Specialized metallurgical processes – compositions for use therei – Processes – Producing solid particulate free metal directly from liquid...
Patent
1996-03-25
1998-04-07
Andrews, Melvyn
Specialized metallurgical processes, compositions for use therei
Processes
Producing solid particulate free metal directly from liquid...
65 19, 425 8, C21B 308
Patent
active
057359318
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.
In our co-pending International Publication No. WO93/06250 we have described a granulator comprising an enclosure, a rotary atomiser disposed within the enclosure, and means for delivering molten material to the atomiser so that, in use, the material is broken into globules without the use of fluid jets. The globules are dispersed within the enclosure where they are at least partially frozen to form granules which are collected in an annular open-topped trough surrounding the atomiser.
The path taken by the globules from the atomiser to the open-topped trough is necessarily rather long so that the globules have time to partially freeze and form granules and so the distance from the atomiser to the outside of the open-topped trough is correspondingly long. This means that a relatively large enclosure is required to house the atomiser and the open-topped trough.
It is an object of the present invention to provide such apparatus but which is more compact than that described in the International application.
According to a first aspect of the present 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;
means providing an annular gaseous curtain with entrained granules around the atomiser and through which the greater part of the globules pass and partially freeze to form granules and an open-topped trough in which the granules are collected and from which they are removed to the exterior of the enclosure.
According to a second aspect of the present invention in a method of granulating a molten material, a stream of the molten material is delivered to a rotating atomiser disposed within an enclosure; the speed of rotation of the atomiser is such that the molten material is ejected from the atomiser in the form of globules without the use of fluid jets,
an annular gaseous curtain with entrained granules is provided around the atomiser such that the greater part of the quantity of globules ejected from the atomiser pass through the curtain which accelerates the cooling of the globules helping them to partially freeze to form granules and reduces the kinetic energy of the granules, the granules being collected in an open-topped trough from which they are removed to the exterior of the enclosure.
In use, the majority of the globules dispersed within the enclosure pass through the gaseous curtain with the entrained granules and this curtain reduces the temperature of the globules causing them to become partially frozen granules and it also reduces the kinetic energy of the granules causing the length of their flight path to be reduced. The reduction in energy of the granules allows the annular trough to be positioned closer to the atomiser than is the case where the annular gaseous curtain with entrained granules is not provided. This has the advantage that the dimensions of the enclosure can be reduced with a subsequent reduction in cost of the granulator.
The gas which is used to form the curtain is usually air and this may already have been passed through the granules previously collected in the annular trough and the already heated air is further heated by the passage of the globules therethrough raising the temperature of the air to a temperature high enough for this air exiting from the enclosure to be used, for example, for steam raising.
The air curtain may be formed at the side of the trough adjacent the atomise
REFERENCES:
patent: 5409521 (1995-04-01), Featherstone et al.
Andrews Melvyn
Davy McKee (Stockton) Limited
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