| Circulating fluidized bed fly ash is the product of coal burning in a circulating fluidized bed boiler and desulfurization of limestone.In 2015,China's coal ash emissions exceeded 620 million tons,with a huge output.A large amount of fly-ash storage occupied a large area of land resources,damaged the nearby ecological environment,polluted the air and groundwater resources,and seriously endangered the survival of humans,animals and plants.Now for the comprehensive utilization of CFB fly ash in cement,concrete and building materials production and other low value-added utilization is given priority to,also carried out in recent years a large number of high value-added integrated application research,mainly in all kinds of valuable metals,such as the extraction of gallium,germanium,iron,aluminum,paper chooses Inner Mongolia datang international a coal-fired power plant production of CFB fly ash was studied,including high aluminum content,efficient extraction has the very good economic value,take the sulfating roasting and microwave roasting to strengthen its leaching process,and carry out the study of sodium carbonate activation,get the following main conclusions:The sulfuric acid leaching experiment of fly ash in circulating fluidized bed was carried out,and the factors affecting the acid leaching effect were investigated.The optimal conditions for acid leaching were as follows: the acid leaching temperature was 85?,the acid leaching time was 120 min,the acid concentration was 6 molˇ L-1,the acid leaching liquid solid ratio was 9:1,and the aluminum leaching rate was 62.87%.It was found that conventional acid leaching could not completely extract aluminum from the fly ash in the circulating fluidized bed.Mullite was not found in the fly ash in the circulating fluidized bed,but aluminum oxide and silicon dioxide combined to form an amorphous aluminosilicate insoluble in acids.To further improve the extraction rate of aluminum,activation of the fly ash in the circulating fluidized bed must be carried out.The dielectric properties of fly ash in circulating fluidized bed and its temperature rise in microwave field are studied.It is found that fly ash has good microwave absorption performance and can be heated rapidly in microwave field.Conventional and microwave sulfurized roasting experiments were carried out to study the influence of roasting technology conditions on leaching results.By using single factor experiment,the optimum conditions of microwave sulfurization roasting are as follows: the roasting temperature is 260?,the roasting time is 60 min,the acid ratio is 1.25:1mLˇg-1,and the leaching rate of aluminum is 76.54%.By characterization of circulating fluidized bed fly ash and its calcined products,the strengthening mechanism of conventional and microwave sulfurization calcination was deduced.By XRD analysis,the study of circulating fluidized bed coal fly ash and different leaching conditions of material phase,found that CFB fly ash,does not contain aluminum oxide crystal phase in the microstructure by SEM and EDX spectrum analysis shows that element enrichment of CFB fly ash,and introduce the conventional leaching mechanism and strengthening mechanisms sulphation roasting.Subsequently,the experiment on the activation of sodium carbonate in circulating fluidized bed fly ash was carried out,and the optimal roasting conditions were determined as follows: the roasting temperature was 850?,the roasting time was 60 min,the molar ratio of sodium carbonate to fly ash was 1:1,and the leaching rate of aluminum was 93.62%.The characterization of the products of sodium carbonate activation was carried out,and the phase transformation of the roasting process was studied. |
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