DE102016010280A1 - Process for the preparation of potassium sulphate from carnallitite with high levels of sulphate minerals without rejection of solid and liquid production residues - Google Patents

Abstract

Non-impacting, without stopping solid and repellent liquid salt residues working production method for potassium sulfate, which processes a mined polymineral crude salt with the main components carnallite, kainite, halite and kieserite to potassium sulfate and NaCl evaporated salt. From coarsely ground crude salt, the soluble chloride minerals are leached cold, extracted from the extract solution by multi-stage evaporation in succession sodium chloride and a KCl-MgSO4-containing mixed salt, which is further processed after previous NaCl removal via a wet classification to potassium sulfate. The magnesium chloride returns as a component of an offset material in the pit cavities.

Description

The invention relates to a manufacturing method for potassium sulfate from complicated composite polymineralic crude potassium salts, both the double salts carnallite (KCl · MgCl ₂ · 6H ₂ O), kainite (KCl · MgSO ₄ · 2,75H ₂ O), langbeinite (K ₂ SO ₄ · 2MgSO ₄ ) as well as kieserite (MgSO ₄ .H ₂ O) and anhydrite (CaSO ₄ ), polyhalite (K ₂ SO ₄ .MgSO ₄ .2CaSO ₄ .2H ₂ O) and alkali metal chlorides (KCl and NaCl) and consequently from chloride and sulfatic components hereinafter referred to as polymineral carnallitite. The method provides as its main product, the chloride-free potash fertilizer potassium sulfate (K ₂ SO ₄ ) and depending on the crude salt composition or market requirements also subsets potassium chloride, magnesium sulfate and K-Mg fertilizer. The sodium chloride always contained in the potash salts is also obtained as a marketable product wholly or largely. Magnesium chloride contained as carnallite in the potash salt as well as the magnesium chloride formed from the conversion of magnesium sulfate to potassium sulfate is not rejected as usual as a water-polluting magnesium chloride solution, but after conversion into a mixture of bischofite (MgCl ₂ .6H ₂ O) and saturated solution to marketable bischofite processes known per se or further incorporated by addition of basic additives for solidification as an offset in the resulting by the crude salt cavities, which are stabilized thereby. Overall, the process works without stopping solid or / and repelling liquid production residues.

The state of the art can be characterized as follows. Potassium sulfate can be prepared from the components potassium chloride and magnesium sulfate by conversion of potassium chloride, which may have only the lowest possible NaCl content, and magnesium sulfate heptahydrate - so-called Epsom salt via the intermediate stage of Schoenit - K ₂ SO ₄ .MgSO ₄ .H ₂ O. according to the reaction equations 2KCl + 2MgSO ₄ .7H ₂ O → K ₂ SO _4. MgSO ₄ .6H ₂ O + MgCl ₂ + 8H ₂ O 2KCl + K ₂ SO _4. MgSO ₄ .6H ₂ O → 2K ₂ SO ₄ + MgCl ₂ + 6H ₂ O forming magnesium chloride remains dissolved in the respective reaction solutions, together with additionally additionally required for the double reaction amounts of water and also required amounts of KCl and MgSO ₄ .

The implementation and the proportions of the so-called. Concentrated potassium sulfate process are summarized in Ullmanns Encyklopadie der technischen Chemie, Vol. 13, p. 481/482, 4th ed. (1977) as in Potassium Südharz-Unstrut Revier, Volume 3, p. 78 Bochum 2005 described. The potassium chloride comes from the processing of any potash, the Epsom salt is obtained from the kieserite contained in hard salts (MgSO ₄ · H ₂ O). Also, the potassium minerals kainite (KCl · MgSO ₄ · 2.75H ₂ O) which occurs in kainitic Kalirohsalzen, is suitable after removal of the sodium chloride for a potassium sulfate, also on Schönit as an intermediate. The processing of polymineral Kalirohsalzen so far is no source of potassium sulfate, since the large number of to be separated by treatment crude salt components, even with hard salts does not lead to the necessary purities of the required starting materials KCl and MgSO ₄ . Likewise, polymineral crude salts which, in addition to the mineral constituents of polymineral hard salts, also contain carnallite and kainite, likewise can not be processed by processing into a repulsive residue and the pure components required for potassium sulfate preparation.

