WO2014094091A1 - Method and apparatus for bioleaching primary ores, flotation wastes and weathered ores with biological production of sulfuric acid from elemental sulfur and/or pyrite - Google Patents

Abstract

The present invention relates to a method and apparatus for bioleaching primary ores containing copper, nickel, zinc, cobalt, molybdenum, uranium, precious metals, flotation wastes from the production of sulfide concentrates of said metals, and also weathered ores (ores said to be oxidized) with the simultaneous biological production of sulfuric acid from elemental sulfur and/or pyrite.

Description

 Process and Apparatus for Bioleaching of Primary Ore, Flotation Tailings and Weathered Ore with Biological Sulfuric Acid Production from Elemental Sulfur and / or Pyrite

The present invention relates to a process and apparatus for the bioleaching of primary copper, nickel, zinc, cobalt, molybdenum, uranium, precious metals, flotation tailings from the production of sulfide concentrates of these metals, and furthermore. weathered ores (so-called oxidized ores) with simultaneous biological production of sulfuric acid. The invention utilizes aliquots of these mineral substrates to simulate pile operation, to fill polypropylene columns with acid leaching irrigation systems, air insufflation and external heating for the use of acidophilic microorganisms. mesophilic and thermophilic (moderate and extreme), aiming to accelerate the bio-oxidative processes involved (bioleaching of mineral sulfides of commercial interest as well as elemental sulfur and pyrite), mainly in the bioleaching of refractory mineral sulfides, such as chalcopyrite (CuFeS ₂ ), which is nowadays the main source of copper. Mineral substrates responsible for the in situ generation of sulfuric acid (elemental sulfur and / or pyrite) are used, after appropriate comminution, as a coating of coarse particles (3mm to ½ inch) of the ores to be bioleached ( weathered primary ores). In the case of the abovementioned flotation tailings, these will be agglomerated together with the sulfuric acid generating mineral substrates (elemental sulfur and / or pyrite) in appropriate proportions and, where appropriate, pelletizing agents will be added for formation of the mineral bed to be used in the columns where the bioleaching process will occur.

Justification of the invention

Through its main derivatives, sulfuric acid, sulfur is classified as one of the most important elements used as industrial raw material. It is of prime importance for all sectors of the industrial complexes and fertilizers in the world. Sulfuric acid production is the major end use of sulfur, and sulfuric acid consumption has been considered one of the best development indices. one nation. Worldwide production of sulfuric acid is over 150 million tons per year.

 There is a wide range of industrial applications for sulfuric acid. Some examples of these include their use in: phosphorus and nitrogen fertilizers; oil refining; mineral leaching; ie the industrial extraction of copper, zinc, nickel and titanium; production of organic and inorganic inputs; in paint and pigment manufacturing processes; in the metallurgical industry in iron, steel and non-ferrous production; rayon and cellulose film production; Paper And Cellulose; and water treatment. Due to its desirable properties, sulfuric acid has retained its position as mineral acid and the most universally produced and consumed chemical by volume.

Sulfuric acid is typically produced via catalytic transformation of sulfur dioxide (SO ₂ ) to sulfur trioxide (SO ₃ ), followed by the reaction of SO ₃ with water to form sulfuric acid. S0 ₂ is typically derived either from direct burning of elemental sulfur or via roasting of base metal mineral sulfides (ze: copper, zinc and lead).

Although technological processes for capturing S0 ₂ from the direct burning of both base metal and sulfur sulfides have been substantially improved, they capture only between 95% and 99% of these emissions. Older smelter-based technologies, where emission restrictions are significantly less severe, are located in remote locations, particularly in South America, South Africa and China, where they have been affected by increasing environmental pressures.

However, even these remote smelters will be under increasing pressure in the future to reduce the amount of harmful emissions. Improving this procedural route would entail substantial cost. Therefore, it would be advantageous to have a process for the production of sulfuric acid that eliminates the risks to. ^: environment that are associated with current sulfuric acid production.

