Salt lake lithium extraction process involving low water consumption and device

Abstract

The present invention relates to a salt lake lithium extraction process involving low water consumption and a device, and belongs to the technical field of salt lake lithium extraction. The present technical solution comprises performing pretreatment on wastewater in a process, which comprises impurity removal and concentration; and then evaporating water in the wastewater by means of evaporation, so as to obtain recyclable water. In this way, water in wastewater is effectively recycled, thus reducing the consumption of water resources.

Description

A low-water-consumption salt lake lithium extraction process and device Technical Field

[0001] The invention relates to a low-water-consumption salt lake lithium extraction process and device, belonging to the technical field of salt lake lithium extraction. Background Art

[0002] Lithium extraction from salt lakes is an important resource development method in water-scarce areas. However, wastewater treatment and recycling are crucial components of this process. This process generates large amounts of wastewater, which contains significant amounts of salts and metal ions. Directly discharging this wastewater into the environment would severely pollute local water resources and the ecological environment. Therefore, increasing wastewater recycling and reuse is crucial. Advanced wastewater treatment technologies can effectively remove salts and metal ions from wastewater, ensuring it meets national discharge standards and reduces environmental pollution. Furthermore, recycling treated wastewater can reduce water consumption during the salt lake extraction process and achieve efficient resource utilization. Lithium extraction from salt lakes in water-scarce areas not only effectively develops local lithium resources but also promotes local economic development. Prioritizing wastewater treatment and recycling is crucial to ensure the rational use of resources and environmental sustainability.

[0003] Generally, direct lithium extraction technology using adsorption requires 150 cubic meters of fresh water to produce 1 ton of lithium carbonate. For example, for a 5,000 ton / year lithium carbonate project, this is equivalent to consuming 104 cubic meters of fresh water per hour. Fresh water consumption mainly includes:

[0004] 1) Membrane purification system, a large amount of water containing impurities is discharged from the membrane system, such as nanofiltration process;

[0005] 2) RO pure water system, the concentrate of pure water reverse osmosis system also causes a lot of water loss;

[0006] 3) Circulating water system: an inefficient circulating water system will consume a large amount of fresh water;

[0007] 4) Desorption process: a large amount of water resources will be consumed during the desorption process of the adsorbent;

[0008] 5) Ion exchange: regeneration of ion exchange resin system will produce wastewater;

[0009] 6) Lithium precipitation system, the mother liquor of lithium precipitation contains a large amount of water;

[0010] 7) Others, such as dripping and leakage during the production process.

[0011] Therefore, how to effectively reuse wastewater in the process will help reduce water consumption in the entire process and make it easier to carry out in areas with water shortages.

[0012] Summary of the Invention

[0013] The purpose of this invention is to provide a new technology for extracting lithium directly from brine, making it more efficient and sustainable, and eliminating the need to extract large amounts of fresh water from the environment, which is crucial for the development of salt lake resources in areas where water resources are scarce or fresh water extraction is limited.

[0014] A low-water-consumption lithium extraction process from salt lakes, characterized by comprising the following steps:

[0015] Obtain wastewater from the lithium extraction process in salt lakes and perform pretreatment;

[0016] After evaporating and condensing the wastewater obtained from the pretreatment, recycled water is obtained;

[0017] The recovered water is returned to the process of extracting lithium from salt lakes.

[0018] The lithium extraction from salt lake is carried out by any one or a combination of the following methods: adsorption extraction, solvent extraction extraction, ion exchange extraction, electrodialysis extraction, membrane separation extraction, and electrochemical deintercalation extraction.

[0019] For the combination of lithium extraction by adsorption and lithium extraction by membrane separation, wastewater refers to one or a combination of brine, adsorption tail brine, leaching water, top water, nanofiltration concentrated water, refined resin regeneration wastewater or lithium precipitation mother liquor.

[0020] The pretreatment refers to one or a combination of oxidation, adsorption, flocculation, filtration, precipitation, sedimentation, and neutralization.

