Study Of Step-Leaching Of Silica And Alumina In Resourcelization Utilization Of Fly Ash By Means Of Alkalescence Meduim

With the development of knowledge about fly ash, the study on it is more and more,.recently,most of study are focused on extracting silica and alumina of fly ash,it makesresourcelizatitonal utilization of fly ash be reality.this paper studied the discinplination of silicaand alumina in fly ash step-leached by means of alkalescence medium.The subject of this paper is fly ash from Meishan plant,Shanghai,it is operated in threemanners:at pressure,under pressure and microwave-heating.the effects of sintertemperature,leaching temperature,time,alkala concentration and the ratio of liquid to solid ofreaction to ratios of silica and alumina leached.are investigated to find the optimal processmethod and process conditions about them.the regional study results are obtained.the resultsindicated that the highest ratio of silica and alumina step-leached is obtained under pressure,theratio of silica leached is about 29.2%,that of alumina leached is 1.26%,the ratio of silica toalumina leached is 23.2.the process condition under pressure is: ⑴heating treatment temperatureof fly ash is 950℃;⑵reaction time is 6h;⑶the ratio of liquid to solid of reaction is 50:1(massratio);⑷alkaline concentration is 2.5mol/L(NaOH);⑸reaction temperature is 140℃.On the base of those studies, the micro-structure of fly ash heat-treated at differenttemperatures is also investigated, The DTA and the X-ray diffraction(XRD) analysis techniquesare integrated to investigate the transformation of crystal structure of silica snd alumina in flyash with temperatures,the infrared ray (IR) is adopted to analyze the change concerning structureof vitreous body formed by SiO2 and Al2O3 in fly ash.the micro-structure analysis resultsindicate that a part of α-quartz and vitreous phase X-ray amorphous silicon transfer to β-quartz,partial γ-Al2O3 transfers to α-Al2O3,kaoline and cristobalite transfer to β-quartz, α-Al2O3 andinert mullite.the transformation of micro-stucture makes the ratio of silica to alumina leachedfrom fly ash rise to 23.2 from 10.5,reinforces the stap-leaching of silica and alumina.