Battery metal manufacturers rely on batch sampling and laboratory analysis to control their processes, but these can be costly, labour intensive, and incur delays of 4-to-10 hours.
Finnish university spin-out Sensmet has developed µDOES (Micro-Discharge Optical Emission Spectroscopy) for installation on site to measure multiple metals, such as any battery metal and their impurities, in real-time. For black mass recycling, µDOES provides stringent online monitoring and control to reduce impurity levels and prevent the cost and delay incurred by retreatment.
An electric spark is created inside the aqueous sample, causing a microscopic volume of the fluid surrounding the spark to be flash-heated to 10,000°C. Molecules in the micro-discharge are split into atoms, which are excited to their respective higher electronic states. When they return to their ground state, the atoms release excess energy by emitting light at their characteristic wavelengths. The patented µDOES measures this atomic emission spectrum to provide a quantitative analysis of the metals in the sample.
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Data from µDOES are displayed locally showing the concentrations and trends for each metal, and alarm levels can be set for each element. Results are transferred digitally to users’ databases and/or the cloud.
Company CEO Dr Toni Laurila said µDOES brings the analytical performance of laboratory ICP-OES (inductively coupled plasma optical emission spectroscopy) to the production process where real-time metal concentration results are needed.
Aappo Roos, M.Sc. chief sales officer at Sensmet explained that µDOES, like ICP-OES, is based on Optical Emission Spectroscopy and the analytical performance is very similar to ICP, a scientific instrument designed for research.
“However, the ICP-OES technology principles have been rethought to achieve the robustness required for continuous and fully automated industrial process measurement,” he said via email. “Our customers have compared laboratory ICP-OES results with Sensmet µDOES online results, and typically the deviation is less than 10 per cent relative, demonstrating excellent analytical performance. Interestingly, we have noticed that, unlike ICP, Sensmet µDOES precision improves when the analyte concentration decreases.” Roos continued: “The innovative design leads to several simplifications over traditional ICP-OES. As the plasma is formed directly inside the sample liquid, the operation is torch free. Consequently, the Sensmet µDOES operation is free from costly carrier gas, and the instrument does not contain any such high-maintenance components as an RF coil, a spray chamber, or a nebulizer. Even an internal standard, which ICP users need to correct for matrix differences between the calibration standards and samples, is unnecessary.”
Finnish mining and battery chemical company Keliber ran a pilot-scale test programme in 2022 to evaluate µDOES in the continuous optimisation of precipitation chemical dosing during lithium production. Nearly 80 samples were drawn from the process with sodium and lithium concentrations analysed in parallel using the µDOES continuous analyser and a laboratory ICP-OES. According to Sensmet, the results showed an excellent degree of correlation between the methods.
Sami Heikkinen, a chemical plant manager at Keliber, said: “Chemical dosing based on reliable real-time data brings stability to the process, which is very important because it avoids drift and optimises…yield and quality while minimising cost.”
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