Preparation of activated carbon from unburned carbon in biomass fly ash and its supercapacitor performance
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摘要: 生物质燃料在锅炉中经过热解和燃烧后,飞灰中含有孔隙丰富的未燃尽炭。但其孔隙率和比表面积无法满足商用超级电容炭的要求,改善材料孔隙结构的活化方法成为未燃尽炭提质改性的关键。本研究通过对筛分粒径 > 0.2 mm的未燃尽炭进行KOH一步活化处理后发现,在浸渍比3.5∶1时活性炭拥有较大的比表面积(1982 m2/g),且在电流密度1 A/g时比电容可达207 F/g。以上结果表明,未燃尽炭基活性炭制备的电极双电层超级电容性能优良,而为生物质飞灰的高附加值利用提供了参考。Abstract: After the fuel undergoes pyrolysis and combustion in a biomass boiler, the fly ash contains some unburned carbon with abundant pores. However, their low porosities and specific surface areas cannot meet the requirements of the activated carbon for commercial supercapacitors, and the activation method to improve their pore structures is the key to enhance their applicability. After the one-step KOH activation treatment of the unburned carbon with the particle sizes > 0.2 mm, the results showed that the activated carbon has the largest specific area (1982 m2/g) at an impregnation ratio of 3.5∶1, and the specific capacitance reached 207 F/g at the current density of 1 A/g. The above results indicate that unburned carbon-based activated carbon has a good double layer capacitance performance, providing a reference for the high value-added utilization of biomass fly ash.
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Key words:
- biomass fly ash /
- unburned carbon /
- KOH activation method /
- supercapacitor
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图 1 未燃尽碳基活性炭的孔结构特性(a)总比表面积和总孔容;(b)微孔比表面积和微孔孔容随浸渍比的变化趋势图;(c)活性炭样品的N2吸附-解吸附等温曲线;(d)活性炭样品的孔径分布图
Figure 1 Porous characterizations of HYC-n (a) The trend of total specific surface areas, total pore volumes; (b) Micropore specific surface areas, volumes change by increase of the impregnation ratios; (c) N2 adsorption-desorption isotherm curves of activated carbon samples; (d) Pore size distribution of activated carbon samples
表 1 生物质飞灰和筛分后粒径 > 0.2 mm未燃尽炭的工业分析
Table 1 Proximate analysis of the biomass fly ash and the unburned carbon with the particle sizes > 0.2 mm
Sample Proximate analysis wad/% w/% Mad Aad Vad FCad Biomass fly ash 0.86 87.37 8.51 3.26 100 Unburned carbon 3.18 54.27 7.22 35.33 5.34 Mad: moisture, Aad: ash, Vad: volatiles, FCad: fixed carbon 表 2 粒径 > 0.2 mm未燃尽炭的元素分析
Table 2 Ultimate analysis of the unburned carbon with the particle sizes > 0.2 mm
Sample Ultimate analysis wad/% C H O N S Unburned carbon 34.92 0.779 0.47 0.621 5.76 表 3 活性炭的比表面积与孔隙结构特性
Table 3 Textural properties of different samples at different impregnation ratios
Sample SBET/
(m2·g−1)VT/
(cm3·g−1)SBET, micro/
(m2·g−1)Vmicro/
(cm3·g−1)HYC-0 406 0.411 51 0.186 HYC-1.5 1062 0.763 587 0.477 HYC-2 1408 0.920 1040 0.605 HYC-2.5 1464 0.941 1038 0.623 HYC-3 1710 1.152 1048 0.739 HYC-3.5 1982 1.273 1119 0.813 HYC-4 1997 1.269 956 0.784 HYC-4.5 2073 1.393 628 0.761 表 4 不同电流密度下活性炭样品的比电容
Table 4 Specific capacitance of activated carbon samples at different current densities
Sample Specific capacitance/(F·g−1) 0.1 A/g 0.5 A/g 1 A/g 2 A/g 5 A/g 10 A/g HYC-1.5 136 128 125 121 118 115 HYC-2 158 145 141 136 131 127 HYC-2.5 160 147 143 137 133 129 HYC-3 196 178 175 171 164 161 HYC-3.5 233 212 207 202 195 190 HYC-4 190 173 169 166 157 155 HYC-4.5 176 163 158 153 150 147 -
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