WO1996025361A1 - Procede de precipitation du cuivre - Google Patents

Procede de precipitation du cuivre Download PDF

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Publication number
WO1996025361A1
WO1996025361A1 PCT/US1996/001910 US9601910W WO9625361A1 WO 1996025361 A1 WO1996025361 A1 WO 1996025361A1 US 9601910 W US9601910 W US 9601910W WO 9625361 A1 WO9625361 A1 WO 9625361A1
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WO
WIPO (PCT)
Prior art keywords
copper
sulfide
solution
sulfur
suspension
Prior art date
Application number
PCT/US1996/001910
Other languages
English (en)
Inventor
Robert C. Emmett, Jr.
Philip J. Gabb
Philip J. Evans
Original Assignee
Baker Hughes Incorporated
Kennecott Utah Copper Corporation
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Baker Hughes Incorporated, Kennecott Utah Copper Corporation filed Critical Baker Hughes Incorporated
Priority to AU48676/96A priority Critical patent/AU4867696A/en
Publication of WO1996025361A1 publication Critical patent/WO1996025361A1/fr

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G3/00—Compounds of copper
    • C01G3/10—Sulfates
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G3/00—Compounds of copper
    • C01G3/12—Sulfides
    • 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
    • C22B15/0063—Hydrometallurgy
    • C22B15/0065—Leaching or slurrying
    • C22B15/0067—Leaching or slurrying with acids or salts thereof
    • C22B15/0071—Leaching or slurrying with acids or salts thereof containing sulfur
    • 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
    • C22B15/0063—Hydrometallurgy
    • C22B15/0084—Treating solutions
    • C22B15/0089—Treating solutions by chemical methods
    • 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 present invention relates to the separation of copper from one or more metals. More particularly, the present invention relates to the precipitation of copper as a sulfide from aqueous acidic solutions while retaining other metals in the liquid phase for later precipitation as desired.
  • Patent 3,218, 161 gives a method for precipitating values of metals which form insoluble sulfides more readily than nickel in acid and neutral solutions having a pH from 1 to 7.
  • the method is aimed at the selective precipitation of metals from nickel and cobalt at temperatures greater than 125 degrees Fahrenheit or 52 degrees Celsius (125°F or 52°C) by the use of sulfur dioxide and finely divided sulfur, the latter in excess of stoichiometric requirements.
  • the major metal to be precipitated is copper and the pH is adjusted to be within pH 1 to 7 at a preferred temperature of 180°F (82°C).
  • the method requires an inert, or substantially inert, atmosphere.
  • U.S. Patent 3,218, 161 claims a working range of pH 1 to pH 7 which is equivalent to a theoretical acidity of approximately 5 grams per liter sulfuric acid to 0.05 milligrams per liter sulfuric acid.
  • the patent embraces solutions with acid strengths greater than the equivalent of pH 1 , e.g., sulfuric acid strengths greater than about 5 grams per liter, by claiming prior adjustment of the pH.
  • acid strengths greater than the equivalent of pH 1 , e.g., sulfuric acid strengths greater than about 5 grams per liter, by claiming prior adjustment of the pH.
  • the solution would need to be neutralized by an alkali to bring it within the stated range.
  • waste waters are generally of low acidity
  • industrial process streams such as refinery electrolyte and acid plant blowdown are high in acidity, being typically 150 to 200 grams per liter sulfuric acid.
  • U.S. Patent 4,404,071 (Abe et al.) achieves precisely this outcome by the purification of copper refinery bleed using hydrogen sulfide as the precipitating reagent, in which case copper is precipitated but in combination with arsenic, antimony and bismuth. This precipitat is commonly returned to the copper smelting stage where the impurity elements, especially bismuth, are re-distributed into the products. If any of these impurities has reached a maximum permissible level in the product copper, the new intake of these impurities in concentrates and other new feeds will need to be controlled. It would be advantageous in the art, therefore, to provide a method wherein the copper in refinery bleed can be separated from other metals in the bleed.
  • Patent 3,728,430 (Clitheroe et al.) gives a method for the extraction of copper from ores by leaching with sulfites or bisulfites and the precipitation of the extracted copper from the leach solution with bisulfite, or sulfur dioxide, and elemental sulfur.
  • a pH between 1 and 6 is preferred at a temperature between 80° and 212°F (27° to 100°C).
  • the two operations can occur in the same reactor.
  • the method provides a way of beneficiating a copper ore and the copper sulfide product is preferably floated away from the residual matter.
  • the copper sulfate solution produced from the reaction may be processed to produce a valuable copper product in a number of ways. It can be chemically precipitated in various forms or, more generally, it may be electrowon to produce metallic copper in the form of a cathode.
  • the electrowinning is usually performed after solvent extraction of the copper from the leach solution followed by transfer into a strong acid electrolyte.
  • the solvent extraction step has the advantage of rejecting impurities in the copper sulfate solution and providing an optimum electrolyte for copper electrolysis.
  • Patent 3,728,430 elects to leach the oxidic, or mixed oxidic-sulfidic ore with sulfites rather than sulfuric acid, then precipitate the copper as a sulfide.
