Production system for obtaining high-purity gypsum from wet-process phosphoric acid
By designing a multi-step wet phosphoric acid production system, the problem of difficulty in producing high-purity and high-whiteness gypsum under industrialized conditions in the prior art is solved, and efficient continuous production is achieved and industrialized application conditions are met.
Patent Information
- Application Number
- CN202421801404.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-07-29
- Publication Date
- 2025-05-13
- Estimated Expiration
- 2034-07-29
AI Technical Summary
The prior art is difficult to effectively produce high-purity and high-whiteness gypsum under industrial conditions, and the pilot equipment cannot achieve continuous production.
A wet phosphoric acid production system is designed, including a phosphoric acid dissolver, a first filter, a centrifugal settler, a decalcifier, a second filter, a solid extractor and a dehydrator. Through a multi-step process, the calcium phosphate is dissolved and impurities are removed by phosphoric acid, and finally a high purity and high whiteness gypsum is obtained through solid extraction and dehydration.
It has achieved efficient production of high-purity and high-whiteness gypsum under industrial conditions, and has successfully achieved continuous production on the pilot plant, meeting the conditions for industrial application.
Smart Images
Figure CN222855402U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the production and preparation field of inorganic phosphorus chemical industry, and discloses a system for producing phosphoric acid and high-quality calcium sulfate by utilizing the dissolving property of phosphoric acid on phosphate ore. Background Art
[0002] In October 2022, Zheng Hanxiao and other scholars published a paper entitled "Leaching Behavior of Phosphate Rock in Phosphoric Acid" in "Inorganic Salt Industry", proposing a phosphorus-sulfur two-step method, which is to carry out the phosphoric acid decomposition reaction of phosphate rock and the calcium sulfate precipitation reaction in steps. First, phosphoric acid is used to decompose the phosphate rock, and the unreacted phosphate rock and acid-insoluble matter are separated by solid-liquid separation to obtain an acidolysis solution, and then sulfuric acid is used to precipitate the calcium ions in the filtrate to obtain phosphoric acid and calcium sulfate precipitate. The by-product gypsum has few impurities and high purity. However, it has remained in the laboratory and cannot be pilot-tested. In order to industrialize it as soon as possible, the patentee began to conduct industrial trials based on this paper and successfully developed a pilot system. Summary of the invention
[0003] The utility model provides a production system for obtaining high-purity gypsum from wet-process phosphoric acid, the purpose of which is to effectively utilize the characteristics of phosphoric acid that dissolves calcium phosphate but does not dissolve other impurities, effectively obtain high-purity phosphogypsum and high-whiteness gypsum, and realize continuous production of a pilot plant, which has the conditions for industrialization.
[0004] In order to achieve the above object, a production system for obtaining high-purity gypsum by wet-process phosphoric acid comprises a phosphoric acid dissolver with a stirring shaft, a first filter, a centrifugal settler, a decalcifier, a second filter, and a solid extractor;
[0005] The phosphoric acid dissolver outlet is connected to the first filter;
[0006] The liquid outlet of the first filter is connected to the centrifugal settler, the liquid outlet of the centrifugal settler is connected to the decalcifier, the liquid outlet of the centrifugal settler is connected to the second filter, and the solid-liquid discharge port of the second filter is connected to the solid extractor;
[0007] The solid extractor is configured to add the semi-hydrated gypsum mixed liquid from the upper end of the solid extractor, add ionized water from the lower end of the solid extractor, discharge the soluble salt water from the upper end of the solid extractor, and discharge the wet white gypsum from the lower end of the solid extractor.
[0008] Further, the system also includes a dehydrator;
[0009] The dehydrator, the solid-liquid discharge port of the first filter is connected to the dehydrator.
[0010] The advantages of the utility model are as follows: 1) it has the conditions for realizing industrialization.
[0011] 2) In addition, "the mixed white precipitated gypsum is sent to the top of the solid continuous extraction tower, and ion water is continuously injected from the bottom of the solid continuous extraction tower, the soluble brine flows out as wastewater from the overflow port at the top of the tower, and the white gypsum slurry is discharged from the bottom of the solid continuous extraction tower" can effectively improve the whiteness of the white gypsum. BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The accompanying drawings further describe the various processes of the utility model and are part of the specification. They are also used to better explain the utility model for specific operations. The utility model does not limit the specific equipment used in the process.
[0013] Figure 1 It is the logic block diagram of the patented method.
[0014] Figure 2 It is a schematic diagram of the utility model system.
