Chlorination of zirconium compounds

This paper examines the main methods of chlorination of natural zirconium compounds, evaluates the efficiency of existing technologies and considers the most promising methods for the development of the industry. Currently, research and development of new, energy‒efficient methods for processing zirconium‒containing natural compounds and man‒made waste are being actively carried out throughout the world. The existing hydrometallurgical methods for processing zirconium‒containing materials have a number of significant disadvantages, such as: multi‒stage nature, low degree and intensity of zirconium extraction, high consumption of reagents, or the need for long‒term disposal in the case of processing nuclear waste. The most promising from a technical and economic point of view are pyrochemical methods of processing zirconium in molten salts due to the greater intensity of the process and the possibility of utilizing a wider range of compounds. Chlorine metallurgy methods are the basis for the production of most rare earth elements, and for elements such as titanium, zirconium, and hafnium, there are no acceptable alternatives and are the only way to obtain high‒purity metal. Most often, chlorination is carried out in melts based on chlorides of alkali and alkaline earth metals, within 1000 °C. Chlorination of oxides with pure chlorine, without the use of a reducing agent, is impossible up to a temperature of 827 °C and higher, due to the positive values of the Gibbs energy of the reaction, therefore, reducing agents are used to carry out the process, in particular various forms of carbon, however, this method makes it difficult to maintain the stoichiometry of the loaded reagents, which leads to the accumulation of carbon in the reaction zone. The main obstacles to the development of the idea of using carbon tetrachloride were its high cost, toxicity, and limited solubility in salt melts, which makes it more suitable for direct chlorination of oxides in CCl₄ vapors. Chlorination using elemental sulfur as a reducing agent seems more promising in terms of energy costs, technological effectiveness, and overall process efficiency. To increase the efficiency of chlorination, it is possible to use a combined method using a chlorine‒carbon‒sulfur system. The proposed method allows to reduce the process temperature and synthesize the necessary compounds directly in the reactor, which will reduce the number of technological operations and increase the profitability of the process.