Acrylic acid production azeotropic agent toluene storage unit

Abstract

This utility model belongs to the technical field of chemical storage devices, specifically relating to a toluene storage device for the azeotropic agent in acrylic acid production. The device includes a toluene tank body with a floating roof inside. A first coil and a second coil are installed at the bottom of the toluene tank body. The lower part of the toluene tank body is connected to the inlet of a circulating pump via a pipeline. The outlet pipeline of the circulating pump is divided into two paths: one is a reflux pipeline connected to a static mixer, which is connected to the toluene tank body and also connected to a polymerization inhibitor pipeline; the other path of the circulating pump outlet pipeline is a toluene outlet pipeline, on which a material cooler is installed. A nitrogen pipeline with a nitrogen regulating valve is installed on the top of the toluene tank body. This utility model's toluene storage device for the azeotropic agent in acrylic acid production is a specialized device with anti-polymerization, precise temperature control, explosion-proof safety, and impurity adaptability capabilities.

Description

Technical Field

[0001] This utility model belongs to the technical field of chemical storage devices, specifically relating to a storage device for toluene, an azeotropic agent in the production of acrylic acid. Background Technology

[0002] In the industrial production of acrylic acid, toluene is often used as an azeotropic agent in the azeotropic dehydration unit of acrylic acid aqueous solutions. It achieves efficient dehydration by forming an azeotrope with water, making it a key auxiliary material ensuring the separation and purification efficiency and product purity of acrylic acid. Toluene is used in a recycling model during production. It is stored in dedicated tanks, pumped to the dehydration unit for azeotropic dehydration, and after use, it is returned to the toluene storage tank for reuse after simple separation. However, recycled toluene inevitably carries moisture, acrylic acid, and small amounts of high-boiling-point organic impurities. Acrylic acid is highly prone to self-polymerization and is flammable and explosive. Toluene itself is also a flammable and explosive hazardous chemical. This results in significant problems in the recycled toluene storage process, including polymerization blockage, temperature runaway, and high safety risks, directly affecting the continuous and stable operation of the unit and the inherent safety of production.

[0003] Patent CN1603296A discloses a storage tank and method for storing easily polymerizable compounds. Its core principle is to establish a circulation pipeline between the receiving and delivery pipelines of the tank, ensuring continuous circulation of the material within the tank and preventing stagnation, polymerization, or freezing. Corrosion-resistant stainless steel is used for flanges, bolts, and other connectors, along with fluoropolymer gaskets to prevent leakage of corrosive materials. Pre-cooling before feeding controls the feed temperature to ensure it does not exceed the storage temperature inside the tank, reducing polymerization risk and heat exchanger load. This technology provides a basic approach for preventing blockages and controlling the temperature during storage of easily polymerizable materials. However, it does not address the specific material system of circulating azeotropic agents containing acrylic acid impurities, nor does it consider the polymerization inhibition of acrylic acid impurities in circulating toluene, trace water separation, and the explosion-proof and temperature-controlled requirements for dedicated azeotropic agent storage.

[0004] Existing toluene storage facilities are mostly designed as conventional hazardous chemical storage tanks, which generally have the following defects: First, they lack a targeted circulation loop, making it easy for dead zones of material to accumulate inside the tank and in the pipelines. Acrylic acid carried in these dead zones can undergo self-polymerization under high temperatures or long-term stagnation, clogging pipelines, pumps, and tank interfaces. Second, the temperature control method is crude, without independent external circulation cooling and feed pre-cooling modules. High temperatures in summer or the accumulation of feed heat can easily lead to excessive temperatures inside the tank, accelerating acrylic acid polymerization and toluene volatilization. Third, safety facilities are inadequate, lacking gas seal protection, pressure interlock control, and online replenishment mechanisms for polymerization inhibitors. This makes it impossible to inhibit acrylic acid polymerization, and the flammable and explosive mixture has a high risk of leakage and overpressure. Fourth, the simple separation of trace amounts of water and acrylic acid impurities in the circulating toluene is not considered. The continuous accumulation of impurities reduces the azeotropic dehydration effect and affects the quality of acrylic acid products. Utility Model Content

[0005] The technical problem to be solved by this utility model is to overcome the problems of polymerization blockage, temperature runaway and major safety hazards in the existing technology, and to provide a storage device for toluene, an azeotropic agent in the production of acrylic acid, which is a special device with anti-polymerization, precise temperature control, explosion-proof safety and impurity adaptability.

