DE3607641C2 - - Google Patents

Description

It is known to be potassium sulfate and magnesium chloride by double reaction of potassium chloride and magne to produce sodium sulfate.

If this double implementation in the conventional way and carried out in aqueous media, can the formation of double salts only by substantial Avoid technical effort.

On the other hand, DE-OS 33 31 416 is a method known, after the potassium chloride by means of anion exchange shear under acidic conditions in potassium or Sodium sulfate is transferred. This procedure leaves are represented by the following reaction equation:

Production: 2 KCl + R₂SO₄ = K₂SO₄ + 2 RCl Regeneration: 2 RCl + CaSO₄ = R₂SO₄ + CaCl₂ CaSO₄ + 2 KCl = K₂SO₄ + CaCl₂

First of all, it is a solution of the desired Sulfate obtained, from which subsequently by adding Salt out the sulfate of potassium or sodium chloride becomes. The separated from the resulting crystals Filtrate is used to regenerate the anion exchanger used.

What was essential for this process was the knowledge that the solubility of calcium sulfate in calcium chloride solution solutions is larger than in water. Thereby the Re generation of the anion exchanger started unexpectedly increases. However, the regeneration of Exchanger with the calcium sulfate suspension the Ge drive that down on the exchange particles hitting calcium sulfate crystals the regeneration badly affect the exchanger and that on calcium sulfate precipitated on the exchanger particles can only be removed with great technical effort is.

This gave rise to the task of other options to develop the production of potassium sulfate which do not have the disadvantages of the aforementioned methods occur.

There has been a process for making potassium sulfate from potassium chloride loaded with sulfate ions NEN anion exchanger found.

Then a saturated potassium is used as the reaction solution chloride solution after saturation with potassium sulfate with the weakly basic, sulfate-loaded anion exchanger contacted intensively and separated again from what the crystals formed therein from the solution obtained are separated and the exhausted anion exchanger through intensive contact with a magnesium sulfate solution is loaded again with sulfate ions.

For performing the method of the invention a saturated potassium chloride solution as the reaction solution used after potassium sulfate in it until saturation has been solved. The content of the reaction solution Potassium sulfate is about 5 to 10% based on the total salinity of the solution.

This reaction solution is mixed with a weakly basic sulfate-loaded anion exchanger contacted intensively. Here, the sulfate ions of the exchanger are removed Replaced chloride ions from the reaction solution as long as until there is a balance between the solution and the exchanger adjusted with respect to the exchanged ions the exchange has ended. That here The resulting potassium sulfate crystallizes because the given reaction solution already saturated with potassium sulfate is.  

After the exchange has ended, the reaction solution of separated from the anion exchanger. It is an advantage here adheres when the particles are preferably in granular form used anion exchanger larger diameter have than that in the reaction solution through the exchange formed potassium sulfate crystals.

Studies have shown that the invention manufactured potassium sulfate in a particle size of less than 0.4 mm. It is enough for the aforementioned Separation process therefore out when the particle diameter of the anion exchanger is more than 0.5 mm. To Separation of the anion exchanger from the reaction solution the exchanger is replaced by a filter Body, its mesh size or pore diameter is 0.5 mm, retained while the solution with the potassium sulfate crystals the sieve body, such as for example a mesh of corresponding meshes wide, unhindered.

The potassium sulfate crystals are then removed from the Reaction solution separated, with a saturated potassium washed sulfate solution and then dried. The abge separate wash solution can be used to make fresher Reaction solution are used as well as that of reaction solution separated from the potassium sulfate crystals after saturation with potassium chloride.

For performing the method of the invention it further proved to be advantageous by adding of solid, preferably powdered potassium chloride the potassium chloride concentration of the reaction solution to keep constant during the exchange reaction. Be The potassium chloride to be added is particularly cheap with a small amount of reaction solution beforehand mixes and fed in this form to the reaction solution. These measures mean increased utilization of the Capacity of the exchanger.  

For contacting the reaction solution with the sul fat-laden, weakly basic anion exchanger there are three known ways.

According to the first possibility, the exchanger can be used as packed bed, preferably in a column be set to which the reaction solution from above leads. The exchanger bed is advantageous over arranged a bottom with passage openings, the Diameter is smaller than the particle size of the Aus exchangers, but larger than the particle size of itself potassium sulfate crystals forming in the reaction solution. Through appropriate measures, e.g. B. passing air, must be ensured that the exchanger and the Reaction solution are mixed thoroughly.

