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

Abstract

According to the system and the method for separating the indane and the naphthalene from the mixture of the naphthalene and the indane, the mixture of the naphthalene and the indane is treated based on the system, and the indane product and the refined naphthalene product can be obtained through synchronous separation. The system comprises an impurity removal unit used for carrying out mixing, crystallization and solid-liquid separation on the mixture of naphthalene and indane and a solvent; the solvent removal unit is used for separating the solvent entrained in the impurity-removed mixture of naphthalene and indane; a solvent outlet of the solvent removal unit is connected with the impurity removal unit; the azeotropic rectification tower is used for carrying out azeotropic rectification on the mixture of the naphthalene and the indane without the solvent and an 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 method for separating 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 separating thionaphthene and naphthalene from a mixture of naphthalene and thionaphthene. The system of the invention is used to process the mixture of naphthalene and thionaphthene, and the required process flow is simple and easy. A thionaphthene product and a refined naphthalene product can be separated synchronously, and the solvent can be recycled, thereby reducing the separation cost.

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

[0012] One aspect of the present invention provides a system for separating thionaphthene and naphthalene from a mixture of naphthalene and thionaphthene, the system comprising:

[0013] An impurity removal unit is used to mix, crystallize and perform solid-liquid separation on the mixture of naphthalene and thionaphthene with a solvent to obtain a mixture of naphthalene and thionaphthene from which impurities have been removed and a solvent containing impurities; the solvent is preferably n-butanol;

[0014] A solvent removal unit, used for separating the solvent entrained in the impurity-removed mixture of naphthalene and thionaphthene and obtaining the mixture of naphthalene and thionaphthene from which the solvent has been removed and obtaining the removed solvent; the solvent outlet of the solvent removal unit is connected to the impurity removal unit to circulate the removed solvent to the impurity removal unit;

[0015] An azeotropic distillation tower, used for azeotropically distilling the mixture of naphthalene and thionaphthene from which the solvent has been removed and an entrainer, and obtaining a thionaphthene material and a mixture of naphthalene and the entrainer; the entrainer is preferably ethylene glycol;

[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, it also includes an azeotrope refining tower, which is used to separate a water flow and an entrainer flow from the heavy phase component. The entrainer refining tower is connected to the naphthalene refining unit and the azeotropic distillation tower, respectively, so as to circulate the water flow to the naphthalene refining unit and circulate the entrainer flow to the azeotropic distillation tower.

[0018] Preferably, the system further comprises a solvent impurity removal unit, which is used to remove impurities from the impurity-containing solvent obtained by the impurity removal unit to obtain a solvent stream with impurities removed; the solvent outlet of the solvent impurity removal unit is connected to the impurity removal unit to circulate the solvent stream with impurities removed to the impurity removal unit;

[0019] Preferably, the system further comprises a circulating solvent tank, the solvent outlet of the solvent impurity removal unit and the solvent outlet of the solvent removal unit are respectively connected to the solvent inlet of the circulating solvent tank, and the solvent outlet of the circulating solvent tank is connected to the solvent inlet of the impurity removal unit;

[0020] In some embodiments, the solvent impurity removal unit includes a first heat exchanger, a first cooler, and a first solvent recovery tower;

[0021] The first solvent recovery tower is used to distill the preheated solvent containing impurities and obtain a solvent stream and an impurity stream that have been cleaned;

[0022] The first heat exchanger is connected between the impurity removal unit and the first solvent recovery tower, and is used to perform heat exchange between the impurity-containing solvent output from the impurity removal unit and the impurity-removed solvent stream output from the first solvent recovery tower so as to preheat the impurity-containing solvent;

[0023] The first cooler is connected to the first heat exchanger and is used to cool the impurity-removed solvent flow output by the first heat exchanger;

[0024] Preferably, the first cooler is connected to the first solvent recovery tower and the circulating solvent tank, respectively, so as to circulate the cooled impurity-free solvent stream to the first solvent recovery tower and the circulating solvent tank.

[0025] In some embodiments, the solvent removal unit includes a heating kettle and a second solvent recovery tower; the heating kettle is used to heat and melt the impurity-removed mixture of naphthalene and thiophthalene output by the impurity removal unit to obtain a melt; the second solvent recovery tower is used to distill the melt to remove the entrained solvent therein; the solvent outlet of the second solvent recovery tower is connected to the solvent inlet of the circulating solvent tank.

[0026] In some embodiments, the impurity removal unit includes a first mixer, a crystallizer, and a filter;

[0027] The first mixer is used to mix the mixture of naphthalene and thionaphthene with the solvent to obtain a mixed solution;

[0028] The crystallizer is used to crystallize the mixed solution obtained by the first mixer to obtain a crystal solution;

[0029] The filter is used to perform solid-liquid separation on the crystal liquid and obtain a filter cake and a filtrate, wherein the filter cake is a mixture of the impurity-removed naphthalene and thionaphthene, and the filtrate is the solvent containing impurities.

[0030] In some embodiments, the naphthalene refining unit comprises a second mixer and a phase separator, and preferably further comprises a dryer;

[0031] The second mixer is used to mix and wash the mixture of the naphthalene and the entrainer output from the azeotropic distillation tower with water to obtain a mixed liquid;

[0032] The phase separator is used to separate the mixed liquid output from the second mixer into phases and obtain the light phase component and the heavy phase component;

[0033] The dryer is used to dry the light phase component to obtain a refined naphthalene product;

[0034] Preferably, the water flow outlet of the entrainer refining tower and the water inlet of the second mixer are connected by a water flow delivery pipeline, and along the flow direction of the water flow, a second heat exchanger and a water flow heater are sequentially arranged on the water flow delivery pipeline, and the second heat exchanger is used to exchange heat between the water flow output from the entrainer refining tower and the thionaphthene material output from the azeotropic distillation tower;

[0035] Further preferably, an entrainer cooler is provided between the azeotropic agent flow outlet of the azeotropic agent refining tower and the azeotropic agent inlet of the azeotropic distillation tower, for cooling the azeotropic agent flow output from the azeotropic agent refining tower.

