JP2007528333A - How to recover potassium sulfate - Google Patents

Abstract

A novel integrated method for recovering potassium sulfate (SOP) from sulfate rich bitter juice is disclosed. This method requires only bitter juice and lime as raw materials. The kainite type mixed salt is obtained by fractional crystallization of bitter juice. By treating kainite with water and the final solution, kainite is converted to schenite while simultaneously removing NaCl, and the final solution is obtained by reacting shonite with MOP to convert to SOP. It is. The final liquid (SEL) obtained by converting kainite to syenite is used for the recovery of MOP. The SEL is desulfated and supplemented with MgCl ₂ using the final bitter juice produced in the process of making carnalite. Carnalite is decomposed to obtain crude potash, which is then processed to obtain MOP. In order to prepare a CaCl ₂ solution and a high purity Mg (OH) ₂ having a low boron content, the carnalite decomposition solution produced in the decomposition of carnalite is reacted with slaked lime. Using the CaCl ₂ solution desulfation of SEL, to produce high purity gypsum as a by-product. The liquid stream containing potash is recycled in the process, and potash recovery in the form of SOP is quantitative.

Description

The present invention provides an integrated method for recovering potassium sulfate (SOP) from bitter juice rich in sulfate. This method requires only bitter and lime as raw materials, and in addition to SOP, low boron content Mg (OH) ₂ , gypsum and salt can be obtained as by-products, all of which are obtained in pure form. .

SOP is a dual fertilizer containing 50% K ₂ O and 18% S. Since it has the lowest salt index and is substantially free of chloride, it makes SOP a better fertilizer than potassium chloride (MOP). On the other hand, especially in the case of low sulfate content of brine / bitter, as in the Dead Sea, MOP can be easily manufactured and therefore cheaper than SOP. There is no low-sulfate bitter, but countries like India that have enough bitter from the sea and subsoil will benefit greatly if SOP can be produced economically from such sources. Become. In addition to its use as a fertilizer, potassium sulfate still has many industrial uses.

Mg (OH) ₂ is used commercially in the pulp and paper industry and is also used as an antacid and flame retardant. In addition, the treatment of wastewater and acidic wastewater is a field that is growing very much as its application. Mg (OH) ₂ is also used in the manufacture of magnesia (MgO), magnesium carbonate and other magnesium chemicals. Mg (OH) _{2 with} low B ₂ O ₃ impurities is particularly suitable for the production of refractory grade MgO. High quality gypsum (CaSO ₄ .2H ₂ O) has applications in the white cement industry and in the production of high strength α and β type gypsum. Sodium chloride containing a small amount of potassium chloride has applications in the edible salt industry.

  Referring to the well-known Mannheim method, which involves reacting MOP with sulfuric acid, the main problem with this method is that it is energy intensive and hinders the management of HCl if there is no comparable amount of use in the vicinity. It is to come. J. et al. A. Fernandez Lozano and A.M. Wint (“Production of potassium sulfate by an ammunition process”, Chemical Engineer, 349, pp 688-690, October 1979) is used to react P by reacting with P in the presence of ammonia. ing. The principle of this method is a metathesis reaction between gypsum and potassium chloride at 0 ° C. in the presence of ammonia. The main drawback of this method is that it is energy intensive and requires careful design of the reactor to operate safely.

H. Scherzberg other ( "Messo pilots new potassium sulphate process', Phosphorous & Potassium, 178, March -April 1992, p-20) is, MOP was reacted with sodium sulfate Gurase write double salt _{(3K 2 SO 4 · Na 2} SO 4) Describes a successful attempt on a method that includes generating Gracelite is then reacted with MOP to produce SOP. The main drawback of this method is that it is not suitable for those who do not have the means to obtain such raw materials, and furthermore, this method has several complex units including the need for cooling. Operations are included. Such a method has limitations on a large scale.

H. Scherzberg and R.M. Schmitz ( "Duisberg's alternative to Mannheim ', Phosphorous & Potassium, 178, March -April 1992, p-20) is described an integrated method for producing an SOP from KCl and MgSO ₄ or Na ₂ SO ₄ Yes. The main drawback of this method is that the amount of NaCl in the raw material has a decisive influence on the process, and as such it is not very applicable to crude mixed salts such as obtained from seawater bitter. That is. Another disadvantage is that this method is energy intensive because it involves heating and cooling. Yet another disadvantage is that the resulting byproduct is MgCl ₂ in a concentrated solution state, which is more marketable than the low B ₂ O ₃ containing Mg (OH) ₂ produced as part of the integrated process of the present invention. Limited and less appealing.

G. D. Bhatt et al. (“Mixed Salt from Sea Bittern”, Salt Research & Industry, 2, 126-128, 1969) have described mixed salts, ie, NaCl and kainite (KCl · MgSO ₄ ) from seawater bitter by sun concentration and fractional crystallization. Describes a method for producing a mixed salt comprising a mixture of 3H ₂ O).

Patel et al. (Salt Research & Industry, Vol. 6, No. 14, 1969) disclose a method for preparing syngenite in pure form from mixed salts. K. P. Patel, R.A. P. Vyas and K.K. Sesadri (“Potassium Sulphate from Syngeneite”, Salt Research & Industry, Vol. 6, No. 2, April 1969) leached singenite (K ₂ SO ₄ , CaSO ₄ , H ₂ O) with hot water and then concentrated in the sun. Discloses a method for preparing SOPs by recovery. The main drawback of this method is that it is energy intensive. In addition, the production of syngenite from mixed salts is a troubling problem in itself.

