GB1567765A - Flotation process - Google Patents

Description

(54) FLOTATION PROCESS (71) We, FLUOR UTAH, INCORPORATED, a corporation of the State of California, 177 Bovet Road, San Mateo, California, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to the hydrometallurgical processing of ores. More particularly, it relates to an improvement in processing ores hydrometallurgically whereby the recovery of desired metallic values from the ores is substantially increased.Still more particularly, it relates to a novel procedure for separating mineral matter from ores containing metallic values whereby the loss of metallic values, normally encountered in solid.liquid separations, is substantially reduced.

For effective recovery of dissolved metallic values from solid mineral matter, it is conventional to make a series of liquid-solid separations following repetitive stages of washing of the the solid phase with counterflow of solution removed from each subsequent stage of liquid-solid separation, washing being done with water and/or barren slution prior to the last stage. Barren solu tion is the commonly used terminology for the solution or solvent remaining after the metallic values have been recovered by processes such as precipitation or electrolytic separation. The most efficient methods to date have involved the application of one of the following equipment systems: countercurrent thickening circuits, selfcleaning filters or solid-bowl centrifuges.By these methods, however, a substantial amount, usually from about 8% to 15two, of metallic values is removed with the solid mineral matter. Frequently, with ores containing a high percentage of clays, fine silicate particles and the like, the percentage of metallic values removed with the mineral matter well exceeds 15%. This is because such constituents either absorb a relatively large amount of the metallic values solution and/or cannot be effectively washed and dewatered. When the foregoing methods are utilized, such constituents are generally separated with the solid mineral matter, carrying metallic values with them. The metallic values lost in the liquid-solid separation steps have nct previously been economically available for recovery through subsequent processing.

In fact, separation of the disolved metallic values from the undissolved mineral matter has meant extremely high capital costs and operating costs per ton of daily plant capacity. Further, a method of separating the dissolved metallic values may be incompatible with other processing steps. For example, in potash metallurgy, a continuous countercurrent decantation (CCD) thickening circuit is not economically combinable with amine flotation of mineral matter particles from particles of potash.

It is an object of the present invention to reduce the significant loss of metallic values associated with liquid-solid separations.

It is also an object of the present invention to provide a method of separating the dissolved metallic values from undissolved mineral matter which offers the possibility of lower capital costs per ton of daily plant capacity or, similarly, a higher recovery of metallic values for comparable capital costs per daily ton.

Another object of the present invention is to provide a process for recovering metallic values from mineral matter which affords better washing action through continuous agitation during separation, which cannot be achieved by conventional practices involving thickeners, centrifuges and/or filters.

Another object of the present invention is to provide a method of obtaining a better contact between particles bearing metallic values and solution through continuous agitation during separation, which affords a better opportunity for leaching the metallic values.

A further object of the present invention is to provide a proces of obtaining metallic values from mineral matter which has a fewer number of washing and separation steps than utilized with conventional practices for equivalent yields.

The present invention provides a process for recovering metallic values from a mixture thereof with mineral impurities, comprising: (A) washing the mixture with a sol vent for the metallic values, in which solvent the impurities are substantially insoluble, forming a solution of the metallic values in the solvent and float ing the insoluble impurities in the solu tion, removing the floated impurities from the solution, (B) subjecting the floated impurities to at least one subsequent flotation and washing step, and where there are two or more such flotation/washing steps, the flow of solution being counter to that of the impurities, the subsequent or the last subsequent flotation/washing being with water or barren solution, the solution from the first subsequent or the subse quent flotation/washing being used as the solvent in step (A), and (C) treating the solution from step (A) to yield the metallic values.

It has been found that by employing the process of this invention, in a preferred embodiment, liquid-solid separation can be effected by a process in which metallic values are leached from host rock and the resultant pulped ore is conditioned with appropriate reagents, followed by froth flotation of the solid mineral matter, accompanied by simultaneous washing with counterflow of solution removed from an immediately subsequent flotation stage. The solution resulting from this first flotationwashing step, referred to herein as 1st countercurrent tails, is further processed as required to recover the desired metallic values in the solution.To abstract the metallic values contained in the resultant mineral matter froth, the froth is subjected to a series of liquid-solid separations by flotation, accompanied by simultaneous washing with counterflow of solution removed from each subsequent stage of flotation, water and/or barren solution being used for washing in the last stage. Processing of pulped ore in this manner is referred to as countercurrent flotation.

Often, it is the practice in the art to subject original ore pulp to preliminary classification steps, such as screening, cycloning and/or hydroseparating, whereby a major proportion of fine particles, or slimes, is separated from the coarse mineral size fraction and either processed separately from the coarse mineral size fraction or discarded.

However, if these slimes are treated by the process of this invention a solution will be obtained containing practically all the soluble metallic values associated therewith, which may be substantially recovered by routing the solution to subsequent well known processing steps, such as precipitation of electrolytic separation.

Also, it is often the practice in the art to subject the mineral matter froth from a flotation process to cleaning by subsequent stages of flotation and grinding, if required, whereby the concentration of desired values is increased by rejection of unwanted mineral matter. If the resultant, rejected mineral matter from such cleaning is treated by the process of the invention, a solution will be obtained which contains practically all the soluble metallic values associated therewith, which may be substantially recovered by routing the solution to subsequent processing steps.

In addition, the mineral matter froth from a flotation process, mentioned above, could be directly treated with the process of this invention with substantially the same results being obtained in regard to the metallic values. This is also true for other mineral concentrates, such as those which are the products of other separation processes, including jigging, tabling, heavy media separation, and magnetic separation.

Figure 1 is a flowsheet depicting a preferred embodiment of this invention, which is basically applicable to all soluble substances, although soluble metals and metal compounds are of primary concern herein.

Figure 2 is a flowsheet for the recovery of gold according to the instant invention, with numerals designating streams described in detail in Example III.

Figure 3 is a flowsheet depicting a preferred embodiment of this invention as used in conjunction with a potash flotation circuit.

