CN111393248B

CN111393248B - Device and method for desulfurizing oil gas and recovering light hydrocarbon

Info

Publication number: CN111393248B
Application number: CN201910636770.8A
Authority: CN
Inventors: 黄孟旗; 吴迪; 丁昱文; 李健; 姚爱智; 江盛阳
Original assignee: Sinopec Engineering Inc; Sinopec Engineering Group Co Ltd
Current assignee: Sinopec Engineering Inc; Sinopec Engineering Group Co Ltd
Priority date: 2019-07-15
Filing date: 2019-07-15
Publication date: 2023-05-26
Anticipated expiration: 2039-07-15
Also published as: CN111393248A

Abstract

The invention belongs to the field of chemical industry, and particularly discloses a device and a method for desulfurizing oil gas and recovering light hydrocarbon, which have the advantages of simple process, mild operation conditions and less cold energy consumption, can realize the separation and recovery of the light hydrocarbon in a catalytic cracking process by using less equipment, and particularly can realize the efficient separation and recovery of each component of heavy gasoline, light gasoline and light hydrocarbon, wherein the total recovery rate of carbon two components is more than 98wt%, the recovery rate of carbon three components is more than 99wt%, the methane content in the recovered carbon two is not more than 0.5vol%, and the ethane content in the recovered carbon three components is not more than 200ppmv. Meanwhile, the method has wide application range, and the device can be used for desulfurizing light oil and gas separation in the process with high gas yield such as catalytic cracking, delayed coking and the like which are common in chemical production.

Description

Device and method for desulfurizing oil gas and recovering light hydrocarbon

Technical Field

The invention belongs to the field of oil refining and chemical industry, and particularly relates to a device and a method for desulfurizing oil gas and recovering light hydrocarbon, in particular to a device and a method for desulfurizing oil gas and recovering light hydrocarbon in processes with higher gas yields, such as catalytic cracking, delayed coking and the like.

Background

The light hydrocarbon refers to the components of methane, ethane, ethylene, propane, propylene, carbon four and the like obtained in the petrochemical process, and the light hydrocarbon separation process is always the focus of the petrochemical process. Wherein, the separation process among the second carbon, the third carbon and the fourth carbon is mature, and a rectification method is generally adopted. Methane, because of its low boiling point, requires cooling to temperatures of-100 ℃ and below if rectification is used to separate methane from carbon two, i.e., cryogenic separation, is typically employed in ethylene plants, which is costly in terms of investment and consumption. Therefore, the separation of methane has been the focus of light hydrocarbon separation process, and the development of light hydrocarbon separation process technology and the design of process flow are all carried out around the separation of methane.

The prior catalytic cracking process generally adopts absorption to stably recycle the liquefied gas (C3/C4) component, thereby realizing the purposes of liquefied gas component and dry gas (H) ₂ Separation of the components/C1/C2). Because the catalytic cracking process has higher dry gas yield, the content of C2 components in the dry gas can reach 25-40 wt%, and 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 recycling cracking ethylene yield is up to 80%, and hydrogen is rich. Therefore, the recovery of C2 resources from dry gas is of great interest. The prior art focuses on recovering the carbon II in the dry gas by adopting an absorption method, and the technical method has the following defects:

(1) The dry gas and the carbon four components are subjected to secondary separation: and separating dry gas from liquefied gas components in the absorption stabilizing part, absorbing carbon two by adopting carbon four in the carbon two recovery part, mixing the carbon four and the dry gas again, and separating.

(2) The absorption and stabilization system adopts heavy gasoline as an absorbent to recover liquefied gas components, and the catalytic cracking process has higher liquefied gas component yield, so that the gasoline circulates among a gasoline absorption tower, an ethane desorption tower and a stabilization tower, the circulation amount is larger, the temperature levels of the ethane desorption tower and the stabilization tower bottom are higher, the thermal load of a tower bottom reboiler is larger, and the energy consumption is higher.

(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 in the catalytic cracking process, simplifying the separation process and reducing the investment and energy consumption.

(4) The prior art carries out desulfurization and mercaptan removal on the dry gas and the liquefied gas after being absorbed and stabilized, H ₂ S and mercaptans circulate throughout the absorption stabilization system, possibly causing related corrosion problems, and the entire absorption stabilization system has H ₂ S leakage can be a safety issue.

Disclosure of Invention

The invention aims at providing a light hydrocarbon separation device and a light hydrocarbon separation method with simple process flow and mild operation conditions, by the method, the components of heavy gasoline, light gasoline and light hydrocarbon can be efficiently separated and recovered, and meanwhile, gas phase and liquid phase are adopted for respectively desulfurizing and sweetening, 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 desulfurizing oil gas and recovering light hydrocarbon, the method comprising:

(1) And (3) first gas-liquid separation: the oil gas from the upstream device is condensed and cooled and then is sent to a gas-liquid separation tank I for gas-liquid separation, the liquid phase at the tank bottom of the gas-liquid separation tank I is sent to a gasoline cutting tower through pressurization, and the gas phase at the tank top is sent to the gasoline cutting tower after being pressurized by a compressor;

(2) Gasoline cutting: the gas phase and the liquid phase from the step (1) enter a gasoline cutting tower, the gas phase distilled from the top of the tower enters a tower top reflux tank through condensation, the gas phase at the top of the tower top reflux tank is sent to a gas-liquid separation tank II after being compressed and cooled, the liquid phase at the bottom of the tower is sent to a liquid phase impurity removing unit, and at least part of the liquid phase at the bottom of the gasoline cutting tower is extracted as a heavy gasoline product;

(3) Second gas phase separation: after the material is in gas-liquid equilibrium in a gas-liquid separation tank II, separating a gas phase and a liquid phase again, and then respectively conveying the gas phase and the liquid phase to a gas phase impurity removal unit and a liquid phase impurity removal unit for impurity removal;

(4) Removing impurities in the gas phase: after the gas phase at the top of the gas-liquid separation tank II is optionally pressurized, cooled and subjected to gas-liquid balance in the gas-liquid separation tank III, the gas phase is sequentially subjected to H removal in a rich gas desulfurization tower by taking lean amine liquid as an absorbent ₂ S and CO ₂ Removing mercaptan by taking alkali liquor as an absorbent in a rich gas alkali washing tower, and then optionally boosting pressure and then delivering to a cooler;

(5) Liquid phase impurity removal: tank bottom liquid phases from a top reflux tank, a gas-liquid separation tank II and an optional gas-liquid separation tank III of a gasoline cutting tower are correspondingly pressurized and then are sequentially removed from H in a liquid hydrocarbon desulfurizing tower ₂ S and CO ₂ Removing mercaptan in the liquid hydrocarbon mercaptan removal reactor and then sending the mercaptan removal reactor to a aftercooler;

