CN117126683A - Separation method and system for aromatic hydrocarbon in diesel oil and related application - Google Patents

Abstract

The invention discloses a separation method, a separation system and related applications of aromatic hydrocarbon in diesel oil, comprising the following steps: adding diesel oil from a diesel oil inlet in the middle of a first cavity of a partition tower, adding an extraction solvent from an extraction solvent inlet at the top of the first cavity, and adding a stripping solvent from a stripping solvent inlet at the bottom of a second cavity; the diesel oil is contacted with an extraction solvent in a first cavity to separate raffinate oil containing non-aromatic hydrocarbon, the raffinate oil is output from a top raffinate oil outlet, and the extraction solvent is output from a bottom extraction solvent outlet; the diesel oil contacts with the back extraction solvent through the communicating area at the bottom of the first cavity and the second cavity, the extracted oil containing aromatic hydrocarbon and the back extraction solvent is separated, the extracted oil is output to the solvent recovery tower from the extracted oil outlet at the upper half part, the separation is carried out in the solvent recovery tower, the back extraction solvent is output from the back extraction solvent outlet at the top of the solvent recovery tower, and the aromatic hydrocarbon is output from the aromatic hydrocarbon outlet at the bottom. The method can efficiently separate aromatic hydrocarbon in diesel oil, and has the advantages of simple process flow, short flow, low energy consumption, less equipment investment and low cost.

Description

A method and system for separating aromatic hydrocarbons from diesel and related applications

Technical Field

The invention relates to the technical field of diesel processing, and in particular to a method and system for separating aromatics from diesel and related applications.

Background Art

Diesel fractions are mainly derived from atmospheric and vacuum, catalytic cracking, hydrocracking and other units. Diesel fractions mainly contain aromatic and non-aromatic components. Monocyclic aromatics and polycyclic aromatics in the aromatic components are not suitable as diesel blending components, while non-aromatics are suitable as diesel blending and chemical raw material components. With the transformation and high-quality development of my country's refining and chemical industry, the trend of diesel surplus has intensified. High efficiency, low energy consumption, flexible production and full utilization of diesel blending components are important ways for petrochemical enterprises to achieve high-quality and sustainable development.

Summary of the invention

The inventors of the present application have found that currently, diesel fraction separation generally uses traditional 3-4 or even up to 6 distillation towers for separation or simulated moving bed adsorption separation to obtain corresponding aromatic and non-aromatic products. These existing fraction separation methods have long process flows, complex operations, large equipment investments, high energy consumption, low product yields, and high production costs when separating aromatics from diesel.

In view of the above problems, the present invention is proposed to provide a method, system and related applications for separating aromatics in diesel that overcome the above problems or at least partially solve the above problems.

The embodiment of the present invention provides a method for separating aromatics in diesel, comprising:

Add diesel from the diesel inlet in the middle of the first cavity of the dividing wall tower, add extraction solvent from the extraction solvent inlet at the top of the first cavity, and add stripping solvent from the stripping solvent inlet at the bottom of the second cavity of the dividing wall tower;

The diesel oil is contacted with the extraction solvent in the first cavity, and the raffinate oil containing non-aromatic hydrocarbons is separated and output from the raffinate oil outlet at the top of the first cavity, and the extraction solvent is output from the extraction solvent outlet at the bottom of the first cavity;

The diesel oil is contacted with the stripping solvent through the communicating area at the bottom of the first cavity and the second cavity, and extracted oil containing aromatic hydrocarbons and stripping solvent is separated and output to a solvent recovery tower from the extracted oil outlet at the upper half of the second cavity. The extracted oil is separated in the solvent recovery tower, and the stripping solvent is output from the stripping solvent outlet at the top of the solvent recovery tower, and aromatic hydrocarbons are output from the aromatic hydrocarbon outlet at the bottom.

In some optional embodiments, the diesel oil is contacted with an extraction solvent in the first chamber to separate the raffinate oil containing non-aromatic hydrocarbons and output the raffinate oil from the raffinate oil outlet at the top of the first chamber, comprising:

The diesel oil is contacted with the extraction solvent in the first cavity and heated by the reboiler of the tower bottom. Under the action of the extraction solvent, the non-aromatic hydrocarbons in the diesel oil are evaporated toward the top. After condensation by the top condenser, the raffinate oil containing non-aromatic hydrocarbons is output from the raffinate oil outlet at the top of the first cavity.

In some optional embodiments, the diesel oil is contacted with the stripping solvent via the bottom communicating area of the first cavity and the second cavity, and the extracted oil containing aromatics and the stripping solvent is separated and outputted from the extracted oil outlet of the upper half of the second cavity, comprising:

The diesel oil is in contact with the stripping solvent in the communicating area at the bottom of the first cavity and the second cavity or in the second cavity, and is heated by the reboiler of the tower bottom. Under the action of the stripping solvent, the remaining aromatics in the diesel oil and the stripping solvent are evaporated upward together. After being condensed by the condenser, the extracted oil containing the aromatics and the stripping solvent is output from the extracted oil outlet of the upper half of the second cavity.

In some optional embodiments, the extracted oil is separated in a solvent recovery tower, the stripping solvent is output from the stripping solvent outlet at the top of the solvent recovery tower, and the aromatic hydrocarbons are output from the aromatic hydrocarbon outlet at the bottom, comprising:

In the solvent recovery tower, the extracted oil is heated by the reboiler in the tower bottom to make the stripping agent evaporate toward the top, and after condensation by the condenser at the top, the stripping solvent is output from the stripping solvent outlet at the top, and the remaining aromatics are output from the aromatics outlet at the bottom.

In some optional embodiments, the ratio of the inner surface areas of the tower walls of the first cavity and the second cavity is 3:7 to 7:3.

In some optional embodiments, the above further includes: after the extraction solvent is output from the extraction solvent outlet at the bottom of the first chamber, it is transported to the extraction solvent inlet and added into the dividing wall tower; and/or

The stripping solvent is output from the stripping solvent outlet at the top of the solvent recovery tower, transported to the stripping solvent inlet of the dividing wall tower, and added into the dividing wall tower.

