Thermodynamic Modeling of Mineral Phases Formation in EAF Slag System and its Application as Agricultural Fertilizer

by Lateef K. Bankole, Sheikh Abdul Rezan, Nurulakmal M. Sharif

Publisher - Universiti Sains Malaysia

Category - General Novel

For every ton of steel production, about 10–20 per cent of slag is being generated as a byproduct. In Malaysia, with more than five major steel-makers, an increase in industrial development will lead to massive steel production and waste slag. The present work demonstrates how chemical thermodynamics modeling via Factsage can be used to characterize the solidification behavior of mineral phases in a modified EAF slag. Besides this, a review of steel slag application to plant and soil amendment will also be presented. The solidification simulation of mineral phases was analyzed in terms of 20 weight percent addition of K2CO3 to EAF slag, where CaO / SiO2 weight per cent ratio, varies from 0.6 to 1.0. Thermodynamic modeling shows that solidification temperature and weight per cent ratio of the slag system can have significant influence on the solidification behavior and mineral phases formed at room temperature. The amount of stable Potassium Silicate (K2Si4O9 & K2Si2O5), reaches a maximum precipitation at a temperature of 1090oC-1140oC with a CaO / SiO2 weight per cent ratio of 0.6. Cooling between this temperature ranges will give a Potassium Silicate composition of 37.7%. Above 1140oC, the Potassium Silicate begins to volatized and transformed completely at 1150oC. At 1125oC, there is a transformation of CaSiO3 (Wollastonite-w) to Pseudo Wollastonite (pw) which is stable until the liquidus temperature of 1300oC. Cooling from the above the liquidus temperature, the Potassium Silicate will not precipitate until 650oC and reaches a maximum value of 27.5% weight percent at 610oC. Increasing the weight per cent ratio of CaO / SiO2 to 1, the formation of Calcium Silicate will be predominant during the solidification process. Properties of cooled EAF slag can be significantly enhanced by understanding the stable mineral phases formed at high temperature and variation of its cooling path allows tailoring of the slag

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