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d e wat e r i n g Assessment of Plate and Frame Presses in Fine Coal Refuse Disposal Using a membrane filter press, the Blue Creek prep plant was able to place tailings in a combined fill area BY JOSEPH WHITE In recent years, traditional fine coal refuse disposal techniques have become increasingly challenging. Increased state and federal regulations on slurry impoundments have required significant modification of disposal techniques within the industry. Secondary options of fine-coal refuse disposal include underground slurry injection, slurry cells, and combined-fill refuse area using belt presses or plate and frame presses. Midland Trail Energy, an affiliate of Patriot Coal Corp., commissioned its Blue Creek Operation in September 2009 with permits that allowed the placement of fine coal refuse in a slurry cell area. Blue Creek faced challenges building and covering each slurry cell with the appropriate amount of coarse refuse required to achieve structural stability. The preliminary ratio calculations of coarse to fine refuse called for 85% coarse material and 15% fine refuse. This presented a construction challenge that could have delayed underground production. Blue Creek needed to consider the future of the refuse area design. Combined Coal-Refuse Placement Midland Trail Energy decided to explore the option of modifying the existing slurry cell permit to allow combined coal-refuse placement. This is also known as a "combined fill" refuse area. This technique combines coarse coal refuse and dewatered fine coal refuse resulting in a homogenous construction material throughout the dump area. The combined fill is permitted to be placed directly above the existing slurry cells, which allows for the current infrastructure to be used for the new refuse area. Selection of appropriate equipment was the next challenge. The two most viable options were to use belt presses or plate and frame presses. Belt presses historically produce a moisture content of 35%-40%, while the plate and frame presses consistently provide fine coal refuse moisture contents of 18%-20% (Parker, 2011). The Blue Creek Prep Plant With this information Midland Trail Energy commissioned two Tons Per Hour/Jingjin plate and frame presses. The plate and frame circuit would need to be able to process the entire fine refuse stream produced by the prep plant. The Blue Creek prep plant operates in the Campbell Creek area about 10 miles east of Charleston, W.Va. It washes coal from one deep mine, cutting coal from the Stockton seam. With a raw feed capacity of 900 tons per hour (tph), it is a heavy-media cyclone (HMC) plant. The primary components include: one 48-inch Krebs HMC, one bank of six 15-inch Krebs raw-coal classifying cyclones, two banks of eight MDL triplestart, compound spirals, and one bank of four Krebs clean-coal classifying cyclones. Secondary components include: two Conn-Weld 10- x 16-ft double-deck, rawcoal screens, two Conn-Weld 10- x 16-ft, double-deck, clean-coal screens, two ConnWeld 8- x 16-ft, double-deck, cyclone-refuse screens, two Conn-Weld 6- x 12-ft finerefuse dewatering screens, two Conn-Weld 72- x 80-inch (rad.) fine clean-coal sieve bends, two Ludowici VM-1400 clean-coal centrifuges, one Decanter 44- x 132-inch screen-bowl centrifuge, and one 120-ft static thickener. Figure 1: The basic filter press design for a 2-m x 2-m x 40-mm quick-opening automatic membrane filter press. (Drawing courtesy of Tons Per Hour) January 2013 www.coalage.com 35