A method and device for pre-treating the raw material of refinery dry gas disproportionation to produce propylene, and a method and system for producing propylene from refinery dry gas

Abstract

The present invention belongs to the field of refinery dry gas treatment, and discloses a method and device for pre-treating the raw material of refinery dry gas disproportionation to produce propylene, as well as a method and system for producing propylene from refinery dry gas. The device includes a dry gas absorption tower, a first desorption tower, and a second desorption tower that are connected in sequence; the top of the dry gas absorption tower is connected to a hydrogen-rich dry gas discharge pipeline and a first recycled C4 feed pipeline; the bottom of the dry gas absorption tower is connected to a refinery dry gas feed pipeline; the top of the first desorption tower is connected to a hydrogen-lean dry gas discharge pipeline and a second recycled C4 feed pipeline; the top of the second desorption tower is connected to an ethylene-rich dry gas discharge pipeline and a fresh C4 feed pipeline. The present invention can remove hydrogen, oxygen, nitrogen, carbon monoxide, methane, propane, and propylene in the refinery dry gas, and the obtained ethylene-rich dry gas meets the raw material feed index requirements for the disproportionation of dilute ethylene to produce propylene.

Description

Technical Field

[0001] The present invention belongs to the field of refinery dry gas processing, and more specifically, relates to a raw material pretreatment method and device for producing propylene by disproportionation of refinery dry gas, and a method and system for producing propylene by refinery dry gas. Background Art

[0002] Refinery dry gas, primarily composed of hydrogen, nitrogen, oxygen, methane, ethylene, ethane, carbon monoxide, carbon dioxide, propane, and propylene, is often burned directly as fuel. This significantly wastes valuable gases, particularly ethylene and ethane.

[0003] CN106609156A relates to a process for removing ethylene from refinery gas. The process involves pre-treating the refinery gas through pressure swing adsorption, dry gas concentration, and dry gas refining, and then introducing the gas into a fixed-bed reactor together with a C4 feedstock containing butene. Under a certain reaction temperature and pressure, the ethylene and butene in the refinery gas are converted into propylene on the surface of an olefin double bond metathesis catalyst.

[0004] CN103588604A relates to a system and method for recovering C2 from refinery dry gas using a combined absorption method. The system comprises a compressor, a pretreatment unit, a refinery dry gas cooling unit, a combined absorption unit, and a distillation unit. The absorption unit comprises a gas-liquid separator, a C2 absorption tower, and a methane stripping tower. The distillation unit comprises a second decarbonization tower and an ethylene distillation tower. The compressed, pretreated, and cooled refinery dry gas is subjected to gas-liquid separation. The resulting gas phase enters the C2 absorption tower, where C2 is absorbed using a mixed C4 or C5 absorbent. The resulting liquid phase is sent to a methane stripping tower for methane stripping through stripping. The mixed absorption oil at the bottom of the C2 absorption tower and the stripped gas at the top of the methane stripping tower are mixed with the refinery dry gas, cooled, and then returned to the gas-liquid separator. The cooled bottoms of the methane stripping tower are sent to the second decarbonization tower and an ethylene stripping tower for distillation to obtain ethylene and ethane products.

[0005] It can be seen from the technologies disclosed in the above-mentioned patent applications that the conventional method for pre-treating the raw materials for the disproportionation of refinery dry gas to produce propylene mentioned in CN106609156A is through pressure swing adsorption, dry gas concentration, dry gas refining and other processes, which has high energy consumption and investment. The combined absorption method provided by CN103588604A aims to obtain ethylene products. Although it can achieve the purpose of purifying ethylene, the combined absorption method is not effective in removing oxygen and carbon monoxide to meet the feed index requirements of the raw materials for the disproportionation of dilute ethylene to produce propylene. In addition, the combined absorption method uses propylene refrigerant in many places, which increases the energy consumption of the process and complicates the process flow. When conventional absorption is used, the hydrogen, oxygen, nitrogen, carbon monoxide, propane and propylene in the refinery gas obtained are difficult to meet the feed index requirements of the dilute ethylene disproportionation to produce propylene.

