Tail gas condensation recovery tank for p-nitrobenzoic acid production

Abstract

The utility model belongs to the technical field of tail gas recovery, and particularly relates to a tail gas condensation recovery tank for p-nitrobenzoic acid production, which comprises a tank body system, a first tank body and a second tank body which are connected in series, a tail gas inlet of the second tank body is connected with a condensation recovery liquid outlet of the first tank body through a pipeline, and the second tank body is used for treating unliquefied gas; the condensation unit comprises a first-stage condensation section and a second-stage condensation section, and the tail gas guider is installed below the tail gas inlet and attached to the condensation unit; the temperature control unit comprises a first temperature control module and a second temperature control module; the pressure regulating unit comprises a first-stage pressure regulator and a second-stage pressure regulator, and the first-stage pressure regulator is mounted in front of the tail gas inlet of the first tank body; the first-stage condensation section is used for recovering high-boiling-point components (such as p-nitrobenzoic acid and water), the second-stage condensation section is used for recovering low-boiling-point components (such as organic solvents), the recovery rate of target substances in tail gas is increased, and resource waste is reduced.

Description

Technical Field

[0001] This utility model belongs to the field of tail gas recovery technology, specifically relating to a tail gas condensation and recovery tank for the production of p-nitrobenzoic acid. Background Technology

[0002] In industrial production processes such as chemical, pharmaceutical, and fine chemical manufacturing, exhaust gases contain large amounts of volatile organic compounds (VOCs), high-boiling-point components (such as p-nitrobenzoic acid and water), and organic solvents. If these exhaust gases are emitted directly without effective treatment, it will not only waste resources but also cause serious air pollution and may even lead to safety hazards such as fires and explosions. Therefore, exhaust gas condensation and recovery technology has become a crucial link in achieving resource recycling and environmental compliance in industrial production.

[0003] The exhaust gas from p-nitrobenzoic acid is complex, typically containing high-boiling-point components (such as solid particles, high-melting-point organic compounds, formic acid, etc.) and low-boiling-point components (such as volatile organic solvents, ethanol, diethyl ether, etc.). Traditional single-stage condensation processes struggle to simultaneously meet the high-efficiency recovery requirements of both high- and low-boiling-point components: if the condensation temperature is too low, while low-boiling-point components can be recovered, it leads to a significant increase in equipment energy consumption and the risk of icing; if the condensation temperature is too high, high-boiling-point components cannot be fully liquefied, resulting in a significant decrease in recovery rate. Furthermore, the exhaust gas often contains high pressure or fluctuating pressure; if not effectively controlled, this can lead to reduced condensation efficiency, unstable equipment operation, and even safety hazards. Therefore, a staged condensation and pressure-coordinated control technology is urgently needed to achieve precise separation and efficient recovery of high- and low-boiling-point components. To address these issues, some technologies attempt to employ multi-stage condensation structures (such as two-stage or multi-stage series condensation), recovering high- and low-boiling-point components by setting different temperatures in stages. For example, the first-stage condensation section is set at a relatively high temperature (e.g., 50°C) to recover high-boiling-point components, while the second-stage condensation section is set at an extremely low temperature (e.g., 5°C) to recover low-boiling-point components. However, existing technologies still have the following shortcomings when implementing staged condensation:

[0004] Low temperature control accuracy: Some systems rely on a single refrigeration unit to regulate the overall temperature, and cannot independently control the temperature of different condensing sections, resulting in uneven temperature distribution and affecting the grading effect.

[0005] Limited cooling structure efficiency: The condenser tube bundle layout is simple, the contact path between the exhaust gas and the cooling water is short, and the heat transfer efficiency is difficult to improve further.

[0006] Poor coordination between pressure regulation and condensation process: The pressure regulating unit and the condensation unit are not deeply linked, and pressure fluctuations may disrupt the stability of the condensation process. Utility Model Content

[0007] To address the above problems, the purpose of this utility model is to provide a tail gas condensation and recovery tank for the production of p-nitrobenzoic acid, thereby solving the problems mentioned in the background art.

