US2331890A

US2331890A - Mining and recovery of potash compounds

Info

Publication number: US2331890A
Application number: US401104A
Authority: US
Inventors: Cross Roy
Original assignee: KANSAS CITY TESTING LAB
Current assignee: KANSAS CITY TESTING LAB; KANSAS CITY TESTING LABORATORY
Priority date: 1941-07-05
Filing date: 1941-07-05
Publication date: 1943-10-19
Anticipated expiration: 1960-10-19

Description

1943. I R cnoSs; 2,331,890

MINING AND RECOVERY OF zogmsa COMPOUNDS 1 Filed July 5, .1941 :5 sheets-sheet- 1 V fly /056 Patented Oct. 19, 1943 MINING AND RECOVERY OF POTASH COMPOUNDS Roy Cross, Kansas City, Mo., assignor to Kansas City Testing Laboratory, Kansas City, -Mo., a

corporation of Missouri Application July 5, 19 41, Serial No. 401,104

8 Claims.

This invention relates to an improved process of recovering potassium salts from brines and ores containing them, and the present application is in part a continuation of my co-pending application Serial No. 267,506, filed April 12, 1939, which in turn is a continuation of my application Serial No. 136,178, filed April 10, 1937, now matured into United States Patent No. 2,161,800.

In the present methods of mining and recovering potash, ores are mined by shaft, room and pillar type of mining, analogous to ordinary shaft type coal mining. It is necessary to leave large amounts of the ore underground for pillars, walls, and ceilings, in order to assure safe working conditions and support. In the Carlsbad area in New Mexico, sylvinite is mined in this manner but only-50% to 60% of the ore is removed from the deposits. As shown in my earlier application which uses asuperheated liquor for dissolving potash salts from deposits, substantially all of the potash salts are removed from the deposits, leaving most of the sodium chloride in situ. In the course of this removal of potassium salts, a certain amount of sodium chloride is always present in the circulating liquor, One of the objects of the present invention is to provide a novel means of recovering the potassium chloride from the hot brine without recovery of this sodium chloride. Obviously, this is of advantage over the present method'of elevating the ore mixture of potassium and sodium chloride to the surface, separating the potassium chloride and sodium chloride, and disposing of the sodium chloride. This disposal of sodium chloride is a source of considerable trouble at -the present time, it being alleged that streams are polluted thereby.

In the present art, the recovery of potassium chloride from sylvinite ore is done in two ways, one of which comprise a flotation and classification system dependent on selective wetability and on the diflerence in specific gravity between potassium chloride and sodium chloride, while the other depends upon a leaching of the sylvinite ore with warm water at atmospheric pressure. The amount of equipment to produce 1,000 tons of potassium chloride per day by ordinary leaching is tremendous, since the brines must be recycled slowly in great quantities to. dissolve the salts at this rate. Another object of the present invention is to provide a more emcient and economical method for producing potash from sylvinite.

Other objects and advantages of the invention will be apparent by reference to the following description in conjunction with the accompanying drawings, in which:

Figure 1 is a diagrammatic or schematic illustration of amining and extracting operation performed in accordance with the present invention;

Figure 2 is a chart showing the solubility of various materials that may advantageously take part in the practice of the invention as applied to sylvinlte;

Figure 3 is a diagrammatic or schematic illustration of another embodiment of the invention;

Figure 4 is a cross-sectional view taken along the line 4-4 of Figure 3; t

Figure 5 is a cross-sectional View taken along the line 5-5 of Figure 3.

Figure 6 is an elevational view with parts broken away of a modified form of the invention illustrating a reflux vaporization vessel 40 of the type shown in Figure 1 in series with a precipitation tank I58 of the type shown in Figure 3.

For purposes of description, a typical operation on sylvinite as the salt ore will be relied upon.

Curves

3 and 4 in Figure 2 show the concentrations in pounds of potassium chloride and sodium chloride respectively, per pounds of water. The respective illustrative maximum and minimum temperatures contemplated in this description, and the solubilities of the salt thereat are as follows:

It should be borne in mind that any increased concentration of the brine solution will precipitate sodium chloride. I

In a mining operation, high pressure is of advantage in securing penetration into the bed as an aid to the high temperature of the solution for dissolving potash salt, although this is-not so important in the extraction above ground from ores that have been broken up.

