System and method for extracting indane and naphthalene from mixture of naphthalene and indane

Abstract

The invention provides a system and a method for synchronously extracting indane and naphthalene from a mixture of naphthalene and indane, and based on the system provided by the invention, an indane product and a refined naphthalene product can be synchronously separated. The system comprises an impurity removal unit used for mixing the mixture of naphthalene and indane with a solvent and carrying out crystallization and solid-liquid separation so as to obtain an impurity-removed mixture of naphthalene and indane and obtain an impurity-containing solvent; the heating kettle is used for heating and melting the impurity-removed mixture of the naphthalene and the indane to obtain molten liquid; the azeotropic rectification tower is used for carrying out azeotropic rectification on the molten liquid and an entrainer to obtain a thioindene material and a mixed material of naphthalene and the entrainer; and the naphthalene refining unit is used for carrying out water washing and phase separation on the mixed material of the naphthalene and the entrainer to obtain a light-phase component rich in naphthalene and a heavy-phase component containing water and the entrainer.

Description

Technical Field

[0001] The invention relates to a separation technology of naphthalene and thionaphthene, and in particular to a system and a method for extracting thionaphthene and naphthalene from a mixture of naphthalene and thionaphthene. Background Art

[0002] Thianaphthene is also known as benzothiophene, with a molecular weight of 134.20, a melting point of 31.3°C, a boiling point of 219.9°C, and is insoluble in water, but soluble in organic solvents such as ethanol, ether, acetone, and benzene. Thianaphthene is an important fine chemical raw material, widely used in the fields of medicine, pesticides, optical materials, and dyes, and is mainly used in the preparation of fungicides, insecticides, herbicides, housefly killers, plant growth hormone raw materials, synthetic dye raw materials, and other intermediates of thiaphthene derivatives.

[0003] Refined 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 organic substances such as benzene, ether, and anhydrous ethanol. Refined naphthalene is widely used in the preparation of fine chemical products such as water reducers, phthalic anhydride, naphthoquinone, naphthol, dye diffusers, and dye intermediates.

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

[0005] Since thionaphthene and naphthalene have similar boiling points, it is very difficult to separate and purify thionaphthene using ordinary distillation methods.

[0006] CN101747317A discloses a method for enriching thionaphthene from a mixture containing thionaphthene and naphthalene. The method uses diol as a solvent, enriches thionaphthene in the diol, and recovers the diol to obtain an enriched thionaphthene fraction.

[0007] CN114315792A discloses a method for enriching thionaphthene from a mixture containing thionaphthene and naphthalene by a solvent crystallization coupled extraction and distillation method. It uses triethylene glycol, tetraethylene glycol, MDEA and other solvents to extract thionaphthene from the mixture of thionaphthene and naphthalene, and then extracts and distills to obtain a thionaphthene fraction.

[0008] CN108558591B discloses a naphthalene residual oil separation and recovery method, wherein light components are removed by a light component removal tower, the bottom material of the light component removal tower is sent to a naphthalene removal tower, naphthalene and thionaphthene are separated by the naphthalene removal tower, a naphthalene component is obtained at the top of the naphthalene removal tower, the bottom material of the tower is sent to a benzothiophene tower, the top component of the benzothiophene tower goes to a static crystallizer, and a thionaphthene product is obtained by crystallization in a static crystallizer. In this method, naphthalene and thionaphthene are separated by ordinary distillation of a naphthalene removal tower, and energy consumption is high.

[0009] CN115504960A discloses a method for extracting thionaphthene from naphthalene residual oil. The method uses naphthalene residual oil obtained by melting and crystallizing industrial naphthalene to prepare refined naphthalene as a raw material. Firstly, a double solvent extraction method is adopted. By utilizing the different distribution coefficients of naphthalene and thionaphthene in solvents of ether and ethanolamine, naphthalene is dissolved in ether and thionaphthene is dissolved in ethanolamine, thereby realizing the preliminary separation of naphthalene and thionaphthene. Then, by utilizing the azeotropic property of naphthalene and ethanolamine, an ethanolamine solution of thionaphthene is subjected to intermittent azeotropic distillation, so that ethanolamine and a small amount of naphthalene in the solution are first azeotropically distilled out, and then a thionaphthene fraction is obtained. The thionaphthene fraction is washed with ether to obtain a thionaphthene product. Summary of the invention

[0010] The invention provides a system and method for synchronously extracting thionaphthene and naphthalene from a mixture of naphthalene and thionaphthene. The system of the invention processes the mixture of naphthalene and thionaphthene to synchronously separate and obtain a thionaphthene product and a refined naphthalene product, and the required process flow is simple and easy to operate.

[0011] To achieve the purpose, the present invention provides the following technical solutions:

[0012] The present invention provides a system for extracting thionaphthene and naphthalene from a mixture of naphthalene and thionaphthene, the system comprising:

[0013] An impurity removal unit is used to mix the mixture of naphthalene and thionaphthene with a solvent and perform crystallization and solid-liquid separation to obtain a mixture of naphthalene and thionaphthene from which impurities are removed and a solvent containing impurities;

[0014] A heating kettle, used for heating and melting the impurity-removed mixture of naphthalene and thionaphthene to obtain a molten liquid;

[0015] An azeotropic distillation tower, used for performing azeotropic distillation on the melted liquid and the entrainer, and obtaining a thionaphthene material and a mixture of naphthalene and the entrainer;

[0016] A naphthalene refining unit is used to wash and phase separate 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;

[0017] Preferably, an entrainer refining tower is further included, wherein the entrainer refining tower 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, and the entrainer refining tower is respectively connected to the azeotropic distillation tower and the naphthalene refining unit so as to be able to circulate at least part of the entrainer stream to the azeotropic distillation tower, and to be able to circulate the water stream to the naphthalene refining unit.

