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March 2017 www.coalage.com 35 bulk material handling Delivering Wet Fuel to the Fire Saturated coal does not have to dampen plant efficiency The Scherer coal plant, operated by South- ern Co., had spent many years suffering from issues with transfer system efficien- cy due to wet coal. Wet coal has forced the coal plant's bulk handling systems to reduce, or "derate," capacity on conveyors for more than 15 years. Power plant operations have become accustomed to derated operation under certain conditions and have begun to ac- cept it as normal. A redesign and retrofit of critical bulk-handling systems, taking wet coal into account by leveraging cut- ting-edge 3-D laser scanning and model- ing technology, increased transfer system efficiency and throughput. After the Scherer retrofit, the rede- signed chute-work systems so effectively conveyed wet coal that the plant was un- prepared for the first time wet material arrived at the pulverizers. The increased throughput in the redesigned transfer systems exposed other weaknesses in the handling system downstream. A thorough analysis of these bottlenecks provided the ability for the Scherer team to budget for rework where necessary. Working in close coordination with the Scherer team, Acensium was able to assess client goals based on their priorities and deliver a ret- rofit that fulfilled the set goal beyond stat- ed expectations. A true partner doesn't limit their fo- cus to project requirements, explained Jason Schwartz, principal, Acensium. "To build value in a relationship, we must discover the deepest challenges to opera- tional efficiency and do whatever it takes to eliminate them," he said. "One of our clients learned the value of this philoso- phy recently. A four-unit, coal-fired plant contracted us originally for new transfer chutes, as the existing equipment was nearing the end of its service life. The over- arching goal was dust control, but we un- covered a much deeper issue that had been plaguing the plant." During discussions with the client, Acensium learned that moving wet coal was a serious bottleneck for this plant, lo- cated in an area that can receive significant amounts of rain. While the normal goal was to move 1,200 tons per hour (tph) of coal, wet coal would drive this figure down to around 800 tph. With four trains coming into the facility delivering 42,000 tons daily, this was a problem. Continuing to run the system at an optimal rate was not an option. Wet coal would clog chutes, and if sensors did not alert operators quickly enough, the poten- tial result was 650 pounds of coal spilling every second. Reducing the transfer rate meant derating generators during periods of wet coal — also not an option for a plant supplying a major metropolitan area. The only option left was for the sys- tem to run 24 hours per day to compen- sate for the lower transfer rate of wet coal, Schwartz explained. "This meant elimi- nating maintenance and inspection peri- ods, and also eliminating any margin for error in the process," Schwartz said. "The facility would push through equipment failures, incur overtime as extra staff was added to watch the system, and basically operate under a 'code red' posture during rainy periods." When redesigning the system, Acensium uses DEM to look at coal flow. An important aspect was controlling the Kinetic energy. After redesigning the chute work, other weaknesses were exposed downstream.