MXPA06007414A - Process for recovery of sulphate of potash - Google Patents

Abstract

A novel integrated process for the recovery of sulphate of potash (SOP) from sulphate rich bittern is disclosed. The process requires only bittern and lime as raw materials. Kainite type mixed salt is obtained by fractional crystallization of the bittern. Kainite is converted to schoenite with simultaneous removal of NaCl by processing it with water and end liquor obtained from reaction of schoenite with MOP for its conversion to SOP. The end liquor from kainite to schoenite conversion (SEL) is used for the recovery of MOP. SEL is desulphated and supplemented with MgC12using end bittern generated in the process of making carnallite. The carnallite is decomposed to get crude potash which in turn processed to get MOP. The carnallite decomposed liquor produced in the decomposition of carnallite is reacted with hydrated lime for preparing CaC12 solution and high purity Mg(OH)2 having low boron content. The CaC12 solution is used for desulphatation of SEL producing high purity gypsum as a byproduct. It is shown that the liquid streams containing potash are recycled in the process, the recovery of potash in the form of SOP is quantitative.

Description

PROCESS FOR THE RECOVERY OF POTASSIUM SULPHATE FIELD OF THE INVENTION The present invention provides an integrated process for the recovery of potassium sulphate (SOP or sulphate of potash) from a mother water rich in sulphate. The process requires only mother liquor and lime as raw materials and provides, in addition to SOP, Mg (OH) 2 which contains a low content of boron, gypsum and salt, as co-products, all of which are obtained in pure form.

BACKGROUND OF THE INVENTION SOP is a double fertilizer containing 50% K20 and 18% S. It has the lowest salt index and is virtually chloride free, which makes it a fertilizer superior to muriate of potash (MOP or muriate of potash). On the other hand, the MOP is easy to produce, especially when the brine / mother water is low in the sulfate content, such as in the Dead Sea, and this is taken into account for its lower price compared to the SOP . Countries such as India, which do not have mother water with a low sulphate content, but which have adequate mother and marine water from the subsoil, would benefit greatly if the SOP can be produced economically from such sources of water. mother water.

In addition to its application as a fertilizer, potassium sulfate also has numerous commercial applications. Mg (OH) 2 is used commercially in the pulp and paper industries and also as an antacid and a fire inhibitor. Wastewater treatment and acid effluent represent additional high growth areas for its application. Mg (OH) 2 is also used for the production of magnesia (MgO), magnesium carbonate and other magnesium chemicals. Mg (OH) 2 which is low in impurities of B203 is especially suitable for the production of refractory grade MgO. High quality plaster (CaS04.2H20) finds applications in the white cement industry and for the manufacture of Paris Plaster a and ß high strength. Sodium chloride containing small amounts of potassium chloride finds application in the edible salt industry. Reference is made to the well-known Mannheim process, which involves the reaction of MOP with sulfuric acid. The main problem with the process is that it consumes energy and poses the problem of handling HCl when no application of the volume commensurate to HCl is available in the vicinity. JA Fernandez Lozano and A. Wint, ("Production of potassium sulfate by an ammonia process" Chemical Engineer, 349, pp 688-690, October 1979) describes a process of manufacturing SOP from MOP through the reaction with plaster in the presence of ammonia. The principle of the process is the double decomposition reaction between gypsum and potassium chloride in the presence of ammonia at 0 ° C. The main disadvantage of the process is that it consumes energy and needs a careful reactor design for safe operation. H. Scherzberg et al. ("Messo undergoes a new process of potassium sulfate," Phosphorous &Potassium, 178, March-April 1992, p-20) describe successful trials in a process involving the reaction of MOP with sodium sulfate to produce salt double glaserite (3K2S04.Na2S04). The glaserite, in turn, reacts with the MOP to produce SOP. The main disadvantage of the process is that it would be inappropriate for those who do not have access to such raw materials. In addition, the process involves several complex unit operations, including the need for cooling. Such processes have their limitation on a large scale. H. Scherzberg and R. Schmitz ("Duisberg Alternative to Mannheim", Phosphorous &Potassium, 178, March-April 1992, p-20), describe an integrated process for the production of SOP from KCl and MgSO4 or Na2SO4 . The main disadvantage of the process is that the amount of NaCl in the raw materials has a critical effect on the process and therefore, is less applicable to raw mixed salt as it is obtained from seawater mother. Another disadvantage is that the process involves heating and cooling, which makes it an energy consumer. Still another disadvantage is that the by-product obtained is MgCl2 in the form of a concentrated solution, which has a limited market and a lower attraction compared to the solid Mg (OH) 2 with a low content of B203, produced as part of the integrated process of the present invention. G. D. Bhatt et al. ("Mixed Salt from Madre del Mar Water", Salt Research &; Industry, 2, 126-128, 1969) describe a process for the manufacture of a mixed salt, that is, comprising a mixture of NaCl and kainite (KCl .MgS04.3H20), from seawater, through of evaporation and fractional crystallization. Patel et al. (Salt Research &Industry, Vol. 6, No.14, 1969) describe a process for the preparation of syngenite from a salt mixed in pure form. KP Patel, RP Vyas and K. Seshadri ("Potassium Sulfate from Singenite", Salt Research &Industry, Vol. 6, No. 2, April 1969) describe a process for the preparation of SOP by leaching syntgenite ( K2S0.CaS0.H20) with hot water and then recovering it by means of solar evaporation. The main disadvantage of the process is that it consumes energy. In addition, the production of syngenite from the mixed salts is by itself a matter involved.

