Device for preparing white gypsum by adjusting phosphoric acid process

Abstract

The utility model relates to the technical field of wet-process phosphoric acid, in particular to a device for preparing white gypsum by adjusting a phosphoric acid process, which comprises an acidolysis tank provided with a phosphorite feed port and a phosphoric acid feed port, a discharge port of the acidolysis tank is connected to first filtering equipment, filtrate enters the upper part of a crystallization tank, and a sulfuric acid spraying pipeline is arranged at the top of the crystallization tank; an overflow weir and a downcomer are arranged on one side of each sieve plate, so that the adjacent upper and lower sieve plates are communicated, a return material outlet is formed in the lower part of the crystallization tank and is connected to a return material inlet in the upper part of the crystallization tank through a circulating pump and a pipeline, and a discharge hole in the bottom of the crystallization tank is connected to second filtering equipment; and a filter residue outlet of the second filtering equipment is connected with a white gypsum conveying belt. By adopting the device provided by the utility model, the white gypsum can be produced, the speed and the yield of the white gypsum production process can be controlled, the content of citrate-soluble phosphorus and fluorine in the gypsum can be effectively reduced, and the quality of the gypsum can be improved.

Description

Technical Field

[0001] This utility model belongs to the field of wet phosphoric acid technology, specifically relating to an apparatus for preparing gypsum by adjusting the phosphoric acid process. Background Technology

[0002] Phosphogypsum is a byproduct of wet-process phosphoric acid production. Producing 1 ton of phosphoric acid generates 4-5 tons of phosphogypsum. Its main component is calcium sulfate, containing significant amounts of soluble phosphorus, fluorine, and other impurities. Furthermore, its low whiteness makes it unsuitable for direct application in the high-end market. Due to its relatively low added value and limited market capacity, large quantities of phosphogypsum accumulate, consuming land resources and potentially negatively impacting the surrounding environment and ecosystem. High-quality white gypsum, compared to traditional phosphogypsum, boasts higher whiteness and purity, meeting the demands of a wider range of high-end markets. Although China has the world's largest gypsum reserves, high-quality gypsum with a whiteness ≥90% accounts for only 1.8% of total reserves.

[0003] In existing white gypsum preparation processes, CN103626143 A discloses a method for producing white gypsum as a byproduct of wet-process phosphoric acid production. This method primarily addresses the problems of high impurity content, poor quality, and yellowish-gray, dark gray, and black appearance of the byproduct phosphogypsum from traditional wet-process phosphoric acid production, which is often disposed of as waste and pollutes the environment. While this process can produce high-purity white gypsum, it suffers from incomplete crystallization in the filtrate and low controllability of the crystallization process. Although CN105948009 A offers some process optimization, it still suffers from a long process flow, slow reaction rate, and difficulty in cleaning calcium sulfate scale. Summary of the Invention

[0004] This invention provides an apparatus for preparing white gypsum by adjusting the phosphoric acid process. Based on the existing refined phosphoric acid apparatus, the process is optimized. This apparatus can produce white gypsum and achieve controllable rate and yield of white gypsum production. It effectively reduces the content of citrate-soluble phosphorus and fluorine in gypsum and improves its quality.

[0005] The technical solution of this utility model is to provide an apparatus for preparing white gypsum by adjusting the phosphoric acid process, including an acid hydrolysis tank, which is provided with a phosphate rock feed port and a phosphoric acid feed port. The discharge port of the acid hydrolysis tank is connected to a first filtration device. The filtrate enters the upper part of the crystallization tank. A sulfuric acid spray pipe is provided at the top of the crystallization tank. Multiple layers of sieve plates are staggered in the crystallization tank. An overflow weir and a downcomer are provided on one side of the sieve plates to connect adjacent upper and lower sieve plates. A return outlet is provided at the lower part of the crystallization tank, which is connected to the return inlet at the upper part of the crystallization tank through a circulation pump and pipeline. The discharge port at the bottom of the crystallization tank is connected to a second filtration device. The filter residue outlet of the second filtration device is connected to a white gypsum conveyor belt.

