US3732090A - Processing of phosphate rock - Google Patents

Abstract

PHOSPHATIC PEBBLE IS UP-GRADED BY SUBJECTING A SLURRY OF PHOSPHATE MATRIX TO THE STEPS OF WASHING AND SIZE CLASSIFICATION, WITH THE PHOSPHATIC PEBBLE RESULTING FROM THE CLASSIFICATION BEING SUBJECTED TO WET GRINDING, THE FINES FROM WET GRINDING AND SUITABLE FOR ACIDULATION TO PRODUCE A FERTILIZER MATERIAL, AND THE COARSER FRACTION FROM WET GRINDNG IS FURTHER BENEFICIATED BY FLOATION.

Description

May 8, 1973 H. W, BREATHITT, JR.. ET AL PROCESSING OF PHOSPHATE ROCK Original Filed March 3. 1967 3 Sheets-Sheet l May 8, 1973 H. w. BREATHITT, JR.. ET AL 3,732,090

PROCESSING OF PHOSPHATE ROCK 3 Sheets-Sheet 2 Original Filed March 3, 1967 May 8, 1973 H. W. BREATHITT, JR., ET AL PROCESSING OF PHOSPHATE ROCK Original Filed March I5, 1967 3 Sheets-Sheet 5 PEBBLE FEED (WET) WATER ROD MILL PUMP ovERFLOw OVERFL w T l |5o MESH T CYCLONE TH|CKENER V TEETER COLUMN HYDRos|zER PUMP T l FILTER PUMP ,1,

-aso MESH FTNEs PRODUCT DOUBLE-COLUMN HYORosuzER -2e+|5o MESH 15o MESH AMINE REAGENTS l E AMTNE FLOTATION TAILING CONCENTRATE PHOSPHATE PUMP SANO OR WASTE OVERFLOW CYCLONE FIG. 4

ovERFLOw INVENTOHS B'N HARv/E w BREATH/TT, JR.

ROBERT O. EVANS WESLEY M. HOUSTON 28H50 MESH CONCENTRATE PRODUCT ATTORNEY United States Patent O M 3,732,090 PROCESSING F PHUSPHATE RGCK Harvie W. Breathitt, Jr., Lakeland, Robert D. Evans,

Pierce, and Wesley M. Houston, Lakeland, Fla., assignors to Agrico Chemical Company, Tulsa, Okla. Continuation of application Ser. No. 633,319, Mar. 3,

1967, which is a continuation-in-part of application Ser. No. 365,269, May 6, 1964, both now abandoned. This application Feb. 17, 1971, Ser. No. 116,244 Int. Cl. C05!) 11/04 U.S. Cl. 71--37 6 Claims ABSTRACT OF THE DISCLOSURE CROSS-REFERENCE TO RELATED APPLICATION This application is a continuation of U.S. Ser. No. 633,319 filed Mar. 3, 1967, now abandoned which in turn is a continuation-in-part of U.S. Ser. No. 365,269, filed May 6, 1964, now abandoned.

This invention relates to the processing of phosphate rock. More particularly this invention relates to the beneciation of phosphate rock. Still more particularly this invention relates to the separation of siliceous contaminant material, such as grains of silica locked in the phosphate itself, from phosphate-containing rock, such as hydraulically mined phosphate rock.

In accordance with one embodiment this invention is directed to the upgrading of phosphate rock material, such as the upgrading of low grade phosphate rock, i.e. phosphate rock having a bone phosphate of lime (BPL) content below about 70% to a higher grade phosphate rock, i.e. phosphate rock having a BPL content of about 7'0-73% or more. iIn accordance with another embodiment this invention is directed to the upgrading of standard grade phosphate rock, having a BPL content in the range about 7\0-73% to high grade or premium grade phosphate rock having a BPL content above about 73%.

In accordance with yet another embodiment this invention is directed to the recovery and utilization of phosphate values, or phosphorus values, from phosphate rock materials.

In the mining of phosphate rock as usually practiced in Florida, after the phosphate rook has been located by prospecting the overburden is stripped and the phosphate rock matrix is exposed. Excavating equipment picks up the phosphate rock matrix and dumps it in a selected area wherein high pressure streams of water break up the matrix and wash the phosphate rock matrix into a sump. The phosphate rock matrix is then pumped as a slurry to the processing plant which usually consists of two units, a washer and a recovery plant. In the washer the larger phosphate rock material, pebble size, is separated from the slurry by disintegrating. The washer product consists of cleaned pebble phosphate rock, which up to the time of our invention has been considered as being a iinished product.

