This study was conducted to develop an understanding of the metallurgical and infrastructure requirements for the retreatment of flotation tailings dams in Zambia.
Earlier studies identified direct acid leaching as the flowsheet of choice for the metallurgical plant. Due to very high acid consumptions during testwork this flowsheet option was demonstrated as non-feasible when assessed economically.
This study considered various flowsheet options and tested these in the laboratory to identify the reagent consumptions and recoveries for each. Throughout the testwork phases the key consideration was to identify a process flowsheet which resulted in reduced acid consumption or alternative reagents but at the same time achieved reasonable recoveries of both copper and cobalt that resulted in an economic viable project.
The study looked at methods to reduce the reagent utilisation by identifying conditions under which lower consumption of reagents was achieved. This thought process was duly followed in carrying out further testwork. This resulted in the identification of a flowsheet with shorter leaching times and in particular the total
acid consumption was reduced down to less than 40kg/t.
The chosen flowsheet is simplistically described as:
- The recovery of tailings.
- AZMET Reduced Leaching (AZ-RLT) of the recovered tailings with sulphuric acid.
- Separation of cobalt and copper in a solvent extraction plant.
- Electrowinning of copper to produce a copper cathode.
- Cobalt will be precipitated out separately as a cobalt salt.
AZMET’s proprietary Reduced Leach Technology (AZ-RLT) was used, which resulted in an economical process on the samples tested.