RU2367693C1 - Device for extraction of noble metals by cement injection - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: device for extraction of noble metals from solutions by cement injection contains tank and container, filled with metal-cement injector. Tank is outfitted by jacket heating and is implemented with conical end, hatch of reactants loading, branches of discharge and filling in of solutions and sealed cover. Container with metal-cement injector is located on sealed cover of tank and allows horizontal branch of feeding of solution into container. It also allows vertical branch, bottom end of which is deepened into tank for abstraction of solution from tank by means of screw electric pump. Bottom of container allows punching with diametre of openings 2.5-3 mm. Tank is implemented from titanium.

EFFECT: efficiency and operating safety of the device.

3 cl, 1 dwg, 2 ex

Description

The invention relates mainly to hydrometallurgical processing of precious metals and can be used as a method for their effective and safe extraction from technological solutions of various mineral composition. In addition, the capabilities of the method can be promising for obtaining particles of platinoids with a much smaller spread than this follows from the normal law of their size distribution.

Cementation deposition of precious metals and some other chemical elements by displacing them from a solution of their salt with a metal with a more negative electrochemical potential (better than 0.2 V) in non-ferrous metallurgy has long been known and has been used almost universally in both laboratory and industrial practice. This is based on some positive features of this process, described in detail in the literature. (Maslenitsky I.N., Chugaev L.V. Metallurgy of noble metals. 1872, p. 182-185). Compared with the chemical precipitation of these metals by reagents of various nature and state of aggregation, the goal is to bring the content of the target metal or element to be extracted to the minimum possible threshold content in solution is achieved quite simply, but not to the end, but only to some minimum (residual for each element) a concentration lying in the range of 0.5-2 μg / ml. This equilibrium is established when the potentials of the displaced and displaced metals become equal. But even such a thermodynamically acceptable concentration (for each element it is different) is not always achieved due to kinetic and diffusion difficulties, in particular, due to the phenomenon of polarization. Cementation is often used in hydrometallurgy as a very useful selective stage for the separation of elements, for example, gold from selenium and tellurium, or for cleaning solutions from impurities, as in the case of ZnSO ₄ solutions from Cu, Cd impurities, etc. In practice, cementation is carried out by powders (granules, shot, scrap) of active metals (Fe, Al, Zn, Mg), which uniquely pollute the precipitation of platinoids. For greater purity of precipitation, this can occasionally be a cementation process on sheets. One of the varieties of cementation is the separation of metals from solutions using amalgams, for example, Zn amalgams or Na amalgams to separate Ga from alkaline aluminate solutions. Despite the simplicity and assimilation in the industry of this operation of demetallization, it has a lot of known shortcomings of objective properties. (Alkatsev M.I. Cementation processes in non-ferrous metallurgy. M., 1981, 5-25, 49-76). Constantly pointing to the negative evolution of hydrogen, all authors note only two factors. First, the anodic dissolution of the metal-cement (1) and the cathodic deposition (2), for example: Fe-2е = Fe ²⁺ (1) and Сu ²⁺ + 2е = Сu ⁰ (2) is accompanied by a competing process of hydrogen evolution in water solutions: (3) 2H ⁺ + 2e = H ₂ (3). Secondly, its release blocks the surface of the metal-cementer, and this side process leads to an increase in its consumption. They try to eliminate these shortcomings by changes in the structures used for this apparatus. It should be noted that there is no typical chemical apparatus for cementing machines intended for use in enterprises dealing with the processing of precious metals from both ore and secondary raw materials! Therefore, each of them makes efforts for its manufacture, using mainly accumulated practical knowledge. All this leads to a huge variety of their designs. It is this fact that indicates empirical approaches to this process and the absence of a strictly scientific method for the design and construction of modern cementers. In practice, these are gutters, columns, drums, ball mills, jet, vibration, centrifugal, etc. reactors are cementers. But, as a rule, mechanical agitators are used. These are enameled or titanium devices equipped with vertical shafts of various designs, a gearbox and a conventional three-phase electric motor, and a ventilation hole. Shavings or other scrap of cement metal is poured directly into the apparatus or immersed in it in perforated containers that can be removed from there for refilling. The main technological inconvenience in the operation of an apparatus of this design is the extremely uneven distribution of metal throughout the apparatus, when large and heavy particles are motionless at the bottom, and the lungs move along the surface due to the reactive forces of hydrogen released from the surface. However, such primitive cementers, dangerous in operation and inconvenient in operation, began to be replaced by reactors of a different design. For example, in patent RU No. 2055923 (1996.03.10) “Method for mounting apparatus for cementing precious metals” experimentally established intervals of the density of packages of metal-cementer (zinc chips) and compressive forces of briquettes made of loose carbon batting as 0.5-1, 0 g / cm ³ and 0.1-0.3 kg / cm ^2, respectively. In the comparative description of this patent with the prototype, it is noted that the "inventive step and technical solution" consists in a comparative comparison with the previously used manual compression of zinc chips. The use of a special press capable of adjusting to the desired values both the density of the metal cementing and the compression pressure of the reagent package significantly improves the cementation efficiency. As a result, the proposed method of mounting the apparatus for cementing precious metals from solutions will increase the manufacturability of the assembly operation and reduce labor costs for its implementation. The main drawback that cannot be excluded with this method of carrying out the cementation process (the design of the apparatus, as well as the packing density and pressure in the assembly do not matter here) is that these initially set values will change dramatically when passing only the first portions of the solution. This will immediately affect the hydrodynamics of the apparatus, a change in the concentration of the external acid background and the viscosity of the liquid, a decrease in the content of both the cementing metal and base metals and their coagulation sorption in the batting pores, an increase in the temperature of the solution, the amount of dissolved gases, etc. etc. All this will lead to the impossibility not only to regulate the process, but also to assume the direction of its course. Even roughly managing this recovery reaction will be difficult because of the difficulty in determining which of the listed experimental factors will be the main (limiting) in the whole process. For the quality of the cementation stage, two conditions must be strictly observed. Firstly, the excess of the amount of metal-cementer relative to the content of recoverable elements from the treated solution during the process should be as large as possible and remain practically unchanged. Secondly, the cement slurry obtained from the solution with the lowest possible concentration at the level of not more than 1-2 μg / ml must be quickly coagulated, filtered from the mother solution, washed and dried. The authors of the patent RU 2027787 (1995.01.27) “Installation for demetallization of gold-containing solutions” offer a more complex structurally, but identical in principle operation of the above described installation. The essence of the method is the additional use of several more cementers (up to five), capable of being rearranged (switched to the processed solution), depending on the percentage of gold remaining in it. In fact, the well-known counterflow principle has been applied as applied to this process - solutions with a low gold content (1-5 wt.%) Are sent to a “freshly charged” zinc chip cementation bag. There is no doubt that this analogue method does not eliminate the main disadvantages of the cementing principle described above. Nevertheless, the second design significantly smoothes them and improves the process itself as a whole. But this effect is achieved due to an additional five-fold increase in the quantity, i.e. the mass of cementing assemblies and the necessary shifts during this replacement, and, consequently, additional labor costs.

