Aug. 24, 1954 W. B. DANCY ET AL 2,687,339 PROCESS FOR THE TREATMENT OF LIQUORS TO RECOWER POTASSIUM AND MAGNESIUM WALUES Filed Jan. 8, 1951

LGRUOR | REACTION TANK-3

4.

15KANTE 7um 6 FTER-5

8 O STORAGEDRYER AND -g FLTRATE

2 CARNATE-29 EVAPORATOR-3 SLURRY

4. OVERFLOW-17-16- THICKENER-15

8 28 CAL CUM} CHLORDE -2O-2--REACTION TANK-9 UNDERFLOW-29 T FER-23

24 2S

SOLDS-25 MAGNESUMYa CHORIDE SOLUTION-27

4TTORNEY Patented Aug. 24, 1954 2,687,339

UNITED STATES PATENT OFFICE 2,687,339 PROCESS FOR THE TREATMENT OF LIQ UORS TO RECOVER POTASSUM AND MAGNESUM WALUES William B. Dancy and Robert A. MacDonald, Carlsbad, N. Mex, assignors to International Minerals & Chemical Corporation, a corpora tion of New York Application January 8, 1951, Serial No. 204,983 11. Claims, (CI. 23-38) 1. 2 This application relates to processes for the AccCording to the general method employed treatment of liquors to recover potassium and in the instant invention for the recovery of potash magnesium values therefrom, and more particu values as kainite salts, and of magnesium values larly to processes for the treatment of potassium as magnesium chloride from solutions Or liquors sulfate reject liquors or their equivalents to re containing chlorides and/or Sulfates of magne cover potassium and magnesium compounds sium and of potassium, the liquor is mixed with therefrom. a slurry, the solid phase of which comprises In the processes of producing potassium Sul carnalite (KC.MgCl2.6H2O), and the aqueous fate by the base exchange or metathesis of the phase of which is substantially saturated with magnesium content of langbeinite with the po 10 respect to magnesium chloride. Magnesium tassium content of potassium chloride, there is chloride from the carnallite results in an in produced a mother liquor from which the potas crease of the magnesium chloride concentration sium sulfate crystals have been separated. This in the solution, and kainite salts are crystallized. mother liquor is usually evaporated and cooled The formation of kainite crystals is accompanied in order to separate potassium chloride and leo 15 with a reduction of the Sulfate ion concentra nite crystals from the liquor. The liquor from tion in the magnesium chloride solution. The which the crystalline Salts have been removed kainite salts are separated from the magnesium has heretofore been sent to Waste even though chloride solution, which is evaporated to a point it contains magnesium and potassium com near Saturation with respect to bischofite. S0 pounds. It would be desirable to recover sale 20 dium chloride and kieserite in addition to car able magnesium and potassium products from nallite crystallize from the Solution which is then such reject liquors. decanted or thickened, for example, in the con It is an object of the instant invention to re ventional type thickener which effects the sep cover the potassium and/or the magnesium com aration of liquid substantially free of solids from pounds from liquors containing chlorides and 25 a mixture containing liquid and Solids. The Sulfates of magnesium and potassium. underflow from the thickener, which contains it is a further object of the instant invention the Solid phase Salts, is recycled to the initial to recover saleable potash and magnesium prod step of the process, in which kainite is formed. lucts from potassium sulfate reject liquors or their The kieserite present in the salts is thought to equivalents. 30 react with potassium chloride to form additional It is a further object to recover potash salts, kainite. The overflow from the thickener, a Substantially free of magnesium chloride, and concentrated magnesium chloride Solution, is a magnesium chloride solution from potassium further processed to produce magnesium chemi sulfate reject liquors or their equivalents. cals. It is a further object of the instant invention 35 The liquors which are used as feed materials to recover potash salts, substantially free of mag contain chlorides and/or sulfates of magnesium nesium chloride, and a magnesium chloride solu and of potassium. In one embodiment of the tion, which may be processed to obtain other instant invention, potassium sulfate reject liq magnesium chemicals, from potassium sulfate uors, Such as reject liquors produced in base ex reject liquors or their equivalents. 