[0018] Preferably, the system further comprises a solvent removal unit for removing impurities from the solvent containing impurities to obtain a recovered solvent with impurities removed; the 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;

[0019] Preferably, the solvent impurity removal unit comprises a first mixer, a first phase separator and a solvent recovery tower, wherein 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, and the solvent recovery tower is used to separate 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;

[0020] Preferably, 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;

[0021] Further preferably, 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.

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

[0023] The mixing device is used to mix the mixture of naphthalene and thionaphthene with the solvent to obtain a mixed liquid;

[0024] The crystallizer is used to crystallize the mixed solution and obtain a crystal solution;

[0025] The filter is used to separate the crystal liquid into solid and liquid and obtain the impurity-free mixture of naphthalene and thionaphthene and the solvent containing impurities.

[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 to wash the mixture of naphthalene and the entrainer with water to obtain a second washed mixed liquid;

[0028] The second phase separator is used to phase-separate the second water-wash mixed liquid and obtain the naphthalene-rich light phase component and the heavy phase component containing water and the entrainer;

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

[0030] Furthermore, a water flow output pipeline is connected between the water flow outlet of the azeotropic agent refining tower and the water inlet of the second mixer;

[0031] The thionaphthene material outlet of the azeotropic distillation tower is connected with a thionaphthene material output pipeline;

[0032] The water flow output pipeline and the thionaphthene material output pipeline are connected via a second heat exchanger, which is used to perform heat exchange between the water flow transported by the water flow output pipeline and the thionaphthene material transported by the thionaphthene material output pipeline;

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

[0034] Preferably, the thionaphthene material output pipeline is further provided with a second cooler located downstream of the second heat exchanger.

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

[0036] Preferably, the entrainer refining tower is also connected to the impurity removal unit so as to be able to circulate at least a portion of the entrainer stream to the impurity removal unit.

[0037] Preferably, the system further comprises a first circulation tank and a second circulation tank which are interconnected; the liquid inlet of the first circulation tank is connected to the recovery 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; further preferably, a third cooler is provided between the second circulation tank and the first circulation tank.

[0038] The present invention also provides a method for extracting thionaphthene and naphthalene from a mixture of naphthalene and thionaphthene using the system described above, the method comprising the following steps:

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

[0040] 2) heating and melting the impurity-removed mixture of naphthalene and thionaphthene in a heating kettle to obtain a melt;

[0041] 3) sending the melted liquid into an azeotropic distillation tower to carry out azeotropic distillation with an entrainer to obtain a mixture of thionaphthene material and naphthalene and the entrainer;

[0042] 4) the mixture of described naphthalene and entrainer is sent into naphthalene refining unit and washed and phase-splitting, obtains the light phase component rich in naphthalene and obtains the heavy phase component that comprises water and entrainer;

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

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

[0045] 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) to be used as the solvent required for the mixing;

[0046] Preferably, the impurity-containing solvent obtained in step 1) is sent to the first mixer of the solvent removal unit for washing with water to obtain a first water-washed mixed liquid; then the first water-washed mixed liquid is sent to 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 sent to the solvent recovery tower of the solvent removal unit to separate 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 water for washing, and the recovered solvent is circulated to the removal unit as the solvent required for 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 heat exchanged in the first heat exchanger, the recovered solvent is further cooled in the first cooler and then recycled to the impurity removal unit, and the solvent containing impurities is heat exchanged in the first heat exchanger and then fed into the first mixer;

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

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

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

[0051] Preferably, the water stream output from the azeotropic agent 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.

[0052] Preferably, the solvent in step 1) is ethylene glycol, and in step 3), the azeotropic agent is ethylene glycol;

[0053] Preferably, in step 5), part of the azeotropic agent 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 thiophanate is 1 to 4:1, preferably 1.5 to 3:1.

[0055] Preferably, in step 1), the crystallization conditions include: a cooling rate of 1 to 3°C / min, cooling to 15-35°C, preferably 20 to 30°C for crystal growth, and a crystal growth time of 30-50min, preferably 35 to 45min.

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

[0057] Preferably, in step 3), the mass ratio of the azeotropic agent used for the azeotropic distillation to the melt is 0.53-0.62:1, preferably 0.55-0.62:1, more preferably 0.55-0.60:1. Preferably, 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.

[0058] In some embodiments, 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; preferably, the temperature of the water used for the water washing in step 4) is 70 to 80° C.; preferably, the temperature of the phase separation in step 4) is 80-85° C.;

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

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

[0061] (1) The system of the present invention is used to simultaneously extract naphthalene and thionaphthene from a mixture of naphthalene and thionaphthene. Not only is the process simple and easy to operate, but thionaphthene and naphthalene having similar boiling points can be well separated, and refined naphthalene products and thionaphthene products can be easily and simultaneously obtained.

[0062] (2) In some preferred embodiments, water and entrainer are separated from the heavy phase component obtained from the naphthalene refining unit by the entrainer treating tower, and the water is circulated for the naphthalene refining unit as water for washing, and at least part of the entrainer is circulated for the azeotropic distillation tower, which can greatly save the system water consumption and reduce the entrainer cost. In some preferred embodiments, the solvent and the entrainer are identical reagents, and at least part of the entrainer obtained by the naphthalene refining unit is recycled for use as a solvent in the impurity removal unit, which is beneficial to reduce the solvent cost. In some preferred embodiments, the impure solvent obtained by the impurity removal unit is also removed from the impurities in the solvent impurity removal unit, and the recovered solvent of the impurity removal obtained is circulated for the impurity removal unit, which can further reduce the solvent cost and improve the solvent utilization rate.

[0063] (3) In some preferred schemes, the recovered solvent output from the solvent recovery tower in the solvent removal unit is first heat exchanged with the solvent containing impurities output from the impurity removal unit, and then reused, so that the heat carried in the recovered solvent can be fully utilized; in some preferred schemes, the thionaphthene material output from the azeotropic distillation tower is heat exchanged with the water stream output from the entrainer refining tower and then output as a subsequent product, so that the heat carried in the thionaphthene material can be fully utilized. The system using the preferred scheme can make the energy in the system integrated and reduce energy consumption.

