A method and system for the adsorption separation of full-fraction naphtha

Abstract

The present disclosure relates to an adsorption separation method and separation system for full-fraction naphtha, which comprises: S1, allowing the full-fraction naphtha to enter a first distillation device for first distillation separation to obtain light naphtha and heavy naphtha; S2, allowing the light naphtha to enter a first adsorption separation device for first adsorption separation to obtain a first extract and a first raffinate; allowing the heavy naphtha to enter a second adsorption separation device for second adsorption separation to obtain a second extract and a second raffinate; S3, allowing at least part of the first extract and at least part of the second extract to enter a bulkhead tower for second distillation separation to obtain a first light fraction, an intermediate fraction and a first heavy fraction; S4, allowing at least part of the first heavy fraction to return to the first adsorption separation device as a first desorbent; allowing at least part of the first light fraction to return to the second adsorption separation device as a second desorbent. Desorbent is obtained from naphtha raw material, desorbent input is reduced, and energy consumption for desorbent separation is reduced.

Description

Technical Field

[0001] The present disclosure relates to the technical field of separation of normal alkanes in naphtha, and in particular to an adsorption separation method and a separation system for full-fraction naphtha. Background Art

[0002] Naphtha originally refers to the light fraction in crude oil between the temperature at which atmospheric distillation begins (i.e., the initial distillation point) and 200°C (it can also be cut to a higher or lower temperature as needed). It is a mixture of various hydrocarbons, including normal alkanes, isoalkanes, cycloalkanes, and aromatics of C4 to C11. Later, hydrocarbon mixtures of this fraction from different sources were also called naphtha, such as hydrocracking naphtha, coking naphtha, catalytic cracking naphtha, or oilfield condensate. The content of each component in naphtha from different sources is different, among which the mass fraction of normal alkanes is usually in the range of 20% to 50%, and the mass fraction of non-normal hydrocarbons is in the range of 50% to 80%. Naphtha can be used as a raw material for steam cracking to produce ethylene, catalytic reforming to produce aromatics, or for gasoline blending.

[0003] When used as a raw material for steam cracking to produce ethylene, the composition of naphtha has an important impact on key indicators such as the yield, operating cycle and production cost of the cracking process. Among them, normal alkanes are high-quality raw materials for producing olefins, followed by isoalkanes. Aromatics basically maintain their ring structure under high-temperature cracking conditions and are easily condensed to produce coke, making them unsuitable as cracking raw materials. When used as a raw material for a reforming unit, cycloalkanes are easily converted into aromatics and are better raw materials, while normal alkanes are relatively difficult to convert into aromatics. When used for gasoline blending, the octane number of branched alkanes, cycloalkanes and aromatics is significantly higher than that of normal alkanes. Therefore, separating the different components of naphtha can significantly improve its utilization value, among which the separation of normal alkanes has the most obvious effect: the separated normal alkanes have a higher olefin yield for steam cracking, and the remaining non-normal alkane components have a higher octane number and a higher aromatic yield for reforming.

[0004] There are a large number of patents disclosed for separating normal alkanes by adsorption. For example, a series of patents such as US4176053, US4210771, US4595490, and US4709116 describe the use of 5A molecular sieve adsorbent to adsorb low-octane normal alkanes in the gas phase, and the use of gas to purge the normal alkanes on the desorbent to recycle them for isomerization reaction. The purge gas used is mainly hydrogen. CN1179410A introduces the separation of normal alkanes in C5 and C6 alkane isomerization products by pressure swing adsorption. The above-mentioned gas phase adsorption separation method is mainly suitable for systems with a narrow fraction range and a low carbon number. CN1710030A discloses a method for separating full-fraction naphtha by gas phase adsorption. It is difficult to desorb normal alkanes with a high carbon number, so it is necessary to purge the adsorption column with nitrogen at 400°C during desorption.

[0005] For materials with wider fractions, liquid phase adsorption separation is a more suitable method. Desorbents need to be used in the liquid phase adsorption separation process, and the selection of desorbents has an important influence on the separation performance. CN102811984A discloses a method for separating normal alkanes in full-fraction naphtha by simulated moving bed adsorption, using C12 hydrocarbons as desorbents. The advantage is that the desorbents are easy to separate from the components in the raw materials, thereby reducing the energy consumption of desorbent separation and circulation. However, in the technical solutions used for large-scale industrial production, on the premise of meeting the separation requirements, there are problems such as large desorbent usage and large energy consumption requirements. And desorbents are generally special chemicals with high value, and large consumption of desorbents will also increase costs. Summary of the invention

[0006] The purpose of the present invention is to provide an adsorption separation method and separation system for full-fraction naphtha, which can obtain a desorbent from naphtha raw materials, reduce the desorbent input and reduce the energy consumption of desorbent separation.

[0007] In order to achieve the above-mentioned purpose, the present disclosure provides an adsorption separation method for full-fraction naphtha, comprising: S1, allowing the full-fraction naphtha to enter a first distillation device for a first distillation separation to obtain light naphtha rich in C5-C6 materials and heavy naphtha rich in C8-C10 materials; S2, allowing the light naphtha to enter a first adsorption separation device for a first adsorption separation to obtain a first extract and a first raffinate; allowing the heavy naphtha to enter a second adsorption separation device for a second adsorption separation to obtain a second extract and a second raffinate; S3, allowing at least a portion of the first extract and at least a portion of the second extract to enter a bulkhead tower for a second distillation separation to obtain a first light fraction, an intermediate fraction and a first heavy fraction; S4, allowing at least a portion of the first heavy fraction to return to the first adsorption separation device as a first desorbent; allowing at least a portion of the first light fraction to return to the second adsorption separation device as a second desorbent.

