CN109678639A - 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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- CN109678639A CN109678639A CN201710979276.2A CN201710979276A CN109678639A CN 109678639 A CN109678639 A CN 109678639A CN 201710979276 A CN201710979276 A CN 201710979276A CN 109678639 A CN109678639 A CN 109678639A
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- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 title claims abstract description 100
- 239000012495 reaction gas Substances 0.000 title claims abstract description 43
- 238000005691 oxidative coupling reaction Methods 0.000 title claims abstract description 35
- 238000000926 separation method Methods 0.000 title claims abstract description 31
- 239000003054 catalyst Substances 0.000 title abstract description 5
- 238000010521 absorption reaction Methods 0.000 claims abstract description 62
- 238000003795 desorption Methods 0.000 claims abstract description 51
- 230000002745 absorbent Effects 0.000 claims abstract description 25
- 239000002250 absorbent Substances 0.000 claims abstract description 25
- 239000000463 material Substances 0.000 claims abstract description 25
- 238000000034 method Methods 0.000 claims abstract description 25
- 239000002904 solvent Substances 0.000 claims abstract description 14
- 238000001816 cooling Methods 0.000 claims abstract description 9
- 230000018044 dehydration Effects 0.000 claims abstract description 4
- 238000006297 dehydration reaction Methods 0.000 claims abstract description 4
- 230000009102 absorption Effects 0.000 claims description 59
- VGGSQFUCUMXWEO-UHFFFAOYSA-N Ethene Chemical compound C=C VGGSQFUCUMXWEO-UHFFFAOYSA-N 0.000 claims description 43
- 239000005977 Ethylene Substances 0.000 claims description 43
- 230000009103 reabsorption Effects 0.000 claims description 41
- 239000007789 gas Substances 0.000 claims description 30
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical group [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 20
- 229910052799 carbon Inorganic materials 0.000 claims description 20
- 239000000047 product Substances 0.000 claims description 20
- 238000000746 purification Methods 0.000 claims description 17
- 230000006835 compression Effects 0.000 claims description 9
- 238000007906 compression Methods 0.000 claims description 9
- ATUOYWHBWRKTHZ-UHFFFAOYSA-N Propane Chemical compound CCC ATUOYWHBWRKTHZ-UHFFFAOYSA-N 0.000 claims description 8
- NNPPMTNAJDCUHE-UHFFFAOYSA-N isobutane Chemical compound CC(C)C NNPPMTNAJDCUHE-UHFFFAOYSA-N 0.000 claims description 8
- 238000000605 extraction Methods 0.000 claims description 7
- 239000002253 acid Substances 0.000 claims description 6
- IJDNQMDRQITEOD-UHFFFAOYSA-N n-butane Chemical compound CCCC IJDNQMDRQITEOD-UHFFFAOYSA-N 0.000 claims description 6
- OFBQJSOFQDEBGM-UHFFFAOYSA-N Pentane Chemical compound CCCCC OFBQJSOFQDEBGM-UHFFFAOYSA-N 0.000 claims description 5
- 239000001282 iso-butane Substances 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
- 239000001294 propane Substances 0.000 claims description 4
- 239000013589 supplement Substances 0.000 claims description 4
- 239000004215 Carbon black (E152) Substances 0.000 claims description 3
- 208000005156 Dehydration Diseases 0.000 claims description 3
- -1 acetylene hydrocarbon Chemical class 0.000 claims description 3
- 229930195733 hydrocarbon Natural products 0.000 claims description 3
- 238000005984 hydrogenation reaction Methods 0.000 claims description 3
- 239000013014 purified material Substances 0.000 claims description 3
- HSFWRNGVRCDJHI-UHFFFAOYSA-N alpha-acetylene Natural products C#C HSFWRNGVRCDJHI-UHFFFAOYSA-N 0.000 claims description 2
- 125000003118 aryl group Chemical group 0.000 claims description 2
- AFABGHUZZDYHJO-UHFFFAOYSA-N dimethyl butane Natural products CCCC(C)C AFABGHUZZDYHJO-UHFFFAOYSA-N 0.000 claims description 2
- 238000005265 energy consumption Methods 0.000 abstract description 6
- 239000007792 gaseous phase Substances 0.000 abstract 3
- 239000003795 chemical substances by application Substances 0.000 abstract 1
- 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 7
- 150000001345 alkine derivatives Chemical class 0.000 description 6
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 5
- 239000007795 chemical reaction product Substances 0.000 description 5