[0064] (4) A method for extracting thionaphthene and naphthalene from a mixture of naphthalene and thionaphthene based on the system of the present invention, wherein the mixture of naphthalene and thionaphthene is first mixed with a solvent (preferably ethylene glycol) for crystallization and impurity removal, and then azeotropic distilled with an entrainer (preferably ethylene glycol) to separate a thionaphthene material and a mixture of naphthalene and the entrainer, wherein the mixture of naphthalene and the entrainer can be washed with water and phase-separated to obtain a refined naphthalene product; the method of the present invention can separate a thionaphthene product and a refined naphthalene product with high yield and high purity from the mixture of naphthalene and thionaphthene.

[0065] (5) The method of the present invention has the characteristics of simple process flow, required operating conditions and temperature, good product quality, etc., and the process operation and control are simple and easy. BRIEF DESCRIPTION OF THE 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 dashed box in the figure is a schematic diagram of the system.

[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 those commonly understood by those skilled in the art to which the present invention belongs. The term "and / or" as may be used herein includes any and all combinations of one or more of the related 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. The reagents or instruments used without specifying the manufacturer are all conventional products that can be purchased commercially.

[0073] The present invention provides a system for extracting thiophanate and naphthalene from a mixture of naphthalene and thiophanate, see 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 tower 11 and a naphthalene refining unit 200, and preferably also comprises an azeotropic agent refining tower 17.

[0074] The impurity removal unit 100 is used to mix the mixture of naphthalene and thiophthalene with a solvent, and to crystallize and perform solid-liquid separation on the mixed liquid, so as to obtain the impurity-free mixture of naphthalene and thiophthalene, and obtain a solvent containing impurities.

[0075] The heating kettle 4 is used to heat and melt the impurity-removed mixture of naphthalene and thionaphthene obtained in the impurity removal unit 100, thereby obtaining a melt.

[0076] The azeotropic distillation tower 11 is used to perform azeotropic distillation on the melt obtained in the heating kettle 4 and the entrainer, thereby separating naphthalene and thionaphthene, obtaining thionaphthene material in the kettle, and obtaining a mixture of naphthalene and the entrainer at the top of the tower.

[0077] The naphthalene refining unit 200 is used to wash the mixture of naphthalene and the entrainer obtained in the azeotropic distillation tower 11 with water and perform phase separation, thereby obtaining a light phase component rich in naphthalene and a heavy phase component containing water and the entrainer.

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

[0079] By the system of the present invention, the mixture of naphthalene and thionaphthene is mixed with a solvent (e.g. ethylene glycol) and crystallized, then the crystallization liquid is subjected to solid-liquid separation, the impurity-removed mixture of naphthalene and thionaphthene is melted and sent to an azeotropic distillation tower 11 and an entrainer (e.g. ethylene glycol) for azeotropic distillation, so that the naphthalene and thionaphthene therein are separated, the thionaphthene material obtained by separation can obtain a thionaphthene product after cooling, the mixture of the naphthalene and the entrainer obtained by separation is washed with water, phase-splitting can obtain a naphthalene-rich component, and the component can obtain a refined naphthalene product after drying. By the system, naphthalene and thionaphthene can be synchronously separated to obtain a product with a simple process flow. Further, the heavy phase component obtained by the naphthalene refining unit 200 is processed by the entrainer refining tower 17, and a water stream that can be reused in the naphthalene refining unit 200 and an entrainer stream that can be reused in the azeotropic distillation tower 11 can also be obtained, which can greatly save the system water consumption and improve the utilization rate of the entrainer, thereby reducing the processing cost.

[0080] See also Figure 1-2Preferably, the system of the present invention further comprises a solvent removal unit 300, which is used to remove impurities from the solvent containing impurities obtained in the impurity removal unit 100, thereby obtaining a cleaned recovery solvent. The recovery solvent outlet of the solvent removal unit 300 is connected to the solvent inlet of the impurity removal unit 100, and the connection includes direct or indirect connection, so that the cleaned recovery solvent obtained by the solvent removal unit is circulated to the impurity removal unit 100 and used as the solvent required for mixing. The use of this preferred method is conducive to improving the utilization rate of the solvent and reducing the amount of solvent and waste liquid.

[0081] Preferably, the solvent impurity removal unit 300 specifically includes a first mixer 6, a first phase separator 7 and a solvent recovery tower 8. The first mixer 6 is used to wash the impurity-containing solvent output from the impurity removal unit 100, thereby obtaining a first water-washed mixed solution; the first phase separator 7 is used to phase-separate the first water-washed mixed solution obtained by the first mixer 6, thereby obtaining a heavy phase component from which impurities are removed and a light phase component containing impurities, wherein the impurities of the light phase component are discharged to the outside of the system through the impurity discharge pipeline 109. The solvent recovery tower 8 is used to separate the water and solvent in the heavy phase component from which impurities are removed obtained in the first phase separator 7, thereby obtaining recovered water and recovered solvent. The recovered solvent outlet of the solvent recovery tower 8 is connected to the solvent inlet of the impurity removal unit 100, so that the recovered solvent can be circulated to the impurity removal unit 100 for continued use as a solvent. The recovered water outlet of the solvent recovery tower 8 is connected to the water inlet of the first mixer 6, so that the water can be circulated for use in the first mixer 6 as water for washing. The "connection" mentioned herein includes direct or indirect connection. By adopting this preferred method, water and solvent that can be reused in the system can be obtained simultaneously, which can reduce the water consumption and solvent consumption of the system and reduce costs.

