The Behaviour of Titania in Metallurgical Slags

Equilibrium studies between CaO-SiO 2 -10 pct MgO-Al 2 O 3 -TiO 1.5 -TiO 2 slags, carbon-saturated iron, and a carbon monoxide atmosphere were performed at 1773 K to determine the activities of TiO 1.5 and TiO 2 in the slag. These thermodynamic parameters are required to predict the formation of titanium carbonitride in the blast furnace. In order to calculate the activity of titanium oxide, the activity coefficient of titanium in carbon-saturated iron-carbon-titanium alloys was determined by measuring the solubility of titanium in carbon-saturated iron in equilibrium with titanium carbide. The solubility and the activity coefficient of titanium obtained were 1.3 pct and 0.023 relative to 1 wt pct titanium in liquid iron or 0.0013 relative to pure solid titanium at 1773 K, respectively. Over the concentration range studied, the effect of the TiO x content on its activity coefficient is small. In the slag system studied containing 35 to 50 pct CaO, 25 to 45 pct SiO 2 , 7 to 22 pct Al 2 O 3 , and 10 pct MgO, the activity coefficients of TiO 1.5 and TiO 2 relative to pure solid standard states range from 2.3 to 8.8 and from 0.1 to 0.3, respectively. Using thermodynamic data obtained, the prediction of the formation of titanium carbonitride was made. Assuming hypothetical 'TiO 2 ,' i.e., total titanium in the slag expressed as TiO 2 , and using the values of the activity coefficients of TiO 1.5 and TiO 2 determined, the equilibrium distribution of titanium between blast furnace-type slags and carbonsaturated iron was computed. The value of [pct Ti]/(pct 'TiO 2 ') ranges from 0.1 to 0.2.

Section: Redox Ratio In Blast Furnace-type Slagssupporting

confidence: 72%

Thermodynamics of TiO x in blast furnace-type slags

Morizane

Ozturk

Fruehan

1999

“…A similar observation was found in the present case for low basicity and low TiO 2 containing slags. Sommerville and Bell [10] reported that TiO 2 lowers the viscosity CaO-SiO 2 -MgOAl 2 O 3 -TiO 2 slag, the decrease being lower at higher basicities. However, they have not mentioned the definition of basicity and range of basicity in which analysis was carried out.…”

Section: Resultsmentioning

confidence: 97%

Experimental Investigation of the Viscosities in CaO-SiO2-MgO-Al2O3 and CaO-SiO2-MgO-Al2O3-TiO2 Slags

Shankar

Görnerup

Lahiri

et al. 2007

137

The viscosities of high alumina blast furnace slags were experimentally determined by the rotating cylinder method using the Brookfield digital viscometer model LVDV-II+ pro. Two different slag systems were considered for the current study, the CaO-SiO 2 -MgO-Al 2 O 3 quaternary and the CaO-SiO 2 -MgO-Al 2 O 3 -TiO 2 quinary system. Experiments were conducted in the temperature range of 1650 to 1873 K. The effects of temperature, basicity, TiO 2 , and silica activity of slags on viscosity were studied. The viscosity decreases with basicity for high alumina blast furnace slags with basicity in the range of 0.46 to 0.8. At high basicity (~0.8), slag viscosity decreases even with a small amount of TiO 2 (~2 pct) addition in the slag. With an increase in silica activity in the range of 0.1 to 0.4, the slag viscosity increases, the increases being steeper below the liquidus temperature.

“…The tetravalent titanium cation is expected (on the grounds of its size and charge [4] ) to show acid (network-forming) behavior, more so than alumina and somewhat less so than silica. The actual behavior of TiO 2 does not agree with this expectation: TiO 2 , in fact, lowers the viscosity of, for example, blast-furnace slags.…”

Section: Viscositymentioning

confidence: 98%

“…The actual behavior of TiO 2 does not agree with this expectation: TiO 2 , in fact, lowers the viscosity of, for example, blast-furnace slags. [5] TiO 2 and SiO 2 act very differently in liquid slags, [4] perhaps in part reflecting the differences in structural behavior in the solid state, where titanium oxides generally prefer an octahedral (sixfold) coordination, compared with the tetrahedral (fourfold) coordination of SiO 2 . [6] The available published data for the viscosity of hightitania slags are for "Sorel slag," produced by smelting Canadian ilmenite, which has somewhat higher impurities.…”

Section: Viscositymentioning

confidence: 99%

Physicochemical aspects of titanium slag production and solidification

Pistorius

Coetzee²

2003

The titanium-rich slags produced by ilmenite smelting are unusual in several respects, including their low viscosity, high electrical conductivity, propensity to solidify predominantly as one phase (pseudobrookite), and reactivity (with oxidizers) in the liquid and solidified form. The low viscosity is related to the unexpectedly "basic" behavior of Ti 4ϩ ; the high conductivity is likely through an electron transfer mechanism involving the Ti 4ϩ -Ti 3ϩ pair; the oxidation behavior is caused by the presence of a significant amount of Ti 3ϩ . Possible reasons for the nearly single-phase structure of the solidified slag are considered, and it is concluded that the most likely cause is the presence of a eutectic groove close to the M 3 O 5 (pseudobrookite) composition. This conclusion was tested by examining the compositions and microstructure of slag samples from a pilot smelter. The results show that the slags do contain a small amount of rutile, in line with predictions.