CN113755201A

CN113755201A - Method for concentrating carbon dioxide and components in dry gas of light and heavy refinery, device and application thereof

Info

Publication number: CN113755201A
Application number: CN202010494296.2A
Authority: CN
Inventors: 邵华伟; 胡志彦; 刘智信; 李东风; 李�一; 常大山; 崔婷
Original assignee: Sinopec Beijing Research Institute of Chemical Industry; China Petroleum and Chemical Corp
Current assignee: Sinopec Beijing Research Institute of Chemical Industry; China Petroleum and Chemical Corp
Priority date: 2020-06-03
Filing date: 2020-06-03
Publication date: 2021-12-07
Anticipated expiration: 2040-06-03
Also published as: CN113755201B

Abstract

The invention relates to the field of waste gas recovery, and discloses a method for concentrating carbon dioxide and components above in dry gas of a light and heavy refinery, and a device and application thereof. The method comprises the following steps: compressing dry gas of a light refinery; compressing the dry gas of the heavy refinery; cooling compressed dry gas in a heavy refinery and carrying out gas-liquid phase splitting to obtain a first gas phase and a first liquid phase; mixing and compressing the compressed dry gas and the first gas phase in the light refinery, then combining with the fourth gas phase, cooling, combining with the third liquid phase, cooling, and performing gas-liquid phase separation to obtain a second gas phase and a second liquid phase; the second gas phase is sent into an absorption tower to contact with an absorbent, and a third liquid phase in the tower kettle is combined with the cooling dry gas; the second liquid phase is sent into a methane desorption tower after being pressurized and preheated, and the fourth gas phase at the top of the tower is combined with the compressed dry gas of the light refinery and the first gas phase; and feeding the fourth liquid phase in the tower kettle into a desorption tower for desorption, and combining the fifth gas phase and the first liquid phase at the tower top to be used as a concentrated gas product. The method can simultaneously recover the carbon dioxide and the above components in the dry gas of light and heavy refineries, and has low energy consumption.

Description

Method for concentrating carbon dioxide and components in dry gas of light and heavy refinery, device and application thereof

Technical Field

The invention relates to the field of waste gas recovery, in particular to a method for concentrating carbon dioxide and components thereof in dry gas of a light and heavy refinery, and a device and application thereof.

Background

For a large-scale oil refining and chemical industry integrated device, oil refining and chemical industry dry gas resources in the device are utilized by the system, high-value-added components such as ethylene and ethane in the device are recycled and serve as ethylene device raw materials, and the method is favorable for improving the profitability of enterprises and improving the diversity of ethylene device raw material supply. The refinery dry gas represented by catalytic dry gas, coking dry gas, PSA desorption gas and the like has a large content of light components such as hydrogen, methane, nitrogen and the like, and has a carbon content of about 10-20% vol, which is hereinafter referred to as light refinery dry gas. The refinery dry gas represented by the cracking dry gas, the aromatic dry gas (including PX disproportionation fuel gas, PX isomerization fuel gas and the like) and the like has higher content of carbon and above components, for example, the content of ethane in the PX disproportionation fuel gas can reach 25-70% vol when the molar content is higher, and the sum of the three components of carbon and carbon in the hydrocracking dry gas can exceed 50% vol, which is collectively referred to as heavy refinery dry gas. The invention mainly aims at the occasion of simultaneously recovering the dry gas of the light refinery and the dry gas of the heavy refinery, and carries out differential treatment on the dry gas of different refineries, and simultaneously realizes resource integration and utilization.

The methods for recovering carbon dioxide and heavier components from refinery dry gas, which have been industrialized at present and are suitable for large-scale raw gas treatment capacity, mainly comprise a cryogenic separation method, a pressure swing adsorption method, a shallow cold oil absorption method and the like, and various methods have the characteristics and are respectively suitable for different occasions and the requirements of owners. The cryogenic separation method has mature process, high ethylene recovery rate and high purity, but needs a propylene refrigeration system or an ethylene-propylene binary composite refrigeration system, and needs to carry out drying and dehydration treatment on the raw material gas, so the device investment is large, and the energy consumption is high; 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 and purifies a gas mixture by utilizing solubility difference of an absorbent on each component in the gas, generally, the absorbent is used for absorbing carbon dioxide and more heavy components in dry gas at high pressure and low temperature (shallow cold temperature, 5-20 ℃), noncondensable gases such as methane, oxygen, hydrogen, nitrogen and the like are separated, and then, each component in the absorbent is separated by a rectification method. The method has the characteristics of high recovery rate of C2C3, safe production, reliable operation, strong adaptability to raw material gas and the like, and is one of the existing competitive technologies. However, the conventional shallow cold oil absorption process does not generally distinguish raw material dry gas, and if the raw material contains light refinery dry gas and heavy refinery dry gas, the light refinery dry gas and the heavy refinery dry gas are mixed together and sent into the main absorption tower after being pressurized and cooled by the compressor. The carbon dioxide and heavier components in the heavy refinery dry gas are also subjected to an absorption-desorption process, and finally are sent out of the battery limit area from the top gas phase of the desorption tower or the extracted absorbent. In the process, the load of a main absorption tower and a desorption tower is large, and the steam consumption of a reboiler at the tower bottom is high.

US10052581B1 discloses a process for recovering steam cracker feedstock from FCC dry gas. The method firstly carries out amine elution on FCC dry gas to remove CO₂、H₂S, COS, removing alkynes by hydrogenation, refining, removing light components such as methane and hydrogen by pressure swing adsorption, and separatingThe separation process finally obtains the raw material flow of the steam cracking device mainly comprising ethane and ethylene. In the method, because the pressure swing absorption tower may have a working condition lower than 0 ℃ in the operation process, in order to avoid freezing, the dry gas needs to be cooled, phase-separated, dehydrated and dried before entering the pressure swing absorption tower, and the device investment is large.

CN104419466A discloses a refinery dry gas recovery system and a dry gas recovery method, wherein the refinery dry gas is compressed, cooled, absorbed, desorbed and liquefied to obtain a carbon-rich product. The product of the method is easy to store and transport, but the liquefaction temperature of the dry gas is lower, 0 ℃ and-40 ℃ propylene refrigerants are adopted for cooling, then the throttling is carried out to the normal pressure, and the liquid phase after the gas-liquid phase separation is carried out is taken as the product to be extracted. In order to avoid freezing and blocking, the process also comprises a drying step, and the investment and energy consumption of the whole process are large.

