Method for recycling used batteries

Abstract

The invention relates to a method for recycling used batteries, in particular used lithium-ion storage batteries, comprising at least the following steps: - deep-freezing the used batteries in a deep-freezing step at temperatures of between -200 °C and -100 °C by supplying the used batteries with a liquid and / or gaseous fluid, in particular with liquid and / or gaseous nitrogen and / or CO2; - comminuting the used batteries in a deep-frozen state in a comminuting step; - vaporizing electrolyte liquid from the used batteries in a drying step; and - separating and sorting the parts of the comminuted used batteries into different classes in a separating step. The deep-freezing step takes place in a cooling vessel into which liquid and / or gaseous nitrogen is continuously supplied and from which gaseous nitrogen is continuously removed during the deep-freezing step.

Description

[0001] Processes for reprocessing used batteries

[0002] According to a first aspect, the present invention relates to a method for reprocessing waste batteries, in particular used lithium-ion batteries, wherein the method comprises at least the following steps:

[0003] Deep freezing of the used batteries in a deep-freezing step at temperatures between -200 °C and -100 °C with the addition of a liquid and / or gaseous fluid, in particular liquid and / or gaseous nitrogen and / or CO2, to the used batteries; shredding of the used batteries in a deep-frozen state in a shredding step; evaporation of the electrolyte fluid of the used batteries in a drying step and separation and sorting of the parts of the shredded used batteries into different classes in a separation step.

[0004] With the planned transition to so-called green technologies, in which electrical energy is increasingly intended to replace energy from fossil fuels, ever-increasing quantities of batteries, and especially lithium-ion batteries, are being produced. These batteries are used particularly in electromobility as energy storage for electric motors, but also as energy storage for renewable energy sources, so that more and more used batteries, especially lithium-ion batteries, are accumulating, which of course have to be disposed of.

[0005] This involves, on the one hand, the recovery of raw materials contained in used batteries, potentially to manufacture new batteries, but the safety aspect also plays a major role. To process and subsequently recycle the raw materials from used batteries, the batteries are first shredded, and the materials are then separated and classified accordingly. However, short circuits with a corresponding fire hazard can naturally occur during the shredding of used batteries, so precautions must be taken to prevent such short circuits.

[0006] It is known in the prior art to first subject the batteries to be recycled to a deep-freeze step in order to inertize them through the low temperatures and the resulting inhibition of ton mobility in the electrolyte. Afterwards, they are shredded, which is also easier at low temperatures due to the brittleness of the materials at these temperatures.

[0007] For the deep-freezing step, the prior art uses a bath of cryogenically liquefied nitrogen, which is kept in a cooling container and into which the used batteries to be processed are immersed to deep-freeze them. This procedure requires a large quantity of liquid nitrogen, and significant nitrogen losses result when the deep-frozen batteries are removed from the liquid nitrogen and the nitrogen subsequently evaporates from the used batteries, calling into question the economic viability of the recycling.

[0008] It is therefore an object of the present invention to provide a method and a device with which the reprocessing of used batteries is carried out more economically, particularly with regard to nitrogen consumption.

[0009] To solve this problem, a method of the type mentioned at the outset is characterized according to the invention in that the deep-freezing step takes place in a cooling vessel into which liquid and / or gaseous nitrogen is continuously supplied and from which gaseous nitrogen is continuously removed during the deep-freezing step. In the method according to the invention, no nitrogen bath is used; instead, cryogenic nitrogen in liquid and / or gaseous form is continuously introduced into a cooling vessel until the used batteries are sufficiently deep-frozen. This approach requires only a fraction of the amount of cryogenic nitrogen compared to the nitrogen bath known from the prior art, so that the method according to the invention is directly more economical than the prior art.

[0010] The present invention is described below with particular reference to the supply of nitrogen for deep-freezing used batteries; however, it is clear to those skilled in the art that other cryogenic fluids can also be used. CO2 is particularly suitable as a refrigerant. Within the scope of the present invention, however, other cryogenically liquefied gases can also be used.

[0011] The economic efficiency of the process according to the invention is significantly increased if the nitrogen continuously removed from the cooling vessel during the deep-freezing step is at least partially recycled into a nitrogen reservoir, from which at least a portion of the nitrogen continuously supplied to the cooling vessel during the deep-freezing step is extracted, as corresponds to a preferred embodiment of the present invention. According to this preferred embodiment, the nitrogen for the deep-freezing step is thus circulated between the cooling vessel and the nitrogen reservoir, so that, apart from unavoidable losses, essentially none of the nitrogen used for the deep-freezing step is lost.

