NMP waste liquid treatment and recovery system

Abstract

The invention belongs to the technical field of waste liquid recovery, and particularly discloses an NMP waste liquid treatment and recovery system which comprises a first dehydration unit, a first de-weighting unit, a second dehydration unit, a third dehydration unit and a second de-weighting unit which are arranged in sequence, and the first dehydration unit comprises a first dehydration tower, a first condenser, a first reflux tank, a first buffer tank and a first heater; the first heavy component removal unit comprises a first heavy component removal tower, a second condenser, a second reflux tank, a second buffer tank and a second heater; the second dehydration unit comprises a second dehydration tower, a third condenser, a third reflux tank, a third buffer tank and a third heater; the third dehydration unit comprises a third dehydration tower, a fourth condenser, a fourth reflux tank, a fourth buffer tank and a fourth heater; and the second de-heavy unit comprises a second de-heavy tower, a fifth condenser, a fifth reflux tank and a fifth heater. The system realizes zero breakthrough in treatment of low-quality NMP waste liquid, can treat low-quality waste liquid and high-quality waste liquid, and improves the production flexibility.

Description

Technical Field

[0001] The invention belongs to the technical field of waste liquid recovery, and in particular relates to an NMP waste liquid treatment and recovery system. Background Art

[0002] NMP is a polar aprotic solvent with the advantages of high boiling point, strong affinity, low toxicity, low volatility, excellent chemical and thermal stability, strong dissolving ability, and recyclability. It has now become an indispensable organic solvent in the lithium battery industry.

[0003] In the coating process of lithium battery positive electrode production, NMP is used as the main liquid carrier of the slurry, and is evenly coated on the metal substrate with a stable thickness, and has good wettability and fluidity with the metal substrate. Generally, NMP is recovered by water washing and condensation in lithium battery production plants. The NMP waste liquid after water washing and condensation recovery needs to be purified to a composition of > 99.9wt% before it can be used again. Some electronics industries require higher purity. Therefore, a stable and efficient waste liquid distillation process plays an extremely important role in the recycling of NMP.

[0004] At present, the main process for the distillation and recovery of common NMP waste liquid is three-tower distillation, which is a two-stage vacuum tower connected in series for dehydration + NMP finished product tower for weight removal.

[0005] Due to market changes, the chemical industry is in a downturn, and NMP recovery has been greatly affected, gradually transforming from high-quality NMP waste liquid recovery to low-quality NMP waste liquid recovery. The original three-tower distillation method cannot be used for effective purification, which seriously affects the quality of the recovered products, making it difficult or even impossible to produce qualified recovered products. Summary of the invention

[0006] The object of the present invention is to provide a NMP waste liquid treatment and recovery system, which realizes zero breakthrough in treating low-quality NMP waste liquid, and the system can treat low-quality waste liquid and high-quality waste liquid, thereby improving production flexibility.

[0007] In order to achieve the above-mentioned object, the technical scheme of the present invention is: an NMP waste liquid treatment and recovery system comprises a first dehydration unit, a first deweighting unit, a second dehydration unit, a third dehydration unit and a second deweighting unit which are arranged in sequence;

[0008] The first dehydration unit comprises a first dehydration tower, a first condenser, a first reflux tank, a first buffer tank and a first heater, wherein the first feed inlet of the first dehydration tower is used to input NMP waste liquid; the first discharge port at the top of the first dehydration tower is connected to the first condenser, the liquid phase outlet of the first condenser is connected to the first reflux tank, the first discharge port at the bottom of the first reflux tank is connected to the second feed inlet at the top of the first dehydration tower; the second discharge port at the bottom of the first dehydration tower is connected to the first buffer tank; the first heater is used to heat the bottom of the first dehydration tower;

[0009] The first de-weighting unit comprises a first de-weighting tower, a second condenser, a second reflux tank, a second buffer tank and a second heater, wherein the first feed inlet of the first de-weighting tower is connected to the first buffer tank; the first discharge port at the top of the first de-weighting tower is connected to the second condenser, and the liquid phase outlet of the second condenser is connected to the second reflux tank; the first discharge port at the bottom of the second reflux tank is connected to the second feed inlet at the top of the first de-weighting tower, and the second discharge port at the bottom of the second reflux tank is connected to the second buffer tank; the second heater is used to heat the bottom of the first de-weighting tower; the second discharge port at the bottom of the first de-weighting tower is connected to the heavy component tank;

