China Nonferrous Metallurgy

The properties of carbonaceous reductants have a significant influence on the product quality and production indicators of titanium slag smelting in electric furnaces. Semi-coke has advantages such as high fixed carbon content， strong reactivity， low ash content， and low sulfur content. However， there have been no literature reports on the use of semi-coke for titanium slag smelting. To investigate the effect of semi-coke on titanium slag smelting， this study compared and analyzed the gasification reactivity， thermogravimetric analysis， thermogravimetric analysis after mixing with ilmenite concentrate， and graphitization degree of semi-coke. A comparative analysis was also conducted between titanium slag smelting using pure coke breeze and that using a mixed reductant， leading to the following main conclusions. The analysis results show that the weight loss rate of semi-coke （89. 7%） is significantly higher than that of coke powder （44. 1%） at the same time， and the volatilization temperature of semi-coke and the graphitization degree is lower， indicating that the gasification reaction speed of semi-coke is faster and the reaction activity is higher， which is beneficial to accelerate the reduction process of titanium slag smelting. The industrial test results show that the content of TiO₂ in titanium slag is 74. 93% after using mixed reducing agent （ coke powder∶semi-coke = 8∶2， mass ratio）， which is slightly lower than the coke powder smelting index of 74. 96%， but the content of FeO in slag increases by 12. 28%， and the content of CaO， MgO， SiO₂ and Al₂O₃ decreases by 10. 76%. The average CO concentration of the gas produced by the mixed reducing agent smelting is increased by 2. 69%， the H₂ content is increased by 0. 51%， and the gas quality is steadily improved. The power consumption of smelting per ton of slag by mixed reducing agent is reduced by 25. 19 kWh/t， and the smelting cycle is shortened by 0. 61 h. Adding an appropriate amount of semi-coke to coke powder as a reducing agent for titanium slag smelting can improve the quality of titanium slag， shorten the smelting cycle and reduce the smelting cost. However， due to the faster gasification reaction speed and high reactivity， the internal gas discharge conditions of electric furnace should be optimized as far as possible to reduce the concentrated gas production. Considering the safety， semi-coke is more suitable for continuous charging smelting process.