In the lead battery recycling process the polypropylene coming from the second sieve of the lead battery breaking and separation plant is sent to a washing basin to remove the last traces of sulphuric acid. Afterwards, the plastic is sent to a crusher in order to reduce the plastic pieces down to a size of less than 10 mm and then washed with a solution containing a natural organic solvent to remove the remaining lead from the plastic matrix.
STC supplies plants for the recovery of polypropylene and polyethylene from lead battery recycling that increase economy for battery recyclers.
The plastic is dried with hot air and sent to a screw extruder for the production of granular pellets which can be reused. The low presence of heavy metals makes it possible to use them for other products apart from new batteries as well.
The polyethylene of the lead battery separators contains a high amount of amorphous silica and is therefore not suitable for recycling. STC has created a technology that allows to transform the polyethylene from lead batteries into gas. The developed process uses pyrogasification at medium temperatures without oxygen.
Through a screw conveyor, the plastic is sent from a hopper into a pyrogasification chamber where a temperature of ca. 700 °C is maintained. At this temperature the plastic undergoes a cracking process, releasing hydrocarbon of various molecular weight with linear chain which can be directly sent into the burners of the reduction furnaces or into any other burner of the lead battery recycling plant.
The remaining inorganic compounds produced by the pyrogasification plant is made of amorphous silica and traces of carbon. This mixture can be burned with oxygen excess to oxygen the present carbon and obtain an amorphous silica that can be used for the production of new separators.
This process has an economic validity because it allows the lead battery recycling industry to recover a source of energy and avoids a dangerous waste to be sent to landfills, reducing disposal costs and protecting the environment.
It is remarkable that the gas obtained from the pyrogasification of the separators of one lead battery, if burned, is enough to smelt all the lead present in the same battery.