Although we don’t hear much about construction of new coal-fired power stations but that doesn’t mean they don’t exist. New plants are being built and are expected to meet up-to-date specifications and requirements. That’s what the owners of the Longview Power Plant expected when their new plant came on-line in 2011. Unfortunately, the plant had some serious design errors which needed immediate remediation.
One of the first repairs needed was the boiler tubing which was constructed from T23 and T24 materials. The boiler nose arch on the unit—a first-of-a-kind once-through BENSON low mass flux vertical tube advanced supercritical design—was a weak link. The design was unstable and the T23 material leaked. To fix it, a nose arch made from T22 with an Inconel overlay was constructed and the results were positive.
Vibration issues were also a problem. The plant was running a Siemens SST6-6000 steam turbine and an SGen6-3000W generator. While the turbine functioned flawlessly, the generator suffered vibration issues and excessive hydrogen leaking through the seals. Siemens overhauled the generator and improved the foundation which resulted in acceptable vibration readings and hydrogen leakage.
The air quality control system was sized incorrectly and not working properly to remove particulates. After modifications and additions the system began operating at 99.5%. The company also replaced the distributed control system which brought about significant improvements.
These changes have turned Longview into the most efficient coal-fired power plant in the U.S. and a model of excellence. The technology utilized at Longview may lead to a future energy plan that includes coal generation as a viable energy source.
Full details on the Longview rehabilitation project can be found here.