Continuous crystallization and centrifugation integrated production process for phosphorous acid

Abstract

The invention provides a continuous crystallization and centrifugation integrated production process for phosphorous acid, which relates to the technical field of phosphorous acid and comprises the following steps: conveying a solid phosphorous acid raw material to a dissolving tank with a stirring function for dissolving and filtering, and pumping into a crystallization system; concentrating the saturated solution to produce crystal grains; putting the solution with the crystal grains into separation and concentration equipment for centrifugation; discharging the collected crystals; the separated mother liquor enters a film evaporation sleeve to be concentrated; according to the method, the centrifugal mechanism at the top end is controlled by single power equipment to perform centrifugal treatment on the solution with crystal grains, so that the crystals and the mother liquor are separated, and the separated mother liquor part is directly subjected to thin film evaporation treatment through the evaporation mechanism; in the process, the lifting process of the film evaporation sleeve is also realized through the power equipment and the transmission mechanism at the bottom, so that the evaporation process of the mother liquor is more efficient.

Description

Technical Field

[0001] The invention relates to the technical field of phosphorous acid, and in particular to a phosphorous acid continuous crystallization and centrifugation integrated production process. Background Art

[0002] Phosphorous acid is a colorless liquid with a distinctive sour smell at room temperature. It is soluble in water and alcohol but is virtually insoluble in most organic solvents. Aqueous solutions of phosphorous acid are acidic and can react with strong bases to form phosphates. The phosphorous acid continuous crystallization and centrifugation integrated production process is a highly integrated, energy-efficient, and modern fine chemical production technology. Its core lies in seamlessly integrating the continuous crystallization of phosphorous acid solution with the centrifugal separation process, achieving automated continuous production from raw liquid to high-purity solid product within a single system. Specifically, the pretreated phosphorous acid solution is continuously fed into a specific crystallizer. Under precisely controlled conditions of temperature, concentration, stirring speed, and supersaturation, continuous and stable nucleation and growth of crystals are achieved, ensuring uniform and controllable crystal size.

[0003] In the prior art, during the continuous crystallization preparation process of phosphorous acid, the mother liquor after vacuum concentration is centrifuged to separate the crystals and liquid, and then the liquid needs to be recovered before it can be reused. This results in the need to concentrate the liquid multiple times, resulting in low production efficiency. In addition, the liquid needs to circulate multiple times, requiring a large number of production equipment and high equipment costs. Summary of the Invention

[0004] In view of the shortcomings of the existing technology, the purpose of the present invention is to provide an integrated production process for continuous crystallization and centrifugation of hypophosphorous acid to solve the problems raised in the above-mentioned background technology. The present invention uses a single power device to control the centrifugal mechanism at the top to centrifuge the solution containing crystals, thereby separating the crystals and the mother liquor, and the separated mother liquor is directly subjected to thin film evaporation through the evaporation mechanism. This process also uses the power device and transmission mechanism at the bottom to realize the lifting process of the thin film evaporation sleeve, making the evaporation process of the mother liquor more efficient.

[0005] In order to achieve the above object, the present invention is implemented through the following technical solution: a phosphorous acid continuous crystallization centrifugal integrated production process, comprising the following steps: S1. Solid phosphorous acid raw material is quantitatively delivered to a dissolution tank with stirring through a screw feeder. Hot water at 80-85°C is introduced into the tank. The saturated solution after dissolution is filtered through a 20μm precision filter to remove insoluble impurities. The solution is preheated to 60-65°C and then pumped into the crystallization system. S2, the saturated solution enters a three-stage series vacuum crystallizer. The vacuum degree of the first stage is controlled at -0.08MPa and the temperature is 50℃. The second stage is raised to -0.09MPa and the temperature is 45℃. The third stage is raised to -0.095MPa and the temperature is 40℃, forming a gradient cooling. The crystals grow cyclically in the guide tube to produce grains. S3. Add the solution containing the crystals into the separation and concentration device, start the power system at the bottom to control the operation of the entire separation and concentration device, and rotate the centrifugal mechanism at the top at high speed to produce a centrifugal effect on the solution inside; S4. The crystals are collected inside the separation and concentration equipment, and the mother liquor is discharged through the first filter. Nitrogen protection is introduced during the centrifugation process to prevent phosphorous acid oxidation. The collected crystals are discharged after the evaporation mechanism descends; S5. The separated mother liquor enters the thin film evaporation sleeve for concentration through centrifugal effect. The crystals produced by concentration are collected independently through the lifting mechanism, and the remaining mother liquor is recycled again to reduce wastewater discharge; S6. Collect the separated and concentrated crystalline parts, and dry them instantaneously using 120°C inert nitrogen as the medium. After drying, the crystals are cooled to 40°C in a fluidized bed, sprayed with 0.5% magnesium stearate anti-caking agent, and finally packaged.

