CN118146828A - System for separating aromatic hydrocarbon in pyrolysis gasoline - Google Patents

Abstract

The application relates to the field of petrochemical industry, in particular to a system for separating aromatic hydrocarbon in pyrolysis gasoline; the system comprises: the extraction unit comprises an extraction tower; the integrated unit comprises an integrated tower, an integrated reboiler and a xylene refining tower, wherein the bottom of the extraction tower is communicated with a feed inlet of the integrated tower, and two ends of the integrated reboiler are communicated with a discharge outlet of the integrated tower; the integrated tower comprises a baffle plate and a plurality of trays, the trays are transversely arranged in the integrated tower at intervals, the baffle plate is arranged in the integrated tower, and the baffle plate is perpendicular to the plane of the trays; the side line xylene and toluene extraction section is communicated with the xylene refining tower, the bottom of the extraction tower is communicated with the middle part of the integrated tower, and the bottom liquid outlet of the xylene refining tower and the bottom discharge outlet of the integrated tower are both communicated with the middle part of the extraction tower; by the system, high-purity separation and collection of various products of aromatic hydrocarbon in the pyrolysis gasoline can be realized, the flow of separating the aromatic hydrocarbon in the pyrolysis gasoline is shortened, and meanwhile, the purities of benzene products, toluene products and xylene products in the aromatic hydrocarbon are improved.

Description

System for separating aromatic hydrocarbon in pyrolysis gasoline

Technical Field

The application relates to the field of petrochemical industry, in particular to a system for separating aromatic hydrocarbon in pyrolysis gasoline.

Background

Aromatic hydrocarbons are important basic raw materials for petrochemical industry, among which benzene, toluene and xylene are the most important, and as the oil refining industry progresses, the demand for aromatic hydrocarbons, which are one of raw materials required for oil refining, is increasing, so petroleum aromatic hydrocarbons have become a major aromatic hydrocarbon source at this stage. However, with the current stricter environmental protection requirements, the specification requirements of petroleum products (such as fuels) are also stricter, and the aromatic hydrocarbon content is generally less than or equal to 35%, wherein the benzene content in the aromatic hydrocarbon is less than 0.8%. But aromatics are important raw materials for petroleum products from petroleum refining, so that separation of aromatics from catalytic pyrolysis gasoline (DCC gasoline) and ethylene pyrolysis gasoline is required in the petroleum refining process.

Because the active ingredients of DCC gasoline and ethylene pyrolysis gasoline at the current stage are C6-C8 components, sulfolane is generally adopted as an organic solvent to separate benzene, toluene and xylene in aromatic hydrocarbon according to the difference of the aromatic hydrocarbon and the main components thereof, and the general separation method comprises extraction, aromatic hydrocarbon recovery, benzene tower, toluene tower and xylene tower, so that the process flow is long, the energy consumption is high, and the final aromatic hydrocarbon separation effect is not ideal due to the multistage process, and high-purity benzene products, toluene products and xylene products cannot be obtained.

Therefore, how to provide a system for separating aromatic hydrocarbon from pyrolysis gasoline, so as to shorten the process of separating aromatic hydrocarbon from pyrolysis gasoline and improve the purity of separated aromatic hydrocarbon products is a technical problem to be solved at present.

Disclosure of Invention

The application provides a system for separating aromatic hydrocarbon in pyrolysis gasoline, which aims to solve the problems that the process of extracting and separating the aromatic hydrocarbon in pyrolysis gasoline in the prior art is overlong and the purity of an aromatic hydrocarbon product is too low.

In a first aspect, embodiments of the present application provide a system for separating aromatics from pyrolysis gasoline, the system comprising:

The extraction unit comprises an extraction tower to realize extraction of the lean solvent on the pyrolysis gasoline;

The integrated unit comprises an integrated tower, an integrated reboiler and a xylene refining tower, wherein the bottom of the extraction tower is communicated with a feed inlet of the integrated tower, and two ends of the integrated reboiler are communicated with a discharge outlet of the integrated tower so as to realize the recycling treatment of the lean solvent after stripping;

The integrated tower comprises a baffle plate and a plurality of tower trays, wherein the tower trays are transversely arranged in the integrated tower at intervals, so that the integrated tower is divided into a rectifying section, a middle treatment section and a stripping section from top to bottom; the baffle is arranged in the integrated tower and is perpendicular to the plane of the tray so as to divide the middle treatment section into a prefractionation section and a side-line xylene and toluene extraction section;

the integrated reboiler is communicated with a bottom discharge port of the integrated tower, and two ends of the integrated reboiler are communicated with the discharge port of the integrated tower so as to realize heating treatment of the lean solvent after stripping;

The side line xylene and toluene extraction section is communicated with the xylene refining tower, the bottom of the extraction tower is communicated with the middle part of the integrated tower, and the bottom liquid outlet of the xylene refining tower and the bottom discharge outlet of the integrated tower are communicated with the middle part of the extraction tower so as to realize the recycling of the lean solvent.