(6) And (3) cooling: primarily cooling the purified gaseous light hydrocarbon in a cooler, then delivering the cooled gaseous light hydrocarbon to a aftercooler, mixing the cooled gaseous light hydrocarbon with liquid light hydrocarbon in the aftercooler, and delivering the cooled gaseous light hydrocarbon to a feeding tank;

(7) Feeding: after the mixture flow from the aftercooler 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 separation unit;

(8) Absorption: in the absorption tower, C2 and components above C2 in the gas phase from the top of the feeding tank are absorbed by taking mixed C4/C5 or C4/C5/C6 as an absorbent, part of methane is simultaneously absorbed together, the gas phase at the top of the absorption tower is sent to a downstream device, and the liquid phase at the bottom of the absorption tower is returned to the aftercooler;

(9) Separating: the liquid phase from the tank bottom of the feed tank is further separated into a C2 component, a C3 component and a mixed C4/C5 or C4/C5/C6 component in a separation unit through a demethanizer, a depropanizer, a deethanizer and an optional propylene rectifying tower, wherein the C2 component and the C3 component are respectively extracted as a C2 product and a C3 product, at least one part of the mixed C4/C5 or C4/C5/C6 component is taken as an absorbent to the absorption tower, and the rest part is subjected to light gasoline separation;

(10) Light gasoline separation: the liquid phase component from the bottom of the depropanizer is further separated in the debutanizer for the mixed C4/C5 or C4/C5/C6 components, the separated C4 component is extracted from the upper part of the debutanizer, and the C5 or C5/C6 component at the bottom is extracted as light gasoline product.

The invention has wide application range, and the oil gas (including H) in the process with higher gas yield such as catalytic cracking, delayed coking and the like which are common in petrochemical production ₂ C1-C4, gasoline component and a small amount of non-hydrocarbon component) can be used for desulfurizing and recovering light hydrocarbon by using the device of the invention.

In the invention, oil gas from an upstream device is condensed and cooled and then is sent to a gas-liquid separation tank I for gas-liquid separation, liquid phase at the bottom of the tank is pumped to a gasoline cutting tower by pump pressurization, and gas phase at the top of the tank is sent to the gasoline cutting tower after being boosted by a compressor.

In the invention, firstly, the cutting temperature of a gasoline cutting tower is controlled to separate oil gas from an upstream device into heavy gasoline and a mixture of light hydrocarbon containing C1-C6 and rich gas, the mixture is further separated to obtain light gasoline, dry gas, C2 component, C3 component and C4 component which are mainly mixed with C5 or mixed with C5/C6 alkane and alkene, and then the light hydrocarbon recovery of the oil gas is realized, preferably, the dry point of the gas phase at the top of the gasoline cutting tower is 60-75 ℃, and the initial distillation point of the heavy gasoline at the bottom of the tower is 65-80 ℃.

Because the heavy gasoline is separated in the gasoline cutting tower in advance, the heavy gasoline does not participate in the downstream light hydrocarbon separation process, the process energy consumption can be greatly reduced, and preferably, the operation temperature at the top of the gasoline cutting tower is 50-75 ℃ and the operation pressure is 0.25-0.6 MPaG; the operating temperature of the tower bottom is 145-180 ℃.

In the invention, in order to meet the requirements of recovery of related products and avoid the influence of impurities in materials on the device of a light hydrocarbon recovery part, the impurities in the light hydrocarbon are required to be removed before the next separation, and the method mainly comprises the steps of eluting H by amine ₂ S and CO ₂ And alkaline washing to remove mercaptans. The invention separates light hydrocarbon into gas phase and liquid phase, then carries out impurity removal respectively, the impurity removal form can be low pressure or high pressure, preferably, the gas phase at the top of the reflux tank is compressed to 1.1-1.6 MPaG, cooled to 35-45 ℃ and then sent to a gas-liquid separation tank II, and the tank is provided with a high pressure gas-liquid separation tankThe bottom liquid phase is pressurized to 3.0-3.5 MPaG and then sent to a liquid phase impurity removing unit. After the materials are in gas-liquid equilibrium in the gas-liquid separation tank II, separating the gas phase and the liquid phase again, and then respectively conveying the gas phase and the liquid phase to a gas phase impurity removal unit and a liquid phase impurity removal unit for impurity removal.

In the present invention, in order to meet the requirements of the recovery of the relevant products, it is preferable that the amine elutes H ₂ S adopts a composite solvent (namely, modified solvent based on MDEA) and can simultaneously remove H ₂ S and CO ₂ Wherein H is ₂ S can be removed to less than 15ppmv, CO ₂ The removal efficiency of the catalyst can reach 88 to 96 weight percent, and the CO in the material flow entering the alkaline leaching mercaptan removal reactor is effectively reduced ₂ Thereby reducing the alkali liquor consumption.

According to the present invention, preferably, the operation temperature of the rich gas desulfurization tower is 35 to 45 ℃ and the operation pressure is 1.1 to 2.9MPaG; the operating temperature of the rich gas alkaline washing tower is 35-45 ℃, and the operating pressure is 1.0-2.8 MPaG; the operating temperature of the liquid hydrocarbon desulfurizing tower is 35-45 ℃ and the operating pressure is 3.0-3.5 MPaG.

According to the invention, the feed tank preferably operates at a temperature of 5 to 25 ℃ and at a pressure of 2.2 to 2.8MPaG.

In the absorption tower, the mixed C4/C5 or C4/C5/C6 is used as an absorbent to absorb C2 and above C2 components in the gas phase from the top of the feeding tank, and simultaneously, partial methane is co-absorbed. When the main component of the light gasoline cut out from the top of the gasoline cutting tower is mixed C5/C6, the mixed C4/C5/C6 is selected as an absorbent; when the main component of the light gasoline cut from the top of the gasoline cutting tower is mixed C5, the mixed C4/C5 is selected as an absorbent, preferably, the operating temperature of the absorption tower is 5-25 ℃, the operating pressure is 2.1-2.7 MPaG, and the absorbent in the absorption tower is from the self-balancing component in the system, and is not required to be introduced from the outside of the system.