This possibility, the use of such complex composite types of crude salt for the production of potash fertilizers, in particular of potassium sulfate is determined by the proposed method according to DE 10 2012 016 992 such as DE 10 2012 010 299 A1 opened. This process dispenses with a treatment, which has the goal to produce a repulsive NaCl solvent residue or repulsive Flotationsberge and a weiterzuverarbeitendes concentrate. The processing starts from coarsely ground polymineral crude salts and first separates soluble chlorides including all of the sodium chloride as a solution of difficult or insoluble crude salt components. By this process of dissolution of the polymineral crude salt in cold water all difficulties are circumvented which oppose the variety of mineral components to be separated and their usually intimate intergrowth of a conventional preparation.

The procedure and the respective end products depend on the composition of the crude salts, which are assigned to the hard salts or carnallitic Kalirohsalzen depending on the magnesium chloride content. In both proposed process routes, the magnesium chloride resulting from the carnallite content of the crude salt or / and from the conversion process of MgSO ₄ with KCl is largely concentrated by evaporation of process solutions, thereby recovering dissolved valuable substances as crystallizates. A production process for potassium sulfate which works without stopping and without repelling saline-containing process solutions does not include the aforementioned process proposals.

The prior art includes a method proposal according to DE 10 2012 015 700 A1 in which the resulting from the processing carnallithaltiger Kalirohsalze magnesium chloride solution of 30 to 33% MgCl ₂ further evaporated to a mixture of magnesium chloride hexahydrate and MgCl ₂ saturated solution and from a pulpy mixture with about 40% MgCl _{2 is} prepared, and this after addition of CaO / MgO binder brings into the cavities formed by the Carnallitabbau in which it solidifies to a stationary or stable offset and avoids rejection of magnesium chloride-containing solutions in this way.

This method proposal relates to a process which extracts chloridic potash fertilizers from conventional composition carnallite and utilizes magnesium chloride solutions for displacement production exclusively from carnallite decomposition.

The object of the invention is a process which extracts from the complex mineral mixture of polymineral carnallite as the main products potassium sulfate and sodium chloride high quality and emerging in the crude salt as well as by the potassium sulfate produced magnesium chloride does not eject as a solution to be repelled from the process, making all Rohsalzbestandteile used and neither a Halting still liquid repellence of production residues are necessary.

The invention must solve the problem of obtaining raw materials for the main product potassium sulfate as well as a grade of pure saline chloride suitable for commercialization from the mineral constituents contained in the complex salt in crude salt and thereby producing a maximum of salable products. Only by transforming all components of the crude salt into marketable products as completely as possible can the task of realizing a potash production without a salt dump be solved. Another problem to be solved is the avoidance of rejection of saline solutions. This is particularly demanding with the crude salt type carnallitite instead of hard salt and with the production target potassium sulfate instead of potassium chloride plus magnesium sulfate products, since magnesium chloride contained as carnallite in a ratio of 1.28 MgCl ₂ per 1% KCl in the crude salt, is dissolved with. In addition, in the conversion of KCl and MgSO ₄ to potassium sulfate further magnesium chloride in a fixed ratio of 0.55 tonnes of MgCl ₂ per 1 ton K ₂ SO ₄ is formed and also in dissolved form as so-called Kalimagnessialauge with about 180 to 200 g / l MgCl ₂ is obtained. Since the manufacturing process of the target products inevitably requires repulsion of the MgCl ₂ -containing solutions, the process according to the invention must solve the further task of concentrating all magnesium chloride obtained in dissolved form in the process in such a way that it can be accommodated in the cavity formed by mining degradation as far as possible in the form of an additive which self-consolidates in the mining cavities after additives have been added, which on the one hand serves for the underground disposal of magnesium chloride and, on the other hand, for the rock-mechanical stabilization of the empty mines.

