Investigation of cigarette effect and elastic-plastic behavior of green iron pellets on the roller screen efficiency

Abstract

The green iron pellet demonstrates elastic–plastic deformation behavior during classification on a roller screen, which has a significant effect on its inefficiency due to the occurrence of phenomena such as the cigarette effect. This phenomenon causes the quantity and quality of produced pellets to drop by transferring the on-size pellets to the fine grain section and especially the oversized pellets to the product section. In this research, the effective factors in creating this phenomenon and the solutions to reduce it are investigated. It is observed that the optimum plastic behavior of the pellet and consequently the efficiency of the roller screen would be achieved when the green pellet is made from magnetite concentrate with 8 % moisture and 1 % bentonite, and roller screen operational parameters include feed rate of 1.5 t/h, the deck inclination angle of 13 degrees and the roll rotation speed of 150 rpm. The results obtained for the optimum fine removal efficiency, product screening efficiency, loss of production to undersize, on-size contamination, and oversize removal efficiency are 92.1 %, 93.7 %, 5.36 %, 5.23 %, and 73.2 %, respectively. The total screening efficiency of the roller screen is also estimated as 86.29 % and the cigarette effect is decreased to the most optimal state.