Apparent Viscosity Measurement of Gas–liquid Multiphase Fluids by the Falling Ball Method

The recovery rate of iron is reduced if iron particles suspended in the refining slag do not sediment. The sedimentation rate of particle iron in the foaming slag is slower than in the slag in the single-phase liquid. Iron particles are especially likely to remain in the foaming slag. To predict the sedimentation rate of iron particles in the slag, it is necessary to derive an accurate viscosity of the foaming slag. However, it is difficult to estimate an appropriate value because the state of gas-liquid multiphase fluid changes the condition with time. Its apparent viscosity varies depending on the measurement method because it is a non-Newtonian fluid. In this study, to understand the sedimentation behavior of iron particles in foaming slag, a gas-liquid multiphase fluid was generated by glycerin solution. Its apparent viscosity was estimated by the Stokes equation using the falling-ball method. The sedimentation rate of stainless steel, titanium, and glass balls with a diameter of 2 mm were measured in a glycerin aqueous solution gas-liquid fluid. The sedimentation rate was non-uniform because the gas-liquid fluid’s state differed depending on the position. The apparent viscosity of the fluid increased with an increase in the gas phase ratio. The variation of apparent viscosity with the conditions of the falling-ball method was also discussed. Furthermore, a comparison was made between the present results and the apparent viscosity measured by the rotational technique.