[0082] Preferably, a first heat exchanger 5 is provided between the solvent recovery tower 8 and the impurity removal unit 100, for exchanging heat between the impurity-containing solvent output from the impurity removal unit 100 and the recovered solvent output from the solvent recovery tower 8 before entering the first mixer 6; specifically, the solvent recovery tower 8 and the impurity removal unit 100 are connected by a recovered solvent pipeline for conveying the recovered solvent, the impurity removal unit 100 and the first mixer 6 are connected by an impure solvent pipeline for conveying the impurity-containing solvent, and the recovered solvent pipeline and the impurity solvent pipeline are connected by the first heat exchanger 5, so that the impurity-containing solvent is preheated by exchanging heat with the recovered solvent output from the solvent recovery tower 8 before entering the first mixer 6, and at the same time, the heat carried in the recovered solvent is fully utilized. Further preferably, a first cooler 10 is provided between the first heat exchanger 5 and the impurity removal unit 100, for cooling the recovered solvent output from the first heat exchanger 5 before entering the impurity removal unit 100.

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

[0084] Preferably, naphthalene refining unit 200 specifically comprises second mixer 14 and second phase splitter 15, preferably also comprises dryer 16.Wherein, second mixer 14 is used for washing the mixed material of naphthalene and entrainer outputted from the tower top of azeotropic distillation tower 11, thereby obtaining the second water-washed mixed liquor.Second phase splitter 15 is used for phase-splitting the second water-washed mixed liquor obtained in second mixer 14, thereby obtaining the light phase component rich in naphthalene, and obtaining the heavy phase component comprising water and entrainer.Dryer 16 is used for drying the light phase component rich in naphthalene obtained in second phase splitter 15, thereby obtaining refined naphthalene product, and refined naphthalene product is outputted by refined naphthalene product output pipeline 124.

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

[0086] In a preferred embodiment, the above-mentioned solvent and the entrainer are the same, and preferably the solvent and the entrainer are both ethylene glycol. Preferably, the entrainer refining tower 17 is also connected to the impurity removal unit 100, and the connection includes direct or indirect connection, so that at least part of the entrainer stream can be circulated to the impurity removal unit 100 and used as the solvent required in the impurity removal unit 100.

[0087] Specifically, in some embodiments, the system of the present invention further includes a first circulation tank 9 and a second circulation tank 20 that are interconnected. The liquid inlet of the first circulation tank 9 is connected to the recovery solvent outlet of the solvent removal unit 300, specifically, for example, connected to the recovery solvent outlet of the solvent recovery tower 8. The liquid outlet of the first circulation tank 9 is connected to the solvent inlet of the impurity removal unit 100, specifically, for example, connected to the solvent inlet of the mixing device 1. The liquid inlet of the second circulation tank 20 is connected to the azeotropic agent flow outlet of the entrainer refining tower 17, and the liquid outlet of the second circulation tank 20 is connected to the azeotropic agent inlet of the azeotropic distillation tower 11; preferably, a third cooler 21 is provided between the second circulation tank 20 and the first circulation tank 9. In this specific manner, the recovered solvent obtained by the solvent removal unit 300 is pre-stored in the first circulation tank 9, and the azeotropic agent flow obtained in the entrainer refining tower 17 is pre-stored in the second circulation tank 20, and then reused in the impurity removal unit 100, or reused in the azeotropic distillation tower 11. The above-mentioned communication is, for example, direct or indirect communication.

[0088] Specifically, a solvent replenishment pipeline 115 is also connected to the first circulation tank 9. When the solvent needs to be replenished, the required amount of solvent can be replenished through the solvent replenishment pipeline 115, thereby compensating for the loss of solvent during the operation of the system. When the solvent and the entrainer are the same reagent, the entrainer can also be replenished through the solvent replenishment pipeline 115, thereby compensating for the loss of the entrainer during the operation of the system.

[0089] Specifically, a water replenishment pipeline 116 is also connected to the first phase separator 7, and water can be replenished into the first phase separator 7 as needed to compensate for the water loss during the operation of the system. A water replenishment pipeline 132 is also connected to the second phase separator 15, and water can be replenished into the second phase separator 15 as needed to compensate for the water loss during the operation of the system.

[0090] By adopting the above system of the present invention, not only can thionaphthene and naphthalene be simultaneously extracted from a mixture of naphthalene and thionaphthene based on a simple and easy-to-operate process flow, but also thionaphthene products and refined naphthalene products can be easily obtained simultaneously; through a preferred method, the solvent, the entrainer and the water can be fully recycled in the system, and the heat in the system can be integrated and utilized, which is beneficial to significantly reduce the processing cost and reduce energy consumption.

[0091] A second aspect of the present invention provides a method for extracting thionaphthene and naphthalene from a mixture of naphthalene and thionaphthene using the system described above, the method comprising the steps of:

[0092] 1) mixing a mixture of naphthalene and thiophanate with a solvent in an impurity removal unit 100, and subjecting the obtained mixed solution to crystallization and solid-liquid separation to obtain a mixture of naphthalene and thiophanate from which impurities are removed and a solvent containing impurities; wherein the impurities are, for example, dimethylphenol, etc.;

[0093] 2) heating and melting the impurity-free mixture of naphthalene and thionaphthene obtained in step 1) in a heating kettle 4 to obtain a melt;

[0094] 3) sending the melt obtained in step 2) into an azeotropic distillation tower 11 to carry out azeotropic distillation with an entrainer to obtain a thionaphthene material and a mixture of naphthalene and the entrainer; the thionaphthene material is cooled to obtain a thionaphthene product;

[0095] 4) sending the mixture of naphthalene and the entrainer into a naphthalene refining unit 200 for washing and phase separation to obtain a light phase component rich in naphthalene and a heavy phase component comprising water and the entrainer; the light phase component rich in naphthalene can be dried to obtain a refined naphthalene product.

