Device and method for refining brine of by-product gypsum and magnesium compounds

Abstract

The present invention discloses a brine refining device and method for by-product gypsum and magnesium compounds, and relates to the technical field of brine refining. The present invention recycles the concentrated brine and washing water generated in the production for use in the production system again, without secondary waste discharge. The prepared gypsum has a whiteness of more than 90% and a purity of more than 96%; the magnesium compound has a whiteness of more than 92% and a purity of more than 95%. Under the premise of ensuring the quality of the primary brine, the brine refining process is subjected to a step-by-step refining process, and the crude magnesium hydroxide and calcium sulfate dihydrate are preliminarily separated, and the crude material is purified by methods such as dissolution, precipitation, washing, and drying. The salt mud that occupies a large amount of land for storage is comprehensively utilized to produce high-value-added magnesium series compounds and semi-hydrate gypsum, turning waste into treasure, and greatly alleviating the problem of salt mud storage in soda ash production.

Description

Technical Field

[0001] The present invention relates to the technical field of brine refining, and in particular to a device and method for refining brine with by-product gypsum and magnesium compounds. Background Art

[0002] In the production process of soda ash by the ammonia-soda process, the concentrated brine after desalination of seawater is used to dissolve the raw salt to prepare the brine. The calcium, magnesium, impurity ions and sediment in the concentrated brine after desalination of seawater and the raw salt enter the brine. In order to ensure the quality of the soda ash product, the crude brine is refined in the brine refining process. In the primary refining process of the brine, ash milk and mirabilite are added to the crude brine at the same time to remove the magnesium ions and part of the calcium ions in the crude brine. The generated magnesium hydroxide precipitate, calcium sulfate dihydrate precipitate and the solid impurities in the concentrated brine after desalination of seawater, raw salt and ash milk are precipitated together in the clarification tank to form a complex mixture of multiple components such as calcium sulfate, magnesium hydroxide, calcium carbonate, sodium chloride, acid insoluble matter, etc. - salt mud. In order to recover the sodium chloride in the salt mud, the salt mud in the clarification tank is washed and filtered, and the filtrate and salt water are returned to the salting process. The salt mud filter cake is used for dam construction, road construction or stockpiling. Summary of the invention

[0003] In order to solve the above technical problems, the present invention provides a brine refining device and method for by-product gypsum and magnesium compounds.

[0004] To achieve this technical purpose, the device of the present invention adopts the following scheme: a brine refining device for by-product gypsum and magnesium compounds, including a salting barrel, a magnesium removal reactor, a magnesium clarification barrel or an air flotation device, a crude magnesium filter, a decalcification reactor, a calcium clarification barrel, a belt filter, a primary brine barrel, a gypsum drying furnace, a refined magnesium filter and a refined magnesium drying furnace; the salting barrel is connected to the magnesium removal reactor, the magnesium removal reactor is connected to the magnesium clarification barrel or the air flotation device, the magnesium clarification barrel or the air flotation device is respectively connected to the crude magnesium filter and the decalcification reactor, the decalcification reactor is connected to the calcium clarification barrel, the calcium clarification barrel is respectively connected to the primary brine barrel and the belt filter, the belt filter is respectively connected to the gypsum drying furnace, the calcium clarification barrel and the salting barrel; the crude magnesium filter is respectively connected to the magnesium clarification barrel or the air flotation device and the crude magnesium dissolving barrel, the crude magnesium dissolving barrel is connected to the filter press, the filter press is connected to the refined magnesium reactor, the refined magnesium reactor is connected to the refined magnesium filter, and the refined magnesium filter is respectively connected to the refined magnesium drying furnace, the salting barrel and the decalcification reactor.

[0005] Compared with the prior art, the beneficial effect of the device of the present invention is that the device is respectively provided with a calcium removal reactor and a magnesium removal reactor for step-by-step refining, and the filtrate and washing water device are connected to the clarification tank and the salt treatment tank, so that all by-products can be recycled and utilized, thereby improving the comprehensive utilization rate of salt mud resources.

[0006] Furthermore, the belt filter is respectively connected to a calcium mother liquor barrel and a calcium washing water barrel, the calcium mother liquor barrel is connected to a calcium clarification barrel, and the calcium washing water barrel is connected to a salting barrel.

[0007] Furthermore, the refined magnesium filter is respectively connected to a refined magnesium washing water bucket and a refined magnesium mother liquor bucket, the refined magnesium washing water bucket is connected to a salt tank, and the refined magnesium mother liquor bucket is connected to a decalcification reactor.

[0008] To achieve this technical purpose, the method of the present invention adopts the following scheme:

[0009] A method for refining brine with by-product gypsum and magnesium compounds, using the above-mentioned brine refining device, is carried out according to the following steps:

[0010] a. Preparation of crude brine: using seawater desalination brine to dissolve the raw salt, and the prepared crude brine is sent to the magnesium removal reactor;

[0011] b. Magnesium removal reaction: crude brine and ash milk are mixed in the magnesium removal reactor and chemically reacted to form a mixed slurry of magnesium hydroxide precipitate and sodium chloride solution. The mixed slurry is settled in a magnesium clarification barrel or an auxiliary air flotation device is used to achieve preliminary solid-liquid separation. The clear liquid enters the decalcification reactor, and the magnesium slurry is transported to the crude magnesium filter by a magnesium slurry pump;

[0012] c. Production of magnesium compounds: magnesium slurry is filtered through a crude magnesium filter and sent to a crude magnesium dissolution barrel, where it is mixed with sulfuric acid and chemically reacted to form a mixed slurry of calcium sulfate dihydrate precipitate and magnesium sulfate solution. The mixed slurry is solid-liquid separated by a filter press, and the crude calcium filter cake is transported out. The magnesium sulfate solution is sent to a refined magnesium reactor, where it is mixed with soda ash or caustic soda and chemically reacted to form a mixed slurry of magnesium hydroxide or magnesium carbonate precipitate and sodium sulfate solution. The mixed slurry enters a refined magnesium filter for solid-liquid separation, washing, impurity reduction and purification, and the filter cake enters a refined magnesium drying furnace to produce magnesium compounds. The magnesium compounds enter a refined magnesium packaging machine after refined magnesium grinding, air separation and conveying equipment for product packaging;

[0013] d. Disposal of magnesium compound filtrate and washing water: the mother liquor filtered by the coarse magnesium filter is transported to the magnesium clarification tank; the mother liquor filtered by the refined magnesium filter is transported to the decalcification reactor, and the washing water filtered by the refined magnesium filter is transported to the salt tank;

[0014] e. Calcium removal reaction: The magnesium-removed crude brine obtained in step b is mixed with the mother liquor transported by the mirabilite and refined magnesium filter in the decalcification reactor and chemically reacts to form a mixed slurry of calcium sulfate dihydrate precipitate and sodium chloride solution. The mixed slurry is settled in a calcium clarification barrel, and the upper clear liquid overflows to the primary brine barrel to continue the secondary refining process. The calcium slurry at the bottom is transported to the belt filter;

[0015] f. Gypsum production: After the calcium mud enters the belt filter, it is separated into solid and liquid and washed with water to obtain dihydrate gypsum. The dihydrate gypsum is sent to the gypsum drying furnace to produce semi-hydrated gypsum. After the semi-hydrated gypsum is ground and winnowed, it enters the gypsum packaging machine through the conveying equipment for product packaging;

[0016] g. Disposal of gypsum filtrate and washing water: the mother liquor filtered by the belt filter is transported to the calcium clarification tank; the washing water filtered by the belt filter is transported to the salt tank.

[0017] Compared with the prior art, the beneficial effect of the method of the present invention is that the concentrated brine and washing water generated in the process are recycled and used in the production system again, and there is no secondary waste discharge. The prepared gypsum has a whiteness of more than 90% and a purity of more than 96%; the magnesium compound has a whiteness of more than 92% and a purity of more than 95%. Under the premise of ensuring the quality of the primary brine, the brine refining process is subjected to a step-by-step refining process to preliminarily separate the crude magnesium hydroxide and dihydrate calcium sulfate, and the crude material is purified by methods such as dissolution, precipitation, washing, and drying. The salt mud that occupies a large amount of land for storage is comprehensively utilized to produce high-value-added magnesium series compounds and semi-hydrate gypsum, turning waste into treasure, which greatly alleviates the problem of salt mud storage in soda ash production.

[0018] Furthermore, in step a, the NaCl content in the raw salt is ≥93%, and the sodium chloride content of the prepared crude brine is ≥310 g / L.

[0019] Furthermore, in step b, the effective calcium oxide content of the lime milk is 224-252 g / L, the stirring speed of the magnesium removal reactor is 5-11 rpm; the magnesium slurry sedimentation rate at the bottom of the magnesium clarification barrel is ≥95%, and the clear liquid layer height is ≥4 m.

[0020] Furthermore, in step b, the compressed air pressure of the flotation device is 0.3-0.5 MPa, and the floating mud sedimentation rate is ≥90%.

[0021] Furthermore, in step c, the moisture content of the crude magnesium filter cake is ≤30%, the sulfuric acid concentration is 60%, the moisture content of the crude calcium filter cake after filter pressing is ≤50%, the Na2CO3 content in soda ash or the NaOH content in caustic soda is ≥98%, and the stirring speed of the refined magnesium reactor is 5-11rpm; the moisture content of the refined magnesium filter cake is ≤30%, the sodium chloride content is ≤0.07%, and the discharge temperature of the refined magnesium drying furnace is 120-140°C.

[0022] Furthermore, in step e, the concentration of sodium sulfate is 142-213 g / L, the stirring speed of the decalcification reactor is 5-11 rpm, the magnesium slurry sedimentation rate at the bottom of the calcium clarification tank is ≥90%, and the height of the clear liquid layer is ≥4 m.

[0023] Furthermore, in step f, the water content of the dihydrate gypsum filter cake is ≤25%, the sodium chloride content is ≤0.07%, and the discharge temperature of the gypsum drying furnace is 125-150°C. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 An equipment connection diagram of a brine refining device for by-product gypsum and magnesium compounds provided in an embodiment of the present invention;

[0025] Figure 2 A process flow chart of brine refining of by-product gypsum and magnesium compounds provided in an embodiment of the present invention;

[0026] The following are marked in the figure: 1. salt tank; 2. crude brine buffer tank; 3. crude brine pump; 4. magnesium removal reactor; 5. magnesium clarification tank; 6. decalcification reactor; 7. calcium clarification tank; 8. primary brine tank; 9. primary brine pump; 10. magnesium slurry pump; 11. crude magnesium filter; 12. crude magnesium mother liquor tank; 13. crude magnesium mother liquor pump; 14. crude magnesium conveyor belt; 15. sulfuric acid tank; 16. acid addition pump; 17. crude magnesium dissolution tank; 18. feed pump; 19. filter press; 20. crude calcium conveyor belt; 21. magnesium sulfate buffer tank; 22. magnesium sulfate pump; 23. silo; 24. Refined magnesium reactor; 25. Refined magnesium filter; 26. Refined magnesium washing water barrel; 27. Refined magnesium washing water pump; 28. Refined magnesium mother liquor barrel; 29. ​​Refined magnesium mother liquor pump; 30. Refined magnesium conveyor belt; 31. Refined magnesium drying furnace; 32. Refined magnesium grinding, air separation and conveying equipment; 33. Refined magnesium packaging machine; 34. Calcium mud pump; 35. Belt filter; 36. Calcium mother liquor barrel; 37. Calcium mother liquor pump; 38. Calcium washing water barrel; 39. Calcium washing water pump; 40. Dihydrate gypsum conveyor belt; 41. Gypsum drying furnace; 42. Gypsum grinding, air separation and conveying equipment; 43. Gypsum packaging machine. DETAILED DESCRIPTION

[0027] In order to fully understand the purpose, features and effects of the present invention, the present invention is described in detail through the following specific implementation methods, but the present invention is not limited thereto.

[0028] like Figure 1 As shown, the present invention provides a brine refining device for by-product gypsum and magnesium compounds, which comprises a salt tank 1, a crude brine buffer tank 2, a crude brine pump 3, a magnesium removal reactor 4, a magnesium clarification tank 5, a decalcification reactor 6, a calcium clarification tank 7, a primary brine tank 8, a primary brine pump 9, a magnesium slurry pump 10, a crude magnesium filter 11, a crude magnesium mother liquor tank 12, a crude magnesium mother liquor pump 13, a crude magnesium conveying belt 14, a sulfuric acid tank 15, an acid addition pump 16, a crude magnesium dissolving tank 17, a feed pump 18, a filter press 19, a crude calcium conveying belt 20, a magnesium sulfate buffer tank 21, and a magnesium sulfate The refined magnesium reactor is composed of a pump 22, a silo 23, a refined magnesium reactor 24, a refined magnesium filter 25, a refined magnesium washing water barrel 26, a refined magnesium washing water pump 27, a refined magnesium mother liquor barrel 28, a refined magnesium mother liquor pump 29, a refined magnesium conveying belt 30, a refined magnesium drying furnace 31, a refined magnesium grinding, air separation and conveying equipment 32, a refined magnesium packaging machine 33, a calcium mud pump 34, a belt filter 35, a calcium mother liquor barrel 36, a calcium mother liquor pump 37, a calcium washing water barrel 38, a calcium washing water pump 39, a dihydrate gypsum conveying belt 40, a gypsum drying furnace 41, a gypsum grinding, air separation and conveying equipment 42, and a gypsum packaging machine 43.

