DE1226090B - Process for the hot dissolving of crude potash salts in main and secondary solvents for the purpose of obtaining potassium chloride - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. Cl .:

COId

German class: 121 - 3/08

Number: 1226 090

File number: W 28370IV a / 121

Filing date: August 13, 1960

Opening day: October 6, 1966

The known continuous dissolving process for potash crude salt works in the usual way with two dissolving devices, which are connected in series according to the countercurrent principle, so that fresh solution with partially released crude salt comes together in the post-dissolver and the lye then in the main dissolver for saturation is associated with the ground crude salt. This way of working has the Disadvantage that the dissolver in the post-dissolver absorbs much more rock salt than the KCl-NaCl equilibrium is equivalent to. If the KCl concentration in the main solvent is then increased by triggering the If the crude salt in the lye increases steadily, a corresponding amount of rock salt is excreted, which ends up in the sewage sludge. This sewage sludge thus contains the secondary and main dissolving apparatus precipitated rock salt in addition to fine fractions carried away from the crude salt, such as rock salt, potassium chloride, Anhydrite, kieserite, syngenite, clay and other minor components. In the usual procedure, this will be the case Fine sludge is discharged from the saturated medium via centrifuges or filters. This method has the disadvantage that the fine sludge that originates from the intermediate residue is not yet fully released is. The further disadvantage is that the separation takes place in the KCl-saturated medium, which in the event of unavoidable cooling in the separating elements, this leads to the excretion of KCl.

According to an older known method, salt and sludge should be removed from sedimentation boxes of the crystals stirred up with lye while blowing in air and thereby fine sludge from potassium chloride in the cold State to be disconnected. However, this proposal does not solve the problem like fine sludge • separated from the final liquor and this can be returned to the cycle. This method also brings kCl-poor intermediate residue from the main dissolver to the secondary dissolver Raffle; Rather, only a sedimentation box is used.

According to another known method, the sludge is separated in two stages. It should be in the first stage sodium chloride and kieserite are separated from a saturated solution, however a crystallization of KCl by cooling in the filters or centrifuges cannot be avoided can, which leads to a reduction in the yield. The remaining sludge should then be stirred up the crystals are separated with cold mother liquor and clarified in an iron container, namely when the KCl and NaCl crystallize out.

This process does not solve the problem of a process for hot dissolving crude potash salts
in main and post-solvers for the purpose of obtaining
of potassium chloride

Applicant:

Wintershall Aktiengesellschaft, Celle;

Kassel, August-Rosterg-Haus

Named as inventor:

Dipl.-Chem. Dr. rer. nat. Karl-Heinz Kießling,

Reyershausen via Göttingen

To circulate the fine sludge of the raw solution and to completely add it to the post-dissolver before it is added Dissolve, so that the dissolving eye is already saturated with rock salt before entering the actual dissolving process is. Rather, the fine sludge sludge should be heated, clarified and excreted so that it can be Operation only relates to a heat clarification. The accumulated sewage sludge can neither continuously subtracted still to be dewatered on filters and centrifuges and is therefore for the claimed process not usable.

From Michels, "Die .Kalirohsalze", p. 138, is only known that sludge is mixed with warm mother liquor in a discontinuous process, the pulp is brought to 80 to 90 ° C and then fed to filter presses. By detaching of the rock salt, which acts as a filter aid, can Sludge cannot be separated with other devices. With complete leaching of the rock salt filter presses have not proven themselves (p. 138, line 34). This procedure also requires additional Energy expenditure and brings unwanted caustic growth by blowing in steam. It is not either clear at which point the returned sludge is to be carried out so that it is in the process must enrich until this comes to a standstill. This known method does not contain either Operation that causes the rock salt saturation of the dissolver before it enters the post-dissolver, and it is no separation of the sludge provided behind the post-release device.

