FACILITY AND METHOD FOR PURIFYING RECOVERED NMP

Abstract

The present invention relates to a facility for purifying recovered NMP from lithium-ion battery production, comprising a first column for separating low-boiling impurities, comprising a supply, in its central part, for the recovered NMP, and which can be heated by means of a first evaporator for supplying thermal energy; and a second column for separating high-boiling impurities, a connection line from a lower part of the first column to a lower part of the second column being provided. In this case, according to the invention, the second column can be heated by means of a second evaporator comprising an inlet and an outlet for purified NMP, and the second column is assigned a compressor portion which extends from a head of the second column to the inlet of the second evaporator and comprises a mechanical vapor compressor for inputting energy to the vapor of the second column. The present invention furthermore relates to a method for operating a facility of this kind.

Claims

1. Facility for purifying recovered NMP from lithium-ion battery production, the facility comprising: a first column for separating low-boiling impurities, comprising a supply, in its central part, for the recovered NMP, and which can be heated by means of a first evaporator for supplying thermal energy; and a second column for separating high-boiling impurities, a connection line from a lower part of the first column to a lower part of the second column being provided; wherein the second column can be heated by means of a second evaporator comprising an inlet and an outlet for purified NMP, and the second column is assigned a compressor portion which extends from a head of the second column to the inlet of the second evaporator and comprises a mechanical vapor compressor for inputting energy to the vapor of the second column.

2. Facility according to claim 1, wherein a heat exchanger, is connected upstream of the supply of the first column, which heat exchanger is also coupled to the outlet of the second evaporator.

3. Facility according to claim 1, further comprising a condenser for condensing the low-boiling impurities, which condenser is coupled to the head of the first column.

4. Facility according to claim 3, wherein the condenser is assigned a vacuum pump which is designed for maintaining a reduced pressure in the facility.

5. Facility according to claim 1, wherein the first and/or the second evaporator is/are designed as a downflow evaporator or a circulation evaporator.

6. Facility according to claim 1, wherein a vapor recovery line is provided between the lower part of the first column and the lower part of the second column, and a vent line comprising a control valve is provided between the second evaporator and a central portion of the first column.

7. Facility according to claim 1, wherein the first column comprises a cup outlet, from which a connection line extends to the lower part of the second column.

8. Facility according to claim 7, further comprising a fluid return which is designed to input high-boiling impurities, removed from a bottom of the second column, into a lower part of the first column, at least in part.

9. Facility according to claim 8, further comprising a discharge line for conducting high-boiling impurities out of the lower part of the first column to a removal line.

10. Method for purifying recovered NMP from lithium-ion battery production, by means of a facility according to claim 1, comprising the steps of: inputting the recovered NMP into the central part of the first column; heating the first column by means of the first evaporator by supplying thermal energy; removing low-boiling impurities at the head of the first column; transferring pre-purified NMP from the lower part of the first column or the cup outlet into the lower part of the second column; vaporizing the pre-purified NMP in the second evaporator and conducting it through the second column; removing the vaporous NMP at the head of the second column and compressing it in the compressor portion by means of the mechanical vapor compressor; inputting the compressed NMP into the inlet of the second evaporator, wherein the NMP condenses in the second evaporator; removing the condensed NMP at the outlet of the second evaporator; and removing high-boiling impurities out of the bottom of the second column.

11. Method according to claim 10, wherein a reduced pressure, is maintained in the first and the second column.

12. Method according to claim 10, wherein the supply of thermal energy to the first evaporator takes place by means of steam or a heat transfer fluid.

13. Method according to claim 10, wherein a portion of the condensed NMP from the second evaporator is returned, as a return flow, into the second column.

14. Method according to claim 10, wherein the low-boiling impurities removed at the head of the first column can furthermore be condensed in the condenser and returned, at least in part, into the first column as a return flow.

15. Method according to claim 10, wherein the recovered NMP contains less than 5% low-boiling impurities; and/or wherein, in the first column, the low-boiling impurities in the pre-purified NMP can be depleted to less than 0.1%.

16. Method according to claim 10, wherein the high-boiling impurities removed from the bottom of the second column are input into a lower part of the first column, at least in part.

17. Method according to claim 16, wherein the concentration of the high-boiling impurities in the bottom of the second column during operation of the facility, based on the initial concentration in the recovered NMP, is approximately 1-5, and the concentration of the high-boiling impurities in the lower part of the first column is increased relative to this value and is in the range of greater than 1 to approximately 100.

Description

[0041] Further features and advantages of the present embodiment will become clearer from the following description of an embodiment, when viewed together with the accompanying drawings, in which, in detail:

[0042] FIG. 1 is a schematic view of a facility according to the invention for purifying recovered NMP; and

[0043] FIG. 2 is a schematic view of a further variant of a facility according to the invention.

