" PLANT FOR THE RECOVERY OF SPENT ELECTRIC BATTERIES"

DESCRIPTION

The present invention relates to a plant for the recovery of spent electric batteries. More particularly, but not exclusively, the present invention refers to a plant for the recovery of so-called lead-acid batteries.

The lead-acid battery is a battery of electrochemical energy accumulators through which the produced current flows in a direction and then in the opposite direction thereof, depending on the reduction-oxidation reactions that occur one after another. A lead-acid battery 10 is represented in Figure 11. The accumulators comprise a positive pole 30 and a negative pole 40 consisting in grids made of lead alloys (for instance, lead- antinomy alloy) coated with a fine lead oxide-based paste (or active material), immersed in an electrolyte consisting in a solution containing sulphuric acid and kept apart one from another by separators 60 made of an insulating material, namely a high molecular weight plastic material (for instance PET , PVC). Said accumulators are housed inside an external casing 20 made of a low molecular weight plastic material, generally polypropylene. Lead-acid batteries are largely widespread in automotive field and they are employed as starting batteries as well as traction batteries in electric motor vehicles; they can also be employed in steady plants, for instance as emergency power supply. The lead-acid battery life varies depending on the field of application and on the conditions of use and it can be estimated around 4 - 6 years. Once the charge is worn-out, the lead- acid battery represents a dangerous waste, since it contains therein toxic substances, namely lead and its compounds as well as sulphuric acid.

For the foregoing reason, plants for the recovery of spent lead-acid batteries have been developed. In these plants, the spent batteries are crushed and the various components of said batteries (grids and poles, paste, polypropylene, separators, electrolyte) are separated, cleansed and recovered.

According to prior art, the crushing, separating, cleansing and recovery operations take place in stationary plants installed in suitable sites. Thus, spent batteries are amassed in suitable stocking sites and periodically drawn therefrom and transported by lorries or similar means of transport to the recovery plants.

It is evident that such a recovery system involves important drawbacks concerning safety, since it implies the transportation of large amounts of highly toxic wastes, even over long distances. It is the main object of the present invention to overcome said drawback, providing a plant

for the recovery of spent electric batteries that allows to keep off from transportation over long distances.

It is another object of the present invention to provide a plant for the recovery of spent electric batteries that allows the recovering of the most components as possible of said batteries.

It is a further object of the present invention to provide a plant for the recovery of spent electric batteries that is compact and inexpensive.

These and other objects are achieved with a plant for the recovery of spent electric batteries as claimed in the appended claims.

Thanks to the fact that the recovery plant according to the invention comprises a mobile unit carrying the spent batteries crushing and separating apparatuses, the transportation of said batteries over long distances is no longer necessary; on the contrary, said mobile unit can be driven to the spent batteries stocking site, so that the recovery of the spent batteries can be carried out 'm loco\

Thanks to the fact that the recovery plant according to the invention comprises a second mobile unit carrying the apparatus for loading the batteries tp the crushing apparatus, said plant can be employed in any stocking site, without the need for special facilities. Advantageously, according to a preferred embodiment of the invention, a third mobile unit is provided for the transportation of the power-supply and control devices, so that the plant turns out to be completely autonomous and self-sufficient.

With similar advantage, according to another embodiment of the invention, said second mobile unit carrying the batteries loading apparatus also carries the power-supply and control devices of the plant, which turns out to be completely autonomous and self- sufficient.

