CN112138420B - Device and method for low-pressure desulfurization and separation of light hydrocarbon from oil gas - Google Patents

Device and method for low-pressure desulfurization and separation of light hydrocarbon from oil gas Download PDF

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CN112138420B
CN112138420B CN201910575640.8A CN201910575640A CN112138420B CN 112138420 B CN112138420 B CN 112138420B CN 201910575640 A CN201910575640 A CN 201910575640A CN 112138420 B CN112138420 B CN 112138420B
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tower
gas
tank
liquid
debutanizer
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CN112138420A (en
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黄孟旗
吴迪
余龙红
丁昱文
郝少博
江盛阳
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Sinopec Engineering Inc
Sinopec Engineering Group Co Ltd
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Sinopec Engineering Group Co Ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/002—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by condensation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/14—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by absorption
    • B01D53/1456—Removing acid components
    • B01D53/1468—Removing hydrogen sulfide
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/14—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by absorption
    • B01D53/1456—Removing acid components
    • B01D53/1475—Removing carbon dioxide
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/14—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by absorption
    • B01D53/1487—Removing organic compounds
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/14—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by absorption
    • B01D53/18—Absorbing units; Liquid distributors therefor
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C7/00—Purification; Separation; Use of additives
    • C07C7/005—Processes comprising at least two steps in series
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C7/00—Purification; Separation; Use of additives
    • C07C7/04—Purification; Separation; Use of additives by distillation
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C7/00—Purification; Separation; Use of additives
    • C07C7/11—Purification; Separation; Use of additives by absorption, i.e. purification or separation of gaseous hydrocarbons with the aid of liquids
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2257/00—Components to be removed
    • B01D2257/70—Organic compounds not provided for in groups B01D2257/00 - B01D2257/602
    • B01D2257/702—Hydrocarbons
    • B01D2257/7022—Aliphatic hydrocarbons
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2257/00—Components to be removed
    • B01D2257/70—Organic compounds not provided for in groups B01D2257/00 - B01D2257/602
    • B01D2257/702—Hydrocarbons
    • B01D2257/7022—Aliphatic hydrocarbons
    • B01D2257/7025—Methane
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02C—CAPTURE, STORAGE, SEQUESTRATION OR DISPOSAL OF GREENHOUSE GASES [GHG]
    • Y02C20/00—Capture or disposal of greenhouse gases
    • Y02C20/20—Capture or disposal of greenhouse gases of methane
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P20/00—Technologies relating to chemical industry
    • Y02P20/50—Improvements relating to the production of bulk chemicals
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/10—Greenhouse gas [GHG] capture, material saving, heat recovery or other energy efficient measures, e.g. motor control, characterised by manufacturing processes, e.g. for rolling metal or metal working

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  • Organic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Analytical Chemistry (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • General Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Water Supply & Treatment (AREA)
  • Production Of Liquid Hydrocarbon Mixture For Refining Petroleum (AREA)

Abstract

The invention belongs to the field of chemical industry, and particularly discloses a device and a method for separating light hydrocarbons by oil gas low-pressure desulfurization, wherein the method has the advantages of simple flow, mild operating conditions and low cold consumption, can realize the separation and recovery of the light hydrocarbons in oil gas by using less equipment, and particularly can realize the high-efficiency separation and recovery of carbon two, carbon three and carbon four components.

Description

Device and method for low-pressure desulfurization and separation of light hydrocarbon from oil gas
Technical Field
The invention belongs to the field of oil refining and chemical engineering, and particularly relates to a device and a method for separating light hydrocarbons by oil gas low-pressure desulfurization, and more particularly relates to a device and a method for separating light hydrocarbons by oil gas low-pressure desulfurization in processes with high gas yield, such as catalytic cracking, delayed coking and the like.
Background
Light hydrocarbon refers to the components of methane, ethane, ethylene, propane, propylene, carbon and the like obtained in the petrochemical process, and the light hydrocarbon separation process is always the key point of attention of the petrochemical process. Among them, the separation process between carbon two, carbon three and carbon four is mature, and the rectification method is usually adopted. Methane, due to its low boiling point, requires cooling to temperatures of-100 ℃ and below, i.e. cryogenic separation, if a rectification process is used to separate methane and carbon dioxide, is commonly used in ethylene plants, which is very costly and costly. Therefore, the separation of methane has been the focus of attention on the light hydrocarbon separation process, and the development of the light hydrocarbon separation process technology and the design of the process flow are all performed around the separation of methane.
The prior catalytic cracking process usually adopts absorption stabilization to recover liquefied gas (C3/C4) components and realize the liquefied gas components and dry gas (H)2/C1/C2). The catalytic cracking process has high dry gas yield, the content of the C2 component in the dry gas can reach 25-40 wt%, the dry gas mainly comprises ethylene and ethane, the ethylene can be used for producing polyethylene, styrene and the like, the ethane can be used for producing ethylene by cracking, the yield of the ethylene by cyclic cracking reaches 80%, and the ethylene is rich in hydrogen. Therefore, the recovery of C2 resource in dry gas is of great interest. The prior art focuses on recovering carbon dioxide in dry gas by adopting an absorption method, and the process method has the following defects:
(1) the dry gas and the carbon four components are separated for the second time: and the dry gas and the liquefied gas are separated in the absorption stabilizing part, the carbon four is adopted to absorb the carbon four in the carbon four recovery part, the carbon four and the dry gas are mixed again, and then the separation is carried out.
(2) The absorption stabilizing system adopts stable gasoline as an absorbent to recover liquefied gas components, and the catalytic cracking process has the advantages that the yield of the liquefied gas components is high, the gasoline circulates among the gasoline absorption tower, the ethane desorption tower and the stabilizing tower, the circulating amount is large, the temperature levels of the ethane desorption tower and the stabilizing tower are high, the heat load of a reboiler at the bottom of the tower is large, and the energy consumption is high.
(3) The whole process flow is longer, and the investment and the energy consumption are correspondingly increased. The invention is provided for recovering light hydrocarbon components such as C2/C3/C4 and the like in a catalytic cracking process, simplifying a separation process and reducing investment and energy consumption.
(4) The prior art carries out desulfurization and sweetening on the dry gas and the liquefied gas which are stably absorbed, H2S and mercaptan are circulated in the whole absorption stabilizing system, and related corrosion problems can be caused, and H exists in the whole absorption stabilizing system2S leakage may present a safety issue.
Disclosure of Invention
The invention aims to provide a light hydrocarbon separation device and a light hydrocarbon separation method which are simple in process flow and mild in operation conditions, can realize efficient separation and recovery of carbon two, carbon three and carbon four components, and simultaneously adopts gas phase and liquid phase to carry out desulfurization and mercaptan removal respectively, so that the desulfurization effect is better, and the operation is more flexible.
