Interfacial Phenomena in Two-Phase systems: Emulsions and slag Foaming

Sammanfattning: In the present work studies were performed to provide understanding for further model development of the two-phase phenomena, film formation from o/w emulsions and slag foaming.The drying of o/w emulsions of different oil viscosities on hydrophobic and hydrophilic substrates was studied. The hydrophobic substrate was found to destabilise the oil droplets and to result in a different mechanism for forming continuous oil film. Studies of adsorption behaviour of a series of non-ionic diblock copolymers at relevant interfaces showed that the adsorption behaviour at hydrophobic and hydrophilic solid surfaces differed at high polymer concentration. Emulsion droplets were found to interact with the hydrophobic interface. Adsorption at silicone oil-water interface resembled adsorption at solid hydrophobic surfaces.Gas was generated through chemical reaction at the interface between two immiscible liquids and the bubbles formation from the generated was studied optically. The gas bubble size was seen to be uninfluenced by the reaction rate. However, bubble formation was seen to take place in one of the phases, held up at the interface before detaching from the interface with a surrounding aqueous film. It was argued that this may affect the final bubble sizes.Slag foaming at high temperatures was studied in laboratory scale with X-ray imaging under dynamic conditions. The foam displayed a fluctuating behaviour, which the presently available models are not able to take into account. The concept of foaming index was found to be unsatisfactory in describing the foaming behaviour under dynamic conditions, thus emphasizing the need for alternative theories. The rate of fluctuations was seen to be related to the difference between rate of gas generation and rate of gas escape from the system (Ug-Ue) as well as the bubble sizes. Thus, it seems like model development of dynamic foaming phenomenon has to take the effective chemical reaction rate as well as the bubble sizes into consideration