CN107986932B - 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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- CN107986932B CN107986932B CN201610949678.3A CN201610949678A CN107986932B CN 107986932 B CN107986932 B CN 107986932B CN 201610949678 A CN201610949678 A CN 201610949678A CN 107986932 B CN107986932 B CN 107986932B
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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 dioxide from a byproduct dry gas generated in the process of preparing aromatic hydrocarbon from methanol, wherein the device comprises a gasoline stabilizer, and a first carbon-four absorption tower, a pressure swing adsorption hydrogen production unit, a second carbon-four absorption tower and a carbon-four desorption tower which are sequentially connected; the method comprises the following steps: contacting carbon four with MTA dry gas to absorb heavy components of more than four carbon in the dry gas; and the light component is subjected to pressure swing adsorption to prepare hydrogen so as to remove hydrogen in the light component, the other carbon four is contacted with the component after hydrogen removal so as to absorb more than two heavy components in the component, the absorbed more than four heavy components are subjected to first rectification so as to obtain carbon four and aromatic hydrocarbon, the obtained carbon four is used in the previous step, and the mixture of the absorbed carbon four and more heavy components is subjected to second rectification so as to obtain carbon two and carbon four. The method can effectively recover the carbon dioxide from the MTA dry gas, and avoids the influence of heavy components in the raw material on the hydrogen production adsorbent and the service life of the device.
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 device, and usually contains a large amount of hydrogen, methane, ethylene, ethane and aromatic hydrocarbon components, so that the MTA dry gas is not suitable for sale and is difficult to use. 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 and the consumption of raw coal can be reduced, and the economic benefit and the social benefit are very obvious.
At present, the 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 various methods have 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 solubilities of the absorbent on each component in the gas, generally, the absorbent is used for absorbing heavy components above carbon dioxide, noncondensable gases such as methane, hydrogen and the like are separated, and then, the distillation method is used for separating each component in the absorbent. The method has the characteristics of high recovery rate of carbon three, safe production, reliable operation, strong adaptability to raw material gas and the like, and is one of the existing competitive technologies. MTA dry gas is recovered by adopting a shallow cold oil absorption process, wherein one process route is that the MTA dry gas is firstly sent into a Pressure Swing Adsorption (PSA) hydrogen production unit, the PSA technology is adopted to separate and purify the hydrogen, and PSA desorption gas is then sent into the shallow cold oil absorption unit so as to save the consumption of an absorbent and energy consumption. However, MTA dry gas contains more aromatic hydrocarbon components, which can affect the service life of the adsorbent of the PSA hydrogen production unit and the long-period stability of the PSA device. On the other hand, a gasoline absorption tower needs to be arranged in the shallow cold oil absorption unit, gasoline is used as an absorbent to recover the carbon-IV absorbent carried in the methane-hydrogen tail gas, and therefore, a gasoline absorbent needs to be introduced from the outside of a battery limit.
US005502971A discloses a low pressure, low temperature process for recovering hydrocarbons above carbon two. The process cancels the traditional high-pressure scheme and adopts a low-pressure technology, so that the recovery temperature can be kept above the temperature of the generated nitric acid resin, the potential possibility of danger is avoided, and simultaneously, the higher olefin yield can be kept. Although the process adopts a low-pressure scheme, the temperature is still as low as-100 ℃, and the process still belongs to a cryogenic separation process, so the investment is large and the energy consumption is high.
CN101063048A discloses a method for separating dry gas by using an intercooling oil absorption method, which comprises the steps of compressing, removing acid gas, drying and purifying, absorbing, desorbing, cold quantity recycling, roughly dividing and the like, and has the advantages of low absorbent cost, low loss and the like. However, the process needs to cool the dry gas to-30 ℃ to-40 ℃ for absorption, belongs to an intercooling separation process, and has large investment and high energy consumption.