[0006] Furthermore, in step S1, the solid phosphorous acid raw material is continuously transported to the dissolution tank through a variable frequency screw feeder; the water source introduced into the tank is the recovered mother liquor and supplementary pure water, the solid-liquid ratio is 1:1.8, and high-speed shear stirring is turned on to accelerate dissolution. During the process, the solution concentration is monitored in real time by an online density meter, and the precision filter includes a pre-100 mesh coarse filter and a post-20 μm titanium rod precision filter for intercepting undissolved particles and mechanical impurities.

[0007] Furthermore, a saturated solution is generated inside the vacuum crystallizer and when 90% of the particles reach 150±50μm, the slurry is discharged from the bottom; the excess fine crystal mother liquor is introduced into an external heater for dissolution and then reinjected into the crystallizer, while the crystallization heat is removed by a vacuum condenser with 12℃ cold water circulation.

[0008] Furthermore, in step S3, the solution containing the crystals is directly transported to the centrifugal chamber inside the centrifugal mechanism. After the motor at the bottom is started, the motor controls the transmission mechanism on the surface of the base to rotate, and the transmission mechanism simultaneously controls the operation of the evaporation mechanism on the outside and the centrifugal mechanism on the inside. After the centrifugal mechanism is running, the crystals in the solution inside the centrifugal chamber are filtered through the first filter.

[0009] Furthermore, the filtered mother liquor is discharged from the outside of the centrifugal chamber through the first filter screen, and the discharged mother liquor diffuses toward the outside along the side guide plate and finally hits the evaporation mechanism on the outside. The evaporation mechanism is a columnar structure as a whole, and an electric heating wire is embedded on the inner wall of the thin film evaporation sleeve. The mother liquor film in contact with the inner wall is evaporated by the electric heating wire.

[0010] Furthermore, the motor drives the driving gear and the driven gear on the surface synchronously through the driving pipe at the output end. After the driven gear rotates, it drives the central screw to rotate. The screw passes through the threaded holes on both sides of the thin film evaporation sleeve, thereby driving the evaporation mechanism to move vertically while the centrifugal mechanism rotates at high speed, and controlling the forward and reverse movement of the motor to control the lifting and lowering movement of the thin film evaporation sleeve.

[0011] Furthermore, the lifting movement process of the thin film evaporation sleeve in step S5 changes the position where the mother liquor inside the centrifugal mechanism is discharged on the inner wall of the thin film evaporation sleeve, and a thin film structure is formed at any position on the inner wall of the thin film evaporation sleeve to quickly concentrate and evaporate the mother liquor to form another crystallization area.

[0012] Furthermore, during the lifting and lowering movement of the evaporation mechanism, the centrifugal mechanism scrapes back and forth on the inner wall of the thin-film evaporation sleeve through the scraper on the outer side of the bottom, and during one cycle of scraping, the crystals formed after concentration on the inner wall of the thin-film evaporation sleeve are directly scraped onto the annular scraper, and after the evaporation mechanism runs for one cycle, the crystals on the scraper and inside the centrifugal bin are directly discharged.

[0013] Furthermore, the residual liquid portion of the mother liquor that contacts the inner wall of the thin-film evaporation sleeve and has not been completely concentrated and crystallized directly passes through the second filter screen and enters the collection bin at the bottom of the centrifugal mechanism, and then enters the driving pipe inside the collection bin. After the evaporation mechanism is pressed onto the bottom support plate through the lifting movement, the entire support plate is controlled to move downward, and the spring rod is compressed until the sealing sleeve is detached from the position of the docking hole on the surface of the driving pipe. At this time, the docking hole is aligned with the hollow enclosure portion on the inner side of the temporary storage interlayer. The residual mother liquor portion directly enters the interior of the temporary storage interlayer, is pumped out through the pipeline and the circulation pump, and is re-delivered to the injection pipe at the top.

