US2927691A - Process of deoiling phosphate concentrate by means of immiscible liquids - Google Patents

Description

7 Claims. (Cl. 209-166) The present invention is concerned with the concentration of phosphate minerals from their ores of the type found in the Florida pebble phosphate field and more especially with an improved double flotation process. Specifically our invention embodies an improved-process for deoiling the rougher phosphate concentrate produced in the first step of the double float process.

.Rhosphate flotation methods were, for many years, confined to the use. of anionic collecting agents with the resultant flotation of a phosphate hearing froth which con- .tained silica to the extent of about 6%. With the advent 2,927,691 7 I Patented 8,

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2 rougher concentrate. Corrosion is a very big problem in the flotation industry and a large amount of this corrosion can be attributed 'to the dilute acids employed in thisxle'aoiling step. To eliminate the use of these acids and thereby to eliminate the need for handling acids in the flotation operation would materially aid in the control of of U.S. Patents 2,222,728 and 2,293,640,, issued respeclively to Francis X. Tartaron and Arthur Crago, the phos- ,pha't'e industry switched almost exclusively to the use of a combination of anionic and cationic reagents. In this combination the phosphate feed is first oiled with a fatty acid (anionic) reagent, in order to float a s'ilicabear'ing phosphate froth. This is followed by a deoiling step to remove the effect of the anionic reagent and finally by a recoating with a cationic reagent and. flotation to produce a low-silica, phosphate machine discharge product. This i's'the essence or the .so-called double flotation process. -.According to the double flotation method now practiced extensively inthe' industry, the phosphate ore of about minus 35-mesh, relatively free of slime and con taining about 70% solids is conditioned with a negativeion (anionic) agent and fed to the flotation cells. The negative-ion agent collects and removes a rougher concentrate containing a high proportion of thephosphate values mixed with some silicious gangue. This first concentra'tion step can be carried'out'in such a. manner as to collect almost the wholeamount' oi the phosphate present in the ore but the r'ougher concentra'teso obtained'w'ill still contain from 10' to 20% of silica.

Examples of negative ion agents in carrying out the first concentrating operation have been listed in Us; 2,293,640 and comprise the-higher fatty acids, such as fish oil fatty acid and oleic acid and'their soaps. They include the resin acids and their soaps, wood by-product fatty acids, naphth'enic acids and their salts, the higher suite-fatty acids and their salts formed ,f Qm appropriate bases, acidJesters offhigh-molecular weight aliphaticalcohols with inorganic acids and their salts and U,.S. 2,293,640. It has been the general belief that itis.

necessary to remove completely the anionic, fatty acid reagent before cmryin'g out the cationic amine flotation;

step. Since the fatty acidsare normally "oil's, "this step has become known as a deoilingprocess. U3. 2,599,530

suggests that if a small amount of mineral acid is allowed ?to remain on the rougher concentrate that the silica be activated and more 'easily'ficated in the succeeding cationic concentration step.

It is a prime object of our invention "to dispense en= tirely with the use of mineral acids for deoiling the corrosion. This deoiling treatment is the only stepinthe entire phosphate flotation process where strong; mineral acids are employed. Their elimination here would thus remove them from the complete process. It is an object of our invention to deoil the rougher concentrate'by a process which does not employ corrosive or hazardous materials. v

An additional and equallyimportant object is 'toprovide a process for deoiling which will be superior to those processes :now. practiced and one which will leave tha surface of the silica, contained admixed with phosphate in the rougher phosphate concentrate, in sucha state that it is more readily floated in the succeeding cationic, amine flotation. g

Before describing the actual process of our invention it is necessary to very briefly outline the succeeding cationic, amine flotation process. Any true tests of amount of deoiling must include the subsequent flotation with analyses of the resultant fractions. 7 The deoiled, rougher phosphate concentrate is returned to the flotation machine where it is formed .with water. into a dilute pulp of about 25% solids and, without prelimi. nary agitation, trothed for one minute or longer in the presence of :a cationic amine reagent and lterosene. almost pure silica is floated and is removed by the scrapers. The material which remains in the machine constitutes the ifinished phosphate concentrate; Examples of cationic amine reagents which may be used, in carrying .out this second flotation step arethe higher aliphatic aminesand salts with water-soluble acids, the resinamines and' their salts with water-soluble acids and the higher aliphtic quaternary ammonium bases, including pyridine, quinoline and otherheterocycl'ics capable of forming quaternary compounds, and their salts with water-soluble acids. These various examples are not, of course, equally eife'c tive or useful inthis process. The use of a cationic active amine or an amine salt generally is preferred. As will be illustrated, the actual reagent used in the tests of our ini-f vention is a mixture of two amine salts. p p M The above and other objects are accomplished by the practice of our invention. We have discovered that excels lent deoiling is obtained by the use of water-immiscible organic solvents, among which the organic esters of carboxylic acids give best results. By water-immiscible organic solvents were'fer to those organic liquids which are substantiallyv insoluble in water (solubility of about more "amenable to flotation in the succeeding. cationic flotation- This is an unusual and entirely unpredictable result. As will be illustrated, these organic liquids are used at a concentration of about 0.5% which is a very small amount when the large amounts of water slurries of phosphate handled in the flotation procedures are considered. (Certainly our process does not embody an organic servant extraction in the sense that such extractions are practiced in the organic chemicals industry where large volumes of solvents are used to dissolve and extract small amounts of other materials. The small amounts of immiscible organic solvents which we employ appear to aggregate the oily fatty acid in droplets orglobules in such a manner that the rougher concentrate is elfectively deoiled, the oil being removed from the mixture in the water washing after the treatment with the organic liquids. Our deoiling agents are referred to as solvents because, although as noted above, their use is-not a solvent extraction of the anionic reagent in the usual sense, they are solvents of the anionic reagents.

