CN109678640A - A kind of separation method and device of Catalyst for Oxidative Coupling of Methane reaction gas - Google Patents
A kind of separation method and device of Catalyst for Oxidative Coupling of Methane reaction gas Download PDFInfo
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- CN109678640A CN109678640A CN201710980447.3A CN201710980447A CN109678640A CN 109678640 A CN109678640 A CN 109678640A CN 201710980447 A CN201710980447 A CN 201710980447A CN 109678640 A CN109678640 A CN 109678640A
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- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 title claims abstract description 102
- 239000012495 reaction gas Substances 0.000 title claims abstract description 40
- 238000005691 oxidative coupling reaction Methods 0.000 title claims abstract description 35
- 238000000926 separation method Methods 0.000 title claims abstract description 28
- 239000003054 catalyst Substances 0.000 title abstract description 5
- 238000010521 absorption reaction Methods 0.000 claims abstract description 62
- 239000000463 material Substances 0.000 claims abstract description 32
- 238000000034 method Methods 0.000 claims abstract description 27
- 230000002745 absorbent Effects 0.000 claims abstract description 17
- 239000002250 absorbent Substances 0.000 claims abstract description 17
- 238000011084 recovery Methods 0.000 claims abstract description 17
- 238000001816 cooling Methods 0.000 claims abstract description 9
- 239000002904 solvent Substances 0.000 claims abstract description 8
- 239000007789 gas Substances 0.000 claims description 58
- VGGSQFUCUMXWEO-UHFFFAOYSA-N Ethene Chemical compound C=C VGGSQFUCUMXWEO-UHFFFAOYSA-N 0.000 claims description 44
- 239000005977 Ethylene Substances 0.000 claims description 44
- 238000003795 desorption Methods 0.000 claims description 35
- 239000000047 product Substances 0.000 claims description 20
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical group [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 19
- 229910052799 carbon Inorganic materials 0.000 claims description 19
- ATUOYWHBWRKTHZ-UHFFFAOYSA-N Propane Chemical compound CCC ATUOYWHBWRKTHZ-UHFFFAOYSA-N 0.000 claims description 14
- 230000006835 compression Effects 0.000 claims description 12
- 238000007906 compression Methods 0.000 claims description 12
- 239000001294 propane Substances 0.000 claims description 7
- 239000002253 acid Substances 0.000 claims description 6
- 238000001035 drying Methods 0.000 claims description 5
- OFBQJSOFQDEBGM-UHFFFAOYSA-N Pentane Chemical compound CCCCC OFBQJSOFQDEBGM-UHFFFAOYSA-N 0.000 claims description 4
- NNPPMTNAJDCUHE-UHFFFAOYSA-N isobutane Chemical compound CC(C)C NNPPMTNAJDCUHE-UHFFFAOYSA-N 0.000 claims description 4
- QWTDNUCVQCZILF-UHFFFAOYSA-N isopentane Chemical compound CCC(C)C QWTDNUCVQCZILF-UHFFFAOYSA-N 0.000 claims description 4
- 238000002360 preparation method Methods 0.000 claims description 4
- 238000005984 hydrogenation reaction Methods 0.000 claims description 3
- 239000004215 Carbon black (E152) Substances 0.000 claims description 2
- -1 acetylene hydrocarbon Chemical class 0.000 claims description 2
- AFABGHUZZDYHJO-UHFFFAOYSA-N dimethyl butane Natural products CCCC(C)C AFABGHUZZDYHJO-UHFFFAOYSA-N 0.000 claims description 2
- 238000001704 evaporation Methods 0.000 claims description 2
- 230000008020 evaporation Effects 0.000 claims description 2
- 229930195733 hydrocarbon Natural products 0.000 claims description 2
- 239000001282 iso-butane Substances 0.000 claims description 2
- 239000007788 liquid Substances 0.000 claims description 2
- IJDNQMDRQITEOD-UHFFFAOYSA-N n-butane Chemical compound CCCC IJDNQMDRQITEOD-UHFFFAOYSA-N 0.000 claims description 2
- 239000013589 supplement Substances 0.000 claims description 2
- HSFWRNGVRCDJHI-UHFFFAOYSA-N alpha-acetylene Natural products C#C HSFWRNGVRCDJHI-UHFFFAOYSA-N 0.000 claims 2
- 238000007599 discharging Methods 0.000 claims 1
- 125000002534 ethynyl group Chemical group [H]C#C* 0.000 claims 1
- 238000005265 energy consumption Methods 0.000 abstract description 5
- 239000007792 gaseous phase Substances 0.000 abstract 2
- 239000012071 phase Substances 0.000 description 20
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 10
- 230000008569 process Effects 0.000 description 10
