This report outlines the proposed conventional nickel and copper flotation concentrator design for the Ntaka Hill Nickel Project as detailed in the April 13, 2012 technical report.
Report context
The processing information in this report is summarized from the "Technical Report on the Ntaka Hill Nickel Project, Lindi and Mtwara Regions, Tanzania" dated October 28, 2011. Lycopodium Minerals Pty Ltd. was engaged by Continental to develop preliminary designs along with capital and operating costs for a 1.0 Mtpa Base Case conventional nickel and copper flotation concentrator and associated infrastructure for the Project. In the absence of detailed project specific test work, a conceptual flowsheet and summary design criteria was provided by Mineralurgy as the basis of the design.
Processing route
Description of facilities
The process plant will consist of comminution, flotation and concentrate dewatering circuits, with associated services and ancillaries, rated to treat up to 1.0 Mtpa of feed and recover nickel and copper to a combined sulphide concentrate suitable for road transport to the port of Mtwara and subsequent shipping to an off-site smelting facility.
Crushing and screening
A two-stage crushing circuit has been selected and sized on the basis of a 24 hour operating day at 80% utilization, with a feed size of 100% passing 600 mm to produce a product size of 80% passing 12 mm. The crushing and screening plant will be designed and provided as a vendor package.
Crushed ore storage and reclaim
Crushed ore will be stored in a fine ore bin to minimize feed fluctuation to the downstream milling circuit, with sufficient capacity to store 12 hours of crushed mill feed material. The fine ore bin will be equipped with a side access door to allow crushed material to be reclaimed by front-end-loader to a dead stockpile. The crushed, stockpiled material will be used to feed the mill during crusher circuit scheduled maintenance periods.
Grinding and classification
Crushed ore will be reclaimed from the fine ore bin by belt feeder onto the mill feed conveyor. The grinding circuit will consist of a single ball mill in closed circuit with a cluster of cyclones. Cyclone overflow at 80% passing 75 µm will gravitate to the trash screens for grit and wood chip removal, prior to feeding the flotation circuit. Underflow from the cyclone cluster will return by gravity to the ball mill feed.
Flotation
The flotation circuit will consist of pre-aeration and conditioning, with rougher and cleaner flotation in open circuit, followed by second and third stages of cleaner flotation in closed circuit.
The cyclone overflow slurry will gravitate to an agitated tank for pre-aeration. Lime will be added to maintain the desired pH, while air will be introduced into the aeration tank to selectively oxidize any pyrrhotite surfaces and suppress its flotation properties. The slurry will gravitate from the aeration tank to an agitated conditioning tank, where collector and promoter additions will be made to the pulp, prior to feeding the rougher tank flotation cells.
Rougher flotation concentrate will be sampled and pumped to the cleaner cells, while the flotation tails will gravitate to the tails hopper. The combined rougher and cleaner tails slurry will be pumped to the tailings storage facility (TSF).
The cleaner flotation circuit will consist of tank cells and cleaner concentrate will be pumped to the recleaner cells, while the cleaner tails will gravitate to the tails hopper. The recleaner concentrate will be pumped to the final cleaner cells while the recleaner tails will gravitate back to the feed of the cleaner cells. The final cleaner concentrate will be pumped to the concentrate thickener, while the final cleaner tails will gravitate to the recleaner cells.
Concentrate dewatering and filtration
The final concentrate will be pumped to a high rate concentrate thickener. Thickener overflow will gravitate to the process water pond, while the thickener underflow will be stored in an agitated filter feed storage tank to isolate the operation of the flotation circuit from the dewatering section.
Thickened concentrate slurry will be pumped from the concentrate storage tank to a plate and frame pressure filter, located high in the concentrate storage shed. The filter cake will discharge via a concentrate discharge conveyor to the floor below for storage. Filtrate will be returned to the concentrate thickener.
Concentrate storage and out-loading
The concentrate will be reclaimed by front end loader into a reloading chute at the tail end of a retractable load-out conveyor. The load-out conveyor will load the concentrate into lined containers on trucks for transport off-site.
Reagents mixing, storage and distribution
Reagents will be delivered to site and mixed for use in batches. Reagents have been assumed to be delivered in 1,000 kg bulk bags for lime, guar and xanthate, 1,000 L bulk boxes for Aero promoter and frother and 25 kg bags for flocculant. Reagents will be distributed throughout the plant in ring-mains or metered using individual dosing pumps.
Future plant expansions
In order to optimize the initial capital cost minimal allowance has been made in the 1.0 Mtpa base case for future expansion. For future plant expansions it will be necessary to reconfigure and/or replace existing equipment and to install additional equipment for the higher throughput rates. Future plant expansions to increase throughput to 2.5 Mtpa would include modification or replacement of the crushing circuit, changes to the grinding circuit and increasing of the flotation and concentrate handling facilities in line with increased plant throughput and changes in head grade.
In general, the plant expansion from 1.0 Mtpa to 2.5 Mtpa would entail modification of the crushing circuit to single stage crushing, the addition of a semi-autogenous grinding (SAG) mill to the grinding circuit, the upgrade of the flotation circuit and minor modifications to the concentrate dewatering areas. The existing 1.0 Mtpa reagent preparation facilities would largely be reused to serve the upgraded plant.
Key reported parameters
| Parameter | Value | Basis |
|---|---|---|
| Plant feed rate | 1.0 Mtpa | Base case design |
| Crushing circuit | Two-stage | Design |
| Crushing utilization | 80% | Design basis |
| Crusher feed size | 100% passing 600 mm | Design |
| Crusher product size | 80% passing 12 mm | Design |
| Grinding circuit | Single ball mill in closed circuit with cyclones | Design |
| Cyclone overflow size | 80% passing 75 µm | Design |
| Fine ore bin capacity | 12 hours of crushed mill feed | Design |
| Flotation | Rougher and cleaner in open circuit, second and third cleaner in closed circuit | Design |
| Concentrate dewatering | High rate thickener plus plate and frame pressure filter | Design |
| Reagent delivery (lime, guar, xanthate) | 1,000 kg bulk bags | Assumed |
| Reagent delivery (Aero promoter, frother) | 1,000 L bulk boxes | Assumed |
| Reagent delivery (flocculant) | 25 kg bags | Assumed |
| Future expansion throughput | 2.5 Mtpa | Proposed expansion scenario |
Project website: https://www.mining.com/web/imx-resources-inks-60-million-joint-venture-deal-to-develop-ntaka-hill-nickel-project/
Project website: https://www.mindat.org/loc-305879.html
Technical qualifications
The processing information in this section is summarized from "Technical Report on the Ntaka Hill Nickel Project, Lindi and Mtwara Regions, Tanzania" dated October 28, 2011. The designs and information presented refer to the initial 1.0 Mtpa facility unless indicated otherwise. In the absence of detailed project specific test work, a conceptual flowsheet and summary design criteria was provided by Mineralurgy as the basis of the design. The crushing and screening plant will be designed and provided as a vendor package. Minimal allowance has been made in the 1.0 Mtpa base case for future expansion.
Source: Technical Report on the Ntaka Hill Nickel Project, Lindi and Mtwara Regions, Tanzania, dated October 28, 2011; Technical Report NI 43-101, April 13, 2012.
