CN115353132A - Preparation method and system of magnesium sulfate heptahydrate based on chlor-alkali salt slurry - Google Patents
Preparation method and system of magnesium sulfate heptahydrate based on chlor-alkali salt slurry Download PDFInfo
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- CN115353132A CN115353132A CN202211170654.XA CN202211170654A CN115353132A CN 115353132 A CN115353132 A CN 115353132A CN 202211170654 A CN202211170654 A CN 202211170654A CN 115353132 A CN115353132 A CN 115353132A
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- WRUGWIBCXHJTDG-UHFFFAOYSA-L magnesium sulfate heptahydrate Chemical compound O.O.O.O.O.O.O.[Mg+2].[O-]S([O-])(=O)=O WRUGWIBCXHJTDG-UHFFFAOYSA-L 0.000 title claims abstract description 37
- 229940061634 magnesium sulfate heptahydrate Drugs 0.000 title claims abstract description 37
- 239000002002 slurry Substances 0.000 title claims abstract description 31
- 238000002360 preparation method Methods 0.000 title claims description 14
- 150000003839 salts Chemical class 0.000 claims abstract description 104
- 238000003756 stirring Methods 0.000 claims abstract description 77
- 239000007788 liquid Substances 0.000 claims abstract description 50
- 238000000034 method Methods 0.000 claims abstract description 41
- 238000002156 mixing Methods 0.000 claims abstract description 40
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 40
- 238000006298 dechlorination reaction Methods 0.000 claims abstract description 34
- 238000001914 filtration Methods 0.000 claims abstract description 33
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 claims abstract description 32
- 239000003546 flue gas Substances 0.000 claims abstract description 32
- 239000002244 precipitate Substances 0.000 claims abstract description 30
- 238000004537 pulping Methods 0.000 claims abstract description 29
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 claims abstract description 24
- 239000011593 sulfur Substances 0.000 claims abstract description 24
- 229910052717 sulfur Inorganic materials 0.000 claims abstract description 24
- 239000008367 deionised water Substances 0.000 claims abstract description 22
- 229910021641 deionized water Inorganic materials 0.000 claims abstract description 22
- 239000013078 crystal Substances 0.000 claims abstract description 19
- 239000011777 magnesium Substances 0.000 claims abstract description 18
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 claims abstract description 17
- 229910052749 magnesium Inorganic materials 0.000 claims abstract description 17
- 238000011084 recovery Methods 0.000 claims abstract description 15
- 238000006477 desulfuration reaction Methods 0.000 claims abstract description 13
- 230000023556 desulfurization Effects 0.000 claims abstract description 13
- 239000007787 solid Substances 0.000 claims abstract description 11
- 238000001816 cooling Methods 0.000 claims abstract description 7
- CSNNHWWHGAXBCP-UHFFFAOYSA-L Magnesium sulfate Chemical compound [Mg+2].[O-][S+2]([O-])([O-])[O-] CSNNHWWHGAXBCP-UHFFFAOYSA-L 0.000 claims description 64
- 229910052943 magnesium sulfate Inorganic materials 0.000 claims description 32
- 235000019341 magnesium sulphate Nutrition 0.000 claims description 32
- 239000003795 chemical substances by application Substances 0.000 claims description 19
- 238000001035 drying Methods 0.000 claims description 19
- 238000001728 nano-filtration Methods 0.000 claims description 18
- 239000010802 sludge Substances 0.000 claims description 16
- 238000002425 crystallisation Methods 0.000 claims description 15
- 230000008025 crystallization Effects 0.000 claims description 15
- 238000000926 separation method Methods 0.000 claims description 15
- 239000000460 chlorine Substances 0.000 claims description 14
- 230000008569 process Effects 0.000 claims description 13
- 238000005406 washing Methods 0.000 claims description 13
- 239000012065 filter cake Substances 0.000 claims description 12
- 150000002500 ions Chemical class 0.000 claims description 12
- 239000012528 membrane Substances 0.000 claims description 10
- 230000020477 pH reduction Effects 0.000 claims description 8
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 claims description 7
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 claims description 7
- 230000002457 bidirectional effect Effects 0.000 claims description 7
- 229910052801 chlorine Inorganic materials 0.000 claims description 7
- 238000000746 purification Methods 0.000 claims description 7
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 claims description 6
- 239000004760 aramid Substances 0.000 claims description 6
- 229920003235 aromatic polyamide Polymers 0.000 claims description 6
- 230000002452 interceptive effect Effects 0.000 claims description 6
- 239000000463 material Substances 0.000 claims description 6
- 238000012545 processing Methods 0.000 claims description 6
- BHPQYMZQTOCNFJ-UHFFFAOYSA-N Calcium cation Chemical compound [Ca+2] BHPQYMZQTOCNFJ-UHFFFAOYSA-N 0.000 claims description 5
- JLVVSXFLKOJNIY-UHFFFAOYSA-N Magnesium ion Chemical compound [Mg+2] JLVVSXFLKOJNIY-UHFFFAOYSA-N 0.000 claims description 4
- 229910001424 calcium ion Inorganic materials 0.000 claims description 4
- 229910001425 magnesium ion Inorganic materials 0.000 claims description 4
- 229910001414 potassium ion Inorganic materials 0.000 claims description 4
- 229910001415 sodium ion Inorganic materials 0.000 claims description 4
- 239000003513 alkali Substances 0.000 claims description 3
- 150000003841 chloride salts Chemical class 0.000 claims description 3
- 239000003480 eluent Substances 0.000 abstract description 9
- 238000004064 recycling Methods 0.000 abstract description 5
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 9
- 230000003009 desulfurizing effect Effects 0.000 description 9
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 6
- RAHZWNYVWXNFOC-UHFFFAOYSA-N Sulphur dioxide Chemical compound O=S=O RAHZWNYVWXNFOC-UHFFFAOYSA-N 0.000 description 6
- 230000006872 improvement Effects 0.000 description 6
- 239000000126 substance Substances 0.000 description 6
- 238000007599 discharging Methods 0.000 description 4
- 238000004062 sedimentation Methods 0.000 description 4
