CN108455636B - Method for producing sodium chloride and magnesium sulfate monohydrate by using high-salt high-sulfur brine - Google Patents

Method for producing sodium chloride and magnesium sulfate monohydrate by using high-salt high-sulfur brine Download PDF

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CN108455636B
CN108455636B CN201810081748.7A CN201810081748A CN108455636B CN 108455636 B CN108455636 B CN 108455636B CN 201810081748 A CN201810081748 A CN 201810081748A CN 108455636 B CN108455636 B CN 108455636B
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magnesium sulfate
evaporation
salt
sulfate monohydrate
magnesium
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CN108455636A (en
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周桓
唐晶晶
郭建
李光壁
白晓琴
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Tianjin University of Science and Technology
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    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F5/00—Compounds of magnesium
    • C01F5/40—Magnesium sulfates
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    • C01P2004/03—Particle morphology depicted by an image obtained by SEM
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
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Abstract

The invention relates to a method for producing sodium chloride and magnesium sulfate monohydrate by high-salt high-sulfur brine, which adopts an evaporation desalting means to obtain chlorine-containing high-concentration magnesium-extracting raw material liquid at 50-80 ℃, wherein the magnesium-extracting raw material liquid meets Cl‑：SO4 2‑The molar ratio was 3.15 to 6 and Mg2+∶Na+The molar concentration ratio is 2-4.1. And (3) carrying out high-temperature evaporation at the temperature of more than 80 ℃, determining the evaporation end point according to the evaporation pressure and the boiling point temperature, using boiling point rise as a control index, wherein the boiling point rise range is 13-18 ℃, carrying out solid-liquid separation on the evaporation completion liquid at the temperature of more than 70 ℃ to obtain a magnesium sulfate monohydrate crystallization wet solid phase, cleaning the magnesium sulfate monohydrate crystallization wet solid phase by adopting a mother liquor replacement or alcohol washing mode, and removing chlorine components to obtain the magnesium sulfate monohydrate crystal. The method is easy for solid-liquid separation, and the product has high purity and good fluidity.

Description

Method for producing sodium chloride and magnesium sulfate monohydrate by using high-salt high-sulfur brine
Technical Field
The patent belongs to the field of salt separation and comprehensive utilization of brine resources, salt-containing wastewater and mixed salt materials, and relates to a method for producing low-chlorine magnesium sulfate monohydrate, in particular to a method for producing sodium chloride and magnesium sulfate monohydrate by using high-salt high-sulfur brine.
Background
Production method of sodium chloride and magnesium sulfate in comprehensive utilization of brine resources
At present, two modes of solarization evaporation salt preparation or solarization saturated brine vacuum evaporation salt preparation are widely adopted for preparing salt by seawater. The salt making mother liquor of the two salt making modes is either discharged or comprehensively utilized by utilizing the traditional method. The use of a venting means is environmentally unfriendly. The traditional comprehensive utilization mode is centered on the production of potassium chloride by a halogen-adding method, and the main products comprise potassium chloride, magnesium chloride (halogen tablets and halogen powder), sodium sulfate, bromine and the like. The concentration ratio of magnesium sulfate to magnesium chloride in brine is reduced and the ratio of magnesium chloride to potassium chloride is increased by adding bromine-extracting mother liquor containing magnesium chloride as main component, the mixed brine after brine addition is evaporated at above 100 deg.C to fully separate out sodium chloride and magnesium sulfate, and the mixed salt containing sodium chloride and magnesium sulfate monohydrate as main components is separated out by heat-insulating sedimentation, commonly called high-low temperature salt. The clear liquid is further cooled to separate out carnallite, and the carnallite is decomposed to produce potassium chloride. The carnallite mother liquor is further used for extracting bromine and producing magnesium chloride.
The high and low temperature salt begins to be used only as waste salt and is separated later to produce magnesium sulfate monohydrate. The separation method is performed in 60-70 s by dissolution freezing method or hot dissolution method. In the 80-90 s, by utilizing the obvious difference of the crystal particle size of the magnesium sulfate monohydrate and the sodium chloride monohydrate in the high-temperature and low-temperature salts, the mixed salt separated by high-temperature evaporation is separated into magnesium sulfate monohydrate slurry (magnesium milk) and sodium chloride slurry by adopting a physical method, such as a vibration method, an overflow method, a cyclone method and the like, the obtained magnesium sulfate and sodium chloride have low quality, and the magnesium sulfate contains a large amount of sodium chloride. Niuguaye (1994) developed a process for separating high temperature salt using a cyclone and decanter centrifuge. The magnesium milk obtained by separating the mixed salt slurry contains mainly magnesium sulfate, but contains fine salts and an evaporation mother liquor, the magnesium milk is directly filtered, and the mother liquor in the magnesium milk is pushed off by water, but the magnesium sulfate is easy to dissolve, so that the loss of the magnesium sulfate is large.
