US1901221A - Mining and treatment of phosphate-rock - Google Patents

Description

March 14, 1933. J. T. BULLwlNKEL 1,901,221

MINING AND TREATMENT OF PHOSPHATEROCK Filed May 9, 1951 ATTORNEY Patented Mar. i4, 1933 UNITED STATES PATENT OFFICE JOHN -'.IJIBEADWELL BULLWINKEL. 0F BROOKLYN, NEW `YORK, ASSIGNOR T0 THE PHOSPHATE MINING C0., OF NEW YORK, N. Y., A. GORVPORATION F NEW YORK MINING AND TREATMENT OF PHOSPHATE-BOCK Application illed Hay'S, 1931. Serial No. 536,182.

This invention relates to the mining and treatment of phosphate rock,.and particularly of Florida "pebble hosphate rock, occurring as a matrix in a mixture with clay and sand, etc. so as to obtain a higher yield of pebble phosphate, as well as pebble phosphate of higher quality.

According to the present invention, pebble phosphate, occurring in a matrix of clay and sand, is subjected to dry mining and is `then subjected to a soaking treatment submerged in water for a considerable period of time suilicient to effect disintegration or softening of the greater part of the clay and sand, after which the disintegrated or softening material is subjected to a screening and washing treatment to remove the distintegrated clay and sand from the pebble phosphate without the necessity of using logs, scrubbers or Crushers, or harsh scrubbing treatment. The pebble phosphate is then further treated, if necessary, to effect further disintegration or softenmg of any remaining undisintegrated clay or sand which is then removed by a further washing treatment.

Phosphate such as Florida pebble phosphate rock is found in a matrix of sand and clay in varying percentages aswell as other substances in lesser quantities. The phosphate, sand and clay are bound together in a mass which must be disintegrated in order to permit the recovery of the pebble phosphate therefrom. The disintegration of the matrix, which is a necessary and important step in the treatment, is not easy to accomplish, and the method commonly employed has been largely a hydraulic disintegration followed by scrubbing and further disintegration in log washers or scrubbers.

lThe hydraulic guns used in hydraulic mining and disintegration use pressures varying from 100l to 250 pounds per square inch, the usual pressure being about 200 pounds. The hydraulic guns are used to mine the matrix and to disintegrate the matrix so that it can be pumped through the pipe lines and also so that the matrix will be sufficiently disintegrated that logs, scrubbers, Crushers or oth- 0 er clay disintegrating equipment can further -which are soft.

tegrated matrix. to the washin terial itself. The disintegration of the matrixv by the hydraulic guns disintegrates or breaks up or cuts olf the edgesA and surfaces of pebbles of phosphate, particularly those Some deposits contain a large percentage of soft pebbles and it is frequently found that these soft pebbles are of the highest grade. When disintegration is accompllshed by a hydraulic gun, there is not only a loss of phosphate material, but losses of phosphate material of high quality. With reduction in size of the phosphate pebbles and reduction of va considerable amount of the phosphate material to a finely divided state, it is then eliminated with the clay and sand and thereby lost. Further disintegration and loss of phosphate may take place due to attrition in pumping the disinequipment.

It has been proposed to mine t e phosphate material dry or as is to avoid the objections and losses due to hydraulic mining, but the disintegration of the phosphate matrix is dilicult. While the mining of the matrix dry or as is with drag lines or mechanical shovels causes a partial disintegration of the matrix, yet due to the sticky condition of the I matrix there is a recombination when the mined material is dumped together, so that disintegration of this sort is of little practical value. Disintegration, after dry mining, can be accomplished by the use of a hydraulic gun, but this method of disintegration has similar objections to those ofV hydraulic mining of the matrix.

I have found that the matrix can be disintegrated and then cleaned with only gentle washing, on a laboratory scale, by using plenty of water and allowing suiiicient time, but such an operation, with the time required, is impractical for large commercial scale operations where the mining and handling of pebble phosphate requires the handling of a large number of cubic yards or tons of matrix 5 ing the mining of the phosphate rock matrix dry by drag lines 'or shovels can be largely retained to advantage and the matrix so mined can be further disintegrated or softened in a simple and effective and advantageous manner by immersing the dry mined eiectivellyl7 can be t matrix in water and permitting it to stand a considerable period of time so immersed. I have found that thematrix can in this way be disintegrated or softened so that it en subjected to a gentle Washing treatment which does not involve any objectionable disintegration of thephosphate maf terial.

