CN217921535U - System for nylon 6 waste water recovery high concentration caprolactam - Google Patents
System for nylon 6 waste water recovery high concentration caprolactam Download PDFInfo
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- CN217921535U CN217921535U CN202221852810.6U CN202221852810U CN217921535U CN 217921535 U CN217921535 U CN 217921535U CN 202221852810 U CN202221852810 U CN 202221852810U CN 217921535 U CN217921535 U CN 217921535U
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Abstract
The utility model discloses a system for recovering high-concentration caprolactam from nylon 6 production wastewater, wherein the middle part of a first-stage falling film circulating pipe is connected with a second-stage falling film circulating pipe through a first-stage falling film discharging pipe, the middle part of the second-stage falling film circulating pipe is connected with a third-stage falling film circulating pipe through a second-stage falling film discharging pipe, the middle part of the third-stage falling film circulating pipe is connected with a forced circulation system through a third-stage falling film discharging pipe, and the outlet of the forced circulation pump is connected with the inlet of a forced circulation evaporator; the middle part of the forced circulation pipe is connected with the middle part of the flash evaporation circulation pipe through a forced circulation discharge pipe, the upper end of the flash evaporation circulation pipe is connected with the bottom outlet of the flash evaporation separator, the lower end of the flash evaporation circulation pipe is connected with the tube pass inlet of the flash evaporation heat exchanger through the flash evaporation circulation pump, the tube pass outlet of the flash evaporation heat exchanger is connected with the top inlet of the flash evaporation separator, and the outlet of the flash evaporation circulation pump is also connected with the product tank through a flash evaporation discharge pipe. The system can obtain caprolactam with the concentration higher than 99 percent, and has high energy utilization rate and good water quality of produced water.
Description
Technical Field
The utility model relates to a processing system of nylon 6 waste water especially relates to a system of nylon 6 waste water recovery high concentration caprolactam, belongs to chemical industry waste water resource utilization technical field.
Background
Caprolactam is an important organic chemical raw material, has white powder or crystal appearance, oily hand feeling, mint and acetone smell, and is dissolved in water, benzene, methanol, ether and the like. When heated, the polymer reacts with high heat, open fire or contact with oxidant, and there is a danger of combustion. The combustion decomposition products include carbon monoxide, carbon dioxide and nitrogen oxides. The polyamide chip is mainly used for generating polyamide chips (usually called nylon 6 chips or nylon-6 chips) through polymerization, and can be further processed into nylon fibers, engineering plastics and plastic films.
In the polymerization production process of nylon 6, pure water is required to be used for countercurrent extraction in an extraction tower, unreacted caprolactam enters the pure water, the extracted water contains about 10% of caprolactam, and in order to avoid environmental pollution, recycle of caprolactam, save of water resources and reduce of production cost, an evaporation concentration system is required to realize the separation of caprolactam and water.
At present, the temperature of the normal-pressure boiling point of a solution rises to be higher than 10 ℃ after the concentration of caprolactam reaches 70 percent, so that the temperature is close to the use limit of a steam compressor, an MVR evaporation concentration system cannot be continuously used, and if the concentration of caprolactam is continuously increased, only a multi-effect evaporation concentration system can be used, so that the concentration of caprolactam reaches more than or equal to 80 percent. The normal pressure boiling point temperature rise of the caprolactam solution at the concentration of 80 percent reaches 18 ℃, the normal pressure boiling point temperature rise at the concentration of 90 percent reaches 36 ℃, and a device is added if the high concentration of the caprolactam solution with the concentration of more than or equal to 99 percent is realized. The evaporation concentration in the current industrial production is mainly a traditional multiple-effect evaporation concentration system or a MVR + multiple-effect concentration system, and the caprolactam concentration can only be evaporated and concentrated to about 80 percent.
Secondly, the difficulty is that in the evaporation process of secondary steam, caprolactam is evaporated in a small amount, so that caprolactam is entrained in condensed water, and the caprolactam has certain toxicity and can cause product loss along with the discharge of the condensed water, so that the concentration of the caprolactam entrained in the condensed water must be reduced to be below 0.1 percent for recycling or discharging. Even if the separation effect of the wire mesh demister and the baffle plate is increased in the conventional evaporation separator, the concentration of caprolactam entrained in condensed water is difficult to be reduced to below 0.1 percent.
