NMP waste liquid recovery energy-saving system

Abstract

The utility model discloses an NMP (N-Methyl Pyrrolidone) waste liquid recovery energy-saving system, which relates to the field of NMP solvent recovery in the lithium battery industry and comprises a raw material inlet, a first preheater, a second preheater, a dehydrating tower, a refining tower, a dehydrating tower condenser, a dehydrating tower reboiler and a refining tower reboiler. A raw material inlet is connected with a first preheater through a pipeline, the first preheater is connected with a second preheater, an outlet pipeline of the second preheater is connected with a dehydrating tower, and a tower kettle of the dehydrating tower is connected with a refining tower. A first dehydrating tower middle reboiler and a second dehydrating tower middle reboiler are respectively arranged at the upper part and the lower part of the dehydrating tower stripping section and are respectively connected with a refining tower top gas phase pipeline and a refining tower side line product pipeline. And shell side condensate water of the dehydrating tower reboiler and the refining tower reboiler is respectively connected with the first preheater and the second preheater. According to the utility model, the preheater and the intermediate reboiler are adopted to recover high-grade heat, so that the steam consumption of the device is greatly reduced, and the energy consumption of the device is saved.

Description

Technical Field

[0001] The utility model belongs to the field of solvent recovery in the lithium battery industry, and specifically relates to an NMP solvent waste liquid recovery and energy-saving system. Background Art

[0002] NMP, short for N-methylpyrrolidone, is a colorless, transparent liquid with excellent chemical and thermal stability. It boasts a high boiling point, is non-corrosive, low toxicity, low volatility, and is biodegradable. Currently, electronic-grade NMP is primarily used as a solvent for lithium battery positive electrode binders. This solvent evaporates at a certain temperature through a drying process and is then condensed and recovered to form NMP waste liquid. NMP waste liquid typically contains impurities such as water, methylamine, and 2-pyrrolidone. For both economic and environmental reasons, recycling and reuse of NMP waste liquid is desirable.

[0003] Patent CN 114432728A discloses a system and process for NMP purification. This patent utilizes an upper bulkhead tower to separate and purify NMP wastewater. The tower is divided into three compartments, with the product withdrawn from a side stream in the second compartment. This system separates multiple components within a single tower, making it difficult to simultaneously control multiple component indicators, which can easily lead to unstable tower operation and substandard product.

[0004] Utility model patent CN 219983945U discloses an energy-saving system for refining NMP waste liquid. The system uses four towers to separate the NMP waste liquid, and the equipment investment and operation costs are relatively high.

[0005] Utility model patent CN 219091131U discloses a process system for recovering and refining NMP waste liquid. Although this system uses two towers to separate the NMP waste liquid and adopts certain heat integration measures, it needs to control the bottom temperature of the first dehydration tower to be lower than the top temperature of the NMP refining tower. This leads to incomplete dehydration in the first dehydration tower and increases the load on the NMP refining tower.

[0006] Therefore, in the existing technology, there are problems such as difficulty in simultaneously controlling multi-component indicators, high equipment investment and operating costs, and incomplete dehydration in the first dehydration tower. A more efficient and energy-saving NMP waste liquid recovery system is needed to solve these problems. Utility Model Content

[0007] In view of the above problems, the utility model provides an NMP waste liquid recovery energy-saving system, which greatly reduces the equipment investment cost and operating cost of NMP solvent recovery by adopting two-tower separation and the use of an intermediate reboiler.

[0008] The technical solution adopted by the utility model to solve the technical problem is:

[0009] An NMP waste liquid recovery and energy-saving system includes a raw material inlet, a first preheater, a second preheater, a dehydration tower, a refining tower, a dehydration tower condenser, a dehydration tower reboiler, a first dehydration tower intermediate reboiler, a second dehydration tower intermediate reboiler, and a refining tower reboiler. The first raw material inlet is connected to the first preheater, the first preheater is connected to the second preheater, the second preheater is connected to the dehydration tower, and the bottom of the dehydration tower is connected to the refining tower.

