. In this study, since the swelling of a coal particle was caused by the growth of bubbles in the coal particle, the bubble growth due to the inflow of volatile matters to the bubbles was calculated involving nucleation, coalescence in the coal particle and emission of bubbles to particle outside during the softening stage.
The production of volatile matters was evaluated by the FLASHCHAIN model.
The pyrolysis experiment of a coal particle was carried out and the expansion behavior was photographed. Then, the swelling ratio was obtained. The calculated results of swelling ratio differed from experimental results because the gas evolution from coal particle was incorrect. In addition, the secondary decomposition of tar and the model of the coal softening behavior were required for the accurate prediction of the swelling behavior.
Bubble growth rate was assumed to be the function of viscosity in this study. In order to understand the effect of the viscosity on swelling ratio, the variation of swelling ratio of the coal with viscosity change was investigated by varying assumed viscosity. The swelling ratio calculated with low viscosity was low because bubble nucleation was decreased by low viscosity. The swelling ratio with high viscosity was inhibited because high viscosity leads to low bubble growth rate. The property of softening coal, which is difficult to measure, can be estimated by more accurate analysis.