K. Sehsadri et al ("Chloride Manufacturing of Potassium and byproducts from Agua Madre del Mar "Salt Research and Industry, April-July 1970, Vol. 7, page 39-44) describe a process in which the mixed salt (NaCl and kainite) obtained from the mother liquor is dispersed with high-density mother liquor in a suitable proportion and heated at a temperature of 110 ° C when the kieserite (MgS04.H20) is formed, which is separated by filtration of the suspension under hot conditions. The filtrate is cooled to room temperature, when the carnallite crystallizes. Carnalite decomposes with water to obtain a solid mixture of sodium chloride and potassium chloride, while magnesium chloride goes to the solution. The solid mixture of potassium chloride and sodium chloride is purified using known techniques to produce pure potassium chloride. The disadvantages of this process are that it fails to make use of the sulphate content in the mother liquor and, instead, offers an elaborate process for the manufacture of MOP, which, in any case, is inferior to the SOP as a fertilizer. The United States Patent Application Number 20030080066 dated October 29, 2001 from Vohra, Rajinder N. et. al., describes an integrated process for the recovery of a high purity salt of potassium chloride, and a final mother liquor containing 7.5 gpl of Br.

The process is based on the desulphurisation of the brine with a waste from the Distiller of the commercial soda industry or the calcium chloride generated from the limestone and the acid. The main disadvantage of the patent application is that the process is less attractive when the distiller's waste is not available in the vicinity and the process becomes less economical when the carnallite has to be obtained from the mother water without industrial grade salt production . Furthermore, as in the case referred to above, it is desirable to use the sulfate content in the mother liquor and to produce the SOP in a preferred manner to the MOP. Michael Freeman ("The Great Salt Lake, a fertile crop for BMI" in Phosphorus &Potassium, 225, January-February, 2000) describes a process that involves concentrating the brine containing 0.2-0.4% KCl, collecting the mixed salt , the separation of the fraction with a high content of sodium chloride through flotation, leaching with sulphate-rich brine to produce schoenite, the dissolution in hot water of the schoenite, the fractional crystallization of the SOP and recycling of the mother liquor that contains 30% of original K to the evaporation pond. The main disadvantages of the process are: (i) need for flotation that involves the use of organic chemicals whose disposal is problematic, (ii) need for external heat for the recovery of SOP from the schoenite through high-temperature fractional crystallization, (iii) the need to recycle as much as 30% of the K to the evaporation ponds, where it is again contaminated with other components of the brine. In the Ullmann Encyclopedia of Industrial Chemistry, Sixth Edition, 1999, under the Chapter, Potassium Compounds, a description is given of a process for the production of SOP in Sicily. The kainite (KCl-MgSO4-2.75H20), is obtained from a potash ore by flotation. It is then converted to schoenite at approximately 25 ° C by shaking with the mother liquor that contains the potassium and magnesium sulphates of the last stages of the process. The schoenite is filtered and decomposed with water at approximately 48 ° C. This causes the magnesium sulfate and part of the potassium sulfate to dissolve and most of the potassium sulfate to crystallize. The crystals are filtered and dried. The sulphate mother liquor is recycled to the kainite-schoenite conversion stage. The main disadvantages of the process are that there is no mention of the fate of the mother liquor obtained after the conversion of kainite into schoenite, which would inevitably include a considerable loss of K, and the need for an external source of heat to effect the fractional crystallization of the SOP.Chinese Patent CN 2000-112497, August 29, 2000, by Song, enyi; Liu, Yu; Zhao, Shixiang; Dai, Fangfa, entitled Method to prepare K2S0 from sulphate of the type of mother water containing K. The method comprises concentrating the mother liquor, separating the NaCl, concentrating it to obtain the crude K-Mg salt containing 10-45% of NaCl, crush it, mix it with saturated mother liquor to obtain a solution with a concentration of 20-40%, eliminate the NaCl by reverse flotation, concentrate, eliminate the water to obtain the refined K-Mg salt containing less than 5% of NaCl, mix the K-Mg salt and water at a specific ratio, allow the mixture to react at -12.22-15.55 ° C (10-60 ° F) for 0.5-3 hours, separate the schoenite, mix with KCl and water at a specified ratio, let the mixture react at -12.22-21.11 ° C (10-70 ° F for 0.25-3 hours and separate to obtain K2S04) The disadvantages of the process are (i) the need for an elaborate method for the purification of the mixed salt which includes removing the NaCl by the less desirable method of reverse flotation involving the use of organic chemicals, (ii) lack of any mention of the manner in which the various effluent streams are treated, and (iii) dependence on external KCl, since no mention is made of any process for the production of KCl as part of the process.

