DE102019004576A1 - Process for the production of potassium sulfate from polymineral hard salts without polluting waste products and the need for salt dumps - Google Patents

Abstract

Manufacturing process for potassium sulfate and NaCl evaporated salt from polymineral crude salts with the following stages: 1. Grinding to <5 mm2. Cold leaching of the chloride minerals using cold water 3. Crystallization of KCl and NaCl from the chloride extract solution by evaporation 4. Hot leaching of MgSO4 from the sulfate minerals kieserite and langbeinite5. Conversion of KCl and MgSO4 to K2SO46. Calcination of polyhaltite and extraction of K2SO4, MgSO4 for K2SO4 production 7. Production of CaSO4. 0.5H2O. The process does not require any salt dumps and no solution discharge if MgCl2 from the K2SO4 process is recycled or used as backfill material.

Description

The invention relates to a process for the production of potassium sulfate from polymineral potash crude salts, so-called hard salts, which neither requires the creation of salt heaps nor the removal of salt solutions. All mineral salts occurring in the polymineral hard salts are completely recycled and processed into products, which means that both stockpiling and solution repulsion are unnecessary.

The raw material for the production of potassium sulfate is polymineral hard salt, which occurs in large deposits in central Germany. Polymineral hard salt consists mainly of the potash minerals sylvine (KCl), langbeinite (K ₂ SO ₄ 2MgSO ₄ ), kainite (KCl MgSO ₄ 2.75H ₂ O) and polyhalite (K ₂ SO ₄ MgSO ₄ 2CaSO ₄ 2H ₂ O) as well as the pure sulfate minerals kieserite (MgSO ₄ .H ₂ O), anhydrite (CaSO ₄ ) and halite (NaCl) and some clay minerals. The potash mineral carnallite (KCI · MgCl2 · 6H ₂ O) is only slightly present in typical hard salts.

The potassium-containing mineral components contained in the extracted hard salt can be used to produce the chloride-free potash fertilizer potassium sulfate (K ₂ SO ₄ ) and sodium chloride in vacuum salt quality from the rock salt content. The sulfate minerals kieserite, kainite and langbeinite are dissolved at a higher temperature and a correspondingly longer residence time after the previous separation of the chlorides, polyhalite must be calcined by thermal treatment or results in a slowly soluble, chloride-free potassium-magnesium-sulfur fertilizer.

Potassium sulphate is obtained from the dissolved sulphates by reaction with potassium chloride. At the end of the extraction process, only calcium sulfate and the magnesium chloride formed by conversion remain as a highly concentrated solution. This can either be recycled, e.g. B. for MgO production or by adding binders from the CaO / MgO group of substances as an offset in pit cavities.

The complete recycling of all mineral components results in valuable products and only a little clay sludge remains.

State of the art

The processing of polymineral hard salts was carried out in Central Germany in the so-called Unstrut potash district for decades on an industrial scale and only stopped in 1991. Potassium-magnesium fertilizers with 38 to 42 percent K ₂ O content and more than 3.5 percent MgO were obtained as products using a flotation process. Potash kieserite products with 18 to 20 percent MgO and 7 to 8 percent K ₂ O were produced by additional kieserite flotation. The polyhalite content of the crude salt was only insufficiently applied as a product. The typical crude salt quality and the state of the art of the processing methods are detailed in "Potash in the Südharz-Unstrut-Revier" Volume 2, S 722 to 767 and Volume 3, pp. 208 to 209, both published by the German Berbaug Museum Bochum 2003 and 2005, described. Both the hot dissolving process of polymineral hard salts and their flotative processing did not lead to high-percentage potassium chloride or potassium sulfate. The production residues always represented a source of loss and, because of the need to stockpile water-soluble salts, a permanent environmental problem. These problems were also a reason why it was not possible to manufacture potassium sulfate in the past.

