Analysing the drying behavior of juvenile and mature Eucalyptus saligna wood in drastic drying test for optimal drying schedule

José Tarcísio Lima,José Reinaldo Moreira da Silva,Bruno Charles Dias Soares

doi:10.4067/s0718-221x2016005000047

José Tarcísio Lima, José Reinaldo Moreira da Silva + Show 1 more

Open Access

https://doi.org/10.4067/s0718-221x2016005000047

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Abstract

The heterogeneity of characteristics observed in the pith-bark direction within a log causes sawn pieces of wood have different behaviors during water removal. Understanding these differences is important for the industry regarding the possibility of classification of the lumber into juvenile wood and mature wood, facilitating the drying in separate loads. Thus, this study aimed to evaluate the behavior of juvenile and mature wood samples of Eucalyptus saligna when subjected to drastic drying. In order to do this, test specimens were submitted to drastic drying at 100°C to obtain the drying times, drying rates and dimensions of end checks. These data were applied in equations to obtain the parameters initial temperature, final temperature and drying potential, used in the elaboration of drying schedules. In juvenile wood we observed that the basic density was lower and the initial moisture content was higher. Mature wood showed a lower drying rate. Drying schedules were developed separately for juvenile and mature wood, the drying schedule for the latter considered milder than the drying schedule developed for juvenile wood.

Highlights

The removal of water during drying causes stress in the internal and external layers of the lumber which may cause defects like warping, checking and casehardening
The average basic density found in E. saligna wood was 686 kg.m-3, close to the 690 Kg.m-3 found by Susin (2012) for the same species with at 40 years of age
The initial moisture content of the samples was inversely proportional to the basic density (Table 3)

Summary

Introduction

The removal of water during drying causes stress in the internal and external layers of the lumber which may cause defects like warping, checking and casehardening. The effect of this process in wood is important, since it is desirable that the dry wood is free of defects. The appearance of drying stress, to a greater or lesser degree, is a function of the intrinsic characteristics of permeability, anatomical structure, density and mechanical strength of wood, together with the drying conditions under which the lumber is subjected. The lumber is subjected to drying following schedules developed according to its characteristics. The humidity-temperature type schedules are the most common, in which the temperature and relative humidity inside the kiln are adjusted according to the wood moisture content (Hildebrand 1970, Pratt 1974)

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