[0036] The present invention also provides a method for separating thionaphthene and naphthalene from a mixture of naphthalene and thionaphthene using the system described above, the method comprising the following steps:

[0037] 1) In an impurity removal unit, the mixture of naphthalene and thiophanate is mixed with a solvent to obtain a mixed solution, and then the mixed solution is crystallized, and the obtained crystal solution is subjected to solid-liquid separation to obtain a mixture of naphthalene and thiophanate that has been impurities removed and a solvent containing impurities; the solvent is preferably n-butanol;

[0038] 2) sending the impurity-removed naphthalene and thiophanate mixture obtained in step 1) into a solvent removal unit to remove the entrained solvent, thereby obtaining a solvent-removed naphthalene and thiophanate mixture, and obtaining the removed solvent; recycling the removed solvent to the impurity removal unit in step 1) for use as the solvent required for the mixing;

[0039] 3) feeding the solvent-free mixture of naphthalene and thionaphthene obtained in step 2) into an azeotropic distillation tower, and performing azeotropic distillation with an entrainer to obtain a thionaphthene material and a mixture of naphthalene and the entrainer; the entrainer is preferably ethylene glycol; preferably, cooling the thionaphthene material to obtain a thionaphthene product;

[0040] 4) sending the mixture of the naphthalene and the entrainer obtained in step 3) into a naphthalene refining unit for washing and phase separation to obtain a light phase component rich in naphthalene and a heavy phase component comprising water and the entrainer; preferably, the light phase component is dried to obtain a refined naphthalene product;

[0041] Preferably, the method further comprises step 5):

[0042] The heavy phase component obtained in step 4) is sent to an entrainer refining tower for separation to obtain a water stream and an entrainer stream; the water stream is circulated to the naphthalene refining unit in step 4) for water washing, and the entrainer stream is circulated to the azeotropic distillation tower in step 3) for the azeotropic distillation.

[0043] Preferably, the method further comprises the following steps:

[0044] The impurity-containing solvent obtained in step 1) is sent to a solvent impurity removal unit to remove impurities in the solvent to obtain a de-impurified solvent stream; at least a portion of the de-impurified solvent stream is recycled to the de-impurity unit in step 1) to be used as the solvent required for the mixing;

[0045] Preferably, the impurity-containing solvent obtained in step 1) is sent to the first solvent recovery tower of the solvent impurity removal unit for distillation to obtain the impurity-free solvent flow and the impurity flow; the impurity-free solvent flow output from the first solvent recovery tower and the impurity-containing solvent flow output from the impurity removal unit are heat exchanged in a first heat exchanger, and then the impurity-free solvent flow is sent to a first cooler for cooling, and then part of the impurity-free solvent flow is circulated to the first solvent recovery tower as reflux, and part of the impurity-free solvent flow is circulated to the impurity removal unit.

[0046] Further, in step 2), the impurity-free mixture of naphthalene and thiophanate obtained in step 1) is first sent to the heating kettle of the solvent removal unit for heating and melting to obtain a melted liquid, and the temperature of the heating and melting is preferably 82-90° C.; then the melted liquid is sent to the second solvent recovery tower of the solvent removal unit for distillation to remove the solvent entrained in the melted liquid, thereby obtaining the solvent-free mixture of naphthalene and thiophanate, and obtaining the removed solvent;

[0047] And / or, the water stream output from the entrainer refining tower in step 5) is first heat-exchanged with the thionaphthene material output from the azeotropic distillation tower in step 3) in a second heat exchanger, and then heated by a water stream heater, and then fed into the naphthalene refining unit in step 4) to be used as the water required for the water washing;

[0048] And / or, in step 5), the azeotropic agent stream output from the azeotropic agent refining tower is first cooled in an azeotropic agent cooler and then recycled to the azeotropic distillation tower in step 3).

[0049] Preferably, in step 1), the mass ratio of the solvent to the mixture of naphthalene and thiophanate is 1:1 to 4:1, preferably 1.5 to 3:1; preferably, the crystallization conditions include: a cooling rate of 1 to 3°C / min, cooling to 8-30°C for crystal growing, preferably cooling to 10 to 25°C for crystal growing, and a crystal growing time of 15-45min, preferably 20 to 40min.

[0050] Preferably, in step 3), the mass ratio of the amount of the entrainer to the mixture of naphthalene and thionaphthene from which the solvent has been removed is 0.53 to 0.62:1, more preferably 0.55 to 0.60:1; preferably, the conditions for the azeotropic distillation include: the top pressure of the azeotropic distillation tower is 5 to 15 kPa, the top temperature is 110 to 125° C., and the reflux ratio is 5 to 10.

[0051] Preferably, in step 4), the mass ratio of water used for the water washing 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 is 70-80°C; preferably, the temperature for the phase separation is 80-85°C.

[0052] Preferably, in step 5), the operating conditions of the azeotropic agent refining tower include: tower top pressure 20-30 kPa, tower top temperature 60-70° C., and reflux ratio 0.2-1.

[0053] In the present invention, 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.

[0054] The technical solution provided by the present invention has the following beneficial effects:

[0055] (1) The system of the present invention is used to treat a mixture of naphthalene and thionaphthene. Not only is the process flow simple and easy, but thionaphthene and naphthalene having similar boiling points can be well separated, and a refined naphthalene product and a thionaphthene product can be obtained simultaneously. At the same time, the system of the present invention can recycle the solvent, which can greatly reduce the solvent cost.

[0056] (2) In some preferred embodiments, water and entrainer are separated from the heavy phase component obtained from the naphthalene refining unit by an entrainer refining tower, and the water is recycled for use in the naphthalene refining unit as washing water, and the entrainer is recycled for use in the azeotropic distillation tower, which can greatly save the system water consumption and reduce the entrainer cost. In some preferred embodiments, the impurity-containing solvent obtained in the impurity removal unit is also removed in a solvent impurity removal unit, and at least a portion of the impurity-removed solvent stream is recycled for use in the impurity removal unit, which can further reduce the solvent cost and improve the solvent utilization rate.

[0057] (3) In some preferred schemes, the impurity-removed solvent obtained by the solvent impurity removal unit is first heat-exchanged with the impurity-containing solvent output from the impurity removal unit and then reused, so that the heat carried by the impurity-removed 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 by the thionaphthene material can be fully utilized. The system using the preferred scheme can integrate the energy in each system and reduce energy consumption.

[0058] (4) A method for separating 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 n-butanol) for crystallization and impurity removal, and after the solvent is removed, azeotropic distillation is performed 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 refined naphthalene with better yield and purity from the mixture of naphthalene and thionaphthene.

[0059] (5) The method of the present invention has the characteristics of simple process flow, mild operating conditions, good product quality, etc., and the process operation and control are simple and easy. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] 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.

[0061] Figure 2 Not drawn Figure 1 The dashed box in the figure is a schematic diagram of the system.