In the usually adjacent recovery plant the smaller size or phosphatic sand material is separated from the sand and clay by hydraulic sizing and flotation. In the hydraulic sizing operation the tine phosphate rock is sizeclassiiied for subsequent treatment by otation for removal of objectionable ne' materials. After completion 3,732,090 Patented May 8., 1973 ICC of the processing and concentration operations both the washed pebble rock and the ner flotation concentrates are stored or dried for subsequent shipment or chemical treatment, such as by acidulation.

It is an object of this invention to provide an improved process for the treatment of phosphate rock material.

Another object of this invention is to provide a process for the beneciation of phosphate rock or ores.

Still another object of this invention is to provide a process suitable for the benefciation of phosphate rock material, such as a process suitable for the upgrading of low grade phosphate rock to standard grade phosphate rock, or a process suitable for the upgrading of standard grade phosphate rock to high grade or premium grade phosphate rock.

Yet another object of this invention is to provide a process for the utilization and recovery of phosphate or phosphorus values from phosphate `rock material.

Still another object of this invention is to provide an improved process for the removal of silica and related siliceous materials from phosphate rock containing such materials as contaminants therein.'

Yet another object of this invention is to provide an economically attractive method for the treatment and/or beneciation of phosphate rock material.

How these and other objects of this invention are achieved will become apparent in the light of the accompanying disclosure made with reference to the accompanying drawings wherein FIGS. 1, 2, 3 and 4 are flow charts diagrammatically illustrating particular cmbodiments of the practice of this invention.

It has been discovered in accordance with this invention that by wet grinding phosphate rock material through approximately 14 mesh (Tyler screen), preferably through 28 or 35 or 48 mesh, followed by removal of the ground phosphate rock material smaller than mesh, or even smaller than 200 or 325 mesh, and subjecting the 14 or -28 or +35 or 48, +150 or +200 or 325 mesh fraction to concentration by flotation, such as a froth dotation operation carried out in the presence of a cationic amine otation agent, a concentrated phosphate rock material can be obtained having an increased BPL content, particularly as compared with the original phosphate rock material supplied to the process. It has further been discovered, according to this invention, that the nes removed after this wet grinding operation can be utilized for their phosphatic values, and that such utilization is in fact presently necessary to an economically feasible process.

Specically, and indicative of the practice of this invention, ground phosphate rock material assaying about 67.5% BPL and having a particle size in the range -35 +150 mesh was pulped in an M.S. air ow flotation machine, conditioned 15 seconds with an amine otation reagent, such as Armoote P, air turned on and the silica iloated off. The machine discharge was the final concentrate. The amounts of notation reagents employed were in the range about 0.200 pound of cationic amine flotation agent, 0.070 pound of caustic and 0.30 pound of kerosene, all per ton of feed. The resulting -35 +150 concentrate recovered from the machine assayed 73.2% BPL in an amount about 91% by weight of the feed, indicating a percent BPL recovery of about 98% of the phosphate in this fraction. The -35 +150 tails floated from the machine assayed 13.1% BPL in an amount of about 9.5% by weight of the machine feed. It appears that in accordance with the practice of this invention by carrying out the grinding of the phosphate rock through 14 or 28 mesh screen, or preferably through 35 mesh screen, the silica released during grinding is of a size particularly suitable for removal by cationic flotation.

In accordance with one feature of this invention, the -150 or -200 or -325 mesh phosphate rock fines of the ground rock material are recovered and are subjected without necessarily being subjected to an intervening drying step to chemical treatment, such as by acidulation with sulfuric acid or phosphoric acid, for the production of valuable phosphate-type fertilizer materials, or to pelletization for use as phosphorus furnace burden, or to drying for direct application as incorporation in fertilizers. Thus it is seen that in accordance with this feature of the invention substantially all of the phosphate or phosphorus values are recovered from the phosphate rock material subjected to treatment.

