US3107214A - Froth flotation method - Google Patents

Description

United States Patent Ofi ice 3,1 6 7,2 1% Patented Oct. 1 5, l 963 3,107,214 FROTH FLGTATIGN R/ETHGD .iarnes B. Duke, Metuchen, N.5., assignor to Minerals 8; Chemicals Philipp Corporation, Menlo Park, N.J., a corporation of Maryland No Drawing. Filed Dec. 16, 1966, Ser. No. 76,694 6 Claims. (Cl. 209-166) The subject invention has to do with a novel method for recovering certain collector coated solid particles which are used as an auxiliary reagent in conditioning discolored kaolin clay for froth flotation to beneficiate the clay, in accordance with the procedure described in a copending patent application, Serial No. 779,061, filed December 9, 1958, now US. 2,990,958, of which I am a coinventor. This application is a continuation-in-part of the aforementioned application. In accordance with the method disclosed and claimed in said application, the grade and recovery of beneficiated kaolin clay obtainable by froth flotation is improved by using, as conditioning reagents for a dispersed aqueous pulp of the clay, the combination of a negative-ion (fatty acid) collector reagent selective to colored impurities in the clay and certain finely divided oiled particles (hereafter referred to as carrier particles) which are floatable in the reagentized pulp. The latter report in the froth product together with colored impurities originally in the clay (principally anatasea colored form of TiO and in so doing promote or enhance the flotation of the latter. The machine discharge product is a clay of enhanced brightness and reduced titania content. The method is applicable to the beneficiation of sedimentary whole kaolin clay as well as fine fractions or coarse fractions thereof. However, the optimum benefits are realized in the treatment of whole clay or fine fractions thereof for the reason that conventional froth flotation treatment is not very effective (and in some instances is completely ineffective) in beneficiating slimed ores such as whole clay or line fractions of clay.

It is obvious that the overall economics of the froth flotation process above described could be improved by recovering the reagentized carrier particles from the colored impurities with which they are intimately associated in the froth product for the purpose, for example, of recycling the auxiliary particles in the flotation machines. However, it is obvious that any economically feasible method for accomplishing the separation of the carrier from the colored impurities must be so low in cost that it would counteract the cost of utilizing fresh carrier particles in each operation. Thus, the equipment and reagents utilized to effect such separation must add little to the overall cost of the process.

The separation is fundamentally diflicult for the reason that both the reagentized carrier particles and color body materials are in finely divided form and adhere tenaciously to each other in the froth product. Acidulation or alkalization of the composite froth has been found to have little effect on breaking up the strong bonds holding the various solid particles together.

Accordingly, it is a principal object of the subject invention to provide, in a process for the froth flotation of discolored kaolin to float colored impurities therefrom and entailing the use of solid particles as one of the conditioning agents, a simple, economical method for separating the solid conditioning particles from the colored impurities with which they are intimately associated in the froth product.

A more particular object of my invention is the provision of a novel method for eifecting such separation by froth flotation.

Still another object of this invention is the provision subject invention,

of a method for the froth flotation of discolored kaolin clay using solid carrier particles as a conditioning reagent in Which the carrier particles are recovered and reused in the process and, at the same time, the colored impurities originally in the clay, which are floated along with the carrier, are separated therefrom.

A specific object of this invention is the provision of a simple, economical method for the froth flotation of finely divided reagentized mineral particles from fatty acid reagentized slimed colored impurities originally in clay.

Further objects and advantages will be readily apparent from a description of my invention which fol lows.

Briefly stated, in accordance with the present invention, an admixed pulp of fatty acid rcagentized mineral particles and slimed finely divided titaniferous matter (obtained by subjecting to froth flotation an alkali silicate dispersed pulp of discolored clay which has been conditioned with fatty acid and collector coated mineral particles) is conditioned with phosphate, especially tetrasodium pyrophosphate, and with a low boiling petroleum hydrocarbon of the type Widely used as a paint thinner or solvent. The conditioning is carried out by initially agitating the composite froth with phosphate and thereafter incorporating the hydrocarbon liquid and agitating the Whole. The pulp thus conditioned is subjected to froth flotation thereby producing a froth product which is a concentrate of the carrier particles, leaving in the underflow the colored impurities which were originally in the clay. The froth product, after washing and being further conditioned with suitable collector reagent, may then be reused in conditioning an aqueous pulp of discolored kaolin clay and the conditioned pulp subjected to froth flotation in accordance with the procedure described in said copending applications. The machine discharge may be treated for recovery of its titanium mineral values or it may be discarded.

