Continuous filtering and washing method and system for long-carbon-chain nylon salt mixture

Abstract

The invention discloses a continuous filtering and washing method and system for long-carbon-chain nylon salt, and the continuous filtering and washing method comprises the following steps: (1) filtering a long-carbon-chain nylon salt mixture to obtain a crude nylon salt solid phase and mother liquor, and carrying out first rectification on the mother liquor to obtain a recovered solvent; (2) sequentially carrying out multiple solvent washing-filtering processes and multiple water washing-filtering processes on the coarse nylon salt solid phase; and (3) drying and discharging. The method and the system mainly solve the problems of complex process flow, low automation degree, high labor cost, low production efficiency, incomplete solvent recovery flow and the like of the intermittent post-treatment process of the long-carbon-chain nylon salt, and have the characteristics of simple flow, high automation degree, labor cost saving, high production efficiency, complete solvent recovery flow, high solvent recovery rate and the like.

Description

Technical Field

[0001] The present invention belongs to the field of post-treatment of nylon salts, and particularly relates to the washing of nylon salts. Specifically, it relates to a continuous filtration and washing method and system for long-chain nylon salts. Background Art

[0002] Nylon, also known as polyamide, abbreviated as PA, is a type of high-molecular compound with amide groups (-NHCO-) in its molecular main chain. They can be made into various plastics, drawn into fibers, and also made into films, coatings, adhesives, etc. Among the family of nylon high-molecular materials, the largest production volumes are nylon 6 and 66. Other varieties include nylon 46, 610, 612, 1010, 11, 12, 1212, 13, etc. As the carbon chain length increases, the properties of nylon change, and the applications of long-chain nylon have covered various fields such as automobiles, electronic and electrical appliances, machinery, and military equipment.

[0003] For long-chain nylons, especially those after nylon 1010, the production process is more complex. The main raw material used is dibasic acid. After a series of complex chemical reactions, the required nylon products are obtained. Mainly, the dibasic acid is subjected to nitrilation and amination treatments, and then mixed with diamine for polymerization treatment to obtain nylon products. The successful independent research and development of this nylon material in China has also provided data references for the research of other long-chain nylon materials, thus resolving the contradiction of long-term dependence on imports and laying a foundation for the further development of the national economy.

[0004] CN1255507A discloses a synthesis process of petroleum bi-fermented nylon 1212, which belongs to the experimental scale of kilograms. Some of the synthesis conditions are relatively harsh, especially the production cycle is relatively long. Applying it to industrial production still requires further optimization and improvement.

[0005] CN 102010506A discloses a synthesis process of petroleum fermented nylon 1212, including the steps of preparing dodecane dinitrile by nitrilation of petroleum fermented dodecanedioic acid, preparing dodecane diamine from dodecane dinitrile, neutralizing dodecane dinitrile and dodecane diamine to prepare petroleum fermented nylon salt 1212, and the polymerization step of petroleum fermented nylon 1212, etc. The process of making nylon salt 1212 is relatively complex, consuming a large amount of solvent, and the post-treatment process after salting is not perfect. How to treat the filtrate, how to recycle the solvent, and how to dry nylon 1212 salt are not described, and it is still in the experimental nature and does not have the conditions for industrial production.

[0006] The existing patents and literature reports mainly focus on the synthesis processes of monomers required for synthesizing long carbon chain nylons. There are few reports on the neutralization reaction process of long carbon chain nylons from monomers to nylon salts, as well as the post-treatment processes after salification. There are even no reports on the continuous post-treatment process of producing long carbon chain nylon salts, as well as the solvent collection, separation, and recycling in the process. Summary of the Invention

[0007] In order to overcome the problems existing in the prior art, the present invention provides a continuous filtration and washing system and method for long carbon chain nylon salts, mainly solving the problems of complex intermittent post-treatment process flow, low automation degree, high labor cost, low production efficiency, and incomplete solvent recovery process of long carbon chain nylon salts, and having the characteristics of simple process, high automation degree, saving labor cost, high production efficiency, complete solvent recovery process, and high solvent recovery rate.

[0008] On the one hand, the present invention provides a continuous filtration and washing method for a long carbon chain nylon salt mixture, including: (1) filtering the long carbon chain nylon salt mixture to obtain a crude nylon salt solid phase and mother liquor, and performing a first rectification on the mother liquor to obtain a recovered solvent; (2) successively performing multiple solvent washing-filtration processes and multiple water washing-filtration processes on the crude nylon salt solid phase; (3) drying and discharging.

[0009] In step (1), the long carbon chain nylon salt mixture includes a long carbon chain nylon salt and a solvent;

[0010] Preferably, the long carbon chain nylon salt is selected from at least one of the nylons shown in - OOC(CH 2 ) m COO - H 3 N(CH 2 ) n NH 3 + where m≥6 and n≥8;

[0011] More preferably, the solvent and water have an azeotropic point under normal pressure; preferably, the solvent is selected from at least one of alcohol solvents; more preferably, the solvent is selected from at least one of the alcohols shown by the formula C i H 2i+2 O, where 5≥i≥2 and i is a natural number.

[0012] The conditions of the first rectification in step (1) include: the top operating pressure is 20KPaA to 350KPaA, preferably 20KPaA to 300KpaA; and / or, the top operating temperature is 40 to 120°C, preferably 40 to 115°C;

[0013] The impurity content in the recycled solvent described in step (1) is independently ≤ 100 ppm.

[0014] Each solvent washing - filtration process independently and sequentially includes a process of introducing a solvent for washing and a process of filtering to obtain a solvent - washed filtrate.

[0015] Preferably, step (2) includes at least two solvent washing - filtration processes; according to the washing sequence or the nylon salt material flow sequence, the washing of the previous solvent washing - filtration process is carried out using the subsequent solvent - washed filtrate filtered in the subsequent solvent washing - filtration process, and the previous solvent - washed filtrate filtered in the previous solvent washing - filtration process is recycled back to the first rectification described in step (1), and the washing of the subsequent solvent washing - filtration process is carried out using the recycled solvent described in step (1).

[0016] More preferably, when the multiple solvent washing - filtration processes described in step (2) are m times, the washing of the 1st to (m / 2)th solvent washing - filtration processes is carried out using the subsequent solvent - washed filtrate filtered in the solvent washing - filtration processes after (excluding) the m / 2th time, and the previous solvent - washed filtrate filtered in the 1st to (m / 2)th solvent washing - filtration processes is recycled back to the first rectification described in step (1); the washing of the solvent washing processes after (excluding) the m / 2th time is carried out using the recycled solvent described in step (1).

[0017] The multiple solvent washing - filtration processes described in step (2) are two times, including: sequentially carrying out the first solvent washing - filtration process and the second solvent washing - filtration process on the crude nylon salt solid phase: among them, the washing of the first solvent washing - filtration process is carried out using the solvent - washed filtrate filtered in the second solvent washing - filtration process, and the solvent - washed filtrate filtered in the first solvent washing - filtration process enters step (1) for the first rectification; the washing of the second solvent washing - filtration process is carried out using the recycled solvent described in step (1).

[0018] Each water washing - filtration process independently and sequentially includes a process of introducing water for washing and a process of filtering to obtain a water - washed filtrate.

[0019] Preferably, step (2) includes at least two water washing - filtration processes; preferably, according to the washing sequence or the nylon salt material flow sequence, the washing of the previous water washing - filtration process is carried out using the subsequent water - washed filtrate filtered in the subsequent water washing - filtration process, and the previous water - washed filtrate filtered in the previous water washing - filtration process is subjected to a second rectification to obtain recycled water and recycled solvent, the washing of the subsequent water washing - filtration process is carried out using the recycled water, and the recycled solvent is mixed with the recycled solvent described in step (1).

[0020] More preferably, when the multiple water washing - filtration process in step (2) is m times, for the 1st to (m / 2)th water washing - filtration processes, the washing is carried out using the filtrate filtered in the water washing - filtration process after the (m / 2)th time (excluding the (m / 2)th time), and the filtrate filtered in the 1st to (m / 2)th water washing - filtration processes is recycled back to the second rectification in step (1); for the water washing process after the (m / 2)th time (excluding the (m / 2)th time), the washing is carried out using the recycled water in step (1).

