MXPA97001575A - Improved process for the obtaining of copper from concentrated minerals containing dichomine - Google Patents

Abstract

A new process for obtaining copper in concentrated minerals of said metal is described and essentially consists of subjecting said concentrates, previously roasted, in case this is necessary, and in an aqueous suspension, to a treatment, under pressure and suitable temperature, with sulfuric acid (H2SO3) and from which two main products are obtained: a solution and a solid residue. The copper contained in the solution can be recovered by known methods and the metallic copper, contained in the residue is re-concentrated by flotation and refined by methods already known, such as "refining to fire", electrolytic refining and / or chemical refining

Description

IMPROVED PROCESS FOR OBTAINING CO BRE FROM D CONCENTRATED MINERALS CONTAINING SUCH METAT.

SUMMARY OF THE DESCRIPTION A new process is described to obtain the copper contained in concentrated minerals of said metal and consists, essentially, in subjecting said concentrates, previously roasted, 3 in case this is necessary, and in an aqueous suspension, to a treatment, at appropriate pressure and temperature, with sulfurous acid (H2S03) and from which two main products are obtained: a solution and a solid residue. The charge contained in the solution can be recovered by known methods and the metallic copper contained in the residue is re-concentrated by flotation and refined by methods already known, such as 0"refining to fire", electrolytic refining and / or chemical refining. Background of the Invention As already indicated, the present invasion refers to the efficient recovery of the copper contained in concentrated minerals of said metal, and is particularly applicable to concentrates in which the copper is contained in any of the main minerals copper, including the following: chalcosite (Cu2S), chalcopyrite (CuFeS2), bornite (Cu5FeS4), covelite (CuS), malachite (Cu2 (OH) 2C03), cuprite (Cu20), and tenorite (CuO), etc. They exist in currently numerous methods to recover and refine the copper contained in 2? concentrated minerals, which, in general terms, can be divided into two large groups: Pyrometallurgical methods, which consist basically of the melting of said concentrates to obtain a mixture of copper sulphides and iron called mata, the conversion of this mixture to an impure copper called blister and the electrolytic refining of the latter to a pure copper called "electr olytic "; and hydro-metallurgical methods, which consist of dissolving the copper concentrates in acid (sulfuric, hydrochloric, etc.) or ammoniacal solutions (NH40, plus carbonate or ammonium sulfate) and recovering the dissolved copper by means of its precipitation with another metal ( iron or zinc), by means of electrorecovery or by chemical methods.

Probably, the methods most used today are the pyrometallurgical ones, being able to estimate that they obtain more than 90 percent of the world copper production. l To better understand the fundamental principles of the different methods currently in use, and their With regard to the present invention, it is convenient to consider that, in the vast majority of Asses, said concentrates are basically formed by copper, iron, sulfur, and impurities.

The latter, which may be very important, consist in turn of gangue particles (silica, alumina silicates, calcite, etc.) and some metals and / or minerals that normally accompany copper, such as gold, silver, arsenic, bismuth, tellurium, selenium, nickel, cobalt, zinc, lead, antimony, molybdenum, etc. Some of these impurities are valuable and, therefore, must be efficiently recovered and others, are very harmful to the end uses of copper, therefore, should be eliminated as much as possible. Normally, modern methods of smelting copper concentrates, begin by adjusting, if necessary, the relationship between copper and sulfur contents. In this case, this adjustment is made through a partial test of the concentrates, which removes part of the sulfur in the form of S02. The second step consists in the fusion of said concentrates, to achieve the recovery of a molten mixture in copper and iron sulphides (matte) and a slag containing part of the iron and most of the silicose impurities, contained in the concentrates. . The molten mixture of copper sulphides and iron (matte) undergoes a so-called conversion operation and in which, by introducing large amounts of air and adding suitable fluxes, first the excess sulfur (in the form of S02) is removed, then the iron, in the form of a slag (iron silicates) and finally the remaining sulfur, also in the form of S02 gases. The final product of this operation is a more or less impure copper, called blister copper or blister (98 to 99% Cu), which contains almost all of the gold and silver of the original ore and most other impurities such as bismuth, arsenic, antimony, selenium, tellurium, nickel, cobalt, lead, zinc, etc. This copper blister, is subjected to "refining to fire" methods, which reduce their content of some scoriable or volatilizable impurities, such as lead, zinc, nickel, etc., and finally, to an electrolytic refining, from which copper is obtained. more than 99.9 per purity slurry (without harmful impurities), "anodic sludge" containing most of the gold, silver, selenium, tellurium, bismuth, and other impurities, and an "electrolytic solution" that It contains copper, nickel, cobalt, iron and other impurities.