- OTMSDBZUPAUEDD-UHFFFAOYSA-N Ethane Chemical compound CC OTMSDBZUPAUEDD-UHFFFAOYSA-N 0.000 description 8
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 6
- 239000001301 oxygen Substances 0.000 description 6
- 229910052760 oxygen Inorganic materials 0.000 description 6
- 239000007795 chemical reaction product Substances 0.000 description 5
- 229910052757 nitrogen Inorganic materials 0.000 description 5
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 4
- 229910002092 carbon dioxide Inorganic materials 0.000 description 4
- 150000001345 alkine derivatives Chemical class 0.000 description 3
- 150000001412 amines Chemical class 0.000 description 3
- 238000004064 recycling Methods 0.000 description 3
- 238000005057 refrigeration Methods 0.000 description 3
- 238000005336 cracking Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- QQONPFPTGQHPMA-UHFFFAOYSA-N propylene Natural products CC=C QQONPFPTGQHPMA-UHFFFAOYSA-N 0.000 description 2
- 125000004805 propylene group Chemical group [H]C([H])([H])C([H])([*:1])C([H])([H])[*:2] 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 230000000630 rising effect Effects 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- JVFDADFMKQKAHW-UHFFFAOYSA-N C.[N] Chemical compound C.[N] JVFDADFMKQKAHW-UHFFFAOYSA-N 0.000 description 1
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 239000013064 chemical raw material Substances 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000010779 crude oil Substances 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 229910001882 dioxygen Inorganic materials 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 150000002430 hydrocarbons Chemical class 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000005120 petroleum cracking Methods 0.000 description 1
- 238000000746 purification Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000005406 washing Methods 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C2/00—Preparation of hydrocarbons from hydrocarbons containing a smaller number of carbon atoms
- C07C2/76—Preparation of hydrocarbons from hydrocarbons containing a smaller number of carbon atoms by condensation of hydrocarbons with partial elimination of hydrogen
- C07C2/82—Preparation of hydrocarbons from hydrocarbons containing a smaller number of carbon atoms by condensation of hydrocarbons with partial elimination of hydrogen oxidative coupling
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C7/00—Purification; Separation; Use of additives
- C07C7/005—Processes comprising at least two steps in series
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C7/00—Purification; Separation; Use of additives
- C07C7/11—Purification; Separation; Use of additives by absorption, i.e. purification or separation of gaseous hydrocarbons with the aid of liquids
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/10—Process efficiency
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/50—Improvements relating to the production of bulk chemicals
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P30/00—Technologies relating to oil refining and petrochemical industry
- Y02P30/40—Ethylene production
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Analytical Chemistry (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Water Supply & Treatment (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
The invention belongs to Catalyst for Oxidative Coupling of Methane fields, are related to the separation method and device of a kind of Catalyst for Oxidative Coupling of Methane reaction gas.Method includes the following steps: 1) OCM reaction gas is sent to absorption tower after compressor boosting, cooling；2) absorbent enters at the top of absorption tower, absorbs C2 fraction and the above component in OCM reaction gas；The top gaseous phase logistics on absorption tower is sent to cold recovery system, and tower reactor logistics is sent to desorber；3) logistics of desorber top gaseous phase is produced as product, and the lean solvent that tower reactor obtains returns at the top of absorption tower after cooling.Methods and apparatus of the present invention substantially increases the operation temperature of separation, requires to be substantially reduced to equipment material, while reducing energy consumption, also, entire work flow is simple, be easy to operate and control.
