Aromatic hydrocarbon extraction system and method

Abstract

The invention relates to an aromatic hydrocarbon extraction system and method. The system comprises an aromatic hydrocarbon extraction distillation tower, a Venturi separator, a condenser and a reflux tank, the aromatic extraction distillation tower comprises an aromatic raw material inlet, an extraction solvent inlet, a side line inlet, a tower bottom liquid phase outlet and a tower top gas phase outlet; the Venturi separator comprises a tower top gas phase inlet, a washing water inlet, a washing liquid phase outlet and a washed gas phase outlet; the reflux tank comprises a reflux tank inlet, a water phase outlet and an oil phase outlet; an oil phase outlet of the return tank forms a raffinate oil product outlet of the system; the venturi separator comprises a vertically arranged liquid phase collecting pipe and a venturi pipe arranged in the liquid phase collecting pipe in a sleeving manner, and a washing water inlet is formed in the throat part of the venturi pipe; and the tower top gas phase outlet of the aromatic hydrocarbon extraction distillation tower is communicated with the tower top gas phase inlet of the Venturi separator. The system disclosed by the invention improves the selectivity of the extraction solvent, and improves the quality and yield of 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 aromatics extractive distillation of C6-C7 fraction is a process that uses solvents to separate benzene, toluene and non-aromatics. It generally includes an extractive distillation tower (ED tower), a non-aromatic distillation tower (NA tower), and a solvent recovery tower (SR tower). The ED tower is mainly used for the separation of aromatics and non-aromatics, and the gas phase at the top of the tower enters the NA tower; the NA tower is used to recover the trace solvent contained in the gas phase at the top of the ED tower, and part of the raffinate oil obtained at the top of the tower is refluxed, and the rest is produced as a product; a reboiler is set at the bottom of the tower to obtain an enriched solvent and return it to the ED tower. The SR tower is used to separate solvents and aromatics. The two tower equipments of the ED tower and the NA tower make the device occupy a large area and the equipment and pipeline investment is high.

[0003] CN216824877U discloses an aromatic extraction device with small footprint and flexible operation, which saves equipment cost by designing the extractive distillation tower and the non-aromatic distillation tower as one tower with two sections. However, since the raffinate oil (i.e., non-aromatic hydrocarbons) in the reflux tank of the ED tower is returned to the top of the ED tower, the solvent has limited solubility for non-aromatic hydrocarbons, which will cause two obvious liquid phases to appear on the upper part of the ED, affecting the extractive distillation separation effect.

[0004] CN100378048C discloses a method for separating aromatic hydrocarbons by extractive distillation. The extractant enters from the upper part of the tower, a heat source is set at the bottom of the non-aromatic hydrocarbon reflux section of the extractive distillation tower for heating, a part of the non-aromatic hydrocarbons at the top of the tower refluxes, and the rest is discharged from the system. The non-aromatic hydrocarbon reflux section is used to recover trace solvents in the raffinate oil, but the problem of the formation of two liquid phases cannot be avoided.

[0005] CN109517619A discloses a desolventizing method for aromatic extraction raffinate oil, wherein the aromatic extraction raffinate oil containing the extraction solvent is subjected to two-stage water washing, the first-stage water washing product is filtered and separated by a hydrophilic polar filter membrane, and the second-stage water washing product is filtered and separated by a hydrophobic polar filter membrane. This method has a large number of equipment and uses a membrane separation process, which may have problems with the service life of the membrane. Summary of the invention

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

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

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

[0009] The top gas phase outlet of the aromatics extraction 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 extraction 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 wash water inlet of the venturi separator.

[0010] Optionally, the venturi separator comprises a venturi tube, a water injection pipe and a liquid phase collecting pipe; the venturi tube is vertically arranged in the liquid phase collecting pipe, and the post-washing gas phase outlet of the venturi separator is arranged at the top of the liquid phase collecting 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 connected in sequence, the water injection pipe passes through the tube 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; the top of the liquid phase collecting tube is connected to an open tube, the top opening of the open tube is formed as 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 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 the 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] The second aspect of the present disclosure provides an aromatics extraction method using the system of the first aspect of the present disclosure, the aromatics extraction method comprising the following steps:

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

[0019] The gas phase at the top 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 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, and the extraction solvent enters from the extraction solvent inlet of the aromatic extractive distillation tower.

[0023] Optionally, the inlet gas 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 scheme, the present invention introduces a venturi separator into the aromatic extraction system, so that the trace solvent in the gas phase at the top of the tower is washed by the venturi separator and then returned to the aromatic extraction distillation tower, and the remaining gas phase enters the reflux tank after condensation, 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 specific embodiments, 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 It is a schematic diagram of the aromatic extraction system in Example 1 of the present disclosure.

