WO1994025167A1

WO1994025167A1 - Method and installation for processing batteries

Info

Publication number: WO1994025167A1
Application number: PCT/NL1994/000092
Authority: WO
Inventors: Bernhard Albertus Kamphuis
Original assignee: Leto Recycling BV
Current assignee: Leto Recycling BV
Priority date: 1993-04-28
Filing date: 1994-04-28
Publication date: 1994-11-10
Anticipated expiration: 1995-10-28
Also published as: NL9300725A

Abstract

Said batteries may be provided with a plastic casing. In order to separate the plastic casing from the batteries it is proposed, according to theinvention, that said batteries, including casing, are first cooled and are then subjected to a controlled impact treatment. As a result of the cooling the plastic casing becomes brittle, and as a result of the impact treatment the battery comes away from the plastic casing. The batteries and the plastic parts are then subject to a separation treatment and the liberated batteries are ground and subjected to a treatment.

Description

Method and installation for processing batteries

The present invention relates to a method according to the pre¬ amble of Claim 1. λ method for separating batteries is disclosed in the "Status of the World's First Commercial Battery Process for Unsorted Household Bat¬ teries" presented at "The Third International Seminar on Battery Waste Management" on 6 November 1991 in the "Ocean Resort Hotel and Conference Center" in Deerfield Beach, Florida, USA. This publication points to the problem of removal of the plastic casing from batteries before the latter are subjected to a wet chemical treatment. This applies particularly to batteries which are very environ¬ mentally unfriendly, such as nickel/cadmium batteries. In the publication concerned it is proposed first to heat the batteries, as a result of which some of the plastic vaporises and burns and an ashy residue is left behind. However, it is necessary to heat the batteries to at least 600°C, which involves the use of an appreciable amount of energy and can cause explosions. Moreover, it is not possible to remove the ashy residues and these are therefore carried along with the batteries and will contaminate the downstream chemical baths. Furthermore, it is desirable to grind the batteries at as low a temperature as possible, with the result that the batteries need to be cooled, which requires further energy. Moreover, the materials formed from the plastic on combustion and vaporisation can not be re-used and can be harmful to the environment. The method described above is disclosed in Swiss Patent 681,401.

In this method batteries having a casing are subjected to appreciable impact energy for comminution. Both the plastic casing and the battery are crushed as a result. The various operations are found to proceed in an optimum manner at relatively low temperatures. With this procedure a mixture of plastic chips and pulverised battery material is produced.

The plastic must be separated from the battery material in a step following comminution. Because the battery material is present in powder form, a separation treatment of this type is relatively complex and the plastic fraction obtained will always be contaminated to some extent. Consequently, it is not easily possible to re-use this plastic and it is necessary to subject it to highly complex treatments before it can be disposed of. The aim of the present invention is so to improve the method described above that a plastic product is obtained which can be employed for re-use straight away.

This aim is achieved with a method described above which has the characteristics of Claim 1.

Surprisingly, it has been found that if the cooling temperature selected is sufficiently low and the impact energy is within specific limits, the plastic casings do detach from the battery shell in a guaranteed manner but the battery shell itself is not so damaged that the battery parts are crushed into pieces. That is to say, following separation as proposed according to the invention, plastic parts and battery parts are produced, no granular battery material being present. The batteries con¬ tinue to exist as (damaged) items. With this procedure it is essential that the battery ("pack") is subjected to this impact energy once only. It has been found that if the battery is subjected to an undefined number of impacts either the battery contents are released or no disintegration at all takes place. Consequently it is impossible to remove plastic casing from batteries with the aid of cutter mills, hammer mills and ball mills. With these constructions the batteries will always be subjected to the impact energy an undefinied number of times.

Taking the above situation as the starting point, it is particularly simple to separate batteries and plastic using, for example, magnetic means. The plastic obtained in this way can be further processed immediately. The (deformed) batteries thus obtained can then be subjected to a comminution treatment which is the first such treatment for the bat¬ teries themselves.

According to an advantageous embodiment of the invention, cool¬ ing is carried out down to at least -100 ^CC. Both the cooling temperature and the duration of cooling depend on the type of battery, the casing and the plastic used for the casing. It has been found that grinding and similar treatments are not suitable for the removal of the plastic casing because with these treatments breakage of the battery takes place, with all of the consequences described above. For this reason it is proposed accord¬ ing to the invention that the impact treatment comprises accelerating the battery with subsequent impingement against a stationary part. Said accel¬ eration can optionally be carried out in two directions. That is to say initially acceleration takes place in, for example, the vertical direction, after which acceleration in the horizontal direction takes place because the battery meets, for example, a rotating object. The battery is then decelerated against a stationary wall and can then drop down again. In this way the battery is subjected to an impact treatment on all sides, so that it is guaranteed that the plastic casing will break at a sufficient number of locations so that the battery simply drops out of the casing. The oper¬ ation described above replaces simply letting the battery drop from the height described above, which is between 5 and 20 metres. Using the method described above, a large number of batteries can simultaneously be sub¬ jected to an impact treatment. With this method the tangential speed of the batteries is between 15 and 35 m/s and more particularly between 20 and 30 m/s. If the radial speed which a battery acquires as a result of the rotary device described above is added thereto, the impact energy supplied is between 100 and 600 J/kg.