[0006] The toluene storage device for the azeotropic agent in acrylic acid production according to this utility model includes a toluene tank body. A floating plate is placed inside the toluene tank body. A first coil and a second coil are arranged at the bottom of the toluene tank body. The two coils are arranged alternately, without overlapping, sharing pipelines, or crossing connections. The lower part of the toluene tank body is connected to the inlet of a circulation pump through a pipeline. The outlet pipeline of the circulation pump is divided into two paths. One path is a return pipeline, which is connected to one end of a static mixer. The other end of the static mixer is connected to the toluene tank body. An inhibitor pipeline is also connected to the static mixer. The other path of the circulation pump outlet pipeline is a toluene outlet pipeline, and a material cooler is installed on the toluene outlet pipeline. A nitrogen pipeline is installed on the top of the toluene tank body, and a nitrogen regulating valve is installed on the nitrogen pipeline.

[0007] Preferably, the floating roof includes a floating roof body with through holes. Multiple balancing legs are arranged in the same direction on the floating roof body, each leg being of the same height. These legs are used to support the floating roof at the bottom of the tank when it is lowered to a low liquid level, preventing the floating roof from tilting. The through holes serve as venting ports and gauging ports.

[0008] Preferably, the floating platform is a one-piece molded aluminum body.

[0009] Preferably, a level gauge, a pressure gauge, and a vent are installed on the top of the toluene tank body.

[0010] Preferably, a tail gas collection pipe is installed at the top center of the toluene tank body, and a flame arrestor is installed on the tail gas collection pipe.

[0011] Preferably, a thermometer is installed on the side of the toluene tank body, and a toluene return pipeline is connected to the side.

[0012] Preferably, the first inlet pipe and the first return pipe of the first coil are independently arranged on the outside of the toluene tank body, serving as a dedicated cold water coil located below the second coil.

[0013] Preferably, the second inlet and return water pipes of the second coil are independently located on the outside of the toluene tank body, serving as a dedicated warm water coil. The first and second coils are staggered vertically, do not overlap, and have no shared pipes. Their function is to separately supply chilled water and warm water, achieving zoned temperature control of the toluene inside the tank, maintaining a constant temperature of 16-20℃ throughout the year. The two coils work together: they can be adjusted independently, with the first coil primarily used for cooling in summer and the second coil primarily used for heating in winter, or they can operate simultaneously to balance the temperature gradient inside the tank.

[0014] Preferably, a circulating pump extracts toluene from the tank to provide power for subsequent mixing and cooling, while continuous reflux ensures material flowability and prevents polymerization stagnation. It works in conjunction with the reflux line and the toluene outlet line to split the toluene into two streams: one for mixing the polymerization inhibitor, and the other for cooling reflux and external delivery.

[0015] Preferably, the static mixer and the polymerization inhibitor pipeline: The static mixer receives toluene from the return pipeline and polymerization inhibitor from the polymerization inhibitor pipeline, mixes them evenly, and then returns them to the tank. It works in conjunction with the circulation pump: The flow rate provided by the circulation pump ensures the turbulent mixing effect within the static mixer, and the polymerization inhibitor can be added promptly to adjust the concentration when the acrylic acid content increases.

[0016] Preferably, the material cooler precisely cools and controls the temperature of the toluene from the toluene outlet pipeline, and then the toluene enters the device system after meeting the parameter requirements.