[0062] Description of some reference numerals:

[0063] Impurity removal unit 100, solvent removal unit 200, naphthalene refining unit 300, solvent impurity removal unit 400, first mixer 1, crystallizer 2, filter 3, first solvent recovery tower 4, first heat exchanger 5, first cooler 6, third cooler 7, heating kettle 8, second solvent recovery tower 9, circulating solvent tank 10, azeotropic distillation tower 11, second heat exchanger 12, second cooler 13, second mixer 14, phase separator 15, dryer 16, entrainer refining tower 17, entrainer cooler 18, water stream heater 19, solvent replenishment pipeline 117, water replenishment pipeline 131, and entrainer replenishment pipeline 132. DETAILED DESCRIPTION

[0064] 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.

[0065] 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", etc. mentioned or may be mentioned in this specification are used for descriptive purposes only and are not to be understood as indicating or implying relative importance.

[0066] 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.

[0067] The present invention provides a system for separating 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 solvent removal unit 200, an azeotropic distillation tower 11, a naphthalene refining unit 300, and preferably also comprises an azeotropic agent refining tower 17.

[0068] The impurity removal unit 100 is used to mix, crystallize and solid-liquid separate the mixture of naphthalene and thiophthalene with a solvent to remove impurities therein, thereby obtaining a mixture of naphthalene and thiophthalene that has been impurified, and obtaining a solvent containing impurities; in a preferred embodiment, the solvent is preferably n-butanol.

[0069] The solvent removal unit 200 is used to separate the solvent entrained in the mixture of naphthalene and thiophthalene obtained in the impurity removal unit 100, so as to obtain the mixture of naphthalene and thiophthalene from which the solvent has been removed, and to obtain the removed solvent; the solvent outlet of the solvent removal unit 200 is connected to the impurity removal unit 100, and the connection includes direct or indirect connection, and the removed solvent is output from the solvent outlet of the solvent removal unit 200, and then circulated to the impurity removal unit 100 for use as the solvent required for mixing.

[0070] The azeotropic distillation tower 11 is used to perform azeotropic distillation on the mixture of naphthalene and thionaphthene from which the solvent has been removed obtained in the solvent removal unit 200 and an entrainer, so that naphthalene and thionaphthene can be separated by azeotropic distillation, and thionaphthene material is obtained in the bottom of the tower, and a mixture of naphthalene and the entrainer is obtained at the top of the tower; preferably, the entrainer is ethylene glycol.

[0071] The naphthalene refining unit 300 is used to wash and phase separate the mixture of naphthalene and the entrainer obtained in the azeotropic distillation tower 11, thereby obtaining a light phase component rich in naphthalene and a heavy phase component containing water and the entrainer. The light phase component rich in naphthalene can be dried to obtain a refined naphthalene product.

[0072] The entrainer refining tower 17 is used for refining and separating the heavy phase components obtained from the naphthalene refining unit 300, which can be specifically distillation separation, so that the water and the entrainer therein are separated, and a water stream is obtained from the tower top, and an entrainer stream is obtained from the tower bottom. The water stream outlet of the entrainer refining tower 17 is connected to the naphthalene refining unit 300, and the entrainer stream outlet of the entrainer refining tower 17 is connected to the azeotropic distillation tower 11, and the above connection includes direct connection or indirect connection, so that the water stream can be circulated to the naphthalene refining unit 300 as washing water, and the entrainer stream can be circulated to the azeotropic distillation tower 11 for azeotropic distillation.

[0073] Through the system of the present invention, the mixture of naphthalene and thionaphthene is mixed with a solvent (preferably n-butyl alcohol), crystallized, and then the crystallization liquid is subjected to solid-liquid separation, the obtained mixture of naphthalene and thionaphthene is subjected to solvent removal in a solvent removal unit 200, the removed solvent is reused in the impurity removal unit 100, and then the mixture of naphthalene and thionaphthene from which the solvent has been removed is sent to an azeotropic distillation tower 11 and an entrainer (preferably butanediol) for azeotropic distillation, so that the naphthalene and thionaphthene therein are separated, the separated thionaphthene material can be cooled to obtain a thionaphthene product, the separated naphthalene and the mixed material of the entrainer are washed with water, and phase separation can be performed to obtain a naphthalene-rich component, and the component can be dried to obtain a refined naphthalene product. Through the system, naphthalene and thionaphthene can be synchronously separated to obtain a product with a simple process flow, and the solvent utilization rate is high. The heavy phase components obtained from the naphthalene refining unit 300 are further processed by the entrainer refining tower 17 to obtain a water flow that can be recycled to the naphthalene refining unit 300 and an entrainer flow that can be recycled to the azeotropic distillation tower 11, which can greatly save the system water consumption, improve the utilization rate of the entrainer, and reduce the processing cost.

[0074] See also Figure 1 Preferably, the system of the present invention further comprises a solvent impurity removal unit 400, which is used to remove impurities from the impurity-containing solvent obtained by the impurity removal unit 100, thereby obtaining a solvent stream with impurities removed. The solvent outlet of the solvent impurity removal unit 400 is connected to the impurity removal unit 100, and the connection includes a direct connection or an indirect connection, so that the solvent stream with impurities can be circulated to the impurity removal unit 100. Through this preferred embodiment, the solvent utilization rate of the system can be improved and the processing cost can be reduced.

[0075] Preferably, see Figure 1 The system of the present invention further includes a circulating solvent tank 10. The solvent outlet of the solvent impurity removal unit 400 and the solvent outlet of the solvent removal unit 200 are respectively connected to the solvent inlet of the circulating solvent tank 10, and the solvent outlet of the circulating solvent tank 10 is connected to the solvent inlet of the impurity removal unit 100; that is, the impurity removal solvent flow used by the solvent impurity removal unit 400 to be recycled to the impurity removal unit 100 and the solvent removed in the solvent removal unit 200 are first stored in the circulating solvent tank 10, and then output from the circulating solvent tank 10 to the impurity removal unit 100 for use. Specifically, a solvent replenishment pipeline 117 can also be connected to the circulating solvent tank 10, and when the solvent needs to be replenished, the solvent is replenished to the circulating solvent tank 10 through the solvent replenishment pipeline 117.