Referring to Figure 1, the operation in accordance with this invention as described now is the mining modification. Assuming the process to be in operation, one cycle will be described for recovering potassium chloride from an underground deposit of sylvinite. A mother liquor, the composition of which is substantially a solution as follows: A well has been drilled into the potash bed, the bottom being approximately level with the bottom of the deposit. A large casing 16 is set in the well, the bottom of the casing being set approximately level with the top of the deposit. It is desirable to tightly seal the casing to the surrounding formation to prevent pressure leaks and also to insulate the casing.

A surface pipe is often desirable. Inside of casing 16 is set smaller diameter production pipe 18. The bottom of pipe 18 is near the bottom of the potash bed and its top passes through pipe l6 above ground in a pressure tight joint. The

superheated unsaturated brine passes downwardly in the annular space between pipes l6 and I8 and into the potash deposit where it dissolves potassium chloride. It should be assumed that a pool of liquor in the deposit is being substantially saturated with potassium chloride and that the hot brine is added to the pool. The hot brine is introduced to the bottom of the pool and gives a stirring action as it travels laterally across the pool. The equilibrium in the pool is disturbed and more potash is dissolved from the faces of the potash bed.

It is characteristic of potassium chloride that it takes up heat upon being dissolved, and therefore the brine becomes cooler and, during its dissolving action travels downwardly along the face of the potash wall. Some radiation of heat takes place into the salt deposit and into the earth above and below the deposit. Also heat equal v to the specific heat of both the potassium chloride being dissolved and the sodium chloride remaining, must be furnished. As the brine becomes saturated, it again travels horizontally at the lower part of the pool toward the well where it is released upwardly through production pipe l8. The brine has lost some of its original heat in radiation and in heat of solution of potassium chloride, and therefore is cooler as it travels upwardly in pipe l8, than is the downgoing liquor surrounding the pipe. This is an important arrangement because the upcoming brine is saturated with respect to potassium chloride and any cooling effect would precipitate potassium chloride and clog the production pipe. From production pipe [8, the superheated saturated brine passes through valve 80, conduit 86, and pressure release valve 38 into separator 40, Conduit 66 is well insulated or heated to prevent drop in 20a. It should be noted that conveyor housing 48 preferably extends above the level of the pool of brine in separator so that a draining action may be obtained.

When the vapor has flashed from the brine, it immediately comes in contact with vapor precooling coils 32 and thence passes to condenser 26. The vapor is thus completely condensed and the condensate, being pure water, refluxes downwardly into the pool of the separator. This water condensate continually washes the condenser and coils and keeps them clear of, salts. In some instances, it is desirable to have an auxiliary condenser to insure complete refluxing of the vapors. This condenser may be cooled in any suitable manner.

The rate of flow of the liquor through separator 4D is slow enough that the desired minimum temperature can be reached. The cooled brine passes out of separator "through conduit which is arranged to form a seal against the escape of vapors from the separator. The brine empties into tank 20.

The potassium chloride salt in zone 42 has 'come down substantially free from sodium chloride, due to the fact that the solubility of the sodium chloride is approximately the same at the temperature of the brine. The brine passes into the body of liquid in separator ill and part of it immediately flashes into vapor, thereby cooling the brine and precipitating potassium chloride. Baiiles ll prevent the mechanical elevation oi. salt into condensing coils 32 and condenser 26. The hot brine may be introduced either above or below the level 01 the liquid in separator 40. The bottom of separator ll is conical or hopper shaped to form a precipitated potash collecting zone12. In the bottom of zone 42 is a conveyor arranged to pick up the precipitated potash and carry it to stock pile low temperature of the pool as it was at the high temperature in the deposit. The material in the stock pile will contain some moisture which is in the'form of the saturated potassium chloridesodium chloride cold brine. The salt may be washed with a solution saturated with respect to potassium chloride, thus removing all sodium chloride. It is then dried and treated in a suitable manner for commercial sale.

