Recent advances in heat recirculating combustion made it possible to use highly preheated combustion air, typically above 1300K. But these highly preheated air combustion is confined to gas or liquid fuel. Combustion characteristics for solid fuel caused by the highly preheated air are reviewed.
A laboratory scale thermogravimetric analyzer was developed to investigate the combustion characteristics of selected solid fuel(wood) in the highly preheated air. A nearly single particle combustion environment is reproduced in the analyzer and the progress of reaction is observed by determining weight loss and exhaust gas.
The aims are to introduce the means to explain the fuel characteristics on the pyrolysis and combustion process of the fuel in the environment of highly preheated air. The temperature was maintained 800℃ ~ 1000℃ and the parameters are air flow rate and oxygen concentration.
For a fuel particle whose characteristic length was a few centimeter, the sub-processes of fuel drying, pyrolysis as well as the combustion of residual carbon were identified. The results also show a weak effect of oxygen concentration and flow rate on the devolatilization. But their remarkable effect on char combustion is observed. Drying and devolatilization occur in parallel during the initial phase but char combustion takes place either in parallel or in series depending on the condition.
