Propylene normal-pressure cryogenic liquefaction recycling system

Abstract

The utility model relates to the technical field of propylene recycling, in particular to a propylene normal-pressure cryogenic liquefaction recycling system which comprises a cryogenic tower and a liquid nitrogen circulating system used for cooling propylene, and the cryogenic tower comprises an upper tower used for propylene gas-liquid separation and a lower tower used for storing and conveying liquid-phase propylene. A propylene inlet of the upper tower is connected with a precooler through a propylene feeding pipeline, a gas-liquid separator is connected to the top of the upper tower, a liquid phase outlet of the gas-liquid separator is connected to the propylene feeding pipeline, a gas phase outlet of the gas-liquid separator is connected to the precooler, and a gas phase outlet of the gas-liquid separator is connected to the precooler. A cold medium outlet of the precooler is connected with a safety relief system, the bottom of the lower tower is connected with a propylene delivery pump, and the propylene delivery pump is respectively connected with the upper tower and a propylene downstream system. According to the utility model, the gas-phase propylene generated in the petrochemical production process can be effectively recovered and utilized, the propylene utilization efficiency is high, and the waste of resources is avoided.

Description

Technical Field

[0001] This utility model relates to the field of propylene recycling technology, specifically to a propylene atmospheric pressure cryogenic liquefaction recycling system. Background Technology

[0002] Propylene is a colorless, odorless, slightly sweet-smelling, extremely flammable gas that burns with a bright flame. It has a low explosion limit (2%–11.1%) and low solubility in water, but is soluble in organic solvents such as ethanol and ether. Propylene is an important chemical raw material, playing a crucial role in modern industry. It is primarily used to produce polypropylene, and can also be used to synthesize acrylonitrile, propylene oxide, isopropanol, phenol, acetone, and other chemicals, finding wide applications in plastics, pharmaceuticals, and agriculture.

[0003] Currently, despite continuous technological advancements, a portion of gaseous propylene in the vast production systems of petrochemical enterprises remains uncaptured and underutilized during the production process. This unrecovered gaseous propylene is mostly simply released into the atmosphere through combustion. This extensive treatment method presents the following problems:

[0004] Environmental pressure: Direct combustion of propylene produces large amounts of CO2 and incompletely combusted hydrocarbon pollutants, exacerbating carbon emissions and the difficulty of air pollution control;

[0005] Resource waste: Propylene, an important chemical raw material (such as a monomer for polypropylene synthesis), is not recycled, leading to increased raw material costs for enterprises;

[0006] Safety issues: When burning gaseous propylene, the large storage volume and long residence time of gaseous propylene can easily lead to leakage risks. In addition, the risk of flash explosion due to open combustion must be eliminated during combustion, resulting in high operational risks for enterprises. Utility Model Content

[0007] To address the shortcomings of existing technologies, this invention provides a propylene atmospheric pressure cryogenic liquefaction and recycling system.

[0008] To achieve the above objectives, the technical solution of this utility model is as follows: a cryogenic liquefaction and recycling system for propylene at atmospheric pressure, comprising a cryogenic tower and a liquid nitrogen circulation system for cooling propylene. The cryogenic tower includes an upper tower for propylene gas-liquid separation and a lower tower for storing and transporting liquid propylene. The propylene inlet of the upper tower is connected to a precooler via a propylene feed pipe. A gas-liquid separator is connected to the top of the upper tower. The liquid phase outlet of the gas-liquid separator is connected to the propylene feed pipe. The gas phase outlet of the gas-liquid separator is connected to the precooler. A safety relief system is connected to the cold medium outlet of the precooler. A propylene transfer pump is connected to the bottom of the lower tower. The propylene transfer pump is connected to both the upper tower and the downstream propylene system.

[0009] Furthermore, the liquid nitrogen circulation system includes a liquid nitrogen storage tank, the outlet of which is connected to the upper tower, the inlet of which is connected to the gas-liquid separator, liquid nitrogen pipelines inside the upper tower and outside the lower tower, a liquid nitrogen separator at the outlet of the liquid nitrogen pipelines, the liquid nitrogen separator being connected to a nitrogen gas delivery pump and a liquid nitrogen delivery pump respectively, the output end of the nitrogen gas delivery pump being connected to a nitrogen gas pipeline network system, and the output end of the liquid nitrogen delivery pump being connected to the gas-liquid separator.

