Chlorination-Volatilization Behavior of Titanium Metal Scraps during Recycling Using Reaction-Mediating Molten Salt

Abstract

In order to develop an ef cient and environmentally friendly process for recycling both titanium scrap and FeCl x (x = 2, 3) waste, the chlorination-volatilization of titanium metal scraps utilizing a MgCl 2 -SmCl 3 reaction-mediating molten salt was examined. After the thermodynamic analyses on the chlorination behavior of representative elements such as the alloying elements and oxygen, fundamental experiments were carried out at 1100 K by reacting off-grade Ti sponge, Ti-6Al-4V alloy rod, and Ti rod with MgCl 2 -SmCl 3 molten salt. The results indicated that TiCl 4 could be effectively produced and volatilized from off-grade sponge and Ti-6Al-4V alloy. It was also con rmed that Fe and Ni in the Ti scrap remain in the molten salt as metal, whereas the Al and V in Ti alloy are chlorinated by SmCl 3 and their chlorides volatilized. Oxygen introduced into the reaction system was found to form TiOCl in the molten salt, and therefore does not consume the SmCl 3 mediator in the molten salt. These ndings con rm that chlorination using a reaction-mediating molten salt is an effective means of recycling both titanium scrap and FeCl x waste.

Sustainable Recovery of Titanium Alloy: From Waste to Feedstock for Additive Manufacturing

“…Deoxidation by Ca/CaO [154] Effective deoxidation Low or insufficient capability for deoxidation VIM with CaAl 2 [155] Short process time Low or insufficient capability for deoxidation Hydrogen plasma arc melting [156] Short process time Low or insufficient capability for deoxidation Deoxidation of Ti alloy by HDH [157] Simple process Low or insufficient capability for deoxidation Electrochemical deoxidation [158] Ultra-high capability for deoxidation Required a molten salt bath Chlorination with reaction-mediating molten salt [99] Applicable to most titanium alloys Required a molten salt bath FFC process [159] Titanium production directly from oxides The process time is too long [163] Inexpensive deoxidant Titanium with a high percentage of Si Leaching after hydrogenation [164] Suitable for Ti-6Al-4V alloy Toxic waste solutions are generated Electrorefining in molten salt [165] The process can remove almost all impurities There is contamination from molten salt Chlorination with FeCl x chloride waste [166] It was possible to control impurities High volatility of FeCl x…”

“…Because of the contamination due to the stainless-steel vessel, a small part of the sponge cannot be employed. It is estimated that there is a residue of 10-20% of titanium sponge in each production [99], causing an energy consumption of 42.96 MJ/kg.…”

Holistic evaluation of the suitability of metal alloys for sustainable marine construction from a technical, economic and availability perspective

“…Thus, by reducing the Fe and especially O content of TiA scrap the need for additional virgin material and down-cycling could be reduced. Technologies for removal of these contaminants are mostly still in the fundamental stage of research [82][83][84][85][86][87]. If further development proves successfully, they could have a high commercial potential.…”

Recent Progress in Titanium Extraction and Recycling

“…Taninouchi et al developed an efficient chlorination process that uses a reaction-mediating molten salt. [88] Ti Titanium metal is efficiently chlorinated in this process because both the chlorination agent and the reaction product are dissolved species in molten salts. This process can be applied not only to pure titanium but also to titanium alloys.…”