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

[0030] Figure 3 It is a 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 tank; 104: condenser; 1: aromatics feed inlet; 2: extraction solvent inlet; 3: tower top gas phase outlet; 4: washed gas phase outlet; 5: reflux tank 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 collecting tube; 17: top opening of the expanded diameter section; 18: open tube. DETAILED DESCRIPTION

[0035] The specific implementation of the present disclosure is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described herein is only used to illustrate and explain the present disclosure, and is not used to limit the present disclosure.

[0036] In the present disclosure, unless otherwise specified, it should be understood that terms such as “front”, “rear”, “left”, “right”, “up”, “down”, “top” and “bottom” indicate directions or positional relationships 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 extraction, the system comprising an aromatic extraction distillation tower, a venturi separator, a condenser, and a reflux drum;

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

[0039] The top gas phase outlet of the aromatics extraction 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 extraction 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 wash water inlet of the venturi separator.

[0040] The aromatic extraction system disclosed in the present invention introduces a venturi separator into the system, so that the trace solvent in the gas phase at the top of the tower is washed by the venturi separator and then returned to the aromatic extraction distillation tower, and the remaining gas phase enters the reflux tank after condensation, and the oil phase in the reflux tank is produced as the raffinate oil product. The system disclosed in the present invention improves the selectivity of the solvent, so that non-aromatic hydrocarbons do not need to be refluxed to the aromatic extraction distillation tower, avoiding the formation of two liquid phases in the aromatic 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 extracted liquid; at the same time, the system disclosed in the present invention occupies a small area, does not require additional heating, and has low energy consumption.

[0041] According to an embodiment of the present disclosure, the venturi separator comprises a venturi tube, a water injection pipe and a liquid phase collecting pipe; the venturi tube is vertically arranged in the liquid phase collecting pipe, and the post-washing gas phase outlet of the venturi separator is arranged at the top of the liquid phase collecting pipe; the washing water 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 washed gas phase outlet of the venturi separator is connected to the top outlet of the venturi tube. The above-mentioned embodiment indirectly increases the water content of the extraction solvent in the aromatic extraction distillation tower by using the 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 avoids the non-aromatic hydrocarbons from returning to the aromatic extraction distillation tower, avoids the formation of two liquid phases in the aromatic extraction distillation tower, and further improves the separation effect of the extractive distillation.

[0043] According to an embodiment of the present disclosure, 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 tube 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; the top of the liquid phase collecting tube is connected to an open tube, 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 the top opening of the expanded-diameter section of the venturi tube; preferably, the tube diameter of the open tube 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-mentioned 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 may 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 raffinate 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] The second aspect of the present disclosure provides an aromatics extraction method using the system of the first aspect of the present disclosure, the aromatics extraction method comprising the following steps:

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

[0048] The gas phase at the top 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 an embodiment of the present disclosure, 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. 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 gas phase at the top of the aromatic extractive distillation tower is 100°C to 130°C, preferably 105 to 120°C; the pressure is 150kPa to 250kPa, preferably 160 to 220kPa; the extraction solvent enters from the extraction solvent inlet of the aromatic extractive distillation tower. The above 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 an embodiment of the present disclosure, the inlet gas velocity of the venturi separator is 1m / s to 30m / s, the pressure loss is 0.2kPa to 5kPa, and the absolute water inlet pressure of the wash water is 200kPa to 1500kPa, preferably 250 to 1000kPa. The inlet gas velocity of the venturi separator in the present disclosure refers to the inlet gas velocity of the top gas phase entering the venturi tube reduction section. The above embodiment is conducive to improving the removal effect of the solvent, so that the solvent content in the raffinate oil product does not exceed 2μg / g.

[0053] According to an 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 by the following 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 aromatics 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, the system comprises an aromatic extractive distillation tower 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 washing 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 washing water inlet 6 of the venturi separator 102; the oil phase outlet 7 of the reflux tank 103 is formed as 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 tower 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, the water injection pipe 15 passes through the tube wall of the liquid phase collecting tube 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 tube 16 is connected to an open tube 18, the top opening of the open tube 18 forms the washed gas phase outlet 4 of the venturi separator 102, the bottom opening of the open tube 18 extends downward into the liquid phase collecting tube 16, and there is a gap between the top opening 17 of the expanded diameter section of the venturi tube 14; the tube diameter of the open tube 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] Aromatic raw materials enter the aromatic extraction distillation tower 101 through the aromatic raw material inlet 1, and the solvent sulfolane enters the aromatic extraction distillation tower 101 through the extraction solvent inlet 2. The aromatic raw materials and sulfolane contact in the aromatic extraction distillation tower 101 to extract aromatics; the top gas phase of the aromatic 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 to form 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 discharged from the reflux tank 103 through the water injection pipe 15. The washing water is contacted, and the washing and removing treatment is carried out to obtain the washed gas phase and the washing liquid phase containing the solvent. The washing liquid phase containing the solvent gradually gathers outside the vortex, and is discharged from the bottom opening of the opening tube 18 of the liquid phase collecting pipe 16, enters the liquid phase collecting pipe 16, and reaches the bottom washing liquid phase outlet 8 under the action of gravity. The washed gas phase is discharged from the washed gas phase outlet 4, passes through the condenser 104, enters the reflux tank 103 for treatment, and the residual oil is discharged from the oil phase outlet 7 of the reflux tank 103; the liquid phase discharged from the washing liquid phase outlet 8 returns to the aromatic extraction distillation tower 101 for recycling. The liquid phase removal rate at the top gas phase outlet of the venturi separator 102 is 99.8%, and the specific operating conditions of the aromatic extraction system are shown in Table 1.