CN106609161A discloses a method for separating refinery saturated dry gas, which comprises compressing refinery saturated dry gas, cooling, and separating gas from liquid, wherein the compressed dry gas and the compressed condensate after gas-liquid separation are respectively sent to a carbon four absorption tower for absorption or sent to a gasoline stabilizer for rectification. The process comprises a gasoline stabilizer used for treating the gasoline-rich solvent and the compressed condensate in the gasoline absorption tower kettle. When the raw dry gas contains both light refinery dry gas and heavy refinery dry gas, the two dry gases (possibly multiple) need to be mixed at the inlet or between the sections of the compressor. The C2+ component in the heavy refinery dry gas is diluted, so that the amount of compression condensate separated out after subsequent compression, cooling and phase separation is reduced. Most of C2+ components in the heavy refinery dry gas still enter the carbon four absorption tower and the desorption tower. The two towers have larger load and higher energy consumption.

CN104560194A discloses a refinery saturated dry gas recovery system and a recovery method, and the system comprises an absorption tower, a desorption tower, a reabsorption tower, a compressor and a heat exchanger, and is provided with a condensate stripper. And (3) delivering compressed condensate obtained after the refinery dry gas is compressed, cooled and separated into liquid to a condensate stripper for treatment, and discharging from the kettle of the condensate stripper to be extracted as a product. When the raw dry gas contains both light refinery dry gas and heavy refinery dry gas, the C2+ components in the heavy refinery dry gas are diluted, so that the amount of compressed condensate entering the condensate stripper is reduced, and a lot of C2+ components in the heavy refinery dry gas still undergo the carbon four absorption-desorption process. The absorption tower and the desorption tower have larger load and higher energy consumption.

In summary, when the carbon dioxide and heavier components in the refinery dry gas are recovered, when the raw material dry gas contains both the light refinery dry gas (with less carbon dioxide and heavier components) and the heavy refinery dry gas (with more carbon dioxide and heavier components), the light and heavy refinery dry gases are mixed in the gas compression stage by the conventional shallow cold oil absorption process, most of the C2+ components in the heavy refinery dry gas are diluted and still undergo the subsequent absorption-desorption process, and the energy consumption for evaporating methane in the main absorption tower and the energy consumption for desorbing the rich absorbent in the desorption tower are higher.

Disclosure of Invention

The invention aims to overcome the problem of high energy consumption caused by the mixing of light and heavy refinery dry gases in the prior art when the refinery dry gas is recovered, and provides a method for concentrating carbon dioxide and above components in the light and heavy refinery dry gas, a device and an application thereof.

In order to achieve the above object, a first aspect of the present invention provides a method for concentrating carbon dioxide and the above components in light and heavy refinery dry gas, characterized in that the method comprises the steps of:

(1) compressing dry gas of a light refinery: increasing the pressure of the light refinery dry gas to 3.2-5 MPaG;

(2) compressing dry gas in a heavy refinery: increasing the pressure of the heavy refinery dry gas to 1-1.9 MPaG;

(3) cooling and phase splitting of dry gas in heavy refineries: cooling the heavy refinery compressed dry gas obtained in the step (2), and performing gas-liquid phase separation to obtain a first gas phase and a first liquid phase;

(4) primary cooling of dry gas: mixing the light refinery compressed dry gas obtained in the step (1) with the first gas obtained in the step (3) to obtain mixed dry gas, compressing the mixed dry gas, combining the compressed mixed dry gas with the fourth gas, and performing primary cooling to obtain cooled dry gas;

(5) secondary cooling of dry gas: combining the cooled dry gas and the third liquid phase obtained in the step (4), carrying out secondary cooling, and carrying out gas-liquid phase separation to obtain a second gas phase and a second liquid phase;

(6) c, C four-C five absorption: feeding the second gas phase obtained in the step (5) into the bottom of an absorption tower, and carrying out countercurrent contact with an absorbent from the top of the absorption tower, feeding a third gas phase obtained at the top of the absorption tower out of a boundary region, returning a third liquid phase obtained at the tower kettle of the absorption tower to the step (5) and combining the third liquid phase with the cooled dry gas;

(7) methane desorption: boosting the pressure of the second liquid phase obtained in the step (5), preheating to 25-80 ℃, then sending the second liquid phase to the top of a methane desorption tower to remove methane, obtaining a fourth gas phase at the top of the methane desorption tower, returning to the step (4), and combining the fourth gas phase with the compressed dry gas of the light refinery and the first gas phase; a fourth liquid phase is obtained at the tower kettle of the methane desorption tower;

(8) desorbing: feeding the fourth liquid phase obtained in the step (7) into the middle part of a desorption tower for desorption, obtaining a fifth gas phase at the top of the desorption tower, combining the fifth gas phase with the first liquid phase obtained in the step (3), and taking the fifth gas phase and the first liquid phase as a concentrated gas product to be sent out of a battery limit; and obtaining the lean absorbent at the tower bottom of the desorption tower.

The second aspect of the present invention provides an apparatus for concentrating carbon dioxide and the above components in light and heavy refinery dry gas, characterized in that the apparatus comprises: the system comprises a first compressor section, a second compressor, a first liquid separation tank, a compressor section inter-tank, a cooler, a circulating water cooler, a chilled water cooler, a second liquid separation tank, an absorption tower, a methane desorption tower and a desorption tower;

the first compressor section is used for compressing the dry gas of the light refinery and is communicated with the compressor section inter-tank;

the second compressor, the cooler and the first liquid separation tank are communicated in sequence and are used for compressing and cooling the dry gas of the heavy refinery and separating the gas phase from the liquid phase;

the compressor section inter-tank is respectively communicated with the first compressor section and the top of the first liquid separation tank and is used for mixing the light refinery compressed dry gas from the first compressor section and the first gas phase from the top of the first liquid separation tank to obtain mixed dry gas;

the compressor inter-stage tank is communicated with the first compressor second stage and is used for compressing the mixed dry gas;

the circulating water cooler, the chilled water cooler, the second liquid separation tank, the absorption tower, the methane desorption tower and the desorption tower are communicated in sequence;

the circulating water cooler is used for cooling the mixed compressed dry gas from the first compressor second section and the fourth gas phase from the top of the methane desorption tower;

the chilled water cooler is used for cooling the cooling material flow from the circulating water cooler and the third liquid phase from the tower bottom of the absorption tower;

the second liquid separation tank is used for carrying out gas-liquid phase separation on the cooled material from the frozen water cooler;

the bottom of the absorption tower is communicated with the top of the second liquid separation tank and is used for enabling the second gas phase to be in countercurrent contact with the absorbent, and the tower top and the tower kettle of the absorption tower discharge a third gas phase and a third liquid phase respectively;

the top of the methane desorption tower is communicated with the bottom of the second liquid separation tank and is used for removing methane in the second liquid phase, and the tower top and the tower kettle of the methane desorption tower discharge a fourth gas phase and a fourth liquid phase respectively;

the middle part of the desorption tower is communicated with the bottom of the methane desorption tower, the top of the desorption tower is communicated with the bottom of the first liquid separation tank, the desorption tower is used for desorbing the fourth liquid phase discharged from the bottom of the absorption tower, the top of the desorption tower obtains a fifth gas phase, the fifth gas phase is combined with the first liquid phase from the first liquid separation tank and is sent out of a boundary zone as a concentrated gas product; and obtaining the lean absorbent from the tower bottom of the desorption tower.