The process requirements can be met by the separation steps of the invention without special limitation on the order of the depropanization and the deethanization, but when the depropanization and the deethanization are different, the operation conditions of the deethanization tower and the composition of the recovered mixed carbon II can be different, and the separation steps can be specifically one of the following two ways according to the conventional technical means in the field:

mode one: the separation step comprises:

demethanization: removing methane from a liquid phase at the bottom of a feed tank in a demethanizer, removing at least part of C2 and components above C2, sending a gas phase at the top of the demethanizer to a aftercooler, and sending a liquid phase at the bottom of the demethanizer to a deethanizer;

deethanizing: separating C2 components from a liquid phase at the bottom of the demethanizer in the deethanizer, optionally passing the separated overhead mixed C2 components through a carbon two treatment unit, then extracting as a mixed C2 product, and delivering the liquid phase components at the bottom of the column C3 and above C3 to the depropanizer;

removing propane: separating a C3 component from a liquid phase component at the bottom of the deethanizer in a depropanizer, wherein the separated C3 component is extracted from the upper part of the depropanizer, part of the bottom component is taken as a mixed C4/C5 or C4/C5/C6 absorbent to be sent to the absorber, and the rest is sent to the depropanizer;

Preferably, the separating step further comprises:

propylene rectification: the C3 component extracted from the upper part of the depropanizer is further rectified in a propylene rectifying tower, the gas phase at the top of the propylene rectifying tower is cooled and then extracted as a propylene product, and the liquid phase at the bottom of the propylene rectifying tower is extracted as a propane product;

mode two:

demethanization: removing methane from a liquid phase at the bottom of a feed tank in a demethanizer, removing at least part of C2 and components above C2, sending a gas phase at the top of the demethanizer to a aftercooler, and sending a liquid phase at the bottom of the demethanizer to a depropanizer;

removing propane: separating a C3 component from a liquid phase component at the bottom of the demethanizer in the depropanizer, taking the separated C3 component from the upper part of the depropanizer, optionally drying, sending the C3 component to the deethanizer, sending part of the bottom component as a mixed C4/C5 or C4/C5/C6 absorbent to the absorber, and sending the rest of the bottom component to the debutanizer;

deethanizing: the gas phase from the upper part of the depropanization is further separated in a deethanizer, the separated tower top mixed C2 component is optionally extracted from the top of the deethanizer as a mixed C2 product after passing through a carbon two treatment unit, and the tower bottom liquid phase is extracted as a mixed C3 component;

preferably, the separating step further comprises:

propylene rectification: the mixed C3 component from the bottom of the deethanizer is further rectified in a propylene rectifying tower, the gas phase at the top of the propylene rectifying tower is cooled and then is taken as a propylene product, and the liquid phase at the bottom of the propylene rectifying tower is taken as a propane product.

According to the present invention, preferably, the demethanizer has an overhead operating temperature of 10 to 40 ℃ and an operating pressure of 2.3 to 2.9MPaG; the operation temperature of the propylene rectifying tower is 45-60 ℃ and the operation pressure is 1.8-2.0 MPaG.

According to the requirement of recycling and utilizing the secondary carbon, when the extracted mixed C2 is sent to a downstream ethylene device, as the mixed C2 product contains 15-20v% of propylene, at the moment, the requirement can be met by adopting lithium bromide refrigeration without setting a drying facility and adopting a refrigerant at the temperature of less than-5 ℃, and NOx and O in the secondary carbon can be removed by a secondary carbon treatment unit ₂ And the related impurities such as heavy metals and the like are sent to an ethylene device to recycle ethylene, ethane, propylene and other resources. Wherein, the impurity removal is carried out by a person skilled in the art according to specific conditions by adopting a conventional impurity removal method in the art, and O can be removed by hydrogenation ₂ Alkyne and NO _x Molecular sieve drying to remove H ₂ O, COS adsorption and removal, mercury adsorption and removal, and the like.

When the extracted mixed C2 is sent to ethylbenzene production, in order to reduce the propylene content in the extracted mixed C2 product as much as possible, a drying facility is required, a refrigerant with the temperature of minus 25 ℃ is required to be adopted at the top of the deethanizer, the propylene content in the extracted mixed C2 product is controlled to be less than or equal to 0.5wt%, and then the mixed C2 product is directly sent to ethylbenzene production, and other impurity removal facilities are not required to be arranged.

For further recovery of mixed C4/C5 or C4/C5/C6 absorbent entrained in the absorber overhead stream, the process preferably further comprises:

(11) And (3) recovering an absorbent: in the absorbent recovery tower, taking part of the heavy gasoline extracted in the step (2) as an absorbent to absorb C4 and more than C4 components in the gas phase from the top of the absorption tower, and simultaneously absorbing a small amount of C2/C3 components, wherein the gas phase at the top of the absorbent recovery tower mainly comprises components such as methane, hydrogen, nitrogen and the like, and is extracted as dry gas, and the liquid phase at the bottom of the absorbent recovery tower returns to the gasoline cutting tower; further preferably, the absorbent recovery column is operated at a temperature of 5 to 25 ℃ and at a pressure of 2.1 to 2.7MPaG.

In another aspect, the present invention provides an apparatus for desulfurizing oil gas and recovering light hydrocarbon, the apparatus comprising: the device comprises an oil-gas feeding pipeline, a gas-liquid separation tank I, a compressor I, a gasoline cutting tower, a compressor II, a cooler I, a gas-liquid separation tank II, a rich gas desulfurization tower, a rich gas alkaline washing tower, a liquid hydrocarbon desulfurization tower, a liquid hydrocarbon sweetening reactor, a compressor III, a cooler II, a aftercooler, a feeding tank, an absorption tower, a demethanizer, a deethanizer, a depropanizer, a debutanizer and optionally a compressor III, a compressor IV, a cooler III and a gas-liquid separation tank III;

The oil gas feeding pipeline is connected with an inlet of a gas-liquid separation tank I, the top of the gas-liquid separation tank I is sequentially connected with a compressor I and a gasoline cutting tower, and the bottom of the gas-liquid separation tank I is connected with the gasoline cutting tower;

the top of the gasoline cutting tower is provided with a reflux tank, the top of the reflux tank is sequentially connected with a compressor II, a cooler I and a gas-liquid separation tank II, the bottom of the reflux tank is connected with a booster pump and then connected with a liquid hydrocarbon desulfurizing tower, and the bottom of the gasoline cutting tower is provided with a heavy gasoline extraction pipeline;

the top of the gas-liquid separation tank II is sequentially connected with a compressor IV, a cooler III, a gas-liquid separation tank III, a rich gas desulfurizing tower, a rich gas alkaline washing tower, a compressor III, a cooler II and a aftercooler, and the bottom of the gas-liquid separation tank II is connected with a liquid hydrocarbon desulfurizing tower;

the liquid hydrocarbon desulfurizing tower is connected with the liquid hydrocarbon sweetening reactor and the aftercooler in sequence;

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 alkaline washing tower is provided with an alkaline liquid feeding pipeline; the upper part of the liquid hydrocarbon desulfurizing tower is provided with a lean amine 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 separation unit;

the top of the absorption tower is connected with a downstream device, the bottom of the absorption tower is connected with a aftercooler, and the upper part of the absorption tower is provided with a mixed C4/C5 or C4/C5/C6 absorbent feeding pipeline;

The separation unit includes: a demethanizer, deethanizer, depropanizer, and optionally a propylene rectifier; the top of the demethanizer is connected with a aftercooler; a mixed C2 extraction pipeline is arranged at the top of the deethanizer, and a carbon two treatment unit is optionally arranged on the mixed C2 extraction pipeline; the bottom of the depropanizer is provided with a mixed C4/C5 or C4/C5/C6 product extraction pipeline, the mixed C4/C5 or C4/C5/C6 product extraction pipeline is divided into two branches, one branch is used as a mixed C4/C5 or C4/C5/C6 absorbent feeding pipeline, and the other branch is connected with the depropanizer;

the upper part of the debutanizer is provided with a C4 component extraction pipeline, and the bottom of the debutanizer is provided with a light gasoline product extraction pipeline.

