Title of Invention

ELECTROLYTIC CELL AND METHOD FOR PRODUCTION OF ALUMINIUM AND RECOVERING ELECTRICITY

Abstract

The present invention relates to an electrolytic cell for the production of aluminum comprising an anode and an electrolytic tank where the electrolytic tank comprises an outer shell made from steel and carbon blocks in the bottom of the tank forming the cathode of the electrolytic cells. At least a part of the sidewall of the electrolytic tank consists of one or more evaporation cooled panels, and wherein high temperature, heat resistant and heat insulating material is arranged between the evaporation cooled panels and the steel shell. The invention also includes a method for maintaining a crust on the sidewall of the tank and for recovering heat from the cooling medium inside the panel for transformation into electrical energy.

Full Text

Title of Invention Electrolytic cell for the production of aluminium and a method for maintaining a crust on a sidewall and for recovering electricity. Field of Invention The present invention relates to an electrotytic cell for time production of aluminium, a motion for maintaining a cost on the sidewalk of an electrolytic cell for producing aluminum and a method for recovering electricity from an electrolytic cell for producing aluminum. Background Art Aluminium is produced in electrolytic cells comprising an electrolytic tank having a cathode and an anode which is either a anode or a plurality of prefaced carbon anodes. Aluminum oaken is supplied to a cryolite-based bath in which the aluminum is dissolved. During the eledrolytic process aluminum is produced at the cathode and fonn a molten aluminum layer on the bottom of the electrolytic tank with the crinoline bath floating on the top of the aluminum layer. CO-gas Is produced at the anode causing consumption of the anode. The operating temperature of the cryolite batik Is normally in the range of about 920 to about 950 The electrolytic tank consists of an outer steel shell having cart blocks in the bottom. The blocks are connected to electrical busbars whereby time cart blocks function as a cathode. The sidewalls of the electrolytic tank are generally lined with refractory material against tie steel shell, and a layer of caisson blocks or paste Is formed on the inset of tie refractory material. There BTB several types of lining materials and ways of nagging the sidewalk lining. During the operation of the electrolytic cell, a crust or ledge of frozen bath funs on the sidewalls of time electrolytic tank. This layer may, during operation of time electrolytic cell, vary in thickness. The formation of this crust and its thickness are critical to time operation of time cell. If Vane crust becomes too thick. it will disturb the operation of the cell as the temperature of the bath near the walls becomes cooler than the temperature in the bulk of the bath, Cells, and more preferably to the heat exchangers 14 for all electrolytic cells in a plotline. This is Indicated in figure 2 where there is shown a second heat exchanger 14Afbr a second electrolytic cell. The electricity produced in generator 20 results in a substantial reduction of the effective energy consumed in the electrolytic cell per ton-produced aluminum. The second closed loop 18 has a pump 22 for circulating the florid cooling medium and a conventional bleed arrangement 23. As noted above, it is prefenred that the majority of parts of the first closed loop 10 and the heat exchanger 14 are arranged in the heat resistant and heat insulating material 6. This prefenred embodiment Is Illustrated in Figure 3 wherein each electrolytic tank has an inlet and an outlet for connecting the piping of the second closed loop 18. The outflow pipe 10A and inflow pipe ' 10B of the first dosed loop 10, as well as the portion of pipe IOC in the upper part 9 of evaporation cooled panel 7, are as shown. These connectors allow the third cooling medium to circulate through the heat exchanger 14. A crust 24 of frozen bath is then formed on the sidewise of the cell. CLAIMS 1. An electrolytic cell for the production of aluminum comprising an anode and an electrolytic tank where the electrolytic tank comprises an outer shell made from steel where carbon blocks in the bottom of the tank forms the cathode of the electrolytic cell, and where high temperature, heat resistant and heat insulating material Is an-aged on the inside of the Inner sidewalls part of the steel shell, characterized in that at least a part of the sidewall of the electrolytic tank consists of one or more evaporation cooled panels. 2. Electrolytic cell according to claim 1, characterized in that , all the sidewalls of the electrolytic cell are equipped with evaporation cooled 3. Electrolytic cell according to claim 1or2, characterized In that the evaporation cooled panels are intended to contain a cooling medium having a boiling point at atmospheric pressure between 850 and 95°C 4. Electrolytic ceil according to claim 3, characterized in that the evaporation cooled panels are intended to contain molten sodium, molten sodium-lithium alloy or molten zinc as a cooling medium. 5. Electrolytic cell according to claims 1or 2, characterized in that each evaporation cooled panel has means in its upper part for circulation of a second cooling medium for convective cooling to condense the cooling medium in the evaporation cooled panel. 6. Electrolytic cell according to claim 5, characterized in that the means for circulation of the second cooling medium is a first closed loop said first closed loop running through the upper part of each evaporation cooled panel In the electrolytic cell. 7. Electrolytic cell according to claim 6, characterized in that the parts of the first closed loop for the second cooling medium that are not inside the upper part of the evaporation cooled panels are managed In the heat resistant and heat insulating material arranged between the evaporation cooled panels and the steel shell. 8. Electrolytic cell according to claim 7. characterized in that the first closed loop for circulating the second cooling medium is connected to a heat exchanger for transcending heat from the second cooling medium to a third cooling medium contained in a second dosed loop. 9. Electrolytic cell according to claim 8, characterized in that the heat exchanger is annex in the heat resistant and heat insulating material between the evaporation panels and the steel shell. 