MXPA01003685A - Method of formulating alkali metal salts - Google Patents

Abstract

Methodology for formulating sodium bicarbonate and potassium sulfate. In one embodiment, sodium sulfate and ammonium bicarbonate are reacted to form sodium bicarbonate with the remaining liquor or brine treated with sulfuric acid to remove carbonates with subsequent precipitation of potassium sulfate. A further embodiment employs ammonium bicarbonate, ammonia gas or carbon dioxide to precipitate sodium bicarbonate. The result of the methods is the production of high quality fertilizer and food grade sodium bicarbonate.

Description

METHOD TO PRODUCE SALTS FROM ALKALINE METALS FIELD OF THE INVENTION The present invention relates to a method for producing alkali metal salts and more particularly, the present invention relates to a method for generating sodium bicarbonate food grade and potassium sulphate fertilizer grade.

BACKGROUND OF THE INVENTION The production of alkali metal salts is widely disclosed in the prior art. As an example, sodium bicarbonate has been prepared in as many different ways as those known. Despite this fact, previous unit operations for the synthesis of bicarbonate have been hampered by the inefficient use of energy that directly affects an increase in the costs of the synthesis. As another limitation, the known processes do not make efficient use of the unit operations involved in the preparation of the salts. In general, a single high quality product is produced, with the inherent formation of a byproduct of inadequate quality for commercial purposes or that would require a considerable investment to convert it into a commercially viable product.

The representative prior art is United States Patent No. 3,429,657 issued on February 25, 1969 to D'Arcy. The reference discloses a method for recovering and producing potassium salts. In the reference, a brine containing potassium is reacted with sodium perchlorate to precipitate potassium perchlorate. The potassium is eliminated by ion exchange with sodium and the free potassium is then combined with chloride, sulfate and nitrate among others.

INDUSTRIAL APPLICATION The present invention has industrial application in the technical field of fertilizers.

EXPOSITION OF THE INVENTION An object of one embodiment of the present invention is to provide a method for producing sodium bicarbonate food grade and potassium sulfate, characterized in that the method comprises the steps of: a) providing a source of liquid sodium sulfate; b) provide a source of ammonium bicarbonate; c) contacting sodium sulfate and ammonium bicarbonate; d) precipitate the sodium bicarbonate and form a liquor; e) precipitating the sodium bicarbonate and forming a liquor by contacting the liquor of step d) with sodium sulfate; f) saturating the liquor of step e) with sodium sulfate; g) filtering liquor solids from step f); h) contacting the liquor of step g) with sulfuric acid to precipitate the carbonates; i) cooling the liquor from step h) to 0 ° C to form a precipitate of Glauber's salt; j) heating the liquor from step i) between 30 ° C and 40 ° C; and k) precipitating the potassium sulfate by contacting the liquor from step j) with potassium chloride. A further object of an embodiment of the present invention is to provide a method for producing sodium bicarbonate of food grade and potassium sulfate, characterized in that the method comprises the steps of: a) providing a source of liquid sodium sulfate; b) provide a source of ammonium bicarbonate; c) contacting sodium sulfate and ammonium bicarbonate; d) precipitate the sodium bicarbonate and form a liquor; e) precipitating the sodium bicarbonate and forming a liquor by contacting the liquor of step e) with sodium sulfate; f) saturating the liquor of step e) with anhydrous sodium sulfate; g) filtering liquor solids from step f); h) contacting the liquor of step g) with at least one compound between ammonium bicarbonate, ammonia gas or carbon dioxide, to precipitate sodium bicarbonate; i) cooling the liquor from step h) to 0 ° C to precipitate sodium bicarbonate and sodium sulfate; and j) precipitating sodium sulfate by contacting the liquor from step i) with potassium chloride. It has been found that after the production of sodium bicarbonate, an important advantage is achieved by cooling the liquor to 0 ° C to remove the sodium sulphate as Glauber's salt and sodium bicarbonate. The solubility of the Glauber salt in the system is provided by the sodium sulfate-sulfate phase diagram. By increasing the sodium sulfate in the bicarbonate circuit with the increase in the recycling of Glauber's salt, there is a tendency to decrease the bicarbonate solubility and increase the efficiency of the process. With respect to the conversion to potassium sulfate of the initial reactants, a particular success has been achieved by maintaining a molar ratio of five (5) or more for the potassium and ammonium ions. This ratio ensures high conversion efficiency in the second stage of the process.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a process flow diagram illustrating a first part of a process according to the present invention; Figure 1 illustrates a second part of the process illustrated in Figure 1; Figure Ib illustrates a third part of the process illustrated in Figure 1; Figure 2 is a process flow diagram illustrating a first part of a variation of the process according to the present invention; Figure 2a illustrates a second part of the process illustrated in Figure 2; and Figure 2b illustrates a third part of the process illustrated in Figure 2. Similar numbers in the figures indicate similar elements.