According to the invention, preferably, the top of the demethanizer is connected with an aftercooler, and the bottom of the demethanizer is connected with a deethanizer;

the top of the deethanizer is provided with a mixed C2 extraction pipeline, a carbon two treatment unit is optionally arranged on the mixed C2 extraction pipeline, and the bottom of the deethanizer is connected with the depropanizer;

the upper part of the depropanizer is provided with a mixed C3 extraction pipeline, the mixed C3 extraction pipeline is optionally connected with a propylene rectifying tower, the bottom of the depropanizer is provided with a mixed C4/C5 or C4/C5/C6 extraction pipeline, the mixed C4/C5 or C4/C5/C6 extraction pipeline is divided into two branches, one branch is used as a mixed C4/C5 or C4/C5/C6 absorbent feeding pipeline, and the other branch is connected with the depropanizer;

The upper part of the debutanizer is provided with a C4 product extraction pipeline, and the bottom of the debutanizer is provided with a light gasoline extraction pipeline;

or alternatively, the process may be performed,

the top of the demethanizer is connected with the aftercooler, and the bottom of the demethanizer is connected with the deethanizer;

the upper part of the depropanizer is optionally connected with a drying unit and then connected with a deethanizer, a mixed C4/C5 or C4/C5/C6 extraction pipeline is arranged at the bottom of the depropanizer, the mixed C4/C5 or C4/C5/C6 extraction pipeline is divided into two branches, one branch is used as a mixed C4/C5 or C4/C5/C6 absorbent feeding pipeline, and the other branch is connected with the debutanizer;

the top of the deethanizer is provided with a mixed C2 extraction pipeline, a carbon two treatment unit is optionally arranged on the mixed C2 extraction pipeline, the bottom of the deethanizer is provided with a mixed C3 extraction pipeline, and the mixed C3 extraction pipeline is optionally connected with a propylene rectifying tower;

the upper part of the debutanizer is provided with a C4 product extraction pipeline, and the bottom of the debutanizer is provided with a light gasoline extraction pipeline; further preferably, 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 tower; 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 gasoline cutting tower, and the upper part of the absorbent recovery tower is provided with a heavy gasoline absorbent feeding pipeline.

In the present invention, in order to maintain a stable operating temperature of the whole column, it is preferable that the absorber is provided with 2 to 5 middle reflux streams, the absorber is not provided with a condenser at the top, a reboiler is not provided at the bottom, the gas phase from the feed tank is fed from the bottom of the absorber, and the absorbent is fed from the top of the absorber.

According to the present invention, preferably, the demethanizer is not provided with a condenser at the top and a reboiler at the bottom, and the liquid phase from the feed tank is fed from the demethanizer top; the light hydrocarbon separation device does not comprise a dehydration device.

Compared with the prior art, the invention has the following advantages:

(1) In the invention, the front-mounted gasoline cutting tower is adopted to separate heavy gasoline, light gasoline and components below C4 and C4 under lower pressure, and the gasoline circulation is not required to absorb the 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 invention has simple flow, mild operation condition and less cold energy consumption, can realize the separation and recovery of light hydrocarbon in oil gas by using less equipment, and particularly can realize the high-efficiency separation and recovery of C2, C3 and C4 components; and no secondary separation process exists between the second carbon component and each component, meanwhile, the total recovery rate of the second carbon component can be ensured to be more than 98wt percent, the recovery rate of the third carbon component can be more than 99wt percent, the methane content in the recovered second carbon component is not more than 0.5vol percent, and the ethane content in the recovered third carbon component is not more than 200ppmv.

(3) The invention further separates the recovered carbon three components into propylene and propane, the recovery rates of the propylene and the propane can reach more than 99wt percent, the purity of the propylene product is not less than 99.6v percent, and the polymerization 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 C2 and components above C2 is not more than 3vol percent, the pressure is 2.1-2.7 MPaG, the purity of hydrogen can reach 40-70 mol percent, and the hydrogen resource can be directly recovered by a pressure swing adsorption method.

(5) According to the invention, the gas phase and the liquid phase are respectively desulfurized and decarbonized, 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, meanwhile, the concentration of the downstream hydrogen sulfide is greatly reduced, and the operation safety is improved; the hydrogen sulfide and the carbon dioxide are removed in advance, so that the load and the energy consumption of a downstream light hydrocarbon recovery system can be reduced, and meanwhile, due to CO ₂ Is removed, and can improve the quality of downstream products.

Additional features and advantages of the invention will be set forth in the detailed description which follows.

Drawings

The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular descriptions of exemplary embodiments of the invention as illustrated in the accompanying drawings wherein like reference numbers generally represent like parts throughout the exemplary embodiments of the invention.

FIG. 1 shows a process flow diagram for hydrocarbon desulfurization and light hydrocarbon recovery in one embodiment of the invention.

FIG. 2 shows a process flow diagram for hydrocarbon desulfurization and light hydrocarbon recovery in one embodiment of the invention.

FIG. 3 shows a process flow diagram for hydrocarbon desulfurization and light hydrocarbon recovery in one embodiment of the invention.

Reference numerals illustrate:

1. a gas-liquid separation tank I; 2. a compressor I; 3. a gasoline cutting tower; 4. a compressor II; 5. a cooler I; 6. a gas-liquid separation tank II; 7. a liquid hydrocarbon desulfurizing tower; 8. a liquid hydrocarbon sweetening reactor; 9. a rich gas desulfurizing tower; 10. a rich gas alkaline washing tower; 11. a compressor III; 12. a cooler II; 13. an aftercooler; 14. a feed tank; 15. an absorption tower; 16. a demethanizer; 17. a deethanizer; 18. a depropanizer; 19. a propylene rectifying column; 20. a carbon two treatment unit; 21. an absorbent recovery tower; 22. a debutanizer; 23. a compressor IV; 24. a cooler III; 25. a gas-liquid separation tank III;

s-1, oil gas from an upstream device; s-2, crude gasoline; s-3, lean amine solution; s-4, rich amine 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 carbon II; s-10, propylene products; s-11, a propane product; s-12, heavy gasoline products; s-13, a carbon four product; s-14, a light gasoline product.

