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

Abstract

The present application provides a system and method for separating sulfur indene and naphthalene from a mixture of sulfur indene and naphthalene, the system based on the present application can simultaneously obtain sulfur indene product and refined naphthalene product by treating the mixture of sulfur indene and naphthalene. The system comprises: a removal unit for mixing the mixture of sulfur indene and naphthalene with a solvent, crystallizing and solid-liquid separating; a solvent removal unit for separating the solvent entrained in the mixture of sulfur indene and naphthalene after removal; the solvent outlet of the solvent removal unit is connected with the removal unit; a azeotropic rectification tower for azeotropic rectification of the mixture of sulfur indene and naphthalene after removal of the solvent with an azeotropic agent; a naphthalene refining unit for water washing and phase separation of the mixture of naphthalene and azeotropic agent to obtain a light phase component rich in naphthalene and a heavy phase component containing water and azeotropic agent.

Description

TECHNICAL FIELD

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

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

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

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

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

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

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

[0008] CN108558591B discloses a naphthalene residual oil separation and recovery method, which removes light components through a light removal column, and the light removal column bottom material is sent to a naphthalene removal column for naphthalene and thionaphthene separation. The naphthalene component is obtained at the top of the naphthalene removal column, and the column bottom material is sent to a benzothiophene column. The benzothiophene column top component is sent to a static crystallizer, and thionaphthene product is obtained by crystallization in the static crystallizer. In this method, ordinary distillation is used in the naphthalene removal column to separate naphthalene and thionaphthene, which has high energy consumption.

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

[0010] The present application provides a system and a method for separating sulfur indene and naphthalene from a mixture of naphthalene and sulfur indene. The system based on the present application can process the mixture of naphthalene and sulfur indene with a simple and easy-to-operate process, and can simultaneously separate sulfur indene product and refined naphthalene product, and the solvent can be recycled, thereby reducing the separation cost.

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

[0012] In one aspect, the present application provides a system for separating sulfur indene and naphthalene from a mixture of naphthalene and sulfur indene, which comprises:

[0013] A impurity removal unit is used to mix the mixture of naphthalene and sulfur indene with a solvent, crystallize, and separate the solid and liquid to obtain a mixture of naphthalene and sulfur indene with impurities removed and a solvent containing impurities; the solvent is preferably n-butanol;

[0014] A solvent removal unit is used to separate the solvent entrained in the mixture of naphthalene and sulfur indene with impurities removed and obtain a mixture of naphthalene and sulfur indene with solvent removed and a removed solvent; the solvent outlet of the solvent removal unit is connected to the impurity removal unit to recycle the removed solvent to the impurity removal unit;

[0015] An azeotropic rectification column is used to azeotropically rectify the mixture of naphthalene and sulfur indene with solvent removed with an azeotrope agent and obtain a sulfur indene material and a mixture of naphthalene and azeotrope agent; the azeotrope agent is preferably ethylene glycol;

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

[0017] Preferably, an azeotrope agent refining column is further included, which is used to separate a water stream and an azeotrope agent stream from the heavy phase component, and the azeotrope agent refining column is connected to the naphthalene refining unit and the azeotropic rectification column respectively to recycle the water stream to the naphthalene refining unit and recycle the azeotrope agent stream to the azeotropic rectification column.

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

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

[0020] In some embodiments, the solvent impurity removal unit comprises a first heat exchanger, a first cooler and a first solvent recovery column.

[0021] The first solvent recovery column is configured to distill the preheated solvent containing impurities to obtain a solvent stream with impurities removed and an impurity stream.

[0022] The first heat exchanger is connected between the impurity removal unit and the first solvent recovery column, and is configured to exchange heat between the solvent containing impurities output from the impurity removal unit and the solvent stream with impurities removed output from the first solvent recovery column to preheat the solvent containing impurities.

[0023] The first cooler is connected to the first heat exchanger and is configured to cool the solvent stream with impurities removed output from the first heat exchanger.

[0024] Preferably, the first cooler is connected to the first solvent recovery column and the circulating solvent tank respectively to recycle the cooled solvent stream with impurities removed to the first solvent recovery column and the circulating solvent tank.

[0025] In some embodiments, the solvent removal unit comprises a heating kettle and a second solvent recovery column; the heating kettle is configured to melt the mixture of naphthalene and indene with impurities removed output from the impurity removal unit to obtain a melting liquid; and the second solvent recovery column is configured to distill the melting liquid to remove solvent entrained therein; and a solvent outlet of the second solvent recovery column is connected to a solvent inlet of the circulating solvent tank.

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

[0027] The first mixer is configured to mix the mixture of naphthalene and indene with the solvent to obtain a mixed liquid.

[0028] The crystallizer is configured to crystallize the mixed liquid obtained from the first mixer to obtain a crystallized liquid.

[0029] The filter is used for solid-liquid separation of the crystallization liquid and obtaining filter cake and filtrate, wherein the filter cake is the mixture of the impurity-removed naphthalene and sulfur indene, and the filtrate is the solvent containing impurities.

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

[0031] The second mixer is used for mixing the mixture of naphthalene and azeotrope agent output by the azeotrope rectification tower with water for water washing and obtaining a mixed liquid;

[0032] The phase separator is used for phase separation of the mixed liquid output by the second mixer and obtaining the light phase component and the heavy phase component;

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

[0034] Preferably, the water stream outlet of the azeotrope agent refining tower and the water inlet of the second mixer are connected by a water stream conveying pipeline, and along the flow direction of the water stream, a second heat exchanger and a water stream heater are sequentially arranged on the water stream conveying pipeline, and the second heat exchanger is used for heat exchange between the water stream output by the azeotrope agent refining tower and the sulfur indene material output by the azeotrope rectification tower;

[0035] Further preferably, an azeotrope agent cooler is arranged between the azeotrope agent stream outlet of the azeotrope agent refining tower and the azeotrope agent inlet of the azeotrope rectification tower, and is used for cooling the azeotrope agent stream output by the azeotrope agent refining tower.

