In a coal dryer system, flexible joints are used on inlets and outlets of the recycle gas fans. These joints are primarily to isolate vibration to the structure and some minor thermal expansion. In this case study, the coal dryer system runs at 160 degCo, at approx. 10kPa, with the fans conveying a hot inert gas with entrained coal dust.
If the coal dust settles or builds up in the expansion joint liner and bolster seal, this will spontaneously combust when the inert coal dryer gets turned off and the dryer returns to normal ambient conditions, i.e. normal 21% O2 air. Hence it is of utmost importance that the internal design does not allow coal dust to build-up in them. The client has had smouldering coal dust and joint failures of fabric joints in the past, so bolster seals and liners will have to be suitable or to have a suitable alternate design.
HMA-POGC & Dekomte came in and offered our bespoke innovative solutions for this application. We have now incorporated a bolster to be directly out and up to the underside of the flow plate in the 10 style expansion joints (see below picture of a standard 10 style expansion joints).