[0012] The nitrogen container used in the present invention is only slightly pressurized relative to atmospheric pressure, so that the return of the gaseous nitrogen from the cooling container to the nitrogen container does not require any conveying means. However, the nitrogen is advantageously deep-frozen and optionally even liquefied by compression and expansion. The method according to the invention is therefore preferably further developed in that the nitrogen is compressed before being fed into the cooling container, with the heat of compression being transferred to a coolant. After the compression of the gaseous nitrogen and the removal of heat, the deep-freezing of the nitrogen can be carried out in a known manner by expansion of the nitrogen.

[0013] The heat of compression transferred to the coolant during the compression step can be advantageously used elsewhere in the process according to the invention. For example, a preferred embodiment of the present invention involves supplying the heat of compression to the drying step. The drying step serves, firstly, to evaporate residual nitrogen, but primarily to liquefy and evaporate the electrolyte liquid of the used batteries. For this purpose, the battery components of the shredded used batteries are heated, and in the process according to the invention, the waste heat from the nitrogen compression can be used for this purpose in a particularly economical manner.

[0014] To further support the evaporation of the electrolyte liquid in the drying step of the process according to the invention, it can be provided according to a preferred embodiment of the present invention that the drying step is carried out under vacuum.

[0015] Naturally, the aforementioned risk of short circuits in the inventive process for reprocessing used batteries is greatest during the battery shredding step. During shredding, the batteries are typically shredded, resulting in the complete destruction of their physical structure. This naturally creates numerous opportunities for short circuits between the loosely stacked battery components and the electrolyte fluid between them. Therefore, as mentioned earlier, the used batteries are shredded while in a deep-freeze state.To further reduce the risk of fires following short circuits, the inventive method, according to a preferred embodiment of the present invention, is characterized in that the comminution step is carried out in an inert atmosphere under nitrogen. Preferably, a comminution chamber for carrying out the comminution step is first evacuated and then filled with nitrogen. Comminuting the batteries in a nitrogen atmosphere serves to immediately extinguish any fires that may occur after short circuits, despite the deep freezing. A further increase in the efficiency of the inventive method can be achieved if the air extracted from the comminution chamber for evacuation is used as control air for a compressor to compress the nitrogen before it is fed into the cooling container.In this case, the nitrogen compressor is at least partially pneumatically operated, so that in the overall process a common pump must be used to evacuate the shredder chamber and to operate the compressor.

[0016] According to a preferred embodiment of the present invention, after the nitrogen has been compressed, the process for deep-freezing and optionally partially liquefying the nitrogen is carried out by directing the compressed nitrogen in gaseous form into a Laval nozzle that opens into the cooling vessel. The Laval nozzle is designed such that the nitrogen is at least partially liquefied during the transition from the convergent to the divergent section of the Laval nozzle. In the convergent compressor section of the Laval nozzle, the nitrogen gas undergoes gas-dynamic compression, and after passing through the throttle in the divergent evaporator section of the Laval nozzle, it expands to the relatively low pressure in the cooling vessel. This results in a dramatic drop in the temperature of the nitrogen, with concomitant liquefaction.In this way, the old batteries to be recycled can be effectively cooled to the desired temperatures of between -200 °C and -100 °C.

[0017] According to a further aspect, the present invention relates to a device for reprocessing used batteries, in particular for carrying out the method according to the invention and for achieving the advantages discussed in connection with the method. The device according to the invention has a cooling container for receiving used batteries, wherein the cooling container has a connection opening for a nozzle device and a nozzle device for continuously supplying liquid and / or gaseous nitrogen into the cooling container and for continuously removing gaseous nitrogen from the cooling container into the connection opening is inserted. According to the invention, the nozzle arrangement comprises an axially arranged Laval nozzle with a convergent compressor side and a divergent expander side, and at least one return flow channel leading from the expander side to the compressor side is arranged next to the Laval nozzle.The nozzle arrangement of the device according to the invention, with its at least one return flow channel, allows liquid and / or gaseous nitrogen to be continuously and extremely cold supplied to the cooling container during the deep-freezing step of the process according to the invention, while gaseous nitrogen is simultaneously continuously removed. In this way, as already discussed in connection with the process according to the invention, the need for a nitrogen bath for the complete immersion of the used batteries can be dispensed with.