40 change processes as above-described, and reject These objects and other objects of the instant liquorS produced in processes Such as are de invention Will become more apparent upon a scribed and claimed in U. S. Serial No. 166,715, fuller understanding of the invention as here filed June 7, 1950, U. S. 2,295,257, issued to Butt in after Set forth. et al., and the like, are used. A typical potassium The instant invention involves the treatment 4 5 Sulfate reject liquor suitable for the practice of of liquors or Solutions containing chlorides and the instant invention contains between about Sulfates of magnesium and potassium under con 5.3% and about 6.7% by weight of potassium ditions hereindescribed with a carnallite slurry chloride, between about 1.8% and about 3.3% under conditionS Which result in the formation by Weight of sodium chloride, between about 6.2% of kainite (KCl.MgSO4.3H2O) and a magnesium 50 and about 7.5% by weight of magnesium sulfate, chloride solution. The Solid kainite Salts are between about 15.5% and 18.3% by weight of separated from the magnesium chloride solu magnesium chloride, and between about 66.0% tion. The potash SaltS can be employed as a and about 68.0% by Weight of Water. fertilizer product. The magnesium chloride so It is not essential in the kainite forming step, lution can be further processed into magnesium 55 that is, in the admixing of a slurry whose aque chemicals as desired. Ous phase is Substantially Saturated with respect 2,687,889 3 4. to magnesium chloride and whose solid phase tween about 36% and about 40% by Weight at contains carnallite and kieserite and minor a temperature of between about 115° C. and amounts of sodium chloride, that kieserite and about 120° C. and is thickened at a temperature sodium chloride be present. The instant process of about 90° C. The underflow from the thick may be practiced and is usually initiated by add ener is recycled to the step in which kainite is ing a substantially saturated solution of magne formed, and the overflow, which is a concen sium chloride which contains a suspension of trated magnesium chloride solution, is further carnallite to potassium sulfate reject liquor of processed to recover its magnesium value. equivalent liquors without substantially altering In a further embodiment of the instant novel the over-all process. The presence of kieserite in process, potassium sulfate reject liquor is al the slurry increases the yield of kainite and thus lowed to react with a hot slurry, obtained from increases the reaction efficiency. Thus in the a subsequent step of the process as herein preferred embodiment of the instant novel proc described, which comprises solid phase carnal ess, the slurry containing carnallite and kieserite lite and minor amounts of kieserite and sodium obtained as above-described as underflow from chloride in a solution of magnesium chloride. the thickener is recycled to the kainite forma The mixture is heated at a temperature of be tion Step. tween about 60° C. and about 85°C. for between In the kainite formation step, Sufficient car about two and about four hours. The carnallite nallite slurry is added to the potassium Sulfate and kieserite are dissolved in the liquor, and a reject liquor so that the resulting liquor will be 20 mixture of salts, comprising kainite with minor nearly saturated with respect to carnallite. For amounts of potassium chloride and sodium chlo example, kainite is obtained by mixing between ride, are crystallized. These salts are separated about 1.15 and about 1.35 parts by Weight of from the resulting solution by filtration and are potassium sulfate reject liquor per part of car washed and dried. The kainite salts have a typ maliite slurry. Kainite is formed in the above 25 ical analysis as follows: described slurry at a temperature of between Percent by weight about 10° C. and about 85° C. However, the re Potassium chloride------34.9 action is preferably carried out at a temperature Magnesium Sulfate ------44.6 of between about 60° C. and about 85° C. Al Sodium chloride------19.77 though kainite is formed in the slurry through 30 The salts analyzed about 22.09% potassium oxide out the entire temperature range mentioned and about 15% magnesium oxide. About 92.7% above, the rate of formation of kainite is Suf of the potassium oxide is recovered in the form. ficiently rapid to be commercially feasible only of kainite SaltS. attemperatures of above about 60° C. The kainite The solution from which the salts have been salts, which are separated from the solution, have separated is then