Glasett (1970) produced magnesium sulfate by evaporating seawater to a concentration of greater than 4% by mass magnesium by the solarization process, adding 10% by volume of brine in clear water, and cooling to-5 deg.C.
Fernandez-Lozano (1974) adds 5% clear water by volume to sun bittern with specific gravity of 1.30g/l, cools to-5 deg.C, and recovers 70% of magnesium sulfate in the bittern. The magnesium sulfate was washed with cold water and dried at 70 ℃ to have a magnesium sulfate heptahydrate content of 96%.
Arakel (1993) differs from Fernandez-Lozano in that a sun bittern with a specific gravity of 1.28-1.30g/l is cooled to 0 ℃ to-5 ℃ to obtain crude magnesium sulfate, which is dissolved in hot water and evaporated to a specific gravity of 1.28-1.30g/l and then crystallized at 20-25 ℃.
Patent DE10256046 of BACH JUERGEN (2004) uses bittern to produce sodium chloride and magnesium sulfate heptahydrate. Two sets of two-effect evaporation devices are adopted. Adding the circulating mother liquor to increase the ratio of magnesium sulfate to magnesium chloride to 0.25-0.5, evaporating and concentrating by using a first set of device until the magnesium sulfate is saturated, and separating the sodium chloride subjected to evaporative crystallization to obtain a refined salt product. Water was added to the evaporation-completed solution to freeze-crystallize magnesium sulfate heptahydrate. And (3) continuously utilizing the second set of evaporation device to carry out second-stage evaporation on the frozen mother liquor, removing impurity salt to purify the mother liquor, circularly returning the purified mother liquor to the raw material to adjust the ratio of magnesium sulfate to magnesium chloride, wherein the ratio of the mother liquor amount to the raw material amount is about 1: 1. in this invention, a set of two-stage evaporation crystallization equipment specially used for producing low-quality miscellaneous salt is required.
The applicant reports a method for producing sodium chloride and magnesium sulfate heptahydrate by using brine in the early stage (Chinese patent CN 200810054198.6): the method comprises the following steps: (1) bittern is used as raw material, SO in bittern4 2-∶Mg2+Is 0.1 to 0.8, and SO4 2-∶Na+The molar ratio of (A) to (B) is 0.025-1; boiling and evaporating under reduced pressure, controlling the pressure to make the boiling point temperature of 75-50 ℃ when the evaporation is finished, and making SO in the solution4 2∶Na+The molar ratio is 0.4-2.5; (2) solid-liquid separation, washing the solid phase with saturated sodium chloride water solution, and drying to obtain sodium chloride; (3) adding water into the salt making mother liquor to prepare a mixed solution; (4) cooling the mixed solution, introducing the cooled mixed solution into a crystallizer, and separating out crystals; (5) and carrying out solid-liquid separation to obtain a solid phase which is a magnesium sulfate heptahydrate crude product. The method has the advantages of simple equipment, simple process, full separation of sodium chloride, high purity and yield of magnesium sulfate heptahydrate, no impurity and salt removal link in the process, and realization of combined production of sodium chloride and magnesium sulfate heptahydrate.
In the method for producing the sodium chloride and the magnesium sulfate by comprehensively utilizing the brine, the sodium chloride and the magnesium sulfate heptahydrate or a mixture of the magnesium sulfate monohydrate and the sodium chloride can be obtained, and then physical separation is carried out. Magnesium sulfate monohydrate with low chlorine content cannot be obtained.
Second, production method of magnesium sulfate monohydrate
Magnesium sulfate monohydrate (MgSO 4. H2O) is a white powdery solid, has high sulfur and magnesium contents, is widely applied to aspects of compound fertilizer drying agents, agricultural fertilizers, feed additives and the like, and is an important basic chemical raw material for industrial and agricultural production.
At present, there are three main methods for producing magnesium sulfate monohydrate:
1. sulfuric acid process
Chinese patent (CN 1109845A) reports that concentrated sulfuric acid and magnesium-containing mineral powder (such as magnesium oxide in calcined magnesite, magnesium carbonate in raw magnesite and the like) are directly mixed to prepare magnesium sulfate monohydrate, the magnesium sulfate monohydrate prepared by the method has low purity, can only be used for agricultural fertilizers, the production equipment is seriously corroded, the product is obviously acidic, and the waste liquid has great pollution to the environment.
2. Dehydration method of magnesium sulfate heptahydrate
(1)2011 Wang Xin 31441in inorganic salt industry (2011, 43: 45-47) reports a method for preparing magnesium sulfate monohydrate by directly drying magnesium sulfate heptahydrate by a disc dryer. Chinese patents (CN 102583459A, CN 103387248A) dehydrate magnesium sulfate heptahydrate by a rotary flash dryer or a fluidized bed to prepare magnesium sulfate monohydrate. The method is greatly influenced by raw materials, and has the advantages of high energy consumption, high content of miscellaneous salt in the product and poor quality.
