A chloroacetic acid tail gas recycling system and aminoacetic acid production line

Abstract

The present application relates to a chloroacetic acid tail gas recycling system and an aminoacetic acid production line. The recycling system includes a waste gas temporary storage tower having an input end connected to a reactor and an output end connected to a mother liquor tank, a mixer disposed within the waste gas temporary storage tower for driving gas flow within the waste gas temporary storage tower, a detection pipeline disposed on the waste gas temporary storage tower and forming a loop with the space within the waste gas temporary storage tower, a circulating pump and two electrically controlled valves disposed on the detection pipeline, a sprinkler disposed within the detection pipeline, a pH value detection sensor having a detection end extending into the detection pipeline, and a drain valve disposed on the detection pipeline. The aminoacetic acid production line includes the above-mentioned chloroacetic acid tail gas recycling system. The chloroacetic acid tail gas recycling system and the aminoacetic acid production line disclosed in the present application utilize secondary utilization of acidic tail gas to neutralize the aminoacetic acid mother liquor, thereby not only saving steam but also reducing the amount of waste liquid, thereby achieving the goals of saving raw material costs and energy conservation and emission reduction.

Description

Technical Field

[0001] The present application relates to the field of chemical production technology, and in particular to a chloroacetic acid tail gas recycling system and an aminoacetic acid production line. Background Art

[0002] During the chloroacetic acid production process, sulfur is used as a catalyst. Due to side reactions, the tail gas produced from liquid chlorine and acetic acid contains not only hydrogen chloride but also sulfur dioxide, sulfur trioxide, and unreacted acetic acid and chlorine. Acetic acid is first recovered in a three-stage acetic acid absorber, followed by a three-stage hydrochloric acid absorber to recover hydrochloric acid. After absorption in the absorber, the tail gas still contains a small amount of acidic gases, primarily hydrogen chloride, which must be absorbed with NaOH before discharge. The waste liquid generated during this treatment process cannot be reused and must be disposed of as waste.

[0003] Using hydrochloric acid to neutralize the mother liquor after the crystallization of aminoacetic acid will increase the overall volume of the mother liquor, thereby increasing the use of steam in the methanol distillation recovery and ammonium chloride concentration and crystallization process, and finally increasing the amount of waste liquid after the crystallization of ammonium chloride. Summary of the Invention

[0004] The present application provides a chloroacetic acid tail gas recycling system and an aminoacetic acid production line, which adopts secondary utilization of acidic tail gas to neutralize aminoacetic acid mother liquor, thereby not only saving steam but also reducing the amount of waste liquid, thereby achieving the purpose of saving raw material costs and energy conservation and emission reduction.

[0005] The above-mentioned purpose of this application is achieved through the following technical solutions:

[0006] In a first aspect, the present application provides a chloroacetic acid tail gas recycling system, comprising:

[0007] The exhaust gas temporary storage tower has its input end connected to the reactor and its output end connected to the mother liquor tank;

[0008] A mixer is provided in the exhaust gas temporary storage tower and is used to drive the gas flow in the exhaust gas temporary storage tower;

[0009] The detection pipeline is installed on the exhaust gas temporary storage tower and forms a loop with the space inside the exhaust gas temporary storage tower;

[0010] The first circulation pump and two electrically controlled valves are all arranged on the detection pipeline;

[0011] Sprinkler, installed in the detection pipeline;

[0012] A pH value detection sensor, the detection end of which extends into the detection pipe; and

[0013] The sewage valve is installed on the detection pipeline.

[0014] In a possible implementation of the first aspect, the mixer includes:

[0015] A rotating shaft, rotatably connected to the exhaust gas temporary storage tower;

[0016] A driving motor is provided on the exhaust gas temporary storage tower and connected to the rotating shaft; and

[0017] The fan blades are arranged on the rotating shaft and located in the exhaust gas temporary storage tower.

[0018] In a possible implementation of the first aspect, a feed pump is provided at the output end of the exhaust gas temporary storage tower.

[0019] In a possible implementation of the first aspect, the method further includes:

[0020] a purge pipe, a first end of which extends into the detection pipe; and

[0021] A purge gas source is connected to the second end of the purge pipeline.

[0022] In a possible implementation of the first aspect, the purge air source includes a cold air source and a hot air source.

[0023] In a possible implementation of the first aspect, the first end of the purge pipe extends into the detection pipe and then extends toward the drain valve.

[0024] In a possible implementation manner of the first aspect, the method further includes a circulation pipe connected to the detection pipe and the sprinkler, and a second circulation pump provided on the circulation pipe.