Detailed Description

Preferred embodiments of the present invention will be described in more detail below. While the preferred embodiments of the present invention are described below, it should be understood that the present invention may be embodied in various forms and should not be limited to the embodiments set forth herein.

The properties of the raw oil gas in the following examples are shown in Table 1, and the properties of the C5+ components in the oil gas are shown in Table 2:

TABLE 1

TABLE 2

Example 1

Oil gas desulfurization and light hydrocarbon recovery device:

the system comprises an oil-gas feeding pipeline, a gas-liquid separation tank I1, a compressor I2, a gasoline cutting tower 3, a compressor II 4, a cooler I5, a gas-liquid separation tank II 6, a rich gas desulfurization tower 9, a rich gas alkaline washing tower 10, a liquid hydrocarbon desulfurization tower 7, a liquid hydrocarbon mercaptan removal reactor 8, a compressor III 11, a cooler II 12, an aftercooler 13, a feeding tank 14, an absorption tower 15, a demethanizer 16, a deethanizer 17, a depropanizer 18 and a propylene rectifying tower 19; an absorbent recovery column 21 and a debutanizer column 22;

the oil gas feeding pipeline is connected with an inlet of a gas-liquid separation tank I1, the top of the gas-liquid separation tank I1 is sequentially connected with a compressor I2 and a gasoline cutting tower 3, and the bottom of the gas-liquid separation tank I1 is connected with the gasoline cutting tower 3;

the top of the gasoline cutting tower 3 is provided with a reflux tank, the top of the reflux tank is sequentially connected with a compressor II 4, a cooler I5 and a gas-liquid separation tank II 6, the bottom of the reflux tank is connected with a booster pump and then connected with a liquid hydrocarbon desulfurizing tower 7, and the bottom of the gasoline cutting tower 3 is provided with a heavy gasoline extraction pipeline;

The top of the gas-liquid separation tank II 6 is sequentially connected with the rich gas desulfurization tower 9, the rich gas alkaline washing tower 10, the compressor III 11, the cooler II 12 and the aftercooler 13, and the bottom of the gas-liquid separation tank II is connected with the booster pump and then connected with the liquid hydrocarbon desulfurization tower 7;

the liquid hydrocarbon desulfurizing tower 7 is connected with the liquid hydrocarbon sweetening reactor 8 and the aftercooler 13 in sequence;

the upper part of the rich gas desulfurization tower 9 is provided with a lean amine liquid feeding pipeline, and the upper part of the rich gas alkaline washing tower 10 is provided with an alkaline liquid feeding pipeline; the upper part of the liquid hydrocarbon desulfurizing tower 7 is provided with a lean amine liquid feeding pipeline;

the aftercooler 13 is connected with the feed tank 14;

the top of the feeding tank 14 is connected with an absorption tower 15, and the bottom of the feeding tank is connected with a demethanizer 16;

the absorption tower 15 is provided with 2-5 middle reflux streams, the tower top is connected with the absorbent recovery tower 21, the tower bottom is connected with the aftercooler 13, and the upper part of the absorption tower 15 is provided with a mixed C4/C5 absorbent feeding pipeline;

the top of the absorbent recovery tower 21 is provided with a dry gas extraction pipeline, the bottom of the absorbent recovery tower is connected with a gasoline cutting tower 22, and the upper part of the absorbent recovery tower 21 is provided with a heavy gasoline absorbent feeding pipeline.

The top of the demethanizer 16 is connected with the aftercooler 13, the bottom of the demethanizer is connected with the deethanizer 17, and the bottom of the demethanizer is provided with a reboiler;

the top of the deethanizer 17 is provided with a mixed C2 extraction pipeline, the mixed C2 extraction pipeline is provided with a carbon two treatment unit 20, and the bottom of the deethanizer is connected with a depropanizer 18;

The upper part of the depropanizer 18 is connected with a propylene rectifying tower 19, a mixed C4 product extraction pipeline is arranged at the bottom of the depropanizer, the mixed C4 product extraction pipeline is divided into two branches, one branch is used as a mixed C4/C5 absorbent feeding pipeline, and the other branch is connected with the debutanizer;

the top of the propylene rectifying tower 19 is provided with a propylene product extraction pipeline, and the bottom of the propylene rectifying tower is provided with a propane product extraction pipeline.

The upper part of the debutanizer 22 is provided with a C4 product extraction line, and the bottom of the debutanizer is provided with a light gasoline extraction line.

The oil gas desulfurization and light hydrocarbon recovery device does not comprise a dehydration device.

The device is adopted to separate light hydrocarbon, and the separation flow is shown in figure 1:

(1) And (3) first gas-liquid separation: the oil gas from the upstream device is condensed and cooled and then is sent to a gas-liquid separation tank I1 for gas-liquid separation, the liquid phase at the tank bottom of the gas-liquid separation tank I1 is sent to a gasoline cutting tower 3 after being pressurized, and the gas phase at the tank top is sent to the gasoline cutting tower 3 after being pressurized by a compressor;

(2) Gasoline cutting: the gas phase and the liquid phase from the step (1) enter a gasoline cutting tower 3, the gas phase distilled from the top of the tower enters a tower top reflux tank through condensation, the gas phase (specific composition shown in table 3) at the top of the tower top reflux tank is compressed to 1.1-1.6 MPaG, cooled to 35-45 ℃ and then sent to a gas-liquid separation tank II 6, the liquid phase (specific composition shown in table 3) at the bottom of the tank is pressurized to 3.0-3.5 MPaG and then sent to a liquid phase impurity removing unit, and at least part of the liquid phase (specific composition shown in table 3) at the bottom of the gasoline cutting tower 3 is taken as a heavy gasoline product S-12; the operation temperature of the top of the gasoline cutting tower 3 is 60-85 ℃ and the operation pressure is 0.25-0.6 MPaG; the operation temperature of the tower bottom is 145-180 ℃;

(3) Second gas phase separation: after the materials are in gas-liquid equilibrium in a gas-liquid separation tank II 6, separating a gas phase and a liquid phase again, and then respectively conveying the gas phase and the liquid phase to a gas phase impurity removal unit and a liquid phase impurity removal unit for impurity removal;

(4) Removing impurities in the gas phase: the gas phase at the top of the gas-liquid separation tank II 6 is sequentially dehydrated in the rich gas desulfurization tower 9 by taking lean amine liquid as absorbent ₂ S and CO ₂ Removing mercaptan by taking alkali liquor as an absorbent in the rich gas alkali washing tower 10, and then sending the product to a cooler II 12 through pressure boosting; wherein, the operating temperature of the rich gas desulfurizing tower 9 is 35-45 ℃ and the operating pressure is 1.1-1.6 MPaG; the operation temperature of the rich gas alkaline washing tower 10 is 35-45 ℃ and the operation pressure is 1.0-1.5 MPaG;

