Study on Preparation of Mullite from Low Grade Coal Gangue

Using the coal gangue after acid leaching and alumina oxide as raw material,the effect of synthetic on mullite phase was researched under different experimental conditions.When the heating temperature is 1 200 ℃ a rod like mullite crystal appears,.With the temperature exceeding 1 500 ℃,significant amount of mullite is obtained and its amount further increases while temperature reaching up to 1 600 ℃.By changing the holding time under highest heating temperature,the degree of mullitization firstly increases and then decreases.With the coal gangue dosage increasing,corundum phase peak enhances,which indicates that the increase of coal gangue dosage has negative role in synthesizing mullite. By changing the rate of silicon and aluminum from 3 ∶ 2 to 1 ∶ 1,the degree of mullitization gradually enhances.When the ratio of silicon and aluminum is 1 ∶ 1,corundum phase peak disappears,which indicates that low-grade coal gangue with lower alumina-silica ratio is beneficial for the synthesis of mullite.