[0014] Furthermore, in step S6, the wet crystal filter cake discharged from the separation and concentration equipment is sent to the bottom of the drying tower, and water flash evaporation is completed in the straight tube drying section with high-purity nitrogen at 120±5°C. The dried crystals fall into the fluidized bed cooler for cooling, and an anti-caking agent is sprayed on the crystal surface to form a coating film.

[0015] Beneficial effects of the present invention: 1. This phosphorous acid continuous crystallization centrifugal integrated production process uses a single power device to control the centrifugal mechanism at the top to centrifuge the solution containing crystals, thereby separating the crystals and mother liquor. The separated mother liquor is directly subjected to thin-film evaporation through the evaporation mechanism. This process also uses the power device and transmission mechanism at the bottom to realize the raising and lowering process of the thin-film evaporation sleeve, making the evaporation process of the mother liquor more efficient.

[0016] 2. In the phosphorous acid continuous crystallization centrifugal integrated production process, during the rotational centrifugation of the centrifuge mechanism, the evaporation mechanism also performs a lifting motion. By virtue of its lifting motion, the scraper portion at the bottom of the centrifuge mechanism can be coordinated to directly scrape and collect the crystallized portion produced after thin film evaporation, thereby significantly increasing the concentration rate of the mother liquor in each cycle and improving processing efficiency.

[0017] In this phosphorous acid continuous crystallization centrifugal integrated production process, the mother liquor discharged through the centrifugal mechanism, even if the liquid portion is still not completely concentrated in the subsequent thin film evaporation process, can be collected and processed by the collection bin at the bottom of the centrifugal mechanism. The liquid portion is directly diverted and discharged as the evaporation mechanism rises and falls, and automatically enters the next cycle, thereby improving equipment utilization, reducing equipment footprint, and reducing equipment costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a flow chart of a phosphorous acid continuous crystallization and centrifugation integrated production process of the present invention; Figure 2 This is a structural diagram of the separation and concentration equipment used in the phosphorous acid continuous crystallization and centrifugation integrated production process of the present invention; Figure 3 It is a structural schematic diagram of the base part of the present invention; Figure 4 for Figure 3 Enlarged view of area A in the middle; Figure 5 This is an exploded view of the evaporation mechanism of the present invention; Figure 6 It is a structural diagram of the centrifugal mechanism part of the present invention; Figure 7 for Figure 6 Enlarged view of area B in the middle; Figure 8 This is a diagram showing the internal structure of the centrifugal bin of the present invention; In the figure: 1. base; 2. support platform; 3. transmission mechanism; 4. evaporation mechanism; 5. centrifugal mechanism; 6. motor; 7. injection port; 8. screw; 9. drive pipe; 10. driving gear; 11. driven gear; 12. docking hole; 13. support plate; 14. spring rod; 15. sealing sleeve; 16. thin film evaporation sleeve; 17. outer convex plate; 18. threaded hole; 19. bottom plate; 20. hollow enclosure; 21. centrifugal chamber; 22. first filter screen; 23. docking sleeve; 24. injection pipe; 25. circulation pipe; 26. circulation pump; 27. guide plate; 28. second filter screen; 29. ​​scraper; 30. collection chamber; 31. telescopic sleeve; 32. partition plate; 33. convex ring; 34. temporary storage interlayer. DETAILED DESCRIPTION

[0019] In order to make the technical means, creative features, objectives and effects achieved by the present invention easier to understand, the present invention is further described below in conjunction with specific implementation methods.

[0020] See also Figures 1 to 8 The present invention provides the following technical solution: a phosphorous acid continuous crystallization centrifugal integrated production process, comprising the following steps: Step 1: The solid phosphorous acid raw material is quantitatively delivered to a dissolution tank with stirring through a screw feeder. Hot water at 80-85°C is introduced into the tank. The saturated solution after dissolution is filtered through a 20μm precision filter to remove insoluble impurities. It is preheated to 60-65°C and then pumped into the crystallization system.

