A production method of high-quality chemical gypsum

Abstract

The present invention belongs to the technical field of inorganic materials, and specifically discloses a production method of high-quality chemical gypsum, which comprises the following steps: mixing and reacting Material 1 and Material 2, and the turbid liquid at the upper part of the reactor enters the clarification section, and the clarified liquid is used as raw materials for salt production, alkali production or mining water; the slurry at the bottom of the reactor enters the gypsum slurry collection system, and the gypsum slurry is primarily separated by a hydrocyclone, the top flow of which returns to the reaction tank for recirculation, and the bottom flow thereof is transferred to the slurry primary dewatering and washing machine; the treated filter material enters the pulping and elutriation tank, the slurry after elutriation enters the secondary dewatering and washing machine, and the filter material is directly packaged into a product after being moderately refined, or is broken, dried and then packaged into a product. The gypsum prepared by the process method of the present invention has high purity, excellent whiteness, and stable and controllable quality.

Description

Technical Field

[0001] The invention belongs to the technical field of inorganic materials, relates to the production of gypsum, and particularly relates to a method for producing high-quality chemical gypsum by using mirabilite-type brine and calcium chloride-type brine. Background Art

[0002] Gypsum is divided into natural gypsum and chemically synthesized gypsum. Natural gypsum refers to gypsum stone (minerals whose main components are calcium sulfate dihydrate or anhydrous calcium sulfate) contained in nature, mainly sediments of ancient salt lakes or lagoons. It is usually white, sometimes gray, light yellow, slightly reddish or light brown due to impurities, and is an important non-metallic mineral resource. Although my country's reserves of natural gypsum are very rich, the proportion of high-quality natural gypsum is very small, and as the national environmental protection policy becomes more and more stringent, the scope and intensity of its mining are greatly limited, which invisibly affects the supply of high-quality gypsum market. Chemically synthesized gypsum, also known as industrial by-product gypsum, is a by-product produced in the industrial production process with calcium sulfate dihydrate (CaSO4·2H2O) as the main component, called industrial by-product gypsum, such as phosphogypsum, flue gas desulfurization gypsum, citric acid gypsum, titanium gypsum, etc. Due to the presence of a large amount of impurities, industrial by-product gypsum has problems such as low purity, poor whiteness, or odor, and its application scenarios are greatly limited. Phosphogypsum and desulfurization gypsum have been gradually developed and utilized by people, with large fluctuations in quality and generally limited to low-level applications in the construction industry.

[0003] Therefore, it is urgent to develop a process method to provide high-quality chemical gypsum with high purity and good whiteness to replace high-quality natural gypsum, so as to solve the problem of shortage of natural resources and meet the demand of the high-quality gypsum market. Summary of the invention

[0004] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a method for producing high-quality chemical gypsum. The present invention is based on the existing salt and nitrate making industries, and adopts ammonia-soda method alkali-making calcium clearing liquid or calcium chloride brine containing calcium ions and nitrate brine with different sodium sulfate contents as raw materials. Through the setting of the process, gypsum with high purity and excellent whiteness is obtained, and the quality is stable and controllable.

[0005] The present invention is achieved through the following technical solutions:

[0006] A method for producing high-quality chemical gypsum comprises the following steps:

[0007] (1) After the material 1 providing the calcium source and the material 2 providing the sulfate ion are mixed and stirred in a reactor, the slurry at the bottom of the reactor continuously enters the gypsum slurry barrel or the clarification barrel, and the turbid liquid at the top of the reactor continuously enters the clarification barrel;

[0008] After the turbid liquid continues to react and clarify in the clarifying tank, the underflow is continuously and appropriately discharged into the gypsum slurry tank, and the slurry concentration in the gypsum slurry tank (referring to the volume concentration of calcium sulfate dihydrate) is controlled at 10-35%; the overflow enters the storage tank of the reacted liquid for recycling.

[0009] (3)Transfer the slurry in the gypsum slurry to a hydrocyclone. The top flow of the hydrocyclone returns to the reaction tank; the underflow goes to the washing and dewatering machine for feeding, and the slurry concentration is controlled at 30-60%.

[0010] (4)Using the washing and dewatering machine, the slurry is filtered by stages, rinsed with fresh water and filtered 2-3 times, and the filter material is transferred to a fresh water elutriation tank with a stirrer for elutriation.

