Electrolyte superheat during electrolytic production of Al

摘要

Different variations of electrolysis control schemes, that take into consideration the degree of electrolyte superheat of each individual electrolytic cell, have found a wide application in primary aluminium production. The objective of this work is to ascertain the correctness of the current superheat determination with the use the industrial mobile sensors for simultaneous measurement of electrolyte temperature and its melting/fusion temperature and to evaluate theoretically the necessary value of the superheat. The results correspond with published data, showing that in order to provide necessary heat for melting and dissolution of 1 percent of alumina in the electrolyte a electrolyte superheat of 13,9 deg C is needed. On the other side as a result of the dissolution of 1 percent of alumina the melting/fusion temperature of electrolyte is decreased by 5,4 deg C. This means that during dissolution of alumina the superheat (SH) is reduced by almost 9 degC. At a given superheat value of electrolyte of about 10 deg C, which is recommended by many scientists and production engineers, and also taking into consideration the imperfection of sampling and the presence of unaccounted solid particles in the electrolyte during analysis, the possibility to establish negative values of electrolyte superheat is extremely increased.