While I do not Wish to be bound to any theory or explanation of how the combination of the molecularly dehydrated phosphate and light petroleum hydrocarbon liquid contribute to eifect the desired flotation of the carrier from the colored impurities in the clay, the following is believed to oifer a plausible explanation. The phosphate, which is an extremely powerful mineral dispersant, appears to physically separate the clay impurities from the carrier particles to which they adhere tenaciously in the froth product, even in the presence of a silicate dispersant. Other mineral dispersants such as, for example, the alkali silicates are not operative in the flotation process of this invention, seemingly for the reason that they are not efiective, as is my molecularly dehydrated phosphate, in reducing the strong interparticle forces that exist between the components of the composite froth. As for the role of the light petroleum hydrocarbon reagent, it is believed that the carrier particles have a greater aflinity for the hydrocarbon collector reagent than do the colored impurities originally in the clay. Therefore, it appears that the hydrocarbon liquid selectively reoils such carrier particles, having but little effect in this manner on the color impurities, thereby permitting the effective flotation of the carrier particles from the colored matter.

More specifically, the composite froth product that is treated by froth flotation in accordance with the subject invention is obtained as follows. initially, raw discolored kaolin clay is dispersed in water in any convenient manner With sodium silicate dispersant. While it has been noted that the phosphate dispersants are, preferred in the carrier mineral recovery process of the they are notas effective as the alkali a molecularly dehydrated of 6% to 25%. In accordance with one form of the invention, described in the copending applications, a pulp of carrier particles is mixed with the dispersed clay pulp and the admixed pulp is conditioned with a higher fatty acid collector reagent such as, for example, tall oil fatty acids, oleic acid, resin acids, sulfonates of these and like acids, such as sulfo-oleic acid, and soaps of the aforementioned acids, or combinations of such fatty acid reagents. In addition to the collector reagent, an alkaline material, typically ammonium or sodium hydroxide, is added to the pulp to bring the pH to 8 to 10. Preferably, an oil-soluble petroleum .sulfonate is added, as well as a material selected from the group of ammonium sulfate, magnesium sulfate and potassium sulfate.

If desired, the silicate dispersed clay pulp may be reagentized with the aforementioned reagents and a pulp of carrier particles separately reagentized with the fatty acid collector together with such auxiliary reagents as will enhance the collector coating of the carrier pulp. These reagentized pulps are then admixed.

The carrier mineral may be any one which has a strong aflinity for fatty acid oiling reagents. While calcite is a preferred carrier because of its low cost and eifectiveness in the process, a variety of other carriers will be suitable since the function of the oil carrier in improving flotation is apparently a physical one, not chemical, As examples of other carriers may be cited barytes, sulfur and fluorspar.

The carrier mineral is finely divided, preferably, substantially all of the particles are minus 100 mesh. Especially good results are obtained with carrier particles which are 200 mesh or finer.

The carrier mineral is usually used in amount of about to 200%, based on the dry clay weight.

Preferably, subsequent to the reagentization of the feed and the auxiliary mineral particles, the pulp is diluted and subjected .to aeration (and usually mechanical agitation) in any suitable flotation machine although, in some instances, it may be advantageous to add additional reagents during the concentration step. As a result of the aeration, the colored impurities, collector coated, report in the froth in association with the reagentized particles of auxiliary mineral (and usually some clay, depending of course on the efiiciency of the flotation). The composite froth is separated from the trailings or machine discharge product whioh comprises a beneficiated clay characterized by an enhanced whiteness and brightness and a reduced titania analysis. Normally the froth product is r'efloated a plurality of times to recover clay values entrained therein. In this case the final froth product or a portion thereof is conditioned in accordance with the method of the subject invention.

The rfroth product, obtained as described above, and comprising an alkaline concentrate of fatty acid reagentized carrier particles and colored impurities originally in clay (and usually some clay), is agitated with a molecularly dehydrated phosphate such as, for example, sodium hexametaphosphate, disodium dihydrogen pyrophosphate or sodium tripolyphosphate. Especially preferred is tetrasodium pyrophosphate. The quantity of dispersant I employ is critical and is within the range of about 2 to 5 pounds per ton of the original clay feed (dry clay basis). When the phosphate is employed in amount less than the minimum indicated, the flotation hereafter described is ineifective because the colored impurities adhere to the concentrate of carrier particles and are not amenable to separation therefrom. On the other hand, when the dispersant is employed in excess of the maximum indicated, the process tends to lose its eifectiveness because carrier mineral particles are depressed and thus they are not amenable to concentration from the colored impurities. A short conditioning time of the order of 1 to 3 minutes will suifice. The froth is then further conditioned, either in an agitated conditioner or in the flotation machine for about 5 minutes, with a light hydrocarbon liquid such as mineral spirits, gasoline, light naphtha (e.g., V.M. & P. naphtha). The hydrocarbon liquid is agitated with the pulp to eifect the desired contact with the solids. Good results have been obtained using about 5 to 15 pounds of hydrocarbon liquid per ton of the original clay feed. When the quantity of hydrocarbon liquid is insufiicient, the froth product will be watery and poor concentration of the carrier particles will result. On the other hand, use of excessive hydrocarbon liquid impairsthe selectivity of the flotation. The conditioned pulp, usually after addition of dilution water to reduce the pulp solids to about 5% to 15%, is aerated thereby producing a froth product which is substantially free from anatase and other coloring material associated with the anatase in the original froth product.