[0036] The present application also provides a method for separating sulfur indene and naphthalene from a mixture of naphthalene and sulfur indene by using the system described above, and the method comprises the following steps:

[0037] 1) In the impurity removal unit, the mixture of naphthalene and sulfur indene is mixed with a solvent to obtain a mixed liquid, and then the mixed liquid is crystallized, and the obtained crystallization liquid is subjected to solid-liquid separation to obtain a mixture of impurity-removed naphthalene and sulfur indene and a solvent containing impurities; the solvent is preferably n-butanol;

[0038] 2) The mixture of impurity-removed naphthalene and sulfur indene obtained in step 1) is sent to a solvent removal unit to remove the entrained solvent to obtain a mixture of naphthalene and sulfur indene from which the solvent is removed, and to obtain removed solvent; the removed solvent is recycled to the impurity removal unit of step 1) for use as a solvent required for the mixing;

[0039] 3) sending the mixture of naphthalene and thionaphthene, from which the solvent is removed, obtained in step 2) into an azeotropic rectification tower to carry out azeotropic rectification with an azeotropic agent, to obtain a thionaphthene material and a mixture of naphthalene and azeotropic agent; the azeotropic agent is preferably ethylene glycol; preferably, the thionaphthene material is cooled to obtain a thionaphthene product;

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

[0041] Preferably, step 5) is further included:

[0042] sending the heavy phase component obtained in step 4) into an azeotropic agent refining tower to separate, to obtain a water stream and an azeotropic agent stream; the water stream is recycled to the naphthalene refining unit in step 4) for water washing, and the azeotropic agent stream is recycled to the azeotropic rectification tower in step 3) for the azeotropic rectification.

[0043] Preferably, the following steps are further included:

[0044] sending the solvent containing impurities obtained in step 1) into a solvent impurity removal unit to remove the impurities in the solvent, to obtain a solvent stream from which the impurities are removed; at least part of the solvent stream from which the impurities are removed is recycled to the impurity removal unit in step 1) to be used as the solvent required for carrying out the mixing;

[0045] Preferably, the solvent containing impurities obtained in step 1) is sent into a first solvent recovery tower of the solvent impurity removal unit to carry out rectification, to obtain the solvent stream from which the impurities are removed and an impurity stream; the solvent stream from which the impurities are removed output from the first solvent recovery tower and the solvent containing impurities output from the impurity removal unit are exchanged in a first heat exchanger, then the solvent stream from which the impurities are removed is sent into a first cooler to be cooled, and then part of the solvent stream from which the impurities are removed is recycled to the first solvent recovery tower as reflux, and part of the solvent stream from which the impurities are removed is recycled to the impurity removal unit.

[0046] Further, in step 2), the mixture of naphthalene and thionaphthene, from which the impurities are removed, obtained in step 1) is first sent into a heating kettle of the solvent removal unit to carry out heating and melting, to obtain a molten liquid, preferably the temperature of the heating and melting is 82-90°C; then the molten liquid is sent into a second solvent recovery tower of the solvent removal unit to carry out rectification, to remove the solvent entrained in the molten liquid, to obtain the mixture of naphthalene and thionaphthene from which the solvent is removed, and to obtain the removed solvent;

[0047] And / or, the water stream outputted from the azeotrope refining tower in step 5) is firstly exchanged heat with the sulfur indene material outputted from the azeotrope rectifying tower in step 3) in a second heat exchanger, then heated by a water stream heater, and then sent into the naphthalene refining unit in step 4) to be used as the water required by the water washing;

[0048] And / or, in step 5), the azeotrope stream outputted from the azeotrope refining tower is firstly cooled in an azeotrope cooler, and then recycled into the azeotrope rectifying tower in step 3).

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

[0050] Preferably, in step 3), the mass ratio of the azeotrope to the mixture of naphthalene and sulfur indene from which the solvent is removed is 0.53-0.62:1, more preferably 0.55-0.60:1; preferably, the azeotrope rectification conditions include: the overhead pressure of the azeotrope rectifying tower is 5-15kPa, the overhead temperature is 110-125℃, and the reflux ratio is 5-10.

[0051] Preferably, in step 4), the mass ratio of the water used for the water washing to the mixture of naphthalene and azeotrope is 0.8-1.5:1; preferably, the temperature of the water used for the water washing is 70-80℃; preferably, the temperature for the phase separation is 80-85℃.

[0052] Preferably, in step 5), the operating conditions of the azeotrope refining tower include: the overhead pressure is 20-30kPa, the overhead temperature is 60-70℃, and the reflux ratio is 0.2-1.

[0053] In the present application, in step 1), the mixture of naphthalene and sulfur indene is industrial naphthalene, or a naphthalene fraction separated from tar distillation, or naphthalene residual oil after melt crystallization of the industrial naphthalene or the naphthalene fraction.

[0054] The technical scheme provided by the present application has the following beneficial effects:

[0055] (1) The system of the present application is used for treating the mixture of naphthalene and sulfur indene, which not only has a simple and easy treatment process, but also can well separate the sulfur indene and naphthalene with similar boiling points, and can simultaneously obtain refined naphthalene product and sulfur indene product; at the same time, the system of the present application can recycle the solvent, which can greatly reduce the cost of the solvent.

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

[0057] (3) In some preferred embodiments, the impurity-removed solvent obtained from the solvent impurity removal unit is first subjected to heat exchange with the impurity-containing solvent output from the impurity removal unit, and then is reused, which can make full use of the heat carried by the impurity-removed solvent; in some preferred embodiments, the sulfur indene material output from the azeotropic distillation tower is subjected to heat exchange with the water stream output from the entrainer refining tower before being output as a subsequent product, which can make full use of the heat carried by the sulfur indene material. The system adopting the preferred embodiments can make integrated use of the energy in each system, thereby reducing the energy consumption.

