A process for recovering refinery dry gas by absorbing cryogenic oil

Abstract

The present invention relates to the field of refinery dry gas processing and discloses a method for recovering refinery dry gas using a cryogenic oil absorption method. The method comprises: subjecting refinery dry gas to acid gas removal treatment, deoxygenating the obtained first treated gas to obtain a second treated gas; sequentially cooling and performing gas-liquid separation on the second treated gas to obtain a third treated gas and a liquid phase stream; introducing the third treated gas and the liquid phase stream into the upper middle portion and lower portion of a demethanizer, respectively, for a first separation treatment to obtain a bottom liquid phase I; introducing the bottom liquid phase I into a deethanizer for a second separation treatment to obtain a bottom liquid phase II; and introducing the bottom liquid phase II into a debutanizer for a third separation treatment to obtain a bottom liquid phase III that can be used as a light hydrocarbon product. The method of the present invention has a simple process, a high recovery rate, and low energy consumption, and is particularly suitable for recovering refinery dry gas in integrated refining and chemical enterprises.

Description

Technical Field

[0001] The present invention relates to the field of refinery dry gas processing, and in particular to a method for recovering refinery dry gas by using a cryogenic oil absorption method. Background Art

[0002] Refinery dry gas is primarily derived from the secondary processing of crude oil, such as catalytic cracking, thermal cracking, delayed coking, and hydrocracking. Currently, most refineries still burn refinery dry gas as fuel, which has low utilization value, causes significant resource waste, and pollutes the environment.

[0003] Catalytic dry gas generally contains a high ethylene content and is considered unsaturated dry gas. Saturated dry gas typically comes from PSA desorption gas, hydrogenation dry gas, and reforming dry gas. Saturated dry gas contains high ethane and propane content, while ethylene and propylene content is very low. Therefore, the composition and application of the concentrated gas after saturated and unsaturated dry gas recovery are very different.

[0004] Ethane is an ideal cracking feedstock. During the steam cracking process, a significant portion is converted into ethylene. Recovering ethane from refinery dry gas and routing it to an ethylene plant not only fully utilizes refinery off-gas resources but also reduces cracking feedstock costs, demonstrating the advantages of integrated refining and chemical operations. As an important organic chemical raw material, directly recovering ethylene from refinery dry gas offers significant economic benefits.

[0005] Currently, the most commonly used methods for refinery dry gas recovery include cryogenic separation, pressure swing adsorption (PSA), and oil absorption. Cryogenic separation is a mature process with high recovery rates, but it requires significant investment and high energy consumption, making it suitable for large-scale dry gas recovery. Pressure swing adsorption offers low energy consumption, but also lower recovery rates, poor operational stability, and high impurity content in the product gas. Oil absorption offers a simple process, stable operation, high recovery rates, and low energy consumption. Each method has its own advantages and disadvantages. Summary of the Invention

[0006] The purpose of the present invention is to provide a method for recovering refinery dry gas by a cryogenic oil absorption method with a simple process, high recovery rate and low energy consumption.

[0007] In order to achieve the above object, the present invention provides a method for recovering refinery dry gas by using a cryogenic oil absorption method, the method comprising:

[0008] (1) performing acid gas removal treatment on refinery dry gas to obtain a first treated gas;

[0009] (2) introducing the first treatment gas into a deoxidation reactor for deoxidation to obtain a second treatment gas;

[0010] (3) cooling and separating the second treated gas into a gas-liquid phase to obtain a third treated gas and a liquid phase stream;

[0011] (4) introducing the third treated gas and the liquid phase stream into the upper middle portion and the lower portion of a demethanizer without a condenser, respectively, for a first separation treatment to obtain a bottom liquid phase I, wherein the temperature of the third treated gas introduced into the demethanizer is -70°C to -110°C;

[0012] (5) introducing the bottom liquid phase I into a deethanizer provided with a partial condenser for a second separation treatment to obtain a bottom liquid phase II;

[0013] (6) introducing the bottom liquid phase II into a debutanizer equipped with a full condenser for a third separation treatment to obtain a top liquid phase I and a bottom liquid phase III that can be used as a light hydrocarbon product; and recycling at least a portion of the top liquid phase I back to the top of the demethanizer as an absorbent.

