A propylene feed method and system

Abstract

This invention provides a propylene feeding method and system. The propylene feeding method of this invention includes: (1) filling a propylene buffer tank with nitrogen; (2) connecting a propylene feedstock tank and a propylene buffer tank, allowing propylene from the propylene feedstock tank to enter the propylene buffer tank until all nitrogen in the propylene buffer tank is replaced by gaseous propylene; (3) achieving gas-phase equilibrium between the propylene feedstock tank and the propylene buffer tank, and adjusting the liquid level difference between the two tanks to allow propylene from the propylene feedstock tank to enter the propylene buffer tank; and (4) cooling the propylene in the propylene buffer tank and transporting it to the propylene reaction unit. The propylene feeding method and system of this invention avoids contamination of the propylene feedstock tank by high-pressure nitrogen and nitrogen recovery issues, and are simple to operate, safe, and stable.

Description

Technical Field

[0001] This invention relates to a method and system for feeding propylene. Background Technology

[0002] Propylene is one of the basic raw materials for the three major synthetic materials, with its largest usage in the production of polypropylene. In addition, propylene can be used to prepare acrylonitrile, propylene oxide, isopropanol, phenol, acetone, butanol, octanol, acrylic acid and its esters, propylene glycol, epichlorohydrin, and synthetic glycerol, among others.

[0003] In the pilot plant using propylene as a raw material, the existing process involves feeding propylene by pressing high-pressure nitrogen gas from a steel cylinder into a propylene buffer tank, and then pumping it to the subsequent reaction system. Because high-pressure nitrogen gas is introduced into the propylene cylinder, it causes contamination of the propylene medium inside the cylinder, which is difficult to recover and poses a safety hazard. Therefore, it is necessary to develop a new propylene feeding method. Summary of the Invention

[0004] To address one of the aforementioned technical problems in the prior art, this invention provides a propylene feeding method and system that can effectively prevent nitrogen contamination of propylene in steel cylinders and achieve a stable supply of propylene.

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

[0006] In a first aspect, the present invention provides a method for feeding propylene, comprising the following steps:

[0007] (1) Fill the propylene buffer tank with nitrogen gas;

[0008] (2) Connect the propylene feed tank and the propylene buffer tank so that the propylene in the propylene feed tank enters the propylene buffer tank until the nitrogen in the propylene buffer tank is completely replaced by gaseous propylene.

[0009] (3) To achieve gas phase equilibrium between the propylene raw material tank and the propylene buffer tank, the propylene in the propylene raw material tank is introduced into the propylene buffer tank by adjusting the liquid level difference between the propylene raw material tank and the propylene buffer tank.

[0010] (4) Cool the propylene in the propylene buffer tank and transport it to the propylene reaction unit.

[0011] According to some embodiments of the present invention, in step (2), the complete replacement of nitrogen in the propylene buffer tank with gaseous propylene is achieved by setting the pressure at the gaseous outlet of the propylene buffer tank to be lower than the propylene vapor pressure, for example, lower than the propylene vapor pressure by 10 to 100 kPaA, for example, lower than the propylene vapor pressure by 10 kPaA, 20 kPaA, 30 kPaA, 40 kPaA, 50 kPaA, 60 kPaA, 70 kPaA, 80 kPaA, 90 kPaA, 100 kPaA or any value between them.

[0012] According to some embodiments of the present invention, in step (3), the propylene feedstock tank and the propylene buffer tank are brought into vapor phase equilibrium by adjusting the pressure at the vapor phase outlet of the propylene buffer tank to be higher than the propylene vapor pressure, for example, higher than the propylene vapor pressure by 10 to 100 kPaA, for example, higher than the propylene vapor pressure by 10 kPaA, 20 kPaA, 30 kPaA, 40 kPaA, 50 kPaA, 60 kPaA, 70 kPaA, 80 kPaA, 90 kPaA, 100 kPaA or any value between them.

[0013] According to some embodiments of the present invention, in step (3), the liquid level in the propylene feed tank is at least 1m higher than the liquid level in the propylene buffer tank. In some preferred embodiments, in step (3), the liquid level in the propylene feed tank is 2m to 5m higher than the liquid level in the propylene buffer tank (e.g., 2m, 3m, 4m, 5m or any value between them).

[0014] According to some embodiments of the present invention, in step (3), the volume of liquid propylene entering the propylene buffer tank is 20% to 80% of the volume of the propylene buffer tank, for example, 20%, 30%, 40%, 50%, 60%, 70%, 80% or any value between them.