[0058] (4) The method for separating sulfur indene and naphthalene from a mixture of naphthalene and sulfur indene based on the system of the present application comprises the following steps: first, the mixture of naphthalene and sulfur indene is mixed with a solvent (preferably n-butanol) to remove impurities by crystallization, and then, after removing the solvent, the mixture is subjected to azeotropic distillation with an entrainer (preferably ethylene glycol), to obtain a sulfur indene material and a mixture of naphthalene and entrainer, wherein the mixture of naphthalene and entrainer can obtain refined naphthalene products after water washing and phase separation; the method of the present application can separate sulfur indene products and refined naphthalene from the mixture of naphthalene and sulfur indene with good yield and purity.

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

[0060] Figure 1 Fig. 1 shows a system schematic diagram for separating sulfur indene and naphthalene from a mixture of naphthalene and sulfur indene in an embodiment.

[0061] Figure 2 is not shown Figure 1 in the dashed box.

[0062] PARTIAL LIST OF REFERENCE NUMBERS:

[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 column 4, first heat exchanger 5, first cooler 6, third cooler 7, heating kettle 8, second solvent recovery column 9, circulating solvent tank 10, azeotrope rectification column 11, second heat exchanger 12, second cooler 13, second mixer 14, phase separator 15, dryer 16, azeotrope refining column 17, azeotrope cooler 18, water stream heater 19, solvent supplement pipeline 117, water supplement pipeline 131, azeotrope supplement pipeline 132. DETAILED DESCRIPTION

[0064] In order to facilitate the understanding of the present application, the present application will be further described below in conjunction with examples. It should be understood that the following examples are only for better understanding of the present application, and do not mean that the present application is limited to the following examples only.

[0065] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items. The terms "first", "second", and the like as mentioned in the specification and / or claims do not denote any

[0066] If the specific experimental steps or conditions are not specified in the examples, they can be operated according to the corresponding conventional experimental steps or conditions in the technical field. If the reagents or instruments used are not specified by the manufacturer, they are all conventional products that can be obtained by purchase.

[0067] The present application provides a system for separating sulfur indene and naphthalene from a mixture of sulfur indene and naphthalene, referring to Figure 1 、 2 wherein Figure 2 and Figure 1 are the same, except that the dashed box in Figure 1 is not marked, so as to more clearly show the contents of the figure. The system of the present application mainly comprises: impurity removal unit 100, solvent removal unit 200, azeotrope rectification column 11, naphthalene refining unit 300, and preferably further comprises azeotrope refining column 17.

[0068] The impurity removal unit 100 is used to mix the mixture of naphthalene and sulfur indene with the solvent, crystallize and solid-liquid separate, remove the impurities therein, so as to obtain the mixture of naphthalene and sulfur indene after impurity removal, and obtain the solvent containing impurities; preferably in the 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 thionaphthene obtained from the impurity removal unit 100, so as to obtain a mixture of naphthalene and thionaphthene from which the solvent is removed, and to obtain the removed solvent; the solvent outlet of the solvent removal unit 200 is connected to the impurity removal unit 100, the connection includes direct or indirect connection, the removed solvent is output from the solvent outlet of the solvent removal unit 200, and then is recycled to the impurity removal unit 100 as the solvent required for mixing.

[0070] The azeotropic rectification tower 11 is used for azeotropic rectification of the mixture of naphthalene and thionaphthene from which the solvent is removed obtained from the solvent removal unit 200 and the azeotropic agent, so that naphthalene and thionaphthene are separated by azeotropic rectification, and a thionaphthene material is obtained at the tower bottom, and a mixture of naphthalene and azeotropic agent is obtained at the tower top; preferably, the azeotropic agent is ethylene glycol.

[0071] The naphthalene refining unit 300 is used for water washing and phase separation of the mixture of naphthalene and azeotropic agent obtained from the azeotropic rectification tower 11, so as to obtain a light phase component rich in naphthalene, and to obtain a heavy phase component containing water and azeotropic agent. The light phase component rich in naphthalene can obtain refined naphthalene product after drying.

[0072] The azeotropic agent refining tower 17 is used for refining separation of the heavy phase component obtained from the naphthalene refining unit 300, which can be distillation separation, so as to separate water and azeotropic agent therefrom, to obtain a water stream at the tower top, and to obtain an azeotropic agent stream at the tower bottom. The water stream outlet of the azeotropic agent refining tower 17 is connected to the naphthalene refining unit 300, and the azeotropic agent stream outlet of the azeotropic agent refining tower 17 is connected to the azeotropic rectification tower 11, the above-mentioned connection includes direct connection or indirect connection, so as to recycle the water stream to the naphthalene refining unit 300 as washing water, and to recycle the azeotropic agent stream to the azeotropic rectification tower 11 for azeotropic rectification.

[0073] By the system of the present application, the mixture of naphthalene and thionaphthene is mixed with solvent (preferably n-butanol), crystallized, and then the crystallized liquid is subjected to solid-liquid separation. The obtained mixture of naphthalene and thionaphthene after impurity removal is subjected to solvent removal in the solvent removal unit 200, the removed solvent is reused to the impurity removal unit 100, and then the mixture of naphthalene and thionaphthene after solvent removal is subjected to azeotropic rectification with azeotropic agent (preferably butanediol) in the azeotropic rectification column 11, so that naphthalene and thionaphthene are separated therefrom. The separated thionaphthene material is cooled to obtain thionaphthene product. The mixture of naphthalene and azeotropic agent after separation is subjected to water washing and phase separation to obtain a component rich in naphthalene, which is dried to obtain refined naphthalene product. By the system, naphthalene and thionaphthene can be simultaneously separated to obtain products by a simple process flow, and the utilization rate of solvent is high. Further, the heavy phase component obtained from the naphthalene refining unit 300 is treated by the azeotropic agent refining column 17, and water stream that can be reused to the naphthalene refining unit 300 and azeotropic agent stream that can be reused to the azeotropic rectification column 11 are obtained, which can greatly save the water consumption of the system and improve the utilization rate of azeotropic agent, and reduce the processing cost.

