CN117700293A - Alpha-olefin production method and device for recycling ethylene - Google Patents
Alpha-olefin production method and device for recycling ethylene Download PDFInfo
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- CN117700293A CN117700293A CN202311582721.3A CN202311582721A CN117700293A CN 117700293 A CN117700293 A CN 117700293A CN 202311582721 A CN202311582721 A CN 202311582721A CN 117700293 A CN117700293 A CN 117700293A
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- 239000005977 Ethylene Substances 0.000 title claims abstract description 185
- VGGSQFUCUMXWEO-UHFFFAOYSA-N Ethene Chemical compound C=C VGGSQFUCUMXWEO-UHFFFAOYSA-N 0.000 title claims abstract description 183
- 239000004711 α-olefin Substances 0.000 title claims abstract description 50
- 238000004064 recycling Methods 0.000 title abstract description 17
- 238000004519 manufacturing process Methods 0.000 title description 8
- 238000011084 recovery Methods 0.000 claims abstract description 99
- 239000002904 solvent Substances 0.000 claims abstract description 60
- 238000000926 separation method Methods 0.000 claims abstract description 47
- 238000000034 method Methods 0.000 claims abstract description 29
- 239000012071 phase Substances 0.000 claims abstract description 24
- 239000007791 liquid phase Substances 0.000 claims abstract description 22
- 239000007788 liquid Substances 0.000 claims abstract description 20
- 230000008569 process Effects 0.000 claims abstract description 19
- 230000006837 decompression Effects 0.000 claims abstract description 13
- 239000007795 chemical reaction product Substances 0.000 claims abstract description 10
- 239000007810 chemical reaction solvent Substances 0.000 claims abstract description 9
- 238000001704 evaporation Methods 0.000 claims abstract description 8
- JRZJOMJEPLMPRA-UHFFFAOYSA-N olefin Natural products CCCCCCCC=C JRZJOMJEPLMPRA-UHFFFAOYSA-N 0.000 claims abstract description 8
- 150000001336 alkenes Chemical class 0.000 claims abstract description 7
- 230000008020 evaporation Effects 0.000 claims abstract description 6
- 238000006243 chemical reaction Methods 0.000 claims description 33
- VXNZUUAINFGPBY-UHFFFAOYSA-N 1-Butene Chemical compound CCC=C VXNZUUAINFGPBY-UHFFFAOYSA-N 0.000 claims description 16
- 239000000047 product Substances 0.000 claims description 12
- LIKMAJRDDDTEIG-UHFFFAOYSA-N 1-hexene Chemical compound CCCCC=C LIKMAJRDDDTEIG-UHFFFAOYSA-N 0.000 claims description 10
- 238000006384 oligomerization reaction Methods 0.000 claims description 10
- 238000010992 reflux Methods 0.000 claims description 7
- 238000004062 sedimentation Methods 0.000 claims description 6
- 239000012808 vapor phase Substances 0.000 claims description 6
- 238000000605 extraction Methods 0.000 claims description 5
- 238000001816 cooling Methods 0.000 claims description 3
- 230000008878 coupling Effects 0.000 claims description 3
- 238000010168 coupling process Methods 0.000 claims description 3
- 238000005859 coupling reaction Methods 0.000 claims description 3
- 238000007670 refining Methods 0.000 claims description 3
- 230000009286 beneficial effect Effects 0.000 abstract 1
- 238000005265 energy consumption Methods 0.000 description 9
- 229910052799 carbon Inorganic materials 0.000 description 5
- 230000000052 comparative effect Effects 0.000 description 5
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 3
- 239000012752 auxiliary agent Substances 0.000 description 3
- 238000005191 phase separation Methods 0.000 description 3
- 239000002994 raw material Substances 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- 238000010586 diagram Methods 0.000 description 2
- -1 polyethylene Polymers 0.000 description 2
- 229920006124 polyolefin elastomer Polymers 0.000 description 2
- 239000004698 Polyethylene Substances 0.000 description 1
- 206010057040 Temperature intolerance Diseases 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 150000001335 aliphatic alkanes Chemical class 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- 238000009833 condensation Methods 0.000 description 1
- 230000005494 condensation Effects 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 230000020335 dealkylation Effects 0.000 description 1
- 238000006900 dealkylation reaction Methods 0.000 description 1
- 230000006204 deethylation Effects 0.000 description 1
- 238000006356 dehydrogenation reaction Methods 0.000 description 1
- 239000012847 fine chemical Substances 0.000 description 1
- 230000008543 heat sensitivity Effects 0.000 description 1
- 239000013067 intermediate product Substances 0.000 description 1
- 239000010687 lubricating oil Substances 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 239000012188 paraffin wax Substances 0.000 description 1
- 239000004014 plasticizer Substances 0.000 description 1
- 229920000573 polyethylene Polymers 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 238000000746 purification Methods 0.000 description 1
- 238000005215 recombination Methods 0.000 description 1
- 230000006798 recombination Effects 0.000 description 1
- 238000007086 side reaction Methods 0.000 description 1
- 239000004094 surface-active agent Substances 0.000 description 1
- 238000001308 synthesis method Methods 0.000 description 1
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Abstract
The invention provides a method and a device for producing alpha olefin for recycling ethylene, comprising the following steps: s1: the reaction product and the solvent are subjected to liquid-liquid separation through a settling tank, the reaction solvent at the bottom of the settling tank is recycled to the reactor, ethylene, alpha olefin and the solvent are sent to a first-stage flash tank, primary decompression is carried out in the first-stage flash tank, first-stage flash steam is obtained, and the first-stage flash steam is sent to an ethylene recovery tower after decompression; s2: after primary decompression, the liquid phase in the primary flash tank is sent to a solvent separation tank, the solvent is recycled from the bottom of the solvent separation tank as a heavy phase, the olefin is sent to a secondary flash tank for flash evaporation as a light phase, and the obtained secondary flash gas is sent to an ethylene recovery tower after decompression; s3: the liquid phase in the second-stage flash tank exchanges heat with the liquid phase from the tower bottom of the ethylene recovery tower and then enters the deethylene tower, and the top of the deethylene tower is extracted through gas phase and sent to the ethylene recovery tower. The invention has the beneficial effects that: the process flow is simple, the practicability is strong, and the operation cost is low.
