Abstract
Abstract Phosphate capability (CP) and phosphorus partition ratio (LP) are usually used to evaluate the thermodynamic efficiency of dephosphorization slags with different compositions in hot metal pretreatment. However, these parameters are only useful in equilibrium conditions, and they are not accurate when they are used to evaluate slag efficiency in industrial processes. The current study evaluated the hot metal dephosphorization efficiency of different synthetic slags in experimental tests at 1400oC. This evaluation was made by using CP and LP, and by the computational thermodynamic software FactSage 6.4. This software allows to calculate the amount of liquid and solid present in the slag, which directly affects kinetic reactions. Therefore, even the computational thermodynamic software calculations are from considering the equilibrium, which in these cases can be used to explain the kinetic behavior of the processes. The obtained results allow concluding that CP and LP are valid, but only when they are used for equilibrium calculations; and that they should not be used to measure slag efficiency in industrial processes. A parameter named Dephosphorization Factor (FDeP) was developed based on data determined by computational thermodynamics. It was developed to be related to the dephosphorization efficiency. The results obtained in the current study allow to conclude that the initial synthetic slags, which presented higher CaO activity value, higher liquid quantity and FeO activity, will be the most efficient ones. And allow to conclude too, that the higher the factor, the greater the slag dephosphorization efficiency.
Highlights
Turkdogan (1996, 2000) and Heally (1970) showed that phosphorus oxidation may occur by the reaction between the metal-dissolved phosphorus and the oxygen provided by the iron oxide found in the slag
The computational thermodynamic software used in the current study evaluates the proposed dephosphorizing slags, since this software identifies both the thermodynamics and the kinetic variables affecting the dephosphorization reaction
According to Campos (1984), hot metal dephosphorization does not reach equilibrium due to kinetic factors associated with the reaction, i.e., the phosphorus mass dissolved in the metal is transported to the metal-slag interface, reacts with the oxygen provided by the oxygen sources in the dephosphorizing slag and enables phosphorus pentoxide (P2O5) formation
Summary
Turkdogan (1996, 2000) and Heally (1970) showed that phosphorus oxidation may occur by the reaction between the metal-dissolved phosphorus and the oxygen provided by the iron oxide found in the slag. In regards to the free energy standard, it is observed that the reaction is favored by low temperatures. They positively influence hot metal dephosphorization, since it presents temperatures lower than those of steel. According to Campos (1984), hot metal dephosphorization does not reach equilibrium due to kinetic factors associated with the reaction, i.e., the phosphorus mass dissolved in the metal is transported to the metal-slag interface, reacts with the oxygen provided by the oxygen sources in the dephosphorizing slag and enables phosphorus pentoxide (P2O5) formation. According to Young (1991), the term involving P2O5 in the equation refers to some slag data about this oxide’s high concentration
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