Figure 4 is a flowsheet for the recovery of potash utilizing a conventional potash flotation recovery system accompanied by a countercurrent flotation system, with numerals designating streams described in detail in Example IV.

The process of the invention may be advantageously applied to either originally mined ore, a slimes fraction and/or particular size fraction obtained by classification, rejected mineral matter from the cleaning of flotation mineral matter froth, or a mineral concentrate generated from a separation process, such as jigging, tabling, heavy media or magnetic separation, and flotation Furthermore, the process of this invention can be adapted for use under varying circumstances. For example, countercurrent flotation can be applied to substantially any flow of slurry within a mineral processing facility, such as the slurry discharged from a leaching circuit.The leaching circuit may handle either crude ore or mineral concentrates, subject only to limitations of particle size or particle size distribution of the mineral impurities and/or reaction products of the leaching, known as leach residue. In general, although flotation is most effective when the top size of the mineral particles does not exceed 48 mesh, there are, however, exceptions. For example, in the potash and phosphate industry, successful flotation has been achieved on particles as coarse as 8 mesh. This is also true for the flotation of coal and silicate minerals at various operating plants in the U.S. and Europe. Throughout this specification, reference to "Mesh" are to Tyler Standard mesh sizes.

If the size of mineral particles in the slurry to countercurrent flotation must be regulated to meet specific process requirements, such regulations may be achieved by utilizing apparatus such as screens, classifiers, cyclones, centrifuges, thickeners, etc.

For example, if circumstances require, cyclones may be used to separate plus 65 mesh material from minus 65 mesh particles, with the fine fraction being processed through a countercurrent flotation circuit.

Likewise, overflow from a thickener (minus 400 mesh), effluent from a centrifuge (minus 200 mesh), filtrate from a filter (minus 150 mesh), underflow from a thickener (minus 65 mesh), etc. may be routed to a countercurrent flotation circuit in appropriate situations.

This invention may be applied to any desired values, elements or compounds, which can be dissolved in the presence of insoluble impurities. Illustrative examples of specific metallic values recoverable by the process of the instant invention, along with repre- sentative leaching media, are as follows:: METALLIC VALUE LEACHING MEDIUM Potassium Water Sodium Water Magnesium Water Lithium Water Copper Aqueous Solution of Sulfuric Acid, Hydrochloric Acid or Ferric Chloride Uranium Aqueous Solution of Sulfuric Acid or Sodium Carbonate and Sodium Bicarbonate Gold Aqueous Solution of Sodium Cyanide Silver Aqueous Solution of Sodium Cyanide, Sodium Hypochlor ite or Potassium Hypochlorite Nickel Aqueous Solution of Ammonia or Ammonia Carbonate Cobalt Aqueous Solution of Sulfuric Acid Zinc Aqueous Solution of Sulfuric Acid Aluminum Aqueous Solution of Sodium Hydroxide Tungsten Aqueous Solution of Hydrochloric Acid Titanium Aqueous Solution of Sulfuric Acid or Hydrochloric Acid Antimony Aqueous Solution of Sodium Sulfide or Hydrochloric Acid Barium Aqueous Solution of Hydrofluoric Acid or Nitric Acid Rhenium Aqueous Solution of Chlorine or Sodium Hypochlorite The impurities typically separated from the metallic values by application of the instant invention are the insoluble constituents of the host rock with which the metallic values are associated and/or the insoluble reaction products of the leaching operation.

The selection of flotation reagents to be used in the process of the instant invention depends on the constituents of the host rock associated with the desired metallic values.

A report by R. A. Wyman, Head, Industrial Minerals Milling Section, Mineral Processing Division, Mines Branch, Department of Energy, Mines and Resources, Ottawa, Canada, entitled "The Floatability of Twenty-One Non-Metallic Minerals", incorporated herein by reference, gives illustractive reagent selection for 21 minerals.

The reagents, mentioned above, with which the pulped ore is conditioned normally include collectors and modifiers.

Collectors are agents which render the surfaces of minerals to be floated hydrophobic, i.e. lacking affinity for water, thus allowing attachment to an air bubble and elevation to the surface. The chemicals involved are the so-called surface active agents, or surfactants.

In general, the collectors used for flotation of insoluble impurities in the process of this invention would be oils, organic hydrocarbons, having cationic or anionic groups, or mixtures of such collectors. Normally, neither alcohols, such as ethanol, nor inorganic salts would be suitable as collectors.

Exemplary collectors or types of collectors are: 1. "Green acid"--type petroleum sul phonate 2. Sodium alkyl-aryl petroleum sul phonic acid 3. Naphthalene sulphonic acid deriva tive 4. Fatty acid aliphatic sulphonate 5. Sulphonated castor oil (60to fats) 6. Sulphonated fatty acids 7. Sodium octyl sulphate 8. Sodium lauryl sulphate 9. Diethyl cyclohexylamine lauryl sul phate 10. Sodium - N - methyl - N - tal'ow acid taurate 11. Sodium - N - methyl - N - oleoyl taurate 12. Technical tallow amine acetate 13. Coco amine acetate 14. Primary beta amine 15. Tallow diamine di-acetate 16. Coco diamine di-acetate 17. Beta diamine 18. Hydroxyethyl alkyl imidazoline (gly oxalidine) 19. Lauryl amine 20.Beta tertiary amine 21. N0auroyl-colamino-formyl-methyl) pyridinium chloride 22. n-alkyl trimethyl ammonium chlor ide 23. Cetyl trimethyl ammonium bromide 24. Cetyl dimethyl benzyl ammonium chloride 25. Tall oil base fatty acid 26. Tall oil fatty acid 27. Oleic acid blend 28. Oleic acid Those familiar with flotation processes are well aware of considerations given to selection of a suitable collector. Thus, none of the 21 minerals evaluated in the Mine's Branch report would respond favourably to flotation using the following collectors: Xanthates Thiocarbamates Dithiosphosphates Thiocarbanilide Xanthogen.

However, if sulfide minerals were present in the host rock, those skilled in the art would recognize that the above collectors would be used in combination with others.

