Synchrotron X-ray microtomography and multifractal analysis for the characterization of pore structure and distribution in softwood pellet biochar  

作　　者：Franziska Srocke Liwen Han Pierre Dutilleul Xianghui Xiao Donald L.Smith Ondřej Mašek 

机构地区：[1]Department of Plant Science,Macdonald Campus,McGill University,21111 Lakeshore Road,Ste-Anne-de-Bellevue,Quebec H9X 3V9,Canada [2]UK Biochar Research Centre,School of Geosciences,University of Edinburgh,King’s Buildings,Alexander Crum Brown Road,Edinburgh EH93FF,UK [3]Advanced Photon Source,Argonne National Laboratory,Lemont,IL 60439,USA [4]Present Address:National Synchrotron Light Source II,Upton,NY 11973,USA

出　　处：《Biochar》2021年第4期671-686,共16页生物炭（英文）

基　　金：The research leading to these results received funding from BiofuelNet Canada(funded by the Canadian Networks of Centers of Excellence)and the Leverhulme Trust.

摘　　要：Biochar pores in the micrometer range(1-100μm)derive from cellular structures of the plant biomass subjected to pyrolysis or can be the result of mechanical processing,such as pelleting.In this study,synchrotron X-ray microtomography was used to investigate the internal pore structure of softwood pellet biochar produced by slow pyrolysis at 550 and 700°C.The microtomographic data sets consisted of 2025 images of 2560×2560 voxels with a voxel side length of 0.87μm.The three-dimensional reconstructions revealed that pelleting and pyrolysis significantly altered the pore structures of the wood feedstock,creating a network of connected pores between fragments that resembled the wood morphology.While higher pyrolysis temperature increased the specific surface area(as determined by BET nitrogen adsorption),it did not affect the total observed porosity.Multifractal analysis was applied to assess the characteristics of the frequency distribution of pores along each of the three dimensions of reconstructed images of five softwood pellet biochar samples.The resulting singular-ity and Rényi spectra(generalized dimensions)indicated that the distribution of porosity had monofractal scaling behavior,was homogeneous within the analyzed volumes and consistent between replicate samples.Moreover,the pore distributions were isotropic(direction-independent),which is in strong contrast with the anisotropic pore structure of wood.As pores at the scale analyzed in this study are relevant,for example,for the supply of plant accessible water and habitable space for microorganisms,our findings combined with the ability to reproduce biochar with such pore distribution offer substantial advantages in various biochar applications.

关 键 词：BIOCHAR Pore structure X‐ray microtomography HOMOGENEITY ISOTROPY Multifractal analysis 

分 类 号：TB33[一般工业技术—材料科学与工程]