[0008] This utility model provides a tail gas condensation and recovery tank for the production of p-nitrobenzoic acid, including a tank system comprising a first tank and a second tank connected in series. Both the first and second tanks have tail gas inlets at their tops and condensate recovery liquid outlets at their bottoms. The tail gas inlet of the second tank is connected to the condensate recovery liquid outlet of the first tank via a pipe for treating unliquefied gas. A condensation unit includes a primary condensation section and a secondary condensation section. The primary condensation section is located inside the first tank and is used to recover high-boiling-point components from the tail gas. The secondary condensation section is located inside the second tank and is used to recover low-boiling-point components from the tail gas. A tail gas guide is installed below the tail gas inlet and is in close contact with the condensation unit to ensure sufficient contact between the tail gas and the cooling medium for rapid cooling of the tail gas. Temperature The control unit includes a first temperature control module, a second temperature control module, and a controller. The first temperature control module includes a first temperature sensor and a first refrigeration unit mounted on a first tank. The second temperature control module includes a second temperature sensor and a second refrigeration unit mounted on a second tank. The controller controls the operating parameters of the first and second refrigeration units based on the monitoring data from the first and second temperature sensors to adjust the cooling temperatures of the primary and secondary condensing sections. The pressure regulating unit includes a primary pressure regulator and a secondary pressure regulator. The primary pressure regulator is installed before the exhaust gas inlet of the first tank and is used to monitor and regulate the exhaust gas pressure entering the first tank. The secondary pressure regulator is installed before the exhaust gas inlet of the second tank and is used to regulate the exhaust gas pressure entering the second tank.

[0009] Preferably, both the primary condensation section and the secondary condensation section are condenser tube bundles with internal exhaust gas flow channels, and the condenser tube bundles are designed in a continuous series S-shape.

[0010] Preferably, the first tank and the second tank each contain two condenser tube bundles, which are arranged opposite each other on both sides of the exhaust gas guide, and the inlet and outlet of the two condenser tube bundles are connected by two connecting pipes respectively.

[0011] Preferably, both the first refrigeration unit and the second refrigeration unit include a cooling water tank, an inlet pipe and an outlet pipe for connecting the cooling water tank to the inlet and outlet of the condenser tube bundle, a circulation pump for conveying cooling water from the cooling water tank to the condenser tube bundle and returning the cooling water discharged from the condenser tube bundle to the cooling water tank, and a heat dissipation component for cooling the cooling water returning from the outlet pipe.

[0012] Preferably, a separator is installed on the pipe at the outlet of the condensate recovery liquid of the first tank. The separator is used to separate the condensate liquefied in the first-stage condensation section from the unliquefied gas. The separator includes a branch pipe connected to the bottom of the pipe for separating the condensate liquefied in the first-stage condensation section; a guide plate disposed at the connection between the branch pipe and the pipe, which is inclined to assist the gas to bypass the branch pipe and be guided along the pipe to the tail gas inlet of the second-stage condensation section; and a collection box connected to the tail end of the branch pipe for collecting the condensate flowing out of the branch pipe.

[0013] Preferably, a tail gas treatment unit is connected to the outlet of the condensate recovery liquid at the bottom of the second tank. The tail gas treatment unit is an activated carbon adsorption device used to treat uncondensed trace organic matter.

[0014] Preferably, both the primary and secondary pressure regulators include a pressure sensor and a compressor with a pressure relief valve, used to monitor and regulate the pressure of the exhaust gas before it enters the tank.

