Light component separation system and method for ethane oxidative dehydrogenation product gas

Abstract

The present invention discloses an ethane oxidative dehydrogenation product gas light component separation system, which comprises: a low temperature condensation unit for primarily cooling an ethane oxidative dehydrogenation product gas to obtain a product gas condensate and a first light component; the crude product separation unit is connected with the low-temperature condensation unit and is used for preliminarily separating the product gas condensate and obtaining an ethylene product crude liquid and a second light component; the heat exchange unit is respectively connected with the low-temperature condensation unit and the crude product separation unit and is used for pre-cooling the second light component and the first light component in the low-temperature condensation unit; and the ethylene recovery unit is connected with the heat exchange unit and is used for secondarily separating the pre-cooled second light component and residual ethylene product recovery liquid in the first light component. A product gas light component separation system comprising key equipment such as a low-temperature condensation unit, a light component removal tower, a low-temperature heat exchanger and an ethylene recovery tower is adopted to separate product gas from an ethane oxidative dehydrogenation device, and the method has the advantages of short whole process flow, strong process coupling, high energy utilization rate, high ethylene yield and the like.

Description

Technical Field

[0001] The invention relates to the field of separation of light component mixtures of gaseous product gases, and in particular to a system and method for separating light components of ethane oxidative dehydrogenation product gases. Background Art

[0002] Due to the huge market demand for ethylene at home and abroad, many production facilities using ethane as raw material and ethane dehydrogenation to ethylene technology are being planned, constructed and operated. In the ethylene production process, the process technology of ethane oxidative dehydrogenation using ethane as raw material has the advantages of low reaction temperature, short process and low energy consumption. It is currently a new ethylene production technology. Since the raw material ethane itself contains and the ethane oxidative dehydrogenation process will produce light components such as methane and CO. In order to ensure the purity of the product ethylene, the light components in the ethane oxidative dehydrogenation product gas need to be separated.

[0003] At present, there is no specific technical solution for the light component separation process of ethane oxidative dehydrogenation device. Patent CN113166003A discloses a separation technology process for ethane oxidative dehydrogenation product gas, but it mainly discloses a simple process separation scheme for obtaining ethylene products by compressing and separating the product gas, but does not study the specific scheme for separating light components in the product gas.

[0004] In the light component separation technology scheme of similar devices (such as naphtha cracking to ethylene, ethane cracking to ethylene or coal to olefins process devices), it is generally necessary to separate the light components in the ethylene product gas. In this separation process, a single or double demethanizer is used to separate the light components, and cryogenic distillation technology is used to liquefy all components except methane and hydrogen in the product gas, and separate the light components (methane, hydrogen) from other components. At present, pre-cooling is often used in the deep cold separation process of ethylene devices, that is, the cold box is before the demethanizer, but this process also has many influencing factors and unstable system operation conditions, which will cause an increase in ethylene loss, thereby affecting the ethylene yield of the device.

[0005] Patent CN110407658B discloses a low-energy consumption ethane cracking gas deep cold separation process, but it needs to use mixed refrigerant refrigeration in the light component separation process and does not carry out the ethylene product recovery process, which has the problems of complex process flow, high energy consumption and low ethylene product yield. In addition, due to the different product gas composition and operating conditions, this process technology is not suitable for the separation of ethane oxidative dehydrogenation product gas. Patent CN113943200A discloses a methanol to olefin light hydrocarbon recovery part cold separation unit and its light hydrocarbon separation method. This process technology is mainly suitable for the separation of light components of product gas obtained by methanol to olefins, and the entire process flow is complex and the energy utilization efficiency is low. The above process technologies all use raw gas obtained by thermal cracking of naphtha, ethane cracking or coal-to-olefins. The light components of the product gas contain a lot of hydrogen. The entire separation system is not well suitable for separating the light components of the ethane oxidative dehydrogenation product gas. In addition, the above separation schemes all use deep cold refrigeration systems using methane as the refrigerant medium for the demethanizer or ethylene recovery process, which has the disadvantages of complex entire process flow, large number of equipment, and high energy consumption.

