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At Elkem, an electrolysis cell will be used to convert rare earth oxides to rare earth metals and alloys. The electrolysis cell operates as a medium-sized furnace equipped with a graphite crucible, operating at around 1100°C, and at 2 000 Amperes.  

Initially, rare earth fluorides are fed into the furnace and pre-melted before the electrolysis process begins. This molten fluoride-medium, known as the electrolyte, is essential for electrolysis, although it does not directly participate in the chemical reaction. You can compare it to the water used to boil potatoes – it facilitates the process without being part of the final product.

Then, rare earth oxides are fed into the molten electrolyte at a controlled rate. Electrolysis is carried out using graphite anodes submerged in the molten bath, and an iron cathode. During the process, the rare earth oxides are transformed into a rare earth alloy, with iron from the cathode being consumed, referred to as a Rare Earth Alloy.

The iron cathode serves a dual purpose: it supplies electrical current to the electrolysis process and provides iron to the final rare earth alloy. As the cathode is gradually consumed during the process, it is replaced at regular intervals to maintain the optimal process parameters. 

The produced rare earth alloy is collected in vessels at the bottom of the electrolysis cell. At regular intervals, the vessels are extracted from the molten electrolyte, and the rare earth alloy is cast into moulds. To minimise operator exposure to high temperatures and toxic fumes, a robot is carrying out this extraction process.  

Could you walk us through the final steps in preparing the High Temperature Electrolysis (HTE) pilot for the validation trials? What are the key technical or logistical elements being finalized before the start of November?

Elkem brings valuable experience in rare earth electrolysis from the Horizon 2020 project REE4EU, carried out between 2015 and 2019. The electrolysis cell used in REEPRODUCE is based on the same design as in REE4EU, with technical upgrades and modifications.

The most significant advancement in REEPRODUCE is the use of a robotic system to discharge the produced rare earth alloy from the cell. This is a highly advanced operation, pushing the limits of what the robot can withstand in terms of temperature and motion. 

Beyond the robot integration, there are literally hundreds of minor and major details that require attention during the final stages of pilot preparation. Fortunately, Elkem’s Technology Pilot department brings extensive experience in managing complex pilot trials. The team has access to in-house resources across engineering, electrical system, IT, mechanical workshops and process knowledge.

A major challenge in preparing for the trials has been sourcing rare earth fluorides from China. Due to current trade regulations, China has imposed strict controls on exporting materials containing of rare earth. 

Finally, it is also worth highlighting Elkem’s strong commitment to health, safety and environment (HSE) throughout the project. The company adheres to a strict “No harm” policy, which applies not only to internal operations but also to external collaborations such as REEPRODUCE.

How has the successful output from the hydrometallurgical pilot influenced the setup and expectations for the HTE phase?

These two pilot processes are not directly linked in terms of technical dependencies. However, the successful completion of the pilot trials at JGI-HYDROMETAL is a key milestone for achieving the overall objectives of the REEPRODUCE project. Elkem has received 600 kg of rare earth oxalates from the pilot located in Belgium, which will serve as the raw material for the HTE pilot operations. At Elkem, these RE oxalates will be dried and calcined  to remove water and carbon.  The resulting rare earth oxides will then be used as feedstock for the High Temperature Electrolysis (HTE) process described above.

What are your expectations for the initial trial phase in November? Are there particular performance indicators or outcomes you’ll be focusing on during this first round of testing?  

SINTEF will be actively involved during the pilot trials at Elkem, playing a key role in defining process parameters and supporting the planning of the trial operations. In addition, SINTEF will carry out online sampling and monitor off-gas emissions, while also collecting all data generated from the electrolysis process.

The overall objective of the pilot is to produce the required amount of rare earth alloy for the next phase of the REEPRODUCE project – and to do so using automated robotic operations.