In-situ observations of the liquid high carbon iron (HCI) and slag flows in coke bed was carried out by using high temperature X-ray fluoroscopy at 1 773 K. Along with the observation, 2-dimensional multiphase computational simulations of the liquid HCI and slag flows in the coke bed was carried out to investigate the effect of the slag on the HCI flow in the coke bed. The liquid HCI cannot pass through the coke bed with the coke diameter of 3-5 mm, however, the HCI can pass through the same size coke bed if the HCI comes into contact with the slag in the coke bed. When the HCI and slag contact each other on the coke surface, the contact angle of the HCI with slag decreases and its wettability increases. On the other hand, the slag's contact angle increases and it changes to non-wettable phase. Based on the experimental and simulation results, it is confirmed that the contact angle change due to the HCI-slag contact makes them pass though the narrow coke slit which is small enough to prevent both of the liquid phases from flowing down if they do not contact each other. Based on the capillary rise model, the driving force of the HCI penetration into the coke bed will be the energy reduction by extending area of the coke surface covered with the liquid HCI.

In-situ observations of metal-slag separation behaviors between CaO-Al2O3 based slag, iron and graphite powder mixed pellets by a confocal laser-scanning microscope (CLSM) have been carried out to find the effective way to use high Al2O3 iron ore in CCA reduction processes. Since a particular type of high Al2O3 iron ore such as laterite contains small amount of NiO and Cr2O3, the effect of NiO and Cr2O3 on the metal-slag separation behaviors were also studied. The observed metal-slag separation behaviors were analyzed based on the equilibrium phase fractions calculated by FactSage and carbon diffusion simulation in an iron sphere particle with a spot carbon source condition. Based on these in-situ observations and carbon diffusion results, starting temperature of metal-slag separation was found to correspond to the eutectic temperature of CaO-Al2O3 based slag. The iron carburization was initiated by slag melting and most of iron particles were melted within about 20 s after slag melting. The rapid carburization after slag melting was introduced by the good wettability between solid iron and molten slag. NiO and Cr2O3 additions did not change the fundamental behaviors of metal-slag separation at least up to about 3 mass%. Based on these results, it was confirmed that high Al2O3 content iron ore can be used in CCA reduction process by using CaO-Al2O3 based slag.KEY WORDS: metal-slag separation; high Al2O3 iron ore; iron carburization; spot source diffusion; CaOAl2O3 based slag.

The effect of graphitisation by the variation of annealing time and temperature on the pore structure and apparent gasification rate at 1200 and 1500°C was investigated. The graphitisation degree of three kinds of coke used in this study was increased with annealing time and temperature. The increase in porosity of annealed coke sample is ascribed to the formation of silicon carbide. Annealing at 1200°C had less significant effect on the change of porosity in comparison with annealing at 1500°C. The mean area of pores was decreased, and pore density was increased with increasing annealing time while annealing had marginal influence on the pore shape. The apparent gasification rates of Coke 1 and Coke 2 with H 2 O were decreased by annealing, but 3 h of annealing increased the apparent gasification rate of Coke 3. The correlation between apparent gasification rate with H 2 O and macroporosity or graphitisation degree was investigated.