Description
Technical Field
The invention belongs to the field of ethylene preparation through oxidative coupling of methane, and particularly relates to a separation method and a separation device for reaction gas in ethylene preparation through oxidative coupling of methane.
Background
Ethylene is the most important basic organic chemical raw material, and its production has long been dependent on petroleum cracking routes, and the problems of environmental pollution and the like caused by the ethylene are becoming serious. Along with the continuous rising of the price of crude oil, the rising of the price of ethylene cracking raw materials is initiated, and simultaneously, the phenomenon of short supply and short demand of the ethylene cracking raw materials is also very prominent. In 2010, with the breakthrough of the united states in the shale gas field, a large amount of methane which is difficult to be exploited is exploited, and the chemical utilization of methane draws high attention from the industry, so that the research on preparing ethylene and ethane by methane oxidative coupling becomes a research hotspot worldwide again.
The aim of preparing ethylene (OCM for short) by oxidative coupling of methane is to convert methane into ethylene under the action of a catalyst, and the reaction products are relatively complex and mainly comprise methane, ethylene, ethane, CO and CO2、O2And the like. Patent application US20150368167 discloses a process for separating the OCM reaction products, by means of which three product streams, a C2-rich stream, a nitrogen-rich stream and a methane-rich stream, are obtained. The OCM reaction product first produces a C2 rich stream and a methane nitrogen rich stream in a first separation column, and then a nitrogen rich stream and a methane rich stream in a second separation column. Because the separation method adopts low-temperature rectification, the temperature of the whole separation unit is very low, the temperature of the top of the first separation tower is as low as-162 ℃, and the temperature of the top of the second separation tower is as low as-210 ℃, which has very high requirements on equipment materials, greatly increases the investment cost and has high energy consumption.
Patent application CN201710006765.X discloses a separation process for preparing ethylene reaction products by oxidative coupling of methane, wherein the process separates components of the reaction products one by one through the working procedures of compression, alcohol amine method, drying, cryogenic rectification and the like, finally obtains polymer-grade ethylene products, and the recovery rate of ethylene is more than 99%. The patent obviously improves the product quality, but the separation is still cryogenic rectification, and a cold box is required to provide low-grade cold energy.
Patent application WO2015105911 discloses an oxidative coupling system for methane to oxidatively couple methane to ethylene, which is in turn converted to an alternative higher hydrocarbon product. However, this patent application is directed to the reaction of ethylene and other components in the OCM product gas, such as unreacted methane, ethane, CO2Separation of nitrogen, water, etc., still using cryogenic rectification, a first separator for separating methane/nitrogen from components above C2, operating at temperatures as low as about-160 ℃, and a second separator for separating methane from nitrogen, operating at temperatures as low as about-200 ℃.
The methods in the prior art all need lower operation temperature, have very high requirements on equipment materials, greatly increase the investment cost and limit the industrial application of the OCM process. Therefore, it is highly desirable to develop a separation method for preparing ethylene reaction gas by oxidative coupling of methane with low energy consumption.
Disclosure of Invention
The invention aims to provide a separation method and a separation device for preparing ethylene reaction gas by oxidative coupling of methane, which greatly improve the separation operation temperature, obviously reduce the requirements on equipment materials, simultaneously reduce the energy consumption, have simple whole flow and are easy to operate and control.
The first aspect of the invention provides a method for separating reaction gas for preparing ethylene by oxidative coupling of methane, which comprises the following steps:
1) the OCM reaction gas is sent to an absorption tower after being pressurized and cooled by a compressor;
2) the absorbent enters from the top of the absorption tower and absorbs C2 fraction and the above components in the OCM reaction gas; the gas phase material flow at the top of the absorption tower is sent to a cold energy recovery system, and the material flow at the bottom of the absorption tower is sent to a desorption tower;
3) and (3) extracting the gas-phase material flow at the top of the desorption tower as a product, and returning the lean solvent obtained at the tower bottom to the top of the absorption tower after cooling.
