Study on Thermal Characteristics of a High Temperature Air Combustion Boiler (2nd Report, Numerical Study)

Thermal characteristics of a high temperature air combustion boiler is numerically examined. The high temperature air combustion is realized using a preheated air of about 800°C∼1000°C under low oxygen content (∼5%). Numerical simulation reveals that more uniform temperature distribution in the boiler and higher heat transfer are obtainable using high temperature air in comparison with using normal temperature air owing to mild reactions in the high temperature field and heat recovery by regenerative burners. High speed injection of high temperature air into the boiler causes in-furnace exhaust gas recirculation, which results in low NO_x emission. There is good agreement between experiment and numerical simulation in particular when using low calorific value gas, because more uniform temperature distribution is realized and average temperature in the boiler becomes lower.