[0074] Referring to Figure 1 Preferably, the system of the present application further comprises a solvent impurity removal unit 400 for removing impurities from the solvent containing impurities obtained from the impurity removal unit 100, so as to obtain a solvent stream after impurity removal. The solvent outlet of the solvent impurity removal unit 400 is connected to the impurity removal unit 100, which includes direct connection or indirect connection, so that the solvent stream after impurity removal can be recycled to the impurity removal unit 100. By this preferred mode, the utilization rate of solvent of the system can be improved, and the processing cost can be reduced.

[0075] Preferably, referring to Figure 1 The system of the present application further comprises 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 solvent stream after impurity removal for reuse to the impurity removal unit 100 and the removed solvent 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 supplement pipeline 117 can also be connected to the circulating solvent tank 10, and when it is necessary to supplement solvent, the solvent is supplemented to the circulating solvent tank 10 through the solvent supplement pipeline 117.

[0076] Preferably, referring to Figure 1The solvent impurity removal unit 400 specifically comprises a first heat exchanger 5, a first cooler 6 and a first solvent recovery column 4. The first solvent recovery column 4 is used to rectify the preheated solvent containing impurities, and the solvent containing impurities is separated by rectification to obtain a solvent stream with impurities removed at the top of the column and an impurity stream at the bottom of the column. The impurity stream is discharged outside the system after being cooled, for example, in a third cooler 7. The first heat exchanger 5 is connected between the impurity removal unit 100 and the first solvent recovery column 4, and is used to exchange heat between the solvent containing impurities output by the impurity removal unit 100 and the solvent stream with impurities removed output by the first solvent recovery column 4, i.e. using the heat carried by the solvent stream with impurities removed output by the first solvent recovery column 4 to preheat the solvent containing impurities output by the impurity removal unit 100; the solvent containing impurities is preheated before entering the first solvent recovery column 4 for treatment. The first cooler 6 is connected with the first heat exchanger 5, and is used to cool the solvent stream with impurities removed output by the first heat exchanger 5. Further, the first cooler 6 is connected with the first solvent recovery column 4 and the circulating solvent tank 10, respectively, so that the cooled solvent stream with impurities removed can be partially circulated to the first solvent recovery column 4 and partially circulated to the circulating solvent tank 10. By the above preferred mode, the heat carried by the top stream of the first solvent recovery column 4 can be fully utilized to preheat the solvent containing impurities to be treated, which is beneficial to improve the impurity removal efficiency of the solvent and reduce energy consumption.

[0077] Preferably, referring to Figure 1 The solvent removal unit 200 specifically comprises a heating kettle 8 and a second solvent recovery column 9. The heating kettle 8 is used to heat and melt the mixture of naphthalene and sulfolene output by the impurity removal unit 100, thereby obtaining a molten liquid. The second solvent recovery column 9 is used to rectify the molten liquid obtained in the heating kettle 8, thereby removing the solvent entrained therein, thereby obtaining the removed solvent at the top of the column and the mixture of naphthalene and sulfolene with the solvent removed at the bottom of the column. The solvent outlet of the second solvent recovery column 9 is connected with 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, referring to Figure 1The impurity removal unit 100 specifically comprises a first mixer 1, a crystallizer 2 and a filter 3. The first mixer 1 is used for mixing the mixture of naphthalene and thionaphthene with solvent, thereby obtaining a mixed solution. The crystallizer 2 is used for crystallizing the mixed solution obtained by the first mixer 1, thereby obtaining a crystallized solution. The filter 3 is used for separating the crystallized solution into a filter cake and a filtrate, wherein the filter cake is the mixture of naphthalene and thionaphthene after impurity removal, and the filtrate is the solvent containing impurities. Specifically, the filtrate outlet of the filter 3 is connected with the first heat exchanger 5 of the solvent impurity removal unit 400, and the overhead stream (impurity-removed solvent stream) output by the first solvent recovery column 4 is exchanged heat in the first heat exchanger 5. Specifically, the filter cake outlet of the filter 3 is connected with 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, referring to Figure 1 The naphthalene refining unit 300 specifically comprises a second mixer 14 and a phase separator 15, and preferably further comprises a dryer 16. The second mixer 14 is used for mixing the mixture of naphthalene and azeotrope agent output by the azeotrope rectification column 11 with water for water washing, thereby obtaining a mixed solution. The phase separator 15 is used for separating the mixed solution output by the second mixer 14 into the aforementioned light phase component and heavy phase component. The dryer 16 is used for drying the light phase component obtained by the phase separator 15, thereby obtaining refined naphthalene product.

[0080] Further preferably, referring to Figure 1 The water stream outlet of the azeotrope refining column 17 and the water inlet of the second mixer 14 are connected by a water stream conveying pipeline, and along the flow direction of the water stream, the water stream conveying pipeline is sequentially provided with the second heat exchanger 12 and a water stream heater 19. The second heat exchanger 12 is also connected with the thionaphthene material outlet of the azeotrope rectification column 11. The second heat exchanger 12 is used for exchanging heat between the water stream output by the azeotrope refining column 17 and the thionaphthene material output by the azeotrope rectification column 11, i.e. the water stream is heated by the thionaphthene material, and the heated water stream obtained in the second heat exchanger 12 continues to be heated by the water stream heater 19, and then is recycled to the second mixer 14 for use as water washing water. By using the above preferred mode, the heat carried by the thionaphthene material can be fully utilized, the heat input required for heating the water stream to the required temperature during recycling of the water stream can be reduced, and the energy consumption can be reduced.