It has been found that at these values the damage which occurs to the battery is not such that material detaches therefrom.

After the battery has been detached from the plastic casing, the mixture of pieces of plastic casing and batteries is subjected to a treat¬ ment for separation of plastic and batteries. If the batteries contain ferromagnetic components, such a separation can be carried out in a par- ticularly simple manner using magnetic means.

To optimise the grinding of the batteries, which have now been separated off, an additional cooling step is employed according to a further advantageous embodiment. Because the batteries are at a relatively low temperature following the first cooling step, it takes comparatively little energy to cool the batteries again so that they become more brittle and the metal shell will break easily.

The invention also relates to an installation according to Claim 7.

As indicated above, the cooling means comprise a bath of liquid nitrogen, but it is readily conceivable to use any other coolant, depending on the various process parameters. The impact means preferably comprise a rotating rotor provided with scoops which are located in the vicinity of the periphery and extend to some distance away from the centre of the rotor, the batteries being fed to the centre of the rotating rotor by dropping. On impinging on the rotating rotor, the batteries, with the casings, are subjected to an initial impact, whilst during acceleration in the radial direction they will impinge on a wall installed around the rotary device and undergo a second impact at a different point on the casing, which second impact produces the effect according to the invention. By this means it is ensured that the plastic casing breaks at various points, as a result of which detachment of the batteries can be achieved in a particularly simple manner. The separating means preferably comprise conveyor means provided with magnetic means.

The invention will be explained in more detail below with refer¬ ence to an illustrative embodiment shown in the drawing. In the drawing:

Fig. 1 shows, in partial cross-section, an example of a battery to be treated using the method and installation according to the invention; Fig. 2 shows, diagrammatically, the installation according to the invention; and

Fig. 3 shows in more detail the impact device shown in Fig. 2. In Fig. 1, 1 indicates a battery. Said battery comprises a num¬ ber of nickel/cadmium cells, indicated by 2, which are stacked in series. Said cells are held together by a plastic casing.

For disposal of batteries of this type it is important to remove the plastic casing 3 from the stack of cells 2, especially if the batteries are to be processed by a wet chemical route. The reason for this is that, in a chemical treatment of this type, the plastic material will constitute waste which contaminates the various baths and interferes in the processes taking place.

Fig, 2 shows the installation according to the invention for separating such a plastic casing from the cells 2. Said installation is indicated in its entirety by 4. As shown diagrammatically, upstream of this installation the batteries packed as chemical waste are supplied and sorted into batteries which give problems, i.e. batteries which have to be sub¬ jected to further chemical treatment and from which the plastic casing has to be removed. Batteries of this type and/or cells which have to be sub¬ jected to a further treatment are placed on a feed conveyor 5 and moved over separating sieve 6. Separating sieve 6 is constructed in such a way that cells which do not have a casing fall through and can be removed via the discharge conveyors 7 and 8. The larger battery packs encased in plas¬ tic are not able to fall through the sieve and are fed to cooling bath 10 with the aid of feed conveyor 9. Said cooling bath 10 is filled with liquid nitrogen and provided with a cover 11 to recover the evaporating nitrogen as far as possible and to restrict evaporation as far as possible. A feed conveyor 27 is present within said cover. By adjusting the speed at which said feed conveyor moves and the length of the liquid bath 10, it is pos- sible to determine the residence time of the batteries in the bath and, thus, the cooling. The batteries pass from conveyor 27 into drop towers 12. The latter comprise an inlet or constriction 13 at which the batteries are subjected to an initial impact. The batteries then impinge on the rotor 26 of impact device 14. The batteries are propelled outwards by the rotor 26 and impinge on the wall 15 of the impact tower and then drop down onto discharge conveyor 16. To this end there is sufficient space available between the rotor and the wall to prevent the batteries coming back onto the rotor. It has been found that, as a result of said impact treatments, on the one hand the batteries do not themselves burst open but, on the other hand, the plastic casing, which has become brittle as a result of subjection to a low temperature, does break open and separates from the batteries. With the aid of conveyor 16, the batteries, together with the plastic which has become detached, are transferred to sorting conveyor 28, above which a magnetic belt 17 moves. Said magnetic belt 17 attracts the batteries, but has no effect on the plastic, which falls into plastic col¬ lector 18 at the end of sorting conveyor 28. Parts adhering to magnetic belt 17 are separated therefrom and fall onto conveyor 19 for subsequent removal to conveyor 8. Said conveyor 8 issues into a further nitrogen bath 21, which likewise contains liquid nitrogen. Said bath is enclosed within a cover 22. Gas originating from nitrogen which vaporises in liquid bath 10 is fed via pipe 20 to the interior of cover 22. The liquid bath contains a feed conveyor 23. The batteries from which the plastic has been removed and the batteries which had no plastic at all are fed through this bath to further cool and embrittle them, so that the grinding treatment which takes place with the aid of hammer 24 can be carried out more effectively. The mixture of battery shell and battery contents is then fed via discharge 25 to a wet chemical treatment process, which is not shown in more detail and with respect to which reference is made to Dutch Patent Application 9001825 or the abovementioned publication "Status of the World's First Commercial Battery Process for Unsorted Household Batteries" dated 6.11.1991.

