A system and method for extracting thionaphthene and naphthalene from a mixture of thionaphthene and naphthalene

Abstract

The present application provides a system and method for simultaneously extracting sulfur indene and naphthalene from a mixture of naphthalene and sulfur indene, based on the system of the present application, sulfur indene product and refined naphthalene product can be simultaneously separated. The system comprises: a removal unit for mixing the mixture of naphthalene and sulfur indene with a solvent and performing crystallization and solid-liquid separation to obtain a mixture of naphthalene and sulfur indene after removal of impurities and obtain a solvent containing impurities; a heating kettle for heating and melting the mixture of naphthalene and sulfur indene after removal of impurities and obtaining a melting liquid; azeotropic rectification tower for azeotropic rectification of the melting liquid with azeotropic agent, and obtaining sulfur indene material and mixture of naphthalene and azeotropic agent; a naphthalene refining unit for water washing and phase separation of the mixture of naphthalene and azeotropic agent, and obtaining a light phase component rich in naphthalene and obtaining a heavy phase component containing water and azeotropic agent.

Description

TECHNICAL FIELD

[0001] The present application relates to a separation technology of naphthalene and thionaphthene, and in particular to a system and method for extracting thionaphthene and naphthalene from a mixture of naphthalene and thionaphthene. BACKGROUND

[0002] Thionaphthene, also known as benzothiophene, has a molecular weight of 134.20, a melting point of 31.3°C, and a boiling point of 219.9°C. It is difficult to dissolve in water, but soluble in organic solvents such as ethanol, ether, acetone, benzene, etc. Thionaphthene is an important fine chemical raw material, widely used in the fields of medicine, pesticide, optical material and dye, mainly used for preparing fungicides, insecticides, herbicides, insect killing drugs, plant growth hormone raw materials, synthetic dye raw materials and other thionaphthene derivatives intermediates.

[0003] Naphthalene, with a molecular weight of 128.16, a melting point of 80.1°C, and a boiling point of 217.9°C, is insoluble in water, but soluble in benzene, ether, anhydrous ethanol and other organic substances. Naphthalene is widely used in the preparation of water reducing agent, phthalic anhydride, naphthalene quinone, naphthalene, dye diffuser, dye intermediate and other fine chemical products.

[0004] The thionaphthene resource in tar is mainly concentrated in the naphthalene fraction after tar distillation. The naphthalene residual oil after industrial naphthalene melt crystallization to obtain refined naphthalene contains 10-15% thionaphthene. Due to the difficulty of separation, this part of naphthalene residual oil is generally used as fuel oil, wasting valuable naphthalene and thionaphthene resources.

[0005] Due to the similar boiling points of thionaphthene and naphthalene, it is very difficult to separate and refine thionaphthene by ordinary rectification method.

[0006] CN101747317A discloses a method for enriching thionaphthene from a mixture containing thionaphthene and naphthalene, which uses dihydric alcohol as a solvent to enrich thionaphthene in dihydric alcohol, and recovers dihydric alcohol to obtain enriched thionaphthene fraction.

[0007] CN114315792A discloses a solvent crystallization coupled with extractive distillation method for enriching thionaphthene from a mixture containing thionaphthene and naphthalene, which selects triethylene glycol, tetraethylene glycol, MDEA and other solvents to extract thionaphthene from the mixture of thionaphthene and naphthalene, and then extractive distillation is carried out to obtain thionaphthene fraction.

[0008] CN108558591B discloses a naphthalene residual oil separation and recovery method, which removes light components through a light removal column, sends the light removal column bottom material to a naphthalene removal column, separates naphthalene and thionaphthene through the naphthalene removal column, obtains naphthalene components at the top of the naphthalene removal column, and sends the column bottom material to a benzothiophene column, and obtains thionaphthene product through static crystallizer crystallization. In this method, ordinary rectification through the naphthalene removal column is used for separation of naphthalene and thionaphthene, which has high energy consumption.

[0009] CN115504960A discloses a method for extracting sulfur indene from naphthalene residual oil, which takes naphthalene residual oil after industrial naphthalene melt crystallization for preparing refined naphthalene as raw material. First, a double solvent extraction method is used to realize preliminary separation of naphthalene and sulfur indene by using the different distribution coefficients of naphthalene and sulfur indene in solvent diethyl ether and ethanolamine, naphthalene is dissolved in diethyl ether, and sulfur indene is dissolved in ethanolamine. Then, the ethanolamine solution of sulfur indene is subjected to intermittent azeotropic rectification by using the azeotropic property of naphthalene and ethanolamine, so that ethanolamine and a small amount of naphthalene in the solution are first azeotropically distilled, and then the sulfur indene fraction is obtained. The sulfur indene fraction is washed with diethyl ether to obtain sulfur indene product. SUMMARY

[0010] The present application provides a system and a method for simultaneously extracting sulfur indene and naphthalene from a mixture of naphthalene and sulfur indene. The system based on the present application can simultaneously separate sulfur indene product and refined naphthalene product from the mixture of naphthalene and sulfur indene, and the required process flow is simple and easy to operate.

[0011] To achieve the purpose of the present application, the following technical solutions are provided:

[0012] The present application provides a system for extracting sulfur indene and naphthalene from a mixture of naphthalene and sulfur indene, which comprises:

[0013] A purification unit is used to mix the mixture of naphthalene and sulfur indene with a solvent, and to crystallize and solid-liquid separate, so as to obtain a purified mixture of naphthalene and sulfur indene, and a solvent containing impurities;

[0014] A heating kettle is used to heat and melt the purified mixture of naphthalene and sulfur indene, and to obtain a molten liquid;

[0015] An azeotropic rectification tower is used to azeotropically rectify the molten liquid with an azeotropic agent, and to obtain a sulfur indene material and a mixture of naphthalene and azeotropic agent;

[0016] A naphthalene refining unit is used to water wash and phase separate the mixture of naphthalene and azeotropic agent, and to obtain a light phase component rich in naphthalene, and a heavy phase component containing water and azeotropic agent;

[0017] Preferably, an azeotropic agent refining tower is further included, which is used to separate water and azeotropic agent in the heavy phase component containing water and azeotropic agent, and to obtain a water stream and an azeotropic agent stream, and is connected with the azeotropic rectification tower and the naphthalene refining unit respectively, so as to circulate at least part of the azeotropic agent stream to the azeotropic rectification tower, and to circulate the water stream to the naphthalene refining unit.

[0018] Preferably, the system further comprises a solvent impurity removal unit for removing impurities from the impurity-containing solvent to obtain a recovered solvent with impurities removed; and a recovery solvent outlet of the solvent impurity removal unit is connected to the impurity removal unit to recycle the recovered solvent to the impurity removal unit.

[0019] Preferably, the solvent impurity removal unit comprises a first mixer, a first phase separator and a solvent recovery column, the first mixer is used for water washing the impurity-containing solvent to obtain a first water washing mixture, the first phase separator is used for phase separation of the first water washing mixture to obtain a heavy phase component with impurities removed, and the solvent recovery column is used for separation of water and solvent in the heavy phase component with impurities removed to obtain recovered water and recovered solvent; a recovered solvent outlet of the solvent recovery column is connected to a solvent inlet of the impurity removal unit, and a recovered water outlet of the solvent recovery column is connected to a water inlet of the first mixer.

[0020] Preferably, a first heat exchanger is arranged between the solvent recovery column and the impurity removal unit to exchange heat between the recovered solvent output from the solvent recovery column and the impurity-containing solvent output from the impurity removal unit before the impurity-containing solvent enters the first mixer.

[0021] Further preferably, a first cooler is arranged between the first heat exchanger and the impurity removal unit to cool the recovered solvent output from the first heat exchanger before the recovered solvent enters the impurity removal unit.

