A water ring pump system for a nitro toluene stripping process

Abstract

The present invention provides a water ring pump system for a mixed nitro toluene stripping process, which includes a water ring pump, a gas-liquid separator, a multi-stage sedimentation separation system, and a heat exchanger that are connected in sequence for circulation; the vacuum extraction pipe of the water ring pump is connected to a stripping column for vacuum extraction of the stripping column; an insulating jacket is provided outside the multi-stage sedimentation separation system; a water supply pipe is connected to the inlet of the heat exchanger; the drainage port of the multi-stage sedimentation separation system is connected to the inlet of the heat exchanger, and the discharge port of the multi-stage sedimentation separation system is connected to a recovery tank through a recovery pipe. By providing an insulating jacket outside the multi-stage sedimentation separation system, when sedimentation separation of the mixed nitro toluene is carried out, para-nitrotoluene entrained in the solution can be prevented from solidifying into crystal powder due to temperature reduction, thus causing pipeline blockage, improving the stability and reliability of the water ring pump operation. At the same time, para-nitrotoluene entrained in the stripping column is recovered, avoiding waste of resources.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical machinery, and particularly relates to a water ring pump system for a mixed nitro toluene stripping process. Background Art

[0002] Mononitrotoluene is widely used as an intermediate for pharmaceuticals, pesticides, dyes, and fragrances. Industrially, it is obtained by nitrating toluene with a mixed acid of nitric acid and sulfuric acid. This process is prone to over-nitration to produce dinitrotoluene. To purify mononitrotoluene, a distillation column is used industrially. To ensure production safety, generally, the dinitrotoluene in the mixed nitro toluene is purified to less than 30%, and further purification uses a stripping process to recover the mononitrotoluene in the dinitrotoluene.

[0003] Currently, the mixed nitro toluene stripping process mainly uses stripping under a vacuum environment, and generally uses a water ring pump to evacuate the stripping column. Since the vacuum environment of the stripping column contains p-nitrotoluene, it is easy to solidify and block the pipeline after the temperature drops, resulting in the inability to recycle the working water of the water ring pump. The p-nitrotoluene is treated as waste, increasing the cost of treating the three wastes; the current water ring pump system has not solved the problem of recovering the p-nitrotoluene in it. Summary of the Invention

[0004] The present invention provides a water ring pump system for a mixed nitro toluene stripping process, which solves the problem that when the stripping column is evacuated by a water ring pump in the prior art, the p-nitrotoluene is easy to solidify and block the pipeline after the temperature drops, resulting in the inability to recycle the working water of the water ring pump.

[0005] The technical solution of the present invention is realized as follows:

[0006] A water ring pump system for a mixed nitro toluene stripping process includes a water ring pump, a gas-liquid separator, a multi-stage sedimentation separation system, and a heat exchanger that are connected in sequence and in a cycle; the evacuation pipe of the water ring pump is connected to the stripping column for evacuating the stripping column; an insulating jacket is provided outside the multi-stage sedimentation separation system; a water supply pipe is connected to the inlet of the heat exchanger; the drain port of the multi-stage sedimentation separation system is connected to the inlet of the heat exchanger, and the discharge port of the multi-stage sedimentation separation system is connected to a recovery tank through a recovery pipe.

[0007] By providing an insulating jacket outside the multi-stage sedimentation separation system, when sedimentation separation is performed on the mixed nitro toluene, it is possible to prevent the p-nitrotoluene entrained in the solution from solidifying into crystal powder due to temperature drop and causing pipeline blockage, improving the stability and reliability of the water ring pump operation. At the same time, the p-nitrotoluene entrained in the stripping column is recovered, avoiding waste of resources.

[0008] As a preferred embodiment of the present invention, the multi-stage sedimentation separation system includes a first-stage sedimentation separator, a second-stage sedimentation separator, and a third-stage sedimentation separator that are connected in sequence. The first-stage sedimentation separator includes a first sedimentation tank. The second-stage sedimentation separator and the third-stage sedimentation separator share a second sedimentation tank. A vertical first partition board is provided on the inner bottom surface of the second sedimentation tank. There is a gap between the top of the first partition board and the top surface of the second sedimentation tank. The first partition board divides the second sedimentation tank into a second-stage sedimentation separator and a third-stage sedimentation separator. The overflow port of the first-stage sedimentation separator is connected to the second-stage sedimentation separator. By designing three sequentially connected sedimentation separators, most of the p-nitrotoluene in the mixed nitrotoluene can be separated and recovered, improving the recovery rate of p-nitrotoluene and avoiding waste.

