DE3434590A1 - Process for the preparation and decomposition of syngenite in order to prepare K3H(SO4)2 crystals and potassium sulphate crystals and to prepare potassium nitrate - Google Patents

Abstract

Process for the preparation of K2SO4 from potassium chloride salts, calcium sulphate salts and another sulphate source, in which syngenite is formed and then decomposed. In one embodiment, syngenite is decomposed to prepare crystalline K3H(SO4)2. The K3H(SO4)2 crystals are recrystallised to prepare K2SO4 crystals. In another embodiment, syngenite is decomposed in order to prepare KNO3 in solution and solid CaSO4. The solution containing the KNO3 is separated from the CaSO4 precipitate and subjected to a crystallisation step, whereupon the solid, crystalline KNO3 is obtained.

Description

Syngenite for the production of K ^ H (SO , ) y -Kr istallen and

Potassium sulphate crystals and for the production of

It has been known for many years that potassium chloride, the main form in which potassium is used in fertilizers, compared to certain other potassium salts Has disadvantages for agriculture. Consequently will sulphate and nitrate presently on a large scale for crops such as tobacco, tomatoes and potatoes, especially for those used in the production of potato chips (roasted potato slices) to be used potatoes.

Chloride ions are toxic to most species of plants when allowed to rise to sufficiently high levels Concentrations accumulate, and their elimination is over a goal that is pursued in the fertilizer industry. In arid areas, the terms of their Completely dependent on irrigation, For example, the accumulation of chloride ions in the soil can be a main reason for achieving a ver

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reduced crop yield. At such times are larger amounts of water are required to wash out the chloride. Such washing out not only wastes large amounts of valuable water, it also wastes it at the same time necessary fertilizer components that are in the ground, washed out.

The main reason, if not the only reason that the continued use of potassium chloride in these circumstances is its ready availability and the consequent low price of chloride compared to other potassium salts.

The most common substitute for potassium chloride is potassium sulfate. This salt is in different mineral forms present in a number of locations, but its separation, usually by crystallization processes, is more complicated and expensive than separating the chloride. Potassium sulfate is used in the western United States immediately in the form of a sulphate double salt made with magnesium sulfate, but has one Material, although inexpensive in itself, has a low concentration of potassium, and consequently its transportation and its storage more expensive.

For many years the chloride salt of potassium has been converted into sulphate by high temperature reaction with sulfuric acid and in this way considerable quantities have been produced, particularly in Belgium.

Such a process is known from US Pat. No. 4,342,737. There are three main reasons for further manufacture restrict by this procedure:

1. the high energy demand;

2. the highly corrosive nature of the reactants and the chlorine obtained as a by-product

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Hydrogen and,

3. the need for local demand according to the hydrogen chloride produced, since otherwise he Must be neutralized before at considerable cost it can be disposed of as waste.

For many years there have been different ways of converting of the chloride using calcium sulfate or sodium sulfate but none of them have been used commercially.

In many of the proposed routes, Glaser it, a double salt of potassium and sodium sulfate, Na ₂ SO, · 3K ₂ SO ,, is produced as an intermediate product, and then with over-

schussigern potassium chloride converted to the sodium sulfate convert to potassium sulfate. The product can be obtained, for example, by evaporation and recrystallization will. U.S. Patent 4,215,100 relates to such a process. In other ways, the calcium doublet Isa Iz syngenite, CaSO, · K-SO, · H_0, is produced as an intermediate product. This can be decomposed by water at increased temperature and pressure, as described in the GB-PS 435 772 is known, or can be decomposed by concentrated ammonia at low temperature, as it is from the FR-PS 787 713 is known. According to GB-PS 2 068 918 sylvinite, a double salt of potassium and sodium chloride with variable composition, and calcium sulfate reacted with aqueous ammonia to produce the potassium sulfate / sodium sulfate double salt, and that Double salt is reacted with sylvinite or additional sylvinite in aqueous ammonia to convert calcium sulphate to crystals to manufacture.

All such routes are complicated, costly and involve higher energy consumption and can

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require operation under undesirable conditions. As a result, there is still a need for a process for producing K _? S 0, using readily available raw materials at low cost, which is relatively uncomplicated, has high energy efficiency and does not require a substantial initial cost for the equipment.

Potassium nitrate is largely made up of one of two Process made. In the first procedure, the only procedure currently practicable in the United States is applied, potassium chloride becomes at a high temperature reacted with nitric acid to produce potassium nitrate and To produce chlorine using the following reactions:

3KCl + 4HNO ₃ - * 3KN0 ₃ + Cl ₂ + NOCl + 2H ₂ O
2NOCl + 4HNO ₃ - * - 6NO ₂ + Cl ₂ + 2H ₂ O
4NO ₂ + O ₂ + 2H ₂ O - * - 4HN0 ₃

The corrosive nature of the various reactants and the resulting construction and Maintenance problems and the need for elimination of the chlorine obtained as a by-product have prevented widespread use of the process.

In the past few years there is an increasing trend in the US Amount of potassium nitrate has been imported. One main source is Israel where a trial is being carried out

ß0 in the case of nitric acid and potassium chloride in solution Reaction are brought and the hydrogen chloride obtained as a by-product by solvent extraction from the Solution is removed. The feasibility or ability to develop such a procedure depends on the economical disposal of the hydrogen chloride,

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for which in many parts of the world there is no greater need exists, from.