In order to achieve the above object, the present invention provides a method for low-pressure desulfurization and separation of light hydrocarbons from oil gas, comprising:
(1) first gas-liquid separation: oil gas from an upstream device is condensed and cooled and then sent to a gas-liquid separation tank I for gas-liquid separation, a liquid phase at the bottom of the tank is pressurized and sent to a debutanizer, and a gas phase at the top of the tank is pressurized by a compressor and then sent to the debutanizer;
(2) removing butane: the gas phase and the liquid phase from the step (1) enter a debutanizer, the gas phase distilled from the top of the debutanizer enters a reflux tank at the top of the tower through condensation to separate a gas phase and a liquid phase, then impurities are respectively removed, and at least part of the liquid phase at the bottom of the debutanizer is taken as a stable gasoline product to be extracted;
(3) gas-phase impurity removal: gas phase on the top of a reflux tank at the top of the debutanizer tower is sequentially subjected to H removal in a rich gas desulfurization tower by taking lean amine liquid as an absorbent2S and CO2Removing mercaptan in the gas-enriched caustic tower by taking alkali liquor as an absorbent, and then pressurizing and conveying the gas-enriched caustic tower to a cooler;
(4) liquid phase impurity removal: removing H from the liquid phase at the bottom of the reflux tank at the top of the debutanizer in turn in a liquid hydrocarbon desulfurization tower2S and CO2The liquid hydrocarbon is sent to a mercaptan removal reactor after mercaptan removalAn aftercooler;
(5) and (3) cooling: the gas-phase light hydrocarbon after impurity removal is primarily cooled in a cooler and then is sent to a post cooler, and is mixed with liquid light hydrocarbon in the post cooler and then is sent to a feeding tank after being cooled again;
(6) feeding: after the mixture flow from the after cooler is mixed, pre-absorbed and gas-liquid balanced in a feeding tank, the gas phase at the top of the tank is sent to an absorption tower, and the liquid phase at the bottom of the tank is sent to a demethanizer;
(7) absorption: in the absorption tower, the mixed C4 is used as an absorbent to absorb components with the content of C2 and above C2 in a gas phase from the top of a feed tank, and simultaneously, part of methane is absorbed, the gas phase at the top of the absorption tower is sent to a downstream device, and a liquid phase at the bottom of the absorption tower is returned to a cooler;
(8) demethanization: removing methane from the liquid phase at the bottom of the feed tank in a demethanizer, simultaneously removing a small part of components with the carbon number of C2 and more than C2, sending the gas phase at the top of the demethanizer to a cooler, and sending the liquid phase at the bottom of the demethanizer to a depropanizer;
(9) depropanizing: separating liquid phase components from the bottom of the demethanizer in a depropanizer, extracting components with the C3 and the C3 or less from the upper part of the depropanizer, optionally drying, and then sending to the depropanizer, wherein at least one part of the tower bottom components is taken as a mixed C4 absorbent and sent to an absorption tower, and the rest is taken as a mixed C4 product;
(10) deethanizing: the gas phase from the upper part of the depropanizing tower is further separated in the deethanizing tower, the separated mixed C2 component at the top of the tower is extracted as a mixed C2 product after being subjected to impurity treatment, and the liquid phase at the bottom of the tower is extracted as a mixed C3 component.
The invention has wide application range, and the oil gas (including H) in the common processes with higher gas yield such as catalytic cracking, delayed coking and the like in chemical production2C1-C4, gasoline components and a small amount of non-hydrocarbon components) can be separated by the device of the invention to recycle liquefied gas.
In the invention, oil gas from an upstream device is condensed and cooled and then sent to a gas-liquid separation tank I for gas-liquid separation, a liquid phase at the bottom of the tank is pressurized by a pump and sent to a debutanizer, a gas phase at the top of the tank is pressurized by a compressor and then sent to the debutanizer, preferably, the compressor is divided into a plurality of sections, and the liquid phase generated between the compression sections is sent to the debutanizer.
In the invention, the stable gasoline is separated in advance in the debutanizer, and the stable gasoline does not participate in the downstream light hydrocarbon separation process, so that the process energy consumption can be greatly reduced, preferably, the operation temperature at the top of the debutanizer is 45-65 ℃, and the operation pressure is 1.0-1.5 MPaG; the operation temperature of the tower bottom is 150-200 ℃, and the temperature of the reflux tank is 35-45 ℃.
In the invention, in order to meet the requirement of related product recovery, impurity removal is required before next separation, and the impurity removal mainly comprises amine elution H2S and alkali washing to remove mercaptan. In the invention, the light hydrocarbon is divided into a gas phase and a liquid phase and then respectively subjected to impurity removal, and as the content of heavy hydrocarbon in the separated gas phase is low, the amount of the heavy hydrocarbon condensed into amine liquid is low during desulfurization, so that the problem that the stable operation of the device is influenced by foam entrainment of a desulfurization device caused by amine liquid foaming is effectively avoided.
In the present invention, in order to meet the requirements of the recovery of the relevant products, it is preferable that the amine elute H2S adopts a compound amine liquid solvent (namely a modified solvent based on MDEA) and carries out H simultaneously2S and CO2In which H is2S can be removed to less than 10ppmv, CO2The removal efficiency can reach 90-95 wt%, and CO in material flow entering the alkaline washing mercaptan removal reactor is effectively reduced2And further reducing the consumption of alkali liquor.
According to the invention, preferably, the operation temperature of the rich gas desulfurization tower is 35-45 ℃, and the operation pressure is 1.0-1.5 MPaG; the operation temperature of the rich gas alkaline washing tower is 35-45 ℃, and the operation pressure is 0.9-1.4 MPaG; the operating temperature of the liquid hydrocarbon desulfurization tower is 35-45 ℃, and the operating pressure is 3.2-3.6 MPaG.
In the invention, the gas phase components after impurity removal are subjected to pressure boosting and cooling before being sent into the feeding tank, the pressure boosting of the gas phase can adopt one-section or multi-section compression, the cooled liquid phase and the cooled and compressed gas phase are both sent into the feeding tank, preferably, the operating temperature of the feeding tank is 5-25 ℃, and the operating pressure is 2.2-2.8 MPaG.
According to the invention, preferably, the operation temperature of the absorption tower is 5-25 ℃, the operation pressure is 2.1-2.7 MPaG, and the absorbent in the absorption tower is from a mixed C4 component with self-balancing in the system and does not need to be introduced from the outside of the system.
According to the invention, preferably, the operation temperature of the top of the demethanizer is 10-40 ℃, the operation temperature of the bottom of the demethanizer is 70-100 ℃, and the operation pressure is 2.3-2.9 MPaG; the operation temperature of the top of the deethanizer is-20 ℃ to 20 ℃, the operation temperature of the bottom of the deethanizer is 55 ℃ to 85 ℃, and the operation pressure is 2.2 MPaG to 3.2 MPaG.
Because the recovered carbon dioxide product needs to be sent to an ethylene device for further recovering ethylene, ethane and other resources, an impurity removal unit needs to be arranged for removing NOx and O in the carbon dioxide product2And heavy metals and other related impurities to an ethylene plant. Wherein, the removal of impurities is performed by adopting the conventional impurity removal method in the field according to specific situations by a person skilled in the art, and can be the removal of O by hydrogenation2Alkyne and NOxMolecular sieve drying to remove H2And O, removing COS by adsorption, removing mercury by adsorption and the like.