[0081] Further preferably, referring to Figure 1 The azeotrope agent stream outlet of the azeotrope refining column 17 and the azeotrope agent inlet of the azeotrope rectification column 11 are provided with an azeotrope agent cooler 18 for cooling the azeotrope agent stream output by the azeotrope refining column 17, and the azeotrope agent stream output by the azeotrope refining column 17 is cooled by the azeotrope agent cooler 18 before being recycled to the azeotrope rectification column 11.

[0082] In some embodiments, a second cooler 13 is further provided for cooling the thiophene material which has been subjected to heat exchange in the second heat exchanger 12, so as to obtain a thiophene product for outputting out of the system.

[0083] In some embodiments, the water supplement pipeline 131 and the azeotrope supplement pipeline 132 are further connected to the phase separator 15, and water and / or azeotrope are supplemented into the phase separator according to the liquid level of the phase separator 15 and the azeotrope concentration in the heavy phase component 125; during operation, the azeotrope concentration in the heavy phase component 125 decreases because the loss of the product entrained solvent is greater than the loss of water; for example, in some embodiments, the initial azeotrope concentration in the heavy phase component 125 is 48% during initial operation, and as the process proceeds, when the difference between the azeotrope concentration and the initial concentration increases (for example, the azeotrope concentration decreases to about 40%, etc.), a certain amount of azeotrope and water is added by calculation to enable the azeotrope concentration of the heavy phase component output by the phase separator 15 to remain at the initial concentration, thereby compensating for the loss of water and azeotrope during operation, and at the same time, the liquid level of the heavy phase in the phase separator is restored to the initial liquid level, which is conducive to stable operation of the system.

[0084] By using the above-mentioned system of the present application, not only can thiophene product and refined naphthalene product be simultaneously separated from the mixture of naphthalene and thiophene based on a simple and easy-to-operate process flow, but also the solvent, azeotrope, and water can be fully recycled in the system, and the heat in the system can be integratedly utilized, which is conducive to greatly reducing the processing cost and reducing energy consumption.

[0085] The second aspect of the present application further provides a method for separating thiophene and naphthalene from a mixture of naphthalene and thiophene by using the system described above, and the method comprises the following steps:

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

[0087] 2) The mixture of naphthalene and thiophene after impurity removal obtained in step 1) is sent to the solvent removal unit 200 to remove the entrained solvent, to obtain a mixture of naphthalene and thiophene after solvent removal, and to obtain removed solvent; and the removed solvent is recycled to the impurity removal unit 100 in step 1) to be used as the solvent required for mixing;

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

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

[0090] By the above method, the thionaphthene product and the refined naphthalene product can be simultaneously separated from the mixture of naphthalene and thionaphthene in a simple process flow, and the obtained products have good yield and purity.

[0091] Preferably, the method of the present application further comprises step 5): sending the heavy phase component obtained in step 4) into the azeotropic agent refining tower 17 to perform separation, to obtain a water stream and an azeotropic agent stream; the water stream is recycled to the naphthalene refining unit 300 in step 4) for water washing, and the azeotropic agent stream is recycled to the azeotropic rectification tower 11 in step 3) for azeotropic rectification. By the preferred mode, the azeotropic agent and water can be recycled, saving the water consumption of the process and reducing the cost of the azeotropic agent.

[0092] In a preferred embodiment, the method further comprises the following steps: sending the solvent containing impurities obtained in step 1) into the solvent impurity removal unit 400 for treatment, to remove the impurities in the solvent, to obtain a solvent stream with impurities removed; and 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 the preferred mode, the solvent can be recycled, reducing the cost of the solvent.

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

[0094] Preferably, in step 2), the impurity-removed mixture of naphthalene and thionaphthalene obtained in step 1) is first fed into the heating kettle 8 of the solvent removal unit 200 to be heated and melted to obtain a melted liquid, and the heating and melting temperature is preferably 82-90°C; then the melted liquid is fed into the second solvent recovery column 9 of the solvent removal unit 200 to be rectified to remove the solvent entrained in the melted liquid, thereby obtaining a mixture of naphthalene and thionaphthalene from which the solvent is removed, and also obtaining the removed solvent. The removed solvent is reused in the impurity removal unit 100 of step 1) as the solvent required for mixing. The mixture of naphthalene and thionaphthalene from which the solvent is removed is then subjected to further processing in step 3).

[0095] Preferably, in step 5), the water stream output from the azeotrope refining column 17 is first subjected to heat exchange with the thionaphthalene material output from the azeotrope rectification column 11 in the second heat exchanger 12, so that the aforementioned water stream is heated and warmed up, and then is further heated by the water stream heater 19, and is then fed into the naphthalene refining unit 300 of step 4) to be used as the water required for water washing. In some specific embodiments, after being cooled by heat exchange in the second heat exchanger 12, the thionaphthalene material is further cooled in the second cooler 13 to obtain the thionaphthalene product.

[0096] In some embodiments, in step 5), the azeotrope stream output from the azeotrope refining column 17 is first cooled in the azeotrope cooler 18, and is then recycled to the azeotrope rectification column 11 of step 3) for reuse.

[0097] In the preferred embodiments, in step 1), the mass ratio of the solvent to the aforementioned mixture of naphthalene and thionaphthalene is 1:1-4:1, and is preferably 1.5-3:1. The use of the preferred mass ratio is conducive to further improving the purity and yield of the refined naphthalene and thionaphthalene products. Preferably, the crystallization conditions include a cooling rate of 1-3°C / min, cooling to 8-30°C for crystal growth, and preferably cooling to 10-25°C for crystal growth, and the crystal growth time is 15-45 min, and is preferably 20-40 min. The use of the preferred crystallization conditions is conducive to further achieving the refined naphthalene and thionaphthalene products with better purity and yield.

