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
  • C22B13/00—Obtaining lead
  • C22B13/06—Refining

Definitions

• the present invention relates to a method of producing crude lead from copper-containing lead raw-materials of a metallic , oxidic, sulphatic or sulphidic type.
• Metallic lead is normally produced from sulphidic lead raw-materials , such as lead concentrates for example, but can also be produced from oxidic and sulphatic lead rau-materials , for example dust, ashes and slags.
• the most common furnace used for melting and chemically reducing lead is the shaft furnace,to which there is charged a lead raw material which, if so desired, has been pre-sintered or roasted to simultaneously oxidize the sulphidic sulphur present with atmospheric oxygen to a content of less than 2% sulphur.
• the lead raw-material can also be melted and reduced,to advantage,in a rotary , inclined furnace, as disclosed in Swedish Patent specification 7317217-3 and 7317219-9, which teach methods for producing crude lead from sulphidic, oxidic and sulphatic lead raw-materials.
• the lead When producing crude lead, i.e. lead which must be purified or refined in order to be retailed as a normal market product, the lead will thus practically always contain impurities undesirable in the finished lead, e.g. such impurities as copper, arsenic and antimony, which substances must therefore be removed from the crude lead.
• impurities e.g. such impurities as copper, arsenic and antimony, which substances must therefore be removed from the crude lead.
• Gold and silver are normally also present in the crude lead.
• the crude lead is refined in so-called pots or chambers of various type , especially designed for refining said lead with respect to said impurities.
• Copper, and also arsenic and antimony present in the lead constitute a particular problem when refining said lead.
• Arsenic and antimony may be present in quantities of up to about 15%, which results in the formation of very large quantities of solid, powder- ous products which float to the surface of the metal bath during the refining process. This so-called dross renders handling of the crude-lead melt difficult.
• crude lead is produced from copper-containing lead raw-materials of a metallic, oxidic, sulphatic or sulphidic type, by melting the raw materials in a furnace in which turbulence can be created in the contents thereof, said raw materials being melted in the presence of a slag former and chemically reduced, uhereaf- ter a slag is tapped-off.
• the novel method is characterized by the fact that subsequent to tapping-off the slag, the crude-lead melt formed is cooled whilst creating a strong turbulence therein,to a temperature above the liquidus point of the lead melt but beneath about 700°C, preferably beneath 500°C, whereafter the copper-containing phase and crude-lead melt separated out when cooling said melt are separated from one another.
• a "speiss” is a compound of arsenic and/or antimony with iron metals and copper, i.e. a “speiss” may comprise arsenides and/or anti- monides of one or more of the metals copper, iron, nickel and cobalt.
• any arsenic or antimony impurities are therefore removed by charging to the melt, whilst creating a strong turbulence therein, iron in a metallic, finely-divided form, or by causing iron to be formed in situ, whereafter the insoluble iron speiss formed in the lead melt is separated therefrom in direct conjunction with gravitational separation of speiss and crude lead, whereafter copperis separated out and removed. If the iron charged to the melt is in powder form or in the form of iron filings or finely-divided pieces, a practically insoluble iron-arsenic speiss or iron-antimony speiss will be formed in the lead melt.
• iron in finely-divided form metallic iron in a form such as to present to the lead melt a good specific surface area and that the iron can be charged to the melt in a simple manner.
• the speiss which is practically insoluble in lead at the prevailing temperatures, is readily separable and can be tapped-off, preferably at a temperature of 850-1200 0 C.
• the iron charged may also have the form of an iron alloy containing 60% iron or more.
• the iron charge may be adapted so that only a part of the arsenic content forms an iron speiss and that there remains in the lead melt a guantity of arsenic corresponding to a molar ratio of copper to arsenic of at least 1.17, so that copper is able to form a copper speiss, which can readily be treated to recover copper and arsenic. Any tin present in the melt will remain therein.