[0015] According to some embodiments of the present invention, step (4) further includes: adjusting the pressure inside the propylene buffer tank to be higher than the propylene vapor pressure before performing the cooling treatment. According to some preferred embodiments of the present invention, step (4) further includes: adjusting the pressure inside the propylene buffer tank to be 10 to 100 kPaA higher than the propylene vapor pressure before performing the cooling treatment (e.g., 10 kPaA, 20 kPaA, 30 kPaA, 40 kPaA, 50 kPaA, 60 kPaA, 70 kPaA, 80 kPaA, 90 kPaA, 100 kPaA or any value between them).

[0016] According to some embodiments of the present invention, in step (4), the temperature of the propylene after cooling treatment is at least 5°C lower than the temperature of the propylene buffer tank, for example, 5°C, 10°C, 15°C, 20°C, 25°C, 30°C or any value between them. In some preferred embodiments, in step (4), the temperature of the propylene after cooling treatment is 10 to 30°C lower than the temperature of the propylene buffer tank (e.g., 10°C, 12°C, 15°C, 18°C, 20°C, 25°C, 28°C, 30°C or any value between them).

[0017] According to some embodiments of the present invention, in step (4), the cooled propylene is transported to the propylene reaction unit by a booster pump; preferably, the propylene temperature at the inlet of the booster pump is at least 5°C lower than the temperature of the propylene buffer tank, more preferably 10 to 30°C lower than the temperature of the propylene buffer tank (e.g., 10°C, 12°C, 15°C, 18°C, 20°C, 25°C, 28°C, 30°C or any value between them).

[0018] According to some embodiments of the present invention, the propylene buffer tank comprises N propylene buffer tanks connected in parallel, where N ≥ 2. Preferably, 2 ≤ N ≤ 5; for example, N is 2, 3, 4, or 5. In some preferred embodiments, N is 2.

[0019] According to some embodiments of the present invention, the propylene buffer tank includes a first propylene buffer tank and a second propylene buffer tank connected in parallel.

[0020] In some embodiments, in step (4), propylene in the first propylene buffer tank is first transported to the propylene reaction unit, and when the liquid level in the first propylene buffer tank drops to below 20%, propylene in the second propylene buffer tank is then transported to the propylene reaction unit.

[0021] In some embodiments, in step (4), propylene in the first propylene buffer tank is first transported to the propylene reaction unit. When the liquid level in the first propylene buffer tank drops to below 20%, propylene in the second propylene buffer tank is then transported to the propylene reaction unit. At the same time, the propylene raw material tank is connected to the first propylene buffer tank and step (3) is repeated so that the propylene in the propylene raw material tank enters the first propylene buffer tank for replenishment.

[0022] Secondly, the present invention provides a propylene feeding system, comprising a propylene feed tank, a propylene buffer device, a cooler, and a booster pump connected sequentially by pipelines; wherein the liquid level of the propylene feed tank is higher than the liquid level of the propylene buffer device; the top of the propylene buffer device is provided with a gas phase port, the gas phase port being connected to the top of the propylene feed tank via a first pipeline, the first pipeline being provided with a high-pressure nitrogen inlet and a first pressure regulating device, the high-pressure nitrogen inlet being used to deliver high-pressure nitrogen to the propylene buffer device, and the first pressure regulating device being used to regulate the pressure at the gas phase port of the propylene buffer device, so that the nitrogen delivered to the propylene buffer device is completely replaced by gaseous propylene, or, so that the propylene feed tank and the propylene buffer device reach gas phase equilibrium.

[0023] The propylene feeding system of the present invention creates a pressure difference between the propylene feed tank and the propylene buffer device by making the liquid level of the propylene feed tank higher than that of the propylene buffer device, and uses the siphon effect to allow propylene in the propylene feed tank to enter the propylene buffer device.

[0024] According to some embodiments of the present invention, the top of the propylene buffer device is also connected to the outlet of the booster pump via a second pipe, and a second pressure regulating device is provided on the second pipe for regulating the pressure in the propylene buffer device.

[0025] According to some embodiments of the present invention, the bottom of the propylene buffer device has a liquid phase port, which is connected to the bottom of the propylene feed tank via a pipe, and the liquid phase port of the propylene buffer device is sequentially connected to a cooler and a booster pump via a pipe.

