System for continuously refining and purifying NMP (N-Methyl Pyrrolidone) waste liquid by thermal coupling reboiler

Abstract

The utility model provides a system for continuously refining and purifying NMP (N-Methyl Pyrrolidone) waste liquid by a thermal coupling reboiler, which comprises a primary dehydrating tower, a secondary dehydrating tower and a refining tower, and further comprises a first heat exchange reboiler, a second heat exchange reboiler, a third heat exchange reboiler, a third heat exchange reboiler and a fourth heat exchange reboiler, the shell pass is mounted in the middle of the primary dehydrating tower, a shell pass inlet of the shell pass is communicated with a top gas outlet of the refining tower, and a shell pass outlet is communicated with a top side inlet of the refining tower; the first heat exchange reboiler utilizes gaseous light components at the top of the refining tower to perform gradient heating on gas in the first-stage dehydrating tower, so that the temperature of the gas is uniform. The first heat exchange reboiler is arranged in the middle of the first-stage dehydrating tower, and a high-temperature gas-phase component at the top of the refining tower is used as a heat source, so that the functions of cascade heat exchange and heat recovery in the rectification process are realized, and the problem of high energy consumption of NMP rectification recovery is solved.

Description

Technical Field

[0001] The utility model relates to the technical field of chemical industry, in particular to a system for continuously refining and purifying NMP waste liquid with a thermally coupled reboiler. Background Art

[0002] N-Methylpyrrolidone, referred to as NMP, is an organic substance with good chemical and thermal stability, high polarity, low volatility, and infinite miscibility with water and many organic solvents. In lithium battery production, NMP is widely used as an electrolyte additive. It can improve the conductivity and stability of the battery, and reduce the gas generation inside the battery, thereby improving the safety and performance of the battery. In the production process of lithium batteries, NMP waste gas will be generated in the coating, baking and other links, and the waste gas will be mixed with pollutants such as lead dust / smoke and acid mist. The waste gas containing NMP will be converted into NMP waste liquid through the recovery device.

[0003] Chinese patent CN217780952U discloses a NMP waste liquid distillation and purification system, which includes a pre-treatment unit for pre-treating the NMP waste liquid; and a three-stage distillation unit, the three-stage distillation unit includes a first distillation unit, a second distillation unit and a third distillation unit connected in series, the first distillation unit is used to remove light components in the NMP waste liquid, the second distillation unit is used to remove water from the waste liquid extracted from the first distillation unit, and the third distillation unit is used to remove heavy components from the waste liquid extracted from the second distillation unit and distill to obtain electronic grade NMP. The system can effectively recycle the NMP waste liquid generated in the production process of lithium-ion batteries to obtain electronic grade NMP, and the whole system has the advantage of low energy consumption.

[0004] However, this technical solution has the following problems: first, each distillation unit is only equipped with a reboiler in the bottom of the tower, the temperature in the tower is uneven, and the distillation efficiency is low; second, no heat recovery is performed during the distillation process, the energy consumption is high, and heat is wasted. Utility Model Content

[0005] The utility model aims to solve the shortcomings of the prior art and provide a system for continuously refining and purifying NMP waste liquid with a heat-coupled reboiler. The system is characterized in that the first heat exchange reboiler is arranged in the middle of a primary dehydration tower and the high-temperature gas phase component at the top of the refining tower is used as a heat source to realize the functions of cascade heat exchange and heat recovery in the distillation process, thereby solving the problem of high energy consumption of NMP distillation recovery.

[0006] In order to achieve the above purpose, the utility model provides the following technical solutions:

[0007] A system for continuously refining and purifying NMP waste liquid using a thermally coupled reboiler, comprising a primary dehydration tower, a secondary dehydration tower and a refining tower, wherein the discharge port of the primary dehydration tower is connected to the feed port of the secondary dehydration tower, the discharge port of the secondary dehydration tower is connected to the feed port of the refining tower, the top outlet of the primary dehydration tower (1) is connected to a first condenser (12), the top outlet of the secondary dehydration tower (2) is connected to a second condenser (21), and further comprising:

[0008] The first heat exchange reboiler is installed in the middle of the first dehydration tower, and its shell side inlet is connected to the gas outlet at the top of the refining tower, and its shell side outlet is connected to the side inlet at the top of the refining tower; the first heat exchange reboiler utilizes the gaseous light components at the top of the refining tower to perform step-heating on the gas inside the first dehydration tower to stabilize the temperature distribution in the tower.

