By Carol Wasson
More and more coal prep operations are realizing the advantages of polyurethane and rubber screen media versus woven wire and steel punch plate—namely, significantly extended wear life, ease of maintenance, greatly improved safety, reduced noise, as well as increased magnetite recovery, plant yield, and product quality. The Martin County, Kentucky-based Pinnacle Processing plant, which is owned by Booth Energy, is experiencing each of these benefits after installing Polydeck modular synthetic screen media in several key processing circuits.
“We’re a very proactive company that thinks outside the box,” said Joe Brumfield, maintenance supervisor, Pinnacle Processing. “Just because we had always gone with wire previously doesn’t mean it’s the only way to go. We found converting to synthetic screen media has extended wear life by more than 60%, while also lowering our screen maintenance and labor costs by more than 40%.” Brumfield also stressed that the use of synthetic media is one more initiative that has allowed the operation to maintain an excellent safety record and remain completely compliant with MSHA regarding noise reduction.
It is Pinnacle’s “outside the box” philosophy that allowed Polydeck Screen Corp. to install its modular synthetic screen media in various applications within the plant. Polydeck guaranteed improved performance and, although skeptical at first, Brumfield and Virgil Mills, plant superintendent finally agreed to run a test on one deslime deck. They quickly became believers. “I’ve worked in the coal industry for more than 30 years and have never experienced better service and expertise. They are hands-on and here whenever we have a problem,” said Brumfield.
Brumfield works closely with Steve Parsons, a Polydeck regional manager. Parsons said the company’s goal is to increase its customers’ performance efficiency while lowering operating costs. “If you can do that, you’re adding to their profit line,” Parsons said.
The first conversion took place at the vessel’s clean coal, drain-and-rinse circuit where woven wire and stainless steel decks on two 8- x 16-ft screens were replaced by polyurethane screen panels. The top deck was fitted with a VR panel design with 38-mm (1.5-inch) openings. “The VR panel, with its zig-zag openings, is a very flexible, active panel. Because the openings are continually moving and vibrating, it is resistant to pegging or blinding, which would reduce magnetite recovery,” said Parsons. “We are also using screen panels with molded dams on this deck and as particles tumble up and over the dam, that is the ideal place to hit it with spray water—and we can place dams anywhere on the deck to achieve maximum efficiency. That is something that cannot be done on a woven wire deck.”
On the bottom deck, 0.5-mm polyurethane continuous slot screen panels replaced a 0.5-mm stainless steel profile wire deck. Parsons said that for drain-and-rinse applications, continuous slot panels provide the maximum amount of open area to allow optimal efficiencies and recovery rates. The openings must be precise and consistent to prevent misplaced material while washing and cleaning magnetite off the coal.
“The magnetite recovery rate was not as good with the prior stainless steel media, which is roughly the same cost per square foot as the polyurethane, but would last only about 25% as long,” said Brumfield.
“Some would think that the efficiencies would be the same between either type of media if each has 0.5-mm openings, but that is not the case,” said Parsons. He explained the stainless steel media limits the retention time and the particles slide off quickly and smoothly. “In truth, you want the particles to tumble a little bit—similar to the agitation in a washing machine—and that is exactly what happens on the polyurethane continuous slot panel. It will outperform stainless steel by providing a more efficient rinse, while increasing wear life by up to four times,” Parsons said.
Raw Coal Separation
Next, Polydeck worked with Pinnacle Processing to increase the efficiency of the raw separation circuit where woven wire was removed and modular polyurethane screen panels were installed on each of four 6- x 16-ft double-deck inclined screens. The top deck was fitted with 19-mm (0.75-inch) slotted openings and the bottom deck featured 11-mm (3/8-inch) zig-zag openings, which eff