[0026] According to some embodiments of the present invention, the propylene buffer device comprises N propylene buffer tanks connected in parallel, where N ≥ 2. Preferably, 2 ≤ N ≤ 5. More preferably, N = 2.

[0027] According to some embodiments of the present invention, the propylene buffer device includes a first propylene buffer tank and a second propylene buffer tank connected in parallel, and the first propylene buffer tank and the second propylene buffer tank are configured as follows:

[0028] Propylene in the first propylene buffer tank is first transported to the propylene reaction unit via a cooler and a booster pump. When the liquid level in the first propylene buffer tank drops below 20%, propylene in the second propylene buffer tank is then transported to the propylene reaction unit via a cooler and a booster pump. At the same time, propylene in the propylene feed tank enters the first propylene buffer tank for replenishment.

[0029] Thirdly, the present invention provides the application of the propylene feeding system described in the first aspect in a reaction using propylene as a raw material.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] The propylene feeding method and system of the present invention first fills the propylene buffer tank with nitrogen to remove gaseous impurities in the propylene buffer tank. Then, propylene gas from the propylene feed tank enters the propylene buffer tank to replace the nitrogen. After the propylene feed tank and the propylene buffer tank reach gas phase equilibrium, the propylene feed tank is positioned higher than the propylene buffer tank, and the pressure difference between the propylene feed tank and the propylene buffer tank is used to achieve a stable output of propylene from the feed tank to the buffer tank. This avoids contamination of the propylene feed tank by high-pressure nitrogen, eliminates the need for high-pressure nitrogen recovery, and is simple to operate, with high feeding efficiency and high safety. Attached Figure Description

[0032] Figure 1 The diagram below shows the propylene feeding process flow of some specific embodiments of the present invention, wherein PCV1 represents a pressure instrument, PCV2 represents a pressure instrument, LI represents a level instrument, PI represents a pressure instrument, and 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 and 15 all represent valves.

[0033] Figure 2 This is a flow chart of the propylene feeding process in the prior art, where PCV represents a pressure gauge, LI represents a level gauge, PI represents a pressure gauge, and 1, 2, 3, 4, and 5 all represent valves. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments and accompanying drawings. The specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention in any way.

[0035] Unless otherwise specified, all reagents used in the following experiments of this invention are commercially available products or reagents prepared according to conventional methods. Unless otherwise specified, all methods used in the experiments are conventional experimental methods. Unless otherwise specified, all instruments used in the experiments are commercially available.

[0036] The term "propylene feedstock tank" as used in this article refers to a steel container that stores propylene.

[0037] As used in this article, the term "propylene buffer tank" refers to a tank that stores gaseous and / or liquid propylene from a propylene feedstock tank. The material of the tank may be the same as or different from that of the propylene feedstock tank. The "propylene buffer tank" can store gaseous and / or liquid propylene from the propylene feedstock tank and then transport it to the subsequent propylene reaction unit.

[0038] The term "gas-phase equilibrium" used in this article refers to the phase equilibrium state between a gas and a liquid under certain temperature and pressure, in which the exchange of matter between the gas and the liquid reaches a dynamic equilibrium, that is, the gas no longer dissolves into the liquid, and the substances in the liquid no longer volatilize into the gas.

[0039] To address the problems of high-pressure nitrogen contamination of the propylene feed tank and the cumbersome high-pressure nitrogen recovery process in existing propylene feeding devices, this invention provides a propylene feeding system. The system includes a propylene feed tank, a propylene buffer device, a cooler, and a booster pump connected sequentially via pipelines. The liquid level in the propylene feed tank is higher than the liquid level in the propylene buffer device. The top of the propylene buffer device has a gas phase port, which is connected to the top of the propylene feed tank via a first pipeline. This first pipeline is equipped with a high-pressure nitrogen inlet and a first pressure regulating device. The high-pressure nitrogen inlet is used to deliver high-pressure nitrogen to the propylene buffer device, and the first pressure regulating device is used to regulate the pressure at the gas phase port of the propylene buffer device, ensuring that the nitrogen delivered to the propylene buffer device is completely replaced by gaseous propylene, or that the propylene feed tank and the propylene buffer device reach gas phase equilibrium.

[0040] The propylene feeding system of the present invention creates a pressure difference between the propylene feed tank and the propylene buffer device by making the liquid level of the propylene feed tank higher than that of the propylene buffer device, and uses the siphon effect to allow propylene in the propylene feed tank to enter the propylene buffer device.