In some optional embodiments, the mass ratio of the stripping agent to diesel is 0.5-6, and the mass ratio of the extracting agent to the stripping agent is 0.01-2.

In some optional embodiments, the extraction solvent is an organic solvent or an ionic liquid, wherein the organic solvent is at least one of N,N-dimethylformamide, dimethyl sulfoxide, N,N-diethylformamide, ethylene glycol methyl ether, furfural or morpholine; the cation in the ionic liquid is one of an imidazole cation and a pyridine cation, and the anion in the ionic liquid is at least one of a tetrafluoroborate anion, a hexafluorophosphate anion and a bistrifluoromethanesulfonate imide anion.

In some optional embodiments, the cation is at least one of 1-methyl-3-ethylimidazolium cation MEIM ⁺ , 1-heptyl-3-methylimidazolium cation C7MIM ⁺ , and 1,3-dimethylpyridine MMPY ⁺ cation; the anion is at least one of tetrafluoroborate and BF4 ^-1 anions and hexafluorophosphate and PF6 ^- anions.

In some optional embodiments, the stripping solvent is at least one of C4-C10 alkanes and cycloalkanes.

In some optional embodiments, the stripping solvent is at least one of cyclohexane, n-heptane, n-octane and n-hexane.

In some optional embodiments, the number of theoretical plates of the dividing wall tower is 20-150. During use, the operating pressure is 0.05-2Mpa, the tower top temperature is 20-120°C, and the tower bottom temperature is 50-150°C.

In some optional embodiments, the number of theoretical plates of the solvent recovery tower is 5-40. During use, the operating pressure is 10Kpa-0.2MPa, the tower top temperature is 20-120°C, and the tower bottom temperature is 45-150°C.

The embodiment of the present invention provides a system for separating aromatics from diesel, comprising: a bulkhead tower and a solvent recovery tower;

The bulkhead tower is provided with a partition wall inside to divide the inside of the tower body into a first inner cavity and a second inner cavity connected at the bottom, and the bottom of the tower body is provided with an extraction solvent outlet; the middle part of the first cavity is provided with a diesel inlet, and the top is provided with an extraction solvent inlet and a raffinate oil outlet; the upper half of the second cavity is provided with an extracted oil outlet, and the bottom is provided with a stripping solvent inlet; the bulkhead tower is used to make the diesel entering from the diesel inlet contact with the extraction solvent entering from the extraction solvent inlet in the first cavity, separate the raffinate oil containing non-aromatic hydrocarbons and output it from the raffinate oil outlet, make the diesel contact with the stripping solvent entering from the stripping solvent inlet through the bottom connecting area of the first cavity and the second cavity, separate the extracted oil containing aromatic hydrocarbons and stripping solvent and output it from the extracted oil outlet, and output the extraction solvent from the extraction solvent outlet;

The solvent recovery tower is provided with an extracted oil inlet in the middle, an aromatics outlet at the bottom, and a stripping solvent outlet at the top; the extracted oil inlet is connected to the extracted oil outlet of the bulkhead tower, and the solvent recovery tower is used to separate aromatics from the extracted oil output from the bulkhead tower and output them from the aromatics outlet and separate stripping solvent from the stripping solvent outlet.

In some optional embodiments, the partition wall of the partition wall tower is an intermediate partition wall;

The dividing wall column is provided with at least one reboiler and/or at least one condenser.

In some optional embodiments, the solvent recovery tower is provided with at least one reboiler and/or at least one condenser.

In some optional embodiments, the ratio of the inner surface areas of the tower walls of the first cavity and the second cavity is 3:7 to 7:3.

In some optional embodiments, the extraction solvent outlet and the extraction solvent inlet of the dividing wall column are connected, so that the extraction solvent is output from the extraction solvent outlet and transported to the extraction solvent inlet to be added to the dividing wall column; and/or

The stripping agent outlet of the solvent recovery tower is communicated with the stripping agent inlet of the dividing wall tower, so as to provide the stripping solvent outputted from the solvent recovery tower to the dividing wall tower.

In some optional embodiments, the number of theoretical plates of the dividing wall tower is 20-150. During use, the operating pressure is 0.05-2Mpa, the tower top temperature is 20-120°C, and the tower bottom temperature is 50-150°C.

In some optional embodiments, the number of theoretical plates of the solvent recovery tower is 5-40. During use, the operating pressure is 10Kpa-0.2MPa, the tower top temperature is 20-120°C, and the tower bottom temperature is 45-150°C.

An embodiment of the present invention provides a bulkhead tower, comprising: a hollow tower body;

A partition wall is provided inside the tower body to divide the inside of the tower body into a first inner cavity and a second inner cavity which are connected at the bottom;

The bottom of the tower body is provided with an extraction solvent outlet;

The middle of the first cavity is provided with a diesel inlet, and the top is provided with an extraction solvent inlet and a raffinate oil outlet;

The upper part of the second chamber is provided with an oil extraction outlet, and the bottom is provided with a stripping solvent inlet.

In some optional embodiments, the ratio of the inner surface areas of the tower walls of the first cavity and the second cavity is 3:7 to 7:3, and the number of theoretical plates is 20-150.

In some optional embodiments, the dividing wall of the dividing wall tower is an intermediate dividing wall; a reboiler is provided at the bottom of the dividing wall tower, and/or at least one condenser is provided at the top of the tower.

An embodiment of the present invention provides a method for separating aromatics from diesel using the above-mentioned system for separating aromatics from diesel.

An embodiment of the present invention provides an application of the above-mentioned method for separating aromatics in diesel in a process for separating aromatics in diesel.

The beneficial effects of the above technical solution provided by the embodiment of the present invention include at least:

By adopting a bulkhead tower and a solvent recovery tower, and by properly adding an extraction solvent and a back-extraction solvent, two towers, namely a bulkhead tower and a recovery tower, can be used to effectively separate aromatics from diesel. The diesel contacts with the extraction solvent in a cavity of the bulkhead tower to separate aromatics, and then enters another cavity and contacts with the back-extraction solvent to separate extracted oil containing the back-extraction solvent and aromatics, and the back-extraction solvent is separated in the solvent recovery tower to obtain aromatics. The method can realize efficient separation of aromatics in diesel through a bulkhead tower and a solvent recovery tower, and has a simple process flow, a short process flow, low energy consumption, small equipment investment, and low cost.

Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the written description, claims, and drawings.

The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

FIG1 is a schematic diagram of the structure of a separation system for aromatics in diesel according to an embodiment of the present invention;

FIG2 is a schematic structural diagram of a bulkhead tower provided with an intermediate bulkhead in an embodiment of the present invention;

FIG3 is a flow chart of a method for separating aromatics from diesel in an embodiment of the present invention.

DETAILED DESCRIPTION

The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

In order to solve the problems existing in the prior art of separating aromatics from diesel, such as long process flow, complicated operation, large equipment investment, high energy consumption, low product yield, high production cost, etc., the embodiment of the present invention provides a method and system for separating aromatics from diesel, which can achieve efficient separation of aromatics in diesel through a bulkhead tower and a solvent recovery tower, and has a simple process flow, short process flow, low energy consumption, small equipment investment and low cost.

An embodiment of the present invention provides a system for separating aromatics from diesel, the structure of which is shown in FIG. 1 , and includes a dividing wall tower 6 and a solvent recovery tower 8 .

A partition wall is provided inside the bulkhead tower 6 to divide the interior of the tower body into a first inner cavity and a second inner cavity connected at the bottom, and an extraction solvent outlet is provided at the bottom of the tower body; a diesel inlet is provided in the middle of the first cavity, and an extraction solvent inlet and a raffinate oil outlet are provided at the top; an extracted oil outlet is provided in the upper half of the second cavity, and a stripping solvent inlet is provided at the bottom; the bulkhead tower is used to make the diesel entering from the diesel inlet contact with the extraction solvent entering from the extraction solvent inlet in the first cavity, separate the raffinate oil containing non-aromatic hydrocarbons and output it from the raffinate oil outlet, make the diesel contact with the stripping solvent entering from the stripping solvent inlet through the bottom connecting area of the first cavity and the second cavity, separate the extracted oil containing aromatic hydrocarbons and stripping solvent and output it from the extracted oil outlet, and the extraction solvent is output from the extraction solvent outlet;

The solvent recovery tower 8 is provided with an extracted oil inlet in the middle, an aromatics outlet at the bottom, and a stripping solvent outlet at the top; the extracted oil inlet is connected to the extracted oil outlet of the next-door tower, and the solvent recovery tower is used to separate aromatics from the extracted oil output from the next-door tower and output them from the aromatics outlet and separate stripping solvent from the stripping solvent outlet.

The oil extraction outlet is provided in the upper part of the second cavity, which means that the oil extraction outlet is provided at a position slightly above the middle of the second cavity, i.e., a position greater than 1/2 of the total height of the bulkhead tower. Preferably, the oil extraction outlet is not provided at the top, i.e., it is provided at a position slightly above the middle, i.e., 2/3-4/5 of the total height of the bulkhead tower.

In some optional embodiments, the bulkhead tower 6 can be a bulkhead rectification tower, and the partition wall of the bulkhead tower 6 is a middle bulkhead. As shown in FIG2 , the bulkhead tower of the middle bulkhead, the bottom and the top are connected, and the middle is separated by a partition wall. Optionally, the bulkhead tower can also be a bulkhead tower structure of the upper bulkhead, only the bottom is connected, and the middle and the top are separated by a partition wall.

Preferably, the raffinate oil outlet arranged at the top of the first cavity of the bulkhead tower is higher than the extraction solvent inlet; the stripping solvent inlet arranged at the bottom of the second cavity is slightly above the bottom and higher than the extraction solvent outlet.

The extraction solvent outlet and the extraction solvent inlet of the dividing wall tower are connected so that the extraction solvent output from the extraction solvent outlet can be transported to the extraction solvent inlet and added to the dividing wall tower. As shown in Figure 1, the extraction solvent output from the extraction solvent outlet can be partially transported to the extraction solvent inlet and added to the dividing wall tower together with new extraction solvent, and partially separated and recovered.

The partition wall in the next-door tower is not arranged in the middle, but is slightly biased to one side, for example, the inner surface area ratio of the tower wall of the first cavity and the second cavity is 3:7-7:3, that is, the area ratio of the feed side and the product output side of the next-door tower is 3:7-7:3. Multilayer plates are arranged in the two cavities of the next-door tower to divide the space in the cavity into multilayer spaces. Preferably, the number of theoretical plates of the next-door tower is 20-150. During use, the operating pressure is 0.05-2Mpa, the tower top temperature is 20-120°C, and the tower bottom temperature is 50-150°C.

The next-door tower is provided with at least one reboiler and/or at least one condenser. Preferably, the next-door tower has at least one reboiler in the tower kettle, and/or at least one condenser in the tower top. The tower kettle refers to the liquid storage area at the lower end of the container, which is a part of the container volume. The tower kettle is not the bottom of the tower, and generally refers to the part where the liquid phase evaporates in the lower part of the tower. The condenser and reboiler in the next-door tower can have different combinations, which may specifically include but are not limited to the following combinations: two condensers and one reboiler; one condenser and one reboiler; no condenser or one reboiler; two condensers and no reboiler, one condenser and no reboiler, and so on. Optionally, the condenser and reboiler can also be arranged in the middle of the tower.

In some optional embodiments, the stripping solvent outlet of the solvent recovery tower is connected to the stripping solvent inlet of the dividing wall tower, so as to provide the stripping solvent output from the solvent recovery tower to the dividing wall tower, so that the separated stripping solvent and the new stripping solvent can be added to the dividing wall tower for reuse, and part of the stripping solvent can be recovered.

The solvent recovery tower is provided with multi-layer plates to divide the space inside the tower into multi-layer spaces. Preferably, the theoretical number of plates of the solvent recovery tower is 5-40. During use, the operating pressure is 10Kpa-0.2MPa, the tower top temperature is 20-120°C, and the tower bottom temperature is 45-150°C.

The solvent recovery tower is provided with at least one reboiler and at least one condenser. Preferably, the bottom of the solvent recovery tower is provided with at least one reboiler, and the top of the tower is provided with at least one condenser. The solvent recovery tower can adopt a conventional distillation tower, and optionally, the condenser and the reboiler can also be arranged in the middle position of the tower.