According to a preferred embodiment of the invention, the method further comprises:
4) the gas phase material flow from the top of the absorption tower enters a cold recovery system consisting of a cold box, an expander and a flash tank, the gas phase material flow is expanded and refrigerated by utilizing the pressure of the gas phase material flow, the gas phase material flow is flashed in the flash tank to recover the C2 fraction and the entrained absorbent which are not absorbed in the gas phase material flow, and the tail gas which does not contain the C2 fraction is discharged after being boosted by a booster driven by the expander; specifically, gas phase material flow from the top of the absorption tower enters a cold box, the temperature is reduced to-35 ℃ to-80 ℃, the gas enters an expansion machine to expand, then enters a flash tank to be flashed, gas at the top of the tank enters the cold box and is discharged after being boosted, and liquid at the bottom of the tank returns to the top of the absorption tower; and/or
5) According to the invention, if necessary, the gas phase at the top of the desorption tower can be subjected to dealkynization treatment, the gas phase at the top of the desorption tower is firstly sent to a dealkynization reactor, alkynes are removed through hydrogenation reaction, and the dealkynized material flow is extracted as a product. The catalyst and process conditions used in the dealkynization treatment of the present invention are not particularly limited, and those skilled in the art can determine the specific operating conditions and methods thereof according to need and general knowledge.
In the compression step, the pressure of the OCM reaction gas generally needs to be increased step by step, preferably to be increased to 2.0-3.5MPa, the number of stages of compression is not particularly limited in the invention, and multi-stage compression is preferably adopted, and five-stage compression is further preferably adopted.
In the cooling step, the reaction gas is preferably cooled to-40 ℃ to-30 ℃, and the required cold is provided by a-40 ℃ grade propylene refrigeration compressor.
Preferably, the present invention comprises a purification step mainly comprising acid gas removal and drying treatment, and the present invention has no particular limitation on the specific process conditions of this step, and the skilled person can determine the specific operation conditions and steps thereof as required. For example, acid gas removal can be performed in an amine scrubber.
According to a particular embodiment of the invention, the method comprises the following steps:
(1) compression: the pressure of the OCM reaction gas is gradually increased to 2.0-3.5 MPa.
(2) Purifying: and in the compression section, the OCM reaction gas is subjected to acid gas removal and drying treatment.
(3) And (3) cooling: gradually cooling the compressed OCM reaction gas obtained in the step 1) -2) to-40 ℃ to-30 ℃.
(4) Absorption: the absorbent enters from the top of the absorption tower and absorbs the carbon dioxide fraction and the above components in the OCM reaction gas; the tower kettle material flow of the absorption tower is sent to a desorption tower for treatment; the gas stream at the top of the tower is sent to a cold energy recovery system.
(5) Desorbing: the tower bottom material flow from the absorption tower enters a desorption tower, the lean solvent obtained from the tower bottom is cooled and returned to the top of the absorption tower to be used as an absorbent for recycling, and the gas phase obtained from the tower top is sent to a dealkynization reactor.
(6) Removing alkyne: and (3) introducing the gas phase from the top of the desorption tower into a dealkynization reactor, and removing the alkyne in the gas phase through hydrogenation reaction.
(7) Cold energy recovery: and the gas phase material flow from the top of the absorption tower enters a cold energy recovery system consisting of a cold box, an expander and a flash drum, the gas phase material flow is subjected to expansion refrigeration by utilizing the pressure of the gas phase material flow, the gas phase material flow is flashed in the flash drum to recover the C2 fraction and the entrained absorbent which are not absorbed in the gas phase material flow, the tail gas without the C2 fraction is discharged after being boosted by a compressor driven by the expander, and the tail gas can be returned to the inlet of the OCM reactor after being treated.
In the absorption step, the absorbent is preferably a carbon three-cut fraction containing propane, a carbon four-cut fraction containing n-butane and isobutane, or a carbon five-cut fraction containing n-pentane and isopentane; more preferably a propane-containing carbon-three fraction. In the process of the invention, there is no particular requirement for the amount of absorbent used, and the skilled person can determine this on the basis of the general knowledge in the art.