[0022] In some embodiments, the impurity removal unit comprises a mixing device, a crystallizer and a filter;

[0023] The mixing device is used for mixing the mixture of naphthalene and sulfolene with the solvent to obtain a mixing solution.

[0024] The crystallizer is used for crystallization of the mixing solution to obtain a crystallization solution.

[0025] The filter is used for solid-liquid separation of the crystallization solution to obtain the impurity-removed mixture of naphthalene and sulfolene and to obtain the impurity-containing solvent.

[0026] In some embodiments, the naphthalene refining unit comprises a second mixer and a second phase separator, and preferably further comprises a dryer;

[0027] The second mixer is used for water washing of the mixture of naphthalene and azeotrope to obtain a second water washing mixture.

[0028] The second phase separator is used for phase separation of the second water washing mixture to obtain a light phase component rich in naphthalene and to obtain a heavy phase component containing water and azeotrope.

[0029] The dryer is used for drying the naphthalene-rich light phase component to obtain a refined naphthalene product.

[0030] Further, a water stream output pipeline is connected between the water stream outlet of the azeotrope refining column and the water inlet of the second mixer;

[0031] A sulfur indene material output pipeline is connected to the sulfur indene material outlet of the azeotrope rectifying column;

[0032] The water stream output pipeline and the sulfur indene material output pipeline are connected through a second heat exchanger for heat exchanging the water stream outputted by the water stream output pipeline with the sulfur indene material outputted by the sulfur indene material output pipeline;

[0033] Preferably, a water stream heater is further arranged on the water stream output pipeline downstream of the second heat exchanger;

[0034] Preferably, a second cooler is further arranged on the sulfur indene material output pipeline downstream of the second heat exchanger.

[0035] Preferably, the solvent and the azeotrope are the same, and preferably the solvent and the azeotrope are both ethylene glycol;

[0036] Preferably, the azeotrope refining column is further connected to the impurity removal unit so as to recycle at least part of the azeotrope stream to the impurity removal unit.

[0037] Preferably, the system further comprises a first circulating tank and a second circulating tank in communication with each other; a liquid inlet of the first circulating tank is in communication with a recovered solvent outlet of the solvent impurity removal unit, and a liquid outlet of the first circulating tank is in communication with a solvent inlet of the impurity removal unit; a liquid inlet of the second circulating tank is in communication with an azeotrope stream outlet of the azeotrope refining column, and a liquid outlet of the second circulating tank is in communication with an azeotrope inlet of the azeotrope rectifying column; further preferably, a third cooler is arranged between the second circulating tank and the first circulating tank.

[0038] The present application further provides a method for extracting sulfur indene and naphthalene from a mixture of naphthalene and sulfur indene by using the system described above, the method comprising the following steps:

[0039] 1) mixing the mixture of naphthalene and sulfur indene with a solvent in an impurity removal unit, and performing crystallization and solid-liquid separation on the obtained mixed liquid to obtain an impurity-removed mixture of naphthalene and sulfur indene and to obtain a solvent containing impurities;

[0040] 2) heating and melting the impurity-removed mixture of naphthalene and sulfur indene in a heating kettle to obtain a melted liquid;

[0041] 3) sending the melted liquid into a azeotropic rectification tower to perform azeotropic rectification with an azeotropic agent, to obtain a sulfur indene material and a mixture of naphthalene and azeotropic agent;

[0042] 4) sending the mixture of naphthalene and azeotropic agent into a naphthalene refining unit to perform water washing and phase separation, to obtain a light phase component rich in naphthalene and a heavy phase component containing water and azeotropic agent;

[0043] Preferably, the method further comprises step 5): sending the heavy phase component containing water and azeotropic agent obtained in step 4) into an azeotropic agent refining tower to perform treatment, to separate water and azeotropic agent in the heavy phase component, to obtain a water stream and an azeotropic agent stream; recycling the water stream to the naphthalene refining unit in step 4) as water washing water, and recycling at least part of the azeotropic agent stream to the azeotropic rectification tower in step 3) for azeotropic rectification.

[0044] Preferably, the method of the present application further comprises the following steps:

[0045] sending the solvent containing impurities obtained in step 1) into a solvent impurity removal unit to perform impurity removal, to obtain a recovered solvent free of impurities; and recycling the recovered solvent free of impurities to the impurity removal unit in step 1) as solvent required for performing the mixing;

[0046] Preferably, the solvent containing impurities obtained in step 1) is sent into a first mixer of the solvent impurity removal unit to perform water washing with water, to obtain a first water washing mixed liquid; and then the first water washing mixed liquid is sent into a first phase separator of the solvent impurity removal unit to perform phase separation, to obtain a heavy phase component free of impurities; and the heavy phase component free of impurities is sent into a solvent recovery tower of the solvent impurity removal unit to separate water and solvent in the heavy phase component, to obtain recovered water and recovered solvent; and the recovered water is recycled to the first mixer as water washing water, and the recovered solvent is recycled to the impurity removal unit as solvent required for performing the mixing.

[0047] Further preferably, after the recovered solvent output from the solvent recovery tower and the solvent containing impurities output from the impurity removal unit are exchanged heat in a first heat exchanger, the recovered solvent is recycled to the impurity removal unit after being cooled in a first cooler again, and the solvent containing impurities is sent into the first mixer after being exchanged heat in the first heat exchanger.

[0048] Further preferably, the mass ratio of water used for performing the water washing in the solvent impurity removal unit to the solvent containing impurities is 0.8-1.5:1; and the temperature for performing the phase separation in the solvent impurity removal unit is 80-85℃.

[0049] Preferably, in step 4), the mixture of naphthalene and the entrainer is sent into the second mixer of the naphthalene refining unit to be washed with water to obtain a second water-washed mixture; and then the second water-washed mixture is sent into the second phase separator of the naphthalene refining unit to be phase separated to obtain the light phase component rich in naphthalene and the heavy phase component containing water and the entrainer;

[0050] Preferably, the light phase component rich in naphthalene is dried in a dryer to obtain refined naphthalene product;

[0051] Preferably, the water stream output from the entrainer refining column in step 5) is heat exchanged with the sulfur indene material output from the entrainer rectifying column in step 3), and then is further heated in a water stream heater before being sent into the second mixer.

[0052] Preferably, in step 1), the solvent is ethylene glycol, and in step 3), the entrainer is ethylene glycol.

[0053] Preferably, in step 5), part of the entrainer stream is also recycled to the impurity removal unit in step 1) to be used as the solvent required for the mixing.

[0054] Preferably, in step 1), the mass ratio of the solvent to the mixture of naphthalene and sulfur indene is 1-4:1, preferably 1.5-3:1.

[0055] Preferably, in step 1), the crystallization conditions include: the cooling rate is 1-3 ℃ / min, the temperature is cooled to 15-35 ℃, preferably 20-30 ℃ for crystal growing, and the crystal growing time is 30-50 min, preferably 35-45 min.

[0056] Preferably, in step 2), the temperature for the heating and melting is 80-85 ℃.

[0057] Preferably, in step 3), the mass ratio of the entrainer to the melted liquid for the azeotropic rectification is 0.53-0.62:1, preferably 0.55-0.62:1, more preferably 0.55-0.60:1, and preferably, the azeotropic rectification conditions include: the overhead pressure of the azeotropic rectification column is 5-15 kPa, the overhead temperature is 110-120 ℃, and the reflux ratio is 5-10.

[0058] In some embodiments, in step 4), when the water washing is performed in the naphthalene refining unit, the mass ratio of the water to the mixture of naphthalene and the entrainer is 0.8-1.5:1; preferably, the temperature of the water used for the water washing in step 4) is 70-80 ℃; and preferably, the temperature for the phase separation in step 4) is 80-85 ℃.