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

[0097] Preferably, the method of the present invention further comprises step 5): sending the heavy phase component containing water and entrainer obtained in step 4) into the entrainer refining tower 17 for treatment, specifically distillation separation, separating the water and entrainer in the heavy phase component by distillation, obtaining a water stream at the top of the tower, and obtaining an entrainer stream in the tower bottom; recycling the water stream to the naphthalene refining unit 200 of step 4) as washing water, and recycling at least part of the entrainer stream to the azeotropic distillation tower 11 of step 3) for azeotropic distillation. By adopting the preferred method, the entrainer and water can be recycled, the process water consumption can be saved, and the entrainer cost can be reduced.

[0098] In a preferred embodiment, the method of the present invention further comprises the following steps: sending the impurity-containing solvent obtained in step 1) to the solvent removal unit 300 to remove impurities to obtain a cleaned recovered solvent; recycling the cleaned recovered solvent to the cleaned unit 100 in step 1) as a solvent required for mixing. By adopting this preferred method, the solvent can be recycled and reused, reducing the solvent cost.

[0099] In some specific embodiments, preferably, the impurity-containing solvent obtained in step 1) is sent to the first mixer 6 of the solvent removal unit 300 for washing with water to obtain a first water-washed mixed liquid; then the first water-washed mixed liquid is sent to the first phase separator 7 of the solvent removal unit 300 for phase separation to obtain a heavy phase component from which impurities have been removed, and the impurities enter the light phase component and are discharged. The heavy phase component from which impurities have been removed is sent to the solvent recovery tower 8 of the solvent removal unit for separation, specifically, for example, by distillation separation, and the water and solvent in the heavy phase component are separated to obtain recovered water and recovered solvent; the recovered water is circulated to the first mixer 6 as washing water, and the recovered solvent is circulated to the impurity removal unit 100 as the solvent required for mixing. By adopting this preferred method, not only the solvent but also the water can be recovered, and both can be reused in the process, which can reduce the water consumption of the process and reduce the solvent cost.

[0100] Further preferably, after the recovered solvent output from the solvent recovery tower 8 and the solvent containing impurities 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 circulated to the impurity removal unit 100; the solvent containing impurities is preheated after heat exchange in the first heat exchanger 5 and then sent to the first mixer 6 for treatment. Through this preferred method, the heat carried by the recovered solvent can be fully utilized, the energy required for heating the solvent containing impurities is reduced, and energy consumption is reduced.

[0101] In some preferred embodiments, the mass ratio of water used for water washing in the solvent removal unit to the solvent containing impurities is 0.8-1.5:1; the temperature for phase separation in the solvent removal unit is 80-85°C; and the preferred processing conditions are adopted to facilitate more thorough removal of impurities and improve the quality of recovered water and recovered solvent.

[0102] In some specific embodiments, preferably, in step 4), the mixture of naphthalene and entrainer is sent to the second mixer 14 of the naphthalene refining unit 200 and washed with water to obtain a second washed mixed liquor; then the second washed mixed liquor 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 entrainer. Specifically, the light phase component rich in naphthalene is dried in the dryer 16 to remove trace moisture, and a refined naphthalene product can be obtained.

[0103] Preferably, the water stream output from the azeotropic agent refining tower 17 in step 5) is heat exchanged with the thionaphthene material output from the azeotropic distillation tower 11 in step 3) in the second heat exchanger 12, and then further heated in the water stream heater 19 before being sent to the second mixer 14. By adopting this preferred method, the heat carried in the thionaphthene material can be fully utilized, reducing the heat energy required to heat the water stream, which is conducive to reducing energy consumption.

[0104] In some preferred embodiments, the solvent used in step 1) is ethylene glycol, and in step 3), the entrainer used is ethylene glycol; the inventors have found that ethylene glycol is used as both a solvent and an entrainer, and the process of the present invention can not only remove impurities, but also form a minimum azeotrope with naphthalene in azeotropic distillation, and can more thoroughly separate naphthalene and thionaphthene, and simultaneously obtain refined naphthalene products and thionaphthene products of excellent quality. Moreover, the reagent used in the present invention is relatively single, does not involve the use of a variety of organic solvents, and the process is more simple and easy to implement, solvent recovery is more convenient, and reuse is more flexible. More preferably, in step 5), part of the entrainer logistics is also circulated to the impurity removal unit 100 of step 1) as the solvent required for mixing.

[0105] In some preferred embodiments, in step 1), the mass ratio of the solvent to the mixture of naphthalene and thionaphthene is 1 to 4:1, preferably 1.5 to 3:1; the preferred mass ratio is used to further improve the purity and yield of naphthalene and thionaphthene products. The crystallization conditions in step 1) preferably include: a cooling rate of 1 to 3°C / min, cooling to 15-35°C, preferably 20 to 30°C for crystal growth, and a crystal growth time of 30-50min, preferably 35 to 45min; the preferred crystallization conditions are used to obtain thionaphthene and refined naphthalene products with higher purity and yield.

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

[0107] In some preferred embodiments, in step 3), the mass ratio of the azeotropic agent used for azeotropic distillation to the melt is 0.53-0.62:1, preferably 0.55-0.62:1, more preferably 0.55-0.60:1. The preferred mass ratio is beneficial to obtain higher purity and yield of thionaphthene and refined naphthalene products. Preferably, the conditions of azeotropic distillation include: the top pressure of the azeotropic distillation tower 11 is 5-15 kPa, the top temperature is 110-120°C, and the reflux ratio is 5-10;

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

[0109] The method of the invention, combined with the preferred process conditions, is conducive to obtaining thionaphthene products and refined naphthalene products with higher purity and higher recovery rate.

[0110] In the present invention, the mixture of naphthalene and thionaphthene can be industrial naphthalene, or a naphthalene fraction separated by tar distillation, or naphthalene residual oil after melt crystallization of industrial naphthalene or a naphthalene fraction.

