US3151062A

US3151062A - Method for the froth flotation of slimed minerals and ores

Info

Publication number: US3151062A
Application number: US86502A
Authority: US
Inventors: James B Duke
Original assignee: Minerals and Chemicals Philipp Corp
Current assignee: Minerals and Chemicals Philipp Corp
Priority date: 1961-02-01
Filing date: 1961-02-01
Publication date: 1964-09-29
Anticipated expiration: 1981-09-29

Description

United States Patent 3,151,962 METHQD FGR THE FRQTH FLQTATEON 0F SLllvliED MENERALS AND GEES James B. Duke, Menlo Park Terrace, Metuchen, N.J., assiguor to idinerals dz Chemicals Phiiipp Corporation,

Menlo Park, Ni, a corporation of Maryland Filed Feb. 1, 1961, Ser. No. 86,502 it tllairns. (Ci. 209-3} The subject invention relates generally to improvements in the froth flotation of finely divided or slimed multicomponent mineral masses and ores. In essence, the subject invention constitutes an improvement over the froth flotation procedure described in a copending US. patent application, Serial No. 779,061, now Patent No. 2,990,958, filed December 9, 1958, of which I am a coinventor.

In accordance with the process of said copending application, the beneficiation of very finely divided (slimed) multicomponent mineral masses and ores by froth flotation is facilitated by conditioning an aqueous pulp of such slimed minerals or ores with a collector reagent selective to one component of such mineral or ore, leaving residual components water wettable, and with collectorcoated, finely divided particles of an auxiliary mineral which are floatable in the reagentized pulp. The latter report in the froth product in intimate association with the oiled component of the feed and, in so doing, they enhance or promote the flotation of the oiled components of the feed which are normally not amenable to efficient selective flotation. The machine discharge product is a concentrate of the water-wettable components of the feed. It is postulated that the oiled auxiliary mineral particles form a nucleus for the attachment of the finely divided oiled fraction of the feed and that the loaded auxiliary particles thus formed are better adapted to air-bubble attachment than the selectively oiled feed particles. Thus, in effect, the oiled auxiliary nflnerals carry the slimed selectively oiled feed into the froth. For this reason, the oiled auxiliary particles are referred to hereafter as the oiled carrier.

By application of the novel conditioning treatment, described above, slimed minerals and ores, never heretofore concentratable by froth flotation, may now be beneficiated with an excellent degree of efficiency. The method thus comprises a novel concept in the flotation art that extends its application to slimed minerals in the minus 10, minus 5, and minus 2 micron particle size ranges.

In carrying out this process, the carrier particles are preferably introduced into the feed pulp and the admixed pulp conditioned. Alternatively, the feed pulp and the pulp of the carrier mineral may be conditioned separately and the reagentized pulps admixed. A wide variety of oiled carrier particles are useful in the process since apparently the oiled carrier particles function by a physical mechanism to improve flotation rather than by a chemical mechanism. The carrier mineral particles are prefer ably largely minus 325 mesh, with extremely fine materials, microns or finer being eminently suitable. The carrier is employed in amount by Weight at least equal to that portion of the feed which is to be floated and usually in appreciably greater quantity.

One of the characteristics of the process is that the froth product, obtained by aerating a pulp conditioned in the novel manner described above, generally tends to be extremely voluminous and persistent. The froths are Wet to the touch in spite of the fact that they are amply mineralized, indicating that the foams have poor drainage properties. In the latter respect, the froths differ fundamentally in nature from the mineral-poor, voluminous froths sometimes developed because of the use of excessive frothing agents in conventional flotation processes.

As a result of the poor drainage of the foams, waterwettable feed slimes in the aqueous pulp tend to become entrained in the froth product. This has the obvious eflect of impairing product recovery in case the valuable mineral reports in the machine discharge product. In case the valuable mineral reports in the froth product, product grade is adversely affected. While these eifects of poor foam drainage are easily coped with in batch laboratory scale flotation tests by allowing sufficient time for the pulp to drain from the foam before refloating the pulp and by proper manipulation of the foam, in continuous flotation circuits the metallurgy of the process is adversely affected.

