A tail gas treatment device and method for polyacrylonitrile production

Abstract

The application discloses a tail gas treatment device and method for polyacrylonitrile production, which comprises a first treatment tower and a second treatment tower, wherein the first treatment tower is connected with the second treatment tower in series; the first treatment tower comprises a first tower body, a first tail gas inlet, a first liquid outlet and a first gas outlet, and a first spraying system; the second treatment tower comprises a second tower body, a second tail gas inlet, a second liquid outlet and a second gas outlet, and a second spraying system; the first tail gas inlet is communicated with a polyacrylonitrile production device and receives waste gas generated from the polyacrylonitrile production device; the first liquid outlet and the second liquid outlet are connected with the polyacrylonitrile production device; and the first gas outlet is communicated with the second tail gas inlet. Through twice washing operations, the monomer adsorption effect is improved, the washing liquid is recycled, the washing water amount is reduced, and the discharge standard is ensured.

Description

Technical Field

[0001] This invention relates to the field of exhaust gas treatment technology, and specifically to an exhaust gas treatment device and method for polyacrylonitrile production. Background Technology

[0002] In addition to acrylonitrile, the exhaust gas generated during the polymerization of polyacrylonitrile contains volatile comonomers. When emitting, the concentrations of acrylonitrile and comonomers in the exhaust gas need to meet environmental protection requirements, so it must be treated to meet the standards before it can be discharged.

[0003] In existing technologies, there are generally two methods for treating the waste gas generated in polyacrylonitrile polymerization production. One method is incineration, where acrylonitrile and comonomers are decomposed at high temperatures before being emitted. This method requires an incinerator, which involves high investment. For general-scale plants, the relatively small amount of waste gas to be treated makes operation very uneconomical. In addition, the monomers are not recovered, increasing monomer consumption. This method is typically used in large-scale integrated plants. The other method is the more commonly used water spray absorption treatment. However, with increasingly stringent environmental emission requirements, the treatment difficulty is also increasing. The production of polyacrylonitrile requires the monomers acrylonitrile and comonomers. Most comonomers are organic compounds. For acrylic fiber products, the comonomer can be the relatively inexpensive vinyl acetate. For the production of polyacrylonitrile-based carbon fiber precursor, there are many comonomers, but some of them have poor water solubility. If water spray washing is used, it is difficult to efficiently absorb the comonomers in the polymerization tail gas. The spray absorption effect is limited, which may ultimately lead to an increase in the amount of washing water and the amount of production wastewater. In severe cases, the concentration of harmful substances in the waste gas emissions may exceed the standards, making it difficult to meet emission standards.

[0004] Therefore, it is necessary to develop a tail gas treatment device and method for polyacrylonitrile production, which utilizes two washing operations to improve monomer adsorption and recycles the washing liquid, thereby reducing the amount of washing water while ensuring compliance with emission standards. Summary of the Invention

[0005] The purpose of this invention is to provide a device and method for treating exhaust gas from polyacrylonitrile production.

[0006] To achieve the aforementioned objectives, the present invention employs the following technical solution: a tail gas treatment device for polyacrylonitrile (PAT) production, connected to a PAT production unit, comprising a first treatment tower and a second treatment tower, wherein the first and second treatment towers are respectively filled with packing material and connected in series; the first treatment tower includes a first tower body and a first tail gas inlet, a first liquid outlet, and a first gas outlet disposed on the first tower body, and a first spray system is provided inside the first tower body; the second treatment tower includes a second tower body and a second tail gas inlet, a second liquid outlet, and a second gas outlet disposed on the second tower body, and a second spray system is provided inside the second tower body; the first tail gas inlet is connected to the PAT production unit and receives waste gas generated from the PAT production unit, the first liquid outlet and the second liquid outlet are both connected to the PAT production unit, and the first gas outlet is connected to the second tail gas inlet.