WAYS TO CARRY OUT THE INVENTION Now with reference to Figures 1 to Ib the process according to a first embodiment is illustrated. A source of liquid sodium sulfate 10 is dissolved in clean water and in the wash water 12 described below. The solution is mixed in vessel 14 at 40 ° C where there is a specific gravity of 1.30. The solution is filtered in the filter 16 which can be, for example, a filter of 5 microns. The solids 18 are removed while the filtrate 20 is passed to a first crystallization vessel for the sodium bicarbonate 27. The feeds of water, ammonia and carbon dioxide indicated by the number 24 are reacted in the vessel 22 in order to synthesize the ammonium bicarbonate. The produced ammonium bicarbonate is centrifuged in the centrifuge 26 and the solid product is passed to the crystallization vessel 27. A recirculation loop 28 recycles the solids and the ammonium bicarbonate liquor to the reaction vessel 29. The result of the combination in the container 29 is the production of sodium bicarbonate. The mixture is filtered through the filter 30 and centrifuged. The sodium bicarbonate is washed with water in the container 32, centrifuged in the centrifuge 34 and the solid is retained as sodium bicarbonate food grade. The wash water is returned to the container 14. The liquor leaving the filter 30 has a specific gravity of 1.25 with a content that includes approximately 10.4% sodium sulfate, 17.1% ammonium sulfate, 8% sodium bicarbonate and an excess of ammonium bicarbonate for the reaction with Glauber's salt (discussed below). The liquor is reacted in vessel 36 at 40 ° C with the Glauber salt produced in the cooling phase of the process, which will be discussed below, to produce sodium bicarbonate from the excess of ammonium bicarbonate from the crystallization 29. Alternatively, the ammonium bicarbonate can be added in the second stage (vessel 36) as a solid, paste or solution. In the vessel 40 the liquor from the vessel 36 and the solid sodium sulfate from the source 41 are added to produce a saturated liquor of sodium sulfate / ammonium sulfate. An amount must be present in the solution 52/113 sufficient of ammonium bicarbonate to complete the reaction in solution or it must be added a bit in order to obtain a liquor with a specific gravity of 1,285. The paste from the container 40 is filtered through the filter 42. The solids of sodium bicarbonate 48 are passed to the container 32 and the liquor 44 is then processed to give an additional separation of sodium bicarbonate, which is returned to the container 32. The liquor 44 is then passed to the container 46 (Figure IA). The volume of the circuit from the sodium bicarbonate circuit can be controlled by evaporating the purified sodium sulfate in the feed to produce solid sodium sulfate which ensures saturation of the circuit. Again with respect to Figure IA, the container 46 contains sulfuric acid to precipitate carbonate compounds. The liquor thus treated is cooled to 0 ° C in the cooler 48 to recover Glauber's salt which is filtered in the filter 50. The recovered Glauber's salt is returned to the sodium bicarbonate 36 crystallization vessel. The filtrate contains 25.25% in Ammonium sulfate weight and up to 11% by weight sodium sulfate is passed to vessel 52 which is heated between 30 ° C and 40 ° C and combined with solids 65 from filter 66. This solution is passed to vessel 54 where it is done 52/113 reacting the solid potassium chloride to produce a 20% by weight ammonium chloride solution, which also contains by weight approximately 20.2% ammonium chloride, 6.7% potassium chloride, 4.9% sodium chloride, 2.3% as (x) 2S04, where x = Na, K and a crystalline mixture of potassium sulfate with 10% to 20% ammonium sulfate. The solution is filtered on the filter 56, the solid fraction contains by weight about 5% potassium chloride, 80% to 85% potassium sulfate, 10% to 15% ammonium sulfate. The solid fraction is combined in vessel 58 with water and potassium chloride brine from vessel 60. The solid potassium sulfate is centrifuged and filtered on filter 62 and recrystallized with a potassium chloride solution at 25 ° C. The remaining ammonium sulfate solution is converted to potassium sulfate. It is feasible to obtain potassium sulfate levels of 98% or more. In other unit operations, the liquor or filtrate from operations with potassium sulfate and specifically from filter 56, are processed according to the unit operations shown in Figure 1. The liquor is evaporated in the evaporator in order to concentrate the ammonium chloride liquor, so that upon cooling, the potassium chloride and the residual sulphates are reduced to 52/113 minimum in the solution. The solution is filtered through the filter 66 and the solid material 67 is recycled to the vessel 54. The filtrate containing about 22% to 30% ammonium chloride is reacted with lime in the reactor 68 and the ammonia released is recycled . The calcium chloride that is formed can be passed to a settling tank 70 or to a scrubber tank 72 depending on the subsequent uses for which it is intended. Once the process according to this first modality has been exposed, reference will now be made to an example of the process.