It should be noted that the slag obtained in the conversion step generally has a high copper content, so it is necessary to retreat, either by flotation (to obtain a new concentrate) or by smelting (to obtain a new matte). This "circulating charge" 35 can become of great relative magnitude. l In very general terms, it can be stated that the main disadvantages of the pyrometallurgical methods described above are: a) The need for numerous operations, at high temperatures (fusion of concentrates, converting, etc.), with consequent high consumption 40energético (more than 3.75 million Kcal per ton of blister copper produced in modernized operations); b) For the same reason as before, difficulties to automate and simplify operations, with the consequent need for a highly specialized workforce willing to work hard; c) Irregular production, of a large quantity of gases, highly polluting and difficult to take advantage of and / or control (mainly of S02), and d) High cost of the 45 facilities and relative high cost of operations in them. It is evident, for all the above mentioned, the convenience of developing a process that, following the fundamental guidelines of those currently used, can obtain, from It is evident, for all the aforementioned, the convenience of developing a process that, following the fundamental guidelines of those currently used, obtain, from concentrated copper ore, products similar to blister copper, avoiding the disadvantages referred to in the previous paragraph. SUMMARY OF THE INVENTION The antenor object and other related objects are obtained through the provision, in a process for obtaining copper from concentrated minerals containing said metal, from a stage in which it is reduced, in an aqueous medium. , copper to metal copper compounds through the action of sulfuric acid H2S03) at pressures and temperatures above atmospheric and, at the same time, oxides of iron are dissolved and reduced to ferrous sulphate, through the joint action of acids sulfuric and sulfurous. DETAILED DESCRIPTION OF THE INVENTION The process to which the present invention refers consists of a series of operations that must be carried out successively in order to obtain a product that, by its characteristics, is similar to the blister copper, currently produced by the melting and conversion of minerals. copper concentrates. These operations must be carried out under the general conditions set out below in detail. The first stage of the process consists of preparing the copper concentrates, for their subsequent reduction in an aqueous suspension, with sulfurous acid. According to our experience and that of other researchers (Shoichiso Hori et al., In the North American patent number 3,573,896 of April 1971), the copper compounds that best react with sulphurous acid are cupric oxide (CuO), sulfate (CuS04), carbonate (CuCCß • Cu (OH) 2) and some complex salts such as oxysulfates, basic sulphates, etc. On the other hand, the iron contained in the concentrates is only easily and rapidly soluble in sulfuric acid solutions, when it is in the form of sulfates or ferric oxide (Fe203), very finely divided.

