DD267975A1 - PROCESS FOR PREPARING CALIUM SULFATE AND MAGNESIUM CHLORIDEOLE - Google Patents

Abstract

The invention relates to a process for the preparation of potassium sulfate and Magnesiumchloridsole in a utilizable for the production of magnesium oxide quality of potassium chloride and magnesium sulfate. The method is particularly suitable for small and medium-sized plants that can be erected at any location. According to the invention, this object is achieved by solid potassium sulfate and a MgCl 2 solution with a content of 300 to 320 g / in an eight-stage process based on the Kalimagnesia and Sulfatesetzungsverfahren and the incorporation of other process stages, such as mixed liquor formation, alkali evaporation and cooling. l be won.

Description

For this 2 pages drawings

Field of application of the invention

The invention relates to a process for the preparation of potassium sulfate and magnesium chloride sols in a usable quality for MgO production of magnesium sulfate and potassium chloride. The production process, unlike known potassium sulphate production processes, is not bound by the fact that excess reaction solutions can be accommodated in an adjacent potassium chloride production process. This eliminates the one hand, the partially undesirable coupling problems, on the other hand, it is possible to produce potassium sulfate at any location, for example in a NPK plant.

Compared to conventional production processes results in a reduced specific demand for raw materials of potassium chloride and magnesium sulfate. The manufacturing process is particularly suitable for small and medium production heights. The by-product magnesium chloride brine has a minimum concentration of 300 g / l MgCl ₂ .

Characteristics of the known state of the art

In the production of potassium sulfate from potassium chloride and a MgSO ₄ component (Epsom salt or magnesium sulfate solution) two reaction steps are necessary:

1st stage: MgSO ₄ component, potassium chloride and a part of the sulfate liquor obtained in the production of K ₂ SO "are added

Schonit (K ₂ SO ₄ · MgSO ₄ · 6H _a O) and Kalimagnesialauge implemented.

2nd stage: Schönit with KCl solution or KCl and water are converted to potassium sulfate and sulfate liquor.

The highest achievable recoverable yields are due to the solubility ratios of sulphatic soil bodies

given. (Serowy: The processing methods of Kalirohsalze, W-Knapp-Verlag, Halle 1952). Inevitable with this

The procedure is that a considerable part of the expanses of potassium and sulphate are left in the process Kalimagnesialauge and in the excess Sulfatlaugenanteil be. In terms of yield, this loss of valuable material is only

that these solutions can be used at least partially in the process of KCI production from Kalirohsatz, wherein a certain proportion of the recyclables is recovered. (DE AS 2227152)

The application parameters of the potassium sulphate production from Epsom salts and potassium chloride are nevertheless still essential

above the theoretical value and in practice are about 1.26-1.28t K ₁ O as KCl and 1.80-1.85t MgSO ₄ per 11K ₁ O.

Potassium sulfate. Some processes of KjSCV production have been reported for specific raw materials, for example kieserite, natural sol or kainitic Rohss'z developed. The one proposed specifically for KaInIt. Processing methods involve effective processing of

mined and processed kainite to potassium sulfate (DE AS 1215667, DH AS 1215? 17, DE AS 1140914,

DE AS 1086220) and are not suitable for Epsom salts or other forms of magnesium sulfate, since the sulfate processing

is closely intertwined with the raffle of Kainitrohsalzes.

DD WP 212 724 describes a method of potassium nucleating. where not primarily the Wersterausbeuto sondurn

the quality of the Piodukt stands in the foreground. In contrast, other Verfahrensvorschlägo (DE PS 938612,926368,926829) only specific P include ^p ozeßführungen in the step of Kalimagnusiaherstellung, partly taking advantage of metastable

Equilibria, without satisfactorily solving the problem of reducing material losses or usability

the MgClfhsltigen implementation solutions to enable.