- 229910052757 nitrogen Inorganic materials 0.000 description 5
- 239000001301 oxygen Substances 0.000 description 5
- 229910052760 oxygen Inorganic materials 0.000 description 5
- 238000004064 recycling Methods 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
- 150000001412 amines Chemical class 0.000 description 2
- 238000005336 cracking Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- AMXOYNBUYSYVKV-UHFFFAOYSA-M lithium bromide Chemical compound [Li+].[Br-] AMXOYNBUYSYVKV-UHFFFAOYSA-M 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 238000011084 recovery Methods 0.000 description 2
- 238000005057 refrigeration Methods 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
- 239000001273 butane Substances 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
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 238000005120 petroleum cracking Methods 0.000 description 1
- QQONPFPTGQHPMA-UHFFFAOYSA-N propylene Natural products CC=C QQONPFPTGQHPMA-UHFFFAOYSA-N 0.000 description 1
- 125000004805 propylene group Chemical group [H]C([H])([H])C([H])([*:1])C([H])([H])[*:2] 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
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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.This method comprises: 1) the boosted cooling of OCM reaction gas, is sent to absorption tower；2) absorbent absorbs the C2 fraction and the above component in OCM reaction gas；The top gaseous phase on absorption tower is sent to reabsorber, and tower reactor logistics is sent to desorber；3) it reabsorbs agent to enter from reabsorber jacking, absorbs the absorbent being carried over and unabsorbed C2 fraction；4) logistics of desorber top gaseous phase is sent to clean unit, and the lean solvent that tower reactor obtains returns at the top of absorption tower；5) in clean unit, de- sour gas, dehydration are carried out to desorption top gaseous phase logistics, logistics that treated is produced as product.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, and entire work flow is simple, easily operated.
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. Due to the fact thatThe 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 ℃, so that the requirement on equipment materials is very high, the investment cost is greatly increased, and the energy consumption is high.
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 invention provides a separation method of reaction gas for preparing ethylene by oxidative coupling of methane, which comprises the following steps:
1) the OCM reaction gas is pressurized and cooled by a compressor and then sent to an absorption tower;
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 at the top of the absorption tower is sent to a reabsorption tower, and the material flow at the bottom of the tower is sent to a desorption tower;
3) the reabsorber enters from the top of the reabsorber and absorbs the carried-out absorbent and the unabsorbed C2 fraction;
4) the gas phase material flow at the top of the desorption tower is sent to a purification unit, and the lean solvent obtained at the bottom of the desorption tower returns to the top of the absorption tower after being cooled;
5) in the purification unit, the gas phase material flow at the top of the desorption tower is subjected to acid gas removal and dehydration treatment, and the treated material flow is taken as a product to be extracted.
According to a preferred embodiment of the invention, the method further comprises:
6) according to the invention, if the reaction gas contains alkyne, the alkyne can be removed, the purified material flow is firstly sent to a alkyne removal reactor, the alkyne is removed through hydrogenation reaction, and the material flow after alkyne removal 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 appropriately determine the specific operating conditions and methods thereof according to other methods. And/or
7) And (3) sending the tower bottom material flow of the reabsorption tower to a gasoline desorption tower, returning the absorbent obtained at the tower top to the absorption tower, and returning the lean solvent at the tower bottom to the reabsorption tower after cooling. The bottom stream of the reabsorption tower can also be sent to the outside of the battery limits.
