抄録
In order to investigate the influence of flame characteristics on the surface area of spherical silica powders, their preparation was carried out in the propane-oxygen flame using ground natural quartz powder with a mean diameter of 11.4 μm as a starting powder. The flow rates of propane and oxygen carrier gas were 5 and 7.5 Nm3/h, and the powder feed rate was 18 kg/h, respectively. Two kinds of oxygen gas, primary and secondary oxygen, were ejected from separate nozzles into the combustion room of burner. Being kept the total amount of oxygen constant, their flow rate ratio was varied. With an increase of the portion of primary oxygen from 16 to 50%, specific surface area of the products, collected between cyclone and bagfilter, decreased from 15 to 7m2/g. Distribution of temperature and particle velocity in the flame were found to depend greatly on the ratio of primary and secondary oxygen. Short residence time of particle in the temperature region >2300 K, where gaseous SiO is generated vigorously, resulted in the formation of smaller particles and increase of specific surface area