[0021] The multiple water washing - filtration process in step (2) includes: successively carrying out the first water washing - filtration process and the second water washing - filtration process on the solid phase obtained from the multiple solvent washing - filtration process: wherein, the washing in the first water washing - filtration process is carried out using the water washing filtrate filtered in the second water washing - filtration process, the water washing filtrate filtered in the first water washing - filtration process is subjected to second rectification to obtain recycled water and recycled solvent, the washing in the second water washing - filtration process is carried out using the recycled water, and the recycled solvent is mixed with the recycled solvent in step (1).

[0022] The second rectification is carried out in a series of azeotropic rectification column, extraction rectification column 1 and extraction rectification column 2;

[0023] Preferably, the second rectification includes: the long - chain nylon salt mixture is fed into the middle of the azeotropic rectification column, wherein the azeotrope of solvent and water enters the middle of extraction rectification column 1 from the top of the azeotropic rectification column; the first stream of recycled water is drawn from the bottom of the azeotropic rectification column; an extractant is introduced into the upper side line of extraction rectification column 1, the recycled solvent is drawn from the top of extraction rectification column 1, the mixture of water and extractant flows from the bottom of extraction rectification column 1 into the middle of extraction rectification column 2; the second stream of recycled water is drawn from the top of extraction rectification column 2, and the bottom material of extraction rectification column 2 is recycled back to the upper side line of extraction rectification column 1;

[0024] More preferably, the extractant is selected from at least one of polyhydric alcohols and ionic liquids, preferably at least one of ethylene glycol, glycerol and ionic liquids.

[0025] The conditions of the azeotropic rectification column include: operating pressure 20KPaA - 350KpaA, top operating temperature 40 - 120°C; and / or, the conditions of extraction rectification column 1 include: operating pressure 20KPaA - 350KPaA, top operating temperature 42 - 120°C; and / or, the conditions of extraction rectification column 2 include: operating pressure 15KPaA - 350KPaA, top operating temperature 45 - 135°C.

[0026] The second aspect of the present invention lies in providing a continuous filtration and washing system for a solvent-containing long-chain nylon salt mixture, preferably used for carrying out the method described in one of the objects of the present invention. The system includes a filtration and water washing machine, a first rectification zone, and a second rectification zone; the filtration and water washing machine includes a feed zone, a feed filtration zone, at least two solvent washing-filtration zones, at least two water washing-filtration zones, a drying zone, and a discharge zone connected in series in sequence.

[0027] A feed inlet for the solvent-containing long-chain nylon salt mixture is provided in the feed zone.

[0028] A mother liquor outlet is provided in the feed filtration zone for outputting the filtered mother liquor.

[0029] A gas purge pipeline is provided in the discharge zone for purging the discharge zone with gas to unload it from the system.

[0030] Each solvent washing-filtration zone independently includes a solvent washing sub-zone and a solvent filtration sub-zone; preferably, a solvent washing liquid inlet is independently provided on each solvent washing sub-zone, and a solvent washing filtrate outlet is independently provided on each solvent filtration sub-zone; more preferably, in the series connection order, the solvent washing liquid inlet of any previous solvent washing sub-zone is connected to the solvent washing filtrate outlet of any subsequent solvent filtration sub-zone through a pipeline for passing the solvent washing filtrate obtained from any subsequent solvent filtration sub-zone into any previous solvent washing sub-zone as the washing liquid; the solvent washing liquid inlet of the subsequent solvent washing sub-zone is connected to the solvent feed pipeline for passing solvent into the subsequent solvent washing sub-zone for washing.

[0031] Each water washing-filtration zone independently includes a water washing sub-zone and a water filtration sub-zone; preferably, a water washing liquid inlet is independently provided on each water washing sub-zone, and a water washing filtrate outlet is independently provided on each water filtration sub-zone; more preferably, in the series connection order, the water washing liquid inlet of any previous water washing sub-zone is connected to the water washing filtrate outlet of any subsequent water filtration sub-zone through a pipeline for passing the water washing filtrate obtained from any subsequent water filtration sub-zone into any previous water washing sub-zone as the washing liquid; the water washing liquid inlet of the subsequent water washing sub-zone is connected to the water feed pipeline for passing water into the subsequent water washing sub-zone for washing.

[0032] The first rectification zone includes a first rectification tower; preferably, the middle part of the first rectification tower is independently connected to the mother liquor outlet of the feed filtration zone and the solvent washing filtrate outlet of the previous solvent filtration sub-zone through pipelines for rectifying the mother liquor and the previous solvent washing filtrate; the top of the first rectification tower is connected to the solvent washing liquid inlet of the subsequent solvent washing sub-zone through the solvent feed pipeline for using the recovered solvent obtained by the first rectification treatment for subsequent washing; a heavy component material flow outlet is provided at the bottom of the first rectification tower.

[0033] The second rectification zone includes an azeotropic rectification column, a first extractive rectification column, and a second extractive rectification column;

[0034] Preferably, a material to be rectified feed port is arranged in the middle of the azeotropic rectification column. The top of the azeotropic rectification column is connected to the middle of the first extractive rectification column through a pipeline. A first recovered water discharge pipeline is arranged at the bottom of the azeotropic rectification column. A recovered solvent discharge pipeline is arranged at the top of the first extractive rectification column. An extractant feed port is arranged at the upper side line of the first extractive rectification column. The bottom of the first extractive rectification column is connected to the middle of the second extractive rectification column through a pipeline. A second recovered water discharge pipeline is arranged at the top of the second extractive rectification column. The bottom of the second extractive rectification column is connected to the upper side line of the first extractive rectification column through a pipeline;

[0035] More preferably, the recovered solvent discharge pipeline on the first extractive rectification column is connected to the solvent washing liquid inlet of the subsequent solvent washing sub-zone through the solvent feed pipeline; and / or, the first recovered water discharge pipeline and the second recovered water discharge pipeline are each independently connected to the water washing liquid inlet of the subsequent water washing sub-zone through the water feed pipeline.

[0036] In the ranges and any values disclosed in the present invention, the endpoints and any values are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein. In the following text, in principle, the various technical solutions can be combined with each other to obtain new technical solutions, which should also be regarded as specifically disclosed herein.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] (1) The present invention provides a continuous filtration and washing process for long-chain nylon salt, mainly solving the problems of complex process flow, low automation degree, high labor cost, and low production efficiency in the intermittent post-treatment process of long-chain nylon salt. It has the characteristics of high automation degree, labor cost saving, high production efficiency, complete solvent recovery process, and high solvent recovery rate;

[0039] (2) The present invention provides a supporting process flow necessary for the continuous filtration and washing process of long-chain nylon salt, that is, a full-process separation and purification process of solvent and water, solving the problem of no continuous solvent recovery process in the prior art, and having the characteristics of simple process flow and high solvent recovery rate;

[0040] (3) The long-chain nylon salt obtained finally by the present invention has a low solvent content and does not require a drying process, and can be continuously sent to the downstream for the reaction process, featuring energy conservation and environmental protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 FIG. 1 is a schematic structural diagram showing one embodiment of the system of the present invention;

[0042] Figure 2 FIG. 2 is a schematic structural diagram showing the structure of the second rectification zone in the system of the present invention;

[0043] In Figure 1 and Figure 2 :

[0044] F-101 Filter and Water Wash Machine, T-101 First Rectification Zone, C-101 Second Rectification Zone, T-202 Azeotropic Rectification Tower, T-203 First Extraction Rectification Tower, T-204 Second Extraction Agent Recovery Tower; Figure 1 The filter and water wash machine in the system shown contains F-101, including a feed zone, a feed filtration zone, two solvent washing-filtration zones (the first solvent washing-filtration zone and the second solvent washing-filtration zone respectively), two water washing-filtration zones (the first water washing-filtration zone and the second water washing-filtration zone respectively), a drying zone and a discharge zone. Among them, the first solvent washing-filtration zone includes a first solvent washing sub-zone and a first solvent filtration sub-zone, and the second solvent washing-filtration zone includes a second solvent washing sub-zone and a second solvent filtration sub-zone. The reference numerals are as follows: 1-a Feed Zone, 1-b Feed Filtration Zone, 2-a First Solvent Washing Sub-zone, 2-b First Solvent Filtration Sub-zone, 3-a Second Solvent Washing Sub-zone, 3-b Second Solvent Filtration Sub-zone, 4-a First Water Washing Sub-zone, 4-b First Water Filtration Sub-zone, 5-a Second Water Washing Sub-zone, 5-b Second Water Filtration Sub-zone, 6-a Drying Zone, 6-b Discharge Zone.