In the compression step, the pressure of the OCM reaction gas generally needs to be increased step by step, preferably to be increased to 3.0-5.0MPa, 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 can be cooled to 5-20 ℃, preferably to 10-20 ℃, and the required cold energy can be provided by a propylene refrigeration compressor or a lithium bromide refrigeration unit.
The purification step of the present invention mainly comprises acid gas removal and drying treatment, and the present invention has no particular limitation on the specific process conditions of the 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 specific embodiment of the present invention, the separation method comprises:
(1) compression: the pressure of the OCM reaction gas is gradually increased to 3.0-5.0 MPa.
(2) And (3) cooling: cooling the compressed OCM reaction gas obtained in the step 1) to 10-20 ℃.
(3) Absorption: the cooled OCM reaction gas is sent to an absorption tower, and an absorbent enters from the top of the absorption tower to absorb the carbon dioxide fraction and the components in the OCM reaction gas; the tower kettle material flow of the absorption tower is sent to a desorption tower for treatment; the overhead gas stream is sent to a reabsorber.
(4) 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 purification unit.
(5) Purifying: the gas phase from the top of the desorption tower is sequentially subjected to acid gas removal and dehydration treatment.
(6) Removing alkyne: and the purified material flow enters a dealkynization reactor, acetylene hydrocarbon in the material flow is removed through hydrogenation reaction, and the material flow after dealkynization is taken as a product to be extracted.
(7) And (3) resorption: the gas phase stream from the top of the absorption tower enters a reabsorption tower, the unabsorbed C2 fraction and the entrained absorbent are recovered, and the reabsorbed tail gas can be sent out.
(8) Desorbing gasoline: the material at the bottom of the reabsorption tower is sent to a gasoline desorption tower, the absorbent recovered at the top of the tower is sent to an absorption tower, the lean gasoline solvent at the bottom of the tower is cooled and cooled, and then the lean gasoline solvent is returned to the reabsorption tower.
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, the carbon four-cut fraction contains n-butane and isobutane. 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 2.0-6.0MPa, and the tower top temperature is 10-35 ℃.
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 reabsorption tower 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 absorbent 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.
In the reabsorption step, the reabsorber is preferably gasoline, heavy naphtha or aromatic raffinate, more preferably gasoline, and more preferably a stable gasoline component of a refinery.
Preferably, the reabsorber has a theoretical plate number of 15 to 60 and an operating pressure of 1.0 to 5.0 MPa.
In the gasoline desorption step, the lean absorbent obtained from the tower kettle of the gasoline desorption tower is cooled step by step and then returns to the reabsorption tower for recycling. Preferably, a strand of reabsorber is introduced into the tower kettle of the gasoline desorber to supplement, and the tower top material flow of the gasoline desorber is cooled and then returns to the absorption tower for recycling.
Preferably, the theoretical plate number of the gasoline desorber is 10-50, and the operating pressure is 0.1-2.0 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, a desorption tower and a reabsorption tower which are connected in sequence; wherein the top of the absorption tower is connected with a reabsorption tower, and the tower kettle is connected with a desorption tower; the top of the desorption tower is connected with the purification unit and then connected with a carbon-rich secondary product extraction line, and the tower kettle is connected with the absorption tower; the top of the reabsorption tower is connected with a tail gas discharge pipeline.
According to a preferred embodiment of the invention, the purification unit is connected with the dealkynization reactor and then connected with the carbon-rich second product extraction line; and/or
The tower kettle of the reabsorption tower is connected to a gasoline desorption tower, the tower top of the gasoline desorption tower is connected to an absorption tower, and the tower kettle is connected to the reabsorption tower.