Thus, for example, in the flotation of colored impurities from discolored kaolin clay. (a naturally slimed mineral) with negative-ion reagents selective to the colored impurities and with oil carrier particles, such as oiled calcite or oiled sulfur, there results a very Wet, voluminous froth containing entrained clay. While the froth product from the initial flotation can be refioated sev-. eral times, as described in said copending application, and the machine discharge products from each of these flotations combined to provide a high brightness kaolin clay product containing a small percentage of TiO and other coloring purities, in practice the clay recovery obtainable in continuous operation has not matched results obtained in laboratory scale batch flotation. Thus, a typical weight recovery in the first flotation in continuous plant scale runs operating on the process with discolored clay is about 50% to 60%, and the overall weight recovery obtained by refloating the initial froth product three times and combining the four machine discharge products is typically to based on the dry weight of the original kaolin clay. In contrast, in batch operations utilizing the same feed and conditioning reagents, recovcry of the order of to is realized. Such results indicate that the recovery problem is a physical one, tied in with the poor drainage characteristics of the froth product, rather than one of inadequate selectivity of reagents. Variations in recovery are experienced with clay feeds of different origin.

In addition to its adverse effect on the metallurgy of the process, other obstacles are associated with the V0- luminous nature of the froth in commercial operation of the carrier flotation process. One of the difliculties is that the flotation machines mustbe equipped with specially large launders which are able to handle the voluminous froths. Further, special discard drains must be equipped to dispose of the persistent froth product when it is not treated for recovery of mineral values therein.

Accordingly, a principal object of my invention is the provision of a method for improving upon the properties of the foam produced by subjecting to froth flotation a pulp of a slimed ore (or multicomponent mineral mass) which has been conditioned with a collector reagent selective to one component of said ore (or multicornponent mineral mass) and with collector-coated carrier particles.

A more particular object of this invention is to improve upon the drainage properties of the foam, so as to eflect an improvement in the metallurgy of the carrier flotation process described above.

Still another object of this invention is to reduce the volume of foam present in the froth product so as to obviate the need for special plant equipment to handle such froth.

Yet another important object is to utilize the improved physical nature of the froth product to improve further the metallurgy of the carrier flotation of slimed multicornponent minerals and ores in a continuous operation in which the froth product is refloated.

A more particular object is to discard an initial portion of the refloated froth product before the second float subjected to an initial froth flotation.

is subjected to further reflotation, whereby only a residual portion of the refloated product is subjected to further reflotation, thereby improving the overall recovery of the composited machine discharge products.

A further more specific object is to'improve upon the recovery of beneficiated clay machine discharge product without sacrifice in product grade in a continuous commercial process in which the froth product is refloated for recovery of'clay values therein.

Still another object of the invention is the provision of an improvement in the method for carrying out a process for the continuous carrier froth flotation of discolored kaolin clay which calls for no additional plant equipment. 7 7

Further objects and advantages will be readily apparent from the description of my invention taken in connection with the accompanying drawing which shows a flowsheet of a typical plant practicing the method on a discolored kaolin clay feed.

The present invention is a result of my discovery that a hydrocarbon oil may be utilized in a novel manner, hereinafter described, to effect a remarkable improvement in the physical nature of the froth product obtained by aerating a slimed feed pulp conditioned with solid carrier particles in accordance with the method of US. Patent No. 2,990,958. One form of this invention is a result of my surprising discovery that when this hydrocarbon oil treatment is used, the initial froth product ob tained by refloating the froth product is of a considerably higher grade than is the froth subsequently developed. Tris phenomenon is utilized to effect an improvement in recovery of the machine discharge product or an improvement in concentrate grade.

Briefly stated, in accordance with the present invention the desired improvement in the physical properties of the froth product obtained by the flotation of a dispersed conditioned pulp of slimed multicomponent mineral mass and carrier mineral particles is obtained by further conditioning such a pulp with inert hydrocarbon oil before the admixed pulp of feed and oiled carrier particles is This is preferably done by forming a dispersed admixed pulp of feed and carrier mineral particles, conditioning the admixed pulp for flotation with a collector reagent selective to a component of the feed and also selective to the carrier mineral particles, then postconditioning the pulp with my hydrocarbon oil and subjecting the thus conditioned pulp to froth flotation. The froth product obtained by aerating the conditioned pulp which has been treated with my hydrocarbon oil is relatively dry, providing good drainage for the pulp, rather than wet and conducive to the entrainment of slimed water-wettable matter in the feed as it would be in the absence of the hydrocarbon oil treatment.

