US3836357A - Direct reduction process for production of aluminium - Google Patents

Direct reduction process for production of aluminium Download PDF

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Publication number
US3836357A
US3836357A US00328747A US32874773A US3836357A US 3836357 A US3836357 A US 3836357A US 00328747 A US00328747 A US 00328747A US 32874773 A US32874773 A US 32874773A US 3836357 A US3836357 A US 3836357A
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Prior art keywords
lead
aluminium
vapour
bismuth
reaction zone
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US00328747A
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English (en)
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E Dewing
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Alcan Research and Development Ltd
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Alcan Research and Development Ltd
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    • 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
    • C22B21/00—Obtaining aluminium
    • C22B21/02—Obtaining aluminium with reducing
    • 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
    • C22B21/00—Obtaining aluminium
    • C22B21/0038—Obtaining aluminium by other processes
    • C22B21/0053—Obtaining aluminium by other processes from other aluminium compounds
    • C22B21/0061—Obtaining aluminium by other processes from other aluminium compounds using metals, e.g. Hg or Mn

Definitions

  • an alloy of aluminium with lead and/or bismuth is produced by direct thermal reduction of alumina in the presence of vapours of lead and/or bismuth and in the presence of liquid lead and/or bismuth so as to form an alloy of aluminium with lead and/or bismuth in the thermal reduction stage.
  • These metals can be very largely separated from a molten lead-aluminium alloy by cooling.
  • Pb-Al alloys will separate into two layers, and the top layer at 660 C, the freezing point of Al, contains only 0.2 atom percent Pb (1.5 wt. percent). Although this is far too much to meet purity specifications of aluminium it is nonetheless a remarkably small quantity of material to remove from aluminium in a final purification stage.
  • the endothermic smelting reaction causes lead to condense from the vapour, and the liquid lead so produced alloys with the aluminium, lowering its activity.
  • the lead therefore serves two functions simultaneously; liquid lead serves as an alloying agent to decrease the activity of the aluminium formed and gase ous lead serves to dilute the carbon monoxide in the gas phase and carry it out of the reaction zone.
  • heat is supplied to the reaction zone through the latent heat of condensation of lead from the vapour phase to the liquid phase. Sufficient heat for the reaction to proceed may be supplied by condensationof lead vapour, and no other heating of the charge is necessary. If all heat for the system is supplied by boiling lead to produce lead vapour, the electrical properties of the charge, which are very important in arc furnace operation, become irrelevant.
  • lead and/or bismuth vapour at a temperature in the range of l,600 to 2,500 C and correspondingly elevated pressure is continuously passed through an alumina-carbon charge, where some of it condenses to provide heat input and the resultant alloy (containing about 10 atom percent Al under optimum conditions) descends to the bottom of the chamber, whilst the uncondensed lead and/or bismuth vapour passes through the charge and is recovered by cooling the gas.
  • the alloy is preferably conducted back into the metal vapour generator until the Al concentration builds up to around 25 atom percent; this liquid is tapped, cooled, separated into two layers, and the lead and/or bismuth layer is recycled.
  • the temperature at which the smelting process operates is governed by the pressure maintained in the system; this controls the temperature at which the lead (and/or bismuth) boils and at which the metal vapour can condense in the alumina-carbon mass to supply the necessary heat to make an alloy.
  • the boiling of lead (and/or bismuth) coupled with condensation of metal vapour at a position beyond the charge results in a pressure difference across the charge to displace carbon monoxide from the reaction zone, so that there is no requirement for any mechanical pump or blower for hot gases.
  • Alumina and carbon are charged in successive increments to a vertical vessel 1, in which the charge 2, which must readily permit passage of gas, is supported on a grid 3, which is located above a mass of boiling lead 4, to which heat is'supplied in any convenient manner.
  • part of the lead vapour condenses in the charge 2 and returns with dissolved aluminiurn to the mass 4, whilst the remaining lead vapour and carbon monoxide generated in the reduction of alumina is passed to a condenser 5, from which the condensed lead is passed back to the mass 4, conveniently, but not essentially, through the column 1.
  • the condenser may form an upper region of the vessel 1.
  • the permanent gas, principally carbon monoxide, which is at substantially the same pressure as in the vessel 1, may be further cooled before discharge through a pressure-reducing device to a gas holder.
  • Lead-aluminium alloy from the mass 4 is periodically withdrawn to a cooling vessel 6, in which it is separated into two layers by cooling to about 700 C, Le. to a temperature somewhat above the melting point of aluminium.
  • the lead layer (containing a small proportion of aluminium) is then. recycled to the mass 4, preferably through the column 1.
  • the liquid lead may be sprayed into the condenser 5 so that it is reheated substantially to reaction temperature before coming into contact with the alumina-carbon charge.
  • the aluminium layer (containing a small proportion of lead) is then withdrawn for purification and removal of the small remaining proportion of lead.
  • Substantiallylead-free aluminium may be obtained by fractional crystallisation of the aluminium-rich layer from the vessel 6. This molten metal may be run into an upright vessel which tapers from its mouth to its bottom end. By slow cooling in this vessel a substantially lead-free layer of solid aluminium will form on the surface, which may be removed in any suitable way when the freezing is about 80 90 percent complete. Fresh molten metal can then be added and the process repeated until there is sufficient lead separated at the bottom of the vessel to warrant recycling it.