[0111] In some embodiments, at the beginning of the process system operation, the required amount of solvent and entrainer can be added to the first circulation tank 9 and the second circulation tank 20 respectively, and the required amount of water can be added to the first phase separator 7 and the second phase separator 15 respectively, according to the usage of solvent and entrainer and the amount of water required for water washing, thereby providing the solvent, entrainer and water required for process startup.

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

[0113] Example 1

[0114] The process system used in this embodiment is shown in Figure 1 For any part of the system and method not specifically described, please refer to the above description and no further description will be given.

[0115] The mixture of naphthalene and thiophanate used in this embodiment is the residual oil obtained by crystallization after extracting refined naphthalene from the naphthalene fraction obtained from a tar processing device through melt crystallization. The raw material contains 12.48wt% of thiophanate, 83.52wt% of naphthalene, and 4wt% of impurities such as dimethylphenol, with a flow rate of 1062.9kg / h.

[0116] The main process is as follows:

[0117] The 80°C crystallization residual oil raw material 101 and the 40°C circulating solvent 114 (ethylene glycol) from the first circulation tank 9 are fully mixed in the mixing device 1, wherein the mass ratio of the solvent to the raw material is 2:1, and a mixed liquid at 73°C is obtained. The mixed liquid 102 enters the crystallizer 2 for cooling and crystallization, and the cooling rate is 2°C / min. It is cooled to a crystal growing temperature of 25°C, and the crystal growing time is 40 minutes.

[0118] The crystal liquid 103 output from the crystallizer 2 enters the filter 3 for solid-liquid separation, and impurities such as dimethylphenol enter the filtrate. The filtrate 106 output from the filter 3 enters the solvent removal unit 300 for impurity removal treatment. The main components in the filter cake are naphthalene, thiophene and entrained solvent. 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 bottom material 112 (i.e., the recovered solvent) of the solvent recovery tower 8 in the first heat exchanger 5 for heat recovery, and the hot filtrate 107 at 111°C obtained by heat exchange enters the first mixer 6 and is fully mixed with the recovered water 111 from the solvent recovery tower 8, and the mass ratio of the recovered water to the filtrate is 1:1. The mixed solution 108 at 83°C is washed in the first mixer 6, and the mixed solution 108 enters the first phase separator 7 for phase separation, and the temperature of the first phase separator 7 is controlled to be 82°C. The light phase components obtained in the first phase separator 7 are organic phases such as impurities, a small amount of naphthalene and thiophane, which are discharged from the system from the pipeline 109, and the heavy phase components are a mixture of water and solvent (i.e., the heavy phase components from which the impurities have been removed), and the heavy phase components 110 are sent to the middle of the solvent recovery tower 8 for rectification and separation. During the process, water is added 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. During the operation, due to the phase separation operation, trace amounts of water will dissolve in the organic phase (the light phase enriched with impurities), 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. Due to the loss of water during the operation, when the solvent concentration in the heavy phase component 110 increases to 55%, a certain amount of water is added to reduce the solvent concentration and restore it to the initial solvent concentration of 50%. At the same time, the water loss during the operation can be compensated by the water supplement, and the liquid level of the heavy phase can be restored to the initial level. The continuous water supplement flow rate is 1.65 kg / h, thereby compensating for the water loss during the operation of the system.

[0120] The heavy phase component 110 outputted from the first phase separator 7 enters the middle of the solvent recovery tower 8 for rectification and separation. The top pressure of the solvent recovery tower 8 is controlled to be 22 kPa, the top temperature is 62°C, and the reflux ratio is 0.8. The recovered water 111 extracted from the top enters the first mixer 6 for recycling. The 155°C recovered solvent 112 extracted from the bottom of the tower first enters the first heat exchanger 5 to recover heat by heating the filtrate. After the recovered solvent is cooled by heat exchange, it enters the first cooler for further cooling to 40°C. The cooled recovered solvent 113 enters the first circulation tank 9. The solvent is replenished through the solvent replenishment pipeline 115 according to the liquid level of the first circulation tank 9. When the solvent liquid level drops to 60%, the solvent is added through the solvent replenishment pipeline 115 to make the solvent liquid level reach 100%. The continuous replenishment amount of the solvent is 3.45 kg / h.

[0121] The filter cake 104 output by the filter 3 enters the heating kettle 4 and is heated and melted at 82°C. The obtained melt 105 enters the middle and upper part of the azeotropic distillation tower 11. The top pressure of the azeotropic distillation tower 11 is controlled to be 10 kPa, the top temperature is 114°C, the reflux ratio is 6, ethylene glycol is selected as the azeotropic agent, and the mass ratio of ethylene glycol to the melt is controlled to be 0.56:1. Naphthalene and ethylene glycol can form a minimum azeotrope. After the azeotropic distillation separation process, a mixture of naphthalene and entrainer is extracted from the tower top, and the thionaphthene stream is extracted from the tower bottom. The tower bottom material 119 at 156° C. (i.e., the thionaphthene material) is first heat-exchanged with the water stream 126 extracted from the tower top of the entrainer refining tower 17 in the second heat exchanger 12 to recover the heat carried by the thionaphthene material. The thionaphthene material 120 cooled to 60° C. is then cooled to 40° C. by the second cooler 13 to obtain a refined thionaphthene product 121.