In a third aspect, the present invention provides the use of the above method or apparatus in refinery dry gas recovery.

Through the technical scheme, the method for concentrating carbon dioxide and the components in the dry gas of the light and heavy refinery, the device and the application thereof provided by the invention have the following beneficial effects:

(1) in the invention, based on the composition characteristics of the light and heavy refinery dry gases, the light and heavy refinery dry gases are respectively compressed and cooled, part of carbon dioxide and the above components in the heavy refinery dry gases enter the liquid phase of the liquid separation tank and are directly merged into the product concentrated gas without undergoing an absorption-methane desorption-desorption process, on the basis of ensuring the recovery rate of carbon dioxide, the reboiler load in the rich absorbent desorption process is saved, and the energy consumption of the device is reduced. Most of light components such as hydrogen, methane, nitrogen and the like in the heavy refinery dry gas are compressed and then sent into an absorption tower, and are separated from the carbon dioxide component through the absorption-methane desorption-desorption process, so that the content requirement of the light components in the final product concentrated gas is ensured.

(2) In the invention, the liquid phase entering the methane desorption tower is preheated in advance, so that the steam consumption of a reboiler of the methane desorption tower is reduced, and the energy consumption of a device is saved.

(3) In the invention, the pressure of the absorption tower is higher, compared with low-pressure absorption, the dosage of the circulating absorbent is smaller, the load of a reboiler at the tower bottom of the desorption tower is smaller, and the energy consumption of the device is saved.

(4) In the preferred embodiment of the invention, the lowest temperature of the compression cooling, absorption and desorption operations in the process flow is 5-15 ℃, a propylene refrigeration compressor is not needed, a lithium bromide refrigeration unit can be selected to provide refrigeration capacity, a drying system is not needed, the investment is low, the operation is simple, and the energy consumption is low;

(5) according to the invention, the method can obviously improve the concentration of the carbon two component in the concentrated gas product, the recovery rate of the carbon two component in the concentrated gas product is more than 92%, and the carbon two component can be used as the raw material of the ethylene device.

Drawings

FIG. 1 is a schematic flow diagram of the process for concentrating the carbon two and above components in the light and heavy refinery dry gas of the present invention.

Description of the reference numerals

1, light refinery dry gas; 2a first compressor section; 3 a first compressor section; 4, heavy refinery dry gas; 5 a second compressor; 6, a cooler; 7 a first liquid separation tank; 8 compressor inter-stage tank; 9 circulating water cooler; 10 a chilled water cooler; 11 a second liquid separation tank; 12 an absorption tower; 13 absorption tower kettle pump; 14 a feed pump; 15 an absorbent; 16 a third gas phase; 17 a preheater; 18 methane desorption tower; 19 a desorber; 20 an absorbent circulation pump; 21 concentrating the gas product.

Detailed Description

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.

The invention provides a method for concentrating carbon dioxide and above components in light and heavy refinery dry gas in a first aspect, which is characterized by comprising the following steps:

(3) cooling and phase splitting of dry gas in heavy refineries: cooling the compressed dry gas obtained in the step (2), and performing gas-liquid phase separation to obtain a first gas phase and a first liquid phase;

(4) primary cooling of dry gas: mixing the light refinery compressed dry gas obtained in the step (1) with the first gas obtained in the step (3) to obtain mixed dry gas, compressing the mixed dry gas, combining the compressed mixed dry gas with fourth gas, and performing primary cooling to obtain cooled dry gas;

In the invention, the dry gas of the light refinery and the dry gas of the heavy refinery are compressed respectively to be compressed and boosted, the dry gas of the heavy refinery is compressed and then is cooled and subjected to gas-liquid phase separation treatment, the gas phase of a liquid separating tank is sent to a compressor intersegmental tank, and is combined with the dry gas of the light refinery, and then is further compressed and cooled and then is sent to a downstream absorption tower to be subjected to absorption-methane desorption-desorption treatment; a preheater is arranged at the feeding stage of the methane desorption tower; the liquid phase obtained by compressing and separating the heavy refinery dry gas is directly merged into the concentrated gas product at the top of the desorption tower and is sent out of the battery limits.

In the invention, the light and heavy refinery dry gases are respectively treated, so that the carbon dioxide and the carbon dioxide in the heavy refinery dry gas are prevented from being diluted, the energy consumption in the rich absorbent desorption process is reduced, the steam consumption in the methane desorption process is saved by preheating the feed of the methane desorption tower, and a dryer and a propylene refrigeration compressor are not required. The carbon recovery rate is more than 92%. The concentrated gas can be sent to an ethylene device to be used as raw material.

In the present invention, the pressure is a gauge pressure unless otherwise specified.

According to the invention, the light refinery dry gas comprises hydrogen, methane, carbon dioxide, hydrogen sulphide, oxygen, nitrogen, a carbon two component, a carbon three component, a carbon four component and heavier components.

Preferably, the content of the carbon two component is 10-20 vol%, the total content of the hydrogen and the methane is 30-75 vol%, the content of the carbon dioxide is 0-20 vol%, the content of the hydrogen sulfide is 0-20 vol%, the content of the carbon three component is 0-20 vol%, and the content of the carbon four and heavier component is 0-10 vol% based on the total volume of the light refinery dry gas.

According to the invention, the heavy refinery dry gas comprises hydrogen, methane, a carbon two component, a carbon three component, a carbon four component and heavier components.

Preferably, the total content of hydrogen and methane is 5-40 vol%, the content of the carbon two component is 20-80 vol%, and the total content of the carbon three, carbon four and heavier components is 5-80 vol%, based on the total volume of the heavy refinery dry gas.

In the invention, the carbon two component refers to a hydrocarbon component with two carbon atoms, including ethane and ethylene; the carbon three component refers to hydrocarbon components with three carbon atoms, and comprises propane and propylene; the carbon four component refers to hydrocarbon component with four carbon atoms, including butane and butylene.

According to the invention, in step (1), the light refinery dry gas compression is a multi-stage compression, preferably a two-stage compression or a three-stage compression.

Preferably, the pressure of the light refinery dry gas is increased to 3.6-4.2 MPaG.

In the invention, in order to ensure that more carbon and the above components in the heavy refinery dry gas enter the first liquid phase in the step (3) so as to reduce the total energy consumption of the device; meanwhile, less light components such as hydrogen, methane and nitrogen in the dry gas of the heavy refinery enter the first liquid phase in the step (3) to avoid the reduction of the content of the light components in the concentrated gas of the final recovered product, and the inventor researches the lifting pressure of the dry gas of the heavy refinery in the step (2), and the research shows that the requirements can be simultaneously met when the pressure of the dry gas of the heavy refinery is increased to 1-1.9 MPaG.