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, a desorption tower, and a reabsorption tower, which are connected in sequence; wherein the top of the absorption tower is connected with a tower kettle of the reabsorption tower, and the tower kettle of the absorption tower is connected with the middle part of the desorption tower; the top of the desorption tower is connected with the purification unit and then connected with the dealkynization reactor, and then connected with the carbon-rich product extraction line, and the tower kettle of the desorption tower is connected with the top of the absorption tower; the top of the reabsorption tower is connected with a tail gas discharge pipeline, the tower kettle is connected to the middle part of the gasoline desorber, the top of the gasoline desorber is connected with the top of the absorption tower, and the tower kettle is connected with the top of the reabsorption tower.
According to a specific embodiment of the present invention, as shown in fig. 2, the separation apparatus includes a compressor, a heat exchanger, an absorption tower, a desorption tower, and a reabsorption tower, which are connected in sequence; wherein the top of the absorption tower is connected with a tower kettle of the reabsorption tower, and the tower kettle of the absorption tower is connected with the middle part of the desorption tower; the top of the desorption tower is connected with the purification unit and then connected with the carbon-rich product extraction line, and the tower kettle of the desorption tower is connected with the top of the absorption tower; the top of the reabsorption tower is connected with a tail gas discharge pipeline, the tower kettle is connected to the middle part of the gasoline desorber, the top of the gasoline desorber is connected with the top of the absorption tower, and the tower kettle is connected with the top of the reabsorption tower.
The separation method for preparing ethylene by oxidative coupling of methane has the following characteristics:
1) the temperature of the separation process is higher, the requirement of the whole process on the material of the equipment is greatly reduced, and the energy consumption and the investment are also obviously reduced.
2) Because the absorption desorption temperature is higher, the purification of the OCM reaction gas can be carried out after the desorption tower, the treatment capacity of the purification unit is greatly reduced, and the energy consumption is reduced.
3) The process flow is simple and easy to operate and control.
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 reabsorption tower; 8. a gasoline desorber; 9. oxygen/oxygen enrichment; 10. methane; 11. a carbon-rich two product; 12. and (4) tail gas.
Detailed Description
Preferred embodiments of the present invention will be described in more detail below.
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, a desorption tower 5 and a reabsorption tower 7; wherein the top of the absorption tower 4 is connected with the tower kettle of the reabsorption tower 7, and the tower kettle of the absorption tower 4 is connected with the middle part of the desorption tower 5; the top of the desorption tower 5 is connected with a purification unit (not shown) and then is connected with a carbon-rich secondary product extraction line, and the bottom of the desorption tower is connected with the top of the absorption tower 4; the top of the reabsorption tower 7 is connected with a tail gas discharge pipeline, the tower bottom is connected with the middle part of the gasoline desorber 8, the top of the gasoline desorber 8 is connected with the top of the absorption tower 3, and the tower bottom is connected with the top of the reabsorption tower 7. 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, oxygen/rich oxygen 9 reacts with methane 10 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, and is compressed in five stages, and the pressure is increased to 4.2 MPag.
(2) And (3) cooling: cooling the OCM reaction gas after pressure rise to 15 ℃, and then feeding the OCM reaction gas to an absorption tower 4.
(3) Absorption: the theoretical plate number of the absorption column 4 was 55, the operating pressure was 3.8MPag, and the column top temperature was 24 ℃. The absorption solvent is n-butane, 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.
(4) Desorbing: the theoretical plate number of the desorber 5 was 40 and the operating pressure was 2.4 MPag. The gas phase at the top of the tower after desorption is sent to a purification unit for purification, and the lean solvent at the bottom of the tower is cooled to 15 ℃ after gradual heat exchange and then returns to the absorption tower 4 for recycling.
(5) Purifying: after acid gas removal treatment is carried out in the amine washing tower, the OCM reaction gas is dried, and the purified gas is extracted as a carbon-rich secondary product 11.
(6) And (3) resorption: the theoretical plate number of the reabsorption tower is 30, and the operating pressure is 3.0 MPa. The gas phase material flow from the top of the absorption tower enters a reabsorption tower 7, the unabsorbed C2 fraction and the entrained absorbent are recovered, the reabsorbed tail gas 12 is sent out, and the tower bottom material of the reabsorption tower 7 is sent to a gasoline desorption tower 8.