Fig. 3 shows the impact device according to the invention in more detail. Said device comprises a motor 29 to which a rotor 26, provided with scoops 30, is fitted. The batteries which fall into the centre of the rotating rotor will be propelled outwards, the scoops 30 generating an additional steering movement and the batteries being propelled against the wall 15 of the drop tower.

The method described above is particularly suitable for nickel/cadmium batteries, but it will be understood that any type of bat¬ tery provided with a plastic or rubbery casing or other material that becomes brittle at low temperature can be used. If the battery contains no ferromagnetic material, the separation of plastic and the remainder of the battery will be carried out using separation means other than the magnetic belt 17 shown here. For example, separation on the basis of weight is poss¬ ible. In the illustrative embodiment shown here liquid nitrogen is used as coolant. Firstly, it is possible to achieve cooling in another way, whilst, moreover, a different coolant can be used. Tests have shown that the speed of rotation of the rotor is important for effective separation of battery and plastic casing. Should too high a speed be used there is a risk that the batteries will shatter, whereas at too low a speed there is inadequate breakage of the plastic material. In the case of conventional nickel/cadmium cells combined with a plastic casing, it has been found that, using the impact device which has been described above, a speed of 580 revolutions per minute was not sufficient to achieve breakage of the casing. At a speed of 725 per minute there was a further improvement. Op¬ timum results were obtained at 870 revolutions per minute. At this speed, on the one hand, the battery came away completely from the plastic casing and, on the other hand, the batteries were not broken open, so that no dust and the like was produced which is difficult to remove with the separation device described above. The impact energy supplied to the batteries was preferably between 100 J/kg and 600 J/kg.

Although the invention has been described above with reference to a preferred embodiment, it must be understood that numerous modifica¬ tions can be made thereto without going beyond the scope of the subject application.

Claims

CLAIMS 1. Method for processing batteries, in particular nickel/cadmium batteries, which batteries are provided with a plastic casing, comprising subjecting of the batteries under reduced temperature conditions to a comminution step by means of an impact treatment, characterised in that

- the comminution step comprises causing the batteries to impinge once against a hard object, such as a wall, with an energy which corresponds to the energy produced by said batteries falling over a height of 5 - 20 metres; - following the comminution step, plastic and batteries which are separate from one another are subjected to a separation step, such as a magnetic separation step, and

- the batteries separated off are then subjected to a comminution treatment which is the first such treatment for the batteries themselves.

2. Method according to Claim 1, wherein cooling is carried out down to at least -100 °C.

3. Method according to one of the preceding claims, wherein the impact energy is between 100 J/kg and 600 J/kg.

4. Method according to one of the preceding claims, wherein the impact treatment comprises acceleration in one direction, impingement of the batteries against a part which is stationary in said direction and is moving in a direction essentially perpendicular thereto, as a result of which the battery undergoes an acceleration essentially perpendicular to the acceleration in the first direction and impingement of the battery against a stationary surface.

5. Method according to one of the preceding claims, wherein, following removal of the plastic and prior to grinding of the batteries, the latter are subjected to a further cooling step.

6. Installation (4) for separating plastic battery casings (3) from said batteries (1), comprising cooling means (10), to which the bat¬ teries are fed, impact means (14) and separation means (17), characterised in that

- the impact means are set up to supply an amount of energy of between 100 J/kg and 600 J/kg to the encased batteries, said separation means com- prising magnetic separation means, and

- comminution means, to which the magnetic fraction separated off by the magnetic separation means are subjected, are installed downstream of the separation means.

7. Installation according to Claim 6, wherein the cooling means comprise a bath (10) of liquid nitrogen.

8. Installation according to Claim 6 or 7, wherein the impact means comprise a feed installed at an elevated height and a discharge located below at a substantially lower height.

9. Installation according to Claim 8, wherein means (14) for acceleration of the falling batteries in the horizontal direction are located between the two heights, which means are surrounded by a wall (15).

10. Installation according to Claim 8, wherein said means for imparting a horizontal acceleration comprise a rotor installed so that it rotates in the horizontal plane.

11. Installation according to Claim 10, wherein the rotor is provided with scoops (30).

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