A system and method for separating ethylbenzene from C8 aromatics

Abstract

The present invention belongs to the field of petroleum refining and chemical industry, and specifically relates to a system and method for separating ethylbenzene from C8 aromatics. The system comprises: a refrigeration system, a cryogenic separation system, and a heating system; the cryogenic separation system comprises a number ≥1 cryogenic separation unit; the cryogenic separation unit comprises a number ≥1 cryogenic separator, and a cold exchange component and an agitator are arranged inside the cryogenic separator. The system and method for separating ethylbenzene from C8 aromatics disclosed in the present invention have high purity and recovery rate of ethylbenzene, reduce the operating energy consumption of the ethylbenzene production process, are flexible in device operation, and are not easy to be blocked in the device equipment and pipelines, and can achieve long-term stable operation.

Description

Technical Field

[0001] The present invention belongs to the field of oil refining and chemical industry, and more specifically, relates to a system and method for separating ethylbenzene from C8 aromatics. Background Art

[0002] In various production units of petrochemical enterprises, reforming oil, catalytic cracking gasoline, and ethylene cracking gasoline all contain a large amount of C8 aromatics. C8 aromatics have four isomers, namely o-xylene (OX), m-xylene (MX), p-xylene (PX), and ethylbenzene (EB). In the prior art, these C8 aromatics are usually used in the production of PX. However, with the large-scale construction of PX units, the market price of PX has been falling, and the resulting economic benefits have become increasingly poor. Therefore, it has become increasingly urgent to seek new uses for C8 aromatics and improve the market competitiveness of products.

[0003] EB is one of the important basic organic raw materials. Its main use is as an intermediate in the production of styrene in the petrochemical industry. Styrene produced by dehydrogenation of ethylbenzene can be used to produce synthetic materials such as polystyrene (PS), expanded polystyrene (EPS), engineering plastics (ABS), styrene-butadiene rubber (SBR) and styrene-butadiene latex. Some ethylbenzene can be used in the organic synthesis industry, such as the production of intermediates such as acetophenone, ethyl anthraquinone, p-nitroacetophenone, methyl phenyl ketone, etc. In medicine, ethylbenzene can be used as an intermediate of synamycin and chloramphenicol, and can also be used in the production of spices and as a solvent.

[0004] Data show that the global ethylbenzene production capacity reached 39 million tons / year in 2018, and it is expected that the capacity will reach 45 million tons / year in 2020. In 2018, the domestic ethylbenzene production capacity was 9 million tons / year, and the output exceeded 6.5 million tons / year, accounting for about 20% of the global ethylbenzene production, and the demand exceeded 11 million tons. In recent years, my country's ethylbenzene / styrene industry has developed very rapidly. In 2005, my country's ethylbenzene self-sufficiency rate was only 30%, and it reached 70% in 2018. China has become the world's largest producer of ethylbenzene and styrene, but a large amount of ethylbenzene still needs to rely on imports.

[0005] At present, the production of ethylbenzene mainly relies on the reaction of benzene and ethylene under the action of a catalyst to produce ethylbenzene. This technology has high production costs, complex processes, and technology that mostly relies on imports. Therefore, based on current market demand and product competitiveness analysis, it is very necessary and promising to seek new technologies and processes to replace or supplement existing ethylbenzene production technologies. Summary of the invention

[0006] The purpose of the present invention is to provide a system and method for separating ethylbenzene from C8 aromatics, so as to solve the problems of long process, large investment, high energy consumption and large land area in the existing ethylbenzene production technology.

[0007] In order to achieve the above object, a first aspect of the present invention provides a system for separating ethylbenzene from C8 aromatics, the system comprising:

[0008] Refrigeration system, cryogenic separation system, heating system;

[0009] The cryogenic separation system is communicated with the refrigeration system and the heating system respectively;

[0010] The cryogenic separation system comprises ≥1 cryogenic separation units; the cryogenic separation unit comprises ≥1 cryogenic separators, wherein a cold exchange component and an agitator are arranged inside the cryogenic separator;

[0011] The refrigeration system and the heating system are communicated with the cold exchange component respectively.

[0012] According to the present invention, a number of ≥2 cryogenic separation units can improve the operational flexibility and elasticity of the device.

