Mitigating material supply risks: evaluation of abrasion specific comminution for commercial recovery of indium from waste liquid crystal displays

Abstract

Indium is a valuable commodity of great importance to the adoption of low carbon energy technologies including solar and nuclear. Many geopolitical entities; however, view the stability of indium’s supply chain with concern. While the United States currently imports 100% of its indium from other countries, waste LCD screens represent a non-trivial potential source of indium if it can be profitably recovered. Broad scoping studies were performed with corresponding high level economic evaluations to identify best candidates for further study, and a wet abrasion approach of removing coatings known as attrition scrubbing was selected as a promising approach for further study due to the ability to upgrade indium by a factor of >10 at >90% recovery in less than 10 minutes at low cost. A business case evaluation of optimal processing plant size was used to estimate the amount of waste LCD screen that might be sourced at a central facility thereby determining production capacity of between 10,000 and 15,000 tonnes per year. Pilot scale studies and discrete element method (DEM) computational models were applied to better understand the feasibility of attrition scrubbing for indium recovery of LCD screens at scale. A model based on particle properties and morphology, scrubber geometry and agitation rate, and single particle fracture behavior was developed capable of successfully predicting power consumption, indium concentrate quantity and quality, and the attrition scrubber geometry which is known to produce the most intense scrubbing action. Applied to five common production scale attrition scrubbers, the model suggests that one would be capable of recovering 99% of contained indium in a concentrate with an upgrade ratio of 14 with a retention time of four minutes. Further insights into the fundamental operating mechanisms and opportunities for improved attrition scrubber design are discussed.