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, and carbon four is used as an absorbent to recover carbon two and carbon three fractions in the dry gas. 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 gasoline absorbent from outside the battery limits.
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 less, the loss is less, but the gasoline absorbent is partially carried away by methane-hydrogen fuel gas, and therefore, the gasoline still needs to be supplemented from the outside of a battery compartment.
CN104045502A discloses a method for recovering hydrogen and ethylene from refinery dry gas with high efficiency and high purity, which comprises a first-stage pressure swing adsorption step, a second-stage pressure swing adsorption step, a cold oil absorption step and a rough distillation step. And simultaneously, the separation of hydrogen, ethylene and ethane is realized. However, when a raw material gas containing a large amount of aromatic hydrocarbon components is treated, if heavy components such as aromatic hydrocarbons are not removed in the temperature swing adsorption column, the heavy components are adsorbed by the PSA adsorbent and are not easily resolved, and the life of the adsorbent and the long-term stability of the apparatus are reduced.
In conclusion, the existing process for separating and recovering the carbon dioxide component in the dry gas has the problems of large investment, high energy consumption, influence on the service life of the PSA adsorbent and the long-period stability of the device due to the introduction of heavy components such as a gasoline absorbent and aromatic hydrocarbons in raw materials from the outside, and the like.
Disclosure of Invention
The invention aims to overcome the defects that in the prior art, a gasoline absorbent needs to be introduced from the outside, and the service life of a PSA (pressure swing adsorption) adsorbent and the long-period stability of a device are influenced by heavy components such as aromatic hydrocarbon in raw materials (particularly MTA dry gas containing more aromatic hydrocarbon), and the like, and provides a device and a method for recovering carbon dioxide from a methanol-to-aromatic hydrocarbon byproduct dry gas.
In order to achieve the above object, in one aspect, the present invention provides a device for recovering carbon two from a methanol to aromatics byproduct dry gas, which includes a gasoline stabilizer, and a first carbon four absorption tower, a pressure swing adsorption hydrogen production unit, a second carbon four absorption tower, and a carbon four desorption tower, which are connected in sequence, wherein the first carbon four absorption tower and the pressure swing adsorption hydrogen production unit are respectively used for separating more than five carbon heavy components and hydrogen from the methanol to aromatics byproduct dry gas, the gasoline stabilizer is used for purifying carbon four from a bottom product of the first carbon four absorption tower, and sending the obtained carbon four to the first carbon four absorption tower and the second carbon four absorption tower as absorbents.
In another aspect, the present invention provides a method for recovering carbon from a dry gas by-product of methanol to aromatics, comprising the following steps:
(1) contacting carbon four with a byproduct dry gas of the preparation of aromatic hydrocarbon from methanol to absorb heavy components of more than five carbon in the dry gas;
(2) performing pressure swing adsorption on the unabsorbed light component in the step (1) to prepare hydrogen so as to remove the hydrogen in the light component;
(3) contacting the other carbon four with the component after the dehydrogenation gas in the step (2) to absorb more than two heavy components in the component;
(4) performing first rectification on heavy components with more than four carbons absorbed in the step (1) to separate carbon four and aromatic hydrocarbon, and reusing four or all of the obtained carbon four in the steps (1) and (3);
(5) and (4) carrying out second rectification on the heavy components of carbon four and more than carbon four absorbed in the step (3) to separate carbon four and carbon four.
The device and the method can effectively recover the carbon dioxide from the MTA dry gas, avoid the influence of heavy components in the raw materials on the PSA adsorbent and the service life of the device, and can recycle the aromatic hydrocarbon fraction in the MTA dry gas, namely, the aromatic hydrocarbon fraction can not be introduced from the outside, thereby avoiding the introduction of various impurities and metal ions.
