Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
  • C22B9/00—General processes of refining or remelting of metals; Apparatus for electroslag or arc remelting of metals
  • C22B9/02—Refining by liquating, filtering, centrifuging, distilling, or supersonic wave action including acoustic waves
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
  • C22B7/00—Working up raw materials other than ores, e.g. scrap, to produce non-ferrous metals and compounds thereof; Methods of a general interest or applied to the winning of more than two metals
  • C22B7/001—Dry processes
  • C22B7/004—Dry processes separating two or more metals by melting out (liquation), i.e. heating above the temperature of the lower melting metal component(s); by fractional crystallisation (controlled freezing)
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P10/00—Technologies related to metal processing
  • Y02P10/20—Recycling

Definitions

• the invention relates to a method for separating a hypo eutectic molten alloy comprising a base metal A and an alloying element B into two melts, namely a melt comprising solely A and a melt comprising an alloy enriched with B in an amount up to the eutectic composition.
• the method according to the invention is particularly suitable for use when refining metal with respect to elements more noble than the metal in question, the elements forming with the metal a eutectic, preferably a eutectic of relatively low melting point, and being present in the metal alloy in amounts smaller than those which correspond to the eutectic composition.
• noble elements cannot be separated from metals by oxidation, which is otherwise a simple method of separation much used when refining iron and non-ferrous materials. Consequently, when refining metals in order to recover the noble elements contained therein, it is necessary to find other, more sophisticated methods. Some of these methods are based on separating crystals from molten baths by cooling.
• those crystals separated from a hypoeutectic melt of a metal alloy contain less of the alloying metal, and thus afford a possibility of purifying the base metal or of concentrating the alloying metal in a molten bath, up to the eutectic composition.
• the process is repeated until there is obtained a eutectic lead-silver-alloy containing about 2.5% silver, from which the silver can be recovered in a pure form after driving off the lead.
• the lead crystals, wliich are of a purer quality, are melted down and treated in a simple manner, and the process is repeated a number of times to obtain a lead which is free from silver.
• This process is extremely uneconomic and impracticable, because of the large quantities of energy consumed and the large work force required. Consequently, the Pattison process has long been abandoned in favour of the Parke s process for desnlvering lead, in which process zinc is added to the molten bath.
• This process is also particularly compli cated and difficult to adapt to present day requirements with regard to productivity and a healthy working environment.
• Zone refining is another example of the use to which the aforementioned principle can be put.
• a melted zone is caused to pass slowly along a length of solid metal.
• a pure metal is constantly separated on the side of the zone where the metal solidifies, while substantially all the impurities remain In the molten zone and accompany the zone as it moves along said length of metal.
• the crystals therefore contain less of the alloying metal B than the earlier separated crystals of composition s 1 .
• the reaction course taken will be the same as that taken previously, to pro vide crystals of composition s 3 .
• the crystals will e-yentually comprise pure A and can be removed from the system at the temperature t a , either as a solid phase or a liquid phase, since the surrounding melt also comprises pure A.
• the bath residue can be treated in a corresponding fashion.
• the bath residue can be brought into contact with crystals of composition s 12 , and having a temperature of t 12 .
• the R-content l 12 of the bath must be slightly higher than l 1 . This procedure can also be repeated a number of times, such that the bath constantly obtains equilibrium with, crystals successively richer in B, until the bath, finally obtains the- desired B-content, which at most can correspond to the composition of the eutectic; the temperature falling, at the same time, to the lowest melting point t eut of the eutectic.
• the end products can be taken out at respective ends of the vessel.
• the flow of alloy to the vessel must take place at that location in said vessel where theraelt has a corresponding composition.
• gravity as the driving force for moving the crystals, it should be possible when applying the theoretically proposed principles discussed above, to carry a smooth, continuous method into effect in a simple and ready fashion, since metal crystals separation from the melt are normally heavier than the mother raelt. It is also possible to maintain with ease a downwardly decreasing temperature gradient, for exaraple in a cylindrical crucible having a vertical axis. When the crystals fall to the bottom of the crucible, the melt should be displaced upwardly therein.
• the method is disclosed in the US patent publications US,A, 4043802, 4 133 517 and 4 138 247.
• An object of the invention is to provide a method in which the aforementioned disadvantages are eliminated.
• the invention proposes a method of separation in which the movement of the crystals, their growth and the quantity in whi ch they are formed can be controlled by moving the crystals mechanically through the melt.
• the method according to the invention is characterized by the procedural steps set forth in the accompanying claims.
• an important characteristic of the invention resides in effecting separation in an elongate reactor vessel in which the melt can be cooled internally, i.e. not through the walls of the reactor vessel, and the crystals are moved mechanically in a desired direction and at a desired speed.
• the crystals are caused to form on a substrate comprising a bunch of narrow pipes through- passed by a temperature-controlling medium.
