Relevant text from the paper: We see immediately that this reaction is different from Equa- tion 1. Here, oxygen is formed at the anode, which environmentally i

Relevant text from the paper: We see immediately that this reaction is different from Equa- tion 1. Here, oxygen is formed at the anode, which environmentally is a highly favorable gas, compared with CO2. The dream would of course be to have anodes that lasted as long as the cell life, which now may be up to 5 years or longer. Anode changes would then not be necessary after the cell has been started. Nevertheless, it is a chemical fact that all materials have a finite solubility in the very corrosive cryolitic melts at about 960◦C, so a totally inert anode will probably never be found for use in these electrolytes. Thus, what we really are looking for is a slowly consumable anode. But how slow a consumption rate can we tolerate? The potential inert anode material must have low solubility and low reactivity in the electrolyte and also show good chemical re- sistance against the anodically produced hot oxygen gas. In addition, the anode material should be physically stable at the operating tem- perature, mechanically robust and resistant to thermal shock. There will be extreme requirements for keeping the wear rates of these anodes low. A wear rate of the order of 10 mm/y may perhaps be sufficient, but lower values would certainly be beneficial. There are two main challenges in the development of inert anode materials. In addition to the requirement that the anode ma- terial should survive sufficiently long in the electrolyte, the metal produced must be of adequate purity. The impurity metal content in the aluminum can indeed be very significant for the customers, and the need for making pure aluminum will become more stringent in coming years. The corrosion products, caused by the dissolution of the anode material into the electrolyte, predominantly will end up in the metal phase and thereby contaminate the aluminum produced. Hence, the anode corrosion should be low enough to give impu- rity contents corresponding to the present specifications for smelter grade aluminum. There are three principal potential advantages in favor of de- veloping a new cell technology with inert anodes: 1. Cost reduction. All costs directly associated with the consumable carbon anode will then be eliminated, including the capital saving and raw materials costs by eliminating the need for the carbon anode fabrication, baking, and also the anode rodding plant. These cost savings may be significant. It has been indicated that there might be 25% to 30% lower capital costs for a new potline with inert anode cell technology.3 2. Environmental friendliness. Inert anodes would eliminate all greenhouse gas generation and emissions from the electrolysis cells. Smelters would no longer generate CO2, carbon monoxide, or perfluorocarbon gases (CF4and C2F6), because carbon would no longer be used as anode material. Carbon residues (butts) will of course disappear. In addition, the fluoride and dust emissions during anode change will also be eliminated. 3. Improved occupational health issues. Inert anodes would reduce the work practices associated with the present prebaked carbon anode change. The frequency of anode changes will certainly be drastically reduced with inert anodes. Working conditions in the potrooms would also be improved by avoiding all anode effects. The outlook of the primary aluminum industry may be sum- marized as follows: This is now a mature industry, which presently (2013) suffers severely from low aluminum prices and a very chal- lenging market situation. Technologically, the present aluminum production process can be a close-to-zero greenhouse gas producer. The first step, which is actually ongoing, is to focus on lower specific energy consumption, and also to eliminate the occurrence of anode effects. Furthermore, it is possible to reduce the inherent production of CO2by reducing the net carbon anode consumption, although this reduction can only be perhaps 10% or even less with the existing carbon anode tech- nology. Here, an inert anode, if such a material can be found and developed for use in industrial aluminum production, would repre- sent a remarkable technological breakthrough, because then oxygen is formed at the anodes instead of CO2