JH Hildebrand ("Extraction of Potash and Other Constituents of Mother Water from Seawater", Journal of Industrial and Engineering Chemistry, vol 10, no.2, 1918 pp 96-106), describes theoretical aspects of the recovery of potash from from a water mother of the sea and proposes a process for the extraction. According to this process, the mother liquor evaporates at a temperature between 100-120 ° C, thus forming a solid mixture of sodium chloride and kieserite (MgS04.H20), separating this mixture under hot conditions in a heated centrifuge and cooling the mother liquor in a cooler for the separation of the carnallite. The carnallite is decomposed and washed with water to produce potassium chloride. The disadvantages of this process is that it is demanding in terms of energy requirements and pure carnallite can not be obtained. The main disadvantage of the process is the contamination of the kieserite with NaCl, which would need additional purification to obtain the products in a commercial form. Another disadvantage of the process is that it requires energy to remove the sulphate from the mother liquor in the form of kieserite, whereas it would be preferable to use the sulfate in the production of SOP. D. J. Mehta et al ("Production of Potassium Sulphate from Mixed Salt obtained from the Salt Works of Little Rann of Kutch Salt Research &Industry, 52-370 Vol. 2, No. 4, October 1965) describe a process using the flotation technique for the production of potassium sulphate from two types of mixed salt, available from the salt works of Little Rann in Kutch. The process suffers from the disadvantage of lack of suitability when seawater with a high sulfate content is used and the need for flotation by foam, which is expensive, problematic and polluting. Reference is made to the Chapter in the Ullmann Encyclopedia of Industrial Chemistry, Sixth Edition, 2002 (Electronic Version), which deals with the Magnesium Compounds written by Margarete Seeger, Walter Otto, Wilhelm Flich, Friedrich Bickelhaupt and Otto. S. Akkerman, where the process of preparation of magnesium hydroxide in seawater is described. It is mentioned therein that the preparation of magnesia containing low boron content requires the excessive liming of seawater up to a pH of 12 to maintain the B203 content of less than 0.05% in the magnesia. Excessive liming involves a higher cost of lime, the need for neutralization of the supernatant, and results in a colloidal suspension that is more difficult to filter. Another disadvantage not overcome is the formation of an effluent that contains calcium chloride, which is discharged back into the sea. Patent Application No. 423211, CA 1203666, of 52-370 Wendling et al, entitled "Process for the manufacture of potassium sulphate by treating a solution containing magnesium chloride and potassium chloride", describes a process for the production of potassium sulfate from solutions containing chloride of magnesium, such as solutions of a carnalite ore and, in particular, mother liquors in equilibrium of a unit for the treatment of carnallite. According to this process, sodium sulfate and potassium chloride are added to the solutions containing magnesium chloride, to precipitate sodium chloride and schoenite, K2S04MgS046H20, and the schoenite obtained is treated in a known manner to produce potassium sulfate. The main disadvantage of the process is the need for external sodium sulfate and the lack of any mention of a solution to the problem of KCl loss in the effluent streams. H. Gurbuz et al. ("Recovery of Potassium Salts from Mother Water by Crystallization of Potassium Pentaborate" in Separation Science &Technology, 31 (6), 1996, pp. 857-870) describe the preparation of sodium pentaborate from the Tincal reaction and of H3B03 recycled in the presence of water and subsequently treated with mother liquor to selectively precipitate the potassium pentaborate, which, in turn, is acidified with sulfuric acid and fractionally crystallized to 52-370 eliminate the K2S04 and recycle the H3BO in the process. The main disadvantages of the process are that the mother liquor contains significant amounts of boron, which implies an elaborate procedure to recover the boron, and in addition, the MgO obtained from such mother liquor would not be suitable for industrial use. In addition, although such a process can still be thought of for mother water deficient in sulfate, it would not be the preferred route when the mother liquor is rich in sulfate content. Yet another disadvantage is the need to cool the acidified product for high yield. A. S. Mehta (Indian Chemical Engineer, 45 (2), 2003, p.73) describes a process for the manufacture of bromine from mother liquor. The mother liquor is acidified with sulfuric acid at a pH of 3.0-3.5 and the bromide ion is then oxidized with chlorine and purified with the help of steam. The de-brominated acid mother liquor is neutralized with lime, the sludge thus formed is removed and the effluent is discharged. Bromine plants located in the vicinity of the natural salt beds in the Greater Rann of Kutch in Gujarat, India, use the natural mother water for bromine production by the above method and discharge their effluents back into the Rann. The disposal of the mud poses a formidable challenge for these plants. Chr. Balarew, D. Rabadjieva and S. Tepavitcharova 52-370 ("Improved Treatment of Waste Brines", International Symposium on Salt 2000, page 551-554), describes the recovery of marine chemicals. The authors describe the use of lime for the precipitation of Mg (OH) 2 from a part of the available mother water, and the desulfation of the remaining mother water with the resulting solution of CaCl2 for the recovery of KCl via carnallite. The authors have not discussed any scheme to use such a methodology for SOP production of sulfate-rich mother liquor. Furthermore, as will be apparent subsequently, the Mg (OH) 2 produced directly from the untreated mother liquor has a much higher B203 content compared to the Mg (OH) 2 prepared from the Mg2 + source of the present invention, which is related with the production of SOP. Chinese Patent No. 1084492, Lu Zheng, describes a SOP manufacturing process of mother liquor and potassium chloride. In this process, the mother liquor is processed by evaporation, cooling, flotation, and then reacted with potassium chloride to make the potassium sulfate and the byproducts of the industrial salt and the residual brine. The main disadvantages of this process are that involved separation techniques are required such as flotation to remove NaCl from the mixed salt and the KCl required for the production of SOP from the schoenite has to 52-370 seek separately. Furthermore, although the total yield in terms of potash recovery is 95%, the yield with respect to such procured KCl is not mentioned.