K. Sehsadri et al. (“Manufacture of Potassium Chloride and Byproducts” from Salt Sea Bitter ”, Salt Research and Industry, April-39, Vol. 7 from Salt Research and Industry, Vol. 7) Disclosed is a method of separating kiselite by dispersing with high density bitter juice at a ratio and heating to 110 ° C. to form kieserite (MgSO ₄ .H ₂ O) and filtering the slurry under high temperature conditions. is doing. The filtrate is cooled to ambient temperature and the carnallite crystallizes. While moving the magnesium chloride into the solution, the carnarite is decomposed with water to obtain a solid mixture of sodium chloride and potassium chloride. A solid mixture of potassium chloride and sodium chloride is purified using known techniques to produce pure potassium chloride. The disadvantage of this method is that the sulfate content in the bitter juice is not available, and instead it has been bothered to produce MOP that is inferior to SOP as a fertilizer in any case. Is to provide a method.

  Vohra, Rajinder N .; US Patent Application No. 20030080066 dated October 29, 2001, et al. Discloses an integrated process for recovering final bitter juice containing high purity salt, potassium chloride, and 7.5 g / L Br. . This process is based on desulfating brine using distillate waste from the soda ash industry or calcium chloride produced from limestone and acid. The main disadvantage of this patent application is that if distillation waste is not available in the vicinity, this method is less attractive and this method is used when carnalite must be obtained from bitter juice without producing industrial grade salts. Is less economical. Further, as described above, it is desirable to generate SOP rather than MOP using sulfate-containing materials in bitter juice.

  Michael Freeman ("Great Salt Lake-A fertile harvest for IMC", Phosphorus & Potassium, 225, Jan-Feb, 2000) concentrates brine containing 0.2-0.4% KCl, collects mixed salt, The high sodium chloride fraction is separated by flotation, schoenite is produced by leaching with brine rich in sulfate, the shonite is dissolved in hot water, and fractional crystallization of SOP is performed. And recycle a mother liquor containing up to 30% of the original K to the evaporation pond. The main disadvantages of this method are (i) the need for flotation, including the use of organic chemicals that are problematic for disposal, and (ii) recovery of SOP from shonite by fractional crystallization at high temperatures. (Iii) as much as 30% K needs to be recycled to the evaporating basin and is again contaminated with other components of the brine.

In the chapter on Potassium compounds in Ullmann's Encyclopedia of Industrial Chemistry, Sixth Edition, 1999, there is a description of a method for producing SOPs in Sicily. Kainite (KCl · MgSO ₄ · 2.75H ₂ O) is obtained from potash ore by flotation. It is then converted to shenite at about 25 ° C. by stirring with a mother liquor containing potassium and magnesium sulfate from a later stage of the process. Shonite is filtered off and decomposed with water at about 48 ° C. As a result, magnesium sulfate and a part of potassium sulfate are dissolved, and most of the potassium sulfate is crystallized. The crystals are filtered and dried, and the sulfate mother liquor is recycled to the kainite-shonite conversion stage. The main disadvantage of this method is that no mention is made of the whereabouts of the mother liquor obtained during the conversion of kainite to shenite, which is inevitably accompanied by a large loss of potassium, and SOP fractional crystallization. It requires an external heat source to make it effective.

Song, Wenyi; Liu, Yu; Zhao, Shixiang; Dai, Fangfa, Chinese Patent CN2000-112497, dated 29 August 2000, titles a method for preparing K ₂ SO ₄ from sulfate-type K-containing bitter juice. . This method concentrates the bitter juice, separates and concentrates NaCl to obtain a K-Mg crude salt containing 10-45% NaCl, crushed and mixed with saturated bitter juice to a concentration of 20-40% The solution is obtained by removing NaCl by reverse flotation, concentrating, dehydrating to obtain K-Mg purified salt containing less than 5% NaCl, and mixing the K-Mg salt and water in a specific ratio. The mixture is allowed to react at 10-60 ° F. for 0.5-3 hours, separated to obtain schernite, mixed with KCl and water in a certain ratio, and the mixture is 0.25 at 10-70 ° F. It reacted 3 hours, and separated by comprising obtaining a K ₂ SO _4. The disadvantages of this method are that (i) the purification of the mixed salt requires an elaborate method that involves removing NaCl by the less desirable method of reverse flotation involving the use of organic chemicals, (Ii) lack of reference to methods of handling various waste streams and (iii) no mention of methods of generating KCl as part of the process, depending on KCl sourced from outside It is that you are.

J. et al. H. Hildebrand (from “Extraction of Potash and other Constituents from Sea Water Bittern”, Journal of Industrial and Engineering Chemistry, Vol. It describes and proposes an extraction method. According to this method, the bitter juice is concentrated at a temperature of 100-120 ° C. to form a solid mixture of sodium chloride and key celite (MgSO ₄ .H ₂ O), and the mixture is heated in a heated centrifuge. Under conditions, the mother liquor is cooled in a cooler to separate carnalite. Carnalite is decomposed and washed with water to produce potassium chloride. The disadvantages of this method are that it is demanding with respect to energy requirements and that sufficiently pure carnalite cannot be obtained. The main drawback of this method is the contamination of key celite with NaCl, which may require further purification in order to obtain a product that is ready for sale. Another disadvantage of this method is that it may be preferable to use sulfate to produce SOP, but it requires energy to remove the sulfate from the bite in the celite state.