[0013] According to the present invention, a stirrer is arranged inside the cryogenic separator to prevent local excessively rapid crystallization and achieve uniform crystallization.

[0014] As a preferred solution, the number of cryogenic separators in the cryogenic separation unit is 1-10, preferably 2-6.

[0015] As a preferred solution, when the number of the cryogenic separators is ≥ 2, the cryogenic separators are connected in parallel or in series-parallel, with one part achieving crystallization of xylene and the other part achieving dissolution of xylene.

[0016] As a preferred solution, the refrigeration system comprises a cooling refrigerant and a heat-exchanged refrigerant, and the cooling refrigerant and the heat-exchanged refrigerant circulate between the cryogenic separation system and the refrigeration system.

[0017] As a further preferred embodiment, the cooling refrigerant is selected from at least one of ethylene, ethane, propane and propylene.

[0018] As a preferred solution, the heating system comprises a heat supplying heating agent and a heat exchange heating agent, and the heat supplying heating agent and the heat exchange heating agent circulate between the deep cold separation system and the heating system.

[0019] As a preferred solution, the heating method of the heating system is selected from at least one of electric heating, fuel gas heating, steam heating and heat transfer medium heating.

[0020] As a preferred solution, the inlet of the cold exchange component is connected to the pipelines of the cooling refrigerant and the heating agent, and the outlet of the cold exchange component is connected to the pipelines of the heat-exchanged refrigerant and the heating agent, respectively.

[0021] According to the present invention, the cold exchange component can be a U-tube, a spiral heat exchange coil or a plate heat exchange component, as long as it can meet the requirements of cold and heat exchange, is not easy to clog, is economical and applicable, and can meet the requirements of stable long-term operation.

[0022] As a preferred solution, the cold exchange component is a U-shaped tube;

[0023] The inlet of the U-shaped tube is connected to the pipelines of the cooling refrigerant and the heating heating agent respectively;

[0024] The outlets of the U-shaped tube are respectively connected to the pipelines of the refrigerant after heat exchange and the heating agent after heat exchange.

[0025] As a preferred embodiment, the system for separating ethylbenzene from C8 aromatics further comprises an energy recovery system, and the energy recovery system comprises a feed heat exchanger connected to the cryogenic separator.

[0026] A second aspect of the present invention provides a method for separating ethylbenzene from C8 aromatics, the method utilizing the above system, the method comprising:

[0027] a) C8 aromatics are sent to a cryogenic separation system for cryogenic separation;

[0028] b) The cryogenic separation system separates ethylbenzene and ethylbenzene-poor C8 aromatics.

[0029] The C8 aromatics referred to in the present invention mainly include o-xylene (OX), m-xylene (MX), p-xylene (PX) and ethylbenzene (EB), which may also contain small amounts of benzene, toluene and other substances; xylene mainly refers to o-xylene (OX), m-xylene (MX) and p-xylene (PX).

[0030] As a preferred solution, when it is detected that xylene in the cryogenic separator has crystallized to a certain extent, the uncrystallized crude ethylbenzene is discharged from the bottom of the cryogenic separator. When the crude ethylbenzene is completely discharged, the refrigeration system stops providing cooling to the cryogenic separation system and switches to the heating system to provide heat to the cryogenic separation system, so that the crystallized xylene in the cryogenic separator is redissolved, thereby achieving complete separation of ethylbenzene and xylene.

[0031] According to the different crystallization temperatures of C8 aromatics, the higher the crystallization temperature, the easier it is to crystallize. As can be seen from Table 1, the crystallization temperature of ethylbenzene is at least 40°C lower than the other three crystallization temperatures. The difference in crystallization temperature between ethylbenzene and hydrocarbons such as p-xylene, o-xylene, and m-xylene can be used to separate ethylbenzene. At a certain temperature, such as -50°C, p-xylene, o-xylene, and m-xylene all crystallize in solid form, while ethylbenzene still remains in liquid form, so the separation of ethylbenzene can be easily achieved.

