Heat-treatment with the vacuum-press dewatering method: chemical properties of the manufactured wood and the condensation water

Certain properties of wood can be improved with thermal modification, allowing its application fields to be considerably extended without the use of any chemical additives. This study focuses on the chemical investigation of hardwood (oak, beech, ash) products heat-treated with an industrial scale vacuum-press dewatering method (Vacu³) as well as on the evaluation of the parameters of the condensation water exhausted during the treatment. Wood modification was carried out at 195 and 210 °C. The pH value, loss of VOCs and total phenols were determined from the samples. Waste waters collected after the treatment cycles were investigated for pH, conductivity, COD, VOCs, total phenols and also for possible utilizable compounds. Release of VOCs from wood can be a health concern. Results show that the losses of the measured components were quite low. The composition of the highly acidic waste waters also depends on wood species, containing mostly phenolic compounds, aldehydes and acids. Possible ways for the utilization of these components need to be worked out in the future.