Chemical grade propylene purification system

Abstract

The utility model provides a kind of chemical grade propylene purification system, including buffer pressure tank, first drying tower, second drying tower, selective hydrogenation reactor, deethanizer, propane propylene separation tower, on-line analyzer, three-way pneumatic fast switch valve and control unit;The material outlet of first drying tower and the material outlet of second drying tower are connected with the valve body import of three-way pneumatic fast switch valve after being converged by pipeline, and on-line analyzer is arranged on the pipeline after convergence;Normal outlet of three-way pneumatic fast switch valve is connected with the first material inlet of selective hydrogenation reactor by pipeline, bypass return outlet of three-way pneumatic fast switch valve is connected with the buffer tank backflow port of buffer pressure tank by pipeline.The utility model carries out organic integration by buffer pressure, continuous drying, on-line analysis and safety cut-off etc., and systematically solves the technical problems such as high safety risk, poor stability and low material management efficiency when introducing external chemical grade propylene into main device.

Description

Technical Field

[0001] This utility model relates to a system for olefin purification, specifically a chemical-grade propylene purification system, belonging to the field of petrochemical technology. Background Technology

[0002] In petrochemical production, some companies generate low-purity chemical-grade propylene. This propylene, due to its insufficient purity to meet polymer-grade standards (typically requiring greater than 99.5%), has a lower added value in the market. Meanwhile, propane dehydrogenation (PDH) units are the mainstream process for producing polymer-grade propylene. These units include a complete and efficient separation and purification system, such as selective hydrogenation reactors, deethanerization towers, and propane-propylene separation towers. Theoretically, external chemical-grade propylene can be introduced into the separation units of a PDH unit for purification, thereby increasing its value.

[0003] However, in practice, especially when the PDH main unit is running at full load and stable, directly introducing external material flows poses significant process risks. Chemical-grade propylene often contains impurities such as moisture, dienes, and alkynes. Moisture can deactivate downstream hydrogenation catalysts, while dienes and alkynes can affect the quality of the final product. The flow rate, pressure, and composition of materials transported through external pipelines may fluctuate. Any fluctuation can impact the separation tower system, leading to substandard products from the main unit, increased energy consumption, and even safety shutdowns. Utility Model Content

[0004] Based on the above background, the purpose of this utility model is to provide a chemical-grade propylene purification system to solve the technical problems of large process fluctuations, high safety risks, and difficulty in stable operation when external low-purity chemical-grade propylene is directly introduced into the main unit in the prior art.

[0005] To achieve the above-mentioned objectives, this utility model provides the following technical solution:

[0006] A chemical-grade propylene purification system includes a buffer pressure tank, a first drying tower, a second drying tower, a selective hydrogenation reactor, an ethane removal tower, a propane-propylene separation tower, an online analyzer, a three-way pneumatic quick-cut valve, and a control unit. The buffer pressure tank has a feed inlet, a discharge outlet, and a reflux outlet. The first and second drying towers are connected in parallel, each with a material inlet, a material outlet, a regeneration gas inlet, and a regeneration gas outlet. The three-way pneumatic quick-cut valve has a valve body inlet, a normal outlet, and a bypass return outlet. The selective hydrogenation reactor has a first material inlet. The selective hydrogenation reactor is connected to the ethane removal tower and the propane-propylene separation tower. The buffer tank outlet of the buffer pressure stabilizing tank is connected sequentially via pipelines to the material inlets of the first drying tower and the second drying tower via pipelines; the material outlets of the first drying tower and the second drying tower are connected to the valve body inlet of the three-way pneumatic quick-cut valve via pipelines, and the online analyzer is installed on the pipeline after the connection; the normal outlet of the three-way pneumatic quick-cut valve is connected to the first material inlet of the selective hydrogenation reactor via pipelines, and the bypass return outlet of the three-way pneumatic quick-cut valve is connected to the buffer tank return port of the buffer pressure stabilizing tank via pipelines; the control unit is electrically connected to the online analyzer and the three-way pneumatic quick-cut valve respectively.

[0007] Preferably, the regeneration gas inlet of the first drying tower and the regeneration gas inlet of the second drying tower are used to connect to an external main unit hot regeneration gas source through pipelines, and the regeneration gas outlet of the first drying tower and the regeneration gas outlet of the second drying tower are used to connect to an external fuel gas system through pipelines.

