Thanks to the research achieved in the project, the ISF was adapted to treat large amounts of residues restricting detrimental effects.
- Shaft offtake/condenser inlet accretions, which represent a very critical point for the process operation (periodic stop of the furnace to clean this area) where lowered by modifications of geometry (blades of rotor altered to splash the lead in a good manner; drosses lying on the molten lead better drained).
- Hard accretions, caused by early condensation of volatiles (mainly chlorides), were suppressed by lowering the amount of chlorine in the briquettes. As chlorine serves as a binding agent for briquetting, the briquetting operation had to be changed : hot briquetting, addition of other types of residues (lead-bearing)...
- The increase of drosses, mainly due to more carry-over, as briquettes are more fragile than sinter - and that was a major cause for the decrease of the zinc condensation efficiency - was restrained by enlarging the shaft as well as the briquettes and changing their composition.
- The dross removal from molten lead or zinc, which causes loss of zinc, was studied by testing different kinds and amounts of fluxes. Improvements may be expected now.
- A mathematical model of the condenser was created and calibrated with temperature data inside the reactor. It gave the key parameters which control the condenser efficiency, namely the size and number of droplets of lead splashed onto the gas stream. As a consequence, industrial trials were undertaken to optimize the condenser operation. An increase of the lead droplet surface area would be beneficial; in case of rebuilding, the condenser should be lengthened.
In zinc and lead metallurgy, the distribution between primary and secondary raw materials is changing to an increase of secondary materials. The Imperial Smelting Process is the only commercial process that can recover both lead and zinc from such residues.
But to increase the amount of those complex residues and waste materials, it appears that the main limitation of the process is the zinc condensation. When the input of secondary materials is increased the condensation yield is lowered.
So the objective of this program is to find out how these residues can be treated with a better recovery yield of zinc in the top of the furnace and during condensation. To achieve this purpose, this program includes the following steps:
- Industrial investigations in order to compare the plants of the two partners which have different design in condensation equipments and different operating conditions.
- Studies and modelling of the phenomena controlling the zinc condensation reoxidation.
Funding SchemeCSC - Cost-sharing contracts
09100 P.vesme Cagliari
30175 Porto Marghera Venezia