[0006] Optionally, the device includes a phosphate rock feed conveyor and a phosphoric acid feed pipe. The phosphate rock feed conveyor is connected to the phosphate rock feed port of the acidolysis tank, and the phosphoric acid feed pipe is connected to the phosphoric acid feed port of the acidolysis tank via a phosphoric acid pump.

[0007] Optionally, the outlet of the acid hydrolysis tank is connected to the first filtration device via an acid hydrolysis tank discharge pump; the first filtration device is a filter press.

[0008] Optionally, an acid buffer tank is also provided between the first filtration device and the crystallization tank, and the acid buffer tank is connected to the filtrate inlet at the top of the crystallization tank via an acid pump.

[0009] Optionally, the filter residue outlet of the first filtration unit and the filtrate outlet of the second filtration unit are both fed to other existing phosphoric acid plants for reuse.

[0010] Optionally, the sulfuric acid pipeline is connected to the sulfuric acid spray pipeline at the top of the crystallization tank via a sulfuric acid pump; the lower part of the crystallization tank is also equipped with an SO4 spray system. 2- Online detection equipment, SO4 2- The signal output of the online detection equipment is electrically connected to the sulfuric acid pump via a controller.

[0011] Optionally, a crystallization chamber is provided at the bottom of the crystallization tank; the circulation pump is a shear pump.

[0012] Optionally, the crystallization tank is provided with an ultrasonic spray cleaning system on its side wall, and multiple nozzles are evenly distributed on the inner wall of the crystallization tank.

[0013] This utility model has the following beneficial effects:

[0014] This invention enables the direct production of high-value-added white gypsum during the acidolysis of phosphate rock, reducing the output of gray gypsum and effectively alleviating the pressure of phosphogypsum stockpiling. Furthermore, the mixed acid and filter residue from the first filtration process can be reused in subsequent phosphoric acid plants, realizing the recycling of phosphorus resources and reducing resource waste.

[0015] To ensure the quality of the produced gypsum, the crystallization tank used in this invention has undergone several improvements. Specifically, sulfuric acid is sprayed into the crystallization tank, and its dispersed addition prevents localized overheating, avoiding the premature encapsulation of phosphorus and fluoride in the gypsum and thus affecting its quality. The multi-layered sieves arranged in a staggered manner within the crystallization tank promote a thorough reaction between the filtrate from the first filtration device and the sulfuric acid, further improving reaction efficiency and gypsum quality. During the reaction, a certain proportion of seed crystals can be added to the crystallizer to promote the rapid precipitation of phosphogypsum. A circulation pump is installed at the bottom of the crystallization tank to circulate the slurry within, increasing the probability of particle collisions and promoting crystal growth, thus improving gypsum quality. Simultaneously, the use of a high-shear pump effectively prevents particle deposition in the slurry, maintaining a uniform distribution of the slurry within the crystallizer and ensuring the continuous and stable progress of the reaction.

[0016] The device described in this invention enables precise control over the rate and yield of gypsum formation, effectively reducing the content of citrate-soluble phosphorus and fluoride in gypsum and significantly improving its quality. Furthermore, this device successfully solves the problem of cleaning gypsum scale buildup. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of the device provided by this utility model.

[0018] In the diagram: 1. Phosphate ore feed conveyor belt; 2. Phosphate pump; 3. Acid hydrolysis tank; 4. Acid hydrolysis tank discharge pump; 5. First filtration equipment; 6. Primary slag conveyor belt; 7. Acid buffer tank; 8. Acid pump; 9. Sulfuric acid pump; 10. Crystallizer; 11. Crystallizer discharge pump; 12. Second filtration equipment; 13. Mixed acid storage tank; 14. Mixed acid pump.

[0019] Figure 2 This is a schematic diagram of the crystallization tank of this utility model.

[0020] In the diagram: sulfuric acid spray pipe 101, filtrate inlet 102, sieve plate 103, overflow weir 104, downcomer 105, return material outlet 106, circulating pump 107, return material inlet 108, discharge port 109, SO4 2- Online testing equipment 1010 and ultrasonic spray cleaning system 1011. Detailed Implementation

[0021] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, those skilled in the art will understand that the following embodiments are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention.