  D. J. et al. Metta et al. ("Production of Potassium Sulphate from Mixed Salt Observed from Salt Works of Little Ran of Kutsch, Salt Research & Indol. In order to produce potassium sulfate from a mixed salt, a method using a flotation method is described. This method has the disadvantage of lacking suitability when using seawater bitter juice containing a high concentration of sulfate, and requires froth flotation that is expensive, cumbersome and causes contamination.

Margaret Seeger, Walter Otto, Wilhelm Frich, Friedrich Bickelhaupt and Otto. S. See the chapter on how to prepare magnesium hydroxide from seawater, which is written by Akkerman, where Ullmann's Encyclopedia of Industrial Chemistry, Sixth Edition, 2002 (Electronic Version) describes magnesium compounds. Yes. Among them, it is described that the preparation of magnesia with low boron content requires the over-lining of seawater up to pH 12 in order to maintain the B ₂ O ₃ content in magnesia below 0.05%. ing. Overlining includes the higher cost of lime, the need to neutralize the supernatant, and the formation of a colloidal suspension that is not easy to filter. Another disadvantage is the lack of use of waste liquids containing calcium chloride that are discharged back into the sea.

Patent No. 36 from Wendling et al., Entitled “Process for the manufacture of potassium sulfate by the solution of the magnesium mineral in the No. 66 solution of the magnesium mineral and the no. A method for producing potassium and in particular a unit of mother liquor in equilibrium for the treatment of carnalite is described. According to this method, sodium sulfate and potassium chloride are added to a solution containing magnesium chloride so that sodium chloride and shonite (K ₂ SO ₄ MgSO ₄ .6H ₂ O) are precipitated. Treatment with known methods produces potassium sulfate. The main drawback of this method is the need to procure sodium sulfate from the outside and the lack of mention of a solution to the problem of losing KCl in the waste stream.

H. Gurbuz other ( "Recovery of Potassium Salts from Bittern by Potassium Pentaborate Crystallisation ", Separation Science & Technology, 31 ( 6), 1996, pp.857~870) is, H ₃ BO that was recycled and natural borax in the presence of water ₃ reacts with ₃ to form sodium pentaborate, which is then treated with bitter to selectively precipitate potassium pentaborate, which is then acidified with sulfuric acid. And fractional crystallization to remove K ₂ SO ₄ and recycle H ₃ BO ₃ during the process. The main drawback of this method is that the mother liquor contains a significant amount of boron, which requires complex procedures to recover the boron, and MgO obtained from such mother liquor is not suitable for industrial applications. There are cases where it is inappropriate. Moreover, such methods are still worth considering for bitter juices with low sulfates, but may not be the preferred means for bitter juices with high sulfate content. Furthermore, another drawback is that the acidified product needs to be cooled for high yields.

  A. S. Mehta (Indian Chemical Engineer, 45 (2), 2003, p. 73) describes a process for producing bromine from bitter juice. The bitter juice is acidified with sulfuric acid to pH 3.0-3.5 and the bromide ions are then oxidized with chlorine and stripped off with the help of steam. The acid debrominated bitter juice is neutralized with lime, and then the generated sludge is removed and the waste liquid is discharged. A bromine plant located in the vicinity of a natural salt bed in the Kutch Great Wetland, Gujarat, India, uses natural bitter juice to produce bromine in the manner described above and discharges waste liquid into the wetland. Sludge treatment is a difficult challenge in these plants.

Chr. Balarew, D.M. Rabadjieva and S. Tempavicharova (“Improved Treatment of Waste Lines”, International Symposium on Salt 2000, pages 551-554) describes the recovery of marine chemicals. The authors use the resulting CaCl ₂ solution to use lime to precipitate Mg (OH) ₂ from some of the available bitter juice and to recover KCl via carnalite. It describes that the remaining bitter juice is desulfated. The authors do not discuss any plans to use a methodology for producing SOPs from sulfate rich bitter juice. Moreover, as will become apparent later, Mg (OH) ₂ produced directly from the raw bitter juice is much higher in B ₂ O than Mg (OH) ₂ prepared from the Mg ²⁺ source of the present invention leading to SOP formation. ₃ content.

  Lu Zheng's Chinese Patent No. 1084492 describes a method for producing SOP from bitter juice and potassium chloride. In this method, the bitter juice is processed by concentration, cooling, and flotation, and then reacts with potassium chloride to form potassium sulfate and industrial salt and residual brine by-products. The main disadvantage of this method is that it requires the inclusion of a separation technique such as flotation to remove NaCl from the mixed salt, and the KCl required to produce SOP from shonite must be procured separately. It must be done. Moreover, the overall yield for potash recovery is 95%, but no mention is made of the yield for separately procured KCl.

  An important objective of the present invention is an excellent fertilizer from sulfate-rich bitter sources such as seawater and natural bitter in a cost-effective manner by integrating with the production of valuable by-products. SOP is generated.

  Another objective is to eliminate the need for flotation to remove NaCl from the mixed salt, instead to wash out NaCl in the mother liquor (SEL) and at the same time convert kainite to syenite. .

  Another objective is to generate SOP from shenite under ambient conditions by a known method of reacting with KCl in the presence of water, where MOP is generated from SEL and does not need to be sourced externally. .

  Another objective is to maximize recovery of potash in the form of SOP from the mixed salt.

