IMPROVEMENT OF ALUMINA EXTRACTION FROM FLY ASH BY ACID-ALKALI METHOD WITH LUMP ROASTING

To solve the problem of environmental pollution caused by the extensive accumulation of the fly ash residue, achieve the maximum utilization value from fly ash and alleviate the shortage of bauxite resources in China, the acid-alkali combination method, which was most commonly used for extracting alumina from fly ash, was combined with block roasting to improve the extraction rate from fly ash. The extraction rate of alumina was greatly improved by lump roasting method. Under the optimum condition, the extraction rate of alumina reached 84%. Through XRD, SEM and other mean, the advantages of blockmaking methods were further analyzed. In addition, the process could not only be used to separate aluminium and silicon, but also recycle sulfuric acid. Kinetic studies showed that the internal capillary channels of fly ash particles and the lumps played a skeleton role similar to that of coke in blast furnaces. Block making treatment created a mesoscopic porous structure for reaction, which not only reduced the distance between solid and liquid phases, but also effectively improved the mass transfer condition of gas and liquid phases, thus enhancing the extraction of aluminium.