US2211396A - Process of treating sylvinite ores - Google Patents

Description

Aug. 13, 1940. A J WEINIG 2,211,396

PROCESS OF TREATING SYLVINITE ORES Filed June 28, 1935 L/Vaf/ /vac/ Nac/ @lem/M Cleaner Cleaner 3&1

a/numan, #fm @WMS Patented Aug. 13, 1940 UNITED sTTEs PROCESS F TREATING SYLVINITE ORES Arthur J. Weinig, Golden, Colo., assignor to Potash Company of America, Denver, Colo., a corporation of Colorado Application June 28, 1935, Serial No. 28,983

16 Claims.

This invention relates to a process for separating the soluble and valuable constituents from sylvinite ores and the product or products to be obtained by such process.

Sylvinite ore consists mainly of sodium chloride and potassium chloride crystals, together with small amounts of other mineral matter, such as iron and manganese oxides, clays and the like. The sodium chloride and potassium chloride crystals in the ore are found as distinct crystals, with a more or less amount of the two crystals intimately associated together. Both are soluble in water, but with different rates of solubility with respect to the temperature of vthe solution. Both are fioatable by the froth otation process in a saturated water solution of the sylvinite ore, but each requires a different reagent or reagent combination, to produce flotation. In the present invention advantage is taken of the differences in rate of solubility and flotation properties to effect a separation between the two salts.

'I'he object of the invention is to obtain potassium chloride in a practically pure form byl treating ore composed essentially of potassium chloride, sodium chloride and various clays and other gangue matter in a method employing a combination of iiotation and crystallization treatments. In this method the sodium chloride, with clays and other gangue matter, is rejected as a waste product.

Generally stated, the invention consists in forming a. saturated solution in water of the constituents of the ore, which mainly consists of 3` sodium chloride and potassium chloride and introducing into this solution the sylvinite ore in a nely divided condition, thus forming a pulp,

and then separating the sodium chloride, as well as any gangue that may be present, from the pulp o by flotation. The specific gravity of sodium chloride is 2.2, while the specific gravity of potassium chloride is 2., -and in order to float ofi' the sodium chloride a selective reagent or reagents is or are employed to cause air bubbles, produced in the solution in any suitable manner, to float the sodium chloride to the surface of the solution without affecting the potassium chloride, or if affecting it, to retard or depress any dotation thereof. 'Ihe reagent employed consists of any fatty acid or as the equivalent thereof a derivative of a fatty acid or mixture thereof which is capable of being dissolved in the saturated brine solution employed, together with lead and/or bismuth salts, also dissolved in the saturated solution. It is to be particularly pointed out, as indicated above, that the fatty acids or derivatives of fatty acids employed must be such as are capable of being dissolved in the saturated solution of the ore, such for example as cocoanut oil soap and palm kernel oil soap. There are certain fatty acids and derivatives of fatty acids which are insoluble in such a solution, and such are not included inthe class of fatty acids or derivatives of fatty acids to be employed as a reagent. But it is to be expressly understood that the term f atty acids as used in this description and in the claims is intended to include not only fatty acids strictly as such but also any derivative or derivatives of fatty acids which are soluble in a saturated solution of sodium l@ chloride and potassium chloride. Furthermore, when a straight saturated solution of potassium chloride and sodium chloride has its temperature reduced, potassium chloride crystallizes out, but when lead and/or bismuth salts are present in 0 the saturated solution, potassium chloride will not crystallize out of the solution, even with material cooling of the solution, unless potassium chloride in solid form is present in the solution to act as seed," and even then the potassium chloride crystallizes only on the seed and not on the surface of pipes, containers and other parts. The result of thisis that clogging of the pipes, etc. is avoided by the presence of the lead and/or bismuth salts in the solution. Another advantage lies in the fact that such salts almost entirely prevent corrosion of iron surfaces by the brine solution.

When potassium chloride and sodium chloride are dissolved in water at approximately 70 F., in the presence of sylvinite ore, the amount of sodium chloride passing into solution greatly exceeds that of the potassium chloride, so that when the saturated solution is obtained it is what may be appropriately termedva brine or salt solution, and it is this saturated solution that is preferably employed in the initial otation of the sodium chloride. It will be understood that inasmuch as the water solution in which the finely divided particles of the sylvinite ore are deposited is a saturated solution containing dissolved lead or bismuth, the ore thus deposited in the solution remains in solid form, and the mixture of this solution and the finely divided ore constitutes, and will hereinafter be, referred to as, the pulp.