For these reasons, in all cases in which copper concentrates consist essentially, or contain substantial amounts of copper and / or iron sulphides, it is necessary to transform these sulphides into mixtures of sulfates and oxides, which is achieved through proper testing. 5The testing of copper concentrates and minerals and their variants (sulfatizing test, etc.), are metallurgical operations widely studied and known by experts in the art, so it is not necessary to expose them in more detail; Suffice it to say that, in order to achieve adequate results with our invention, it is necessary to transform, in this operation, as many copper sulphurs as possible, to sulfates and cupric oxides and sulphides of ferrous sulfates and oxides; which is generally achieved by carrying out this test at low temperatures (450 ° to 500 ° C) and with excess air. It is important to note that an adequate test is essential for the achievement of good results in the process to which the present invention refers. The second stage of the process, ie the essential part of the present invention, is based on the chemical reactions that occur when treating, in an aqueous medium and at temperatures and pressures above atmospheric, copper concentrates previously prepared (in if necessary), with sulfuric acid (H2S03). Fundamentally, these reactions can be expressed with the following chemical equations CuO + H2S03 > Cu ° + H2SO4 0) CuSO4 + H2SO3 + JH20 - - > Cu ° + 2H2S04 (2) CuC03-Cu (0H) 2 + 2H2S03 - > 2Cu ° + 2H2S04 + C02 + H20 (3) Fe203 + 3H2S04 - > Fe2 (S04) 3 + 3H20 (4) Fe2 (S04) 3 + H2SO3 + H20 ~ > 2FeS04 + 2H2S04 (5) Fe203 + H2S04 + H2S03 - > 2FeS04 + 2H20 0 (6) As can be seen from the previous equations, each Cu molecule, in the form of CuO or CuC03-Cu (OH) 2 when reacting with. the sulphurous acid, produces a metallic copper molecule and a molecule of sulfuric acid (H2S04) (reactions 1 and 3) and each molecule of copper sulphate, reacts with one of sulphurous acid, producing one of metallic copper and two of acid sulfuric (equation 2). For its part, each molecule of ferric oxide, reacts with three molecules of sulfuric acid, producing a molecule of ferric sulfate (equation 4) which, in turn, reacts with one of sulfurous acid (H2S03) to produce two molecules of ferrous sulfate (FeS04) and two 0 molecules of sulfuric acid (equation 5). The net result of equation 6, which indicates that the reaction of a ferric oxide molecule with one of sulfuric acid and one of sulphurous acid, results in two molecules of ferrous sulfate (FeS04) and two of water. Considering what has been previously indicated with respect to the composition of the copper concentrates and the chemical reactions mentioned above, it can be concluded that, when reacting a copper concentrate, previously prepared (toasted in the appropriate manner as indicated above) , with an aqueous solution of sulfurous acid, at high temperature and pressure, two main products will be obtained: a) a solution containing ferrous sulphate (FeS04), sulfuric acid (H2S04) and the soluble sulfates of some impurities such as zinc, nickel, 0 aluminum, etc. and b) a solid residue, formed by metallic copper, gold, silver, lead sulphate, silica, calcium sulfate and other insoluble impurities (bismuth, arsenic, antimony, etc.) in sulfuric acid solutions. In. In practice, we have been able to achieve the theoretical conditions described above, using large excesses of sulphurous acid and longer ovmenos treatment times, using moderate amounts of sulfurous acid and short treatment times (of the order of 15 to 30 minutes), manages to obtain the following products: a) A solution containing ferrous sulfate, cupric sulfate, sulfuric acid, and other soluble sulfates (zinc, nickel, aluminum, etc.); b) a solid residue, containing metallic copper, silica, ferric oxide, lead sulfate, gold, silver and other impurities insoluble in sulfuric acid, and c) gases, basically consisting of SO2 and water vapor.