[0021] Solid phosphorous acid raw material is continuously delivered to the dissolution tank via a variable frequency screw feeder. The water source entering the tank is recycled mother liquor and supplementary pure water. The solid-liquid ratio is 1:1.8, and high-speed shear stirring is turned on to accelerate dissolution. During the process, the solution concentration is monitored in real time by an online density meter. The precision filter includes a pre-100 mesh coarse filter and a post-20μm titanium rod precision filter to intercept undissolved particles and mechanical impurities. Step 2: The saturated solution enters a three-stage vacuum crystallizer in series. The vacuum degree of the first stage crystallizer is controlled at -0.08MPa and the temperature is 50°C. The second stage is increased to -0.09MPa and the temperature is 45°C. The third stage is -0.095MPa and the temperature is 40°C, forming a gradient cooling. The crystals grow cyclically in the guide tube to produce grains.

[0022] A saturated solution is generated inside the vacuum crystallizer and when 90% of the particles reach 150±50μm, the slurry is discharged from the bottom; the excess fine crystal mother liquor is introduced into an external heater for dissolution and then re-injected into the crystallizer, while the crystallization heat is removed by circulating 12℃ cold water in a vacuum condenser; Step 3. In this step, a base 1 and a centrifugal mechanism 5 are used. A motor 6 is screwed to the bottom of the base 1, and a drive pipe 9 is inserted into the output end of the motor 6. The end of the drive pipe 9 is welded with a centrifugal mechanism 5. The centrifugal mechanism 5 includes a centrifugal chamber 21, a first filter screen 22, a second filter screen 28, a guide plate 27 and a scraper 29. A first filter screen 22 is provided on the side of the centrifugal chamber 21, and a partition is installed inside the centrifugal chamber 21. A docking sleeve 23 is provided at the top of the centrifugal chamber 21, and an injection pipe 24 is inserted into the interior of the docking sleeve 23, and an injection port 7 is provided at the top of the injection pipe 24.

[0023] A guide plate 27 is provided at the bottom of the centrifugal chamber 21, and a convex ring 33 is integrally formed at the edge of the guide plate 27. A second filter screen 28 is provided at the bottom of the guide plate 27, and a collecting chamber 30 is provided at the bottom of the second filter screen 28. A support platform 2 is welded to the side of the base 1, and a circulation pump 26 is bolted to the surface of the support platform 2. One end of the circulation pump 26 is connected to a part of the injection pipe 24 through a circulation pipe 25, and the interior of the collecting chamber 30 is connected to the interior of the drive pipe 9.

[0024] The solution containing the crystals is put into the separation and concentration device, the power system at the bottom is started to control the operation of the entire separation and concentration device, and the centrifugal mechanism 5 at the top rotates at high speed to produce a centrifugal effect on the solution inside.

[0025] The solution containing the crystals is directly transported to the centrifugal chamber 21 inside the centrifugal mechanism 5. After the motor 6 at the bottom is started, the motor 6 controls the transmission mechanism 3 on the surface of the base 1 to rotate. The transmission mechanism 3 simultaneously controls the operation of the evaporation mechanism 4 on the outside and the centrifugal mechanism 5 on the inside. After the centrifugal mechanism 5 is in operation, the crystals in the solution inside the centrifugal chamber 21 are filtered through the first filter 22.

[0026] The filtered mother liquor is discharged from the outside of the centrifugal chamber 21 through the first filter screen 22. The discharged mother liquor diffuses outward along the side guide plate 27 and eventually hits the evaporation mechanism 4 on the outside. The evaporation mechanism 4 is a columnar structure as a whole. An electric heating wire is embedded on the inner wall of the thin film evaporation sleeve 16. The electric heating wire evaporates the mother liquor film in contact with the inner wall. Step 4. The transmission mechanism 3 is used in this step. The transmission mechanism 3 includes a driving gear 10 and a driven gear 11. The driving gear 10 is keyed to the surface of the driving pipe 9. Driven gears 11 are provided on both sides of the driving gear 10. A screw rod 8 is installed in the middle of the driven gear 11. The bottom end of the screw rod 8 is embedded in the surface of the base 1 through a bearing. A telescopic sleeve 31 is welded on the surface of the driving gear 10. A spring rod 14 is inserted into the inside of the telescopic sleeve 31. A support plate 13 is welded to the top of the spring rod 14. A sealing sleeve 15 is integrally formed on the bottom of the support plate 13. A docking hole 12 is opened on the surface of the driving pipe 9. The sealing sleeve 15 covers the surface of the docking hole 12 under the push of the spring rod 14.

