MXPA01003686A - Method of ammonium sulfate purification - Google Patents

Abstract

A process for synthesizing ammonium sulfate and United States Pharmacopoeia grade sodium bicarbonate. The process allows an energy efficient conversion of precursor sodium sulfate and bicarbonate to ammonium sulfate high grade fertilizer and the pharmaceutical grade sodium bicarbonate by saturation of process brine with sodium sulfate. This step was previously unrecognized in the art, which resulted in prior art methods being ineffectual from engineering, energy and product quality points of view. The present process reintroduces sodium sulfate into the process brine or solution to perpetuate the conversion process in the absence of separation problems and energy expenditures inherent in the prior art techniques.

Description

METHOD FOR THE PURIFICATION OF AMMONIUM SULPHATE TECHNICAL FIELD The present invention relates to a method for purifying ammonium sulfate and, more particularly, the present invention relates to a method for forming high purity ammonium sulfate with sodium sulfate and sodium bicarbonate by progressive precipitation without a high introduction of energy.

BACKGROUND OF THE INVENTION In the prior art the preparation of sodium bicarbonate and sodium sulfate has been analyzed in detail. One of the most recent patents with respect to this technology is Canadian Patent No. 2,032,627, issued on January 14, 1997 to Thompson et al. This reference teaches a process for producing sodium carbonate and ammonium sulfate from natural sodium sulfate. This reference also has to do with the preparation of a double salt of ammonium sulfate and sodium. This is a source of contamination when trying to form reasonably pure ammonium sulfate and the presence of any double salt and sodium in an ammonium sulfate product only reduces the value of ammonium sulfate to a non-commercial product . In the methodology, it is clearly stated on page 13, beginning in line 8: "... the brine that remains after sieving the solid sodium bicarbonate contains a mixture of unreacted sodium sulfate, ammonium sulfate, Ammonium bicarbonate and smaller quantities of sodium bicarbonate This brine is transferred, by means of a pump 36, to a gas heat recovery boiler 31, where it is heated to a temperature of 95 ° to 100 ° C. Under these conditions, the bicarbonate The ammonia is decomposed and the sodium bicarbonate dissolved in the brine reacts with ammonium sulfate to produce sodium sulfate, carbon dioxide and ammonia.The carbon dioxide and ammonia dissolved in the brine are removed by boiling, leaving The solution is a mixture composed mainly of sodium sulfate and ammonium, and the regenerated carbon dioxide and ammonia are cooled in a gas cooler 32 and returned to the reactor. 21 through a blower 33, after being further cooled in a gas cooler 34. This regeneration step minimizes the amount of carbon dioxide and ammonia used in the process. "It is clear that the brine evaporates and that the ammonium sulfate is reacted with the brine to produce, among other things, sodium sulfate The relationship of the phase balance between the elements present in the system was not recognized. of this reference only stipulate a closed cycle system for a saturated solution system of sodium sulfate and ammonium sulfate.This system can only result in the formation of double salt.On the basis of these teachings, no other result is possible. The teachings are limited, as it is believed that the difference in solubility could provide an ammonium sulfate product This is incorrect, the result is a contaminated ammonium sulfate system In U.S. Patent No. 3,493,329, Stiers et al., The teachings are aimed at the preparation of sodium bicarbonate and hydrochloric acid.This goal is consistent with the teachings of Stiers et al. column 11 of the presentation, beginning in row 23 to row 43, where the following is indicated: "If, instead of precipitating double salt in the first stage of the process, it is preferred to precipitate ammonium sulfate, it can be adopted The following procedure. Referring now to Figure 10, it will be observed that each of the three curves that divide this figure into three parts corresponds to the simul taneous precipitation of two salts. At any given temperature, the point representing the system can move vertically by removing some of the water from the solution. To precipitate ammonium sulfate instead of double salt, it is necessary to operate at a higher temperature than the triple point, that is, approximately 59 ° C. Point A, which corresponds to approximately 63 ° C, is adequate, since it is far enough from the triple point to avoid undesirable precipitation of the double salt without requiring much heat. It is clear that at point A, there is the simul- taneous precipitation of sodium sulfate and ammonium sulfate, but these are in the form of a mixture of the two salts rather than as a double salt. " Stiers et al., Are not only insufficient to instruct someone for the formulation of ammonium sulfate in a purity greater than 75%, but the disclosure also completely lacks any teaching on how to obtain only ammonium sulfate. de Stiers et al. does not and can not result in the generation of ammonium sulfate as a single product, as is clearly possible thanks to the teachings of the present invention.