[0006] It can be seen that for the separation process of light components in the product gas of ethane oxidative dehydrogenation, how to propose a light component separation process technology with the characteristics of short process flow, small number of equipment, high energy utilization rate, and high ethylene product recovery rate is of great significance in the ethane oxidative dehydrogenation unit. Summary of the invention

[0007] In order to solve the problems existing in the prior art, the present invention mainly aims at the separation problem of light components in ethylene product gas of ethane oxidative dehydrogenation process. In order to ensure the purity and yield of product ethylene, the product gas of ethane oxidative dehydrogenation device is used as raw material, and the light components in the product gas are efficiently removed through low-temperature multi-stage condensation, distillation, gas-liquid separation and other processes. Moreover, by optimizing the design of the entire ethane oxidative dehydrogenation light component separation process, the removal efficiency of the light components is guaranteed and the recovery rate of the ethylene product is improved. The whole process has the characteristics of strong process coupling, short process flow, small number of equipment, high energy utilization efficiency and high ethylene yield, and the product ethylene yield can be achieved to be above 99.0%.

[0008] In a first aspect, the present invention provides a light component separation system for ethane oxidative dehydrogenation product gas, comprising:

[0009] A low temperature condensation unit, used for preliminary cooling of the ethane oxidative dehydrogenation product gas to obtain a crude product gas condensate and a first light component;

[0010] A crude product separation unit, which is connected to the low-temperature condensation unit and is used to preliminarily separate the crude product gas condensate and obtain the ethylene product crude liquid and the second light component;

[0011] a heat exchange unit, which is connected to the cryogenic condensation unit and the crude product separation unit, respectively, and is used for precooling the second light component and the first light component in the cryogenic condensation unit;

[0012] The ethylene recovery unit is connected to the heat exchange unit and is used for secondary separation of the second light component after pre-cooling and the remaining ethylene product recovery liquid in the first light component.

[0013] Furthermore, the low-temperature condensation unit and the heat exchange unit both include a low-temperature heat exchanger; the crude product separation unit includes a light-removal tower; and the ethylene recovery unit includes an ethylene recovery tower.

[0014] A light component removal tower and an ethylene recovery tower are used to remove light components from the ethane oxidative dehydrogenation product gas, while increasing the product ethylene yield, which can achieve an ethylene yield of more than 99.0%. A low-temperature heat exchanger is used to condense the feed gas of the ethylene recovery tower using the low-temperature light component exhaust gas, which can effectively reduce the condensation load at the top of the ethylene refining tower, while achieving energy coupling between logistics and maximizing the use of low-temperature cooling capacity in process logistics.

[0015] Furthermore, the low-temperature condensation unit includes at least two low-temperature heat exchangers and two gas-liquid separation tanks, the heat exchange interval temperature is -130 to 20°C, and the condensation stages include 2 to 8 stages. Through the multi-stage low-temperature condensation unit, the ethane oxidative dehydrogenation product gas is condensed at different temperatures, realizing the rational use of low-temperature cooling capacity.

[0016] Furthermore, the low-temperature cold source of the low-temperature heat exchanger includes at least one of propylene refrigerant, ethylene refrigerant, methane refrigerant, and binary or ternary composite refrigerant of propylene / ethylene / methane.

[0017] Furthermore, a lightness removal tower reboiler is also provided outside the lightness removal tower.

[0018] Furthermore, a lightness removal tower reflux tank is provided outside the lightness removal tower, two passages are provided between the lightness removal tower reflux tank and the lightness removal tower, a lightness removal tower condenser is provided on the outlet of the lightness removal tower, and a lightness removal tower reflux pump is provided on the inlet of the lightness removal tower; an ethylene recovery tower reflux tank is provided outside the ethylene recovery tower, two passages are provided between the ethylene recovery tower reflux tank and the ethylene recovery tower, an ethylene recovery tower condenser is provided on the outlet of the ethylene recovery tower, and an ethylene recovery tower reflux pump is provided on the inlet of the ethylene recovery tower.

