SE176930C1 - - Google Patents

Description

Inventor: W A 0 Herrmann Priority Required April 10, 1954 (Canada) The present invention relates to a process for the extraction of metals from metallic materials.

The process according to the invention relates to the extraction of at least one metal from metal-containing solid material by dissolving this metal in a lacquer solution and it can be characterized in that a slurry of finely divided particles of the metal-containing material and the lacquer solution and a gas stream under pressure are continuously fed in the lower part of a vertically arranged column and in the column is kept at elevated temperature and a pressure above atmospheric pressure p0. so that a continuously rising turbulent suspension, consisting of gas bubbles, the metal-containing particles and the leaching rising towards the upper part of the column, is obtained and that the suspension is imparted substantially uniform cross-section and substantially uniform hasleness to the feed stall in the lower part of the column. the owe part of the column and that the solid particles without sinking are caused to rise continuously from the feed stall in the lower part of the column to the upper part of the column, where the leach solution, the gas and unresolved particles are continuously discharged, the slurry and gas being fed into the lower part of the column. at such a rate that optimal extraction of the metal is obtained.

Hydrometallurgical methods for extracting metals from metallic materials by means of a solvent or leaching agent are widely used and widely used. Heretofore, except for leaching metallic materials by percolation, these methods have usually involved dispersing a slurry of finely powdered metallic material and a solvent or leaching agent for the metals which it is desired to extract into a mechanical stirring reaction vessel.

As a result of recent discoveries, the use of hydrometallurgical methods, or "vata" methods, has been extended to include treatment of metallic materials, which have previously been treated by pyrometallurgical methods. These newer discoveries include leaching of metallic materials at elevated temperature and elevated pressure. Furthermore, they may involve the use of gases under pressure, which take part in the reactions, by means of which metals are extracted from the starting material and dissolved in leaching solution. It is essential that the leaching step in such a hydrometallurgical process is carried out in as short a time as possible with a maximum extraction of the desired metal or metals from the metal-containing material with efficient absorption of the reacting gas and with a minimum of capital and operating costs.

It has been found that conventional reaction vessels, such as autoclaves, which are intended to operate at temperatures and pressures above atmospheric, can be used in the leaching step, but the results are not fully satisfactory. The factors affecting the rate and efficiency of the extraction of metals and their conversion into salts, which are soluble in the leaching solution, the temperature, the pressure interface between gas and liquid, the absorption of gas in the solution and the passage of gas through the liquid film p5. the interface between solids and liquids and the rate and efficiency at which reactive constituents in the gas are absorbed by the surfaces of the metal-containing solids. The rate and efficiency of the extraction of metals and their dissolution in the leach solution thus largely depend on the agitation of the slurry.

It provides no greater responsibility to achieve a relatively even dispersion of solid particles in a liquid and a satisfactory interface between the gas and the liquid by mechanical agitation in a relatively small vessel. However, the efficiency of man with mechanical agitation decreases as the size of the man alias due to -Rad responsibility to obtain uniform agitation throughout the slurry, where & the fast, efficient and economical extraction of metals depends. Furthermore, the slurry in the reaction vessel is often corrosive, and it can be extremely corrosive at the temperatures and pressures used. These properties of the slurry bring about significant operational difficulties, especially with regard to the agitators, agitator bearings, stuffing boxes and mechanical seals.

It has been found that similarities which arise during leaching in an ordinary pressure vessel equipped with a mechanical stirrer can be overcome by carrying out the leaching in a vertically arranged reaction column, in which a slurry consisting of finely divided metal-containing particles and leaching solution is stirred and the solid metal-containing particles in the charge is dispersed in the slurry of a gas which is blown under pressure into the bottom of the reaction column. Finely divided solid metal-containing particles and a leaching for the metals to be extracted, as well as a pressurized gas are fed closer continuously into the lower part of a vertically arranged tower or reaction column, which is kept at a temperature and a pressure above atmospheric temperature and atmospheric pressure.

