Specialized metallurgical processes – compositions for use therei – Processes – Producing solid particulate free metal directly from liquid...
Patent
1994-03-02
1995-04-25
Kastler, Scott
Specialized metallurgical processes, compositions for use therei
Processes
Producing solid particulate free metal directly from liquid...
75333, 425 8, C21B 308
Patent
active
054095212
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a method of, and apparatus for, granulating a molten material. The material may be a metal, 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. The invention is particularly applicable to the granulation of slag tapped from an iron blast furnace. The granulated slag can be used as a Portland cement substitute in the manufacture of concrete.
GB-B-2148330 discloses an apparatus and method for the granulation of slag. The granulator includes a rotary atomiser located within an enclosure. The base of the enclosure is in the form of a hopper containing a fluidised bed. In use, a stream of molten slag is poured on to the atomiser which is rotated at a speed such that the slag is ejected from the atomiser as a sheet or ribbon. Air jets from nozzles surrounding the atomiser impinge upon the sheet or ribbon and break it up into granules and impart an upward motion to them. The granules then fall towards the base of the enclosure where they pass through a countercurrent stream of secondary air and then enter into the fluidised bed.
This apparatus and method suffer from the disadvantage of the need to provide the air jets which impinge upon the sheet or ribbon to break it up into granular form. A considerable input energy requirement is necessary to provide air jets of sufficient force to break up the sheet or ribbon of slag and provide upward motion to the granules.
It is known from DE-A-2211682 to use an atomiser which includes a rapidly rotating plate to granulate molten slag without the necessity of employing air jets to break up the slag ejected from the rotating plate. In the disclosure of this German patent application, a substantially horizontal refractory-lined plate is rotated about a vertical axis in an enclosure. A stream of molten slag is poured on to the rotating plate and it is flung off the plate in the form of droplets. The droplets impinge against an inner wall of the enclosure and roll alarm a conically converging lower part of the wall to an exit point below the atomiser.
It is considered that this form of granulator is unreliable because it depends on the granules rolling down the inner wall of the enclosure to the exit point. If some granules stick to the wall, they prevent others from rolling down the wall and a build up of hardened granules on the wall soon occurs.
An object of the present invention is to provide a method of, and apparatus for, granulating molten material in which the disadvantages of the prior art arrangements are overcome.
According to a first aspect of the invention, a granulator comprises an enclosure; a rotary atomiser disposed within the enclosure; means for delivering molten material to the atomiser so that, in use, the material is broken into globules without the use of fluid jets and the globules are dispersed within the enclosure; an annular open-topped trough surrounding the atomiser to collect the granules formed from the at least partially frozen globules; and means for injecting gas into the trough to induce a circumferential movement of the granules in the trough towards at least one exit from the trough.
The trough surrounding the atomiser collects and cools the granules, forming a mobile bed of granulate in the process. The circumferential motion of the bed is brought about by gas, normally air, which is injected at a small angle to the horizontal into the bed through a slotted plate or gas distributor. The granulate bed moves circumferentially around the trough to one or more exits from the trough.
Granulation may start with no material in the trough, in which case a granulate bed is gradually built up, or a bed of cooled granulate from a previous run may be left in the trough to assist in the cooling process. The motion of the bed serves to encourage heat transfer between hot granulate and the injected gas and between hot and cold granulate. In addition, the bed motion acts to prevent re-agglomeration of the granules.
The desig
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Featherstone William B.
Macauley Derek
Davy McKee (Stockton) Limited
Kastler Scott
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