Comparative physiochemical studies of porous ceramics for filtration of hot gases

Various porous ceramics have been utilised in the shape of filter candles for filtration of hot combustion gases (1,400–1,900°F). Principally, silicon carbide with silicate binder, mullite with mullite binder, and silicon carbide with mullite binder have been evaluated. Typically, the candle wall thickness is 10mm. In alternate embodiments, the candle wall has been of uniform pore size (viz 35–40 microns) or the candle wall has been layered so that the main structural faction has pores of large size (viz 125 microns), and the thin ‘skin’ that captures the particulate matter may have a mean pore of 10–25 microns. Scanning electron microscopy (SEM) studies of the pore structures of candles that have been in service under different dust and operating conditions reveal patterns of dust penetration and non-penetration. Energy dispersive analysis of x-rays (EDAX) was used to identify the make-up of particles that had penetrated the pore structure. Both analytical techniques provided data useful in verifying proper candle selection, particulate removal efficiency, etc.