The closest analogue prototype to the claimed device is the application RU No. 20006114855 "Device for the extraction of metals by cementation with rotation of the flow of the solution." The method used by the author consists in passing a hydrochloric acid solution from leaching through a layer of iron powder or cathode-deposited antimony located between layers of carbon batting. The main structural feature of this device is the use of two containers located one above the other. This allows you to pump solutions by gravity through a spiral perforated and filled with a metal-cement basket, giving the solutions both vibrational and vibrational motion. Oscillatory movements of solutions in both tanks provide vibratory drives. In addition, there is a device capable of creating a rotation of the tanks relative to each other by 360 °. Thus, such a complex metal-consuming structure, located on the platform and equipped with unbalance vibrators, shock absorbers, etc., serves only one purpose - to mechanically create rotation of the flow and to pass such a swirling mortar through the cement basket. Critically analyzing the shortcomings of the previous analogues and the prototype, we note that all inventors focus on the qualitative characteristics of the purity of the metals obtained, the quantitative values of their residual content in the solution, the metal consumption of their bulkiness, high maintenance time, etc. A general analysis of the various drawbacks of analogues directly indicates that the main and main drawback of them is not included in the number of operational inconveniences in the practical use of cementers, especially in production. The authors "forget" to note their special explosiveness during operation, especially in closed workshops of enterprises. Nevertheless, the evolved hydrogen (explosive group A) is capable of easily forming explosive mixtures with atmospheric oxygen, especially in heated solutions and in the presence of catalysts, the role of which is played by any produced precious metal blacks, which sharply reduce the flash point. The volume of gas released during the dissolution of 1 g / mole of metal-cement is clearly defined. For example, 22.4 liters of hydrogen will be released by dissolving 27 g of aluminum, 24 g of magnesium, 65 g of zinc. The actual scale of cementation by aluminum weighing 2.7 kg or more is not an extremely large amount in practice, but it is capable of emitting 2.24 m ^{3 of} hazardous gas. The intervals of the explosive limits of hydrogen in the air are quite wide: the lower one is 4 vol.%, And the upper one is 74 vol.%. These values "help" in practice to determine the degree of filling devices with solutions so as not to fall into the dangerous range, but the main danger lies in the occasional situations of a sudden (emergency) power outage. At the same time, ventilation devices stop working, and hydrogen from the devices is completely released into the atmosphere, because its solubility in water is very low (0.02 volume per 1 volume of water) and uncontrolled without the ability to stop its generation.

