Energy-saving recovery system for liquid-phase loop pipe polyethylene device
By designing a liquid phase loop pipe polyethylene device energy-saving recovery system in a polyethylene device, optimizing gas circulation and recovery, the efficient reuse of raw gas is achieved, and the problems of high power of the membrane recovery compressor and loss of ethylene raw materials are solved, the device stability and energy utilization efficiency are improved, and the production cost and environmental impact are reduced.
Patent Information
- Application Number
- CN202422001977.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-19
- Publication Date
- 2025-06-10
- Estimated Expiration
- 2034-08-19
AI Technical Summary
In the existing polyethylene devices, the membrane recovery compressor has high operating power, and light hydrocarbon emissions during the production process lead to loss of ethylene raw materials, affecting unit consumption, causing waste of resources, and poor device stability.
An energy-saving recovery system for liquid phase loop pipe polyethylene equipment was designed. By optimizing the gas circulation and recovery system, it can realize efficient reuse of raw gas and reduce energy consumption. The system is equipped with multi-level energy recovery links, such as reuse of compressed gas, thermal energy recovery, and circulation of active components in the gas.
It improves the ethylene recovery rate, reduces the number of manual maintenance times of the recycling system, increases the stable operation cycle of the device, reduces production fluctuations, reduces energy consumption and the impact on the environment, and reduces production costs.
Smart Images
Figure CN222956175U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the technical field of chemical production, in particular to an energy-saving recovery system for a liquid-phase loop polyethylene plant. Background Technique
[0002] The polyethylene plant adopts the CPC double-loop pipe technology, and uses ethylene, hexene-1, and hydrogen as raw materials, and isobutane as a solvent to produce polyethylene products. The tail gas discharged from the top of the degassing bin of the plant is separated by the membrane recovery compressor system through the compression membrane separation technology. The recovered isobutane is returned to the dehexanizer tower, and the recovered nitrogen is returned to the degassing bin for reuse, and the light hydrocarbons are discharged to the flare system. The existing membrane recovery compressor needs to be compressed repeatedly during operation, the operating power of the compressor is relatively high, and the membrane recovery light hydrocarbons are discharged to the flare during the production process, resulting in the loss of ethylene raw materials, affecting the increase of the raw material unit consumption of the plant, causing waste of resources, and having many manual maintenance times and poor stability of the plant.
[0003] To solve the above problems, an energy-saving recovery system for a liquid-phase loop polyethylene plant is urgently needed to improve the ethylene recovery rate, reduce the number of manual maintenance times of the recovery system, increase the stable operation period of the plant, reduce the production fluctuations of the plant, and the compressor has a small floor area, simple operation, and few wearing parts. Summary of the Invention
[0004] An energy-saving recovery system for a liquid-phase loop polyethylene plant improves the ethylene recovery rate, can reduce the number of manual maintenance times of the recovery system, increase the stable operation period of the plant, reduce the production fluctuations of the plant, and the compressor has a small floor area, simple operation, and few wearing parts.
[0005] An energy-saving recovery system for a liquid-phase loop polyethylene plant includes a degassing bin, wherein:
[0006] A raw material gas pipeline is provided on one side of the degassing bin. One end of the raw material gas pipeline is connected to a compressor suction tank. A connecting pipeline is connected to the top of the compressor suction tank. One end of the connecting pipeline is connected to a screw compressor. A connecting pipeline is provided on the screw compressor. One end of the connecting pipeline is connected to a process condenser. The connecting pipeline at the bottom of the process condenser is connected to one side of a final separator. An isobutane recovery pipeline is provided at the bottom of the final separator. The isobutane recovery pipeline is connected to an isobutane recovery system;
[0007] An outlet pipeline of the final separator is provided at the top of the final separator. The outlet pipeline of the final separator is connected to a gas-phase dryer. A connecting pipeline on the gas-phase dryer is connected to an expander cold box. A connecting pipeline on one side of the expander cold box is connected to a first separator. An isobutane circulation pipeline is provided at the bottom of the first separator. The other end of the isobutane circulation pipeline is connected to the raw material gas pipeline. A first separator pipeline is provided at the top of the first separator. One end of the first separator pipeline is connected to one side of the expander cold box;
[0008] One side of the top of the expander cold box is provided with a recycled ethylene pipeline, one end of the recycled ethylene pipeline is connected to the ethylene recovery system, the top of the expander cold box is provided with an expansion gas pipeline, one end of the expansion gas pipeline is connected to the first-stage expander, the bottom end of one side of the first-stage expander is provided with a first-stage expander circulation pipeline, the first-stage expander circulation pipeline is connected to the second-stage expander after accessing the expander cold box, the connecting pipeline at the bottom of the second-stage expander is connected to the bottom end of the expander cold box, the connecting pipeline at the bottom end of the expander cold box is connected to the second separator, the top of the second separator is provided with a second separator pipeline, one end of the second separator pipeline is connected to the expander cold box, one side of the top of the expander cold box is provided with an expander cold box output pipeline, one end of the expander cold box output pipeline is connected to one side of the second-stage expander, the second-stage expander is provided with a connecting gas pipeline, one end of the connecting gas pipeline is connected to the first-stage expander, the first-stage expander is provided with a recycled nitrogen pipeline, and the other end of the recycled nitrogen pipeline is connected to the nitrogen recovery system.