The manufacturing processes for potassium sulfate based on the raw material of potassium chloride and soluble magnesium sulfate hydrates (e.g. MgSO ₄ · 7H ₂ O) are well known and also in "Kali im Südharz-Unstrut-Revier", Volume 3, Bochum 2005, pages 231 to 242 described. The usual processes are based on the so-called concentrated process, which works with potassium chloride and Epsom salt and produces Schönite (potassium magnesia) as an intermediate product in two conversion stages. The magnesium chloride formed by conversion from MgSO ₄ and KCl leaves the manufacturing process as a so-called potassium magnesium eye that is as concentrated as possible. This can be further concentrated in order to recover dissolved potassium and sulfate.

It can be seen from the prior art that potassium sulfate processes require the use of raw materials that are low or free of sodium chloride. Therefore, the potassium chloride crystals used in particular must have a KCI content of over 95 percent. Another prerequisite for low-loss potassium sulphate production is a ratio of the components K: SO ₄ in the raw materials that comes close to the molar ratio of potassium to sulphate, such as 2: 1, as well as being able to carry out the magnesium chloride formed in the conversion reaction from KCl and MgSO ₄ without polluting the water.

Object of the invention

The aim of the invention is to produce potassium sulfate as the main product from multicomponent polymineral hard salts and to completely avoid the accumulation of possible solid and liquid waste products, whereby neither salt piles nor salt solution repulsion are required. All components of the multi-component crude salt should be obtained as high-quality products, including the rock salt as vacuum salt.

Objects of the invention

The invention must first solve the problem of separating the multitude of different mineral components very sharply and completely from one another despite their extremely fine intergrowth. The components potassium chloride, sodium chloride, magnesium sulphate and calcium sulphate must be obtained separately from one another as intermediate products, so that potassium sulphate is obtained separately from the other components through conversion of MgSO ₄ and KCl and the sodium chloride. In detail it means that K ₂ SO _{4 has to be} obtained from the components KCl and MgSO ₄ by conversion. NaCl must be obtained in pure form and the sulfate minerals polyhalite and anhydrite must be obtained as chloride-free K-Mg-S fertilizers or used as raw materials for additional K ₂ SO ₄ production. Furthermore, the task to be solved is to use the sulfate minerals polyhalite and anhydrite either for fertilization purposes in the form of a chloride-free K ₂ OM ₉ O-CaO-SO4 fertilizer or as a further raw material for potassium sulfate.

Essence of the invention

The production of potassium sulfate as well as the production of NaCl evaporated salt from a multi-component mineral mixture requires a practically complete separation of the components KCl, K ₂ SO ₄ , MgSO ₄ , CaSO ₄ and NaCl from one another. Because of the complicated composition of the crude salt and because of the extremely intensive intergrowth of the minerals, this necessary condition can neither be met by a wet nor a dry sorting process. A conventional hot dissolving process is also ruled out as a separation process. The essence of the invention consists in the separation of the complex mineral mixture and the separation into the individual components using the solubilities at different temperatures.

• 1. Das auf < 4mm zerkleinerte Rohsalz wird mit einer berechneten Menge kalten Wasser bei 10-25°C behandelt. Die Dauer dieser Behandlung soll 30 Minuten nicht überschreiten. Dabei lösen sich chlorichischen Minerale Syloin, Halit und soweit vorhanden, Carnallit und Kainit vollständig auf. Die sulfatischen Minerale Kieserit, Langbeinit, Polyhalit und Anhydrit verbleiben im Löserückstand. Aus dieser selektive Auslaugung entstandenen, an KCl und NaCI gesätigtrn Extraktlösung, können durch bekannte Eindampfkristallisationsverfahren die Alkalichloride KCl und NaCl als ausreichend reine Produkte gewonnen werden.
• 2. Die im Rückstand verbliebenen, in kaltem Wasser wenig bzw. langsam löslichen, sulfatischen Minerale Langbeinit und Kieserit werden nun bei Temperaturen von 60-80°C und ausreichender Verweilzeit von 6-12 haus dem Rückstand 1 extrahiert und bilden den Sulfatrohstoff für eine Kaliumsulfatproduktion. Der in diesem Schritt anfallende Rückstand 2 enthält Polyhalit und Anhydrit.
• 3 Der Rückstand 2 enthält Polyhalit und Anhydrit. Aus diesem Rückstand 2 kann nach einer Thermischen Behandlung und der damit verbundenen Strukturumwandlung dad Polyhalit weiteres K₂SO₄ und MgSO₄ gelöst und für eine Gewinnung von K₂SO₄ und MgSO₄ gelöst und für eine Gewinnung von K₂SO₄ nutzbarer gemacht werden. Alternativ dazu ist die Nutzung des Polyhalit als Langzeitdünger (K-MG-S) möglich.