The residual effects of these liquids on the phosphate and silica can not be entirely explained. Certainly it is an unusual one and one which was entirely unexpected. It is diflicult to see how these organic liquids can a'ctivate" the surface of the inorganic silica in the sense referred to in U.S. Patent 2,599,530. It is equally diflicult to fit these'liquids into the theory that silica floats in the cationic flotation step because of the formation of hy drated silicic acid on the surface of the silica particles. We otfer'as a possible explanation of the resultant excellent flotation of silica the fact that very small amounts of the organic liquids which remain on the silica and phos phate act as frothers themselves or these liquids, which are normally commercial products, may contain even smaller amounts of unesterified organic alcohols which are known frothers. This would result in 'a better froth and could conceivably result in a better flotation separation. Our invention is not limited to any of the suggested explanations as to how and why these immiscible organic solvents function. We have discovered a new and novel method for deoiling the rougher phosphate concentrate employing immiscible organic solvents and this process results in a superior froth flotation in the succeeding cationic separation.

Immiscible organic solvents which we have found to be operable in the practice of our invention include normally liquid aliphatic hydrocarbons as included in petroleum oils, terpene hydrocarbons and their derivatives, normally liquid halogenated hydrocarbons, and esters, Water-immiscible liquids which possess low vapor pressures and are not hazardous and which do not contain hydrolysable or water-reactive groupings generally are operable. Such compounds include, aromatic hydrocarbons of higher molecular weight, higher molecular weight alcohols, aldehydes, glycols and glycol derivatives, ketones, ethers or higher molecular weight, acetals, nitrogen'derivatives, sulfur derivatives and mixtures of these and other groupings. Having described our invention in general terms we will illustrate the process with specific examples which include samples of organic liquid from the many chemical groupings listed above.

All samples used in the illustrative examples of this invention. were taken from the rougher concentrate produced in the No.'91 Flotation Plant of Virginia-Carolina Chemical Corporation, Bartow, Florida. The rougher concentrate from this plant is at least about 90% minus 35-mesh and contains about 80% solids.

To produce this rougher concentrate, phosphate debris, which contains phosphate rock and silica and runs roughlyjminus l4-mesh in size, is hydraulically classified in order to separate the minus 35-mesh fraction. The minus 35-mesh product is dewatered and deslimed in a rake classifier. The discharge, which runs approximately 70% solids, is fed to a conditioner where 0.6 lbs/ton of caustic soda, 3 lbs./ton of Bunker C-No. 2 fuel oil (resultant specific gravity 18-20 API), and 0.7 lb./ton of tall oil are added, with agitation. Conditioning time is two minutes. The discharge is diluted with about 4 parts of water to each part of discharge and the mixture is fed to the flotation cells. The froth product from these cells is known as the rougher concentrate and contains a high percentage of phosphate but also some silica.

1270 gram-samples (1000 g., dry weight) of this rougher concentratewere placed in a beaker and the deoiling agent to be evaluated was added and the resultant mixture was stirred for three minutes. The thus deoiled mixture was washed by decantation until a relatively clear wash water was obtained. Normally 12 to 16 liters of water was required for this washing. The washed solid material was placed in a Fagergren laboratory flotation machine and water was added to the top of the conical part of the test-bowl. This corresponds to a dilution of approximately 2-3 parts of water to 1 part of solids. The cationic amine reagent and kerosene were added and the mixture was agitated without frothing for about 15 secs. In all tests the cationic amine reagent was a mixture composed of 50% rosin amine D acetate, a product of theI-Iercules Powder Co., and 50% Armac T, produced by Armour & Co. Armac 'I comprises the acetate salts of a mixture of 30% hexadecyl, 25% octadecyl and octadecenyl amines. After the 15-second agitation the flotation machine was filled with water. Air was admitted to begin frothing and the thus formed matterfroth float was carefully removed, normally with a flexible rubber scraper.