  Another objective is to cost-effectively desulfate SEL to promote carnalite formation.

  Another objective is to concentrate the desulfated SEL in a multi-effect evaporator to recover water for reuse.

  Another object is to utilize the separated NaCl as an edible salt.

Another object is to utilize a MgCl ₂ rich carnalite decomposition solution (CDL) to cost-effectively produce CaCl ₂ and Mg (OH) ₂ by treatment with lime.

Another object is to utilize the wash from Mg (OH) ₂ filtration in the preparation of slaked lime from quick lime, which saves water and recycles residual CaCl ₂ in the wash.

Another object is to utilize the CaCl ₂ solution for SEL desulfation.

  Another object is to recover KCl lost in CDL by recycling CDL in the manner described above.

Another object is to show that the MgO produced from the Mg (OH) ₂ contains very low (<0.03%) levels of B ₂ O ₃ impurities.

  Another objective is to minimize the production of effluent during the process, and instead use the effluent to enhance potash recovery or convert it to value-added products.

Another objective is to use an acid such as sulfuric acid to acidify the bitter and instead make it useful for the formation of mixed salts quickly to eliminate sludge formation. For the purpose of neutralizing the debrominated bitter juice, the conventionally used slaked lime is replaced with Mg (OH) ₂ produced during the process of the present invention.

The present invention provides an integrated method for preparing potassium sulfate from bitter juice, including:
(I) fractionating crystallization of bitter juice to obtain a kainite-type mixed salt having a high kainite content and final bitter juice rich in MgCl ₂ , and further desulfating the final bitter juice rich in MgCl ₂ .
(Ii) treating the kainite-type mixed salt with water and the mother liquor obtained in the following step (xiii) to wash out almost all NaCl from the mixed salt and at the same time convert the kainite to schnite.
(Iii) filtering the shonite to separate the filtrate.
(Iv) Desulfating the filtrate with an aqueous CaCl ₂ solution.
(V) filtering the gypsum produced in step (iv) and mixing the filtrate with the MgCl ₂ rich filtrate obtained in the following step (vii).
(Vi) concentrating the solution obtained in step (v) and cooling to ambient temperature to crystallize the crude carnalite.
(Vii) centrifuging the crude carnalite and recycling the required amount of filtrate to step (v).
(Viii) Decomposing the crude carnalite with an appropriate amount of water from step (vi) to produce crude KCl and carnalite decomposition solution.
(Ix) filtering the crude KCl, washing with water to remove the deposited MgCl ₂ , and leaching at high temperature to produce MOP and NaCl.
(X) mixing the carnalite decomposition solution from step (viii) and the washing solution from step (ix) and treating with slaked lime.
(Xi) filtering the slurry to wash the cake to produce a Mg (OH) ₂ and CaCl ₂ containing filtrate for the desulfation treatment of step (iv).
(Xii) treating the shenite produced in step (iii) by known methods using the MOP produced in step (ix) to produce SOP under ambient conditions.
(Xiii) Filtering the SOP and separating and collecting the mother liquor (hereinafter referred to as “KEL”).
(Xiv) recycling the KEL of step (xiii) in the treatment of step (ii).

It should be noted that certain steps of the method are first triggered by externally sourced CaCl ₂ and water, but since then most of them are produced in the above-described method of the present invention.

  In an embodiment of the present invention, bitter juice having a density of 29 to 34 ° Be ′ (specific gravity 1.25 to 1.31) is used to produce the mixed salt described in the prior art, and then NaCl is simultaneously added from the solid mass. Converts to shenite while leaching.

In another embodiment of the present invention, water, KCl, and KCl are used for the purpose of minimizing the loss of K from the mixed salt without interfering with the conversion of kainite to shenite and leaching of the NaCl from the mixed salt. The mixed salt is treated with KEL rich in MgSO ₄ and low in NaCl and MgCl _{2 in} a ratio of 0.3-0.5: 1.

  In another embodiment of the present invention, shonite is reacted with MOP and water in a ratio of 1: 0.3 to 0.6: 1 to produce SOP and KEL. Here, the MOP is generated from the SEL in situ.

In another embodiment of the method, MOP is produced from carnalite, which in turn desulfates SEL, and MgCl ₂ solution 0.7-0. It is obtained by treatment with a 400-440 g / L MgCl ₂ solution in a ratio of 9 parts and forced concentration until the solution reaches a temperature of 120-128 ° C. at atmospheric pressure.

In another embodiment of the method, the filtrate obtained after removal of NaCl is cooled to room temperature and then filtered to obtain carnalite. On the other hand, the filtrate contains 400-440 g / L MgCl ₂ and is recycled back to a new lot of desulfated SEL to further produce carnalite.

  In another embodiment of the method, wet carnalite is treated with water in a ratio of 1: 0.4 to 0.6 to obtain crude KCl.

In another embodiment of the method, the magnesium chloride in the carnalite decomposition liquor is added to the MgCl ₂ in the final liquor and treated with lime to be necessary for desulfation of Mg (OH) ₂ and SEL. To produce an aqueous solution of calcium chloride (concentration 20-30% w / v).

In another embodiment of the method, Mg (OH) ₂ is calcined at a temperature of 800-900 ° C. to produce MgO containing less than 0.04% B ₂ O ₃ .

In another embodiment of the method, the amount of fresh water is minimized by recirculating the water from the forced concentration stage, along with the wash resulting from the purification of gypsum, Mg (OH) ₂ and KCl. It can be suppressed to the limit.

