CZ20011176A3 - Process for preparing 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

Technical field

The present invention relates to a process for the preparation of alkali metal salts, and more particularly to a process for the production of food grade sodium bicarbonate and potassium sulphate of a purity suitable for fertilization.

BACKGROUND OF THE INVENTION

Many work has already been done to prepare alkali metal salts. For example, many different methods are known for the preparation of sodium bicarbonate. In spite of this, energy inefficiencies in previous sodium bicarbonate synthesis units interfere with the energy efficiency, which results in a direct increase in the cost of the synthesis. Another limiting factor of the known processes is the inefficient use of the production equipment to prepare these salts. A single high-quality product is produced at the same time as its by-products q of a quality that is not commercially viable or requires too heavy investments to be commercially paid and to ensure a return on investment.

Representative of the prior art is US Patent No. 3,429,657, issued February 25, 1969 to D'Arcy. This reference describes a process for the isolation and production of potassium salts. In this reference, the potassium-containing brine is reacted with sodium perchlorate to precipitate potassium perchlorate. The potassium is removed with sodium ion exchanger and the free potassium is then reacted with, inter alia, chloride, sulfate or nitrate.

The essence of the invention ·····················

One object of one embodiment of the present invention is to provide the formation of food grade sodium bicarbonate and potassium sulfate, characterized in that the process consists of the following steps:

(a) providing a source of liquid sodium sulfate;

b) providing a source of ammonium bicarbonate;

c) contacting sodium sulfate and ammonium bicarbonate;

d) precipitating sodium bicarbonate and forming a lye;

e) precipitating sodium bicarbonate and forming a caustic by bringing the caustic from step d) into contact with sodium sulfate;

f) saturating the caustic from step e) with sodium sulfate;

g) filtering the solids from the caustic from step f);

h) contacting the caustic from step g) with sulfuric acid to precipitate carbonates;

i) cooling the caustic from step h) to 0 ° C to form a precipitate of Glauber's salt;

j) heating the liquor from step i) to 30 ° to 40 ° C; and

k) precipitating the potassium sulfate by contacting the caustic from step j) with potassium chloride.

It is a further object of one of the solutions of the present invention to provide a process for producing food grade sodium bicarbonate and potassium sulfate characterized in that the process comprises the steps of:

(a) providing a source of liquid sodium sulfate;

b) providing a source of ammonium bicarbonate;

c) contacting sodium sulfate and ammonium bicarbonate;

d) precipitating sodium bicarbonate and forming a lye;

e) precipitating sodium bicarbonate and forming a liquor by contacting the liquor from step e) with sodium sulfate;

f) saturating the liquor of step e) with anhydrous sodium sulfate;

g) filtering the solid from the caustic from step f);

(h) contacting the caustic from step (g) with at least one of the following: ammonium bicarbonate, ammonia gas or carbon dioxide;

- 3 precipitation of sodium bicarbonate;

i) cooling the caustic from step h) to 0 ° C to precipitate sodium bicarbonate and sodium sulfate; and

j) precipitating potassium sulfate by contacting the caustic from step i) with potassium chloride.

It has been found that after formation of sodium bicarbonate, cooling of the caustic to 0 ° C results in significant success in removing sodium sulfate as the Glauber's salt and sodium bicarbonate. The solubility of the Glauber salt in the system can be seen in the phase diagram of the ammonium sulfate-sodium sulfate system. By increasing the sodium sulfate content of the bicarbonate circuit by increasing the amount of Glauber's salt returned, there is a tendency to decrease the bicarbonate solubility and increase the efficiency of the process.

Regarding the conversion of the starting reagents to potassium sulfate, we have been partially successful in keeping the molar ratio for potassium and ammonium ions at five (5) or higher. This ratio ensures high conversion efficiency in the second stage of the process.

Overview of pictures

Brief description of the drawings

Figure 1 is a block diagram showing a first part of one process according to the present invention;

Figure 1a shows a second part of the process shown in Figure 1;

Figure 1b shows a third part of the process shown in Figure 1;

Figure 2 is a block diagram showing a first part of a modified process according to the present invention;

Figure 2a shows a second part of the process shown in Figure 2; and

Figure 2b shows the third part of the process shown in Figure 2.

