A Further Evaluation of the Coupling Relationship between Dephosphorization and Desulfurization Abilities or Potentials for CaO-based Slags: Influence of Slag Chemical Composition

The coupling relationships between dephosphorization and desulfurization abilities or potentials for CaO–FeO–Fe2O3–Al2O3–P2O5 slags over a large variation range of slag oxidization ability during the secondary refining process of molten steel have been proposed by the present authors as logLp + 5logLs or logCpo3-4 + logCs2- in the reducing zone and as logLp + logLs - 5logNFetO or logCPO3-4 + logCs2- in the oxidizing zone based on the ion and molecule coexistence theory (IMCT). In order to further verify the validation and feasibility of the proposed coupling relationships, the effects of chemical composition of the CaO-based slags are provided. The chemical composition of slags was described by three group parameters including reaction abilities of components represented by the mass action concentrations Ni , two kinds of slag basicity as simplified complex basicity and optical basicity , and the comprehensive effect of iron oxides FetO and basic oxide CaO. Comparing with the strong effects of chemical composition of the CaO-based slags on dephosphorization and desulfurization abilities or potentials, the proposed coupling relationships have been confirmed to not only be independent of slag oxidization ability as expected but also irrelevant to the aforementioned three groups of parameters for representing the chemical composition of the CaO-based slags. Increasing temperature from 1811 to 1927 K (1538 to 1654 °C) can result in a decreasing tendency of the proposed coupling relationships. In terms of the proposed coupling relationships, chemical composition of slags or fluxes with assigned dephosphorization ability or potential can be theoretically designed or optimized from its desulfurization ability or potential, and vice versa. Considering the large difference of magnitude between phosphate capacity CPO3-4 and sulfide capacity CS2- , the proposed coupling relationships between dephosphorization and desulfurization abilities for CaO-based slags are recommended to design or optimize chemical composition of slags.

The Effect of Slag on the Effectiveness of Phosphorus Removal from Ferrous Alloys Containing Carbon, Chromium and Nickel

The aim of this study was to determine the impact of slag composition on phosphorus removal from ferrous solutions containing carbon, chromium and nickel. Additions of cryolite, Na3AlF6, were applied for better fluxing and higher phosphate capacity of the slag. An X-ray analysis of final slags formed during dephosphorization of ferrous solutions containing chromium and nickel with CaO-CaF2or CaO-CaF2-Na3AlF6mixtures of different chemical compositions was carried out. The equilibrium composition of the liquid and the solid phase while cooling the slags from 1673K to 298K was computed using FactSage 6.2 software. The performed equilibrium computations indicated that the slags were not entirely liquid at those temperatures. The addition of cryolite causes a substantial increase of the liquid phase of the slag. It also has a favourable effect on the dephosphorization grade of hot metal. The obtained results were statistically processed and presented in the form of regression equations.

Thermodynamics Analysis of Hot Metal Dephosphorization Flux Reaction Process

In this paper, CaO-Fe2O3-CaCl2and CaO-Fe3O4-CaCl2system dephosphorizer depho- -sphorization of the thermodynamics of the use of FactSage thermodynamic calculation software Equilib module of hot metal dephosphorization flux and the balance between the response calculated, to find the right dephosphorizer dephosphorization ratio and the conditions for optimal phosphorus removal. First of all, by the beginning of slag and the final calculated optical basicity slag and phosphate capacity, calculated on the balance FactSage software phosphorus content mapping, and comparative analysis. Followed by software at different temperatures to calculate the iron liquid, liquid slag, slag liquid solid phase of calcium phosphate and calcium phosphate and quality data on the thermodynamic equilibrium temperature mapping analysis..