Abstract：In order to get the optimal process conditions for silica extraction from Junggar alumina-rich fly ash in alkali solution, the orthogonal experiment design was applied. The results show that the optimal conditions are as follows: reaction temperature is 95 ℃, caustic alkali concentration is 15%, reaction time is 1 h, fly ash-alkali ratio is 1:0.6. Under these conditions, the extraction rate of silica from high alumina fly ash achieves 48.6%, and the mass ratio of alumina and silica in the desilicated fly ash can be improved from 1.27 to 2.23 after pre-desilication.

Keywords：alumina rich fly ash; pre-desilication; sodalit