• the melt is located in an elongate, preferably horizontal reactor vessel, and one end of the melt is maintained at a temperature t A and the ottier end of said melt at a temperature t B by supplying heat from without, with a uniform terapera ture fall within the vessel.
• the invention will be described in more detail hereinafter with reference to a preferred .embodiment employing bunches of pipes for cooling the melt and transporting the crystals.
• the pipe bunches are caused to move through the melt or bath in a direction away from the colder end to the warmer end.
• By adjusting the surface temperature of the pipes for example by passing different, adjusted flows of coolant therethrough, there is formed a thin coating of crystals on the surface of the pipes.
• the remainder of the process is similar to that described in the introduction.
• a given portion of the pure A-metal must be allowed to flow back at the warmer end, in order to obtain a back-flow of melt in counterflow to the crystals.
• the invention also affords the advantage whereby the crystals can be maintained at a temperature slightly beneath the temperature of the melt, owing to the fact that the temperature of the pipe bunches can be controlled and regulated.
• the crystals will always be surrounded by a melt whose equilibrium solidus has a slightly lower B-content than the crystals, causing the melt to dissolve metal, preferably B-metal, from the crystals. Because the crystals are maintained at a temperature which is slightly lower than the temperature of the melt, a further quantity of metal poor in B will be separated from the melt, this quantity corresponding to the amount dissolved from the crystals.
• This back-flow should be at least 20% of the amount of metal advanced in crystal form, which means that it is not possible to enrich a metal more than five times.
• a preferred embodiment of the invention carried out in a reactor vessel having the form of a circular trough for refining lead with respect to silver will be discussed hereinafter in detail with reference to Figure 2, whi ch is a schematic top-plan view of a horizontal trough.
• the molten bath of silver-containing lead, heated to an equilibrium temperature t, for separating crystals of composition s 1 is introduced into a trough 1, as shown by the arrow labelled " ING.Pb,t 1 o C
• Located in the trough 1 is a bath 2 of molten lead.
• the temperature of the bath 2 is controlled and regulated by means of heating elements (not shown), connected to the trough, such that the temperature at one end 3 of the-trough 1, called the colder end, is about 305° C, while the temperature at the other, warmer end 4 of the trough is somewhat higher than the melting point of lead, namely about 328°C, said trough ends being mutually separated by a bath-impermeable heat-insulating partition 5.
• the temperature between the ends 3 and 4 is controlled so as to obtain a substantially linear temperature gradient therebetween.
• Crystals of composition s 1 corresponding to the solidus at at temperature t 1 are separated from the bath onto a cooling means 6, having, for example, the form of a suitable helical metal pipe, which is moved continuosly or intermittently around the trough towards the warmer end 4, as indicated by the arrow 7.
• a coolant such as air, is passed to the helical pipe through stationary, flexible supply means 8a, 8, 9.
• stationary, flexible supply means 8a, 8, 9 Although only the cooling means 6 are shown, it will be understood that a greater number of such cooling means are distributed over the entire periphery of the trough in substantially uniform spaced relationship.
• the cooling means 6 When a cooling means 6 reaches the warmer end 4, the cooling means is heated to at least 328 ⁇ C and then lifted from the bath, thus being liberated from the crystals being formed on said cooling means, and which are of pure lead practically free from silver, having melted and having been tapped-off from the trough, as indicated by arrow 10.
• the cooling means 5 When the cooling means 5 has been freed from its coating of crystals, said means is immersed in the cold end 3 of the trough to begin a further crystallization cycle. Because the crystals separated from the bath are forced to move clockwise by the action of the cooling means 6, the melt in which the silver is concentrated is forced to move counter clockwise in the trough, as shown by the arrows labelled (1). The silver-enriched melt is removed from the trough at the cold end 3, as shown by the arrow 11.
• sil ⁇ er-containing lead Division of the sil ⁇ er-containing lead was effected in two stages. In the first stage relatively pure lead containing about 1 gram of silver per ton was recovered, together with a silver-enriched alloy containing 4055 grams of silver per ton. This alloy was treated in the second stage, in which there was obtained a silverdepleted alloy containing 910 grams of silver per ton, together with an alloy rich in silver, containing 21500 grams of silver per ton.
• the energy consumed in this division of the lead-silver alloy was estimated to be between 20 and 30 KWh per ton of l ead at each s tage .
• the division of metal alloys in accordance with the invention does not enable complete separation of the alloy constituents, it does afford a relatively simple method of concentrating the alloying metals in a minor portion of the amount of base metal contained; this enables complete separation processes, such as electrolysis, which are relatively expensive, to be restricted to this minor part of the base metal content.

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• 1981
  • 1981-07-10 SE SE8104304A patent/SE8104304L/ not_active Application Discontinuation
• 1982
  • 1982-06-22 ZA ZA824402A patent/ZA824402B/xx unknown
  • 1982-07-01 GR GR68609A patent/GR76849B/el unknown
  • 1982-07-08 WO PCT/SE1982/000238 patent/WO1983000166A1/en unknown
  • 1982-07-08 EP EP82902101A patent/EP0083615A1/en not_active Withdrawn
  • 1982-07-09 ES ES513849A patent/ES8305837A1/es not_active Expired
  • 1982-07-09 IT IT2232382A patent/IT1151921B/it active

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