Coal Age

JAN-FEB 2019

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January/February 2019 31 fines dewatering continued The key technology in the system is the downcomer, which feature no moving parts and is based on simple physics to optimize efficiency and cost effectiveness, Lawson said. "You create a hydraulic field and the slurry is drawn up into the down- comer because there is a pressure differ- ence as that plunging jet goes through that orifice," she said. "It naturally draws air from the atmosphere, so you don't actually have to use compressors, or any energy as- sociated with compressing air." The cell is advertised as excelling at re- covering coal particles smaller than 500 mi- crons, which are typically uneconomical to pursue via conventional flotation technolo- gies and usually end up as waste, Glencore Technologies reported. "The fine bubble size, high intensity and froth washing abili- ty offer major advantages over conventional cells for recovery of the highly hydrophobic, fast floating coal fines," the company re- ported. "These advantages provide superi- or, more consistent flotation performance, lower ash concentrates and high recovery." The original seed idea for the down- comer is attributed to Laureate Professor Graeme Jameson of the University of New- castle. In search of a means to optimize flo- tation performance of a lead/zinc concen- trator, he was commissioned by Mount Isa Mines, in Queensland, Australia, to develop the idea, which he patented in 1986 on be- half of Newcastle Innovation Ltd. That year the resulting pilot cell was tested. Three years later, two full-scale cells were installed in the lead-zinc concentrator at the mine. Two more were built that year for a similar concentrator at the nearby Hilton mine. Soon thereafter, the solution was ad- opted by a major coal miner in the Bowen Basin in Australia. Within a half-decade, Newlands Coal employed six Jameson Cells, scaled up for the requisite through- put, at recovering coal fines. In Australia, the Jameson Cell is "now the industry stan- dard," Glencore Technology reported. The largest installation at Curragh (Australia) treats more than 5 million tons per year of coal, using only 12 cells, Glencore Technology reported. The cells have been deployed to coal operations in Africa, North America, Asia and Europe, the company reported. In 2013, Jameson was named New South Wales Scientist of the year. That year, Jameson Cells at Australian sites were credited with recovering some $30 billion in export coal. In 2015, the solution won the Prime Minister's Award for Innovation for its role in the Australian economy. Such accolades and figures hint at the value the cells could bring to a circuit and plant, Lawson said. To bring peace of mind to a plant manager, she said, the cells offer something invaluable: certainty. "Other devices rely on probability," Lawson said. "We are now 100% certain that a particle has an opportunity to attach to a bubble." Currently, roughly 350 units are oper- ating in almost 30 countries around the globe. In each case, the cells were selected as technical solutions to technical prob- lems, Lawson said. "The Jameson Cell can recover all of the coal fines, usually in a single step, to improve the performance of dewatering and now lower the level of chemicals needed," she said. "By operat- ing the Jameson Cells in series, the second Jameson Cell is able to scalp the tail at low- er chemical addition, leading to improved dewatering conditions." Adoption is easy, as the Jameson Cell "has direct scale-up from pilot testing," she said. "So, if you have an existing operation and we pilot on your site, then we will know exactly how our Jameson Cell will operate." With four generations in operation, three decades of history, and field results from around the world attesting to the vi- ability of the solution, the primary barrier to adoption now is normalcy bias, Lawson said. "We just have to get over some of those barriers that people have to adopt- ing something different," she said. "The technology does it, and it speaks for itself; they just need to be willing to adopt and reap the benefits of change." In Q4 2018, Glencore Technologies an- nounced a 25% capital back performance guarantee on the cells. The guarantee for- malizes the confidence the company has in how well the cells will perform, Law- son said. "Show us what you need to get done," she said. "Work with us and we will demonstrate what can be done and that we stand behind it." Recovering Ultrafine Coal Minerals Refining Co. (MRC) reported it is building the first commercial Hydro- phobic-Hydrophilic Separation (HHS) system-based plant at a coal mine in east- ern Kentucky. The plant will process 40 tons per hour (tph) of solids from a fine-coal slurry that would otherwise be destined for the thick- ener. "Typically, mines throw away 3% to 5% of the coal mined," Dr. Stanley Subole- ski, president, MRC, said. "We are focused on recovering that material." The system should enable the plant to capture 20 tph of high-quality coal fines for market. "About half of the slurry solids is ash," Suboleski said. The final product will average under 4% ash, he said. "We can control the mois- ture," he added. "We can dial that in." The partnership framework with the mine is complicated, Suboleski said, but ensures MRC will have coal to sell. HHS shares characteristics with tradi- tional flotation systems. Instead of being attracted to bubbles in a water tank, the coal fines are captured using an oil to coat the particles and form agglomerates. Oil molecules simply perform better at grabbing hydrophobic particles, Suboleski said. "It is a matter of contact angle," he said. The system can recover particles that are both larger and smaller than those re- covered by traditional flotation methods. "We've recovered particles down to sin- gle-micron size and even smaller," Subole- ski said. "We don't know how fine we can go with this technology." The system employs several steps. In the first step, the oil and slurry are mixed mechanically. "We have to mix this stuff pretty thoroughly, because if we don't get the oil on the coal, it doesn't get recov- ered," Suboleski said. The mix is then piped to a second tank to be more gently agitated. Gentle agitation is a crucial step in separating the coal from the water and ash. "These oil-covered particles are attracted to each other," Suboleski ex- plained. "They bump into each other and form coal-oil agglomerates that float on the water-ash mixture." However, at this stage, those agglomerates contain entrapped water droplets. "The impuri- ties are hydrophilic, so they want to go where the water goes," Suboleski said. "And when the moisture is trapped inside the agglomerate, it also raises the impu- rity level, which is the reason that agglo- meration has not been used widely in the past, even though it was first discovered in the early 1900s."

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