Following the methodology of Stiers et al., A pure ammonium sulfate product can not be generated, since the reference fails completely to recognize the limitations of the salt balance of the salt system and the combination of steps necessary to overcome the inherent contaminant steps associated with this saline system. Although there is a reference to a point A in Figure 10 of Stiers et al. for the preparation of the product, it is clear that although it is not indicated that there is a double salt in the mixture, there is no indication that the product does not include the mixed salt. This is reflected in the discovery, where Stiers et al., Indicate that there is simultaneous precipitation of sodium sulfate and ammonium sulfate. This is consistent with the data provided by Stiers et al., As indicated in column 12, beginning in line 21. Data are not presented where the amount of ammonium sulfate is exposed, which rises by itself. In each case, the data presented is expressed as a proportion precipitated in a compound, that is, among other things, double salt. Finally, from the text that is exposed and that begins in row 32, Stiers et al. indicate that: "... From the foregoing, it will be noted that the process, according to the invention, can be carried out by precipitating ammonium sulfate in the form of the double salt or as (NH4) 2S04, simultaneously with sulphate. of sodium or by precipitating them simultaneously in the form of ammonium sulfate and in the form of double salt ". Starting from the review of Figures 10 and 11, it becomes evident that no ammonium sulfate was generated alone. No data are presented for the generation of ammonium sulfate; the results of putting this methodology into practice are only a mixed salt and a double salt. Nothing else can be obtained by putting this method into practice. Finally, Kresnyak et al., In U.S. Patent No. 5,830,442, issued November 3, 1998, teach an improved process for producing ammonium sulfate. This process is attractive where the energy consumption and the conversion efficiency are not of main interest. In this process, sodium sulphate is eliminated by means of the important introduction of energy to the evaporators with a subsequent cooling. The result is a 2: 1 ratio of the double salt to the solution which must then be evaporated to recover ammonium sulfate. As the experienced process designer will appreciate, this separation creates difficulties in terms of filtering a significant amount of precipitated double salt. In addition, the process uses the technique of redissolving the double salt and adding it to the evaporator to prepare sodium sulphate for the recycle stream. This procedure adds to the evaporative load of the process. In previous attempts to maximize yields and productivity, there was no awareness that the initial solution containing sodium sulfate was below saturation, that is, it was under-saturated; this detail is important in the perpetuation of the reactions involved in the synthesis of ammonium sulfate. In view of the limitations of the prior art, it is evident that there continues to be a need for a process by which ammonium sulfate can be formulated with high yield and high purity, using unit operations that make efficient use of energy, in a appropriate sequence. The present invention meets these objectives in an elegant form to formulate US-type Pharmacopeia-type sodium bicarbonate and ammonium sulfate.

