CN107986933B - Device and method for recycling carbon dioxide from byproduct dry gas generated in preparation of aromatic hydrocarbon from methanol - Google Patents
Device and method for recycling carbon dioxide from byproduct dry gas generated in preparation of aromatic hydrocarbon from methanol Download PDFInfo
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- CN107986933B CN107986933B CN201610949747.0A CN201610949747A CN107986933B CN 107986933 B CN107986933 B CN 107986933B CN 201610949747 A CN201610949747 A CN 201610949747A CN 107986933 B CN107986933 B CN 107986933B
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- C07C7/005—Processes comprising at least two steps in series
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- C—CHEMISTRY; METALLURGY
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- C07C7/04—Purification; Separation; Use of additives by distillation
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Abstract
The invention relates to the field of gas organic matter recovery, and discloses a device and a method for recovering carbon two from a byproduct dry gas generated in the process of preparing aromatic hydrocarbon from methanol, wherein the device comprises an absorbent raw material supply unit, a light component removal tower, a gasoline stabilizing tower, a carbon four absorption tower and a carbon four desorption tower which are sequentially connected, wherein the light component removal tower and the gasoline stabilizing tower are used for purifying carbon four in the absorbent raw material supplied by the absorbent raw material supply unit; the method comprises the steps of removing light components from an absorbent raw material to remove light components with carbon number less than three, performing first rectification on the absorbent raw material after light removal to separate carbon number four and aromatic hydrocarbon, and contacting the obtained carbon number four with a methanol-to-aromatic hydrocarbon byproduct dry gas to absorb heavy components with carbon number more than two in the dry gas; and performing second rectification on the obtained mixture of the carbon four and the heavy components above the carbon four to separate the carbon four and the carbon four. By the device and the method, other various impurities and metal ions are not introduced from the outside of the MTA device, so that the recovery efficiency and the product quality are improved.
Description
Technical Field
The invention relates to the field of recovery of gas organic matters, in particular to a device and a method for recovering carbon dioxide from methanol-to-aromatics byproduct (MTA) dry gas.
Background
MTA dry gas comes from a methanol to aromatics plant, which usually contains a large amount of ethylene, ethane and aromatic components, is not suitable for sale, and is difficult to utilize. If the carbon dioxide component in the MTA dry gas is recycled and returned to the methanol-to-aromatics device as the raw material, the production cost of aromatics can be reduced, and the economic benefit and the social benefit are very obvious.
At present, methods for recovering ethane and ethylene components from dry gas mainly comprise a cryogenic separation method, a pressure swing adsorption method, a shallow cold oil absorption method and the like, and all the methods have respective characteristics. The cryogenic separation method has mature process, high ethylene recovery rate but large investment, and higher energy consumption for recovering the dilute ethylene; the pressure swing adsorption method has simple operation, low energy consumption, low product purity, low ethylene recovery rate and large occupied area.
The shallow cold oil absorption method mainly separates gas mixture by utilizing different solubility of an absorbent to each component in gas, generally, the absorbent is used for absorbing heavy components above carbon two and carbon two to separate out non-condensable gas such as methane, hydrogen and the like, and then a rectification method is used for separating each component in the absorbent. The method has the characteristics of high recovery rate of carbon two and carbon three, safe production, reliable operation, strong adaptability to raw material gas and the like, and is one of the existing competitive technologies. However, in the shallow cold oil absorption process, a small amount of the carbon four absorbent and the gasoline absorbent are sent out of a battery compartment along with methane hydrogen gas, and in order to ensure the circulating dosage of the carbon four absorbent and the gasoline absorbent, a strand of the carbon four absorbent and a strand of the gasoline absorbent are generally required to be respectively introduced from the outside to be used as supplements. The supplemental carbon four absorbent and/or gasoline absorbent needs to be dominated by carbon four and/or gasoline components to avoid affecting the absorption effect of the carbon four and/or gasoline absorbent and the product concentration of the carbon two concentrate gas. However, the MTA unit does not have a carbon four-component main stream, but only a mixed stream containing carbon three, carbon four and aromatic hydrocarbon, such as carbon four absorbent and/or gasoline absorbent introduced from the outside of the MTA unit, may introduce various impurities and metal ions, thereby affecting the product gas specification of the dry gas recovery unit.