Modifiers are agents which are capable of performing many functions. Such agents may be utilized to aid in getting the collector onto the surface of the mineral to be floated, an action called activation. On the other hand, modifying agents may be employed to prevent a collector from getting onto the surface of unwanted minerals, an action called depression. The former use is that to which modifiers are normally put in accordance with the process of the present invention.

In addition, modifiers may be used for pH regulation, the cleaning of mineral particle surfaces, dispersion of ultra-fine solids or precipitation of dissolved salts. Some modifiers may even serve more than one purpose, e.g., sodium carbonate may act as an activator, depressant, pH regulator or dispersant.

The modifiers used for flotation in accordance with the process of the present invention generally include all flotation reagents whose principal function is neither collecting nor frothing.

Exemplary modifiers are H2SO, NaCO3, FeSOs, AL(SOA)3, HF, starch, dextrin and citric acid.

In commercial flotation practices, the addition of frothers is normally required to promote the formation of froth capable of supporting mineral-laden bubbles on the surface of the slurry or solution within the flotation cells. Frothers accomplish this objective by imparting temporary toughness to the covering film of the bubble and lowering the surface---tension -of the - water.

Customarily added into the feedboxes of the flotation cells, frothers conventionally used are organic heteropolar compounds, for example, glycol, hexanol, methyl isobutyl carbinol, terpenol, mixed capryl alcohol, and cresylic acid.

Operating parameters for the process of the present inventior, including flow rates, recycle rations and degree of agitation, are discussed below.

In practising the process of the present invention, flow rates are readily determinable by those skilled in the art by a consideration of the following well known factors: (a) design capacity of a particular faci lity; (b) time required for separation of solids by flotation from the solution in volved; (c) percent solids of the feed slurry re quired for flotation; (d) specific gravity of solution and solids; and (e) size of the flotation cells used.

Hydrometallurgical plants have ranged in daily production capacity from several tons to over 15,000 tons.

Flotation time and percent solids in the feed are interdependent and are established by the flotation characteristics of the solids.

Both variables may range widely from one type of ore to another. Flotation time may vary from about 1 to over about 30 minutes.

Solids concentration may vary from about 10 to about 50 percent.

An excellent reference for recycle ratios and the number of washing stages required is a paper by R. J. Woody entitled "Geographical Representation of Theoretical Soluble Losses by CCD", incorporated herein by reference.

Although this paper is related to thickeners, the same principles apply to countercurrent flotation. It is expected, however, that either the number of wash stages or volume of wash solution would be less than required using a CCD thickening circuit.

Generally, the number of washing stages may vary between one and about eight and the recycle ratio, expressed as liquid volume of solution (W) r= liquid volume in froth product (D) may range between one and about six.

The degree of agitation would be that utilized in currently practised flotation processes, well known to those skilled in the art, for comparable particle size and tank volume.

One other important variable is process temperature. In certain leaching operations, the temperature may be elevated to accelerate reaction rates. For flotation of various minerals, results are improved by heating the feed slurry. Temperatures for the process of invention could range from about OOC to about 105"C.

Another variable is pressure. Pressure may be used in some flotation processes to induce air agitation rather than mechanical agitation. For example, in one pressure flotation cell, the Eimco's Flotator vessel, the feed slurry is introduced at a pressure between 15 and 60 psi. By sudden pressure release, a mild aeration results which promotes the formation of a mineral froth at the surface of the vessel. "Eimco", besides being the name by which a certain company is known, is also its trade mark for some products.

Referring to Figure 1, which depicts a preferred embodiment of the present invention, host rock 10 containing the desired metallic values and mineral matter impurities is introduced, usually after appropriate grinding and classification, into a leaching unit 11 concurrently with a leaching medium 9. (The leaching medium or a portion thereof may be introduced during grinding and classification.) Ore pulp 12, containing a metallic values solution and solid mineral matter impurities, is drawn from the leaching vat 11 and introduced into a conditioner 13, along with selected reagents 14 comprising conditioners and/or modifiers.

The conditioned ore pulp 15 is then introduced into 1st countercurrent flotation cells 16, along with a frother 17 and a stream from a subsequent flotation step for washing the conditioned ore pulp 15, as will be discussed below. This mixture is agitated in the 1st countercurrent flotation cells 16 to facilitate simultaneous washing and flotation.

Mineral froth, called 1st countercurrent froth 18 herein, then floats to the top of the Ist couontercurrent flotation cells 16 leaving a solution of the desired metallic values.

This solution, the 1st countercurrent tails 19 herein, is taken from the approximate bottom of the 1st countercurrent flotation cells 16 and directed to subsequent processing for extraction of the desired metallic values.

The 1st countercurrent froth 1S, on the other hand, is taken from the top of the 1st countercurrent flotation cells 16 and introduced into 2nd countercurrent flotation cells 20 along with countercurrent tails from a subsequent countercurrent flotation step (as will be discussed below) for washing - and flotation. Here they are agitated by means of impellers and/or air injection', as will the 1 sot countercurrent flotation cells 16, and 2nd countercurrent froth 21 raises to the top of the cells, leaving a solution containing the desired metallic values, i.e. 2nd countercurrent tails 22.This solution, which is taken from the approximate bottom of the 2nd countercurrent flotation cells 20, is the stream referred to above that is introduced into the 1st countercurrent flotation cells 16, along with the conditioned ore pulp, for washing and flotation.

The 2nd countercurrent froth 21 is taken from the top of the 2nd countercurrent flotation cells 20 and introduced into 3rd countercurrent flotation cells 23 concurrently with countercurrent tails from a subsequent countercurrent flotation step (as will be discussed below) for washing and flotation. Here they are agitated as described above for the 1st and 2nd countercurrent flotation cells with 3rd countercurrent froth 24 rising to the top, leaving a metallic values solution, i.e. 3rd countercurrent tails 25. It is this solution that is used to wash the mineral froth 18 in the 2nd countercurrent flotation cells 20.

