DE1092401B - Process for processing carnallite-containing potassium salts by electrostatic separation of the carnallite - Google Patents

Description

LIBRARY OF THE GERMAN PATENT OFFICE

Where carnallite (KCl-MgCl ₂ -OH ₂ O) is found in potash mines together with sylvinite (KCl + NaCl) or with hard salt (KCl + NaCl + MgSO ₄ -H ₂ O), both salt rocks are generally used for economic and technical reasons also dismantled and promoted together. The presence of carnallite in these so-called "carnallitic mixed salts" requires special processing methods, in the course of which the carnallite decomposes and the KCl contained in it is separated _{from the MgCl 2.} A number of such methods, all of which operate by the wet route, are known.

According to the recently found methods of electrostatic processing of potash salts by chemical conditioning of the material to be processed with anionic substances, it is possible to separate the carnallite from the rock salt (see patent application K 31075 / Ib). If carnallitic mixed salts, i.e. salts containing sylvine in addition to carnallite, are subjected to this process, the carnallite is found in the sylvine concentrate after electrostatic separation. This initially has the effect that the level of the Sylvinkonzentrates is noticeably lowered as a result of the very low K ₂ O content of the carnallite (17 ° / ₀ K ₂ O). will. _{The addition of MgCl 2} (as a constituent component of carnallite) to the sylvinite concentrate is even more unpleasant for another reason: As a markedly plant-damaging agent, MgCl ₂ makes it unusable as a fertilizer as soon as it occurs in significant quantities in the obtained chlorine potassium. On the other hand, since the decomposition of the carnallite and the intended separation of KCl and MgCl _{2 is} only possible by wet means, it is absolutely necessary to separate the carnallite from the other components, in particular from sylvine, in order to be able to process it separately.

It has now been found that the carnallite can be separated electrostatically from the mixed salts conveyed without chemical conditioning if only certain climatic conditions are observed, which primarily relate to the relative humidity of the atmosphere. It has been found that the electrostatic separation of the carnallite from the carnallite mixed salt works best at partial pressures of water vapor of 5.6 to 13 mm, preferably 7.4 to 13 mm of mercury. ^{At 21 °} C., these water vapor partial pressures correspond to a relative humidity of 30 or 40 to 70%. The separation temperature of the salt should preferably be between 30 and 8O ⁰ C, 35 C and 70 ^0.

A proposal is known for mixtures of hygroscopic and non-hygroscopic components to exploit the hygroscopicity for the electrostatic separation, that one the mixture pretreated in an air-conditioned atmosphere in such a way that the hygroscopic components are removed from the atmosphere Process for processing carnallite

containing potassium salts

by electrostatic separation

of carnallite

Applicant:

Potash Research Institute G. mb H.,
Hanover, Georgs tr. 29

Dr.-Ing. Hans Autenrieth, Hanover,

and Dr. rer. nat. Gerd Peuschel, Benthe (Hann.),

have been named as inventors

Absorb water and thereby change its conductivity, while the non-hygroscopic components remain unchanged. The method according to the invention differs fundamentally from these known methods in that water absorption by the carnallite is absolutely avoided here. With the invention the water vapor partial pressures to be used, no moisture can build up at the separation temperatures precipitate the carnallite because the water vapor partial pressures of a saturated carnallite solution are greater are than those of the applied atmosphere.

It has been shown that it is beneficial to use the raw mixed salt, for example ground to -4 mm, in grain fractions, for example, to be divided into a fraction from 0 to 1 mm, from 1 to 2 mm and from 2 to 4 mm, and these fractions separately and under the most favorable temperatures and water vapor pressures for the respective fraction to prepare electrostatically.

The knowledge that hygroscopic salts are processed electrostatically using the method described here is new and quite surprising. One has indeed in the electrostatic processing of Stones and ores have long known the effects of moisture on the success of processing appropriate measures taken to eliminate the harmful influence of moisture. These measures consist in the fact that the moisture adhering to the material is removed by heating the material to be processed removed and by as dry an atmosphere as possible ensures that during the electrostatic Separation does not re-coat the goods with moisture. So here it is simply a matter of the existing natural differences in the electrical behavior of the components covering and ineffective

009 647/81

Eliminate the sam-making liquid layer, so that the aforementioned existing differences in the electrostatic Separation can have its full effect.

Clay-like impurities have also been separated electrostatically from crude salts by that the material to be processed was only "partially" dried, d. H. the drying only went so far that the their crystal structure were completely dry according to compact salt components, which have a layered lattice On the other hand, clayey accompanying minerals still retained a certain residual moisture, which means that these components remained conductive and could thereby be separated from the non-conductive salt components. In contrast for these known processes, salts of one another are electrostatically used in the process according to the invention separately, and the procedure is such that the entire material to be processed is initially completely dried and then electrostatically separated at temperatures and humidities that only allow the hygroscopic carnallite to cover itself with a layer of moisture and thereby to become conductive in contrast to the other salts.

