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
  • C22B15/00—Obtaining copper
  • C22B15/0026—Pyrometallurgy
  • C22B15/0028—Smelting or converting
  • C22B15/003—Bath smelting or converting
  • C22B15/0041—Bath smelting or converting in converters
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C5/00—Alloys based on noble metals
  • C22C5/02—Alloys based on gold
• • 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
  • C22B23/00—Obtaining nickel or cobalt
  • C22B23/02—Obtaining nickel or cobalt by dry processes
  • C22B23/025—Obtaining nickel or cobalt by dry processes with formation of a matte or by matte refining or converting into nickel or cobalt, e.g. by the Oxford process

Definitions

• the instant invention relates to the pyrometallurgical production of refined nickel-copper matte from sulf ide ores in general and, more particularly, to a converter process using nitrogen, air, oxygen and combinations thereof.
• the introduction of nitrogen or nitrogen/oxygen containing gas controls the oxidation of the resultant matte and assists in cooling it. Debilitating mush formation is substantially reduced resulting in more efficient converter operations.
• Nickel-copper Bessemer matte is typically produced by converting molten matte from a primary smelting furnace in Peirce Smith converters which employ blowing of air or air/oxygen mixtures into the bath via tuyeres.
• the Peirce Smith converter is the most common type of converter used for this application and consists of a horizontally oriented cylinder which has a hooded opening at the top and is rotatable through an arc of about 180 degrees.
• the plurality of tuyeres are located below the normal working level of the molten matte when in the blowing position and the tuyeres are raised above the bath for pouring and holding.
• the feed to the converters usually consists of a homogeneous molten matte including Ni3S2, Cu2S, FeS, and small quantities of oxygen, precious metals and other elements. Much of the rock and iron that were in the original metal bearing concentrate were eliminated in the upstream furnacing operation.
• the objective of the conversion process is to oxidize the FeS in the matte to form iron oxides, liberating sulfur dioxide and leaving matte comprising nickel and copper sulfides with small but variable amounts of cobalt, precious metals and dissolved oxygen. This is accomplished by blowing an oxygen containing gas (air, oxygen enriched air or oxygen) into the matte through the tuyeres.
• the oxygen combines with the iron and sulfur to form iron oxide and sulfur dioxide.
• the sulfur dioxide passes off as a gas and is subsequently treated to prevent fugitive emissions.
• the iron oxide unites with added silica flux to form an iron silicate slag that floats on top of the matte now richer in nickel and copper and much lower in iron.
• the oxidation process is exothermic and the heat generated is usually sufficient to cause the operation to be self-sustaining.
• the resulting matte is generally cooled, cast and further treated for recovery of valuable base and precious metals.
• the copper and nickel in the matte form copper sulfide (Cu2S), nickel sulfide (Ni3S2), and a metallic fraction containing small amounts of dissolved sulfur.
• the desired composition of the Bessemer matte product is highly dependent upon the requirements of the downstream processing. Important parameters are the final iron and sulfur contents. These levels are generally controlled by the degree of blowing and the temperature of blowing. Conversion of the Ni-Cu matte is normally a batch process and is carried out in the following stages:
• the function of the cooling step is two-fold; removal of most of the iron by cooling and/or minor blowing of the melt, and cooling of the converter melt to temperatures appropriate for the subsequent treatment of the Bessemer matte. Cooling takes place by natural convection and radiation and typically lasts up to four hours.
• molten nickel-copper mattes are finished to Bessemer quality and cooled to the appropriate casting temperature by blowing with nitrogen and/or nitrogen-oxygen (air) mixtures.
• nitrogen promotes cooling and aids in controlled iron oxidation thus improving control over the final iron level in the Bessemer matte.
• the instant invention utilizes tonnage nitrogen or nitrogen/oxygen (air) mixtures as an operating gas to both control the oxidation of and improve the cooling of Ni/Cu converter matte. More specifically, it relates to controlling the oxidation rate toward the end of the conversion cycle of Cu/Ni Bessemer matte; minimizing mush formation; regulating the converting temperature and matte composition during the last stages of conversion; and accelerating the cooling of the matte to a temperature consistent with good skimming, casting and the subsequent refining process.
• Cooling by blowing with nitrogen enriched gas streams shortens cycle times and improves converter productivity.