[0029] The salt tank 1 is connected to the crude brine buffer tank 2 through a pipeline, the crude brine buffer tank 2 is connected to the magnesium removal reactor 4 through a crude brine pump 3 and a matching pipeline, and the magnesium removal reactor 4 is connected to the magnesium clarification tank 5 (or an air flotation device) through a pipeline. The magnesium clarification tank 5 (or an air flotation device) is connected to the decalcification reactor 6 through a pipeline, the decalcification reactor 6 is connected to the calcium clarification tank 7 through a launder, the calcium clarification tank 7 is connected to the primary brine tank 8 through a pipeline, and the primary brine tank 8 is connected to the primary brine pump 9 through a pipeline.

[0030] The calcium clarification tank 7 is also connected to the belt filter 35 through the calcium mud pump 34 and the supporting pipeline. The belt filter 35 is connected to the gypsum drying furnace 41 through the dihydrate gypsum conveying belt 40. The gypsum drying furnace 41 is connected to the gypsum packaging machine 43 through the gypsum grinding, air selection and conveying equipment 42.

[0031] The belt filter 35 is also connected to the calcium mother liquor bucket 36 and the calcium washing water bucket 38 through pipelines respectively, and the calcium mother liquor bucket 36 is connected to the calcium clarification bucket 7 through the calcium mother liquor pump 37. The calcium washing water bucket 38 is connected to the salting bucket 1 through the calcium washing water pump 39.

[0032] The magnesium clarification tank 5 (or air flotation device) is connected to the crude magnesium filter 11 through the magnesium slurry pump 10, and the crude magnesium filter 11 is connected to the crude magnesium mother liquor tank 12 through a pipeline, and the crude magnesium mother liquor tank 12 is connected to the magnesium clarification tank 5 (or air flotation device) through the crude magnesium mother liquor pump 13. The crude magnesium filter 11 is also connected to the crude magnesium conveyor belt 14, and the crude magnesium conveyor belt 14 is connected to the crude magnesium dissolution tank 17, and the sulfuric acid tank 15 is connected to the crude magnesium dissolution tank 17 through the acid addition pump 16. The crude magnesium dissolution tank 17 is also connected to the filter press 19 through the feed pump 18, and the filter press 19 is respectively connected to the crude calcium conveyor belt 20 and the magnesium sulfate buffer tank 21. The magnesium sulfate buffer tank 21 is connected to the refined magnesium reactor 24 through the magnesium sulfate pump 22 and the supporting pipeline. The silo 23 is connected to the refined magnesium reactor 24 through the feeder and the supporting pipeline, and the refined magnesium reactor 24 is connected to the refined magnesium filter 25. The refined magnesium filter 25 is connected to the refined magnesium drying furnace 31 through the refined magnesium conveying belt 30 , and the refined magnesium drying furnace 31 is connected to the refined magnesium packaging machine 33 through the refined magnesium grinding, air separation and conveying equipment 32 .

[0033] The refined magnesium filter 25 is also connected to the refined magnesium washing water bucket 26 and the refined magnesium mother liquor bucket 28 through pipelines respectively. The refined magnesium washing water bucket 26 is connected to the salt tank 1 through the refined magnesium washing water pump 27 and supporting pipelines; the refined magnesium mother liquor bucket 28 is connected to the decalcification reactor 6 through the refined magnesium mother liquor pump 29 and supporting pipelines.

[0034] A method for refining brine with by-product gypsum and magnesium compounds, the process flow is as follows: Figure 2 As shown, proceed as follows:

[0035] a. Using seawater desalination brine to dissolve raw salt in a salt tank 1, a crude brine with a sodium chloride content of 313 g / L is prepared. The crude brine overflows into a crude brine buffer tank 2 and is then delivered to a magnesium removal reactor 4 via a crude brine pump 3.