EXAMPLE 1 ELIMINATION OF BICARBONATE BEFORE THE PROCESS OF POTASSIUM SULPHATE Feeding - 1 liter at 1.3 G.E. (specific gravity) Ia STAGE NaHC03 production Brine outlet at the end of the reaction: 130g Na2S04 10.4% Na2S0 40 ° C 213.8g (NH4) 2S04 17.1% (NH4) 2S0 1.250 G.E. to 0.951 lOOg NaHC03 8.0% NaHC03 solution 907g H20 1350.8 This gives 172 g of solids ESTIMATED OF THE SECOND STAGE of NaHC03 consumed 55g NH3 A) 25.07g NH3 + 64.9g C02 142.5g C02 B) 51.2g NH3 + 132.6g C02 2- STAGE. In 0.951 1 of brine the following will dissolve: A) 1 Mol B) 2 Moles Na2S04 10H2O (332g) Na2S0 10H2O (644g) 272g Na2S04 16.2% Na2S04 414g Na2S04 20.7% Na2S0 213. 8g 12.8% (NH4) 2S04 213.9g 10.7% (NH4) 2S0 (NH4) 2S04 (NH4) 2S04 lOOg NaHC03 5.9% NaHCO3 lOOg NaHCO3 5.0% NaHCO3 1087g H20 65.1% H20 1267g H20 63.4% H20 1672. 8 1999 1. 275 G.E. and 1,313 1 of 1,300 G.E. and 1.5 1 brine brine 2nd STAGE Composition of the final solution B) 167.3g Na2S0 10% Na2S0 200g Na2S0 10% Na2S04 311g (NH4) 2S04 18.9% 412g (NH4) 2S04 20.2% (NH4) 2S04 (NH4) 2S04 13 lg NaHC03 8% NaHC03 160g NaHC03 8% NaHC03 52/113 1087g H20 63 1% H20 1267g H20 61.8% H20 1644. 5g 2039g Solution Solution Production of NaHC03 92. 9g Production of NaHC03 193.2g G.E. 1,265 and gives 1. 31 1 of G.E. 1,285 and gives 1 .6 1 of brine solution ELIMINATION OF SODIUM BICARBONATE 412g (NH4) 2S04 200g Na2S04 160g NaHC03 + 160 X 98 = 93.3g H2S04 84 (2) 1267g H20 2039g (1.6 1) 1285 G.E. This is converted to: 412g (NH4) 2S04 335g Na2S04 1267g H20 2014g to 1.265 = (1.61) Na2SO should be added until saturation, with G.E. of 1.30 1.61 x 1.30 = 2080 Therefore: 412g (NH4) 2S04 400g Na2S04 52 / ll3 1267g H20 2079g total (1.61) Cooling 412g (NH4) 2S04 28.7% 116g Na2S04 8.0% 907 H20 63% 1435g Solution Feeding to the evaporator NH4C1 330.8g 21.9 KCl 130g 8.6% NaCl 94.7g 6.3% x-S0 50 3.3% H20 907g 60.0 1512g to 33% NH4C1 then: -2.8% KCl then: -2.0% K2S04 Therefore: 330.8 = 1002g .33 Evaporation charge - 907 - 623 = 284g 0.79t / t Na2S04 add 0.5t for washing 1.29t H20 / t Na2S04 Reaction of K2SQ a) K2S04 of (NH4) 2S04 = 412 x 174 = 543g 132 52/113 b) K2S04 of Na2S0 = 116 x 174 = 142g 142 c) Losses of K2S0 = -43g TOTAL of K2S04 642g Recovery of KCl a) KCl of mixed reaction = 685 x 2 x 74 = 582 174 b) Lost KCl in the tails = 50 gc) Therefore: Required KCl = 632g Yield of K2S0 = 642 x 100 = 93.7% 685 KCl conversion efficiency = 582 x 100 = 92.1% 632 BASE: One ton of Na2S0 charge First Product Inputs Stage 0.153t NH3 0.48t NaHC03 0.396t C03 2.52t H20 Second stage 644g 0.53t NaHC03 Na2S0 10H2O 0.142t NH3 0.368t C02 Elimination of Bicarb + Filter to produce Saturation with Na2S04 clear brine 0.26t H2S04 0.18t Na2S04 Again with reference to Figures 2 to 2b, an alternative process diagram is represented schematically. In this reaction diagram, before