[0009] Preferably, at least two layers of fillers are provided inside the primary dehydration tower, the secondary dehydration tower and the refining tower, and the tube side inlet and the tube side outlet of the first heat exchange reboiler are located between the two layers of fillers of the primary dehydration tower.

[0010] As a preference, a waste liquid inlet is provided in the middle of the primary dehydration tower, the waste liquid inlet is located above the filler in the lower layer, and is connected to an input pipeline.

[0011] As a preference, a preheater is installed on the input pipeline.

[0012] As a preferred embodiment, the first dehydration tower, the second dehydration tower and the refining tower are all equipped with a steam reboiler at the bottom for heating the bottom liquid of the three towers.

[0013] As a preference, the shell-side inlet of the steam reboiler is connected to a steam source, and the shell-side outlet thereof is connected to the shell-side inlet of the preheater.

[0014] Preferably, the first condenser outlet comprises a first reflux branch and an external discharge branch.

[0015] Preferably, the second condenser outlet comprises a second reflux branch and a condensate recovery branch, and the condensate recovery branch is connected to the input pipeline.

[0016] As a preference, the refining tower is provided with a product outlet.

[0017] As a preferred embodiment, it also includes:

[0018] The second heat exchange reboiler is installed in the middle of the secondary dehydration tower to heat the gas inside the secondary dehydration tower and stabilize the temperature distribution in the tower.

[0019] The beneficial effects of the utility model are:

[0020] (1) The utility model reduces the energy consumption of the NMP distillation process by using the gaseous light component at the top of the refining tower as the heat source of the first heat exchange reboiler and recovering the heat of the gaseous light component to heat the gas inside the primary dehydration tower.

[0021] (2) The utility model arranges a first heat exchange reboiler in the middle of the first dehydration tower to perform step-by-step heating on the gas in the middle of the first dehydration tower, thereby reducing the condensation amount of the gas phase in the first dehydration tower during the ascending process, allowing more gas phase to condense in the first condenser, thereby improving the dehydration efficiency of the first dehydration tower and ensuring the stable operation of the distillation process.

[0022] (3) The utility model can extend the heat exchange time of the first heat exchange reboiler by arranging the tube side inlet and the tube side outlet of the first heat exchange reboiler between two layers of fillers, so that the gas phase in the middle of the primary dehydration tower can fully exchange heat and stabilize the temperature distribution in the tower. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic diagram of the structure of the process system of the utility model;

[0024] Figure 2 This is a schematic diagram of the structure of the second and third embodiments of the present utility model. DETAILED DESCRIPTION

[0025] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0026] In the description of the present utility model, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present utility model and simplifying the description, rather than indicating or implying that the equipment or elements referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present utility model. In addition, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present utility model, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0027] Embodiment 1

[0028] like Figure 1 As shown, this embodiment provides a thermally coupled reboiler continuous refining and purification system for NMP waste liquid, including a primary dehydration tower 1, a secondary dehydration tower 2 and a refining tower 3, wherein the discharge port of the primary dehydration tower 1 is connected to the feed port of the secondary dehydration tower 2, the discharge port of the secondary dehydration tower 2 is connected to the feed port of the refining tower 3, the top outlet of the primary dehydration tower 1 is connected to a first condenser 12, and the top outlet of the secondary dehydration tower 2 is connected to a second condenser 21, and further includes: a first heat exchange reboiler 4, which is installed in the middle of the primary dehydration tower 1, and its shell side inlet is connected to the top outlet of the refining tower 3, and the shell side outlet is connected to the top side inlet of the refining tower 3; the heat source of the first heat exchange reboiler 4 is the gaseous light component at the top of the refining tower 3, and its heat is recovered to heat the gas inside the primary dehydration tower 1, and the gas inside the primary dehydration tower is stepped and heated, thereby reducing the energy consumption of the NMP distillation process. It should be noted that in the present utility model, the refining tower 3 is preferably a product tower.