[0032] Table 1 Boiling points and crystallization points of C8 aromatic components

[0033] Ethylbenzene p-Xylene o-Xylene m-p-Xylene Boiling point℃ 136.2 138.4 144.4 139.1 Crystallization point, ℃ -94.9 +13.26 -25 -48

[0034] Furthermore, in order to achieve smooth removal of crystallized material in the cryogenic separator, a heating medium is introduced into the cryogenic separator to dissolve it. Common heating methods can adopt at least one of electric heating, fuel gas heating, steam heating, and heat transfer medium heating, and heat transfer medium and steam heating are preferred.

[0035] Furthermore, in order to reduce equipment investment and increase space utilization efficiency within the cryogenic separator, the present invention preferably adopts a refrigeration system and a heating system that can be connected to the cold exchange components within the cryogenic separation system, and the refrigeration system and the heating system share a set of heat exchange components.

[0036] In order to improve the separation purity of ethylbenzene in the whole system, a multi-stage cryogenic separation unit is used, for example, it can include a 1# cryogenic separation unit and a 2# cryogenic separation unit; at the same time, the number of cryogenic separators in the 1# cryogenic separation unit and the 2# cryogenic separation unit can be set to 1-10, preferably 2-6. A pressurized cryogenic method can also be used to increase the crystallization rate of xylene.

[0037] As a preferred embodiment, the conditions for cryogenic separation include: cryogenic temperature of -80 to -20°C, dissolution temperature of 130 to 250°C, and cryogenic pressure of normal pressure to 4.0 MPa.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] 1. The method for separating ethylbenzene from C8 aromatics proposed in the present invention utilizes the difference in crystallization temperature between ethylbenzene and hydrocarbons such as p-xylene, o-xylene, and m-xylene to achieve separation, and adopts a combination of crystallization + dissolution process, which greatly reduces the operating energy consumption of the separation process. The ethylbenzene obtained has high purity, the device operation is flexible, and long-term stable operation can be achieved.

[0040] 2. The method for separating ethylbenzene from C8 aromatics proposed by the present invention adopts a deep cold separator connected to a refrigeration system to provide cooling capacity, so that xylene is preferentially crystallized and precipitated, thereby obtaining high-purity ethylbenzene; xylene is redissolved by the heat provided by the heating system to become liquid and be excluded from the crystallization separation system, thereby achieving efficient separation of ethylbenzene and xylene.

[0041] 3. The method for separating ethylbenzene from C8 aromatics proposed by the present invention comprises a plurality of cryogenic separators arranged in a cryogenic separation unit, the cryogenic separators being arranged in parallel, one part of which realizes the crystallization of xylene and the other part of which realizes the dissolution of xylene.

[0042] 4. The method for separating ethylbenzene from C8 aromatics proposed by the present invention is provided with multiple cryogenic separation units in order to obtain ethylbenzene with higher purity. The crude ethylbenzene separated by the previous cryogenic separation unit is crystallized and dissolved multiple times by the subsequent multiple cryogenic separation units to ensure the purity of ethylbenzene. At the same time, in order to improve the energy utilization efficiency, an energy recovery system is provided.

[0043] 5. The method for separating ethylbenzene from C8 aromatics proposed by the present invention adopts stirring and introducing cooling medium into the deep cold separator to provide cooling capacity, which can achieve uniform crystallization of xylene, prevent blockage of the deep cold separator, and further improve the recovery rate of ethylbenzene.

[0044] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the present invention, but do not constitute a limitation of the present invention. The above and other purposes, features and advantages of the present invention will become more apparent by describing the exemplary embodiments of the present invention in more detail in conjunction with the accompanying drawings, wherein the same reference numerals generally represent the same components in the exemplary embodiments of the present invention.

[0046] Figure 1 The present invention provides a schematic diagram of a flow chart for separating ethylbenzene from C8 aromatics.

[0047] Figure 2 It is another schematic diagram of a flow chart for separating ethylbenzene from C8 aromatics provided by the present invention.

[0048] Figure 3 It is a schematic diagram of a crystallization separation process according to a specific embodiment of the present invention.

[0049] Figure 4 It is a schematic diagram of the crystallization separation process of another specific embodiment provided by the present invention.

[0050] Figure 5 It is a schematic diagram of the crystallization separation process of another specific embodiment provided by the present invention.

