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EP-4578526-B1 - NMP BATCH DISTILLATION DEVICE AND PROCESS

EP4578526B1EP 4578526 B1EP4578526 B1EP 4578526B1EP-4578526-B1

Inventors

  • YAN, YONGJUN
  • LI, TIANYOU
  • MENG, Jili
  • ZHU, Chunfang

Dates

Publication Date
20260506
Application Date
20240326

Claims (9)

  1. A 1-Methyl-2-pyrrolidone batch distillation device, comprising a batch distillation tower (1), a scraper falling-film evaporation reboiler (2), a reboiler pump (5), a tower top condenser (3), a tower top vacuum condenser (4), a raw material and intermediate product transfer pump (7), a water receiving tank (9), an intermediate product receiving tank (10), a product receiving tank (11), and a reflux controller (12), wherein the top of the batch distillation tower (1) is connected to the tower top condenser (3), one outlet of the tower top condenser (3) is connected to the tower top vacuum condenser (4), and another outlet of the tower top condenser (3) is connected to the reflux controller (12); one outlet of the reflux controller (12) is connected to the batch distillation tower (1), and another outlet of the reflux controller (12) is connected to the water receiving tank (9), the intermediate product receiving tank (10), and the product receiving tank (11); the raw material and intermediate product transfer pump (7) is connected to the batch distillation tower (1), the intermediate product receiving tank (10), and a raw material feed pipe (S1); the reboiler pump (5) is connected to the batch distillation tower (1) to form a deoxygenation circulation passage, wherein the reboiler pump (5) has a gas inlet configured to introduce nitrogen, by the deoxygenation circulation passage, the reboiler pump pumps out 1-Methyl-2-pyrrolidone waste liquid from the batch distillation tower, and transfers the 1-Methyl-2-pyrrolidone waste liquid back to a tower kettle of the batch distillation tower after the nitrogen introduced by the reboiler pump (5) is mixed with the 1-Methyl-2-pyrrolidone waste liquid; and the reboiler pump (5) is also connected to the scraper falling-film evaporation reboiler (2) to form a passage for transferring the 1-Methyl-2-pyrrolidone waste liquid to the scraper falling-film evaporation reboiler (2) for heating and evaporating, and the scraper falling-film evaporation reboiler (2) is connected to the batch distillation tower (1), such that a gas phase part of the 1-Methyl-2-pyrrolidone waste liquid enters a column of the batch distillation tower (1), and a liquid phase part of the 1-Methyl-2-pyrrolidone waste liquid that is not vaporized enters the tower kettle of the batch distillation tower, and the reboiler pump (5) is a magnetic gas-liquid mixing pump.
  2. The 1-Methyl-2-pyrrolidone batch distillation device according to claim 1, further comprising a water transfer pump (6) connected to the water receiving tank (9).
  3. The 1-Methyl-2-pyrrolidone batch distillation device according to claim 1, further comprising a product transfer pump (8) connected to the product receiving tank (11).
  4. The 1-Methyl-2-pyrrolidone batch distillation device according to claim 1, wherein the batch distillation tower (1) is filled with a BX500 mesh filler, and a height of the filler is 3 to 6 m.
  5. A 1-Methyl-2-pyrrolidone batch distillation process based on the NMP batch distillation device according to any one of claims 1 to 4, comprising a pre-treatment stage and a distillation stage, wherein the pre-treatment stage comprises the following steps: transferring 1-Methyl-2-pyrrolidone waste liquid to the batch distillation tower (1) by using the raw material and intermediate product transfer pump (7); introducing nitrogen into the batch distillation tower (1) to replace air in the batch distillation tower (1); starting a vacuum system of the batch distillation tower (1) to maintain a pressure of 8 to 9 kPa at the top of the tower, and starting a jacketed heating system of a tower kettle, to perform total reflux at the top of the tower; performing deoxygenation treatment when a temperature of the 1-Methyl-2-pyrrolidone waste liquid in the tower kettle of the batch distillation tower (1) reaches 0 to 6 °C below a bubble point temperature, wherein a procedure of the deoxygenation treatment is as follows: the reboiler pump (5) pumps out the 1-Methyl-2-pyrrolidone waste liquid from the batch distillation tower, and transfers the 1-Methyl-2-pyrrolidone waste liquid back to the tower kettle of the batch distillation tower (1) after nitrogen is mixed with the 1-Methyl-2-pyrrolidone waste liquid; after the deoxygenation treatment is completed, closing the gas inlet of the reboiler pump (5) and a passage between the reboiler pump (5) and the batch distillation tower (1), and opening a passage between the reboiler pump (5) and the scraper falling-film evaporation reboiler (2), to heat and evaporate the 1-Methyl-2-pyrrolidone waste liquid; during the heating procedure, the scraper falling-film evaporation reboiler (2) evaporates the 1-Methyl-2-pyrrolidone waste liquid, a gas phase part enters the column of the batch distillation tower (1), and a liquid phase part that is not vaporized enters the tower kettle of the batch distillation tower (1); and when a temperature of the tower kettle of the batch distillation tower (1) reaches a specified temperature and a reflux temperature of the batch distillation tower (1) is stable, performing the distillation stage, wherein the distillation stage comprises the following steps: opening a passage between the reflux controller (12) and the water receiving tank (9), keeping the pressure at the top of the batch distillation tower (1) unchanged, and adjusting a reflux ratio and heating power, to perform water extraction; closing the passage between the reflux controller (12) and the water receiving tank (9), opening a passage between the reflux controller (12) and the intermediate product receiving tank (10), and adjusting the reflux ratio, the heating power, and the pressure at the top of the batch distillation tower (1), to perform intermediate product extraction; and closing the passage between the reflux controller (12) and the intermediate product receiving tank (10), opening a passage between the reflux controller (12) and the product receiving tank (11), keeping the pressure at the top of the batch distillation tower (1) unchanged, and adjusting the reflux ratio and the heating power, to perform 1-Methyl-2-pyrrolidone product extraction.
  6. The 1-Methyl-2-pyrrolidone batch distillation process according to claim 5, wherein the procedure of the deoxygenation treatment is repeated at least twice in the pre-treatment stage.
  7. The 1-Methyl-2-pyrrolidone batch distillation process according to claim 5, wherein when the water extraction is performed, the heating power of the jacketed heating system is at full load, the pressure at the top of the batch distillation tower (1) is 8 to 9 kPa, and the reflux ratio at the top of the batch distillation tower (1) is adjusted to 0.1 to 0.3.
  8. The1-Methyl-2-pyrrolidone batch distillation process according to claim 5, wherein when the intermediate product extraction is performed, the heating power of the jacketed heating system is 30% to 40% of full load, the pressure at the top of the batch distillation tower (1) is reduced from 8 to 9 kPa to 2 to 3 kPa, and the reflux ratio at the top of the batch distillation tower (1) is adjusted to 0.2 to 0.4.
  9. The1-Methyl-2-pyrrolidone batch distillation process according to claim 5, wherein when the 1-Methyl-2-pyrrolidone product extraction is performed, the heating power of the jacketed heating system is 30% to 40% of full load, the pressure at the top of the batch distillation tower (1) remains unchanged at 2 to 3 kPa, and the reflux ratio at the top of the batch distillation tower (1) is adjusted to 0.5 to 1.2.