In conclusion, the concentration of caprolactam recovered by the conventional evaporation concentration system is difficult to reach a high concentration of more than or equal to 99 percent, the steam energy consumption is high, the investment is high, the energy utilization rate is low, the operation intensity is high, more manpower is used, the secondary steam is seriously entrained, and the quality of condensed water is poor and cannot be recycled or discharged.
SUMMERY OF THE UTILITY MODEL
An object of the utility model is to overcome the problem that exists among the prior art, provide a system of nylon 6 waste water recovery high concentration caprolactam, can obtain the caprolactam that is higher than 99% concentration through evaporative concentration, and evaporative concentration system's energy utilization is high, and steam unit consumption is low, and environment-friendly, product yield is high, and the product water quality is good.
In order to solve the technical problems, the utility model discloses a system for recovering high-concentration caprolactam from nylon 6 production wastewater, including feeding tank and one to three-stage falling film evaporator, the bottom of feeding tank links to each other with the entry of feeding pump, the bottom of each stage falling film evaporator links to each other with the entry of falling film circulating pump respectively, the export of each falling film circulating pump links to each other with the top entry of corresponding falling film evaporator through falling film circulating pipe respectively, the export of feeding pump links to each other with the top entry of one-stage falling film evaporator through preheating unit, the middle part of one-stage falling film circulating pipe links to each other with second grade falling film circulating pipe through one-stage falling film discharging pipe, the middle part of second grade falling film circulating pipe links to each other with third grade falling film circulating pipe through third grade falling film discharging pipe, the middle part of third grade falling film circulating pipe links to each other with the bottom entry of forced circulation evaporator through third grade falling film discharging pipe, the upper end export of forced circulation evaporator links to each other with the feed inlet of forced circulation separator, the bottom export of forced circulation separator links to each other with the entry of forced circulation circulating pump through forced circulation circulating pipe, the export of forced circulation pump with the bottom entry of forced circulation evaporator links to each other; the middle part of the forced circulation pipe is connected with the middle part of the flash evaporation circulation pipe through a forced circulation discharge pipe, the upper end of the flash evaporation circulation pipe is connected with the bottom outlet of the flash evaporation separator, the lower end of the flash evaporation circulation pipe is connected with the tube pass inlet of the flash evaporation heat exchanger through a flash evaporation circulation pump, the tube pass outlet of the flash evaporation heat exchanger is connected with the top inlet of the flash evaporation separator, and the outlet of the flash evaporation circulation pump is also connected with the product tank through a flash evaporation discharge pipe.
As an improvement of the utility model, the raw steam pipe with the shell side upper portion entry of forced circulation evaporimeter links to each other, the upper portion export of forced circulation separator through force the separation secondary steam pipe with the steam inlet of second grade falling film separator links to each other, the top gas vent of second grade falling film separator links to each other with vapor compressor's entry, vapor compressor's outlet pipe respectively with the shell side steam inlet of one-level falling film separator and tertiary falling film evaporimeter links to each other, the top gas vent of one-level falling film separator with the shell side steam inlet of second grade falling film evaporimeter.
As a further improvement of the utility model, the raw steam pipe still with the shell side entry of flash heat exchanger links to each other, the shell side export of flash heat exchanger through flash heat exchanger condenser pipe with the shell side middle part entry of forced circulation evaporimeter links to each other.
As a further improvement, the forced circulation evaporator, the shell side outlet of the one-to-three-stage falling membrane separator are respectively connected with the condensed water tank, the bottom outlet of the condensed water tank is connected with the inlet of the condensed water pump, the outlet of the condensed water pump is connected with the condensed water outer discharge pipe and the condensed water return pipe, and the condensed water return pipe is respectively connected with the washing water inlet at the top of the one-stage falling membrane separator and the second-stage falling membrane separator.
As a further improvement of the utility model, the inner chamber upper portion that membrane separator and second grade were fallen to the one-level is equipped with the baffling board respectively in turn, and the free end of each baffling board is equipped with the portion of bending perpendicularly downwards respectively, washs water and drenches alternating downflow on the baffling board of top layer and form multistage water curtain.
As a further improvement, the top gas vent of the flash separator is connected with the hot side inlet of the flash surface cooler, the hot side outlet of the flash surface cooler is connected with the reflux port of the feeding tank.
