CN114452924B - System and method for improving quality of recovered caprolactam and recovery process - Google Patents
System and method for improving quality of recovered caprolactam and recovery process Download PDFInfo
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- CN114452924B CN114452924B CN202210058963.1A CN202210058963A CN114452924B CN 114452924 B CN114452924 B CN 114452924B CN 202210058963 A CN202210058963 A CN 202210058963A CN 114452924 B CN114452924 B CN 114452924B
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- JBKVHLHDHHXQEQ-UHFFFAOYSA-N epsilon-caprolactam Chemical compound O=C1CCCCCN1 JBKVHLHDHHXQEQ-UHFFFAOYSA-N 0.000 title claims abstract description 26
- 238000011084 recovery Methods 0.000 title claims abstract description 21
- 238000000034 method Methods 0.000 title claims abstract description 16
- 238000005406 washing Methods 0.000 claims abstract description 71
- 239000000126 substance Substances 0.000 claims abstract description 54
- 239000007788 liquid Substances 0.000 claims abstract description 53
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 claims abstract description 30
- 229910021645 metal ion Inorganic materials 0.000 claims abstract description 27
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 22
- 239000012535 impurity Substances 0.000 claims abstract description 19
- 229910000147 aluminium phosphate Inorganic materials 0.000 claims abstract description 15
- 238000001914 filtration Methods 0.000 claims abstract description 15
- 238000001816 cooling Methods 0.000 claims abstract description 10
- 238000001704 evaporation Methods 0.000 claims abstract description 7
- 230000008020 evaporation Effects 0.000 claims abstract description 6
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 claims description 33
- 238000005507 spraying Methods 0.000 claims description 20
- 239000012286 potassium permanganate Substances 0.000 claims description 18
- 238000006243 chemical reaction Methods 0.000 claims description 15
- 239000000498 cooling water Substances 0.000 claims description 10
- 230000007246 mechanism Effects 0.000 claims description 10
- 239000007921 spray Substances 0.000 claims description 8
- 238000009298 carbon filtering Methods 0.000 claims description 6
- 230000000694 effects Effects 0.000 claims description 3
- 125000004122 cyclic group Chemical group 0.000 claims description 2
- 229910019142 PO4 Inorganic materials 0.000 abstract description 9
- 238000000926 separation method Methods 0.000 abstract description 8
- 238000006116 polymerization reaction Methods 0.000 abstract description 6
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 abstract description 5
- 239000010452 phosphate Substances 0.000 abstract description 5
- 239000002699 waste material Substances 0.000 abstract description 2
- 239000000047 product Substances 0.000 description 12
- 230000009471 action Effects 0.000 description 10
- 239000002893 slag Substances 0.000 description 8
- 239000000243 solution Substances 0.000 description 7
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 6
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 6
- 230000008569 process Effects 0.000 description 6
- 238000004519 manufacturing process Methods 0.000 description 5
- 229910052799 carbon Inorganic materials 0.000 description 4
- 239000003054 catalyst Substances 0.000 description 4
- 238000012691 depolymerization reaction Methods 0.000 description 4
- 238000000605 extraction Methods 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- 238000010438 heat treatment Methods 0.000 description 3
- 230000006872 improvement Effects 0.000 description 3
- 238000004458 analytical method Methods 0.000 description 2
- 238000005336 cracking Methods 0.000 description 2
- 230000018044 dehydration Effects 0.000 description 2
- 238000006297 dehydration reaction Methods 0.000 description 2
- 238000007599 discharging Methods 0.000 description 2
- 239000000706 filtrate Substances 0.000 description 2
- NUJOXMJBOLGQSY-UHFFFAOYSA-N manganese dioxide Chemical compound O=[Mn]=O NUJOXMJBOLGQSY-UHFFFAOYSA-N 0.000 description 2
- 230000033116 oxidation-reduction process Effects 0.000 description 2
- 238000001179 sorption measurement Methods 0.000 description 2
- 238000003860 storage Methods 0.000 description 2
- 229920002292 Nylon 6 Polymers 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 239000000110 cooling liquid Substances 0.000 description 1
- 230000031700 light absorption Effects 0.000 description 1
- 239000006166 lysate Substances 0.000 description 1
- 239000012528 membrane Substances 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 125000000896 monocarboxylic acid group Chemical group 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 238000005086 pumping Methods 0.000 description 1
- 239000002351 wastewater Substances 0.000 description 1
Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
- B01J19/18—Stationary reactors having moving elements inside
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D15/00—Separating processes involving the treatment of liquids with solid sorbents; Apparatus therefor
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
- B01J19/0006—Controlling or regulating processes
- B01J19/0013—Controlling the temperature of the process