Another object to be achieved is the preparation of a sufficiently depleted of sodium chloride material for the two-stage conversion of potassium chloride and magnesium sulfate. By prior depletion of sodium chloride, it must be ensured that the KCl-Schönit mixture resulting from the Schönit process does not contain any solid sodium chloride. According to the invention, NaCl which can no longer be discharged by the effluent as Schönitmutterlauge must be removed in solid form before the Schönitstufe. Obviously, a depletion by the known NaCl flotation with N-alkylmorpholine as flotation appears. However, it was found that this flotative separation process does not lead to the required degree of NaCl depletion.

In addition, a contaminated with flotation sodium chloride would not be marketed or only very limited.

This abundance of objects to be solved is first of all solved by carrying out the separation of the soluble constituents of the crude salt, including the sodium chloride, from the sparingly soluble sulfate minerals, as described in the aforementioned patents. However, with the crude salt type of a polymineral carnallite having a high proportion of kainite, the difficulty arises that no smooth separation of soluble chlorides as the extract solution and sparingly soluble sulfate minerals is possible. Polymineral carnallitic hard salts have substantial admixture of the mineral kainite, which is both a potassium mineral and a sulfate mineral and consists of 30.5% KCl, 49.2% MgSO ₄ and 20.3% water of crystallization and together with the chloride minerals carnallite, sylvite and Halit dissolves in cold water.

Although the resulting extract solution is also evaporated on the basis of the aforementioned method proposals to the limit of the solubility of potassium-containing soil body with the aim of a fractional crystallization of sodium chloride. Because of the MgCl ₂ content of the extract solution resulting from the carnallite dissolution and the MgSO ₄ content resulting from the kainite dissolution, the possible formation of both the evaporation temperature and the degree of evaporation must be determined Kainit (KCl · MgSO ₄ · 2.75H ₂ O) or Langbeinit (K ₂ SO ₄ · 2MgSO ₄ ) are taken into consideration and thus the contamination of the crystallized sodium chloride can be avoided.

After separation of the sodium chloride, the hot solution is further evaporated, thereby cooled and a crystallizate mixture of the salts potassium chloride Kainit and sodium chloride won. The possible endpoint of this subsequent evaporation process is the coexistence point of the salts KCl, kainite, carnallite and NaCl. Depending on the temperature, such a solution has 320 to 340 g / l of MgCl ₂ but only 20 to 30 g / l of MgSO ₄ .

The removal of water leads to a reduction of the volume during the evaporation of the solution and an increase of the MgCl ₂ -concentration to> 300 g / l MgCl ₂ to max. <340 g / l MgCl ₂ . This produces a mixture of crystallized sylvin KCl, crystallized double salt kainite and crystallized sodium chloride, which must be separated from the solution phase and contains the majority of the components necessary for potassium sulfate extraction KCl and MgSO ₄ .

More magnesium sulphate resulting from the MgSO _4, which can be obtained from the existing in the dissolution residue kieserite. According to the invention, further potassium chloride is likewise added in order to adjust the K: SO ₄ ratio necessary for potassium sulfate production. As with any potassium sulfate manufacturing process, the presence of sodium chloride in this conversion process feedstock, the maximum admixture of which may be minimal, presents difficulties.

The mixture of KCl, kainite, additional magnesium sulfate and sodium chloride is the starting material for the two-stage potassium sulfate production process with Schönitherstellung as the first conversion stage. However, the sodium chloride dissolves only to a small extent in the solution leaving the Schönitstufe. It was found that exceeding the limit of about 1.12 to 1.15 t NaCl entry to 1.0 t Mg entry in the conversion process, the limit of NaCl compatibility is exceeded. Up to this limit, both the magnesium and the sodium chloride with the beautifying mother liquor are carried out in the two-stage conversion process, and sodium-free crystallizates are formed in both stages of the potassium sulfate production process. Since more NaCl is contained in the mixed salt resulting from the evaporative cooling crystallization than corresponds to the mentioned limit, sodium chloride must be removed. For this purpose, according to the invention, a known wet classification for the depletion of sodium chloride is provided, the essential separation-sharpening function being a flotative NaCl separation. It has been found that this is the wet sieving with a cut size of 0.25 mm, which is a fraction of> 0.25 mm with high content of NaCl and KCl and a fraction <0.25 mm with low NaCl content and high Shares kainite and KCl generated.

