Title: Improvement of anode properties by coke modification with additives
Abstract: In aluminum production, carbon anodes that are made of petroleum coke, coal tar pitch and recycled carbon materials are used to provide carbon required for the electrolysis process. The anode quality directly affects not only the energy consumption and the production cost but also the emission of greenhouse gases. The raw materials quality has a significant effect on anode quality. The good quality anodes should have high density, low electrical resistivity, low air/CO2 reactivity as well as good mechanical properties. Pitch binds the solid particles together. The quality of raw materials can change depending on its source and the processes parameters used in the refineries. However, industry still has to produce good quality anodes. In general, good coke/pitch interaction results in better quality anodes. This study was undertaken to enhance the wettability of coke by pitch, with the objective of improving the anode properties, based on coke modification by adding additives and surfactants and to determine the effect of additives on anode quality. The results showed that the wettability of coke by pitch is dependent on the heteroatom containing functional groups present on the coke surface. The interaction between coke and pitch increases with increasing amount of heteroatom-containing functional groups. Thus, it is possible to improve the anode quality by modifying coke with additives. The study indicated that different cokes have different amounts of functional groups. Therefore, each coke has a different wetting behavior. It was found that, before modifying a coke, its surface chemistry should be taken into account for the determination of suitable additive type and amount. The surface functional groups of pitch are as important as those of the coke, however, this is outside the scope of this project. In this study, the effect of the contact time between the additive and the coke on the anode quality was also investigated, and a coke modification method was developed. Based on the experimental results, the anode quality improved more when the coke was pre-treated before it was mixed with pitch.
Dans la production de l’aluminium, les anodes de carbone qui consistent en coke de petrole, brai de goudron de houille et materiaux carbones recycles fournissent le carbone requis pour le procede d’electrolyse. La qualite des anodes affecte directement non seulement la consommation energetique et le cout de production, mais aussi l’emission des gaz a effet de serre. La qualite des matieres premieres a un impact considerable sur la qualite des anodes. Les anodes de bonne qualite doivent avoir de haute densite, de basse resistivite electrique, de basse reactivite a l’air et au CO2 et de bonnes proprietes mecaniques. Le brai lie les particules solides ensemble. La qualite des matieres premieres peut varier dependant de sa source et des parametres des procedes utilises dans les raffineries. Neanmoins, l’industrie doit produire des anodes de bonne qualite. En general, des fortes interactions entre le coke et le brai resultent en des anodes de meilleure qualite. Cette etude a ete entreprise pour accroitre la mouillabilite du coke par le brai, pour but d’ameliorer les proprietes d’anodes, en modifiant le coke par l’ajout d’un additif ou un tensioactif et aussi pour determiner les effets de l’ajout des additifs sur la qualite des anodes. Les resultats ont demontre que la mouillabilite du coke par le brai depende des groupes fonctionnels, presents sur la surface du coke, qui contiennent des heteroatomes L’interaction entre le coke et le brai augmente avec la quantite des groupes fonctionnels contenant des heteroatomes. Donc, il est possible d’ameliorer la qualite des anodes en modifiant le coke par des additifs. Cette etude a indique que les differents cokes ont des quantites differentes des groupes fonctionnels. Donc, chaque coke a un comportement de mouillabilite different. On a trouve que, avant de modifier un coke, sa chimie surfacique doit etre considerer pour la determination du type et de la qualite appropries de l’additif. Les groupes fonctionnels du brai sont aussi importants que ceux du coke, mais cela n’est pas inclus dans la portee de ce projet. Dans cette etude, l’effet du temps de contact entre l’additif et le coke sur la qualite d’anodes est aussi examine, et une methode pour la modification de coke a ete developpee. Base sur les resultats experimentaux, la qualite de l’anode a ameliore plus lorsque le coke a ete pretraite avant de le melanger avec le brai.
Publication Year: 2017
Publication Date: 2017-08-01
Language: en
Type: article
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