[0017] The working process of this utility model is as follows: Toluene, having completed azeotropic dehydration in the device, carries a small amount of water and acrylic acid into the toluene tank body through the toluene return pipeline. A level gauge displays the liquid level; when the level is too low, new toluene must be added to ensure the floating plate does not touch the ground, keeping it always above the toluene and other materials for isolation. A circulation pump delivers toluene to the device for use through the toluene outlet pipeline, while simultaneously performing continuous reflux operation through the return pipeline to maintain the fluidity of the material in the tank and prevent polymerization stagnation. Because acrylic acid readily polymerizes and releases heat during storage, and toluene has a very low flash point, a first and second coil are installed at the bottom of the tank to control the tank temperature and ensure safety. By adjusting the flow rate of chilled water in the first inlet and return water pipelines, the material in the tank is kept at a temperature of 16-20°C, especially in summer, reducing the risk of polymerization. Simultaneously, by adjusting the flow rate of warm water in the second inlet and return water pipelines, the material in the tank is kept at a temperature of 16-20°C, especially in winter. The tank temperature is maintained constant by switching between cold and hot water, and is adjusted via a thermometer display. A polymerization inhibitor line connected to a static mixer is installed on the reflux line. If the acrylic acid content in the toluene tank rises significantly under abnormal conditions, an appropriate amount of polymerization inhibitor can be added through this line to prevent polymerization. A nitrogen line is installed on the tank top. Nitrogen is supplied through a nitrogen regulating valve linked to a pressure gauge to maintain a slight positive pressure in the toluene tank, providing nitrogen sealing. An explosion vent is also provided to prevent further danger to the tank. A flame arrestor is installed on the tank top. Acrylic acid volatiles emitted from the tank top are discharged through the flame arrestor and led to the waste gas treatment system via a tail gas collection line, ensuring environmental protection requirements are met.

[0018] Compared with the prior art, the beneficial effects of this utility model are:

[0019] (1) By setting up a circulating pump, a return pipeline and a static mixer, this utility model realizes the continuous circulation of toluene in the tank, avoids dead corners where materials are stationary, and simultaneously replenishes polymerization inhibitors online, effectively inhibiting the self-polymerization of acrylic acid, preventing blockage of pipelines, pump bodies and tank interfaces, and ensuring long-term stable operation of the device.

[0020] (2) This utility model adopts a first coil (cold water) and a second coil (warm water) arranged in an alternating manner and controlled independently. With the help of a thermometer, it achieves precise temperature control in different zones and maintains a constant temperature of 16-20℃ for toluene in the tank throughout the year, avoiding problems such as accelerated polymerization and increased volatilization caused by overheating in summer or overcooling in winter.

[0021] (3) This utility model integrates a nitrogen pipeline, a pressure gauge linkage regulating valve, an explosion relief port, a flame arrestor and a tail gas collection pipeline to form a multi-level pressure protection and relief system, ensuring that the tank is always under a slight positive pressure, effectively isolating air, suppressing the flammability and explosion risk of the toluene and acrylic acid mixture system, while meeting environmental emission requirements and significantly improving the intrinsic safety level of storage. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the toluene storage device for the azeotropic agent in the production of acrylic acid according to this utility model.

[0023] Figure 2 This is a schematic diagram of the floating roof structure.

[0024] Figure 3 This is a schematic diagram of the floating roof structure.

[0025] Figure 1 The components are as follows: 1. Toluene return pipeline; 2. Level gauge; 3. Circulation pump; 4. Toluene outlet pipeline; 5. Return pipeline; 6. Float; 7. First coil; 8. Second coil; 9. First inlet water pipeline; 10. First return water pipeline; 11. Second inlet water pipeline; 12. Second return water pipeline; 13. Thermometer; 14. Polymer inhibitor pipeline; 15. Nitrogen pipeline; 16. Nitrogen regulating valve; 17. Pressure gauge; 18. Explosion vent; 19. Flame arrestor; 20. Tail gas collection pipeline; 21. Material cooler; 22. Static mixer.

[0026] Figure 2 , Figure 3 6-1. Floating plate body; 6-2. Through hole; 6-3. Balance support leg. Detailed Implementation

[0027] The present invention will be further described below with reference to specific embodiments.

[0028] Example 1

[0029] like Figure 1As shown, the toluene storage device for the azeotropic agent in acrylic acid production provided in this embodiment includes a vertical cylindrical toluene tank body. A floating roof 6 is placed inside the toluene tank body. Figures 2 to 3 As shown, the floating plate 6 is a one-piece molded aluminum body. Its structure includes a circular floating plate body 6-1. Multiple through holes 6-2 are evenly opened on the floating plate body 6-1. Multiple balance legs 6-3 are vertically fixed along the circumference on the upper surface of the floating plate body 6-1. Each balance leg 6-3 has the same height and is used to support the bottom of the tank when the floating plate is lowered to a low liquid level to prevent the floating plate from tilting.