Preferably, the number of theoretical plates of the absorption tower is 30-80, the operating pressure is 1.5-5.0MPa, and the tower top temperature is-40 ℃ to-20 ℃.
In the desorption step, the desorbed absorbent obtained at the bottom of the desorption tower is cooled step by step and then returns to the absorption tower for recycling. Part of the absorbent enters the cold energy recovery system along with the gas phase at the top of the absorption tower, so that a strand of absorbent is preferably introduced into the bottom of the desorption tower to supplement the cold energy recovery system, so as to ensure the dosage of the absorbent in the absorption tower in the system.
Preferably, the theoretical plate number of the desorption tower is 20-60, and the operating pressure is 1.0-4.0 MPa.
The second aspect of the invention provides a separation device for preparing ethylene reaction gas by oxidative coupling of methane, which comprises a compressor, a heat exchanger, an absorption tower and a desorption tower which are connected in sequence; wherein the top of the absorption tower is connected with a cold recovery system, and the tower kettle is connected with a desorption tower; the cold energy recovery system preferably comprises a cold box, an expander and a flash tank; the tank top of the flash tank is connected with the cold tank, and the tank bottom is connected with the top of the absorption tower; the top of the desorption tower is connected with a carbon-rich product pipeline, and the tower kettle is connected with the top of the absorption tower; optionally, the top of the desorption tower is connected with a dealkynization reactor and then connected with a carbon-rich product pipeline.
According to the invention, the separation device is directly connected with the reactor for preparing ethylene by oxidative coupling of methane through the compressor so as to separate the reaction gas for preparing ethylene by oxidative coupling of methane.
According to a specific embodiment of the present invention, as shown in fig. 1, the separation apparatus includes a compressor, a heat exchanger, an absorption tower and a desorption tower, which are connected in sequence; wherein, the top of the absorption tower is connected with a cold box and then connected with an expander and a flash tank, and the tower kettle is connected with the middle part of the desorption tower; the top of the flash tank is connected with a cold box and then connected with a supercharger, and then connected with a tail gas discharge pipeline, and the bottom of the flash tank is connected with the top of the absorption tower; the top of the desorption tower is connected with a dealkynization reactor and then connected with a carbon-rich product pipeline, and the tower kettle is connected with the top of the absorption tower.
According to another embodiment of the present invention, as shown in fig. 2, the separation apparatus comprises a compressor, a heat exchanger, an absorption tower and a desorption tower, which are connected in sequence; wherein, the top of the absorption tower is connected with a cold box and then connected with an expander and a flash tank, and the tower kettle is connected with the middle part of the desorption tower; the top of the flash tank is connected with a cold box and then connected with a supercharger, and then connected with a tail gas discharge pipeline, and the bottom of the flash tank is connected with the top of the absorption tower; the top of the desorption tower is connected with a carbon-rich product pipeline, and the tower kettle is connected with the top of the absorption tower.
The separation method for preparing ethylene by oxidative coupling of methane has the following characteristics:
1) the separation process has higher temperature, the requirement of the whole process on the cooling capacity can be met by adopting the propylene refrigeration compressor, the requirement on equipment materials is reduced, and the energy consumption and the investment are also greatly reduced.
2) The process flow is simple, and the product quality is high.
Additional features and advantages of the invention will be set forth in the detailed description which follows.
Drawings
Exemplary embodiments of the present invention will be described in more detail by referring to the accompanying drawings.
FIG. 1 is a schematic diagram of a process for separating reaction gas from ethylene produced by oxidative coupling of methane according to an embodiment of the present invention.
FIG. 2 is a schematic diagram of a process for separating reaction gas in the preparation of ethylene by oxidative coupling of methane according to another embodiment of the present invention.
Description of reference numerals:
1. a reactor for preparing ethylene by oxidative coupling of methane; 2. a compressor; 3. a heat exchanger; 4. an absorption tower; 5. a desorption tower; 6. a dealkynization reactor; 7. a cold box; 8. a flash tank; 9. an expander; 10. a supercharger; 11. oxygen/oxygen enrichment; 12. methane; 13. a carbon-rich two product; 14. and (4) tail gas.
