Improved Charging Device for Blast Furnace

The present invention concerns a device and method for distributing material during the charging of a blast furnace.

It is well known that, when charging a blast furnace, it is desirable to distribute the charging material evenly or according to a chosen pattern. To this end, charging arrangements are know in the prior art in which material is directed into the blast furnace via a movable spout.

WO2006056350 discloses a system in which the charging material enters the furnace through a conical conduit suspended on gimbals. By this arrangement, the orientation of the conduit may be varied allowing distribution of the material within the furnace and more even wear on the internal surfaces of the conduit.

The object of the invention is to provide a conduit for charging blast furnaces which offers improved material flow and trajectory characteristics.

According to the invention, a conduit for charging a blast furnace comprises the features set out in claim 1 attached hereto.

The invention will now be described by non-limiting example with reference to the following figures in which figure 1 shows a conduit for charging a blast furnace according to the prior art and figures 2 - 4 show various embodiments of a conduit for charging a blast furnace according to the invention.

Referring to figure 1 , a conduit 1 for charging a blast furnace (not shown) according to the prior art has a substantially frusto-conical profile. During operation, the conduit is inclined according to a desired trajectory of material entering the furnace. The charging material falls into the conduit, strikes the inner surface of the conduit at a point 2 and travels along its wall under gravity in a path indicated by the arrows.

It will be apparent to those skilled in the art that the trajectory of material entering the furnace increases with the angle A, between the direction of the material on exiting the funnel and the vertical 3, up to a limit dependant on the charge material properties and conduit construction. The trajectory also increases with the velocity of the material on exiting the funnel.

The angle A is determined by (equals) the angle B between the vertical and the side 4 of the conduit along which the material travels (B depends on the cone angle and the degree of inclination of the cone).

However, while the angle A increases with B, the velocity of material entering the furnace decreases because, as B increases, the material is slowed down to a greater degree on striking point 2 and because its subsequent path along the inner surface of the conduit is along a slope of lesser gradient.

Hence the maximum trajectory obtainable is given by an optimum value of B having regard to these two conflicting effects.

Referring to figure 2, one example of a conduit for a blast furnace according to the present invention includes two substantially frusto-conical sections 5 and 6 providing for two angles, B and C between surfaces 4, 7 of the conduit along which material passes (or their projection), and the vertical 3.

This provides for a 'Ski Jump' effect whereby charging material travels through the major part of the conduit section 6 with minimal impedance due to a smaller deflection at point 2 and a steeper slope along surface 7 and then, after a further deflection at point 8, exits the conduit at a greater angle A defined by the angle B between surface 4 and the vertical 3.

It can be shown that, as the number of conduit sections is increased, the trajectory of the charge material is improved for any given end angle, up to the limiting example in Figure 4.

In figure 2, section 6 is shown as a frustro cone having a smaller cone angle than section 5. In the extreme, section 6 could be cylindrical.

The region around point 2 in figure 2 is an area of increased wear on the conduit and the same is true of the region around point 8 when section 6 is not cylindrical. Figure 3 illustrates how this wear can be reduced or spread by increasing the number of frusto- conical sections in the device. In the example shown, three sections 5, 6 and 9 give rise to three changes in direction of the charging material at points 2, 8 and 10 respectively. It will be apparent, however that further increasing the number of frusto-conical sections will further distribute the wear along the surface of the conduit.

Figure 4 illustrates the limiting example where the profile of the conduit surface is a curve and the direction of the charging material changes continuously from a first direction forming a relatively small angle C with the vertical and a second direction forming a relatively large angle with the vertical.

In addition, the conduit is preferably mounted on gimbal or other type of universal joint which allows the conduit to be directed towards different areas of the blast furnace without rotation (of the conduit). This arrangement provides for a more evenly distributed wear pattern around the internal surface of the conduit.