The main objective of the presented invention is the creation of a device that is capable of carrying out the reaction efficiently with the highest possible degree of extraction of the target metal and safely by reducing the risk of explosion.

To fulfill the first condition, the proposed device contains a container filled with metal-cementer of various sizes, through which the processed solution flows. The design of the container allows you to always have a metal cement with a developed surface and organize its long-term contact with the treated solution. The second condition is provided by the use of a screw electric pump for pumping the solution through the container. In the event of a power outage, the pump stops supplying the solution and hydrogen evolution ceases immediately.

Thus, all the conditions presented for the implementation of the task are carried out by the fact that the extraction of precious metals by cementation in the proposed device includes pumping the treated solution through a layer of metal-cement during heating and it is carried out by organizing multiple circulation of the solution, and the metal-cement has particles of different sizes, while in the device for the extraction of precious metals by cementation containing a container and a container filled with metal-cement: the device consists from a container with a conical bottom, equipped with a heating jacket, reagent loading hatch, drain and fill nozzles, a sealed lid, on which a container with a cement-metal is located, having a horizontal solution supply pipe to the container and a vertical, lower end of which is recessed into the collection container solution from the tank using a screw electric pump, and the bottom of the container has a perforation with a hole diameter of 2.5-3 mm, while the tank is made of titanium.

Distinctive features of the device should be considered the use of a container with a conical bottom, equipped with a heating jacket, as well as a reagent loading hatch, drain and fill nozzles, a sealed lid on which a container with a cementing metal is located, having a horizontal pipe for pumping mortar into it and a vertical pipe, the lower end of which is buried in the container for collecting the solution using a screw electric pump.

The essence of the invention lies in the fact that all the essential features presented allow us to solve the problem, namely, to carry out the process under conditions when the mass of the metal-cement is many times greater than its amount necessary to extract the platinoids contained in the solution. This is also facilitated by the proposed device, which allows, by pumping the treated solution with an electric pump into the volume of the container with a cementation metal precipitator, to carry out the reduction of target metals in a continuous circulation of the solution. As a result, this allows one to achieve high rates of the degree of extraction of precious metals and to exclude their irretrievable loss.

A general view of the apparatus is shown in the drawing.

The device consists of a container (1) (for example, titanium) with a conical bottom and a bottom drain equipped with a heated jacket (2). On the top cover (3) there is a container shell (4) for metal scrap with an upper flange (5) for connection to exhaust ventilation. The bottom bottom of the container has a perforation with a hole diameter of 2.5-3 mm. In addition, a loading hatch (6) is located here to fill the reactor with the processed material in the form of pulp or solution. To adjust the chemical composition of the solution (acidity, for example), there is a nozzle for filling or filling the reagents on the lid (7). The container shell is equipped with two nozzles (8, 9) with an upper flange for mounting a screw pump with an electric drive. One of the nozzles is immersed in the capacity of the cementer, the second is hermetically inserted into the container (4).

The operation of the apparatus is as follows. The cementer container (4) is completely filled, for example, with aluminum scrap, closed with a flange (5) and connected to a separate local exhaust line. Through the loading hatch (6), the reactor is filled with a solution containing platinum metals, in which the desired initial acidity is set. The reaction mass is heated by means of a heating jacket (2) and upon reaching a temperature of 70-80 ° C, a pump is turned on, which raises the solution from the reactor and pumps it through the container (4). A situation is always created in the volume of the container that is necessary for the maximum possible metal separation, when both the mass of the cementing metal and its surface are many times higher than the stoichiometric values necessary for this. In addition, the method and device for its implementation create in the container volume an excess concentration of hydrogen, which does not allow the obtained powders of precious metals to be oxidized and again turn into a soluble state. Moreover, most of the resulting platinum concentrate is located in the container. For its subsequent extraction, aluminum scrap is washed with water and metal powders are discharged to the filter through the lower discharge pipe of the apparatus.