[0041] Preferably, the top of the propylene buffer device is also connected to the outlet of the booster pump via a second pipe, and a second pressure regulating device is provided on the second pipe for regulating the pressure in the propylene buffer device.

[0042] Preferably, the bottom of the propylene buffer device has a liquid phase port, which is connected to the bottom of the propylene raw material tank through a pipe, and the liquid phase port of the propylene buffer device is connected in sequence to a cooler and a booster pump through a pipe.

[0043] Preferably, the propylene buffer device includes at least two propylene buffer tanks connected in parallel. Preferably, the propylene buffer device includes two to five propylene buffer tanks connected in parallel. Preferably, the propylene buffer device includes two propylene buffer tanks connected in parallel.

[0044] Preferably, the propylene buffer device includes a first propylene buffer tank and a second propylene buffer tank connected in parallel, and the first propylene buffer tank and the second propylene buffer tank are configured as follows:

[0045] Propylene in the first propylene buffer tank is first transported to the propylene reaction unit via a cooler and a booster pump. When the liquid level in the first propylene buffer tank drops below 20%, propylene in the second propylene buffer tank is then transported to the propylene reaction unit via a cooler and a booster pump. At the same time, propylene in the propylene feed tank enters the first propylene buffer tank for replenishment.

[0046] As one specific implementation method, such as Figure 1 As shown, the propylene feeding system of the present invention includes a propylene tank (i.e., a propylene raw material tank), a propylene buffer tank, a cooler, and a propylene pump connected in sequence by pipelines. The propylene tank is installed 2m-5m higher than the propylene buffer tank. The propylene buffer tank consists of propylene buffer tank A and propylene buffer tank B connected in parallel.

[0047] Furthermore, each of the propylene buffer tanks, A and B, is equipped with a level gauge LI and a pressure gauge PI.

[0048] Furthermore, each of the propylene buffer tanks, A and B, is equipped with a gas phase port at its top. These two gas phase ports are connected in parallel and then via a pipeline to the top inlet of the propylene tank. A high-pressure nitrogen inlet and a pressure gauge, PCV1, are installed on the pipeline connecting the two gas phase ports to the top inlet of the propylene tank. In this invention, by setting PCV1 within a certain pressure range, all nitrogen in the propylene buffer tank can be replaced with propylene, and gas phase equilibrium can be achieved between propylene buffer tanks A and B and the propylene tank.

[0049] Furthermore, the tops of propylene buffer tank A and propylene buffer tank B are connected to the outlet of a booster pump via pipes, and a pressure gauge PCV2 is installed on these pipes. In this invention, by setting PCV2 within a certain pressure range, the pressure in propylene buffer tank A and / or propylene buffer tank B can be regulated.

[0050] Furthermore, each of the propylene buffer tanks A and B has a liquid phase port at its bottom. The two liquid phase ports are connected in parallel and are respectively connected to the bottom of the propylene tank through pipes.

[0051] Furthermore, the liquid phase ports of propylene buffer tank A and propylene buffer tank B are connected in parallel and then sequentially connected to a cooler and a booster pump via pipelines.

[0052] According to some specific embodiments of the present invention, the propylene feeding method includes employing, for example... Figure 1 The feeding system shown performs feeding, specifically including the following steps:

[0053] (S1) Replace all gaseous impurities in the propylene buffer tank with nitrogen: Close valves 2, 5, 6, 7, 8, 9, 10, and 11, and open valves 1, 12, and 13 in sequence. High-pressure nitrogen enters propylene buffer tank A and propylene buffer tank B after passing through the pressure reducing valve. When the pressure in propylene buffer tank A and propylene buffer tank B no longer rises, close valve 1 and open valves 3 and 4. When the pressure in propylene buffer tank A and propylene buffer tank B no longer drops (at normal pressure), close valves 3 and 4 and open valve 1 again. Repeat the above steps in sequence until the gaseous phase at the outlet of valve 4 is all nitrogen.

[0054] (S2) Replace all the nitrogen in the propylene buffer tank with gaseous propylene: Close valves 1, 3 and 4, set the PCV1 pressure to be 10-100 kPaA lower than the propylene vapor pressure, and open valves 4, 5, 6, 9, 12 and 13 in sequence. At this time, the pressure of the propylene tank is higher than the pressure of propylene buffer tank A and propylene buffer tank B. The propylene in the propylene tank will discharge the nitrogen in propylene buffer tank A and propylene buffer tank B through the PCV system, thus completing the replacement of nitrogen with propylene.

