Interface wetting behavior between iron and coke during the carbon dissolution process in a blast furnace

Good gas permeability is an essential factor for the smooth operation and high performance in the lower part of the blast furnace. Under the present low carbon blast furnace smelting conditions, the coke layer is thinner, and the proportion of the molten metal in the coke layer is significantly higher, resulting in a major reduction in gas permeability, which seriously affects blast furnace operations. Also, the lower thickness of the coke layer weakens the process of solid-liquid carbon dissolution when the molten iron passes through the coke layer, which reduces the carbon content of the molten iron and further deepens the erosion of the refractory by the unsaturated molten iron. The carbon dissolution in the molten iron in a blast furnace core was measured by a high-temperature vacuum wettability test tool that analyzed the interface wetting activity between Fe−C melts with specific carbon mass fraction (3.8%, 4.3%, 4.8%) and 99.9% of high temperatures graphite plates. Besides, the scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS) were used to analyze the graphite substrate’s carburizing morphology and carburizing distances. The results show that, with the increase of carbon content, the interface contact angle becomes bigger. The contact angle decreases with time, and eventually reaches a steady-state during the melting process, and the Fe−C melt with saturated carbon cannot be wet. The scanning electron microscopy analysis shows that a spherical cap-like depression is created by a cross-section of the Fe−C melt and the graphite substrate, and the radius and volume of the depression decrease with increasing carbon content. The study of the EDS scanning analysis shows that the amount of dissolved carbon atoms in the graphite substrate penetrates the Fe−C melt and decreases with increasing initial carbon concentration. The smaller the carburizing effect, the better the wetting is conducive to carbon mass transfer. It is found that by measuring carburizing of the carbon atoms in the graphite substrate into the Fe−C melt by calculating the surface energy reduces the surface energy between the two. Thus, the surface tension decreases and the melt spreads slowly with contact angle gradually decreasing during melting.