[0011] (5)Transfer the slurry in the elutriation tank to a hydrocyclone. Part of the top flow of the hydrocyclone returns to the waste water tank and part is discharged to the slag injection system; its underflow goes to the washing and dewatering machine for feeding, and the slurry concentration is controlled at 40-60%.

[0012] (6)Using the washing and dewatering machine, the slurry is dewatered and rinsed with fresh water, and the washing water is not less than 3 times. The filter material is transferred to a screw feeder with a disintegrator.

[0013] (7)Through the screw feeder, the material is evenly fed into the low-temperature dryer, and the dried material enters the collection hopper of the flash dryer; then it is transferred to the finished product high-level storage bin and packaged into finished products separately; when ensuring that the moisture content is controlled at a low level, it can be directly packaged without entering the dryer.

[0014] A further improvement scheme of the present invention is:

[0015] The material 1 is selected from the clear calcium liquid in ammonia soda process or the calcium chloride type brine prepared by using the clear calcium liquid or a mixture of the two; the main components of the clear calcium liquid for soda making are 35-65 g / l of sodium chloride and 80-120 g / l of calcium chloride, and the main components of the prepared calcium chloride type brine are 240-295 g / l of sodium chloride and 15-80 g / l of calcium chloride.

[0016] Further, the material 2 is selected from one or more mixtures of mirabilite type brine, the mother liquor produced during the salt production process using mirabilite type brine, high nitrate salt brine or nitrate brines with different sodium sulfate contents. The main components of the mirabilite type brine are 280-305 g / l of sodium chloride and 10-35 g / l of sodium sulfate; the main components of the mother liquor for salt production are 270-295 g / l of sodium chloride and 35-65 g / l of sodium sulfate; the main components of the nitrate brine are 150-330 g / l of sodium sulfate and 20-150 g / l of sodium chloride; the main components of the high nitrate salt brine are 150-280 g / l of sodium chloride and 65-150 g / l of sodium sulfate. Further, the material 1 and the material 2 are in a "calcium to sulfur ratio" (referring to the molar ratio of calcium chloride to sodium sulfate) of 1:1.2~1.8.

[0017] Further, the stirring reaction time in step (1) is 15 - 120 min; the continuous reaction time in step (2) is 5 - 15 h.

[0018] Further, in step (4), the mother liquor after filtration is collected into a filtrate bucket and then pumped back to the reactor; the waste liquid after filtration after freshwater washing is collected into a waste water bucket and can be intermittently transferred to the workshop sewage treatment system.

[0019] Further, in step (6), the waste liquid after filtration is collected into a waste liquid bucket, part of which is sent back to the reactor and part is discharged to the slag injection system.

[0020] Further, the moisture content of the filter media in both step (4) and step (6) is lower than 20%.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] Since the inherent quality of the raw materials for synthesizing dihydrate gypsum is relatively stable, and the feeding method, ratio, stirring intensity, reaction time, separation method, washing times, etc. are all controllable, the quality of the synthesized gypsum is relatively stable.

[0023] The process method of the present invention can organize production continuously and on a large scale, and the quality of the product is stable and controllable; the purity and whiteness of the product are better than those of all by - product gypsums, and it can replace natural stone raw materials of grade one and above for use.

[0024] The comprehensive utilization rate of resources in the present invention is higher. The reaction synthesis product is washed and purified into a high - quality product, the completed reaction liquid can also be used as a raw material for general industrial salt brine, and the waste water generated during the washing process is used as the water medium for mining. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is the process flow chart adopted in Embodiments 1 - 8 of the present invention;

[0026] Figure 2 is the process flow chart adopted in Embodiments 7 - 16 of the present invention DETAILED DESCRIPTION OF THE INVENTION

[0027] The present invention will be introduced in detail below in conjunction with specific embodiments. Embodiment 1

[0028] The process flow chart of this embodiment is as Figure 1 :

[0029] Step 1: Take soda ash production clear calcium solution (sodium chloride 35 - 65 g / l, calcium chloride 80 - 120 g / l) as Material 1 and centrally input it into the calcium source barrel; take salt-making mother liquor (sodium chloride 270 - 280 g / l, sodium sulfate 35 - 65 g / l) as Material 2 and input it into the nitrate source barrel.

