From the point of view of resource grade, difficulty and mining cost, the brine resources of the "lithium triangle" in South America and the ore resources in Australia are the most valuable in the world.

From the point of view of resource endowment, the salt lakes of the "lithium triangle" in South America (northern Chile, western Bolivia, northern Argentina) have congenital advantages: the resource endowment is better (the lowest ratio of magnesium to lithium in the world). The salt lake can be precipitated by mature precipitation method (the complete cost is more than 1-15000 yuan / ton). Long-term development and continuous infrastructure investment, has formed a mature industrial cluster.

In addition, the advantages of lithium ore in western Australia lie in high ore taste, mature lithium extraction technology from downstream ore and long mining life. At present, the Green bushes lithium mine owned by Telison Company in Australia (underwritten by Tianqi Lithium Industry and Yapao in the United States) has proven reserves of 61.5 million tons, equivalent to 4.3 million tons of lithium carbonate equivalent, and the average grade of lithium oxide is 2.8%. It is the highest grade lithium ore in the world. The complete cost of extracting lithium is about 38000 yuan / ton.

According to the morphological classification of lithium deposits in the world, they can be divided into two categories: brine type and hard rock type. 66% of them exist in brine and 34% in ores.

. The lithium resources of salt lakes in China are mainly distributed in the salt lakes of the Qinghai-Tibet Plateau, and the brine types are mainly carbonate type and sulfate type. The carbonate lithium resources are mainly concentrated in Zabuye Salt Lake in the west of Tibet and Bango-Dujiali Salt Lake in the east. The sulfate lithium resources are mainly distributed in the Chaidamu Basin and the north of Tibet.

Among them, the morphological composition of salt lake accounts for 80%. The reserves of lithium salt lakes in China are geographically distributed in Qinghai and Tibet. The reserves of lithium resources in salt lakes account for about 80% of the total reserves of lithium resources in China, of which nearly 50% are in Qinghai and 28.36% in Tibet. Spodumene is mainly distributed in Xinjiang, Sichuan and Henan, and spodumene deposits are mainly distributed in Jiangxi, Hunan and other places, accounting for less than 20%.

There are mainly the following four salt lakes in China:

Inner Mongolia Yanhu District

This salt lake area is mainly carbonate and sulfate type salt lake, lack of chloride type salt lake. The salt lake resources in the area are quite rich, especially solid rock salt, mirabilite and natural alkali, while the brine resources are inferior to other lakes. The reserves of stone salt in the region are about 200m tons, mirabilite (Na:SO.) The reserves are about 3.3 billion tons and the total reserves of natural alkali (NaHCO3+Na:C03) are nearly 40 million tons.

Xinjiang salt lake area

Sulfate is the main salt lake in this salt lake area, followed by carbonate and chloride salt lake. Sodium sulfate is the main type of sulfate, magnesium sulfate is the second, boron is relatively concentrated in some sulfate and individual carbonate salt lakes, but it is much inferior to Qinghai and Tibet lakes. The whole region has 6.6 billion tons of stone salt reserves (excluding liquid reserves), 50 billion tons of gypsum reserves, 225 million tons of mirabilite reserves, 50 million tons of sodium saltpetre reserves, and 40.237 million tons of potash resources in Lop Nur alone, which will become a reserve base for potash production in China.

Qinghai salt lake area

This area is the lake area with the most abundant salt lake resources in China. It is mainly distributed in Chaidamu Basin, Hoh Xili and Kumukuli Basin. The type of salt lake is mainly sulfate, and most of them are magnesium sulfate subtypes. There are also a considerable number of chloride salt lakes. In magnesium sulfate subtypes of salt lakes, in addition to the deposition of a large number of stone salt, mirabilite, some lakes also deposited a considerable scale of borate, others also deposited a certain amount of potassium and magnesium salt. Lithium and boron are highly enriched in some sulfate and chloride type salt lake brine to form sulfate type lithium lake and chloride type potassium magnesium lake. The reserves of stone salt in this area are 365 billion tons and gypsum (CaSO. 2H). 0) 47 billion tons, mirabilite (NaSO). 7.2 billion tons of 10H:0, 5 million tons of celestite (SrSOt), 670000 tons of natural alkali, 6.5 billion tons of magnesium salt, 590 million tons of potassium chloride, tens of millions of tons of borate and lithium each.

