Effects of cutting direction and average chip thicknesses on the wood and bamboo milling dust morphological characteristics

Dust exposure has now become a significant hazard, posing risks to both worker health and equipment safety. It is important to understand the characteristics of milling dust and take appropriate measures to reduce dust emissions. This study provides a comprehensive analysis of milling dust generated from three biomass materials–Scots pine, red oak and Moso bamboo, primarily focusing on the influence of cutting directions and average chip thickness on the morphological characteristics of dust from these materials. The research uses the sieving method to investigate particle size distribution across varying average chip thicknesses. Furthermore, flatbed scanning image analysis is utilized to investigate the correlations between particle size characteristics such as area-equivalent diameter and minimum Feret diameter, and various morphological parameters including aspect ratio, roundness, and convexity. The study also observes the morphology of representative particles using an optical microscope. It is found that Moso bamboo could produce more inhalable dust than red oak and Scots pine, while the lowest median area-equivalent diameter and aspect ratio are discovered in dust from Scots pine and red oak, respectively. Moso bamboo milling dust shows a higher roundness and convexity. Longitudinal and transverse cutting have different effects on large size particles and fine dust. A minor influence of average chip thickness on roundness and convexity is found. This study reveals the relationship between the angle between the cutting direction and the fiber direction and different sizes of dust, as well as its specific effects on the aspect ratio, roundness, and convexity of particles of different sizes. The study provides essential data for cleaner production and health protection of milling dust including wood and bamboo in the environment.