OBJECTS OF THE INVENTION It is an important object of the present invention to produce a superior fertilizer, SOP, from sulfate-rich mother water sources, such as seawater mother and natural mother water, in an effective cost manner, through integration with the production of valuable co-products. Another object is to eliminate the need for flotation to remove the NaCl from the mixed salt and instead, leach the NaCl in the mother liquor (SEL) and simultaneously, convert the kainite into schoenite. Another object is to produce an SOP from schoenite under environmental conditions through the known method of reaction with KCl in the presence of water and where the MOP is generated from the SEL, eliminating the need to provide it externally. Another object is to maximize the recovery of potash in the form of SOP from a mixed salt. Another object is to desulfurize the SEL effectively in cost to encourage the formation of carnallite. 52-370 Another object is to evaporate the desulfated SEL in a multi-effect evaporator to recover the water for reuse. Another object is to use the separated NaCl as an edible salt. Another object is to use the decomposed liquor of carnallite (CDL or carnalli te decomposed liquor) rich in MgCl2 for the effective production in cost of CaCl2 and Mg (OH) 2 through the treatment with lime. Another object is to use the filtration washes of Mg (0H) 2 for the preparation of slaked lime from quicklime to conserve water and recycle CaCl2 in the washes. Another object is to use the above CaCl2 solution for the desulfation of the SEL. Another object is to recover the KCl that is lost in the CDL, recycling the latter in the manner described above. Another object is to demonstrate that the MgO produced from the above Mg (OH) 2 contains very low levels (< 0.03%) of B203 impurities. Another purpose is to minimize the generation of effluents in the process and instead of using the effluent to improve the recovery of potash or convert it to value-added products. 52-370 Another object is to replace the slaked lime conventionally used with Mg (OH) 2 generated in the process of the invention for the neutralization of the debrominated acidic mother liquor to eliminate the formation of sludge when acids such as sulfuric acid are used. they use for the acidification of the mother water and instead, make such mother liquor immediately useful for the production of the mixed salt.

SUMMARY OF THE INVENTION The present invention provides an integrated process for the preparation of potassium sulfate from mother liquors, comprising: (i) subjecting the mother liquor to fractional crystallization to obtain mixed salt of the kainite type with a high content of kainita and the final mother water in MgCl2, and subjecting the final mother liquor rich in MgCl2 to desulfurization; (ii) treating the mixed salt of the kainite type with the water and the mother liquor obtained in step (xiii) below to leach substantially all the NaCl from the mixed salt and simultaneously convert the kainite into schoenite, - (iii) filter the schoenite and separating the filtrate; (iv) desulfate the filtrate with aqueous CaCl2; (v) filter the gypsum produced in step (iv) and 52-370 mix the filtrate with the MgCl2-rich filtrate obtained in step (vii) below, (vi) evaporate the solution resulting from step (v) and cool to room temperature to crystallize the crude carnallite, (vii) centrifuge the carnallite raw and recycle the required amount of filtrate to step (v), (viii) decompose the raw carnalite with an appropriate amount of water from step (vi) to provide the crude KCl and the decomposed liquor of the carnallite; (ix) filter the crude KCl, and wash with water to remove the MgCl2 that adheres and subject to hot leaching for the production of MOP and NaCl, (x) mix the decomposed liquor of the carnallite from step (viii) and wash from step (ix) and treat with hydrated lime, (xi) filter the suspension and wash the cake to produce Mg (OH) 2 and CaCl2- which contains the filtrate for the desulphation process of step (iv). (xii) treat by a known method the schoenite produced in step (iii) with the MOP produced in step (ix) to produce the SOP under ambient conditions, (xiii) filter the SOP and collect the mother liquor separately, hereinafter referred to as KEL, 52-370 (xiv) recycle the KEL of step (xiii) in the process of step (ii). It can be noted that certain steps of the previous process are triggered initially with the CaCl2 and the water procured externally and subsequently, these are generated to a large extent in the process of the invention as described above. In one embodiment of the present invention, the mother liquor of density in the range of 29-34 ° Be '(specific gravity of 1.25-1.31) is used for the production of mixed salt, as described in the prior art and then converts into schoenite with the simultaneous leaching of NaCl from the solid mass. In another embodiment of the present invention, the mixed salt is treated with a ratio of 0.3-0.5: 1 of water and KEL rich in KCl and MgSO4 and with low content of NaCl and MgCl2 to minimize the K loss of the salt mixed without preventing the transformation of kainite into schoenite and leaching the NaCl from the mixed salt. In another embodiment of the present invention, the schoenite is reacted with the MOP and water in a ratio of 1: 0.3-0.6: 1.2 to produce the SOP and the KEL and where the MOP is produced in itself from the SEL . In another modality of the present process, MOP is produced from carnallite, which, in turn, is obtained from 52-370 through the desulfation of the SEL, the treatment with 400- 440 g / L of MgCl2 liquor in the ratio of 1 part of desulfated mother water and 0.7-0.9 parts of MgCl2 liquor, and forced evaporation until the solution reaches a temperature of 120-128 ° C at atmospheric pressure. In another embodiment of the present process, the filtrate obtained after the removal of NaCl is cooled to room temperature, after which the carnallite is obtained after filtration, while the filtrate contains 400-440 g / L of MgCl 2 and is recycled again towards a fresh batch of desulfated SEL for the additional production of carnallite. In another embodiment of the present process, the wet carnallite is treated with water in a ratio of 1: 0.4-0.6 to obtain the crude KCl. In another embodiment of the present process, the magnesium chloride in the decomposed liquor of carnallite is supplemented with MgCl 2 in the final liquor and treated with lime to produce Mg (OH) 2 and the required amount of calcium chloride solution (concentration 20-30% weight / volume) for the desulfation of SEL. In another embodiment of the present process, Mg (OH) 2 is calcined in the temperature range of 800-900 ° C to produce MgO with < 0.04% of B203. In another modality of the present process, the 52-370 requirement of fresh water is kept to a minimum by recycling the water from the forced evaporation step along with the wash generated in the purification of the gypsum, Mg (OH) 2 and KCl. In another embodiment of the present process, the acidified de-brominated mother liquor, which is an ideal raw material for the mixed production, is neutralized with crude Mg (OH) 2, instead of lime to eliminate the formation of sludge.