[0051] Description of reference numerals:

[0052] 1—C8 aromatics, 2—ethylbenzene, 3—C8 aromatics with poor ethylbenzene, 5—C8 aromatics with rich ethylbenzene, 6—precooling C8 aromatics, 7—crude ethylbenzene, 8—precooling crude ethylbenzene, 9—refined ethylbenzene, 10—refrigeration refrigerant, 11—refrigerant after heat exchange, 12—heating heating agent, 13—heating heating agent after heat exchange,

[0053] 101—Refrigeration system, 102—1# cryogenic separation unit, 103—Heating system, 104—2# cryogenic separation unit

[0054] 201—cryogenic separator, 202—cold exchange component, 203—agitator, 204—feed heat exchanger. DETAILED DESCRIPTION

[0055] The preferred embodiments of the present invention will be described in more detail below. Although the preferred embodiments 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 embodiments set forth herein. On the contrary, these embodiments 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.

[0056] In the present invention, unless otherwise specified, directional words such as "upper" and "lower" generally refer to the upper and lower parts of the device in normal use, and "inside" and "outside" refer to the outline of the device.

[0057] Example 1

[0058] This embodiment provides a system and method for separating ethylbenzene from C8 aromatics.

[0059] like Figure 1 , Figure 3 As shown, the steps of separating ethylbenzene from C8 aromatics in this embodiment are as follows:

[0060] a) C8 aromatics 1 are sent to the 1# deep cold separation unit 102;

[0061] b) the 1# cryogenic separation unit 102 is connected to the refrigeration system 101 and the heating system 103; the 1# cryogenic separation unit 102 is provided with a cryogenic separator 201 including a cold exchange component 202 and an agitator 203;

[0062] c) The 1# cryogenic separation unit 102 separates ethylbenzene 2 and ethylbenzene-poor C8 aromatics 3.

[0063] The 1# cryogenic separation unit 102 in this embodiment includes two cryogenic separators 201 of the same size and arranged in parallel, and the bottom of the cryogenic separator 201 is respectively provided with a discharge pipeline for ethylbenzene 2 and ethylbenzene-poor C8 aromatics 3. A heat exchange component 202 is provided inside the cryogenic separator 201, and this heat exchange component is preferably a U-shaped tube, and the inlet of the U-shaped tube is respectively connected to the pipelines of the cooling refrigerant 10 and the heating agent 12 of the refrigeration system 101; the outlet of the U-shaped tube is respectively connected to the pipelines of the refrigerant 11 after heat exchange and the heating agent 13 after heat exchange of the refrigeration system. In addition, an agitator 203 is also provided in the cryogenic separator.

[0064] This embodiment uses ethane as a refrigerant and 0.5 MPa steam as a heating source. The cryogenic temperature in the cryogenic separator 201 is -55°C, and the dissolution temperature of the ethylbenzene-poor C8 aromatics is selected to be 150°C. Two cryogenic separators 201 are arranged in parallel, one realizes the crystallization of xylene, and the other realizes the dissolution of xylene, so as to achieve the purpose of continuous separation of ethylbenzene.

[0065] Table 2 shows the composition of each isomer of C8 aromatics of raw material 1. The method for separating ethylbenzene from C8 aromatics disclosed in the present invention is compared with the prior art, as shown in Table 3. As can be seen from the table, the method for separating ethylbenzene from C8 aromatics proposed by the present invention has better ethylbenzene yield and purity than the conventional technology. In addition, the separation method proposed by the present invention occupies 30% less space and consumes 20% less energy than the conventional device of the same scale.

[0066] Table 2

[0067] wt% Raw material 1 Ethylbenzene 17.66 p-Xylene 18.39 Meta-Xylene 39.98 o-Xylene 23.97 total 100.00

[0068] Table 3 Performance comparison table

[0069]

[0070] Example 2

[0071] This embodiment provides a system and method for separating ethylbenzene from C8 aromatics.

[0072] like Figure 1 , Figure 4 As shown, the reaction process conditions of this embodiment are the same as those of embodiment 1, except that an energy recovery system, i.e., a feed heat exchanger 204, is provided between the C8 aromatic feed and the ethylbenzene product. The ethylbenzene product at about -55°C exchanges heat with the C8 aromatic feed to recover the cold in the ethylbenzene product, which can further reduce the supply of refrigerant in the refrigeration system. Compared with embodiment 1, the energy consumption in this embodiment is reduced by about 10%, which has a significant energy-saving effect.

