A system and method for comprehensive recovery of lithium, potassium and sodium resources in salt lake brine

Abstract

The application discloses a system and method for comprehensive recovery of lithium, potassium and sodium resources in salt lake brine. The recovery system comprises an ultrafiltration device, a nanofiltration device, an adsorption device, a sand filtration-ultrafiltration combined treatment device, a qualified liquid reverse osmosis device, a boron removal resin, a lithium chloride MVR device, a lithium precipitation device and a separation and recovery device. The system separates divalent ions such as calcium, magnesium, sulfate and carbonate in the brine by using a membrane method, and then uses adsorption, membrane method and evaporation concentration to reduce the evaporation scale, extract high-purity lithium resources under low energy consumption and low cost conditions. The unqualified adsorption liquid is treated by a low-temperature evaporation device, a sodium chloride hot melting device and a potassium chloride cold separation device to realize the recovery of potassium and sodium resources in the salt lake brine. Therefore, the application can realize the recovery and utilization of multiple resources such as lithium carbonate, sodium carbonate, sodium chloride and potassium chloride, and the lithium, sodium and potassium are recovered by parallel resource recovery routes without affecting each other. The lithium extraction process route is short, the time is fast, the overall system has more membranes and less evaporation equipment, the operation cost is low, and the investment return rate is high.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of salt lake brine resource recovery, and particularly relates to a system and method for comprehensive recovery of lithium, potassium and sodium resources in salt lake brine. BACKGROUND

[0002] Salt lake brine refers to water bodies containing high-concentration salts and minerals existing in salt lakes, which are formed by long-term accumulation and evaporation of natural underground water. The salt lake brine is a kind of natural resource and has a wide range of application fields. The salt lake brine contains a large amount of lithium resources. Compared with hard rock mining of lithium, the development of lithium resources in the salt lake brine has the advantages of simple process, low cost, high product purity and strong market competitiveness, and gradually becomes the main way for the development and production of lithium at home and abroad.

[0003] In addition to lithium, the salt lake brine also contains a large amount of sodium, potassium, boron, magnesium and other elements, so it is necessary to separate and purify the impurity ions in the process of extracting lithium, among which the separation of magnesium and lithium is the most difficult. Compared with foreign countries, the magnesium-lithium ratio of most salt lakes in China (such as Qinghai salt lake) is high, the sodium-lithium ratio is high, and the separation is difficult, which leads to high lithium loss rate, high development cost and low comprehensive exploitation and utilization degree in the process of extracting lithium.

[0004] Due to different parameters such as composition, magnesium-lithium ratio and sodium-lithium ratio, various processes such as precipitation method, calcination method, adsorption method, extraction method and solar pond + carbonization method are usually used for lithium extraction in salt lakes, and usually one process is used for one type of salt lake.

[0005] The principle of solvent extraction method is to add a second liquid which is not soluble in the solution but has a large solubility for the solute in the solution containing the solute, and to promote part of the solute to migrate into the second phase through the interface by using the solubility difference of the solute in the two phases, so as to achieve the purpose of phase transfer and concentration. The solvent extraction method is suitable for treating high magnesium-lithium ratio brine, and the process flow is long, the extractant is organic matter, and the environmental pressure is large.

[0006] The precipitation method is to use solar energy to evaporate, concentrate and produce salt from lithium-containing brine in an evaporation pond, and then to separate and purify the lithium by removing boron, calcium, magnesium and other elements. When the lithium content reaches an appropriate concentration, lithium is precipitated in the form of lithium carbonate by using carbonate as a precipitant. The precipitation method is mature and has high reliability, but it is not suitable for brine containing a large amount of alkaline earth metals and brine with low lithium concentration, and the efficiency is not high.

[0007] The calcination leaching method is to evaporate the brine after boron extraction to obtain old brine, then add a precipitant to the old brine to make magnesium and lithium come out in the form of precipitation, and finally, the precipitate is calcined and decomposed, and through carbonation, lithium is dissolved in the solution and magnesium remains in the precipitate, so as to realize the separation of magnesium and lithium. The calcination leaching method can comprehensively utilize magnesium and lithium resources, but the process flow is complex, the environmental pollution is serious, the energy consumption is high, the cost is high, and the investment is large.

[0008] The adsorption method is to use an adsorbent with selective adsorption of lithium ions to adsorb lithium ions, and then elute the lithium ions to separate lithium ions from other impurity ions. Therefore, the key is to seek an adsorbent with good adsorption selectivity, high recycling rate and relatively low cost. For halide water with low lithium content, the adsorption method is a good method. The adsorption method is simple, and is particularly suitable for the separation of lithium in halide water. However, the process has high requirements for the adsorbent, the cost of the adsorbent is high, and the aluminum-based adsorbent has the problem of high consumption of fresh water, and the titanium-based adsorbent has high acid and alkali consumption.

[0009] The selective semi-permeable membrane method is divided into nanofiltration membrane method and electrodialysis method. The nanofiltration membrane method is a pressure-driven membrane separation between reverse osmosis and ultrafiltration, which can effectively separate monovalent and multivalent ions. The electrodialysis method uses a one-stage or multi-stage electrodialyzer, one-way cation selective ion exchange membrane and one-way anion selective ion exchange membrane to cyclically concentrate lithium, and adds soda ash to precipitate lithium carbonate. This method is suitable for relatively high magnesium and lithium halide water to separate lithium from magnesium and other ions, but the lithium content must be above 2 g / L, otherwise the power consumption is too large.

[0010] Therefore, the above various lithium extraction processes have some defects: the extraction method has a long process flow, is easy to cause equipment corrosion, and the extractant usually has water solubility, flammability, volatility and other physical and chemical properties. The precipitation method has a long process flow, large material consumption and complex operation, and is only suitable for low magnesium-lithium ratio salt lakes. The calcination method has a complex process, the equipment is easy to corrode, and the energy consumption is high. The adsorption method has poor flowability and adsorbability due to the powder of the adsorbent, which easily causes the decline of the adsorption performance. The selective semi-permeable membrane method is a new separation technology, which has ultrafiltration, nanofiltration and reverse osmosis technologies, and can effectively separate one-valent and two-valent anions and cations to realize the recovery and purification of lithium ions. However, the existing lithium purification technology based on membrane separation still has problems of poor purification efficiency and low purity, and the cost of the lithium purification technology based on membrane separation is generally high.

[0011] In addition, salt lake brine usually contains sodium chloride, magnesium chloride, potassium chloride and other salts, as well as sulfate, carbonate and other minerals. The concentration of these salts and minerals is higher than that of general seawater. Therefore, it is of great significance to recover lithium, potassium and sodium elements from salt lake brine and apply them in industrial production. Therefore, it is urgent to propose a new technical solution to solve the problems in the prior art and comprehensively recover resources in salt lake brine. SUMMARY

[0012] The present application provides a system and method for comprehensive recovery of lithium, potassium and sodium resources in salt lake brine to solve the problems of low recovery rate and high recovery and processing cost of existing salt lake brine resources.

[0013] In order to achieve the above purpose, the present application provides the following technical solution:

[0014] In a first aspect, the application provides a system for comprehensive recovery of lithium, potassium and sodium resources in salt lake brine, comprising, in sequence, an ultrafiltration device, a nanofiltration device, an adsorption device, a sand filtration-ultrafiltration combined treatment device, a qualified liquid reverse osmosis device, a boron removal resin, a lithium chloride MVR device, a lithium precipitation device and a separation and recovery device.

[0015] The water inlet end of the ultrafiltration device is connected to a pipeline for conveying salt lake brine, the water outlet end of the ultrafiltration device is connected to the nanofiltration device, the nanofiltration device is connected to the adsorption device, the qualified liquid outlet of the adsorption device is connected to the inlet end of the sand filtration-ultrafiltration combined treatment device, the water outlet end of the sand filtration-ultrafiltration combined treatment device is connected to the water inlet end of the qualified liquid reverse osmosis device, the concentrated water outlet end of the qualified liquid reverse osmosis device is connected to the boron removal resin, the water outlet end of the boron removal resin is connected to the water inlet end of the lithium chloride MVR device, the water outlet end of the lithium chloride MVR device is connected to the liquid inlet of the lithium precipitation device, a sodium carbonate addition port is provided on the lithium precipitation device, the sodium carbonate in the lithium precipitation device reacts with the lithium chloride solution to generate lithium carbonate precipitate, and the discharge port of the lithium precipitation device is connected to the separation and recovery device, which is used to realize solid-liquid separation and recover the lithium carbonate precipitate.

[0016] Further comprising, in sequence, a low-temperature evaporation device, a sodium chloride hot melting device and a potassium chloride cold separation device connected to the unqualified liquid discharge outlet of the adsorption device.

[0017] In the above technical solution, optionally, the low-temperature evaporation device comprises a first solar low-temperature evaporation module and a second solar low-temperature evaporation module, the inlet end of the first solar low-temperature evaporation module is connected to the unqualified liquid discharge outlet of the adsorption device, the sodium chloride hot melting device is a solar hot melting device, the inlet end of the solar hot melting device is connected to the outlet end of the second solar low-temperature evaporation module, and the outlet end of the solar hot melting device is connected to the potassium chloride cold separation device.

[0018] In the above technical solution, optionally, the adsorption device is an aluminum adsorption device, and the aluminum adsorption device has a liquid inlet, a qualified liquid discharge outlet, a water addition port and an unqualified liquid discharge outlet.

[0019] Optionally, the nanofiltration device comprises a plurality of nanofiltration modules, and the plurality of nanofiltration modules at least comprise a first nanofiltration module and a second nanofiltration module; the water inlet end of the first nanofiltration module is connected to the water outlet end of the ultrafiltration device, the water outlet end of the first nanofiltration module is connected to the water inlet end of the second nanofiltration module through a connecting pipe, an alkali addition port is provided on the connecting pipe, and the water outlet end of the second nanofiltration module is connected to a carbon remover.

[0020] Optionally, the carbon remover has a first inlet, an exhaust outlet and a liquid outlet, the water outlet of the secondary nanofiltration module is connected to the first inlet through a connecting pipeline, an acid inlet is arranged on the connecting pipeline, the exhaust outlet is used to exhaust carbon dioxide gas, and the liquid outlet is connected to the liquid inlet of the aluminum adsorption device; the qualified liquid outlet of the aluminum adsorption device is connected to the inlet end of the sand filter-ultrafiltration combined treatment device; and the unqualified liquid outlet of the aluminum adsorption device is connected to the low-temperature evaporation device.

