RESUMO
Under conventional processing conditions, the resistivity of wood dust is in the range of insulating materials, which can induce a dust cloud explosion when there are static sparks. This paper took the fast-growing poplar wood commonly used in Chinese wood processing and studied the effects of moisture content, temperature, and particle size on the electrical resistivity value of sanded wood dust. Orthogonal analysis was conducted on the influencing factors. The results showed that the influence of moisture content on electrical resistivity was the most significant factor, followed by temperature and particle size. Further experiments have shown that when the moisture content increased from 6% to 32%, the resistivity decreased from 109 Ω cm to 105 Ω cm, which reached the suitable resistivity range of static discharge method. The ion concentration of wood dust extracted in cold water and hot water and the resistivity of poplar dust residue after extraction were determined. Nine metal ions (a total of 105.02 mol/g) were detected in cold-water extract, and the concentrations of K+, Na+, Mg2+ and Ca2+ accounted for 99.8%. The original poplar dust and the extracted poplar dust were measured and analyzed. The changes in water-soluble ion content, functional groups, crystallinity, and complexes of the wood dust before and after ion dissolution, jointly led to changes in the electrical resistivity of the wood dust (a difference of 2-4 orders of magnitude). It was verified that the way wood dust conducts electricity is through ion conduction. There were more abundant capillary system structures between poplar dust particles, allowing water-soluble ions to move more freely with water channels. The larger specific surface area and higher temperature also promoted the dissolution of water-soluble ions, which affected the electrical resistivity.