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- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Organic Chemistry (AREA)
- Analytical Chemistry (AREA)
- Removal Of Specific Substances (AREA)
Abstract
The invention relates to the field of polymerization, in particular to a system and a method for improving the quality of recovered caprolactam and improving a recovery process. The system is added on a depolymerization evaporation pipeline from a depolymerization tower to a pre-removal water tower and comprises washing equipment, chemical treatment equipment and filtering separation equipment which are connected in sequence. The depolymerized substance evaporated from the depolymerization tower enters a washing device to finish washing, cooling and collecting the depolymerized substance, then enters a chemical treatment device to oxidize and reduce phosphoric acid and oligomers in the washing liquid, finally enters a filtering and separating device, and returns to a pre-removing water tower after removing yellow impurities and metal ions. The invention fully solves the problems of phosphoric acid and oligomers, changes waste into valuable, and prevents pipeline equipment of a pre-dewatering and rectifying system from being blocked by phosphate and oligomers; the quality of the CPL recovered finished product is greatly improved, the index UV value and PN value of the CPL recovered finished product are greatly improved and become stable, the color is yellowish and disappears, the content of impurities and metal ions is greatly reduced, and the pH value becomes more stable and easier to control.
Description
Technical Field
The invention relates to the field of polymerization, in particular to a system and a method for improving the quality of recovered caprolactam and improving a recovery process.
Background
The extraction water recovery system of the polyamide 6 polymerization plant generally adopts a Gimar recovery process, and the specific process is as follows (shown in figure 1): the extraction water in the polymerization section is collected in an extraction water storage tank 1', the extraction water (aqueous solution containing 10% of caprolactam CPL) in the storage tank is conveyed to a triple-effect evaporation system 2' through a pump, heated and evaporated to be concentrated to 85% of CPL solution, then conveyed to a low-element separation tower 3' for heating and separation through Heating Medium (HMS), CPL and water vapor are evaporated to a pre-removal tower 4', the low-element is conveyed to a depolymerization tower 5' through a low-element conveying pump, the low-element is cracked under the action of phosphoric acid (H 3PO4) serving as a catalyst under the action of heat provided by 10bar Superheated Steam (SSL), lysate (CPL+water vapor+a little low-element+a little H 3PO4) is evaporated to a pre-removal tower 4', the low-element and dregs which are not cracked are discharged from the bottom of the tower, the pre-removal tower 4' is circulated and used for cooling and collecting materials evaporated from the low-element separation tower 3' and the depolymerization tower 5' under the action of a circulating pump, the action of a circulating pump is heated and circulated through a heater 6', then water is completed under the action of vacuum pump pumping, and at the same time, a proper amount of sodium hydroxide is added into the pre-removal tower 4' under the action of a proper amount of heat pump to the action of the cooling liquid to adjust pH value of the acidic substance in the solution. The 98% CPL solution after water removal is sent to a first-effect rectifying tower 7 '(a first-effect rectifying heater 71'), a second-effect rectifying tower 8 '(a second-effect rectifying heater 81'), rectified and separated under the action of absolute vacuum and heat provided by 10bar steam, qualified CPL separated by rectification enters a CPL collecting tank 9', and then is sent to a polymerization tower for polymerization, the bottom slag which cannot be separated is left at the bottom of the second-effect rectifying tower, and then is sent to an evaporation film device 10' for separation through a second-effect rectifying circulating pump, the evaporated CPL returns to the first-effect rectifying tower 7', and the residue flows to a residue collecting tank 11'.
However, in Ji Ma actual production of recovered caprolactam, the inventors of the present application found that there are problems that the existing recovery system cannot solve:
1. The UV value (ultraviolet light absorption value) and PN value (potassium permanganate absorption value) of the recovered CPL finished product are unstable and low, the color is yellow, and the content of impurities and metal ions is high;
2. the bottom slag of the secondary rectifying tower is more, the content of the oligomer is higher, and the slag discharge amount of the evaporating film is larger;
3. The pipeline equipment of the pre-dewatering and rectifying system is easy to be blocked, in particular to a residue discharging pipe;
4. The depolymerization reaction in the depolymerization tower is not well controlled, and the volatile phosphoric acid and the oligomer go to a pre-dewatering system.