[0021] Optionally, the carbon remover further has a second inlet, the second inlet is connected to a sodium carbonate nanofiltration device; the inlet end of the sodium carbonate nanofiltration device is connected to the concentrated water outlet end of the secondary nanofiltration module through a connecting pipeline, and a water inlet is arranged on the connecting pipeline; the water outlet of the sodium carbonate nanofiltration device is connected to the second inlet, the concentrated water outlet end of the sodium carbonate nanofiltration device is connected to a sodium carbonate recovery device, and the discharge outlet of the sodium carbonate recovery device is connected to the sodium carbonate adding inlet on the lithium precipitation device.

[0022] Optionally, the sodium carbonate recovery device comprises a sodium carbonate MVR device and a boron removal device.

[0023] In the above technical solution, optionally, the tail halogen nanofiltration device and the bipolar membrane electrodialysis device are further included, the tail halogen nanofiltration device and the primary solar low-temperature evaporation module are respectively connected to the unqualified liquid outlet of the adsorption device, the water outlet end of the tail halogen nanofiltration device is connected to the inlet end of the bipolar membrane electrodialysis device, the concentrated water outlet end of the tail halogen nanofiltration device is connected to the inlet end of the primary solar low-temperature evaporation module; the pure water outlet end of the bipolar membrane electrodialysis device is connected to the inlet end of the primary solar low-temperature evaporation module, the anode of the bipolar membrane electrodialysis device forms liquid alkali, and the cathode of the bipolar membrane electrodialysis device forms hydrochloric acid.

[0024] In the above technical solution, optionally, the adsorption device is a titanium adsorption device, and the titanium adsorption device has a water inlet, an acid water adding inlet, a qualified liquid outlet and an unqualified liquid outlet.

[0025] Optionally, the nanofiltration device comprises a primary nanofiltration module, the water inlet end of the primary nanofiltration module is connected to the water outlet end of the ultrafiltration device, the concentrated water outlet end of the primary nanofiltration module is connected to the water inlet of the titanium adsorption device, the qualified liquid outlet of the titanium adsorption device is connected to the inlet end of the sand filter-ultrafiltration combined treatment device; and the unqualified liquid outlet of the titanium adsorption device is connected to a tail halogen discharge pipeline, and unqualified liquid is discharged to a salt lake through the tail halogen discharge pipeline.

[0026] Optionally, the titanium adsorption device further has a lithium precipitation mother liquor adding port, the lithium precipitation mother liquor adding port is connected with the mother liquor discharge port of the lithium precipitation device, and the lithium precipitation mother liquor adding port is connected with the regeneration liquid discharge port of the boron removal resin.

[0027] In the technical scheme, optionally, the water production end of the qualified liquid reverse osmosis device is connected with the inlet end of a water production reverse osmosis device, the concentrated water outlet end of the water production reverse osmosis device is connected with the inlet end of the sand filtration and ultrafiltration combined treatment device, and the water production end of the water production reverse osmosis device is connected with the user water end.

[0028] In the technical scheme, optionally, the sand filtration and ultrafiltration combined treatment device comprises a sand bed and an ultrafiltration membrane assembly connected on the water outlet side of the sand bed.

[0029] In the technical scheme, optionally, the lithium chloride MVR device comprises an evaporator, a compressor, a heat exchanger, a condenser, a separator and a recirculation pump, the evaporator is used to heat the lithium chloride solution and make it generate steam, the compressor is used to compress the steam into high-temperature and high-pressure steam, the heat exchanger is used to exchange heat between the high-temperature and high-pressure steam and the lithium chloride solution, the condenser is used to cool the high-temperature and high-pressure steam, the separator is used to separate the condensed water and the lithium chloride solution, and the recirculation pump is used to circulate the lithium chloride solution in the separator back to the evaporator, so as to concentrate the lithium chloride solution and obtain lithium chloride concentrated solution; the lithium chloride concentrated solution enters the lithium precipitation device, the lithium precipitation device has a reaction chamber, lithium chloride and sodium carbonate react in the reaction chamber to generate lithium carbonate precipitate, the aqueous lithium carbonate precipitate in the reaction chamber enters the separation and recovery device to realize solid-liquid separation and recover the lithium carbonate precipitate; the separation and recovery device comprises a lithium carbonate centrifuge.

[0030] In a second aspect, the application further provides a method for comprehensively recovering lithium, potassium and sodium resources in salt lake brine, which uses the above-mentioned system for comprehensively recovering lithium, potassium and sodium resources in salt lake brine, and comprises the following steps:

[0031] S1: inputting the salt lake brine into an ultrafiltration device to remove suspended solids and colloids in the salt lake brine through the ultrafiltration device;

[0032] S2: inputting the salt lake brine treated by the ultrafiltration device into a primary nanofiltration module, and using the primary nanofiltration module to remove sulfate and carbonate in the salt lake brine;

[0033] S3: discharging the liquid from the concentrated water outlet end of the primary nanofiltration module into a titanium adsorption device, and using the titanium adsorption device to adsorb lithium in the liquid;

[0034] S4: The adsorption qualified liquid discharged from the titanium adsorption device enters the sand filtration and ultrafiltration combined treatment device, which is used to remove liquid suspended solids and colloids and reduce turbidity;

[0035] S5: The liquid treated by the sand filtration and ultrafiltration combined treatment device enters the qualified liquid reverse osmosis device, and the liquid discharged from the concentrated water outlet end of the qualified liquid reverse osmosis device enters the boron removal resin for boron removal;

[0036] S6: The liquid flowing out from the water production end of the boron removal resin enters the lithium chloride MVR device, and the lithium chloride MVR device concentrates the liquid entering it;

[0037] S7: The lithium chloride concentrated liquid obtained by concentrating the lithium chloride MVR device enters the lithium precipitation device to react with a sodium carbonate solution, lithium carbonate precipitate is generated in the solution, and the generated lithium carbonate precipitate is separated and recovered from the solution by the separation and recovery device.

[0038] In a third aspect, the application also provides another method for comprehensively recovering lithium, potassium and sodium resources in salt lake brine, which uses the above-mentioned system for comprehensively recovering lithium, potassium and sodium resources in salt lake brine. The method for comprehensively recovering lithium, potassium and sodium resources includes the following steps:

[0039] S1: Inputting the salt lake brine into an ultrafiltration device, and removing suspended solids and colloids in the salt lake brine by the ultrafiltration device;

[0040] S2: The salt lake brine treated by the ultrafiltration device enters a primary nanofiltration module, and the primary nanofiltration module is used to remove sulfate and carbonate in the salt lake brine;

[0041] S3: The liquid discharged from the water production end of the primary nanofiltration module enters a secondary nanofiltration module to remove carbonate;

[0042] S4: The liquid discharged from the water production end of the secondary nanofiltration module enters a carbon removal device to remove bicarbonate;

[0043] S5: The liquid discharged from the carbon removal device enters an aluminum adsorption device, and the aluminum adsorption device is used to adsorb lithium in the liquid;

[0044] S6: The adsorption qualified liquid discharged from the aluminum adsorption device enters the sand filter-ultrafiltration combined treatment device, which is used to remove liquid suspended matter and colloid and reduce turbidity; a part of the unqualified liquid discharged from the aluminum adsorption device is made into sodium chloride through the low-temperature evaporation device and the sodium chloride hot melting device, and is made into potassium chloride through the potassium chloride cold separation device; another part of the unqualified liquid discharged from the aluminum adsorption device is discharged into the tail brine nanofiltration device, the water discharged from the water production end of the tail brine nanofiltration device is discharged into the bipolar membrane electrodialysis device, liquid caustic soda is recovered at the anode of the bipolar membrane electrodialysis device, and hydrochloric acid is recovered at the cathode of the bipolar membrane electrodialysis device; the water discharged from the concentrated water outlet end of the tail brine nanofiltration device is made into sodium chloride through the low-temperature evaporation device and the sodium chloride hot melting device, and is made into potassium chloride through the potassium chloride cold separation device;

[0045] S7: The liquid treated by the sand filter-ultrafiltration combined treatment device enters the qualified liquid reverse osmosis device, and the liquid discharged from the concentrated water outlet end of the qualified liquid reverse osmosis device enters the boron removal resin for boron removal;

[0046] S8: The liquid flowing out from the water production end of the boron removal resin enters the lithium chloride MVR device, and the lithium chloride MVR device concentrates the liquid entering it;

[0047] S9: The lithium chloride concentrated liquid obtained by concentrating the lithium chloride MVR device enters the lithium precipitation device to react with the sodium carbonate solution, lithium carbonate precipitate is generated in the solution, and the generated lithium carbonate precipitate is separated and recovered from the solution by the separation and recovery device.

[0048] Compared with the prior art, the present application has the following beneficial effects:

[0049] 1. The application provides a kind of lithium potassium sodium resource comprehensive recovery system in salt lake brine, including ultrafiltration device, nanofiltration device, adsorption device, sand filter ultrafiltration combination processing device, qualified liquid reverse osmosis device, boron removal resin, lithium chloride MVR device, lithium precipitation device and separation and recovery device connected in sequence, it is functionally treated to salt lake brine by above-mentioned device, by ultrafiltration, nanofiltration, sand filter ultrafiltration combination processing device and reverse osmosis device, realize membrane method treatment, by adsorption device and boron removal resin, realize adsorption treatment, i.e. the application adopts the original brine membrane method coupling adsorption lithium extraction process, utilize membrane method to separate calcium, magnesium, sulfate, carbonate and other divalent ions and lithium and other monovalent ions, then utilize adsorption, membrane method and evaporation concentration, reduce evaporation scale, achieve the purpose of high-purity lithium resource extraction under the condition of low energy consumption and low cost;In addition, the method of membrane method and adsorption combination can completely remove impurities, improve the purity of lithium, reduce the consumption of adsorbent, and the adsorption and desorption efficiency is high;Further, the lithium potassium sodium resource comprehensive recovery system provided by the application further comprises a chloride production unit composed of a low-temperature evaporation device, a sodium chloride hot melting device and a potassium chloride cold separation device, and the unqualified liquid discharged from the adsorption device is discharged into the low-temperature evaporation device and the sodium chloride hot melting device to prepare sodium chloride, and then the liquid in the sodium chloride hot melting device is discharged into the potassium chloride cold separation device for cooling. Based on the temperature difference between sodium chloride and potassium chloride, the sodium resource and potassium resource in the salt lake brine are recovered. Therefore, the lithium potassium sodium resource comprehensive recovery system in salt lake brine provided by the application can improve the recovery rate of salt lake brine resources, comprehensively recover lithium, potassium and sodium, and reduce energy consumption, operating and investment costs and processing costs through the original brine membrane method coupling adsorption lithium extraction process.