(2) The invention patent CN201310320368.1 discloses a method for preparing magnesium sulfate monohydrate from magnesium sulfate heptahydrate, which is characterized in that the method comprises the following steps: and (2) enabling the magnesium sulfate heptahydrate material to sequentially pass through at least two fluidized beds with gradually increased bed body temperature so as to dehydrate step by step, thereby obtaining the magnesium sulfate monohydrate, wherein the bed body temperature of the fluidized beds is in the range of 50-200 ℃. The method utilizes the multi-furnace fluidized bed to dry magnesium sulfate heptahydrate, prepares magnesium sulfate monohydrate through a step-by-step dehydration process, is easy to control the drying temperature, has good dehydration effect, simple process flow, energy conservation and environmental protection, and has excellent economic benefit.
(3) The invention patent CN201210040066.4 discloses a process for preparing magnesium sulfate monohydrate by using hydrous magnesium sulfate heptahydrate, which comprises the following steps: (i) feeding wet materials: delivering hydrous magnesium sulfate heptahydrate into a drying chamber of a rotary flash evaporation dryer; (ii) hot air conveying: heating air to 220-320 ℃, pressurizing by using a fan, and sending into a rotary flash evaporation dryer; (iii) and (3) drying: the wet material to be dried stays in a drying chamber of a rotary flash evaporation dryer for 2-6 seconds to obtain a finished product of magnesium sulfate monohydrate with free water of less than or equal to 3 wt%; (iv) discharging, tail gas treatment and emission: the dried material is sent into a discharging device by airflow, and is subjected to cyclone dust removal and water film dust removal, the dried magnesium sulfate monohydrate is collected, and the tail gas is discharged. The process for preparing the magnesium sulfate monohydrate by using the hydrous magnesium sulfate heptahydrate has the advantages of easily controlled drying temperature, short process flow, strong adaptability, continuous, stable and reliable drying process and good drying effect.
3. By evaporation of solutions
(1) The invention patent CN02155485.4 reports a production method of magnesium sulfate monohydrate, which is to evaporate a magnesium sulfate solution containing 15-35 wt% to Be' with 45-65 degrees at 30-180 ℃, separate the magnesium sulfate solution at 70-150 ℃ and then dry the magnesium sulfate monohydrate. Has the advantages of low impurity content, high product purity, low energy consumption and low production cost.
(2) The invention patent CN200810031775.X reports a method for extracting magnesium sulfate monohydrate by using mixed salt of sodium chloride and epsomite. Which comprises the following steps: (i) mixing the mixed salt of sodium chloride and epsomite; (ii) preparing ingredients according to 545-555 parts by weight of mixed salt, 246-256 parts by weight of water and 535-545 parts by weight of brine; (iii) heating the prepared mixture material to 74-76 ℃ to promote the dissolution of the mixed salt; (iv) undissolved NaCl is filtered out; (v) heating the mother liquor after filtering out undissolved NaCl to 74-76 ℃, and evaporating and concentrating until fine magnesium sulfate monohydrate and coarse sodium chloride are crystallized; (vi) filtering to obtain a mixture of fine-grain magnesium sulfate monohydrate and coarse-grain sodium chloride; (vii) sieving with 325 mesh standard sieve at 74-76 deg.C to obtain sodium chloride as oversize product and drying at 74-76 deg.C to obtain magnesium sulfate monohydrate. The invention has the advantages of mild operation condition, low energy consumption, low production cost, no waste liquid discharge and no pollution to the environment.
In the above-mentioned production method of magnesium sulfate monohydrate, the sulfuric acid method or dehydration of magnesium sulfate heptahydrate to produce magnesium sulfate monohydrate is not relevant to the present invention. In the solution evaporation method, the raw material adopted by CN02155485.4 is magnesium sulfate solution, while the raw material adopted by CN200810031775.X adopts mixed salt, the evaporated salt is still mixed salt, and the separation needs to be carried out by adopting the particle size difference, so that pure magnesium sulfate monohydrate and sodium chloride products cannot be obtained.
The invention content is as follows:
the invention aims to overcome the defects of the prior art and provide a method for directly producing sodium chloride and low-chlorine crystalline magnesium sulfate monohydrate by using high-salt high-sulfur brine through an evaporative crystallization process.
The technical problem solved comprises the following steps:
(1) the method and conditions for preparing salt by evaporating high-salt high-sulfur brine and preparing magnesium extracting solution.
(2) Method and conditions for the preparation of crystalline magnesium sulfate monohydrate by evaporation of a high chlorine solution.
(3) A method for purifying and dechlorinating magnesium sulfate monohydrate.
