生物质热解过程中碱及碱土金属迁徙规律研究

Releasing Behavior of Alkali and Alkaline Earth Metals During Biomass Pyrolysis

研究了固定床上生物质热解过程中碱及碱土金属的迁徙规律,并结合扫描电镜–能谱分析对热解焦颗粒表面的相关无机元素富集状态进行了探索。研究发现在低温下钾的析出量较少,高温时则析出量迅速增加。钾的析出量与焦炭的堆积状态和生物质中的硅含量有较大关系。由于与焦炭的结合能力较弱,钠的析出比例较大。钙、镁在较低的热解温度下主要为有机钙、镁组分的分解,而在高温下则主要以较为稳定的形式存在于焦炭中。扫描电镜–能谱分析研究结果表明高温下生物质焦的形态稳定性与硅含量有关,钾元素的富集量与Cl存在明显的相关性。在焦炭的外表面,钾元素主要以硅酸盐形式存在,在焦炭的内表面,则主要以氯化钾形式存在。

The releasing characteristics of alkali and alkaline earth metals（AAEMs） during biomass pyrolysis process were explored in a fixed bed reactor,and the enrichment of related inorganic elements inside and outside char particle surfaces was also researched using scanning electron microscope combined with energy-dispersive X-ray analytical system（SEM/EDX）.It is found that the releasing amount of K at high temperature range increases obviously and is affected by the K adsorption capacity of char and the content of Si.The releasing proportion of Na is larger than K due to its weaker binding ability with char.The release of calcium and magnesium is mainly because of the decomposition of organic calcium and magnesium components during the pyrolysis process.SEM-EDX studies show that the Si content determines the integrity of biomass char under high temperature.The existence of K shows remarkable relationship with Cl.On the outer surface of char particles,the main existence form of K is silicate,but KCl on the inner surface.