[0045] The feed stream 101 contains a solvent and long-chain nylon salt (i.e., long-chain nylon salt mixture), 102 mother liquor, 103 solvent wash filtrate filtered during the second solvent washing-filtration process, 104 solvent wash filtrate filtered during the first solvent washing-filtration process, 108 water wash filtrate filtered during the first water washing-filtration process, 109 recycled water, 110 water wash filtrate filtered during the second water washing-filtration process, 111 purge gas, 112 nylon salt stream, 113 heavy component stream, 114 first recovered solvent, 211 azeotrope of solvent and water, 212 first recovered water, 213 second recovered solvent, 214 water and extraction agent stream, 215 second recovered water, 216 extraction agent stream.

[0046] In the present invention, Figure 1The feed stream (i.e., long-chain nylon salt mixture) 101 containing solvent and long-chain nylon salt is continuously fed into the feed zone 1-a of the filtration and water-washing machine F-101 with six working zones. In the feed filtration zone 1-b, the stream 101 containing solvent and long-chain nylon salt is separated into long-chain nylon salt and mother liquor 102. The long-chain nylon salt is fed into the first solvent washing sub-zone 2-a, and the mother liquor 102 is sent to the first rectification zone T-101. After the long-chain nylon salt in the first solvent washing sub-zone 2-a is mixed with the solvent washing filtrate 103 filtered during the second solvent washing - filtration process, it is separated into long-chain nylon salt and the solvent washing filtrate 104 obtained by filtration during the first solvent washing - filtration process in the first solvent filtration sub-zone 2-b. The long-chain nylon salt is fed into the second solvent washing sub-zone 3-a, and the solvent washing filtrate 104 obtained by filtration during the first solvent washing - filtration process is sent to the first rectification zone T-101. After the long-chain nylon salt in the second solvent washing sub-zone 3-a is mixed with the recovered solvent 114, it is separated into long-chain nylon salt and the solvent washing filtrate 103 filtered during the second solvent washing - filtration process in the second solvent filtration sub-zone 3-b. The long-chain nylon salt is fed into the first water washing sub-zone 4-a, and the solvent washing filtrate 103 filtered during the second solvent washing - filtration process is sent to the first solvent washing sub-zone 2-a. After the long-chain nylon salt in the first water washing sub-zone 4-a is mixed with the water washing filtrate 110 filtered during the second water washing - filtration process, it is separated into long-chain nylon salt and the water washing filtrate 108 obtained by filtration during the first water washing - filtration process in the first water filtration sub-zone 4-b. The long-chain nylon salt is fed into the second water washing sub-zone 5-a, and the water washing filtrate 108 obtained by filtration during the first water washing - filtration process is sent to the second rectification zone C-101. After the long-chain nylon salt in the second water washing sub-zone 5-a is mixed with the recovered water 109, it is separated into long-chain nylon salt and the water washing filtrate 110 filtered during the second water washing - filtration process in the second water filtration sub-zone 5-b. The long-chain nylon salt is fed into the drying zone 6-a and sent out of the filtration and water-washing machine from the discharge zone 6-b as the nylon salt stream 112. The water washing filtrate 110 filtered during the second water washing - filtration process is sent to the first water washing sub-zone 4-a. The mother liquor 102 and the solvent washing filtrate 104 obtained by filtration during the first solvent washing - filtration process are separated in the first rectification zone into the first recovered solvent 114 and the heavy component stream 113. At least part of the first recovered solvent 114 is sent to the second solvent washing sub-zone 3-a. The water washing filtrate 108 obtained by filtration during the first water washing - filtration process is sent to the second rectification zone to be separated into the second recovered solvent 213 and the recovered water 109. After the second recovered solvent 213 is mixed with the first recovered solvent 114, at least part of it is sent to the second solvent washing sub-zone 3-a, and at least part of the recovered water 109 is sent to the second water washing sub-zone 5-a.

[0047] In the present invention, Figure 2In the process, the water-washing filtrate 108 obtained by filtration during the first water-washing and filtration process is sent to the azeotropic distillation column T202 in the second rectification zone. The azeotrope 211 of the solvent and water taken from the top of the column is sent to the extraction distillation column T203. The first recovered water 212 is taken from the bottom of the azeotropic distillation column T202; the second recovered solvent 213 is taken from the top of the extraction distillation column T203, and the water and extractant stream 214 taken from the bottom of the column is sent to the extraction distillation column T204; the second recovered water 215 is taken from the top of the extraction distillation column T204, and at least a part of the extractant stream 216 taken from the bottom of the column is returned to the extraction distillation column T204. Detailed implementation mode

[0048] One of the objectives of the present invention is to provide a continuous filtration and washing method for a long-chain nylon salt mixture, including: (1) filtering the long-chain nylon salt mixture to obtain a crude nylon salt solid phase and a mother liquor, and subjecting the mother liquor to a first rectification to obtain a recovered solvent; (2) sequentially performing multiple solvent washing and filtration processes and multiple water washing and filtration processes on the crude nylon salt solid phase; (3) drying and discharging.

[0049] In a preferred implementation mode, the long-chain nylon salt mixture in step (1) includes a long-chain nylon salt and a solvent.

[0050] In a further preferred implementation mode, the weight percentage of the solvent in the long-chain nylon salt mixture is ≥50%.

[0051] In an even more preferred implementation mode, in the long-chain nylon salt mixture, the weight ratio of the solvent to the nylon salt is (2-5):1, such as 2:1, 3:1, 4:1 or 5:1.

[0052] In a preferred implementation mode, the solvent and water have an azeotropic point under normal pressure; preferably, the solvent is selected from at least one of alcohol solvents; more preferably, the solvent is selected from at least one of the alcohols represented by the formula C i H 2i+2 O, where 5≥i≥2 (for example, i = 2, 3, 4 or 5), and i is a natural number.

[0053] In a further preferred implementation mode, the solvent is selected from ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-butanol, tert-butanol, and more preferably ethanol, isopropanol, tert-butanol.

[0054] In a preferred implementation mode, the long-chain nylon salt is selected from - OOC(CH 2 ) m COO - H 3 N(CH 2 ) n NH3 + At least one of the nylon shown, wherein m≥6 and n≥8.

[0055] In a further preferred embodiment, the long-chain nylon salt is selected from - OOC(CH 2 ) m COO - H 3 N(CH 2 ) n NH 3 + At least one of the nylon shown, wherein m≥8 and n≥10.

[0056] In a preferred embodiment, the conditions of the first rectification in step (1) include: the top operating pressure is 20 KPaA to 350 KPaA, preferably 20 KPaA to 300 KPaA, such as 20 KPaA, 50 KPaA, 80 KPaA, 100 KPaA, 150 KPaA, 200 KPaA, 250 KPaA, 300 KPaA or 350 KPaA; and / or, the top operating temperature is 40 to 120 °C, preferably 40 to 115 °C, such as 40 °C, 60 °C, 80 °C, 100 °C or 120 °C.

[0057] Among them, the mother liquor in step (1) and the filtrate obtained by filtration during the solvent washing - filtration process in step (2) for several times are recycled to the first rectification in step (1). Since the vast majority of them are solvents and contain trace amounts of unreacted raw materials (mainly long-chain diamines, with a weight percentage of ≤1%) and nylon salts with smaller particle sizes, and since the boiling points of the solvent, long-chain diamines, and nylon salts are quite different, separation can be completed using a conventional single rectification column or flash distillation. The solvent is taken out from the top (top of the flash tank) (recovered solvent), and at least part of it is recycled to the subsequent solvent washing - filtration process as the washing solvent. The heavy component stream can be continuously or intermittently taken out from the bottom of the column (bottom of the flash tank) in a small flow rate.

[0058] In a preferred embodiment, the impurity content in the recovered solvent in step (1) is independently ≤100 ppm.

[0059] In a preferred embodiment, each solvent washing - filtration process independently and sequentially includes a process of introducing a solvent for washing and a process of filtering to obtain a solvent-washed filtrate.

[0060] In a further preferred embodiment, step (2) includes at least two solvent washing - filtration processes; according to the washing sequence or the nylon salt material flow sequence, the washing in the previous solvent washing - filtration process is carried out using the subsequent solvent washing filtrate filtered in the subsequent solvent washing - filtration process, and the previous solvent washing filtrate filtered in the previous solvent washing - filtration process is recycled back to the first rectification in step (1), and the washing in the subsequent solvent washing - filtration process is carried out using the recovered solvent in step (1).