The present inventors have found through production studies and analyses that the problems are mainly caused by the depolymerization reaction of the low-order components in the depolymerization tower and the imperfect treatment of the depolymerization product evaporated into the pre-removal tower in the latter stage. The depolymerization reaction in the depolymerization tower takes phosphoric acid as a catalyst, high-temperature steam of 10bar is used for providing heat to cause forced cracking of low-element bodies, in the cracking process, the feeding amount and concentration of the low-element bodies, the concentration of the catalyst and the content in the catalyst, and the pressure/temperature/flow of the high-temperature steam all have fluctuation to different degrees, which is the incapability of realizing accurate control of external factors, and emergency conditions such as power jump, feeding failure of the low-element bodies, pressure drop and temperature drop of the high-temperature steam, production failure at the later stage and the like can be caused, the temperature, the liquid level and the pressure of materials in the depolymerization tower are unstable, fluctuation exceeding a controllable range can also occur from time to time, and further, excessive phosphoric acid and oligomer are contained in the evaporated depolymerization products and enter the pre-dehydration tower to react with sodium hydroxide in the pre-dehydration tower, and a large amount of phosphate is generated. The CPL solution has excessive phosphate and oligomer, is easy to block the pipeline equipment of the pre-dewatering and rectifying system, has more slag at the bottom of the rectifying system, has larger slag discharge amount, and has poor quality (such as unstable UV value and PN value and lower recovered CPL finished product). The depolymerization reaction characteristic in the depolymerization tower causes the color of the depolymerized matter to be yellow when the depolymerized matter is condensed into CPL solution, impurities and metal ions which are not easy to volatilize circulate in the whole production system, and the pre-dewatering and rectifying system has no treatment equipment, so that the color of the recovered CPL finished product is yellow, and the content of the impurities and the metal ions is high.
Disclosure of Invention
The invention aims to solve the technical problems of improving the quality of recovered caprolactam and improving the recovery process, and provides a system and a method for improving the quality of recovered CPL, reducing the amount of rectification slag discharge, solving the problems of pre-dewatering and blockage of rectification pipeline equipment, and treating phosphoric acid and oligomers evaporated from a depolymerization tower.
The invention is realized in the following way:
the invention firstly provides a system for improving the quality of recovered caprolactam and improving the recovery process, which is added on a depolymerization product evaporation pipeline from a depolymerization tower to a pre-removal tower and comprises the following devices connected in sequence:
(1) Washing equipment for washing, cooling and collecting depolymerization products;
(2) Chemical treatment equipment for carrying out chemical treatment on chemical impurity components in the washing liquid generated by the washing equipment;
(3) And the filtering and separating equipment is used for removing yellow and impurities and separating metal ions from the chemical treatment liquid generated by the chemical treatment equipment.
Specifically:
the washing equipment comprises a washing tower with a spraying mechanism, a cooling water heat exchanger, a condensate collecting tank and a condensate spraying pump which are sequentially and circularly connected; the bottom of the washing tower is connected with the chemical treatment equipment through a washing liquid delivery pump.
Further, the spraying mechanism is arranged at the top of the washing tower, and the condensate spraying pump is connected with the spraying mechanism and used for conveying condensate to the spraying mechanism.
The chemical treatment equipment comprises a reaction kettle with a jacket and a stirrer, wherein the top of the reaction kettle is provided with a potassium permanganate inlet and a hydrogen peroxide inlet, and the potassium permanganate inlet and the hydrogen peroxide inlet are respectively connected with corresponding adding devices; the bottom of the reaction kettle is connected with the filtering and separating equipment through a chemical treatment liquid conveying pump; mainly uses potassium permanganate and hydrogen peroxide to oxidation-reduce phosphoric acid and oligomer in the washing liquid.
The filtering and separating equipment comprises an active carbon filtering device and a metal ion separating device which are connected in sequence, wherein the active carbon filtering device is mainly used for removing yellow and impurities by adsorption, and the metal ion separating device is used for separating metal ions.
Further, a filtrate outlet of the active carbon filtering device is connected with a feed inlet of the metal ion separation device.
After the improvement of the system, the invention also provides a recovery process for improving the quality of recovered caprolactam by using the system:
The depolymerization evaporated from the depolymerization tower enters a washing device to finish washing, cooling and collecting the depolymerization, then is conveyed to a chemical treatment device by a washing liquid conveying pump, phosphoric acid, oligomers and the like in the washing liquid are subjected to oxidation reduction treatment under the action of potassium permanganate and hydrogen peroxide, and then is conveyed to a filtering separation device by the chemical treatment liquid conveying pump after chemical treatment, and finally returns to a pre-removal water tower after removing yellow impurities and separating metal ions, and is continuously involved in the subsequent stage of production.