The 3rd countercurrent froth 24 taken from this step is introduced into 4th countercurrent flotation cells 26 along with water and/or barren solution 29 for washing and flotation. Again, they are subjected to agitation with 4th countercurrent froth 27 rising to the top, leaving the 4th countercurrent tails 28, which are used for washing the 2nd countercurrent froth 21.

The 4th countercurrent froth 27 which is taken from this step has had substantially all of the desired metallic values removed therefrom by the process just described and can be discarded or utilized for purposes apparent to those skilled in the art.

It should be noted in regard to the process just described that the number of flotation steps utilized is optional. One or more flotation steps subsequent to the first, may be utilized depending upon the total yield of metallic values desired. In general, the more steps that are utilized, the greater the total yield will be. However, a point will be reached where the utilization of additional flotation steps will cause such a small increase in the total yield that it will normally be impractical to make such an addition.

When more than one subsequent flotation step is utilized, water and/or barren solution may be utilized in conjunction with countercurrent tails for washing in flotation steps prior to the last, and a portion of the 1st countercurrent tails stream, described above as going to subsequent processing, may be used for washing in the last flotation stage.

It should be further noted that the water and/or barren solution which is used for washing may be controlled to maintain desired concentrations of advancing solutions in order to optimize recovery of the desired metallic values.

The invention is further illustrated by the examples which follow.

EXAMPLE I The ore to be treated is found in a deposit which contains malachite, azurite and chrysocolla as copper values with the host rock comprising diorite. A diorite usually contains plagioclase, quartz, hornblende, biotite and pyroxene. The diorite constituents constitute the mineral matter impurities, while the copper values are the desired metallic values.

Material from the deposit is mined, then crushed and ground to a particle size to accommodate successful leaching of the copper minerals with an aqueous solution of sulfuric acid.

After leaching, countercurrent flotation is applied either to the entire flow of slurry (solids, dissolved copper acid solution) or a portion of the flow (a fine solids size fraction) obtained by use of mechanical classifiers, cyclones and/or dewatering.

The pH for flotation is established by use of sulfuric acid for leaching. Consequently, reagent selection must be based on response to an acid circuit.

A tabulation based on the aforementioned Mine's Branch report shows the following for acid circuit flotation of the minerals present in diorite: Mineral Collector Section Modifiers Plagioclase (response similar to Tertiary Amine Citric Acid orthoclase) Quartz Tertiary Amine Citric Acid Hornblende Diamine Fluorine Biotite Tertiary Amine Citric Acid Pyroxene (response similar to Diamine Fluorine hornblende) Based on the above tabulation, the selected reagent schedule would include use of two amines, a tertiary amine and a diamine, as collectors, with either a combination of two modifiers, citric and hydrofluoric acid (or elemental fluorine, applied by bubbling into the solution), or just one, citric acid. The frother is selected from well known frothers for such systems including an alcohol, a glycol, a surfactant or a combination thereof.

In addition, the reagent combination which includes a polyacrylamide flocculant as modifier and an ethanolated alkyl guanidineamine complex as collector may be employed for diorite, since this combination appears to behave as a universal reagent combination.

EXAMPLE II As in Example I, the host rock is diorite, but the metallic value is gold. After crushing and grinding, the gold may be leached with an aqueous solution of cyanide, using lime to maintain a basic pH. Under these circumstances, the pH for flotation is basic.

Consequently, reagent selection must be made accordingly. Based on the Mine's Branch Report, the reagent schedule would include use of a primary amine as the collector with additions of iron and aluminum sulfates as modifiers. The frother should be either an alcohol, a glycol, a surfactant or a combination thereof.

As in Example I, the reagent combination including a polyacrylamide flocculant and an ethanolated alkyl guanidineamine complex may also be employed here.

EXAMPLE III Figure 2 is a flowsheet for the recovery of gold according to the instant invention. The following are illustrative flow rates for such a process: GALLONS PER SPECIFIC UNIT OPERATION TONS PER HOUR PERCENT MINUTE GRAVITY Pulp or Solids Solution Solids Solids Solution Pulp Solution Grinding & Classification Feed Streams (1) Host Rock 475 25 95 717 100 817 2.45 (2) Cyanide solution - 2 - - 8 8 1.08 (20) Barren Solution - 176.6 - - 706 706 1.00 Discharge (3) 475 203.6 70 717 814 1531 1.77 Leaching & Conditioner (4) & (5) 475 203.6 70 717 814 1531 1.77 1st Countercurrent Flotation Cells Feed Streams (5) Conditioner Discharge 475 203.6 70 717 814 1531 1.77 (11) 2nd Countercurrent Tails - 1696.4 - - 6786 6786 1.00 (6) Total Feed 475 1900.0 20 717 7600 8317 1.14 Products (7) 1st Countercurrent Froth 475 882.1 35 717 3528 4245 1.28 (8) 1st Countercurrent Tails - 1017.9 - - 4072 4072 1.00 GALLONS PER SPECIFIC UNIT OPERATION TONS PER HOUR PERCENT MINUTE GRAVITY Pulp of Solids Solution Solids Solids Solution Pulp Solution 2nd Courtercurrent Flotation Cells Feed Streams (7) 1st Countercurrent Froth 475 882.1 35 717 3528 4245 1.28 (14) 3rd Countercurrent Tails - 1696.4 - - 6786 6786 1.00 (9) Total Feed 475 2578.5 13.5 717 10314 11031 1.11 Products (10) 2nd Countercurrent Froth 475 882.1 35 717 3528 4245 1.28 (11) 2nd Countercurrent Tails - 1696.4 - - 6786 6786 1.00 3rd Counterurrent Flotation Cells Feed Streams (10) 2nd Countercurrent Froth 475 882.1 35 717 3528 4245 1.28 (18) 4th Countercurrent Tails - 1696.4 - - 6786 6786 1.00 (12) Total Feed 475 2578.5 13.5 717 10314 11031 1.11 Products (13) 3rd Countercurrent Froth 475 882.1 35 717 3528 4245 1.28 (14) 3rd Countercurrent Tails - 1696.4 - - 6736 6736 1.00 GALLONS PER SPECIFIC UNIT OPERATION TONS PER HOUR PERCENT MINUTE GRAVITY Pulp or Solids Solution Solids Solids Solution Pulp Solution 4th Countercurrent Flotation Cells Feed Streams (13) 3rd Countercurrent Froth 475 882.1 35 717 3528 4245 1.28 (21) Barren Solution - 841.3 - - 3366 3366 1.00 (15) Water - 855.1 - - 3420 3420 1.00 (16) Total Feed 475 2578.5 13.5 717 10314 11031 1.11 Products (17) 4th Countercurrent Froth 475 882.1 35 717 3528 4245 1.28 (18) 4th Countercurrent Tails - 1696.4 35 - 6786 6786 1.00 Solution Purification & Gold Precipitation Feed Stream (8) 1st Countercurrent Tails - 1017.9 - - 4072 4072 1.00 - 4072 4072 1.00 Discharge - 1017.9 (19) Barren Solution Barren Solution Distribution (20) Grinding & Classification - 176.6 - - 706 706 1.00 (21) 4th Countercurrent Flotation - 841.3 - - 3366 3366 1.00 The process of the present invention is particularly adaptable for use with a conventiop potash flotation recovery system. In such a system, flotation is utilized to separate solid potash particles, e.g. particles of K2Co, and miscellaneous other potassium salts, from solid mineral matter particles.