[0009] As a preferred embodiment of the present invention, a heat-insulating jacket is provided outside the first-stage sedimentation separator, and the heat-insulating range of the heat-insulating jacket is 52-55°C. By providing a heat-insulating jacket outside the first-stage sedimentation separator, the temperature of the solution inside it can be controlled within the range of 52-55°C, preventing the p-nitrotoluene in it from condensing into crystal powder due to too low temperature and avoiding pipeline blockage.

[0010] As a preferred embodiment of the present invention, a vertical baffle is provided in the middle of the top surface of the first sedimentation tank, and the height of the baffle is less than the depth of the first sedimentation tank. By providing the baffle, the solution entering the first-stage sedimentation separator can be guided, extending its flow path, enabling the solution to be fully heated, further preventing the solution in the upper layer of the first-stage sedimentation separator from not being heated to cause crystallization of p-nitrotoluene in it; at the same time, it can also avoid the solution flowing into the first-stage sedimentation separator directly flowing into the second-stage sedimentation separator from the upper layer through the overflow port without effective sedimentation separation.

[0011] As a preferred embodiment of the present invention, a weir plate is provided at the position of the overflow port of the first-stage sedimentation separator, and there is a gap between the top surface of the weir plate and the top surface of the first-stage sedimentation separator. By providing a weir plate at the overflow port of the first-stage sedimentation separator, the amount of p-nitrotoluene solution flowing into the second-stage sedimentation separator from the overflow port can be further reduced, improving the separation effect of the first-stage sedimentation separator.

[0012] As a preferred embodiment of the present invention, the recovery pipe includes a recovery main pipe and a first recovery pipe, a second recovery pipe, and a third recovery pipe that are respectively connected to the recovery main pipe. The end of the first recovery pipe far from the recovery main pipe is connected to the discharge port of the first-stage sedimentation separator. The end of the second recovery pipe far from the recovery main pipe is connected to the discharge port of the second-stage sedimentation separator. The end of the third recovery pipe far from the recovery main pipe is connected to the discharge port of the third-stage sedimentation separator. The p-nitrotoluene solutions obtained through sedimentation separation in the three sedimentation separators are respectively collected into the recovery main pipe through the three recovery pipes and finally flow into the recovery tank.

[0013] As a preferred embodiment of the present invention, a vertical second partition board is provided on the bottom surface of the three-stage sedimentation separator. There is a gap between the top of the second partition board and the top surface of the second sedimentation tank. The second partition board divides a buffer tank in the three-stage sedimentation separator. The water adding pipe is communicated with the buffer tank, and the overflow port of the buffer tank is the drain port of the multi-stage sedimentation separation system. A float valve is provided in the buffer tank. The float valve is communicated with the water adding pipe. The liquid level height in the buffer tank is higher than the height of the overflow port and lower than the height of the second partition board. A buffer tank is separated in the three-stage sedimentation separator by the second partition board for buffering industrial water. A float valve is arranged in the buffer tank. When the liquid level height in the buffer tank is lower than the preset value, the float valve opens, and the buffer tank is filled with water through the water adding pipe to ensure the normal operation of the water ring pump. When the liquid level height in the buffer tank is higher than the preset value, the float valve closes to prevent the industrial water from flowing back into the three-stage sedimentation separator.

[0014] Advantages

[0015] Compared with the prior art, the advantages of the present invention are as follows:

[0016] (1) By arranging a heat preservation jacket outside the multi-stage sedimentation separation system, when separating the mixed nitro toluene, it can prevent the p-nitrotoluene entrained in the solution from solidifying into crystal powder due to temperature reduction, causing pipeline blockage, improving the stability and reliability of the water ring pump operation. At the same time, the p-nitrotoluene entrained in the stripping column is recovered, avoiding waste of resources.

[0017] (2) By arranging a baffle at the top of the first-stage sedimentation separator, the solution entering the first-stage sedimentation separator can be guided, extending its flow path, enabling the solution to be fully heated, further preventing the solution in the upper layer of the first-stage sedimentation separator from not being heated to cause crystallization of p-nitrotoluene. At the same time, it can also prevent the solution flowing into the first-stage sedimentation separator from directly flowing into the second-stage sedimentation separator through the upper layer via the overflow port without effective sedimentation separation.

