Some factors influencing the fluidity of coal blends: Particle size, blend ratio and inherent oxygen species

The fluidity performance of blended coals prepared from caking coal and non- or slightly-caking coal of different particle sizes, and the evolution of gaseous oxygen containing compounds (CO, CO2 and H2O) during carbonization are examined using the Gieseler plastometer method, and a flow-type fixed-bed quartz made reactor, respectively. The heating rate and temperature are 3 °C/min and 1000 °C, respectively. The Gieseler fluidity decreases with increasing blend ratio of non- or slightly-caking coal to caking coal. In addition, the fluidity tends to decrease with the decreasing particle size of non- or slightly-caking coal in blended coals. The evolution of CO, CO2 and H2O during the carbonization of single coals begins at 200–400 °C, and the main peak of the formation rate appears at 450–700 °C. The amount of gaseous O-containing compounds evolved until 1000 °C from the non- or slightly-caking coals is greater than that of evolved from the caking coal. Additionally, a negative correlation is observed between the amounts of CO, CO2, and H2O that evolve up to the initial softening temperature and the maximum fluidity value. The profiles of formation rates of the three gaseous O-containing compounds from the blended coal during carbonization are different with additive average based on the results of single coals. Furthermore, for the blended coal, the starting temperature H2O evolution measured shifts to higher temperature in comparison with that of calculated based on the results of single coals. Therefore, it is possible that the H2O produced from non- or slightly-caking coal in blended coal or that the H2O formation reactions in blended coal during carbonization affects the fluidity performance of the blended coal.