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Angas Zinc mine exceeds start-up expectations

The Angas Zinc Mine, located in South Australia, is 100% owned and operated by Terramin Australia Ltd. The mine exceeded all production start-up expectations by using technology in Outotec Larox CC filters (formerly Larox Ceramec capillary action disc filters), which is drying higher than expected grades of zinc and lead concentrate.

Following commissioning in July 2008, site was brought into full production six months early, in January 2009. In its first year of life, the low-cost mine, with a resource of 2.4 million tonnes and situated only 60 kilometres from Adelaide, has produced nearly 23,000 tonnes of high-grade lead and zinc concentrate by the end of its second quarter.

The mine’s start-up performance exceeded expectations and is due in part to an advanced filtering and drying system. Angas’s installation of two Outotec Larox CC filters (formerly Larox Ceramec capillary action disc filters) for its zinc and lead concentrators, is fed by two Larox Flowsys peristaltic pumps.

The feed pumps employ a single, bearing-mounted eccentric roller design that compresses each hose once during a 360 degree operating cycle. This feature reduces the hose compressions required by 50%, when compared to traditional peristaltic pumps that use two sliding shoes.

The two Outotec Larox CC filters in situ use capillary action within ceramic disks to dewater the lead and zinc concentrates. The extracted filtrates are very high in clarity while the dried filter cakes meet required transport moisture limits (TMLs) for their ore grades. After slurry thickening, the pumps feed the relatively coarse lead (P80, 50μm) and zinc (P80, 71μm) concentrates into their respective filtering system.

Here, concentrates coat the ceramic disk segments during immersion in slurry baths, dewatering starts immediately via capillary action. Extracted filtrate passes through the microporous structure in each disk before being transferred away by a small 2.2 kW vacuum pump. The dried filter cake that remains is continuously scraped off as the disks rotate.

When lead grades rose higher than expected soon after installation, the filters were quickly upgraded, providing Angas with a 30% increase in filtration capacity, allowing the handling of higher lead concentrates when the ore grade is high. As a result of this upgrade, the lead filter can capably handle higher lead head grade ore and increase production while still producing filter cake under the required TML.

The Outotec Larox CC filter has undergone extensive development to establish itself as a top performer in the global mineral, metallurgical and mining market. This filter, with new ultrasonic positioning between the disks, is currently being utilised by Angas at rates of 75% to 90% over a 24-hour period, depending on the ore grade being received.

The many benefits of using the Outotec Larox CC filters and Larox Flowsys Peristaltic include a plug-and-play design, no downtime is required for maintaining filter disks, only once-a-month maintenance checks are needed for filter ultrasonics and seals, and routine filter backwashing is automatic and takes only half an hour per shift.

Also feed pump hose leaks can be easily detected, revolution counters can record pump hose life (thereby reducing unscheduled stoppages) and processing noise levels can be kept to a minimum.
Angas’s general manager John Burgess reports he is “pleasantly surprised” at the ongoing performance of his dewatering system.

“It’s a good mine that is professionally set out and producing on its investment because things are done right”. So much so in fact, that the Algerian government is interested in what Terramin are doing at the Angas mine for Terramin’s development of its large Tala Hamza zinc deposit in Algeria.

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