The tower is completely filled with a continuously ascending turbulent suspension of gas bubbles, solid, metal-containing particles and liquid solvent with a substantially uniform cross-section and with a substantially uniform velocity without recurrence of solid particles from the inlet stall for the metal-containing particles to the outlet stall. The distribution of the metal-containing particles in the column, the discharge of solid particles and leaching as well as gas from the upper part of the reaction column and the extraction of metals to obtain optimal extraction of the metallic material during its tightening up through the column are controlled byboard. regulating the feed of slurry and gas in the lower part of the reaction column. A mixture of undissolved solid particles and liquor solution containing dissolved metal and solid particles as well as gas is continuously discharged from the upper part of the reaction column.

Stirring of the slurry is accomplished by introducing gas into the lower part of the tower, and extraction of metal is carried out by reacting the Indian particles of the metal-containing material, constituents of the gas and the leaching solution. The rate of the upward flow of the mixture of gas and slurry through the vessel is controlled so that the largest possible interface between gas and liquid is obtained and by thorough stirring of the slurry, thereby obtaining an efficient and economical extraction of metals from the metal-containing material. As metal 'is extracted from the metal-containing material, the particles become lighter and Rams up by the opposing mixture of gas and slurry, while heavier and less leached particles tend to remain in the lower part of the tower, whereby a deposit is obtained by which the degree to which metal is extracted from the starting material and can be easily controlled and controlled. Ga: sen and the slurry are diverted frau it. the upper part of the tower, the gas is separated from the slurry, and the slurry of unresolved solids and solution containing 15th metals can be treated to recover metals.

The process according to the invention is further elucidated by the following detailed description in connection with the accompanying drawing. Fig. 1 is a side view of a tower reactor, which is suitable for use in carrying out the method according to the invention, together with auxiliary equipment. Fig. 2 shows another embodiment, in which a series of tower reactors are used. Fig. 3 shows a third embodiment, in which gas is discharged from the top of the tower and slurry is discharged at a point below the top of the tower. Fig. 4 shows a fourth embodiment, in which the tower is provided with means for slowing down the circulation of the slurry. The same designations refer to the same parts in the drawing and description.

The embodiment of the process according to the invention will now be described with reference to the treatment of mineral sulphide concentrates which contain metals such as copper, nickel and. cobalt. An oxygen-containing, oxidizing gas such as kilt, with oxygen-enriched air or oxygen with or without one. inert gas is used as the stirring medium, and the oxygen serves to supply at least a portion of the oxidizing agent. The leach solution consists of a concentrated ammonia solution consisting of about 1 part of 28% NH3 and about 1.5 parts of water. Sufficient water was added to give a slurry containing from 15% or less to 60% or more solids. The Whet of the slurry or the ratio between solids and solution depends on the metals which are to be extracted. A high concentration of metals usually requires a lower ratio of solids to solution, and a low concentration of metals allows a higher ratio. The process can of course be used in the treatment of other types of ores and concentrates, secondary metals, metallurgical residues and other metallic materials. The leaching solution may be any organic or inorganic leaching solution which acts as a solvent for the metals which it is desired to recover, and the gas may be of a suitable type for agitating the slurry and, if necessary, for participating in the reaction by which metals are extracted from the starting material and hoisted into the leach solution.

In the embodiment shown in Fig. 1, the numeral 10 denotes an elongate, vertically arranged tower with an inverted, conical bottom 11. The tower is made of or lined with material which can withstand. the corrosive and erosive effects of the gas and the slurry. The tower was built to withstand the mixtures to which it was exposed. For example, a tower made of or lined with carbon steel can be used to treat alkaline slurries in the presence of an oxygen-containing oxidizing gas at moderate temperatures and pressures. Acidic slurries may require a tower made of or lined with stainless steel or titanium or some other acid-resistant material.

