Metallurgical apparatus – Process
Patent
1988-09-20
1990-02-13
McDowell, Robert
Metallurgical apparatus
Process
222590, 222600, 266220, 266236, 266270, C22C 548, B22D 3700
Patent
active
048999920
DESCRIPTION:
BRIEF SUMMARY
The invention relates to devices and apparatus for injecting gas into high temperature liquids, e.g. molten metals.
It may often be necessary to introduce gas into molten metal in a container or vessel. Gas is injected, for instance into the bottom area of a vessel for diverse purposes, including rinsing; clearing the relatively cool bottom area of solidification products, to help remove them from the vicinity of the vessel bottom outlet where the vessel has such an outlet; equalising the temperature throughout the melt; and stirring to help disperse alloying additions uniformly in the melt. Usually an inert gas is used, e.g. argon. Reactive gases are sometimes substituted if the melt needs some particular chemical treatment such as deoxidising.
Previous gas injection proposals have included the provision of a solid porous plug or brick in the refractory lining of the vessel, and of solid porous plugs in sliding gate teeming valves. Installations featuring porous plugs have the virtue of simplicity, but are potentially hazardous, inter alia because they may crack due to thermal shock when molten metal is introduced into the vessel. Failure of the plug can obviously have extremely dangerous consequences. Sliding gate valves adapted for gas injection are safer, but unless overly complicated they are not able to offer the possibility of gas injection simultaneously with teeming.
The present invention aims to overcome drawbacks associated with prior gas injection systems, and to provide safer and more cost effective equipment for use in gas injection.
According to one aspect of the present invention, there is provided an injection cartridge, for use in injecting gas through the wall of a vessel into a high temperature liquid contained therein, the cartridge comprising an open-ended gas-impermeable sleeve blocked adjacent each of its opposite ends by a wad of fibrous refractory material and containing a filling of particulate refractory matter, the cartridge being permeable to gas flow from one end to the other and impermeable to liquid flow therethrough. Such cartridges are well able to cope with thermal shock and, in conjunction with further gas injection components, provide valuable measures of added safety to gas injection operations as will become apparent as the description proceeds.
Gas injection apparatus according to the invention can comprise a cartridge as defined in the preceding paragraph, and a refractory gas-discharge block arranged in tandem therewith, the discharge block having one end interfitting with one end of the cartridge and being porcus or foraminous to allow gas but not liquid to traverse the block.
The gas discharge block can be made of porous refractory; alternatively, it can be made of substantially gas-impermeable refractory material pierced by one or more capillary passageways.
According to another aspect of the invention, there is provided a gas injection nozzle, for installation in the wall of a vessel and for use in injecting gas into a high temperature liquid, comprising a refractory nozzle body having a passage therein and a gas porous or foraminous end portion closing the passage at a discharge end of the body, and closely fitted in the passage is a porous gas injection cartridge comprising an open-ended, gas-impermeable sleeve having upstream and downstream ends, closed adjacent each end by a compressible wad of fibrous refractory material and containing a filling of particulate refractory matter, the cartridge being permeable to gas flow from the upstream to the downstream end and impermeable to liquid flow therethrough. In the event of liquid, such as molten metal, traversing the passage-closing end portion e.g. after a failure of the latter, the cartridge can prevent a serious leakage of said liquid from the passage. Gas inlet means for conveying gas from a supply to an upstream end of the cartridge can be arranged to urge the cartridge into sealing contact with the said end portion; the cartridge and end portion can be designed to interfit one with the other.
Further ac
REFERENCES:
patent: 3373986 (1968-03-01), Spire
patent: 3971548 (1976-07-01), Folgero et al.
patent: 4575393 (1986-03-01), Bates et al.
patent: 4742995 (1988-05-01), Bates
Radex Rundschau, Heft 3, 1983, pp. 179 to 209.
Gelsthorpe John R.
Thrower Anthony
Injectall Limited
McDowell Robert
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