- 239000011575 calcium Substances 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 230000004048 modification Effects 0.000 description 3
- 238000012986 modification Methods 0.000 description 3
- 239000011734 sodium Substances 0.000 description 3
- 239000011780 sodium chloride Substances 0.000 description 3
- 239000002699 waste material Substances 0.000 description 3
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 2
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 2
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 239000011449 brick Substances 0.000 description 2
- 229910052791 calcium Inorganic materials 0.000 description 2
- 239000004568 cement Substances 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 235000013305 food Nutrition 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 239000011591 potassium Substances 0.000 description 2
- 229910052700 potassium Inorganic materials 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 239000002893 slag Substances 0.000 description 2
- 229910052708 sodium Inorganic materials 0.000 description 2
- 235000017550 sodium carbonate Nutrition 0.000 description 2
- 229910000029 sodium carbonate Inorganic materials 0.000 description 2
- 239000002689 soil Substances 0.000 description 2
- 239000002910 solid waste Substances 0.000 description 2
- 229910021653 sulphate ion Inorganic materials 0.000 description 2
- 235000008733 Citrus aurantifolia Nutrition 0.000 description 1
- NPYPAHLBTDXSSS-UHFFFAOYSA-N Potassium ion Chemical compound [K+] NPYPAHLBTDXSSS-UHFFFAOYSA-N 0.000 description 1
- FKNQFGJONOIPTF-UHFFFAOYSA-N Sodium cation Chemical compound [Na+] FKNQFGJONOIPTF-UHFFFAOYSA-N 0.000 description 1
- 238000009621 Solvay process Methods 0.000 description 1
- 235000011941 Tilia x europaea Nutrition 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- -1 anions Chemical class 0.000 description 1
- 150000001450 anions Chemical class 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 238000009395 breeding Methods 0.000 description 1
- 230000001488 breeding effect Effects 0.000 description 1
- 239000004566 building material Substances 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 238000005352 clarification Methods 0.000 description 1
- 239000003245 coal Substances 0.000 description 1
- 239000004567 concrete Substances 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 230000018044 dehydration Effects 0.000 description 1
- 238000006297 dehydration reaction Methods 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 239000003814 drug Substances 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000012467 final product Substances 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 239000004571 lime Substances 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- 244000144972 livestock Species 0.000 description 1
- 239000008267 milk Substances 0.000 description 1
- 210000004080 milk Anatomy 0.000 description 1
- 235000013336 milk Nutrition 0.000 description 1
- 238000005191 phase separation Methods 0.000 description 1
- 244000144977 poultry Species 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 238000007670 refining Methods 0.000 description 1
- 239000011435 rock Substances 0.000 description 1
- 238000007569 slipcasting Methods 0.000 description 1
- 230000008719 thickening Effects 0.000 description 1
- 239000002912 waste gas Substances 0.000 description 1
Images
Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- 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
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
- C01D3/00—Halides of sodium, potassium or alkali metals in general
- C01D3/04—Chlorides
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/80—Compositional purity
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Life Sciences & Earth Sciences (AREA)
- Geology (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Treatment Of Sludge (AREA)
Abstract
The invention discloses a method and a system for preparing magnesium sulfate heptahydrate based on chlor-alkali salt mud, wherein the method comprises the following steps: primary dechlorination treatment: mixing, stirring and separating the chlor-alkali salt mud by using an eluent to obtain primary dechlorinated salt mud and clear liquid A; pulping treatment: mixing the primary dechlorinated salt mud with deionized water, stirring and pulping to obtain primary dechlorinated salt mud homogenate; desulphation treatment: mixing and stirring the first-stage dechlorinated salt slurry homogenate and sulfur-containing flue gas, and separating the acidified salt slurry to obtain a salt slurry solid and a clear liquid B; and (3) magnesium recovery treatment: cooling and crystallizing the clear liquid B, fully separating out crystals, and filtering to obtain a precipitate which is high-purity MgSO 4 ·7H 2 And O. The invention provides a method for preparing magnesium sulfate heptahydrate by combining sulfur-containing flue gas desulfurization and chlor-alkali salt mud dechlorination, which can realize harmless and recycling treatment of chlor-alkali salt mud.
Description
Technical Field
The invention belongs to the technical field of harmless and resource utilization of solid wastes, and particularly relates to a method and a system for preparing magnesium sulfate heptahydrate based on chlor-alkali salt mud.
Background
At present, the soda industry has become an important part of basic chemical industry, and soda is widely applied to the fields of light industry, daily chemicals, building materials, chemical industry, food industry and the like. According to calculation and statistics, the ammonia-soda process is adopted to prepare 1t of soda ash, about 400-600 kg of salt mud is generated, and the soda ash industry is always troubled by the technical problem of disposal of salt mud waste residues (specifically, the salt mud has the obvious characteristics of large generation amount, complex components and serious pollution, and contains a large amount of soluble salt which is not beneficial to vegetation growth after entering the soil). At present, the main disposal mode of the salt mud waste residue is to reinject waste ores, and the traditional mode not only occupies a large amount of open space, but also easily corrodes surrounding soil, pollutes underground water and harms the ecological environment.