[0025] In a second aspect, the present application provides a glycine production line, comprising the chloroacetic acid tail gas recycling system as described in the first aspect and any implementation of the first aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a schematic diagram of the principle of a chloroacetic acid tail gas recycling system provided in this application.

[0027] Figure 2 This is a schematic diagram of the principle of the internal structure of a detection pipeline provided by this application.

[0028] Figure 3 This is a schematic diagram of the circulation of exhaust gas in an exhaust gas temporary storage tower and a detection pipeline provided by the present application.

[0029] In the figure, 1. waste gas temporary storage tower, 2. mixer, 3. detection pipeline, 4. first circulation pump, 5. electric control valve, 6. sprinkler, 7. pH value detection sensor, 8. drain valve, 11. feed pump, 21. rotating shaft, 22. drive motor, 23. fan blade, 31. purge pipeline, 32. purge air source, 33. circulation pipeline, 34. second circulation pump, 321. cold air source, 322. hot air source. DETAILED DESCRIPTION

[0030] The technical solution in this application is further described in detail below with reference to the accompanying drawings.

[0031] See also Figure 1 and Figure 2 , which is a chloroacetic acid tail gas recycling system disclosed in this application. The recycling system consists of a waste gas temporary storage tower 1, a mixer 2, a detection pipeline 3, a first circulation pump 4, an electric control valve 5, a sprayer 6, a pH value detection sensor 7 and a drain valve 8. The input end of the waste gas temporary storage tower 1 is connected to the reactor, and the output end is connected to the mother liquor tank. The function of the waste gas temporary storage tower 1 is to collect the tail gas generated during the preparation process of chloroacetic acid.

[0032] It should be understood that in the production process of chloroacetic acid, sulfur is used as a catalyst. Due to the existence of side reactions in the process of producing chloroacetic acid from liquid chlorine and acetic acid, the tail gas produced by the reaction includes sulfur dioxide, sulfur trioxide, and unreacted acetic acid and chlorine in addition to hydrogen chloride.

[0033] The current treatment method is to first use an acetic acid three-stage absorption tower to recover acetic acid, and then use a hydrochloric acid three-stage absorption tower to recover hydrochloric acid. After absorption in the absorption tower, the tail gas will still contain a small amount of acidic gas, mainly hydrogen chloride, which needs to be absorbed by NaOH solution before it can be discharged.

[0034] Hydrogen chloride, sulfur dioxide, sulfur trioxide, acetic acid and chlorine will produce acid when dissolved in water. That is to say, the tail gas produced during the production of chloroacetic acid can react with the alkaline mother liquor, turning the alkaline mother liquor into a neutral mother liquor.

[0035] The mixer 2 is installed in the waste gas storage tower 1 and is used to drive the gas flow in the waste gas storage tower 1. The purpose is to make the gas in the waste gas storage tower 1 more evenly distributed in the waste gas storage tower 1, so that the pH value measured during the sampling process can more accurately reflect the amount of acidic gas in the waste gas storage tower 1.

[0036] See also Figure 3The detection pipeline 3 is installed on the exhaust gas temporary storage tower 1 and forms a loop with the space inside the exhaust gas temporary storage tower 1. A first circulation pump 4 and two electric control valves 5 are also installed on the detection pipeline 3. The function of the first circulation pump 4 is to drive the gas in the detection pipeline 3 to circulate. The purpose is also to make the pH value measured during the sampling process more accurately reflect the amount of acidic gas in the exhaust gas temporary storage tower 1.

[0037] A one-way valve is installed between the electrically controlled valve 5 (located at the bottom) and the waste gas temporary storage tower 1. This valve opens during gas circulation and closes after the circulation is complete. When the drain valve 8 is open, the valve remains closed because water flowing solely under gravity cannot activate it.

[0038] The function of the electric control valve 5 is to create a closed space in the detection pipe 3. The function of the closed space is to detect the pH value of the gas in the closed space, and the amount of acidic gas in the exhaust gas temporary storage tower 1 can be understood through the pH value.

[0039] A sprayer 6 is installed within the test pipe 3 and sprays clean water into the test pipe 3, using the acidic gas to dissolve in the clean water to form a test liquid sample. The detection end of a pH sensor 7 extends into the test pipe 3 to detect the pH value of the test liquid sample. A drain valve 8 is installed on the test pipe 3 to drain the test liquid sample after the pH test is completed. Once the test pipe 3 is empty, the next pH test can be performed.

