Production of glass spheres from blast furnace slags by a thermal flame projection process

Blast furnace slags (BFS) were transformed into glass porous spheres by applying a natural gas/oxygen thermal projection process. Three types of BFS were selected as a function of their age or storage time. Effect of type of precursor, as well as gases mixture, feeding distance and feeding rate on density, morphology, microstructure and particles size of generated spheres were evaluated. It was found that despite of the slag age, obtained spheres are completely amorphous, and that the feeding distance has an important effect on spheres densities. Optimum treatment conditions were established in order to generate glass porous spheres with lower densities than their precursors.