[0050] 2. The lithium potassium sodium resource comprehensive recovery system in salt lake brine provided by the application includes two lithium extraction routes, one potassium chloride and sodium chloride preparation route (potassium and sodium recovery route), one sodium carbonate preparation route, and one hydrochloric acid liquid alkali preparation route. Each processing route is parallel, and each route can be independently constructed and put into use without affecting each other. In particular, lithium resources are very valuable. In the application, the lithium extraction route and the potassium and sodium recovery route are parallel. When actually constructing and putting into use, the lithium extraction route can be preferentially constructed according to the actual situation.

[0051] 3. For the original brine with low lithium content and mineralization degree, and high sodium sulfate and sodium chloride content, the traditional process is to directly use solar energy to concentrate the lithium-containing brine, which has the problems of large water quantity, low efficiency, and difficult post-treatment of magnesium carbonate after concentration due to easy scaling. The lithium potassium sodium resource comprehensive recovery system provided by the application can extract high-purity lithium from the original brine with low lithium content and mineralization degree, and high sodium sulfate and sodium chloride content. The membrane method is used to remove calcium, magnesium, sulfate, carbonate and other easy scaling factors. The adsorption, membrane method and evaporation concentration are used, which not only reduces the evaporation scale and energy consumption, but also completely removes impurities to achieve high-purity lithium extraction.

[0052] 4. Traditional adsorption methods suffer from problems such as high acid and alkali consumption and high adsorbent cost of titanium-based adsorbents, and small capacity and high freshwater consumption of aluminum-based adsorbents. The lithium, potassium and sodium resource integrated recovery system provided in this application combines titanium adsorption devices and aluminum adsorption devices with membrane separation technologies (such as ultrafiltration devices, nanofiltration devices, sand filtration and ultrafiltration combined treatment devices and reverse osmosis devices) to realize membrane separation coupled adsorption process, which specifically solves the above problems, reduces adsorbent consumption, reduces freshwater resource consumption, and reduces overall operating and investment costs.

[0053] 5. In the lithium, potassium and sodium resource integrated recovery system provided in this application, there are more membrane separation devices and fewer evaporation devices and high-temperature devices, which reduces the probability of equipment failure and the amount and difficulty of maintenance.

[0054] 6. The ultrafiltration device in the lithium, potassium and sodium resource integrated recovery system provided in this application is preferably a submerged ultrafiltration device. Compared with the traditional multi-media + external pressure ultrafiltration, the submerged ultrafiltration device used in this application is resistant to extremely high suspended solids, resists high turbidity shocks from incoming water, has strong shock resistance, is easy to operate and manage, produces good effluent quality, has a recovery rate of up to 95%, low operating costs, and comparable investment costs.

[0055] 7. Based on the lithium, potassium and sodium resource integrated recovery system provided in this application, this application also provides a corresponding lithium extraction method from salt lakes. The lithium extraction route is short and efficient. Compared with traditional lithium extraction methods, it can save about 20% of electricity and reduce the total operating cost by 10-15%. Under the condition of comparable investment costs, the lithium extraction method provided in this application can obtain a higher rate of return on investment. Attached Figure Description

[0056] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the embodiments will be briefly described below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. It should be understood that the specific shapes and structures shown in the drawings should not generally be regarded as limiting conditions for implementing this application; for example, based on the technical concepts disclosed in this application and the exemplary drawings, those skilled in the art are able to easily make conventional adjustments or further optimizations to the addition / reduction / classification, specific shapes, positional relationships, connection methods, and size ratios of certain units (components).

[0057] Figure 1 This is a schematic diagram of the processing flow of the comprehensive recovery system for lithium, potassium, and sodium resources in salt lake brine provided in this application, as one embodiment.

[0058] Figure 2 Is Figure 1Fig. 1 is a schematic diagram of a treatment process of a lithium extraction route remaining after removing a potassium and sodium resource recovery route and a hydrochloric acid and alkali recovery route from the basis;

[0059] Figure 3 Fig. 2 is a schematic diagram of a treatment process of a first lithium extraction route using a titanium adsorption device in the present application;

[0060] Figure 4 Fig. 3 is a schematic diagram of a partial treatment process of a second lithium extraction route using an aluminum adsorption device in the present application, which only shows the treatment process between a secondary nanofiltration module and sand filtration + ultrafiltration;

[0061] Figure 5 Fig. 4 is a schematic diagram of a treatment process of a sodium carbonate recovery route provided by the present application, which only shows the treatment process after a secondary nanofiltration module. DETAILED DESCRIPTION

[0062] The present application will be further described in detail below with reference to the accompanying drawings.

[0063] In the description of the present application: unless otherwise specified, the meaning of "a plurality of" is two or more. The terms "first", "second", "third" and the like in the present application are intended to distinguish the objects referred to, and do not have special technical connotations (for example, should not be understood as emphasizing importance or order, etc.). The expressions "include", "contain", "have" and the like also mean "not limited to" (certain units, components, materials, steps, etc.).

[0064] Example 1

[0065] In order to solve the problems existing in the prior art, the present application provides a lithium, potassium and sodium resource comprehensive recovery system in salt lake brine, which can comprehensively recover low-grade lithium ore with low lithium content and low mineralization. The process treatment route of the lithium, potassium and sodium resource comprehensive recovery system in salt lake brine provided by the present application considers the separation of mono- and divalent ions, removes alkalinity and boron, and at the same time guarantees the resource recovery and utilization of sodium carbonate, sodium chloride, potassium chloride and lithium carbonate. Overall, the lithium, potassium and sodium resource comprehensive recovery system in salt lake brine provided by the present application adopts a raw brine membrane method coupled with an adsorption lithium extraction process route, which mainly includes raw brine filtration, membrane separation, adsorption section, membrane purification and concentration section, bipolar membrane electrolysis section, lithium chloride evaporation and crystallization section, lithium precipitation section and bipolar membrane acid and alkali production section, etc.

[0066] The salt lake brine lithium potassium sodium resource comprehensive recovery system provided by the application mainly comprises an ultrafiltration device, a nanofiltration device, an adsorption device (a titanium adsorption device and an aluminum adsorption device), a sand filtration-ultrafiltration combined treatment device, a qualified liquid reverse osmosis device, a boron removal resin, a lithium chloride MVR device, a lithium precipitation device and a separation and recovery device, which realize salt lake lithium extraction; further comprising a low-temperature evaporation device, a sodium chloride hot melting device and a potassium chloride cold separation device, which realize salt lake brine potassium sodium resource recovery; further comprising a tail brine nanofiltration device and a bipolar membrane electrodialysis device, which realize tail brine reprocessing and utilization after lithium extraction adsorption, and can prepare hydrochloric acid and liquid caustic soda. The above-mentioned various functional devices are used in sequence according to the process requirements in the whole process treatment route, and realize the purpose of comprehensive recovery of salt lake brine resources.

[0067] The structure principle of the salt lake brine lithium potassium sodium resource comprehensive recovery system provided by the application and the function structure of each device in the system architecture are described in detail below.

[0068] I. Ultrafiltration device

[0069] In the application, the salt lake brine can be directly sent into the membrane tank of the ultrafiltration device, or the salt lake brine can be preliminarily filtered according to specific process conditions and then discharged into the membrane tank.

[0070] In the application, submerged flat plate ultrafiltration is used to reduce the content of suspended solids in the salt lake brine, so as to meet the water inlet requirements of subsequent equipment. The ultrafiltration device in the application directly immerses the submerged flat plate ultrafiltration into the membrane tank, and uses a pump or siphon to realize negative pressure to suck water and dissolved small molecules out of the membrane, so as to remove suspended solids, colloidal particles and macromolecular organic matter in water and improve water clarity.

[0071] In the application, the ultrafiltration device can comprise a membrane tank, submerged ultrafiltration immersed in the membrane tank, and a suction pump, a cleaning pump and a backwashing air blower arranged outside the membrane tank. The submerged ultrafiltration in the membrane tank can be submerged flat plate ultrafiltration, which comprises one or more submerged ultrafiltration membrane assemblies.

[0072] The submerged ultrafiltration membrane module includes hollow fiber membranes fixed on a horizontal or vertical frame, and permeate water collecting pipes arranged at the top and bottom of the frame. Each collecting pipe contains a layer of special resin sealing the membrane fibers, so that the inner cavity of the membrane is connected to the pipe to collect product water. Several or dozens of membrane modules are connected to form a complete membrane tank. Several membrane tanks are connected in parallel and submerged in a membrane tank to form a membrane column, and several membrane columns are connected in parallel to form a membrane treatment system of different treatment scales. The operation mode of periodic backwashing and gentle and mild air scrubbing can reduce the membrane pollution rate. Unlike traditional pressure membrane filtration, the submerged ultrafiltration membrane operates under a lower negative pressure state. The principle is to use siphon or pump suction to perform negative pressure filtration from the outside to the inside to achieve low transmembrane pressure difference and stable operation of moderate membrane flux. The overall energy consumption cost of the submerged ultrafiltration membrane module is lower than that of pressure membrane filtration, and the main characteristics are as follows: 1) It can effectively separate solid and liquid, and the separation effect is much better than that of a traditional sedimentation tank. The effluent water quality is good, and the suspended solids and turbidity are close to zero, which can be directly reused, realizing the resource utilization of wastewater; 2) The membrane module design is standardized and modularized, and can adapt to different water treatment capacities, and the water supply scale is flexible; 3) It is beneficial to the interception, growth and reproduction of slow-growing nitrifying bacteria, and the system nitrification efficiency is improved. The membrane bioreactor (MBR) process formed by combining the submerged ultrafiltration membrane module with the biochemical process has better denitrification and phosphorus removal functions than the traditional biological treatment process.

[0073] Compared with pressure ultrafiltration, the submerged flat plate ultrafiltration device used in the application can tolerate high suspended solids content. The inlet water does not need to be filtered and can directly enter the high-strength membrane to obtain high-quality product water. However, the traditional pressure ultrafiltration usually needs to pass through a sand filter before entering the ultrafiltration. Therefore, the use of the submerged flat plate ultrafiltration device no longer needs a sand filter or a multi-medium filter, greatly simplifying the process; at the same time, negative pressure suction is adopted, the operating pressure is low, energy consumption is saved, and there is no risk of overpressure operation; in addition, an open membrane tank is adopted, the membrane fiber condition can be directly observed, and the operation and management are convenient.

