Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
  • C25C3/00—Electrolytic production, recovery or refining of metals by electrolysis of melts
  • C25C3/04—Electrolytic production, recovery or refining of metals by electrolysis of melts of magnesium

Definitions

• This invention relates to production of magnesium by electrolysis.
• the molten salt electrolyte typically comprises one or more alkali metal or alkaline earth metal chlorides in which the magnesium chloride is dissolved.
• This invention seeks to provide a new electrolytic process for the production of magnesium from magnesium chloride, in which hydrogen chloride is produced as the by-product.
• This invention also seeks to provide a new electrolytic process for the production of magnesium from magnesium chloride at a lower energy requirement.
• a process for the electrolytic production of magnesium comprising: i) electrolysing magnesium chloride in a molten salt electrolyte in an electrolysis cell having a cathode and an anode, with formation of magnesium metal at said cathode, ii) feeding hydrogen gas to said anode and reacting chloride ions at said anode with the hydrogen gas to form hydrogen chloride, iii) recovering the magnesium metal from said cell, and iv) recovering the hydrogen chloride from said cell.
• an electrolytic cell for production of magnesium metal from magnesium chloride comprising: a) a cell for housing magnesium chloride in a molten salt electrolyte, said cell having a cathode and an anode, b) means for feeding hydrogen gas to said anode, c) means for recovery from said cell of magnesium metal developed at said cathode, and d) means for recovery from said cell of hydrogen chloride developed at said anode.
• the anode is a high surface area anode, for example, a porous anode in which case the hydrogen gas permeates the pores of the anode, such as by diffusion, or molten electrolyte containing the magnesium chloride permeates the pores of the anode, to provide the contact between the hydrogen gas and the chloride ions.
• the hydrogen gas may be fed along a non-porous tube or conduit to the porous anode. If this tube or conduit is in contact with the bath it should not be of a material which will function as an anode for the electrolysis.
• any anode having a structure permitting delivery of hydrogen to the cell bath at the anode may be employed, for example, an anode having drilled channels for communication with a source of hydrogen gas.
• the requirement is that the anode structure delivers hydrogen gas to the cell bath at the anode, so that chloride ions at the anode react with the hydrogen gas to form hydrogen chloride, rather than discharging as chlorine gas.
• suitable anodes may be of graphite, silicon carbide or silicon nitride.
• the method has the advantage that this hydrogen chloride gas is produced with minimal, if any, production of chlorine gas.
• Table I shows how the decomposition voltage of the electrolysis decreases, with the process of the invention, as compared with the conventional process and how the minimum voltage required to maintain energy balance changes.
• E adiab is the minimum voltage required to carry out the process, assuming 100% current efficiency and that the M g Cl 2 and H 2 are fed at room temperature.
• Table I shows the calculated decomposition voltage (1000 K) and adiabatic voltage required to cover the energy requirements of the process without heat losses.
• Table I further shows that the decomposition voltage decreases by 1.04V and that the overall energy requirement decreases by 0.86V. This means that with HCl formation, another 0.18V per mole can be dissipated in the cell without causing overheating. The decrease of 0.86V translates to a reduction of about 25% less electricity consumption for magnesium production. With magnesium cells currently requiring an average of 12.5 MW-hr per tonne, and an average energy cost of 4 cents per KW-hrs, this translates to a savings of about $125 per tonne of magnesium produced in electrical consumption.
• the hydrogen gas may be considered to form a hydrogen anode in the cell, for discharge of the chloride ions.
• an anode structure is provided which, can be of any suitable material, for example, graphite, silicon carbide or silicon nitride.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Electrolytic Production Of Metals (AREA)
• Manufacture And Refinement Of Metals (AREA)

Applications Claiming Priority (3)

Related Parent Applications (1)

Publications (1)

Family

ID=4163374

Family Applications (1)

Country Status (4)

Cited By (13)

Family Cites Families (1)

• 1999
  • 1999-03-11 CA CA002265183A patent/CA2265183C/fr not_active Expired - Fee Related
• 2000
  • 2000-03-09 AU AU31390/00A patent/AU3139000A/en not_active Abandoned
  • 2000-03-09 WO PCT/CA2000/000248 patent/WO2000053826A1/fr active Application Filing
• 2001
  • 2001-08-22 US US09/933,802 patent/US20020014416A1/en not_active Abandoned

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