Thus, for example, in the beneficiation of discolored kaolin clay by carrier flotation in a continuous process in which the froth is refioated a plurality of times, the total quantity of beneficiated clay reporting in the underflow is greater, without sacrifice in clay grade, than when the postconditioning hydrocarbon oil treatment is omitted, all other factors being equal. With certain hydrocarbon oils an improvement in clay brightness is also realized.

Further, the froth volume is reduced appreciably as a result of the hydrocarbon oil treatment so that the froth may be handled in the usual launders or plant drains, thereby avoiding the requirement for specialized plant equipment.

From the above, it is apparent that my use of a hydrocarbon oil with a collector-coated slimed feed to improve upon the physical properties of the froth product is different from the prior art use of similar oils with conventional (i.e., deslimed) flotation feed as a replacement for a part of the ionic collector reagent for the purpose of reducing reagent costs or to improve upon the selectivity of the collector. My oil is incorporated into a pulp in which mineral particles have already been collector coated and, while in some instances an improvement in collection may be realized, such result is incidental to the principal benefit of foam control in the froth product.

In accordance with an embodiment of this invention, the initial froth product obtained with the hydrocarbon oil postconditioning treatment is subjected to continuous reflotation in a second machine containing a plurality of cells in series. The float product from the initial cells of the second machine is separated and only the float products from the other cells of this machine are refloated in a separate machine. In many instances, the refloated material is handled in the third machine in the same manner that it was treated in the second machine. This may be repeated in subsequent machines until the final machine in which the froth is handled as a whole. The machine discharge products of the various machines are combined when valuable minerals are contained therein. When valuable minerals are in the froth products, all of these are combined, including those separated out in the intermediate reflotation machines. By handling the froth products in this manner, optimum yield of machine discharge product is obtaincd without sacrifice in grade and without the requirement for additional equipment.

' To obtain such a result with carrier flotation by separating an initial froth product, it is essential that the process operate on a slimed feed pulp which has been conditioned, as described above, with my hydrocarbon oil since the method depends upon the excellent drainage of the foam obtained with the oil post-treatment, especially the exceptional drainage properties of the initial part of the froths obtained by reflotation of froth of a previous flotation step.

Even a cursory review of this procedure for handling the froth product indicates that it involves a departure fromthe usual procedure for froth flotation of minerals and ores which, in general, treat the concentrates or underflows from individual flotation machines as a unit, either treating, recycling or discarding such products as a whole.

This invention will be described in detail with especial reference to its application to the beneficiation of dis colored kaolin clay. It will be distinctly understood that my novel hydrocarbon oil conditioning treatment is applicable to improving the nature of the froth obtained by aerating other slimed pulps conditioned with other oiled carrier particles in accordance with US. Patent No. 2,990,958. It follows that the improved quality of froth obtained in this manner may be utilized, in adapting the process to continuous flotation with reflotation of the froth product, to effect an improvement in yield of machine discharge product or improvement in concentrate grade with feeds other than clay.

Initially, raw clay is dispersed in water, preferably using sodium silicate as the dispersant for the clay. The clay must be in a dispersed state in the subsequent conditioning treatment since clay in a flocculated condition is not amenable to proper conditioning. The clay may be Whole clay or a fine fraction thereof.

Before oiling the clay pulp, I prefer to add my carrier particles, using such'particles in an amount of 5% to 200%, based on the weight of clay feed. As examples of suitable particulate auxiliary minerals, which, when collector coated, are used in conditioning the clay feed, may be mentioned calcite, sulfur, barytes, kyanite, silica sand, marble, magnetite and fluorspar admixtures. Suitable reagents for floating the auxiliary minerals above specified are described in Taggarts Handbook of Mineral Dressing, Section 12, pp. 116-120 (1950 edition), 'or may be experimentally determined' However, it will be readily apparent to those skilled in the froth flotation art that any mineral which may be appropriately conditioned for flotation in the presence of the reagentized kaolin pulp is within the compass of my invention. The particle size of the particulate auxiliary material may vary within a relatively wide range, which, of course, must lie within the range of particles floatable in the presence of the reagentized clay. Generally speaking, particles somewhat finer than 325 mesh may be preferred to particles coarser than 325 mesh.

