Engineering & Mining Journal

MAY 2017

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48 E&MJ; • MAY 2017 www.e-mj.com PROCESSING SOLUTIONS Rana Gruber, a Norwegian company that operates an iron ore mine and concentra- tor near the Arctic Circle, recently ordered two of FLSmidth's Refl ux RCTM-3000- HY-SS Classifi er units following success- ful pilot trials. FLSmidth reported that in the pilot trials conducted at Rana Gruber's facility, the Refl ux classifi er technology demon- strated consistent separation and high separation effi ciency in the 0–150 mi- crometer (µm) size fraction from material currently discarded to tailings. While the ore grade of the feed to the Refl ux classi- fi er was approximately 10% Fe, the concentrate produced by the Refl ux classifi er was more than 60% Fe, with a yield of more than 20% of the iron in the 0–150 µm size fraction that is currently lost to waste. According to the company, its Refl ux classifi er technology is attracting inter- est for iron ore applications because of its high separation effi ciency and the ability to easily handle varying feed con- ditions when compared with traditional gravity separation technology. FLSmidth offers commercial units ranging from the RC850 up the RC3000 models. Andrew Dixon, sales director–EME- NA, noted the results achieved with RC technology are derived from greater pro- cess fl exibility in operation and high re- covery compared with available alterna- tives. "RC incorporates a 'laminar high shear rate' mechanism, which represents the latest in fi ne particle gravity-based separation technology," he said. "The lamella section enhances the Refl ux classifi er's capacity, producing a more compact, higher effi cient separation unit when compared to competing iron ore and mineral processing equipment such as spirals, up-current classifi ers and tee- ter bed separators." As explained in FLSmidth's product literature, a Refl ux classifi er separates small particles based on a difference in density or particle size. The feed distrib- utor delivers the slurry into the Refl ux classifer mixing chamber. The slurry in- side the Refl ux classifi er then undergoes a sorting process due to the force of grav- ity and the up fl ow of fl uidization water. At the bottom of the mixing chamber, a higher density bed of settling solids is formed. The high-density bed is kept in suspension by jets of incoming fl uidiza- tion water at the base of the chamber. The coarse and fi ne low-density parti- cles that may be trapped in the dense fl uidized bed tend to be sorted upward due to the turbulent motion created by the fl uidization water injected from be- low. The high-density particles sink to the bottom of the fl uidized bed due to gravity and migrate to the central under- fl ow valve. The density of the middle section of the mixing chamber is measured and used to determine when to allow high- density solids to be discharged from the bottom of the Refl ux classifi er fl uid- ization chamber via the central under- fl ow valve. The low-density particles are held in the slurry suspension and migrate to the lamella section of the Refl ux classifi er. The lamella channels enhance the set- tling rate of any misplaced fi ne high-den- sity solids, which slide down the plates and slowly re-circulate back into the feed zone of the mixing chamber. This forms a slightly higher density zone under the lamella plates. The low- density and small particles tend to overfl ow from the Refl ux classifi er Lamellas in their fi rst pass, whereas the slightly denser and larger particles will require the autogenous pro- cess density within the vessel to rise to enable them to be displaced to overfl ow. The overfl ow from the Refl ux classifi er contains most of the process water, the low- density solids and any misplaced slimes in the feed. Rana Gruber operates the Kvanne- vann underground mine in Norway's Dunderland Valley as well as satellite deposits, which are mined by open-pit methods. Ore from the mining operations New Process Technologies Help Producers Recover More Metal FLSmidth says its Refl ux Classifi er technology, pictured here, can offer better recovery results through greater process fl exibility. Model capacities range from 20 t/h to 200 t/h.

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