[0009] Preferably, a pressure relief gas recovery pipeline is provided on one side of the outlet pipeline of the last-stage separator, and one side of the pressure relief gas recovery pipeline is connected to the raw material gas pipeline.
[0010] Preferably, a standby pipeline is provided on the side of the outlet pipeline of the last-stage separator close to the last-stage separator.
[0011] Preferably, a micro control valve is provided on the second-stage expander.
[0012] Preferably, a liquid-phase ethylene pipeline is provided under the second separator, and the liquid-phase ethylene pipeline is connected to the expander cold box.
[0013] Preferably, the number of gas-phase dryers is two, and the two gas-phase dryers are connected in parallel.
[0014] Advantages of the present utility model: The energy-saving recovery system of the liquid-phase loop polyethylene device of the present utility model realizes the efficient reuse of raw material gas and reduces energy consumption by optimizing the gas circulation recovery system; the system improves the energy utilization efficiency by setting multiple levels of energy recovery links, such as the reuse of compressed gas, heat energy recovery, and the circulation of effective components in the gas. It reduces the waste gas emissions during the production process, and at the same time reduces the environmental impact by recovering and recycling fuel. By improving the energy use efficiency, the production cost is directly reduced. In addition, the recovered raw material gas such as isobutane can reduce the external purchase demand and further save expenses. The system improves the purity of the polyethylene product through multi-stage separation and recovery, especially the efficient recovery and reuse of ethylene and isobutane. The high-purity raw materials contribute to the production of higher-quality polyethylene products to meet the market demand for high-quality products. By adding spare pipelines and relief gas recovery pipelines, the stability and safety of the system are enhanced. The relief gas recovery pipeline helps to avoid system failures caused by pressure fluctuations and improves the overall safety of the system. Brief Description of the Drawings
[0015] Figure 1 It is a schematic diagram of the energy-saving recovery system of the liquid-phase loop polyethylene device of the present utility model.
[0016] In the figure: degassing bin 1, raw material gas pipeline 2, compressor suction tank 3, screw compressor 4, process condenser 5, final separator 6, isobutane recovery pipeline 7, isobutane recovery system 8, final separator outlet pipeline 9, gas phase dryer 10, expander cold box 11, first separator 12, isobutane circulation pipeline 13, first separator pipeline 14, recovered ethylene pipeline 15, ethylene recovery system 16, expansion gas pipeline 17, first-stage expander 18, first-stage expander circulation pipeline 19, second-stage expander 20, second separator 21, second separator pipeline 22, expander cold box output pipeline 23, connecting gas pipeline 24, recovered nitrogen pipeline 25, nitrogen recovery system 26, relief gas recovery pipeline 27, spare pipeline 28, liquid-phase ethylene pipeline 29. Detailed Embodiments
[0017] In order to make the technical solution of the present utility model easier to understand, the technical solution of the present utility model will be clearly and completely described below in conjunction with the drawings by using specific embodiments.