CN103087772A discloses a device and a method for separating dry gas by an oil absorption method, wherein the method comprises the steps of carbon four absorption, carbon four desorption, gasoline absorption and the like, carbon four is adopted as an absorbent, and carbon two and carbon three fractions in the dry gas are recovered. And recovering carbon four in the tail gas by adopting a gasoline absorbent. The process has high ethylene recovery rate and less loss of the carbon four absorbent, but introduces a stream of carbon four absorbent and a stream of gasoline absorbent from the outside of the battery limits. The carbon four absorbent can be selected from refinery mixed carbon four, ether carbon four or other carbon four fractions, and the gasoline absorbent is common gasoline for refineries.
CN101759516A discloses a method for oil absorption separation of refinery catalytic dry gas, which uses carbon pentahydrocarbon containing pentane as an absorbent, absorbs carbon dioxide components in the catalytic dry gas after compression and cooling in a main absorption tower, feeds tower bottom material flow into a desorption tower to desorb carbon dioxide concentrated gas, and adopts a reabsorption tower to recover the carbon pentahydrocarbon absorbent carried by the tower top gas of the main absorption tower. The process needs to supplement carbon five absorbent and gasoline absorbent from outside the battery limits, and the gasoline absorbent is preferably refinery crude gasoline.
CN104557387A discloses a mixed dry gas recovery system of refinery, including absorption tower, desorber, purifier, rough separation tower, gasoline absorption tower and gasoline desorber. The process recovers the carbon two component in the dry gas by a set of carbon four absorption-desorption, and recovers the entrained carbon four absorbent by a set of gasoline absorption-desorption. The process can recycle the carbon four absorbent and the gasoline absorbent, the consumption of the absorbent is low, the loss is low, but the carbon four absorbent and the gasoline absorbent are still partially carried away by methane-hydrogen fuel gas, so the carbon four absorbent and the gasoline absorbent still need to be supplemented from outside the battery limits. The supplementary carbon four absorbent is carbon four fraction, saturated liquefied gas or carbon five fraction, etc. The supplemented gasoline fraction is stabilized gasoline, heavy naphtha or aromatic raffinate oil, etc.
In summary, the existing process for separating and recovering the carbon two component in the dry gas needs to supplement the carbon four (or carbon five) absorbent and the gasoline absorbent, and the available carbon four (or carbon five) absorbent comes from the material of the refinery which mainly contains carbon four (or carbon five); the supplementary gasoline absorbent can be used from products such as refinery gasoline/heavy naphtha/raffinate oil. It is clear that if the carbon-four absorbent or gasoline absorbent is introduced from outside the MTA plant, various impurities and metal ions may be introduced therewith, thereby affecting the product quality.
Disclosure of Invention
The invention aims to overcome the defect that the product quality is affected by introducing a carbon four absorbent or a gasoline absorbent from the outside of an MTA device and possibly introducing various impurities and metal ions, and provides a device and a method suitable for recovering carbon dioxide from a byproduct dry gas of methanol-to-aromatics under the condition of only using an air flow in the MTA device.
In order to achieve the above object, in one aspect, the present invention provides an apparatus for recovering carbon two from a dry byproduct gas from methanol to aromatics, the apparatus comprising an absorbent raw material supply unit, a light ends removal column, a gasoline stabilization column, a carbon four absorption column and a carbon four desorption column, which are connected in sequence, the light ends removal column and the gasoline stabilization column being used for purifying carbon four in the absorbent raw material supplied by the absorbent raw material supply unit.
In another aspect, the invention further provides a method for recovering carbon from a byproduct dry gas generated in the preparation of aromatic hydrocarbons from methanol, which comprises the following steps:
(1) removing light components of the absorbent raw material to remove light components with carbon number less than three;
(2) carrying out first rectification on the absorbent raw material subjected to light component removal so as to separate carbon four and aromatic hydrocarbon;
(3) contacting the carbon four obtained in the step (2) with the byproduct dry gas of the aromatic hydrocarbon preparation from methanol to absorb heavy components more than two carbon in the dry gas;
(4) and (4) performing second rectification on the mixture of the carbon four and the heavy components above carbon four obtained in the step (3) to separate carbon four and carbon four.
The device and the method of the invention can recover carbon from MTA dry gas without introducing carbon four absorbent or gasoline absorbent from the outside of the MTA device, thereby not introducing other various impurities and metal ions, and improving the recovery efficiency and the product quality.
Additional features and advantages of the invention will be set forth in the detailed description which follows.
