Iron drop ejection into slags by bursting gas bubbles

Heat and mass transfer between metal and slag frequently occur via iron droplets emulsified in the slag. One mechanism of drop formation is bursting of gas bubbles passing the interface. Published results of the mechanism of this phenomenon were applied to the results gained with the 6-t pilot plant of the Jupiter process, which was developed by Irsid (Groupe Usinor), France. A new formula for the calculation of the drop formation rate is proposed in dose relation to a formula published by Reiter and Schwerdtfeger. This formula yields an improved description of plant results. It is confirmed by a theoretical model which describes the drainage of liquid metal out of the bubble skin while the bubble passes the slag/metal interface, and with which the mass of droplets at bubble bursting can be determined. The drop formation rate is proportional to the gas flow through the metal melt. It is further a function of the gas bubble size distribution in the melt. Published measurements of bubble sizes in liquid Wood's metal and in liquid iron were evaluated. They yield the bubble size distribution function in liquid iron. Equations which allow the calculation of the residence time of droplets in the slag, are also cited. Calculated drop concentrations in the slag are in rough agreement with drop concentrations obtained from slag samples.