RU2133290C1 - Method of metal recovery from metal-containing granular materials - Google Patents

Abstract

FIELD: methods of leaching metal-containing granular materials; may be used in heavy metals recovery from slimes of electroplating processes, sludges of sewage waters and ores in nonferrous metallurgy. SUBSTANCE: method includes multistage counterflow treatment with leaching solution and subsequent withdrawal of solution and separation of solved metals from treated leaching solution, correction and return of solution for leaching, washing of undissolved sediments with water, concentration of washing waters to content corresponding to leaching solution, and its return to leaching cycle. Treatment with leaching solution and washing are carried out troughs with filtering bottom, with granular metal-containing material placed on troughs with their vibration in vertical plane relative to leaching solution. EFFECT: simplified process, intensified leaching, reduced power consumption and labor input. 1 dwg, 1 tbl

Description

 The invention relates to the leaching of metal-containing granular materials and can be used in the extraction of heavy metals from galvanic sludge, sewage sludge and ores in non-ferrous metallurgy.

 A known method for removing heavy metals from heaps of waste, sewage sludge and soil (German patent N 3836035, MKI A 65 D 3/00 from 06/13/90), which consists in the fact that waste containing heavy metals is irrigated with acids or water enriched hydrogen ions. Due to this, the displacement of mineral or biological substances that bind heavy metals is displaced and their washing out of the processed waste. A heavy metal treatment solution is separated from the solid phase by a drainage system.

 The disadvantage of this method is that during irrigation, the treated waste is densified, which leads to a decrease in the flow rate of the treatment solution and, as a result, to a decrease in the leaching rate. This, in turn, leads to an increase in the duration of the process and reduces the productivity of the equipment. At the same time, with this method of processing metal-containing waste, the removal of small fractions of the processed waste increases, which contributes to the clogging of pipelines, valves, etc. In addition, the unloading of the processed material is difficult to mechanize and is associated with high energy consumption.

 A known method of leaching granular metal-containing materials (RF patent N 2044083, class C 22 B 11/00 11/08 of 05/11/93), which consists in the fact that a solution leaks through a layer of material, and then the solution and material removed from the leaking process are combined , subjected to agitation (mixing), then separated and re-served in the process of seepage. Moreover, 10-100 wt.% Per hour of the total amount of material is brought to agitation and agitation leaching is carried out with the ratio of liquid (W) and solid (T) phases W: T = (3-10): 1. The liquid phase is separated from the solid using hydrocyclones.

 This method provides a high degree of metal extraction (85-95%), but is ineffective both with dense (L: T <3: 1) and diluted pulps (L: T> 10: 1). Another disadvantage of this method is the need for additional equipment (agitators, hydrocyclones), large volumes of solutions used.

 Of the known technical solutions, the closest method of the same purpose, selected as a prototype, is a method of leaching metals (Yu. V. Baimakov, A. I. Zhurin. Electrolysis in hydrometallurgy. M.: Metallurgizdat, 1963, p. 420-427) consisting in the fact that a layer of solid granular metal-containing material is placed in a container on a horizontally located grate, through which a processing solution is passed. Liquid seeps from below through a layer of metal-containing material (the so-called “percolation” process), due to which the leaching of metals occurs.

 As a rule, leaching is performed countercurrently on a cascade of containers. The circulating solution enters the container with the most leached granular metal-containing material and, as the metals are enriched, passes through the container with material that has been less leached. The last container is filled with fresh metal-containing material.

 After leaching for a period of time determined by the technological regulations, the tank is put to washing and then to unload leached material. Part of the wash water enters the general circuit of the processing solution to replenish water losses, and the rest goes to the treatment.

 After saturation with the metals, the treatment solution is fed to the extraction of metals in a known manner, for example by electrolysis. After the separation of metals, the solution again enters the leach according to the scheme described above.

 The disadvantage of this method is the low speed of the process, the low degree of metal extraction (70-80%). If light and small fractions are present in the processing solution, they are carried away, and pipelines and fittings are clogged. If these fractions can be disposed of, their collection and processing is difficult.

 To separate the solid phase from the liquid after leaching, special equipment is required (sedimentation tanks, filters, hydrocyclones, etc.).

 The problem solved by the proposed method is the improvement of the leaching process during the extraction of heavy metals from granular metal-containing materials (sludge, sewage sludge, ores, etc.).

 The technical result from the use of the invention is to simplify the process, to intensify the leaching process, reduce energy consumption, reduce the complexity.

 The specified technical result is achieved by the fact that in the method of extracting metals from metal-containing granular materials by multistage countercurrent treatment with a leaching solution, followed by separation of dissolved metals from the spent leaching solution, adjustment, and returning the solution to leaching, washing the insoluble precipitate with water and concentrating the wash water to the composition, corresponding to the leaching solution, and returning to the leaching cycle, leaching treatment yuschim solution and washing is carried out on trays with a filter bottom are placed on the metal-containing particulate material with the vibrational movement of the tray in a vertical plane relative to the leach solution.