DETAILED DESCRIPTION The main inventive step is the recognition that the transformation step of the kainite in the salt mixed in schoenite and the leaching of the NaCl from the mixed salt can be carried out simultaneously in a single operation with a minimum loss of KCl in the mixed salt . Another inventive step is safe self-operation, where the need for external MOP is minimized, producing it instead of waste filtrate from schoenite manufacture. Another inventive step is the desulfation of the SEL required for the production of MOP using the calcium chloride generated in itself from the MgCl 2 in the desulfated SEL which is shown as MgCl rich streams of decomposed liquor of the carnallite and the final liquor. Another inventive step is the coupling of the production of Mg (OH) 2 with the desulfation of the SEL and eliminating 52-370 therefore, the problem of the handling of the CaCl2 waste found in another way in the production of Mg (OH) 2 from the brine or the mother water. Another inventive step is the use of CDL mainly for the production of Mg (OH) 2, which greatly reduces the impurity of B203 in Mg (OH) 2 and, as a result, in the MgO obtained from it. Another inventive step is the local use of crude Mg (OH) 2 for the neutralization of the debrominated acidified mother liquor before the production of the mixed salt. Another inventive step is the recycling of liquid effluents to minimize the requirement for fresh water, while simultaneously improving recoveries and addressing the problem of effluent disposal. The following examples are given by way of illustration and should not be construed as limiting the scope of the present invention.

EXAMPLE 1 In a typical process, 200 M3 of a sea mother water of 29.5 ° Be '(specific gravity of 1.255) were subjected to solar evaporation in a lined tundish. The first fraction (20 Tons) containing mainly raw salt was removed at 34 ° Be '(specific gravity of 1,306). The mother liquor was further evaporated at 35.5oBe '(specific gravity of 1324) and the mixture fraction of six (15 tons) was separated. The resulting mother water (100 M3) 52-370 transferred to a second lined tundish and solar evaporation continued until 16 tons of the mixed salt of the kainite type and 26 M3 of the final mother water were obtained. The mixed salt was further processed for the production of schoenite as described in the following examples, while a part of the final mother liquor was desulfatized with external calcium chloride to generate the final desulfated mother liquor. A portion of the final desulfated mother liquor was subsequently treated with hydrated lime to produce calcium chloride and magnesium hydroxide. The calcium chloride solution was filtered and used for the desulfation of the SEL of Example 6. The other part of the final desulphated mother water was used as a source of MgCl2 in the same example to promote the formation of carnallite from the desulfated SEL. Similar experiments were also carried out with other sources of mother water such as mother water from the subsoil and mother water obtained after recovery of the bromine.

EXAMPLE 2 142.0 kg of mixed salt of the kainite type, which has the chemical composition: KC1-15.5%, NaCl-14.6%, MgSO4-39.5% and, was treated with 140 L of water and stirred during 2. 5 hours in a container. The suspension was filtered using a basket centrifuge and provided 32.0 kg of schoenite as a solid product, analysis K2SO-38.0%, MgSO4-30.2% and NaCl-1.2%, and 200 L of the filtrate (SEL), analysis KC1-7.6, NaCl -16.1%, MgSO4-21.1% and MgCl2-8.4%. The schoenite was treated with a solution of 12.5 kg of MOP in 49.0 L of water under stirring for 3.5 hours. The suspension was filtered to obtain 16.0 kg of SOP, analysis K2SO4-95.0%, NaCl-1.0%, MgSO4-1.0% and 60 L of filtrate (KEL), analysis KCl-15.0%, NaCl-1.5%, MgSO4-9.7% and MgCl2-3.9%.

EXAMPLE 3 60.0 kg of the mixed salt having the same composition as in Example 2 was taken together with the KEL obtained in Example 2. 27 L of water were further added and the contents were stirred for 2.5 hours. The suspension was filtered in a centrifuge to obtain 26.0 kg of schoenite, analysis K2S04-39.7%, MgSO4-29.5%, NaCl-0.7%, and MgCl2-0.6% and 95.0 L of filtrate (SEL), analyzed as KCl-9.9% , NaCl-13.0%, MgSO4-18.6% and MgCl2-6.0%. The schoenite was reacted with a solution of 10.4 kg of MOP in 38 L of water in a vessel under stirring for 3.5 hours. The resulting suspension was filtered using a centrifuge to obtain 14.5 kg of SOP, analysis K2S0-98.1, NaCl-0.2%, MgSO4-1.4% and 45 L of the filtrate (KEL) analyzed as K2S04-12.4%, KC1-6.15%, NaCl -0.9%, MgSO4-l0% and MgCl2-10.2%. 52-370 EXAMPLE 4 104 kg of the mixed salt, analysis KC1-14.1%, NaCl-16.5%, MgSO4-41.6%, were reacted with 100 L of KEL, analyzed as K2S04-13.9%, NaCl-2.8% and MgCl2 -11.6%, and 40 L of water for 2 hours. The suspension was centrifuged to obtain 34.8 kg of schoenite, analysis K2SO4-37.0%, MgSO4-30.3% and NaCl-4.9% and 190.0 L of filtrate (SEL), analyzed as KCl-9.5%, NaCl-13.0%, MgSO4-15.1 %, MgCl2-8.0% and (sic). The schoenite was further reacted with a solution of 12.5 kg of MOP in 46.0 L of water for 3.5 hours to provide 17.5 kg of SOP and 80 L of KEL. SOP analyzed as K2S04-97.3%, NaCl-0.2% and MgSO4-3.0% and KEL as KCl-16.7%, NaCl-1.3%, MgSO4-11.0%, and MgCl2-2.7%.

