China Nonferrous Metallurgy

Coal ash leaching test was conducted using sulfuric acid, for the purpose of investigating the influence of the main process conditions on the leaching rate of Al and Fe in the coal ash, meanwhile the compositions and phase of the leaching residue were analyzed. The test results showed that: hightemperature acid leaching of coal ash using sulfuric acid could achieve a highefficiency leaching of aluminum and iron elements, and the leaching temperature was the main influencing factor; under the acid leaching conditions of leaching temperature 230℃, sulfuric acid mass fraction 20%, reaction time 120min, and liquidsolid ratio 10∶1, the leaching rate of Al was 89.43%, and the leaching rate of Fe was 69.78%; the main chemical composition of the acid leaching residue was SiO₂, its content was 79.1%, and it also contained a small amount of unleached Al₂O³ and Fe₂O₃ which could be used as raw materials to prepare Portland cement clinker. There was no secondary waste residue discharge in this test, and no waste liquid discharge in the subsequent treatment of the leachate. The method provided a reference for realization of comprehensive utilization of coal ash with zero discharge.