[0015] The beneficial effects of this invention are as follows: By setting up a primary condensation section and a secondary condensation section, the primary condensation section is used to recover high-boiling-point components, and the secondary condensation section is used to recover low-boiling-point components, significantly improving the recovery rate of target substances in the exhaust gas and reducing resource waste; the temperature control unit dynamically adjusts the cooling temperature according to real-time monitoring data to avoid energy waste caused by excessive cooling; the pressure regulating unit ensures pressure regulation when the exhaust gas enters the tank, and with the cooperation of the temperature control unit, the primary condensation section is at 50 degrees Celsius and atmospheric pressure, where formic acid and water condense into liquid; the secondary condensation section is at 5 degrees Celsius and slightly positive pressure (e.g., 1.1-1.2 atm), where residual formic acid and trace amounts of organic matter condense, preventing a decrease in condensation efficiency or equipment damage due to pressure fluctuations, and improving system safety. Attached Figure Description

[0016] Figure 1 This is a three-dimensional structural diagram of the present invention;

[0017] Figure 2 This is a schematic diagram of the planar structure of the present invention;

[0018] Figure 3 This is a side view cross-sectional three-dimensional structural schematic diagram of the present invention;

[0019] Figure 4 This is a side view sectional planar structural diagram of the present invention;

[0020] Figure 5 This is an enlarged structural diagram of point A in this utility model.

[0021] In the diagram: 1. First tank; 2. Second tank; 3. Exhaust gas inlet; 4. Condensate recovery liquid outlet; 5. Pipeline; 6. First-stage condensation section; 7. Second-stage condensation section; 8. Exhaust gas guide; 9. First temperature sensor; 10. Second temperature sensor; 11. First-stage pressure regulator; 12. Second-stage pressure regulator; 13. Condensate tube bundle; 14. Cooling water tank; 15. Liquid inlet pipe; 16. Liquid outlet pipe; 17. Circulation pump; 18. Heat sink; 19. Compressor; 20. Pressure sensor; 21. Branch pipe; 22. Guide plate; 23. Collection box. Detailed Implementation

[0022] To enable those skilled in the art to better understand the technical solution of this utility model, the present utility model will be described in detail below with reference to the accompanying drawings. The description in this part is only exemplary and explanatory, and should not be used to limit the scope of protection of this utility model in any way.