In another embodiment of the process, acidified and debrominated bitter juice, which is an ideal raw material for mixed production, is replaced with crude Mg (OH) ₂ in place of lime to eliminate sludge formation. To neutralize.

The main inventive step is that the step of converting kainite in the mixed salt to schonite and leaching NaCl from the mixed salt can be performed simultaneously in a single operation with minimal loss of KCl in the mixed salt. It is recognized. It is recognized that another inventive step is that the need for externally procured MOP is minimized by generating MOP from shenite-generated waste filtrate instead. Another inventive step is to desulfate the SEL required for MOP generation using calcium chloride generated in situ from MgCl _{2 in} the desulfurized SEL, and the MgCl ₂ is the carnalite decomposition solution. And a flow rich in MgCl ₂ in the final solution. Other inventive step, Mg generation of (OH) ₂ thanks to the with desulfation of SEL, from brine or bittern Mg (OH) ₂ in the management of CaCl ₂ waste encountered when other to produce There is no problem. Other inventive mainly using the CDL to generate Mg (OH) _2, in Mg (OH) _2, and the result Mg (OH) is B ₂ O ₃ impurities in the resulting MgO from ₂ significantly reduced Is. Another inventive step is the local use of crude Mg (OH) ₂ to neutralize the acidified and debrominated bitter juice prior to the formation of mixed salts. Another inventive step is to recycle liquid waste to minimize the need for fresh water while enhancing recovery and simultaneously addressing waste disposal issues.

  The following examples are given by way of illustration and should not be considered as limiting the scope of the invention.

Example 1 In a typical manner, 200 m ³ of seawater bitter juice of 29.5 ° Be ′ (specific gravity 1.255) was concentrated in the sun in a lined pan. The first fraction (20 tons) containing mainly crude salt was removed at 34 ° Be ′ (specific gravity 1.306). The bitter juice was further concentrated to 35.5 ° Be ′ (specific gravity 1.324), and the sels mixture fraction (15 tons) was separated. The obtained bitter juice (100 m ³ ) was transferred to the second lined pan and concentrated in the sun to obtain 16 tons of kainite-type mixed salt and 26 m ³ of the final bitter juice. The mixed salt was further processed as described in the following examples to produce shonite. On the other hand, a part of the final bitter juice was desulfurized using calcium chloride procured from outside to produce the final bitter juice which was desulfated. A portion of the final desulfurized bitter juice was subsequently treated with slaked lime to produce calcium chloride and magnesium hydroxide. The aqueous calcium chloride solution was filtered and used to desulfate the SEL of Example 6. The other part of the desulfurized final bitter was used as the MgCl ₂ source in the same example to promote the formation of carnalite from the desulfated SEL. Moreover, the same experiment was conducted using other bitter sources such as lower soil bitter juice and bitter juice obtained after bromine recovery.

Example 2: KCl-15.5%, NaCl -14.6%, the kainite type mixed salt 142.0kg having a chemical composition of MgSO ₄ -39.5% treated with water 140L, in a container Stir for 2.5 hours. The slurry was filtered using a basket type centrifuge, shea night 32.0kg as a solid product (analysis _{K 2 SO 4 -38.0%, MgSO} 4 -30.2%, NaCl-1.2%) And 200 L of filtrate (SEL) (analysis results KCl-7.6%, NaCl-16.1%, MgSO ₄ -21.1%, MgCl ₂ -8.4%) were obtained. Shonite was treated with stirring for 3.5 hours using a solution of 12.5 kg of MOP dissolved in 49.0 L of water. The slurry was filtered, and 16.0 kg of SOP (analysis result K ₂ SO ₄ -95.0%, NaCl-1.0%, MgSO ₄ -1.0%) and 60 L of filtrate (KEL) (analysis result KCl-15 0.0%, NaCl-1.5%, MgSO ₄ -9.7%, MgCl ₂ -3.9%).

Example 3: 60.0 kg of mixed salt having the same composition as in Example 2 was combined with KEL obtained in Example 2. An additional 27 L of water was added and the contents were stirred for 2.5 hours. The slurry was filtered in a centrifuge, Shea Knight 26.0 kg (analysis _{K 2 SO 4 -39.7%, MgSO} 4 -29.5%, NaCl-0.7%, MgCl 2 -0.6 %) and a filtrate (SEL) 95.0L (analysis KCl-9.9%, NaCl-13.0 %, MgSO 4 -18.6%, was obtained MgCl ₂ -6.0%). Shonite was reacted with a solution obtained by dissolving 10.4 kg of MOP in 38 L of water while stirring in a container for 3.5 hours. The obtained slurry was filtered using a centrifuge, and 14.5 kg of SOP (analysis results K ₂ SO ₄ -98.1%, NaCl-0.2%, MgSO ₄ -1.4%) and a filtrate (KEL ) 45L (analysis _{K 2 SO 4 -12.4%, KCl} -6.15%, NaCl-0.9%, MgSO 4 -1.0%, to give the MgCl ₂ -10.2%).

