Preparation of Carbon-Containing Iron Ore with Enhanced Crushing Strength from Limonite by Impregnation and Vapor Deposition of Tar Recovered from Coke Oven Gas

The optimum conditions for preparing carbon-containing iron ore (composites), in which coke-oven-gas-tar-derived carbonaceous materials completely filled the pores in Indonesian limonite (IL), are investigated using impregnation (IM) and vapor deposition (VD). A peak around 2 nm is observed in the pore size distribution profiles for the as-received IL and IL absolutely heated to a predetermined temperature. The intensity of the peak decreased with increasing ratio of tar to IL (tar/IL) for the IM-prepared composites, and it completely disappeared for the composites prepared with tar/IL > 1.0; the corresponding S_BET and V_BJH are <1 m²/g and <0.01 cm³/g, respectively. The peak at 2 nm in the pore size distribution profiles for the VD-prepared composites almost disappears for treatment times longer than 60 min for any combination of conditions for tar pyrolysis temperature (TPT) and VD temperature (VDT). The composite prepared using a combination of TPT–VDT of 700–350 °C for 60 min shows the highest carbon content and crushing strength. The C content and crushing strength of the IM- and VD-prepared composites increase with increasing tar/IL and VD time. The composite prepared with tar/IL = 3.0 and VD time of 240 min shows a C content and crushing strength of 48–50 wt %-dry and 10 daN, respectively. The cross-sectional analyses of composite particles prepared using both methods show that the tar-derived carbonaceous materials has completely filled the pores.