[0023] like Figure 1-5 As shown, the tail gas condensation and recovery tank for p-nitrobenzoic acid production comprises a tank system, a condensation unit and guide installed inside the tank system, a temperature control unit, and a pressure regulating unit. The tank system includes a first tank 1 and a second tank 2 connected in series. Both the first tank 1 and the second tank 2 have tail gas inlets 3 at their tops and condensate recovery liquid outlets 4 at their bottoms. The tail gas inlet 3 of the second tank 2 is connected to the condensate recovery liquid outlet 4 of the first tank 1 via a pipe 5 for treating unliquefied gas. To separate the condensate recovery liquid from the unliquefied gas, a separator is also installed on the pipe 5. Figure 5As shown, the separator mainly includes a branch pipe 21 connected to the bottom of the pipe 5 for separating the condensate liquefied in the first-stage condensation section 6, a guide plate 22 set at the connection between the branch pipe 21 and the pipe 5 for assisting the gas to bypass the branch pipe 21 and be guided along the pipe 5 to the tail gas inlet 3 of the second-stage condensation section 7, and a collection box 23 connected to the tail end of the branch pipe 21 for collecting the condensate flowing out of the branch pipe 21. The guide plate 22 is designed in an arc shape, with one end near the first tank 1 connected to the inner wall of the pipe 5, and a gap between the other end and the inner wall of the pipe 5, so that the condensate recovery liquid can enter the branch pipe 21 through the gap and enter the collection box 23 along the branch pipe 21. It is installed at the tail gas inlet 3 of both the first tank 1 and the second tank 2. Under the action of the fan, it provides the flow thrust for the gas, which will not affect the unliquefied tail gas from entering the second tank 2 for secondary condensation along the pipe 5, and also facilitates the recovery of the condensate. The condensation unit includes a primary condensation section 6 and a secondary condensation section 7. The primary condensation section 6 is located inside the first tank 1 and is used to recover high-boiling-point components (such as p-nitrobenzoic acid and water) from the exhaust gas. The secondary condensation section 7 is located inside the second tank 2 and is used to recover low-boiling-point components (such as organic solvents) from the exhaust gas. To achieve staged condensation, the cooling temperature and gas pressure of the primary condensation section 6 and the secondary condensation section 7 need to be adjusted in cooperation with the temperature control unit and the pressure regulating unit. Specifically, the temperature control unit includes a first temperature control module, a second temperature control module, and a controller. The first temperature control module includes a first temperature sensor 9 and a first refrigeration unit located on the first tank 1. The second temperature control module includes a second temperature sensor 10 and a second refrigeration unit located on the second tank 2. The controller controls the operating parameters of the first refrigeration unit and the second refrigeration unit according to the monitoring data of the first temperature sensor 9 and the second temperature sensor 10 to adjust the cooling temperature of the primary condensation section 6 and the secondary condensation section 7. To improve the accuracy of temperature monitoring, multiple temperature sensors are set at both the primary and secondary condensation sections and are evenly distributed on the condenser tube bundle. Secondly, both the first and second refrigeration units include a cooling water tank 14, an inlet pipe 15 and an outlet pipe 16 for connecting the cooling water tank 14 to the inlet and outlet of the condenser tube bundle 13, a circulation pump 17 for transporting cooling water from the cooling water tank to the condenser tube bundle 13 and returning the cooling water discharged from the condenser tube bundle 13 to the cooling water tank 14, and a heat dissipation component 18 for cooling the cooling water returning from the outlet pipe 16.For example, if the temperature in the primary condenser needs to be set to 50 degrees Celsius, when the first temperature sensor 9 detects that the temperature of the cooling water in the condenser tube bundle 13 is 100 degrees Celsius, the controller increases the power of the circulation pump 17 to increase the circulation speed of the cooling water, thereby quickly reducing the temperature of the cooling water in the condenser tube bundle 13 until it approaches 50 degrees Celsius. As another example, if the temperature in the secondary condenser needs to be set to 5 degrees Celsius, when the first temperature sensor 9 detects that the temperature of the cooling water in the condenser tube bundle 13 is 30 degrees Celsius, the controller increases the power of the circulation pump 17 to increase the circulation speed of the cooling water, thereby quickly reducing the temperature of the cooling water in the condenser tube bundle 13 until it approaches 5 degrees Celsius. The pressure regulating unit includes a primary pressure regulator 11 and a secondary pressure regulator 12. Both the primary and secondary pressure regulators 11 and 12 include a pressure sensor 20 and a compressor 19 with a pressure relief valve. The compressor 19 automatically adjusts the output pressure based on pressure monitoring data. The pressure relief valve automatically releases pressure when the pressure exceeds the limit. The primary pressure regulator 11 is installed before the exhaust gas inlet 3 of the first tank 1 to monitor and regulate the exhaust gas pressure entering the first tank 1. The secondary pressure regulator 12 is installed before the exhaust gas inlet 3 of the second tank 2 to regulate the exhaust gas pressure entering the second tank 2. For example, if the gas pressure in the first tank 1 needs to be maintained at atmospheric pressure, when the pressure sensor 20 detects that the exhaust gas pressure before the first tank 1 is higher than atmospheric pressure, the pressure relief valve is activated to reduce the exhaust gas pressure to atmospheric pressure. Alternatively, if the gas pressure in the second tank 2 needs to be maintained at a slightly positive pressure (e.g., 1.1–1.2 atm), when the pressure sensor 20 detects that the gas pressure before the second tank 2 is lower than this pressure, the compressor 19 performs work to raise the gas pressure to this level.