[0061] Wherein, the "previous" refers to the first 50% times, and the "subsequent" refers to the last 50% times.

[0062] In a still further preferred embodiment, when the multiple solvent washing - filtration processes in step (2) are m times, the washing in the solvent washing - filtration processes of the 1st to (m / 2) times is carried out using the subsequent solvent washing filtrate filtered in the solvent washing - filtration processes after the (m / 2)th time (excluding the (m / 2)th time), and the previous solvent washing filtrate filtered in the solvent washing - filtration processes of the 1st to (m / 2) times is recycled back to the first rectification in step (1); the washing in the solvent washing processes after the (m / 2)th time (excluding the (m / 2)th time) is carried out using the recovered solvent in step (1).

[0063] Preferably, the multiple solvent washing - filtration processes in step (2) are two times, including: successively carrying out the first solvent washing - filtration process and the second solvent washing - filtration process on the solid phase of the crude nylon salt: wherein, the washing in the first solvent washing - filtration process is carried out using the solvent washing filtrate filtered in the second solvent washing - filtration process, and the solvent washing filtrate filtered in the first solvent washing - filtration process enters step (1) for the first rectification; the washing in the second solvent washing - filtration process is carried out using the recovered solvent in step (1).

[0064] More preferably, the multiple solvent washing - filtration processes in step (2) are two times, including: carrying out the first washing and the first filtration on the solid phase of the crude nylon salt to obtain the nylon salt solid phase after the first solvent washing and the first solvent washing filtrate, and the first solvent washing filtrate enters step (1) for the first rectification; using the recovered solvent in step (1) to carry out the second washing and the second filtration on the nylon salt solid phase after the first solvent washing to obtain the nylon salt solid phase after the second solvent washing and the second solvent washing filtrate, and the second solvent washing filtrate is used as the washing liquid for the first washing.

[0065] In a preferred embodiment, each water washing - filtration process independently and successively includes a process of introducing water for washing and a process of filtering to obtain the water washing filtrate.

[0066] In a further preferred embodiment, step (2) includes at least two water washing - filtration processes; preferably, according to the washing sequence or the nylon salt material flow sequence, the washing in the previous water washing - filtration process is carried out using the subsequent water washing filtrate filtered in the subsequent water washing - filtration process, the previous water washing filtrate filtered in the previous water washing - filtration process is subjected to a second rectification to obtain recovered water and recovered solvent, the washing in the subsequent water washing - filtration process is carried out using the recovered water, and the recovered solvent is mixed with the recovered solvent in step (1).

[0067] Among them, the "previous" refers to the first 50% times, and the "subsequent" refers to the last 50% times.

[0068] In an even more preferred embodiment, when the multiple water washing - filtration processes in step (2) are m times, the washing in the 1st to (m / 2)th water washing - filtration processes is carried out using the filtrate filtered in the water washing - filtration processes after the (m / 2)th time (excluding the (m / 2)th time), and the filtrate filtered in the 1st to (m / 2)th water washing - filtration processes is recycled back to the second rectification in step (1); the washing in the water washing processes after the (m / 2)th time (excluding the (m / 2)th time) is carried out using the recovered water in step (1).

[0069] Preferably, the multiple water washing - filtration processes in step (2) include: successively carrying out a first water washing - filtration process and a second water washing - filtration process on the solid phase obtained from the multiple solvent washing - filtration processes: among them, the washing in the first water washing - filtration process is carried out using the water washing filtrate filtered in the second water washing - filtration process, the water washing filtrate filtered in the first water washing - filtration process is subjected to a second rectification to obtain recovered water and recovered solvent, the washing in the second water washing - filtration process is carried out using the recovered water, and the recovered solvent is mixed with the recovered solvent in step (1).

[0070] More preferably, the multiple water washing - filtration processes in step (2) are two times, including: carrying out a first water washing and a first filtration on the solid phase obtained from the multiple solvent washing - filtration processes to obtain the nylon salt solid phase after the previous water washing and the previous water washing filtrate, the previous water washing filtrate is subjected to a second rectification to obtain recovered water and recovered solvent, the recovered solvent is mixed with the recovered solvent in step (1), carrying out a second water washing and a second filtration on the nylon salt solid phase after the previous water washing using the recovered water to obtain the nylon salt solid phase after the subsequent water washing and the subsequent water washing filtrate, and the subsequent water washing filtrate is sent to the first water washing and used as the washing liquid.

[0071] Among them, the previous washing filtrate contains the solvent and water, and the weight percentage of the solvent is 1-15 wt%, such as 1 wt%, 2 wt%, 4 wt%, 6 wt%, 8 wt%, 10 wt%, 12 wt%, 14 wt% or 15 wt%.

[0072] In the present invention, the multiple water washing - filtration process is relatively complex. In order to achieve continuous production of the whole process, multiple water washings are used to wash and remove the residual solvent after the previous solvent washing. By weight percentage, the solvent content in the nylon salt after water washing is ≤50 ppm, providing a process guarantee for the subsequent continuous polymerization reaction process.

[0073] In a preferred embodiment, the second rectification is carried out in a series of an azeotropic rectification column, an extraction rectification column 1 and an extraction rectification column 2.

[0074] In a further preferred embodiment, the second rectification includes: the long-chain nylon salt mixture is fed into the middle of the azeotropic rectification column. Among them, the azeotrope of the solvent and water enters the middle of the extraction rectification column 1 from the top of the azeotropic rectification column; the first recovered water is drawn from the bottom of the azeotropic rectification column; the extractant is introduced into the upper side line of the extraction rectification column 1, the recovered solvent is drawn from the top of the extraction rectification column 1, and the mixture of water and the extractant flows from the bottom of the extraction rectification column 1 into the middle of the extraction rectification column 2; the second recovered water is drawn from the top of the extraction rectification column 2, and the bottom material of the extraction rectification column 2 (mainly including the extractant) is recycled to the upper side line of the extraction rectification column 1.

[0075] Among them, the weight percentage of the solvent in the azeotrope of the solvent and water from the top of the azeotropic rectification column is ≥50%, preferably ≥55%. The first recovered water and the second recovered water are combined to obtain the recovered water; the impurity weight content in the recovered water is ≤500 ppm, preferably ≤200 ppm. The bottom material of the extraction rectification column 2 contains the extractant, optional solvent and optional water, and the total weight content of the solvent and water is ≤20 ppm, preferably ≤10 ppm.

[0076] Preferably, a feed port for the material to be rectified is arranged in the middle of the azeotropic rectification column. The top of the azeotropic rectification column is connected to the middle of the extraction rectification column 1 through a pipeline. A first recovered water discharge pipeline is arranged at the bottom of the azeotropic rectification column. A recovered solvent discharge pipeline is arranged at the top of the extraction rectification column 1. An extractant feed port is arranged on the upper side line of the extraction rectification column 1. The bottom of the extraction rectification column 1 is connected to the middle of the extraction rectification column 2 through a pipeline. A second recovered water discharge pipeline is arranged at the top of the extraction rectification column 2. The bottom of the extraction rectification column 2 is connected to the upper side line of the extraction rectification column 1 through a pipeline.

[0077] In a further preferred embodiment, the extractant is selected from at least one of polyols and ionic liquids, preferably at least one of ethylene glycol, glycerol and ionic liquids.

[0078] In a preferred embodiment, the conditions of the azeotropic distillation column include: an operating pressure of 20 KPaA to 350 KpaA and a top operating temperature of 40 to 120 °C; and / or, the conditions of the first extractive distillation column include: an operating pressure of 20 KPaA to 350 KPaA and a top operating temperature of 42 to 120 °C; and / or, the conditions of the second extractive distillation column include: an operating pressure of 15 KPaA to 350 KPaA and a top operating temperature of 45 to 135 °C.

[0079] For example, the conditions of the azeotropic distillation column include: an operating pressure of 20 KpaA, 50 KpaA, 100 KpaA, 150 KpaA, 200 KpaA, 250 KpaA, 300 KpaA or 350 KpaA and a top operating temperature of 40 °C, 60 °C, 80 °C, 100 °C or 120 °C; and / or, the conditions of the first extractive distillation column include: an operating pressure of 20 KPaA, 50 KPaA, 100 KPaA, 150 KPaA, 200 KPaA, 250 KPaA, 300 KPaA or 350 KPaA and a top operating temperature of 42 °C, 50 °C, 60 °C, 70 °C, 80 °C, 90 °C, 100 °C, 110 °C or 120 °C; and / or, the conditions of the second extractive distillation column include: an operating pressure of 15 KPaA, 50 KPaA, 100 KPaA, 150 KPaA, 200 KPaA, 250 KPaA, 300 KPaA or 350 KPaA and a top operating temperature of 45 °C, 50 °C, 60 °C, 80 °C, 100 °C, 120 °C or 135 °C.

