Preparation of Ti-rich Feedstock by Hydrochloric Acid Leaching of High Titanium Blast Furnace Slag

Abstract

Ti-rich feedstock was prepared by acidic decomposition of air-cooled high-Ti blast furnace slag. Ti-rich feedstock with over 45% TiO2 can be obtained at the condition of hydrochloric acid concentration = 7 mol/L, mass ratio of acid and slag = 1.7:1, decomposition temperature at 90 oC and reactive time = 7 h. Panzhihua is a well-known capital city of vanadium and titanium and its proved titanium storage accounts for 90.54% in China and 35.17% in the world, with a potential economic value of 8000 billion dollars. However, the current steel production process only utilizes 20% (mass fraction) of titanium in vanadium titano-magnetite. The TiO2 in iron concentrate, after processing in the blast furnace, generally is passed to blast furnace slag and finally discarded together with slag [1]. The Panzhihua Iron and Steel Co. (short for Pangang) blast furnace slag contains up to 20% - 23% of TiO2 (mass fraction). On this basis, with an annual production of 4 million tons of iron, the annual production of blast furnace slag is 3.2 million tons, which is estimated to be about 0.9 million tons of TiO2 or an economic loss up to 5 billion RMB. PanGang has discharged an accumulation of 50 million tons of Ti-bearing blast furnace slag. Besides a small part used as building materials, the majority has been stacked in two slag fields. The current comprehensive utilization rate is below 15%, which indicates severe resource waste and potential risks of environmental pollution. Thus, comprehensive and efficient use of Ti-bearing PanGang blast furnace slag is of significant economic values and social benefits [1]. The titanium iron ores used in blast furnaces outside of China generally only contain 3% -4% (mass fraction) of TiO2, and the resulting blast furnace slag contains less than 10% of TiO2, which does not need special treatment. Researchers from Germany, US and Japan have studied Ti extraction from PanGang blast furnace slag, but nearly all pointed out the severe difficulty and have not given any efficient solution [2]. To solve the problem of comprehensively utilizing high-Ti blast furnace slag, Chinese researchers have conducted numerous studies in recent years and preliminarily identified some techniques, including compound method, application phase separation method, high-temperature carbonization & low-temperature chlorination, selective separation of valuable components, and TiCl4 preparation from Ti-containing blast furnace slag [3-7]. These methods have respective advantages, but are restricted by some limitations. So far, none of these methods can be industrialized. PanGang high-Ti blast furnace slag is divided into water-cooled slag and air-cooled slag, which are cooled down by water and by air after outputted from the blast furnace, respectively. Compared with water-cooled slag, the air-cooled high-Ti blast furnace slag is featured by high crystal orderness, stable physiochemical properties, and acid insolubility of TiO2 at normal temperature [8]. According to these properties, HCl decomposition can be conducted to remove the soluble impurities from the slag and to prepare Ti-rich feedstock. However, there is no report in this field.