[0076] Preferably, see Figure 1, the solvent impurity removal unit 400 specifically includes a first heat exchanger 5, a first cooler 6 and a first solvent recovery tower 4. The first solvent recovery tower 4 is used to distill the preheated impurity-containing solvent, and obtain a decontaminated solvent flow at the top of the tower and an impurity flow at the bottom of the tower through distillation separation. The impurity flow is discharged from the system after cooling, for example, the impurity flow is cooled in the third cooler 7. The first heat exchanger 5 is connected between the impurity removal unit 100 and the first solvent recovery tower 4, and is used to exchange heat between the impurity-containing solvent output from the impurity removal unit 100 and the impurity-free solvent flow output from the first solvent recovery tower 4, that is, the heat carried by the impurity-free solvent flow output from the first solvent recovery tower 4 is used to preheat the impurity-containing solvent output from the impurity removal unit 100; the impurity-containing solvent is preheated and then enters the first solvent recovery tower 4 for treatment. The first cooler 6 is connected to the first heat exchanger 5, and is used to cool the impurity-free solvent flow output from the first heat exchanger 5. Furthermore, the first cooler 6 is connected to the first solvent recovery tower 4 and the circulating solvent tank 10, respectively, so that the cooled impurity-removed solvent flow can be partially circulated to the first solvent recovery tower 4, and partially circulated to the circulating solvent tank 10. Through the above preferred manner, the heat carried by the top flow in the first solvent recovery tower 4 can be fully utilized to preheat the impurity-containing solvent to be treated with the help of this heat, which is beneficial to improving the impurity removal efficiency of the solvent and reducing energy consumption.

[0077] Preferably, see Figure 1 The solvent removal unit 200 specifically includes a heating kettle 8 and a second solvent recovery tower 9. The heating kettle 8 is used to heat and melt the mixture of naphthalene and thiophthalene outputted from the impurity removal unit 100, thereby obtaining a melted liquid. The second solvent recovery tower 9 is used to rectify the melted liquid obtained in the heating kettle 8, thereby removing the entrained solvent therein, thereby obtaining the removed solvent at the top of the tower, and obtaining the mixture of naphthalene and thiophthalene from which the solvent is removed in the tower bottom. The solvent outlet of the second solvent recovery tower 9 is connected to the solvent inlet of the circulating solvent tank 10, so that the removed solvent is stored in the circulating solvent tank 10 for reuse.

[0078] Preferably, see Figure 1, the impurity removal unit 100 specifically includes a first mixer 1, a crystallizer 2 and a filter 3. The first mixer 1 is used to mix a mixture of naphthalene and thiophthalene with a solvent to obtain a mixed solution. The crystallizer 2 is used to crystallize the mixed solution obtained by the first mixer 1 to obtain a crystallized liquid. The filter 3 is used to perform solid-liquid separation on the crystallized liquid to obtain a filter cake and a filtrate, wherein the filter cake is a mixture of naphthalene and thiophthalene that has been impurized, and the filtrate is a solvent containing impurities. Specifically, the filtrate outlet of the filter 3 is connected to the first heat exchanger 5 of the solvent impurity removal unit 400, and heat is exchanged with the top stream (the impurity-removed solvent stream) output by the first solvent recovery tower 4 in the first heat exchanger 5. Specifically, the filter cake outlet of the filter 3 is connected to the heating kettle 8 of the solvent removal unit 200, and the filter cake enters the heating kettle 8 for heating and melting.

[0079] Preferably, see Figure 1 The naphthalene refining unit 300 specifically includes a second mixer 14 and a phase separator 15, and preferably also includes a dryer 16. The second mixer 14 is used to mix and wash the mixture of naphthalene and the entrainer output by the azeotropic distillation tower 11 with water to obtain a mixed solution. The phase separator 15 is used to separate the mixed solution output by the second mixer 14 to obtain the aforementioned light phase component and heavy phase component. The dryer 16 is used to dry the light phase component obtained by the phase separator 15 to obtain a refined naphthalene product.

[0080] More preferably, see Figure 1 , the water flow outlet of the entrainer refining tower 17 and the water inlet of the second mixer 14 are connected through a water flow delivery pipeline, and along the flow direction of the water flow, the water flow delivery pipeline is provided with a second heat exchanger 12 and a water flow heater 19 in sequence. The second heat exchanger 12 is also connected to the thionaphthene material outlet of the azeotropic distillation tower 11. The second heat exchanger 12 is used to exchange heat between the water flow output from the entrainer refining tower 17 and the thionaphthene material output from the azeotropic distillation tower 11, that is, the water flow is heated by the thionaphthene material, and the water flow heated in the second heat exchanger 12 continues to be heated by the water flow heater 19, and then circulated to the second mixer 14 for use as washing water. By adopting the above preferred method, the heat carried in the thionaphthene material can be fully utilized, the heat required to be input to heat the water flow to the required temperature when the water flow is recycled can be reduced, and energy consumption can be reduced.

[0081] More preferably, see Figure 1 An azeotropic agent cooler 18 is provided between the azeotropic agent flow outlet of the azeotropic agent refining tower 17 and the azeotropic agent inlet of the azeotropic distillation tower 11, which is used to cool the azeotropic agent flow output from the azeotropic agent refining tower 17. The azeotropic agent flow output from the azeotropic agent refining tower 17 is cooled by the azeotropic agent cooler 18 and then enters the azeotropic distillation tower 11 for reuse.

[0082] In some specific embodiments, a second cooler 13 is further provided for cooling the thionaphthene material that has undergone heat exchange in the second heat exchanger 12, thereby obtaining a thionaphthene product for output outside the system.

[0083] In some specific embodiments, the phase separator 15 is also connected to a water replenishment pipeline 131 and an entrainer replenishment pipeline 132, and water and / or entrainer are replenished into the phase separator according to the liquid level of the phase separator 15 and the entrainer concentration in the heavy phase component 125; during operation, since the loss of solvent entrained in the product is greater than the loss of water, the entrainer concentration in the heavy phase component 125 will decrease during operation; for example, in some embodiments, during initial operation, the initial concentration of the entrainer in the heavy phase component 125 is 48%. As the process proceeds, when the gap between the entrainer concentration and the initial concentration increases (for example, the entrainer concentration decreases to about 40%), a certain amount of entrainer and water is calculated and added so that the entrainer concentration of the heavy phase component output by the phase separator 15 can be maintained at the initial concentration, thereby compensating for the loss of water and entrainer during operation, and at the same time restoring the liquid level of the heavy phase in the phase separator to the initial liquid level, which is beneficial to the stable operation of the system.

[0084] By adopting the above system of the present invention, not only can the thionaphthene product and the refined naphthalene product be synchronously separated from the mixture of naphthalene and thionaphthene based on a simple and easy-to-operate process flow; through a preferred embodiment, 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.

