University of Oulu

Koskela, A.; Heikkilä, A.; Bergna, D.; Salminen, J.; Fabritius, T. Effects of Briquetting and High Pyrolysis Temperature on Hydrolysis Lignin Char Properties and Reactivity in CO-CO₂-N₂ Conditions. Minerals 2021, 11, 187.

Effects of briquetting and high pyrolysis temperature on hydrolysis lignin char properties and reactivity in CO-CO₂-N₂ conditions

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Author: Koskela, Aki1,2; Heikkilä, Anne1,2; Bergna, Davide3,4;
Organizations: 1Process Metallurgy, University of Oulu, P.O. Box 4300, FI-90014 Oulu, Finland
2Centre for Advanced Steels Research, CASR, University of Oulu, FI-90014 Oulu, Finland
3Sustainable Chemistry, University of Oulu, P.O. Box 3000, FI-90014 Oulu, Finland
4Applied Chemistry, University of Jyvaskyla, Kokkola University Consortium Chydenius, Talonpojankatu 2B, FI-67100 Kokkola, Finland
5Boliden Kokkola Oy, P.O. Box 26, FI-67101 Kokkola, Finland
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 4.9 MB)
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Language: English
Published: Multidisciplinary Digital Publishing Institute, 2021
Publish Date: 2021-04-26


Carbonaceous reductants for pyrometallurgical applications are usually obtained from fossil-based sources. The most important properties of the reductants greatly depend on the application and the feeding of the reductant into the process. However, the mechanical strength, calorific value, fixed carbon content, and reactivity of the reductant are the properties that usually define the applicability of the reductant for different processes. The reactivity of the biochars is usually high in comparison to metallurgical coke, which may restrict the applicability of the biochar in reduction processes. One cause of the higher reactivity is the higher surface area of the biochars, which can be suppressed with agglomeration treatment, e.g., briquetting. In this work, hydrolysis lignin was used for slow pyrolysis experiments to produce biochars. The biochars were pyrolyzed in briquetted form and in as-received form at various temperatures. The reactivity values of the biochars were tested in dynamic reactivity tests in a CO-CO₂-N₂ gas atmosphere at temperatures of up to 1350 °C. It was found that the yield of the hydrolysis lignin char only decreased by 3.36 wt% when the pyrolysis temperature was elevated from 600 to 1200 °C, while a decrease in yield of 4.88 wt% occurred when the pyrolysis temperature was elevated from 450 to 600 °C. The mass loss of hydrolysis lignin biochar in the reactivity experiment in CO-CO₂-N₂ atmosphere was significantly decreased from 79.41 wt% to 56.80 wt% when the hydrolysis lignin was briquetted before the slow pyrolysis process and the temperature of the pyrolysis process was elevated from 600 to 1200 °C. This means that the mass loss of the material was suppressed by 22.61 wt% due to the higher pyrolysis temperature and briquetting process.

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Series: Minerals
ISSN: 2075-163X
ISSN-E: 2075-163X
ISSN-L: 2075-163X
Volume: 11
Issue: 2
Article number: 187
DOI: 10.3390/min11020187
Type of Publication: A1 Journal article – refereed
Field of Science: 216 Materials engineering
Funding: This research was funded by European Regional Development Fund (ERDF) project Carbotech, project number A75548.
Copyright information: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (