Four Lithium Extraction Technologies
At present, there are four kinds of lithium extraction technologies, namely lithium extraction from spodumene, lithium extraction from mica, lithium extraction from clay, and lithium extraction from brine. Among them, the first three have been industrialized, and the extraction of lithium from clay is expected to be industrialized by 2023-2024.
Salt Lake Lithium Extraction Technology Route
Lithium extraction from salt lakes will use completely different process routes according to different brines:
(1) Tanning method: Chile uses a more traditional method, because its brine contains high lithium content, magnesium content is less impurity, and extraction is simple, so the traditional classic tessellation method is used.
(2) Adsorption method: The adsorption method technology has gradually matured and achieved industrialization, especially when the ratio of magnesium to lithium is relatively high. The adsorption method is suitable for the ratio of magnesium to lithium in Chaerhan Salt Lake if it exceeds 100:1.
(3) Electrodialysis: mainly used in Dongtai Salt Lake;
(4) Membrane method: used in Xitai Salt Lake;
(5) Extraction method: Dahua uses more.
At present, these technical routes have been industrialized in China. In the future, through continuous technological progress, the competitiveness of the adsorption method will be stronger, because the advantage of the adsorption method is that the efficiency of the adsorbent is higher and the kinetics are faster through the improvement of the yield. , the cost will be low, and the yield of lithium extraction will be high. This is the main research direction in the future.
Comparison of four lithium extraction methods
There is no difference in the lithium salt produced by different lithium extraction methods. Lithium extraction from ore and brine is only different in some impurity indicators. For example, lithium extraction from ore, such as Ganfeng Lithium Industry, has a high index of sulfuric acid, and lithium extraction from brine has high halide ions.
However, the quality can be purified through the processing process to achieve quality consistency. For example, lithium carbonate can be purified through deep carbonization, and lithium hydroxide can also improve product quality through the increase of recrystallization process and cost increase, and will not lead to lithium loss due to method differences. difference in quality.
(1) Lithium extraction from ore: The ore method is currently relatively mature. In the past, the Xinjiang Lithium Salt Factory used limestone. The disadvantage is that the limestone ratio of 1:3 is calcined, and the overall income will be relatively low. Now the mainstream method is the sulfuric acid method. The main cost of lithium extraction from ore lies in the purchase of raw materials, and the direct processing cost is actually lower than that of brine.
(2) Lithium extraction from brine: The overall cost of brine is still low, because the brine is self-owned and the ore is purchased upstream, but the processing cost is relatively high separately, so the processing cost is basically the full cost. And by adding a process, it is not a problem to make the product high-quality technology, and many domestic companies can do it.
(3) Lithium extraction from mica: Lithium extraction from mica is the technology of Jiangxi Lithium Salt Factory. In the past, the taste of lepidolite was 4.4~4.5, which was relatively high, so the limestone method can be used to calcine through 1:3 limestone.
Now the ore grade is declining, and the grade of lepidolite is about 2.2, so the limestone method is not suitable. The sulfate method is generally used, lepidolite+sodium sulfate+calcium sulfate+a small amount of potassium sulfate for calcination, which is still relatively good at present.
4) Lithium extraction from clay: It has not yet been industrialized. In principle, there are three methods, sulfuric acid method (the impurity content is relatively high, and the impact on the environment will be greater), sulfate method (similar to mica lithium extraction method, lithium leaching rate 95%) and pressure cooking (higher yield but higher cost).
What is the difficulty of extracting lithium from salt lake and mica to expand production?
(1) Lithium extraction from salt lakes: From a global perspective, the quality of foreign salt lakes is relatively good, especially in Chilean salt lakes, where the lithium content is more than 1,000 mg/L, and the ratio of magnesium to lithium is 1:3. Domestically, the grade of brine is relatively low, and the lithium content in the original brine is 30-50 mg, which leads to high investment and expansion costs. It may cost 500-800 million to build a 10,000-ton plant.
The concentration of salt lakes in my country is low, and the grade is also low, so domestic expansion will be more limited by resources, and limited by the amount of effective brine, it is difficult to make a large-scale production.
However, China's lithium extraction technology is very advanced, and various technical means such as adsorption, membrane, electrodialysis, and extraction are the most advanced in China, and other countries should learn from China. Moreover, if a domestic enterprise builds a factory in a foreign salt lake, the total foreign construction cost is actually relatively high. For example, the construction site in Argentina is purchased domestically and even the photovoltaic power generation equipment is purchased domestically and sent to Argentina. However, resources such as natural gas are cheaper than domestic ones, and other costs It is not easy to compare. If the accessories are all purchased domestically, it will increase the freight and customs declaration fees, and the cost may also be higher.
(2) Lithium extraction from mica: The grade of domestic mica raw ore is relatively low, and there are very few mines that can reach more than 0.8%. If the standard is lowered to 0.3% and 0.4%, although there are more mines, the yield is low. Lithium oxide ore of 2.2 is used to produce lithium carbonate and lithium hydroxide, so the output of lithium extracted from mica will be limited by the grade.
If you use 0.4 grade ore, 8 tons of raw ore to make 1 ton of concentrated ore, 25 tons of concentrated ore to produce 1 ton of lithium carbonate, and 200 tons of concentrated ore to produce 1 ton of lithium carbonate, obviously the lower the grade, the more difficult the production will be.
The impact of environmental protection on lithium extraction methods
The implementation of ESG will have a great impact on the industry as a whole. my country has also proposed the goal of carbon peaking and carbon neutrality.
Therefore, some changes need to be made in the way of extracting lithium, and it is necessary to save energy and reduce the use of water resources. For example, Ganfeng has a water recycling project, which needs to recycle more than 1 million tons of water.
At the same time, there is also a development effort for energy conservation and environmental protection, such as using photovoltaic power generation instead of thermal power generation. Specifically look at the three methods of lithium extraction:
(1) Lithium extraction from salt lakes: There are certain restrictions at present, but relatively speaking, the impact is relatively light. The comprehensive utilization of elements in brines will be considered in the construction of salt fields. For example, the development of brines in Chile first extracts potassium and then lithium, such as using adsorption The chemical method, after the adsorption is completed, is discharged into the salt pan, without adding organic matter or other impurities, so it has no impact on the salt pan, and has no impact from the perspective of environmental protection;
(2) Lithium extraction from mica: It is greatly affected, because mica contains fluorine, and the fluorine process needs to be strengthened, otherwise the release of fluorine will pollute the environment, and because sulfuric acid method is currently used to extract lithium from mica, the waste residue contains sodium, potassium, Calcium, etc. are also unfavorable to the cement industry that uses these waste residues, and the amount of waste residues is gradually increasing. The cement industry has limited digestion capacity, and the remaining slag still needs to be processed;
(3) Lithium extraction from ore: There are not as many impurities in the waste residue as lithium extraction from mica, only hydrogen is in it, but it has some impact on energy consumption (natural gas and coal gas), tail gas emissions, and water emissions;