[0019] Furthermore, the reflux tank of the light-removal tower is also connected to the low-temperature heat exchanger of the heat exchange unit and is simultaneously connected to the ethylene recovery tower.

[0020] Furthermore, it also includes an expander, which can expand the light component gas at the top of the ethylene recovery tower, and use the expanded low-temperature logistics as a cold source for the top of the ethylene recovery tower. This process technology solves the problem of low-temperature cold sources in the ethylene recovery process, and does not require the use of external low-temperature cold sources and deep-cold refrigeration systems. It realizes efficient thermal coupling inside the product gas light component separation system, simplifies the process flow, and improves the efficiency of cold utilization.

[0021] Further heat exchanger types of the ethylene recovery tower condenser include shell and tube heat exchangers or plate heat exchangers.

[0022] Furthermore, the lightness removal tower comprises a plate tower or a packed tower, the operating pressure comprises 0.5 to 5.0 MPaG, the operating temperature comprises -130°C to 20°C, and the number of theoretical plates is 30 to 50.

[0023] Furthermore, the ethylene recovery tower comprises a plate tower or a packed tower, the operating pressure comprises 0.5 to 4.0 MPaG, the operating temperature comprises -160°C to -60°C, and the number of theoretical plates is 5 to 25.

[0024] The second object of the present invention is to provide a method for separating light components from ethane oxidative dehydrogenation product gas, comprising the following steps:

[0025] S1: After the ethane oxidative dehydrogenation product gas is subjected to low-temperature multi-stage condensation, a cooling liquid phase material and a first light component are obtained;

[0026] S2: The product gas condensate is subjected to the first distillation treatment to obtain the ethylene product crude liquid and the second light component;

[0027] S3: the first light component and the second light component are mixed, pre-cooled and subjected to a second distillation treatment to obtain ethylene recovery liquid and a third light component;

[0028] S4: The third light component is expanded and cooled, and is used as a cold source at the top of the ethylene recovery tower to perform the first cold recovery to obtain the third light component after heat exchange;

[0029] S5: After heat exchange, the third light component undergoes a second cooling recovery and a third cooling recovery in sequence to obtain a light component tail gas.

[0030] Beneficial effects:

[0031] The present invention separates the product gas from the ethane oxidative dehydrogenation device by adopting a product gas light component separation system including key equipment such as a low-temperature condensing unit, a light component removal tower, a low-temperature heat exchanger, an ethylene recovery tower, etc., thereby overcoming the problems of difficulty in separating light components from ethylene products in the product gas, low ethylene product yield, poor light component impurity removal effect, etc., and has the advantages of short overall process flow, high energy utilization rate, high ethylene yield, etc.; and removes the light components in the ethane oxidative dehydrogenation product gas through a light component removal tower and an ethylene recovery tower, thereby achieving efficient separation of the light components in the ethane oxidative dehydrogenation product gas, while ensuring the product ethylene yield, and achieving an ethylene yield of more than 99.0%. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 : Layout of the process unit of the ethane oxidative dehydrogenation light component separation system in Example 1;

[0033] Figure 2 : Layout of the process unit of the ethane oxidative dehydrogenation light component separation system in Example 2;

[0034] Figure 3 : Layout of the process unit of the ethane oxidative dehydrogenation light component separation system in Example 3;

[0035] Figure 4 : Layout of the process flow of the ethane oxidative dehydrogenation light component separation system in Example 4.