Description
Technical Field
The invention belongs to the field of polymer production, and particularly relates to a method and a device for producing alpha-olefins for recycling ethylene.
Background
Alpha olefin is an important raw material in the field of fine chemical industry, generally refers to olefin with double bonds at the end, has carbon number of mainly between C4 and C40, is an important organic raw material and an intermediate product, and is widely applied to products such as polyethylene comonomer, polyolefin elastomer (POE), high-grade lubricating oil, plasticizer, surfactant, auxiliary agent and the like. The alpha olefin synthesis method mainly comprises paraffin cracking method, alkane dehydrogenation method, separation extraction method, ethylene oligomerization method and the like. The ethylene oligomerization process is relatively simple, has high product linearity, and has the advantages of even-numbered carbon olefin as main component and low separation and purification cost.
The oligomerization of ethylene is carried out by taking ethylene as raw material, oligomerization reacting under the action of catalyst and reaction auxiliary agent to obtain even-carbon linear alpha-olefin, and the single-pass conversion rate of ethylene is less than 50%. Thus, in order to reduce the consumption of feed ethylene, it is desirable to separate unreacted ethylene from the alpha olefin product and recycle it back to the reactor for further reaction.
However, recovery of unreacted ethylene has the following problems:
1. because the ethylene oligomerization temperature is about 70-90 ℃, the reaction pressure is 8-10 MpaG, the critical temperature (9.6 ℃) and the critical pressure (5.07 MpaG) of ethylene are exceeded, the ethylene is in a supercritical phase, and the ethylene in the supercritical phase has the advantages of strong solubility and good diffusivity, so that unreacted ethylene, a reaction product alpha olefin and a reaction auxiliary agent are well dissolved together, and the three are in a quasi-homogeneous state, and the ethylene cannot be recovered through simple gas-liquid two-phase separation.
2. Because ethylene normal pressure boiling point is extremely low (-135 ℃), ethylene and reaction product alpha olefin (C4-C40) need to be pressurized and separated, the temperature difference of tower top and tower bottom is close to 250 ℃, and the efficiency of rectifying tower plates is extremely low, so that the rectifying tower is higher in tower height, higher in equipment investment and operation cost and difficult in industrial application.
3. High carbon alpha olefin (above C18) has certain heat sensitivity, side reaction can occur at higher temperature, so that light components and recombination components are increased, and the recovery rate of products is reduced.
Disclosure of Invention
In view of the above, the present invention aims to provide a method and a device for producing alpha-olefins for recovering ethylene, which are capable of recovering incompletely reacted ethylene from reaction products and solvents in the process of producing alpha-olefins by an ethylene oligomerization method, and solving the problems of difficult supercritical phase separation, large temperature difference of an olefin separation rectifying tower, high energy consumption, low recovery rate and purity while satisfying the requirements of high purity and high recovery rate of recycled ethylene, and have the advantages of strong industrial applicability, low operation cost and low separation cost.
In order to achieve the above purpose, the technical scheme of the invention is realized as follows:
a process for producing alpha olefins for the recovery of ethylene comprising the steps of:
s1: the reaction product and the solvent are subjected to liquid-liquid separation through a settling tank, the reaction solvent at the bottom of the settling tank is recycled to the reactor, ethylene, alpha olefin and the solvent are sent to a first-stage flash tank, primary decompression is carried out in the first-stage flash tank, first-stage flash steam is obtained, and the first-stage flash steam is sent to an ethylene recovery tower after decompression;
s2: after primary decompression, the liquid phase in the primary flash tank is sent to a solvent separation tank, the solvent is recycled from the bottom of the solvent separation tank as a heavy phase, the olefin is sent to a secondary flash tank for flash evaporation as a light phase, and the obtained secondary flash gas is sent to an ethylene recovery tower after decompression;
s3: the liquid phase in the second-stage flash tank exchanges heat with the liquid phase from the tower bottom of the ethylene recovery tower and then enters the deethylene tower, and the top of the deethylene tower is extracted through gas phase and sent to the ethylene recovery tower.
