By Steve Fiscor, Editor-in-Chief
The coal business in the United States softened during 2009 and that is evident on the drawing boards at many of the engineering, procurement, construction, and maintenance (EPCM) firms that build prep plants. During 2008, business was brisk with a record number of orders for new plants and upgrades being placed worldwide. Many of those projects have been completed. Early this year, mining companies did cancel a few orders for new installations. While a few firms have a couple of large projects on the books, the volume of business certainly slowed in 2009.
The 2009 U.S. Prep Plant Census includes information on 283 prep plants. The largest change had to do with Alpha Natural Resources’ acquisition of Foundation Coal, and its associated prep plants. Those names have been updated accordingly. Kentucky and West Virginia are the leaders with 76 and 73 plants respectively. With a raw feed capacity of 6,200 tons per hour (tph), CONSOL Energy’s Bailey is the largest plant. There are now a dozen prep plants processing 2,000 tph or more.
Nine new plants where added to the annual U.S. Prep Plant Census: the Signal Peak plant in Montana; Buckingham Coal, Cline Resources’s Buckeye plant, and Rosebud Mining’s Tusky plant in Ohio; Imagin Natural Resources’ Saunders plant, Licking River Resources, Mepco’s Coresco plant, and Patriot Coal’s Blue Creek plant in West Virginia; and PBS Coal’s Cambria Plant in Pennsylvania. All of these plants were constructed by Taggart Global, one of the largest prep plant EPCM firms.
Last year, Taggart built 14 plants around the world, which was a really incredible pace. “In the last year, we have completed seven plants in the U.S., which represents about 75% of the greenfield projects in the U.S.,” said Rick McCormick, president and CEO, Taggart Global. Taggart is on schedule to commission two more prep plants by the end of 2009. The combined processing capacity for the eight new plants constructed by Taggart in 2009 will be in excess of 40 million tons per year.
Even though the dynamics within the industry have changed, some notable trends have also emerged. As it is with any aspect of mining, safety is the utmost concern and that is now a factor in plant design. The industry continues to migrate toward larger equipment and away from dual arrangements, which has brought plant costs down in relative terms (e.g., construction costs per ton per hour). Dewatering and capturing fines are two areas that remain important and the mines will focus their attention on in the future.
Circuit Design
Similar to the mines, plant construction is really site specific. What works in southern Indiana may not work in eastern Kentucky and/or West Virginia. “EPCM companies have to evaluate plant design needs on a case-by-case basis,” said Surendra Jain, president, The Daniels Co., a leading prep plant EPCM firm based in Bluefield, W.Va. “There is an application for large-diameter, heavy-media cyclones (HMC)and there is also an application for heavy media vessels (HMV) along with heavy media cyclones to process raw coal down to 1 mm size. Many of the new plants being built in the Illinois Basin now prefer HMV over large diameter cyclones. The same is true for southern West Virginia,” Jain said.
“When a plant is pumping 2-1/2- and 3-inch raw coal, a lot of wear and tear takes place in the pumps and pipes,” Jain said. “Why not increase the top size in the plant feed to 8 inches unless the chemistry suggests otherwise and let the HMV handle everything from 8-inch down to 1/2-inch?”
Banana screens give the prep plant added flexibility. Raw coal sizing and desliming can all be handled on one set of screens, Jain explained. “In the old days, we used to have raw coal and desliming screens,” Jain said. “Now with the Banana screens the top deck reports to the vessel; the bottom deck reports to the HMC circuit, and it is all done with one set of screens.”
Jain also cautions prep plant managers/designers about overloaded screens. “A lot of new plants have been built wherein a Banana screen is constantly operating under its maximum capacity and/or overloaded conditions,” Jain said. “Some preparation plant operators have claimed that after operating for only a couple years, these screens become a pain in the neck. Banana screens work very well if loaded properly, but a few sales people in the past over sold the capabilities of these screens.”
Jigs and tables continue to disappear, and the interest in columns seems to be tapering off a little. “Columns are good, but expensive to build and operate,” Jain said. “If the critical components are not operating right, the cell loses its efficiency and it’s no better than a conventional cell. Conventional cells these days no longer need air compressors, blowers, paddles, etc. So in regions where the fine fraction [325 mesh x 0] is not significantly contaminating the +325 mesh froth product, conventional cells are the way to go.”