10. Electrolytic cell according to claim 5. characterized in that means are arranged for adjusting the temperature of the second cooling medium before it enters into the upper part of each evaporation cooled panel. 11. Electrolytic cell according to daim 10, characterized In that the means for adjusting the temperature of the second cooling medium is electric heating elements. 12. Electrolytic cell according to claim 10, characterized in that in that the means for adjusting tiie temperature of the second cooling medium is adjustable valves. 13. Electrolytic cell according to claim 10, characterized in tint the mean for adjusting the temperature of the second cooling medium is bypass conduits with adjustable valves. 14. Electrolytic cell according to claim 8, characterized in that the second closed loop for circulating the third cooling medium is connected to a turbine and a generator for converting thermal energy to electric energy. 15. A potion having a plurality of electrolytic cells for production of aluminum characterized in that: a) each electrolytic cell comprises an anode and an eledrolytic tank wherein the electrolytic tank has an outer shell made from steel, cardio blocks In the bottom of the tank funning the cathode of the electrolytic cell, ^ heat resistance and heat insulating material arranged on all of the side walls of the tank, and one or more evaporation cooled panels positioned on at least a part of the heat resistant and heat insulating material that forms the side wall such that the evaporation cooled panel faces the inside of the tank, a first cooling medium contained within said evaporation cooled panel, a first closed loop circulating a second cooling medium, a part of the first closed loop running through the upper part of the evaporation cooled panel for cooling the first cooling medium and the parts of the first closed loop that are not inside the upper part of the evaporatiofi cooled panel are annex in the heat resistant and heat insulating material and a heat exchanger connected to the first closed loop and positioned in the heat resistant and heat insulating material; and b) a second closed loop connected to the heat exchanger of each electrolytic cell in the potion, a third cooling medium circulating in the second closed loop, the heat exchanger transferring heat from the second cooling medium to the third cooling medium. 16. Potion according to claim 15, characterized in that the second dosed loop for circulating the third cooling medium is connected to a turbine and a generator for converting tiara energy to electric energy. 17. A method for maintaining a crust on a sidewall of an electrolytic cell used for producing aluminum, characterized in that: (a) one or more evaporation cooled panels are arranged on time insole of the electrolytic ceil such that one side of the panels is in contact with a molten battier inside the ceil and time outlier side is in contact with a high temperature, heat resistant and heat insulating material, the insulating material being in contact with a steel shell of the cell, the panels having a first cooling medium therein; and - (b) the temperature of time first cooling medium in the evaporation cooled panels is maintained such that the temperature of the one side of time panels is slightly below the temperature of the molten bath, thereby forming a cost on the one side of panels. 18. Method according to claim 17. c h a r a c t e r i z e d i n that the temperature on the one side of the panel is about 2 to about SO^C below the temperature of the molten bath. 19. Method according to claim 17, characterized in that the temperature of the first cooling medium Is maintained by means of a second cooling medium which is circulated through a first closed loop such that heat Is exchanged between the first cooling medium and the second cooling medium; and that heat is also exchanged between the second cooling medium and a third cooling medium by means of a heat exchanger, thereby cooling the second cooling medium. 20. Method according to claim 19, characterized In atthe amount of second cooling medium or the temperature of the second cooling medium that exchanges heat with the first cooling medium is effective to control the temperature of the first cooling medium. 21: Method according to claim 19, characterized in that heat is recovered from the third cooling medium as electrical energy. 22. A method for recovering electricity from an electrolytic cell used for producing aluminum and for maintaining a cost on a sidewall of the electrolytic cell, characterized In that (a) one or more evaporation cooled panels are arranged on the Inside of the electrolytic cell such that one side of the panels Is In contact with a molten bath Inside the cell and the other side is in contact with a high temperature, heat resistant and heat Insulating material, the Insulating material being In contact with a steel shell of the cell, the panels having a first cooling medium therein; (b) the temperature of the first cooling medium In the evaporation cooled panels Is maintained in order to keep the temperature of the one side of the panels slightly below the temperature of the molten bath, thereby fondling a crust on the one side of the panels, by means of a second cooling medium which is circulated in a first closed loop such that heat is exchanged between the first cooling medium and the second cooling medium; and (c) heat is exchanged between the second cooling medium and a third cooling medium by means of a heat exchanger, thereby cooling the second cooling medium; and that heat is removed from the third cooling medium by means of a gas turbine and an electrical generator so as to generate electricity. An electrolytic cell substantially as herein described with reference to the accompanying dramas. A method for recovering electricity substantially as herein described with reference to the accompanying drawings.

Documents:

in-pct-2002-2006-che-abstract.pdf

in-pct-2002-2006-che-claims filed.pdf

in-pct-2002-2006-che-claims grand.pdf

in-pct-2002-2006-che-correspondnece-others.pdf

in-pct-2002-2006-che-correspondnece-po.pdf

in-pct-2002-2006-che-description(complete) filed.pdf

in-pct-2002-2006-che-description(complete) grand.pdf

in-pct-2002-2006-che-drawings.pdf

in-pct-2002-2006-che-form 1.pdf

in-pct-2002-2006-che-form 18.pdf

in-pct-2002-2006-che-form 26.pdf

in-pct-2002-2006-che-form 3.pdf

in-pct-2002-2006-che-form 5.pdf

in-pct-2002-2006-che-other documents.pdf

in-pct-2002-2006-che-pct.pdf

in-pct-2002-2006-che-priority documents.pdf