Effect of Titanium tetrachloride on the rate of chlorination of Yarega quartz-leucoxene concentrate

Abstract

This paper considers the results of a study that looked at chlorination of the Yarega quartz-leucoxene concentrate in an ebullated bed reactor (EBR) that feeds titanium tetrachloride vapours and their mixture with chlorine to the reaction mass. The experiments were conducted at a temperature of 850 oC and an incoming gas flow rate of 1,600 ml/min. 250–315 μm concentrate grains mixed with 160–250 μm calcined petroleum coke (the carbon to titanium dioxide molecular ratio was 5) were subjected to chlorination. The reaction products were analyzed with the help of inductively coupled plasma optical emission spectroscopy. It was found that, in the absence of chlorine, titanium tetrachloride only interacts with iron oxides. Feeding a mixture of titanium tetrachloride vapours and chlorine into the reactor leads to an intensified chlorination of the main concentrate components, including TiO2, SiO2, Al2O3 and Fe2O3. The TiO2 chlorination rate rises proportionally to the square root of the partial pressure of titanium tetrachloride in the gas-vapour mixture. The risen rate can be attributed to a higher concentration of active chlorine atoms, which in this case occur on carbon surface not only due to dissociation of molecular chlorine but also as a result of decomposition of titanium tetrachloride. A higher partial pressure of chlorine atoms leads to higher rates of reaction between the chlorine atoms and the concentrate components. According to the proposed reaction mechanism, the TiO2 chlorination rate is proportional to the square root of the product of the partial pressure of TiCl4 and the carbon grains surface area. The excessive chlorine does not impact the chlorination rate. It would be advisable to take into account the discovered ability of TiCl4 to intensify the titanium dioxide chlorination process when designing a chlorine feeding unit in the ebullated bed reactor. Feeding chlorine mixed with titanium tetrachloride vapours into the lower section of the reactor can help enhance the process performance while avoiding using too much chlorine.The work weas carried out under financial support of the Russian Foundation for Basic Research grant, the project No. 18-29-24187mk.