Tibet Yanhu District

The type of salt lake in this area is sulfate or carbonate type, most of the sulfate type salt lakes are sodium sulfate subtypes, the main salt deposits are mirabilite, stone salt and borate, and water magnesite and other deposits are also found in some lakes. The region's stone salt reserves are 1 billion tons, mirabilite billions of tons, borate and lithium salt are 1000-20 million tons, water magnesite 700000 tons, brine potassium chloride hundreds of millions of tons.

The quality of Tibet salt lake in China is higher than that in Qinghai, which is the most valuable for development. The brine of Tibet salt lake is characterized by high content of lithium and boron. The remarkable characteristic is that the Mg/ Li value of brine is low, and lithium carbonate can be obtained by evaporation of almost no Mg2+, brine. The salt lake resources in Tibet are mainly concentrated in Zabuye Salt Lake, Jiezhaka Salt Lake and Longmucuo Salt Lake in Ali region of Tibet.

Zabuye Salt Lake is the first salt lake in China and the third largest in the world, with lithium carbonate reserves of about 1.84 million tons. The natural carbonate lake of Zabuye salt lake has excellent resources, and its ratio of magnesium to lithium is only 0.019, which determines its low theoretical processing cost.

Tibet is mainly engaged in salt lake lithium extraction production enterprises for Tibet mining industry and Tibet city investment, due to geographical constraints, Tibet salt lake lithium extraction development is in the initial stage, with output of less than 5000 tons in 2017.

Although the endowment of the salt lake in Tibet is good, there are many problems in the specific operation. First of all, the elevation of the salt lake in Tibet is more than 4500 meters on average, and there is a lack of skilled workers in the area, and it is difficult for the transferred personnel to adapt to the harsh local environment. In addition, most of the salt lakes in Tibet are between peaks, so there are fewer flat bottoms that can be used to install plant equipment, which limits the substantial expansion of production capacity. Therefore, most of the lithium extraction enterprises in salt lakes, such as the mining industry in Tibet, carry out preliminary processing of brine from salt lakes. It is then transported to silver for secondary processing to form lithium carbonate over a distance of more than 2000 km.

Generally speaking, the production expansion of salt lake enterprises in Tibet is mostly limited by operating factors, large-scale development to achieve capacity enhancement requires a large amount of capital investment, economic feasibility is relatively poor.

Relatively speaking, after years of hard work, Qinghai salt lake lithium has entered the harvest period.

Qinghai salt lake resources are mainly concentrated in Chaerhan, Dongxitai, Dachaidan Salt Lake and so on.

There are 33 salt lakes in Chaidamu Basin, Qinghai Province, with proven LiCl reserves of 13.9677 million tons and retained reserves of 13.909 million tons. The lithium content in 11 sulfate type salt lakes identified in Chaidamu Basin has reached industrial grade, and all of them are dominated by brine deposits. It has the advantages of shallow burial, high grade and simple hydrogeological conditions, among which the lithium resources of Chaerhan Salt Lake, (Dongxitai) Jinai Salt Lake, Yiliping Salt Lake and Dachaidan Salt Lake are relatively enriched. The reserves of lithium resources account for 37.16%, 26.77% (east-west Taiwan), 13.93% and 22.13% of salt lake resources in China, respectively.

The high ratio of magnesium to lithium in Qinghai salt lake is one of the biggest obstacles to the large-scale industrial production of lithium carbonate.

Qinghai salt lake is rich in resources and good drying conditions, but the high mg / Li ratio of salt lake resources brings great difficulties to the enrichment and separation of lithium. The mg / Li ratio of Atacama Salt Lake, which is the benchmark of salt lake resources in the world, is only 6 / 1. Although the reserves of Chaerhan Salt Lake are the largest, the ratio of magnesium to lithium halide is 1577 / 1, and the concentration of lithium ion is low. The reserves of Dongtai Jinai Salt Lake are the smallest, but the ratio of magnesium to lithium is the smallest, which is 35.2 (old halogen is 18:1), and the ratio of magnesium to lithium in Xitai Jinai Salt Lake is similar to that of Dongtai, the ratio of magnesium to lithium is 61 to 1. The ratio of magnesium to lithium in Yiliping salt lake is 90.51 (old halogen is 51:1), the reserve of Dachaidan salt lake is the second, and the ratio of magnesium to lithium is 134 (old halogen is 92:1).