evaporated to a point near a K2O content of about 22% and magnesium saturation with respect to bischofite, for example, oxide content of about 15%. the solution is evaporated to a magnesium chlo After the removal of the kainite salts from the ride concentration of between about 36% aid magnesium chloride solution, said solution is about 40% by weight. During this evaporation, evaporated to a point near saturation with re 40 carnallite and some kieserite and Sodium chlo spect to bischofite, that is to a magnesium chlo ride are crystallized from the solution. The ride concentration of between about 36.0% and evaporation is carried out at a temperature above about 40% by weight. The evaporation is usually about 60° C., and usually water is removed to carried out at a temperature above about 60 C, the extent of approximately 25% of the feed preferably at a temperature between about 115 solution, but more or less water is driven off, C. and about 120° C. The resulting mixture is depending on the concentration of dissolved then cooled and thickened, preferably at a ten Solids therein. The evaporated slurry is then perature of about 90° C., which is the maximum decanted, for example, in a conventional type temperature for this thickening step. However, thickener to produce in the underflow a slurry temperatures below about 90° C. may also be of approximately 45% solids. This carnallite employed for the thickening step. If the evap slurry is recycled to the step in which kainite is oration is carried out at a temperature above formed. The concentrated magnesium chloride about 90° C., the concentrated mixture is cooled Solution, which overflows the thickener, is treated and thickened at a temperature below about 90 with calcium chloride to remove additional C. If the evaporation is carried out at a ten announts of Sulfate and is then processed into perature below about 90° C., the slurry is thick ragnesium chemicals. The magnesium chloride ened at the evaporating temperature without liquor from the thickener has a typical compo additional cooling. sition approximately as follows: In the preferred embodiment, the instant proc Percent by weight ess comprises the steps of adding a slurry of 60 Magnesium chloride------36.07 carnallie, the aqueous phase of which is substan Magnesium Sulfate------80 tially Saturated with respect to magnesium chlo Sodium chloride------0.51 ride, to a potassium Sulfate reject liquor or equiv Potassium chloride------0.65 alent, liquor at a temperature of between about Water ------6089 60° C. and about 85° C. The resulting mixture 65 is agitated for between about two and about four This liquor is further purified for use in the hours or until the formation of kainite is Sub preparation of magnesium compounds by add stantially complete. The salts produced con ing an exceSS of calcium chloride to the Solition prise kainite, potassium chloride, and Sodium at an elevated temperature and removing the chloride and are removed from the magnesiunin Solids which are formed. The calcium chloride chloride liquor, for example, by filtration. This treated liquor Will have approximately the foll product is suitable for use as a fertilizer con lowing analysis: position or component. The liquor from which Percent by weight the solid product has been removed is evaporated Magnesium ------9.65 to a magnesium chloride concentration of be 5 Chloride ------28.44 2,687,889 5 6 Percent by weight ened in a conventional type thickener at a tem Potassium ------0.0 perature of about 90° C. The underflow from the Sodium ------0.17 thickener was recycled to the kainite formation Sulfate ------0.07 step. The magnesium chloride solution overflow Water ------61.50 is was then treated with calcium chloride at a tem For a lore Complete understanding of the in- perature of between about 85° C. and about 95 C. stant novel process, reference may be had to the About 1.7 parts of calcium chloride per 100 parts figure which is a flow sheet of a preferred en- of concentrated liquor were used. The solids bodiment of the instant novel process. which formed were removed by filtration from A potassium sulfate reject liquor f is allowed 10 the purified magnesium chloride solution and dis to enter reaction tank 3 by means of line 2. Carded, Table I shows the analysis of the ma Carnalite slurry underflow 29 from the thick- terials used and recovered. Table I.--Analysis of materials (weight percent) Material "SF" | K Mg Na C so Ho