The admixed pulp, preferably at a 20% to 30% solids level, is then conditioned with a negative-ion collector reagent capable of selectively oiling the colored impurities in the clay concurrently with oiling of the carrier particles by coating these particles with an oriented hydrophobic film. Higher fatty acids such as oleic acid are particularly suitable collectors. Other fatty acid collectors include tall oil fatty acids, resin acids, sulfonates of these and like acids, such as sulfo-oleic acid, and soaps of the aforementioned acids. The negative ion reagent may comprise one or more of the above collectors. In addition to the negative-ion collector, I incorporate an alkaline material, preferably ammonium hydroxide, since I realize optimum concentration in a circuit having a pH between 8 and it). Also, preferably I incorporate a mat rial selected from the group consisting of ammonium sulfate, magnesium sulfate and potassium sulfate. Preferably, the fatty acid is used in the form of an emulsified mixture with a mahogany sulfonate. The latter is an oil-soluble petroleum sulfonate prepared by sulfonating, usually with concentrated or fuming sulfuric acid, certain petroleum fractions. Mahogany sulfonates are commercially available in the form of sodium, calcium, barium, and ammonium salts, neutral or not neutral, and of varying solubility properties dependent on the molecular weight.

While the conditioned pulp is in the conditioner, and before it is subjected to aeration, I add my hydrocarbon oil, which may be any inert high boiling oil, such as, for example, lube oil, diesel oil, mineral oil, fuel oil, kerosene or mixtures thereof. The quantity of oil I add will depend on the nature of the pulpspecifically, the nature of the foam produced when such pulp is agitated. The optimum quantity is readily determined by simple experiment. Recommended proportions of oil lie within the range of about 3 to 12 (preferably about 6 to pounds per ton of clay feed (dry clay basis). When the postconditioning oil is used in amount less than about 6 pounds per ton of clay feed, the treatment loses much of its effectiveness. When used in excess of about 10 pounds per ton, the oil treatment impairs the collection. I have obtained exceptional results with oil of about 15 to API gravity, although other oils, such as oils heving an API gravity as low as about 12 and as high as about may be used. it will be readily apparent that the quantity of oil I employ is considerably in excess of the amount of oil used as an auxiliary col lector reagent in various prior art flotation processes. The oil must be lightly agitated with the conditioned pulp before air is introduced thereto and the oil conditioning may be carried out in a conditioning machine or in the flotation cell with the air off.

Referring to the flowsheet shown in the drawing, it is evident that the process illustrated involves four distinct froth flotation steps in a continuous process. The first step involves continuously feeding a pulp of raw clay feed which has been conditioned with a negative-ion collector reagent and oiled carrier particles, and then with hydrocarbon oil, as described above, to a 5 cell flotation machine, thereby continuously obtaining from each cell a froth which is withdrawn and combined in a launder to form a first froth product and a beneficiated clay machine discharge product from the fifth cell.

The first froth product is continuously fed into a second flotation machine, this one containing 4 cells; the froth product from the first cell of this machine is continuously withdrawn separately from the froth products of the second, third and fourth cells which are continuously withdrawn in a common launder. In like manner, the froth product in the first cell of the third machine (which operates on the froth product of the second, third and fourth cells of the second machine) is discarded separately from the froth products of the second, third and fourth cells of the third machine. The latter froth products, as in the second machine, are combined in a common launder and are further refloated in a fourth machine, thereby producing a froth product, all of which is sent to waste and a machine discharge product which is combined with the machine discharge product of the first, second and third machines in the usual manner.

While a four machine flotation operation is illustrated, with the two intermediate machines operated in a manner such that the froth product of the first cell is separated from the froth of subsequent cells in the machines, it will be understood that the process may be operated with 5 flotation machines or more.

Although the accompanying flowsheet and the description of my invention refer to the fact that various froth products go to waste, it will be clearly understood that such terminology is used merely to simplify the explanation of my invention and focus upon its essential features. Thus, the froth which goes to Waste may be further treated for separation of the carrier from colored impurities.

The continuous process, described immediately above, may be carried out in existing flotation equipment which is modified only to the extent that the launder line to the first cell of each of the intermediate lines is blocked off and discharge lines for handling the froth products from each of the first cells are provided.

The following examples illustrate the benefits of postconditioni-ng a reagentized dispersed admixed aqueous pulp of kaoline clay and calcite carrier with hydrocarbon oil, in accordance with this invention.

The clay used in all of the tests was a crude sedimentary Georgia kaolin. The clay was used in the form of a soduim silicate dispersed aqueous slip which was prepared -by stirring the crude kaolin clay at 26% to 28% solids with deionized water until practically all of the clay lumps were disintegrated. The slurry was screened to remove all plus 325 mesh grit. The degritted clay had a particle size distribution such that 98% by weight was minus 15 microns and was minus 1.5 micron (all particle sizes referring to equivalent spherical diameters, as determined by the Casagrande water sedimentation method). The slurry was dispersed with 0.4% (based on the dry clay weight), of sodium silicate in a Fagergren flotation machine (air 01f).