  • a feature of the patent is the production of sulfuric acid by the copper precipitation process and the use of this excess acid to meet, to a greater or lesser extent, the natural acid demand of basic components in the oxide ore.
  • the value of the copper sulfide precipitate is lower than cathode copper obtained by electrowinning the copper sulfate and many copper oxide ore-bodies are exploited by solvent extraction and electrowinning (SX-EW) to maximize the added value.
  • the method uses sulfur and sulfur dioxide to precipitate copper sulfide from solutions that are adjusted to an acidity of less than pH 4 at a preferred temperature between 60° to 90°C.
  • the method requires air to be essentially excluded.
  • Canada Patent 1 ,020,363 claims a pH less than 4 to effect the separation of copper from other more acid soluble metal sulfides. The description does not give a range for acidity and, in effect, the method relates to slurries and solutions having sulfuric acid concentrations of 15 grams per liter (patent examples 1 and 2), equivalent to a theoretical pH of 0.5.
  • the dust can be processed by hydrometallurgical means to produce a liquid that contains copper and other metals.
  • the liquid streams can be processed to extract copper and other metals by precipitation as sulfides using hydrogen sulfide gas or liquids such as sodium hydrosulfide.
  • the cost of reagents based on hydrogen sulfide is high, however, and the quality of the resulting precipitates can be poor.
  • copper is precipitated as a sulfide from aqueous acidic solutions, such as those produced from the processing of ore concentrates or non-ferrous smelter by-products, while retaining other metals in the liquid phase for optional downstream processing.
  • the copper is precipitated over a wide range of acidity with relatively inexpensive reagents, at a desirable precipitation rate, and the copper precipitate is readily filterable.
  • This invention also provides more economical means of precipitating copper by using less expensive and more readily available reagents.
  • copper sulfide is precipitated from an aqueous acidic solution containing soluble copper values by contacting the aqueous acidic solution with (i) sulfur, (ii) sulfur dioxide, and (iii) an added copper sulfide.
  • the sulfur is usually supplied in the form of elemental sulfur or chalcopyrite
  • the sulfur dioxide is usually supplied as a soluble sulfite or bisulfite or as smelter gas
  • the added copper sulfide as a thickened recycled stream of copper sulfide (which was originally precipitated as a product of the process).
  • Sufficient copper sulfide is added to the process to ensure that the solids content of the precipitation zone (the zone in which the soluble copper is reacted with the precipitating sulfur reagents) exceeds the maximum solids content that would result in the zone if the precipitation reaction proceeded to completion (batch mode) or reached steady state (continuous mode) under the particular conditions of the precipitation of interest.
  • copper is precipitated as a sulfide from an aqueous solution of copper and other metals, the solution having a free acid range of about 0.05 to about 200 grams per liter (gpl).
  • the solution is contacted with elemental sulfur and a material selected from the group consisting of soluble sulfites or bisulfites, the contacting conducted at a temperature from about 40° to about 90°C.
  • the precipitated copper sulfide is removed from the precipitation zone, thickened by any conventional technology, optionally filtered, and then a portion recycled to the precipitation zone.
  • a variable part of the thickened suspension is recycled to the precipitation stage to promote the reaction, increase the operable range of acidity, increase the rate of reaction, reduce the reaction time and enhance the degree of completion, all relative to a non-recycled operation.
  • the precipitation may occur in a multicompartmental reactor, such as four compartments in series.
  • the method may use chalcopyrite as a source of sulfur or as a material to be processed in its own right.
  • FIG. 1 is a flow diagram of a first embodiment of the invention in which an aqueous solution of impure copper sulfate is processed using elemental sulfur and sulfur dioxide;
  • FIG. 2 is a flow diagram of a second embodiment of the invention in which a weak, impure solution of copper sulfate is processed into a strong, pure solution;
  • FIG. 3 is a flow diagram of a third embodiment of the invention in which previous embodiments of FIGS. 1 and 2 are used to extract copper from oxidic copper to produce cathode copper;
  • FIG. 4 is a flow diagram of a fourth embodiment of the invention, similar to the previous embodiments of FIGS. 1 and 2, wherein elemental sulfur is substituted with sulfur derived from chalcopyrite-bearing ore;
  • FIG. 5 is a flow diagram of a fifth embodiment of the invention in which the embodiment illustrated if FIG. 4 is modified by routing a majority of the thickened solids and liquids to an oxidation stage;
  • FIG. 6 is a flow diagram of a sixth embodiment of the invention in which the embodiment of FIG. 5 is modified to include a leach of oxidic copper ore;
  • FIG. 7 is a schematic diagram showing a seventh embodiment of the invention illustrating operational parameters and conditions
  • FIG. 8 is a schematic diagram of a vessel used to simulate a reactor of the present invention.
  • FIG. 9 is a drawing of a laboratory simulation of the present invention shown in FIG. 7;
  • FIG. 10 is a correlation between rate and solids concentration in the reactors in Test 14 through 17 of the present invention
  • FIG. 11 is an illustration of separation of metals in each stage versus EMF for Test 14 of the present invention
  • FIG. 12 is an illustration of separation of metals in each stage versus EMF for Test 16 of the present invention.
