多级深度还原法直接制备钛粉

Direct preparation of titanium powder by multistage deep reduction

摘要:

钛是一种重要的战略商用金属,目前钛工业建立在高能耗的Kroll工艺的基础上,而目前电化学法和金属还原法制备单质钛存在不同程度的困境。针对传统钙、镁等金属热还原TiO₂制备金属钛粉过程存在的效率低、脱氧不彻底的技术瓶颈,本论文基于TiO₂分步还原的热力学平衡特点,结合镁钙电负性差异,提出了多级深度还原法直接制备钛单质的工艺：即TiO₂先镁热自蔓延一次还原得到一次还原产物,然后将一次还原产物进行钙热深度还原制备还原钛粉的新思路。采用对比研究法,考察了TiO₂镁热还原和钙热还原的热力学及动力学差异；考察了镁热一次还原过程中TiO₂机制与还原程度,以及一次还原产物不同深度还原模式下脱氧机制。结果表明：一次还原产物先酸浸预除杂,然后进行钙热深度还原更利于彻底脱氧,最终制备出氧含量仅为0.21%,纯度>99.0%可以商用的钛粉。

Abstract:

Titanium is an important strategic commercial metal. At present, the titanium industry is based on the high-energy Kroll process. At present, electrochemical methods and metal thermal reduction methods have different degrees of difficulty in preparing elemental titanium.There is a technical bottleneck in the preparation of metallic titanium powder by conventional thermal reduction of TiO₂ with calcium, magnesium, or other metals, such as low efficiency and incomplete deoxidation. Based on the thermodynamic equilibrium characteristics of the step-by-step reduction of TiO₂, a comparative study method was used, and the thermodynamic and kinetic differences between magnesia and calcium heat reduction of TiO₂ were investigated in this paper. Considering the difference in the electronegativity between magnesium and calcium, a new idea was put forward that the primary reduction product is prepared through a primary reduction process of TiO₂ in the form of magnesiothermic self–propagation high–temperature synthesis (SHS), and then the reduced titanium powder is obtained through the primary reduction product for a deep calcium-thermal reduction reaction. The reduction degree and mechanism of TiO₂ during the primary magnesium thermal reaction and deoxidation mechanism of primary reduction products in different deep reduction modes were investigated in this paper. The results showed that it is more conducive to undergo complete deoxygenation such that the primary reduction product is first acid-impregnated followed by deep calciothermic reduction. High purity reduced titanium powder with a final oxygen content of only 0.21% and purity greater than 99.0% was obtained.