[0073] Example 3

[0074] This embodiment provides a system and method for separating ethylbenzene from C8 aromatics.

[0075] like Figure 2 , Figure 5As shown, the reaction process conditions of this embodiment are the same as those of embodiment 2, except that this embodiment adopts a two-stage cryogenic separation unit, both of which are connected to the refrigeration system 101 and the heating system 103, and the crude ethylbenzene separated by the 1# cryogenic separation unit 102 is sent to the 2# cryogenic separation unit 104 for re-crystallization separation to improve the purity of ethylbenzene. The purity of ethylbenzene in this embodiment can be increased to 99.5%. Compared with embodiment 2, the purity of ethylbenzene is increased by 1.5%, and the energy consumption is increased by 10%. It is necessary to decide whether to adopt two-stage cryogenic separation according to the actual product purity.

[0076] The method for separating ethylbenzene from C8 aromatics proposed in the present invention adopts a deep cooling + dissolution + reaction method, which greatly reduces the operating energy consumption of the ethylbenzene production process, has high ethylbenzene yield and purity, and is flexible in device operation, and can achieve long-term stable operation.

[0077] The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A method for separating ethylbenzene from C8 aromatics, characterized in that: The method utilizes a system for separating ethylbenzene from C8 aromatics, the system comprising: Refrigeration system (101), cryogenic separation system, heating system (103); The cryogenic separation system is in communication with the refrigeration system (101) and the heating system (103) respectively; The cryogenic separation system comprises ≥1 cryogenic separation units; the cryogenic separation unit comprises ≥2 cryogenic separators (201), each cryogenic separator (201) is arranged in parallel, and a cold exchange component (202) and a stirrer (203) are arranged inside the cryogenic separator (201); The refrigeration system (101) and the heating system (103) are respectively connected to the cold exchange component (202); The refrigeration system (101) comprises a cooling refrigerant (10) and a heat-exchanged refrigerant (11), and the cooling refrigerant (10) and the heat-exchanged refrigerant (11) circulate between the cryogenic separation system and the refrigeration system (101); The heating system (103) comprises a heat supply heating agent (12) and a heat exchange heating agent (13), and the heat supply heating agent (12) and the heat exchange heating agent (13) circulate between the cryogenic separation system and the heating system (103); The inlet of the cold exchange component (202) is respectively connected to the pipelines of the cooling refrigerant (10) and the heating agent (12); The outlet of the cold exchange component (202) is respectively connected to the pipelines of the refrigerant (11) after heat exchange and the heating agent (13) after heat exchange; The system for separating ethylbenzene from C8 aromatics further comprises an energy recovery system, wherein the energy recovery system comprises a feed heat exchanger (204) connected to the cryogenic separator (201); The method includes: a) sending the C8 aromatics (1) to a cryogenic separation system for cryogenic separation; b) a cryogenic separation system separates ethylbenzene (2) and ethylbenzene-poor C8 aromatics (3); The conditions for cryogenic separation include: cryogenic temperature of -80 to -20°C, dissolution temperature of 130 to 250°C, and cryogenic pressure of normal pressure to 4.0 MPa.

2. The method for separating ethylbenzene from C8 aromatics according to claim 1, wherein: The number of the cryogenic separators (201) in the cryogenic separation unit is 2-10.

3. The method for separating ethylbenzene from C8 aromatics according to claim 1, wherein: The number of the cryogenic separators (201) in the cryogenic separation unit is 2-6.

4. The method for separating ethylbenzene from C8 aromatics according to claim 1, wherein: The cooling refrigerant is selected from at least one of ethylene, ethane, propane and propylene.

5. The method for separating ethylbenzene from C8 aromatics according to claim 1, wherein: The heating method of the heating system (103) is selected from at least one of electric heating, fuel gas heating, steam heating and heat transfer medium heating.

6. The method for separating ethylbenzene from C8 aromatics according to claim 1, wherein: The conditions for cryogenic separation include: cryogenic temperature of -80 to -20°C, dissolution temperature of 130 to 250°C, and cryogenic pressure of normal pressure to 4.0 MPa.

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