The above-mentioned dividing wall tower and solvent recovery tower are provided with necessary auxiliary equipment such as pumps and heat exchangers, which will not be described one by one in this application.

The embodiment of the present invention further provides a bulkhead tower, comprising: a hollow tower body;

A partition wall is provided inside the tower body to divide the interior of the tower body into a first inner cavity and a second inner cavity which are connected at the bottom; an extraction solvent outlet is provided at the bottom of the tower body; a diesel inlet is provided in the middle of the first cavity, and an extraction solvent inlet and a residual oil outlet are provided at the top; an extracted oil outlet is provided in the upper half of the second cavity, and a reverse extraction solvent inlet is provided at the bottom.

The partition wall arranged in the next-door tower is a partition plate, which divides the next-door tower into two sides. For the next-door tower on the upper next-door wall, the partition plate extends to the top of the next-door tower, so that the two sides at the top of the tower are not connected. There is a gap between the lower end of the partition plate and the bottom of the next-door tower, so that the two sides are connected in the tower kettle section; diesel and extraction solvent enter from the upper and lower parts of the same side respectively, and the back-extraction solvent enters from the lower part of the other side, and the raffinate oil is separated from the diesel feed side of the tower top, and the extracted oil is separated from the back-extraction solvent feed side of the tower top and enters the solvent recovery tower; the extraction solvent is discharged from the next-door kettle.

The ratio of the inner surface area of the tower wall of the first cavity to that of the second cavity is 3:7 to 7:3, and the number of theoretical plates is 20-150.

The dividing wall of the dividing wall tower is an upper dividing wall or a middle dividing wall; the tower kettle of the dividing wall tower is provided with a reboiler, and/or the tower top is provided with at least one condenser.

The separation system of aromatics in diesel has a simple process flow. In practical applications, the extraction solvent and the stripping solvent can be new, or the extraction solvent recovered from the bulkhead tower and the stripping solvent recovered from the recovery tower can be used, or the new and the stripping solvent can be mixed together. The following is an example of using the mixed together. As shown in FIG1 , it mainly includes a bulkhead tower 6 and a solvent recovery tower 8. The bulkhead tower 6 realizes the separation of the aromatic fraction, the non-aromatic fraction and the extraction solvent in the diesel; the solvent recovery tower 8 realizes the separation of the stripping solvent and the aromatics; finally, the efficient utilization of the aromatic and non-aromatic fractions in the diesel is realized. Diesel 1 enters from the middle of the next-door tower 6, the new extraction solvent 2 and the extraction solvent 14 returned from the bottom of the next-door tower 6 are mixed with the extraction solvent 4 and the diesel 1 and enter from the upper part of the same side of the next-door tower, and the side where the diesel and the extraction solvent enter from the top of the next-door tower is separated to extract the raffinate oil 5, which is mainly non-aromatic hydrocarbons, and the stripping solvent 12 (including the new stripping solvent 11 and the stripping solvent 15 returned from the solvent recovery tower) enters from the bottom of the other side of the next-door tower 6, and the side where the stripping solvent enters from the next-door tower 6 extracts the extracted oil 7 from the upper part of the tower, which is mainly stripping solvent and aromatic hydrocarbons. Entering the solvent recovery tower 8, the extraction solvent 3 distilled from the bottom of the tower 6 is divided into two parts. A part of the extraction solvent 14 is mixed with the fresh extraction solvent 2 and then returned to the tower 6 for recycling, and a part of the extraction solvent 13 can be discharged from the tower for recovery; the extracted oil 7 from the tower 6 enters the solvent recovery tower 8, and the stripping solvent 9 is separated from the top of the tower. The stripping solvent 9 can be divided into two parts. A part of the stripping solvent 15 is mixed with the fresh stripping solvent 11 and then returned to the tower 6 for recycling, and a part of the stripping solvent 16 can be discharged from the tower for recovery.

Based on the same inventive concept, an embodiment of the present invention provides a method for separating aromatics from diesel, the process of which is shown in FIG3 and comprises the following steps:

Step S101: adding diesel from the diesel inlet in the middle of the first cavity of the dividing wall tower, adding extraction solvent from the extraction solvent inlet at the top of the first cavity, and adding stripping solvent from the stripping solvent inlet at the bottom of the second cavity of the dividing wall tower.

Diesel, extraction solvent and stripping solvent enter the bulkhead tower, and the amount entering can be adjusted as needed. Preferably, the mass ratio of stripping agent to diesel is 0.5-6, and the mass ratio of extraction agent to stripping agent is 0.01-2.

Step S102: Diesel oil is contacted with an extraction solvent in the first chamber to separate raffinate oil containing non-aromatic hydrocarbons and output from the raffinate oil outlet at the top of the first chamber, and the extraction solvent is output from the extraction solvent outlet at the bottom of the first chamber.

The raffinate oil 5 is separated from the diesel feed side at the top of the bulkhead tower 6, which is mainly non-aromatic hydrocarbons, and the extraction solvent 3 is separated from the bottom of the bulkhead tower 6. Specifically, the diesel oil contacts with the extraction solvent in the first cavity, and is heated by the reboiler of the bottom of the tower. Under the action of the extraction solvent, the non-aromatic hydrocarbons in the diesel oil evaporate to the top, and after condensation by the top condenser, the raffinate oil containing non-aromatic hydrocarbons is output from the raffinate oil outlet at the top of the first cavity.

Step S103: The diesel oil is contacted with the stripping solvent through the bottom connecting area of the first cavity and the second cavity, and the extracted oil containing aromatics and the stripping solvent is separated and output to the solvent recovery tower from the extracted oil outlet of the upper part of the second cavity.

Extracted oil 7, which is mainly aromatic hydrocarbons and stripping solvent, is separated at the stripping solvent feed side of the top of the bulkhead tower 6 and enters the solvent recovery tower 8. Specifically, the diesel oil contacts with the stripping solvent in the communicating area at the bottom of the first cavity and the second cavity or in the second cavity, and is heated by the reboiler of the tower kettle. Under the action of the stripping solvent, the remaining aromatic hydrocarbons in the diesel oil and the stripping solvent are evaporated upward together. After condensation in the condenser, the extracted oil containing aromatic hydrocarbons and stripping solvent is output from the extracted oil outlet of the upper half of the second cavity.