Further, the liquid phase of the second-stage flash tank exchanges heat with the liquid phase from the tower bottom of the ethylene recovery tower and then enters the ethylene removal tower, all ethylene and part of 1-butene are removed in the ethylene removal tower, the tower bottom liquid is an alpha olefin product and is sent to a product refining process, and the tower top is sent to the ethylene recovery tower through gas phase extraction;
and/or flash gas from the primary flash tank and the secondary flash tank and gas phase at the top of the deethylene tower enter an ethylene recovery tower together, high-purity ethylene is obtained at the top of the tower, the high-purity ethylene is recycled to the reaction system, 1-butene and 1-hexene are circulated to the tower kettle, and the high-purity ethylene is sent to the deethylene tower to be used as top reflux after being subjected to heat exchange and cooling with liquid phase of the secondary flash tank through a tower kettle pump.
Further, the ethylene oligomerization reaction product in the reaction system is even carbon alpha olefin between C4 and C40, the outlet operating pressure of the reactor is 8.0-10.0 MpaG, and the operating temperature is 70-90 ℃.
Further, the operating pressure of the sedimentation tank is 8.0-10.0 MpaG, and the operating temperature is 70-90 ℃;
further, the operating pressure of the primary flash tank is 4.0-5.0 MpaG, and the operating temperature is 30-70 ℃.
Further, the operating pressure of the solvent separation tank is 4.0-5.0 MpaG, and the operating temperature is 30-70 ℃.
Further, the operating pressure of the secondary flash tank is 3.0-4.0 MpaG, and the operating temperature is 30-70 ℃.
The deethylene column adopts positive pressure operation, the operation pressure is 2.5-3.5 MpaG, the temperature of the column top is 100-120 ℃, the temperature of the column bottom is 200-220 ℃, the reflux ratio is 5-50, the theoretical plates are 10-30, the column top is provided with a dephlegmator, and the vapor phase fraction of distillate is 10-20%.
And further, carrying out liquid-phase coupling heat exchange cooling on the bottom liquid of the ethylene recovery tower and the bottom liquid of the secondary flash tank, then conveying the bottom liquid to 1 st to 4 th theoretical plates at the top of the deethylene tower, preheating the bottom liquid of the secondary flash tank, and then conveying the bottom liquid to 5 th to 15 th theoretical plates at the middle part of the deethylene tower.
The ethylene recovery tower is operated by positive pressure, the operating pressure is 2.5-3.5 MpaG, the temperature of the tower top is minus 19-minus 12 ℃, the temperature of the tower bottom is 86-100 ℃, the reflux ratio is 5-50, theoretical plates are 10-30, a dephlegmator is arranged on the tower top, and the vapor phase fraction of distillate is 10-20%.
The method for producing the alpha olefin for recycling the ethylene reasonably selects the operating pressure of the deethylene tower and the ethylene recycling tower, the temperature of the tower bottom is lower than the thermosensitive temperature of the alpha olefin, and the method has few byproducts and high product recycling rate.
The device used in the method for producing the alpha olefin for recycling the ethylene comprises a reaction system, a settling tank, a primary flash tank, a solvent separation tank, a secondary flash tank, a de-ethylene tower and an ethylene recycling tower;
the top of the reaction system is connected with a settling tank through a pipeline, the bottom of the settling tank is connected with the reaction system through a pipeline, the top of the settling tank is connected with a first-stage flash tank through a pipeline, the bottom of the first-stage flash tank is connected with a solvent separation tank through a pipeline, the top of the first-stage flash tank is connected with an ethylene recovery tower through a pipeline, the top of the solvent separation tank is connected with the ethylene recovery tower through a pipeline, and the bottom of the solvent separation tank is connected with the bottom of the reaction system through a pipeline; the solvent separation tank is connected with the secondary flash tank through a pipeline, the secondary flash tank is connected with the ethylene recovery tower through a pipeline, the secondary flash tank is connected with the deethylene tower through a pipeline, the top of the deethylene tower is connected with the ethylene recovery tower, and the ethylene recovery tower is connected with the fresh ethylene through a feeding pipe and a reaction system.
Further, the bottom of the settling tank is connected with the bottom of the reactor system through a first pipeline, a first valve is arranged on the first pipeline, a first pressure sensor is arranged on one side of the settling tank, and the first pressure sensor is electrically connected with the first valve; the first pressure sensor is electrically connected with the controller, and the first valve is electrically connected with the controller;
one side of the reaction system is provided with a fresh ethylene pipeline, and the bottom of the reaction system is provided with a fresh solvent pipeline.
Further, the settling cask is connected with the one-level flash tank through the second pipeline, is equipped with the second valve on the second pipeline, and the settling cask is equipped with second pressure sensor, second valve and controller electric connection, second pressure sensor and controller electric connection, the controller adopts prior art.
