A propylene recovery system in a crude propylene material

Abstract

The application discloses a crude propylene material propylene recycling system, and belongs to the technical field of propylene recycling systems. A reaction unit is arranged on the upstream of a crude propylene tank, the reaction unit is connected with a propylene recycling unit through pipelines, the propylene recycling unit is connected with a propylene reflux tank through pipelines, the temperature in the propylene reflux tank is 35+ / -2 DEG C, and the pressure is 2.0+ / -0.15 MPaG. A liquid collector is arranged in the propylene reflux tank, the liquid collector is connected with the crude propylene tank through pipelines, and a sampler a, a flowmeter c and a valve are arranged on the pipelines. Tail gas pipelines on the top of the propylene reflux tank are connected with an absorption tower. On the basis of removing propane, ethylene, butylene, CO, CO2 and the like in the crude propylene, the crude propylene is purified, propylene in the crude propylene and propylene in the exhaust gas discharged from the propylene reflux tank are recycled, propylene unit consumption is reduced, and cost is saved.

Description

Technical Field

[0001] This invention relates to the field of propylene recovery system technology, specifically to a propylene recovery and utilization system for crude propylene materials. Background Technology

[0002] Propylene oxide is an important basic organic chemical raw material, ranking third in production volume among propylene derivatives after polypropylene and acrylonitrile. It is widely used in the chemical, pharmaceutical, food, and textile industries. Currently, the main industrial production processes for propylene oxide are the chlorohydrin process and the co-oxidation process. However, the chlorohydrin process consumes large amounts of chlorine, lime, and water, suffers from severe equipment corrosion, generates large amounts of wastewater and waste residue, causing serious environmental pollution, and has low raw material utilization. Therefore, this method is gradually being phased out by various countries. The co-oxidation process, based on the type of co-product, is further divided into the PO / SM (styrene) process, the PO / TBA (tert-butanol) process, and the PO / MTBE (methyl tert-butyl ether) process. The disadvantages of the co-oxidation process are large co-product yields, complex production processes, and high investment costs.

[0003] The direct hydrogen peroxide oxidation process (HPPO process) for producing propylene oxide has a high hydrogen peroxide conversion rate, high propylene oxide selectivity, and few by-products. It has been listed as an encouraged process by the National Development and Reform Commission. At the same time, the propylene oxide produced by this process is currently the only product in China that is allowed to be exported, and it represents the future direction of propylene oxide production technology.

[0004] In the HPPO production process, propylene and hydrogen peroxide are used as raw materials, and methanol is used as a solvent to react and produce propylene oxide. During the reaction, the hydrogen peroxide reacts completely, resulting in an excess of propylene. Therefore, a propylene recovery unit is needed to recover the propylene, and the unreacted propylene in the system is recycled into a propylene reflux tank for use in the reaction unit. During the propylene recovery unit's separation and recovery of propylene, propylene and light component impurities such as propane, ethylene, butene, CO, and CO2 cannot be separated and accumulate in the system. This leads to a high impurity content in the recycled propylene, forming crude propylene. To maintain a stable propylene concentration and ensure the stable progress of the propylene oxide reaction, the crude propylene in the propylene reflux tank must be discharged, and high-purity raw material propylene must be used for replacement. The discharged crude propylene has a high propylene content (propylene > 80 wt%), resulting in propylene loss, high propylene consumption, and increased operating costs. Therefore, it is necessary to purify propylene from crude propylene for recycling. Although the inventions with application numbers 201711458909.1 and 202121389537.3 have optimized and adjusted the process and compression method of the original propylene recycling process, they have not taken into account the impact of impurities in propylene and the treatment measures, and have not removed impurities from crude propylene, thus failing to purify propylene. Summary of the Invention

[0005] To address the technical problems mentioned in the background section, the present invention provides a propylene recovery and utilization system for crude propylene materials, employing the following technical solution:

[0006] The system includes a crude propylene tank equipped with pressure gauge a. The crude propylene tank is connected via pipeline to a light propylene removal tower, which is equipped with a crude propylene transfer pump, flow meter a, and valves. The light propylene removal tower is equipped with pressure gauge b. A reboiler a is connected to one side of the light propylene removal tower via pipeline, and a reboiler heat source a is connected to reboiler a. The light propylene removal tower is connected to a distillation column via pipeline, which is equipped with flow meter b and valves. The distillation column is equipped with pressure gauge c. A reboiler b is connected to one side of the distillation column via pipeline. A reboiler heat source b is connected to the boiling vessel b. A reaction unit is installed upstream of the crude propylene tank. The reaction unit is connected to the propylene recovery unit via a pipeline. The propylene recovery unit is connected to the propylene reflux tank via a pipeline. A pressure gauge d is installed on the propylene reflux tank. The temperature inside the propylene reflux tank is 35±2℃ and the pressure is 2.0±0.15MPaG. A liquid collector is installed inside the propylene reflux tank. The liquid collector is connected to the crude propylene tank via a pipeline, and a sampler a, a flow meter c, and a valve are installed on the pipeline.

[0007] Preferably, the propylene reflux tank is connected to the reaction unit and the propylene recovery unit via pipelines, and a circulating propylene pump is installed on the pipelines.

[0008] Preferably, the propylene reflux tank is connected to the absorption tower via a tail gas pipeline; the absorption tower uses an absorbent to absorb the propylene in the tail gas.

[0009] Preferably, after the absorbent tower has absorbed propylene, the absorbent is transported to the reaction unit via an absorbent circulation pipeline using an absorbent bottom pump.

[0010] Preferably, the exhaust gas from the top of the absorption tower is sent to the incinerator for incineration via a waste gas pipeline.

[0011] Preferably, the upper part of the light-light removal tower is connected to a light-light removal tower reflux tank via a pipeline, and a cooler a (21) and a thermometer a are installed on the pipeline.

[0012] Preferably, the bottom of the light-light-removal tower reflux tank is connected to the light-light-removal tower via a pipeline, and a light-light-removal tower reflux pump is installed on the pipeline.

[0013] Preferably, the upper part of the distillation column is connected to a distillation column reflux tank via a pipeline, and a cooler b and a thermometer b are installed on the pipeline. The distillation column reflux tank is equipped with a tail gas discharge pipeline, and the tail gas discharge pipeline is connected to the light-duty removal column reflux tank via a pipeline.

[0014] Preferably, the bottom of the distillation column reflux tank is connected to the distillation column via a pipeline, and a distillation column reflux pump is installed on the pipeline. A pipeline extends from the pipeline on the distillation column reflux pump, and a flow meter d, a valve, a sampler b, and a pressure gauge d are installed on the extended pipeline. The extended pipeline is connected to the propylene reflux tank.

[0015] Preferably, the bottom of the distillation column is provided with a pipeline and a flow meter e, a valve, a cooler c, a sampler c, and a thermometer c are installed on the pipeline.

[0016] Preferably, a level gauge is installed on the propylene reflux tank.

[0017] The present invention has the following advantages:

[0018] Before removing light components such as propane, ethylene, butene, CO, and CO2 through the crude propylene tank, light component removal tower, and distillation tower, the crude propylene remaining after the reaction in the reaction unit is sent to the propylene recovery unit. The crude propylene in the propylene recovery unit then enters the propylene reflux tank, which is equipped with a liquid collector. At this point, propylene, propane, and small amounts of impurities such as methanol and water in the crude propylene are collected in the liquid collector. Since the pressure inside the propylene reflux tank is 2.0 ± 0.15 MPaG, the crude propylene in the liquid collector enters through the pipeline under the action of the pressure difference. A crude propylene tank is used, and sampler A periodically extracts a small portion of the mixed liquid from the pipeline to analyze the propylene and propane content. The propylene content in the pipeline is maintained between 85-95%. If it's below this range, the crude propylene discharge flow rate is low. In this case, the flow rate setpoint of flow meter C is increased, and flow meter C sends a signal to the valve on the pipeline, causing the valve to increase the pipeline flow rate. If the propylene content in the pipeline is above this range, the crude propylene discharge flow rate is high, and the flow rate setpoint of flow meter C is decreased. By stabilizing the amount of discharged propylene, the propylene content in the crude propylene tank is controlled, thereby ensuring a stable propylene concentration in the circulating propylene system.