In the present invention, the separated mixed C3 component can be further rectified to obtain a propylene product and a propane product, and preferably, the method further comprises:
(11) and (3) propylene rectification: and sending the mixed C3 component extracted from the bottom of the deethanizer to a propylene rectifying tower for further rectification, wherein the gas phase at the top of the propylene rectifying tower is cooled and extracted as a propylene product, and the liquid phase at the bottom of the propylene rectifying tower is extracted as a propane product.
According to the invention, the operation temperature of the propylene rectifying tower is preferably 48-60 ℃, and the operation pressure is preferably 1.8-2.0 MPaG.
To further recover the mixed C4 absorbent entrained in the absorber overhead stream, preferably, the process further comprises:
(12) and (3) recovering the absorbent: in the absorbent recovery tower, a part of the stable gasoline product extracted in the step (2) is used as an absorbent to absorb components of C4 and above C4 in a gas phase from the top of the absorption tower, a small amount of C2/C3 components are absorbed at the same time, the gas phase at the top of the absorbent recovery tower is extracted as dry gas, and a liquid phase at the bottom of the absorbent recovery tower is returned to the debutanizer.
According to the invention, the operation temperature of the absorbent recovery tower is preferably 5-25 ℃, and the operation pressure is preferably 2.0-2.6 MPaG.
In another aspect, the present invention provides a device for low-pressure desulfurization and separation of light hydrocarbons from oil gas, comprising: the system comprises an oil gas feeding pipeline, a gas-liquid separation tank, a compressor I, a debutanizer, a rich gas desulfurization tower, a rich gas alkaline washing tower, a liquid hydrocarbon desulfurization tower, a liquid hydrocarbon sweetening reactor, a compressor II, a cooler, an after cooler, a feeding tank, an absorption tower, a demethanizer, a deethanizer and a depropanizer;
the oil-gas feeding pipeline is connected with an inlet of a gas-liquid separation tank, the top of the gas-liquid separation tank is sequentially connected with a compressor I and a debutanizer, and the bottom of the gas-liquid separation tank is connected with the debutanizer;
a reflux tank is arranged on the top of the debutanizer, and the top of the reflux tank is sequentially connected with a rich gas desulfurization tower, a rich gas alkaline washing tower, a compressor II, a cooler and an after-cooler; the tank bottom is connected with a liquid hydrocarbon desulfurizing tower, a liquid hydrocarbon sweetening reactor and an after-cooler in sequence; a stable gasoline extraction pipeline is arranged at the bottom of the debutanizer;
the upper part of the rich gas desulfurization tower is provided with a lean amine liquid feeding pipeline, and the upper part of the rich gas caustic tower is provided with an alkali liquid feeding pipeline;
the aftercooler is connected with the feeding tank;
the top of the feeding tank is connected with the absorption tower, and the bottom of the feeding tank is connected with the demethanizer;
the top of the absorption tower is connected with a downstream device, the bottom of the absorption tower is connected with an aftercooler, and the upper part of the absorption tower is provided with a mixed C4 absorbent feeding pipeline;
the top of the demethanizer is connected with the aftercooler, and the bottom of the demethanizer is connected with the depropanizer;
the upper part of the depropanizing tower is connected with a drying unit optionally and then connected with the deethanizing tower, a mixed C4 product extraction pipeline is arranged at the bottom of the depropanizing tower, the mixed C4 product extraction pipeline is divided into two branches, and one branch is used as a mixed C4 absorbent feeding pipeline;
the top of the deethanizer is provided with a mixed C2 produced pipeline, the mixed C2 produced pipeline is optionally provided with an impurity treatment unit, and the bottom of the deethanizer is provided with a mixed C3 produced pipeline.
According to the invention, preferably, the device further comprises a propylene rectifying tower, the mixed C3 extraction pipeline is connected with the propylene rectifying tower, a propylene product extraction pipeline is arranged at the top of the propylene rectifying tower, and a propane product extraction pipeline is arranged at the bottom of the propylene rectifying tower.
According to the present invention, preferably, the downstream apparatus further comprises an absorbent recovery column; the top of the absorbent recovery tower is provided with a dry gas extraction pipeline, the bottom of the absorbent recovery tower is connected with a debutanizer, the upper part of the absorbent recovery tower is provided with a stabilized gasoline absorbent feeding pipeline, the stabilized gasoline extraction pipeline of the debutanizer is divided into two branches, and one branch is used as the stabilized gasoline absorbent feeding pipeline.
In the invention, the compressor I can be divided into a plurality of sections, and an intersegment liquid phase extraction pipeline is connected with the debutanizer.
In order to maintain the operating temperature of the whole tower uniform and ensure the absorption effect, the absorption tower is preferably provided with 2-5 middle-section refluxes, a condenser is not required to be arranged at the top of the absorption tower, a reboiler is not required to be arranged at the bottom of the absorption tower, the gas phase from a feeding tank is fed from the bottom of the absorption tower, and the absorbent is fed from the top of the absorption tower.
According to the invention, preferably, the top of the demethanizer is not provided with a condenser, the bottom of the demethanizer is provided with a reboiler, and the liquid phase from the feeding tank is fed from the top of the demethanizer; the light hydrocarbon separation device does not include a dehydration device.
Compared with the prior art, the invention has the following advantages:
(1) in the invention, the front-mounted debutanizer is adopted, components below C4 and C4 are firstly separated from gasoline components, and gasoline circulation is not required to absorb liquefied gas components, so that the gasoline circulation amount is greatly reduced, and the energy consumption of the whole separation process is reduced.
(2) The method has the advantages of simple flow, mild operating conditions and low cold consumption, can realize the separation and recovery of light hydrocarbons in oil gas by using less equipment, and particularly can realize the high-efficiency separation and recovery of C2, C3 and C4 components; and secondary separation process does not exist between the carbon two and each component, and meanwhile, the total recovery rate of the carbon two component can be ensured to be more than 98 wt%, the recovery rate of the carbon three component can be ensured to be more than 99 wt%, the content of methane in the recovered carbon two component is not more than 1 vol%, and the content of ethane in the recovered carbon three component is not more than 200 ppmv.
(3) The method further separates the recovered carbon three components into propylene and propane, the recovery rate of the propylene and the propane can also reach more than 99 wt%, the purity of the propylene product is not less than 99.6 v%, and the polymer-grade propylene can be obtained without further treatment.
(4) The dry gas recovered from the top of the absorbent recovery tower has less impurities, the content of components with the concentration of C2 and more than C2 is not more than 2 vol%, the pressure of the absorbed dry gas is 2.1-2.7 MPa, the purity of the hydrogen can reach 40-70 mol%, and the hydrogen resource can be directly recovered by a pressure swing adsorption method.
(5) The invention can respectively desulfurize and desulfurize the gas phase and the liquid phase, and can prevent heavy hydrocarbon from being condensed into amine liquid due to the reduction of the content of the heavy hydrocarbon in the gas phase, thereby effectively avoiding foam entrainment of a desulfurization device caused by the foaming of the amine liquid and ensuring the stable operation of the device.
