A total of four lead – acid recycling facilities are active in Greece in this sector.
Altogether in 2002, roughly 17,000 tonnes were processed, with a yield of about 50%, in metallic lead and lead alloys.
The recovery of lead recovered from the lead contained in the accumulators is of the order of 99%.
From the lead produced around 70% was used for the production of new accumulators, thus closing the cycle of the lead recycling process, while the remainder was used for the production of pigments, rags, linings for electric cables, lead sheets, etc.
Accumulator recycling and lead recovery are based on the pyro-metallic process.
The installation is schematically defined in three areas, which are:
- Cutting, sorting, separating and storing the various components of the battery
- Separation and “melting” by producing the so-called “secondary lead”
- Cleaning and shaping
Recycling of batteries offers energy savings of 70% of the production of primary lead equivalent. Similarly, there is the benefit of recycling plastic packaging materials for accumulators. The flow diagram below depicts the basic processing phases of spent batteries in secondary lead.
- Selection – breakage – separation of accumulators
Used accumulators are collected in recycling units in properly designed spaces for first sorting and load control.
This phase of screening is necessary to remove possible incompatible materials (nickel-cadmium accumulators, ferrous parts, various wastes). The accumulators are loaded into conveyor belts and through a hopper, shipped to their crushing and shredding areas.
The electrolyte is then removed and the plastic and leaded parts of the accumulators are separated and washed.
At the end of this phase, we have the lead paste, partition meshes, battery poles, polypropylene mix and plastic. The lead paste, in the form of sludge, is recovered in the filterable unit.
The typical lead concentration is about 99% in metallic form and is recovered by redox in cylindrical melting furnaces. The dividing grid and poles are led to the melting furnace.
The polypropylene at the exit from the separator is recovered by air separation and floating and sent for shredding.
From the plastic mix a part, after rinsing, clean and free from any residual materials, is sold as a product to plastics manufacturers. While the rest, to a maximum of polyethylene, is recovered or sent for deposition.
- Melting and reduction of metal compounds
From the melting and reducing furnace, lead and rust are continuously exported. Processes taking part in this phase, synthetically can be described:
- Reduction of carbon oxides and lead sulphate
- release of lead, which is found as lead sulphate, using sodium carbonate and iron
The operating temperature in this phase is greater than 1,100 ° C and is achieved by the addition of liquid oxygen, natural gas or diesel.
The lead exiting the oven is at 900 ° C and must be cleaned to obtain the desired degree of purity or the corresponding metals added to obtain the desired alloy composition.
Finally, the processes that are being developed at this stage are:
- removal of surface oxides
- partial or total removal of copper
- partial or total removal of tin
- partial or total removal of antimony
- controlled addition of metal elements for the desired alloy composition
Processing of electrolyte in recycling facilities
The electrolyte treatment of the accumulators follows the following schematic process:
- collecting battery electrolyte and acidic production solutions
- neutralizing solutions
- separation (sludge is promoted to lead recovery furnaces)
- sanding on sand filters
- fraction as waste and the remaining quantities are going to be re-used in the plant
Recycling plant installations operate with corresponding work steps, taking into account the quantities and organization of production work required for the recycling of batteries and protection from gaseous and liquid pollution.