As a result, there is still a demand for a process for the production of KNO, by a alternative method that has no maintenance or construction problems there are still problems related to the elimination of a by-product.

It is an object of the invention to provide one for agriculture provide acceptable form of potassium.

Furthermore, the invention is intended to provide potassium in the form of potassium sulfate or potassium nitrate.

Furthermore, the invention is intended to provide a method for Manufacture of Potassium Sulphate or Potassium Nitrate are available that is relatively uncomplicated and carried out with a high degree of energy efficiency can be.

The invention is also intended to provide a method of production of potassium sulfate or potassium nitrate from Syngenit.

Furthermore, according to the invention, potassium sulfate is to be used a process are produced in which various By-products of the process in the production cycle to be led back.

The object of the invention is achieved by a simple method in which syngenite is produced and then is broken down to obtain potassium sulfate or potassium nitrate.

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In reaction stage 1, potassium chloride and a Sulphate with a calcium sulphate or pentasaIz suspension, which are returned from a subsequent decomposition stage 2 may have been stirred to make sodium chloride and syngenite in suspension according to the following equation to manufacture:

2KCl + Na ₀ SO. + CaSO. + H ₀ O- ^ CaSO ₇ -K ₀ SO ₇ -H ₀ O + 2NaCl 2 4 4 2 4242

or

8KCl + 4Na ₀ SO. + 5CaSO. · K., S 0, · H _ 0 + 4 H _ 0 2 4 4 2 4 2 2

in - * 5 (CaSO. · K ₀ SO, · H _o 0) + 8NaCl

^{x w} 4 2 4 2

After separation, the syngenite is fed to reaction stage 2, where it is mixed with a suitable acidic Solution, for example with a hot, sulfuric acid Solution, implemented and therefore dependent on the reaction conditions in calcium sulfate or penta salt and potassium hydrogen sulfate is decomposed. The stoichiometry is as follows:

H ₀ SO. + CaSO, - K ₀ SO. · H _o 0 -I-CaSO. + 2KHS0. + H _o 0 24 4242 4 42 or

4H ₀ SO ₇ + 5 (CaSO ₇ - K ₀ SO ₇ * H _o 0) - * - 5CaSO ₇ -K ₀ SO ₇ · H _o 0 24 4242 4242

+ 8KHSO ₇ + 4H _o 0 4 d.

The suspension thus produced is separated at the reaction temperature, and the calcium sulfate removed or penta salt can be returned to stage 1 for a further syngenite synthesis. The received hot Solution, the Ka I i um-, Su I f at- and hydrogen sulfate ions in contains suitable concentrations, is cooled to K, H (SO,) _, a double salt of potassium sulfate and hydrogen sulfate, to crystallize out. This is done by filtering or other appropriate measures removed, and the recovered mother liquor can be heated again and returned to stage 2 in order to break down further syngenite.

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The crystallization of an aqueous solution of the double salt K_H (SO,) _ provides crystals of the desired product Potassium sulfate and a potassium hydrogen sulfate and mother liquor containing free sulfuric acid, which is separated off and can be returned to stage 2 to break down further syngenite.

If syngenite with nitric acid instead of sulfuric acid is decomposed, after the removal of the calcium sulfate, potassium, hydrogen, hydrogen sulfate and nitrate ions in solution.

CaSO. K ₀ SO. · H ₀ O + 2H ⁺ + 2N0 ~ - »CaSO.i +
4 c _4 c _ 5 4

HSO. + 2K + 2N0-. + H + H, 0
4 3 2

To the decomposition with the use of nitric acid To bring the maximum amount, the Salpetersauregeha It must be in the solution as a result will be sufficient to make up all of the potassium sulfate to convert into a potassium hydrogen sulfate solution.

The addition of lime or calcium carbonate in appropriate Amounts to such a solution leads to the precipitation of further calcium sulfate and leaves a solution, which effectively contains potassium and nitrate ions and is made up of the potassium nitrate can be crystallized from crystals.

K ⁺ + HSO. "+ H ⁺ + 2NO, ~ + CaCO, - *

⁴ + - ^{3 3}
CaSO. ^ + 2K + 2N0, + H _o 0 + CO ₀ f

2K ⁺ + HSO. "+ H ⁺ + 2NO, ~ + CaCO

4th 3

The presence of excess nitric acid can be beneficial as this will reduce the Solubility of potassium nitrate and leads to less Potassium is returned to the circulation. Alternatively can be added to the solution calcium nitrate Calcium sulfate precipitate, and after crystallization and the removal of the potassium nitrate can remove the remaining Nitric acid solution containing some potassium nitrate.

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can be returned to the syngenite decomposition stage.

2K ⁺ + HSO ~ + H ⁺ + 2NO, ~ + Ca ²⁺ + 2NO, ~ -> - ⁴ + ³ + ³

CaSO, + 2K + 4NO ₃ + 2Η
2K ⁺ + 4NO ₃ "+ 2H ⁺ 2KN0 ₃ | f 2NO ₃ " ₊ 2H ⁺
5

During the development of the aforementioned processes using nitric acid, was It is clear that any process in which the sulfate concentration in the solutions of the reactants is up a value is decreased which is below the concentration which is in equilibrium with syngenite even in the absence of hydrogen ions to release of potassium ions from the syngenite.

