Trace Element Enrichment and Behavior in Wood Pellet Production and Combustion Processes

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• 作者：Christoffer Boman ; Marcus Ö ; hman ; and Anders Nordin
• 刊名：Energy & Fuels
• 出版年：2006
• 出版时间：May 2006
• 年：2006
• 卷：20
• 期：3
• 页码：993 - 1000
• 全文大小：372K
• 年卷期：v.20,no.3(May 2006)
• ISSN：1520-5029

文摘

The extensive and well-documented concerns regarding environmental dispersion of toxic trace metalsconstitute solid motives for a special focus of their fate and forms in fuel treatment and conversion processes.The potential enrichment of trace elements during fuel pellet production processes and behavior duringcombustion was, therefore, studied in a combined field sampling and chemical equilibrium modeling work.Raw materials, pellet fuels, and particulate matter in the drying gases in two different pelletizing plants weresampled and analyzed. In addition, chemical equilibrium model calculations were performed with variationsin the content of trace elements, moisture, sulfur, and chlorine, at both oxidizing and reducing conditions. Asignificant enrichment of Zn, Cu, Cd, and Pb was documented when using bark combustion gases for directdrying of the sawdust and was also supported by the chemical equilibrium results. This is presumably causedby the volatilization of these elements from the bark fuel during combustion, subsequently forming fine particlesin the flue gases and being captured by the sawdust during drying. The magnitude and importance for thesetrace elements were, however, found to be relatively small, regarding concentrations in different fuels as wellas potential increased emissions to air during combustion compared to national total emission estimations. Inaddition, some alternative measures for prevention of trace metal contamination during fuel pellet productionwere suggested, including fuel quality aspects, high-temperature particle separation, and indirect drying processes.