PREPARATION OF M50 MULLITE DERIVED DIRECTLY FROM HIGH-ALUMINA FLY ASH:A CASE STUDY FOR THE JUNGAR POWER PLANT IN INNER MONGOLIA,NORTHERN CHINA

Preparation of mullite derived from coal fly ash is an important research field for value-adding utilization of the fly ash.However,this technique is restricted duo to the high cost resulted from adding a large amount of Al2O3 to the fly ash in order to increase a deficient alumina composition to mullite.In this paper,M50 mullite derived directly from high-alumina fly ash of the Jungar power plant was prepared based on orthogonal test.The physical properties of the mullite samples were determined by Archimedes′ method,and the phase constitutes and microstructures were analyzed by using XRD and SEM.It was showed that these M50 mullites could meet the demand of quality for sintered mullite.The phase constitutes of the sintered samples are dominantly composed of mullite and a small amount of glassy materials.The major factor affecting the preparation of mullite is sintering temperature,followed by holding time and molding pressure.Decrease of the holding time at a higher temperature is more profitable than increase of the holding time at a lower temperature during the formation of mullite.The feasible sintering temperature and holding time are 1 400 ℃～1 500 ℃ and 2 h～3 h respectively for preparation of M50 mullite derived directly from high-alumina fly ash.