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 pressure swing adsorption hydrogen production unit
3 dry gas compressor 4 second carbon four absorption tower
5-carbon four-desorption tower 6 gasoline absorption tower
7 gasoline stabilizer 8 carbon four-circulating pump
9-carbon four-cooler 10 dry gas cooler
11 carbon four-circulation pipe 12 gasoline solvent feed inlet
13 carbon dioxide discharge port 14 hydrogen discharge port
15 methane hydrogen discharge port 16 noncondensable gas discharge port
Discharge port for 18-rich absorbent of 17-carbon four-recovery pipe
19 aromatic hydrocarbon discharge port 20 first carbon four absorption tower
21 pressure swing adsorption desorption gas discharge port
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); "carbon five" refers to the general name of hydrocarbon compounds having five carbon atoms (mainly including pentene and pentane); the term "aromatic hydrocarbon" refers to a general term for hydrocarbon compounds containing benzene rings, mainly including benzene, toluene and xylene, having six to eight carbon atoms.
The invention provides a device for recovering carbon from a methanol-to-aromatics byproduct dry gas, which comprises a gasoline stabilizer 7, and a first carbon four absorption tower 20, a pressure swing adsorption hydrogen production unit 2, a second carbon four absorption tower 4 and a carbon four desorption tower 5 which are sequentially connected, wherein the first carbon four absorption tower 20 and the pressure swing adsorption hydrogen production unit 2 are respectively used for separating more than five carbon heavy components and hydrogen in the methanol-to-aromatics byproduct dry gas, the gasoline stabilizer 7 is used for purifying carbon four in a product from the bottom of the first carbon four absorption tower 20, and the obtained carbon four is sent to the first carbon four absorption tower 20 and the second carbon four absorption tower 4 to be used as absorbents (namely, the top of the gasoline stabilizer 7 is respectively connected with the first carbon four absorption tower 20 and the second carbon four absorption tower 4).
According to the invention, in order to reuse the carbon four entrained in the top product of the second 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 second carbon four absorption tower 4 and a gasoline stabilizing tower 7, so as to recover the material containing carbon four from the top product of the second 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.
According to the invention, the component after dehydrogenation which is to be contacted with the carbon four can be pretreated, and preferably, the device further comprises a dry gas compressor 3 and a dry gas cooler 10 which are arranged between the pressure swing adsorption hydrogen production unit 2 and the second carbon four absorption tower 4, so that the component after dehydrogenation enters the second carbon four absorption tower 4 after being compressed and cooled.
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 an absorbent in the carbon four absorption tower, and preferably, the tower bottom of the carbon four desorption tower 5 is respectively connected with the first carbon four absorption tower 20 and the second 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.
Further, as shown in fig. 1, the apparatus of the present invention may further comprise some equipments and components commonly used in the art, for example, a carbon four circulation pump 8, a carbon four cooler 9 and a carbon four circulation pipe 11 are provided between the carbon four desorption tower 5 and the first carbon four absorption tower 20 and the second carbon four absorption tower 4, and are sequentially used to pressurize, cool and recycle the carbon four obtained in the carbon four absorption tower 4 to the first carbon four absorption tower 1 and the second carbon four absorption tower 4.
For example, the pressure swing adsorption hydrogen production unit 2 is provided with a hydrogen discharge port 14 and a PSA desorption gas discharge port 21, which are respectively used for pressure swing adsorption to obtain hydrogen and PSA desorption gas to flow out; the gasoline absorption tower 6 is provided with an aromatic hydrocarbon feed inlet 12 and a methane hydrogen discharge outlet 15 which are respectively used for introducing aromatic hydrocarbon into the gasoline absorption tower 6 and discharging light component products of the gasoline absorption tower 6; an aromatic hydrocarbon discharge port 19 and a non-condensable gas discharge port 16 are formed in the gasoline stabilizer 7 and are respectively used for discharging products at the bottom and the top of the gasoline stabilizer 7; the bottom of the first carbon four absorption tower 1 is provided with a rich absorbent (carbon four and aromatic hydrocarbon) discharge port 18 for discharging the bottom product of the first carbon four absorption tower 1, and the like.
