Uneven Distribution of Burden Materials at Blast Furnace Top in Bell-less Top with Parallel Bunkers

Abstract

In the blast furnace operation equipped with parallel bunker-type bell-less top, the uneven charging of materials in circumferential direction is an important issue to be avoided. This unexpected circumferential imbalance is caused by dynamics of burden materials in charging system. Full analysis is necessary for overcoming this problem. In this paper, on-site measurements such as charging rates of coke at different flow control gate openings, burden falling trajectories in the air, height distribution of burden stock surface at furnace peripheral and at orthogonal two diameter directions, were done during the filling-up stage. Dislocation of center point was found in this measurement. Mechanical equations of burden materials flow are derived for three successive regions such as bunker-to-chute colliding point, materials motion on the chute and free falling in the air. Influence of operational factors such as flow control gate opening, rotating speed and tilting angle of chute, and stock line on circumferential weight and falling point distribution was investigated. By making use of the mathematical model, H value and K value are introduced to quantitatively evaluate the circumferential height and ore/coke distribution in several charges. Measured results and simulation results matched well. Observed dislocation of center point was explained well by the mathematical simulation. It is concluded that change of rotation direction is thought to be much effective in correcting the unevenness of circumferential height distribution. On the other hand, application of bunker change in turn at coke and ore charging is effective to realize circumferential even distribution of ore/coke.