Failure and redesign of a pressurised circulating fluidized bed and cyclone

As part of an ongoing Combined Cycle Power Generation research program at Dalhousie University in Halifax, Nova Scotia, Canada, a Pressurized Circulating Fluidized Bed (CFB) was constructed. Initial experimentation resulted in some leaks in the unit and an approximate cyclone efficiency of 65%, when an efficiency in excess of 98% was expected. Teardown of the failed unit revealed manufacturing and design anomalies in the cyclone. Distortion and fracture due to thermal expansion were also discovered. Prior to building a larger unit, it was decided that failure modes had to be determined and rectified. Given the design changes involved, it was decided to first build a low temperature pressurized unit from transparent PVC to quantify cyclone efficiency and prove the new design. The redesign process also involved dimensional analysis to enable this laboratory scale room temperature unit to model an industrial scale unit, as well as design and manufacturing changes to accommodate thermal expansion. All thermal distortion was eliminated, and a cyclone efficiency in excess of 99% was achieved. This study details the structural failure of the unit and the corrective action taken. (C) 2003 Elsevier Science Ltd. All rights reserved.