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 principles of the invention and not to limit the invention. In the drawings:
fig. 1 is a schematic structural view of an apparatus according to a preferred embodiment of the present invention.
Description of the reference numerals
1 MTA dry gas supply unit 2 dry gas compressor
3 dry gas cooler 4 carbon four absorption tower
5-carbon four-desorption tower 6 gasoline absorption tower
7 gasoline stabilizer 8 absorbent raw material cooler
9 absorbent raw material gas-liquid separator 10 absorbent raw material pump
12-carbon four-circulating pump of 11 light component removing tower
13-carbon four-cooler 14 gasoline circulating pump
15 aromatic hydrocarbon discharge port and 16 methane hydrogen discharge port
17 carbon three-outlet 18 carbon two-outlet
19 carbon four feed inlet 20 aromatics feed inlet
21-carbon four-outlet 22 absorbent raw material supply unit
23 discharge port of non-condensable gas
Detailed Description
The following describes in detail specific embodiments of the present invention. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.
The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.
In the present invention, the term "carbon two" is used to refer to a generic term for hydrocarbon compounds having two carbon atoms (mainly including ethylene and ethane) unless otherwise specified; the term "carbon three" refers to a generic term for hydrocarbon compounds having three carbon atoms (mainly including propylene and propane); the term "C four" refers to the generic term for hydrocarbons having four carbon atoms (mainly including butenes, butanes); the term "aromatic hydrocarbon" refers to a generic term for hydrocarbon compounds containing benzene rings and having six and seven carbon atoms (mainly including benzene and toluene).
The invention provides a device for recovering carbon from a byproduct dry gas generated in the preparation of aromatic hydrocarbon from methanol, which comprises an absorbent raw material supply unit 22, a light component removal tower 11, a gasoline stabilizing tower 7, a carbon four absorption tower 4 and a carbon four desorption tower 5 which are sequentially connected, wherein the light component removal tower 11 and the gasoline stabilizing tower 7 are used for purifying carbon four in the absorbent raw material supplied by the absorbent raw material supply unit 22.
The absorbent raw material can be a mixed gas containing carbon three, carbon four and aromatic hydrocarbon in the preparation of the aromatic hydrocarbon by using methanol, the purified carbon four can be used as an absorbent, heavy components above carbon two in MTA dry gas are absorbed in a carbon four absorption tower 4, and the heavy components are rectified and separated in a carbon four desorption tower 5 so as to be used for purifying and recovering the carbon two in the MTA dry gas.
According to the present invention, the absorbent raw material which does not enter the lightness-removing column 11 can be pretreated. Preferably, the apparatus further includes an absorbent raw material cooler 8 and an absorbent raw material gas-liquid separator 9 disposed between the absorbent raw material supply unit 22 and the lightness-removing column 11 so that the absorbent raw material is cooled and subjected to gas-liquid separation before entering the lightness-removing column 11.
According to the present invention, the apparatus may further include an MTA dry gas supply unit 1 connected to the carbon four absorption tower 4, and may further pre-treat the MTA dry gas that does not enter the carbon four absorption tower 4. Therefore, preferably, the apparatus further comprises a dry gas compressor 2 and a dry gas cooler 3 which are arranged between the MTA dry gas supply unit 1 and the carbon four absorption tower 4, so that the methanol to aromatics byproduct dry gas is compressed and cooled and then enters the carbon four absorption tower 4.
According to the present invention, the carbon four separated by rectification in the carbon four desorption tower 5 can be partially or completely reused as the absorbent in the carbon four absorption tower 4, and preferably, the tower bottom of the carbon four desorption tower 5 is connected with the carbon four absorption tower 4, so that the carbon four separated by rectification in the carbon four desorption tower 5 can enter the carbon four absorption tower 4.
According to the invention, in order to reuse the carbon four entrained in the top product of the carbon four absorption tower 4, the device preferably further comprises a gasoline absorption tower 6, wherein the gasoline absorption tower 6 is respectively connected with the carbon four absorption tower 4 and a gasoline stabilizing tower 7, so as to recover the material containing the carbon four from the top product of the carbon four absorption tower 4 and send the material into the gasoline stabilizing tower 7 for further purifying the carbon four, and the bottom product in the gasoline stabilizing tower 7 is led into the gasoline absorption tower 6 for absorbing the carbon four.
