Applications of laser-induced breakdown spectroscopy in the aluminum electrolysis industry

Highlights: • LIBS was first applied to calculate molecular ratios, which is an important control parameter of aluminum reduction process. • A new method for calculating the molecular ratio was proposed. By building a PLSR model using the reciprocal of the molecular ratio and the normalized line intensity, both the determination coefficients and RSDs were improved greatly. • In situ measurements of the molten aluminum and electrolyte were performed in industrial aluminum induction cells using a developed LIBS equipment. The industrial aluminum reduction cell is an electrochemistry reactor that operates under high temperatures and corrosive conditions. Monitoring the molten aluminum and electrolyte components is very important for controlling the chemical reaction process. Due to the lack of fast methods to monitor the components, controlling aluminum reduction cells is difficult. In this work, laser-induced breakdown spectroscopy (LIBS) was applied to aluminum electrolysis. A new method for calculating the molecular ratio, which is an important control parameter that represents the acidity of the electrolyte, was proposed. Experiments were first performed on solid electrolyte samples to test the performance of the proposed method. Using this method, the average relative standard deviation (RSD) of the molecular ratio measurement was 0.39%, and the average root mean square error (RMSE) was 0.0236. These results prove that LIBS can accurately measure the molecular ratio. Then, in situ measurements of the molten aluminum and electrolyte were performed in industrial aluminum induction cells using the developed LIBS equipment. The spectra of the molten electrolyte were successfully obtained and were consistent with the spectra of the solid electrolyte.