Method of treating wet-washed silica dust

Claim 1

A process for treating the waste gasses generated from metallurgical furnaces for the production of materials high in silicon content comprising: (a) wet-washing the waste gasses whereby a sludge is obtained comprising silica dust, phenols and cyanides; (b) introducing the sludge to a rotary kiln; (c) heating the sludge at temperatures not in excess of about 500° C. until substantially all of the water is driven off from the sludge; (d) thereafter raising the temperature of the sludge in the rotary kiln to from about 800° C. to about 1,400° C. while simultaneously treating it with an agent selected from the group consisting of those oxidizing and reducing agents capable of rendering phenols and cyanides harmless; (e) continuing the heating of step (d) until a substantial portion of the phenols and cyanides are rendered harmless; (f) and wherein pellets comprising silica dust are formed by the rotary action of the rotary kiln at the elevated temperatures of step (d).