[0030] Step 2: Mix Material 1 and Material 2 from the calcium source barrel and the nitrate source barrel according to a calcium-sulfur ratio of 1:1.5, and feed them into a reactor equipped with a stirrer. Control the reaction at normal temperature for 55 - 75 minutes. Continuously discharge the slurry from the bottom of the reactor into the gypsum slurry barrel (equipped with a stirring mechanism), and control the solid-liquid ratio of the slurry at 10 - 35%; continuously discharge the turbid liquid from the upper part of the reactor into the clarification barrel, and continue the reaction in the clarification barrel for 5 - 15 hours, then carry out clarification; after clarification, continuously and appropriately discharge the underflow of the clarification barrel into the gypsum slurry barrel, and control the solid-liquid ratio at 10 - 35%; the overflow of the clarification barrel enters the storage barrel of the reaction-complete liquid and serves as the raw material for other processes.

[0031] Step 3: Use transfer pump 1 to transfer the slurry in gypsum slurry 2 to cyclone 1. The top flow of cyclone 1 returns to the reaction barrel (the particle size of fine particles is below 5 mm); its bottom flow feeds the washing and dewatering machine 1, and control the slurry concentration at 40 - 60%.

[0032] Step 4: Use washing and dewatering machine 1 to conduct grading filtration, fresh water rinsing and filtration for 2 - 3 times on the slurry; collect the filtrate of the filtration into the filtrate barrel and then pump it back to the reaction barrel; collect the waste liquid after fresh water rinsing and filtration into waste water barrel 1, and intermittently transfer it to the workshop slag injection system; transfer the filter material (with moisture content controlled below 20%) to a fresh water elutriation barrel equipped with a stirrer for elutriation.

[0033] Step 5: After elutriation, use transfer pump 2 to transfer the slurry in the elutriation barrel to cyclone 2. Part of the top flow of cyclone 2 can return to waste water barrel 1 and part can be discharged to the slag injection system (the particle size of fine particles is below 5 mm); its bottom flow feeds the washing and dewatering machine 2, and control the concentration at 40 - 60%; use washing and dewatering machine 2 to dehydrate the slurry, conduct fresh water rinsing, and the washing water is not less than 3 times; collect the filtered liquid into waste liquid barrel 1, or part of it is discharged to the slag injection system; transfer the filter material (with moisture content controlled below 20%) to screw feeder 1 equipped with a disaggregator.

[0034] Step 6: Evenly feed the filter material from screw feeder 1 into the dryer, and the dried material enters the aggregate hopper of the flash dryer; then transfer it to the finished product high-level storage bin through screw feeder 2 or bucket elevator 1, and then subcontract it into finished products of various packages; finally collect the powder of the dust removal system into the powder bin (the moisture content of the powder is controlled below 8%), and it can be separately packaged into finished products.

[0035] The gypsum products produced by this process have an attached water moisture content that can be controlled below 10%, a chloride ion content of ≤200 ppm, and a dihydrate calcium sulfate content of ≥98% (dry basis). Example 2

[0036] In this example, the ammonia-soda process clear calcium solution (sodium chloride 35 - 65 g / l, calcium chloride 80 - 120 g / l) is used as Material 1, and the high-nitrate brine (sodium chloride 150 - 280 g / l, sodium sulfate 65 - 15 g / l) is used as Material 2. Other operations are roughly the same as those in Example 1.

[0037] The gypsum products produced in this example have an attached water moisture content that can be controlled below 10%, a chloride ion content of ≤200 ppm, and a dihydrate calcium sulfate content of ≥98% (dry basis). Example 3

[0038] In this example, the ammonia-soda process clear calcium solution (sodium chloride 35 - 65 g / l, calcium chloride 80 - 120 g / l) is used as Material 1, and the nitrate brine (sodium sulfate 150 - 330 g / l, sodium chloride 20 - 15 g / l) is used as Material 2. Other operations are roughly the same as those in Example 1.

[0039] The gypsum products produced in this example have an attached water moisture content that can be controlled below 10%, a chloride ion content of ≤200 ppm, and a dihydrate calcium sulfate content of ≥98% (dry basis). Example 4

[0040] In this example, the ammonia-soda process clear calcium solution (sodium chloride 35 - 65 g / l, calcium chloride 80 - 120 g / l) is used as Material 1, and the mirabilite-type brine (sodium chloride 280 - 305 g / l, sodium sulfate 10 - 35 g / l) is used as Material 2. Other operations are roughly the same as those in Example 1.