[0059] In some embodiments, in step 1), the mixture of naphthalene and thionaphthene is industrial naphthalene, or is a naphthalene fraction separated from tar distillation, or is a naphthalene residue after melt crystallization of the industrial naphthalene or the naphthalene fraction.

[0060] The technical solution provided by the present application has the following beneficial effects:

[0061] (1) The system of the present application is used for simultaneous extraction of naphthalene and thionaphthene in the mixture of naphthalene and thionaphthene, which not only has a simple and easy process flow, but also can well separate thionaphthene and naphthalene with similar boiling points, and can easily obtain naphthalene product and thionaphthene product simultaneously.

[0062] (2) In some preferred solutions, water and the entrainer are separated from the heavy phase component obtained from the naphthalene refining unit through the entrainer refining tower, and the water is recycled to the naphthalene refining unit as water washing water, and at least part of the entrainer is recycled to the azeotropic distillation tower, which can greatly save the water consumption of the system and reduce the cost of the entrainer. In some preferred solutions, the solvent and the entrainer use the same reagent, and at least part of the entrainer recovered from the naphthalene refining unit is recycled to the impurity removal unit as a solvent, which is conducive to reducing the cost of the solvent. In some preferred solutions, the solvent containing impurities obtained from the impurity removal unit is also subjected to impurity removal in the solvent impurity removal unit, and the recovered solvent obtained after impurity removal is recycled to the impurity removal unit, which can further reduce the cost of the solvent and improve the utilization rate of the solvent.

[0063] (3) In some preferred solutions, the recovered solvent output from the solvent recovery tower in the solvent impurity removal unit is first heat exchanged with the solvent containing impurities output from the impurity removal unit, and then reused, which can make full use of the heat carried by the recovered solvent; in some preferred solutions, the thionaphthene material output from the azeotropic distillation tower is heat exchanged with the water stream output from the entrainer refining tower before being output as a subsequent product, which can make full use of the heat carried by the thionaphthene material. The system using the preferred solution can make integrated use of the energy in the system, thereby reducing energy consumption.

[0064] (4) The method for extracting thionaphthene and naphthalene from the mixture of naphthalene and thionaphthene based on the system of the present application first uses a solvent (preferably ethylene glycol) to mix and crystallize to remove impurities, and then performs azeotropic distillation with an entrainer (preferably ethylene glycol), to separate thionaphthene material and a mixture of naphthalene and entrainer, wherein the mixture of naphthalene and entrainer can obtain naphthalene product after water washing and phase separation; the method of the present application can separate thionaphthene product and naphthalene product from the mixture of naphthalene and thionaphthene with high yield and high purity.

[0065] (5) The method of the present application has the characteristics of simple process flow, required operating temperature, good product quality, and simple and easy process operation and control. BRIEF DESCRIPTION OF DRAWINGS

[0066] Figure 1 Shown is a schematic diagram of a system for separating thionaphthene and naphthalene from a mixture of naphthalene and thionaphthene in one embodiment.

[0067] Figure 2 Not drawn Figure 1 The system diagram is shown in the dashed box.

[0068] Description of some reference numerals:

[0069] Impurity removal unit 100, naphthalene refining unit 200, solvent impurity removal unit 300, mixing device 1, crystallizer 2, filter 3, heating kettle 4, first heat exchanger 5, first mixer 6, first phase separator 7, solvent recovery tower 8, first circulation tank 9, first cooler 10, azeotropic distillation tower 11, second heat exchanger 12, second cooler 13, second mixer 14, second phase separator 15, dryer 16, boiling agent refining tower 17, fourth cooler 18, water stream heater 19, second circulation tank 20, third cooler 21. DETAILED DESCRIPTION

[0070] In order to facilitate the understanding of the present invention, the present invention will be further described below in conjunction with examples. It should be understood that the following examples are only for a better understanding of the present invention and do not mean that the present invention is limited to the following examples.

[0071] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one skilled in the art to which this invention belongs. The term "and / or" as may be used herein includes any and all combinations of one or more of the associated listed items. The terms "first," "second," "third," etc., are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

[0072] Where specific experimental steps or conditions are not specified in the examples, the corresponding conventional experimental steps or conditions in the art can be used. Reagents or instruments used without specifying the manufacturer are all commercially available conventional products.

[0073] The present invention provides a system for extracting thionaphthene and naphthalene from a mixture of naphthalene and thionaphthene. Figure 1 、 2 ,in Figure 2 and Figure 1 Same, just without the label Figure 1 The system of the present invention mainly comprises: an impurity removal unit 100, a heating kettle 4, an azeotropic distillation column 11 and a naphthalene refining unit 200, and preferably also comprises an entrainer refining column 17.

[0074] The impurity removing unit 100 is used to mix the mixture of naphthalene and thionaphthene with solvent, and to crystallize and solid-liquid separate the mixed solution, so as to obtain the mixture of naphthalene and thionaphthene with impurities removed, and the solvent containing impurities.

[0075] The heating kettle 4 is used to melt the mixture of naphthalene and thionaphthene with impurities removed obtained in the impurity removing unit 100, so as to obtain a melting solution.

[0076] The azeotropic rectification tower 11 is used to azeotropically rectify the melting solution obtained in the heating kettle 4 with an azeotropic agent, so as to separate the naphthalene and thionaphthene, and obtain the thionaphthene material in the kettle and the mixture of naphthalene and azeotropic agent on the top.

[0077] The naphthalene refining unit 200 is used to water wash and phase separate the mixture of naphthalene and azeotropic agent obtained in the azeotropic rectification tower 11, so as to obtain the light phase component rich in naphthalene, and the heavy phase component containing water and azeotropic agent.

[0078] The azeotropic agent refining tower 17 is used to separate the water and azeotropic agent in the heavy phase component containing water and azeotropic agent obtained in the naphthalene refining unit 200, so as to obtain a water stream and an azeotropic agent stream. The azeotropic agent refining tower 17 is connected with the azeotropic rectification tower 11 and the naphthalene refining unit 200 respectively, and the connection includes direct or indirect connection, so that at least part of the azeotropic agent stream can be recycled to the azeotropic rectification tower 11 for azeotropic rectification, and the water stream can be recycled to the naphthalene refining unit 200 as water for water washing.

[0079] Through the system of the present application, the mixture of naphthalene and thionaphthene is mixed with solvent (for example, ethylene glycol), crystallized, and then solid-liquid separated, the mixture of naphthalene and thionaphthene with impurities removed obtained is melted and sent to the azeotropic rectification tower 11 and the azeotropic agent (for example, ethylene glycol) for azeotropic rectification, so that the naphthalene and thionaphthene are separated, the thionaphthene material obtained by separation is cooled to obtain the thionaphthene product, and the mixture of naphthalene and azeotropic agent obtained by separation is water washed and phase separated to obtain the component rich in naphthalene, which is dried to obtain the refined naphthalene product. Through the system, the naphthalene and thionaphthene can be simultaneously separated to obtain the products by a simple process flow. Further, the heavy phase component obtained by the naphthalene refining unit 200 is treated by the azeotropic agent refining tower 17, and the water stream that can be recycled to the naphthalene refining unit 200 and the azeotropic agent stream that can be recycled to the azeotropic rectification tower 11 are also obtained, so that the water consumption of the system is greatly saved, the utilization rate of the azeotropic agent is improved, and the processing cost is reduced.

[0080] Reference is made to Figures 1-2Preferably, the system of the present application further comprises a solvent impurity removal unit 300 for removing impurities from the solvent containing impurities obtained from the impurity removal unit 100, so as to obtain the impurity-removed recycled solvent. The recycled solvent outlet of the solvent impurity removal unit 300 is connected to the solvent inlet of the impurity removal unit 100, and the connection includes direct or indirect connection, so as to recycle the impurity-removed recycled solvent obtained from the solvent impurity removal unit 300 to the impurity removal unit 100 as the solvent required for mixing. With this preferred mode, the solvent utilization rate can be improved, and the amount of solvent and waste liquid can be reduced.