Unfortunately, substantial amounts of potash are entrained with the mineral matter particles which are thereby separated. The potash associated with this mineral matter portion has heretofore been considered economically uncoverable. However, such is not the case when the process of the present invention is utilized.

Referring to Figure 3, which depicts a preferred embodiment of such utilization, host rock 10 containing the potash, i.e., the desired potassium values, as well as mineral matter impurities is, normally after crushing and classification, introduced into a scrubbing unit 11 concurrent with a scrubbing medium 9, such as saturated brine.

Saturated brine, as used herein, refers to an aqueous solution containing the maximum possible amount of potash dissolved therein. The scrubbing unit 11 is used to attrite the potash particles thereby liberating mineral matter particles which are contained in the host rock 10. Unlike the process of the present invention in which a leaching medium is utilized to bring the desired values into solution, the conventional potash flotation recovery proces utilizes scrubbing media, such as saturated brine, to keep potash values from going into solution so that a solid-solid separation can be made of the potash particles and the mineral matter particles in the initial flotation step of the process.

Scrubbing unit discharge 12, containing solid potash values and solid mineral matter particles is discharged from the scrubbing unit 11 and introduced into a container 13, along with selected reagents 14 comprising modifiers and/or collectors, e.g. a poly acrylamide flocculant as a modifier and an ethanolated alkyl guanidineamine complex as a collector. Additional saturated brine may sometimes be added into conditioner 13 to reduce the percentage of solids therein and thereby facilitate the conditioning of scrubber discharge 12. The desirability of such addition depends upon the nature of the host rock 10 being processed and will be readily apparent to those skilled in the art.

The conditioned scrubber discharge 15 is then introduced into rougher flotation cells 16, normally along with a frother 17, and agitated by impellers and/or air injection.

Rougher froth 18, including mineral matter particles and entrained potash particles, then floats to the top of the rougher flotation cells 16, leaving rougher tails 19, including saturated brine and solid potash particles.

The rougher tails 19 are directed to subsequent processing for extraction of the desired values, while the rougher froth 18 is introduced into 1st countercurrent flotation cells 20, along with 2nd countercurrent tails 25 from 2nd countercurrent flotation cells 23. It should be noted that for the purposes of the process of the present invention, these 2nd countercurrent tails 25 become the initial leaching medium for the potash in rougher froth 18 and that usually no more reagents need be added to the rougher froth 18, since the particles therein have already been subjected to conditioning in conditioner 13. To achieve desired flotation results with some ores, however, introduction of additional amounts of reagents into selected countercurrent flotation cells may be required.

From this point on, countercurrent flotation is conducted just as described earlier.

The 1st countercurrent tails 22 are directed to subsequent processing, while the 1st countercurrent froth 21 is introduced into 2nd countercurrent flotation cells 23, along with 3rd countercurrent tails 28 from 3rd countercurrent flotation cells 26, etc.

Although Figure 3 depicts three countercurrent flotation stages, as was discussed earlier, more or less might be used, depending upon the yield of potash desired from the countercurrent flotation operation.

It should be noted that although the entire stream of 1st countercurrent tails 22 could be directed to a unit, such as a crystallizer, for the extraction of substantially all the potash therein, it is more advantageous to regulate the addition of water and/or barren solution to the last countercurrent flotation cells such that the 1st countercurrent tails 22 will be a saturated brine solution and then to combine this stream with other saturated brine streams which are normally generated in a conventional potash flotation recovery system. By doing this, sufficient saturated brine is made available for operation of the conventional potash recovery system without additional saturated brine having to be generated, and the saturated brine from these combined streams which is not needed for operation of the conventional potash recovery system may be routed to an appropriate extraction unit, such as a crystallizer, for the recovery of potash values therein. An illustration of such an arrangement is given in the following example.