[0019] A small amount of propylene, along with non-condensable gases such as ethylene, CO, CO2, and nitrogen, from the propylene reflux tank enters the absorption tower through the tail gas pipeline. The propylene in the tail gas is recovered by an absorbent in the absorption tower and then pumped to the reaction unit for reaction through the bottom pump of the absorption tower, which further reduces the loss of propylene. At the same time, light component impurities such as ethylene, CO, CO2, and nitrogen in the system are discharged to the incinerator for incineration.

[0020] Compared with existing processes, the present invention provides a propylene recovery and utilization system for crude propylene material. The system recovers propylene from the crude propylene material and propylene from the exhaust gas. Impurities in the crude propylene are separated by a light propylene removal tower and a distillation tower to obtain refined propylene, which is then returned to the unit for recycling. The system requires less equipment investment and occupies less space. It effectively recovers propylene from the crude propylene material and exhaust gas, reducing energy waste and achieving energy saving and consumption reduction. It greatly saves the consumption of propylene raw materials and reduces the unit's propylene consumption. At the same time, the recovery system uses the unit's abundant low-pressure steam condensate or hot water as a heat source for heating, making reasonable and effective use of the unit's energy, avoiding energy waste and saving costs. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the process of the present invention.

[0022] Attached diagrams: 1. Reaction unit; 2. Propylene recovery unit; 3. Propylene reflux tank; 4. Pressure gauge d; 5. Liquid collector; 6. Interface gauge; 7. Circulating propylene pump; 8. Sampler a; 9. Flow meter c; 10. Crude propylene tank; 11. Pressure gauge a; 12. Crude propylene transfer pump; 13. Tail gas pipeline; 14. Flow meter a; 15. Absorbent tower; 16. Reboiler heat source a; 17. Pressure gauge b; 18. Light propylene removal tower; 19. Reboiler a; 20. Absorbent; 21. Cooler a; 22. Thermometer a; 23. Reboiler heat source b; 24. Light propylene removal tower. 25. Reflux tank for distillation column, 26. Reflux pump for light precipitator, 27. Flow meter b, 28. Pressure gauge c, 29. Distillation column, 30. Reboiler b, 31. Propylene feedstock pipeline, 32. Cooler b, 33. Thermometer b, 34. Reflux pump for distillation column, 35. Sampler b, 36. Pressure gauge d, 37. Reflux tank for distillation column, 38. Flow meter e, 49. Cooler c, 40. Sampler c, 41. Thermometer c, 42. Tail gas discharge pipeline, 43. Absorber bottom pump, 44. Absorbent circulation pipeline, 45. Waste gas pipeline.

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] For an example, please refer to... Figure 1 :

[0025] This invention provides a propylene recovery and utilization system for crude propylene material, including a crude propylene tank 10. A pressure gauge a11 is installed on the crude propylene tank 10 to monitor the pressure inside the tank. The crude propylene tank 10 is connected to a light propylene stripping tower 18 via a pipeline, which is equipped with a crude propylene transfer pump 12, a flow meter a14, and a valve. Wet steam enters the light propylene stripping tower 18 through the transfer pump 12. The flow meter a14 and the valve control the flow rate in the pipeline. A pressure gauge b17 is installed on the light propylene stripping tower 18 to monitor the pressure inside. A reboiler a19 is connected to one side of the light propylene stripping tower 18 via a pipeline. A reboiler heat source a16 is connected to the reboiler a19, which provides heat to the light propylene stripping tower 18 from hot water or low-pressure steam condensate.

