Electrolyte used for aluminum electrolysis and electrolysis process using the electrolyte

Abstract

An electrolyte for aluminum electrolysis employs a pure fluoride salt system and includes the following components by mass percent: 20-29.9% of NaF, 60.1-66% of AlF 3 , 3-10% of LiF, 4-13.9% of KF and 3-6% of Al 2 O 3 , in which the molar ratio of NaF to AlF 3 is 0.6-0.995; or the electrolyte includes the following components by mass percent: 30-38% of NaF, 49-60% of AlF 3 , 1-5% of LiF, 1-6% of KF and 3-6% of Al 2 O 3 , in which the molar ratio of NaF to AlF 3 is 1.0-1.52.

1 . An electrolyte for aluminum electrolysis, being composed of the following components by mass percent: 20-29.9% of NaF, 60.1-66% of AlF 3 , 3-10% of LiF, 4-13.9% of KF and 3-6% of Al 2 O 3 , wherein the molar ratio of NaF to AlF 3  is 0.6-0.995;
 or being composed of the following components by mass percent: 30-38% of NaF, 49-60% of AlF 3 , 1-5% of LiF, 1-6% of KF and 3-6% of Al 2 O 3 , wherein the molar ratio of NaF to AlF 3  is 1.0-1.52.   
     
     
         2 . The electrolyte according to  claim 1 , wherein the molar ratio of NaF to AlF 3  is 0.6-0.7 or 1.12-1.52. 
     
     
         3 . The electrolyte according to  claim 1 , wherein the liquidus temperature of the electrolyte ranges from 620 to 670° C. 
     
     
         4 . The electrolyte according to  claim 3 , wherein the liquidus temperature of the electrolyte ranges from 640 to 670° C. 
     
     
         5 . The electrolyte according to  claim 1 , wherein the electrolysis temperature of the electrolyte ranges from 720 to 760° C. 
     
     
         6 . An electrolysis process using the electrolyte for aluminum electrolysis according to  claim 1 , comprising the steps of:
 ( 1 ) mixing specified amounts of NaF, AlF 3 , LiF, KF and Al 2 O 3 , and heating the resultant mixture to form a melt; or mixing specified amounts of NaF, AlF 3 , LiF and KF, heating the resultant mixture until the mixture is molten, and then adding Al 2 O 3  to obtain a melt; and   (2) raising the temperature of the melt prepared in step (1) to 720-760° C. and then carrying out electrolysis.   
     
     
         7 . The electrolysis process using the electrolyte for aluminum electrolysis according to  claim 6 , wherein the melt prepared in step (1) is electrolyzed at 730-750° C. 
     
     
         8 . The electrolysis process using the electrolyte for aluminum electrolysis according to  claim 6 , wherein Al 2 O 3  is quantitatively supplied in the electrolysis process. 
     
     
         9 . The electrolyte according to  claim 2 , wherein the liquidus temperature of the electrolyte ranges from 620 to 670° C. 
     
     
         10 . The electrolyte according to  claim 2 , wherein the electrolysis temperature of the electrolyte ranges from 720 to 760° C. 
     
     
         11 . The electrolyte according to  claim 3 , wherein the electrolysis temperature of the electrolyte ranges from 720 to 760° C. 
     
     
         12 . The electrolyte according to  claim 4 , wherein the electrolysis temperature of the electrolyte ranges from 720 to 760° C. 
     
     
         13 . An electrolysis process using the electrolyte for aluminum electrolysis according to  claim 2 , comprising the steps of:
 (1) mixing specified amounts of NaF, AlF 3 , LiF, KF and Al 2 O 3 , and heating the resultant mixture to form a melt; or mixing specified amounts of NaF, AlF 3 , LiF and KF, heating the resultant mixture until the mixture is molten, and then adding Al 2 O 3  to obtain a melt; and   (2) raising the temperature of the melt prepared in step (1) to 720-760° C. and then carrying out electrolysis.   
     
     
         14 . An electrolysis process using the electrolyte for aluminum electrolysis according to  claim 3 , comprising the steps of:
 (1) mixing specified amounts of NaF, AlF 3 , LiF, KF and Al 2 O 3 , and heating the resultant mixture to form a melt; or mixing specified amounts of NaF, AlF 3 , LiF and KF, heating the resultant mixture until the mixture is molten, and then adding Al 2 O 3  to obtain a melt; and   (2) raising the temperature of the melt prepared in step (1) to 720-760° C. and then carrying out electrolysis.   
     
     
         15 . An electrolysis process using the electrolyte for aluminum electrolysis according to  claim 4 , comprising the steps of:
 (1) mixing specified amounts of NaF, AlF 3 , LiF, KF and Al 2 O 3 , and heating the resultant mixture to form a melt; or mixing specified amounts of NaF, AlF 3 , LiF and KF, heating the resultant mixture until the mixture is molten, and then adding Al 2 O 3  to obtain a melt; and   (2) raising the temperature of the melt prepared in step (1) to 720-760° C. and then carrying out electrolysis.   
     
     
         16 . An electrolysis process using the electrolyte for aluminum electrolysis according to  claim 5 , comprising the steps of:
 (1) mixing specified amounts of NaF, AlF 3 , LiF, KF and Al 2 O 3 , and heating the resultant mixture to form a melt; or mixing specified amounts of NaF, AlF 3 , LiF and KF, heating the resultant mixture until the mixture is molten, and then adding Al 2 O 3  to obtain a melt; and   (2) raising the temperature of the melt prepared in step (1) to 720-760° C. and then carrying out electrolysis.   
     
     
         17 . The electrolysis process using the electrolyte for aluminum electrolysis according to  claim 7 , wherein Al 2 O 3  is quantitatively supplied in the electrolysis process. 
     
     
         18 . The electrolyte according to  claim 9 , wherein the liquidus temperature of the electrolyte ranges from 640 to 670° C. 
     
     
         19 . The electrolyte according to  claim 9 , wherein the electrolysis temperature of the electrolyte ranges from 720 to 760° C. 
     
     
         20 . The electrolyte according to  claim 18 , wherein the electrolysis temperature of the electrolyte ranges from 720 to 760° C.