The refractory lining in anode baking furnaces is exposed to harsh chemical environment and thermal cycling. Spent refractory lining from an anode baking furnace after 4000 days in operation was investigated. Variation in the density and porosity across the bricks revealed that carbon build up in pores had taken place towards the anode side. The spent refractory bricks were investigated with respect to chemical and mineralogical composition by X-ray diffraction and electron microscopy. No significant change in the mineralogical composition across the brick could be detected by X-ray diffraction. Fluoride was not found in the bricks, while traces of sodium was shown to accumulate together with other impurities in the bricks. The changes in the chemical and mineralogical composition across the bricks are discussed in relation to possible chemical reactions taking place during anode baking.
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