System for realizing stable feeding of high-quality acrylic acid in production of 3-mercaptopropionic acid

Abstract

The utility model relates to the technical field of production of 3-mercaptopropionic acid, in particular to a system for realizing stable feeding of high-quality acrylic acid in production of 3-mercaptopropionic acid. The system comprises an acrylic acid storage tank (1) and a heat exchanger (3), a circulating pump (2) is arranged on a pipeline for connecting the discharging end of the acrylic acid storage tank (1) and the feeding end of the heat exchanger (3), the discharging end of the heat exchanger (5) is connected to a metering pump (4) through a pipeline, and a circulating pipeline is further arranged on the pipeline at the discharging end of the heat exchanger (3) and connected with the feeding end of the acrylic acid storage tank (1). The system aims at a hydrogen sulfide-acrylic acid continuous production process, and circulation between the acrylic acid storage tank and the heat exchanger can be kept in the feeding process of the acrylic acid raw material, so that the temperature of the acrylic acid raw material can be stably controlled, and the acrylic acid is prevented from self-polymerization and crystallization.

Description

Technical Field

[0001] The invention relates to the technical field of 3-mercaptopropionic acid production, and in particular to a system for realizing stable feeding of high-quality acrylic acid in the production of 3-mercaptopropionic acid. Background Art

[0002] 3-Mercaptopropionic acid is an important chemical raw material, and its main application fields are medicine, auxiliary agent and water reducing agent. At present, its main process route at home and abroad is to produce with acrylonitrile and sodium hydrosulfide as raw materials. This process can be carried out under normal pressure, but its process flow is long, has strict requirements on reaction temperature and time, has low operating flexibility, has many three wastes, and has large environmental pollution. This process has a trend of being gradually eliminated. In recent years, there are also many reports on the continuous synthesis of 3-mercaptopropionic acid by hydrogen sulfide-acrylic acid method. Patent CN107501147A discloses a method for synthesizing 3-mercaptopropionic acid by reacting acrylic acid and hydrogen sulfide as raw materials in a plasma reactor. CN112608259 discloses a method for synthesizing 3-mercaptopropionic acid by using nitrogen-containing ionic liquid containing hydrogen sulfide as solvent and then reacting with acrylic acid through microchannel.

[0003] Our company has successfully developed the above-mentioned hydrogen sulfide-acrylic acid continuous production process. Unlike the intermittent process, the key technology is to realize the large-scale production promotion and application of this continuous process and to control the quality stability of acrylic acid raw materials and achieve continuous and stable feeding.

[0004] Acrylic acid is unstable, and the content of acrylic acid dimer increases during storage. Our technicians have found that in the production process of 3-mercaptopropionic acid, when the content of acrylic acid dimer in the raw material acrylic acid exceeds 0.5wt%, impurities will be retained in the reaction liquid, and decomposed to produce acrylic acid during the distillation separation process, resulting in residual acrylic acid in the product, which reduces the product quality and affects downstream applications. In addition, acrylic acid has a low freezing point, and when there is a dead zone in pipeline transportation, it may crystallize and block the pipeline, and promote the increase of acrylic acid dimer content. It can be seen that it is crucial to achieve high-quality acrylic acid with stable quality and continuous and stable feeding.

[0005] GB / T 17529 clearly states that acrylic acid is easy to freeze and polymerize, and should be stored in a warehouse at 15-30°C. Most of the patents published so far use the method of external or internal insulation of acrylic acid storage containers, which makes it difficult to detect internal leakage and creates safety risks due to dead zones in the tank area. In addition, the control method and technical effect of the acrylic acid dimer content are not involved.

[0006] Patent CN212988085U discloses an environmentally friendly acrylic acid storage tank heating system, which uses the waste heat released by the addition reaction to keep the acrylic acid tank warm, but the insulation coil is only outside the acrylic acid tank, and there is a temperature difference inside, which is prone to produce a storage dead zone. CN217397401U discloses a chemical storage tank for storing acrylic acid with high safety performance. By providing a temperature sensor and a heating rod, the heat pipe between the annular shells heats the raw materials inside the storage tank. In this way, the storage tank still cannot avoid the risk of dead zones, and does not reflect the technical effect of controlling acrylic acid dimers. Patent CN204223544U discloses an acrylic acid anti-crystallization storage device, which heats the acrylic acid in the storage device by arranging a coil-type heating component and a heating circulation pipeline in the storage device. Patent CN214826015U discloses an acrylic acid anti-polymerization and anti-crystallization device, which can effectively prevent acrylic acid from crystallizing by means of temperature detection, heating and self-circulation. However, both of them are more focused on solving the crystallization problem of acrylic acid at low temperatures. When the ambient temperature is too high in summer, the temperature field may be difficult to control, and local acrylic acid self-polymerization may occur, resulting in excessive acrylic acid dimer content. In addition, the patent sets a coil-type heating component in the acrylic acid storage tank, which still has the risk of internal leakage. Utility Model Content

[0007] In view of the problems of the prior art, the utility model provides a system for achieving stable feeding of high-quality acrylic acid in the production of 3-mercaptopropionic acid. The system is aimed at the hydrogen sulfide-acrylic acid continuous production process. During the feeding process of acrylic acid raw materials, the system can also maintain the circulation between the acrylic acid storage tank and the heat exchanger, thereby achieving stable control of the acrylic acid raw material temperature and preventing acrylic acid from self-polymerization and crystallization.