[0006] In view of the above technical status quo, the present invention has developed a method and system for pre-treating the raw materials for the disproportionation of refinery dry gas to propylene, and the treated refinery dry gas meets the requirements of the raw material feeding index for the disproportionation of dilute ethylene to propylene. Summary of the Invention

[0007] The object of the present invention is to address the deficiencies of the prior art and propose a method and device for pre-treating the raw materials for the disproportionation of refinery dry gas to propylene, as well as a method and system for producing propylene from refinery dry gas. The present invention can remove hydrogen, oxygen, nitrogen, carbon monoxide, methane, propane, and propylene from refinery dry gas, and the obtained ethylene-rich dry gas meets the requirements of the raw material feeding index for the disproportionation of dilute ethylene to propylene.

[0008] To achieve the above object, in the first aspect of the present invention, there is provided a device for pre-treating the raw materials for the disproportionation of refinery dry gas to propylene, which device includes a dry gas absorption tower, a first-stage desorption tower, and a second-stage desorption tower connected in sequence;

[0009] The top of the dry gas absorption tower is connected with a hydrogen-rich dry gas discharge pipeline and a first recycled C4 feed pipeline;

[0010] The bottom of the dry gas absorption tower is connected with a refinery dry gas feed pipeline;

[0011] The discharge port at the bottom of the dry gas absorption tower is connected with the feed port in the first-stage desorption tower through an ethylene-rich C4 material pipeline;

[0012] The top of the first-stage desorption tower is connected with a hydrogen-poor dry gas discharge pipeline and a second recycled C4 feed pipeline;

[0013] The discharge port at the bottom of the first-stage desorption tower is connected with the feed port in the second-stage desorption tower through a first-stage desorbed C4 material pipeline;

[0014] The top of the second-stage desorption tower is connected with an ethylene-rich dry gas discharge pipeline and a fresh C4 feed pipeline;

[0015] The discharge port at the bottom of the second-stage desorption tower is connected with the feed port of a recycled C4 cooler through a recovered C4 material pipeline; the discharge port of the recycled C4 cooler is respectively connected with the feed port at the top of the dry gas absorption tower and the feed port at the top of the first-stage desorption tower through the first recycled C4 feed pipeline and the second recycled C4 feed pipeline;

[0016] The discharge port of the recycled C4 cooler is also connected with an external discharged C4 discharge pipeline.

[0017] According to the present invention, preferably, a reboiler is provided at the bottom of both the first-stage desorption tower and the second-stage desorption tower.

[0018] According to the present invention, preferably, a circulating water cooler and a chilled water cooler are provided inside the recycled C4 cooler.

[0019] According to the present invention, preferably, the device further includes an alkali washing unit, and the alkali washing unit is connected to the bottom of the dry gas absorption tower through the refinery dry gas feed pipeline.

[0020] According to the present invention, preferably, the number of theoretical plates of the dry gas absorption tower is 10 to 40, and the theoretical feed plate is the 5th plate to the 25th plate counted from the top of the tower downwards.

[0021] According to the present invention, preferably, the number of theoretical plates of the first-stage desorption tower is 10 to 40, and the theoretical feed plate is the 5th plate to the 25th plate counted from the top of the tower downwards.

[0022] According to the present invention, preferably, the number of theoretical plates of the second-stage desorption tower is 20 to 100, and the theoretical feed plate is the 10th plate to the 70th plate counted from the top of the tower downwards.

