A system and method for aromatic extraction

Abstract

The present disclosure relates to a system and method for aromatic extraction, which comprises an aromatic extraction distillation column, a venturi separator, a condenser and a reflux tank; the aromatic extraction distillation column comprises an aromatic feedstock inlet, an extraction solvent inlet, a side inlet, a liquid phase outlet at the bottom of the column and a gas phase outlet at the top of the column; the venturi separator comprises a gas phase inlet at the top of the column, a water washing water inlet, a washing liquid phase outlet and a post-washing gas phase outlet; the reflux tank comprises a reflux tank inlet, a water phase outlet and an oil phase outlet; the oil phase outlet of the reflux tank is formed as an raffinate oil product outlet of the system; the venturi separator comprises a vertically arranged liquid phase collection pipe and a venturi pipe sleeved in the liquid phase collection pipe, a throat of the venturi pipe is provided with a water washing water inlet; the gas phase outlet at the top of the column of the aromatic extraction distillation column is in communication with the gas phase inlet at the top of the column of the venturi separator. The system of the present disclosure improves the selectivity of the extraction solvent and improves the quality and yield of the aromatic hydrocarbons in the extract.

Description

Technical Field

[0001] The present disclosure relates to the field of petrochemical aromatic separation, and in particular, to a system and method for extracting aromatics. Background Art

[0002] The extractive distillation of aromatics from the C6-C7 fraction uses solvents to separate benzene and toluene from non-aromatics. This process typically involves an extractive distillation tower (ED tower), a non-aromatic distillation tower (NA tower), and a solvent recovery tower (SR tower). The ED tower primarily separates aromatics from non-aromatics, with the overhead vapor entering the NA tower. The NA tower recovers trace solvent from the ED overhead vapor. Part of the raffinate oil obtained from the tower is refluxed, while the remainder is recovered as product. A reboiler is located at the bottom of the tower to enrich the solvent and return it to the ED tower. The SR tower separates the solvent from aromatics. The combination of the ED and NA towers results in a large footprint and high equipment and pipeline investments.

[0003] CN216824877U discloses an aromatics extraction apparatus that occupies a small footprint and offers flexible operation. This design utilizes a two-stage extractive distillation column and a non-aromatic distillation column, saving equipment costs. However, because the raffinate (i.e., non-aromatics) in the reflux tank of the ED column is returned to the top of the ED column, the solvent's limited ability to dissolve non-aromatics results in two distinct liquid phases in the upper portion of the ED column, compromising the extractive distillation separation effect.

[0004] CN100378048C discloses a method for separating aromatic hydrocarbons by extractive distillation. The extractant is introduced from the top of a column and heated by a heat source at the bottom of the non-aromatic reflux section of the extractive distillation column. A portion of the non-aromatic hydrocarbons are refluxed from the top of the column, while the remainder is discharged from the system. While the non-aromatic reflux section is used to recover trace solvent from the raffinate, the formation of two liquid phases is still not avoided.

[0005] CN109517619A discloses a desolventizing method for aromatic extraction raffinate oil. The aromatic extraction raffinate oil containing an extraction solvent is subjected to a two-stage water washing process. The product of the first-stage water washing is filtered and separated through a hydrophilic polar filter membrane, and the product of the second-stage water washing is filtered and separated through a hydrophobic polar filter membrane. This method requires a large amount of equipment and uses a membrane separation process, which may have issues with membrane life. Summary of the Invention

[0006] The purpose of the present disclosure is to provide a system and method for extracting aromatic hydrocarbons, which can improve the selectivity of the extraction solvent, increase the mass content of non-aromatic hydrocarbons in the raffinate oil product, and further improve the quality and yield of the aromatic hydrocarbon product in the extract.

