Batch tests were carried out during the autumn of 2019 to support the planning of the pilot plant. The scope of the pilot project was wide, and it was successfully completed thanks to the efforts of ORC’s experimental and analytical laboratories as well as its mechanical, electrical, and automation maintenance teams. Additional support was provided by four test-work engineers from the Outotec Dewatering Technology Center in Lappeenranta.
Continuous lithium hydroxide pilot plant
The LiOH pilot plant was continuously operated for 336 hours from January 7th until January 20th, 2020. The main process stages were soda leaching, LiOH conversion, ion exchange, and LiOH crystallization. There were solid-liquid separation stages after soda leaching and LiOH conversion as well as a polishing filtration stage after secondary conversion. The solid-liquid separations were carried out using pressure filters and the polishing filtration was carried out with a filter press. After crystallization, the solids and liquids were separated with a pusher centrifuge and some of the centrifuge product was dried with a fluidized bed dryer. The whole process, including all the unit operations as well as a high number of process stream recycles, was operated 24/7. Approximately 100 kg/d of spodumene concentrate was processed in the pilot plant during operation, and the total number of samples analyzed during the pilot was 675, including solution and solids samples.
The operation of the pilot process was smooth, with some adjustments made to operating conditions during the pilot to improve and stabilize the process. In general, the unit operations of the pilot process worked very well. The pressure filters produced consistent cakes with low moisture content, while the filtrate produced by the polishing filtration stage was clear. The solution polishing was successful as well, with the result being a high-purity LiOH solution, which was fed to the crystallizer. The objectives of the pilot were met, and the results are currently being used in an ongoing engineering and delivery project with the customer. The consumption of reagents was investigated and the impact of recycling different process streams in the process was seen. The LiOH solution produced by the pilot plant was extremely pure, resulting in battery-grade lithium hydroxide monohydrate produced in a single crystallization stage. An average impurity profile is shown below along with an image of a dry LiOH·H2O sample.
The results of the pilot project demonstrated the potential of our LiOH process as well as the ability of ORC to carry out extensive test-work campaigns on a pilot scale. The pilot plant is also available to new customers who are interested in piloting the LiOH process with their concentrate. The world-class facilities, experienced personnel in the experimental and analytical laboratories, and excellent maintenance capabilities mean that ORC has a unique capability to execute this sort of project.