Effect of debris mixing on ignition and propagation of dust clouds in fine rice husk

As the associated product of rice husk dust, large particles of crushed brown rice (abbreviated as debris) are widely found in grain dust processing and transportation industry. The rice husk dust is combined with huge pieces of debris, which can reduce the consequences of dust explosion in the mixed dust cloud. Debris added at a 70 % ratio considerably slows the spread of flames. However, at 500 g/m³ of dust cloud concentration, including a 10 % percentage of debris increases the average flame spread velocity (AFSV) by 16.9 % and the maximum flame spread velocity (MFSV) by 33.3 %. This intensify phenomenon persists across varying dust cloud concentrations. Tests on the dispersibility of blended dust clouds revealed that fine dust particles that have been adsorbed on top of bigger particles typically stripped off upon lifted, increasing the blended dust cloud's dispersibility. This leads to the formation of a dust cloud system with efficiently smaller particle sizes, consequently resulting in an increase in flame spread velocity (FSV). Moreover, owing to the enhanced dispersibility of the dust cloud due to the inclusion of larger particles, the minimum ignition temperature (MIT) of rice husk dust clouds decreases. Analysis of the angle of repose (AOR) and Hausner ratio (HR) indicates that the incorporation of larger particles improves the flowability of the blended dust cloud, thereby increasing the risk of dust explosions.