[0026] Light component removal tower 18 is connected to distillation tower 28 via pipeline, which is equipped with flow meter b26 and valve. Crude propylene, after the removal of light components, enters distillation tower 28 through the pipeline. Flow meter b26 and valve control the flow rate in the pipeline. Pressure gauge c27 is installed on distillation tower 28 to monitor the pressure inside. A reboiler b29 is connected to one side of distillation tower 28 via pipeline. A reboiler heat source b23, which is hot water or low-pressure steam condensate, is connected to reboiler b29 and then supplied to distillation tower 28 to provide the necessary conditions for the distillation reaction. A reaction unit 1 is located upstream of crude propylene tank 10. The crude propylene mixture remaining after the reaction in reaction unit 1 enters propylene recovery unit 2 via pipeline. Reaction unit 1 is connected to propylene recovery unit 2 via pipeline. Propylene recovery unit 2 is connected to propylene return tank 3 via pipeline. Propylene mixture in propylene recovery unit 2 enters propylene return tank 3 via pipeline. Propylene return tank 3 is equipped with pressure gauge d4 to monitor the pressure inside propylene return tank 3. The temperature inside propylene return tank 3 is 35±2℃ and the pressure is 2.0±0.15MPaG. Propylene return tank 3 is equipped with liquid collector 5. At this time, propylene, propane and a small amount of methanol, water and other impurities in crude propylene are collected in liquid collector 5. Crude propylene in liquid collector 5 enters crude propylene tank 10 through pressure difference. Liquid collector 5 is connected to crude propylene tank 10 via pipeline, and the pipeline is equipped with sampler a8, flow meter c9 and valve.

[0027] The propylene reflux tank 3 is located at the bottom of the partition and is connected to the reaction unit 1 and the propylene recovery unit 2 via pipelines. A circulating propylene pump 7 is installed on the pipelines. The reaction liquid intercepted in the propylene reflux tank 3 can be transported to the reaction unit 1 and the propylene recovery unit 2 through the pipelines and the circulating propylene pump 7, so that the propylene in the crude propylene can be fully extracted.

[0028] The propylene reflux tank 3 is connected to the absorption tower 15 via the tail gas pipeline 13; the absorption tower 15 uses absorbent 20 to absorb the propylene in the tail gas.

[0029] After the propylene is absorbed by the absorption tower 15, the absorbent is transported to the reaction unit 1 through the absorbent circulation pipeline 44 via the absorption tower bottom pump 43.

[0030] The exhaust gas from the top of the absorption tower 15, such as nitrogen, ethylene, CO, and CO2, is sent to the incinerator for incineration through the waste gas pipeline 45.

[0031] The upper part of the light component removal tower 18 is connected to the light component removal tower reflux tank 24 via a pipeline, and a cooler a21 and a thermometer a22 are installed on the pipeline. The light components removed by the light component removal tower 18—propane, ethylene, butene, CO, and CO2—may carry a small amount of propylene, which can be further recovered through the light component removal tower reflux tank 24, effectively recovering more propylene.

[0032] The bottom of the light tower reflux tank 24 is connected to the light tower 18 via a pipeline, and a light tower reflux pump 25 is installed on the pipeline.

[0033] The upper part of the distillation column 28 is connected to the distillation column reflux tank 36 via a pipeline, and a cooler b31 and a thermometer b32 are installed on the pipeline. The light components that are further removed during the distillation of the distillation column 28—propane, ethylene, butene, CO, and CO2—enter the distillation column reflux tank 36 through the pipeline, are cooled by the cooler b3, and then enter the distillation column reflux tank 36, so that the liquid still carried in the light components remains in the distillation column reflux tank 36. The distillation column reflux tank 36 is equipped with a tail gas discharge pipeline 42, which is connected to the light component removal tower reflux tank 24 via a pipeline. The light components—propane, ethylene, butene, CO, and CO2—in the distillation column reflux tank 36 and the light component removal tower reflux tank 24 are discharged through the tail gas discharge pipeline 42.