[0041] The gypsum products produced in this example have a moisture content (attached water) that can be controlled below 10%, a chloride ion content of ≤200 ppm, and a dihydrate calcium sulfate content of ≥98% (dry basis). Example 5

[0042] In this example, the calcium chloride-type brine (sodium chloride 240 - 295 g / l, calcium chloride 15 - 80 g / l) is used as Material 1, and the salt-making mother liquor (sodium chloride 270 - 280 g / l, sodium sulfate 35 - 65 g / l) is used as Material 2. Other operations are roughly the same as those in Example 1.

[0043] The gypsum products produced in this example have an attached water moisture content that can be controlled below 10%, a chloride ion content of ≤200 ppm, and a dihydrate calcium sulfate content of ≥98% (dry basis). Example 6

[0044] In this example, calcium chloride type brine (sodium chloride 240 - 295 g / l, calcium chloride 15 - 80 g / l) is used as Material 1, and high nitrate brine (sodium chloride 150 - 280 g / l, sodium sulfate 65 - 150 g / l) is used as Material 2. Other operations are roughly the same as those in Example 1.

[0045] For the gypsum product produced in this example, the moisture content of the adhering water can be controlled below 10%, the chloride ion content ≤ 200 ppm, and the content of calcium sulfate dihydrate reaches ≥ 98% (dry basis). Example 7

[0046] In this example, calcium chloride type brine (sodium chloride 250 - 260 g / l, calcium chloride 60 - 75 g / l) is used as Material 1, and nitrate brine (sodium chloride 240 - 15 g / l, sodium sulfate 100 - 330 g / l) is used as Material 2. Other operations are roughly the same as those in Example 1.

[0047] For the gypsum product produced by this process, the moisture content of the adhering water can be controlled below 10%, the chloride ion content ≤ 200 ppm, and the content of calcium sulfate dihydrate reaches ≥ 98% (dry basis). Example 8

[0048] In this example, calcium chloride type brine (sodium chloride 250 - 260 g / l, calcium chloride 60 - 75 g / l) is used as Material 1, and mirabilite type brine (sodium chloride 280 - 305 g / l, sodium sulfate 10 - 35 g / l) is used as Material 2. Other operations are roughly the same as those in Example 1.

[0049] For the gypsum product produced by this process, the moisture content of the adhering water can be controlled below 10%, the chloride ion content ≤ 200 ppm, and the content of calcium sulfate dihydrate reaches ≥ 98% (dry basis). Example 9

[0050] The process flow diagram of this example is as Figure 2 shown. In this example, the raw materials are the same as those in Example 1. The bottom and overflow of the materials that have completed the reaction in the reactor both enter the clarification tank, and its overflow and bottom flow are determined according to the need for material balance control; the turbid liquid entering the clarification tank undergoes clarification and subsequent reactions for 5 - 15 hours, and then the bottom flow of the clarification tank is continuously and appropriately discharged into the gypsum slurry tank; other operations are roughly the same as those in Example 1.

[0051] For the gypsum product produced in this example, the moisture content of the adhering water can be controlled below 10%, the chloride ion content ≤ 200 ppm, and the content of calcium sulfate dihydrate reaches ≥ 98% (dry basis). Example 10

[0052] The process flow diagram of this example is as Figure 2As shown in the figure, in this embodiment, the raw materials are the same as those in Embodiment 1. The bottom and overflow of the materials that have completed the reaction in the reactor both enter the clarification tank, and its overflow and bottom flow are determined according to the needs of material balance control; the turbid liquid entering the clarification tank undergoes clarification and subsequent reactions for 5 - 15 hours, and then the bottom flow of the clarification tank is continuously and appropriately discharged into the gypsum slurry tank; other operations are roughly the same as those in Embodiment 1.

[0053] For the gypsum product produced in this embodiment, the moisture content of the adhering water can be controlled below 10%, the chloride ion content ≤ 200 ppm, and the content of calcium sulfate dihydrate reaches ≥ 98% (dry basis). Embodiment 11

[0054] The process flow chart of this embodiment is as Figure 2 As shown in the figure, in this embodiment, the raw materials are the same as those in Embodiment 2. The bottom and overflow of the materials that have completed the reaction in the reactor both enter the clarification tank, and its overflow and bottom flow are determined according to the needs of material balance control; the turbid liquid entering the clarification tank undergoes clarification and subsequent reactions for 5 - 15 hours, and then the bottom flow of the clarification tank is continuously and appropriately discharged into the gypsum slurry tank; other operations are roughly the same as those in Embodiment 2.

