Electrolytic cell with improved feed device

Abstract

A cell for the electrowinning of a metal ( 70 ) from a compound thereof dissolved in a molten electrolyte comprises: a thermally insulated cell trough ( 10,20 ) and a thermally insulated cell cover ( 30 ) which are arranged to contain an electrolyte ( 40 ) and maintain it in a substantially crustless molten state; and a feeder ( 50 ) for feeding a particulate ( 60 ) of the metal compound to the molten electrolyte ( 40 ). The feeder ( 50 ) comprises a feeding tube ( 51 ) extending into the cell trough ( 10,20 ) and has a tubular end portion ( 52 ) which is located between the molten electrolyte ( 40 ) and the insulating cell cover ( 30 ) and which has a substantially horizontal axial direction. The feeder ( 50 ) is arranged to feed the particulate ( 60 ) into the feeding tube ( 51 ), along the feeding tube ( 51 ) and through an opening ( 53 ) in the tubular end portion ( 52 ) from where it is delivered over the molten electrolyte ( 40 ). The opening ( 53 ) is located at an end of the tubular end portion ( 52 ) and is arranged to deliver the particulate ( 60 ) from the feeding tube ( 51 ) substantially along the axial direction of the tubular end portion ( 52 ). The end opening ( 53 ) can be coaxial with the tubular end portion ( 52 ) or off-axis.

1 . A cell for the electrowinning of a metal from a compound thereof dissolved in a molten electrolyte, comprising: 
 a thermally insulated cell trough and a thermally insulated cell cover which are arranged to contain an electrolyte and maintain it in a substantially crustless molten state; and    means for feeding a particulate of the metal compound to the molten electrolyte comprising at least one feeding tube extending into the cell trough and having a tubular end portion which is located between the molten electrolyte and the insulating cell cover and which has a substantially horizontal axial direction, the feeding means being arranged to feed said particulate into the feeding tube, along the feeding tube and through an opening in the tubular end portion from where it is delivered over the molten electrolyte,    characterised in that said opening is located at an end of the tubular end portion and is arranged to deliver the particulate from the feeding tube over the molten electrolyte substantially along the axial direction of the tubular end portion.    
   
   
       2 . The cell of  claim 1 , wherein the end opening is coaxial with the tubular end portion.  
   
   
       3 . The cell of  claim 1 , wherein the end opening is off-axis.  
   
   
       4 . The cell of any preceding claim, wherein the feeding tube is substantially linear or gradually curved.  
   
   
       5 . The cell of any preceding claim, wherein the feeding means comprise a plurality of tubular end portions, each end portion having a substantially horizontal axial direction and an end opening arranged to deliver the particulate from the feeding tube over the molten electrolyte substantially along the axial direction of the tubular end portion.  
   
   
       6 . The cell of  claim 5 , wherein several tubular end portions are part of the same feeding tube.  
   
   
       7 . The cell of any preceding claim, wherein the feeding means comprise a plurality of feeding tube, each having a tubular end portion with an end opening for delivering the particulate.  
   
   
       8 . The cell of any preceding claim, wherein the feeding means are arranged to fluidise the particulate in the feeding tube and to feed the fluidised particulate through the end opening of the end portion over the molten electrolyte.  
   
   
       9 . The cell of any preceding claim, wherein the feeding means are arranged to feed and disperse the particulate over substantially the entire molten electrolyte.  
   
   
       10 . The cell of any preceding claim, wherein the feeding tube extends into the cell trough through a cell sidewall.  
   
   
       11 . The cell of any one of  claims 1  to  9 , wherein the feeding tube extends into the cell trough through the cell cover.  
   
   
       12 . The cell of any preceding claim, wherein the feeding means comprise a fan or a blower for driving the particulate along the feeding tube and through the end opening.  
   
   
       13 . The cell of any preceding claim, wherein the feeding means comprise a heater arranged to heat the particulate before it is delivered from the end opening over the molten electrolyte.  
   
   
       14 . The cell of any preceding claim, which is an aluminium electrowinning cell and wherein the molten electrolyte is a fluoride-based electrolyte.  
   
   
       15 . The cell of  claim 14 , which comprises one or more oxygen-evolving anodes, in particular metal-based or ceramic-based anodes.  
   
   
       16 . The cell of  claim 15 , wherein the or each oxygen-evolving anode comprises an active anode structure having through-openings for the flow of alumina-depleted electrolyte from below to above the anode and/or through-openings for the flow of alumina-enriched electrolyte from above to below the anode.  
   
   
       17 . The cell of  claim 16 , wherein the feeding means are arranged to deliver and disperse alumina over an expanse which includes at least part of the perpendicular projection onto the molten electrolyte surface of an active anode structure.  
   
   
       18 . The cell of any one of  claims 14  to  17 , comprising an aluminium-wettable cathode.  
   
   
       19 . The cell of  claim 18 , wherein the cathode is a drained cathode.  
   
   
       20 . A method of electrowinning a metal from a compound thereof dissolved in a substantially crustless molten electrolyte comprising: 
 feeding particulate of the metal compound into and along a feeding tube having a tubular end portion with an axial direction extending substantially horizontally over the substantially crustless molten electrolyte and delivering the particulate through an opening in the tubular end portion over the molten electrolyte where it is dissolved and then electrolysed to produce said metal,    said method being characterised by delivering the particulate over the substantially crustless molten electrolyte from the feeding tube substantially along said axial direction of the tubular end portion through said opening which is located at an end of the tubular end portion.    
   
   
       21 . The method of  claim 20 , comprising delivering a particulate comprising particles, the sizes of which are in the range of 20 to 200 micron, in particular 30 to 50 micron.  
   
   
       22 . The method of  claim 20  or  21 , wherein said particulate is alumina and said metal is aluminium.  
   
   
       23 . A cell for the electrowinning of a metal from a compound thereof dissolved in a molten electrolyte, comprising means for feeding a particulate of the metal compound to the molten electrolyte, the feeding means comprising at least one feeding tube having a tubular end portion which is located above the molten electrolyte and which has a substantially horizontal axial direction, said feeding means being arranged to feed said particulate into the feeding tube, along the feeding tube and through an opening in the tubular end portion from where it is delivered over the molten electrolyte,  
     characterised in that said opening is located at an end of the tubular end portion and is arranged to deliver the particulate from the feeding tube over the molten electrolyte substantially along the axial direction of the tubular end portion.