A purification system for low and medium boiling acids in sulfuric acid

Abstract

This application belongs to the field of chemical equipment technology and discloses a purification system for low-boiling acids in sulfuric acid, including a fractionation tower, a primary absorption tower, and a secondary absorption tower. The fractionation tower is located upstream of the primary absorption tower, and its gas outlet is connected to the primary absorption tower. The secondary absorption tower is located downstream of the primary absorption tower, and its gas outlet is connected to the secondary absorption tower. The gas outlet of the secondary absorption tower is also connected to the fractionation tower. The liquid outlet of the secondary absorption tower is connected to the primary absorption tower. By setting up the fractionation tower, primary absorption tower, and secondary absorption tower, low-boiling acids in sulfuric acid are separated with high separation efficiency and no waste liquid or waste gas is generated, making it green and clean.

Description

Technical Field

[0001] This application belongs to the field of chemical equipment technology and relates to a purification system, specifically a purification system for low-boiling acids in sulfuric acid. Background Technology

[0002] The new energy industry has experienced rapid growth in the domestic market in recent years. Electrolytes, as a crucial component of new energy batteries, play a key role in improving battery performance through excellent product quality. However, the production process of electrolytes often results in the generation of sulfuric acid as a byproduct. Therefore, the effective treatment of this byproduct has become a primary goal for companies seeking to reduce costs and increase efficiency.

[0003] In chemical production processes, the byproduct sulfuric acid often contains low-boiling-point acid hydrogen fluoride. It is necessary to separate the sulfuric acid to obtain the sulfuric acid product required for industrial applications. A common method for purifying low-boiling-point acids is to heat the original solution to vaporize and separate the low-boiling-point acid, thus purifying the original solution. However, this method is time-consuming, results in uneven heating of the original solution, and leads to a slow separation and purification rate. Utility Model Content

[0004] To address the aforementioned problems, this invention provides a purification system for low-boiling acids in sulfuric acid.

[0005] A purification system for low-boiling acids in sulfuric acid includes a fractionation tower, a primary absorption tower, and a secondary absorption tower. The fractionation tower is located upstream of the primary absorption tower, and its outlet is connected to the primary absorption tower. The secondary absorption tower is located downstream of the primary absorption tower, and its outlet is connected to the primary absorption tower. The outlet of the secondary absorption tower is also connected to the fractionation tower, and its liquid outlet is connected to the primary absorption tower.

[0006] During the production process, sulfuric acid usually contains a large amount of low-boiling acid. The inventors discovered through research that the low-boiling acid in sulfuric acid can be removed by the cooperation of a distributor, a primary absorption tower and a secondary absorption tower. During operation, sulfuric acid is fed into the fractionation tower. The tower is started, and low-boiling-point acids (mainly hydrogen fluoride and hydrogen chloride) are vaporized and separated. The separated low-boiling-point acids enter the primary absorption tower, where most are absorbed by water. A small portion that is not absorbed enters the secondary absorption tower, where it is also absorbed by water. During the circulation process, the absorbent from the secondary absorption tower returns to the primary absorption tower, becoming its bottom liquid and participating in the primary absorption tower's circulation. This simultaneous water replenishment and extraction method stabilizes the concentration of low-boiling-point acids, improving the efficiency of extracting and recovering them from the by-product sulfuric acid. The outlet of the secondary absorption tower is connected to the fractionation tower. Gas treated in the secondary absorption tower enters the fractionation tower, solving the problem of exhaust gas discharge while ensuring the efficiency of gas-liquid separation within the fractionation tower. Furthermore, the device achieves continuous purification, significantly improving the efficiency of purifying by-product sulfuric acid.

[0007] Preferably, the fractionation tower is equipped with a circulating pump, the feed end of the circulating pump is connected to the lower end of the fractionation tower, and the discharge end of the circulating pump is connected to the upper end of the fractionation tower.

[0008] By setting up a circulation pump, the sulfuric acid in the fractionation tower is circulated, thereby increasing the reaction time of the by-product sulfuric acid in the fractionation tower. This ensures that the by-product sulfuric acid is heated evenly, and that low-boiling-point acids in the sulfuric acid are separated as much as possible, thus improving the recovery rate of low-boiling-point acids.