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

EXPOSITION OF THE INVENTION An object of the present invention is to provide an improved process for preparing industrial grade sodium bicarbonate and ammonium sulfate. A further object of an embodiment of the present invention is to provide a method for recovering purified solution of ammonium sulfate from a solution of sodium sulfate, carbon dioxide, ammonia or ammonium ions, characterized in that the method comprises the steps of: a) precipitate, in at least one precipitation operation, a precipitate of sodium bicarbonate to increase the concentration of sodium sulphate in solution, while reducing the concentration of sodium bicarbonate in the solution; b) centrifuge and wash the precipitated sodium bicarbonate to convert the precipitate into industrial grade sodium bicarbonate; c) saturating the solution from step a) with either sodium sulfate or ammonium bicarbonate by adding sodium sulfate or ammonium bicarbonate to the solution at a temperature between 35 ° C and 50 ° C to form a second precipitate of sodium bicarbonate; d) conditioning the solution of step c) by at least any of the heating of the solution at 95 ° C to release ammonia and carbon dioxide and contacting the solution of step c) with sulfuric acid to degas any carbonate minerals; e) cooling the solution from step d) to a temperature between -2 ° C and 2 ° C to form a third precipitate of sodium bicarbonate; f) recycling the precipitates of steps d) and e) to step a); g) treating the solution of step e) with sulfuric acid to degas any carbonate minerals remaining from the sodium bicarbonate and reducing the sodium sulfate to less than 7% by weight; and, subsequently h) recover the purified solution of ammonium sulfate. Advantageously, the double salt found during the formulation of the ammonium sulfate is in a ratio of about 0.3: 1. This has a major influence on the energy consumption of the process. As an example, it requires approximately 5 MBtu to 7 MBtu of energy to compete with the evaporation of the solution. Clearly, when the proportion of double salt increases, the input of energy also increases, thus reducing the efficiency of the process. In addition, when the ratio is maintained in a relatively small number, the separation of ammonium sulfate from sodium sulfate is significantly facilitated, since one does not have to compete with massive amounts of the solid double salt for a small amount of liquid product. In this way, filtering is simplified without risking equipment failure or other complications that lead to degradation of efficiency. Another object of an embodiment of the present invention is to provide a method for recovering purified solution of ammonium sulfate from a solution of sodium sulfate, carbon dioxide, ammonia or ammonium ions, characterized in that the method comprises the steps of: a ) precipitate, at least in a precipitation operation, a precipitate of sodium bicarbonate to increase the concentration of ammonium sulfate in solution, while reducing the concentration of sodium bicarbonate in solution; b) centrifuging and washing the precipitate of sodium bicarbonate to convert the precipitate into industrial grade sodium bicarbonate; c) saturate the solution from step a) with sodium sulfate or with ammonium bicarbonate, by adding sodium sulfate or ammonium bicarbonate to the solution at a temperature between 35 ° C and 50 ° C to form a second precipitate of sodium bicarbonate; d) conditioning the solution of step c) by either heating the solution to 95 ° C to release ammonia and carbon dioxide and contacting the solution of step c) with sulfuric acid to degas any carbonate minerals; e) cooling the solution from step d) to a temperature between -2 ° C and 2 ° C to form a third precipitate of sodium bicarbonate; f) recycling the precipitates of steps d) and e) to step a); g) heating the solution from step e) to a temperature of 95 ° C to convert the residual sodium bicarbonate into sodium sulfate and release ammonia and carbon dioxide for recycling; and, subsequently h) recover the purified solution of ammonium sulfate. A further object of an embodiment of the present invention is to provide a method for forming ammonium sulfate from sodium sulfate and sodium bicarbonate, characterized in that the method comprises the steps of: a) providing a solution of sodium sulfate; b) contacting the sodium sulfate solution with carbon dioxide and ammonia or ammonium ions to form a first precipitate of sodium bicarbonate and a solution containing ammonium sulfate; c) progressively precipitate sodium bicarbonate from the solution to increase the concentration of ammonium sulfate and reduce the concentration of sodium bicarbonate in the solution; d) recover as product the first precipitate of sodium bicarbonate; e) centrifuging and washing the first precipitate of sodium bicarbonate to convert the sodium bicarbonate into industrial grade sodium bicarbonate; f) treating the remaining solution of part d) with sodium sulfate at a temperature between 35 ° C and 50 ° C to form a second precipitate of sodium bicarbonate; g) recovering the second precipitate of sodium bicarbonate and recycling the second precipitate recovered to step b); h) conditioning the solution of step g) by either heating the solution to 95 ° C to release ammonia and carbon dioxide and contacting the solution of step g) with sulfuric acid to degas any carbonate minerals; i) cooling the solution remaining from step h) to a temperature between -5 ° C and 2 ° C to form a third precipitate of sodium bicarbonate and precipitates of sodium sulfate and ammonium sulfate; j) recovering the third precipitate of sodium bicarbonate and the precipitates of sodium sulfate and ammonium sulfate from the solution of step i) and recycling the recovered third precipitate and the precipitates of sodium sulfate and ammonium sulfate to step b); k) treating