[0010] The second dehydration unit includes a second dehydration tower, a third condenser, a third reflux tank, a third buffer tank and a third heater; the first feed inlet of the second dehydration tower is connected to the second buffer tank; the first discharge port at the top of the second dehydration tower is connected to the third condenser, and the liquid phase outlet of the third condenser is connected to the third reflux tank; the first discharge port at the bottom of the third reflux tank is connected to the second feed inlet at the top of the second dehydration tower, and the second discharge port at the bottom of the second dehydration tower is connected to the third buffer tank; the third heater is used to heat the bottom of the second dehydration tower;

[0011] The third dehydration unit includes a third dehydration tower, a fourth condenser, a fourth reflux tank, a fourth buffer tank and a fourth heater, wherein the first feed inlet of the third dehydration tower is connected to the third buffer tank; the first discharge port at the top of the third dehydration tower is connected to the fourth condenser; the liquid phase outlet of the fourth condenser is connected to the fourth reflux tank, the first discharge port at the bottom of the fourth reflux tank is connected to the first feed inlet of the third dehydration tower, the second discharge port at the bottom of the fourth reflux tank is connected to the first feed inlet of the second dehydration tower; the second discharge port at the bottom of the third dehydration tower is connected to the fourth buffer tank; the fourth heater is used to heat the bottom of the third dehydration tower;

[0012] The second de-weighting unit includes a second de-weighting tower, a fifth condenser, a fifth reflux tank and a fifth heater; the first feed inlet of the second de-weighting tower is connected to the fourth buffer tank; the first discharge port at the top of the second de-weighting tower is connected to the fifth condenser, and the liquid phase outlet of the fifth condenser is connected to the fifth reflux tank; the first discharge port at the bottom of the fifth reflux tank is connected to the second feed inlet at the top of the second de-weighting tower, and the second discharge port at the bottom of the fifth reflux tank is connected to the finished product tank; the fifth heater is used to heat the bottom of the second de-weighting tower; the second discharge port at the bottom of the second de-weighting tower is connected to the heavy component tank.

[0013] Furthermore, the front end of the first feed inlet of the first dehydration tower, the front end of the first feed inlet of the first deweighting tower, the front end of the first feed inlet of the second dehydration tower, the front end of the first feed inlet of the third dehydration tower, the front end of the first feed inlet of the second deweighting tower, and the front end of the feed inlet of the finished product tank are respectively provided with a first feed regulating valve, a second feed regulating valve, a third feed regulating valve, a fourth feed regulating valve, a fifth feed regulating valve and a sixth feed regulating valve.

[0014] Furthermore, tail gas exhaust ports are provided on the tops of the first reflux tank, the second reflux tank, the third reflux tank, the fourth reflux tank and the fifth reflux tank.

[0015] Furthermore, the second discharge ports at the bottom of the first reflux tank and the third reflux tank are respectively connected to the sewage system.

[0016] Furthermore, a first reflux regulating valve, a second reflux regulating valve, a third reflux regulating valve, a fourth reflux regulating valve and a fifth reflux regulating valve are respectively provided between the first discharge port at the bottom of the first reflux drum and the second feed port at the top of the first dehydration tower, between the first discharge port at the bottom of the second reflux drum and the second feed port at the top of the first dehydration tower, between the first discharge port at the bottom of the third reflux drum and the second feed port at the top of the second dehydration tower, between the first discharge port at the bottom of the fourth reflux drum and the first feed port at the second dehydration tower, and between the first discharge port at the bottom of the fifth reflux drum and the second feed port at the top of the second dehydration tower.

[0017] Furthermore, a first discharge pump, a second discharge pump, a third discharge pump, a fourth discharge pump, a fifth discharge pump and a wastewater circulation pump are respectively provided between the first feed inlet of the first deweighting tower and the first buffer tank, between the first feed inlet of the second dehydration tower and the second buffer tank, between the first feed inlet of the third dehydration tower and the third buffer tank, between the first feed inlet of the second deweighting tower and the fourth buffer tank, between the second discharge port at the bottom of the fifth reflux tank and the finished product tank, and between the second discharge port at the bottom of the fourth reflux tank and the first feed inlet of the second dehydration tower.

[0018] Furthermore, a fifth buffer tank is provided between the fifth discharge pump and the fifth reflux tank, and a sixth buffer tank is provided between the second discharge port at the bottom of the fourth reflux tank and the first feed port of the second dehydration tower.

[0019] Furthermore, the first heater, the second heater, the third heater, the fourth heater and the fifth heater all adopt reboilers, and the front ends of the oil inlets of the first heater, the second heater, the third heater, the fourth heater and the fifth heater are respectively provided with a first oil inlet regulating valve, a second oil inlet regulating valve, a third oil inlet regulating valve, a fourth oil inlet regulating valve and a fifth oil inlet regulating valve.