[0009] Preferably, a discharge branch is connected between the discharge end of the first circulating pump and the fractionation tower, and a sulfuric acid cooler is provided on the first discharge branch, with a first storage tank provided at the discharge end of the sulfuric acid cooler.

[0010] Preferably, the fractionation tower is provided with multiple distributors, which are arranged sequentially along the height direction of the fractionation tower.

[0011] To increase the contact area between the by-product sulfuric acid and steam in the fractionation tower and thus improve the reaction rate, multiple distributors are installed in the fractionation tower. When a certain liquid level is reached in the fractionation tower, the fractionation tower circulation pump is turned on to circulate the sulfuric acid in the fractionation tower, thereby increasing the reaction time of the by-product sulfuric acid in the fractionation tower, so as to ensure that the by-product sulfuric acid is heated evenly and to separate the low-boiling acid in the by-product sulfuric acid as much as possible.

[0012] Preferably, the primary absorption tower is provided with a cooling circulation loop one, which includes a circulation pump two and an absorption cooler one, arranged sequentially along the material flow direction of the cooling circulation loop one.

[0013] Preferably, the first cooling circulation loop is connected to the second discharge branch, and the connection between the second discharge branch and the first cooling circulation loop is located between the second circulation pump and the first absorption cooler. The discharge end of the second discharge branch is provided with a second storage tank.

[0014] The liquid material obtained in the primary absorption tower can be recycled into the second storage tank through the second discharge branch.

[0015] Preferably, a discharge branch line two is connected to the first cooling circulation loop, and the connection between the second discharge branch line two and the first cooling circulation loop is located between the second circulation pump and the first absorption cooler. A distillation kettle is provided at the discharge end of the second discharge branch line, and a condenser and a third storage tank are sequentially connected to the gas outlet end of the distillation kettle along the material flow direction. A circulation loop three is provided on the distillation kettle, and a fourth circulation pump and a distillation kettle cooler are sequentially provided in the third circulation loop along the material flow direction. A recovery pipe three is connected between the fourth circulation pump and the distillation kettle cooler, and the liquid outlet end of the recovery pipe three is connected to the first-stage absorption tower.

[0016] In practical applications, the low-boiling acids in sulfuric acid are usually hydrogen chloride and hydrogen fluoride. Both hydrogen chloride and hydrogen fluoride are readily soluble in water. The acid entering the second storage tank is a mixture of hydrogen chloride and hydrogen fluoride, requiring further separation. To separate hydrogen chloride and hydrogen fluoride, a saturated sodium chloride solution can be used to absorb hydrogen chloride in the primary absorption tower. The mixed solution of sodium chloride and hydrogen chloride is then transferred to a distillation vessel. After distillation, hydrogen chloride escapes as a gas, passes through a condenser, and is stored in a receiving tank. The material obtained after distillation (sodium chloride) is returned to the primary absorption tower to compensate for the sodium chloride lost in the primary absorption tower.

[0017] Preferably, the secondary absorption tower is provided with a second cooling circulation loop, which includes a third circulation pump and a second absorption cooler. The third circulation pump and the second absorption cooler are arranged sequentially along the material flow direction of the second cooling circulation loop.

[0018] The gas phase temperature is high after heating, and the solubility of low-boiling-point acids in deionized water decreases under high temperature conditions. Therefore, it is necessary to add coolers to the circulation pipelines of the primary and secondary absorption towers and use circulating water to cool the materials in the primary and secondary absorption towers, thereby improving the solubility of low-boiling-point acids in water.

[0019] Preferably, the outlet of the secondary absorption tower is provided with and connected to a recovery pipeline, the outlet of the recovery pipeline is connected to the fractionation tower, and a tail gas fan is provided in the recovery pipeline.

[0020] Connecting the secondary absorption tower to the fractionation tower via the recovery pipeline and installing a tail gas fan facilitates the recovery of gaseous materials from the secondary absorption tower.