(5) Liquid phase impurity removal: the liquid phase light hydrocarbon from the bottom of the reflux tank at the top of the gasoline cutting tower 3 and the gas-liquid separation tank II 6 is sequentially removed H in the liquid hydrocarbon desulfurizing tower 7 ₂ S and CO ₂ Removing mercaptan in the liquid hydrocarbon mercaptan removal reactor 8 and then sending the mercaptan removal reactor to a aftercooler 13; wherein, the operating temperature of the liquid hydrocarbon desulfurizing tower 7 is 35-45 ℃ and the operating pressure is 3.0-3.5 MPaG;

(6) And (3) cooling: the gaseous light hydrocarbon after impurity removal is primarily cooled in a cooler II 12 and then is sent to a aftercooler 13, mixed with the liquid light hydrocarbon in the aftercooler 13 and sent to a feed tank 14 after being cooled again;

(7) Feeding: after mixing, pre-absorption and gas-liquid balancing in a feed tank 14, the mixed stream from the aftercooler 13 is sent to an absorption tower 15 from the top gas phase and a demethanizer 16 from the bottom liquid phase; wherein, the operation temperature of the feed tank 14 is 5-25 ℃ and the operation pressure is 2.2-2.8 MPaG;

(8) Absorption: in the absorption tower 15, the mixed C4/C5 is used as an absorbent to absorb C2 and components above C2 in the gas phase from the top of the feeding tank 14, and simultaneously, partial methane is absorbed together, the gas phase at the top of the absorption tower 15 is sent to an absorbent recovery tower 21, and the liquid phase at the bottom of the absorption tower is returned to the aftercooler 13; wherein the operating temperature of the absorption tower 15 is 5-25 ℃, the operating pressure is 2.1-2.7 MPaG, the absorbent in the absorption tower 15 comes from the self-balanced mixed C4/C5 component in the system, and the absorbent is not required to be introduced from the outside of the system;

(9) Separating:

demethanization: the liquid phase from the bottom of the feed tank 14 is subjected to methane removal in a demethanizer 16, and at the same time, a small part of C2 and components above C2 are removed, the gas phase at the top of the demethanizer 16 is sent to an aftercooler 13, and the liquid phase at the bottom of the demethanizer is sent to a deethanizer 17; wherein, the operation temperature of the top of the demethanizer is 10-40 ℃ and the operation pressure is 2.3-2.9 MPaG;

deethanizing: separating C2 components in a deethanizer 17 from a liquid phase at the bottom of the demethanizer 16, extracting the separated overhead mixed C2 components as a mixed C2 product after passing through a carbon two treatment unit 20, and delivering liquid phase components at the bottom of the column C3 and above C3 to a depropanizer 18;

Removing propane: the liquid phase component from the bottom of the deethanizer 17 separates the C3 components in the depropanizer 18, the separated C3 components are withdrawn from the upper portion of the depropanizer 18, part of the bottom components are sent as mixed C4/C5 absorbent to the absorber 15, and the remainder is sent to the debutanizer 22;

propylene rectification: the C3 component extracted from the upper part of the depropanizer 18 is further rectified in a propylene rectifying tower 19, the gas phase at the top of the propylene rectifying tower 19 is cooled and then extracted as a propylene product S-10, and the liquid phase at the bottom of the tower is extracted as a propane product S-11, wherein the operating temperature of the propylene rectifying tower 18 is 45-60 ℃ and the operating pressure is 1.8-2.0 MPaG;

(10) Light gasoline separation: the liquid phase component from the bottom of the depropanizer 18 further separates the C4 component in the debutanizer 22, the separated C4 component is withdrawn from the upper portion of the debutanizer 22, and the bottom component is withdrawn as light gasoline product S-14;

(11) And (3) recovering an absorbent: in the absorbent recovery tower 21, the heavy gasoline extracted in the step (2) is used as an absorbent to absorb C4 and more than C4 components in the gas phase from the top of the absorption tower 15, and simultaneously absorb a small amount of C2/C3 components, the gas phase from the top of the absorbent recovery tower 21 is extracted as dry gas S-8, and the liquid phase at the bottom of the tower returns to the gasoline cutting tower 3, wherein the operation temperature of the absorbent recovery tower is 5-25 ℃ and the operation pressure is 2.1-2.7 MPaG.

The composition and properties of the products such as light and heavy gasoline, light hydrocarbon and the like in the separated oil gas by the method are shown in table 4, wherein the light and heavy gasoline is shown in table 5.

TABLE 3 Table 3

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Note that: PC in the above table represents a pseudo component.

TABLE 4 Table 4

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TABLE 5

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Example 2

The process flow chart shown in figure 1 is adopted for carrying out oil gas desulfurization and light hydrocarbon recovery.

Among them, the present embodiment differs from embodiment 1 in that:

the main components distilled from the top of the gasoline cutting tower are C1-C4 light hydrocarbon components and C5/C6 alkane and alkene components, the mixed C4/C5/C6 is used as an absorbent in the absorption tower, wherein the main components of all the materials distilled from the gasoline cutting tower are shown in table 6, and the compositions and properties of all the separated products are shown in table 7, and the properties of the light and heavy gasoline products are shown in table 8.

TABLE 6

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Note that: PC in the above table represents a pseudo component.

TABLE 7

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TABLE 8

Example 3

Oil gas desulfurization and light hydrocarbon recovery device:

the device comprises an oil gas feeding pipeline, a gas-liquid separation tank I1, a compressor I2, a gasoline cutting tower 3, a compressor II 4, a cooler I5, a gas-liquid separation tank II 6, a compressor IV 23, a cooler III 24, a gas-liquid separation tank III 25, a rich gas desulfurization tower 9, a rich gas alkaline washing tower 10, a liquid hydrocarbon desulfurization tower 7, a liquid hydrocarbon sweetening reactor 8, a cooler II 12, a aftercooler 13, a feeding tank 14, an absorption tower 15, a demethanizer 16, a deethanizer 17, a depropanizer 18 and a propylene rectifying tower 19; an absorbent recovery column 21 and a debutanizer column 22;

the top of the gas-liquid separation tank II 6 is sequentially connected with a compressor IV 23, a cooler III 24 and a gas-liquid separation tank III 25, and the bottom of the gas-liquid separation tank II is connected with a booster pump and then connected with the liquid hydrocarbon desulfurizing tower 7;

the top of the gas-liquid separation tank III 25 is sequentially connected with the rich gas desulfurization tower 9, the rich gas alkaline washing tower 10, the cooler II 12 and the aftercooler 13, and the bottom of the gas-liquid separation tank III is connected with the booster pump and then connected with the liquid hydrocarbon desulfurization tower 7;

the aftercooler 13 is connected with the feed tank 14;