The flotation step may be carried out in any suitable flotation cell, and preferably it is carried out in a plurality of such cells associated together in series, in which cells the ratio of ore to solution may be varied. Thus. in the first flotation cell a large portion of the sodium chloride, and gangue if present, may be oated out while still leaving in the pulp some of the sodium chloride, and this is removed by a repetition of the flotation process in the succeeding cells to the end that the pulp passing from the final cell is a nearly pure potassium chloride in solid form carried by the saturated solution, together with small quantities of iron oxide and manganese oxide.

Furthermore, it has been found that the flotation froth passing from the several flotation cells carries not only sodium chloride (in solid form) but also more or less of potassium chloride (likewise in solid form), and in order to effect a complete recovery of the potassium chloride, it is necessary that this potassium chloride, associated with the sodium chloride froth, be also recovered.

If the temperature oflthe saturated solution carrying the sodium chloride froth with its associated potassium chloride be raised, the amount of potassium chloride that will be dissolved in the heated saturated solution will be largely increased over that dissolved at a lower temperature, whereas the amount of sodium chloride that will be carried by such heated solution will be decreased. Advantage is taken of this to pass the potassium chloride that is thus associated with the sodium chloride in the flotation froth into solution and afterwards to recover the same from this enriched solution. To this end the saturated solution carrying the sodium chloride froth from the flotation cells is rst heated under agitation, and then While still heated, sodium chloride is permitted to settle out of the solution, and after separating the settled sodium chloride from the solution, the solution is cooled in the presence of solid potassium chloride otherwise obtained in the practice of the' process. The solid potassium chloride affords seed upon which potassium chloride carried in the heated solution, referred to above, will crystallize out upon cooling, and such solidV potassium seed may be derived from the flotation cells or otherwise. The result of this procedure is that very nearly all of the potassium chloride contained in the sylvinite ore under treatment is recovered.

The sodium chloride that settles out of the heated solution and separated, as indicated above, may be purified and freed from moisture, and is then ready for sale or other disposition.

The potassium chloride sludge, which is the pulp remaining from the above sodium chloride flotation and is freed from the sodium chloride,

has the liquidi separated therefrom in any suitable dewaterer, which liquid, with more or less finely divided solid potassium chloride, is passed to a potassium chloride thickener, While thebody of the thickened sludge from the dewaterer combined with the settled solids from the thickener is transferred to a centrifuge where the remaining solution is removed, the solid potassium chloride washed and prepared for drying.

The several steps of the process above described will be best understood from a reference to the accompanying ow sheet which is, in effect, a plan view of a milling operation embodying the process of my invention. Reference numeral I indicates a grinding mill, which is preferably a pebble mill, it being essential to avoidl any class of grinding mills that present polished iron surfaces, since the lead or bismuth in the saturated solution wouldbe precipitated out of the solution ii' brought in contact with polished iron surfaces; 2 indicates a suitable hopper for delivering the ore to the mill, and 3 indicates a tank containing the saturated solution of sylvinite ore from which tank the solution is transferred through conduits indicated by the dotted ,linea to the several flotation cells and other parts of the apparatus, including the pebble mill I. The crushed ore from the pebble mill is delivered, preferably by a pump 4. to any suitable classifier 5 where the finer particles suitable for treatment in the flotation process are separated from the coarser particles, which latter are returned from the classifier to the mill I through the hopper 2, while the finer particles are delivered to the initial notation cell 6, where, being mixed with the saturated solution of constitutients of the sylvinite ore, they form a pulp. Suitable reagents in the form of fatty acids or derivatives of fatty acids that are soluble in the saturated solution are added to the saturated solution at any suitable point, as well as lead and/or bismuth salts. The amounts of the reagents may vary under different conditions, but it has been found that about four pounds of the fatty acid or de rivatives of fatty acids per ton of ore treated is usually required when the solution contains about two pounds of dissolved lead and/or bismuth per ton of the solution. These reagents are freely dissolved in the solution, and during thepractice of the process the fatty acid or derivatives of fatty acid will be more or less consumed and additions will have to be made thereto, but the lead and/or bismuth remains unconsumed except for a very slight loss that is carried off in the saturated solution that adheres as moisture to the concentrate. This slight loss is taken care of by suitable additions. As a matter of practice the main part of the reagent is added to the saturated solution in the flotation cell 6, but other additions may be and generally are made at other points as hereinafter referred to. There may be, and preferably there are, a plurality of such original flotation cells, as shown for example at 6 and 6. These flotation cells 6 and 6' are provided with suitable agitators whereby, with proper introduction of air, bubbles are formed in the pulp, and the effect of the reagents is to cause the sodium chloride to adhere to the bubbles which rise to the surface and are floated of! in the shape of froth into the flotation trough 6". It has been found that the froth thus delivered from the flotation cells 6 and 6' carries with it not only solid sodium particles but also the gangue material of the ore and some of the solid particles of potassium chloride, and therefore, in order to effect a maximum recovery of all of the potassium chloride in the ore, steps are taken to separate this potassium chloride from the sodium chloride froth. To this end the froth is passed into one or more, and preferably a series (here shown as three) of so-called cleaner cells `I-'I, arranged in series, which cells operate on identically the same principle as the original flotation cells 6 and 6', floating oi the sodium chloride in the form of froth into the froth trough 1', to the end that the froth thus delivered from the last cleaner cell 'I is substantially free from potassium chloride, except certain small particles of potassium chloride and sodium chloride which are intimately associated together.