EXAMPLE IV Figure 4 is a flowsheet for the recovery of potash according to the adaptation of the instant invention just discussed. The following are illustrative flow rates for such a process: GALLONS PER SPECIFIC UNIT OPERATION TONS PER HOUR PERCENT MINUTE GRAVITY Pulp or Solids Solution Solids Solids Solution Pulp Solution Scrubbing Unit Feed Streams (1) Potash Ore 400 20 95 800 65 865 1.94 (2) Brine - 151 - - 487 487 1.24 Discharge (3) 400 171 70 800 552 1352 1.69 Conditioner Feed Streams (3) Scrubbing Unit Discharge 400 171 70 800 552 1352 1.69 (4) Brine - 762 - - 2458 2458 1.24 Discharge (5) 400 933 30 800 3010 3810 1.40 Rougher Flotation Cells Feed Streams (5) Conditioner Discharge 499 933 30 800 3010 3810 1.40 Products (6) Rough Tails 366 627 36.8 732 2023 2755 1.44 (7) Rougher Froth 34 306 10 68 987 1055 1.29 GALLONS SPECIFIC UNIT OPERATION TONS PER HOUR PERCENT MINUTE GRAVITY Pulp or Solids Solution Solids Solids Solution Pulp olution 1st Countercurrent Flotation Cells Feed Streams (7) Rougher Froth 34 306 10 68 987 1055 1.29 (8) 2nd Countercurrent Tails - 340 - - 1104 1104 1.23 (9) Total Feed 34 646 - 68 2091 2159 1.26 Products (10) 1st Countercurrent Tails - 375 - - 1210 1210 1.24 (11) 1st Countercurrent Froth 32 273 10.5 64 881 945 1.29 2nd Countereurrent Flotation Cells Feed Streams (11) 1st Countercurrent Froth 32 273 10.5 64 881 945 1.29 (12) 3rd Countercurrent Tails - 251 - - 838 838 1.20 (13) Total Feed 32 524 - 64 1719 1783 1.25 Products (8) 2nd Countercurrent Tails - 340 - - 1104 1104 1.23 (14) 2nd Countercurrent Froth 27 189 12.5 54 615 669 1.29 GALLONS PER SPECIFIC UNIT OPERATION TONS PER HOUR PERCENT MINUTE GRAVITY Pulp or Solids Solution Solids Solids Solution Pulp Solution 3RD Countercurrent Flotation Cells Feed Streams (14) 2nd Countercurrent Froth 27 189 12.5 54 615 669 1.29 (15) Water . . ... - 40 - - 160 160 1.00 (16) Crystallizer Muds (Barren Solution) ... ... ... - 126 - - 430 430 1.17 (17) Total Feed ... 27 355 - 54 1205 1259 1.21 Products (12) 3rd Countercurrent Tails - 251 - - 838 838 1.20 (18) 3rd Countercurrent Froth 21 110 16 42 267 409 1.28 Potash Flotation Circuit Feed Stream (6) Rougher Flotation Tails 366 627 36.8 732 2023 2755 1.44 Products (19) Potash Froth Product 80 149 35 160 481 641 1.43 (20) Potash Flotation Tails .... 286 478 37.4 572 1542 2114 1.45 GALLONS PER SPECIFIC UNIT OPERATION TONS PER HOUR PERCENT MINUTE GRAVITY Pulp or Solids Solution Solids Solids Solution Pulp Solution Potash Froth Dewatering Feed Stream (19) Potash Froth Product 80 149 35 160 481 641 1.43 Products (21) Filtrate (Saturated Brine) - 142 - - 458 458 1.24 (25) Potash Cake ... ... 80 7 92 160 23 183 1.90 Potash Dryer Feed Stream (25) Potash Cake 80 7 92 160 23 183 1.90 Products (26) Standard Red Product 66 0.3 99.5 132 - 132 2.00 (27) Dryer Dust ... 15 0.3 93 30 - 30 2.00 (M) Water Vapor . - 5.4 - - 21 21 1.00 Potash Flotation Tails Dewatering Feed Stream (20) Potash Flotation Tails 386 478 37.4 572 1542 2114 1.45 Products (22) Filtrate (Saturated Brine) - 453 - - 1461 1461 1.24 (34) Tails Cake ...... 286 25 92 572 81 653 1.91 GALLONS PER SPECIFIC UNIT OPERATION TONS PER HOUR PERCENT MINUTE GRAVITY Pulp or Solids Solution Solids Solids Solution Pulp Solution Dryer Dust Agitator Feed Stream (27) Dryer Dust 15 0.3 98 30 1 31 2.00 (28) Water - 62 - - 248 248 1.00 Product (29) Brine - 77.4 - - 249 249 1.24 Brine Balance Recovered Brine (23) Dewatering Circuits (21) & (22) - 595 - - 1919 1919 1.24 (10) 1st Countercurrent Tails ... - 375 - - 1210 1210 1.24 Total Brine Recovered (24) - 970 - - 3129 3129 1.24 Prepared Brine (29) Dryer Dust Agitator .. - 77 - - 249 249 1.24 Total Available Brine (24) & (29) - 1047 - - 3378 3378 1.24 Brine Distribution (31) Returned to Process (2) & (4) . - 913 - - 2945 2945 1.24 (32) Routed to Crystallizer ... - 134 - - 433 433 1.24 Crystallizer Operation Feed Stream (32) Brine - 134 - - 433 433 1.24 Products (33) White Product - 8 - 16 - 16 2.00 (16) Muds ... - 126 - - 430 430 1.17 The size of commercial flotation cells presently available range from 1 cubic foot to 2,000 cubic feet. Under these circumstances, it is necessary to calculate cell volume based on laboratory and/or pilot data for each particular installation. Calculations for a recovery system employing the process of the invention for a commercial size plant are given below, by way of example.

EXAMPLE V Rougher Flotation Cells: Hourly Design Tonnage 420 short tons of mine-run ore (400 short tons dry) Flotation Time 12 minutes Percent Solids of Flotation Feed 30 (undissolved) Specific Gravity of Solids 2.0 gms/cu. cm.

Specific Gravity of Brine 1.24 gms/cu. cm.

Tons/Hr of Slurry 400/.30=1333 Tons/Hr of Brine 1333-400=933 (933) (2000) GPM of Brine = = 3010 (1.24 (8.33) (60) (400) (4) GPM of Solids = 800 2.0 GPM of Slurry 3010+800=3810 Cell Volume Required 2010x12 minutes=45.720 gals.

Flotation Cell Specified 500 cu. ft.

Active Cell Volume 3200 gallons/cell Number of Flotation Cells Required 45,720/3200=14.3 To maintain circuit synunetry 16 cells would generally be utilized.