Since it is desirable to maintain the pool of liquor in the potash deposit full of liquid, makeup fluid is added to tank 20 or at some suitable point. The make-up fluid is added in a volume equivalent to the volume of salts removed from the deposit. Brine seepage is also made up. The make-up fluid is ordinarily plain water. If

- it is convenient to make a sodium chloride brine for make-up fluid, this may be done in order that.

there will be no solution of sodium chloride from the deposit.

The cool brine is circulated from tank 20 by pump 24 through line 22 into condenser 26.

The rate of circulation of the brine through condenser 2a is sufllciently fast to prevent the brine from absorbing more than enough heat to raise it to approximately its boiling point. Thus, the coolest brine is the cooling medium for the condenser in what ordinarily is the final refluxing stage of the condenser. An important feature of the invention is the fact that in many instances approximately the amount or brine in the system can be used as the cooling medium for condensing the vapors and absorb a considerable quantity of heat from the vapors prior to being reheated in'the heater 34. This makes for economy of operation and equipment. From condenser 25 the brine passes through conduit II and is pumped by pump III at high pressure through vapor precooling coil 32 of the separator and thence is recycled through the system heretofore. described The circulating of the brine at high pressure through coil 32 is an important feature of the invention inasmuch as it allows sufllcient precooling of the vapors by a brine which is already under pressure and therefore need not vaporize to allow a complete flnal absorption ofhea-t from the vapors by condenser 28 where the cooling medium is at or near this extraction,

been dumped into salt basin 88.

assnseo T atmospheric pressure. If precool'ing coil 82 is not used, condenser 26 must be'larger in order to accomplish its purpose and a large amount of cooling agent other than the recycling brine is refluxed. The factors controlling this feature are the final temperature of the brine introduced into the potash bed and the amount of make-up water required to replace the volume of salt taken from the bed.

It is'sometimes of advantage to pass the makeup fluid through auxiliary condenser i? before adding it to the brine to be recirculated.-

A modified application of the invention is an operation Where the salt is dissolved from an ore which has been brought above ground and placed in extractors. For purposes of description it is assumed that the ore is sylvinite and that the salt desired to be recovered is potassium chloride. Multiple extractors are used so that while the ore in two of the extractors is being contacted with brine, the third extractor may be filled with chloride, extractor 54 is cut out o! the system and the superheated brine enters extractorbt through valve its, exits through valves cc and "12, conduit we and valve ltd, into extractor 52, valve 92 ore, thus making a continuous system. Any I number of batteries of extractors may be used. Since the treatment of the brine in various stages has been described in connection with the mining operation, this description will describe a typical cycle in the recovery of the potassium chloride from sylvinite ore.

Well it is by-passed from the system by closing valves 88 and 8%. Mother liquor is superheated in heater and passes through valve it, conduit 58, and valve l2, into extractor $2. The rate of flow is such that the brine issuing from the extractor is substantially saturated with potassium chloride. The saturated brine circulates from extractor 52 through conduit 6t, valve 76, conduit it, valve it, conduit to, and pressure release valve 38, into separator cc. Potassium chloride crystallizes, settles and is carried out by conveyor '45 to stock pile 28a. The brine is cooled by reflux vaporization without concentration of the brine and the potassium chloride recovered as described in' the mining operation. The cooled brine leaves separator an .by conduit 50, falling into tank 29. It is then recirculated by pump 24 through conduit 22, through condenser 2t, conduit 28, high pressure pump 36, and vapor precooling coils 32, to-heater as previously described. In this instance, it is not necessary to add any considerable amount of make-up fluid since there is no requirement to fill a cavity as in the case of the mining operation;

