Some recent innovations in the Kroll process of titanium sponge production

Abstract

Titanium and its alloys have emerged as cost-effective structural materials in many spheres of chemical and engineering industries including aerospace and power generation. Titanium in its pure form is invariably prepared starting from pure titanium tetrachloride. Titanium tetrachloride obtained by chlorination of the oxide mineral is purified and reduced with either liquid magnesium or sodium or electrolysed to obtain titanium in sponge form. The metal extraction processes are so complex that large scale production technology is limited so far only to a few countries in the world viz. the USA, Japan, CIS, UK and China. India is attempting to enter this arena shortly with a 1000 TPY commercial plant based entirely on home-grown technology.

Among the extraction methods, the magnesium reduction of titanium tetrachloride, patented by W J Kroll in 1940, has received wider attention because of the inherent and relative merits of the process and its viability for economic production on an industrial scale. The original Kroll process, however, has undergone several modifications in the past few decades. The recent technological breakthroughs in the Kroll process as well as in the magnesium recycling technology has resulted in a significant reduction in the production cost of the metal. The paper describes these important innovations and also the efforts that are being put in for the establishment of a commercial plant for metal production in India based on indigenously developed technology.