IL217175A - Polyhalite imi process for kno3 production - Google Patents

Description

PROCESS N03 PRODUCTION KN03 and Development POLYHALITE IMI PROCESS FOR PRODUCTION REFERENCE TO RELATED PUBLICATION This application claims priority from provisional application dated 25 June which is hereby incorporated by reference in its FIELD OE INVENTION This invention concerns methods for production of N in methods that use polyhalite as the starting BACKGROU OF INVENTION Potassium nitrate is a commercially important chemical with uses from explosives to Polyhalite is a and readily available source of Reaction of polyhalite with acids is known in the literature as a means of producing crude salt mixtures containing mineral For discloses a method for production of a mixture containing KN0 and from the reaction of polyhalite with Russian a method for production of a solution containing a mixture of O and NH4N 3 from reaction of polyhalite with ITNO3 followed by neutralizaion with Thus the processes described in the literature allow to produce a solution containing a mixture of including potassium and magnesium as well as gypsum that had not been separated in early stages of the Several such as the Southwest Potash and are known for the production of KNO3 by reaction of KCI with 334 Production of essentially pure KNO3 directly from the reaction of polyhalite with strong acid remains there remains a need for a process that can produce essentially puce from polyhalite without the complications of known processes such as production of complicated product mixtures and necessity of neutralization with SUMMARY OF THE INVENTION The process disclosed in the present invention produces NO3 from polyhalile wilh almost total without any necessity for preliminary thermal treatment and without the necessity washing out of NaCI from the The separation of from the is effected by the different temperature dependences of the solubility of the the solubility of NaCI changes very l ittle with while that of strongly increases with increasing In the process herein Mg is recovered as which is precipitated with The thus recovered can be used directly as a slurry with dried or transformed into Mg salts such as It is therefore an object of the present invention to disclose a process for producing wherein the starting material for the process is It is a further objeel of the present invention to disclose a process for producing KNO3 from comprising steps of contacting with a substance comprising adding at least one inorganic base the solution obtained in the step of contacting polyhalile wilh thereby precipitating as a solid at least part of the sul fate present in said precipitating as at least part of the Mg2 remaining in said solution by adding least one basic compound to the remaining concentrating the solution obtained after said step of precipitating at part of the remaining in said precipitating at least of the NaCI derived from said if from the solution obtained after said step of concentrating the solution obtained after said step of precipitating at leasl pari of the remaining in said separating said precipitated if from the reaction and separating as solid KNO3 at least part of the and contained in the solution remaining after the step of precipitating at leasl part of the NaCI derived from said It is within the essence of the invention wherein said process is adapted to produce commercially usable from It is a further object of this invention to disclose such a further including an additional step of washing said polyhalite prior lo said step contacting polyhalile wilh a substance comprising thereby removing at least a part of contained within said It is a further object of this invention to disclose such a process as defined in any of the wherein said step of contacting polyhalite with a substance comprising takes place at a temperature between about 60 and about 90 It is a object of this invention to disclose such a process as in any of the wherein said substance comprising ΝΟ is chosen from the group consisting of C any combination of the is a further object of this invention to disclose such a wherein said substance comprising is Ι and further wherein said step of contacting polyhalite with a substance containing further includes an additional step of contacting polyhalite with a quantity of Ι ΝΟ3 sufficient that the amount of in the solution thus obtained is at least It is a further object of this invention to disclose such a wherein said substance comprising is and further wherein said step of contacting polyhalite with a substance containing further includes an additional step of contacting polyhal ite with a quantity ΙΝΟ3 sufficient that the amount of I in the solution thus obtained is at least It is a further object of this invention to disclose such a process as defined in of the wherein said step of contacting polyhalite with a substance comprising further includes an additional step of contacting polyhal ite with is a further object of this invention to disclose such a process as defined in any of the further including an additional step of reeycling into the reaction vessel at least pari of the solution remaining after said step of separating solid It is a further of this invention to disclose such a wherein at least a part of said substance comprising is obtained from said solution recycled into said reaction It is a further object of this invention to disclose such a process as defined in any of the further including an additional step removing from the reaction stream at least of the solid produced during said step of contacting polyhalite with is a f urther object of this invention to disclose such a further including an additional step of removing by filtration at least part of the solid produced during said step of contacting polyhalite with It is a further object of this invention to disclose such a further including an additional step of washing said It is a further object of this invention to disclose such a process as defined in any the wherein said step of adding at least one inorganic base the solution obtained in the step contacting polyhalile with a substance includes an additional step of adding at least one inorganic base chosen from the group consisting of and It is a further object of this invention to disclose such a process as in any of the wherein said wherein said step of adding at least one inorganic base to the solution obtained in the step of contacting polyhalite with a substance comprising further includes an additional step of adding sufllcient inorganic base to reduce substantially the content of said It is a further object this invention