The Oxidizing and Reducing Characteristics of Flame Produced by a Premixing Ceramic Kiln Burner

Abstract

Controllability of operation of kilns and some characteristics of combustion gas produced by a natural gas fired-premixing burner were studied from various points of view with an experimental kiln. The radial and directory temperature distributions inside the kiln equipped with a premixing burner were more uniform than those with low-speed diffusion-type burners. Simultaneous control of the temperature and the firing atmospheres were achieved for a set period of time in which the temperature is varied at a constant rate. The equilibrium compositions of the gas flame calculated at different temperatures and air ratios were and compared with the measured compositions. The results calculated for CO2, O2, CO and H2 agreed very well with the measured values, but the discrepancy was remarkable in NO owing to the low rate of NO formation. The average NO emission in the combustion gas was reduced by supplying substoichiometric quantities of primary air to the burner, while keeping the total air rate constant. The H2/CO ratio in the reducing atmosphere was not constant, as has usually been assumed, but depend on the temperature and air ratio.