[0074] In a specific installation application example, the working pressure of the submerged flat plate ultrafiltration device is -0.02 MPa to -0.08 MPa, the filtration period is 30 to 50 min, the total duration of backwashing is 90 seconds, and the design flux is not greater than 20 L / m 2 .h, the water backwashing intensity is 25 to 50 L / m 2 .h, the self-water rate is ≤5%, and the product water turbidity is <1 NTU.

[0075] II. Nanofiltration device

[0076] The nanofiltration device is used to remove sulfate and carbonate in salt lake brine. The nanofiltration device includes multiple nanofiltration modules, and the nanofiltration modules are connected in sequence.

[0077] In a specific embodiment, the multi-stage nanofiltration module includes a first-stage nanofiltration module and a second-stage nanofiltration module; of course, a third-stage nanofiltration module can also be reserved as needed. The structure of each stage of the nanofiltration module is generally the same, including a corrosion-resistant shell, a nanofiltration membrane assembly arranged in the shell, and a water inlet and a concentrated water outlet and a water outlet formed on the shell. In order to realize cleaning and stability monitoring, a cleaning system and a control system are provided on each stage of the nanofiltration module, the cleaning system is used to clean the nanofiltration membrane assembly regularly or on demand to remove dirt and blockages on the membrane surface, to ensure normal operation of the device and maintain a long service life. The cleaning system can include physical cleaning (such as backwashing) and chemical cleaning (such as acid-base cleaning) methods. The control system is used to monitor and control the operating state of the device, and the control system can monitor the inlet and outlet water pressure, temperature and other parameters, and automatically control according to the set parameters to ensure the stability of the nanofiltration device.

[0078] The processing route of the lithium, potassium and sodium resource comprehensive recovery system provided by the present application can be divided into five parallel processing routes at the first-stage nanofiltration module and the second-stage nanofiltration module: A, the concentrated water of the above-mentioned first-stage nanofiltration module is used for subsequent lithium precipitation, which is the first lithium extraction route; B, the water outlet of the first-stage nanofiltration module is connected with the second-stage nanofiltration module, and the concentrated water of the second-stage nanofiltration module participates in the subsequent sodium carbonate recovery, which is the sodium carbonate recovery route, or the lithium precipitation reagent preparation route; C, the water outlet of the second-stage nanofiltration module is further adsorbed to prepare adsorption qualified liquid, which is used for subsequent lithium precipitation, which is the second lithium extraction route; D, the unqualified liquid of the adsorption device is discharged into a low-temperature evaporation device, a sodium chloride hot melting device and a potassium chloride cold separation device, which is used for potassium and sodium resource recovery, which is the potassium and sodium resource recovery route; E, the unqualified liquid of the adsorption device is discharged into a tail brine nanofiltration device and a bipolar membrane electrodialysis device, which is a liquid caustic soda and hydrochloric acid preparation route.

[0079] The system architecture of processing route A is as follows: the water inlet end of the ultrafiltration device is connected with the pipeline conveying salt lake brine, the water outlet end of the ultrafiltration device is connected with the inlet end of the first-stage nanofiltration module, the concentrated water outlet end of the first-stage nanofiltration module is connected with the titanium adsorption device, the qualified liquid discharge outlet of the titanium adsorption device is connected with the inlet end of the sand filtration and ultrafiltration combined treatment device, the water outlet end of the sand filtration and ultrafiltration combined treatment device is connected with the water inlet end of the qualified liquid reverse osmosis device, the concentrated water outlet end of the qualified liquid reverse osmosis device is connected with the boron removal resin, the water outlet end of the boron removal resin is connected with the water inlet end of the lithium chloride MVR device, the water outlet end of the lithium chloride MVR device is connected with the liquid inlet of the lithium precipitation device, a sodium carbonate adding port is arranged on the lithium precipitation device, the sodium carbonate in the lithium precipitation device reacts with the lithium chloride solution to generate lithium carbonate precipitate, and the discharge port of the lithium precipitation device is connected with the separation and recovery device, and the separation and recovery device (lithium carbonate centrifuge) realizes solid-liquid separation and recovers lithium carbonate precipitate.

[0080] The system architecture of the processing route B is that the water outlet of the first-stage nanofiltration module is connected with the water inlet of the second-stage nanofiltration module, the concentrated water outlet of the second-stage nanofiltration module is connected with the inlet of the sodium carbonate nanofiltration device, the concentrated water outlet of the sodium carbonate nanofiltration device is connected with the sodium carbonate recovery device, and the outlet of the sodium carbonate recovery device is connected with the sodium carbonate adding port of the lithium precipitation device.

[0081] The sodium carbonate recovery device comprises a sodium carbonate MVR device and a boron removal device; an alkali adding port is arranged on the pipeline connecting the water outlet of the first-stage nanofiltration module with the water inlet of the second-stage nanofiltration module; and a water adding port is arranged on the pipeline connecting the concentrated water outlet of the second-stage nanofiltration module with the inlet of the sodium carbonate nanofiltration device.

[0082] The system architecture of the processing route C is that the water outlet of the second-stage nanofiltration module is connected with the first inlet of the carbon removal device, the water outlet of the sodium carbonate nanofiltration device is connected with the second inlet of the carbon removal device, the liquid outlet of the carbon removal device is connected with the liquid inlet of the aluminum adsorption device, and the qualified liquid outlet of the aluminum adsorption device is connected with the inlet of the sand filtration and ultrafiltration combined treatment device.

[0083] The pipeline connecting the water outlet of the second-stage nanofiltration module with the first inlet of the carbon removal device is provided with an acid adding port, so that bicarbonate is removed and converted into CO2 in the carbon removal device; the carbon removal device is provided with an exhaust port for exhausting carbon dioxide gas; and the aluminum adsorption device is provided with a water adding port and an unqualified liquid outlet.

[0084] The processing route D and the processing route E can be built on the basis of the processing route C, and in practice, the target construction and operation route can be selectively built according to specific needs.

[0085] The system architecture of the processing route D is that the liquid outlet of the carbon removal device is connected with the inlet of the aluminum adsorption device, the tail halogen outlet of the aluminum adsorption device is sequentially connected with a low-temperature evaporation device, a sodium chloride hot melting device and a potassium chloride cold precipitation device, so as to realize the preparation of potassium chloride and sodium chloride.

[0086] The low-temperature evaporation device comprises a first-stage solar low-temperature evaporation module and a second-stage solar low-temperature evaporation module, and the inlet of the first-stage solar low-temperature evaporation module is connected with the tail halogen outlet; the sodium chloride hot melting device is a solar hot melting device, the inlet of the solar hot melting device is connected with the outlet of the second-stage solar low-temperature evaporation module, and the outlet of the solar hot melting device is connected with the potassium chloride cold precipitation device.

[0087] The system architecture of the treatment route E is as follows: the tail brine outlet of the aluminum adsorption device is connected with the tail brine nanofiltration device, the water production end of the tail brine nanofiltration device is connected with the inlet end of the bipolar membrane electrodialysis device, and the concentrated water outlet end of the tail brine nanofiltration device is connected with the inlet end of the first solar low-temperature evaporation module; the concentrated water outlet end of the bipolar membrane electrodialysis device is connected with the inlet end of the first solar low-temperature evaporation module, the liquid alkali is prepared from the anode of the bipolar membrane electrodialysis device, and the hydrochloric acid is prepared from the cathode of the bipolar membrane electrodialysis device.

[0088] In a specific installation and use example, the nanofiltration device uses a nanometer-sized aperture membrane for filtration, and the aperture is usually between 0.001 and 0.01 microns. Compared with the ultrafiltration membrane, the nanofiltration membrane has a smaller aperture, and can more effectively remove dissolved substances, most inorganic salts and organic substances. According to actual needs, different separation effects and permeation rates can be achieved by selecting different nanofiltration membrane materials, operating pressures and operating conditions.

[0089] The working principle of the nanofiltration device is described below:

[0090] The nanofiltration membrane has ion selectivity, and the removal rate of monovalent ions is low, and the removal rate of multivalent ions is high, which is caused by the Donnan equilibrium effect of the nanofiltration membrane, which is mostly a charged membrane, on anions of different valence. The positively charged ions in water can pass through the membrane under the action of concentration difference, but the negatively charged ions are blocked by the negatively charged membrane and cannot (or rarely) pass through the membrane to reach the fresh water side. Due to the principle of electrical neutrality, the diffusion of positively charged ions to the fresh water side is also limited, which achieves the purpose of desalination. The permeability of the nanofiltration membrane to salt is mainly determined by the valence of the ions. Monovalent ions can pass through the membrane in large quantities (but not without resistance), and the removal rate of multivalent ions (such as sulfate and carbonate) is higher. Therefore, the nanofiltration device is used in the present application to effectively separate the concentrated water of monovalent salt and divalent salt.

[0091] The nanofiltration membrane is separated by an anti-pollution material, and the rejection rate of sulfate ions can reach more than 98%. By efficiently rejecting sulfate ions in concentrated brine, the concentrated brine is effectively separated into two parts after being treated by the nanofiltration system: nanofiltration water which is almost entirely composed of NaCl, and nanofiltration concentrated water which is mainly composed of Na2SO4, thereby achieving the initial salt separation goal of the concentrated brine.

[0092] Since inorganic salts can pass through the nanofiltration membrane, the osmotic pressure is much lower than that of reverse osmosis membranes, so under the same flux, the additional pressure required by the nanofiltration membrane process is much lower than that of reverse osmosis; and under the same pressure, the flux of nanofiltration is much larger than that of reverse osmosis. Nanofiltration can simultaneously concentrate and desalt. Therefore, when nanofiltration is used instead of reverse osmosis, the concentration process can be effectively and quickly carried out, and a large concentration factor can be achieved.

[0093] The special nanofiltration membrane has the advantages of salt separation and high rejection of organic matters with a molecular weight of more than 200, so that the divalent salt water can be concentrated and reduced in quantity, the treatment capacity of the subsequent nanofiltration concentrated water quality crystallization is reduced, sodium sulfate products are obtained through evaporation crystallization and freezing crystallization, the TOC (Total Organic Carbon) and divalent ion content in the permeate water are low, the pressure of the nanofiltration product water on the organic matter pollution in the reverse osmosis concentration process is reduced, and the TOC impurity residual content in the product is effectively controlled through the subsequent sodium chloride evaporation crystallization process, so that the purity of the sodium chloride product is very high.

[0094] III. Titanium adsorption device

[0095] The inorganic ion adsorbent has strong selectivity to lithium ions and specific memory effect, and can effectively selectively extract lithium from a dilute solution. The inorganic ion exchange adsorbent can be divided into aluminum-based, manganese-based and titanium-based adsorbents. In the present application, aluminum-based and titanium-based adsorbents are selected.