[0021] Preferably, a recovery pipe 2 is provided and connected between the circulating pump 3 and the absorption cooler 2, and the discharge end of the recovery pipe 2 is connected to the primary absorption tower.

[0022] The liquid material in the secondary absorption tower is transported to the primary absorption tower through the second recovery pipeline. The secondary absorption tower transfers material to the primary absorption tower at a certain transfer rate to ensure the stability of the acid concentration in the primary absorption tower. During the transfer process in the secondary absorption tower, deionized water is also added to ensure the stability of the liquid level in the secondary absorption tower.

[0023] Compared with the prior art, one or more technical solutions provided by the present invention have at least one of the following beneficial effects: (1) By setting up a fractionation tower, a primary absorption tower and a secondary absorption tower, low-boiling acid in sulfuric acid is separated. The separation efficiency is high and no waste liquid or waste gas is generated, making it green and clean.

[0024] (2) By setting up the second discharge branch and cooperating with the first-stage absorption tower, hydrogen fluoride and sodium fluoride in the low-boiling acid are separated and recycled separately. No waste liquid or waste gas is generated during the recycling process, which is green and clean. The raw materials used in the recycling process can be reused, which is conducive to industrialization. Attached Figure Description

[0025] The accompanying drawings are provided to further understand this application and form part of the specification. They are used together with the embodiments of this application to explain this application and do not constitute a limitation thereof.

[0026] Figure 1 This is a schematic diagram of the overall structure of Example 1; Figure 2 This is a partial structural diagram of the discharge branch, distillation kettle, and circulation loop three in Example 2.

[0027] Labeling Explanation: 1. Fractionating Tower; 2. Primary Absorption Tower; 3. Secondary Absorption Tower; 4. Steam Pipe; 5. Feed Pipe; 6. Distributor; 7. Circulation Pump 1; 8. Discharge Branch 1; 9. Sulfuric Acid Cooler; 10. First Storage Tank; 11. Cooling Circulation Loop 1; 12. Circulation Pump 2; 13. Absorption Cooler 1; 14. Discharge Branch 2; 15. Second Storage Tank; 16. Cooling Circulation Loop 2; 17. Circulation Pump 3; 18. Absorption Cooler 2; 19. Recovery Pipe 1; 20. Tail Gas Fan; 21. Recovery Pipe 2; 22. Distillation Kettle; 23. Condenser; 24. Third Storage Tank; 25. Circulation Loop 3; 26. Circulation Pump 4; 27. Distillation Kettle Cooler; 28. Recovery Pipe 3. Detailed Implementation

[0028] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0029] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the equipment or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0030] Example 1: A purification system for low-boiling acids in sulfuric acid, referring to Figure 1 It includes a fractionation tower 1, a primary absorption tower 2, and a secondary absorption tower 3. The fractionation tower 1 is located upstream of the primary absorption tower 2, and its gas outlet is connected to the primary absorption tower 2. The secondary absorption tower 3 is located downstream of the primary absorption tower 2, and its gas outlet is connected to the secondary absorption tower 3. The gas outlet of the secondary absorption tower 3 is connected to the fractionation tower 1. The liquid outlet of the secondary absorption tower 3 is connected to the primary absorption tower 2.

[0031] Fractionating column 1 is externally connected to a steam pipe 4 and a feed pipe 5. The steam pipe 4 is connected to the lower part of the fractionating column 1 and is used to supply steam into the fractionating column 1. The steam pipe 4 is located in the lower part of the fractionating column 1, utilizing the physical property of steam rising upwards, which facilitates full contact between the steam and the material in the fractionating column 1, improves heat conduction, and thus improves the fractionation effect. The feed pipe 5 is connected to the upper part of the fractionating column 1 and is used to supply sulfuric acid raw material. The feed pipe 5 is located above the fractionating column 1, which facilitates the feeding of sulfuric acid and reduces the possibility of sulfuric acid reflux.

[0032] The fractionation column 1 is equipped with multiple distributors 6, which are arranged sequentially along the height of the fractionation column 1. The presence of multiple distributors 6 within the fractionation column 1 increases the contact area between the by-product sulfuric acid and the vapor, thereby improving the reaction rate.