In recent years, new methods for treating the salt mud are continuously sought in the field of chemical industry; the method comprises the following steps of mixing salt slurry, carbide slag and the like generated in the chlor-alkali industry with a curing agent by some enterprises, and making bricks and cement by processes of stirring, slip casting, drying and the like, wherein a large amount of chlorine elements in the salt slurry greatly influence the strength of bricks, cement and concrete structures, easily cause the problems of cracking and the like, and are difficult to popularize and apply; some enterprises mix and process the salt slurry rich in calcium element and the pulverized coal slag to prepare the desulfurizer, but the technical cost investment is large, the process requirement is high, the universality is not high, and whether negative effects can be caused needs to be further verified.
In summary, a new harmless and recycling treatment method for chlor-alkali salt mud is urgently needed to overcome the defects of the existing harmless treatment and recycling technology for salt mud.
Disclosure of Invention
The invention aims to provide a method and a system for preparing magnesium sulfate heptahydrate based on chlor-alkali salty mud, so as to solve one or more technical problems. The invention provides a preparation method of magnesium sulfate heptahydrate based on chlor-alkali salt mud, in particular to a method for preparing magnesium sulfate heptahydrate by combining sulfur-containing flue gas desulfurization and chlor-alkali salt mud dechlorination, which can realize harmless and resource recycling of chlor-alkali salt mud.
In order to achieve the purpose, the invention adopts the following technical scheme:
the invention provides a preparation method of magnesium sulfate heptahydrate based on chlor-alkali salt mud, which comprises the following steps:
primary dechlorination treatment comprising: mixing, stirring and separating the chlor-alkali salt mud by using an eluting agent to obtain primary dechlorinated salt mud and clear liquid A;
pulping treatment comprising: mixing, stirring and pulping the primary dechlorinated salt mud and deionized water to obtain a primary dechlorinated salt mud homogenate;
a desulphation treatment comprising: mixing and stirring the primary dechlorinated salt mud homogenate and sulfur-containing flue gas to realize the acidification of chlor-alkali salt mud and the bidirectional purification of flue gas desulfurization, and separating the acidified salt mud to obtain salt mud solid and clear liquid B;
magnesium recovery treatment, comprising: cooling and crystallizing the clear liquid B, fully separating out crystals, and filtering to obtain a precipitate which is high-purity MgSO (MgSO) as a material 4 ·7H 2 O。
The invention is further improved in that the method also comprises the following steps:
secondary dechlorination treatment comprising: fully mixing the salt mud solid with deionized water, stirring to perform secondary dechlorination, and separating to obtain a precipitate and a clear liquid C; and washing, filtering and drying the precipitate to obtain low-chloride salt mud.
The further improvement of the invention is that the process of washing, filtering and drying the precipitate to obtain the low-chloride salt mud specifically comprises the following steps:
filtering the washed precipitate by adopting a belt type filter, and sending the filtered clear liquid C to a circulating water tank; the water content of the filter cake after filtration is reduced to 20-30 percent;
drying the filter cake for 7-8 h at the temperature of 105-125 ℃ to obtain low-chloride salt mud; with Cl — And (4) the chlorine content of the low-chlorine salt mud is reduced to be below 0.04 percent.
The invention is further improved in that the separation in the primary dechlorination treatment and the desulfation treatment adopts a natural settling separation mode.
In the further improvement of the invention, in the primary dechlorination treatment,
the allowable limit value of the interfering ions in the eluting agent is as follows: the content of chloride ions is less than or equal to 25.0g/L, the content of sulfate ions is less than or equal to 5.0g/L, the content of sodium ions is less than or equal to 20.5g/L, the content of magnesium ions is less than or equal to 2.0g/L, the content of calcium ions is less than or equal to 0.7g/L, the content of potassium ions is less than or equal to 0.5g/L, and the content of other trace ions is less than or equal to 0.25g/L.
The invention is further improved in that the primary dechlorination treatment specifically comprises the following steps:
when the chlor-alkali salt mud and the eluent are mixed for pulping under the conditions of normal temperature and normal pressure, the volume ratio of the chlor-alkali salt mud to the eluent is controlled to be 1: (2-6), stirring by a propeller with the stirring speed of 100 r/min-500 r/min.
The invention has the further improvement that the pulping treatment specifically comprises the following steps:
under the conditions of normal temperature and normal pressure, the volume ratio of the primary dechlorinated salt mud to the deionized water is controlled to be 1: (5.0-7.5), stirring by a propeller at 100 r/min-200 r/min.
A further improvement of the invention consists in that the desulphation treatment comprises:
mixing and stirring the first-stage dechlorinated salt mud homogenate and sulfur-containing flue gas at the temperature of 40-70 ℃; wherein the stirring adopts a propeller with the stirring speed of 100 r/min-500 r/min; the flow rate range of the sulfur-containing flue gas is 2.5-6.0 m/s, and the conveying capacity of the first-stage dechlorinated salt mud homogenate is 40-90 kg/s.
