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ISSN Online: 2377-424X

ISBN Print: 978-1-56700-421-2

International Heat Transfer Conference 15
August, 10-15, 2014, Kyoto, Japan

An Investigation of Anisotropic Structure of Wood-Derived Char Using X-ray CT and Effect of Particle Aspect Ratio on its Gasification Reactivity

Get access (open in a dialog) DOI: 10.1615/IHTC15.pmd.008763
pages 6827-6834

摘要

The anisotropic structure of wood-derived char was visualized by using X-ray CT. And, the effect of particle aspect ratio on the char reactivity during gasification was also studied. The char sample for X-ray CT analysis was prepared by pyrolyzing Japanese cypress wood cylinder with a diameter of 8 mm and length of 9 mm. Pores with diameter larger than 2–3 ?m inside the char sample were well visualized using X-ray CT. The 3D image of char structure clearly showed the anisotropic alignment of pores inside the char sample and pores mainly aligned in the axial direction of wood cylinder used in this study. Wood cylinders with three aspect ratios were pyrolyzed to produce char samples and then gasified in an O2/Ar atmosphere. Gasification temperature was set to 873 or 1423 K at which gasification reaction occurred in the transition zone (between the kinetically controlled and the internal diffusion-controlled zone) and the internal diffusion-controlled zone, respectively. The results showed that char reactivities at 873 K (the transition zone) did not significantly depend on particle aspect ratio. However, at high temperature of 1423 K (the internal diffusion-controlled zone), the char reactivity was significantly increased with decreasing particle aspect ratio. Pores aligned in the axial direction played an important role in the O2 transport; therefore, a decrease in aspect ratio (an increase in top surface area) improved O2 transport, leading to enhancing the char gasification when the gasification rate was controlled by the internal diffusion. It was shown that wood cylinders with low aspect ratio had the high reactivity in gasification due to its anisotropic intraparticle structure.