[0007] Preferably, the first exhaust gas inlet is located below the first spray system, and the first gas outlet is located above the first spray system; the second exhaust gas inlet is located below the second spray system, and the second gas outlet is located above the second spray system.

[0008] Preferably, the first exhaust gas inlet is located in the middle of the first tower body, the first spray system is located in the upper middle part of the first tower body, the first liquid outlet is located at the bottom and / or slightly lower middle part of the first tower body, and the first gas outlet is located at the top of the first tower body; the slightly lower middle part refers to a location at 1 / 15 to 1 / 5 of the height of the first tower body.

[0009] The second exhaust gas inlet is located in the middle of the second tower body, the second spray system is located in the upper middle part of the second tower body, the second liquid outlet is located at the bottom and / or slightly lower middle part of the second tower body, and the second gas outlet is located at the top of the second tower body; the slightly lower middle part refers to the location at 1 / 15 to 1 / 5 of the height of the second tower body.

[0010] Preferably, the waste gas generated from the polyacrylonitrile production unit includes acrylonitrile, comonomer, water vapor, and air.

[0011] Preferably, the detergents used in the first spray system and the second spray system are different; the first spray system uses an organic detergent, and the second spray system uses washing water.

[0012] Preferably, the first spray system includes a first spray device and a first detergent pipe; the second spray system includes a second spray device and a second detergent pipe.

[0013] Preferably, the first detergent pipeline is connected to the polyacrylonitrile production unit and receives acrylonitrile from the polyacrylonitrile production unit. By using acrylonitrile from the polyacrylonitrile production unit as the detergent in the first treatment tower, acrylonitrile has both good organic solubility and high water solubility. Direct spraying with acrylonitrile can dissolve the water-insoluble comonomers and acrylonitrile in the tail gas into the acrylonitrile liquid, thereby greatly reducing the amount of water-insoluble comonomers in the tail gas. The tail gas treated by acrylonitrile scrubbing then passes through the second treatment tower and is washed with washing water. The gaseous saturated acrylonitrile in the tail gas after being treated in the first treatment tower is dissolved in water after scrubbing and absorbed by the water. Finally, the concentrations of acrylonitrile and water-insoluble comonomers in the emitted tail gas reach sufficiently low levels to ensure compliance with emission standards. After adsorption, the gas is returned to the polyacrylonitrile production unit, which reduces the amount of detergent used and does not generate additional impurities that affect the production process.

[0014] Preferably, the first detergent pipe is connected to an organic detergent supply device to receive organic detergent from the organic detergent supply device, wherein the organic detergent is preferably acrylonitrile.

[0015] Preferably, the second detergent pipe is connected to a washing water supply device to receive washing water from the washing water supply device.

[0016] Preferably, an induced draft fan is provided at the second gas outlet, and the induced draft fan discharges the gas treated by the second treatment tower through the second gas outlet.

[0017] Preferably, a first valve and a first level controller are provided at the connection between the first liquid outlet and the polyacrylonitrile production device, and the first level controller is electrically connected to the first valve;

[0018] A second valve and a second liquid level controller are provided at the connection between the second liquid outlet and the polyacrylonitrile production unit. The second liquid level controller is electrically connected to the second valve.

[0019] This application also claims a method for treating tail gas from polyacrylonitrile production, employing the tail gas treatment apparatus for polyacrylonitrile production described above, comprising the following steps:

[0020] S1. The waste gas generated by the polyacrylonitrile production unit enters the first tower body through the first tail gas inlet. At the same time, the first spray system in the first tower body is started to send detergent to the first tower body.

[0021] S2. The first spraying system sprays detergent into the interior of the first tower body. The detergent comes into contact with the exhaust gas and dissolves substances in the exhaust gas that are difficult to dissolve in water.

[0022] S3. The detergent carries the dissolved substances in the waste gas to accumulate in the first tower. After reaching the specified liquid level, it flows back to the polyacrylonitrile production unit through the first liquid outlet. The waste gas flows upward from the first gas outlet into the second tower through the second tail gas inlet. At the same time, the second spray system in the second tower is started to send the detergent into the second tower.