[0081] Preferably, the solvent impurity removal unit 300 specifically comprises a first mixer 6, a first phase separator 7, and a solvent recovery column 8. The first mixer 6 is used for water washing the solvent containing impurities output from the impurity removal unit 100, so as to obtain a first water washing mixed solution. The first phase separator 7 is used for separating the first water washing mixed solution obtained from the first mixer 6, so as to obtain a heavy phase component from which impurities are removed and a light phase component containing impurities, wherein the impurities in the light phase component are discharged to the outside of the system through an impurity discharge pipeline 109. The solvent recovery column 8 is used for separating water and solvent in the heavy phase component from which impurities are removed obtained from the first phase separator 7, so as to obtain recycled water and recycled solvent. The recycled solvent outlet of the solvent recovery column 8 is connected to the solvent inlet of the impurity removal unit 100, so as to recycle the recycled solvent to the impurity removal unit 100 for continuous use as the solvent. The recycled water outlet of the solvent recovery column 8 is connected to the water inlet of the first mixer 6, so as to recycle the water to the first mixer 6 for use as water washing water. The “connection” mentioned herein includes direct or indirect connection. With this preferred mode, the water and solvent that can be recycled to the system can be obtained simultaneously, and the water consumption and solvent consumption of the system can be reduced, thereby reducing the cost.

[0082] Preferably, a first heat exchanger 5 is arranged between the solvent recovery column 8 and the impurity removal unit 100, and is used for exchanging heat between the solvent containing impurities output from the impurity removal unit 100 and the recycled solvent output from the solvent recovery column 8 before the solvent containing impurities enters the first mixer 6. Specifically, the solvent recovery column 8 and the impurity removal unit 100 are connected through a recycled solvent pipeline for conveying the recycled solvent, the impurity removal unit 100 and the first mixer 6 are connected through a solvent containing impurities pipeline for conveying the solvent containing impurities, and the recycled solvent pipeline and the solvent containing impurities pipeline are connected through the first heat exchanger 5, so that the solvent containing impurities is preheated by exchanging heat with the recycled solvent output from the solvent recovery column 8 before entering the first mixer 6, and at the same time, the heat carried by the recycled solvent is fully utilized. Further preferably, a first cooler 10 is arranged between the first heat exchanger 5 and the impurity removal unit 100, and is used for cooling the recycled solvent output from the first heat exchanger 5 before entering the impurity removal unit 100.

[0083] Referring to Figure 1 , 2Preferably, the impurity removal unit 100 specifically comprises a mixing device 1, a crystallizer 2 and a filter 3. The mixing device 1 is used to mix the mixture of naphthalene and thionaphthene with the solvent, thereby obtaining a mixed solution. The crystallizer 2 is used to crystallize the mixed solution obtained in the mixing device 1, thereby obtaining a crystallized solution. The filter 3 is used to filter the crystallized solution obtained in the crystallizer 2 to realize solid-liquid separation, thereby obtaining a filter cake and a filtrate, wherein the filter cake is the impurity-removed mixture of naphthalene and thionaphthene, and the filtrate is the solvent containing impurities. Specifically, the filtrate outlet of the filter 3 is connected with the first mixer 6, and the filter cake outlet of the filter 3 is connected with the heating kettle 4.

[0084] Preferably, the naphthalene refining unit 200 specifically comprises a second mixer 14 and a second phase separator 15, and preferably further comprises a dryer 16. The second mixer 14 is used to water-wash the mixture of naphthalene and azeotrope agent output from the top of the azeotropic rectification tower 11, thereby obtaining a second water-washed mixed solution. The second phase separator 15 is used to separate the second water-washed mixed solution obtained in the second mixer 14, thereby obtaining a light phase component rich in naphthalene, and obtaining a heavy phase component containing water and azeotrope agent. The dryer 16 is used to dry the light phase component rich in naphthalene obtained in the second phase separator 15, thereby obtaining a refined naphthalene product, which is output through a refined naphthalene product output pipeline 124.

[0085] Preferably, the water stream outlet of the azeotrope agent refining tower 17 and the water inlet of the second mixer 14 are connected through a water stream output pipeline; and the thionaphthene material outlet of the azeotropic rectification tower 11 is connected with a thionaphthene material output pipeline. The water stream output pipeline and the thionaphthene material output pipeline are connected through the second heat exchanger 12, which is used to exchange heat between the water stream conveyed by the water stream output pipeline and the thionaphthene material conveyed by the thionaphthene material output pipeline, so that the heat of the thionaphthene material is fully utilized, and the water stream is preheated. Preferably, the water stream output pipeline is further provided with a water stream heater 19 located downstream of the second heat exchanger 12, which is used to further heat the water stream to reach the water temperature required by the second mixer 14; and preferably, the thionaphthene material output pipeline is further provided with a second cooler 13 located downstream of the second heat exchanger 12, so that the thionaphthene material is further cooled, and finally a thionaphthene product is obtained for output outside the system.

[0086] In the preferred embodiment, the aforementioned solvent and azeotrope agent are the same, and preferably both are ethylene glycol. Preferably, the azeotrope agent refining tower 17 is further connected with the impurity removal unit 100, which includes direct or indirect connection, so as to circulate at least part of the azeotrope agent stream to the impurity removal unit 100 for use as the required solvent in the impurity removal unit 100.

[0087] Specifically, in some embodiments, the system of the present application further comprises a first circulating tank 9 and a second circulating tank 20 which are in communication with each other. The liquid inlet of the first circulating tank 9 is in communication with the recovered solvent outlet of the solvent decontamination unit 300, specifically, for example, the recovered solvent outlet of the solvent recovery column 8. The liquid outlet of the first circulating tank 9 is in communication with the solvent inlet of the decontamination unit 100, specifically, for example, the solvent inlet of the mixing device 1. The liquid inlet of the second circulating tank 20 is in communication with the azeotrope stream outlet of the azeotrope refining column 17, and the liquid outlet of the second circulating tank 20 is in communication with the azeotrope inlet of the azeotrope distillation column 11; preferably, a third cooler 21 is provided between the second circulating tank 20 and the first circulating tank 9. In this specific manner, the recovered solvent obtained from the solvent decontamination unit 300 is pre-stored in the first circulating tank 9, and the azeotrope stream obtained from the azeotrope refining column 17 is pre-stored in the second circulating tank 20, and then reused in the decontamination unit 100 or in the azeotrope distillation column 11. The above communication is, for example, direct or indirect communication.

[0088] Specifically, the first circulating tank 9 is further connected with a solvent supplementing line 115, and when it is necessary to supplement the solvent, the required amount of solvent can be supplemented through the solvent supplementing line 115, so as to make up for the loss of the solvent during the operation of the system. When the solvent and the azeotrope are the same reagent, the supplementing of the solvent through the solvent supplementing line 115 can also achieve the supplementing of the azeotrope, so as to make up for the loss of the azeotrope during the operation of the system.

[0089] Specifically, the first phase separator 7 is further connected with a water supplementing line 116, and according to the need, water can be supplemented into the first phase separator 7, so as to make up for the loss of water during the operation of the system. The second phase separator 15 is further connected with a water supplementing line 132, and according to the need, water can be supplemented into the second phase separator 15, so as to make up for the loss of water during the operation of the system.

[0090] By using the above-mentioned system of the present application, not only can naphthalene and thionaphthene be simultaneously extracted from the mixture of naphthalene and thionaphthene based on a simple and easy-to-operate process, and thionaphthene product and refined naphthalene product can be easily obtained simultaneously; but also, by the preferred mode, the solvent, the azeotrope and water can be fully recycled in the system, and the heat in the system can be integratedly utilized, which is conducive to greatly reducing the processing cost and reducing the energy consumption.

