Impact of post-torrefaction process on biochar formation from wood pellets and self-heating phenomena for production safety

Emmanuel Arriola, Wei-Hsin Chen, Yi-Kai Chih, Mark Daniel De Luna and Pau Loke Show

Energy, 2020, vol. 207, issue C

Abstract: The advancement of torrefaction in the industry raises safety issues lately. This work aims to investigate the impact of post-torrefaction upon biochar formation and the self-heating phenomena of torrefied wood pellets. Three operating scenarios are taken into account. Specifically, dried wood pellets are first torrefied in nitrogen at various temperatures (200–300 °C) followed by immediate exposure to N2 or air with/without keeping temperature, namely, the post-torrefaction, to examine the self-heating behavior. Meanwhile, the influences of torrefaction temperature, duration, and self-heating on biochar’s characteristics are analyzed. It is found that self-heating with the highest temperature rise of 61 °C is triggered when the biochars are in an oxidative post-torrefaction process with keeping temperature. Alternatively, oxidative post-torrefaction without keeping temperature can efficiently intensify the pellets’ calorific value up to 42%. The X-ray photoelectron spectroscopy analysis reveals the depletion of the CO functional group. It is concluded that uncontrolled self-heating in large scale production will lead to combustion and make biochar unsafe. Alternatively, if heat accumulation inside the biochar piles can be prevented, the oxidative environment that causes self-heating can open a lot of research opportunities that can help in the advancement of torrefaction technologies for biomass as an alternative source of energy.

Keywords: Torrefaction and post-torrefaction; Biomass and bioenergy; Self-heating and heat accumulation; Biochar; Safety; X-ray photoelectron spectroscopy (XPS) (search for similar items in EconPapers)
Date: 2020
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Citations: View citations in EconPapers (4)

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Persistent link: https://EconPapers.repec.org/RePEc:eee:energy:v:207:y:2020:i:c:s0360544220314316

DOI: 10.1016/j.energy.2020.118324

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