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:: Talvivaara's Primary Crushing Capacity Boosted by Crusher Cavity Optimization
Talvivaara mine, located in Northern Finland, is today the biggest sulfide nickel ore mine in Europe. In close cooperation with Metso, and with crusher cavity optimization, Talvivaara recently boosted its primary crushing capacity annually by up to 3.5 million tons.
An open pit nickel deposit with 0.22% average content, Talvivaara is a mine of many superlatives. Today, about 22 million tons of nickel ore is excavated at the mine annually. Using bioheapleaching, the mine currently produces 30,000 tons of metallic nickel per year.
After huge, up to 300,000-ton blasts, the feed material is dumped into the primary gyratory crusher and then transported along a more than two kilometer long conveyor to the secondary and tertiary crushing stages. After activating the ore, bioheapleaching of the ore takes place in four piles, each 400 x 1200 meters in size. The natural bacteria are used to extract the nickel out of the ore.
The nickel ore in Talvivaara is hidden inside black schist, which is extremely slippery material to crush. Already the first crushing test indicated that normal capacities would not be easily achievable.
After installing the huge 60 x 89 inch primary gyratory crusher, it immediately became apparent that the capacity would fall far behind the planned capacities. For the total mine economy, this presented a real challenge.
"Our main problem was caused by the profile of the original crusher wear mantle. Its cavity was not the right one for processing slippery ore, and it caused the feed material to jump up from the cavity, thus decreasing the capacity," explains Erkki Kärkkäinen, Manager of Materials Handling at Talvivaara mine.
In order to quickly find a solution to the primary crusher cavity issue, Talvivaara contacted Metso's crusher wear parts specialists at the Tampere office in Finland. The task presented was to find a cavity that can better process the slippery ore and guarantee the capacities required for the mine economy.
"Actually, we studied all of our crushing-related parameters with Metso in order to find the right solution. Throughout the entire development process, our cooperation has been very open and honest," recalls Jyrki Lahenius, Department Engineer, ore processing, at Talvivaara.
After several meetings, using Metso's crusher cavity optimization process know-how, including 3D mantle design tools, the right angle for the mantle cavity was found, and the suitable manganese type selected. Metso's Tampere foundry casted the huge, two-piece wear mantles in the spring of 2010.
In May of 2010, the Metso mantles and outer wear parts were installed into the primary gyratory. After crushing for 8 months, the results are quite positive. The primary crushing capacity has increased by an average of 15%.
Given as a percentage, the increase sounds quite modest. However, when calculating the annual capacity increase, Erkki Kärkkäinen ends up with a figure of 3.5 million tons of extra capacity.
In terms of hourly capacities, the primary gyratory's original capacity during test drive was under 3,000 tons, and, after installing the Metso wear parts, it is about 3,500 tons per hour.
"I believe that with more efficient feeding, we can achieve a continuous production that exceeds 3,000 tons per hour. We currently feed the crusher using big Hitachi dump trucks, dumping 150 tons of ore into the crusher every 2.5 minutes," says Kärkkäinen.
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