Method and a System for Energy Recovery and/or Cooling

Abstract

The present invention relates to a method and a system of energy recovery and/or cooling in at least one electrolysis cells ( 1 ) for the production of a metal, in particular aluminium, where the cell(s) is provided with one or more heat exchangers and where a heat exchange medium circulates through said heat exchanger(s) and is further directed to at least one heat conversion unit, such as an open circuit expander turbine ( 3 ). The expander turbine is connected with a compressor ( 2 ) that supplies the heat exchange medium to the cells ( 1, 51 ). In one embodiment, a second expander turbine ( 40 ) is connected to a generator ( 41 ) that can be applied for production of electricity. The system is substantially self propelled and the heat exchange medium is preferably air applied in an open circuit.

1 - 14 . (canceled)  
   
   
       15 . A method of energy recovery and/or cooling in at least one electrolysis cell ( 1 ,  51 ) for the production of aluminium, where the cell(s) is provided with one or more heat exchangers and where a heat exchange medium circulates through said heat exchanger(s) and is further directed to at least one heat conversion unit, such as an expander turbine ( 3 ), wherein the expander turbine ( 3 ) is mechanically connected with a compressor ( 2 ) that supplies an oxygen containing medium, in particular ambient air, at elevated pressure to the cell ( 1 ,  51 ) for heat exchange and cooling of the cell in a substantially self propelling manner, and where the heat is extracted by heat exchanger(s) consisting of a material that is substantially inert with respect to oxygen at its operating pressure and temperatures.  
   
   
       16 . A method in accordance with  claim 15 , wherein the heat exchange medium is air taken from the surroundings.  
   
   
       17 . A method in accordance with  claim 15 , wherein the heat exchange medium after passing through the heat conversion unit is let out to the surroundings.  
   
   
       18 . A method in accordance with  claim 15 , wherein the heat exchange medium is led through a combustor ( 30 ) for increasing the temperature thereof before entering at least one heat conversion unit ( 3 ,  40 ).  
   
   
       19 . A method in accordance with  claim 15 , wherein the surplus of cold heat exchange medium is led through valves ( 81 , 82 ) before entering heat/pressure to electricity conversion unit ( 70 ).  
   
   
       20 . A system for energy recovery and/or cooling in at least one electrolysis cell ( 1 , 51 ) for the production of aluminium, where the cell has one or more heat exchangers and where a heat exchange medium circulates through said heat exchanger(-s) and is further directed to at least one first heat conversion unit, such as an expander turbine ( 3 ), wherein the expander turbine ( 3 ) is mechanically connected via one axle with a compressor ( 2 ) that supplies an oxygen containing medium, in particular ambient air, at elevated pressure for heat exchange to the cells ( 1 ,  51 ), and where the heat exchanger(-s) is made out of a material that is substantially inert with respect to oxygen at its operating pressure and temperatures.  
   
   
       21 . A system in accordance with  claim 20 , wherein the heat exchange medium is air that circulates in one circuit ( 5 ,  6 ,  8 ,  9 ) that is open with respect to the surroundings.  
   
   
       22 . A system in accordance with  claim 20 , wherein a combustor ( 30 ) is arranged between the cell(-s) ( 1 ,  51 ) and the heat conversion unit ( 3 ).  
   
   
       23 . A system in accordance with  claim 20 , wherein one second expansion turbine ( 40 ) is arranged downstream the first heat conversion unit ( 3 ).  
   
   
       24 . A system in accordance with  claim 23 , wherein the second turbine ( 40 ) is connected with one generator ( 41 ), for electricity production.  
   
   
       25 . A system in accordance with  claim 24 , wherein the electricity produced is reverted back to the cell(s) or the public grid.  
   
   
       26 . A system in accordance with  claim 20 , wherein cold medium pressurized by the compressor(-s) ( 2 ,  72  or others) is expanded in an expansion engine ( 70 ) that preferably drives one generator ( 71 ).  
   
   
       27 . A system in accordance with  claim 20 , wherein the material of the heat exchanger(-s) comprises a ceramic material  
   
   
       28 . A system in accordance with  claim 20 , wherein the material of the heat exchanger(-s) comprises silicon carbide.  
   
   
       29 . A system in accordance with  claim 20 , wherein a motor-generator is mechanically connected with the expander turbine ( 3 ) and the compressor ( 2 ).  
   
   
       30 . A system in accordance with  claim 20 , wherein the pressure of the oxygen containing medium that enters the heat exchangers is between 3 to 5 bars.  
   
   
       31 . A system in accordance with  claim 20 , wherein the temperature of the oxygen containing medium that enters the heat exchangers is between 200 and 300° C.