[0007] In order to achieve the above-mentioned object, the present disclosure provides, in a first aspect, a system for extracting aromatic hydrocarbons, the system comprising an aromatic hydrocarbon extraction distillation tower, a venturi separator, a condenser, and a reflux drum;

[0008] The aromatics extractive distillation tower includes an aromatics feed inlet, an extraction solvent inlet, a side line inlet, a bottom liquid phase outlet, and a top gas phase outlet; the venturi separator includes a top gas phase inlet, a wash water inlet, a wash liquid phase outlet, and a washed gas phase outlet; the reflux tank includes a reflux tank inlet, a water phase outlet, and an oil phase outlet; the oil phase outlet of the reflux tank forms the raffinate oil product outlet of the system; the venturi separator includes a vertical liquid phase collecting pipe and a venturi tube sleeved within the liquid phase collecting pipe, and the throat of the venturi tube is provided with a wash water inlet;

[0009] The top gas phase outlet of the aromatics extractive distillation tower is connected to the top gas phase inlet of the venturi separator; the washing liquid phase outlet of the venturi separator is connected to the side line inlet of the aromatics extractive distillation tower, and the washed gas phase outlet of the venturi separator is connected to the reflux tank inlet through the condenser; the water phase outlet of the reflux tank is connected to the water washing water inlet of the venturi separator.

[0010] Optionally, the Venturi separator includes a Venturi tube, a water injection pipe, and a liquid phase collection pipe; the Venturi tube is vertically arranged in the liquid phase collection pipe, and the post-wash gas phase outlet of the Venturi separator is arranged at the top of the liquid phase collection pipe; the washing water inlet of the Venturi separator is connected to the throat of the Venturi tube through the water injection pipe;

[0011] The bottom inlet of the venturi tube is formed as the tower top gas phase inlet of the venturi separator, and the washed gas phase outlet of the venturi separator is communicated with the top outlet of the venturi tube.

[0012] Optionally, the venturi tube includes, from bottom to top, a constant diameter section, a reduced diameter section, and an expanded diameter section that are sequentially connected; the water injection pipe passes through the wall of the liquid phase collection pipe and is connected to the reduced diameter section of the venturi tube, close to the throat of the venturi tube; an open pipe is connected to the top of the liquid phase collection pipe, the top opening of the open pipe forms the post-washing gas phase outlet of the venturi separator, and the bottom opening of the open pipe extends downward into the liquid phase collection pipe, with a gap between it and the top opening of the expanded diameter section of the venturi tube;

[0013] Optionally, the diameter of the open tube is the same as the diameter of the top opening of the expanded section;

[0014] Optionally, the angle between the water injection pipe and the venturi tube is 10 to 90 degrees.

[0015] Optionally, the Venturi separator also includes a vortex core tube, the interior of which is provided with a spiral guide vane, the vortex core tube is sleeved on the equal-diameter section of the Venturi tube, and the bottom inlet of the vortex core tube forms the top gas phase inlet of the Venturi separator; the number of the vortex core tubes is one or more, and multiple vortex core tubes are arranged in parallel.

[0016] Optionally, the aromatic feed inlet of the aromatic extractive distillation tower is arranged in the middle of the tower, the extraction solvent inlet is arranged in the upper part of the tower, and the side line inlet of the aromatic extractive distillation tower is arranged above the aromatic feed inlet.

[0017] A second aspect of the present disclosure provides an aromatics extraction method using the system described in the first aspect of the present disclosure, the aromatics extraction method comprising the following steps:

[0018] The raw material containing aromatics enters the aromatics extraction distillation tower and contacts with the lean solvent to extract aromatics;

[0019] The top gas phase of the aromatics extraction distillation tower enters the venturi separator, contacts with washing water, and undergoes water washing and removal treatment to obtain a washed gas phase and a washing liquid phase containing a solvent;

[0020] The washing liquid phase is returned to the aromatics extraction distillation tower for recycling, the washed gas phase is condensed and then enters the reflux tank for separation to obtain a raffinate oil product and an aqueous phase, and the aqueous phase is returned to the Venturi separator as washing water.

[0021] Optionally, in the Venturi separator, the mass flow rate ratio of the wash water to the top gas phase is (0.2-1.0):1, preferably (0.2-0.5):1.

[0022] Optionally, the temperature of the top gas phase of the aromatic extractive distillation tower is 100° C. to 130° C., and the pressure is 150 kPa to 250 kPa, and the extraction solvent enters from the extraction solvent inlet of the aromatic extractive distillation tower.

[0023] Optionally, the inlet air velocity of the Venturi separator is 1 m / s to 30 m / s, the pressure loss is 0.2 kPa to 5 kPa, and the inlet absolute pressure of the washing water is 200 kPa to 1500 kPa.

[0024] Optionally, the liquid phase removal rate of the Venturi separator is 90% to 99.9%, and the liquid phase separation accuracy is 1 μm to 10 μm.