(6) In the invention, hydrogen sulfide and mercaptan are removed before entering the absorption tower and cannot be brought to a downstream light hydrocarbon recovery part, so that the problem of corrosion related to the light hydrocarbon recovery part caused by hydrogen sulfide is avoided, and meanwhile, the concentration of the downstream hydrogen sulfide is greatly reduced, thereby improving the safety; the hydrogen sulfide and the carbon dioxide are separated in advance, so that the load and the energy consumption of a downstream light hydrocarbon recovery system can be reduced, and simultaneously, CO is generated2Is removed, and the quality of downstream products can be improved.
Additional features and advantages of the invention will be set forth in the detailed description which follows.
Drawings
The above and other objects, features and advantages of the present invention will become more apparent by describing in more detail exemplary embodiments thereof with reference to the attached drawings, in which like reference numerals generally represent like parts throughout.
FIG. 1 shows a process flow diagram of low-pressure desulfurization and separation of light hydrocarbons from oil gas in example 1 of the present invention.
FIG. 2 shows a process flow diagram of low-pressure desulfurization and separation of light hydrocarbons from oil gas in example 2 of the present invention.
Description of reference numerals:
1. a gas-liquid separation tank; 2. a first section of a compressor I; 3. a second section of the compressor I; 4. a debutanizer column; 5. a rich gas desulfurization tower; 6. a rich gas caustic wash tower; 7. a liquid hydrocarbon desulfurization tower; 8. a liquid hydrocarbon sweetening reactor; 9. a compressor II; 10. a cooler; 11. an aftercooler; 12. a feed tank; 13. an absorption tower; 14. a demethanizer; 15. a depropanizer; 16. a deethanizer; 17. an impurity processing unit; 18. a propylene rectification column; 19. an absorbent recovery column; 20. a drying unit;
s-1, oil gas from an upstream device; s-2, crude gasoline; s-3, lean amine liquid; s-4, amine-rich liquid; s-5, alkali liquor; s-6, alkali liquor to be regenerated; s-7, a carbon four absorbent; s-8, dry gas; s-9, mixing a carbon dioxide product; s-10, propylene products; s-11, propane product; s-12, stabilizing the gasoline product; s-13 and C four products.
Detailed Description
Preferred embodiments of the present invention will be described in more detail below. While the following describes preferred embodiments of the present invention, it should be understood that the present invention may be embodied in various forms and should not be limited by the embodiments set forth herein.
The properties of the feed oil and gas in the following examples are shown in table 1, and the properties of the C5+ component in the oil and gas are shown in table 2:
TABLE 1
Figure BDA0002112030250000091
Figure BDA0002112030250000101
TABLE 2
Item Numerical value
Density (20 ℃ C.), g/cm3 0.753
D86 curve, v% Temperature, C
0 35.0
5 44.1
10 52.0
30 73.0
50 95.0
70 128.0
90 177.0
95 188.7
100 200.0
Example 1
Oil gas low pressure desulfurization separates the device of light hydrocarbon:
the system comprises an oil gas feeding pipeline, a gas-liquid separation tank 1, a compressor I first section 2, a compressor I second section 3, a debutanizer 4, a rich gas desulfurization tower 5, a rich gas alkaline washing tower 6, a liquid hydrocarbon desulfurization tower 7, a liquid hydrocarbon sweetening reactor 8, a compressor II 9, a cooler 10, an after cooler 11, a feeding tank 12, an absorption tower 13, a demethanizer 14, a depropanizer 15, a deethanizer 16, an impurity treatment unit 17, a propylene rectification 18, an absorbent recovery tower 19 and a drying unit 20;
the oil-gas feeding pipeline is connected with an inlet of a gas-liquid separation tank 1, the top of the gas-liquid separation tank 1 is sequentially connected with a compressor I, a first section 2 of the compressor I, a second section 3 of the compressor I and a debutanizer 4, and the bottom of the tank is connected with the debutanizer 4; the first section 2 of the compressor I is connected with a liquid phase extraction pipeline and a debutanizer 4
A reflux tank is arranged at the top of the debutanizer 4, and the top of the reflux tank is sequentially connected with a rich gas desulfurization tower 5, a rich gas alkaline washing tower 6, a compressor II 9, a cooler 10 and an aftercooler 11; the tank bottom is connected with a liquid hydrocarbon desulfurizing tower 7, a liquid hydrocarbon sweetening reactor 8 and an after-cooler 11 in sequence; a stable gasoline extraction pipeline is arranged at the bottom of the debutanizer 4;
the upper part of the rich gas desulfurization tower 5 is provided with a lean amine liquid feeding pipeline, and the upper part of the rich gas caustic wash tower 6 is provided with an alkali liquid feeding pipeline;
the after-cooler 11 is connected with the feeding tank 12;
the top of the feeding tank 12 is connected with an absorption tower 13, and the bottom of the tank is connected with a demethanizer 14;
the absorption tower 13 is provided with 2-5 middle-section refluxes, the tower top is connected with an absorbent recovery tower 19, the tower bottom is connected with the aftercooler 11, and the upper part of the absorption tower 13 is provided with a mixed C4 absorbent feeding pipeline;
the top of the absorbent recovery tower 19 is provided with a dry gas extraction pipeline, the bottom of the absorbent recovery tower 19 is connected with the debutanizer 4, the upper part of the absorbent recovery tower 19 is provided with a stable gasoline absorbent feeding pipeline, the stable gasoline extraction pipeline of the debutanizer 4 is divided into two branches, one branch is used as the stable gasoline absorbent feeding pipeline
The top of the demethanizer 14 is connected with the aftercooler 11, and the bottom of the demethanizer is connected with the depropanizer 15; the top of the demethanizer 14 is not provided with a condenser, and the bottom of the demethanizer is provided with a reboiler;
the upper part of the depropanizing tower 15 is connected with the deethanizing tower 16, the bottom of the depropanizing tower is provided with a mixed C4 product extraction pipeline, the mixed C4 product extraction pipeline is divided into two branches, and one branch is used as a mixed C4 absorbent feeding pipeline;
a mixed C2 produced pipeline is arranged at the top of the deethanizer 16, an impurity processing unit 17 is arranged on the mixed C2 produced pipeline, and the bottom of the deethanizer is connected with a propylene rectifying tower 18;
a propylene product extraction pipeline is arranged at the top of the propylene rectifying tower 18, and a propane product extraction pipeline is arranged at the bottom of the tower;
the apparatus does not include a dehydration apparatus.