Optionally, the extraction unit further comprises an extraction reboiler, and both ends of the extraction reboiler are communicated with the extraction tower, so as to realize the recycling treatment of the rich solvent containing aromatic hydrocarbon.

Optionally, the extraction unit further comprises an extraction condenser, the extraction condenser is communicated with the top of the extraction tower, the extraction condenser comprises a first discharge port and a second discharge port, the feed inlet of the extraction condenser is communicated with the first discharge port of the extraction tower, and the second discharge port of the extraction condenser is used for discharging raffinate oil products without aromatic hydrocarbon.

Optionally, the integrated unit further comprises an integrated condenser, and two ends of the integrated condenser are communicated with the top of the integrated tower, so as to realize rectification of aromatic hydrocarbon.

Optionally, the integrated unit further comprises a xylene reboiler, and two ends of the xylene reboiler are communicated with two ends of the xylene refining tower, so that recycling treatment of xylene separated from aromatic hydrocarbon is realized.

Optionally, the operating pressure of the extraction tower is less than or equal to 0.1MPa, the operating temperature of the top of the extraction tower is 90-110 ℃, and the operating temperature of the bottom of the extraction tower is 165-178 ℃.

Optionally, the operating pressure of the rectifying section is 20kPa to 60kPa; the operation temperature of the rectifying section is 45-60 ℃.

Optionally, the temperature of the outlet section of the side line product is 75-90 ℃; and/or the number of the groups of groups,

The operation temperature of the stripping section is 165-178 ℃.

Optionally, the number of theoretical trays of the extraction tower is 40-60; and/or the number of the groups of groups,

The theoretical tray number of the integrated tower is 45-75; and/or the number of the groups of groups,

The theoretical tray number of the dimethylbenzene refining tower is 5-15.

Optionally, the mass ratio of the lean solvent and the pyrolysis gasoline in the extraction tower is 2-6.

Compared with the prior art, the technical scheme provided by the embodiment of the application has the following advantages:

According to the system for separating aromatic hydrocarbon in pyrolysis gasoline, provided by the embodiment of the application, countercurrent contact extraction is carried out between lean solvent pyrolysis gasoline and lean solvent pyrolysis gasoline by adopting an extraction tower, so that aromatic hydrocarbon in C6-C8 components of pyrolysis gasoline is fully extracted by the lean solvent, then the integrated tower comprises an integrated tower, an integrated reboiler and a xylene refining tower, the integrated tower is utilized to carry out prefractionation, rectification, stripping and refining of xylene on rich solvent absorbing aromatic hydrocarbon, the prefractionation section can be used for carrying out primary separation on lean solvent and extracted aromatic hydrocarbon, meanwhile, benzene and part of mixture of toluene and xylene in aromatic hydrocarbon are separated, the rectification section is used for carrying out separation and collection on mixture of benzene and toluene and xylene, and as the boiling point of benzene is the lowest, benzene products with high purity can be obtained, the integrated tower is internally provided with a partition plate, the integrated tower can be divided into a plurality of working areas comprising a prefractionation section, a rectification section, a side line xylene and a toluene extraction section, and a plurality of working areas between gas phase and liquid phase can be avoided, the mixed toluene products are improved, the purity of the toluene products is further improved, the xylene is further separated by the prefractionation section and the lean solvent is further separated by the rectification section, the xylene is separated by the rectification section, the xylene and the xylene is separated by the side line, and the xylene is separated by the separation of the lean solvent, and the high purity of the xylene is further separated by the separation tower, and the high purity of the toluene is further separated by the separation of the separation tower, and the toluene is further separated by the separation of the side toluene and the separation tower, and the high purity is further separated by the separation of toluene is separated by the side toluene and has improved by the side separation of the side toluene, and has high purity of the separation by the side toluene and has high purity separation stage and has high purity separation, purity of toluene product and xylene product.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the application and together with the description, serve to explain the principles of the application.

In order to more clearly illustrate the embodiments of the application or the technical solutions of the prior art, the drawings which are used in the description of the embodiments or the prior art will be briefly described, and it will be obvious to a person skilled in the art that other drawings can be obtained from these drawings without inventive effort.