[0055] For the gypsum product produced in this embodiment, the moisture content of the adhering water can be controlled below 10%, the chloride ion content ≤ 200 ppm, and the content of calcium sulfate dihydrate reaches ≥ 98% (dry basis). Embodiment 12

[0056] The process flow chart of this embodiment is as Figure 2 As shown in the figure, in this embodiment, the raw materials are the same as those in Embodiment 3. The bottom and overflow of the materials that have completed the reaction in the reactor both enter the clarification tank, and its overflow and bottom flow are determined according to the needs of material balance control; the turbid liquid entering the clarification tank undergoes clarification and subsequent reactions for 5 - 15 hours, and then the bottom flow of the clarification tank is continuously and appropriately discharged into the gypsum slurry tank; other operations are roughly the same as those in Embodiment 3.

[0057] For the gypsum product produced in this embodiment, the moisture content of the adhering water can be controlled below 10%, the chloride ion content ≤ 200 ppm, and the content of calcium sulfate dihydrate reaches ≥ 98% (dry basis). Embodiment 13

[0058] The process flow chart of this embodiment is as Figure 2 As shown in the figure, in this embodiment, the raw materials are the same as those in Embodiment 4. The bottom and overflow of the materials that have completed the reaction in the reactor both enter the clarification tank, and its overflow and bottom flow are determined according to the needs of material balance control; the turbid liquid entering the clarification tank undergoes clarification and subsequent reactions for 5 - 15 hours, and then the bottom flow of the clarification tank is continuously and appropriately discharged into the gypsum slurry tank; other operations are roughly the same as those in Embodiment 4.

[0059] The gypsum product produced in this example has an attached water moisture content that can be controlled below 10%, a chloride ion content of ≤200 ppm, and a calcium sulfate dihydrate content of ≥98% (dry basis). Example 14

[0060] The process flow chart of this example is as Figure 2 shown. In this example, the raw materials are the same as those in Example 5. The bottom and overflow of the materials that have completed the reaction in the reactor both enter the clarification tank, and their overflow and bottom flow are determined according to the requirements of material balance control. The turbid liquid entering the clarification tank undergoes clarification and subsequent reactions for 5 - 15 hours, and then the bottom flow of the clarification tank is continuously and appropriately discharged into the gypsum slurry tank. Other operations are roughly the same as those in Example 5.

[0061] The gypsum product produced in this example has an attached water moisture content that can be controlled below 10%, a chloride ion content of ≤200 ppm, and a calcium sulfate dihydrate content of ≥98% (dry basis). Example 15

[0062] The process flow chart of this example is as Figure 2 shown. In this example, the raw materials are the same as those in Example 6. The bottom and overflow of the materials that have completed the reaction in the reactor both enter the clarification tank, and their overflow and bottom flow are determined according to the requirements of material balance control. The turbid liquid entering the clarification tank undergoes clarification and subsequent reactions for 5 - 15 hours, and then the bottom flow of the clarification tank is continuously and appropriately discharged into the gypsum slurry tank. Other operations are roughly the same as those in Example 6.

[0063] The gypsum product produced in this example has an attached water moisture content that can be controlled below 10%, a chloride ion content of ≤200 ppm, and a calcium sulfate dihydrate content of ≥98% (dry basis). Example 16

[0064] The process flow chart of this example is as Figure 2 shown. In this example, the raw materials are the same as those in Example 7. The bottom and overflow of the materials that have completed the reaction in the reactor both enter the clarification tank, and their overflow and bottom flow are determined according to the requirements of material balance control. The turbid liquid entering the clarification tank undergoes clarification and subsequent reactions for 5 - 15 hours, and then the bottom flow of the clarification tank is continuously and appropriately discharged into the gypsum slurry tank. Other operations are roughly the same as those in Example 7.

[0065] The gypsum product produced in this example has an attached water moisture content that can be controlled below 10%, a chloride ion content of ≤200 ppm, and a calcium sulfate dihydrate content of ≥98% (dry basis). Example 17

[0066] The process flow chart of this example is as Figure 2As shown, the raw materials in this embodiment are the same as those in Embodiment 8. The bottom and overflow of the materials that have completed the reaction in the reactor both enter the clarifying tank, and its overflow and bottom flow are determined according to the material balance control requirements; the turbid liquid entering the clarifying tank undergoes clarification and subsequent reactions for 5 to 15 hours, and then the underflow of the clarifying tank is continuously and appropriately discharged into the gypsum slurry tank; other operations are substantially the same as those in Embodiment 8.