[0020] The working principle of this technical solution is:

[0021] After the flow rate of NMP waste liquid is controlled by the first feed regulating valve, it enters the first dehydration tower through the first feed port of the first dehydration tower for dehydration and rectification. The light components at the top of the first dehydration tower enter the first condenser through the first discharge port at the top of the first dehydration tower for condensation, and the condensed liquid phase enters the first reflux tank. Part of the liquid phase flows back to the first dehydration tower after the flow rate is controlled by the first reflux regulating valve, and part of the liquid phase is discharged into the sewage system through the second discharge port at the bottom of the first reflux tank. The bottom of the first dehydration tower is heated by the first heater, and the supply of heat transfer oil is adjusted by the first oil inlet regulating valve to control the system heat, thereby controlling the top temperature and bottom temperature of the first dehydration tower. The material at the bottom of the first dehydration tower enters the first buffer tank through the second discharge port at the bottom of the first dehydration tower.

[0022] The NMP in the first buffer tank passes through the first discharge pump and enters the first de-weighting tower for further de-weighting and distillation under the regulation and control of the second feed regulating valve. The light components at the top of the first de-weighting tower enter the second condenser through the first discharge port at the top of the first de-weighting tower for condensation, and the condensed liquid phase enters the second reflux tank. Part of the liquid phase flows back to the first de-weighting tower after the flow is controlled by the second reflux regulating valve, and part of the liquid phase is discharged into the second buffer tank through the second discharge port at the bottom of the second reflux tank. The bottom of the first de-weighting tower is heated by the second heater, and the supply of heat transfer oil is adjusted by the second oil inlet regulating valve to control the system heat, thereby controlling the top temperature and bottom temperature of the first de-weighting tower. The heavy components at the bottom of the first de-weighting tower are intermittently discharged to the heavy component tank to control the heavy component content of the top product.

[0023] The material in the second buffer tank passes through the second discharge pump and enters the second dehydration tower for further dehydration and distillation under the regulation and control of the third feed regulating valve. The light components at the top of the second dehydration tower enter the third condenser through the first discharge port at the top of the second dehydration tower for condensation, and the condensed liquid phase enters the third reflux tank. Part of the liquid phase flows back to the second dehydration tower after the flow is controlled by the third reflux regulating valve, and part of the liquid phase is discharged into the sewage system through the second discharge port at the bottom of the third reflux tank. The bottom of the second dehydration tower is heated by the third heater, and the supply of heat transfer oil is adjusted by the third oil inlet regulating valve to control the heat of the system, thereby controlling the top temperature and bottom temperature of the second dehydration tower. The material at the bottom of the second dehydration tower enters the third buffer tank through the second discharge port at the bottom of the second dehydration tower.

[0024] The material in the third buffer tank passes through the third discharge pump and enters the third dehydration tower under the regulation and control of the fourth feed regulating valve for further dehydration and distillation. The light components at the top of the third dehydration tower enter the fourth condenser through the first discharge port at the top of the third dehydration tower for condensation, and the condensed liquid phase enters the fourth reflux tank. Part of the liquid phase flows back to the third dehydration tower after the flow is controlled by the fourth reflux regulating valve, and part of the liquid phase flows into the sixth buffer tank through the second discharge port at the bottom of the fourth reflux tank. The material in the sixth buffer tank is transported to the second dehydration tower through the wastewater circulation pump. The bottom of the third dehydration tower is heated by the fourth heater, and the supply of heat transfer oil is adjusted by the fourth oil inlet regulating valve to control the system heat, thereby controlling the top temperature and bottom temperature of the third dehydration tower. The material at the bottom of the third dehydration tower enters the fourth buffer tank through the second discharge port at the bottom of the third dehydration tower.

[0025] The material in the fourth buffer tank passes through the fourth discharge pump and enters the second de-weighting tower for further de-weighting and distillation under the regulation and control of the fifth feed regulating valve. The light components at the top of the second de-weighting tower enter the fifth condenser through the first discharge port at the top of the second de-weighting tower for condensation, and the condensed liquid phase enters the fifth reflux tank. Part of the liquid phase is refluxed into the second de-weighting tower after the flow is controlled by the fifth reflux regulating valve, and part of the liquid phase is discharged into the fifth buffer tank through the second discharge port at the bottom of the fifth reflux tank, and then transported to the finished product tank through the fifth discharge pump. The sixth feed regulating valve is used to adjust the flow entering the finished product tank. The bottom of the second de-weighting tower is heated by the fifth heater, and the supply of heat transfer oil is adjusted by the fifth oil inlet regulating valve to control the system heat, thereby controlling the top temperature and bottom temperature of the second de-weighting tower. The heavy components at the bottom of the second de-weighting tower are intermittently discharged to the heavy component tank to control the heavy component content of the top product.

[0026] The beneficial effects of this technical solution are: achieving zero breakthrough in treating low-quality NMP waste liquid, and the system can treat low-quality waste liquid and high-quality waste liquid, improving production flexibility and achieving economic benefits for the company. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a connection schematic diagram of the NMP waste liquid treatment and recovery system of the present invention;

[0028] Figure 2 It is a product quality trend chart of the prior art (before process optimization) and the present invention (after process optimization). DETAILED DESCRIPTION

[0029] The following is further described in detail through specific implementation methods:

[0030] The reference numerals in the drawings of the specification include: first dehydration tower 1, first deweighting tower 2, second dehydration tower 3, third dehydration tower 4, second deweighting tower 5, first condenser 6, second condenser 7, third condenser 8, fourth condenser 9, fifth condenser 10, first feed regulating valve 11, second feed regulating valve 12, third feed regulating valve 13, fourth feed regulating valve 14, fifth feed regulating valve 15, sixth feed regulating valve 16, first reflux tank 17, second reflux tank 18, third reflux tank 19, fourth reflux tank 20, fifth reflux tank 21, first buffer tank 22, second buffer tank 23, third buffer tank 24, the fourth buffer tank 25, the fifth buffer tank 26, the sixth buffer tank 27, the first discharge pump 28, the second discharge pump 29, the third discharge pump 30, the fourth discharge pump 31, the fifth discharge pump 32, the wastewater circulation pump 33, the first reflux regulating valve 34, the second reflux regulating valve 35, the third reflux regulating valve 36, the fourth reflux regulating valve 37, the fifth reflux regulating valve 38, the first heater 39, the third heater 40, the fourth heater 41, the fifth heater 42, the first oil inlet regulating valve 43, the second oil inlet regulating valve 44, the third oil inlet regulating valve 45, the fourth oil inlet regulating valve 46, the fifth oil inlet regulating valve 47.

[0031] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] The embodiment is basically as shown in the attached Figure 1-2 As shown: the NMP waste liquid treatment and recovery system comprises a first dehydration unit, a first deweighting unit, a second dehydration unit, a third dehydration unit and a second deweighting unit which are arranged in sequence;

[0033] The first dehydration unit includes a first dehydration tower 1, a first condenser 6, a first reflux tank 17, a first buffer tank 22 and a first heater 39. The first feed port of the first dehydration tower 1 is used to input NMP waste liquid, and the NMP waste liquid is stored in a waste liquid tank. The waste liquid tank is connected to the first feed port of the first dehydration tower 1, and a first feed regulating valve 11 is provided between the two. The first discharge port at the top of the first dehydration tower 1 is connected to the first condenser 6, and the liquid phase outlet of the first condenser 6 is connected to the first reflux tank 17. A tail gas exhaust port is provided at the top of the first reflux tank 17, and the first discharge port at the bottom of the first reflux tank 17 is connected to the second feed port at the top of the first dehydration tower 1, and a first reflux regulating valve 34 is provided between the two; the second discharge port at the bottom of the first reflux tank 17 is connected to the sewage system. The second discharge port at the bottom of the first dehydration tower 1 is connected to the first buffer tank 22. The first heater 39 is used to heat the bottom of the first dehydration tower 1 . The first heater 39 is a reboiler. A first oil inlet regulating valve 43 is provided at the front end of the oil inlet of the first heater 39 .

[0034] The first de-weighting unit includes a first de-weighting tower 2, a second condenser 7, a second reflux tank 18, a second buffer tank 23 and a second heater. The first feed port of the first de-weighting tower 2 is connected to the first buffer tank 22. Specifically, the outlet of the first buffer tank 22 is connected to the inlet of the first discharge pump 28. The outlet of the first discharge pump 28 is connected to the first feed port of the first de-weighting tower 2, and a second feed regulating valve 12 is provided between the two. The first discharge port at the top of the first de-weighting tower 2 is connected to the second condenser 7, and the liquid phase outlet of the second condenser 7 is connected to the second reflux tank 18. The top of the second reflux tank 18 is provided with a tail gas exhaust port, the first discharge port at the bottom of the second reflux tank 18 is connected to the second feed port at the top of the first de-weighting tower 2, and a second reflux regulating valve 35 is provided between the two. The second discharge port at the bottom of the second reflux tank 18 is connected to the second buffer tank 23. The second heater is used to heat the bottom of the first de-weighting tower 2. The second heater adopts a reboiler, and a second oil inlet regulating valve 44 is provided at the front end of the oil inlet of the second heater. The second discharge port at the bottom of the first deweighting tower 2 is connected to the heavy component tank (V1209).

[0035] The second dehydration unit includes a second dehydration tower 3, a third condenser 8, a third reflux tank 19, a third buffer tank 24 and a third heater 40; the first feed port of the second dehydration tower 3 is connected to the second buffer tank 23, specifically, the outlet of the second buffer tank 23 is connected to the inlet of the second discharge pump 29, the outlet of the second discharge pump 29 is connected to the first feed port of the second dehydration tower 3, and a third feed regulating valve 13 is provided between the two. The first discharge port at the top of the second dehydration tower 3 is connected to the third condenser 8, and the liquid phase outlet of the third condenser 8 is connected to the third reflux tank 19. The top of the third reflux tank 19 is provided with a tail gas exhaust port, the first discharge port at the bottom of the third reflux tank 19 is connected to the second feed port at the top of the second dehydration tower 3, and a third reflux regulating valve 36 is provided between the two, and the second discharge port at the bottom of the third reflux tank 19 is connected to the sewage system. The second discharge port at the bottom of the second dehydration tower 3 is connected to the third buffer tank 24. The third heater 40 is used to heat the bottom of the second dehydration tower 3 . The third heater 40 is a reboiler. A third oil inlet regulating valve 45 is provided at the front end of the oil inlet of the third heater 40 .

[0036] The third dehydration unit includes a third dehydration tower 4, a fourth condenser 9, a fourth reflux tank 20, a fourth buffer tank 25 and a fourth heater 41. The first feed inlet of the third dehydration tower 4 is connected to the third buffer tank 24, specifically, the outlet of the third buffer tank 24 is connected to the inlet of the third discharge pump 30, and the outlet of the third discharge pump 30 is connected to the first feed inlet of the third dehydration tower 4, and a fourth feed regulating valve 14 is provided therebetween. The first discharge port at the top of the third dehydration tower 4 is connected to the fourth condenser 9; the liquid phase outlet of the fourth condenser 9 is connected to the fourth reflux tank 20, the top of the fourth reflux tank 20 is provided with a tail gas exhaust port, the first discharge port at the bottom of the fourth reflux tank 20 is connected to the first feed port of the third dehydration tower 4 and a fourth reflux regulating valve 37 is provided between the two, the second discharge port at the bottom of the fourth reflux tank 20 is connected to the first feed port of the second dehydration tower 3, specifically, the second discharge port at the bottom of the fourth reflux tank 20 is connected to the inlet of the sixth buffer tank 27, the outlet of the sixth buffer tank 27 is connected to the inlet of the wastewater circulation pump 33, the outlet of the wastewater circulation pump 33 is connected to the first feed port of the second dehydration tower 3, and the outlet of the wastewater circulation pump 33 is connected between the second discharge pump 29 and the third feed regulating valve 13. The second discharge port at the bottom of the third dehydration tower 4 is connected to the fourth buffer tank 25; the fourth heater 41 is used to heat the bottom of the third dehydration tower 4. The fourth heater 41 adopts a reboiler, and a fourth oil inlet regulating valve 46 is provided at the front end of the oil inlet of the fourth heater 41.

[0037] The second de-weighting unit includes a second de-weighting tower 5, a fifth condenser 10, a fifth reflux tank 21 and a fifth heater 42; the first feed port of the second de-weighting tower 5 is connected to the fourth buffer tank 25, specifically, the outlet of the fourth buffer tank 25 is connected to the inlet of the fourth discharge pump 31, the outlet of the fourth discharge pump 31 is connected to the first feed port of the second de-weighting tower 5, and a fifth feed regulating valve 15 is provided between the two. The first discharge port at the top of the second de-weighting tower 5 is connected to the fifth condenser 10, and the liquid phase outlet of the fifth condenser 10 is connected to the fifth reflux tank 21. The top of the fifth reflux tank 21 is provided with an exhaust port for tail gas, and the first discharge port at the bottom of the fifth reflux tank 21 is connected to the second feed port at the top of the second de-weighting tower 5, and a fifth reflux regulating valve 38 is provided between the two. The second discharge port at the bottom of the fifth reflux tank 21 is connected to the finished product tank, specifically, the second discharge port at the bottom of the second reflux tank 18 is connected to the inlet of the fifth buffer tank 26, the outlet of the fifth buffer tank 26 is connected to the inlet of the fifth discharge pump 32, the outlet of the fifth discharge pump 32 is connected to the finished product tank, and a sixth feed regulating valve 16 is provided between the two. The fifth heater 42 is used to heat the bottom of the second de-weighting tower 5, the fifth heater 42 adopts a reboiler, and a fifth feed regulating valve 47 is provided at the front end of the oil inlet of the fifth heater 42. The second discharge port at the bottom of the second de-weighting tower 5 is connected to the heavy component tank (V1209).

