EP2748344B1

EP2748344B1 - Dry slag granulation device & method

Info

Publication number: EP2748344B1
Application number: EP12753099.6A
Authority: EP
Inventors: Ian Mcdonald
Original assignee: Siemens PLC
Current assignee: Primetals Technologies Ltd
Priority date: 2011-08-26
Filing date: 2012-08-17
Publication date: 2015-06-24
Anticipated expiration: 2032-08-17
Also published as: GB2493968B; CN103764853B; IN2014DN00174A; WO2013030016A1; CN103764853A; EP2748344A1; UA114182C2; GB2493968A; RU2627825C2; RU2014111466A; GB201114762D0

Description

This invention relates to a dry slag granulation device and a method of granulating slag.
The slag material may be metal based, such as iron; a metal oxide, such as titanium oxide; a non-metal, such as slag generated as a by-product of a metals production process; or a mixture thereof.
Dry slag granulation is a relatively undeveloped technology which uses a rotary atomiser, typically a spinning cup or dish, to convert molten slag (for example obtained as a by-product of iron making in a blast furnace) into granules, without the addition of water to cool and harden the slag. Examples of dry slag granulation apparatus and methods are given in GB2148330 , EP0605472 and EP0804620 . The molten slag from the blast furnace is supplied to a dry slag granulation device for granulation, either onto the centre of the cup, or disk, or on an annulus concentric with the centreline of the cup or disk, as in GB840632 , in order to add air to the granulate through the centre of the annulus and the rotary atomiser granulator ejects molten globules which pass through an enclosure and are partially frozen to form granules. A spray of these granules is emitted over the 360° circumference of the rotary atomiser and the granules are collected in a trough at the base of the atomiser. As a result it is difficult to install the slag granulation plant close to the blast furnace cast house, so the molten slag must be transported over a long distance before granulation and the plant has a large footprint. For a 20m diameter plant, the pouring point of the molten slag is 10m into the granulation plant.
Additionally, US5259861 discloses a method for fast solidification of particles in which the particle trajectory is adapted by changing the relative position of the various components of the device.
In accordance with a first aspect of the present invention, a directional dry slag granulation device comprises a rotary atomising granulator having a centreline axis of rotation; a slag stream feed; and a position controller; wherein a slag stream fall point on the rotary granulator for slag from the slag stream feed is offset from and non-concentric with the centreline axis of rotation of the rotary granulator.
The position controller determines a position of the slag stream feed and of the rotary granulator and adapts the position of one relative to the other, such that the slag stream falls onto the rotary granulator at a single fall point a predetermined distance from the centreline axis of rotation of the rotary granulator, non-concentric with the axis.
Preferably, the rotary granulator comprises one of a cup, disk or annulus, adapted for rotation about the centreline.
As the slag stream fall point is offset, an annulus coupled to the drive shaft, e.g. via spokes, can be used for granulation.
Although, in theory, the position controller could cause either the slag steam feed, the rotary granulator, or both to move to get the correct relative position, in practice, the likelihood of damage to the refractory lining of the slag stream feed means that, preferably, the device further comprises an actuator to move the rotary granulator with respect to the slag stream feed.
Preferably, the actuator comprises a moveable lance.
Preferably, the lance comprises a hollow guide and an air blast.
Preferably, the device further comprises sensors to determine an expected fall point of the slag stream; wherein the position controller further comprises a comparator for comparing the determined expected fall point with a predetermined fall point position and an output for outputting a signal to the actuator to move the granulator in response to the result of the comparison.
Preferably, the rotary granulator is mounted on a support.
Preferably, the support further comprises air blast vents.
Preferably, the device further comprises a deflector plate.
The deflector plate provides further control of the direction of the granulated slag.
In accordance with a second aspect of the present invention, a method of granulating slag comprises supplying a stream of slag from a slag feed to a rotary atomising granulator; determining an expected fall point position of the slag stream, the predetermined fall point being offset from and non-concentric with the centreline axis of rotation of the rotary granulator; comparing the expected fall point with a predetermined fall point for the granulator; and when the position of the expected fall point is outside an acceptable range of the predetermined fall point, adjusting the relative position of the slag feed and granulator.
Preferably, the method further comprises the controller causing an actuator to move the rotary granulator relative to the slag feed.
Preferably, the method further comprises setting the rotary granulator to a position, such that the slag stream fall point is at a distance of at least 10% and preferably between 20% and 40% of the radius of the granulator from the granulator centreline.
An example of a slag granulation device and method of operation according to the present invention will now be described with reference to the accompanying drawings in which:

Figure 1 is a plan view of a blast furnace site comparing a conventional dry slag granulation plant and a slag granulation device according to the present invention;
Figure 2 is a perspective view of a slag granulation device according to the present invention;
Figure 3 is an exploded view of part of Fig.2;
Figure 4 is a plan view from above of the device of Fig.2;
Figure 5 is a section X-X of Fig.2; and,
Figure 6 illustrates the device of the present invention in operation.

