The wear of industrial refractory materials was studied in contact with slag containing high amounts of FeO using the rotating finger technique. The thermodynamic equilibrium of the refractory slag systems was also determined in Thermo-calc ® and FactSage™. The studied refractories were alumina spinel, zirconia, graphite, silicon carbide (SiC), magnesia-carbon (MgO-C), chromite (Cr2O3), and MgO-Spinel (MgO-Al 2 O 3). The fingers were rotated in a FeO x (90wt%)-SiO 2 (5wt%)-CaO (5wt%) slag for 3 hours in a molybdenum crucible at 100 RPM at 1700K. The wear of the refractory fingers was determined by dimensional changes and changes in composition of the slags. Only MgO-spinel refractories exhibited resistance to the slag. The thermodynamic equilibrium calculations were able to predict the experimental behavior when appropriate databases were used, with the exception of the chromite slag.
The IronArc process is a novel approach to ironmaking which aims to reduce the associated $${\hbox {CO}}_{2}$$ CO 2 emissions. By superheating gas using electricity in a plasma generator (PG) the heat required for the process can be supplied without burning of coke. Reduction of hematite and magnetite ores is facilitated by additions of hydrocarbons from liquid natural gas (LNG). The melting and reduction of ore will produce a molten slag containing 90 pct wüstite, which will be corrosive to most refractory materials. A freeze-lining can prevent refractory wear by separating the molten slag from the refractory. This approach is evaluated in CFD simulations by studying the liquid flow and solidification of the slag using the enthalpy–porosity model in two different slag transfer designs. It was found that a fast moving slag causes a high near-wall turbulence, which prevents solidification in the affected areas. The RSM turbulence model was verified against published experimental research on solidification in flows. It was found to accurately predict the freeze-lining thickness when a steady state was reached, but with lacking accuracy for predicting the time required for formation of said freeze-lining. The results were similar when the $$k{-}\omega $$ k - ω SST model was used. A design with a slower flow causes more solidified material on the walls and can protect all areas of the refractory wall from the corrosive slag. A parameter study was done on the effect of viscosity, mushy zone parameter, heat conductivity and mass flow on the amount of solidified material, thickness of solidified material, heat flux, and wall shear stress. In the current geometry, freeze-linings completely protect the refractory for mass flow rates of up to 3 $${\text {kg}} \, {\text {s}}^{-1},$$ kg s - 1 , and are stable for the expected viscosity (0.05 to 0.3 Pa), heat conductivity (2 $${\text {W}}\, {\text {m}}^{-1}\,{\text {K}}^{-1}),$$ W m - 1 K - 1 ) , and used mushy zone parameter (10,000).
The flow behavior of gas in compressible and incompressible systems was investigated at an ambient temperature in an air–water system and at an operating process temperature in the IronArc system, using computational fluid dynamics. The simulation results were verified by experiments in the air–water system and established empirical equations to enable reliable predictions of the penetration length. The simulations in the air–water system were found to replicate the experimental behavior using both the incompressible and compressible models, with only small deviations of 7–8%. A lower requirement for the modified Froude number of the gas blowing to produce a jetting behavior was also found. For gas blowing below the required modified Froude number, the results illustrate that the gas will form large pulsating bubbles instead of a steady jet, which causes the empirical equation calculations to severely underpredict the penetration length. The lower modified Froude number limit was also found to be system dependent and to have an approximate value of 300 for the studied IronArc system. For submerged blowing applications, it was found that it is important to ensure sufficiently high modified Froude numbers of the gas blowing. Then, the gas penetration length will remain stable as a jet and it will be possible to predict the values using empirical equations.
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