At present, adsorption method (represented by blue lithium industry) and membrane method (electrodialysis method and nanofiltration membrane method) are the most widely used in extracting lithium from Qinghai salt lake in China (nanofiltration membrane method is represented by Hengxin melting). Lanke lithium industry has been involved in the field of lithium extraction from salt lake since 2011. Through the introduction of Russian second-generation adsorption technology, after many years of running-in and improvement and innovation of adsorbents, the technology made a major breakthrough in 2014 and began mass production. Citic Guoan relied on the study of separation and extraction of lithium from Xitaijinai Salt Lake with high mg / Li ratio. In 2006, a breakthrough was made. The technology adopted calcination method to extract lithium, but due to serious pollution to the environment, it was stopped until 2016. Production resumed. During this period, Hengxin Rong was established to purchase the brine resources of CITIC Guoan and use nanofiltration membrane to extract lithium.

For many years, part of the deep ploughing route has broken through, and now it has entered the stage of large-scale production.

Technical core links, such as adsorption: adsorption of raw materials on Lanxiao science and technology, Xianfeng holding have been mastered; membrane method: inspiration has independent research and development of membrane lithium extraction process, but Hengxin melt uses imported film. In 2017, the number of lithium extraction enterprises in Qinghai salt lake reached 12, and the lithium extraction industry in Qinghai salt lake officially entered the stage of large-scale mining.

The cost of lithium extraction from salt lake is its biggest relative advantage after maturity.

From the cost point of view: lithium extraction cost of lithium mica > lithium extraction cost of spodumene > lithium extraction cost of salt lake.

Yichun Silver Lithium New Energy, a subsidiary of Jiangte Motor, adopts lithium mica extraction technology, and its production cost can be controlled at 70000 yuan / ton. Because the quality and output of spodumene in China are not ideal, domestic enterprises use imported spodumene to extract lithium, such as Ganfeng lithium industry and Tianqi lithium industry. The cost of producing 1 ton lithium products (raw material cost + production cost) is 45-6000 yuan. At present, the direct production cost of industrial lithium carbonate in foreign salt lakes is between 15000 yuan / ton, but in China, due to the different quality of each salt lake, the difference in production cost is large: the complete cost of Tibet mining industry can be controlled at 20,000 yuan / ton; The complete cost of adsorption is 30,000 yuan / ton, the complete cost of extraction method is 230000 yuan / ton, and the cost of electrodialysis method of Qinghai lithium industry is 20,000 yuan / ton. The membrane system of Hengxin fusion nanofiltration membrane method has a large investment, and the complete cost is about 60,000 yuan / ton (inferred).

Foreign brine resources are of high quality, with a cost of about 20,000 yuan / ton. The benchmark enterprise of lithium extraction cost, SQM, has a low magnesium-lithium ratio of brine, which can reach 30g/L by drying (directly adding NAOH to remove magnesium, and then adding calcium carbonate), so only sodium bicarbonate can precipitate. Resource endowment determines that its complete cost is absolutely competitive. According to the SQM valuation report released by Tianqi Lithium Industry, the direct cash costs of lithium operations from 2015 to 2017 were US $1789, US $2243 and US $2266 per tonne (1.11,1.49 and 15300 yuan / tonne at the annual average exchange rate). This cost does not include depreciation and amortization that do not need to be paid cash and rental fees paid to Corfo. After a combined estimate of other expenses, the estimated cost is 20, 000 yuan per ton.

The total cost of extracting lithium from Qinghai salt lake in China is in the range of 260000 yuan / ton. The technical path of salt lake is very different, which determines that the complete cost of lithium extraction enterprises in Qinghai salt lake is different. According to the caliber of investigation and public data, it is estimated that the comprehensive cost of China's Qinghai salt lake lithium extraction enterprises is in the range of 20,000 yuan / ton: Dongtai, Xitai Jinnai, Minmetals own Yiliping brine quality is better, mg / Li ratio is about 50. The content of lithium reaches 4G / L, so Dongtai Qinghai lithium industry can use ion membrane process to produce battery grade lithium carbonate with a cash cost of 30,000 yuan, which is about 40,000 after considering the cost of brine and investment amortization. However, the ratio of magnesium to lithium in Chaerhan salt lake is as high as 136, and the concentration of lithium is very low. After using adsorption resin + membrane filtration process, Lanke lithium industry is expected to gradually release with Qinghai salt lake in the future, and the market price will gradually achieve a new balance between supply and demand.

In the long run, China's salt lake lithium extraction is completely released, which will impact the hard rock lithium industry of countries all over the world and China at a lower cost. In 1997, SQM lowered the price of lithium carbonate by virtue of high quality brine and mature technology. As a result, most of the hard rock type lithium mines and lithium extraction enterprises in the world have been shut down. However, considering that the technical difficulty of extracting lithium from Qinghai salt lake has gradually broken through, the new production capacity will be released gradually in the next two years, the supply will be gradually sufficient, and the market will be expected to achieve a new balance between supply and demand.

