Size Effect on Flow Field and Dynamic Deposition of Bottom Dross in a Molten Zinc Pot

Abstract

During the continuous hot-dip galvanizing process, the effect and mechanisms of production parameters on flow field and dynamic deposition behaviors of bottom dross are critical issues for solving problems on harmless accumulation and control technologies of bottom dross. In this paper, a combined method of numerical simulation and water modeling experiment is presented to investigate the effects of steel strip width and velocity on flow field and dynamic deposition of bottom dross in a zinc pot. The molten zinc flow in an industrial-sized model were numerically simulated by the computational fluid-dynamics method. A 1/5 reduced-scale physical water model is established to study deposition behaviors of bottom dross based on the theoretical framework of similarity. NaCl aqueous solutions and black particles of acrylonitrile butadiene styrene are employed as model fluid and bottom dross, respectively. The results show that the width of strip is a key factor for the intensity of two impact flows in the bath. The condition of interaction between two impact flows determines the accumulation morphology of bottom dross. The influence of the strip width on the deposition directon of bottom dross exhibits an obvious size effect. With the decreasing of strip width, the deposition direction of the scattered bottom dross under sink roll is gradually changed from backward to backward as well as forward. The velocity of strip has no significant impact on the flow characteristics, but shows a strong positive correlation with the intensity of flow field and the number of scatted bottom drosses.