[0024] Furthermore, such as Figure 3-4 As shown, to improve the cooling effect of the exhaust gas, both the primary condensing section 6 and the secondary condensing section 7 are condenser tube bundles 13 with internal exhaust gas flow channels. The condenser tube bundles 13 are designed as a continuous series of S-shapes. Two condenser tube bundles 13 are placed in both the first tank 1 and the second tank 2. The two condenser tube bundles 13 are positioned opposite each other on both sides of the exhaust gas guide 8, and their inlets and outlets are connected by two connecting pipes. When cooling water reaches the top of the tank along the liquid delivery pipe, it is diverted to the two condenser tube bundles 13 through the connecting pipes. The cooling water in the two condenser tube bundles 13 then merges through the bottom connecting pipe and flows to the outlet pipe 16. Figure 5As shown, the shape of the exhaust gas guide 8 is adapted to the condenser tube bundle 13, and is also a continuous series S-shape, which can extend the passage time of cooling water and exhaust gas in the tank, so that the exhaust gas can fully contact the cooling water and improve the cooling efficiency. When the cooling water flows out of the condenser tube bundle 13, the heat sink 18 is used to dissipate heat from the cooling water, quickly reducing the temperature of the return cooling water, improving the refrigeration efficiency, and extending the service life of the equipment. The heat sink 18 can be a water-cooled radiator (cooling water directly or indirectly contacts the cooling water for heat exchange, with high cooling efficiency and a heat transfer coefficient of 500-1000W / (m²·K), but requires a cooling tower or water tank for heat dissipation). Air-cooled condenser (forced air convection, cooling water exchanges heat with air, no water resources are required, but the heat transfer efficiency is lower, with a heat transfer coefficient of about 50-100W / (m²·K), and a larger heat exchange area is required). Evaporative condenser (combining the advantages of water and air cooling, cooling water evaporates on the condenser surface). (The process involves heat absorption and a fan accelerating airflow, with heat transfer efficiency between water cooling and air cooling.) These heat dissipation methods are all existing technologies well-known to those skilled in the art, and are not shown in detail in the diagram; therefore, they will not be elaborated upon here. A tail gas treatment unit is also connected to the condensate recovery liquid outlet 4 at the bottom of the second tank 2. This tail gas treatment unit is an activated carbon adsorption device, filled with coconut shell activated carbon at a rate of 50-100 kg. This further removes trace amounts of organic matter from the tail gas, ensuring that the exhaust gas meets environmental standards and reducing environmental pollution. The secondary condensation section 7 has already recovered most of the organic matter, and the activated carbon only needs to treat trace residues, extending the activated carbon replacement cycle and reducing operating costs.

[0025] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Specific examples have been used in this document to illustrate the principles and implementation methods of this utility model. The above examples are merely to aid in understanding the method and core ideas of this utility model. The above descriptions are only preferred embodiments of this utility model. It should be pointed out that, due to the limitations of written expression, there are objectively infinite specific structures. For those skilled in the art, several improvements, modifications, or variations can be made without departing from the principles of this utility model, and the above technical features can be combined in an appropriate manner. These improvements, modifications, variations, or combinations, or the direct application of the inventive concept and technical solution to other situations without modification, should all be considered within the scope of protection of this utility model.