Similar numbering in the figures points to similar elements.

- 4 List of references first vessel14 first filter16 second vessel22 first centrifuge26 first crystallizer27 recycling circuit28 first reactor29 second filter30 third vessel32 second centrifuge34 second reactor36 eighth filter38 fourth vessel46 first cooler48 fourth filter50 fifth vessel52 sixth vessel 54 sixth filter56 seventh vessel58 eighth vessel ....................... 60 seventh filter ......................... 62 first evaporator ................... 64 fifth filter ............................ .66 third reactor ....................... 68 settler70 skubr72 ninth vessel80 ninth filter82 second cooler84 tenth filter86 tenth vessel88 eleventh filter90 eleventh vessel92 twelfth vessel94 washing stage96 second evaporator98 twelfth filter100 third evaporator102

Examples

Reference is now made to the drawings in Figures 1 to 1b, which illustrate the process of the first solution.

A source of liquid sodium sulfate 10 dissolved in fresh water and tap water 12 will be discussed below. The solution is mixed in the first vessel 14 at 40 ° C to obtain a specific gravity of 1.30. The solution is filtered on a first filter 16, which may for example have a 5 micron filter. The solid particles 18 are removed while the filtrate passes to the first sodium bicarbonate crystallizer 27.

Feed water, ammonia and carbon dioxide, all labeled with number 24, react in the second vessel 22 by synthesizing ammonium bicarbonate. The formed ammonium bicarbonate is centrifuged in the first centrifuge 26 and the solid product is transferred to the first crystallizer 27. The recycle circuit 28 recirculates the solid and liquid ammonium bicarbonate to the first reactor 29. As a result of combining in the first reactor 29, sodium bicarbonate is formed. The mixture is filtered through a second filter 30 and centrifuged. The sodium bicarbonate is washed with water in vessel 32, centrifuged in a second centrifuge 34, and the collected solid is food grade sodium bicarbonate. The wash water is returned to the first vessel 14.

The liquor from the second 1.25 density filter 30 containing approximately 10.4% sodium sulfate, 17.1% ammonium sulfate, 8% sodium bicarbonate, and an excess of ammonium bicarbonate is designed to react with Glauber's salt (discussed below). The liquor in the second 36 ° C 40 ° C reactor reacts with the Glauber salt formed in the cooling phase of the process to be discussed later to form sodium bicarbonate from excess ammonium bicarbonate from the first crystallizer 27. Alternatively, ammonium bicarbonate may be added to the second stage (second reactor 36). ) as a solid, slurry or solution.

The liquor from the second reactor 36 is added to solid sodium sulfate from source 41 in the fourth vessel 40 to form a saturated sodium sulfate and ammonium sulfate liquor. Sufficient ammonium bicarbonate to be added as a solution or a portion of it may be added to complete the reaction to obtain a final liquor having a specific gravity of 1.285 to complete the reaction. The slurry from the fourth vessel 40 is filtered on the third filter 42. Solid sodium bicarbonate 48 passes to the third vessel 32 and the caustic 44 is further treated by additional separation of sodium bicarbonate, which is returned to the third vessel 32. The caustic 44 then passes to the fourth vessel 46 1A). The volume of the sodium bicarbonate circuit can be controlled by evaporating the purified sodium sulfate in the feed to

- 6 obtaining solid sodium sulphate to ensure saturation of the circuit.

Returning to Figure 1A: the fourth vessel 46 contains sulfuric acid to precipitate carbonates. The treated liquor is cooled to 0 ° C in a cooler 48 to isolate the Glauber's salt and filtered on a fourth filter 50. The isolated Glauber's salt is returned to the sodium bicarbonate crystallizer - second reactor 36.

The filtrate contains 25.25% by weight ammonium sulfate and up to 11% by weight sodium sulfate and transferred to a fifth vessel 52 heated to between 30 ° C and 40 ° C and combined with the solid phase 67 of the fifth filter 66 (Figure 1B). . This solution passes into a sixth vessel 54 where the solid potassium chloride reacts to form a 20% by weight ammonium chloride solution, also containing 20.2% ammonium chloride, 6.7% potassium chloride, 4.9% sodium chloride, 2.3 % (x) 2SO ₄ where x = Na and K and solid mixed potassium sulfate crystals with 10-20% ammonium sulfate.