Attempts have been made to get rid of at least part of the potassium sulfite preparation reaction solutions Recovering valuable materials by using these solutions to decompose carnallite (for example, ΟΓΞ AS 1122930) and from the decomposition solution by evaporation again carnallite wins. Hi he leaves everything üulf the Implementation solutions unused. It is also possible according to DE PS 813849. Crystallize out potassium chloride at the expense of the addition of magnesium sulfate. Not only is no sulfate recovered, but additional sulfate is used. According to DE AS 1108672 has been proposed to evaporate the mother liquors and then by addition of

anhydrous magnesium sulfate to bring the existing potassium chloride as Kainit for crtallisation. Also in this case, the sulfate contained in the reaction solutions remains in the final liquor and this is not usable for the production of MgO.

According to DD AP 27199, it is proposed that the surplus not covered by the abovementioned procedures should also be included Sulfatlaugenanteil be included in the KCI recovery by evaporation and by separate reaction of

low-crystallinity kieserite (MgSO ₄ .H ₂ O) and the kainite (KCl · MgSO ₄ 2.75H ₂ O) obtained by evaporation

To use maximum of the resulting sulphate liquor in the production of the Schönits. An evolution of this The method described in DE PS 1159414 operation of the. The Kalimagnesialösung is evaporated far beyond the carnallite point and obtained a Verda.npfsalx, the

It consists of a mixture of carnallite, langbeinite and NaCl, which is used in the production of one part of Schoenits, while the other part of schistite is obtained from kieserite and sulphate lye.

This process requires high evaporation temperatures of 120-145'C to ensure adequate velocity To ensure long-legite crystallization. According to DE AS 2120604 a method is described which the Langbeinitkristallieation separates from that of the evaporating salt, and only works with kieserite as MgS0 ₄ -Componento. A similar process is described in DE AS 2513947. This works with separate Langbeinitkristallisationsstufe and

used for recovery of valuable material by evaporation solution mixtures, which are derived both from the potassium sulfate process and the Kalirohsalzverarbeitung or Aussolprozessen and are saturated with NaCl. Because of the NaCl content, the carnallite and NaCl-containing evaporation salt which is obtained after the selective long-fiber crystallization must also be decomposed separately and fed to the crude salt processing process. This process is particularly intertwined with the process of KCI production.

Altogether the known procedures for the recycling of material, in which reaction lungs of the Potassium sulphate production process we'den subjected to evaporation, usually very complicated process by

a complicated workup multicomponent mixtures, which in addition to K ₂ SO ₄ -containing Dcppelsalzen carnallite and

NaCI included, gekennzeichr-oi are. In addition, MgSO ₄ solution or Epsom salt does not signify for the processes mentioned

but MgS0 ₄ -Kompon inte must be at least partially supplied in the form of kieserite, or anhydrous MgSO _4.

Because of the complexity of the processes and the need for close coupling with adjacent potash salt processing

Also, known methods are not suitable for isolated operation independent of potassium chloride production.

There are known methods in which the Wortstoffrückgewinnung from reaction solutions of Potash salt processing by deep-freezing (DDWP 156255) or by selective salting out using organic matter

(DD WP 34115, FR PS 1396212) is effected. However, these processes do not lead to a usable magnesium chloride solution suitable, for example, for the preparation of MgO, since only MgCl 2 solutions of low concentration result and only the portion of the magnesium chloride formed by conversion, which is obtained as potassium magnesia, is included in the recycle processes mentioned ,

Aim of the breeder

The object of the invention is to provide a process for the production of potassium sulphate which works on the raw material basis of potassium chloride and MgSO ₄ solution or Epsom salts without intertwining with the process of potassium chloride preparation with high recovery of valuable material and in which the magnesium chloride formed by double reaction takes the form of a usable solution high MgCl2 concentration can be obtained as a by-product.

Explanation of the essence of the invention The invention must solve the problem, starting from potassium chloride and MgSO ₄ solution or Epsom salt in addition Potassium sulfate in honor yield to produce a magnesium chloride solution with a MyClj content> 300g / l, without doing so

Rc'wierig incurred further processable complicated mixtures.

The invention solves this technical problem in that the Kaliumsulfathstellung with a recovery of in the Reaction solutions of potassium sulfate and Schönitherstellung dissolved valuable potassium and sulfate is connected so that

a closed material cycle ensues. If only the desired products of potassium sulfate and magnesium chloride can be left, the recovered valuable materials are immediately recycled to the formation of schoenite.