Step S104: Separating the extracted oil in a solvent recovery tower, outputting the stripping solvent from the stripping solvent outlet at the top of the solvent recovery tower, and outputting the aromatic hydrocarbons from the aromatic hydrocarbon outlet at the bottom.

The stripping solvent is separated at the top of the solvent recovery tower 8, and the aromatic hydrocarbons are separated at the bottom of the tower. Specifically, in the solvent recovery tower, the extracted oil is heated by the reboiler in the tower kettle to make the stripping agent evaporate to the top, and after condensation by the condenser at the top, the stripping solvent is output from the stripping solvent outlet at the top, and the remaining aromatic hydrocarbons are output from the aromatic hydrocarbon outlet at the bottom.

Optionally, the method further includes delivering the extraction solvent from the extraction solvent outlet at the bottom of the first cavity to the extraction solvent inlet and adding it to the bulkhead tower, thereby realizing the recovery and reuse of the extraction solvent. That is, the extraction solvent 3 is separated from the bottom of the bulkhead tower 6, part of which is recycled and part of which is recovered from the tower.

Optionally, the method further comprises outputting the stripping solvent from the stripping solvent outlet at the top of the solvent recovery tower, transporting it to the stripping solvent inlet of the next-door tower and adding it to the next-door tower, thereby realizing the recovery and reuse of the stripping solvent. That is, the stripping solvent is separated from the top of the solvent recovery tower 8, part of which is recycled and part of which is recovered from the tower.

In the above method, the extraction solvent is an organic solvent or an ionic liquid, wherein:

The organic solvent is at least one of N,N-dimethylformamide, dimethyl sulfoxide, N,N-diethylformamide, ethylene glycol methyl ether, furfural or morpholine.

The ionic liquid includes cations and anions. The cations in the ionic liquid are one of imidazole cations and pyridinium cations, and the anions in the ionic liquid are at least one of tetrafluoroborate anions, hexafluorophosphate anions, and bistrifluoromethanesulfonimide anions.

Preferably, the cation is at least one of 1-methyl-3-ethylimidazolium cation (MEIM ⁺ ), 1-heptyl-3-methylimidazolium cation (C7MIM ⁺ ), and 1,3-dimethylpyridinium (MMPY ⁺ ) cation; the anion is at least one of tetrafluoroborate (BF4 ^-1 ) anion and hexafluorophosphate (PF6 ^- ) anion.

The stripping solvent is at least one of C4-C10 alkanes and cycloalkanes. Preferably, the stripping solvent is at least one of cyclohexane, n-heptane, n-octane and n-hexane.

In the above method, the preferred range of the theoretical plate number of the dividing wall tower is 20-150. During use, the operating pressure is 0.05-2Mpa, the tower top temperature is maintained at 20-120°C, and the tower bottom temperature is 50-150°C; the preferred range of the theoretical plate number of the solvent recovery tower is 5-40. During use, the operating pressure is 10Kpa-0.2MPa, the tower top temperature is maintained at 20-120°C, and the tower bottom temperature is 45-150°C; so as to effectively separate aromatics and non-aromatics in diesel, and recover the extraction solvent and the back-extraction solvent.

The above method of this embodiment is a method for producing aromatics and non-aromatics using diesel in an efficient, short process, low energy consumption and low investment. The use of a bulkhead tower to replace the traditional distillation tower can not only achieve efficient separation and fractional utilization of aromatics and non-aromatics, but also reduce the number of equipment such as distillation towers, shorten the recovery process, and achieve reduced energy consumption and investment. It is a method that can efficiently, energy-savingly and flexibly utilize diesel, realize the high-value utilization of diesel fractions, and can separate aromatics and non-aromatics from diesel, providing high-quality raw materials for downstream high-value utilization.

Based on the same inventive concept, an embodiment of the present invention further provides a method for separating aromatics from diesel using the above-mentioned system for separating aromatics from diesel.

Based on the same inventive concept, an embodiment of the present invention further provides an application of the above-mentioned method for separating aromatics in diesel in a process for separating aromatics in diesel.

Regarding the separation method and related system of aromatics in diesel in the above embodiments, the relevant contents have been described in one part and will not be elaborated in detail in the other part.

The following is an explanation through specific embodiments.

The diesel fraction mainly contains aromatic hydrocarbons such as monocyclic aromatic hydrocarbons, dicyclic aromatic hydrocarbons and polycyclic aromatic hydrocarbons, as well as non-aromatic hydrocarbons such as paraffins and cycloalkanes. It mainly comes from atmospheric and vacuum diesel, catalytic cracking diesel, hydrocracking diesel, coking diesel, etc., but is not limited to the above sources. The composition of typical atmospheric and vacuum diesel (also called straight-run diesel) is shown in Table 1, and the composition of typical catalytic cracking diesel is shown in Table 2.

Table 1

Table 2

The above table is only an example of the component content in diesel. In fact, the component content of diesel is closely related to its source, but it does not affect the applicability of the present invention.

The following lists some experiments and related experimental data on separating aromatics from diesel using the system and method for separating aromatics from diesel provided by the embodiments of the present invention.

Example 1

The raw material is diesel with the component content listed in Table 1, the feed pressure is 0.3Mpa; the feed temperature is 35°C; the bulkhead tower 6 adopts the middle bulkhead form, the theoretical plate number is 20, the operating conditions are the operating pressure of 0.1Mpa, the tower top temperature is 25°C, the tower bottom temperature is 50°C, and the area ratio of the two sides of the bulkhead tower 6 is 4:6; the solvent recovery tower 8 has a theoretical plate number of 5, and the operating conditions are: operating pressure 50Kpa, tower top temperature 60°C, and tower bottom temperature 80°C. In this embodiment, the extraction solvent is an ionic liquid, wherein the ionic liquid cation is 1-methyl-3-ethylimidazole (MEIM+), and the anion is tetrafluoroborate helium (BF4-1); the stripping solvent is cyclohexane; the mass ratio of the stripping agent to the diesel is 0.5, and the mass ratio of the extracting agent to the stripping agent is 0.1. The mass fraction of aromatics in the extracted oil is more than 95%; the mass fraction of non-aromatics in the raffinate oil is more than 85%.