The solution is filtered on a sixth filter 56, wherein the solid fraction contains about 5 wt% potassium chloride, 80 to 85 wt% potassium sulfate, and 10 to 15 wt% ammonium sulfate. The solid fraction was combined with water and potassium chloride brine from vessel 8 in vessel 7 (58). The solid potassium sulfate was centrifuged and filtered on filter 7 (62) and recrystallized with potassium chloride solution at 25 ° C. The remaining ammonium sulfate was converted to potassium sulfate. Potassium sulfate with a purity of more than 98% can be obtained.

In further operations, the caustic or filtrate is treated from the potassium sulfate process units and in particular from the sixth filter 56 according to the process procedure for the process units shown in Figure 1A. The liquor is evaporated in a first evaporator 64 to concentrate the ammonium chloride liquor by minimizing the solution's potassium chloride and residual sulphate content in the solution. The solution is filtered on the fifth filter 66, returning solid 67 to the sixth vessel 54. The filtrate containing about 22% to 30% ammonium chloride is reacted with lime in the third reactor 68 to release ammonia, which is recycled. Created

The calcium chloride may be passed to the settler 70 or scrubber 72 according to the intended further use.

Now that the procedure of this first solution has been mentioned, let us turn to an example of this procedure.

Example 1

Neutralization of bicarbonate prior to the potassium sulphate production process

Charge -1 liter by weight wt. 1.3

360 gr ¹ Na ₂ SO ₄

1st degree

Production of NaHCO ₃

Brine output at completion of reaction:

130 g Na ₂ SO ₄ 10.4% Na ₂ SO ₄ Deň: 32 ° C 213.8 g (NH ₄ ) ₂ SO ₄ 17.1% (NH ₄ ) ₂ SO ₄ m. 1,250 @ 0.95 100g NaHCOs 8.0% NaHCO 3 solution 907 q H _? O

1350.8

This produces 172 g of solid NaHCO ₃ consumes 55 g of NH ₃

142.5 g CO ₂

Second level calculation

A) 25.07 g NH ₃ + 64.9 g CO ₂

B) 51.2 g NH ₃ + 132.6 g CO ₂

2nd degree. 0.95 I brine dissolves:

A) 1 mol

Na ₂ SO ₄ .10H ₂ O (332g)

B) 2 moles

Na ₂ SO ₄ .10H ₂ O (644 g)

272 g Na ₂ SO ₄

213.8 g (NH ₄ ) ₂ SO ₄

100 g NaHCO 3 1087 q H 2 O

1672.8

16.2% Na ₂ SO ₄

12.8% (NH ₄ ) ₂ SO ₄

5.9% NaHCO ₃

65.1% H ₂ O

414 g Na ₂ SO ₄

213.9 g (NH ₄ ) ₂ SO ₄

100 g NaHCO ₃ 1267 q H 2 O

1999

20.7% Na ₂ SO ₄

10.7% (NH ₄ ) ₂ SO ₄ 5.0% NaHCO 3

63.4% H ₂ O

m.hm. 1,275 and 1,313 l of brine m.hm. 1,300 and 1,5 L brine

2nd degree. Composition of the resulting solution

A) 167.3 g Na ₂ SO ₄ 10% Na ₂ SO ₄ 311 g (NH ₄ ) ₂ SO ₄ 18.9% (NH ₄ ) ₂ SO ₄ 131 g NaHCO ₃ 8% NaHCO ₃ 1087 qH 2 O 63, 1% H ₂ O B) 200 g Na ₂ SO ₄ 10% Na ₂ SO ₄ 412 g (NH ₄ ) ₂ SO ₄ 20.2% (NH ₄ ) ₂ SO ₄ 160g NaHCO ₃ 8% NaHCO ₃ 1267 q H2O 61.8% H2O 2039 g of solution Made 193.2 g of NaHCO ₃ wt. 1.285 to form 1.6 L of solution 1644.5 g of solution Made 92.9 g of NaHCO ₃ m. 1,265 and form 1,311 brine

Neutralization of bicarbonate

412 g (NH ₄ ) ₂ SO ₄

200 g Na ₂ SO ₄

160g NaHCO ₃ +

1267 g H ₂ O__________________________

2039 g (1.61)

m. 1,285

160 x 98 = 93.3 g H ₂ SO ₄

82 (2)

