生物质固定床热解碳烟结构特征及反应活性

Characterization and reactivity of soot from biomass pyrolysis in a fixed bed reactor

在固定床上进行了麦秆与木屑2种生物质的热解实验,对热解碳烟产物的产率、微观形貌等理化性质进行了表征,并在热天平上测定其氧化/气化特性。研究了在不同热解温度下两种生物质产生碳烟的产率、粒径分布及内部纳观结构的变化趋势,在此基础上分析了碳烟反应活性的影响因素,并将结果与采用一维沉降炉热解方式获得的碳烟对比。结果表明:采用固定床热解获得的碳烟具有较高的纯度。随着生成温度的升高,碳烟结构排列更加有序,石墨化程度提高,基本粒子的几何平均粒径变小,同时碳烟的反应活性变差,说明碳烟内部结构的变化对反应活性的影响起主要的控制作用。单位空间内生物质的燃料浓度会影响碳烟的产率、粒径等特性。高的原料空间浓度倾向于生成更多的碳烟,并且碳烟具有更大的粒径。木屑碳烟相比麦秆碳烟石墨化程度更高,反应活性较差。

The pyrolysis experiments of two biomasses,wheat straw and wood chips,were carried out on a fixed bed.The physicochemical properties of the pyrolysis soot were characterized,and their oxidation/gasification characteristics were determined on a thermobalance.The yield,particle size distribution and internal nanostructure of the two biomass soots were studied at different pyrolysis temperatures.On this basis,the influencing factors of the soot reactivity were analyzed,and the results were compared with the adopted comparison of soot obtained by one-dimensional settling furnace pyrolysis.The results show that soot obtained by fixed bed pyrolysis has higher purity.With the increase of the generation temperature,the structure of soot becomes more ordered,which indicates the increases of graphitization.Besides,the geometric average particle size of the single soot particle becomes smaller.However,the reactivity of soot becomes worse at elevated temperature,indicating the change of the internal structure of soot plays a major role in its oxidative activity.The fuel concentration of biomass in a limited space affects the yield,inter-structure and particle size of soot.High feedstock spatial concentrations tend to generate more soot with larger particle size.Compared with wheat straw soot,sawdust soot has higher graphitization degree,thus showing poor reactivity.