[0010] Furthermore, the upper tower is provided with several packing layers, and a tray is provided between two adjacent packing layers. A distributor is provided at the top inside the upper tower, and the distributor is connected to the propylene reflux pipeline between the propylene delivery pump and the upper tower. A distributor is provided at the bottom inside the upper tower, and the distributor is connected to the propylene feed pipeline. The liquid nitrogen pipeline in the upper tower bends and shuttles under the tray, distributor one and distributor two. A liquid collection tank is provided at the bottom of the upper tower, and a pipeline connecting to the lower tower is provided at the bottom of the liquid collection tank.

[0011] Furthermore, the liquid nitrogen pipeline inside the upper tower is provided with several finned tubes, which are located below the tray, distributor one, and distributor two.

[0012] Furthermore, a distributor three is provided inside the lower tower, and the distributor three is connected to the pipe at the bottom of the liquid collection tank one. A liquid collection tank two is provided at the bottom of the lower tower, and a pipe connected to the propylene delivery pump is provided at the bottom of the liquid collection tank two. A liquid nitrogen pipe is spirally wound around the outside of the lower tower.

[0013] Furthermore, a nitrogen pressurization port is provided at the top of the upper tower sidewall, and the nitrogen pressurization port is connected to the nitrogen pipeline system through a pipeline.

[0014] Furthermore, the connecting pipe between the cryogenic tower and the gas-liquid separator is a U-shaped pipe.

[0015] Furthermore, a pressure control valve is installed between the precooler's cold medium outlet and the safety relief system.

[0016] Furthermore, the propylene downstream system includes a propylene liquid phase downstream system and a propylene gas phase downstream system, and an ambient temperature vaporizer is installed on the main pipeline of the propylene gas phase downstream system.

[0017] Furthermore, the propylene vapor phase downstream system includes propylene vapor phase downstream system one and propylene vapor phase downstream system two, and a water bath vaporizer is installed on the input pipeline of propylene vapor phase downstream system two.

[0018] The beneficial effects achieved by this utility model are as follows:

[0019] 1. This utility model can effectively recover and utilize gaseous propylene generated in the petrochemical production process, with high propylene utilization efficiency and avoidance of resource waste; through the design of liquid nitrogen circulation system and cryogenic tower, the gas-liquid separation and liquefaction of propylene are realized, improving the recovery rate and utilization rate of propylene, reducing the raw material cost of enterprises, and improving economic benefits.

[0020] 2. This utility model reduces the emissions of carbon dioxide and incompletely burned hydrocarbon pollutants generated by direct combustion by liquefying and recycling gaseous propylene, which helps to reduce carbon emissions and alleviate the pressure of air pollution control.

[0021] 3. This utility model reduces the storage volume and residence time of flammable and explosive media in petrochemical enterprises, lowers the risk of propylene leakage, and achieves safe handling and storage of propylene through the design of cryogenic tower and gas-liquid separator, thereby improving the operational safety of enterprises and reducing their operational risks.

[0022] 4. This utility model takes into account the needs of various downstream propylene systems, including downstream liquid propylene systems and downstream gaseous propylene systems, as well as downstream gaseous propylene systems with different temperature requirements. This flexibility enables the system to adapt to different production processes and needs, thus improving the applicability of the system. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the overall structure of this utility model;

[0024] Figure 2 This is a schematic diagram of the overall structure of the cryogenic tower.

[0025] Explanation of markings in the diagram: 1. Precooler; 2. Cryogenic tower; 3. Gas-liquid separator; 4. Liquid nitrogen separator; 5. Propylene transfer pump; 6. Nitrogen transfer pump; 7. Liquid nitrogen transfer pump; 8. Liquid nitrogen storage tank; 9. Water bath vaporizer; 10. Ambient air vaporizer; 11. Safety relief system; 12. Downstream propylene liquid phase system; 13. Downstream propylene gas phase system one; 14. Downstream propylene gas phase system two; 15. Nitrogen pipeline system; 101. Propylene feed pipeline; 102. Pressure control valve; 21. Upper tower; 22. Lower tower; 211. Packing layer; 212. Tray; 213. 214. Finned tube; 215. Distributor 1; 216. Distributor 2; 221. Liquid collection tank 1; 222. Distributor 3; 222. Liquid collection tank 2; 223. Liquid nitrogen pipeline; 31. U-shaped pipeline; 201. Propylene inlet; 202. Gaseous propylene outlet; 203. Nitrogen pressurization port; 204. Liquid propylene reflux port; 205. Upper tower liquid nitrogen inlet; 206. Upper tower liquid nitrogen outlet; 207. Upper tower propylene outlet; 208. Lower tower propylene inlet; 209. Lower tower propylene outlet; 2010. Lower tower liquid nitrogen inlet; 2011. Lower tower liquid nitrogen outlet. Detailed Implementation

[0026] To better understand the purpose, structure, and function of this utility model, the following description, in conjunction with the accompanying drawings, provides a more detailed account of a cryogenic liquefaction and recycling system for propylene under atmospheric pressure.

