LU88380A1 - Granulation process and device - Google Patents

Description

GRANULATION PROCESS AND DEVICE

The present invention relates to a liquid slag granulation process in which a flow of liquid slag is made to fall on a jet of water under pressure.

The present invention also relates to a device for implementing this method.

There are currently several methods and devices for granulating blast furnace slag by injecting a stream of granulation water into a stream of molten slag. The granulation water is, in general, injected into a slag flow which is substantially in free fall by means of a granulation head. Generally, the slag is brought directly from the blast furnace by a channel, one end of which is located above the injection head. The water jet from the granulation head disintegrates the slag flow during its fall and granules of various sizes are formed. The granules thus formed and the granulation water are transported by means of a channel into a cooling tank. The granules are then evacuated from the basin then dried and stored before use.

However, the use of these systems has shown that there is a danger of explosion due to the formation of hydrogen on contact with water with the molten slag. Also there is the formation of hydrogen sulfide which presents a nuisance for people working living near such facilities.

The object of the present invention is to make the slag granulation safer and more efficient.

This object is achieved by a slag granulation process in which a slag stream, brought into a channel, is dropped onto a pressurized water jet characterized in that the end part of said channel is enlarged, flattened and present a more marked inclination than the channel and in that the slag flow is accelerated and spread out in a thin layer by crossing the terminal part of said channel.

In the context of the present invention, it has been shown that the slag flow effectively spreads out and occupies the entire width at the end of the channel since it was thought until now that a product of the consistency of the slag in fusion could not spread out to occupy the entire width of the terminal part of the channel in such a short path.

One of the main advantages of the present invention is that the slag flow forms a thin layer before being disintegrated by the water jet. The water jet therefore more easily disintegrates the slag flow. The granules formed are cooled more quickly and solidify almost instantaneously, at least on their surface.

In this way the quantity of hydrogen and hydrogen sulphide formed is lower because these two products are formed especially on contact with water with slag in the liquid state.

As the slag layer to be disintegrated is thin, the strength of the granulating water jet can be weaker compared to that of a traditional installation. The granulation water pumps and pipes can be reduced in size and therefore less expensive.

According to a first advantageous embodiment, the mixture of granulation water and of granules formed are injected directly into a cooling tank. It is not, as seen in most traditional systems, discharged into a channel which brings it, at the end of the journey, into a cooling basin. The granules are consequently cooled more quickly because they fall immediately into a large volume of cold water.

According to another preferred embodiment, the inclination of the water jet is adjustable around a horizontal axis. This makes it possible to choose the point of impact of the mixture of granules and granulation water in the cooling basin. It has been found, in the context of the present invention, that if the point of impact is distant, that is to say if the inclination of the jet is almost horizontal, the particle size of the product obtained is finer than if the impact point is closer to the granulation head, i.e. if the inclination of the jet is almost vertical downwards.

The present invention also includes a device for implementing the method.

The device according to the present invention comprises a channel for supplying molten slag, a granulation head, situated below the level of the channel, which is connected to a supply of granulation water characterized by a terminal part of the enlarged channel, flattened and presenting a more marked inclination than the channel.

According to a first embodiment, the angle of inclination is between 5 ° and 30 °. Preferably the angle is between 10 ° and 25 ° and optimally between 12 ° and 18 °.

According to another preferred embodiment, the granulation head is fixed in a tiltable manner on a horizontal axis. The inclination of the head can therefore be adapted as a function of the particle size which it is desired to obtain since the particle size of the product can be influenced by varying the distance between the granulation head and the point of impact of the water mixture and granules in the cooling tank.

In fact, it has been observed in the context of this invention, that if the point of impact is distant from the granulation head, that is to say if the granulation head is horizontal, the particle size of the slag is fine . If the point of impact of the pulp, i.e. the mixture of granules and granulation water, is closer to the granulation head, i.e. if the granulation head is the more inclined downwards, the particle size of the product obtained becomes coarser.

It is therefore possible to influence the particle size of the product obtained by modifying the angle of inclination of the granulation head.

The cooling basin preferably comprises a flat bottom, a drain and an overflow. Water is injected at high speed into the basin, below the water level and near the point of impact of the granulated slag. The turbulence created by the injected water contributes to the accelerated cooling of the granules by keeping the granules in suspension and preventing them from forming a more or less compact heap below the point of impact. This avoids the risk of explosion which results from trapping water in a pile of granules still hot.

Preferably the flat bottom of the basin is equipped, at regular intervals, with tongues or protuberances. In this way, the granules form a layer whose thickness is approximately equal to the height of the tongues and protect the bottom of the basin against abrasion due to the granules in suspension.

It is obvious that the present invention can also be used to granulate other molten products such as copper matte, slag, etc.

Other particularities and characteristics will emerge from the detailed description of an embodiment presented below, by way of nonlimiting example, with reference to the appended drawings in which: Figure 1 shows a general diagram of an installation granulation; - Figure 2 shows a longitudinal view of the channel which brings the slag into the granulation plant; - Figure 3 shows a cross section along the plane A-A of Figure 2; - Figure 4 shows a cross section along the plane B-B of Figure 2; - Figure 5 shows a top view of the channel.