In the treatment of phosphate rock material in aocordance with this invention the cleaned pebble phosphate rock is ground and sized in a novel manner. The grinding operation in accordance with the practice of this invention is a wet grinding operation, desirably carried out in a rod mill, and results in the substantial liberation of the silica or siliceous contaminants from the phosphate rock. These siliceous contaminants generally occur in two distinct manners, i.e., as free grains of silica and as silica which is physically bound or otherwise included in the phosphate particles themselves. The nes resulting from the grinding operation are not slimes as usually encountered in phosphate rock processing but are ground phosphate rock often having an improved BPL content as compared to the feed rock and, therefore, resembles dry ground phosphate rock. The fine portion, e.g. 150 mesh (Tyler) or smaller, of the ground phosphate rock usually comprising 20-30% of the feed phosphate rock supplied to the grinding operation is treated in accordance with this invention, such as by acidulation, e.g. reaction with sulfuric acid, for the recovery of phosphorus and/or phosphorus values therefrom, e.g. phosphoric acid. As stated, the subject process usually results in upgrading the fine fraction as to BPL content. There are instances, for example when treating a pebble having a relatively high content of friable impurities such as carbonates or clay, vwhen the fines fraction does not show an increase in BPL content; this is, however, relatively unusual.

In the practice of this invention it has been observed that the silica released or liberated by grinding is very ne and is readily floated out, such as by amine flotation alone. Usually, and in accordance with previous practice, phosphate rock processing plants using -35 +150 mesh feed phosphate rock must resort to fatty acid flotation to eliminate coarse silica, then deoil the phosphate rougher oat with acid and Ifinally float the remaining ne silica by amine flotation. In the practice of this invention the ground phosphate rock is a much higher grade than a normal float feed and contains much less silica, particularly the coarser fraction silica. By bypassing the fatty acid float and deoiling operations the processing of the ground phosphate rock in accordance with this invention is much simpler and more economical.

Referring now to FIG. 1 of the drawings which is a flow chart diagrammatically illustrating various steps in accordance with one embodiment of the practice of this invention, regular deslimed phosphate rock is subjected to wet grinding in a rod mill so that substantially all of the ground rock passes through a 28 mesh screen. In accordance with the preferred practice of this invention, however, the rock is ground to pass through a 35 mesh screen. The ground rock is then classified to remove the smaller than 150 mesh fraction. PIG. 1 illustrates this classification in a screw, while FIG. 4 illustrates the preferable hydraulic classification. The remaining 28, or 35, +150 mesh fraction comprising the bulk or the major amount of the ground rock is then subjected to amine flotation for the separation of siliceous materials, such as silica, which may then be discarded as tailings or waste. The resulting concentrate having an increased BPL content is recovered as product.

EXAMPLE NO. l

Regular production phosphate rock analyzing 65.9% BP-L and 9.6% by weight insolubles was stage ground in a rod mill. The +35 mesh from the rod mill for each charge was recycled to the next mill charge and the --35 mesh ground rock was screened on a 150 mesh screen. The materials analyzed as follows:

Percent By BPL dis- Material weight BPL Insoluble tribution Feed rock 100 -35 +150 fraction 73 65. 8 9. 02 72. 7 grinding fines 27 66. 7 6. 39 27. 3

The 35 `+15() fraction was subjected to amine flotation employing 0.5 pound amine flotation reagent, 0.38 pound kerosene, 0.17 pound NaOH per ton of feed. The materials of the amine flotation operation analyzed as follows:

Percent By BPL dis- Material Weight BPL Insoluble tributon -35 +150 feed 100 66. 3 108 89. 7 72. 6 98. 2 10.3 1l. 4 1. 8

EXAMPLE NO. 2

Regular phosphate rock having a particle size in the range -6 +14 mesh and having the screen and chemical analysis set forth in accompanying Table I TABLE I.SCREEN AND CHEMICAL ANALYSIS Percent Cum. Cum.

Weight Weight B PL B PL Insoluble l Calculated value.

was ground in a rod mill. 'I'he -28 mesh fraction was then screened on a 150 mesh screen. The grinding results are set forth in accompanying Table II.

TABLE II.GRINDIN G RESULTS Percent .By BPL disweight BPL Insoluble tribution Total sample ground l 100.0 68.42 100. 0 Total -28 +150 74. 2 68.46 74. 2 Total, 150 grind lines 25. 8 68.31 5. 39 25. 8

l Calculated value.