Moreover, it is evident that the recovery plant according to the invention has a very limited overall size, substantially equal to the area covered by the aforesaid mobile units (i.e. by one or two semi-trailers); thus, there is no need for large areas or specific structures and the plant can be operated in any stocking site, independently from the present facilities. The above and other advantages of the invention will become more evident from the detailed description of some preferred embodiments of the invention, given hereinafter by way of non-limiting example, with reference to the attached drawings, wherein:

- Figure 1 is a plan view of the plant according to a first embodiment of the invention;

- Figure 2 is a cross-section along line H-II of the plant of Figure 1 ;

- Figure 3 is a cross-section along line III-III of the plant of Figure 1 ;

- Figure 4 is a cross-section along line IV-IV of the plant of Figure 1 ;

- Figure 5 is a cross-section along line V-V of the plant of Figure 1;

- Figure 6 is a cross-section along line VI-VI of the plant of Figure I ;

- Figure 7 is a cross-section along line IH-III of the plant of Figure 1, according to a constructional variant of the invention;

- Figure 8a is a lateral view of the second mobile unit of the plant according to a second embodiment of the invention, during operation;

- Figure 8b is a lateral view of the second mobile unit of the plant according to a second embodiment of the invention, at rest;

Figure 9a is a lateral view of the first mobile unit of the plant according to a second embodiment of the invention, during operation;

- Figure 9b is a lateral view of the first mobile unit of the plant according to a second embodiment of the invention, at rest;

- Figure 10 is a block diagram schematically showing the operation of the plant according to the invention;

- Figure 11 is a perspective view of a so-called lead-acid type battery.

In the Figures the same numerals have been employed for denoting equal or operationally equivalent components.

With reference to Figures 1 to 3, the plant 100 for the recovery of electric batteries is shown, said plant being particularly but not exclusively suitable for recovering batteries 10 of the kind shown in Figure 11 and comprising an external casing 20 made of a low molecular weight plastic material (namely polypropylene), a plurality of grid and poles

30,40 based on lead alloys, a paste or active material based on fine lead oxide, a plurality of separators 50 made of a high molecular weight plastic material (for instance PET and/or

PVC) and an electrolyte containing a sulphuric acid solution (if the so-called lead-acid batteries are concerned).

With particular reference to Figure 3, said plant comprises at least a batteries crushing apparatus 301 and a plurality of apparatuses 401-701 for separating and recovering the different components of the treated batteries, apparatuses that will be described in detail later on.

According to the invention, said crushing apparatus 301 and said separating apparatuses

401-701 are advantageously carried on a mobile unit, that in the represented example consists in a semi-trailer 101.

In this way, the recovery plant 100 can be directly driven to the spent batteries stocking

sites and the recovery of said batteries can be carried out 'in loco', without the need for transporting the batteries over long distances, thus avoiding the risks related to this transportation.

To this aim, the semi-trailer 101 is provided in its lower portion with one or more collecting tanks 103, allowing to recover possible dripping of electrolyte (generally a solution containing 15-20% of sulphuric acid) coming from the crushing 301 and separating 401-701 apparatuses placed above, avoiding the risk of dispersion in the surrounding environment.

Moreover, the semi-trailer 101 is advantageously provided with a plurality of telescopic supports 105 allowing to support and uniformly distribute the weight of the crushing 301 and separating 401-701 apparatuses during operation.

The crushing apparatus 301 comprises a hopper 303 wherein batteries are loaded, entire and still containing the electrolyte inside, and a hammer mill 305 allowing to shred the batteries so as to obtain a ground product with size lower than about 30 mm. Downstream the mill 305, the crushing apparatus 301 comprises a transferring screw conveyor 307 for measuring and transferring the ground product to the successive separating apparatuses.

Since batteries contain inside them the electrolyte, formed by notoriously corrosive substances, the body and the coatings of the mill 305, as well as the screw conveyor 307, will be preferably made of stainless steel AISI 316, while the hammers of said mill 305 will be preferably made of a thermally treated austenitic-ferritic alloy.

Downstream the crushing apparatus 301 there is the first separating apparatus 401, which receives the ground material from the screw conveyor 307 and allows to separate the metallic components of the batteries - namely grids and poles - frorri the plastic components thereof.

The grids and poles separating apparatus 401 is better shown in Figure 4. Said apparatus

401 comprises a dynamic gravimetric separator 403, for instance a cyclone separator. At the outlet of this gravimetric separator 403, the crushed grids and poles - now separated from most plastic components - are forced to pass through a fine separator 405, of the screw conveyor type, in order to eliminate possible fragments of heavy plastic materials and they are finally ejected through an outlet duct 407.

