Engineering & Mining Journal

NOV 2018

Engineering and Mining Journal - Whether the market is copper, gold, nickel, iron ore, lead/zinc, PGM, diamonds or other commodities, E&MJ takes the lead in projecting trends, following development and reporting on the most efficient operating pr

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Page 59 of 83

FILTRATION & THICKENERS 58 E&MJ • NOVEMBER 2018 Determining the best thickener or filtra- tion system for a new or existing plant will invoke a decision tree that reads like a list of calculated tradeoffs. "We are always compromising on the choices," engineer and thickener expert Tom Keirn said in a recent presentation. Fortunately, several of the solutions on the market today seek to minimize the cons while maximizing the pros. A summary of the highlights of several illustrates this point. Maximizing Space and Water Usage McLanahan Corp. hosted a webinar in late September that explained the needs for, the benefits of, and the basic operations of six different types of thickeners. The type of thickener that will best serve a miner depends on site specifics, goals, and the desired level of commitment to monitoring and maintenance, according to Tom Keirn, territory manager, wet pro- cessing, North America, McLanahan. Generally speaking, a thickener would be optimum in the event the miner faces restrictions related to pond permitting, water supply limitations, certain com- plications with existing ponds and plant infrastructure, or unwanted pond mainte- nance requirements. The primary benefit of deployment of a thickener is increased availability of clean water for use in the plant. "Approximately 85% of the water is recovered," Keirn re- ported. What water is lost is lost through the thickened solids. Via a thickener, the miner can reduce the use of settling ponds to the point of, in some circumstances, eliminating them, Keirn reported. Thickeners work by applying chemi- cals to a slurry being piped into a pool or silo. Those chemicals, called flocculants, cause certain particles within the slurry to clump together, or form flocs, and sink. "Larger flocs settle more quickly to allow for recovery of water and consolidation or thickening of solids," Keirn said. The clean water at the top overflows contain- ment at a set location and is captured while the mud at the bottom is collected and channeled into an underflow pump for further processing. Thickener performance and process outcome depend on many variables, fore- most of which is often the flocculant se- lected, Keirn reported. McLanahan offers a service that assists the miner with the selection process. The company will research to com- pare the different options, run a model to home in on costs and possible out- comes, and then customize the features to the possible methodologies. "And we will reiterate those with the custom- er's input and make sure we have the right features and the right thickener design for the customer," Keirn said. "Fi- nally, we'll do a finite engineering analy- sis final model." The Complexity vs. Performance Dilemma Modern thickener and filtration solutions can be customized to meet brownfield site or plant expansion project needs, but within limits By Jesse Morton, Technical Writer McLanahan reports its deep cone thickener, an ultra-high-rate thickener, offers sludge monitoring via PLC, increased control over the dewatering process, and a reduced footprint. (Photo: McLanahan Corp.)

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