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

Abstract

Lignocellulosic biomass has a complex, species-specific microstructure that governs heat and mass transport during conversion processes. A quantitative understanding of the evolution of pore size and structure is critical to optimize conversion processes for biofuel and bio-based chemical production. Further, improving our understanding of the microstructure of biochar coproduct will accelerate development of its myriad applications. This work quantitatively compares the microstructural features and the anisotropic permeabilities of two woody feedstocks, red oak and Douglas fir, using X-ray computed tomography (XCT) before and after the feedstocks are subjected to pyrolysis. Quantitative analysis of the three-dimensional (3D) reconstructions allows for direct calculations of void fractions, pore size distributions and tortuosity factors. Next, 3D images are imported into an immersed boundary based finite volume solver to simulate gas flow through the porous structure and to directly calculate the principal permeabilities along longitudinal, radial, and tangential directions. The permeabilities of native biomass are seen to differ by three to four orders of magnitude in the different principal directions, but we find that this anisotropy is substantially reduced in the biochar formed during pyrolysis. The quantitative transport properties reported here enhance the ability of pyrolysis simulations to account for feedstock-specific effects and thereby provide a useful touchstone for the biorefining community.

Atomistic origins of biomass recalcitrance in organosolv pretreatment

“…Beyond direct application to separation processes, the binding free energies of lignocellulosic interactions in different organic solvents (∆G binding ) and solvent diffusion constants, calculated using all-atom molecular dynamics, are essential inputs into future continuum scale finite element models (FEM) to investigate reaction-diffusion mass transport properties of plant biomass [44,101]. Experimentally validated continuum based models can effectively quantify structural and transport properties of woody biomass, before and after pyrolysis, and critical towards engineering and optimizing the conversion processes for plant biomass based chemical production [102].…”

Atomistic Origins of Biomass Recalcitrance in Organosolv Pretreatment

“…Beyond direct application to separation processes, the binding free energies of lignocellulosic interactions in different organic solvents (∆G binding ) and solvent diffusion constants, calculated using all-atom molecular dynamics, are essential inputs into future continuum scale finite element models (FEM) to investigate reaction-diffusion mass transport properties of plant biomass [44,101]. Experimentally validated continuum based models can effectively quantify structural and transport properties of woody biomass, before and after pyrolysis, and critical towards engineering and optimizing the conversion processes for plant biomass based chemical production [102].…”

Part 1─Impact of Pyrolysis Temperature and Wood Particle Length on Vapor Cracking and Char Porous Texture in Relation to the Tailoring of Char Properties

“…Nonetheless, a validation of PSD for the material macrostructure can be made with the results of 3D reconstructions of X-ray microcomputed tomography (known as μ-CT or XCT). 50,51 For quantitative assessment of changes in PSD with T C , V pore and the corresponding SSA were divided into specific ranges (see Section 2.9). The V pore as a function of T C for all investigated scenarios are presented in Figure 8 and, in addition, Tables S9 and S10 report the values of V pore and SSA, respectively.…”