FIG. 1 is a schematic diagram of a system according to an embodiment of the present application;

FIG. 2 is a schematic diagram of a process system according to a comparative example of the present application;

Wherein, the device comprises a 1-extraction unit, a 11-extraction tower, a 12-extraction reboiler, a 13-extraction condenser, a 2-integration unit, a 21-integration tower, a 22-integration reboiler, a 23-baffle, a 24-tower tray, a 25-integration condenser, a 26-xylene refining tower, a 27-xylene reboiler, a 3-recovery tower, a 4-benzene tower, a 5-toluene tower, A-pyrolysis gasoline, B-raffinate oil, C-rich solvent, D-benzene, E-toluene, F-xylene, G-lean solvent, I-prefractionation section, II-rectification section, III-side line xylene and toluene extraction section and IV-stripping section.

Detailed Description

For the purpose of making the objects, technical solutions and advantages of the embodiments of the present application more apparent, the technical solutions of the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application, and it is apparent that the described embodiments are some embodiments of the present application, but not all embodiments of the present application. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.

Unless otherwise specifically indicated, the various raw materials, reagents, instruments, equipment and the like used in the present application are commercially available or may be prepared by existing methods.

As shown in fig. 1, an embodiment of the present application provides a system for separating aromatic hydrocarbons from pyrolysis gasoline, the system comprising:

An extraction unit 1, wherein the extraction unit 1 comprises an extraction tower 11 for realizing extraction of the lean solvent on the pyrolysis gasoline;

the integrated unit 2 comprises an integrated tower 21, an integrated reboiler 22 and a xylene refining tower, wherein the bottom of the extraction tower 11 is communicated with a feed inlet of the integrated tower 21, and two ends of the integrated reboiler 22 are communicated with a discharge outlet of the integrated tower 21 so as to realize circulation treatment of the lean solvent after stripping;

The integrated tower 21 comprises a baffle 23 and a plurality of trays 24, wherein the trays 24 are transversely arranged in the integrated tower 21 at intervals, so that the integrated tower 21 is divided into a rectifying section II, a middle treatment section and a stripping section IV from top to bottom; the baffle plate 23 is arranged in the integrated tower 21, and the baffle plate 23 is perpendicular to the plane of the tray 24 so as to divide the middle treatment section into a prefractionation section I and a side-line xylene and toluene extraction section III;

the integrated reboiler 22 is communicated with a bottom discharge port of the integrated tower 21, and two ends of the integrated reboiler 22 are communicated with the discharge port of the integrated tower 21 so as to realize heating treatment of lean solvent after stripping;

The side line xylene and toluene extraction section III is communicated with the xylene refining tower 26, the bottom of the extraction tower 11 is communicated with the middle part of the integrated tower 21, and a bottom liquid outlet of the xylene refining tower 26 and a middle discharge outlet of the integrated tower 21 are communicated with the middle part of the extraction tower 11 so as to realize the recycling of lean solvent.

In the embodiment of the application, the limiting system comprises an extraction unit 11 and an integration unit 22, the countercurrent contact between the lean solvent and the pyrolysis gasoline is realized by using the extraction unit 11, aromatic hydrocarbon is extracted, and then the rich solvent from which the aromatic hydrocarbon is extracted is treated by using the integration unit 22, so that the separation of benzene, toluene and the lean solvent in the aromatic hydrocarbon is realized.

The extraction tower 11 is a device for reversely contacting a lean solvent with C6-C8 components of pyrolysis gasoline in the tower, extracting benzene, toluene and xylene in the gasoline components into the lean solvent, and obtaining alkane without aromatic hydrocarbon at the top of the extraction tower 11, wherein the obtained alkane without aromatic hydrocarbon is called raffinate oil in the industry, the raffinate oil can be directly discharged out of the system to enter the next step, and the rich solvent rich in aromatic hydrocarbon can be obtained at the bottom of the extraction tower 11. The extraction tower 11 can adopt a liquid-liquid extraction technology or an extractive distillation technology, when the extraction tower 11 adopts the extractive distillation technology, a cooling facility is arranged at the top of the extraction tower 11, a reboiler is arranged at the bottom of the extraction tower, and the tray 24 can adopt a sieve-mesh tray 24 or a floating valve tray 24.