Compared with the prior art, the utility model discloses following beneficial effect has been obtained: 1. the evaporation concentration system is suitable for caprolactam concentrated solution with higher concentration and high boiling point temperature rise, can realize the accurate control of caprolactam concentration from 10 percent evaporation concentration to more than 99 percent, is in place in one step, does not need multiple working sections, has simple process, is continuous and stable, saves labor and has less investment;
2. the first-stage falling-film evaporator and the second-stage falling-film evaporator are connected in parallel after forming two-effect series connection, so that reasonable heat exchange temperature difference of low-concentration caprolactam solution and high-concentration caprolactam solution is guaranteed, the evaporation is mild, and the tubes are not easy to dry; the secondary steam generated by the primary falling film evaporation is fully utilized, the energy utilization rate is high, the installed power of a steam compressor is low, and the investment cost and the steam unit consumption are low;
3. the three-stage falling-film evaporator and the two-stage falling-film evaporator share the two-stage falling-film separator, so that one device is saved, large pipelines are few, a steel structure and occupied land are saved, a set of instruments such as a valve, pressure and temperature are saved, and monitoring points are few.
4. The forced circulation evaporation system is arranged, single-effect forced circulation and MVR are integrated, the conventional MVR supplements heat source raw steam on an outlet pipeline of a steam compressor, the raw steam enters a shell of the forced circulation evaporator, and secondary steam of the forced circulation separator is mixed with a secondary falling film separator to be used as a supplementary steam source of the steam compressor, so that secondary utilization of the supplemented raw steam is realized, the caprolactam concentration of the MVR system is directly increased to be more than 80%, the energy utilization rate is high, the control points are few, investment is saved, and the MVR system is economical and efficient.
5. The secondary steam of the first-stage falling film separator is washed for multiple times and then used as a heat source of the first-stage falling film evaporator, the secondary steam of the second-stage falling film separator and the forced circulation separator is washed for multiple times and then enters a steam compressor for compression, the purpose of reducing caprolactam entrainment is achieved, caprolactam in condensed water can be less than 0.1%, the purity of condensed water produced by a system is high, the condensed water can be directly recycled, and compared with a rectifying tower, the method has the advantages of low investment cost, water resource saving and environmental protection.
Drawings
The invention is described in further detail below with reference to the attached drawings and the detailed description, wherein the drawings are provided for reference and illustration purposes only and are not intended to limit the invention.
FIG. 1 is a flow chart of a system for recovering high-concentration caprolactam from nylon 6 production wastewater of the utility model;
in the figure: 1. a feed tank; 2. a condensate water preheater; 3. a noncondensable gas preheater; 4. a condensed water tank; 5. a first-stage falling-film evaporator; 6. a first-stage falling film separator; 7. a second-stage falling-film evaporator; 8. a secondary falling film separator; 9. a three-stage falling-film evaporator; 10. a forced circulation evaporator; 11. a forced circulation separator; 12. a flash heat exchanger; 13. a flash separator; 14. a flash evaporation surface cooler; 15. a product tank;
m1, a vapor compressor; B1. a feed pump; B2. a condensate pump; B3. a first-stage falling film circulating pump; B4. a two-stage falling film circulating pump; B5. a three-stage falling film circulating pump; B6. a forced circulation pump; B7. a flash circulating pump; B8. a vacuum pump set;
G1. a feeding pipe; G2. a first-level falling film circulating pipe; G3. a first-stage falling film discharging pipe; G4. a secondary falling film circulating pipe; G5. a two-stage falling film discharging pipe; G6. a three-stage falling film circulating pipe; G7. a three-stage falling film discharging pipe; G8. a forced circulation pipe; G9. a forced circulation discharge pipe; G10. a flash evaporation discharge pipe; G11. a first-stage falling film steam inlet pipe; G12. a secondary falling film steam inlet pipe; G13. a compressor inlet pipe; G14. a primary separation secondary steam pipe; G15. forcibly separating a secondary steam pipe; G16. a raw steam pipe; G17. separating a secondary steam pipe by flash evaporation; G18. the condensed water is discharged from the pipe; G19. a condensed water return pipe; G20. a falling film evaporation condenser pipe; G21. a forced circulation evaporation condenser pipe; G22. a condensate pipe of the flash heat exchanger; G23. falling film non-condensation gas pipe; G24. flash evaporation non-condensation pipe; G25. a condenser pipe of the flash evaporation condenser; G26. and cooling the water pipe.
Detailed Description
In the following description of the present invention, the terms "upper", "lower", "front", "rear", "left", "right", "inner", "outer", and the like indicate orientations or positional relationships based on orientations or positional relationships shown in the drawings, and are merely for convenience of description and simplified description, and do not mean that the device must have a specific orientation.