[0091] The second aspect of the present application provides a method for extracting thionaphthene and naphthalene from a mixture of naphthalene and thionaphthene by using the above-mentioned system, and the method comprises the following steps:

[0092] 1) mixing the mixture of naphthalene and thionaphthene with the solvent in the decontamination unit 100, and performing crystallization and solid-liquid separation on the obtained mixed liquid, to obtain a decontaminated mixture of naphthalene and thionaphthene and a solvent containing impurities; wherein the impurities are, for example, dimethyl phenol and the like;

[0093] 2) The mixture of impurities-removed naphthalene and thionaphthene obtained in step 1) is heated and melted in a heating kettle 4 to obtain a melted liquid;

[0094] 3) The melted liquid obtained in step 2) is sent into the azeotropic rectification tower 11 to perform azeotropic rectification with an azeotropic agent to obtain a thionaphthene material and a mixture of naphthalene and the azeotropic agent; the thionaphthene material can obtain a thionaphthene product after cooling;

[0095] 4) The mixture of naphthalene and the azeotropic agent is sent into the naphthalene refining unit 200 to perform water washing and phase separation to obtain a light phase component rich in naphthalene and a heavy phase component containing water and the azeotropic agent; the light phase component rich in naphthalene can obtain a refined naphthalene product after drying.

[0096] Through the above method, the thionaphthene product and the refined naphthalene product can be simultaneously separated from the mixture of naphthalene and thionaphthene in a simple process flow.

[0097] Preferably, the method of the present application further comprises step 5): the heavy phase component containing water and the azeotropic agent obtained in step 4) is sent into the azeotropic agent refining tower 17 to be treated, specifically, to be separated by rectification, the water and the azeotropic agent in the heavy phase component are separated by rectification, a water stream is obtained at the top of the tower, and an azeotropic agent stream is obtained at the kettle of the tower; the water stream is recycled to the naphthalene refining unit 200 of step 4) as water washing water, and at least part of the azeotropic agent stream is recycled to the azeotropic rectification tower 11 of step 3) for azeotropic rectification. In the preferred manner, the azeotropic agent and the water can be recycled, the water consumption of the process is saved, and the cost of the azeotropic agent is reduced.

[0098] In a preferred embodiment, the method of the present application further comprises the following steps: the solvent containing impurities obtained in step 1) is sent into the solvent impurity removal unit 300 to remove impurities to obtain an impurity-removed recycled solvent; and the impurity-removed recycled solvent is recycled to the impurity removal unit 100 of step 1) to be used as a solvent required for mixing. In the preferred manner, the solvent can be recycled, and the cost of the solvent is reduced.

[0099] In some embodiments, preferably, the impurity-containing solvent obtained in step 1) is sent to the first mixer 6 of the solvent impurity removal unit 300 for water washing with water to obtain a first water washing mixture; then the first water washing mixture is sent to the first phase separator 7 of the solvent impurity removal unit 300 for phase separation to obtain a heavy phase component from which impurities are removed, and the impurities are discharged into a light phase component. The heavy phase component from which impurities are removed is sent to the solvent recovery column 8 of the solvent impurity removal unit for separation, for example, rectification separation, to separate water and solvent in the heavy phase component to obtain recovered water and recovered solvent; the recovered water is recycled to the first mixer 6 as water washing water, and the recovered solvent is recycled to the impurity removal unit 100 as solvent required for mixing. By using this preferred mode, not only the solvent but also the water can be recovered and reused in the process, which can reduce water consumption and reduce the cost of the solvent.

[0100] Further preferably, after the recovered solvent output from the solvent recovery column 8 and the impurity-containing solvent output from the impurity removal unit 100 are heat exchanged in the first heat exchanger 5, the recovered solvent is further cooled in the first cooler and then recycled to the impurity removal unit 100; and after the impurity-containing solvent is preheated in the first heat exchanger 5, it is then sent to the first mixer 6 for treatment. By using this preferred mode, the heat carried by the recovered solvent can be fully utilized, and the energy required for heating the impurity-containing solvent can be reduced, which is conducive to reducing energy consumption.

[0101] In some preferred embodiments, the mass ratio of water used for water washing in the solvent impurity removal unit to the impurity-containing solvent is 0.8-1.5:1; and the temperature for phase separation in the solvent impurity removal unit is 80-85°C; and by using the preferred treatment conditions, the impurities can be more thoroughly removed, and the quality of the recovered water and the recovered solvent can be improved.

[0102] In some embodiments, preferably, in step 4), the mixture of naphthalene and the entrainer is sent to the second mixer 14 of the naphthalene refining unit 200 for water washing with water to obtain a second water washing mixture; then the second water washing mixture is sent to the second phase separator 15 of the naphthalene refining unit 200 for phase separation to obtain a light phase component rich in naphthalene and a heavy phase component containing water and the entrainer. Specifically, after the light phase component rich in naphthalene is dried in the dryer 16 to remove trace amount of water, a refined naphthalene product can be obtained.

[0103] Preferably, the water stream output from the entrainer refining column 17 in step 5) and the sulfur indene material output from the entrainer rectification column 11 in step 3) are heat exchanged in the second heat exchanger 12, and then the water stream is further heated in the water stream heater 19 before being sent to the second mixer 14. By using this preferred mode, the heat carried by the sulfur indene material can be fully utilized, and the heat energy required for heating the water stream can be reduced, which is conducive to reducing energy consumption.

[0104] In some preferred embodiments, the solvent used in step 1) is ethylene glycol, and the azeotrope agent used in step 3) is also ethylene glycol; the inventors have found that, by using ethylene glycol as both the solvent and the azeotrope agent in the process of the present application, not only can impurities be removed, but also the lowest azeotrope can be formed between naphthalene and thionaphthene in the azeotrope distillation, so that naphthalene and thionaphthene can be separated more completely, and high-quality refined naphthalene and thionaphthene products can be obtained simultaneously. Moreover, the reagents used in the present application are relatively simple, and the use of multiple organic solvents is not involved, so that the process is more simple and easy to implement, the recovery of the solvent is more convenient, and the reuse is more flexible. More preferably, part of the azeotrope agent stream in step 5) is recycled to the impurity removal unit 100 in step 1) to be used as the solvent required for mixing.

[0105] In some preferred embodiments, the mass ratio of the solvent to the mixture of naphthalene and thionaphthene in step 1) is 1-4:1, preferably 1.5-3:1; by using the preferred mass ratio, the purity and yield of the naphthalene and thionaphthene products can be further improved. The conditions for crystallization in step 1) are preferably as follows: the cooling rate is 1-3℃ / min, the temperature is lowered to 15-35℃, preferably 20-30℃ for aging, and the aging time is 30-50min, preferably 35-45min; by using the preferred crystallization conditions, the thionaphthene and refined naphthalene products with higher purity and yield can be obtained.

[0106] In some preferred embodiments, the temperature for heating and melting in step 2) is 80-85℃.

[0107] In some preferred embodiments, the mass ratio of the azeotrope agent to the melted liquid for azeotrope distillation in step 3) is 0.53-0.62:1, preferably 0.55-0.62:1, more preferably 0.55-0.60:1; by using the preferred mass ratio, the thionaphthene and refined naphthalene products with higher purity and yield can be obtained. Preferably, the conditions for azeotrope distillation include: the pressure at the top of the azeotrope distillation column 11 is 5-15kPa, the temperature at the top is 110-120℃, and the reflux ratio is 5-10;

[0108] In some preferred embodiments, the mass ratio of the water to the mixture of naphthalene and azeotrope agent used in the water washing in the naphthalene refining unit 200 in step 4) is 0.8-1.5:1; preferably, the temperature of the water used for water washing in step 4) is 70-80℃; preferably, the temperature for phase separation in step 4) is 80-85℃.

