As of now, in the quest to intensify the iron-making process the efforts are directed to improving the blast-furnace process through optimum distribution of a gas flow over a shaft section of the blast furnace, which determines the quality of iron produced, the specific fuel consumption for its production and the blast furnace output as a whole. The uniform distribution of the gas flow over the furnace section is attained by controlling the rate of blowing and changing the layer contours of ore and coke components of the burden which is fed into a throat zone by a charging device installed on the furnace cone. Therefore, the requirements that are placed upon the charging device are to provide a desired contour of the burden layer over the furnace cross section with minimum nonuniformity in the circumferential grain-size distribution of the burden in the throat zone, and, essentially, a controlled thickness of the burden layer charged.
Conventional blast furnace charging apparatuses include a double-cone charging apparatus equipped with movable throat plates, which is disclosed in DE A 2125062.
The above apparatus for charging a shaft furnace comprises a bin having an inlet and an outlet, the bin being connected through flanges with a top portion of the furnace. The bin outlet is located in a furnace chamber, within its throat zone, and closed by a cone-shaped locking member. The locking member is adapted to move vertically. The furnace throat zone is provided with movable plates which carry distributing plates with a reflecting surface facing the bin outlet. The plates are uniformly circumferentially disposed and adapted to radially move along the guides which are rigidly fixed to the furnace shell.
In operation of the apparatus, the locking member is displaced towards the furnace chamber, and a burden is admitted through an annular gap formed to the peripheral region of the throat zone. If the blast-furnace process is disturbed, it is required to change the contour of the charged burden layer. To this end, the plates are radially displaced towards the furnace axis until they reach a position in which the path of the falling burden intersects the surface of the distributing plates, which results in altering the burden flow direction so that the burden moves towards the furnace axis. The above prior art apparatus, however, changes the contour of the burden layer charged only in the peripheral annular region due to the restricted displacement of the movable plate, which reduces the potentials of the apparatus, limiting the burden laying control only to 1/3 the furnace radius.
Most closely approaching the present invention by the combination of technical features and the achieved result is an apparatus for charging a shaft furnace, comprising a bin for a burden, the bin having an inlet and an outlet, a unit for distributing the burden over a cross section of the furnace, said unit being mounted in a throat zone beneath the bin outlet and adapted to rotate about the furnace axis. The burden distributing unit comprises a horizontal member having at least two guiding members circumferentially disposed around its periphery, each of the guiding members being connected with the horizontal member and consisting of two segments which are arranged sequentially in the direction of the burden flow. A first segment is located in the immediate vicinity to the horizontal member, and a second segment is comprised of at least two plane faces and has a burden shoot edge facing the furnace throat zone (WO Application No. 92/19776, C21B 7/20).
Owing to the design of the distributing unit, the burden body leaving the bin outlet is divided into at least two flows which form a charge layer in the throat zone with approximately even circumferential grain-size distribution. This is attained due to laying the burden pellets of the same size symmetrically about the furnace axis, thereby significantly reducing the nonuniformity of the circumferential burden weight distribution in the furnace. The uniform circumferential arrangement of the guiding members, with the first segment being disposed in the immediate vicinity to the horizontal member, makes it possible to change the radial direction of the burden flow to the circumferential one. On the guiding member second segments, the circumferential direction of the burden flow changes to the tangential one or towards the furnace axis under the effect of the resultant of frictional, centrifugal and Coriolis forces. This enables the burden to be charged to any throat region and provides the possibility to form a required stockline contour in the throat zone. This is attained by a single type of motion, in particular, by rotation of the burden distributing unit about the furnace axis. The above structural features of the charging unit provide the improvement in the blast-furnace process parameters and the reduction in energy losses. The rotary drive of the unit has a simpler structure.
In operation, a burden portion is charged from the burden bin on the horizontal member of the burden distributing unit and further along the guiding members into the furnace chamber. A burden layer is formed in the furnace throat zone by virtue of rotation of the burden distributing unit. Owing to the possibility to vary the rotational speed of said unit, the apparatus provides a desired stockline contour in the shaft furnace. This improves the blast-furnace process characteristics. However, a required stockline contour is not provided when laying the burden by the above apparatus in the region adjacent to the furnace axis, since the non-optimal spatial orientation of the plane faces of the guiding member second segment hinders the admission of a sufficient amount of material into the furnace axial region. As a consequence, the optimum gas distribution over the furnace cross section is not provided, resulting in the increased coke consumption and some reduction in the output. In addition, in the prior art apparatus the position of plane faces of the guiding members fails to be unambiguously defined which makes the manufacture of the apparatus as such problematic, and further hampers the attainment of a desired stockline contour in the furnace throat zone.