[0055] (S3) Convert the propylene in the propylene buffer tank into a gas-liquid two-phase system: Close valve 4, set the PCV1 pressure to be 10-100 kPa higher than the propylene vapor pressure, open valves 2, 5, 6, and 9 to establish a gas-phase balance between the propylene tank and propylene buffer tanks A and B. Since the installation height of the propylene tank is higher than that of propylene buffer tanks A and B, the propylene in the propylene tank is transferred to the propylene buffer tank through the liquid level difference between the propylene tank and the buffer tank until the liquid level of propylene buffer tanks A and B reaches 20-80%.

[0056] (S4) By using a cooler, the temperature of propylene at the inlet of the propylene pump is at least 5°C lower than the temperature of the propylene buffer tank, preferably 10-30°C. Valves 5, 6 and 9 are closed in sequence. The PCV2 pressure is set 10-100 kPaA higher than the propylene vapor pressure. Valves 7, 14 and 10 are opened in sequence to start the propylene pump. The liquid level of propylene buffer tank A is observed to realize the delivery of propylene to the subsequent reaction unit.

[0057] (S5) When the liquid level in propylene buffer tank A drops below 20%, close valve 7 and open valves 6 and 8 to transfer propylene from propylene tank A to propylene buffer tank B and transfer propylene from propylene buffer tank B to the subsequent reaction unit, thereby realizing the switching and replenishment of propylene buffer tanks A and B.

[0058] Example 1

[0059] A pilot plant uses Figure 1 The propylene feeding method and system shown above, as well as the specific implementation method described above, and the main process operating parameters of the system during stable operation are listed in Table 1.

[0060] Table 1

[0061] project numerical values Propylene feedstock tank pressure (propylene saturated vapor pressure), kPaA 2000 The level difference between the propylene feedstock tank and the propylene buffer tank, in meters. 3 PCV1 is set to pressure, kPaA 1950 PCV2 sets the pressure, kPaA 2050

[0062] Through this implementation method, after nitrogen replacement, the nitrogen content in the propylene buffer tank is 0.01 vol%, the propylene content in the outlet stream of valve 4 is 0.01 vol%, and the valve is closed after replacement, resulting in almost no pollution to the environment.

[0063] Comparative Example 1

[0064] Adopting such Figure 2 The apparatus shown is used for propylene feeding.

[0065] A pilot plant uses Figure 2 The propylene feeding method and system shown above, as well as the specific implementation method described above, and the main process operating parameters of the system during stable operation are listed in Table 2.

[0066] Table 2

[0067] project numerical values Propylene tank pressure (propylene saturated vapor pressure), kPaA 2000 High-pressure nitrogen pressure, kPaA 5000 Nitrogen gas volume fraction in propylene tank, vol%. 20 Nitrogen gas volume fraction (vol%) in propylene buffer tank 2

[0068] As can be seen from the table, in this embodiment, propylene filling requires high-pressure nitrogen purging, the nitrogen content in the propylene tank reaches 20%, and the nitrogen content in the propylene buffer tank reaches 2%, causing contamination of the propylene tank. Furthermore, due to the presence of nitrogen in the propylene buffer tank, the liquid propylene contains a certain amount of nitrogen during the transport of propylene, which can easily cause cavitation of the propylene pump during the propylene transport process, affecting the stable operation of the equipment.

[0069] The technical solutions of the present invention are not limited to the specific embodiments described above. Any technical modifications made in accordance with the technical solutions of the present invention fall within the protection scope of the present invention.

Claims

1. A method for feeding propylene, comprising the following steps: (1) Fill the propylene buffer tank with nitrogen gas; (2) Connect the propylene feed tank and the propylene buffer tank so that the propylene in the propylene feed tank enters the propylene buffer tank until the nitrogen in the propylene buffer tank is completely replaced by gaseous propylene. (3) To achieve gas phase equilibrium between the propylene raw material tank and the propylene buffer tank, the propylene in the propylene raw material tank is introduced into the propylene buffer tank by adjusting the liquid level difference between the propylene raw material tank and the propylene buffer tank. (4) Cool the propylene in the propylene buffer tank and transport it to the propylene reaction unit.