In FIG. 1, we recognize at 10 the granulation installation comprising a chimney 14, a channel 18 which brings the slag 22, a granulation head 26 and a cooling basin 30. The basin 30 comprises a nozzle 34 for injecting water, a drain 38 protected by a grid to evacuate the granules and an overflow 42.

The slag 22 is brought from a blast furnace into the granulation installation 10 by a channel 18. In the terminal part 46 the flow of slag 22 is accelerated and spread out in a thin layer which falls in free fall towards the cooling tank 30. During its fall, the slag layer 22 is disintegrated by a powerful jet of water 50 coming from the granulation head 26. The slag granules formed during the disintegration of the thin layer of slag fall directly into the basin 30 where they cool very quickly. By the nozzle 34, a powerful stream of water is injected into the basin 10. The granules are kept in suspension for some time by the turbulence created by the stream of water and are finally evacuated by the drain 38 towards a dewatering installation. .

The granulation head 26 comprises a horizontal axis 54 around which the head 26 can pivot. The distance between the head 26 and the point of impact of the mixture of water and granules on the surface of the cooling tank 30 can be varied by changing the inclination of the granulation head 26. By bringing the head 26 closer to the horizontal , this distance increases and the granules formed will be finer. By bringing the inclination of the head 26 towards the vertical, downwards, the distance between the head 26 and the point of impact decreases. The granules formed will be coarser.

Injecting water at high speed below the surface into the cooling tank prevents the granules from settling below the point of impact, forming a more or less dense heap. This avoids the risk of explosion which results from trapping water in a pile of granules still hot.

The turbulence created in the tank 30 increases the cooling rate of the granules and contributes to transporting the granules in the direction of the drain 38 from where they will be evacuated.

The flat bottom of the tank is provided with tabs 58 at regular intervals, extending over the entire width of the basin. A layer of granules, the thickness of which is approximately equal to the height of the tongues, forms on the bottom of the basin. This layer of granules protects the bottom of the basin against abrasion by moving granules.

FIG. 2 shows a longitudinal view of the channel 18. In this figure we have clearly seen the accentuated loss of the terminal part 46.

Figure 3 shows a cross section through the first part of the channel 18 according to the plane A-A of Figure 2. The channel 18 comprises a channel 62 through which the slag 22 flows. The channel 62 is formed in suitable refractory material 66 which is located in a box 70 of refractory steel.

Figure 4 shows a cross section through the end portion 46 of the channel 18 along the plane BB of Figure 2. We see that the channel 62 is significantly wider and that the slag layer 22 is significantly thinner than Figure 3. The fact that the slag layer is thinner at the time of its disintegration by the water jet 50 from the granulation head 26, increases the safety of the installation. Indeed, the more the layer is thin, the more the risks that the water is trapped inside the molten slag are reduced, if water was trapped inside the liquid slag, this layer s would instantly evaporate and an explosion would occur.

Figure 5 shows a view from the top of the channel 18 and the end portion 46. It can be seen that the channel 62 in the end portion 46 gradually widens.

Claims (11)

1. A method of granulating slag in which a slag flow (22) is brought into a channel (18), on a jet of water (22) under pressure, characterized in that the end part (46) of the channel (18) is widened, flattened and has a more marked inclination than the channel (18) and in that the slag flow (22) is accelerated and spread out in a thin layer by crossing said end portion (46) of the laughs (18). 2. Granulation method according to claim 1, characterized in that the mixture of granulation water (50) and of granules formed are injected directly into a cooling tank (30). 3. Granulation method according to any one of claims 1 or 2, characterized in that the inclination of the water jet is adjustable around a horizontal axis (54). 4. Granulation method according to any one of claims 2 to 3, characterized in that water is injected at high speed below the level of the cooling tank (30) near the point of impact of the mixture granulation water and granules formed. 5. Device for implementing the method according to claim 1 comprising a channel (18) for bringing molten slag, a granulation head (26) located below the level of the channel (18) which is connected to a granulation water supply, characterized by an enlarged and flattened end portion (46) of the channel (18) and having a more marked inclination than the channel (18). 6. Device according to claim 5, characterized by an angle of inclination of the end portion (46) of the channel (18) between 5 ° and 30 °. 7. Device according to claim 6, characterized by an angle of inclination of the end portion (46) of the channel (18) between 10 ° and 25 ° and preferably between 12 ° and 18 °. 8. Device according to any one of claims 5 to 7, characterized in that the granulation head (26) comprises a horizontal axis (54) around which the granulation head (26) is tiltable. 9. Device according to any one of claims 5 to 8, characterized by a granulation tank (30) into which is directly poured the mixture of granulation water and granules. 10. Device according to claim 9, characterized by a cooling tank (30) with a flat bottom comprising a water injection nozzle (34) located below the water level and near the point of impact of the mixed. 11. Device according to claim 10, characterized by tongues (58) or protuberances at regular intervals on the bottom of the cooling tank (30).