Xstrata-Nickel: Tailings Intake

Posted in: , on 21. Feb. 2011 - 20:33

Xstrata-Nickel: Tailings Intake - Safely Solving a Sticky Problem

Ely, February 2011 - Canadian miner Xstrata-Nickel has installed two heavy-duty „sub-surface B&W SamsonTM Feeders to intake mine tailings at its Nickel Rim South mine site in the Sudbury Basin located in northern Ontario. This is the first Canadian installation for the UK based B&W Mechanical Handling Ltd. The sub-surface concept has been extensively developed for under rail applications and designated type SUR. As a track-hopper-feeder the benefits that make the Samson concept attractive are equally valid. But it is in particular the shallow pit depth that is highly desirable in any areas where the ground conditions are challenging; especially in ports where the ground water table is high and water ingress to deep pits is often a major operational hazard.

Tailings, or leach residues, are the materials left over after the process of separating the valuable fraction from the worthless fraction of an ore. The material may be recovered from tailings dams and has a typical density range of 1.4 to 1.8 tons per cubic meter with a moisture content ranging from 2 to 18% depending upon location and weather. Mostly the moisture content is at the high end of the spectrum and as a result the material is extremely cohesive and does not flow well and is very prone to bridging and blockage during handling, particularly in transfer chutes and tapered hoppers.

Classified Tailings are brought from the Strathcona Mill, 85 kilometres distant or legacy tailings from the nearby Nickel Rim North Site in various tipping and self-discharging 40 tons capacity trucks to the new processing plant which is part of Xstratas ongoing sustainability initiatives. The tailings are screened and processed for backfill into the mine shafts representing an environmentally friendly solution to this age old issue of tailings disposal contributing to Xstratas environmental performance and design which continues to surpass project targets and industry standards.

One of the specialised road trucks is fitted with a movable body for effective weight distribution over the eight carrying axles and a system to move the body to the end of the trailer for discharge. These are not tipping vehicles but feature a moving bulkhead within the tubular body which is forced back towards the end of the trailer to discharge the load. These vehicles are very difficult to manoeuvre in a confined space. For this reason Xstrata preferred the “drive-over-tip” intake arrangement. In this design the truck moves forward over the feeder such that only when the truck is in the discharge position is the feeder intake revealed. B&W offered this customised solution based on the drive-over-tip concept developed originally for the intake of fuels and clays in the cement industry. For handling wet and sticky materials the SamsonTM is the ideal solution with a belt width greater than the stored material depth and with near vertical hopper sides there is no risk of bridging or blockage. This design principle combined with the deflected chassis arrangement permits a shallow excavation depth, reducing civil works costs and complications, and a simplified transfer to the following belt conveyors.

To control the volumetric discharge rate from the SamsonTM a levelling blade at the discharge controls, the material bed depth and a variable speed (VFD) drive system permits adjustment of the final output rate by varying the belt speed and therefore the output, in line with the process demands. Considering the material characteristics a rotating Picker shaft is provided at the discharge to break up agglomerated slabs and ensure a continuous output.

For the Xstrata project two sub-floor feeders were supplied installed in parallel and each arranged to discharge to a separate belt conveyor. The SamsonTM 1600 Series have an entry capacity of 30 cubic metres to receive the entire truck contents. The length of the feeders is stagger at 7 metres and 9 metres allowing the units to discharge onto two parallel conveyors running at 90 degrees and thus allowing near vertical transfer chutes to minimise risk of blockage between the SamsonTM and the conveyor feed boot. Each SamsonTM is designed for a discharge rate of 200 m3 per hour and at this rate either unit can satisfy the plant demand offering 100% redundancy in operation.

The plant is designed to run continuously 24/7 and the feeders are required to receive all types of tailings under all operating conditions with an ambient temperature of plus 30 degrees C. in the summer months and down to minus 30 degrees C. in the winter. In these extremes of weather the condition of the tailings, the legacy tailings in particular, will be very variable and often frozen in blocks.

As a result of the wide belt technology the free fall distance from the truck body to the belt is minimised. With that the velocity of the displaced air is significantly reduced. Therefore for dry materials dust generation is mitigated also and very often no dust plant is required.

This new project for Xstrata-Nickel demonstrates the clear benefits of the SamsonTM concept handling this most difficult of bulk materials in a professional environment where reliability and availability are paramount.

About Xstrata-Nickel

Xstrata-Nickels Sudbury operations consist of the Nickel Rim South mine, Fraser Copper mine, a mill and a smelter. The facilities are spread throughout the 60 kilometre, oval-shaped geological formation known as the Sudbury Basin. Nickel and copper are the primary metals but cobalt and precious metals, such as platinum are also produced.

Nickel Rim South was discovered in 2001 and is expected to provide high value ore feed for more than 15 years. The project is located nine kilometres north of the Sudbury smelter. Full mine production was achieved in 2010.

About B&W Mechanical Handling

B&W enjoys the benefits of being fully integrated into the substantial and respected International Aumund Group with strategically placed offices in more than 10 countries and representatives in over 40. The bulk handling specialists have over 500 installed SamsonTM feeder units around the Globe with more than 40 of them installed underground handling a wide variety of materials including sugar, coal and petroleum coke, cement clinker, gypsum, iron ore and blast furnace slag to name but a few.

About the AUMUND Group

The AUMUND Group is active on four continents. The conveying and storage specialists have special expertise at their disposal when dealing with bulk materials. With their high degree of individuality, both its technically sophisticated as well as innovative products have contributed to the AUMUND Group today being a market leader in many areas of conveying and storage technology. The manufacturing companies AUMUND Förder- technik GmbH, SCHADE Lagertechnik GmbH, B&W Mechanical Handling Ltd. as well as AUMUND Logistik GmbH are consolidated under the umbrella of the AUMUND Group. In conjunction with the headquarters of the manufacturing companies, the global conveying and storage technology business is spearheaded by a total of eight locations in Asia, Europe, North and South America.

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