The pulp remaining in the original flotation cells 6 and 6', after the sodium chloride has been floated therefrom, is passed from the cells 6, 6

directly to cells technically known as middling cells. This pulp is composed largely of theV saturated solution and potassium chloride, but

there are almost invariably small particles of sodium chloride attached to particles of potassium chloride and these attached particles are floated to the surface in the cell 3 and delivered into the trough 8'., additional reagents. being added at the cell 8. From the trough 3' the froth is delivered to any suitable dewaterer 3. where the saturated solution is to a very large extent separated from the solid particles. these particles being delivered to the hopper 2 to be reground, while the solution is delivered through the pump I to the classifier and returns to the system.

The sodium chloride froth, with small particles of potassium chloride attached thereto or intimately associated therewith, and which has been passed to the cleaner cells 1 is delivered from the last one of the cells I to a container IIl provided with means for heating its contents and also with means for agitating the same. This is technically known as a heating agitator. The sodium chloride froth with the accompanying potassium chloride particles carries with it, of course, more or less of the saturated solution but it may be and frequently is desirable to'supply an additional amount of the saturated solution to the heating agitator, and this is accomplished by withdrawing such saturated solution from the stock tank 3 through conduits, indicated by Iii) The pulp from the heating agitator is thenl passed directly into the container II where it is maintained free from agitation, and the sodium chloride is thus permitted to settle out. The temperature of the pulp is maintained in the container i I at approximately the same as the temperature in the heating chamber Ill so that the potassium chloride remains in solution, and only sodium chloride settles out.

Referring now to the so-called middling cells B, the pulp from those cells, the solid part of which is practically pure potassium chloride, is passed directly therefrom to a cooling agitator I2, where the temperature is lowered to approximately that of the entire system other than that in the tanks I and Ii. The sodium chloride solids having been settled out of the heated solution in the thickener tank II and separated therefrom, this solution is also passed into the cooling agitator where it comes in' contact with the particles of potassiiun chloride that have been delivered thereto from the middling flotation cells il, which particles act as seed upon which the potassium chloride in the solution from the thickener tank II crystallizes as the result of the drop in temperature in the cooling tank, the contents of this tank being agitated during the operation. A further result of the lower temperature in the cooling agitator I2 ising to the dewaterer I3,- as hereinafter described,

consists of approximately pure potassium chloride.

From the cooling agitator I2 the pulp is pass to a dewaterer I3 in which the saturated soluti n is largely removed from the potassium chloride solids and then passed to a potassium chloride thickener Il. This saturated solution thus re moved from the dewaterer and passed to the thickener I4 will carry more or less fine particlestank 3.