But there is also the possibility of the exchanger bed the reaction solution under pressure from below lead and the mixed with the potassium sulfate crystals Reaction solution from the top of the exchanger increase.

These measures ensure that the packed Exchanger by the flow pressure of the reaction solution is whirled up in this.

There is also the possibility of the granular Mix exchanger with the reaction solution and to keep the mixture in constant motion, for example by stirring or shaking. The exchange is finished after about 10 to 20 min, and the mixture can according to the procedure given above be prepared.

It has proven beneficial for the method of the invention proved the exchange mix during the exchange to keep at temperatures between 10 and 40 ° C.

With the exchange reaction carried out according to the invention become 80 to 95% of the total capacity of the anions load the exchanger with chloride ions.  

The remaining sulfate ions in the exchanger To win largely, it can be beneficial to Exchanger before regeneration with a saturated Contact the potassium chloride solution intensively. The remaining after the exchange of the exchanger In addition to potassium chloride, the solution contains the newly formed one Potassium sulfate. Both salts can be obtained from this solution by evaporation and fractional crystallization can be obtained in a manner known per se.

After separating the reaction solution from the anions The exchanger is also used in a manner known per se Washed water before going through intensive contact regenerated with a magnesium sulfate solution, d. H., is loaded again with sulfate ions. From that of the regenerated exchanger separate regeneration solution that ent magnesium chloride and magnesium sulfate holds, these salts in a conventional manner by evaporation and fractional crystallization be won.

For the method of the invention, particular Use of weakly basic anion exchangers, those made of polyacrylate with secondary and tertiary amino groups exist.

It has also proven to be cheap, all with these weakly basic anion exchanger according to the invention previously contacted solutions by adding acids adjust to a pH of 3 to 6. The solutions, which are used for the production of potassium sulfate advantageously acidified with sulfuric acid while the pH of the ver used to regenerate the exchanger applied solutions adjusted with hydrochloric acid becomes.

The inventive method avoids the technical Difficulties and disadvantages of the prior art Technically known processes largely and can without technical difficulties with high effectiveness carry out.

Example 1

Exchange process with the weakly basic anion exchange resin Kastel based on polyacrylics with predominantly secondary amino groups with 2.2 val / l total capacity
Test with 500 l resin volume in an exchange column
Adjust all solutions to pH 3 with HCl or H₂SO₄

I. Exchange half cycle of loading the resin with SO₄ ^- ions

After driving through 4 cycles and establishing a steady state, at the end of the half cycle described under II, a resin bed filled with water containing small amounts of potassium salts was obtained, 86% of its capacity with Cl ^- ions and 14% of its capacity was loaded with SO₄ ^- ions.

The following were successively placed on the bed from above at 25.degree Solutions abandoned:

- A1150 l with 0.64 val MgCl₂ / l and 0.06 val MgSO₄ / l - A2698 l with 1.40 val MgSO₄ / l - A3150 l with 0.04 val MgCl₂ / l and 0.66 val MgSO₄ / l - A4150 l water

When solutions A1-A4 were discontinued the column as elements:

- E1150 l with 0.13 val KCl / l 0.01 val K₂SO₄ / l 0.10 eq MgCl₂ / l and 0.01 val MgSO₄ / l - E2150 l with 0.64 val MgCl₂ / l and 0.06 val MgSO₄ / l  - E3698 l with 1.26 val MgCl₂ / l and 0.10 val MgSO₄ / l - E4150 l with 0.04 val MgCl₂ / l and 0.66 val MgSO₄ / l

Eluates E1 and E3 were run from the process that Eluates E2 and E4, which are identical to A1 and A3, were stored for reuse in the next cycle.

The resin was now 94% of its capacity loaded with SO₄ ^- ions and 6% of its capacity with Cl ^- ions.

II. Exchange half cycle of K₂SO₄ extraction

On that with water, which now has small amounts of magnesium salts contained, filled bed were then first following Lö sung abandoned:

- A5150 l with 0.02 val KCl / l and 0.64 val K₂SO₄ / l - A6150 l with 0.06 val KCl / l and 1.24 val K₂SO₄ / l - A7150 l with 4.08 val KCl / l and 0.14 val K₂SO₄ / l

The following were eluted:

- E5150 l with 0.01 val MgCl₂ / l, 0.08 val MgSO₄ / l, «0.01 val KCl / l and 0.09 val K₂SO₄ / l - E6150 l with 0.02 val KCl / l and 0.64 val K₂SO₄ / l - E7150 l with 0.06 val KCl / l and 1.24 val K₂SO₄ / l

E5 was executed from the process, E6 and E7 became Reused in the next cycle.

