ADVANCED TECHNOLOGY FROM BROCHOT
A PROVEN SOLUTION FOR ANODE SLOT CUTTING
the build-up of a layer of gas increases the cell resistance. The distance needed by a gas bubble to escape from the underside of the anode is a determining factor in the development of the layer thickness and basically, the shorter the escape distance the lower the resistance created by the gas layer will be. As anode sizes grow, the problem of the gas layer increases. The introduction of slots into the anode therefore simulates, for as long as the slot exists, the effect of using a smaller anode by providing an escape path for the gas bubbles formed on the underside of the anode. Slot configurations Brochot anode slot cutting machine during workshop testing The French based company : Brochot is a well-established supplier of production process equipment to the non-ferrous metals industry. The company is represented on a worldwide basis with offices in Canada, China, Russia and Middle-East and 3 workshops in Quebec, France and China. The company’s portfolio is extensive and increasing, in particular with the addition of recent equipment supply to the copper and zinc industries by the Brochot Hydromet division. Brochot’s principal activity remains the design, development, manufacturing and supply of equipment for the primary aluminium sector. In this sector Brochot is well known for supply of individual machines and complete turnkey projects for anode rodding shops and anode handling installations. A recent successful installation is the supply of an anode slot cutting machine to the NALCO plant in Angul, India. This machine is part of an ongoing development of the Brochot anode slot cutting design, which seeks to improve and adapt the design to the
AWJ 2013
varying criteria of individual smelter sites. Brochot continues to invest in the development of new and revised designs for its slot cutting machine, and future orders will incorporate a number of improvements to cycle times and adaptations to client slotting requirements Advantages of slotted anodes The use of slotted anodes is now well established in aluminium smelter pot lines. The slotting of anodes is known to give improvements in pot efficiency by reducing the formation of bubble films (which create higher electrical resistance), reducing anode cracking and allowing use of increased pot currents. The cost of aluminium production is highly dependent on the cost of energy used in the reduction process and efficiency gains from slotted anodes have a direct cost benefit. Studies have shown that a large part of the gases (mostly carbon dioxide and carbon monoxide) generated by the reduction process are formed on the underside of the anode block and
Anode slotting arrangements have existed in two configurations – lengthwise slots and transverse slots. These slots can be formed in two ways – by moulding during the formation of green anodes or by machining the slots in baked anodes. It is accepted that the longitudinal slot configuration delivers the greatest benefit and the Brochot slot cutting machine produces slots in this direction. The use of moulded slots has a number of disadvantages compared to machined slots. Slot forming plates introduced in green anode moulds can affect the paste distribution and compaction around the slots. The slots are wider than machined slots and they can become clogged with packing coke at the anode baking stage. The wider slots also reduce the overall mass of carbon consequently reducing the life of an anode. Such slots create more fragile green anodes and increase rejection rates during the green anode forming, cooling and transportation stage. These problems are exacerbated with increases in the slot depth which would be potentially useful in maintaining the slot through a greater part of the anode life.
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