[0021] The pretreatment is nanofiltration membrane filtration, after the nanofiltration membrane filters the salt water wastewater, the permeate is returned to the lithium extraction process;

[0022] The start time of the nanofiltration membrane cleaning process is calculated as follows:

[0023] Take a certain time, and during the nanofiltration operation, monitor the COD values ​​on the retention side and the permeation side, and calculate the increase rate of the COD retention rate on the nanofiltration membrane surface during this time interval;

[0024] If the rate of increase of the retention rate in a period of time is less than α×H β ×A% threshold, it is considered that densification pollution has begun to occur, so the nanofiltration process is stopped and membrane cleaning is started; where α and β are coefficients, H is the water hardness in ppm, and A is the rate of change of retention rate.

[0025] The evaporation process adopts one or a combination of multiple-effect evaporation, flash evaporation, thin film evaporation, freezing evaporation, vacuum evaporation and MVR evaporation.

[0026] A low-water-consumption salt lake lithium extraction system, comprising:

[0027] Pretreatment system, used to pretreat wastewater from the lithium extraction process in salt lakes;

[0028] The evaporation and condensation system is used to evaporate and condense the wastewater obtained from pretreatment to obtain recycled water.

[0029] The salt lake lithium extraction adopts any one or a combination of adsorption lithium extraction system, solvent extraction lithium extraction system, ion exchange lithium extraction system, electrodialysis lithium extraction system, membrane separation lithium extraction system, and electrochemical deintercalation lithium extraction system.

[0030] For the combination of adsorption lithium extraction system and membrane separation lithium extraction system, wastewater refers to one or a combination of: brine, adsorption tail brine, leaching water, top water, nanofiltration concentrated water, refined resin regeneration wastewater or lithium precipitation mother liquor.

[0031] The pretreatment system refers to one or a combination of oxidation system, adsorption system, flocculation system, filtration system, and sedimentation system.

[0032] The evaporation and condensation system adopts one or a combination of multiple-effect evaporation system, flash evaporation system, thin film evaporation system, freezing evaporation system, vacuum evaporation system, and MVR evaporation system. Beneficial effects

[0033] The present invention provides a wastewater treatment technology solution for extracting lithium from salt lakes in areas with a shortage of water resources. This technology solution pre-treats the wastewater in the process, including removing impurities and concentrating the wastewater, and then evaporates the water in the wastewater to obtain recyclable water. In this way, the effective recycling of water in the wastewater is achieved, and the consumption of water resources is reduced. The beneficial effects of this technology solution include: saving water resources: in areas with a shortage of water resources, by pre-treating and evaporating the wastewater, the effective recycling of water resources is achieved, and the consumption of regional water resources is reduced. Environmental protection and energy saving: recyclable water is obtained by evaporation during the wastewater treatment process, avoiding the pollution to the environment caused by the direct discharge of wastewater, while reducing energy consumption, and having the advantages of environmental protection and energy saving. Improved resource utilization: by treating wastewater with this technology solution, the water in the wastewater is recycled, the utilization rate of resources is improved, and the production cost is reduced. Therefore, the technology solution of the present invention has significant economic and social benefits in the treatment of wastewater in the process of extracting lithium from salt lakes, and is an innovative technology with broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 is a flow chart of this patent;

[0035] FIG2 is a graph showing changes in rejection during nanofiltration membrane concentration; DETAILED DESCRIPTION

[0036] The present invention provides a salt lake lithium extraction and water recovery system. This system aims to produce fresh water by utilizing waste products from the lithium extraction process (such as adsorption tail brine, rinse water, topwater, nanofiltration concentrate, refined resin regeneration wastewater, and lithium precipitation mother liquor), thereby reducing the salt lake lithium extraction process's dependence on fresh water resources.

