Wettability in water/iron ore powder systems: To the universality of the Cassie model

During iron ores granulation process minimization of the volume of water is of vital economic importance due to the associated energy cost of evaporation in the second sintering step. The optimisation of water addition demands understanding of capillarity properties of iron ore mixtures to ensure at the same time good mechanical strength of iron ore granules and just needed minimum of water in the granulation drum. Thus, in the current work wettability and capillarity properties of 7 iron ores, 7 additives and 7 mixtures of those components were studied. It was found that particles with size below 0.1 mm have a big influence on the contact angle and percentage of infiltrated water of mixtures. Particularly, the content of hematite Ore 1 had a significant effect on the contact angle. The use of calcine and dolomite additives affects slightly the magnitude of the water surface tension, but modifies the wettability of iron ores. The adaptation of the Cassie model for mixtures of iron ores of > 2-phases gave an excellent estimation of the contact angle for mixtures with size particles below 0.1 mm. A good estimation for mixtures with particles larger than 0.1 mm was also obtained.