[0025] Through the above technical solution, the present invention introduces a Venturi separator into the aromatics extraction system, so that the trace solvent in the overhead gas phase is washed with water by the Venturi separator and then returned to the aromatics extraction distillation tower. The remaining gas phase is condensed and enters the reflux tank, and the oil phase in the reflux tank is extracted as the raffinate oil product. The system of the present invention improves the selectivity of the extraction solvent, increases the content of non-aromatic hydrocarbons in the raffinate oil, reduces the content of aromatic hydrocarbons in the raffinate oil, and further improves the quality and yield of the aromatic hydrocarbon product in the extract. At the same time, the system of the present invention occupies a small area, does not require additional heating, and has low energy consumption.

[0026] Other features and advantages of the present disclosure will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings are used to provide a further understanding of the present disclosure and constitute a part of the specification. Together with the following detailed description, they are used to explain the present disclosure but do not constitute a limitation of the present disclosure. In the accompanying drawings:

[0028] Figure 1 Schematic diagram of the aromatics extraction system in Example 1 of the present disclosure.

[0029] Figure 2 It is a structural schematic diagram of the Venturi separator in Example 1 of the present disclosure.

[0030] Figure 3 Schematic diagram of the process of Comparative Example 1 of the present disclosure.

[0031] Figure 4 It is a schematic diagram of the process of Comparative Example 2 of the present disclosure.

[0032] Description of Reference Numerals

[0033] Figure 1 In the figure, 101: aromatics extraction distillation tower; 102: venturi separator; 103: reflux drum; 104: condenser; 1: aromatics feed inlet; 2: extraction solvent inlet; 3: tower top gas phase outlet; 4: washed gas phase outlet; 5: reflux drum inlet; 6: wash water inlet; 7: oil phase outlet; 8: washing liquid phase outlet; 9: tower bottom liquid phase outlet; 10: side line inlet; 11: tower top gas phase inlet; 12: water phase outlet.

[0034] Figure 2 In the figure, 13: vortex core tube; 14: Venturi tube; 15: water injection tube; 16: liquid phase collection tube; 17: top opening of the expanded section; 18: open tube. DETAILED DESCRIPTION

[0035] The following describes the specific embodiments of the present disclosure in detail with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present disclosure and are not intended to limit the present disclosure.

[0036] In the present disclosure, unless otherwise specified, it should be understood that terms such as "front", "back", "left", "right", "up", "down", "top", and "bottom" indicating directions or positional relationships are based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present disclosure and simplifying the description. They do not indicate that a device or component must have a specific direction, be constructed and operated in a specific direction. Therefore, they should not be understood as limitations on the present disclosure.

[0037] A first aspect of the present disclosure provides a system for aromatic hydrocarbon extraction, the system comprising an aromatic hydrocarbon extraction distillation column, a venturi separator, a condenser, and a reflux drum;

[0038] The aromatics extractive distillation tower includes an aromatics feed inlet, an extraction solvent inlet, a side line inlet, a bottom liquid phase outlet, and a top gas phase outlet; the venturi separator includes a top gas phase inlet, a wash water inlet, a wash liquid phase outlet, and a washed gas phase outlet; the reflux tank includes a reflux tank inlet, a water phase outlet, and an oil phase outlet; the oil phase outlet of the reflux tank forms the raffinate oil product outlet of the system; the venturi separator includes a vertical liquid phase collecting pipe and a venturi tube sleeved within the liquid phase collecting pipe, and the throat of the venturi tube is provided with a wash water inlet;

[0039] The top gas phase outlet of the aromatics extractive distillation tower is connected to the top gas phase inlet of the venturi separator; the washing liquid phase outlet of the venturi separator is connected to the side line inlet of the aromatics extractive distillation tower, and the washed gas phase outlet of the venturi separator is connected to the reflux tank inlet through the condenser; the water phase outlet of the reflux tank is connected to the water washing water inlet of the venturi separator.

[0040] The aromatics extraction system disclosed herein introduces a venturi separator into the system, so that trace solvents in the overhead gas phase are washed with water by the venturi separator and then returned to the aromatics extraction distillation tower. The remaining gas phase is condensed and then enters a reflux tank, and the oil phase in the reflux tank is extracted as a raffinate oil product. The system disclosed herein improves the selectivity of the solvent, eliminating the need for non-aromatic hydrocarbons to reflux into the aromatics extraction distillation tower, thus avoiding the formation of two liquid phases in the aromatics extraction distillation tower, increasing the content of non-aromatic hydrocarbons in the raffinate oil, reducing the content of aromatic hydrocarbons in the raffinate oil, and further improving the quality and yield of the aromatic hydrocarbon product in the extract. At the same time, the system disclosed herein occupies a small area, does not require additional heating, and has low energy consumption.