[0037] The salt lake lithium extraction and water recovery system consists of two main components: the lithium extraction system and the water recovery system. The lithium extraction system is responsible for extracting lithium from the salt lake; the water recovery system is responsible for evaporating the water in the waste generated during the lithium extraction process and producing fresh water. These two systems are independent but can be used in conjunction to achieve optimal lithium extraction results.

[0038] In the lithium extraction system of the present invention, the lithium extraction methods that may be included include:

[0039] Lithium extraction by adsorption: Lithium in salt lakes is adsorbed using a specific adsorbent, and then released from the adsorbent through desorption. Commonly used adsorbents include aluminum-based lithium adsorbents, titanium-based lithium adsorbents, and manganese-based lithium adsorbents.

[0040] Solvent extraction of lithium: Utilizing the difference in distribution coefficients between the organic phase and the aqueous phase, lithium in the salt lake is extracted from the aqueous phase into the organic phase, and then delithiation is performed.

[0041] Lithium extraction by ion exchange: Ion exchange resin is used to adsorb lithium ions in salt lakes, and then the lithium ions are released from the resin through desorption.

[0042] Electrodialysis lithium extraction: Based on the principle of electrodialysis, the ions in the solution migrate to the anode or cathode under the action of the electric field, and the lithium ions and other impurity ions in the salt lake brine are separated by a selective permeable membrane, realizing the selective lithium extraction process.

[0043] Membrane separation for lithium extraction: Membrane separation technology is used to separate lithium ions from other ions in salt lakes through a semipermeable membrane. Materials used: The membrane material is usually a nanofiltration membrane or a reverse osmosis membrane.

[0044] The wastewater generated by the above lithium extraction process mainly includes:

[0045] 1. Adsorbed tail brine: The adsorbed tail brine obtained during lithium extraction by adsorption is primarily derived from brine from which most of the lithium has been removed. During the extraction process, lithium ions are adsorbed by the adsorbent, resulting in a high salt concentration of tail brine. The water quality characteristics of adsorbed tail brine typically include the following: High salt concentration: In addition to a small amount of lithium ions, the adsorbed tail brine also contains other salts, such as chlorides and sulfates, which require treatment to reduce environmental impact.

[0046] 2. Leaching water: In the process of lithium extraction from brine by adsorbent, the leaching water of the adsorption resin refers to the wastewater obtained from the initial rinsing of the adsorption resin. The leaching water of the adsorption resin also contains other salt substances, such as sodium salts, potassium salts, chlorides, sulfates, etc. The leaching water is usually a neutral or weakly acidic solution after adjusting the pH value to effectively elute the lithium ions on the adsorbent. The leaching water may contain a small amount of organic matter, which may be eluted from the adsorption resin and requires further treatment to purify the water quality. The leaching water usually needs to be treated and reused in the lithium extraction process to achieve efficient utilization of resources.

[0047] 3. Top water: In the process of lithium extraction from salt lakes using inorganic adsorbents, the top water of the adsorbent refers to the wastewater obtained by washing or other treatment of the adsorbent after the adsorbent adsorbs lithium ions.

[0048] 4. Nanofiltration Concentrate: During nanofiltration lithium extraction from salt lakes, separation of lithium ions and magnesium ions typically requires separation through a nanofiltration membrane. During the nanofiltration process, the solution passing through the membrane is divided into two parts: the product liquid that permeates the membrane and the concentrate retained by the membrane. In this process, the nanofiltration concentrate refers to the magnesium-rich liquid retained by the membrane.

[0049] 5. Refined resin regeneration wastewater: During the adsorption resin regeneration process, wastewater used for acid and alkali regeneration and washing of adsorption resin will also be generated. These wastewaters contain impurities remaining on the adsorption resin and other components in the salt lake, which also need to be treated and processed.