[0038] The specific implementation process is as follows:

[0039] After the flow rate of NMP waste liquid is controlled by the first feed regulating valve 11, it enters the first dehydration tower 1 through the first feed port of the first dehydration tower 1 for dehydration and rectification. The light components at the top of the first dehydration tower 1 enter the first condenser 6 through the first discharge port at the top of the first dehydration tower 1 for condensation, and the condensed liquid phase enters the first reflux tank 17. Part of the liquid phase is refluxed into the first dehydration tower 1 after the flow rate is controlled by the first reflux regulating valve 34, and part of the liquid phase is discharged into the sewage system through the second discharge port at the bottom of the first reflux tank 17. The bottom of the first dehydration tower 1 is heated by the first heater 39, and the supply of heat transfer oil is adjusted by the first oil inlet regulating valve 43 to control the system heat, thereby controlling the top temperature and bottom temperature of the first dehydration tower 1. The material at the bottom of the first dehydration tower 1 enters the first buffer tank 22 through the second discharge port at the bottom of the first dehydration tower 1.

[0040] The NMP in the first buffer tank 22 passes through the first discharge pump 28 and enters the first de-weighting tower 2 under the regulation and control of the second feed regulating valve 12 for further de-weighting and rectification. The light components at the top of the first de-weighting tower 2 enter the second condenser 7 through the first discharge port at the top of the first de-weighting tower 2 for condensation, and the condensed liquid phase enters the second reflux tank 18. Part of the liquid phase refluxes into the first de-weighting tower 2 after the flow rate is controlled by the second reflux regulating valve 35, and part of the liquid phase is discharged into the second buffer tank 23 through the second discharge port at the bottom of the second reflux tank 18. The bottom of the first de-weighting tower 2 is heated by the second heater, and the supply of heat transfer oil is adjusted by the second oil inlet regulating valve 44 to control the system heat, thereby controlling the top temperature and bottom temperature of the first de-weighting tower 2. The heavy components at the bottom of the first de-weighting tower 2 are intermittently discharged to the heavy component tank to control the heavy component content of the top product.

[0041] The material in the second buffer tank 23 passes through the second discharge pump 29 and enters the second dehydration tower 3 under the regulation and control of the third feed regulating valve 13 for further dehydration and rectification. The light components at the top of the second dehydration tower 3 enter the third condenser 8 through the first discharge port at the top of the second dehydration tower 3 for condensation, and the condensed liquid phase enters the third reflux tank 19. Part of the liquid phase flows back to the second dehydration tower 3 after the flow rate is controlled by the third reflux regulating valve 36, and part of the liquid phase is discharged into the sewage system through the second discharge port at the bottom of the third reflux tank 19. The bottom of the second dehydration tower 3 is heated by the third heater 40, and the supply of heat transfer oil is adjusted by the third oil inlet regulating valve 45 to control the system heat, thereby controlling the top temperature and bottom temperature of the second dehydration tower 3. The material at the bottom of the second dehydration tower 3 enters the third buffer tank 24 through the second discharge port at the bottom of the second dehydration tower 3.

[0042] The material in the third buffer tank 24 passes through the third discharge pump 30 and enters the third dehydration tower 4 under the regulation and control of the fourth feed regulating valve 14 for further dehydration and rectification. The light component at the top of the third dehydration tower 4 enters the fourth condenser 9 through the first discharge port at the top of the third dehydration tower 4 for condensation, and the condensed liquid phase enters the fourth reflux tank 20. Part of the liquid phase flows back to the third dehydration tower 4 after the flow is controlled by the fourth reflux regulating valve 37, and part of the liquid phase flows into the sixth buffer tank 27 through the second discharge port at the bottom of the fourth reflux tank 20. The material in the sixth buffer tank 27 is transported to the second dehydration tower 3 through the wastewater circulation pump 33. The bottom of the third dehydration tower 4 is heated by the fourth heater 41, and the supply of heat transfer oil is adjusted by the fourth oil inlet regulating valve 46 to control the system heat, thereby controlling the top temperature and bottom temperature of the third dehydration tower 4. The material at the bottom of the third dehydration tower 4 enters the fourth buffer tank 25 through the second discharge port at the bottom of the third dehydration tower 4.