[0044] In FIG. 1, the facility according to the invention for purifying recovered NMP is denoted very generally by reference sign 10. In this case, firstly, at point 12, recovered NMP from lithium-ion battery production is input into the facility, which typically contains less than 5% low-boiling impurities, in particular water, and, additionally, high-boiling impurities, such as remaining electrode material.

[0045] In the facility 10, the NMP input into the facility firstly passes through a heat exchanger 14, in which it is pre-heated, before it is input, at point 16a, into the central part of a first column 16. In this case, the first column 16 is assigned a first evaporator 18 which can be supplied, from point 20, with steam or heat transfer fluid, for operation, by means of a circuit 22 which is driven by a pump 22a. Due to the supply of thermal energy into the first column 16 by means of the first evaporator 18, the low-boiling impurities of the supplied NMP to be recovered vaporize there, and can be removed at the head region 16b in the first column and supplied to a condenser 24 in which condensation of the low-boiling impurities is achieved by means of water cooling 26. Said condensed impurities can subsequently be collected in a tank 28 and removed from the facility, as a waste product, at point 30 by means of a pump 28a, and be returned in part into the first column 16 as a return flow, via a return line 32.

[0046] In contrast, on the lower part 16c of the first column a circulation loop 34 having a pump 34a for supplying pre-purified NMP, removed there, to the first evaporator 18 is provided, and in addition a connection line 36 is provided, via which the pre-purified NMP can be transferred from the lower part 16c of the first column 16 into the lower part 38c of a second column 38. The second column 38 can be operated in such a way as to separate the already pre-purified NMP from high-boiling impurities, in that the NMP itself vaporizes and is removed in the head region 38b of said second column 38.

[0047] For this purpose, said second column 38 is assigned a second evaporator 40 which is supplied, by means of a circuit 42a driven by a pump 42a, with bottom product that is removed from the lower part 38c of the second column 38 and has a concentration of high-boiling impurities, while in addition the vapor removed in the head region 38b of the second column 38, i.e. vaporized purified NMP, is supplied for heating the second evaporator 40. Said vapor was compressed, in the meantime, by means of a mechanical vapor compressor 46, in a compressor portion 44 extending from the head region 38b of the second column 38 to the corresponding inlet 40a of the second evaporator 40, and thus its energy content and condensation temperature were increased, as a result of which the energy required for the operation of the second column 38 is input in this way.

[0048] When passing through the second evaporator 40, which can be designed for example as a downflow evaporator or circulation evaporator, which furthermore also applies for the first evaporator 18, the purified NMP condenses and can subsequently be transferred from an outlet 40b of the second evaporator 40 into a tank 48. From there, it can subsequently be returned into the second column 38, as a return flow, by means of a pump 48a via a return line 50, and also removed from the facility 10 as an end product via an outlet line 52.

[0049] Subsequently, upon passing through the heat exchanger 14, already discussed above, the purified and condensed NMP can subsequently emit further heat to the NMP that is to be recovered and is newly supplied at point 12.

[0050] In the facility 10 according to the invention, according to the invention the use of the mechanical vapor compressor 46 for heating the second evaporator 40 achieves a significant energy saving during operation, for the sake of completeness reference finally being made again to the removal line 54, by means of which the high-boiling impurities can also be removed from the facility 10, as a waste product, from the lower part 38c of the second column 38, which impurities, as discussed above, are in part circulated into the second evaporator 40 as a return flow.

[0051] In contrast, FIG. 2 shows a further variant of a facility according to the invention, which differs from the embodiment shown in FIG. 1 with respect to a few advantageous structural features, which will be discussed in the following, while a repeated description of identical components will be omitted.

[0052] Firstly, in this variant the first column 16 comprises a cup outlet 36b, from which a connection line 36a extends to the lower part 38c of the second column 38. In this variant, this arrangement replaces the simple connection line 36 according to the first embodiment and also extends, within the meaning of the present invention, from the lower part 16c of the first column 16 to the lower part 38c of the second column 38.

[0053] Furthermore, a fluid return 42b is provided, which is designed to input high-boiling impurities, removed from the bottom 38c of the second column 38, into the lower part 16c of the first column 16, at least in part. Since, according thereto, in this variant concentration of the high-boiling impurities occurs in the lower part 16c of the first column 16, a discharge line 62 is furthermore provided, which makes it possible to conduct high-boiling impurities out of the lower part 16c of the first column 16 to the removal line 54.

[0054] Furthermore, in the variant shown in FIG. 2, a connection between the lower part 16c of the first column 16 and the lower part 38c of the second column 38 is created by a vapor recovery line 56, and at the same time a vent line comprising a control valve 58 is provided between an upper part of the second evaporator 40 and a central portion of the first column 16.

[0055] Finally, reference is also made to the vacuum pump 60, which is assigned to the condenser 24 and accordingly allows for generation and setting of a reduced pressure in the facility at the point of the facility 10 according to FIG. 2 at which a minimum pressure prevails.