Peabody Energy constructed and commissioned the new Wild Boar preparation plant during 2010. Despite an accelerated construction timeline, developers were able to incorporate ease of maintenance and accessibility into a simplified flowsheet, which included heavy medium cyclones, compound spirals and de-slimed flotation circuit. Strategically located on a rail line near Lynnville, Ind., the 650-ton-per-hour (tph) Wild Boar today processes coal effectively from three local surface mines, maintaining a high availability at a low operating cost.
Peabody owns the plant and United Minerals operates the plant. During the front end engineering process, prep professionals from both companies collaborated with General Mine Contractors, the company selected to construct the plant, and Ezra Smith, a consultant who used to manage the Black Beauty prep plants. The design team considered several options to minimize plant construction costs while still building a quality facility with good operating and maintenance features. The options included relocating an existing idled facility, building an all-new plant, and building a plant with as much used equipment as possible. They settled on a final design that included several pieces of used equipment, a three-circuit plant for efficient processing of each size fraction, and an overhead bridge crane for improved maintenance access.
“We considered several options for Wild Boar,” said Dan Pilcher, senior preparation manager for Peabody Energy’s Midwest Division. “A few idled plants in the region could have been relocated. A cost analysis was performed on that option. New plant construction is the easiest path, but not necessarily the most cost effective. The third option, which is the one we selected, combined used equipment with a new structure. We wanted a low cost facility, not just with construction costs, but also as far as operating costs.”
One of the more daunting aspects of this project was the accelerated construction schedule. One of the mines that would feed coal to the Wild Boar prep plant came online early. Coal was being trucked to an existing plant one-way 13 miles and those expenses were mounting, Pilcher explained. Construction began during mid-March 2010 and the plant came online and under budget during mid-November 2010—nine months from concept to reality.
The Wild Boar plant can be broken into three main areas: the raw coal handling system, preparation plant and clean coal handling system. The raw coal system includes a truck dump, rotary breaker and a radial stacker with the ability to divert raw, saleable material from the prep plant. Material directed to the plant is cleaned in a simplified three-circuit system (See Figure 1).
“The plant uses a large diameter heavy-media cyclone, compound spirals and a deslime flotation circuit,” Pilcher said. “It’s the only place in the Midwest that [Peabody Energy] is using compound spirals. We have considered them at other locations, but because of the height requirement, it has been too difficult to implement them in existing plants. So we decided early-on it was something we wanted to do with this new plant and they have been performing well.” After cleaning, coal is stored in one of three product piles before being shipped by rail.
“The Wild Boar prep plant has a simplified circuit and the flow sheet emphasizes ease of maintenance and reliability,” Pilcher said. “The primary design considerations focused on safety, followed by process performance and maintenance. We wanted an efficient plant with plenty of room for access.”
Run-of-mine coal is delivered by trucks to a series of ground storage piles. “We are processing coal from three surface mines,” Pilcher said. “Trying to keep those coals separated creates another set of difficulties.”
A front-end loader then blends this material into a 150 ton hopper. After being conveyed to a scalping screen for initial sizing, a rotary breaker reduces the coal top size and removes oversize rock and foreign material. A radial stacker after the sizing station enables diversion of material to a direct ship pile if the product quality is sufficient. If the raw coal requires cleaning, it is instead stored in a raw coal pile which feeds the plant by way of a single vibratory feeder.
The plant feed belt delivers material from the raw coal feeder to a 10- x 20-ft, double-deck Banana screen. The oversized material is nominally 3-inches x 1-mm and reports to a 51-inch heavy medium cyclone (HMC). The HMC underflow reports to a single 8- x16-ft, double-deck horizontal screen for magnetite recovery. A flume screen precedes the vibrating screen to increase drainage area and ensure optimum magnetite recovery.
“One of the key design elements with the screens is the sieve bends in front of the double-deck clean coal screens, which gets the media off of those