After the expiry of E7 was for an intense Mix resin and solution A7 by blowing in Compressed air is provided via the inlets in the column.

During continuous mixing, a further 828 l of solution A7 were added. The solution A7 saturated with KCl and K₂SO₄ reacted with the SO₄ ^- loaded resin under KCl depletion and K₂SO₄ crystallization. The converted solution and the K₂SO₄ formed were continuously discharged through the lower sieve bottom of the column, the sieve openings of which the larger resin grains could not pass.

With the following task solution

- A8150 l with 2.68 val KCl / l and 0.32 val K₂SO₄ / l

was the remaining reaction solution with K₂SO₄ crystals ousted from the pillar.

Overall, the eluate was formed from A7

- E8978 l with 3.14 eq KCl / l and 0.22 val K₂SO₄ / l

and a K₂SO₄ amount of crystals of 69.8 kg.

By saturating E8 with 68.5 kg KCl the Solution A7 made that turned on again in the next cycle was set. At the same time, another 6.8 kg of K₂SO₄ were precipitated, so the total amount produced 76.6 kg K₂SO₄ amounted to.  

The following solutions have now been applied to the column:

- A9150 l with 1.84 val KCl / l and 0.16 val K₂SO₄ / l - A10150 l with 0.94 val KCl / l and 0.06 val K₂SO₄ / l - A11150 l water

The following were eluted:

- E9150 l with 2.68 val KCl / l and 0.32 val K₂SO₄ / l - E10150 l with 1.84 val KCl / l and 0.16 val K₂SO₄ / l - E11150 l with 0.94 val KCl / l and 0.06 val K₂SO₄ / l

Solutions E9-E11 were also reused in the stored in the next cycle.

After starting solution E11, the resin was in the same Loading condition as described at the beginning of I. Half cycle.

Yielding the process:

SO₄ ^- 90.1% K96.1%

(the losses were:

SO₄ ^- 0.3% in E1
7.0% in E3
2.6% in E5 K2.3% in E1
1.6% in E5)

Example 2

Exchange process with the weakly basic resin Anion exchanger based on polyacrylics with secondary and tertiary amino groups Duolit with 2.5 val / l total capacity.
Test with 500 l resin volume
Adjust all solutions to pH 4 with HCl or H₂SO₄.

I. Exchange half cycle of loading the resin with SO₄ ^- ions

After 6 cycles had been carried out and a steady state had been set, a resin bed filled with water containing small amounts of potassium salts was obtained at the end of the half cycle described under II. 93% of its capacity was containing Cl ^- ions and 7% of it Capacity was loaded with SO₄ ^- ions.

The following were successively placed on the bed at 60 ° C. from above Solutions abandoned:

- A1150 l with 0.85 val MgCl₂ / l and 0.12 val MgSO₄ / l - A2150 l with 1.58 val MgCl₂ / l and 0.30 val MgSO₄ / l - A3900 l with 1.45 val MgCl₂ / l and 1.50 val MgSO₄ / l - A4413 l with 3.0 val MgSO₄ / l - A5150 l with 0.74 val MgCl₂ / l and 1.35 val MgSO₄ / l  - A6150 l with 0.34 val MgCl₂ / l and 0.71 val MgSO₄ / l - A7150 l water

When solutions A1-A7 dropped out of the column as eluate from:

- E1150 l with 0.15 val KCl / l 0.01 val K₂SO₄ / l 0.12 val MgCl₂ / l and 0.01 val MgSO₄ / l - E2150 l with 0.85 val MgCl₂ / l and 0.12 val MgSO₄ / l - E3150 l with 1.58 val MgCl₂ / l and 0.30 val MgSO₄ / l - E4413 l with 2.33 val MgCl₂ / l and 0.56 val MgSO₄ / l - E5900 l with 1.45 val MgCl₂ / l and 1.50 val MgSO₄ / l - E6150 l with 0.74 val MgCl₂ / l and 1.35 val MgSO₄ / l - E7150 l with 0.34 val MgCl₂ / l and 0.71 val MgSO₄ / l

Eluates E1 and E4 were carried out from the process, the eluates E2, E3, and E5-E7, which are identical to A1, A2 and A4-A6, were stored for reuse in the next cycle.  