It comes out:

412 g (NH ₄ ) ₂ SO ₄

335 g Na ₂ SO ₄

1267 q H? O

2014 g @ 1.265 = (1.61) Na ₂ SO ₄ must be added to saturate per m / m. 1.30

1.61 x 1.30 = 2080

Therefore:

412 g (NH ₄ ) ₂ SO ₄

400 g Na ₂ SO ₄

1267q H ₂ O

2079 g total (1.61)

Cooling

412 g (NH ₄ ) ₂ SO ₄

116 g Na ₂ SO ₄

907 q H ₂ O

1435 g of solution

28.7%

8,0%%

Evaporator power supply

NH ₄ CI 330.8 g 21.9%

KCI 130 g 8.6%

NaCl 94.7 g 6.3% x-SCU 50 3.3%

H 2 O 907 g 60.0

1512 g @ 33% NH ₄ Cl then: -2.8% KCl then: -2.0% K ₂ SO ₄

Therefore: 330.8 = 1002 g

0.33

Evaporator content = 907 - 623 = 284 g

0.79 Mp ^-1 Na ₂ SO ₄ addition of 0.5 tons per wash

1.29tH ₂ O.ť ¹ Na ₂ SO ₄

Reaction of K ₂ SO ₄

a) K ₂ SO ₄ from (NH ₄ ) ₂ SO ₄ = 412 x 174 = 543 g

132

b) K ₂ SO ₄ from Na ₂ SO ₄ = 116x 174 = 142 g

142

c) losses of K ₂ SO ₄ -43 g

The resulting K ₂ SO ₄ 642 g

Insulation KCI

a) Reaction intermediate KCl = 685 x 2 x 74 = 582 g

174

b) loss of KCl in the residue = 50 g

(c) therefore: consumption of KCI = 632 g

Yield of K 2 SO ₄ = 642x100 = 93.7%

685

KCI conversion efficiency = 582 x 100 = 92.1%

632

Basis: one tonne of Na ₂ SO ₄ charge Input

Product »· ··» ·

First stage 0.153 t NH ₃ 0.396 t CO ₂ 2.52 t H ₂ O 0.48 t NaHCO ₃ Second stage Na ₂ SO ₄ .10H ₂ O 644 g 0.142 t NH ₃ 0.368 t CO ₂ 0.53 t NaHCO ₃ neutralization of bicarbonate + saturation of Na ₂ SO ₄ 0.26 t H ₂ SO ₄ 0.18tNa ₂ SO ₄ Filtration to obtain clear brine Cooling to 0 ° C -BTU 1.8t Na ₂ SO ₄ .10H ₂ O Brine cooler 1,141 (NH ₄ ) ₂ SO ₄ 0,32 t Na ₂ SO ₄ 2,52 t H _? About 3.99 t total 28.7% 8,0% 63% KCI = 1.76 t 1.78tK ₂ SO ₄ Evaporation to 33% NH ₄ Cl 1.29 m.p. ¹ Na ₂ SO ₄ 0,92 t NH ₄ CI brine 0,08 t KCI 0,05 t K ₂ SO ₄ 1,73 tH ₂ O 2,78 total solids 0,28 t KCl 0,08 t K ₂ SO ₄ 0,36 t recyclate Calcium process @ 85% of 0.57 t CaO 0,29 t NH ₃ Brine: 0.9551 CaCl ₂ 0.08 t KCI 0.051 K ₂ SO ₄ 1.73 t H ₂ O 2.815 t @ 75 to 90 ° C

• 4 • · • ··

Figures 2 to 2b show an alternative flow diagram. In this reaction scheme, the caustic soda is saturated with anhydrous salt prior to sodium bicarbonate production.

According to another embodiment of the process for producing sodium bicarbonate, ammonium bicarbonate is prepared in the crystallizing second vessel 22 and generally followed by steps similar to those in Figures 1 to 1B. The brine or filtrate was saturated with anhydrous sodium sulfate in the second reactor 36 and filtered through an eighth filter 38 to remove insoluble matter. The filtrate from this operation is allowed to react with ammonium bicarbonate in ninth vessel 80. Alternatively, the filtrate may be reacted with ammonia or carbon dioxide to precipitate sodium bicarbonate. The solution was filtered through ninth filter 82 to leave sodium bicarbonate. This was combined with sodium bicarbonate from the second filter 30, then washed, centrifuged and dried. These steps are not shown.

