Synthesis of Ti(C, O, N) from ilmenite at low temperature by a novel reducing and carbonitriding approach

Abstract

Summary The clean and effective utilization of titanium‐bearing minerals has challenged the titanium industry all over the world. In order to realize the high‐efficiency, clean, and high value‐added comprehensive utilization of ilmenite concentrate, a novel process has been proposed in this study by reducing and carbonitriding ilmenite with the CH4‐N2‐H2 gas mixture at low temperature. Carbonitride performance and mechanism have been investigated experimentally and theoretically. The obtained results showed that the reaction process could be divided into three stages: formation of metallic iron, reduction of titanium oxide to titanium suboxides, and formation of Ti(C, O, N). The metallic iron congregated at the first two stages, but dispersed once the Ti(C, O, N) formed. The effects of both reaction temperature and preoxidation treatment on the reaction have been studied as well. It was found that the increase of temperature was conducive to the formation of Ti(C,O), and the ilmenite could be reduced completely to Ti(C,O) at 1170°C for 8 hours. The preoxidation treatment could improve the kinetics of reduction. At 1170°C, the introduction of N2 could apparently increase the reduction rate, with the complete reduction time decreasing from 8 hours in CH4‐H2 gas mixture to 3 hours in CH4‐N2‐H2 gas mixture. The proposed novel process has been assessed and it showed many potential advantages and feasibility.

Effect of Top Gas Recycling Technology on the Softening, Melting and Dropping Behavior of V–Ti Bearing Burden in COREX Process

“…It is found that the weight loss rate is small when using Ar as protective gas, indicating that N 2 increases the carbonization reduction of TiO 2 and the formation of Ti(C, N). Fan et al [22][23][24] also confirm that when rutile is reduced by CH 4 -H 2 , the introduction of N 2 apparently increases the reduction rate, with the complete reduction time decreasing from 8 hours in CH 4 -H 2 gas mixture to 3 hours in CH 4 -H 2 -N 2 gas mixture. To sum up, N 2 has an accelerating effect on the reduction of TiO 2 and the formation of Ti(C, N).…”

“…The added N 2 in reducing gas promotes the formation of the solid particle Ti(C, N) with high melting point ( > 2 950°C) in molten slag. [20][21][22][23][24] As shown in Fig. 7, based on the composition of the dropping slag obtained from the SMD test without N 2 ratio, the thermodynamic effects of different N 2 partial pressures on the reduction of TiO 2 in slag to TiN and TiC are calculated by FactSage 8.0 ( P P N total 2 0 0 6 = − .…”

“…The microstructure and element distribution of the residual slag also indicate that the introduction of N 2 promotes the formation of Ti(C, N). [20][21][22][23][24] As presented in Fig. 8, the erosion of coke by slag is intensified as the increasing N 2 concentration.…”

“…Secondly, the deterioration of the gas permeability of the V-Ti bearing burden with the increasing N 2 concentration is also attributed to the N 2 promoting the formation of Ti(C, N). [20][21][22][23][24] In stage Ⅰ of the pressure drop curve, the increase in N 2 concentration causes more Ti(C, N) to be generated by the reaction of slag and coke (Fig. 8).…”