Enrichment Characteristics of Critical Trace Elements in Coal Combustion Products of Power Plants
The critical trace elements associated with coal measures can be enriched in coal combustion solid residues.A basis can be provided for the preenrichment,extraction and utilization of critical trace elements by studying their enrichment and differentiation characteristics in coal combustion products.Taking coal combustion products of different power plants in eastern and western China as examples,the contents of major elements and trace elements in coal combustion products were measured by Wavelength dispersive fluorescence spectrometer(Axios mAX)and inductively coupled plasma source mass spectrometer(iCAP-Qc)respectively,and the general law of distribution and enrichment of key trace elements in coal products was clarified.The results show that ① the main constants elements in fly ash are Si,Al and Fe,and their oxides account for 87.79%.The contents of rare earth elements,lithium,gallium,uranium and germanium are 456.95μg/g,163.58μg/g,49.07μg/g,8.67μg/g and 4.59μg/g,respectively,which are all higher than the world average value of coal ash except uranium and germanium.②Phosphorus tends to be enriched in fine ash,while Fe and Ca are more likely to be enriched in coarse ash.The distribution pattern of rare earth elements is consistent in different samples,and the content of rare earth elements in fine ash is higher than that in coarse ash.Lithium,gallium,uranium and germanium are more enriched in fine coal combustion product,and their differentiation coefficients are 1.17,2.45,1.53 and 2.14,respectively.③Mathematical statistical analysis shows that rare earth elements are related to inorganic minerals and are enriched in non-magnetic components.Lithium is mainly related to clay minerals and exists mainly in the form of LiAlO2 after combustion.The occurrence forms of gallium and uranium are not simple,and have a certain relationship with clay minerals.The weak correlation between germanium and inorganic indicates that germanium is mainly combined with organic matters.
coal combustion solid residuesrare earth elementscritical elements enrichment
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