[0036] In the figure: 1-product gas from ethane oxidative dehydrogenation unit, 2-cryogenic condensing unit, 3-light-removal tower, 4-cryogenic heat exchanger, 5-light-removal tower reboiler, 6-ethylene product crude liquid, 7-light-removal tower condenser, 8-light-removal tower reflux tank, 9-light-removal tower reflux pump, 10-ethylene recovery tower reflux tank, 11-ethylene recovery tower, 12-ethylene recovery tower condenser, 13-expander, 14-ethylene recovery tower reflux pump, 15-light component tail gas. DETAILED DESCRIPTION

[0037] If the specific conditions are not specified in the examples, the experiments were carried out under conventional conditions or conditions recommended by the manufacturer. If the manufacturers of the reagents or instruments are not specified, they are all conventional products that can be purchased from the market.

[0038] The endpoints and any values ​​of the ranges disclosed in this article 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 endpoint values ​​of each range, the endpoint values ​​of each range and the 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 as specifically disclosed in this article.

[0039] For the purpose of this specification and the appended claims, unless otherwise stated, all numbers expressing amounts, percentages or ratios and other numerical values ​​used in this specification and the appended claims are understood to be modified in all cases by the term "about". In addition, all ranges disclosed herein are inclusive and independently combinable.

[0040] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below.

[0041] The present invention provides a light component separation system for ethane oxidative dehydrogenation product gas, comprising:

[0042] A low temperature condensation unit, used for preliminary cooling of the ethane oxidative dehydrogenation product gas to obtain a product gas condensate and a first light component;

[0043] A crude product separation unit, which is connected to the low-temperature condensation unit and is used to preliminarily separate the product gas condensate and obtain the ethylene product crude liquid and the second light component;

[0044] a heat exchange unit, which is connected to the cryogenic condensation unit and the crude product separation unit, respectively, and is used for precooling the second light component and the first light component in the cryogenic condensation unit;

[0045] The ethylene recovery unit is connected to the heat exchange unit and is used for secondary separation of the second light component after pre-cooling and the remaining ethylene product recovery liquid in the first light component.

[0046] In consideration of separation efficiency, equipment expenditure cost and process complexity, the low-temperature condensation unit and the heat exchange unit in the present invention both include a low-temperature heat exchanger; the crude product separation unit includes a light component removal tower; and the ethylene recovery unit includes an ethylene recovery tower. The product gas from the ethane dehydrogenation unit is separated by a product gas light component separation system including key equipment such as a light component removal tower, a low-temperature heat exchanger, and an ethylene recovery tower, which has the advantages of a short overall process flow, high energy utilization, and high ethylene yield, wherein the ethylene recovery rate can reach more than 99.0%.

[0047] The low-temperature condensation unit includes at least two low-temperature heat exchangers and two gas-liquid separation tanks, the heat exchange interval temperature is -130 to 20°C, and the condensation stages include 2 to 8 stages. The low-temperature cold source of the low-temperature heat exchanger includes at least one of propylene refrigerant, ethylene refrigerant, methane refrigerant, and binary or ternary composite refrigerant of propylene / ethylene / methane. A light-removal tower reboiler is also provided outside the light-removal tower.