to disclose such a as dellned in any of the wherein said step of adding at least one inorganic base to the solution obtained in the step of contacting polyhalite with a substance comprising further includes an additional step of adding sull ieient inorganic base to reduce the content of said solution by at least It is a further object of this invention to disclose such a wherein said inorganic base is chosen from the group consisting of basic Ca basic any combination of the is a further object of invention to disclose such a process as dellned in any of the further including an additional step of removing from the reaction stream at least of the insoluble sulfate produced during said step of contacting polyhalite with It is a further object of this invention to disclose such a process as defined in any of the further including an additional step of separating by llltration at least part of the insoluble sulfate produced during said step of contacting polyhalite with It is a further object this invention to disclose such a process as dellned in any of the wherein said step of precipitating as at least part of the remaining in said solution further comprises an additional step of adding a sufficient amount of at least one basic Ca compound to precipitate more than of the remaining in said solution as It is a further object of this invention to disclose such a process as defined in any of the wherein said step of precipitating as al least part of the remaining in said solution further comprises an additional step of adding a sufllcient amount of at least one basic Ca compound to precipitate more than of the remaining in said solution as It is a further object of this to disclose such a process as defined in any of the wherein said step of precipitating as at least part of ihe remaining in said sol ution further comprises an additional step of adding least one basic Ca compound chosen from the group consisting of and is a further object of this invention to disclose such a process as defined in any of the further including an additional step of removing from the reaction stream at least part of said obtained in said step of precipitating as at least part of the remaining in said It is a further object of this invention to disclose such a further including an additional step of washing said It is a further object of this invention to disclose such a wherein said is at least It is a further object of this invention to disclose such a process as defined in any of the wherein said step of concentrating the sol ution remaining after said step of precipitating at least part of the Mg2 remaining in said solution further comprises a step chosen from the group consisting of using a multiple effect evaporator to concentrated said sol ution and concentrating said sol ution by mechanical vapor It is a further object of this invention to disclose such a process as defined in any of the wherein said step of preci pitating at least part of the NaCI further includes an additional step of precipitating NaCI by evaporative crystal is a further object of this invention to disclose such a wherein said step of precipitating NaCI by evaporative crystal l ization occurs at a temperature exceeding about 60 I t is a further object of this invention to disclose such a process as defined i n any of the wherein said step of separating as solid at least part of the and contained in the solution remaining after said step of adding a basic Ca compound further incl udes an additional step of crystal l izing from said It is a further object of this invention to disclose such a wherein said step of crystallizing from said solution further includes an additional step of cooling said solut ion in order to affect crystal l ization of It is a f object of this invention to disclose such a said step of cooling said solution includes a further step of cooling said solution to a temperature below 40 It is a further object of this invention to disclose such a process as defined in any of the further including an additional step of purifying said obtained in said step of separating It is a further object of this invention to disclose such a wherein said step of puri fying said further includes an additional step of puri fying said by at least one method chosen from the group consisting of washing said pulping with a substantially pure and It is a further object of this invention to disclose such a process as defined in any of the wherein the purity of said exceeds It is a further object of this invention to disclose a process as defined in any of he wherein said step of precipitating at least part of the is carried out to said step of separat ing It is a further object of this invention to disclose such a process as defined in any of the wherein said step of precipitating at least part of the is carried out subsequent to said step of separating BRIEF DESCRIPTION OF THE shows a schematic flowchart of the process herein DETAI DESCRIPTION OF THE PREFERRED T S The present invention is described hereinafter with reference to the drawings and in which preferred embodiments are For the purposes of specific details are set forth in order to provide a thorough understanding of the It will be apparent to one skilled in the art there are other embodiments of the invention di ffer in details without affecting the essential nature Therefore the invention is not limited by which is illustrated in the figures and described in the but only as indicated in the accompanying with the proper scope determined only by the broadest interpretation of said the detailed description that formulas indicating water of hydration arc given according to conventional literature As no claims are made regarding the speci fic level of hydration of the compounds those for which no water of hydration is indicated and the invention herein disclosed is not limited to the specific of hydration The fundamental chemistry involved in the process herein disclosed can be summarized as 2IT 4H20 j The produced is precipitated as by further reaction with In the present i in contrast to methods known in the nitrate ion and calcium ion are added in separate independent steps of In some embodiments of the recovered from later stages of the process is recycled and reacted with the In a preferred embodiment of the invention herein following series of steps is employed to produce a commercial grade of K from the reaction of polyhalite with The various are listed with the schematic flowchart given in 1 for a preferred embodiment 10 of the invention herein In some embodiments of the is washed from the This step is entirely optional there is no requirement