GB1193981A - Method and Apparatus for the Activation of an Electrolytic Cell - Google Patents

Abstract

1,193,981. Electro-winning aluminium. I.M. DILLER. April 3, 1967 [April 4, 1966], No. 15071/67. Heading C7B. A method of activating a fused salt, i.e. subjecting it to the application of energy which induce strains in the fused salt to produce a lasting increase in its conductivity, so as to increase the yield of metal per kWh for a given rate of production when the salt is employed in the electro-winning of aluminium, comprises applying to the fused salt a level of neutron bombardment or radiant energy to induce strains in the crystal structure of the fused salt which raise the fused salt above the threshold strain level. The neutron bombardment or radiant energy may be applied discontinuously in one or more pulses. As described the fused salt is cryolite alumina, electrolyzed at 1000‹ C. With neutrons, activation may be effected by applying to 0À1% of the melt surface 3Î10<SP>16</SP> n/sq. in.; with γ-rays a cobalt source may be used to provide 3Î10<SP>9</SP> R; while with visisble light a hole is made in the melt crust and a xenon flash of intensity 5 MW/sq in and duration 10 Á secs. or a ruby laser pulse of about 10<SP>6</SP> times this intensity and a duration of 10 nanosecs may be employed. Activation with x-rays may also be effected. The activation may be effected in the electro-winning cell or in a separate container of molten salt which is used to seed the melt of an electrolysis cell as in Specification 1, 072, 890. Activation using both radiant energy and electric pulses may be employed, typically employing light to bring the molten salt to a subthreshold state and producing a persistent activation by means of electrical pulses, especially to produce successive upgrading of the activated conductivity as in Specification 1, 071, 441. In such a process, 2%by weight of varium oxide, titanuim oxide or barium titanate may be added to the melt to increase its dielectric strength and so reduce the risk of unintentional breakdown with destruction of activation due to accidental application of energy above the maximum determined by the strength of the melt.