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MEI Online: Plant Operation News: Australasia: March 24th 2009


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:: Solutions for Angas Mine

Angas Mine exceeds all production start-up expectations by using the latest technology in Ceramec filters, which is drying higher than expected grades of zinc and lead concentrate.

In the face of the 2008/09 credit crunch, Angas Mine in South Australia (SA) is outperforming its metal recovery targets and expected mining grades for a projected 400,000 tonnes per annum of concentrate for the life of mine. Full production capacity for the new lead-zinc mine was brought forward by six months to January 2009.

Aided by a lean start-up and lower consumable costs for grinding, milling reagents, diesel, as well as lower costs for smelting and shipping, the mine's site operating cash costs for 2009 have now been revised downwards, despite a weaker Australian dollar.

The Angas zinc mine is one of Terramin Australia Pty Ltd's base metal projects selected for its high grade ore, proximity to infrastructure such as ports, roads, water and power, and potential for expansion. Sempra Metals and Concentrates Corporation holds a life-of-mine off take for Angas's concentrate, forecasted to be 60,000 tonnes per annum for zinc and 22,000 tonnes per annum for lead.

In its first year of life, the lowcost mine with a resource of 2.4 million tonnes and situated only 60 kilometres (i.e. 45 minutes) from Adelaide, has produced nearly 23,000 tonnes of high-grade lead and zinc concentrate by the end of its second quarter.

The transporting of lead and zinc concentrate commenced shortly after the mine's commissioning on 18 July 2008. Lead concentrate is being trucked to Port Pirie's smelter while zinc concentrate is delivered to Port Adelaide before shipping to Korea.

Stringent mine and rehabilitation plan conditions for Angas mine are helping to reduce the potential of any impact on a nearby local development Strathalbyn. Noise levels cannot exceed 47 dB by day or 40 dB by night. Groundwater contamination is minimised by the containment of processing waste in a state-of-theart tailings storage facility, valued at AU$7.5M with double-lined high density polyethylene (HDPE) and sized for mine expansion.

The South Australian Centre for Economic Studies predicts that Angas's initial seven-year mine life, with its 64 site-based roles and future expansion possibilities, will boost the local economy by $29M per annum.

The mine's remarkable start-up performance far exceeds expectations and is due in part, to an advanced filtering and drying system for the two concentrates, supplied and serviced by Larox Corporation. Angas's installation of two Ceramec- filters, fed by two Larox peristaltic rollercompressing pumps, is proving to be an excellent dewatering investment.

While sized for expansion and variable production rates, the two Ceramec filter systems 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.

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

After slurry thickening, the Larox 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 into slurry baths and dewatering starts immediately via capillary action. Extracted filtrate passes through microporous holes 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.

Larox has undertaken extensive work to develop its Ceramec filters as top performers in the global mineral, metallurgical and mining markets.

Now the latest Ceramec filter, with new ultrasonic positioning between the disks, is being utilised by Angas at rates of 75% to 90% over a 24-hour period, depending on the ore grade being received.

Angas's general manager John Burgess initially planned to install Larox pressure filters instead of Ceramec filters after he experienced optimisation issues with an earlier version of Ceramec filters at Broken Hill in 1985. Once convinced by extensive tests and other site successes that the latest Ceramec filter would be ideal for Angas, John Burgess installed a Ceramec disc filter model CC30 (i.e. 30 m2 filter area) for the zinc and model CC6/15 (i.e. 6 m2 filter area; expandable to 15 m2) for the lead.

When lead grades rose higher than expected soon after installation, Larox suggested to Angas a filter upgrade from the CC6/15 to a CC9/15 would provide the greatest economical expansion benefit. The extra disk, now installed, is providing Angas with a 30% increase in filtration capacity, allowing for the handling of higher lead when the ore grade is high. As a result of this upgrade, the lead filter can capably handle higher lead head grade and increase production while still producing filter cake under the required TML.

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 Angas mine is doing for Terramin's development of its large Tala Hamza zinc deposit in Algeria.

The many benefits of using Ceramec filters and Larox peristaltic pumps are being realized at Angas mine as well as other sites. The benefits include a plug-and-play design, no downturn is required for maintaining filter disks, only once-a-month maintenance checks are needed for filter ultrasonics and seals, routine filter backwashing is automatic and takes only half an hour per shift, 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.




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