DE2513947C3 - Process for the preparation of NaCl-saturated, KCl-, MgCl2-, MgSO4 -containing solutions to obtain a solution highly saturated with MgCl2 - Google Patents

Description

lowered so that no kainite arises, while in contrast for this purpose the Kainitbüldung according to the method described in German Patent 11 06 300 is stimulated and perfected as far as possible by the addition of magnesium sulphate.

From the German patent specification 15 67 984 it is also known, in the crystallization of potassium chloride from hard salt solutions with contents of KCl, NaCl, MgClj and MgSO _4, the supersaturation of double sulfates by crystallization of leonite

(K _a SO ₄ MgSO ₄ 4 H ₂ O)

to be canceled by adding seed crystals at a temperature between 30 and 50 ^° C.

According to the method of the invention is, however, from the decomposition solution of the extracted the final stage carnallitic salt at iiner temperature between 90 and 130 ⁰ C with the addition of langbeinite (K ₂ SO ₄ · 2 MgSO ₄₎ -lmpfkrista! Len the Langbeinitübersättigung partially canceled, while at the same the supersaturation is increased by evaporating the solution to almost KCl and NaCl saturation.

A corresponding process in which Leonite crystallizes out would only be possible with even higher MgSO ₄ contents and at a lower temperature, with NaCl and KCl also crystallizing out. Such a Leonite could not be used for the production of potassium sulphate.

Furthermore, in the German Auslcgeschrift 19 32 813 a method is described in which the in the first Process stage from the brine crystallized kainite is converted into carnallite. In contrast is it is essential for the process of the invention that the carnallite contained in the evaporation salt is decomposed. It is therefore obtained according to the known process in the first stage, a product that after Process of the invention is decomposed in the first stage of the process.

According to the process described in German Offenlegungsschrift 19 14 311, crude potash salt is used first mixed with calcium chloride and calcined. The resulting product becomes a solution extracted, which in addition to magnesium chloride and sodium chloride contains soluble potassium salts, which are separated will. A decomposition of carnallite does not take place.

In none of these processes are the measures provided, a Langbeinit mother liquor that still Contains potassium, sodium and magnesium chloride, to be evaporated and from it a carnallitic evaporation salt to win, which is fed back into the initial stage of the process. These measures but are an integral part of the method of the invention.

A method of processing potassium and magnesium chloride saturated in sodium chloride has been established as well as solutions containing magnesium sulphate with the recovery of potassium and sodium chloride poor, magnesium sulfate content decreased and magnesium chloride highly saturated solutions as well as high percentage potassium chloride and potassium sulfate found in several stages. Mark this procedure is a combination of the following measures:

a) In the saturated sodium chloride, potassium chloride and magnesium chloride and magnesium sulfate-containing starting solution 1 is recirculated carnallitisches Eindampfsalz 2 stirred d from process stage and at temperatures of 35 to 70 ⁰ C to a decomposition solution 4, which contains up to 300 g / l MgCl ₂ , decomposed,

b) consists of potassium and sodium chloride decomposition salt 3 is νυη of the decomposition solution 4 separated at a temperature of 35 to 70 ⁰ C,

c) the decomposition solution 4 is evaporated at temperatures from 90 to 130 ⁰ C to almost saturation of potassium and sodium chloride and after the addition of Langbeinit seed crystals Langbeinit crystallized and separated,

d) the remaining solution is evaporated isothermally at temperatures of 80 to 95 ° C and thoroughly

direct cooling is adiabatically cooled to a temperature of 25 to 40 ⁰ C, whereupon the carnallitic evaporation salt 2 is separated off and returned to process stage a, while the ao remaining caustic is repelled,

e) the Langbeinit is converted to potassium sulfate in a manner known per se.

For the implementation of the method of the invention, for example, Aussol solutions of carnallitic, kieserite-containing salt stores as well as NaCl-containing potassium magnesia solution from the production process of potassium sulfate via schoenite or leonite or a mother liquor from the processing of hard salts (KCl , NaCl, MgSO ₄ , H ₂ O). For the production of potash salt with a high K ₂ O content, it is advantageous in the context of the process of the invention if the decomposition salt 3 is converted into a potash salt 8 with 55 to 62% K ₂ O by recrystallization with water and with a recycled mother liquor transferred and the excess mother liquor 9 is introduced in place of a portion of the solution 1 in stage a.

The method according to the invention also offers the advantageous possibilities of using a subset of the potassium salt 8 while avoiding evaporation in stage c to saturate the solution 4 to almost To use KCl and NaCl saturation, and the Langbeinit S of level c with potassium salt 8 in itself as is known, either directly or via the intermediate Schönite to add potassium sulfate, and the Kailimagnesia solution 10 arising in the production of Schönither in stage a instead of a subset of the Solution 1 to use.

The method of the invention is further illustrated by the following example and FIGS. 1 and 2 explained.