[0036] b. Magnesium removal reaction: crude brine and ash milk with an effective calcium oxide content of 231g / L enter the magnesium removal reactor 4 at a flow ratio of 60:1, and are mixed by continuous stirring in the magnesium removal reactor 4, and a chemical reaction occurs to form a mixed slurry of magnesium hydroxide precipitation and sodium chloride solution. The mixed slurry is subjected to preliminary solid-liquid separation by a magnesium clarification barrel 5 or an air flotation device, and the mud sedimentation rate at the bottom of the magnesium clarification barrel 5 is controlled to be ≥95%, the height of the clear liquid layer is ≥4m, or the mud sedimentation rate of the air flotation device is ≥90%. The clear liquid in the magnesium clarification barrel 5 is the magnesium removal crude brine, which flows to the decalcification reactor 6, and the magnesium slurry is transported to the crude magnesium filter 11 by a magnesium slurry pump 10.

[0037] c. Production of magnesium compounds: The magnesium slurry is filtered through the crude magnesium filter 11, and the moisture content of the crude magnesium filter cake is controlled to be ≤30%. The crude magnesium filter cake is sent to the crude magnesium dissolution tank 17 through the crude magnesium conveyor belt 14 and the 60% sulfuric acid added by the acid pump 16 at a mass ratio of 1:3.5. In the crude magnesium dissolution tank 17, continuous stirring is used to achieve mixing and chemical reaction to form a mixed slurry of calcium sulfate dihydrate precipitate and magnesium sulfate solution. The mixed slurry enters the filter press 19 through the filter press feed pump 18, and solid-liquid separation is performed in the filter press 19. The pressure of the filter press 19 is controlled to be 0.5~0.6MPa, and the moisture content of the filter cake is ≤50%. The crude calcium filter cake is transported out through the crude calcium conveyor belt 20, and the magnesium sulfate solution overflows to the magnesium sulfate buffer barrel 21, and is sent to the refined magnesium reactor 24 through the magnesium sulfate pump 22 and the soda ash under the silo 23 at a molar ratio of 1:0.525 (or caustic soda 1:1.05). In the refined magnesium reactor 24, the mixture is mixed and chemically reacted by continuous stirring to form a mixed slurry of magnesium hydroxide or magnesium carbonate precipitation and sodium sulfate solution. The mixed slurry enters the refined magnesium filter 25 for solid-liquid separation and washing, and the moisture content of the refined magnesium filter cake is controlled to be ≤30% and the sodium chloride content is controlled to be ≤0.07%. After washing, the filter cake enters the refined magnesium drying furnace 31 through the refined magnesium conveyor belt 30, and the magnesium compound is indirectly heated by steam in the refined magnesium drying furnace 31 to produce magnesium compounds. The discharge temperature of the refined magnesium drying furnace 31 is controlled to be 120~140℃. The magnesium compound enters the refined magnesium packaging machine 33 after refined magnesium grinding, air separation and conveying equipment 32 for product packaging.

[0038] d. Disposal of magnesium compound filtrate and washing water: the mother liquor filtered by the crude magnesium filter 11 enters the crude magnesium mother liquor barrel 12, and is transported to the magnesium clarification barrel 5 through the crude magnesium mother liquor pump 13; the mother liquor filtered by the refined magnesium filter 25 enters the refined magnesium mother liquor barrel 28, and is transported to the decalcification reactor 6 through the refined magnesium mother liquor pump 29; the washing water filtered by the refined magnesium filter 25 enters the refined magnesium washing water barrel 26, and is transported to the salt barrel 1 through the refined magnesium washing water pump 27.

[0039] e. Decalcification reaction: The magnesium-removed crude brine obtained in step b and the mother liquor transported by the 178g / L sodium sulfate and refined magnesium mother liquor pump 29 enter the decalcification reactor 6 at a flow ratio of 14:1, and are mixed and chemically reacted by continuous stirring in the decalcification reactor 6 to form a mixed slurry of calcium sulfate dihydrate precipitate and sodium chloride solution. The mixed slurry is settled in the calcium clarification barrel 7, and the bottom mud sedimentation rate is controlled to be ≥90%, and the thickness of the clear liquid layer is ≥4m. The upper clear liquid overflows to the primary brine barrel 8, and is then transported to the secondary refining process by the primary brine pump 9, and the bottom calcium mud is transported to the belt filter 35 by the calcium mud pump 34.