[0029] By arranging the first heat exchange reboiler 4 in the middle of the primary dehydration tower 1, the gas in the middle of the primary dehydration tower 1 is heated in steps, thereby reducing the condensation amount of the gas phase in the primary dehydration tower 1 during the rising process, allowing more gas phase to condense in the first condenser 12, thereby improving the dehydration efficiency of the primary dehydration tower 1.

[0030] At least two layers of fillers 5 are arranged inside the primary dehydration tower 1, the secondary dehydration tower 2 and the refining tower 3, and the tube side inlet 41 and the tube side outlet 42 of the first heat exchange reboiler 4 are located between the two layers of fillers 5 of the primary dehydration tower 1. Since the filler has a certain blocking effect on the gas phase in the dehydration tower, the tube side inlet 41 and the tube side outlet 42 of the first heat exchange reboiler 4 are arranged between the two layers of fillers 5, which can extend the heat exchange time of the first heat exchange reboiler 4, so that the gas phase and the liquid phase in the middle of the primary dehydration tower 1 can fully exchange heat and stabilize the temperature distribution in the tower.

[0031] A waste liquid inlet 11 is provided in the middle of the primary dehydration tower 1, and the waste liquid inlet 11 is located above the filler 5 in the lower layer, and is connected to an input pipeline 6. A preheater 70 is installed on the input pipeline 6.

[0032] The first dehydration tower 1, the second dehydration tower 2 and the refining tower 3 are all equipped with a steam reboiler 8 at the bottom for heating the bottom liquid of the three towers. The shell side inlet of the steam reboiler 8 is connected to the steam source, and the shell side outlet is connected to the shell side inlet of the preheater 70.

[0033] A preheater 70 is provided on the input pipeline 6 to recycle the heat of the steam condensate to preheat the NMP waste liquid so that it has a higher initial temperature before entering the primary dehydration tower 1, thereby reducing the steam usage of the steam reboiler 8 at the bottom of the primary dehydration tower 1.

[0034] The outlet of the first condenser 12 includes a first reflux branch 121 and an external discharge branch 122 .

[0035] The top pressure of the primary dehydration tower 1 is controlled at 0.1-0.2 bar, the top temperature is controlled at 50-65° C. The gas phase at the top of the tower is condensed by the first condenser 12, and the condensed liquid phase is partially refluxed into the primary dehydration tower 1 through the first reflux branch 121, and partially discharged as waste water from the external discharge branch 122. The treated NMP waste liquid has a concentration of about 85% before entering the primary dehydration tower 1. Most of the water is removed from the primary dehydration tower 1, and its concentration rises to more than 98%, and enters the secondary dehydration tower 2.

[0036] The outlet of the second condenser 21 includes a second reflux branch 211 and a condensate recovery branch 212 , and the condensate recovery branch 212 is connected to the input pipeline 6 .

[0037] The top pressure of the secondary dehydration tower 2 is controlled at 0.1-0.2 bar, and the top temperature is controlled at 60-75° C. The gas phase at the top of the tower is condensed by the second condenser 21, and the condensed liquid phase is partially refluxed to the secondary dehydration tower 2 through the second reflux branch 211, and partially enters the input pipeline 6 through the condensate recovery branch 212, and returns to the primary dehydration tower 1 after mixing with the NMP waste liquid. The NMP product treated by the secondary dehydration tower 2 has a water content of <100 ppm and enters the refining tower 3.

[0038] The refining tower 3 is provided with a product outlet 31, and the product outlet 31 is arranged in the upper middle part of the refining tower 3 for outputting the NMP product after distillation.