[0033] A circulating pump 7 is installed on the fractionation tower 1. The feed end of the circulating pump 7 is connected to the lower end of the fractionation tower 1, and the discharge end of the circulating pump 7 is connected to the upper end of the fractionation tower 1. By installing the circulating pump 7, the sulfuric acid in the fractionation tower 1 is circulated, thereby increasing the reaction time of the by-product sulfuric acid in the fractionation tower 1, so as to achieve uniform heating of the by-product sulfuric acid, and to separate the low-boiling acid from the sulfuric acid as much as possible, thereby improving the recovery rate of low-boiling acid. A discharge branch line 8 is provided and connected between the discharge end of the circulating pump 7 and the fractionation tower 1. A sulfuric acid cooler 9 is installed on the discharge branch line 8, and a first storage tank 10 is installed at the discharge end of the sulfuric acid cooler 9.

[0034] The primary absorption tower 2 is equipped with a cooling circulation loop 11, which includes a second circulation pump 12 and an absorption cooler 13. The second circulation pump 12 and the absorption cooler 13 are arranged sequentially along the material flow direction of the cooling circulation loop 11. A discharge branch 14 is provided and connected to the cooling circulation loop 11. The connection between the discharge branch 14 and the cooling circulation loop 11 is located between the second circulation pump 12 and the absorption cooler 13. A second storage tank 15 is installed at the discharge end of the discharge branch 14. The liquid material obtained in the primary absorption tower 2 can be recovered by entering the second storage tank 15 through the discharge branch 14.

[0035] The secondary absorption tower 3 is equipped with a second cooling circulation loop 16, which contains a third circulation pump 17 and an absorption cooler 18. The third circulation pump 17 and the absorption cooler 18 are arranged sequentially along the material flow direction of the second cooling circulation loop 16. Because the gas phase temperature is high after heating, and the solubility of low-boiling-point acids in deionized water decreases at high temperatures, absorption coolers need to be added to the circulation pipelines of the primary and secondary absorption towers 3. Circulating water is used to cool the materials in the primary absorption tower 2 and the secondary absorption tower 3, thereby improving the solubility of low-boiling-point acids in water.

[0036] The outlet of the secondary absorption tower 3 is connected to a recovery pipe 19, which in turn connects to the fractionation tower 1. A tail gas fan 20 is installed in the recovery pipe 19, which facilitates the recovery of gaseous materials from the secondary absorption tower 3. A recovery pipe 21 connects the conveying pipe between the circulating pump 17 and the absorption cooler 18. The liquid outlet of the recovery pipe 21 connects to the primary absorption tower 2. The liquid material from the secondary absorption tower 3 is transported to the primary absorption tower 2 via the recovery pipe 21. The secondary absorption tower 3 transfers material to the primary absorption tower 2 at a certain transfer rate to ensure the stability of the acid concentration in the primary absorption tower 2. During the transfer process, deionized water is also added to the secondary absorption tower 3 to maintain a stable liquid level.

[0037] The working process of the purification system for low-boiling acids in sulfuric acid is as follows: First, deionized water is added to the primary absorption tower 2 and the secondary absorption tower 3 to ensure the absorption of the low-boiling acid produced in the fractionation tower 1. The fan of the fractionation unit is turned on to allow the gas phase to flow inside the unit. The sulfuric acid material to be separated is introduced into the fractionation tower 1. When the liquid level in the fractionation tower 1 reaches 15%~40%, the self-circulation of the fractionation tower 1 is started, and the addition of by-product sulfuric acid to the fractionation tower 1 is stopped. At the same time, steam is introduced into the fractionation tower 1, with the steam feed rate controlled in the range of 1~10 kg / h, and the tower bottom temperature is controlled between 80~150℃. The low-boiling acid is vaporized and enters the primary absorption tower 2. When the tower bottom liquid level reaches 20%~60%, the liquid phase of the fractionation tower 1 is started to be discharged. At the same time, the sulfuric acid material to be separated is introduced into the fractionation tower 1, and the feed rate is controlled to balance the discharge flow rate of the fractionation tower 1 to maintain a stable liquid level.