The device is adopted to separate light hydrocarbon, and the separation flow is shown in figure 2:

(1) And (3) first gas-liquid separation: the oil gas from the upstream device is condensed and cooled and then is sent to a gas-liquid separation tank I1 for gas-liquid separation, the liquid phase at the bottom of the tank is sent to a gasoline cutting tower 3 through pressurization, and the gas phase at the top of the tank is sent to the gasoline cutting tower 3 after being pressurized by a compressor;

(2) Gasoline cutting: the gas phase and the liquid phase from the step (1) enter a gasoline cutting tower 3, the gas phase distilled from the top of the tower enters a reflux tank at the top of the tower through condensation, the gas phase (specific composition shown in table 9) at the top of the reflux tank at the top of the tower is compressed to 1.1-1.6 MPaG, cooled to 35-45 ℃ and then sent to a gas-liquid separation tank II 6, the liquid phase (specific composition shown in table 9) at the bottom of the tank is pressurized to 3.0-3.5 MPaG and then sent to a liquid phase impurity removing unit, and at least part of the liquid phase (specific composition shown in table 9) at the bottom of the gasoline cutting tower 3 is taken as a heavy gasoline product S-12; the operation temperature of the top of the gasoline cutting tower 3 is 60-85 ℃ and the operation pressure is 0.25-0.6 MPaG; the operation temperature of the tower bottom is 145-180 ℃;

(4) Removing impurities in the gas phase: the gas phase at the top of the gas-liquid separation tank II 6 is sequentially pressurized by a compressor IV 23 and cooled by a cooler III 24, then is subjected to gas-liquid balance in a gas-liquid separation tank III 25, H2S and CO2 are removed by taking lean amine liquid as an absorbent in a rich gas desulfurization tower 9 in sequence, mercaptan is removed by taking alkali liquor as an absorbent in a rich gas alkaline washing tower 10, and then is sent to a cooler II 12, and the bottom of the gas-liquid separation tank III 25 is sent to a liquid hydrocarbon desulfurization tower 7; wherein, the operating temperature of the rich gas desulfurizing tower 9 is 35-45 ℃ and the operating pressure is 2.3-2.9 MPaG; the operation temperature of the rich gas alkaline washing tower 10 is 35-45 ℃ and the operation pressure is 2.2-2.8 MPaG;

(9) Separating:

The composition and properties of the products such as light and heavy gasoline and light hydrocarbon in the separated oil gas by the method are shown in table 10, wherein the light and heavy gasoline is shown in table 11.

TABLE 9

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Table 10

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TABLE 11

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Example 4

The process flow chart shown in fig. 3 is adopted for carrying out oil gas desulfurization and light hydrocarbon recovery, and the difference from the embodiment 1 is that:

(9) Separation step

Demethanization: the liquid phase from the bottom of the feed tank 14 is subjected to methane removal in a demethanizer 16, and at the same time, a small part of C2 and components above C2 are removed, the gas phase at the top of the demethanizer 16 is sent to an aftercooler 13, and the liquid phase at the bottom of the demethanizer is sent to a depropanizer 18; wherein, the top operation temperature of the demethanizer 16 is 10-40 ℃ and the operation pressure is 2.3-2.9 MPaG;

Removing propane: the liquid phase component from the bottom of the demethanizer 16 separates the C3 component in the depropanizer 18, the separated C3 component is extracted from the upper part of the depropanizer 18 and dried to the dew point of less than minus 60 ℃ and then sent to the deethanizer 17, part of the bottom component is sent to the absorber 15 as mixed C4/C5 absorbent, and the rest is sent to the debutanizer 22;

deethanizing: the gas phase from the upper part of the depropanizer 18 is further separated in the deethanizer 17, a condenser at the top of the deethanizer is cooled by adopting a propylene refrigerant at the temperature of minus 25 ℃, the propylene content in the mixed C2 product distilled from the top of the deethanizer is lower, the separated mixed C2 component at the top of the deethanizer 17 is taken as a mixed C2 product after passing through a carbon two treatment unit 20, and the bottom liquid of the deethanizer is sent to a propylene rectifying tower;

propylene rectification: the mixed C3 component extracted from the bottom of the deethanizer 17 is further rectified in a propylene rectifying tower 19, the gas phase at the top of the propylene rectifying tower 19 is cooled and then extracted as a propylene product S-10, and the liquid phase at the bottom of the tower is extracted as a propane product S-11, wherein the operation temperature of the propylene rectifying tower 18 is 45-60 ℃ and the operation pressure is 1.8-2.0 MPaG;

the corresponding separation units are:

the top of the demethanizer 16 is connected with the aftercooler 13, the bottom of the demethanizer is connected with the depropanizer, and the bottom of the demethanizer is provided with a reboiler;

The upper part of the depropanizer is connected with the drying unit and then connected with the deethanizer, the bottom of the depropanizer is provided with a mixed C4/C5 extraction pipeline, the mixed C4/C5 extraction pipeline is divided into two branches, one branch is used as a mixed C4/C5 absorbent feeding pipeline, and the other branch is connected with the depropanizer;

the top of the deethanizer is provided with a mixed C2 extraction pipeline, the mixed C2 extraction pipeline is provided with a carbon two treatment unit 20, the bottom of the deethanizer is provided with a mixed C3 extraction pipeline, and the mixed C3 extraction pipeline is connected with a propylene rectifying tower 19;

The composition and properties of the products such as light and heavy gasoline and light hydrocarbon in the separated oil gas by the method are shown in table 12, wherein the light and heavy gasoline is shown in table 13.

Table 12

TABLE 13

As can be seen from the data in the table, the invention has simple flow, mild operation condition and less cold energy consumption, and can realize the separation and recovery of light hydrocarbon in the catalytic cracking process by using less equipment, wherein the total recovery rate of the two carbon components is more than 98wt%, the recovery rate of the three carbon components is more than 99wt%, the methane content in the recovered two carbon components is not more than 1vol%, and the ethane content in the recovered three carbon components is not more than 200ppmv; meanwhile, the recovered carbon three components are further separated into propylene and propane, the recovery rates of the propylene and the propane can reach more than 99wt%, the impurities in the recovered dry gas are less, the content of C2 and components above C2 is not more than 2vol%, and the purity of the hydrogen can reach more than 40 mol%. The initial distillation point of the extracted heavy gasoline is 65-80 ℃, the heavy gasoline is mainly composed of six or more carbon components, the olefin content is low, sulfide such as thiophenic sulfur is mainly contained, and the heavy gasoline can be sent to the downstream for desulfurization; the light gasoline has a dry point of 60-75 deg.C, mainly C-five or C-five-C-hexaalkane and alkene components, and its alkene content is high, mainly contains sulfides of mercaptan and thioether, etc., and can be sent to downstream for further treatment.