[0027] The crystals are collected inside the separation and concentration device, and the mother liquor is discharged through the first filter 22. Nitrogen is introduced into the centrifugal process to prevent the phosphorous acid from being oxidized. The collected crystals are discharged after the evaporation mechanism 4 descends.

[0028] The motor 6 synchronously drives the driving gear 10 and the driven gear 11 on the surface through the driving pipe 9 at the output end. When the driven gear 11 rotates, it drives the central screw 8 to rotate. The screw 8 passes through the threaded holes 18 on both sides of the thin film evaporation sleeve 16. As a result, while the centrifugal mechanism 5 rotates at high speed, it drives the evaporation mechanism 4 to move vertically. The forward and reverse movements of the motor 6 are controlled to control the lifting and lowering movement of the thin film evaporation sleeve 16. During the rotation and centrifugation of the centrifugal mechanism 5, since the evaporation mechanism 4 also performs a lifting motion, its lifting motion can cooperate with the scraper 29 at the bottom of the centrifugal mechanism 5 to directly scrape and collect the crystallized part produced after the thin film evaporation, thereby greatly increasing the concentration rate of the mother liquor in each cycle and improving the processing efficiency.

[0029] Step 5: In this step, the evaporation mechanism 4 is used. The evaporation mechanism 4 includes a thin film evaporation sleeve 16, a bottom plate 19 and a temporary storage interlayer 34. The bottom of the thin film evaporation sleeve 16 is integrally formed with the bottom plate 19, and the bottom of the bottom is provided with a temporary storage interlayer 34. The side of the thin film evaporation sleeve 16 is provided with an outer convex plate 17, and the middle of the outer convex plate 17 is provided with a threaded hole 18. The screw 8 passes upward from the inside of the threaded hole 18. A hollow panel 20 is provided on the inner side of the temporary storage interlayer 34. The hollow panel 20 is provided on the inner side of the temporary storage interlayer 34. 0 is sleeved on the surface of the drive pipe 9. After the bottom of the thin-film evaporation sleeve 16 presses the supporting plate 13 downward, the hollow enclosure 20 will be directly aligned with the position of the docking hole 12, and one end of the circulation pump 26 is connected to the interior of the temporary storage interlayer 34 through a pipeline. An electric heating wire is embedded in the shell of the thin-film evaporation sleeve 16. The edge of the scraper 29 is always in contact with the inner wall of the thin-film evaporation sleeve 16, and a gap is set between the edge of the convex ring 33 and the inner wall of the thin-film evaporation sleeve 16.

[0030] The mother liquor after separation enters the thin film evaporation sleeve 16 for concentration through the centrifugal effect. The crystals produced by the concentration are collected independently through the lifting mechanism, and the remaining mother liquor is circulated again to reduce wastewater discharge.

[0031] The thin film evaporation sleeve 16 moves up and down, changing the position of the mother liquor discharged from the centrifugal mechanism 5 on the inner wall of the thin film evaporation sleeve 16. A thin film structure is formed at any position on the inner wall of the thin film evaporation sleeve 16 to quickly concentrate and evaporate the mother liquor to form another crystallization area.

