The Chumpe Mill treats complex polymetallic, copper, and lead oxide ores from the Yauricocha Mine using crushing, grinding, and flotation to produce multiple concentrates.
Report context
This technical report on the Yauricocha Property, dated October 19, 2012, describes the recovery methods employed at the Chumpe Mill for Dia Bras Exploration. The mill treats ore from the Yauricocha Mine, processing three ore types: polymetallic (PM), copper, and lead oxide (PbOx) ores, which contain silver, lead, copper, zinc, and gold values.
Processing route
Crushing and Screening
All ore from the mine passes through a common crushing-screening circuit. PM and copper ores are received in a 450 tonne bin, while PbOx ore uses a separate 150 tonne bin. The two ore types are crushed separately in campaigns. The crushing circuit incorporates a 24-inch by 36-inch jaw crusher, a 48-inch standard cone crusher, and three screens. Fine PM and copper ores are stored in three fine ore bins, with fine PbOx ore stored in a single dedicated bin.
Polymetallic Circuit
When treating PM ore, the polymetallic circuit produces three final concentrates: copper, lead, and zinc. A bulk copper-lead concentrate is produced initially and then separated into lead and copper fractions. When treating copper ore, the circuit produces only a copper concentrate, with no lead or zinc concentrates produced.
Grinding
Ore from the fine ore bins is fed to a 7-foot by 12-foot rod mill operating in open circuit. Rod mill discharge enters a cyclone sump, with cyclone underflow ground in an 8-foot by 10-foot ball mill. Ball mill discharge passes through three unit flotation cells producing copper-lead bulk concentrate, with tails returned to the cyclone sump. Cyclone overflow is treated in three circular flotation cells also producing copper-lead bulk concentrate. Tailings from these cells feed the cyclone sump of a fine grinding circuit comprising two 8-foot by 6-foot ball mills in closed circuit. This sump also receives scavenger concentrates and cleaner tails from downstream copper-lead operations.
Copper-Lead Flotation and Separation
Cyclone overflow from the fine grinding circuit undergoes bulk copper-lead rougher-scavenger flotation followed by four stages of cleaning. The final cleaner concentrate, along with copper-lead bulk concentrates from the earlier flotation cells, is sent to a copper-lead separation circuit. Scavenger tails report to the zinc circuit.
In the separation circuit, lead minerals are depressed while copper minerals are floated in a rougher-scavenger configuration. Scavenger tails (lead concentrate) go to the lead concentrate thickener. Copper rougher concentrate passes through three stages of cleaning, then to a recleaner stage comprising four recleaner cells where copper is depressed and remnant lead is floated. The recleaner tails form the final copper concentrate and report to the copper concentrate thickener; the recleaner lead concentrate reports to the lead thickener.
Zinc Flotation
Scavenger tails from the copper-lead bulk circuit form the zinc circuit feed. The feed is conditioned and floated using pre-roughers, roughers, cleaners, rougher-scavengers, and cleaner-scavengers. A final zinc concentrate is produced and sent to the zinc thickener. Final zinc scavenger tails are sent to the PM tailings thickener.
Lead Oxide Circuit
The lead oxide circuit produces a sulphide concentrate (sent to the lead thickener and combined with polymetallic circuit lead concentrate) and a separate lead oxide concentrate. Crushed PbOx ore is fed directly to a 7-foot by 12-foot rod mill. Discharge is sent to a cyclone, with underflow to a 5-foot by 6-foot ball mill in closed circuit. Cyclone overflow feeds the lead oxide sulphide circuit.
Sulphide Flotation
The sulphide circuit consists of six rougher cells, with the first two serving as conditioners. The available flowsheet indicates a sulphide cleaner circuit is contemplated but not yet installed. Concentrate from the final four cells is sent to the lead concentrate thickener, where it is mixed with lead concentrate from the polymetallic circuit. Sulphide circuit tails become the feed for the lead oxide circuit.
Oxide Flotation
The lead oxide circuit uses two rougher stages, three rougher-scavenger stages, two cleaner stages, and one cleaner-scavenger stage. Conditioners are employed before the first rougher, first rougher-scavenger, and first cleaner. Third rougher-scavenger tails are sent to the tailings thickener, where they are mixed with polymetallic circuit tailings before being pumped to disposal. Second cleaner concentrate is pumped to the lead oxide concentrate thickener.
Thickening and Filtration
Four concentrates (lead sulphide, copper, zinc, and lead oxide) and final tailings are sent to separate thickeners. Underflows from the concentrate thickeners are filtered using drum filters and filter presses. Tailings thickener underflow is sent through two tailings lines, each with a dedicated pump, to the tails dam. A third standby pump can serve either line.
Reagents and Consumables
The two milling circuits share some reagents and grinding media, though most are used in only one circuit. The polymetallic circuit treats both PM and copper ores with somewhat different reagent schemes, but separate consumptions are not available. Annual reagent usage for 2011 is reported, with notable consumptions including: zinc sulphate (366,800 kg), copper sulphate (110,300 kg), sodium cyanide (83,600 kg), and sodium sulphide (850,000 kg for the lead oxide circuit). Grinding media consumption includes various ball sizes and 3-inch rods.
Key reported parameters
| Parameter | Value | Unit | Basis |
|---|---|---|---|
| Mill throughput (2011) | 816,289 | tonnes | Historical operating data |
| Mill throughput (2010) | 837,048 | tonnes | Historical operating data |
| PM ore head grade – Pb (2011) | 2.19 | % | Historical operating data |
| PM ore head grade – Cu (2011) | 0.65 | % | Historical operating data |
| PM ore head grade – Zn (2011) | 4.6 | % | Historical operating data |
| Copper ore head grade – Cu (2011) | 2.35 | % | Historical operating data |
| PbOx ore head grade – Pb (2011) | 6.75 | % | Historical operating data |
| PM circuit Cu recovery (2011) | 58.1 | % | Historical operating data |
| PM circuit Pb recovery (2011) | 78.8 | % | Historical operating data |
| PM circuit Zn recovery (2011) | 88.6 | % | Historical operating data |
| Copper ore Cu recovery (2011) | 90.06 | % | Historical operating data |
| PbOx circuit Pb recovery – oxide (2011) | 50.73 | % | Historical operating data |
| Total power usage (2011) | 22,817,152 | kWh | Historical operating data |
| Mill operating cost (2011) | 9.48 | $/t | Historical operating data |
| Mill operating cost (2010) | 8.36 | $/t | Historical operating data |
Project website: https://www.mining.com/sierra-metals-yauricocha-mine-in-peru-hits-full-production/
Technical qualifications
Specific limitations from the report include: gold assays for 2011 and 2012 are not presented due to unit conversion errors and mathematical inconsistencies in the supplied data; silver assays for 2011 and 2012 are not reported due to these same issues; impurity elements such as arsenic and antimony are not routinely monitored in the mill; gold has not been tracked in the mill until recently; PM and copper ore reagent consumptions are not available separately; and the feed-recovery estimation equation for copper from copper ore exhibits nonstandard behavior where recovery decreases as feed grade increases, suggesting possible circuit overloading.
Source: Yauricocha Property NI 43-101 Technical Report, October 19, 2012, Sections 17.1–17.3, 17.5.