The integrated column 21 is a dividing wall column which is a rectifying device provided with a baffle plate 23 in the middle of a conventional rectifying column, and the middle baffle plate 23 is vertically installed to prevent the liquid phase and the gas phase at both sides from being transversely mixed, and the operations of separating aromatic hydrocarbons from the solvent in the rich solvent and separating the aromatic hydrocarbons into products such as benzene and toluene are completed in one column. The internal structure of the dividing wall tower is divided into a rectifying section II, a prefractionation section I, a side line xylene and toluene extraction section III and a stripping section IV. The prefractionation section I and the side xylene and toluene extraction section III are separated into the prefractionation section I by a partition plate 23, the feed is subjected to crude fractionation, so that a mixture of benzene and part of toluene and xylene enters the rectification section II to be distilled to generate benzene gas, the mixture of toluene and xylene is further separated into toluene and xylene in the side xylene and toluene extraction section III, at the moment, a mixture of lean solvent and part of toluene and xylene is separated by the stripping section IV, the lean solvent is obtained at the bottom of the integrated tower 21, and a mixture of part of toluene and xylene is further separated into toluene and xylene in the side xylene and toluene extraction section III, thereby completing separation of aromatic hydrocarbon and lean solvent in the integrated tower and obtaining a high-purity product; the side xylene and toluene extraction section III and the rectifying section II and the stripping section IV are called a main tower together, and light, medium and heavy components are separated. The top of the tower is provided with a condenser, and the bottom of the tower is provided with a reboiler. The rich solvent enters an integrated tower 21 to be fed into a prefractionation section I, benzene is obtained at the top of the integrated tower, products of side line extraction of a side line xylene and toluene extraction section III are toluene, products of side line xylene and toluene extraction section III are xylene, and a lean solvent is obtained at the bottom of the integrated tower and is recycled to the extraction tower 11. The integrated column 21 is a vacuum column operated at negative pressure. Xylene refining column 26 is a device for refining the side xylenes and the xylenes produced in toluene recovery section III, which may contain a small amount of lean solvent, requiring removal of the lean solvent from the xylenes to produce a high purity xylene product; the xylene refining column 26 may be a tray column or a packed column.

In order to ensure that the lean solvent is not decomposed, the bottoms of the extraction tower 11 and the integrated tower 21 are heated by adopting steam, heat conduction oil or other media, the temperature of the heating media is controlled to be 200-220 ℃, and the operating temperature in the extraction tower 11 and the integrated tower 21 is ensured to be in an expected range.

Lean solvent refers to a solvent capable of extracting aromatic hydrocarbons from reformed gasoline but not yet extracting aromatic hydrocarbons, and includes sulfolane-based organic solvents.

The rich solvent refers to the lean solvent from which aromatic hydrocarbons are extracted. Tray 24 of integrated column 21 is generally set to 45 to 75, preferably 51 to 69. Correspondingly, the tray 24 of the extraction column 11 is generally 40 to 60, preferably 45 to 50. The number of theoretical trays 24 of the xylene refining tower 26 is 5 to 15, preferably 10 to 15.

In some alternative embodiments, the extraction unit 1 further comprises an extraction reboiler 12, both ends of the extraction reboiler 12 being in communication with the extraction column 11 to effect recycle of the rich solvent comprising aromatic hydrocarbons.

In the embodiment of the application, the limited extraction unit 1 further comprises an extraction reboiler 12, and the extraction reboiler 12 is utilized to reboil the rich solvent, so that the rich solvent enters the extraction tower 11 again for re-extraction, and the lean solvent can be fully extracted from C6-C8 components of the pyrolysis gasoline.

In some alternative embodiments, the extraction unit 1 further comprises an extraction condenser 13, the extraction condenser 13 is communicated with the top of the extraction tower 11, the extraction condenser 13 comprises a first discharge port and a second discharge port, the feed port of the extraction condenser 13 and the first discharge port are communicated with the top of the extraction tower 11, and the second discharge port of the extraction condenser 13 is used for discharging raffinate oil products without aromatic hydrocarbons.

In the embodiment of the application, the limiting extraction unit 1 further comprises an extraction condenser 13, the extraction condenser 13 is utilized to condense non-C6-C8 components in the pyrolysis gasoline after countercurrent contact to form raffinate oil components, so as to be collected and enter the next stage, and the integrated unit 2 further comprises an integrated condenser 25, and both ends of the integrated condenser 25 are communicated with the top of the integrated tower 21 to realize rectification of rich solvent, so that rectification separation of benzene, toluene and xylene can be realized.

In some alternative embodiments, the integrated unit 2 further comprises an integrated condenser 25, both ends of the integrated condenser 25 being in communication with the top of the integrated column 21 to effect rectification of aromatic hydrocarbons.

In the embodiment of the application, the limiting integrated unit 2 further comprises an integrated condenser 25, and the integrated condenser 25 is utilized to further separate the mixture of benzene, toluene and xylene separated from the aromatic hydrocarbon in the rectification stage, so that the benzene is condensed into liquid and discharged out of the integrated tower 21, and the collection of high-purity benzene is completed.

In some alternative embodiments, the integrated unit 2 further comprises a xylene reboiler 27, wherein two ends of the xylene reboiler 27 are connected to two ends of the xylene refining tower 26, so as to implement recycling treatment of xylene separated from aromatic hydrocarbon.

