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Column flotation has become widely accepted throughout the minerals industry. It is no longer considered to be new or risky technology and many new concentrators have incorporated column cells into the flow sheet.
Flotation columns derive their name from the geometric shape of the vessel. Unlike conventional mechanical cells, column cells are tall vessels ranging in height from 7.6 m to over 15.2 m. The surface area of a column cell is smaller than that of a mechanical cell, promoting a stable and deep froth. An important feature of the column cell is the froth washing system, which removes unwanted impurities. Wash water added at the top filters through the froth zone displaces pulp water and entrained particles, resulting in a stable froth with improved concentrate grades.
Unlike conventional flotation cells, columns do not use mechanical agitation. Feed slurry enters the column in the upper third of the body, and descends against a rising swarm of fine bubbles generated by an air-sparging system. Targeted particles collide with, and attach to, the bubbles, and rise to the top of the column.
The Eriez Flotation Division (EFD), represented by HMA Wear Solutions, provides advanced engineering, metallurgical testing, and innovative flotation technology for the mining and minerals-processing industries. Strengths in process engineering, equipment design and fabrication have enabled EFD to assume a leadership role in meeting increasing global demands for minerals flotation systems.
Applications for EFD equipment and systems include, but are not limited to, metallic and non-metallic minerals, bitumen recovery, fine coal recovery, organic recovery (solvent extraction and electro-winning), and /silver cyanidation. The company’s product line encompasses flotation cells, gas spargers, mini-pilot plants, slurry distributors and flotation test equipment.
EFD has designed, supplied, and commissioned over 800 flotation column systems worldwide for cleaning, roughing, and scavenging applications in metallic and non-metallic processing operations. In addition, it is a leading producer of modular column flotation systems for recovering bitumen from oil sands. EFD has also made significant advances in fine coal recovery with flotation systems to recover classified and unclassified coal fines. The group’s flotation columns are used extensively in many major coal preparation plants in North America and internationally.
Designs are founded upon data collected in laboratory, pilot and plant tests, and audits of flotation rate constants, grade to recovery ratios, residence time requirements, and practical operating experience. Results are analysed and integrated into key column design parameters that include cell body geometry, height-to-diameter ratio, launder design, instrumentation selection, and the most critical element in column flotation performance and gas-sparging requirements. EFD proprietary sparging systems are recognised as an industry standard, with over 5 000 in operation globally.
EFD’s engineering capabilities provide for continuous refinement of its equipment and process systems, as well as introducing new flotation technologies to the minerals-processing industry. Recent achievements include the StackCell, which offers a reduced footprint, and reduced capital, operating, and maintenance costs for high volume applications. Placing these units in series provides recovery while allowing for a high-grade float product through froth washing.