[0023] The second aspect of the present invention provides a raw material pretreatment method for refinery dry gas disproportionation to propylene. This method uses the raw material pretreatment device for refinery dry gas disproportionation to propylene, and includes the following steps:

[0024] S1: Making the refinery dry gas entering the tower from the bottom of the dry gas absorption tower contact with a part of the recycled C4 cooled by the recycled C4 cooler and entering the tower from the top of the dry gas absorption tower in the dry gas absorption tower. Rich ethylene C4 is obtained at the bottom of the dry gas absorption tower, and rich hydrogen dry gas is obtained at the top of the dry gas absorption tower;

[0025] S2: Making the rich ethylene C4 enter the first-stage desorption tower from the middle of the first-stage desorption tower for first-stage desorption, and using a part of the recycled C4 cooled by the recycled C4 cooler as the top reflux. First-stage desorbed C4 is obtained at the bottom of the first-stage desorption tower, and hydrogen-lean dry gas is obtained at the top of the first-stage desorption tower;

[0026] S3: Making the first-stage desorbed C4 enter the second-stage desorption tower from the middle of the second-stage desorption tower for second-stage desorption, and using fresh C4 as the top reflux. Recycled C4 is obtained at the bottom of the second-stage desorption tower, and after being cooled by the recycled C4 cooler, it is respectively sent to the top of the dry gas absorption tower, used as the top reflux of the first-stage desorption tower, and discharged from the device. Rich ethylene dry gas is obtained at the top of the second-stage desorption tower.

[0027] In the present invention, the waste heat of the recycled C4 discharged from the bottom of the second-stage desorption tower can be used as the heat source of the reboiler of the first-stage desorption tower, and can also be used as the heat source for preheating the rich ethylene dry gas discharged from the top of the second-stage desorption tower.

[0028] According to the present invention, preferably, in step S1, the refinery dry gas is the refinery dry gas after removing carbon dioxide and hydrogen sulfide through the alkali washing unit.

[0029] According to the present invention, preferably, in step S1, the source of the refinery dry gas before removing carbon dioxide and hydrogen sulfide is at least one of the processes of crude oil distillation, catalytic cracking, thermal cracking, coking, hydrocracking, catalytic reforming, and hydrofining.

[0030] According to the present invention, preferably, in step S1, the top operating pressure of the dry gas absorption tower is 1.0 - 4.0 MPaA, and the top operating temperature is -20 - 60 °C. Further preferably, the top operating pressure of the dry gas absorption tower is 2.0 - 3.5 MPaA, and the top operating temperature is 10 - 40 °C.

[0031] According to the present invention, preferably, in step S2, the top operating pressure of the first-stage desorption tower is 0.5 - 3.0 MPaA, and the top operating temperature is -20 - 60 °C; further preferably, the top operating pressure of the first-stage desorption tower is 1.5 - 2.0 MPaA, and the top operating temperature is 10 - 40 °C.

[0032] According to the present invention, preferably, in step S3, the fresh C4 is at least one of isobutane, n-butane, 1-butene, isobutene, and 2-butene; the top operating pressure of the second-stage desorption tower is 0.5 - 4.0 MPaA, and the top operating temperature is 40 - 140 °C. Further preferably, the top operating pressure of the second-stage desorption tower is 2.0 - 3.0 MPaA, and the top operating temperature is 60 - 90 °C.

[0033] According to the present invention, preferably, the outlet temperature of the circulating C4 cooler is 0 - 30 °C, and further preferably, the outlet temperature of the circulating C4 cooler is 10 - 20 °C.

[0034] According to the present invention, preferably, the proportion of the first circulating C4 entering the dry gas absorption tower in the total circulating C4 is 50% - 90%; the proportion of the second circulating C4 as the top reflux of the first-stage desorption tower in the total circulating C4 is 5% - 40%; the proportion of the circulating C4 discharged from the device in the total circulating C4 is 2% - 20%.

[0035] The third aspect of the present invention provides a system for disproportionating refinery dry gas to produce propylene. The system includes a disproportionation reactor, a decarbonization tower, a depropylene tower, and a decarbonization tower connected in sequence, and the system further includes the raw material pretreatment device for disproportionating refinery dry gas to produce propylene;

[0036] The rich ethylene dry gas discharge pipeline of the raw material pretreatment device for disproportionating refinery dry gas to produce propylene is connected upstream of the disproportionation reactor.

