Spatial methods for characterising carbon anodes for aluminium production
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Original versionLight Metals. 2015, 2015-January 1141-1146. 10.1002/9781119093435.ch191
Pilot test anodes were designed by Hydro Aluminium for laboratory studies using controlled blends of <2 mm aggregate from two single source cokes. Spa- tial and imaging methods were used to characterise anode surfaces with respect to consumption, density, pore distribution and real active area before and after electrolysis. The methods include X-ray computed tomography (CT), confocal microscopy, scanning elec- tron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). It was found that during electro- lysis, the electrolyte does not completely wet the carbon inside large pores on the surface. Hence, even large pores do not contribute to the electrochemically active surface area. Large grains of isotropic cokes and anisotropic sponge cokes are consumed at approxi- mately the same rate, and bubble coke in anisotropic sponge cokes are consumed at a slower rate than the bulk material. This is due to higher resistivity through the bubble coke.