[0034] The bottom of the distillation column reflux tank 36 is connected to the distillation column 28 via a pipeline, and a distillation column reflux pump 33 is installed on the pipeline. A small portion of the wet vapor in the distillation column reflux tank 36 is sent into the distillation column 28 through the pipeline and the distillation column reflux pump 33 to further recover propylene from the wet vapor. A pipeline on the distillation column reflux pump 33 extends out to a line equipped with a flow meter d37, a valve, a sampler b34, and a pressure gauge d35. The extended line is connected to the propylene reflux tank 3. The sampler b34 is used to analyze some of the light components in the pipeline of the distillation column reflux tank 36 to detect whether the light components in the pipeline still contain propylene.

[0035] The bottom of the distillation column 28 is equipped with a pipeline containing a flow meter e38, a valve, a cooler c39, a sampler c40, and a thermometer c41. The distillation column 28 ultimately yields purified propylene after recovery. The propylene is cooled in the cooler c39 by opening the valve, and the propylene content in the pipeline is detected by the sampler c40 to check whether the purity of the finally recovered propylene meets the conditions for recycling.

[0036] A level gauge 6 is installed on the propylene reflux tank 3 to monitor the liquid level interface position of propylene in the propylene reflux tank 3.

[0037] Working principle of the invention:

[0038] The crude propylene mixture remaining after the reaction in reaction unit 1 enters propylene recovery unit 2 through a pipeline. The crude propylene mixture in propylene recovery unit 2 then enters propylene reflux tank 3, which is equipped with a collector 5. At this point, propylene, propane, and small amounts of methanol, water, and other impurities in the crude propylene are collected in collector 5. Since the pressure inside propylene reflux tank 3 is 2.0 ± 0.15 MPaG, the crude propylene in collector 5 enters crude propylene tank 10 through a pipeline under the pressure difference. Meanwhile, sampler a8 is used every [time period missing]. A small sample of the mixed liquid from the pipeline is taken periodically and analyzed to determine the propylene and propane content. The propylene content in the pipeline is maintained between 85-95%. If it falls below this range, the crude propylene discharge flow rate is low. In this case, the flow rate setpoint of flow meter C9 is increased. Flow meter C9 sends a signal to the valve on the pipeline, causing the valve to increase the pipeline flow rate. If the propylene content in the pipeline exceeds this range (85-95%), the crude propylene discharge flow rate is high. In this case, the flow rate setpoint of flow meter C9 is decreased. By stabilizing the amount of discharged propylene, the crude propylene content is controlled, thereby ensuring a stable propylene concentration in the circulating propylene system. A small amount of propylene, along with non-condensable gases such as ethylene, CO, CO2, and nitrogen, in the propylene reflux tank 3 enters the absorption tower 15 through the tail gas pipeline 13. The propylene in the tail gas is recovered by the absorbent 20 in the absorption tower 15, and then transported to the reaction unit 1 for reaction through the absorption tower bottom pump 43, which further reduces the loss of propylene. At the same time, light component impurities such as ethylene, CO, CO2, and nitrogen in the system are discharged to the incinerator for incineration. The crude propylene in crude propylene tank 10 enters the light component removal tower 18 through a pipeline. The light component removal tower 18 removes light components, such as propane, ethylene, butene, CO, and CO2. The propylene remaining in the light component removal tower 18 enters the distillation tower 28 through a pipeline. The distillation tower 28 further removes a small amount of light components carried in the propylene. The final purified propylene obtained in the distillation tower 28 is then cooled in the cooler c39 by opening a valve. The propylene content in the pipeline is tested by a sampler c40 to see if the purity of the final recovered propylene meets the conditions for recycling.

