Study of the effect of some process parameters on powder injection refining by a mathematical model

Influence of some process parameters like carried-over slag, top flux, bath stirring intensity and residence time of the flux on the refining ability of the injected flux by a mathematical model are studied. Refining is considered to occur both by transitory and permanent contact mechanisms. The differential equation is solved by the finite difference method for a wide range of amounts of carry-over slag, composition and amounts of flux, bath stirring intensity and residence time of the flux. The refining curves and the separate contribution of transitory and permanent rate to total rate are presented and discussed as a function of the aforesaid parameters. The model is used to analyze the desulphurizing reaction in the presence of slag carried-over from the previous steelmaking unit. It is found that for only the permanent contact desulphurizing reaction, the type, composition and amount of flux is less critical than stirring gas rate to achieve a high desulphurization % in the presence of carried-over slag. For injection desulphurization, residence time of the flux, fraction of particles carried by the bubbles and the partition coefficient, are important parameters controlling the transitory contribution to the total rate in relation to type, composition and amount of flux. High desulphurization can be obtained both by permanent contact and injection method. It is asserted that the selection of any one method would depend more on locally available facilities like powder injection system, ladle free board height and availability of ladle with the stirring gas injection device.