Chemical behaviour of nitrogen in metallurgical slags

According to previous experimental work, nitride capacity C_N, in opposition to sulfide capacity C_S, decreases with increasing optical basicity of metallurgical slags. This tendency is also confirmed by the contradictory behaviour of the free energy changes of oxide-nitride and oxide-sulfide transformation reactions as a function of basicity. From the present metal-slag equilibrium studies, denitrogenation potentials P_N = %(N)/{%[N] · %[Al]} were obtained characterizing denitrogenation efficacy of slags at given compositions and temperatures. From these potentials, factors were derived which mark the effects of individual slag components. It was found that these factors feature the same basicity dependence as nitride capacities C_N and denitrogenation potentials P_N. The factors are increased, e.g., as less basic oxides are increasingly present in the slag phase in the order BaO → SrO → CaO → MgO.     

Processing of metallurgical slags

Magnitogorsk Metallurgical Combine. Translated from Metallurg, No. 10, p. 38, October, 1990.     

钢铁冶金渣的资源化利用

开展冶金渣资源化利用,对于减少冶金渣弃埋用占地和防止环境污染,促进我国钢铁工业的持续高效发展具有重要意义.通过对我国冶金渣资源化综合利用的现状、目前存在的主要问题以及未来发展趋势的分析,得出了在不断完善现有冶金渣资源化利用方法的同时,还应进一步研究和开发利用冶金渣生产具有高附加值制品的结论。     

The composition and temperature dependence of the sulfide capacity of metallurgical slags

The concept of optical basicity and its applicability as a means of correlating the available data on the sulfide capacity of metallurgical slags has been reviewed. An excellent correlation based on very extensive data at 1500 °C, which was discussed in a previous paper, is combined with good correlations based on considerably less data at 1550 °C and 1650 °C to quantify the effect of temperature on the sulfide capacity of slags. The combined effects of slag composition and temperature have been expressed in the equation, logC _s = [(22690 – 54640A)/7] + 43.6A − 25.2. Use of this equation permits the calculation of the sulfide capacity of a slag at any temperature between 1400 °C and 1700 °C simply from a knowledge of its chemical composition, and can be employed for virtually any oxide slag of interest in the field of iron and steelmaking. This, in turn, permits calculation of the equilibrium distribution of sulfur between this slag and iron or steel, provided that the oxygen potential is known or can be calculated from the degree of deoxidation applied.     

Thermodynamics of nitrogen in Ca-CaF2 slags

Formerly with the Department of Metallurgical Engineering and Materials Science, Carnegie Mellon University.     

Kinetics of evolution of SO2 from hot metallurgical slags

The kinetics of the evolution of SO₂ gas from a liquid synthetic blast furnace -type slag (CaO-Al₂O₃-SiO₂) in an atmosphere of O₂ + Ar gas at a total pressure of 1 atm for 0.003 ≤ Po₂ ≤ 1.00 atm has been studied in the range 1360 to 1460°C. The process has been followed by collecting and analyzing the SO₂ as it forms, and also by observing the change in weight of the slag sample with time. The effect of slag composition has also been studied. For partial pressures of oxygen less than about 0.1 atm, the rate is very rapid and is controlled by transport in the gas phase. At greater values of Po₂, the rate is much slower and is controlled by a chemical process. In the high Po₂ region, the process is half-order with respect to the concentration of sulfur in the slag. This half-order dependence on sulfur concentration in the slag may be explained by an initial fast irreversible reaction to form two intermediate species which then decompose at equal rates to give the final products. Additions to the slag of iron or manganese oxides greatly accelerate the rate of evolution of SO₂ at Po₂ = 1.00 atm. This is interpreted to mean that a charge transfer process, possibly involving S^2- and O^2- ions, is rate-controlling at Po₂ = 1 atm. It is also apparent that Fe²⁺ and Fe³⁺ (or Mn²⁺ and Mn³⁺) ions can act as charge carriers. Some measurements with actual industrial blast furnace slags are also reported. Formerly Visiting Scientist, Massachusetts Institute of Technology     

Measurement of the thermal diffusivity of liquid oxides and metallurgical slags

The methods of heat transfer in stagnant bodies of glass and slag are reviewed, and it is shown that the effective thermal diffusivity determines the rate at which heat is transferred in glasses similar in composition to metallurgical slags. A new experimental apparatus is also described for measuring the effective thermal diffusivity of these glasses. The results of experiments performed on glasses containing between 10.9 and 26.8 pct FeO, with lime/ silica ratios,B, of 1.0 and 1.5, and at temperatures ranging from the liquidus temperatures of the glasses to 1750 K are represented by A theoretical basis is used to develop the form of this relationship, and consequently, it should yield reasonable estimates for glasses of other composition and at other temperatures. H. Allan Fine and T. Engh were formerly Research Assistant and Visiting Scientist, respectively.     

Physicochemical properties and structure of titania-containing metallurgical slags:a review

The titanium industry can hardly bypass the titania-containing slags,and the slag physicochemical properties are essential in the metallurgical reactor design a...     

Activity determinator for the automatic measurements of the chemical potentials of FeO in metallurgical slags

An automatic system for rapid determinations of the activities of FeO in metallurgical slags has been developed. With this facility, one datum is obtainable within 5 minutes. The facility was applied for the activity measurements in the system CaO + SiO₂ + FeO, while activity data obtained were consistent with those deduced from the phase diagram.     

Photon conductivity of metallurgical slags of the three component system CaO-SiO2-Al2O3

The measuring method proposed by Keene and Quinn has been further developed to investigate 3-component slags of the system CaO-SiO₂-Al₂O₃ at temperatures of 800–1600°C in the wavelength range of 550 to 850 nm. The results are presented with the aid of the complex refraction index, which embodies all information on the optical properties of the slags investigated, including photon conductivity and thermal emissivity. Comparison of the photon conductivities determined shows good agreement with the corresponding values of various types of glass cited in literature. The discontinuous pattern of the phonon conductivity curve in the melting range of 40% CaO-40% SiO₂-20% Al₂O₃ slag, as already found by Gammal and Li, is also evident from the data of the present investigation.     

Nitrogen solubility in metallurgical slags equilibrated with Fe–Al or Fe–Ca melts

Considerations are directed to the denitrogenation potential of metallurgical slags with respect to steel melts under reducing conditions. Experiments were made to determine partition ratios of nitrogen between molten slag and iron. The investigated systems were aluminate-based slags, containing CaO, MgO, SrO, BaO, CaF₂ or ZrO₂, in equilibrium with Fe–AI melts and Ca–CaO–CaF₂ slags equilibrated with Fe–Ca melts. Denitrogenation efficiency of aluminate-based slags is comparatively low and essentially determined by oxygen potential and basicity of the slag. Denitrogenation efficiency of Ca–CaO–CaF₂ slags is much higher and is dependent on calcium activity.