It was surprisingly found that by dehydration in the temperature range of 65-90 ° C at Zugrundeleguni a

certain ratio of MgClj: MgS (V.KCi: NaCl is a directly usable in the production of Schoenither

Mineral mixture nut KCI and kainite (KCi MgSO ₄ 2,7SH ₂ O) Nus the reaction solutions can be crystallized and

thereby ain can build up a material skating, the magnesium chloride only in the form of a concentrated solution with a

Concentration> 300 g / l MgCl ₂ can leave. It was expaiimentoll found that it is possible, after a vacuum evaporation in water from the MgCl ₂ -, KCI, MgSO ₄ and NaCI-containing recirculation solutions by applying certain crystallization temperatures, Concentration and Vorweilzeiton a selective crystallization of potassium chloride and kainite in high yield

to achieve without the carnallite must be exceeded and without it being difficult to separate education

Crystal mixtures auk carnallite, kainite, leonite or MgSO ₄ · * / * M ₂ O and sodium chloride comes. According to the invention, this is mainly due to the fact that

(1) the MgCl ₂ -containing conversion solution to be supplied to a certain ratio

MgCl ₂ : MgSC ₄ : KCl: NaCl is adjusted

2) d! O evaporation is steered so that the evaporation of water is still below the Carnallitpunkt lying MgCl ₂ -

Content of the solution is reached and the target MgCl ₂ concentration between 280 and 320g / l MgCl ₂ is.

(3) the evaporation in vacuum at a temperature> 65 but <90 "C, whereby the formation of undesirable soil bodies such as langbeinite (K ₂ SO ₄ · MgSO ₄ ) or MgSO ₄ · * / * H ₂ O is prevented.

(4) subsequent to the evaporation of the mixture is evaporated and crystallized salts solution at least 0.8 hours and a maximum 6 hours isothermally at a temperature of 65-80 ⁰ C is stirred.

(5) the K'iitallsuepeniion then cooled to ambient temperature (20-35 C ^c) and then the MgCl, solution of KCI Kainitkristallisat is disconnected.

(6) the KCI Kainitkristaltisat with magnesium sulfate in the form of MgSO ₄ solution and / or Epsom salt and solid potassium chloride is mixed and is reacted with sulfate to schoerite.

Under these conditions according to the invention, on the one hand, schoenite which can be converted to potassium sulphate by a known process and a mixture of potassium manganese dioxide and sulphate liquor, which is adjustable in composition, are present in the proportions MgCl / MgSO.sub.2 KChNaCl required for a selective KCl crystallization according to the invention , Dat 'H is the case when the components mentioned are approximately in the ratio 1: 0.4 - 0.55: 0.80 - 1.10: 0.05 - 0.1.

The inventive method consists of a first reaction stage, in which from KCI Kainitgemisch, magnesium sulfate solution or Epsom salt, potassium chloride and sulfate liquor (reaction liquor of process stage 2) on the one hand Schönit with a lower. KCI excess and on the other hand Kalimagnesialauge is produced.

This is followed by a second reaction stage, in which the separated from the Kalimagnesialauge Schönit with potassium chloride of at least 60% K ₂ O content and water is reacted to potassium sulfate and sulfate liquor and works by a known method. The sulfate liquor is partially used for Schönitherstellung after their separation from the potassium sulfate and partially mixed with the Kalimagnesialauge, whereby the ion ratio according to the invention can be adjusted. In a third process step, water is evaporated from the mixed solution formed from the excess of sulphate liquor and the potassium hydroxide solution in vacuo such that the concentration of magnosium chloride increases to just below the coexistence concentration KCl-cumallite, the subsequent removal of water being precipitated by the formation of kainite as crystal water (2, 75 moles of H ₂ O / mol of MgSO ₄ ) and without exceeding the carnallite point. Such a water vapor evaporation is preferred that, after kainite crystallization and cooling to ambient temperature, the coexistence concentration KCl-carnallite (about 320 g / l MgCl ₂ ) is just reached. In practice, a MgCl ₂ concentration between 300 and 320 g / l MgCl _{2 is} realized. Subsequent to the water evaporation at 65-90 ° C., preferably 70-80 ° C., in vacuo, an isothermal stirring process of 0.6-6 hours duration, preferably 2 hours, is connected, the double salt kainite, KCl MgSO ₄ .2, 75 H ₂ O crystallized in pure form

 As a particularly favorable temperature was determined about 70 * C.

