Solid material comminution or disintegration – Processes – With classifying or separating of material
Patent
1995-05-22
1996-09-24
Husar, John M.
Solid material comminution or disintegration
Processes
With classifying or separating of material
241 29, 2411522, B02C 904, B02C 2308
Patent
active
055582796
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
Spent potlinings are carbonaceous products resulting from the demolition of the lining of the walls and bottom of the electrolytic pots which constitutes the cathode. This lining wears out and deteriorates and it is necessary to replace it periodically by a new lining. The lining-demolition operation, called unlining, is carried out by means of pneumatic tools and gives large-size lumps which may contain inclusions of metals such as iron and aluminium. Next, these lumps are reduced, by conventional means, to a size allowing them to go through a more or less 400 mm square-mesh grate.
2. Description of the Prior Art
Spent potlinings are strongly impregnated with noxious products, fluorides and cyanides for example. Up to now, they have been tipped in waste dumps, but the new regulations about pollution and environmental protection make it an obligation to treat them, e.g. to calcine them, in order to eliminate the noxious products and, possibly, to recover carbonaceous constituents.
The invention relates more particularly to the aluminium smelters in which the spent potlinings must be reduced into pieces not bigger than a few millimetres in size before being treated, and is concerned with a process and a grinding plant permitting to reach this result with only two size reduction stages and a screening operation.
SUMMARY OF THE INVENTION
The process forming the subject of this invention is characterized in that it includes a crushing operation in which the spent potlinings are reduced into pieces not bigger than 50 mm, a screening operation permitting to separate those grains measuring a few millimetres and constituting the finished product, and a grinding operation permitting to reduce the screen oversize to the finished product dimensions. Preferably, all the grains of the finished product shall be smaller than 2.5-3 mm. The products of the grinding operation may be recirculated to the screen.
The plant for embodying the invention is characterized in that it includes a crusher, a screen with an opening size corresponding to that of the finished product, a vibrating cone mill, means to convey the products discharged from the crusher, and possibly those discharged from the mill, to the screen and means to recirculate the screen oversize to the mill inlet.
The vibrating cone mill is a mill in which the cone or the bowl is set vibrating, and the other part, bowl or cone, of the mill is stationary or moving. Mills of this type are capable of high reduction ratio as compared with conventional cone mills the movements of which are controlled by an eccentric.
The crusher can be a jaw crusher whose jaws form with each other an angle below 20.degree.. This reduced angle improves the ability to grip products reputed to be soapy as spent potlinings are.
A peripheral discharge autogenous or semi-autogenous mill can be substituted for the jaw crusher.
BRIEF DESCRIPTION OF THE DRAWINGS
Other features of the invention will be brought to the fore by the following description which refers to the drawings appended thereto which show, as a non-limiting example, two embodiments of the invention. In which:
FIG. 1 is a diagram of a spent potlining grinding plant designed according to the invention;
FIG. 2 is a vertical section of a vibrating cone mill; and
FIG. 3 is the diagram of another plant in conformity with the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The plant shown in FIG. 1 consists basically of a feed hopper 10, a jaw crusher 12, a vibrating cone mill 14, a screen 16, two endless belt conveyors 18 and 20, an elevator 22, a dust collecting filter 24 and a silo 26.
Hopper 10 is provided with a vibrating feeder 28 permitting to load the lumps contained in the same onto conveyor 18 which feeds crusher 12. Magnetic separators 30 and eddy-current separators 31, which permit to eliminate the iron scraps and other metal pieces, are mounted on conveyors 18 and 20 and/or at their discharge point.
Crusher 12 is a single toggle jaw crusher. It is a conventio
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patent: 4113832 (1978-09-01), Bell et al.
patent: 4765546 (1988-08-01), Stewart
patent: 4889289 (1989-12-01), Lohnherr et al.
patent: 5462234 (1995-10-01), Patzelt et al.
patent: 5505389 (1996-04-01), Sussegger et al.
FCB
Husar John M.
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