[0018] Embodiment 1:
[0019] As Figure 1 shown, the Figure 1 of this embodiment is the energy-saving recovery system of the liquid-phase loop polyethylene device of the present utility model, including a degassing bin 1, where:
[0020] On one side of the degassing bin 1, there is a raw gas pipeline 2. One end of the raw gas pipeline 2 is connected to the compressor suction tank 3. The top of the compressor suction tank 3 is connected with a communication pipeline. One end of the communication pipeline is connected to a screw compressor 4. A communication pipeline is provided on the screw compressor 4. One end of the communication pipeline is connected to a process condenser 5. The communication pipeline at the bottom of the process condenser 5 is connected to one side of the final separator 6. The bottom of the final separator 6 is provided with an isobutane recovery pipeline 7, and the isobutane recovery pipeline 7 is connected to an isobutane recovery system 8;
[0021] The top of the final separator 6 is provided with a final separator outlet pipeline 9. The final separator outlet pipeline 9 is communicated with a gas-phase dryer 10. The communication pipeline on the gas-phase dryer 10 is connected to an expander cold box 11. The communication pipeline on one side of the expander cold box 11 is connected to a first separator 12. The bottom of the first separator 12 is provided with an isobutane circulation pipeline 13, and the other end of the isobutane circulation pipeline 13 is connected to the raw gas pipeline 2. The top of the first separator 12 is provided with a first separator pipeline 14, and one end of the first separator pipeline 14 is connected to one side of the expander cold box 11;
[0022] On one side of the top of the expander cold box 11, there is a recovered ethylene pipeline 15. One end of the recovered ethylene pipeline 15 is connected to an ethylene recovery system 16. The top of the expander cold box 11 is provided with an expansion gas pipeline 17. One end of the expansion gas pipeline 17 is connected to a primary expander 18. At the bottom end on one side of the primary expander 18, there is a primary expander circulation pipeline 19. After the primary expander circulation pipeline 19 is connected to the expander cold box 11, it is connected to a secondary expander 20. The communication pipeline at the bottom of the secondary expander 20 is connected to the bottom end of the expander cold box 11. The communication pipeline at the bottom end of the expander cold box 11 is connected to a second separator 21. The top of the second separator 21 is provided with a second separator pipeline 22. One end of the second separator pipeline 22 is connected to the expander cold box 11. On one side of the top of the expander cold box 11, there is an expander cold box output pipeline 23. One end of the expander cold box output pipeline 23 is connected to one side of the secondary expander 20. A communication gas pipeline 24 is provided on the secondary expander 20. One end of the communication gas pipeline 24 is connected to the primary expander 18. A recovered nitrogen pipeline 25 is provided on the primary expander 18, and the other end of the recovered nitrogen pipeline 25 is connected to a nitrogen recovery system 26.
[0023] On one side of the final separator outlet pipeline 9, there is a pressure relief gas recovery pipeline 27, and one side of the pressure relief gas recovery pipeline 27 is connected to the raw gas pipeline 2.
[0024] Near the side of the final separator 6 of the final separator outlet pipeline 9, there is a spare pipeline 28.
[0025] A micro control valve is provided on the secondary expander 20.
[0026] A liquid-phase ethylene pipeline 29 is provided below the second separator 21, and the liquid-phase ethylene pipeline 29 is connected to the expander cold box 11.
[0027] The number of the gas-phase dryers 10 is two, and the two gas-phase dryers 10 are connected in parallel.
[0028] When the device is in use, the maximum flow rate of the raw material gas from the degassing bin 1 is 6114.80 kg / h, and the pressure is about 20 Kpa. First, it is compressed to 1.5 MPa by the screw compressor 4. The compressed gas passes through two-stage oil-gas separators and an activated carbon filter to remove the lubricating oil entrained in the product gas. The clean product gas is then cooled to 40°C by the process condenser 5. The cooled gas-phase part becomes liquid, and the liquid-phase isobutane product is separated by the final separator 6. The isobutane is sent to the isobutane recovery system 8 for recycling after being decompressed by the throttle valve. The gas phase of the final separator 6 enters the gas-phase dryer 10.
[0029] The gas from the final separator 6 is first cooled to -65°C by the expander cold box 11, and then the liquid-phase isobutane product is separated through the first separator pipeline 14. After being decompressed by the throttle valve, it provides cold energy for the expander cold box 11, and returns to the inlet of the compressor suction tank 3 through the first separator pipeline 14 for repeated recycling. The cooled gas enters the second separator pipeline 22 to separate the liquid-phase ethylene product. The liquid-phase ethylene product is decompressed by the throttle valve, reheated by the expander cold box 11, and then enters the second separator pipeline 22. The separated gas-phase product enters the first-stage expander 18 and expands to 0.7 MPa, with a rotational speed of 45000 revolutions per minute. After the first-stage expander 18 does work, the temperature drops to -165°C, providing cold energy for the expander cold box 11. The reheated gas enters the second-stage expander 20 and expands to 0.32 MPa, with a rotational speed of 45000 revolutions per minute. The expanded low-temperature gas enters the expander cold box 11 again to provide cold energy for the expander cold box 11. The reheated gas is basically nitrogen with a purity > 98%. It enters the braking ends of the second-stage expander 20 and the first-stage expander 18 in sequence, is pressurized, and then enters the first-stage expander 18 for repeated use. When the gas-phase dryer 10 needs to be overhauled or both gas-phase dryers 10 are saturated, the spare pipeline 28 can be used for cross-line production and overhaul. When the gas-phase dryer 10 is cut out of the system, in order to prevent waste of the pressure relief gas, the hydrocarbon in the gas-phase dryer 10 is recycled through the pressure relief gas recovery pipeline 27.
