STC’s revolutionary hydrometallurgical process for the regeneration of lead oxide from exhausted lead acid batteries

After several years of research and fine tuning of the technology, STC S.r.l., an Italian engineering and contracting company operating in the field of battery recycling and lead production, has realized a demo plant (see Figure 1) that is able to regenerate about 2 t/d of lead oxides starting from exhausted lead paste without involving pyrometallurgical processes, the company announced yesterday.

Figure 1: Lead Oxide regeneration pilot plant

The system is based on a patented process, which employs ammonium carbonate for the transformation of lead sulphate into lead carbonate. Although the aforementioned reaction has been known for many years, in this case the adopted engineering expedients allowed to achieve yields close to 100%.

A lead paste treatment, where the drying temperature is higher than the PbCO3 decomposition temperature, leads to the formation of oxide, a compound that is easily leached in the following step in order to reprecipitate high purity lead carbonate. The following heat treatment leads to the production of pure lead oxides of different types: litharge, massicot or minium which might be used both for the production of active material for batteries (starter and traction batteries), and for any other use this pure compound is thought for (ceramic, glass and rubber industries, etc).

The by-product deriving from the whole cycle, ammonium sulphate, is a fertilizer to be sold and used for agricultural applications. Both the abatement of pollution caused by old systems and the final production of a fertilizer confirm the ‘green’ essence of this cycle.

Figure 2: Lead3 experimental battery

Furthermore, an experimental batch of about 1000 starter batteries (see Figure 2) has been produced with the hydro-metallurgical Lead Oxide Regeneration technology proposed by STC. After several tests, it has been proved that the obtained batteries containing the regenerated nanostructured oxides have a greater capacity and a longer life than those produced with traditional processes.

In other words, this technology makes it possible to have a remarkable economic saving, a virtually non-existent environmental impact and the possibility to supply battery producers with oxides that are ready for the production of new batteries with better characteristics than the traditional ones (see Figure 3).

Characteristic Standard STC
Gripping, Weight Loss [%] 79% 15%
Available Power Midtronics [CCA – Cold Cranking Amps] 600 625
C20 [Ah] 67 70
C10 [Ah] 65 65
C5 [Ah] 58 58
Ciclability [N° cycles] 115 136
C20 afterciclability test [Ah] 22 27

Figure 3: Comparison of standard and STC batteries

The results are stunning for a conservative sector, that of lead acid batteries, which is still too bound to old design dogmas that do not keep up with the times. The achieved success opens up new frontiers for lead batteries. Now, the next step for STC is the construction of an industrial plant that will demonstrate to the scientific community and to all main actors of the energy storage sector the great potential of its process.

“The success of this project, says the company, is the result of the commitment and dedication of the whole STC team and in particular of Gianluca Fusillo, Francesco Scura and Giorgio La Sala. Special thanks are in memory of Prof. Renato Guerriero, as the project would not have been possible without his inspiration and guidance”.

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