Example 4: 104 kg of mixed salt (analysis results KCl-14.1%, NaCl-16.5%, MgSO ₄ -41.6%) was added to KEL100L (analysis results K ₂ SO ₄ -13.9%, NaCl-2). 0.8%, MgCl ₂ -11.6%) and 40 L of water for 2 hours. The slurry was centrifuged, shea night 34.8 kg (analysis _{K 2 SO 4 -37.0%, MgSO} 4 -30.3%, NaCl-4.9%) and a filtrate (SEL) 190.0L (Analysis results KCl-9.5%, NaCl-13.0 %, MgSO 4 -15.1%, was obtained MgCl ₂ -8.0%). Shonite was further reacted with a solution prepared by dissolving 12.5 kg of MOP in 46 L of water for 3.5 hours to obtain 17.5 kg of SOP and KEL80 L. Analysis of the _{SOP, K 2 SO 4 -97.3%} , NaCl-0.2%, a MgSO ₄ -3.0%, KEL is, KCl-16.7%, NaCl- 1.3%, They were MgSO ₄ -11.0% and MgCl ₂ -2.7%.

Example 5: In this experiment, mixed salt 150 kg (analysis KCl-13.1%, NaCl-19.8 %, MgSO 4 -38.0%, MgCl 2 -1.9%) a KEL160L (analysis KCl- (17.0%, NaCl-3.3%, MgSO ₄ -9.0%, MgCl ₂ -1.9%) and 60 L of water were placed in a container and stirred for 2 hours. The obtained slurry was centrifuged, and 49.9 kg of shonite (analysis results K ₂ SO ₄ -42.0%, MgSO ₄ -32.2%, NaCl-0.7%) and 255 L of filtrate (SEL) ( analysis KCl-10.5%, NaCl-12.3 %, MgSO 4 -13.7%, was obtained MgCl ₂ -6.70%). Shonite was reacted with a solution obtained by dissolving 19.0 kg of MOP in 75 L of water while continuously stirring in a container for 3.5 hours. The slurry was centrifuged, 27.0 kg of SOP (analysis results K ₂ SO ₄ -94.3%, NaCl-0.2%, MgSO ₄ -3.7%) and 85 L of filtrate (KEL) (KCl-15.5). %, NaCl-0.8%, MgSO ₄ -10.5%, MgCl ₂ -3.0%).

Example 6: 59 L of the desulfated final bitter juice obtained in Example 1 having a chemical composition of KCl—1.15%, NaCl—1.3%, MgCl ₂ —41.2%, CaSO ₄ —trace amount. The solution was diluted with 40 L of water and treated with 14.7 kg of freshly prepared slaked lime (active concentration 87.7%) for 1 hour. The resulting slurry was filtered and the cake was washed with 30 L of water. 90 L of a total filtrate containing CaCl ₂ -22.3% and MgCl ₂ -3.0% was obtained. Solid magnesium hydroxide was further washed with 100 L of water to remove soluble impurities. 15.7 kg of Mg (OH) ₂ having an Mg (OH) ₂ content of 86.9% was obtained by drying in a tray dryer. A part of Mg (OH) ₂ was fired at 850 ° C. to obtain 90.0% MgO. Using the filtrate 90L containing 22.3% of CaCl _2, and the SEL90L obtained in Example 3 was desulphated. The resulting slurry was filtered to obtain 21.0 kg of desulfurized SEL142L and a gypsum byproduct. Desulfated SEL57L was mixed with 41 L of the final desulfated bitter juice of Example 1 with a Mg concentration of 10.3%. The resulting solution was forcibly concentrated in an open pan evaporator until the solution reached a boiling point of 120 ° C. The hot liquid was filtered to separate 5.5 kg of crude NaCl having a composition of NaCl-85%, KCl-2.9%, MgCl ₂ -12.1%. The filtrate was cooled in a tank to crystallize the carnalite. The resulting slurry was filtered, carnallite 11.3 kg (analysis KCl-21.7%, NaCl-9.7 %, MgCl 2 -31.4%, CaSO 4 -2.7%) and end bittern 48L (analysis result MgCl ₂ -40.2%, KCl-0.8%, NaCl-1.1%) was obtained. 9.2 kg of carnalite was decomposed with 3.6 L of water, filtered, and chemical composition of KCl-4.6%, NaCl-2.8%, MgCl ₂ -30.5%, CaSO ₄ -trace amount carnallite decomposed liquor (CDL) 8.0 L and KCl-75.3%, NaCl-20.2 % with, MgCl ₂ -2.0%, CDP2.9kg having the chemical composition of CaSO ₄ -2.5% Got. CDP was treated with 1.9 L of water at ambient temperature (30 ° C.), composition of KCl-90.0%, NaCl-3.3%, MgCl ₂ -0.4%, CaSO ₄ -6.0% 2.0 L of KCl having a pH of 2.2 and a saturated solution of 2.2 L having a chemical composition of KCl-14.0%, NaCl-20.0%.

