Preparation method of long-carbon-chain nylon salt, method and system for recycling mixed solvent and application

Abstract

The invention discloses a preparation method of long-carbon-chain nylon salt, a method and a system for recycling a mixed solvent and application of the long-carbon-chain nylon salt. The preparation method of the long-carbon-chain nylon salt comprises the following steps: reacting powder I and powder II in a mixed solvent in a protective atmosphere; the mixed solvent comprises a first component and a second component; the first component and the second component are independently selected from compounds with the molecular formula of CnH2n + 2O, and the compounds corresponding to the first component and the second component are different; 0 < = n < = 6; the first component and the second component are azeotropic. The mixed solvent is adopted in the preparation process of the long-carbon-chain nylon salt, so that the reaction temperature is low, the reaction pressure is low, the adiabatic temperature rise in the salt forming process is small, and the safety in the salt forming process can be effectively ensured; meanwhile, the method can give consideration to the occupational health environment of operators. By adopting the method for recycling the mixed solvent, the mixed solvent is convenient to recycle, can be recycled, is low in recycling energy consumption, and is beneficial to environmental protection and energy conservation.

Description

Technical Field

[0001] The invention relates to the technical field of preparation of long carbon chain nylon salt, and more particularly to a preparation method of long carbon chain nylon salt, a method and system for recycling a mixed solvent and applications thereof. Background Art

[0002] In the production process of long-chain nylon salt, a solvent is needed to dissolve the long-chain diacid and diamine so that the subsequent salt-forming reaction can proceed smoothly. Currently, there are two main types of solvents: pure water and alcohol solvents.

[0003] Compared with alcohol dissolution, using pure water to dissolve dibasic acids and diamines can reduce the investment in equipment sealing and explosion-proof, but it consumes a lot of heat energy in the drying stage after salt formation. In addition, long-chain diacids and diamines have poor solubility in water. To dissolve them completely requires considerable equipment volume and energy. While consuming a large amount of pure water resources, it also increases investment from another perspective, greatly increasing the difficulty of process scale-up and continuous production of nylon salt.

[0004] Nylon salt has a high solubility in alcohol solvents, which is conducive to the salt-forming reaction. After the salt is formed, the nylon salt is still washed with alcohol solvents instead of water. The advantage is that there is no need to separate the solvent and water. The disadvantage is that the entire device requires an explosion-proof design, and personal occupational hygiene is poor. The adiabatic temperature rise is relatively large during the salt-forming reaction, and more circulation ratios are required for heat removal, which consumes more energy.

[0005] Chinese patent CN111039791A discloses a method and device for continuously producing a long-chain nylon salt solution. The method comprises the following steps: melting a powdered or granular long-chain diacid at a melting temperature of 140-180°C, mixing the molten long-chain diacid, long-chain diamine and deionized water in a first-stage reaction unit; controlling the molar ratio of the long-chain diacid to the long-chain diamine to be 1.01-1.1, controlling the first-stage reaction temperature to be 120-150°C, controlling the salt concentration to be 40-60%, controlling the pH value of the salt solution to be 6.0-9.0, filtering the salt solution after the reaction, and entering the second-stage reaction unit; controlling the temperature of the second-stage reaction unit to be 120-150°C, and controlling the pH value of the salt solution to be 7.0-8.5; filtering the salt solution after the pH value of the second-stage reaction unit is adjusted, and entering the salt storage tank unit for standby use.

[0006] Chinese patent CN 109180931 A discloses a preparation process of long carbon chain nylon 1313 salt: 1,13-tridecanediamine is added to water with a mass number of 3 to 8 times, heated to 60-80°C, then a measured amount of 1,13-tricarbondiamine is added according to a molar ratio of 1,13-decanedicarboxylic acid to 1,13-tricarbondiamine of 1:0.98-1.2, heated to 120-180°C in an inert gas atmosphere, the pressure in the autoclave is maintained at 0.4-2.2MPaG, the pH value of the system is measured, and an appropriate amount of 1,13-tridecanedicarboxylic acid or 1,13-tricarbondiamine is added according to the measured pH value, the pH value of the system is adjusted to between 7.0 and 7.4, and the reaction is continued for 20-30 minutes to obtain PA1313 salt. The preparation of long carbon chain nylon salt requires higher temperature and pressure, and an intermittent production method is usually used.

[0007] In the production methods of long carbon chain nylon salts reported in existing articles and patents, the solvent is mostly pure water, and the salt-forming temperature is mostly above 120°C and the pressure is above 0.4MPaG. The temperature and pressure of the salt-forming process are both high, and the energy consumption is high. If the solvent is reused, the solvent needs to be evaporated once and then reused, which has high energy consumption and has great defects in energy saving and environmental protection. Summary of the invention

[0008] In order to solve the problems in the prior art, the present invention proposes a method for preparing a long carbon chain nylon salt, a method and system for recycling a mixed solvent, and an application thereof. The present invention adopts a mixed solvent in the process of preparing a long carbon chain nylon salt, so that the reaction temperature and reaction pressure are low, and the adiabatic temperature rise in the salt-forming process is small, which can effectively ensure the safety in the salt-forming process; at the same time, the crude product logistics prepared by the present invention adopts the first component circulating logistics (mainly water) generated in the mixed solvent recycling system for washing and separation, which can take into account the occupational health and environment of the operator. At the same time, the present invention adopts a mixed solvent in the process of preparing a long carbon chain nylon salt, and adopts the method of recycling a mixed solvent of the present invention, which is convenient for recycling the mixed solvent, can be recycled, and the energy consumption used during recycling is small, which is beneficial to environmental protection and energy saving. Therefore, the method of recycling a mixed solvent of the present invention effectively solves the problem that the safety, energy consumption and occupational health and environment of the operator of the long carbon chain dibasic acid and diamine in the continuous salt-forming process of the polyamide industry cannot be taken into account.

[0009] One of the purposes of the present invention is to provide a method for preparing a long carbon chain nylon salt, comprising the following steps:

[0010] Under a protective atmosphere, reacting powder material 1 and powder material 2 in a mixed solvent;

[0011] The mixed solvent comprises a first component and a second component; the first component and the second component are each independently selected from n H2n+2 O, and the compounds corresponding to the first component and the second component are different; 0≤n≤6, n is a natural number;

[0012] There is an azeotrope between the first component and the second component;

[0013] The powder material 1 and the powder material 2 are raw materials for preparing long carbon chain nylon salt.

