DD244740A1 - METHOD FOR PRODUCING PURE CONCENTRATED MAGNESIUM CHLORIDE OLE - Google Patents

Abstract

The invention relates to the preparation of pure concentrated magnesium chloride sols from complex-composed MgCl2 sols. The aim is to improve the quality of the brine, whereby the degree of purity should be achieved without the hitherto usual lengthy cleaning steps. According to the invention, the object is achieved by the fact that the MgCl 2 sols produced as the end product, in contrast to the previous process, are not produced from the solution phase resulting from concentration processes, but from the carnallite crystallite which is formed during the brine concentration. The carnallite crystallizate is decomposed and the decomposition solution free from impurities is converted into a pure concentrated MgCl.sub.2 brine according to essentially known process steps. The invention can be used where complex magnesium chloride solutions are involved, in the processing of carnallitic crude salts, in the processing of brines from carnallite deposits or natural brine occurrences.

Description

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Field of application of the invention

The invention relates to a process for preparing concentrated Magnesiumchloridsole, so-called Magnesiumchloridedelsole of complex compound magnesium chloride solutions of lower concentration. In addition to magnesium, potassium, sodium, calcium and trace metals, chloride, sulfate, bromide, boron, and other elements, these complex magnesium chloride solutions are intermediate intermediates in the processing of carnallitic crude salts, the extraction of camallite deposits, or recent natural brine occurrences Salt lakes included.

Characteristic of the known technical solutions

Concentrated magnesium chloride sols are needed for the production of magnesium oxide, magnesium metal and for the preparation of magnesium compounds such as bischofite (MgC.fwdarw.6H.sub.2O) or magnesium carbonate as a raw material. In addition, such magnesium chloride solutions are used in the sugar industry for the regeneration of ion exchangers on a larger scale and for Kühlsolherstellung and in various branches of the chemical industry as a raw material. As a quality standard, for such a magnesium chloride solution, which is referred to as Magnesiumchloridedelsohle, a quality is enforced, which is characterized by the following requirements:

MgCl content> 450 g / l MgCl ₂

MgSO ₄ content <24 g / l MgSO ₄

KCl, NaCl content <10 g / l KCl and NaCl

Bromide content <0.5 g / l bromide

In addition, other quality parameters of interest, such as neutrality, boron content, heavy metal content and solids content, nitrogen content and others, are of interest for certain uses. For most uses, the sulphate content must be additionally lowered by precipitation of the sulphate as calcium sulphate, calcium being added as impurity to the brine. Magnesiumchlorideelsohle is prepared from complex magnesium chloride solutions with said components (Mg, K, Na, Ca, trace elements, Cl, SO4, Br, NO3, B) through a chain of sequential concentration and purification stages in which the magnesium chloride solution concentrates in lengthy processes and the levels of the minor components potassium, sodium, sulfate, bromide, boron and heavy metals are reduced to the required level. According to DD-WP 200272 as follows from so-called mixed salt mother solution, the following preparation:

The complex crude brine is first mixed with the Eindampftcamallit, this decomposed and converted into a KCl-NaCl mixture. The decomposition solution formed contains all the magnesium chloride, but also all impurities present in the process, such as sulfate, boron, iron, copper, nickel, nitrogen compounds and others. The warmed up and adjusted to a required KCl: MgCl ₂ ratio solution is concentrated by evaporation at temperatures up to 125 ° C, separated from crystallizing sodium chloride and the magnesium sulfate also formed by crystallization - ⁵ A hydrate. In this case, the crystallization of the persistent crystallization tending prone magnesium sulfate must be promoted by special measures.

The hot, evaporated magnesium chloride solution must now be freed by cooling and Carnallitkristallisation of their content of alkalis, wherein the crystallized carnallite is returned to the starting point of the process and decomposed. The separated camellitol mother liquor contains 430 to 460 g / l MgCl ₂ and all impurities contained in the original raw brine. Further methods in use are described in detail in the journal Erzmetall, Vol. 31.1978, No. 7/8, p.313ff. shown. Also in these methods, the return of the carnallite obtained by evaporation and cooling to the starting point of the process for decomposition by means of raw brine and the fate of all impurities of the raw brine in the Camallitmutterlauge (noble brine) is characteristic.

Since this solution is not pure enough for most uses, it must be further desulfated by precipitation, entbort by ion exchange resins and where this is necessary to be freed from other trace components. According to DD-WP 211105 a method is known, are prepared by the high purity magnesium chloride or magnesium chloride from carnallite, which are characterized by very high purity. Raw material for this process is Carnaliit> which is totally dehydrated and selectively leached with anhydrous acetone. From the acetone extract magnesium chloride can be obtained by adding water as a pure hydrate or as a pure aqueous solution. Although this method guarantees a very high purity of the products produced, it is however bound to the presence of pure, dehydrated carnallite and, because of the use of acetone, is not suitable for the production of mass products and remains limited on a small scale.