It has surprisingly been found that the necessary depletion of sodium chloride prior to the introduction of the kainitic mixed salt in the stage of Schönitkristallisation can be achieved by utilizing the different grain sizes of KCl, NaCl and kainite by a Nassklassierverfahren and no further additional NaCl separation from the fines more is required.

Sodium chloride and part of potassium chloride are significantly coarser than kainite. If the mixture of salts before being fed into the Schönitstufe by a Klassierverfahren, preferably a selective wet sieving with a separation grain size of 0.25 to 0.35 mm into a coarse grain fraction and a fine grain fraction decomposed, the coarse grain consists almost only of coarse sodium and Potassium chloride and only very small amounts of kainite. Conversely, the fines contain very little sodium chloride and consist mainly of kainite and some KCl. This mixture of substances is suitable after addition of KCl or MgSO ₄ as starting material for the two-stage production of potassium sulfate with Schönit as an intermediate analogous to the proven implementation of KCl and Epsom salts.

This surprising finding that a wet classification on the one hand provides a NaCl-KCl mixture with very low kainite content and vice versa, the fines contains only about 6% sodium chloride and therefore can be converted to potassium sulfate without further depletion in a conversion process, it allows for any flooding separations to refrain in the course of the process. The coarse fraction consisting of almost all the solid sodium chloride and part of the potassium chloride gives, by further processing, both pure sodium chloride and pure potassium chloride.

After removal of the coarse fraction> 0.25 mm, the sieve passage consists of a salt mixture of kainite, KCl and a little sodium chloride, which is converted after the addition of further magnesium sulfate and potassium chloride to a Schönit-KCl mixture containing only NaCl from adhering solution.

The separated as coarse grain fraction sodium chloride-KCl mixture can be separated by known methods of KCl-NaCl separation in both individual components or the KCl-NaCl mixture is fed into the evaporation process for the extract solution in which KCl dissolves and NaCl Not. The separated from the hot solution NaCl crystals form the basis of NaCl-Evolved salt. In the simplest case, the required purity of> 99% NaCl can be achieved by washing the NaCl crystallizate with NaCl solution.

Potassium sulfate is prepared by adjusting the required for a two-step conversion process K: SO ₄ ratio according to known per se procedure. The magnesium chloride formed from MgSO ₄ and KCl leaves the conversion process as Schönitmutterlauge with a typical composition of about 190 g / l MgCl ₂ , 70 g / l MgSO ₄ , 60 g / l KCl and 75 g / l NaCl. This Schönitmutterlauge is mixed after separation of the NaCl crystals of the further evaporated hot solution. All magnesium chloride resulting from the carnallite portion of the crude salt and the magnesium chloride from the conversion leaves the process chain according to the invention as MgCl ₂ -saturated final liquor with a typical concentration of about 450 g / l MgCl ₂ , about 30 g / l MgSO ₄ and only about each 5 g / l KCl or NaCl. This solution is also prepared by evaporation. From this evaporation, the alkali chlorides result as a crystallizate of carnallite and sodium chloride, which is attributed to the process as such or after decomposition of carnallite. The MgCl _{2 end} liquor, which is stable and indifferent to all salt minerals, is returned to the cavities formed by the decomposition of crude salts, expediently as a stable or stable offset, as already described in the document DE 10 2012 015 760 A1 is described.

The process of the invention utilizes all of the constituents of the polymineral crude salt to produce high quality potash fertilizers, mainly potassium sulfate, high purity sodium chloride (> 99% NaCl), which does not need to be bottled, and discards all magnesium chloride as an offset into the pit cavities. Subsets can be exported as bischofite (MgCl ₂ · 6H ₂ O) from the process and marketed as a product.