[0050] 6. Lithium precipitation mother liquor: In the process of extracting lithium from salt lakes, the lithium-containing solution is subjected to precipitation to prepare lithium carbonate, and then the lithium carbonate is separated by solid-liquid separation. The supernatant obtained is the mother liquor. Mother liquor refers to the remaining part of the substance required for crystal growth during the crystal growth process. Its properties usually have the following characteristics: Contains unprecipitated lithium ions and other impurities: The mother liquor contains incompletely precipitated lithium ions and other impurities. These substances are not fixed in the lithium carbonate crystals during the solid-liquid separation process and therefore exist in the mother liquor. Contains a certain concentration of carbonate ions: Since lithium carbonate is produced by the reaction of carbonate ions and lithium ions in solution, the mother liquor will also contain a certain concentration of carbonate ions. Acidity and alkalinity: The pH value of the mother liquor is alkaline.

[0051] Based on the above wastewater, the water recovery system used in this patent mainly includes: at least one (or more) pretreatment units and at least one (or more) evaporation units. The pretreatment unit is used to pretreat the water recovery raw materials to meet the operating requirements of the subsequent evaporation unit. The specific operating steps of the pretreatment unit may include oxidation, adsorption, filtration, precipitation, sedimentation, neutralization, etc., the purpose of which is to remove impurities and pollutants in the water to ensure that the subsequent evaporation process can proceed smoothly.

[0052] The filtration pretreatment can refer to microfiltration, ultrafiltration, nanofiltration, reverse osmosis, forward osmosis and other methods; impurities in wastewater can be removed, preferably by nanofiltration, reverse osmosis, and forward osmosis, which can not only remove solid impurities in wastewater, but also partially concentrate ions in wastewater. Since the concentration process of these methods has the advantage of low energy consumption, the specific energy consumption of subsequent evaporation and recovery of fresh water can be further saved. In addition, since the membrane separation process requires cleaning during operation of the membrane, especially in areas lacking water resources, it is more important to avoid excessive water consumption during the membrane cleaning process. On the one hand, the cleaning frequency should not be too high, and on the other hand, if a dense contamination layer is formed on the surface of the membrane, the cleaning efficiency will be reduced, which will in turn cause excessive waste of water resources. In the technical solution of the present invention, combined with the actual pretreatment concentration of the nanofiltration membrane, the following calculation method for the starting node of the cleaning time is adopted. Specifically, the idea is: the wastewater contains both organic matter and inorganic salt ions (calcium and magnesium ions have a greater impact), and a composite pollution layer of organic matter and calcium and magnesium ions will be generated on the surface of the nanofiltration membrane at the same time. In the early stage of filtration and concentration, the attachment process of organic matter on the surface of the nanofiltration membrane is relatively loose and the deposition rate is fast. Therefore, the actual retention rate of organic matter will continue to increase with time. When a dense organic pollution layer begins to form on the surface of the membrane, the rate of increase of the organic matter retention rate will slow down. Therefore, by calculating the absolute value of the rate of change of the retention rate of the nanofiltration membrane at a certain time interval, when the absolute value drops to the set threshold, it is considered that a dense pollution layer begins to occur, and it needs to be cleaned in time; and because calcium and magnesium ions can promote the formation of a dense pollution layer on the surface during scaling, calcium and magnesium ion concentration is used to correct this absolute value at the same time. If the concentration of calcium and magnesium ions is high, the absolute value threshold can be increased, which means that the occurrence time of the dense pollution layer will be advanced, and if the concentration of calcium and magnesium ions is low, the absolute value threshold can be decreased, which means that the occurrence time of the dense pollution layer will be delayed.

[0053] The evaporation unit evaporates the pre-treated water to achieve water separation and concentration. The operating conditions of the evaporation unit may include temperature, pressure, flow rate, etc. The specific parameters can be set according to actual needs.

[0054] The evaporation mentioned in the present invention can be selected from the following:

[0055] Multi-effect evaporation: Multi-effect evaporation is to connect the evaporators in series so that the steam and condensed water between the evaporators can exchange heat, thereby improving energy efficiency and evaporation efficiency.