Detailed Description
Preferred embodiments of the present invention will be described in more detail below.
Examples
The device shown in figure 2 is adopted to separate the reaction gas for preparing the ethylene by the oxidative coupling of the methane. The device comprises a compressor 2, a heat exchanger 3, an absorption tower 4 and a desorption tower 5 which are connected in sequence; wherein the top of the absorption tower 4 is sequentially connected with a cold box 7, an expander 9 and a flash tank 8; the top of the flash tank 8 is connected with a cold box 7 and then connected with a supercharger 10, and then connected with a tail gas discharge pipeline, and the bottom of the flash tank is connected with the top of the absorption tower 4; the top of the desorption tower 5 is connected with a carbon-rich product pipeline, and the tower kettle is connected with the top of the absorption tower 4. Wherein, the compressor 2 is connected with the reactor 1 for preparing ethylene by oxidative coupling of methane, and in the reactor 1 for preparing ethylene by oxidative coupling of methane, the oxygen/oxygen-enriched gas 11 reacts with methane 12 to obtain OCM reaction gas.
The composition of the outlet of the reactor 1 for ethylene production by oxidative coupling of methane is shown in Table 1.
TABLE 1
| Composition of | mol％ |
| Oxygen gas | 0.55 |
| CO | 5.69 |
| CO2 | 6.15 |
| Methane | 34.06 |
| Ethylene | 7.72 |
| Ethane (III) | 2.52 |
| Propane | 0.55 |
| Water (W) | 42.75 |
The separation method comprises the following steps:
(1) compression: the OCM reaction gas from the reactor 1 for preparing ethylene by oxidative coupling of methane is sent to a compressor 2, is compressed in three sections, the pressure is raised to 1.0MPag, and then is sent to an amine scrubber for acid gas removal treatment.
(2) Purifying: and after acid gas removal treatment in an amine washing tower, drying the OCM reaction gas.
(3) And (3) cooling: the purified gas enters a compressor 2 for four sections, after four-five sections of compression, the pressure is raised to 3Mpag, and then the gas is cooled to-35 ℃ step by step through a heat exchanger 3 and then enters an absorption tower 4.
(4) Absorption: the theoretical plate number of the absorption column 4 was 55, the operating pressure was 2.7MPag, and the column top temperature was-27 ℃. The absorption solvent is a propane-rich carbon three-fraction, the solvent enters the absorption tower from the top of the absorption tower 4, and the OCM reaction gas enters from the 30 th tower plate. The carbon and the above components in the OCM reaction gas are absorbed by the solvent, extracted from the tower kettle and enter a desorption tower, and the tower top contains light components such as methane, oxygen, CO and the like and is carried with a small amount of absorbent.
(5) Desorbing: the theoretical plate number of the desorber 5 was 30 and the operating pressure was 2.2 MPag. The gas phase at the top of the desorption tower 5 is taken out as a carbon-rich second product 13, and the lean solvent at the bottom of the tower is cooled to-35 ℃ after being subjected to gradual heat exchange and then returns to the absorption tower 4 for recycling.
(6) Cold energy recovery: the unabsorbed gas at the top of the absorption tower 4 enters a cold box 7, the temperature is reduced to minus 45 ℃, the unabsorbed gas enters a flash tank 8 after passing through an expansion machine 9 for flash evaporation, the gas at the top of the flash tank 8 enters the cold box 7, and the liquid phase at the bottom of the tank returns to the absorption tower 4. After entering the cold box 7, the gas enters the supercharger 10, and finally the tail gas 14 rich in components such as methane, oxygen, CO and the like is obtained.
The composition of the resulting carbon-enriched di-product 13 is shown in table 2.
TABLE 2
| Composition of | mol％ |
| Methane | 0.26 |
| Ethylene | 42.61 |
| Ethane (III) | 13.74 |
| Propane | 43.39 |
In this example, the recovery of ethylene and ethane was 99.4%.
Having described embodiments of the present invention, the foregoing description is intended to be exemplary, not exhaustive, and not limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments.
