Mathematical modeling and computer simulation of molten metal cleansing by the rotating impeller degasser: Part I. Fluid flow

The removal of dissolved hydrogen and solid impurity particles from molten alloys by rotary degassing is a widely used foundry practice. Rotary degassing involves purging a gas into the molten alloy through holes in a rotating impeller. Monatomic dissolved hydrogen either diffuses into these gas bubbles or it forms diatomic hydrogen gas at the bubbles’ surface; in any case, hydrogen is removed from the melt with the rising bubbles. Simultaneously, solid particles in the melt collide with one another due to turbulence created by the impeller rotation and the gas flow and form aggregates. These aggregates either settle to the furnace floor, or are captured by the rising gas bubbles and are also removed from the melt. A mathematical model has been developed to simulate the turbulent multiphase flow field that develops in the melt during rotary degassing. The mathematical model allows calculation of the mean turbulence dissipation energy and the distribution of gas bubbles in the melt. Both these quantities are input into other mathematical models that simulate the removal of dissolved hydrogen and impurity solid particles from the melt.