[0030] It should be noted that the embodiments described herein are only partial embodiments of the present utility model, rather than all implementation manners of the present utility model. The embodiments are only exemplary, and their functions are only to provide a more intuitive and clear way to understand the content of the present utility model, rather than a limitation on the technical solutions described in the present utility model. Without departing from the concept of the present utility model, all other implementation manners that can be thought of by those of ordinary skill in the art without creative labor, as well as other simple substitutions and various changes to the technical solutions of the present utility model, all fall within the protection scope of the present utility model.
Claims
1. A liquid phase loop polyethylene device energy-saving recovery system, characterized in that: It comprises a degassing chamber (1), wherein: A raw gas pipeline (2) is provided on one side of the degassing bin (1), one end of the raw gas pipeline (2) is connected to a compressor suction tank (3), a connecting pipeline is connected to the top of the compressor suction tank (3), one end of the connecting pipeline is connected to a screw compressor (4), a connecting pipeline is provided on the screw compressor (4), one end of the connecting pipeline is connected to a process condenser (5), a connecting pipeline at the bottom of the process condenser (5) is connected to one side of a final-stage separator (6), an isobutane recovery pipeline (7) is provided at the bottom of the final-stage separator (6), and the isobutane recovery pipeline (7) is connected to an isobutane recovery system (8); A final-stage separator outlet pipeline (9) is provided at the top of the final-stage separator (6), the final-stage separator outlet pipeline (9) is connected to a gas phase dryer (10), a connecting pipeline on the gas phase dryer (10) is connected to an expander cold box (11), a connecting pipeline on one side of the expander cold box (11) is connected to a first separator (12), an isobutane circulation pipeline (13) is provided at the bottom of the first separator (12), the other end of the isobutane circulation pipeline (13) is connected to the raw gas pipeline (2), a first separator pipeline (14) is provided at the top of the first separator (12), one end of the first separator pipeline (14) is connected to one side of the expander cold box (11); A recovery ethylene pipeline (15) is provided on one side of the top of the expander cold box (11), one end of the recovery ethylene pipeline (15) is connected to an ethylene recovery system (16), an expansion gas pipeline (17) is provided on the top of the expander cold box (11), one end of the expansion gas pipeline (17) is connected to a first-stage expander (18), a first-stage expander circulation pipeline (19) is provided on the bottom of one side of the first-stage expander (18), the first-stage expander circulation pipeline (19) is connected to the expander cold box (11) and then to a second-stage expander (20), a connecting pipeline at the bottom of the second-stage expander (20) is connected to the bottom of the expander cold box (11), and a connecting pipeline at the bottom of the expander cold box (11) is connected to a second separation system (20). A separator (21) is provided on the top of the second separator (21), one end of the second separator pipeline (22) is connected to the expander cold box (11), one side of the top of the expander cold box (11) is provided with an expander cold box output pipeline (23), one end of the expander cold box output pipeline (23) is connected to one side of the secondary expander (20), the secondary expander (20) is provided with a communication pipeline (24), one end of the communication pipeline (24) is connected to the primary expander (18), the primary expander (18) is provided with a nitrogen recovery pipeline (25), the other end of the nitrogen recovery pipeline (25) is connected to a nitrogen recovery system (26).
2. The energy-saving recovery system for a liquid phase loop polyethylene device according to claim 1, characterized in that: A depressurized gas recovery pipeline (27) is provided on one side of the final separator outlet pipeline (9), and one side of the depressurized gas recovery pipeline (27) is connected to the raw gas pipeline (2).
3. The energy-saving recovery system for a liquid phase loop polyethylene device according to claim 1, characterized in that: A spare pipeline (28) is provided on the side of the final separator outlet pipeline (9) close to the final separator (6).
4. The energy-saving recovery system for a liquid phase loop polyethylene device according to claim 1, characterized in that: The secondary expander (20) is provided with a micro control valve.
5. The energy-saving recovery system for a liquid phase loop polyethylene device according to claim 1, characterized in that: A liquid-phase ethylene pipeline (29) is provided below the second separator (21), and the liquid-phase ethylene pipeline (29) is connected to the expander cold box (11).
6. The energy-saving recovery system for a liquid phase loop polyethylene device as claimed in claim 1, characterized in that: The number of the gas phase dryers (10) is two, and the two gas phase dryers (10) are connected in parallel.