[0008] Optionally, the content of normal alkanes in the full-fraction naphtha is 20-50% by weight; the distillation range cut point of the light naphtha and the heavy naphtha is a temperature of any value between 60 and 95°C; preferably, the content of C5-C6 normal alkanes in the light naphtha is 20-55% by weight, and the content of C8-C10 normal alkanes in the heavy naphtha is 15-35% by weight; the content of normal alkanes of C5 and below in the first light fraction is more than 90% by weight; the content of normal alkanes of C9 and above in the first heavy fraction is more than 90% by weight.

[0009] Optionally, the method also includes: allowing at least part of the first raffinate liquid to enter a first raffinate liquid distillation tower for a third distillation separation to obtain a second light fraction and a second heavy fraction; allowing at least part of the second raffinate liquid to enter a second raffinate liquid distillation tower for a fourth distillation separation to obtain a third light fraction and a third heavy fraction; allowing at least part of the second heavy fraction to return to the first adsorption separation device as the first desorbent; allowing at least part of the third light fraction to return to the second adsorption separation device as the second desorbent.

[0010] Optionally, in step S1, the operating conditions of the first distillation separation include: a tower top pressure of 0.2 to 0.6 MPa, preferably 0.3 to 0.5 MPa, and a tower top temperature of 50 to 125°C, preferably 70 to 110°C.

[0011] Optionally, in step S2, the first adsorption separation device and the second separation device are liquid simulated moving bed adsorption separation devices; the operating conditions of the first adsorption separation and the second adsorption separation each independently include: an operating temperature of 80 to 220°C, preferably 100 to 180°C; an operating pressure of 0.5 to 3.0 MPa, preferably 0.8 to 2.5 MPa.

[0012] Optionally, the adsorbents of the first adsorption separation device and the second adsorption separation device each independently include 80 to 98 weight percent of an active component and 2 to 20 weight percent of a binder; optionally, the active component comprises a type A molecular sieve; and the binder is selected from one or more of alumina, kaolin, bentonite and attapulgite.

[0013] Optionally, in step S3, the number of theoretical plates of the dividing wall tower is 40 to 90; the number of theoretical plates of the dividing wall section is 25 to 45, the number of theoretical plates of the common distillation section is 5 to 15, and the number of theoretical plates of the common stripping section is 10 to 30; the method also includes: at least part of the first extract and at least part of the second extract are fed from the same side of the dividing wall section of the dividing wall tower; the feed position of the raw material of the dividing wall tower is the 10th to 25th theoretical plates from the top to the bottom of the dividing wall section, and the intermediate distillate extraction position is the 5th to 20th theoretical plates from the bottom to the top of the dividing wall section; optionally, the conditions for the second distillation separation include: the operating pressure of the dividing wall tower is 0.1 to 0.5 MPa; the reflux ratio of the top of the dividing wall tower by mass is 1.5 to 4.

[0014] Optionally, the method further comprises: sending another portion of the first light fraction and / or another portion of the first heavy fraction from the dividing wall tower to a cracking device.

[0015] The second aspect of the present disclosure provides an adsorption separation system for full-fraction naphtha, the system comprising: a first rectification device, a first adsorption separation device, a second adsorption separation device, and a dividing wall tower; the first rectification device comprises a naphtha feedstock inlet, a light naphtha outlet, and a heavy naphtha outlet; the first adsorption separation device comprises a light naphtha inlet, a first extract outlet, a first raffinate outlet, and a first desorbent inlet; the light naphtha inlet is connected to the light naphtha outlet of the first rectification device; the second adsorption separation device comprises a heavy naphtha inlet, a second extract outlet, a second raffinate outlet, and a second desorbent inlet; desorbent inlet; the heavy naphtha inlet is connected to the heavy naphtha outlet of the first distillation unit; the bulkhead tower is provided with a first extracted liquid inlet, a second extracted liquid inlet, a first light fraction outlet, an intermediate fraction outlet and a first heavy fraction outlet; the first extracted liquid inlet is connected to the first extracted liquid outlet of the first adsorption separation unit, the second extracted liquid inlet is connected to the second extracted liquid outlet of the second adsorption separation unit; the first light fraction outlet is connected to the second desorbent inlet of the second adsorption separation unit; the first heavy fraction outlet is connected to the first desorbent inlet of the first adsorption separation unit.

[0016] Optionally, the system also includes a first raffinate distillation tower and a second raffinate distillation tower; the first raffinate distillation tower includes a first raffinate inlet, a second light fraction outlet and a second heavy fraction outlet; the first raffinate inlet is connected to the first raffinate outlet of the first adsorption separation device, and the second heavy fraction outlet is connected to the first desorbent inlet of the first adsorption separation device; the second raffinate distillation tower includes a second raffinate inlet, a third light fraction outlet and a third heavy fraction outlet; the second raffinate inlet is connected to the second raffinate outlet of the second adsorption separation device, and the third light fraction outlet is connected to the second desorbent inlet of the second adsorption separation device.

[0017] Through the above technical scheme, the present disclosure provides an adsorption separation method and separation system for full-fraction naphtha, which separates the full-fraction naphtha into light naphtha rich in C5-C6 materials and heavy naphtha rich in C8-C10 materials, and makes the light naphtha enter the first adsorption separation device and the heavy naphtha enter the second adsorption separation device for further adsorption separation, respectively, to obtain a first extract rich in normal alkanes and a second extract rich in normal alkanes, and then the first extract and the second extract are distilled in a distillation tower to achieve the separation of normal alkanes with different carbon numbers. The multi-component separation between the alkanes is achieved, and the distillation tower next door can obtain more types of components, so that the energy saving effect is remarkable; then the normal alkanes with a carbon content of 5 or less (the first light fraction) obtained at the upper part of the distillation tower next door are returned to the second adsorption separation device as the second desorbent, and the normal alkanes with a carbon content of 9 or more (the first heavy fraction) obtained at the bottom of the distillation tower next door are returned to the first adsorption separation device as the first desorbent, thereby realizing the use of the material obtained by the distillation of the naphtha raw material itself as the desorbent, improving the resource utilization effect, reducing the desorbent cost and reducing the energy consumption required for separating the desorbent.