2. The method according to claim 1, characterized in that, In step (2), the nitrogen in the propylene buffer tank is completely replaced with gaseous propylene by setting the pressure at the gaseous outlet of the propylene buffer tank to be lower than the propylene vapor pressure, preferably 10 to 100 kPaA lower than the propylene vapor pressure.

3. The method according to claim 1 or 2, characterized in that, In step (3), achieving vapor-phase equilibrium between the propylene feedstock tank and the propylene buffer tank is accomplished by adjusting the pressure at the vapor outlet of the propylene buffer tank to be higher than the propylene vapor pressure, preferably 10–100 kPaA higher; and / or, In step (3), the liquid level in the propylene feedstock tank is at least 1m higher than the liquid level in the propylene buffer tank, preferably 2m to 5m; and / or, In step (3), the volume of liquid propylene entering the propylene buffer tank is 20% to 80% of the volume of the propylene buffer tank.

4. The method according to any one of claims 1 to 3, characterized in that, Step (4) further includes: before cooling, adjusting the pressure inside the propylene buffer tank to be higher than the propylene vapor pressure, preferably 10–100 kPaA higher than the propylene vapor pressure; and / or, In step (4), the temperature of the propylene after cooling is at least 5°C lower than the temperature of the propylene buffer tank, more preferably 10–30°C lower; and / or, In step (4), the cooled propylene is transported to the propylene reaction unit by a booster pump; preferably, the propylene temperature at the inlet of the booster pump is at least 5°C lower than the temperature of the propylene buffer tank, more preferably 10-30°C lower than the temperature of the propylene buffer tank.

5. The method according to any one of claims 1 to 4, characterized in that, The propylene buffer tank comprises N propylene buffer tanks connected in parallel, where N≥2, preferably 2≤N≤5; Preferably, the propylene buffer tank includes a first propylene buffer tank and a second propylene buffer tank connected in parallel; More preferably, in step (4), the propylene in the first propylene buffer tank is first transported to the propylene reaction unit, and when the liquid level in the first propylene buffer tank drops to below 20%, the propylene in the second propylene buffer tank is then transported to the propylene reaction unit. More preferably, in step (4), while the propylene in the second propylene buffer tank is being transported to the propylene reaction unit, the propylene raw material tank is connected to the first propylene buffer tank and step (3) is repeated, so that the propylene in the propylene raw material tank enters the first propylene buffer tank for replenishment.

6. A propylene feeding system, comprising a propylene feed tank, a propylene buffer device, a cooler, and a booster pump connected sequentially by pipelines; wherein, The liquid level in the propylene feed tank is higher than the liquid level in the propylene buffer device; The propylene buffer unit is provided with a gas phase port at the top, which is connected to the top of the propylene feedstock tank through a first pipe. The first pipe is provided with a high-pressure nitrogen inlet and a first pressure regulating device. The high-pressure nitrogen inlet is used to deliver high-pressure nitrogen to the propylene buffer unit, and the first pressure regulating device is used to regulate the pressure at the gas phase port of the propylene buffer unit so that the nitrogen delivered to the propylene buffer unit is completely replaced by gaseous propylene, or so that the propylene feedstock tank and the propylene buffer unit reach gas phase equilibrium.

7. The system according to claim 6, characterized in that, The top of the propylene buffer unit is also connected to the outlet of the booster pump via a second pipe. A second pressure regulating device is installed on the second pipe to regulate the pressure within the propylene buffer unit; and / or, The bottom of the propylene buffer device has a liquid phase port, which is connected to the bottom of the propylene feed tank via a pipe. The liquid phase port of the propylene buffer device is also connected to a cooler and a booster pump in sequence via pipes.

8. The system according to claim 6 or 7, characterized in that, The propylene buffer device comprises N propylene buffer tanks connected in parallel, where N≥2, preferably 2≤N≤5, and more preferably N=2.

9. The system according to any one of claims 6 to 8, characterized in that, The propylene buffer unit includes a first propylene buffer tank and a second propylene buffer tank connected in parallel, and the first propylene buffer tank and the second propylene buffer tank are configured as follows: Propylene in the first propylene buffer tank is first transported to the propylene reaction unit via a cooler and a booster pump. When the liquid level in the first propylene buffer tank drops below 20%, propylene in the second propylene buffer tank is then transported to the propylene reaction unit via a cooler and a booster pump. At the same time, propylene in the propylene feed tank enters the first propylene buffer tank for replenishment.

10. The application of the propylene feeding system according to any one of claims 6 to 9 in a reaction using propylene as a raw material.

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