[0038] Most of the low-boiling acid entering the primary absorption tower 2 dissolves in water. The cooling circulation loop 11 of the primary absorption tower 2 operates continuously, and the deionized water is circulated in the absorption tower through the circulation pump to absorb the low-boiling acid. The absorption cooler 13 is used to regulate the temperature of the material in the primary absorption tower 2 to prevent the low-boiling acid from continuously entering the primary absorption tower 2, which would cause the temperature of the primary absorption tower 2 to rise and thus affect the absorption effect.

[0039] A small portion of the unabsorbed low-boiling acid enters the secondary absorption tower 3, where it further dissolves in the deionized water. The untreated gaseous material in the secondary absorption tower 3 enters the distillation tower through recovery pipe 19 and participates in the cycle again. The absorbent liquid (the liquid obtained by dissolving low-boiling acid in deionized water) in the secondary absorption tower 3 enters the primary absorption tower 2 through recovery pipe 21. The secondary absorption tower 3 transfers material to the primary absorption tower 2 at a certain transfer rate to ensure the stability of the acid concentration in the primary absorption tower 2. During the material transfer process in the secondary absorption tower 3, deionized water is also added to ensure the stability of the liquid level in the secondary absorption tower 3.

[0040] By coordinating fractionation tower 1, primary absorption tower 2, and secondary absorption tower 3, continuous production can be achieved, improving the purification rate of by-product sulfuric acid; avoiding the external emission of tail gas, thus enhancing safety and environmental protection; in practical applications, by monitoring the density of low-boiling acid and controlling the ratio of the makeup water volume of primary absorption tower 2 to the low-boiling acid generation rate, low-boiling acid of the target concentration can be prepared according to requirements.

[0041] Example 2: Further research by the inventors revealed that the byproduct sulfuric acid produced during industrial production varies depending on the production line, and its low-boiling acids include not only hydrogen fluoride but also hydrogen chloride. Both hydrogen fluoride and hydrogen chloride are readily soluble in water. Using the purification system described in Example 1, the low-boiling acids entering the second storage tank 15 are a mixture of hydrogen fluoride and hydrogen chloride, which cannot be directly applied to industrial production. Based on this, the inventors further optimized the purification system, obtaining a purification system for low-boiling acids in sulfuric acid, as described in Example 1. Figure 2 The difference from Example 1 is that: The cooling circulation loop 11 is provided with a discharge branch 2 14. The connection between the discharge branch 2 14 and the cooling circulation loop 11 is located between the circulation pump 7 and the absorption cooler 13. The discharge end of the discharge branch 2 14 is provided with a distillation vessel 22. The gas outlet of the distillation vessel 22 is connected to a condenser 23 and a third storage tank 24 in sequence along the material flow direction.

[0042] The distillation vessel 22 is provided with a circulation loop 3 25. The circulation loop 3 25 is provided with a circulation pump 4 26 and a distillation vessel cooler 27 in sequence along the material flow direction. The circulation pump 4 26 and the distillation vessel cooler 27 are connected by a recovery pipe 3 28. The liquid outlet end of the recovery pipe 3 28 is connected to the primary absorption tower 2.

[0043] To separate hydrogen chloride and hydrogen fluoride, a saturated sodium chloride solution can be used to absorb hydrogen chloride in the primary absorption tower 2. The mixed solution of sodium chloride and hydrogen chloride is then transferred to the distillation vessel 22. After distillation, the hydrogen chloride overflows in the gas phase and is processed by the condenser 23 before entering the third storage tank 24 for storage. The material obtained after distillation (sodium chloride) is returned to the primary absorption tower 2 through the recovery pipeline 28 to make up for the sodium chloride lost in the primary absorption tower 2. At the same time, deionized water is continuously added to the distillation vessel 22 to maintain the liquid level in the distillation vessel 22.

