Coal Age

OCT-NOV 2017

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40 October/November 2017 operating ideas Modeling Solves Coal Flow Problems by jason schwartz The James H. Miller Jr. plant in Alabama is one of the top 10 largest coal-fired power plants in the United States, responsible for 46% of the power generation in Alabama. The plant converted to Powder River Basin (PRB) coal about 20 years ago to gain the environmental benefits of the coal's low sulfur properties. The downside of PRB coal is the 12,000 tons per hour (tph) that the facility needs to consume to maintain an equivalent power output. With 3,000 tph moving on one belt alone, the Miller plant still passed 100% of its coal through a single transfer sys- tem. There were both spillage and heavy dusting issues so management was con- sidering new chute work to replace end- of-life equipment. The engineer assigned to fossil fuels had other ideas. He created an aggressive scope of work that included all of Miller management's and operations' collective wishes over 20 years, combined with his vision of how to add reliability and redun- dancy paths for the plant. With so much coal traveling through one building, the engineer was trying to address the fact that any upset condition could knock out half the power for state of Alabama. This concern translated into a 28- page document, outlining requirements for probably the largest and most compli- cated material-handling project ever un- dertaken at a running power plant — one where a principal mandate was that the plant continued to move coal through the same area that was to be updated. This work was to take place in a building that was overstressed structurally and mechan- ically, and the concept was to add 50% in additional material-handling capacity. Acensium was one of two contractors that responded to the Request for Propos- als (RFP) and the only one willing to put in a bid and move forward. Working with the Miller team, Acensi- um developed retrofit plans encompassing the needs of both operations and manage- ment at the facility. By providing 3-D laser scanning, digitization and modeling of the plant, risks of schedule delay and work stoppage due to design issues or unfore- seen conflicts during installation were sig- nificantly reduced. The on-site consulting team con - firmed that the building, which had an ad- ditional floor added in 1998, was severely overstressed. Laser scans detected deflec- tion in some of the support beams. In re- sponse, Acensium performed all necessary structural retrofit design, creating a new skeleton to put into the existing building while it was still operational. The largest beam of this skeleton, weighing in at more than 21,000 pounds (lb), had to be placed under the existing structure and utilities. Maintaining tolerances were absolute- ly critical during this retrofit. With most projects, plus or minus 1 inch (in.) is ac- ceptable to get the job done. At Miller, with so much material moving through such a confined space, it was a fundamental project requirement to maintain toleranc- es within 1/16-in. to avoid critical system failures. This was accomplished through progressive laser scanning, supporting the installers all the way through the entire job. Part of the design included splitting the coal flow to facilitate feeding multiple sys- tems at one time. The flow was split through an unconventional geometry arrangement that helps to ensure redundancy and in- crease overall efficiency at the plant. Acensium was able to accomplish ev- ery goal set by the Miller plant, and this was accomplished while not interrupting operations. The final system is very com- plex with multiple coal flow paths, includ- ing significant falls. This highly redundant system runs with no pluggage or interrup- tions of any kind. The Miller fossil fuels engineer is already looking ahead to projects into 2020 and Acensium built dedicated fu- ture-proofing into the new system to sup- port this growth. The organization record- ed detailed scans of as-built conditions, including changes in conduit, electrical, fire protection, wash-down, structural members and chute work. In the current phase, the team is running models to ex- amine different ways of bringing coal into the building and forecasting the impact of any future changes. The final facet to this very detailed, complex engagement was time. Miller needed this project fast-tracked, and while this process should have taken anywhere from 12-18 months to move from concept to design, Acensium took 9 months from the initial purchase order to the day the client started demolition. Jason Schwartz is the principal for Ascensi- um and be reached at Part of the design includes splitting the coal flow to facilitate feeding multiple systems at one time.

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