Convective Drying of Beech Lumber without Color Changes of Wood

This paper presents the results of analyzing the influence of suggested regimes of chamber drying of beech lumber with the thickness h = 40 mm, h = 60 mm and h = 80 mm from the initial moisture content Wp = 70 % to the final moisture content Wk = 8 %. The regimes ensure the preservation of the natural color of the wood. The study results show that the drying of beech lumber according to the suggested regimes causes no changes in the chromophoric compounds of the wood and the beech lumber preserves its original white-yellow color. Quality parameters of the dried lumber, such as: difference between the average final moisture content and the required final moisture content, and the range of the final moisture and moisture gradient in dried beech lumber, classify this dried lumber into the first quality class. The suggested regimes for drying beech lumber using hot air in the temperature range ts = 37 ÷ 65 °C has a negative impact on the duration of the drying process. In comparison with the regimes of beech lumber drying according to ON 49 0651, carried out at temperatures t = 60 ÷ 80 °C, the duration of drying beech lumber with the thickness h = 40 mm according to the suggested regime is 1.9 times longer, the duration of drying beech lumber with the thickness h = 60 mm is 2.3 times longer and the duration of drying beech lumber with the thickness h = 80 mm is 2.9 times longer. The specifi c heat energy consumption of beech lumber with the initial moisture content Wp = 70 % to the final moisture content Wk = 8 % in a chamber type KWC 121, according to the suggested regimes, is equals to QTZN = 514.46 kWh⋅m-3 for the thickness h = 40 mm, QTZN = 557.62 kWh⋅m-3 for lumber with the thickness h = 60 mm, and QTZN = 643.16 kWh⋅m-3 for lumber with the thickness h = 80 mm. The specifi c heat energy consumption needed for the drying of 1 m3 of beech lumber with the thickness h = 60 mm according to the suggested regime is by 26.89% higher than the specifi c heat energy consumption used to dry beech lumber of the same thickness according to the regime of beech lumber drying by Vzduchotechnika a.s. which does not preserve the natural color of the wood.