[0043] The material in the fourth buffer tank 25 passes through the fourth discharge pump 31, and enters the second de-weighting tower 5 under the regulation and control of the fifth feed regulating valve 15 for further de-weighting and rectification. The light component at the top of the second de-weighting tower 5 enters the fifth condenser 10 through the first discharge port at the top of the second de-weighting tower 5 for condensation, and the condensed liquid phase enters the fifth reflux tank 21. Part of the liquid phase is refluxed into the second de-weighting tower 5 after the flow is controlled by the fifth reflux regulating valve 38, and part of the liquid phase is discharged into the fifth buffer tank 26 through the second discharge port at the bottom of the fifth reflux tank 21, and then transported to the finished product tank through the fifth discharge pump 32, and the sixth feed regulating valve 16 is used to adjust the flow entering the finished product tank. The bottom of the second de-weighting tower 5 is heated by the fifth heater 42, and the supply of heat transfer oil is adjusted by the fifth oil inlet regulating valve 47 to control the system heat, thereby controlling the top temperature and bottom temperature of the second de-weighting tower 5. The heavy component at the bottom of the second de-weighting tower 5 is intermittently discharged to the heavy component tank to control the heavy component content of the top product.

[0044] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0045] The above is only an embodiment of the present invention. The common sense such as the known specific structure and characteristics in the scheme is not described in detail here. The ordinary technicians in the relevant field know all the common technical knowledge in the technical field of the invention before the application date or priority date, can obtain all the existing technologies in the field, and have the ability to apply the conventional experimental means before that date. The ordinary technicians in the relevant field can improve and implement this scheme in combination with their own abilities under the enlightenment given by this application. Some typical known structures or known methods should not become obstacles for ordinary technicians in the relevant field to implement this application. It should be pointed out that for those skilled in the art, without departing from the structure of the present invention, several deformations and improvements can be made, which should also be regarded as the protection scope of the present invention, which will not affect the effect of the implementation of the present invention and the practicality of the patent. The protection scope required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. NMP waste liquid treatment and recovery system, characterized by: It includes a first dehydration unit, a first deweighting unit, a second dehydration unit, a third dehydration unit and a second deweighting unit which are arranged in sequence; The first dehydration unit comprises a first dehydration tower (1), a first condenser (6), a first reflux tank (17), a first buffer tank (22) and a first heater (39); the first feed inlet of the first dehydration tower (1) is used to input NMP waste liquid; the first discharge port at the top of the first dehydration tower (1) is connected to the first condenser (6), the liquid phase outlet of the first condenser (6) is connected to the first reflux tank (17), the first discharge port at the bottom of the first reflux tank (17) is connected to the second feed inlet at the top of the first dehydration tower (1); the second discharge port at the bottom of the first dehydration tower (1) is connected to the first buffer tank (22); the first heater (39) is used to heat the bottom of the first dehydration tower (1); The first de-weighting unit comprises a first de-weighting tower (2), a second condenser (7), a second reflux tank (18), a second buffer tank (23) and a second heater, wherein the first feed inlet of the first de-weighting tower (2) is connected to the first buffer tank (22); the first discharge port at the top of the first de-weighting tower (2) is connected to the second condenser (7), and the liquid phase outlet of the second condenser (7) is connected to the second reflux tank (18); the first discharge port at the bottom of the second reflux tank (18) is connected to the second feed inlet at the top of the first de-weighting tower (2), and the second discharge port at the bottom of the second reflux tank (18) is connected to the second buffer tank (23); the second heater is used to heat the bottom of the first de-weighting tower (2); the second discharge port at the bottom of the first de-weighting tower (2) is connected to the heavy component tank; The second dehydration unit comprises a second dehydration tower (3), a third condenser (8), a third reflux tank (19), a third buffer tank (24) and a third heater (40); the first feed inlet of the second dehydration tower (3) is connected to the second buffer tank (23); the first discharge port at the top of the second dehydration tower (3) is connected to the third condenser (8), and the liquid phase outlet of the third condenser (8) is connected to the third reflux tank (19); the first discharge port at the bottom of the third reflux tank (19) is connected to the second feed inlet at the top of the second dehydration tower (3), and the second discharge port at the bottom of the second dehydration tower (3) is connected to the third buffer tank (24); the third heater (40) is used to heat the bottom of the second dehydration tower (3); The third dehydration unit comprises a third dehydration tower (4), a fourth condenser (9), a fourth reflux tank (20), a fourth buffer tank (25) and a fourth heater (41); the first feed inlet of the third dehydration tower (4) is connected to the third buffer tank (24); the first discharge port at the top of the third dehydration tower (4) is connected to the fourth condenser (9); the liquid phase outlet of the fourth condenser (9) is connected to the fourth reflux tank (20); the first discharge port at the bottom of the fourth reflux tank (20) is connected to the first feed inlet of the third dehydration tower (4); the second discharge port at the bottom of the fourth reflux tank (20) is connected to the first feed inlet of the second dehydration tower (3); the second discharge port at the bottom of the third dehydration tower (4) is connected to the fourth buffer tank (25); the fourth heater (41) is used to heat the bottom of the third dehydration tower (4); The second de-weighting unit comprises a second de-weighting tower (5), a fifth condenser (10), a fifth reflux tank (21) and a fifth heater (42); the first feed inlet of the second de-weighting tower (5) is connected to the fourth buffer tank (25); the first discharge port at the top of the second de-weighting tower (5) is connected to the fifth condenser (10), and the liquid phase outlet of the fifth condenser (10) is connected to the fifth reflux tank (21); the first discharge port at the bottom of the fifth reflux tank (21) is connected to the second feed inlet at the top of the second de-weighting tower (5), and the second discharge port at the bottom of the fifth reflux tank (21) is connected to the finished product tank; the fifth heater (42) is used to heat the bottom of the second de-weighting tower (5); the second discharge port at the bottom of the second de-weighting tower (5) is connected to the heavy component tank.