The technical scheme adopted by the invention for solving the technical problem is as follows:
1. scheme for producing magnesium sulfate monohydrate by vacuum evaporation of high-salt high-sulfur brine and then salt production of mother liquor
The raw material brine comprises salt-making mother liquor or contains Na as main ingredient+,Mg2+,Cl-,SO4 2-,H2Bittern of O, especially SO4 2-∶Cl-High sulfur brine with a molar ratio of greater than 0.08.
a. The composition of the raw material brine meets SO4 2-∶Mg2+Is less than 0.8, and SO4 2-∶Cl-The molar ratio is less than 0.25, and the salt can be directly evaporated to produce high-magnesium solution.
b. The composition of the raw material brine meets SO4 2-∶Mg2+When the molar ratio of (B) is more than 0.8 but less than 1, the magnesium extraction mother liquor is needed to be used as the circulating liquid.
c. The composition of the raw material brine meets SO4 2-∶Mg2+When the molar ratio is more than 1, part of sodium sulfate is removed or other brine containing high-concentration magnesium chloride is added, so that the raw material composition meets the requirements of (a) or (b).
And (3) evaporating to prepare salt, wherein a negative pressure single-effect or multi-effect continuous forced evaporation crystallization process is adopted, the salt is prepared through multi-effect evaporation, a raw material liquid enters a system in a high-boiling-point evaporation crystallizer, a mother liquid is discharged in a smooth manner, and the mother liquid is discharged out of the system in the evaporation crystallizer with the lowest boiling point temperature. Solid-liquid mixture discharged from each effect is subjected to solid-liquid separation, washing by saturated sodium chloride salt water and drying to obtain a sodium chloride product;
if the salt-making mother liquor adopts multi-effect evaporation, the mother liquor is discharged in a concurrent flow manner, and is discharged from the evaporation tank with the lowest evaporation boiling point out of the salt-making system. The salt-making mother liquor can be used as magnesium extraction brine when the following conditions are met: the boiling point of the evaporator for discharging the mother liquor is 50-75 DEG C℃，SO4 2-∶Na+A molar ratio of more than 1.0 and Mg2+∶Na+The molar concentration ratio is more than 2. The magnesium extraction brine is obtained by heat preservation separation or overflow direct discharge in an evaporation crystallization device.
Introducing magnesium-extracting raw material liquid into evaporation container, mixing with mother liquid in the container, and adding Cl into the mother liquid-：SO4 2-Molar ratio of more than 6, SO4 2-∶Na+A molar ratio of more than 0.25 and Mg2+∶Na+The molar concentration ratio is more than 2, high-temperature evaporation at the temperature of more than 80 ℃ is carried out in a high-chlorine environment, the evaporation end point is determined according to evaporation pressure and boiling point temperature, the boiling point rise can be used as a control index, and the boiling point rise is not higher than 18 ℃. Such as: the absolute pressure of 25kPa corresponds to the boiling point of water of 65 ℃, and the end temperature does not exceed 83 ℃; evaporating at normal pressure, the final temperature should not exceed 118 deg.C, evaporating at 200kPa, and the boiling point temperature should not exceed 138 deg.C. And (3) performing solid-liquid separation on the evaporated solution at the temperature of more than 70 ℃ to obtain a wet solid phase of magnesium sulfate monohydrate crystals and a wet solid phase with the mother liquor, and removing chlorine components carried in the mother liquor by adopting a mother liquor replacement or alcohol washing mode.
2. Technical scheme for obtaining crystalline magnesium sulfate monohydrate in high-chlorine environment
a. Preparing magnesium extraction raw material liquid, obtaining chlorine-containing high-concentration magnesium extraction raw material liquid at 50-80 ℃, wherein the magnesium extraction raw material liquid meets Cl-：SO4 2-A molar ratio of less than 6 and Mg2+∶Na+The molar concentration ratio is more than 2;
b. introducing magnesium-extracting raw material liquid into evaporation container, mixing with mother liquid in the container, and adding Cl into the mother liquid-：SO4 2-Molar ratio of more than 6, SO4 2-∶Na+A molar ratio of more than 0.25 and Mg2+∶Na+The molar concentration ratio is more than 2, high-temperature evaporation at the temperature of more than 80 ℃ is carried out in a high-chlorine environment, the evaporation end point is determined according to evaporation pressure and boiling point temperature, the boiling point rise can be used as a control index, and the suitable range of the boiling point rise is 13 ℃ to 18 ℃. Such as: the boiling point of water is 65 ℃ under the absolute pressure of 25kPa, and the suitable end point temperature is 78 ℃ to 83 ℃; the mixture is evaporated under the normal pressure,the end point is suitably from 113 ℃ to 118 ℃ and the boiling point is not more than 133 ℃ to 138 ℃ when evaporating at 200kPa absolute.
c. The evaporation finished solution is subjected to solid-liquid separation at the temperature of more than 70 ℃ to obtain a wet solid phase of magnesium sulfate monohydrate crystals, and impurities are mainly carried by the mother solution.