[0018] Other features and advantages of the present disclosure will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings are used to provide a further understanding of the present disclosure and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the present disclosure but do not constitute a limitation of the present disclosure. In the accompanying drawings:

[0020] Figure 1 The figure is an exemplary flow diagram of the adsorption separation method of full-fraction naphtha provided in the present invention.

[0021] Figure 2 The figure is an exemplary flow diagram of the adsorption separation method of full-fraction naphtha provided in the present invention.

[0022] Description of Reference Numerals

[0023] 01-full fraction naphtha, 02-desorbent, 03-desorbent, 10-rectifier, 11-light naphtha, 12-heavy naphtha, 20-first adsorption separation device, 21-first extract, 22-first raffinate, 26-product, 30-second adsorption separation device, 31-second extract, 32-second raffinate, 36-product, 40-next-wall rectifying tower, 41-first light fraction, 42-first heavy fraction, 43-middle fraction, 44-first light fraction used as steam cracking raw material, 45-first heavy fraction used as steam cracking raw material, 50-rectifier, 51-first raffinate, 52-desorbent, 60-rectifier, 61-desorbent, 62-second raffinate DETAILED DESCRIPTION

[0024] The specific implementation of the present disclosure is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described herein is only used to illustrate and explain the present disclosure, and is not used to limit the present disclosure.

[0025] The first aspect of the present disclosure provides a method for the adsorption separation of full-fraction naphtha, the method comprising the following steps:

[0026] S1, allowing the full-fraction naphtha to enter the first distillation device for first distillation separation to obtain light naphtha rich in C5-C6 materials and heavy naphtha rich in C8-C10 materials;

[0027] S2, allowing the light naphtha to enter a first adsorption separation device for first adsorption separation to obtain a first extract and a first raffinate; allowing the heavy naphtha to enter a second adsorption separation device for second adsorption separation to obtain a second extract and a second raffinate;

[0028] S3, allowing at least part of the first extract and at least part of the second extract to enter a dividing wall tower for second distillation separation to obtain a first light fraction, a middle fraction and a first heavy fraction;

[0029] S4. Return at least a portion of the first heavy fraction as a first desorbent to the first adsorption separation device; return at least a portion of the first light fraction as a second desorbent to the second adsorption separation device.

[0030] The method provided by the present invention separates the whole fraction naphtha into light naphtha rich in C5-C6 materials and heavy naphtha rich in C8-C10 materials, and makes the light naphtha enter the first adsorption separation device and the heavy naphtha enter the second adsorption separation device for further adsorption separation, respectively, to obtain a first extract rich in normal alkanes and a second extract rich in normal alkanes, and then the first extract and the second extract are distilled by a distillation tower next door to achieve multi-component separation between normal alkanes with different carbon numbers, and the distillation tower next door can obtain more types of components, so that the energy saving effect is significant; then the normal alkanes with carbon five or less (first light fraction) obtained at the upper part of the distillation tower next door are returned to the second adsorption separation device as the second desorbent, and the normal alkanes with carbon nine or more (first heavy fraction) obtained at the bottom of the distillation tower next door are returned to the first adsorption separation device as the first desorbent, so that the material obtained by the distillation of the naphtha raw material itself is used as the desorbent, the resource utilization effect is improved, the desorbent cost is reduced, and the energy consumption required for separating the desorbent is reduced.

[0031] In a preferred embodiment, the distillation range cut point between the light naphtha and the heavy naphtha is any temperature between 60 and 95°C.

[0032] The present invention cuts the whole fraction naphtha into light naphtha rich in C5-C6 materials and heavy naphtha rich in C8-C10 materials according to the distillation range; most of the normal alkanes in the light naphtha enter the first extraction liquid, and most of the non-normal alkanes in the light naphtha enter the first extraction residual liquid. The normal alkanes separated from the light naphtha can be used as high-quality raw materials for steam cracking devices, and the non-normal alkanes separated from the light naphtha are high-octane components; the normal alkanes can also be converted into high-octane components or non-normal alkanes can be converted into normal alkanes as high-quality cracking raw materials as needed. Most of the normal alkanes in the heavy naphtha enter the second extraction liquid, and most of the non-normal alkanes in the heavy naphtha enter the second extraction residual liquid; the normal alkanes separated from the heavy naphtha can be used as high-quality raw materials for steam cracking devices, and the non-normal alkanes separated from the heavy naphtha are high-quality reforming raw materials. By utilizing the method provided in the present disclosure, each component in the full-fraction naphtha can be fully utilized according to its characteristics, and can be flexibly adapted to various product requirements.

[0033] In a specific embodiment, the content of C5-C6 normal alkanes in the light naphtha is 20-55% by weight, and the content of C8-C10 normal alkanes in the heavy naphtha is 15-35% by weight.

[0034] The full-range naphtha in the present disclosure may be various naphthas, preferably one or a mixture of straight-run naphtha, hydrocracked naphtha, coker naphtha, catalytic cracked naphtha and oilfield condensate.

[0035] In a preferred embodiment, the content of normal alkanes in the whole fraction naphtha is 20 to 50% by weight.

[0036] In one embodiment, the method further comprises:

[0037] Allowing at least a portion of the first raffinate to enter a first raffinate distillation tower for third distillation separation to obtain a second light fraction and a second heavy fraction; allowing at least a portion of the second raffinate to enter a second raffinate distillation tower for fourth distillation separation to obtain a third light fraction and a third heavy fraction;

[0038] returning at least a portion of the second heavy fraction to the first adsorption separation device as the first desorbent;

[0039] At least a portion of the third light fraction is also returned to the second adsorption separation device as the second desorbent.