Example 1

A solution of 160 liters obtained from the processing of used automotive catalytic converters weighing 102.6 kg after alkalization to pH = 1 has the initial concentrations of palladium, platinum and rhodium: 0.768 g / l, 0.102 g / l and 0.026 g / l, respectively . The platinum content in it is determined by atomic absorption spectrophotometry. The resulting solution is pumped into the cementer and heated to a temperature of 70 ° C. The container (4) of the device is filled with pieces of different lengths of aluminum cable with a wire thickness of 2.5 mm with a total weight of 2.6 kg. After reaching the set temperature, a screw pump is turned on, which circulates the treated solution for 1 hour. After that, the heating from the reactor is removed and the treated solution cooled to a temperature of 40 ° С is drained for filtration on a suction filter. The solution from washing the container with water is also sent there. The combined precipitate of the collective concentrate obtained from the filtration of the main productive solution and wash water is removed from the filter and dried. The content of the amount of precious metals in it is 76 wt.%. The concentration of platinum metals in the filtered solution is determined by atomic absorption analysis. The values of the residual metal content in the treated solution are as follows for Pd - 2.8 mg / L, Pt - 1.6 mg / L, Rh - 1.8 mg / L. Thus, the direct yield of metals after this process corresponds to: Pd - 99.6%, Pt - 98.4%, Rh - 93.8%. The solutions formed from this treatment are sent to sorption columns for complete metal deposition.

Example 2

Filtered combined solution with a volume of 130 l obtained from leaching and washing of spent 99.8 kg engine fuels afterburning catalysts with an average content of the total platinum group metals of 0.171 wt.%, Which according to atomic absorption analysis contains: 1.093 g / l Pd , 0.182 g / l Pt, 0.040 g / l Rh is poured into a cement reactor. The device is heated to a temperature not exceeding 60 ° C and neutralize the acidic solution of dry NaOH to a pH in the range of 1.0-2.0. During alkaline treatment, the temperature of the solution is raised to 80 ° C, after which the pump is turned on to pump the solution through a container filled with 3.1 kg of iron scrap. The cementation reduction process is carried out for 2 hours and then 200 g of dry sodium sulfite (Na ₂ SO ₃ ) is added to the reaction mass to reduce the effect of Fe ³⁺ formed in the solution that impedes cementation. Then the solution is cooled, a sample is taken for analysis and filtered, and the container is thoroughly washed with water. Residual metal concentrations are 2.6 mg / L for Pd, 1.8 mg / L for Pt and 2.2 mg / L for Rh, which is in line with accepted drainage standards. Nevertheless, the solutions formed after cementation are sent to the final sorption treatment in columns filled with activated carbon. The value of through extraction of each of the metals during cementation of the target metals (Pd, Pt, Rh) corresponds to 99.8%, 99.0% and 94.5%, respectively.

The proposed device can reduce the loss of platinum metals due to the achievement of high values of the degree of their selection in the form of well-filtered powders. The content of platinum metals in the concentrate sharply increases due to a decrease in the level of pollution of the resulting precipitation. This effect occurs due to the exclusion of the introduction of cementation metals into the reactor volume. Thus, the advantages of the device lead to a significant simplification of all subsequent separation and refining procedures of the selected metals. The achieved results are determined, first of all, by the construction of the cementer used. The inventive device provides an almost quantitative precipitation of target metals, implements the best conditions for the stage of cementation, simple structurally and safely in operation. Any typical chemical apparatus of the required volume, equipped with a heating jacket can be easily converted into the proposed cementing apparatus.

Claims (3)

1. A device for extracting precious metals from solutions by cementation, containing a container and a container filled with metal-cement, characterized in that the container is equipped with a heating jacket and is made with a conical bottom, reagent loading hatch, drain and fill nozzles and a sealed lid, a container with metal-cement is located on the sealed lid of the tank and has a horizontal nozzle for supplying the solution to the container and a vertical nozzle, the lower end of which is buried in the container for collecting the solution from the vessel via the screw of the electric pump. 2. The device according to claim 1, characterized in that the bottom of the container has a perforation with a hole diameter of 2.5-3 mm 3. The device according to claim 1, characterized in that the container is made of titanium.

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