In actual use, the MTA dry gas supply unit 1 can be used to provide MTA dry gas, the MTA dry gas passes through the first carbon-four absorption tower 20 and contacts with carbon four as an absorbent to absorb heavy components above carbon five, the absorbed heavy components are sent to the gasoline stabilizer 7 to be subjected to first rectification separation of carbon four and aromatic hydrocarbons, the light components of the first carbon-four absorption tower 20 enter the pressure swing adsorption hydrogen production unit 2 to remove hydrogen, the components after hydrogen removal enter the second carbon-four absorption tower and contact with carbon four as an absorbent to absorb heavy components above carbon two, the heavy components above carbon two absorbed enter the carbon-four desorption tower 5 to be subjected to second rectification separation of carbon two and carbon four, carbon four is recycled to the first carbon-four absorption tower 20 and the second carbon-four absorption tower 4, the light components in the gasoline of the second carbon-four absorption tower 4 enter the absorption tower 6 to be contacted with the aromatic hydrocarbons obtained in the gasoline stabilizer 7, absorbing carbon four carried in the light component, sending the heavy component absorbed in the gasoline absorption tower 6 into the gasoline stabilizer 7, separating carbon four and aromatic hydrocarbon through first rectification, recycling four parts or all of the carbon obtained by the first rectification in the gasoline stabilizer 7 into the first carbon four absorption tower 20 and the second carbon four absorption tower 4, and recycling part or all of the obtained aromatic hydrocarbon into the gasoline absorption tower 6.
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) contacting carbon four with a byproduct dry gas of the preparation of aromatic hydrocarbon from methanol to absorb heavy components of more than five carbon in the dry gas;
(2) performing pressure swing adsorption on the unabsorbed light component in the step (1) to prepare hydrogen so as to remove the hydrogen in the light component;
(3) contacting the other carbon four with the component after the dehydrogenation gas in the step (2) to absorb more than two heavy components in the component;
(4) performing first rectification on heavy components with more than four carbons absorbed in the step (1) to separate carbon four and aromatic hydrocarbon, and reusing four or all of the obtained carbon four in the steps (1) and (3);
(5) and (4) performing second rectification on the mixture of the carbon four and the heavy components above carbon four absorbed in the step (3) to separate carbon four and carbon four.
According to the present invention, there is no particular limitation on the purity of carbon four in steps (1) and (3). Preferably, the purity of carbon four in steps (1) and (3) is 70% by weight or more (80%, 90% by weight or 98% by weight), more preferably, carbon four is at least one of refinery mixed carbon four, ether carbon four and n-butane (the purity of carbon four is 80% by weight or more).
According to the present invention, the conditions under which carbon four is contacted with the MTA dry gas in step (1) are not particularly limited as long as carbon four can absorb the heavy components of carbon four or more in the dry gas. Preferably, the conditions for contacting the carbon four in the step (1) with the dry byproduct gas for preparing the aromatic hydrocarbon from the methanol comprise: the number of theoretical plates is 5-20, the pressure is 0.6-2MPaG, the temperature at the top of the tower is 0-15 ℃, and the temperature at the bottom of the tower is 0-40 ℃. The amount of carbon four can be 0.2-2t per ton of dry gas by-product of preparing aromatic hydrocarbon from methanol.
According to the present invention, the pressure swing adsorption hydrogen production conditions are not particularly limited as long as hydrogen in the light fraction can be removed. Preferably, the pressure swing adsorption hydrogen production process comprises at least one of a one-stage PSA (e.g., a 10 column VPSA process), a two-stage PSA, and a PSA + membrane separation process.