[0032] The mother liquor that contacts the inner wall of the thin-film evaporation sleeve 16 and the residual liquid portion that has not been completely concentrated and crystallized directly passes through the second filter 28 and enters the collection chamber 30 at the bottom of the centrifugal mechanism 5, and enters the drive pipe 9 inside the collection chamber 30. After the evaporation mechanism 4 is pressed on the bottom support plate 13 through the lifting movement, the entire support plate 13 is controlled to move downward, and the spring rod 14 is compressed until the sealing sleeve 15 is separated from the position of the docking hole 12 on the surface of the drive pipe 9. At this time, the docking hole 12 is aligned with the hollow enclosure 20 on the inner side of the temporary storage interlayer 34. The residual mother liquor portion directly enters the interior of the temporary storage interlayer 34, is extracted through the pipeline and the circulation pump 26, and is re-delivered to the injection pipe 24 at the top. The mother liquid discharged by the centrifugal mechanism 5, even if the liquid portion is still not completely concentrated in the subsequent thin film evaporation process, can be partially collected and processed by the collection chamber 30 at the bottom of the centrifugal mechanism 5. As the evaporation mechanism 4 rises and falls, the liquid portion is directly diverted and discharged and automatically enters the next cycle, thereby improving equipment utilization, reducing equipment footprint, and reducing equipment costs. Step 6: The wet crystal cake discharged from the centrifuge is conveyed via a sealed screw conveyor at a flow rate of 1.2 m³ / h to the bottom of a pulsed airflow drying tower. It is then mixed with high-purity nitrogen at 120±5°C. The crystals undergo flash evaporation in the straight tube drying section. The outlet gas is then captured by a cyclone separator, and the exhaust is then discharged through a condensation and dehumidification system to recover excess heat. The dried crystals (moisture ≤ 0.1%) fall into a fluidized bed cooler, where they are cooled to below 40°C by convection in nitrogen at 35±2°C. Simultaneously, an anti-caking agent with a particle size of <10 μm is evenly sprayed on the crystal surface via a rotating atomizing disk, forming a nano-scale coating. Finally, a static eliminator neutralizes surface charge, resulting in a finished product with excellent fluidity and no dust. Finally, packaging is complete.

[0033] This production process uses a single power device to control the centrifugal mechanism 5 at the top to centrifuge the solution containing crystals, thereby separating the crystals and the mother liquor. The separated mother liquor is directly subjected to thin film evaporation through the evaporation mechanism 4. This process also uses the power device and transmission mechanism 3 at the bottom to realize the raising and lowering process of the thin film evaporation sleeve 16, making the evaporation process of the mother liquor more efficient.

[0034] The basic principles, main features and advantages of the present invention are shown and described above. It is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or basic features of the present invention.

[0035] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A phosphorous acid continuous crystallization centrifugal integrated production process, characterized in that: The following steps are involved: S1. Solid phosphorous acid raw material is quantitatively delivered to a dissolution tank with stirring through a screw feeder. Hot water at 80-85°C is introduced into the tank. The saturated solution after dissolution is filtered through a 20μm precision filter to remove insoluble impurities. The solution is preheated to 60-65°C and then pumped into the crystallization system. S2, the saturated solution enters a three-stage series vacuum crystallizer. The vacuum degree of the first stage is controlled at -0.08MPa and the temperature is 50℃. The second stage is raised to -0.09MPa and the temperature is 45℃. The third stage is raised to -0.095MPa and the temperature is 40℃, forming a gradient cooling. The crystals grow cyclically in the guide tube to produce grains. S3. Add the solution containing the crystals into the separation and concentration device, start the power system at the bottom to control the operation of the entire separation and concentration device, and rotate the centrifugal mechanism at the top at high speed to produce a centrifugal effect on the solution inside; S4. The crystals are collected inside the separation and concentration equipment, and the mother liquor is discharged through the first filter. Nitrogen protection is introduced during the centrifugation process to prevent phosphorous acid oxidation. The collected crystals are discharged after the evaporation mechanism descends; S5. The separated mother liquor enters the thin film evaporation sleeve for concentration through centrifugal effect. The crystals produced by concentration are collected independently through the lifting mechanism, and the remaining mother liquor is recycled again to reduce wastewater discharge; S6. Collect the separated and concentrated crystalline parts, and dry them instantaneously using 120°C inert nitrogen as the medium. After drying, the crystals are cooled to 40°C in a fluidized bed, sprayed with 0.5% magnesium stearate anti-caking agent, and finally packaged.

2. The phosphorous acid continuous crystallization and centrifugal integrated production process according to claim 1, characterized in that: In step S1, the solid phosphorous acid raw material is continuously transported to the dissolution tank through a variable frequency screw feeder; the water source introduced into the tank is the recovered mother liquor and supplementary pure water, the solid-liquid ratio is 1:1.8, and high-speed shear stirring is turned on to accelerate the dissolution. During the process, the solution concentration is monitored in real time by an online density meter. The precision filter includes a pre-100 mesh coarse filter and a post-20μm titanium rod precision filter for intercepting undissolved particles and mechanical impurities.