Without disintegration of the matrix it is impossible to separate the phosphate from it by screening butafter the disintegration of the matrix in the manner described, I have found it is an easy matter to separate and clean the phosphate in submerged screens, classifiers, fiat screens, etc.

While the present process will be more particularly described in connection with the treatment of Florida pebble phosphate rock, any phos hate material admixed with clay and clay alls can be advantageously disintegrated and softened in a similar manner, accordin t0 the present process, by immersing the ry mined matrix in water and permitting it to stand for a considerable period of time so immersed.

In carrying out the present process, accordingly, I mine the phosphate rock by a dry mining operation, such as by the use of a drag line or a mechanical shovel, and I transfer the mined matrix to a soaking pit where it is immersed in water and permitted to soak for a considerable period of time. The soaking-pit may have a capacity, for example, of about 1,000 cubic yards or about 1,400 short tons of matrix, and as many soaking pits may be provided as needed. One pit may be filled While another is being emptied' after disintegration. The period of time required for eii'ective disintegration and softening in the soaking pit will vary with different materials and to some extent with the size of the lumps of matrix. A period of as little as an hour or less may be suiiicient or a period of hours may be required. It is not necessary to leave the matrix in the pit for a suicient period of time to accomplish complete disintegration, and the soaking may be continued only until the greater part of the matrix is disintegrated or softened and further disintegration subsequentlyV accomplished, for example, as hereinafter described.

The disintegration and softening of the matrix can be and isaccelerated during the operation of removing the disintegrated and tegration and softening can also be accelerated by changing the location of the matrix in the pit or permitting freer access of the water to the matrix by using any equipment or means suitable for such Work, for example, l

a hoist and bucket may be usedI to lift and cause relocation of the material. The disintegration or softening can also be promoted by adding disintegratlng or dispersing agents in small'amunt to the water, and the water containing such agents can be used repeatedly or over and over again in the soaking treatment.

I have found it is not necessary to leave the matrix in the soaking treatment for a suiicient period of time to accomplish complete disintegration because the soaking and disintegration can be continued after the matrix has been mostly disintegrated and the remainder softened in the first soaking treatment suiiiciently to permit classifiers or rotary submerged screens to continue the disintegration and at the same time eliminate the disintegrated clay and fine sand.

I'have also found that the use of logs, scrubbers or crushers for disintegration of matrix or clay is an unnecessary and harsh treatment, particularly when soft phosphate pebbles are present, causir 1; losses of phosphate, and t vantageously eliminated and the losses of phosphate saved by substitutingrotary screens partially submerged or classlfiers for continuing the disintegration after the material or matrix has been permitted to soak immersed in Water for a period sufficiently long to disintegrate or soften the material or matrix.

The soaking of the relatively large lumps of matrix in the soaking pit both softens and disintegrates the lumps and for the most part the material can then be separated from fine clay and sand which readily passes through a fine screen, While any remaining large lumps which have not been suiiciently disintegrated can similarly be separated as an over-size product and returned 'for further soaking treatment, leaving an lntermediate product, between the fine clay and sand which are separated, and the coarse over-slze product which is returned, which is then further treated to recover the phosphate therefrom.

The disintegrated and softened material from the soaking pit can be transferred to a hopper feeding a suitable separator, such as a rotary separator, which will screen outy all over-size particles of predetermined size, for example, lumps of more than 4 inches in size. Such lumps can be returned to the soaking pit for further soaking and disintegration, and may conveniently be returned on a conat these equipments can be adi veyor so as to permit hand picking .removal of any bed rock or other impurities which may have been mined with the matrix. In this way over-size lumps can bereturned for further disintegration or softening and 'only the finer material, of a predetermined finer size, such as minus 4 inches in size, can be further treated.

