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FLOTATION Pneumatic flotation systems—which don't require any rotational components—are designed to mix air and pulp in a continuous stream, maximize air bubble size as it is fed into the pulp, and allow the highest possible number of particle/bubble collisions for better recovery. same equipment can be used for all flota- tion stages, from rougher through cleaner to scavenger. The technology is widely accepted by coal, potash and iron ore pro- ducers, with trials having taken place for other minerals. However, pumping and feed-sump designs need to be done prop- erly to ensure a successful application. Testwork Options Following successful applications in ferrous metals, there has been increased interest in Pneuflot from the base- and precious- metals industries. The technology consis- tently delivers higher selectivity compared to conventional agitator-flotation systems, and higher recoveries in fewer stages than column flotation. Because of this, MBE- CMT has been receiving more requests from its customers for pilot-plant testing for base- and precious-metal applications, fol- lowing on from bench-scale testwork. Before an industrial-scale flotation plant can be designed, laboratory-scale testwork and—where possible—semi- industrial pilot testwork is needed. The pilot plant can be installed anywhere in an existing circuit as a 'plug and play' system, and the results generated can be scaled up directly to a full-scale application. Responding to its customers' requests, MBE-CMT now offers a full on-site testing program. The Pneuflot laboratory machine has a 50-liter-capacity conditioning agitator tank and can handle feed rates of 300– 400 liter/h, while the pilot-plant version has a 2 m3 agitated feed/conditioning tank. Ore- based testwork typically uses a feed con- centration of 400 g/liter, with 20 kg of feed material being needed for each test run on the laboratory machine, rising to 400– 800 kg for the pilot-scale unit. www.e-mj.com Scaling Up for Industrial Applications Since the early 1990s, Pneuflot systems have been commissioned successfully for industrial minerals, non-ferrous ores, iron ore, rock salt and potash. MBE-CMT pro- duces industrial-scale machines in sizes ranging in diameter from 800 mm to 6 m. Slurry feed rates of 10–1,400 m3/h (4–560 mt/h of dry solids) can be processed in a single cell, depending on its diameter. The number of cells required for each stage of the flotation process (rougher, scavenger and cleaner) is calculated from the testwork results, with the company designing the flowsheet accordingly. Pneuflot technology works very effectively at lower operating costs than for column or mechanical-agitator flotation, producing high- er yields and metallurgical recoveries, espe- cially when used on ultra-fine feed material. Turbulence in a Pneuflot cell is comparative- ly low, and the bubble size range in the self- aspirated aerator can be reduced by changing the feed-slurry rate—using a frequency con- verter on the motor's power supply. Treating the final tails from existing flota- tion plants can present major challenges that a Pneuflot system can help to overcome. For example, using a Pneuflot unit has upgraded a 0.2-g/mt gold tailings feed to 5 g/mt gold at 2% yield and 18% metallurgical recovery. Similarly, the technology has been used to treat ultra-fine platinum ore grading 5.1 g/mt (0.15 oz/ton) that could not be processed using conventional technology to give 20 oz/ton in the final concentrate. Proving its Case MBE-CMT's sister companies and the main research institutes have successfully in- stalled laboratory testwork-scale Pneuflot machines in Brazil, South Africa and Russia, with MBE-CMT holding a large database of lab- and semi-industrial-scale test results for a variety of different minerals. As an exam- ple of the testwork that the company can undertake, one of its customers asked for its help after experiencing high gold losses in a copper oxide flotation circuit. In the test- work, the samples were ground sequentially, then run through flotation. In the first run, the ore was treated using a Humboldt Wedag-type agitator flotation machine, which recovered 30 g/mt of gold after one rougher stage (d100 = 71 µm) followed by two cleaner stages. Metallurgical recovery was 47.3%. The same type of ore was then run through a lab-scale MBE-CMT Pneuflot cell, using the same reagent regime. A rougher and two scavenger stages produced a concentrate grading 32 g/mt gold at and 92% metallur- gical gold recovery, with subsequent semi- industrial pilot tests having confirmed the results of Pneuflot lab testwork. Testwork using pneumatic flotation from deposits in North America, Brazil, Chile, Russia, South Africa, Namibia, Kazakhstan and China is reporting results that should offer food for thought for operators in the base- and precious-metals industries. Technical advantages such as the wide range of bubble sizes, online control of the froth level and turbulence-free flotation make Pneuflot a technical leader. Evren Ören is a process development man- ager and Lutz Markworth is a senior process engineer with MBE Coal & Minerals Technology GmbH in Germany. John van der Heever is a process and pro- duct-development manager for MBE Minerals SA in South Africa. NOVEMBER 2012 • E&MJ; 61