EXAMPLE I his example demonstrates the improved yield of beneficiated clay that is realized in a batch flotation test by postconditioning the reagentized admixed clay-carrier pulp with hydrocarbon oil, in accordance with this invention.

Control Carrier Flotation Test While the Fagergren flotation machine was running with the air off, No. 1 white calcite was added to the sodium silicate dispersed kaolin clay pulp in the machine in the amount of 30% (based on the dry clay weight). The calcite was 98% by weight finer than 40 microns, 35% minus 10 microns, and 10% minus 3 microns. After 30 seconds of agitation, the following reagents were added to the admixed pulp in the order indicated: Ammonium sulfate, 6 pounds; ammonium hydroxide, 4.0 pounds; and an aqueous emulsion containing 4.5 pounds tall oil and 4.5 pounds of a commercial oil-soluble neutral calcium sulfonate complex, analyzing about 41% calcium sulfonate complex and the balance substantially all mineral oil. All reagents are reported on the basis of pounds per ton of dry clay in the pulp. The conditioned slurry containing about 750 grams of clay (dry basis) was transferred to a 1000 gram Minerals Separation Airflow flotation machine, diluted to about 25% solids with soft water and subjected to froth flotation removing a froth product for 10 minutes. The first froth product was refioated a three additional times without addition of reagents and all machine discharge products combined.

Flotation Tests Using Hydrocarbon Oil Conditioning Reagent The procedure followed in carrying out the control test was repeated in every detail through the step of adding the ammonium sulfate, ammonium hydroxide and emulsified tall oil collector reagent and conditioning for minutes. fied in the accompanying table, were added to the pulp and the whole conditioned for 12 minutes, making for a total conditioning time of 17 minutes. As in the control flotation test, the conditioned pulp containing 750 grams of dry clay solids was transferred to a 100 gram Minerals Separation Airflow machine, diluted to about 25% solids with soft water and subjected to flotation removing a froth product for minutes. The first froth product was refioated three additional times and all of the machine discharge products were combined.

The clay brightness values referred to in the table were obtained by TAPPT Standard Method T-646 ltd-54, as described on pages 159A and 160A of the October 1954 issue of TAPPI (a monthly publication of the Technical Association of Pulp and Paper Industry). The method measures the light reflectance of a clay sample and thus gives a quantitative indication of its brightness or whiteness.

The data reported in the table bring out the fact that by postconditioning the admixed reagentized kaolin claycalcite pulp with various hydrocarbon oils, an improvement in recovery of beneficiated clay was realized in all instances. With some of the oils, an exceptional improvement in clay recovery was realized. Also shown is that in some instances a slight improvement in clay grade was obtained simultaneously with the improvement in clay recovery.

EXAMPLE II The following example illustrates the benefit, in a continuous flotation operation, of refioating the froth product of the hydrocarbon oil conditioned admixed pulp and discarding the initial froth of the cleaner flotation operation and further refloati'ng the remainder of the froth from the cleaner flotation, in accordance with a form of this invention.

The starting clay was the discolored unf-ractionated sedimentary Georgia kaolin used in the previous example. As in that example, the clay was in the form of a sodium silicate dispersed clay slip containing 10% clay solids and 0.4% sodium silicate (based on the dry clay weight).

A control test was carried out using the four machines illustrated in the flowsheet but with the first cell of the second and third machines open to the launder line in the Thereafter, various hydrocarbon oils, identi-' ver machine, with 5, 4, 4 and 3 cells in series, as illustrated. In a continuous pilot plant operation employing about 1064 pounds per hour of the crude kaolin clay (dry basis), about 320 pounds per hour of natural calcite (No. 1 White) was added to the silicate dispersed clay slip. The particle size of the calcite was 98% by weight minus 40 microns, 36% minus 10 microns, and 10% minus 3 microns. The dispersed admixed pulp of crude clay and calcite was conditioned in the order given, with about 6 pounds of ammonium sulfate, an emulsified mixture of 4.5 pounds crude tall oil fatty acid and 4.5 pounds of a neutral oil-soluble petroleum sulfo-nate, analyzing 41% calcium sulfonate complex and the balance substantially all mineral oil. Conditioning time was 5 minutes. Eight pound of Eureka M lube oil was added to the pulp and conditioned for 12 minutes. Sufiicient ammonium was added to maintain a pH of about 8.5 in the conditioned pulp. All reagents are reported on the basis of pounds per ton of the dry clay feed. The percent solids in the conditioner was about 18%.