In order to make the technical means, creation characteristics, achievement purpose and efficacy of the utility model easy to understand and understand, the utility model is further explained by combining with the specific figure below.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.
As shown in figure 1, the utility model discloses system of nylon 6 waste water recovery high concentration caprolactam, including feed tank 1, one-level falling film evaporator 5, second grade falling film evaporator 7, tertiary falling film evaporator 9, forced circulation evaporimeter 10, flash heat exchanger 12 and flash separator 13, inlet pipe G1 links to each other with feed tank 1's entry, feed tank 1's bottom links to each other with feed pump B1's entry, feed pump B1's export and the cold side export of comdenstion water pre-heater 2 link to each other with the cold side entry of noncondensable gas pre-heater 3, the cold side export of noncondensable gas pre-heater 3 links to each other with the top entry of one-level falling film evaporator 5.
The shell pass tops of the first-stage falling-film evaporator 5, the second-stage falling-film evaporator 7 and the third-stage falling-film evaporator 9 are respectively provided with a non-condensable gas exhaust port, each non-condensable gas exhaust port is respectively connected with a falling-film non-condensable gas pipe G23, the outlet of the falling-film non-condensable gas pipe G23 is connected with the hot-side inlet of the non-condensable gas preheater 3, and the hot-side outlet of the non-condensable gas preheater 3 is connected with the inlet of the vacuum pump group B8. Before operation, the vacuum pump set B8 is started firstly, non-condensable gas in the system is pumped out, the system is maintained at a certain vacuum degree, and the first-stage falling-film evaporator 5, the second-stage falling-film evaporator 7 and the third-stage falling-film evaporator 9 are all evaporated at low temperature of 85 ℃ under negative pressure. The temperature of the feed liquid is controlled to be less than 100 ℃ in the whole process, so that the polymerization reaction of the material at high temperature is prevented, the temperature fluctuation is stable, and the caprolactam is not easy to denature. The noncondensable gas preheater 3 utilizes the heat of the noncondensable gas and the steam heat carried by the vacuumized noncondensable gas to heat materials, reduces the heat loss of the system, saves energy consumption, ensures that the vacuum pump unit B8 can not suck steam and has high efficiency.
The method comprises the following steps of feeding the nylon 6 production wastewater into a feeding tank 1 for temporary storage through a feeding pipe G1 at a flow rate of 33t/h, feeding the wastewater with a caprolactam concentration of 10% at a feeding temperature of 30 ℃, discharging the wastewater by a feeding pump B1, carrying out primary preheating by a condensed water preheater 2, carrying out secondary preheating by a noncondensable gas preheater 3, and feeding the wastewater into a primary falling film evaporator 5 for evaporation.
The bottom of the first-stage falling film evaporator 5 is connected with an inlet of a first-stage falling film circulating pump B3, and an outlet of the first-stage falling film circulating pump B3 is connected with an inlet at the top of the first-stage falling film evaporator 5 through a first-stage falling film circulating pipe G2. The caprolactam solution with low concentration of about 10 percent enters the primary falling-film evaporator 5 to be subjected to film-hanging evaporation on the inner wall of the falling-film tube, and the primary concentrated solution flowing out of the bottom of the primary falling-film evaporator 5 is sent back to the top inlet of the primary falling-film evaporator 5 by the primary falling-film circulating pump B3 and the primary falling-film circulating tube G2 to be subjected to circulation evaporation, so that the caprolactam concentration reaches 25 percent.
The middle part of the first-stage falling film circulating pipe G2 is connected with the second-stage falling film circulating pipe G4 through a first-stage falling film discharging pipe G3, the upper end of the second-stage falling film circulating pipe G4 is connected with the top inlet of the second-stage falling film evaporator 7, the bottom of the second-stage falling film evaporator 7 is connected with the inlet of the second-stage falling film circulating pump B4, and the outlet of the second-stage falling film circulating pump B4 is connected with the lower end of the second-stage falling film circulating pipe G4. The primary falling film circulating pump B3 sends the primary concentrated solution into the secondary falling film circulating pipe G4 through the primary falling film discharging pipe G3, and the secondary falling film system evaporates and concentrates the caprolactam concentration in the solution to 50%.