Possible Ar@angements: 4 rows having 4 cells each 2 rows having 8 cells each (preferred to prevent short circuiting of feed slurry) Flow Rates: 4 rows- 952 GPM of slurry each 2 rows-1905 GPM of slurry each Products yew Flotation: Rougher Froth (advanced to 1st countercurrent flotation cells) 34 tons/hr of slurry at 10% solids; 1055 GPM flotation Tails (feed to potash flotation circuit) 993 tons/hr. of slurry at 36.8% solids: 2755 GPM -1st Countercurrent Flotation Cells: Rougher Froth 340 tons/hr of slurry at 10% solids; 1055 GPM Counterflow of 2nd Countercurrent Tails 340 tons/hr of solution at 1.23 gms/cu.

cm. specific gravity; 1104 GPM Total Flotation Feed 680 tons/hr of slurry at 5% solids; 2159 GPM Flotation Time 15minutes Total GPM of Feed Slurry 2159 Total Volume Required 2159 GPM X 15 minutes--32,385 gals.

Flotation Cell Specified 500 cu. ft.

Active Cell Volume 3200 gals.

Number of Flotation Cells Re quired 32,385/3200----10.1 Arrangement One row of 10 cells Flow rate 2159 GPM of slurry Products from Flotation: 1st Countercurrent Froth (advanced to 2nd countercurrent flotation cells) 305 tons/hr at 10.5% solids; 945 GPM 1st Countercurrent Tails (advanced to subsequent pro cessing for extraction of desired potash values) 375 tons/hr at 1.24 specific gravity; 1210 GPM The recycle ratio r (see above) is calculated as follows: 340 tons/hr froth at 10% solids represents a liquid filow of 987 GPM.

340 tons/hr tails at 1.23 specific gravity represents a liquid flow of 1104 GPM.

1104 Consequently, r= =1.12 987 WHAT WE CLAIM IS:- 1. A process for recovering metallic values from a mixture thereof with mineral impurities, comprising: (A) washing the mixture with a sol vent for the metallic values, in which solvent the impurities are substantially insoluble, forming a solution of the metallic values in the solvent and float ing the insoluble impurities in the solu tion, removing the floated impurities from the solution, (B) subjecting the floated impurities to at least one subsequent flotation and washing step, and where there are two or more such flotation/washing steps, the flow of solution being counter to that of the impurities, the subsequent or the last subsequent flotation/washing being with water or barren solution, the solution from the first subsequent or the subse quent flotation / washing being used as the solvent in step (A), and (C) treating the solution from step (A) to yield metallic values.

2. The process of claim 1, wherein step B comprises three subsequent stages of flotation/washing, the first subsequent stage being carried out with counterflow of solution removed from the second stage, the second subsequent stage being carried out with counterflow of solution from the third stage, the third subsequent stage being carried out with water or barren solution and the solution portion of the first subsequent stage being used as the solvent in step (A).

3. The process of claim 1 or claim 2 wherein at least one flotation reagent selected from the group consisting of collectors and modifiers is added to the solution to achieve flotation of the insoluble mineral impurities.

4. The process of claim 3 wherein the values are copper values, the floated impurities are plagioclash quartz, hornblende, biotite and pyroxene, the collectors are a tertiary amine and a diamine, the modifier is citric acid and the solvent is an aqueous solution of sulfuric acid.

5. The process of claim 3 wherein the values are gold values, the floated impurities are plagioclase, quartz, hornblende, biotite and pyroxene, the collector is a primary amine, the modifiers are iron sulfate and aluminum sulfate, the solvent is an aqueous solution of cyanide, and lime is used to maintain a basic pH.

6. The process of any one of claims 1

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (42)

1. **WARNING** start of CLMS field may overlap end of DESC **.

   Total Flotation Feed 680 tons/hr of slurry at 5% solids; 2159 GPM Flotation Time 15minutes Total GPM of Feed Slurry 2159 Total Volume Required 2159 GPM X 15 minutes--32,385 gals.

   Flotation Cell Specified 500 cu. ft.

   Active Cell Volume 3200 gals.

   Number of Flotation Cells Re quired 32,385/3200----10.1 Arrangement One row of 10 cells Flow rate 2159 GPM of slurry Products from Flotation: 1st Countercurrent Froth (advanced to 2nd countercurrent flotation cells) 305 tons/hr at 10.5% solids; 945 GPM 1st Countercurrent Tails (advanced to subsequent pro cessing for extraction of desired potash values) 375 tons/hr at 1.24 specific gravity; 1210 GPM The recycle ratio r (see above) is calculated as follows:

   340 tons/hr froth at 10% solids represents a liquid filow of 987 GPM.

   340 tons/hr tails at 1.23 specific gravity represents a liquid flow of 1104 GPM.

   1104 Consequently, r= =1.12 987 WHAT WE CLAIM IS:- 1. A process for recovering metallic values from a mixture thereof with mineral impurities, comprising: (A) washing the mixture with a sol vent for the metallic values, in which solvent the impurities are substantially insoluble, forming a solution of the metallic values in the solvent and float ing the insoluble impurities in the solu tion, removing the floated impurities from the solution, (B) subjecting the floated impurities to at least one subsequent flotation and washing step, and where there are two or more such flotation/washing steps, the flow of solution being counter to that of the impurities, the subsequent or the last subsequent flotation/washing being with water or barren solution, the solution from the first subsequent or the subse quent flotation / washing being used as the solvent in step (A), and (C) treating the solution from step (A) to yield metallic values.
2. 2. The process of claim 1, wherein step B comprises three subsequent stages of flotation/washing, the first subsequent stage being carried out with counterflow of solution removed from the second stage, the second subsequent stage being carried out with counterflow of solution from the third stage, the third subsequent stage being carried out with water or barren solution and the solution portion of the first subsequent stage being used as the solvent in step (A).
3. 3. The process of claim 1 or claim 2 wherein at least one flotation reagent selected from the group consisting of collectors and modifiers is added to the solution to achieve flotation of the insoluble mineral impurities.
4. 4. The process of claim 3 wherein the values are copper values, the floated impurities are plagioclash quartz, hornblende, biotite and pyroxene, the collectors are a tertiary amine and a diamine, the modifier is citric acid and the solvent is an aqueous solution of sulfuric acid.
5. 5. The process of claim 3 wherein the values are gold values, the floated impurities are plagioclase, quartz, hornblende, biotite and pyroxene, the collector is a primary amine, the modifiers are iron sulfate and aluminum sulfate, the solvent is an aqueous solution of cyanide, and lime is used to maintain a basic pH.
6. 6. The process of any one of claims 1