[0010] Furthermore, a dehydration tower condenser is provided at the top of the dehydration tower, a dehydration tower reboiler is provided at the bottom, a first dehydration tower intermediate reboiler and a second dehydration tower intermediate reboiler are provided above and below the stripping section respectively, and a refining tower reboiler is provided at the bottom of the refining tower.

[0011] Furthermore, the shell-side inlet of the intermediate reboiler of the first dehydration tower is connected to the gas phase pipeline at the top of the refining tower. A portion of the shell-side outlet is returned to the refining tower through the shell-side outlet pipeline, and the other portion is extracted outside the device.

[0012] Furthermore, the shell-side inlet of the intermediate reboiler of the second dehydration tower is connected to the side line pipeline of the top of the refining tower, and the shell-side outlet is extracted to the outside of the device through the shell-side outlet pipeline 2.

[0013] Furthermore, steam is introduced into the shell side inlet of the dehydration tower reboiler, and the shell side outlet is connected to the first preheater.

[0014] Furthermore, steam is introduced into the shell side inlet of the refining tower reboiler, and the shell side outlet is connected to the second preheater.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] By rationally utilizing the refining tower overhead steam, side product heat, dehydration tower reboiler condensate and refining tower reboiler condensate heat sources, efficient energy utilization is achieved and production costs are reduced.

[0017] The use of a double-tower distillation system can simultaneously control multiple component indicators, improving the stability and operating efficiency of the system.

[0018] By using a reboiler in the middle of the dehydration tower, it is not affected by the temperature of the dehydration tower kettle, effectively recovers heat while avoiding the problem of incomplete dehydration in the dehydration tower in the prior art, thereby reducing the separation load of the two towers and improving the separation effect of the two towers.

[0019] In summary, compared with the existing technology, this technical solution has obvious advantages in equipment investment and operating costs, separation efficiency and energy consumption, and can recover and purify NMP waste liquid more efficiently and energy-savingly. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic diagram of an NMP waste liquid recovery and energy-saving system of the utility model;

[0021] In the figure: 1. Raw material inlet; 2. First preheater; 3. Second preheater; 4. Dehydration tower; 5. Refining tower; 101. Dehydration tower condenser; 102. Dehydration tower reboiler; 103. First dehydration tower intermediate reboiler; 104. Second dehydration tower intermediate reboiler; 201. Refining tower reboiler; 202. Tower top gas phase pipeline; 203. Shell-side outlet pipeline; 204. Tower top side line; 205. Shell-side outlet pipeline 2. DETAILED DESCRIPTION

[0022] The following examples clearly and completely describe the technical solutions of the present invention. It is obvious that the examples described are only some of the embodiments of the present invention, not all of them. Based on the examples of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0023] like Figure 1 As shown, an NMP waste liquid recovery and energy-saving system includes a raw material inlet 1, a first preheater 2, a second preheater 3, a dehydration tower 4, a refining tower 5, a dehydration tower condenser 101, a dehydration tower reboiler 102, a first dehydration tower intermediate reboiler 103, a second dehydration tower intermediate reboiler 104 and a refining tower reboiler 201.

[0024] The recovered liquid enters the dehydration tower 4 through the first preheater 2 and the second preheater 3 from the raw material inlet 1. The first preheater 2 and the second preheater 3 are used to recover the heat of the condensed water in the dehydration tower reboiler 102 and the refining tower reboiler 201.

[0025] The preheated recovered liquid is dehydrated in the dehydration tower 4. A dehydration tower condenser 101 is provided at the top of the dehydration tower 4, a dehydration tower reboiler 102 is provided at the bottom, and two upper and lower intermediate reboilers are provided in the distillation section: a first dehydration tower intermediate reboiler 103 and a second dehydration tower intermediate reboiler 104.

[0026] The shell-side inlet of the intermediate reboiler 103 of the first dehydration tower is connected to the gas phase pipeline 202 at the top of the refining tower 5, which is used to recover the gas phase heat at the top of the refining tower; the shell-side outlet of the intermediate reboiler 103 of the first dehydration tower is connected through the shell-side outlet pipeline 203 and is divided into two paths, one path is connected to the side of the top of the refining tower 5, and the other path transports the light components to storage outside the device.

