The measurement of silica activities in liquid slags

Baird, James D (1957) The measurement of silica activities in liquid slags. PhD thesis, University of Glasgow.

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In the manufacture of iron in the blast furnace one of the most important variables in the composition of the iron produced is the silicon content. Silicon must be kept as low as possible in the manufacture of basic iron in order to reduce the slag bulk in the open hearth furnace. It must also be kept to fairly low limits in making iron for the basic Bessemer process, but in the acid Bessemer process the reverse is true, since here silicon largely determines the heat produced in blowing the iron. Silicon control is also important in the manufacture of foundry iron as it has a major influence on the structure of the cast product. The main reactions controlling the composition of pig iron in the blast furnace take place in the hearth, where drops of molten iron fall through the slag layer into the bath below, and in so doing react with it. A study of the equilibria between slags and metals of the type obtained in the blast furnace is therefore necessary if the factors controlling pig iron composition are to be fully understood. Sufficient thermodynamic data are now available for the compounds taking part in these reactions to enable equilibrium constants for the various reactions to be calculated. These equilibrium constants indicate qualitatively the effect which different variables will have on the equilibria, but a quantitative treatment is only possible if the activities of all the reactants in the slag and metal solutions are known. In the case of some simple systems activities can be estimated or calculated on the basis of thermochemical data, but in the great majority of cases they must be measured experimentally. Usually this is done by bringing the phase being examined into equilibrium with a phase or phases of known thermodynamic properties. The present work is concerned mainly with the measurement of silica activities in lime-silica and lime-alumina-silica slags. In Part I the method adopted was to measure the carbon monoxide pressure in equilibrium with the slag, silicon carbide and carbon. In Part II the calculation of silica activities from data available on laboratory slag-metal equilibrium measurements has been investigated.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Additional Information: Adviser: R Hay
Keywords: Materials science
Date of Award: 1957
Depositing User: Enlighten Team
Unique ID: glathesis:1957-73568
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 14 Jun 2019 08:56
Last Modified: 14 Jun 2019 08:56

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