Comparison of leaching behaviors of aluminum in ash from combustion and catalytic gasification

The leaching behaviors of aluminum in ash from combustion and catalytic gasification, and effects of Na₂CO₃ addition (0-15%), temperature (600-1 000℃) on Al leaching behaviors and mineral composition were investigated. The compositions of ash from combustion and gasification, and acid leaching residue were investigated by XRD. The results shows that the combustion ash is predominantly composed of mullite, while that from catalytic gasification is sodium aluminum silicate ((Na₂O)_0.33NaAlSiO₄). The Al extraction yield of combustion ash only reaches 40% at leaching conditions of 6 mol/L H₂SO₄, 60℃ and 30 min, while that of catalytic gasification ash with 10% Na₂CO₃ addition can reach 88%. The catalytic gasification with Na₂CO₃ addition can achieve higher Al extraction yield.