Another known method by which potash salts are made accessible for electrostatic separation by thermal treatment consists in that sylvinite crude salt is ^{heated to temperatures between 300 and 700 °} C., then cooled to about 40 to 200 ^° C. and electrostatically at this temperature is separated. It is known that this process fails completely in the presence of carnallite. As a result, the opinion has established itself among experts that carnallitic mixed salts cannot be processed electrostatically by thermal and climatic conditioning. The present invention does away with this technical prejudice. In practice, the method according to the invention is designed as follows:

The ground and dried raw mixed salt is divided into two or three grain size fractions and these fractions at the water vapor partial pressures determined for them as the most favorable to the separation temperature brought and then given to the electro separator and possibly repeated several times of the separation process of the carnallite deposited in high percentage form. After separating the carnallite the residues can now be further processed according to the various known methods, whereby The absence of carnallite results in very significant advantages in all processes.

In the dissolving process, the presence of carnallite brings magnesium chloride into the dissolving liquor, which has the following disadvantages. The magnesium chloride introduced into the process must be removed from the process again. If this takes place in the form of very dilute magnesium chloride liquor, then the losses of K ₃ O are considerable. If you want to keep these K ₂ O losses as low as possible, then you have to bring the circulating lye to the highest possible chlorine magnesium content, which on the other hand, the dissolving capacity of the lye is very much reduced because the presence of magnesium chlorine in the solution increases the solubility of the Potassium chlorine very strong

ίο lowers. Furthermore, the presence of the Chloromagnesium is the solubility temperature coefficient of the rock salt found in the magnesium chloride-free solution is negative, positive, so that during the crystallization process rock salt with crystallized and the products deteriorate considerably. So overall you have the presence of carnallite the following disadvantages in the crude salt or chlorine magnesium in the lye: lower yield, lower throughput, poorer products and higher K Cl losses. All

ao these disadvantages are abruptly eliminated by the pre-separation of the carnallite.

The ratios are similar for the flotation of carnallitic mixed salts. First of all, the carnallite is decomposed cold in a preliminary stage. The resulting decomposition potassium chloride can be obtained without flotation as a product with a maximum of 40% K ₂ O, which is why the decomposition is followed by flotation in which the potassium chlorine is removed from the decomposition liquor. However, since flotation from alkaline solutions containing magnesium chloride is more difficult than flotation from alkaline solution free from magnesium chloride, the flotation in this process only gives a product with about 50% K ₂ O and, in addition, has to remove the introduced magnesium chloride from the process , K Cl losses in the repulsion liquor. A preliminary separation of the carnallite makes it possible to obtain a KCl concentrate with 60% K ₂ O with a decidedly improved yield without difficulty.

In the electrostatic processing of carnallitic mixed salts according to the chemical conditioning process by means of anionic substances, the above-mentioned disadvantages of the deteriorated concentrates and the loss of the potassium chloride obtained in this way for fertilization purposes occur. _{After the carnallite has been pre-separated according to the new process, the residue can be processed electrostatically to concentrates of 60% K 2} O with over 90% yield after chemical conditioning by means of anionic substances according to patent applications K 30921, K 31075, K 31784, all class Ib) .

The following examples illustrate how the new process works.

Table 1 a

Separating
temperature Relative
Humidity
at 21 ° C
space
temperature Approx
Carnallite rnallitkonzent
KCl advice
Carnallite
yield Carnallite Residue
KCl K CI yield ⁰ C % % V. V. % Ve V 80 40 18.9 19.6 72.9 2.8 9.2 54.3 60 40 31.8 9.0 94.6 0.4 13.2 87.1 40 40 36.2 9.2 96.9 0.2 12.9 88.9 35 40 33.5 10.4 95.1 0.3 13.2 87.9 60 60 26.0 11.9 90.6 0.6 12.5 82.6 40 62 27.6 11.8 96.9 0.3 12.3 81.5 60 70 17.3 10.5 93.0 0.6 13.8 73.9

example 1

A carnallite mixed salt with 9.6% K ₂ O content, 6.4% carnallite and 13.4% KCl (remainder rock salt and kieserite) was divided into the fractions 0 to 1 mm, 1 to 2 mm and 2 to 4 mm . Quantitatively, the 1st fraction was 49.7, the 2nd fraction 31.2, the 3rd fraction 19.1 ° / _0th The 1st fraction had a K ₂ O content of 9.0% and contained 5.8% carnallite and 12.6% KCl. At various separation temperatures and different relative humidity of the surrounding atmosphere at 21 ⁰ C, the results of the following Table 1 were obtained a.

