Kipushi 2022 Feasibility Study Designs an 800 ktpa Concentrator That Pre-Concentrates High-Grade Zinc Ore by DMS Before a Single Bulk Flotation Stage

Ivanhoe Mines' 2022 feasibility study for the Kipushi zinc-copper mine in the Democratic Republic of Congo builds a new plant on the brownfield Kipushi site. It treats ore hoisted up the refurbished P5 shaft and makes a bagged zinc concentrate.

The Kipushi 2022 Feasibility Study was prepared for Ivanhoe Mines Limited by OreWin, The MSA Group, SRK Consulting (South Africa) and others. Its recovery methods cover the new Kipushi Corporation SA (KICO) concentrator, designed for a nominal 800,000 t a year of run-of-mine ore from the high-grade zinc zone of the underground mine. Testwork showed the ore suits pre-concentration by dense media separation (DMS) followed by bulk flotation. The plant is built at the existing Kipushi Mine facility, where free space is limited. The layout aims for safe ore transfer from the P5 shaft, minimal demolition of existing structures, little pumping and efficient product dispatch. The design feed grade averages 31.9% Zn and 0.7% Cu.

Critical Data

Overview

Ore and waste are crushed underground to a top size of 280 mm, hoisted up P5 and conveyed over existing and new overland conveyors to separate ore and waste stockpiles at the old Kipushi concentrator. A front-end loader feeds a two-stage crushing plant set up to limit fines. The –12 +1 mm fraction goes to DMS, and the –1 mm fines and DMS effluent go to a fines circuit. DMS sinks are ground in a single ball mill. Mill product and thickened fines go to one bulk sulphide flotation stage, which recovers zinc and rejects pyrite and dolomite. Zinc concentrate is thickened, filtered and bagged. Flotation tails are thickened and pumped to the tailings storage facility (TSF). DMS floats and development waste are used as stope backfill.

Key Process Stages

Ore transfer. Crushed ore and waste are hoisted separately into one bin in the P5 headframe. A vibrating feeder and the 900 m overland conveyor T5A, with transfer conveyors T5 to T8, carry them away. A movable tripper on T8 places waste and ore on separate stockpiles.

Crushing and DMS. An open-circuit secondary jaw crusher and a closed-circuit tertiary cone crusher limit fines generation. Screens send –12 +1 mm feed to the DMS cyclones. Sinks report to the cyclone underflow, are washed of ferrosilicon and conveyed to the mill feed bin. Floats go to a discard stockpile. Densifiers and magnetic drums control the medium density.

Fines handling. DMS effluent and –1 mm fines are cycloned. The overflow is thickened to 55% solids and sent through a trash screen to flotation conditioning, and the underflow goes to the mill discharge sump.

Milling and flotation. The variable-speed ball mill is closed with cyclones at P80 106 µm. Five 20 m³ cells give 25 minutes of bulk rougher flotation at pH 11.5 to depress pyrite. SIPX collector, copper sulphate to activate sphalerite and MIBC frother are used. Most of the copper and lead float with the zinc.

Concentrate and tailings. Concentrate is thickened at a design solids flux of 6 t/m²/day and filtered at 406 kg/m²/h to a 9% moisture cake. It is bagged in a semi-automated facility, and each bag is sampled and tagged before dispatch. Tailings are thickened and pumped to the TSF.

Water. Underground water from P5 hurt metallurgical performance in testwork, so it is used only for flushing, hosing and dust suppression. Potable water from the existing borehole field supplies process top-up, gland service and reagent make-up.

Additional Interesting Data and Summary

Design assumptions include little or no clay in the ore, and DMS concentrate milling like run-of-mine ore. The concentrate is assumed to be free flowing, non-reactive and not to age harden.

In summary, the 2022 Kipushi feasibility study uses the very high zinc grade of the deposit with a compact 800 ktpa plant. DMS rejects light gangue before milling, and a single bulk flotation stage produces a saleable zinc concentrate.

Key Processes

• Underground primary crushing and shaft hoisting
• Two-stage surface crushing to 12 mm top size
• Dense media separation with ferrosilicon
• Fines dewatering and thickening
• Ball milling to P80 106 µm
• Single-stage bulk zinc sulphide flotation
• Concentrate thickening, tower press filtration and bagging
• Tailings thickening to the TSF and coarse waste backfill

Source: Kipushi 2022 Feasibility Study, NI 43-101 Technical Report, prepared for Ivanhoe Mines Limited by OreWin Pty Ltd, The MSA Group and others.