Claims

1. A tail gas condensation and recovery tank for p-nitrobenzoic acid production, characterized in that, include: The tank system includes a first tank (1) and a second tank (2) connected in series. The top of the first tank (1) and the second tank (2) are provided with exhaust gas inlets (3) and the bottom is provided with condensate recovery liquid outlets (4). The exhaust gas inlet (3) of the second tank (2) is connected to the condensate recovery liquid outlet (4) of the first tank (1) through a pipe (5) for treating unliquefied gas. The condensation unit includes a primary condensation section (6) and a secondary condensation section (7). The primary condensation section (6) is located inside the first tank (1) and is used to recover high-boiling-point components in the exhaust gas. The secondary condensation section (7) is located inside the second tank (2) and is used to recover low-boiling-point components in the exhaust gas. The exhaust gas guide (8) is installed below the exhaust gas inlet (3) and is in contact with the condensation unit to enable the exhaust gas to come into full contact with the cooling medium in order to achieve rapid cooling of the exhaust gas. The temperature control unit includes a first temperature control module, a second temperature control module, and a controller. The first temperature control module includes a first temperature sensor (9) and a first refrigeration unit installed on the first tank (1). The second temperature control module includes a second temperature sensor (10) and a second refrigeration unit installed on the second tank (2). The controller controls the operating parameters of the first refrigeration unit and the second refrigeration unit according to the monitoring data of the first temperature sensor (9) and the second temperature sensor (10) to adjust the cooling temperature of the first condensing section (6) and the second condensing section (7). The pressure regulating unit includes a primary pressure regulator (11) and a secondary pressure regulator (12). The primary pressure regulator (11) is installed before the exhaust gas inlet (3) of the first tank (1) and is used to monitor and regulate the exhaust gas pressure entering the first tank (1). The secondary pressure regulator (12) is installed before the exhaust gas inlet (3) of the second tank (2) and is used to regulate the exhaust gas pressure entering the second tank (2).

2. The tail gas condensation and recovery tank for p-nitrobenzoic acid production according to claim 1, characterized in that: The primary condensing section (6) and the secondary condensing section (7) are both condensing tube bundles (13) with exhaust gas flow channels inside, and the condensing tube bundles (13) are continuously connected in an S-shape.

3. The tail gas condensation and recovery tank for p-nitrobenzoic acid production according to claim 2, characterized in that: The first tank (1) and the second tank (2) each have two condenser tube bundles (13). The two condenser tube bundles (13) are arranged opposite each other on both sides of the exhaust gas guide (8), and the inlet and outlet of the two condenser tube bundles (13) are connected by two connecting pipes respectively.

4. The tail gas condensation and recovery tank for p-nitrobenzoic acid production according to claim 1, characterized in that: Both the first refrigeration unit and the second refrigeration unit include a cooling water tank (14), an inlet pipe (15) and an outlet pipe (16) for connecting the cooling water tank (14) to the inlet and outlet of the condenser tube bundle (13), a circulation pump (17) for transporting cooling water from the cooling water tank to the condenser tube bundle (13) and returning the cooling water discharged from the condenser tube bundle (13) to the cooling water tank (14), and a heat dissipation component (18) for cooling the cooling water returning from the outlet pipe (16).

5. The tail gas condensation and recovery tank for p-nitrobenzoic acid production according to claim 1, characterized in that: A separator is installed on the pipe (5) at the condensate recovery outlet (4) of the first tank (1). The separator is used to separate the condensate water liquefied by the first-stage condensation section (6) from the unliquefied gas. The separator includes: Branch pipe (21) is connected to the bottom of pipe (5) and is used to separate the condensate liquefied by the first-stage condensation section (6); The guide plate (22) is set at the connection between the branch pipe (21) and the pipeline (5) to assist the gas to bypass the branch pipe (21) and be guided along the pipeline (5) to the tail gas inlet (3) of the secondary condensation section (7). The collection box (23) is connected to the end of the branch pipe (21) and is used to collect the condensate flowing out of the branch pipe (21).

6. The tail gas condensation and recovery tank for p-nitrobenzoic acid production according to claim 1, characterized in that: The tail gas treatment unit is connected to the condensate recovery liquid outlet (4) at the bottom of the second tank (2). The tail gas treatment unit is an activated carbon adsorption device used to treat uncondensed trace organic matter.

7. The tail gas condensation and recovery tank for p-nitrobenzoic acid production according to claim 1, characterized in that: Both the primary pressure regulator (11) and the secondary pressure regulator (12) include a pressure sensor (20) and a compressor (19) with a pressure relief valve, used to monitor and regulate the pressure of the exhaust gas before it enters the tank.

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