In addition, operations such as metal leaching are associated with mining and facilities located in remote areas and countries with poor infrastructure for handling concentrated sulfuric acid, an extremely hazardous chemical. Many of the leaching operations use aqueous sulfuric acid solutions containing less than 20g.lL ^"1. With technological advancement, sulfuric acid is produced in high concentration and then transported to the place of use where it is diluted with water to produce the aqueous solutions used in many leaching operations. Accordingly, it would be advantageous to have a process that allows the production of aqueous sulfuric acid solutions very close to the point of use and eliminates the hazards associated with the transport and handling of concentrated sulfuric acid.

 As illustrated in Figure 1, there has long been a need for a more cost effective and environmentally friendly process to produce sulfuric acid. The object of this invention is to provide an alternative process for producing sulfuric acid utilizing commercially available non-hazardous mineral products such as elemental sulfur and / or minerals containing mineral sulfides, and / or separate mineral sulfides that allow sufficient mass transfer between solid / liquid / gas in its commercial production. This process should have a significantly lower capital cost than any other production process in use reducing the environmental impact of almost total emissions elimination.

The concept of small-scale production of sulfuric acid in reactors using biological media has been discussed in the literature by Cerruti et al, in the theme "Bio-dissolution of spent nickel-cadmium batteries using Thiobacillus Ferroxidans, Journal of Biotechnology, 62, 209. -211 (1998); Curutchet et al, Combined degradation of covellite by Thiobacillus Thiooxidans and Thiobacillus Ferroxidans, Biotechnol. Let, 18, 1471-1476 (1996); Tichy et al. Bioresource Technology, 48, 221-227 (1994); Tichy et al, Oxidation of biologically-produced sulfur in a continuous mixed-suspension reactor, Wat. Res., Vol. 32, 701-719 (1998); ; Otero et al., Action of Thiobacillus Thiooxidans on sulfur in the presence of a surfactant agent and its application in the indirect dissolution of phosphorous, Process Biochemistry, vol. 30, 747-750 (1995); and Brissette et al., Bacteri aleaching of cadmium sulphide, The Canadian Mining and Metallurgical (CM) Bulletin for October, 1971, 85-88, (1971). However, in these studies elemental sulfur was used as a powder in laboratory tests. Tichy (1994) indicated that sulfuric acid production rates using sulfur flower are very low and that industrial applications of this process are questionable. Accordingly, it would be advantageous to have a process that generates sulfuric acid by biological means at production rates that are appropriate for industrial applications.

BACKGROUND OF THE INVENTION

Bioleaching is a biochemical process that is based on the ability of certain microorganisms to transform insoluble elements, present in certain ores, into soluble and easily extracted elements. Among the various types of minerals, we can highlight mineral sulfides that can be identified as Calcocite (Cu ₂ S), Bomita (Cu ₅ FeS ₄ ), Galena (PbS), Sphererite (ZnS), Calcopyrite (CuFeS ₂ ), Pyrrhotite. (Fel-xS), Pentlandite (Fe, Ni) 9S ₈ , Covelite (CuS), Cinnabar (HgS), Orpigmenta (As ₂ S ₃ ), Stibnite (Sb ₂ S ₃ ), Pyrite (FeS ₂ ), Marcasite (FeS ₂ ), Molybdenite (MoS ₂ ), Arsenopyrite (FeAsS), Enargite (Cu ₃ AsS ₄ ), Tenantite (Cui ₂ As ₄ Si ₃ ), among others. Certain elements such as copper, uranium, zinc, mercury, lead and arsenic are some of the metals that can be extracted via the biochemical process. Leaching microorganisms are characterized by their unique ability to thrive in virtually uninhabitable environments for most microorganisms, as they live in places with extremely low pH and temperatures that can range from 25 to 80 ° C. In a mineral sulfide leaching process they can be extracted from flotation concentrates, fresh ore, flotation process tailings and, even more recently, from weathered ores.

 Biological leaching, or bioleaching, is quite attractive when it comes to eliminating gaseous fumes, due to mild process conditions and obtaining an acidic bleach containing the metal of interest. In the bioleaching process, autotrophic microorganisms, strict and chemilithotrophic acidophils, mesophiles and thermophiles may be used to extract the metal of interest. Noteworthy as mesophilic microorganisms are those that act at temperatures between 25 and 40 ° C. Moderate thermophiles are microorganisms whose operating temperature ranges between 40 and 55 ° C, while extreme thermophilic microorganisms are those microorganisms that act in the temperature range between 55 and 80 ° C.

