Production of Wood Fibers from Thermally Treated Wood

• Published in: Fluid dynamics & materials processing Vol. 18; no. 5; pp. 1427 - 1439
• Main Authors: Gibier, Maximilien, Girods, Pierre, Rogaume, Yann
• Format: Journal Article
• Language: English
• Published: Tech Science Press 2022
• Subjects: Chemical Sciences; Material chemistry; fibers; Wood; thermal treatment; fibers properties improvement; hygroscopicity; energy consumption; defibering process
• ISSN: 1555-2578; 1555-256X; 1555-2578
• DOI: 10.32604/fdmp.2022.022057

The reduction of the hygroscopicity of wood fibers was investigated through a Thermal Treatment (TT) on wood chips performed before the defibering process. The TT and defibering tests were both carried out on a continuous pilot at semi-industrial scale. The thermal treatment study of wood chips, equivalent to a low temperature pyrolysis, was achieved for four conditions (280 degrees C-320 degrees C) for a duration of 10 min. Mass quantification of solids, condensables and gases (FTIR) at the outcome of the thermal treatment allowed to achieve the mass balances for each condition. The increase of the reactor temperature from 280 degrees C to 320 degrees C leads to a lower solid yield (94%-82%) while gaseous (1%-3.8%) and condensable (3%-11%) products increase significantly. Thermally treated wood samples were afterwards successfully defibered in different conditions to produce suitable fibers for insulation panel production. The aim of the study is also to evaluate the effects of the TT on the lowering of energy consumption necessary for the defibering process while producing good quality fibers. Energy consumption during defibering process shows a significant decrease with the increase the TT severity. Fiber morphology is affected by TT and the morphological quality of the fibers decreases as TT severity increases. The mass percentage of dust was also quantified as a quality marker of produced fibers. Measurements of equilibrium moisture (at 20 degrees C and 65% RH) of the different materials (wood chips before and after TT, produced fibers) show a significant effect of the TT on wood chips hygroscopicity (8.2% for untreated wood to 4.1% for TT at 320 degrees C). However, the effect of the TT on the hygroscopicity reduction of thermally treated wood fibers is drastically less significant due to breaking of the wood structure during defibering process.