3. Method for purifying and dechlorinating magnesium sulfate monohydrate
In a high-chlorine environment, magnesium sulfate monohydrate crystals are obtained through high-temperature evaporation and crystallization, and mother liquor is entrained after solid-liquid separation, so that the chlorine content is high. The method for removing the mother liquor and the chlorine is implemented as follows:
a. the wet solid phase with the mother liquor adopts a mother liquor replacement mode or an alcohol washing mode to remove chlorine components carried in the mother liquor.
b. Mother liquor replacement means that during solid-liquid separation, a replacement solvent is sprayed on a solid-phase filter cake, and filtration is continued; the alcohol washing is to mix the wet solid phase with alcohol and stir and wash.
c. And (3) carrying out solid-liquid separation on the slurry washed by the alcohol to obtain a magnesium sulfate monohydrate wet solid phase, and drying to obtain a low-chlorine magnesium sulfate monohydrate product, wherein the chlorine component is usually below 1%.
d. Mother liquor replacement or alcohol washing, wherein the adopted alcohol is ethanol or methanol;
e. the washing liquid is distilled to recover methanol or ethanol, the bottom liquid is distilled and returned to the evaporation salt-making working section.
Advantages and advantageous effects of the invention
(1) The invention can utilize SO4 2-∶Cl-The high-sulfur brine with the molar ratio of more than 0.08 is subjected to negative pressure forced evaporation to prepare salt, and the magnesium sulfate monohydrate is produced from the salt preparation mother liquor, so that the brine is comprehensively utilized.
(2) The invention obtains the crystal magnesium sulfate monohydrate by high-temperature evaporation and boiling point rising range control in a high-chlorine environment, the average granularity of the obtained magnesium sulfate monohydrate is more than 160 microns, and the solid-liquid separation and product purification are easy.
(3) The invention adopts the method of solvent replacement or alcohol washing to achieve the dechlorination effect, and the magnesium sulfate monohydrate after the alcohol washing and the drying is not caked and has good fluidity.
Drawings
FIG. 1 is a schematic diagram of the main physical flow of high-salt high-magnesium brine for producing sodium chloride and magnesium sulfate monohydrate
A1-An multi-effect evaporation 1-n-effect evaporation crystallizer; b1, extracting magnesium and evaporating a crystallizer; b2 solid-liquid separation of magnesium sulfate monohydrate; b3 magnesium sulfate monohydrate wet solid phase mother liquor replacement; b4: drying the magnesium sulfate monohydrate; b5 solvent recovery; c, solid-liquid separation, washing and drying of the sodium chloride salt slurry.
a-a feed stream; b-preparing a salt mother liquor; c-sodium chloride salt slurry; d-extracting magnesium brine; e-extracting magnesium mother liquor; f-monohydrate magnesium salt slurry; g-magnesium monohydrate wet solid phase; wet solid phase of magnesium monohydrate
FIG. 2 is an electron micrograph of magnesium sulfate monohydrate obtained by the method of the present invention (500 times magnification)
FIG. 3 is an electron micrograph of magnesium sulfate monohydrate obtained by the method of the present invention (9000 times magnified)
Detailed Description
The present invention will be described in further detail with reference to the following embodiments, which are illustrative only and not limiting, and the scope of the present invention is not limited thereby.
The bittern related by the invention relates to seawater, sea salt bittern, salt lake old bittern and the like. The salt-containing wastewater and the mixed salt material are salt-containing liquid or mixed salt containing three substances of four salts of sodium chloride, sodium sulfate, magnesium sulfate and magnesium chloride, and the like, and do not limit whether the salt-containing wastewater and the mixed salt material contain other components, such as potassium ions, bromide ions, borate and the like. High-salt high-sulfur bittern refers to the above-mentioned bittern or material with high content of sodium chloride and sulfate radical. The high-salt high-sulfur material can be prepared into corresponding brine, so the high-salt high-sulfur brine is simply called as the high-salt high-sulfur brine in the specification.
By using SO4 2-∶Cl-Evaporating the high-sulfur brine with the molar ratio of more than 0.08 to prepare salt.
For with Na+,Mg2+,Cl-,SO4 2-,H2Bittern containing O as main ingredient, if SO4 2-∶Cl-At a molar ratio of greater than 0.08, the precipitate is formed as sodium astrophite or sodium sulfate at ambient temperature (e.g., 25 deg.C)A crystalline region; the crystal region of the astrakanite and the anhydrous astrakanite is positioned at 50-100 ℃, and the production of pure sodium chloride cannot be obtained.