[0008] Preferably, the selective hydrogenation reactor is further provided with a second material inlet, which is used to connect to the product outlet of an external propane dehydrogenation reaction unit via a pipeline.

[0009] Preferably, the propane-propylene separation tower is provided with a propylene outlet and a propane outlet, which are used to connect to the feed inlet of an external propane dehydrogenation reaction unit via pipeline.

[0010] Preferably, the online analyzer is an online gas chromatograph.

[0011] Preferably, the control unit is configured to, when receiving a signal triggered by the online analyzer indicating that the concentration of impurities in chemical-grade propylene on the pipeline after the material outlets of the first drying tower and the second drying tower merge is higher than a preset threshold, operate the three-way pneumatic quick-cut valve to close the normal outlet and open the bypass return outlet.

[0012] Preferably, a first valve is provided on the pipeline connecting the outlet of the buffer tank of the buffer pressure stabilizing tank and the material inlet of the first drying tower; a second valve is provided on the pipeline connecting the outlet of the buffer tank of the buffer pressure stabilizing tank and the material inlet of the second drying tower; a third valve is provided on the pipeline connecting the material outlet of the first drying tower and the valve body inlet of the three-way pneumatic quick-cut valve; and a fourth valve is provided on the pipeline connecting the material outlet of the second drying tower and the valve body inlet of the three-way pneumatic quick-cut valve. The first, second, third, and fourth valves are used to switch between the flow of chemical-grade propylene through the first drying tower and the second drying tower.

[0013] Preferably, a fifth valve is provided on the pipeline connecting the regenerated gas inlet of the first drying tower, a sixth valve is provided on the pipeline connecting the regenerated gas inlet of the second drying tower, a seventh valve is provided on the pipeline connecting the regenerated gas outlet of the first drying tower, and an eighth valve is provided on the pipeline connecting the regenerated gas outlet of the second drying tower. The fifth, sixth, seventh, and eighth valves are used to switch the flow of hot regenerated gas through the first drying tower or the second drying tower.

[0014] Compared with the prior art, the present invention has the following advantages:

[0015] This invention relates to a chemical-grade propylene purification system. By organically integrating functional modules such as buffering and stabilizing, continuous drying, online analysis, and safety shut-off, it systematically solves the technical problems of high safety risks, poor stability, and low material management efficiency when introducing external chemical-grade propylene into the main unit. The system constructs a control loop consisting of an online analyzer, a three-way pneumatic quick-cut valve, and a control unit. Combined with a buffering and stabilizing tank, it pre-processes incoming material fluctuations, enabling real-time monitoring of the pre-treated material quality. Upon detecting an anomaly, it automatically cuts off the entry channel into the main unit and initiates an internal circulation system via a bypass return pipeline, sending the substandard material back to the system front for remixing. By setting up a first and second drying tower in parallel, the system achieves a continuous operation mode with one tower in use and one in standby. When one drying tower is operating online, the other saturated tower can simultaneously undergo offline regeneration. The entire switching process does not affect the continuous supply of the main material flow, ensuring uninterrupted system operation. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of a chemical-grade propylene purification system according to this utility model;

[0018] In the diagram: 1. Feed pump; 2. Buffer and pressure stabilizing tank; 3. First drying tower; 4. Second drying tower; 5. Online analyzer; 6. Control unit; 7. Three-way pneumatic quick-cut valve; 8. First valve; 9. Second valve; 10. Third valve; 11. Fourth valve; 12. Fifth valve; 13. Sixth valve; 14. Seventh valve; 15. Eighth valve; 16. Selective hydrogenation reactor; 17. Ethane removal tower; 18. Propane-propylene separation tower. Detailed Implementation

[0019] The technical solution of this utility model will be further described in detail below through specific embodiments and in conjunction with the accompanying drawings. It should be understood that the implementation of this utility model is not limited to the following embodiments, and any modifications and / or alterations made to this utility model will fall within the protection scope of this utility model.

[0020] In this invention, unless otherwise specified, all parts and percentages are by weight, and the equipment and raw materials used are commercially available or commonly used in the field. Unless otherwise specified, the methods in the following embodiments are conventional methods in the field. Unless otherwise specified, the components or equipment in the following embodiments are general standard parts or components known to those skilled in the art, and their structures and principles can be learned by those skilled in the art through technical manuals or conventional experimental methods.

