Coal Age

MAR 2019

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24 www.coalage.com March 2019 coal preparation continued causing bottlenecks. Options include "do I put more spirals in, do I go from standard spirals to the two-stage spi- rals, or do I look at reflux classifiers," Trygstad said. Phillips agreed. "Probably the lat- est and greatest that people are want- ing to try is the low-cut gravity spi- rals," Phillips said. "They historically have been 1.8 to 1.9 specific-gravity cut, and we're seeing the manufactur- ers claiming reasonable efficiencies down to 1.6 gravity, even 1.55," he said. "I am interested in them as well. I think they do have a chance." While helping overall plant effi- ciency, an issue with low-cut grav- ity spirals is lower tons per hour per start, Phillips said. "The thing that makes me comfortable with putting them in is that at a minimum, the claim is that they'll work as good as the existing spirals and if you crowd them with tons per hour and go back to the higher tonnage we saw with the current models, they perform just as well," he said. "It is one of those you can't lose by trying them situations." Another solution making inroads is the reflux classifier, they said. The solution "is relatively com- pact and offers more control than spirals," Trygstad said. "Spirals are one set point where you make your separation," he said. "With the reflux classifier, you now have the ability to dial-in lower separation points with decent performance." Paul Preece, technical sales direc- tor, reflux classifiers, FLSmidth, said one of the main draws is the "smaller installation footprint, allowing it to be installed in tight spaces in existing plants." Further, the components are designed to minimize wear and re- duce maintenance. "The reflux classifier incorporates the new Laminar high-shear rate mechanism, the latest in fine particle gravity-based separation technolo- gy," Preece said. "This, along with advancements in channel spacing and width mean the reflux classifiers are more efficient and more compact than competing fine coal and mineral processing equipment." Phillips said he was ambivalent toward the solution. The practicali- ty of it varies from situation to situ- ation, he said. "It was hailed as the latest and greatest a few years ago," he said. Froth flotation solutions are see- ing an uptick in demand in the Mid- west, Phillips said. "Thermal coals in the Midwest, we are seeing more attention paid to the finer sizes, try- ing to get a little extra tons that way," Phillips said. "Some flotation is going in in the Midwest where they haven't considered it before." Many of those considering it are typically burdened with efficiency questions, Trygstad said. "Do I go from a conventional-type mechani- cal froth flotation cells to a column flotation? Do I do some re-flotation, taking some tailings and see if I can scavenge some more coal out of the tailings?" he said. "Something you can do for the most part in an exist- ing plant or with very little change to your structure." One emergent trend, however, is away from column flotation, Phillips said. "A lot of people are going back to conventional just because of the difficulty of operating column flo- tation," Phillips said. "I say that as someone who did a lot of work on column flotation and understands and likes it." The prospects for 2019 are promis- ing, except when they're not, they said. "I've heard in 2017 we produced more steel for all the years since 2007," Hopwood said. "There is a lot of steel being produced in the United States now." Beyond that, the new normal in business volume is forcing suppliers to adapt, they said. "What I don't see in that area is a lot of new construction," Trygstad said. Phillips agreed. "The growth is probably there, it is just going to be slow," Phillips said. "I do think there will be some growth, but slow, small amounts." And that won't be enough for some business models based on the boom times of yore, he said. "My prediction is on average there will be one coal processing plant built per year in the U.S.," Phillips said. "So far it has been proven to be true: One complete processing plant per year." That will either force suppliers in the space to downsize or diversify, he said. "The point is, with four or five plant builders, that is not enough to keep any of us in business," Phillips said. "No one group is going to get ev- ery one of those plants," he said. "To get one plant every three or four years is not going to keep you in business. Everybody has had to diversify." Raw Resources, he said, is break- ing into the frac sand and gravel plant construction space. "Fortunately, coal processing is more complicated than sand and gravel," Phillips said. "So our expertise is of some value in those industries." The FLSmidth Ludowici REFLUX Classifier is advertised as more efficient and compact than competing solutions. (Photo: FLSmidth)

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