Understanding the Anode Porosity as a Means for Improved Aluminium Smelting

The anode pore structure affects gas diffusion as well as air and carboxy reactivity burn-off during the aluminium electrolysis. The coarse porosity was investigated using X-ray computed tomography, the mid-range porosity using optical microscopy, and the finest porosity using mercury intrusion porosimetry. These methods were combined to gain a deeper understanding of porosity and how this affects anode quality and the potential for energy savings. Test materials were received from Hydro Aluminium with different coke sources, particle sizes, binder levels, and mixing temperatures. The paper will present measurement results and link these to production and process factors. The findings indicate that direct comparison for each technique is challenging because of the physical basis of the measurement and the different measurable pore size ranges. However, the combination of different techniques gives valuable insight to understanding anode porosity. Coke type, granulometry, pitch content and baking process affecting anode porosity, properties and reactivity.