Further, as shown in fig. 1, the apparatus of the present invention may further include some devices or components commonly used in the art, for example, an absorbent raw material pump 10 is provided between the absorbent raw material gas-liquid separator 9 and the lightness-removing column 11, and is configured to pressurize and feed the liquid phase obtained in the absorbent raw material gas-liquid separator 9 to the lightness-removing column 11.
For example, a carbon four circulation pump 12 and a carbon four cooler 13 are provided between the bottom of the carbon four desorption tower 5 and the carbon four absorption tower 4, and are sequentially used to pressurize and cool the carbon four separated in the carbon four absorption tower 5 and the gasoline stabilizer 7, and to recycle the carbon four to the carbon four absorption tower 4.
For example, a gasoline circulating pump 14, an aromatic hydrocarbon discharge port 15 and an aromatic hydrocarbon feed port 20 are arranged between the bottom of the gasoline stabilizer 7 and the gasoline absorber 6, and are sequentially used for pressurizing the bottom product of the gasoline stabilizer 7, discharging part of the bottom product from the aromatic hydrocarbon discharge port 15, and feeding part of the bottom product into the gasoline absorber 6 from the aromatic hydrocarbon feed port 20.
For example, the top of the absorbent raw gas-liquid separator 9 is provided with a carbon three discharge port 17 for discharging carbon three (gas phase part) obtained after gas-liquid separation; a carbon four discharge port 21 and a non-condensable gas discharge port 23 are formed in the top of the gasoline stabilizer 7 and are respectively used for discharging carbon four and non-condensable gas separated from the top of the gasoline stabilizer 7; the top of the gasoline absorption tower 6 is provided with a methane hydrogen discharge port 16 for discharging light component products of the gasoline absorption tower 6, and the like.
In practical use, the absorbent raw material can be introduced into an absorbent raw material supply unit 22, the liquid phase obtained after cooling by an absorbent raw material cooler 8 and an absorbent raw material gas-liquid separation tank 9 and gas-liquid separation is carried out, light components below carbon three are removed, heavy components are introduced into a gasoline stabilizer 7, carbon four and aromatic hydrocarbons are separated by first rectification, the obtained carbon four is used as an absorbent in a carbon four absorption tower 4, in addition, an MTA dry gas supply unit 1 provides MTA dry gas, the MTA dry gas is compressed and cooled by an MTA dry gas compressor 2 and an MTA dry gas cooler 3, and then enters a carbon four absorption tower 4 to be in contact with carbon four serving as an absorbent to absorb the heavy components above carbon two, a mixture of the carbon four and the heavy components above carbon two is used as the absorbent and enters a carbon four desorption tower 5, and the obtained carbon four is used in the carbon four absorption tower 4 by second rectification separation and carbon four, and the unabsorbed light component in the carbon four absorption tower 4 enters the gasoline absorption tower 6 and contacts with the aromatic hydrocarbon obtained in the gasoline stabilizing tower 7 to absorb the carbon four carried in the light component, and the heavy component absorbed in the gasoline absorption tower 6 is sent to the gasoline stabilizing tower 7 to separate the carbon four and the aromatic hydrocarbon.
The invention also provides a method for recovering carbon from the byproduct dry gas generated in the preparation of aromatic hydrocarbon from methanol, which comprises the following steps:
(1) removing light components of the absorbent raw material to remove light components with carbon number less than three;
(2) carrying out first rectification on the absorbent raw material subjected to light component removal so as to separate carbon four and aromatic hydrocarbon;
(3) contacting the carbon four obtained in the step (2) with the byproduct dry gas of the aromatic hydrocarbon preparation from methanol to absorb heavy components more than two carbon in the dry gas;
(4) and (4) performing second rectification on the mixture of the carbon four and the heavy components above carbon four obtained in the step (3) to separate carbon four and carbon four.
According to the present invention, there is no particular limitation on the source of the absorbent raw material, and in order to avoid introducing various impurities and metal ions from the outside and affecting the quality of dry gas recovery, it is preferable that the absorbent raw material is a mixed gas containing carbon three, carbon four and aromatic hydrocarbons in the aromatics preparation from methanol. Wherein, the raw materials of the absorbent comprise 10-70 mol% of carbon three, 10-70 mol% of carbon four and 5-20 mol% of aromatic hydrocarbon.
According to the present invention, the conditions for removing light components in step (1) are not particularly limited as long as light components of carbon three or less can be removed. Preferably, the conditions for lightness removal include: the number of theoretical plates is 10-40, the pressure is 0.4-2MPaG, the temperature at the top of the tower is 10-50 ℃, and the temperature at the bottom of the tower is 55-120 ℃. Where the unit MPaG refers to the pressure unit of gauge pressure, i.e. 1MPaG refers to a gauge pressure of 1 MPa.
