The role of heat transfer limitations in polymer pyrolysis at the microscale
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Published version
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Author(s)
Richter, Franz
Rein, Guillermo
Type
Journal Article
Abstract
Pyrolysis of synthetic or natural polymers is an important process in many industries such as fire safety, thermal recycling, and biomass power generation. The kinetics of pyrolysis is usually studied by thermogravimetric analysis (TGA), which is based on measuring the mass loss of a microscale sample and measuring the temperature of the surrounding fluid during controlled heating. The literature is rich in TGA measurements, which are often assumed to be governed solely by chemical kinetics. Heat and mass transfer effects, however, can occur when the sample mass is too large. Only a few studies in the literature quantify the threshold for the initial mass, above which heat transfer effects are significant. Here, we systematically analyse the role of heat transfer in TGA measurements, review existing formulations, and provide a novel threshold for the maximum sample mass. We focus on the natural polymer cellulose, a surrogate for biomass, and split the problem into heat transfer within the sample (intraparticle) and between the sample and the fluid (interparticle). Using dimensional analysis we derive two upper bound thresholds for the initial sample mass as a function of heating. One threshold is calculated based on interparticle heat transfer and depends on flow and heating conditions as well as material and fluid properties. The other is calculated based on intraparticle heat transfer and depends on heating conditions and material properties. Both thresholds were validated with measurements and previous studies from the literature. Comparing both thresholds shows that the maximum sample mass in a TGA is dictated by interparticle heat transfer and rapidly reduces with heating rate from 1.8 mg at 10 K/min to 0.15 mg at 50 K/min. These results enable the selection of appropriate sample masses and heating conditions in TGA measurements, which in turn will lead to a better understanding of polymer pyrolysis.
Date Issued
2018-11-20
Date Acceptance
2018-10-26
Citation
Frontiers in Mechanical Engineering, 2018, 4, pp.1-13
ISSN
2297-3079
Publisher
Frontiers Media
Start Page
1
End Page
13
Journal / Book Title
Frontiers in Mechanical Engineering
Volume
4
Copyright Statement
© 2018 Richter and Rein. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
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Sponsor
Commission of the European Communities
EPSRC
Identifier
https://www.frontiersin.org/articles/10.3389/fmech.2018.00018/full
Grant Number
682587
EP/M506345/1
Subjects
0913 Mechanical Engineering
0915 Interdisciplinary Engineering
Publication Status
Published
Article Number
18
Date Publish Online
2018-11-20