The inventive problem is solved step by step as follows:

• 1. The crude salt, crushed to <4mm, is treated with a calculated amount of cold water at 10-25 ° C. The duration of this treatment should not exceed 30 minutes. Chlorichic minerals syloin, halite and, if present, carnallite and kainite dissolve completely. The sulphate minerals kieserite, langbeinite, polyhalite and anhydrite remain in the solution residue. The alkali chlorides KCl and NaCl can be obtained as sufficiently pure products from this selective leaching, which is saturated in KCl and NaCl.
• 2. The sulphatic minerals langbeinite and kieserite remaining in the residue, which are poorly or slowly soluble in cold water, are now extracted at temperatures of 60-80 ° C and a sufficient residence time of 6-12 from the residue 1 and form the sulphate raw material for potassium sulphate production . The residue 2 obtained in this step contains polyhalite and anhydrite.
• 3 The residue 2 contains polyhalite and anhydrite. From this residue 2, after thermal treatment and the associated structural transformation of the polyhalite, further K ₂ SO ₄ and MgSO ₄ can be dissolved and dissolved for the production of K ₂ SO ₄ and MgSO ₄ and made more useful for the production of K ₂ SO ₄ . Alternatively, the polyhalite can be used as a long-term fertilizer (K-MG-S).

This means that, even with multi-component mineral stocks and intensive mineral intergrowth, treatment of the crushed crude salt with a calculated amount of cold water at around 10 to 25 ° C dissolves the chloride minerals sylvine (KCl), halite (NaCl) and, if present, carnallite and kainite . Low dissolving temperature and limited dissolving time of max. 30 minutes lead to a complete dissolution of the chloride minerals while the sulfate minerals kieserite (MgSO ₄ · H ₂ O), langbeinite (K ₂ SO ₄ · 2MgSO ₄ ), polyhalite (K ₂ SO ₄ · MgSO ₄ · 2CaSO ₄ · 2H ₂ O) and anhydrite (CaSO ₄ ) remain as a dissolving residue. This selective leaching of soluble chloride minerals results in an extract solution saturated with KCl and NaCl with only minor contamination from clay minerals and dissolved CaSO ₄ , MgSO ₄ and MgCl ₂ . This extract solution can be separated into sufficiently pure alkali chlorides (KCl and NaCl) using known evaporation crystallization processes. The condensation of the evaporated solvent water results in pure condensate, which can be used again for cold dissolution or as process water for the production of potassium sulfate.

The suspended clay can be completely removed by sedimentation before the extract solution is evaporated. The poorly soluble sulphate minerals are used as sulphate raw materials for the production of potassium sulphate. The minerals kieserite and long-legged are very little or very slowly soluble in cold water and remain in the solution residue at the temperatures and residence times used.

At elevated temperatures, however, the rate of dissolution of kieserite and langbeinite increases many times over. In contrast to polyhalite and anhydrite, both sulfate minerals dissolve at higher temperatures, around 60 to 80 ° C and sufficient residence time, from about 6 to 12 hours, completely. The mineral polyhalite, which is about 9 to 12 percent by mass in the crude salt, and the anhydrite remain as an insoluble residue. Since polyhalite consists of 30 percent potassium sulfate, 20 percent magnesium sulfate and 45 percent calcium sulfate, this residue is also a useful K-MG fertilizer. By treating at high temperatures of about 450 ° C, polyhalite is calcined, whereby the potassium sulfate and magnesium sulfate contained therein become water-soluble. The calcination with subsequent leaching makes both the potassium sulfate and the magnesium sulfate of the polyhalite accessible for an additional potassium sulfate production. After leaching, the only residual material that remains is calcium sulfate in the form of gypsum or anhydrite.