As can be seen from Fig.1, a blast furnace 1 is provided in a cast house 2. On the left hand side of this figure, the footprint of a conventional dry slag granulation plant is illustrated. A slag runner 3a supplies slag from the blast furnace to the centre 5 of a rotary atomiser granulator 6 and the granulated slag is distributed around an enclosure 4 in a 360° spread 7a. The slag runner 3a must extend over at least half the circumference of the granulation plant enclosure 4 in order that the slag falls onto the centre of the granulator, which typically means over a distance of at least 10m. Furthermore, the walls of the enclosure must be a certain distance from the rotating disk in all directions, so the footprint of this conventional granulation enclosure is large.
The present invention addresses the problems of the existing dry slag granulation plants by means of a slag granulation device 8 in which the rotary atomising granulator, e.g. a spinning disk, is adapted to broadcast over a reduced angle resulting in a substantially reduced spread pattern 7b, rather than over the full 360 degrees of the conventional device. As can be seen from Fig.1, by modifying the direction in which the granulated slag is projected, the reduced spread pattern also allows the size of the granulation device enclosure 9 to be reduced and the shape modified to a smaller rectangular enclosure. A shorter slag runner 3b can be used and may, for example, only extend of the order of 2m into the enclosure 9. A typical spread pattern in the invention is in the range of 10° to 30° and preferably no more than 20°. As a result a slag pouring point can be at, or nearer to, a side wall of the enclosure, closer to the cast house, rather than having to be at the centre of the granulator, as has been the case with all previous dry slag granulation plants.
One example of the invention is illustrated in more detail in Figs. 2 to 5, although other embodiments are possible. A rotary granulator 8, illustrated in Fig.2 as a housing 18 supporting a plate 30, which may be provided with raised sections 27, angled about a central rotatable drive shaft 16, the granulator may also be provided with cooling air vents 15 in a support 28 for the plate housing 18 and a drive shaft 16, is moveable by an actuator 12, illustrated as a moveable lance connected to the support 28. The lance 12 is configured as a hollow guide through which air blast 14 can be directed to provide the cooling air to the rotary granulator and which can also accept a second drive shaft 13 which is coupled to the drive shaft 16 to cause rotation of the rotary granulator. A slag fall spot 19 is off-set from the centreline axis of rotation 29 of the granulator plate and non-concentric with the axis and the direction of rotation 17 is indicated. If the slag were deposited in an annular fashion, then the directional control achieved by offsetting a single fall point from the centreline could not be achieved and slag granulate would be projected over 360 degrees in the same way as if it had been dropped onto the centre of the rotating disk.
The construction of the drive shaft 16 is shown in more detail in Fig. 3. The housing 18 with its plate 30 and sections 27 is mounted into a drive hub 23 by means of a coned spline 21 which fits a coned receptor 22 that fits inside the hub 23 and the hub is bolted onto a spiroid drive shaft 25 and provided with a receptor locking pin 24. A benefit of the present invention is that should the plate need to be changed during maintenance, this can be easily done by moving the lance away from the danger area and if necessary substituting with another, or changing the lance if the replacement time is likely to be longer than the time between slag batches. Use of a coned spline means that a mechanical grab arm can be used to extract the housing and plate and drop on a replacement, without the need for personnel to be in the area of the slag stream. The locking pin, if used, can also be extracted using a remote arm. From Fig.4, it can be seen that the drive shaft 16 is coupled to the second drive shaft 13 through coupling 31. The slag fall point 19 is at a position off-set from the centreline 29 of the rotary granulator disk 30.
A deflector plate 26 is provided to one side of the rotary granulator and this allows control of the directional distribution of granulated slag from the rotating disk. When the slag falls on the plate of the rotary granulator, any friction between the slag and the plate causes the slag to move to the edge of the plate. To prevent the slag simply pooling at the fall point, the raised sections assists this process. If the process works correctly, the deflector plate is not required. However, the advantage of the deflector plate is that it acts as a back wall, so that any granulated slag which does not go in the correct direction will land on the deflector plate and if required, the complete lance, granulator, deflector can be removed for cleaning, rather than having to send personnel into the enclosure to clean it..
As further illustrated in Fig.6, the present invention allows the disk 30 fitted to the lance 12 to be moved in and out of the stream of slag 11, to ensure that the slag falls onto the rotary atomising granulator at a point 19 which is offset from the centre line 29 of the disk, thereby ensuring a constant direction of throw. By having a controlled distribution direction, the walls of the enclosure can be brought inwards through the area where granulated slag will not be distributed, resulting in a significant reduction in the overall size of the granulator enclosure.
The precise direction and spread of the granulated slag in the present invention is dependent upon the distance from the centre line of the slag fall spot. In order to maintain a constant direction of discharge, the cup rotational speed may be changed. Typically, the speed is between 800 and 2000 rpm.
Fig.6 illustrates a simplified example of how the rotary granulator on the lance can be moved to adjust the position of the disk and hence the fall spot, relative to the outlet of the slag runner 3b. In a first position 8a, the slag from the slag runner falls onto a fall spot away from the centreline 30a. However, if the position sensor 32 shows that the slag stream is falling further from the end of the slag runner and closer to that centreline 30a, then the position sensor 32 picks up this change and sends data back to a position controller 33 which adapts the position of the disk 30 by causing an actuator to move the lance to position 12b and the disc to position 8b, with its centre at position 30b. If the slag stream moves even further away out from the end of the slag runner, then the controller causes the actuator to move the lance away again to position 12c and the disk to position 8c, with its centre at position 30c. This example has been simplified, but clearly the actuator may need to move the lance and disk laterally to some extent, as well as directly away from the end of the slag runner, in order that the fall point 19 is correctly positioned for the slag stream as it falls on the disk.
In operation, the stream of slag is fed from a slag feed to the rotary atomising granulator and the controller determines, from the data provided by the position sensor, an expected fall point position of the slag stream. A fall point on the granulator to obtain a desired direction of throw and spread pattern can be stored as part of a set-up process, or entered during the granulation process. As well as the fall point, a range of tolerance either side of this position may be set. Using the data received and processed by the controller, the comparator may compare the expected fall point with the predetermined fall point for the granulator and the tolerance applied to determine whether the position of the expected fall point is acceptable. If the expected fall point falls outside the acceptable range, then the relative positions of the slag feed and granulator are adjusted. Typically, this means that the granulator is moved, rather than the slag feed.
The disks shown in Figs. 2 to 6 are disks mounted on the drive shaft 16. The disks may be continuous across the top of the drive shaft, or formed as annular disks with a sleeve fitting over the drive shaft and spokes joining the sleeve to the annulus. The form of the disk or annulus may be substantially flat with baffles on the surface, or concave. The choice of position of the fall point depends upon slag flow, but a slag runner spout position giving a fall point of the order of one third of the distance from the centreline to the circumference of the disk is effective.
The examples have been described with respect to a device with an actuator in order to modify the position of the fall point in response to sensed data about the actual fall point, but the invention does not exclude a simplified embodiment in which the rotary atomising granulator is positioned at start-up with an expected fall point that is offset from the centreline axis of rotation of the disk, without having the feedback and in-use adjustment of position of the preferred embodiment.