It is to be noted that the product ejected from the duct 407 will generally have a moisture content of about 3-4% and it will contain a percentage of lead and antinomy on dry bases of about 94%.

Also the gravimetric separator 403 and the fine separator 405 will be preferably made of

stainless steel AISI 316 so as to take into consideration the presence of the sulphuric acid.

At the outlet of the grids and poles separating apparatus 401, the plastic material is transferred by means of a screw conveyor 503 to a second separating apparatus 501 - shown in Figure 5 - comprising a gravimetric separator, namely a flotation separator 505.

Said flotation separator 505 allows to separate polypropylene (low molecular weight plastic material), forming the casings of the spent batteries, from PET, PVC and other high molecular weight plastic material contained in the separators of said batteries.

With reference again to Figure 3, at the outlet of the flotation separator 505, the polypropylene is ejected through a first outlet duct 507, while the high molecular weight plastic materials are ejected through a second duct 509.

It is to be noted that the product ejected through the first duct 507 will generally have a moisture content of about 5-6% and it will contain a percentage of polypropylene on dry bases greater than 95%. Heavy plastic material ejected through duct 509 (which can be considered as the only non recyclable waste coming out from the plant 100) will contain lead in a percentage greater than 0.5% and they will a moisture content of about 15-30 %.

Also the flotation separator 505 will be preferably made of stainless steel AISI 316 so as to take into account the presence of sulphuric acid.

All the above-disclosed operations will be carried out in presence of a stream of water which is made to re-circulate by means of a suitable pump and which, by washing the ground material, drags the paste through suitable screening diaphragms (not shown) and conveys it, as a suspension, to a third separating apparatus 601.

Said paste separating apparatus 601, shown in Figures 4 and 6, comprises a settling tank

603, wherein the thickening of the solid phase and the clarification of the liquid phase are obtained; the settling process is preferably aided by the introduction of a flodculant in the tank 603.

A scraping chain 605 is provided on the bottom of the settling tank 603 for continuously removing the paste, while the clarified water is transferred to a second tank 607.

With particular reference to Figure 6, the scraping chain 605 transfers the paste to a dehydrating screw conveyor 609 and from said screw conveyor the paste is introduced by falling in polypropylene bags 603 of the kind employed in the field of sludge filtration, allowing a final draining for obtaining the desired moisture content degree.

It is to be noted that after the draining the obtained product will generally have a moisture content of about 13 -14% and it will have the appearance of a tixotropic material, principally consisting in a mixture of lead oxide and lead sulphate (with a percentage of

lead on dry bases greater than 65%).

As the components of the previously disclosed apparatuses, also the tanks 603,607, the dehydrating screw conveyor 609 and the scraping chain 605 are preferably made of stainless steel AISI 316 so as to take into account the presence of sulphuric acid. Referring back to Figures 1 to 3, the plant according to the invention further comprises an electrolyte separation apparatus 701 comprising a knit mesh filter 703, preferably made of a polypropylene fabric, and a draining pump 705, that allows to transfer to the filter 703 the draining water of the bags 613 as well as the water collected in the tank 103. After the filtration, an electrolyte with a concentration in sulphuric acid of about 10-15% and with a content in solid particles lower than 100 ppm will be obtained. Advantageously, in order to avoid the dispersion of acid mists and contaminated powders, forced ventilation is provided in correspondence of all the zones wherein said substances could be released, so as to convey the possibly contaminated air towards a purifying apparatus, comprising a plate scrubber of the known type.

Always referring to Figures 1 to 3, the plant further comprises an apparatus 801 for loading the spent batteries to the crushing apparatus 301, said loading apparatus 801 being in its turn carried on a second mobile unit, which in the represented example consists in a second semi-trailer 201.