The hot mixture of KCl and kainite on the one hand and solution containing all of the MgCl ₂ and NaCl and remaining XCl and MgSO ₄ portions is rapidly cooled to ambient temperature without phase separation and separated by filtration or centrifugation.

The process of the invention is preferably carried out in continuous process control in crystallization reactors which ensure the residence time of the components required for a complete reaction. This is the case when the average residence time in the crystallization reactor is between 0.6 and β hours, the residence time of the solution and crystal phases may be different.

In the method according to the invention, a MgCl ₂ -SoIo with a MgCl ₂ content between 300 and 320 g / l and contents of KCl NaCl and MgSO ₄ according to the determined by the MgC * content and the temperature solubility of these components.

It is possible to use this solution in the original form if permitted by the following procedure. The solution resulting from the process can be concentrated and purified by subsequent further treatment after processes of evaporation, cooling or precipitation which are essentially already known for MgCl ₂ solutions from carnallite processing, if this is necessary. It is possible, above the

Coexistence Concentration KCI: Carnallite lying MgClr concentration (called carnallite point for short) in the MgCIj soli leaving the process.

For this purpose, after separation of the KCl-kainite mixture, the MgCl ₂ sols to an arbitrary between Carnallitpunkt (about 320g / l MgCl,) and Bischoffitpunkt (coexistence of KCI MgCI ₁ · 6H ₂ O and MgCl ₂ 6H ₂ O at saturation NaCI about 460g / l MgCl ₂ lying MgCl ₂ concentration evaporated and after renewed cooling to ambient temperature consisting of carnallite, sodium chloride and at very high MgCl ₂ concentrations also Langbeinit or MgSO ₄ 'Α hydrate existing crystals of the highly concentrated and only slightly Alkatichlorid containing "MgCl ₂ sols isolated. Because of the content of not or difficult to be processed in the process of potassium sulfate production components will be given a separate use of this Kristalllsates outside the KiSCvHerstellungsprozesses preferred. a partial use in the allowable NaCl VertrSglichkeitsgrenzen is possible in principle, complicated but significant the claims to the process control.

It is also possible to precipitate the magnesium sulfate still contained in the MgCl ₂ solution after crystallization with calcium chloride and to convert the sulfate into gypsum and the magnesium into additional magnesium chloride.

The invention is explained in more detail by two exemplary embodiments: Explanatory Leaflet 1 For this figure 1

983 kg MgSO ₄ and in 1968 kg of water are in the form of a saturated magnesium sulfate solution together with 1.02 m ^J sulfate liquor of the composition B5G / I MgSO _4, 80g / l MgCl ,, 196g / l KCI, 9g / l NaCl, 886g / l H ₂ O and 1138kg KCI-Kainitgemisch the composition 24.4% MgSO ₄ , 2.6% MgCl ₁ , 55.7% KCl, 0.2% NaCl, 17.1% H ₂ O and 188kg potassium chloride with 80.5% K _: 0 content continuously reacted at residence times of 4.5 hours and at reaction temperatures of 25 to 28'C in a Kristallisatiohsreaktor reacted. The resulting beautiful suspension is fed to a drum cell filter and in 2400kt filter moist Schönit the composition 24.1% MgSO ₄ , 2.9% MgCl ₂ , 5.0% KCl, 33.3% K ₂ SO ₄ , 34, 't% H ₂ O and 2.53m ³ Kalimagnesialauge the composition 73g / l MgSO ₄ , 189g / l MgCl ₂ , 76g / l KCl, 5g / l NaCl, 888g / l H ₂ O separated. The aforementioned composition is formed from the schoenite in a second crystallization reactor by reaction with 1100kg potassium chloride and 2.69 m ^J water at average residence times of 3.5 to 5.5 hours and reaction temperatures of 25 to 3O ⁰ C potassium sulfate and sulfate liquor. Centrifugation gives 1.5t of wet potassium sulfate containing 83.6% K ₁ SO ₄ , 3.9% MgSO ₄ , 2.8% KCl, 0.8% MgCl ₂ and 8.9% H ₂ O, and 3.81 ¹ sulfate liquor aforesaid composition of which 1.02 m ¹ are used to Schöniterzeugung m.