To carry out, in practice, this second stage of the process, the copper concentrate roasted, (in the case of sulphide minerals), is suspended in adequate quantities of water (the Does dilution basically depend on the amount of S02 that can be dissolved in the water and the amount of soluble FeS04 in the final solution). This suspension is saturated with the necessary amount of S02 (minimum teónco, one mole of S02 for every mole of Cu present), and small amounts of sulfuric acid (between 1% and 5%) are added, to accelerate the reactions The pulp thus prepared is introduced into a closed container (autoclave), in which its temperature is increased and pressures greater than atmospheric are reached According to the type of material being treated and the characteristics of the pulp itself, (dilution, amount of S02 and of H2S04, etc.), the reaction is controlled at temperatures that vary between 130 ° and 180 ° C, and if the generated gases are not released, pressures of the order of 12 65 to 21 09 Kg cm2 can be reached. 10 Even though the equipment used by us does not allow to study in detail the reactions that are carried out inside the autoclave, it can be indicated that these reach their maximum intensity for 10 to 20 minutes after reaching an initiation temperature (generally between 120 ° and 140 ° C) and reach their full completion in times ranging from 30 to 120 minutes, 5 after reaching that temperature We consider that, for practical purposes, (obtaining appropriate products for post-treatment), and for reasons economic, it will not be necessary, in most cases, to reach the total termination of the reactions, being able to take advantage of only the period in which they are reared with greater intensity (10 to 30 minutes after they are started) Completed, practiced or totally reactions, cooled below its boiling point, the pulp and expelled the excess gases (which must industnalmente be recovered for their content of S02), proceeds, by well known means (settlement and filtration), to the separation of the residue solid and the resulting solution In the event that the reaction has not been carried to its full completion, the resulting solution and the wash water of the residue will contain, normal In this case, appreciable amounts of copper in solution, in the form of copper sulphate, can easily be recovered by any of the usual methods, such as metal-iron cementation, LIX-Electrowining methods or the process invented by the undersigned for the recovery of copper from acid solutions, and whose patent application was filed on September 5, 1974 and registered under No. 153595. Not being part of the present invention, it is not considered necessary to give more details regarding these operations, 5 most are also widely known by those skilled in the art. In case the concentrated copper ores being treated contain substantial amounts of nickel, zinc and / or cobalt, most of these metals will pass to the solution and can be recovered from it, by means of extraction by solvents or other known processes 0 After recovered the valuable metals contained in The solution will basically consist of a mixture of sulfur-ferrous (aluminum, sodium, potassium, etc.) This solution will be very similar to the "pickling" liquors, produced in the steel industry and whose use or neutralization has been and is Widely studied and applied The solid waste, obtained in the autoclave, the reactions are carried out, usually consists of a mixture of metallic copper (between 70 and 90 percent of its weight), silica, iron oxides, gold, silver, lead and other insoluble impurities in sulfuric acid In some cases (especially when starting from very pure concentrates and long treatments are used), this residue will be of sufficient purity to be fused directly into anodes, for its electrolytic refining or to be treated by chemical refining methods (patent application No. 146375, filed on September 25, 1973). However, in most cases, the content of impurities (especially silica and iron oxide), requires a new stage of concentration of this residue. In this new stage of concentration, in which it is a matter of separating metallic copper and valuable impurities (gold and silver), from the rest of the residue (mainly silica and lead sulphate), numerous known methods can be used, such as those of flotation, gravimetric concentration or leaching. Due to its simplicity and effective results, in our experiences we have basically used the flotation method, without this implying that other methods are not advantageously applicable, according to the specific conditions of each case. In the case of being used for this stage of the process, the flotation method is carried out under the conditions and with the normal reagents for the metallic copper flotation and, in the general case, three products are obtained: "concentrate clean "," means "and" tails ". Clean concentrates generally contain more than 90 percent metallic copper, most gold and silver, and in a very small proportion, other insoluble impurities, such as iron oxides, aluminum silicates, lead sulfates, calcium and barium. , silica, etc. In their normal form, these "clean concentrates" are easy to dry and melt in an anode furnace, in which, by means of refining to fire, some of the impurities can be eliminated, partially or totally. present, finally obtaining metallic copper, in the form of anodes, of very good quality for its electrolytic refining. ? 