the production of sodium bicarbonate, the liquors become saturated 52 / ll3 with anhydrite. In this embodiment, the sodium bicarbonate is produced in the crystallization unit 22 and is usually subjected to the steps shown in Figures 1 to IB. The brine or filtrate is saturated with anhydrous sodium sulfate in vessel 36 and filtered with filter 38 to remove insoluble matter which is discarded. The filtrate from this operation is reacted with ammonium bicarbonate in vessel 80. As an alternative, the filtrate can be reacted with ammonia or carbon dioxide to precipitate the sodium bicarbonate. The solution is filtered with the filter 82 and the sodium bicarbonate remains. The latter is combined with the sodium bicarbonate filter 30 and then washed, centrifuged and dried. These steps are not shown. The remaining filtrate has a composition by weight of approximately 10% sodium sulfate, 24% ammonium sulfate and 8% sodium bicarbonate. The solution has a specific gravity of 1,285 at 40 ° C. From this step, the solution of the filtrate is cooled in the cooler 84 to about 0 ° C in order to produce a filtrate containing by weight, about 5% sodium sulfate, 28% ammonium sulfate and 6% sodium bicarbonate. The solution is filtered with the filter 86 and the precipitated sodium bicarbonate and the sulphate of Sodium is recycled and returned to the bicarbonate crystallization vessel 32, while the filtrate is reacted with potassium chloride in vessel 88 to synthesize potassium sulfate in a first step with a purity in the range of about between 75% and 90%. Solid potassium sulfate is repulped in vessel 94 with potassium chloride brine from vessel 92. This results in high-grade, high-grade potassium sulfate. The product is washed with water in the conventional washing stage 96 and recycled to the container 94. The solution of the filter 90 is evaporated in the evaporator 98 (FIG. 2A) to concentrate the ammonium chloride liquor so that upon cooling they are reduced at least potassium chloride and sulfates. The solution is filtered through filter 100 and precipitated potassium chloride and (x) S04, where x = K, Na, are recycled to vessel 88. Filtrate from filter 100 containing ammonium chloride, potassium chloride and Potassium sulphate is passed to evaporator 102. Sodium bicarbonate reverses the reaction and consequently ammonia and carbon dioxide are released. These gases are then purified and handled by means of suitable techniques. The calcium chloride that is generated, discarded or commercialized. 52/113 EXAMPLE 2 THERE IS NO ELIMINATION OF BICARBONATE Feeding - 1 liter at 1.3 G.E. 360 g / 1 Na2S04 Ia STAGE NaHC03 production Brine outlet at the end of the reaction: 13 Og Na2S04 10.4% Na2S04 40 ° C 213.8g (NH4) 2S04 17.1% (NH4) 2S04 1.250 G.E. to 0.95 1 lOOg NaHC03 8.0% NaHCO, solution 907g HA) 1350.8 This gives 172g of solids of NaHCO3 consumes 55g NH3 142.5g C02 When saturating again with Na2S04: the brine retains 150g of Na2S04. The brine is then filtered and fed to a second stage in the NaHCO crystallizer. 