3,437,451 United States Patent Office Patented Apr. 8, 1969 1. 2 3,437,451. SELECTIVE PRECIPITATION OF POTAS In a more limited aspect of this invention, the added SHUM CHILORIDE FROM BRINE USENG compounds exhibit inverse solubility in water with heat. ORGANOAMNES As has been indicated, in extracting KCl from KCl Richard L. Every, James O. Thieme, and Burton M. NaCl salt deposits, hot brine is circulated in the forma Casad, Ponca City, Okla., assignors to Continental tion. Generally, two boreholes or wells are drilled into Oil Company, Polaca City, Okla., a corporation of the KCl rich formation and a fracture is created between Delaware the two wells by well known fracturing methods widely No Drawing. Filed Dec. 28, 1965, Ser. No. 517,154 used in the petroleum art. Water is circulated initially Int. CI. B01j 17/06 forming a brine. It should be understood that the rate U.S. C. 23-300 8 Claims 10 of NaCl solution is relatively rapid, whereas, the rate of KCl solution is comparatively slow. For example, with water at 110 F. it is frequently found that the KCl so ABSTRACT OF THE DISCLOSURE lution rate will be in the range 0.01 pound per hour Potassium chloride is precipitated from a sodium chlo per square foot extracting surface. Thus, the water ra ride solution by adding an alkylaminoamine at a tem 5 pidly becomes saturated with respect to NaCl. This brine perature at which the amine is soluble in the solution. solution is returned to the surface through the produc ing well and is heated to at least 100 F. and prefer ably to 125 to 160 F. The brine should be essentially This invention relates to recovery of potassium chlo saturated with respect to NaCl prior to the time the re ride (KCl) from brine. 20 covery of KCl is undertaken. That is, the brine will con Potassium chloride usually occurs in mineral deposits tain 95 to 100% of its saturation capacity at the operat closely associated with sodium chloride (NaCl). In many ing temperature and more preferably 98 to 100%. The cases, potassium chloride exists in admixture or in com hot brine is recirculated via the injection well and since bination with sodium chloride in the form of a potas it is substantially saturated with respect to NaCl will sium chloride-rich strata, containing 15 to 60 percent by selectively dissolve the KCl. The brine then containing weight of KCl based upon the total weight of KCl and NaCl-KCl is pushed to the earth's surface where it is NaCl in the strata. These mineral deposits frequently cooled and KCl crystallizes out. The brine is reheated also contain other materials such as clay and salts of and again passed to the injection well. calcium, magnesium, usually as the sulphate, and the like We have now found that alcohols, amines and ketones in small quantities, e.g., 2 to 15 weight percent. 30 will cause increased precipitation of the KCl, thus in Subterranean deposits of such potassium chloride-so creasing the amount of KCl which can be recovered per dium chloride strata are frequently very deep. For ex cycle. These compounds may exhibit inverse solubility ample, Canadian deposits of this character are often in water with heat, thus upon reheating the brine, the found 3,000 feet or more below the ground surface. addition is either vaporized and condensed for further In recent years a great deal of interest has been shown 35 use or forms a separate liquid phase which is decanted in solution mining such deposits with water. Theoreti for further use depending upon the boiling point and cally, solution mining would appear to be attractive since the injection temperature. For example, the low molec sodium chloride is substantially as soluble in cold water ular weight alcohols such as methanol, ethanol, isopro as in hot water, whereas, potassium chloride is substan panol and the like are vaporized and condensed, where tially more soluble in hot water, thus the salt formation 40 as the amines and ketones generally employed form a can be dissolved by contacting with hot water and the liquid phase. potassium chloride precipitated after bringing the solu The additives include, but are not limited to, 2-butoxy tion to the surface by cooling. The hot salt water is then ethanol, dimethylaminopropylamine, diethylaminopropyl reheated and circulated back to the subterranean forma amine, n-amylamine, diethylaminoethanol, diisopropyl tion to selectively remove additional KCI. 45 amine, methylethylketone, diethylketone, ethylpropylke A number of solution mining schemes have been pro tone, methanol, ethanol, isopropanol, butanol, hexanol, posed for removing the KCl from such salt formations. ethylenediamine, allyl alcohol, 2-pentanol, 1,7-heptane Both single wells with hot