The further'treatment is advantageously one which subjects the Vlnaterial to a continuing disintegrating and screening operatlon, with washing during treating, to remove all fine clay and sand, for example, all that wlll pass through a El; inch screen. Rotary screens, operating partly submer d 1n water, are advantageously used for t 1s continued disintegration and screening operation. The reater part of the clay and sand of the matrix is thus removed, leaving a concentrated phosphate material which will ordinarily represent considerably less than half of the original matrix treated. As much as or more of the matrix may be removed as fine clay and sand during the screening and washing treatments. A series of additional screening and washing treatments can be used to effect a more complete washing away of the fine clay and sand. This is accomplished with only gentle movement of the material, and without objectionable attrition and loss of hosphate.

The concentrated material, freed from fine clay and also fromover-size lumps, is then advantageously subjected to a further classification or separation to separate the larger pebbles of phosphate rock and any larger lumps of material from the smaller pebbles. For this separation a screen of about 1/ inch mesh, more or less, may be employed, and this will separate out all of the smaller pebbles, which pass through the screen, from any larger pebbles or lumps which are too large to pass through.

The over-size from this second classification, that is, pebbles and balls or lumps ofmore than about 1/2 inch in size, and which usually forms only a small part of the phosphate at this point of the operation, may be treated in various ways. The materiall is conveniently treated in a scrubber or log Washer to effect disintegration of any undis-` integrated cIay, and the resulting material may then be subjected to a further separation treatment using rotary or vibrating screens, for example, of around 1A; inch mesh, to give an over-size product of larger pebbles, and an under-size product which can conveniently be admixed with the under-size product from the first 1/ inch'screen. Instead of using a scrubber for treating the over-size material, it can be subjected to a further soaking treatment, by permittingit to stand for a suicient time submerged in or wet with water to permit disintegration or softening of undisintegrated clay, and it can then be subjected to further move the disintegrate phate pebbles. The under-size material, which ,passes through the 1/2 inch screen, usually needs no clay from the phosentle washing to re-l further treatment than passing over lthe usual vibrators and rotary screens, with water spray to wash away adhering clay and sand and to give a phosphate product of hi her phosphate content. This lphosphate pr uct will contain pebbles less than 1/2 inch in size, where a half inch screen is employed, or less than 378 inch size where a three eighth inch screen is employed. It will be evident that the size of the screen .can be somewhat varied depending upon the classification of bbles* which is desired, for example, peb les of more than 1/2 inch in size and pebbles less than yz inch in size. Y

The under-size pebbles, that is, the pebbles less than 1/2 inch or 378 inch in size may still be admixed with small lumps of clay or clay balls or may have clay adhering to' the pebbles, or may have soft sand rock admixed therewith, particularly if the preliminary and continuing soaking operation has not been carried so far as to effect complete disintegration. Such pebbles are advantageously subjected to a further soaking treatment which in this case does not need to be submerged in' water, but whichcan advantageously be carried out merely by letting the material stand for a sufiicient time to permit the water which the material itself carriesv rotary screens and by passing over vibrating screens with waterspray and washing to remove slimes and disintegrated clay and sand from the pebbles and to give a purer phosphate product.

This above mentioned additional further soaking treatment without submerging in Water, while advantageous and desirable, may be omitted where a cleaner and purer product is not required, but it is advantageously used to obtain a cleaner and purer product where the previous treatment still leaves adhering or admixed clay or clay balls, etc. with the phosphate rock.

The complete process, from the dry mining of the matrix to the complete disintegration and removal of clay and sand from the phosphate rock, is accomplished without objectionable loss of phosphate from attrition or disintegration of the phosphate rock itself, so that even the softer phosphate rock remains substantially intact and is recovered as part of the phosphate product. Objectionable losses of phosphate are thus avoided, and an increased yield of phosphate rock is obtained and of higher quality.