When most of the potassium chloride has been extracted from extractor 52, valve 13 is closed and the brine passes through valve 82 into extractor 54, and thence to the separator it through conduit 62, valves 5% and 86, conduit 66, and pressure release valve 38,, and the cycle is continued. In this manner unsaturated brine cleans up the ore residue in extractor 52 before entering extractor 55. When the ore in extractor 54 is nearly exhausted of potassium chloride, extractor 52 is by-passed and the superheated brine enters extractor 54 through valve 88 and exits through conduit 62 and

valves

85 and 98 into extractor 56, valve 86 being closed. In this manner, the unsaturated brine passes through the mostly exhausted ore in extractor 5d, thence through extractor 56 being closed. From extractor 52, it continues through conduit to, valve N, valve i8, conduit 86, and pressure release valve 38, into separator 4c, and the cycle is continued. In the meantime, the sodium chloride and other residue %is dumped from extractor ed and the extractor is recharged with fresh sylvinite. In this manner, the most complete extraction of the ore maybe obtained at a given rate of flow of the brineby thus continuously rotating the flow through the extractors and continuous operation is maintained.

Only one extractor may be used,or only two extractors may be used, the latter being the more desirable.

The novel method'of o ling a saturated brine .to obtain crystallization of a desired salt is a great improvement over the present art,particularly when it is combined with the feature of preheating the cooled brine by passing it in heat exchange relationship with the vapors to be condensed and passing the brineagain through the heater. Equipment requirements are much smaller than in the present art. Higher circulation rates may be continually used and mechanical cooling difiiculties are eliminated.

On properties already in operation by shaft mining methods, it is desirable to decrease the production costs of at least part of the ore mined by using the well type method covered in my co-pending application, and to also continue the use of the shaft mining equipment. Thus, it is convenient by using one system to extract salt from underground and from ores brought above ground, in a combination unit as shown in the drawings. J p

This invention has another feature which is important. This feature consists of adding to the saturated brine entering the separator or in the separator, a volatile vaporization agent having a boiling point lower than that of the brine. In this modification of the'process the volatile liquid, in which potash not more than slightly soluble, is continuously added to the brine, continuously vaporized from the brine to eliminate the vaporization of water from the brine, condensed by suitable means, and continuously recycled into the brine for further cooling by vaporization. An arrangement of an outside condenser connected to the separator and means for recycling the vaporization agent is shown in Fig. 3. The cooled brine may be circulated through the condenser in heat exchange relationship with the vapors in the same manner as with the previously described system.

I sometimes cool the brine in two stages, the

I Figure 1 is shown in series with the precipitation and out through conduits E i and 96, valve 92,

fresh ore, the sodium tank wt of Figure 3. The conduit 50 is connected .directly to the conduit I48 and all other numerals indicate like parts of the apparatus as previbusly described.

It is preferred that the volatile vaporization agent be one which is immiscible in the brine, although this is not a requirement.

A miscible vaporization agent may alsobe easily separated from the brine leaving the separator 40 by distilling oil any traces of the agent by a separate still treating the brine or by passing the brine in heat receiving relationship with the hot unsaturated brine leaving the condenser coils 26 or 02. Petroleum ether, butane or pentane may be used. Examples of other vaporization agents are suliuric into conduit I48 through valve I60, which is normally open, to a distributing member I52, which distributes the hot liquid having a relatively high ether, benzene, alcohol, low boiling point gasoline hydrocarbons, acetone, etc.

In Figure 1, pre-coolirm coil 82 has been illustrated diagrammatically as being in heat exchange relationship with the vaporizing zone 01' separator 40 which in turn is in direct communication with reflux condenser coils 26. Since the vapors are preferably brought into contact while still under pressure with pre-cooling coil 32, it will readily be recognized that coil 82 may be in a separate pressure chamber into which the vapors. are first flashed and then released to the reflux condenser 26. Any other suitable modification or arrangement of the apparatus illustrated may be used to accomplish the same purpose, namely, contacting the flashed vapors while still under super-atmospheric pressure with the pre-cooling coil in which the circulating liquid is likewise under superatmospheric pressure. In this manner, thebrine is depressured in several stages. An important feature of the system is that the hot brine containing salts is not brought in contact with cooling coils which would make a hard precipitate of the walls of the coils.

In carrying. out the process described it is highly important to prevent pecipitation of salts due to cooling in production pipes I8 and 66; As already indicated, this may be accomplished by heating the conduits to slightly unsaturate the solution contained therein. An alternative method is to maintain the rate of circulation of the dissolving material into and out of the potash deposit sufliciently fast to dissolve less potash than will form asaturated solution at the temperature of the production pipes above ground.