Reject Liquor------3.40 5.44 1.2 16, 84 5, 19 68, 0. Thickener Overflow------90 0.269.57 0.38. 27.44 1.75 60.60 Thickener. Underflow------90 6.01 8.94 1.29 32.20 1.78 49,78 Kainite Liquor------65 3.02 6.96 0.79 22.90 i. 84 64.49 Water-Wa,Unwashed Product she di (Solids).------Product 14.19 8.54 3.98 21.00 31.00 21, 18 (Solids)------14.26 8, 25 3.32 18.80 31.58 23.79

30.ener The 5 entersmixture reaction is agitated tank and3 by allowed means ofto linere- 25 theTable kainite II showsSalts. the estimated composition of act at a temperature of between about 60° C. and about 85° C. until kainite formation is Substan- Table II-Estimated composition of kainite salts tially complete. Thereafter the reacted mixture --- w is transferred to filter 5 by means of line 4. 30 Material Kainite KCl MgCl, NaCl HO The Solid kainite product is removed from filter ------5 by means of line S. The kainite product 7 is Unwashed.------80.66 2.91 2.60 0.14 3. 69 conveyed to dryer and storage 9 by line 8. Water-Washed.------81.85 2.68 1.00 8, 44 6.03 The filtrate is transferred from filter 5 by line2. The0 and filtrate is conveyed is evaporated to evaporator to between f3 by about line '35 The Water-washed productw salts were substan 36% and about 40% by weight of magnesium tially free of carnallite. Water washing the salts chloride at a temperature above about 60° C. removed carnallite liquor and reduced the lag The concentrated liquor is then transferred by Sir Ontent of the solids from about 2.6% to line 4 to thickener 5 where it is cooled to at 40 aboutbout 1.0%. . -- least below about 90° C. and thickened. The con- Having thus fully described and illustrated the Centrated magnesium chloride Solution Which character of the invention, what is desired to be overflows from the thickener soy line 6 is secured and claimed by Letters Patent is: transferred by line 8 to reaction tank 9 and 1. A process for the treatment of potassium sul calcium chloride 20 is likewise conveyed to the fate reject iglior which comprises treating a po same through line 2. The reacted mixture is 45 assium sulfate reject liquor comprising essen conveyed by line 22 to filter 23. Solid calcium tially sulfate, chloride, magnesium and potassium compounds 25 are removed by line 24, and the ions with Carnalite Suspended in an aqueous me concentrated, purified magnesium chloride solu- diuin Substantially Saturated with respect to mag tion 27 which is obtained by line 26 is processed nesiun chloride, at a temperature of between into magnesium chloride chemicals. The under- to about 60° C. and about 85 C., and separating flow 29 from thickener 5 is a slurry of about kaihite from the resulting mixture upon substan 45% solids, the solids of which comprise carnal- tial conpletion of the reaction. lite, kieserite, and sodium chloride. Underflow 2. A process for the treatment of liquors which 29 is removed from the thickener 5 by line 28 Comprises treating a liquor comprising essentially and is returned by line 26 to reaction tank 3 for 5 sulfate, chloride, magnesium, and potassium ions use in the reaction as previously described. With carnalite Suspended in an aqueous medium In order to more fully illustrate the nature and Substantially Saturated with respect to magnesium character of the instant invention, but With no chloride, at a temperature of between about 60° intention of being limited thereto, the following C. and about 85 C., separating kainite from the example is given. 60 resulting mixture upon Substantial completion of EXAMPLE the kainite-forming reaction, evaporating the About 121 parts by weight of potassium sulfate o from which the kainite has been separated reject liquor having the composition indicated O a point near Saturation. With respect to bisch in Table was added to about 00 parts by weight ofte, and separating solids from the resulting of a thickened slurry of crude carrialite salts and 65 mixture to obtain a concentrated magnesium carnallite mother liquor of the composition indi- chloride Solution. cated in Table . The resulting minixture WaS agi- 3. A process for the treatment of liquors which tated at a temperature of about 65 C. until the Comprises treating a potassium sulfate reject Sulfate concentration of the liquor had been re- liquor with carallite Suspended in an aqueous duced to below about 2%. The kainite salts which 70 medium Substantially Saturated with respect to crystalized Were Separated fron the liquor. The magnesium chloride, at a temperature of between kainite liquor was then evaporated at a tempera- about 60° C. and about 85° C., separating kainite ture of about 115° C. to a magnesium chloride from the resultant mixture upon substantial com concentration of about 38% by Weight. The pletion of the kainite-forming reaction, evapo slurry discharged from the evaporator was thick- 75 rating the liquor from which the kainite has been 2,687,389 7 8 separated to a point near saturation with respect ride solution with calcium chloride, and removing to bischofite, and decanting the resulting mixture the resulting solids from the purified magnesium to obtain a concentrated magnesium chloride So chloride Solution. lution and a slurry containing kieserite and car 9. A process for the treatment of liquors which nallite. comprises treating a potassium Sulfate reject 4. A process for the treatment of potassium liquor with carnalite suspended in an aqueous sulfate reject liquor which comprises treating a medium substantially saturated with respect to potassium sulfate reject liquor with carnallite SuS magnesium chloride, at a temperature between pended in an aqueous medium substantially Sat about 60° C. and about 85° C. for between about urated with respect to magnesium chloride, at a 