Dec. 17, 1935. o KASELITZ 2,024,370 PRODUCTION OF POTASSIUM NITRATE Filed April 12, 1932 SATURaed solution of KNO3 + 25oaf M35C. K250 POTAS5UM MAGNESUM SUFATE 5ATURATED 5OLUTION OF KNoshkz50th M85O1, 25Ca POASSUM MAGNSUM SULFATE Patented Dec. 17, 1935 2,024,370 UNITED STATES PATENT OFFICE 2,024,370 PRODUCTION OF POTASSIUM. NTRATE Oskar Kaselitz, Berlin, Germany Application April 12, 1932, Serial No. 604,873 In Germany September 1, 1931 1. Claims. (C. 23-102) My invention refers to the production of potas to Which it should be cooled. When Separating out sium nitrate from potassium Sulfate. It is an the potassium nitrate, can be varied Within Wide object of my invention to provide an improved ranges, and I Wish it to be understood that my method which is more efficient and less liable to invention is not limited-to any exact Saturating cause OSSes in available nitrogen than other or separating temperature, the only condition be- 5 methods heretofore known. ing that the Saturating temperature is higher If it is desired to convert potassium chloride than the separating temperature. The best into potassium nitrate the starting product is yields are however obtained if the Solution is treated as a rule with magnesium nitrate and saturated at a temperature of about 50° C., so 10 water, whereby potassium nitrate is separated that it contains about O out, while magnesium chloride remains in Solu tion together With Some potassium chloride. In order to dispose of this mother liquor and to re Mg (NO3)2 K. SO O cover therefrom the dissolved potassium, this 5 liquor must be evaporated to a considerable ex 1.5% 23.0% 13.9% 5.3% 56.3% tent, so that carnallite crystallizes out. This double salt must be washed in order to avoid and is cooled in the separating step to tem losses in available nitrogen, but considerable dif peratures not above 25 C., still lower tempera tures, for instance a temperature of 0° C. being ficulties are encoutered in view of the high Solu preferred. 20 bility of this double salt. The decomposition of 20 the carnalite in Order to recover the potassium The amount of potassium nitrate which can chloride contained therein also causes consider be separated from a given volume of the start able losses in potassium chloride. ing Solution, can be materially increased by add According to my invention I avoid these draw ing to this solution before cooling additional 25 backs by a conversion method, which consistS, quantities of potassium Sulfate and magnesium 25 broadly speaking, in converting magesium ni nitrate in such proportions that the mother liq trate and potassium sulfate in the presence of uor obtained on cooling and on separating the Water into potassium nitrate and potassium potassium nitrate is Saturated also with regard magnesium sulfate K2SO4MgSO4, which is easily to the double salt potassium-magnesium Sulfate. 30 handled and can be utilized without Suffering Such a mother liquor may also be treated in the 30 any losses in available nitrogen or in potassium, subsequent step with potassium sulfate and mag in accordance with the following equation: nesium nitrate at an elevated temperature, whereupon any surplus Water is evaporated and potassium magnesium sulfate is separated Out 35 In practising my invention I provide a Watery so as to exactly regenerate the starting Solution. 35 solution of potassium nitrate, potassium sulfate The evaporation of Water mentioned above and potassium magnesium sulfate, which is Satu should be controlled to expel exactly that quan rated with respect to these salts at an elevated tity, which is introduced into the Solution in the temperature, for instance at 50 C. On cooling form of water of crystallization when using 40 such solution to lower temperatures, for in solid magnesium nitrate having the formula 40 stance to 25° C. or to 0° C., pure potassium ni Mg(NO3)2.6H2O, for otherwise the Solution would trate separates out while the mother liquor re not regain its starting composition. In order to mains saturated with potassium nitrate. I now avoid the evaporating step, I may, however, form add potassium sulfate and magnesium nitrate, I the magnesium nitrate Within the Solution by 45 then heat the solution to evaporate part of the adding thereto magnesium oxide, hydroxide, car- 45 water, and I so control the proportions of the bonate or basic magnesium carbonate and nitric two additions and of the evaporated water that acid or nitrous gases and air or oxygen for in the double salt potassium-magnesium Sulfate stance the gases formed in the process of oxi K2SO4MgSO4 separates out in an amount equiv dizing ammonia, whereby magnesium nitrate is 50 alent to the potassium nitrate Separated in the formed, while the introduction of additional 50 first step. In this way the starting solution is Water is avoided. regenerated and can