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About 80% of all magnesium is produced by an electrolytic process, The electrolytic route is an energy-intensive process, and many of the developed countries have realized the need to produce magnesium in a more cost-effective manner. Toward this goal, a less energy-intensive, more compact electrolytic cell has been developed at the Central Electrochemical Research Institute, India. A 2,200 A cell was operated for more than six weeks to study the feasibility of the technology. Higher current and energy efficiencies were realized, and specific energy consumption was reduced to around 11.5 kWh/kg of metal,
INTRODUCTION
Magnesium is the third most abundant metal in the Earth's crust, surpassed by only aluminum and iron, and is widely distributed in almost all parts of the world as oxides, carbonates, sulfates, chlorides, and their combinations. It is also found in abundant quantities in sea water.
About 80% of total magnesium production is carried out by an electrolytic process. Many producers use sea water as a main source of magnesium by precipitating Mg(OH)^sub 2^ from sea water and either converting the Mg(OH)^sub 2^ to anhydrous magnesium chloride by direct carbochlorination of MgO or by dissolving Mg(OH)^sub 2^ in concentrated hydrochloric acid to get MgC1^sub 2^ solution, which is subsequently dehydrated. The magnesium chloride is then electrolyzed at elevated temperatures by adopting a molten-salt electrolysis technique. Electrolytic processes for producing magnesium are energy-intensive, driving research to develop more cost-effective methods. The development of a modular cell design at the Central Electrochemical Research Institute (CECRI), India, reduced specific-energy consumption to around 14 kWh/kg of magnesium metal. A multipolar cell was also developed to address the needs of titanium and zirconium manufacturers for their captive use; specific energy consumption was reduced to around 12 kWh/kg of metal.
The cells produce magnesium metal from sea bittern, a highly concentrated solution of magnesium chloride obtained as a by-product in the salt industry after the crystallization of common salt.1 The impurities are removed, and the MgC1^sub 2^ solution is converted into dehydrated magnesium chloride by employing a spray drier. The spray-dried MgC1^sub 2^ is then either further dehydrated or used in electrolytic cells for producing magnesium metal by molten salt electrolysis. The major advantage of the process lies in the utilization of a concentrated solution of...