Furthermore, when the pressure of the dry gas of the heavy refinery is increased to 1.5-1.8MPaG, the comprehensive effect is more excellent.

According to the invention, in step (2), the heavy refinery dry gas compression is one-stage compression or two-stage compression.

In the present invention, in step (3), in order to ensure that the gas-liquid phase has an appropriate gas-liquid ratio and methane has an appropriate portion in the gas-liquid two-phase, the inventors have studied the cooling temperature of the compressed dry gas in the refinery in step (3), and found that the above requirements can be satisfied simultaneously when the cooling temperature is 5 to 30 ℃.

Further, when the cooling temperature is preferably 10 to 20 ℃, the overall effect is more excellent.

According to the invention, the cooling step is performed by a refrigerant supplied by a lithium bromide absorption refrigerator.

In the present invention, in the step (3), the gas-liquid separation may be performed in an apparatus capable of achieving gas-liquid separation which is conventional in the art, for example, the gas-liquid separation is performed in the first liquid-separation tank described in the present invention.

In the invention, the refrigerant provided by the lithium bromide absorption refrigerator is adopted to cool the compressed gas, and the lithium bromide refrigerator takes waste heat steam from a refinery or hot water at 96-100 ℃ as a heat source.

In the present invention, the refrigerant may be a refrigerant conventional in the art, for example, cold water of 7-12 ℃ is selected as the refrigerant.

In the invention, the liquid-gas ratio of the liquid separation tank in the step (3) is determined by the composition of the refinery dry gas, the operation pressure and the cooling temperature, and preferably, the volume ratio of the carbon dioxide and heavier components in the first liquid phase to the carbon dioxide and heavier components in the refinery dry gas is more than 3: 10, preferably 4: 10-7: 10.

in the invention, the gas-liquid ratio of the liquid separation tank refers to the ratio of the gas phase discharge quantity at the top of the liquid separation tank to the liquid phase discharge quantity at the bottom of the liquid separation tank.

According to the invention, in step (4), the dry gas mixture is compressed, combined with a fourth gas, and subjected to primary cooling to 35-45 ℃, preferably 40-45 ℃.

In the present invention, the primary cooling may be performed by using a cooler conventional in the art, and preferably, a circulating water cooler.

According to the present invention, in the step (4), the pressure of the mixed dry gas is raised to 3.2 to 5MPaG, preferably 3.6 to 4.2 MPaG.

According to the invention, in step (5), the cooled dry gas obtained in step (4) and the third liquid phase are combined and subjected to secondary cooling to a temperature of 5-30 ℃, preferably 10-20 ℃.

In the present invention, the secondary cooling may be performed by using a cooler conventional in the art, and preferably, a chilled water cooler.

According to the invention, in the step (6), the absorbent is carbon four and/or carbon five fraction, preferably at least one of n-butane, isobutane, mixed butane, carbon four after ether and carbon five in refinery.

According to the invention, the theoretical plate number of the absorption column can be 15 to 30, preferably 20 to 25.

According to the invention, the operating pressure of the absorption column can be between 3.2 and 4.5MPaG, preferably between 3.6 and 4.2 MPaG.

According to the invention, the temperature at the top of the absorption column can be between 10 and 30 ℃ and preferably between 15 and 25 ℃.

According to the invention, the temperature of the bottom of the absorption tower can be 20-60 ℃, preferably 20-35 ℃.

In the invention, the method also comprises the step of sending a third gas phase obtained at the tower top of the absorption tower into an absorbent recovery device; or alternatively, into a fuel gas network.

In one embodiment of the invention, the second gas phase is introduced into the bottom of the absorption tower and is in countercurrent contact with an absorbent from the top of the absorption tower to absorb the carbon dioxide and the above fraction in the second gas phase, the third gas phase at the top of the absorption tower is sent out of a boundary zone, and the third liquid phase at the bottom of the absorption tower is returned to the step (5) to be combined with the cooled dry gas.

In the invention, in order to fully utilize low-temperature preheating in the process flow, the energy required by downstream cooling material flow is reduced; meanwhile, the feeding temperature of the methane desorption tower is increased, and the steam consumption of a reboiler in the tower kettle of the methane desorption tower is reduced.

According to the invention, in step (7), the preheated heat source is selected from at least one of the light refinery compressed dry gas in step (1), the heavy refinery compressed dry gas in step (2) and the lean absorbent in step (8).

Preferably, in the step (8), the lean absorbent obtained from the bottom of the desorption tower is used as a heat source after being pressurized in the step (7) for preheating the second liquid phase.

More preferably, the second liquid phase obtained in step (5) is subjected to pressure increase and preheated to 35-70 ℃.

In the present invention, in the step (7), the pressure of the second liquid phase obtained in the step (5) is preferably raised to 3.5 to 5 MPaG. Preheating to 40-70 ℃.

According to the present invention, the theoretical plate number of the methane desorption column may be 20 to 50, preferably 20 to 35.

According to the present invention, the operating pressure of the methane desorption column may be 3.3 to 4.9MPaG, preferably 3.7 to 4.3 MPaG.

According to the present invention, the overhead temperature of the methane desorption column may be 20 to 80 ℃, preferably 40 to 75 ℃.

According to the invention, the temperature of the bottom of the methane desorption tower can be 40-120 ℃, and preferably 70-120 ℃.

According to the invention, the number of theoretical plates of the desorber may be from 10 to 40, preferably from 20 to 35.

According to the present invention, the operating pressure of the desorption column may be 1 to 2.8MPaG, preferably 1.2 to 2.2 MPaG.

According to the invention, the temperature at the top of the desorption column can be between 15 and 70 ℃ and preferably between 15 and 50 ℃.

According to the invention, the temperature of the bottom of the desorption tower can be 100-.

According to the invention, the method may further comprise passing the enriched gas product to a cracking unit for a cracking reaction.

In the invention, the method can also comprise that the concentrated gas is heated to the normal temperature (30 ℃) by a heater and then is sent out of the boundary area.

According to the invention, the concentrate gas product comprises hydrogen, methane, a carbon two component, a carbon three component and more than four carbon components.

Preferably, the hydrogen is present in an amount of 0 to 1 vol%, preferably 0 to 0.1 vol%, based on the total volume of the concentrate gas product; the content of the methane is 1-5 vol%, preferably 1-3 vol%; the content of the carbon dioxide component is 50-85 vol%, preferably 60-80 vol%; the content of the carbon three component is 0-40 vol%, preferably 10-22 vol%; the content of the carbon four or more component is 0 to 20 vol%, preferably 1 to 15 vol%.

the middle part of the desorption tower is communicated with the bottom of the methane desorption tower, the top of the desorption tower is communicated with the bottom of the first liquid separation tank, and the desorption tower is used for desorbing the fourth liquid phase discharged from the bottom of the absorption tower, and the top of the desorption tower obtains a fifth gas phase which is combined with the first liquid phase from the first liquid separation tank and is sent out of a battery compartment as a concentrated gas product; and obtaining the lean absorbent from the tower bottom of the desorption tower.