[0021] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings. In the following detailed description, many specific details are set forth to facilitate explanation and provide a comprehensive understanding of the embodiments of the present invention. However, one or more embodiments may be practiced by those skilled in the art without these specific details.

[0022] like Figure 1 As shown, an embodiment of this utility model discloses a chemical-grade propylene purification system, including a buffer pressure stabilizing tank 2, a first drying tower 3, a second drying tower 4, a selective hydrogenation reactor 16, an ethane removal tower 17, a propane-propylene separation tower 18, an online analyzer 5, a three-way pneumatic quick-cut valve 7, and a control unit 6.

[0023] The buffer pressure stabilizing tank 2 is equipped with a buffer tank inlet, a buffer tank outlet, and a buffer tank reflux outlet. The first drying tower 3 and the second drying tower 4 are connected in parallel, and each of the first drying tower 3 and the second drying tower 4 is equipped with a material inlet, a material outlet, a regenerated gas inlet, and a regenerated gas outlet. The regenerated gas inlet of the first drying tower 3 and the regenerated gas inlet of the second drying tower 4 are used to connect to an external main unit hot regenerated gas source through pipelines, and the regenerated gas outlet of the first drying tower 3 and the regenerated gas outlet of the second drying tower 4 are used to connect to an external fuel gas system through pipelines.

[0024] The three-way pneumatic quick-cut valve 7 has a valve body inlet, a normal outlet, and a bypass return outlet. The selective hydrogenation reactor 16 has a first material inlet and is sequentially connected to the deethaner 17 and the propane-propylene separator 18 via pipelines. The selective hydrogenation reactor 16 also has a second material inlet, which is used to connect via pipelines to the product outlet of an external propane dehydrogenation reaction unit. The propane-propylene separator 18 has a propylene outlet and a propane outlet, which are used to connect via pipelines to the feed inlet of an external propane dehydrogenation reaction unit.

[0025] The outlet of the buffer tank of the pressure stabilizing tank 2 is connected to the material inlet of the first drying tower 3 and the material inlet of the second drying tower 4 via pipelines. The material outlets of the first drying tower 3 and the second drying tower 4 are merged via pipelines and connected to the valve body inlet of the three-way pneumatic quick-cut valve 7, with the online analyzer 5 installed on the merged pipeline. The normal outlet of the three-way pneumatic quick-cut valve 7 is connected to the first material inlet of the selective hydrogenation reactor 16 via a pipeline, and the bypass return outlet of the three-way pneumatic quick-cut valve 7 is connected to the buffer tank reflux port of the pressure stabilizing tank 2 via a pipeline.

[0026] The control unit 6 is electrically connected to the online analyzer 5 and the three-way pneumatic quick-cut valve 7. The online analyzer 5 is an online gas chromatograph. The control unit 6 is configured to, when it receives a signal from the online analyzer 5 indicating that the concentration of impurities in the chemical-grade propylene at the confluence of the material outlets of the first drying tower 3 and the second drying tower 4 exceeds a preset threshold, operate the three-way pneumatic quick-cut valve 7 to close the normal outlet and open the bypass return outlet.

[0027] In addition, a first valve 8 is installed on the pipeline connecting the outlet of the buffer tank 2 to the material inlet of the first drying tower 3; a second valve 9 is installed on the pipeline connecting the outlet of the buffer tank 2 to the material inlet of the second drying tower 4; a third valve 10 is installed on the pipeline connecting the material outlet of the first drying tower 3 to the valve body inlet of the three-way pneumatic quick-cut valve 7; and a fourth valve 11 is installed on the pipeline connecting the material outlet of the second drying tower 4 to the valve body inlet of the three-way pneumatic quick-cut valve 7. The first valve 8, the second valve 9, the third valve 10, and the fourth valve 11 are used to switch between the flow of chemical-grade propylene through the first drying tower 3 and the second drying tower 4.

[0028] A fifth valve 12 is installed on the pipeline connecting to the regeneration gas inlet of the first drying tower 3; a sixth valve 13 is installed on the pipeline connecting to the regeneration gas inlet of the second drying tower 4; a seventh valve 14 is installed on the pipeline connecting to the regeneration gas outlet of the first drying tower 3; and an eighth valve 15 is installed on the pipeline connecting to the regeneration gas outlet of the second drying tower 4. The fifth valve 12, sixth valve 13, seventh valve 14, and eighth valve 15 are used to switch the flow of hot regeneration gas through either the first drying tower 3 or the second drying tower 4.