The present invention aims to control, in an orderly manner, the biological processes that occur: i- in a pile of mineral sulfide flotation concentrate of a given In this case, it is necessary to use a support rock (/. <?.: primary ore that gave rise to the said concentrate, marginal ore of the same origin and an inert rock - quartz) to anchor the rock. said concentrate; primary ore of a given metal of interest; (ii) flotation residues from a given process for obtaining a mineral sulphide concentrate, in which case the same process as mentioned in (i) may be used, it may also be agglomerated and the resulting pellets used in the construction of the pile and finally weathered ore which requires a source of sulfur for the in situ generation of sulfuric acid which is provided in the present invention by the addition of pyrite and / or elemental sulfur to the mineral bed. In an uncontrolled bioleaching cell, it is observed that mesophilic microorganisms are active in the outermost areas of the cell, ie, the areas where there is the greatest heat exchange, and the moderate and extreme thermophiles act on the innermost parts of the cell. their corresponding temperature ranges. The oxidative processes that occur have an exothermic character and there is a tendency of intense temperature rise inside the body of the cell, and as a result of this heat intensification, the death of part of these microorganisms may occur. However, with temperature control in combination with the air insufflation flow, the death of microorganisms can be prevented and a significant result of the extraction of the metal of interest can be achieved.

The present invention manages to monitor, by computer, the redox potential, temperature, pressure and pH, as well as to identify the performance of different microbial consortia, namely: mesophiles, moderate and extreme thermophiles, using a column equipment containing the mineral bed in which a heating ramp of the mineralized body is established by the supply of external heat, identifying the temperature levels proper to each acting consortium. The bioleaching column also has windows (2 and 15) that serve to sample the mineral bed during the bioleaching process, for the proper identification of microorganisms adhered to the mineral sulfide particles from which the metals of interest are extracted. Thus, by taking the sample and identifying microorganisms through molecular biology techniques, it is possible to monitor the bacterial community. Similarly, microbial population density, which is adhered to existing mineral sulfide particles, can be verified. Allying the Microbiological monitoring to redox potential measurements, which are directly associated with permanent computerized monitoring of the spine, it is possible to interpret the bio-oxidative processes that take place throughout the mineral bed constituting the interior of the spine.

SUMMARY OF THE INVENTION

 Bioleaching of primary ores of copper, nickel, zinc, cobalt, molybdenum, uranium, precious metals, flowering tailings from sulfide concentrate production of these metals, and weathered ores (oxidized ores) with simultaneous biological acid production sulfuric.

 The bioleaching process in question, with simultaneous biological production of sulfuric acid, proceeded from the insertion of pyrite and / or sulfur in the mineral bed, on a pilot scale, with computational control of the action of autotrophic microorganisms, strict acidophils, in the extraction of these. metals of interest in the form of sulphate, the starting point for obtaining these metals in their metal forms.

 In the case of the bioleaching process under analysis, with simultaneous production of sulfuric acid from elemental sulfur and / or pyrite, object of this patent application, it is possible to investigate the performance of the different mesophilic and thermophilic microbial consortia used in a reaction system consisting of from a 4-meter-high column with a diameter of 50cm, establishing a heating ramp of the mineralized body by the external heat supply, with temperature levels of each acting consortium.

Considering the mechanical and electro-electronic devices used in the reaction system in question, it is possible to predict the action of the different microbial consortia by associating the continuously measured redox potential values with the temperature ranges experienced by the mineral bed and also with the microorganisms. organisms acting in different regions of this bed, as well as evaluate the production of sulfuric acid from the biological oxidation of pyrite and / or elemental sulfur, which processes provide the supply of sulfuric acid for the maintenance of acidophilic microorganisms used. The reactions that translate the generation of sulfuric acid from the sources minerals in the bed of the sulfide sources of interest, ie elemental sulfur and pyrite, are:

S ° + 30 ₂ + 2H ₂₀ ° - ° ^r? ° ~> 2H ₂ SO ₄ (1)

 Microorganisms

2FeS ₂ + 7 _? 5¾ + / f _z 0 * Fe ₂ (S0 ₄ ) ₂ + H ₂ SO _i (2)

However, the pyrite oxidation reaction has continued its process by its chemical oxidation by the generated ferric sulfate, ie:

FeS ₂ + 7 Fe ₂ (SO ₄ % + SH ₂ 0 ^ ISFe ^ O. + SH ^ O, (3)

However, sulfuric acid is also generated from the oxidation of the sulfides of interest, such as chalcopyrite, as shown in their respective oxidation reactions:

+H₂0 (4) 2CuFeS ₂ + 8.5 <¾ + H ₂ SO _A

+ H ₂ 0 (4)

CuFeS ₂ + 2Fe ₂ (S0 ₄ ) ₃ <»** ° & ^« * ^* CuSe ₄ + 5FeS0 ₄ + 25 ° (5)

S ° + 30 ₂ + 2H ₂ 0 ^ o- ⁰ '* "™para * 2H ₂ SO, (6)

 The inoculation form of microbial consortia, together with the mineral ensemble (mineral substrates from which the metals of interest, + elemental sulfur and / or pyrite) are to be extracted, allows a greater adhesion of these microorganisms to the surface of the sulfide particles. minerals of interest and the extra sulfuric acid generating sources, being a direct mechanism of bioavailability of these metals of interest to the aqueous phase, during the initial cure phase of this mineral set, which precedes the irrigation operation. from the mineral bed.

BRIEF DESCRIPTION OF DRAWINGS

 In order to clarify the present invention, the following describes the computerized equipment capable of monitoring the steps of a bioleaching process composed of a bioleaching column as illustrated in Figures 1, 2 and 3 below:

Figure 1 - Equipment consisting of a bioleach column with details of mineral bed temperature monitoring, air and C0 ₂ insufflation system, bleach tank, metering and pneumatic pumps, solid phase inspection and sampling portholes and heating system of the bleach tank solution. Figure 2 - Mechanical device, positioned at various heights of mineral bed, fixed to the column wall, for monitoring the redox potential of bleach.

Figure 3 - Bottom of the bioleach column, with details of the air and C0 ₂ insufflation and dosing system and drainage valve of solids drawn from the mineral bed during the irrigation operation of this bed with leach solution.

DETAILED DESCRIPTION OF THE INVENTION

 To clarify the present invention, the mineral filler to be added to the mineral bed column (1) is. prepared following an appropriate experimental procedure.

 In order to facilitate the understanding of this column (1) and its devices presented in figures 1 to 3, we will have:

 Column (1) itself; an inspection window (2); the column support (3)

(1); input (4) for the supply of C0 ₂ ; the inlet (5) for the air supply; the air humidifying device (6); the immersion resistance control device (7); the temperature gauge sensor (8); the pneumatic pump (9); the metering pump (10); the bleach tank (11); the bleach outlet (12); the pressure transmitter (13); the bleach spray (14); solid sampling windows (15); Redox potential measuring devices (16); solution collectors (17) within the column (1); perforated stainless steel plate (18) over the solution manifold nozzles (17); stainless steel fixing element (19) for fixing the Redox potential measuring devices (1) to the wall (20) of the column (1); Redox potential measuring electrode (21); bleach renewal control valves (22); Redox potential measuring reservoir (23); mineral substrate in bioleaching process (24); elemental sulfur (25); pyrite (26); output for analyzing the composition of the gas mixture (air + C0 _2); drainage of solids (28) and the bleach return element (29) to the tank (11).

Firstly, the mass of the mixture consisting of the mineral substrate from which the metal of interest (ie flotation concentrate, anchored in a suitable supporting rock), or a primary ore, in the particle size of 3 to 6 mm, or flotation tailings anchored, as in the case of flotation concentrate, in an appropriate "supporting rock" and, finally, weathered ore. More recommended, when using flotation concentrates and flotation tailings, 90% of the "supporting rock" and 10% of the mineral substrates of interest are weighed. As supporting rock a marginal ore of the metal of interest (ore with low content of the metal of interest), a tradable ore or an inert rock (ie: quartz) for bioleaching can be used. To these mineral substrates are added external mineral sources which will provide biological generation of sulfuric acid (ie: pyrite and / or elemental sulfur), either separately or together. At the end of mixing these mineral materials, there will be a mineral bed consisting of regions where the minerals of extractive interest and additional sulfuric acid generating sources (S ° and FeS ₂ ) will co-exist as illustrated in Figure 2.