Medium and large size plants (500 tph and greater) should consider a screenbowl centrifuge to dewater product (1 mm x 100 mesh) and froth flotation, Jain explained. “A screenbowl centrifuge captures more fine coal,” Jain said. “They are somewhat expensive, but the advantages are low moisture and better recovery. In the long run, a plant can get around 8,000 hours before a rebuild of a screenbowl is needed.”
With improvements in technology, plant controls are becoming more sophisticated. “Plant operations, interlocking, density controls, level controls, flop gates, etc., everything is controlled by PLCs,” Jain said. “An operator can start and stop a plant by one click of the mouse. The control stations in some new plants have as many as three monitors. Basically, the operators do not have to leave the control room. If anything goes down, an alarm is sounded on the computer screen indicating the nature of the problem. Ladder logic helps to make quick changes in certain plant operating aspects in the field. Multiple cameras can watch the entire site and provide a video feed to the computer. The systems can also store the records—operating hours, spare parts, etc.—for all of the equipment.”
Jain takes pride in the fact that The Daniels plants have worked at the level they were designed. “Our commissioning period is the shortest after plant construction is completed,” Jain said. “When it comes to starting it, balancing it, and getting it online, a Daniels plant always does what it’s supposed to do. We do not pull a plant from the shelf and force it on a client. We custom design the plant. We do not design a plant to operate constantly under the maximum condition that the client gives us, otherwise in the end, it costs the client too much in maintenance.”
Construction Trends
“Safety is of utmost concern and is the overriding factor in plant design,” said Larry Watters, director, Taggart Global. “Our recent designs have included low profile designs with large modularized equipment. Our designs are not modular as understood traditionally but in the sense that a single screen is supported by an individual set of structural steel from the screen to the floor. Vibration and noise are significantly reduced.
“Designs are provided with sufficient remote monitoring to remove workers from the plant during operation,” Watters said. “Our goal is a plant with no in-plant operators.”
The quality of raw coal reserves is declining. “We are encountering more high-clay situations and processing lower rank coals,” Watters said. “We’re reviewing several options in coarse cleaning including minimal raw coal crushing, cleaning 24-inch top size and adjusting the basic designs of heavy-media cyclone circuitry. These designs are an attempt to counteract the clay and coal friability problems.”
Taggart Global is also working closely with Virginia Tech to determine optimal fine coal circuitry. “Several innovative designs are being considered in the 2-mm x 100-mesh size range,” said Patrick Brindle, vice president-engineering, Taggart Global. “Definitive data is necessary to establish efficiencies and design criteria and capital and operating costs for various options.”
The 100 mesh x 0 circuit designs are also being reviewed. Different techniques, some very innovative, are being tested in the lab and in the field. “Within the next year, we should be able to provide a full range of options in attacking the very difficult and variable fines cleaning circuit,” Brindle said.
Capital Costs
Capital costs for plant construction are on the rise. “From 1984 until we started Taggart Global in 1993, plant capital cost changed very little ranging from $10,000 to $15,000 per tph capacity,” said Dan Placha, COO, Taggart Global. “Today, capital costs have escalated by 50% to 100% in some cases due to increases in scope, labor equipment, materials and electrical costs. During the last two years, it has been difficult to accurately assess the cost changes. It has been difficult for our estimators and difficult for our clients to budget accurately.”
Also causing the rise in capital costs are the more complex fine circuits, particularly the plants with closed water circuits. Safety considerations have also lead to increases in cost. “Capital costs today are estimated at $12,000 to $21,000 per tph capacity depending on client requirements,” Placha said.
In the 1980s, 70% of the costs for a greenfield facility would have been in the preparation plant “black box,” Placha explained. “Today, on average, 60% of the costs are associated with material handling,” Placha said “As an industry, we have kept preparation plant costs reasonably low, but material handling costs, due to material costs and increased scope, have risen dramatically.”
Average plant operating costs have risen over the last few years as more and more water circuits are being closed. “Labor rates are on the rise, as is power, but flocculants costs are the main driver in increased operating costs,” said Dennis Davis, manager of Taggart Global’s seven operating plants.
Coal facility pricing is the overriding concern of coal owners, but schedule is becoming a major consideration. “Once a mining company decides to spend the money, the question becomes: How quickly can we bring the project on line?,” McCormick said. “We are currently working on two 1,600 tph to 1,800 tph projects in the U.S., that will be completed—start to finish—in nine months. This is a much faster schedule than could be performed 10 years ago and is nearly twice as fast as a typical international project.”