EXAMPLE 5 In this experiment, 150.0 kg of mixed salt, analyzed as KC1-13.1%, NaCl-19.8%, MgSO4-38.0%, MgCl2-1.9% and (sic), were taken in a vessel together with 160 L of KEL, analysis KC1-17.0%, NaCl-3.3%, MgSO4-9.0%, MgCl2-1.9% and 60 L of water and stirred for 2 hours. The resulting suspension was centrifuged to obtain 49.9 kg of schoenite, analysis K2SO4-42.0%, MgSO4-32.2%, NaCl-0.7% and 255 L of filtrate (SEL), analyzed as KC1-10.5%, NaCl-12.3%, MgSO4-13.7%, MgCl2-6.70%. The schoenite was reacted with a solution of 19.0 kg of MOP in 75 L of water for 3.5 hours in a vessel with continuous agitation. The suspension was centrifuged to obtain 27.0 kg of SOP, analyzed as K2S04-94.3%, NaCl-0.2% and MgS04-3.7%, and 85 L of filtrate (KEL), analyzed as KC1-15.5%, NaCl- 0.8%, MgSO4 -10.5% and MgCl2-3.0%.

EXAMPLE 6 59 L of the final desulphated mother liquor obtained in Example 1, having the chemical composition: KCl-1.15%, NaCl-1.3%, MgCl2-41.2%, CaS04-traces were diluted with 40 L of water and treated with 14.7 kg of freshly prepared hydrated lime (active concentration of 87.7%) for 1 hour. The resulting suspension was filtered and the cake was washed with 30 L of water. 90 L of the total filtrate were obtained, containing CaCl2-22.3% and MgCl2-3.0%. The solid magnesium hydroxide was further washed with 100 L of water to liberate it from the insoluble impurities. 15.7 kg of Mg (OH) 2 with a content of 86.9% Mg (OH) 2 were obtained by drying in a tray dryer. A portion of Mg (OH) 2 was calcined at 850 ° C providing 90.0% MgO. The 90 L filtrate containing 22.3% CaCl 2 was used to desulfate 90 L of SEL obtained in Example 3. The resulting suspension was filtered to obtain 142 L of desulfated SEL and 21.0 kg of gypsum as a by-product. 57 L of 52-370 desulphated SEL were mixed with 41 L of desulfated final mother liquor of Example 1 having an Mg concentration of 10.3%. The resulting solution was subjected to forced evaporation in an open-pan evaporator until the solution reached a boiling point of 120 ° C. The hot liquor was filtered to remove 5.5 kg of crude NaCl having the composition: 85% NaCl, 2.9% KCl and 12.1% MgCl2. The filtrate was cooled in a tank to crystallize the carnallite. The resulting suspension was filtered to obtain 11.3 kg of carnallite, analyzed as KCl-21.7%, NaCl-9.7%, MgCl2-31.4% and CaS04-2.7% and 48 L of final mother water, analyzed as MgCl2-40.2%, KCl- 0.8%, NaCl-1.1%. 9.2 kg of carnallite was decomposed using 3.6 of water and filtered to obtain 8.0 L of the decomposed lichen of the carnallite (CDL) having the chemical composition: KCl-4.6%, NaCl-2.8%; MgCl2-30.5%; CaS04-traces and 2.9 kg of CDP having the chemical composition: KCl-75.3%, NaCl-20.2%, MgCl2-2.0% and CaS04-2.5%. The CDP was treated with 1.9 L of water at room temperature (30 ° C) to obtain 2.0 kg of KCl having the composition: KCl-90.0%, NaCl-3.3%; MgCl2-0.4% and CaSO4-6.0 and 2.2 L of saturated solution having the chemical composition KCl-14.0% and NaCl-20.0%.