The ground rock fraction having a particle size in the range -28 +150 mesh was pulped into an M.S. (Mineral Separations) Air Flow flotation machine and the cell lled and the pulp conditioned with amine reagents with air off. The air was then turned on. A froth product rich in silica was removed. The cell discharge was the final 6 concentrate. The results of these tests are set forth in ac- TABLE V companying Table I II:

Percent TABLE III Insol- BPL Products Weight BPL uble FezOo A1203 dist. Percent l -35 +i50iee 11 100.0 74. 03 6.77 100.0 BPL dis- -35 +150 cono 93.0 77. 82 2.20 0.90 0. 46 97.8 Product Weight BPL Irisoluble tributiou 35 +150 tails 7.0 23.65 67.57 2.2

Iig. 139'? 732 "m- 189? Calculated head- -28 -150 tails; 8:3 23 71 2:9 10 The -150 mesh fraction of ground rock was filtered on 1 Analytical value on dry basis. rgiolliighner funnel to produce a filter cake analyzing 68.5%

EXAMPLE NO. 6 EXAMPLE No' 3 Samples of various phosphate rock were treated in ac- Ground phosphate rock fines fraction having a particle cordance with the practice of this invention involving wet size less than 150 mesh analyzing about 68.3% BPL and grinding in a rod mill to a particle size -35 mesh, fol- 22.8% moisture acidulated with 58 Baum sulfuric lowed by concentration of the -35 +150 ground rock acid. As a result of the treatment with sulfuric acid on fraction by amine flotation. The -150 ground rock fracthe basis of about 487 parts by weight of 66 Baum tion was further screened and the above fractions were sulfuric acid per 1000 parts by weight Wet finely ground tested for percent BPL content. The results of these tests rock, an acidulated rock having the following analysis, are set forthn accompanying Table VI: was obtained. TABLE VI Percent Moisture 15.82 Percent fr?? iioiiodsi;23:12:12: lii Wi APA (available phosphoric acid) 15.69 Rock N01 1m -i Free acid 4-61 -150 iii-serraggio.-- 10:7 61:52 11170 i115 EXAMPLE No. 4 30 Rock No.2.. Rir riiiflfi Z oso ---iff +150 oono 65.4 71. ss 2. 0i 0. s0 68.6 Regular page@ grade Phosphate fork treated naar; ai as is is ai in accordance with this invention by Wet grinding in a rod 400111185 11,3 @9 25 2,71 2 18 11.1 t0 a. Size Smaller than. mesh. The mesh .ffac Rock No' 3"' "i tion of the ground rock was removed and the remaining 150 +325 fines 13 8 m27 8.17 1,75 13,7 ground rock having a particle size in the range -35 +150 35 '-325 fmes 25-5 70-31 7-53 L90 2M mesh was concentrated by amine flotation. The results of these tests are set forth in accompanying Table IV: EXAMPLE NO 7 Regular production grade phosphate rock, the coarse fraction from the rougher flotation concentrate, having TABLE Iv the screen analysis Percent Mesh: Percent wt. 14 23.5 Product Weight BPL Insoluble BPL rec. 20 318 No. i; 28 22-3 Regular rock.. 100.0 67.01 8.39 100.0 35 112 Ground conc.. 63.3 72. 64 2.25 67.7 Ground fmos 2s.7 68.96 6.13 29.5 35 112 was ground in the rod mill to pass 35 mesh. The +35 mesh fraction was then screened on 150 mesh and the -150 mesh nes were then Wet screened on 325 mesh. Twenty'etgh Percent of. the mk tested Wai reduc.ed The analysis of the grinding products is set forth in acto -150 grinding fines. This material filtered fairly easily companying Table VH. to 75-78% solids filter cake. The filtered solids analyzed 68.96% BPL. Preliminary aoiduiaiiorr rest indicate this TABLE VH filtered material would acidulate satisfactorily. Percent EXAMPLE NO- 5 Produois weight BPL hirsiiilo Foros A1203 1diari' Regular grade production phosphate rock having a par- Feed 100.0 1 60.10 5. s0 1. 24 0. 07 100.0 ticle size in the range -6 +14 mesh'and analyzing 73.2% :go'lgsflie-S' I 8,23 ggg gigs BPL, 6.03% insoluble was ground in a rod mill to pass 60 -325 fines 13.5 60.06 2.85 2.20 1.0i 13.7 35 mesh. The +35 mesh ground rock was then screened ,Calculated hem on a 150 mesh screen. The -35 +150 ground rock fraction analyzed 72.9% BPL, 6.9% insoluble and the -150 The -35 +150 fraction was then subjected to amine mesh grinding fines analyzed 73.77% BPL, 4.17% insoluflotation, the feed being conditioned with amine (air off) bles, 1.48% Fe2O3 and 0.99% A1203. The -35 +150 65 for 15 seconds, the air turned on and the siliceous froth mesh fraction made up 67% of the ground rock. product oated off. The cell discharge was the final con- The -35 +150 fraction was conditioned with amine centrate. In the flotation operation the reagents were conreagents for 15 seconds (air oi) in an M.S. Air Flow cell, sumed in the following amounts based on the one ton of the air then turned on and the siliceous froth product reground rock feed (-35 +150 mesh), amine reagent moved. The cell discharge Was the inal concentrate. The 70 0.15 pound, NaOH 0.02 pound, kerosene 0.08 pound. reagents employed during concentration (froth flotation) The -35 +150 concentrate recovered from the flota- Were in the amounts 0.40 pound amine, 0.12 pound NaOH tion operation amounted to 93.1% of the feed thereto and 0.30 pound kerosene, all per ton of feed (-35 +150 and analyzed 71.7% BPL, 2.13% insoluble, 1.32% Fe203 mesh). The results of the dotation or concentration opand 0.74% A1203 for 97.5% BPL recovered based on the eration are set forth in accompanying Table V: feed. The -35 +150 tails discharged during the flotation operation analyzed 24.45% BPL and amounted to 6.9% by weight based on the feed.

