Investigation of thermal properties of blast furnace slag to improve process energy efficiency

Blast furnace slag (BFS) is the main by-product of iron making and is produced in large amounts worldwide. Analysing the properties of BFS, such as viscosity and heat exchange, at high-temperature conditions will help improve energy efficiency during the process. One of the steps in the iron making process is to heat the pig iron up to 1500°C for the next phase of steel-making. During this heating, a significant amount of energy is transferred to the BFS, and utilising some of this heat energy from the slag to contribute to heating pig iron would achieve energy efficiency. To improve energy usage, it is necessary to understand behaviour of the slags with differing compositions at varying temperatures. This knowledge is also important to assess the slag for further applications, such as use as concrete or cementitious material; however, the cooling process is known to have a significant effect on the end product properties and determine the end use of the slag. This study determines the thermal properties of selected slag samples using several in-situ experimental techniques. By comparing the chemical composition of the slags and their thermal behaviour, the effect of magnesium oxide and aluminium oxide was evident. Besides, the content of silicon dioxide had an effect on crystallization temperature and network strength.