Example 7: CDL10L obtained in the previous example, KCl-7.0%, NaCl-8. Used to wash the crude salt produced in the previous example to recover the magnesium content therein. 5.7 L of cold leachate having a chemical composition of 2%, MgCl ₂ -21.5%, CaSO ₄ -trace amount and 15 L of water were treated with 2.5 kg of freshly prepared slaked lime with 90% activity for 1 hour. The obtained slurry was filtered, and the solid cake was washed with 10 L of water to obtain 34 L of a filtrate containing 7.7% CaCl ₂ . Solid magnesium hydroxide was further washed with 30 L of water to remove soluble impurities. Mg (OH) ₂ was dried to obtain 2.3 kg of Mg (OH) ₂ and calcined to obtain 92% MgO containing 0.034% B ₂ O ₃ as impurities. Use the CaCl ₂ 34L containing brine, KCl-7.2%, NaCl- 12.4%, MgSO 4 -16.0%, the SEL17L having a chemical composition of MgCl ₂ -6.5% to desulfation It was. The resulting slurry was filtered to remove 5.2 kg of wet calcium sulfate to obtain desulfated SEL49L with a Mg content of 2.03%. 75 L of the final bitter juice having a Mg concentration of 9.6% obtained from the experiment was added to the desulfurized SEL. The resulting solution mixture was forcibly concentrated in an open pan evaporator until the boiling point of the solution was 126 ° C. The hot liquid was cooled in the tank to crystallize the carnalite. The resulting slurry was filtered, KCl-14.3%, NaCl- 12.7%, MgCl 2 -31.9%, carnallite 18.8kg having a chemical composition of CaSO ₄ -1.9%, and yield _{MgCl 2 -46.1%, KCl-0.2} %, the end bittern 46.5L with NaCl-0.5% of the chemical composition. 18.8 kg of carnalite is decomposed with 8 L of water and filtered to have a chemical composition of KCl-4.8%, NaCl-3.2%, MgCl ₂ -32.5%, CaSO ₄ -trace amount. CDL 15.5 L and CDP 5.7 kg having a chemical composition of KCl-33.9%, NaCl-46.3%, MgCl ₂ -1.4%, CaSO ₄ -5.1%, moisture -13% were obtained. . As will be described in detail later, this CDP was hot leached together with the CDP obtained in the following examples by a known method to separate KCl.

Example 8: KCl-5.0%, NaCl-3.2%, MgCl ₂ -32.5%, CaSO ₄ -CDL 15.5L and 15L water obtained in the above experiment with trace amounts of chemical composition Treated for 1 hour with 3.0 kg of freshly prepared slaked lime with 0.0% activity. The obtained slurry was filtered, and the solid was washed with 10 L of water to obtain 27.5 L of a filtrate containing 10.60% CaCl ₂ . Solid magnesium hydroxide was further washed with 30 L of water to remove soluble impurities. Mg (OH) ₂ is dried to obtain 2.9 kg of Mg (OH) ₂ , followed by calcination to produce corrosive calcinated MgO with 95% MgO content and 0.03% B ₂ O ₃ impurities. Got. Using a solution containing _{CaCl 2, KCl-7.2%,} NaCl-12.4%, MgSO 4 -16.0%, and the SEL25L having a chemical composition of MgCl ₂ -6.5% and desulphated. The resulting slurry was filtered to remove 5.7 kg of calcium sulfate to obtain desulfated SEL46L having a Mg content of 3.05%. 33 L of final bitter juice obtained from the experiment with an Mg concentration of 11.8% was added to the desulfurized SEL. The resulting solution mixture was forcibly concentrated in an open pan evaporator until the boiling point of the solution was 125 ° C. The hot liquid was cooled in the tank to crystallize the carnalite. The resulting slurry was filtered, KCl-15.0%, NaCl- 24.7%, MgCl 2 -25.1%, carnallite 14kg with a chemical composition of CaSO ₄ -4.0%, and MgCl ₂ - A final bitter juice of 33.8 L having a chemical composition of 44.8%, KCl-0.1%, NaCl-0.46% was obtained. 14.0 kg of carnalite was decomposed with 6.3 L of water, filtered, and the chemical composition of KCl-5.6%, NaCl-4.4%, MgCl ₂ -27.6%, CaSO ₄ -trace amount CDL12L having, and KCl-26.1%, NaCl-51.1 %, MgCl 2 -7.1%, CaSO 4 -5.1%, the CDP5.0kg having the chemical composition of the water -9.0% Obtained. Together with 10.8 kg of the CDP of Example 7, the resulting CDP was hot leached in a known manner to give 3.5 kg of MOP having a 93.6% KCl content.

Example 9: In this example, an SOP was prepared using the MOP produced in Example 8 above. Kainite type mixed salt 9.0 kg (analysis KCl-14.2%, NaCl-16.5 %, MgSO 4 -40.2%, MgCl 2 -1.2%) were reacted water 8L and 2 hours. The slurry was centrifuged, shea Knight 3.0 kg (analysis _{K 2 SO 4 -35.5%, MgSO} 4 -31.0%, NaCl-3.3%) and a filtrate (SEL) 9.5 L (Analysis results KCl-7.6%, NaCl-12.6 %, MgSO 4 -15.1%, was obtained MgCl ₂ -9.5%). 0.488 kg of shenite was further reacted for 3.5 hours with a solution prepared by dissolving 0.190 kg of MOP (obtained from Example 8) in 0.753 L of water to obtain 0.255 kg of SOP and 0.860 L of KEL. As a result of analysis of SOP, K ₂ SO ₄ -93.0%, NaCl-0.6%, MgSO ₄ -5.4%, and KEL are KCl-14.8%, NaCl-1.4%, They were MgSO ₄ -7.7% and MgCl ₂ -4.1%.