Claims

A directional dry slag granulation device, the device comprising a rotary atomising granulator having a centreline axis of rotation; a slag stream feed; and a position controller; wherein a slag stream fall point on the rotary granulator for slag from the slag stream feed is offset from and non-concentric with the centreline axis of rotation of the rotary granulator;wherein the rotary granulator comprises one of a cup, disk or annulus, adapted for rotation about the centreline; and wherein the device further comprises sensors to determine an expected fall point of the slag stream; wherein the position controller further comprises a comparator for comparing the determined expected fall point with a predetermined fall point position and an output for outputting a signal to the actuator to adjust the relative position of the slag feed and granulator in response to the result of the comparison.
A device according to claim 1, wherein the device further comprises an actuator to move the rotary granulator with respect to the slag stream feed.
A device according to claim 2, wherein the actuator comprises a moveable lance.
A device according to claim 3, wherein the lance comprises a hollow guide and an air blast.
A device according to any preceding claim, wherein the rotary granulator is mounted on a support.
A device according to claim 5, wherein the support further comprises air blast vents.
A device according to any preceding claim, wherein the device further comprises a deflector plate.
A method of operating a directional dry slag granulation device, the method comprising supplying a stream of slag from a slag feed to a rotary atomising granulator of the device; determining an expected fall point position of the slag stream; comparing the expected fall point with a predetermined fall point for the granulator, the predetermined fall point being offset from and non-concentric with the centreline axis of rotation of the rotary granulator; and when the position of the expected fall point is outside an acceptable range of the predetermined fall point, adjusting the relative position of the slag feed and granulator.
A method according to claim 8, wherein the method further comprises the controller causing an actuator to move the rotary granulator relative to the slag feed.
A method according to claim 8 or claim 9, the method comprising setting the rotary granulator to a position, such that the slag stream fall point is at a distance of at least 10% and preferably between 20% and 40% of the radius of the granulator from the granulator centreline.