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It is possible to decrease specific consumption of electricity and increase CE (current efficiency) in aluminium electrolysis process with reduction of ACD (anode-cathode distance), and decrease horizontal currents in aluminum at the same time.

Results of an experimental study of the physicomechanical properties of refractory materials for the lining of aluminum electrolyzers are reported. INSTRUMENTATION AND TEST METHODOLOGIESIK-4 and TÉP test complexes and a tensile testing machine equipped with an electric furnace for heating specimens were used in the study of physicomechanical properties of hearth blocks and mixes, refractory and heat-insulating materials for the lining of electrolyzers.IK-4 test complex (Fig. 1), equipped with automatic control and computer-assisted data processing facilities, is used for determining the so-called sodium expansion, thermal linear expansion coefficient (TLEC), for measuring thermal expansion, compression, shrinkage, elastic modulus, and compressive strength of refractory lining materials.Sodium expansion. Test unit 1 in the IK-4 test complex is used to determine the linear sodium expansion of the hearth and wall blocks during electrolysis (Rapoport test). The components of the test unit are: an electric furnace for heating the test specimen and electrolyte; a mechanism for lifting and letting down the furnace; a loading device to apply a constant pressure (from 1 to 10 MPa) to the specimen; conductors to carry current to the specimen and crucible. To prevent oxidation of the material of specimen and crucible, the electrolysis is carried out under argon.The sodium expansion test for the carbon-graphite lining includes the following operations:-preparing cylindrical specimens of diameter 30 mm and length 100 mm;-preparing an electrolyte with a cryolite ratio of 3 ± 0.05 and composition (wt.%): Na 3 AlF 6 , 86.0 (658 g); CaF 2 , 5.0 (38 g); Al 2 O 3 , 9.0 (69 g); -drying the specimen, crucible, and alundum disk at 100°C for 3 h;-placing a graphite crucible with the specimen and electrolyte in an electric furnace;-applying a load of 1 MPa to the specimen; -heating to 980 ± 10°C and holding until a steadystate regime is attained; -performing electrolysis for 2 h at a current density of 0.7 A/cm 2 , with the measured data stored in a computer and graphically displayed on the screen; -plotting the sodium expansion diagrams. Temperature expansion. Test unit 3 of the IK-4 test complex serves to measure the expansion of the "green" hearth mix (on heating from room temperature to 950°C) and the TLEC of lining materials. It is composed of an electric furnace, a heat insulator, a quartz retort, a quartz measuring rod, a displacement sensor, and a fume hood.Methodology for measuring the temperature expansion of the lining involved the following operation:-preparing cylindrical specimens of diameter and length 50 mm;-placing a retort with the specimen and measuring rod in the furnace;-heating the hearth mix specimen to 950°C at a rate of 200°C/h and holding time of 2 h; to measure TLEC, the heating rate is 200°C/h up to 520°C (when needed, to 950°C) and holding time 2 h; -processing data on a computer and displaying results. Elastic modulus and compressive strength. Test specimens of diameter 40 mm and length 50 mm are prepared. ...

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