 In possession of the mineral mixture, it is placed in a concrete mixer and mixed with a suspension of microbial consortia in sulfuric acid solution, sufficient to maintain the initial pH between 1 and 2, containing the nutrient elements (N, P and K) necessary for metabolism. of microorganisms. This mineral filler is placed inside the column (1) and remains for at least 24 hours to cure the mineral filler with the sulfuric acid solution. The purpose of this cure is to digest the constituent mineral species of the original ore gangue.

After the curing period is over, the leaching solution contained in the bleach tank is started (11 - Figure 1). This leaching medium is composed of sulfuric solution in pH ranging from 1 to 2, containing nutrient elements essential to the metabolism of microorganisms acting in the bio-oxidative process, a culture medium whose composition has the presence of 5 to 15 g / L in FeS0 ₄ , 0,5 to 5% w / v in elemental sulfur, 0,5 to 5% of flotation concentrate containing the sulphides of the metal of interest, aiming at the acclimatization of the microorganisms to the metals contained in said sulphides, using Also, inorganic salts containing the nutrients N, P and K whose concentration will depend on a previous analysis of the deficiency or excess of these salts in the mineral substrates in bio-extraction process. More recommended and not limiting, from 0.1 to 2 g / l in (NH ₄ ) ₂ S0 ₄ , 0.01 to 0.05 g / l in K ₂ HP0 ₄ , 0.2 to 0.6 g / L in MgS0 .7H ₂ 0. This solution aims to meet the nutritional needs of micro- organisms acting in the bioleaching process. Moreover, more recommended and more efficient, 10g / L in FeS0 ₄ , 1% elemental sulfur and 1% flotation concentrate are used. The population density of the microorganisms to be used is calculated as a function of the sulfide mass to be used in the biooxidative process and ranges from 10 ⁵ to 10 ⁷ cells of each microorganism pool per gram of sulfide used in the biooxidative process. -oxidative that, in case of use of primary ore or flotation tailings, this density is calculated taking into account the sulfide content in these mineral substrates.

In this bioleaching process three types of microbial consortiums are used, constituted by the so-called moderate and extreme thermophilic mesophilic microorganisms, as described above, which have the function of oxidizing the ferrous to ferric ions that act as an oxidizing agent of the mineral sulfides, and sulfur in the form of sulfide (S ^{2 "} ), elemental sulfur (S °) or, more vigorously, sulfate ions (S0 ₄ ² -).

The computer equipment in question proves to be very efficient with regard to the digestion of mineral sulfides with availability of the metal of interest in the form of sulfate. With electronic and mechanical devices such as thermocouples, air flow meters and C0 ₂ , electronic data acquisition circuits and data manipulation software, it becomes possible to unravel the path of action of micro- organisms in the different consortia used, in their characteristic temperature ranges, reliably simulating the action of these microorganisms on a larger scale.

The microorganisms involved in the bioleaching process of the present invention may be the mesophilic microorganisms, and the main microorganisms used in this bioleaching process are: Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans and Leptospirillum ferrooxidans. The other consortium consists of moderate thermophilic microorganisms which, like mesophilic microorganisms, have the task of digesting the above sulfides, acting in a higher temperature range (40 to 55 ° C), with the same function of oxidizing the ions. ferrous metals, sulfides and the elemental sulfur added. The main microorganisms used of this kind in the bioleaching process are: Sulfobacillus thermosulfidooxidans, Acidithiobacillus caldns, Acidimicrobium ferrooxidans and Sulfobacillus acidophilus. Finally, there is a consortium of extreme thermophilic microorganisms that act similarly to those of the first two consortia, and in a higher temperature range (55 to 80 ° C). Microorganisms of this genus used in the composition of the consortium are: Acidianus brierleyi, Acidianus infernas, Metallosphaera sedula, Sulfolobulus metallicus, Sulfolobulus acidocaldarius and Sulfolobulus shibatae.