the remaining solution of step j) with sulfuric acid to degas any carbonate minerals remaining from sodium bicarbonate and reducing sodium sulfate to less than 7% by weight; and, subsequently 1) recover the purified solution of ammonium sulfate. As a particularly advantageous feature of the present methodology, the solution, before cooling, contains at least 24% of ammonium sulfate which, when cooled, prevents the formation of double salt, since the sodium salt is used efficiently. A further object of an embodiment of the present invention is to provide a method for forming ammonium sulfate from sodium sulfate and sodium bicarbonate, characterized in that the method comprises the steps of: a) providing a solution of sodium sulfate; b) contacting the sodium sulfate solution with carbon dioxide and ammonia or ammonium ions to form a first precipitate of sodium bicarbonate and a solution containing ammonium sulfate; c) progressively precipitate sodium bicarbonate from the solution to increase the concentration of ammonium sulfate and reduce the concentration of sodium bicarbonate in the solution; d) recover as product the first precipitate of sodium bicarbonate; e) centrifuging and washing the first precipitate of sodium bicarbonate to convert the sodium bicarbonate into industrial grade sodium bicarbonate; f) treating the remaining solution of part d) with sodium sulfate at a temperature of 38 ° C to form a second precipitate of sodium bicarbonate; g) recovering the second precipitate of sodium bicarbonate and recycling the second precipitate recovered to step b); h) conditioning the solution of step g) by either heating the solution to 95 ° C to release ammonia and carbon dioxide and contacting the solution of step g) with sulfuric acid to degas any carbonate minerals; i) cooling the solution remaining from step h) to a temperature of 2 ° C to form a third precipitate of sodium bicarbonate and precipitates of sodium sulfate and ammonium sulfate; j) recover the third precipitate of sodium bicarbonate and the precipitates of sodium sulfate and ammonium sulfate from the solution of step i) and recycle the recovered third precipitate and the precipitates of sodium sulfate and ammonium sulfate to step b); k) treating the remaining solution of step j) with sulfuric acid to degas any carbonate minerals remaining from sodium bicarbonate and reducing sodium sulfate to less than 7% by weight; 1) removing the precipitates formed in the solution of step k); and m) recovering the purified solid of ammonium sulfate. With regard to the formulation of sodium bicarbonate, from the centrifugation and washing of sodium bicarbonate, the result is a product of industrial grade, in accordance with the Pharmacopoeia of the States United . In a variant of the processes set forth herein, a single sodium bicarbonate precipitation operation may be used instead of at least two of these operations. This can be achieved by using an excess of sulfuric acid to remove the carbonate compounds. Another additional object of an embodiment of the present invention is to provide a method for forming ammonium sulfate from sodium sulfate and sodium bicarbonate, characterized in that the method comprises the steps of: a) providing a solution of sodium sulfate; b) contacting the sodium sulfate solution with carbon dioxide and ammonia or ammonium ions to form a first precipitate of sodium bicarbonate and a solution containing ammonium sulfate; c) progressively precipitate sodium bicarbonate from the solution to increase the concentration of ammonium sulfate and reduce the concentration of sodium bicarbonate in the solution; d) recover as product the first precipitate of sodium bicarbonate; e) centrifuging and washing the first precipitate of sodium bicarbonate to convert the sodium bicarbonate into industrial grade sodium bicarbonate; f) treating the remaining solution of part d) with sodium sulfate at a temperature between 35 ° C and 50 ° C to form a second precipitate of sodium bicarbonate; g) conditioning the solution of step f) by either heating the solution to 95 ° C to release ammonia and carbon dioxide and contacting the solution of step f) with sulfuric acid to degas any carbonate minerals; h) cooling the solution containing the second sodium bicarbonate precipitation from step f) to a temperature between -5 ° C and 2 ° C to further precipitate sodium bicarbonate and form precipitates of sodium sulfate and ammonium sulfate; i) treating the solution, the precipitate of sodium bicarbonate and the precipitates of sodium sulfate and ammonium sulfate from step h) with sulfuric acid to precipitate the rest of the sodium bicarbonate; j) recover the precipitate of sodium bicarbonate and the precipitates of sodium sulfate and ammonium sulfate from the solution of step i) and recycle the precipitate of sodium bicarbonate recovered and the precipitates of sodium sulfate and ammonium sulfate to step b ); and k) recovering the purified solution of ammonium sulfate. Another object of an embodiment of the present invention is to provide a method for desulfurizing a gaseous stream containing sulfur, characterized in that the method comprises the steps of: a) exposing the stream to oxidant conditions to generate a sulfur-containing compound; b) contacting the sulfur-containing compound with sodium bicarbonate to generate sodium sulfate; and, c) processing the sodium sulfate according to the method of claim 1.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a process flow diagram according to the prior art; Figure 2 is another process flow diagram according to the prior art; Figure 3 is an additional process flow diagram, in accordance with the prior art; Figure 4 is a process flow diagram in accordance with one embodiment of the present invention; and Figure 5 is a further embodiment of the process of the present invention. In the different figures the numbers are used correspondingly.