to wash out the NaCI from the polyhal nor is there any need for preliminary thermal treatment of the In Sta e of the process polyhal ite 1 is contacted with a substance comprising In preferred embodi substance 102 is in most preferred the is provided in preferred embodiments of the a sufficient amount of ITN O3 is added such that concentration 0ΙΊΤΝΟ3 in the resulting solution including the polyhal is at least In preferred embodiments of the the polyhalite and ITNO3 are brought into contact at a temperature of between about 60 and about 90 I n other embodiments of the temperatures outside of the range used i n preferred embodiments are In other substance 102 may comprise another nitrate salt such as or a mixture of a nitrate sail and typical embodiments in which is it is added at the beginning of stage in addition to or instead of the added at the beginning of the stage and the Ca compound added at the end of this described In preferred embodiments of the at least part the solution obtained in stage 5 is recycled into the reaction vessel in which the contact between polyhalite and the substance comprising takes The reaction mixture is then brought into contact with a base preferred a slurry in preferred slurry is added to bring the to substantially Addition of the slurry thereby yields a solution comprising primarily Mg2 NO and along with solid CaS04 In preferred sufficient base is added to precipitate at least of the present in the In preferred embodiments of the solid gypsum precipitated during the reaction between the polyhalite and the is filtered and washed with wash water 103 preferred by washing on a fi lter in order to reduce the nitrate The mother liquor transferred to stage while the wet gypsum aftcr washing is discharged from the The wash 104 is then returned to the reaction vessel in which stage takes In Stage 2 of the process additional slurry is added to the solution obtained in 1 1 after removal of solid gypsum in order to precipitate the major part of the contained in the solution as in preferred sufficient is added to precipitate at least of the The is washed and After precipitation of a solution comprising primarily Ca2 Na and residual Mg2 In sonic this stage is carried out after Stage 5 on the solutions to be recycled in stage 1 The chemical purity of the produced is dependent on the purity of the CaO or In preferred with a purity exceeding is The process then proceeds to Stage 3 in which the solution obtained in Stage 2 is In preferred the concentration is effected by evaporation using any technique known in the a multiple effect evaporator or by mechanical vapor In a preferred at least part of the residual CaS04 thus precipitated is separated from the supernatant solution at the exit of the vessel in which the concentration lakes The evaporation can be also carried by solar evaporation in an evaporation pond and thus the calcium sulfate precipitated can be left o the bottom of the The process then continues to Stage 4 in which NaCl and a small part of the present in the solution are partially separated from the solution remaining after 3 by crystallization in an evaporative at a temperature exceeding 60 The solids are separated preferred by filtration and 5 of the process is crystallized from the solution by cooling the solution remaining from Stage crystallization can be carried out by any technique known the in a cooling crystallizer of the various types including cooling disc In typical embodiments of the purity of the product obtained after washing in the tests exceeds In typical embodiments of the the main impurities Ca CT Na Mg and Sr The thus produced can be further purified by any technique known in the for by repulping with a pure solution or by The solution 210 remaining from Stage 5 is recycled to the vessel in which Stage takes The contained in the solution remaining from Sta e 5 reacts with the sulfate in the solution in stage 1 to precipitate XA 1 crushed and screened to 400 was added to a mixture of nitric acid and recycled solution made from combining mother liquor from NO3 crystallization presented in Example 3 and gypsum wash water from a previous The eoncenlralion of the nitric acid is modified by dilution with wash water from previous runs in order to maintain a constant nitrate concentration of in the final The reaction mixture was heated to 65 and stirred for 3 After that milk of lime in was added via pump over a 1 h period to the hot mixture in order to neutralize the acidity of the When the mixture reached of the addition was stopped and the mixture was filtered while hot under The gypsum cake was then washed with water x so that the nitrate content of the cake was satisfactorily The washed gypsum was dried overnight in an oven at 60 yielding of gypsum K Mg 1 00 The filtrate 1 K Mg Ca S0 1 was used as the basis for the separation step Example 2 while the wash water was combined with the recycled solution for the next EXAM PLE 2 A sample of solution obtained after completion of the reaction presented in Example I above g of solution were treated at a temperature of with solution of milk of l ime As a result of this the Mg concentration decreased from to less than The sol ids precipitated were sett led fi ltered and The dry solids contai ned more than I The mai n impurities were Ca and Cf EXAM PLE 3 A sample of the solution of remaining a l ter the precipitation of described in Example 2 comprising on basis relative to the total 1 1 and was concentrated by evaporation at a temperature exceedi ng 80 The total concentration of dissolved salts increased by as a result of the The NaCl thus crystal l ized was separated at a temperature exceeding 80 and its purity a ter washi ng exceeded The remaining solution was then cooled down lo a temperature leadi ng to precipitation of which was then separated the mother l iquor and he purity of the obtained exceeded whi le the concentration of dissolved salts in the mother solution to be recycled to the reaction was in the range of 55 ABSTRACT A process for producing Irom is In a the process comprises steps contacting with adding to the thereby precipiLating as al least part of the sulfate present in said precipitating as al least of the remaining in said solution by further addition of to the remaining concentrating the thereby precipitating as a sulfate compound at least part of the sulfate remaining in separating at least part of the NaCI from the solution and crystallizing as solid al least part of the and contained in the The process enables direct conversion of polyhalite to of purity exceeding and that is essentially free of and sulfate insufficientOCRQuality