According to the invention, the absorbent raw material which is not lightened can be pretreated. Preferably, the method further comprises: before lightness removal, the absorbent raw material is cooled to 0-20 ℃ (gas-liquid separation) and then a liquid phase is collected.
According to the present invention, there is no particular limitation on the conditions of the first rectification in step (2), as long as carbon four and aromatic hydrocarbons can be separated. Preferably, the conditions of the first rectification include: the number of theoretical plates is 10-60, the pressure is 0.4-2MPaG, the temperature at the top of the tower is 50-100 ℃, and the temperature at the bottom of the tower is 120-200 ℃.
According to the present invention, there is no particular limitation on the conditions under which carbon four is contacted with the MTA dry gas in step (3), as long as carbon four can be allowed to absorb two or more heavy components in carbon in the dry gas. Preferably, the conditions under which the carbon four is contacted with the dry gas include: the number of theoretical plates is 25-50, the pressure is 3-5MPaG, the temperature at the top of the tower is 10-40 ℃, and the temperature at the bottom of the tower is 90-160 ℃. The amount of carbon four can be 50-200kg for each ton of the byproduct dry gas of the methanol-to-aromatics.
According to the present invention, the conditions for the second rectification in step (4) are not particularly limited as long as the carbon two and the carbon four can be separated. Preferably, the conditions of the second rectification include: the number of theoretical plates is 20-50, the pressure is 1.5-2.8MPaG, the tower top temperature is 15-70 ℃, and the tower bottom temperature is 100-160 ℃.
According to the present invention, the dry MTA gas may also be pretreated before it is contacted with carbon four. Preferably, the method further comprises: the MTA dry gas is compressed and cooled before contacting with carbon four. More preferably, the pressure and temperature of the MTA dry gas after compression and cooling are 3-5MPaG and 0-20 ℃ respectively. In order to avoid excessive temperature during the compression process, the compression may be segmented compression, preferably two-segment compression or three-segment compression. The type of the refrigerant used for cooling is not particularly limited, and may be propylene or chilled water of about 5 ℃, may be supplied from a lithium bromide absorption refrigerator, or may be another refrigerant such as ammonia refrigeration, and is preferably a propylene refrigerant.
According to the present invention, in order to improve the utilization rate of carbon four as an absorbent, it is preferable to reuse the carbon four or all obtained in step (4) in step (2).
According to the present invention, in order to be able to utilize carbon four entrained in the light component of the dry methanol-to-aromatics by-product gas, it is preferable that the method further comprises contacting the aromatics in step (2) with the light component in step (3) where the dry methanol-to-aromatics by-product gas has not been absorbed to absorb carbon four entrained in the light component, and returning the resulting mixture of carbon four and aromatics to step (2) for the first rectification.
According to the present invention, the conditions for contacting the aromatic hydrocarbon with the light component are not particularly limited as long as the aromatic hydrocarbon can be caused to absorb the carbon four entrained in the light component. Preferably, the conditions under which the aromatic hydrocarbon is contacted with the light components include: the number of theoretical plates is 15-30, the pressure is 2.5-4.5MPaG, the temperature at the top of the tower is 10-40 ℃, and the temperature at the bottom of the tower is 20-60 ℃.
According to the invention, the method is preferably carried out in the apparatus described above. Specifically, step (1) may be performed in the lightness-removing column 11, step (2) may be performed in the gasoline stabilizer 7, step (3) may be performed in the carbon four absorption column, and step (4) may be performed in the carbon four desorption column. Further, cooling and gas-liquid separation before the lightness-removing of the extender raw material may be performed in the extender raw material cooler 8 and the extender raw material gas-liquid separator 9, respectively, compression and cooling before the contacting of the MTA dry gas with the carbon four may be performed in the MTA dry gas compressor 2 and the MTA dry gas cooler 3, and the contacting of the aromatic hydrocarbon and the light component of the MTA dry gas may be performed in the gasoline absorption tower 6 (specifically, refer to the method of using the aforementioned apparatus).
The present invention will be described in detail below by way of examples.
In the following examples, the compositions and parameters of the MTA dry gas and absorbent feedstock are shown in table 1, from a methanol to aromatics production process.