134 m ³ / h of a saline solution 1 from a salt store containing carnallitic kieserite with the following composition:

g / l

KCl NaCl MgCU MgSO ₄ H ₂ O 98 130 132 59 853

and a temperature of 6O ⁰ C with 27.8 m ³ of a mixed solution of the potassium magnesia solution 10 of producing potassium sulfate from the mother liquor and 9, the processing of potassium salts on KaIidüngesalze high k _s O-Gchalt having the composition:

g / l

KCl NaCl MgCl ₂ MgSO ₄ HO 109 61 142 57 882

mixed, and with this mixture 90 t / h of a moist carnallitic evaporation salt 2 are as follows Composition:

KCl NaCl MgCl ₂ MgSO ₄ H _a O
% 17.31 11.76 27.40 7.38 36.13

siert, with 12.5 t / h of a moist potassium salt 8 following Composition obtained:

5%

decomposed at a temperature of 55 ° C in stage a, the MgCl _{2 of the carnallite and the MgSO 4} - 5/4 H ₂ O contained in the evaporation salt going into solution. This resulted in 36.9 t / h of a moist decomposition salt 3 of the following composition:

KCl

35.20

NaCl
51.16

MgCl ₂
2.70

MgSO ₄ H ₂ O
0.94 10.00

and 198 m ³ / h decomposition solution 4 of the following composition:

KCl NaCl MgCl ₂ MgSO ₄ H ₂ O
g / l 95 55 229 80 847

KCl
86

NaCl
59

MgCl ₂
258

MgSO ₁
47

H ₂ O

824

KCI

92.04

NaCl
1.16

MgCl ₂
0.60

MgSO ₄
0.20

H ₂ O
6.0

The excess lye from the recrystallization system of 9.3 m ³ / h with the composition:

KCI
116

NaCl
167

MgCl ₂
85

MgSO ₁
28

H ₂ O
856

The moist decomposition salt is separated from the decomposition solution at a temperature of 55 ° C in stage b and then the decomposition solution 4 is heated in stage c to a temperature of 110 ° C and 17.1 t of water up to almost: · KCl and NaCl saturation evaporated and with the addition of 40 t / h of seed crystals from circulating Langbeinit the MgSO ₄ content up to a MgSO ₄ content of 47 g / l through the separation of 9.9 t / h moist Langbeinit the following Composition:

KCl K ₂ SO ₄ NaCl MgCl ₂ MgSO ₄ H ₂ O% 1.04 35.50 0.72 3.13 49.6 t 10.00

lowered and separated with the Langbeinit for vaccination in stage c. 40 t Langbeinite are returned in stage c. 182 m ³ / h of the hot solution 6 obtained after separating off the Langbeinite at a temperature of 100 ° C and the following composition:

is introduced into the decomposition, stage a.

7.1 t of the wet salt are used for the production of potassium sulphate. The remainder is dried and yields 5.0 t 60 potash salt with 61.9% K ₂ O.

The 7.1 t / h moist salt 8 and 9.9 t / h moist Langbeinite from stage c, as well as 15.9 t / h water are converted into potassium sulfate in two stages, with 18.5 m from the first stage (Schönit stage) ^{3 of} a potassium magnesium solution of the following composition:

40

KCL

1.4

NaCl
4.1

MgCl ₂
453

MgSO ₄ H ₂ O
38 854

are isothermally evaporated in stage d at 90 ° C. and then cooled adiabatically and by direct cooling to a temperature of 35 ° C., a total of 75.3 t / h of H ₂ O being evaporated.

After separating 90 t of moist carnallitic evaporation salt 2, which are introduced in stage a, 49.2 m ^{3 of} highly concentrated solution 7 of the following composition is obtained:

Executed for further processing on magnesium compounds and magnesium metal.

The 36.9 t / h of moist decomposition salt are recrystallized KCl in a mother liquor _{with the addition of 7 t / h of H 2 O}
105

NaCl

MgCl ₂
170

MgSO ₄ H, O
71 895

which are introduced into the decomposition and processed again with.

In the second stage of the sulphate process, 9.3 t of moist potassium sulphate are obtained

KCl
1.99

K ₂ SO ₄ NaCl
88.58 0.13

MgCl ₂
0.75

MgSO ₄
0.55

H ₂ O
8.00.

The method of the invention provides over the prior art the advantage that MgCl ₂ solutions with lower contents MGCU which also contain KCl, NaCl and MgSO _4, to highly concentrated in KCl, NaCl and MgSO ₄ content decreased MgCl ₂ LOTS can be processed. These solutions can serve as raw material for the production of magnesium compounds and metallic magnesium, whereby the raw material base for the extraction of this metal is expanded.

According to the method of the invention, a separation of KCl and NaCl from MgCl ₂ and MgSO _{4 is} achieved at the same time, both in the form of Langbeinite (K ₂ SO ₄ · 2 MgSO ₄ ) and in the form of KCl / NaCl mixtures which by conversion or recrystallization high-percentage potassium chloride and potassium sulfate are generated, which increase the economic efficiency of the process.

The method of the invention represents a meaningful combination of the production of three products; a starting solution containing _{MgCl 2} that has not been economically viable up to now.