From Fulda, "Das Kali", p. 249, is only known, a subset of the sludge of the raw

609 669/276

3 4

especially to dissolve solution in an agitator. If this dissolving solution meets with countercurrent operation of the This partial amount falls in the last cone of the clarifying and subsequent dissolver on a practically KCl-free coarse residue, apparatus and can therefore only consist of clayey components, the NaCl content of the resulting solution increases with which the claimed with unchanged KCl -Content on the limit saturation NaCl-On saturation of the dissolving solution not reached 5 supply value to; 48.0MoI Na _{2 Cl 2} . With increasing can. Rather, the NaCl-containing lamb for the KCl content of the solution should be separated during the passage and fed to the kieserite wash. The NaCl content of the be sinks through the dissolving apparatus. During further processing, the respective KCl concentration can be reduced accordingly. Theder-like fine sludge could not oretically clarify the equilibrium concentration B in the flowing medium (clarifiers 4 and 7), but only with a total of 10 39.9 mol K ₂ Cl ₂ and 40.2 mol Na ₂ Cl ₂ . Rest in sedimentation boxes. This fine sludge can therefore not be drawn off continuously in the dissolving apparatus 48.0-40.2 and cannot be precipitated on filters = 7.8 mol Na ₂ Cl ₂ . This or centrifugal can be dewatered. NaCl comes from the coarse residue and is discharged in the case of The invention now relates to a method for the method according to the prior art as hot dissolving of crude potash salts in main and crude solution sludge. Subsequent dissolving for the purpose of obtaining potassium chloride, the dissolving lye is circulated before contact with the coarse, and a residue is provided with sufficient NaCl from the fine sludge intermediate residue and crude solution sludge from the clarification of the crude solution. in this way is recovered, and in which the sludge or 20 filterable KCl-poor coarse residue obtained during clarification when entering the post-dissolver of the good centrifugal or potassium chloride crude solution. Fine sludge is treated with solvent solution, which. In practice, the change in concentration, which is characterized by the fact that the fine sludge from dissolving lye, in secondary and main dissolver analytically, the clarification of the crude solution in the dissolving lye before each related to IQQO mol H ₂ O, is determined. : the introduction of which is introduced into the post-dissolver ^ and _{dissolving solution before entry of the post-dissolver} .. ₂ 0.5Mol K ₂ Cl ₂ this alkali next to the intermediate residue 25 which is poor in KCl. . 39 5 Mol-Na Claus the main dissolver is added to the secondary dissolver,. . ,,.:. , ..- .. '. ^{2 2} or the fine sludge from the clarification of the raw solution. .- ■ -...

was separated from the main solvent and the secondary solvent measuring point 1. "...-., ..." 21.0 mol K ₂ Cl ₂

are supplied, the KCl-enriched intermediate 30. 47 ^ y [ _O \ Na ₂ O ₂

solution clarified, a reduced amount of KCi-poor. . - ■ «'01 iVrt ■

Separated sludge and the intermediate solution to the measuring point 2.; ... '.: ... 21.8 mol K ₂ CIa.

Main solvent for dissolving crude salt is supplied. - 47.5 moles Na ₂ C] ₃

and at which also fine sludge and solvent solution measuring point 3: ......., ....., .. 21.9 · Mol K ₂ Cl ₂

against each other, especially the solution from below 35 ..- .. · 47.4MoI Na ₂ Cl ₃

'"teSSniSbSS * Oe ₈ ^ W:' Bringing in kä ^^^ tarä ^ tarf -

setting of the prior art procedure measuring point 4 27.0 mol K ₂ Cl ₂

to that of the .claimed procedure. . ; '. . 45.2 moles Na ₂ Cl ₂

This example relates to the dissolving process of a ₄₀ outlet Naehlöser. '... ,,., ... 27.2MoI K ₂ Gl ₂ -sylvMtischen crude salt with an MgCl ₂ -content of, ^

4 MoVlDOO Mol H ₅ O in the solution. From fig.! Incorporation of crude salt results in the same equation for the 95 ° C isotherm

Weight concentrations of Na ₂ Cl ₂ and K ₂ CI ₂ from the main outlet solver 37.5 mole K ₂ Cl ₂

Curve ABC. ... 45 41.0 MoINa ₂ Cl ₂

The changes in the concentration of the solution eye are ^{point A:} can be seen from A bb, 2,