[0096] The liquid discharged from the outlet end of the primary nanofiltration module belongs to neutral alkaline brine, and the titanium adsorption device is selected to adsorb and treat the concentrated water discharged from the primary nanofiltration module.

[0097] Specifically, the titanium adsorbent in the titanium adsorption device is used to adsorb lithium, mainly through the selective adsorption function of the adsorbent to adsorb lithium ions from salt lake brine. The titanium adsorbent is usually made of titanium fiber, titanium particle or titanium nanometer material to increase its surface area and pore structure and improve the adsorption performance. Lithium can be captured and stored by the adsorbent, and then collected by desorption of the lithium on the adsorbent to obtain qualified liquid, such as desorption under the action of eluent to obtain a lithium-rich solution, realizing the separation and purification of lithium; and the unqualified liquid (or tail brine) after adsorption is directly discharged to the salt lake.

[0098] The titanium adsorption device used in the present application has the advantages of large adsorption capacity, wide application range, high selectivity and low solution loss rate.

[0099] In the present application, the titanium adsorption device has a water inlet, an acid water adding port, a lithium precipitation mother liquor adding port, a qualified liquid discharge port and an unqualified liquid discharge port. Since the lithium precipitation device mother liquor and the boron removal resin regeneration liquid both contain a certain amount of lithium, in accordance with the principle of the highest resource recovery rate, they are returned to the titanium adsorption device for treatment. Therefore, the lithium precipitation mother liquor adding port is connected with the mother liquor discharge port of the lithium precipitation device, and the lithium precipitation mother liquor adding port is connected with the regeneration liquid discharge port of the boron removal resin.

[0100] IV. Sand filter and ultrafiltration combined treatment device

[0101] The sand filtration and ultrafiltration combined treatment device in the present application can be understood as "sand filtration + ultrafiltration". Sand filtration is a technology for filtering through multiple sand beds; when water passes through the sand bed, suspended solids, silt and large particles are filtered out, thereby obtaining relatively clear water; sand filtration is often used in the primary filtration stage to remove larger solid particles and reduce turbidity and suspended solids content in water. Ultrafiltration is a membrane filtration technology that uses micro-porous membranes for separation. The pore size of the ultrafiltration membrane is usually between 0.01 and 0.1 microns, which can effectively remove suspended solids, colloids, bacteria, viruses and most high-molecular-weight organic matter, and can achieve higher water quality requirements.

[0102] The sand filtration and ultrafiltration combined treatment device adopted in the present application can achieve better water treatment effect. First, sand filtration can be used as a pretreatment step to remove larger particles and suspended solids in water, thereby reducing the burden on the ultrafiltration membrane and prolonging its service life. Second, the ultrafiltration is arranged on the outlet side of the sand filtration and used as a fine filtration step to remove smaller particles, colloids and other substances that cannot be completely removed by sand filtration.

[0103] Five, qualified liquid reverse osmosis device

[0104] The qualified liquid reverse osmosis device in the present application is a reverse osmosis device for treating adsorbed qualified liquid, and its structure and principle can be briefly described as follows: the reverse osmosis device mainly includes a water inlet system, a high-pressure pump, a reverse osmosis membrane assembly, a concentrated water discharge pipeline, a pure water collection pipeline and a corresponding control system. The water inlet system includes a water inlet pipeline, a water inlet valve and a pretreatment device for introducing the water source to be treated. The pretreatment device generally includes a particle filter, an activated carbon filter and the like for removing suspended particles, chlorine and organic compounds in water. The high-pressure pump is connected behind the water inlet system to provide sufficient water pressure to overcome the permeation resistance of the reverse osmosis membrane; the high-pressure pump increases the pressure of the water flow through the membrane, prompting the water molecules to pass through the membrane pores, while the solutes and particles are intercepted. The reverse osmosis membrane assembly is the core part of the entire device and is composed of multiple membrane layers; the membrane layer usually adopts a semi-permeable membrane (semi-permeable membrane) with micro-porous or nano-porous pores, which can intercept most ions, solutes and particles and only allow water molecules to pass through; when water passes through the membrane, the solutes and particles in the water are left on the surface of the membrane or discharged from the device. In the reverse osmosis process, a part of the water that does not pass through the membrane (concentrated water) is discharged from the concentrated water discharge pipeline to dilute the concentrated solutes in the inlet water. The pure water (clean water) intercepted on the membrane assembly flows out through the membrane pores and is collected into the pure water collection pipeline. The control system is used to monitor the inlet and outlet water pressure, membrane assembly state and other parameters and automatically controls as needed to ensure the normal operation of the device.

[0105] The water production end of the qualified liquid reverse osmosis device in the application is connected with the inlet end of the water production reverse osmosis device. Since the concentrated water outlet end of the water production reverse osmosis device still contains a certain amount of lithium, the concentrated water outlet end of the water production reverse osmosis device is connected with the inlet end of the sand filtration and ultrafiltration combined treatment device, so as to recover lithium in the concentrated water discharged by the water production reverse osmosis device and improve the lithium recovery rate. The water treated by the water production reverse osmosis device can be used as pure water for self-use, so the water production end of the water production reverse osmosis device can be connected with the user water end. Therefore, the lithium, potassium and sodium resource comprehensive recovery system provided by the application not only can realize high-purity lithium resource extraction, but also can produce pure water for self-use, and the resource recovery utilization rate is extremely high.

[0106] Six, boron removal resin

[0107] Boron removal resin is an adsorbent material used to remove boron from water, which can help purify water sources and reduce the content of boron in water.

[0108] Boron removal resin usually uses organic functional resin as the base material, and after special treatment, its surface has specific adsorption performance, which can selectively adsorb boron ions in water. This resin material has a large surface area and pore size, providing sufficient contact opportunity and adsorption capacity to effectively remove boron from water.

[0109] The working principle of boron removal resin is mainly through the adsorption of the resin surface to capture and fix the boron ions in water. When water passes through the boron removal resin device, boron ions will undergo adsorption reaction with active sites on the surface of the resin, thereby removing boron ions from water. Once the resin is saturated, it needs to be regenerated to restore its adsorption performance. Generally, the regeneration methods of boron removal resin include acid washing, alkali washing or other special regeneration processes.

[0110] Seven, lithium chloride MVR device

[0111] Lithium chloride MVR (Mechanical Vapor Recompression) device is a device that uses mechanical compression vapor regeneration technology to recover and purify lithium chloride solution.

[0112] The lithium chloride MVR device realizes the regeneration of lithium chloride solution through the following steps: using an evaporator to heat the lithium chloride solution to evaporate water and generate steam; using a compressor to compress the steam to increase temperature and pressure; using a heat exchanger to exchange heat between the high-temperature high-pressure steam and the lithium chloride solution to warm it up and evaporate part of the water; using a condenser to cool the high-temperature high-pressure steam to condense it into steam with higher heat; using a separator to separate the condensed water and lithium chloride solution; using a recirculation pump to recirculate the lithium chloride solution in the separator back to the evaporator for the next cycle.

[0113] Through the continuous circulation of the above steps, the lithium chloride MVR device realizes the removal of water in the lithium chloride solution and the concentration of lithium chloride. Compared with the traditional thermal evaporation method, the MVR technology utilizes the high temperature and high pressure of compressed steam, realizes the recycling of energy, reduces the energy consumption and operation cost; improves the quality and stability of lithium chloride solution, realizes the recycling of lithium chloride, and reduces the discharge of waste liquid.

[0114] Eight, lithium precipitation device

[0115] In this application, when lithium chloride and sodium carbonate enter the lithium precipitation device, a reaction occurs in the lithium precipitation device to generate lithium carbonate precipitate. The lithium precipitation mother liquor discharged is a solution containing lithium ions, which mainly contains lithium chloride, sodium carbonate and other impurities. In the lithium precipitation device, lithium chloride and sodium carbonate react to form lithium carbonate precipitate and sodium chloride. The reaction equation is as follows:

[0116] 2LiCl + Na2CO3→ Li2CO3 + 2NaCl

[0117] After the reaction, the water-containing lithium carbonate precipitate enters the separation and recovery device to remove water. There may be some unreacted lithium chloride, sodium carbonate and other impurity substances such as metal ions and impurity salts in the lithium precipitation mother liquor discharged from the lithium precipitation device. According to the needs, the lithium precipitation mother liquor can be further treated to extract and purify the lithium carbonate therein for the preparation of lithium compounds or other industrial applications. Common treatment methods include filtration, leaching, crystallization, ion exchange and other processes. Through these steps, lithium carbonate in the lithium precipitation mother liquor can be separated and purified to obtain high-purity lithium compound products.

[0118] In this application, the lithium precipitation mother liquor is discharged into the titanium adsorption device for further treatment and purification to improve the purification rate and resource recovery rate.

[0119] Nine, separation and recovery device

[0120] The separation and recovery device in this application includes a lithium carbonate centrifuge, and its main structural principles include a centrifuge body, a feeding system, a centrifugal separation system, a liquid phase discharge system, a solid phase collection system and a corresponding control system. Among them: the centrifuge body includes a shell, a centrifuge rotor, a motor and the like, which is usually made of corrosion-resistant materials (such as stainless steel) to adapt to the special properties of lithium carbonate solution.

[0121] The feed system includes a feed pipeline and a feed pump, and the water-containing lithium carbonate precipitate discharged from the lithium precipitation device is input into the centrifuge through the feed pipeline, and the feed pump provides pressure and flow speed. The core part of the lithium carbonate centrifuge is a centrifugal separation system, including a centrifuge rotor and a centrifugal force field. The high-speed rotating centrifuge rotor generates a strong centrifugal force to separate the solid particles (lithium carbonate precipitate) in the water-containing lithium carbonate precipitate. Generally, a centrifuge plate or centrifuge basket is arranged inside the centrifuge rotor for collecting the separated solid particles. After centrifugal separation, the liquid phase (lithium carbonate-rich solution) needs to be discharged, and the centrifuge discharges the liquid phase from the centrifuge rotor through a liquid phase discharge system, which can be discharged into the titanium adsorption device in the present application for further treatment. The solid phase (lithium carbonate solid particles containing impurities) needs to be collected and treated, and is generally collected through the centrifuge plate or centrifuge basket inside the centrifuge rotor, and can be further treated by drying, filtering, etc. The control system is used to monitor the operating state, speed, temperature and other parameters of the centrifuge, and automatically controls according to the set conditions to ensure the safe and stable operation of the device.