According to the present invention, the dehydrogenated component may be pretreated prior to contact with carbon four. Preferably, the method further comprises: compressing and cooling the dehydrogenated component before the carbon four contacts the dehydrogenated component, more preferably, the compressed component is at a pressure of 3 to 5MPaG and cooled to 0 to 20 ℃. 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, the condition under which the additional carbon four is contacted with the dehydrogenated component is not particularly limited as long as the carbon four can be allowed to absorb the carbon two or more component of the dehydrogenated component. Preferably, the conditions under which the additional carbon four is contacted with the dehydrogenated component 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 the additional carbon four can be 2-5t relative to each ton of the byproduct dry gas of the preparation of the aromatic hydrocarbon from the methanol.
According to the present invention, there is no particular limitation on the conditions of the first rectification as long as the carbon four and the aromatic hydrocarbon 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 50-120 ℃, and the temperature at the bottom of the tower is 120-200 ℃.
According to the present invention, the conditions for the second rectification 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 100-200 ℃.
According to the present invention, in order to improve the utilization of carbon four as an absorbent, it is preferable to reuse the carbon four obtained in step (5) or all of it in steps (1) and (3).
According to the present invention, in order to be able to utilize the carbon four entrained in the light component remaining in step (3), it is preferable that the method further comprises contacting the aromatic hydrocarbon obtained by the first rectification with the light component remaining in step (3) to absorb the carbon four entrained in the light component, and returning the obtained mixture of the carbon four and the aromatic hydrocarbon to the first rectification step.
According to the present invention, there is no particular limitation on the conditions under which the aromatic hydrocarbon obtained by the first rectification is contacted with the light components remaining in step (3), as long as the aromatic hydrocarbon can be caused to absorb carbon four entrained in the light components. 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 first carbon four absorption tower 20, step (2) may be performed in the pressure swing adsorption hydrogen production unit 2, step (3) may be performed in the second carbon four absorption tower 4, step (4) may be performed in the gasoline stabilizer 7, and step (5) may be performed in the carbon four desorption tower 5 (specifically, reference may be made to the method of using the foregoing apparatus).
The present invention will be described in detail below by way of examples.
In the following examples, the composition and parameters of MTA dry gas are shown in Table 1, and it comes from the methanol-to-aromatics production process; carbon four is from refinery n-butane, and the purity is 80 wt%; the pressure swing adsorption hydrogen production is a 10-tower VPSA process.
TABLE 1
| MTA dry gas | |
| Temperature, C | 40 |
| Pressure, MPaG | 1.5 |
| Mass flow, t/h | 30 |
| H2，mol％ | 51.4 |
| N2，mol％ | 0.7 |
| CH4，mol％ | 26 |
| C2H6，mol％ | 15 |
| C2H4，mol％ | 4 |
| C3H8，mol％ | 2 |
| C3H6，mol％ | 0.2 |
| C4H10，mol％ | 0.2 |
| C6H6+C7H8+C8H10，mol％ | 0.7 |
In the following examples, the process for recovering carbon dioxide from MTA dry gas comprises:
(1) contacting carbon four with MTA dry gas to absorb heavy components of more than five carbon in the dry gas;
(2) performing pressure swing adsorption on the unabsorbed light component in the step (1) to prepare hydrogen so as to remove the hydrogen in the light component;
(3) contacting the other carbon four with the component after the dehydrogenation gas in the step (2) to absorb more than two heavy components in the component;
(4) performing first rectification on heavy components with more than four carbon atoms absorbed in the step (1) to separate carbon four and aromatic hydrocarbon, wherein the carbon four is used in the steps (1) and (3);
(5) 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; all the obtained carbon four is recycled in the steps (1) and (3);
(6) and (3) contacting the aromatic hydrocarbon obtained by the first rectification with the light component remained 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 first rectification step.
The amounts of the respective components in the feed and the product were measured in accordance with ASTM D1945, and the carbon two recovery rate was calculated as × 100% in terms of the weight of the carbon four desorber overhead product (ethylene + ethane)/the weight of the MTA dry gas (ethylene + ethane), and the ethylene recovery rate was calculated as × 100% in terms of the weight of ethylene in the carbon four desorber overhead product/the weight of ethylene in the MTA dry gas.