[0109] By using the method of the present application in combination with the preferred process conditions, the thionaphthene and refined naphthalene products with higher purity and yield can be obtained.

[0110] In the present application, the mixture of naphthalene and thionaphthalene can be industrial naphthalene, or a naphthalene fraction separated from tar distillation, or a naphthalene residue after melt crystallization of industrial naphthalene or the naphthalene fraction.

[0111] In some embodiments, at the beginning of the operation of the process system, the required amounts of solvent and azeotrope can be added into the first circulation tank 9 and the second circulation tank 20 respectively, and the required amount of water can be added into the first phase separator 7 and the second phase separator 15 respectively, according to the amounts of solvent and azeotrope, and the amount of water required for water washing, so as to provide the solvent, azeotrope and water required for the start of the process.

[0112] The system and method of the present application are exemplarily described below by way of examples:

[0113] Example 1

[0114] The process system used in the present example is shown in Figure 1 For the system and method not particularly described, reference can be made to the foregoing description, and no further detailed description is given.

[0115] The mixture of naphthalene and thionaphthalene used in the present example is a crystallization residue after extraction of refined naphthalene from a naphthalene fraction obtained from a tar processing device, which contains thionaphthalene 12.48wt%, naphthalene 83.52wt%, and impurities such as dimethyl phenol 4wt%, and has a flow rate of 1062.9kg / h.

[0116] The main process is as follows:

[0117] The crystallization residue raw material 101 at 80℃ is mixed with the circulating solvent 114 (ethylene glycol) at 40℃ from the first circulation tank 9 in the mixing device 1, and the mass ratio of the solvent to the raw material is 2:1, to obtain a mixed liquid at 73℃, which is then introduced into the crystallizer 2 for cooling crystallization, and the cooling rate is 2℃ / min, and the temperature is lowered to the crystal growing temperature of 25℃, and the crystal growing time is 40min.

[0118] The crystallized liquid 103 output from the crystallizer 2 is introduced into the filter 3 for solid-liquid separation, and the impurities such as dimethyl phenol are introduced into the filtrate, and the filtrate 106 output from the filter 3 is introduced into the solvent impurity removal unit 300 for impurity removal treatment, and the main components in the filter cake are naphthalene, thionaphthalene and entrained solvent, and the filter cake 104 output from the filter 3 is sent to the heating kettle.

[0119] Specifically, the filtrate 106 at 25°C is first heat-exchanged with the column bottom material 112 (i.e. recovered solvent) of the solvent recovery column 8 in the first heat exchanger 5 to recover heat, and the heat-exchanged filtrate 107 at 111°C is then mixed with the recovered water 111 from the solvent recovery column 8 in the first mixer 6 at a mass ratio of 1:1, and water washing is performed in the first mixer 6 to obtain a mixture at 83°C, which is then separated into light and heavy phases in the first phase separator 7 at a temperature of 82°C. The light phase component obtained in the first phase separator 7 is an organic phase containing impurities, a small amount of naphthalene and sulfur indene, etc., which is discharged from the system through the pipeline 109, and the heavy phase component is a mixture of water and solvent (i.e. the heavy phase component after removal of impurities), which is sent to the middle part of the solvent recovery column 8 for rectification and separation. During the operation of the process, water is supplemented to the first phase separator according to the liquid level of the first phase separator 7 and the solvent concentration in the heavy phase component 110. Due to the phase separation operation, a small amount of water will dissolve in the organic phase (light phase enriched with impurities) during the operation, resulting in water loss during the operation. In this embodiment, the solvent concentration in the heavy phase component 110 is 50% during the initial operation. When the solvent concentration in the heavy phase component 110 increases to 55% due to the water loss during the operation, a certain amount of water is added to reduce the solvent concentration to the initial solvent concentration of 50%. At the same time, the continuous water supplementing flow rate is 1.65 kg / h, so as to compensate for the water loss during the operation of the system.

[0120] The heavy phase component 110 output from the first phase separator 7 is sent to the middle part of the solvent recovery column 8 for rectification and separation. The overhead pressure of the solvent recovery column 8 is controlled at 22 kPa, the overhead temperature is controlled at 62°C, and the reflux ratio is controlled at 0.8. The recovered water 111 collected from the overhead of the solvent recovery column 8 is sent to the first mixer 6 for recycling. The recovered solvent 112 collected from the column bottom of the solvent recovery column 8 at 155°C is first sent to the first heat exchanger 5 to recover heat by heating the filtrate. After being cooled by heat exchange, the recovered solvent is further cooled to 40°C in the first cooler, and then the cooled recovered solvent 113 is sent to the first circulating tank 9. According to the liquid level of the first circulating tank 9, solvent is supplemented through the solvent supplementing pipeline 115. When the solvent level decreases to 60%, solvent is added through the solvent supplementing pipeline 115 to make the solvent level reach 100%. The continuous solvent supplementing amount is 3.45 kg / h.

[0121] The filter cake 104 outputted from the filter 3 is heated and melted in the heating kettle 4 at 82°C, and the melted liquid 105 is inputted into the middle and upper part of the azeotropic rectification tower 11. The pressure at the top of the azeotropic rectification tower 11 is controlled at 10 kPa, the temperature at the top is controlled at 114°C, the reflux ratio is 6, and ethylene glycol is selected as the azeotropic agent. The mass ratio of the ethylene glycol and the melted liquid is controlled at 0.56:1. Naphthalene and ethylene glycol can form the lowest azeotrope. Through the azeotropic rectification separation process, the mixture of naphthalene and azeotropic agent is collected from the top of the tower, and the sulfur indene material is collected from the bottom of the tower. The tower bottom material 119 (i.e. the sulfur indene material) at 156°C is first exchanged heat with the water stream 126 collected from the top of the azeotropic agent refining tower 17 in the second heat exchanger 12 to recover the heat carried by the sulfur indene material, and the sulfur indene material 120 cooled to 60°C is further cooled in the second cooler 13 to 40°C to obtain the refined sulfur indene product 121;

[0122] The mixture of naphthalene and azeotropic agent 118 collected from the top of the azeotropic rectification tower 11 is inputted into the second mixer 14. The water stream 129 heated to 68°C in the second heat exchanger 12 is further heated by the water stream heater 19 to obtain the water stream 130 at 75°C, which is continuously inputted into the second mixer 14 to mix with the mixture of naphthalene and azeotropic agent 118. The mass ratio of water to the mixture of naphthalene and azeotropic agent in the second mixer 14 is 1:1. After water washing, the second water-washed mixture 122 is inputted into the second phase separator 15 to separate phases. The temperature of the phase separator is controlled at 82°C, and the pressure is controlled at 101.325 kPa. During the operation of the process, the concentration of the azeotropic agent in the heavy phase component 125 decreases because the loss of the product carrying the solvent is greater than the loss of water. The azeotropic agent can be supplemented by the aforementioned solvent supplementing pipeline 115 to the first circulating tank 9, and the loss of water during the operation can be supplemented by the water supplementing pipeline 132 to adjust the concentration of the azeotropic agent in the heavy phase component 125 when the initial concentration (47% in this embodiment) decreases (for example, to 40%) to restore the initial concentration of the azeotropic agent, and at the same time, the liquid level of the heavy phase in the second phase separator 15 is restored to the initial level. The continuous supplementing flow of water is 0.61 kg / h, and the amount of the azeotropic agent to be supplemented is implemented by supplementing the solvent to the first circulating tank 9 through the aforementioned solvent supplementing pipeline 115.