[0014] In the method for preparing the long carbon chain nylon salt of the present invention, preferably,

[0015] In the first component, n is 0, that is, the first component is water; and / or,

[0016] In the second component, n is 2≤n≤6, preferably 2≤n≤4, and n is a natural number.

[0017] The technical solution of the present invention adopts a mixed solvent solution, wherein a mixture of the first component and the second component is used as a solvent and has an azeotropic composition. When the reaction of the long carbon chain nylon salt is carried out, the adiabatic temperature rise is small, and the solvent is easy to recycle and requires less energy. At the same time, the wet product of the generated long carbon chain nylon salt after separation can be exposed to air, and can be exposed to air during the post-processing process of drying the wet product into a product, which is easy to operate.

[0018] A second object of the present invention is to provide a method for recycling a mixed solvent, comprising the following steps:

[0019] a) Under a protective atmosphere, the mixed solvent circulation stream is fully mixed and reacted with the powder material one stream and the powder material two stream in the mixing zone to generate a crude product stream;

[0020] The mixed solvent circulating stream includes a first component and a second component; the first component and the second component are each independently selected from a solvent having a molecular formula of C n H 2n+2 O, and the first component and the second component correspond to different compounds; 0≤n≤6, n is a natural number; there is azeotropic interaction between the first component and the second component;

[0021] b) sending the crude product stream into separation zone 1 to be separated into a wet product stream and a first mixed solvent stream, sending the wet product stream into separation zone 2 to be separated into a second mixed solvent stream and a product stream, sending the product stream out of the system, returning the second mixed solvent stream to separation zone 1 for recycling and / or sending the second mixed solvent stream into separation zone 3;

[0022] c) The first mixed solvent stream and optionally the second mixed solvent stream are fed into separation zone three and separated into a mixed solvent circulating stream and a first component circulating stream. The first component circulating stream is returned to separation zone one for recycling, and the mixed solvent circulating stream is returned to the mixing zone for recycling.

[0023] In the method for recycling a mixed solvent according to the present invention, preferably,

[0024] Step a),

[0025] The first component and the second component have an azeotropic state at 80-400 KPaA;

[0026] Preferably,

[0027] In the first component, n is 0; and / or,

[0028] In the second component, n is 2≤n≤6, preferably 2≤n≤4, and n is a natural number;

[0029] Further preferably, the second component is selected from at least one of ethanol, n-propanol, isopropanol, n-butanol, isobutanol and tert-butanol, preferably at least one of ethanol, isopropanol and tert-butanol.

[0030] In the method for recycling a mixed solvent according to the present invention, preferably,

[0031] Step a),

[0032] In the mixed solvent circulating stream, the content of the second component is ≥80wt%, preferably ≥85wt%;

[0033] Further preferably, the mixed solvent circulating stream is an azeotropic composition of the first component and the second component at the separation pressure; preferably, in the mixed solvent circulating stream, the content of the first component is 4% to 15% by mass; the content of the second component is 96% to 85%; for example, in the mixed solvent circulating stream, the water and ethanol compositions are 4.5% and 95.5%, the water-isopropanol azeotropic composition is 12.1% and 87.9%, and the water and tert-butanol azeotropic composition is 11.7% and 88.3%; and / or,

[0034] The mass ratio of the mixed solvent circulating flow to the sum of the powder material 1 and the powder material 2 is (4-2):1; and / or,

[0035] Taking the total molar amount of powder one and powder two as 100%, the molar proportion of powder one is 0.495-0.499, and the molar proportion of powder two is 0.505-0.501; and / or,

[0036] The particle size range of the powder 1 and the powder 2 is independently 20 to 100 μm.

[0037] In the method for recycling a mixed solvent according to the present invention, preferably,

[0038] Step a),

[0039] The powder material 1 and the powder material 2 are raw materials for preparing long carbon chain nylon salt;

[0040] Preferably, the powder is a dibasic acid, preferably a dibasic acid with a carbon number of ≥10; preferably C 10 ~C 14 More preferably, the dibasic acid has a straight chain and carboxyl groups at both ends; and / or,

[0041] The powder is a diamine, preferably a diamine with a carbon number ≥ 10; preferably C 10 ~C 16 further preferably a diamine having a straight molecular chain and amine groups at both ends.

[0042] In the method for recycling a mixed solvent according to the present invention, preferably,

[0043] Step a), in the technical solution of the present invention, since the content of the second component in the mixed solvent circulating flow in the mixing zone C is relatively high, the solubility of the powder 1 and the powder 2 is relatively high at a relatively low temperature, so the neutralization reaction conditions are controlled as follows: the reaction temperature of the mixing zone is 50 to 80°C, preferably 55 to 75°C;

[0044] The reaction time of the mixing zone is 3 to 12 hours, preferably 3 to 10 hours;

[0045] The reaction pressure in the mixing zone is 35-400 KPaA, preferably 40-380 KPaA;

[0046] Preferably,

[0047] In the mixing zone, the temperature rise of the neutralization reaction is controlled to be ≤10°C, preferably ≤8°C, more preferably ≤5°C.

[0048] In the technical solution of the present invention, the first powder and the second powder undergo a neutralization reaction between carboxyl groups and amine groups in the mixing zone to generate long carbon chain nylon salt.

[0049] In the technical solution of the present invention, the mixing zone is in the mixed solvent. Due to the neutralization reaction between the carboxyl group and the amine group of the powder one and the powder two, the material temperature will increase. It is necessary to remove the heat by means of a jacket, a coil, or an external circulation depending on the reaction situation.

[0050] In the technical solution of the present invention, after the powder in the mixing zone is sucked in, the powder quickly dissolves into the mixed solvent, and under the action of external force, the molecular motion of powder 1 and powder 2 increases, the probability of collision increases, and the reaction process is accelerated.

[0051] In the method for recycling a mixed solvent according to the present invention, preferably,

[0052] Step b),

[0053] The crude product flow extracted from the mixing zone is a solid-liquid two-phase, and the solid material accounts for 20.0% to 35.0% by mass; and / or,

[0054] The separation method of the separation zone 1 is solid-liquid separation under the washing action of the first component circulating stream and the optional mixed solvent second stream; preferably, the solid-liquid separation method is filtration separation; and / or,

[0055] After separation in the separation zone 1, the content of the second component in the wet product stream is ≤0.25%, preferably ≤0.15%, and more preferably ≤0.1% by mass percentage; since the second component of the mixed solvent contained in the solid is less, the obtained solid can be directly transported in the air and subjected to the next separation operation; and since the second component of the mixed solvent contained in the solid is less, the occupational health environment of the operator is greatly improved, and the emission of unorganized VOC is also greatly reduced accordingly; and / or,

[0056] In terms of mass percentage, the content of the second component in the first mixed solvent stream is ≤50%, preferably ≤45%.