[0048] Example 1

[0049] like Figure 1As shown, in this embodiment, a light component separation system for ethane oxidative dehydrogenation product gas is provided, wherein the crude product gas 1 after reaction and pretreatment in the ethane oxidative dehydrogenation device is passed into a low-temperature condensation unit 2 through a pipeline, and the low-temperature condensation unit 2 includes at least 2 low-temperature heat exchangers and 2 gas-liquid separation tanks, the heat exchange interval temperature is -104°C to 13°C, and the number of condensation stages includes 3 stages. An outlet passage of the low-temperature condensation unit 2 is connected to a light removal tower 3, which is used to transport the condensed crude product condensate to the light removal tower 3 for distillation and separation. The bottom of the light removal tower 3 is provided with a light removal tower reboiler 5 connected to the light removal tower 3 in a closed loop and an outlet pipeline of an ethylene product crude liquid 6, and the outlet pipeline is connected to a subsequent refining unit; the top of the light removal tower 3, the light removal tower condenser 7, the light removal tower reflux tank 8 and the light removal tower reflux pump 9 are also connected by a closed-loop pipeline. The light removal tower reflux tank 8 is also connected to the pipeline from the low-temperature condensation unit 2, and is also connected to the low-temperature heat exchanger 4 pipeline, which is used to mix the first light component in the low-temperature condensation unit 2 and the second light component separated by the light removal tower 3 to form a light component mixed gas condensation. The low-temperature heat exchanger 4 is also connected to the ethylene recovery tower 11 through a pipeline, and the condensed light component mixed gas is further distilled and recovered for ethylene. The recovered ethylene recovery liquid is refluxed to the light removal tower through the pipeline connected to the light removal tower reflux tank 8 of the tower kettle of the ethylene recovery tower 11 through the light removal tower reflux tank 8-light removal tower reflux pump 9-light removal tower 3 to the light removal tower for product distillation separation; the top of the ethylene recovery tower 11, the ethylene recovery tower condenser 12, the ethylene recovery tower reflux tank 10 and the ethylene recovery tower reflux pump 14 are connected in a closed loop pipeline, which is used to condense the third light component and reflux it to the ethylene recovery tower 11 again for distillation and separation again. An expansion machine 13 is additionally provided between the ethylene recovery tower reflux tank 10 and the ethylene recovery tower condenser 12. The third light component is expanded and cooled by the expansion machine 13 as a cold source for the ethylene recovery tower condenser 12, and the gas phase at the top of the ethylene tower is condensed and refluxed. The third light component finally heat-exchanged from the ethylene recovery tower condenser 12 enters the low-temperature heat exchanger (4) for the second cold recovery. The third light component after the second heat exchange is sent to the low-temperature cooling system (2) for the third cold recovery. The light component gas 15 rich in CO, N2, and methane obtained at last can be sent out as fuel gas or by-product.

[0050] Example 2

[0051] like Figure 2 As shown, in this embodiment, the difference from Embodiment 1 is that the lightness removal tower 3 and the ethylene recovery tower 11 are stacked to reduce the floor space.

[0052] Example 3

[0053] like Figure 3As shown, in this embodiment, the difference from Embodiment 1 is that the condenser of the ethylene recovery tower is placed above the ethylene recovery tower, so that the condenser at the top of the ethylene refining tower is coupled with the ethylene recovery tower, simplifying the process flow of the ethylene recovery tower.

[0054] Example 4

[0055] like Figure 4 As shown, in this embodiment, the difference from Example 1 is that the ethylene recovery tower condenser is placed above the ethylene recovery tower, which simplifies the process flow of the ethylene recovery tower, and the entire ethylene recovery tower is placed on the top of the light removal tower, reducing the footprint of the entire device.

[0056] Test Example 1

[0057] like Figure 1 As shown, this test example uses the separation system flow chart described in Example 1, and uses the product gas of 500,000 tons / year ethane oxidative dehydrogenation unit as raw material for simulation testing. The typical product gas feed conditions (15°C, 2.4MpaG, 3944kmol / h) are as shown in the following table:

[0058] Table 1 Main composition of product gas feed of typical ethane oxidative dehydrogenation unit

[0059] composition Content (mass%) <![CDATA[H2]]> 0.01～1.0％ CO 5.0～11.0％ <![CDATA[N2]]> 1.5～2.5％ Methane 3.5～5.0％ Ethylene 40.0～56.0％ Ethane 30.0～45.0％ C3 and above components 1.0～5.0％

[0060] by Figure 1 For example, a specific process scheme of a light component separation process and method for ethane oxidative dehydrogenation product gas is as follows: the crude product gas 1 after reaction and pretreatment in the ethane oxidative dehydrogenation device first enters the low-temperature condensation unit 2.