As can be seen from this table, the most favorable results for this fraction are at separation temperatures from 30 to 60 ° C and water vapor partial pressures of 7.4 mm Hg = 40% relative humidity at 21 ° C. Here Carnallite yields of 90% and above are achieved, and the carnallite contents of the residue are extraordinary small.

The 2nd fraction (1 to 2 mm) had a K ₂ O content

of 9.9% and contained 6.4% carnallite and 13.9% KCl.

ίο The variation of the separation temperature and the relative The humidity of the room atmosphere gives the results in Table 1 b.

Table Ib

Separating
temperature Relative
Humidity
at 21 ° C
space
temperature Approx
Carnallite rnallitkonzent
KCl advice
Carnallite
yield Carnallite Residue
KCl KCl yield ⁰ C % 7o 7o % 7o Vo 40 42 50.2 11.2 62.7 2.3 14.9 94.5 60 42 47.0 13.6 44.0 3.6 14.7 94.7 40 61 67.8 5.0 88.4 0.8 15.8 97.2 60 60 66.2 7.8 68.0 2.1 15.5 96.7 40 70 28.2 6.2 88.8 0.9 15.6 90.9 60 69 44.9 5.7 76.8 1.6 15.0 95.7

While with the 1st fraction the best result was achieved at a separation temperature of 40 ⁰ C and a water vapor partial pressure of 7.4 mm of mercury (40% relative humidity at 21 ° C room temperature), the 2nd fraction delivers the optimum at a separation temperature of 4O ⁰ C and a water vapor partial pressure of 11.4 mm Hg = 61% relative humidity at 21 ° C. it is particularly noteworthy thereby the height of the Carnallitkonzentrate achieved.

The 3rd fraction (2 to 4 mm) with a K ₂ O content of 10.5%, 7.7% carnallite and 14.7% KCl gave the results in Table 1c below.

As the table shows Ic, is an even higher moisture content of the atmosphere, namely a water vapor partial pressure of 12.9 mm Hg = 69% relative humidity at 21 ⁰ C at best for this coarse fraction.

Table Ic

Separating
temperature Relative
Humidity
at 21 ° C
space
temperature Approx
Carnallite rnallitkonzent
KCl advice
Carnallite
yield Carnallite Residue
KCl KCl yield ⁰ C Vo % 7o % Vo 7o V ₀ 35 61 52.5 5.4 75.4 2.4 18.0 96.0 40 60 37.9 6.2 51.1 3.9 17.1 96.2 60 60 68.1 4.7 47.1 4.7 16.9 97.7 35 69 22.9 11.2 85.2 1.7 18.5 79.0 40 70 31.1 6.8 61.1 3.6 18.5 93.6 60 69 42.4 6.1 42.1 4.7 17.4 97.2

Example 2

With the most favorable conditions for the separation temperature and air humidity determined in Example 1 the same crude salt was processed on high-percentage carnallite. There were again three grain size fractions produced with the same grain size ranges as in Example 1. In a 1st separation stage, the results of Table 2 a below achieved.

lot Table 2 a salary distribution salary KCl- distribution Raw salt eff. Vo Vo Vo fraction Vo Carnallite Vo 47.2 12.6 45.2 49.7 6.3 30.6 13.9 31.2 mm 31.2 6.4 22.4 14.7 23.6 Obis I 19.1 7.7 1 to 2 2 to 4

Pre-concentration

fraction

Separation temperature

Relative

Humidity

at 21 ° C

Room temperature

Carnallite concentrate

Carnallite

salary
Vo

yield Vo KCl-

salary
O/

/ 0

yield

O/ /O

Residue

Carnallite

salary

yield

KCl-

salary
Vo

yield

10

Obis 1

1 to 2

2 to 4

40 40 35

40 61 69

34.2
59.1
41.0

90.7 88.6 74.1 6.6
5.4
8.2

8.7
3.6
7.8

0.7 0.8 2.3

9.3
11.4
25.9

13.8
14.8
15.7

91.3
96.4
92.2

The carnallite concentrates of the three fractions were again divorced under the same conditions as subjected to the preconcentration, and after repeating this operation several times, one obtained the results of the following table 2 b.

Table 2 b

Post-concentration

fraction Carnallite concentrate yield
Vo Ge
stop
Vo KCl- Medium good Carnallite yield
Vo Ge
stop
Vo KCl- Residue yield
% Ge
stop
O/
/O KCl- Separating Carnallite 5 6th yield
Vo Ge
stop
Vo 9 10 yield
Vo Carnallite 13th 14th yield
° / o temperature
relative humidity Ge
stop
Vo 65.1
78.6
47.5 1.4
2.0
3.7 7th 8th 23.8
10.0
26.6 5.3
11.1
9.8 11 Ge
hait
Vo 11.6
11.4
25.9 13.5
14.8
15.7 15th 1 to 3 4th 1.1
0.9
1.2 39.2
17.8
22.6 1.6
2.7
6.0 12th 96.7
96.4
92.8 as with table
2a 86.4
84.1
76.8 0.9
0.8
2.3

The carnallite concentrates of the three fractions are used or for further processing (decomposition) executed from the process. The middle goods go back to the beginning of the carnallite separation, and the residues, which contain practically all of the potassium chloride, are removed by known methods further processed.