Example 2

The raw material is diesel with the component content listed in Table 2, the feed pressure is 0.3Mpa; the feed temperature is 40℃; the bulkhead tower 6 adopts the middle bulkhead form, the theoretical plate number is 150, and its operating conditions are operating pressure 0.3Mpa, tower top temperature 20℃, tower bottom temperature 50℃, and the area ratio of both sides of the bulkhead tower 6 is 6:4; the solvent recovery tower 8 has 20 theoretical plates, and the operating conditions are: operating pressure 20Kpa, tower top temperature 53℃, and tower bottom temperature 75℃. In this embodiment, the extraction solvent is: ionic liquid, wherein the ionic liquid cation is 1-heptyl-3-methylimidazole (C7MIM+), and the anion is hexafluorophosphate (PF6-); the stripping solvent is n-heptane; the mass ratio of stripping agent to diesel is 1, and the mass ratio of extracting agent to stripping agent is 0.05. The mass fraction of aromatics in the extracted oil is more than 90%; the mass fraction of non-aromatics in the raffinate oil is more than 80%.

Example 3

The raw material is diesel with the component content listed in Table 1, the feed pressure is 0.4Mpa; the feed temperature is 40°C; the bulkhead tower 6 adopts the middle bulkhead form, the theoretical plate number is 90, and its operating conditions are: operating pressure 0.2Mpa, tower top temperature 50°C, tower bottom temperature 80°C, and the area ratio of both sides of the bulkhead tower 6 is 5:5; the solvent recovery tower 8 has 30 theoretical plates, and the operating conditions are: operating pressure 10Kpa, tower top temperature 50°C, and tower bottom temperature 70°C. In this embodiment, the extraction solvent is: ionic liquid, wherein the ionic liquid cation is 1-methyl-3-ethylimidazole (MEIM ⁺ ), and the anion is tetrafluoroborate (BF4 ^-1 ); the stripping solvent is n-hexane; the mass ratio of stripping agent to diesel is 0.5, and the mass ratio of extracting agent to stripping agent is 0.01. The mass fraction of aromatics in the extracted oil is more than 85%; the mass fraction of non-aromatics in the raffinate oil is more than 75%.

Example 4

The raw material is diesel with the component content listed in Table 1, the feed pressure is 0.3Mpa; the feed temperature is 30°C; the bulkhead tower 6 adopts the middle bulkhead form, the theoretical plate number is 50, and its operating conditions are: operating pressure 0.05Mpa, tower top temperature 80°C, tower bottom temperature 110°C, and the area ratio of both sides of the bulkhead tower 6 is 3:7; the solvent recovery tower 8 has a theoretical plate number of 40, and the operating conditions are: operating pressure 100Kpa, tower top temperature 20°C, and tower bottom temperature 45°C. In this embodiment, the extraction solvent is: ionic liquid, wherein the ionic liquid cation is 1,3-dimethylpyridine (MMPY+), and the anion is tetrafluoroborate helium (BF4-1); the stripping agent is cyclohexane. The mass ratio of stripping agent to diesel is 6, and the mass ratio of extractant to stripping agent is 2. ; The mass fraction of aromatics in the extracted oil is more than 85%; The mass fraction of non-aromatics in the raffinate oil is more than 75%.

Example 5

The raw material is diesel with the component content listed in Table 2, the feed pressure is 0.4Mpa; the feed temperature is 40°C; the bulkhead tower 6 adopts the middle bulkhead form, the theoretical plate number is 120, and its operating conditions are: operating pressure 1Mpa, tower top temperature 100°C, tower bottom temperature 130°C, and the area ratio of both sides of the bulkhead tower 6 is 7:3; the solvent recovery tower 8 has a theoretical plate number of 10, and the operating conditions are: operating pressure 150Kpa, tower top temperature 100°C, and tower bottom temperature 130°C. In this embodiment, the extraction solvent is: ionic liquid, wherein the ionic liquid cation is 1-heptyl-3-methylpyridine (C7MPY ⁺ ), and the anion is hexafluorophosphate (PF6 ^- ); the organic solvent is dimethyl sulfoxide, and the stripping agent is n-heptane; the mass ratio of the stripping agent to the diesel is 2, and the mass ratio of the extracting agent to the stripping agent is 0.05. The mass fraction of aromatics in the extracted oil is more than 85%; the mass fraction of non-aromatics in the raffinate oil is more than 80%.

With reference to the test process of the above embodiment, the experimental data using the ionic solution as the extractant can be shown in the following Table 3, which includes embodiments and comparative examples.

Table 3

With reference to the test process of the above embodiment, the experimental data using an organic solvent as an extractant can be shown in the following Table 4, which includes embodiments and comparative examples.

Table 4

As can be seen from Tables 3 and 4 above, the method for separating aromatics from diesel provided by the embodiment of the present invention can effectively separate aromatics and non-aromatics by using a bulkhead tower with a middle bulkhead, and the mass fraction of aromatics in the extracted oil is as high as more than 85%, and the mass fraction of non-aromatics in the raffinate oil is as high as more than 70%. As can be seen from the comparative example, without using the method of the present invention, it is not possible to achieve a good separation of aromatics and non-aromatics from diesel.

Unless otherwise specifically stated, terms such as processing, computing, calculating, determining, displaying, etc. may refer to the actions and/or processes of one or more processing or computing systems, or similar devices, which operate and convert data represented as physical (e.g., electronic) quantities within registers or memories of a processing system into other data similarly represented as physical quantities within memories, registers, or other such information storage, transmission, or display devices of the processing system. Information and signals may be represented using any of a variety of different techniques and methods. For example, data, instructions, commands, information, signals, bits, symbols, and chips mentioned throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, light fields or particles, or any combination thereof.