The remaining filtrate has a weight composition of about 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 filtrate is cooled in a second condenser 84 to about 0 ° C to obtain a filtrate containing about 5% sodium sulfate, 28% ammonium sulfate and 6% sodium bicarbonate. The solution is filtered through tenth filter 86 and the precipitated sodium bicarbonate and sodium sulfate are filtered. it is returned to the bicarbonate crystallizer - third vessel 32, while the filtrate is allowed to react with potassium chloride in tenth vessel 88 to synthesize a first stage of potassium sulfate of about 75 to 90% purity. The solid sodium sulfate is stirred with potassium chloride brine from the eleventh vessel 92 in the twelfth vessel 94. This results in a highly pure potassium sulfate. The product is washed with water in a conventional washing step 96 and returned to the twelfth vessel 94.

The solution from eleventh filter 90 is evaporated in a second evaporator 98 (Figure 2A) to concentrate the ammonium chloride liquor, thereby minimizing cooling by cooling

potassium chloride and sulfates. Filter the solution through twelve potassium chloride precipitated filter 100 and (x) SO ₄ , where x = K and Na, and return to the tenth vessel 88.

The filtrate from the twelfth filter 100 containing ammonium chloride, potassium chloride and potassium sulfate is transferred to a third evaporator 102. Sodium bicarbonate is decomposed resulting in the release of ammonia and carbon dioxide. The gases are then properly scrubbed in a scrubber and handled appropriately. The calcium chloride formed is then disposed of or sold.

Example 2

No neutralization of bicarbonate

Charge -1 liter by weight wt. 1.3

360 gr ¹ Na ₂ SO ₄

1st degree

Production of NaHCC> 3

Brine output at the end of the reaction:

130 g Na ₂ SO ₄ 10.4% Na ₂ SO ₄ Deň: 32 ° C 213.8 g (NH ₄ ) ₂ SO ₄ 17.1% (NH ₄ ) ₂ SO ₄ m. 1,250 @ 0.95 100 g NaHCO ₃ 8.0% NaHCO ₃ solution

907 g H2O

1350.8

This creates a 172 g of solid NaHCO ₃ consume 55 g of NH3

142.5 g CO ₂

Re-saturation of Na ₂ SO ₄ : the brine will contain 150 g of Na ₂ SO ₄ . The brine was then filtered and passed to the second stage of the NaHCO 3 crystallizer.

Batch Reaction Output brine Product

280 g Na ₂ SO 4 213.8 g (NH ₄ ) 2 SO ₄ 100 g NaHCO 3 907 q H ₂ O 1490.8 g 1.151 @ m / m. 1.32 35.9 g NH ₃ 92.9 g CO ₂ 130 g Na ₂ SO 4 353 g (NH ₄ ) ₂ SO ₄ 100 g NaHCO ₃ 907 q H ₂ O 1490 g m / m. 1.285 1.151 23.7% (NH ₄ ) 2 SO ₄ 177 g NaHCO ₃

The outlet brine was then cooled to 0 ° C.

The brine composition is: 5.0% Na ₂ SO 4 which is 60 g Na ₂ SO 4 precipitate as 136 g Na ₂ SO 4 .10H ₂ O precipitate and 76 g water removed.

Therefore: 907-76 = 831 g of H ₂ O.

Brine composition at 0 ° C and mw wt. 1.26.

g Na ₂ SO ₄

353 g (NH ₄ ) ₂ SO ₄

100g NaHCOa

831 q H ₂ O

1354 q total

About 1 liter of brine.

K ₂ SO ₄

a) 70 q Na ₂ SO 4 x 174 = 85.8

142

b) 353 q (NH 4) ₂ SO 4 x 174 = 465.3 g

132

Output brine:

283 g NH ₄ Cl 57 g NaCl 119 g (KNaHCO ₃ ) 831 q H 2 O 1290 g 21.9% 4.8% 9.2%

Boil to 33.0% NH ₄ Cl.

