Characterisation of coke packed beds after liquid slag flow at 1 500°C by image analysis

The flow of slag in the lower zone of the ironmaking blast furnace was experimentally simulated by adding slag to a high temperature laboratory scale coke packed bed. The flow of slag through packed beds of coke with packing densities varying from 50% to 65% was examined at 1 500°C. Since the liquid flow through a packed bed depends on packing properties such as particle size, particle shape, pore size and pore neck size, it was necessary to characterise these properties of the beds. In this work, image analysis of successive sections of the tested beds was utilised to characterise the bed packing properties. In addition, the slag distribution and holdup was also measured. The procedure was that at the end of each experiment, the beds were cooled down, cold mounted in resin, then sectioned into approximately 4 mm thick slices. Each section was then analysed to measure particle and pore geometric properties, and slag distribution. It was found that the slag holdup was well distributed within the bed and was varied in position between bed cross sections, indicating no significant wall effect. The average pore size and average pore neck size were found to decrease as the packing density increased. Slag flow caused the particle sphericity and the average pore neck size to increase in comparison to an unreacted bed due to the slag-coke interaction.