[0057] In the method for recycling a mixed solvent according to the present invention, preferably,

[0058] Step b),

[0059] The separation method of the separation zone 2 is dry separation; preferably,

[0060] The drying pressure of the separation zone 2 is 20 to 85 KPaA, preferably 20 to 60 KPaA; and / or,

[0061] The drying temperature in the separation zone 2 is 60 to 95°C, preferably 60 to 85°C; and / or,

[0062] In terms of mass percentage, the content of the mixed solvent in the product stream is ≤ 0.05%, preferably ≤ 0.02%.

[0063] In the technical solution of the present invention, since the solvent content in the wet product flow separated by the following separation zone 1 is already very small, especially the content of the second component is very small, when the second flow of mixed solvent produced by evaporation during drying in the separation zone 2 is recycled to the separation zone 1 for utilization, there is no specific ratio requirement between it and the first component circulating flow.

[0064] In the method for recycling a mixed solvent according to the present invention, preferably,

[0065] Step c),

[0066] The separation method of the separation zone three is azeotropic distillation separation, which separates the mixed solvent from the first component of the mixed solvent; preferably,

[0067] The operating pressure of the separation zone 3 is 40 to 300 KPaA, preferably 40 to 250 KPaA; and / or,

[0068] The operating temperature of the separation zone 3 is 55 to 110°C, preferably 55 to 105°C; and / or,

[0069] In terms of mass percentage, the content of the first component in the first component circulating flow separated from the separation zone three is ≥99.90%, preferably ≥99.95%.

[0070] The third object of the present invention is to provide a system for recycling a mixed solvent, comprising a mixing zone, a separation zone 1, a separation zone 2 and a separation zone 3:

[0071] The mixing zone is provided with a mixed solvent feed port, a powder material one logistics feed port, a powder material two logistics feed port and a protective gas feed port; the discharge port of the mixing zone is connected to the solid-liquid two-phase feed port of the separation zone one;

[0072] The wet material discharge port of separation zone one is connected to the feed port of separation zone two; the liquid discharge port of separation zone one is connected to the liquid feed port of separation zone three;

[0073] The liquid discharge port of separation zone 2 is connected to the liquid feed port of separation zone 1 and / or the liquid discharge port of separation zone 2 is connected to the liquid feed port of separation zone 3;

[0074] The first component circulating flow outlet of separation zone three is connected to the liquid feed inlet of separation zone one; the mixed solvent circulating flow outlet of separation zone three is connected to the liquid feed inlet of the mixing zone;

[0075] Preferably, the method for recycling a mixed solvent described in the second object of the present invention adopts the system.

[0076] In the mixed solvent recycling system of the present invention, preferably,

[0077] The mixing zone is a reactor; and / or,

[0078] The first separation zone is a pressure filter; and / or,

[0079] The second separation zone is a drying device; and / or,

[0080] The separation zone three is an azeotropic distillation tower.

[0081] In the technical solution of the present invention, the feeding method of powder material 1 and powder material 2 in the mixing zone is suction feeding.

[0082] In the technical solution of the present invention, the power for sucking the powders when feeding the first and second powders into the mixing zone comes from the vacuum generated by the mixed solvent circulating flow through the venturi jet, or the vacuum caused by the motor driving the rotor to rotate.

[0083] In the technical solution of the present invention, the first powder and the second powder should be fed into the mixing zone to react in a protective atmosphere (such as nitrogen), and the mixing zone is provided with a protective gas feeding pipeline.

[0084] The fourth object of the present invention is to provide a method for recycling a mixed solvent as described in the second object of the present invention or an application of a mixed solvent recycling system as described in the third object of the present invention in the production of long-chain nylon salts.

[0085] The existing technical solution adopts a single solvent. The organic solvent has a low flash point, the equipment needs to be explosion-proof, the specific heat is small, the dissolution temperature is low, and the heating amount during dissolution is small, but the adiabatic temperature rises during mixing, and the separated wet products need to be transported in a closed environment; the water solvent has good safety and large specific heat, but the dissolution temperature is high, the amount of solvent added during dissolution is large, and more energy is required for dissolution. The adiabatic temperature rise is small during mixing, but more energy is required for recovery.

[0086] The technical solution adopted by the present invention mainly comprises the following steps: the molecular formula is C n H 2n+2 O, and the mixed solvent circulating logistics composed of the first component and the second component with azeotropy is fully mixed with the powder material one logistics and the powder material two logistics in the mixing zone to generate a crude product logistics. The crude product logistics is sent to the separation zone one, separated into a wet product logistics and a mixed solvent circulating logistics, the wet product logistics is sent to the separation zone two, separated into a first component circulating logistics and a product logistics, the product logistics is sent out of the system, and the first component circulating logistics is returned to the separation zone one for recycling. The mixed solvent circulating logistics is sent to the separation zone three, separated into a first component circulating logistics and a mixed solvent circulating logistics, the first component circulating logistics is returned to the separation zone one for recycling, and the mixed solvent circulating logistics is returned to the mixing zone for recycling. The scheme solves the above problems well and can be used in the production process of long carbon chain nylon salt. It has the advantages of safety, energy consumption and occupational health environment of operators in the salt-forming process, and small adiabatic temperature rise in the salt-forming process. It can be seen that the present invention adopts a technical solution of a mixed solvent, in which a mixture of an organic solvent and an aqueous solvent is used as a solvent, and has an azeotropic composition. It is safer than a single organic solvent, the wet product can be exposed to air, the adiabatic temperature rise is small, and the energy consumption is lower than that of a single aqueous solvent, and it has the advantages of both solvents.

[0087] The endpoints and any values ​​of the scope disclosed in the present invention are not limited to the precise scope or value, and these scopes or values ​​should be understood to include values ​​close to these scopes or values. For numerical ranges, the endpoint values ​​of each scope, the endpoint values ​​of each scope and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be regarded as specifically disclosed in this article. Hereinafter, in principle, each technical solution can be combined with each other to obtain a new technical solution, which should also be regarded as specifically disclosed in this article.