The method specifically comprises the following steps:
(1) The water vapor evaporated from the depolymerization tower enters a washing tower, becomes condensate under the heat exchange effect of a cooling water heat exchanger, and part of condensate is circularly sprayed to the washing tower through a spray pump, and the rest of condensate is discharged; the depolymerization substance evaporated after the depolymerization tower is cooled and collected at the bottom of a washing tower under the cyclic spraying of condensate, the pressure is controlled to be at micro negative pressure (800-900 mbar) by a control valve on a spraying mechanism at the top of the washing tower, the temperature of washing liquid in the washing tower is controlled to be 85-100 ℃ by a cooling water heat exchanger and the flow rate of spraying liquid, and the CPL concentration in the washing liquid is 30-60%, so that the washing, cooling and collection of the depolymerization substance is completed;
(2) The tower bottom washing liquid obtained in the step (1) is sent to chemical treatment equipment through a washing liquid conveying pump, a stirrer is started, the temperature of the solution in the reaction kettle is controlled to be 45-60 ℃, and then potassium permanganate and hydrogen peroxide are respectively added for chemical reaction, so that the chemical treatment of phosphoric acid, oligomers and the like in the washing liquid is completed;
(3) And (3) conveying the chemical treatment liquid obtained in the step (2) to filtering and separating equipment through a chemical treatment liquid conveying pump, removing yellow and impurities through an active carbon filtering device, separating metal ions through a metal ion separating device, and returning to the pre-removing water tower.
Further:
In the step (2), the concentration of potassium permanganate and hydrogen peroxide is 5-8% (mass flow ratio of materials). The main chemical reactions that occur are as follows:
① (oligomer ）n+KMnO4+H2O2→H2N(CH2)5COOH+MnO2+KOH+O2)
②4KMnO4+5H2O2+6H3PO4→2K2PO4+4MnPO4+14H2O+6O2
Wherein H 2N(CH2)5 COOH is recovered CPL.
The invention improves the recovery process flow based on the original Ji Ma recovery process flow, and designs and adds three systems of depolymerization washing, chemical treatment and filtrate chemical treatment on a depolymerization evaporation pipeline from a depolymerization tower to a pre-dehydrating tower, and the following benefits obviously appear after the improvement:
1. After the depolymerization substance evaporated from the depolymerization tower is fully treated by chemical treatment equipment, the phosphoric acid and the oligomer in the depolymerization substance are oxidized and reduced, so that the problem of changing waste into valuable is fully solved, and phosphate and oligomer are not produced in the later stage;
2. the pipeline equipment of the pre-water and rectification system is not blocked by phosphate and oligomer;
3. the bottom slag of the rectifying tower is also greatly reduced, the slag discharge amount is greatly reduced, and the cost is saved;
4. after the depolymerization is treated by the filtering and separating equipment, impurities and metal ions in the depolymerization are separated, and the color of the material is absorbed;
5. The quality of the CPL recovered finished product is greatly improved, the index UV value and PN value of the CPL recovered finished product are greatly improved and become stable, the color is yellowish and disappears, the content of impurities and metal ions is greatly reduced, and the pH value becomes more stable and easier to control;
6. the recovery process is more perfect, the exception handling is more convenient, and the occurrence of large exceptions due to emergency can be reduced to the greatest extent.
Drawings
The invention will be further described with reference to examples of embodiments with reference to the accompanying drawings.
Fig. 1 is a flow chart of the execution of a conventional CPL recovery process.
FIG. 2 is a system for improving the recovery process and a flow chart for performing the process of the present invention (the dashed box represents the addition of the present invention to an existing system).
In the figure: SSL is 10bar superheated steam, WC is cooling water, WCC is chilled water, WW is wastewater, and HMS is liquid heating medium.
Detailed Description
The invention relates to a system for improving the quality of recovered caprolactam and improving the recovery process (each device contained in the following equipment is an existing conventional device, and the devices are connected through pipelines to form corresponding equipment), which comprises (as shown in figure 2):
1. the washing equipment 1 mainly washes, cools and collects depolymerization evaporated from a depolymerization tower 5', and the system consists of a washing tower 11 with a spray mechanism, a cooling water heat exchanger 12, a condensate collecting tank 13, a condensate spray pump 14 and a washing liquid conveying pump 15.