The desulfurization and sweetening effects of examples 1 and 3 were compared, and the comparison results are shown in Table 14.

TABLE 14

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As is clear from Table 14, H in light hydrocarbons can be realized by either the high-pressure desulfurization and demercaptan or the low-pressure desulfurization and demercaptan of the present invention ₂ S content not exceeding 15ppmw, mercaptan sulfur content not exceeding 20ppmw, CO ₂ The removal rate can reach 96wt%; h in liquid phase light hydrocarbon ₂ S content of 15ppmw, mercaptan sulfur content of not more than 20ppmw, CO ₂ The removal rate can reach 88wt percent.

The foregoing description of embodiments of the invention has been presented for purposes of illustration and description, and is not intended to be exhaustive or 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 various embodiments described.

Claims

1. A method for desulfurizing oil gas and recovering light hydrocarbon, which is characterized by comprising the following steps:

(5) Liquid phase impurity removal: the tank bottom liquid phase from the top reflux tank, the gas-liquid separation tank II and the optional gas-liquid separation tank III of the gasoline cutting tower is pressurized and then sequentially removed H in the liquid hydrocarbon desulfurizing tower ₂ S and CO ₂ Removing mercaptan in the liquid hydrocarbon mercaptan removal reactor and then sending the mercaptan removal reactor to a aftercooler;

(10) Light gasoline separation: the liquid phase component from the bottom of the depropanizer is further separated in the depropanizer to mix the C4/C5 or C4/C5/C6 components, the separated C4 component is extracted from the upper part of the depropanizer, and the bottom component is extracted as light gasoline product.

2. The method of claim 1, wherein the separating step of step (9) comprises one of:

mode one: the separation step comprises:

mode two:

deethanizing: the gas phase from the upper part of the depropanization is further separated in the deethanizer, the separated overhead mixed C2 component is optionally extracted from the top of the deethanizer as a mixed C2 product after passing through a carbon two treatment unit, and the bottom liquid phase is extracted as a mixed C3 component.

3. The method of claim 2, wherein the step of determining the position of the substrate comprises,

mode one: the separating step further comprises:

mode two: the separating step further comprises:

4. The method according to claim 1, wherein the method further comprises:

(11) And (3) recovering an absorbent: in the absorbent recovery tower, part of the heavy gasoline extracted in the step (2) is used as an absorbent to absorb C4 and more than C4 components in the gas phase from the top of the absorption tower, and simultaneously absorb a small amount of C2/C3 components, the gas phase at the top of the absorbent recovery tower is used as dry gas to be extracted, and the liquid phase at the bottom of the absorbent recovery tower is returned to the gasoline cutting tower.

5. The method of claim 1, wherein the step of determining the position of the substrate comprises,

the dry point of the gas phase distilled from the top of the gasoline cutting tower is 60-75 ℃, and the initial point of the heavy gasoline distilled from the bottom of the tower is 65-80 ℃;

The operating temperature of the top of the gasoline cutting tower is 60-85 ℃, and the operating pressure is 0.25-0.6 MPaG; the operation temperature of the tower bottom is 145-180 ℃;

the gas phase at the top of the reflux tank is compressed to 1.1-1.6 MPaG, cooled to 35-45 ℃ and then sent to a gas-liquid separation tank II, and the liquid phase at the bottom of the reflux tank is pressurized to 3.0-3.5 MPaG and then sent to a liquid phase impurity removing unit;

the operating temperature of the rich gas desulfurizing tower is 35-45 ℃ and the operating pressure is 1.1-2.9 MPaG;

the operating temperature of the rich gas alkaline washing tower is 35-45 ℃, and the operating pressure is 1.0-2.8 MPaG;

the rich gas at the outlet of the rich gas alkaline washing tower top is compressed to 2.3-2.9 MPaG;

the operating temperature of the liquid hydrocarbon desulfurizing tower is 35-45 ℃ and the operating pressure is 3.0-3.5 MPaG;

the operation temperature of the feed tank is 5-25 ℃, and the operation pressure is 2.2-2.8 MPaG;

the operating temperature of the absorption tower is 5-25 ℃, the operating pressure is 2.1-2.7 MPaG, and the absorbent in the absorption tower is from self-balanced mixed C4/C5 or C4/C5/C6 components in the system, and the absorbent does not need to be introduced from outside the system.

6. The method of claim 3, wherein the step of,

the operation temperature of the top of the demethanizer is 10-40 ℃ and the operation pressure is 2.3-2.9 MPaG

The operation temperature of the propylene rectifying tower is 45-60 ℃ and the operation pressure is 1.8-2.0 MPaG.

7. The method according to claim 4, wherein the absorbent recovery column is operated at a temperature of 5 to 25 ℃ and a pressure of 2.1 to 2.7MPaG.

8. An apparatus for desulfurizing oil gas and recovering light hydrocarbon, comprising: the system comprises an oil-gas feeding pipeline, a gas-liquid separation tank I, a compressor I, a gasoline cutting tower, a compressor II, a cooler I, a gas-liquid separation tank II, a rich gas desulfurization tower, a rich gas alkaline washing tower, a liquid hydrocarbon desulfurization tower, a liquid hydrocarbon sweetening reactor, a cooler II, a aftercooler, a feeding tank, an absorption tower, a demethanizer, a deethanizer, a depropanizer, a debutanizer and an optional compressor III, a compressor IV, a cooler III and a gas-liquid separation tank III;

the top of the gas-liquid separation tank II is sequentially connected with an optional compressor IV, an optional cooler III, an optional gas-liquid separation tank III, a rich gas desulfurizing tower, a rich gas alkaline washing tower, an optional compressor III, a cooler II and an aftercooler, and the bottom of the gas-liquid separation tank II is connected with a liquid hydrocarbon desulfurizing tower;

the aftercooler is connected with the feeding tank;

9. The apparatus of claim 8, wherein the device comprises a plurality of sensors,

or alternatively, the process may be performed,

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 debutanizer is provided with a C4 product extraction pipeline, and the bottom of the debutanizer is provided with a light gasoline extraction pipeline.

10. The device according to claim 9, wherein the propylene rectifying tower is provided with a propylene product extraction pipeline at the top and a propane product extraction pipeline at the bottom.

11. The apparatus of claim 8, wherein 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 gasoline cutting tower, and the upper part of the absorbent recovery tower is provided with a heavy gasoline absorbent feeding pipeline.

12. The apparatus of claim 8, wherein the device comprises a plurality of sensors,

the absorption tower is provided with 2-5 middle section reflux streams;

a reboiler is arranged at the bottom of the demethanizer;

the device does not include a dewatering device.