NaCi saturation in the absence of KCl. An amount of solution with 1000 moles of H ₂ O is capable of

P ₁₁₁₁ ] Jj g _: 17 mol of K ₂ Q ₂ to be dissolved, this corresponds to 8427.8 g of crude

Equilibrium concentration of NaCl and K (I; ⁵ ° ⁸⁸ If- ??, ¹ J ⁰ ^ " ^{K &} ? '■ u _mjI1 rA _1Äft1 ,

Both salts can be present as sediments _ ¹ ^ Md K ₂ Cl ₂ correspond to 17 mol K ₂ O - 1601.3 g

his JS-a'J

At a yield of 91.8%, 72.40% total point C falls: residue = 6101.7 g (coarse residue + sludge),

KCl saturation "in the absence of NaCl. ₅₅ based on 8427, -8 g of crude salt, as by weighing

Between A and B ^1- S ^and solids content determinations in the raw

Naa-Grenzko'flzentration ha KCl-Untersättl · · ^l f ^ f ..! ^{nd of} , f ^en 6101 7g total return

stood 45% raw solution sludge = 2743.2 g.

^ss * dissolve 1000 mol of H ₂ O as a solution «, 0 mol

Between B and C: 60 Na ₂ Cl ₂ = 935.26 g NaCl from the coarse residue,

KCl limit concentration in the case of NaCl undersaturation, of which 2.5 mol Na ₂ Cl ₂ = 292.26 g NaCl im

supply, Naehlöser and 4.0 mol Na ₂ Cl ₂ = 467.66 g NaCl im

Main solver to re-elimination.

The dissolving process takes place below or on top of the. NaCl saturation of the dissolving solution before

Curve A-B from, there is constantly NaCl in a rich dissolving apparatus through the import of fine sludge from the

Excess is present. . _: ; Clarification of the crude solution made so reduced

The dissolving solution contains 20.5 mol of K ₂ Cl ₂ and 39.5 mol, the amount of sludge by 935.26 g, by which

Na ₂ Cl ₂ to 100Q mol H ₂ O. Amount of NaCl in the coarse residue.

The fine sludge from the clarification of the raw solution is discharged with an average humidity of 8%; this contains 2.7% KCl. In practice, however, sludge with an average of 4.5% KCl obtained. This 'KCl content comes in a small amount from' undissolved KCl from the crude salt, the main amount of the crystallized KCl of the adhering approximately saturated crude solution through Cooling in pumps, pipes, centrifuges and filters.

In the claimed process, the KClarme sludge is discharged from the intermediate solution. The intermediate solution is far from the KCl saturation, so that when cooling occurs, it is not KCl but NaCl that precipitates; moreover, the adhering moisture does not consist of an approximately saturated solution with 37.5 mol of K ₂ Cl ₂ , but of KCl- unsaturated intermediate solution with only 27.2 mol of K ₂ Cl ₂ .

If the low-KCl sludge is discharged from the intermediate solution with 8% moisture, this is calculated from this a KCl content of 1.96% KCl. In practice, sludges with 2.0 to 2.2% KCl achieved. The coarse residue is increased by 951.4 g, with a KCl content of 1.7% an increased export of 16.2 g of KCl via this residue route.

Comparison of the
K ₂ O losses through discharge of the fine sludge

1. from the raw solution according to the state of the art,

2. from the interim solution according to the claimed method.

1000 mol of H ₂ O as dissolving solution with 4 mol of MgCl ₂ , 20.5 mol of K ₂ Cl ₂ and 39.5 mol of Na ₂ Cl ₂ are used to raffle 8427.8 g of crude salt with 19.0% K ₂ O = 1601.3 g K ₂ O used.

1. Discharge of 2743.2 g calc. 4.5% sludge KCl.

8.0% moisture before calcination.
The adhering moisture consists of a solution of 4 mol MgCl ₂ , 37.5 mol K ₂ Cl ₂ and 41.0 mol Na ₂ Cl ₂ in 1000 mol H ₂ O.