DETAILED DESCRIPTION OF THE PREFERRED MODALITIES Before describing the present invention, a general overview of the prior art will be made together with Figures 1 to 3. Figure 1 illustrates the process flow diagram of the Thompson et al. The process flow diagram of Thompson et al. clearly shows the use of two steps of fertilizer processing, namely an evaporator step that raises the temperature of the mother liquor 2b (ML2b) to 100 ° C and a subsequent cooling step in the fertilizer crystallizer at 60 ° C. The solid is removed as the claimed ammonium sulfate product, while the liquor from this precipitation step is then passed to a double salt cooler at 20 ° C. The liquid from the cooling passage of the double salt is then reintroduced to the fertilizer evaporator at 100 ° C. In the Thompson et al. Process, it was believed that by using the solubility difference, the sodium ion would not act as a contaminant in the generation of ammonium sulfate. This has been found to be a source of complications and, in fact, the reintroduction of the double salt cooler liquor contains sodium and this is reintroduced into the fertilizer evaporator to contaminate the ammonium sulfate product. In this way, the process of Thompson the al.

It effectively provides a closed cycle of contamination, although it claims a product of high purity ammonium sulfate. This result is not possible on the basis of the process illustrated and taught in this patent. The process flow diagram of Stiers et al., Shown in Figure 2, simply shows a process for generating a double salt or a mixed salt, based on similar ingredients initially introduced in the well-known reaction of sodium bicarbonate. The teachings of this reference simply establish what was already known for decades and provide no instruction to the one skilled in the art with respect to the synthesis of ammonium sulfate. Figure 3 shows the process of Kresnyak et al. The process depends on an important input of energy to heat the solution and result in the precipitation of sodium sulphate and formulates massive quantities of the double salt precipitate with respect to the ammonium sulfate solution (ratio of 2: 1). The process, which has a clear utility and merit, does not include an important step necessary to avoid high energy costs and to increase the production of ammonium sulfate; the addition of sodium sulfate to saturate the solution that was not saturated, that is, it was subsaturated. This concept results in the additional availability of sodium and sulfate for an increase in the yields of ammonium sulfate and sodium bicarbonate. Figure 4 illustrates the complete process according to a first embodiment and globally referred to as 10. Initially water, ammonia or a source of ammonium ions and carbon dioxide are mixed in a vessel 12 to form ammonium bicarbonate. The container can be heated to a temperature between 20 ° C and 50 ° C and preferably at 30 ° C. The mixture is subjected to two individual precipitation operations to maximize the removal efficiency of sodium bicarbonate. In the first operation, the ammonium bicarbonate is passed into a crystallization vessel 14 to which sodium sulfate from a source 15 thereof is added, to formulate sodium bicarbonate. At this point, the solution contains approximately 22% by weight of sodium bicarbonate. The bicarbonate is passed to a settler 16 and a filter 18. The solution, after having been filtered, has a composition, by weight, of between 13% and 15% ammonium sulfate, of between 13% and 15% of sodium sulfate and between 8% and 12% sodium bicarbonate. The solution is then repulped with the introduction of water at 40 ° C into the container 20. The mixture is then centrifuged and washed by the centrifuge 22 with practically dry sodium bicarbonate in a drying step. The remaining filtrate is passed to a container 24 and then reintroduced to the container 12. After having been centrifuged and washed, the sodium bicarbonate comprises 99.80% NaHCO 3 with Na 2 SO 4 occluded at a concentration of 600 ppm. By additional processing (Figure 5), bicarbonate can become the standards of the United States Pharmacopoeia and, in this way, has the following composition: Sodium bicarbonate (Specification of the degree of the USP) Dry base Baking soda > 99.9x wt.% Sodium carbonate < xx ppm Insoluble < xx ppm Calcium (as Ca) < xx ppm Magnesium (as Mg) < xx ppm Chloride (as Cl) < xx ppm Sulfate (as S0) < xx ppm Silica (as Yes) < xx ppm Aluminum (as Al) < xx ppm Moisture content < xx% by weight The remaining filtrate from settler 16 is passed to a second crystallization vessel 26 to which anhydrous sodium sulfate is added from source 28 thereof. This is the second precipitation operation of sodium bicarbonate. In this step, the solution contains approximately 15% to 16% of sodium bicarbonate crystals. The solution and precipitated sodium bicarbonate are passed to a separation device, shown in the example as cyclone 29, where the solids will be reintroduced to the settler 16 and the filtrate or solution is passed to the vessel 30 at a temperature between 35 ° C and 50 ° C. The most desirable thing is that this operation on the solution is conducted at 38 ° C. The composition of the solution at this point is, by weight, between 18% and 28% of ammonium sulfate, between 5% and 10% of sodium sulfate and about 8% of sodium bicarbonate. The addition of anhydrous sodium sulfate, as described above, contributes to the success of the process and is a particularity that was not appreciated in the prior art, as discussed supra herein. This facilitates the saturation of the solution with respect to ammonium sulfate. This is a marked difference from the prior art; in this step of the above techniques, the concentration of ammonium sulfate was about 13% by weight (Kresnyak et al., Supra) demonstrating that the addition of sodium sulfate contributes in the present invention to an improvement in the concentration of ammonium sulfate. This particularity has significant consequences in the process and leads to higher yields of the ammonium sulfate product, without problems of contamination or an increase in the evaporative load. By processing the solution or filtrate prior to this operation, the solution is subsaturated with respect to sodium sulfate and, thus, the addition of sodium sulfate increases the saturation of the ammonium sulfate. The solution is passed to a double salt crystallizer 32, cooled by the cooler 34 at a temperature between -5 ° C and 2 ° C and, more desirably, 2 ° C. The temperature can be as low as -15 ° C, although there is a practical limit, since the saturation of ammonium sulfate is reduced with lower temperatures, thus hampering the economy of the process. The solids are filtered in the filter 36 and form a cake. The cake contains water and approximately, by weight, 30% sulfur, 10% sodium and 5% nitrogen and can be recycled to the container 24. The solution contains approximately, by weight, 6% sodium bicarbonate, 5% sulfate of sodium and between 25% and 35% of ammonium sulfate. In this step, the solution could be heated to about 95 ° C to release gaseous ammonia or carbon dioxide. As a second possibility, the solution is passed to the vessel 38 and contacted with sulfuric acid to degas any remaining carbonate minerals of the sodium bicarbonate. In the art this is generally referred to as "neutralization or elimination of bicarbonate". In general, these steps are referred to by number 31 of Figure 5. The remainder of the solution is passed to a crystallization vessel 40 of sodium sulfate at a temperature in the range as stated with respect to crystallizer 32 of double salt and, preferably, at 2 ° C and separated in cyclone 42. The solids are recycled to the filter 36 and the solution, which is now purified ammonium sulfate liquor, is stored in vessel 44. At this point, the solution contains between 3% and 5% by weight of sodium sulfate and thus, there is a significant amount of ammonium sulfate present with respect to sodium sulfate. In view of this difference, large quantities of solid ammonium sulfate can be produced by evaporation in the evaporator 46 without contamination by sodium sulfate. This can be achieved, since the double salt point (16% by weight) of sodium sulphate is clearly avoided by means of a sodium content of 3% to 5% by weight. Accordingly, evaporation at approximately 110 ° C avoids sulphate contamination to ensure process control and product quality. The solid product and the remainder of the liquid are passed to cyclone 48 with the solid ammonium sulfate leaving the dryer 50 and any quantity of liquids transferred to the container 44 for recycling, as indicated by A in Figure 4. The product of Ammonium sulfate from the dryer 50 contains less than 0.5% by weight of sodium sulfate and, thus, is an importantly improved product with respect to that synthesized in the prior art. Turning to Figure 5, the process flow diagram illustrates a variant of the process set forth in Figure 4. In this embodiment, the double salt crystallizer 32 is removed and an excess of sulfuric acid is used to reduce the sodium bicarbonate in solution. This variant of the process is an economically viable alternative where sulfuric acid can be supplied economically. In this process, the solution of vessel 30 is heated to 95 ° C to release gaseous C02 and NH3 and the degassed solution is subsequently cooled to 0 ° C. This is then passed to the sodium sulphate crystallization vessel 40 where the rest of the process steps continue in accordance with the procedure set forth with respect to Figure 4. As an example of the process, the following demonstrates the success of the process. methodology.