The patent limits that the composition of raw material brine meets the evaporation salt-making condition (1), SO4 2-∶Mg2+Is less than 0.8, and SO4 2-∶Cl-The molar ratio is less than 0.25; (2) and a vacuum forced evaporation crystallization process is adopted. Thus, the salt manufacturing process with high yield can be obtained.
Case one (75 ℃ isothermal forced evaporation salt production): taking 2000 g of brine with the composition of Na+：4.03％，Mg2+：3.33％，Cl-：11.95％，SO4 2-：5.40％，H2O: 75.29 percent; wherein SO4 2-∶Mg2+Is 0.41; SO (SO)4 2-∶Cl-The molar ratio is 0.17, and the salt preparation range defined in the patent is satisfied. In the evaporative crystallization, isothermal forced evaporation is carried out at 75 ℃, 950 g of water is evaporated, and isothermal filtration is carried out to obtain mother liquor with the composition of Na+：1.86％，Mg2+：7.70％，Cl-：15.64％，SO4 2-：13.11％，H2O: 61.69 percent. The solid phase is washed and dried by saturated saline, the mass of the obtained sodium chloride is 162 g, the purity is 99.2 percent, and the precipitation rate of the sodium chloride is 79.13 percent.
Case two (100 mbar absolute pressure, isobaric forced evaporation salt production): taking 2000 g of brine with the composition of Na+：4.03％，Mg2 +：3.33％，Cl-：11.95％，SO4 2-：5.40％，H2O: 75.29 percent; wherein SO4 2-∶Mg2+Is 0.41; SO (SO)4 2-∶Cl-The molar ratio is 0.17, and the salt preparation range defined in the patent is satisfied. Isothermal evaporation at 100 mbar is carried out in evaporative crystallization, the evaporation end temperature is 61 ℃, 960 g of water is evaporated, and the mixture of solid and liquid is subjected to isothermal filtration to obtain mother liquor with the composition of Na+：1.68％，Mg2+：7.88％，Cl-：15.56％，SO4 2-：13.58％，H2O: 61.30 percent. Washing the solid phase with saturated saline and drying to obtain chloridizationThe mass of the sodium is 167 g, the purity is 99.5 percent, and the precipitation rate of the sodium chloride is 81.5 percent.
Case three (60 ℃ isothermal forced evaporation salt production): taking 2000ml of brine with the composition concentration of MgCl2：120.0g/l，MgSO4：118.0g/l，NaCl：140g/l，H2O: 818.0g/l, wherein SO4 2-:Mg2+Is 0.44, SO4 2-∶Cl-Heating in a three-neck flask with an electric heating jacket at a molar ratio of 0.2, connecting the three-neck flask with a vacuum pump, controlling pressure to evaporate the feed liquid at 60 ℃ to evaporate 437.2g of water, performing solid-liquid separation, washing the solid phase with a saturated sodium chloride aqueous solution, and drying to obtain 110g of sodium chloride with the purity of 99.5%;
case four (forced evaporation salt preparation after blending raw materials): taking 1041 g of brine with the composition of Na+：6.33％，Mg2+：2.23％，Cl-：8.87％，SO4 2-：10.03％，H2O: 72.54 percent; wherein SO4 2-∶Mg2+Is 1.14; SO (SO)4 2-∶Cl-The molar ratio is 0.41; both indexes exceed the salt-making conditions defined in the patent. Adding magnesium extracting mother liquor 938 and 22 g water into brine, dissolving out the separated salt to form Na+：4.05％，Mg2+：4.33％，Cl-：13.75％，SO4 2-：6.97％，H2O: 70.90 percent. Wherein SO4 2-∶Mg2+Becomes 0.407; SO (SO)4 2-∶Cl-The molar ratio became 0.187. The isobaric forced evaporation under 0.1atm and 380 g water obtain 187.4 g sodium chloride, which is not washed, the amount of mother liquor carried by the sodium chloride is 9 percent, and the purity of the sodium chloride after washing reaches 99.3 percent.
Thus, the production of sodium chloride from high sulfur brines can be achieved using the process and limitations of this patent.
Evaporating at high temperature in high chlorine environment to obtain crystalline magnesium sulfate monohydrate
Extracting magnesium raw material liquid at a temperature of more than 50-80 ℃ to form a solution satisfying Cl-：SO42-A molar ratio of less than 6 and Mg2+∶Na+Molarity isDegree ratio of more than 2, and Mg2+∶Na+The molar concentration ratio is more than 2. End point control conditions: the boiling point temperature is determined according to the evaporation pressure and the boiling point temperature, the boiling point temperature can be used as a control index, and the boiling point temperature is in an appropriate range of 13 ℃ to 18 ℃.
