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
  • C22B34/00—Obtaining refractory metals
  • C22B34/30—Obtaining chromium, molybdenum or tungsten
  • C22B34/36—Obtaining tungsten

Definitions

• THIS invention relates to the recovery of tungsten values from tungsten bearing nres or concentrates.
• Tungsten is generally found in nature in scheelite type ores and wolframite type ores. These two ores differ substantially in their chemical composition being a calcium tungstate and an iron-manganese tungstate, respectively. Consequentljr, different processes have generally been used to recover the tungsten values from each type of ore.
• scheelite ores the classical prior art process is to treat the ore with hydrochloric acid to produce insoluble tungstic acid. The tungstic acid is taken up in an ammonia solution to produce ultimately ammonium paratungstate (APT).
• Wolframite on the other hand is usually decomposed by fusing the ore with sodium hydroxide/sodium carbonate which extracts the tungsten as sodium tungstate.
• the cooled fused product is leached with water to extract the soluble sodium tungstate.
• this may be treated with hydrochloric acid to precipitate tungstic acid which is taken up in an arnonia solution to produce APT.
• British patent specification No. 1,089,913 describes a process for recovering tungsten values from both scheelite and wolframite type ores or concentrates. This process comprises fusing powdered scheelite and/or wolframite tupe ores or concentrates with a fluxing mixture of sodium carbonate, sodium chloride and sodium nitrate (which mixture also contains, in the case of the starting material containing calcium, at least sufficient siliceous material tc form calcium silicate therewith) , .
• Fox U.S. Patent Specification No. 3,800,025 describes a process of extracting tungsten values from low grade tungsten ores which includes the steps of roasting a particulated tungsten-containing ore in a water containing atmosphere in the presence of sodium chloride and at least one of the reagents selected from sodium carbonate and sodium phosphate at a temperature in the range of about 600°C to about 900°C for about 1 to 3 hours, water leaching the resulting calcines to dissolve soluble tungsten values and filtering.
• This process is restricted in application to low grade tungsten ores and requires a water containing atmosphere for its operation.
• relatively high roast temperatures and relatively low amounts of sodium re d ctant are generally used.
• a process for recovering tungsten values from a high grade tungsten-bearing ore or concentrate including the steps of roasting without fusion the ore or concentrate in the presence of a reactive composition selected from an alkali metal chloride, an alkali metal carbonate and mixtures thereof, and extracting water-soluble tungsten values from the roasted product.
• a reactive composition selected from an alkali metal chloride, an alkali metal carbonate and mixtures thereof
• the tungsten values in the roasted product will be in the form of water-soluble alkali metal tungstate.
• This product may thereafter be treated in known manner to recover the tungsten values as tungsten metal, for example, the tungsten values may be water leached from the roasted mixture and the leach liquor then treated in the manner described in British patent specification No. 1,'089,913.
• These treatment steps are essentially an application of chemistry known in the art.
• the alkali metal for both the chloride and the carbonate will invariably be sodium.
• the tungsten-bearing ore or concentrate is a high grade one, i.e. one containing at least 20 percent by weight tungsten as tungsten oxide (WO 3 ).
• tungsten oxide tungsten oxide
• Such materials will generally be of the schellite or wolframite type and may contain up to 80,5 percent tungsten as tungsten oxide.
• the reactive composition may be an alkali metal chloride, an alkali metal carbonate or a mixture thereof. It is a particularly preferred feature of the process that the reactive composition consists solely of an alkali metal carbonate such as sodium carbonate. It has surprisingly been found that excellent tungsten recoveries, at relatively mild temperatures can be achieved using sodium carbonate alone.
• the roasting temperature will vary according to the nature of the ore or concentrate being treated and the type and quantity of reactive composition present. The important point is that a temperature must be chosen which will not result in fusion of the ore or concentrate taking place but will yet be high enough for the desired reaction to take place in a reasonable time. As a general rule temperatures in the range 600° to 800°C will be used. For wolframite ores, lower temperatures down to 500°C can be used and good extractions still obtained. When the recoveries are low then the roasted product, after filtration, can be dried and remixed with reactive reagent and then re-roasted. This can be continued until as.much of the tungsten as desired has been extracted from the ore. The re-roasting of ore to increase the tungsten extraction may be used particularly with scheelite ores.
