Mixing variables for prebaked anodes used in aluminum production

Identifying optimum anode baking level and mixing temperature are important when producing high quality anodes. The effect of varying mixing temperature and baking level were investigated in terms of the resulting apparent anode density, specific electrical resistivity (SER), air permeability, coefficient of thermal expansion (CTE), air reactivity, and CO 2 reactivity. Six pilot-scale anodes were prepared at Hydro Aluminium using a single source petroleum coke and <2 mm coke fractions. A coal tar pitch was used with Mettler softening point of 119.1 • C. The aggregate was mixed at 150 • C or 210 • C and baked to a low, medium, or high baking level. A 2 2 full-factorial design analysis was performed to determine the response of the analyzed properties to the applied mixing and baking temperature. Apparent density, SER, and air permeability were found to be highly dependent on mixing temperature. Apparent density and SER were also slightly affected by baking level. CTE was found to be independent of both baking level and mixing temperature. Air reactivity was found to be mainly dependent on baking level, while CO 2 reactivity was dependent on both mixing temperature and baking level.

Section: Resultssupporting

confidence: 88%

“…At the same binder level, the higher mixing temperature will lower the viscosity of the pitch and hence spread the binder better and thinner between and within coke particles. This leads to higher density and more homogeneous anodes [11].…”

Section: Resultsmentioning

confidence: 99%

The Effect of Varying Mixing Temperatures and Baking Level on the Quality of Pilot Scale Anodes—A Factorial Design Analysis

Sommerseth

Thorne

Ratvik

et al. 2017

“…X-ray computed tomography has been used for decades in science to reveal the internal structures of objects, from living beings to engineering materials (e.g., [31][32][33][34]) including the carbon materials used in the aluminum production industry [35][36][37][38][39]. Its main advantage is that it is a non-destructive technique.…”

Section: X-ray Computed Tomographymentioning

confidence: 99%

Application of Boron Oxide as a Protective Surface Treatment to Decrease the Air Reactivity of Carbon Anodes

Ishak

Picard

Laroche

et al. 2017

Self Cite

Abstract:The oxidation of a carbon anode with air and CO 2 occurs during the electrolysis of alumina in Hall-Héroult cells, resulting in a significant overconsumption of carbon and dusting. Boron is well known to decrease the rate of this reaction for graphite. In this work, the application of boron oxide has been investigated to evaluate its inhibition effect on the air oxidation reaction, and to provide an effective protection for anodes. Different methods of impregnation coating have been explored. Impregnated anode samples were gasified under air at 525 • C according to the standard measurement methods. X-ray tomography was used to obtain the microstructural information of the samples before and after air-burning tests. The impregnated samples showed a very low oxidation reaction rate and dust generation.

“…X-ray computed tomography has been used for decades now in science to reveal the internal structures of objects from living beings to engineering materials (e.g., [15][16][17][18]) including the carbon materials used in the aluminium production industry [19][20][21][22][23]. Its main advantage is that it is a non-destructive technique.…”

Section: X-ray Computed Tomographymentioning

confidence: 99%

Crack Detection Method Applied to 3D Computed Tomography Images of Baked Carbon Anodes

Picard

Lauzon-Gauthier

Duchesne

et al. 2016

Self Cite

Carbon anodes used in the aluminium industry were imaged through destructive and non-destructive testing (NDT) methods. For the latter case, computed tomography (CT), which has previously been used to map the 3D apparent density distribution, was extended to crack detection. Previous work has shown how to overcome technical hurdles related to crack detection by using percolation-based algorithms operating on low-resolution images of full-scale baked carbon anodes. The previous application to 2D images was extended here to the 3D case. The crack detection algorithm has been performed on anode slices containing several independent macro cracks with different morphologies.