[0056] Flash evaporation: Flash evaporation is to release high-pressure liquid into a low-pressure area through a throttle valve, causing it to evaporate instantly to obtain condensed water.

[0057] Thin film evaporation: Thin film evaporation is to pass the liquid through the thin film evaporator to form a thin film layer on the surface of the film, and then obtain condensed water by heating and evaporation.

[0058] Freeze evaporation: Freeze evaporation is to cool the liquid to a low temperature through a condenser, and then evaporate it by heating to obtain condensed water.

[0059] Vacuum evaporation: Vacuum evaporation is carried out under low pressure conditions to reduce the boiling point of the liquid and thus improve the evaporation efficiency.

[0060] MVR evaporation: It is mechanical vapor recompression. During the MVR evaporation process, the liquid is heated to evaporate and generate steam. The steam is then compressed by a compressor to increase the temperature and pressure of the steam. The high-temperature and high-pressure steam is then sent back to the evaporator to heat the liquid, thus realizing a cycle of evaporation and concentration.

[0061] Example 1

[0062] The wastewater generated in the process of lithium extraction from salt lakes by adsorption-membrane separation is recycled. The wastewater generated in the process of lithium extraction mainly includes resin regeneration water, leaching water, top feed water, and nanofiltration concentrated water. After preliminary mixing, the main ions in the wastewater obtained are Na, K, Ca, Mg, and Cl. - 、SO4 2- etc., with a total salt content of 30-150 g / L.

[0063] First, adjust the pH value of the incoming water and add reagents to precipitate and flocculate precipitable harmful impurities, such as Ca and Mg, to delay the evaporator cleaning cycle. Then, most of the precipitates are removed through filtration equipment. The filtered liquid is further filtered through ultrafiltration equipment to remove suspended impurities before evaporation. MVR evaporation is used, the evaporation temperature is controlled at 95-105°C, the evaporation pressure is 50-100kPa, and the water recovery rate is above 65%.

[0064] Example 2

[0065] For the recycling of wastewater in the process of lithium extraction from salt lakes using the adsorption-membrane separation method, condensed water is obtained by evaporation and condensation through the evaporation system. The water entering the evaporation system can be salt lake brine, adsorption tail brine, leaching water and top feed water.

[0066] Salt lake brine and adsorbed tail brine can be mixed in any proportion and then enter the pretreatment system, with a total salt content of 100-350g / L. The pretreatment system filters and removes suspended impurities, and then enters the evaporation system for evaporation and condensation to obtain a condensate water reuse system. The evaporated concentrate can be mixed with brine and returned to the lithium extraction system to improve lithium recovery. The evaporation system uses a four-effect evaporation system with an evaporation temperature of 100°C, an evaporation pressure of 60kPa, and a water recovery rate of 41%.

[0067] For rinse water and top feed water, the conductivity of the effluent can be tested with a conductivity meter to accurately obtain the effluent with different salt content. The effluent with a conductivity less than 5mS / cm is directly reused in the system. The effluent with a conductivity no greater than 200mS / cm is collected and, after simple filtration, sent to the evaporation system. The evaporation system uses MVR evaporation, with an evaporation temperature of 90°C, an evaporation pressure of 75kPa, and a water recovery rate of 88%. The effluent with a conductivity greater than 200mS / cm enters the tail brine system.

[0068] Example 3

[0069] In the process of extracting lithium from salt lakes using methods such as adsorption, membrane separation, electrodialysis, electro-deintercalation, and solar ponds with lithium carbonate as the final product, a lithium precipitated mother liquor will be produced in the process of finally obtaining the lithium carbonate product. The main components of the mother liquor are sodium carbonate, sodium chloride, lithium chloride, and water. The pH value of the mother liquor is alkaline, and the total salt content is 100-200g / L.