EXAMPLE 1 - SOLID CRYSTALS OF NH4HCO Feed 1 liter of saturated Na2SO brine @ 38 ° C and S.G. 1,300 One liter of brine contains 390 g of Na2SO4 in solution. Assume perfect separations of S / L First step 390 g / 1 Na2S04 + 263.7g NH4HC03 150g / l Na2S04 + 223g (NH4) 2S0 + Reaction product # 1 125g / l NaHC03 + 160g NaHC03 (5) The exit brine is now 1,250 S.G. at 38 ° C. This brine is then resaturated with Na2SO4 S.G. of brine 1.34 @ 38 ° C to the brine are added 150g of Na2S0. The composition is now: 300 g / 1 Na2S04: 223 g / 1 (NH4) 2S04 @ 1340 S.G. : 125 g / 1 NaHC03 Second step Now 190 g of NH HC03 was added New composition of the brine: Product 384 g / 1 (NH4) 2S04 204. 6 g of the reaction product # 2 127 g / 1 Na2S04 + 22. 2 reduction in saturation 102 8 g / 1 NaHC? 3 226. 8 g of NaHCQ3 Reactions # 1 + # 2 Product recovered: 160 + 226.8 = 386.8 g of NaCH03 per liter of Na2S04 feed solution.

Cooling step: The brine is cooled to 0 ° C and filtered. Analysis of the brine S.G. 1,250 Solids 62.5 g of Na2S04 64.5 g of Na2S04 350 g of (NH4) 2S04 34 g of (NH4) 2S04 75 g of NaHCO3 27.8 g of NaHCO3 The solids are a wet cake of solids and contain the hydrates of Na2S04, (NH4) 2S04, and NaHCO3 that are recycled to step 1 or step 2.

This wet cake is: Na2S04 - 10 H20 = 144. 7 g (NH4) 2S04-8 H20 = 71. 2 NaHCO3 + 10 H20 = 87 .4 Hydrates of H20: 303 are assumed. g These hydrates are a convenient way to remove water from recycling, which reduces the evaporation load. The total NaHCO3 recovered is: 409 + 27.8 + 436.8 g The efficiency of the conversion process of Na2SO4 into NaHCO3 is: Feeding = 540 g; brine outlet = 62.5 g 75 x 142 (for example, Na2S0) 84 (2) Brine outlet = 126. g Efficiency of the circuit = 76.6% Neutralization of bicarbonate 62.5 g of Na2S04 350 g of (NH4) 2S04 + 43.7 g of H2S04 ® C02 75 g of NaHC03 New composition of the brine. 126 g of Na2SO4 + heat of H2S04 solution 350 g of (NH4) 2S04 This solution is cooled again to 0 ° C 1.24 S.G. 143 g of Na2S04 10H2O 62.5 g of Na2S04 + of Glauber 350 g of (NH4) 2S04 827.5 g of H20 The Glauber salt is recycled to step 1 or 2. The brine is evaporated to 16% Na2SO4 at the outlet. The brine is reached @ 60 ° C and S.G. 1.320 70g of Na2SO4 122.5 g of (NH4) 2S04 yield (NH4) 2S04 = 227.5 g / 1 of evaporator feed 245 g of H20 437. 5 g total The brine is recycled to neutralize bicarbonate to cool it and remove Na2S0.

EXAMPLE 2 As will be evident, the process is particularly well suited to the desulfurization of sulfur-containing streams. The stream is simply exposed to oxidizing conditions to generate a sulfur containing compound, which is then contacted with sodium bicarbonate to formulate sodium sulfate. Respect, U.S. Patents 5,830,422 and 5,654,351 are incorporated herein by reference. The oxidation of S03 to S04 can be carried out by bubbling air or using a peroxide or ozone type oxidant. Also, metals can be precipitated with simple reductions of C03 or sulfur and filtration. NH4HC03 (using anhydrous Na2S0) The saturated solution of NH4HC03 @ 30 ° C contains 263.7 g / 1 of NH4HC03 Therefore: 1 1 of solution + 390g Na2S0 -? H 150 g Na2S04? + 223g (NH4) 2S04? + 125 g C03W + 160 g of NaHC03 (s)? H heat addition. { ¿) Solid liquid (s) The brine is resaturated with 150 g of Na2SO4 to produce a brine of 1.34 @ 38 ° C. NH3 + C02 can be added as a gas or as an NHHC03 solid to complete the reaction. Then 190 g of NH 4 HCO 3 are added.

New brine composition Product 384 g / 1 (NH4) 2S04 204.6 g NaHC03 127 g / 1 Na2S04 80 g / 1 NaHC03 Primary yield of the process 160 + 204.6 = 364.6 g of NaHC03 Although the embodiments of the invention have been described above, they are not limited thereto and it will be apparent to those skilled in the art that numerous modifications form part of the present invention, provided they do not depart from the spirit, nature and scope of the invention. claimed and described.