TABLE 1
In the following examples, the process for recovering carbon dioxide from MTA dry gas comprises:
(1) removing light components of the absorbent raw material to remove light components with carbon number less than three;
(2) carrying out first rectification on the absorbent raw material subjected to light component removal so as to separate carbon four and aromatic hydrocarbon;
(3) contacting the carbon four obtained in the step (2) with the byproduct dry gas of the aromatic hydrocarbon preparation from methanol to absorb heavy components more than two carbon in the dry gas;
(4) contacting the aromatic hydrocarbon in the step (2) with the light component which is not absorbed by the byproduct dry gas of the preparation of the aromatic hydrocarbon from methanol in the step (3) to absorb the carbon four carried in the light component, and returning the obtained mixture of the carbon four and the aromatic hydrocarbon to the step (2) for first rectification;
(5) and (3) performing second rectification on the mixture of the carbon four and the heavy components above the carbon four obtained in the step (3) to separate the carbon four and the carbon four, and reusing all the obtained carbon four in the step (2).
The amounts of the respective components in the raw material and the product were measured by ASTM D1945, and the carbon recovery was calculated as × 100% carbon recovery, which is the weight of the overhead product of the second rectification (ethylene + ethane)/the weight of the MTA dry gas (ethylene + ethane).
Example 1
Cooling the absorbent raw material to 8 ℃, collecting a liquid phase, and removing light, wherein the conditions of light removal comprise: the number of theoretical plates is 15, the pressure is 0.6MPaG, the temperature at the top of the tower is 17 ℃, and the temperature at the bottom of the tower is 70 ℃; the conditions of the first rectification include: the number of theoretical plates is 40, the pressure is 0.5MPaG, the temperature at the top of the tower is 51 ℃, and the temperature at the bottom of the tower is 160 ℃; second compressing MTA dry gas to 4MPaG, cooling to 15 ℃, and then contacting with carbon four, wherein the conditions of the contact of the carbon four with the MTA dry gas comprise: the number of theoretical plates is 40, the pressure is 3.8MPaG, the temperature at the top of the tower is 23 ℃, and the temperature at the bottom of the tower is 110 ℃; the conditions of the second rectification include: the number of theoretical plates is 40, the pressure is 2.1MPaG, the temperature at the top of the tower is 67 ℃, and the temperature at the bottom of the tower is 120 ℃; the conditions for contacting the aromatic hydrocarbon and the light components of the MTA dry gas comprise: the number of theoretical plates was 20, the pressure was 3.5MPaG, the overhead temperature 29 ℃ and the bottom temperature 42 ℃. The overhead product of the second rectification was collected and the components and parameters thereof were checked and the results are shown in table 2, calculated to give a carbon dioxide recovery of 93.90 wt%.
Example 2
Cooling the absorbent raw material to 20 ℃, collecting a liquid phase, and removing light, wherein the conditions of light removal comprise: the number of theoretical plates is 35, the pressure is 1.6MPaG, the temperature at the top of the tower is 50 ℃, and the temperature at the bottom of the tower is 113 ℃; the conditions of the first rectification include: the number of theoretical plates is 15, the pressure is 1.5MPaG, the temperature at the top of the tower is 94 ℃, and the temperature at the bottom of the tower is 190 ℃; second compressing MTA dry gas to 5MPaG, cooling to 5 ℃, and then contacting with carbon four, wherein the conditions of the contact of the carbon four with the MTA dry gas comprise: the number of theoretical plates is 25, the pressure is 4.8MPaG, the temperature at the top of the tower is 22 ℃, and the temperature at the bottom of the tower is 140 ℃; the conditions of the second rectification include: the number of theoretical plates is 20, the pressure is 2.7MPaG, the temperature at the top of the tower is 31 ℃, and the temperature at the bottom of the tower is 132 ℃; the conditions for contacting the aromatic hydrocarbon and the light components of the MTA dry gas comprise: the number of theoretical plates was 27, the pressure 4.5MPaG, the top temperature 23 ℃ and the bottom temperature 34 ℃. The overhead product of the second rectification was collected and the components and parameters thereof were checked, the results are shown in table 2, and the calculated recovery of carbon dioxide was 95.85% by weight.