[0023] S4. The second spray system sprays detergent into the interior of the second tower. The detergent comes into contact with the exhaust gas and dissolves water-soluble substances in the exhaust gas.

[0024] S5. The detergent causes the dissolved substances in the waste gas to accumulate in the second tower. After reaching the specified liquid level, the waste gas flows back to the polyacrylonitrile production unit through the second liquid outlet; the waste gas is discharged upwards from the second gas outlet in compliance with standards.

[0025] S6. Repeat steps S1 to S5 above until the production of polyacrylonitrile is completed.

[0026] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0027] 1. This invention improves monomer adsorption by using two washing operations and recycles the washing liquid, reducing the amount of washing water while ensuring that the discharge meets the standards.

[0028] 2. This invention utilizes the characteristics of acrylonitrile, which has both good organic solubility and high water solubility. The exhaust gas is first treated by acrylonitrile scrubbing, so that substances that are difficult to dissolve in water are dissolved in the acrylonitrile medium. Then, the exhaust gas treated by acrylonitrile is scrubbed and absorbed with water, so that the emission concentrations of comonomers and acrylonitrile that are difficult to dissolve in water in the polymerization exhaust gas meet the emission standards.

[0029] 3. The present invention uses acrylonitrile from the polyacrylonitrile production unit as the detergent adsorbed in the first treatment tower and then recycled back to the polyacrylonitrile production unit, which reduces the amount of detergent used and does not generate additional impurities that affect the production process.

[0030] 4. This invention has a simple structure, requires no heating, has high adsorption efficiency, can reduce harmful impurities in exhaust gas, achieve emission standards, and is green, energy-saving and environmentally friendly. Attached Figure Description

[0031] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, some of the drawings in the following description are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. (The meaning is unclear.)

[0032] Figure 1 This is a schematic diagram of the structure of Embodiment 1 of the present invention.

[0033] Among them: 1. First processing tower; 2. Second processing tower; 3. Exhaust fan;

[0034] 11. First tower body; 12. First tail gas inlet; 13. First liquid outlet; 14. First gas outlet; 15. First spray system; 16. First valve; 17. First liquid level controller;

[0035] 21. Second tower body; 22. Second tail gas inlet; 23. Second liquid outlet; 24. Second gas outlet; 25. Second spray system; 26. Second valve; 27. Second liquid level controller. Detailed Implementation

[0036] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0037] Example 1

[0038] A tail gas treatment device for polyacrylonitrile (PAB) production, connected to a PAB production unit, includes a first treatment tower 1 and a second treatment tower 2. The first and second treatment towers are respectively filled with packing material and connected in series. The first treatment tower includes a first tower body 11 and a first tail gas inlet 12, a first liquid outlet 13, and a first gas outlet 14 disposed on the first tower body. A first spray system 15 is provided inside the first tower body. The second treatment tower includes a second tower body 21 and a second tail gas inlet 22, a second liquid outlet 23, and a second gas outlet 24 disposed on the second tower body. A second spray system 25 is provided inside the second tower body. The first tail gas inlet is connected to the PAB production unit and receives waste gas generated from the PAB production unit. The first and second liquid outlets are both connected to the PAB production unit, and the first gas outlet is connected to the second tail gas inlet.

[0039] Preferably, the first exhaust gas inlet is located below the first spray system, and the first gas outlet is located above the first spray system; the second exhaust gas inlet is located below the second spray system, and the second gas outlet is located above the second spray system.

[0040] Preferably, the first exhaust gas inlet is located in the middle of the first tower body, the first spray system is located in the upper middle part of the first tower body, the first liquid outlet is located at the bottom and / or slightly lower middle part of the first tower body, and the first gas outlet is located at the top of the first tower body; the slightly lower middle part refers to a location at 1 / 15 to 1 / 5 of the height of the first tower body.