[0088] Compared with the prior art, the present invention has at least the following advantages:

[0089] The present invention adopts a mixed solvent in the preparation process of long carbon chain nylon salt, so that the reaction temperature and reaction pressure are low, the adiabatic temperature rise in the salt formation process is small, and the safety in the salt formation process can be effectively guaranteed; at the same time, the crude product logistics prepared by the present invention adopts the first component circulating logistics (mainly water) generated in the mixed solvent recycling system for washing and separation, and the occupational health environment of the operator can be taken into account. At the same time, the present invention adopts a mixed solvent in the preparation process of long carbon chain nylon salt, and the mixed solvent recycling method of the present invention is adopted, which is convenient for recycling the mixed solvent, can be recycled, and the energy consumption used during recycling is small, which is beneficial to environmental protection and energy saving. Therefore, the method of recycling mixed solvents of the present invention effectively solves the problem that the safety, energy consumption and occupational health environment of the long carbon chain dibasic acid and diamine in the continuous salt formation process of the polyamide industry cannot be taken into account. BRIEF DESCRIPTION OF THE DRAWINGS

[0090] Figure 1 A process flow adopted in one embodiment of the present invention;

[0091] Figure 2 This is a process flow adopted in another embodiment of the present invention.

[0092] Figure 1 , 2 The process used by this institute

[0093] Figure 1 , Figure 2 Marking Description:

[0094] 101. Mixed solvent circulation logistics

[0095] 102. Powder material logistics

[0096] 103. Powder secondary logistics

[0097] 104. Crude product logistics

[0098] 105. Second logistics of mixed solvent

[0099] 106. First component circulation logistics

[0100] 107. Mixed solvent first logistics

[0101] 108. Wet product logistics

[0102] 109. Product Logistics

[0103] 110. Mixed solvent circulation logistics

[0104] C. Mixed Zone

[0105] D. Separation Zone 1

[0106] E. Separation Zone 2

[0107] F. Separation Zone 3

[0108] Figure 1 The mixed solvent circulating logistics 101, the powder material logistics 102 and the powder material logistics 103 are fully mixed in the mixing zone C to generate a crude product logistics 104; the crude product logistics 104 is sent to the separation zone D, separated into a wet product logistics 108 and a mixed solvent first logistics 107, the wet product logistics 108 is sent to the separation zone E, separated into a mixed solvent second logistics 105 and a product logistics 109, the product logistics 109 is sent out of the system, and the mixed solvent second logistics 105 is returned to the separation zone D for recycling; the mixed solvent first logistics 107 is sent to the separation zone F, separated into a first component circulating logistics 106 and a mixed solvent circulating logistics 110, the first component circulating logistics 106 is returned to the separation zone D for recycling, and the mixed solvent circulating logistics 110 is returned to the mixing zone C for recycling.

[0109] Figure 2 The mixed solvent circulating logistics 101, powder material logistics 102 and powder material logistics 103 are fully mixed in the mixing zone C to generate a crude product logistics 104; the crude product logistics 104 is sent to the separation zone D, separated into a wet product logistics 108 and a mixed solvent first logistics 107, the wet product logistics 108 is sent to the separation zone E, separated into a mixed solvent second logistics 105 and a product logistics 109, the product logistics 109 is sent out of the system, and the mixed solvent second logistics 105 is sent to the separation zone F; the mixed solvent first logistics 107 is sent to the separation zone F, separated into a first component circulating logistics 106 and a mixed solvent circulating logistics 110, the first component circulating logistics 106 is returned to the separation zone D for recycling, and the mixed solvent circulating logistics 110 is returned to the mixing zone C for recycling. DETAILED DESCRIPTION

[0110] The present invention is described in detail below in conjunction with specific drawings and embodiments. It is necessary to point out that the following embodiments are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made to the present invention by those skilled in the art based on the content of the present invention still fall within the scope of protection of the present invention.

[0111] It should also be noted that the various specific technical features described in the following specific embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0112] In addition, the various embodiments of the present invention may be arbitrarily combined as long as they do not violate the concept of the present invention. The technical solutions thus formed belong to part of the original disclosure of this specification and also fall within the protection scope of the present invention.

[0113] The raw materials used in the examples and comparative examples, unless otherwise specified, are disclosed in the prior art, for example, they can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0114] Example 1

[0115] like Figure 1 As shown, a system for recycling a mixed solvent of the present invention comprises a mixing zone C, a separation zone D, a separation zone E and a separation zone F:

[0116] The mixing zone C is provided with a mixed solvent feed port, a powder material one logistics feed port, a powder material two logistics feed port and a protective gas feed port; the discharge port of the mixing zone is connected to the solid-liquid two-phase feed port of the separation zone one;

[0117] The wet material discharge port of separation zone 1D is connected to the feed port of separation zone 2; the liquid discharge port of separation zone 1 is connected to the liquid feed port of separation zone 3;

[0118] The liquid outlet of separation zone 2 E is connected to the liquid feed port of separation zone 1;

[0119] The first component circulating flow outlet of separation zone three F is connected to the liquid feed inlet of separation zone one; the mixed solvent circulating flow outlet of separation zone three is connected to the liquid feed inlet of the mixing zone;

[0120] Among them, the mixing zone is a reactor; the first separation zone is a pressure filter; the second separation zone is a drying device; and the third separation zone is an azeotropic distillation tower.

[0121] Specifically,

[0122] Figure 1The mixed solvent circulating logistics 101, the powder material logistics 102 and the powder material logistics 103 are fully mixed in the mixing zone C to generate a crude product logistics 104; the crude product logistics 104 is sent to the separation zone D, separated into a wet product logistics 108 and a mixed solvent first logistics 107, the wet product logistics 108 is sent to the separation zone E, separated into a mixed solvent second logistics 105 and a product logistics 109, the product logistics 109 is sent out of the system, and the mixed solvent second logistics 105 is returned to the separation zone D for recycling; the mixed solvent first logistics 107 is sent to the separation zone F, separated into a first component circulating logistics 106 and a mixed solvent circulating logistics 110, the first component circulating logistics 106 is returned to the separation zone D for recycling, and the mixed solvent circulating logistics 110 is returned to the mixing zone C for recycling.