[0080] In a further preferred embodiment, the conditions of the azeotropic distillation column include: an operating pressure of 20 KPaA to 300 KPaA and a top operating temperature of 40 to 115 °C; and / or, the conditions of the first extractive distillation column include: an operating pressure of 20 KPaA to 300 KPaA and a top operating temperature of 42 to 115 °C; and / or, the conditions of the second extractive distillation column include: an operating pressure of 15 KPaA to 300 KPaA and a top operating temperature of 45 to 130 °C.

[0081] The present invention discloses a continuous filtration and washing process for long-chain nylon salt. Among them, a feed stream containing a solvent that forms an azeotrope with water under normal pressure and accounts for ≥50% by weight in the azeotropic composition and long-chain nylon salt is passed through a filtration and water washing machine with at least six working areas that are connected end to end in a disc shape. After one separation of nylon salt and solvent, at least two solvent washings of nylon salt, at least two water washings of nylon salt, and one separation of nylon salt and the water washing filter, a purified nylon salt product is obtained.

[0082] Preferably, the number of times of solvent washing the crude nylon salt solid phase separated in the first working area in the filtration and water washing machine is 1 - 5 times, preferably 2 - 4 times. As the number of washing times increases, the working areas of the filtration and water washing machine also increase accordingly, and countercurrent sleeve washing is used for washing. Preferably, the number of times of water washing the nylon salt obtained after at least two solvent washings in the filtration and water washing machine is 1 - 5 times, preferably 2 - 4 times. As the number of washing times increases, the working areas of the filtration and water washing machine also increase accordingly, and countercurrent sleeve washing is used for washing.

[0083] Preferably, the method is carried out in a system including a filtration and water washing machine, a first rectification area, and a second rectification area. The filtration and water washing machine includes a feed area, a feed filtration area, two solvent washing - filtration areas (the first solvent washing - filtration area and the second solvent washing - filtration area respectively), two water washing - filtration areas (the first water washing - filtration area and the second water washing - filtration area respectively), a drying area, and a discharge area, and includes the following steps:

[0084] a) A feed stream containing a solvent and long-chain nylon salt is continuously fed into the feed area, and then separated into a crude nylon salt solid phase and mother liquor in the feed filtration area. The crude nylon salt solid phase is fed into the first solvent washing - filtration area, and the mother liquor is sent to the first rectification area;

[0085] b) In the first solvent washing - filtration area, the crude nylon salt solid phase is washed with the filtrate from the second solvent washing - filtration area and then filtered to obtain nylon salt solid phase i and filtrate i. The nylon salt solid phase i is fed into the second solvent washing - filtration area, and the filtrate i is sent to the first rectification area;

[0086] c) In the second solvent washing - filtration area, the nylon salt solid phase i is washed with the recycled solvent and then filtered to obtain nylon salt solid phase ii and filtrate ii. The nylon salt solid phase ii is fed into the first water washing - filtration area, and the filtrate is sent to the first solvent washing - filtration area;

[0087] d) In the first water washing - filtration area, the nylon salt solid phase ii is washed with the filtrate from the second water washing - filtration area and then filtered to obtain nylon salt solid phase iii and filtrate iii. The nylon salt solid phase iii is fed into the second water washing - filtration area, and the filtrate iii is sent to the second rectification area;

[0088] e) The nylon salt solid phase iii in the second water washing - filtration zone is washed with recycled water and then filtered to obtain the nylon salt solid phase iv and filtrate iv. The nylon salt solid phase iv is sent to the drying zone and sent out of the filtration water washer from the discharge zone as the feed for the subsequent process, and the filtrate iv is sent to the first water washing - filtration zone;

[0089] f) The mother liquor in step a) and the filtrate i from the first solvent washing - filtration zone are separated in the first rectification zone to obtain the first recycled solvent and the heavy component stream;

[0090] g) The filtrate obtained in the first water washing - filtration zone is sent iii to the second rectification zone to be separated into recycled water and the second recycled solvent, and the second recycled solvent is mixed with the first recycled solvent to form the recycled solvent.

[0091] Wherein, each washing - filtration zone of the filtration water washer is divided into two sub - zones. The previous sub - zone receives external materials, and the latter sub - zone separates (such as filters) the materials.

[0092] In the technical solution of the present invention, the filtration water washer has an automatic unloading function for nylon salt.

[0093] In the technical solution of the present invention, the nylon salt is purged and unloaded from the system by gas in the last working zone of the filtration water washer, and this working zone then receives the feed stream containing solvent and long - carbon - chain nylon salt.

[0094] In the technical solution of the present invention, the purging gas is carbon dioxide, or / and nitrogen, or other inert gases.

[0095] In the technical solution of the present invention, the filtration percentage of nylon salt with a particle size of 10 - 45 μm by the filtration water washer is ≥99.6%.

[0096] Wherein, the filtration percentage of the filtration water washer can be achieved by the selection of filter cloth and filtration pressure.

[0097] In the technical solution of the present invention, through a large number of experiments and solvent screening work, the inventors finally determined the type and proportion of the solvent required for solvent washing, and then, according to the common characteristics of the selected solvents, creatively proposed the solvent separation and purification process described in the present invention, providing technical support for continuous filtration and washing.

[0098] A second object of the present invention is to provide a continuous filtration and washing system for a solvent-containing long carbon chain nylon salt mixture, preferably for carrying out the method described in one of the objects of the present invention. The system includes a filtration and water washing machine, a first rectification zone, and a second rectification zone; the filtration and water washing machine includes a feed zone, a feed filtration zone, at least two solvent washing-filtration zones, at least two water washing-filtration zones, a drying zone, and a discharge zone connected in series in sequence.

[0099] Preferably, the feed zone and the discharge zone are connected end to end, and the system is in a disc shape and rotates around the center.

[0100] In a preferred embodiment, a feed port for a solvent-containing long carbon chain nylon salt mixture is provided in the feed zone; and / or, a mother liquor outlet is provided in the feed filtration zone for outputting the filtered mother liquor.

[0101] In a preferred embodiment, a gas purge pipeline is provided in the discharge zone for purging the discharge zone with gas to unload it from the system.

[0102] In a preferred embodiment, each solvent washing-filtration zone independently includes a solvent washing sub-zone and a solvent filtration sub-zone.

[0103] In a further preferred embodiment, a solvent washing liquid inlet is independently provided on each solvent washing sub-zone, and a solvent washing filtrate outlet is independently provided on each solvent filtration sub-zone.

[0104] In a further preferred embodiment, in the series connection order, the solvent washing liquid inlet of any previous solvent washing sub-zone is connected to the solvent washing filtrate outlet of any subsequent solvent filtration sub-zone through a pipeline for introducing the solvent washing filtrate obtained from any subsequent solvent filtration sub-zone into any previous solvent washing sub-zone as the washing liquid; the solvent washing liquid inlet of the subsequent solvent washing sub-zone is connected to the solvent feed pipeline for introducing solvent into the subsequent solvent washing sub-zone for washing.

[0105] Wherein, the "previous" refers to the first 50%, and the "subsequent" refers to the last 50%.

[0106] In a preferred embodiment, in the series connection order, the at least two solvent washing-filtration zones include a first solvent washing-filtration zone and a second solvent washing-filtration zone. The first solvent washing-filtration zone includes a first solvent washing sub-zone and a first solvent filtration sub-zone, and the second solvent washing-filtration zone includes a second solvent washing sub-zone and a second solvent filtration sub-zone.

[0107] In a further preferred embodiment, a solvent washing liquid inlet is independently provided on each of the first solvent sub-region and the second solvent sub-region, and a solvent washing filtrate outlet is independently provided on each of the first solvent sub-region and the second solvent sub-region.

[0108] In an even more preferred embodiment, the solvent washing liquid inlet of the first solvent washing sub-region is connected to the solvent washing filtrate outlet of the second solvent filtering sub-region through a pipeline for introducing the solvent washing filtrate obtained from the second solvent filtering sub-region into the first solvent washing sub-region as a washing liquid; the solvent washing liquid inlet of the second solvent washing sub-region is connected to (preferably connected to the top of the first rectification column and / or the top of the first extractive rectification column through) a solvent feed pipeline for introducing a solvent (preferably a recycled solvent) into the second solvent washing sub-region for washing.