[0037] The fourth aspect of the present invention provides a method for the disproportionation of refinery dry gas to produce propylene. This method utilizes the system for the disproportionation of refinery dry gas to produce propylene and includes the following steps:

[0038] (1): Feed the refinery dry gas into the raw material pretreatment device for the disproportionation of refinery dry gas to produce propylene to obtain ethylene-rich dry gas;

[0039] (2): Use the ethylene-rich dry gas as raw material and successively process it through a disproportionation reactor, a decarbonization tower II, a depropylene tower, and a decarbonization tower IV to obtain a polymer-grade propylene product.

[0040] The technical solution of the present invention has the following beneficial effects:

[0041] (1) The process of the present invention is simple. It uses conventional water cooling (circulating C4 cooler). The refinery dry gas passes through the pretreatment device once, and simultaneously removes hydrogen, oxygen, nitrogen, carbon monoxide, and methane. Without using propylene refrigerant, it also simultaneously removes propane and propylene, making it unnecessary to separate propane and propylene in the separation unit after the disproportionation reaction.

[0042] (2) By using C4, one of the raw materials for the disproportionation to produce propylene, as an absorbent, through absorption and desorption, hydrogen, oxygen, nitrogen, carbon monoxide, methane, propane, and propylene in the refinery dry gas can be removed. The obtained ethylene-rich dry gas meets the raw material feed index requirements for the disproportionation of dilute ethylene to produce propylene, and can greatly reduce the methane content in the ethylene-rich dry gas.

[0043] Other features and advantages of the present invention will be described in detail in the following specific implementation section. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] By describing the exemplary embodiments of the present invention in more detail in conjunction with the drawings, the above and other objects, features, and advantages of the present invention will become more apparent. Among them, in the exemplary embodiments of the present invention, the same reference numerals generally represent the same components.

[0045] Figure 1 FIG. shows a schematic diagram of a raw material pretreatment device for the disproportionation of refinery dry gas to produce propylene provided in Example 1 of the present invention.

[0046] Figure 2 FIG. shows a schematic diagram of a raw material pretreatment device for the disproportionation of refinery dry gas to produce propylene provided in Comparative Example 1 of the present invention.

[0047] The description of the reference numerals in the drawings is as follows:

[0048] 1 - Dry gas absorption tower; 2 - First - stage desorption tower; 3 - Second - stage desorption tower; 4 - First - cycle C4 feed pipeline; 5 - Refinery dry gas feed pipeline; 6 - Ethylene - rich C4 material pipeline; 7 - Hydrogen - rich dry gas discharge pipeline; 8 - Hydrogen - poor dry gas discharge pipeline; 9 - First - stage desorption C4 material pipeline; 10 - Fresh C4 feed pipeline; 11 - Ethylene - rich dry gas discharge pipeline; 12 - Desorption tower; 13 - External - discharge C4 discharge pipeline; 14 - Cycle C4 cooler; 15 - Recovered C4 material pipeline; 16 - Second - cycle C4 feed pipeline. Detailed implementation manners

[0049] The preferred implementation manners of the present invention will be described in more detail below. Although the preferred implementation manners of the present invention are described below, it should be understood that the present invention can be implemented in various forms and should not be limited by the implementation manners set forth herein. On the contrary, these implementation manners are provided to make the present invention more thorough and complete, and to fully convey the scope of the present invention to those skilled in the art.

[0050] Example 1

[0051] This example provides a raw material pretreatment device for the disproportionation of refinery dry gas to propylene, as Figure 1 shown. The device includes a dry gas absorption tower 1, a first - stage desorption tower 2, and a second - stage desorption tower 3 that are connected in sequence;

[0052] The top of the dry gas absorption tower 1 is connected with a hydrogen - rich dry gas discharge pipeline 7 and a first - cycle C4 feed pipeline 4; <www

[0053] The bottom of the dry gas absorption tower 1 is connected with a refinery dry gas feed pipeline 5;

[0054] The discharge port at the bottom of the dry gas absorption tower 1 is connected to the feed port in the first - stage desorption tower 2 through an ethylene - rich C4 material pipeline 6;

[0055] The top of the first - stage desorption tower 2 is connected with a hydrogen - poor dry gas discharge pipeline 8 and a second - cycle C4 feed pipeline 16;