In this way, the recovery plant 100 turns out to be completely autonomous and it can be employed in any stocking site, independently from the facilities available Hn loco\ Also the second semi-trailer 201 is advantageously provided in the lower portion with one or more tanks 203 for collecting drippings and with a plurality of telescopic supports 205 allowing to support and uniformly distribute the weight of the loading apparatus 801. Said loading apparatus 801 substantially comprises a hopper 803, onto which the spent electric batteries can be loaded by means of a mechanical shovel or similar machine, said hopper 803 is provided with an extracting device 805, which measures and transfers the batteries to a conveyor belt 807, which transfers the batteries from the hopper 803 of the loading apparatus 801 to the hopper 303 of the crushing apparatus 301. According to the preferred embodiment of the invention shown in Figures 1 to 3, the loading apparatus 801 further comprises a magnetic separator 809, which removes possible foreign bodies in ferrous materials from the spent batteries carried on the belt 807. It is to be noted that a third semi-trailer (not shown) can be advantageously provided for the transportation of the electric and mechanical devices necessary for the power-supply and control of the plant 100, said devices substantially comprising a power generating set

and an air compressor.

In this way, the plant 100 is made totally autonomous, thus ensuring the maximum flexibility and versatility in performances.

Referring now to Figure 7, a constructional variant of the invention is shown, wherein the crushing 301 and separating 401-701 apparatuses, instead of being permanently fixed to the semi-trailer 101, are mounted on said semi-trailer so that they can be detached therefrom when the semi-trailer has arrived to the site wherein the recovery operations have to be performed.

Therefore, according to this variant, the aforesaid apparatuses 301-701 will be transported on the semi-trailer 101 for instance to a stocking site in a configuration completely similar to the one shown in Figure 3. Once the place of destination is reached, these apparatuses will be released from the semi-trailer and they will directly rest on the ground, on telescopic supports 105, that in this case will be provided integral with the bottom wall of said apparatuses or with a frame below, instead that with the bottom wall of the semitrailer.

According to this constructional variant, also the loading apparatus — if available - could be detachably mounted on the second semi-trailer.

Referring now to Figures 8a,8b,9a,9b, the plant for the recovery of spent electric batteries according to a second embodiment of the invention is schematically shown, said embodiment allowing to obtain an even more compact and autonomous plant. As shown in Figures 8 a and 8b, the second mobile unit or second semi-trailer 201' of said plant carries not only the hopper 803' of the loading apparatus 801', but also a control cabin 209' as well as the electric and mechanical devices 211' for the power-supply and control of the plant, which will substantially comprise a power generating set 213' and an air compressor (not shown).

Thus, according to this second embodiment, it is possible to avoid the use of a third semitrailer for transporting said devices for power-supply and control.

According to the invention, in order to obtain a more compact and more easily transportable plant, the conveyor belt 807' of the loading apparatus 801' is telescopic, it is detachably connected to the second mobile unit 201' and, when the plant is at rest, it can be folded, removed from the second mobile unit 201' and laid down onto the hopper 803' and the cabin 209', as shown in Figure 8b. More particularly, in the example represented in Figure 8b, the conveyor belt 807' comprises a first section 807'a that during transportation stands in upright position, leaned against the wall of the hopper 803', and a second section

807'b that during transportation lies in horizontal position, laid down onto the hopper 803' and the cabin 209'.

In this way, during transportation, second mobile unit 201' has a reduced overall size and, more particularly, an overall height lower than 4.30 meters, in accordance with the traffic regulations in force in Italy (Art. 61). It is to be noted that such height is largely lower than the height of 7.00 meters that can be reached by the conveyor belt 807' in extended configuration during the loading operations.

Always referring to Figure 8 a, it is to be noted that, in the represented example, the conveyor belt 807' of the loading apparatus 801' during operation is placed orthogonal to the longitudinal axis of the semi-trailer 201' (denoted by L arrow in the Figure) and, accordingly, the first and second mobile units 101 ',201' are placed orthogonal to each other, forming a 'L' shape.