The oil gas low-pressure desulfurization and light hydrocarbon separation are carried out by adopting the device, and the process flow is shown in figure 1:
(1) first gas-liquid separation: condensing and cooling oil gas S-1 from an upstream device, sending the oil gas S-1 to a gas-liquid separation tank 1 for gas-liquid separation, pressurizing a liquid phase at the bottom of the tank, sending the liquid phase to a debutanizer 4, and pressurizing a gas phase at the top of the tank by a compressor, and sending the gas phase to the debutanizer 4;
(2) removing butane: the gas phase and the liquid phase from the step (1) enter a debutanizer 4, the gas phase distilled from the top of the debutanizer 4 enters a reflux tank at the top of the tower after condensation to separate a gas phase and a liquid phase, then impurity removal is respectively carried out, and at least part of the liquid phase at the bottom of the debutanizer 4 is taken as a stable gasoline product S-12 to be extracted; wherein the operation temperature at the top of the debutanizer is 45-65 ℃, and the operation pressure is 1.0-1.5 MPaG; the tower bottom operating temperature is 150-200 ℃, and the temperature of the reflux tank is 35-45 ℃;
(3) gas-phase impurity removal: the gas phase on the top of the reflux tank on the top of the debutanizer 4 is orderly dehydrated in a rich gas desulfurizing tower 5 by taking lean amine liquid as an absorbent2S and CO2In the rich gas caustic tower 6, mercaptan is removed by taking alkali liquor as an absorbent, and then the rich gas caustic tower is pressurized and sent to a cooler 10; wherein the operation temperature of the rich gas desulfurization tower is 35-45 ℃, and the operation pressure is 1.0-1.5 MPaG; the operation temperature of the rich gas alkaline washing tower is 35-45 ℃, and the operation pressure is 0.9-1.4 MPaG;
(4) liquid phase impurity removal: the liquid phase at the bottom of the reflux tank at the top of the debutanizer 4 is sequentially removed with H in the liquid hydrocarbon desulfurizing tower 72S and CO2After mercaptan is removed in the liquid hydrocarbon mercaptan removal reactor 8, the liquid hydrocarbon mercaptan removed is sent to a aftercooler; wherein the operation temperature of the liquid hydrocarbon desulfurization tower is 35-45 ℃, and the operation pressure is 3.2-3.6 MPaG;
(5) and (3) cooling: the gas-phase light hydrocarbon after impurity removal is primarily cooled in a cooler 10 and then sent to an after-cooler 11, and is mixed with liquid light hydrocarbon in the after-cooler 11 and then sent to a feeding tank 12 after being cooled again;
(6) feeding: after the mixture flow from the after-cooler 11 is mixed, pre-absorbed and gas-liquid balanced in the feeding tank 12, the gas phase at the top of the tank is sent to the absorption tower 13, and the liquid phase at the bottom of the tank is sent to the demethanizer 4; wherein the operating temperature of the feeding tank is 5-25 ℃, and the operating pressure is 2.2-2.8 MPaG;
(7) absorption: in the absorption tower 13, the mixed C4 is used as an absorbent to absorb components with the content of C2 and above C2 in the gas phase from the top of the feed tank 12, and simultaneously, part of methane is absorbed, the gas phase at the top of the absorption tower 13 is sent to an absorbent recovery tower 19, and the liquid phase at the bottom of the absorption tower is returned to the cooler 10; wherein the operation temperature of the absorption tower is 5-25 ℃, the operation pressure is 2.1-2.7 MPaG, and the absorbent in the absorption tower is a self-balancing mixed C4 component in the system and does not need to be introduced from the outside of the system;
(8) demethanization: the liquid phase from the bottom of the feed tank 12 removes methane in the demethanizer 14, and simultaneously removes a small part of components with the carbon number of 2 and more than 2, the gas phase at the top of the demethanizer 14 is sent to the cooler 10, and the liquid phase at the bottom of the demethanizer is sent to the depropanizer 15; wherein the operation temperature of the top of the demethanizer is 10-40 ℃, the operation temperature of the bottom of the demethanizer is 70-100 ℃, and the operation pressure is 2.3-2.9 MPaG;
(9) depropanizing: separating liquid phase components from the bottom of the demethanizer 14 in a depropanizer 15, extracting the separated components with the carbon number of 3 and the carbon number of less than 3 from the upper part of the depropanizer 15, sending the extracted components to a deethanizer 16, sending at least one part of the tower bottom components to an absorption tower 13 as a mixed C4 absorbent, and extracting the rest of the tower bottom components as a carbon four product S-13;
(10) deethanizing: the gas phase from the upper part of the depropanizing tower 15 is further separated in the deethanizing tower 16, the separated mixed C2 component at the top of the tower is extracted as a mixed C2 product S-9 after being subjected to impurity treatment, and the liquid phase at the bottom of the tower is extracted as a mixed C3 component; wherein the operation temperature of the top of the deethanizing tower is 5-20 ℃, the operation temperature of the bottom of the deethanizing tower is 55-85 ℃, and the operation pressure is 2.6-3.2 MPaG;
(11) and (3) propylene rectification: sending the mixed C3 component extracted from the bottom of the deethanizer 16 to a propylene rectifying tower 18 for further rectification, cooling the gas phase at the top of the propylene rectifying tower 18 to be extracted as a propylene product S-10, and extracting the liquid phase at the bottom of the tower as a propane product S-11; wherein the operating temperature of the propylene rectifying tower is 48-60 ℃, and the operating pressure is 1.8-2.0 MPaG;
(12) and (3) recovering the absorbent: in the absorbent recovery tower 19, a part of the stable gasoline product extracted in the step (2) is used as an absorbent to absorb components of C4 and above C4 in the gas phase from the top of the absorption tower 13, and simultaneously absorb a small amount of components of C2/C3, the gas phase at the top of the absorbent recovery tower 19 is extracted as dry gas S-8, and the liquid phase at the bottom of the tower is returned to the debutanizer 4; wherein the operation temperature of the absorbent recovery tower is 5-25 ℃, and the operation pressure is 2.0-2.6 MPaG;
the light hydrocarbon in the oil gas is separated by the method, the composition and the property of each product are shown in table 3, and the property of the stable gasoline is shown in table 4.