[0056] The discharge port at the bottom of the first - stage desorption tower 2 is connected to the feed port in the second - stage desorption tower 3 through a first - stage desorption C4 material pipeline 9;

[0057] The top of the second - stage desorption tower 3 is connected with an ethylene - rich dry gas discharge pipeline 11 and a fresh C4 feed pipeline 10;

[0058] The outlet at the bottom of the secondary desorption tower 3 is connected to the inlet of the circulating C4 cooler 14 through the recovered C4 material pipeline 15. The outlet of the circulating C4 cooler 14 is respectively connected to the inlet at the top of the dry gas absorption tower 1 and the inlet at the top of the primary desorption tower 2 through the first circulating C4 feed pipeline 4 and the second circulating C4 feed pipeline 16. The outlet of the circulating C4 cooler is also connected to the external discharged C4 pipeline 13;

[0059] Reboilers (not shown) are provided at the bottom of the primary desorption tower 2 and the bottom of the secondary desorption tower 3.

[0060] A circulating water cooler (not shown) and a chilled water cooler (not shown) are provided inside the circulating C4 cooler;

[0061] The number of theoretical plates of the dry gas absorption tower 1 is 30, and the theoretical feed plate is the 15th plate counted from the top of the tower downwards;

[0062] The number of theoretical plates of the primary desorption tower 2 is 30, and the theoretical feed plate is the 15th plate counted from the top of the tower downwards;

[0063] The number of theoretical plates of the secondary desorption tower 3 is 60, and the theoretical feed plate is the 30th plate counted from the top of the tower downwards.

[0064] The device further includes an alkali washing unit (not shown), and the alkali washing unit is connected to the bottom of the dry gas absorption tower through the refinery dry gas feed pipeline.

[0065] A system for disproportionating refinery dry gas to produce propylene including the above device further includes a disproportionation reactor, a de-carbon dioxide tower, a de-propylene tower, and a de-carbon four tower connected in sequence; the other end of the rich ethylene dry gas pipeline of the above device is connected upstream of the disproportionation reactor.

[0066] Example 2

[0067] This example provides a method for pre-treating the raw materials for disproportionating refinery dry gas to produce propylene. This method uses the raw material pre-treatment device for disproportionating refinery dry gas described in Example 1 and includes the following steps:

[0068] S1: Make the refinery dry gas entering the tower from the bottom of the dry gas absorption tower 1 contact and react with a part of the circulating C4 cooled by the circulating C4 cooler 14 entering the tower from the top of the dry gas absorption tower 1 in the dry gas absorption tower 1. Rich ethylene C4 is obtained at the bottom of the dry gas absorption tower 1, and rich hydrogen dry gas is obtained at the top of the dry gas absorption tower 1;

[0069] S2: Feed the ethylene-rich C4 into the middle of the first-stage desorption column 2 for first-stage desorption, and use a part of the recycled C4 cooled by the recycled C4 cooler 14 as the top reflux. The first-stage desorbed C4 is obtained at the bottom of the first-stage desorption column 2, and the hydrogen-lean dry gas is obtained at the top of the first-stage desorption column 2.

[0070] S3: Feed the first-stage desorbed C4 into the middle of the second-stage desorption column 3 for second-stage desorption, and use fresh C4 as the top reflux. The recovered C4 is obtained at the bottom of the second-stage desorption column. After being cooled by the recycled C4 cooler 14, it is respectively fed into the top of the dry gas absorption column 1, used as the top reflux of the first-stage desorption column 2, and discharged from the device through the external C4 discharge pipeline 13 (C4 external discharge). The ethylene-rich dry gas is obtained at the top of the second-stage desorption column 3.

[0071] The refinery dry gas is the refinery dry gas after removing carbon dioxide and hydrogen sulfide through the caustic washing unit, and its component composition is shown in Table 1; the source of the refinery dry gas before removing carbon dioxide and hydrogen sulfide is catalytic cracking dry gas.

[0072] The component composition of the fresh C4 entering the top of the second-stage desorption column 3 is shown in Table 2.