EXAMPLE 7 Of 10 L of CDL obtained in the experiment 52-370 above, 5.7 L of the cold leachate with the crude salt produced in the previous example, were also washed to recover the magnesium content in them, which has the chemical composition: KCl-7.0%, NaCl-8.2%, MgCl2 -21.5%, and CaS0 -traces, and 15 L of water were treated with 2.5 Kg of freshly prepared hydrated lime that has an activity of 90%, for 1 hour. The resulting suspension was filtered and the solid cake was washed with 10 L of water to obtain 34 L of the filtrate containing 7.7% CaCl2. The solid magnesium hydroxide was further washed with 30 L of water to liberate it from the soluble impurities. The Mg (0H) 2 was dried to obtain 2.3 Kg of Mg (0H) 2, which was calcined to obtain the MgO, analyzed as 92% MgO containing 0.034% of B203 as impurities. 34 L of CaCl2 containing brine, were used to desulfate 17 L of SEL having the chemical composition KCl-7.2%, NaCl-12.4%, MgSO4-16.0% and MgCl2-6.5%. The resulting suspension was filtered to remove 5.2 kg of wet calcium sulfate and obtain 49 L of desulfated SEL having an Mg content of 2.03%. 75 L of final mother liquor having an Mg concentration of 9.6%, obtained from the previous experiment, were added to the desulfated SEL. The mixture of the resulting solution was subjected to forced evaporation in an open-pan evaporator until the boiling point of the solution is 126 ° C. The hot liquor 52-370 was cooled in a tank to crystallize the carnallite. The resulting suspension was filtered to obtain 18.8 kg of carnallite having a chemical composition: KCl-14.3%, NaCl-12.7%, MgCl2-31.9% and CaS04-1.9% and 46.5 L of final mother liquor having a chemical composition of MgCl2. -46.1%, KCl-0.2%, NaCl-0.5%. 18.8 kg of carnallite were decomposed using 8 L of water and filtered to obtain 15.5 L of CDL having a chemical composition of: KCl-4.8%, NaCl 3.2%, MgCl2-32.5% and CaS04-traces and 5.7 kg of CDP It has a chemical composition of: KCl-33.9% and NaCl-46.3%, MgCl2-1.4%, CaS04-5.1% and Humidity-13%. The CDP was subjected to hot leaching together with the CDP obtained in the following example, by a known method for separating the KCl as detailed below.

EXAMPLE 8 15.5 L of the CDL obtained in the previous experiment, which has the chemical composition: KCl-5.0%, NaCl-3.2%, MgCl2-32.5% and CaS04-traces and 15 L of water, were treated with 3.0 kg of hydrated lime recently prepared, which has an activity of 90.0%, for 1 hour. The resulting suspension was filtered and the solids were washed with 10 L of water to obtain 27.5 L of filtrate, containing 10.60% CaCl2. The solid magnesium hydroxide was further washed with 30 L of water to liberate it from the 52-370 soluble impurities. Mg (OH) 2 was dried to obtain 2.9 kg of Mg (OH) 2 and subsequently calcined to obtain calcined caustic MgO, which has an MgO content of 95% and 0.03% of B03 as impurities. The solution containing CaCl2 was used to desulfate 25 L of SEL having the chemical composition KCl-7.2%, NaCl-12.4%, MgSO4-16.0% and MgCl2-6.5%. The resulting suspension was filtered to remove 5.7 kg of calcium sulfate and obtain 46 L of desulfated SEL having a Mg content of 3.05%. 33 L of final mother liquor having an Mg concentration of 11.8%, obtained from the previous experiment, was added to the desulfated SEL. The mixture of the resulting solution was subjected to forced evaporation in an open-pan evaporator until the boiling point of the solution is 125 ° C. The hot liquor was cooled in a tank to crystallize the carnallite. The resulting suspension was filtered to obtain 14 kg of carnallite having the chemical composition: KC1-15.0%, NaCl-24.7%, MgCl2-25.1%, and CaSO4-4.0% and 33.8 L of final mother liquor having the chemical composition: MgCl2-44.8%, KCl-0.1% and NaCl-0.46%. 14.0 kg of carnallite were decomposed using 6.3 L of water and filtered to obtain 12 L of CDL having the chemical composition: KCl-5.6%, NaCl-4.4%; MgCl2-27.6% and CaS04-traces and 5.0 kg of CDP having the chemical composition: KCl-26.1% and NaCl-51.1%, MgCl2-7.1%, CaS04-5.1% and 52-370 humidity-9.0%. The CDP obtained together with the CDP of Example 7 weighing 10.8 kg, was subjected to hot leaching by a known method to obtain 3.5 kg of MOP having a content of 93.6% KCl.

EXAMPLE 9 In this example, the MOP produced in Example 8 above was used to prepare the SOP. 9.0 kg of the mixed salt of the kainite type, analyzed as KCl-14.2%, NaCl-16.5%, MgSO4-40.2%, MgCl2-1.2%, was reacted with 8 L of water for 2 hours. The suspension was centrifuged to obtain 3.0 kg of schoenite, analyzed as KS04-35.5%, MgSO4-31.0% and NaCl-3.3% and 9.5 L of the filtrate (SEL) analyzed as and KCl-7.6%, NaCl-12.6%, MgSO4- 15.1%, MgCl2-9.5%, 0.488 kg of schoenite were further reacted with the 0.190 kg MOP solution (from the one obtained in Example 8 above) in 0.753 L of water for 3.5 hours to provide 0.255 kg of SOP and 0.860 L of KCl. The SOP was analyzed as K2SO4-93.0%, NaCl-0.6%, MgSO4-5.4% and KEL as KCl-14.8%, NaCl-1.4%, MgSO4-7.7%, MgCl2-4.1%. 52-370

Claims (21)