Example 1:

With an hourly crude salt processing of 200 tons of a polymineral hard salt consisting of the typical components with 10% sylvine KCI, 45% NaCl, 14% MgSO ₄ · H ₂ O, 6% K ₂ SO ₄ · 2 MgSO ₄ , 1% KCl · MgCl ₂ 6H ₂ O, 0.5% KCl · MgSO ₄ · 2.75 H ₂ O and 0.5% clay, the crude salt delivered from the mine is crushed to a grain size of <4 mm and continuously fed to the cold dissolving process. The leaching takes place in two screw loosening devices connected in series with water at a temperature of 10 to 20 ° C and a residence time of max. 15 to 20 minutes per dissolving device.

The amount of water required is around 300 t / h. About 130 t / h of chloride minerals dissolve and 350 m3 / h of extract solution with 105 g / l KCl, 257 g / l NaCl, 2 g / l MgCl ₂ , 2 g / l MgSO ₄ and 860 g / l H _{2 are produced} O and 68 t / h of residue consisting of undissolved kieserite, polyhalite, langbeinite and anhydrite. The clay remains suspended in the extract solution and can be completely removed by thickening and filtration. Interfering levels of calcium in the extract solution are precipitated as CaCO ₃ and also separated off before further processing.

• Möglichkeit 1: Mehrstufiges Eindampfen im Vakuum bis an die Grenze der Sulfatlöslichkeit, Abtrennung des KCl-, NaCI-Kristallisates von der eingedampften Lösung und Trennung des KCI-, NaCI-Kristallisates durch heißes Umlösen.
• Möglichkeit 2: Eindampfen der Extraktlösung zusammen mit Mutterlauge der KCI-Kristallisation bei etwa 100 °C bis nahe an die Grenze der KCI-Löslichkeit. Abtrennung des NaCl-Kristallisates bei Eindampftemperatur, anschließend Kühlkristallisation der KCl-, NaCl-gesättigten Lösung auf 25 bis 30 °C und Abtrennung des KCI-Kristallisates von der Mutterlauge, wonach diese in den Eindampfprozess zurückgeführt wird.

Potassium and sodium chloride are obtained from the extract solution by evaporating the solution in several stages. There are two alternative options:

• Option 1: Multi-stage evaporation in vacuo to the limit of sulfate solubility, separation of the KCl, NaCl crystals from the evaporated solution and separation of the KCl, NaCl crystals by hot dissolving.
• Option 2: Evaporation of the extract solution together with mother liquor from the KCI crystallization at about 100 ° C. to close to the limit of the KCI solubility. Separation of the NaCl crystals at evaporation temperature, then cooling crystallization of the KCl-, NaCl-saturated solution to 25 to 30 ° C and separation of the KCl crystals from the mother liquor, after which this is returned to the evaporation process.

The potassium chloride crystals are adjusted to a quality of> 95% KCl by known washing with a little water (covering process). 36 t / h of potassium chloride are obtained. Because of the crystallization from a KCl-saturated solution, sodium chloride contains up to 1 percent KCl and> 99% NaCl. If it cannot be used as a chemical raw material in this quality, dissolving it in pure condensate and subsequent recrystallization through water evaporation leads to an NaCl quality of> 99.9% NaCl with a slight elutriation of KCl-enriched mother liquor. The further processing of the sulphatic dissolution residue takes place according to a known method with a mixture of hot water and Epsom salt mother liquor at a high dissolving temperature and a long dissolving time. A total of 28 t / h kieserite and 12 t / h langbeinite dissolve and 22 t / h polyhalite and 6 t / h anhydrite remain as the dissolving residue.

The hot solution after the kieserite-Langbeinite dissolution process consists of 5 t / h K ₂ SO ₄ , 31 t / h MgSO ₄ and about 64 t / h H ₂ O. When it is cooled to about 25 ° C, part of the magnesium sulfate crystallizes out as heptahydrate . The conversion to potassium sulfate can take place with the resulting suspension. However, partial quantities of the magnesium sulfate can also be introduced into the process of producing potassium sulfate as Epsom salt.

