Impact of Cooling Air Temperature and Airflow on Wood Fuel Pellet Durability, Hardness, and Off-Gassing During Industrial Storage

The cooling of pellets is necessary because pellets reach 70 to 90 °C after the pellet press. The reduction in temperature solidifies the pellets, which increases the pellet quality and reduces the risk of self-heating during storage. Industrially, pellet plants use outdoor air in counterflow cooler...

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Main Authors: Magnus Ståhl, Jonas Berghel
Format: Article
Language:English
Published: North Carolina State University 2025-03-01
Series:BioResources
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Online Access:https://ojs.bioresources.com/index.php/BRJ/article/view/24286
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author Magnus Ståhl
Jonas Berghel
author_facet Magnus Ståhl
Jonas Berghel
author_sort Magnus Ståhl
collection DOAJ
description The cooling of pellets is necessary because pellets reach 70 to 90 °C after the pellet press. The reduction in temperature solidifies the pellets, which increases the pellet quality and reduces the risk of self-heating during storage. Industrially, pellet plants use outdoor air in counterflow coolers and cooling ends when the pellet temperature is approximately 5 °C above ambient temperature. Cooling performed in the summer could result in high temperatures in the pellet stacks during storage, and cooling at low temperatures and high airflows in the winter could cause quality problems. Therefore, the aim was to determine how cooling air temperature, airflow, and storage time impact the durability, hardness, and off-gassing of the pellets. The results showed that the highest durability (97.7%) and hardness (310 N) were achieved when cooling with low-temperature air and low airflow. Additionally, durability and hardness stabilized at high values (98.9% and 640 N) after 30 to 40 days of storage, regardless of the airflow and cooling air temperature used. Furthermore, it was found that high airflows reduce off-gassing regardless of the cooling air temperature. It is recommended that the industry reduce airflow during the winter and increase it during the summer to produce high-quality pellets and minimize the risk of self-heating.
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spelling doaj-art-10fbcc28a1574e19b70da8baffa30b212025-08-20T03:52:07ZengNorth Carolina State UniversityBioResources1930-21262025-03-01202328632982557Impact of Cooling Air Temperature and Airflow on Wood Fuel Pellet Durability, Hardness, and Off-Gassing During Industrial StorageMagnus Ståhl0https://orcid.org/0000-0003-2528-4399Jonas Berghel1https://orcid.org/0000-0002-9707-8896Environmental and Energy Systems, Department of Engineering and Chemical Sciences, Karlstad University, Karlstad SE-651 88, SwedenEnvironmental and Energy Systems, Department of Engineering and Chemical Sciences, Karlstad University, Karlstad SE-651 88, SwedenThe cooling of pellets is necessary because pellets reach 70 to 90 °C after the pellet press. The reduction in temperature solidifies the pellets, which increases the pellet quality and reduces the risk of self-heating during storage. Industrially, pellet plants use outdoor air in counterflow coolers and cooling ends when the pellet temperature is approximately 5 °C above ambient temperature. Cooling performed in the summer could result in high temperatures in the pellet stacks during storage, and cooling at low temperatures and high airflows in the winter could cause quality problems. Therefore, the aim was to determine how cooling air temperature, airflow, and storage time impact the durability, hardness, and off-gassing of the pellets. The results showed that the highest durability (97.7%) and hardness (310 N) were achieved when cooling with low-temperature air and low airflow. Additionally, durability and hardness stabilized at high values (98.9% and 640 N) after 30 to 40 days of storage, regardless of the airflow and cooling air temperature used. Furthermore, it was found that high airflows reduce off-gassing regardless of the cooling air temperature. It is recommended that the industry reduce airflow during the winter and increase it during the summer to produce high-quality pellets and minimize the risk of self-heating.https://ojs.bioresources.com/index.php/BRJ/article/view/24286industrial coolingwood pelletsairflowdurabilitystorageair temperatureoff-gassing
spellingShingle Magnus Ståhl
Jonas Berghel
Impact of Cooling Air Temperature and Airflow on Wood Fuel Pellet Durability, Hardness, and Off-Gassing During Industrial Storage
BioResources
industrial cooling
wood pellets
airflow
durability
storage
air temperature
off-gassing
title Impact of Cooling Air Temperature and Airflow on Wood Fuel Pellet Durability, Hardness, and Off-Gassing During Industrial Storage
title_full Impact of Cooling Air Temperature and Airflow on Wood Fuel Pellet Durability, Hardness, and Off-Gassing During Industrial Storage
title_fullStr Impact of Cooling Air Temperature and Airflow on Wood Fuel Pellet Durability, Hardness, and Off-Gassing During Industrial Storage
title_full_unstemmed Impact of Cooling Air Temperature and Airflow on Wood Fuel Pellet Durability, Hardness, and Off-Gassing During Industrial Storage
title_short Impact of Cooling Air Temperature and Airflow on Wood Fuel Pellet Durability, Hardness, and Off-Gassing During Industrial Storage
title_sort impact of cooling air temperature and airflow on wood fuel pellet durability hardness and off gassing during industrial storage
topic industrial cooling
wood pellets
airflow
durability
storage
air temperature
off-gassing
url https://ojs.bioresources.com/index.php/BRJ/article/view/24286
work_keys_str_mv AT magnusstahl impactofcoolingairtemperatureandairflowonwoodfuelpelletdurabilityhardnessandoffgassingduringindustrialstorage
AT jonasberghel impactofcoolingairtemperatureandairflowonwoodfuelpelletdurabilityhardnessandoffgassingduringindustrialstorage