The further improvement of the invention is that the magnesium recovery treatment specifically comprises:
nanofiltration of the clear liquid B is carried out by selecting a separation membrane made of aromatic polyamide material, and a magnesium sulfate solution after nanofiltration is obtained;
introducing magnesium sulfate seed crystals into the nanofiltration magnesium sulfate solution according to a preset proportion of the magnesium sulfate seed crystals to chlor-alkali salt slurry under the conditions of initial crystallization temperature of 50-80 ℃, stirring speed of 50-200 r/min and final crystallization temperature of 10-30 ℃ to obtain MgSO (magnesium sulfate) with purity of more than 99 percent 4 ·7H 2 O。
The invention provides a system for preparing magnesium sulfate heptahydrate based on chlor-alkali salt mud, which comprises the following components:
the first-stage dechlorination processing unit is used for mixing, stirring and separating the chlor-alkali salt mud by using an eluent to obtain first-stage dechlorinated salt mud and clear liquid A;
the pulping treatment unit is used for mixing, stirring and pulping the primary dechlorinated salt mud and deionized water to obtain primary dechlorinated salt mud homogenate;
the desulphation treatment unit is used for mixing and stirring the primary dechlorinated salt sludge homogenate and sulfur-containing flue gas to realize the acidification of chlor-alkali salt sludge and the bidirectional purification of flue gas desulphurization, and the acidified salt sludge is separated to obtain a salt sludge solid and a clear liquid B;
a magnesium recovery processing unit for cooling and crystallizing the clear liquid B, filtering after full crystallization, and obtaining a precipitate of high-purity MgSO 4 ·7H 2 O。
Compared with the prior art, the invention has the following beneficial effects:
the invention provides a novel preparation process method of magnesium sulfate heptahydrate based on chlor-alkali salt mud, aiming at the defects of harmless treatment and resource utilization of chlor-alkali salt mud in the prior art and considering the characteristics of large content of magnesium in chlor-alkali salt mud produced in the soda industry and high recovery value of magnesium sulfate heptahydrate. The method provided by the invention is simple to operate, has short flow, can realize harmless treatment of the solid waste of the salt slurry produced in the soda industry, and simultaneously uses sulfur-containing flue gas to replace sulfuric acid to acidify the salt slurry, so that sulfur dioxide is converted into magnesium sulfate under the process condition, and the recycling of sulfur dioxide waste gas is realized; the high-purity magnesium sulfate heptahydrate prepared by the magnesium recovery link can be widely applied to a plurality of fields such as chemical industry, medicine, food, livestock and poultry breeding and the like, realizes harmless treatment and resource utilization of salt slurry, and has good environmental protection value and economic value.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the embodiments or the description of the prior art are briefly introduced below; it is obvious that the drawings in the following description are some embodiments of the invention, and that for a person skilled in the art, other drawings can be derived from them without inventive effort.
Fig. 1 is a schematic block diagram of a process flow of a preparation method of magnesium sulfate heptahydrate based on chlor-alkali salt mud provided by the embodiment of the invention.
Detailed Description
The present invention is further illustrated below with reference to specific examples, which are intended to be illustrative only and not to limit the scope of the invention.
The following embodiments of the present invention are provided by way of specific examples, and other advantages and effects of the present invention will be readily apparent to those skilled in the art from the disclosure herein. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention.
It is to be understood that the processing equipment or apparatus not specifically identified in the following examples is conventional in the art.
Furthermore, it is to be understood that one or more method steps mentioned in the present invention does not exclude that other method steps may also be present before or after the combined steps or that other method steps may also be inserted between these explicitly mentioned steps, unless otherwise indicated; it is also to be understood that a combined connection between one or more devices/apparatus as referred to in the present application does not exclude that further devices/apparatus may be present before or after the combined device/apparatus or that further devices/apparatus may be interposed between two devices/apparatus explicitly referred to, unless otherwise indicated. Moreover, unless otherwise indicated, the numbering of the various method steps is merely a convenient tool for identifying the various method steps, and is not intended to limit the order in which the method steps are arranged or the scope of the invention in which the invention may be practiced, and changes or modifications in the relative relationship may be made without substantially changing the technical content.
Referring to fig. 1, a method for preparing magnesium sulfate heptahydrate based on chlor-alkali salt mud provided by the embodiment of the present invention includes the following steps:
1) Primary dechlorination: mixing and stirring the salt mud by using an eluent, naturally settling and separating, respectively discharging primary dechlorinated salt mud and clear liquid A, and conveying the primary dechlorinated salt mud to a pulping unit;
2) Pulping: mixing, stirring and pulping the primary dechlorinated salt mud and deionized water to obtain a primary dechlorinated salt mud homogenate;
3) Acidifying the desulfurizing tower: the first-stage dechlorinated salt mud homogenate is fully stirred in a desulfurizing tower and is mixed with sulfur-containing flue gas, so that the acidification of the salt mud and the bidirectional purification of flue gas desulfurization are realized, the acidified salt mud is naturally settled and separated and is discharged from the bottom of the desulfurizing tower, clear liquid B is sent to a magnesium recovery unit, and precipitates are sent to a second-stage dechlorination unit;
4) Secondary dechlorination: fully mixing the salt mud solid discharged from the desulfurizing tower with deionized water, stirring, performing secondary dechlorination, naturally settling and separating, sending clear liquid C to a circulating water tank, and washing, filtering and drying the precipitate to obtain low-chlorine salt mud;
5) And (3) magnesium recovery: cooling and crystallizing clear liquid B discharged from the desulfurizing tower, fully separating out crystals, filtering, and obtaining precipitates which are the obtained high-purity MgSO (MgSO) by using precipitates 4 ·7H 2 O。
In step 1) of the embodiment of the invention, the allowable limit value of the interfering ions in the eluent is that chloride ions are not more than 25.0g/L, sulfate ions are not more than 5.0g/L, sodium ions are not more than 20.5g/L, magnesium ions are not more than 2.0g/L, calcium ions are not more than 0.7g/L, potassium ions are not more than 0.5g/L, and the rest trace ions are not more than 0.25g/L. Further specifically, step 1) is realized by directly mixing salt slurry and the eluting agent to prepare pulp under normal temperature and pressure, wherein the volume ratio of the salt slurry to the eluting agent is controlled to be 1: (2-6), stirring by a propeller with the stirring speed of 100-500 r/min. Further specifically, the characteristics of loose texture, strong desertification and easy sedimentation of the dechlorinated salt mud are exerted, the solid-liquid separation after the primary dechlorination can be directly performed by sedimentation separation, after natural sedimentation is performed for 40-60 min, clear liquid A and the primary dechlorinated salt mud can be respectively discharged due to obvious solid-liquid phase separation, and the clear liquid A can be conveyed to the links of crude salt refining and the like of the soda process.
The step 2) in the embodiment of the invention is realized by controlling the volume ratio of the salt mud to the deionized water to be 1: (5.0-7.5), stirring with a propeller at 100-200 r/min to promote the slurry to be uniform.
In the implementation process of the step 3) in the embodiment of the invention, the temperature in the desulfurization tower is controlled to be 40-70 ℃, the stirring speed is 100-500 r/min, the rotating propeller is adopted for stirring to promote the acidification of acid media such as sulfur dioxide in the flue gas and the like to the salty mud, the sulfur-containing media is mixed with the salty mud for reaction and is converted into sulfate ions, and the effect of thickening the magnesium sulfate in the acidizing fluid is further achieved. Further specifically, the solid-liquid separation in the step 3) also adopts a natural sedimentation mode, and precipitates and the clear liquid B are respectively discharged after 40-60 min. The flow velocity range of the flue gas in the step 3) is 2.5-6.0 m/s, and the conveying capacity of the salt mud homogenate is 40-90 kg/s.
In step 4) of the embodiment of the invention, the volume ratio of the salt slurry discharged from the desulfurizing tower to the washing water is controlled to be (8-10): 1. the washed dechlorinated salt mud is filtered by a belt type and bypasses a press roll under the tension of a filter belt to obtain the squeezing force required by removing the water in the salt mud for dehydration. Clear liquid C after filtration is sent to a circulating water tank and can be circularly applied to units such as pulping and the like; the water content of the filter cake after filtration can be reduced to 20-30%. Drying the filter cake at 105-125 deg.c for 7-8 hr to obtain low-chlorine salt mud product with chlorine content (Cl) — Calculated) can be reduced to below 0.04 percent.
The further preferable improvement of the invention is that the nanofiltration of the clear liquid B in the step 5 selects a separation membrane made of aromatic polyamide, the membrane aperture is 1nm, a one-stage two-stage design (6-core membrane shell) is adopted, and the number ratio of the first-stage membrane shell to the second-stage membrane shell is 2; the nanofiltration system can intercept the molecular weight range of 200-1000 daltons, has negative charges on the surface, can efficiently intercept divalent or high-valence ions, particularly anions, has the interception rate of sodium chloride of over 97 percent, and can obtain sodium chloride concentrated solution with the purity of over 96 percent through the precipitation and clarification of lime milk. Step 5) after nanofiltration, the magnesium sulfate solution is stirred at the initial crystallization temperature of 50-80 ℃ and the stirring speed of 50-200 r/min and finally crystallizedAt the temperature of 10-30 ℃, according to the mass ratio of the magnesium sulfate seed crystal to the salt slurry of 1:200, to the clear solution B, seed crystals of magnesium sulfate were introduced. In the step 5), the clear liquid obtained by filtering is recycled to the pulping unit to replace deionized water, and finally the obtained MgSO 4 4 ·7H 2 The purity of the O product is more than 99 percent.
Example 1
According to the novel process for preparing magnesium sulfate heptahydrate by combining desulfurization and salty mud dechlorination, the salty mud selected by experiments comes from salty mud produced by a certain Shandong Weifang chemical industry enterprise, the water content of the salty mud is known to be 40% -48%, and the main elements of the salty mud are shown in Table 1.
TABLE 1 complete rock index element analysis of salt mud
| Element type | Mass ratio% | Atomic ratio of% |
| C | 10.30 | 19.95 |
| O | 28.93 | 42.06 |
| Na | 1.37 | 1.39 |
| Mg | 0.72 | 0.70 |
| Al | 0.21 | 0.18 |
| Si | 0.38 | 0.31 |
| S | 10.73 | 7.79 |
| Cl | 1.70 | 1.12 |
| Ca | 45.66 | 26.50 |
(1) Fully mixing 100g of salt mud and 250mL of eluent in a stirring system, mixing and stirring, then naturally settling and separating, and respectively discharging primary dechlorinated salt mud and clear liquid A;
(2) Mixing the primary dechlorinated salt mud obtained in the step (1) with 500mL of deionized water, stirring and pulping to obtain primary dechlorinated salt mud homogenate;
(3) Under the condition of 50 ℃, stirring by adopting a propeller with the stirring speed of 200r/min, mixing the first-stage dechlorinated salt mud homogenate with sulfur-containing flue gas, controlling a gas transmission port to be 0.5-0.8 m below the liquid level, and naturally settling and separating the acidified salt mud to obtain acidified salt mud and clear liquid B;
(4) Adding 10mL of deionized water into the acidified salt slurry obtained in the step (3), fully mixing and stirring, performing secondary dechlorination, naturally settling and separating, and washing, filtering and drying the precipitate to obtain low-chloride salt slurry;
(5) By using nanofiltrationSeparating divalent ions from the clear liquid obtained in the step (4) to obtain 96 percent NaCl solution and 97 percent MgSO 4 A solution;
(6) According to the mass ratio of the magnesium sulfate seed crystal to the salt slurry of 1:200 to MgSO 4 Introducing magnesium sulfate seed crystals into the solution; the temperature is reduced and crystallized under the conditions that the initial crystallization temperature is 70 ℃, the stirring speed is 120r/min and the final crystallization temperature is 20 ℃, and the final product, namely the magnesium sulfate heptahydrate is obtained after washing, filtering and drying, and the purity of the magnesium sulfate heptahydrate is as high as 99%.
Example 2
The embodiment of the invention provides a preparation method of magnesium sulfate heptahydrate based on chlor-alkali salt mud, which comprises the following steps:
primary dechlorination treatment, which comprises: mixing, stirring and separating the chlor-alkali salt mud by using an eluent to obtain primary dechlorinated salt mud and clear liquid A;
pulping treatment comprising: mixing, stirring and pulping the primary dechlorinated salt mud and deionized water to obtain a primary dechlorinated salt mud homogenate;
a desulphation treatment comprising: mixing and stirring the primary dechlorinated salt mud homogenate and sulfur-containing flue gas to realize the acidification of chlor-alkali salt mud and the bidirectional purification of flue gas desulfurization, and separating the acidified salt mud to obtain salt mud solid and clear liquid B;
magnesium recovery treatment, comprising: cooling and crystallizing the clear liquid B, fully separating out crystals, and filtering to obtain a precipitate which is high-purity MgSO 4 ·7H 2 O。
In the embodiment of the invention, the separation in the primary dechlorination treatment and the desulfation treatment adopts a natural settling separation mode. The primary dechlorination treatment specifically comprises the following steps: when the chlor-alkali salt mud and the eluting agent are mixed for pulping under the conditions of normal temperature and normal pressure, the volume ratio of the chlor-alkali salt mud to the eluting agent is controlled to be 1:2, stirring by a propeller with the stirring speed of 100 r/min. The allowable limit values of the interfering ions in the eluting agent are as follows: chloride ion equal to 25.0g/L, sulfate ion equal to 5.0g/L, sodium ion equal to 20.5g/L, magnesium ion equal to 2.0g/L, calcium ion equal to 0.7g/L, potassium ion equal to 0.5g/L, and the rest tracesThe quantum ion is equal to 0.25g/L. The pulping treatment specifically comprises the following steps: under the conditions of normal temperature and normal pressure, the volume ratio of the primary dechlorinated salt mud to the deionized water is controlled to be 1:5.0, stirring by a propeller at 100 r/min. The desulphation treatment comprises the following steps: mixing and stirring the primary dechlorinated salt sludge homogenate and sulfur-containing flue gas at the temperature of 40 ℃; wherein the stirring is performed by a propeller with the stirring speed of 100 r/min; the flow rate range of the sulfur-containing flue gas is 2.5m/s, and the conveying capacity of the first-stage dechlorinated salt mud homogenate is 40kg/s. The magnesium recovery treatment specifically comprises: nanofiltration of the clear liquid B is carried out by selecting a separation membrane made of aromatic polyamide material, and a magnesium sulfate solution after nanofiltration is obtained; introducing magnesium sulfate seed crystals into the nanofiltration magnesium sulfate solution according to the preset proportion of the magnesium sulfate seed crystals and chlor-alkali salt sludge under the conditions of initial crystallization temperature of 50 ℃, stirring speed of 50r/min and final crystallization temperature of 10 ℃ to obtain MgSO (magnesium sulfate) with purity of more than 99 percent 4 ·7H 2 O。
Example 3
The difference between the preparation method of magnesium sulfate heptahydrate based on chlor-alkali salt mud provided by the embodiment of the invention and the embodiment 2 is that the first-stage dechlorination treatment specifically comprises the following steps: when the chlor-alkali salt mud and the eluting agent are mixed for pulping under the conditions of normal temperature and normal pressure, the volume ratio of the chlor-alkali salt mud to the eluting agent is controlled to be 1:5, stirring by a propeller with the stirring speed of 300 r/min. The allowable limit values of the interfering ions in the eluting agent are as follows: chloride equal to 20.0g/L, sulphate equal to 4.0g/L, sodium equal to 18g/L, magnesium equal to 1.5g/L, calcium equal to 0.5g/L, potassium equal to 0.4g/L, the remaining traces equal to 0.20g/L. The pulping treatment specifically comprises the following steps: under the conditions of normal temperature and normal pressure, the volume ratio of the primary dechlorinated salt mud to the deionized water is controlled to be 1:6.0, stirring with a propeller at 150 r/min. The desulphation treatment comprises the following steps: mixing and stirring the primary dechlorinated salt sludge homogenate and sulfur-containing flue gas at the temperature of 50 ℃; wherein the stirring is carried out by adopting a propeller with the stirring speed of 300 r/min; the flow rate range of the sulfur-containing flue gas is 4.0m/s, and the conveying capacity of the first-stage dechlorinated salt mud homogenate is 60kg/s. The magnesium recovery treatment specifically comprises: nanofiltration of the clear liquid B is carried out by selecting a separation membrane made of aromatic polyamide material, and a magnesium sulfate solution after nanofiltration is obtained;introducing magnesium sulfate seed crystals into the nanofiltration magnesium sulfate solution according to a preset proportion of the magnesium sulfate seed crystals to the chlor-alkali salt slurry under the conditions of initial crystallization temperature of 60 ℃, stirring speed of 100r/min and final crystallization temperature of 20 ℃ to obtain MgSO (magnesium sulfate) with purity of more than 99 percent 4 ·7H 2 O。
Example 4