Claims (21)

An integrated method for preparing potassium sulfate (SOP) from bitter juice,
(I) fractionated crystallization of bitter juice to obtain a kainite mixed salt having a high kainite content and final bitter juice rich in MgCl ₂ , and further desulfating the final bitter juice rich in MgCl ₂ ;
(Ii) treating the kainite-type mixed salt with water and the mother liquor obtained in the following step (xiii) to wash out almost all NaCl from the mixed salt and at the same time convert the kainite to schoenite. ,
(Iii) filtering the shonite to separate the filtrate;
(Iv) Desulfating the filtrate with an aqueous CaCl ₂ solution;
(V) filtering the gypsum produced in step (iv) and mixing the filtrate with the MgCl ₂ rich filtrate obtained in step (vii) below,
(Vi) concentrating the resulting solution of step (v) and cooling to ambient temperature to crystallize the crude carnallite;
(Vii) centrifuging the crude carnalite and recycling the required amount of filtrate to step (v);
(Viii) cracking the crude carnalite with an appropriate amount of water from step (vi) to produce crude KCl and carnalite cracking solution;
(Ix) filtering the crude KCl, washing with water to remove adhering MgCl ₂ , and hot leaching to produce MOP and NaCl;
(X) mixing the carnalite decomposition solution from step (viii) and the wash solution from step (ix) and treating with slaked lime;
(Xi) filtering the slurry to wash the cake to produce a Mg (OH) ₂ and CaCl ₂ containing filtrate for the desulfation treatment of step (iv);
(Xii) treating the shenite produced in step (iii) by known methods using the MOP produced in step (ix) to produce SOP under ambient conditions;
(Xiii) filtering the SOP and separating and collecting its mother liquor (hereinafter referred to as “KEL”);
(Xiv) A method comprising recycling the KEL of step (xiii) in the treatment of step (ii). The method according to claim 1, wherein the bitter juice contains K, Mg, and SO ₄ at concentrations suitable for kainite production.   The bitter juice is seawater bite and subsoil bitter, and preferably bitter juice having a higher potassium content and requiring minimal concentration to produce a kainite-type mixed salt, and debrominated bitter effluent A method according to claim 2 selected from waste bitter sources such as The mixed salt is 15 to 22% of KCl, from 15 to 22% of NaCl, 28 to 40% of the MgSO _4, containing 5-10% MgCl _2, according to any one of claims 1 to 3 Method.   The method according to any one of the preceding claims, wherein 1 part by weight of the mixed salt is treated with 0.75 to 1.25 parts by volume of KEL and 0.3 to 0.7 parts by volume of water. The KEL is typically 15-17% of KCl, 1 to 3 percent of NaCl, 10 to 12 percent of MgSO _4, and including 2-3% MgCl _2, The method according to any one of the preceding claims . SEL is typically 8-10 percent of KCl, 6 to 12 percent NaCl, 12 to 14 percent of MgSO _4, and including 5-7% of MgCl _2, The method according to any one of the preceding claims. The shea night usually 40 to 45 percent of K ₂ SO _4, 30 to 35 percent of MgSO _4, and 0.5 to 2.0 percent NaCl, the method according to any one of the preceding claims . Any one of the preceding claims, wherein in the desulfation reaction of step (iv), the stoichiometric ratio of CaCl ₂ to sulfate is 1.1: 1 to 0.9: 1, preferably 1: 1. The method described in one. 1 part by volume of desulfurized SEL is 0.5 to 1.5 parts by volume of final bitter juice rich in MgCl ₂ with a specific gravity of 36 to 38 ° Be ′ (specific gravity 1.33 to 1.38), preferably 37 ° Be ′. and end bittern 0.7-0.9 parts (specific gravity 1.342), and more preferably is mixed with the end bittern rich MgCl ₂ containing no sulfate, a method according to claim 7.   11. The method according to any one of claims 1 to 10, wherein the concentration of desulfated SEL to produce carnalite is performed while simultaneously collecting water in a solar pan or a multi-effect evaporator.   A process according to any one of the preceding claims, wherein the concentration is continued until the solution reaches a temperature in the range of 120-128 ° C, more preferably 122-124 ° C. The carnallite obtained was identified as 15-20% of KCl, 15-20% of NaCl, and a 28 to 32% of MgCl _2, The method according to any one of the preceding claims.   The method according to any one of the preceding claims, wherein 1 part by weight of the carnalite is decomposed with 0.4 to 0.6 parts by volume of water and then the cake is washed with a small amount of water. In the production of Mg (OH) ₂ and CaCl _{2 according} to any one of the preceding claims, wherein the molar ratio of active lime to MgCl ₂ is in the range of 0.8 to 1.0, preferably 0.90. The method described. The Mg (OH) ₂ obtained is fired to produce MgO with a purity of 94-98% and 0.02-0.04% B ₂ O _3. The method described in one. Any of the preceding claims, wherein the Mg (OH) ₂ is used without increasing purity to neutralize acidified and debrominated bitter juice, and such bitter juice is used as a source of potash. The method according to one.   The said MOP obtained upon high temperature leaching of crude KCl has a purity in the range of 92-98% and a NaCl content of 1-5%, preferably more than 95% KCl and less than 2% NaCl. The method as described in any one of these.   4. A process according to claims 1 to 3, wherein the NaCl obtained upon high temperature leaching of crude KCl comprises more than 97% NaCl.   At an ambient temperature in the range of 20 to 45 ° C., 1 part by mass of shonite is 0.3 to 0.6 parts by mass of MOP and 1 to 2 parts by volume of water, more preferably 0.4 parts by mass of MOP and 1.5 parts by volume of water. A method according to any one of the preceding claims, wherein the method is used to process. The method according to generated the SOP is, having a chloride in the range of K ₂ O content and 0.5 to 2.0% in the range of 50 to 52%, any one of the preceding claims.