[0039] This invention is simple to operate, convenient to use, and suitable for widespread promotion and application. Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A propylene recovery system for crude propylene material, comprising a crude propylene tank (10), a pressure gauge a (11) installed on the crude propylene tank (10), a light propylene removal tower (18) connected to the crude propylene tank (10) via a pipeline, and a crude propylene transfer pump (12), a flow meter a (14) and a valve installed on the pipeline, a pressure gauge b (17) installed on the light propylene removal tower (18), a reboiler a (19) connected to one side of the light propylene removal tower (18) via a pipeline, a reboiler heat source a (16) connected to the reboiler a (19), a distillation tower (28) connected to the light propylene removal tower (18) via a pipeline, and a flow meter b (26) and a valve installed on the pipeline, a pressure gauge c (27) installed on the distillation tower (28), a reboiler b (29) connected to one side of the distillation tower (28) via a pipeline, and a reboiler heat source b (23) connected to the reboiler b (29), characterized in that, A reaction unit (1) is installed upstream of the crude propylene tank (10). The reaction unit (1) is connected to the propylene recovery unit (2) via a pipeline. The propylene recovery unit (2) is connected to the propylene return tank (3) via a pipeline. A pressure gauge d (35) is installed on the propylene return tank (3). The temperature inside the propylene return tank (3) is 35±2℃ and the pressure is 2.0±0.15MPaG. A liquid collector (5) is installed inside the propylene return tank (3). The liquid collector (5) is connected to the crude propylene tank (10) via a pipeline, and a sampler a (8), a flow meter c (9) and a valve are installed on the pipeline.

2. The propylene recovery and utilization system for crude propylene material according to claim 1, characterized in that, The propylene reflux tank (3) is connected to the reaction unit (1) and the propylene recovery unit (2) respectively via pipelines, and a circulating propylene pump (7) is installed on the pipelines.

3. The propylene recovery and utilization system for crude propylene material according to claim 2, characterized in that, The propylene reflux tank (3) is connected to the absorption tower (15) via the tail gas pipeline (13); the absorption tower (15) uses an absorbent (20) to absorb the propylene in the tail gas.

4. The propylene recovery and utilization system for crude propylene material according to claim 3, characterized in that, After the absorber (15) absorbs propylene, the absorbent is transported to the reaction unit (1) by the absorber bottom pump (43) through the absorbent circulation pipeline (44).

5. The propylene recovery and utilization system for crude propylene material according to claim 4, characterized in that, The exhaust gas from the top of the absorption tower (15) is sent to the incinerator for incineration through the waste gas pipeline (45).

6. The propylene recovery and utilization system for crude propylene material according to claim 5, characterized in that, The upper part of the light removal tower (18) is connected to the light removal tower reflux tank (24) by a pipeline, and a cooler a (21) and a thermometer a (22) are installed on the pipeline.

7. The propylene recovery and utilization system for crude propylene material according to claim 6, characterized in that, The bottom of the light tower reflux tank (24) is connected to the light tower (18) via a pipeline and a light tower reflux pump (25) is installed on the pipeline.

8. The propylene recovery and utilization system for crude propylene material according to claim 7, characterized in that, The upper part of the distillation column (28) is connected to the distillation column reflux tank (36) by a pipeline, and a cooler b (31) and a thermometer b (32) are installed on the pipeline. The distillation column reflux tank (36) is equipped with a tail gas discharge pipeline (42), and the tail gas discharge pipeline (42) is connected to the light tower reflux tank (24) by a pipeline.

9. The propylene recovery and utilization system for crude propylene material according to claim 8, characterized in that, The bottom of the distillation column reflux tank (36) is connected to the distillation column (28) via a pipeline and a distillation column reflux pump (33) is installed on the pipeline. A pipeline extends from the pipeline on the distillation column reflux pump (33) and a flow meter d (37), a valve, a sampler b (34) and a pressure gauge d (35) are installed on the extended pipeline. The extended pipeline is connected to the propylene reflux tank (3).

10. The propylene recovery and utilization system for crude propylene material according to claim 9, characterized in that, The bottom of the distillation column (28) is equipped with a pipeline and a flow meter e (38), a valve, a cooler c (39), a sampler c (40), and a thermometer c (41).

11. The propylene recovery and utilization system for crude propylene material according to claim 1, characterized in that, A level gauge (6) is installed on the propylene reflux tank (3).

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