Plant-level problem-solving
Not all of the presentations at the 49th Annual POWID Symposium involved advanced control technologies and techniques. Several offered solutions to common plant problems. Among them were those that close this article.
Donald Andrasik of Mirant Mid-Atlantic LLC described a program to evaluate ways to eliminate coal-burner pipe-flow stoppage at Morgantown Generating Station, which hosts two 625-MW tangentially fired boilers. At the heart of the solution ultimately implemented were acoustic flow devices, which monitor the flow in the coal pipes. The data delivered by the devices are then trended by, and alarmed in, the plant's distributed control system (DCS).
Engineers from Oklahoma City–based OG&E Electric Services—a regulated electric utility serving 735,000 customers in Oklahoma and western Arkansas—discussed a programmable logic controller upgrade of aging ash-removal system controls at Muskogee Generating Station. The retrofit has yielded a more flexible and reliable system for handling bottom ash, flyash, and pyrites.
Sandeep Shah of Atlanta-based Clyde Bergemann Inc. told of Xcel Energy's efforts to integrate a water cannon–based intelligent sootblowing system with the DCS at Xcel's Tolk Station in Muleshoe, Texas, in the hope of achieving closed-loop control. Tolk, with two 540-MW units that burn Powder River Basin coal, had experienced severe slagging events before the water cannons were installed several years ago.
David Runkle and other engineers from the Lower Colorado River Authority described a project at Sim Gideon Power Plant to achieve ramp rates of 10%/min over a wide load range for a 350-MW gas-fired unit. The speed was deemed essential so the plant could meet its new dispatch obligations in the Electric Reliability Council of Texas market. The important elements of the control scheme implemented are MPC in the DCS, modified sliding-pressure operation for the boiler/turbine-generator, and a feedback loop from an on-line turbine cyclic life estimator to the turbine's front-end controls. Before the plant had achieved this critical flexibility for the unit, said Runkle, "the smell of mothballs began to permeate the organization."
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