The middle part of the second-stage falling film circulating pipe G4 is connected with the third-stage falling film circulating pipe G6 through a second-stage falling film discharging pipe G5, the upper end of the third-stage falling film circulating pipe G6 is connected with the top inlet of the third-stage falling film evaporator 9, the bottom of the third-stage falling film evaporator 9 is connected with the inlet of the third-stage falling film circulating pump B5, and the outlet of the third-stage falling film circulating pump B5 is connected with the lower end of the third-stage falling film circulating pipe G6. And the secondary falling film circulating pump B4 sends the secondary concentrated solution into a tertiary falling film circulating pipe G6 through a secondary falling film discharging pipe G5, and the tertiary falling film system evaporates and concentrates the caprolactam concentration in the solution to 70%.
Because the boiling point temperature rise of the high-concentration 70% caprolactam solution is close to 11.0 ℃, the system adopts the first-stage falling-film evaporator 5 and the second-stage falling-film evaporator 7 to form a two-effect series connection and then is connected with the third-stage falling-film evaporator 9 in parallel, so that the reasonable heat exchange temperature difference of the low-concentration caprolactam solution during the low-boiling point temperature rise evaporation and concentration can be ensured to be about 6 ℃; the heat exchange temperature difference of the high-concentration and high-boiling temperature rise of the three-stage falling-film evaporator 9 is also ensured to be about 8 ℃, the system is mild in evaporation and is not easy to dry. Compared with the vapor compressor M1 with the same excess gas amount corresponding to the evaporation amount in the conventional design, the vapor amount of the vapor compressor M1 is saved by more than or equal to 30 percent, thereby achieving the purposes of energy conservation, high efficiency and investment saving. Taking the design of evaporation capacity of 30t/h as an example, the conventional design needs to select the compressor with the steam passing capacity of more than or equal to 30t/h to meet the requirement, and the system only needs the compressor with the steam passing capacity of 20t/h.
The bottom outlet of the forced circulation separator 11 is connected with the inlet of a forced circulation pump B6 through a forced circulation pipe G8, and the outlet of the forced circulation pump B6 is connected with the bottom inlet of a forced circulation evaporator 10; the middle part of the three-stage falling film circulating pipe G6 is also connected with the bottom inlet of the forced circulation evaporator 10 through a three-stage falling film discharging pipe G7, and the upper end outlet of the forced circulation evaporator 10 is connected with the feed inlet of the forced circulation separator 11.
The three-stage falling film circulating pump B5 is sent into a forced circulation evaporation system through a three-stage falling film discharging pipe G7, firstly enters a forced circulation evaporator 10, the circulating liquid is heated by raw steam, then enters a forced circulation separator 11 to realize separation, the separated steam is recycled, the circulating liquid enters a forced circulation pump B6 through a forced circulation pipe G8, and the circulating liquid is sent into the forced circulation evaporator 10 again by the forced circulation pump B6 to be circularly evaporated. After forced circulation evaporation, the caprolactam concentration reached 80%.
Because the boiling point temperature rise of the high-concentration 80% caprolactam solution is close to 18.0 ℃, the system adopts a forced circulation evaporation system, single-effect forced circulation and MVR are integrated, raw steam is used as a heat source for the heat source, a secondary steam outlet of a forced circulation separator is connected with a secondary falling film separator 8, secondary steam evaporated by a forced circulation evaporator 10 also enters a steam compressor M1 through the secondary falling film separator 8, the temperature and the pressure of the steam are raised through the compressor, and then the heat exchange is carried out by a primary falling film evaporator 5 and a tertiary falling film evaporator 9, and the secondary steam is recycled. The secondary steam outlet of the forced circulation separator needs to be provided with a condenser, the condenser needs to use circulating cooling water as a medium to condense the secondary steam into water, and circulating water resources and a secondary steam heat source evaporated by forced circulation are wasted. The raw steam of the whole system is supplemented through the forced circulation evaporator 10, thus solving the problem that the temperature rise of a compressor cannot continue to provide heat exchange temperature difference due to the limited temperature rise of high boiling point after the concentration of caprolactam is more than 70 percent, the concentration of caprolactam can be directly increased to be more than 80 percent by using an MVR system, and simultaneously the secondary steam evaporated after the supplemented raw steam is firstly utilized once by the forced circulation evaporator 10 enters the steam compressor M1 through the secondary membrane reduction separator 8 to realize secondary utilization, thereby saving the energy consumption of the raw steam, further improving the concentration without using multiple effects, having high energy utilization rate, saving investment, economy and high efficiency.
