PDF Publication Title:
Text from PDF Page: 014
Molten Salt Electrolysis for Sustainable Metals Extraction and Materials Processing 13 pot life is to be expected when new carbon cathodes are slowly heated to 700 °C. Molten pools of cathodic aluminium have rippling surfaces which is the result of magneto- hydrodynamic effects which necessitates in large anode-to-cathode distances (high iR losses) to prevent contact of molten aluminium to the anodes. Aluminium cells with drained cathodes which are wet by molten aluminium allow smaller anode-to-cathode distance and lower cell voltages. Coatings of TiB2 and TiC on carbon have been used in these cells. The development of oxygen-evolving inert anode materials for the HHC has met only with limited success so far. However, there have been other advances and innovations. For instance, automation and process control have been furthered by new sensor technologies allowing the bath chemistry to be characterised, to follow alumina feeding, and even to manage the electromagnetic fields in the cell. In mathematical modelling, thanks to improvements in computational capacity, it is now possible to model many physical properties of the electrolyte melts as well as transport phenomena in the HHC, including current distribution, thermal profile, and position of sidewall ledge. Rapp evaluated the possibility of using modified solid oxide fuel cell (SOFC)-type anode for retrofit in the HHC [23-25]. With the SOFC-type anode, oxide ions dissolved in the cryolite-based electrolytes can transport through the dense oxide-ion-conducting membrane and then electrochemically oxidize the fuel inside the electrode according to anodic reactions below: H2 + O2- (ZrO2) = H2O + 2e (anode) (5) CO + O2- (ZrO2) = CO2 + 2e (anode) (6) Using methane as a fuel, the net electrolytic reaction may be expressed as: 4Al2O3 + 3CH4 = 8Al + 3CO2 + 6H2O (7) According to Reaction 7, less than half of the CO2 gas would be evolved at the SOFC-type anode and no perfluorocarbons or volatile organic compounds (VOC) gases would be formed, either in the fabrication or in the use of this type of the anode. It is expected that application of such a non-consumable anode (NCA) retrofitted into the HHC can potentially increase the energy efficiency and reduce the cost of producing primary aluminium significantly compared to the best current and emerging anode replacement technologies. Rapp and Zhang, however, found that that a ZrO2-based solid electrolyte membrane readily dissolved into any cryolite-based fluoride electrolytes containing dissolved Al2O3, from which aluminium could no longer be electrowon due to the resulting low Al2O3 solubility in the electrolytes [25]. (3) Alternative Molten Salt Electrowinning of Aluminium Aluminium has been also produced industrially by electrolysis of AlCl3 in molten NaCl- LiCl electrolytes at 700 °C [18]. The electrowinning cells developed by The Aluminium Company of America (Alcoa) utilised a bipolar multi-carbon electrodes unit so that chlorine is evolved on the bottom surface and molten Al is deposited on the top surface of each electrode, shown in figure 5. The overall electrolytic cell reaction is simply expressed as AlCl3(l) = Al + 3/2Cl2(g) (8)PDF Image | Molten salt electrolysis for sustainable metals extraction
PDF Search Title:
Molten salt electrolysis for sustainable metals extractionOriginal File Name Searched:
Electrolysis-Chapter6.pdfDIY PDF Search: Google It | Yahoo | Bing
Salgenx Redox Flow Battery Technology: Power up your energy storage game with Salgenx Salt Water Battery. With its advanced technology, the flow battery provides reliable, scalable, and sustainable energy storage for utility-scale projects. Upgrade to a Salgenx flow battery today and take control of your energy future.
CONTACT TEL: 608-238-6001 Email: greg@salgenx.com (Standard Web Page)