Example (see Fig. 1):

100 tonnes of kainitic carnallitic potash crude salt with an average composition of 42% carnallite, 23% kainite, 5% kieserite and 30% halite, together with minor admixtures of anhydrite, polyhalite and clay, are stirred at + 10 ° C with 132 m ^{3 of} water. In the process, carnallite, kainite and halite dissolve, while the kieserite and the insoluble fractions of the crude salt remain as residue. In addition to water, the washing water from the process can be included in the cold-dissolving process.

In total, in addition to about 5 tons of solvent residues, which consist essentially of undissolved kieserite, about 200 m ³ extract solution of the chloride minerals of the crude salt with a composition of 97 g / l KCl, 58 g / l MgSO ₄ , 72 g / l MgCl ₂ , 177 g / l NaCl and 852 g / l H ₂ O. This solution is filtered as needed, especially when the crude salt contains clay constituents.

The extract solution is evaporated after addition of NaCl-KCl-containing solutions from subsequent process stages in a three-stage countercurrent evaporation plant at evaporation temperatures of 35, 55 and 75 ° C in vacuo. After removal of about 57 t H ₂ O crystallize about 22 t of sodium chloride, while the components KCl, MgSO ₄ and MgCl _{2 of} the injected extract solution remain in solution. After separation of this NaCl crystals, the remaining solution is further evaporated. In this further evaporation process, the Schönitmutterlauge is included. From solution with 160 g / l KCl, 97 g / l MgSO ₄ , 120 g / l MgCl ₂ and 110 g / l NaCl 75 t of H ₂ O are removed in vacuo in a three-stage DC evaporation plant and the solution gradually to about 45 Cooled to ± 10 ° C. After stirring for a further 2 hours at this temperature, a suspension of crystallized KCl, kainite and NaCl and of KCl and kainitol-saturated solution is formed. After separation of 53 t of mixed salt with 36% KCl, 27% MgSO ₄ , 26% NaCl and 11% H ₂ O (kainitic mixed salt) about 71 m ^{3 of} solution of composition 60 g / l KCl, 20 g / l MgSO ₄ , 335 g / l MgCl ₂ , 25 g / l NaCl and 845 g / l H ₂ O.

The mixed salt separated from this solution is mixed in a carrier saturated with KCl, NaCl and kainite and separated by wet sieving. The fraction> 0.25 mm consists to about 60% of NaCl, 30% of KCl and contains only about 2-3% MgSO ₄ as kainite.

This coarse fraction is combined with the potassium chloride derived from carnallite decomposition and separated by hot redissolution in NaCl and KCl to give the introduced sodium chloride as a pure crystal, yielding pure sodium chloride product with> 99% NaCl after blanketing with NaCl solution. The potassium chloride is mainly used for potassium sulfate production.

The KCl-kainitol saturated solution is further evaporated. In this evaporation process, the decomposition solution derived from the decomposition of carnallite crystal is included. From the evaporation of the KCl and NaCl-saturated solution from 325 g / l to 450 g / l results in a cooled to about 30 ° C solution and consisting of carnallite and NaCl crystallizate that contains almost all of the alkali chlorides. After separation of the Carnallite crystallizate, which consists of 18 t of carnallite and 2 t of NaCl, results in 53 m ^{3 of} MgCl ₂ final liquor containing 450 g / l MgCl ₂ , 30 g / l MgSO ₄ and in each case <5 g / l NaCl and KCl, from which by further Evaporation to 40 ± 2% MgCl ₂ produces a pulpy mixture.

From the wet classification of the kainitischen mixed salt results in about 40 t of KCl-MgSO ₄ raw material, from the dissolution of kieserite from the Löserrückstand result about 4 t of MgSO ₄ as MgSO ₄ · 7H ₂ O and from the decomposed with water Carnallitkristallisat result in 3.6 t KCl. From this mixture, 23 t of schistite and 14 t of KCl are obtained by conversion at about 10-15 ° C. by a known method. The reaction is carried out with potassium sulfate mother liquor. The resulting 50 m ³ Schönitmutterlauge the composition 80 g / l KCl, 80 g / l MgSO ₄ , 190 g / l MgCl ₂ , 50-80 g / l NaCl and 880 g / l H ₂ O is further concentrated by evaporation as described , The separated salt mixture of schoenite and KCl is reacted with about 34 m ^{3 of} water to potassium sulfate. This gives 17 t of K ₂ SO ₄ and 45 m ³ potassium sulfate mother liquor with 200 g / l KCl, 55 g / l MgSO ₄ , 80 g / l MgCl ₂ , 10 g / l NaCl and 885 g / l H ₂ O, which Production of Schönit be used.