In the embodiment of the present application, the integrated unit 2 is further defined to include a xylene reboiler 27, which can perform multiple circulation treatments on the separated xylene, so as to ensure that a small amount of lean solvent in the xylene is treated, thereby obtaining a pure xylene product.

In some alternative embodiments, the operating pressure of the extraction column 11 is less than or equal to 0.1MPa, the operating temperature of the top of the extraction column 11 is between 90 ℃ and 110 ℃, and the operating temperature of the bottom of the extraction column 11 is between 165 ℃ and 178 ℃.

In the embodiment of the application, the operating pressure, the operating temperature at the top of the tower and the operating temperature at the bottom of the tower of the extraction tower 11 are limited, so that the aromatic hydrocarbon in the pyrolysis gasoline enters the lean solvent to form a rich solvent according to the requirements of countercurrent contact of benzene, toluene and xylene in the aromatic hydrocarbon in the lean solvent and the specificity of the pyrolysis gasoline and the lean solvent, and the subsequent processing work of the integrated tower 21 is facilitated.

In some alternative embodiments, the operating pressure of the rectifying section II is 20kPa to 60kPa; the operating temperature of the rectifying section II is 45-60 ℃.

In the embodiment of the application, the specific operating pressure and operating temperature of the rectifying section II are limited, so that the rectification of the mixture of toluene and xylene aiming at the same part of benzene can be ensured to be smoothly carried out

In some alternative embodiments, the temperature of the side product outlet section iii is from 75 ℃ to 90 ℃; and/or the number of the groups of groups,

The operation temperature of the stripping section is 165-178 ℃.

In the embodiment of the application, the temperature of the side line product outlet section III is limited to 75-90 ℃, and the positive effect is that in the temperature range, toluene and xylene can be ensured to be respectively discharged out of the system through the side line xylene and the toluene outlet section III, wherein toluene is discharged from side line outlet sections of the side line xylene and the toluene outlet section III, and xylene products are discharged from lower outlet sections of the side line xylene and the toluene outlet section III.

In some alternative embodiments, the theoretical trays of the extraction column 11 are 40 to 60; and/or the number of the groups of groups,

The theoretical tray number of the integrated tower 21 is 45-75; and/or the number of the groups of groups,

The number of theoretical trays of the xylene purification column 26 is 5 to 15.

In the embodiment of the application, the theoretical tray numbers of the extraction tower 11, the integrated tower 21 and the xylene refining tower 26 are limited, so that on one hand, the countercurrent contact time of pyrolysis gasoline and lean solvent in the extraction tower 11 can be ensured to be enough, on the other hand, the normal operation of each working area in the integrated tower 21 can be ensured, the separation effect of benzene, toluene and xylene in aromatic hydrocarbon and the separation purity of benzene and toluene in aromatic hydrocarbon can be ensured, and meanwhile, the purification effect of the separated xylene in the xylene refining tower 26 can be ensured, thereby ensuring the purity and separation efficiency of products.

The actual number of trays will generally be higher than the theoretical number of trays due to the environmental conditions in which the actual device is located and the different reformed gasoline specifications.

In some alternative embodiments, the lean solvent to pyrolysis gasoline mass ratio in the extraction column 11 is 2 to 6.

In the embodiment of the application, the positive effect of limiting the mass ratio of the lean solvent to the reformed gasoline to 2-6 is that in the mass ratio range, the lean solvent can be ensured to extract aromatic hydrocarbon in the reformed gasoline, thereby ensuring the collection of benzene and toluene in the aromatic hydrocarbon in the subsequent rectification stage.

The application will be further illustrated with reference to specific examples. It is to be understood that these examples are illustrative of the present application and are not intended to limit the scope of the present application. The experimental procedures, which are not specified in the following examples, are generally determined according to national standards. If the corresponding national standard does not exist, the method is carried out according to the general international standard, the conventional condition or the condition recommended by the manufacturer.

Example 1

As shown in fig. 1, an embodiment of the present application provides a system for separating aromatic hydrocarbons from pyrolysis gasoline, including:

an extraction unit 1 comprising an extraction tower 11 for extracting pyrolysis gasoline by lean solvent;

The integrated unit 2 comprises an integrated tower 21, an integrated reboiler 22 and a xylene refining tower 26, wherein the bottom of the extraction tower 11 is communicated with a feed inlet of the integrated tower 21, and two ends of the integrated reboiler 22 are communicated with a discharge outlet of the integrated tower 21 so as to realize the recycling treatment of the lean solvent after stripping;

the integrated reboiler 22 is communicated with a bottom discharge port of the integrated tower 21, and two ends of the integrated reboiler 22 are communicated with a discharge port of the integrated tower 21 so as to realize heating treatment of the lean solvent after stripping;