[0014] The method of the present invention has a simple process, a high recovery rate, and low energy consumption. It can utilize ethylene and propylene refrigerators of an ethylene plant to reduce investment and energy consumption, and is particularly suitable for recovering refinery dry gas in integrated refining and chemical enterprises.

[0015] At the same time, the method of the present invention also has the following advantages:

[0016] (1) In the method of the present invention, after the dry gas is compressed and cooled, the liquid phase stream is dried and directly sent to the demethanizer, which reduces the load of the cold box and saves energy consumption;

[0017] (2) In the method of the present invention, the demethanizer is not provided with a condenser, thereby reducing the consumption of cooling capacity. The light hydrocarbon in the liquid phase at the debutanizer top is used as the absorbent, and no external absorbent is required.

[0018] (3) In the method of the present invention, the required cooling capacity can be utilized by the ethylene and propylene refrigeration compressors of the ethylene plant, without the need for an expander, resulting in low investment and simple operation;

[0019] (4) The method of the present invention adopts cryogenic temperature and oil absorption technology, with low energy consumption and high recovery rate.

[0020] (5) In the method of the present invention, if the feedstock is saturated dry gas, the obtained C2 enriched gas product is ethane-rich gas, which can be directly sent to the cracking furnace of an ethylene plant as a high-quality cracking feed. If the feedstock is unsaturated dry gas, the obtained C2 enriched gas product is ethylene-rich gas, which can be sent to the separation system of an ethylene plant or directly passed through an ethylene distillation tower to obtain polymerization-grade ethylene and high-quality cracking feedstock ethane. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1The present invention is a schematic diagram of a process flow for recovering refinery dry gas by using a cryogenic oil absorption method according to a preferred embodiment of the present invention.

[0022] Description of Reference Numerals

[0023] 1-Compression equipment; 2-Amine scrubber; 3-Alkali scrubber; 4-Deoxygenation reactor; 5-Condenser; 6-Separation tank; 7-Liquid phase dryer; 8-Gas phase dryer; 9-Cold box; 10-Demethanizer; 11-Deethanizer; 12-Debutanizer; 13-Refinery dry gas; 14-Methane hydrogen; 15-C2 concentrated gas; 16-Light hydrocarbon products. DETAILED DESCRIPTION

[0024] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0025] As mentioned above, the present invention provides a method for recovering refinery dry gas by cryogenic oil absorption, the method comprising:

[0026] (1) performing acid gas removal treatment on refinery dry gas to obtain a first treated gas;

[0027] (2) introducing the first treatment gas into a deoxidation reactor for deoxidation to obtain a second treatment gas;

[0028] (3) cooling and separating the second treated gas into a gas-liquid phase to obtain a third treated gas and a liquid phase stream;

[0029] (4) introducing the third treated gas and the liquid phase stream into the upper middle portion and the lower portion of a demethanizer without a condenser, respectively, for a first separation treatment to obtain a bottom liquid phase I, wherein the temperature of the third treated gas introduced into the demethanizer is -70°C to -110°C;

[0030] (5) introducing the bottom liquid phase I into a deethanizer provided with a partial condenser for a second separation treatment to obtain a bottom liquid phase II;

[0031] (6) introducing the bottom liquid phase II into a debutanizer equipped with a full condenser for a third separation treatment to obtain a top liquid phase I and a bottom liquid phase III that can be used as a light hydrocarbon product; and recycling at least a portion of the top liquid phase I back to the top of the demethanizer as an absorbent.

