酸洗预处理对生物质热解焦物理化学特性的影响

EFFECT OF ACID WASHING PRETREATMENT ON PHYSICAL AND CHEMICAL PROPERTIES OF BIO-CHAR

选用松木、杨木、玉米秸秆和稻壳4种生物质为原料,采用3%(体积分数)乙酸溶液进行洗涤除灰后,进行快速热解实验,对比研究酸洗预处理对4种生物质热解焦物理化学特性的影响。结果表明:乙酸酸洗可有效去除松木、杨木、玉米秸秆和稻壳灰分中的大部分无机元素,从而促进热解过程中挥发分的释放、显著改善热解焦的表面化学特性。酸洗可促进热解焦孔隙结构的形成,提高比表面积和总孔容积,但会使平均孔径减小,这表明酸洗主要提高微孔率,对微孔的形成有较大的促进作用。同时,酸洗使得更多的含氧官能团保留在生物质热解焦表面,这种影响对玉米秸秆和稻壳尤为明显。气化焦油的吸附实验结果表明酸洗后热解焦的吸附能力有所增加。

Four biomass including pine,poplar,maize straw and rice husk were selected as raw materials.After washing and ash removal with 3 vol.%acetic acid solution,a fast pyrolysis experiment was conducted to compare the effects of acid washing pretreatment on the physical and chemical properties of char during pyrolysis of the four biomass.The results show that the acetic acid can effectively remove the pine,poplar,maize straw and rice husk ash content of inorganic elements,so as to promote the release of volatile matter in the process of pyrolysis,significantly improve the surface chemistry characteristic of the bio-char.Acid washing can promote the formation of pore structure of bio-char and improve the specific surface area and total pore volume.However,the average pore size decreased,indicating that acid washing can improve the micropore rate and promote the formation of micropores.At the same time,the acid washing keeps more oxygen containing functional groups in the surface of bio-char,which is especially significant for maize straw and rice husks.The adsorption experiment results of gasified tar showed that the adsorption capacity of pyrolysis char increased after washing.