Gas is introduced at the tip of the cone-shaped bottom. As shown, the leaching agent can be 111110 together with the gas or at a higher level. Finely powdered, metallic material, preferably in the form of a slurry, Taurus can be introduced at the bottom of the tower or at a higher coated point, as shown.

The gas is rapidly adsorbed on the first contact with the metal-containing particles and then more slowly, regardless of the concentration of the reactive constituents, as the leaching proceeds. Consequently, the gas and the slurry are allowed to flow together and the particles are brought into herring with the gas cla the reactive constituents have their greatest concentration, ie. in the lower part of the tower, the slurry and gas flowing in from the bottom of the tower to its top.

Particles of metallic material tend to settle in the inverted conical bottom 11 and serve to divide the gas stream into a mass of bubbles and disperse them over the entire cross section of the tower, so that the mixture in the tower will be formed by a mass of bubbles, which are separated by barrels. sections of the slurry. The dot interior of the tower consists of a turbulent mixture of a fatally large (5 cm and daraver) and many small (5 cm to 1 mm) gas bubbles. The large gas bubbles appear to cause the agitation or turbulence, and the small gas bubbles are carried in the streams caused by the large bubbles.

If in large towers sufficient dispersion joke is provided by the metal-containing particles which have deposited at the cone-shaped bottom, dispersion means of the type shown in Fig. 4 can be inserted and the cone-shaped bottom will be described later. Furthermore, additional wool and / or leaching agent and / or metal-containing material can be added to the slurry above the lower part of the tower.

The mixture of gas bubbles and slurry rises up through the tower at a rate which depends on the rate at which metal-containing material, gas and leach are supplied. The relative velocities above solids, unloading and gas are installed and regulated to achieve maximum extraction of metals during the passage through the tower. As metal is extracted from the particles of metallic material, the particles become lighter and rise in the tower. Heavier particles rise more slowly and are thus retained longer in the tower for extraction of metal. Other metals On jam, such as zinc, copper, cobalt and nickel. Extracted rapidly from the metallic materials and dissolved in the leach solution. Jain is converted to insoluble ferric hydrate and is found in the unloaded residue.

A mixture of gas, leaching agent and leached or partially leached metallic particles is taken from the upper part of the tower, from the top in Figs. 1 and 2 or from a point below the top according to Fig. 1. If the leaching step is completed in a single tower, the mixture is treated separately. of gas, and the slurry is passed to other apparatus for separating oliist residue and recovering metals. If the leaching step joke is completed in a single tower, the mixture was added to the bottom of a second tower, and the procedure is repeated in this tower or in a series of towers, as shown in Fig. 2, until the metals are extracted to the desired degree.

The numeral 12 denotes cooling or heating coils or jackets which may be required to measure the temperature of the slurry in the tower within the range where the most satisfactory extraction rate and efficiency are obtained. The extraction of metals from mineral sulphides is usually an exoteric reaction, at least in the earlier stages of the reaction, and it may be necessary to cool at least the first tower, as shown in Fig. 1, or the first and second towers, as shown in Figs. 2 and 3, to line the temperature within the desired boundaries. The towers are consequently cooled, for example by means of cooling coils. If a series of towers is used, it may be necessary to cool the towers in which strongly exothermic reactions take place, and to heat the following towers in which less exothermic reactions take place. The extraction of metals from oxidized ores and concentrated metallurgical residues, secondary metals and the like, is endothermic, and it may be necessary to supply heat to the towers, for example by means of heating coils or heating mantles.