[0073] The top operating pressure of the dry gas absorption column 1 is 3.0 MPaA, and the top operating temperature is 10 °C.

[0074] The top operating pressure of the first-stage desorption column 2 is 2.0 MPaA, and the top operating temperature is 16 °C.

[0075] The top operating pressure of the second-stage desorption column 3 is 3.0 MPaA, and the top operating temperature is 70 °C.

[0076] The recycled C4 cooler adopts two-stage cooling with circulating water and chilled water, and the outlet temperature of the recycled C4 is 10 °C.

[0077] Table 1

[0078] % mol Hydrogen 3.54 Oxygen 1.29 Nitrogen 22.70 Carbon monoxide 3.14 Methane 25.19 Ethylene 21.12 Ethane 19.65 Propylene 1.97 Propane 1.40 Total 100.00

[0079] Table 2

[0080] % wt Isobutane 47.08 n-Butane 0.50 1-Butene 12.17 Isobutene 0.16 2-Butene 40.09 Total 100.00

[0081] Taking the ethylene-rich dry gas obtained in this embodiment as the raw material and successively passing through disproportionation reaction, carbon dioxide removal, propylene removal, and carbon tetrachloride removal treatments, a polymer-grade propylene product can be obtained.

[0082] Comparative Example 1

[0083] This comparative example provides a raw material pretreatment device for disproportionating refinery dry gas to produce propylene, as shown in Figure 2As shown, the device includes a dry gas absorption tower 1 and a desorption tower 12 that are connected in sequence;

[0084] At the top of the dry gas absorption tower 1, a hydrogen-rich dry gas discharge pipeline 7 and a first recycled C4 feed pipeline 4 are connected;

[0085] At the bottom of the dry gas absorption tower 1, a refinery dry gas feed pipeline 5 is connected;

[0086] The discharge port at the bottom of the dry gas absorption tower 1 is connected to the feed port in the desorption tower 12 through a C4-rich ethylene material pipeline 6;

[0087] At the top of the desorption tower 12, a C4-rich ethylene dry gas discharge pipeline 11 and a fresh C4 feed pipeline 10 are connected;

[0088] The discharge port at the bottom of the desorption tower 12 is connected to the feed port of the recycled C4 cooler 14 through a recovered C4 material pipeline 15. The discharge port of the recycled C4 cooler 14 is connected to the feed port at the top of the dry gas absorption tower 1 through the first recycled C4 feed pipeline 4.

[0089] The number of theoretical plates of the dry gas absorption tower 1 is 30, and the theoretical feed plate is the 15th plate from the top of the tower downwards;

[0090] The number of theoretical plates of the desorption tower 12 is 30, and the theoretical feed plate is the 15th plate from the top of the tower downwards;

[0091] The raw material pretreatment method for the disproportionation of refinery dry gas to propylene using the above device includes the following steps:

[0092] S1: Make the refinery dry gas entering the tower from the bottom of the dry gas absorption tower 1 contact and react with a part of the recycled C4 cooled by the recycled C4 cooler 14 entering the tower from the top of the dry gas absorption tower 1 in the dry gas absorption tower 1. Rich C4 ethylene is obtained at the bottom of the dry gas absorption tower 1, and hydrogen-rich dry gas is obtained at the top of the dry gas absorption tower 1;

[0093] S2: Make the C4-rich ethylene enter the desorption tower 12 from the middle of the desorption tower 12, and use the C4 entering the top of the desorption tower 12 through the fresh C4 feed pipeline 10 for top reflux treatment. Recovered C4 is obtained at the bottom of the desorption tower 12. After being cooled by the recycled C4 cooler 14, a part is sent to the top of the dry gas absorption tower 1, and the remaining part is discharged from the device (C4 is discharged externally), and C4-rich ethylene dry gas is obtained at the top of the desorption tower 12.

[0094] The operating pressure at the top of the dry gas absorption tower 1 is 3.0 MPaA, and the operating temperature is 10 °C.