TABLE 3
Figure BDA0002112030250000141
Figure BDA0002112030250000151
TABLE 4
Item Numerical value
Density (20 ℃ C.), g/cm3 0.754
C4The content of the components is v% 1.63
Reid vapor pressure, kPa 67.5
D86 curve, v% Temperature, C
0 38.5
5 46.2
10 49.3
30 72.1
50 94.4
70 127.6
90 176.9
95 187.3
100 197.8
Example 2
Oil gas low pressure desulfurization separates the device of light hydrocarbon:
the system comprises an oil gas feeding pipeline, a gas-liquid separation tank 1, a compressor I first section 2, a compressor I second section 3, a debutanizer 4, a rich gas desulfurization tower 5, a rich gas alkaline washing tower 6, a liquid hydrocarbon desulfurization tower 7, a liquid hydrocarbon sweetening reactor 8, a compressor II 9, a cooler 10, an after cooler 11, a feeding tank 12, an absorption tower 13, a demethanizer 14, a depropanizer 15, a deethanizer 16, an impurity treatment unit 17, a propylene rectification 18, an absorbent recovery tower 19 and a drying unit 20;
the oil-gas feeding pipeline is connected with an inlet of a gas-liquid separation tank 1, the top of the gas-liquid separation tank 1 is sequentially connected with a compressor I, a first section 2 of the compressor I, a second section 3 of the compressor I and a debutanizer 4, and the bottom of the tank is connected with the debutanizer 4; the first section 2 of the compressor I is connected with a liquid phase extraction pipeline and a debutanizer 4
A reflux tank is arranged at the top of the debutanizer 4, and the top of the reflux tank is sequentially connected with a rich gas desulfurization tower 5, a rich gas alkaline washing tower 6, a compressor II 9, a cooler 10 and an aftercooler 11; the tank bottom is connected with a liquid hydrocarbon desulfurizing tower 7, a liquid hydrocarbon sweetening reactor 8 and an after-cooler 11 in sequence; a stable gasoline extraction pipeline is arranged at the bottom of the debutanizer 4;
the upper part of the rich gas desulfurization tower 5 is provided with a lean amine liquid feeding pipeline, and the upper part of the rich gas caustic wash tower 6 is provided with an alkali liquid feeding pipeline;
the after-cooler 11 is connected with the feeding tank 12;
the top of the feeding tank 12 is connected with an absorption tower 13, and the bottom of the tank is connected with a demethanizer 14;
the absorption tower 13 is provided with 2-5 middle-section refluxes, the tower top is connected with an absorbent recovery tower 19, the tower bottom is connected with the aftercooler 11, and the upper part of the absorption tower 13 is provided with a mixed C4 absorbent feeding pipeline;
the top of the absorbent recovery tower 19 is provided with a dry gas extraction pipeline, the bottom of the absorbent recovery tower 19 is connected with the debutanizer 4, the upper part of the absorbent recovery tower 19 is provided with a stable gasoline absorbent feeding pipeline, the stable gasoline extraction pipeline of the debutanizer 4 is divided into two branches, one branch is used as the stable gasoline absorbent feeding pipeline
The top of the demethanizer 14 is connected with the aftercooler 11, and the bottom of the demethanizer is connected with the depropanizer 15; the top of the demethanizer 14 is not provided with a condenser, and the bottom of the demethanizer is provided with a reboiler;
the upper part of the depropanizing tower 15 is sequentially connected with the drying unit 20 and the deethanizing tower 16, a mixed C4 product extraction pipeline is arranged at the bottom of the depropanizing tower, the mixed C4 product extraction pipeline is divided into two branches, and one branch is used as a mixed C4 absorbent feeding pipeline;
a mixed C2 produced pipeline is arranged at the top of the deethanizer 16, an impurity processing unit 17 is arranged on the mixed C2 produced pipeline, and the bottom of the deethanizer is connected with a propylene rectifying tower 18;
a propylene product extraction pipeline is arranged at the top of the propylene rectifying tower 18, and a propane product extraction pipeline is arranged at the bottom of the tower;
the apparatus does not include a dehydration apparatus.
The oil gas low-pressure desulfurization and light hydrocarbon separation are carried out by adopting the device, and the process flow is shown in figure 2:
(1) first gas-liquid separation: condensing and cooling oil gas S-1 from an upstream device, sending the oil gas S-1 to a gas-liquid separation tank 1 for gas-liquid separation, pressurizing a liquid phase at the bottom of the tank, sending the liquid phase to a debutanizer 4, and pressurizing a gas phase at the top of the tank by a compressor, and sending the gas phase to the debutanizer 4;
(2) removing butane: the gas phase and the liquid phase from the step (1) enter a debutanizer 4, the gas phase distilled from the top of the debutanizer 4 enters a reflux tank at the top of the tower after condensation to separate a gas phase and a liquid phase, then impurity removal is respectively carried out, and at least part of the liquid phase at the bottom of the debutanizer 4 is taken as a stable gasoline product S-12 to be extracted; wherein the operation temperature at the top of the debutanizer is 45-65 ℃, and the operation pressure is 1.0-1.5 MPaG; the tower bottom operating temperature is 150-200 ℃, and the temperature of the reflux tank is 35-45 ℃;
(3) gas-phase impurity removal: the gas phase on the top of the reflux tank on the top of the debutanizer 4 is orderly dehydrated in a rich gas desulfurizing tower 5 by taking lean amine liquid as an absorbent2S and CO2In the rich gas caustic tower 6, mercaptan is removed by taking alkali liquor as an absorbent, and then the rich gas caustic tower is pressurized and sent to a cooler 10; wherein the operation temperature of the rich gas desulfurization towerThe temperature is 35-45 ℃, and the operation pressure is 1.0-1.5 MPaG; the operation temperature of the rich gas alkaline washing tower is 35-45 ℃, and the operation pressure is 0.9-1.4 MPaG;
(4) liquid phase impurity removal: the liquid phase at the bottom of the reflux tank at the top of the debutanizer 4 is sequentially removed with H in the liquid hydrocarbon desulfurizing tower 72S and CO2After mercaptan is removed in the liquid hydrocarbon mercaptan removal reactor 8, the liquid hydrocarbon mercaptan removed is sent to a aftercooler; wherein the operation temperature of the liquid hydrocarbon desulfurization tower is 35-45 ℃, and the operation pressure is 3.2-3.6 MPaG;
(5) and (3) cooling: the gas-phase light hydrocarbon after impurity removal is primarily cooled in a cooler 10 and then sent to an after-cooler 11, and is mixed with liquid light hydrocarbon in the after-cooler 11 and then sent to a feeding tank 12 after being cooled again;
(6) feeding: after the mixture flow from the after-cooler 11 is mixed, pre-absorbed and gas-liquid balanced in the feeding tank 12, the gas phase at the top of the tank is sent to the absorption tower 13, and the liquid phase at the bottom of the tank is sent to the demethanizer 4; wherein the operating temperature of the feeding tank is 5-25 ℃, and the operating pressure is 2.2-2.8 MPaG;
(7) absorption: in the absorption tower 13, the mixed C4 is used as an absorbent to absorb components with the content of C2 and above C2 in the gas phase from the top of the feed tank 12, and simultaneously, part of methane is absorbed, the gas phase at the top of the absorption tower 13 is sent to an absorbent recovery tower 19, and the liquid phase at the bottom of the absorption tower is returned to the cooler 10; wherein the operation temperature of the absorption tower is 5-25 ℃, the operation pressure is 2.1-2.7 MPaG, and the absorbent in the absorption tower is a self-balancing mixed C4 component in the system and does not need to be introduced from the outside of the system;
(8) demethanization: the liquid phase from the bottom of the feed tank 12 removes methane in the demethanizer 14, and simultaneously removes a small part of components with the carbon number of 2 and more than 2, the gas phase at the top of the demethanizer 14 is sent to the cooler 10, and the liquid phase at the bottom of the demethanizer is sent to the depropanizer 15; wherein the operation temperature of the top of the demethanizer is 10-40 ℃, the operation temperature of the bottom of the demethanizer is 70-100 ℃, and the operation pressure is 2.3-2.9 MPaG;
(9) depropanizing: separating liquid phase components from the bottom of the demethanizer 14 in a depropanizing tower 15, extracting components with the C3 and the C3 or less from the upper part of the depropanizing tower 15, drying, and then sending to a deethanizing tower 16, wherein at least one part of the tower bottom components is used as a mixed C4 absorbent and sent to an absorption tower 13, and the rest is used as a C-IV product S-13;
(10) deethanizing: the gas phase from the upper part of the depropanizing tower 15 is further separated in the deethanizing tower 16, the separated mixed C2 component at the top of the tower is extracted as a mixed C2 product S-9 after being subjected to impurity treatment, and the liquid phase at the bottom of the tower is extracted as a mixed C3 component; wherein, the deethanizer 16 adopts fine separation, the operation temperature at the top of the deethanizer is-20 ℃ to-5 ℃, the operation pressure is 2.2-2.8 MPaG, and the operation temperature at the bottom of the deethanizer is 55-80 ℃. Because the temperature at the top of the deethanizer is lower, a propylene refrigerant or other refrigerants at-25 ℃ to-15 ℃ are needed, and a set of independent propylene refrigeration system can be designed for meeting the requirements of the top of the deethanizer, or other refrigerants capable of meeting the requirements are adopted;
(11) and (3) propylene rectification: sending the mixed C3 component extracted from the bottom of the deethanizer 16 to a propylene rectifying tower 18 for further rectification, cooling the gas phase at the top of the propylene rectifying tower 18 to be extracted as a propylene product S-10, and extracting the liquid phase at the bottom of the tower as a propane product S-11; wherein the operating temperature of the propylene rectifying tower is 48-60 ℃, and the operating pressure is 1.8-2.0 MPaG;
(12) and (3) recovering the absorbent: in the absorbent recovery tower 19, a part of the stable gasoline product extracted in the step (2) is used as an absorbent to absorb components of C4 and above C4 in the gas phase from the top of the absorption tower 13, and simultaneously absorb a small amount of components of C2/C3, the gas phase at the top of the absorbent recovery tower 19 is extracted as dry gas S-8, and the liquid phase at the bottom of the tower is returned to the debutanizer 4; wherein the operation temperature of the absorbent recovery tower is 5-25 ℃, and the operation pressure is 2.0-2.6 MPaG;
the light hydrocarbon in the oil gas is separated by the method, the composition and the property of each product are shown in table 5, and the property of the stable gasoline is shown in table 6.