For this purpose 2 sheets of drawings

Claims (4)

Patent claims: I. Process for the preparation of potassium and magnesium chloride saturated in sodium chloride as well as solutions containing magnesium sulphate with the recovery of potassium and sodium chloride poor, low in magnesium sulfate content and highly saturated in magnesium chloride Solutions as well as high percentage potassium chloride and potassium sulfate in several stages, characterized by the combination of the following measures: a) Recirculated carnallitic evaporation salt (2) from process step (d) is stirred into the sodium chloride-saturated, potassium and magnesium chloride and magnesium sulfate-containing starting solution (1) and at temperatures from 35 to 70 ⁰ C to a decomposition solution (4), which up to contains up to 300 g / l MgCl ₂ , decomposes, b) consists of potassium and sodium chloride decomposition salt (3) is separated from the decomposition solution (4) at a temperature of 35 to 7O ⁰ C, c) decomposition solution (4) is evaporated at temperatures of 90 to 13O ⁰ C to near saturation in potassium and sodium chloride and crystallized from it by addition of seed crystals langbeinite langbeinite and separated, d) the remaining solution is isothermally evaporated at temperatures of 80 to 95 ° C and adiabatically cooled by direct cooling to a temperature of 25 to 4U ° C, whereupon the carnallitic evaporation salt (2) separated and returned to process step (a) while the remaining lye is expelled, e) the Langbeinit is converted into potassium sulfate in a manner known per se. 2. The method according to claim 1, characterized in that the decomposition salt (3) converted by recrystallization with water and with a recycled mother liquor from a recrystallization in a potassium salt (8) with 55 to 62% K ₂ O and the excess mother liquor (9 ) is introduced into step (a) instead of a portion of the solution (1). 3. The method according to claims 1 to 2, characterized in that a subset of the Potash salt (8) while avoiding evaporation in stage (c) to saturate the solution (4) to almost used for KCI and NaCI saturation. 4. The method according to claims 1 to 3, characterized in that the Langbeinit (5) of the Stage (c) with potash salt (8) in a manner known per se, either directly or via the intermediate stage Schönite is converted to potassium sulphate and the potassium magnesia solution resulting from the production of Schöni (10) is used in step (a) instead of a portion of the solution (1). For the production of magnesium metal, concentrated magnesium chloride solutions, z. B. the potash industry used. Such solutions arise during processing Carnallitic raw salts. These have an average MgCl content of 260 to 320 g / l MgCl ₂ and also contain KCl, NaCl and MgSO ₄ , the MgSO ₄ content being between 40 and 60 g / l. As today for the ίο Magnesium production requires larger quantities of MgCl ₂ solutions and the dolomite used up to that point is also to be replaced by MgCl ₂ , solutions with a lower MgCl ₂ must also be used because of the increased MgCl ₂ requirement. Content, but the same high content of MgSO ₄ as well as a higher content of KCi and NaCl can be used for the production of concentrated MgCU solutions. Because of the lower MgCl ₂ content, the solutions must be evaporated more strongly, whereby ao the MgSO ₄ content increases so that a practically not Usable, difficult to process mixture of KCl, NaCl and KMg double salts as a by-product accrues. It was therefore looked for ways to do this aj Solutions with a low MgCl ₂ content to be worked up into concentrated MgCl ₂ solutions while avoiding the formation of such double salts. The method of the invention offers the possibility of solutions with a low MgCl ₂ content, as for example in the Processing carnallitic crude salts accumulate in addition to highly concentrated MgCl ₂ solutions to obtain directly usable salt mixtures. According to the method of the invention, the starting solution produces a moist salt which, in addition to KCl and NaCl, contains only small amounts of MgCl _{2 and MgSO 1} and this by simple recrystallization into a potassium fertilizer salt _{with a high K 2} O content and a residue containing NaCl that is discarded is disconnected. According to the method of the invention, the sulfate ions contained in the solution are excreted as Langbeinite, which is separated and, because of its low NaCl content, with the potassium chloride obtained by recrystallization either directly or to improve the yield via the intermediate Schönite in a manner known per se Potassium sulfate is implemented. The process of the invention results in a highly concentrated MgCl ₂ solution with reduced contents of KCl, NaCl and MgSO ₁ , which can be used as a raw material for the production of magnesium. The residual amount of SO ₄ ions can be removed in a known manner by precipitation with CaCl ₂ and BaCl ₂ . In the final stage of the process of the invention, a carnallitic evaporation _{salt containing NaCl and MgSO 4 is produced.} According to German patent specification 11 06 300 it is known to implement a carnallitic evaporation salt, which consists of practically pure carnallite, with supplied MgSO ₄ and potassium magnesia, whereby ^fi o Kainit is obtained as an intermediate product for further processing into potassium sulphate. However, this method did not suggest the decomposition of a carnallitic evaporation salt according to the method of the invention, since if kainite were to be formed it would then not be NaCl-free. According to the method of the invention, the MgSO ₄ content of the evaporation salt is so far removed by the crystallization of Langbeinite in a previous stage.