[0098] In the preferred embodiments, in step 3), the mass ratio of the azeotrope to the aforementioned mixture of naphthalene and thionaphthalene from which the solvent is removed is 0.53-0.62:1, and is preferably 0.55-0.62:1, and is more preferably 0.55-0.60:1. The use of the preferred mass ratio is conducive to further improving the purity and yield of the refined naphthalene and thionaphthalene products. Preferably, the azeotrope rectification conditions include a column top pressure of the azeotrope rectification column 11 of 5-15 kPa, a column top temperature of 110-125°C, and a reflux ratio of 5-10.

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

[0100] By using the method of the present application in combination with the preferred process conditions, the product of sulfur indene and the product of refined naphthalene with higher purity and higher recovery rate can be obtained.

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

[0102] In the present application, the mixture of naphthalene and sulfur indene can be industrial naphthalene, or naphthalene fraction obtained after tar distillation, or naphthalene residual oil obtained after melt crystallization of industrial naphthalene or naphthalene fraction.

[0103] In some embodiments, at the beginning of the operation of the process system, the required amount of solvent can be added to circulating solvent tank 10, and the required amount of water and azeotrope agent can be added to phase separator 15, so as to provide the required solvent, azeotrope agent and water for the start of the process.

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

[0105] Example 1

[0106] The process system used in this example is shown in Figure 1 For the system and method not specifically described, please refer to the foregoing description, which will not be described one by one.

[0107] In this example, the mixture of naphthalene and sulfur indene is the crystallization residual oil obtained after extraction of refined naphthalene from naphthalene fraction from a tar processing device by melt crystallization. The crystallization residual oil contains 12.48wt% of sulfur indene, 83.52wt% of naphthalene, and 4.0wt% of impurities such as dimethyl phenol, and 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 circulating solvent tank 10 at 50°C are fully mixed in the first mixer 1, and the mass ratio of solvent to crystallization residual oil raw material is 2:1. The mixed liquid 102 obtained in the first mixer 1 is 54°C, and the mixed liquid enters the crystallizer 2 for cooling crystallization, the cooling rate is 2°C / min, the temperature is lowered to 20°C for crystal growth, and the crystal growth time is 30 min.

[0110] The crystallizer output crystallization liquid 103 enters the filter 3 for solid-liquid separation, and impurities such as dimethyl phenol enter the filtrate. The filter 3 output filtrate 104 enters the solvent impurity removal unit 400 for impurity removal treatment. The filter cake obtained by the filter 3 mainly contains naphthalene, indene and entrained solvent, and the filter cake 111 output by the filter 3 is sent to the solvent removal unit 200 for solvent removal treatment.

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

[0112] Specifically, the 20℃ filter cake 111 output by the filter 3 enters the heating kettle 8 and is heated to 85℃ to melt, obtaining a mixed liquid of naphthalene, indene and solvent. The melted liquid 112 output by the heating kettle 8 is sent to the middle part of the second solvent recovery column 9 for rectification separation. The overhead pressure of the second solvent recovery column 9 is controlled at 22kPa, the overhead temperature is 80℃, and the reflux ratio is 0.8. A condenser (not shown in the figure) is arranged at the top of the second solvent recovery column 9 to obtain 50℃ overhead material (i.e. removed solvent). The removed solvent 113 enters the circulating solvent tank 10 as recovered solvent, and the column bottom material mainly contains a mixture of naphthalene and indene, i.e. a mixture of naphthalene and indene from which the solvent has been removed. The mixture of naphthalene and indene 114 enters the upper middle part of the azeotropic rectification column 11.

[0113] The solvent in the circulating solvent tank 10 enters the first mixer 1 as circulating solvent 116 and is mixed with the crystallization residue raw material. The solvent is continuously supplemented through the solvent supplement line 117 according to the liquid level of the circulating solvent tank 10, and the continuous supplement amount of the solvent is 0.6kg / h.

[0114] In the azeotropic distillation column 11, ethylene glycol is selected as the azeotrope agent, naphthalene and ethylene glycol can form the lowest azeotrope, in the azeotropic distillation column 11, the mass ratio of the azeotrope agent and the mixture of the aforementioned naphthalene and sulfolane from which the solvent is removed is controlled to be 0.56, the overhead pressure of the azeotropic distillation column 11 is controlled to be 10 kPa, the overhead temperature is controlled to be 115°C, and the reflux ratio is controlled to be 6. Through the azeotropic distillation separation process, the mixture of naphthalene and azeotrope agent 118 is discharged from the top of the column, and the sulfolane material 119 is discharged from the bottom of the column. The column bottom material 119 (i.e. the sulfolane material) at 157°C is first heat exchanged with the water stream 126 at 60°C output from the top of the azeotrope agent refining column 17 in the second heat exchanger 12, the heat carried by the sulfolane material is recovered, and the sulfolane material 120 after being cooled to 60°C is further cooled to 40°C through the second cooler 13 to obtain the refined sulfolane product 121.

[0115] The mixture of naphthalene and azeotrope agent 118 is discharged from the top of the azeotropic distillation column 11 and enters the second mixer 14; after the water stream 126 is heat exchanged in the second heat exchanger 12 to obtain the water stream 129 at 68°C, it continues to be further heated to 75°C through the water stream heater 19, and the water stream 130 at 75°C enters the second mixer 14 and is fully mixed with the aforementioned mixture of naphthalene and azeotrope agent 118, and the mass ratio of water to the aforementioned mixture of naphthalene and solvent is 1:1, through mixing with water, the obtained mixture 122 enters the phase separator 15 for phase separation, the temperature of the phase separator is controlled to be 82°C, and the pressure is controlled to be 101.325 kPa.