[0122] The mixture 118 of naphthalene and entrainer extracted from the top of the azeotropic distillation tower 11 enters the second mixer 14, and the water stream 129 that is heat-exchanged to 68° C. in the second heat exchanger 12 is further heated by the water stream heater 19 to obtain a water stream 130 of 75° C., which continues to enter the second mixer 14 and is fully mixed with the mixture 118 of naphthalene and entrainer. The mass ratio of water to the mixture of naphthalene and entrainer in the second mixer 14 is 1:1. After washing, the obtained second washed mixed liquor 122 enters the second phase separator 15 for phase separation, and the temperature of the phase separator is controlled to be 82° C. and the pressure is 101.325 kPa. During the process, since the loss of the entrained solvent in the product is greater than the loss of water, the concentration of the entrainer in the heavy phase component 125 will decrease during the operation. The entrainer can be replenished by replenishing the solvent in the first circulation tank 9 mentioned above, and the water can be replenished through the water replenishment pipeline 132 to replenish the water loss during the operation, so that the entrainer concentration of the heavy phase component 125 can be adjusted when it is reduced from the initial concentration (47% in this embodiment) (for example, reduced to 40%), so that the entrainer concentration is restored to the initial concentration, and the liquid level of the heavy phase in the second phase separator 15 is restored to the initial liquid level. The continuous replenishment flow rate of water is 0.61kg / h, and the amount of entrainer to be replenished is implemented by replenishing the solvent in the first circulation tank 9 through the aforementioned solvent replenishment pipeline 115.

[0123] The light phase component separated in the second phase separator 15 is a naphthalene-rich material. The light phase component 123 enters the dryer 16, and the pressure of the dryer 16 is controlled to be 40 kPa and the temperature is 95 ° C. After removing trace moisture by heating, a refined naphthalene product is obtained and output by pipeline 124;

[0124] The heavy phase component 125 in the second phase separator 15 enters the entrainer refining tower 17, and the top pressure of the entrainer refining tower 17 is controlled to be 22 kPa, the top temperature is 62°C, and the reflux ratio is 0.3. After distillation separation, the water flow is extracted from the top of the tower, the entrainer flow is extracted from the bottom of the tower, the top water flow 126 is reused, and the bottom entrainer flow 127 enters the fourth cooler 18 to be cooled to 110°C and then enters the second circulation tank 20. A part of the solvent in the second circulation tank 20 enters the middle and upper part of the azeotropic distillation tower 11 as a circulating entrainer 129, and a part of the solvent enters the third cooler 21 as a recovered solvent 130 and is further cooled to 40°C. The recovered solvent 131 at 40°C enters the first circulation tank 9.

[0125] In this example, a thionaphthene product with a purity of 99.03% and a refined naphthalene product with a purity of 99.62% were obtained. The yield of thionaphthene was 96.0% and the yield of naphthalene was 95.9%.

[0126] In this embodiment, the main material flow rates and main component contents are shown in Table 1, and the tower parameters are shown in Table 2.

[0127] Table 1 Main logistics flow and composition of Example 1

[0128]

[0129] Table 2 Main equipment parameters of Example 1

[0130]

[0131]

[0132] Example 2

[0133] The process is carried out in accordance with Example 1, except that in step 1), the mass ratio of ethylene glycol to the crystallized residual oil is 1:1.

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

[0135] Example 3

[0136] The process is carried out in accordance with Example 1, except that in step 1), the mass ratio of ethylene glycol to the crystallized residual oil is 4:1.

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

[0138] Example 4

[0139] The process is carried out in accordance with Example 1, except that in step 1), the crystal growing temperature is 15°C.

[0140] Experimental results: the purity of the obtained thionaphthene product was 98.3%, and the yield was 96.1%; the purity of the obtained refined naphthalene product was 99.1%, and the yield was 96.0%.

[0141] Example 5

[0142] The process is carried out in accordance with Example 1, except that in step 1), the crystal growing temperature is 35°C.

[0143] Experimental results: the purity of the obtained thionaphthene product was 98.4%, and the yield was 94.2%; the purity of the obtained refined naphthalene product was 99.0%, and the yield was 91.5%.

[0144] Example 6

[0145] The process is carried out in accordance with Example 1, except that in step 1), the crystal growing time is 30 min.

[0146] Experimental results: the purity of the obtained thionaphthene product was 98.8%, and the yield was 93.1%; the purity of the obtained refined naphthalene product was 99.3%, and the yield was 91.4%.

[0147] Example 7

[0148] The process is carried out in accordance with Example 1, except that in step 1), the crystal growing time is 50 min.

[0149] Experimental results: the purity of the obtained thionaphthene product was 98.6%, and the yield was 96.2%; the purity of the obtained refined naphthalene product was 99.0%, and the yield was 96.1%.

[0150] Example 8

[0151] The process is carried out in accordance with Example 1, except that in step 2), the mass ratio of the amount of the azeotropic agent ethylene glycol to the melt is 0.53:1.

[0152] Experimental results: the purity of the obtained thionaphthene product was 82.8%, and the yield was 95.7%; the purity of the obtained refined naphthalene product was 99.2%, and the yield was 87.1%.

[0153] Example 9

[0154] The process is carried out in accordance with Example 1, except that in step 3), the mass ratio of the amount of the azeotropic agent ethylene glycol to the melt is 0.62:1.

[0155] Experimental results: the purity of the obtained thionaphthene product was 98.9%, and the yield was 95.8%; the purity of the obtained refined naphthalene product was 99.0%, and the yield was 95.5%.

[0156] It is easy to understand that the above embodiments are only examples for clear explanation and do not mean that the present invention is limited thereto. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from this are still within the protection scope of the present invention.

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 is used to mix the mixture of naphthalene and thionaphthene with a solvent and perform 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 molten liquid; An azeotropic distillation tower, used for performing azeotropic distillation on the melted liquid and the entrainer, and obtaining a thionaphthene material and a mixture of naphthalene and the entrainer; A naphthalene refining unit is used to wash and phase separate 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; Preferably, an entrainer refining tower is further included, wherein the entrainer refining tower 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, and the entrainer refining tower is respectively connected to the azeotropic distillation tower and the naphthalene refining unit so as to be able to circulate at least part of the entrainer stream to the azeotropic distillation tower, and to be able to circulate the water stream to the naphthalene refining unit.

