Advanced Gas Treatment in Aluminium Electrolysis

The AGATE project aims to test a completely new concept for gas treatment in aluminium smelters. Today's gas treatment centres ensure low emissions and return fluoride materials back to the cells where they are needed as reaction medium for the aluminium electrowinning. The main challenge today is that the electrolysis process is conducted in hundreds of individual electrolysis cells. While all of these have different fluoride losses, the centralised gas treatment centre will return the same average amount to all cells instead of the actual amount each cell has lost, this will over time gives a fluoride imbalance that needs corrective actions. The solution to this is PIA (Pot Integrated Abart), which is a miniaturised gas treatment centre that will be integrated into each electrolysis cell. In this way the fluoride loss will be captured and returned to the cell that it originated from, and hence keeping the fluoride levels stable. The effect of the stabilised aluminium fluoride levels is expected to be more stable operations, lower energy consumption and lower overall emissions. In AGATE we will do research on the first PIA unit in the world and integrate it with one of the electrolysis cells at Alcoa Mosjøen. We will conduct campaigns in order to establish knowledge about the synergies between electrolysis cell and PIA, and to collect data to verify if the theoretical predictions correspond to the measured data. New and more accurate data for future modelling and predictions will also be established. So far the main effort in the project has been towards detail planning, and how the PIA concept can be integrated to one of the existing electrolysis cells at Alcoa Mosjøen. Adaptions and adjustments to ensure optimised performance for the combined system, and the production of the test unit has been initiated. A considerable effort has also been dedicated to risk assessments to ensure at the experimental trials will not affect the operations at Alcoa Mosjøen negatively, and how to avoid operational interruptions during installation.

The AGATE project will develop a new and modular concept for integrated gas treatment in aluminium cells, with the additional benefit of reducing the fluctuations in electrolyte chemistry. This will improve the overall process efficiency of the electrolysis operations by increasing the current efficiency and lower energy consumption per kg produced metal. Compared to the existing technology of large, centralised gas treatment centres (GTC), the Pot Integrated Abart (PIA) is a revolutionary new way of designing a gas treatment unit. A PIA unit will serve only one electrolysis cell. In that way the fluoride emissions from each cell will be directly returned, and hence stabilise the fluoride levels in a completely new way. The concept involves modular units for fluoride capture and return. The units can be constructed off site and shipped as container sized units ready to be put into production. This offers easier logistics of construction, including increased flexibility when it comes to expansion of existing plants where the GTC is operating at limiting capacity.