The latest coal dewatering screen panel innovations give customers more options and better results
by Jesse Morton, technical writer
The premier coal dewatering screen panels from the top suppliers feature more open area than do predecessor panels. They are also made to last longer. Most importantly, they are increasingly customizable, which makes them an option for more customers. The suppliers told Coal Age they are ready to work with new customers to help them achieve their dewatering goals.
Unique Solutions Improve Drain Rates
Polydeck Screen Corp. said the modular coal dewatering Maxi- and SD-style Polydex panels are customizable solutions that address unique challenges plants face at a local level.
“The combination of a modular system and customized panels, like the Maxi and SD, means that Polydeck can fine tune a specific machine by using several different panels installed down the deck of the machine to allow for maximum dewatering with the lowest life cycle cost,” said Aaron Boggess, director of sales, energy and industrial.
The polyurethane Maxi-style panels offer greater open area for operations that prioritize throughput. “The Maxi-style panel offers some of the highest open area in the industry,” he said.
“Another advantage with both Polydeck’s SD- and Maxi-style panels is that they are injection molded,” Boggess said. “This gives Polydeck the ability to mold in surface features, giving Polydeck the ability to design unique solutions to help customers improve drain rates.”
SD-style panels are for operations that prioritize extending wear life.
Both panels offer “superior quality, faster production rates, and better dimensional consistency,” Polydeck said. “With Polydeck’s internal tooling capabilities, new features or changes can be made quickly.”
For quicker, easier maintenance compared to traditional media, Polydeck panels offer “several fastening systems that allow for ease of installation and removal,” Boggess said.
Both panels are field proven with a storied history. “More recently, we were able to convert a deck to our Maxi-style Polydex panel, providing a 30% increase in open area over competitive screen media,” Boggess said.
The panels arose from the company’s focus on research and development. “As part of Polydeck’s continuous improvement philosophy, we invest heavily in ongoing research and development, improving products through prototyping, testing, and evaluation,” he said. “The Maxi-style panel is an example of our continuous improvement process.”
The process led Polydeck to invest in researching “the boundaries of synthetic poly and rubber media,” Boggess said. “Once thought of as solely a wear-life solution, Polydeck is now able to offer panels with open area that are more competitive with other media offerings,” he said. “We continue to push the boundaries with open area in our DMAX-style panels and are working on a new panel design that we believe will be the next evolution in media for dewatering applications.”
The SD and Maxi-style panels are part of a collection of over 1,500 dies Polydeck has available to help customers fine tune their systems to meet production needs. With the vast selection of panel options “and a team of over 50 application experts, we have a solution for your specific screening need,” Boggess said.
“Additionally, Polydeck has a direct sales network with over 150 years of combined knowledge in the energy and industrial sector who are available to consult and recommend solutions customers may face,” he said. “Polydeck regularly conducts onsite training so that our customers gain the most benefits from our products and experience. We call this ‘Together Strong.’”
The company offers customers “short lead times and the application expertise to solve the most difficult challenges,” he said.
“Polydeck’s strategically located distribution centers across the United States ensure our products are close to our customers,” Boggess said. “Often, most products are delivered to the customer within 48 hours after receipt of the purchase order.”
Aperture Orientation Quadruples Drain Rate
TEMA ISENMANN announced the Injection Molded TeePee Panels are now compatible with screens using the WS85 fastening system.
“The mine already using the WS85 system just has to change out panels to obtain the benefits of the Injection Molded TeePee Panels,” said Anthony Yell, mining division manager, TEMA ISENMANN.
“With the different variations of fastening systems available now for the Injection Molded TeePee Panels, we cover all the bases for our clients so there is no major deck modifications required to install these panels,” he said. “It completes the range of Injection Molded TeePee Panels for our clients in North America and Europe.”
The announcement caps a year of research and development that sought to answer a core need of certain customers. “The WS85 Fastening System was developed in 1985 by Isenmann in Germany, our sister company, and has become a mainstay fastening system in Europe and North America,” Yell said.
“It therefore made sense to be able to offer the modular Injection Molded TeePee not only with the H-Type fastening, Pin-and-Leg fastening, P3 Pinless fastening, but WS85 fastening as well,” he said. “So that our clients that use the WS85 fastening system can interchange the TeePee with conventional WS85 panels to increase dewatering capacity on their existing dewatering screens if required.”
The panel has a corrugated surface that offers maximal surface area for optimal drainage.
“The main usage of the modular Injection Molded TeePee Panel is dewatering and degrit applications where you want to efficiently remove water and ultra-fines from the feed material,” Yell said.
The panel reportedly outperforms conventional panels at dewatering.
