Structural analysis of biomass pyrolysis and oxidation using in-situ X-ray computed tomography

Measurement of Transport Properties of Woody Biomass Feedstock Particles Before and After Pyrolysis by Numerical Analysis of X-Ray Tomographic Reconstructions

“…The calculated values from the current study agree with the previously reported values, with slight variations likely due to variability of the material. Particularly, our calculated value for the void fraction of red oak is significantly higher than that reported by Boigné et al (2022). We attribute this difference to our sample being taken from early wood red oak, which contains more vessel elements than the bulk material and thus a higher void fraction.…”

“…The Douglas fir samples show a 15.9% increase in void fraction after pyrolysis, while that of the red oak show a 22.8% increase in void fraction after pyrolysis. Previously reported values of void fraction for Oak and Douglas Fir from Boigné et al (2022) are also listed in Table 1. The calculated values from the current study agree with the previously reported values, with slight variations likely due to variability of the material.…”

“…Confocal scanning laser microscopy (CSLM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) are commonly employed to visualize biomass microstructure, yet each have their limitations (Ciesielski et al, 2014). Sample preparation via microtomy for CSLM and TEM can be challenging and may result in artifacts that significantly affect the quality of the images (Boigné et al, 2022). While these methods can be used to produce 3D information about microstructure, by using z-stacking in the case of confocal microscopy, stereo pairs for SEM, and tomography for TEM, the reconstructions often suffer from limited resolution (Shah et al, 2017) and/or missing regions (Bartesaghi et al, 2008) which reduce confidence in measurements of pore geometry.…”

“…X-ray computed tomography (XCT) is a widely used imaging method to analyze solid samples that produces 3D volumetric images of the microstructure of materials. XCT can provide high spatial resolution while mitigating optical limitations such as beam steering or limited depth of field (Boigné et al, 2022). The 3D reconstructions provided by XCT permit detailed, nondestructive, and direct characterization of the pore microstructure of biomass without the need for any histochemical treatments or intensive sample preparation.…”

“…Sun et al (2021) calculated the porosity and pore size distribution of loblolly pine samples from XCT reconstructions in a novel study, but important features such as the permeability tensor, tortuosity, or void fraction were not calculated. Boigné et al (2022) analyzed volume shrinkage within biomass during pyrolysis and oxidation using real-time, in situ XCT, but the effects of pyrolysis on transport properties were not quantitatively investigated. Zolghadr et al (2019) used XCT imaging to characterize the microstructure of crystalline cellulose, switchgrass, and tall fescue microspheres, calculating void fraction and tortuosity but not directional permeabilities.…”