[0061] In the low temperature condensation unit 2, propylene refrigeration and ethylene refrigeration units are used to provide cooling capacity from -104℃ to 13℃ for product gas cooling. According to the different temperature positions and heat exchange schemes, the step-by-step condensation stages in this test example are 3 stages, and the liquid condensed from the product gas and the uncondensed first light component at 3 different temperatures are obtained. The specific compositions are shown in Tables 2 and 3.

[0062] Table 2 Product gas condensate material composition

[0063] Composition (mass%) Condensate 1 Condensate 2 Condensate 3 <![CDATA[H2]]> 0.00％ 0.00％ 0.00％ CO 1.45％ 2.91％ 6.55％ <![CDATA[N2]]> 0.02％ 0.05％ 0.11％ Methane 0.13％ 0.24％ 0.51％ Ethylene 52.69％ 60.09％ 65.58％ Ethane 38.02％ 34.23％ 26.71％ C3 and above components 7.69％ 2.48％ 0.54％

[0064] In this test example, the light-removal tower 3 is a plate tower with an operating pressure of 2.2 MPaG and a theoretical plate number of 45. The liquid of the crude product gas condensate obtained by condensation at different temperatures is sequentially sent to the light-removal tower 3, where light component liquids such as CO and methane are removed by distillation separation. The ethylene product crude liquid 6 is obtained in the bottom of the light-removal tower 3 (3483 kmol / h) and sent to the subsequent refining unit, while the second light component is obtained at the top of the light-removal tower 3. The composition of the second light component is shown in Table 3.

[0065] Table 3 Light component gas composition

[0066] Composition (mass%) The first light component The second light component The third light component <![CDATA[H2]]> 0.02％ 0.00％ 0.02％ CO 63.19％ 81.54％ 93.00％ <![CDATA[N2]]> 1.22％ 1.37％ 1.74％ Methane 1.41％ 8.50％ 3.50％ Ethylene 27.66％ 8.08％ 1.72％ Ethane 6.48％ 0.49％ 0.02％ C3 and above components 0.02％ 0.02％ 0.00％

[0067] The ethylene recovery tower 11 is a plate tower with an operating pressure of 2.05MPaG and a theoretical plate number of 10. The first light component and the second light component are mixed and cooled to -105°C by the low-temperature heat exchanger 4 before entering the ethylene recovery tower 11. The ethylene recovery liquid obtained from the bottom of the ethylene recovery tower 11 is returned to the reflux tank 8 at the top of the light removal tower to realize product ethylene recovery. The third light component (461kmol / h, composition see Table 3) obtained at the top of the ethylene recovery tower 11 is expanded to (-159.6°C, 0.45MPaG) by the expander 13 and then used as the cold source at the top of the ethylene recovery tower 11. The first cold recovery is performed to condense and reflux the gas phase at the top of the ethylene recovery tower 11. The third light component tail gas after heat exchange enters the low temperature heat exchanger 4 for the second cold recovery, and then is sent to the low temperature condensation unit 2 for the third cold recovery. The light component gas 15 rich in CO, N2, and methane can be sent out as fuel gas or by-product. Through this process, the light component content in the ethylene crude liquid obtained at the bottom of the light component tower is less than 0.02%, and the ethylene yield reaches more than 99.0%.

[0068] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A light component separation system for ethane oxidative dehydrogenation product gas, characterized in that: include: A low temperature condensation unit, used for preliminarily condensing the raw product gas of ethane oxidative dehydrogenation to obtain raw product gas condensate and a first light component; A crude product separation unit, connected to the cryogenic condensation unit, is used to preliminarily separate the crude product gas condensate and obtain the ethylene product crude liquid and the second light component; a heat exchange unit, which is connected to the cryogenic condensation unit and the crude product separation unit, respectively, and is used for precooling the second light component and the first light component in the cryogenic condensation unit; The ethylene recovery unit is connected to the heat exchange unit and is used for secondary separation of the second light component after pre-cooling and the remaining ethylene product recovery liquid in the first light component.