[0041] According to one embodiment of the present disclosure, the venturi separator includes a venturi tube, a water injection pipe, and a liquid phase collection pipe; the venturi tube is vertically arranged in the liquid phase collection pipe, and the post-wash gas phase outlet of the venturi separator is arranged at the top of the liquid phase collection pipe; the water washing inlet of the venturi separator is connected to the throat of the venturi tube through the water injection pipe;

[0042] The bottom inlet of the venturi tube forms the top gas phase inlet of the venturi separator, and the post-wash gas phase outlet of the venturi separator is connected to the top outlet of the venturi tube. The above-described embodiment indirectly increases the water content of the extraction solvent in the aromatics extraction distillation tower through the use of a venturi separator, thereby improving the selectivity of the extraction solvent, increasing the content of non-aromatic hydrocarbons in the raffinate oil, and further improving the quality and yield of the aromatic hydrocarbon product in the extract. At the same time, it prevents non-aromatic hydrocarbons from returning to the aromatics extraction distillation tower, avoiding the formation of two liquid phases in the aromatics extraction distillation tower, and further improving the separation effect of the extractive distillation.

[0043] According to one embodiment of the present disclosure, the venturi tube includes, from bottom to top, a constant diameter section, a reduced diameter section, and an expanded diameter section that are connected in sequence, the water injection pipe passes through the wall of the liquid phase collecting pipe and is connected to the reduced diameter section of the venturi tube, and is close to the throat of the venturi tube; the top of the liquid phase collecting pipe is connected to an open pipe, the top opening of the open pipe forms the post-washing gas phase outlet of the venturi separator, the bottom opening of the open pipe extends downward into the liquid phase collecting pipe, and there is a gap between the top opening of the expanded diameter section of the venturi tube; preferably, the diameter of the open pipe is the same as the diameter of the top opening of the expanded diameter section; preferably, the angle between the water injection pipe and the venturi tube is 10 to 90°. The above embodiment indirectly increases the water content of the extraction solvent in the aromatics extraction distillation tower by using a venturi separator, thereby improving the selectivity of the extraction solvent.

[0044] According to one embodiment of the present disclosure, the venturi separator further includes a vortex core tube, which is sleeved on the equal-diameter section of the venturi tube, and the bottom inlet of the vortex core tube forms the top gas phase inlet of the venturi separator; the number of the vortex core tubes is one or more, and a plurality of the vortex core tubes are arranged in parallel. The interior of the vortex core tube is provided with a spiral guide vane, which can be a conventional structure in the field, for example, a three-head thread structure or a four-head thread structure. In the above embodiment, the vortex shear of the vortex core tube strengthens the mixing of the top gas phase and water, thereby improving the solvent removal effect, and further making the solvent content in the residual oil product not exceed 2μg / g.

[0045] According to one embodiment of the present disclosure, the aromatic feed inlet of the aromatic extractive distillation tower is arranged in the middle of the tower, the extraction solvent inlet is arranged in the upper part of the tower, and the side line inlet of the aromatic extractive distillation tower is arranged above the aromatic feed inlet.

[0046] A second aspect of the present disclosure provides an aromatics extraction method using the system described in the first aspect of the present disclosure, the aromatics extraction method comprising the following steps:

[0047] The raw material containing aromatic hydrocarbons enters the aromatic hydrocarbon extraction distillation tower and contacts with the extraction solvent to extract the aromatic hydrocarbons;

[0048] The top gas phase of the aromatics extraction distillation tower enters the venturi separator, contacts with washing water, and undergoes water washing and removal treatment to obtain a washed gas phase and a washing liquid phase containing a solvent;

[0049] The washing liquid phase is returned to the aromatics extraction distillation tower for recycling, the washed gas phase is condensed and then enters the reflux tank for separation to obtain a raffinate oil product and an aqueous phase, and the aqueous phase is returned to the Venturi separator as washing water.