be used for the recovery of If the washing liquors obtained by washing the further amounts of potassium nitrate. ultimately obtained potassium nitrate or the ulti The temperature at which the starting Solu mately obtained potassium magnesium Sulfate 55 tion should be saturated, and the temperature shall be utilized in the process, I may add them 55 2 2,024,870 to the mother liquor prior to evaporation, but the nitrate and substantially also with respect to po amount of water which must be evaporated is taSSium Sulfate and potassium magnesium sulfate thereby increased. In such cases may also form to precipitate potassium nitrate, Separating the the magnesium nitrate within the solution as potassium nitrate, incorporating with the mother explained above in Order to reduce the proportion liquor potassium sulfate and magnesium nitrate, 5 of Water which must be eliminated by evaporation. heating this mixture, to evaporate part of the The pota SSium-magnesium Sulfate precipitated Water cooling it to a limited extent so that po in the process is separated from the mother liquor taSSium magnesium Sulfate separates out, and and may be washed with Water or, preferably, reusing the resultant liquor in cycle, taking care O With Suitable Solutions Saturated with potassium to regulate the percentage of Water in the liquor 0 magnesium Sulfate, and Washing may be con in Such manner that the quantity and concentra tinued until the salt is substantially free from tion of the liquor are equal to those of the starting nitrogen compounds. It may be dried and used Solution. as fertilizer or as an addition in the production of 2. The method of producing potassium nitrate 5 mixed fertilizers, but as it contains considerable Comprising cooling a Solution Saturated at an 15 quantities of magnesium, which are frequently elevated temperature with respect to potassium not desired, I may also decompose the salt by nitrate and Substantially also with respect to treating it with regulated quantities of Water to potassium Sulfate and potassium magnesium Sul recover the potassium sulfate component as such, fate to precipitate potassium nitrate, separating 20 which may be returned into the cycle. In prac the potassium nitrate, incorporating with the 20 tising my invention I may for instance proceed mother liquor potassium Sulfate and magnesium as follows: nitrate, heating this mixture to evaporate part of Eacample 1 the Water, cooling it to a limited extent So that 557 kgs. of a solution containing potaSSium-magnesium sulfate Separates out, con 25 trolling the quantity of the evaporated Water, of 25 1.5 per cent Mg the precipitated potassium magnesium sulfate 23.0 per cent NO3 and the additions of potassium Sulfate and mag 13.9 per cent K nesium nitrate While considering the quantity of 5.3 per cent SO4 Crystal water in the magnesium nitrate added and 30 56.3 per cent H2O in the potassium-magnesium Sulfate precipitated, 30. as obtained in a prior operation at a temperature so as to ultimately obtain a liquor corresponding of 50 C., are cooled to about 25°C., whereby 100 to the starting Solution. With respect to quantity kgS. of solid potassium nitrate are precipitated in and composition, and reusing this liquor in cycle. a crystalline form. To the mother liquor sepa 3. The method of producing potassium nitrate 35 rated from the Solid Salt 126.6 kgS. magnesium Comprising cooling a Solution Saturated at a ten- 35 nitrate (Mg(NO3)2.6H2O) and 72.4 kgS. potas perature of about 50 C. With respect to potassium sium sulfate are added, and the mixture is heated nitrate, and Substantially also With respect to to evaporate 17.8 kgs. Water. On cooling to about potassium Sulfate and potassium magnesium sul 50 C., 181.2 kgS. potassium-magnesium sulfate fate to a temperature substantially not exceeding 40. Crystallize out and on Separation there are ob 25 C. to precipitate potassium nitrate, separating 40 tained 570.0 kgs. Of a mother liquor which is the potassium nitrate, incorporating with the identical with the starting Solution in weight, mother liquor potassium Sulfate and magnesium composition and temperature. nitrate, heating this mixture to evaporate part of the Water, Cooling it to a limited extent, SO 45 Eacample 2 that potaSSium magnesium sulfate separates out, 45 To 381 kgS. of a starting Solution, as described and reusing the resultant liquor in cycle, taking With reference to Example 1 are added under stir Care to regulate the percentage of Water in the ring 33.6 kgS. magnesium nitrate liquor in Such manner that the quantity and con Centration of the liquor are equal to those of the 50 starting solution. SO and 20.8 kgS. potassium sulfate and the mixture 4. In the method as claimed in claim 3, is allowed to cool down to about 25° C., whereby the step of So controlling the two precipitation i00.0 kgS.