[0041] The second exhaust gas inlet is located in the middle of the second tower body, the second spray system is located in the upper middle part of the second tower body, the second liquid outlet is located at the bottom and / or slightly lower middle part of the second tower body, and the second gas outlet is located at the top of the second tower body; the slightly lower middle part refers to the location at 1 / 15 to 1 / 5 of the height of the second tower body.

[0042] Preferably, the waste gas generated from the polyacrylonitrile production unit includes acrylonitrile, comonomer, water vapor, and air.

[0043] Preferably, the detergents used in the first spray system and the second spray system are different; the first spray system uses an organic detergent, and the second spray system uses washing water.

[0044] Preferably, the first spray system includes a first spray device and a first detergent pipe; the second spray system includes a second spray device and a second detergent pipe.

[0045] Preferably, the first detergent pipeline is connected to the polyacrylonitrile production unit and receives acrylonitrile from the polyacrylonitrile production unit. By using acrylonitrile from the polyacrylonitrile production unit as the detergent in the first treatment tower, acrylonitrile has both good organic solubility and high water solubility. Direct spraying with acrylonitrile can dissolve the water-insoluble comonomers and acrylonitrile in the tail gas into the acrylonitrile liquid, thereby greatly reducing the amount of water-insoluble comonomers in the tail gas. The tail gas treated by acrylonitrile scrubbing then passes through the second treatment tower and is washed with washing water. The gaseous saturated acrylonitrile in the tail gas after being treated in the first treatment tower is dissolved in water after scrubbing and absorbed by the water. Finally, the concentrations of acrylonitrile and water-insoluble comonomers in the emitted tail gas reach sufficiently low levels to ensure compliance with emission standards. After adsorption, the gas is returned to the polyacrylonitrile production unit, which reduces the amount of detergent used and does not generate additional impurities that affect the production process.

[0046] Preferably, the second detergent pipe is connected to a washing water supply device to receive washing water from the washing water supply device.

[0047] Preferably, an induced draft fan 3 is provided at the second gas outlet, and the induced draft fan discharges the gas treated by the second treatment tower through the second gas outlet.

[0048] Preferably, a first valve 16 and a first level controller 17 are provided at the connection between the first liquid outlet and the polyacrylonitrile production device, and the first level controller is electrically connected to the first valve.

[0049] A second valve 16 and a second liquid level controller 17 are provided at the connection between the second liquid outlet and the polyacrylonitrile production device. The second liquid level controller is electrically connected to the second valve.

[0050] Example 2

[0051] This embodiment is based on the first embodiment described above, and the similarities with the first embodiment will not be repeated.

[0052] In this embodiment, the first detergent pipeline is connected to an organic detergent supply device to receive organic detergent from the organic detergent supply device, wherein the organic detergent is preferably acrylonitrile.

[0053] Example 3

[0054] This embodiment is based on the first embodiment described above, and the similarities with the first embodiment will not be repeated.

[0055] This embodiment relates to a method for treating tail gas from polyacrylonitrile production, employing the tail gas treatment device for polyacrylonitrile production described above, and includes the following steps:

[0056] S1. The waste gas generated by the polyacrylonitrile production unit enters the first tower body through the first tail gas inlet. At the same time, the first spray system in the first tower body is started to send detergent to the first tower body.

[0057] S2. The first spraying system sprays detergent into the interior of the first tower body. The detergent comes into contact with the exhaust gas and dissolves substances in the exhaust gas that are difficult to dissolve in water.

[0058] S3. The detergent carries the dissolved substances in the waste gas to accumulate in the first tower. After reaching the specified liquid level, it flows back to the polyacrylonitrile production unit through the first liquid outlet. The waste gas flows upward from the first gas outlet into the second tower through the second tail gas inlet. At the same time, the second spray system in the second tower is started to send the detergent into the second tower.

[0059] S4. The second spray system sprays detergent into the interior of the second tower. The detergent comes into contact with the exhaust gas and dissolves water-soluble substances in the exhaust gas.