The addition of calcium ions to such a solution accordingly actually leads to the precipitation of calcium sulfate and the release of potassium ions.

CaSO. · K ₀ SO, - H ₀ O + Ca ^{+ +} - * "2 Ca SO. A + 2K ⁺ + H ₀ O
4 c 4 d 4 * c

The addition of calcium ions in the form of calcium nitrate, the "in situ" of nitric acid and calcium carbonate or hydroxide can be produced, leads to the formation of a potassium nitrate solution, from which solid KNO., crystallizes out can be, i.e.

CaSO. K ₀ SO. "H _o 0 + Ca ⁺⁺ + 2NO" - * · 2CaSO. 1 + 2K ⁺ + 2NO ~ + H ₀ O.
4 pounds 4 pounds 5 4 5 c

This can be interpreted as follows:

CaSO. · K ₀ SO.-H ₀ O + Ca (N0,) _o - ^ 2CaSO.ψ + 2KN0, + H ₀ O.
4242 32 4 5 c

Fig. 1 is a flow chart of the invention Process in which SyIvinit is converted into potassium sulphate will.

Fig. 2 is a process flow diagram showing an embodiment in which syngenite is _{broken down with HNO 3} and further sulfate ions by adding CaI-

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cium in the form of calcium carbonate, calcium hydroxide or Ca Lcium Nitrate be precipitated, whereupon crystalline is won.

Figure 3 is one process flow diagram which is another Embodiment reproduces when Syngenit by addition is broken down by calcium ions in the form of calcium nitrate, whereupon crystalline KNO is obtained.

The preferred embodiment of the invention is as follows described.

A large proportion of the potassium chloride mined in the world is in the form of sylvinite, a double salt of sodium and potassium chloride with variable composition, available. The process used to make syngenite from potassium chloride can can be modified without difficulty for the use of sylvinite as a starting material. Indeed it is the use of sylvinite is advantageous in that the sodium chloride produced by syngenite synthesis is produced without separate exudation or evaporation along with the sodium chloride contained in the sylvinite is present as waste can be disposed of.

The by Hill, AE, J. Am. Chem. Soc. 5 ^, 1071-8 (1934) and loc. Cit. 5_9, 2242-4 (1937) and Bodaleva, NV and
Lepeshkov, IN, Zh. Neorgan. Khim. 1_, 995-1007 (1956) show that the stability of S y η gen it decreases, while the temperature increases from 40 ⁰ C to 100 C. This shows that syngenite is best synthesized at lower temperatures and is broken down into calcium and potassium sulfate at higher temperatures.

The same data also show that the concentration

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of the potassium sulphate in the solution approx. 4% (w / w) at 40 C and to about 11% (w / w) must rise at 100 C in order to produce stable syngenite .

Any process in which syngenite is synthesized from potassium sulfate solutions must therefore operate within these parameters. We have shown that with solid calcium sulphate it is possible to obtain syngenite to IQ from solutions which contain potassium ions added in the form of potassium chloride and sulphate ions added in the form of sodium sulphate, ammonium sulphate or other soluble sulphates in concentrations which the solubility product for Meet syngenite at the reaction temperature.

Furthermore, on the basis of the information provided by Cornec,

E. and Krombach, H., Compt. Rend. 194 , 714-6 (1932) showed that sufficient concentrations of potassium chloride can be obtained directly from sylvinite by utilizing the mutual solubility of sodium and potassium chloride.

The compositions of solutions that are in equilibrium with both sodium and potassium chloride at various temperatures can be shown diagrammatically using the information provided by Cornec et al. When a solution which is at 20 C in equilibrium, warmed to 8O ⁰ C and is used for the leaching of sylvite, it triggers accordingly, potassium chloride and separates solid

QQ sodium chloride until it is combined with both sodium and also reached equilibrium with potassium chloride.

If such a solution is now brought into contact with the appropriate amount of calcium sulfate at 80 C and to the Solution is given an amount of sodium sulfate that the

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Ca Lciumsulfat is equivalent ^ and the solution is ^{allowed to cool to 2O 0} C, syngenite is formed.

By choosing the appropriate amounts of calcium and sodium sulfate, the concentration of potassium chloride can be reduced to the value of this concentration in the invariant or equilibrium point at 20 ^° C. The sodium chloride produced by the reaction

CaSO, + 2KCl + Na_, SO. + H _o 0-> 2NaCl + CaSO, - K-SO. · HO
4,242,4242

is generated with respect to the sodium chloride present in the solution in the invariant point at 2O ⁰ C in excess, so that the excess precipitates together with the syngenite, while the remainder in the invariant or equilibrium point is at 20 C in solution. After separating the precipitated solids, the solution can be heated to 80 C and recycled to leach out sylvinite and dissolve fresh potassium chloride, while discarding the remainder of the sodium chloride generated by the syngenite synthesis step. This sodium chloride is then disposed of as waste along with the sodium chloride that remains after the potassium chloride has been dissolved out of the sylvinite. Alternatively, potassium chloride alone can be added to the 80 ° C solution in which it will dissolve until equilibrium is reached and sodium chloride will precipitate and can be removed.