[0050] According to one embodiment of the present disclosure, in the Venturi separator, the mass flow rate ratio of the wash water to the overhead gas phase is (0.2-1.0):1, preferably (0.2-0.5):1. The above embodiment is conducive to improving the solvent removal effect, so that the solvent content in the raffinate oil product does not exceed 2 μg / g.

[0051] According to one embodiment of the present disclosure, the temperature of the overhead gas phase of the aromatics extractive distillation tower is 100°C to 130°C, preferably 105°C to 120°C; the pressure is 150kPa to 250kPa, preferably 160kPa to 220kPa; and the extraction solvent is introduced through the extraction solvent inlet of the aromatics extractive distillation tower. This embodiment is conducive to improving the solvent removal effect, so that the solvent content in the raffinate oil product does not exceed 2μg / g.

[0052] According to one embodiment of the present disclosure, the inlet gas velocity of the Venturi separator is 1 m / s to 30 m / s, the pressure drop is 0.2 kPa to 5 kPa, and the absolute inlet pressure of the wash water is 200 kPa to 1500 kPa, preferably 250 to 1000 kPa. In the present disclosure, the inlet gas velocity of the Venturi separator refers to the inlet gas velocity of the overhead gas phase entering the reduced diameter section of the Venturi tube. The above embodiment is conducive to improving the solvent removal effect, so that the solvent content in the raffinate oil product does not exceed 2 μg / g.

[0053] According to one embodiment of the present disclosure, the liquid phase removal rate of the venturi separator is 90% to 99.9%, and the liquid phase separation accuracy is 1 μm to 10 μm. The above embodiment is conducive to improving the solvent removal effect, so that the solvent content in the raffinate oil product does not exceed 2 μg / g.

[0054] The present invention is further illustrated below by way of examples, but the present invention is not limited thereto.

[0055] The raw material used in the examples and comparative examples is the C6-C7 fraction of reformed oil, and the mass fraction of aromatic hydrocarbons in the raw material is 65%.

[0056] The sulfolane used was a chemical reagent purchased from Inokai Technology Co., Ltd. Unless otherwise specified, the other reagents were obtained through commercial channels.

[0057] Example 1

[0058] like Figure 1 The aromatics extraction system shown and Figure 2 The venturi separator shown in the figure comprises an aromatics extractive distillation column 101, a venturi separator 102, a reflux drum 103 and a condenser 104;

[0059] The aromatics extractive distillation tower 101 includes an aromatics feed inlet 1, an extraction solvent inlet 2, a side line inlet 10, a bottom liquid phase outlet 9, and a top gas phase outlet 3; the venturi separator 102 includes a top gas phase inlet 11, a wash water inlet 6, a wash liquid phase outlet 8, and a washed gas phase outlet 4; the reflux tank 103 includes a reflux tank inlet 5, a water phase outlet 12, and an oil phase outlet 7;

[0060] The top gas phase outlet 3 of the aromatics extractive distillation tower 101 is connected to the top gas phase inlet 11 of the venturi separator 102; the wash liquid phase outlet 8 of the venturi separator 102 is connected to the side line inlet 10 of the aromatics extractive distillation tower 101, and the washed gas phase outlet 4 of the venturi separator 102 is connected to the inlet 5 of the reflux tank 103; the water phase outlet 12 of the reflux tank 103 is connected to the wash water inlet 6 of the venturi separator 102; the oil phase outlet 7 of the reflux tank 103 forms the raffinate oil product outlet of the system; the condenser 104 is arranged between the washed gas phase outlet 4 of the venturi separator 102 and the inlet 5 of the reflux tank;