Claims (22)

1. CLAIMS: 1. A method for recovering purified solution of ammonium sulfate from a solution of sodium sulfate, carbon dioxide, ammonia or ammonium ions, comprising the steps of: a) precipitating, at least in an operation of precipitation, precipitate of sodium bicarbonate to increase the concentration of sodium bicarbonate in solution, the solution contains ammonium sulfate and the elimination of the precipitate of sodium bicarbonate from the solution; b) centrifuging and washing the precipitate of sodium bicarbonate to convert the precipitate into industrial grade sodium bicarbonate; c) saturating the solution of step a) with one of sodium sulfate or ammonium bicarbonate, by adding sodium sulfate or ammonium bicarbonate to the solution at a temperature of between 35 ° C and 50 ° C to form a second precipitate of sodium bicarbonate, which is removed from the solution; d) conditioning the solution of step c) by at least any of the heating of the solution at 95 ° C to release ammonia and carbon dioxide and contacting the solution of step c) with sulfuric acid to decompose any carbonate minerals; e) cooling the solution from step d) to a temperature between -2 ° C and 2 ° C to form a third precipitate of sodium bicarbonate in the absence of double salt formation; f) recycling the precipitates of steps c) and e) to step a); g) treating the solution of step e) with sulfuric acid to decompose any carbonate minerals remaining from the sodium bicarbonate and reduce the sodium sulfate to less than 7% by weight; and, subsequently h) recover the purified solution of ammonium sulfate.
2. 2. The method according to claim 1, further comprising the step of heating the solution from step g) to about 95 ° C, to liberate ammonia and carbon dioxide.
3. 3. The method according to claim 1. wherein the step of recovering the purified solution of ammonium sulfate further includes cooling the solution to a temperature between -5 ° C and 2 ° C.
4. 4. The method according to claim 3, wherein the solution is cooled to a temperature between -2 ° C and 2 ° C.
5. The method according to claim 3, wherein the cooling results in precipitation of Glauber's salt.
6. 6. The method according to claim 5 which further includes the step of filtering the Glauber's salt to provide a solution of ammonium sulfate.
7. The method according to claim 5, further comprising the step of releasing, during cooling, gaseous carbon dioxide.
8. 8. The method according to claim 6. wherein the ammonium sulfate solution contains less than 5% by weight of sodium sulfate.
9. 9. The method according to claim 6, wherein the ammonium sulfate solution is evaporated to form solid ammonium sulfate.
10. The method according to claim 9, wherein the solid ammonium sulfate contains less than 0.5% by weight of sodium sulfate.
11. 11. A method for recovering purified solution of ammonium sulfate from a solution of sodium sulfate, carbon dioxide, ammonia or ammonium ions, comprising the steps of: a) precipitating, at least in a precipitation operation, precipitate of sodium bicarbonate to increase the concentration of sodium bicarbonate in solution, the solution contains ammonium sulfate and the elimination of the precipitate of sodium bicarbonate from the solution; b) centrifuging and washing the precipitate of sodium bicarbonate to convert the precipitate into industrial grade sodium bicarbonate; c) saturating the solution of step a) with one of sodium sulfate or ammonium bicarbonate, by adding sodium sulfate or ammonium bicarbonate to the solution at a temperature of between 35 ° C and 50 ° C to form a second precipitate of sodium bicarbonate, which is removed from the solution; d) conditioning the solution of step c) by at least any of the heating of the solution at 95 ° C to release ammonia and carbon dioxide and contacting the solution of step c) with sulfuric acid to decompose any carbonate minerals; e) cooling the solution from step d) to a temperature between -2 ° C and 2 ° C to form a third precipitate of sodium bicarbonate in the absence of double salt formation; f) recycling the precipitates of steps c) and e) to step a); g) heating the solution from step e) to a temperature of 95 ° C to convert the residual sodium bicarbonate into sodium sulfate and liberate ammonia and carbon dioxide to recycle it to step a); and subsequently h) recover the purified solution of ammonium sulfate.
12. 12. A method for forming ammonium sulfate from sodium sulfate and sodium bicarbonate, comprising the steps of: a) providing a solution of sodium sulfate; b) contacting the sodium sulfate solution with carbon dioxide and ammonia or ammonium ions to form a first precipitate of sodium bicarbonate and a solution containing ammonium sulfate; c) progressively precipitate sodium bicarbonate to reduce the concentration of sodium bicarbonate in the solution, the solution contains ammonium sulfate; d) recover as product the first precipitate of sodium bicarbonate; e) centrifuging and washing the first precipitate of sodium bicarbonate to convert the sodium bicarbonate into industrial grade sodium bicarbonate; f) treating the remaining solution of part d) with sodium sulfate at a temperature between 35 ° C and 50 ° C to form a second precipitate of sodium bicarbonate; g) recovering the second precipitate of sodium bicarbonate and recycling the second precipitate recovered to step b); h) conditioning the solution of step g) by either heating the solution to 95 ° C to release ammonia and carbon dioxide and contacting the solution of step g) with sulfuric acid to decompose any carbonate minerals; i) cooling the remaining solution from step h) to a temperature between -5 ° C and 2 ° C to form a third precipitate of sodium bicarbonate and precipitates of sodium sulfate and ammonium sulfate in the absence of salt formation double; j) recovering the third precipitate of sodium bicarbonate and the precipitates of sodium sulfate and ammonium sulfate from the solution of step i) and recycling the recovered third precipitate and the precipitates of sodium sulfate and ammonium sulfate to step b); k) treating the remaining solution of step j) with sulfuric acid to decompose any carbonate minerals remaining from sodium bicarbonate and reducing the sodium sulfate to less than 7% by weight; and, subsequently 1) recover the purified solution of ammonium sulfate.