[0116] The light phase component and the 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 azeotrope agent, the light phase component 123 enters the dryer 16, the pressure of the dryer 16 is controlled to be 40 kPa, and the temperature is controlled to be 95°C, and after being heated to remove a small amount of water, the refined naphthalene product 124 is obtained.

[0117] The heavy phase component 125 (a mixture of water and azeotrope agent) of the phase separator enters the middle part of the azeotrope agent refining column 17, the overhead pressure of the azeotrope agent refining column 17 is controlled to be 22 kPa, the overhead temperature is controlled to be 62°C, and the reflux ratio is controlled to be 0.3, the water stream 126 separated through rectification is discharged from the top of the column, the azeotrope agent stream 127 is discharged from the bottom of the column, the water stream 126 discharged from the top of the column is recycled, and the azeotrope agent stream 127 discharged from the bottom of the column is cooled to 110°C in the azeotrope agent cooler 18 and enters the middle and upper part of the azeotropic distillation column 11 as the circulating azeotrope agent 128.

[0118] The water and the entrainer are continuously supplemented into 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 the present embodiment, the concentration of the entrainer in the heavy phase component 125 is 48%, and when the concentration of the entrainer decreases to 40%, a certain amount of the entrainer and water are added to compensate for the loss of the water and the entrainer during the operation and to restore the concentration of the entrainer in the heavy phase component 125 to 48% and the liquid level of the heavy phase in the phase separator 15 to the initial liquid level. In the present embodiment, the continuous supplementing flow rates of the water and the entrainer are 0.7 kg / h and 1.3 kg / h, respectively.

[0119] Finally, the product of indenothiophene with a purity of 99.02% and the product of refined naphthalene with a purity of 99.27% are obtained in the present embodiment, and the yield of indenothiophene is 94.6% and the yield of naphthalene is 97.8%.

[0120] In the present embodiment, the flow rates of the main materials and the contents of the main components are shown in Table 1, and the parameters of the columns are shown in Table 2.

[0121] Table 1 Flow rates and compositions of main streams in Example 1

[0122]

[0123]

[0124] Table 2 Parameters of main equipment in Example 1

[0125]

[0126] Example 2

[0127] The procedure of Example 1 is followed, except that in step 1), the mass ratio of n-butanol to the crystallization residual oil is 1:1.

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

[0129] Example 3

[0130] The procedure of Example 1 is followed, except that in step 1), the mass ratio of n-butanol to the crystallization residual oil is 4:1.

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

[0132] Example 4

[0133] The procedure of Example 1 is followed, except that in step 1), the crystal growth temperature is 8°C.

[0134] The experimental results are as follows: the purity of the obtained thionaphthene product is 98.2%, and the yield is 94.8%; the purity of the obtained refined naphthalene product is 98.8%, and the yield is 98.0%.

[0135] Example 5

[0136] Example 1 is referred to, except that in step 1), the temperature of crystallization is 30°C.

[0137] The experimental results are as follows: the purity of the obtained thionaphthene product is 98.3%, and the yield is 92.7%; the purity of the obtained refined naphthalene product is 98.6%, and the yield is 92.2%.

[0138] Example 6

[0139] Example 1 is referred to, except that in step 1), the crystallization time is 15 min.

[0140] The experimental results are as follows: the purity of the obtained thionaphthene product is 98.9%, and the yield is 91.5%; the purity of the obtained refined naphthalene product is 99.1%, and the yield is 93.4%.

[0141] Example 7

[0142] Example 1 is referred to, except that in step 1), the crystallization time is 45 min.

[0143] The experimental results are as follows: the purity of the obtained thionaphthene product is 98.5%, and the yield is 94.7%; the purity of the obtained refined naphthalene product is 98.8%, and the yield is 97.9%.

[0144] Example 8

[0145] Example 1 is referred to, except that in step 3), the mass ratio of the amount of the azeotrope to the mixture of naphthalene and thionaphthene removed from the solvent is 0.53:1.

[0146] The experimental results are as follows: the purity of the obtained thionaphthene product is 81.2%, and the yield is 94.5%; the purity of the obtained refined naphthalene product is 99.1%, and the yield is 88.5%.

[0147] Example 9

[0148] Example 1 is referred to, except that in step 3), the mass ratio of the amount of the azeotrope to the mixture of naphthalene and thionaphthene removed from the solvent is 0.62:1.

[0149] The experimental results are as follows: the purity of the obtained thionaphthene product is 98.8%, and the yield is 94.4%; the purity of the obtained refined naphthalene product is 98.9%, and the yield is 97.2%.

[0150] It is readily understood that the above-described embodiments are only illustrative of the application and not intended to limit the scope of the application. Other variations and modifications can be made to the embodiments described and illustrated herein, without departing from the spirit of the application, the scope of which is defined by the appended claims.

Claims

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

2. The system according to claim 1, wherein: It also includes an entrainer 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, to circulate the water flow to the naphthalene refining unit and to circulate the entrainer flow to the azeotropic distillation tower.

3. The system according to claim 1, wherein: The solvent is n-butanol; the entrainer is ethylene glycol.

4. The system according to claim 1, wherein: The system also includes a solvent impurity removal unit for removing impurities from the impurity-containing solvent obtained by the impurity removal unit to obtain a cleaned solvent flow; the solvent outlet of the solvent impurity removal unit is connected to the impurity removal unit to circulate the cleaned solvent flow to the impurity removal unit.

5. The system according to claim 4, characterized in that 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.

6. The system according to claim 5, 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 impurity-containing solvent to obtain a cleaned solvent stream and an impurity stream; 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.