The brine endowment of each salt lake determines the route of lithium extraction is very different.

Similarities and differences of Lithium extraction process determined by the characteristics of Salt Lake

Different salt lakes correspond to different lithium enrichment and extraction processes. Lithium in salt lake is generally extracted from the old halogen left after the production of sodium and potassium. After lithium enrichment, lithium ion is extracted to produce lithium carbonate after evaporation, magnesium removal and concentration. The quality of Tibet salt lake is good, but the mining environment is not ideal. At present, Qinghai salt lake can still be developed, but it is difficult to extract lithium due to high Mg/Li ratio. Compared with overseas salt lake, it is necessary to carry out additional lithium enrichment steps, and salt lake due to different brine concentration corresponding to different lithium enrichment and lithium extraction process. The calcination method has high requirements for raw materials, and the brine must reach the lithium concentration of 8-9g/L. The extraction method is suitable for brine resources with high magnesium and high lithium content (generally required to reach 2g/L). Precipitation method requires that the mass concentration of lithium ion in salt lake is more than 0.5g / L, and the content of lithium in salt lake brine is more than 1g/L when the weight ratio of magnesium to lithium is 1 to 200 / 1. The mass concentration of lithium ion in salt lake is more than 0.5g / L, and the mass concentration of lithium ion in salt lake is more than 0.5g / L. The adsorption method is suitable for 0.1g/L brine.

At present, there are seven methods for extracting lithium from salt lake, among which adsorption and electrodialysis are the most widely used in Qinghai. At present, the main salt lake brine extraction technologies used in the world are precipitation method (including carbonate precipitation method, aluminate precipitation method, hydrated lithium sulfate crystallization precipitation method, boron magnesium and boron lithium co-precipitation method), calcination leaching method, carbonation method, solvent extraction method, Adsorption, electrodialysis, membrane separation, etc., Among them, the solvent extraction method has not yet realized large-scale industrial application.

Precipitation / solar cell method

Also known as solar cell method, it is often used in salt ponds with high lithium concentration. The concentrated lithium-rich brine was prepared by evaporating the old brine, and the boron and calcium-magnesium ions were removed by acidizing or extraction to obtain the brine with high lithium content. After that, soda ash precipitator was added to separate lithium from other salts. Li2CO3, was directly separated from the intergranular brine of alkaline carbonate lake. Disodium hydrogen phosphate was used as precipitant. Lithium and phosphate ions were separated by hydrogen or sodium cationic resin. Lithium carbonate was precipitated from the concentrated eluent.

At present, the precipitation / solar pool method is mainly used in Tibet mining industry.

The company's main resource assets are Zabuye Salt Lake, resource reserves of about 1.84 million tons, magnesium-lithium ratio of about 0.02, rich in by-products, including mirabilite (15.92 million tons in terms of potassium chloride) and borax (9.63 million tons in terms of boron oxide).

Zabuye salt lake belongs to carbonate salt lake, which can reach 60% and 70% crude lithium carbonate ore by drying directly, so the lithium extraction process adopts gradient solar pool to heat up and precipitate lithium. The specific process method is as follows: a certain thickness of salt gradient layer is formed between the freshwater layer and the brine layer (to prevent the upward emission of heat), so that the solar energy is stored in the brine part of the bottom of the pool to form an energy storage area, and the temperature of the brine is increased. The brine can be heated by 40 to 100 degrees in the solar pond, the condition of lithium carbonate precipitation at high temperature is realized, and the lithium carbonate is concentrated and precipitated.

However, the difficulty of expanding production lies in the large loss of halogen drying process caused by carbonate in salt lake, coupled with the lack of fossil fuel, inconvenient transportation, high cold and anoxia at 4000 meters above sea level. In addition, the Tibetan salt lake is located between the peaks, the construction of salt fields need a flat place, this contradiction has brought about difficulties in construction.

The crude lithium carbonate ore was transported to Gansu silver for processing, and the caustic-carbonation method was used to purify 99.2% high purity lithium, and the recovery rate of lithium was 95%. Baiyin Lithium Salt Plant has built a production capacity of 3000 tons of lithium hydroxide and 1500 tons of lithium carbonate. In 2017, it produced 1786 tons of industrial grade lithium carbonate, 186tons of battery grade and 755.7 tons of lithium hydroxide, totaling 2728 tons.

