Fundamentals of CO2 Capture in Primary Aluminum Smelting

The primary aluminum industry emits over 1 billion tons of greenhouse gases (GHGs) each year. As part of the efforts to manage global GHG emissions and to stay in the 1.5° window, the industry must make efforts to lower its GHG intensity for Scope 1, 2, and 3 emissions. Some efforts are being made to develop different processes that overcome some of the challenges related to the traditional Hall-Héroult process; however, in the foreseeable future, the Hall-Héroult process using carbon-based anodes for electrochemical production of aluminum will remain the main method. This means that different tools are required to address the various aspects that make up the overall GHG footprint. In line with this, it has been established that the capturing carbon dioxide (CO 2 ) from the process gases of electrolysis cells is a key pathway to reducing the GHG emissions from primary smelters. This has never been attempted in a full-scale aluminum smelter, and before diving into CO 2 capture technology, how the CO 2 is formed in the process must must be investigated so that its fundamentals are understood. However, this also provides insights into potential changes to the process that could optimize the capture of CO 2 gases. Once this is established, different CO 2 capture processes are discussed, and a rationale is provided for why currently the application of amine-type solvents for the separation of CO 2 is best suited for this application. To investigate this, process modeling is performed to validate whether high removal efficiencies of CO 2 at low concentrations are feasible, and at what energy penalties the CO 2 can be recovered before it is transported to storage or an end-user.