  • FIG. 13 is an illustration of copper concentration as a function of precipitation time of the present invention for Test 18 through 20;
  • FIGS. 14(a) and (b) are summaries of the sedimentation test on the precipitate produced in the process as set forth in Table 5 herein;
  • FIG. 15 is a summary of cake weight versus thickness from the filtration tests on the precipitate as set forth in Table 5 herein;
  • FIG. 16 is a summary of cake weight versus formation time of the precipitate as set forth in Table 5 herein;
  • FIG. 17 is a summary of cake moisture versus dry time of the precipitate as set forth in Table 5 herein;
  • FIG. 18 is a summary of wash time versus cake weight versus wash volume of the precipitate as set forth in Table 5 herein;
  • FIG. 19 is an illustration of residual copper concentration in solution as a function of precipitation time of the present invention using chalcopyrite with various EMF potentials;
  • FIGS. 20(a) and (b) illustrate settling data derived from thickening tests performed on precipitation slurry using chalcopyrite
  • FIG. 21 is a graph illustrating test results of the inventive process conducted at high acidity levels.
  • FIG. 22 is a schematic diagram of a generalized description of the invention.
  • FIG. 22 describes the process of this invention in a generic manner.
  • Soluble copper e.g. , copper sulfate, CuSOi
  • S° elemental sulfur
  • SO2 sulfur dioxide
  • the contacting is typically conducted with agitation (the stirrer) and at a temperature above ambient (e.g., in excess of 25°C).
  • the soluble copper is usually associated with other soluble metals in an aqueous acidic solution with a free acid content in excess of 0.05 gpl.
  • Copper sulfide will continue to precipitate until the soluble copper or the precipitating reagents are depleted if the process is conducted in a batch mode, or until steady state is achieved if the process is conducted in a continuous mode.
  • one hallmark of this invention is to increase the solids content, i.e., the copper sulfide, of the precipitation zone (here the reaction vessel) by adding copper sulfide. This addition has the desirable effect of increasing the precipitation rate.
  • the copper sulfide that is added to the reaction vessel is usually and preferably a thickened recycled stream.
  • the copper sulfide is formed in the reaction vessel, it is transferred to a thickening tank by any conventional means, e.g. , gravity overflow, pumping, etc.
  • the copper sulfide content is thickened (in FIG. 22, from 30 gpl to 500 gpl).
  • the thickened copper sulfide is then divided into two streams, a product stream for further processing (e.g., smelting or converting) and a recycle stream for return to the reaction vessel. Clear overflow is removed from the thickener as necessary to maintain a working balance of liquids and solids in the thickener. While FIG.
  • the thickener 22 depicts the thickener as a separate vessel, the action of thickening the CuS can occur in the same vessel in which the CuS is precipitated. Vessels such as these will have a precipitation zone and a thickening zone and will allow for the transfer of thickened CuS from the latter to the former zone.
  • the use of sulfur and SO2 as the precipitating reagents produces a precipitate that has desirable settling and filtering properties, and this is another hallmark of this invention.
  • this combination of precipitating reagents affords a more selective precipitation of copper than generally possible with the use of other precipitating a reagents, e.g., hydrogen sulfide (H2S).
  • H2S hydrogen sulfide
  • the conditions at which the process of this invention is operated will vary with the reagents, equipment, starting materials and the like. As such, operating conditions such as temperature, pressure, agitation, contact or residence time, molar ratios, solids content, acid strength, etc. , are selected to optimize copper precipitation in terms of rate, selectivity and completion.
  • operating conditions such as temperature, pressure, agitation, contact or residence time, molar ratios, solids content, acid strength, etc.
  • the practicality of the process is enhanced in the present invention by the application of smelter gas (SO2) containing appreciable quantities of free oxygen, whereas the prior art claims the substantial absence of oxygen.
  • SO2 smelter gas
  • the prior art uses the chemistry of the method to separate copper from other metals by controlling the acidity of the system
  • the present invention provides for the sequential separation of metals by the control of the reduction potential, especially in those situations whereby copper, bismuth and antimony need to be sequentially separated.
  • the first reaction (1) above represents one embodiment of the invention which utilizes elemental sulfiir (S) and SO2 as reactants from suitable sources.
  • the second reaction (2) above represents an alternative source of sulfur-bearing reagent in the preferred embodiment.
  • the term "copper sulfide” is used interchangeably for both the cupric and cuprous forms of this sulfide.
  • the cuprous form of this sulfide may be formed as a secondary product during the precipitation reaction as described by equation (5).
  • the precipitation reaction or step in all of the embodiments of this invention can be practiced using one or more, and preferably more, reaction vessels.
  • This first embodiment of the invention is practiced by employing the impure aqueous sulfate solution from the natural (e.g. , mine run-off), or engineered (e.g., heap leaching), leaching process of a copper-containing material.
  • a copper-containing aqueous sulfate stream from a production process e.g. , refinery bleed
  • the copper-containing aqueous sulfate streams are subjected to a precipitation process in a precipitation system.