5 The "means" obtained in the flotation, usually represent good copper concentrates (between 30 and 70 percent Cu) with similar impurities, but in greater quantity than in the "clean concentrates", and can be easily melted or recirculated, either in the flotation stage, or throughout the process. 30 Finally, the "tailings" of the flotation consist, for the most part, of insoluble impurities (silica, lead sulphate, calcium sulfate, barium sulfate, iron oxides, etc.), with low copper content (between 1.0 and 5.0 percent Cu). In case it is economically convenient, this copper can be recovered by leaching with ammonia and ammonium sulfate, and 35precipitated as ammoniacal cuprous sulfite, with S02 (patent application No. 146375, filed September 25, 1973). When copper concentrates originally contain substantial amounts of lead, these "glues" can become a good concentrate of this metal. In other cases, the only appreciable value of the flotation "tails" will be their gold and silver content, which can be recovered by cyanidation and, finally, in some cases, the tails will not have any economically recoverable value and will constitute real waste. BEHAVIOR OF SOME OF THE MAIN IMPURITY. 45 As already indicated, copper mineral concentrates usually consist of copper, iron, sulfur and variable amounts of a series of metallic and non-metallic impurities, which can be economically valuable or harmful and which, in any case, is necessary to separate or eliminate the jjjjial product. It is appropriate, for the purposes of the present invention, to analyze in summary form the way in which each of these substances behaves during the various stages of the process. 5 a) Copper As already indicated, one part may remain in the autoclave solution (as soluble sulphate) and the rest as metallic copper in the solid residue. 0 b) Iron Most of the iron contained in the concentrates, (between 70 and 80 percent), should be left in the solution of the autoclave, in the form of ferrous sulfate (FeS04). The rest remains as iron oxides (mainly hematide and magnetite) in the solid waste, and must be distributed mainly between the "media" and the "tails" of the flotation of said residue. 5 c) Sulfur Most of the sulfur contained in the concentrates, it is converted to S02 during the roasting of them, and it is later used for the treatment in the autoclave, where it is combined with oxygen and water to form sulfuric acid H2S04). Small amounts of sulfur combine 0 with lead, zinc, nickel, aluminum, calcium, etc. present, to form soluble or insoluble sulfates of these elements. It is considered that, for normal concentrates of copper sulphide minerals, in which the content of copper and iron is practically equal to the sulfur content, it will be possible, in the process to which the present invention refers, to consume in the products before mentioned (sulfates and H2S04), all the sulfur present, thus avoiding any problem of air pollution. d) Gold and Silver. All of these metals remain in the solid residue of the autoclave and then accompany the copper in the flotation concentrate of said residue. 0 e) Silica, silicates, lime carbonate and other minerals constituting the gangue. For the most part, they remain with the solid residue of the autoclave and are eliminated in the form of flotation "tails". ^ 5 f) Zinc and Cadmium For the most part, they pass to the solution of the autoclave in the form of zinc and cadmium sulfates, recoverable by solvent extraction and electrolysis processes. g) Lead and Tin. 0 In their entirety, they remain as insoluble sulfates in the solid waste of the autoclave and, for the most part, are eliminated in the "tailings" of the flotation of said residue. h) Arsenic, Antimony, Selenium and Tellurium. For the most part, they are eliminated by volatilization during the roasting of the concentrates. The rest remains as insoluble compounds in the solid residue of the autoclave, and accompanies the copper in the flotation concentrates. i) Bismuth. This impurity is extremely harmful and difficult to eliminate in normal foundry processes. In our process, it remains in the solid waste of the autoclave; but, for the most part, it is eliminated in the flotation "tails" of said waste. j) Nickel and Cobalt. For the most part, they pass as soluble sulfates to the solution of the autoclave, from which, if economically feasible, they can be recovered in a similar way to zinc.

