Carbon Lining Cathode Materials for the Production of Aluminum by Electrolysis. Improvement of the Properties
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Vol. 61, No. 1, May, 2020
CARBON LINING CATHODE MATERIALS FOR THE PRODUCTION OF ALUMINUM BY ELECTROLYSIS. IMPROVEMENT OF THE PROPERTIES A. L. Yurkov,1,2 A. P. Malakho,1 and V. V. Avdeev1 Translated from Novye Ogneupory, No. 1, pp. 9 – 13, January, 2020.
Original article submitted October 17, 2019. We present the data on the improvement of carbon cathode lining materials used in the production of aluminum by electrolysis and discuss some issues from the materials science related to the technology of production of carbon cathode materials. Keywords: carbon cathode lining materials, production of aluminum by electrolysis, electrolyzer.
The hearth of electrolytic bath is lined with carbon cathode blocks. A negative potential is applied to these blocks. The hearth serves for two purposes: first, it is a part of the volume (nozzle or bath) of a metallurgical unit in which certain levels of the metals and electrolytes are maintained and, second, it plays the role of cathode on the surface of which the electrochemical reaction of reduction of aluminum is realized. Since the very beginning of commercial production of aluminum by the Héroult – Hall method, the hearths of electrolytic baths are permanently improved. Thus, as the materials of carbon hearths of the first electrolytic baths, it was customary to use metallurgical coke, oil coke, and resinous binders [1]. The material was not formed, i.e., it was packed into the hearth as a plastic packing mass. The first preliminarily burnt carbon sole blocks appeared in 1920 [1]. In 1927, the so-called steel blooms (current suppliers) were introduced for the first time into the slots between the sole blocks by the method of casting of melted cast iron. The producers of carbon sole blocks try to improve their characteristics by increasing the sizes of the blocks, changing their shape and composition, and improving their properties. Earlier, carbon sole blocks were formed of several pieces 1.8 – 2.2 m in length with a short side 1 – 1.2 m in size. At present, it is customary to use continuous sole blocks up to 3.8 m in length (Fig. 1). The width of the blocks is now as large as 0.7 m, their height varies within the range
0.4 – 0.55 m. The shape of the slots is also changed (Fig. 2). The contemporary sole blocks are actually massive structures whose mass is sometimes greater than 1 ton. As a rule, the producers of carbon cathode materials propose the following compositions: anthracite + 30, 75 – 80, or 100% of graphite [1, 2] and graphitized blocks. In order to decrease the electric resistance and power losses, it is reasonable to use graphitized sole blocks. Thus, there are graphitized sole blocks made of isotropic and acicular coke and blocks with one or two impregnations. We now mention
1
Fig. 1. Hearth of an electrolytic bath formed by carbon sole blocks, either composed of several pieces or continuous.
2
Lomonosov Moscow State University, Moscow, Russia. [email protected]
5 1083-4877/20/06101-05 © 2020 Springer Science+Business Media, LLC
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A. L. Yurkov, A. P. Malakh
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