  • the carbon electrode in the conventional electrolytic process is made of petroleum coke, bound together with pitch.
  • petroleum coke will preferably be used as the source of carbon in the furnace charge since it is low in metallic impurities. Any other similar source of relatively pure carbon will also be acceptable.
  • the coke requires to be combined with the alumina into pieces large enough and strong enough to allow gas and molten lead to pass between them and to withstand crushing.
  • purified alumina produced in conventional manner by the Bayer process, is preferably incorporated with a liquid residual oil before it is coked. Coking of the oil produces a very intimate mixture of alumina and coke. The alumina-containing coke product can be broken to the size required. The expense of the pitch, normally provided as a binder for the anodes in the conventional electrolytic process, may thus be avoided.
  • the system in the vessel in which the mass of lead is boiled to generate lead vapour and the column of charge 2 operates under the following conditions l.
  • the alloy in the boiler has a vapour pressure of Pb equal to the total pressure in the system;
  • the alloy in the boiler should not be so rich in Al that it forms Al,C with the carbon lining, if carbon is used for that purpose;
  • each local region of the charge in column 2 approaches the conditions of mass balance, heat balance, equilibrium between Pb in the alloy. and Pb vapour in the gas, and equilibrium between Al in the alloy, A1 0 C and CO in the gas phase.
  • the charge must remain solid when using a vertical column of charge arranged in the illustrated manner. This in practice limits the temperature range of the incoming metal vapour to a temperature in the range of l,600 to 2,040 C to avoid melting of the alumina. In terms of thermal efficiency it would be desirable to let it melt and with differently engineered apparatus the charge might be molten. However, it is preferred to operate at a temperature above l,600 C and preferably above l,700 C, but below 2,040 C. Most preferably the temperature of the incoming metal vapour is at about 2,000 C.
  • the efficiency was thus 0.961, and the power required was the latent heat of evaporation of lead plus the heat required to raise the returned liquid lead alloy back to the boiler temperature, divided by the efficiency.
  • the required lead boiler temperature was 2,010 C and the alloy in it contained 27.6 atom percent Al.
  • the activity of Al in this alloy is 0.529, whereas the critical value for formation of Al C is at least 0533; ALC should therefore not form.
  • the lead to be circulated is 2.733 mol per mol of Al produced, or 21.0 lb. of lead per lb. of aluminium.
  • the alloy tapped from the boiler in the present example of the operation of the invention is at 2,0] 0 C and contains 27.6 atom percent Al; its vapour pressure is 2.75 atm. To separate the aluminium it needs to be cooled to below 700 C. As far as possible the alloy should be cooled by evaporation of lead.
  • An advantage of the evaporative cooling is that it not only removes heat from the system, but also removes lead. This improves the overall efficiency, since evaporated lead does not recycle aluminium to the top of the converter.
  • the evaporated lead is first cooled to the liquid state and then introduced to the stream of liquid lead returned to the converter.
  • the charge is composed of Bayer alumina and petroleum coke there are only two major impurities which enter the system.
  • the alumina contains -0.5 percent Na O and the coke contains l-4 percent sulphur. Both of these are volatilized from the top of the column, the sodium as Na atoms and the sulphur as COS and PbS molecules.
  • the Na will react with the sulphur compounds to form Na S, and any remaining sulphur will be left as PbS, which is undesirable.
  • Na and S are present in equivalent amounts so that formation of Na s is complete and neither is left over, thus avoiding any discharge of sulphur into the atmosphere.
  • To get the sodium and sulphur into balance is not difficult by addition of soda or other alkali metal oxide or carbonate to the charge.
  • the power requirements are comparable with or lower than the conventional electrolytic process
  • the relative proportions of soda and sulphur in the ingredients may readily be controlled so that the sulphur from the coke is left in the concentrated form of sodium sulphide which would be a great advantage in overcoming pollution resulting from release of sulphur to the atmosphere.
  • a process for the production of aluminium which comprises reacting a charge of alumina and carbon in a reaction zone at a temperature in the range of l,600 to 2,500 C in the presence of liquid lead and/or bismuth and in an atmosphere consisting essentially of lead and/or bismuth vapour, supplying heat to the reaction zone to maintain the charge within the temperature range by introducing a stream of lead and/or bismuth vapour into the reaction zone and into contact with the charge and allowing lead and/or bismuth to condense from the vapour phase to the liquid phase in the reaction zone to form an alloy with aluminium produced by the reaction of the alumina and carbon of the charge, leading the resultant alloy out of the reaction zone, and recovering aluminium from such lead and/or bismuth-aluminium alloy.
  • a process according to claim 1 which comprises maintaining in a reaction zone a charge in the form of solid pieces of an intimate mixture of carbon and alumina, maintaining a body of boiling metal composed of lead and/or bismuth in a vapour generating zone, passing the evolved metal vapour into the solid charge to maintain the temperature of the charge in the range of l,600 to 2,040 C, maintaining liquid lead and/or his muth in contact with the charge to alloy with aluminium formed in the reaction zone, withdrawing such alloy from the reaction zone to the vapour generating zone, withdrawing aluminium-enriched lead and/or bismuth from the vapour generating zone to a cooling zone, cooling to a temperature somewhat above the melting point of aluminium such withdrawn metal to produce an aluminium-rich layer and a lead and/or bismuth-rich layer, returning the lead and/or bismuth-rich metal in the liquid state to the reaction zone to pass therethrough in a direction countercurrent to the stream of metal vapour, cooling the gas issuing from the reaction zone to condense the lead and/or bismut

