Mass Distribution in the Falling Stream of Burden Materials

Abstract

The burden material in a blast furnace is essentially a collection of particles having wide range of size and shape. It is discharged from the hopper and distributed on the stock level. The mass distribution of the falling stream determines the shape of the stock profile. The stock profile dictates the radial variation of ore/coke ratio, size segregation, gas distribution and burden descent, which in turn influence the formation and shape of the cohesive zone. Knowledge of the stock profile is therefore essential for understanding these phenomena. The complex nature of the flow has made a first-principle prediction of the mass distribution in the falling stream extremely difficult. Kondoh et al. 1) have reported mass fraction distribution in the falling stream at different elevation but the complete description as a function of chute angle is not reported. The present work attempts to predict the mass fraction distribution in the falling stream for three burden materials, viz. iron ore, coke and sinter. ExperimentationThe experiments were conducted using actual bell less top charging equipment of the furnace in a trial rig. Figure 1 shows a schematic diagram of the experimental setup. The rig was comprised of the complete material charging system including receiving hopper, common hopper, upper seal valve, lower seal valve, flow control gate and rotation chute. A brick-walled cylindrical tank of 5 m diameter and 1.5 m height was built for simulating the furnace throat. A small section of the cylindrical wall was kept open for removal of the charged materials. Proper electrical and mechanical arrangements were made for the rotational motion of the distributing chute. Tilting angle of the chute was changed manually and the chute was set to rotate at a constant speed. To feed the material in the receiving hopper, a special charging hopper of volume 1.43 m 3 was fabricated with a discharge gate at the bottom.For the purpose of collecting the materials from the falling particle stream, a semi-cylindrical pipe was inserted along the throat diameter at 1.6 m below the chute tip (design stock level). The pipe was divided into 25 compartments of 20 cm width each. In the experiment, rotating chute distributed the material along the peripheral direction and completed full rings. When the falling stream crossed the inserted pipe, material was collected in the different compartments, as shown in Fig. 2. For each full ring rotation of the chute, material was collected in two different locations, one on either side of the throat centre-line. Materials from individual compartments were weighed and mass fraction distribution was calculated. Results and DiscussionThe striking position of the falling stream of sinter for different chute inclination angle is shown in Fig. 3. The stream moves toward furnace wall with the increase in chute angle. In the figure, the filled points are the striking positions of the outer stream and the void points are the striking points of the inner stream. The stream width, defined as the distance...

Particle Size Segregation in the Falling Stream of Burden Materials

“…It has already been established as part of this study 6) that the distribution of material along the radial direction is almost symmetrical about the central axis of furnace. With samples collected from each compartments, mass of different size fraction of materials were analysed.…”

“…Results of trajectory measurements in bell-less top and prediction of mass fraction distribution were discussed by Nag et al 6) In the present work, estimation of size segregation in the falling stream of burden materials (iron ore, coke, and sinter) has been attempted.…”

“…Details of the experimental setup have been mentioned elsewhere. 6) For size segregation measurements in the falling trajectory, a half cut pipe with 24 compartments as shown in schematic drawing ( Fig. 1) was used at stock line level (1.6 m from chute tip) supported at both end with the brick wall (furnace throat).…”

Effect of the Main Feeding Belt Position on Burden Distribution during the Charging Process of Bell-less Top Blast Furnace with Two Parallel Hoppers

“…Additionally, some investigators studied the size distribution and falling point of particles by small scale experiments. [9][10][11][12][13][14][15][16][17] However, the information obtained from experiments or single particle mathematical model on size segregation and flow patterns is still limited. Therefore, more detailed work is needed in order to understand the burden distribution in the hopper and throat.…”

Comprehensive Mathematical Model for Particle Flow and Circumferential Burden Distribution in Charging Process of Bell-less Top Blast Furnace with Parallel Hoppers

“…The research methods mainly includes lab scale experiments, [4][5][6][7] industry-scale investigations, 8,9) mathematical model studies and Discrete Element Method 10) simulations. [11][12][13][14] Among them, the mathematical model is the most fundamental which reflects the essence and mechanism of particle flow and distribution, and can be efficiently applied to predict the burden charging process.…”