Further, the top of the primary flash tank is connected with the ethylene recovery tower through a third pipeline, a third valve is arranged on the third pipeline, a third pressure sensor is arranged on the top of the primary flash tank, the third pressure sensor is electrically connected with a controller, and the controller is electrically connected with the third valve;
the top of the solvent separation tank is communicated with a third pipeline through a pipeline, and a third valve is arranged on the pipeline between the primary flash tank and the ethylene recovery tower.
Further, the solvent separation tank is connected with the middle part of the secondary flash tank through a fourth pipeline, a fourth valve is arranged on the fourth pipeline, a fourth pressure sensor is arranged at the top of the solvent separation tank, the fourth pressure sensor is electrically connected with the controller, and the controller is electrically connected with the fourth valve.
The bottom of the solvent separating tank is communicated with a fresh solvent pipeline through a solvent recovery pipeline.
Further, the top of the secondary flash tank is connected with the ethylene recovery tower through a fifth pipeline, a fifth valve is arranged on the fifth pipeline, a fifth pressure sensor is arranged on the top of the secondary flash tank, the fifth pressure sensor is electrically connected with a controller, and the controller is electrically connected with the fifth valve;
the bottom of the second-stage flash tank is connected with a deethylene tower through a sixth pipeline, and a feeding heat exchanger is arranged on the sixth pipeline;
a seventh pipeline is arranged at the bottom of the deethylene tower, the other end of the seventh pipeline is arranged at one side of the deethylene tower, and a deethylene tower kettle circulating pump and a deethylene tower reboiler are arranged on the seventh pipeline;
the bottom of the deethylenizing tower is provided with an alpha olefin outlet pipeline.
The top of the deethylene tower is connected with an ethylene recovery tower through an eighth pipeline, a deethylene tower condenser is arranged on the eighth pipeline and is connected with one side of the deethylene tower through a ninth pipeline.
Further, the bottom of the ethylene recovery tower is connected with one side of the deethylene tower through a tenth pipeline, and the tenth pipeline is communicated with the feeding heat exchanger;
the bottom of the ethylene recovery tower is connected with one side of the ethylene recovery tower through an eleventh pipeline, and an ethylene recovery reboiler is arranged on the eleventh pipeline.
The top of the ethylene recovery tower is connected with a fresh ethylene pipeline through a twelfth pipeline, an ethylene recovery tower condenser is arranged on the twelfth pipeline, and the ethylene recovery tower condenser is connected with one side of the ethylene recovery tower through the twelfth pipeline.
Compared with the prior art, the method and the device for producing the alpha olefin for recycling the ethylene have the following advantages:
1. the method for producing the alpha olefin for recycling the ethylene adopts a two-stage flash evaporation method to break the supercritical phase, realizes the effective separation of the olefin phase and the reaction solvent through three devices of a settling tank, a first-stage flash evaporation and a solvent separation tank, simultaneously realizes the preliminary separation of the ethylene and the alpha olefin product with low energy consumption, and greatly reduces the energy consumption of a subsequent ethylene recycling tower by flashing about 35-45% of the ethylene into the gas phase. The process flow is simple, the practicability is strong, and the operation cost is low.
2. The method for producing the alpha olefin for recycling the ethylene adopts the double-tower rectification of the deethylene tower and the ethylene recycling tower, realizes the recycling of the ethylene, and ensures that the recycling rate of the ethylene recycled to a reaction system is more than 99.9 percent and the purity can reach 99.9 percent by weight.
3. The alpha olefin production method for recycling ethylene solves the problem of large temperature gradient of single-tower rectification, has the advantages of small temperature gradient and high plate efficiency, and reduces the height of a rectification tower; meanwhile, the modes of feeding thermal coupling and vapor phase fraction extraction are adopted, so that the effective utilization of heat is realized, the vapor phase condensation and regasification process at the top of the deethylenization tower is reduced, and the energy consumption is lower.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention. In the drawings:
FIG. 1 is a schematic diagram of an apparatus for producing alpha olefins for recovering ethylene according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of an apparatus for producing alpha olefins according to a comparative example of the present invention.
Reference numerals illustrate:
1. a reaction system; 2. a settling tank; 3. a primary flash tank; 4. a solvent separation tank; 5. a secondary flash tank; 6. a deethylene column; 7. an ethylene recovery column; 8. a first pressure sensor; 9. a first valve; 10. fresh ethylene pipe; 11. fresh solvent; 12. a second valve; 13. a second pressure sensor; 14. a third valve; 15. a third pressure sensor; 16. a fourth valve; 17. a fourth pressure sensor; 18. a fifth valve; 19. a fifth pressure sensor; 20. a feed heat exchanger; 21. a circulating pump of the deethylenizing tower kettle; 22. a deethylene column reboiler; 23. an alpha olefin pipeline is discharged; 24. a dealkylation column condenser; 25. an ethylene recovery reboiler; 26. an ethylene recovery column condenser.
Detailed Description
It should be noted that, without conflict, the embodiments of the present invention and features of the embodiments may be combined with each other.
The invention will be described in detail below with reference to the drawings in connection with embodiments.