[0040] Overall, the chloroacetic acid tail gas recycling system provided herein uses dynamic pH detection to detect the pH value of the tail gas generated during the chloroacetic acid production process. During the test preparation phase, the tail gas stored in the waste gas temporary storage tower 1 is first driven into a flowing state. The purpose of the flow is to ensure that the tail gas stored in the waste gas temporary storage tower 1 is evenly mixed. During this process, the first circulation pump 4 on the detection pipeline 3 is simultaneously activated, driving the tail gas in the detection pipeline 3 into a flowing state.

[0041] After a period of time, the two electric control valves 5 of the detection pipe 3 are closed, and a portion of the uniform exhaust gas of the mixer remains in the detection pipe 3. Then the sprayer 6 is started to spray a certain amount of clean water into the detection pipe 3. The purpose of spraying clean water is to dissolve the exhaust gas in the detection pipe 3 in the clean water.

[0042] After spraying the clean water and waiting for a while, pH sensor 7 acquires the pH value of the solution in detection pipe 3. Finally, drain valve 8 opens to drain the solution in detection pipe 3. This completes the detection process. Based on the pH value, an appropriate amount of tail gas is then injected into the mother liquor tank. This tail gas injection method uses an aeration tube, which can generate a large number of tiny bubbles.

[0043] The advantage of the detection method provided in the present application is that the mixer 2 is used to mix the waste gas temporarily stored in the waste gas storage tower 1, and the first circulation pump 4 is used to mix the waste gas temporarily stored in the detection pipe 3. The combination of these two mixing methods can make the waste gas in the detection pipe 3 consistent with the waste gas in the waste gas storage tower 1.

[0044] In addition, this application uses water dissolution to test the acid gas content in the waste gas, which can simulate the dissolution of the waste gas in the mother liquor. As mentioned above, the waste gas is fed into the mother liquor tank by aeration, which means that the contact time between the waste gas and the mother liquor is fixed, and the waste gas cannot be 100% absorbed by the mother liquor.

[0045] The estimation of this absorption rate can be determined by time. The rising time of the bubbles formed by the exhaust gas in the mother liquor is T1, and the injection time of the sprinkler 6 is T2. The relationship between T1 and T2 is T2=K*T1, where K represents the conversion coefficient. In general calculation process, K=1.

[0046] By measuring the pH of the solution sprayed by sprayer 6, the acid gas content in the waste gas (fixed volume) within detection pipeline 3 can be estimated, and thus the acid gas content in the waste gas (fixed volume) within waste gas temporary storage tower 1 can be estimated. The amount of waste gas introduced is then calculated based on the pH value of the mother liquor in the mother liquor tank.

[0047] The advantage of this estimation method is that it simulates the generation of acid gases from waste gas in the mother liquor through spraying, making the calculation process closer to the actual acid gas dissolution process and providing more accurate results. The spraying process also solves the problem of undetectable pH values ​​of acid gases.

[0048] See also Figure 1 and Figure 3 As a specific embodiment of the chloroacetic acid tail gas recycling system provided in the application, the mixer 2 is composed of a rotating shaft 21, a drive motor 22 and a fan blade 23. The rotating shaft 21 is rotatably connected to the waste gas temporary storage tower 1, the drive motor 22 is installed on the waste gas temporary storage tower 1 and connected to the rotating shaft 21, and the fan blade 23 is fixed on the rotating shaft 21 and is located inside the waste gas temporary storage tower 1.

[0049] When the drive motor 22 is started, it can drive the fan blades 23 to rotate through the rotating shaft 21. When the fan blades 23 rotate, they can drive the exhaust gas in the exhaust gas temporary storage tower 1 to circulate, so that the exhaust gas in the exhaust gas temporary storage tower 1 can be mixed more evenly.

[0050] Because the production process of chloroacetic acid adopts an intermittent feeding method, the production process is discontinuous and the amount of waste gas in the mother liquor tank is not fixed each time. This results in the waste gas in the waste gas temporary storage tower 1 being generated in multiple batches. When measuring the pH value of the acidic gas contained therein, it needs to be mixed first and then measured.

[0051] See also Figure 1 and Figure 3 As a specific embodiment of the chloroacetic acid tail gas recycling system provided in the application, a feed pump 11 is provided on the output end of the waste gas temporary storage tower 1. The function of the feed pump 11 is to transport the waste gas in the waste gas temporary storage tower 1 to the mother liquor tank.

[0052] See also Figure 2 As a specific embodiment of the chloroacetic acid tail gas recycling system provided in the application, a purge pipe 31 and a purge gas source 32 are added. The first end of the purge pipe 31 extends into the detection pipe 3, and the second end is connected to the purge gas source 32. The function of the purge pipe 31 is to remove the residual solution on the inner wall of the detection pipe 3 to prevent the residual solution from the previous test from affecting the next test result.