The froth product is then filtered, Washed with water, slurried with water and recycled to the conditioning macnines preceding the primary flotation machines handling dispersed disclored kaolin clay pulp.

The following example illustrates the successful adaptation of my process to the recovery of a calcite carrier from the anatase and other coloring materials associated with the anatase in the froth and the re-use of the recovered calcite in the froth flotation of discolored kaolin clay.

The starting clay was a crude discolored sedimentary Georgia kaolin clay known as Klondylre crude and analyzing 1.78% TiO and about 1% Fe O Twenty-five pounds (dry basis) of the crude kaolin clay was stirred with about 100 pounds of deionized water until practically all of the clay lump-s were disintegrated. The slurry was screened to remove all plus 325 mesh material. The degritted clay had the following particle size distribution: 98% by weight, minus 15 microns, 92% minus 10 microns, minus 5 microns, 50% minus 1.5 microns, and 15% minus 0.5 micron. All particle sizes refer to equivalent spherical diameters, as determined by the Casagrande water sedimentation method. The slip was pulped with water to a concentration of about 10% clay solids and agitated for about a minute with sodium silicate in the amount of 0.3% (based on the dry clay weight).

In a continuous pilot plant operation employing about 1064 pounds per hour of the crude kaolin clay (dry clay basis), 52 pounds per hour of natural calcite (No. 1 white) was continuously added to the silicate dispersed kaolin slip. The particle size of the calcite was 98% by weight minus 40 microns, 36% minus 10 microns, and 7 10% minus 3 microns. The admixed pulp of crude clay and calcite was conditioned with about 6 pounds of ammonium sulfate, 7 pounds of a 1:1 emulsified mixture of crude tall oil fatty acid and a neutral, oil-soluble petroleum sulfonate (analyzing 41.0% calcium sulfonate complex and the balance substantially mineral oil) and sufficient ammonium hydroxide 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. The percent solids in the conditioner was about 18% and the retention time was about 25 minutes. This conditioned pulp was continuously fed to a 5 cell No. 8 Denver flotation machine, with dilution water added to the second, third and fourth cells. A finished machine discharge product was taken from the fifth cell, which was a high brightness kaolin clay slip and amounted to about 58%, weight basis, of the original kaolin clay. The froth product from this operation was refloated three times in additional machines, thus producing three additional beneficiated machine discharges which were combined with the first machine discharge product to yield about weight recovery of high brightness clay containing a very small percentage of TiO and other coloring impurities.

The final froth product, carrying a major weight pro enc'zgaia 5 portion of the original anatase and substantially all of the calcite carrier, was treated as follows. In the sump pump, tetrasodium pyrophosphate was added to the froth in the amount of about 4.5 pounds per ton of original. dry clay feed. The froth was added to an agitating machine and agitated for about 2 minutes. Mineral spirits the amount of about 13 pounds per ton of original dry clay feed was added to the froth product and conditioned for about 5 minutes. This material was then subjected to continuous froth flotation. The froth product from this operation was a clean white calcite, substantially free from anatase and other coloring materials associated with the calcite in the original froth. The machine discharge product was a concentrate of the anatase and other coloring impurities associated with about 10% of the original kaolin clay.

The calcite froth product was filtered and washed with water on a continuous rotary filter. The calcite filter cake was slurried with water to about 40% solids and continuously recycled to the conditioning step preceding the primary flotation machine in the amount of about 250 pounds per hour.

I claim:

1. In a process for the froth flotation of kaolin clay containing color body impurities which comprises forming a dispersed aqueous pulp of kaolin clay using an alkali silicate as a dispersant for said clay, conditioning said pulp for froth flotation with a fatty acid collector reagent selective to color body impurities in said clay and finely divided insoluble mineral particles which are reagentized with a fatty acid collector reagent and are fioatable in said pulp, subjecting the thus conditioned aqueous pulp to froth flotation in an alkaline circuit thereby producing a froth product which is a concentrate of said color body impurities in intimate association with said collector coated mineral particles and a machine discharge product which is a concentrate of clay of enhanced brightness, the improvement which comprises conditioning the froth product in the form of an aqueous pulp thereof with a molecularly dehydrated phosphate dispersant in an amount within the range of about 2 /2 to 5 pounds per ton of the original kaolin clay employed in the process and with a light petroleum hydrocarbon liquid, subjecting the thus conditioned aqueous pulp to froth flotation thereby producing a froth product which is a concentrate of said mineral particles and a machine i3 discharge which is a concentrate of color body impurities originally in said clay.