The integrated tower 21 comprises a baffle 23 and a plurality of trays 24, the trays 24 are transversely arranged in the integrated tower 21 at intervals, so that the integrated tower 21 is divided into a rectifying section II, a middle treatment section and a stripping section IV from top to bottom, the baffle 23 is arranged in the integrated tower 21, and the baffle 23 is perpendicular to the plane of the trays 24, so that the middle treatment section is divided into a prefractionation section I and a side line xylene and toluene extraction section III;

The side line xylene and toluene extraction section III is communicated with the xylene refining tower 26, the bottom of the extraction tower 11 is communicated with the middle of the integrated tower 21, and a bottom liquid outlet of the xylene refining tower 26 and a middle discharge outlet of the integrated tower 21 are communicated with the middle of the extraction tower 11 so as to realize the recycling of the lean solvent.

The extraction unit 1 further comprises an extraction reboiler 12, and both ends of the extraction reboiler 12 are communicated with the extraction column 11 to realize recycling treatment of the rich solvent containing aromatic hydrocarbon.

The extraction unit 1 further comprises an extraction condenser 13, the extraction condenser 13 is communicated with the top of the extraction tower 11, the extraction condenser 13 comprises a first discharge port and a second discharge port, the feed inlet of the extraction condenser 13 and the first discharge port are communicated with the top of the extraction tower 11, and the second discharge port of the extraction condenser 13 is used for discharging raffinate oil products without aromatic hydrocarbon.

The integrated unit 2 further comprises an integrated condenser 25, both ends of the integrated condenser 25 being in communication with the top of the integrated column 21 to effect rectification of aromatic hydrocarbons.

The integrated unit 2 further comprises a xylene reboiler 27, and both ends of the xylene reboiler 27 are connected to both ends of the xylene refining tower 26 to realize recycle treatment of xylene separated from aromatic hydrocarbons.

Wherein the theoretical tray number of the extraction tower 11 is 45-50, the tower top operation temperature is 105-109 ℃, the tower bottom operation temperature is 170-174 ℃, the tower top operation pressure is 0.04-0.1 MPa (g), and the mass ratio of the lean solvent to the pyrolysis gasoline is 3-4;

The theoretical tray number of the integrated tower 21 is 51-69, the operating temperature of the tower top is 50-55 ℃, the temperature of the side line xylene and toluene extraction section III is 75-90 ℃, the operating temperature of the tower bottom is 170-174 ℃, and the operating pressure of the tower top is 20-60 kPa (a);

The tray number of the dimethylbenzene refining tower 26 is 10-15, the operating temperature of the tower top is 105-110 ℃, the operating temperature of the tower bottom is 160-166 ℃, and the operating pressure of the tower top is 30kPa (a) to 0.04MPa (a).

Example 2

Example 2 and example 1 were compared, and the difference between example 2 and example 1 is that:

The raw materials are typical DCC gasoline C6-C8 components, the compositions are shown in table 1, the feeding amount is 40 ten thousand tons/year, the feeding pressure is 0.15MPa (g), the feeding temperature is 110 ℃, and the mass ratio of the lean solvent to the pyrolysis gasoline is 4.

The operating pressure of the extraction tower is 0.04MPa (g), and 86 layers of actual trays are required; the integrated tower is a dividing wall tower, the operating pressure is 30kPa (a), and the actual tower tray 116 layers are required; the xylene finishing column 26 is operated at normal pressure, with a total of 20 layers of actual trays. The system used was as shown in figure 1 and the process parameters are shown in table 2.

Comparative example 1

Comparative example 1 and example 3 were compared, and the difference between comparative example 1 and example 3 is that:

The separation process of the extraction tower 11, the recovery tower 3, the benzene tower 4 and the toluene tower 5 is adopted.

The process conditions are as follows: the raw materials are typical DCC gasoline C6-C8 components, the compositions are shown in table 1, the feeding amount is 40 ten thousand tons/year, the feeding pressure is 0.15MPa (g), the feeding temperature is 110 ℃, and the mass ratio of the lean solvent to the pyrolysis gasoline is 4.

The operating pressure of the extraction tower 11 is 0.05MPa (g), and the actual tower tray 86 layers are required; the operating pressure of the recovery column 3 is 30kPa (a), with a total of 34 layers of actual trays; the operating pressure of the benzene tower 4 is 0.07MPa (g), and 66 layers of actual trays are required; the toluene column 5 was operated at a pressure of 0.4MPa (g) with a total of 66 layers of actual trays. The system adopted in the process flow is shown in fig. 2, and the process parameters are shown in table 2.