From the above, it turns out that the metallic copper contained in the flotation concentrates, of the solid residue of the autoclave, is remarkably low in harmful impurities and therefore constitutes a product easy to refine with fire and very suitable for its electrolytic refining. .

It should also be noted that, when presented in economically recoverable quantities, 5 the main valuable impurities of copper concentrates (gold, silver, lead, zinc, etc.), can be efficiently recovered with the process to which the present invention refers. . EXAMPLES OF THE PROCESS o To indicate some of the results obtained in the laboratory with the process to which the present invention refers and some of the factors that may affect said results, the following examples are detailed below: A) Autoclave treatment series of a Cu2S concentrate (chalcosite) obtained from the mining of a disseminated copper deposit with dilutions and varying amounts of S02. B) Treatment series of a 5 concentrate consisting mainly of chalcopyrite, with autoclave treatment times, variable; C) Treatment and metallurgical balance of the same concentrate of Example A, with autoclave time of 35 minutes, dilution of 7.5 to 1.0 amount of S02 from 1.0 to 1.0 of copper, and D) Treatment and complete metallurgical balance of a concentrate of chalcopyrite ( CuFeS2), obtained in a mining operation, from a hydrothermal deposit of sulfides Qcomplejos (lead, zinc, copper, gold and silver).

EXAMPLE A Original Concentrate Law Cu 31.0% Law Fe 26.9% Law S 31.0% a) Toasting Load 1000 grms. Temperature 550 ° C Time 4 Hrs. Product 1035 grms. , Laws: Cu ... 30.0%; Faith ... 26.0%; S ... 4.0% b) Treatment in Autoclave Load 200 grms Dilution Variable Time 2 total hours S02 Variable EXAMPLE B Original concentrate consisting mainly of chalcopyrite (CuFeS2) and appreciable amounts of silica, blende (ZnS), galena (PbS) and other impurities. a) Roasting: Load 1500 grms Temperature 550 ° C Time 3.5 Hrs Product 1550 grms Analysis: Cu ... 26.5%; Fe ... 26.0% b) Autoclave treatment: Load 200 grms of toasted H20 1500 ce. H2S04 3 ce. S02 50 ce Variable Time 10, 30, 45, 90 and 120 minutes after reaching 130 ° C EXAMPLE C Original Concentrate: Cu 26.5% Fe 26.2% S N.A. a) Roasting: Concentrate 300 grms Plaster 30 grms Temperature 450 ° C Time 3.5 Hours Product: 320 grms; Cu ... 24.8%; Fe ... 24.55% b) Autoclave treatment: Toast charge 200 grms H20 1500 grms S02 50 grms H2S04 5 grms Total Time, 60 minutes; that is 35 minutes after reaching 130 ° C EXAMPLE D Original concentrate: Cu 28.00% Fe 25.30% S 30.00% Au 3.0 grms / Ton Ag 1600 grrns / Ton Pb 2.00% Zn 4.00% Insoluble 6.00%

Claims (3)

a) Toasting Load 550 grms Temperature 450 ° C Time 3.5 Hours Product- 555 grms; Cu 28.0%, Fe ... 25 3% b) Autoclave treatment: Roasting 555 grms H20 3500 c c S02 200 grms, H2S04 15 Ogrms Total time, 60 minutes, 34 minutes after reaching 130 ° C NO DUE OF THE INVENTION Having described the invention, it is considered as a novelty and, therefore, the content of the following clauses is claimed as property

1 - . 1 - Improved process for obtaining, from copper mineral concentrates, a product similar to that known in the mining industry as "bhster" copper, that is, a metallic copper containing most of the gold, silver of the copper contained in the concentrates and small amounts of harmful impurities, characterizing the process, basically, by a stage in which, in an aqueous method, copper compounds are reduced to metallic copper, through the action of sulfurous acid (H2S03) to pressures and temperatures above atmospheric and, at the same time, oxides of iron are dissolved and reduced to ferrous sulphate, by the joint action of sulfuric and sulfurous acids

2 - Process improved according to clause 1, characterized also because The pulp of concentrate and water is saturated with an amount of sulfur dioxide (S02) comprised between about 1 0 and 1 5 to 1.0 by weight, in relation to the contained copper. in the pulp

3. - Improved process according to clause 1, characterized in that the reactions between sulphurous and sulfuric acids and the sulfates and oxides of copper and iron contained in the roasted concentrate are carried out at temperatures above 120 ° C and at pressures higher than the atmospheric, sufficient to compensate the pressure of the water vapor and the gaseous S02 formed. 4. Process improved according to clause 3, further characterized in that the reactions are carried out at temperatures of the order of 150 ° C to 200 ° C. and at pressures of the order of 7.03 to l 4.06 Kg / cm2. 5. - Improved process according to clause 1, further characterized because the times necessary for the aforementioned reactions to be carried out, vary between 10 minutes and 90 minutes, after reaching the temperature of 130 ° C. Mexico, D.F., February 26, 1997