Substrate effect of coke particles on the structure and reactivity of coke/pitch mixtures in carbon anodes

Chevarin, F.; Azari, Kamran; Ziegler, Donald; Gauvin, R; Fafard, Mario; Alamdari, Houshang

doi:10.1016/j.fuel.2016.06.070

Cited by 15 publications

(9 citation statements)

References 16 publications

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“…Nevertheless, it has higher overvoltage which is with low porosity, high purity and high structural order or even heat up rate. The standard deviation indicator, showing more variability in values for both smelters are in a good agreement with data from previous absence of a direct correlation further studies directed at pitch interaction [27] at high temperatures, graphitization processes and impurities behavior would be valuable…”

Section: Resultssupporting

confidence: 89%

“…According to the different researchers [10,11,23], there is a significant difference in the magnitude of overvoltage even for one class of carbon materials; the difference in overvoltages can reach more than 300 mV when measured on samples made from different industrial anode blocks. It can be assumed that in different experiments carbon materials of different degree of graphitization, as well as with different content of impurities, were used, which, apparently, affected the structure of surface layers and their reactivity [26][27][28][29][30][31][32].…”

Section: Introductionmentioning

confidence: 99%

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Anode Overvoltages on the Industrial Carbon Blocks

et al. 2019

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40 years ago W.Haupin stressed that anode overvoltages on the carbon materials have a scatter more than 300 mV under the same current density. This is a reason to attempt to find out the reason for greater differences because decreasing the overvoltage promises high energy saving. Experiments in lab.cells in galvanostatic conditions have been conducted to determine the overvoltages for the smelter anodes used in Sayanogorsk and Boguchany smelters (Russia) (more than 80 curves currentsovervoltages are received). Overvoltages are compared with other carbon block properties. Recommendations to use these values as a parameter of carbon block quality were made.

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Section: Resultssupporting

confidence: 89%

Section: Introductionmentioning

confidence: 99%

Anode Overvoltages on the Industrial Carbon Blocks

et al. 2019

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“…Bio-oil was produced from biomass composed of 80 wt % white pine sawdust and 20 wt % cedar sawdust by using vacuum pyrolysis at 475 °C under 150 Torr. A CTP sample, typically used in the carbon anode manufacturing, was used as a reference pitch for comparison. ,, Commercial calcined petroleum coke, the same as those typically used in anode formulation, was chosen as the substrate for wettability tests. The substrate was made by making a particle bed using petroleum coke with a particle size of 106–150 μm.…”

Section: Methodsmentioning

confidence: 99%

Biochar as an Additive to Modify Biopitch Binder for Carbon Anodes

Hussein

Lauzon-Gauthier

et al. 2021

ACS Sustainable Chem. Eng.

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Looking for alternative materials to coal-tar pitch (CTP), as a binder in anode manufacturing, in aluminum production is of great interest. Such a material should be able to mitigate the cost and health issues without decreasing the carbon anode quality. Biopitch (BP) could be considered as a potential candidate. Previous studies show that biomass-based pitch has generally a low coking value compared to that of CTP, which might negatively affect its properties as a binder in carbon anodes. To increase its coking value, biopitch was modified by using additives. A solid bio-based material, namely, biochar, was considered as an additive. The prepared biopitch samples, containing different quantities of biochars, were analyzed for their softening point (SP), QI content, coking value (CV), molecular weight distribution, viscosity, surface tension, chemical groups, and surface composition, as well as their wettability with coke particles. The differences in texture and topography of different pitches, as well as the interface between pitch and aggregate particles in sessile drop after wettability test, were studied. The results revealed that increasing the quantities of biochars in biopitch increases their coking value, QI content, density, viscosity, and softening point. Furthermore, biochar addition only shows a minor influence on surface tension and molecular weight distribution of biopitch. An optimum amount (9.0 wt %) of biochar addition in biopitch could therefore be beneficial in anode formulation while using biopitch as a binder, compared to those of the reference anodes. The properties of the laboratory anodes (green/baked density, air/CO2 reactivity, compressive strength and electrical resistivity, carbon structure of the carbonized pitch) were investigated. Addition of biochar into biopitch could reduce the overall consumption of biopitch in the carbon anode formulation.

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“…The specific surface area, pore volume and pore size distribution of anode particles were measured by two different techniques [43]: -Between 0.0014 and 0.100 µm of pore size, a gas adsorption analyzer (Tristar II 3020, Micromeritics, Norcross, GA, USA) with the Density Functional Theory (DFT) equation and the nitrogen adsorptive gas was used; -For the pores superior to 0.1 µm to about 1000 µm (ISO 15901-1), a mercury porosimeter (Auto Pore IV, Micromeritics, Norcross, GA, USA) was used.…”

Section: Analytical Instrumentsmentioning

confidence: 99%

“…According to the literature, carbon reactivity could be controlled by the level of impurities [2,41,49] and by specific surface area [43,50]. Based on the Density Functional Theory model (DFT) for the gas adsorption and with the assumption that the pores are cylindrical for the mercury analysis, it is possible to obtain the specific surface area as a function of pore size distribution.…”

Section: Specific Surface Areamentioning

confidence: 99%

Evolution of Anode Porosity under Air Oxidation: The Unveiling of the Active Pore Size

Chevarin

Ishak

Ziegler

et al. 2017

Metals

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Abstract:The carbon anode, used in aluminum electrolysis (Hall-Héroult process), is over-consumed by air oxidation and carboxy-reaction (with CO 2 ). Several anode features may affect this over-consumption, such as impurity content, graphitization level and anode porosity features (e.g., porosity volume fraction or pore size distribution). The two first parameters are basically related to the quality of raw materials and coke calcination conditions. Anode porosity is, however, greatly affected by anode manufacturing conditions, and is possible to be modified, to some extent, by adjusting the anode recipe and the processing parameters. This work aims to investigate the effect of anode porosity on its air reactivity. Baked anode samples were prepared in laboratory scale and then crushed into powder form (−4760 + 4000 µm). The recipe for anode preparation was similar to a typical industrial recipe, except that in the lab scale no butt particles were used in the recipe. Anode particles were then gasified at six different conversion levels (0, 5, 15, 25, 35 and 50 wt %) under air at 525 • C. The porosity was characterized in several pore size ranges, measured by nitrogen adsorption and mercury intrusion (0.0014-0.020, 0.002-0.025, 0.025-0.100, 0.1-40.0 and superior at 40 µm). The volume variation of each pore range, as a function of carbon conversion, was assessed and used to determine the size of the most active pores for air oxidation. The most active pore size was found to be the pores inferior at 40 µm before 15 wt % of gasification and pores superior at 40 µm between 15 and 50 wt % of carbon conversion. Limitation of pore size range could be used as an additional guideline, along with other targets such as high homogeneity and density, to set the optimum anode manufacturing parameters.

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Substrate effect of coke particles on the structure and reactivity of coke/pitch mixtures in carbon anodes

Cited by 15 publications

References 16 publications

Anode Overvoltages on the Industrial Carbon Blocks

Anode Overvoltages on the Industrial Carbon Blocks

Biochar as an Additive to Modify Biopitch Binder for Carbon Anodes

Evolution of Anode Porosity under Air Oxidation: The Unveiling of the Active Pore Size

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