According to the invention, the plant also comprises a feed pump and a preheater.

In the invention, the feed pump and the preheater are respectively communicated with the second liquid separation tank and the methane desorption tower and are used for feeding the second liquid phase from the bottom of the second liquid separation tank into the top of the methane desorption tower after boosting and preheating the second liquid phase.

According to the invention, the device also comprises an absorbent circulation pump.

In the invention, the absorbent circulating pump is communicated with the bottom of the desorption tower and is used for partially returning the poor absorbent obtained from the tower kettle of the desorption tower to the top of the absorption tower after the pressure of the poor absorbent is increased.

According to the invention, a reboiler is arranged in the methane desorption tower.

In a third aspect the invention provides the use of a method or apparatus as described above in the recovery of refinery dry gas.

The method and apparatus of the present invention are further described with reference to fig. 1.

The pressure of the light refinery dry gas 1 is boosted to 1-1.9MPaG through a first compressor section 2, and the compressed dry gas is sent to a compressor section inter-tank 8;

the pressure of the dry gas 4 of the heavy refinery is increased to 1-1.9MPaG through a second compressor 5, the dry gas is cooled to 5-30 ℃ in a cooler 6, the dry gas is sent into a first liquid separation tank 7 for gas-liquid phase separation, a first gas phase obtained by the first liquid separation tank is sent to a compressor inter-segment tank 8, and a first liquid phase obtained by the first liquid separation tank is merged into a concentrated gas product 21;

the pressure of the mixed gas phase discharged from the top of the compressor inter-stage tank 8 is boosted to 3.2-5MPaG through the first compressor second stage 3, and is cooled to 35-45 ℃ in the circulating water cooler 9 after being converged with the fourth gas phase obtained from the top of the methane desorption tower 18, the outlet material flow of the circulating water cooler 9 is converged with the third liquid phase (after being boosted by the absorption tower kettle liquid pump 13) obtained from the tower kettle of the absorption tower 12, is cooled to 5-30 ℃ in the chilled water cooler 10, enters the second liquid separation tank 11 for gas-liquid phase separation, and the second gas phase obtained from the second liquid separation tank 11 is sent to the bottom of the absorption tower 12; the second liquid phase obtained from the second separation tank 11 is pressurized by the feed pump 14 and then sent to the preheater 17.

In an absorption tower 12, a carbon four-carbon five fraction is used as an absorbent 15 and is sprayed from the top of the absorption tower to absorb a carbon two fraction and heavier components in dry gas, a third gas phase 16 which is not absorbed at the top of the absorption tower and contains methane and hydrogen is sent out of a boundary area and sent to an absorbent recovery device or discharged into a fuel gas pipe network, and a third liquid phase obtained at the tower bottom of the absorption tower 12 is converged with an outlet material flow of a circulating water cooler 9 through an absorption tower bottom liquid pump 13 and enters a chilled water cooler 10;

the second liquid phase obtained from the second separation tank 11 is pressurized by a feed pump 14, heated to 25 to 80 ℃ in a preheater 17, and sent to the top of a methane desorption column 18. The preheater 17 uses the process stream in the battery compartment as a heat source, and preferably uses the lean absorbent (after being boosted by the absorbent circulating pump 20) obtained at the bottom of the desorption tower 19 as a heat source.

The material flow from the preheater 17 enters the top of a methane desorption tower 18, and the bottom of the methane desorption tower is provided with a reboiler for distilling out and removing methane in the feeding material. And a fourth gas phase obtained at the top of the methane desorption tower 18 is merged with a material flow at the outlet of the second compressor and sent to the circulating water cooler 9, and a fourth liquid phase obtained at the bottom of the methane desorption tower 18 is sent to the desorption tower 19 for treatment.

The fourth liquid phase from the tower bottom of the methane desorption tower 18 is sent to the middle part of the desorption tower 19, and the fifth gas phase obtained from the tower top of the desorption tower 19 is combined with the second liquid phase of the first liquid separation tank 7 to be used as a concentrated gas product 21 which is sent to an ethylene device to be used as a raw material; the lean absorbent obtained from the bottom of the desorption tower 19 is pressurized by an absorbent circulating pump 20, and after the methane tower is preheated, the lean absorbent returns to the absorption tower 12 for recycling.

The present invention will be described in detail below by way of examples. In the following examples of the present invention,

the carbon dioxide recovery is calculated by the formula: x 100% of (ethane + ethylene) in the concentrated gas, (ethane + ethylene) in the light refinery dry gas and (ethane + ethylene) in the heavy refinery dry gas); the calculation formula of the carbon recovery rate is as follows: the x is 100% of (propane + propylene) in the concentrated gas, (propane + propylene) in the light refinery dry gas and (propane + propylene) in the heavy refinery dry gas).

Examples and comparative examples the compositions of the light and heavy refinery dry gases are shown in table 1. The gas composition was tested using the standard ASTM D1945.

TABLE 1 Dry gas flowrate composition of refinery

	Light refinery dry gas	Heavy refinery dry gas
			Temperature, C	40.0	40.0
Pressure, MPaG	0.60	0.30
			Mass flow, t/h	50.0	20.0
Composition in mol%
			H₂	40.34	6.99
H₂S	0.06	0.00
			CO	0.74	0.00
CO₂	0.57	0.00
			O₂	0.82	0.00
N₂	5.56	0.00
			CH₄	25.85	3.94
C₂H₆	16.24	60.12
			C₂H₄	0.42	0.00
C₃H₈	5.05	19.01
			C₃H₆	0.04	0.00
C₄H₁₀	2.94	6.21
			C₄H₈	0.02	0.00
C5+	1.28	3.72
			H₂O	0.07	0.00

Example 1

The method for concentrating the carbon dioxide and the components in the light and heavy refinery dry gas by adopting the shallow cold oil absorption method is adopted to separate and recover the refinery dry gas.

The specific process comprises the following steps:

the light refinery dry gas, with the composition shown in table 1 and pressure of 0.6MPaG, enters the first compressor stage, increases the pressure to 1.8MPaG, and is sent to the light refinery dry gas compressor stage intermediate tank.

The heavy refinery dry gas, with the composition shown in table 1, was fed to the second compressor at a pressure of 0.3MPaG, increasing the pressure to 1.8 MPaG. And (3) cooling the pressurized dry gas to 20 ℃ by using cold water provided by a lithium bromide absorption refrigerator, then sending the cooled dry gas into a first liquid separation tank for gas-liquid phase separation, sending the first gas phase at the top of the liquid separation tank into a compressor section tank, combining the first liquid phase compression condensate at the bottom of the liquid separation tank into a concentrated gas product, and sending the concentrated gas product out of a boundary area.