[0040] Through the above steps, the first raffinate and the second raffinate containing non-normal alkanes are further distilled, and the suitable second heavy fraction and the third light fraction are fully utilized as desorbents, thereby further expanding the source of desorbents, improving resource utilization effects, and reducing desorbent investment.

[0041] The conditions for the third distillation separation and the fourth distillation separation in the present disclosure are conventional operating conditions in the art and can be adjusted according to the raw material composition and the target separation effect. In an exemplary embodiment, the conditions for the third distillation separation and the fourth distillation separation may include: a tower top pressure of 0.12 to 0.2 MPa and a reflux ratio of 0.3 to 1.0.

[0042] In one embodiment, in step S1, the operating conditions of the first distillation separation include: a tower top pressure of 0.2 to 0.6 MPa, preferably 0.3 to 0.5 MPa, and a tower top temperature of 50 to 125°C, preferably 70 to 110°C.

[0043] In one embodiment, in step S2, the first adsorption separation device and the second separation device are liquid phase simulated moving bed adsorption separation devices;

[0044] The operating conditions of the first adsorption separation and the second adsorption separation independently include: an operating temperature of 80 to 220° C., preferably 100 to 180° C.; an operating pressure of 0.5 to 3.0 MPa, preferably 0.8 to 2.5 MPa.

[0045] In a specific embodiment, the adsorbents of the first adsorption separation device and the second adsorption separation device each independently include 80 to 98 weight percent of active components and 2 to 20 weight percent of a binder;

[0046] The active component comprises type A molecular sieve;

[0047] The binder is selected from one or more of alumina, kaolin, bentonite and attapulgite.

[0048] In a specific embodiment, the simulated moving adsorption bed adopts a device conventionally selected in the art, specifically including one or more adsorption towers, preferably one adsorption tower, each adsorption tower is divided into multiple adsorption beds by a grid, and the function of the grid is to redistribute the material from the upper bed to the next bed, mix the material introduced from the outside with the material from the upper bed, and lead a part of the material from the upper bed out of the adsorption tower. The grid allows liquid to pass through and intercepts the adsorbent particles from escaping the adsorbent bed, and its upper and lower surfaces generally use a metal wire mesh, a metal sintered mesh or a Johnson mesh. The material introduced from the outside to a certain bed, and the material led out of the adsorption tower from the upper bed, enter and lead out of the adsorption bed through a pipeline connected to the bed grid.

[0049] Specifically, the materials entering and exiting the adsorption tower include at least raw materials, desorbents, extracts and residual liquids. The raw material is naphtha, and the adsorbent has a higher adsorption selectivity for normal alkanes in the raw material. The desorbent used should have a large difference in boiling point from the raw material, and can be separated from the components in the raw material by distillation. The first adsorption separation device processes materials rich in C5-C6 alkanes, and uses C9 and above normal alkanes or C10 and above normal alkanes as the first desorbent. The first desorbent can be obtained from the bottom of the next-door tower that processes the extract to supplement the first desorbent for the first adsorption separation device; the second adsorption separation device processes materials rich in C8 and above alkanes, and uses C5 and below normal alkanes as the second desorbent. The second desorbent can be obtained from the top of the next-door tower that processes the extract to supplement the second desorbent for the second adsorption separation device. The extract separated by the first adsorption separation device and the second adsorption separation device is enriched with the preferentially adsorbed normal alkane components and also contains a part of desorbent; the raffinate contains a small amount of normal alkanes, and the lower the content, the higher the efficiency of adsorption separation. The main components of the raffinate are the desorbent and the non-normal alkane components in the raw material. The raffinate obtained by the first adsorption separation device and the second adsorption separation device are respectively introduced into the distillation tower (the first raffinate distillation tower and the second raffinate distillation tower), and the desorbent contained in the two raffinates is separated and recycled. The first desorbent is separated from the bottom of the first raffinate distillation tower, and the second desorbent is separated from the top of the second raffinate distillation tower.

[0050] In one embodiment, a portion of the first extracted liquid in the first adsorption separation device may not enter the distillation tower next door, but directly serve as the normal alkane product delivery device, and the reduced circulating desorbent may be supplemented from the bottom of the distillation tower next door, thereby reducing the energy consumption of desorbent separation. In one embodiment, a portion of the second extracted liquid in the second adsorption separation device may not enter the distillation tower next door, but directly serve as the normal alkane product delivery device, and the reduced circulating desorbent may be supplemented from the top of the distillation tower next door, thereby reducing the energy consumption of desorbent separation.

[0051] In one embodiment, in step S3, the number of theoretical plates of the dividing wall tower is 40 to 90; wherein the number of theoretical plates of the dividing wall section is 25 to 45, the number of theoretical plates of the common distillation section is 5 to 15, and the number of theoretical plates of the common stripping section is 10 to 30; the method further comprises:

[0052] At least part of the first extract and at least part of the second extract are fed from the same side of the dividing wall section of the dividing wall tower; the raw material feeding position of the dividing wall tower is the 10th to 25th theoretical plates from the top to the bottom of the dividing wall section, and the intermediate distillate extraction position is the 5th to 20th theoretical plates from the bottom to the top of the dividing wall section.

[0053] In a preferred embodiment, the conditions for the second distillation separation include: the operating pressure of the dividing wall tower is 0.1-0.5 MPa; and the reflux ratio of the top of the dividing wall tower is 1.5-4 by mass.

[0054] Specifically, in the present disclosure, all or part of the first extract and the second extract are fed from one side of the dividing wall section of the dividing wall tower, and normal alkanes with carbon six to carbon eight are extracted from the other side of the dividing wall section; normal alkanes with carbon five and below are obtained at the top of the common distillation section above the dividing wall section of the dividing wall tower; and normal alkanes with carbon nine and above are obtained at the bottom of the common stripping section below the dividing wall section of the dividing wall tower.