By adding 38.5 t / h of potassium chloride, around 90 percent of the magnesium sulfate contained is converted into potassium sulfate, resulting in a total of 45 t / h of potassium sulfate. The magnesium chloride formed by conversion is obtained as a beautifully saturated solution, which has about 180 g / l MgCl2 content and after evaporation down to about 300 g / l MgCl ₂ and recovery of part of the dissolved valuable substances as KCl and kainite has the following composition: 300 g / l MgCl ₂ , 40 g / l MgSO ₄ , 50 g / l KCl, 20 g / l NaCl.

In the potassium sulphate process, 45 t / h of potassium sulphate and about 73 m3 / h of MgCl ₂ final solution are produced from 2 t / h of potassium chloride added and 36.5 t / h from the crude salt.

The polyhalitic-anhydritic dissolution residue is dried and yields 28 t / h chloride-free long-term fertilizer with the nutrient contents 12% K ₂ O, 5% MgO, 23% CaO, 22% S.

The MgCl ₂ final solution is mixed with about 8 - 10 percent dolomite lime hydrate as a self-hardening, pumpable backfill material and brought into existing or crude salt mining.

• - 350.000 t/a Kaliumsulfat (50 / 52 % K2O)
• - 650.000 t/a NaCI-Siedesalz
• - 200.000 t/a K-Mg-Ca-S-Dünger (12 % K₂0, 5 % MgO).

The following products are produced from 1,500,000 tons of crude salt every year:

• - 350,000 t / a potassium sulfate (50/52% K2O)
• - 650,000 t / a NaCI vacuum salt
• - 200,000 t / a K-Mg-Ca-S fertilizer (12% K ₂ 0, 5% MgO).

The production process requires 14,000 t / a of additional potassium chloride and approx. 40,000 t / a of branded dolomite.

Example 2:

The process management and the crude salt composition are shown in Example 1. In contrast to Example 1, the remaining solution residue of 22 t / h polyhalite and 6 t / h anhydrite is max. Thermally treated for 1 hour. Leaching of the cooled calcine gives 60 m3 / h of K ₂ SO ₄ -M ₉ SO ₄ extract with about 102 g / l K ₂ SO ₄ , 70 g / l MgSO ₄ , 3 g / l CaSO ₄ and 940 g / l H ₂ O and about 16 t / h CaSO ₄ hemihydrate.

Complete evaporation of the water gives 10.5 t / h of solids. Press granulation results in a chloride-free K-Mg fertilizer with> 30% K2O,> 12% MgO,> 20% S.

• - 350.000 t/a Kaliumsulfat (50 / 52 % K₂O)
• - 650.000 t/a NaCI-Siedesalz
• - 80.000 t/a K-Mg-Düngemittel (30 % K₂0, 12 % MgO, 20 % S)
• - 120.000 t/a CaS04-Halbhydrat

als Produkte hergestellt.Every year, 1,500,000 tons of raw salt are produced

• - 350,000 t / a potassium sulfate (50/52% K ₂ O)
• - 650,000 t / a NaCI vacuum salt
• - 80,000 t / a K-Mg fertilizer (30% K ₂ 0, 12% MgO, 20% S)
• - 120,000 t / a CaS04 hemihydrate

manufactured as products.

KCI requirement and binder requirement correspond to example 1

Example 3:

From 200 tons of processed crude salt according to example 2 45 t / h potassium sulfate and 60 m3 / h K ₂ SO ₄ -MgSO ₄ extract of the composition according to example 2 result. By adding 7.9 t / h potassium chloride and evaporation of 35 t / h of water and cooling to 25 ° C, 10.3 t / h of potassium sulfate and 24 m3 / h of K ₂ SO ₄ -saturated solution with the composition 180 g / l KCI, 55 g / l MgSO ₄ , 95 g / l MgCl2, 895 g / l H ₂ O obtained. Further evaporation of this solution gives a 7.6 m ³ / h solution with 300 g / l MgCl ₂ , 40 g / l MgSO ₄ and 50 g / l KCl. 3.9 t / h of KCl and 1.0 t / h of MgSO ₄ crystallize as a KCl / kainite mixture. The recovered valuable materials are fed back into the process of producing potassium sulfate.