[0032] Preferably, the step of removing acid gas from the refinery dry gas comprises:

[0033] (1a) introducing the refinery dry gas into an amine scrubber to perform acid gas removal treatment I to obtain dry gas I;

[0034] (1b) introducing the dry gas I into an alkali scrubber to perform acid gas removal treatment II to obtain the first treated gas;

[0035] The eluent in the amine washing tower is methyldiethanolamine; the eluent in the alkali washing tower is sodium hydroxide.

[0036] Preferably, the eluents are each independently present in the form of a solution, preferably the concentration of the methyldiethanolamine is 20-40% by mass, and the concentration of the sodium hydroxide is 1-20% by mass.

[0037] Preferably, the eluent is contacted with the dry gas in countercurrent.

[0038] Preferably, before performing step (1), the refinery dry gas is first introduced into a compression device for compression treatment, so that the pressure of the refinery dry gas obtained for acid gas removal treatment is 1.5-2.5 MPa.

[0039] Preferably, in step (1a), the refinery dry gas introduced into the amine scrubber at least meets the following requirements: a pressure of 1.5-2.5 MPa and a temperature of 30-50°C.

[0040] Preferably, the conditions of the acid gas removal treatment I are controlled so that the CO2 concentration of the dry gas I is ≤100 ppm.

[0041] Preferably, the conditions of the acid gas removal treatment II are controlled so that the concentration of CO 2 in the first treatment gas is ≤1 ppm, and the concentration of H 2 S is ≤1 ppm.

[0042] Preferably, in step (2), the first treatment gas introduced into the deoxidation reactor at least meets the following conditions: a pressure of 1.5-4.5 MPa and a temperature of 60-300°C.

[0043] According to a preferred embodiment, the method further comprises: before performing the step (2), introducing the first treatment gas into a compression device for compression treatment, so that the pressure of the first treatment gas introduced into the deoxidation reactor is 2.5-4.5 MPa.

[0044] Preferably, the compression process is two-stage compression or three-stage compression.

[0045] Preferably, the deoxidation treatment conditions include at least: a pressure of 1.5-4.5 MPa and a temperature of 60-300°C.

[0046] Preferably, the deoxygenation reactor is filled with a deoxygenation catalyst so that the O2 concentration of the second process gas is ≤10 ppm.

[0047] The present invention has no particular limitation on the type and loading method of the deoxidation catalyst. Known deoxidation catalysts can be used. The present invention will not be described in detail herein, and those skilled in the art should not interpret this as a limitation on the present invention.

[0048] Preferably, in step (3), the cooling conditions are controlled so that the temperature of the cooled material is 5-30°C.

[0049] Preferably, in step (3), the gas-liquid separation is carried out in a separation tank.

[0050] The present invention has no particular limitation on the operation mode of the gas-liquid separation, and known operations can be adopted. The present invention will not be described in detail here, and those skilled in the art should not understand this as a limitation on the present invention.

[0051] Preferably, in step (4), the first separation treatment is carried out in a medium-pressure demethanizer or a high-pressure demethanizer.

[0052] More preferably, in step (4), the conditions for the first separation treatment include at least: the theoretical plate number of a single tower of the demethanizer is 30-70, the operating pressure is 1.0-4.0 MPa, the top temperature is -60°C to -110°C, and the bottom temperature is -20°C to 50°C.

[0053] Preferably, in step (4), the third treated gas is introduced into a demethanizer without a condenser for a first separation treatment, and a tower top gas phase I is obtained.

[0054] Preferably, the overhead gas phase I is methane hydrogen.

[0055] Preferably, the methane hydrogen at the top of the tower is led out after recovering cold energy in a cold box.

[0056] According to another particularly preferred embodiment, the method further comprises: in step (4), before introducing the third treated gas and the liquid phase stream into the demethanizer respectively, drying the third treated gas and the liquid phase stream respectively.