From the dewaterer I3 and the thickener Il the potassium chloride solids having a small amountv of solution associated therewith, is

. passed to a centrifuge I5 wherein the remaining amount of the solution is removed and passes by way of the container Il to the vstock tank 3. The centrifuging removes nearly all of the saturated solution accompanying the potassium chloride, but there remains a very small amount of suchA solution attached to the patassium chloridel particles, and this solution contains sodium chloride which it is essential to remove from the potassium chloride particles, if the potassium chloride isto be entirely free from sodium chloride. Accordingly, the centrifuged potassium chloride particles are submitted to a washing operation and thus freed from the sodium chloride contained in the original solution. To accomplish this washing without loss of any potassium chloride, and to assure the removal of the sodium chloride, the solids in the centrifuge I5 are washed with a saturated solution of potassium chloride. If perchance there are any stray particles of sodium chloride with the potassium chloride in the centrifuge IE, this saturated solution of potassium chloride will dissolve them without dissolving any of the potassium .chloride, and furthermore the saturated solution of the potassium chloride acts as the means of washing the potassium chloride in the centrifuge free from any of the original solution which contains sodium chloride. If desired, water may be used as the washing medium, in which case, the water will become saturated with potassium chloride shortly after it comes in contact with the material. This washing is preferably effected in the centrifuge IE, and this washing solution, as well as any of the original saturated solution, passes from the centrifuge I5 to the thickener I4 where any solid potassium chloride is settled out and the solution is then returned to the system by way of the stock tank 3.

While as illustrated in the flow sheet, the heating agitator I0 is shown as separate from the cleaner cells 1, this heating of the pulp may, if desired, be effected in one or more of the cleaner cells 1. Moreover, it will be recognized that inasmuch as the middlings flotation cells 8 are at a lower temperature than that maintained in the heating agitator (or if preferred, in the heated cells l), the overflow from the sodium chloride thickener Ii may be discharged directly into the middlings flotation cells 8, where the function above indicated as pertaining vto the cooling agitator I2 will take place, in which case it will be understood that cooling means will be provided in connection with the middlings flotation cells 8, vfrom which cells the potassium chloride solids with the saturated solution is passed directly to the dewaterer I3.

While the invention has been described m connection with a ow sheet, setting forth in detail certain -arrangement of the notation cells, heating and cooling agitators, thickeners, etc.. it will be appreciated by one skilled in the art that various changes and modifications in the arrangement thereof may be made without departing from the spirit of the invention as herein set forth, and it will be understood that such,

flow sheet is merely for the purpose of illustrating the invention, and not for the purpose of defining the limits thereof, reference being had to the appended claims for this purpose.

It will also be understood that fatty acids, and derivatives of fatty acids, as well as mixtures of these -are equivalents, provided only that they are soluble in a saturated solution of the sylvinite ore, and the term fatty acid used in the claims is intended to include any and all such derivatives and mixtures.

It will also be understood that, if desired, the ore may be subjected to dry grinding and the product of such grinding then introduced into a saturated solution of the ore.

It will be found that the potassium chloride secured as the result of the process herein described is not the ordinary white, chemically refined potassium chloride. On the contrary, it is granular in form and of a pinkish color due to small amounts of iron oxide and manganese oxide in the sylvinite ore and which remain with and color the potassium chloride obtained as a product. This is a product never heretofore produced and constitutes a new result achieved by combining the steps of the process herein set forth. One of the important uses of the potash produced by this invention is'in fertilizers, and the iron and manganese oxides are of value therein, and the particular form and coloring afford means as identifying the product of this process.

Where the expression containing dissolved lead is used in the claims, it is intended to designate the presence of either lead or bismuth in solution, or any or all equivalents and mixtures of the type hereinbefore described.

The invention here described and claimed utilizes the principle of selective flotation of sodium chloride forming the subject-matter of my copending application filed November 8, 1937, Serial No. 173,431 and of which one example is the subject-matter of my prior Patent 2,105,295 January 11, 1938.4 Features of the entire process disclosed but not claimed herein form the subject-matter of my copending application iiled May 25, 1936, Serial No. 81,729.

Having thus described the invention, what .is claimed is:

1. In a cyclic process of treating sylvinite ores, the steps of introducing sylvinite ore in finelydivided condition into a saturated solution of the ore, containing dissolved lead, to form a pulp, removing gangue and a substantial part of the sodium chloride from the pulp in an initial froth flotation treatment in the presence of a reagent having a selective alnity for sodium chloride and gangue, and purifying the potassium chloride in the non-floated residue of said flotation treatment by a second froth dotation treatment in the presence of a reagent having a selective aiinity for sodium chloride and returning the resulting sodium chloride froth to the cycle for reworking Aand removal'in the initial flotation treatment.

