Monument Mining's November 2011 technical report on the Mengapur project describes a historic flowsheet with three-stage crushing, two 5 m by 7 m ball mills, copper and pyrrhotite flotation and a tailings dam sized for 23 years.
Mengapur is a copper and iron sulphide project in Malaysia, covered by a Monument Mining Limited technical report dated November 2011 and prepared by Snowden. The report compiles historic information supplied to Snowden by Monument, and the report says all economic assessments and resource statements in it are historic in nature, with no certainty that any economic assessments will be realized. Mineralogical and methodological test work between 1988 and 1993, reported in Volume 5 of a definitive feasibility study, tested the sulphide ore against several process options, and a pilot plant was built for bulk testing. The most viable route, after technical and economic evaluation, produces a copper concentrate and a pyrrhotite concentrate by conventional crushing, grinding and flotation. Copper concentrate would be sold for direct smelting, while pyrrhotite concentrate would be roasted to make sulphur dioxide gas.
Critical Data
| Parameter | Value | Unit | Notes |
|---|---|---|---|
| ROM hopper | 100 | m3 | Fed by 40 to 44 t haul trucks |
| ROM stockpile | 50,000 | t | Reclaimed by front-end loader |
| Jaw crusher | 2000 x 1500 | mm | Single toggle, 200 mm close side setting |
| Secondary cone crusher | 1500 | mm | 32 mm close side setting, open circuit |
| Tertiary cone crushers | 2 | x 1500 mm | 10 mm close side setting, closed circuit |
| Product screen | 3 x 6.1 | m double deck | 25 mm top, 10 mm product screen |
| Fine ore stockpile | 7,000 | t live | Minus 10 mm |
| Ball mills | 2 | x 5 m x 7 m | Overflow, in parallel |
| Cyclones | 4 | x 660 mm | Underflow to a flash cell |
| Flash flotation cell | 28 | m3 | Outokumpu |
| Cyclone overflow | 80% passing 125 | µm | 35% solids |
| Copper rougher cells | 5 | x 16 m3 | Outokumpu, pH 11.5 |
| Regrind | 80 to 45 | µm P80 | Closed with hydrocyclones |
| Pyrrhotite flotation pH | 5.7 | pH | Sulphuric acid |
| Pyrrhotite rougher and scavenger cells | 9 | x 38 m3 | Plus two cleaning columns |
| Cleaner columns | 3.66 x 15 | m | Pyrrhotite |
| Tailings thickener | 20 | m | Dewaters to 55% solids |
| Pyrrhotite moisture | Under 8.5 | % | Transportable limit 9.5% |
| Tailings storage | 23 | years | About 2.0 Mt annually |
Overview
The concentrator would be at Mengapur and would make a copper concentrate and a pyrrhotite concentrate. Pyrrhotite concentrate would be treated further by roasting to generate sulphur dioxide, with an acid plant converting the roaster gas to sulphuric acid. The sulphuric acid would be processed to phosphoric acid using imported phosphate rock and exported overseas. The by-products, phosphogypsum and calcine cinder, would be sold to local and overseas buyers. Heat from roasting and acid manufacture would be recovered as steam and converted to electricity, with surplus power sold to the national grid supplier TNB.
Key Process Stages
Crushing
Haul trucks tip onto a 1.3 m grizzly above a 100 m3 ROM hopper, and a 50,000 t ROM stockpile area stores ore. A 2.4 m by 6 m vibrating grizzly feeder passes fines of minus 150 mm directly to a conveyor, while oversize feeds a single toggle jaw crusher. Jaw product goes to an open circuit secondary cone crusher, then to a 3 m by 6.1 m double deck screen with 25 mm top and 10 mm product apertures. Oversize goes to a tertiary hopper with two parallel tertiary cone crushers in closed circuit, and minus 10 mm screen product goes to a 7,000 t live fine ore stockpile. Tramp metal magnets and metal detectors protect the cone crushers.
Grinding
Ore is reclaimed from the fine ore stockpile in a tunnel through two static slots and a vibrating discharger, with feed rate controlled by a weightometer. Two overflow ball mills of 5 m by 7 m run in parallel into a common cyclone feed hopper and a cluster of four 660 mm classifying cyclones. Cyclone underflow is diluted and fed to a 28 m3 Outokumpu flash flotation cell, whose copper concentrate may be cleaned or sent straight to the copper thickener, and whose tails return to the ball mills. Cyclone overflow at 35% solids and 80% passing 125 microns gravitates to flotation.
Copper and pyrrhotite flotation
Five 16 m3 Outokumpu rougher cells float copper, and lime conditions the pulp to pH 11.5 before the regrind mill grinds the concentrate from 80 to 45 µm in closed circuit with hydrocyclones. The product goes to a copper cleaner column, with cleaner tails returned to the roughers. Copper rougher tailings go to a conditioning tank where sulphuric acid brings the pH to 5.7, and nine 38 m3 pyrrhotite rougher and scavenger cells follow. Rougher concentrate goes to two parallel cleaning columns, and their tails go to a cleaner scavenger column cell whose concentrate returns to the cleaners. Pyrrhotite rougher tailings and cleaner scavenger tails are the final tails.
Reagents and control
Copper sulphate, potassium amyl xanthate, sodium ethyl xanthate and lime are mixed to 10% solutions, Cyanamid AP3418 and AF208 and MIBC are held in drums, and weak sulphuric acid from the Kuantan acid plant is stored in a holding tank. Most reagent control is manual, by rotameter, while lime and acid additions are automatically controlled by pH measurement. An in-stream analysis system monitors copper and iron concentrations and pulp density in various streams.
Thickening, filtration and tailings
Flotation tailings are dewatered to 55% solids in a 20 m thickener. Copper and pyrrhotite concentrates are thickened in 3 m and 10 m thickeners to 65% solids and filtered, pyrrhotite on two Lasta plate and frame pressure filters with a compressed air blow to reach under 8.5% moisture, and copper on a single dedicated 16 m2 pressure filter. A total of 770 m2 of filtering area is required to stay under the transportable moisture limit of 9.5%. The tailings storage is designed for 23 years of production, about 2.0 Mt a year or 46 Mt over a 25 year period, at 1.6 t/m3.
Additional Interesting Data and Summary
The main embankment would be built in two stages, with the first stage holding the first five years of tailings and a staged temporary spillway system maintained during construction. Hydrological studies show that a 200 ML water storage is needed in the two-year pre-production phase to secure process water before start-up.
Concentrates are loaded from stockpiles by front-end loader for transport to the roaster or to port.
Key Processes
- Three-stage crushing with magnets and metal detectors
- Parallel overflow ball milling with flash flotation of copper
- Copper rougher flotation, regrinding and column cleaning
- Acid-conditioned pyrrhotite flotation with column cleaners
- Thickening and pressure filtration of concentrates
- Roasting of pyrrhotite for sulphuric acid
- Embankment tailings storage
Source: Monument Mining Limited: Mengapur Project, Technical Report, November 2011.
Project website: Mengapur Project