As shown in fig. 1, the reactor comprises a reaction system 1, a sedimentation tank 2, a primary flash tank 3, a solvent separation tank 4, a secondary flash tank 5, a deethylenizing tower 6 and an ethylene recovery tower 7; the top of the reaction system 1 is connected with a settling tank 2 through a pipeline, the bottom of the settling tank 2 is connected with the reaction system 1 through a pipeline, the settling tank 2 is connected with a primary flash tank 3 through a pipeline, the bottom of the primary flash tank 3 is connected with a solvent separation tank 4 through a pipeline, the top of the primary flash tank 3 is connected with an ethylene recovery tower 7 through a pipeline, the top of the solvent separation tank 4 is connected with the ethylene recovery tower 7 through a pipeline, and the bottom of the solvent separation tank 4 is connected with the bottom of the reaction system 1 through a pipeline; the solvent separation tank 4 is connected with the secondary flash tank 5 through a pipeline, the secondary flash tank 5 is connected with the ethylene recovery tower 7 through a pipeline, the secondary flash tank 5 is connected with the deethylene tower 6 through a pipeline, the top of the deethylene tower 6 is connected with the ethylene recovery tower 7, and the ethylene recovery tower 7 is connected with fresh ethylene through a feeding pipe and the reaction system 1.
The bottom of the settling tank 2 is connected with the bottom of the reactor system through a first pipeline, a first valve 9 is arranged on the first pipeline, a first pressure sensor 8 is arranged on one side of the settling tank 2, and the first pressure sensor 8 and the first valve 9 are electrically connected with a controller; one side of the reaction system 1 is provided with a fresh ethylene pipeline 10, and the bottom of the reaction system 1 is provided with a fresh solvent 11 pipeline. The settling tank 2 is connected with the primary flash tank 3 through a second pipeline, a second valve 13 is arranged on the second pipeline, the settling tank 2 is provided with a second pressure sensor 12, and the second valve 13 and the second pressure sensor 12 are electrically connected with a controller.
The top of the primary flash tank 3 is connected with the ethylene recovery tower 7 through a third pipeline, a third valve 15 is arranged on the third pipeline, a third pressure sensor 14 is arranged at the top of the primary flash tank 3, and the third pressure sensor 14 and the third valve 15 are electrically connected with a controller; the top of the solvent separation tank is communicated with a third pipeline through a pipeline, and a third valve 15 is arranged on the pipeline between the primary flash tank 3 and the ethylene recovery tower 7. The solvent separation tank is connected with the middle part of the secondary flash tank 5 through a fourth pipeline, a fourth valve 17 is arranged on the fourth pipeline, a fourth pressure sensor 16 is arranged at the top of the solvent separation tank, and the fourth pressure sensor 16 and the fourth valve 17 are electrically connected with the controller. The bottom of the solvent separating tank is communicated with a fresh solvent 11 pipeline through a solvent recovery pipeline.
The top of the secondary flash tank 5 is connected with the ethylene recovery tower 7 through a fifth pipeline, a fifth valve 18 is arranged on the fifth pipeline, a fifth pressure sensor 19 is arranged on the top of the secondary flash tank 5, and the fifth pressure sensor 19 and the fifth valve 18 are electrically connected with a controller; the bottom of the secondary flash tank 5 is connected with a deethylene tower 6 through a sixth pipeline, and a feeding heat exchanger 20 is arranged on the sixth pipeline;
a seventh pipeline is arranged at the bottom of the deethylene tower 6, the other end of the seventh pipeline is arranged at one side of the deethylene tower 6, and a deethylene tower kettle circulating pump 21 and a deethylene tower reboiler 22 are arranged on the seventh pipeline; the bottom of the deethylenizer 6 is provided with an alpha olefin outlet pipeline 23. The top of the deethylene tower 6 is connected with the ethylene recovery tower 7 through an eighth pipeline, a deethylene tower condenser 24 is arranged on the eighth pipeline and is connected with one side of the deethylene tower 6 through a ninth pipeline, and the deethylene tower condenser 24 is connected with one side of the deethylene tower 6.
The bottom of the ethylene recovery tower 7 is connected with one side of the deethylene tower 6 through a tenth pipeline which is communicated with the feeding heat exchanger 20; the bottom of the ethylene recovery column 7 is connected to one side of the ethylene recovery column 7 through an eleventh pipe provided with an ethylene recovery reboiler 25. The top of the ethylene recovery column 7 is connected with a fresh ethylene pipe 10 through a twelfth pipe, an ethylene recovery column condenser 27 is arranged on the twelfth pipe, and the ethylene recovery column condenser 27 is connected with one side of the ethylene recovery column 7 through the twelfth pipe.