A total of around 430,000 t / a potassium sulphate and 650,000 t / a NaCI evaporated salt as well as 120,000 t / a CaSO4 hemihydrate are obtained as products from 1,500,000 t / a crude salt as the main product.

Example 4:

The process is carried out according to Example 1. The further treatment of the MgCl ₂ final solution obtained is different. An amount of 10 m3 / h is first desulphated by adding 370 kg of CaCl ₂ . After the precipitated gypsum has been separated off, the solution is mixed with an equivalent amount of 20 percent sodium hydroxide solution. This causes the magnesium to fall as magnesium hydroxide and an equivalent amount of sodium chloride is formed. The precipitated magnesium hydroxide is separated, washed and can be used as a flame retardant material.

The solution consisting of NaCl and KCl is mixed with the solution from the cold leaching process and evaporated.

Neben

350.000 t/a Kaliumsulfat 650.000 t/a NaCl-Siedesalz aus dem Hauptprozess 200.000 t/a K-Mg-Ca-S-Dünger

werden mittels Zusatz von 21 kt/a NaOH und 2,8 kt/a CaCl₂ etwa 11.500 t/a Mg-Hydroxid als Nebenprodukt hergestellt.The remaining MgCl ₂ final solution is mixed with the binding agent dolomite lime hydrate and fed to the mine as a backfill.

Next

350,000 t / a potassium sulfate 650,000 t / a NaCl evaporated salt from the main process 200,000 t / a K-Mg-Ca-S fertilizer

With the addition of 21 kt / a NaOH and 2.8 kt / a CaCl _2, about 11,500 t / a Mg hydroxide are produced as a by-product.

Example 5:

The process is carried out as in Example 3. However, deviating from the process management described, 6.5 t / h of magnesium sulfate in the form of 13 t / h Epsom salt are branched off from the process stage of the kieserite dissolution process, dried and thus about 100,000 t / a MgSO.7H ₂ O generated as a by-product. This eliminates the need for external KCl and the amount of potassium sulphate produced is reduced by 9.5 t / h or around 70,000 t / a to around 360,000 t / a produced potassium sulphate.

Claims (19)