2. The NMP waste liquid treatment and recovery system according to claim 1, wherein: A first feed regulating valve (11), a second feed regulating valve (12), a third feed regulating valve (13), a fourth feed regulating valve (14), a fifth feed regulating valve (15) and a sixth feed regulating valve (16) are respectively provided at the front end of the first feed inlet of the first dehydration tower (1), the front end of the first feed inlet of the first deweighting tower (2), the front end of the first feed inlet of the second dehydration tower (3), the front end of the first feed inlet of the third dehydration tower (4), the front end of the first feed inlet of the second deweighting tower (5) and the front end of the feed inlet of the finished product tank.

3. The NMP waste liquid treatment and recovery system according to claim 1, wherein: The tops of the first reflux tank (17), the second reflux tank (18), the third reflux tank (19), the fourth reflux tank (20) and the fifth reflux tank (21) are provided with tail gas exhaust ports.

4. The NMP waste liquid treatment and recovery system according to claim 1, wherein: The second discharge ports at the bottom of the first reflux tank (17) and the third reflux tank (19) are respectively connected to the sewage system.

5. The NMP waste liquid treatment and recovery system according to claim 1, wherein: A first reflux regulating valve (34), a second reflux regulating valve (35), a third reflux regulating valve (36), a fourth reflux regulating valve (37) and a fifth reflux regulating valve (38) are respectively provided between the first discharge port at the bottom of the first reflux tank (17) and the second feed port at the top of the first dehydration tower (1), between the first discharge port at the bottom of the second reflux tank (18) and the second feed port at the top of the first dehydration tower (2), between the first discharge port at the bottom of the third reflux tank (19) and the second feed port at the top of the second dehydration tower (3), between the first discharge port at the bottom of the fourth reflux tank (20) and the first feed port at the second dehydration tower (3), and between the first discharge port at the bottom of the fifth reflux tank (21) and the second feed port at the top of the second dehydration tower (5).

6. The NMP waste liquid treatment and recovery system according to claim 1, characterized in that: A first discharge pump (28), a second discharge pump (29), a third discharge pump (30), a fourth discharge pump (31), a fifth discharge pump (32) and a wastewater circulation pump (33) are respectively provided between the first feed inlet of the first dehydration tower (2) and the first buffer tank (22), between the first feed inlet of the second dehydration tower (3) and the second buffer tank (23), between the first feed inlet of the third dehydration tower (4) and the third buffer tank (24), between the first feed inlet of the second dehydration tower (5) and the fourth buffer tank (25), between the second discharge port at the bottom of the fifth reflux tank (21) and the finished product tank, and between the second discharge port at the bottom of the fourth reflux tank (20) and the first feed inlet of the second dehydration tower (3).

7. The NMP waste liquid treatment and recovery system according to claim 6, characterized in that: A fifth buffer tank (26) is provided between the fifth discharge pump (32) and the fifth reflux tank (21), and a sixth buffer tank (27) is provided between the second discharge port at the bottom of the fourth reflux tank (20) and the first feed port of the second dehydration tower (3).

8. The NMP waste liquid treatment and recovery system according to claim 1, characterized in that: The first heater (39), the second heater, the third heater (40), the fourth heater (41) and the fifth heater (42) all use reboilers, and the front ends of the oil inlets of the first heater (39), the second heater, the third heater (40), the fourth heater (41) and the fifth heater (42) are respectively provided with a first oil inlet regulating valve (43), a second oil inlet regulating valve (44), a third oil inlet regulating valve (45), a fourth oil inlet regulating valve (46) and a fifth oil inlet regulating valve (47).

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