[0122] Therefore, the present application effectively separates the solid particles in the lithium carbonate solution by using the centrifugal separation principle of the lithium carbonate centrifuge, and realizes dehydration and solid-liquid separation.

[0123] Ten, carbon remover

[0124] The carbon remover in the present application can realize gas-liquid separation and carbon removal. The acid is added into the carbon remover from the water produced by the secondary nanofiltration module, and the water produced by the sodium carbonate nanofiltration can be discharged into the carbon remover. The bicarbonate in the liquid reacts with the acid to generate gas and is discharged, realizing liquid decarburization.

[0125] Eleven, aluminum adsorption device

[0126] The aluminum adsorption device includes an aluminum-based adsorbent, which is suitable for sulfate or chloride type brine, and the application environment is neutral to slightly acidic. The present application uses an aluminum-based adsorbent after the two-stage nanofiltration module, because the sulfate is separated in the concentrated water of the first-stage nanofiltration module at this time, and the water produced by the secondary nanofiltration module is mainly chloride. The present application uses a titanium-based adsorbent after the concentrated water of the first-stage nanofiltration module, mainly because the concentration of sulfate is high, and in addition, the water quantity of the concentrated water is generally much smaller than that of the produced water, so the aluminum adsorption device can already meet the use requirements.

[0127] The aluminum adsorption device in the present application has a liquid inlet, a qualified liquid discharge outlet, a water inlet, and an unqualified liquid discharge outlet. The liquid inlet is connected with the carbon remover, and the qualified liquid discharge outlet is connected with the sand filtration and ultrafiltration combined treatment device.

[0128] The application discharges the liquid from the decarbonator into the aluminum adsorption device to adsorb lithium ions by the aluminum-based adsorbent, and then desorbs the lithium on the adsorbent to collect the qualified liquid, such as desorbing under the action of the eluent to obtain a lithium-rich solution, realizing the separation and purification of lithium; and the unqualified liquid (or tail halogen) after adsorption can be discharged to a salt lake, or the tail halogen is further treated: part of the unqualified liquid discharged from the aluminum adsorption device is prepared into sodium chloride by the low-temperature evaporation device and the sodium chloride hot melting device, and is prepared into potassium chloride by the potassium chloride cold separation device; another part of the unqualified liquid discharged from the aluminum adsorption device is discharged into the tail halogen nanofiltration device, the water discharged from the water outlet of the tail halogen nanofiltration device is discharged into the bipolar membrane electrodialysis device, liquid caustic soda is recovered at the anode of the bipolar membrane electrodialysis device, and hydrochloric acid is recovered at the cathode of the bipolar membrane electrodialysis device; the water discharged from the concentrated water outlet of the tail halogen nanofiltration device is prepared into sodium chloride by the low-temperature evaporation device and the sodium chloride hot melting device, and is prepared into potassium chloride by the potassium chloride cold separation device; realizing the recovery of sodium and potassium resources in the unqualified liquid.

[0129] The application uses the aluminum adsorption device, which has the advantages of being suitable for industrial production, good selectivity, and environmentally friendly.

[0130] Twelve, sodium carbonate nanofiltration device

[0131] The main difference between the sodium carbonate nanofiltration device and the general nanofiltration device lies in the filter membrane characteristics and the treatment effect. In terms of filter membrane characteristics, the filter membrane used in the sodium carbonate nanofiltration device has a specific pore size, usually several nanometers to several tens of nanometers, which can filter out most of the small particles, dissolved substances and organic matter. While the general nanofiltration device may use different types of filter membranes, the pore size range can be wider. Due to the difference in filter membrane pore size, the sodium carbonate nanofiltration device is more suitable for removing small particles and organic matter in water, and concentrating the solute. Therefore, the main function of the sodium carbonate nanofiltration device is to remove impurities and dissolved substances in water by nanofiltration technology, and to separate and concentrate water.

[0132] Thirteen, low-temperature evaporation device

[0133] The low-temperature evaporation device in the present application is preferably a solar low-temperature evaporation device, which can utilize solar heat to evaporate and separate water, and has two-stage low-temperature evaporation modules, each of which comprises an evaporator, a heat transfer system, a condenser, and a collection and separation device. The evaporator is usually composed of a flat or cover type evaporator, and has a rolling or stationary film inside for uniformly distributing the adsorbed unqualified liquid to be evaporated on the surface. The evaporator utilizes solar energy to evaporate water and separate pure water vapor. The heat transfer system converts solar energy into heat required for evaporation, and can adopt heat absorbers, pipelines, heat sinks and other components to absorb solar radiation through a solar collector, and then transmit heat to the evaporator to promote water evaporation. The condenser is used to cool and convert the evaporated water vapor into liquid water, which can be cooled by discharging a cooling medium or by other means to cause the water vapor to be cooled and condensed into water droplets inside the condenser. The low-temperature evaporation device and the sodium chloride hot melting device are used to evaporate sodium chloride.

[0134] Fourteenth, sodium chloride hot melting device

[0135] The sodium chloride hot melting device generally comprises a heater, a melting tank, a temperature control system and safety facilities. Specifically, the sodium chloride hot melting device usually comprises a heater for providing sufficient heat energy to heat the sodium chloride to the melting point. The melting tank is used to contain the sodium chloride and melt it at high temperature; the melting tank is usually made of high-temperature resistant materials such as stainless steel or ceramic materials; the tank is provided with heating elements inside to heat the sodium chloride to the melting point and keep it in a constant molten state. The melting tank is usually provided with a discharge port for discharging the melted sodium chloride out of the device, and by controlling the opening and closing of the discharge port, the melting speed and melting amount can be adjusted as needed. The temperature control system can ensure that the sodium chloride remains molten in a suitable temperature range. The temperature control system can monitor the temperature in the melting tank through a temperature sensor and adjust the power of the heater according to the set value to maintain a constant melting temperature. The safety facilities include but are not limited to an over-temperature protection system and a pressure control device to ensure the safe operation of the device.

[0136] When the heater provides sufficient heat energy to heat the sodium chloride in the melting tank to its melting point, the sodium chloride will gradually melt into a liquid state, and under the heating action of the heater, the sodium chloride in the melting tank remains molten and flows out through the discharge port at the bottom of the melting tank. In the sodium chloride hot melting device, the temperature control system realizes accurate control of the temperature in the melting tank to ensure that the sodium chloride is melted in a suitable temperature range. At the same time, the safety facilities can protect the safety of the device and the operator.

[0137] The salt lake brine lithium, potassium and sodium resource comprehensive recovery system provided by the present application utilizes the temperature difference between sodium chloride and potassium chloride, and uses a low-temperature evaporation device and a sodium chloride hot melting device to prepare sodium chloride.

[0138] Fifteen, potassium chloride cooling device

[0139] Potassium chloride cooling device is used for separating and extracting potassium chloride (KCl) crystals from solution. It generally includes a solution tank, a cooling system, a crystallization tank, a dehydration and drying system, and a crystallization collection and processing device. Specifically, the potassium chloride cooling device usually includes a solution tank for containing a solution containing potassium chloride; the solution tank is usually made of corrosion-resistant materials such as stainless steel or plastic; the solution tank is filled with a solution containing potassium chloride, and the cooling system is used to lower the temperature of the solution to promote the formation of potassium chloride crystals; the cooling system usually includes a cooler, a cooling medium (such as cold water or cold air) supply and circulation system, which can quickly lower the temperature of the solution by heat exchange between the cooling medium and the solution in the cooler.

[0140] The cooled solution enters the crystallization tank, which is usually equipped with a guide device or a crystallization seed to promote the formation of potassium chloride crystals; the guide device can help guide the aggregation of potassium chloride molecules in the solution and form a crystallization nucleus, thereby promoting crystallization.

[0141] When the potassium chloride crystals reach a certain degree, the residual solution and moisture are removed through the dehydration and drying system to obtain purer potassium chloride crystals; this can be achieved by centrifugal separation, vacuum drying or other appropriate methods.

[0142] The mature potassium chloride crystals will deposit and accumulate in the cooling device and can be collected by the crystallization collection and processing device; the collected potassium chloride crystals can be subjected to subsequent processing, drying and packaging steps to obtain the final potassium chloride product. The present application recovers potassium resources from salt lake brine through the potassium chloride cooling device.

[0143] Sixteen, bipolar membrane electrodialysis device

[0144] Bipolar membrane electrodialysis device is a device that separates and concentrates substances using electrochemical principles. It usually includes a membrane electrolytic cell, a bipolar membrane, a power supply, and a stirring system. Specifically, the membrane electrolytic cell includes an anode tank and a cathode tank, which are assembled by one or more membranes, including an anode-side membrane and a cathode-side membrane, which play a separating role.

[0145] The bipolar membrane is the core component of the bipolar membrane electrodialysis device, which is composed of an anode-side membrane, a cathode-side membrane, and an intermediate layer; the anode-side membrane has ion selectivity and only allows positive ions to pass through; the cathode-side membrane only allows negative ions to pass through; the intermediate layer plays a role in isolating and stabilizing the electrolyte.

[0146] In the bipolar membrane electrodialysis device, a power source delivers direct current to the anode and cathode, creating a fixed potential difference that drives the migration and separation of ions. The device is equipped with inlet and outlet ports for introducing the solution to be treated and discharging the product after electrodialysis treatment.

[0147] To improve separation efficiency and increase reaction rate, the bipolar membrane electrodialysis device is usually equipped with a stirring system to ensure uniform distribution of the solution on the membrane surface and promote ion migration.

[0148] The bipolar membrane electrodialysis device utilizes the characteristics of electric field force and selective membrane to enable ions to migrate to the corresponding membrane surface under the action of electric field force, thereby achieving ion separation and concentration. At the anode side membrane, cations are attracted and migrate to the membrane; at the cathode side membrane, anions are attracted and migrate to the membrane. In this way, the device can separate different ions in the mixed solution to achieve purification and concentration.

[0149] Therefore, the present application uses a bipolar membrane electrodialysis device to separate and concentrate the lithium extraction adsorption tail halogen. Sodium chloride solution is introduced into the middle layer of the bipolar membrane electrodialysis device, and chloride ions across the cathode side membrane react with hydroxyl ions to form hydrochloric acid, and sodium ions across the anode side membrane react with hydroxyl ions to form liquid alkali. Therefore, when the aluminum adsorption device tail halogen is subjected to nanofiltration, a large amount of sodium ions and chloride ions are enriched in the nanofiltration water, and hydrochloric acid and liquid alkali are formed at the anode and cathode of the bipolar membrane electrodialysis device. The hydrochloric acid and liquid alkali can be reused in the lithium, potassium and sodium resource comprehensive recovery system provided by the present application, or sold externally.