It is sometimes desirable to filter the potash brine before passing it into the separator in order to remove impurities such as dirt, iron compounds, etc., although usually settlement takes place in the deposit.

One of the preferred embodiments of this in-. vention is illustrated in Figures 3, 4 and 5. As shown in Figure 3, in this embodiment a brine is superheated in a heater IIO, then pumped through a conduit II2 controlled by a valve II4 by means of a, pump II6 thence through a conduit II 8, controlled by valves I20, I22 and I 24 into a conduit I26. The conduit I26 passes through a casing I28 into a potash bed I30 and the superheated brine from the conduit I26 impinges against the far end I32 of the potash bed, causing a backward horizontal component of cirrculation along conduit I26 into the space between conduit I26 and casing I28. The liquid passing backward is substantially more saturated with respect to potash than the entering liquid. This more saturated liquid passes through an exit in the casing I28 into a conduit I34, thence through a conduit I36 to pump I38; Valve I24 and pump I38 coact to keep pressure of the liquid in the potash bed to a desired maximum, when desirable. Valve I24 is closed to the degree necessary to decrease hydrostatic head on the bed and pump I 38 iorces the saturated brine upwardly. In normal operation the valve I40 controlling conduit I36 is open and valve I is closed. The liquid in conduit I36 is pumped by means of pump potash content in a body of liquid I 64 below the liquid level I66. The body of liquid I64 is contained in what is termed a primary precipitation tank I68. The size of this tank may vary depending upon the volume of liquid being processed and other factors.

In the central part of the tank I68 is an open ended pipe or well I60 with one end disposed in the body of the liquid and the other end above the liquid level. Also disposed in the body of the liquid is a bubbler conduit I62 provided with a number of fine holes, spray-nozzles, on simi-- lar devices I64 through which a volatile vaporizable liquid is passed and vaporized simultaneously or contemporaneously. This volatile liquid,

and the potash therein, being less soluble in the cold than the hot liquid, is precipitated and carried by means of a, conveyor I66 or other similar device, in an upward direction in the manner shown so that as it moves upwardly in the conveyor, the entrained liquid tends to flow backward down the conveyor shaft I68. The remaining solid is continuously dropped onto ,a pile I10, or into any suitable container outside of the primary precipitation tank.

A conduit I12 passes through the wall of the tubular casing I 60 and residual liquor is withdrawn from the primary precipitation tank I58 through this conduit. The residual liquor passing through conduit "2 enters conduit I18 through valve 212 controlled bythe liquid level control device 268 by means of arms 210 and then passes to conduit I80, from which it enters a secondary precipitation tank I82 at a point below the liquid level I84, as illustrated in Figure 3. Valve I16 in conduit I 14 is normally closed but in certain instances it may be desirable to bypass valve 212 by opening valve. I16. In the secondary. precipitation tank I82, further precipitation of salts occurs due to the influence 0f the cooling coils I86. Precipitated salts are carried from the bottom of the precipitation tank by means of a conveyor mechanism dropped onto a pile I80 in the manner illustrated. Residual mother liquor is drawn off by means of a. conduit I92 and is pumped by means of a pump I84 through a conduit I98 into a condenser I88 where it assists in cooling and condensing the butane, or other volatilized liquid previously employed as a direct cooling medium in the primary precipitation tank I58. The mother liquor passing through the condenser I88 enters a, conduit 200 through which it passes to a conduit 202 controlled by valve 204. Generally it is desired to return thismother liquor to the It will be understood thatmany diiierent types oi heaters may employed and hence, the parl88 and ticular structure of the heater will not be described in detail. In some instance it may be desirable to by-pass a part or all of the liquid passing through conduit 42 to a conduit MB. In this latter event, the valve 206 is closed or partly closed and the valve 853 is open or partly open, permitting the by-passed liquid to go as a refrigerant and simultaneously cooling the body of liquid i5 1 and the hot liquid entering through the distributing member H52. The volatilized vapors or gases rise upwardly in primary precipitation tank I58 and the mist is largely separated therefrom by a mist screen 2i ,6. The gases and vapors which pass the mist screen 2 lb enter a conduit 2l8 from which they pass into a suction chamber 220. From the suction chamber 220, gases or mixtures of gases and liquids, are passed through a conduit 22d controlled by a valve 226 and are compressed by means of compressor'228, after which they are passed

