Reactivity of charcoal during and after pyrolysis
Abstract
Wood is one of the most important materials for a carbon-neutral future of building products, but it has one major drawback: it is combustible. The ignition of wood is subject to complex mechanisms that are not yet fully understood. Generally, flame formation is always considered to be the same as ignition, but before any ignition of gases, a reactive carbon layer is formed on the surface. Such layers can already form at temperatures significantly below the generally accepted ignition temperatures of wood (spruce 280 °C) and subsequently undergo an oxidation process, which leads to glowing without flame formation. It is known that temperatures below 200 °C are already sufficient for the formation of this charcoal layer, if the exposure time to the temperature is correspondingly long. The exact duration has not yet been scientifically proven. Cases have been documented where wood is said to have ignited by itself after long-term exposure to temperatures far below the ignition point. It is assumed that chemical sorption processes take place which enrich the charcoal surface with additional oxygen atoms and can significantly reduce the activation energy necessary for ignition, thus leading to spontaneous combustion at lower temperatures. The extent to which the presumed influencing variables such as the degree of pyrolisation of the charcoal and the duration of temperature exposure have an effect on surface enrichment with oxygen and lead to ignition at temperatures below 200 °C is the subject of this basic research project. In order to be able to look at the hierarchical structure of wood as holistic as possible, investigations are being carried out on small samples in the micro range as well as on macroscopic samples in the centimetre range. The results should bring clarity to the processes involved in the spontaneous combustion of wood at low temperatures and thus provide the basis for even safer and more efficient handling of wood as a natural building material.
keywords Reactivity Pyrolysis Charcoal Thermal Analysis Ignition behaviour
Publikationen
Project staff
Anita Grausam
Dipl.-Ing. Anita Grausam
anita.grausam@boku.ac.at
Tel: +43 1 47654-89353
BOKU Project Leader
27.11.2023 - 30.09.2026
Christoph Pfeifer
Univ.Prof. Dipl.-Ing. Dr.techn. Christoph Pfeifer
christoph.pfeifer@boku.ac.at
Tel: +43 1 47654-89301, 89351
BOKU Project Leader
01.10.2023 - 26.11.2023
Jitka Hrbek
Dipl.-Ing. Dr. Jitka Hrbek
jitka.hrbek@boku.ac.at
Tel: +43 1 47654-89361
Project Staff
01.10.2023 - 30.09.2026
BOKU partners
External partners
Kompetence centre wood GmbH
Christian Hansmann
coordinator