The conditioned pulp was continuously fed to the 5 cell No. 1 flotation machine, with dilution water added to the second, third and fourth cells. A machine discharge product was taken from the fifth cell which was a slip of high brightness kaolin clay amounting to about 58%, weight basis, of the original kaolin clay. The froth product from this operation was continuously refioated in an additional machine, in accordance with conventional flotation practice, with the froth product from each of the four cells in the second machine being combined and refioated in a third machine. This procedure was repeated in the third machine, i.e., the entire froth product from the second machine was refloated and the froth from each of the cells in the third machine were combined. The combined froth product from the third machine was continuously fed to a 3 cell fourth machine, thus producing a final froth product which was sent to waste and a machine discharge product which was combined with the machine discharges from the first, second and third machines to yield about 84% weight recovery of kaolin clay of improved brightness containing a very small percentage of TiO and other coloring impurities.

A second test was carried out to illustrate the advantage of operating the general process described in the first test, in accordance with the method of this invention. The first test procedure was duplicated in every respect, except that provision was made to pass directly to waste the froths from the first cells of machines N0. 2 and No. 3, as shown in the flowsheet. The brightness of the combined machine discharges of this test was substantially the same as that of the first test product. However, about a 10% improvement in weight recovery of beneficiated clay was realized, thereby illustrating the value of discarding the initial froth product from the cleaner flotation conventional manner. Each machine wasa No. 8 Denoperations.

THE RESULT OF POSTCONDITIONING REAGENTIZED ADMIXED PULP OF DISCOLORED KAOLIN CLAY 1 AND GALCIIE CARRIER WITH VARIOUS HYDROCARBON OILS Oil Beneficiated Clay Product Lbs. Oil/ Unbleached Increase in Type Hydrocarbon O11 Ton Clay API Wt. Brightness, Brightness,

Feed (Dry Gravity Percent Percent Percent Clay Basis) None 90. 5 83.7 4. 8 95% Bunker C, 5% Diesel Oil 8 91. 9 83.8 4. 9 90% Bunker C, 10% Diesel Oil. 8 94.1 83. 9 5.0 85% Bunker C, 15% Diesel Oil- 8 3 83. 9 5.0 80% Bunker C, 20% Diesel Oil 8 96. 4 84. 0 5. 1 75% Bunker C, 25% Diesel OiL.-- 8 95. 7 83. 9 5.0 Bunker O, 30% Diesel Oil. 8 95. 7 83. 9 5.0 Eureka h! Lube Oil, 25% M 8 92. 7 83. 9 5. 0 Eureka lvi Lube Oil" 8 91. 9 83. 7 4. 8 Ebony Oil 8 93. 5 83. 5 4. 6 Conventional Parafiinic Neutral Oil 8 98. 1 83. 7 4. 8 Solvent Neutral Oil 8 97. 5 83. 9 5.0

1 Unbleached brightness of Starting Clay was 78.9%.

I claim:

1. In the method for improving the brightness of kaolin clay having color body impurities mechanically associated therewith comprising forming a dispersed aqueous pulp of said clay, without any grinding action conditioning said pulp for froth flotation with a negative-ion collector reagent capable of selectively oiling said color body impurities and collector-coated particles of an auxiliary mineral, said particles being further characterized by being floatable in said pulp, and subjecting the thus conditioned pulp to froth flotation at a pH within the range of 8 to 10, thereby producing a froth product which is a concentrate of said color body impurities in intimate association with said auxiliary mineral particles and a machine discharge product which is a concentrate of clay of increased brightness, the improvement which comprises further conditioning said aqueous pulp of clay with a hydrocarbon oil after it has been conditioned with said negative-ion collector reagent and said collector-coated auxiliary mineral particles and before said pulp has been subjected to an initial froth flotation.