[0044] Although embodiments of this application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A purification system for low and medium boiling acids in sulfuric acid, characterized in that, The absorption tower includes a fractionation tower (1), a primary absorption tower (2), and a secondary absorption tower (3). The fractionation tower (1) is located upstream of the primary absorption tower (2), and the gas outlet of the fractionation tower (1) is connected to the primary absorption tower (2). The secondary absorption tower (3) is located downstream of the primary absorption tower (2), and the gas outlet of the primary absorption tower (2) is connected to the secondary absorption tower (3). The gas outlet of the secondary absorption tower (3) is connected to the fractionation tower (1). The liquid outlet of the secondary absorption tower (3) is connected to the primary absorption tower (2).

2. The purification system of low and medium boiling acids from sulfuric acid as claimed in claim 1, wherein, The fractionation tower (1) is equipped with a circulating pump (7), the feed end of the circulating pump (7) is connected to the lower end of the fractionation tower (1), and the discharge end of the circulating pump (7) is connected to the upper end of the fractionation tower (1).

3. The purification system of low to medium boiling acids from sulfuric acid according to claim 1 or 2, characterized in that, The fractionation tower (1) is provided with a plurality of distributors (6), which are arranged sequentially along the height direction of the fractionation tower (1).

4. The purification system of low to medium boiling acids from sulfuric acid as claimed in claim 1 wherein, The primary absorption tower (2) is provided with a cooling circulation loop one (11), which includes a circulation pump two (12) and an absorption cooler one (13). The circulation pump two (12) and the absorption cooler one (13) are arranged sequentially along the material flow direction of the cooling circulation loop one (11).

5. The purification system of low to medium boiling acids from sulfuric acid as claimed in claim 4 wherein, The cooling circulation loop one (11) is connected to the discharge branch two (14), and the connection between the discharge branch two (14) and the cooling circulation loop one (11) is located between the circulation pump two (12) and the absorption cooler one (13). The discharge end of the discharge branch two (14) is provided with a second storage tank (15).

6. The purification system of low to medium boiling acids from sulfuric acid as claimed in claim 4 wherein, The cooling circulation loop one (11) is connected to the discharge branch two (14). The connection between the discharge branch two (14) and the cooling circulation loop one (11) is located between the circulation pump two (12) and the absorption cooler one (13). The discharge end of the discharge branch two (14) is provided with a distillation kettle (22). The gas outlet of the distillation kettle (22) is connected to a condenser (23) and a third storage tank (24) in sequence along the material flow direction. The distillation kettle (22) is provided with a circulation loop three (25). The circulation loop three (25) is provided with a circulation pump four (26) and a distillation kettle cooler (27) in sequence along the material flow direction. The circulation pump four (26) and the distillation kettle cooler (27) are connected to a recovery pipe three (28). The liquid outlet of the recovery pipe three (28) is connected to the first-stage absorption tower (2).

7. The purification system of low to medium boiling acids from sulfuric acid as claimed in claim 1 wherein, The secondary absorption tower (3) is provided with a second cooling circulation loop (16), and the second cooling circulation loop (16) is provided with a third circulation pump (17) and a second absorption cooler (18). The third circulation pump (17) and the second absorption cooler (18) are arranged sequentially along the material flow direction of the second cooling circulation loop (16).

8. The purification system of low to medium boiling acids from sulfuric acid as claimed in claim 1 wherein, The outlet of the secondary absorption tower (3) is provided with and connected to a recovery pipe (19). The outlet of the recovery pipe (19) is connected to the fractionation tower (1). A tail gas fan (20) is provided in the recovery pipe (19).

9. The purification system of low to medium boiling acids from sulfuric acid as claimed in claim 7 wherein, A recovery pipe 2 (21) is provided and connected between the circulating pump 3 (17) and the absorption cooler 2 (18), and the discharge end of the recovery pipe 2 (21) is connected to the primary absorption tower (2).

10. The purification system of low to medium boiling acids from sulfuric acid as claimed in claim 2 wherein, The discharge end of the circulating pump (7) is connected to the fractionation tower (1) by a discharge branch (8), and a sulfuric acid cooler (9) is provided on the discharge branch (8). A first storage tank (10) is provided at the discharge end of the sulfuric acid cooler (9).

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