The -150 +325 mesh fines recovered from the rod mill grinding operation ltered very rapidly in the matter of seconds and gave a filter cake analyzing 86.1% solids. The -325 mesh fines recovered grom the grinding operation iiltered satisfactorily and gave a filter cake analyzing 78.3% by weight solids.

EXAMPLE NO. 8

Further tests on various production grade phosphate rock were carried out substantially as described in EX- ample No. 7, the r-35 mesh fraction being concentrated. The results of these tests are set forth in accompanying Table VIII:

having a particle size in the range -150 +200 mesh and -200 +325 mesh fractions. Each of these fractions is then subjected to a cationic (amine) flotation operation to yield an amine discharge concentrate having an improved BPL value, particularly as compared with the BPL value of the particular fraction subjected as feed to the flotation operation.

As indicated hereinabove in the practice of this invention when the phosphate rock is subjected to a wet grinding operation to grind the rock through a 35 mesh screen substantially all of the siliceous contaminant, silica, contained in the rock is liberated. It has been observed, however, that in accordance with this invention substantial improvement and upgrading of the phosphate rock is obtained when the rock is ground to a coarser size, specifical- TABLE VIII Percent Feed Concentrate Total -150 fines Amine, Tails, BPL l Product ground Procedure Weight BPL Welght BPL Weight BPL weight BPL rise Coarse rock (-6 mesh) Std. 35 M. grind 100 65. 91 61. 8 69. 99 31. 7 67. 17 6. 5 15. 21 3. 08 Coarse rock (-I-( mesh) .d0 100 64. 29 64. 7 70. 34 27. 2 67. 46 8. 1 80. 47 G. 05 Rougher sizer product Std. recycle to mill 100 62.31 62. 0 69. 66 26.0 65. 69 12.0 14.18 7. 35 D0 Not recycled to mill 100 62. 93 71. 4 69. 21 17. 7 65.56 10. 9 14.99 6, 28

1 Percent BPL of flotation concentrate above grade of original pebble.

Referring now to the drawings, particularly FIG. 2 thereof, there is illustrated another embodiment of the practice of this invention wherein phosphate pebble is wet ground to pass through a 35 mesh screen. The -35 mesh fraction was then screened to yield a -35 +150 mesh fraction and a 150 fines fraction. The -35 +150 mesh fraction, so-called feed fraction, is then subjected to cationic (amine) flotation to yield a machine discharge amine concentrate having an increased BPL content as compared with the phosphate pebble originally subjected to wet grinding. The 150 mesh fines fraction is subjected to filtering to yield a filter cake which, although not illustrated, is suitable in the wet state for acidulation to yield valuable fertilizer material, or to pelletization to yield a useful phosphorus furnace burden.

