Abstract
In ilmenite smelting furnaces, a freeze lining of solidified slag is used to protect the furnace refractories against the aggressive titanium slag. Freeze lining thickness cannot be measured directly due to harshness of conditions inside the process, thus process modelling is required. Several parameters influence the thickness of the freeze-lining, one of them being thermal conductivity of the frozen slag. However, there is a lack of thermal conductivity values for high titanium slags −especially as a function of temperature. In this study, thermal conductivity of three titanium slag samples and an additional sample of freeze-lining was measured from room temperature to 1100/1400 °C with the laser flash analysis method. In addition, thermal expansion and microstructures of the samples were studied to provide an extensive understanding of how microstructure will affect thermal conductivity. The thermal conductivity of the slag samples was found to increase from 1.2 to a maximum of 2.4 W/(m K) when increasing temperature from room temperature to 1100 °C. An additional experiment at 1400 °C showed that the thermal conductivity increased further as the temperature increased. The freeze-lining sample behaves differently, with conductivity being the highest at room temperature, 2.2 W/(m K).
Highlights
Titanium is the ninth most abundant element in the earth’s crust, occurring in the mineable forms of ilmenite (FeTiO3) and rutile (TiO2)
Past research indicates that decrepitation of high-titania slags is present at 400 °C, and this could be the cause for the sharp reduction in thermal conductivity for K19 at 400 °C. (Bessinger 2000) The results are presented in Figure 15 below
The incentive for finding this knowledge is to better be able to optimize the necessary freeze-lining in ilmenite smelters
Summary
Titanium is the ninth most abundant element in the earth’s crust, occurring in the mineable forms of ilmenite (FeTiO3) and rutile (TiO2). Rutile is the less common of the two, with a global production of 850 000 metric tonnes per annum (tpa) in 2015 (USGS Titanium Yearbook). Most of the rutile is used in the production of welding rods and titanium metal (Zhang, Zhu et al 2011). According to the USGS, the global production of ilmenite reached 7.23 million metric tons in 2015, the majority of which is used in pigment production. 2018) puts the global production capacity of TiO2-pigment 7.3 million tpa, and titanium sponge metal production capacity at 277 000 tpa. China accounts for upwards of 3 million tons of the annual pigment production capacity, and the United States for another 1.36 million tons
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