Claims (10)
1. A separation method for preparing ethylene reaction gas by methane oxidative coupling comprises the following steps:
1) the OCM reaction gas is sent to an absorption tower after being pressurized and cooled by a compressor;
2) the absorbent enters from the top of the absorption tower and absorbs C2 fraction and the above components in the OCM reaction gas; the gas phase material flow at the top of the absorption tower is sent to a cold energy recovery system, and the material flow at the bottom of the absorption tower is sent to a desorption tower;
3) and (3) extracting the gas-phase material flow at the top of the desorption tower as a product, and returning the lean solvent obtained at the tower bottom to the top of the absorption tower after cooling.
2. The method for separating the reaction gas for the oxidative coupling of methane to ethylene according to claim 1, further comprising:
4) the gas phase material flow from the top of the absorption tower enters a cold recovery system consisting of a cold box, an expander and a flash tank, the gas phase material flow is expanded and refrigerated by utilizing the pressure of the gas phase material flow, the gas phase material flow is flashed in the flash tank to recover the C2 fraction and the entrained absorbent which are not absorbed in the gas phase material flow, and the tail gas which does not contain the C2 fraction is discharged after being boosted by a booster driven by the expander; and/or
5) And the gas phase at the top of the desorption tower is firstly sent to a dealkynization reactor, acetylene hydrocarbon is removed through hydrogenation reaction, and the material flow after acetylene removal is extracted as a product.
3. The method for separating the reaction gas for the oxidative coupling of methane to ethylene according to claim 2, wherein the step 4) comprises: and (3) introducing the gas phase material flow from the top of the absorption tower into a cold box, reducing the temperature to-35 ℃ to-80 ℃, introducing the gas into an expansion machine to expand the gas, introducing the gas into a flash tank to carry out flash evaporation, introducing the gas at the top of the tank into the cold box, boosting the pressure and discharging, and returning the liquid at the bottom of the tank to the top of the absorption tower.
4. The method for separating the reaction gas in the oxidative coupling of methane to ethylene according to claim 1, wherein in the step 1), the pressure of the compressor is increased to 2.0-3.5MPa, and the compressor is cooled to-40 ℃ to-30 ℃.
5. The method for separating the reaction gas in the oxidative coupling of methane to ethylene according to claim 1, wherein the compressor in the step 1) adopts multi-stage compression, preferably five-stage compression.
6. The method for separating a reaction gas in the oxidative coupling of methane to ethylene according to claim 5, wherein the OCM reaction gas is subjected to acid gas removal and drying treatment in the compression section.
7. The method for separating the reaction gas for preparing the ethylene by oxidative coupling of the methane according to claim 1, wherein the absorbent is a carbon three-fraction containing propane, a carbon four-fraction containing n-butane and isobutane, or a carbon five-fraction containing n-pentane and isopentane; preferably a propane containing carbon three cut.
8. The method for separating the reaction gas in the preparation of ethylene by oxidative coupling of methane as claimed in claim 1, wherein, in the step 3), a strand of absorbent is introduced into the bottom of the desorption tower as a supplement.
9. The method for separating a reaction gas in the oxidative coupling of methane to ethylene according to any one of claims 1 to 8,
the theoretical plate number of the absorption tower is 30-80, the operation pressure is 1.5-5.0MPa, and the tower top temperature is-40 ℃ to-20 ℃;
the theoretical plate number of the desorption tower is 20-60, and the operation pressure is 1.0-4.0 MPa.
10. A separation device for preparing ethylene reaction gas by oxidative coupling of methane comprises a compressor, a heat exchanger, an absorption tower and a desorption tower which are sequentially connected; wherein,
the top of the absorption tower is connected with a cold energy recovery system, and the tower kettle is connected with a desorption tower; the cold energy recovery system preferably comprises a cold box, an expander and a flash tank; the tank top of the flash tank is connected with the cold tank, and the tank bottom is connected with the top of the absorption tower;
the top of the desorption tower is connected with a carbon-rich product pipeline, and the tower kettle is connected with the top of the absorption tower;
optionally, the top of the desorption tower is connected with a dealkynization reactor and then connected with a carbon-rich product pipeline.
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