• the major part of the copper content of the lead raw-materials will remain in the crude-lead melt, however, but, as above mentioned, will be segregated as metallic copper and/or speiss subsequent to cooling the melt under strong turbulence to a temperature above the melting point of the lead-melt but beneath about 700°C, whereafter the crude-lead is tapped-off and recovered.
• Cooling of the crude-lead melt can be effected by adding, for example,,additional oxidic or sulphatic lead raw materials or crushed iron-silicate slag. Cooling of the crude-lead melt can also be effected by adding a slag former intended for a subsequent melting cycle.
• the crude-lead melt can be cooled by spraying water in liquid , finely-divided form directly onto the turbulent crude-lead melt.
• the melting process, and any possible speiss formation and copper separation, are effected in a furnace in which the melt can be treated whilst being subjected to strong turbulence.
• a furnace is suitably a top blown rotary converter , for example a so-called TBRC or a Kaldo furnace.
• a TBRC or Kaldo furnace can be rotated at a speed of from 10 to 60 r.p.m . and the choice of suitable rotary speed is controlled by the diameter of the furnace.
• a suitable turbulence is obtained when the inner surface of the furnace is rotated at a peripheral speed of 0.5 - 7 m/s, preferably 2 - 5 m/s, which enables the melt to accompany the rotating inner surface of the furnace and fall down onto the surface of the bath in a shower of droplets, which results in extremely good contact between solid phase, liquid phase and gas phase.
• Such good contact is a requisite for rapid chemical and physical sequences, such as a reduction sequence, cooling and separation.
• the formation of dust is avoided to a surprisingly large extent , by the fact that the shower of droplets drive the dust down,which would otherwise pass out of the furnace with the reaction gases.
• the slag and the crude-lead bath were reduced chemically with 1.9 tons of coke until the lead content of the slag was about 1.5 % Pb at a temperature of about 1100°C, whereafter the slag was tapped-off.
• a part of the thus obtained crude-lead melt was cooled whilst continuing said agitation,down to a temperature of 400°C, it being possible to segregate out and remove a further copper-containing phase.
• the resultant copper content of the crude-lead melt was 0.2% Cu.
• the resultant slag and crude-lead bath were chemically reduced with 1.9 tons of coke until the lead content in the slag was about 1.5% Pb at a temperature of about 1100°C, Whereafter the slag was tapped-off. Whilst strongly agitating the resultant crude-lead melt , a further 2.25 tons of crushed iron-silicate slag were charged to the furnace, the temperature of the crude-lead melt decreasing from 1100°C to about 850 °C over a period of 60 minutes, and a large quantity of copper-containing phase was obtained. This large quantity of copper-containing phase could be separated from the crude-lead melt with less lead losses than when only one freezing or segregation process with iron-silicate slag was carried out. In addition, a considerable saving in time per ton of lead produced was made , since only one segregation process was required.
• the slag and the crude-lead bath were chemically reduced with 1.9 tons of coke until the lead content of the slag was about 1.5% Pb at a temperature of about 1100°C, whereafter the slag was tapped-off.
• the crude lead obtained contained 7% As and 3% Cu. 3 tons of iron in a metallic,finely-divided form was charged to the turbulent crude-lead melt, to form an iron speiss at about 1000 C, which speiss was then tapped-off in liquid form.
• a crushed iron-silicate slag was then charged to the furnace whilst strongly agitating the crude-lead melt, as in Example 1, the temperature of the bath decreasing, a copper-containing phase segregating out and being removed from the melt.

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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)
• Treatment Of Steel In Its Molten State (AREA)

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Publications (1)

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Cited By (3)

Citations (6)

• 1978
  • 1978-06-29 SE SE7807358A patent/SE413105B/sv unknown
• 1979
  • 1979-06-15 EP EP79850059A patent/EP0006832A1/de not_active Withdrawn
  • 1979-06-27 DK DK271579A patent/DK271579A/da not_active Application Discontinuation
  • 1979-06-28 NO NO792175A patent/NO792175L/no unknown
  • 1979-06-29 FI FI792061A patent/FI792061A/fi not_active Application Discontinuation
  • 1979-06-29 PL PL1979216722A patent/PL117460B1/pl unknown

Patent Citations (6)

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