The difference between the preparation method of magnesium sulfate heptahydrate based on chlor-alkali salt mud provided by the embodiment of the invention and the embodiment 2 is only that the first-stage dechlorination treatment specifically comprises the following steps: when the chlor-alkali salt mud and the eluting agent are mixed for pulping under the conditions of normal temperature and normal pressure, the volume ratio of the chlor-alkali salt mud to the eluting agent is controlled to be 1: and 6, stirring by using a propeller with the stirring speed of 500 r/min. The allowable limit values of the interfering ions in the eluting agent are as follows: chloride equal to 22.0g/L, sulphate equal to 4.5g/L, sodium equal to 20g/L, magnesium equal to 1.8g/L, calcium equal to 0.6g/L, potassium equal to 0.45g/L, the remaining traces equal to 0.18g/L. The pulping treatment specifically comprises the following steps: under the conditions of normal temperature and normal pressure, the volume ratio of the primary dechlorinated salt mud to the deionized water is controlled to be 1:7.5, stirring by a propeller at 200 r/min. The desulphation treatment comprises the following steps: mixing and stirring the primary dechlorinated salt sludge homogenate and sulfur-containing flue gas at the temperature of 70 ℃; wherein the stirring is carried out by adopting a propeller with the stirring speed of 500 r/min; the flow rate range of the sulfur-containing flue gas is 6.0m/s, and the conveying capacity of the first-stage dechlorinated salt mud homogenate is 90kg/s. The magnesium recovery treatment specifically comprises: nanofiltration of the clear liquid B is carried out by selecting a separation membrane made of aromatic polyamide material, and a magnesium sulfate solution after nanofiltration is obtained; introducing magnesium sulfate seed crystals into the nanofiltration magnesium sulfate solution according to the preset proportion of the magnesium sulfate seed crystals and chlor-alkali salt sludge under the conditions of initial crystallization temperature of 80 ℃, stirring speed of 200r/min and final crystallization temperature of 130 ℃ to obtain MgSO (magnesium sulfate) with purity of more than 99 percent 4 ·7H 2 O。
Example 5
The method for preparing magnesium sulfate heptahydrate based on chlor-alkali salt mud provided by the embodiment of the invention is only different from the embodiment 2, and further comprises the following steps:
secondary dechlorination treatment, comprising: fully mixing the salt mud solid with deionized water, stirring to perform secondary dechlorination, and separating to obtain a precipitate and a clear liquid C; and washing, filtering and drying the precipitate to obtain low-chloride salt mud.
The process of washing, filtering and drying the precipitate to obtain the low-chloride salt mud specifically comprises the following steps: filtering the washed precipitate by adopting a belt type filter, and sending the filtered clear liquid C to a circulating water tank; the water content of the filter cake after filtration is reduced to 20 percent; drying the filter cake for 7h at the temperature of 105 ℃ to obtain low-chloride salt mud; with Cl — And (4) the chlorine content of the low-chlorine salt mud is reduced to be below 0.04 percent.
Example 6
The difference between the preparation method of magnesium sulfate heptahydrate based on chlor-alkali salt mud provided by the embodiment of the present invention and the above embodiment 5 is only that the process of washing, filtering and drying the precipitate to obtain low chloride salt mud specifically comprises: filtering the washed precipitate by adopting a belt type, and sending the filtered clear liquid C to a circulating water tank; the water content of the filter cake is reduced to 25 percent after filtration; drying the filter cake for 7.5 hours at the temperature of 115 ℃ to obtain low-chloride salt mud; with Cl — And (3) the chlorine content of the low-chlorine salt mud is reduced to be below 0.04 percent.
Example 7
The difference between the preparation method of magnesium sulfate heptahydrate based on chlor-alkali salt mud provided by the embodiment of the present invention and the above embodiment 5 is only that the process of washing, filtering and drying the precipitate to obtain low chloride salt mud specifically comprises: filtering the washed precipitate by adopting a belt type, and sending the filtered clear liquid C to a circulating water tank; the water content of the filter cake is reduced to 30 percent after filtration; drying the filter cake for 8 hours at the temperature of 125 ℃ to obtain low-chloride salt mud; with Cl — And (3) the chlorine content of the low-chlorine salt mud is reduced to be below 0.04 percent.
In summary, the new process for preparing magnesium sulfate heptahydrate by combining desulfurization and dechlorination of salt slurry provided by the embodiment of the invention comprises the following steps: mixing and stirring the salt slurry by using an eluent, then naturally settling and separating, respectively discharging primary dechlorinated salt slurry and clear liquid A, mixing the primary dechlorinated salt slurry with deionized water, stirring and pulping to obtain primary dechlorinated salt slurry homogenate; the first-level dechlorinated salt mud homogenate is in a desulfurizing towerFully stirring the mixture internally, mixing the mixture with sulfur-containing flue gas to realize the acidification of salty mud and the bidirectional purification of flue gas desulfurization, naturally settling and separating the acidified salty mud, and discharging the salty mud from the bottom of the desulfurization tower; fully mixing the salt mud solid discharged from the desulfurizing tower with deionized water, stirring, performing secondary dechlorination, naturally settling and separating, sending clear liquid C to a circulating water tank, and washing, filtering and drying the precipitate to obtain low-chlorine salt mud; cooling and crystallizing clear liquid B discharged from the desulfurizing tower, fully separating out crystals, and filtering to obtain precipitate which is the obtained high-purity MgSO 4 ·7H 2 And (O). The invention provides a preparation method of magnesium sulfate heptahydrate based on chlor-alkali salt mud, in particular to a method for preparing magnesium sulfate heptahydrate by combining sulfur-containing flue gas desulfurization and chlor-alkali salt mud dechlorination, which can realize harmless and resource treatment of chlor-alkali salt mud.
Finally, it should be noted that: although the present invention has been described in detail with reference to the above embodiments, it should be understood by those skilled in the art that: modifications and equivalents may be made to the embodiments of the invention without departing from the spirit and scope of the invention, which is to be covered by the claims.