[0085] A second aspect of the present invention also provides a method for separating thionaphthene and naphthalene from a mixture of naphthalene and thionaphthene using the system described above, the method comprising the steps of:

[0086] 1) In the impurity removal unit 100, a mixture of naphthalene and thiophanate is mixed with a solvent to obtain a mixed solution, and then the mixed solution is crystallized, and the obtained crystal solution is subjected to solid-liquid separation to obtain a mixture of naphthalene and thiophanate that has been impurized, and a solvent containing impurities; wherein the solvent is preferably n-butanol; wherein the impurities are, for example, dimethylphenol, etc.;

[0087] 2) sending the impurity-removed mixture of naphthalene and thiophanate obtained in step 1) into a solvent removal unit 200 to remove the entrained solvent, thereby obtaining a mixture of naphthalene and thiophanate from which the solvent has been removed, and obtaining the removed solvent; recycling the removed solvent to the impurity removal unit 100 of step 1) for use as the solvent required for mixing;

[0088] 3) sending the mixture of naphthalene and thionaphthene from which the solvent has been removed obtained in step 2) into an azeotropic distillation tower 11, and performing azeotropic distillation with an entrainer to obtain a thionaphthene material and a mixture of naphthalene and the entrainer; the entrainer is preferably ethylene glycol; preferably, the thionaphthene material is cooled to obtain a thionaphthene product;

[0089] 4) sending the mixture of naphthalene and entrainer obtained in step 3) into a naphthalene refining unit 300 for washing and phase separation to obtain a light phase component rich in naphthalene and a heavy phase component containing water and entrainer; preferably, the light phase component is dried to obtain a refined naphthalene product.

[0090] 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, and the obtained products have good yield and purity.

[0091] Preferably, the method of the present invention further comprises step 5): sending the heavy phase component obtained in step 4) into the entrainer refining tower 17 for separation to obtain a water stream and an entrainer stream; recycling the water stream to the naphthalene refining unit 300 in step 4) for water washing, and recycling the entrainer stream to the azeotropic distillation tower 11 in 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.

[0092] In a preferred embodiment, the following steps are further included: sending the impurity-containing solvent obtained in step 1) to a solvent impurity removal unit 400 for treatment, thereby removing impurities in the solvent and obtaining a solvent stream with impurities removed; recycling at least part of the solvent stream with impurities removed to the impurity removal unit 100 in step 1) as the solvent required for mixing. By adopting this preferred method, the solvent can be recycled and the solvent cost can be reduced.

[0093] More specifically, the impurity-containing solvent obtained in step 1) is sent to the first solvent recovery tower 4 of the solvent impurity removal unit 400 for rectification, and a decontaminated solvent stream is obtained from the top of the tower, and an impurity stream is obtained from the bottom of the tower. The decontaminated solvent stream output from the first solvent recovery tower 4 and the impurity-containing solvent stream output from the impurity removal unit 100 are heat exchanged in the first heat exchanger 5, so that the impurity-containing solvent is preheated before entering the first solvent recovery tower 4; then the decontaminated solvent stream is sent to the first cooler 6 for cooling, and then part of the decontaminated solvent stream is circulated to the first solvent recovery tower 4, and part of the decontaminated solvent stream is circulated to the impurity removal unit 100.

[0094] Preferably, in step 2), the impurity-removed naphthalene and thiophanate mixture obtained in step 1) is first sent to the heating kettle 8 of the solvent removal unit 200 for heating and melting to obtain a melted liquid, preferably at a temperature of 82 to 90°C; then the melted liquid is sent to the second solvent recovery tower 9 of the solvent removal unit 200 for rectification to remove the solvent entrained in the melted liquid, thereby obtaining a solvent-removed naphthalene and thiophanate mixture and a removed solvent. The removed solvent is recycled to the impurity removal unit 100 of step 1) as a solvent required for mixing. The solvent-removed naphthalene and thiophanate mixture enters step 3) for further treatment.

[0095] Preferably, the water stream output from the azeotropic agent refining tower 17 in step 5) is first heat exchanged with the thionaphthene material output from the azeotropic distillation tower 11 in step 3) in the second heat exchanger 12, so that the aforementioned water stream is heated and heated, and then further heated by the water stream heater 19, and then sent to the naphthalene refining unit 300 in step 4) as water required for water washing. In some specific embodiments, after the thionaphthene material is heat exchanged and cooled in the second heat exchanger 12, it continues to enter the second cooler 13 for cooling to obtain the thionaphthene product.

[0096] In some embodiments, in step 5), the azeotropic agent stream output from the azeotropic agent refining tower 17 is first cooled in the azeotropic agent cooler 18 and then recycled to the azeotropic distillation tower 11 in step 3) for reuse.

[0097] In a preferred embodiment, in step 1), the mass ratio of the solvent to the mixture of naphthalene and thionaphthene is 1:1 to 4:1, preferably 1.5 to 3:1. The preferred mass ratio is used to further improve the purity and yield of refined naphthalene and thionaphthene products. Preferably, the crystallization conditions include: a cooling rate of 1 to 3 ° C / min, cooling to 8-30 ° C for crystal cultivation, preferably cooling to 10 to 25 ° C for crystal cultivation, and a crystal cultivation time of 15-45 min, preferably 20 to 40 min; using the preferred crystallization conditions, it is beneficial to further take into account the acquisition of refined naphthalene and thionaphthene products with better purity and yield.

[0098] In a preferred embodiment, in step 3), the mass ratio of the amount of the entrainer to the mixture of naphthalene and thionaphthene from which the solvent has been removed is 0.53 to 0.62:1, preferably 0.55 to 0.62:1, more preferably 0.55 to 0.60:1; the preferred mass ratio is used to further improve the purity and yield of the refined naphthalene and thionaphthene products. Preferably, the conditions for azeotropic distillation include: the top pressure of the azeotropic distillation tower 11 is 5 to 15 kPa, the top temperature is 110 to 125°C, and the reflux ratio is 5 to 10.

[0099] In a preferred embodiment, in step 4), the mass ratio of water used for water washing to the mixture of naphthalene and the entrainer is 0.8 to 1.5: 1. Preferably, the temperature of the water used for water washing is 70 to 80° C. Preferably, the temperature for phase separation is 80 to 85° C.

[0100] 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.

[0101] In some embodiments, in step 5), the operating conditions of the azeotropic agent refining tower 17 include: a tower top pressure of 20 to 30 kPa, a tower top temperature of 60 to 70° C., and a reflux ratio of 0.2 to 1.

[0102] 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.