The resin was now loaded with SO₄ ^- ions to 85% of its capacity and with Cl ^- ions to 15% of its capacity.

II. Exchange half cycle of K₂SO₄ production

On that with water, the small amounts of magnesium salts contained, filled bed were then at 25 ° C first fol abandoned the following solutions:

- A8150 l with 0.03 val KCl / l and 0.61 val K₂SO₄ / l - A9150 l with 0.08 val KCl / l and 1.17 val K₂SO₄ / l - A10150 l with 4.08 val KCl / l and 0.14 val K₂SO₄ / l

The following were eluted:

- E8150 l with 0.04 val MgCl₂ / l 0.01 val MgSO₄ / l <0.10 val KCl / l and 0.08 val K₂SO₄ / l - E9150 l with 0.03 val KCl / l and 0.61 val K₂SO₄ / l - E10150 l with 0.08 val KCl / l and 1.17 val K₂SO₄ / l

E8 was carried out from the process, E9 and E10 became re- used in the next cycle.  

After E10 ran out quantitatively, it became A10 standing resin in with another 300 l of solution A10 Flushed the stirring vessel into the 75.3 kg KCl crystal at the same time lisat were added.

The desorption of the SO₄ ^- ions from the resin and the crystallization of K₂SO₄ took place in the stirred vessel, while the KCl and K₂SO₄ concentrations of the solution did not change by redissolving KCl. By the end of the reaction, all KCl had gone into solution.

The contents of the mixing vessel were passed through a sieve which was permeable for the fine K₂SO₄ crystals and impermeable for the coarser ones Resin particles. By rinsing with another 200 l A10 was for a complete separation of the K₂SO₄ from the resin. There were thus 84.5 kg K₂SO₄ won. Finally the resin was in again transferred the exchange column, where now its spaces with 150 l of solution A10 were filled. This solution A10 was with the Task solution

A11150 l with 2.95 val KCl / l and 0.28 val K₂SO₄ / l

repressed.

All solutions A10 (as eluate: E11), a total of 800 l had the composition of the original A10, became Reused stored in the next half cycle.

The following solutions have now been abandoned:

- A12150 l with 2.01 val KCl / l and 0.20 val K₂SO₄ / l - A13150 l with 0.96 val KCl / l and 0.11 val K₂SO₄ / l  - A14 150 l water

The following were eluted:

- E12150 l with 2.95 val KCl / l and 0.28 val K₂SO₄ / l - E13150 l with 2.01 val KCl / l and 0.20 val K₂SO₄ / l - E14150 l with 0.96 val KCl / l 0.11 val K₂SO₄ / l

E12-E14 were used for reuse in the next cycle stored.

After the solution E14 had run out completely, the resin was present again in the loading state that it was at the beginning of the loading under I. had written half cycle.

Yielding the process:

SO₄ ^- 78.7% K⁺96.4%

(Losses:

-SO₄ ^- 0.2% in E1
2.2% in E4
18.9% in E8 -K⁺2.4% in E1
1.2% in E8)

Claims (6)

1. A process for the preparation of potassium sulfate from potassium chloride by means of an anion exchanger loaded with sulfate ions, characterized in that a saturated potassium chloride solution after saturation with potassium sulfate is contacted intensively with the weakly basic, sulfate-laden anion exchanger and is separated again therefrom as the reaction solution, whereupon ge is separated from this solution, the crystals formed therein are separated and that the exhausted anion exchanger is again loaded with sulfate ions by intensive contact with a magnesium sulfate solution. 2. The method according to claim 1, characterized in that that the particles of the anion exchanger have a larger diameter than that in the solution formed crystals. 3. The method according to claims 1 to 2, characterized records that the concentration of the reaction solution of potassium chloride during the exchange reaction Addition of solid potassium chloride kept constant becomes. 4. The method according to claims 1 to 3, characterized characterizes that before the regeneration of the anions exchanger with a saturated potassium chloride solution is contacted intensively and separated again. 5. The method according to claims 1 to 4, characterized records that the exchange mixture during the off exchanges at temperatures between 10 and 40 ° C will hold. 6. The method according to claims 1 to 4, characterized records that all contact with anion exchanger solutions beforehand by adding acid a pH of 3 to 6 can be set.