[0027] like Figures 1 to 2 As shown, a cryogenic propylene liquefaction and recycling system under atmospheric pressure includes a cryogenic tower 2 and a liquid nitrogen circulation system for cooling propylene. A precooler 1 is connected to the propylene inlet 201 of the cryogenic tower 2 via a propylene inlet pipe 101. A gaseous propylene outlet 202 at the top of the cryogenic tower 2 is connected to a gas-liquid separator 3 via a pipe. The liquid outlet of the gas-liquid separator 3 is connected to the propylene inlet pipe 101, and the gaseous outlet of the gas-liquid separator 3 is connected to the cold medium inlet of the precooler 1. A safety relief system 11 is connected to the cold medium outlet of the precooler 1. The cryogenic tower 2 includes an upper tower 21 for propylene gas-liquid separation and a lower tower 22 for storing and transporting liquid propylene. The upper tower 21 and the lower tower 22 are connected by a pipe. An propylene transfer pump 5 is connected to the bottom of the lower tower 22 via a pipe. The propylene transfer pump 5 is connected to the upper tower 21 and the downstream propylene system.

[0028] The hot medium inlet of the precooler 1 is connected to the propylene gas phase generated during chemical production. The hot medium outlet is connected to the propylene inlet 201 through the propylene feed pipe 101. The cold medium inlet is connected to the gas phase outlet of the gas-liquid separator 3. The cold medium outlet is connected to the safety relief system 11. A pressure control valve 102 is installed on the pipe between the cold medium outlet and the safety relief system 11. The propylene generated during chemical production enters the cryogenic tower 2 through the precooler 1.

[0029] The liquid nitrogen circulation system includes a liquid nitrogen storage tank 8. The outlet of the liquid nitrogen storage tank 8 is connected to the upper column liquid nitrogen inlet 205 of the upper column 21 via a pipeline. The inlet of the liquid nitrogen storage tank 8 is connected to the gas-liquid separator 3. The upper column 21 is equipped with a liquid nitrogen pipeline 223 for liquefied propylene. The upper column liquid nitrogen inlet 205 is located at the top of the side wall of the upper column 21, and the upper column liquid nitrogen outlet 206 is located at the bottom of the side wall of the upper column 21. The liquid nitrogen pipeline 223 enters the upper column from the upper column liquid nitrogen inlet 205. Inside tower 21, liquid nitrogen pipe 223 extends from the upper tower liquid nitrogen outlet 206 and is wound around the outer wall of the lower tower 22. The end of the liquid nitrogen pipe 223 is connected to a liquid nitrogen separator 4. The liquid nitrogen separator 4 is connected to a nitrogen transfer pump 6 and a liquid nitrogen transfer pump 7 respectively. The output end of the liquid nitrogen transfer pump 7 is connected to a gas-liquid separator 3. The output end of the nitrogen transfer pump 6 is connected to a nitrogen pipeline system 15. The nitrogen outlet of the nitrogen pipeline system 15 is connected to the nitrogen pressure replenishment port 203 of the upper tower 21 through a pipe.

[0030] Liquid nitrogen flows out from the liquid nitrogen storage tank 8 and enters the upper column 21 through the upper column liquid nitrogen inlet 205. Inside the upper column 21, the liquid nitrogen pipeline 223 cools the propylene gas phase delivered from the propylene inlet 201, liquefying most of the propylene gas phase into liquid propylene. The liquid propylene enters the lower column 22 through the connecting pipeline between the upper column 21 and the lower column 22. The liquid nitrogen pipeline 223 is wrapped around the outer wall of the lower column 22 to control the temperature inside the lower column 22, forming a cold insulation zone to prevent the propylene inside the lower column 22 from condensing. The liquid nitrogen in the liquid nitrogen pipeline 223 eventually flows into the liquid nitrogen separator 4. The nitrogen separated by the liquid nitrogen separator 4 is transported to the nitrogen pipeline system 15 by the nitrogen transfer pump 6. The nitrogen in the nitrogen pipeline system 15 enters the upper tower 21 through the nitrogen pressure replenishment port 203. The liquid nitrogen separated by the liquid nitrogen separator 4 enters the gas-liquid separator 3 to further cool the gaseous propylene in the gas-liquid separator 3, and then flows out from the gas-liquid separator 3 and returns to the liquid nitrogen storage tank 8 to complete the cycle. The nitrogen pipeline system 15 replenishes the pressure in the upper tower 21 through the nitrogen pressure replenishment port 203 to prevent the pressure inside the upper tower 21 from falling below the external pressure due to low temperature, thus protecting the upper tower 21 from being crushed by external forces.