Calcination leaching method

The calcination leaching method realizes the extraction of lithium carbonate by calcination, leaching, precipitation and so on. The calcination leaching method is that magnesium chloride tetrahydrate is obtained by evaporation of boron extracted brine, magnesium oxide is obtained after calcination, lithium is leached with water, calcium, magnesium and other impurities are removed with lime milk and pure alkali, and the solution is evaporated to about 2% Li. Lithium carbonate was precipitated by adding soda ash, and the magnesium oxide slag after calcination was refined to obtain a magnesium oxide by-product with a purity of 98.5%.

The calcination method is beneficial to the comprehensive utilization of lithium and magnesium and other resources, and the consumption of raw materials is low, but the extraction of magnesium makes the process complex, the equipment corrodes seriously, the amount of water that needs evaporation is large, the energy consumption is large, and there are problems of environmental pollution. In the current environmental protection strict control of the regulatory environment, facing greater environmental risks.

Calcination leaching method is mainly used by Citic Guoan.

Xitai Jinai Salt Lake, which the company has the right to develop, is located in the middle of the Chaidamu Basin, covering an area of about 570 square kilometers. Xitai Jinai Salt Lake is a large comprehensive salt deposit dominated by liquid brine deposit with high grade water and salt system rich in lithium, potassium, boron, magnesium and sodium, with reserves of 2.3 million tons of lithium carbonate equivalent. The ratio of magnesium to lithium halide is 40:1. At present, the production capacity has reached about 5000 tons, and the stable production of battery-grade lithium carbonate has been realized.

The company uses the solid phase calcination method to separate magnesium, the cost is high and the benefit is low, the processing cost is about 60,000 yuan per ton.

The use of the original technology is difficult to sustain: first, the calcination method has relatively high requirements for raw materials, and must reach the concentration of 8 to 9 grams per liter of brine. The lower concentration of Xitai Jinai Salt Lake itself is difficult to carry out calcination, and secondly, calcination will produce salt and acid. There is the problem of waste gas pollution, the re-expansion of production needs to increase electricity, the lack of local fuel, not enough to support further production.

Solvent extraction method

After removing boron from old halogen, adding FeCl3 solution to form LiFeCl4, LiFeCl4 was extracted into organic phase with tributyl phosphate (TBP)-coal oil extraction system to form LiFeCl4+2TBP extraction complex, which was washed with acid and extracted with hydrochloric acid. Anhydrous lithium chloride can be obtained by evaporating concentration, roasting, leaching and removing impurities, and finally sodium carbonate is added to form lithium carbonate.

The advantage of this method is that it is suitable for extracting lithium salt from relatively high mg-Li ratio salt lake brine, but the amount of brine to be treated in the extraction process is large, which is corrosive to the equipment, and there is the problem of solution loss of extractant. In the process of implementation, the requirement of equipment material is high, which is suitable for brine resources with high magnesium and high lithium content (generally required to reach 2 g / L).

Because the high content of organic matter in waste liquid will cause great pollution to the salt lake, the extraction method can not meet the requirements of the industry under the higher and higher environmental protection standards.

The solvent extraction method is mainly Dahua Chemical Industry.

Dahua Chemical has the mining right of 80 square kilometers of Dachaidan Salt Lake. Dachaidan Salt Lake has proved that intergranular brine contains 2.859 million tons of potassium chloride, 450000 tons of boron and 301900 tons of lithium (1.61 million tons of lithium carbonate equivalent). The ratio of magnesium to lithium is 65 / 1, and the content of lithium is about 0.38g/L. After extracting potassium, the content of lithium in old brine is 2.5g / L, which ranks second in Qinghai.

The company's Dachaidan Salt Lake development project has a total investment of 1.25 billion yuan, divided into three phases of development and construction. The first phase of development products are: annual production of potassium chloride 50, 000 tons; boric acid 12000 tons; potassium magnesium sulfate fertilizer 90, 000 tons, lithium chloride (lithium carbonate) 4500 tons and by-products; The second and third phases focus on the development of potassium series products, magnesium series products and sodium series products.

At present, the company has a production capacity of about 5000 tons of lithium carbonate, which has just been put into production to build 10, 000 tons of battery-grade lithium carbonate.

The cost of extracting lithium by extraction method can be controlled at about 20 000 / ton. The disadvantage is that the equipment corrosion is serious, the material separation is difficult, and a large number of hydrochloric acid acidizing treatment is needed, so the acid production facilities need to be equipped and the pollution is serious. The residual organic matter of extractant pollutes the environment.