13. The method according to claim 12, wherein the solution containing the first precipitate of sodium bicarbonate comprises at least 22% by weight of sodium bicarbonate.
14. The method according to claim 12, wherein the solution of step d) contains between 18% and 28% of ammonium sulfate, between 5% and 15% of sodium sulfate and at least 12% of sodium bicarbonate.
15. 15. The method according to claim 12, wherein the solution of step d) is treated at a temperature of 38 ° C.
16. The method according to claim 12, wherein the solution of step j) contains between 25% and 35% of ammonium sulfate and between 3% and 5% of sodium sulfate.
17. 17. The method according to claim 16, wherein the solution is evaporated to concentrate ammonium sulfate as a solid product.
18. 18. A method for forming ammonium sulfate from sodium sulfate and sodium bicarbonate, comprising the steps of: a) providing a solution of sodium sulfate; b) contacting the sodium sulfate solution with carbon dioxide and ammonia or ammonium ions to form a first precipitate of sodium bicarbonate and a solution containing ammonium sulfate; c) progressively precipitate sodium bicarbonate to reduce the concentration of sodium bicarbonate in the solution, the solution contains ammonium sulfate; d) recover as product the first precipitate of sodium bicarbonate; e) centrifuging and washing the first precipitate of sodium bicarbonate to convert the sodium bicarbonate into industrial grade sodium bicarbonate; f) treating the remaining solution of part d) with sodium sulfate at a temperature of 38 ° C to form a second precipitate of sodium bicarbonate; g) recovering the second precipitate of sodium bicarbonate and recycling the second precipitate recovered to step b); h) conditioning the solution of step g) by either heating the solution to 95 ° C to release ammonia and carbon dioxide and contacting the solution of step g) with sulfuric acid to decompose any carbonate minerals; i) cooling the remaining solution from step h) to a temperature of 2 ° C to form a third precipitate of sodium bicarbonate and precipitates of sodium sulfate and ammonium sulfate in the absence of double salt formation; j) recovering the third precipitate of sodium bicarbonate and the precipitates of sodium sulfate and ammonium sulfate from the solution of step i) and recycling the recovered third precipitate and the precipitates of sodium sulfate and ammonium sulfate to step b); k) treating the remaining solution of step j) with sulfuric acid to decompose any carbonate minerals remaining from sodium bicarbonate and reducing the sodium sulfate to less than 7% by weight; 1) remove the precipitates formed in the solution of step k); and m) recovering purified solid ammonium sulfate.
19. 19. The method according to claim 18. wherein the ammonium sulfate solid contains 0% by weight of sodium sulfate.
20. 20. A method for forming ammonium sulfate from sodium sulfate and sodium bicarbonate, comprising the steps of: a) providing a solution of sodium sulfate; b) contacting the sodium sulfate solution with carbon dioxide and ammonia or ammonium ions to form a first precipitate of sodium bicarbonate and a solution containing ammonium sulfate; c) progressively precipitate sodium bicarbonate to reduce the concentration of sodium bicarbonate in the solution, the solution contains ammonium sulfate; d) recover as product the first precipitate of sodium bicarbonate; e) centrifuging and washing the first precipitate of sodium bicarbonate to convert the sodium bicarbonate into pharmaceutical grade sodium bicarbonate; f) treating the remaining solution of part d) with sodium sulfate at a temperature between 35 ° C and 50 ° C to form a second precipitate of sodium bicarbonate; g) conditioning the solution of step f) by either heating the solution to 95 ° C to release ammonia and carbon dioxide and contacting the solution of step f) with sulfuric acid to decompose any carbonate minerals; h) cooling the solution of step (g) to a temperature between -5 ° C and 2 ° C to further precipitate sodium bicarbonate and form precipitates of sodium sulfate and ammonium sulfate in the absence of double salt formation; i) treating the solution, the precipitate of sodium bicarbonate and the precipitates of sodium sulfate and ammonium sulfate from step h) with sulfuric acid to precipitate the rest of the sodium bicarbonate; j) recover the precipitate of sodium bicarbonate and the precipitates of sodium sulfate and ammonium sulfate from the solution of step i) and recycle the precipitate of sodium bicarbonate recovered and the precipitates of sodium sulfate and ammonium sulfate to step d ); and k) recover purified solution of ammonium sulfate.
21. The method according to claim 20 which further includes the step of evaporating the purified ammonium sulfate solution to form a solid ammonium sulfate product.
22. 22. The method according to claim 21, wherein the solid ammonium sulfate contains 0% by weight of sodium sulfate.