Function
The Metallic Fraction Separation Unit by STC carries out a complete treatment of the metallic components with the final aim to reduce the environmental and economic impact of the following grids smelting operations. The Metallic Fraction resulting from the battery breaking and separation unit, may be furtherly processed in an additional step where metallic grids are separated from poles/connectors and possible paste residues and heavy plastic fragments are eventually removed. The main scope is the classification of the metallic fraction into three products:
- Fines separation (lead paste and very fine grids) to be mixed with paste and processed inside the rotary furnace
- Metallic grids to be melted in traditional rotary furnace or in STC special tilting rotary furnace
- Poles and connectors to be melted in traditional rotary furnace or directly in refining kettles or in STC special Tilting rotary furnace.
Depending on the quality of the battery components separation inside the breaking and separation area, the unit may also include the heavy plastics removal. The operation is carried out in special rotary screen with washing system in order to obtain very clean fractions.
The metallic fraction can also be desulphurised in order to remove the PbSO4 resulting from the electrochemical reactions during the battery life (sulphation and corrosion) thus reducing the SO2 emission during smelting operation as well as the amount of fluxants and of generated slag.
Desulphurization is performed in rotary drums using an alkali chemical (caustic soda or urea) as reactant with consequent production of sodium sulphate or ammonium sulphate as by-product.
Advantages
- Increase of lead recovery - Increase efficiency of the Smelting and Refining area;
- Abatement of SO2 emissions;
- Reduction of slags production;
- Reduction of fluxant consumption;
- Reduction of possible shortfalls of grids trade & transport.