• nitrogen also aids in the overall cost effectiveness of the entire nickel-copper refining operation since oftentimes the site must generate and store pure oxygen for various unrelated purposes. Rather than throwing off the nitrogen as waste gas, it is collected and further utilized in the instant process.
• the addition of nitrogen to the air or oxygen blast can also be used as a control over the sulfur levels in Bessemer matte.
• the final sulfur content in Bessemer matte is primarily controlled by blowing temperature - raising the temperature decreases the sulfur level and lowering the blowing temperature tends to increase final sulfur. Dilution of the blast with nitrogen tends to purge the bath of sulfur giving added control over the composition of the final Bessemer matte.
• Nitrogen addition to the air or oxygen blast is useful for a number of different converter processes.
• the nitrogen/air or nitrogen/oxygen mixture may be used to finish the matte and control the iron and sulfur contents.
• the nitrogen may be used primarily for cooling the matte -- iron and sulfur control in this instance may not be a major factor.
• the quantity and duration of the nitrogen addition is a function of the type, temperature and quantity of the matte.
• the matte generally contains about 3% iron or less.
• Nitrogen should preferably be mixed with air in about a 0.5-2:1 volume ratio and the mixture delivered to the converter at a rate of about 2.5 - 7.5 cubic meters/minute per metric tonne of matte.
• the volume ratio should be about 6-14:1 and delivery rate is about 2.5 - 7.5 cubic meters/minute per metric tonne of matte.
• these parameters may be varied to adjust the conditions at hand.
• the finished matte generally contains 1-3% iron or less at a temperature of about 1100°C - 1250°C.
• Nitrogen should preferably be mixed with air or oxygen in about 3 -­20:1 or 20-100:1 volume ratios respectively.
• the delivery rates should be about 2.5-7.5 cubic meters/minute per metric tonne of matte.
• the volumes of gas introduced into the converter should be chosen to reduce the temperature by about 50°C- 200°C. Again, the numbers may be varied depending on the circumstances.
• nitrogen only may be used to cool the matte.
• Preferably about 2-4 cubic meters/minute per metric tonne of matte may be added to reduce the temperature of the matte.
• the blast may contain about 5-15% oxygen (or about 23-70% air) for oxidizing purposes and about 1-5% oxygen (or 5-20% air) for cooling purposes.
• the converter was turned into the blowing position and a mixture of 311.5 m3 min ⁇ 1 (11,000 scfm) of air and 215.2 m3 min ⁇ 1 (7600 scfm) of nitrogen was blown through 42 tuyeres for 21 minutes.
• An oxygen analyzer installed in the line indicated that the blast contained 11.6% O2 by volume.
• the matte assayed 1.3% Fe and was at 1150°C.
• About 5261 kg (5.8 tons) of mush remained in the converter in the form of an 203 mm (8 inch) layer of hard finish.
• the matte was transferred for further processing and the mush was sampled. Assays showed the mush to be approximately 43% matte, 26% flux and 31% base metal oxides.
• Example A Using the same equipment as in Example A, approximately 120 tonnes of finishing matte assaying 0.89% Fe and at 1160°C were blown with a nitrogen-air mixture to cool it to the casting temperature.
• the blast mixture consisted of about 31.1 m3 min ⁇ 1 (1100 scfm) of air and 229.3 m3 min ⁇ 1 (8100 scfm) of N2 and was blown for 22 minutes through 25 tuyeres.
• An oxygen analyzer indicated that the blast contained 3.1% O2 by volume.
• the matte Assayed 0.29% Fe and had been cooled to 1000°C.
• the matte was cast. Only a small amount of mush remained in the converter. Assays showed this mush to be 59% Bessemer matte, 22% flux and 19% base metal oxides.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Manufacturing & Machinery (AREA)
• Manufacture And Refinement Of Metals (AREA)

Applications Claiming Priority (2)

Publications (2)

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Cited By (1)

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Citations (5)

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• 1989
  • 1989-07-31 CA CA000607085A patent/CA1338426C/en not_active Expired - Lifetime
• 1990
  • 1990-07-23 KR KR1019900011193A patent/KR940000492B1/ko not_active IP Right Cessation
  • 1990-07-25 PE PE1990172633A patent/PE15791A1/es not_active Application Discontinuation
  • 1990-07-27 BR BR909003670A patent/BR9003670A/pt active Search and Examination
  • 1990-07-27 JP JP2201073A patent/JPH0397814A/ja active Pending
  • 1990-07-30 FI FI903792A patent/FI903792A0/fi not_active IP Right Cessation
  • 1990-07-30 EP EP90308320A patent/EP0416738B1/de not_active Expired - Lifetime
  • 1990-07-30 ZA ZA905967A patent/ZA905967B/xx unknown
  • 1990-07-30 AU AU59990/90A patent/AU632603B2/en not_active Ceased

Patent Citations (5)

Non-Patent Citations (1)

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