2. The light component separation system of ethane oxidative dehydrogenation product gas according to claim 1, characterized in that: The low-temperature condensing unit and the heat exchange unit both include a low-temperature heat exchanger; And / or, the crude product separation unit comprises a lightness removal tower; And / or, the ethylene recovery unit comprises an ethylene recovery tower.

3. The light component separation system of ethane oxidative dehydrogenation product gas according to claim 2 is characterized in that: The low-temperature condensation unit includes multiple low-temperature heat exchangers and gas-liquid separation tanks to perform multi-stage low-temperature condensation and gas-liquid separation at different temperatures on the ethane oxidative dehydrogenation product gas. The heat exchange interval temperature is -130 to 20°C, and the condensation stages include 2 to 8 stages.

4. The light component separation system of ethane oxidative dehydrogenation product gas according to claim 2, characterized in that: The low-temperature cold source of the low-temperature heat exchanger includes at least one of propylene refrigerant, ethylene refrigerant, methane refrigerant and binary or ternary composite refrigerant of propylene / ethylene / methane.

5. The light component separation system of ethane oxidative dehydrogenation product gas according to claim 2, characterized in that: A lightness removal tower reboiler is also provided outside the lightness removal tower.

6. The light component separation system of ethane oxidative dehydrogenation product gas according to claim 2, characterized in that: A lightness removal tower reflux tank is also provided outside the lightness removal tower, an outlet and an inlet passage are provided between the lightness removal tower reflux tank and the lightness removal tower, a lightness removal tower condenser is provided on the outlet passage of the lightness removal tower, and a lightness removal tower reflux pump is provided on the inlet passage of the lightness removal tower; And / or, an ethylene recovery tower reflux tank is further provided outside the ethylene recovery tower, an outlet and an inlet passage are provided between the ethylene recovery tower reflux tank and the ethylene recovery tower, an ethylene recovery tower condenser is provided on the outlet passage of the ethylene recovery tower, and an ethylene recovery tower reflux pump is provided on the inlet passage of the ethylene recovery tower; preferably, the heat exchanger type of the ethylene recovery tower condenser includes a shell and tube heat exchanger or a plate heat exchanger.

7. The light component separation system of ethane oxidative dehydrogenation product gas according to claim 6, characterized in that: The reflux tank of the light-removal tower is also connected to the low-temperature heat exchanger of the heat exchange unit and is simultaneously connected to the ethylene recovery tower.

8. The light component separation system of ethane oxidative dehydrogenation product gas according to claim 2, characterized in that: The system also includes an expander, which expands and cools the light component gas at the top of the ethylene recovery tower to obtain lower temperature cooling capacity.

9. The light component separation system of ethane oxidative dehydrogenation product gas according to any one of claims 2 to 8, characterized in that: The light-removal tower comprises a plate tower or a packed tower, the operating pressure comprises 0.5 to 5.0 MPaG, the operating temperature comprises -130°C to 20°C, and the number of theoretical plates is 30 to 50; And / or, the ethylene recovery tower comprises a plate tower or a packed tower, the operating pressure comprises 0.5 to 4.0 MPaG, the operating temperature comprises -160°C to -60°C, and the number of theoretical plates is 5 to 25.

10. A method for separating light components from ethane oxidative dehydrogenation product gas, characterized in that: The following steps are involved: S1: The crude product gas after ethane oxidative dehydrogenation is subjected to low-temperature multi-stage condensation to obtain a crude product gas condensate and a first light component; S2: The crude product gas condensate is subjected to the first distillation treatment to obtain the ethylene product crude liquid and the second light component; S3: the first light component and the second light component are mixed, pre-cooled and subjected to a second distillation treatment to obtain ethylene recovery liquid and a third light component; S4: The third light component is expanded and cooled, and is used as a cold source at the top of the ethylene recovery tower to perform the first cold recovery to obtain the third light component after heat exchange; S5: After heat exchange, the third light component undergoes a second cooling recovery and a third cooling recovery in sequence to obtain a light component tail gas.

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