Related experiment and effect data:

Separation requirements: for the practical separation effect of each example and comparative example, benzene was required to satisfy the national standard GB/T3405 with a purity of 99.9 mass%, toluene was required to satisfy the national standard GB/T3406 with a purity of 99.9 mass%, and xylene was required to satisfy the national standard GB/T3406 with a purity of 98.5 mass%.

TABLE 1 composition of C6-C8 Components of typical DCC gasoline (wt%)

Table 2 table of process parameters

As can be seen from Table 2, the energy savings of 25.4% were achieved using the process flow and process system of the present application.

As can be seen from the data of examples 1-3, the process system of the present application can realize the high purity separation and collection of each product of aromatic hydrocarbon in pyrolysis gasoline by only using two main treatment towers and one xylene refining tower 2626, thereby shortening the flow of separating aromatic hydrocarbon in pyrolysis gasoline and improving the purity of benzene product, toluene product and xylene product in aromatic hydrocarbon.

For the purpose of further illustrating the operation of the system of the present application, a further detailed description is provided herein in connection with fig. 1, but is not limited to the embodiment:

As shown in figure 1, C6-C8 components A of DCC gasoline enter the middle part of an extraction tower, circulating lean solvent (sulfolane) enters the middle and upper parts of the extraction tower 11, the two components are in reverse contact in the extraction tower 11, the lean solvent extracts aromatic hydrocarbon in the gasoline components, the aromatic hydrocarbon is extracted from the bottom of the tower as rich solvent C and enters an integrated tower 21, and the top material of the extraction tower 11 is condensed and cooled to obtain raffinate oil products without aromatic hydrocarbon.

The rich solvent C enters the middle lower part of the prefractionation section I of the integrated tower 21 to perform crude separation of aromatic hydrocarbon and solvent, the separated aromatic hydrocarbon flows upwards to enter the rectification section II to perform separation of benzene and toluene, the benzene at the top of the tower is totally refluxed after being condensed, and the benzene product is extracted from 4-5 layers of trays at the top of the tower to ensure that the benzene product does not contain water.

The solvent flows downwards in the prefractionation section I to enter the stripping section IV for the fine separation of the solvent and aromatic hydrocarbon, the lean solvent without aromatic hydrocarbon is obtained at the bottom of the tower and is returned to the extraction tower 11 for recycling. Toluene and xylene are separated in a side-line xylene and toluene extraction section III, toluene products are obtained in the middle of the extraction section, xylene obtained in the lower part of the extraction section enters a xylene refining tower 2626 for xylene lean solvent removal refining, xylene with purity of more than 98.5 percent (mass) can be obtained at the top of the xylene refining tower 2626, and a solvent containing a small amount of aromatic hydrocarbon at the bottom of the tower and lean solvent are returned to the extraction tower 11 for recycling.

The bottom of the extraction tower 11 and the bottom of the integration tower 21 are heated by steam, and the steam temperature is controlled between 200 ℃ and 220 ℃ to prevent the solvent sulfolane from decomposing.

One or more technical solutions in the embodiments of the present application at least have the following technical effects or advantages:

(1) According to the system for separating aromatic hydrocarbon in pyrolysis gasoline provided by the embodiment of the application, the adopted integrated tower 21 is only a dividing wall tower, replaces a recovery tower 3, a benzene tower 4 and a toluene tower 5 in the traditional process, reduces 2 towers and auxiliary supporting facilities thereof, has short process, occupies less land, and can reduce the land occupation by about 70%.

(2) According to the system for separating aromatic hydrocarbon in pyrolysis gasoline, provided by the embodiment of the application, due to the adoption of the dividing wall tower structure of the integrated tower 21, the back mixing effect of intermediate components is avoided, the separation efficiency is high, and separation of 4 products such as benzene, toluene, xylene and solvents is completed in one tower, so that compared with the conventional process, the public engineering consumption is reduced by more than 25%.

(3) Compared with the traditional process, the system for separating aromatic hydrocarbon in pyrolysis gasoline provided by the embodiment of the application has the advantages that the number of main equipment is reduced by more than 65%, and the total equipment investment can be saved by more than 50%.

Various embodiments of the application may exist in a range of forms; it should be understood that the description in a range format is merely for convenience and brevity and should not be construed as a rigid limitation on the scope of the application; it is therefore to be understood that the range description has specifically disclosed all possible sub-ranges and individual values within that range. For example, it should be considered that a description of a range from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5, and 6, wherever applicable. In addition, whenever a numerical range is referred to herein, it is meant to include any reference number (fractional or integer) within the indicated range.