The dimensions of the tower can be easily determined with regard to the properties of the materials from which metals are to be extracted, the amount of metallic material to be treated for a prescribed time, the desired degree of agitation and the maximum dispersion of gas bubbles in the mixture from the bottom of the tower to its top. Preferably a cylindrical tower is used, which gives the most satisfactory operating results. The ratio between the 116.0 and the diameter of the tower of the special properties of the material to be treated and of the reaction to be carried out and the reaction rate. As the tower height is lowered to handle larger volumes of feed material, better gas pressure is required to compensate for the static pressure in the slurry in the tower. As the diameter of the tower increases, it can become black to maintain a sufficient dispersion of gas bubbles. In view of these factors, it has been found that very satisfactory results are obtained with towers, in which the ratio between the diameter and the height is from 1: 200 to 1: 10 with a maximum diameter of about 3 m and a maximum height of about 50 m. .

A mixture of gas and slurry is withdrawn from the lower part of the tower through a line 16, and the mixture is led to an apparatus for separating gas and liquid, for example the eiclones 17-18. A mixture of air and ammonia is released and taken out of the cyclones. This mixture can be returned to the lower part of the tower 11 for re-use, or the ammonia can be dewatered from the gas and re-used for re-use, whereby the air, which is depleted of oxygen and substantially free of ammonia, can be led to the atmosphere. .

Slurry, which is substantially free of gas, can be led to a container 19 for storage, the treatment being obtained from the extraction of metals. The slurry can be removed from the container 19, and non-unloaded solids can be separated from solution, for example by filtration in a filter 20. The solution coming from the filter 20 is ready to be treated for recovery of unloaded metals. The filter cake or residue after washing with water so that the off-adhesive solution can be discarded, or it can also be treated to recover the remaining undissolved metals.

Fig. 2 shows leaching in a plurality of towers without obstacle means. Leaching agent, gas and finely powdered metal-containing particles are fed into the lower part of the first tower 21, and a mixture of slurry and gas is taken from the top of the first tower and led to the bottom of a second tower 22. The mixture taken from the top of the part the second tower is led to the bottom of the third tower 23. A mixture of gas, leaching agent and leached solids is taken from the top of the third tower and led to the cyclones 24 and 25. The resulting slurry is led to a storage container 26 and thence through a filter 27. , from which the filtrate is led to a container 28. The leaching step is carried out in three steps, but one can also use fewer or more towers depending on the properties of the treated material. This embodiment has the advantage that it is possible to use a plurality of relatively low towers instead of a single Mgt tower.

The embodiment shown in Fig. 3 is especially intended for the treatment of metal-containing materials, a selective flotation being used in the tower. Particles of metallic material with special flotation properties tend to be carried upwards in the tower at a higher speed than other particles, which pa. normally sat rising up in the tower while metal was extracted. In the treatment of such materials it has been found that the slurry at the top of the tower may contain particles from which metal has been extracted to varying degrees, i.e. that some particles have passed the leaching step and still contain a relatively high percentage of extractable metals, while other particles are normally leached. It has been found that slurry taken from the fine tower at a point below the level of this heterogeneous mixture contains solid particles with a relatively uniform composition in the case of non-extracted metal. It is therefore preferred to divert slurry from said point and regulate the extraction rate of such salt that a water level is maintained above the extraction point, while only gas is extracted from the top of the tower. When using this method, the retention time in the upper part of the tower becomes sufficiently large to extract metal from the precipitated particles to the same degree as from the normally leached particles. The gas discharged from the top of the tower can be supplied to the slurry taken from said point in the tower and each of these can be led to the above-described slurry treatment steps or led to the bolt of the next tower in the series, as shown in Fig. 3. , until metals are extracted from the metal-containing material to a reduced degree, after which the mixture of gas and slurry is drained from the upper part of the last tower and led to the treatment steps before the slurry.

The embodiment of the invention shown in Fig. 1 is particularly suitable for applying the process in high towers and for treating metallic material with selective flotation properties or for making a mousetrap in which it is desirable to separate products alit as the reaction proceeds.