brine flowing down one con diol, tertiary butyl alcohol, erythritol, arabitol, 1,4-pen duit and brine being produced through another and dual tanediol, cyclohexanol and the like. Mixtures of such or multiple wells have been employed. In the multiple materials can sometimes be used to advantage. well schemes, hot water or brine is pumped into an in From the above examples it can be seen that the put well and KCl enriched brine produced from one or alcohols, ketones and amines can be aliphatic, cyclic, more recovery wells. The hot KCl enriched brine is aromatic, saturated or unsaturated and can have one or cooled to precipitate KCl and the brine reheated and more functional groups, e.g., mono or di or more func pumped back into the salt formation. tional groups. It should be understood that the pressure Unfortunately, due to the large amount of fluid which and temperature conditions in the well will be such that must be heated and cooled, solution mining has not been the additive is liquid and in admixture with the brine. as economically attractive as it might be. If a larger In general, the amount of additive will depend upon percent of KCl could be recovered per cycle, solution the particular additive and its solubility; however, 2 to mining would be more competitive and large deposits of 60 100 volumes of additive per 100 volumes of brine will KCl in NaCl deposits could be tapped. be used, more generally 10 to 50 volumes additive per It is, therefore, an object of this invention to provide 100 volumes of brine are utilized. a method of precipitating a larger percent of KCl from The temperature at which the additive is added will be KCl-NaCl brine than that which is recovered simply by in the temperature range where the solvent is partially cooling. completely miscible with the brine. This temperature Other objects, features and advantages of this inven will, for most additives, be in the range 40-100° C. tion will be apparent to those skilled in the art having The KCl crystals then can be recovered from the brine been given this disclosure and the appended claims. with or without additional cooling depending upon the According to this invention, KCl is precipitated from economics of heating and cooling at the particular site. KCl-NaCl brines by addition of certain oxygen and/or 70 After recovcery of the precipitated or crystallized KCl, nitrogen-containing organic, water-soluble solvents which the brine phase is heated to injection temperature and are normally liquid such as alcohols, ketones and amines. passed through a separator to recover the additive which 3,437,451 3 4. becomes immiscible with water at the elevated temper Other materials tested as in runs 1-32 but which were ature. The additive is then cooled and recycled. only slightly effective, if at all, include acetic acid, hydro Several runs were made to determine the effectiveness gen sulfide, sulfur dioxide, carbon dioxide, diethyl ether, of the solvent additive in precipitating KCI from phthalic acid, chloroform, ammonium sulfide and butyl KC-NaCl aqueous solutions. 5 alcohol. In the first series of runs, various compounds were In this series of runs, the materials tested would be added to a saturated aqueous solution of NaCl and KCl those which would be recovered by distillation and con at room temperature (70-75 F). The NaCl and KCl densation. It can be seen in Table I that ethanol and left in solution was determined. The results are given in ethylenediamine at 10% concentration are much more Table I. effective in removing KCl than is ammonia. It is also TABLE I shown in Table III that at elevated temperatures, the alco Wol. Per- Pelicent hols were more effective than ammonia. Run No. Additive cent Con- It was also found that the precipitate formed with am ofcentration Additive SolutionNaCl in SolutionKCl in monia was slimy and extremely difficult to filter. How lb ever, the precipitate formed by the compounds of this in 10O 2017 1.4.5 ventionw was crystalline and readily0. filtered out. E8 l; A typical operation using these low boiling additives 10 20 9.5 would be: a brine saturated with KCl and NaCl from a 3. 3: 5.5 solution mining operation at high temperature is first 50 8 2.5 20 cooled to 70° C. precipitating a portion of the KCl and Ethylenedianine: 19 5 5 at which time the salt in solution is 17%. KCl and 18% -- Acetonitrile- 10 16, 5 1. NaCl. A material such as ethanol is then mixed into the 5010 1917 I brine to about 10% concentration by volume precipitat Es : ing additional salt to about 9%. KCl concentration while 40 16.5 1. 25 the solubility- - - of the NaCl is not altered appreciably. Since magnesium chloride and/or magnesium sulfate T E. C 1SE.