Release of NH ₃ and CO ₂ from the NH ₄ Cl evaporator outside KCl and NaCl. KCI is returned as in Example 1.

Basis: 1 ton of Na ₂ SO 4.

inputs product First stage 0.15 tNH ₃ 0.396 t CO ₂ 2.52 t H ₂ O 0.48 t NaHCO ₃ Second stage 0.10 t NH ₃ 0.26 t CO ₂ 0.42 t Na ₂ SO ₄ 0.49 t NaHCO ₃ Cooling to 0 ° C 0.4 t Na ₂ SO ₄ .10H ₂ O Brine cooler 0.19 t Na ₂ SO ₄ 5% 0.98 t (NH ₄ ) ₂ SO ₄ 26% 0.28 t NaHCO ₃ 7.4% 2.31 t H? O 61.4% 3.76 t total

input product KCI 1,62 t 1.8 t K ₂ SO ₄ Evaporation to 33% NH ₄ Cl Solanka Solids circuit control = 0.7 t H ₂ O 0.98 t NH ₄ CI 0.28 t KCI Washing = 0.5 t 1.2 t H ₂ O.ť ¹ Na ₂ SO ₄ 0.08 t KCI 0,08 t K ₂ SO ₄ Into the evaporator 0.15 t NaCl 0,36 t 0.19 t NaCl from CO 1.57 t H ₂ O 2.97 t 3 Lime process @ 85% efficiency 1.01 tCl ₂ 0.61 t CaO 0.08 t KCl 0.34 t NaCl 1.57 t H ₂ O 3.0 t @ 75-90 ° C

Example 3 - Neutralization of bicarbonate - without evaporation of ammonium chloride

Batch solution: from # 1412 g (NhU ^ SCU

335 g Na 2 SO ₄

1267 q H? O

2014 g @ 1.265 = 1.601

Cooling to 0 ° C has the following filtered solution yield:

412 g (NH ₄ ) ₂ SO ₄ 28.7%

116gNa ₂ SO ₄ 8.0%

907 g of l-bO

1435 g of solution

The brine is then heated to 25 ° C when solid KCl is added to form K ₂ SO ₄ . The rising brine from the K ₂ SO ₄ circuit has the following composition:

NH ₄ Cl 330.8 g 21.9% KCl 130 g 8.6% NaCl 94.7 g 6.3% x-SO ₄ 50 g 3.3% H ₂ O 907 q 60 1512 g

x = Na / K

The brine is then heated and reacted with lime to release ammonia and bypass the residue. KCI refers to CaCl ₂ brine rather than isolated in an evaporator. This represents a 15-20% loss of K in the CaCl ₂ brine. The KCI content of CaCl ₂ can be reduced to 1.0% by adding solid Na ₂ SO ₄ to CaCl ₂ / KCI. Potassium is effectively collected as recovered syngenite (CaSO ₄ .K ₂ SO ₄ .xH ₂ O) in the range temperatures of from 0 ° C to 100 ° C, but a temperature of between 20 and 30 ° C is preferred, so that the solubility of the sulphates is kept to a minimum and the reaction is run at a reasonable rate.

CaCl ₂ brine composition 343.3 g CaCl ₂ 22.5% 130 g KCl 8.5% 94.7 g NaCl 6.3% 50 g xSO ₄ 32% (Na / K) 909 q H _? O 59.5% 1525 g 100%

Addition of 140 g of Na ₂ SO ₄ :

Output brine Output cake 234.8 g CaCl ₂ 17.8% 310 g CaSO ₄ .K ₂ SO ₄ 15.25 g KCl 1.1% + 100g H ₂ O 209 g NaCl 15.9%

- 16 50 g xSO ₄ 3.8% 807 61.3%

The outlet brine can be disposed of in the wells and the filter cake can be mixed into the produced K ₂ SO ₄ as a binder or further processed to remove CaSO ₄ .

The filter cake can react with NH ₄ HCO 3 from the NaHCO 3 and CaSO ₄ batch to react rapidly to form brine (NH ₄ ) ₂ SO ₄ and K ₂ SO _4, and the filtered CaCl ₂ precipitate is discarded. The brine (NH ₄ ) ₂ SO ₄ / K ₂ SO ₄ returns to the first stage to the K ₂ SO ₄ crystallizer.