1. CLAIMS: 1. An integrated process for the preparation of potassium sulphate (SOP) from mother liquor, comprising: (i) submitting the mother liquor for fractional crystallization to obtain mixed salt of the kainite type with a high content of kainite and the final mother liquor rich in MgCl2, and subjecting the final water rich in MgCl2 to desulfurization; (ii) treating the mixed salt of the kainite type with the water and the mother liquor obtained in step (xiii) below to leach substantially all the NaCl from the mixed salt and simultaneously convert the kainite into schoenite; (iii) filter the schoenite and separate the filtrate; (iv) desulfate the filtrate with aqueous CaCl2; (v) filtering the gypsum produced in step (iv) and mixing the filtrate with the MgCl 2 -rich filtrate obtained in step (vii) below, (vi) evaporating the solution resulting from step (v) and cooling to room temperature to crystallize the raw carnallite, (vii) centrifuge the raw carnallite and recycle the required amount of filtrate to step (v), (viii) decompose the raw carnallite with an appropriate amount of water from step (vi) to provide the i 52-370 Crude KCl and the decomposed liquor of carnallite; (ix) filter the crude KCl, and wash with water to remove the MgCl2 that adheres and subject to hot leaching for the production of MOP and NaCl, (x) mix the decomposed liquor of the carnallite from step (viii) and wash Step (ix) and treat with hydrated lime, (xi) filter the suspension and wash the cake to produce Mg (OH) 2 and CaCl2- containing the filtrate for the desulfation process of step (iv). (xii) treat by a known method the schoenite produced in step (iii) with the MOP produced in step (ix) to produce the SOP under ambient conditions, (xiii) filter the SOP and collect the mother liquor separately, hereinafter referred to as KEL, (xiv) recycle the KEL of step (xiii) in the process of step (ii).
2. 2. The process according to claim 1, wherein the mother liquor contains K, Mg and S0 in concentrations that are suitable for the production of kainite.
3. 3. The process according to claim 2, wherein the mother liquor is selected from sea mother water and subsoil mother water, and preferably mother water with a high potassium content and which also requires the 52-370 minimum evaporation to produce the mixed salt of the kainite type, and sources of waste mother water such as an effluent of de-brominated mother liquor.
4. 4. The process according to any of claims 1 to 3, wherein the mixed salt contains 15-22% KCl, 15-22% NaCl, 28-40% MgSO4, 5-10% MgCl2.
5. The process according to any preceding claim, wherein one part by weight of the mixed salt is treated with 0.75-1.25 parts by volume of KEL and 0.3-0.7 parts by volume of water.
6. The process according to any preceding claim, wherein the KEL typically contains 15-17% KCl, 1-3% NaCl, 10-12% MgSO4 and 2-3% MgCl2.
7. The process according to any preceding claim, wherein the SEL typically contains 8-10% of KCl, 6-12% NaCl, 12-14% MgSO4 and 5-7% MgCl2.
8. The process according to any preceding claim, wherein the schoenite typically contains 40-45% K2SO4, 30-35% MgSO4 and 0.5-2.0% NaCl.
9. The process according to any preceding claim, wherein the stoichiometric ratio of CaCl 2 to sulfate for the desulphation reaction of step (iv) is from 1.1: 1 to 0.9: 1, preferably 1: 1.
10. The process according to claim 7, wherein 1 part by volume of the desulfated SEL is mixed with 0.5-1.5 52-370 parts by volume of final mother liquor rich in MgCl2 of 36-38 ° Be '(specific gravity of 1.33-1.38), preferably 0.7-0.9 parts of final mother water of 37 ° Be' (specific gravity of 1342), and more preferably, final mother liquor rich in MgCl2 that does not contain sulfate.
11. 11. The process according to any of claims 1 to 10, wherein the concentration of the desulfated SEL to produce the carnallite, is carried out in a solar pan or in a multiple effect evaporator with simultaneous water recovery.
12. The process according to any preceding claim, wherein the evaporation continues until a temperature in the range of 120-128 ° C and more preferably 122-124 ° C is reached.
13. The process according to any preceding claim, wherein the obtained carnallite has 15-20% KCl, 15-20% NaCl and 28-32% MgCl2.
14. The process according to any preceding claim, wherein one part by weight of the carnallite is decomposed with 0.4-0.6 parts by volume of water, followed by washing the cake with a small amount of water.
15. The process according to any preceding claim, wherein the molar ratio of active lime to MgCl 2 for the production of Mg (OH) 2 and CaCl 2 is in the range of 0.8-1.0, preferably 0.90. 52-370 16.
16. The process according to any preceding claim, wherein the Mg (OH) 2 obtained is calcined to produce the MgO with 94-98% purity and with 0.02-0.04% B203.
17. The process according to any preceding claim, wherein the Mg (0H) 2 is used without over-degradation for the neutralization of acidified debrominated mother liquor, where the mother liquor is used as a source of potash.
18. The process according to any preceding claim, wherein the MOP obtained after the hot leaching of the crude KCl, has a purity in the range of 92-98% and a NaCl content of 1-5%, preferably > 95% KCl and < 2% NaCl.
19. 19. The process according to claims 1-3, wherein the NaCl obtained with the hot leaching of the crude KCl contains > 97% NaCl.
20. The process according to any preceding claim, wherein one part by weight of the schoenite is treated with 0.3-0.6 parts by weight of MOP and 1-2 parts by volume of water, and more preferably 0.4 parts by weight of MOP. and 1.5 parts by volume of water, in the range of room temperature of 20-45 degrees C.
21. 21. The process according to any preceding claim, wherein the SOP produced has a K20 content in the range of 50-52% and chloride in the range of 0.5-2.0%. 52-370