[0150] In summary, the lithium, potassium and sodium resource comprehensive recovery system provided by the present application realizes the original halogen membrane method coupled with adsorption lithium extraction process by sequentially connecting the ultrafiltration device, nanofiltration device, adsorption device, sand filtration ultrafiltration combined treatment device, qualified liquid reverse osmosis device, boron removal resin, lithium chloride MVR device, lithium precipitation device and separation and recovery device. The system utilizes membrane method to separate divalent ions such as calcium, magnesium, sulfate and carbonate from monovalent ions such as lithium, and then utilizes adsorption, membrane method and evaporation concentration to reduce the evaporation scale, achieving the purpose of high-purity lithium resource extraction under low energy consumption and low cost conditions.

[0151] In addition, the lithium-potassium-sodium resource comprehensive recovery system provided by the application further comprises a chloride production unit composed of a low-temperature evaporation device, a sodium chloride hot melting device and a potassium chloride cold separation device. The unqualified liquid discharged from the adsorption device is discharged into the low-temperature evaporation device and the sodium chloride hot melting device to prepare sodium chloride. Then, the liquid of the sodium chloride hot melting device is discharged into the potassium chloride cold separation device for cooling. Based on the temperature difference between sodium chloride and potassium chloride, the sodium resource and the potassium resource in the salt lake brine are recovered. Therefore, the lithium-potassium-sodium resource comprehensive recovery system in the salt lake brine provided by the application can improve the recovery rate of the salt lake brine resource, comprehensively recover lithium, potassium and sodium, and reduce energy consumption, operation and investment costs, and processing costs through the original brine membrane method coupled with the adsorption lithium extraction process.

[0152] Further, the lithium-potassium-sodium resource comprehensive recovery system in the salt lake brine provided by the application comprises two lithium extraction routes, one potassium chloride and sodium chloride preparation route (potassium-sodium recovery route), one sodium carbonate preparation route, and one hydrochloric acid liquid alkali preparation route. The above-mentioned processing routes are parallel, and each route can be independently constructed and put into use without affecting each other.

[0153] Embodiment two

[0154] With the above-mentioned lithium-potassium-sodium resource comprehensive recovery system in the salt lake brine, the application provides a lithium-potassium-sodium resource comprehensive recovery method in the salt lake brine. The first lithium extraction route is mainly embodied in this embodiment, and the process principle of the comprehensive recovery method is as follows:

[0155] The original brine first enters the ultrafiltration device (immersed ultrafiltration), removes the turbidity such as suspended solids and colloids in the water through the ultrafiltration device to avoid blocking the subsequent membrane unit. The immersed ultrafiltration water enters the primary nanofiltration module to separate the divalent ions such as sulfate and carbonate from the monovalent ions such as lithium and chlorine. The concentrated water of the primary nanofiltration module contains a large amount of divalent ions, but the flow is small. The concentrated water of the primary nanofiltration module is discharged into the titanium adsorption device. After the lithium is adsorbed by the titanium adsorption device, the lithium adsorption qualified liquid enters the sand filtration and ultrafiltration combined treatment device (ultrafiltration + sand filtration), and the remaining brine (unqualified liquid) returns to the salt lake. The titanium adsorption device adsorption qualified liquid enters the ultrafiltration + sand filtration to remove the turbidity such as suspended solids in the brine. The ultrafiltration + sand filtration effluent enters the qualified liquid reverse osmosis device (qualified liquid RO) to concentrate and enrich lithium on the RO concentrated water side. The qualified liquid RO concentrated water enters the lithium chloride MVR device after removing boron by the boron removal resin, and then enters the lithium precipitation device. Lithium reacts with sodium carbonate to generate lithium carbonate precipitate. Finally, solid-liquid separation is performed by a centrifuge to realize lithium carbonate solid recovery.

[0156] In this embodiment, the mother liquor of the lithium precipitation device and the regeneration liquid of the boron removal resin both contain a certain amount of lithium. In accordance with the principle of the highest resource recovery rate, they are returned to the titanium adsorption device for treatment.

[0157] In this embodiment, the qualified liquid RO water is treated by the water production reverse osmosis device (water production RO) to produce water (pure water) for the production process, and the water production reverse osmosis concentrated water is returned to the ultrafiltration + sand filtration unit for further lithium extraction.

[0158] Embodiment three

[0159] The above-mentioned comprehensive recovery system of lithium, potassium and sodium resources in salt lake brine provides a comprehensive recovery method of lithium, potassium and sodium resources in salt lake brine, and the embodiment mainly embodies the second lithium extraction route. The process principle of the comprehensive recovery method is as follows:

[0160] The raw brine first enters the ultrafiltration device (immersed ultrafiltration), removes suspended solids, colloids and other turbidity in the water through the ultrafiltration device to avoid blocking the subsequent membrane unit; the immersed ultrafiltration water enters the first nanofiltration module to separate divalent ions such as sulfate and carbonate from monovalent ions such as lithium and chlorine; the first nanofiltration module produces a large amount of HCO3 - , Cl - , etc. in addition to lithium; alkali is added to the produced water, and the bicarbonate alkalinity (HCO3 - ) in the brine is converted into carbonate (CO3 2- ); the produced water after the alkali addition reaction enters the second nanofiltration module to retain the carbonate on the concentrated water side, and the second nanofiltration module produces water by adding acid, a small amount of HCO3 - in the produced water is converted into carbon dioxide, and the carbon dioxide in the brine is removed by the carbon removal device; the lithium in the carbon removal device is adsorbed by the aluminum adsorbent device, and the aluminum adsorption qualified liquid enters the ultrafiltration + sand filtration to remove suspended solids and other turbidity in the brine; the aluminum adsorption unqualified liquid can be discharged into the salt lake or treated again as tail brine, and the ultrafiltration + sand filtration effluent enters the qualified liquid reverse osmosis device (RO) to concentrate and enrich lithium on the RO concentrated water side, and the RO concentrated water of the qualified liquid is removed by the boron removal resin and then enters the lithium chloride MVR device for concentration, and then enters the lithium precipitation device, lithium reacts with sodium carbonate to generate lithium carbonate precipitate, and finally the lithium carbonate is separated by the centrifuge to realize the recovery of lithium carbonate solid.

[0161] Embodiment four

[0162] Based on the comprehensive recovery method of lithium, potassium and sodium resources provided in the above-mentioned embodiment three, the method provided in the embodiment three is used as the basis for sodium carbonate recovery, which can be used as the source of sodium carbonate added in the lithium precipitation device.

[0163] On the basis of the embodiment three, the concentrated water of the second nanofiltration module is discharged into the sodium carbonate nanofiltration device, the carbonate is separated and retained on the concentrated water side, the produced water of the sodium carbonate nanofiltration device is combined with the produced water of the second nanofiltration module and then enters the carbon removal device, the concentrated water of the sodium carbonate nanofiltration device is removed by the boron removal device, and the sodium carbonate is recovered by the sodium carbonate MVR device.

[0164] Embodiment five

[0165] The method for extracting lithium provided in the above embodiment two to embodiment three can be combined, and the flow chart can be seen from Figure 1 The combined lithium extraction method has two parallel lithium extraction routes, which not only realizes sufficient lithium extraction, but also recovers sodium carbonate, which is used as the source of sodium carbonate added in the lithium precipitation device, thereby reducing the operation investment cost.

[0166] Embodiment six

[0167] Based on the two parallel lithium extraction methods provided in embodiment five, the potassium and sodium resource recovery method is added based on embodiment five in this embodiment.

[0168] In this embodiment, the unqualified liquid discharged from the aluminum adsorption device is reprocessed to realize the recovery of potassium ions, sodium ions and chloride ions in the salt lake brine.

[0169] Specifically, the unqualified liquid discharged from the aluminum adsorption device contains a large amount of monovalent ions such as potassium ions, sodium ions and chloride ions. A small part of the unqualified liquid is reused or sold by producing acid and alkali through nanofiltration + bipolar membrane electrodialysis, and most of the unqualified liquid enters the chloride production unit. By using the temperature difference between sodium chloride and potassium chloride, sodium chloride is evaporated first by one / two-stage solar low-temperature evaporation + solar heat melting, and finally potassium chloride products are precipitated by cold precipitation.

[0170] In this embodiment, the process of recovering potassium, sodium and chloride ions from the unqualified liquid discharged from the adsorption device is parallel to the lithium extraction route and the sodium carbonate recovery route provided in the above multiple embodiments. The construction and commissioning of the potassium, sodium and chloride ion recovery system do not affect each other, and the construction and operation of the lithium extraction system can be carried out separately.

[0171] The lithium-potassium-sodium resource comprehensive recovery method provided in this embodiment can be applied to salt lakes with low lithium content and mineralization degree, and high sodium sulfate and sodium chloride content. In one specific example, the method can extract lithium from the salt lake brine with the water quality shown in Table 1.

[0172] Table 1 Salt lake brine water quality table

[0173] Ion name Unit Value mg 2+ ]] mg / L 3.7 K + ]]> mg / L 16230 Ca 2+ ]] mg / L 3.3 Na + ]]> mg / L 78000 Li + ]] mg / L 200 B - ]]> mg / L 860 SO4 2- ]] mg / L 14200 CL - ]] mg / L 56700 CO3 2- ]] mg / L 13500 HCO3 - ]]> mg / L 4500

[0174] The lithium-potassium-sodium resource comprehensive recovery method provided in this application considers the separation of monovalent and divalent ions, removes alkalinity and boron, and at the same time guarantees the resource recovery and utilization of sodium carbonate, sodium chloride, potassium chloride and lithium carbonate.

[0175] The lithium extraction method provided in this application will be compared with the traditional lithium extraction method below, see Table 2.

[0176] Table 2 Comparison of advantages of lithium extraction method provided in this application and traditional lithium extraction method in various aspects

[0177]

[0178]

[0179] In summary, the application provides a lithium, potassium and sodium resource comprehensive recovery system for salt lake brine, which comprises, in sequence, an ultrafiltration device, a nanofiltration device, an adsorption device, a sand filtration and ultrafiltration combined treatment device, a qualified liquid reverse osmosis device, a boron removal resin, a lithium chloride MVR device, a lithium precipitation device and a separation and recovery device. The system performs functional treatment on the salt lake brine through the above devices, realizes membrane treatment through the ultrafiltration, nanofiltration, sand filtration and ultrafiltration combined treatment device and the reverse osmosis device, and realizes adsorption treatment through the titanium adsorption device and the boron removal resin. That is, the application adopts a raw brine membrane coupling adsorption lithium extraction process, separates calcium, magnesium, sulfate, carbonate and other ions from lithium ions through membrane method, and then uses adsorption, membrane method and evaporation concentration to reduce the evaporation scale, so as to extract lithium resources with high purity under the conditions of low energy consumption and low cost.