  • the solids suspension from the precipitation process is thickened and a portion of the thickened suspension is recycled to the precipitation stage as a slurry to initiate the reaction, increase the operable range of acidity, increase the rate of reaction, reduce the reaction time, and enhance the degree of completion, all relative to a non-recycled operation.
  • the product sulfide precipitate from the preferred embodiment may be separated from the thickened suspension by filtration and processed to final copper-containing product by other means, such as pyrometallurgical smelting methods.
  • the residual filtrate solution (containing sulfuric acid, among others) from the reaction in this first case is either neutralized and discarded, or returned to the process for beneficial use (e.g., as described in FIG. 3).
  • the residual filtrate solution which may contain additional valuable metals, e.g., molybdenum, cadmium, zinc, antimony, bismuth, arsenic, etc., may be processed to recover one or more of these metals.
  • the product sulfide precipitate may be separated from the solution by filtration and re-oxidized to copper sulfate in an additional reactor system:
  • the copper can be selectively removed from impure solutions and concentrated in solution so that the resulting copper sulfate can be electrowon to copper cathode, or processed to other products such as copper sulfate crystals.
  • the sulfuric acid solution remaining after removal of the copper sulfide precipitate may be utilized to provide acid for reaction with the basic minerals of an oxidic copper ore-body (e.g., an ore- body containing copper in a non-sulfidic form).
  • an oxidic copper ore-body e.g., an ore- body containing copper in a non-sulfidic form.
  • Oxidic copper ore-bodies may contain relatively high proportions of basic minerals that consume acid from circulating leach solutions used to convert the oxidized form of copper to soluble copper sulfate. Ore-bodies may consume inefficiently 10 to 20 kilograms (kg) of 100% sulfuric acid per ton of rock, and in extreme cases may consume as much as 100 kg of 100% sulfuric acid per ton of rock. This inefficiency has a large impact on the economics of the extraction process because processing sites are often in remote areas thereby necessitating the transport of acid to, or the generation of acid at, the site.
  • sulfur may be brought to site to produce acid according to the preferred embodiment of the first reaction:
  • the amount of sulfur brought to site can be reduced by using the cupric sulfide to react with additional copper sulfate and sulfur dioxide to produce cuprous sulfide:
  • the copper sulfides produced in the third embodiment may be oxidized according to the method expounded in the second embodiment, and the copper sulfate so produced routed to the SX/EW stage for production of cathode copper.
  • the SX/EW stage liberates an equivalent quantity of sulfuric acid from the input copper sulfate for return to the ore leaching step, an additional equivalent quantity of acid is available from the precipitation stage to meet the demands of the basic components of the ore-body.
  • a cuprous sulfide precipitate is produced that can be readily oxidized to copper sulfate according to the reaction:
  • the cuprous sulfide precipitate may be removed from the solids suspension produced in reaction (2) by filtration or flotation.
  • the sulfuric acid used in the oxidation reaction may be at least partially derived from the precipitation reaction and as such will contain ferrous sulfate (FeSO ). Depending on the conditions of the oxidation reaction, some of the ferrous sulfate may be oxidized to ferric sulfate (Fe2(SO 4 ) 3 ). Since ferric ions can contaminate the SX/EW, the oxidation reaction is preferably conducted to disfavor the production of ferric sulfate.
  • the sulfuric acid required in the oxidation of the cuprous sulfide by reaction (6) may be provided from the acid produced in reaction (2).
  • reaction (2) half of the solution produced in reaction (2) is required to meet the acid demand of reaction (6).
  • the remaining half of the solution from reaction (2) is withdrawn as a bleed stream for iron and any other solubilized species.
  • the aqueous solution produced in reaction (2) may have lost some of the indicated sulfuric acid through neutralization of these minerals. The remainder may be treated with alkali to neutralize the excess acid and precipitate iron.
  • Three fourths of the copper sulfate solution produced by reaction (6) is returned to continue reaction (2) with new chalcopyrite.
  • the other one fourth is removed and purified from soluble iron.
  • the resulting copper sulfate may be electrowon to copper cathode, or processed to other products such as copper sulfate crystals.
  • Sufficient sulfuric acid is produced in the SX stage to meet the acid demands of the copper oxidation reaction.
  • chalcopyritic- bearing ores or concentrates are processed as in the fourth embodiment given above.
  • the whole solution and solids suspension produced by reaction (2) is oxidized as follows: 2 C S + 4 H2SO4 + FeSO ⁇ + 5 V* O: ⁇ 4 CuSO- + V4 Fe:(S ⁇ 4)3 + 2V4 H2O + V ⁇ H2SO4 (7)
  • the quantity of acid available for this reaction will be affected by the basic materials present in the chalcopyritic-bearing ores or concentrates.
  • the ferric sulfate that may be produced by this reaction is a strong oxidant and will assist in the oxidation of copper species in the concentrate or ore-body when three fourths of the copper sulfate solution is returned to continue reaction (2) with new chalcopyrite, as in the fourth embodiment above.
  • the oxidation reaction product is separated into solid and liquid fractions using conventional technology.
  • the solid fraction may be subjected to flotation to separate gangue material from a copper concentrate. This flotation operation is facilitated by the preceding precipitation and oxidation reactions.