The middle part of the forced circulation pipe G8 is connected with the middle part of the flash evaporation circulation pipe through a forced circulation discharge pipe G9, the upper end of the flash evaporation circulation pipe is connected with the bottom outlet of the flash evaporation separator 13, the lower end of the flash evaporation circulation pipe is connected with the tube pass inlet of the flash evaporation heat exchanger 12 through a flash evaporation circulation pump B7, the tube pass outlet of the flash evaporation heat exchanger 12 is connected with the top inlet of the flash evaporation separator 13, and the outlet of the flash evaporation circulation pump B7 is connected with the product tank 15 through a flash evaporation discharge pipe G10.
A part of circulating liquid of the forced circulation evaporation system enters a flash evaporation system through a forced circulation discharge pipe G9, the circulating liquid and concentrated liquid flowing out of a flash evaporation separator 13 are sent into a flash evaporation heat exchanger 12 through a flash evaporation circulating pump B7 to be heated, the flash evaporation heat exchanger 12 adopts raw steam as a heat source, the heating intensity is high, and after the heated circulating liquid enters the flash evaporation separator 13 to be flashed, the caprolactam concentration is more than or equal to 99%. Qualified concentrated solution enters the product tank 15 through the flash evaporation discharge pipe G10, so that the caprolactam concentration is in place from 10 percent to 99 percent in one step without multiple working sections, and the labor is saved.
Because of the discharge temperature of forced circulation evaporation system is about 100 ℃, the caprolactam concentration can be further improved by flash evaporation by utilizing the waste heat of the material, and the purpose of cooling is achieved, the system designs a set of flash evaporation system to improve the caprolactam concentration from 80% to 99%, the flash evaporation system is provided with a flash evaporation heat exchanger 12 to realize that the concentration after flash evaporation does not meet the requirement, the circulating material can be heated by raw steam again to reach the required concentration through negative pressure flash evaporation, the flash evaporation vacuum system and MVR share, the flash evaporation system has less equipment, the operation is simple, the investment is low, the waste heat of the material is fully utilized, and the energy consumption is saved.
The raw steam pipe G16 is connected with the inlet at the upper part of the shell side of the forced circulation evaporator 10, because the evaporation pressure of the forced circulation separator 11 is the same as that of the second-stage falling-film evaporator 7 and the third-stage falling-film evaporator 9, the system connects the upper outlet of the forced circulation separator 11 with the steam inlet of the second-stage falling-film separator 8 through the forced separation secondary steam pipe G15, the upper part of the inner cavity of the second-stage falling-film separator 8 is respectively and alternately provided with baffle plates, the free ends of the baffle plates are respectively provided with a bending part which is vertically downward, and cleaning water is sprayed on the baffle plate at the top layer to alternately flow downward and form a multi-stage water curtain. The steam inlet of the secondary falling film separator 8 is positioned below the bottom layer baffle plate.
The top exhaust port of the secondary falling film separator 8 is connected with the inlet of a steam compressor M1 through a compressor steam inlet pipe G13, the outlet pipeline of the steam compressor M1 is respectively connected with the shell-side steam inlet of the primary falling film separator 6 through a primary falling film steam inlet pipe G11, and is connected with the shell-side steam inlet of the tertiary falling film evaporator 9 through a secondary falling film steam inlet pipe G12, the top exhaust port of the primary falling film separator 6 is connected with the shell-side steam inlet of the secondary falling film evaporator 7 through a primary separation secondary steam pipe G14, and secondary steam generated by the primary falling film separator 6 is used as a heat source of the secondary falling film evaporator 7, so that the energy utilization rate is high, the installed power of the compressor is low, and the investment cost is low.
The secondary steam discharged from the top of the forced circulation separator 11 enters the secondary falling film separator 8 and is mixed with the secondary steam generated by the secondary falling film separator 8, and in the upward flowing process, the secondary steam firstly passes through the water curtain at the free end of the baffle plate at the bottom layer to be subjected to primary washing, then enters the lower part of the baffle plate at the upper layer, passes through the water curtain at the free end of the baffle plate to be subjected to secondary washing, is deflected upwards repeatedly in this way, and is discharged from the top of the secondary falling film separator 8 after being subjected to multiple times of washing. The secondary steam is washed by the water curtain for multiple times by using a simple structure, so that the equipment investment is reduced, the entrainment of caprolactam in the secondary steam can be greatly reduced, the content of caprolactam in condensed water is less than 0.1 percent, the purity of condensed water produced by a system is high, the condensed water can be directly recycled, water resources are saved, and the environment is protected.