throughconduits

230 and 232 into a pressure condenser 230 where they are converted substantially completely to a liquid form. The volatilizable liquid passes from condenser 230 through a conduit 236 to a cylinder or reservoir 238 where it is held under pressure suficient to maintain it in a liquid state under the existing temperature conditions. From the reservoir 238, the liquid is passed through

conduits

240, 242, 240, 246 and valve 208 to the distributing conduit 182. In this manner the volatile liquid is continuously re-cycled in the process and the refrigerating effect thereof is utilized over and over again.

Figure 4 is a cross-sectional view of the primary precipitation tank taken along the line -4 of Figure 3, and Figure 5 is a cross-sectional along the line 5-5 of Figure 3.

In the foregoing description certain by-pass arrangements are not described. These arrangements are intended to be used under certain spepump MB is by-passed by

conduits

250, 252 and 25 3, controlled by valve 256. It willbe understood that the valve 258 is normally closed unless the by-pass arrangement is being used, in which case valve H4 would be closed. This bypass arrangementmay be employed where the pump is unnecessary, as, for example, where a source of a salt containing liquid-is available under superatmospheric temperatures and pressures. Conversely, pump H6 may furnish pressure to circulate brine into and out of the potash bed to the surface where pump I38 is by-passed.

A second arrangement of conduits compris- 255, is provided to circulate some hot unsaturated potash carrying liquid into conduit M2 to prevent precipitation on the way to the cooler I58. This is accomplished by partly op ning valve 284, and. partly closing valve I24. Valve I22 is open. This is an important feature of the invention. Since the only means of heating the potash bed and pool therein is by

heat transing conduits

258, 260 and 262 controlled by valve ferred' from the brine circulated to the bed, the amount of heating in the bed is limited to heat available from the circulated brine. Furthermore, the amount of brine circulated to obtain a desired rate of potash production per unit of time is usually insumcient to furnish the desired amount of heat to the bed and pool. To overcome this difficulty part of the brine from the deposit isrouted through the cooler and another part is by-passed and recycled through the heater without, cooling, and thu transfers view of the secondary precipitation tank taken cial circumstances or conditions. For instance,

more heat in the potash bed. Another means of accomplishing this feature is to onli Partially cool and precipitate a large quantity of brine in the cooling stage of the operation, thus giving greater heat transfer in the bed than would be available if only the brine necessary to provide' a given production rate of potash were used. This however requires handling larger volumes of liquor in the cooling stage. ,A pressure gauge 200 is proved in order to indicate the pressure of the liquid flowing in conduit 502. The liquid level in the primary precipitation tank i583 is maintained substantially constant by a liquid.

level control device 208 provided with arms 2% controlling the opening and closing of valve 212 in conduit W8. A similar device 2% maintains.

a substantially constant liquid level in tank 238 in conjunction with arms 27% and valve 270.

A typical illustration of the operation of the foregoing process is as follows: The solvent liquid passing through heater H0 is heated to a temperature of between 400 and 000 F. The pump H 3 pumps the at about 50 gallons per minute under a maximum of about 500 lbs. per square inch pressure. The pump H38 pumps the solvent more saturated with respect-to potash atabout 50 gallons per minute'under a maximum of about 600 lbs. per square inch pressure. Pump 0% is suitable ior pumping the mother liquor at 50 gallons per minute under 500 lbs. per square inch pressure. The butane tank 238 is under a pressure of about 125 lbs. per square inch and the condenser 200 is under approximately the same pressure. The temperature of the more saturate liquor entering the primary precipitation tank from conduit M0 isaround 300 to 500 F. The temperature of the liquor leaving the primary precipitation tank 558 through conduit H2 is around 200", F. The temperature of the brine leaving the secondary precipitation tank 82 through conduit 892 is around 60 to F.

