LEAD AND LEAD ALLOYS – THE LEAD BATTERY RECYCLING
Engitec Technologies S.p.A. supplies industrial plants throughout the world, offering its services from the definition of the technology up to the turn-key construction, start-up, commissioning and taking over by the client.
Engitec is very active in the technologies innovation, specially in the field of hydrometallurgy and electrolysis for the production of metals. Its Ezinex, Flubor and Ecuprex processes are the most revolutionary approaches to the extraction and production of Zinc, Lead and Copper of the last twenty years.
These innovative technologies have been developed by Engitec technical researchers from the invention phase up to the industrial pilot plant.
THE BATTERY RECYCLING SYSTEM
The battery recycling system can be composed as follows:
Unit 100: Electrolyte collecting and filtration unit
The electrolyte drained from scrap batteries is collected and filtered to remove the solids and stored for other use. It can be neutralized or processed within the paste desulphurization unit.
Unit 200: CX® Breaker, separation and filtration unit
The batteries delivered in the collection bunker are loaded into the feeding and metering system of the battery breaking and separation Plant.
The battery scrap is processed through a crushing mill and then separated in two streams, one for paste and one for the coarse part, in order to obtain the following products:
Lead Paste: The paste slurry collected in a tank can be delivered either to the desulphurization process or pumped to a filter-press for dewatering from where the paste cake is discharged in a dedicated area ready for smelting.
Polypropylene, discharged in a dedicated area
Metallic fraction (grids and posts), which can additionally pass through a washing-desulphurization system and is finally divided in fine-sized fraction (mainly Grids and Pb-Ca part), and in coarse fraction (mainly posts and Pb-Sb part) which are discharged in dedicated boxes
Heavy Plastics, discharged in a dedicated area
Unit 300: Lead paste desulphurization
The benefit of the desulphurization of paste is the extreme diminution of SO2 emission and the production of slag reduced down to less than 10% of produced lead. The productivity of the smelting furnace is increased due to a lower quantity of reagents and fluxes to be added to the process.
The paste slurry is pumped into a reaction tank and it is mixed with the waste acid collected in the battery storage area. The desulphurization reaction can be carried out through addition of the Sodium Carbonate, or Sodium Hydroxide or Ammonium Bicarbonate.
The reacted paste slurry is pumped to the filter-press for dewatering then the paste cake is discharged in a dedicated area ready for smelting, while the filtrated sulphate solution is conveyed to the subsequent treatment for removal of heavy metals. The purified sodium sulphate solution, separated by a further polishing filter press, is sent to sulphate salt production unit.
Unit 300c: Super-desulphurization of paste (optional addition): This step allows the amount of slag produced in smelting phase to be reduced to less than 5% of Pb produced.
After the first desulphurization phase the paste is re-pulped and additionally carbonated before undergoing a second filter press de-watering.
Unit 400: Sulphate salt production
The sodium sulfate solution is processed through a crystallization system from where the final brine is extracted and centrifuged. The mother liquor is returned to the process while the crystals are pneumatically conveyed into a storage silo.
Unit 500: Gaseous effluents scrubbing system
Polluted air, containing acidic mist, is collected from different points of the plant and treated in a wet scrubber which releases the purified air to the atmosphere.
Unit 700: Lead smelting
The adopted technology is the smelting of lead-based materials in fixed-axis or in tilting rotary furnaces, equipped either with air-fuel burner or with oxygen-fuel burner.
The unit includes the charging system through a dedicated machine or through an automated materials metering and feeding group as well as a furnace-dedicated bag-house filter .
The product from the foundry is raw lead.
Unit 800: Lead refinery
The raw lead produced out of rotary furnaces is processed in kettles under different procedures and temperatures. The scope is the removal of many of the foreign metals and of impurities in order to produce either soft lead and all the alloys required by the market. All the ancillary equipment like pumps, agitators, dross removers, oxy injectors etc are used for such operations. The final products are cast in ingots in a dedicated line which provides to final robotized stacking and strapping in automatic way.
The process fumes from kettle hoods and the hygiene air from refinery area are processed in a dedicated bag-house.
LEAD – PRIMARY LEAD FROM CONCENTRATE
The FLUBOR Process – Patented system for the hydrometallurgical recovery of lead from Galena-based concentrates
The unique features of the FLUBOR Process include:
- Direct leaching of Pb concentrate with no pre-treatment
- Production of Pb and S
- Elimination of slag production and SO2 emissions
- Environmental impact reduction to the minimum values
- Limited fuel consumption
- Improved workplace environment
The FLUBOR Process uses a chemical stable fluoboric acid based electrolyte as solvent for Pb. The process is composed by the following units
- Leaching: the leaching of the PbS concentrate is accomplished in an acidic oxidising solution where the Galena mineral is contacted with a solution containing fluoboric acid and ferric fluoborate. The sulphur of the galena is oxidised to elemental sulphur while lead is taken in solution as lead fluoborate. This leaching is higly selective with metals more noble than Pb reporting to the leaching residue.
- Electrowinning: The solution from the leaching unit is then sent to a diaphragm divided electrowinning cell. The Pb is plated in the cathodic compartment while the iron is oxidized in the anodic compartment to regenerate the leaching solution. This unique electrowinning cell allows the Flubor process to operate as a closed loop leach and EW system.
- Bleed treatment: although highly selective, the leaching of mineral concentrates allows some impurities into the solution. These impurities can eventually affect downstream processes and also consume free fluoboric acid in the solution. The bleed treatment it is based on the precipitation of metal sulphates less noble than lead. In this unit impurities consuming fluoboric acid are removed from the process and the free acid is recovered to the process.
- Residue treatment: sulphur contained as elemental S° can be removed and recovered allowing the metal values contained in the remaining residue to be recovered using existing processes. Engitec has developed a patented technology that is able to directly treat the Flubor leach residue without prior S° removal.
- The Lead extraction rate is > 97 %
- The produced lead cathodes have a Pb content of 99.99 % free of Bi, Ag, Se, Te.
- The operating cost is exceptionally attractive and substantially lower than the thermal processes used today.
INSPIRING INNOVATION is the key Company Mission of Engitec, which is pursued daily by developing reciclying technologies to enable efficiency and environmental compliance.
Engitec Clients rely on the ability of the Company to minimize environmental impacts and can develop their solutions in partnership with Engitec, in order to minimize time to market and reduce costs.