[0040] f. Gypsum production: The calcium mud enters the belt filter 35 for solid-liquid separation and washing with water to obtain dihydrate gypsum. The water content of the dihydrate gypsum filter cake is controlled to be ≤25% and the sodium chloride content is ≤0.07%. After washing, the dihydrate gypsum is transported to the gypsum drying furnace 41 via the dihydrate gypsum conveyor belt 40. In the gypsum drying furnace 41, steam is used for indirect heating to produce semi-hydrated gypsum. The discharge temperature of the gypsum drying furnace 41 is controlled to be 125~150℃. The semi-hydrated gypsum enters the gypsum packaging machine 43 after the gypsum grinding, air separation and conveying equipment 42 for product packaging.

[0041] g. Disposal of gypsum filtrate and washing water: the mother liquor filtered by the belt filter 35 enters the calcium mother liquor barrel 36 and is transported to the calcium clarification barrel 7 through the calcium mother liquor pump 37; the washing water filtered by the belt filter 35 enters the calcium washing water barrel 38 and is transported to the salting barrel 1 through the calcium washing water pump 39.

[0042] Gypsum and magnesium compounds are obtained by step-by-step calcium and magnesium removal, and are packaged. The magnesium compound filtrate and gypsum filtrate produced in the reaction process are returned to the magnesium clarification tank 5 and the calcium clarification tank 7, respectively. The magnesium compound washing water and the gypsum washing water are returned to the salt tank 1. All by-products in the production process are recycled and utilized, effectively realizing the comprehensive utilization of resources.

[0043] Finally, it should be noted that the above-listed embodiments are only preferred embodiments of the present invention. Of course, those skilled in the art can make changes and modifications to the present invention. If these modifications and variations fall within the scope of the claims of the present invention and their equivalent technologies, they should be considered to be within the scope of protection of the present invention.

Claims

1. A method for refining brine produced by producing gypsum and magnesium compounds, using a device for refining brine produced by producing gypsum and magnesium compounds, characterized in that: Proceed as follows: a. Preparation of crude brine: using seawater desalination brine to dissolve the raw salt, and the prepared crude brine is sent to the magnesium removal reactor; b. Magnesium removal reaction: crude brine and ash milk are mixed in the magnesium removal reactor and chemically reacted to form a mixed slurry of magnesium hydroxide precipitate and sodium chloride solution. The mixed slurry is settled in a magnesium clarification barrel or an auxiliary air flotation device is used to achieve preliminary solid-liquid separation. The clear liquid enters the decalcification reactor, and the magnesium slurry is transported to the crude magnesium filter by a magnesium slurry pump; c. Production of magnesium compounds: magnesium slurry is filtered through a crude magnesium filter and sent to a crude magnesium dissolution barrel, where it is mixed with sulfuric acid and chemically reacted to form a mixed slurry of calcium sulfate dihydrate precipitate and magnesium sulfate solution. The mixed slurry is solid-liquid separated by a filter press, and the crude calcium filter cake is transported out. The magnesium sulfate solution is sent to a refined magnesium reactor, where it is mixed with soda ash or caustic soda and chemically reacted to form a mixed slurry of magnesium hydroxide or magnesium carbonate precipitate and sodium sulfate solution. The mixed slurry enters a refined magnesium filter for solid-liquid separation, washing, impurity reduction and purification, and the filter cake enters a refined magnesium drying furnace to produce magnesium compounds. The magnesium compounds enter a refined magnesium packaging machine after refined magnesium grinding, air separation and conveying equipment for product packaging; In step c, the moisture content of the crude magnesium filter cake is ≤30%, the sulfuric acid concentration is 60%, the moisture content of the crude calcium filter cake after filter pressing is ≤50%, the Na2CO3 content in soda ash or the NaOH content in caustic soda is ≥98%, and the stirring speed of the refined magnesium reactor is 5-11rpm; the moisture content of the refined magnesium filter cake is ≤30%, the mass content of sodium chloride is ≤0.07%, and the discharge temperature of the refined magnesium drying furnace is 120-140°C; d. Disposal of magnesium compound filtrate and washing water: the mother liquor filtered by the coarse magnesium filter is transported to the magnesium clarification tank; the mother liquor filtered by the refined magnesium filter is transported to the decalcification reactor, and the washing water filtered by the refined magnesium filter is transported to the salt tank; e. Calcium removal reaction: The magnesium-removed crude brine obtained in step b is mixed with the mother liquor transported by the mirabilite and refined magnesium filter in the decalcification reactor and chemically reacts to form a mixed slurry of calcium sulfate dihydrate precipitate and sodium chloride solution. The mixed slurry is settled in a calcium clarification barrel, and the upper clear liquid overflows to the primary brine barrel to continue the secondary refining process. The calcium slurry at the bottom is transported to the belt filter; f. Gypsum production: After the calcium mud enters the belt filter, it is separated into solid and liquid and washed with water to obtain dihydrate gypsum. The dihydrate gypsum is sent to the gypsum drying furnace to produce semi-hydrated gypsum. After the semi-hydrated gypsum is ground and winnowed, it enters the gypsum packaging machine through the conveying equipment for product packaging; g. Disposal of gypsum filtrate and washing water: the mother liquor filtered by the belt filter is transported to the calcium clarification tank; the washing water filtered by the belt filter is transported to the salt tank; The brine refining device for by-product gypsum and magnesium compounds comprises a salting barrel, a magnesium removal reactor, a magnesium clarification barrel or an air flotation device, a crude magnesium filter, a decalcification reactor, a calcium clarification barrel, a belt filter, a primary brine barrel, a gypsum drying furnace, a refined magnesium filter and a refined magnesium drying furnace; characterized in that: The salting tank is connected to the magnesium removal reactor, the magnesium removal reactor is connected to the magnesium clarification tank or the air flotation device, the magnesium clarification tank or the air flotation device is respectively connected to the coarse magnesium filter and the decalcification reactor, the decalcification reactor is connected to the calcium clarification tank, the calcium clarification tank is respectively connected to the primary brine tank and the belt filter, the belt filter is respectively connected to the gypsum drying furnace, the calcium clarification tank, and the salting tank; The crude magnesium filter is respectively connected to the magnesium clarification barrel or flotation device and the crude magnesium dissolution barrel, the crude magnesium dissolution barrel is connected to the filter press, the filter press is connected to the refined magnesium reactor, the refined magnesium reactor is connected to the refined magnesium filter, and the refined magnesium filter is respectively connected to the refined magnesium drying furnace, the salt barrel and the decalcification reactor.