The tower Or denoted by 40 is the same as the tower 10 in Fig. 1 except that a series of inverted cones 11 and 12 are arranged in the tower, preferably at the same mutual distance, the cone 41 being approximately 1/3 ay the distance from the bottom of the tower and the cone 42 are covered about 2/3 of the distance from the bottom. Each lion Or at its periphery attached to the inner cradle of the tower. An Opp-fling 43-44 Or arranged at the tip of the habit of converting the lion, each such opening having - - the same or approximately the same diameter as the inlet opening 15 of the inverted cone at the bottom of the tower.

Gas is fed into the inlet port 45 at the tower bed, and leaching agent and metallic material are charged on the same salt as in the tower 10. The mixture of suction and gas rises through the first section of the tower towards the tip of the converted cone 41 and passes through the port 43 with approximately the same speed as the materials are fed into the tower. The mixture of gas and slurry ascends through the compartment 48 to and through the opening 44 at the tip of the converted cone 42 and passes through the opening 44 to the compartment 29. The mixture of gas and slurry rises through the compartment 49 to the outlet line 50, through which the mixture is discharged for further treatment. .

The high gas velocity through the openings 43 and 44 prevents backflow of suction from. section 49 to section 48 and from section 48 to section 47. On this salt a smoothing effect is obtained, and the rate of flow of gas and slurry through the tower can be regulated, so that maximum extraction of metal and maximum utilization of the gas are obtained. This embodiment of the invention further has a significant advantage in that metal-containing material with selective flotation properties tends to stick in the spaces Indian perimeters of the converted cones 41 and 42, thereby subjecting it to the reaction conditions for a longer time.

The execution of the procedure is illustrated by the following example. Three towers are used in sane, as shown in Fig. 2. Each tower was about 25.4 cm in diameter and about 9.84 in height. Air pressure of about 7.5-9.0 ata was initiated at the bottom of the first tower. This resulted in a pressure at the top of the first tower of omitting 7.0 ata and a pressure of about 5, ata at the top of the third tower. The stirring agent consisted of air, which at the same time supplied the oxygen necessary for the leaching reaction. The air bubbles had a velocity of about 25-45 cm / sec at the tip of the cone and about 5-25, and averaged about 11 cm / sec at the full diameter of the tower. The tower was filled with a strong ammoniacal aqueous solution. Ammonia was added to the slurry in significant excess beyond what was required for reaction with the metals to be extracted from the metal-containing material. Water was added to the slurry in sufficient quantity to give a slurry containing about 14-17% solids. The gauge was about 60% smaller than 0.74 mm. The tower was filled to about 3060% and preferably to about 40% of its capacity with air bubbles.

Example I.

Copper sulfide concentrate containing about 22.91% copper, 25.7% sulfur, 31.03% μm and 1.22% insoluble material was fed continuously at the bottom of the first tower at a rate of about 11-14 kg / h. Ammonia was fed continuously at a rate of about 16-19 kg / h. Sufficient water was supplied to give a solution containing about 15-18% solids. Air was supplied to the bottom of the tower at a pressure of about 7.5 ata at a velocity of 94-97 N & Aim. The temperature in the towers is maintained at about 72-82 ° C, preferably around 80 ° G. The normalization of the slurry was regulated, so that the retention time was about 10 hours. It was found that 81.495.5% of the copper and 73.3-78.2% of the sulfur were extracted from the starting material and dissolved in the solution. The iron was converted to insoluble ferric hydrate, which was found in the insoluble residue. Virtually no iron was dissolved in the leach solution.

Example IA.

The conditions of Example I were repeated with the difference that the air flow was reduced to about 54 N ms / h. The reduced air volume improved the extraction of copper and sulfur from 93.5% -95.3resp. from 85.6% -87.7% at a retention time of about 10 hours.

This extraction of up to 95% of the copper and up to 87.7% of the sulfur in ten hours is about the same extraction as obtained at a retention time of about 16 hours. The mineral sulphides were leached in autoclaves by mechanical stirring.

Example II.