[0029] The workflow of this chemical-grade propylene purification system is described below.

[0030] External chemical-grade propylene is pressurized by feed pump 1 and then enters buffer pressure stabilizing tank 2 through the feed inlet of buffer tank.

[0031] Stable propylene is drawn from the outlet of the buffer tank 2. Assuming the first drying tower 3 is currently operating online, valves 8 and 10 are open, while valves 9 and 11 are closed. Propylene flows through valve 8 into the material inlet of the first drying tower 3. Inside the tower, the propylene comes into full contact with the desiccant, such as the molecular sieve, removing trace amounts of moisture. The dried propylene flows out from the material outlet of the first drying tower 3 and enters the subsequent pipeline via valve 10.

[0032] The dried propylene flows through an online analyzer 5 installed on the main pipeline, which analyzes the purity and impurity content of the propylene in real time. The analysis results are transmitted to the control unit 6 via a signal line. If the impurity content is lower than a preset safety threshold, the control unit 6 determines that the material is qualified and maintains the three-way pneumatic quick-cut valve 7 in its normal state, i.e., its normal outlet is open and the bypass return outlet is closed. The qualified propylene flows through the valve body inlet and normal outlet, enters the connecting pipeline, and is sent to the first material inlet of the selective hydrogenation reactor 16.

[0033] If the online analyzer 5 detects that the impurity concentration exceeds the standard, it will immediately send an alarm signal to the control unit 6. Upon receiving the signal, the control unit 6 immediately executes the preset safety procedure, issuing a command to the three-way pneumatic quick-cut valve 7 to activate it instantly, closing the normal outlet and simultaneously opening the bypass return outlet. At this time, the substandard propylene flow will be immediately cut off, preventing it from entering the downstream main unit. This substandard propylene will enter the return pipeline through the bypass return outlet and eventually return to the buffer tank return port of the buffer pressure tank 2. Inside the buffer tank, the substandard material is mixed and diluted with the subsequent incoming material. After the overall material quality of the system returns to normal, it will re-enter the purification process.

[0034] Qualified propylene enters the selective hydrogenation reactor 16, where it mixes with the main product stream from the propane dehydrogenation unit, which enters from the second feed inlet. Under the action of a catalyst, trace amounts of residual dienes and alkynes in the propylene are selectively hydrogenated into propylene and propane. Subsequently, the mixture sequentially enters the deethanizer 17 and the propane-propylene separator 18. In the deethanizer 17, light components such as methane and ethane are separated from the top and enter the fuel gas system. The bottom material enters the propane-propylene separator 18, ultimately yielding high-purity polymer-grade propylene at the top and unreacted propane at the bottom, which is returned to the propane dehydrogenation unit for recycling through the propane outlet.

[0035] After the first drying tower 3 has been operating online for a period of time, the desiccant inside will become saturated with water. At this point, it needs to be regenerated, and the system switched to the second drying tower 4 for online drying to ensure continuous system operation. During the switchover, first valve 8 and third valve 10 are closed, while second valve 9 and fourth valve 11 are opened, switching the main material flow to the second drying tower 4. Subsequently, the first drying tower 3 is regenerated. Fifth valve 12 and seventh valve 14 are opened, and sixth valve 13 and eighth valve 15 are closed. Hot regeneration gas from the main unit enters the regeneration gas inlet of the first drying tower 3 through fifth valve 12, purging the desiccant and carrying away the moisture. The regeneration exhaust gas containing moisture flows out from the regeneration gas outlet and enters the fuel gas system through seventh valve 14. After regeneration is complete, the corresponding valves are closed, putting the first drying tower 3 into standby mode, awaiting the next switchover.

[0036] This article uses specific examples to illustrate the principles and implementation methods of this utility model. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this utility model. It should be noted that for those skilled in the art, several improvements and modifications can be made to this utility model without departing from the principles of this utility model, and these improvements and modifications also fall within the protection scope of the claims of this utility model.