52/113 The exit brine is then cooled to 0 ° C. The composition of the brine is: 5% Na2SO4 which means that 60g of Na2SO4 is precipitated as 136g of Na2SO410H2O and 76g of H20 are removed. Therefore: 907 - 76 = 831g H20. Composition of the brine at 0 ° C and 1.26 G.E. 70g Na2SO4 353g (NH4) 2S04 lOOg NaHCO3 831g H2O 1354g TOTAL Approximately 1 liter of brine K2S04 a) 70s Na.SQ1 x 174 = 85 142 B 353a (NH) SO x 174 = 465.3g 132 EXIT BRANCH: 283g NH4C1 21. 9% 57g NaCl 4. 8% 52/113 119g (KNaHC03) 9.2% 83lg HO 1290 Boiling to 33.0% of NH4C1 is boiled NH3 and CO2 are released from the evaporator, but NH4C1 precipitates KCl and not NaCl. The KCl is recovered in the same manner as in Example 1. BASE: A ton of carcass of Na SO, 52 / ll3 EXAMPLE 3 - ELIMINATION OF BICARBONATE - WITHOUT EVAPORATION OF AMMONIUM CHLORIDE Feed solution: from # 1 412g (NH) 2S0 335g Na2S0 1267g H2Q 2014g to 1.265 = 1.60 1 Cool at 0 ° C gives a filtered solution of: 412g (NH4) 2S04 28.7% 116g Na2S04 8.0% 907g H20 1435g solution 52 / ll This brine is heated to 25 ° C and KCl solids are added to produce K2S0. The exit brine from the K2S0 circuit has the following composition: NH4C1 330.8g 21.9% KCl 130g 8.6% NaCl 94.7g 6.3% x-S04 50g 3.3% x = Na / K H20 907g 60 1512g This brine is heated and reacted with lime to recover ammonia and avoid passing through the evaporator. KCl is reported in the CaCl2 brine rather than recovered in the evaporator. This represents a loss of 15 to 20% K in the CaCl2 brine. The KCl in the CaCl2 brine can be reduced to as low as 1.0% by adding solid Na2SO to the brine CaCl2 / KCl. Potassium is in fact collected as a singenite precipitate (CaS04 • K2S04 • xH20) at 0-100 ° C at preferred temperatures of 20 to 30 ° C so that the solubility is kept to a minimum and the reaction is carried out at a reasonable speed. Composition of CaCl2 brine 343. 3g CaCl2 22.5% 130g KCl 8.5% 52 / ll3 94. 7g NaCl 6.3% 50g x S0 32% (Na / K) 907g H20 59.5% 1525g 100% Addition of 140g Na2S0: Output brine Output cake 234.8g CaCl2 17.8% 15.25g NaCl 1.1% 310g CaS04 • K2S0 209g NaCl 15.9% + lOOg H20 50g x S04 3.8% 807 61.3% Exit brine can be discarded and the Cake can be mixed with the product K2S0 as a binder or subsequently processed to remove CaS04. The cake can react with (NH4) 2HC03 from the feed to the NaHCO3 process and the CaS0 reacts rapidly to produce a brine of (NH) 2S0 and K2S04 and a precipitate of CaCl3 which is discarded after filtration. The brine (NH4) 2S04 / K2S0 is recycled to the crystallizer from the first stage of K2S0. 52/113