[0057] More preferably, the steps of drying the third process gas and the liquid phase flow respectively include at least: introducing the third process gas into a gas phase dryer for drying treatment I, and introducing the liquid phase flow into a liquid phase dryer for drying treatment II.

[0058] Preferably, the conditions of the drying process I are controlled so that the water concentration of the third treated gas introduced into the demethanizer is ≤1 ppm.

[0059] Preferably, the conditions of the drying treatment II are controlled so that the water concentration of the liquid phase stream introduced into the demethanizer is ≤1 ppm.

[0060] According to a particularly preferred embodiment, the method further comprises: in step (4), drying the third process gas I and then cooling the third process gas so that the temperature of the third process gas is -70°C to -110°C.

[0061] Preferably, the cooling process is carried out in a cold box.

[0062] More preferably, the refrigerant for the cooling treatment is multi-temperature propylene or ethylene.

[0063] The present invention has no particular limitation on the amount of the refrigerant, which can be adjusted according to the raw materials. The present invention will not be described in detail here, and those skilled in the art should not understand it as a limitation of the present invention.

[0064] Preferably, in step (5), the conditions for the second separation treatment include at least: the theoretical plate number of the deethanizer is 40-80, the operating pressure is 1.5-3.5 MPa, the gas phase temperature after condensation at the top of the tower is -40°C to 10°C, and the bottom temperature is 50-100°C.

[0065] Preferably, the partial condenser aims to achieve partial condensation, which is achieved by controlling the operating parameters in the condenser. After the goal is determined, feasible operating parameters can be implemented in a manner known in the art.

[0066] According to a preferred embodiment, in step (5), the bottom liquid phase I is introduced into a deethanizer equipped with a partial condenser for a second separation treatment, and a top gas phase II is obtained.

[0067] Preferably, the tower top gas phase II is C2 enriched gas.

[0068] Preferably, in step (5), at least a portion of the bottom liquid phase II is withdrawn as a light hydrocarbon product.

[0069] Preferably, in step (6), the conditions of the third separation treatment include at least: the theoretical plate number of the debutanizer is 30-60, the operating pressure is 0.5-1.0 MPa, the temperature of the top liquid phase I is 15-40°C, and the bottom temperature is 90-130°C.

[0070] Preferably, before recycling at least a portion of the top liquid phase I back to the top of the demethanizer as an absorbent, at least a portion of the top liquid phase I is first cooled to -70 to -110° C. in a cold box and then introduced into the top of the demethanizer.

[0071] The present invention has no particular limitation on the amount of the absorbent recycled back to the demethanizer, and any amount known in the art may be used. The present invention will not be described in detail herein, and those skilled in the art should not interpret this as a limitation on the present invention.

[0072] According to a particularly preferred embodiment, the method of the present invention adopts Figure 1 The process shown is carried out, specifically:

[0073] (1) introducing refinery dry gas 13 into compression equipment 1 for compression treatment, and then introducing it into amine scrubber 2 for acid gas removal treatment I to obtain dry gas I, and introducing the dry gas I into alkali scrubber 3 for acid gas removal treatment II to obtain the first treated gas;

[0074] (2) introducing the first treatment gas into the deoxidation reactor 4 for deoxidation to obtain a second treatment gas;

[0075] (3) introducing the second treated gas into the condenser 5 for cooling, and then introducing it into the separation tank 6 for gas-liquid separation to obtain a third treated gas and a liquid phase stream;

[0076] (4) introducing the liquid phase stream into the liquid phase dryer 7 for drying treatment and then introducing it into the demethanizer 10; and introducing the third treated gas into the gas phase drying box 8 and the cold box 9 in sequence for drying and cooling respectively, and then introducing it into the demethanizer 10 for a first separation treatment, to obtain the bottom liquid phase I and methane hydrogen 14;

[0077] (5) introducing the bottom liquid phase I into a deethanizer 11 for a second separation treatment to obtain a bottom liquid phase II and a C2 concentrated gas 15;

[0078] (6) introducing the bottom liquid phase II into the debutanizer 12 for a third separation treatment to obtain a top liquid phase I and a bottom liquid phase III that can be used as a light hydrocarbon product 16; and recycling at least a portion of the top liquid phase I back to the top of the demethanizer 10 as an absorbent.

