Model studies of metal-slag reactions in reaction generated foams.

A room temperature model lias been developed which simulates certain aspects of the slag-raetal-gas reactions that occur in L.3). steelmaking. In the model the molten iron was represented by a pool of sodium amalgam, the slag by a mixture of water and glycerol and the oxygen by a hydrogen chloride-nitrogen jet. Droplets of amalgam ejected from the bath by the impinging gas jet, reacted with the hydrogen chloride dissolved in the model slag to produce bubbles, thus forming a dynamic foam. To gain more information about the fundamental refining processes in the model, the behaviour of single droplets of amalgam in acid media has been studied. When the sodium content of individual droplets was high, the rate of reaction was controlled by the discharge of hydrogen ions at the reaction interface, with rate dependence on the hydrogen ion concentration in the aqueous phase. This is analogous to decarburisation rate control by transport of oxygen ions in the slag phase.Under hydrogen ion discharge control, the refining rate in the model converter initially increased but eventually attained an approximately steady value. The level of this rate plateau was shown to be strongly influenced by the rate of transfer of hydrogen chloride from the jet gases to the slag phase. Similarly in oxygen steelmaking the decarburisation rate plateau has been shown to be determined mainly by the oxygen blowing rate. The model converter has been used to qualitatively investigate the effect of lance height, jet momentum and mass flow rate of gaseous reactant into the reaction vessel on the mean plateau refining rate. The results obtained compare favourably with analogous variables in steelmaking practice. In addition the effect on the refining rate of pressurising the reaction vessel has also been investigated. An improvement in refining rate was achieved, partly due to improved slag-metal drop contact and partly to increased hydrogen chloride flow rate. It is not believed that such asignificant improvement would be achieved for steelmaking conditions although there might be some advantage derived from improved control over slopping at high oxygen flow rates. When the sodium content of single amalgam droplets fell below a critical level, determined by the acid concentration in the aqueous phase, the rate of reaction became controlled by sodium transport to the reaction interface. This is analogous to decarburisation rate control by carbon transport within iron droplets. In both the model converter and in steelmaking this gives rise to a progressively decreasing refining rate.