Phase considerations also limit the conditions for the decomposition of the syngenite and for the separation of the potassium sulfate produced in this way. The phase diagram

for K-SO. - H _, S 0. in water, using the information in c 4 2 4

D'Ans, J.Z., Anorg. Chem. Έκ3, 225-9 (1909), Stör t enbec ker, W., Rec. Trav. Chem. _2J_, 407 (1909), and Babaewa, A.W., Trans. Inst. Pure Chem. Reagents (Moscow) 111 114 (1931).

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Our investigations have shown that syngenite in the presence of hydrogen ions at elevated temperature ( > 6 ° C), depending on the conditions, either in Ca L ci umsu L f at or in pentaset (5CaSO.- K-.SO. «H _n O )

4 d 4 c

is dismantled. It seems that the mechanism is through the conversion of sulfate ions in solution in hydrogen sulfate ions and the resulting leaching out from KpSO, from the Syngenit, in which the restoration aimed at the sulfate concentration in the solution is, is conditional.

If there is enough hydrogen ions in the form of sulfuric acid or another acid with a dissociation constant greater than the second dissociation constant of sulfuric acid, 1.2 10, are present, the syngenite is completely converted into solid CaSO, and in Dissolved potassium and hydrogen sulfate ions in the solution.

To the decomposition with the use of sulfuric acid on To bring the maximum, the sulfuric acid content in the solution is sufficient to remove all of the potassium sulphate, both the potassium sulfate originally in solution and the potassium sulfate released from the syngenite, to convert into potassium hydrogen sulfate solutions.

Solutions that have a composition according to Syngenit-Ze riegung with a K: S 0, (sulfate) molar ratio, the greater than 1: 1, and have excess potassium sulfate compared to a solution of potassium hydrogen sulfate are technically applicable, but economical unsatisfactory, since the amount of potassium sulfate released from the syngenite corresponds to the amount in the decomposition solution available free sulfuric acid directly is equivalent because it is the hydrogen ions that

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Convert sulfate to hydrogen sulfation.

The statements by D'Ans, Stortenbecker and Babaewa show that even solutions, the free sulfuric acid in excess beyond what is required for the formation of hydrogen sulfate Amount included when cooled under suitable conditions Provide crystals, and not potassium hydrogen sulfate crystals, but crystals of the double salt K, H (SO,) p. At low starting temperatures (> 30 ° C) deliver solutions with the composition of hydrogen sulfate however, when it cools, it is actually potassium sulfate. The mother liquor contains free acid and can be decomposed fed back into the cycle by fresh syngenite will.

The information from D'Ans, Stortenbecker and Babaewa show also that at any given temperature with concentrations of sulfuric acid, which are lower than the sulfuric acid concentration in the invariant point (i.e. at the point where the solid double salt K, H (S0,) p together with solid potassium sulfate in equilibrium with the solution is}, the solid in equilibrium Phase is potassium sulfate. For example, leads to 30 C the addition of the double salt to solutions that contain less than 20g H-, SO per 100g water, to crystallize of potassium sulfate, until such additions bring the sulfuric acid concentration in the mother liquor to 20g bring per 100g of water. After separating the solid Potassium sulphate can cause such a mother liquor to decompose after suitable concentration by evaporation to be led back. At higher temperatures A similar result is obtained up to the boiling point of the solution, but solutions with a higher concentration be returned to the cycle. This reduces the amount of evaporation required.

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Although such an isothermal crystallization of Potassium sulfate is preferred, the double salt K, H (SO.)

to be dissolved in hot water. Such a solution provides on cooling potassium sulfate as a solid phase, and the acid-rich mother liquor can lead to syngenite decomposition to be led back.

The preferred temperature for this dissolving step is at or near the boiling point. A solution,

which at 95 ⁰ C 46.5% (wt./wt.) K ₃ H (S0 _{4) 2 [3} H 87,5g K (S0 _{4) 2}

Contains 10Og water}, when it is ^{cooled to 0} ° C, typically leads to precipitation of voi
(68.5g K-SO, per 187.5g starting solution)

is typically used to precipitate K _? SO, -Krist a Ilen

To keep the process at its financially most economical To carry out this manner, it is desirable to keep the size of the operating equipment to a minimum, what means that the process is carried out under conditions appropriate for a given unit size result in the maximum throughput.

For this reason it is undoubtedly best to use the SyI-vinit leach out at the highest temperature that is applicable, around 100 C., thereby producing the maximum amount extracted on potassium chloride and the invariant solution with the highest concentration is obtained. Under assuming that it is desired to adjust the calcium chloride concentration after the synthesis to keep at more than 3.5%, this increases the amount of KCl that can be converted and consequently the amount of NaCl produced is determined. It can be seen that the temperature in this part the solubility curve is unimportant.

The lowest potassium concentration indicated above-Q5 was given by a review of the above

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The information discussed and presented by HiLl and Bodaleva et al. Define this information the lowest K_SO, concentration at 40 C with Syngenite is in equilibrium, as about 4g per 100g Solution, which is a potassium concentration of 3.5g KCl per 100g of solution is equivalent. In fact we have shown that at 20 C KC l concentrations down to 2.9g per 100g are sufficient. The data presented by Hill and Bodaleva et al also show that the stability range of the syngenite is greater at lower temperatures, thereby determining that the most suitable synthesis temperature range is below 60 C and probably below 40 C, which is actually proven by experiments has been confirmed.

