Abstract
The special interest in Europe for the properties and the use of poplar and its hybrids, especially for the wood technological properties and their effect on the industrial processing of poplar wood, as well as the growing need for fast drying processes producing wood with a low final moisture content, led to this study. It was to be investigated whether high temperature drying (HTD) could also be applied to light hardwoods with properties similar to that of softwoods, like e.g. poplar. Poplar has some peculiar properties, e.g. large heterogenity, wet pocket formation, tension wood, juvenile wood., ..., complicating the application of HTD and increasing the risk for drying defects. Eleven different high temperature drying schedules and one low temperature drying schedule were performed in an experimental electrical drying oven on piles of small sizes of fresh poplar. For reference, five piles of fresh poplar were subjected to accelerated air-drying. Equations were obtained from two seperate multivariate regression analyses with wood characteristics for the first and typical drying-schedule parameters for the second regression, as independent variables, and a number of quantified drying defects as dependent variables for both regressions.
Zusammenfassung
Veranlaßt waren diese Untersuchungen einerseits durch das spezielle Interesse in Europa für die technologische Verwendung von Pappelholz, andererseits durch den wachsenden Bedarf an schnellen Trocknungsprozessen. Zu untersuchen war, inwieweit die Hochtemperaturtrocknung (HTD) auch auf leichte Laubhölzer, am Beispiel der Pappel, anwendbar ist. Pappelholz weist einige spezielle Eigenschaften auf (starke Heterogenität in Dichte und Feuchte, Zugholz, juveniles Holz etc.), welche die Anwendung der HTD schwierig machen. Elf unterschiedliche Hochtemperaturprogramme und eines bei niedriger Temperatur wurden in einem elektrisch beheizten Umlufttrockner mit frischgesägtem Pappelholz von kleiner Abmessung geprüft. Zum Vergleich wurden fünf Stapel frischen Pappelholzes einer beschleunigten Lufttrocknung unterzogen. Durch multivariate Analyse ergaben sich Regressionsgleichungen, wobei einmal die Holzeigenschaften zum andern die Trocknungsparameter als Variablen enthalten sind. Zusätzlich wurden Regressionsgleichungen für Trocknungsfehler abhängig von beiden Variablentypen ermittelt.
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Vansteenkiste, D., Stevens, M. & Van Acker, J. High temperature drying of fresh sawn poplar wood in an experimental convective dryer. Holz als Roh- und Werkstoff 55, 307–314 (1997). https://doi.org/10.1007/s001070050235
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DOI: https://doi.org/10.1007/s001070050235