It should be understood that the specific order or hierarchy of steps in the disclosed process is an example of an exemplary method. Based on design preferences, it should be understood that the specific order or hierarchy of steps in the process can be rearranged without departing from the scope of protection of the present disclosure. The attached method claims present the elements of the various steps in an exemplary order and are not intended to be limited to the specific order or hierarchy described.

In the above detailed description, various features are grouped together in a single embodiment to simplify the disclosure. This method of disclosure should not be interpreted as reflecting an intention that the embodiments of the claimed subject matter require more features than are clearly stated in each claim. On the contrary, as reflected in the appended claims, the invention is in a state of having less than all the features of the disclosed individual embodiments. Therefore, the appended claims are hereby expressly incorporated into the detailed description, with each claim standing alone as a separate preferred embodiment of the invention.

Those skilled in the art will also appreciate that the various illustrative logic blocks, modules, circuits, and algorithmic steps described in conjunction with the embodiments herein can all be implemented as electronic hardware, computer software, or a combination thereof. In order to clearly illustrate the interchangeability between hardware and software, various illustrative components, blocks, modules, circuits, and steps are generally described above around their functions. Whether such functions are implemented as hardware or software depends on specific applications and the design constraints imposed on the entire system. A skilled person can implement the described functions in an alternative manner for each specific application, but such implementation decisions should not be interpreted as departing from the scope of protection of the present disclosure.

The steps of the method or algorithm described in conjunction with the embodiments herein may be directly embodied as hardware, a software module executed by a processor, or a combination thereof. The software module may be located in a RAM memory, a flash memory, a ROM memory, an EPROM memory, an EEPROM memory, a register, a hard disk, a mobile disk, a CD-ROM, or any other form of storage medium well known in the art. An exemplary storage medium is connected to the processor so that the processor can read information from the storage medium and can write information to the storage medium. Of course, the storage medium may also be an integral part of the processor. The processor and the storage medium may be located in an ASIC. The ASIC may be located in a user terminal. Of course, the processor and the storage medium may also be present in a user terminal as discrete components.

For software implementation, the techniques described in this application can be implemented with modules (e.g., procedures, functions, etc.) that perform the functions described in this application. These software codes can be stored in a memory unit and executed by a processor. The memory unit can be implemented within the processor or outside the processor. In the latter case, it is coupled to the processor in a communication manner via various means, which are well known in the art.

The above description includes examples of one or more embodiments. Of course, it is impossible to describe all possible combinations of components or methods for the purpose of describing the above embodiments, but it should be recognized by those skilled in the art that the various embodiments may be further combined and arranged. Therefore, the embodiments described herein are intended to cover all such changes, modifications and variations that fall within the scope of protection of the appended claims. In addition, with respect to the term "comprising" used in the specification or claims, the word is covered in a manner similar to the term "including", just as "including," is explained as a transitional word in the claims. In addition, any term "or" used in the specification of the claims is intended to mean "non-exclusive or".

Claims (25)

1. A method for separating aromatic hydrocarbon from diesel oil, which is characterized by comprising the following steps:

adding diesel oil from a diesel oil inlet in the middle of a first cavity of a dividing wall tower, adding an extraction solvent from an extraction solvent inlet at the top of the first cavity, and adding a stripping solvent from a stripping solvent inlet at the bottom of a second cavity of the dividing wall tower;

the diesel oil contacts with an extraction solvent in a first cavity, raffinate oil containing non-aromatic hydrocarbon is separated, the raffinate oil is output from a raffinate oil outlet at the top of the first cavity, and the extraction solvent is output from an extraction solvent outlet at the bottom of the first cavity;

The diesel oil contacts the back extraction solvent through a communication area at the bottom of the first cavity and the second cavity, the extracted oil containing aromatic hydrocarbon and the back extraction solvent is separated, the extracted oil is output to a solvent recovery tower from an extracted oil outlet at the upper half part of the second cavity, the extracted oil is separated in the solvent recovery tower, the back extraction solvent is output from a back extraction solvent outlet at the top of the solvent recovery tower, and the aromatic hydrocarbon is output from an aromatic hydrocarbon outlet at the bottom of the solvent recovery tower.

2. The method of claim 1, wherein the diesel is contacted with an extraction solvent in a first cavity to separate a raffinate comprising non-aromatic hydrocarbons, and wherein the raffinate exits a raffinate outlet at the top of the first cavity, comprising:

the diesel oil contacts with the extraction solvent in the first cavity, is heated by a reboiler of the tower kettle, enables non-aromatic hydrocarbon in the diesel oil to evaporate to the top under the action of the extraction solvent, and outputs raffinate oil containing non-aromatic hydrocarbon from a raffinate oil outlet at the top of the first cavity after being condensed by a top condenser.

3. The method of claim 1, wherein the diesel fuel is contacted with the stripping solvent via a first cavity and a second cavity bottom communication zone, and a stripping oil containing aromatic hydrocarbon and stripping solvent is separated, and is output from a stripping oil outlet in the upper half of the second cavity, comprising:

The diesel oil contacts with the back extraction solvent in the bottom communication area of the first cavity and the second cavity or in the second cavity, is heated by a reboiler of a tower kettle, and enables the residual aromatic hydrocarbon and the back extraction solvent in the diesel oil to be evaporated upwards together under the action of the back extraction solvent, and after being condensed by a condenser, the extracted oil containing the aromatic hydrocarbon and the back extraction solvent is output from an extracted oil outlet in the upper half part of the second cavity.

4. The method of claim 1, wherein said separating said extracted oil in a solvent recovery column outputs a stripping solvent from a stripping solvent outlet at the top of the solvent recovery column and aromatic hydrocarbons from an aromatic hydrocarbon outlet at the bottom of the solvent recovery column, comprising:

in the solvent recovery tower, the extraction oil is heated by a reboiler at the tower kettle to evaporate the stripping agent to the top, the stripping solvent is output from a stripping solvent outlet at the top after condensation by a condenser at the top, and the residual aromatic hydrocarbon is output from an aromatic hydrocarbon outlet at the bottom.

5. The method of claim 1, wherein the first and second cavities have a tower wall inner surface area ratio of 3:7 to 7:3.

