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A Study on the Influencing Factors of Migration of Trace Elements in a Pulverized Coal-fired Boiler

By using a Z-8200 atomic absorption spectrophotometer and a VF-320 X-ray fluorescent spectrograph the content of nine trace elements in raw coal, bottom slag and fly ash was measured quantitatively in a 220 th pulverized coal-fired boiler. On the basis of an improved relative enrichment factor of Meij and from the perspective of two aspects, namely, bottom slag and fly ash, a systematic analysis was performed of the influence of various factors on the law of migration. Such factors include: temperature, oxygen content, fly ash diameter, the properties of trace elements per se and the characteristics of coal rank. The results of the analysis indicate that an rise in furnace temperature can quicken the volatilization of some of the trace elements. The content of Cr and Mn in fly ash and bottom slag is comparable, but the two elements differ markedly in respect of relative enrichment factor. Low oxygen content does not always promote the volatilization of all trace elements. The content of Pb, Cd, Zn and Cr in the bottom slag and fly ash does not assume a linear relationship with their respective boiling points. The smaller the diameter of the fly ash, the greater the enrichment factor of the trace elements. The tendency of variation of various trace elements with the decrease in fly ash diameter has been found to be not identical for different trace elements.