[0060] S5. The detergent causes the dissolved substances in the waste gas to accumulate in the second tower. After reaching the specified liquid level, the waste gas flows back to the polyacrylonitrile production unit through the second liquid outlet; the waste gas is discharged upwards from the second gas outlet in compliance with standards.

[0061] S6. Repeat steps S1 to S5 above until the production of polyacrylonitrile is completed.

[0062] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to the above embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A tail gas treatment device for polyacrylonitrile production, characterized in that: The system is connected to a polyacrylonitrile (PA) production unit and includes a first treatment tower and a second treatment tower. Both towers are internally packed with packing material and connected in series. The first treatment tower includes a first tower body and a first exhaust gas inlet, a first liquid outlet, and a first gas outlet. A first spray system is installed inside the first tower body. The second treatment tower includes a second tower body and a second exhaust gas inlet, a second liquid outlet, and a second gas outlet. A second spray system is installed inside the second tower body. The first exhaust gas inlet is connected to the PA production unit and receives waste gas generated from it. The first liquid outlet and the second liquid outlet are both connected to the PA production unit, and the first gas outlet is connected to the second exhaust gas inlet. The first spray system includes a first spray device and a first detergent pipe; the second spray system includes a second spray device and a second detergent pipe. The first detergent pipeline is connected to the polyacrylonitrile production unit and receives acrylonitrile from the polyacrylonitrile production unit.

2. The tail gas treatment device for polyacrylonitrile production according to claim 1, characterized in that: The waste gas generated from the polyacrylonitrile production unit includes acrylonitrile, comonomer, water vapor, and air.

3. The tail gas treatment device for polyacrylonitrile production according to claim 1, characterized in that: The first spray system and the second spray system use different detergents; the first spray system uses an organic detergent, while the second spray system uses washing water.

4. The tail gas treatment device for polyacrylonitrile production according to claim 1, characterized in that: The second detergent pipe is connected to the washing water supply device and receives washing water from the washing water supply device.

5. The tail gas treatment device for polyacrylonitrile production according to claim 1, characterized in that, An induced draft fan is provided at the second gas outlet, and the induced draft fan discharges the gas treated by the second treatment tower through the second gas outlet.

6. The tail gas treatment device for polyacrylonitrile production according to claim 1, characterized in that: A first valve and a first level controller are provided at the connection between the first liquid outlet and the polyacrylonitrile production device, and the first level controller is electrically connected to the first valve; A second valve and a second liquid level controller are provided at the connection between the second liquid outlet and the polyacrylonitrile production unit. The second liquid level controller is electrically connected to the second valve.

7. A method for treating tail gas from polyacrylonitrile production, characterized in that, The tail gas treatment device for polyacrylonitrile production according to any one of claims 1-6 includes the following steps: S1. The waste gas generated by the polyacrylonitrile production unit enters the first tower body through the first tail gas inlet. At the same time, the first spray system in the first tower body is started to send detergent to the first tower body. S2. The first spraying system sprays detergent into the interior of the first tower body. The detergent comes into contact with the exhaust gas and dissolves substances in the exhaust gas that are difficult to dissolve in water. S3. The detergent carries the dissolved substances in the waste gas to accumulate in the first tower. After reaching the specified liquid level, it flows back to the polyacrylonitrile production unit through the first liquid outlet. The waste gas flows upward from the first gas outlet into the second tower through the second tail gas inlet. At the same time, the second spray system in the second tower is started to send the detergent into the second tower. S4. The second spray system sprays detergent into the interior of the second tower. The detergent comes into contact with the exhaust gas and dissolves water-soluble substances in the exhaust gas. S5. The detergent causes the dissolved substances in the waste gas to accumulate in the second tower. After reaching the specified liquid level, the waste gas flows back to the polyacrylonitrile production unit through the second liquid outlet; the waste gas is discharged upwards from the second gas outlet in compliance with standards. S6. Repeat steps S1 to S5 above until the production of polyacrylonitrile is completed.

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