Pine and eucalyptus log moisture determination using the radiofrequency capacitance method

Abstract

The development of statistical models that correlate the relative electrical permittivity ε’ and the dielectric loss factor ε’’ to the amount of water present in wood, is a key step in the development instantaneous moisture methods. The correlation between those variables is widely applied in the instant moisture measurement for lumber and recently for woodchips, but it is not yet applied for the measurement of logwood. This work consisted in the evaluation of this same method applied also to the logwood. Once approved, the method can be used in the timber trade, in the selection of the logs that feed the pulp production line or that feed the power boiler, until then stored in the patio. The materials used in the present research were pine logs with moisture between 10% and 50% on wet basis and eucalypts logs with moisture between 40% and 60% on wet basis, coming from different plantations, all located in the province Paraná. The evaluation was performed by correlating the primary reading of a capacitive sensor when inserted into the logs and the wood moisture obtained by the gravimetric method. The determination coefficients R² related to the correlation between the capacitive sensor readings and the moisture determination results were 88,3% for the pines logs and 68,1% for the eucalyptus logs. This correlation allowed to affirm that the capacitive method can be applied to estimate the moisture content of the two investigated genera with sufficient accuracy to commercialize and classify the raw material for the pulp production process or for energy production from biomass.