   to 3 wherein the values are potassium values and the solvent is water.
7. 7. The process of any one of claims 1 to 3 wherein the values are sodium values and the solvent is water.
8. 8. The proces of any one of claims 1 to 3 wherein the values are magnesium values and the solvent is water.
9. 9. The process of any one of claims 1 to 3 wherein the values are lithium values and the solvent is water.
10. 10. The process of any one of claims 1 to 3 wherein the values are copper values and the solvent is an aqueous solution of sulfuric acid.
11. 11. The process of any one of claims 1 to 3 wherein the values are copper values and the solvent is an aqueous solution of hydrochloric acid.
12. 12. The process of any one of claims 1 to 3 wherein the values are copper values and the solvent is an aqueous solution of ferric chloride.
13. 13. The process of any one of claims 1 to 3 wherein the values are uranium values and the solvent is an aqueous solution of sulfuric acid.
14. 14. The process of any one of claims 1 to 3 wherein the values are uranium values and the solvent is an aqueous solution of sodium carbonate and sodium bicarbonate.
15. 15. The process of any one of claims 1 to 3 wherein the values are gold values and the solvent is an aqueous solution of sodium cyanide.
16. 16. The process of any one of claims 1 to 3 wherein the values are silver values and the solvent is an aqueous solution of sodium cyanide.
17. 17. The process of any one of claims 1 to 3 wherein the values are silver values and the solvent is an aqueous solution of sodium hypochlorite.
18. 18. The process of any one of claims 1 to 3 wherein the values are silver values and the solvent is an aqueous solution of potassium hypochlorite.
19. 19. The process of any one of claims 1 to 3 wherein the values are nickel values and the solvent is an aqueous solution of ammonia.
20. 20. The process of any one of claims 1 to 3 wherein the values are nickel values and the solvent is an aqueous solution of ammonium carbonate.
21. 21. The process of any one of claims 1 to 3 wherein the values are cobalt values and the solvent is an aqueous solution of sulfuric acid.
22. 22. The process of any one of claims 1 to 3 wherein the values are zinc values and the solvent is an aqueous solution of sulfuric acid.
23. 23. The process of any one of claims 1 to 3 wherein the values are aluminum values and the solvent is an aqueous solution of sodium hydroxide.
24. 24. The process of any one of claims 1 to 3 wherein the values are tungsten values and the solvent is an aqueous solution of hydrochloric acid.
25. 25. The process of any one of claims 1 to 3 wherein the values are titanium values and the solvent is an aqueous solution of sulfuric acid.
26. 26. The process of any one of claims 1 to 3 wherein the values are titanium values and the solvent is an aqueous solution of hydrochloric acid.
27. 27. The process of any one of claims 1 to 3 wherein the values are antimony values and the solvent is an aqueous solution of sodium sulfide.
28. 28. The process of any one of claims 1 to 3 wherein the values are antimony values and the solvent is an aqueous solution of hydrochloric acid.
29. 29. The process of any one of claims 1 to 3 wherein the values are barium values and the solvent is an aqueous solution of hydrofluoric acid.
30. 30. The process of any one of claims 1 to 3 wherein the values are barium values and the solvent is an aqueous solution of nitric acid.
31. 31. The process of any one of claims 1 to 3 wherein the values are rhenium values and the solvent is an aqueous solution of chlorine.
32. 32. The process of any one of claims 1 to 3 wherein the values are rhenium values and the solvent is an aqueous solution of sodium hypochlorite.
33. 33. The process of any one of claims 1 to 3 wherein the values are potassium values, recovered from potash, and the solvent is water.
34. 34. The process of claim 4 wherein hydrofluoric acid is also employed as a modifier.
35. 35. The process of any one of claims 1 to 3 and 6 to 33 wherein the modifier is polyacrylamide and the collector is an ethanolated alkyl guanidineamine.
36. 36. A process for recovering potassium values from a mixture of impurities and potassium as potash, comprising: a. adding to the mixture an aqueous solution containing the maximum amount of potash dissolved therein: b. adding to the mixture and aqueous solution at least one flotation reagent selected from the group consisting of collectors and modifiers to effect flotation of the impurities; c. floating the impurities in the aqueous solution; d. removing the floated impurities from said aqueous solution; e. processing the aqueous solution and the undissolved potash associated therewith to separate the undissolved potash, f. subjecting the floated impurities to subsequent stages of flotation! washing with counterflow of solution removed from each subsequent stage of flotation, water being used in the last stage; solution from the first subsequent stage being used as the solution for step (a) and g. processing either (1) solution portion of the first subsequent stage or (2) the aqueous solution from step (e), or both (1) and (2), to yield the potassium values dissolved therein.
37. 37. The process of claim 36 wherein the modifier is polyacrylamide and the collector is ethanolated alkyl guanidineamine.
38. 38. The process of claim 36 or claim 37 wherein: a. the water added to the last stage is regulated such that the solution portion of the first subsequent stage is a solution with the maximum amount of potash dissolved therein; b. the solution portion from the first subsequent stage is mived with the aqueous solution formerly associated with the undissolved potash after the undissolved potash has been separated therefrom; c. a portion of the resulting solution mixture is used as the aqueous solution containing the maximum amount of potash dissolved therein initially added to the mixture of potash and impurities; and d. the portion of the resulting solution mixture not needed for addition to the mixture of potash and impurities is processed to yield the potassium dissolved therein.
39. 29. The process of any one of claims 1 to 38, wherein washing and flotation are facilitated in at least one step by agitation.
40. 40. The process of claim 1 conducted substantially as described in any one of the Examples herein.
41. 41. The process of claim 1 conducted substantially as described with reference to the reaction schemes set out in any one of Figures 1 to 4 herein.
42. 42. A purified value obtained by the process of any one of claims 1 to 41.