  • one fourth of the above copper sulfate solution i.e. the liquid fraction from the thickening operation
  • the resulting copper sulfate may be electrowon to copper cathode, or processed to other products such as copper sulfate crystals.
  • chalcopyritic- bearing ores or concentrates are processed as in the fourth and fifth embodiments given above.
  • the free acid produced by reaction (2) in the fourth case and reaction (7) in the sixth case is utilized for the purpose of reacting with oxidic copper material and acid-consuming basic components.
  • oxidic copper material and acid-consuming basic components may be part of the chalcopyritic-bearing material, or separate oxidic and basic material. If the former, the material will be processed in the vessel. In the latter, the material will be processed on a heap.
  • oxide ore-bodies are found associated with sulfides that contain chalcopyrite.
  • the economics of copper extraction may be improved by the above- described leaching of chalcopyrite-bearing ore, or concentrate, to provide acid for the basic components of the ore or concentrate. It may be only necessary to leach that quantity of chalcopyrite-bearing material needed to provide the required sulfuric acid, as the remaining sulfide minerals containing the chalcopyrite can be concentrated and transported to pyrometallurgical processing sites.
  • copper concentrate may be extracted after the chalcopyrite consuming stage of the sixth embodiment.
  • ores and concentrates that contain chalcopyrite may be processed to cathode copper, at the mine site or in other locations, by simple hydrometallurgical operations.
  • the major reagent to be supplied is sulfur dioxide which can be produced by the roasting of iron pyrite or the combustion of elemental sulfur.
  • oxidic ores can be processed to produce saleable copper sulfide concentrates.
  • the process of this invention is preferably conducted such that a thermal balance is maintained between the various operational steps.
  • Each of the operational steps 13 conducted at conditions and in equipment that maximize their individual performance.
  • the maintenance of the thermal balance between the various operational steps is accomplished using known and conventional techniques, i.e., heat exchangers.
  • FIGS. 7-21 The invention is further described by reference to FIGS. 7-21.
  • a precipitation vessel 20 containing four reaction compartments 22 in series may be used.
  • Each reaction compartment 22 includes a turbine 24 for mixing, baffles 26, reagent sparger 28, suitable temperature and sample ports and level control system means.
  • the aqueous solution containing copper is introduced into the precipitation vessel 20 and is subjected to the reagents therein while being transferred from one compartment 22 to the next.
  • the discharge from the precipitation vessel 20 has flocculent added thereto and flows to the continuous thickener 30 where part of the underflow 31 therefrom is recirculated to the precipitation process and part (equivalent to the new copper fed to the process when in material balance) is fed to a filter 32 to produce a valuable filter cake.
  • the overflow 33 from the thickener 30 is recirculated, in whole or in part, to the copper leaching process, or is passed forward, in whole or in part, to downstream systems 34 for removal of other metals.
  • the liquid from these downstream systems 34 may also be returned, in whole or in part, to the copper leaching process.
  • One aspect of the embodiment shown in FIG. 7 is the processing of secondary copper materials such as flue dust, bag house dust, etc. These materials are leached in an acid media, e.g., sulfuric acid, to produce an impure solution containing copper sulfate and soluble species, e.g., bismuth, arsenic, antimony, cadmium, zinc, molybdenum, and iron, and a solid residue depleted of these metals.
  • the product from this leach operation is separated into solid and liquid fractions.
  • the solid fraction is routed for further processing, e.g. , recovery of precious metals.
  • the liquid fraction is routed to a precipitation operation as shown in FIG. 1.
  • copper sulfide is selectively precipitated from the impurities in the aqueous copper sulfate solution, more specifically arsenic, antimony, molybdenum, bismuth, cadmium, zinc and iron.
  • the solution resulting from the separation of copper sulfide from the impurities is optionally in part recycled to provide acid for the dust leach operation, or is bled to further processing (which may consist of further removal of impurity elements for resale (e.g. , As) or an environmentally acceptable disposal, e.g., Bi or Sb).
  • Another feature of this embodiment is the introduction of copper-containing bleeds (e.g., acid plant blowdown (APB), refinery electrolytes, etc.) into the precipitation operation or stage to selectively precipitate the copper values.
  • copper-containing bleeds e.g., acid plant blowdown (APB), refinery electrolytes, etc.
  • APB acid plant blowdown
  • refinery electrolytes etc.
  • bleeds may and usually do introduce additional acidity into the process and this enhanced acidity promotes selective precipitation of the copper values.
  • one hallmark of this invention is the ability to precipitate copper at the high acidity while promoting the solubility of the impurities, e.g., Bi and Sb.
  • the supply of sulfur dioxide in this embodiment may be provided, for example, from an associated smelter off-gas stream and in part from various bleed streams, e.g., APB, that contains soluble sulfur dioxide.
  • the sulfur for the copper precipitation reaction may be provided, like in the other embodiments of this invention, from elemental sulfiir or chalcopyrite-containing concentrates from an associated smelter.
  • FIG. 23 shows an alternative embodiment of FIG. 7 whereby the leach and precipitation operations are combined in a single reaction step.