[0070] First, a pretreatment system is used to filter and remove suspended impurities, and then the sodium carbonate and chloride salts are separated through a pretreatment nanofiltration membrane system. The nanofiltration concentrated water is directly reused in the sodium carbonate preparation link, and nanofiltration product water mainly containing sodium chloride and lithium chloride is obtained.

[0071] The nanofiltration water can directly enter the evaporation system for evaporation operation. The evaporation adopts double-effect evaporation, the evaporation temperature is controlled at 100℃, the evaporation pressure is 80kPa, and the water recovery rate is 89%.

[0072] Example 4

[0073] Wastewater is recycled during the lithium extraction process from salt lakes using the electro-deintercalation-membrane separation method. The main products produced during the lithium extraction process are lithium extraction tail brine, nanofiltration concentrated water, and resin regeneration wastewater. Since the lithium content in the lithium extraction tail brine is relatively high, and the divalent ion content in the nanofiltration concentrated water and resin regeneration wastewater is relatively high, different systems are used for evaporation water recovery.

[0074] For lithium extraction tail brine, after being filtered through the pretreatment system to remove suspended impurities, it is directly sent to the evaporation system. Scale inhibitors are added according to the water quality. Then, the mother liquor obtained by evaporation is mixed with the raw brine and sent into the lithium extraction system to improve the lithium recovery rate. The evaporated condensed water is reused in the system. The evaporation system adopts four-effect evaporation, with an evaporation temperature of 105°C, an evaporation pressure of 80kPa, and a water recovery rate of 40%.

[0075] For nanofiltration concentrated water and resin regeneration wastewater, most of the impurity ions such as Ca and Mg that are prone to precipitation are removed through precipitation in the pretreatment system. The filtered water is then passed through a multi-media filter, ultrafiltration or other filter to remove suspended impurities. The water is then sent to the evaporation system, which uses MVR evaporation with an evaporation temperature of 95°C, an evaporation pressure of 75kPa, and a water recovery rate of 70%.

[0076] Example 5

[0077] Lithium-containing brine is extracted by adsorption using a titanium-based adsorbent. The eluate is then concentrated by nanofiltration, and the nanofiltration permeate is purified using an ion exchange resin to deeply remove divalent calcium and magnesium ions. Lithium is then precipitated and separated by adding sodium carbonate to obtain a lithium carbonate product. The adsorbent eluate, top material wastewater, nanofiltration membrane concentrate, resin regeneration wastewater, and lithium carbonate separation mother liquor generated in the above process are mixed to stabilize the concentrations of the various impurity components. The pH values ​​of the various wastewaters are then used to neutralize each other after mixing. The mixed wastewater has a pH of 6.0-6.5, a COD of 20-100 ppm, and a hardness of 3000-6500 ppm.

[0078] The obtained mixed solution was concentrated by nanofiltration membrane using a polyamide nanofiltration membrane with a molecular weight cutoff of 800Da. The nanofiltration pressure range under different test conditions was between 1.0-1.5Mpa. The COD value was monitored by an online COD detector, and the retention rate of organic matter was calculated based on the COD value.

[0079] C 进 is the concentration of organic matter entering the membrane system, C 出 The concentration of organic matter after passing through the membrane system. After different operation times, the nanofiltration membrane was cleaned with the main components of the cleaning agent: pH 10.0, 3% sodium tripolyphosphate solution, 1.5% tetrasodium EDTA, temperature 35-40℃, and time 45 minutes.

[0080] As shown in Figure 3, in a typical filtration operation, as time goes by, the amount of fouling layer deposition and density change, the COD retention rate on the nanofiltration membrane surface will also change accordingly. The increase is faster in the initial stage, and after the densification occurs in the later stage, the increase in the retention rate is no longer obvious. Take 5 minutes as the time period, and the increase rate of the retention rate during this period is less than 0.4×H 0.1 ×A% threshold, it is considered that densification pollution begins to occur. Where A is the absolute value of the increase rate of COD retention rate, A is 0.2; H is the water hardness, ppm, 0.4×H 0.1 As a correction item.

