Coal Age

MAR 2017

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36 www.coalage.com March 2017 bulk material handling When they heard this, Acensium asked: What transfer rate was needed to alleviate the burden from the plant? The operators told them 1,200 tph during wet conditions as well as dry. "Our response was, let's get to work," Schwartz said. 3 Steps to Efficiently Move Wet Coal When redesigning the system, Acensium used discrete element modeling (DEM) to look at every particle of coal. They used more than 30 coefficients to replicate the condition of the coal as it moved through the transfer process. But modeling is only the start. Building a successful system in- volved three key components: Get in the field — Modeling only ac- complishes so much, if it is not validated through real-world observation. "Our mod- eling parameters come from observations of systems in the field," Schwartz said. "We create a feedback loop from these observa- tions to drive every system improvement we consider, from liners to flow design. Firms that do not follow this process tend to strug- gle at the start of the project, and this nega- tive impact will carry all the way through to limitations in long-term performance." Control the kinetic energy —"Our de- signs pay careful attention to the kinetic energy of the coal as it moves through the transfer," Schwartz said. "We want to know where coal comes to rest and where it might be approaching a terminal velocity." Shape matters—"We also focus heavi- ly on the shape of our chutes, as the most efficient shape will enable us to achieve optimal velocity throughout the transfer," Schwartz said. "When it comes to shape, a minute change can have an exponen- tial impact on kinetic energy and velocity. We've experienced significant improve- ments to our system designs by changing a single flange by 0.5°." Dry Coal Performance From Wet Coal Transfer Acensium applied the above techniques and upgraded one of the five main transfer points in the yard of the plant in December 2013. "It performed very well, but at first, we did not hear anything back from the cli- ent," Schwartz said. "It turned out that in the spring of that same year, the yard was able to push wet coal at such a high rate that it exposed previously unknown bottle- necks inside the boiler house." The redesigned chute-work systems performed so effectively in the conveyance of wet coal that the plant was unprepared 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 bottle- necks provided the ability for the plant team to budget for rework where neces- sary. "And, they were so impressed with the performance of our previous work, that we are now contracted to eliminate all bottlenecks throughout the entire sys- tem," Schwartz said. "We are in the pro- cess of finishing the upgrade to the re- maining four transfer points in the yard, and from there we move to the feeders and the pulverizers within the boiler house." Working in close coordination with the plant's internal team, Acensium was able to assess client goals based on their prior- ities and deliver a retrofit that fulfilled the set goal beyond stated expectations. And they are working to a point where there will be a system that can handle virtually any coal — in any condition — and deliver it at a rate demanded by the boiler. This article was submitted by Acensi- um with approval from the Scherer power plant. www.acensium.com The shape of the chute was also an important consideration. A feedback loop from field observations offers more detail and drives improvement.

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