Abstract
A new method was developed to study the dissolution of a solid cylinder in a liquid under forced convection at elevated temperature. In the new design, a rotating cylinder was placed concentrically in a crucible fabricated by boring four holes into a blank material for creating an internal volume with a quatrefoil profile. A strong flow in the radial direction in the liquid was created, which was evidently shown by computational fluid dynamic (CFD) calculations and experiments at both room temperature and elevated temperature. The new setup was able to freeze the sample as it was at experimental temperature, particularly the interface between the solid and the liquid. This freezing was necessary to obtain reliable information for understanding the reaction mechanism. This was exemplified by the study of dissolution of a refractory in liquid slag. The absence of flow in the radial direction in the traditional setup using a symmetrical cylinder was also discussed. The differences in the findings by past investigators using the symmetrical cylinder are most likely due to the extent of misalignment of the cylinder in the containment vessel.
Highlights
The absence of radial flow is clearly evident. These results clearly indicate that the radial flow could be introduced efficiently by the new rotating method with the use of a baffled container with a quatrefoil profile
To further confirm the conclusion based on computational fluid dynamic (CFD) calculations, experiments using the setup shown in Figure 5 were conducted
The composition of slag around the rod is very close to the initial slag composition. This indicates that the diameter change of porous MgO rod is not due to chemical dissolution followed by mass transfer in the bulk slag, but by detachment of the slag-penetrated layer
Summary
THE rotating disk/cylinder (rod) method has been widely applied to study the dissolution of solids in liquids for decades,[1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20] in particular for high-temperature systems such as dissolution of solid metals into liquid metals, and dissolution of ceramic solids into liquid oxides (slags). While valuable information have been gained by these studies, some misconceptions in using this method need to be addressed and analyzed. This is especially true when a cylinder and a small crucible are used. A number of researchers have studied the dissolution rate by rotating a rod concentrically placed in liquid in a small crucible. Umakoshi et al.[7] used this method to investigate the dissolution rate of burnt dolomite in converter slag. They reported that the dissolution rate was not affected by the porosity of the sample.
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