2. The method of claim 1 wherein said oil is employed in amount of 6 to 10 pounds per ton of dry clay feed.

3. The method of claim 1 wherein said oil has an API gravity of about 12 to 25.

4. The method of claim 1 wherein said oil has an API gravity of about 15 to 20.

5. The method of claim 1 wherein said pulp is conditioned with said oil for about 12 minutes.

6. The method of claim 1 wherein all of the first froth product is refloated, discarding the initial froth and refloating the balance of the froth.

7. The method of claim 1 wherein the froth product is continuously refloated in separate machines, each containing a plurality of cells arranged in series, and the froth product from the first cells of each machine is separated from the froth product of the remaining cells and the froth product from said remaining cells further subjected to froth flotation.

8. In a method for beneficiating a slimed multicomponent mineral mass which comprises forming a dispersed aqueous pulp of said mass, conditioning said aqueous pulp for froth flotation with a collector reagent selective to a component of said mass, leaving a residual component water-wettable, and with collector-coated particles of an auxiliary mineral, said particles being further characterized by being floatable in said pulp, and subjecting the thus conditioned aqueous pulp to froth flotation thereby producing a froth product which is a concentrate of said collector-coated component of said mass in intimate association with said auxiliary mineral particles and a machine discharge product which is a concentrate of said water-wettable component of said mass, the: improvement which comprises conditioning said aqueous pulp with a hydrocarbon oil after it has been conditioned with said collector reagent and said collector-coated particles of an auxiliary mineral and before it has been subjected to an initial froth flotation, and carrying out the flotation of the resulting pulp in a manner such that all of the first froth product is refloated, the initial refloated froth is separated and the balance of the refloated froth is refloated to obtain additional froth products and machine discharge products.

9. The method of claim 8 wherein the machine discharge product contains a valuable mineral and the machine discharge products of all of the fiotations are combined, whereby an increase in product. recovery is obtained.

10. The method of claim 8 wherein said first froth product is continuously refloated in separate machines, each machine containing a plurality of cells arranged in series, and the froth product from the first cells is separated from the froth product of the remaining cells and the froth product from said remaining cells is further subjected to froth flotation.

References Cited in the file of this patent UNITED STATES PATENTS 2,165,268 Vogel-Jorgensen July 11, 1939 2,259,420 Hills Oct. 14, 1941 2,373,688 Keck Apr. 17, 1945 2,569,680 Leek Oct. 2, 1951 2,669,355 Archibald Feb. 16, 1954 2,695,101 Booth Nov. 23, 1954 2,849,113 Bourne Aug. 26, 1958 2,894,628 Duke July 14, 1959 2,984,348 Adams et a1 May 16, 1961 2,990,958 Greene et al. July 4, 1961 FOREIGN PATENTS 610,817 Great Britain Oct. 21, 1948

Claims

1. IN THE METHOD FOR IMPROVING THE BRIGHTNESS OF KAOLIN CLAY HAVING COLOR BODY IMPURITIES MECHANICALLY ASSOCIATED THEREWITH COMPRISING FORMING A DISPERSED AQUEOUS PULP OF SAID CLAY, WITHOUT ANY GRINDING ACTION CONDITIONING SAID PULP FOR FROTH FLOTATION WITH A NEGATIVE-ION COLLECTOR REAGENT CAPABLE OF SELECTIVELY OILING SAID COLOR BODY IMPURITIES AND COLLECTOR-COATED PARTICLES OF AN AUXILIARY MINERAL, SAID PARTICLES BEING FURTHER CHARACTERIZED BY BEING FLOATABLE IN SAID PULP, AND SUBJECTING THE THUS CONDITIONED PULP TO FROTH FLOTATION AT A PH WITHIN THE RANGE OF 8 TO 10, THEREBY PRODUCING A FROTHE PRODUCT WHICH IS A CONCENTRATE OF SAID COLOR BODY IMPURITIES IN INTIMATE ASSOCIATION WITH SAID AUXILIARY MINERAL PARTICLES AND A MACHINE DISCHARGE PRODUCT WHICH IS A CONCENTRATE OF CLAY OF INCREASED BRIGHTNESS, THE IMPROVEMENT WHICH COMPRISES FURTHER CONDITIONING SAID AQUEOUS PULP OF CLAY WITH A HYDROCARBON OIL AFTER IT HAS BEEN CONDITIONED WITH SAID NEGATIVE-ION COLLECTOR REAGENT AND SAID COLLECTOR-COATED AUXILIARY MINERAL PARTICLES AND BEFORE SAID PULP HAS BEEN SUBJECTED TO AN INITIAL FROTH FLOTATION.