[0022] like Figures 1-2 As shown, this utility model provides an apparatus for preparing white gypsum by adjusting the phosphoric acid process, including an acid hydrolysis tank 3, which is provided with a phosphate rock feed port and a phosphoric acid feed port. The discharge port of the acid hydrolysis tank is connected to a first filtration device 5. The filtrate enters the upper filtrate inlet 102 of the crystallization tank 10. A sulfuric acid spray pipe 101 is provided at the top of the crystallization tank. Multiple layers of sieve plates 103 are staggered in the crystallization tank. An overflow weir 104 and a downcomer 105 are provided on one side of the sieve plates to connect adjacent upper and lower sieve plates. A return outlet 106 is provided at the bottom of the crystallization tank, which is connected to the return inlet 108 at the top of the crystallization tank through a circulation pump 107 and a pipe. The discharge port 109 at the bottom of the crystallization tank is connected to a second filtration device 12. The filter residue outlet of the second filtration device is connected to a white gypsum conveyor belt.

[0023] In some embodiments, the apparatus includes a phosphate rock feed conveyor 1 and a phosphoric acid feed pipe. The phosphate rock feed conveyor is connected to the phosphate rock feed port of the acidolysis tank, and the phosphoric acid feed pipe is connected to the phosphoric acid feed port of the acidolysis tank via a phosphoric acid pump 2.

[0024] In some embodiments, the outlet of the acid hydrolysis tank is connected to the first filtration device 5 via the acid hydrolysis tank discharge pump 4; the first filtration device is preferably a plate and frame filter press.

[0025] In some embodiments, an acid buffer tank 7 is provided between the first filtration device 5 and the crystallization tank 10, and the acid buffer tank 7 is connected to the filtrate inlet at the top of the crystallization tank via an acid pump 8.

[0026] In some embodiments, the filter residue outlet of the first filtration device and the filtrate outlet of the second filtration device are both fed to other existing phosphoric acid plants for reuse. The filter residue outlet of the first filtration device is conveyed to an existing phosphoric acid process unit via a primary slag conveyor belt for continued reaction. The filtrate outlet of the second filtration device is conveyed through a pipeline to a mixed acid storage tank 13, and then by a mixed acid pump 14 to an existing phosphoric acid plant for reuse.

[0027] In some embodiments, the sulfuric acid pipeline is connected to the sulfuric acid spray pipeline 101 at the top of the crystallization tank via a sulfuric acid pump 9; the lower part of the crystallization tank is also provided with SO4. 2- Online detection equipment 1010, SO4 2- The signal output of the online detection equipment is electrically connected to the sulfuric acid pump via a controller. SO4 2- The online monitoring equipment can monitor the concentration of sulfate ions in real time. When the sulfate ion concentration is too high or too low, the controller adjusts the delivery rate of the sulfuric acid pump 9 to ensure that the sulfate ion content is within the optimal range during the reaction process. This effectively controls the gypsum formation rate while ensuring high-quality white gypsum production. This design not only improves the automation level of the production process but also significantly enhances the stability and consistency of the product.

[0028] In some embodiments, a crystallization chamber is provided at the bottom of the crystallization tank; the circulation pump is a shear pump. The slurry in the crystallizer 10 is circulated, increasing the probability of particle collision in the slurry, which is beneficial to crystal growth and further improves the quality of the white gypsum. At the same time, the use of the shear pump can also effectively prevent particle deposition in the slurry, maintain a uniform distribution of the slurry in the crystallizer, and ensure the continuous and stable progress of the reaction.

[0029] In some embodiments, an ultrasonic spray cleaning system 1011 is provided on the sidewall of the crystallization tank, and multiple nozzles are evenly distributed on the inner wall of the crystallization tank. The ultrasonic spray cleaning system performs timed cleaning of the inner wall of the crystallizer, effectively removing impurities and deposits adhering to the inner wall and preventing scaling problems caused by prolonged operation. This design not only ensures the efficient operation of the crystallizer but also extends its service life. Simultaneously, the evenly distributed nozzles of the ultrasonic spray cleaning system ensure that the cleaning fluid fully covers the inner wall of the crystallizer, and the high-frequency vibration of the ultrasonic waves effectively breaks down and disperses scale, ensuring a thorough and efficient cleaning effect and guaranteeing the purity and quality of the gypsum products.