Example 1
Take a 500 ton/year alpha olefin plant as an example:
the reaction product and solvent from the ethylene oligomerization reactor were first liquid-liquid separated at 8.0MpaG,85℃through a settling tank, the reaction solvent at the bottom of the settling tank was recycled back to the reactor, and the ethylene, alpha olefin and small amount of solvent at the top were sent to a first stage flash tank. The first decompression is carried out in a first-stage flash tank so as to break the supercritical phase into gas-liquid two phases, wherein the operation temperature of the flash tank is 40 ℃, the operation pressure is 4.5MpaG, about 20-25% of ethylene is carried with a small amount of 1-butene and 1-hexene to be flashed out, the liquid phase is sent to a solvent separation tank to complete the liquid-liquid two-phase separation, the solvent is recycled from the tank bottom of the separation tank as a heavy phase, the olefin is sent to a second-stage flash tank from the tank top as a light phase, the second-stage flash tank is arranged in the second-stage flash tank, the operation temperature of the second-stage flash tank is 40 ℃, the operation pressure is 3.5MpaG, about 15-20% of ethylene is carried with a small amount of 1-butene and 1-hexene to be further flashed out, the second-stage flash steam and the first-stage flash steam are sent to an ethylene recovery tower together after being decompressed, and the liquid phase is sent to a deethylation tower after being preheated.
The liquid phase from the second-stage flash tank exchanges heat with the liquid phase from the tower bottom of the ethylene recovery tower to 100 ℃, then enters the ethylene removal tower, all ethylene and part of 1-butene are removed in the ethylene removal tower, the tower bottom liquid is an alpha olefin product and is sent to a product refining process, and the tower top is sent to the ethylene recovery tower through gas phase extraction. The flash steam from the first-stage flash tank and the second-stage flash tank and the gas phase at the top of the deethylene tower enter an ethylene recovery tower together, high-purity ethylene is obtained at the top of the tower and is recycled to the reaction system, 1-butene and 1-hexene are circulated to the tower kettle, and the high-purity ethylene is sent to the deethylene tower to be used as the top reflux after being cooled to 90 ℃ through the liquid phase of the second-stage flash tank by a tower kettle pump.
The column operating parameters are shown in table 1.
TABLE 1 operating parameters of rectifying column
According to this example, the amount of recycled ethylene was 62.5kg/h, the ethylene recovery rate was over 99.9%, the purity was up to 99.9% wt, and the temperature difference at the top of the rectifying column was reduced to about 100℃as shown in Table 2 for specific theoretical plates and energy consumption.
TABLE 2 energy consumption of rectifying column
Example 2
Example 2 differs from example 1 in that the amount of recycled ethylene was 50kg/h, keeping the operating temperature and pressure of the primary flash tank, the secondary flash tank, the deethylenizer and the ethylene recovery column unchanged.
According to this example, the amount of recycled ethylene was 50kg/h, the ethylene recovery was likewise above 99.9% and the purity could reach 99.9% wt, the specific theoretical plate and energy consumption being shown in Table 3.
TABLE 3 energy consumption of rectifying column
Comparative example 1
Take a 500 ton/year alpha olefin plant as an example:
the reaction product and solvent from the ethylene oligomerization reactor were first subjected to liquid-liquid separation at 8.0MpaG at 85deg.C in a settling tank, the reaction solvent at the bottom of the settling tank was recycled back to the reactor, and compared with example 1, the top ethylene, alpha olefin and a small amount of solvent were not subjected to primary flash evaporation and secondary flash evaporation to break the supercritical state to complete the gas-liquid separation, and at the same time, the ethylene was recovered without adopting the double-column mode, but directly fed into an ethylene recovery column to recover ethylene, as shown in FIG. 2. The ethylene recovery was 62.5kg/h, and the recovery and purity were the same as in example 1. The tower heights and energy consumption comparisons of example 1 and comparative example 1 are shown in table 4.
Table 4 single column operating parameters
As can be seen from table 4, under the same operation conditions, the single tower top tower bottom temperature difference in comparative example 1 is close to 200 ℃, and the lower plate efficiency results in the need of higher theoretical plate for separation, and the equipment investment and operation cost are higher, so that the industrial application is difficult; meanwhile, under the conditions that the recovery rate and the purity of the ethylene are the same, the total cold quantity and the total heat quantity of the single tower and the double tower are basically consistent, and the total heat quantity of the double tower is smaller than that of the single tower because the two-stage pre-flash evaporation method is adopted to remove part of ethylene. In addition, the top of the deethylene tower in the embodiment 1 can be cooled by using lower grade circulating water, the bottom of the ethylene recovery tower can be heated by using lower grade steam, and the top of the single tower and the bottom of the tower can only be cooled by using high-specification chilled water due to large temperature difference, and the bottom of the tower can only be heated by using high-specification steam. In addition, the chilled water consumption in the embodiment 1 is reduced by 48% compared with that in the comparative example 1, the high-grade steam can be saved by more than 67%, meanwhile, the temperature difference of the tower top and the tower bottom is smaller than that of a single tower, the total theoretical plate number is smaller, and the industrial feasibility is higher.
The foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, alternatives, and improvements that fall within the spirit and scope of the invention.