7. The system according to claim 6, characterized in that The first cooler is connected to the first solvent recovery tower and the circulating solvent tank, respectively, so as to circulate the cooled impurity-removed solvent stream to the first solvent recovery tower and the circulating solvent tank.

8. The system according to claim 5, wherein: The solvent outlet of the second solvent recovery tower is connected to the solvent inlet of the circulating solvent tank.

9. The system according to claim 1, wherein: 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 liquid; The crystallizer is used to crystallize the mixed liquid obtained by the first mixer to obtain a crystal liquid; The filter is used to perform solid-liquid separation on the crystallization liquid and obtain a filter cake and a filtrate, wherein the filter cake is the mixture of the impurity-removed naphthalene and thionaphthene, and the filtrate is the solvent containing impurities.

10. The system according to any one of claims 1 to 9, characterized in that: The naphthalene refining unit includes a second mixer and a phase separator; the naphthalene refining unit also includes a dryer; The second mixer is used to mix and wash the mixture of the naphthalene and the entrainer output from the azeotropic distillation column 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.

11. The system according to claim 10, wherein: The water flow outlet of the entrainer refining tower and the water inlet of the second mixer are connected by a water flow pipeline, and along the flow direction of the water flow, a second heat exchanger and a water flow heater are sequentially provided on the water flow pipeline. 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.

12. The system according to claim 11, wherein: An entrainer cooler is provided between the entrainer flow outlet of the entrainer refining tower and the entrainer inlet of the azeotropic distillation tower, for cooling the entrainer flow output from the entrainer refining tower.

13. 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 12, characterized in that: The method comprises the following steps: 1) In an impurity removal unit, the mixture of naphthalene and thionaphthene is mixed with a solvent to obtain a mixed solution, the mixed solution is then crystallized, and the obtained crystal solution is subjected to solid-liquid separation to obtain a mixture of naphthalene and thionaphthene that has been impurity-removed and a solvent containing impurities; 2) feeding the impurity-removed naphthalene and thionaphthene mixture obtained in step 1) into a solvent removal unit to remove the entrained solvent, thereby obtaining a solvent-removed naphthalene and thionaphthene mixture and a removed solvent; recycling the removed solvent to the impurity removal unit in step 1) for use as the solvent required for 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; 4) The mixture of naphthalene and the entrainer obtained in step 3) is fed into a naphthalene refining unit for water washing and phase separation to obtain a naphthalene-rich light phase component and a heavy phase component containing water and the entrainer.

14. The method according to claim 13, wherein: Also includes 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 recycled to the naphthalene refining unit in step 4) for water washing, and the entrainer stream is recycled to the azeotropic distillation tower in step 3) for the azeotropic distillation.

15. The method according to claim 13, characterized in that In step 1), the solvent is n-butanol; In step 3), the entrainer is ethylene glycol; the thionaphthene material is cooled to obtain a thionaphthene product; In step 4), the light phase component is dried to obtain a refined naphthalene product.

16. The method according to claim 13, 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 cleaned solvent stream; at least part of the cleaned solvent stream is recycled to the cleaned solvent unit in step 1) to be used as the solvent required for mixing.

17. The method according to claim 16, characterized in that The impurity-containing solvent obtained in step 1) is fed into the first solvent recovery tower of the solvent impurity removal unit for distillation to obtain the impurity-free solvent stream and the impurity stream; the impurity-free solvent stream output from the first solvent recovery tower and the impurity-containing solvent output from the impurity removal unit are heat exchanged in a first heat exchanger, and then the impurity-free solvent stream is fed into a first cooler for cooling, and then part of the impurity-free solvent stream is circulated to the first solvent recovery tower, and part of the impurity-free solvent stream is circulated to the impurity removal unit.

18. The method according to claim 13, characterized in that In step 2), the impurity-removed naphthalene and thionaphthene mixture obtained in step 1) is first fed into the heating kettle of the solvent removal unit for heating and melting to obtain a melt; then the melt is fed into the second solvent recovery tower of the solvent removal unit for rectification to remove the solvent entrained in the melt, thereby obtaining the solvent-removed naphthalene and thionaphthene mixture and 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 entrainer stream output from the entrainer refining tower is first cooled in an entrainer cooler and then recycled to the azeotropic distillation tower in step 3).

19. The method according to claim 18, characterized in that In step 2), the heating and melting temperature is 82-90°C.

20. The method according to claim 13, wherein In step 1), the mass ratio of the solvent to the mixture of naphthalene and thionaphthene is 1:1 to 4:1; 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 0.53-0.62:1; 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; And / or, in step 5), the operating conditions of the entrainer refining tower include: tower top pressure 20-30 kPa, tower top temperature 60-70° C., and reflux ratio 0.2-1.

21. The method according to claim 20, characterized in that In step 1), the mass ratio of the solvent to the mixture of naphthalene and thianaphthene is 1.5 to 3:1; 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 0.55-0.60:1; And / or, in step 4), the temperature of the water used for the water washing is 70-80°C, and the temperature for the phase separation is 80-85°C.

22. The method according to claim 20, characterized in that The crystallization conditions include: cooling at a rate of 1-3°C / min, cooling to 8-30°C for crystal growth, and a crystal growth time of 15-45 minutes; And / or, the conditions for performing the azeotropic distillation include: a top pressure of the azeotropic distillation tower of 5-15 kPa, a top temperature of 110-125° C., and a reflux ratio of 5-10.

23. The method according to claim 22, characterized in that In step 1), the temperature is lowered to 10-25°C for crystal growth, and the crystal growth time is 20-40 minutes.

24. The method according to any one of claims 13 to 23, characterized in that In step 1), the mixture of naphthalene and thionaphthene is industrial naphthalene, or a naphthalene fraction obtained after tar distillation, or naphthalene residual oil obtained after melt crystallization of the industrial naphthalene or the naphthalene fraction.

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