[0079] The present invention will be described in detail below by way of examples. In the following examples, unless otherwise specified, all raw materials used can be obtained from commercial channels.

[0080] Refinery dry gas: see Table 1 for specific composition and flow rate;

[0081] Table 1

[0082]

[0083]

[0084] Example 1

[0085] The cryogenic oil absorption method of the present invention is used to recover refinery dry gas. The specific process is as follows:

[0086] (1) Refinery dry gas A (pressure of 0.5 MPa) is introduced into a compression device for compression treatment to increase the pressure to 2 MPa, cooled to 40° C., and then introduced into an amine scrubber (eluent: methyldiethanolamine, concentration: 30% by mass) for acid gas removal treatment I to obtain dry gas I; the dry gas I is introduced into an alkali scrubber (eluent: sodium hydroxide, concentration: 5% by mass) for acid gas removal treatment II to obtain the first treated gas;

[0087] (2) The first treatment gas is compressed to 4 MPa and heated to 150° C., and then introduced into a deoxygenation reactor for deoxygenation to obtain a second treatment gas; the deoxygenation treatment is carried out under the following conditions: temperature of 150° C. and pressure of 3.9 MPa;

[0088] (3) introducing the second treated gas into a condenser and cooling it to 15° C., and then introducing it into a separation tank for gas-liquid separation to obtain a third treated gas and a liquid phase stream;

[0089] (4) introducing the liquid phase stream into a liquid phase dryer for drying and then introducing it into the lower part of the demethanizer; and introducing the third treated gas into a gas phase drying oven and a cold box in sequence for drying and cooling to -97°C, respectively, and then introducing it into the middle and upper part of the demethanizer for a first separation treatment to obtain a bottom liquid phase I and methane hydrogen, and the methane hydrogen is sent out after recovering the cold in the cold box; the demethanizer has a single tower theoretical plate number of 52, an operating pressure of 3.1 MPa, a tower top temperature of -89°C, and a tower bottom temperature of 48°C;

[0090] (5) introducing the bottom liquid phase I into a deethanizer (the theoretical plate number of the deethanizer is 63, the operating pressure is 2.4 MPa, the gas phase temperature after the top condensation is -9°C, and the bottom temperature is 88°C) for a second separation treatment to obtain the bottom liquid phase II and the C2 enriched gas (ethane-rich gas), and a portion of the bottom liquid phase II is sent out as a light hydrocarbon product;

[0091] (6) introducing the remaining portion of the bottom liquid phase II into a debutanizer (the number of theoretical plates of the debutanizer is 33, the operating pressure is 0.7 MPa, the temperature of the top liquid phase I is 23° C., and the bottom temperature is 106° C.) for a third separation treatment to obtain the top liquid phase I and the bottom liquid phase III that can be used as a light hydrocarbon product; and recycling at least a portion of the top liquid phase I back to the top of the demethanizer as an absorbent.

[0092] The composition of the outflow device is shown in Table 2.

[0093] Table 2

[0094] C2 enriched gas Methane hydrogen Light hydrocarbon products Mass flow rate KG / hr 40854 48126 42556 Molar composition (%) hydrogen 0 55.93 0 Nitrogen 0 6.13 0 oxygen 0 0 0 carbon monoxide 0 0.42 0 carbon dioxide 0 0 0 methane 0 36.89 0 Ethane 99.00 0.25 0.19 Propane 1.00 0.35 57.40 Isobutane 0 0.02 20.27 n-butane 0 0.01 10.04 Pentane 0 0 8.97 Hexane 0 0 3.13 water 0 0 0

[0095] As can be seen from Table 2, in the method of the present invention, the recovery rate of carbon dioxide in the carbon dioxide enriched gas is greater than 98.5%, and the energy consumption is 68 kg standard oil / t raw material.