Claims (10)
1. A process for producing alpha olefins for the recovery of ethylene, characterized by: the method comprises the following steps:
s1: the reaction product and the solvent are subjected to liquid-liquid separation through a settling tank (2), the reaction solvent at the bottom of the settling tank (2) is recycled back to the reactor, ethylene, alpha olefin and solvent are sent to a first-stage flash tank (3), primary decompression is carried out in the first-stage flash tank (3), first-stage flash steam is obtained, and the first-stage flash steam is sent to an ethylene recovery tower (7) after decompression;
s2: after primary decompression, the liquid phase in the primary flash tank is sent to a solvent separation tank (4), the solvent is recycled from the tank bottom of the solvent separation tank as a heavy phase, the olefin is sent to a secondary flash tank (5) for flash evaporation as a light phase, and the obtained secondary flash gas is sent to an ethylene recovery tower (7) after decompression;
s3: the liquid phase in the second-stage flash tank exchanges heat with the liquid phase from the tower kettle of the ethylene recovery tower (7) and then enters the ethylene removal tower (6), and the top of the ethylene removal tower (6) is extracted through the gas phase and sent to the ethylene recovery tower (7).
2. A process for producing alpha olefins for recovering ethylene according to claim 1, wherein: the liquid phase of the second-stage flash tank (5) exchanges heat with the liquid phase from the tower kettle of the ethylene recovery tower (7) and then enters the ethylene removal tower (6), all ethylene and part of 1-butene are removed in the ethylene removal tower (6), the tower kettle liquid is an alpha olefin product and is sent to a product refining process, and the tower top is sent to the ethylene recovery tower (7) through gas phase extraction;
and/or flash steam from the primary flash tank (3) and the secondary flash tank (5) and gas phase at the top of the deethylene tower (6) enter an ethylene recovery tower (7) together, high-purity ethylene is obtained at the top of the tower and is recycled to the reaction system (1), and 1-butene and 1-hexene are in the tower kettle, and are sent to the deethylene tower (6) to be used as top reflux after being subjected to heat exchange cooling with liquid phase of the secondary flash tank (5) through a tower kettle pump.
3. A process for producing alpha olefins for recovering ethylene according to claim 1, wherein: the ethylene oligomerization reaction product in the reaction system (1) is even-numbered alpha olefin between C4 and C40, the operation pressure of the outlet of the reactor is 8.0-10.0 MpaG, and the operation temperature is 70-90 ℃;
and/or the operation pressure of the sedimentation tank (2) is 8.0-10.0 MpaG, and the operation temperature is 70-90 ℃;
and/or the operation pressure of the primary flash tank (3) is 4.0-5.0 MpaG, and the operation temperature is 30-70 ℃;
and/or the operation pressure of the solvent separation tank is 4.0-5.0 MpaG, and the operation temperature is 30-70 ℃;
and/or the operating pressure of the secondary flash tank (5) is 3.0-4.0 MpaG, and the operating temperature is 30-70 ℃;
and/or the deethylene tower (6) adopts positive pressure operation, the operation pressure is 2.5-3.5 MpaG, the tower top temperature is 100-120 ℃, the tower bottom temperature is 200-220 ℃, the reflux ratio is 5-50, the theoretical plates are 10-30, the tower top is provided with a dephlegmator, and the vapor phase fraction of distillate is 10-20%;
and/or, the tower bottom liquid of the ethylene recovery tower (7) and the tank bottom liquid of the secondary flash tank (5) are subjected to liquid-phase coupling heat exchange and cooled and then are sent to the 1 st to 4 th theoretical plates at the top of the deethylene tower (6), and the tank bottom liquid of the secondary flash tank (5) is preheated and then is sent to the 5 th to 15 th theoretical plates at the middle part of the deethylene tower (6);
and/or the ethylene recovery tower (7) adopts positive pressure operation, the operation pressure is 2.5-3.5 MpaG, the tower top temperature is-19 to-12 ℃, the tower bottom temperature is 86-100 ℃, the reflux ratio is 5-50, the theoretical plates are 10-30, the tower top is provided with a dephlegmator, and the vapor phase fraction of the distillate is 10-20%.
4. A device for a process for producing alpha olefins for recovering ethylene according to any of claims 1-3, characterized in that: comprises a reaction system (1), a sedimentation tank (2), a primary flash tank (3), a solvent separation tank (4), a secondary flash tank (5), a de-ethylene tower (6) and an ethylene recovery tower (7);
the top of the reaction system (1) is connected with a settling tank (2) through a pipeline, the bottom of the settling tank (2) is connected with the reaction system (1) through a pipeline, the settling tank (2) is connected with a primary flash tank (3) through a pipeline, the bottom of the primary flash tank (3) is connected with a solvent separation tank (4) through a pipeline, the top of the primary flash tank (3) is connected with an ethylene recovery tower (7) through a pipeline, the top of the solvent separation tank (4) is connected with the ethylene recovery tower (7) through a pipeline, and the bottom of the solvent separation tank (4) is connected with the bottom of the reaction system (1) through a pipeline; the solvent separation tank (4) is connected with the secondary flash tank (5) through a pipeline, the secondary flash tank (5) is connected with the ethylene recovery tower (7) through a pipeline, the secondary flash tank (5) is connected with the deethylene tower (6) through a pipeline, the top of the deethylene tower (6) is connected with the ethylene recovery tower (7), and the ethylene recovery tower (7) is connected with fresh ethylene through a feeding pipe and the reaction system (1).