In the present application, unless otherwise specified, terms such as "upper" and "lower" are used specifically to refer to the orientation of the drawing in the figures. In addition, in the description of the present specification, the terms "include", "comprising" and the like mean "including but not limited to". Relational terms such as "first" and "second", and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Herein, "and/or" describing an association relationship of an association object means that there may be three relationships, for example, a and/or B, may mean: a alone, a and B together, and B alone. Wherein A, B may be singular or plural. Herein, "at least one" means one or more, and "a plurality" means two or more. "at least one", "at least one" or the like refer to any combination of these items, including any combination of single item(s) or plural items(s). For example, "at least one (individual) of a, b, or c," or "at least one (individual) of a, b, and c," may each represent: a, b, c, a-b (i.e., a and b), a-c, b-c, or a-b-c, wherein a, b, c may be single or multiple, respectively.

The foregoing is only a specific embodiment of the application to enable those skilled in the art to understand or practice the application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (10)

1. A system for separating aromatics from pyrolysis gasoline, the system comprising:

An extraction unit (1), the extraction unit (1) comprising an extraction column (11) to effect extraction of pyrolysis gasoline with a lean solvent;

The integrated unit (2), the integrated unit (2) comprises an integrated tower (21), an integrated reboiler (22) and a xylene refining tower (26), the bottom of the extraction tower (11) is communicated with a feed inlet of the integrated tower (21), and two ends of the integrated reboiler (22) are communicated with a discharge outlet of the integrated tower (21) so as to realize the recycling treatment of the lean solvent after stripping;

The integrated tower (21) comprises a baffle plate (23) and a plurality of trays (24), wherein the trays (24) are transversely arranged in the integrated tower (21) at intervals, so that the integrated tower (21) is divided into a rectifying section, a middle treatment section and a stripping section from top to bottom; the baffle (23) is arranged in the integrated tower (21), and the baffle (23) is perpendicular to the plane of the tray (24) so as to divide the middle treatment section into a prefractionation section and a side-line xylene and toluene extraction section;

The integrated reboiler (22) is communicated with a bottom discharge port of the integrated tower (21), and two ends of the integrated reboiler (22) are communicated with the discharge port of the integrated tower (21) so as to realize heating treatment of the lean solvent after stripping;

the side line xylene and toluene extraction section is communicated with the xylene refining tower (26), the bottom of the extraction tower (11) is communicated with the middle of the integrated tower (21), and a bottom liquid outlet of the xylene refining tower (26) and a bottom discharge outlet of the integrated tower (21) are communicated with the middle of the extraction tower (11) so as to realize the recycling of the lean solvent.

2. The system according to claim 1, characterized in that the extraction unit (1) further comprises an extraction reboiler (12), both ends of the extraction reboiler (12) being in communication with the extraction column (11) for effecting a recycle treatment of the rich solvent containing aromatic hydrocarbons.

3. The system according to claim 1, wherein the extraction unit (1) further comprises an extraction condenser (13), the extraction condenser (13) being in communication with the top of the extraction column (11), the extraction condenser (13) comprising a first discharge port and a second discharge port, the feed port of the extraction condenser (13) and the first discharge port being in communication with the top of the extraction column (11), the second discharge port of the extraction condenser (13) being for discharging an aromatic-free raffinate oil product.

4. The system according to claim 1, characterized in that the integrated unit (2) further comprises an integrated condenser (25), both ends of the integrated condenser (25) being in communication with the top of the integrated column (21) for effecting the rectification of aromatic hydrocarbons.

5. The system according to claim 1, wherein the integrated unit (2) further comprises a xylene reboiler (27), and both ends of the xylene reboiler (27) are connected to both ends of the xylene refining tower (26) to achieve recycling of xylenes separated from aromatic hydrocarbons.

6. The system according to claim 1, wherein the operating pressure of the extraction column (11) is less than or equal to 0.1MPa, the top operating temperature of the extraction column (11) is 90 ℃ to 110 ℃, and the bottom operating temperature of the extraction column (11) is 165 ℃ to 178 ℃.

7. The system of claim 1, wherein the operating pressure of the rectifying section is 20kPa to 60kPa; the operation temperature of the rectifying section is 45-60 ℃.

8. The system of claim 1, wherein the temperature of the side product offtake is 75 ℃ to 90 ℃; and/or the number of the groups of groups,

The operation temperature of the stripping section is 165-178 ℃.

9. The system according to claim 1, characterized in that the theoretical number of trays of the extraction column (11) is 40-60; and/or the number of the groups of groups,

The theoretical tray number of the integrated tower (21) is 45-75; and/or the number of the groups of groups,

The theoretical tray number of the xylene refining tower (26) is 5-15.

10. The system according to claim 1, characterized in that the mass ratio of lean solvent and pyrolysis gasoline in the extraction column (11) is 2-6.