One side effect of the increasing demand for lithium is a rush-to-market tendency from mining companies. “Over the next several years, a number of companies are coming online to extract lithium carbonate from spodumene ore, which is typically about 8% Li 2O by weight. In order to meet demand, it’s been a rush to start up,” says Josh Marion, a project engineer from Jenike & Johanson Inc. This rush, combined with the high value of lithium and its specific physical properties, underlines the importance of proper design throughout all stages of lithium processing — from initial mining all the way to the final refining steps. This forces processors to approach bulk solids handling in a new way when trying to achieve the desired benchmarks for product purity, particle size, and density. “A lot of the processing demands can be likened more to pharmaceutical manufacturing than traditional mineral processing. There’s a premium on the quality of material that goes to battery manufacturers, and without reliable solids handling, you cannot achieve the product uniformity that is required,” explains Marion.
Some of the main operational issues experienced by lithium processors include caking, buildup and flow stoppage. To extract lithium from spodumene ore after mining, the raw ore goes through a series of crushing and size-classification steps to generate ore of the required particle size. The fine ore is then sent to a concentrator plant where it goes through several drying, milling, separation, dewatering and further size-classification steps to generate spodumene concentrate. The concentrate then proceeds to a processing plant, where it is calcined, and various aqueous solutions, acids and other chemicals are added to extract different impurities, such as iron, aluminum, silicon and magnesium. Finally, the wet cake is recrystallized and dried into the lithium hydroxide (LiOH) or lithium carbonate (Li 2CO3) product. “Particularly during those steps where the lithium is in a wet cake, if you don’t have an adequate dryer or the handling equipment is not properly designed to handle slightly wet material, you often experience buildup of lithium and lithium cake throughout the plant. Also, due to the hygroscopic nature of lithium salts, even when the material is dry, it may tend to absorb moisture and cake,” says Marion. He emphasizes that attention to detail during the equipment design phase is crucial in avoiding these bottlenecks and ensuring consistent product quality. “When selecting and designing equipment, it is critical to ensure that the characteristics of the material at each stage of the process be considered,” he adds.
As the performance demands of LIBs have evolved, equipment manufacturers are developing new technologies to meet those needs. “The key parameters for lithium producers right now are purity and particle size,” says Ananta Islam, sales director for the North American chemicals division of GEA Group AG (Düsseldorf, Germany; www.gea.com). The presence of certain impurities directly impacts battery performance, so lithium producers must align with a strict set of purity specifications. “Users are looking for a very low concentration of sodium, potassium, sulfur and heavy metals inside a battery-grade product,” explains Christian Melches, senior sales and technology manager at GEA. Whether starting with brine materials, as is common in South America, or spodumene ore, the typical lithium source in Canada and Australia, these impurities are usually present in considerable amounts. To address purity concerns, GEA provides crystallization units (Figure 1) that can be combined to optimize purification, says Melches. “The edge comes from knowing how to guide the flows through the process itself to several crystallizers to get the purest product,” he states. Another important consideration in combined crystallization units is energy efficiency. One energy-saving measure is the use of mechanical recompression of vapors from the crystallizer to create steam for driving the process.
LiOH — currently the preferred lithium form for most LIB makers — demands an extremely precise particle-size distribution, which requires specialized spray-drying equipment. A typical particle-size range for conventional spray drying might be 40–50 μm, but for LiOH processing, the range is around 5–7 μm, explains Islam. To ensure that materials meet requirements, GEA developed and patented a specific nozzle for lithium handling (Figure 2). “The Combi-Nozzle utilizes a high-pressure nozzle and compressed air for secondary atomization to further reduce the particle size,” says Islam. Lithium producers say that a smaller particle size is needed for properly compacting powders, which directly affects LIB performance. According to Islam, this particular nozzle was developed based on technologies used in the pharmaceutical sector for spray drying particles for inhalable drugs, which require very fine particle sizes.
While brine and spodumene produce the majority of today’s lithium, in the next few years, other sources may arise due to high demand. “The mining companies are starting to invest in alternative lithium sources, so in the future, processing equipment may need to adjust to handle more impure raw materials,” says Melches.