Some Investigations into the Dynamic Mass Transfer at the Slag–Metal Interface Using Sulfur: Concept of Interfacial Velocity

Abstract

In the current work, dynamic studies of mass transfer of sulfur from the gas phase to the metal phase of pure iron through CaO-SiO 2 -Al 2 O 3 -FeO quaternary slag were carried out. X-ray videos were taken that were later processed to identify the oscillation of the metal drop occurring during the mass transfer. It was observed that the metal drop had hybrid oscillations. Each of these oscillations could be identified as composed of a symmetric and an asymmetric element, which was attributed to the changes in the shape of the droplet. The latter (asymmetric part) could be identified by the deviation of the left and right contact angles from the stable configuration. The symmetric oscillations were traced to the surface movement of sulfur at the interface, which created an instantaneous area change at the slag-metal interface. This area change was due to the combined effect of Marangoni flow and interface dilatation. The velocity of sulfur at the interface was calculated from the area change and had a maximum order of magnitude as 10 À4 m/s. It was also observed that the interfacial velocity increased with increase in temperature.

Investigation into the Cause of Spontaneous Emulsification of a Free Steel Droplet; Validation of the Chemical Exchange Pathway

“…[8][9][10] Current levels of understanding have extended beyond equilibrium conditions to include the description of mass transport in the slag and metal phases. [11][12][13][14] It is however known that under dynamic conditions the interface between phases can display significant perturbation in comparison to a relaxed planar state, and may even lead to emulsification. [15][16][17][18][19][20] A proper description of the slag/metal reaction necessitates an elucidation of the dynamic change of interfacial area and the coupling of this change to the interfacial reactions.…”

Understanding the Properties of Slags

“…The measurements were extended to higher temperatures by the X-ray sessile drop method. 36) The values were found to be mutually compatible. One interesting feature was that it could be extrapolated to estimate the density of pure, super-cooled CaO, which could be used to optimize the model for densities.…”

“…From the oscillations, which were monitored by X-ray radiography, the surface velocity of sulphur was computed. 58) The results are shown in Fig. 16.…”

Some Novel Studies of Thermodynamics, Kinetics and Transport Phenomena in Slags

“…The concentration profile of sulfur in silver metal obtained by sampling was compared with that obtained by the model under the assumption of uniform composition. To calculate the diffusion coefficient of sulfur, the model was used [17]. In the model, the only term assumed was the diffusion coefficient; hence fitting the concentration curve to the experimental concentra tion profile would help in backcalculating the diffusion coefficient.…”

“…A mathematical model [17] was formulated through which appropriate design parameters for the experimental setup was obtained. For this, the order of magnitude for the diffusion coefficient for sulfur was taken from the classic works of Saitô and Kawai [15], the sulfide capacity and sulfur partition ratio were retrieved from the works of Taniguchi et al [18], and the slag density was retrieved from earlier experimental results of the present authors [19].…”