[0027] The shell side inlet of the second dehydration tower intermediate reboiler 104 is connected to the top side line pipeline 204 of the refining tower 5, which is used to recover the heat of the top side line product of the refining tower; the shell side outlet of the second dehydration tower intermediate reboiler 104 is transported to the product tank for storage through the shell side outlet pipeline 2 205.

[0028] The locations of the two intermediate reboilers are determined according to the temperature of the gas phase at the top of the refining tower and the side product at the top of the refining tower, ensuring that the temperature difference between the two sides is around 10~20℃.

[0029] The recovered liquid after being completely dehydrated by the dehydration tower 4 is connected to the refining tower 5 through a pipeline from the tower bottom. After separation in the refining tower 5, the light components are extracted from the top of the tower and the heavy components are extracted from the tower bottom. The side line product of the distillation section is condensed in the intermediate reboiler 104 of the second dehydration tower and then transported to the product tank for return utilization.

[0030] In the above technical solution, the dehydration tower pressure is controlled at 10~50kPa, the tower top temperature is 46℃~81℃, and the tower bottom temperature is 126℃~175℃. The refining tower pressure is controlled at 10~50kPa, the tower top temperature is 71℃~112℃, and the tower bottom temperature is 135℃~183℃.

[0031] While the water content in the dehydration tower bottom of conventional systems is affected by the refining tower top temperature, this system completely removes water from the bottom, achieving electronic-grade standards. In terms of energy conservation, taking the recovery of 100,000 tons of NMP wastewater as an example, based on an annual operating time of 8,000 hours, the steam consumption without heat integration is 1.03 tons per ton of product. With this system, the steam consumption is reduced to 0.49 tons per ton of product, reducing steam usage by half. This demonstrates that the energy-saving system for NMP wastewater recovery and production in this utility model can significantly reduce energy consumption, improve the operating economy of the device, and effectively reduce the device's carbon emissions.

Claims

1. A NMP waste liquid recovery and energy-saving system, characterized in that: The invention comprises a raw material inlet (1), a first preheater (2), a second preheater (3), a dehydration tower (4), a refining tower (5), a dehydration tower condenser (101), a dehydration tower reboiler (102), a first dehydration tower intermediate reboiler (103), a second dehydration tower intermediate reboiler (104) and a refining tower reboiler (201); the raw material inlet (1) is connected to the first preheater (2), and the first preheater (2) is connected to the second preheater (3). The second preheater (3) is connected to the dehydration tower (4), the bottom of the dehydration tower (4) is connected to the refining tower (5), the top of the dehydration tower (4) is provided with a dehydration tower condenser (101), the bottom of the dehydration tower (4) is provided with a dehydration tower reboiler (102), the upper and lower parts of the stripping section of the dehydration tower (4) are provided with a first dehydration tower intermediate reboiler (103) and a second dehydration tower intermediate reboiler (104), respectively, and the bottom of the refining tower (5) is provided with a refining tower reboiler (201).

2. A NMP waste liquid recovery and energy-saving system according to claim 1, characterized in that, The shell side inlet of the intermediate reboiler (103) of the first dehydration tower is connected to the gas phase pipeline (202) at the top of the refining tower (5), and a portion of the shell side outlet is returned to the refining tower (5) through the shell side outlet pipeline (203), and the other portion is extracted outside the device.

3. A NMP waste liquid recovery and energy-saving system according to claim 2, characterized in that, The shell side inlet of the intermediate reboiler (104) of the second dehydration tower is connected to the top side line pipeline (204) of the refining tower (5), and the shell side outlet is produced outside the device through the shell side outlet pipeline 2 (205).

4. A NMP waste liquid recovery and energy-saving system according to claim 3, characterized in that, Steam is introduced into the shell side inlet of the dehydration tower reboiler (102), and the shell side outlet is connected to the first preheater (2).

5. The NMP waste liquid recovery and energy-saving system according to claim 3, characterized in that, Steam is introduced into the shell side inlet of the refining tower reboiler (201), and the shell side outlet is connected to the second preheater (3).

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