THE EFFECT OF THE IRON OXIDE CONTENT IN MOLTEN SLAGS UPON DESULPHURIZATION
WEI SHOU-KUN (Peking Institute of Ferrous Metallurgy)
Cite this article:
WEI SHOU-KUN (Peking Institute of Ferrous Metallurgy). THE EFFECT OF THE IRON OXIDE CONTENT IN MOLTEN SLAGS UPON DESULPHURIZATION. Acta Metall Sin, 1964, 7(2): 157-164.
Abstract As regards the effect of the iron oxide content of molten slags upon desulphurization in iron- and steelmaking, different conclusions have been given in the literature: (1) pure iron oxide slag has a desulphurizing effect and gives a sulphur-distribution ratio of 3.6 at 1600℃; (2) variation of the iron oxide content of openhearth slags from 3 to 70％ has practically no effect upon the sulphur-distribution ratio; (3) with electric furnace (or blast furnace) slags, the less the iron oxide content, the higher the sulphur-distribution ratio; and (4) with less basic slags within a certain range of basicity, increase in the iron oxide content brings about an increase in the sulphur-distribution ratio. In the present paper, through calculations with the help of the sulphur-distribution ratio formula: (％S)/[％S]=2.56fs/γ_s--·(Σn+Σn_-)/n_(FeO) derived from the complete-ionization theory of slag constitution and with the introduction of activity coefficients, it has been shown that the above-mentioned four conclusions are not contradictory against one another, and between them there exists an intimate relation. They simply signify that under different conditions iron oxide exerts different actions, and all these different actions could be amalgamated and generalized under the same formula. On the assumption that SiO_2 is present as SiO_4~(4-)in the slag, the formula is not suitable for application to acid slags, while at the same time the effect of temperature upon the sulphur-distribution ratio needs further investigation. The formula has been used to evaluate the sulphur-distribution ratio of basic cupola and basic side-blown converter slags from data in actual practice, and the following resuits have been obtained: (1) desulphurization in the basic cupola practice has practically reached equilibrium; and (2) in basic side-blown converter practice, owing to the presence of gaseous desulphurization, the sulphur-distribution ratio found in actual practice is less than that calculated from the formula.