The mixed gas phase on the top of the tank between the compressor sections is subjected to pressure increase to 4.2MPaG through the first compressor section, is converged with the fourth gas phase on the top of the methane desorption tower, is cooled to 40 ℃ by circulating water in a circulating water cooler, is converged with the third liquid phase boosted by a tower liquid pump of the absorption tower, is cooled to 15 ℃ by the chilled water in the chilled water cooler, and is sent to a second liquid separation tank for gas-liquid phase separation. And the second gas phase at the top of the second liquid separation tank is sent to the bottom of the absorption tower, and the second liquid phase at the bottom of the second liquid separation tank is sent to the preheater after being boosted by the feed pump.

Wherein the volume ratio of the carbon dioxide and heavier components in the first liquid phase to the carbon dioxide and heavier components in the refinery dry gas is 4.2: 10

In the absorption tower, refinery mixed butane (propane 8 vol%, n-butane 28 vol%, isobutane 33 vol%, pentane 31 vol%) is used as an absorbent (the circulation amount of the absorbent is 145t/h), and the absorbent is sprayed from the top of the tower to absorb the carbon dioxide fraction and the components in the dry gas. The number of theoretical plates of the absorption tower is preferably 20, the operating pressure is 4.1MPaG, the temperature at the top of the tower is 20 ℃, and the temperature at the bottom of the tower is 23 ℃. And the third gas phase which is not absorbed at the tower top is discharged into a fuel gas pipe network, and the third liquid phase at the tower bottom is boosted by a liquid pump at the tower bottom of the absorption tower, then is converged with the material flow at the outlet of the circulating water cooler and returns to the chilled water cooler.

And a second liquid phase obtained from the second liquid separation tank is boosted by a feed pump, heated to 70 ℃ in a preheater and then enters the top of the methane desorption tower. The preheater adopts the lean absorbent from the tower bottom of the desorption tower as a heat source. The theoretical plate number of the methane desorption tower is 20, the operation pressure is 4.2MPaG, the tower top temperature is 71 ℃, and the tower kettle temperature is 120 ℃. And the methane desorption tower is heated by low-pressure steam, the fourth gas phase at the top of the tower is converged with the material flow at the outlet of the second compressor and sent to a circulating water cooler, and the fourth liquid phase obtained at the bottom of the methane desorption tower is sent to a desorption tower for treatment.

And the fourth liquid phase from the tower kettle of the methane desorption tower enters the middle part of the desorption tower. The theoretical plate number of the desorption tower is 20, the operation pressure is 2.2MPaG, the tower top temperature is 27 ℃, and the tower bottom temperature is 126 ℃. The desorption tower is heated by low-pressure steam, a reboiler at the tower bottom is in 9472kW load, lean absorbent obtained at the tower bottom of the desorption tower is boosted by an absorbent circulating pump, and the feed of the methane desorption tower is preheated and then returned to the absorption tower for recycling. And (3) combining the gas phase at the top of the desorption tower with the liquid phase compression condensate at the bottom of the dry gas liquid separation tank of the heavy refinery, heating to 40 ℃, taking the gas as a concentrated gas product, delivering the gas out of a boundary zone, and delivering the gas to a cracking furnace of an ethylene device to be used as a raw material.

In this example, the composition of the concentrate gas product is shown in Table 2, where the carbon recovery was 93.8%.

TABLE 2

	Concentration gas
		Temperature, C	40.0
Pressure, MPaG	1.71
		Mass flow, t/h	35.9
Composition in mol%
		H₂	0.02
H₂S	0.15
		CO₂	0.51
CH₄	2.82
		C₂H₆	73.22
C₂H₄	0.74
		C₃H₈	19.06
C₃H₆	0.10
		C₄H₁₀	1.82
C5+	1.52
		H₂O	0.04

Example 2

The method for concentrating the carbon dioxide and the components in the light and heavy refinery dry gas by adopting the shallow cold oil absorption method of the invention is adopted to separate and recover the refinery dry gas in the table 1.

The specific process comprises the following steps:

the light refinery dry gas, with the composition shown in table 1 and pressure of 0.6MPaG, enters the first compressor stage, increases the pressure to 1.5MPaG, and is sent to the light refinery dry gas compressor stage intermediate tank.

The heavy refinery dry gas, with the composition shown in table 1, was fed to the second compressor at a pressure of 0.3MPaG, increasing the pressure to 1.5 MPaG. And (3) cooling the pressurized dry gas to 10 ℃ by using cold water provided by a lithium bromide absorption refrigerator, then sending the cooled dry gas into a first liquid separation tank for gas-liquid phase separation, sending the first gas phase at the top of the liquid separation tank into a compressor section tank, merging the first liquid phase compression condensate at the bottom of the liquid separation tank into a concentrated gas product, and sending the concentrated gas product out of a boundary area.

The mixed gas phase on the top of the tank between the compressor sections is subjected to pressure increase to 3.7MPaG through the first compressor section, is converged with the fourth gas phase on the top of the methane desorption tower, is cooled to 45 ℃ by circulating water in a circulating water cooler, is converged with the third liquid phase boosted by a tower liquid pump of the absorption tower, is cooled to 10 ℃ by the chilled water in the chilled water cooler, and is sent to a second liquid separation tank for gas-liquid phase separation. And the second gas phase at the top of the second liquid separation tank is sent to the bottom of the absorption tower, and the second liquid phase at the bottom of the second liquid separation tank is sent to the preheater after being boosted by the feed pump.

Wherein, the volume ratio of the carbon dioxide and heavier components in the first liquid phase to the carbon dioxide and heavier components in the dry gas of the heavy refinery is 5: 10

In the absorption tower, refinery mixed butane (propane 5 vol%, n-butane 36 vol%, isobutane 17 vol%, pentane 42 vol%) is used as an absorbent (the circulation amount of the absorbent is 155t/h), and the absorbent is sprayed from the top of the tower to absorb the carbon dioxide fraction and the components in the dry gas. The number of theoretical plates of the absorption tower is preferably 25, the operating pressure is 3.6MPaG, the temperature at the top of the tower is 20 ℃, and the temperature at the bottom of the tower is 20 ℃. And the third gas phase which is not absorbed at the tower top is discharged into a fuel gas pipe network, and the third liquid phase at the tower bottom is boosted by a liquid pump at the tower bottom of the absorption tower, then is converged with the material flow at the outlet of the circulating water cooler and returns to the chilled water cooler.