Referring again to the drawings, this time to FIG. 3 thereof, there is illustrated therein another embodiment of the practice of this invention. In the embodiment of this invention illustrated in FIG. 3 of the drawings phosphate pebble is wet ground to pass through a 14 mesh screen. The -14 mesh ground phosphate pebble is then passed through a 35 mesh screen to segregate a -14 +35 mesh fraction and a -35 mesh fraction. The -14 +35 mesh fraction is employed as feed to a cationic (amine) otation operation to yield as discharge an amine concentrate having an increased BPL value.

The -35 mesh fraction is subjected to a screening operation through a 150 mesh screen to yield a -35 +150 mesh fraction and a -150 fines fraction. The -35 +150 fraction is employed as feed to a cationic (amine) otation operation from which there is recovered a discharge amine concentrate having an increased BPL value particularly as compared to the -35 +150 feed fraction to the flotation operation and also as compared to the phosphate pebble originally subjected to wet grinding.

Desirably, in accordance with the practice of this invention, the -150 mesh fines fraction is recovered, such as by filtration, and then subjected to a subsequent treatment, such as acidulation with sulfuric acid or phosphoric acid to yield a useful fertilizer material, or to pelletization for use as a phosphorus furnace burden or to drying for direct application as or incorporation in fertilizer material.

In accordance with still another embodiment of the practice of this invention the -150 fines fraction, such as may be recovered in the various flow schemes illustrated in FIGS. 1, 2, 3, and 4 of the drawings, may be further segregated into a -150 +200 mesh fraction or a -150 +325 mesh fraction or other fractions, such as a fraction ly through a 14 mesh screen. By carrying out the wet grinding operation to produce a coarser ground phosphate rock, i.e. through a 14 mesh screen, the total amount of grinding fines produced is reduced. Also, advantageously, capital and operating expenditures or requirements for associated thickening and filtering equipment employed in the practice of this invention are also reduced. It has been observed that in the practice of this invention even when the phosphate rock is wet ground to pass through a. 14 mesh screen a substantial portion of the silica contaminant material is liberated for subsequent removal in the cationic otation operation. Larger amounts of silica, of course, are liberated when the wet grinding operation is carried out to extent that the ground phosphate rock al1 passes through a 35 mesh or 48 mesh screen.

Accompanying Table IX sets forth various test data showing the applicability of the practice of this invention to the upgrading of phosphate rock wherein portions of the phosphate rock are subjected to wet grinding to pass through a 14 mesh screen, a 28 mesh screen, a 35 mesh screen and a 48 mesh screen.

TABLE IX 5() lm thllf* 14 28 35 48 Head pebble, percent:

Weight- 100 100 100 100 BPL 65. 98 65. 98 65. 98

Insolub 8. 53 8. 53 8. 53

55 BPL 100. 0 100. 0 100. 0 100. 0

dist. +14 mesh (not rec cled ercc t:

Weights r.. 1.?.

BPL dist -35 +1.50 mesh feed, percent:

Weight Insoluble BPL dist Total concentrate, percent:

BPL dist Flotatlon concentrate, percent:

W gh

ei 69. 2 65.2 58. 7 BPL 70. 01 71. 38 73. 29 insoluble-.. 3. 12 2. 4S l. 82 BPL 73. 4 69. 2 63. 1

Further illustrative of the practice of this invention the filter cake fines having a particle size smaller than 150 mesh, after recovery, were segregated into a +200 mesh fraction and a +325 mesh fraction. The total -150 mesh fines making up the filter cake in the particular sample tested represented 35.5% by weight of the regular ground rock. The +200 mesh fraction of this filter cake, representing 47.3% by weight of the filter cake, was subjected to cationic (amine) flotation. Also, the +325 mesh fraction of the filter cake, representing 68.4% by Weight of the filter cake, were subjected to cationic (amine) flotation. These various fractions of the filter cake were subjected to cationic flotation in order to upgrade the -BPL value of these fractions. The results of these tests are set forth in accompanying Table X:

1 Percentage of lter cake. 2 Percentage of regular rock to grlndlng circuit.

Up-grading `on +200 cake: 72.2;1-'6.46v=`5.75% BPL Up-grading on +325 cake: 71.63-66.75=4.88% BPL.

The test data presented in Table X illustrating the upgrading potential of a large portion of the filter cake. It should be particularly noted that the +200 filter cake fraction was upgraded 5.75% BPL.

