Paper No. 427
RECOVERY OF TITANIUM FROM BLAST FURNACE SLAG USING FRACTIONAL FACTORIAL DESIGN OF EXPERIMENTS Farzaneh Valighazvini1, Fereshteh Rashchi2,*, and Rasoul Khayyam Nekouei3 ABSTRACT Titanium is one of the most valuable elements found in blast furnace slag with a concentration of approximate 2.7%. Due to the low level of titanium in the slag, the best method of extraction is hydrometallurgy. In this study parameters such as; slag particle size, temperature, concentration of acid, the ratio solid to liquid, and ultrasonic time, was used to determine the recovery of titanium. Parameters such as time and stirring speed were kept constant. To examine the result two level fractional factorial experimental design method was used. Particle size in the range of 2.35-3.36 and ＜0.85 mm, temperature of 25-65°C, acid concentration of 1-2 M, the solid to liquid ratio of 1:10-1:30 g/l and the ultrasonic wave's time of 0-20 min were studied. A total of 20 tests were performed and using statistical analysis and ANOVA replies, the optimum condition was identified and confirmation test was also performed. The recovery of titanium of over 98% was determined and predicted results and actual results were determined to be almost identical. Keywords: blast furnace slag, acid leaching, design of experiment, fractional factorial design
INTRODUCTION Nowadays, several studies especially in hydrometallurgy have focused on the recovery of metals including titanium (Ti) from secondary sources and tailings such as blast furnace slag. The slag is a by-product of the iron production industries. At present, Ti-bearing ores are treated as feedstock in iron making plants. Consequently, most of the Ti component, which is about 2.7% TiO2, is concentrated in the molten slag. As Yuanbo et al (2010) found titanium appears in three oxidation stages: TiO, Ti2O3, and TiO2. As Xiao-hua et al (2008) mentioned titanium, the fourth richest element among all structural metals and the ninth most abundant element in the earth’s crust, is primarily used in the form of TiO 2. Titanium is one of the elements that have versatile uses in various industries. Titanium and its alloys are used in numerous industrial fields; such as, aerospace, marine and automobile; further, they are used for chemical plant materials, medical equipments, buildings, and consumer products. In recent years, many efforts have been made for the recovery of titanium from this type of slag. Processes used to recover titanium from its sources have been hydrometallurgical and pyrometallurgical. El-hazek et al, 2007; Xiao-hua et al, 2008 have both stated that pyrometallurgical approaches are the traditional method employed to recover these elements; however, hydrometallurgical are currently receiving increased attention. Australia, Canada, and South Africa are the main players in the titanium industry regarding both production and export. Titanium slag is produced in Canada, Norway, and South Africa. Generally, titanium production from the Ti-bearing ores is very limited. In the next decade, global demand growth for TiO2 is expected to increase at an 1. MSc, School of Metallurgy and Materials Engineering, Azad University of Tehran, Branch Jonob, Tehran, Iran. Email:
[email protected] 2. Associate professor, School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, Tehran, Iran. Email:
[email protected] 3. MSc, School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, Tehran, Iran. Email:
[email protected]
XXVI INTERNATIONAL MINERAL PROCESSING CONGRESS(IMPC) 2012 PROCEEDINGS / NEW DELHI, INDIA / 24 - 28 SEPTEMBER 2012
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average rate of about 3% annually. Growth higher than the average is expected to occur in Asia. As Xiao-hua et al (2008) illustrated that China in particular is expected to lead the world growth in both production and consumption of titanium. However, the methods used so far have resulted in a low extraction rate at steep costs. As Yuanbo et al (2010) indicated, it is necessary to find more efficient and economical ways to utilize the slag. Also, in 2006, Yan et al have presented a two-step sulfuric acid process for leaching of Ti-bearing blast furnace slag. These investigations show that the acid leaching process effectively recovers Ti from Ti-bearing blast furnace slag. In 2008, Chen et al leached Ti-bearing blast furnace slag with 90% of sulfuric acid and Ti, Al, Mg and Sc were recovered. In this study, to recover titanium from a Ti-bearing slag, statistically designed experiments were performed. Effects of different leaching parameters; solid to liquid ratio, temperature, acid concentration, and particle size on the extraction of titanium were studied. Also, for the first time, the effect of ultrasonic waves was investigated.
EXPERIMENTAL DETAILS Materials The blast furnace slag was collected from disposal sites of waste materials at the Esfahan steel company, Iran. After crushing and grinding, the sample was divided into three size fractions,