Process for the production of potassium sulfate from polymineral hard salt without polluting waste products and the need for salt dumps characterized in that the mined ground crude salt is treated with cold water at a temperature of 10 to 25 ° C with a dissolution time of less than one hour, whereby all chloride minerals including the rock salt content of the crude salt dissolve completely while the sulfatic minerals are undissolved as residue remain, after which this residue is separated from the chloride extract solution and processed further to potassium sulfate while the KCl-NaCl-containing extract solution is evaporated and the dissolved salts are crystallized by known processes and obtained as KCl crystals and NaCl crystals. Procedure according to Claim 1 , characterized in that the crude salt is crushed by dry grinding to a grain size of <5 mm, preferably> 4 mm, and the chloride minerals are dissolved with water in two dissolving apparatuses working continuously in countercurrent, from which the undissolved residue is discharged by mechanical discharge, preferably elevators takes place. Procedure according to the Claims 1 and 2 , characterized in that two screw-type looseners are used as the loosening device, from which the residue is discharged by means of elevators and the residue is drained with filters or centrifuges. Procedure according to the Claims 1 and 2 , characterized in that a two-stage ring washing system consisting of two nozzle tasks, two pipeline loops, two round clarifiers, two discharge elevators and a residue filter or centrifuge as the dissolving apparatus. Procedure according to the Claims 1 to 4th , characterized in that the clarified extract solution separated from clayey components is evaporated in a multi-body evaporator system in a vacuum, the dissolved chlorides crystallize out as a KCl-NaCl mixture and the crystallizate is redissolved in potassium chloride with> 95% KCl and in sodium chloride using a known method is separated with> 99% NaCl. Procedure according to the Claims 1 to 4th , characterized in that the clarified extract solution, separated from clayey components, is additionally purified by precipitation of calcium carbonate and evaporated together with mother liquor from the KCl crystallization at around 100 ° C until the solution is almost saturated with KCl and contains NaCl crystals in a known manner separated and the evaporated vapor is compressed in mechanical compressors and used to heat the evaporation plant, after which the hot solution separated from the crystallized sodium chloride is cooled in a known manner in a multi-stage vacuum crystallization plant, whereby potassium chloride with about 95% KCl content crystallizes out, which after separation of the mother liquor to be returned is used as a potassium component for the production of potassium sulphate. Procedure according to the Claims 1 to 6th , characterized in that the sodium chloride separated from the hot solution containing potassium and sodium chloride leaves the production process as a product, either wet or dried, with a purity of> 99% NaCl. Procedure according to the Claims 1 to 6th , characterized in that the potassium-containing NaCl crystals are dissolved in pure condensate and the NaCl brine obtained is evaporated by evaporation with vapor compression, whereby the purity of the crystals is increased to> 99.9% NaCl, the product of the recrystallization process leaves the process and the resulting pure condensate is used to dissolve the NaCl crystals. Procedure according to the Claims 1 to 8th , characterized in that the concentration of potassium in the mother liquor of the recrystallization process according to Claim 8 is regulated by discharging mother liquor fractions, preferably 3 to 10 percent. Procedure according to the Claims 1 to 9 , characterized in that the sulfate minerals obtained after the dissolution of the chloride minerals are selectively dissolved at dissolving temperatures of 60 to 80 ° C and residence times of several hours according to a method known per se with water and MgSO4 solutions, kieserite and langbeinite dissolving and polyhalite and Anhydrite remain as a residue. Procedure according to the Claims 1 to 10 , characterized in that the solution resulting from the hot dissolution of the sulphate minerals kieserite and langbeinite is cooled, whereby the dissolved magnesium sulphate crystallizes out as heptahydrate and this is used alone or together with the mother liquor to produce potassium sulphate as sulphate raw material. Procedure according to Claim 11 , characterized in that the magnesium sulfate heptahydrate formed by cooling crystallization of the hot magnesium sulfate solution is separated off and partially or wholly leaves the process as a product. Process the Claims 1 to 12 , characterized in that the solution residue consisting of polyhalite and anhydrite from the hot Dissolution of the sulphate minerals is dried and leaves the process as a chloride-free potassium-magnesium-calcium-sulfur fertilizer. Procedure according to the Claims 1 to 12 , characterized in that the solution residue consisting of polyhalite and anhydrite is dried and then calcined according to a method known per se at temperatures of about 450 ° C and the calcine is treated with hot water, with a K ₂ SO ₄ -MgSO ₄ extract solution about 100 g / l K ₂ SO ₄ and 70 g / l MgSO ₄ and a residue consisting of calcium sulfate hydrates result. Procedure according to the Claims 1 to 14th , characterized in that the K ₂ SOa-MgSO ₄ extract solution obtained from calcined polyhalite is evaporated and the crystallized salts are processed into a chloride-free K-Mg-sulfur fertilizer with> 30% K ₂ O and> 12% MgO, which the process leaves. Procedure according to the Claims 1 to 15th , characterized in that the calcium sulphate residue is processed into calcium sulphate hemihydrate, which leaves the process as a by-product. Procedure according to the Claims 1 to 16 , characterized in that the mixture of K ₂ SO ₄ and MgSO ₄ obtained by leaching calcined polyhalite is fed to the potassium sulphate process and converted to potassium sulphate with additional potassium chloride. Procedure according to the Claims 1 to 17th , characterized in that the magnesium chloride and magnesium sulphate-containing reaction solutions from the potassium sulphate process are evaporated to a MgCl ₂ concentration between 300 and 320 g / l MgCl2, whereby some of the dissolved salts as kainite (KCI · MgSO ₄ · 2.75 H ₂ O) and this kainite crystallizate is used in the process of potassium sulfate production. Procedure according to the Claims 1 to 18th , characterized in that the MgCl ₂ -MgSO ₄ solutions originating from the conversion processes are further evaporated above the MgCl ₂ concentration of 320 g / l Mgl ₂ and the dissolved KCl is crystallized out as carnallite.

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