And a second liquid phase obtained from the second liquid separation tank is boosted by a feed pump, heated to 40 ℃ in a preheater and then enters the top of the methane desorption tower. The preheater adopts the lean absorbent from the tower bottom of the desorption tower as a heat source. The theoretical plate number of the methane desorption tower is 35, the operation pressure is 3.7MPaG, the tower top temperature is 43 ℃, and the tower kettle temperature is 115 ℃. And the methane desorption tower is heated by low-pressure steam, the fourth gas phase at the top of the tower is converged with the material flow at the outlet of the second compressor and sent to a circulating water cooler, and the fourth liquid phase obtained at the bottom of the methane desorption tower is sent to a desorption tower for treatment.

And the fourth liquid phase from the tower kettle of the methane desorption tower enters the middle part of the desorption tower. The theoretical plate number of the desorption tower is 35, the operation pressure is 1.2MPaG, the tower top temperature is 38 ℃, and the tower bottom temperature is 102 ℃. The desorption tower is heated by low-pressure steam, the lean absorbent obtained at the tower bottom of the desorption tower loaded with 5724kW by a reboiler at the tower bottom is boosted by an absorbent circulating pump, and the feed to the methane desorption tower is preheated and then returned to the absorption tower for recycling. And (3) combining the gas phase at the top of the desorption tower with the liquid phase compression condensate at the bottom of the dry gas liquid separation tank of the heavy refinery, heating to 40 ℃, taking the gas as a concentrated gas product, delivering the gas out of a boundary zone, and delivering the gas to a cracking furnace of an ethylene device to be used as a raw material.

In this example, the composition of the concentrate gas product is shown in Table 3, where the carbon recovery was 93.9%.

TABLE 3

	Concentration gas
		Temperature, C	40.0
Pressure, MPaG	1.16
		Mass flow, t/h	43.3
Composition in mol%
		H₂	0.02
H₂S	0.13
		CO₂	0.55
CH₄	2.57
		C₂H₆	65.00
C₂H₄	0.70
		C₃H₈	18.86
C₃H₆	0.09
		C₄H₁₀	10.58
C5+	1.46
		H₂O	0.04

Comparative example 1

The dry gas shown in table 1 was recovered according to the typical shallow cold oil absorption process scheme of CN103087772A, wherein the feed conditions and carbon dioxide recovery were the same as in example 1, and the resulting enriched gas product had the composition shown in table 4, wherein the carbon dioxide recovery was 93.8%. The process conditions and energy consumption are shown in table 5.

TABLE 4

Comparative example 2

The dry gas shown in Table 1 was recovered by a cryogenic separation process, wherein the feed conditions and the carbon dioxide recovery rate were the same as in example 1, and the process conditions are shown in Table 5.

TABLE 5

Comparative example 3

The same raw material and recovery rate as in example 1, and the same connection mode of the apparatus, except that: the first compressor second stage raises the mixed dry gas compression pressure to 3MPaG, and the operation pressure of the absorption tower is 3 MPaG.

The method comprises the following specific steps:

The mixed gas phase on the top of the tank between the compressor sections is increased to 3MPaG through the first compressor section, is converged with the fourth gas phase on the top of the methane desorption tower, is cooled to 40 ℃ by circulating water in a circulating water cooler, is converged with the third liquid phase boosted by a tower liquid pump of the absorption tower, is cooled to 15 ℃ by chilled water in the chilled water cooler, and is sent into a second liquid separation tank for gas-liquid phase separation. And the second gas phase at the top of the second liquid separation tank is sent to the bottom of the absorption tower, and the second liquid phase at the bottom of the second liquid separation tank is sent to the preheater after being boosted by the feed pump.

In the absorption tower, refinery mixed butane (propane 8 vol%, n-butane 28 vol%, isobutane 33 vol%, pentane 31 vol%) is used as an absorbent (the circulation amount of the absorbent is 197t/h), and the absorbent is sprayed from the top of the tower to absorb the carbon dioxide fraction and the components in the dry gas. The number of theoretical plates of the absorption tower is preferably 20, the operation pressure is 3MPaG, the tower top temperature is 20 ℃, and the tower bottom temperature is 23 ℃. And the third gas phase which is not absorbed at the tower top is discharged into a fuel gas pipe network, and the third liquid phase at the tower bottom is boosted by a liquid pump at the tower bottom of the absorption tower, then is converged with the material flow at the outlet of the circulating water cooler and returns to the chilled water cooler.

And a second liquid phase obtained from the second liquid separation tank is boosted by a feed pump, heated to 70 ℃ in a preheater and then enters the top of the methane desorption tower. The preheater adopts the lean absorbent from the tower bottom of the desorption tower as a heat source. The theoretical plate number of the methane desorption tower is 20, the operation pressure is 3.1MPaG, the tower top temperature is 72 ℃, and the tower kettle temperature is 102 ℃. And the methane desorption tower is heated by low-pressure steam, the fourth gas phase at the top of the tower is converged with the material flow at the outlet of the second compressor and sent to a circulating water cooler, and the fourth liquid phase obtained at the bottom of the methane desorption tower is sent to a desorption tower for treatment.

And the fourth liquid phase from the tower kettle of the methane desorption tower enters the middle part of the desorption tower. The theoretical plate number of the desorption tower is 20, the operation pressure is 2.2MPaG, the tower top temperature is 28 ℃, and the tower bottom temperature is 124 ℃. The desorption tower is heated by low-pressure steam, the reboiler at the tower bottom is loaded with 11442kW, the lean absorbent obtained at the tower bottom of the desorption tower is boosted by an absorbent circulating pump, and the feed to the methane desorption tower is preheated and then returned to the absorption tower for recycling. And (3) combining the gas phase at the top of the desorption tower with the liquid phase compression condensate at the bottom of the dry gas liquid separation tank of the heavy refinery, heating to 40 ℃, taking the gas as a concentrated gas product, delivering the gas out of a boundary zone, and delivering the gas to a cracking furnace of an ethylene device to be used as a raw material.

In this comparative example, the composition of the enriched gas product is shown in Table 6, in which the carbon recovery rate is 93.8%. The circulating absorbed dose and the column bottom heat load of comparative example 3 were increased compared to example 1.

TABLE 6

	Concentration gas
		Temperature, C	40.0
Pressure, MPaG	1.71
		Mass flow, t/h	35.9
Composition in mol%
		H₂	0.02
H₂S	0.15
		CO₂	0.46
CH₄	3.49
		C₂H₆	72.95
C₂H₄	0.70
		C₃H₈	18.46
C₃H₆	0.09
		C₄H₁₀	2.11
C5+	1.51
		H₂O	0.0

As can be seen from tables 2 to 6, the lowest temperature of the process material flow of the process is 5-15 ℃, the propylene refrigeration capacity at a low temperature position is not needed, a propylene refrigeration system and a drying system are not needed, and the equipment investment is low. Compared with the conventional shallow cold oil absorption process, the process has the advantages that the light and heavy refinery dry gas is respectively compressed and cooled, most of the carbon and the components in the heavy refinery dry gas are directly merged into a concentrated gas product along with a compressed condensate, and the process of the methane desorption tower preheater is additionally arranged, so that the reboiler load in the methane desorption process and the rich absorbent desorption process is reduced, the energy consumption of the device is reduced, the water content in the concentrated gas is lower, and the risk of freezing and blocking of an outgoing pipeline is reduced.