3. The phosphorous acid continuous crystallization and centrifugal integrated production process according to claim 2, characterized in that: A saturated solution is generated inside the vacuum crystallizer and when 90% of the particles reach 150±50μm, the slurry is discharged from the bottom; the excess fine crystal mother liquor is introduced into an external heater for dissolution and then re-injected into the crystallizer, while the crystallization heat is removed by a vacuum condenser with 12℃ cold water circulation.

4. The phosphorous acid continuous crystallization and centrifugal integrated production process according to claim 1, characterized in that: In step S3, the solution containing the crystals is directly transported to the centrifugal chamber inside the centrifugal mechanism. After the motor at the bottom is started, the motor controls the transmission mechanism on the surface of the base to rotate. The transmission mechanism simultaneously controls the operation of the evaporation mechanism on the outside and the centrifugal mechanism on the inside. After the centrifugal mechanism is running, the crystals in the solution inside the centrifugal chamber are filtered through the first filter.

5. The phosphorous acid continuous crystallization and centrifugal integrated production process according to claim 4, characterized in that: The outside of the centrifugal chamber discharges the filtered mother liquor through the first filter screen, and the discharged mother liquor diffuses outward along the side guide plate and finally hits the evaporation mechanism on the outside. The evaporation mechanism is a columnar structure as a whole. An electric heating wire is embedded on the inner wall of the thin film evaporation sleeve, and the mother liquor film in contact with the inner wall is evaporated by the electric heating wire.

6. The phosphorous acid continuous crystallization and centrifugal integrated production process according to claim 4, characterized in that: The motor drives the driving gear and driven gear on the surface synchronously through the driving pipe at the output end. After the driven gear rotates, it drives the central screw to rotate. The screw passes through the threaded holes on both sides of the thin film evaporation sleeve, thereby driving the evaporation mechanism to move vertically while the centrifugal mechanism rotates at high speed, and controlling the forward and reverse movement of the motor to control the lifting and lowering movement of the thin film evaporation sleeve.

7. The phosphorous acid continuous crystallization and centrifugal integrated production process according to claim 6, characterized in that: The thin film evaporation sleeve lifting movement process in step S5 changes the position where the mother liquid inside the centrifugal mechanism is discharged on the inner wall of the thin film evaporation sleeve, and a thin film structure is formed at any position on the inner wall of the thin film evaporation sleeve to quickly concentrate and evaporate the mother liquid to form another crystallization area.

8. The phosphorous acid continuous crystallization and centrifugal integrated production process according to claim 7, characterized in that: During the lifting and lowering movement of the evaporation mechanism, the centrifugal mechanism scrapes back and forth on the inner wall of the thin-film evaporation sleeve through the scraper on the outer side of the bottom. During one cycle of scraping, the crystals formed after concentration on the inner wall of the thin-film evaporation sleeve are directly scraped onto the annular scraper. After the evaporation mechanism runs for one cycle, the crystals on the scraper and inside the centrifugal bin are directly discharged.

9. The phosphorous acid continuous crystallization and centrifugal integrated production process according to claim 8, characterized in that: The residual liquid part of the mother liquor that contacts the inner wall of the thin-film evaporation sleeve and is not completely concentrated and crystallized directly passes through the second filter screen and enters the collection bin at the bottom of the centrifugal mechanism, and then enters the driving pipe inside the collection bin. After the evaporation mechanism is pressed on the bottom support plate through the lifting movement, the entire support plate is controlled to move downward, and the spring rod is compressed until the sealing sleeve is separated from the position of the docking hole on the surface of the driving pipe. At this time, the docking hole is aligned with the hollow enclosure part on the inner side of the temporary storage interlayer. The residual mother liquor directly enters the interior of the temporary storage interlayer, is pumped out through the pipeline and the circulation pump, and is re-delivered to the injection pipe at the top.

10. The phosphorous acid continuous crystallization and centrifugal integrated production process according to claim 1, characterized in that: In step S6, the wet crystal filter cake discharged from the separation and concentration equipment is sent to the bottom of the drying tower, and the water is flashed in the straight tube drying section with high-purity nitrogen at 120±5°C. The dried crystals fall into the fluidized bed cooler for cooling, and an anti-caking agent is sprayed on the crystal surface to form a coating film.

Images