[0123] Example 2

[0124] like Figure 2 As shown, Figure 1 As shown, a system for recycling a mixed solvent of the present invention comprises a mixing zone C, a separation zone D, a separation zone E and a separation zone F:

[0125] The mixing zone C is provided with a mixed solvent feed port, a powder material one logistics feed port, a powder material two logistics feed port and a protective gas feed port; the discharge port of the mixing zone is connected to the solid-liquid two-phase feed port of the separation zone one;

[0126] The wet material discharge port of separation zone 1D is connected to the feed port of separation zone 2; the liquid discharge port of separation zone 1 is connected to the liquid feed port of separation zone 3;

[0127] The liquid discharge port of separation zone 2 is connected to the liquid feed port of separation zone 3;

[0128] The mixed solvent circulating stream outlet of separation zone three is connected to the liquid feed inlet of the mixing zone;

[0129] Among them, the mixing zone is a reactor; the first separation zone is a pressure filter; the second separation zone is a drying device; and the third separation zone is an azeotropic distillation tower.

[0130] Specifically,

[0131] Figure 2The mixed solvent circulating logistics 101, powder material logistics 102 and powder material logistics 103 are fully mixed in the mixing zone C to generate a crude product logistics 104; the crude product logistics 104 is sent to the separation zone D, separated into a wet product logistics 108 and a mixed solvent first logistics 107, the wet product logistics 108 is sent to the separation zone E, separated into a mixed solvent second logistics 105 and a product logistics 109, the product logistics 109 is sent out of the system, and the mixed solvent second logistics 105 is sent to the separation zone F; the mixed solvent first logistics 107 is sent to the separation zone F, separated into a first component circulating logistics 106 and a mixed solvent circulating logistics 110, the first component circulating logistics 106 is returned to the separation zone D for recycling, and the mixed solvent circulating logistics 110 is returned to the mixing zone C for recycling.

[0132] The following examples take 1000 tons / year of product as an example, powder one is dodecane dicarboxylic acid, with a flow rate of about 75.4 kg / h, and powder two is dodecane diamine, with a flow rate of about 65.6 kg / h.

[0133] [Example 3]

[0134] Use Figure 1 The technical scheme shown in Example 1 is a method for preparing a long carbon chain nylon salt and a method for recycling a mixed solvent in the production process of a long carbon chain nylon salt of the present invention, wherein the first component in the mixed solvent circulating logistics is water, and the second component is ethanol. In terms of mass percentage, the first component accounts for 4.50% of the mixed solvent circulating logistics, and the second component accounts for 95.50%. The mass ratio of the mixed solvent circulating logistics to the sum of the powder one and the powder two is 2:1. The neutralization reaction in the mixing zone C is controlled at 55°C, the reaction time is 10h, and the reaction pressure is 80KPaA; the adiabatic temperature rise is 72.5°C when there is no heat removal measure. In the present invention, heat removal is provided to control the neutralization reaction temperature rise to 8°C.

[0135] The crude product flow extracted from the mixing zone is a solid-liquid two-phase, and the solid material accounts for 33.33% by mass percentage; the crude product flow extracted from the mixing zone flows into the separation zone 1, and the separation method of the separation zone 1 is a solid-liquid separation method of pressure filtration under the washing action of the first component circulating flow and the mixed solvent second flow; after separation in the separation zone 1, a wet product flow and a mixed solvent first flow are obtained. In terms of mass percentage, the content of the second component in the wet product flow is 0.14%; in terms of mass percentage, the content of the second component in the mixed solvent first flow is 35.81%.

[0136] The wet product flow separated in separation zone one enters separation zone two. The separation method of separation zone two is dry separation, and the flow is separated into a mixed solvent second flow and a product flow. The product flow is sent out of the system, and the mixed solvent second flow is returned to separation zone one for recycling. The drying pressure of separation zone two is 80 KPaA; the drying temperature of separation zone two is 93.5°C; after separation in separation zone two, the mixed solvent content in the product flow is 0.03% by mass.

[0137] The first mixed solvent stream separated in separation zone one enters separation zone three. The separation mode of separation zone three is azeotropic distillation separation, and the mixed solvent circulating stream and the first component circulating stream are separated. The operating pressure of separation zone three is 40KPaA, and the operating temperature is 56.6°C. Under this pressure, the first component accounts for 4.50% and the second component accounts for 95.50% in the mixed solvent circulating stream obtained in separation zone three (i.e., the mixed solvent circulating stream circulated to the mixing zone) by mass percentage. In terms of mass percentage, the first component accounts for more than 99.99% of the first component circulating stream obtained in separation zone three, and the impurity content is 58ppm.

[0138] The yield and purity of the long carbon chain nylon salt prepared by the above method and the energy consumption of the device used are shown in Table 1.

[0139] [Example 4]

[0140] Use Figure 1 The technical scheme shown in Example 1 is a method for preparing a long-chain nylon salt and a method for recycling a mixed solvent in the production process of a long-chain nylon salt of the present invention, wherein the first component in the mixed solvent circulating logistics is water, and the second component is ethanol. In terms of mass percentage, the first component accounts for 4.50% of the mixed solvent circulating logistics, and the second component accounts for 95.50%. The mass ratio of the mixed solvent circulating logistics to the sum of the powder one and the powder two is 3:1. The neutralization reaction in the mixing zone C is controlled at 65°C, the reaction time is 8h, and the reaction pressure is 250KPaA; the adiabatic temperature rise is 70.0°C when there is no heat removal measure. In the present invention, heat removal is provided to control the neutralization reaction temperature rise to 6°C.

[0141] The crude product flow extracted from the mixing zone is a solid-liquid two-phase, and the solid material accounts for 25.00% by mass percentage; the crude product flow extracted from the mixing zone flows into the separation zone 1, and the separation method of the separation zone 1 is a solid-liquid separation method of pressure filtration under the washing action of the first component circulating flow and the mixed solvent second flow; after separation in the separation zone 1, a wet product flow and a mixed solvent first flow are obtained. In terms of mass percentage, the content of the second component in the wet product flow is 0.11%; in terms of mass percentage, the content of the second component in the mixed solvent first flow is 34.38%.

[0142] The wet product flow separated in separation zone one enters separation zone two. The separation method of separation zone two is dry separation, and the flow is separated into a mixed solvent second flow and a product flow. The product flow is sent out of the system, and the mixed solvent second flow is returned to separation zone one for recycling. The drying pressure of separation zone two is 60 KPaA; the drying temperature of separation zone two is 86°C; after separation in separation zone two, the mixed solvent content in the product flow is 0.02% by mass.

[0143] The first mixed solvent stream separated in the separation zone 1 enters the separation zone 3 and is separated into a mixed solvent circulating stream and a first component circulating stream. The operating pressure of the separation zone 3 is 100 KPaA, and the operating temperature is 77.9°C. Under this pressure, the first component accounts for 4.50% of the mixed solvent circulating stream obtained in the separation zone 3 (i.e., the mixed solvent circulating stream circulated to the mixing zone) and the second component accounts for 95.50% by mass percentage. In terms of mass percentage, the first component accounts for more than 99.99% of the first component circulating stream obtained in the separation zone 3, and the impurity content is 54 ppm.