Example 1
The conditions for contacting carbon four (flow rate of 14t/h) with MTA dry gas include: the number of theoretical plates is 10, the pressure is 1.45MPaG, the temperature at the top of the tower is 5 ℃, and the temperature at the bottom of the tower is 16 ℃; the dehydrogenated component was second compressed to 4MPaG and cooled to 15 ℃ before being contacted with another carbon four (at a flow rate of 99t/h) under conditions comprising: the number of theoretical plates is 40, the pressure is 3.6MPaG, the temperature at the top of the tower is 23 ℃, and the temperature at the bottom of the tower is 114 ℃; 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 154 ℃; 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 34 ℃, and the temperature at the bottom of the tower is 118 ℃; the conditions for contacting the aromatic hydrocarbon with the light components include: the number of theoretical plates was 20, the pressure was 3.5MPaG, the overhead temperature 23 ℃ and the bottom temperature 39 ℃. Collecting the overhead product of the second rectification, and detecting the components and parameters thereof, wherein the results are shown in Table 2, and the calculated recovery rate of the carbon dioxide is 95 wt%, and the recovery rate of the ethylene is 92%; and the flow rate (kg/h) of the aromatic hydrocarbon in the feed of the pressure swing adsorption hydrogen production unit is detected, and the result is shown in table 2.
Example 2
The conditions for contacting carbon four (flow rate of 21t/h) with MTA dry gas include: the number of theoretical plates is 5, the pressure is 1.92MPaG, the temperature at the top of the tower is 12 ℃, and the temperature at the bottom of the tower is 3 ℃; the dehydrogenated component was compressed to 3MPaG in two stages and cooled to 5 ℃ before being contacted with another carbon four (at a flow rate of 140t/h) under conditions comprising: the number of theoretical plates is 25, the pressure is 3MPaG, the temperature at the top of the tower is 21 ℃, and the temperature at the bottom of the tower is 105 ℃; the conditions of the first rectification include: the number of theoretical plates is 10, the pressure is 2MPaG, the temperature at the top of the tower is 96 ℃, and the temperature at the bottom of the tower is 181 ℃; the conditions of the second rectification include: the number of theoretical plates is 50, the pressure is 2.7MPaG, the temperature at the top of the tower is 35 ℃, and the temperature at the bottom of the tower is 129 ℃; the conditions for contacting the aromatic hydrocarbon with the light components include: the number of theoretical plates was 30, the pressure was 2.5MPaG, the overhead temperature 23 ℃ and the bottom temperature 30 ℃. Collecting the overhead product of the second rectification, and detecting the components and parameters thereof, wherein the results are shown in Table 2, and the calculated recovery rate of the carbon dioxide is 95 wt%, and the recovery rate of the ethylene is 96%; and the flow rate (kg/h) of the aromatic hydrocarbon in the feed of the pressure swing adsorption hydrogen production unit is detected, and the result is shown in table 2.
Example 3
The conditions for contacting carbon four (flow rate of 60t/h) with MTA dry gas include: the number of theoretical plates is 20, the pressure is 0.6MPaG, the temperature at the top of the tower is 10 ℃, and the temperature at the bottom of the tower is 2 ℃; the dehydrogenated component was second compressed to 5MPaG and cooled to 20 ℃ before being contacted with additional carbon four (at a flow rate of 85t/h) under conditions comprising: the number of theoretical plates is 50, the pressure is 4.2MPaG, the temperature at the top of the tower is 24 ℃, and the temperature at the bottom of the tower is 127 ℃; the conditions of the first rectification include: the number of theoretical plates is 55, the pressure is 0.5MPaG, the temperature at the top of the tower is 52 ℃, and the temperature at the bottom of the tower is 153 ℃; the conditions of the second rectification include: the number of theoretical plates is 30, the pressure is 1.7MPaG, the temperature at the top of the tower is 55 ℃, and the temperature at the bottom of the tower is 104 ℃; the conditions for contacting the aromatic hydrocarbon with the light components include: the number of theoretical plates was 15, the pressure 4.5MPaG, the top temperature 24 ℃ and the bottom temperature 41 ℃. Collecting the overhead product of the second rectification, and detecting the components and parameters thereof, wherein the results are shown in Table 2, and the calculated recovery rate of the carbon dioxide is 95 wt%, and the recovery rate of the ethylene is 94%; and the flow rate (kg/h) of the aromatic hydrocarbon in the feed of the pressure swing adsorption hydrogen production unit is detected, and the result is shown in table 2.