[0030] In actual production, phosphate rock from the phosphate rock feed conveyor belt 1 and dilute phosphoric acid from the phosphoric acid pump 2 are fed into the acid hydrolysis tank 3 for mixing and reaction. The resulting slurry is then sent to the first filtration device 5 via the acid hydrolysis tank discharge pump 4 for separation, yielding primary reaction residue and acid hydrolysis liquid. The primary reaction residue is sent to the existing phosphoric acid process extraction tank for secondary reaction, while the acid hydrolysis liquid is transported to the acid buffer tank 7. The solution is then sent to the crystallizer 10 via the acid pump 8, while simultaneously, sulfuric acid is pumped into the crystallizer 9 for circulating crystallization. The crystallized slurry is pumped to the second filtration device 12 via the crystallizer discharge pump 11. After washing and drying, the filtered solids yield high-white gypsum. The filtrate is sent to the mixed acid storage tank 13, and then transported by the mixed acid pump 14 to the existing phosphoric acid unit for reuse.

[0031] The above embodiments describe preferred embodiments of the present invention, but the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, including combining the various technical features in any other way. These simple modifications and combinations should also be considered as the content disclosed by the present invention and all fall within the protection scope of the present invention. Therefore, the protection scope of the present invention patent should be determined by the appended claims.

Claims

1. An apparatus for preparing gypsum using phosphoric acid process adjustment, characterized in that: The system includes an acid leaching tank with a phosphate rock feed port and a phosphoric acid feed port. The outlet of the acid leaching tank is connected to the first filtration device. The filtrate enters the upper part of the crystallization tank. A sulfuric acid spray pipe is installed at the top of the crystallization tank. Multiple layers of sieves are staggered inside the crystallization tank. An overflow weir and a downcomer are installed on one side of each sieve to connect adjacent upper and lower sieves. A return outlet is provided at the bottom of the crystallization tank, which is connected to the return inlet at the top of the crystallization tank via a circulation pump and pipeline. The outlet at the bottom of the crystallization tank is connected to the second filtration device. The filter residue outlet of the second filtration device is connected to a gypsum conveyor belt.

2. The apparatus for preparing gypsum by adjusting the phosphoric acid process according to claim 1, characterized in that: The device includes a phosphate ore feed belt conveyor and a phosphoric acid feed pipe. The phosphate ore feed belt conveyor is connected to the phosphate ore feed port of the acidolysis tank, and the phosphoric acid feed pipe is connected to the phosphoric acid feed port of the acidolysis tank via a phosphoric acid pump.

3. The apparatus for preparing gypsum by adjusting the phosphoric acid process according to claim 1, characterized in that: The outlet of the acid hydrolysis tank is connected to the first filtration device via an acid hydrolysis tank discharge pump; the first filtration device is a filter press.

4. The apparatus for preparing gypsum by adjusting the phosphoric acid process according to claim 1, characterized in that: An acid buffer tank is also provided between the first filtration device and the crystallization tank. The acid buffer tank is connected to the filtrate inlet at the top of the crystallization tank via an acid pump.

5. The apparatus for preparing gypsum by adjusting the phosphoric acid process according to claim 1, characterized in that: The filter residue outlet of the first filtration unit and the filtrate outlet of the second filtration unit are both supplied to other existing phosphoric acid plants for reuse.

6. The apparatus for preparing gypsum by adjusting the phosphoric acid process according to claim 1, characterized in that: The sulfuric acid pipeline is connected to the sulfuric acid spray pipeline at the top of the crystallization tank via a sulfuric acid pump; the lower part of the crystallization tank is also equipped with an SO4 spray system. 2- Online detection equipment, SO4 2- The signal output of the online detection equipment is electrically connected to the sulfuric acid pump via a controller.

7. The apparatus for preparing gypsum by adjusting the phosphoric acid process according to claim 1, characterized in that: The crystallization tank has a crystallization chamber at the bottom; the circulation pump is a shear pump.

8. The apparatus for preparing gypsum by adjusting the phosphoric acid process according to claim 1, characterized in that: The crystallization tank is equipped with an ultrasonic spray cleaning system on its side wall, and multiple nozzles are evenly distributed on the inner wall of the crystallization tank.

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