[0008] The technical solution of the utility model includes:

[0009] A system for achieving stable feeding of high-quality acrylic acid in the production of 3-mercaptopropionic acid comprises an acrylic acid storage tank and a heat exchanger. A circulating pump is provided on a pipeline connecting a discharge end of the acrylic acid storage tank and a feed end of the heat exchanger. The discharge end of the heat exchanger is connected to a metering pump through a pipeline. A circulating pipeline is also provided on the pipeline at the discharge end of the heat exchanger to connect to the feed end of the acrylic acid storage tank.

[0010] A circulation pump is provided on the pipeline connecting the discharge end of the acrylic acid storage tank and the feed end of the heat exchanger, which is used to transport the liquid in the storage tank to the next-stage heat exchange equipment and continue to circulate back to the storage tank.

[0011] Preferably, a temperature transmitter is provided at least at one of the discharge end of the heat exchanger, the front end of the circulation pump, and the acrylic acid storage tank.

[0012] More preferably, a temperature transmitter is provided at the discharge end of the heat exchanger.

[0013] Preferably, the heat exchanger further comprises a heat exchange medium water inlet pipeline and a heat exchange medium water outlet pipeline, and the heat exchange medium pressure in the heat exchanger is lower than the acrylic acid material pressure.

[0014] More preferably, an online pH detector is provided on the heat exchange medium outlet pipe.

[0015] Preferably, the acrylic acid storage tank is an earth-covered tank, which has good airtightness, a relatively stable temperature inside the tank, and is less affected by the atmospheric temperature.

[0016] When the system of the utility model is in operation, the raw materials from the acrylic acid storage tank are transported to the heat exchanger through the circulation pump and pipelines, and the acrylic acid material reaches the target temperature after heat exchange in the heat exchanger. The first acrylic acid material at the discharge end of the heat exchanger returns to the acrylic acid storage tank along the circulation pipeline, and the second acrylic acid material is transported to the metering pump through the pipeline to enter the next stage to participate in the reaction. At the same time, the temperature of the acrylic acid material is monitored at any time through the temperature transmitter on the discharge end of the heat exchanger, the front end of the circulation pump, and the acrylic acid storage tank (the target temperature after heat exchange is set to 15-25°C, acrylic acid will crystallize below 14°C, and acrylic acid is prone to self-polymerization above 25°C, so the target temperature of acrylic acid after heat exchange is preferably 15-25°C, and more preferably 18-22°C), and the flow rate of the heat exchanger medium can be further controlled by the signal returned by the temperature transmitter, so as to achieve stable control of the temperature of the acrylic acid raw material and prevent acrylic acid from self-polymerization and crystallization.

[0017] Compared with the heating coil installed in the storage tank in the prior art, the acrylic acid material of the utility model continuously circulates heat exchange in the heat exchanger and the acrylic acid storage tank, the temperature control is more precise, the temperature distribution in the storage tank is uniform, the material temperature in the storage tank is stable, and there is no solid deposition or dead zone in the tank. During the operation of the system, the water pressure of the heat exchanger is always controlled to be lower than the pressure of the acrylic acid material, and the outlet water line of the heat exchanger is equipped with an online pH detector, which avoids the risk of undetectable internal leakage, and is very suitable for the continuous feeding of acrylic acid. In addition, compared with the acrylic acid material replacement cycle of the acrylic acid storage tank in the prior art of about one week, the use of the utility model system can extend the replacement cycle to 2 months, and control from the source to prevent acrylic acid from self-polymerization and crystallization, reducing safety risks. The quality of the raw acrylic acid feed is stable, and the high-performance liquid chromatography content of acrylic acid dimer in acrylic acid is ≤0.5wt%, which provides a guarantee for the stable operation of the production system. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Schematic diagram of the structure of the utility model;

[0019] Among them, 1 is an acrylic acid storage tank, 2 is a circulation pump, 3 is a heat exchanger, 4 is a metering pump, 5 is a temperature transmitter, 6 is a heat exchange medium inlet pipeline, and 7 is a heat exchange medium outlet pipeline. DETAILED DESCRIPTION

[0020] The following is a further detailed description of the above contents of the utility model through specific implementation methods in the form of embodiments, but this should not be understood as the scope of the above subject matter of the utility model being limited to the following examples. All technologies implemented based on the above contents of the utility model belong to the scope of the utility model. Unless otherwise specified, the following embodiments are all completed using conventional technical operations.