[0123] The light phase component separated in the second phase separator 15 is the naphthalene-rich material, which is inputted into the dryer 16. The pressure of the dryer 16 is controlled at 40 kPa, and the temperature is controlled at 95°C. After heating to remove trace amount of water, the refined naphthalene product is outputted from the pipeline 124;

[0124] The heavy phase component 125 in the second phase separator 15 enters the entrainer refining column 17, the overhead pressure of the entrainer refining column 17 is controlled at 22 kPa, the overhead temperature is 62°C, the reflux ratio is 0.3, and after rectification and separation, a water stream is taken from the top of the column, an entrainer stream is taken from the bottom of the column, the overhead water stream 126 is recycled, and the entrainer stream 127 from the bottom of the column enters the second cooler 18 and is cooled to 110°C, and then enters the second circulating tank 20, part of the solvent in the second circulating tank 20 enters the middle and upper part of the azeotropic rectification column 11 as the circulating entrainer 129, and part of the solvent enters the third cooler 21 as the recovered solvent 130, and the recovered solvent 131 at 40°C enters the first circulating tank 9.

[0125] In this example, the purity of the thionaphthene product is 99.03%, the purity of the refined naphthalene product is 99.62%, the thionaphthene yield is 96.0%, and the naphthalene yield is 95.9%.

[0126] In this example, the main material flow rate and main component content are shown in Table 1, and the parameters of each column are shown in Table 2.

[0127] Table 1 Main stream flow rate and composition of Example 1

[0128]

[0129] Table 2 Main equipment parameters of Example 1

[0130]

[0131]

[0132] Example 2

[0133] Refer to Example 1, except that in step 1), the mass ratio of ethylene glycol to crystallization residual oil is 1:1.

[0134] Experimental results: the purity of the obtained thionaphthene product is 94.0%, and the yield is 95.6%; the purity of the obtained refined naphthalene product is 97.9%, and the yield is 95.3%.

[0135] Example 3

[0136] Refer to Example 1, except that in step 1), the mass ratio of ethylene glycol to crystallization residual oil is 4:1.

[0137] Experimental results: the purity of the obtained thionaphthene product is 98.8%, and the yield is 93.9%; the purity of the obtained refined naphthalene product is 98.9%, and the yield is 92.0%.

[0138] Example 4

[0139] The procedure of Example 1 was followed except that in Step 1), the temperature of the crystallization was 15°C.

[0140] The experimental results were as follows: the purity of the obtained thioindigo product was 98.3%, and the yield was 96.1%; the purity of the obtained purified naphthalene product was 99.1%, and the yield was 96.0%.

[0141] Example 5

[0142] The procedure of Example 1 was followed except that in Step 1), the temperature of the crystallization was 35°C.

[0143] The experimental results were as follows: the purity of the obtained thioindigo product was 98.4%, and the yield was 94.2%; the purity of the obtained purified naphthalene product was 99.0%, and the yield was 91.5%.

[0144] Example 6

[0145] The procedure of Example 1 was followed except that in Step 1), the crystallization time was 30 min.

[0146] The experimental results were as follows: the purity of the obtained thioindigo product was 98.8%, and the yield was 93.1%; the purity of the obtained purified naphthalene product was 99.3%, and the yield was 91.4%.

[0147] Example 7

[0148] The procedure of Example 1 was followed except that in Step 1), the crystallization time was 50 min.

[0149] The experimental results were as follows: the purity of the obtained thioindigo product was 98.6%, and the yield was 96.2%; the purity of the obtained purified naphthalene product was 99.0%, and the yield was 96.1%.

[0150] Example 8

[0151] The procedure of Example 1 was followed except that in Step 2), the mass ratio of the amount of the azeotrope agent ethylene glycol to the melting solution was 0.53:1.

[0152] The experimental results were as follows: the purity of the obtained thioindigo product was 82.8%, and the yield was 95.7%; the purity of the obtained purified naphthalene product was 99.2%, and the yield was 87.1%.

[0153] Example 9

[0154] The procedure of Example 1 was followed except that in Step 3), the mass ratio of the amount of the azeotrope agent ethylene glycol to the melting solution was 0.62:1.

[0155] The experimental results were as follows: the purity of the obtained thioindigo product was 98.9%, and the yield was 95.8%; the purity of the obtained purified naphthalene product was 99.0%, and the yield was 95.5%.

[0156] It is readily understood that the above-described embodiments are only illustrative of the application and not intended to limit the scope of the application. Other variations and modifications can be made to the embodiments described and illustrated herein, without departing from the spirit of the application, the scope of which is defined by the appended claims.

Claims

1. A system for extracting thionaphthene and naphthalene from a mixture of naphthalene and thionaphthene, characterized in that: The system comprises: an impurity removal unit for mixing the mixture of naphthalene and thionaphthene with a solvent and performing crystallization and solid-liquid separation to obtain a mixture of naphthalene and thionaphthene from which impurities are removed and a solvent containing impurities; A heating kettle, used for heating and melting the impurity-removed mixture of naphthalene and thionaphthene to obtain a melt; an azeotropic distillation tower for performing azeotropic distillation on the melt and the entrainer to obtain a thionaphthene material and a mixture of naphthalene and the entrainer; The naphthalene refining unit is used for washing and phase-separating the mixture of naphthalene and the entrainer to obtain a light phase component rich in naphthalene and a heavy phase component containing water and the entrainer.

2. The system according to claim 1, wherein: The system also includes an entrainer refining tower, which is used to separate the water and the entrainer in the heavy phase component containing water and the entrainer and obtain a water stream and an entrainer stream. The entrainer refining tower is connected to the azeotropic distillation tower and the naphthalene refining unit, respectively, so that at least a portion of the entrainer stream can be circulated to the azeotropic distillation tower, and the water stream can be circulated to the naphthalene refining unit.

3. The system according to claim 1, wherein: The system further comprises a solvent removal unit for removing impurities from the solvent containing impurities to obtain a recovered solvent with impurities removed; a recovered solvent outlet of the solvent removal unit is connected to the impurity removal unit to circulate the recovered solvent to the impurity removal unit.

4. The system according to claim 3, characterized in that The solvent removal unit includes a first mixer, a first phase separator and a solvent recovery tower. The first mixer is used to wash the solvent containing impurities with water to obtain a first water-washed mixed liquid. The first phase separator is used to phase-separate the first water-washed mixed liquid and obtain a heavy phase component from which impurities have been removed. The solvent recovery tower is used to separate the water and solvent in the heavy phase component from which impurities have been removed and obtain recovered water and recovered solvent. The recovered solvent outlet of the solvent recovery tower is connected to the solvent inlet of the impurity removal unit, and the recovered water outlet of the solvent recovery tower is connected to the water inlet of the first mixer.

5. The system according to claim 4, characterized in that A first heat exchanger is provided between the solvent recovery tower and the impurity removal unit, for exchanging heat between the impurity-containing solvent output from the impurity removal unit and the recovered solvent output from the solvent recovery tower before entering the first mixer.

6. The system according to claim 5, characterized in that A first cooler is provided between the first heat exchanger and the impurity removal unit, for cooling the recovered solvent output from the first heat exchanger before entering the impurity removal unit.

7. The system according to claim 1, wherein: The impurity removal unit includes a mixing device, a crystallizer and a filter; The mixing device is used to mix the mixture of naphthalene and thionaphthene with the solvent to obtain a mixed liquid; The crystallizer is used to crystallize the mixed solution and obtain a crystal liquid; The filter is used to perform solid-liquid separation on the crystallization liquid and obtain the impurity-free mixture of naphthalene and thionaphthene and the impurity-containing solvent.

8. The system according to any one of claims 1 to 7, characterized in that: The naphthalene refining unit includes a second mixer and a second phase separator; The second mixer is used to wash the mixture of naphthalene and the entrainer with water to obtain a second washing mixed liquid; The second phase separator is used to separate the second water-wash mixed liquid into phases and obtain the naphthalene-rich light phase component and the heavy phase component containing water and the entrainer.