Description

TECHNICAL FIELD The present invention relates to the field of NMP recovery liquid purification technologies, and in particular, to an NMP batch distillation device and process. BACKGROUND Differences in volatility of components of a liquid mixture are utilized in distillation for vaporizing a part of the liquid mixture and then condensing a part of vapor, so as to implement separation of the components of the liquid mixture. Distillation can be classified into continuous distillation and batch distillation according to different operating manners. Batch distillation means adding a batch of to-be-treated materials to a tower kettle of a distillation tower all at once, then performing heating for distillation until a product from the tower kettle or the top of the tower satisfies a requirement, and discharging nonconforming materials. After the materials are discharged, a new batch of materials is added for distillation. The distillation tower does not distinguish between a rectifying section and a stripping section. During batch distillation operation, liquid in the tower kettle is indirectly heated to boiling, and vapor generated in the tower kettle rises into the distillation tower, where heat and mass exchange are performed. The rising vapor in the tower is led from the top of the tower to a condenser, and a part of condensate liquid obtained from the condenser is then led to a tray at the top of the tower as reflux. If there is a need to obtain distillates with different boiling point ranges, several storage tanks need to be disposed to collect them separately based on different boiling points. Batch distillation is generally performed until composition of the liquid in the tower kettle satisfies specified composition. Compared with continuous distillation, batch distillation has the following features: Materials are fed in batches in batch distillation, and therefore materials cannot be discharged continuously from the tower kettle or the top of the tower. A concentration of discharged materials changes over time. Batch distillation has lower production capacity, but requires a lower construction investment without a need for precise and expensive control instruments, and is suitable for small-scale production. 1-Methyl-2-pyrrolidone (NMP) is an important chemical solvent with low toxicity, high boiling point, a strong dissolving capability, and good selectivity and stability. 1-Methyl-2-pyrrolidone (NMP) is widely used in lithium battery manufacturing. Currently, there are many methods for NMP recovery in the lithium battery industry, and the most widely used method is continuous distillation for a liquid mixture containing NMP, which can effectively remove impurities such as water. Batch distillation is generally not used for NMP recovery in the industry, and reasons are as follows: NMP is stable in a neutral condition, but is prone to ring opening to form acid and other products in an acid or alkaline condition, and oxygen, water, and temperature have impact on decomposition of NMP. Feed liquid for batch distillation stays for a long time in the tower kettle of the distillation tower, and if the feed liquid for batch distillation is at high temperature for a long time, NMP in NMP waste liquid reacts with dissolved oxygen in raw materials, resulting in a decrease in a product recovery rate and affecting a purified amount of the NMP waste liquid. However, a device that can implement continuous distillation has many components and a large volume, and requires a higher device investment. Installations wherein NMP is purified by distillation are disclosed in CN109336803A and CN111494977B. SUMMARY A main objective of the present invention is to propose an NMP batch distillation device and process, so as to solve problems of a complex structure of an existing NMP recovery device and a small recovered and purified amount of NMP. To solve the foregoing technical problems, technical solution 1 used in the present invention is as follows: An NMP batch distillation device is provided, including a batch distillation tower, a scraper falling-film evaporation reboiler, a reboiler pump, a tower top condenser, a tower top vacuum condenser, a raw material and intermediate product transfer pump, a water receiving tank, an intermediate product receiving tank, a product receiving tank, and a reflux controller. The top of the batch distillation tower is connected to the tower top condenser, one outlet of the tower top condenser is connected to the tower top vacuum condenser, and another outlet of the tower top condenser is connected to the reflux controller. One outlet of the reflux controller is connected to the batch distillation tower, and another outlet of the reflux controller is connected to the water receiving tank, the intermediate product receiving tank, and the product receiving tank. The raw material and intermediate product transfer pump is connected to the batch distillation tower, the intermediate product re