Experimental Design for the Mechanism Study of Lime Dissolution in Liquid Slag

Abstract

The applicability of rotating rod technique in the study of lime dissolution in slag was investigated. Both computational fluid dynamic (CFD) and cold model experiments showed that the mass transfer due to radial velocity introduced by forced convection was zero if the rod was long. The mass transfer by forced convection was also less important in comparison with natural convection and diffusion when the rod was half length of the height of the bath. This finding was in accordance with the criteria put forward by the original work that the method could only be applicable when a thin disk (instead of rod) with big diameter and big liquid bath were used. To study the lime dissolution by forced convection a new experimental technique was developed. A cube was placed in the slag that was eccentrically stirred. The whole system, viz. the sample along with the slag could be quenched. The new technique could study the effect of forced convection on the dissolution. The microscopic study on the quenched slag-lime samples could reveal the dissolution mechanism successfully.

A New Experimental Design to Study the Kinetics of Solid Dissolution into Liquids at Elevated Temperature

“…The effect of non-concentricity of the rod and the distance between the tip of the rod and the bottom of the vessel have been analyzed in detail in an earlier publication. [22] A comparison between Figures 8(a) and (b) shows evidently that the flow in the radial direction as predicted by the CFD calculation (see Figures 2 and 3) does create the mass transfer along this direction. Although misalignment of the rod from the exact center of the cylinder would also introduce experimental uncertainties in the rotation method even in the new setup, a comparison of Figures 8(a) and (b) indicates that this uncertainty is negligible with respect to the effect of rotation speed.…”

“…In a previous work, [22] both experimental measurements at room temperature and CFD calculations were carried out to evaluate the traditional rotating rod method. The result of CFD calculation reveals that rotating a cylinder concentrically in a small circular container is ineffective in generating radial velocity in the liquid.…”

“…[1] The constraints of the rotating disk method emphasized by those authors were confirmed in a previous study. [22] Here, the authors reported that the method of a rotating rod in a crucible was unsuitable for the study of dissolution phenomena. CFD calculations were employed to evaluate the velocity distribution of the liquid flow when a rod is rotated concentrically in liquid in a small container.…”

“…[22] For example, the cylinder usually is attached to a very long shaft in a high-temperature experiment. When high-speed rotation is employed, the long shaft along with the cylinder is very difficult to be kept exactly in the center of the container.…”

“…This mechanism is well demonstrated by earlier studies where the peeling off of solid particles led to fast dissolution in liquid slag. [22] An increase of the rotation speed would result in the increase of shear stress and therefore an increase in ''dissolution'' rate.…”