K ₂ O loss through the sludge 123.4 g KCl = 77.98 g K ₂ O.

Based on K ₂ O in the crude salt, 4.87% loss.

2a) Theoretical calculation:

Discharge of 1808.0 g calc. 1.957% KCl sludge.

8% moisture before calcination.
The adhering moisture consists of an intermediate solution of 4 mol MgCl ₂ , 27.2 mol K ₂ Cl ₂ and 45.0 mol Na ₂ Cl ₂ in 1000 mol H ₂ O.

6o loss through the mud

35.39 g KCl = 22.36 g K ₂ O

Increased coarse residue

discharge of 951.4 g with 1.7%

KCl = 16.2 g KCl = 10.23 g K ₂ O

Total loss = 32.59 grams of K ₂ O

Relative to K ₂ O in the crude salt, 2.04% loss.

2b) Value achieved in practice:

Discharge of 1808.0 g calc. mud
with 2.2% KCl.

8% moisture before calcination.
The adhering moisture consists of an intermediate solution of 4MoI MgCl ₂ , 27.2MoI K ₂ Cl ₂ and 45.0 mol Na ₂ Cl ₂ in 1000 mol H ₂ O.

Loss through the mud
ίο 39.78 g KCl = 25.13 g K ₂ O

Increased coarse residue

discharge of 951.4 g with 1.7%

KCl = 16.2 g KCl = 10.23 g K ₂ O

_1S total loss = 35.36 g K ₂ O

Based on K ₂ O in the crude salt, 2.21% loss.

A K ₂ O loss of 4.87% in the raffle for crude salt according to the known method corresponds to a theoretical K ₂ O loss of 2.04% and an in compared to the loss of 2.21% achieved in practice.

The progress achieved with the method according to the invention is thus considerable.

The operation according to the invention is illustrated by the A b b. 3 explained. In the dissolving vessel 1 is Fine sludge in the dissolving solution for NaCl saturation and the resulting dissolving solution in the post-dissolver 2 introduced to dissolve low-KCl intermediate residue. The separation takes place in the clarifier 4 the intermediate solution of the sludge poor in KCl, which is removed via the sludge centrifuges 5 and comes to discharge. The intermediate solution becomes the main solvent for dissolving the ground crude salt 6, from which the KCl-poor intermediate residue is fed into the post-dissolver 2 by means of an elevator 3 is carried out. The practically KCl-saturated crude solution is fed to the clarifier 7, in which the Separated fine sludge and then to the dissolution vessel 1 in the circuit for treating the dissolving solution is fed. The clarified raw solution is used in a known manner in the vacuum cooling system for crystallization of the product.

Claims (2)

Patent claims: 1. Process for hot dissolving of crude potash salts in main and secondary dissolvers for the purpose of extraction of potassium chloride, in which the solution is circulated and an intermediate residue and raw solution sludge is recovered and in which the clarification of the potassium chloride raw solution obtained sludge or fine sludge is treated with dissolving lye, characterized in that that the fine sludge from the clarification of the raw solution is stirred into the solvent solution before it is introduced into the subsequent solvent and this lye in addition to the KCl-poor intermediate residue from the main solvent and the secondary solvent is supplied or the fine sludge from the clarification of the raw solution and the solvent solution as well the KCl-poor intermediate residue from the main solvent is fed separately to the secondary solvent, the KCl-enriched intermediate solution clarified, a reduced amount of KCl-poor sludge separated and the intermediate solution is fed to the main solvent for dissolving crude salt. 2. The method according to claim 1, characterized in that fine sludge and solvent solution against each other, in particular, the dissolving eye can be introduced into the dissolving vessel from below. Considered publications:
German Patent Nos. 283182, 850 452; S er ο wy, "Processing Methods of Potash Crude Salts", 1952, p. 74; E. Fulda, "Das Kali", Part II, 1928, p. 249; W. Michels, "Die Kalirohsalze", "1916, p. 138. 1 sheet of drawings 609 669/276 9.66 © Bundesdruckerei Berlin