2. The method for refining brine of by-product gypsum and magnesium compounds according to claim 1, characterized in that: The belt filter is respectively connected with a calcium mother liquor barrel and a calcium washing water barrel, the calcium mother liquor barrel is connected with a calcium clarification barrel, and the calcium washing water barrel is connected with a salt tank.

3. The method for refining brine of by-product gypsum and magnesium compounds according to claim 1, characterized in that: The refined magnesium filter is respectively connected with a refined magnesium washing water bucket and a refined magnesium mother liquor bucket, the refined magnesium washing water bucket is connected with a salt tank, and the refined magnesium mother liquor bucket is connected with a decalcification reactor.

4. The method for refining brine of by-product gypsum and magnesium compounds according to claim 1, characterized in that: In step a, the NaCl content in the raw salt is ≥93%, and the sodium chloride content of the prepared crude brine is ≥310 g / L.

5. The method for refining brine of by-product gypsum and magnesium compounds according to claim 1, characterized in that: In step b, the effective calcium oxide content of the lime milk is 224-252 g / L, the stirring speed of the magnesium removal reactor is 5-11 rpm; the magnesium slurry sedimentation rate at the bottom of the magnesium clarification barrel is ≥95%, and the clear liquid layer height is ≥4 m.

6. The method for refining brine of by-product gypsum and magnesium compounds according to claim 1, characterized in that: In step b, the compressed air pressure of the flotation device is 0.3-0.5 MPa, and the mud settling rate is ≥90%.

7. The method for refining brine of by-product gypsum and magnesium compounds according to claim 1, characterized in that: In step e, the concentration of sodium sulfate is 142-213 g / L, the stirring speed of the decalcification reactor is 5-11 rpm, the magnesium slurry sedimentation rate at the bottom of the calcium clarification tank is ≥90%, and the height of the clear liquid layer is ≥4 m.

8. The method for refining brine of by-product gypsum and magnesium compounds according to claim 1, characterized in that: In step f, the water content of the dihydrate gypsum filter cake is ≤25%, the sodium chloride content is ≤0.07%, and the discharge temperature of the gypsum drying furnace is 125-150° C.

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