Case five (evaporation of magnesium): 2000 g of salt-making mother liquor, 60 ℃ and Na composition+：1.78％，Mg2+：7.75％，Cl-：16.18％，SO4 2-：12.44％，H2O: 61.85 percent; wherein Cl-: SO (SO)4 2-The molar ratio is 3.15; mg (magnesium)2+∶Na+The molar ratio is 4.1, and the requirement of magnesium extraction is met. Evaporating at normal pressure until the boiling point reaches 115.4 ℃, stopping evaporation, and carrying out isothermal solid-liquid separation. Mother liquor concentration Na+：2.22％，Mg2+：6.89％，Cl-：20.51％，SO4 2-：4.11％，H2O: 66.27%, wherein Cl-: SO (SO)4 2-Molar ratio of 13.49, SO4 2-∶Na+Mg in a molar ratio of 0.44 to more than 0.252+∶Na+The molar ratio is 2.92 and is more than 2. The material balance is that the evaporation capacity is 195g, the precipitation amount of the magnesium sulfate monohydrate is 230 g, the precipitation rate is 74.04%, and no sodium chloride is precipitated.
Case six (evaporation of magnesium): 1000 g of salt-making mother liquor with the composition of Na at 61 DEG C+：1.28％，Mg2+：7.98％，Cl-：15.79％，SO4 2-：12.83％，H2O: 62.12 percent; wherein Cl-: SO (SO)4 2-Molar ratio of 3.33, SO4 2-∶Na+The molar ratio is 2.39; mg (magnesium)2+∶Na+The molar ratio is 5.88, and the requirement of magnesium extraction is met. Evaporating at normal pressure until the boiling point reaches 116.8 deg.C, and filtering with G3 sand core. Isothermal solid-liquid separation and rapid filtration. Mother liquor concentration Na+：1.39％，Mg2+：6.78％，Cl-：19.32％，SO4 2-：3.52％，H2O: 68.99%, wherein Cl-: SO (SO)4 2-Molar ratio of 14.84, SO4 2-∶Na+Mg in a molar ratio of 0.60 to more than 0.252+∶Na+The molar ratio is 4.60 and is more than 2.. The evaporation capacity was 47g, the precipitation of magnesium sulfate monohydrate was 166.2 g, the purity was 86.7%, the sodium chloride content was 2.6%, and the mother liquor entrainment was 10.7%.
The mother liquid carried by the magnesium sulfate monohydrate is replaced by solvent or washed by alcohol to achieve the effect of removing chlorine
Case seven (magnesium sulfate monohydrate high temperature wash): in the high-temperature washing experiment, magnesium sulfate becomes hexahydrate or heptahydrate magnesium sulfate at the temperature of below 70 ℃, and the magnesium sulfate is required to be washed at high temperature while maintaining the form of magnesium sulfate monohydrate. 150G of magnesium sulfate hexahydrate is taken and added into 500G of 75 ℃ magnesium sulfate saturated solution, the mixture is stirred for 10 minutes to be in a porridge shape, and the mixture is filtered by a G3 sand core, fails and is filtered at a very slow speed. Failure to isolate at high temperatures was unsuccessful under laboratory conditions.
Case eight (normal temperature washing of magnesium sulfate monohydrate): and in a normal-temperature washing experiment, the high-temperature material is easy to agglomerate when being placed at room temperature, and the mother liquor is entrained to form a mixture of various crystal waters. The normal-temperature washing is adopted, the washing effect cannot be achieved due to the fact that materials are agglomerated and the washing is difficult, and expected products cannot be obtained when the magnesium sulfate monohydrate is wrapped by the sulfuric acid heptahydrate.
Case nine (continuous feed continuous evaporative crystallization, mother liquor displacement to produce low chlorine magnesium sulfate monohydrate): adding bottom material into crystallizer, extracting magnesium bittern by 1.5L, controlling pressure at 1013mba, and heating oil at 145 deg.C. When the boiling temperature of the feed liquid rises to 114.8 ℃, intermittent feeding is started, and the temperature of the feed liquid in the kettle is enabled to be not higher than 115 ℃ by feeding. The make-up charge amounted to 1.5L. The feed was evaporated for 3 hours and the process was run 2 times. The slurry was discharged and filtered through a G3 sand core, very smoothly. The wet solid phase filter cake is respectively replaced by 50 g of methanol and ethanol for 2 times. After natural air drying, 284 and 345 g of white crystal products are obtained. The magnesium sulfate monohydrate is detected by XRD; particle size analysis mean particle sizes of 168 and 178 microns; observed by an electron microscope, the crystal is a spherical crystal cluster. The product has good fluidity and the whiteness is 91 and 92. The purity of the magnesium sulfate monohydrate is higher than 95 percent through chemical analysis detection, and the content of chlorine is 0.75 percent and 0.95 percent respectively.