2. The chemical treatment equipment 2 is mainly used for oxidizing and reducing phosphoric acid, oligomers and the like in the washing liquid by potassium permanganate and hydrogen peroxide, and mainly comprises a reaction kettle 21 with temperature control, a stirrer 22, a potassium permanganate adding device 23, a hydrogen peroxide adding device 24 and a chemical treatment liquid conveying pump 25.
3. The filtering and separating device 3 mainly comprises an active carbon filter and a metal ion separator, wherein the active carbon is used for adsorbing and removing yellow and impurities, and the metal ion separator is used for separating metal ions.
The process improvement through the system is as follows:
The depolymerization substance evaporated from the depolymerization tower 5 'enters the washing tower 11 to finish washing, cooling and collecting the depolymerization substance, then is sent to the reaction kettle 21 through the washing liquid conveying pump 15, is subjected to oxidation reduction treatment on phosphoric acid, oligomers and the like in the washing liquid under the action of potassium permanganate and hydrogen peroxide, is sent to the filtering and separating equipment 3 through the chemical treatment liquid conveying pump 25 after being subjected to chemical treatment, is subjected to adsorption and impurity removal by activated carbon, is returned to the pre-removal water tower 4' after being separated by the metal ion separator, and is continuously participated in the later-stage process.
The specific process flow and operation are as follows:
(1) The water vapor evaporated from the depolymerization tower 5' enters the washing tower 11, becomes condensate under the heat exchange effect of the cooling water heat exchanger 12, and part of condensate circularly sprays the washing tower 11 through the spray pump 14, and the excessive water is discharged; the depolymerized substance evaporated after the depolymerization tower 5' is cooled and collected at the bottom of the washing tower 11 under the circulating spraying of condensate liquid, and meanwhile, the spraying liquid flows to the bottom of the washing tower after spraying, and does not enter the circulation, so that the concentration and the temperature of the washing liquid are controlled;
The pressure is controlled at micro negative pressure (800-900 mbar) by a control valve 16 on a cooling spray pipe at the top of the washing tower, the temperature of the washing liquid in the washing tower is controlled at 85-100 ℃ by a cooling water heat exchanger 12 and the flow rate of the spray liquid, the CPL concentration in the washing liquid is 30-60%, so that the depolymerization product is washed and cooled, and the washing liquid at the bottom of the tower is collected.
(2) The washing liquid at the bottom of the tower is sent to a reaction kettle 21 through a washing liquid conveying pump 15, a stirrer 22 is started when a proper liquid level exists in the washing liquid conveying pump, the temperature of the solution in the reaction kettle 21 is controlled to be 45-60 ℃ through a chilled water jacket, and potassium permanganate and hydrogen peroxide with the concentration of 5-8% are added through a potassium permanganate adding device 23 and a hydrogen peroxide adding device 24 (the adding devices are containers for respectively placing potassium permanganate and hydrogen peroxide, and a conveying pump can be added on a discharging pipeline), so that the chemical treatment of phosphoric acid, oligomers and the like in the washing liquid is completed.
(3) The chemical treatment liquid is sent to a filtering and separating device 3 through a chemical treatment liquid conveying pump 25, and after the active carbon is used for absorbing and removing yellow and impurities and the metal ion separator is used for separating metal ions, the chemical treatment liquid returns to a pre-removing water tower 4'; the chemical treatment liquid is treated by an active carbon filter 31, then flows into a metal ion separation membrane device 32 for treatment through a pipeline, and finally enters a pre-dewatering tower 4' through the pipeline.
TABLE 1 index analysis and comparison of recovery System for newly added chemical treatment and recovered CPL product produced by original Ji Ma recovery System
As shown in table 1, after the system treatment, the quality of the recovered CPL product is greatly improved, the indexes UV value and pN value are greatly improved and stabilized, the color is yellowish and vanished, the impurity and metal ion content is greatly reduced, and the pH value becomes more stable and easier to control.
While specific embodiments of the invention have been described above, it will be appreciated by those skilled in the art that the specific embodiments described are illustrative only and not intended to limit the scope of the invention, and that equivalent modifications and variations of the invention in light of the spirit of the invention will be covered by the claims of the present invention.