[0018] (3) A buffer tank is separated in the three-stage sedimentation separator by the second partition board for buffering industrial water. A float valve is arranged in the buffer tank. When the liquid level height in the buffer tank is lower than the preset value, the float valve opens, and the buffer tank is filled with water through the water adding pipe to ensure the normal operation of the water ring pump. When the liquid level height in the buffer tank is higher than the preset value, the float valve closes to prevent the industrial water from flowing back into the three-stage sedimentation separator. Description of the Drawings

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0020] Figure 1 This is the schematic diagram of a water ring pump system for a mixed nitro toluene stripping process of the present invention;

[0021] In the figure: 1. Water ring pump; 2. Gas-liquid separator; 3. Heat exchanger; 4. Thermal insulation jacket; 5. Water supply pipe; 6. Recovery pipe; 7. Primary sedimentation separator; 8. Secondary sedimentation separator; 9. Tertiary sedimentation separator; 10. First partition; 11. Baffle; 12. Weir plate; 13. Second partition; 14. Buffer tank; 15. Float valve; 16. Vacuum extraction pipe. Detailed implementation manners

[0022] The following will clearly and completely describe the technical solutions of the present invention in combination with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0023] Referring to Figure 1 As shown, this embodiment provides a water ring pump system for a mixed nitro toluene stripping process, including a water ring pump 1, a gas-liquid separator 2, a multi-stage sedimentation separation system, and a heat exchanger 3 that are sequentially connected in a cycle; the vacuum extraction pipe 16 of the water ring pump 1 is connected to the stripping tower for evacuating the stripping tower; a thermal insulation jacket 4 is provided outside the multi-stage sedimentation separation system; a water supply pipe 5 is connected to the inlet of the heat exchanger 3; the drainage port of the multi-stage sedimentation separation system is connected to the inlet of the heat exchanger 3, and the discharge port of the multi-stage sedimentation separation system is connected to a recovery tank through a recovery pipe 6.

[0024] In this embodiment, the heat exchanger 3 is a plate heat exchanger. By circulating a low-temperature medium in the heat exchanger 3, the industrial water about to enter the water ring pump 1 is cooled to prevent the high-temperature industrial water from damaging the water ring pump 1.

[0025] As a preferred solution of this embodiment, the multi-stage sedimentation separation system includes a first-stage sedimentation separator 7, a second-stage sedimentation separator 8, and a third-stage sedimentation separator 9 that are connected in sequence. The first-stage sedimentation separator 7 includes a first sedimentation tank. The second-stage sedimentation separator 8 and the third-stage sedimentation separator 9 share a second sedimentation tank. A vertical first partition 10 is provided on the inner bottom surface of the second sedimentation tank. There is a gap between the top of the first partition 10 and the top surface of the second sedimentation tank. The first partition 10 divides the second sedimentation tank into the second-stage sedimentation separator 8 and the third-stage sedimentation separator 9. The overflow port of the first-stage sedimentation separator 7 is connected to the second-stage sedimentation separator 8. By designing three sedimentation separators connected in sequence, most of the p-nitrotoluene in the mixed nitrotoluene can be separated and recovered, improving the recovery rate of p-nitrotoluene and avoiding waste.

[0026] As a preferred solution of this embodiment, a heat-insulating jacket 4 is provided outside the first-stage sedimentation separator 7. The heat-insulating range of the heat-insulating jacket 4 is 52 to 55 °C. By providing the heat-insulating jacket 4 outside the first-stage sedimentation separator 7, the temperature of the solution inside it can be controlled within the range of 52 to 55 °C, preventing the p-nitrotoluene therein from condensing into crystal powder due to too low temperature and avoiding pipeline blockage.

[0027] As a preferred solution of this embodiment, a vertical baffle 11 is provided in the middle of the top surface of the first sedimentation tank. The height of the baffle 11 is less than the depth of the first sedimentation tank. By providing the baffle 11, the solution entering the first-stage sedimentation separator 7 can be guided, extending its flow path, enabling the solution to be fully heated, further preventing the solution in the upper layer of the first-stage sedimentation separator 7 from not being heated to cause crystallization of p-nitrotoluene therein; at the same time, it can also avoid the solution flowing into the first-stage sedimentation separator 7 directly flowing into the second-stage sedimentation separator 8 from the upper layer through the overflow port without effective sedimentation separation.

