生物质固定床热解碳烟结构特征及反应活性

doi:10.11949/0438-1157.20221152

摘要/Abstract

摘要：

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。

关键词: 生物质, 固定床热解, 碳烟, 氧化活性

Abstract:

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.

Key words: biomass, fixed bed pyrolysis, soot, oxidation activity

中图分类号:

TK 123

李艳, 曹进辉, 刘原一, 谭厚章. 生物质固定床热解碳烟结构特征及反应活性[J]. 化工学报, 2022, 73(12): 5564-5571.

Yan LI, Jinhui CAO, Yuanyi LIU, Houzhang TAN. Characterization and reactivity of soot from biomass pyrolysis in a fixed bed reactor[J]. CIESC Journal, 2022, 73(12): 5564-5571.

图/表 9

图1 管式炉固定床高温热解反应实验系统

Fig.1 The experimental system of the fixed bed reactor

图2 热解温度对不同生物质固定床热解碳烟产率的影响

Fig.2 The effect of pyrolysis temperature on the soot yield from different biomasses

图3 生物质固定床热解碳烟形貌随温度的变化

Fig.3 Changes of soot morphology from different biomasses with temperature

图4 不同温度两种生物质固定床热解碳烟粒径分布

Fig.4 Soot particle size distribution of two biomasses at different temperatures

图5 不同温度两种生物质固定床热解碳烟XRD谱图

Fig.5 XRD patterns of two biomass soots generated from different temperatures

表1 不同温度热解碳烟晶体结构参数

Table 1 Crystal structure parameters of soot samples from different formed temperatures

碳烟样品	晶面间距d₀₀₂/nm	堆垛高度L_c/nm	片层直径L_a/nm	晶层数目N
麦秆-1100℃	0.3568	1.84	3.09	6.2
麦秆-1200℃	0.3522	1.97	3.24	6.7
木屑-1100℃	0.3533	2.04	3.47	6.7
木屑-1200℃	0.3523	1.93	4.28	6.5

图6 两种生物质不同热解温度生成碳烟的氧化曲线

Fig.6 Oxidation curves of biomass soot generated from different temperatures

图7 两种生物质不同热解温度生成碳烟的气化曲线

Fig.7 Gasification curves of biomass soot generated from different temperatures

表2 生物质固定床不同温度热解碳烟热重氧化曲线特征参数

Table 2 Characteristic parameters from soot oxidation curves

碳烟样品	T_i/℃	T_p/℃	T_f/℃	W_max/(%/min)	W_mean/(%/min)	M_C/%	M_K/%	M_r/%
麦秆-1100℃	530.6	575.2	593.4	-13.80	-6.58	87.15	9.01	3.84
麦秆-1200℃	532.5	607.1	622.6	-9.94	-6.06	87.89	6.50	5.61
木屑-1100℃	591.7	647.1	675.6	-12.06	-6.31	90.48	0	9.52
木屑-1200℃	615.6	670.0	703.5	-11.36	-6.04	95.05	0	4.95

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