Claims

1. A chemical-grade propylene purification system, characterized in that: The chemical-grade propylene purification system includes a buffer pressure tank (2), a first drying tower (3), a second drying tower (4), a selective hydrogenation reactor (16), a deethaner (17), a propane-propylene separation tower (18), an online analyzer (5), a three-way pneumatic quick-cut valve (7), and a control unit (6). The buffer pressure tank (2) is provided with a buffer tank inlet, a buffer tank outlet, and a buffer tank reflux outlet. The first drying tower (3) and the second drying tower (4) are connected in parallel, and both the first drying tower (3) and the second drying tower (4) are respectively provided with a material inlet, a material outlet, a regenerated gas inlet, and a regenerated gas outlet. The three-way pneumatic quick-cut valve (7) is provided with a valve body inlet, a normal outlet, and a bypass return outlet. The selective hydrogenation reactor (16) is provided with a first material inlet. The selective hydrogenation reactor (16) is connected to the deethaner (17) and the propane-propylene separation tower (18). The alkane-propylene separation tower (18) is connected in sequence by pipelines; the outlet of the buffer tank of the buffer pressure stabilizing tank (2) is connected to the material inlet of the first drying tower (3) and the material inlet of the second drying tower (4) by pipelines; the material outlet of the first drying tower (3) and the material outlet of the second drying tower (4) are connected to the valve body inlet of the three-way pneumatic quick-cut valve (7) after they are merged by pipelines, and the online analyzer (5) is set on the pipeline after the merger; the normal outlet of the three-way pneumatic quick-cut valve (7) is connected to the first material inlet of the selective hydrogenation reactor (16) by pipelines, and the bypass return outlet of the three-way pneumatic quick-cut valve (7) is connected to the buffer tank return port of the buffer pressure stabilizing tank (2) by pipelines; the control unit (6) is electrically connected to the online analyzer (5) and the three-way pneumatic quick-cut valve (7) respectively.

2. The chemical-grade propylene purification system according to claim 1, characterized in that: The regeneration gas inlet of the first drying tower (3) and the regeneration gas inlet of the second drying tower (4) are used to connect to the external main unit heat regeneration gas source through pipelines, and the regeneration gas outlet of the first drying tower (3) and the regeneration gas outlet of the second drying tower (4) are used to connect to the external fuel gas system through pipelines.

3. The chemical-grade propylene purification system according to claim 1, characterized in that: The selective hydrogenation reactor (16) is also provided with a second material inlet, which is used to connect to the product outlet of an external propane dehydrogenation reaction unit via a pipeline.

4. The chemical-grade propylene purification system according to claim 1, characterized in that: The propane-propylene separation tower (18) is equipped with a propylene outlet and a propane outlet, which are used to connect to the raw material inlet of an external propane dehydrogenation reaction unit via pipeline.

5. The chemical-grade propylene purification system according to claim 1, characterized in that: The online analyzer (5) is an online gas chromatograph.

6. The chemical-grade propylene purification system according to claim 1, characterized in that: The control unit (6) is configured to, when it receives a signal triggered by the online analyzer (5) indicating that the concentration of impurities in chemical-grade propylene on the pipeline after the material outlet of the first drying tower (3) and the material outlet of the second drying tower (4) merges is higher than a preset threshold, operate the three-way pneumatic quick-cut valve (7) to close the normal outlet and open the bypass return outlet.

7. The chemical-grade propylene purification system according to claim 1, characterized in that: A first valve (8) is provided on the pipeline connecting the outlet of the buffer tank (2) to the material inlet of the first drying tower (3). A second valve (9) is provided on the pipeline connecting the outlet of the buffer tank (2) to the material inlet of the second drying tower (4). A third valve (10) is provided on the pipeline connecting the material outlet of the first drying tower (3) to the valve body inlet of the three-way pneumatic quick-cut valve (7). A fourth valve (11) is provided on the pipeline connecting the material outlet of the second drying tower (4) to the valve body inlet of the three-way pneumatic quick-cut valve (7). The first valve (8), the second valve (9), the third valve (10) and the fourth valve (11) are used to switch between chemical grade propylene flowing through the first drying tower (3) or the second drying tower (4).

8. The chemical-grade propylene purification system according to claim 1, characterized in that: A fifth valve (12) is provided on the pipeline connecting the regenerated gas inlet of the first drying tower (3), a sixth valve (13) is provided on the pipeline connecting the regenerated gas inlet of the second drying tower (4), a seventh valve (14) is provided on the pipeline connecting the regenerated gas outlet of the first drying tower (3), and an eighth valve (15) is provided on the pipeline connecting the regenerated gas outlet of the second drying tower (4). The fifth valve (12), the sixth valve (13), the seventh valve (14) and the eighth valve (15) are used to switch the flow of hot regenerated gas through the first drying tower (3) or the second drying tower (4).

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