[0028] As a preferred solution of this embodiment, a weir plate 12 is provided at the position of the overflow port of the first-stage sedimentation separator 7. There is a gap between the top surface of the weir plate 12 and the top surface of the first-stage sedimentation separator 7. By providing the weir plate 12 at the overflow port of the first-stage sedimentation separator 7, the amount of p-nitrotoluene solution flowing into the second-stage sedimentation separator 8 from the overflow port can be further reduced, improving the separation effect of the first-stage sedimentation separator 7.

[0029] As a preferred solution of this embodiment, the recovery pipe 6 includes a main recovery pipe, a first recovery pipe, a second recovery pipe, and a third recovery pipe that are respectively connected to the main recovery pipe. One end of the first recovery pipe away from the main recovery pipe is connected to the discharge port of the primary settling separator 7, one end of the second recovery pipe away from the main recovery pipe is connected to the discharge port of the secondary settling separator 8, and one end of the third recovery pipe away from the main recovery pipe is connected to the discharge port of the tertiary settling separator 9; the p-nitrotoluene solutions obtained by sedimentation separation in the three settling separators are respectively collected into the main recovery pipe through the three recovery pipes 6 and finally flow into the recovery tank.

[0030] As a preferred solution of this embodiment, a vertical second partition plate 13 is provided on the bottom surface of the tertiary settling separator 9. There is a gap between the top of the second partition plate 13 and the top surface of the second settling tank. The second partition plate 13 divides a buffer tank 14 in the tertiary settling separator 9. The water addition pipe 5 is connected to the buffer tank 14, and the overflow port of the buffer tank 14 is the drainage port of the multi-stage sedimentation separation system; a float valve 15 is provided in the buffer tank 14, and the float valve 15 is connected to the water addition pipe 5. The liquid level height in the buffer tank 14 is higher than the height of the overflow port and lower than the height of the second partition plate 13; a buffer tank 14 is separated in the tertiary settling separator 9 by the second partition plate 13 for caching industrial water, and a float valve 15 is provided in the buffer tank 14. When the liquid level height in the buffer tank 14 is lower than the preset value, the float valve 15 opens, and the buffer tank 14 is filled with water through the water addition pipe 5 to ensure the normal operation of the water ring pump 1; when the liquid level height in the buffer tank 14 is higher than the preset value, the float valve 15 closes to prevent industrial water from flowing back into the tertiary settling separator 9.

[0031] In this embodiment, the air extraction rate of the water ring pump 1 is 60 L / s, and the working water consumption is 1 m3 / h;

[0032] The specifications of the gas-liquid separator 2 are Φ300×500 mm, and an exhaust port with a diameter of Φ57 mm is provided at the top. The height from the bottom of the gas-liquid separator 2 to the outlet of the water ring pump 1 is 500 mm;

[0033] The specifications of the primary settling separator 7 are 1000×500×1000 mm;

[0034] The float valve 15 controls the liquid level height in the buffer tank 14 to be 50-100 mm higher than the highest point of the outlet of the water ring pump 1.

[0035] In this embodiment, the working process of the water ring pump system is as follows:

[0036] Before starting the water ring pump 1, open the inlet valve on the water filling pipe 5. The float valve 15 will automatically open to replenish water to the buffer tank 14. When the liquid level in the buffer tank 14 is higher than the preset value, the float valve 15 will automatically close. Then open the inlet valve of the water ring pump 1, start the water ring pump 1 after filling a certain amount of liquid, open the outlet valve of the water ring pump 1 and the air extraction valve on the vacuum extraction pipe 16, and start to evacuate the stripping column. At the same time, the p-nitrotoluene entrained in the air in the stripping column is pumped into the water ring pump 1. The p-nitrotoluene dissolves in the working water of the water ring pump 1 and enters the gas-liquid separator 2. The non-condensable gas therein is discharged from the exhaust port of the gas-liquid separator 2. The mixed solution of p-nitrotoluene and working water is successively subjected to sedimentation separation in the first-stage sedimentation separator 7, the second-stage sedimentation separator 8, and the third-stage sedimentation separator 9. The working water located in the upper layer of the sedimentation separator overflows to the buffer tank 14 above the second partition 13 and flows out of the buffer tank 14 to the heat exchanger 3 for cooling. The low-temperature (or normal-temperature) working water flowing out of the outlet of the heat exchanger 3 flows back into the water ring pump 1, forming a cycle process. The p-nitrotoluene solution obtained through three-stage sedimentation separation is recovered by three recovery pipes 6, then converges to the main recovery pipe and flows into the recovery tank. Through continuous cycle process, the stripping column can be evacuated, and at the same time, the p-nitrotoluene entrained in the air in the stripping column can be recovered and utilized.