[0081] According to the above method, nanofiltration pretreatment was carried out under different water hardness conditions. The nanofiltration concentration test was stopped at the time before densification and 30 minutes after densification, and the above membrane cleaning was carried out. The flux recovery rate after cleaning was calculated. For comparison, A% was used as the threshold for judgment. The results under the two test conditions are as follows:

[0082] As can be seen from the above table, the determination method of the present invention can distinguish the time nodes of densification membrane pollution, and can effectively guide the frequency of membrane cleaning, which helps to reduce water resource consumption.

Claims

1. A low water consumption salt lake lithium extraction process, characterized in that: The steps include: Obtaining saline wastewater from the lithium extraction process in salt lakes and pre-treating it; After evaporating and condensing the salty water obtained from the pretreatment, recycled water is obtained; The recovered water is returned to the process of extracting lithium from salt lakes.

2. The low water consumption salt lake lithium extraction process according to claim 1, characterized in that: The lithium extraction from salt lake is carried out by any one or a combination of the following methods: adsorption extraction, solvent extraction extraction, ion exchange extraction, electrodialysis extraction, membrane separation extraction, and electrochemical deintercalation extraction.

3. The low water consumption salt lake lithium extraction process according to claim 1, characterized in that: For the combination of lithium extraction by adsorption and lithium extraction by membrane separation, the salt water refers to one or a combination of brine, adsorption tail brine, leaching water, top water, nanofiltration concentrated water, refined resin regeneration wastewater, and lithium precipitation mother liquor.

4. The low water consumption salt lake lithium extraction process according to claim 1, characterized in that: The pretreatment refers to one or a combination of oxidation, adsorption, flocculation, filtration, precipitation, membrane separation, sedimentation, and neutralization.

5. The low water consumption salt lake lithium extraction process according to claim 4, characterized in that: The pretreatment is nanofiltration membrane filtration. After the nanofiltration membrane filters the salty wastewater, the permeate is returned to the lithium extraction process. The start time of the nanofiltration membrane cleaning process is calculated according to the following method: Take a certain time, and during the nanofiltration operation, monitor the COD values ​​on the retention side and the permeation side, and calculate the increase rate of the COD retention rate on the nanofiltration membrane surface during this time interval; If the rate of increase of the retention rate in a period of time is less than α×H β ×A% threshold, it is considered that densification pollution has begun to occur, so the nanofiltration process is stopped and membrane cleaning is started; where α and β are coefficients, H is the water hardness in ppm, and A is the rate of change of retention rate.

6. The low water consumption salt lake lithium extraction process according to claim 1, characterized in that: The evaporation process adopts one or a combination of multiple-effect evaporation, flash evaporation, thin film evaporation, freezing evaporation, vacuum evaporation and MVR evaporation.

7. A low water consumption salt lake lithium extraction system, characterized in that: include: Pretreatment system, used to pretreat the brine during lithium extraction from salt lakes; The evaporation and condensation system is used to evaporate and condense the salt water obtained from pretreatment to obtain recycled water.

8. The low water consumption salt lake lithium extraction system according to claim 7, characterized in that: The salt lake lithium extraction adopts any one or a combination of adsorption lithium extraction system, solvent extraction lithium extraction system, ion exchange lithium extraction system, electrodialysis lithium extraction system, membrane separation lithium extraction system, and electrochemical deintercalation lithium extraction system.

9. The low water consumption salt lake lithium extraction system according to claim 7, characterized in that: The pretreatment system refers to one or a combination of oxidation system, adsorption system, flocculation system, filtration system, and sedimentation system.

10. The low water consumption salt lake lithium extraction system according to claim 7, characterized in that: The evaporation and condensation system adopts one or a combination of multiple-effect evaporation system, flash evaporation system, thin film evaporation system, freezing evaporation system, vacuum evaporation system, and MVR evaporation system.

Images