As already mentioned, the data of D'Ans, Stortenbecker and Babaewa show that the most effective conditions for the decomposition of syngenite are conditions which lead to the composition of the solution after decomposition to a K: SO, -Mo Iverhä Itnis of 1: 1 corresponds. These compositions should also provide the double salt K ^ H (SO,) -, on cooling, and the solution with the highest concentration that meets these criteria is the solution with a concentration of about 31.6 g KpSO, and 17.8 g HpSO , per 100g of solution, which, when cooled to 0 C, yields a solution with a concentration of about 12g of KpSO and 18.5g of HpSO per 100g of solution. As a result, when cooling down, a double salt crystallizes out, which is the equivalent of 22.86g of K _{? Per 100g of the starting solution.} S0 together with 4.3g HpSO contains. No other composition of the solution shows such a result

advantageous K ₀ SO, yield with such a good K-SO./ 2 4 2 4

H ₀ SO. Ratio.
2 4

The invention can best be understood with reference to FIG

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to be discribed. A potassium chloride salt such as SyLvinit or KCL and a recycle solution A, which is described below, are brought into contact in a leaching system 1, in which potassium chloride is dissolved and solid sodium chloride is precipitated. The sodium chloride is discarded. The preferred temperatures for this step are in the range between about ambient temperature and the bottom of the solution. The most preferred temperature range lies between 8O ⁰ C and the boiling point.

The leaching solution B now becomes the Syngenit manufacturing unit 2, wherein it is allowed to cool while being treated with a calcium sulphate salt and additional SuLfat is implemented. Suitable sources of additional sulfate include (NH.) -, S 0. and alkali

k c. 4th

met a LLsuI fate, but are not limited to. Suitable calcium sulfate salts include CaSO, and the penta salt 5CaS0, -K _? S0, «H-, 0 a, however, are not on it

limited. At least part of this addition can be of the extraction of by-products during the subsequent syngenite decomposition come here. In the unit 3, the syngenite slurry D thus produced is for example by Filter separately and washed to sodium chloride to remove. The mother liquor and the washing liquids E can be used to remove the washing water in the concentration device 4 concentrated and returned as concentrate A to the leaching stage.

Solid Syngenit F is used together with a mineral acid the Syngenit dismantling container 5, which is used at increased Temperature is maintained, supplied. The mineral acid can be added in liquids G and H recycled from later stages in the process. One "Gypsum" Slurry J is filtered into the

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Separation unit 6 is separated, and the solid "plaster" I becomes washed in 7 with water. This "gypsum" can be returned as C to the Syngenit-Manufacture Lung 2.

Suitable temperatures for the acidic decomposition of syngenite are in the range of ambient to boiling point, with temperatures higher than about 70 ° C being preferred. Most preferred temperatures are 80 C or above. The reaction proceeds to completion at atmospheric pressure, generally requiring a time of about 30 minutes to 2 hours. Suitable concentrations for the transition to the next step are 31.6% (w / w) KpSO, and 17.8% (w / w) H ₂ SO ₄ .

The KHSO, mother liquor containing K from 6 is cooled in the crystallizer 8 to 0 ⁰ C, to a slurry L K _T H (SO ^). J-Kr i st a I Len precipitate, which is separated into 9 for example by filtration .

It is preferred that the KHSO, containing solution be cooled to a temperature in the range from about 0.degree. C. to 45.degree. C., and preferably in the range from about 0.degree. C. to 30.degree. The area most preferred is about O ⁰ C to 2O ⁰ C. The mother liquor G can be returned to the syngenite decomposition in Fig.5.

_{The double salt K 3} H (SO, ^ obtained from the above-mentioned cooling step is suspended in the washing liquids N and O at 100 ° C. in the crystallization device 10. The washing liquid N is returned from the plaster of paris wash 7, while the washing liquid 0 is returned from a subsequent potassium sulfate wash is returned.

The potassium sulfate crystals P thus produced are

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separated in 11, and the mother liquor Q is after Constriction in the evaporator 12 to the syngenite decomposition 5 returned. The crude Kaliumsulfatkrist a L Le R are washed in 13 with saturated potassium sulphate solution S, before they are conveyed as moist potassium sulfate T to the dryer 14, from which the product K-.SO. is obtained.

d. 4th

In the process explained in FIG. 2, syngenite 136, recycle solution 148 and the appropriate amount of fresher Nitric Acid 137 in a Syngenit dismantling container 138 reacted. Suitable temperatures for the acidic decomposition of syngenite are in the range from ambient temperature to the boiling point, temperatures above 70 ° C. being preferred. the most preferred temperatures are 80 ° C or above. The reaction runs at atmospheric pressure until completion, generally taking a time from about 5 minutes to 2 hours is required.

The calcium sulfate slurry thus prepared 140 is separated in a separation device of the first stage 142, for example by filtration. The Calcium Sulphate Solids 144 are washed in 132 with water 134, and the washing liquids 139 are "through." through vaporizer 146 is returned to container 138 as part of solution 148. The washed calcium sulfate 130 depending on how it is expedient, discarded or returned to the syngenite synthesis.

The solution 143 separated in 142 is deposited in the calcium sulphate trap Iation device of the second stage 152 with the appropriate amounts of calcium carbonate, calcium hydroxide or calcium nitrate 150 implemented. The one made in this way Calcium sulfate 154 slurry is used in the separation device of the second stage 156 for example

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wisely separated by filtration. Calcium Sulphate 158 is washed in 160 with water 162 and depending on as appropriate, discarded in 164 or returned to syngenite manufacture. The washing liquid 161 passes through vaporizer 146 as part of solution 148 to syngenite decomposition vessel 138 returned.