Claims (2)

1. CLAIMS. A method for producing sodium bicarbonate of food grade and potassium sulfate, characterized in that the method comprises the steps of: a) providing a liquid source of sodium sulfate; b) provide a source of ammonium bicarbonate to precipitate sodium bicarbonate; c) contacting sodium sulfate and ammonium bicarbonate; d) precipitate the sodium bicarbonate and form a liquor; e) filter the sodium bicarbonate; f) saturating the liquor from step e) with sodium sulfate; g) contacting the liquor with ammonium carbonate, ammonia gas or carbon dioxide to precipitate additional sodium bicarbonate; h) filtering the precipitated sodium bicarbonate from step g); i) combining the precipitate of sodium bicarbonate from step e) and h) and washing to form sodium bicarbonate food grade; j) cooling the liquor from step i) to at least 0 ° C to form Glauber's salt precipitate; 52 / ll3 k) treat the liquor from step j) with sulfuric acid to convert the carbonate minerals to sulphate minerals and release carbon dioxide gas; 1) heat the liquor from step k) at a temperature between 30 ° C and 40 ° C; and m) precipitating potassium sulfate by contacting the liquor from step 1) with potassium chloride. The method according to claim 1, characterized in that the method further includes the step of separating the precipitated potassium sulfate and washing with potassium chloride. 3. The method according to claim 2, characterized in that the method further includes the step of treating with lime the liquor from the step of separating the precipitated potassium sulfate to release ammonia gas. 4. The method according to claim 3, characterized in that the method further includes the step of recycling the ammonia gas to step g. The method according to claim 4, characterized in that the method further includes the step of evaporating the filtrate from claim 4. 6. The method according to claim 1, characterized in that the sodium sulfate has a specific gravity between 1.30 and 1.34. at 40 ° C. 52/113 7. The method according to claim 1, characterized in that the liquor of step d) has a specific gravity of 1.25 and contains by weight, 10.4% of sodium sulfate, 17.1% of ammonium sulfate, between 8% and 12% sodium bicarbonate and an excess of ammonium bicarbonate. 8. The method according to claim 1, characterized in that the liquor of step e) comprises Na2SO4 • 10H2O. The method according to claim 1, characterized in that the liquor of step f) has a specific gravity of 1285 at 40 ° C. The method according to claim 1, characterized in that the liquor of step k) is a liquor of sodium sulfate, ammonium sulfate and saturated sodium bicarbonate. The method according to claim 1, characterized in that the potassium sulphate is generated with a yield of at least 80% with a purity of at least 98%. The method according to claim 1, characterized in that the potassium sulphate is generated with a yield of at least 80% with a purity of at least 98%. 13. A method to produce sodium bicarbonate 52/113 food grade and potassium sulfate, characterized in that the method comprises the steps of: a) providing a source of liquid sodium sulfate; b) provide a source of ammonium bicarbonate; c) contact the sodium sulphate and the ammonium bicarbonate. d) precipitate sodium bicarbonate and form a liquor; e) precipitating sodium bicarbonate and forming a liquor by contacting the liquor of step d) with sodium sulfate; f) saturating the liquor of step d) with sodium sulfate; g) filtering liquor solids from step e); h) contacting the liquor of step f) with sulfonic acid and precipitating carbonates; i) cooling the liquor from step h) to 0 ° C to form Glauber's salt precipitate; j) heating the liquor from stage 1) between 30 ° C and 40 ° C; and k) treating the liquor from step j) with potassium chloride to precipitate potassium sulfate; 52/113 1) evaporate the liquor from step k) to recover potassium minerals which are recycled to step k); and m) drying the potassium sulfate. The method according to claim 13, characterized in that the method further includes the step of treating the liquor remaining from step 1) with lime and ammonium chloride. 15. The method according to claim 14, characterized in that the ammonia gas is released and recycled. The method according to claim 13, characterized in that the potassium chloride solution used is recycled to step k).
2. 2/113