[0055] According to the present disclosure, the adsorption tower is divided into a desorption zone, a purification zone, an adsorption zone and an isolation zone along the material flow direction in the adsorption tower. The adsorbent bed between the desorbent injection and the extraction of the extracted liquid is the desorption zone, the adsorbent bed between the extraction of the extracted liquid and the raw material injection is the purification zone, the adsorbent bed between the raw material injection and the extraction of the residual liquid is the adsorption zone, and the adsorbent bed between the extraction of the residual liquid and the desorbent injection constitutes the isolation zone. The number of simulated moving beds is 6 to 24, preferably 8 to 12.

[0056] In one embodiment, the method further comprises: sending another portion of the first light fraction and / or another portion of the first heavy fraction from the dividing wall column to a cracking device.

[0057] The second aspect of the present disclosure provides an adsorption separation system for full-fraction naphtha, the system comprising: a first rectification device, a first adsorption separation device, a second adsorption separation device, and a dividing wall tower; the first rectification device comprises a naphtha raw material inlet, a light naphtha outlet, and a heavy naphtha outlet;

[0058] The first adsorption separation device comprises a light naphtha inlet, a first extract outlet, a first raffinate outlet and a first desorbent inlet; the light naphtha inlet is connected to the light naphtha outlet of the first distillation device;

[0059] The second adsorption separation device comprises a heavy naphtha inlet, a second extract outlet, a second raffinate outlet and a second desorbent inlet; the heavy naphtha inlet is connected to the heavy naphtha outlet of the first distillation device;

[0060] The dividing wall tower is provided with a first extracted liquid inlet, a second extracted liquid inlet, a first light fraction outlet, an intermediate fraction outlet and a first heavy fraction outlet; the first extracted liquid inlet is connected to the first extracted liquid outlet of the first adsorption separation device, the second extracted liquid inlet is connected to the second extracted liquid outlet of the second adsorption separation device; the first light fraction outlet is connected to the second desorbent inlet of the second adsorption separation device; the first heavy fraction outlet is connected to the first desorbent inlet of the first adsorption separation device.

[0061] In one embodiment, the system further comprises a first raffinate distillation tower and a second raffinate distillation tower;

[0062] The first raffinate distillation tower comprises a first raffinate inlet, a second light fraction outlet and a second heavy fraction outlet; the first raffinate inlet is connected to the first raffinate outlet of the first adsorption separation device, and the second heavy fraction outlet is connected to the first desorbent inlet of the first adsorption separation device;

[0063] The second raffinate distillation tower includes a second raffinate inlet, a third light fraction outlet and a third heavy fraction outlet; the second raffinate inlet is connected to the second raffinate outlet of the second adsorption separation device, and the third light fraction outlet is connected to the second desorbent inlet of the second adsorption separation device.

[0064] Any device used in the present disclosure is a structure conventionally selected in the art.

[0065] In a specific implementation, see Figure 1 The specific process flow of the full-fraction naphtha adsorption separation method provided by the present disclosure includes the following steps:

[0066] Material 01 (full fraction naphtha) is subjected to the first distillation separation in a distillation tower 10 (first distillation device) to obtain material 11 (light naphtha) and material 12 (heavy naphtha); material 11 is a light naphtha fraction, and is subjected to the first adsorption separation device 20 to obtain a first extract 21 and a first raffinate 22, and the entire first extract 21 can enter the distillation tower 40 next door, or a portion of the first extract 21 can be directly separated as a product 26, and the rest enters the distillation tower 40 next door; the first raffinate enters the distillation tower 50 (first raffinate distillation tower), and the first raffinate oil 51 (second light fraction) is separated from the top of the distillation tower 50, and the desorbent 52 (second heavy fraction) is at the bottom of the tower. The material 12 is a heavy naphtha fraction, which passes through the second adsorption separation device 30 to obtain a second extract 31 and a second raffinate 32. The entire second extract 31 can enter the distillation tower 40 next door, or a portion of the second extract 31 can be directly separated as the product 36, and the rest enters the distillation tower 40 next door; the second raffinate 32 enters the distillation tower 60 (second raffinate distillation tower), and the desorbent 61 (the third light fraction) is separated from the top of the distillation tower 60, and the bottom of the tower is the second raffinate oil 62 (the third heavy fraction).

[0067] In the distillation tower 40, three streams of materials are separated. A C5 and below normal alkane material 41 (first light fraction) is separated at the top of the distillation tower 40, a C9 and above normal alkane material 42 (first heavy fraction) is separated at the bottom of the distillation tower 40, and a material 43 (middle fraction) mainly containing C6 to C8 normal alkanes is obtained from the middle of the distillation tower 40. At least a portion of the material 41 (first light fraction) is combined with the desorbent 61 (third light fraction) from the distillation tower 60 as the second desorbent 03 of the second adsorption separation device 30, and at least a portion of the material 42 (first heavy fraction) is combined with the desorbent 52 (second heavy fraction) from the distillation tower 50 as the first desorbent 02 of the first adsorption separation device 20.

[0068] The following examples will further illustrate the present disclosure, but are not intended to limit the present disclosure.

[0069] In the following examples, the adsorbent properties of the first adsorption separation device and the second adsorption separation device refer to the RAN-520 adsorbent of Sinopec Catalyst Co., Ltd. Nanjing Branch, which includes an active component 5A molecular sieve (content> 90 weight%) and the rest is a binder kaolin.

[0070] Example 1

[0071] use Figure 2 The method shown specifically comprises the following steps:

[0072] In this embodiment, full-fraction naphtha is used as the raw material, and its flow rate is 100 t / h. The composition of naphtha is shown in Table 1, including C5-C11 hydrocarbons, of which the mass fraction of normal alkanes is 28.7% by weight.