• the amount of reactive composition.present during roasting will also vary according to the nature of the ore or concentrate. There should be at least sufficient sodium present to combine with all the tungsten to form sodium tungstate. It has been found, however, that a stoichiometric excess of sodium is generally necessary when the ore b p ing treated is a wolframite ore.
• the rodsting must take place for a sufficient time to convert as much as possible of the tungsten to sodium tungstate.
• the roasting time is typically up to 120 minutes, although for many ores no particular-advantage has been found by heating for a period of longer than 60 minutes.
• the reactive composition may also contain a suitable oxidising agent such as sodium nitrate.
• a suitable oxidising agent such as sodium nitrate.
• Such an oxidising agent is particularly useful where wolframite ores or concentrates are being treated.
• the tungsten-bearing ore or concentrate also contains a substantial quantity of calcium it may be desirable in some cases to include finely divided silica in the reactive composition. The silica reacts with the calcium to form tricalcium silicate which is subsequently readily separable from the sodium tungstate.
• the tungsten-bearing ore or concentrate and the reactive composition will generally both be provided in finely divided state and will be intimately mixed prior to roasting.
• the product may be leached with water. It has been found experimentally that one leach and a replacement wash under appropriate conditions are generally sufficient.
• leaching may take place on the roasted product as such without subjecting th d t product to a crushing or like step. Moreover, leaching may take place while the roasted product is still hot.
• the leach liquor is treated by commonly known methods to remove impurities such as aluminium, magnesium, phosphorous, silicon, antimony, arsenic and molybdenum.
• the filtrate may be further purified by treatment with a fluoride or hydrofluoric acid.
• the adequately purified solution is then subjected to a conventional solvent extraction procedure.
• the tungsten contained in the organic phase may be extracted with ammonium hydroxide to provide an aqueous ammonium tungstate solution.
• Tungsten metal powder may be produced from the ammonium tungstate by known methods.
• Experiments 1 to 4 The ore used was a wolframite ore containing 68,1% tungstic oxide; the reactive composition was sodium carbonate and the roast temperature was 650°C.
• the stoichiometric ratio of tunstic oxide (W0 3 ) content to the reactive composition is about 2,2.
• the tungsten extractions are relatively low. The reason for this is that a less than the stoichiometric quantity of sodium carbonate was required to prevent fusion taking place.
• the roasted product was powdery and could be directly leached, and while still hot.
• the leached residue after drying, can again be roasted in the presence of sodium carbonate and leached to increase the tungsten extranction. This can be repeated as often as desired to extract as much of the tungsten as possible.
• a scheelite concentrate containg 74,8% of W0 3 and a wolframite concentrate containing 66,1% W0 3 were mixed 1 : 1 by weight and the mixture was mixed with sodium carbonate in the proportion of 1 part of sodium carbonate to four parts of the mixture. Roasting was conducted at 660°C for four hours.
• the overall tungsten extraction is 90 and 95 percent at residue: Na 2 C0 3 ratios of 7:3 and 1:3.
• the particular ratio chosen will depend on the particular economic circumstances under which any process operates at any given time.

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• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Manufacture And Refinement Of Metals (AREA)
• Inorganic Compounds Of Heavy Metals (AREA)

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Citations (7)

• 1978
  • 1978-11-17 ZA ZA786478A patent/ZA786478B/xx unknown
• 1979
  • 1979-11-13 AT AT79302549T patent/ATE1681T1/de active
  • 1979-11-13 DE DE7979302549T patent/DE2963902D1/de not_active Expired
  • 1979-11-13 EP EP79302549A patent/EP0011475B1/de not_active Expired
  • 1979-11-14 BR BR7907441A patent/BR7907441A/pt unknown
  • 1979-11-16 AU AU52918/79A patent/AU525137B2/en not_active Ceased
  • 1979-11-16 JP JP54148745A patent/JPS595657B2/ja not_active Expired
  • 1979-11-16 PT PT70465A patent/PT70465A/pt unknown
  • 1979-11-16 ES ES486063A patent/ES486063A1/es not_active Expired
  • 1979-11-16 TR TR21615A patent/TR21615A/xx unknown
  • 1979-11-16 AR AR278927A patent/AR224633A1/es active
  • 1979-11-19 CA CA000340128A patent/CA1136422A/en not_active Expired

Patent Citations (7)

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