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Manufacture And Refinement Of Metals (AREA)
US00328747A 1972-02-08 1973-02-01 Direct reduction process for production of aluminium Expired - Lifetime US3836357A (en)

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GB590172A GB1366808A (en) 1972-02-08 1972-02-08 Direct reduction process for production of aluminium

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US (1) US3836357A (sv)
JP (1) JPS531729B2 (sv)
AU (1) AU476496B2 (sv)
BR (1) BR7300926D0 (sv)
CA (1) CA968164A (sv)
CH (1) CH575470A5 (sv)
DE (1) DE2305924C3 (sv)
FR (1) FR2171169B1 (sv)
GB (1) GB1366808A (sv)
IT (1) IT978647B (sv)
NO (1) NO133718C (sv)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4394167A (en) * 1980-04-22 1983-07-19 Mitsui Aluminum Co., Ltd. Method of carbothermically producing aluminum
US20130220077A1 (en) * 2012-02-24 2013-08-29 John Joseph Barsa Method and apparatus for high temperature production of metals

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS63112922U (sv) * 1987-01-17 1988-07-20
JPH0549434U (ja) * 1991-12-17 1993-06-29 山川工業株式会社 自動車用ドアガードビーム

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2198673A (en) * 1938-07-11 1940-04-30 Israel Jacob Foundaminsky Process for the manufacture of aluminum
US3234008A (en) * 1962-05-04 1966-02-08 Arthur F Johnson Aluminum production

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2198673A (en) * 1938-07-11 1940-04-30 Israel Jacob Foundaminsky Process for the manufacture of aluminum
US3234008A (en) * 1962-05-04 1966-02-08 Arthur F Johnson Aluminum production

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4394167A (en) * 1980-04-22 1983-07-19 Mitsui Aluminum Co., Ltd. Method of carbothermically producing aluminum
US20130220077A1 (en) * 2012-02-24 2013-08-29 John Joseph Barsa Method and apparatus for high temperature production of metals
US9039805B2 (en) * 2012-02-24 2015-05-26 John Joseph Barsa Method and apparatus for high temperature production of metals

Also Published As

Publication number Publication date
NO133718B (sv) 1976-03-08
GB1366808A (en) 1974-09-11
AU476496B2 (en) 1976-09-23
AU5171173A (en) 1974-08-08
DE2305924A1 (de) 1973-09-06
CH575470A5 (sv) 1976-05-14
IT978647B (it) 1974-09-20
FR2171169B1 (sv) 1977-08-19
FR2171169A1 (sv) 1973-09-21
JPS4889110A (sv) 1973-11-21
CA968164A (en) 1975-05-27
DE2305924C3 (de) 1975-04-24
BR7300926D0 (pt) 1973-09-13
NO133718C (sv) 1976-06-16
JPS531729B2 (sv) 1978-01-21
DE2305924B2 (de) 1974-09-05

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