[0073] Material 01 (full fraction naphtha) is subjected to the first distillation separation in the distillation tower 10 (first separation device) to obtain material 11 (light naphtha) mainly composed of C5 and C6, wherein C5 hydrocarbons account for 38.6% by weight, C6 hydrocarbons account for 58.3% by weight, normal alkanes account for about 42.4% by weight, and the content of C5-C6 normal alkanes in light naphtha is about 41.6% by weight; material 12 (heavy naphtha) containing C7 and above fractions is obtained at the bottom of the tower, wherein C5-C6 hydrocarbons account for 5.3% by weight, normal alkanes account for 23.5% by weight, and the content of C8-C10 normal alkanes in heavy naphtha is about 15.6% by weight. The distillation range of light naphtha is 27.6-73.0°C, and the distillation range of heavy naphtha is 85.5-169°C. The operating conditions of the first distillation separation include: the tower top pressure is 0.35MPa, and the tower top temperature is 84°C.

[0074] The material 11 (light naphtha) is passed through the first adsorption separation device 20 for the first adsorption separation, using C9 normal hydrocarbons as the first desorbent to obtain the first extract 21 and the first raffinate 22. The operating conditions of the first adsorption separation include: an operating temperature of 140°C, an operating pressure of 2.0 MPa, and a feed flow rate of the liquid phase material in the first adsorption separation device of 27.5 t / h. The first extracted liquid 21 is composed of a desorbent for normal hydrocarbons of C9 and above and most of the normal alkanes in the C5 and C6 fractions, so that all of the first extracted liquid 21 enters the distillation tower 40 next to the wall; the first raffinate 22 is obtained from the first adsorption separation device 20, including a desorbent for normal hydrocarbons of C9 and above and most of the non-normal alkanes in the C5 and C6 fractions, and the first raffinate 22 enters the distillation tower 50 (the first raffinate distillation tower) for the third distillation separation, and the desorbent for normal hydrocarbons of C9 and above is separated from the non-normal alkanes in the C5 and C6 fractions to obtain a desorbent for normal hydrocarbons of C9 and above 52 (the second heavy fraction) which is recycled back to the first adsorption separation device 20 to obtain non-normal alkanes in the C5 and C6 fractions 51 (the second light fraction) as a product, which can be used as a high-octane gasoline blending component.

[0075] The material 12 (heavy naphtha) is sent to the second adsorption separation device 30 for second adsorption separation, using C5 normal hydrocarbons as the second desorbent to obtain a second extract 31 and a second raffinate 32. The operating conditions of the second adsorption separation include: an operating temperature of 120°C, an operating pressure of 2.0 MPa, and a flow rate of the liquid phase material in the second adsorption separation device of 72.5 t / h. The second extract 31 is composed of C5 normal hydrocarbon desorbent and most of the normal alkanes in C7 and above fractions, and the second extract 31 enters the distillation tower 40 next door; the obtained second raffinate 32 includes C5 normal hydrocarbon desorbent and most of the non-normal alkanes in C7 and above fractions, and the second raffinate 32 enters the distillation tower 60 (second raffinate distillation tower) for the fourth distillation separation, and the C5 normal hydrocarbon desorbent and the non-normal hydrocarbons in C7 and above fractions are separated to obtain C5 normal hydrocarbon desorbent 61 (the third light fraction) which is recycled to the second adsorption separation device 30 to obtain C7 and above fraction non-normal alkanes 62 (the third heavy fraction) as the raw material for the reforming device.

[0076] In the dividing wall distillation tower 40, the material 21 (the first extract) and the material 31 (the second extract) are combined as the raw material for the second distillation separation, and three streams of materials are separated. The C5 normal alkane material 41 (the first light fraction) is separated at the top of the dividing wall tower, and the C9 and above normal alkane material 42 (the first heavy fraction) is separated at the bottom of the dividing wall tower. The normal alkane material 43 (the middle fraction) mainly consisting of C6 to C8 is obtained from the middle of the dividing wall tower. The operating conditions of the second distillation separation include: the operating pressure of the top of the dividing tower is 0.23 MPa, and the reflux ratio of the top of the dividing tower is 2.38 by mass; then a part of the material 41 (first light fraction) is combined with the desorbent 61 (third light fraction) from the distillation tower 60 as the second desorbent 03 of the second adsorption separation device 30, and the remaining part is used as the steam cracking raw material 44; a part 48 of the material 42 (first heavy fraction) is combined with the desorbent 52 from the distillation tower 50 as the first desorbent 02 of the first adsorption separation device 20, and part of it is also used as the steam cracking raw material 45. Among them, the mass fraction of n-pentane in the first light fraction is 94.4% by weight, the composition of the middle fraction is shown in Table 6, the mass fraction of n-nonane in the first heavy fraction is 61.4% by weight, and the mass fraction of n-decane is 33% by weight.

[0077] The flow and composition of material 01 (full fraction naphtha) and two adsorption feeds 11 (light naphtha) and 12 (heavy naphtha) obtained by distillation are shown in Table 2. The flow and composition of the materials in and out of the first adsorption device 20 are shown in Table 3, and the flow and composition of the materials in and out of the second adsorption device 30 are shown in Table 4. The mass fraction of C9 and above normal alkanes in the first desorbent 02 is 95% by weight, and the mass fraction of C5 normal alkanes in the second desorbent 03 is 94.4% by weight.

[0078] In this embodiment, the first extract 21 and the second extract 31 are mixed as feed to the distillation tower 40, with a total of 51 t / h. The composition is shown in Table 5.