Claims (34)

CLAI MS We claim:

1. A process for producing NO.-¾ of at least 98% puri ty, wherein the starting material for said process is polyhal ite and said process comprises: a. contacting polyhalite with a substance comprising ΝΟ ; b. adding al least one inorganic base to the sol ulion obtained in the step o f contacting polyhalite with MNO.i. thereby precipitating as a sol id at least part of the sul fate present in said solulion; c. precipitating as Mg(OH )2 at least part of the Mg2 ' remaining in said sol ution by adding at least one basic compound to the remai ni ng sol ution: d. concentrati ng the solution obtained after said slep o f precipitating at least part of the Mg2 ' remaining in said solution: e. precipitati ng at least part o f the NaCI derived from said polyhalite. i f any, from the solulion obtained after said step of concentrating the solution obtained after said slep of precipitating at least part of the Mg" 1 remaining in said solution; ('. separating said precipitated NaCI. i f any. from the reaction stream; g. separating as sol id .NO at least part of the K ' and NO contained in the solution remaining after the step of precipitating at least part o f the NaCI derived from said polyhal ite; and, h. recycl ing into the reaction vessel at least pari of the solution remaining after said step of separating sol id KN(¾.

2. The process according lo claim 1 , further incl uding an additional step of washing said polyhalite prior lo said slep of contacting polyhalite with a substance comprising NO/, thereby removing at least a part of the NaCI contained withi n said polyhal ite.

3. The process according to claim 1 . wherei n said slep of contacting polyhal ite with a substance comprising NO/ lakes place al a temperature bet ween about 60 °C and about 90 °C.

4. The process according to claim 1 , wherein said substance comprising NO./ is chosen from the group consisting of (a) l-IN03; (b) Ca(NO/)2; (c) any combination of (he above.

5. The process according lo claim 4. wherei n said substance comprising NO/ is HN03. and further wherein said step of contacting polyhal ite with a substance containing NOT furl her includes an additional step ofcontacting polyhalite with a c|iianlity of IINO3 sufficient that the amount of HNO;> in the solution thus obtained is at least 0.5% (vv/w).

6. The process according to claim 4. wherein said substance comprising NO3" is HNO3, and further wherein said step of contacting polyhalite with a substance containing NOT further includes an additional step ofcontacting polyhalite with a quantity of IINO sufficient (hat the amount 0Π-ΙΝΟ3 in the solution thus obtained is at least 5% (w/w).

7. The process according to claim 1. wherein said step of contacting polyhalite with a substance comprising NOT further includes an additional step of contacting polyhalite with 60% l-INO.L

8. The process according to claim 1, wherein at least a part of said substance comprising NOT is obtained from said solution recycled into said reaction vessel,

9. The process according to claim 1. further including an additional step removing from the reaction stream at least part of the solid produced during said slep ofcontacting polyhalite with HNO .

10. The process according to claim 9, further including an additional step of removing by llltration at least part of the solid produced during said step of contacting polyhalite with UNO.,.