[0037] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A water ring pump system for a nitro toluene stripping process, comprising a water ring pump (1), a gas-liquid separator (2), a multi-stage sedimentation and separation system, and a heat exchanger (3) that are connected in sequence and in a cycle; characterized in that, The vacuum extraction pipe (16) of the water ring pump (1) is connected to the stripping column for vacuum extraction of the stripping column; a heat preservation jacket (4) is provided outside the multi-stage sedimentation and separation system; a water adding pipe (5) is connected to the inlet of the heat exchanger (3); the drain outlet of the multi-stage sedimentation and separation system is connected to the inlet of the heat exchanger (3), and the discharge outlet of the multi-stage sedimentation and separation system is connected to a recovery tank through a recovery pipe (6).

2. The water ring pump system for the stripping process of mixed nitro toluene as described in claim 1, characterized in that, The multi-stage sedimentation and separation system includes a primary sedimentation separator (7), a secondary sedimentation separator (8), and a tertiary sedimentation separator (9) that are connected in sequence. The primary sedimentation separator (7) includes a first sedimentation tank. The secondary sedimentation separator (8) and the tertiary sedimentation separator (9) share a second sedimentation tank. A vertical first partition board (10) is provided on the inner bottom surface of the second sedimentation tank. There is a gap between the top of the first partition board (10) and the top surface of the second sedimentation tank. The first partition board (10) divides the second sedimentation tank into the secondary sedimentation separator (8) and the tertiary sedimentation separator (9); the overflow port of the primary sedimentation separator (7) is connected to the secondary sedimentation separator (8).

3. The water ring pump system for a mixed nitro toluene stripping process according to claim 2, characterized in that, A heat preservation jacket (4) is provided outside the primary sedimentation separator (7).

4. The water ring pump system for a mixed nitro toluene stripping process according to claim 3, characterized in that, The heat preservation range of the heat preservation jacket (4) is 52 - 55 °C.

5. The water ring pump system for a mixed nitro toluene stripping process according to claim 2, wherein, A vertical baffle (11) is provided in the middle of the top surface of the first sedimentation tank, and the height of the baffle (11) is less than the depth of the first sedimentation tank.

6. The water ring pump system for a mixed nitro toluene stripping process according to claim 2, wherein A weir plate (12) is provided at the position of the overflow port of the primary sedimentation separator (7), and there is a gap between the top surface of the weir plate (12) and the top surface of the primary sedimentation separator (7).

7. The water ring pump system for a mixed nitro toluene stripping process according to claim 2, characterized in that, The recovery pipe (6) includes a recovery main pipe and a first recovery pipe, a second recovery pipe, and a third recovery pipe that are respectively connected to the recovery main pipe. The end of the first recovery pipe far from the recovery main pipe is connected to the discharge outlet of the primary sedimentation separator (7), the end of the second recovery pipe far from the recovery main pipe is connected to the discharge outlet of the secondary sedimentation separator (8), and the end of the third recovery pipe far from the recovery main pipe is connected to the discharge outlet of the tertiary sedimentation separator (9).

8. A water ring pump system for a mixed nitro toluene stripping process according to claim 2, characterized in that, A vertical second partition board (13) is provided on the bottom surface of the tertiary sedimentation separator (9). There is a gap between the top of the second partition board (13) and the top surface of the second sedimentation tank. The second partition board (13) divides a buffer tank (14) in the tertiary sedimentation separator (9). The water adding pipe (5) is connected to the buffer tank (14), and the overflow port of the buffer tank (14) is the drain outlet of the multi-stage sedimentation and separation system; a float valve (15) is provided in the buffer tank (14), and the liquid level height in the buffer tank (14) is higher than the height of the overflow port and lower than the height of the second partition board (13).

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