The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including combinations of various technical features in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.

Claims

1. A method for concentrating carbon dioxide and above components in light and heavy refinery dry gas, which is characterized by comprising the following steps:

2. The method of claim 1, wherein the light refinery dry gas comprises hydrogen, methane, carbon dioxide, hydrogen sulfide, oxygen, nitrogen, a carbon two component, a carbon three component, a carbon four component, and heavier components;

preferably, the content of the carbon two component is 10-20 vol%, the total content of the hydrogen and the methane is 30-75 vol%, the content of the carbon dioxide is 0-20 vol%, the content of the hydrogen sulfide is 0-20 vol%, the content of the carbon three component is 0-20 vol%, and the content of the carbon four and heavier component is 0-10 vol% based on the total volume of the light refinery dry gas;

preferably, the heavy refinery dry gas comprises hydrogen, methane, a carbon two component, a carbon three component, a carbon four component and heavier components;

more preferably, the total content of hydrogen and methane is 5-40 vol%, the content of the carbon two component is 20-80 vol%, and the total content of the carbon three, carbon four and heavier components is 5-80 vol%, based on the total volume of the heavy refinery dry gas.

3. The process according to claim 1 or 2, wherein in step (1), the light refinery dry gas compression is a multi-stage compression, preferably a two-stage compression or a three-stage compression;

4. The method according to any one of claims 1-3, wherein in step (2), the heavy refinery dry gas compression is one-stage compression or two-stage compression;

preferably, the pressure of the heavy refinery dry gas is increased to 1.5-1.8 MPaG.

5. The process according to any one of claims 1 to 4, wherein in step (3), the heavy refinery compressed dry gas is cooled to 5 to 30 ℃, preferably 10 to 20 ℃;

preferably, the step of cooling is performed by a refrigerant provided by a lithium bromide absorption refrigerator;

preferably, the volume ratio of carbon dioxide and heavier components in the first liquid phase to carbon dioxide and heavier components in the refinery dry gas is greater than 3: 10, preferably 4: 10-7: 10.

6. the method according to any one of claims 1 to 5, wherein in the step (4), the mixed dry gas is compressed, combined with a fourth gas, and subjected to primary cooling to 35-45 ℃, preferably 40-45 ℃;

more preferably, in step (4), the pressure of the dry gas mixture is raised to 2.5-5MPaG, preferably 3.6-4.2 MPaG;

preferably, in step (5), the cooled dry gas obtained in step (4) and the third liquid phase are combined and subjected to secondary cooling to 5-30 ℃, preferably 10-20 ℃.

7. The process according to any one of claims 1 to 6, wherein in step (6), the absorbent is a carbon four and/or carbon five fraction, preferably at least one of n-butane, isobutane, mixed butanes, post-etheric carbon four and refinery carbon five;

preferably, the theoretical plate number of the absorption tower is 15 to 30, preferably 20 to 25;

preferably, the operating pressure of the absorption column is from 3.2 to 4.8MPaG, preferably from 3.6 to 4.2 MPaG;

preferably, the tower top temperature of the absorption tower is 10-30 ℃, preferably 15-25 ℃;

preferably, the temperature of the bottom of the absorption tower is 20-60 ℃, preferably 20-35 ℃.

8. The method of any one of claims 1 to 7, wherein in step (7) the preheated heat source is selected from at least one of the light refinery compressed dry gas in step (1), the heavy refinery compressed dry gas in step (2) and the lean absorbent in step (8);

preferably, preheating to 40-70 ℃;

preferably, the theoretical plate number of the methane desorption tower is 20-50, preferably 20-35;

preferably, the operating pressure of the methane desorption column is 3.3 to 4.9MPaG, preferably 3.7 to 4.3 MPaG;

preferably, the tower top temperature of the methane desorption tower is 20-80 ℃, and preferably 40-75 ℃;

preferably, the temperature of the tower bottom of the methane desorption tower is 40-120 ℃, and preferably 70-120 ℃.

9. The process according to any one of claims 1 to 8, wherein in step (8), the theoretical plate number of the desorber is from 10 to 40, preferably from 20 to 35;

preferably, the operating pressure of the desorber is from 1 to 2.8MPaG, preferably from 1.2 to 2.2 MPaG;

preferably, the temperature of the top of the desorption tower is 15-70 ℃, preferably 15-50 ℃;

preferably, the temperature of the tower bottom of the desorption tower is 100-200 ℃, and preferably 100-130 ℃.

10. The method according to any one of claims 1-9, wherein the method further comprises: introducing the concentrated gas product into a cracking device for cracking reaction;

preferably, the concentrate gas product comprises hydrogen, methane, a carbon two component, a carbon three component and more than four carbon components;

more preferably, the hydrogen is present in an amount of 0 to 1 vol%, preferably 0 to 0.1 vol%, based on the total volume of the concentrate gas product; the content of the methane is 1-5 vol%, preferably 1-3 vol%; the content of the carbon dioxide component is 50-85 vol%, preferably 60-80 vol%; the content of the carbon three component is 0-40 vol%, preferably 10-22 vol%; the content of the carbon four or more component is 0 to 20 vol%, preferably 1 to 15 vol%.

11. An apparatus for concentrating carbon dioxide and components thereof from light and heavy refinery dry gas, said apparatus comprising: the system comprises a first compressor section, a second compressor, a first liquid separation tank, a compressor section inter-tank, a cooler, a circulating water cooler, a chilled water cooler, a second liquid separation tank, an absorption tower, a methane desorption tower and a desorption tower;

12. The apparatus of claim 11, wherein the apparatus further comprises a feed pump and a preheater,

the feed pump and the preheater are respectively communicated with the second liquid separation tank and the methane desorption tower and are used for feeding the second liquid phase from the bottom of the second liquid separation tank into the top of the methane desorption tower after boosting and preheating the second liquid phase;

preferably, the apparatus further comprises an absorbent circulation pump;

the absorbent circulating pump is communicated with the bottom of the desorption tower and is used for partially returning the poor absorbent obtained at the tower kettle of the desorption tower to the top of the absorption tower after the pressure of the poor absorbent is increased;

preferably, a reboiler is arranged in the methane desorption tower;

preferably, the device further comprises an absorption tower kettle pump for pressurizing the third liquid phase discharged from the absorption tower kettle and then sending the third liquid phase into the chilled water cooler.

13. Use of the method of any one of claims 1 to 10 or the apparatus of claim 11 or 12 in refinery dry gas recovery.