  • copper- containing solids e.g., electrostatic precipitation dusts, are fed to a reaction vessel optionally in conjunction with copper-containing aqueous bleeds.
  • the copper- containing solids are leached by sulfuric acid introduced as a separate reagent, or optionally recycled in an aqueous stream.
  • the leachate so formed contains soluble copper, Bi, As, Sb, Cd and Fe.
  • the soluble copper so formed is reacted in situ with sulfur dioxide and a source of sulf ir, such as elemental sulfur or chalcopyrite to form a copper sulfide precipitate.
  • the aqueous suspension of copper sulfide and leach residue is removed from the reaction vessel to a thickening stage. In this stage the copper sulfide and leach residue are settled to form a thickened suspension, part of which is recycled to the reaction vessel.
  • a portion of this thickened suspension is removed, optionally filtered, and routed for further processing, e.g. , through a copper smelter.
  • the clear solution produced from the thickening stage is optionally partially recycled to the reaction vessel to utilize sulfuric acid and a portion is removed for further processing, e.g., removal of Bi, Sb, As, Cd and Fe, or to waste water treatment.
  • a series of tests substantially embodying these conditions were run to simulate a continuous plant arrangement as generally described in FIG. 7. As shown in FIG. 8, to simulate the precipitation vessel 20 containing four reaction compartments 22, simulated reactors were used comprising four 2-liter glass beakers 36 each having an effective operating volume of 1.6 liters.
  • Each simulated reactor was equipped with a Rushton turbine 38, baffles 40, reagent sparger 42, a temperature port 44 having a thermometer 46, an inlet 48 for feed liquid, and an outlet 50.
  • Four such glass beaker reactors 36 were used in series to simulate the precipitation vessel 20 of FIG. 7.
  • the laboratory system is shown in its assembled arrangement in FIG. 9.
  • Pumps 52 were used to provide a continuous flow of reactants, copper sulfate feed liquor, sulfur slurry, and sulfite solutions.
  • Interstage transfer pumps 54 were also used to transfer slurry from one glass beaker reactor 36 to the next, and other pumps (not shown) were used to add flocculent to the final discharge and to recirculate the underflow from the continuous thickener.
  • rotameters (not shown) were provided to monitor the flow of gas.
  • a peristaltic pump was used to add sodium hydroxide to each of the reactors. Not shown in FIG. 9 is the continuous thickener.
  • the present invention is directed to the following preferred conditions using a reaction temperature of about 60°C and a solution pH corresponding to a free acid range of about 0.05 to about 180 gpl (grams per liter) H2SO4, although 10-20 gpl may be preferred. Approximately 10% excess sulfur may be added, although less may be required.
  • Test 4 shows that an excess amount of SO2, when supplied by NaHSO 3 , is not required for the recycle ratio and acidity conditions employed.
  • increased acidity, or reduced solids density, or shallow reactor vessel configuration may result in the necessity of adding an excess of SO2, supplied in gaseous form. That is, increased acidity will tend to decrease the solubility of SO2, reduced solids density will tend to decrease the adsorption of SO2, and shallow vessels will tend to decrease SO: contact time and bubble dispersion.
  • SO2 may be introduced into the reaction vessels in a countercurrent manner to that of the copper-bearing solution, with the gas which exits from the last stage being returned to the second to the last stage and so on sequentially to the first stage.
  • Solids precipitation substantially begins in the measured pH range of 2.7 to 3.0 for a feed liquor containing approximately 20 gpl copper as sulfate, 1 gpl arsenic, 10 gpl iron, and minor quantities of bismuth, cadmium, antimony and zinc.
  • a solution containing the constituents as described was fed into the glass beaker reactors 36 at a rate of about 40 milliliters per minute (40 ml/min.), equivalent to 48 grams per hour (48 gm/hr) of copper or, in terms of equivalent copper sulfide, 72 gm/hr.
  • other reactants, including recycled underflow could add 15 to 40 ml/min. reactive volume such that the nominal retention time in the system could vary from 80 minutes to 116 minutes.
  • Elemental sulfur was provided having a particle size in the 10-20 micron range.
  • An elemental sulfiir of the described particle size designated "Super Fine” may be obtained from a process licensed to Innochem Engineering Company of Canada, such sulfur being produced by a process of injecting molten sulfur through a nozzle into a water bath. Alternately, flowers of sulfiir, a sulfur product from Geneva Steel, Provo, Utah, or sulfiir made from natural gas may be used. All types of elemental sulfur may require crushing and grinding before use.
  • Sulfur dioxide sources may include sulfites and bisulfites, sulfur dioxide in a pure state or a blend of sulfur dioxide, nitrogen and oxygen, such as from smelter gas.
  • the sulfites and bisulfites may be derived from the sodium or calcium salts of sulfites and bisulfites.
  • Table 1 represents the various test conditions with sodium bisulfite as the SO2 donor which were employed to evaluate the process in a continuous operating mode. Different types of sulfur and varying dosages of the reactants were utilized while employing a moderately high recycle ratio of precipitated solids to the reaction zone. This approach had been found to be very critical in batch tests in making the reaction proceed at a practical rate and with a high degree of completion. The continuous system confirmed the observations made from the batch test results.