[0063] Table 1

[0064]

[0065] Example 2

[0066] The method is the same as that in Example 1, except that the venturi tube in this example does not include a vortex core tube. The liquid phase removal rate at the gas phase outlet of the top 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 in this embodiment, the mass flow rate ratio of the water phase to the top gas phase is 0.18:1; the liquid phase removal rate at the top 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 inlet of the venturi tube in this embodiment is 40m / s, and the absolute water inlet pressure is 180kPa; the liquid phase removal rate at the top gas phase outlet of the venturi separator 102 is 95%, and 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 gas phase at the top of the ED tower. 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 that a non-aromatic distillation section is set in the upper section of the extractive distillation tower (ED tower) 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 composition of the raffinate oil was analyzed by ASTM D-6536 and GGBM-04-2005 standard methods for aromatic content and solvent content. The product composition is shown in Table 4.

[0081] Table 4

[0082] Non-aromatic mass fraction / % 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 aromatic extraction system disclosed in the present invention increases the water content of the extraction solvent in the aromatic extraction distillation tower, improves the selectivity of the extraction solvent, increases the content of non-aromatics in the raffinate oil, reduces the content of aromatics in the raffinate oil, and further improves the quality and yield of the aromatic products 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 water phase in the aromatic extraction distillation tower of the present invention improves the solvent selectivity, so that the aromatic content in the raffinate oil is lower, and there is no 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, the effect of removing the solvent from the raffinate oil is improved.

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

[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 the water inlet absolute pressure disclosed in the present invention, the removal rate of the liquid phase 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 in the above embodiments. Within the technical concept of the present disclosure, a variety of simple modifications can be made to the technical solution of the present disclosure, and these simple modifications all fall within the protection scope 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. In order to avoid unnecessary repetition, the present disclosure will not further describe various possible combinations.

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

Claims

1. A 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 extraction distillation tower comprises an aromatics feedstock inlet, an extraction solvent inlet, a side line inlet, a tower bottom liquid phase outlet and a tower top gas phase outlet; the venturi separator comprises a tower top gas phase inlet, a water wash water inlet, a wash liquid phase outlet and a washed 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 forms the raffinate oil product outlet of the system; the venturi separator comprises a vertical liquid phase collecting pipe and a venturi tube sleeved in the liquid phase collecting pipe, and the throat of the venturi tube is provided with a water wash water inlet; The top gas phase outlet of the aromatics extraction 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 extraction 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 wash water inlet of the venturi separator.

2. The system according to claim 1, wherein: The venturi separator comprises a venturi tube, a water injection pipe and a liquid phase collecting pipe; the venturi tube is vertically arranged in the liquid phase collecting pipe, and the post-washing gas phase outlet of the venturi separator is arranged at the top of the liquid phase collecting pipe; the washing water 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, a constant diameter section, a reduced diameter section and an expanded diameter section which are connected in sequence; the water injection pipe passes through the tube 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, 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 the top opening of the expanded diameter section of the venturi tube and the open tube; Optionally, the diameter of the open tube is the same as the diameter of the top opening of the expanded section; Optionally, the angle between the water injection pipe and the venturi tube is 10 to 90 degrees.

4. 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 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 the multiple vortex core tubes are arranged in parallel.

5. The system according to claim 1, wherein: The aromatic raw material 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 raw material inlet.

6. A method for extracting aromatics using the system according to any one of claims 1 to 5, characterized in that: The aromatics extraction method comprises the following steps: The raw material containing aromatic hydrocarbons enters into an aromatic hydrocarbon extraction distillation tower and contacts with an extraction solvent to extract aromatic hydrocarbons; The gas phase at the top 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.

7. The method according to claim 6, 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, preferably (0.2-0.5):

1.

8. The method according to claim 6, 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.

9. The method according to claim 6, wherein: The inlet gas velocity of the Venturi separator is 1m / s to 30m / s, the pressure loss is 0.2kPa to 5kPa, and the inlet absolute pressure of the washing water is 200kPa to 1500kPa.

10. The method according to claim 6, 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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