[0053] In addition, during the purging process, the detection pipeline 3 can be flushed with the help of the sprayer 6, and then purged after the flushing is completed.

[0054] See also Figure 2 Furthermore, the purge gas source 32 includes a cold air source 321 and a hot air source 322. The cold air source 321 is used to remove the solution or water attached to the inner wall of the detection pipe 3, and the hot air source 322 is used to dry the inner wall of the detection pipe 3.

[0055] In some possible implementations, a one-way valve is installed at the connection between the cold air source 321 and the hot air source 322 and the purge pipe 31 respectively. The function of the one-way valve is to prevent gas blowby.

[0056] In some possible implementations, after the first end of the purge pipe 31 extends into the detection pipe 3 , it extends toward the drain valve 8 , so that the purge pipe 31 can cover the inner wall of the detection pipe 3 as much as possible.

[0057] See also Figure 2 As a specific embodiment of the chloroacetic acid tail gas recycling system provided in the application, a circulation pipe 33 and a second circulation pump 34 are added. The circulation pipe 33 is connected to the detection pipe 3 and the sprinkler 6, and the second circulation pump 34 is installed on the circulation pipe 33.

[0058] The purpose of using the circulation pipe 33 and the second circulation pump 34 is to reduce the volume of the detection pipe 3. For example, the rising time of the exhaust gas in the mother liquor is one minute. If water is sprayed in the detection pipe 3 for one minute, the volume of the detection pipe 3 needs to be matched. However, when the spraying water used by the sprinkler 6 can be recycled, the volume of the detection pipe 3 can be reduced. After adding the circulation pipe 33 and the second circulation pump 34, the detection pipe 3 can estimate the amount of acidic gas contained in the exhaust gas inside it under the premise of limited volume.

[0059] The present application also discloses a glycine production line, comprising any one of the chloroacetic acid tail gas recycling systems described above.

[0060] The embodiments of this specific implementation method are all preferred embodiments of the present application and are not intended to limit the scope of protection of the present application. Therefore, any equivalent changes made based on the structure, shape, and principle of the present application should be included in the scope of protection of the present application.

Claims

1. A chloroacetic acid tail gas recycling system, characterized in that: include: The waste gas temporary storage tower (1) has an input end connected to the reactor and an output end connected to the mother liquid tank; A mixer (2) is provided in the waste gas temporary storage tower (1) and is used to drive the gas flow in the waste gas temporary storage tower (1); A detection pipeline (3) is provided on the exhaust gas temporary storage tower (1) and forms a loop with the space inside the exhaust gas temporary storage tower (1); A first circulation pump (4) and two electrically controlled valves (5) are both provided on the detection pipeline (3); A sprayer (6) is provided in the detection pipe (3) and is located between the two electrically controlled valves (5); A pH value detection sensor (7), the detection end of which extends into the area between the two electrically controlled valves (5) in the detection pipe (3); as well as A drain valve (8) is provided on the detection pipeline (3), and the drain valve (8) is used to discharge the detection liquid sample after the pH value detection is completed; After the detection process is completed, the tail gas is injected into the mother liquor tank according to the obtained pH value.

2. The chloroacetic acid tail gas recycling system according to claim 1, wherein The mixer (2) comprises: A rotating shaft (21) is rotatably connected to the exhaust gas temporary storage tower (1); A driving motor (22) is provided on the exhaust gas temporary storage tower (1) and connected to the rotating shaft (21); and The fan blade (23) is provided on the rotating shaft (21) and is located in the exhaust gas temporary storage tower (1).

3. The chloroacetic acid tail gas recycling system according to claim 1, wherein A feeding pump (11) is provided at the output end of the waste gas temporary storage tower (1).

4. The chloroacetic acid tail gas recycling system according to any one of claims 1 to 3, characterized in that Also includes: A purge pipe (31), a first end of which extends into the detection pipe (3); as well as The purge gas source (32) is connected to the second end of the purge pipe (31).

5. The chloroacetic acid tail gas recycling system according to claim 4, wherein The purge gas source (32) includes a cold gas source (321) and a hot gas source (322).

6. The chloroacetic acid tail gas recycling system according to claim 4, characterized in that: The first end of the purge pipe (31) extends into the detection pipe (3) and then extends in a direction close to the drain valve (8).

7. The chloroacetic acid tail gas recycling system according to claim 1, characterized in that: It also includes a circulation pipe (33) connected to the detection pipe (3) and the sprayer (6) and a second circulation pump (34) provided on the circulation pipe (33).

8. A glycine production line, characterized in that: The invention comprises the chloroacetic acid tail gas recycling system as described in any one of claims 1 to 7.

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