Impact of Solid Particles and Liquid Droplets on Foams - Cold Model and High Temperature Experiments

In order to obtain a realistic view of the foam in metallurgical slag, high temperature experiments where the foaming heights of FeO-CaO-SiO2-MgO slags containing precipitated MgO center dot FeO particles were measured. The foaming height slightly increased when small amounts of particles were present in the slag, but decreased to half height already when approximately 8 vol% particles were present in the liquid phase of the foam. To help the understanding, the foaming heights of silicone oil and food oil containing liquid insoluble droplets and non-reacting particles were also studied at room temperature. In these experiments, insoluble oil droplets were found to stabilize the foam, increasing the foaming height, while the addition of water droplets or solid particles had very little effect on foaming height. In line with the literature, it is believed that the interfacial energy between the droplets or particles and the bulk liquid as well as the interfacial energy between the droplets or particles and gas plays an important role. When the interfacial energy between the different phases becomes too high, the foaming height decreases, while when it's low enough, the foaming height increases.