GB2075248A - Processing of discarded batteries - Google Patents

Abstract

Used batteries are reduced to discrete pieces each consisting substantially of only one material, the pieces separated in accordance with their densities and pieces of the same or similar densities are collected in separate lots.

Description

SPECIFICATION Processing of discarded batteries This invention relates to a method and plant for processing discarded batteries of the lead acid type to separate and collect component materials for recycling.

Batteries consist of cases normally constructed from hard rubber, polyethylene or polypropylene, solid lead pieces (terminals etc.), plate packs comprised of lead grids coated with lead oxide and lead sulphate, and plate separators which are now universally made from polyvinyl chloride. In addition to the remaining acid spent batteries will contain a quantity of lead sulphate sludge.

Lead solids and grids will normally have high antimony contents whereas lead oxides and sulphates will be virtually free of antimony.

Plants currently processing lead acid batteries use primitive labour intensive means to break open cases, drain off acid and separate lead containing materials from case materials.

It is normal practice to smelt all lead containing materials together for lead recovery. Lead recovered in such a manner has an antimony content which must either be increased or reduced to provide marketable products.

P.V.C. separators are normally charged into the smelting furnace because they cannot conveniently be separated from the plate packs. PVC contained in the smelter charge is a pollutant and necessitates costly power consuming treatment of exhaust gases.

Case materials are normally disposed of by dumping on a refuse site and may involve road transport over long distances between the battery material reclamation plant and an available disposal area.

Battery cases as normally discarded are bulky for transport and disposal and often contain considerable quantities of lead in the form of lead sulphate sludge.

It is an object of this invention to provide a method and plant for the processing of used batteries of the lead acid type which provides maximum recovery of component materials with a minimum of labour required.

This object is achieved according to the invention by a method of processing used batteries of the lead acid type for the separation and recovery of recyclable materials comprising the steps of reducing the used batteries to discrete pieces of such size that said pieces each consist substantially of one material only, separating said pieces in accordance with their densities and collecting pieces of the same or similar density in separate lots.

The invention also relates to the plant devised to carry out the beforementioned method in the most efficent manner.

Such plant may include means of dismembering battery cases, plates and plate separators and reducing them to pieces of such size and in such a manner that said pieces will be substantially of one material only and lead oxide and sulphate coatings will be dislodged from plate grid sections. Further means may be provided to wash off and drain away acid and to neutralise acid remaining with dismembered pieces of battery components. In addition means are included to separate component pieces of case material of density less than water from all heavier materials, means to separate sludge from other component pieces and further means for separating lead and grid pieces from pieces of case materials heavier than water, and for separating small grid pieces from larger lead pieces.

Particular advantages derived from the invention are: 1. Reduced labour costs.

2. Elimination of unpleasant and hazardous manual operations.

3. Recovery of premium marketable grades of lead with minimum refining and processing.

4. Reduction of pollution controls necessary in smelter fume processing.

5. Recovery of recyclable plastic case materials.

6. Reduction in quantity and volume of reject case materials.

7. Reduction in smelter capacity required (larger lead pieces require melting only).

8. Improved recovery of lead sulphate sludge from discarded cases.

One embodiment of the invention is described hereinafter in more detail with reference to the accompanying figure.

A combination of a double toothed roll crusher (1 ) and a hammer mill (2) are provided to dismember batteries and reduce component materials to suitable size for subsequent separation. A lime slurry preparation and dosing plant (3) is provided to neutralise residual acid and an acid collecting system (4) is provided to collect acid released during - primary crushing of battery cases.

Sized pieces from the secondary crusher (hammer mill) pass with flushing water into the feed tank (5) of a screw classifier (6) wherein solid pieces lighter than water are carried by the flow of water over a weir (7) and onto a dewatering screen (8) thence by way of an elevating screw (9) to a storage bin (10).

Solids heavier than water sink to the bottom of the screw classifier feed tank (5) and are carried by the screw (11 ) to the discharge point (12) from where they are directed into a rotary screen (13). Said rotary screen (13) has two screening sections viz a fine screen section (24) followed by a coarse screen section (25).

Sludge is washed from the solid pieces by sprays (14) through the fine screen section (24) into a storage bin (23): small grid sections pass through the coarse screen section (25) into a storage basket (26), while larger solid particles are discharged from the rotary screen (13) into an elutriator separator (15).

This separator is provided with a recirculating pump (16) and so arrnged that the rising column of water in the branch (17) has a velocity such that solids only slightly heavier than water (that is case materials and PVC separators) will be carried with the rising current of water into an overflow launder (18) and thence to a dewatering basket (19). Solids which are considerably heavier than water sink to the bottom of the separator (15) and are conveyed by means of a drainage elevator (20) to a discharge chute (21) and thence to a storage bin (22).

Thus the plant described above allows for the separation of (A) the acid from the solid parts of the battery; (B) the separate collection of polyethylene and propylene pieces which are valuable recyclable products; (C) the sludge consisting mainly of lead sulphate and lead oxides for production of low antimony lead; (D) materials slightly heavier than water, in particular hard rubber and PVC, (E) small lead grid portions with adhering oxides and sulphates for smelting and refining to low antimony lead, and (F) lead terminals and heavier grid portions for melting to provide high antimony lead.

The foregoing detailed description gives only one embodiment of the invention and changes in the plant can be made without departing from the scope of the invention.

Claims (11)

1. A method of processing used batteries of the lead acid type for the separation and recovery of recyclable materials comprising the steps of reducing the used batteries to discrete pieces of such size that said pieces each consist substantially of one material only, separating said pieces in accordance with their densities and collecting pieces of the same or similar density in separate lots.

2. A method according to claim 1 wherein the acid is collected during the reducing step, and further including the steps of passing the discrete pieces of batteries over a seiving and washing system whereby the sludge is separated so that it can be processed to form a low antimony lead.

3. A method according to claim 1 wherein after the reduction step the discrete pieces of batteries are fed into a separator apparatus containing water whereby the pieces of battery lighter than water are removed, the remaining pieces of battery are then passed over a screening system and water spray whereby the lead sludge is removed, the remaining pieces of the battery then being fed to an elutriator separator in which the velocity of the fluid is controlled so that only materials slightly heavier than water are carried away by the movement of the fluid.

4. An apparatus adapted to separate and recover the recyclable materials from used batteries comprising a reduction stage wherein the batteries are reduced to discrete pieces of such size that said pieces each consist substantially of one material only, and a gravity separation stage whereby the materials are separated and collected in accordance with their densities.

5. An apparatus according to claim 4 wherein said gravity separation stage comprises a separation apparatus containing water whereby material less dense than water are removed, a screening apparatus over which the remaining material passes with the sludge being removed and collected and an elutriator separator the movement of water therethrough separates the materials slightly denser than water from the higher density metallic materials.

6. An apparatus adapted to separate and recover the recyclable materials from used batteries substantially as hereinbefore described with reference to the accompanying drawing.

7. An apparatus as claimed in claim 4 substantially as hereinbefore described with reference to and as shown in the accompanying drawing.

8. A method as claimed in claim 1 carried out substantially as hereinbefore described with refer- ence to the accompanying drawing.

9. A method as claimed in claim 1 carried out in an apparatus as claimed in any one of claims 4 to 7-

10. Material that has been reclaimed from a used battery of the lead acid type by a method as claimed in any one of claims 1 to 3, 8 and 9.

11. Any novel feature of method or apparatus hereinbefore described.