EXAMPLE NO. 9

Following is a table showing analyses of the feed and various product streams obtained by operation in accordance with the flow diagram shown in the presently preferred method of FIG. 4. As can be seen from this table, a substantial upgrading in BPL was obtained in both the concentrate product and the nes product.

As will be apparent to those skilled in the art in the light of the foregoing disclosure many modifications, alterations and improvements are possible in the practice of this invention without departing from the spirit or scope thereof.

What is claimed is:

1. In the process of recovering phosphatic values from pebble phosphate matrix wherein the matrix is slurried in water and the resulting slurry is washed and size classified to produce a phosphatic clay slurry, a phosphatic sand material and phosphate pebble rock, the improvement which comprises subjecting said phosphatic pebble rock containing siliceous contaminant material and having a particle size greater than 35 mesh to a wet grinding operation to produce a ground phosphatic material having a particle size smaller than 35 mesh through 150 mesh, separating from said ground phosphatic material a fine fraction having a particle size smaller than 150 mesh and an increased phosphate content as compared with said ground phosphatic material, said fine fraction being suitable for acidulation Without subsequent beneficiation to yield a phosphatic fertilizer material.

Z. The process of claim 1 further comprising subjecting the remaining fraction of said ground phosphatic material having a particle size smaller than 35 mesh and larger than 150 mesh to flotation to separate siliceous material, and recovering as a product of said flotation a concentrated fraction having a substantially reduced content of siliceous material and an increased phosphate content as compared with said ground phosphatic material.

3. The process of claim 2 wherein said flotation is effected in the presence of a cationic flotation reagent.

4. The process of claim 3 wherein said cationic flotation reagent is an amine flotation reagent.

5. In the process of recovering phosphatic Values from pebble phosphate matrix wherein the matrix is slurried in water and the resulting slurry is Washed and size classified to produce a phosphatic clay slurry, a phosphatic sand material, and phosphate pebble rock, the improvement which comprises subjecting said phosphatic pebble rock containing siliceous contaminate material to a wet grinding operation to comminute the same and yield a ground phosphatic material having a particle size smaller than 14 mesh through 325 mesh, separating from said ground phosphatic material a line fraction having a particle size smaller than 150 mesh and an increased phosphate content as compared with said ground phosphatic material, said fine fraction being suitable for acidulation without subsequent beneficiation to yield a phosphatic fertilizer material.

6. In the process of recovering phosphatic values from pebble phosphate matrix wherein the matrix is slurried in Water and the resulting slurry is washed and size classied to produce a phosphatic clay slurry, a phosphatic sand material and phosphate pebble rock, the improvement which comprises passing said phosphate pebble rock containing siliceous contaminant material to a wet grinding operation to comminute the same and yield a ground phosphatic material having a particle size smaller than about 14 mesh through 325 mesh, selecting a fraction consisting essentially of particles having sizes greater than 150 mesh from said ground phosphatic material, sub- TABLE XI Percent Product BPL Insel FezOa A1203 CaO CO1 MgO Wt Pebble feed 65. 69 10. 8B l. 50 0. 74 45. 33 3. 95 0. 47 100. o Concentrate product 71. 83 4.10 1. 78 0.58 49. 03 4. 10 O. 50 65.0 Fines product 67. 59 7. 90 1. 78 0. 83 45. 87 3. 93 0. 52 26, 9 Amine froth. product 16. 85 79. 01 4, 6 Thickener overflow 1 70. 18 3. 87 1. 68 3. 24 48. 15 4. 04 U. 64 3.

1 This stream can be treated, as by ilocculation, to recover phosphate which can be added to the fines product.

1l f jecting said selected fraction to a cationic flotation opera- References Cited tion to separate siliceous contaminant material therefrom, UNITED STATES PATENTS recovering from said flotation operation a concentrate having a phosphate content higher than that of said 2571866 10/1951 Greene 241-120 X ground phosphatic material, recovering from said ground 5 1547732 7/1925 Broadbndge 71-'37 X phosphatic material a remaining fraction finer than said selected fraction and having a phosphate content higher SAMIH N' ZAHARNA Pnmary Examiner than that of said ground phosphatic material, and sub- R. BARNES, Assistant Examiner jecting said remaining fraction without subsequent beneficiation to acidulation to yield a phosphate-containing 10 U.S. Cl. X.R. fertilizer material. 241-20

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