The separated solution 180 is cooled in the crystallizer 182 in order to crystallize out solid potassium nitrate, which is separated in the separator 186 from the mother liquor contained in the slurry 184. The solution 180 is typically cooled in the crystallization device 182 to a temperature in the range from approximately 0 ° C. to 45 ° C., and in particular in the range from approximately 0 ° C. to 30 ° C. The preferred range is about 0 ° C to 2O ⁰ C. The filtrate 198 is through the evaporator 146 through part of the solution to the syngenite decomposition attributed 148th

In the process shown in FIG. 3, syngenite 236 and recycle solution 248 at the same temperatures as in Fig. 1 in the Syngenit Zerlegungsvor direction 238 with the equivalent amount of calcium nitrate 237 implemented. The calcium sulfate slurry thus prepared 240 is fed to the separator 242, wherein the calcium sulfate 244 is removed, which in 232 is washed with water 234 before it is discarded or, for example, returned to syngenite production 230 will.

The washing liquid 239 is fed to the evaporator 246 and from there returned to 238 as part of the return solution 248.
35

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The solution 254 separated from the calcium sulfate is now cooled in the crystallizer 282 to Eliminate potassium nitrate. The crystallizer 282 is operated at the same temperatures as crystallizer 182 in FIG. The Slurry of Potassium Nitrate 284 so prepared is separated in the separator 286. The mother liquor 298 is fed to the evaporator 246 before it as part of solution 248 to syngenite decomposition 238 is returned. The produced potassium nitrate is washed and suitably dried to get KNO, crystals 296.

example 1
15th

This example shows that potassium chloride and sodium sulfate can be used to produce syngenite.

By dissolving 859g of potassium chloride in 2500g of water at 23 C became a saturated solution of potassium chloride manufactured. To this solution were 115g potassium chloride, 216.5g sodium sulfate and 186g crystalline anhydrous calcium sulfate given. This mixture was reacted at 23 ° C. for 2 hours. The slurry was filtered and the product washed and dried. The product contained 22.3% potassium and 60.43% sulfate. The 414.2g of the dried product means one up the calcium sulfate-related yield of 92.3%.

Example 2

This example shows that ammonium sulfate can be used for production from Syngenit by reaction with potassium chloride and calcium sulfate can be used.

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A calcium sulfate slurry was prepared by adding 77g calcium hydroxide to 730g water

and this mixture with 101.6g concentrated (97%) 5

Sulfuric acid was reacted and cooled to 10 C.

The mixture mentioned above became by adding of 149.1g potassium chloride, 132g ammonium sulfate and 520g Syngenit is made with additional water. This mixture was stirred for 1 hour at 10 C and filtered, and that Product was washed with about 600 g of water.

After drying, the washed product weighed 266.9 g (yield: 81%) and contained potassium,
Sulphate, calcium, ammonium (as nitrogen) and chloride ions of 18.46%, 62.65%, 14.17%, 0.0% and 0.07%, respectively. This translates to a 100% conversion to potassium when account is taken of the potassium sulfate that remains in equilibrium with the syngenite in the solution and wash fluids.

Example 3

This example explains that syngenite can be extracted from a SyL-vinite leaching liquid can be made that are saturated with potassium and sodium chloride together and contains potassium chloride, sodium chloride and water in an amount of 20%, 17.5% and 62.5%, respectively.

1kg of the mentioned above, the clear solution at a temperature of 8O ⁰ C was charged into a reaction vessel, and this in turn 71g sodium sulfate, and 68g of calcium sulfate was added. The mixture was reacted at 80 ° C for 30 minutes and then cooled to 23 ° C. The total duration of the reaction was about 2 hours. The reaction slurry was filtered, washed

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and dried. The dried product contained 140.7 g 22.3% potassium? 59.1% sulfate and 0% chloride ions. the 140.7g of the product means one on the calcium sulfate based yield of 96%.

Example 4

This example shows that syngenite is effective with sulfuric acid can be disassembled.

476g ei η er filtrate solution from a previous decomposition, which contained 29.2% potassium sulfate and 14.7% sulfuric acid, was reacted with 47.9g 97% sulfuric acid and 140g syngenite for 2 hours at 100 ° C., and the resulting slurry became hot (at 9O ⁰ C) filtered. The residue was washed and dried to give 43.2 g of calcium sulfate solids containing 2.6% potassium, 64.2% sulfate and 0% chloride. The efficiency of the dismantling was about 100%, if 5.9 g of potassium sulphate were taken into account, which was contained in the solution, which was held by the moist plaster residue before drying.

At game 5

This example shows that nitric acid also breaks down syngenite. 241 g of Syngenit were reacted with 500 g of an acidic, 1.51 molar HNO solution containing 48.3 g of HNO _{3 for 2 hours at 60 ° C.}

The resulting slurry was filtered and the wet solids (166g) were washed and dried. The dry solids (116.8g) contained 9.5% Potassium and 63.9% sulfate. That related to the potassium left in the residues of the decomposition

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gene efficiency of the decomposition to calcium sulfate was under these conditions 81%, and the efficiency of the The decomposition to the penta salt was 95%.