[0021] The endpoints of the ranges disclosed herein and any values ​​are not limited to the exact ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. In the present invention, unless otherwise specified, the directional words used, such as "front end, rear end" generally refer to the upstream or downstream of the material flow direction, and "upper end, lower end" generally refer to the upper and lower parts of the equipment in the attached drawings.

[0022] A system for achieving stable feeding of high-quality acrylic acid in the production of 3-mercaptopropionic acid, such as Figure 1 As shown, it includes an acrylic acid storage tank 1 and a heat exchanger 3. A circulation pump 2 is provided on the pipeline connecting the discharge end of the acrylic acid storage tank 1 and the feed end of the heat exchanger 3. The discharge end of the heat exchanger 3 is connected to a metering pump 4 through a pipeline. A circulation pipeline is also provided on the discharge end pipeline of the heat exchanger 3 to connect to the feed end of the acrylic acid storage tank 1.

[0023] A temperature transmitter 5 is provided at the discharge end of the heat exchanger 3 and the acrylic acid storage tank 1 .

[0024] The heat exchanger 3 further comprises a heat exchange medium water inlet pipeline 6 and a heat exchange medium water outlet pipeline 7. The heat exchange medium pressure in the heat exchanger 3 is lower than the acrylic acid material pressure.

[0025] An online pH detector is provided on the heat exchange medium outlet pipe 7 .

[0026] The acrylic acid storage tank 1 is an earth-covered tank.

[0027] More specifically, valves are provided on each pipeline and the circulation pipeline.

[0028] When the system of the utility model is in operation, the raw materials from the acrylic acid storage tank are transported to the heat exchanger through the circulation pump and the pipeline. The acrylic acid material reaches the target temperature after heat exchange in the heat exchanger. The first acrylic acid material at the discharge end of the heat exchanger returns to the acrylic acid storage tank along the circulation pipeline, and the second acrylic acid material is transported to the next stage through the pipeline to participate in the reaction. At the same time, the temperature of the acrylic acid material is monitored at any time through the temperature transmitter on the discharge end of the heat exchanger, the front end of the circulation pump, and the acrylic acid storage tank (the target temperature after heat exchange is set to 15-25°C. Acrylic acid will crystallize below 14°C, and acrylic acid is prone to self-polymerization above 25°C. Therefore, the target temperature of acrylic acid after heat exchange is preferably 15-25°C, and more preferably 18-22°C), and the flow rate of the heat exchanger medium can be further controlled by the signal returned by the temperature transmitter, so as to achieve stable control of the temperature of the acrylic acid raw material and prevent acrylic acid from self-polymerization and crystallization.

Claims

1. A system for achieving stable feeding of high-quality acrylic acid in the production of 3-mercaptopropionic acid, characterized in that: The invention comprises an acrylic acid storage tank (1) and a heat exchanger (3). A circulation pump (2) is arranged on a pipeline connecting the discharge end of the acrylic acid storage tank (1) and the feed end of the heat exchanger (3). The discharge end of the heat exchanger (3) is connected to a metering pump (4) through a pipeline. A circulation pipeline is also arranged on the discharge end pipeline of the heat exchanger (3) to connect the feed end of the acrylic acid storage tank (1).

2. A system for achieving stable feeding of high-quality acrylic acid in the production of 3-mercaptopropionic acid according to claim 1, characterized in that: A temperature transmitter (5) is provided at least at one of the discharge end of the heat exchanger (3), the front end of the circulation pump (2), and the acrylic acid storage tank (1).

3. The system for achieving stable feeding of high-quality acrylic acid in the production of 3-mercaptopropionic acid according to claim 1, characterized in that: A temperature transmitter (5) is provided at the discharge end of the heat exchanger (3).

4. The system for achieving stable feeding of high-quality acrylic acid in the production of 3-mercaptopropionic acid according to claim 1, characterized in that: The heat exchanger (3) further comprises a heat exchange medium water inlet pipeline (6) and a heat exchange medium water outlet pipeline (7), and the heat exchange medium pressure in the heat exchanger (3) is lower than the acrylic acid material pressure.

5. The system for achieving stable feeding of high-quality acrylic acid in the production of 3-mercaptopropionic acid according to claim 1, characterized in that: An online pH detector is provided on the heat exchange medium outlet pipe (7).

6. The system for achieving stable feeding of high-quality acrylic acid in the production of 3-mercaptopropionic acid according to claim 1, characterized in that: The acrylic acid storage tank (1) is an earth-covered tank.

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