Investigation of wetting behavior of coal-chars with liquid iron by sessile drop method.

Using the sessile drop approach, the wettability of four non-graphitic coal-chars with electrolytic iron and Fe-2 % C-0.01 % S alloy has been determined at 1550°C, in a horizontal tube resistance furnace with an argon atmosphere. The ash concentration in chars ranged between 9.04 to 12.61 wt %, with alumina and silica as predominant ash components. The contact angles of these chars with liquid Fe-2 % C-0.01 % S alloy showed lesser variations with time as compared to corresponding angles with electrolytic iron. While the initial contact angles ranged between 106° and 137°, the contact angles for all coal-chars were quite similar after 60 minutes of contact (105 - 110°). While no well defined correlations could be observed between the initial char structure (Lc values) and ash concentration / composition and contact angles in the initial stages of contact, the contact angles over extended periods were significantly affected by the presence of reaction products and impurity deposits in the interfacial region. With coal-chars generally showing a non-wetting behavior with liquid iron, these results are discussed in terms of the transfer of carbon and sulphur by mass transport across the interface, the formation of an enriched interfacial layer containing calcium, sulphur and alumina, reduction of reducible oxides such as silica and iron oxides, and possible transfer of these elements into the liquid iron.