[0015] As shown in the figure, there are a phosphoric acid dissolver 1, a first filter 2, a centrifugal settler 3, a decalcifier 4, a second filter 5, a solid extractor 6, and a dehydrator 7. DETAILED DESCRIPTION
[0016] like Figure 1 A method for producing high-purity gypsum while producing phosphoric acid comprises the following steps:
[0017] The first step is to react and dissolve the phosphate slurry with phosphoric acid, preferably the mass ratio of the phosphate slurry to the phosphoric acid is 10:8-9.5, and the liquid is filtered after the reaction. Preferably, the reaction temperature is 80-140°C, and the optimal reaction temperature is 110°C;
[0018] The second step is to filter and separate the phosphate aqueous solution by centrifugal sedimentation;
[0019] The third step is to mix the calcium phosphate phosphate water with sulfuric acid or ammonium sulfate, sodium sulfate, and potassium sulfate for reaction, and stir to generate a mixed slurry of white precipitated gypsum and dilute phosphoric acid, and the reaction temperature rise is controlled within 0.1-10°C, preferably, the reaction temperature rises by 0.8-1.2°C.
[0020] The fourth step is to separate the mixed slurry in the third step into solid and liquid to obtain wet white precipitated gypsum and dilute phosphoric acid solution;
[0021] In the fifth step, the mixed white precipitated gypsum in the fourth step is fed into the top of a solid continuous extraction tower, and ion water is continuously injected from the bottom of the solid continuous extraction tower, and the soluble salt water flows out as wastewater from the overflow port at the top of the tower, and white gypsum slurry is discharged from the bottom of the solid continuous extraction tower;
[0022] Step 6: dehydrate the white gypsum slurry in step 5 to obtain high-purity white gypsum.
[0023] like Figure 2 The production system for obtaining high-purity gypsum from wet-process phosphoric acid includes a phosphoric acid dissolver 1 with a stirring shaft, a first filter 2, a centrifugal settler 3, a decalcifier 4, a second filter 5, a solid extractor 6, and a dehydrator 7;
[0024] The phosphoric acid dissolver 1, phosphate slurry and phosphoric acid are injected into the phosphoric acid dissolver to produce a first mixed solution;
[0025] The first filter 2, the mixed liquid passes through the first filter to discharge the phosphoric acid insoluble matter, and produces a second mixed liquid;
[0026] The centrifugal sedimentation vessel 3, the second mixed solution is centrifuged to discharge insoluble matter after sedimentation in the centrifugal sedimentation vessel, the reaction temperature rises by 0.1-10°C, generally controlled at 1°C, to produce a third mixed solution;
[0027] The decalcifier 4, in which sulfuric acid or ammonium sulfate is added to remove calcium in the third mixed solution to produce a fourth mixed solution; the second filter 5, in which the fourth mixed solution passes through the second filter to remove phosphate to produce a semi-hydrated gypsum mixed solution;
[0028] The solid extractor 6 is used to add the semi-hydrated gypsum mixed liquid from the upper end of the solid extractor, add ionized water from the lower end of the solid extractor, discharge the soluble salt water from the upper end of the solid extractor, and discharge the wet white gypsum from the lower end of the solid extractor; the dehydrator 7 is used to add the wet white gypsum into the dehydrator for dehydration to generate high-purity white gypsum.
[0029] The gypsum in the following examples was tested using the method of GB T 5483-1996 gypsum and anhydrite standard.
[0030] Example 1
[0031] 7.5 tons of phosphate slurry with a solid content of 60% is added to a phosphoric acid dissolver 1, and then 6.75 tons of 85% phosphoric acid and 50 tons of water are diluted and stirred continuously. The reaction temperature is controlled at 75-85°C, and the reaction is carried out for 2-8 hours. The first filter 2 is filtered to obtain a calcium phosphate aqueous solution and a black filter cake, respectively. The gray-black filter cake can be directly buried in the soil.
[0032] The obtained phosphate solution is filtered by a centrifugal settler 3, and the insoluble matter is discharged. The solution flows into a decalcifier 4, and 4.5 tons of 98% sulfuric acid is slowly added to the decalcifier 4, and a white precipitate is produced with continuous stirring. The reaction temperature rises and is controlled at 0.1-3°C. The white precipitate is filtered by a second filter 5, and the filtrate is phosphate. The wet white precipitate (i.e., white gypsum) is input into a solid extractor 6 to obtain 9.4 tons of wet white precipitate, and then the white precipitate is input into a dehydrator 7 for dehydration to obtain 6.19 tons of white precipitate;
[0033] Chemical inspection shows that the solid calcium sulfate content is 99.5%, the iron ion content is 20ppm, the fluorine content is 3ppm, the magnesium content is 12ppm, and the whiteness is 92.
[0034] Example 2
[0035] Take 10 tons of phosphate slurry with a solid content of 60% and add it into a phosphoric acid dissolver 1, then dilute 9.1 tons of 85% phosphoric acid with 64 tons of water, and stir continuously. The reaction temperature is controlled at 75-90°C, and the reaction is carried out for 2-8 hours. The first filter 2 is filtered to obtain a calcium phosphate aqueous solution and a black filter cake, respectively. The black filter cake can be directly buried in the soil.