[0144] The yield and purity of the long carbon chain nylon salt prepared by the above method and the energy consumption of the device used are shown in Table 1.

[0145] [Example 5]

[0146] Use Figure 1 The technical scheme shown in Example 1 is a method for preparing a long carbon chain nylon salt and a method for recycling a mixed solvent in the production process of a long carbon chain nylon salt of the present invention, wherein the first component in the mixed solvent circulating logistics is water, and the second component is ethanol. In terms of mass percentage, the first component accounts for 4.50% of the mixed solvent circulating logistics, and the second component accounts for 95.50%. The mass ratio of the mixed solvent circulating logistics to the sum of the powder one and the powder two is 4:1. The neutralization reaction in the mixing zone C is controlled at 75°C, the reaction time is 4h, and the reaction pressure is 350KPaA; the adiabatic temperature rise is 68.0°C when there is no heat removal measure. In the present invention, heat removal is provided to control the neutralization reaction temperature rise by 4°C.

[0147] The crude product flow extracted from the mixing zone is a solid-liquid two-phase, and the solid material accounts for 20.00% by mass percentage; the crude product flow extracted from the mixing zone flows into the separation zone 1, and the separation method of the separation zone 1 is a solid-liquid separation method of pressure filtration under the washing action of the first component circulating flow and the second mixed solvent flow; after separation in the separation zone 1, a wet product flow and a first mixed solvent flow are obtained. In terms of mass percentage, the content of the second component in the wet product flow is 0.09%; in terms of mass percentage, the content of the second component in the first mixed solvent flow is 33.71%.

[0148] The wet product flow separated in separation zone one enters separation zone two. The separation method of separation zone two is dry separation, and the product flow is separated into a mixed solvent second flow and a product flow. The product flow is sent out of the system, and the mixed solvent second flow is returned to separation zone one for recycling. The drying pressure of separation zone two is 20 KPaA. The drying temperature of separation zone two is 60°C. After separation in separation zone two, the mixed solvent content in the product flow is 0.01% by mass.

[0149] The first mixed solvent stream separated in the separation zone 1 enters the separation zone 3 and is separated into a mixed solvent circulating stream and a first component circulating stream. The operating pressure of the separation zone 3 is 250 KPaA, and the operating temperature is 102.9°C. Under this pressure, the first component accounts for 4.50% of the mixed solvent circulating stream obtained in the separation zone 3 (i.e., the mixed solvent circulating stream circulated to the mixing zone) and the second component accounts for 95.50% by mass percentage. In terms of mass percentage, the first component accounts for more than 99.99% of the first component circulating stream obtained in the separation zone 3, and the impurity content is 54 ppm.

[0150] The yield and purity of the long carbon chain nylon salt prepared by the above method and the energy consumption of the device used are shown in Table 1.

[0151] [Example 6]

[0152] Use Figure 1 The technical scheme shown in Example 1 is a method for preparing a long carbon chain nylon salt and a method for recycling a mixed solvent in the production process of a long carbon chain nylon salt of the present invention, wherein the first component in the mixed solvent circulating logistics is water, and the second component is isopropanol. In terms of mass percentage, the first component accounts for 12.1% of the mixed solvent circulating logistics, and the second component accounts for 87.9%. The mass ratio of the mixed solvent circulating logistics to the sum of the powder one and the powder two is 3:1. The neutralization reaction in the mixing zone C is controlled at 65°C, the reaction time is 8h, and the reaction pressure is 200KPaA; the adiabatic temperature rise is 71.0°C when there is no heat removal measure. In the present invention, heat removal is provided to control the neutralization reaction temperature rise to 6°C.

[0153] The crude product flow extracted from the mixing zone is a solid-liquid two-phase, and the solid material accounts for 25.00% by mass percentage; the crude product flow extracted from the mixing zone flows into the separation zone 1, and the separation method of the separation zone 1 is a solid-liquid separation method of pressure filtration under the washing action of the first component circulating flow and the mixed solvent second flow; after separation in the separation zone 1, a wet product flow and a mixed solvent first flow are obtained. In terms of mass percentage, the content of the second component in the wet product flow is 0.12%; in terms of mass percentage, the content of the second component in the mixed solvent first flow is 31.64%.

[0154] The wet product flow separated in separation zone one enters separation zone two. The separation method of separation zone two is dry separation, and the flow is separated into a mixed solvent second flow and a product flow. The product flow is sent out of the system, and the mixed solvent second flow is returned to separation zone one for recycling. The drying pressure of separation zone two is 30 KPaA. The drying temperature of separation zone two is 69.1°C. After separation in separation zone two, the content of mixed solvent in the product flow is 0.02% by mass.

[0155] The first mixed solvent stream separated in the separation zone 1 enters the separation zone 3 and is separated into a mixed solvent circulating stream and a first component circulating stream. The operating pressure of the separation zone 3 is 80 KPaA, and the operating temperature is 74.4°C. Under this pressure, the first component accounts for 12.1% and the second component accounts for 87.9% of the mixed solvent circulating stream obtained in the separation zone 3 (i.e., the mixed solvent circulating stream circulated to the mixing zone) by mass percentage. In terms of mass percentage, the first component accounts for more than 99.99% of the first component circulating stream obtained in the separation zone 3, and the impurity content is 49.7 ppm.

[0156] The yield and purity of the long carbon chain nylon salt prepared by the above method and the energy consumption of the device used are shown in Table 1.

[0157] [Example 7]

[0158] Use Figure 2 The technical scheme shown in Example 2 is a method for preparing a long-chain nylon salt and a method for recycling a mixed solvent in the production process of a long-chain nylon salt of the present invention, wherein the first component in the mixed solvent circulating logistics is water, and the second component is tert-butanol. In terms of mass percentage, the first component accounts for 11.7% of the mixed solvent circulating logistics, and the second component accounts for 88.3%. The mass ratio of the mixed solvent circulating logistics to the sum of powder one and powder two is 3:1. The neutralization reaction in the mixing zone C is controlled at 65°C, the reaction time is 8h, and the reaction pressure is 150KPaA; the adiabatic temperature rise is 70.0°C when there is no heat removal measure. In the present invention, heat removal is provided to control the neutralization reaction temperature rise to 6°C.