[0030] The bottom of the toluene tank body is equipped with a first coil 7 and a second coil 8. Both the first coil 7 and the second coil 8 are spiral coils, arranged vertically in an alternating pattern. That is, from a top view, the coils of the first coil 7 and the coils of the second coil 8 alternate, but they do not overlap, share any pipes, or cross each other. The first coil 7 is located below the second coil 8. The inlet end of the first coil 7 is connected to the first inlet pipe 9, and the outlet end is connected to the first return pipe 10. Both pipes independently exit the lower side wall of the toluene tank body and are used to introduce chilled water (e.g., chilled water at 5~10℃), serving as a dedicated cold water coil. The inlet end of the second coil 8 is connected to the second inlet pipe 11, and the outlet end is connected to the second return pipe 12. Both pipes independently exit the side wall of the toluene tank body and are located above the first coil 7, used to introduce warm water (e.g., warm water at 30~50℃), serving as a dedicated warm water coil. By controlling the flow rates of the two sets of coils separately, the temperature of toluene inside the tank can be precisely adjusted. In summer, cooling is mainly achieved by the first coil 7, while heating is mainly achieved by the second coil 8 in winter, so that the material inside the tank can be kept in a suitable temperature range of 16-20℃ throughout the year.

[0031] An outlet is located on the lower side wall of the toluene tank, connected to the inlet of the circulating pump 3 via a pipeline. The outlet pipeline of the circulating pump 3 is divided into two paths: one is a return pipeline 5, which connects to one end of the static mixer 22, and the other end of the static mixer 22 connects to the middle side wall of the toluene tank. A polymerization inhibitor pipeline 14 is also connected to the static mixer 22 for injecting polymerization inhibitor into it. When toluene circulates through the circulating pump 3, some toluene enters the static mixer 22 via the return pipeline 5, mixes thoroughly with the polymerization inhibitor, and then returns to the tank, ensuring that the polymerization inhibitor is evenly dispersed in the toluene. The other path of the circulating pump 3 outlet pipeline is a toluene outlet pipeline 4, which connects to one end of the material cooler 21, and the other end of the material cooler 21 connects to the system. The material cooler 21 uses circulating water or chilled water as the cooling medium to precisely control the temperature of the delivered toluene before it enters the system.

[0032] A nitrogen pipeline 15 is located at the center of the top of the toluene tank. A nitrogen regulating valve 16 is installed on the nitrogen pipeline 15, which is interlocked with a pressure gauge 17 on the top of the tank. When the pressure inside the tank is lower than the set value (e.g., 0.2 kPa gauge pressure), it automatically opens to replenish nitrogen, maintaining a slight positive pressure and achieving nitrogen sealing. A level gauge 2, pressure gauge 17, and explosion vent 18 are also installed on the top of the tank. A tail gas collection pipeline 20 is also located at the center of the top of the tank, and a flame arrester 19 is installed on the tail gas collection pipeline 20. The tail gas collection pipeline 20 is connected to the plant's waste gas treatment system. Organic gases such as acrylic acid volatilized from the top of the tank are discharged through the flame arrester 19 and led to the waste gas treatment system by the tail gas collection pipeline 20, meeting environmental protection requirements. A thermometer 13 is installed on the side of the toluene tank to monitor the temperature of the toluene inside the tank. The flow rate of cold or warm water is adjusted based on the temperature display. The side is also connected to a toluene return pipeline 1, which is used to return to the tank the toluene containing a small amount of water and acrylic acid after the azeotropic dehydration of the production unit has been completed.

[0033] The working process of this device is described below:

[0034] Toluene, having completed azeotropic dehydration in the unit, carries a small amount of water and acrylic acid back into the toluene tank via toluene return line 1. Level gauge 2 indicates the liquid level; when the level is too low, new toluene must be added to ensure the floating roof 6 does not touch the ground, keeping it always above the toluene and other materials for isolation and to reduce the gas phase space. Circulation pump 3 delivers toluene to the unit for use via toluene outlet line 4, and simultaneously performs continuous reflux operation via return line 5 to maintain the fluidity of the material in the tank and prevent polymerization stagnation.