[0018] The area of ​​the Laval nozzle and the area of ​​the at least one return flow channel naturally exhibit a large temperature difference during the execution of the method according to the invention. The present invention is therefore further developed according to a preferred embodiment in such a way that the Laval nozzle and the at least one return flow channel are separated from each other by an insulating layer, preferably a Teflon layer. In this way, the very low temperatures in the area of ​​the expander are prevented from reaching the at least one return flow channel, so that icing of the at least one return flow channel can be avoided as far as possible.In the context of the present invention, an insulating material is understood to be a layer of a material having a thermal conductivity that is at most 10%, preferably at most 5% and particularly preferably at most 1.5% of the thermal conductivity of the material or materials for the Laval nozzle and the at least one return flow channel.

[0019] Preferably, the at least one return flow channel has a larger diameter on the expander side than on the compressor side. The smaller diameter on the compressor side serves to limit the return flow of nitrogen from the cooling tank to a suitable level, while the larger diameter on the expander side serves to prevent icing of the at least one return flow channel.

[0020] According to a preferred embodiment of the present invention, the nozzle device has several axially extending return flow channels, the return flow channels preferably being arranged in an annular shape radially outside the Laval nozzle. This serves to ensure that, even with a relatively large volume of nitrogen returning through the return flow channels into the nitrogen reservoir, the pressure in the cooling vessel necessary for effective cooling can be achieved due to the relatively small diameters of the return flow channels, particularly on the compressor side. The preferred arrangement of the return flow channels in an annular shape radially outside the Laval nozzle is advantageous because, in this case, the nozzle device can be inserted into a relatively simple bore or circular recess in the cooling vessel.For this purpose, the return flow channels are preferably formed in a first sleeve into which the Laval nozzle immerses, thereby achieving a very compact design of the nozzle device for the inventive device for reprocessing used batteries.

[0021] From a structural point of view, the nozzle assembly of the device according to the invention is preferably formed by the first sleeve consisting of a first sleeve part on the expander side and a second sleeve part on the compressor side, wherein the first sleeve part and the second sleeve part are preferably screwed together. In this way, it is also particularly easy to form the at least one return flow channel, and in particular the return flow channels on the compressor side and the expander side, with different diameters, since in this case the first and the second sleeve part are simply provided with bores of different diameters.

[0022] Due to the problem of large temperature differences between the Laval nozzle and the area of ​​the nozzle device's bores, as discussed above, a preferred embodiment of the present invention provides that the first sleeve and the Laval nozzle are separated from each other by a second sleeve made of an insulating material, preferably Teflon, arranged radially between them. For the purposes of this invention, an insulating material is understood to be a layer of a material having a thermal conductivity that is at most 10%, preferably at most 5%, and particularly preferably at most 1.5% of the thermal conductivity of the material(s) used for the Laval nozzle and the at least one return flow channel. The invention is explained in more detail below with reference to an exemplary embodiment illustrated in the drawing.In this work, Figure 1 shows a perspective view of the nozzle device of the device according to the invention from the evaporator side, Figure 2 shows a sectional view of the nozzle device and Figure 3 shows a perspective view of the nozzle device from the compressor side.

[0023] In Figure 1, the nozzle assembly of the device according to the invention is designated by reference numeral 1. The nozzle assembly 1 essentially consists of a Laval nozzle 2, of which only the expander side 2a is visible in Figure 1, and of a plurality of return channels 3 that surround the Laval nozzle 2 radially outside the circle. The return channels 3 are formed in a first sleeve 4, which consists of a first sleeve part 4a on the expander side and a second sleeve part 4b on the compressor side. The return channels 3 completely pass through the sleeve parts 4a and 4b and open into a ring line 5 with a corresponding outlet 6. The nozzle assembly 1 can be inserted into a bore or recess of a cooling tank (not shown in the figures), and cryogenic nitrogen can be supplied to the cooling tank via the Laval nozzle 2.As a result, an equilibrium is established between the nitrogen f supplied through the Laval nozzle 2 or 2a and the nitrogen f discharged via the return channels 3, so that the nitrogen f, after being collected in the ring line 5, can be returned to the nitrogen f tank via the outlet 6.

[0024] In the following figures, identical parts are designated with the same reference numerals. Figure 2 shows that the Laval nozzle 2 extends through the entire nozzle assembly 1 and, in particular, comprises an expander section or expander side 2a and a compressor section or compressor side 2b. The sleeve 4 consists of the first and second sleeve sections 4a and 4b, and it is evident that the return channels 3 extend completely through these sleeve sections 4a and 4b. The return channels 3 have a larger diameter on the expander side or in sleeve section 4a than on the compressor side or in sleeve section 4b. The sleeve sections 4a and 4b and the Laval nozzle 2 are separated from each other by a second sleeve 7 or insulating sleeve 7 made of Teflon, arranged radially between them.The bores for receiving screws 8 are sealed with plugs 9 made of Teflon or another insulating material to prevent icing and to increase the insulating effect of the second sleeve 7. A connecting pipe for supplying compressed, gaseous nitrogen is designated by reference numeral 10 and is pressure-tightly connected to the compressor side 2b of the Laval nozzle 2 by means of a thread 11.