[0031] The upper column 21 of the cryogenic tower 2 is equipped with several packing layers 211. A tray 212 is set between two adjacent packing layers 211. A distributor 1 214 is set at the top inside the upper column 21. The distributor 1 214 is connected to the propylene reflux pipeline between the propylene transfer pump 5 and the upper column 21. A distributor 215 is set at the west side inside the upper column 21. The distributor 215 is connected to the propylene feed pipeline 101. The liquid nitrogen pipeline 223 in the upper column 21 meanders below the tray 212, distributor 1 214 and distributor 215. Several finned tubes 213 are set on the liquid nitrogen pipeline 223 in the upper column 21. The finned tubes 213 are set below the tray 212, distributor 1 214 and distributor 215. A liquid collection tank 1 216 is set at the bottom of the upper column 21. The liquid collection tank 1 216 is used to collect the liquid phase propylene after condensation by the liquid nitrogen pipeline 223. A pipeline connecting the bottom of the liquid collection tank 1 216 to the lower column 22 is set.

[0032] A distributor 3 221 is installed in the lower tower 22 of the cryogenic tower 2. The distributor 3 221 is connected to the pipe at the bottom of the liquid collection tank 1 216. A liquid collection tank 222 is installed at the bottom of the lower tower 22. A pipe connected to the propylene transfer pump 5 is installed at the bottom of the liquid collection tank 222.

[0033] Propylene produced during chemical production mixes with liquid propylene flowing from gas-liquid separator 3 and enters distributor 214. Cooled by liquid nitrogen pipeline 223, most of the gaseous propylene liquefies into liquid propylene and falls into collection tank 216. A small portion of the gaseous propylene enters gas-liquid separator 3, where the temperature is lower. Another portion of the gaseous propylene liquefies into liquid propylene and enters propylene feed pipeline 101. A very small portion of the propylene passes through precooler 1 and enters safety relief system 11 for treatment. The liquid propylene in collection tank 216 enters lower tower 22 through pipelines, and is then pumped by propylene transfer pump 5 to distributor 214 in the downstream propylene system and upper tower 21, respectively. The vast majority of the propylene enters the downstream propylene system, while a small portion flows back to upper tower 21 of cryogenic tower 2 to cool the gaseous propylene.

[0034] The propylene downstream system includes a propylene liquid phase downstream system 12 and a propylene gas phase downstream system. An ambient temperature vaporizer 10 is installed on the main pipe of the propylene gas phase downstream system. The propylene gas phase downstream system also includes a first propylene gas phase downstream system 13 and a second propylene gas phase downstream system 14. A water bath vaporizer 9 is installed on the input pipe of the second propylene gas phase downstream system 14. The propylene liquid phase downstream system 12 is suitable for production systems using liquid propylene as feedstock. The first propylene gas phase downstream system 13 is suitable for production systems using ambient temperature gas phase propylene as feedstock. The second propylene gas phase downstream system 14 is suitable for production systems using gas phase propylene at a specific temperature as feedstock.

[0035] The connecting pipe between the cryogenic tower 2 and the gas-liquid separator 3 is a U-shaped pipe 31. The U-shaped pipe 31 can effectively form a pressure drop, preventing the gaseous propylene in the cryogenic tower 2 from flowing directly into the gas-liquid separator 3 through a straight pipe.

[0036] It is understood that this utility model has been described through some embodiments, and those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of this utility model. Furthermore, under the teachings of this utility model, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of this utility model. Therefore, this utility model is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the protection scope of this utility model.