 The following are examples illustrating the procedures for practicing the invention. These examples should not be construed as limiting. Technology application example:

A 37g mass of elemental sulfur, previously hydrophilized by the use of 20ppm of a biosurfatant (ramnolipid), was placed in contact with 3700g of primary copper ore, containing in addition to the gangue minerals of this ore, chalcopyrite sulfides ( CuFeS ₂ ), Bornite (CusFeS ₄ ) and Pyrite (FeS ₂ ). This mixture was placed in a agglomerator and irrigated with a solution containing nutrients and microorganisms. After production of the mineral agglomerate, it was placed inside a 10cm diameter semi-pilot column making up a 60cm mineral bed. This column was placed in a 20 liter useful volume tank loaded with aqueous 9K culture medium solution inoculated with acidophilic microorganisms. This culture medium contained the following salts: (NH ₄ ) ₂ S0 ₄ , MgS0 .7H ₂ 0, CaCl ₂ , KH ₂ P0 ₄ and FeS0 ₄ .7H ₂ 0. This leaching solution was circulated through the mineral bed with a flow of 3L.min ^_1 , when the leaching process began. Daily additions of distilled water were made to maintain the tank volume at 20 liters. The aqueous solution was circulated until the sulfuric acid concentration reached 20 gL ^-1 (0.2M) which corresponds to a pH of 0.7. At this stage, an appropriate volume of aqueous solution was removed and the same amount of aqueous solution was removed. , with the same saline composition mentioned above, was added to raise the pH of the solution to 1.8 (0.016M in sulfuric acid.) During the 120 days of leaching 18.4 liters of solution was removed from the bleach tank. Total sulfuric acid produced was 360.64 g totaling a production of 3 grams of bioleaching acid per day.

Claims

 CLAIMS: (1) "BIOLIXRIATION OF PRIMARY ORES, FLOATING REJECTS AND INTEMPERIZED ORE WITH BIOLOGICAL SULFURIC ACID PRODUCTION FROM ELEMENTARY AND / OR RIPING SULFUR", characterized by a pilot-scale reaction control system with computational control. autotrophic microorganisms, acidophilic extrites, in the extraction of the elements of interest from these mineral substrates, in the form of sulfate, starting point for obtaining these elements in their metallic forms. 2) "BIOLIXIVIATION OF PRIMARY ORES, FLOTATION WASTE AND INTEMPERIZED ORE WITH BIOLOGICAL SULFURIC ACID PRODUCTION FROM ELEMENTARY AND / OR LYRIC SULFUR", characterized by the process of bioleaching under analysis of sulfuric acid and in situ generation From this patent application, it is possible to investigate the performance of the different consortia used in a reaction system consisting of a column of 4 meters in height with 50 cm in diameter, establishing a heating ramp of the mineralized body, with temperature levels of each one. acting consortium.  3) "BIOLIXIVIATION OF PRIMARY ORE, FLETATION REJECT AND INTEMPERIZED ORE WITH PRODUCTION SULFURIC ACID BIOLOGICAL FROM ELEMENTARY SULFUR AND / OR LYRICS ", being characterized by the fact that considering the mechanical and electro-electronic devices used in the reaction system in question it is possible to predict the action of the different microbial consortia associating the redox potential values , measured continuously, with the temperature ranges experienced by the mineral bed and also with the microorganisms acting in different regions of this bed. 4) "BIOLIXIVIATION OF PRIMARY ORES, FLOTATION WASTE AND INTEMPERIZED ORE WITH SULFURIC ACID BIOLOGICAL PRODUCTION FROM SULFUR ELEMENTARY AND / OR LYRICS ", being characterized by the form of inoculation of microbial consortia, together with the mineral set (mineral substrates, from which the metals of interest, + elemental sulfur and / or pyrite) are extracted, allows a greater adhesion of these microorganisms on the surface of the mineral sulfide particles of interest, as a direct mechanism for the bioavailability of metals to the aqueous phase during the initial cure of this mineral ensemble, which precedes the irrigation operation of the minerals. mineral bed. 5) "BIOLIXIVIATION OF PRIMARY ORE, FLETATION REJECT AND INTEMPERIZED ORE WITH BIOLOGICAL SULFURIC ACID PRODUCTION FROM ELEMENTARY AND / OR LYRICS", being characterized by the mineral sources responsible for the biological generation of sulfuric acid. added to the mineral bed, containing the mineral sulfides which will make the metals of interest available to the aqueous medium, either together or separately. The amount of these mineral sources to be added to the mineral bed will take into account the need to maintain the pH within the recommended range for the acidophilic microorganisms used.