As illustrated, a portion of the butane in conduit 240 is directed through conduit 200 controlled by valve 282 to cooling coils 180 from whence it passes through conduit 280 to suction chamber 220. Thereafter, it is re-compress'ed by compressor 220 and condensed in condenser N0, as already described.

In practicing the invention it is possible to recover and mine the potash from a plurality of separate beds. As is well known, manypotash deposits lie in multiple beds of comparatively thin character, for example, from 6 in. to 3 ft.

in thickness. By ordinary methods these beds cannot be mined practically because working brine heated solvent liquid mented. At predetermined points opposite the beds of potash pieces of a soft material are placed in the casing which are of such nature that they can easily be cut out and removed. These are usually of an aluminum type and one casing suitable for this purpose is called by the trade name Securalloy. When the casing has been properly set and cemented, a drill bit and reamer are used to cut out the soft aluminum casing and any cement back of it thus opening up the formation at the desired horizon and leaving the casing tightly cemented otherwise. The liquid mining of the potash may then be carried out in the manner herein described. The particular method of dissolving the potash from the vein may be, for example, any one of the methods described in my U. 8. application Serial No. 278,663, filed June 12,1939, now Patent No. 2,251,916 issued August 12, 1941. By boring a series of holes in the casing at the proper levels, a plurality of potash deposits may be mined simultaneously. This is preferably accomplished by directing a jet of liquid laterally along the potash vein in the direction in which the potash is to be mined thereby progressively creating a channel in the potash and causing a backward component of circulation toward an exit conduit along or within the casing, or to another exit hole. Thus, where horizontal circulation is obtained, beds of 3 ft. thickness will average the value of a single bed in the pres ent operations having a 15 ft. thickness.

In some ores such as polyhalite, it is of great value to use a superheated solutionof a salt for contacting the ore which, under heat and pressure, will convert the salt desired to a more soluble form. Thus, the use of sodium chloride or calcium chloride brine for the mining of poly halite and obtaining potash and magnesium salts as chlorides rather than sulfates, is highly desirable.

The use of superheated brines or dissolving liquors for extracting reduces the production of calcium sulfate as an impurity and this is an important feature of the invention. Also, the mother liquor being a brine contributes a better heat transfer in the heater than would plain water.

In order to reduce corrosive action of the brine of the process, the pH of the brine may be raised by adding a convenient alkaline agent. Calcium or sodium hydroxide is usually satisfactory for this purpose. Inhibitors such as nicotine, arsenious oxide, quinoline ethiodide and the like are added to decrease or eliminate corrosive effects.

becomes more concentrated with respect to potassium chloride, the steps of passing said more concentrated liquor into a substantially constant volume body of a relatively cooler mother liquor whereby potassium chloride is precipitated, refluxing and returning to the body of pounds, passing said heated solvent liquor into a In attacking refractory ores, it is desirable to add CO2 gas to the water being charged into the ores. In such cases the C0: is recovered by release of pressure and sent back into the well with the entering brine.

Where bromine and iodine occur with the potash ores, it is convenient to treat the brine at intervals with chlorine and steam to recover such bromine and iodine by fractional condensation.

Having thus described the invention, what I claim as new and desire to secure by Letters Patent of the United States is:

1. In a process of mining sylvinite from subterranean deposits thereof and of recovering potassium chloride therefrom wherein a heated solvent liquor unsaturated with respect to potassium chloride is circulated in contact with saidsubterranean deposit of said ores, circulating said solvent liquor in contact with said subterranean deposit until said liquor becomes more concentrated with respect to said potassium compounds, removing said solvent liquor from said subterranean deposit and passing it into a main body of mother liquor, separating potassium compounds from said mother liquor, continuously removing a portion of said mother liquor from said volume of liquor and subjecting it to further cooling, separating a further amount of potassium compounds from said further cooled .portion of said mother liquor, adding to said main body of mother liquor a water immiscible volatilizable liquid vaporizable at the temperature of said mother liquor, continuously volatilizing and condensing said solvent and using a portion of said solvent for the further cooling of the portionof mother liquor withdrawn from the main body thereof.

relatively more concentrated liquor out of the sylvinite deposit, circulating part of said liquor to a depressuring and cooling zone and recirculating the other part of said potash liquor through a heating stage and thence through the sylvinite deposit.