“A conventional dewatering panel is flat with slotted apertures typically 0.5 by 13 mm long,” Yell said. “These conventional panels have 10.1% open area, and can drain 48 m3/h/m2 of screen area,” he said. “The equivalent TeePee Panel with 0.5- by 9.8-mm across-flow slotted apertures has 20.74% open area, and can drain 150 m3/h/m2, almost three times the drainage of the conventional panel.”
Tests show slots with or across flow that have the same open area will drain the same; however, the cut point changes.
“With-flow slots generally cut at the slot width,” Yell said. “So a 0.5 mm by 13 mm slot will cut at 0.5 mm,” he said. “The TeePee has the 0.5- by 9.8-mm slots across flow, which means it tends to cut about 20% less than a slot with flow or at 0.4 mm.”
That means that a 0.63-mm slot which has 26.21% open area will cut at 0.5 mm, he said. With that capability and with the additional open area, the panel “can typically drain 210 m³/h/m² of screen area,” Yell said. “So, this is a four times higher drain rate than the conventional dewatering panel.”
The announcement means customers that use the WS85 fastening system can make an inexpensive upgrade and get the benefits offered by the Injection Molded TeePee Panel. “This means that for the same size dewatering screen you can significantly increase your throughput,” Yell said. “If you are designing new dewatering screens, you can look at using smaller dewatering screens with the TeePee Panel.”
Another benefit of adopting the panels is increased efficiency. “Because of the sharp ridges on the top of the TeePees, this cuts through the underside of the filter bed releasing more water from the bed,” he said. “So this further increases the efficiency of the dewatering process.”
The Injection Molded TeePee Panel first launched as a larger open-cast version roughly 25 years ago. It was designed “for a heavy minerals plant where the dewatering screens installed were found to be too small for the required duty,” Yell said.
“There was no space in the plant to increase the size of the dewatering screens, so we developed the first three-dimensional cast polyurethane panel that doubled the open area of conventional panels,” he said. “This is still in operation today with extremely heavy-duty dewatering screens.”
Afterwards, “in Australia, there was a requirement for a modular, cost-effective, high-open-area, dewatering screen panel for the dewatering of iron ore,” Yell said. “Once we saw the benefit of these three-dimensional cast TeePee Panels, the natural progression was to develop the Injection Molded TeePee Panel range,” he said. “So, the range of Injection Molded TeePee Panels has been around for 20 years and has proven itself to be a highly efficient Dewatering Panel.”
TEMA ISENMANN still makes custom-designed Tee Pee Panels for select customers.
Injection Molded TeePee Panels have met with success in the global market and feedback from customers show the design has “proven its worth all over the world,” Yell said.
For example, “Northern Canada diamond mines used Injection Molded TeePee Panels successfully on their degrit screens, and have reduced moisture contents significantly,” he said. “This has increased the recovery of plant water for reuse, reducing the amount of fresh water required at these plants.”
The panels are offered in a range, with aperture widths of 0.3, 0.5, 0.63, 0.8, 1.0, 1.2 and 1.4 mm. “All have 9.8-mm slot lengths, which covers most of these types of applications,” Yell said.
“If a client wants to increase the retention time of the feed on the screen and build up the bed depth we can supply these panels with cast on 50-mm-high dams as well,” he said. “The only criteria that one needs to take into account using Injection Molded TeePee Panels is that you need a minimum bed depth of 40 mm to cover the tops of the Injection Molded TeePee Panels to maximize drainage.”
Thickener Upgrades Reduce Downtime, Flocculant Usage
WesTech reported its two newest plug-and-play thickener upgrade solutions help improve thickener performance and reduce costs. The MudMax bed monitoring system helps plants avoid shutdowns, optimize flocculant usage, and save water. The EvenFlo feedwell reduces flocculant usage and costs while improving both clarity and overall thickener performance. WesTech offers both solutions as retrofits.
MudMax uses differential pressure cells attached to the rake to detect bed level, which is reported on either a standalone screen or to a larger plant equipment management system. Development started roughly a decade ago and sought to address “customer complaints about their lack of bed-level monitoring instruments,” said Jaron Stanley, applications engineer.
“It started with strain gauges, and eventually moved to differential pressure cells,” he said. “Typically, there are four differential pressure cells spaced a foot or a couple of feet apart, one above another, and mounted on the rake arm.”
The rake moves through the bed. When the bed “reaches those different differential pressure cells, it starts to show as a force,” Stanley said. A battery-operated signal device on the rake sends findings to a receiver package on the bridge.
From there the data goes to either a standalone screen, which is part of the package, or to the “DCS, whatever the plant prefers,” Stanley said. “The MudMax comes with all of the hardware necessary to provide the ability to watch the display and use it in your system,” he said. “It can also send out a signal that can be used in the plant’s existing control system.”