Example 6

This example shows the crystallization of the double salt K-, H (SO,) _? from solutions with a sulfuric acid: potassium sulfate molar ratio of 1: 1, which is equivalent to potassium hydrogen sulfate. 300 g of potassium sulfate and 180.9 g of 94% strength sulfuric acid were dissolved in 519.1 g of water at 50 ° C. The solution was cooled to 0 C and the solids that crystallized out were removed by filtration to give 283.6 g of wet solids which, when dried, yielded 260.8 g of dry crystals of the double salt, when analyzed 40, 1% K and 61.8% SO ₄ were found. ["KjHCSO ^^
corresponds to 37.7% K and 61.9% SO,]. The yield based on potassium sulfate was 77.8%.

Example 7

This example illustrates the isothermal crystallization of K SO _2, from a K, H (SO,) ₂ ~ solution at 3O ⁰ C. 250g K, H (SO,) _ were added to 200 g of water having a temperature of 30 ⁰ C, and the slurry thus prepared was stirred for 2 hours. At the end of this time the solids were removed by filtration and dried to provide, after washing with water, 148.9 g of dry solids which, when analyzed, found 44.4% K and 54.7% SO ₄ . (KpSO ₄ corresponds to 44.8% K and 55.2% SO ₄ ). The mother liquor contained 8.4% K and 19.9% SO ₄ , which corresponds to 26.2 g K ₂ SO ₄ ZIOOg H ₃ O and 13.7 g H ₂ SO ₄ ZIOOg HpO.

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At spie L 8

This example shows the separation of potassium sulfate crystals from solutions of the double salt K ^ H (SO,) - ,.
5

225g of the double salt prepared in Example 6 were dissolved in 250g of water at about 100.degree. When the solution was cooled to 0 C, it gave 152.4 g of moist potassium sulfate crystals, which after drying gave 144.3 g of a material which, when analyzed, found 44.9% K and 54.9% SO ₄ . (K ₂ SO ₄ corresponds to 44.8% K and 55.2% SO,). The yield based on potassium sulfate was 72.0%.

Example 9 '

This example shows that a solution from a previous Syngenite production by leaching a composite sylvinite-type ore before reuse can be regenerated.

845,6g of a solution containing 6% potassium, 0.91% of sulphate and chloride 17.2% or about 11.5% KCl and 20% NaCl was 1h mixed at 8O ⁰ C with 175g of potassium chloride and 132 g sodium chloride. The slurry was filtered to give 253.3 g of wet solid and 831.9 g of solution. The wet solid was dried to give 244 g containing 21.8% potassium, 2.11% sulfate and 55.0% chloride. The leach solution obtained contained 10.2% potassium, 19.5% chloride and 0.8% sulfate or 19.4% KCl and 16.9% NaCl.

The solution with this composition is. for the production from Syngenit satisfactory, as in example 3 is shown.

3A3A590

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Be js ρ ie L 10

This example shows the use of nitric acid and calcium carbonate.
5

256g syngenite with a K content of 67g were stirred for 2 hours at 100 ° C. in a nitric acid solution containing 155g nitric acid with a ΗΝΟ -, - content of 69% and 345g water. The calcium sulfate produced was removed by filtration and weighed 113 g after washing with water and drying. (The washing waters were discarded). The mother liquor, 535 g, was neutralized with stirring by adding Ca L ci umcarbonat at 50 C to a pH of 7. Filtration of the slurry produced in this way yielded 89 g of dry, washed calcium sulfate and 306 g of filtrate. The washing liquids were discarded. When the filtrate was cooled to 0 ° C., 67 g of moist potassium nitrate crystals were obtained, which were dried to give 61.5 g of a product whose analysis found 38.23% K. (KNO ₃ corresponds to 38.67% K).

Example 11

This example shows the use of nitric acid and calcium nitrate. 149 g of Syngenit were stirred for 2 hours at 100 ° C. with a solution of 137 g of 69% strength nitric acid in 458 g of water. The calcium sulfate so produced was removed by filtration and weighed 52 g after washing and drying. (The washing liquids were discarded). The mother liquor, 593g, was stirred for 30 min at 5O ⁰ C with 147,5g Ca (NO,) _ · 4H ^ O (calcium nitrate tetrahydrate). Filtration of the slurry so prepared provided 54 g of dry washed calcium sulfate and 574 g of filtrate. (The washing liquids were

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discarded). When the solution was cooled to ⁰ ° C., 70 g of moist potassium nitrate crystals were obtained, which were dried, whereby 38.5 g of a product were obtained in the analysis of which 38.5% K was found.

(KNO ₃ corresponds to 38.67% K).

EXAMPLE 12

This example shows the direct decomposition of syngenite using calcium nitrate.

149g of Syngenit were used for 2 hours at 100 C with a solution of 14 7.5 g calcium nitrate tetrahydrate in 500 g water .

The calcium sulfate produced was filtered through removed and weighed 122g after washing with water and drying. The wash waters were discarded. That Filtrate, 426g, yielded 33.7g on cooling to 0C wet crystals which have been dried to obtain 25.2 g of potassium nitrate, when analyzed, 38.1% K were found.