5. An apparatus for a process for producing alpha olefins for recovering ethylene as claimed in claim 4, wherein: the bottom of the settling tank (2) is connected with the bottom of the reactor system through a first pipeline, a first valve (9) is arranged on the first pipeline, a first pressure sensor (8) is arranged on one side of the settling tank (2), and the first pressure sensor (8) and the first valve (9) are electrically connected with a controller;
one side of the reaction system (1) is provided with a fresh ethylene pipeline (10), and the bottom of the reaction system (1) is provided with a fresh solvent (11) pipeline.
6. An apparatus for a process for producing alpha olefins for recovering ethylene as claimed in claim 4, wherein: the sedimentation tank (2) is connected with the primary flash tank (3) through a second pipeline, a second valve (13) is arranged on the second pipeline, the sedimentation tank (2) is provided with a second pressure sensor (12), and the second valve (13) and the second pressure sensor (12) are electrically connected with the controller.
7. An apparatus for a process for producing alpha olefins for recovering ethylene as claimed in claim 4, wherein: the top of the primary flash tank (3) is connected with the ethylene recovery tower (7) through a third pipeline, a third valve (15) is arranged on the third pipeline, a third pressure sensor (14) is arranged at the top of the primary flash tank (3), and the third pressure sensor (14) and the third valve (15) are electrically connected with a controller;
the top of the solvent separating tank is communicated with a third pipeline through a pipeline, and a third valve (15) is arranged on the pipeline between the primary flash tank (3) and the ethylene recovery tower (7).
8. An apparatus for a process for producing alpha olefins for recovering ethylene as claimed in claim 4, wherein: the solvent separation tank is connected with the middle part of the second-stage flash tank (5) through a fourth pipeline, a fourth valve (17) is arranged on the fourth pipeline, a fourth pressure sensor (16) is arranged at the top of the solvent separation tank, and the fourth pressure sensor (16) and the fourth valve (17) are electrically connected with the controller.
The bottom of the solvent separating tank is communicated with a fresh solvent (11) pipeline through a solvent recovery pipeline.
9. An apparatus for a process for producing alpha olefins for recovering ethylene as claimed in claim 4, wherein:
the top of the secondary flash tank (5) is connected with the ethylene recovery tower (7) through a fifth pipeline, a fifth valve (18) is arranged on the fifth pipeline, a fifth pressure sensor (19) is arranged on the top of the secondary flash tank (5), and the fifth pressure sensor (19) and the fifth valve (18) are electrically connected with a controller;
the bottom of the second-stage flash tank (5) is connected with a deethylene tower (6) through a sixth pipeline, and a feeding heat exchanger (20) is arranged on the sixth pipeline;
a seventh pipeline is arranged at the bottom of the deethylene tower (6), the other end of the seventh pipeline is arranged at one side of the deethylene tower (6), and a deethylene tower kettle circulating pump (21) and a deethylene tower reboiler (22) are arranged on the seventh pipeline;
the bottom of the deethylenizing tower (6) is provided with an alpha olefin outlet pipeline (23).
The top of the deethylene tower (6) is connected with an ethylene recovery tower (7) through an eighth pipeline, a deethylene tower condenser (24) is arranged on the eighth pipeline and is connected with one side of the deethylene tower (6) through a ninth pipeline, and the deethylene tower condenser (24) is connected with the other side of the deethylene tower (6) through a third pipeline.
10. An apparatus for a process for producing alpha olefins for recovering ethylene as claimed in claim 4, wherein: the bottom of the ethylene recovery tower (7) is connected with one side of the deethylene tower (6) through a tenth pipeline which is communicated with a feed heat exchanger (20);
the bottom of the ethylene recovery tower (7) is connected with one side of the ethylene recovery tower (7) through an eleventh pipeline, and an ethylene recovery reboiler (25) is arranged on the eleventh pipeline.
The top of the ethylene recovery tower (7) is connected with a fresh ethylene pipeline (10) through a twelfth pipeline, an ethylene recovery tower condenser (26) is arranged on the twelfth pipeline, and the ethylene recovery tower condenser (26) is connected with one side of the ethylene recovery tower (7) through the twelfth pipeline.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202311582721.3A CN117700293A (en) | 2023-11-24 | 2023-11-24 | Alpha-olefin production method and device for recycling ethylene |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202311582721.3A CN117700293A (en) | 2023-11-24 | 2023-11-24 | Alpha-olefin production method and device for recycling ethylene |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN117700293A true CN117700293A (en) | 2024-03-15 |
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ID=90148846
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202311582721.3A Pending CN117700293A (en) | 2023-11-24 | 2023-11-24 | Alpha-olefin production method and device for recycling ethylene |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN117700293A (en) |
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2023
- 2023-11-24 CN CN202311582721.3A patent/CN117700293A/en active Pending
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