Title: Impacts of Anisotropic Porosity on Heat Transfer and Off-Gassing during Biomass Pyrolysis

Abstract

The pore structure of biogenic materials imbues the ability to deliver water and nutrients through a plant from root to leaf. This anisotropic pore granularity can also play a significant role in processes such as biomass pyrolysis that are used to convert these materials into useful products like heat, fuel, and chemicals. Evolutions in modeling of biomass pyrolysis as well as imaging of pore structures allow for further insights into the concerted physics of phase change-induced off-gassing, heat transfer, and chemical reactions. In this work, we report a biomass single particle model which incorporates these physics to explore the impact of implementing anisotropic permeability and diffusivity on the conversion time and yields predicted for pyrolysis of oak and pine particles. Simulation results showed that anisotropic permeability impacts predicted conversion time more than 2 times when the Biot number is above 0.1 and pyrolysis numbers (Py₁, Py₂) are less than 20. Pore structure significantly impacts predicted pyrolytic conversion time (>8 times) when the Biot number is above 1 and the pyrolysis number is below 1, i.e., the “conduction controlled” regime. Therefore, these nondimensional numbers reflect that when internal heat conduction limits pyrolysis performance, internal pyrolysis off-gassing further retards effective heat transfermore » rates as a closely coupled phenomenon. Overall, this study highlights physically meaningful opportunities to improve particle-scale pyrolysis modeling and experimental validation relevant to a variety of feedstock identities and preparations, guiding the future design of pyrolyzers for efficient biomass conversion.« less

Authors:

Pecha, M. Brennan  ^[1];

• Search DOE PAGES for author "Pecha, M. Brennan"
• Search DOE PAGES for ORCID "0000-0002-0894-8504"

Thornburg, Nicholas E. ^[2]; Peterson, Chad A. ^[3]; Crowley, Meagan F. ^[1]; Gao, Xi ^[4]; Lu, Liqiang  ^[4];

• Search DOE PAGES for author "Lu, Liqiang"
• Search DOE PAGES for ORCID "0000-0002-5101-1688"

Wiggins, Gavin  ^[5];

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• Search DOE PAGES for ORCID "0000-0002-4737-6596"

Brown, Robert C.  ^[6];

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• Search DOE PAGES for ORCID "0000-0003-0847-9557"

Ciesielski, Peter N.  ^[1]

• Search DOE PAGES for author "Ciesielski, Peter N."
• Search DOE PAGES for ORCID "0000-0003-3360-9210"

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+ Show Author Affiliations

1. National Renewable Energy Lab. (NREL), Golden, CO (United States). Renewable Resources and Enabling Sciences Center
2. National Renewable Energy Lab. (NREL), Golden, CO (United States). Center for Integrated Mobility Sciences
3. Iowa State Univ., Ames, IA (United States)
4. National Energy Technology Lab. (NETL), Morgantown, WV (United States); Leidos Research Support Team, Morgantown, WV (United States)
5. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
6. Iowa State Univ., Ames, IA (United States); Iowa State Univ., Ames, IA (United States). Bioeconomy Inst.

Publication Date:

Mon Dec 06 00:00:00 EST 2021

Research Org.:

Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

Sponsoring Org.:

USDOE Office of Energy Efficiency and Renewable Energy (EERE), Transportation Office. Bioenergy Technologies Office

OSTI Identifier:

1841476

Grant/Contract Number:  

AC05-00OR22725; AC36-08GO28308

Resource Type:

Accepted Manuscript

Journal Name:

Energy and Fuels

Additional Journal Information:

Journal Volume: 35; Journal Issue: 24; Journal ID: ISSN 0887-0624

Publisher:

American Chemical Society (ACS)

Country of Publication:

United States

Language:

English

Subject:

09 BIOMASS FUELS; pyrolysis; single particle model; permeability; diffusion; heat transfer