MFiX based multi-scale CFD simulations of biomass fast pyrolysis: A review

Lu, Liqiang; Gao, Xi; Dietiker, Jean-François; Shahnam, Mehrdad; Rogers, William A.

doi:10.1016/j.ces.2021.117131

Cited by 52 publications

(25 citation statements)

References 134 publications

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“…Recently, particle rocketing due to explosive devolatilization along its longitudinal axis has been observed for small particles in benchtop reactor systems with high temperatures (1200 °C), which is evidently due to vapors escaping one end of a particle at high velocities (Llamas et al, 2022). Evidently, anisotropic pore structure and porosity evolution play integral roles in the motion of particles inside of a high-temperature fluidized reactor (Ciesielski et al, 2021;Lu et al, 2021;Llamas et al, 2022;Lu et al, 2022).…”

Section: Discussionmentioning

confidence: 99%

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

et al. 2022

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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.

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Section: Discussionmentioning

confidence: 99%

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

et al. 2022

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“…The λ is the thermal conductivity of the gas phase, W·m –1 ·K –1 , which can be solved by the formula below. The Nusselt number, Nu , is evaluated by the Ranz–Marshall method correlation. , In addition, Lu et al also summarized the prediction method of the heat transfer coefficients for a variety of nonspherical biomass particles, which can provide great help for our study, that is, the effect of particle shape on the combustion behavior of dust …”

Section: Numerical Modelmentioning

confidence: 99%

Numerical Simulation of Combustion Characteristics in the Dome Zone of the COREX Melter-Gasifier: The Effect of Rising Gas

Zhou

She

et al. 2021

Ind. Eng. Chem. Res.

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The dome zone is one of the most significant areas of the COREX melter-gasifier. The coupled fields in the dome vary with the transport phenomena, which is one of the key factors that impact the smooth operation of the reactor. In this work, a three-dimensional steady-state mathematical model was developed to study the inner characteristics of the dome zone. First, the model was validated by comparing the simulated and experimental results. Then, the effects of key operating parameters of rising gas (e.g., flow rate, component, and temperature) on the hydrodynamics and thermochemical behaviors in the dome zone were analyzed. The results show that the main reaction zone can be divided into three parts, which are controlled by homogeneous reaction, heterogeneous reaction, and diffusion effect in turn. Due to the adequate reaction zone and long residence time, the burnout rate of the dust particle can reach more than 99.9%. Increasing the flow rate of rising gas leads to the increase of CO and H2 in the gas yields. When the proportion of (CO + H2) increases from 80 to 95%, the average temperature of the dome first increases and then decreases, attributed to the heat consumption of excessive H2. The temperature of rising gas insignificantly affects the component of the generator gas at the outlet.

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“…1,2 Although many cutting-edge technologies have been introduced into the handling process of biomass, the commercialization of biomass utilization is still limited. 3 One of the challenges comes from the fact that complicated gas-solid two-phase interactions involving mass, momentum, and energy transfer have not been well understood yet, which hinders the proper designing and upscaling of efficient reactors. Moreover, after pulverization and palletization, biomass particles in fluidized beds feature elongated shapes in nature.…”

Section: Introductionmentioning

confidence: 99%

Development and verification of coarse‐grain CFD‐DEM for nonspherical particles in a gas–solid fluidized bed

Zhou

Liu

et al. 2022

AIChE Journal

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Computational fluid dynamics coupled with discrete element method (CFD‐DEM) has been widely used to understand the complicated fundamentals inside gas–solid fluidized beds. To realize large‐scale simulations, CFD‐DEM integrated with coarse‐grain model (CG CFD‐DEM) provides a feasible solution, and has led to a recent upsurge of interest. However, when dealing with large‐scale simulations involving irregular‐shaped particles such as biomass particles featuring elongated shapes, current CG models cannot function as normal because they are all developed for spherical particles. To address this issue, a CG CFD‐DEM for nonspherical particles is proposed in this study, and the morphology of particles is characterized by the super‐ellipsoid model. The effectiveness and accuracy of CG CFD‐DEM for nonspherical particles are comprehensively evaluated by comparing the hydrodynamic behaviors with the results predicted by traditional CFD‐DEM in a gas–solid fluidized bed. It is demonstrated that the proposed model can accurately model gas–solid flow containing nonspherical particles, merely the particle dynamics are somewhat lost due to the scaleup of particle size. Finally, the calculation efficiency of CG CFD‐DEM is assessed, and the results show that CG CFD‐DEM can largely reduce computational costs mainly by improving the calculation efficiency of DEM. In general, the proposed CG CFD‐DEM for nonspherical particles strikes a good balance between efficiency and accuracy, and has shown its prospect as a high‐efficiency alternative to traditional CFD‐DEM for engineering applications involving nonspherical particles.

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MFiX based multi-scale CFD simulations of biomass fast pyrolysis: A review

Cited by 52 publications

References 134 publications

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

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

Numerical Simulation of Combustion Characteristics in the Dome Zone of the COREX Melter-Gasifier: The Effect of Rising Gas

Development and verification of coarse‐grain CFD‐DEM for nonspherical particles in a gas–solid fluidized bed

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