It is evident that, if required by the circumstances of the specific application, thanks to the detachable connection to the mobile unit 201', the conveyor belt 807' could also be placed parallel to the longitudinal axis of the semi-trailer 201'; in this case, the first and second mobile units 101',20I' are lined up with each other.

Still referring to Figures 8a,8b, in order to avoid the dispersion of acid mists and contaminated powders coming from the recovery process of the spent batteries, the second mobile unit 201' can also carry a purifying device or scrubber 207'.

In Figures 9a and 9b, the first mobile unit 101' of the plant for the recovery of spent batteries is shown. Said first mobile unit 101' carries the crashing apparatus 301' and the different separating apparatuses, among which the grids and poles separating apparatus

401', the low and high molecular weight plastic materials separating apparatus 501', the paste separating apparatus 601' and, in case, the electrolyte separating apparatus (not shown).

Always in order to obtain a more compact and easily transportable plant, according to the invention the hopper 303' of the crashing apparatus 301' is detachably connected to the mill 305' of said crushing apparatus, so that, when the plant is at rest, this hopper can be removed from the mill 305'. More particularly, the hopper 303' is designed so as to be capable of being laid down on the mobile unit 101' onto the plastic materials separating apparatus 501'. In this way, during transportation, also the first mobile unit 101', which during the recovery process of spent batteries has an overall height of about 7,00 meters, has a limited overall size and, more particularly, an overall height lower than 4,30 meters, in accordance with the traffic regulations in force in Italy (Art. 61).

With reference now to Figure 10, the process carried out in the plant according to the invention is schematically shown as a block diagram, said process comprising the following steps:

- the spent lead-acid batteries are loaded on the plant (step 901) by means of a conveyor belt 807,807';

- during the loading step, possible ferrous foreign bodies are removed from said batteries (step 903), for instance by means of a magnetic separator 809; the batteries are crushed, for instance by means of a hammer mill 305,305', thus obtaining a ground product with small size (step 905);

- said ground product undergoes washing and screening (step 907), for instance by means of a rotary or vibrating screen, so as to separate the solid fragments from the paste (step 909);

- said paste is made to settle (step 911) in a settling tank 603 so as to clarify the liquid phase and to thicken the solid phase, in case with the aid of a flocculant (step 913);

- the thickened paste undergoes dehydration (step 915) and it is finally extracted (step 917), for instance thanks to a dehydrating screw conveyor 609;

- the extracted paste undergoes draining (step 919) and the draining water is filtered (step 921), for instance by means of a knit mesh filter 703, so as to recover the electrolyte (step 923);

- the solid fragments undergoes gravimetric separation (step 925) by means of a suitable separator 403, for separating lead-based grids and poles from the plastic materials (step 927);

- grids and poles successively undergo a further dynamic fine separation (step 929) and they are finally extracted (step 931); plastic materials undergo a further step of flotation separation (step 933) by means of a suitable separator 505 for separating the low molecular weight materials (steps 935- 937) from the high molecular weight materials (step 939);

From the above disclosure it is evident that the plant according to the invention fulfils the pre-set objects, since it allows to recover all the components of spent electric batteries (more particularly lead-acid batteries), directly at a stocking site, without the need for transporting said batteries over long distances and independently from the facilities available at this site.

Moreover, it is evident that the plant according to the invention has a very limited size, substantially equal to the size of two semi-trailers 101,201.

It is finally evident that, even if the present invention has been disclosed making reference to particular embodiments, several variants and modifications can be provided without departing from the scope of the invention.

By way of example, even if the invention has been disclosed with reference to the recovery of lead-acid batteries, it can be employed as well for recovering, and recycling different kinds of spent batteries, for instance nickel-cadmium batteries. In these batteries the electrodes are respectively made of metallic cadmium and of nickel hydroxide and an alkaline electrolyte (containing potassium hydroxide and lithium hydroxide) is employed.