6. The method of any one of claim 1, further comprising: the extraction solvent is delivered from an extraction solvent outlet at the bottom of the first cavity, then is delivered to the extraction solvent inlet and is added into the dividing wall tower; and/or

And the stripping solvent is output from a stripping solvent outlet at the top of the solvent recovery tower, and is conveyed to a stripping solvent inlet of the dividing wall tower to be added into the dividing wall tower.

7. The method of claim 1, wherein the mass ratio of stripping agent to diesel is 0.5-6 and the mass ratio of extraction agent to stripping agent is 0.01-2.

8. The method of claim 1, wherein the extraction solvent is an organic solvent or an ionic liquid, wherein the organic solvent is at least one of N, N-dimethylformamide, dimethyl sulfoxide, N-diethylformamide, ethylene glycol methyl ether, furfural, or morpholine; the cation in the ionic liquid is one of imidazole cation and pyridine cation, and the anion in the ionic liquid is at least one of tetrafluoroboric acid heel anion, hexafluorophosphoric acid heel anion and bistrifluoromethyl sulfinate anion.

9. The method of claim 8, wherein the cationic 1-methyl-3-ethylimidazole cation MEIM ⁺ 1-heptyl-3-methylimidazole cationic C7MIM ⁺ 1, 3-lutidine MMPY ⁺ At least one of the cations; the anion is tetrafluoroboric acid and BF4 ^-1 Anionic and hexafluorophosphoric acid with PF6 ^- At least one of anions.

10. The process of claim 1, wherein the stripping solvent is at least one of a C4-C10 alkane and a cycloalkane.

11. The method of claim 10, wherein the stripping solvent is at least one of cyclohexane, n-heptane, n-octane, and n-hexane.

12. The process according to any one of claims 1 to 11, wherein the dividing wall column has a theoretical plate number of 20 to 150, an operating pressure of 0.05 to 2Mpa, a column top temperature of 20 to 120 ℃ and a column bottom temperature of 50 to 150 ℃ during use.

13. The process according to any one of claims 1 to 11, wherein the theoretical plate number of the solvent recovery column is 5 to 40, the operating pressure during use is 10Kpa to 0.2MPa, the column top temperature is 20 to 120 ℃, and the column bottom temperature is 45 to 150 ℃.

14. A system for separating aromatic hydrocarbons from diesel fuel, comprising: a dividing wall column and a solvent recovery column;

the inside of the partition tower is provided with a partition wall which divides the inside of the tower body into a first inner cavity and a second inner cavity which are communicated with each other at the bottom, and the bottom of the tower body is provided with an extraction solvent outlet; the middle part of the first cavity is provided with a diesel oil inlet, and the top of the first cavity is provided with an extraction solvent inlet and a raffinate oil outlet; the upper half part of the second cavity is provided with an oil extraction outlet, and the bottom is provided with a back extraction solvent inlet; the partition tower is used for enabling diesel oil entering from the diesel oil inlet to contact with extraction solvent entering from the extraction solvent inlet in a first cavity, separating raffinate oil containing non-aromatic hydrocarbon to be output from a raffinate oil outlet, enabling the diesel oil to contact with stripping solvent entering from the stripping solvent inlet through a bottom communication area of the first cavity and a second cavity, separating raffinate oil containing aromatic hydrocarbon and the stripping solvent to be output from a raffinate oil outlet, and outputting the extraction solvent from an extraction solvent outlet;

The solvent recovery tower is provided with an oil extraction inlet in the middle, an aromatic hydrocarbon outlet at the bottom and a back extraction solvent outlet at the top; the extraction oil inlet is communicated with the extraction oil outlet of the partition tower, and the solvent recovery tower is used for separating aromatic hydrocarbon from the extraction oil output by the partition tower and outputting the separated stripping solvent from the stripping solvent outlet.

15. The system of claim 14, wherein the dividing wall of the divided wall column is an intermediate dividing wall;

the divided wall column is provided with at least one reboiler and/or at least one condenser.

16. The system of claim 14, wherein the solvent recovery column is provided with at least one reboiler and/or at least one condenser.

17. The system of claim 14, wherein the first and second chambers have a tower wall inner surface area ratio of 3:7 to 7:3.

18. The system of claim 14, wherein the extraction solvent outlet and the extraction solvent inlet of the divided wall column are in communication to feed the extraction solvent output from the extraction solvent outlet to the extraction solvent inlet to the divided wall column; and/or

The stripping agent outlet of the solvent recovery tower is communicated with the stripping agent inlet of the partition tower and is used for providing the stripping solvent output by the solvent recovery tower to the partition tower.

19. The system of any of claims 14-18, wherein the dividing wall column has a theoretical plate count of 20-150, and in use, an operating pressure of 0.05-2Mpa, a column top temperature of 20-120 ℃, and a column bottom temperature of 50-150 ℃.

20. The system of any one of claims 14-18, wherein the theoretical plate number of the solvent recovery column is 5-40, and the operating pressure is 10Kpa-0.2MPa, the column top temperature is 20-120 ℃, and the column bottom temperature is 45-150 ℃ during use.

21. A divided wall column, comprising: a hollow tower body;

the inside of the tower body is provided with a separation wall which divides the inside of the tower body into a first inner cavity and a second inner cavity which are communicated with each other at the bottom;

the bottom of the tower body is provided with an extraction solvent outlet;

the middle part of the first cavity is provided with a diesel oil inlet, and the top of the first cavity is provided with an extraction solvent inlet and a raffinate oil outlet;

the upper half part of the second cavity is provided with an oil extraction outlet, and the bottom is provided with a back extraction solvent inlet.

22. The divided wall column of claim 21, wherein the column wall inner surface area ratio of the first and second cavities is from 3:7 to 7:3, and the theoretical plate number is from 20 to 150.

23. The divided wall column of claim 21 or 22, wherein the dividing wall of the divided wall column is an intermediate dividing wall; the tower bottom of the partition tower is provided with a reboiler, and/or the tower top is provided with at least one condenser.

24. A method of separating aromatic hydrocarbons from diesel fuel using the separation system of aromatic hydrocarbons in diesel fuel according to any one of claims 14 to 20.

25. Use of a method for separating aromatic hydrocarbons from diesel according to any one of claims 1 to 13 in a process for separating aromatic hydrocarbons from diesel.