[0159] The crude product flow extracted from the mixing zone is a solid-liquid two-phase, and the solid material accounts for 25.00% by mass percentage; the crude product flow extracted from the mixing zone flows into the separation zone 1, and the separation method of the separation zone 1 is a solid-liquid separation method of pressure filtration under the washing action of the first component circulating flow and the mixed solvent second flow; after separation in the separation zone 1, a wet product flow and a mixed solvent first flow are obtained. In terms of mass percentage, the content of the second component in the wet product flow is 0.13%; in terms of mass percentage, the content of the second component in the mixed solvent first flow is 31.79%.

[0160] The wet product flow separated in separation zone one enters separation zone two, and the separation method of separation zone two is dry separation, wherein the drying pressure of separation zone two is 40KPaA; the drying temperature of separation zone two is 75.9°C; after separation in separation zone two, the mixed solvent content in the product flow is 0.02% by mass percentage.

[0161] The first mixed solvent stream and the second mixed solvent stream separated in the separation zone 1 enter the separation zone 3 and are separated into a mixed solvent circulating stream and a first component circulating stream. The operating pressure of the separation zone 3 is 150 KPaA, and the operating temperature is 90.2°C. Under this pressure, the first component accounts for 11.7% and the second component accounts for 88.3% of the mixed solvent circulating stream obtained in the separation zone 3 (i.e., the mixed solvent circulating stream circulated to the mixing zone) by mass percentage. In terms of mass percentage, the first component accounts for more than 99.99% of the first component circulating stream obtained in the separation zone 3, and the impurity content is 50.0 ppm.

[0162] The yield and purity of the long carbon chain nylon salt prepared by the above method and the energy consumption of the device used are shown in Table 1.

[0163] [Comparative Example 1]

[0164] The method adopts the same technical scheme as that of Example 4, except that the ethanol solvent is replaced with DMAC which does not produce azeotropy with water, and the mass ratio of the solvent to the sum of the first powder and the second powder is 3:1.

[0165] The whole process can be carried out and products can be obtained. The difference is that in separation zone three, water and solvent need to be completely separated. The first tower separates water and solvent, the second tower removes light components from the obtained water, and the third tower removes heavy components from the obtained solvent. In this way, the water and solvent separated by at least three distillation towers can be recycled. The whole process has high energy consumption.

[0166] The yield and purity of the long carbon chain nylon salt prepared by the above method and the energy consumption of the device used are shown in Table 1.

[0167] [Comparative Example 2]

[0168] It adopts a technical solution basically the same as that of Example 3, the only difference being that the ethanol solvent is replaced with water, the mass ratio of water to the sum of powder one and powder two is 6:1, and the temperature in the mixing zone must be above 120°C for dissolution and reaction to proceed.

[0169] The whole process can be carried out and the product can be obtained. The difference is that higher temperature and pressure are required in the mixing zone to ensure that the powder is dissolved and then reacted.

[0170] After the reaction is completed, the water needs to be purified in the separation zone three. To remove the light components and heavy components, two distillation towers are needed to remove the light components and heavy components respectively. The obtained water can be recycled and reused. The process consumes a lot of energy.

[0171] The yield and purity of the long carbon chain nylon salt prepared by the above method and the energy consumption of the device used are shown in Table 1.

[0172] [Comparative Example 3]

[0173] It adopts a technical scheme basically the same as that of Example 3, with the only difference being that water is replaced with ethanol solvent, and the entire process is carried out without water, only ethanol, and the process can be carried out to obtain the product. The difference is that the adiabatic temperature rise during the reaction exceeds 100°C (without heat removal), and the adiabatic temperature rise when heat removal is present is 5 to 10°C higher than that of Example 3 (under the same heat removal conditions as Example 3), which affects the product quality.

[0174] In addition, during the transfer of wet product logistics, solvents will evaporate to the work site, affecting the occupational health environment. Due to the evaporation of solvents at the work site, there will be hidden dangers in safety.

[0175] The yield, purity, occupational health environment, reaction exothermic temperature rise, and energy consumption of the device used of the long carbon chain nylon salt prepared by the above method are shown in Table 1.

[0176] Table 1

[0177]

[0178] From the results in Table 1, it can be seen that the present invention uses a mixed solvent in the preparation process of the long carbon chain nylon salt. The mixed solvent recycling method of the present invention is convenient for recycling the mixed solvent, which can be recycled, and the energy consumption during recycling is small, which is beneficial to environmental protection and energy saving. At the same time, the nylon salt obtained by the method of the present invention has a high yield, a high purity of the nylon salt, and a good occupational health environment for operators.

[0179] The present invention has been described in detail above in conjunction with specific implementations and exemplary examples, but these descriptions cannot be understood as limiting the present invention. Those skilled in the art understand that, without departing from the spirit and scope of the present invention, a variety of equivalent substitutions, modifications or improvements may be made to the technical solution of the present invention and its implementation methods, all of which fall within the scope of the present invention. The scope of protection of the present invention shall be subject to the attached claims.

[0180] All publications, patent applications, patents and other references mentioned in this specification are incorporated herein by reference. Unless otherwise defined, all technical and scientific terms used in this specification have the meanings conventionally understood by those skilled in the art. In the event of a conflict, the definition in this specification shall prevail.

[0181] When this specification uses the prefix "well-known to those skilled in the art", "prior art" or similar terms to introduce materials, substances, methods, steps, devices or components, etc., the objects introduced by the prefix cover those commonly used in the art when this application is filed, but also include those that are not commonly used at present but will become generally recognized in the art to be suitable for similar purposes.

[0182] In the context of the present specification, any matters or items not mentioned are directly applicable to those known in the art without any changes except those explicitly stated.

Claims

1. A method for preparing a long carbon chain nylon salt, comprising the following steps: Under a protective atmosphere, reacting powder material 1 and powder material 2 in a mixed solvent; The mixed solvent comprises a first component and a second component; the first component and the second component are each independently selected from n H 2n+2 O, and the compounds corresponding to the first component and the second component are different; 0≤n≤6, n is a natural number; There is an azeotrope between the first component and the second component; The powder material 1 and the powder material 2 are raw materials for preparing long carbon chain nylon salt.

2. The method for preparing a long carbon chain nylon salt according to claim 1, characterized in that: In the first component, n is 0; and / or, In the second component, n is 2≤n≤6, preferably 2≤n≤4, and n is a natural number.

