Complex copper-lead-zinc ores can be difficult to separate because valuable minerals may occur closely associated with each other and with gangue minerals. The appropriate copper-lead-zinc ore dressing process therefore needs to be determined according to the ore characteristics and flotation test results.
In this Indonesian case, Xinhai developed a flotation flowsheet for a complex polymetallic ore. The process consisted of copper-lead bulk flotation, copper-lead separation, and zinc flotation from the tailings.
Longteng Co., Ltd. had a mine containing copper, lead and zinc in Indonesia. The company sought a mining machinery company with mineral processing expertise to undertake the project.
After signing the contract, Xinhai sent technicians to conduct sampling and mineralogical analysis. The main metallic minerals included pyrite, iron sphalerite, galena, sphalerite and chalcopyrite. The main non-metallic minerals included quartz and feldspar, followed by calcite, dolomite, sericite, chlorite and carbon.
Further analysis showed that chalcopyrite, magnetite, sphalerite and galena occurred in close association. Some minerals occurred as marmatite, while part of the chalcopyrite was enclosed in gangue particles. This made direct separation difficult and could result in copper losses to the tailings.
Iron sphalerite was the main zinc-bearing mineral. Fine-grained galena, pyrrhotite and carbon were also associated with the mineral, making sufficient liberation difficult. The average iron content of marmatite was more than 10%, which affected the zinc concentrate grade.
Based on the mineralogical characteristics and multiple flotation tests, Xinhai developed a suitable flotation flowsheet for the ore.
The selected flowsheet followed three main stages:
Copper-Lead Bulk Flotation → Copper-Lead Separation → Zinc Flotation from Tailings
This type of partial bulk-selective approach is used when copper and lead can first be recovered together and then separated, while zinc is subsequently recovered from the flotation tailings. The exact flowsheet and reagent conditions should be determined through mineralogical analysis and flotation testwork.
The first stage was copper-lead bulk flotation.
With the pulp pH maintained at around 7.5, Ty-1 and zinc sulfate were used to inhibit sphalerite and iron sphalerite. Ethyl xanthate at 70 g/t and J-21 at 35 g/t were used as collectors.
The flotation conditions were adjusted to separate copper and lead from zinc minerals while maintaining suitable froth characteristics for the subsequent copper-lead separation stage.
The copper-lead bulk concentrate was then treated for copper-lead separation.
CMC and potassium dichromate were used in the separation process. B butter and 2# were used as flotation reagents to maintain stable flotation conditions and recover copper.
The copper concentrate was recovered efficiently, while the lead concentrate grade was initially only about 4%, making it a coarse lead concentrate.
To further improve the lead concentrate, a shaking table was subsequently used for gravity separation based on the density difference between the minerals.
After copper-lead flotation, zinc was recovered from the tailings.
The zinc flotation stage used lime at 3,500 g/t, copper sulfate at 500 g/t, butyl xanthate at 60 g/t and 2# oil at 60 g/t. The flotation pH was maintained between 12 and 13.
The zinc flotation circuit included two cleaning stages and one scavenging stage to improve the concentrate result.
The flotation process developed by Xinhai achieved the following concentrate grades and recoveries:
| Product | Grade | Recovery |
| Copper concentrate | 24.06% Cu | 51.70% Cu |
| Lead concentrate | 58.30% Pb | 89.24% Pb |
| Zinc concentrate | 47.08% Zn | 87.21% Zn |
The final results exceeded Longteng's expectations for the project.
This case demonstrates the importance of developing a flotation flowsheet according to the specific characteristics of a polymetallic ore.
For this Indonesian ore, close mineral associations and difficult liberation affected the separation process. Xinhai therefore used a staged approach:
Cu-Pb Bulk Flotation → Cu-Pb Separation → Zinc Flotation
The reagent conditions and separation stages were established through repeated flotation tests based on the characteristics of the ore.
For a broader overview of copper-lead-zinc flotation options, see Xinhai's guide to Four Flotation Flowsheets for Copper-Lead-Zinc Ore.
Xinhai develops mineral processing flowsheets based on ore characteristics, mineral associations, liberation conditions and flotation test results.
For copper-lead-zinc and other polymetallic ores, the appropriate separation method depends on the specific mineralogy and processing requirements. Xinhai provides mineral processing testwork, process design, equipment supply and EPC services for mineral processing projects.
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