Claims

1. A propylene atmospheric pressure cryogenic liquefaction and recycling system, characterized in that: The system includes a cryogenic tower (2) and a liquid nitrogen circulation system for cooling propylene. The cryogenic tower (2) includes an upper tower (21) for propylene gas-liquid separation and a lower tower (22) for storing and transporting liquid propylene. The propylene inlet (201) of the upper tower (21) is connected to a precooler (1) via a propylene feed pipe (101). A gas-liquid separator (3) is connected to the top of the upper tower (21). The liquid phase outlet of the gas-liquid separator (3) is connected to the propylene feed pipe (101), and the gas phase outlet of the gas-liquid separator (3) is connected to the precooler (1). A safety relief system (11) is connected to the cold medium outlet of the precooler (1). A propylene transfer pump (5) is connected to the bottom of the lower tower (22). The propylene transfer pump (5) is connected to the upper tower (21) and the downstream propylene system.

2. The propylene atmospheric pressure cryogenic liquefaction and recycling system according to claim 1, characterized in that: The liquid nitrogen circulation system includes a liquid nitrogen storage tank (8), the outlet of which is connected to the upper tower (21), the inlet of which is connected to the gas-liquid separator (3), a liquid nitrogen pipeline (223) is provided inside the upper tower (21) and outside the lower tower (22), a liquid nitrogen separator (4) is provided at the outlet of the liquid nitrogen pipeline (223), the liquid nitrogen separator (4) is connected to a nitrogen transfer pump (6) and a liquid nitrogen transfer pump (7) respectively, the output end of the nitrogen transfer pump (6) is connected to a nitrogen pipeline network system (15), and the output end of the liquid nitrogen transfer pump (7) is connected to the gas-liquid separator (3).

3. The propylene atmospheric pressure cryogenic liquefaction and recycling system according to claim 2, characterized in that: The upper tower (21) is provided with several packing layers (211), and a tray (212) is provided between two adjacent packing layers (211). A distributor (214) is provided at the top inside the upper tower (21), and the distributor (214) is connected to the propylene reflux pipeline between the propylene delivery pump (5) and the upper tower (21). A distributor (215) is provided at the bottom inside the upper tower (21), and the distributor (215) is connected to the propylene feed pipeline (101). A liquid nitrogen pipeline (223) in the upper tower (21) meanders under the tray (212), distributor (214) and distributor (215). A liquid accumulation tank (216) is provided at the bottom of the upper tower (21), and a pipeline connecting to the lower tower (22) is provided at the bottom of the liquid accumulation tank (216).

4. The propylene atmospheric pressure cryogenic liquefaction and recycling system according to claim 3, characterized in that: The liquid nitrogen pipeline (223) inside the upper tower (21) is provided with several finned tubes (213), which are located below the tray (212), distributor one (214) and distributor two (215).

5. The propylene atmospheric pressure cryogenic liquefaction and recycling system according to claim 3, characterized in that: The lower tower (22) is equipped with a distributor three (221), which is connected to the pipe at the bottom of the liquid collection tank one (216). The lower tower (22) is equipped with a liquid collection tank two (222) at the bottom, and the liquid collection tank two (222) is equipped with a pipe connected to the propylene delivery pump (5) at the bottom. The lower tower (22) is spirally wound with a liquid nitrogen pipe (223) on the outside.

6. The propylene atmospheric pressure cryogenic liquefaction and recycling system according to claim 1, characterized in that: The top of the side wall of the upper tower (21) is provided with a nitrogen pressure port (203), which is connected to the nitrogen pipeline network system (15) through a pipeline.

7. The propylene atmospheric pressure cryogenic liquefaction and recycling system according to claim 1, characterized in that: The connecting pipe between the cryogenic tower (2) and the gas-liquid separator (3) is a U-shaped pipe (31).

8. The propylene atmospheric pressure cryogenic liquefaction and recycling system according to claim 1, characterized in that: A pressure control valve (102) is provided between the cold medium outlet of the precooler (1) and the safety relief system (11).

9. The propylene atmospheric pressure cryogenic liquefaction and recycling system according to claim 1, characterized in that: The propylene downstream system includes a propylene liquid phase downstream system (12) and a propylene gas phase downstream system, wherein an ambient temperature vaporizer (10) is installed on the main pipeline of the propylene gas phase downstream system.

10. A propylene atmospheric pressure cryogenic liquefaction and recycling system according to claim 9, characterized in that: The propylene vapor phase downstream system includes propylene vapor phase downstream system one (13) and propylene vapor phase downstream system two (14), and a water bath vaporizer (9) is installed on the input pipe of propylene vapor phase downstream system two (14).

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