3. A method for recycling a mixed solvent, comprising the following steps: a) under a protective atmosphere, the mixed solvent circulation stream is mixed and reacted with the powder material one stream and the powder material two stream in a mixing zone to generate a crude product stream; in, The mixed solvent circulating stream comprises a first component and a second component; the first component and the second component are each independently selected from a solvent having a molecular formula of C n H 2n+2 O, and the compounds corresponding to the first component and the second component are different; 0≤n≤6, n is a natural number; There is an azeotrope between the first component and the second component; b) sending the crude product stream into separation zone 1 to be separated into a wet product stream and a first mixed solvent stream; sending the wet product stream into separation zone 2 to be separated into a second mixed solvent stream and a product stream, the product stream is sent out of the system, the second mixed solvent stream is returned to separation zone 1 for recycling and / or the second mixed solvent stream is sent into separation zone 3; c) The first mixed solvent stream and optionally the second mixed solvent stream are fed into separation zone three and separated into a mixed solvent circulating stream and a first component circulating stream. The first component circulating stream is returned to separation zone one for recycling, and the mixed solvent circulating stream is returned to the mixing zone for recycling.

4. The method for recycling a mixed solvent according to claim 3, characterized in that: Step a), The first component and the second component have an azeotropic state at 80-400 KPaA; Preferably, In the first component, n is 0; and / or, In the second component, n is 2≤n≤6, preferably 2≤n≤4, and n is a natural number; Further preferably, the second component is selected from at least one of ethanol, n-propanol, isopropanol, n-butanol, isobutanol and tert-butanol, preferably at least one of ethanol, isopropanol and tert-butanol.

5. The method for recycling a mixed solvent according to claim 3, characterized in that: Step a), In the mixed solvent circulating stream, the content of the second component is ≥80wt%, preferably ≥85wt%; Further preferably, the mixed solvent circulating stream is an azeotropic composition of the first component and the second component at the separation pressure; preferably, in the mixed solvent circulating stream, the content of the first component is 4% to 15% by mass; the content of the second component is 96% to 85% by mass; and / or, The mass ratio of the mixed solvent circulating flow to the sum of the powder material 1 and the powder material 2 is (4-2):1; and / or, Taking the total molar amount of powder one and powder two as 100%, the molar proportion of powder one is 0.495-0.499, and the molar proportion of powder two is 0.505-0.501; and / or, The particle size range of the powder 1 and the powder 2 is independently 20 to 100 μm.

6. The method for recycling a mixed solvent according to claim 3, characterized in that: Step a), The powder material 1 and the powder material 2 are raw materials for preparing long carbon chain nylon salt; Preferably, the powder is a dibasic acid, preferably a dibasic acid with a carbon number of ≥10; preferably C 10 ~C 14 More preferably, the dibasic acid has a straight chain and carboxyl groups at both ends; and / or, The powder is a diamine, preferably a diamine with a carbon number ≥ 10; preferably C 10 ~C 16 further preferably a diamine having a straight molecular chain and amine groups at both ends.

7. The method for recycling a mixed solvent according to claim 3, characterized in that: Step a), The reaction temperature of the mixing zone is 50-80°C, preferably 55-75°C; and / or, The reaction time of the mixing zone is 3 to 12 hours, preferably 3 to 10 hours; and / or, The reaction pressure in the mixing zone is 35-400 KPaA, preferably 40-380 KPaA; Preferably, In the mixing zone, the temperature rise of the neutralization reaction is controlled to be ≤10°C, preferably ≤8°C, more preferably ≤5°C.

8. The method for recycling a mixed solvent according to claim 3, characterized in that: Step b), The crude product flow extracted from the mixing zone is a solid-liquid two-phase, and the solid material accounts for 20.0% to 35.0% by mass; and / or, The separation method of the separation zone 1 is solid-liquid separation under the washing action of the first component circulating stream and the optional mixed solvent second stream; preferably, the solid-liquid separation method is filtration separation; and / or, After separation in the separation zone 1, the content of the second component in the wet product stream is ≤0.25%, preferably ≤0.15%, more preferably ≤0.1%, by mass percentage; and / or, In terms of mass percentage, the content of the second component in the first mixed solvent stream is ≤50%, preferably ≤45%.

9. The method for recycling a mixed solvent according to claim 3, characterized in that: Step b), The separation method of the separation zone 2 is dry separation; preferably, The drying pressure of the separation zone 2 is 20 to 85 KPaA, preferably 20 to 60 KPaA; and / or, The drying temperature of the separation zone 2 is 60 to 95°C, preferably 60 to 85°C; and / or, In terms of mass percentage, the content of the mixed solvent in the product stream is ≤ 0.05%, preferably ≤ 0.02%.

10. The method for recycling a mixed solvent according to claim 3, characterized in that: Step c), The separation method of the separation zone three is azeotropic distillation separation; preferably, The operating pressure of the separation zone 3 is 40 to 300 KPaA, preferably 40 to 250 KPaA; and / or, The operating temperature of the separation zone 3 is 55 to 110°C, preferably 55 to 105°C; and / or, In terms of mass percentage, the content of the first component in the first component circulating flow separated from the separation zone three is ≥99.90%, preferably ≥99.95%.

11. A system for recycling a mixed solvent, comprising a mixing zone, a separation zone 1, a separation zone 2 and a separation zone 3: in, The mixing zone is provided with a mixed solvent feed port, a powder material one logistics feed port, a powder material two logistics feed port and a protective gas feed port; the discharge port of the mixing zone is connected to the solid-liquid two-phase feed port of the separation zone one; The wet material discharge port of separation zone one is connected to the feed port of separation zone two; the liquid discharge port of separation zone one is connected to the liquid feed port of separation zone three; The liquid discharge port of separation zone 2 is connected to the liquid feed port of separation zone 1 and / or the liquid discharge port of separation zone 2 is connected to the liquid feed port of separation zone 3; The first component circulating flow outlet of separation zone three is connected to the liquid feed inlet of separation zone one; the mixed solvent circulating flow outlet of separation zone three is connected to the liquid feed inlet of the mixing zone; Preferably, the method for recycling a mixed solvent as described in any one of claims 3 to 10 adopts the system.

12. The system for recycling mixed solvents according to claim 11, characterized in that: The mixing zone is a reactor; and / or, The first separation zone is a pressure filter; and / or, The second separation zone is a drying device; and / or, The separation zone three is an azeotropic distillation tower.

13. Use of the mixed solvent recycling method as claimed in any one of claims 3 to 10 or the mixed solvent recycling system as claimed in any one of claims 11 to 12 in the production of long carbon chain nylon salt.

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