 The method is as follows.

 Granular metal-containing material is placed on trays with a filter bottom, which are rectangular in shape, made of materials resistant to the processing solution. In the bottom of the tray, holes were drilled in a certain order for the passage of liquid, and filter material from a chemically resistant fabric, for example polypropylene, was fixed on the inside of the bottom. The layer of granular material on the tray is 15-25 mm, while the sides of the tray should be 20-30 mm higher than the layer of granular material.

 Trays with granular material are fed to the first stage of treatment with a leach solution. The treatment is carried out in such a way that a layer of granular material located on the tray performs oscillatory movements together with the tray in a vertical plane in the container with the processing solution. Due to such oscillatory movements during the downward movement of the tray, the treatment solution leaks through the filtering bottom of the tray and a layer of granular material into the tray. When the tray moves upward, the treatment solution flows into the volume of the container with the treatment solution, while the filter bottom prevents the entrainment of particles of granular material from the tray. The course of the tray is chosen so that when it is at the bottom point, the entire layer of granular material is covered with a solution, and when it is at the top point, the layer of material is free of solution, while the tray itself would not completely leave the solution contained in the container. Such a process reduces the energy consumption for the process, as the buoyant force of Archimedes acts on bodies immersed in a liquid. Oscillatory movements of the trays are attached by a mechanical drive of any known type, for example, using a cam mechanism (A.F. Krainev. Dictionary - a reference to mechanisms. M: Engineering, 1987, 190 p.).

 The next time the tray moves down through the filter bottom and a layer of granular material, a fresh portion of the treatment solution seeps out. The successive execution by the tray with the granular material of the oscillatory movements in the vertical plane and the corresponding change in the flow direction of the processing solution relative to the layer of granular material bring the layer of granular material into suspension. Due to this, there is an increase in the interaction surface of the liquid and solid phases, a decrease in diffusion restrictions and an increase in the leaching rate. In addition, the oscillatory movements of the trays with a filter bottom in a vertical plane prevent clogging of the pores of the filter material of the bottom due to ascending flows of the liquid phase during the trays down.

 After processing in the first stage, the tray with granular material is moved to the second stage, where the treatment with a cleaner solution takes place in the same way as in the first stage, then the tray is moved to the third stage with an even cleaner solution and so on. The number of stages of processing is determined by the required degree of extraction of metals and physico-chemical properties of the processed material and leach solution.

 The treatment solution from the first leaching stage, as the content of dissolved metals increases, is partially or completely withdrawn to the extraction of metals, replacing it with a cleaner one from the second stage of processing, the solution in the second stage is replaced by a solution from the third stage, etc. .. At the last leaching stage the granular material is treated with a fresh solution.

 Extraction of metals from spent leaching solutions is carried out by any known method, for example, by electrolysis (Yu.V. Baimakov, A.I. Zhurin. Electrolysis in hydrometallurgy. M: Metallurgy, 1963). After that, the processing solution is adjusted according to the composition and returned to leaching, thus creating a closed process cycle for the leaching solution.

 After passing through all the stages of processing, a precipitate remains on the trays that does not contain leached heavy metals, but which mechanically carries away the processing solution with a volume approximately equal to the volume of a layer of granular material.

 To reduce losses of recoverable metals due to ablation with a tray and a layer of granular material and, consequently, to increase the degree of extraction of metals, trays with undissolved sludge are washed, which is also countercurrent when the trays are swinging in a vertical plane in the same way as leaching was performed.

 Wash water is sent for concentration in a known manner, for example by evaporation (Chernobyl P.I. Evaporation plants. Kiev .: Higher School, 1970), to concentrations corresponding to the leaching solution, after which the concentrated solution is returned to the leaching cycle, which reduces consumption reagents, increase the degree of metal extraction.

 Water vapor after condensation is returned to the washing and thus create a closed process cycle for washing water.

 The residue remaining on the trays after leaching and washing, if necessary (for example, in case of their further disposal), is sent to the drying operation.

 An example implementation of the method.

 The method of leaching granular metal-containing materials is carried out in accordance with the diagram shown in the drawing, where 1 is a tray with granular metal-containing material, 2, 3, 4, 5 are containers with a leach solution, 6 is an electrolyzer for metal recovery, 7 is a container for preparation and adjustments of the leach solution, 8, 9, 10 - tanks with washing water, 11 - evaporator, 12 - condenser, 13 - dryer.