The scheme of producing magnesium sulfate monohydrate by using high-salt high-sulfur brine through vacuum evaporation firstly and then using a salt-making mother solution is shown in figure 1, a raw material liquid a reaches a limited condition after being blended and respectively enters a salt-making multi-effect evaporation crystallizer A (1-n-1), and the multi-effect evaporation is recommended to adopt 3-4 effects; and (5) carrying out solid-liquid separation, washing and drying on the salt slurry c for preparing salt to obtain a sodium chloride product. The salt making mother liquor is changed from 1 effect to 2 effects in a concurrent flow mode until the Nth effect; and (3) determining the discharge amount of the mother liquor d according to the pressure and the boiling point of the feed liquid. The mother liquor d meeting the conditions is used as a magnesium extraction solution and enters a magnesium extraction evaporative crystallizer B1; determining the discharge amount of the magnesium extraction mother liquor e according to the pressure and the boiling point temperature; the magnesium extraction mother liquor returns to the multi-effect evaporation stage of salt making. And (3) extracting magnesium slurry f, performing solid-liquid separation B2, replacing B3 with mother liquor, and drying B4 to obtain a magnesium sulfate monohydrate product. The alcohol-containing liquid and gas generated in the mother liquor replacement and drying section are subjected to solvent recovery B5 to recover the solvent.
Fig. 2 and 3 illustrate: by adopting the high-chlorine high-temperature evaporation condition of the patent, crystalline magnesium sulfate monohydrate is obtained, the average particle size obtained by a laboratory device is larger than 160 microns, an industrial device is expected to obtain larger particle size, solid-liquid separation and product purification are easy to realize, and the magnesium sulfate monohydrate after mother liquor replacement and drying has good fluidity.

Claims (3)

1. A method for producing sodium chloride and magnesium sulfate monohydrate by using high-salt high-sulfur brine is characterized by comprising the following steps: completing salt making at 50-80 ℃ and obtaining chlorine-containing high-concentration magnesium-extracted raw material liquid which meets Cl-：SO4 2-A molar ratio of 3.15 to 6, and Mg2+∶Na+The molar concentration ratio is 2-4.1; in a high-chlorine environment, performing high-temperature evaporation at the temperature of more than 80 ℃, determining an evaporation end point according to evaporation pressure and boiling point temperature, using boiling point rise as a control index, wherein the boiling point rise range is 13-18 ℃, and the evaporation completion liquid completes solid-liquid separation at the temperature of more than 70 ℃ to obtain a magnesium sulfate monohydrate crystallization wet solid phase, cleaning the magnesium sulfate monohydrate crystallization wet solid phase by adopting a mother liquor replacement or alcohol washing mode, and removing chlorine components to obtain a magnesium sulfate monohydrate crystal;
the method for completing salt production at 50-80 ℃ and obtaining the chlorine-containing high-concentration magnesium raw material solution is obtained by adopting an evaporation desalting method, and the evaporation desalting process is divided into the following three conditions:
a. the composition of the high-sulfur brine meets SO4 2-∶Mg2+Is less than 0.8, and SO4 2-∶Cl-The molar ratio is less than 0.25, and the magnesium extraction raw material liquid is generated by directly evaporating salt;
b. the composition of the high-sulfur brine meets SO4 2-∶Mg2+When the molar ratio is more than 0.8 and less than 1, mother liquor obtained after separating a magnesium sulfate monohydrate wet solid phase is used as circulating liquid, and evaporation is carried out to prepare salt, so as to generate magnesium extraction raw material liquid;
c. the composition of the high-sulfur brine meets SO4 2-∶Mg2+When the molar ratio is more than 1, removing part of sodium sulfate or adding brine containing high-concentration magnesium chloride to ensure that the raw material composition meets the requirements of a or b;
the evaporation salt preparation adopts a negative pressure single-effect or multi-effect continuous forced evaporation crystallization process, the multi-effect evaporation salt preparation is to enter a raw material liquid into a system in an evaporation crystallizer with a high boiling point, salt preparation mother liquid is discharged by smooth distillation, the salt preparation mother liquid is discharged out of the system in the evaporation crystallizer with the lowest boiling point temperature, the boiling point of a discharged salt preparation mother liquid evaporator is 50-80 ℃, the salt preparation mother liquid is used for producing magnesium sulfate monohydrate, and a solid-liquid mixture discharged from each effect is subjected to solid-liquid separation, saturated sodium chloride brine washing and drying to obtain a sodium chloride product.
2. The process of claim 1 for producing sodium chloride and magnesium sulfate monohydrate from high salt and high sulfur brine, wherein: the mother liquor replacement is to spray replacement alcohol on a solid-phase filter cake during solid-liquid separation and continue to filter; the alcohol washing is to mix the wet solid phase with alcohol and stir and wash.
3. The process of claim 2 for producing sodium chloride and magnesium sulfate monohydrate from high salt and high sulfur brine, wherein: the alcohol used for mother liquor replacement or alcohol washing is ethanol or methanol.
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