And the secondary steam discharged by the secondary falling film separator 8 enters a steam inlet pipe G13 of the compressor and is used as a steam source of the steam compressor M1. The inlet temperature of the steam compressor M1 is designed to be 85 ℃, the outlet temperature is designed to be 105 ℃, the temperature difference is 20 ℃, and the air passing amount is 20t/h. The vacuum system and the compressor maintain the MVR system to evaporate at a low negative pressure and a low temperature of 85 ℃, the temperature of the solution can be controlled to be less than 100 ℃ in the whole process, the polymerization reaction of the materials at a high temperature is prevented, the temperature fluctuation is stable, and caprolactam is not easy to denature.
The raw steam pipe G16 is also connected with a shell pass inlet of the flash evaporation heat exchanger 12, a shell pass outlet of the flash evaporation heat exchanger 12 is connected with a shell pass middle inlet of the forced circulation evaporator 10 through a flash evaporation heat exchanger condensate pipe G22, so that high-temperature condensate water discharged by the flash evaporation heat exchanger 12 enters the shell pass of the forced circulation evaporator 10 to be continuously flashed, and heat is further recovered.
The membrane separator 6 falls in the one-level, the comdenstion water that the shell side export of membrane separator 8 and tertiary falling membrane separator discharged all gets into condensate water tank 4 through falling liquid film evaporation condensate pipe G20 and keeps in temporarily, the comdenstion water that the shell side export of forced circulation evaporimeter 10 was discharged gets into condensate water tank 4 through forced circulation evaporation condensate pipe G21, the bottom export of condensate water tank 4 links to each other with condensate water pump B2's entry, condensate water pump B2's export links to each other with condensate water back flow G19, condensate water back flow G19 falls the washing water entry at membrane separator 6 and the secondary falling membrane separator 8 top with the one-level respectively and links to each other.
The outlet of the condensate pump B2 is also connected with the hot side inlet of the condensate preheater 2, and the hot side outlet of the condensate preheater 2 is connected with a condensate water outer discharge pipe G18. Condensed water caprolactam in the condensed water tank 4 is less than 0.1 percent and can be directly recycled, and one part of the condensed water caprolactam enters the hot side of the condensed water preheater 2 to be preheated with feed liquid in a first stage and then can be directly discharged. The other part of the secondary steam enters the tops of the first-stage falling film separator 6 and the second-stage falling film separator 8 through a condensate water return pipe G19 to be used as washing water of the secondary steam, so that the entrainment amount of caprolactam in the secondary steam is reduced from the source.
The upper parts of the inner cavities of the first-stage falling film separator 6 and the second-stage falling film separator 8 are respectively and alternately provided with baffle plates, the free ends of the baffle plates are respectively provided with a bent part which is vertically downward, and the cleaning water sprays on the baffle plates on the top layer to alternately flow downward to form a multi-stage water curtain.
The top gas vent of flash separator 13 links to each other through flash separation secondary steam pipe G17 and the hot side entry of flash distillation surface air cooler 14, and the hot side exit linkage of flash distillation surface air cooler 14 has flash distillation noncondensable gas pipe G24 and flash evaporation condenser condensate pipe G25, and flash evaporation noncondensable gas pipe G24 links to each other with vacuum pump group B8, takes noncondensable gas out, and flash evaporation condenser condensate pipe G25 links to each other with the backward flow mouth of feed tank 1, and the flash evaporation comdensable water is because of smuggleing caprolactam secretly and returns feed tank 1 and advance the system again and handle. The cold side of the flash surface cooler 14 is connected to a cooling water line G26, which carries heat away by circulating cooling water.
The foregoing is only a preferred and exemplary embodiment of the present invention, and the basic principles and main features of the present invention and the advantages of the present invention have been shown and described, without thereby limiting the scope of the present invention, which should be understood by those skilled in the art, and the present invention is not limited by the foregoing exemplary embodiments. In addition to the above embodiments, other embodiments of the present invention are also possible without departing from the spirit and scope of the present invention. The utility model discloses still can have various changes and improvements, all adopt to equate the technical scheme that replacement or equivalent transform formed, all fall in the utility model discloses the protection scope that requires. The scope of the invention is defined by the appended claims and equivalents thereof. The undescribed technical features of the present invention can be realized by or using the prior art, and are not described herein again.