[0025] Figure 3 shows the compressor side of the nozzle assembly 1, and it can be seen that the return channels 3 open into the ring line 5, which in turn leads into the outlet 6. The entire nozzle assembly 1 can be inserted into a bore or recess adapted to the circumference of the sleeves 4a and, if applicable, 4b in a cooling container for the used batteries to be recycled, in order to supply nitrogen via the connecting pipe 10 and discharge it via the return channels 3 or the ring line 5 and the outlet 6.

Claims

Patent claims 1. Method for reprocessing waste batteries, in particular used lithium-ion batteries, comprising at least the following steps: Deep freezing of the used batteries in a deep-freeze step at temperatures between -200 °C and -100 °C with the addition of a liquid and / or gaseous fluid, in particular liquid and / or gaseous nitrogen and / or CO2, to the used batteries. Shredding of used batteries in a deep-frozen state in a single shredding step Evaporation of electrolyte liquid from waste batteries in a drying step and separation and sorting of the parts of the shredded waste batteries into different classes in a separation step, characterized in that the deep-freezing step takes place in a cooling container into which liquid and / or gaseous nitrogen is continuously supplied and from which gaseous nitrogen is continuously removed during the deep-freezing step.

2. Method according to claim 1, characterized in that the nitrogen continuously removed from the cooling container during the deep-freezing step is at least partially returned to a nitrogen container from which at least a part of the nitrogen continuously supplied to the cooling container during the deep-freezing step is taken.

3. Method according to claim 1 or 2, characterized in that the nitrogen is pre-treated before being introduced into the cooling container. is compressed, whereby the heat of compression is transferred to a coolant.

4. Method according to claim 3, characterized in that the heat of compression is supplied to the drying step.

5. Method according to one of claims 1 to 4, characterized in that the drying step is carried out under vacuum.

6. Method according to one of claims 1 to 5, characterized in that the comminution step is carried out in an inert environment under nitrogen, wherein preferably a comminution chamber for carrying out the comminution step is first evacuated and then filled with nitrogen.

7. Method according to claim 6, characterized in that the air extracted for evacuation from the comminution chamber is used as control air for a compressor to compress the nitrogen before feeding it into the cooling container.

8. Method according to one of claims 3 to 7, characterized in that the compressed nitrogen is directed in gaseous form into a Laval nozzle which opens into the cooling vessel, wherein the Laval nozzle is designed such that the nitrogen is at least partially liquefied during the transition from the convergent to the divergent part of the Laval nozzle.

9. Device for reprocessing used batteries, in particular for carrying out the method according to one of claims 1 to 8, with a cooling container for receiving Used batteries, wherein the cooling container has a connection opening for a nozzle device (1) and a nozzle device (1) is inserted for the continuous supply of liquid and / or gaseous nitrogen into the cooling container and for the continuous discharge of gaseous nitrogen from the cooling container into the connection opening, wherein the nozzle arrangement (1) comprises an axially arranged Laval nozzle (2) with a convergent compressor side (2b) and a divergent expander side (2a) and at least one return flow channel (3) leading from the expander side (2a) to the compressor side (2b) is arranged next to the Laval nozzle (2).

10. Device according to claim 9, characterized in that the Laval nozzle (2) and the at least one return flow channel (3) are separated from each other by an insulating layer, preferably a Teflon layer.

11. Device according to claim 9 or 10, characterized in that the at least one return flow channel (3) has a larger diameter on the expander side than on the compressor side.

12. Device according to claim 9, 10 or 11, characterized in that the nozzle device (1) has several axially extending return flow channels (3), wherein the return flow channels (3) are preferably arranged in an annular shape radially outside the Laval nozzle (2).

13. Device according to one of claims 9 to 12, characterized in that the return flow channels (3) are formed in a first sleeve (4) into which the Laval nozzle (2) is immersed.

14. Device according to claim 13, characterized in that the first sleeve (4) consists of an expander-side first sleeve part (4a) and a compressor-side second sleeve part (4b), wherein the first sleeve part (4a) and the second sleeve part (4b) are preferably screwed together.

15. Device according to claim 13 or 14, characterized in that the first sleeve (4) and the Laval nozzle (2) are separated from each other by a second sleeve (7) arranged radially between them, made of an insulating material, preferably Teflon.

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