Object of the invention

The invention has the ZFeI, a simple process for the production of concentrated, and compared to the previous MgCl ₂ brine quality much purer MgCl ₂ -SoIe to create, which starts from complex compound magnesium chloride solutions as a raw material, leads in only a few process steps to the goal and for the Production of large quantities of brine is suitable.

Another object of the invention is that the method is also applicable to sols obtained by solar evaporation of natural brines. ,

Explanation of the essence of the invention

The invention is based on the technical object, starting from a complex composed magnesium chloride solution (raw brine) with the components potassium, sodium, sulfate, bromide, boron, heavy metals, nitrogen compounds and other secondary components a pure, practically sulfate-free, sufficiently heavy metal, nitrogen and boreararms magnesium chloride solution containing <10 mg / l which is suitable for all uses and offers substantial advantages over the previous quality of brine in some of these uses, without the hitherto required lengthy cleaning steps being required.

According to the invention, this object is achieved in that the magnesium chloride sols produced as end product, in contrast to the previous method, is not produced from the solution phase resulting from concentration processes, but from the carnallite crystallizate, which is inevitably formed during the brine concentration. The contaminated solution phase (Camallitmutterlauge), which contains all impurities of the raw brine is either fed to another purpose or used as a suitable for certain applications MgCl ₂ -SoIee or purified by previous methods. It could be found that all secondary components of the original, complex magnesium chloride solution accumulate in the liquid phase, from which they must be removed in a complicated manner, while the crystallized carnallite is much purer than the solution phase and in addition to magnesium contains only the alkali metals , According to the invention, this crystallized carnallite is used to produce a pure brine quality which exceeds the previous brine quality in all respects and can be obtained purely in accordance with the invention, in particular without additional borehole and desulfurization processes. It has been found that completely sulphate-free and sufficiently boron-free magnesium chloride sols can be obtained from carnallite crystallites if they are freed from adhering solution phase and decomposed separately with decomposition media which are free of sulphate, bromide and boron and the remaining interfering trace elements are not or only in small quantities contain. In the simplest case, water can be used. The process according to the invention consists of much fewer process steps than the previous production process and is characterized by the following process sequence according to the invention:

The complex brine is concentrated as usual by evaporation or where possible by solar evaporation to saturation of the brine with carnallite, whereby sodium chloride and partially magnesium sulfate crystallize. After separation of these calf-free crystals, the carnallite crystallizate is formed from the camalite-saturated magnesium chloride sols after further evaporation and / or cooling and subsequently separated from the mother liquor. The mother liquor contains the secondary components sulfate, bromide and the remaining trace components, the carnallite crystallizate in substantial quantities the alkali chlorides of the original complex solution and some bromide. The crystallized carnallite, which still contains sodium chloride in solid form and adhesive solution, is separated from this adhesive solution and washed. As a washing medium, a part of the final product (magnesium chloride solution) is suitable. This carnallite thus treated is now decomposed with a suitable Zersetzuhgsmedium, in the simplest case, water in the form of condensate. The decomposition yields a decomposition solution saturated with alkali chloride at the decomposition temperature, the magnesium chloride content of which is just below the coexistence concentration KCl-carnallite. The liberated potassium and sodium chloride is separated in solid form. The required MgCl ₂ final concentration is ensured by evaporation of the decomposition solution and subsequent cooling of the evaporated solution. If the Carnallitzersetzung performed cold, a larger amount of water to evaporate than hot decomposition of carnallite. In both cases, after the separation of the alkali metal chlorides, a hot solution is formed, which must be cooled to about 20 to 30 ° C, which in turn crystallizes carnallite. After its separation, a concentrated magnesium chloride solution with> 430g / l MgCl _{2 can be} obtained, which neither has to be deboned nor subsequently desulfated. The alkali chloride content depends on the cooling end temperature and the MgCl ₂ concentration and is easily regulated thereby. All other trace elements are contained in the inventive method in lower concentration than in the produced by known methods

Magnesiumchloridedelsohle, so that either can be completely dispensed cleaning, or the cleaning is at least significantly easier. Another advantage is the omission of the Entbohrungsstufe, which is also very expensive. The sole produced by the process according to the invention is also practically free of calcium sulfate and nitrogen compounds and completely free of solids, which is very important for some uses. The invention is explained in more detail by the following exemplary embodiments:

Embodiment 1

1000m ³ brine from the Kalirohsalzverarbeitung with 300g / l MgCl ₂ , 30g / l MgSO ₄ , 39g / l KCl, 28g / l NaCl and 882g / l H ₂ 0.3.1 g / l bromide and small amounts of Fe, Cu, Ni , Ca, NH ₄ and NO ₃ are evaporated by known methods to a concentration of 425g / l MgCl ₂ to 120 ⁰ C, the deposited mixture of solid sodium chloride and magnesium sulfate ^5/4 hydrate separated hot and cooled by cooling to 25 ° C. Carnallite crystallization brought. The Carnallitmutterlauge contains all impurities mentioned above and about 25g / l MgSO ₄ and is also used in a Camallitsolprozeß by a known method as a solvent. It crystallize 143t Camallite and 12t NaCl. By centrifuging and washing the crystals with 12m ^{3 of} final product sol are added 167t crystallizate of composition 31.5% MgCl ₂ , 23.3% KCl, 7.5% NaCl, 37.5% H ₂ O, <0.1% MgSO ₄ and about 0.15% of bromide, which is decomposed with 87t of water at 20 ° C.

After separation of 50% decomposition crystals with 64.3% KCl, 16.3% NaCl, 5.0% MgCl ₂ and 14.3% H ₂ O, 161 m ^{3 of} decomposition solution with 310 g / l MgCl ₂ , 40 g / l KCl, 26 g / 1 L NaCl, <1 g / L MgSO ₄ , 886 g / L H ₂ O and 1.5 g / L bromide. This solution is evaporated with removal of 45.8t H ₂ O and again cooled to 20 ⁰ C, whereby 22.9 t of camalite and 3.7 t NaCl crystallize, of the remaining 101 m ³ Endproduktsole the composition 435g / l MgCl ₂ 2.3 g / l KCl, 5 g / l NaCl, <1 g / l MgSO ₄ , 2.0 g / l bromide separated. *

The final product sol is virtually free of any interfering minor components and contains <1 mg / l Fe, Ni, Cu and <10 mg / l boron and N0 ₃ nitrogen. The final product sol can be entbromt by known method. The secondary carnallite can in turn be decomposed, producing a further amount of final product brine.

Embodiment 2

By solar evaporation of a natural brine carnallite crystallizate is obtained by known methods, which after centrifuging and washing with 6 m ³ Endproduktsole per 100 t of crystals of the following composition:

29.9% MgCl ₂ , 22.1% KCl, 12.1% NaCl, 35.7% H ₂ O and a maximum of 0.2% MgSO ₄ , CaSO ₄ , bromide and trace elements (Fe, Cu, Ni, B and Nitrogen compounds), 105 tons of camallite of this composition are mixed with 45 tons of secondary carnallite having the composition 32.2 percent MgCl ₂ , 23.4 percent KCl, 6.3 percent NaCl, 38.0 percent H ₂ O with 42.7 tons of water at the temperature of 100 ° C decomposed to give 22.9t KCl and 12.3 t NaCl, which are separated at 100 ⁰ C from the decomposition solution.

From the resulting 119m ³ decomposition solution is obtained by removal of 16.7t H ₂ O and cooling to 20 ° C in addition to 45t Sekundärcarnallit that is recycled, 71.5 m ³ noble sole as the final product of the same composition as in Example 1.

Claims (5)

Invention claim: A process for the preparation of pure concentrated magnesium chloride brines, comprising <1 g / l magnesium sulfate having low contents <10 mg / l of boron, heavy metals and nitrogen compounds from complex magnesium chloride brines by evaporation and subsequent cooling crystallization of carnallite, characterized in that the carnallite crystallizate is removed from the carnallite mother liquor, which separates virtually all impurities of the original MgCl ₂ sols, by centrifuging and washing further from adhering residues of the contaminated ones. Carnallitmutterlauge is freed, the purified Carnallitkristallisat by decomposition with a pure decomposition medium, preferably water, is decomposed into solid alkali chloride and a decomposition solution largely free from impurities, after which they are separated after their separation from the decomposition crystals after essentially known process steps such as evaporation and cooling in a pure MgCl ₂ -SoIe and a secondary carnallite is transferred. 2. The method according to item 1, characterized in that the Carnallitzersetzung and separation of the alkali metal chlorides cold, preferably between 10 and 3O ⁰ C, takes place and the decomposition solution is then evaporated and cooled. 3. The method according to item!, Characterized in that the Carnallitzersetzung hot, preferably between 80 and 105 ° C, and the decomposition solution is then evaporated and cooled. 4. The method according to item 1 to 3, characterized in that the Sekundärcarnallit is returned to the decomposition stage. 5. The method according to item 1 to 4, characterized in that for washing the carnallite part of the Endproduksols is used.