2. In a cyclic process of treating sylvinite ores, the steps of: introducing sylvinite ore in finelydivided condition into a saturated solution of the ore, containing dissolved lead, to form a pulp, removing gangue and a substantial part of the sodium chloride from the'pulp in an initial frothl notation treatment in the presence of a reagent 5 having a selective amnity for sodium chloride and gangue, and purifying the potassium chloride in the non-floated residue of said flotation treatment by a second froth flotation treatment at a controlled temperature, in the presence of a reagent having a selective affinity for sodium chloride and returning the resulting suitably cooled sodium chloride froth to the cycle for reworking and removal in the initial flotation treatment. l5

3. In a process of treating sylvinite ores, the steps of introducing sylvinite ore in finelydivided condition into a saturated solution of the ore, containing dissolved lead, to form a pulp, removing gangue and a substantial part of the zo sodium chloride from the pulp in an initial froth flotation treatment in the presence of a reagent having a selective afiinity for sodium chloride and gangue, mixing the residue of the initial flotation with a saturated sodium chlolride, potassium chloride solution at a lower temperature than the residue, and purifying potassium chloride in the mixture by a second froth flotation treatment in the* presence of a reagent having a selective afllnity for sodium chloride to thereby remove the remaining sodium chloride as a froth concentrate.

4. In a cyclic process of treating sylvinite ores, the steps of introducing sylvinite ore in finelydivided condition into a saturated solution of the ore, containing dissolved lead, to form a pulp, removing gangue and a substantial part of the sodium chloride from the pulp in an initial froth flotation treatment in the presence of a reagent having a selective ailinity for sodium chloride 40 and gangue, purifying the potassium chloride in the non-floated residue of said flotation treatment by a second froth flotation treatment in the presence of a reagent havinga selective ailinity for sodium chloride, and separating potassium chloride and sodium chloride constituents of the froth concentrate of the initial flotation in a cleaner circuit in the presence of a reagent having a selective aiinity for sodium chloride and gangue, said cleaner circuit returning 60 the non-floated residue to the cycle for reworking and separation in the initial flotation treatment.

5. In a cyclic process of treating sylvinite ores, the steps of introducing sylvinite ore in finelydivided condition into a saturated solution of the ore, containing dissolved lead, to form a pulp, removing gangue and a substantial part of the sodium chloride from the pulp in an initial froth otation treatment in the presence of a reagent having a selective anity for sodium chloride and gangue, purifying the potassium chloride in the non-oated residue of said notation treatment by a second froth flotation treatment in the presence of a reagent having a selective amnity for sodium chloride, and separating potassium chloride and sodium chloride constituents of the froth concentrate of the initial flotation in a cleaner circuit at a controlled temperature, in the presence of a reagent having a selective aflnity for sodium chloride and gangue, said cleaner circuit returning the suitably heated non-floated residue to the cycle for reworking and separation in the initial flotation treatment.

6. In a process of treating sylvinite ores, the

stepsof introducing sylvinite ore in finely-di- 76 vided condition into a saturated solution of the oreI containing dissolved lead, to form a pulp. removing gangue and a substantial part of the sodium chloride from the pulp in an initial froth flotation treatment in the presence of a reagent having a selective affinity for sodium chloride and gangue, mixing the froth concentrate of the initial flotation' with a saturated sodium chloride, potassium chloride solution at a lower temperature than the concentrate, and separating potassium chloride and sodium chloride constituents of the mixture in a cleaner circuit in the presence of a reagent having a selective amnity for sodium chloride and gangue.

7. In a cyclic process of treating sylvinite ores, the steps of introducing sylvinite ore in finelydivided condition into a saturated solution of the ore, containing dissolved lead, to form a pulp, removing gangue and a substantial part of the sodium chloride from the pulp in an initial froth flotation treatment in the presence of a reagent having a selective afilnlty for sodium chloride and gangue, purifying the potassium chloride in the non-floated residue of the said flotation V treatment by a second froth flotation treatment in the presence of a reagent having a selective aflinlty forsodium chloride to thereby remove the remaining sodium chloride as a frothconcentrate, separating the potassium chloride and sodium chloride of the froth concentrate of the initial flotation in a cleaner circuit in the presence of a reagent having a selective aillnity for sodium chloride and gangue, and returning the froth of the second flotation, and the tailings of the cleaner circuit to the feed of the initial flotation.

