The FAST Pb Process and Its Impact on Secondary …
585
The reactions in the cell are very similar to the ones of the EZINEX
® Process.
On the cathodic side of the electrode, the following reaction takes place:
NH 4 PbCl 3 + 2e
−
→ Pb + NH 4 Cl + 2Cl
−
(8)
producing the metallic flakes that are the product of this electrolysis. On the anodic
side of the electrode, the following reaction takes place:
2Cl
−
→ Cl 2 + 2e
−
(9)
The chlorine management is, fortunately, not required because the anodic reaction
is followed by the following very fast chemical reaction:
Chemical reaction : 2
3 NH 3 + Cl 2 → 1
3 N 2 + 2HCl
(10)
Some recent test on different anodes seems to demonstrate that on some of them
the direct de-hydrogenation of ammonia is also possible as a competing reaction
having, in any case, no impact on the process.
The overall cell reaction (8 + 9 + 10):
NH 4 PbCl 3 + 8
3 NH 3 → Pb + 1
3 N 2 + 3NH 4 Cl
(11)
shows that, in the cell, the process is able to regenerate the leaching reactant to make
a closed loop system. Some NH 3 is consumed in the chemical reaction following the
anodic reaction, and the Pb/NH 3 molar ratio is the same for all the possible battery
paste components.
Several factors, such as the operative current density, the solution temperature, and
the electrolyte composition, impact the cell voltage. In optimized working conditions,
cell voltage is in the range 2.9–3.1 V at current densities ranging between 8000 and
10,000 A/m
2 . The current efficiency does not depend substantially on the current
density and it is between 85 and 90%, and one of the main factors for this is the
narrow working gap between the anode and cathode. Some flakes can contact the
anode and re-dissolve. The direct current energy consumption is between 870 and
900 kW/t of produced lead.
The flakes produced take with them some electrolyte that needs to be squeezed
out, for instance by rolling or briquetting, before feeding them to a crucible for
converting them into a commercial cast ingot.
Engitec’s long demonstration plant campaigns, lasting more than three years during which more than 15 tons of sulphurized paste have been treated, have provided
all the data and parameters required to design the industrial cell and the complete
industrial plant.
585
The reactions in the cell are very similar to the ones of the EZINEX
® Process.
On the cathodic side of the electrode, the following reaction takes place:
NH 4 PbCl 3 + 2e
−
→ Pb + NH 4 Cl + 2Cl
−
(8)
producing the metallic flakes that are the product of this electrolysis. On the anodic
side of the electrode, the following reaction takes place:
2Cl
−
→ Cl 2 + 2e
−
(9)
The chlorine management is, fortunately, not required because the anodic reaction
is followed by the following very fast chemical reaction:
Chemical reaction : 2
3 NH 3 + Cl 2 → 1
3 N 2 + 2HCl
(10)
Some recent test on different anodes seems to demonstrate that on some of them
the direct de-hydrogenation of ammonia is also possible as a competing reaction
having, in any case, no impact on the process.
The overall cell reaction (8 + 9 + 10):
NH 4 PbCl 3 + 8
3 NH 3 → Pb + 1
3 N 2 + 3NH 4 Cl
(11)
shows that, in the cell, the process is able to regenerate the leaching reactant to make
a closed loop system. Some NH 3 is consumed in the chemical reaction following the
anodic reaction, and the Pb/NH 3 molar ratio is the same for all the possible battery
paste components.
Several factors, such as the operative current density, the solution temperature, and
the electrolyte composition, impact the cell voltage. In optimized working conditions,
cell voltage is in the range 2.9–3.1 V at current densities ranging between 8000 and
10,000 A/m
2 . The current efficiency does not depend substantially on the current
density and it is between 85 and 90%, and one of the main factors for this is the
narrow working gap between the anode and cathode. Some flakes can contact the
anode and re-dissolve. The direct current energy consumption is between 870 and
900 kW/t of produced lead.
The flakes produced take with them some electrolyte that needs to be squeezed
out, for instance by rolling or briquetting, before feeding them to a crucible for
converting them into a commercial cast ingot.
Engitec’s long demonstration plant campaigns, lasting more than three years during which more than 15 tons of sulphurized paste have been treated, have provided
all the data and parameters required to design the industrial cell and the complete
industrial plant.