Adsorption method

First of all, the adsorption production process is that the lithium ion in the salt lake brine is adsorbed by the selective adsorbents, and then the lithium ion is washed off to achieve the separation of lithium ion and other ions, which is convenient for the subsequent conversion and utilization. The key of this process is lithium adsorbents, which require that the adsorbents can eliminate the interference of a large number of coexisting alkali metals and alkaline earth metal ions in brine, selectively adsorb lithium ions in brine, and have high adsorption capacity and strength.

This method is especially suitable for the separation of lithium from high magnesium and low lithium brine (mg / Li ratio is 500 / 1 or higher). It is also suitable for dew with relatively low lithium content (lithium content is generally more than 300 mg / L). It has good selectivity in this kind of brine. Compared with other methods, it has great advantages. The production efficiency of ion adsorption is high, and the content of lithium ion (mg/L) after desorption is more than 3 times of that in raw brine. The biggest advantage of adsorption exchange method is that it has great advantages in economy and environmental protection, and the process is simple, the recovery rate is high and the selectivity is good.

Adsorption + membrane concentration is mainly used in blue lithium industry.

The main resource of Lanke lithium industry is Chaerhan Salt Lake, which has a total area of 5856 square kilometers, equivalent to about 7.175 million tons of lithium carbonate. The ratio of magnesium to lithium halide in salt lake is 400 and 1, and the concentration of lithium ion is 0.25g/L.

The company introduced the Russian adsorption technology in Foshan Lighting in 2011. After many years of testing, the company completed the complete production line of lithium extraction from salt lake in 2014. after the process transformation, the adsorption transformation, the optimization of adsorbents, the plant area and the equipment were optimized and upgraded. Production began in 2017 (while upgrading the equipment, adding Na filter membrane, adding 24 adsorption towers to prepare for the expansion of the future 30,000 tons of lithium carbonate in advance, and forced evaporation equipment). 5002 tons were produced in the first half of 2018, and this year is dominated by high-quality industrial grade lithium carbonate.

The company has 88 adsorption towers in operation and is expected to produce about 10,000 tons in 2018. At present, the company is installing boron removal devices in the processing process to achieve the goal of 10,000 tons of battery-grade lithium carbonate this year.

The company adopts the technical path of front adsorption + back end membrane + chemical lithium deposition. The brine concentration of the blue family is low (0.1 to 0.2 g / L) and requires adsorbents and then washed with fresh water to reduce the ratio of magnesium to lithium to 5:1. The refined lithium chloride (concentration 0.5 g / L) was obtained by interception, and the solution of 4 g / L was obtained by pressure infiltration.

In 2018, the Lanke lithium industry process was improved, and the membrane magnesium-lithium separation process replaced the cationic resin demagnetization process. The qualified liquid after washing and leaching in a single tower (the ratio of magnesium to lithium is 500 to 1) is provided to enlighten water affairs, through enlightening the process of water supplies film process, After enlightening water purification, the concentrated solution (the ratio of magnesium to lithium is 3 to 400) is handed over to Lanke lithium industry to produce lithium carbonate products after drying in the salt field.

At present, Lanke lithium industry added 20, 000 tons of battery-grade lithium carbonate production capacity, the planned total investment of 3.2 billion yuan, the actual investment may be more than 2 billion. The total cost of one ton of lithium carbonate in Lanke lithium industry is about 40, 000 (233 million / 8000 tons). After technical transformation, the cost of lithium carbonate has been reduced, and the manufacturing cost is similar to that of Qinghai lithium industry.

Membrane method

The membrane methods are mainly electrodialysis and nanofiltration membrane separation.

The electrodialysis membrane separation technology has been industrially produced in Dongtai Salt Lake, Chaidamu Basin. This technology is used to separate salt lake brine with a weight ratio of magnesium to lithium ranging from 1 to 200. 1, through a primary or multistage electrodialyzer, Lithium is concentrated by using univalent cation selective ion exchange membrane and monovalent anion selective exchange membrane (continuous, continuous partial circulation or batch circulation) process, and soda ash is added to precipitate lithium carbonate. The resulting mother liquor can be recycled. This method is suitable for the separation of lithium from magnesium and other ions in brine with relatively high magnesium and high lithium. However, the process requirement is that the salt content of light brine is less than 100 g / L, otherwise the separation effect will not be good and the cost will be greatly increased. The process is characterized by simple setting, convenient operation and no pollution to the environment, but the separation efficiency is not high. The service cycle of filter membrane is short.

The magnesium lithium salt lake brine or salt field sun concentrated old brine is concentrated by electrodialysis through a primary or multistage electrodialyzer, using univalent cation selective ion exchange membrane and monovalent anion selective ion exchange membrane to concentrate lithium. Adding soda ash to precipitate lithium carbonate, the mother liquor can be recycled.