4. A cyclic process of mining potassium compounds from underground deposits thereof which comprises establishing a zone containing a main body of an aqueous mother liquor which is a solvent for said potassium compounds when unsaturated with respect thereto, withdrawing from said main body of mother liquor a portion thereof, heating said withdrawn portion of mother liquor whereby to produce a solvent liquor unsaturated with respect to the potassium compounds to be mined, passing said heated solvent liquor into a subterranean deposit ofsaid potassium compounds, circulating said solvent liquor in contact with said subterranean deposit until said liquor becomes more concentrated with respect to potassium compounds, adding to the mother liquor at some stage during the cycle of 5. A cyclic process of mining potassium com pounds from underground deposits thereof which comprises establishing a zone containing a main body of an aqueous mother liquor which is a solvent for said potassium compounds when unsaturated with respect thereto, withdrawing from said main body of mother liquor a portion thereof, heating said withdrawn portion of mother liquor whereby to produce a solvent liquor unsaturated with respect to the potassium compounds to be mined, passing said heated solvent liquor into a subterranean deposit of said potassium compounds, circulating said solvent liquor in consium chloride, the steps of cooling said concentrated liquor in one stage by reflux vaporization from self-contained heat of the liquor, andcooling the liquor in a second stage by vaporization of an added water immiscible volatile agent at least partially by the self-contained heat of the liquor, while separating solid potassium chloride therefrom during said cooling stages.

7. in a cyclic process of the character described for recovering a potassium compound from an ore containing it, the steps which comprise establishing a zone containing a main body of a saline mother liquor, which is a solvent for said potassium compound when unsaturated with respect thereto, continuously withdrawin from said main body of mother liquor a portion thereof, treating said withdrawn portion to increase its dissolving action on said potassium compound, passing the treated portion into contact with said ore containing said potassium compound to thereby increase the concentration of tact with said subterranean deposit until said liquor becomes more concentrated with respect to potassium compounds, adding butane directly to the zone containing the main body of mother liquor, passing said more concentrated liquor into said main body of mother liquor to continuously volatilize said butane, condensing and returning to said zone the butane thus volatilized, said main body of mother liquor thereby being maintained at a relatively lower temperature than said more concentrated liquor, adding to said main body of mother liquor a suflicient amount of water to maintain the concentration of dissolved solids with respect to the volume of solvent liquor in said main body substantially constant, at least a-- portion of said added water being derived by refiuxing the vapors arising from said main body, whereby the potassium compounds are precipitated without substantial precipitation or other compounds, and separating said precipitated potassium compounds from said main body of mother liquor. q

6. In a process of mining potassium chloride from an ore containing it wherein a heated solvent liquor rmsatm'ated with respect to potassium chloride is circulated in contact with a subterranean deposit of the ore until said liquor becomes relatively more concentrated with respect to potasthe potassium compound therein, returning the more concentrated liquor to said main body of mother liquor, adding water to the main body of mother liquor to maintain the concentration substantially constant and to prevent the precipitation of other than potassium compounds, and separating the potassium compound from said body of mother liquor.

8. In a process of mining potassium compounds from subterranean deposits thereof and'oi recovering potassium compounds therefrom wherein a heated solvent liquor unsaturated with respe'dt to the potassium compound is circulated in contact with said subterranean deposit containing the potassium compound until the liquor becomes more concentrated with respect to the potassium compound, the steps of passing said more concentrated liquor into a substantially constant volume body of a relatively cooler mother liquor whereby the potassium compound is precipitated, refluxing and returning to the body of said mother liquor the vapors arising therefrom, separating the precipitated potassium compound from the both of said cooler mother liquor, ccm-' tinuously removing aportion of said cooler mother liquor and continuously passing it'into heat archange relationship with said more concentrated hot liquor thereby to assist in cooling said more concentrated liquor and at the same time causing said cooler mother liquor portion to be heated,

reheating said mother liquor portion further and recycling it as a mining fluid in the process.

soreness.