9. The system according to claim 8, characterized in that The naphthalene refining unit also includes a dryer; The dryer is used for drying the naphthalene-rich light phase component to obtain a refined naphthalene product.

10. The system according to claim 8, wherein: A water stream output pipeline is connected between the water stream outlet of the entrainer refining tower and the water inlet of the second mixer; The thionaphthene material outlet of the azeotropic distillation tower is connected to a thionaphthene material output pipeline; The water flow output pipeline and the thionaphthene material output pipeline are connected through a second heat exchanger for exchanging heat between the water flow transported by the water flow output pipeline and the thionaphthene material transported by the thionaphthene material output pipeline.

11. The system according to claim 10, wherein: The water stream output pipeline is further provided with a water stream heater located downstream of the second heat exchanger; The thionaphthene material output pipeline is further provided with a second cooler located downstream of the second heat exchanger.

12. The system according to any one of claims 2 to 7, characterized in that: The solvent and the entrainer are the same.

13. The system according to claim 12, wherein: The solvent and the azeotropic agent are both ethylene glycol.

14. The system according to claim 12, wherein: The entrainer refining tower is also connected to the impurity removal unit so as to be able to recycle at least a portion of the entrainer stream to the impurity removal unit.

15. The system according to claim 12, wherein: The system also includes a first circulation tank and a second circulation tank that are interconnected; the liquid inlet of the first circulation tank is connected to the recovered solvent outlet of the solvent removal unit, and the liquid outlet of the first circulation tank is connected to the solvent inlet of the removal unit; the liquid inlet of the second circulation tank is connected to the entrainer stream outlet of the entrainer refining tower, and the liquid outlet of the second circulation tank is connected to the entrainer inlet of the azeotropic distillation tower.

16. The system according to claim 15, wherein: A third cooler is provided between the second circulation tank and the first circulation tank.

17. A method for extracting thionaphthene and naphthalene from a mixture of naphthalene and thionaphthene using the system according to any one of claims 1 to 16, characterized in that: The method comprises the following steps: 1) the mixture of described naphthalene and thionaphthene is mixed with a solvent in a removal of impurities unit, and the gained mixed solution is carried out crystallization and solid-liquid separation, to obtain the mixture of naphthalene and thionaphthene removed from impurities and to obtain a solvent containing impurities; 2) heating and melting the impurity-removed mixture of naphthalene and thionaphthene in a heating kettle to obtain a melt; 3) sending the melt into an azeotropic distillation tower and carrying out azeotropic distillation with an entrainer to obtain a mixture of thionaphthene material and naphthalene and the entrainer; 4) the mixture of described naphthalene and entrainer is sent into and washed and phase-splitting in naphthalene refining unit, obtain the light phase component rich in naphthalene and obtain the heavy phase component that comprises water and entrainer.

18. The method according to claim 17, characterized in that The process further comprises step 5): feeding the heavy phase component containing water and entrainer obtained in step 4) into an entrainer refining tower for treatment, separating the water and the entrainer in the heavy phase component to obtain a water stream and an entrainer stream; The water stream is circulated to the naphthalene purification unit in step 4) as washing water, and at least a portion of the entrainer stream is circulated to the azeotropic distillation tower in step 3) for azeotropic distillation.

19. The method according to claim 17, wherein The following steps are also included: The impurity-containing solvent obtained in step 1) is sent to a solvent removal unit to remove impurities to obtain a cleaned recovered solvent; the cleaned recovered solvent is recycled to the cleaned unit in step 1) and used as the solvent required for mixing.

20. The method according to claim 19, characterized in that The impurity-containing solvent obtained in step 1) is fed into the first mixer of the solvent removal unit and washed with water to obtain a first water-washed mixed liquid; the first water-washed mixed liquid is then fed into the first phase separator of the solvent removal unit for phase separation to obtain a heavy phase component from which impurities have been removed; the heavy phase component from which impurities have been removed is fed into the solvent recovery tower of the solvent removal unit to separate the water and solvent in the heavy phase component to obtain recovered water and recovered solvent; the recovered water is circulated to the first mixer as washing water, and the recovered solvent is circulated to the removal unit as the solvent required for mixing.

21. The method according to claim 20, characterized in that After the recovered solvent output from the solvent recovery tower and the solvent containing impurities output from the impurity removal unit undergo heat exchange in the first heat exchanger, the recovered solvent is further cooled in the first cooler and then recycled to the impurity removal unit. The solvent containing impurities is sent to the first mixer after heat exchange in the first heat exchanger.

22. The method according to claim 20, characterized in that The mass ratio of water used for the water washing in the solvent decontamination unit to the solvent containing impurities is 0.8-1.5:1; the temperature for the phase separation in the solvent decontamination unit is 80-85°C.

23. The method according to claim 17, wherein Step 4) in, the mixture of described naphthalene and entrainer is sent in the second mixing tank of described naphthalene refining unit and washed with water to obtain the second washing mixed liquor; Then the second washing mixed liquor is sent in the second phase splitter of described naphthalene refining unit and carries out phase-splitting to obtain the described light phase component rich in naphthalene and obtain the described heavy phase component comprising water and entrainer.

24. The method according to claim 23, wherein The naphthalene-rich light phase component is dried in a dryer to obtain a refined naphthalene product.

25. The method according to claim 23, characterized in that The water stream output from the entrainer refining tower in step 5) is heat exchanged with the thionaphthene material output from the azeotropic distillation tower in step 3), and then further heated in a water stream heater before being fed into the second mixer.

26. The method according to claim 17, wherein In step 1), the solvent is ethylene glycol; in step 3), the entrainer is ethylene glycol.

27. The method according to claim 26, characterized in that In step 5), part of the azeotropic agent stream is recycled to the impurity removal unit in step 1) to be used as the solvent required for mixing.

28. The method according to any one of claims 17 to 27, characterized in that In step 1), the mass ratio of the solvent to the mixture of naphthalene and thianaphthene is 1 to 4:1; And / or, in step 1), the crystallization conditions include: cooling at a rate of 1 to 3°C / min, cooling to 15-35°C for crystal growth, and a crystal growth time of 30-50 min; And / or, in step 2), the heating and melting temperature is 80-85°C; And / or, in step 3), the mass ratio of the entrainer used for the azeotropic distillation to the melt is 0.53-0.62:1; And / or, in step 4), when the water washing is performed in the naphthalene refining unit, the mass ratio of the water used to the mixture of the naphthalene and the entrainer is 0.8 to 1.5:1; And / or, in step 1), the mixture of naphthalene and thionaphthene is industrial naphthalene, or a naphthalene fraction obtained after tar distillation, or naphthalene residual oil obtained after melt crystallization of the industrial naphthalene or the naphthalene fraction.

29. The method according to claim 28, characterized in that In step 1), the mass ratio of the solvent to the mixture of naphthalene and thionaphthene is 1.5 to 3:1; And / or, in step 1), the crystallization conditions include: cooling to 20-30° C. for crystal growth, and the crystal growth time is 35-45 minutes; And / or, in step 3), the mass ratio of the entrainer used for the azeotropic distillation to the melt is 0.55-0.62:1; And / or, the temperature of the water used for the water washing in step 4) is 70-80°C; the temperature of the phase separation in step 4) is 80-85°C.

30. The method according to claim 28, wherein In step 3), the mass ratio of the entrainer used for the azeotropic distillation to the melt is 0.55-0.60:

1.

31. The method according to claim 28, wherein The conditions of the azeotropic distillation include: the top pressure of the azeotropic distillation tower is 5-15 kPa, the top temperature is 110-120° C., and the reflux ratio is 5-10.

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