Regenerating thermal oxidizers (RTO) are widely used across the US to destroy fugitive
emissions from wood-processing plants and other industries. The use of ceramic beds in order
to store and recover significant portions of the heat energy used for oxidizing the exhaust gasfuel
mix allows achieving up to 97% thermal efficiency. Dryers of wood chips in a typical wood
processing plant are usually heated by burning wood-based biomass material. Some of the
ash from the combustion is transported through the dryer and filtration devices making its way
into the RTO and associated ceramic heat exchange beds. In addition, small wood particles
entrained in the dryer exhaust gas escape capture as well and end up being burned inside the
ceramic bed contributing to the total ash loading to the RTO. This ash typically contains
Sodium and Potassium salts, which when exposed to high temperatures of the upper portions
of the heat recovery bed and combustion chamber, can react with the ceramic materials
contributing to their deterioration within a relatively short service period. The paper discusses
factors responsible for the deterioration of the ceramic material within the heat recovery bed
and in particular, the effects of temperature. It describes methods of semi-quantitative
evaluation of the rate and extent of deterioration, which can be used to predict the time for
changing the media.
Key words: RTO, ceramic bed, Alkali corrosion, phase transformation