Table I is a summary of the results of deoiling rougher phosphate concentrate with immiscible organic solvents. Test No. 1 has been included to illustrate the results 01 tained with present deoiling practices which employ sulfuric acid, as for example in U.S. Patent 2,293,640. The percent of BPL recovery in the froth fraction is inversely proportional to the effectiveness of the deoiling. The most efficient or effective deoiling compounds will give the lowest grade froth product. Phosphate which has not been deoiled will, of course, float with the silica in the cationic floatation step. A low percentage of insoluble matter in the concentrate, expressed as percent Insol. in Table I is also desirable but is not quite as accurate an evalution of deoiling as is a low percent BPL recovery in the froth. The percent insol. should be kept in mind as it is a measure of unfloated silica which remains in the final phosphate concentrate. Both low BPL in the froth and low insol. in the concentrate are desirable.

The deoiling agents may be added as such or in admixture with water.

In the following table all weights refer to dry weights.

The mixture of ore and deoiler must be sufficiently fluid to be stirrable, the upper limit of solids content being about 80%. If more dilute mixtures are used the stirring of the mixture must be prolonged.

In the table the last column headed Deoiled at solids refers to the solids content of the mixture of ore, deoiler and water.

Table l Percent Lbs. per Deolled Test Product Percent Percent Percent BPL Deolling and cationic Ton of at- No. Weight BPL Insol. Recovagents Feed Percent ered Solids Feed 100. 0 60. 0 100. 0 6. 00 1 Froth-- 25. 7 16.4 7.0 1.00

Cone 74. 3 75. 1 6. 9 93. 0 0.22 100. 0 2 100. 0 9. 60 2 27. 2 12. 3 5. 6 1. 00

Cone 72. 8 78. 1 3. 7 94. 4 0. 20

See tootnotee at and q: table.

aoarfeoi Table I-Cont1nued Percent Lbs. per Deoiled Test Product Percent Percent Percent BPL Dcoiling and cationic Ton at- 1 N 0. Weight BPL Insol. Recovagents Feed Percent ered Solids 4 100. Diesel oil 10.00 1 2. Kerosene. 0. 75 75 3 97. Amine, 0. 21 100. "Yarmor "Pine oil 10. 5 3 3. 0. 5 .75 6' 96. m e 0.22 2 100. "Frother B 23"; 9. 4 5 4. Kerosene 0.5 76 8 95. Amine 0. 22 0 100. Ohloroform- 16. 50 A v 1 7. Kerosene. 1.00 75 9 es. Amman--. 0.20 2. 100. Carbon tetrachloride--. 17. 70 7 3. Kerosene 1. 00 75 1 96. 0. 8 100. 9.

1s. 00 84. 20 100. Alpha pinene. 50

Kerosene 00' Amine- 20 Butyl acetate- 00 Kerosene--- 75 21 Amine Dloctyl adlphate- Kerosene NOTES TO TABLE I Test 4.Yarmour F Pine Oil is a product of Hercules Powder Company. It is produced by the solvent extraction of southern pine stump wood and consists largely of terpene alcohols.

Composition varies but it is normally 70 to 80% of a mixture of the tertiary and secondary terpene alcoholsalpha terpineol, borneol, and fenchyl alcohol. The balance is composed mainly of the hydrocarbondipentene, with minor amounts of the ketones-ienchone and camphorand the ethers-anethole and estragole.

Test 5.Frother B23 is a product marketed by E. I. du Pont de Nemours & Co. and consists of 40-45% of 2,4-dimethylpentanol, 40-45% of 2,4-dirnethylhcxanol and 810% of unidentified ketones.

Test 19.Foilene is an ester obtained from cottonseed oil.

It can be readily seen that substantially all of these immiscible organic solvents are at least equal, and most of them are superior, to the sulfuric acid of present practice. They yield froth products which contain a lower percent of BPL than the froth obtained after deoiling with sulfuric acid and their percent insol. in the concentrate is as low or less than that which remains after sulfuric acid treatment. The deoiling obtained with the organic esters, tests 10-l8, is particularly outstanding as shown by the very low percentBPL recoveries in the froth products.

Tests 2 and 3 which employed diesel oil as a deoiler are also important from an economic standpoint since diesel oil sells for only a few cents a pound. This deoiling process can compete cost-wise with even the mildest sulfuric acid deoiling of present practice. It is also noted that the other organic solvents disclosed as deoilers are all commercially available in quantities and price ranges which would render them competitive when the higher grade products which they yield are considered. Also the organic liquids illustrated are non-hazardous, easily handled and thoroughly eliminate the necessity of handling corrosive mineral acids.

