Optimization of Disc Parameters Producing More Suitable Size Range of Green Pellets

Pelletization is an agglomeration technique, beneficial with finer iron ores over other agglomeration processes. For Corex and Blast furnace feed, a certain size range of pellets is required for attaining the operating bed permeability along with other furnace parameters for smooth operation. The size distribution of pellets mainly depends on the nature of raw materials, balling equipment, disc inclination, disc rotating speed, rim height, size of the feed, feed rate, amount of moisture added, nozzle combination and position, residence time in disc pelletizer etc. The present work is aimed at to optimize the operating parameters improving the disc pelletizer efficiency which can enable to choose more suitable green pellets size range (8-12) so as to improve the plant productivity and minimizing the oversize and undersized green pellets. Experiments were conducted with varying disc inclination, disc rotation, nozzle combination or position and feed rate keeping other parameters constant to produce the desired size range (8-12 mm) pellets. The properties viz, green compressive strength (GCS), drop strength, moisture content, loss on ignition (LOI) of green pellet were tested and recorded. The experimental observation shows that finer the particle size, more the compactness and thereby, higher the green compressive strength and drop strength of pellets. The disc inclination of 430 is the optimum value at which maximum efficiency of balling disc was observed. At higher feed rate, the disc rpm needs to be increased to nullify the effect of decreased required size range. At JSW Steel Ltd., upon implementation at pellet plant the benefits are as under. i)Production of indurated pellet increased by 95 t/day (i.e., ~ 0.9%). ii)Recirculation load of under/over size pellets reduced from 20.06 to 11.55 %. iii)Unfired pellets reduced from 8.47 to 5.90 %.