It is particularly important that the residues can now also be processed electrostatically using the method of chemical conditioning using anionic substances according to the above-mentioned patents, so that the advantages of the dry process over the wet process can now also be used for the first time in the processing of carnallitic mixed salts. Because without pre-separation of the carnallite, there is no avoiding wet treatment of the entire material to be processed, with all the associated disadvantages compared to the dry process. In processing technical terms, it has been particularly unfortunate when the Carnallitgehalte are so low (<10 ° / ₀₎ that a preliminary decomposition of carnallite is not worthwhile, but yet so high (> l ° / o) that they require special processing methods, otherwise they would affect the usability of the products.

Example 3

45 In the following table 3 tests with other crude salts and very different carnallite contents are given compiled. As the table shows, the new process also works with higher carnallite contents perfect.

Tabel

Raw salt
Carnallite K ₂ O ί 48.0. 17.6 Separating
temperature Relative
Humidity
at 21 ⁰ C
space
temperature Carr
Carnallite lallitkonzer
KCl itrat
Carnalut
yield Carnallite
salary Residue
KCI
salary KCl-
yield Vo 28.0 19.5 \ 68.5 j 18.6 ⁰ C Vo Vo Vo Vo % Vo Vo 8.2 '17 .2 1 40 38 38.9 19.9 77.7 2.2 26.1 87.0 i ί 60 36 68.9 15.4 96.2 1.8 29.3 74.5 28.0: 19.0 \ 40 38 62.3 18.4 96.8 2.1 29.8 67.6 \ 60 59 65.2 9.8 96.4 1.7 35.0 83.7 40 38 82.6 3.1 98.4 0.7 31.2 95.1 40 60 71.2 4.7 98.2 0.9 33.6 91.0 60 58 74.5 3.8 96.5 1.8 31.2 92.5 40 39 78.9 4.5 99.4 0.7 31.2 81.7 40 38 84.3 7.7 99.8 0.6 25.6 43.9

The extraction of carnallite in a high percentage form made possible by the new process and demonstrated by Example 2 also improves the further processing of the carnallite itself, ie its decomposition into potassium chloride, in a decisive manner. A carnallite can be decomposed with the less lye or water and with the higher the yield, the higher it is, because the K Cl losses in the decomposition liquor are lower, the higher the concentration of magnesium chloride in the lye can be driven . In addition, due to the reduced content of NaCl, the decomposed _{potassium chloride is immediately obtained in a high percentage form (about 60% K 2} O) without the need to follow a special process step for enrichment (covering, floating).

All in all, the new method of pre-separating the carnallite from the material to be processed brings up electrostatic means a whole series of considerable technical advances in the processing of carnallitic Mixed salts, the most important of which are briefly summarized:

Completely dry preparation of carnallitic mixed salts by electrostatic means.

During the dissolving process: higher throughput, higher yield, improved products, lower energy consumption, lower K ₂ O losses.

With flotation: higher concentrates, reduced K ₂ O losses.

During the decomposition of carnallite: improved products, lower K ₂ O losses, reduced energy costs.

With this new process, a problem has been solved in a technically advanced way that has been for some time Time became more urgent every day, since the existing deposits became increasingly carnallitic Mixed salts are promoted.

Claims (4)

PATENT CLAIMS: 1. A method for electrostatic separation of carnallite from such containing potassium salts, characterized in that the processing material to a temperature between 30 and 8O ⁰ C, preferably between 35 and 70 ⁰ C is heated, and water vapor partial pressures from 5.6 to 13, preferably 7.4 to 13 Torr, the carnallite is separated electrostatically in a high percentage form. 2. The method according to claim 1, characterized in that the material to be processed in grain size fractions divided, the individual fractions separately subjected to the electrostatic carnallite separation and the coarser fractions at higher humidity and possibly lower temperatures than the lighter fractions are processed electrostatically. 3. A method for the electrostatic processing of carnallite-containing potassium salts, characterized in that that after the electrostatic preliminary separation of carnallite according to claims 1 and 2 the residue is subjected to chemical conditioning with anionic substances and is further processed electrostatically. 4. A method for processing carnallite containing potassium salts, characterized in that after the electrostatic pre-separation of carnallite according to claims 1 and 2, the residue is further processed according to the known methods of the dissolution or flotation process. Considered publications:
German patent specification No. 755 155. © 009 647/81 11.