Tray 1 with a filter bottom with a layer of granular material - galvanic sludge (composition see table) - 1-2 cm thick enters the container 2 with a leaching solution, for example 7 - 12% sulfuric acid at a temperature of 40 - 50 ^o C and the ratio of the liquid phase and solid W: T = 10: 1. Using a rolling device, the galvanized sludge tray oscillates in a vertical plane with a frequency of 0.5-2 s ^-1 . Processing time 15-30 minutes. In this case, the reaction proceeds.
MeO + H ₂ SO ₄ ---> MeSO ₄ + H ₂ O.

Then the tray is moved to the tank 3, where it is treated with a fresh portion of 7-12% sulfuric acid at a temperature of 40-50 ^o C for 15-20 minutes and a vibration frequency of 0.5-2 s ^-1 . Next, the tray is sequentially transferred to containers 4 and 5, where it is also treated with 7-12% sulfuric acid at a temperature of 40-50 ^o C, the oscillation frequency of the tray is 0.5-2.0 s ^-1 and the processing time is 15-30 minutes.

In this case, the bulk of the metals passes into the solution (table). A precipitate remains on the tray, containing mainly calcium sulfate. After that, the tray is sequentially transferred to containers 8.9, 10, where the undissolved sediment remaining on the tray after leaching at positions 2, 3, 4, 5 is washed. The washing is carried out with water at room temperature (20-25 ^o C) and frequency oscillations of the trays 0.5 - 2.0 s ^-1 . Processing time - 15-30 minutes at each stage. Sludge washing allows to increase the degree of metal extraction from galvanic sludge (table). In the dryer 13, the undissolved precipitate is dried with an air stream at Т = 25-45 ^o C to an air-dry state (humidity is 20-30%) and can be used as an additive to cementitious materials (cement, gypsum) in an amount of up to 10% by weight cementitious material. As leaching occurs, the metal content in the processing solutions increases, while the metal content in the tanks corresponds to the following series C2>C3>C4> C5. The free acid content decreases in the opposite direction. An increase in the metal content in the processing solutions and a corresponding decrease in the content of free acid leads to a decrease in the process speed and a decrease in the degree of extraction of metals from galvanic sludge. To ensure a high leaching rate, more pure acid is constantly supplied in the direction from position 5 to position 2. Pure acid displaces the solution from tank 5, which flows by gravity into tank 4, from tank 4, the solution flows into tank 3, from tank 3 to tank 2. From the tank 2, the solution most saturated with heavy metals is fed to the extraction of metals in a known manner, for example by electrolysis.

In the electrolyzer, metal is released at the cathode, and oxygen is released at the anode. The total reaction in the electrolyzer can be written as follows:
MeSO ₄ + H ₂ O ± 2e ---> Me + H ₂ SO ₄ + 1 / 2O ₂ .

 Thus, along with the release of metal in the electrolyzer, the leaching reagent, sulfuric acid, is regenerated. If necessary, purification from other metals contained in the spent leach solution can be carried out by any known method, for example, by the ion exchange method (A. I. Rodionov et al. Environmental protection engineering. M: Chemistry, 1989).

 The regenerated treatment solution is returned to leaching, after preliminary adjustment and mixing with a clean treatment solution in the tank 7.

After the leaching of metals from the granular material, the undissolved precipitate remaining on the trays is washed in containers 8, 9, and 10 in the same way as the leaching process, i.e. trays and water move in opposite directions, while clean water enters the tank 10, and water with the highest content of soluble components flows from the tank 8. Since sludge from the last leaching stage, where “fresh” acid is used, comes to the washing, the main component of the washing water is a dissolving agent - sulfuric acid. Therefore, in order to avoid loss of solvent and metal with wash water, the latter also undergo regeneration. Regeneration is carried out by evaporation of part of the water in the evaporator 11 and thus bringing the content of the dissolving agent, sulfuric acid, to a concentration corresponding to the leaching solution, i.e. 7-12% H ₂ SO ₄ . After which the acid returns to the leaching cycle.

 Water vapor is condensed in the condenser 12 and the condensate is returned to the washing cycle.

 Thus, the proposed leaching method provides a high degree of extraction of metals from granular materials, increases the environmental safety of the process by creating closed cycles for processing solutions and in wash water, can significantly simplify the process, reduce energy consumption and reduce the complexity due to the fact that all operations metal precipitations are carried out on trays; material overload is not required during the transition from one processing step to another; operations and equipment for separating the liquid phase from the solid, such as vacuum filtration, sedimentation tanks, etc.

Claims (1)

 The method of extracting metals from metal-containing granular materials by multi-stage countercurrent treatment with a leach solution, followed by separation of dissolved metals from the spent leach solution, adjustment, return of the solution to leach, washing the insoluble precipitate with water, concentrating the wash water to the composition corresponding to the leach solution and returning to the cycle characterized in that the treatment with leach solution and washing t on trays with a filter bottom with granular metal-containing material placed on them during oscillatory movements of the trays in a vertical plane relative to the leach solution.

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