[0079] Aspen plus process simulation software was used to simulate the distillation process of the dividing wall tower. The theoretical number of plates in the dividing wall section is 36, the theoretical number of plates in the public distillation section is 10, and the theoretical number of plates in the public stripping section is 18. The feed position is the 16th plate from the top to the bottom of the dividing wall section, the dividing wall is set from the 11th to the 46th plate in the main tower, and the middle extraction position is the 8th plate from the bottom to the top of the dividing wall section, and is located on both sides of the dividing wall with the feed position. The tower top pressure is 0.23MPa, and the reflux ratio is 2.38. The flow rate and composition of the extracted material of the dividing wall tower are shown in Table 6.

[0080] The material 41 (first light fraction) produced from the top of the adjacent tower is 17.0 t / h in total, of which a part of the material 47 has a flow rate of 12.0 t / h, which is combined with the material 61 (with a flow rate of 27.9 t / h) produced from the top of the distillation tower 60 to serve as the second desorbent 03 for the second adsorption separation unit; the material 42 (first heavy fraction) produced from the bottom of the adjacent tower is 17.6 t / h in total, of which a part of the material 48 has a flow rate of 11.6 t / h, which is combined with the material 52 (with a flow rate of 26.7 t / h) produced from the bottom of the distillation tower 50 to serve as the first desorbent 02 for the first adsorption separation unit.

[0081] The final material 44 (flow rate is 5.0 t / h), material 43 (flow rate is 16.4 t / h), and material 45 (flow rate is 6.0 t / h), totaling 27.4 t / h of materials, are used as steam cracking raw materials; the material 51 (flow rate is 16.4 t / h) produced from the top of the distillation tower 50 is used as a high-octane gasoline blending component; the material 62 (flow rate is 56.4 t / h) produced from the bottom of the distillation tower 60 is used as a reforming raw material.

[0082] This embodiment illustrates that the method provided by the present disclosure achieves effective separation of full-fraction naphtha without the need for an external desorbent, thereby reducing costs; it can also obtain fractions of steam cracking feedstock, high-octane gasoline blending components and reforming feedstock, thereby having high economic benefits.

[0083] Example 2

[0084] The same process as in Example 1 is used, but the difference from Example 1 is that:

[0085] The operating conditions of the first distillation separation are: the tower top pressure is 0.32MPa, and the tower top temperature is 90°C.

[0086] The operating conditions of the first adsorption separation include: an operating temperature of 155°C, an operating pressure of 2.5 MPa, and a flow rate of the liquid phase material in the first adsorption separation device of 31.2 t / h;

[0087] The operating conditions of the second adsorption separation include: an operating temperature of 105° C., an operating pressure of 1.2 MPa, and a flow rate of the liquid phase material in the second adsorption separation device of 68.8 t / h.

[0088] This example illustrates that the distillation separation of materials can be achieved through different operating conditions.

[0089] Example 3

[0090] use Figure 1 The process flow shown is different from that of Example 1 in that:

[0091] 25 wt % of the material 21 (first extract) is directly withdrawn as the product 26, and the remaining first extract is introduced into the dividing wall distillation column 40; and

[0092] 25 wt% of material 31 (second extract) is directly withdrawn as product 36, and the remaining second extract is introduced into the distillation column 40. The remaining part of materials 21 and 31, totaling 38.25 t / h, is mixed as feed to the distillation column 40.

[0093] The output 41 from the top of the adjacent tower is 12.75 t / h in total, of which a part of the material 47 has a flow rate of 12.0 t / h, which is combined with the output 61 from the top of the distillation tower 60 (with a flow rate of 27.9 t / h) to serve as the desorbent 03 for the second adsorption separation unit; the output 42 from the bottom of the adjacent tower is 13.2 t / h in total, of which a part of the material 48 has a flow rate of 11.6 t / h, which is combined with the output 52 from the bottom of the distillation tower 50 (with a flow rate of 26.7 t / h) to serve as the desorbent 02 for the first adsorption separation unit.

[0094] The final materials 26 (flow rate is 5.7 t / h), 36 (flow rate is 7.05 t / h), 44 (flow rate is 0.75 t / h), 43 (flow rate is 12.3 / h), and 45 (flow rate is 1.6 t / h), totaling 27.4 t / h of materials, are used as steam cracking raw materials; the top extraction 51 of the distillation tower 50 (flow rate is 16.4 t / h) is used as a high-octane gasoline blending component; the bottom extraction 62 of the distillation tower 60 (flow rate is 56.4 t / h) is used as a reforming raw material.

[0095] According to Example 3, a portion of the first extract in the first adsorption separation device may not enter the distillation tower next door, but can be directly used as the normal alkane product delivery device; a portion of the second extract in the second adsorption separation device may not enter the distillation tower next door, but can be directly used as the normal alkane product delivery device, thereby reducing the energy consumption of desorbent separation.

[0096] Table 1 Naphtha composition

[0097]

[0098] Table 2 Flow rate and composition of adsorption feed

[0099]

[0100] Table 3 Flow rate and composition of materials entering and leaving the first adsorption device 20

[0101]

[0102] Table 4 Flow rate and composition of materials entering and leaving the second adsorption device 30

[0103]

[0104] Table 5 Dividing tower feed composition

[0105]

[0106]

[0107] Table 6 Flow rate and composition of the material produced from the distillation tower

[0108]

[0109] The preferred embodiments of the present disclosure are described in detail above in conjunction with the accompanying drawings, but the present disclosure is not limited to the specific details of the above embodiments, and within the technical concept of the present disclosure, a variety of simple modifications can be made to the technical solution of the present disclosure, and these simple modifications all belong to the protection scope of the present disclosure.

[0110] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present disclosure will not further describe various possible combinations.

[0111] In addition, various embodiments of the present disclosure may be arbitrarily combined, and as long as they do not violate the concept of the present disclosure, they should also be regarded as the contents disclosed by the present disclosure.

