AAluminiumMetals digital twinDigital twin for optimization of the primary aluminaAlumina feed to the Gas Treatment CenterGas treatment center (GTC) has been developed and implemented online at a test plant. The goal of the digital twinDigital twin is to stabilize the fluorideFluoride content of secondary alumina leaving the GTC to generate a stable and predictable raw material forPrimary aluminium primary aluminiumAluminium productionAluminium production. The digital twin is based on a first principles process model that predicts fume concentrations, adsorption and H \(_2\) O and HF transport via gas and alumina flows. The digital twin uses data from the plant and local weather stations and incorporates an estimation routine to adapt the model based on online measurementsMeasurements, including concentration measurements from an HF laser in the main raw gas duct. The digital twinDigital twin follows the process with high fidelity and is deployed for Model Predictive ControlModel predictive control. Results show that the digital twin can stabilize adsorbed fluorideFluoride levels in secondary aluminaAlumina.