  • Recycle ratio based on amount of solids recycled to maintain this concentration prior to precipilation, based on total amount of CuS that could be precipitated, if 100% were achieved.
  • a second series of tests numbered 8 through 13, employed pure sulfur dioxide gas under conditions similar to those of the first series of tests. These test results are summarized in Table 2. These tests demonstrate the effectiveness of gaseous SO2 in the process, even under conditions not conducive to efficient gas abso ⁇ tion, the high acidity of the solution and the shallow liquid depth in the reactors.
  • Recycle ratio based on amount of solids recycled to maintain this concentration prior to precipilation, based on total amount of CuS that could be precipitated, if 100% were achieved.
  • the third series of tests confirmed the applicability of a simulated feed to a smelter acid plant, such as may apply from a copper flash smelting process. It was shown that despite the presence of a partial pressure of 5% oxygen in the simulated gas, there was little or no interference with the reductive power of the SO2. In addition, the level of excess SO2 was decreased to as low as 54% , and high precipitation efficiencies were confirmed. As previously described, it is not considered that this represents a lower limit to the SO2 requirement since several factors are involved in its utilization, not least of which is the shallowness of the test reactors.
  • This third series of tests utilized sulfur dioxide derived from a simulated flash smelter gas containing 35 % SO2, 60% N2 and 5 % 02.
  • the smelting operation is continuous and the off-gas which passes to an acid plant contains a high level of sulfur dioxide with a relatively low oxygen content.
  • the gas composition is also fairly constant due to the continuous nature of the process.
  • Other continuous processes like the Noranda, Mitsubishi, and Isasmelt Processes produce high strength off-gases that may prove acceptable as a source of SO2 reductant.
  • the recycle ratios for precipitated solids were varied from 0 to as high as 23, with the reaction times decreasing proportionately.
  • Recycle ratio based on amount of solids recycled lo maintain this concentration prior to precipitation based on lotal amount of CuS that could be precipitated, if 100% were achieved
  • Test 16 which would represent a desirable operating level in terms of good separation of copper from the other elements, illustrates these preferred conditions.
  • the EMF in this case was slightly lower than that noted in the previous test, although this may have been due to a difference in the sulfur dioxide concentration in the different samples.
  • Tests 18, 19 and 20, as shown in Table 4 were carried out on a batch basis, but with the simulated smelter gas as the source of sulfur dioxide. Since the process solution could be present at a higher temperature in a flue dust leach process, these tests were carried out at 80°C which would be anticipated to increase the reaction rate. The amount of precipitate solids present in the reactor corresponded to that which would exist with the recycle ratio of 23.
  • the material produced in the inventive process was more easily thickened and filtered than that, for example, resulting from the use of hydrogen sulfide precipitant.
  • a settling test and several filtration tests were carried out on the material produced during the continuous precipitation study, with the test conditions and results shown in Tables 5 and 6, and FIGS. 8 through 12.
  • Feed Tot Solids (weight percent): 66.000 Liquid Sp. Gr: 1.0900 Feed Diss Solids (weight percent): 0.000 Slurry Sp. Gr: 2.2600 Calcd Feed Susp SIds (weight percent): 66.000 Calcd Solid Sp. Gr.: 5.0555
  • Dry Vacuum 38.100 38.100 38.100 38.100 38.100
  • Air Reading Bef (cubic meters) 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000
  • Air Reading Aft (cubic meters) 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000
  • Air Flow (cubic meters per minute 0.000 0.000 0.000 0.000 per square meter)
  • Moist Factor 2 (graph 4) 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000
  • the quantity of recycled precipitate solids appears to be less important in maintaining a high reaction rate if the measured pH is maintained close to 2.
  • high recycle ratios that may be used to maintain a productive reaction rate incidentally will also produce a substantially coarser particle that will yield lower cake moisture and give higher filtration rates on the product slurry.
  • a pH reduction stage e.g. , a bismuth precipitation stage
  • caustic soda or other suitable alkaline material may be advantageous to add caustic soda or other suitable alkaline material to maintain the pH constant since this will maximize the precipitation rate.
  • FIGS. 14(a) and (b) A thickening test was run on the slurry produced, the results being shown in FIGS. 14(a) and (b).
  • the upper line in FIG. 20(b) represents the settling rate values calculated from the settling test data illustrated in FIG. 20(a), while the lower line represents a scale-up application to a full-sized thickener of the values calculated in the upper line.
  • the underflow from this test was filtered at a rate/ of about 2.53 kilograms per hour per square meter (60 pounds per hour per square foot) yielding a filter cake having a solids concentration of 74.6% .
  • An alternative approach to grinding chalcopyrite for use in the precipitation process described above is to process an amount of chalcopyrite through a cyclone of a diameter suitable to remove only the fine particles in the slurry — for example, the particles sized at equal to or less than 15 microns.
  • This material may be thickened and added to the reactors.
  • the test work indicated that a retention time of about 80 minutes in a continuous circuit with a recycled solids concentration in the reactors of 300-400 gpl copper sulfide solids would yield almost 100% recovery of the copper and at the same time provide a good separation from the impurities, arsenic, iron, and other minor elements.