Claims

1. A method for the adsorption separation of full-fraction naphtha, characterized in that: The method comprises the following steps: S1, allowing the full-fraction naphtha to enter the first distillation device for first distillation separation to obtain light naphtha rich in C5-C6 materials and heavy naphtha rich in C8-C10 materials; the operating conditions of the first distillation separation include: a tower top pressure of 0.2-0.6 MPa, and a tower top temperature of 50-125°C; S2, the light naphtha is fed into a first adsorption separation device for first adsorption separation to obtain a first extract and a first raffinate; the heavy naphtha is fed into a second adsorption separation device for second adsorption separation to obtain a second extract and a second raffinate; the first adsorption separation device and the second adsorption separation device are liquid phase simulated moving bed adsorption separation devices; the operating conditions of the first adsorption separation and the second adsorption separation are independently: the operating temperature is 80-220°C, and the operating pressure is 0.5-3.0MPa; S3, allowing at least part of the first extract and at least part of the second extract to enter a dividing wall tower for second distillation separation to obtain a first light fraction, a middle fraction and a first heavy fraction; The number of theoretical plates of the dividing wall tower is 40-90; the number of theoretical plates of the dividing wall section is 25-45, the number of theoretical plates of the common distillation section is 5-15, and the number of theoretical plates of the common stripping section is 10-30; the method further comprises: at least part of the first extract and at least part of the second extract are fed from the same side of the dividing wall section of the dividing wall tower; the raw material feeding position of the dividing wall tower is the 10th to 25th theoretical plates from the dividing wall section from top to bottom, and the intermediate distillate extraction position is the 5th to 20th theoretical plates from the dividing wall section from bottom to top; The conditions of the second distillation separation include: the operating pressure of the dividing wall tower is 0.1-0.5 MPa; the reflux ratio of the top of the dividing wall tower by mass is 1.5-4; S4. Return at least a portion of the first heavy fraction as a first desorbent to the first adsorption separation device; return at least a portion of the first light fraction as a second desorbent to the second adsorption separation device.

2. The method according to claim 1, characterized in that The content of normal alkanes in the full-fraction naphtha is 20 to 50% by weight; The distillation range cut point between the light naphtha and the heavy naphtha is a temperature of any value between 60 and 95° C.; the content of C5 to C6 normal alkanes in the light naphtha is 20 to 55% by weight, and the content of C8 to C10 normal alkanes in the heavy naphtha is 15 to 35% by weight; The content of normal alkanes of C5 and below in the first light fraction is greater than 90 wt %; the content of normal alkanes of C9 and above in the first heavy fraction is greater than 90 wt %.

3. The method according to claim 1, characterized in that: The method further includes: Allowing at least a portion of the first raffinate to enter a first raffinate distillation tower for third distillation separation to obtain a second light fraction and a second heavy fraction; allowing at least a portion of the second raffinate to enter a second raffinate distillation tower for fourth distillation separation to obtain a third light fraction and a third heavy fraction; returning at least a portion of the second heavy fraction to the first adsorption separation device as the first desorbent; At least a portion of the third light fraction is also returned to the second adsorption separation device as the second desorbent.

4. The method according to claim 1, characterized in that: In step S1, the operating conditions of the first distillation separation include: a tower top pressure of 0.3-0.5 MPa and a tower top temperature of 70-110°C.

5. The method according to claim 1, characterized in that In step S2, the operating conditions of the first adsorption separation and the second adsorption separation independently include: an operating temperature of 100-180°C and an operating pressure of 0.8-2.5 MPa.

6. The method according to claim 1, characterized in that The adsorbents of the first adsorption separation device and the second adsorption separation device each independently include 80 to 98 weight % of active components and 2 to 20 weight % of a binder; The active component comprises type A molecular sieve; The binder is selected from one or more of alumina, kaolin, bentonite and attapulgite.

7. The method according to claim 1, characterized in that The method further comprises: sending another portion of the first light fraction and / or another portion of the first heavy fraction from the dividing wall column to a cracking device.

8. The adsorption separation system used in the adsorption separation method according to any one of claims 1 to 7, characterized in that: The system comprises: a first distillation device, a first adsorption separation device, a second adsorption separation device, and a dividing wall tower; the first distillation device comprises a naphtha raw material inlet, a light naphtha outlet, and a heavy naphtha outlet; The first adsorption separation device comprises a light naphtha inlet, a first extract outlet, a first raffinate outlet and a first desorbent inlet; the light naphtha inlet is connected to the light naphtha outlet of the first distillation device; The second adsorption separation device comprises a heavy naphtha inlet, a second extract outlet, a second raffinate outlet and a second desorbent inlet; the heavy naphtha inlet is connected to the heavy naphtha outlet of the first distillation device; The dividing wall tower is provided with a first extracted liquid inlet, a second extracted liquid inlet, a first light fraction outlet, an intermediate fraction outlet and a first heavy fraction outlet; the first extracted liquid inlet is connected to the first extracted liquid outlet of the first adsorption separation device, the second extracted liquid inlet is connected to the second extracted liquid outlet of the second adsorption separation device; the first light fraction outlet is connected to the second desorbent inlet of the second adsorption separation device; the first heavy fraction outlet is connected to the first desorbent inlet of the first adsorption separation device.

9. The system according to claim 8, characterized in that The system also includes a first raffinate distillation tower and a second raffinate distillation tower; The first raffinate distillation tower comprises a first raffinate inlet, a second light fraction outlet and a second heavy fraction outlet; the first raffinate inlet is connected to the first raffinate outlet of the first adsorption separation device, and the second heavy fraction outlet is connected to the first desorbent inlet of the first adsorption separation device; The second raffinate distillation tower includes a second raffinate inlet, a third light fraction outlet and a third heavy fraction outlet; the second raffinate inlet is connected to the second raffinate outlet of the second adsorption separation device, and the third light fraction outlet is connected to the second desorbent inlet of the second adsorption separation device.

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