Separation of Ti from Bi-Ti alloy by Solid-Liquid Separation at High Temperature and Vacuum Distillation

Abstract

A new Ti smelting process via. Bi–Ti alloy is proposed. This process comprises reduction of TiCl₄ to Bi–10 mol%Ti alloy by Bi–Mg alloy, precipitation of Ti-rich compound from the alloy, and vacuum distillation. In this study, we investigated the precipitation and distillation processes. In the precipitation process, the Bi–10 mol%Ti liquid alloy is cooled from 900 ℃ to 500 ℃ to precipitate Bi₉Ti₈ in the liquid alloy. The Bi₉Ti₈ is recovered by a two-step separation method: recovery of mixture of Bi₉Ti₈ and Bi and further removal of Bi by centrifugal filtration. We demonstrated the recovery of mixture. As the results, Ti concentration in the mixture was 31 mol%, and the Ti yield was about 45 %. Because the remained liquid alloy after the recovery contains a large amount of Bi₉Ti₈, it is required to reuse the remained alloy in the precipitation process. Assuming the reuse of remained alloy, the material flow of the process was designed based on the experimental results. The centrifugal filtration of the mixture of Bi₉Ti₈ and Bi was also carried out at 500 ℃. By the centrifugal filtration at 50 G, alloys with a size of 1.5 mm were obtained, and the Ti concentration in the alloys was increased from 31 mol% to 40 mol%. Vacuum distillation of alloy powder and ingot was demonstrated. The distillation rate was enhanced when using the powder than when using alloy ingot as a starting material.