[0095] The operating pressure at the top of the desorption tower 12 is 2.0 MPaA, and the operating temperature is 64 °C.

[0096] The refinery dry gas is the same as that in Example 2, and its composition is shown in Table 1;

[0097] The fresh C4 entering the top of the desorption column 12 is the same as that in Example 2, and its composition is shown in Table 2.

[0098] Test Example

[0099] In this test example, the feed conditions (including the feed amount of refinery dry gas and the feed amount of fresh C4), the C4 recycle amount, the C4 discharge amount, the gas composition in the ethylene-rich dry gas, and the impurity removal rate in Example 2 and Comparative Example 1 are compared, as shown in Tables 3 - 5 respectively.

[0100] From the comparison results in Tables 3 - 5, it can be seen that through a single absorption process, the present invention can achieve a removal efficiency of more than 99.99% for hydrogen, oxygen, nitrogen, and carbon monoxide in the refinery dry gas. At the same time, the methane removal rate reaches 87.93%, and the ethylene loss during the process is only 1.82%. The propylene and propane in the treated dry gas are only 0.55% mol and 0.23% mol respectively, and this propane content can ensure obtaining a polymer-grade propylene product without setting up a propane and propylene separation column.

[0101] Table 3

[0102]

[0103] Table 4

[0104]

[0105] Table 5

[0106]

[0107] The embodiments of the present invention have been described above. The above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations are obvious to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A raw material pretreatment device for producing propylene by disproportionation of refinery dry gas, characterized in that: The device comprises a dry gas absorption tower, a primary desorption tower and a secondary desorption tower which are connected in sequence; The top of the dry gas absorption tower is connected to a hydrogen-rich dry gas discharge pipeline and a first cycle C4 feed pipeline; The bottom of the dry gas absorption tower is connected to a refinery dry gas feed pipeline; The discharge port at the bottom of the dry gas absorption tower is connected to the feed port in the first-stage stripping tower through an ethylene-rich C4 material pipeline; The top of the first-stage desorption tower is connected to a hydrogen-poor dry gas discharge pipeline and a second circulating C4 feed pipeline; The discharge port at the bottom of the first-stage desorption tower is connected to the feed port in the second-stage desorption tower through the first-stage desorption carbon four material pipeline; The top of the secondary stripping tower is connected to an ethylene-rich dry gas discharge pipeline and a fresh C4 feed pipeline; The discharge port at the bottom of the secondary stripping tower is connected to the feed port of the circulating C4 cooler through the C4 material recovery pipeline; the discharge port of the circulating C4 cooler is connected to the feed port at the top of the dry gas absorption tower and the feed port at the top of the primary stripping tower through the first circulating C4 feed pipeline and the second circulating C4 feed pipeline respectively; The discharge port of the circulating C4 cooler is also connected to an external C4 discharge pipeline.

2. The raw material pretreatment device for producing propylene by disproportionation of refinery dry gas according to claim 1, wherein: The first-stage stripping tower kettle and the second-stage stripping tower kettle are both provided with a reboiler; The circulating C4 cooler is provided with a circulating water cooler and a chilled water cooler; The device further comprises an alkali washing unit, which is connected to the bottom of the dry gas absorption tower through the refinery dry gas feed pipeline.

3. The raw material pretreatment device for producing propylene by disproportionation of refinery dry gas according to claim 1, wherein: The dry gas absorption tower has a theoretical plate number of 10 to 40, and the theoretical feed plate is the 5th to 25th plate from the top of the tower; The theoretical number of plates of the first-stage stripping tower is 10 to 40, and the theoretical feed plate is the 5th to 25th plate from the top of the tower; The theoretical number of plates of the secondary desorption tower is 20 to 100, and the theoretical feed plates are the 10th to 70th plates from the top of the tower.