[0067] For the gypsum product produced in this embodiment, the moisture content of the adhering water can be controlled below 10%, the chloride ion content ≤ 200 ppm, and the content of calcium sulfate dihydrate ≥ 98% (dry basis).

[0068] The above embodiments are only for illustrating the technical concept and features of the present invention, and the purpose is to enable those who are familiar with this technology to understand the content of the present invention and implement it accordingly, and it cannot be used to limit the protection scope of the present invention. Any equivalent transformation or modification made according to the spirit and essence of the present invention should be covered within the protection scope of the present invention.

Claims

1. A production method of high-quality chemical gypsum, characterized in that, It includes the following steps: (1) After mixing and stirring the material 1 providing calcium source and the material 2 providing sulfate radical in a reactor, the turbid liquid at the top of the reactor continuously enters a clarifying tank, and the slurry at the bottom of the reactor is intermittently or continuously discharged into a gypsum slurry tank; (2) After the turbid liquid continues to react and clarify in the clarifying tank, the underflow is continuously and appropriately discharged into the gypsum slurry tank, and the slurry concentration in the gypsum slurry tank is controlled at 10 - 35%; the overflow enters the storage tank of the reaction-complete liquid for recycling; (3) Transfer the slurry in the gypsum slurry tank to a hydrocyclone, and the top flow of the hydrocyclone returns to the reaction tank; the bottom flow is fed to a primary dewatering and washing machine, and the slurry concentration is controlled at 30 - 60%; (4) Using the primary dewatering and washing machine, dehydrate the slurry in stages and wash it with fresh water, and transfer the filter material to a fresh water elutriation tank with a stirrer for elutriation; (5) Transfer the slurry in the elutriation tank to a hydrocyclone for solid-liquid separation. Part of the top flow of the hydrocyclone returns to the waste water tank or is discharged to the sewage treatment system; Its bottom flow goes to a secondary dewatering and washing machine, and the slurry concentration is controlled at 30 - 60%; (6) Using the secondary washing and dewatering machine, dehydrate the slurry in stages and wash it with fresh water, and transfer the filter material to a screw feeder with a disintegrator; (7) Feed the material evenly into a low-temperature dryer through the screw feeder. After the material is moderately dried, it enters the aggregate hopper; then it is transferred to a finished product high-level storage bin and packaged into finished products separately; The material 1 is selected from the clear calcium liquid produced by the ammonia-alkali method for soda production or the calcium chloride-type brine prepared by using the clear calcium liquid or a mixture of the two; the main components of the clear calcium liquid for soda production are 35 - 65 g / l of sodium chloride and 80 - 120 g / l of calcium chloride, and the main components of the prepared calcium chloride-type brine are 240 - 295 g / l of sodium chloride and 15 - 80 g / l of calcium chloride; The material 2 is selected from one or more mixtures of mirabilite-type brine, the mother liquor produced during the salt production process using mirabilite-type brine, high-nitrate salt brine, or nitrate brines with different sodium sulfate contents; the main components of the mirabilite-type brine are 280 - 305 g / l of sodium chloride and 10 - 35 g / l of sodium sulfate; the main components of the mother liquor for salt production are 270 - 295 g / l of sodium chloride and 35 - 65 g / l of sodium sulfate; the main components of the nitrate brine are 150 - 330 g / l of sodium sulfate and 20 - 150 g / l of sodium chloride; the main components of the high-nitrate salt brine are 150 - 280 g / l of sodium chloride and 65 - 150 g / l of sodium sulfate.

2. The production method of a high-quality chemical gypsum according to claim 1, characterized in that: The material 1 and the material 2 are fed according to a calcium-sulfur ratio of 1:0.8 - 1.

6.

3. The production method of a high-quality chemical gypsum according to claim 1, characterized in that: The stirring reaction time in step (1) is 15 - 120 min; the subsequent reaction and clarification time in step (2) is 5 - 15 h.

4. The production method of a high-quality chemical gypsum according to claim 1, characterized in that: In step (4), the filtered liquid is collected into a filtrate tank and then pumped back to the reactor; the waste liquid after fresh water washing is collected into the waste water tank and intermittently transferred to the workshop sewage treatment system.

5. The production method of a high-quality chemical gypsum according to claim 1, characterized in that: In steps (5) and (6), the filtered liquid is collected into a waste liquid tank, and the waste liquid after washing is discharged to the sewage treatment system.

6. The production method of a high-quality chemical gypsum according to claim 1, characterized in that: The moisture content of the filter material in both step (4) and step (6) is lower than 20%.

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