The disintegration and softening of the matrix and the retaining of any disintegration caused by drag lines or shovels is accomplished for the most part in the rst soaking treatment to which the dry mined matrix is subjected. Where the material from such first disintegrating treatment and from the continued soaking treatment still contains lumps which have not been completely disintegrated, they may be returned as over-size lumps to the soaking pit for further soaking and disintegration. In this way the soaking treatment in the soaking pit can be carried to the extent which will insure that all of the material will be disintegrated or softened to less than the predetermined size so that it can then be carried forward for further treatment, without the necessity of harsh treatment of logs, scrubbers or crushers.

Further disintegration or softening of any` undisintegrated clay if desired can then be accomplished after the removal of most of the clay and sand from the phosphate rock, by a further soaking operation carried out without submerging the material in liquid and with such wateras the material itself carries. The treatments, including the soaking treatment to which the material is subjected, are all relatively entle treatments which conserve even the sot phosphate rock but which nevertheless insure the washing away and removal from the rock of admixed and adhering clay and sand.

A flow sheet illustrative of therpresent process is shown in the accompanying drawlng. As shown in the How sheet, the phosphate rock is mined by dry mining by such mechanical equipment as shovels or drag lines and is then conveyed to soaking pits where rit is kept submerged in water for a suicient time to effect disintegration and softening of the material. It is then passed through a rotary separator such as a four inch screen to remove the over-size lumps which are returned to the soaking pit for further soaking and disintegration. The undersize material is then passed through one or more separating devices such as rotary screens partially submerged of, for example, 31; inch openings or classifiers which remove the fine sand and clay as waste material. The remaining material is passed to a rotary separator suoli as a 378 inch screen which separates the phosphate pebbles and admixed clay balls or soft sand rock, etc. into an oversize material and an under-size material, that is, material passing through the 578 inch screen and the over-size material over the screen.

The amount of over-size material, with Florida pebble phosphate rock, willordinarily be small and may conveniently be subjected totreatment in logs or a scrubber or rotary screens partially submerged where further disintegration of adhering or admixed clay is accom lished, after which the material is subjecte to a se arating treatment, for example, on a 1/8 inc rotary screen to give over-size pebbles which, after further treatment on vibrating screens and washing give an over-size phosphate pebble product, that is, containing pebbles of more than about 378 inch size.

The undersize materials from the rotary separators, having 3/8 inch screens, are subjeoted to a further screening treatment, with washing, to remove fine sand and clay therefrom after which they may be passed to soaking bins and permitted to soak therein for a Sulicient time to cause disintegration of any remaining admixed clay balls or soft sand rock and adherin clay. After this soaking in the soaking tbins, where the remaining small amount of undisintegrated clay is permitted to disintegrate, the material is passed through classifiers, submerged screens or other rinsing equipment and vibrating screens where further cleaning is accomplished, giving a phosphate rock produ ct made up of pebbles of less than 3/8 inch size.

It will be evident that the particular type of separators and screens, and of screen sizes, etc., including the rotary screens partly submerged, can be varied, but that in all stages of the treatment, except when the scrubbing treatment is used on the' larger phosphate pebbles (the amount of which is usually small with Florida pebble phosphate rock), the treatment is such that objectionable attrition and disintegration of the phosphate itself is avoided while the necessary disintegration of the matrix is easily accomplished and the sand and clay are removed by the various screening and washing treatments. So also, the details of the treatment and the nature and sequence of steps and operations described and shown in the flow sheet, can be varied with different matrices which differ solnewhat in nature and in their requirements of handling.

The present process thus makes possible the complete elimination of hydraulic min- -ing and the objectionable losses, etc. result- 5 have been recovered by using the dry'mining methods with disintegration and softening in asoaking treatment and continuing disintegration in rotary screens partially submer d or classifiers and eliminating harsh 10 scru bing treatment, according to the present invention. The present process thus makes possible the recovery of a'higher .grade phosphate product.- I have found by'tbis process an actual improvement in quality of several percent., with resulting increase in value of products of higher quality command.

I claim:

1. The method of mining and treating phosphate rock embedded in a matrix of clay and sand, etc., which comprises dry mining the material or matrix, transferring the dry mined material to one or more soaking pits where it .is submerged in Water, causing the material to remain submerged for a sufficient period of time to effect disintegration or softening of the phosphate matrix ormaterial preparatory to further treatment for the separation of the phosphate rock and maintaining the material substantially free throughout said-steps from any disintegrating force which would break down any soft pebbles.