0. two and about four hours, separating kainite temperature of between about 60° C. and about from the resulting mixture, evaporating the 85° C. for between about two and about four liquor from which the kainite has been Sepa hours, separating kainite from the resultant mix rated at a temperature of between about 115° C. ture, evaporating the liquor from which kainite and about 120° C. to a point near Saturation has been separated at a temperature above about 5 With respect to bischofite, cooling the resulting 60° C., to a point near saturation with respect to mixture to a temperature of about 90° C., decant bischofite, cooling the resulting mixture, and de ing the resultant mixture to obtain a concen canting the resultant slurry to obtain a concen trated magnesium chloride Solution and a slurry trated magnesium chloride solution and a Slurry containing kieserite and carnallite, and recycling containing kieserite and carnallite. 20 the slurry to the kainite-forming reaction mix 5. A process for the treatment of potassium ture. sulfate reject liquor which comprises treating a 10. A process for the treatment of liquors which potassium sulfate reject liquor with a slurry comprises treating a potassium sulfate reject whose aqueous phase is Substantially Saturated liquor with carnallite Suspended in an aqueous with respect to magnesium chloride, and Whose 25 medium substantially saturated with respect to solid phase comprises kieserite and Sufficient magnesium chloride, at a temperature of between carnallite to produce Saturation with respect to about 60° C. and about 85 C. for between about carnallite in the resulting reaction mixture, at two and about four hours, Separating kainite a temperature between about 60° C. and about from the resulting mixture, evaporating the 85° C., separating kainite from the resulting mix 30 liquor from which the kainite has been sepa ture upon substantial completion of the kainite rated at a temperature between about 115 C. forming reaction, evaporating the liquor from and about 120° C. to a point near Saturation which the kainite has been separated to a point with respect to bischofite, cooling the resulting near saturation with respect to bischofite, and mixture to a temperature of about 90° C., decant cooling and decanting the resulting mixture to 35 ing the resultant mixture to obtain a concen obtain a concentrated magnesium chloride Solu trated magnesium chloride Solution and a slurry tion and a slurry containing kieserite and carnal containing kieserite and carnallite which is re lite. cycled to the kainite-forming reaction mixture, 6. A process for the treatment of liquors which treating the concentrated magnesium chloride comprises treating a liquor comprising essentially 40 solution with calcium chloride, and removing the sulfate, chloride, magneisum, and potassium ions. resulting solids from the purified magnesium with carnallite suspended in an aqueous medium chloride Solution. substantially saturated with respect to magne 11. A process for the treatment of liquors which sium chloride, at a temperature of between about comprises treating a potassium sulfate reject 60° C. and about 85° C., separating kainite from 45 liquor with a slurry whose aqueous phase is Sub the resulting mixture upon substantial comple stantially saturated with respect to magnesium tion of the kainite-forming reaction, evaporating chloride, and whose Solid phase comprises car the liquor from which the kainite has been Sepa nallite and kieserite, at a temperature between rated to a point near saturation. With bischofite, about 60° C. and about 85° C. for between about decanting the resulting mixture to obtain a con 50 two and about four hours, separating kainite centrated magnesium chloride Solution and a from the resulting mixture, evaporating the slurry containing kieserite and carnallite, treat liquor from which the kainite has been separated ing the concentrated magnesium chloride Solu at a temperature between about 135° C. and tion with calcium chloride, and removing the about 120° C. to a point near Saturation with resulting solids from the purified magnesium 55 bischofite, cooling the resulting mixture to a chloride solution. temperature of about 90° C., decanting the result 7. The process for the treatment of liquors of ant mixture to obtain a concentrated magnesium claim 6 wherein the slurry containing kieserite chloride solution and a slurry containing kieserite and carnallite is recycled to the reaction mixture. and carnallite which is recycled to the kainite 8. A process for the treatment of liquors which 60 forming reaction mixture, treating the concen comprises treating a potassium Sulfate reject trated magnesium chloride Solution with calcium liquor with carnallite suspended in an aqueous chloride, and removing the resulting Solids from medium substantially saturated with respect to the purified magnesium chloride Solution. magnesium chloride, at a temperature of between about 60° C. and about 85° C. for between about 65 two and about four hours, separating kainite References Cited in the file of this patent from the resulting mixture, evaporating the liquor UNITED STATES PATENTS from which the kainite has been separated at a temperature above about 90° C. to a point near Number Nane Date saturation with respect to bischofite, cooling the 70 1801,661 Collins ------Apr. 21, 1932. resulting mixture to a temperature at least below 2,479,001 Burke et al. ------Aug. 16, 1949 about 90° C., decanting the resultant mixture to obtain a concentrated magnesium chloride Solu FOREIGN PATENTS tion and a slurry containing kieserite and carnal Number Country Date lite, treating the concentrated magnesium chlo 75 676,406 Germany ------June 3, 1939