[0061] The venturi separator 102 includes a vertical liquid phase collecting pipe 16 and a venturi tube 14 sleeved in the liquid phase collecting pipe 16, and a washing water inlet 6 is provided at the throat of the venturi tube 14; the venturi separator includes a venturi tube 14, a vortex core tube 13, a water injection pipe 15 and a liquid phase collecting pipe 16; the venturi tube 14 is vertically arranged in the liquid phase collecting pipe 16, and the washed gas phase outlet 4 of the venturi separator 102 is arranged at the top of the liquid phase collecting pipe 16; the washing water inlet 6 of the venturi separator 102 is connected to the throat of the venturi tube 14 through the water injection pipe 15; the bottom inlet of the venturi tube is formed as the top gas phase inlet of the venturi separator, and the washed gas phase outlet of the venturi separator is connected to the top outlet of the venturi tube; the venturi tube 14 includes, from bottom to top, equal diameters connected in sequence The venturi tube 14 has a plurality of sections, a reduced diameter section and an expanded diameter section, and the water injection pipe 15 passes through the wall of the liquid phase collecting pipe 16 and is connected to the reduced diameter section of the venturi tube 14, and is close to the throat of the venturi tube; the top of the liquid phase collecting pipe 16 is connected to an open pipe 18, the top opening of the open pipe 18 forms the washed gas phase outlet 4 of the venturi separator 102, and the bottom opening of the open pipe 18 extends downward into the liquid phase collecting pipe 16, and there is a gap between the top opening 17 of the expanded diameter section of the venturi tube 14; the diameter of the open pipe 18 is the same as the diameter of the top opening of the expanded diameter section; the angle between the water injection pipe 15 and the venturi tube 14 is 90°; the vortex core tube 13 is sleeved on the equal diameter section of the venturi tube, and the bottom inlet of the vortex core tube 13 forms the tower top gas phase inlet 11 of the venturi separator 102; the number of vortex core tubes is one.

[0062] The raw material containing aromatic hydrocarbons enters the aromatic hydrocarbon extraction distillation tower 101 through the aromatic hydrocarbon raw material inlet 1, and the solvent sulfolane enters the aromatic hydrocarbon extraction distillation tower 101 through the extraction solvent inlet 2. The raw material containing aromatic hydrocarbons and sulfolane contact in the aromatic hydrocarbon extraction distillation tower 101 to extract aromatic hydrocarbons; the top gas phase of the aromatic hydrocarbon extraction distillation tower 101 is discharged from the top gas phase outlet 3, passes through the vortex core tube 13 of the venturi separator 102, forms an upward vortex gas phase, and enters the venturi tube 14; the water phase from the reflux tank 103 enters the venturi tube 14 through the water injection pipe 15; the vortex gas phase and the water phase are mixed. The washed liquid phase contacts the washing water and undergoes a water-washing and removal process, producing a washed gas phase and a solvent-containing washing liquid phase. The solvent-containing washing liquid phase gradually gathers outside the vortex and is discharged from the bottom opening of the open tube 18 of the liquid phase collection pipe 16. It then enters the liquid phase collection pipe 16 and, under the action of gravity, reaches the bottom washing liquid phase outlet 8 for discharge. The washed gas phase is discharged from the washed gas phase outlet 4, passes through the condenser 104, and enters the reflux drum 103 for treatment. The raffinate oil is discharged from the oil phase outlet 7 of the reflux drum 103. The liquid phase discharged from the washing liquid phase outlet 8 is returned to the aromatics extraction distillation column 101 for recycling. The liquid phase removal rate at the top vapor phase outlet of the Venturi separator 102 is 99.8%. The specific operating conditions of the aromatics extraction system are shown in Table 1.

[0063] Table 1

[0064]

[0065] Example 2

[0066] The method is the same as that of Example 1, except that the venturi tube in this embodiment does not include a vortex core tube. The liquid phase removal rate at the top gas phase outlet of the venturi separator 102 is 83%. The specific operating conditions of the aromatics extraction system are shown in Table 1.

[0067] Example 3

[0068] The method is the same as that in Example 1, except that the mass flow rate ratio of the water phase to the overhead gas phase in this embodiment is 0.18:1; the liquid phase removal rate at the overhead gas phase outlet of the Venturi separator 102 is 99.8%, and the specific operating conditions of the aromatics extraction system are shown in Table 1.

[0069] Example 4

[0070] The method is the same as that in Example 1, except that the inlet gas velocity at the venturi tube inlet is 40 m / s and the absolute water inlet pressure is 180 kPa; the liquid phase removal rate at the top gas phase outlet of the venturi separator 102 is 95%. The specific operating conditions of the aromatics extraction system are shown in Table 1.

[0071] Comparative Example 1

[0072] use Figure 3 The conventional process shown, i.e., an extractive distillation tower (ED tower) and a non-aromatic distillation tower (NA tower) are connected in series to recover trace solvents in the ED tower top gas phase. The raw materials, solvents and solvent ratios used are the same as those in Example 1. The operating conditions of this comparative example 1 are shown in Table 2.