Altogether, about 17 t of potassium sulfate result from the polymineral potassium salt used and, after washing the NaCl crystallizate with water or NaCl brine, up to 30 t of sodium chloride as salable products. As a by-product, magnesium chloride hexahydrate can be produced. The remaining magnesium chloride gives a thick matter mixture with 40% MgCl ₂ , which is introduced after CaO / MgO addition in a pit cavity as an offset.

The volume of the offset material is smaller than the subsurface volume gain resulting from crude salt degradation, even if no bischofite subset is produced as a product.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102012016992 [0004]
• DE 102012010299 A1 [0004]
• DE 102012015700 A1 [0006]
• DE 102012015760 A1 [0023]

Cited non-patent literature

• Ullmanns Encyklopadie der technischen Chemie, Vol. 13, p. 481/482, 4th ed. (1977) [0003]
• Potassium Südharz-Unstrut Revier, Volume 3, p. 78 Bochum 2005 [0003]

Claims (7)

Process for the preparation of potassium sulfate from kainitic-carnallitic polymineral Kalirohsalzen without necessary Halthalung solid or reject liquid processing residues, by preparing a chloride extract solution and a sulfatic solvent residue from the mined crushed crude salt by dissolving in cold water whereby the chloride salt components carnallite, kainite and halite Extracted solution and separated from the insoluble or sparingly soluble sulfate minerals kieserite, anhydrite and polyhalite, characterized in that the solution is evaporated to the limit of saturation potassium-containing sulphate salts, while the sodium chloride containing washings in the further process added and after separation of the solid Natrriumchlorids the KCl, MgCl ₂ , MgSO ₄ and NaCl containing solution together with the resulting from the potassium sulfate Schönitmutterlauge g is further evaporated by evaporation, followed by evaporation and subsequent cooling crystallization and further stirring for several hours at 45 ± 10 ° C a saturated KCl, NaCl and kainite solution with a MgCl ₂ content of 325 ± 15 g / l MgCl ₂ and a KCl from , NaCl and kainite existing mixed salt is formed, from which after its separation from the solution by wet classification, a coarse fraction consisting mainly of sodium chloride and potassium chloride and a fine fraction, which consists mainly of KCl and kainite, which is further processed to potassium sulfate, are prepared , A method according to claim 1, characterized in that the wet classification is preferably carried out as wet screening with a separation grain size of preferably 0.25 to 0.30 mm. A method according to claim 1 and 2, characterized in that the resulting from the co-evaporation of MgCl ₂ -containing process solution to 325 ± 15 g / l MgCl ₂ solution is further evaporated to about 450 g / l MgCl ₂ , wherein carnallite is recovered , which is decomposed to potassium chloride. A method according to claim 1 to 3, characterized in that the MgCl _{2 end} liquor of about 450 g / l MgCl ₂ , corresponding to about 33% MgCl _{2, is} further evaporated to 40 ± 2% MgCl ₂ . A method according to claim 1 to 4, characterized in that the obtained by evaporation and cooling crystallization mixture of magnesium chloride hexahydrate and MgCl ₂ -saturated solution is used in whole or in part as a component for an offset material. A method according to claim 1 to 5, characterized in that a portion of the crystallized Magnesiumchloridhexahydrates is centrifuged off and further processed to Bischofit with 47% MgCl ₂ . Process according to Claims 1 to 6, characterized in that the intermediates consisting of sodium chloride and potassium chloride are separated by hot-dissolving in potassium chloride and sodium chloride and the potassium chloride is used wholly or partly in the potassium sulfate production process and all the sodium chloride is purified by washing and the final product contains> 99% NaCl will be produced.

Images