[0109] In a preferred embodiment, each water washing - filtering zone independently includes a water washing sub-region and a water filtering sub-region.

[0110] In a further preferred embodiment, a water washing liquid inlet is independently provided on each water washing sub-region, and a water washing filtrate outlet is independently provided on each water filtering sub-region.

[0111] In an even more preferred embodiment, in a series order, the water washing liquid inlet of any previous water washing sub-region is connected to the water washing filtrate outlet of any subsequent water filtering sub-region through a pipeline for introducing the water washing filtrate obtained from any subsequent water filtering sub-region into any previous water washing sub-region as a washing liquid; the water washing liquid inlet of the subsequent water washing sub-region is connected to a water feed pipeline for introducing water into the subsequent water washing sub-region for washing.

[0112] Wherein, the "previous" refers to the first 50%, and the "subsequent" refers to the last 50%.

[0113] In a preferred embodiment, in a series order, the at least two water washing - filtering zones include a first water washing - filtering zone and a second water washing - filtering zone. The first water washing - filtering zone includes a first water washing sub-region and a first water filtering sub-region, and the second water washing - filtering zone includes a second water washing sub-region and a second water filtering sub-region.

[0114] In a further preferred embodiment, a water washing liquid inlet is independently provided on each of the first water washing sub-region and the second water washing sub-region, and a water washing filtrate outlet is independently provided on each of the first water filtering sub-region and the second water filtering sub-region.

[0115] In a further preferred embodiment, the water washing liquid inlet of the first water washing sub-region is connected to the water washing filtrate outlet of the second water filtration sub-region through a pipeline, for introducing the water washing filtrate obtained from the second water filtration sub-region into the first water washing sub-region as the washing liquid; the water washing liquid inlet of the second water washing sub-region is connected to (preferably connected to the bottom of the azeotropic distillation column and / or the top of the second extractive distillation column through) a water feed pipeline, for introducing water into the second water washing sub-region for washing.

[0116] In a preferred embodiment, the first distillation zone includes a first distillation column.

[0117] In a further preferred embodiment, the middle part of the first distillation column is independently connected to the mother liquor outlet of the feed filtration zone and the solvent washing filtrate outlet of the previous solvent filtration sub-region through pipelines, for rectifying the mother liquor and the previous solvent washing filtrate; the top of the first distillation column is connected to the solvent washing liquid inlet of the subsequent solvent washing sub-region through the solvent feed pipeline, for using the recovered solvent obtained by the first rectification treatment for subsequent washing; a heavy component material flow outlet is provided at the bottom of the first distillation column.

[0118] In a preferred embodiment, the second distillation zone includes an azeotropic distillation column, a first extractive distillation column, and a second extractive distillation column.

[0119] In a further preferred embodiment, a material to be rectified feed port is provided in the middle part of the azeotropic distillation column, the top of the azeotropic distillation column is connected to the middle part of the first extractive distillation column through a pipeline, a recovered water discharge pipeline I is provided at the bottom of the azeotropic distillation column, a recovered solvent discharge pipeline is provided at the top of the first extractive distillation column, an extractant feed port is provided on the upper side line of the first extractive distillation column, the bottom of the first extractive distillation column is connected to the middle part of the second extractive distillation column through a pipeline, a recovered water discharge pipeline II is provided at the top of the second extractive distillation column, and the bottom of the second extractive distillation column is connected to the upper side line of the first extractive distillation column through a pipeline.

[0120] In a further preferred embodiment, the recovered solvent discharge pipeline on the first extractive distillation column is connected to the solvent washing liquid inlet of the subsequent solvent washing sub-region through the solvent feed pipeline; and / or, the recovered water discharge pipeline I and the recovered water discharge pipeline II are each independently connected to the water washing liquid inlet of the subsequent water washing sub-region through the water feed pipeline.

[0121] The present invention will be specifically described below in conjunction with specific embodiments. It is necessary to point out here that the following embodiments are only used for further illustration of the present invention and cannot be understood as limiting the protection scope of the present invention. Some non-essential improvements and adjustments made by those skilled in the art to the present invention based on the content of the present invention still fall within the protection scope of the present invention.

[0122] In addition, it should be noted that the various specific technical features described in the following specific embodiments can be combined in any appropriate manner without contradiction. To avoid unnecessary repetition, the present invention will not separately describe various possible combinations.

[0123] In addition, any combination can be made among various different embodiments of the present invention as long as it does not violate the idea of the present invention. The technical solutions thus formed belong to a part of the original disclosure of this specification and also fall within the protection scope of the present invention.

[0124] The raw materials used in the examples and comparative examples, if not particularly limited, are those disclosed in the prior art. For example, they can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0125]

Example 1

[0126] Adopt Figure 1 and Figure 2 the said system.

[0127] The feed stream (i.e., long-chain nylon salt mixture) 101 containing a solvent and long-chain nylon salt is continuously fed into the feed zone 1-a of the filtration and washing machine F-101 with six working zones. In the feed filtration zone 1-b, the stream 101 containing a solvent and long-chain nylon salt is separated into long-chain nylon salt and mother liquor 102. The long-chain nylon salt is fed into the first solvent washing sub-zone 2-a, and the mother liquor 102 is sent to the first rectification zone T-101; after the long-chain nylon salt in the first solvent washing sub-zone 2-a is mixed with the solvent washing filtrate 103 filtered during the second solvent washing-filtration process, it is separated into long-chain nylon salt and the solvent washing filtrate 104 filtered during the first solvent washing-filtration process in the first solvent filtration sub-zone 2-b. The long-chain nylon salt is fed into the second solvent washing sub-zone 3-a, and the solvent washing filtrate 104 filtered during the first solvent washing-filtration process is sent to the first rectification zone T-101; after the long-chain nylon salt in the second solvent washing sub-zone 3-a is mixed with the recovered solvent 114, it is separated into long-chain nylon salt and the solvent washing filtrate 103 filtered during the second solvent washing-filtration process in the second solvent filtration sub-zone 3-b. The long-chain nylon salt is fed into the first water washing sub-zone 4-a, and the solvent washing filtrate 103 filtered during the second solvent washing-filtration process is sent to the first solvent washing sub-zone 2-a; after the long-chain nylon salt in the first water washing sub-zone 4-a is mixed with the water washing filtrate 110 filtered during the second water washing-filtration process, it is separated into long-chain nylon salt and the water washing filtrate 108 filtered during the first water washing-filtration process in the first water filtration sub-zone 4-b. The long-chain nylon salt is fed into the second water washing sub-zone 5-a, and the water washing filtrate 108 filtered during the first water washing-filtration process is sent to the second rectification zone C-101; after the long-chain nylon salt in the second water washing sub-zone 5-a is mixed with the recovered water 109, it is separated into long-chain nylon salt and the water washing filtrate 110 filtered during the second water washing-filtration process in the second water filtration sub-zone 5-b. The long-chain nylon salt is fed into the drying zone 6-a and sent out of the filtration and washing machine from the discharge zone 6-b as the nylon salt stream 112, and the water washing filtrate 110 filtered during the second water washing-filtration process is sent to the first water washing sub-zone 4-a; the mother liquor 102 and the solvent washing filtrate 104 filtered during the first solvent washing-filtration process are separated into the first recovered solvent 114 and the heavy component stream 113 in the first rectification zone. At least part of the first recovered solvent 114 is sent to the second solvent washing sub-zone 3-a; the water washing filtrate 108 filtered during the first water washing-filtration process is sent to the second rectification zone to be separated into the second recovered solvent 213 and the recovered water 109. After the second recovered solvent 213 is mixed with the first recovered solvent 114, at least part of it is sent to the second solvent washing sub-zone 3-a, and at least part of the recovered water 109 is sent to the second water washing sub-zone 5-a.

[0128] The water-washing filtrate 108 obtained by filtration during the first water-washing and filtration process is sent to the azeotropic distillation column T202 in the second rectification zone. The azeotrope 211 of the solvent and water taken from the top of the column is sent to the extraction distillation column T203. The first recovered water 212 is taken from the bottom of the azeotropic distillation column T202; the second recovered solvent 213 is taken from the top of the extraction distillation column T203, and the water and extractant stream 214 taken from the bottom of the column is sent to the extraction distillation column T204; the second recovered water 215 is taken from the top of the extraction distillation column T204, and at least part of the extractant stream 216 taken from the bottom of the column is returned to the extraction distillation column T204.