On the side of the potassium hydroxide solution and the excess sulphate liquor, a mixed liquor containing 64 g / l MgSO ₄ , 132 g / l MgCl ₃ , 139 g / l KCl, 6 g / l NaCl, 887 g / l H ₁ O with MgC ₂ : MgSO ₄ : KCl: NaCl such as 1: 0.5: 1: 0.5, from which 2.685 kg of water are evaporated at 75'C.

By stirring in a continuous crystallization reactor under isothermal conditions at a mean residence time of 2.5 hours, selective precipitation of pure potassium chloride in addition to potassium is achieved. In a subsequent cooling process to 25-28 * C by means of cooling water flowed through cooling tubes in a stirred vessel, the crystallization of more potassium chloride is achieved, with about the coexistence KCLCarnallit sets in the solution. By centrifuging the cooled suspension, 1.116 kg of KCl-kainite mixture is obtained, which consists of about 550 kg of kainite, 465 kg of sylvin and 92 liters of adhesive solution.

As a byproduct 2,1 m are ¹ Magnesium chloride brine of the composition 320g / l MgCl _1, 29g / l MgSO _4, 50g / l KCl, 15 g / l NaCl, 875g / l H ₂ O obtained. The loading factors per 1000kg K ₂ O potassium sulfate are only 1400kg MgSO ₄ and 1095kg K ₁ O in the form of potassium chloride. From the magnesium chloride solution obtained can be prepared by adding 30kg CaCl ₂ Zm ¹ another MgClj amount of 22 kg / m ¹ produce. The magnesium chloride solution formed after separation of the precipitation gypsum has in addition to 300 to 330 g / l MgCl ₂ (depending on the concentration of CaCl ₂ used as precipitant) about 1.5 g / l CaSO ₄ , 1.5-4 g / l CjCl ₂ and 50 -65g / l KCl and NaCl.

Embodiment 2 For this purpose FIG. 2

1,413kg MgSO ₄ and 1.951 kg water in the form of moist Epsom salt, 1,343kg KCI Kainitgemisch, 570kg potassium chloride 60.0% K ₁ O and ¹ 2,83m sulfate liquor of the composition 52g / l MgSO _4, 87g / l MgCl _2, 186 g / l KCl, 10 g / l NaCl, 891 g / l H ₂ O are reacted at 23-25 ° C. in a crystallization reactor at 2.5 hours average residence time, the residence time of the crystal phase being 30 to 50% higher as the solution phase in which thickened crystals are recycled from the filter trough into the reactor. By means of a centrifuge 3,330kg KCI-containing Schönit the composition 26.2% MgSO ₄ , 0.8% MgCl ₁ , 15.5% KCl, 26.8% H ₂ O of 4.31 m ¹ Kalimagnesialauge with 73g / l MgSO ₄ , 189 g / l MgCl ₂ , 76 g / l KCl, 15 g / l NaCl, 888 g / l H ₁ O separated. From the Schönit under the conditions mentioned in Example 1 with 1.25 t of potassium chloride and 4.12 m ^{1 of} process water 2.11 wet potassium sulfate ₍ , ₁ K ₁ O) and 5.29 m ¹ Sulfatlauge the aforementioned composition formed of which 2.83m ¹ are required for the Schonitkristellisation. From the excess sulphate liquor and the potassium hydroxide solution, 6.77 m ^{1 of} mixed liquor having the composition 65 g / l MgSO ₄ , 152 g / l MgCl ₁ , 129 g / 1 KCl, 11 g / l NaCl and a quantitative ratio of MgCl ₂ : MgSO ₄ : KCl: NaCl as 1: 0.43: 0.85: 0.07 formed, from which by evaporation at 84 * C 3040kg of water are removed.