8. In a cyclic process of treating sylvinite ores,

l the steps of introducing sylvinite ore in finelydivided condition into a saturated solution of the ore, containing dissolved lead, to form a pulp, removing gangue and a substantial part of the sodium chloride from the pulp in an initial froth flotation treatment in the presence of a reagent having a selective aillnity for sodium chloride and gangue, purifying the potassium chloride in the non-floated residue of the said flotation treatment by a second froth flotation treatment in the presence of a reagent having a selective affinity for sodium chloride to thereby remove the remaining sodium chloride as a froth concentrate, separating the potassium chloride and sodium chloride of the froth concentrate of the initialflotation in a cleaner circuit in the presence of a reagent having a selective afilnity for sodium chloride and gangue, and returning the froth of the second flotation to the feed of Y the initial flotation.

9. In a cyclic process of treating sylvinite ore the steps of introducing sylvinite ore in finelydivided condition into a saturated solution of the ore, containing dissolved lead, to form a pulp, removing gangue and a substantial part of the sodium chloride from the pulp in an initial froth flotation treatment in the presence of a reagent having a selective affinity for sodium chloride and gangue, purifying the potassium chloride in the non-floated residue of the said flotation treatment by a second froth flotation treatment in the presence of a reagent having a selective ailinity for sodium chloride land gangue to thereby remove the remaining sodium chloride as a froth concentrate, separating the potassium chloride and sodium chloride of the froth concentrate of the initial flotation in a cleaner circuit in the presence of a, reagent having a selective affinity for sodium chloride and gangue, and returning the tailings of the cleaner circuit to the feed of the initial flotation.

10. In a cyclic process of treating sylvinite ores for-the recovery of a purified potassium chloridefp'oduct, the steps of introducing sylvinite ore in finely-divided condition into a saturated solution of the ore, containing dissolved 4 lead, to form a pulp. removing gangue `and a finely-divided condition into a saturated solution of the ore, containing dissolved lead, to form a pulp, removing gangue and a substantial part of the sodium chloride from the pulp in an initial froth flotation treatment in the presence of a reagent having a selective aillnity for sodium chloride and gangue, purifying the potassium chloride in the non-floated residue of said flotation treatment by a second froth flotation treatment in the presence of a reagent having a selective affinity for sodium chloride to thereby remove the remaining sodium chloride as a froth lconcentrate, and returning the froth of the second flotation treatment to the initial treatment stage.

12. In a cyclic process of treating sylvinite ores, the steps of introducing sylvinite ore in finely-divided condition into a saturated solution of the ore, 'containing dissolved lead, to form a pulp, removing gangue and a substantial 'part of the sodium chloride from the pulp in an initial froth flotation treatment in the presence of a reagent having a selective ailinity for sodium chloride and gangue, purifying vthe potassium chloride in the non-floatedv residue of said flotation treatment by a second froth flotation treatment in the presence of a reagent havingv a selective affinity for sodium chloride to thereby remove the remaining sodium chloride as a froth concentrate, returning the froth of the second flotation treatment to the initial treatment stage, and removing the non-floated residue of the second flotation treatment separately from the froth. v

13. In a cyclic process of treating sylvinite ores, the steps of introducing sylvinite ore in finely-divided condition into a saturated solution Vin the presence of a reagent having a selective afllnity for sodium chloride and gangue.

14. In a process of treating sylvinite ores, including wet grinding of sylvinite ore in a saturated sodium chloride, potassium chloride solution, the improvement which comprisesv introducing a saturated sodium chloride, potassium chloride solution into the grinding operation at a lower temperature than the mill discharge to prevent undue rise in temperature in the pulp occasioned by the grinding action.

15. In a process of treating sylvinite ores, including wet grinding of sylvinite ore in a saturated sodium chloride, potassium chloride solution containing lead, the improvement which comprises introducing a. saturated sodium chloride, potassium chloride solution into the grinding operation at a lower temperature than the mill discharge to prevent undue rise in tempera-

Images