MudMax was designed to be a plug-and-play solution. “It can be added to any thickener or clarifier,” Stanley said.
And so can the EvenFlo feedwell, a “pre-feedwell that evenly distributes the solids all the way around the feedwell,” he said. The solution is designed to give “even distribution of solids into the bottom of the thickener so you don’t get that piling that causes torque issues.”
Ideally, EvenFlo is paired with a main feedwell employing auto-dilution. Flocculant is added near the auto-dilution port. The two feedwells then “enhance flocculation,” resulting in “better clarity and lower polymer consumption,” Stanley said.
The solution was developed to answer feed-distribution challenges faced by certain customers in South Africa. “It is common in a feedwell to have inefficiencies where the feed tends to circulate and drop out of the feedwell to one side,” he said. “That can cause piling of solids on the floor of the thickener, which leads to torque issues.” It also leads to the creation of “currents and poor distribution of the finer solids, which can cause turbidity and total-suspended-solids (TSS) events in the outlet of the thickener.”
The EvenFlo feedwell is field-proven, and case studies document its ability to deliver the desired results.
For example, Transalta recently upgraded a feedwell to the EvenFlo feedwell as part of a project to relocate tailings at a mine in Washington. In the project, the tailings from the Centralia coal mine would first be reprocessed and then moved to an empty pit to ultimately be stored deep under water. “Reprocessing the refuse helps fund the venture,” WesTech reported.
The miner tapped WesTech and a contractor to “refurbish an existing high-rate thickener.” The supplier provided a 35-m-diameter HiDensity paste thickener as well as the EvenFlo feedwell to attain the desired results.
Another case study reported that Luossavaara-Kiirunavaara Aktiebolag (LKAB) replaced two “very old feedwells” at its iron ore mine near Gällivare, Sweden, with EvenFlo feedwells to improve effluent clarity in process water, WesTech said. Effluent from the old thickeners “contained about 190 parts per million (ppm) TSS, with spikes of 1,000 ppm or more. LKAB wanted the TSS to be below 100 ppm.
To replace the existing 5-m-diameter feedwells, two 10-m-diameter EvenFlo feedwells were adopted for their
“design features and capabilities,” and for the proximity of WesTech’s “nearby fabrication shops,” WesTech said.
EvenFlo features include an advanced two-stage design. “The first stage uses an inner channel to convert the tangential feed energy into a concentric radial flow,” WesTech reported. “The second stage, which begins when the flow exits the inner channel via bottom ports, directs the flow radially outward into the main feedwell for optimal solids-flocculant mixing.”
In trials, the upgraded thickeners “achieved lower TSS” than the target. They were then calibrated for the desired flow rate and achieved “an average TSS level of 70 ppm,” 30% below the target.
“The units achieve this remarkable clarity with possibilities to also attain much lower chemical dosages, reducing the plant’s operational costs,” WesTech reported. “LKAB is pleased with the outcome of this project.”
Separately, a trona mine in Wyoming selected WesTech for a clarifier audit. The process engineers identified several problems with the feedwell, including poor flocculation, short circuiting, poor clarity, and high flocculant cost.
The mine adopted an EvenFlo feedwell customized to receive the existing feed pipe and to fit under the existing roof. “WesTech supplied modified overflow weirs to level the overflow launder,” the supplier reported.
Results showed a “significant improvement in overflow clarity, reduction of flocculant dosage, and increase in underflow density,” WesTech reported.
Such results prove the EvenFlo feedwell is “a great retrofit opportunity,” Stanley said. “It is something we can offer for most thickeners.”
Adoption usually follows a consultation visit. Ideally, “we would evaluate the thickener,” he said. “That may even involve a trip to come and look at the thickener and check the measurements, check the flows and the sizing, and ensure that we can make it happen,” Stanley said. “But the majority of our recent EvenFlo installations have been retrofits of existing units that typically were manufactured by another company.”
The EvenFlo can also be adopted as an add-on to the company’s flagship HiFlo high-rate thickeners and paste thickeners. With a 30-year history, the HiFlo thickeners are offered in a standard design with a performance record that has made it popular among customers.
“It is what they’ve come to expect,” Stanley said. “When they come to us, they typically just say I want another 60-ft unit, or I am looking for an 80-ft unit, and we know exactly what they want.”
These solutions are “tried and true products that we believe will strengthen the plants and create very little downtime for our customers,” he said. “Our main goal is to help our customers be successful. And we believe our products, when maintained properly, will give them very little grief and allow them to focus on the parts of their plant that need their attention.”