[0096] Example 2

[0097] The cryogenic oil absorption method of the present invention is used to recover refinery dry gas. The specific process is as follows:

[0098] (1) Refinery dry gas B (pressure of 0.6 MPa) is introduced into a compression device for compression treatment to increase the pressure to 2.2 MPa, cooled to 45° C., and then introduced into an amine scrubber (eluent: methyldiethanolamine, concentration: 25% by mass) for acid gas removal treatment I to obtain dry gas I; the dry gas I is introduced into an alkaline scrubber (eluent: sodium hydroxide, concentration: 7% by mass) for acid gas removal treatment II to obtain the first treated gas;

[0099] (2) heating the first treatment gas to 130° C. and introducing the first treatment gas into a deoxygenation reactor for deoxygenation to obtain a second treatment gas; the deoxygenation treatment conditions are: temperature 130° C., pressure 2.1 MPa;

[0100] (3) introducing the second treated gas into a condenser for cooling to 20° C., and then introducing the second treated gas into a separation tank for gas-liquid separation to obtain a third treated gas and a liquid phase stream;

[0101] (4) introducing the liquid phase stream into a liquid phase dryer for drying and then introducing it into the lower part of the demethanizer; and introducing the third treated gas into a gas phase drying oven and a cold box in sequence for drying and cooling to -85°C, respectively, and then introducing it into the middle and upper part of the demethanizer for a first separation treatment to obtain a bottom liquid phase I and methane hydrogen, and the methane hydrogen is sent out after recovering the cold in the cold box; the demethanizer has a single tower theoretical plate number of 54, an operating pressure of 1.4 MPa, a tower top temperature of -72°C, and a tower bottom temperature of 24°C;

[0102] (5) introducing the bottom liquid phase I into a deethanizer (the theoretical plate number of the deethanizer is 68, the operating pressure is 2.3 MPa, the gas phase temperature after the top condensation is -12°C, and the bottom temperature is 85°C) for a second separation treatment to obtain the bottom liquid phase II and the C2 enriched gas (ethylene-rich gas), and a portion of the bottom liquid phase II is sent out as a light hydrocarbon product;

[0103] (6) introducing the remaining portion of the bottom liquid phase II into a debutanizer (theoretical plate number of the debutanizer is 43, the operating pressure is 0.6 MPa, the temperature of the top liquid phase I is 24° C., and the bottom temperature is 120° C.) for a third separation treatment to obtain the top liquid phase I and the bottom liquid phase III that can be used as a light hydrocarbon product; and recycling at least a portion of the top liquid phase I back to the top of the demethanizer as an absorbent.

[0104] The composition of the logistics out of the device is shown in Table 3.

[0105] Table 3:

[0106]

[0107]

[0108] As can be seen from Table 3, in the method of the present invention, the recovery rate of carbon dioxide in the carbon dioxide enriched gas is greater than 98.4%, and the energy consumption is 76 kg standard oil / t raw material.

[0109] Comparative Example 1

[0110] Comparative Example 1 was carried out using a process similar to that of Example 1, except that:

[0111] Step (6), that is, the third separation treatment is not performed, and the bottom liquid phase II obtained after the second separation treatment is directly drawn out as a light hydrocarbon product.

[0112] The composition of the logistics out of the device is shown in Table 4.

[0113] Table 4:

[0114]

[0115]

[0116] As can be seen from Table 4, the carbon dioxide recovery rate in the carbon dioxide enriched gas of this comparative example is only 88%.