After further treatment of the isothermal Eindampfsuspension at 75 to 78'C, and cooling to ambient temperature as in Example 1 1343kg Kainitgemisch KCI and 3.21 m ¹ MgCl ₂ sols of the composition 35g / l MgSO _4, 310g / l MgCl _2, 4Ig / 1 KCl, 23 g / l NaCl, 870 g / l H ₁ O.

From this solution, further water is evaporated in an open vessel. The resulting hot lemonade will open Cooled ambient temperature, whereby 535 kg carnallite, 65kg NaCl, and 40-70kg MgSO ₄ Ά H ₂ O crystallize. When By-product is 2.0 m ^{1 of} magnesium chloride in the form of a concentrated brine containing 450 g / l MgCl ₂ , 2 g / l KCl, 5 g / l NaCl, 860 g / l H ₂ O received. Depending on the crystallization conditions of the magnesium sulfate, the MgSO ₄ content of the MgCi ₂ -SoIe is in between The specific consumption figures per 1.000kg K ₂ O potassium sulfate are 1410kg MgSO ₄ and 1050kg K ₂ O potassium chloride. From the carnallite can be gained another 75 to 85kg K ₂ O.

Claims (4)

1. A process for the preparation of potassium sulfate and magnesium chloride brine from magnesium sulfate solution and / or Epsom salt and potassium chloride, with Schönit as an intermediate and its conversion to potassium sulfate and sulfate liquor by a known method, characterized in that a) formed in a first process stage from the components magnesium sulfate solution and / or Epsom salt, potassium chloride, from process stage b) resulting sulfate liquor and from process stage g) KCl crystallizing kaiite Schönit (K ₂ SO ₄ · MgSO ₄ 6 H ₂ O) and Kalimagnssialauge is formed . b) the separated from the Kalimagnesialauge schoenite is further processed with potassium chloride to potassium sulfate and sulfate liquor by a known method, c) from Kalimagnesialauge and excess Sulfatlauge a mixed liquor is formed, the quantitative ratio of the components MgCl ₂ : MgSO ₄ : KCl: NaCl such as 1: 0.4 to 0.55: 0.8 to 1,10: 0.05 bisO, 1O is set, d) this mixed liquor is evaporated in vacuo at evaporation temperatures between 65 to 9O ⁰ C to a MgCl ₂ concentration of 280 to 320g / l MgCl ₂ , with potassium chloride and kainite (KCl · MgSO ₄ · 2.75 H ₂ O) partially crystallize, e) resulting from the evaporation suspension isothermally be><temperatures between 65 to 85 ⁰ C and stirred for the crystallization of the kainite is completed with residence times between 0.8 to 6.0 hours, f) the suspension is then cooled to room temperature (20 to 35 ^° C.) with further crystallization of potassium chloride, g) the KCl-kainite mixture is separated from the magnesium chloride sols and recycled to the first process stage, h) the magnesium chloride solution obtained with a MgCl ₂ content of between 300 and 320 g / l of MgCl _{2 is used} as such or is further concentrated or purified. 2. The method according to item 1, characterized in that the reaction of the reaction components in the process stages a) and b) and the process in the isothermal crystallization process of kainite according to e) takes place in continuous crystallization reactors at average residence times of preferably 2 hours, wherein the residence time the solution phase and the Kristallisatphase may be different. 3. The method according to item 1 and 2, characterized in that the remaining after the separation of the KCI Kainitgemisches MgCl ₂ -SoIe is evaporated beyond the carnallite point and cooled to ambient temperature and the end product is a MgCl ₂ -SoIe is generated, the MgCl ₂ Concentration between carnallite point (about 320g / l MgCl ₂ ) and Bischoffitpunkt (about 460g / l MgCl ₂ ) is. 4. The method according to item 1 and 2, characterized in that following the separation of the KCI Kainitgemisches the existing sulfate precipitated by known methods using calcium chloride as gypsum and the magnesium sulfate is converted into further magnesium chloride.