A copper liquid concentrate containing about 29.7% copper, about 1.25% nickel, about 30% sulfur and about% iron was leached at about 80 ° C with an aqueous solution of ammonia in a sufficient amount to correspond to about 100 g of free ammonia. per 1, adding a sufficient amount of water to give a solution containing about 18% solid anine. Air was supplied at a rate of about 1900 N m2 per m2 in cross section and per hour at a pressure of about 7.5 ata. At a retention time of about 10 hours, about 97% of the copper, 8% of the nitrous oxide and 92.6% of the total sulfur were extracted from the starting material and dissolved in the solution.

Example IIA.

The conditions in Example II were repeated with the difference that the air flow was reduced to about 1170 N m3 per m2 of cross section and hour. It was found that about 94.3% of the copper, 89% of the nickel and 94.5% of the sulfur were extracted from the starting material pa. 6- - about 12 hours and loaded into the leach solution.

Example III.

A nickel sulfide concentrate containing about 11.8% nickel, 2% copper, 0.3% cobalt, 32 '2'y sulfur and 31% jam was leached at about 80 ° C with ammonia in a sufficient amount to give about 100 g free ammonia per Water was added in sufficient quantity to give a slurry containing about 18% solids. Air is supplied to the first tower at a rate of about 1070 N ms per m2 of cross section and hour at a pressure of about 7.5 ata. After 20 hours of leaching, about 94% of the nickel, 95.3% of the copper, about 74% of the cobalt and about 88.1% of the sulfur had been extracted from the starting material and dissolved in leaching solution.

Example IIIA.

The conditions in Example III were repeated with the difference that the air flow was increased to about 1200 N m3 per m2 of cross section and hour. Subsequent yields are recovered during the specified leaching times.

Time NickelCopper CobaltSulfur% yield% yield% yield% yield 4 hours 86,% 90.8% 52% 46.1% 8 93.1% 91,% 58% 59.7% 16 96.3% 96.0% 64% 67.9% 97.1% 97.3% 72% 79.2% Example IIIB.

The conditions in Example III were repeated with the difference that the Inft current was increased to 1330 N m3 per 1112 cross section and hour. The following yields were obtained during the indicated time NickelCopperCobaltSulfur% yield% yield% yield% yield 4 hours 70.4% 76.7% 52% 32.0% 8 »90.8% 88.7% 58% 43.0% 12 a 93.9% 90.4% 64% 49.5% 16 92.6 ° A, 93.3% 68% 49.8% 97.0% 92.6% 72% 76.0% Example The conditions of Example III repeated with that difference, aft the air flow was increased to 1450 N m3 per m2 cross section and hour. Subsequent yields are recovered during the specified leaching hours.

TM NickelCopper CobaltSulfur% yield% yield% yield% yield 4 hours 70.0% 77.1% 46.4% 44.4% 6 »88.7% 86.8% 54.8% 53.2% 8 90.9 % 91,% 64,% 59.8 ° A a 95.1% 91.3% 66.4% 65.3% 12 97.0% 95.0% 70.6% 79.3% Example III D.

The conditions in Example III were repeated with the difference that the air flow was increased to 1620 N m3 per m2 of cross section and hour.

The following yields are obtained during the specified leaching times.

Time NickelCopper CobaltSulfur% yield% yield% yield% yield 4 hours 84.1% 83.6% 54.6% 40.0% 6 91.7% 87.8% 61.2% 47.0% 8 97.6% 93.3% 69.8% 52.7% 91.2% 82.7% 70.2% 53.1% 12 94.6% 93.6% 71.0% 69.3% At the higher speed for the air in this example, it was found that maximum extraction of nickel and copper was obtained in about 8 hours. The dissolved nickel and copper showed a tendency to hydrolyze and form insoluble compounds with ferric oxide particles, as the leaching time was allowed to increase the extraction of swivel. The process can of course be easily adapted to the conditions for the treatment of different kinds of metal-containing materials. For example, the process can be easily adapted to extract metals from metallic materials in two steps, whereby fresh metallic material is mixed with leaching solution containing 18 metals from a previous leaching step and fed into a tower of the type previously described. The slurry taken from this tower is filtered after separating the gas. The filtrate is treated for the separation and extraction of loose metals. The filter cake is inserted into a second tower, where it is leached with fresh leaching agent for extraction of residual metals. The slurry from the second tower is filtered after separating the gas. The filtrate, which contains loose metals, is led to the first borne !, and the filter cake can be removed from the cycle.