Industrial applicability

The present invention is applicable in the field of artificial nutrients.

· · · · · · · · · · · · · · · · · · · · · · · · · · · · · ·

PK <ŽW - Ί176

Claims (15)

Patent claims A process for the preparation of food grade sodium bicarbonate and potassium sulphate, the process comprising the steps of: (a) providing a source of liquid sodium sulfate; b) providing a source of ammonium bicarbonate to precipitate sodium bicarbonate; c) contacting said sodium sulfate and said ammonium bicarbonate; d) precipitating sodium bicarbonate and forming a lye; e) filtering said sodium bicarbonate; f) saturating the caustic from step e) with sodium sulfate; g) contacting said lye with ammonium carbonate, ammonia gas or carbon dioxide to precipitate further sodium bicarbonate; h) filtering the precipitated sodium bicarbonate from step g); i) combining the sodium bicarbonate precipitate of steps e) and h) and washing to form food grade sodium bicarbonate; j) cooling the liquor from step i) to 0 ° C to form at least a precipitate of Glauber's salt; k) treating the liquor from step j) with sulfuric acid to convert mineral carbonates to sulfates and release carbon dioxide gas; l) heating the liquor from step k) to a temperature between 30 ° C and 40 ° C; and k) precipitating the potassium sulfate by contacting said liquor from step I) with potassium chloride. The method of claim 1, wherein the method further comprises the step of separating the precipitated potassium sulfate and washing with potassium chloride. The method of claim 2, wherein the method further comprises the step of treating the caustic from said step of separating the precipitated potassium sulfate with lime to release ammonia gas. 4. The method of claim 3, wherein the method further comprises the step of returning said ammonia gas to step g. The method of claim 4, wherein the method further comprises the step of evaporating the filtrate of claim 4. 6. The method of claim 1 wherein said sodium sulfate at 40 &lt; 0 &gt; C has a density of between 1.30 and 1.34. 7. The process of claim 1 wherein said liquor of step (d) has a specific gravity of 1.25 and comprises 10.4% by weight sodium sulfate, 17.1% by weight ammonium sulfate, between 8 and 12% by weight sodium bicarbonate, and the excess is ammonium bicarbonate. 8. The process of claim 1 wherein said sodium sulfate of step (b) e) consists of Na2SO4.10H ₂ O. 9. The process of claim 1 wherein said liquor from step f) has a specific gravity of 1.285 at 40 ° C. 10. The process of claim 1 wherein said liquor of step k) is a saturated liquor of sodium sulfate, ammonium sulfate, and sodium bicarbonate. 11. The process of claim 1 wherein said potassium sulfate is formed in at least 80% yield with a purity of at least 98%. • ·· · ♦ 00 · 0 0 0 0 · 9 9 9 0 · · ···> 0 0000 0 0 9 9 9 9 9 9 9 9 9 12. The process of claim 1 wherein said potassium sulfate is formed in a yield of at least 80% with a purity of at least 98%. 13. A process for forming sodium bicarbonate and potassium sulfate, the process comprising the steps of: (a) providing a source of liquid sodium sulfate; b) providing a source of ammonium bicarbonate; c) contacting said sodium sulfate and said ammonium bicarbonate; d) precipitating sodium bicarbonate and forming a lye; e) precipitating sodium bicarbonate and forming a liquor by contacting said liquor from step d) with sodium sulfate; f) saturating said liquor from step d) with sodium sulfate; g) filtering the solids from said liquor of step e); h) contacting said liquor from step f) with sulfonic acid to precipitate carbonates; i) cooling the caustic from step h) to 0 ° C to form a precipitate of Glauber's salt; j) heating said liquor from step I) to 30 ° C to 40 ° C; and k) treating said lye from step j) with potassium chloride to precipitate potassium sulfate; l) evaporating the caustic from step k) to recover the potassium concentration to return to step k); and m) drying said potassium sulfate. The method of claim 13, wherein the method further comprises the step of treating the caustic remaining from step (I) with lime and ammonium chloride. 15. The process of claim 14 wherein the ammonia gas is released and recycled. 16. The process of claim 13, wherein the potassium chloride solution used is returned to step k).