2. The method of mining and treating phosphate rock embedded in a matrix of clay and sand, etc., which comprises dry mining the material or matrix, transferring the dry mined material -to one or more soaking pits where it is submergedin water, causing the material to remain submerged for a suicient period of time to effect disintegration or softening thereof preparatory to further treatment, then subjecting thedisintegrated material to. a separating treatment to remove or separate disintegrated clay, etc. from the phosphate rock and maintaining the material substantially free throughout said steps from any disintegrating force which would break down any soft pebbles.v

3. The further improvement in the process of claim 1 in which the disintegrated material, after the soaking treatment, is subjected to a preliminary sizing treatment to remove larger lumps therefrom which are returned to soaking pits for further soaking and disintegration. v

4. The further improvement in the process of claim 1 in which the disintegrated material, after the preparatory treatment, is then subjected to a further continuing disintegrating or softening treatment and to removal of fine sand and disintegrated clay and scrubbers, practically all and' attherefrom without harsh .scrubbing treatment.

5. The further improvement .in the process of claim 1 in which the disintegration or softening of the material or matrix during the soaking treatment is accelerated or quickcned by causing a relocation or shifting ofV the material in the pit thereby -permitting a freer and quicker access of the water to the material to be disintegrated or softened.

6. .The further improvement in the process ofclaiml in which the disintegrated or softened material is subjected to a seriesof screening and washing treatments to remove or separate clay and sand, etc. from the phosphate rock, said screening and washing treat-- the product due to the higher price which ments being carried out without crushing or harsh scrubbin of the material.

7 The further improvement in the process of cla-im 2 in which the-'phosphate material, after the removal of a large part of the line sand and clay therefrom, is subjected to a further soaking treatment in water to effect further disintegration or softening of undisintegrated clay and sand admixed therewith, with subsequent screenin and washing of the thus disintegrated an softened material to remove the disintegrated clayand sand, etc. therefrom.

8. The further improvement in the process of claim 2 in which the. disintegrated material, after the removal of a large part of `smaller phosphate materials which are separately further treatedl to effect disintegration of remaining admixed or adhering clay and sand followed by screening and washing to remove the disintegrated clay and sand from the respective sizes of phosphate materials. 9. The further improvement in the process of claim 2 in which the disintegrated and partially cleaned material is subjected to a further soaking treatment while still Wet from the preliminary treatment and without submersion in water until admixed and adhering clay or sand is disintegrated or softened, and subsequently treatingv the soaked material by a further Washing and screening treatment to remove disintegrated clay and sand from the phosphate rock.

10. The further improvement in the process of claim 2 in which disinte rated and partially cleaned phosphate peble material is subjected to a separating treatment which separates the phosphate material into a portion containing pebbles larger than a predetermined size and a portion containing smaller pebbles, with subjecting of these re' spective portions to further separate treatments for the disintegration or softening of admixed clay and sand, etc. and to subsequent washing and screening treatments to therefrom.

11. The further improvement inthe rocess of claim 1 in which the soaking o the material is promoted by the presence in the water of small amounts of disintegrating agents.

12. The further improvement in the process of claim 2 in which disintegrated and partially cleaned phosphate pebble material is subjected to a separating treatment whichl separates the phosphate material into a portion containing pebbles larger than a predetermined size and a portion containing smaller pebbles, subjecting the portion containing the smaller pebbles to further treatments for the disintegration or softening of admixed clay and sand, and to subsequent Washing and screening treatments to remove disintegrated clay and sand therefrom, and subjecting the portion containing the pebbles larger than the redetermined size to a further disintegrating and softening treatment for disintegrating clay and sand and then to a further sizing treatment to separate pebbles smaller than the predetermined size therefrom, admixing the smaller pebbles with the portion previously separated and containing similar smaller pebbles, and subjecting the admixed smaller pebbles to further treatment to remove admixed clay and sand therefrom.

In testimony whereof I affix my signature.

J. TREADWELL BULLWINKEL.

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