The process of the present invention has several very significant advantages over conventional leaching processes which are carried out in reaction vessels with mechanical stirring. The cost of the leaching towers is very considerable in relation to the cost of ordinary pressure vessels, which are adapted for the treatment of equal volumes of slurry. A significant saving on Ores's capital costs, as it is not necessary to use mechanical stirring devices. Furthermore, the operating durations which otherwise arise due to faults in the mechanical agitators which are exposed to corrosive and erosive slurries in closed reaction vessels at elevated temperature and elevated pressure and the associated costs as well as construction and maintenance of deposits, packing boxes and seals are avoided. Furthermore, the leaching can be carried out for a much shorter time and with a considerably higher yield than that obtained in conventional reaction vessels with mechanical agitation.

In the foregoing the invention has been elucidated by the treatment of mineral sulphides with an ammoniacal leaching solution in the present leaching times. - —7 of an oxygen-containing, oxidizing gas, but the procedure is also used for other types of metallic materials with other suitable acidic, basic or neutral solvents or leaching agents for the metals to be extracted, and other suitable gases containing constituents which participate in the leaching reaction or aro inert, can be used as stirring medium.

Claims (5)

Patent claim: A process for extracting at least one metal from a metal-containing solid by dissolving this metal in a leach solution, characterized in that a slurry of finely divided particles of the metal-containing material and the leach solution and a gas stream under pressure are continuously fed into the lower part. of a vertically arranged column and in the column Mlles at elevated temperature and a pressure Above atmospheric pressure so that a continuously rising turbulent suspension rising towards the upper part of the column, consisting of gas bubbles, the metal-containing particles and the leach solution is obtained and that the suspension is substantially uniform cross section and substantially uniform velocity Iran the feed stall in the lower part of the column to the 5th part of the column semi that the solid particles without sinking are caused to rise continuously from the feed stall in the lower part ay the column to the owe part of the column, where the leach solution, gas and unloaded particles accounts is generally discharged, the slurry and gas being fed into the lower part of the column at such a rate that optimum extraction of the metal is obtained. 2. A method according to claim 1, characterized in that gas and unresolved solid particles are separated in the said order from the discharged leach solution. 3. A method according to claim 1, characterized in that undissolved particles and the leach solution are continuously diverted from the column on a stalk below its top and that gas is continuously diverted from the top of the column. 4. A method according to claim 1, characterized in that a plurality of successively arranged columns are used and that the slurry of the metal-containing particles and the leach solution and the gas are continuously fed into the lower part of a first column from the upper part of which a slurry of (Aosta particles and leachate is continuously diverted and together with gas is led into the lower part of the nearest column following from the upper part of which a slurry of unresolved particles and leachate is continuously diverted and fed to the bottom of the Rasta column together with gas. A method according to claim 1, wherein the column is vertically divided by means of partitions in a number of compartments, which communicate with each other through a narrow opening in each partition, the usual compartment being filled with the suspension rising continuously towards the upper part of the column. and wherein the slurry of the solid, metal-containing particles, the leach solution and the gas under pressure are fed into the lower part of the column, and the suspension is passed up through the usual compartment, the unresolved solid particles, the leach solution saint the gas being discharged from the upper compartment. Cited publications: Patentskrifter frein France 926 347. Stockholm 1961. Kungl. Books. P. A. Norstedt & Saner. 610089 ao -.....