The use of electrodialysis + nanofiltration membrane Dongtai lithium resources company + Qinghai lithium industry (Dongtai Jinai salt lake).

Dongtai Salt Lake is a salt lake with the highest lithium concentration in Qinghai salt lake. The exploitable reserves of 2.44 million tons of LCE, brine lithium concentration is more than 0.4 g / L on average, and the potassium is more than 10 g / L, which supports the sustainable mining scale of producing 40 000 tons of lithium carbonate per year.

Lithium Resources plans to produce 20,000 tons of capacity, and the first production line (10,000 tons) will be put into production in 2018. The second 10,000-ton production line is expected to begin before 2020 and the third 10,000-ton production line after 2020. Dongtai Salt Lake in the future lithium upgrading space mainly from lithium resources companies.

The company purchased the ion membrane exchange technology of the Salt Lake Institute, and used the nanofiltration membrane on the basis of electrodialysis, mainly by separating lithium ion and chloride ion from lithium ion and chloride ion exchange technology (from 5g/L to 15g/L) by anion and cation electrodes to obtain lithium chloride solution. The back end was separated and concentrated to 30g / L, and finally precipitated to produce battery grade lithium carbonate.

The first phase of 10,000 tons of lithium carbonate plant, the investment cost of about 400 million yuan. Peripheral power plants and other supporting investment is high, lithium carbonate plant itself needs to invest about 278 million. The membrane loss rate is about 5% / year.

Nanofiltration membrane separation method

Membrane separation technology not only has the functions of separation, concentration, purification and purification, but also has the characteristics of high efficiency, energy saving, environmental protection, simple molecular filtration and filtration process, easy to control and so on. Among them, nanofiltration membrane separation technology is a new membrane separation technology developed and studied at home and abroad in recent years.

The main technology of nanofiltration membrane + reverse osmosis membrane is constant fusion.

The company is engaged in the development and utilization of Sinai salt lake lithium resources, old halogen purchased from Citic Guoan, the price fluctuates with the season.

On November 9, 2017, the company officially completed and put into production an annual production capacity of 20,000 tons of battery-grade lithium carbonate. The main product is industrial grade lithium carbonate (99.2%). At present, the company has the ability to extract battery-grade lithium carbonate, but the problem of impurities remains to be further solved. The back end will process the stage to deal with impurities, battery-grade products will come up slowly, mainly considering the processing cost and time cost. Production increases are likely to continue in the future. The current output is 20 tons per day and is expected to reach production soon. It could reach 30,000 tons or more next year. The current output is 20 tons per day, which is expected to reach production soon, and the future output will reach more than 30,000 tons.

In addition, there are Minmetals Salt Lake (Yiliping Salt Lake).

Yiliping Salt Lake, with an area of about 422.7 square kilometers, is located in the middle of the Chaidamu Basin and belongs to the dry salt lake type. Mineral resources include brine resources and solid salt resources, mainly brine resources, brine resources are intergranular brine, there is no lake surface brine, solid salt mineral resources are stone salt, mirabilite, gypsum, sodium magnesium alum and potassium salt and so on. At present, the proven reserves contain 1.7995 million tons of lithium chloride, 918000 tons of boron oxide, 16.805 million tons of potassium chloride, 47.141 million tons of magnesium chloride and 2.977 billion tons of sodium chloride. The mg / Li ratio of Yiliping Salt Lake is as high as 100 / 1, which belongs to the super difficult development brine with high mg / Li ratio.

The company's pre-project product plan and scale for the annual production of 10, 000 tons of lithium carbonate, 300000 tons of potassium chloride, 10, 000 tons of boric acid and supporting soda ash project, salt field 39.5 square kilometers. At present, the construction of salt fields has been completed and lithium carbonate is being produced.

Based on the patent technology of "multi-stage lithium ion concentration" of Freiberg University of Technology in Germany, the company has developed a new method of extracting lithium to overcome the high ratio of magnesium to lithium in combination with the Salt Lake Institute of the Chinese Academy of Sciences. The ratio of magnesium to lithium in salt lake is high. Magnesium is separated directly by nanofiltration membrane, and the concentration of lithium can reach 2-5g/L after separation. The pilot test has separated magnesium and lithium through nanofiltration membrane. The total investment in the project is 4.6 billion yuan.

However, the actual future release of lithium from salt lakes still needs to be observed, and there are other variables that may affect future development:

First of all, the supply capacity of old brine determines the supply ceiling of Qinghai salt lake.