[0103] In some embodiments, at the beginning of the process system operation, the required amount of solvent can be added to the circulating solvent tank 10, and the required amount of water and entrainer can be added to the phase separator 15 according to the amount of solvent, the amount of entrainer and the amount of water required for water washing, thereby providing the solvent, entrainer and water required for process startup.

[0104] The system and method of the present invention are exemplarily described below by way of examples:

[0105] Example 1

[0106] 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.

[0107] In this embodiment, the mixture of naphthalene and thioguanidine is the residual oil after the refined naphthalene is extracted by melt crystallization from the naphthalene fraction obtained from the tar processing device. The crystallization residual oil raw material contains 12.48wt% of thioguanidine, 83.52wt% of naphthalene, and 4.0wt% of impurities such as dimethylphenol. The flow rate is 1063kg / h.

[0108] The process is as follows:

[0109] The crystallization residual oil raw material 101 at 80°C and the circulating solvent 116 (n-butanol) from the circulating solvent tank 10 at 50°C are fully mixed in the first mixer 1, and the mass ratio of the solvent to the crystallization residual oil raw material is 2:1. A mixed solution at 54°C is obtained in the first mixer 1, and the mixed solution 102 enters the crystallizer 2 for cooling and crystallization, and the cooling rate is 2°C / min, and the temperature is cooled to 20°C crystal growing temperature, and the crystal growing time is 30min.

[0110] The crystal liquid 103 outputted from the crystallizer enters the filter 3 for solid-liquid separation, and impurities such as dimethylphenol enter the filtrate. The filtrate 104 outputted from the filter 3 enters the solvent impurity removal unit 400 for impurity removal treatment. The filter cake obtained from the filter 3 mainly contains naphthalene, thiophene and entrained solvent, and the filter cake 111 outputted from the filter 3 is sent to the solvent removal unit 200 for solvent removal treatment.

[0111] Specifically, the 20°C filtrate 104 output by the filter 3 is first heat-exchanged with the top vapor phase 106 (the impurity-removed solvent flow) of the first solvent recovery tower 4 in the first heat exchanger 5 to recover the heat of the top vapor phase material, and the 64°C hot filtrate 105 enters the middle of the first solvent recovery tower 4 for rectification and separation, and the top pressure of the first solvent recovery tower 4 is controlled to be 12kPa, the top temperature is 68°C, and the reflux ratio is 0.3. In the first solvent recovery tower 4, the gas-liquid mixture 107 obtained after the 68°C top vapor phase 106 (the impurity-removed solvent flow) recovers part of the heat in the first heat exchanger 5 enters the first cooler 6, is cooled to 50°C, part of the condensate 108 enters the top of the first solvent recovery tower 4 for reflux, and part of the condensate 109 enters the circulating solvent tank 10 as a recovered solvent. The bottom flow 110 (i.e., the impurity flow) of the first solvent recovery tower 4 is impurities such as dimethylphenol, enters the third cooler 7 to be cooled to 80°C, and the impurities 115 are discharged from the system.

[0112] Specifically, the filter cake 111 at 20°C outputted from the filter 3 enters the heating kettle 8 and is heated to 85°C to melt, and the obtained melted liquid is a mixture of naphthalene, thiophene and solvent, and the melted liquid 112 outputted from the heating kettle 8 is sent to the middle of the second solvent recovery tower 9 for rectification and separation, and the tower top pressure of the second solvent recovery tower 9 is controlled to be 22kPa, the tower top temperature is 80°C, and the reflux ratio is 0.8. A tower top material (i.e., the removed solvent) at 50°C is obtained after a condenser (not shown) configured at the top of the second solvent recovery tower 9, and the removed solvent 113 enters the circulating solvent tank 10 as a recovered solvent, and the tower bottom material is mainly a mixture of naphthalene and thiophene, that is, a mixture of naphthalene and thiophene from which the solvent is removed, and the mixture 114 of naphthalene and thiophene enters the middle and upper part of the azeotropic distillation tower 11.

[0113] The solvent in the circulating solvent tank 10 is used as the circulating solvent 116 to enter the first mixer 1 to mix with the crystallized residual oil feedstock. The solvent is replenished through the solvent replenishment pipeline 117 according to the liquid level of the circulating solvent tank 10. The continuous solvent replenishment amount is 0.6 kg / h.

[0114] In the azeotropic distillation tower 11, ethylene glycol is selected as the entrainer, and naphthalene and ethylene glycol can form a minimum azeotrope. In the azeotropic distillation tower 11, the mass ratio of the entrainer to the mixture of naphthalene and thionaphthene from which the solvent has been removed is controlled to be 0.56, and the tower top pressure of the azeotropic distillation tower 11 is controlled to be 10kPa, the tower top temperature is 115°C, and the reflux ratio is 6. After the azeotropic distillation separation process, the mixture 118 of naphthalene and the entrainer is discharged from the tower top, and the thionaphthene material 119 is discharged from the tower bottom. The tower bottom material 119 at 157°C (i.e., the thionaphthene material) is first heat-exchanged with the 60°C water stream 126 output 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.

[0115] After being discharged from the tower top of the azeotropic distillation tower 11, the mixture 118 of naphthalene and entrainer enters the second mixer 14; after the water stream 126 is heat-exchanged in the second heat exchanger 12 to obtain a water stream 129 of 68° C., it is further heated to 75° C. by the water stream heater 19, and the water stream 130 of 75° C. enters the second mixer 14 to be fully mixed with the mixture 118 of naphthalene and entrainer, and the mass ratio of water to the mixture of naphthalene and solvent is 1:1, and is washed by mixing with water, and the obtained mixture 122 enters the 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.

[0116] A light phase component and a heavy phase component are obtained in the phase separator 15, wherein the light phase component is mainly naphthalene, and the heavy phase component is mainly a mixture of water and an entrainer. 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 to be 95°C. After removing trace moisture by heating, a refined naphthalene product 124 is obtained.

[0117] The heavy phase component 125 (a mixture of water and entrainer) of the phase separator enters the middle part of 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. The water flow 126 separated by distillation is discharged from the top of the tower, and the entrainer flow 127 is discharged from the bottom of the tower. The water flow 126 discharged from the top of the tower is reused, and the entrainer flow 127 discharged from the bottom of the tower enters the entrainer cooler 18 to be cooled to 110°C, and enters the middle and upper part of the azeotropic distillation tower 11 as a circulating entrainer 128.