4. A method for pretreating raw materials for producing propylene by disproportionation of refinery dry gas, characterized in that: The method utilizes the raw material pretreatment device for producing propylene by disproportionation of refinery dry gas as described in any one of claims 1 to 3, comprising the following steps: S1: contacting the refinery dry gas entering the dry gas absorption tower from the bottom with a portion of the circulating C4 cooled by the circulating C4 cooler entering the dry gas absorption tower from the top of the dry gas absorption tower in the dry gas absorption tower, thereby obtaining ethylene-rich C4 at the bottom of the dry gas absorption tower and obtaining hydrogen-rich dry gas at the top of the dry gas absorption tower; S2: allowing the ethylene-rich C4 to enter the primary stripping tower from the middle of the primary stripping tower to perform primary stripping, and utilizing a portion of the circulating C4 cooled by the circulating C4 cooler as a tower top reflux, obtaining primary desorbed C4 at the bottom of the primary stripping tower, and obtaining hydrogen-depleted dry gas at the top of the primary stripping tower; S3: The first-stage desorbed C4 is allowed to enter the second-stage desorption tower from the middle of the second-stage desorption tower for second-stage desorption, and fresh C4 is used as the top reflux. The recovered C4 is obtained at the bottom of the second-stage desorption tower, and after being cooled by the circulating C4 cooler, it is respectively sent to the top of the dry gas absorption tower, used as the top reflux of the first-stage desorption tower, and discharged from the device. Ethylene-rich dry gas is obtained at the top of the second-stage desorption tower.

5. The method for pretreating raw materials for preparing propylene by disproportionation of refinery dry gas according to claim 4, wherein: In step S1, The refinery dry gas is the refinery dry gas after carbon dioxide and hydrogen sulfide are removed by the alkali washing unit; The source of the refinery dry gas before removal of carbon dioxide and hydrogen sulfide is at least one of crude oil distillation, catalytic cracking, thermal cracking, coking, hydrocracking, catalytic reforming and hydrofining processes; The top operating pressure of the dry gas absorption tower is 1.0-4.0 MPaA, and the top operating temperature is -20-60°C.

6. The method for pretreating raw materials for preparing propylene by disproportionation of refinery dry gas according to claim 4, wherein: In step S2, the top operating pressure of the first-stage stripping tower is 0.5-3.0 MPaA, and the top operating temperature is -20-60°C.

7. The method for pretreating raw materials for preparing propylene by disproportionation of refinery dry gas according to claim 4, wherein: In step S3, The fresh C4 is at least one of isobutane, n-butane, 1-butene, isobutene and 2-butene; The top operating pressure of the secondary stripping tower is 0.5-4.0 MPaA, and the top operating temperature is 40-140°C.

8. The method for pretreating raw materials for preparing propylene by disproportionation of refinery dry gas according to claim 4, wherein: The outlet temperature of the circulating C4 cooler is 0-30°C; The proportion of the circulating carbon four entering the dry gas absorption tower accounts for 50% to 90% of the total circulating carbon four; the proportion of the circulating carbon four used as reflux from the top of the first-stage stripping tower accounts for 5% to 40% of the total circulating carbon four; and the proportion of the circulating carbon four discharged from the device accounts for 2% to 20% of the total circulating carbon four.

9. A system for producing propylene by disproportionation of refinery dry gas, characterized in that: The system comprises a disproportionation reactor, a second decarbonization tower, a propylene removal tower, and a fourth decarbonization tower connected in sequence, and the system further comprises a raw material pretreatment device for producing propylene by disproportionation of refinery dry gas according to any one of claims 1 to 3; The ethylene-rich dry gas discharge pipeline of the raw material pretreatment device for producing propylene by disproportionation of the refinery dry gas is connected to the upstream of the disproportionation reactor.

10. A method for producing propylene by disproportionation of refinery dry gas, characterized in that: The method utilizes the system for producing propylene by disproportionation of refinery dry gas as claimed in claim 9, comprising the following steps: (1): feeding the refinery dry gas into a raw material pretreatment device for producing propylene by disproportionation of the refinery dry gas to obtain ethylene-rich dry gas; (2): The ethylene-rich dry gas is used as a raw material and is sequentially processed through a disproportionation reactor, a second decarbonization tower, a propylene removal tower, and a fourth decarbonization tower to obtain a polymerization-grade propylene product.

Images