Example 3
Cooling the absorbent raw material to 4 ℃, collecting a liquid phase, and removing light, wherein the conditions of light removal comprise: the number of theoretical plates is 15, the pressure is 0.4MPaG, the temperature at the top of the tower is 27 ℃, and the temperature at the bottom of the tower is 57 ℃; the conditions of the first rectification include: the number of theoretical plates is 57, the pressure is 0.5MPaG, the temperature at the top of the tower is 54 ℃, and the temperature at the bottom of the tower is 120 ℃; second compressing the MTA dry gas to 3MPaG, cooling to 18 ℃, and then contacting with carbon four, wherein the conditions of the contact of the carbon four with the MTA dry gas comprise: the number of theoretical plates is 50, the pressure is 3.2MPaG, the temperature at the top of the tower is 23 ℃, and the temperature at the bottom of the tower is 99 ℃; the conditions of the second rectification include: the number of theoretical plates is 50, the pressure is 1.7MPaG, the temperature at the top of the tower is 46 ℃, and the temperature at the bottom of the tower is 106 ℃; the conditions for contacting the aromatic hydrocarbon and the light components of the MTA dry gas comprise: the number of theoretical plates was 15, the pressure was 2.5MPaG, the temperature at the top of the column 23 ℃ and the temperature at the bottom of the column 39 ℃. The overhead product of the second rectification was collected and the components and parameters thereof were checked, the results are shown in table 2, and the calculated recovery of carbon dioxide was 93.71 wt%.
Comparative example 1
The MTA dry gas was compressed and cooled according to the conditions of example 1, then contacted with an externally introduced pure carbon-four gas stream (the content of impurity hydrogen sulfide is 5ppm), and subjected to a second rectification under the same conditions as in example 1. The overhead product of the second rectification was collected and the components and hydrogen sulfide content thereof were measured and the results are shown in table 2, calculated to give a carbon dioxide recovery of 92.89 wt%.
TABLE 2
| Composition and parameters | Example 1 | Example 2 | Example 3 | Comparative example 1 |
| Temperature, |
13 | 13 | 13 | 13 |
| Pressure, MPaG | 2.1 | 2.7 | 1.7 | 2.1 |
| Mass flow, t/ |
16 | 16 | 16 | 16 |
| H2，mol％ | 0.0 | 0.0 | 0.0 | 0.0 |
| CH4，mol％ | 0.7 | 2.1 | 2.1 | 0.7 |
| C2H6，mol％ | 68.7 | 72.6 | 71.2 | 68.7 |
| C2H4，mol％ | 14.3 | 17.2 | 13.7 | 14.3 |
| C3H8，mol％ | 9.4 | 6.5 | 6.8 | 9.4 |
| C3H6，mol％ | 1.0 | 0.7 | 0.8 | 1.0 |
| C4H10，mol％ | 5.8 | 0.9 | 5.3 | 5.8 |
| C4H8，mol％ | 0.1 | 0.0 | 0.1 | 0.1 |
| H2O，mol％ | 0.0 | 0.0 | 0.0 | 0.0 |
| H2S，ppm | 0.0 | 0.0 | 0.0 | 20.0 |
From examples 1-3, it can be seen that the method of the present invention can effectively recover carbon dioxide from MTA dry gas, and the product quality is high; in particular, as can be seen from example 1 and comparative example 1, the process of the present invention does not require the introduction of an absorbent from the outside, thereby avoiding the introduction of various other impurities (such as hydrogen sulfide) from outside the MTA plant, and thus improving the efficiency of recovery and the quality of the product.
The preferred embodiments of the present invention have been described in detail, however, the present invention is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solution of the present invention within the technical idea of the present invention, and these simple modifications are within the protective scope of the present invention.
It should be noted that the various technical features described in the above embodiments can be combined in any suitable manner without contradiction, and the invention is not described in any way for the possible combinations in order to avoid unnecessary repetition.
In addition, any combination of the various embodiments of the present invention is also possible, and the same should be considered as the disclosure of the present invention as long as it does not depart from the spirit of the present invention.
Claims (12)
1. The device for recovering carbon dioxide from the byproduct dry gas generated in the process of preparing the aromatic hydrocarbon from the methanol is characterized by comprising an absorbent raw material supply unit (22), a light component removal tower (11), a gasoline stabilizing tower (7), a carbon four absorption tower (4) and a carbon four desorption tower (5) which are sequentially connected, wherein the light component removal tower (11) and the gasoline stabilizing tower (7) are used for purifying carbon four in the absorbent raw material supplied by the absorbent raw material supply unit (22); the device also comprises a gasoline absorption tower (6), wherein the gasoline absorption tower (6) is respectively connected with the carbon four absorption tower (4) and the gasoline stabilizing tower (7) so as to recover the material containing carbon four from the tower top product of the carbon four absorption tower (4) and send the material into the gasoline stabilizing tower (7) for further purifying the carbon four, and the tower bottom product in the gasoline stabilizing tower (7) is led into the gasoline absorption tower (6) for absorbing the carbon four; the raw material of the absorbent is mixed gas containing C three, C four and arene in the process of preparing arene by using methanol.
