Wood Heat Treatment, Optimization and Control

PI : Mathieu Pétrissans (EA 4370 Laboratoire d’Études et de Recherche sur le Matériau Bois – LERMAB)

Co-applicants : UMR 1092 Laboratoire d’Études des Ressources Forêts-Bois (LERFOB) Nancy, France

Collaboration : CRITT BOIS Epinal, France

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Context — when unprotected wood is exposed to outdoor conditions it undergoes a variety of degradation induced essentially by fungi attacks. Wood heat treatment by mild pyrolysis is a preservation process with a weak environmental impact, consequently it is viewed as an interesting alternative to the chemical impregnation methods for the valorization of low-value local wood species improving their dimensional stability, durability and economic added value.

Objectives — the literature stemming from laboratories of the consortium WOHTOC highlighted for the first time the strong relations between the resulting from curing wood mass loss (ML), treatment intensity and conferred durability. Also, the elementary composition modification is strongly correlated to the O/C ratio and seems to be a good quality indicator. Throughout the developed studies, according to the initial wood characteristics and the choice of treatment parameters, it will be possible to predict the final-end quality of the product: thermodegradation mass loss, mechanical properties, durability. It will also be possible to model the thermodegradation kinetic required for the piloting of the non-existent today oven. Nowadays, available data necessary to describe exactly the chemical mechanisms of wood thermal degradation are not sufficient.

Approaches — the ambition of the project WOHTOC is to improve the knowledge of the reaction schemes of thermodegradation in order to integrate the results in the mathematical models. Mathematical formulation have to take into account the coupled heat and mass transfers in wood porous media, introducing heat effects due to the reactions of polymer decomposition, production of volatiles and non-degradable solid products. The accuracy of the numerical simulation will be tested a laboratory scale. Prediction will be applied in the conditions of industrial production.

A more empirical approach would consist in using a statistical regression in order to predict the probability of a successful heat treatment carried out on individual boards from observations. The technique of life expectancy analyses is well adapted and could be a good alternative or a complement to the process modeling.