[0036] The obtained phosphate solution is filtered by sedimentation in a centrifugal settler 3, and the solution flows into a decalcifier 4. 6.2 tons of 46% ammonium sulfate are slowly added to the decalcifier 4, and white precipitate is produced with continuous stirring. The reaction temperature rise is controlled at 0.1-4°C. The white precipitate is filtered by a second filter 5, and the filtrate is diammonium phosphate. The wet white precipitate (i.e., white gypsum) is input into a solid extractor 6 to obtain 12.6 tons of wet white precipitate, and then the white precipitate is input into a dehydrator 7 for dehydration to obtain 8.29 tons of white precipitate;
[0037] Chemical inspection shows that the solid calcium sulfate content is 99.4%, the iron ion content is 21ppm, the fluorine content is 4ppm, the magnesium content is 13ppm, and the whiteness is 92.
[0038] Example 3
[0039] Take 15kg of phosphate slurry with a solid content of 60% and add it into the phosphoric acid dissolver 1, then dilute 42kg of 85% phosphoric acid with 95kg of water, and stir continuously. The reaction temperature is controlled at 90°C, and the reaction is carried out for 2-8 hours. The first filter 2 is filtered to obtain a calcium phosphate aqueous solution and a gray filter cake, respectively. The gray-black filter cake can be directly buried in the soil.
[0040] The obtained phosphate solution is filtered by sedimentation in a centrifugal settler 3, and the solution flows into a decalcifier 4. 9.3 kg of 32% sodium sulfate is slowly added to the decalcifier 4, and a white precipitate is produced while stirring continuously. The reaction temperature rises and is controlled at 0.1-4.5° C. The white precipitate is filtered by a second filter 5, and the filtrate is phosphate. The wet white precipitate (i.e., white gypsum) is input into a solid extractor 6 to obtain 19.1 kg of wet white precipitate, and then the white precipitate is input into a dehydrator 7 for dehydration to obtain 12.4 kg of white precipitate;
[0041] Chemical inspection shows that the solid calcium sulfate content is 99.36%, the iron ion content is 21ppm, the fluorine content is 5ppm, the magnesium content is 14ppm, and the whiteness is 92.
[0042] Example 4
[0043] Take 3kg of phosphate slurry with a solid content of 60% and add it into a phosphoric acid dissolver 1, then dilute 2.7kg of 85% phosphoric acid with 5.5kg of water, and stir continuously. The reaction temperature is controlled at 80-105°C, and the reaction is carried out for 2-8 hours. The first filter 2 is filtered to obtain a calcium phosphate aqueous solution and a gray-black filter cake, respectively. The gray-black filter cake can be directly buried in the soil.
[0044] The obtained phosphate solution is filtered by centrifugal settling device 3, and the solution flows into decalcifier 4. 18.8 kg of 18% potassium sulfate is slowly added into decalcifier 4, and white precipitate is produced by continuous stirring. The reaction temperature rises and is controlled at 0.1-6°C. The white precipitate is filtered by second filter 5. The filtrate is phosphate. The wet white precipitate (i.e., white gypsum) is input into solid extractor 6 to obtain 3.96 kg of wet white precipitate. The white precipitate is then input into dehydrator 7 for dehydration to obtain 2.5 kg of white precipitate.
[0045] Chemical inspection shows that the solid calcium sulfate content is 99.32%, the iron ion content is 22ppm, the fluorine content is 6ppm, the magnesium content is 14ppm, and the whiteness is 92.
Claims
1. A production system for obtaining high-purity gypsum from wet-process phosphoric acid, characterized in that: The system comprises a phosphoric acid dissolver with a stirring shaft, a first filter, a centrifugal settler, a decalcifier, a second filter, and a solid extractor; The phosphoric acid dissolver outlet is connected to the first filter; The liquid outlet of the first filter is connected to the centrifugal settler, the liquid outlet of the centrifugal settler is connected to the decalcifier, the liquid outlet of the centrifugal settler is connected to the second filter, and the solid-liquid discharge port of the second filter is connected to the solid extractor; The solid extractor is configured to add the semi-hydrated gypsum mixed liquid from the upper end of the solid extractor, add ionized water from the lower end of the solid extractor, discharge the soluble salt water from the upper end of the solid extractor, and discharge the wet white gypsum from the lower end of the solid extractor.
2. The production system for obtaining high-purity gypsum from wet-process phosphoric acid according to claim 1, characterized in that: The system also includes a dehydrator; The dehydrator, the solid-liquid discharge port of the first filter is connected to the dehydrator.