[0035] Because acrylic acid readily polymerizes and releases heat during storage, and toluene has a very low flash point, a first coil 7 and a second coil 8 are installed at the bottom of the tank to control the temperature and ensure safety. By adjusting the flow rate of chilled water in the first inlet pipe 9 and the first return pipe 10, the material in the tank is kept at a temperature of 16-20°C, especially in summer, to reduce the risk of polymerization. Simultaneously, by adjusting the flow rate of warm water in the second inlet pipe 11 and the second return pipe 12, the material in the tank is kept at a temperature of 16-20°C, especially in winter. The tank temperature is kept constant by switching between cold and hot water, and the tank temperature is adjusted via a thermometer 13.

[0036] A polymerization inhibitor line 14 (via static mixer 22) is installed on the return line 5. When the acrylic acid content in the toluene tank increases significantly under abnormal conditions, an appropriate amount of polymerization inhibitor can be added through the inhibitor line 14 to adjust the level and prevent polymerization. A nitrogen line 15 is installed on the top of the tank. Nitrogen is supplied through a nitrogen regulating valve 16 linked to a pressure gauge 17 to maintain a slight positive pressure in the toluene tank, serving as a nitrogen seal. An explosion vent 18 is also provided to prevent further danger to the tank. A flame arrestor 19 is installed on the top of the tank. Acrylic acid organic gases volatilized from the top of the tank are discharged through the flame arrestor 19 and led to the waste gas treatment system by the exhaust gas collection line 20, ensuring environmental protection requirements are met.

Claims

1. A storage device for toluene, an azeotropic agent in the production of acrylic acid, characterized in that: The toluene tank body includes a floating roof (6) inside the toluene tank body. The bottom of the toluene tank body is equipped with a first coil (7) and a second coil (8). The two coils (7 and 8) are arranged alternately, without overlapping, sharing pipelines, or cross-connection. The lower part of the toluene tank body is connected to the inlet of the circulating pump (3) through a pipeline. The outlet pipeline of the circulating pump (3) is divided into two paths. One path is a return pipeline (5), which is connected to one end of the static mixer (22). The other end of the static mixer (22) is connected to the toluene tank body. The static mixer (22) is also connected to a polymerization inhibitor pipeline (14). The other path of the outlet pipeline of the circulating pump (3) is a toluene outlet pipeline (4), which is equipped with a material cooler (21). The top of the toluene tank body is equipped with a nitrogen pipeline (15), which is equipped with a nitrogen regulating valve (16).

2. The toluene storage device for the azeotropic agent in acrylic acid production according to claim 1, characterized in that: The floating platform (6) includes a floating platform body (6-1), a through hole (6-2) is provided on the floating platform body (6-1), and multiple balance legs (6-3) are provided in the same direction on the floating platform body (6-1).

3. The toluene storage device for the azeotropic agent in acrylic acid production according to claim 1, characterized in that: The floating platform (6) is a one-piece molded aluminum body.

4. The toluene storage device for the azeotropic agent in acrylic acid production according to claim 1, characterized in that: The top of the toluene tank body is equipped with a level gauge (2), a pressure gauge (17), and an explosion vent (18).

5. The toluene storage device for the azeotropic agent in acrylic acid production according to claim 4, characterized in that: A tail gas collection pipe (20) is installed at the top center of the toluene tank body, and a flame arrestor (19) is installed on the tail gas collection pipe (20).

6. The toluene storage device for the azeotropic agent in acrylic acid production according to claim 1, characterized in that: A thermometer (13) is installed on the side of the toluene tank body, and a toluene return pipeline (1) is connected to the side.

7. The toluene storage device for the azeotropic agent in acrylic acid production according to claim 1, characterized in that: The first inlet pipe (9) and the first return pipe (10) of the first coil (7) are independently set on the outside of the toluene tank body, and are located below the second coil (8) as a special coil for cold water.

8. The toluene storage device for the azeotropic agent in acrylic acid production according to claim 7, characterized in that: The second inlet pipe (11) and the second return pipe (12) of the second coil (8) are independently set on the outside of the toluene tank body as a special coil for warm water.

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