(7) Desorbing gasoline: the top of the gasoline desorber 8 is the recycled absorbent which is sent to the absorption tower 4, the bottom of the tower is the poor gasoline solvent, and the poor gasoline solvent returns to the reabsorption tower 7 after cooling.
The composition of the resulting carbon-rich di-product 11 is shown in table 2.
TABLE 2
| Composition of | mol％ |
| Methane | 0.82 |
| Ethylene | 66.64 |
| Ethane (III) | 20.67 |
| Propane | 3.85 |
| Butane | 8.03 |
In this example, the recovery of the carbon two component was 99%.
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 pressurized and cooled by a compressor and then sent to an absorption tower;
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 at the top of the absorption tower is sent to a reabsorption tower, and the material flow at the bottom of the tower is sent to a desorption tower;
3) the reabsorber enters from the top of the reabsorber and absorbs the carried-out absorbent and the unabsorbed C2 fraction;
4) the gas phase material flow at the top of the desorption tower is sent to a purification unit, and the lean solvent obtained at the bottom of the desorption tower returns to the top of the absorption tower after being cooled;
5) in the purification unit, the gas phase material flow at the top of the desorption tower is subjected to acid gas removal and dehydration treatment, and the treated material flow is taken as a product to be extracted.
2. The method for separating the reaction gas for the oxidative coupling of methane to ethylene according to claim 1, further comprising:
6) the purified material flow is firstly sent to a dealkynization reactor, acetylene hydrocarbon is removed through hydrogenation reaction, and the material flow after dealkynization is taken as a product to be extracted; and/or
7) And (3) sending the tower bottom material flow of the reabsorption tower to a gasoline desorption tower, returning the absorbent obtained at the tower top to the absorption tower, and returning the lean solvent at the tower bottom to the reabsorption tower after cooling.
3. 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 3.0-5.0MPa, and the compressor is cooled to 10-20 ℃.
4. 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.
5. 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; the carbon four-cut fraction containing n-butane and isobutane is preferred.
6. The method for separating reaction gas in the oxidative coupling of methane to ethylene according to claim 1, wherein the reabsorber is gasoline, heavy naphtha or aromatic raffinate oil, preferably gasoline, more preferably stable gasoline component of a refinery.
7. 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 4), a strand of absorbent is introduced into the bottom of the desorption tower as a supplement.
8. The separation method of the reaction gas for preparing the ethylene by the oxidative coupling of the methane according to claim 2, wherein in the step 7), a strand of reabsorber is introduced into the bottom of the gasoline desorber to supplement the reabsorber; preferably, the theoretical plate number of the gasoline desorber is 10-50, and the operating pressure is 0.1-2.0 MPa.
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 2.0-6.0MPa, and the tower top temperature is 10-35 ℃;
the theoretical plate number of the desorption tower is 20-60, and the operating pressure is 1.0-4.0 MPa;
the theoretical plate number of the reabsorption tower is 15-60, and the operation pressure is 1.0-5.0 MPa.
10. A separation device for preparing ethylene reaction gas by oxidative coupling of methane comprises a compressor, a heat exchanger, an absorption tower, a desorption tower and a reabsorption tower which are connected in sequence; wherein,
the top of the absorption tower is connected with a reabsorption tower, and the tower kettle is connected with a desorption tower;
the top of the desorption tower is connected with the purification unit and then connected with a carbon-rich secondary product extraction line, and the tower kettle is connected with the absorption tower;
the top of the reabsorption tower is connected with a tail gas discharge pipeline;
optionally, in the apparatus:
the purification unit is connected with the dealkynization reactor and then connected with the carbon-rich secondary product extraction line; and/or
The tower kettle of the reabsorption tower is connected to a gasoline desorption tower, the tower top of the gasoline desorption tower is connected to an absorption tower, and the tower kettle is connected to the reabsorption tower.
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