It will be understood from the foregoing disclosure that our invention is not concerned the anionic and cationic flotation agents used in the two flotation steps which precede and follow the deoiling step, such agents being well known in the art. a

The quantity of the deoiling agent to be used is generally within the range from about 5 to about 25 pounds per ton of ore treated. As shown by the tests, about 10 pounds per ton generally gives good results. The quantity to be used in any particular intance may of course readily be determined by a series of tests. As little as 3 pounds of diesel oil has been used efiectively.

The deoiling agent conveniently and efiectively is applied as disclosed above by stirring'it with the wet ore, i.e. a mixture of ore and water containing about 75 to by weight of ore, but the agent may be applied by stirring it with the dry ore or with orewater mixtures containing higher ratios of water.

The pH of the ore-water mixtures have been observed and have not been found to exert an appreciable eifect. It may be said that a pH within the range from 7 to 8 gives satisfactory results.

We claim:

1. In a process for the beneficiation of phosphate ore containing silicious impurities involving the steps in sequence of anionic flotation, deoiling the resulting concentrate and cationic flotation of the deoiled concentrate,

selected from the group consisting of diesel oil, a prod-. uct containing from 70% to 80% of a mixture of second-' ary and tertiary terpene alcohols, a productcontaining 4045% of 2,4-dimethylpentanol' and id-45% of 2,4-dimethylhexanol, chloroform, carbon tetrachloride, crudesulfate turpentine, alpha pinene, the alkyl esters of mono-' and dicarboxylic acids the alkyl groups of which contain from 2 to 8 carbon atoms, diethyl carbonate, hexyl' furoate and an ester of cotton seed oil.

2. Process as defined in claim 1' in which a mixture of about 2000 parts by weight of ore concentrate with about 600 parts by weight of water is mixed with about 10 parts by weight of the solvent.

3. Process as defined in claim 1 in which the organic solvent is diesel oil.

4. Process as defined in claim- 1 in which: the organic solvent is a product containing from to of a mixture of secondaryand tertiary terpene alcohols.

5. Process as defined inclaim 1- inwhich the organic solvent is a product containing 40-45% of 2,4-dimethylpent'anol and 40-45 of 2 ,4-dimetl1ylh'exanol.

6. Process as defined in claim 1 in which the organic solvent is an alkyl ester of acetic acid the alkyl group of which contains from 2 to 8 carbon atoms.

7. Process as defined in claim 1 in which the organic solvent is an alkyl ester of phthalic acid the alkyl group of which contains frornZ to 8 carbon atoms.

References'Cited in the file of this patent UNITED STATES PATENTS 1,312,266 Navin Aug. 5, 1919 1,515,121 Flyeman e Jan. 18, 1927 2,173,842 Horner Sept. 26, 1939 2,293,640 Crago Aug. 18, 1942 2,461,813 Duke Feb. 15, 1949 2,524,859 Van-Dongen Oct. 10, 1950 2,763,997 Duke et a1. July I0, 1956

Claims (1)

1. IN A PROCESS FOR THE BENEFICIATION OF PHOSPHATE ORE CONTAINING SILICOUS IMPURITIES INVOLVING THE STEPS IN SEQUENCE OF ANIONIC FLOTATION, DEOILING THE RESULTING CONCENTRATE AND CTIONIC FLOTATION OF THE DEOILED CONCENTRATE, THE IMPROVEMENT WHICH CONSISTS IN DEOILING THE CONCENTRATE PRODUCED BY THE ANIONIC FLOTATION BY MIXING THE CONCENTRATE CONTAINING NOT MORE THAN ABOUT 80% OF SOLIDS AND AT LEAST ABOUT 20% OF WATER IN THE ABSENCE OF A WATERSOLUBLE STRONG MINERAL ACID WITH FROM ABOUT 3 TO ABOUT 25 POUNDS PER TON OF SOLIDS OF A NORMALLY LIQUID ORGANIC SOLVENT WHICH IS IMMISICIBLE AND NON-REACTIVE WITH WATER SELECTED FROM THE GROUP CONSISTING OF DIESEL OIL, A PRODUCT CONTAINING FROM 70% TO 80% OF A MIXTURE OF SECONDARY AND TERITARY TERPENE ALCOHOLS, A PRODUCT CONTAINING 40-45% OF 2,4-DIMETHYLPENTANOL AND 40-45% OF 2,4-DIMETHYLHENOXANOL, CHLOROFORM, CARBON TETRACHLORIDE, CRUDE SULFATE TURPENTINE, ALPHA PIENE, THE ALKYL ESTERS OF MONOAND DICARBOXYLIC ACIDS THE ALKYL GROUPS OF WHICH CONTAIN FROM 2 TO 8 CARBON ATOMS, DIETHYL CARBONATE, HEXYL FUROATE AND AN ESTER OF COTTON SEED OIL.