TABLE 5
Figure BDA0002112030250000191
Figure BDA0002112030250000201
TABLE 6
Item Numerical value
Density (20 ℃ C.), g/cm3 0.753
C4The content of the components is v% 1.63
Reid vapor pressure, kPa 67.8
D86 curve, v% Temperature, C
0 38.7
5 46.1
10 49.1
30 72.0
50 94.4
70 127.6
90 176.9
95 187.3
100 197.7
The data in the table show that the process is simple, the operation condition is mild, and the separation and recovery of light hydrocarbon in oil gas can be realized by using less equipment, wherein the total recovery rate of the carbon two component is more than 98 wt%, the recovery rate of the carbon three component is more than 99 wt%, the content of methane in the recovered carbon two component is not more than 1 vol%, and the content of ethane in the recovered carbon three component is not more than 2000 ppmv; meanwhile, the recovered carbon three components are further separated into propylene and propane, the recovery rates of the propylene and the propane can also reach more than 99 wt%, the purity of the propylene product is not less than 99.6 v%, and the polymer-grade propylene can be obtained without reprocessing; the recovered dry gas contains less impurities, the content of components of C2 and above C2 is not more than 2 vol%, the pressure of the absorbed dry gas is 2.1-2.7 MPa, the purity of the hydrogen can reach 40-70 mol%, and the hydrogen resource can be directly recovered by a pressure swing adsorption method; the dry point of the produced stable gasoline is 197 ℃, the content of carbon four is only 1.63 vol%, and the gasoline product quality requirement can be met after desulfurization treatment.
Meanwhile, as can be seen from examples 1 and 2, when no propylene refrigeration system is provided, the deethanizer has no refrigerant below 0 ℃, which results in that the separated mixed C2 contains about 20 v% of mixed C3 component, and the mixed C2 component after impurity removal treatment still needs to be sent to a downstream ethylene plant to continue to recover carbon two and carbon three (mainly propylene products); when a propylene refrigeration system is arranged, the distillate at the top of the depropanizing tower is dried and then sent into the deethanizing tower, the deethanizing tower adopts fine separation, a propylene refrigerant with the temperature of-25 ℃ to-15 ℃ is adopted at the top of the deethanizing tower, so that the separated carbon dioxide basically does not contain carbon III, the overhead stream of the deethanizing tower after impurity removal can be directly sent to a downstream ethylene device for recycling carbon dioxide or directly utilized, and the recovery of the carbon three components (mainly propylene products) in the propylene rectification tower is realized.
As the gas phase and liquid phase of the above examples 1-2 have the same conditions and the same impurity removal capability, see Table 7:
TABLE 7
Figure BDA0002112030250000221
As can be seen from Table 7, by using the desulfurization and mercaptan removal process of the present invention, the gas phase is desulfurized at low pressure to remove H in light hydrocarbon2S content of 10ppmw, mercaptan sulfur content of not more than 20ppmw, CO2The removal rate can reach 95 wt%; desulfurizing liquid-phase light hydrocarbon to obtain H2S content of 10ppmw, mercaptan sulfur content of not more than 20ppmw, CO2The removal rate can reach nearly 90 wt%.
Having described embodiments of the present invention, the foregoing description is intended to be exemplary, not exhaustive, and not limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments.

Claims (6)

1. A method for low-pressure desulfurization and separation of light hydrocarbon from oil gas is characterized by comprising the following steps:
(1) first gas-liquid separation: oil gas from an upstream device is condensed and cooled and then sent to a gas-liquid separation tank for gas-liquid separation, a liquid phase at the bottom of the tank is pressurized and sent to a debutanizer, and a gas phase at the top of the tank is pressurized by a compressor and then sent to the debutanizer;
(2) removing butane: the gas phase and the liquid phase from the step (1) enter a debutanizer, the gas phase distilled from the top of the debutanizer enters a reflux tank at the top of the tower through condensation to separate a gas phase and a liquid phase, then impurities are respectively removed, and at least part of the liquid phase at the bottom of the debutanizer is taken as a stable gasoline product to be extracted;
(3) gas-phase impurity removal: gas phase on the top of a reflux tank at the top of the debutanizer tower is sequentially subjected to H removal in a rich gas desulfurization tower by taking lean amine liquid as an absorbent2S and CO2Removing mercaptan in the gas-enriched caustic tower by taking alkali liquor as an absorbent, and then pressurizing and conveying the gas-enriched caustic tower to a cooler;
(4) liquid phase impurity removal: removing H from the liquid phase at the bottom of the reflux tank at the top of the debutanizer in turn in a liquid hydrocarbon desulfurization tower2S and CO2After mercaptan is removed in the liquid hydrocarbon mercaptan removal reactor, the liquid hydrocarbon mercaptan removed is sent to a aftercooler;
(5) and (3) cooling: the gas-phase light hydrocarbon after impurity removal is primarily cooled in a cooler and then is sent to a post cooler, and is mixed with liquid light hydrocarbon in the post cooler and then is sent to a feeding tank after being cooled again;
(6) feeding: after the mixture flow from the after cooler is mixed, pre-absorbed and gas-liquid balanced in a feeding tank, the gas phase at the top of the tank is sent to an absorption tower, and the liquid phase at the bottom of the tank is sent to a demethanizer;
(7) absorption: in the absorption tower, the mixed C4 is used as an absorbent to absorb components with the content of C2 and above C2 in a gas phase from the top of a feed tank, and simultaneously, part of methane is absorbed, the gas phase at the top of the absorption tower is sent to a downstream device, and a liquid phase at the bottom of the absorption tower is returned to a cooler;
(8) demethanization: removing methane from the liquid phase at the bottom of the feed tank in a demethanizer, simultaneously removing a small part of components with the carbon number of C2 and more than C2, sending the gas phase at the top of the demethanizer to a cooler, and sending the liquid phase at the bottom of the demethanizer to a depropanizer;
(9) depropanizing: separating liquid phase components from the bottom of the demethanizer in a depropanizer, extracting components with the C3 and the C3 or less from the upper part of the depropanizer, optionally drying, and then sending to the depropanizer, wherein at least one part of the tower bottom components is taken as a mixed C4 absorbent and sent to an absorption tower, and the rest is taken as a mixed C4 product;
(10) deethanizing: the gas phase from the upper part of the depropanizing tower is further separated in the deethanizing tower, the separated mixed C2 component at the top of the tower is extracted as a mixed C2 product after being optionally subjected to impurity treatment, and the liquid phase at the bottom of the tower is extracted as a mixed C3 component;
(11) and (3) propylene rectification: sending the mixed C3 component extracted from the bottom of the deethanizer to a propylene rectifying tower for further rectification, wherein the gas phase at the top of the propylene rectifying tower is cooled and extracted as a propylene product, and the liquid phase at the bottom of the propylene rectifying tower is extracted as a propane product;
(12) and (3) recovering the absorbent: in the absorbent recovery tower, a part of the stable gasoline product extracted in the step (2) is used as an absorbent to absorb components of C4 and above C4 in a gas phase from the top of the absorption tower, a small amount of C2/C3 components are absorbed at the same time, the gas phase at the top of the absorbent recovery tower is extracted as dry gas, and a liquid phase at the bottom of the absorbent recovery tower is returned to the debutanizer.