Comparative example 1
Carbon dioxide was recovered from dry MTA gas according to the method of example 1 except that the method did not include step 1, hydrogen was produced by pressure swing adsorption of dry MTA gas directly, and in addition, the source of aromatics in step (6) was changed to direct introduction of aromatics at a flow rate of 1t/h since no aromatics were recovered from dry MTA gas. Collecting the overhead product of the second rectification, and detecting the components and parameters thereof, wherein the results are shown in Table 2, and the calculated recovery rate of the carbon dioxide is 95 wt%, and the recovery rate of the ethylene is 92%; and the flow rate (kg/h) of the aromatic hydrocarbon in the feed of the pressure swing adsorption hydrogen production unit is detected, and the result is shown in table 2.
TABLE 2
| Composition and parameters | Example 1 | Example 2 | Example 3 | Comparative example 1 |
| Temperature, |
13 | 15 | 15 | 13 |
| Pressure, MPaG | 2.1 | 2.7 | 1.7 | 2.1 |
| Mass flow, t/h | 15.8 | 15.4 | 17.4 | 15.8 |
| H2，mol％ | 0.0 | 0.0 | 0.0 | 0.0 |
| CH4，mol％ | 1.5 | 3.1 | 4.8 | 1.5 |
| C2H6，mol％ | 71.4 | 70.9 | 65.6 | 71.4 |
| C2H4，mol％ | 16.4 | 16.5 | 15.0 | 16.4 |
| C3H8，mol％ | 7.1 | 7.6 | 7.4 | 7.1 |
| C3H6，mol％ | 0.8 | 0.8 | 0.8 | 0.8 |
| C4H10，mol％ | 2.8 | 1.1 | 6.4 | 2.8 |
| H2O，mol％ | 0.0 | 0.0 | 0.0 | 0.0 |
| Flow of aromatic hydrocarbons, kg/h | 0.3 | 9.1 | 21.1 | 1110 |
From examples 1-3 it can be seen that carbon dioxide can be efficiently recovered from MTA dry gas using the process of the present invention; in particular, as can be seen from example 1 and comparative example 1, the method of the present invention can greatly reduce the content of the heavy aromatic hydrocarbon component entering the pressure swing adsorption hydrogen production unit, and avoid the heavy aromatic hydrocarbon component in the raw material from seriously affecting the service life of the pressure swing adsorption hydrogen production unit. In addition, the part of aromatic hydrocarbon fraction can be recycled, namely, the aromatic hydrocarbon fraction can not be introduced from the outside, and various impurities and metal ions are prevented from being introduced therewith.
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 (16)
1. The device for recovering carbon dioxide from the methanol-to-aromatics byproduct dry gas is characterized by comprising a gasoline stabilizer (7), a first carbon four absorption tower (20), a pressure swing adsorption hydrogen production unit (2), a second carbon four absorption tower (4) and a carbon four desorption tower (5) which are sequentially connected, wherein the first carbon four absorption tower (20) and the pressure swing adsorption hydrogen production unit (2) are respectively used for separating more than five carbon heavy components and hydrogen in the methanol-to-aromatics byproduct dry gas, the gasoline stabilizer (7) is used for purifying carbon four in a tower bottom product from the first carbon four absorption tower (20), and the obtained carbon four is sent to the first carbon four absorption tower (20) and the second carbon four absorption tower (4) to serve as absorbents.
