Estimating the Alumina Concentration During Aluminum Electrolysis by Identifying the Sensitive Frequency Band Using Marginal Kurtosis

The accurate and timely online estimation of the alumina concentration in an industrial aluminum electrolysis cell can improve its feed control performance. By using the proposed marginal kurtosis (MK), marginal kurtosis dominant frequency (MK-DF), integral feed frequency and sensitive frequency band (SFB), this study reveals that a normalized cell voltage with different current intensities and feed schemes has different alumina concentration SFBs and determines the general formula for calculating the SFB. On this basis, a general algorithm for acquiring the pseudo alumina concentration (PAC) using translation-invariant filtering is proposed in which the upper limit of the SFB provides the cutoff frequency of the low-pass filter. The PAC was used to estimate the absolute and relative concentrations of alumina. The absolute concentrations are validated using measured concentrations. Additionally, improved feed control performance of the industrial cells is presented using the relative concentration PAC-slope.