[0073] Table 2

[0074]

[0075] Comparative Example 2

[0076] use Figure 4 The process shown is to set a non-aromatic distillation section in the upper section of the extractive distillation column (ED column) to recover trace solvents in the raffinate oil. The raw materials, solvents and solvent ratios are the same as those in Example 1. The operating conditions are shown in Table 3.

[0077] Table 3

[0078]

[0079] Test Example 1

[0080] The components of the raffinate oil products obtained in Examples 1 to 4 and Comparative Examples 1 to 2 were analyzed. The aromatic content and solvent content of the raffinate oil were analyzed using ASTM D-6536 and GGBM-04-2005 standard methods. The product composition is shown in Table 4.

[0081] Table 4

[0082] Mass fraction of non-aromatic hydrocarbons / % Aromatics mass fraction / % Solvent mass concentration / (μg / g) Example 1 99.95 0.05 1 Example 2 99.95 0.05 5 Example 3 99.95 0.05 10 Example 4 99.95 0.05 4 Comparative Example 1 99.90 0.10 1 Comparative Example 2 99.47 0.53 2

[0083] According to the data in Table 4, the aromatics extraction system disclosed herein increases the water content of the extraction solvent in the aromatics extraction distillation tower, improves the selectivity of the extraction solvent, increases the content of non-aromatic hydrocarbons in the raffinate oil, reduces the content of aromatic hydrocarbons in the raffinate oil, and further improves the quality and yield of the aromatic hydrocarbon product in the extract; and the Venturi separator occupies a small area and does not require additional heating, further reducing energy consumption.

[0084] By comparing Example 1 with Comparative Example 1, it can be seen that the solvent content in the raffinate oil product obtained by the system of the present invention can reach a level comparable to that of Comparative Example 1. However, the addition of the aqueous phase to the aromatic extraction distillation tower of the present invention improves the solvent selectivity, resulting in a lower aromatic content in the raffinate oil, and eliminates the need for a reboiler at the bottom of the NA tower and reflux at the top of the tower, thereby saving energy consumption.

[0085] By comparing Example 1 with Comparative Example 2, it can be seen that the system disclosed in the present invention avoids the reflux of non-aromatic raffinate oil into the aromatic extraction distillation tower, increases the content of non-aromatic hydrocarbons in the raffinate oil, reduces the content of aromatic hydrocarbons in the raffinate oil, and further increases the yield of aromatic hydrocarbons in the extract; at the same time, it improves the effect of removing solvent from the raffinate oil.

[0086] By comparing Example 1 with Example 2, it can be seen that the Venturi separator disclosed herein has a higher liquid phase removal rate and a lower solvent content in the raffinate oil product when it includes a vortex core tube.

[0087] By comparing Example 1 with Example 3, it can be seen that within the mass flow rate ratio range of the wash water / tower top gas phase disclosed in the present invention, the solvent content in the raffinate oil product is lower.

[0088] By comparing Example 1 with Example 4, it can be seen that under the range of the venturi tube inlet gas velocity and water inlet absolute pressure disclosed in the present invention, the liquid phase removal rate is higher and the solvent content in the raffinate oil product is lower.

[0089] The preferred embodiments of the present disclosure are described in detail above in conjunction with the accompanying drawings. However, the present disclosure is not limited to the specific details of the above embodiments. Within the technical concept of the present disclosure, various simple modifications can be made to the technical solutions of the present disclosure, and these simple modifications all fall within the scope of protection of the present disclosure.

[0090] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present disclosure will not further describe various possible combinations.

[0091] In addition, the various embodiments of the present disclosure may be arbitrarily combined, and as long as they do not violate the concept of the present disclosure, they should also be regarded as the contents disclosed by the present disclosure.

Claims

1. A system for extracting aromatics, characterized in that: The system includes an aromatics extractive distillation tower, a venturi separator, a condenser and a reflux tank; The aromatics extractive distillation tower includes an aromatics feed inlet, an extraction solvent inlet, a side line inlet, a bottom liquid phase outlet, and a top gas phase outlet; the venturi separator includes a top gas phase inlet, a wash water inlet, a wash liquid phase outlet, and a washed gas phase outlet; the reflux tank includes a reflux tank inlet, a water phase outlet, and an oil phase outlet; the oil phase outlet of the reflux tank forms the raffinate oil product outlet of the system; the venturi separator includes a vertical liquid phase collecting pipe and a venturi tube sleeved within the liquid phase collecting pipe, and the throat of the venturi tube is provided with a wash water inlet; The top gas phase outlet of the aromatics extractive distillation tower is connected to the top gas phase inlet of the venturi separator; the washing liquid phase outlet of the venturi separator is connected to the side line inlet of the aromatics extractive distillation tower, and the washed gas phase outlet of the venturi separator is connected to the reflux tank inlet through the condenser; the water phase outlet of the reflux tank is connected to the water washing water inlet of the venturi separator.