Claims (6)
1. The utility model provides a system for nylon 6 industrial waste water retrieves high concentration caprolactam, includes feeding tank and one to third grade falling film evaporator, and the bottom of feeding tank links to each other with the entry of charge pump, and the bottom of each grade falling film evaporator links to each other with the entry of falling film circulating pump respectively, and the export of each falling film circulating pump links to each other through falling film circulating pipe and corresponding falling film evaporator's top entry respectively, its characterized in that: the system comprises a feed pump, a forced circulation separator, a forced circulation pump, a preheating unit, a primary falling film evaporator, a secondary falling film circulating pipe, a secondary falling film discharging pipe, a tertiary falling film circulating pipe, a forced circulation evaporator, a forced circulation separator, a forced circulation pipe and a forced circulation pump, wherein an outlet of the feed pump is connected with a top inlet of the primary falling film evaporator through the preheating unit; the middle part of the forced circulation pipe is connected with the middle part of the flash evaporation circulation pipe through a forced circulation discharge pipe, the upper end of the flash evaporation circulation pipe is connected with the bottom outlet of the flash evaporation separator, the lower end of the flash evaporation circulation pipe is connected with the tube pass inlet of the flash evaporation heat exchanger through a flash evaporation circulation pump, the tube pass outlet of the flash evaporation heat exchanger is connected with the top inlet of the flash evaporation separator, and the outlet of the flash evaporation circulation pump is also connected with the product tank through a flash evaporation discharge pipe.
2. The system for recovering high-concentration caprolactam from nylon 6 production wastewater according to claim 1, which is characterized in that: the raw steam pipe is connected with the upper inlet of the shell side of the forced circulation evaporator, the upper outlet of the forced circulation separator is connected with the steam inlet of the secondary falling film separator through a forced separation secondary steam pipe, the top exhaust port of the secondary falling film separator is connected with the inlet of a steam compressor, the outlet pipeline of the steam compressor is respectively connected with the shell side steam inlets of the primary falling film separator and the tertiary falling film evaporator, and the top exhaust port of the primary falling film separator is connected with the shell side steam inlet of the secondary falling film evaporator.
3. The system for recovering high-concentration caprolactam from nylon 6 production wastewater as recited in claim 1, wherein: the steam generation pipe is also connected with a shell pass inlet of the flash evaporation heat exchanger, and a shell pass outlet of the flash evaporation heat exchanger is connected with a shell pass middle inlet of the forced circulation evaporator through a flash evaporation heat exchanger condensate pipe.
4. The system for recovering high-concentration caprolactam from nylon 6 production wastewater as recited in claim 1, wherein: the shell pass outlets of the forced circulation evaporator and the first-level to third-level membrane-falling separators are respectively connected with a condensate water tank, the bottom outlet of the condensate water tank is connected with the inlet of a condensate water pump, the outlet of the condensate water pump is connected with a condensate water outward-discharging pipe and a condensate water return pipe, and the condensate water return pipe is respectively connected with cleaning water inlets at the tops of the first-level membrane-falling separator and the second-level membrane-falling separator.
5. The system for recovering high-concentration caprolactam from nylon 6 production wastewater as claimed in claim 4, wherein: the upper parts of the inner cavities of the first-stage falling membrane separator and the second-stage falling membrane separator are respectively and alternately provided with baffle plates, the free ends of the baffle plates are respectively provided with a bent part which is vertically downward, and the cleaning water sprays on the baffle plates on the top layer to alternately flow downward to form a multi-stage water curtain.
6. The system for recovering high-concentration caprolactam from nylon 6 production wastewater as claimed in any one of claims 1 to 5, wherein: and a top exhaust port of the flash separator is connected with a hot side inlet of the flash surface cooler, and a hot side outlet of the flash surface cooler is connected with a reflux port of the feeding tank.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202221852810.6U CN217921535U (en) | 2022-07-18 | 2022-07-18 | System for nylon 6 waste water recovery high concentration caprolactam |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202221852810.6U CN217921535U (en) | 2022-07-18 | 2022-07-18 | System for nylon 6 waste water recovery high concentration caprolactam |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115784511A (en) * | 2022-12-07 | 2023-03-14 | 常州中源工程技术有限公司 | Zero-discharge treatment process for electroplating wastewater |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115784511A (en) * | 2022-12-07 | 2023-03-14 | 常州中源工程技术有限公司 | Zero-discharge treatment process for electroplating wastewater |
| CN115784511B (en) * | 2022-12-07 | 2023-08-29 | 常州中源工程技术有限公司 | Electroplating wastewater zero-emission treatment process |
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