Calcining process of synthesizing hollow silica alumina ball

The calcining process of synthesizing hollow silica-alumina ball includes the steps of crushing sawdust, mixing with water and adhesive, making wet ball kernel, turning the wet ball kernel in ball forming machine in proper rotation speed while throwing proper amount of refractory silica-alumina powder for coating the ball kernel, and calcining at high temperature to produce the hollow silica-alumina ball. The hollow silica-alumina ball has low bulk density, low production cost and other advantages, and is used as the material for producing high grade refractory material. The present invention makes it possible to producing light refractory material with bulk density smaller than 0.6 g/cu cm.