Spheroidizing mechanisms and simulation of spherical silica in Oxygen-Acetylene flame

摘要

In order for heat transferring and spheroidizing mechanisms of silica powders in Oxygen-Acetylene flame to be observed, the experiments were conducted and the Finite Element (FE) simulation method was employed. It has been certified that powder spheroidization occurred only at molten states, primarily depending on two major factors: melting time and particle size. Various particle sizes and various process parameters were studied systematically, whereas following the spheroidization mechanisms were concluded. At a flow rate of 40 L/min, the spheroidization rate percentage of 20 mu m silica powders reached the maximum value. At a flow rate of 45 L/min, melting time of all particles were lower than 0.08 s, where it was difficult for 40 mu m sized or larger powders to be spheroidized, also sharp corners of bigger powders were still observed. SEM results also revealed that powder spheroidization was affected by flow rate. The silica particle heat transfer time inside the gas flame furnace was reported and compared to SEM results. Through comparative analysis, the simulation results were in agreement with experimental results. The numerical model was capable of particle melting time calculation and can be used in spheroidizing results prediction to a certain extent. (C) 2017 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.