Claims (1)

TlEDTKE - BüHL.NG - KlNNE -ClRiJPi '' SSSTSK . -Representative at the EPO gasa r \ ^ v O Dip! .-- Ing. H. Tiedtke m HtLLMANN - URAMS "OTRUiF Dipl.-Chem. G. Bühling 4 34 5 9 0 Dipl.-Ing. R. Kinne Dipl.-Ing. R Group Dipl.-Ing. B. Pellmann Dipl.-Ing. K. Grams Dipl.-Chem. Dr. B. Struif Bavariaring 4, Postfach 20 8000 Munich 2 Tel .: 0 89-539653 Telex: 5-24845 tipat Telecopier: O 89 - 537377 cable: Germaniapatent Munich 20th September 1984 DE 4235 / case 699 / Q41936 / PR0DEC0-4 claims 1. Process for the decomposition of syngenite, thereby characterized by the fact that the syngenite is treated with an acid, those from the acids that have a dissociation constant of at least 1.2 χ 10 is selected at a temperature and for a time sufficient to that the syngenite is broken down to CaSO, or the penta salt and KHSO. 2. The method according to claim 1, characterized in that that the acid is a mineral acid. 3. The method according to claim 1, characterized in that that the mineral acid is H-, SO,. 4. The method according to claim 1, characterized in that that the mineral acid is nitric acid and that during the decomposition of the syngenite KNO-, is formed. 5. The method according to claim 1, characterized in chd
lies. net that the temperature is in the range of 60 to 100 C 6. The method according to claim 1, characterized in that that by the equation: CaSO. K-.SO. · H-, 0 + H-.SO. - ^ CaSO. + 2KHS0. + H ₀ O
4 £ 4 <i 24 4 4 c. is reproduced. Dretdi.sr Bank-Munr ^ .- in. KK, ^ ν-ιί.ί., OMiiUch-- Ba: · '· Mu ₁ I- ¹ Ij u "''Jr·'! Ff >ί;? Ι3ι. L-.acknml iMür-chen) Mo R / '· - -2- DE 4235 7. The method according to claim 1, characterized in that it is represented by the equation: 4H-.S0, + 5 (CaSO. · K-.SO. · H-.O) - + · 5CaSO. · K-.SO. · H-O 24 4242 4242 + 8KHS0. + 4H_, 0 4 c. is reproduced. 8. The method of claim 1, further characterized through the step of separating the KHSO. from the CaSO. 4 4 or the pentasalt 5CaSO ₇ -K ₀ SO ₇ -HO and the recycling 4 <L 4 c of the CaSO obtained. or 5CaSO ₇ -KTSO. * H., 0 in the circle 4 hook Run. 9. Process for the production of K-SO ,, thereby marked that (a) syngenite is formed, (b) the syngenite from (a) decomposed with sulfuric acid to produce a solution from KHSO, Cc) the KHSO. Solution from (b) is crystallized to form crystals of the double salt K ₃ H (SO,) -, (d) the K ₃ H (SO, K from (c) is recrystallized to crystalline KpSO, to form, and (e) the K _? S 0, crystals can be obtained. 10. Process for the preparation of K _? SO, according to Claim 9, characterized in that the syngenite in (a) is formed by reacting a calcium sulfate salt with a water-soluble sulfate and a potassium chloride salt in an aqueous solution. 11. A method for the production of K ₂ SO, according to claim 10, characterized in that the potassium chloride salt is potassium chloride. 12. A method for producing K _ S 0 according to claim 10, characterized in that the potassium chloride salt -3- DE 4235 Sylvinite is. 13. Process for the production of K _? SO, according to claim 10, characterized in that the potassium chloride is produced in aqueous solution by leaching sylvinite at a higher temperature with a solution saturated with NaCl and KCl at a lower temperature. 14. Process for the production of potassium nitrate, characterized in that (a) Syngenite (CaSO, K _? SO, H ₂ O) is decomposed in the presence of nitrate ions to form KNO in solution and a CaSO, precipitate, (b) the KNO in solution, from the CaSO, precipitate is separated and (c) from the KNO in solution, solid KNO, is won. 15. The method according to claim 14, characterized in that the decomposition of syngenite in (a) consists in that (a) the syngenite with ENT, is reacted to a Solution of K, HSO, and NO, ions and a CaSO, precipitate to build, Cb) the CaSO, precipitate separated from the solution will and (c) a further precipitation of CaSO is carried out,
30th to obtain KNO in solution. 16. The method according to claim 14, characterized in that the further precipitation of CaSO, in (c) by Addition of lime or CaCO2 is carried out. 17. The method according to claim 14, characterized -4- DE 4235 net that the further precipitation of CaSO, in (c) by Addition of Ca (NO,) -, is carried out. 18. The method according to claim 14, characterized in that the decomposition of syngenite in (a) consists in that (a) the syngenite is reacted with Ca and NO, ions to form a CaSO, precipitate and K and NO, ions in solution,
O (b) the Ca SO, -Niede rschI ag and the K - and NO, -ions in solution are separated and (c) the K ^{+ are} obtained. (c) the K and NO, ions in the form of solid KNO, 19. The method according to claim 18, characterized in that the Ca ions in (a) in the form of Ca (NO,) - added will. 20. The method according to claim 19, characterized in that the Ca (NO,) - by the in situ reaction of HNO, and CaCO, or Ca (OH) _{2 is} produced. 21. The method according to claim 14, characterized in that step (c) is a crystalline from 11 of the in solution located KNO, includes. 22. The method according to claim 21, characterized in that the crystallization is carried out at a temperature in the range from 0 to 45 C.
30th