11. The process according to claim 9. further including an additional step of washing said solid.

12. The process according to claim 1, wherein said step of adding at least one inorganic base lo the solution obtained in the slep ofcontacting polyhalite with a substance comprising NOT further includes an additional step of adding at least one inorganic base chosen from the group consisting of Ca(OH)2, CaCO.i. and CaO.

13. The process according to claim I, wherein said step of adding at feast one inorganic base to the solution obtained in the step ofcontacting polyhalite with a substance comprising NOT further includes an additional step of adding sufficient inorganic base to reduce substantially the S ,|2" content of said solution.

14. The process according to claim 13. wherein said step of adding at least one inorganic base lo the solution obtained in the step ofcontacting polyhalite with a substance comprising NOT further includes an additional step of adding sufficient inorganic base to reduce the SO,]2* content of said solution by at least 85%.

15. The process according to claim 13. wherein said inorganic base is chosen from the group consisting of (a) basic Ca compounds; (b) basic Ba compounds; (c) any combination of the above.

16. The process according to claim 1. further including an additional step of removing from the reaction stream at least part of the insoluble sulfate produced during said step of contacting polyhalite with HNC .

17. The process according to claim I, further including an additional step of separating by filtration at least part of the insoluble sulfate produced during said step of contacting polyhalite with IT O.i.

18. IS. The process according to claim I. wherein said step of precipitating as Mg(CTI)2 at least part ol" the Mg2 remaining in said solution further comprises an additional step of adding a suftlcienl amount of at least one basic Ca compound to precipitate more than 50% oi' the Mg2'1' remaining in said solution as Mg(OI-l .

19. The process according to claim I. wherein said step of precipitating as Mg(OH)2 at least part of the Mg2'1' remaining in said solution further comprises an additional step of adding a sufficient amount of at least one basic Ca compound to precipitate more than 85% of the Mg2+ remaining in said solution as Mg(OH)2.

20. The process according to claim I, wherein said step of precipitating as Mg(OH)2 at least part of the Mg2' remaining in said solution further comprises an additional step of adding at least one basic Ca compound chosen from the group consisting of Ca(Ol l)2 and CaO.

21. The process according to claim 1. further including an additional step of recovering from the reaction stream at least part of said Mg((.)i l)2 obtained in said step of precipitating as Mg(OH)2 at least part of the Mg2' remaining in said solution.

22. The process according to claim 21. further including an additional step oi' washing the Mg(OH)2 recovered from the reaction stream.

23. The process according to claim 21. wherein said recovered Mg(OiT)2 is at least 92% pure.

24. The process according to claim 1, wherein said step of concentrating the solution remaining after said step of precipitating at least part of the Mg2t remaining in said solution further comprises a step chosen from the group consisting of (a) using a multiple effect evaporator to concentrated said solution and ( ) concentrating said solution by mechanical vapor recompression.

25. The process according to claim 1. wherein said step of precipitati ng at least part of the NaCl further includes an additional step of precipitating NaCl by evaporative crystallization.

26. The process according to claim 25. wherein said step of precipitating NaCl by evaporative crystall i/ation occurs al a temperature exceeding about 60 °C.

27. The process according to claim I , wherein said step of separating as solid ΚΝ(¾ at least part of (he '1 and NO contained in the solul ion remaining after said step of adding a basic Ca compound further i ncludes an additional step o f crystal l izing KNO3 from said sol tion.

28. The process according to claim 27, wherei n said step of crystal l izing KNO3 from said solution further i ncludes an additional step o f cool ing said sol ution in order to affect c r s ta 11 izat i o n 01* N Oj .

29. The process according to claim 28. wherein said step of cool ing said sol ution includes a further step of cool ing said solulion to a temperature below 40 "C.

30. The process according to clai m 1. further incl uding an additional step of purifying said NO3 obtai ned in said step of separating K.NO3.

31. The process according to claim 30. wherein said step of puri fying said K NO3 further includes an additional step of puri fying said K NO3 by at least one method chosen from the group consisting of (a) washing said KNO.¾: ( b) pulping with a substantially pure K.NO3 solution; and (c) recry.slall ization.

32. The process according to claim I . wherein the purity of said KN( , is greater than 99%.

33. The process according to claim 1 , wherein said step of precipitat ing at least part of the Mg2+ is carried out prior to said step of separating NO3.

34. The process accordi ng to claim 1 . wherein said step of prccipilaling at least part of the Mg + is carried out subsequent to said step of separating NO3.