[0129] The feed includes 16.7 wt% of long-chain nylon salt and 83.3 wt% of ethanol solvent, and the long-chain nylon salt is selected from - OOC(CH 2 ) m COO - H 3 N(CH 2 ) n NH 3 + at least one of the nylons shown, where m = 12 and n = 14.

[0130] The conditions for the first rectification include: the operating pressure at the top of the column is 20 KPaA, and the operating temperature at the top of the column is 42.6 °C; the conditions for the azeotropic distillation column include: the operating pressure is 20 KpaA, and the operating temperature at the top of the column is 42.8 °C; the conditions for the first extraction distillation column include: the operating pressure is 20 KPaA, and the operating temperature at the top of the column is 42.6 °C; the conditions for the second extraction distillation column include: the operating pressure is 15 KPaA, and the operating temperature at the top of the column is 53.6 °C, and the extractant is ethylene glycol.

[0131] The alcohol solvent content in the final nylon salt is 42.5 ppm.

[0132] In this embodiment, it is not necessary to rectify all the filtrates. Only partial filtrates, especially the previous filtrates, need to be rectified. This not only reduces the energy consumption, but also the solvent content in the obtained nylon salt is low and is equivalent to the effect of the comparative example, achieving unexpected technical effects.

[0133]

Example 2

[0134] Repeat the process of Example 1, with the difference that:

[0135] The feed includes 20 wt% of long-chain nylon salt and 80 wt% of ethanol solvent, and the long-chain nylon salt is selected from - OOC(CH 2 ) m COO - H 3 N(CH 2 )n NH 3 + At least one of the nylons shown, m = 11, n = 13.

[0136] The conditions of the first rectification include: the top operating pressure is 50 KPaA, and the top operating temperature is 61.6 °C; the conditions of the azeotropic rectification column include: the operating pressure is 80 KpaA, and the top operating temperature is 72.7 °C; the conditions of the first extractive rectification column include: the operating pressure is 60 KPaA, and the top operating temperature is 65.7 °C; the conditions of the second extractive rectification column include: the operating pressure is 70 KPaA, and the top operating temperature is 89.6 °C, and the extractant is ethylene glycol.

[0137] The alcohol solvent content in the final nylon salt is 41.3 ppm.

[0138]

Example 3

[0139] Repeat the process of Example 1, with the differences being:

[0140] The feed includes 25 wt% long-chain nylon salt and 75 wt% ethanol solvent, and the long-chain nylon salt is selected from - OOC(CH 2 ) m COO - H 3 N(CH 2 ) n NH 3 + At least one of the nylons shown, m = 10, n = 12.

[0141] The conditions of the first rectification include: the top operating pressure is 100 KPaA, and the top operating temperature is 78.0 °C; the conditions of the azeotropic rectification column include: the operating pressure is 150 KpaA, and the top operating temperature is 88.7 °C; the conditions of the first extractive rectification column include: the operating pressure is 120 KPaA, and the top operating temperature is 82.7 °C; the conditions of the second extractive rectification column include: the operating pressure is 130 KPaA, and the top operating temperature is 106.7 °C, and the extractant is ethylene glycol.

[0142] The alcohol solvent content in the final nylon salt is 40.0 ppm.

[0143]

Example 4

[0144] Repeat the process of Example 1, with the differences being:

[0145] The feed includes 28.6 wt% long-chain nylon salt and 72.4 wt% isopropanol solvent, and the long-chain nylon salt is selected from - OOC(CH 2 ) mCOO - H 3 N(CH 2 ) n NH 3 + At least one of the nylons shown, m = 9, n = 11.

[0146] The conditions for the first rectification include: the top operating pressure is 200 KPaA, and the top operating temperature is 100.9 °C; the conditions for the azeotropic rectification column include: the operating pressure is 250 KpaA, and the top operating temperature is 105.1 °C; the conditions for the first extractive rectification column include: the operating pressure is 220 KPaA, and the top operating temperature is 102.5 °C; the conditions for the second extractive rectification column include: the operating pressure is 240 KPaA, and the top operating temperature is 125.4 °C, and the extractant is glycerol.

[0147] The alcohol solvent content in the final nylon salt is 38.8 ppm.

[0148]

Example 5

[0149] Repeat the process of Example 1, with the difference that:

[0150] The feed includes 33.3 wt% long-chain nylon salt and 66.7 wt% tert-butanol solvent, and the long-chain nylon salt is selected from - OOC(CH 2 ) m COO - H 3 N(CH 2 ) n NH 3 + At least one of the nylons shown, m = 8, n = 10.

[0151] The conditions for the first rectification include: the top operating pressure is 300 KPaA, and the top operating temperature is 114.6 °C; the conditions for the azeotropic rectification column include: the operating pressure is 350 KpaA, and the top operating temperature is 115.4 °C; the conditions for the first extractive rectification column include: the operating pressure is 350 KPaA, and the top operating temperature is 116.9 °C; the conditions for the second extractive rectification column include: the operating pressure is 350 KPaA, and the top operating temperature is 137.7 °C, and the extractant is ionic liquid 1-butyl-3-methylimidazolium chloride.

[0152] The alcohol solvent content in the final nylon salt is 37.5 ppm.

[0153]

Comparative Example 1

[0154] The process of Example 1 is repeated, with the difference that: the solvent washing filtrate 103 filtered during the second solvent washing - filtration process and the solvent washing filtrate 104 filtered during the first solvent washing - filtration process are both fed into the first rectification zone, and the recycled solvent is introduced into both the first solvent washing sub - zone 2 - a and the second solvent washing sub - zone 3 - a. Other conditions remain unchanged.

[0155] The solvent content in the final nylon salt of Comparative Example 1 is similar to that of Example 1. However, in the first rectification zone of Comparative Example 1, due to the too large processing volume, the energy consumption increases by 206.5% compared with Example 1.

[0156] The present invention has been described in detail above in combination with specific embodiments and exemplary examples. However, these descriptions should not be construed as limiting the present invention. Those skilled in the art understand that without departing from the spirit and scope of the present invention, various equivalent substitutions, modifications or improvements can be made to the technical solutions and their implementation manners of the present invention, and these all fall within the scope of the present invention. The protection scope of the present invention is subject to the appended claims.

Claims

1. A continuous filtration and washing method for a long carbon chain nylon salt mixture, comprising: (1) Filtering the long carbon chain nylon salt mixture to obtain a crude nylon salt solid phase and mother liquor, and performing a first rectification on the mother liquor to obtain a recovered solvent; (2) Sequentially performing multiple solvent washing - filtration processes and multiple water washing - filtration processes on the crude nylon salt solid phase; (3) Drying and discharging.

2. The continuous filtration and washing method according to claim 1, characterized in that the long carbon chain nylon salt mixture in step (1) comprises a long carbon chain nylon salt and a solvent; Preferably, the long-chain nylon salt is selected from - OOC(CH 2 ) m COO - H 3 N(CH 2 ) n NH 3 + at least one of the nylons shown, where m ≥ 6 and n ≥ 8; More preferably, the solvent and water have an azeotropic point under normal pressure; preferably, the solvent is selected from at least one of alcohol solvents; more preferably, the solvent is selected from at least one of the alcohols represented by the formula C i H 2i+2 O, where 5≥i≥2 and i is a natural number.

3. The continuous filtration and washing method according to claim 1, characterized in that the conditions of the first rectification in step (1) include: the top operating pressure is 20 KPaA to 350 KPaA, preferably 20 KPaA to 300 KpaA; and / or, the top operating temperature is 40 to 120 °C, preferably 40 to 115 °C; and / or, the impurity content in the recovered solvent in step (1) is independently ≤ 100 ppm.

4. The continuous filtration and washing method according to claim 1, characterized in that each solvent washing - filtration process independently and sequentially includes a process of introducing a solvent for washing and a process of filtering to obtain a solvent - washed filtrate; preferably, step (2) includes at least two solvent washing - filtration processes; according to the washing sequence or the nylon salt material flow sequence, the washing of the previous solvent washing - filtration process is carried out using the subsequent solvent - washed filtrate filtered in the subsequent solvent washing - filtration process, and the previous solvent - washed filtrate filtered in the previous solvent washing - filtration process is recycled to the first rectification in step (1), and the washing of the subsequent solvent washing - filtration process is carried out using the recovered solvent in step (1); more preferably, when the multiple solvent washing - filtration processes in step (2) are m times, the washing of the 1st to (m / 2)th solvent washing - filtration processes is carried out using the subsequent solvent - washed filtrate filtered in the solvent washing - filtration processes after the m / 2th time, and the previous solvent - washed filtrate filtered in the 1st to (m / 2)th solvent washing - filtration processes is recycled to the first rectification in step (1); the washing of the solvent washing process after the m / 2th time is carried out using the recovered solvent in step (1).