2. The method of claim 1,
sending the compressor intersegment liquid phase to a debutanizer;
the operation temperature of the top of the debutanizer is 45-65 ℃, and the operation pressure is 1.0-1.5 MPaG; the tower bottom operating temperature is 150-200 ℃, and the temperature of the reflux tank is 35-45 ℃;
the operation temperature of the rich gas desulfurization tower is 35-45 ℃, and the operation pressure is 1.0-1.5 MPaG;
the operation temperature of the rich gas alkaline washing tower is 35-45 ℃, and the operation pressure is 0.9-1.4 MPaG;
the operating temperature of the liquid hydrocarbon desulfurization tower is 35-45 ℃, and the operating pressure is 3.2-3.6 MPaG;
the operating temperature of the feeding tank is 5-25 ℃, and the operating pressure is 2.2-2.8 MPaG;
the operation temperature of the absorption tower is 5-25 ℃, the operation pressure is 2.1-2.7 MPaG, and the absorbent in the absorption tower is a self-balancing mixed C4 component in the system and does not need to be introduced from the outside of the system;
the operating temperature of the top of the demethanizer is 10-40 ℃, the operating temperature of the bottom of the demethanizer is 70-100 ℃, and the operating pressure is 2.3-2.9 MPaG;
the operation temperature of the top of the deethanizer is-20 ℃ to 20 ℃, the operation temperature of the bottom of the deethanizer is 55 ℃ to 85 ℃, and the operation pressure is 2.2 MPaG to 3.2 MPaG.
3. The method of claim 1,
the operating temperature of the propylene rectifying tower is 48-60 ℃, and the operating pressure is 1.8-2.0 MPaG.
4. The method of claim 1,
the operating temperature of the absorbent recovery tower is 5-25 ℃, and the operating pressure is 2.0-2.6 MPaG.
5. An apparatus for use in the method of any one of claims 1 to 4, the apparatus comprising: the system comprises an oil gas feeding pipeline, a gas-liquid separation tank, a compressor I, a debutanizer, a rich gas desulfurization tower, a rich gas alkaline washing tower, a liquid hydrocarbon desulfurization tower, a liquid hydrocarbon sweetening reactor, a compressor II, a cooler, an after cooler, a feeding tank, an absorption tower, a demethanizer, a deethanizer and a depropanizer;
the oil-gas feeding pipeline is connected with an inlet of a gas-liquid separation tank, the top of the gas-liquid separation tank is sequentially connected with a compressor I and a debutanizer, and the bottom of the gas-liquid separation tank is connected with the debutanizer;
a reflux tank is arranged on the top of the debutanizer, and the top of the reflux tank is sequentially connected with a rich gas desulfurization tower, a rich gas alkaline washing tower, a compressor II, a cooler and an after-cooler; the tank bottom is connected with a liquid hydrocarbon desulfurizing tower, a liquid hydrocarbon sweetening reactor and an after-cooler in sequence; a stable gasoline extraction pipeline is arranged at the bottom of the debutanizer;
the upper part of the rich gas desulfurization tower is provided with a lean amine liquid feeding pipeline, and the upper part of the rich gas caustic tower is provided with an alkali liquid feeding pipeline;
the aftercooler is connected with the feeding tank;
the top of the feeding tank is connected with the absorption tower, and the bottom of the feeding tank is connected with the demethanizer;
the top of the absorption tower is connected with a downstream device, the bottom of the absorption tower is connected with an aftercooler, and the upper part of the absorption tower is provided with a mixed C4 absorbent feeding pipeline;
the top of the demethanizer is connected with the aftercooler, and the bottom of the demethanizer is connected with the depropanizer;
the upper part of the depropanizing tower is connected with a drying unit optionally and then connected with the deethanizing tower, a mixed C4 product extraction pipeline is arranged at the bottom of the depropanizing tower, the mixed C4 product extraction pipeline is divided into two branches, and one branch is used as a mixed C4 absorbent feeding pipeline;
a mixed C2 produced pipeline is arranged at the top of the deethanizer, an impurity treatment unit is optionally arranged on the mixed C2 produced pipeline, and a mixed C3 produced pipeline is arranged at the bottom of the deethanizer;
the device also comprises a propylene rectifying tower, wherein the mixed C3 extraction pipeline is connected with the propylene rectifying tower, a propylene product extraction pipeline is arranged at the top of the propylene rectifying tower, and a propane product extraction pipeline is arranged at the bottom of the propylene rectifying tower;
the downstream apparatus further comprises an absorbent recovery column;
the top of the absorbent recovery tower is provided with a dry gas extraction pipeline, the bottom of the absorbent recovery tower is connected with a debutanizer, the upper part of the absorbent recovery tower is provided with a stabilized gasoline absorbent feeding pipeline, the stabilized gasoline extraction pipeline of the debutanizer is divided into two branches, and one branch is used as the stabilized gasoline absorbent feeding pipeline.
6. The apparatus of claim 5,
the absorption tower is provided with 2-5 middle-section refluxes;
the top of the demethanizer is not provided with a condenser, and the bottom of the demethanizer is provided with a reboiler;
the compressor I is divided into a plurality of sections, and an intersegment liquid phase extraction pipeline is connected with the debutanizer;
the apparatus does not include a dehydration apparatus.
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