2. The system according to claim 1, wherein: The venturi separator includes a venturi tube, a water injection pipe and a liquid phase collection pipe; the venturi tube is vertically arranged in the liquid phase collection pipe, and the post-wash gas phase outlet of the venturi separator is arranged at the top of the liquid phase collection pipe; the water washing inlet of the venturi separator is connected to the throat of the venturi tube through the water injection pipe; The bottom inlet of the venturi tube is formed as the tower top gas phase inlet of the venturi separator, and the washed gas phase outlet of the venturi separator is communicated with the top outlet of the venturi tube.

3. The system according to claim 2, wherein: The venturi tube includes, from bottom to top, an equal-diameter section, a reduced-diameter section, and an expanded-diameter section that are connected in sequence. The water injection pipe passes through the wall of the liquid phase collecting tube and is connected to the reduced-diameter section of the venturi tube, and is close to the throat of the venturi tube. An open tube is connected to the top of the liquid phase collecting tube, and the top opening of the open tube forms the post-washing gas phase outlet of the venturi separator. The bottom opening of the open tube extends downward into the liquid phase collecting tube, and there is a gap between it and the top opening of the expanded-diameter section of the venturi tube.

4. The system according to claim 3, wherein: The diameter of the open tube is the same as the diameter of the top opening of the expanded section.

5. The system according to claim 3, wherein: The angle between the water injection pipe and the venturi tube is 10-90 degrees.

6. The system according to claim 3, wherein: The Venturi separator also includes a vortex core tube, the interior of which is provided with a spiral guide plate, the vortex core tube is sleeved on the equal-diameter section of the Venturi tube, and the bottom inlet of the vortex core tube forms the top gas phase inlet of the Venturi separator; the number of the vortex core tubes is one or more, and multiple vortex core tubes are arranged in parallel.

7. The system according to claim 1, wherein: The aromatics raw material inlet of the aromatics extraction distillation tower is arranged in the middle of the tower, the extraction solvent inlet is arranged in the upper part of the tower, and the side line inlet of the aromatics extraction distillation tower is arranged above the aromatics raw material inlet.

8. A method for extracting aromatics using the system according to any one of claims 1 to 7, characterized in that: The aromatics extraction method comprises the following steps: The raw material containing aromatic hydrocarbons enters the aromatic hydrocarbon extraction distillation tower and contacts with the extraction solvent to extract the aromatic hydrocarbons; The top gas phase of the aromatics extraction distillation tower enters the venturi separator, contacts with washing water, and undergoes water washing and removal treatment to obtain a washed gas phase and a washing liquid phase containing a solvent; The washing liquid phase is returned to the aromatics extraction distillation tower for recycling, the washed gas phase is condensed and then enters the reflux tank for separation to obtain a raffinate oil product and an aqueous phase, and the aqueous phase is returned to the Venturi separator as washing water.

9. The method according to claim 8, wherein In the Venturi separator, the mass flow rate ratio of the wash water to the top gas phase is (0.2-1.0):

1.

10. The method according to claim 9, wherein: In the Venturi separator, the mass flow rate ratio of the wash water to the top gas phase is (0.2-0.5):

1.

11. The method according to claim 8, wherein The temperature of the gas phase at the top of the aromatic extractive distillation tower is 100° C. to 130° C., and the pressure is 150 kPa to 250 kPa. The extraction solvent enters from the extraction solvent inlet of the aromatic extractive distillation tower.

12. The method according to claim 8, wherein The inlet gas velocity of the Venturi separator is 1m / s~30m / s, the pressure loss is 0.2kPa~5kPa, and the absolute inlet pressure of the washing water is 200kPa~1500kPa.

13. The method according to claim 8, wherein The liquid phase removal rate of the Venturi separator is 90% to 99.9%, and the liquid phase separation accuracy is 1 μm to 10 μm.

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