Claims (2)
1. A method for improving the quality of recovered caprolactam and improving the recovery process, which is characterized in that: the method for improving the quality of recovered caprolactam and improving the recovery process is carried out by using the following systems, wherein the systems are added on a depolymerization product evaporation pipeline from a depolymerization tower to a pre-removal tower, and the following devices are connected in sequence:
(1) Washing equipment for washing, cooling and collecting depolymerization products;
(2) Chemical treatment equipment for carrying out chemical treatment on chemical impurity components in the washing liquid generated by the washing equipment;
(3) The filtering and separating equipment is used for removing yellow and impurities and separating metal ions from the chemical treatment liquid generated by the chemical treatment equipment;
the washing equipment comprises a washing tower with a spraying mechanism, a cooling water heat exchanger, a condensate collecting tank and a condensate spraying pump which are sequentially and circularly connected; the bottom of the washing tower is connected with the chemical treatment equipment through a washing liquid delivery pump;
The condensate spraying pump is connected with the spraying mechanism and used for conveying condensate to the spraying mechanism;
the chemical treatment equipment comprises a reaction kettle with a jacket and a stirrer, wherein the top of the reaction kettle is provided with a potassium permanganate inlet and a hydrogen peroxide inlet, and the potassium permanganate inlet and the hydrogen peroxide inlet are respectively connected with corresponding adding devices; the bottom of the reaction kettle is connected with the filtering and separating equipment through a chemical treatment liquid conveying pump;
the filtering and separating equipment comprises an active carbon filtering device and a metal ion separating device which are connected in sequence;
the method for improving the quality of recovered caprolactam and improving the recovery process comprises the following steps:
(1) The water vapor evaporated from the depolymerization tower enters a washing tower, becomes condensate under the heat exchange effect of a cooling water heat exchanger, and part of condensate is circularly sprayed to the washing tower through a spray pump, and the rest of condensate is discharged; cooling and collecting depolymerized substances evaporated after the depolymerization tower at the bottom of a washing tower under the cyclic spraying of condensate, controlling the pressure at a slight negative pressure of 800-900mbar by a control valve on a spraying mechanism at the top of the washing tower, controlling the temperature of washing liquid in the washing tower at 85-100 ℃ by a cooling water heat exchanger and the flow rate of spraying liquid, and controlling the concentration of CPL in the washing liquid to be 30-60%, thereby completing washing, cooling and collecting the depolymerized substances;
(2) The tower bottom washing liquid obtained in the step (1) is sent to chemical treatment equipment through a washing liquid conveying pump, a stirrer is started, the temperature of the solution in the reaction kettle is controlled to be 45-60 ℃, and then potassium permanganate and hydrogen peroxide are respectively added for chemical reaction, so that the chemical treatment of phosphoric acid and oligomers in the washing liquid is completed;
(3) And (3) conveying the chemical treatment liquid obtained in the step (2) to filtering and separating equipment through a chemical treatment liquid conveying pump, removing yellow and impurities through an active carbon filtering device, separating metal ions through a metal ion separating device, and returning to the pre-removing water tower.
2. The method according to claim 1, characterized in that: in the step (2), the concentration of potassium permanganate and hydrogen peroxide is 5-8%.
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| US2250949A (en) * | 1936-12-13 | 1941-07-29 | William E Currie | Process for the separation of hydrocarbons from gases containing them |
| CN1535263A (en) * | 2001-03-01 | 2004-10-06 | Dsm Ip �Ʋ�����˾ | Process for recovering and purifying caprolactam from organic solvent |
| CN101880386A (en) * | 2010-07-09 | 2010-11-10 | 北京三联虹普纺织化工技术有限公司 | Recovery method of hexanolactam in polyamide-6 continuous polymerization production process |
| CN104177250A (en) * | 2014-09-16 | 2014-12-03 | 上海华谊（集团）公司 | Process for producing glycollic acid from methyl glycolate |
| CN205328644U (en) * | 2015-12-28 | 2016-06-22 | 长乐力恒锦纶科技有限公司 | Remove useless system that subtracts of water tower in advance |
| CN106823754A (en) * | 2017-04-18 | 2017-06-13 | 长沙紫宸科技开发有限公司 | A kind of hydrate continuously traps CO in cement kiln flue gas2Change system |
| CN107400231A (en) * | 2017-09-04 | 2017-11-28 | 阳煤集团太原化工新材料有限公司 | A kind of method for reclaiming caprolactam and being used for PA6 polymerizations |
| CN111574419A (en) * | 2020-06-16 | 2020-08-25 | 河北美邦工程科技股份有限公司 | Method for recovering and refining caprolactam monomer |
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