5. The continuous filtration and washing method according to claim 4, characterized in that the multiple solvent washing - filtration processes in step (2) are two times, including: sequentially performing a first solvent washing - filtration process and a second solvent washing - filtration process on the crude nylon salt solid phase: wherein, the washing of the first solvent washing - filtration process is carried out using the solvent - washed filtrate filtered in the second solvent washing - filtration process, and the solvent - washed filtrate filtered in the first solvent washing - filtration process enters step (1) for the first rectification; the washing of the second solvent washing - filtration process is carried out using the recovered solvent in step (1).

6. The continuous filtration and washing method according to claim 1, characterized in that Each water washing - filtration process independently and sequentially includes a process of introducing water for washing and a process of filtering to obtain water - washed filtrate; Preferably, step (2) includes at least two water washing - filtration processes; preferably, according to the washing sequence or the nylon salt material flow sequence, the washing of the previous water washing - filtration process is carried out using the subsequent water - washed filtrate filtered in the subsequent water washing - filtration process, the previous water - washed filtrate filtered in the previous water washing - filtration process is subjected to a second rectification to obtain recovered water and recovered solvent, the washing of the subsequent water washing - filtration process is carried out using the recovered water, and the recovered solvent is mixed with the recovered solvent in step (1); More preferably, when the multiple water washing - filtration processes in step (2) are m times, the washing of the 1st to (m / 2)th water washing - filtration processes is carried out using the filtrate filtered in the water washing - filtration processes after the m / 2th time, and the filtrate filtered in the 1st to (m / 2)th water washing - filtration processes is recycled back to the second rectification in step (1); the washing of the water washing processes after the m / 2th time is carried out using the recovered water in step (1).

7. The continuous filtration and washing method according to claim 6, characterized in that, the multiple water washing - filtration processes in step (2) include: sequentially carrying out a first water washing - filtration process and a second water washing - filtration process on the solid phase obtained from the multiple solvent washing - filtration processes: wherein, the washing of the first water washing - filtration process is carried out using the water - washed filtrate filtered in the second water washing - filtration process, the water - washed filtrate filtered in the first water washing - filtration process is subjected to a second rectification to obtain recovered water and recovered solvent, the washing of the second water washing - filtration process is carried out using the recovered water, and the recovered solvent is mixed with the recovered solvent in step (1).

8. The continuous filtration and washing method according to any one of claims 1 to 7, characterized in that, the second rectification is carried out in a series of azeotropic rectification column, extraction rectification column one and extraction rectification column two; Preferably, the second rectification includes: the long - chain nylon salt mixture is fed into the middle of the azeotropic rectification column, wherein the azeotrope of solvent and water enters the middle of the extraction rectification column one from the top of the azeotropic rectification column; the first stream of recovered water is drawn from the bottom of the azeotropic rectification column; an extractant is introduced into the upper side line of the extraction rectification column one, the recovered solvent is drawn from the top of the extraction rectification column one, and the mixture of water and extractant flows from the bottom of the extraction rectification column one into the middle of the extraction rectification column two; the second stream of recovered water is drawn from the top of the extraction rectification column two, and the bottom material of the extraction rectification column two is recycled back to the upper side line of the extraction rectification column one; More preferably, the extractant is selected from at least one of polyols and ionic liquids, preferably at least one of ethylene glycol, glycerol and ionic liquids.

9. The continuous filtration and washing method according to claim 8, characterized in that, The conditions of the azeotropic distillation column include: an operating pressure of 20 KPaA to 350 KpaA and a top operating temperature of 40 to 120 °C; and / or, the conditions of the first extractive distillation column include: an operating pressure of 20 KPaA to 350 KPaA and a top operating temperature of 42 to 120 °C; and / or, the conditions of the second extractive distillation column include: an operating pressure of 15 KPaA to 350 KPaA and a top operating temperature of 45 to 135 °C.

10. A continuous filtration and washing system for a solvent-containing long-chain nylon salt mixture, preferably used for carrying out the method according to any one of claims 1 to 9. The system includes a filtration and water washing machine, a first distillation zone, and a second distillation zone; the filtration and water washing machine includes a feed zone, a feed filtration zone, at least two solvent washing-filtration zones, at least two water washing-filtration zones, a drying zone, and a discharge zone connected in series in sequence.

11. The continuous filtration and washing system according to claim 10, characterized in that a feed port for the solvent-containing long-chain nylon salt mixture is provided in the feed zone; and / or, a mother liquor outlet is provided in the feed filtration zone for outputting the filtered mother liquor; and / or, a gas purge pipeline is provided in the discharge zone for purging the discharge zone with gas to unload the system.

12. The continuous filtration and washing system according to claim 10, characterized in that each solvent washing-filtration zone independently includes a solvent washing sub-zone and a solvent filtration sub-zone; preferably, a solvent washing liquid inlet is independently provided on each solvent washing sub-zone, and a solvent washing filtrate outlet is independently provided on each solvent filtration sub-zone; more preferably, in the series connection order, the solvent washing liquid inlet of any previous solvent washing sub-zone is connected to the solvent washing filtrate outlet of any subsequent solvent filtration sub-zone through a pipeline for introducing the solvent washing filtrate obtained from any subsequent solvent filtration sub-zone into any previous solvent washing sub-zone as the washing liquid; the solvent washing liquid inlet of the subsequent solvent washing sub-zone is connected to the solvent feed pipeline for introducing solvent into the subsequent solvent washing sub-zone for washing; and / or each water washing-filtration zone independently includes a water washing sub-zone and a water filtration sub-zone; preferably, a water washing liquid inlet is independently provided on each water washing sub-zone, and a water washing filtrate outlet is independently provided on each water filtration sub-zone; more preferably, in the series connection order, the water washing liquid inlet of any previous water washing sub-zone is connected to the water washing filtrate outlet of any subsequent water filtration sub-zone through a pipeline for introducing the water washing filtrate obtained from any subsequent water filtration sub-zone into any previous water washing sub-zone as the washing liquid; the water washing liquid inlet of the subsequent water washing sub-zone is connected to the water feed pipeline for introducing water into the subsequent water washing sub-zone for washing.

13. The continuous filtration and washing system according to any one of claims 10 to 12, characterized in that The first rectification zone includes a first rectification column; preferably, the middle part of the first rectification column is independently connected to the mother liquor outlet of the feed filtration zone and the solvent washing filtrate outlet of the previous solvent filtration sub-zone through pipelines, for rectifying the mother liquor and the previous solvent washing filtrate; the top of the first rectification column is connected to the solvent washing liquid inlet of the subsequent solvent washing sub-zone through the solvent feed pipeline, for using the recovered solvent obtained by the first rectification treatment for subsequent washing; a heavy component material flow outlet is provided at the bottom of the first rectification column; and / or, The second rectification zone includes an azeotropic rectification column, an extraction rectification column 1 and an extraction rectification column 2; Preferably, a material to be rectified feed inlet is provided in the middle of the azeotropic rectification column, the top of the azeotropic rectification column is connected to the middle of the extraction rectification column 1 through a pipeline, a recovered water discharge pipeline 1 is provided at the bottom of the azeotropic rectification column, a recovered solvent discharge pipeline is provided at the top of the extraction rectification column 1, an extractant feed inlet is provided at the upper side line of the extraction rectification column 1, the bottom of the extraction rectification column 1 is connected to the middle of the extraction rectification column 2 through a pipeline, a recovered water discharge pipeline 2 is provided at the top of the extraction rectification column 2, and the bottom of the extraction rectification column 2 is connected to the upper side line of the extraction rectification column 1 through a pipeline; More preferably, the recovered solvent discharge pipeline on the extraction rectification column 1 is connected to the solvent washing liquid inlet of the subsequent solvent washing sub-zone through the solvent feed pipeline; and / or, the recovered water discharge pipeline 1 and the recovered water discharge pipeline 2 are each independently connected to the water washing liquid inlet of the subsequent water washing sub-zone through the water feed pipeline.

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