[0118] Water and entrainer are added to the phase separator according to the liquid level of the phase separator 15 and the concentration of the entrainer in the heavy phase component 125. In the initial operation of this embodiment, the concentration of the entrainer in the heavy phase component 125 is 48%. When the concentration of the entrainer drops to 40%, a certain amount of entrainer and water are added to make up for the loss of water and entrainer during the operation, and the concentration of the entrainer in the heavy phase component 125 is restored to 48%, and the liquid level of the heavy phase in the phase separator 15 is restored to the initial liquid level. In this embodiment, the continuous replenishment flow rates of water and entrainer are 0.7 kg / h and 1.3 kg / h, respectively.

[0119] Finally, this embodiment obtained a thionaphthene product with a purity of 99.02% and a refined naphthalene product with a purity of 99.27%, respectively. The yield of thionaphthene was 94.6%, and the yield of naphthalene was 97.8%.

[0120] 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.

[0121] Table 1 Main logistics flow and composition of Example 1

[0122]

[0123]

[0124] Table 2 Main equipment parameters of Example 1

[0125]

[0126] Example 2

[0127] The process is carried out in accordance with Example 1, except that in step 1), the mass ratio of n-butanol to the crystallized residual oil is 1:1.

[0128] Experimental results: the purity of the obtained thionaphthene product was 94.2%, and the yield was 94.3%; the purity of the obtained refined naphthalene product was 97.5%, and the yield was 97.3%.

[0129] Example 3

[0130] The process is carried out in accordance with Example 1, except that in step 1), the mass ratio of n-butanol to the crystallized residual oil is 4:1.

[0131] Experimental results: the purity of the obtained thionaphthene product was 98.7%, and the yield was 92.1%; the purity of the obtained refined naphthalene product was 98.9%, and the yield was 93.8%.

[0132] Example 4

[0133] The process is carried out in accordance with Example 1, except that in step 1), the crystal growing temperature is 8°C.

[0134] Experimental results: the purity of the obtained thionaphthene product was 98.2%, and the yield was 94.8%; the purity of the obtained refined naphthalene product was 98.8%, and the yield was 98.0%.

[0135] Example 5

[0136] The process is carried out in accordance with Example 1, except that in step 1), the crystal growing temperature is 30°C.

[0137] Experimental results: the purity of the obtained thionaphthene product was 98.3%, and the yield was 92.7%; the purity of the obtained refined naphthalene product was 98.6%, and the yield was 92.2%.

[0138] Example 6

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

[0140] Experimental results: the purity of the obtained thionaphthene product was 98.9%, and the yield was 91.5%; the purity of the obtained refined naphthalene product was 99.1%, and the yield was 93.4%.

[0141] Example 7

[0142] The process is carried out in accordance with Example 1, except that in step 1), the crystal growing time is 45 min.

[0143] Experimental results: the purity of the obtained thionaphthene product was 98.5%, and the yield was 94.7%; the purity of the obtained refined naphthalene product was 98.8%, and the yield was 97.9%.

[0144] Example 8

[0145] The method is carried out with reference to Example 1, except that in step 3), the mass ratio of the amount of the entrainer to the mass ratio of the mixture of naphthalene and thionaphthene from which the solvent is removed is 0.53:1.

[0146] Experimental results: the purity of the obtained thionaphthene product was 81.2%, and the yield was 94.5%; the purity of the obtained refined naphthalene product was 99.1%, and the yield was 88.5%.

[0147] Example 9

[0148] The method is carried out with reference to Example 1, except that in step 3), the mass ratio of the amount of the entrainer to the mass ratio of the mixture of naphthalene and thionaphthene from which the solvent is removed is 0.62:1.

[0149] Experimental results: the purity of the obtained thionaphthene product was 98.8%, and the yield was 94.4%; the purity of the obtained refined naphthalene product was 98.9%, and the yield was 97.2%.

[0150] 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 separating thionaphthene and naphthalene from a mixture of naphthalene and thionaphthene, characterized in that: The system comprises: An impurity removal unit is used to mix, crystallize and perform solid-liquid separation on the mixture of naphthalene and thionaphthene with a solvent to obtain a mixture of naphthalene and thionaphthene from which impurities have been removed and a solvent containing impurities; the solvent is preferably n-butanol; A solvent removal unit, used for separating the solvent entrained in the impurity-removed mixture of naphthalene and thionaphthene and obtaining the mixture of naphthalene and thionaphthene from which the solvent has been removed and obtaining the removed solvent; the solvent outlet of the solvent removal unit is connected to the impurity removal unit to circulate the removed solvent to the impurity removal unit; An azeotropic distillation tower, used for azeotropically distilling the mixture of naphthalene and thionaphthene from which the solvent has been removed and an entrainer, and obtaining a thionaphthene material and a mixture of naphthalene and the entrainer; the entrainer is preferably ethylene glycol; 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, it also includes an azeotrope refining tower, which is used to separate a water flow and an entrainer flow from the heavy phase component. The entrainer refining tower is connected to the naphthalene refining unit and the azeotropic distillation tower, respectively, so as to circulate the water flow to the naphthalene refining unit and circulate the entrainer flow to the azeotropic distillation tower.

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 impurity-containing solvent obtained by the impurity removal unit to obtain a solvent stream with impurities removed; a solvent outlet of the solvent impurity removal unit is connected to the impurity removal unit to circulate the solvent stream with impurities removed to the impurity removal unit; Preferably, the system further comprises a circulating solvent tank, the solvent outlet of the solvent impurity removal unit and the solvent outlet of the solvent removal unit are respectively connected to the solvent inlet of the circulating solvent tank, and the solvent outlet of the circulating solvent tank is connected to the solvent inlet of the impurity removal unit.

3. The system according to claim 2, characterized in that The solvent impurity removal unit includes a first heat exchanger, a first cooler and a first solvent recovery tower; The first solvent recovery tower is used to distill the preheated solvent containing impurities and obtain a solvent stream and an impurity stream that have been cleaned; The first heat exchanger is connected between the impurity removal unit and the first solvent recovery tower, and is used to perform heat exchange between the impurity-containing solvent output from the impurity removal unit and the impurity-removed solvent stream output from the first solvent recovery tower so as to preheat the impurity-containing solvent; The first cooler is connected to the first heat exchanger and is used to cool the impurity-removed solvent flow output by the first heat exchanger; Preferably, the first cooler is connected to the first solvent recovery tower and the circulating solvent tank, respectively, so as to circulate the cooled impurity-free solvent stream to the first solvent recovery tower and the circulating solvent tank.

