Abstract
Abstract The effect of cooling rate on the crystallization of perovskite in high Ti-bearing blast furnace (BF) slag was studied using confocal scanning laser microscopy (CSLM). Results showed that perovskite was the primary phase formed during the cooling of slag. On the slag surface, the growth of perovskite proceeded via the successive production of quasi-particles along straight lines, which further extended in certain directions. The morphology and structure of perovskite was found to vary as a function of cooling rate. At cooling rates of 10 and 30 K/min, the dendritic arms of perovskite crossed obliquely, while they were orthogonal at a cooling rate of 20 K/min and hexagonal at cooling rates of 40 and 50 K/min. These three crystal morphologies thus obtained at different cooling rates respectively corresponded to the orthorhombic, cubic and hexagonal crystal structures of perovskite. The observed change in the structure of perovskite could probably be attributed to the deficiency of O2−, when Ti2O3 was involved in the formation of perovskite.
Highlights
China has abundant titanium resources, about 90% of which exist as vanadium-titanium bearing magnetite, mostly in deposits found around the Panzhihua–Xichang area in the southwestern part of China
According to the experimental results, the perovskite crystals grow by the successive appearance of quasi-particles along straight lines, which further extended in certain directions to form various dendritic morphologies, including fork, orthogonal, and snowflake shapes
(3) The observed change in the perovskite structure is probably caused by the following reasons. (i) Under the given experimental conditions, Ti2O3 exists in the slag, resulting in perovskite with formula of Ca2Ti2O5 (Ti3+)
Summary
China has abundant titanium resources, about 90% of which exist as vanadium-titanium bearing magnetite, mostly in deposits found around the Panzhihua–Xichang area in the southwestern part of China. The BF process is not efficient to collect titanium resources, as approximately 54% of titanium in the raw ores is collected into iron ore concentrates and enriches in blast furnace slag (TiO2, 22wt% to 23wt%). The extraction of valuable secondary titanium resources from high Ti-bearing BF slag and the effective use of waste slag remain to be a serious problem in China. The rutile-based Ti extraction process generates more low activity waste slag, which is unsuitable for use in cement making [12]. The perovskite-based Ti extraction process offers the advantages of small secondary pollution and low cost, the perovskite yield is rather low owing to the adverse effects of fine and uneven perovskite grains on the mineral separation.
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