2. The system according to claim 1, characterized in that The system further comprises a solvent impurity removal unit, which is used to remove impurities from the solvent containing impurities to obtain a recovered solvent with impurities removed; a recovered solvent outlet of the solvent impurity removal unit is connected to the impurity removal unit to circulate the recovered solvent to the impurity removal unit; Preferably, the solvent impurity removal unit comprises a first mixer, a first phase separator and a solvent recovery tower, wherein 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, and the solvent recovery tower is used to separate 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; Preferably, 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; Further preferably, 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.

3. The system according to claim 1, characterized in that 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 solution; The filter is used to separate the crystal liquid into solid and liquid and obtain the impurity-free mixture of naphthalene and thionaphthene and the solvent containing impurities.

4. The system according to any one of claims 1 to 3, characterized in that: The naphthalene refining unit comprises a second mixer and a second phase separator, and preferably further comprises a dryer; The second mixer is used to wash the mixture of naphthalene and the entrainer with water to obtain a second washed mixed liquid; The second phase separator is used to phase-separate the second water-wash mixed liquid and obtain the naphthalene-rich light phase component and the heavy phase component containing water and the entrainer; The dryer is used for drying the naphthalene-rich light phase component to obtain a refined naphthalene product.

5. The system according to claim 4, characterized in that A water flow output pipeline is connected between the water flow 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 with a thionaphthene material output pipeline; The water flow output pipeline and the thionaphthene material output pipeline are connected via a second heat exchanger, which is used to perform heat exchange between the water flow transported by the water flow output pipeline and the thionaphthene material transported by the thionaphthene material output pipeline; Preferably, the water stream output pipeline is further provided with a water stream heater located downstream of the second heat exchanger; Preferably, the thionaphthene material output pipeline is further provided with a second cooler located downstream of the second heat exchanger.

6. The system according to claim 2 or 3, characterized in that: The solvent and the entrainer are the same, preferably the solvent and the entrainer are both ethylene glycol; Preferably, the entrainer refining tower is also connected to the impurity removal unit so as to be able to circulate at least a portion of the entrainer stream to the impurity removal unit. Preferably, the system further comprises a first circulation tank and a second circulation tank which are interconnected; the liquid inlet of the first circulation tank is connected to the recovery 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; further preferably, a third cooler is provided between the second circulation tank and the first circulation tank.

7. 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 6, characterized in that: The method comprises the following steps: 1) mixing the mixture of naphthalene and thionaphthene with a solvent in an impurity removal unit, and subjecting the obtained mixed solution to crystallization and solid-liquid separation to obtain the impurity-removed mixture of naphthalene and thionaphthene and 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 melted liquid into an azeotropic distillation tower to carry 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 naphthalene refining unit and washed and phase-splitting, obtains the light phase component rich in naphthalene and obtains the heavy phase component that comprises water and entrainer; Preferably, the method further comprises step 5): sending 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, and obtaining a water stream and an entrainer stream; The water stream is circulated to the naphthalene refining unit in step 4) as washing water, and at least a part of the entrainer stream is circulated to the azeotropic distillation tower in step 3) for azeotropic distillation.

8. The method according to claim 7, characterized in that 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) to be used as the solvent required for the mixing; Preferably, the impurity-containing solvent obtained in step 1) is sent to the first mixer of the solvent removal unit for washing with water to obtain a first water-washed mixed liquid; then the first water-washed mixed liquid is sent to 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 sent to the solvent recovery tower of the solvent removal unit to separate 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 water for washing, and the recovered solvent is circulated to the removal unit as the solvent required for the mixing; Further preferably, after the recovered solvent output from the solvent recovery tower and the solvent containing impurities output from the impurity removal unit are heat exchanged in the first heat exchanger, the recovered solvent is further cooled in the first cooler and then recycled to the impurity removal unit, and the solvent containing impurities is heat exchanged in the first heat exchanger and then fed into the first mixer; Further preferably, the mass ratio of water used for the water washing in the solvent removal unit to the solvent containing impurities is 0.8-1.5:1; and the temperature for the phase separation in the solvent removal unit is 80-85°C.

9. The method according to claim 7, characterized in that: Step 4), the mixture of described naphthalene and entrainer is sent into 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 into the second phase separator of described naphthalene refining unit and phase-splitting is carried out to obtain the described light phase component rich in naphthalene and obtain the described heavy phase component comprising water and entrainer; Preferably, the naphthalene-rich light phase component is dried in a dryer to obtain a refined naphthalene product; Preferably, the water stream output from the azeotropic agent 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.

10. The method according to claim 7, characterized in that In step 1), the solvent is ethylene glycol, and in step 3), the azeotropic agent is ethylene glycol; Preferably, in step 5), part of the azeotropic agent stream is also recycled to the impurity removal unit in step 1) to be used as the solvent required for the mixing.

11. The method according to any one of claims 7 to 10, characterized in that: In step 1), the mass ratio of the solvent to the mixture of naphthalene and thiophanate is 1 to 4:1, preferably 1.5 to 3:1; And / or, in step 1), the crystallization conditions include: cooling rate of 1-3°C / min, cooling to 15-35°C, preferably 20-30°C for crystal growth, and the crystal growth time is 30-50min, preferably 35-45min; And / or, in step 2), the heating and melting temperature is 80-85°C; And / or, in step 3), the mass ratio of the azeotropic agent used for the azeotropic distillation to the melt is 0.53-0.62:1, preferably 0.55-0.62:1, more preferably 0.55-0.60:1, preferably, 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; 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 0.8-1.5:1; preferably, the temperature of the water used for the water washing in step 4) is 70-80°C; preferably, the temperature of the phase separation in step 4) is 80-85°C; And / or, in step 1), the mixture of naphthalene and thionaphthene is industrial naphthalene, or a naphthalene fraction separated by tar distillation, or naphthalene residual oil obtained by melt crystallization of the industrial naphthalene or the naphthalene fraction.

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