2. The apparatus according to claim 1, wherein the apparatus further comprises a gasoline absorber (6), the gasoline absorber (6) being connected to the second carbon four absorber (4) and the gasoline stabilizer (7), respectively, to recover the carbon four-containing material from the overhead product of the second carbon four absorber (4) and feed it to the gasoline stabilizer (7) for further purification of carbon four, and to introduce the bottoms product of the gasoline stabilizer (7) into the gasoline absorber (6) for absorption of carbon four.
3. The apparatus according to claim 1 or 2, wherein the apparatus further comprises a dry gas compressor (3) and a dry gas cooler (10) arranged between the pressure swing adsorption hydrogen production unit (2) and the second carbon four absorption tower (4), so that the dehydrogenated component is compressed and cooled before entering the second carbon four absorption tower (4).
4. 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) contacting carbon four with a byproduct dry gas of the preparation of aromatic hydrocarbon from methanol to absorb heavy components of more than five carbon in the dry gas;
(2) performing pressure swing adsorption on the unabsorbed light component in the step (1) to prepare hydrogen so as to remove the hydrogen in the light component;
(3) contacting the other carbon four with the component after the dehydrogenation gas in the step (2) to absorb more than two heavy components in the component;
(4) performing first rectification on heavy components with more than five carbons absorbed in the step (1) to separate carbon four and aromatic hydrocarbons, and reusing four or all of the obtained carbon four in the steps (1) and (3);
(5) and (4) carrying out second rectification on the heavy component above the carbon two absorbed in the step (3) to separate carbon two and carbon four.
5. The method according to claim 4, wherein the purity of carbon four in steps (1) and (3) is 70% by weight or more.
6. The method of claim 4, wherein the conditions for contacting carbon four with the dry byproduct gas from the production of aromatics from methanol in step (1) comprise: the number of theoretical plates is 5-20, the pressure is 0.6-2MPaG, the temperature at the top of the tower is 0-15 ℃, and the temperature at the bottom of the tower is 0-40 ℃.
7. The method of claim 4, wherein the method further comprises: compressing and cooling the dehydrogenated component before the carbon four contacts the dehydrogenated component.
8. The process of claim 7, wherein the dehydrogenated component is compressed at a pressure of 3 to 5MPaG and cooled to 0 to 20 ℃.
9. The process of claim 4, wherein the conditions under which carbon four is contacted with the dehydrogenated component in step (3) 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 ℃.
10. The method of claim 4, 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 50-120 ℃, and the temperature at the bottom of the tower is 120-200 ℃.
11. The method of claim 4, 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 100-200 ℃.
12. The method according to claim 4, wherein the carbon obtained in step (5) is recycled in four or all parts to be used in steps (1) and (3).
13. The process according to claim 4, wherein the process further comprises contacting the aromatic hydrocarbons obtained by the first rectification with the light components remaining in the step (3) to absorb carbon four entrained in the light components, and returning the mixture of carbon four and aromatic hydrocarbons obtained to the first rectification step.
14. The process of claim 13, 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 ℃.
15. A method according to any one of claims 4 to 14, wherein the method is carried out in an apparatus according to claim 1 or 2.
16. A method according to any one of claims 4 to 14, wherein the method is carried out in an apparatus according to claim 3.
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| CN104419465A (en) * | 2013-09-10 | 2015-03-18 | 中国石油化工股份有限公司 | Dry gas recovery system and dry gas recovery method for refinery plant |
| 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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| CN104419465A (en) * | 2013-09-10 | 2015-03-18 | 中国石油化工股份有限公司 | Dry gas recovery system and dry gas recovery method for refinery plant |
| 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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