4. The system according to claim 2, characterized in that The solvent removal unit includes a heating kettle and a second solvent recovery tower; the heating kettle is used to heat and melt the impurity-removed naphthalene and thiophthalene mixture output by the impurity removal unit to obtain a melt; the second solvent recovery tower is used to distill the melt to remove the entrained solvent; the solvent outlet of the second solvent recovery tower is connected to the solvent inlet of the circulating solvent tank.

5. The system according to claim 1, characterized in that The impurity removal unit includes a first mixer, a crystallizer and a filter; The first mixer is used to mix the mixture of naphthalene and thionaphthene with the solvent to obtain a mixed solution; The crystallizer is used to crystallize the mixed solution obtained by the first mixer to obtain a crystal solution; The filter is used to perform solid-liquid separation on the crystal liquid and obtain a filter cake and a filtrate, wherein the filter cake is a mixture of the impurity-removed naphthalene and thionaphthene, and the filtrate is the solvent containing impurities.

6. The system according to any one of claims 1 to 5, characterized in that: The naphthalene refining unit comprises a second mixer and a phase separator, and preferably further comprises a dryer; The second mixer is used to mix and wash the mixture of the naphthalene and the entrainer output from the azeotropic distillation tower with water to obtain a mixed liquid; The phase separator is used to separate the mixed liquid output from the second mixer into phases and obtain the light phase component and the heavy phase component; The dryer is used to dry the light phase component to obtain a refined naphthalene product; Preferably, the water flow outlet of the entrainer refining tower and the water inlet of the second mixer are connected by a water flow delivery pipeline, and along the flow direction of the water flow, a second heat exchanger and a water flow heater are sequentially arranged on the water flow delivery pipeline, and the second heat exchanger is used to exchange heat between the water flow output from the entrainer refining tower and the thionaphthene material output from the azeotropic distillation tower; Further preferably, an entrainer cooler is provided between the azeotropic agent flow outlet of the azeotropic agent refining tower and the azeotropic agent inlet of the azeotropic distillation tower, for cooling the azeotropic agent flow output from the azeotropic agent refining tower.

7. A method for separating 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) In an impurity removal unit, the mixture of naphthalene and thiophanate is mixed with a solvent to obtain a mixed solution, and then the mixed solution is crystallized, and the obtained crystal solution is subjected to solid-liquid separation to obtain a mixture of naphthalene and thiophanate that has been impurities removed and a solvent containing impurities; the solvent is preferably n-butanol; 2) sending the impurity-removed naphthalene and thiophanate mixture obtained in step 1) into a solvent removal unit to remove the entrained solvent, thereby obtaining a solvent-removed naphthalene and thiophanate mixture, and obtaining the removed solvent; recycling the removed solvent to the impurity removal unit in step 1) for use as the solvent required for the mixing; 3) feeding the solvent-free mixture of naphthalene and thionaphthene obtained in step 2) into an azeotropic distillation tower, and performing azeotropic distillation with an entrainer to obtain a thionaphthene material and a mixture of naphthalene and the entrainer; the entrainer is preferably ethylene glycol; preferably, cooling the thionaphthene material to obtain a thionaphthene product; 4) sending the mixture of the naphthalene and the entrainer obtained in step 3) into a naphthalene refining unit for washing and phase separation to obtain a light phase component rich in naphthalene and a heavy phase component comprising water and the entrainer; preferably, the light phase component is dried to obtain a refined naphthalene product; Preferably, the method further comprises step 5): The heavy phase component obtained in step 4) is sent to an entrainer refining tower for separation to obtain a water stream and an entrainer stream; the water stream is circulated to the naphthalene refining unit in step 4) for water washing, and the entrainer stream is circulated to the azeotropic distillation tower in step 3) for the 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 impurity removal unit to remove impurities in the solvent to obtain a de-impurified solvent stream; at least a portion of the de-impurified solvent stream is recycled to the de-impurity 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 solvent recovery tower of the solvent impurity removal unit for distillation to obtain the impurity-free solvent flow and the impurity flow; the impurity-free solvent flow output from the first solvent recovery tower and the impurity-containing solvent flow output from the impurity removal unit are heat exchanged in a first heat exchanger, and then the impurity-free solvent flow is sent to a first cooler for cooling, and then part of the impurity-free solvent flow is circulated to the first solvent recovery tower, and part of the impurity-free solvent flow is circulated to the impurity removal unit.

9. The method according to claim 7, characterized in that: In step 2), the impurity-free mixture of naphthalene and thiophanate obtained in step 1) is first sent to the heating kettle of the solvent removal unit for heating and melting to obtain a melted liquid, and the temperature of the heating and melting is preferably 82-90° C.; then the melted liquid is sent to the second solvent recovery tower of the solvent removal unit for distillation to remove the solvent entrained in the melted liquid, thereby obtaining the solvent-free mixture of naphthalene and thiophanate, and obtaining the removed solvent; And / or, the water stream output from the entrainer refining tower in step 5) is first heat-exchanged with the thionaphthene material output from the azeotropic distillation tower in step 3) in a second heat exchanger, and then heated by a water stream heater, and then fed into the naphthalene refining unit in step 4) to be used as the water required for the water washing; And / or, in step 5), the azeotropic agent stream output from the azeotropic agent refining tower is first cooled in an azeotropic agent cooler and then recycled to the azeotropic distillation tower in step 3).

10. The method according to claim 7, characterized in that In step 1), the mass ratio of the solvent to the mixture of naphthalene and thiophanate is 1:1-4:1, preferably 1.5-3:1; preferably, the crystallization conditions include: a cooling rate of 1-3°C / min, cooling to 8-30°C for crystal growth, preferably cooling to 10-25°C for crystal growth, and a crystal growth time of 15-45min, preferably 20-40min; And / or, in step 3), the mass ratio of the amount of the entrainer to the mixture of naphthalene and thionaphthene from which the solvent has been removed is 0.53 to 0.62:1, more preferably 0.55 to 0.60:1; preferably, the conditions for the azeotropic distillation include: the top pressure of the azeotropic distillation tower is 5 to 15 kPa, the top temperature is 110 to 125° C., and the reflux ratio is 5 to 10; And / or, in step 4), the mass ratio of water used for the water washing 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 is 70-80° C.; preferably, the temperature for the phase separation is 80-85° C.; And / or, in step 5), the operating conditions of the azeotropic agent refining tower include: tower top pressure 20-30 kPa, tower top temperature 60-70° C., and reflux ratio 0.2-1.

11. The method according to any one of claims 7 to 10, characterized in that: 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.

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