2. The apparatus according to claim 1, wherein the apparatus further comprises an absorbent raw material cooler (8) and an absorbent raw material gas-liquid separator (9) provided between the absorbent raw material supply unit (22) and the lightness-removing column (11), so that the absorbent raw material is cooled and subjected to gas-liquid separation before entering the lightness-removing column (11).
3. A method for recovering carbon from a byproduct dry gas generated in the preparation of aromatic hydrocarbon from methanol is characterized by comprising the following steps:
(1) removing light components of the absorbent raw material to remove light components with carbon number less than three;
(2) carrying out first rectification on the absorbent raw material subjected to light component removal so as to separate carbon four and aromatic hydrocarbon;
(3) contacting the carbon four obtained in the step (2) with the byproduct dry gas of the aromatic hydrocarbon preparation from methanol to absorb heavy components more than two carbon in the dry gas;
(4) performing second rectification on the mixture of the carbon four and the heavy components above the carbon four obtained in the step (3) to separate the carbon four and the carbon four;
the raw material of the absorbent is mixed gas containing C three, C four and arene in the process of preparing arene by using methanol.
4. The method of claim 3, wherein the conditions for lightness removal comprise: the number of theoretical plates is 10-40, the pressure is 0.4-2MPaG, the temperature at the top of the tower is 10-50 ℃, and the temperature at the bottom of the tower is 55-120 ℃.
5. The method of claim 3, wherein the method further comprises: before lightness removal, the absorbent raw material is cooled to 0-20 ℃ and then a liquid phase is collected.
6. The method of claim 3, wherein the conditions of the first rectification comprise: the number of theoretical plates is 10-60, the pressure is 0.4-2MPaG, the temperature at the top of the tower is 50-100 ℃, and the temperature at the bottom of the tower is 120-200 ℃.
7. The method of claim 3, wherein the conditions under which carbon four is contacted with the dry gas comprise: the number of theoretical plates is 25-50, the pressure is 3-5MPaG, the temperature at the top of the tower is 10-40 ℃, and the temperature at the bottom of the tower is 90-160 ℃.
8. The method of claim 3, wherein the conditions of the second rectification comprise: the number of theoretical plates is 20-50, the pressure is 1.5-2.8MPaG, the tower top temperature is 15-70 ℃, and the tower bottom temperature is 100-160 ℃.
9. The method according to claim 3, wherein the carbon obtained in step (4) is recycled in four or all parts to step (2).
10. The method according to claim 3, wherein the method further comprises the steps of contacting the aromatic hydrocarbon in the step (2) with the light component which is not absorbed in the dry byproduct gas of the preparation of the aromatic hydrocarbon from methanol and is obtained in the step (3) to absorb carbon four entrained in the light component, and returning the obtained mixture of the carbon four and the aromatic hydrocarbon to the step (2) for the first rectification.
11. The process of claim 10, wherein the conditions under which the aromatic hydrocarbon is contacted with the light component comprise: the number of theoretical plates is 15-30, the pressure is 2.5-4.5MPaG, the temperature at the top of the tower is 10-40 ℃, and the temperature at the bottom of the tower is 20-60 ℃.
12. A method according to any one of claims 3 to 11, wherein the method is carried out in an apparatus according to claim 1 or 2.
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| CN103087772A (en) * | 2011-11-02 | 2013-05-08 | 中国石油化工股份有限公司 | Device and method for separating refinery dry gas through oil absorption |
| CN104557387A (en) * | 2013-10-23 | 2015-04-29 | 中国石油化工股份有限公司 | Refinery mixed dry gas recovery system and recovery method |
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| CN103087772A (en) * | 2011-11-02 | 2013-05-08 | 中国石油化工股份有限公司 | Device and method for separating refinery dry gas through oil absorption |
| CN104557387A (en) * | 2013-10-23 | 2015-04-29 | 中国石油化工股份有限公司 | Refinery mixed dry gas recovery system and recovery method |
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