[0117] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A method for recovering refinery dry gas by cryogenic oil absorption, characterized in that: The method includes: (1) Removing acid gas from the refinery dry gas to obtain a first treated gas; The acid gas removal treatment step includes: (1a) introducing the refinery dry gas into an amine scrubber for acid gas removal treatment I to obtain dry gas I; (1b) introducing the dry gas I into an alkaline scrubber to perform acid gas removal treatment II to obtain the first treated gas; The eluent in the amine washing tower is methyldiethanolamine; the eluent in the alkali washing tower is sodium hydroxide; (2) introducing the first treatment gas into a deoxygenation reactor for deoxygenation to obtain a second treatment gas; (3) cooling and separating the second treated gas into a gas-liquid phase to obtain a third treated gas and a liquid phase stream; (4) introducing the third treated gas and the liquid phase stream into the upper middle portion and the lower portion of a demethanizer without a condenser, respectively, for a first separation treatment to obtain a bottom liquid phase I, wherein the temperature of the third treated gas introduced into the demethanizer is -70°C to -110°C; (5) introducing the bottom liquid phase I into a deethanizer equipped with a partial condenser for a second separation treatment to obtain a bottom liquid phase II; (6) introducing the bottom liquid phase II into a debutanizer equipped with a full condenser for a third separation treatment to obtain a top liquid phase I and a bottom liquid phase III that can be used as a light hydrocarbon product; and recycling at least a portion of the top liquid phase I back to the top of the demethanizer as an absorbent.

2. The method according to claim 1, wherein In step (1a), the refinery dry gas introduced into the amine scrubber at least meets the following requirements: a pressure of 1.5-2.5 MPa and a temperature of 30-50°C.

3. The method according to claim 1 or 2, wherein: The conditions of the acid gas removal treatment I are controlled so that the CO2 concentration of the dry gas I is ≤100 ppm.

4. The method according to claim 1 or 2, wherein: The conditions of the acid gas removal treatment II are controlled so that the concentration of CO 2 in the first treatment gas is ≤1 ppm and the concentration of H 2 S is ≤1 ppm.

5. The method according to claim 1 or 2, wherein: In step (2), the first treatment gas introduced into the deoxidation reactor at least meets the following conditions: a pressure of 1.5-4.5 MPa and a temperature of 60-300°C.

6. The method according to claim 5, wherein: The method further includes: before performing the step (2), introducing the first treatment gas into a compression device for compression treatment, so that the pressure of the first treatment gas introduced into the deoxidation reactor is 2.5-4.5 MPa.

7. The method according to claim 6, wherein: The compression process is two-stage compression or three-stage compression.

8. The method according to claim 1 or 2, wherein: In step (3), the cooling conditions are controlled so that the temperature of the cooled material is 5-30°C.

9. The method according to claim 1 or 2, wherein: In step (3), the gas-liquid separation is carried out in a separation tank.

10. The method according to claim 1 or 2, wherein: In step (4), the first separation treatment is carried out in a medium-pressure demethanizer or a high-pressure demethanizer.

11. The method according to claim 10, wherein: In step (4), the conditions of the first separation treatment include at least: the number of theoretical plates of the demethanizer is 30-70, the operating pressure is 1.0-4.0 MPa, the top temperature is -60°C to -110°C, and the bottom temperature is -20°C to 50°C.

12. The method according to claim 1 or 2, wherein: The method further includes: in step (4), before introducing the third treated gas and the liquid phase flow into the demethanizer respectively, drying the third treated gas and the liquid phase flow respectively.

13. The method according to claim 1 or 2, wherein: In step (5), the conditions for the second separation treatment include at least: the theoretical plate number of the deethanizer is 40-80, the operating pressure is 1.5-3.5 MPa, the gas phase temperature after condensation at the top of the tower is -40°C to 10°C, and the bottom temperature is 50-100°C.

14. The method according to claim 1 or 2, wherein: In step (6), the conditions of the third separation treatment include at least: the theoretical plate number of the debutanizer is 30-60, the operating pressure is 0.5-1.0 MPa, the temperature of the top liquid phase I is 15-40°C, and the bottom temperature is 90-130°C.

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