The Micro-Changes of Fly Ash in the Utilization of “Dip in One Acid Twice/Unite Two Kinds of Alkalis”

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Determined the new technology of element leaching in fly ash’s utilization---- “dip in one acid twice/unite two kinds of alkalis” through comparison tests, the technique consist of four phases: acidleaching、alkali dissolution, calcination and second acid leaching, the maximum fine utilization rates of silicon, aluminum, iron are respectively 97.07%, 86.67%, 96.54%, the total utilization rate is 100%.Analyzed the micro-changes of fly ash in the utilization process by X-ray diffraction and scanning electron microscope, the results show that: (1)there are mineral changes exist in acid leaching process,and some amorphous active substance is dissolved, it destroy the surface structure of fly ash, conducive to the conduct of following response; (2)after alkali leaching, most of the amorphous SiO2is dissolved, crystalline SiO2 (quartz) has not changed; (3)after calcination with sodium carbonate, all the mine phases are transformed into nepheline and a small amount of pyroxene which are layer(film) structure , except a small amount of residual quartz crystal;(4)after the second acid leaching, the fly ash is transformed into silica II which mainly constitute by the amorphous SiO2.