2. The method of claim 1 in which said phosphate is tet-rasodium pyrophosphate.

3. The method of claim liquid is mineral spirits.

4. The method of claim 1 in which the froth product obtained by subjecting to froth flotation the conditioned aqueous pulp of collector coated nnneral particles and colored impurities is washed, reconditioned with a fatty acid collector reagent and reused in conditioning an aqueous pulp of discolored kaolin clay for froth flotation.

5. in a process for the froth flotation of kaolin clay contain ng color body impurities which comprises form ing a dispersed aqueous pulp of kaolin c ay using an alkali silicate as a dispersant for said clay, conditioning said pulp for froth flotation with a fatty acid collector reagent selective to color body impurities in said clay and finely divided insoluble mineral particles which are reagentized with a fatty acid collector reagent and are floatable in said pulp, subjecting the thus conditioned aqueous pulp to froth flotation in an alkaline circuit thereby producing a froth product which is a concentrate of said color body impurities in intimate association with said collector coated mineral particles and a machine discharge product which is a concentrate of clay of enhanced brightness, the improvement which comprises conditioning the froth product in the form of an aqueous pulp thereof with tetrasodiurn pyrophosphate in amount within the range of about 2 /2 to 5 pounds per ton of the original kaolin employed in the process and thereafter with a light petroleum hydrocarbon liquid, subjecting the thus conditioned aqueous pulp to froth flotation thereby producing a froth product which is a concentrate of said mineral particles and a machine discharge which is a concentrate of color body impurities originally in said clay.

6. The method of claim 5 wherein said finely divided insoluble mineral particles are calcite particles.

1 in which said hydrocarbon References Cited in the file of this patent UNITED STATES PATENTS UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 107 ,214 October 15, 1963 James B Duke It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Colomn 3, line 27, for "oil" read oiled line 47, for tra11ings" read tailings column 4, line 21, for "disc lored" read discolored Signed and sealed this 14th day of April 1964.

(SEAL) Attest: EDWARD J. BRENNER ERNEST W. SWIDER Attesting Officer Commissioner of Patents

Claims (1)

1. IN A PROCESS FOR THE FROTH FLOTATION OF KAOLIN CLAY CONTAINING COLOR BODY IMPURITIES WHICH COMPRISES FORMING A DISPERSED AQUEOUS PULP OF KAOLIN CLAY USING AN ALKALI SILICATE AS A DISPERSANT FOR SAID CLAY, CONDITIONING SAID PULP FOR FROTH FLOTATION WITH A FATTY ACID COLLECTOR REAGENT SELECTIVE TO COLOR BODY IMPURITIES IN SAID CLAY AND FINELY DIVIDED INSOLUBLE MINERAL PARTICLES WHICH ARE REAGENTIZED WITH A FATTY ACID COLLECTOR REAGENT AND ARE FLOATABLE IN SAID PULP, SUBJECTING THE THUS CONDITIONED AQUEOUS PULP TO FROTH FLOTATION IN AN ALKALINE CIRCUIT THEREBY PRODUCING A FROTH PRODUCT WHICH IS A CONCENTRATE OF SAID COLOR BODY IMPURITIES IN INTIMATE ASSOCIATION WITH SAID COLLECTOR COATED MINERAL PARTICLES AND A MACHINE DISCHARGE PRODUCT WHICH IS A CONCENTRATE OF CLAY OF ENHANCED BRIGHTNESS, THE IMPROVEMENT WHICH COMPRISES CONDITIONING THE FROTH PRODUCT IN THE FORM OF AN AQUEOUS PULP THEREOF WITH A MOLECULARLY DEHYDRATED PHOSPHATE DISPENSANT IN AN AMOUNT WITHIN THE RANGE OF ABOUT 2 1/2 TO 5 POUNDS PER TON OF THE ORIGINAL KAOLIN CLAY EMPLOYED IN THE PROCESS AND WITH A LIGHT PETROLEUM HYDROCARBON LIQUID, SUBJECTING THE THUS CONDITIONED AQUEOUS PULP TO FROTH FLOTATION THEREBY PRODUCING A FROTH PRODUCT WHICH IS A CONCENTRATE OF SAID MINERAL PARTICLES AND A MACHINE DISCHARGE WHICH IS A CONCENTRATE OF COLOR BODY IMPURITIES ORIGINALLY IN SAID CLAY.