The role of Metso Analyzers in enhancing battery metals production

The increasing electrification of society is fueling a significant surge for rechargeable batteries and the raw materials used in their production. Lithium is one of the key elements enabling electrification, as a typical electric vehicle battery contains several kilograms of lithium. Lithium-ion batteries generally have high energy density with good rechargeability and efficiency compared to other battery types. Main sources of lithium include brine deposits and hard rock minerals, with spodumene being the major mineral source.

The lithium from brine and minerals sources is further refined into various lithium chemical products by the means of hydrometallurgical methods. Typical end products are LiOH, Li₂CO₃ and LiPF₆. Depending on the battery technology, LiOH and Li₂CO₃ are usually used for the cathode and LiPF6 for the electrolyte of the battery.

Metso has a long history of developing analyzer and automation solutions in minerals processing and hydrometallurgical processes. Metso’s first commercial Courier® X-Ray Fluorescence analyzer was installed in the 1960's for copper flotation process control. With lithium being one of the first elements in the periodic table, new methods have been developed to analyze it in real-time in both separation and hydrometallurgical processes.

Spodumene concentration

Spodumene concentration differs from the traditional base and precious metals concentration processes, as it leaves the final grind size relatively large. Typical P80 values from the grinding circuit range between 100 to 300 microns. The grinding step is usually followed by the desliming of fine particles such as clay minerals before further concentration. The fine material may hinder the follow up processing by diluting concentrate grade and preventing the attachment of air bubbles to spodumene particles in flotation.

Monitoring the particle size in the grinding process is an important parameter as it influences the downstream processing. On-stream particle size analysis also helps prevent overgrinding and reduces the energy consumption used for grinding.

Since the 1990’s, Metso particle size analyzers have been utilized for grinding particle size control. Two analyzer models can be utilized for the process control: PSI 300i which is based on direct mechanical measurement of the largest particles in a sample flow, or PSI 500i which is based on laser diffraction. If the only interest is in the coarse end of the particle size distribution, PSI 300i is usually the best option. If the whole particle size distribution of the sample is needed, then the PSI 500i would be the preferable option.

Spodumene grade is usually upgraded by means of froth flotation. The concentrate properties are usually the key driver for the flotation process, leaving recovery as secondary. Concentrate quality should fulfill certain specifications depending on the refining method for lithium chemicals. For example, if the refining method is acid leaching, the Fe₂O₃ content in the final concentrate should not exceed 1%.

Laboratory analysis of spodumene can be time consuming since the results may take up to a day to complete, while up to date information is essential for process control. On-stream chemical analysis of the flotation circuit can lead to improved process stability, increased recovery and enhanced product quality. It allows for more precise and timely adjustments in the process.

Metso Courier 8X SL analyzer has been developed specifically to analyze lighter elements (starting from lithium) in flotation processes. The analysis method is Laser-Induced Breakdown Spectroscopy (LIBS). LIBS method utilizes a high energy laser which is focused on a vertically falling slurry sample. The laser produces plasma from the sample at the focal point. Elements presenting in the plasma emit light at unique wavelengths, and by measuring the light emitted from the sample by a spectrometer, the elemental concentrations can be calculated.

On-stream analysis of particle size and chemical content in spodumene concentration gives real time data from the current state of the process, which can be utilized for process control and optimization. The data can also be used in a digital twin model e.g. Metso Geminex.

Lithium brines processing

Salar brines are the second major source of lithium after hard rock sources. Major lithium brine deposits are located in the lithium triangle in South America, which includes parts of Argentina, Bolivia and Chile. These sources are attractive due to their relatively high Li contents and relatively low environmental impact compared to hard rock mining.

Usually, the processing of brines starts by extracting the brine from underground reservoirs, where they are pumped to large evaporation ponds. Over time, as the water evaporates, various impurities including Na, K, Mg and Ca precipitate out from the brines. Reagents can also be used to precipitate out impurity elements like Mg. The concentrated brine is further purified by various methods including solvent extraction and ion exchange to separate Li from remaining ions. The purified brine is then processed to produce Li₂CO₃ and/or LiOH compounds.

Elemental analysis by Metso Courier HX analyzer system can be utilized in different stages of the brines processing. For example, it can be used starting from the extraction of the brine to analyze the lithium and impurity contents. This allows operations to better plan the extraction and purification steps. The analyzer system can also be utilized in the evaporation ponds to track the concentrations to find the optimal time for transferring the brine to the next processing stage. In the impurity removal stage, the analysis of e.g. Mg in the brine can be used for optimal dozing of lime and to monitor that the Mg reduction in the brine is sufficient.

In solvent extraction, the optimal aqueous to organic ratio can be adjusted by measuring the lithium concentration in the feed and raffinate. Organic solvents can be costly and optimizing the A/O ratio can allow operators to use the necessary organic solvent at a minimum level to achieve desired extraction efficiency. Optimized A/O ratio can also increase the throughput, further improving the economics of the operation.

Ion exchange solution purification can also benefit by applying elemental analyzers. By monitoring the ion concentrations before and after the resin, the flow rates and resin regeneration cycles can be optimized, thus maintaining optimal performance of the ion exchange. The quality of the final product meets specifications by continuous measurement of the purified lithium stream, enabling immediate corrective actions if trace levels of impurities are detected.

Lithium chemical production

Raw material from hard rock or brine sources is processed to various lithium chemicals in refineries. Typical products are Li2CO3 and LiOH, depending on the requirements of the final battery product. Spodumene, being insoluble in its native α-form, requires calcination to convert its crystal structure to soluble β-form. Two alternative leaching methods are typically used to leach the lithium out of the β-spodumene: Acid leaching and Metso’s latest innovation, the alkali leaching method.

In the alkali leaching method, the spodumene is leached at high pressure and high temperature inside an autoclave using soda ash (Na2CO3) as the leaching reagent. The soda ash reacts with the spodumene to produce lithium carbonate and analcime sand. The Li2CO3 can be further converted to hydroxide by cold conversion leach with hydrated lime (Ca(OH)2). The resulting LiOH solution is usually purified from multivalent cations e.g. Ca by ion exchange. The resulting solution is finally crystallized, yielding battery grade LiOH product.

Monitoring the lithium yield and impurities in various process steps in the refining process allows operations to maintain the product quality and optimize chemical dosages. Metso Courier HX analyzer system has been designed to measure element contents in liquid samples in refining processes. The analyzer system can collect samples from various points in the process to a centralized analyzer location. The system can consist of one or several different analyzers, depending on the analysis needs.

Lithium, alkali and earth alkali metals can be measured using a micro plasma optical emission spectroscopy method (µDOES). Other complimentary analysis methods e.g. automatic titration or ion chromatography can be added to the same sampling system.

The Courier HX system is also suitable for other lithium refining processes.