Solid material comminution or disintegration – Processes
Patent
1997-05-01
1999-06-29
Rosenbaum, Mark
Solid material comminution or disintegration
Processes
241 20, 241 2413, 241301, B02C 1918
Patent
active
059156341
DESCRIPTION:
BRIEF SUMMARY
The present invention is related to a method and a device for separating harder from less harder substances, according to the preamble of the claims.
Known methods for extracting metal from slag and waste containing magnesium and aluminium, or for separating corresponding combinations of material compositions are technically complicated, very often environmentally demanding and consequently costly.
Magnesium metal is for example recovered from magnesium sludge which is moulded into blocks or filled on steel barrels when still in the melting phase and which contain magnesium in a matrix of salts and oxides. It is common to crush the blocks in several steps and simultaneously pick metal manually and also to screen the metal, whereby the residual sludge is removed from the process for final deposing or used in other connections. The process need huge mechanical units, independently of the need for capacity, to treat the material. Simultaneously relatively small amounts of magnesium sludge is generated at the different plants. Of this reason very few central plants in the world are performing recovering, hence the transport costs to such plants may be expensive, due to the distance and also because there are strong regulations connected with transport and packing of the magnesium sludge.
The process develops dangerous and troublesome gases which must be controlled. Additionally, the strongly hygro-scopical properties makes that for dry treatment of magnesium sludge there are quite specific demands for the choice of crushing and screening equipment as well as to the conveyors and equipment for treatment of dust and gases.
Many plants are depositing or until recently they have deposited, the sludge, as the cheapest and most convenient solution. As the environmental regulations have been sharpened more and more industrialized countries now have forbidden such depositing.
Another example is recovering of aluminium metal from white dross, being as today performed by circumstantial and expensive methods. The first step in the treatment of dross cooled in pans, normally is a mechanical concentration through several crushing steps, with screen separation of the metallics from the non-metallics. Concentrates of approximately 60-70% aluminium metal is achieved before transportation for melting to a rotary salt furnace. By cooling the dross in pans it is, however, calculated with a metal loss of approximately 1% aluminium metal per minute in the initial cooling period after the skimming has been performed.
Cooling drums have in the latest ten years increasingly been used as substitute for the pan-cooling. Hereby is rapid cooling achieved and less burning of the metal grains. Dross from cooling drums have 35-60% aluminium.
Dross which is cooled in a drum is easy to handle but has the disadvantage that is not easily can be concentrated substantially in a crushing or sieving plant because the cooling method tangles metal and oxides in such a way that direct treatment in a rotary salt furnace becomes the inevitable next production link.
The rotary salt furnace process is expensive and harmful to the environment as it produces substantially the same amount of refuse as the dross concentrate input. A dross having 50% aluminium and 50% oxides claims 50% salt additives or the same amount of salt as the non-metal portion of the dross.
Deposition of salt cake refuse has developed to be a large problem in several industrialized countries as the salt solution penetrates into the ground and pollutes the subsoil water. Recovery plants for salt are constructed in several countries, but the salt from the recovery is more expensive than new salt. Nevertheless, the secondary smelters in such countries are forced to deliver, and to pay a tonnage fee for delivered salt cake. Moreover, they are forced to buy the expensive salt back again.
Lacks and negative sides by existing processes have initiated substantial efforts to simplify the same or develop new processes, so far this has not led to results which are in practical use.
The above ment
REFERENCES:
patent: 4662893 (1987-05-01), McIntosh
patent: 4986479 (1991-01-01), Swarden et al.
patent: 5115983 (1992-05-01), Rutherford
patent: 5234172 (1993-08-01), Chupka et al.
A.F. Taggart, Handbook of Mineral Dressing: Ores and Industrial Materials, John Wiley and Sons, Inc., New York, 1947, Section 10, Articles 1 and 2, pp. 10-01 to 10-03.
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