The preparation of old halogen generally takes about 8 to 10 months. At present, the enterprises that carry out the extraction of lithium from salt lakes in Qinghai are often chemical enterprises, which have the production capacity of extracting potassium and making potash fertilizer from salt lakes. So lithium extraction is often after the potassium extraction process. Lithium extraction raw materials, often in the chemical business after the extraction of potassium old halogen (so the low cost is also directly related to the raw materials are not priced or lower pricing). To meet the requirements of potassium extraction, the concentrated brine needs to be prepared in the drying pool for 8 to 10 months.

Considering the economy of the whole project, the ratio of production capacity of potassium and lithium is about 30:1. Considering the economic benefits of the whole project, at present, when considering the production capacity of lithium carbonate projects in Qinghai salt lake enterprises, they often take into account such factors as resource endowment, potash fertilizer, lithium carbonate price outlook, and so on. In fact, the disguised constraints of the salt lake to produce lithium carbonate ceiling. According to the calculation, the total production capacity of lithium salt supported by old halogen in Qinghai salt lake is about 12 ~ 150000 tons LCE.

Secondly, two potential conditions need to be considered for large-scale replication of mature technology.

The mature technology of high mg / Li ratio and low Li concentration brine condition replicates to the salt lake with low mg / Li ratio and high Li concentration brine condition. According to the adsorption and extraction methods used in Chaerhan and Dachaidan, which are relatively high in magnesium and lithium, if they migrate to the east-west technology, they can be realized in theory. However, the replication of this model does not take into account the effect of different impurities in brine on lithium carbonate products, especially the battery grade with higher requirements. The same salt lake is similar to replication in brine environment. If it is located in the same salt lake, different enterprises can adopt the same technical route, whether the success or failure depends on the technical strength and financial strength of the company itself. For example, the lithium carbonate project promoted by Zangge Holdings is located in Chaerhan Salt Lake, the source of old halogen is the same (the old halogen after potassium extraction), and the technical route is the same (the adsorption material is provided by Lanxiao Technology). Remove miscellaneous and enlighten clear source cooperation).

In addition to these major issues to be seen, there are a few risks that are worthy of attention.

First, the impact of climate fluctuations. Most of the salt lake areas in China do not meet the special geographical conditions of drought, low rainfall, long sunshine and large annual evaporation, while the supply of old brine depends on climatic conditions.

Second, the industry competition intensifies. Lithium battery industry chain has been concerned by the market, a large number of enterprises have entered, the pace of capacity investment has been greatly accelerated, the overall risk of overcapacity in the industry has been highlighted; Coupled with the decline of policy subsidies, enterprises are likely to face increased competition and squeeze profit margins in the future.

Third, the progress of new energy vehicles is not as good as expected. The sales volume of new energy vehicles is closely related to the demand for lithium resources, and the growth of consumption of new energy vehicles has become an important factor driven by the demand growth of lithium resources. In recent years, the high growth rate of consumption of new energy vehicles is largely due to the support of government policies, and the growth of new energy vehicle sales will be hindered after the policy ebb in the next few years. There are also the following factors affecting future sales of new energy vehicles:

At present, the mileage, performance-to-price ratio and safety reliability of new energy vehicles do not meet the psychological expectations of consumers. And there are many types of charging equipment, so it is difficult to realize the interconnection between different brands and models of vehicles and charging equipment. Charging infrastructure construction as a whole is slow, consumer service system needs to be improved and other supporting system construction is also restricting the further promotion of new energy vehicles.

Fourth, the risk of lithium carbonate price fluctuation. In the first half of the year, industrial grade lithium carbonate fluctuated at 12-160000 yuan / ton, down 21.05%, battery-grade lithium carbonate price fluctuated at 13-180000 yuan / ton, down 24.42%, and lithium hydroxide price fluctuated at 14-158000 yuan / ton. Down 8.50%. At the beginning of the year, the high price of lithium carbonate pushed upstream suppliers to release production capacity, but in March, the output of Qinghai salt lake lithium extraction enterprises began to be released, superimposed on the uncertainty of the subsidy policy of the positive materials factory in the first half of the year, and at the same time actively removed the inventory. Lithium carbonate market as a whole slightly oversupply, price correction.

Finally, the technical route of new energy power battery is changed. At this stage, lithium-ion power batteries are widely used in new energy vehicles, among which the cathode materials are mainly lithium iron phosphate, ternary, and so on. If the future power batteries break through in a short period of time, bypass the lithium route, It will subvert the industrial logic at this stage and bring risks.