Claims (10)
1. A preparation method of magnesium sulfate heptahydrate based on chlor-alkali salt mud is characterized by comprising the following steps:
primary dechlorination treatment comprising: mixing, stirring and separating the chlor-alkali salt mud by using an eluting agent to obtain primary dechlorinated salt mud and clear liquid A;
pulping treatment comprising: mixing the primary dechlorinated salt mud with deionized water, stirring and pulping to obtain primary dechlorinated salt mud homogenate;
a desulphation treatment comprising: mixing and stirring the primary dechlorinated salt mud homogenate and sulfur-containing flue gas to realize the acidification of chlor-alkali salt mud and the bidirectional purification of flue gas desulfurization, and separating the acidified salt mud to obtain salt mud solid and clear liquid B;
magnesium recovery treatment, comprising: subjecting the clear liquid B toCooling, crystallizing, filtering to obtain precipitate (MgSO) 4 ·7H 2 O。
2. The method for preparing magnesium sulfate heptahydrate based on chlor-alkali salt sludge as claimed in claim 1, further comprising:
secondary dechlorination treatment, comprising: fully mixing the salt mud solid with deionized water, stirring to perform secondary dechlorination, and separating to obtain a precipitate and a clear liquid C; and washing, filtering and drying the precipitate to obtain low-chloride salt mud.
3. The method for preparing magnesium sulfate heptahydrate based on chlor-alkali salt sludge as claimed in claim 2, wherein the process of washing, filtering and drying the precipitate to obtain low chloride salt sludge specifically comprises:
filtering the washed precipitate by adopting a belt type filter, and sending the filtered clear liquid C to a circulating water tank; the water content of the filter cake after filtration is reduced to 20-30 percent;
drying the filter cake for 7-8 h at the temperature of 105-125 ℃ to obtain low-chloride salt mud; with Cl — And (4) the chlorine content of the low-chlorine salt mud is reduced to be below 0.04 percent.
4. The method for preparing magnesium sulfate heptahydrate based on chlor-alkali salt mud of claim 1, wherein the separation in the primary dechlorination and the desulfation is natural settling separation.
5. The method for preparing magnesium sulfate heptahydrate based on chlor-alkali salt mud of claim 1, characterized in that in the primary dechlorination treatment,
the allowable limit values of the interfering ions in the eluting agent are as follows: the content of chloride ions is less than or equal to 25.0g/L, the content of sulfate ions is less than or equal to 5.0g/L, the content of sodium ions is less than or equal to 20.5g/L, the content of magnesium ions is less than or equal to 2.0g/L, the content of calcium ions is less than or equal to 0.7g/L, the content of potassium ions is less than or equal to 0.5g/L, and the content of other trace ions is less than or equal to 0.25g/L.
6. The method for preparing magnesium sulfate heptahydrate based on chlor-alkali salt sludge as claimed in claim 1, wherein the primary dechlorination treatment comprises:
when the chlor-alkali salt mud and the eluting agent are mixed for pulping under the conditions of normal temperature and normal pressure, the volume ratio of the chlor-alkali salt mud to the eluting agent is controlled to be 1: (2-6), stirring by a propeller with the stirring speed of 100 r/min-500 r/min.
7. The method for preparing magnesium sulfate heptahydrate based on chlor-alkali salty mud as claimed in claim 1, wherein the pulping treatment specifically comprises:
under the conditions of normal temperature and normal pressure, the volume ratio of the primary dechlorinated salt mud to the deionized water is controlled to be 1: (5.0-7.5), stirring by a propeller at 100 r/min-200 r/min.
8. The process for the preparation of magnesium sulfate heptahydrate based on chlor-alkali salt sludge as claimed in claim 1, characterized in that said desulphation treatment comprises:
mixing and stirring the primary dechlorinated salt sludge homogenate and sulfur-containing flue gas at the temperature of 40-70 ℃; wherein the stirring adopts a propeller with the stirring speed of 100 r/min-500 r/min; the flow rate range of the sulfur-containing flue gas is 2.5-6.0 m/s, and the conveying capacity of the first-stage dechlorinated salt mud homogenate is 40-90 kg/s.
9. The method for preparing magnesium sulfate heptahydrate based on chlor-alkali salt sludge as claimed in claim 1, wherein said magnesium recovery treatment comprises:
nanofiltration of the clear liquid B is carried out by selecting a separation membrane made of aromatic polyamide material, and a magnesium sulfate solution after nanofiltration is obtained;
introducing magnesium sulfate seed crystals into the nanofiltration magnesium sulfate solution according to the preset proportion of the magnesium sulfate seed crystals and chlor-alkali salt slurry under the conditions of initial crystallization temperature of 50-80 ℃, stirring speed of 50-200 r/min and final crystallization temperature of 10-30 ℃ to obtain MgSO (magnesium sulfate) with purity of more than 99 percent 4 ·7H 2 O。
10. A system for preparing magnesium sulfate heptahydrate based on chlor-alkali salt mud is characterized by comprising the following components:
the first-stage dechlorination processing unit is used for mixing, stirring and separating the chlor-alkali salt mud by using an eluting agent to obtain first-stage dechlorinated salt mud and clear liquid A;
the pulping treatment unit is used for mixing, stirring and pulping the primary dechlorinated salt mud and deionized water to obtain primary dechlorinated salt mud homogenate;
the desulfation processing unit is used for mixing and stirring the primary dechlorinated salt slurry homogenate and sulfur-containing flue gas to realize the acidification of chlor-alkali salt slurry and the bidirectional purification of flue gas desulfurization, and the acidified salt slurry is separated to obtain salt slurry solid and clear liquid B;
a magnesium recovery processing unit for cooling and crystallizing the clear liquid B, filtering after full crystallization, and obtaining MgSO as precipitate 4 ·7H 2 O。
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Application publication date: 20221118 |