[0039] Embodiment 2

[0040] like Figure 2 As shown, the components identical or corresponding to those in the first embodiment are marked with the corresponding reference numerals in the first embodiment. For the sake of simplicity, only the differences from the first embodiment are described below. The second embodiment is different from the first embodiment in that it further includes a second heat exchange reboiler 9 installed in the middle of the second-stage dehydration tower 2 to heat the gas inside the second-stage dehydration tower 2 and stabilize the temperature distribution in the tower.

[0041] Embodiment 3

[0042] like Figure 2 As shown, the same or corresponding parts as those in the second embodiment are marked with the corresponding reference numerals in the second embodiment. For the sake of simplicity, only the differences from the second embodiment are described below. The third embodiment is different from the second embodiment in that: the input pipeline 6 is further equipped with another preheater 71, the product outlet 31 is connected to the shell side inlet of the other preheater 71, and the NMP product is passed into the preheater to perform heat exchange with the NMP waste liquid, so as to recover the heat of the NMP product and further reduce the energy consumption of the utility model.

[0043] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A thermally coupled reboiler continuous refining and purification system for NMP waste liquid, comprising a primary dehydration tower, a secondary dehydration tower and a refining tower, wherein the discharge port of the primary dehydration tower is connected to the feed port of the secondary dehydration tower, the discharge port of the secondary dehydration tower is connected to the feed port of the refining tower, the top outlet of the primary dehydration tower is connected to a first condenser, and the top outlet of the secondary dehydration tower is connected to a second condenser, characterized in that: Also includes: The first heat exchange reboiler is installed in the middle of the first dehydration tower, and its shell side inlet is connected to the gas outlet at the top of the refining tower, and its shell side outlet is connected to the side inlet at the top of the refining tower; the first heat exchange reboiler utilizes the gaseous light components at the top of the refining tower to perform step-by-step heating on the gas inside the first dehydration tower.

2. A thermally coupled reboiler continuous refining and purification system for NMP waste liquid according to claim 1, characterized in that: At least two layers of fillers are arranged inside the primary dehydration tower, the secondary dehydration tower and the refining tower, and the tube side inlet and the tube side outlet of the first heat exchange reboiler are located between the two layers of fillers of the primary dehydration tower.

3. A thermally coupled reboiler continuous refining and purification system for NMP waste liquid according to claim 2, characterized in that: A waste liquid inlet is arranged in the middle of the primary dehydration tower, and the waste liquid inlet is located above the filler in the lower layer and is connected with an input pipeline.

4. A thermally coupled reboiler continuous refining and purification system for NMP waste liquid according to claim 3, characterized in that: A preheater is installed on the input pipeline.

5. A thermally coupled reboiler continuous refining and purification system for NMP waste liquid according to claim 4, characterized in that: The bottoms of the primary dehydration tower, the secondary dehydration tower and the refining tower are all equipped with steam reboilers for heating the bottom liquids of the three towers.

6. A thermally coupled reboiler continuous refining and purification system for NMP waste liquid according to claim 5, characterized in that: The shell side inlet of the steam reboiler is connected to a steam source, and the shell side outlet of the steam reboiler is connected to the shell side inlet of the preheater.

7. A thermally coupled reboiler continuous refining and purification system for NMP waste liquid according to claim 1, characterized in that: The outlet of the first condenser includes a first reflux branch and an external discharge branch.

8. A thermally coupled reboiler continuous refining and purification system for NMP waste liquid according to claim 3, characterized in that: The outlet of the second condenser includes a second reflux branch and a condensate recovery branch, and the condensate recovery branch is connected to the input pipeline.

9. A thermally coupled reboiler continuous refining and purification system for NMP waste liquid according to claim 1, characterized in that: The refining tower is provided with a product outlet.

10. A thermally coupled reboiler continuous refining and purification system for NMP waste liquid according to claim 1, characterized in that: Also includes: The second heat exchange reboiler is installed in the middle of the secondary dehydration tower to heat the gas inside the secondary dehydration tower.

Images