  • the tests show that all the sulfur and sulfur dioxide sources tested are equally applicable.
  • the solution acidity was found to be a major factor in controlling the rate of reaction.
  • approximately 3 gpl H 2 SO 4 was produced for every gram per liter of copper that was precipitated using sulfur dioxide.
  • the reaction rate in a solution at 60°C and an initial pH of about 2 will decrease from approximately 10 kilograms copper per cubic meter per hour to about half that rate as the reaction progresses.
  • caustic soda or other suitable alkali can be added to maintain acidity at a constant level to yield a relatively constant precipitation rate.
  • NaHSO3 to provide the necessary SCh for the reaction, also results in a simultaneous neutralization of the acidic solution to help maintain acidity at a constant level.
  • Sodium bisulfite can be obtained commercially or by reaction of SO2 with caustic soda.
  • a soluble neutralization product such as is obtained by use of caustic soda or sodium bisulfite, is preferred to prevent the dilution of the copper sulfide by insoluble products of neutralization.
  • a high concentration in the range of 500 gpl copper sulfide, effectively doubles the reaction rate. Higher concentrations also produce a precipitate with a substantially coarser particle size.
  • the average acidity varied from approximately 125 gpl to 40 gpl of HiSOt acid resulting in the reaction rate increasing from 5 to 30 kilograms copper per cubic meter per hour.
  • This concentration of solids requires a recycle ratio of about 20 times the amount of solids being precipitated on each pass.
  • Tests 22 and 23 were conducted. In these tests the acidity of a solution containing a final 20 grams per liter copper as copper sulfate was adjusted to 180 grams per liter sulfuric acid prior to reaction at 80°C.
  • Results from the two tests are shown on FIG. 21.
  • Test 22 with no added copper sulfide, there was only a small decrease in the copper concentration of the solution over a period of 4 hours.
  • Test 23 there was almost a complete precipitation of copper in 2 hours demonstrating the benefits of the present invention.
  • the precipitate resulting from the process was easily thickened and filtered, with a thickener unit area in the range of 0.015 square meter per metric ton per day (0.15 square feet per ton per day) and filtration rates varying from 5.06 to 12.64 kilograms per hour per square meter (120 to 300 pounds per hour per square feet). Filter cake moistures ranged from 25% to as low as 12% when a simulated cyclone underflow was dewatered.
  • the preferred temperature of the precipitation reaction is between 60° and 80°C whereas the temperature of the leach solutions may be in the range 5° to 80°C depending on source.
  • the heat required for the precipitation reaction can be provided by recuperation of the heat content in the outgoing stream with the incoming stream, or the sensible heat of the SO 2 -bearing gas stream or both.

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Abstract

La présente invention concerne un procédé de séparation du cuivre et d'autres métaux dans une solution. Ce procédé consiste à précipiter le cuivre dans un réacteur contenant environ 0,05 à 180 grammes d'acide libre par litre, à une température allant d'environ 25 °C à environ 90 °C dans une solution aqueuse comprenant du soufre élémentaire ou de la chalcopyrite, et une matière appartenant au groupe des sulfites solubles et bisulfites solubles. Le procédé consiste ensuite à séparer le cuivre précipité, sous forme de sulfures de cuivre, en épaississant la solution, en recyclant une partie par la phase de précipitation, et en séparant par filtration les sulfures de cuivre des autres parties.
PCT/US1996/001910 1995-02-17 1996-02-14 Procede de precipitation du cuivre WO1996025361A1 (fr)

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US08/390,920 1995-02-17

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0815269A2 (fr) * 1995-03-24 1998-01-07 Kennecott Holdings Corporation Amelioration du traitement hydrometallurgique des impuretes degagees par le traitement pyrometallurgique du cuivre

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA120363A (fr) * 1908-11-06 1909-09-07 The Canadian General Electric Company, Limited Dispositif a limitation de la vitesse pour generateurs a turbines
US3728430A (en) * 1970-12-14 1973-04-17 Anlin Co Method for processing copper values
BE832682A (fr) * 1974-08-22 1976-02-23 Procede de separation du cuivre a partir de solutions et de boues en contenant

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA120363A (fr) * 1908-11-06 1909-09-07 The Canadian General Electric Company, Limited Dispositif a limitation de la vitesse pour generateurs a turbines
US3728430A (en) * 1970-12-14 1973-04-17 Anlin Co Method for processing copper values
BE832682A (fr) * 1974-08-22 1976-02-23 Procede de separation du cuivre a partir de solutions et de boues en contenant

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0815269A2 (fr) * 1995-03-24 1998-01-07 Kennecott Holdings Corporation Amelioration du traitement hydrometallurgique des impuretes degagees par le traitement pyrometallurgique du cuivre
EP0815269A4 (fr) * 1995-03-24 1998-07-15 Kennecott Holdings Corp Amelioration du traitement hydrometallurgique des impuretes degagees par le traitement pyrometallurgique du cuivre

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CA2212378A1 (fr) 1996-08-22
PE52097A1 (es) 1998-01-07

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