[0180] Further, the lithium, potassium and sodium resource comprehensive recovery system provided by the application further comprises a chloride production unit composed of a low-temperature evaporation device, a sodium chloride hot melting device and a potassium chloride cold precipitation device. The unqualified liquid discharged from the aluminum adsorption device is discharged into the low-temperature evaporation device and the sodium chloride hot melting device to prepare sodium chloride, and then the liquid in the sodium chloride hot melting device is discharged into the potassium chloride cold precipitation device for cooling. Based on the temperature difference between sodium chloride and potassium chloride, the sodium resource and the potassium resource in the salt lake brine are recovered.

[0181] Further, the lithium, potassium and sodium resource comprehensive recovery system provided by the application can also prepare sodium carbonate, which serves as a source of lithium precipitation sodium carbonate, thereby reducing the preparation investment cost.

[0182] Further, the lithium, potassium and sodium resource comprehensive recovery system provided by the application can also recover liquid caustic soda and hydrochloric acid, thereby improving the return on investment.

[0183] Further, the lithium, potassium and sodium resource comprehensive recovery system provided by the application can also prepare pure water for self-use in the lithium extraction process, thereby reducing the water resource input cost.

[0184] As can be seen, the lithium, potassium and sodium resource comprehensive recovery system provided by the application can improve the recovery rate of salt lake brine resources, comprehensively recover lithium, potassium and sodium resources, and reduce energy consumption, operating and investment costs, processing costs and the return on investment through the raw brine membrane coupling adsorption lithium extraction process.

[0185] The technical features of the above embodiments can be combined in any manner (as long as the combination of the technical features does not exist contradictions). In order to make the description simple, not all possible combinations of the technical features in the above embodiments are described. The embodiments not explicitly described are also considered to be within the scope of the present application.

[0186] The application has been described in detail above by specific embodiments and general description. It should be understood that based on the technical concept of the application, some conventional adjustments or further innovations can also be made to these specific embodiments; but as long as they do not deviate from the technical concept of the application, the technical solutions obtained by these conventional adjustments or further innovations also fall within the protection scope of the claims of the application.

Claims

1. A system for comprehensive recovery of lithium, potassium and sodium resources in salt lake brine, characterized in that, The device comprises, in sequence, an ultrafiltration device, a nanofiltration device, an adsorption device, a sand filtration-ultrafiltration combined treatment device, a qualified liquid reverse osmosis device, a boron removal resin, a lithium chloride MVR device, a lithium precipitation device, and a separation and recovery device. The water inlet end of the ultrafiltration device is connected to a pipeline for conveying salt lake brine, the water outlet end of the ultrafiltration device is connected to the nanofiltration device, the nanofiltration device is connected to the adsorption device, the qualified liquid outlet of the adsorption device is connected to the inlet end of the sand filtration-ultrafiltration combined treatment device, the water outlet end of the sand filtration-ultrafiltration combined treatment device is connected to the water inlet end of the qualified liquid reverse osmosis device, the concentrated water outlet end of the qualified liquid reverse osmosis device is connected to the boron removal resin, the water outlet end of the boron removal resin is connected to the water inlet end of the lithium chloride MVR device, the water outlet end of the lithium chloride MVR device is connected to the liquid inlet of the lithium precipitation device, a sodium carbonate inlet is arranged on the lithium precipitation device, the sodium carbonate in the lithium precipitation device reacts with the lithium chloride solution to generate lithium carbonate precipitate, the discharge port of the lithium precipitation device is connected to the separation and recovery device, and the separation and recovery device is used to realize solid-liquid separation and recover the lithium carbonate precipitate. The device further comprises, in sequence, a low-temperature evaporation device, a sodium chloride hot melting device, and a potassium chloride cold precipitation device connected to the unqualified liquid discharge port of the adsorption device. The adsorption device comprises a titanium adsorption device and an aluminum adsorption device, the titanium adsorption device has a water inlet, an acid water inlet, a qualified liquid outlet, and an unqualified liquid outlet, and the aluminum adsorption device has a liquid inlet, a qualified liquid outlet, a water inlet, and an unqualified liquid outlet. The nanofiltration device comprises a multi-stage nanofiltration module, which at least comprises a first-stage nanofiltration module and a second-stage nanofiltration module. The water inlet end of the first-stage nanofiltration module is connected to the water outlet end of the ultrafiltration device, the water outlet end of the first-stage nanofiltration module is connected to the water inlet end of the second-stage nanofiltration module through a connecting pipe, an alkali inlet is arranged on the connecting pipe, and the water outlet end of the second-stage nanofiltration module is connected to a carbon removal device. The carbon removal device has a first inlet, an exhaust port, and a liquid discharge port, the water outlet end of the second-stage nanofiltration module is connected to the first inlet through a connecting pipeline, an acid inlet is arranged on the connecting pipeline, the exhaust port is used to discharge carbon dioxide gas, and the liquid discharge port is connected to the liquid inlet of the aluminum adsorption device. The qualified liquid outlet of the aluminum adsorption device is connected to the inlet end of the sand filtration-ultrafiltration combined treatment device, and the unqualified liquid outlet of the aluminum adsorption device is connected to the low-temperature evaporation device. The concentrated water outlet end of the first-stage nanofiltration module is connected to the water inlet of the titanium adsorption device, the qualified liquid outlet of the titanium adsorption device is connected to the inlet end of the sand filtration-ultrafiltration combined treatment device, and the unqualified liquid outlet of the titanium adsorption device is connected to a tail brine discharge pipeline, and the unqualified liquid is discharged to a salt lake through the tail brine discharge pipeline. The titanium adsorption device further has a lithium precipitation mother liquor inlet, the lithium precipitation mother liquor inlet is connected to the mother liquor discharge port of the lithium precipitation device, and the lithium precipitation mother liquor inlet is connected to the regenerated liquid discharge port of the boron removal resin.

2. The system for comprehensive recovery of lithium, potassium and sodium resources from salt lake brine according to claim 1, characterized in that, The low-temperature evaporation device comprises a first solar low-temperature evaporation module and a second solar low-temperature evaporation module, and the inlet end of the first solar low-temperature evaporation module is connected with the outlet of the adsorption device for unqualified liquid; The sodium chloride hot melting device is a solar hot melting device, the inlet end of the solar hot melting device is connected with the outlet end of the second solar low-temperature evaporation module, and the outlet end of the solar hot melting device is connected with the potassium chloride cold separation device.

3. The system for comprehensive recovery of lithium, potassium and sodium resources from salt lake brine according to claim 2, characterized in that, The carbon remover also has a second inlet, and the second inlet is connected with the sodium carbonate nanofiltration device; The inlet end of the sodium carbonate nanofiltration device is connected with the outlet end of the second nanofiltration module through a connecting pipeline, and a water inlet is arranged on the connecting pipeline; the water outlet of the sodium carbonate nanofiltration device is connected with the second inlet, the concentrated water outlet end of the sodium carbonate nanofiltration device is connected with the sodium carbonate recovery device, and the outlet of the sodium carbonate recovery device is connected with the sodium carbonate adding port of the lithium precipitation device; The sodium carbonate recovery device comprises a sodium carbonate MVR device and a boron removal device.

4. The system for comprehensive recovery of lithium, potassium and sodium resources from salt lake brine according to claim 2, characterized in that, The tail halogen nanofiltration device and the bipolar membrane electrodialysis device are connected with the outlet of the adsorption device for unqualified liquid respectively, the water outlet end of the tail halogen nanofiltration device is connected with the inlet end of the bipolar membrane electrodialysis device, and the concentrated water outlet end of the tail halogen nanofiltration device is connected with the inlet end of the first solar low-temperature evaporation module; The water outlet end of the bipolar membrane electrodialysis device is connected with the inlet end of the first solar low-temperature evaporation module, the anode of the bipolar membrane electrodialysis device forms liquid alkali, and the cathode of the bipolar membrane electrodialysis device forms hydrochloric acid.

5. The system for comprehensive recovery of lithium, potassium and sodium resources from salt lake brine according to claim 1, characterized in that, The water outlet end of the qualified liquid reverse osmosis device is connected with the inlet end of the water production reverse osmosis device, the concentrated water outlet end of the water production reverse osmosis device is connected with the inlet end of the sand filtration and ultrafiltration combined treatment device, and the water outlet end of the water production reverse osmosis device is connected with the user water end. The sand filtration and ultrafiltration combined treatment device comprises a sand bed and an ultrafiltration membrane assembly connected on the water outlet side of the sand bed.

6. The system for comprehensive recovery of lithium, potassium and sodium resources from salt lake brine according to claim 1, characterized in that, The lithium chloride MVR device comprises an evaporator, a compressor, a heat exchanger, a condenser, a separator and a recirculation pump, the evaporator is used to heat the lithium chloride solution and generate steam, the compressor is used to compress the steam into high-temperature and high-pressure steam, the heat exchanger is used to exchange heat between the high-temperature and high-pressure steam and the lithium chloride solution, the condenser is used to cool the high-temperature and high-pressure steam, the separator is used to separate the condensed water and the lithium chloride solution, and the recirculation pump is used to circulate the lithium chloride solution in the separator back to the evaporator, so as to concentrate the lithium chloride solution and obtain lithium chloride concentrate; The lithium chloride concentrate enters the lithium precipitation device, the lithium precipitation device has a reaction chamber, lithium chloride reacts with sodium carbonate in the reaction chamber to generate lithium carbonate precipitate, and the aqueous lithium carbonate precipitate in the reaction chamber enters the separation and recovery device to realize solid-liquid separation and recover the lithium carbonate precipitate. The separation and recovery device comprises a lithium carbonate centrifuge.

7. A method for comprehensive recovery of lithium, potassium and sodium resources in salt lake brine, characterized in that, The salt lake brine lithium, potassium and sodium resource comprehensive recovery system comprises the following steps: S1: inputting the salt lake brine into an ultrafiltration device, and removing the suspended solids and colloids in the salt lake brine through the ultrafiltration device; S2: inputting the salt lake brine treated by the ultrafiltration device into a primary nanofiltration module, and removing the sulfate and carbonate in the salt lake brine through the primary nanofiltration module; S3: inputting the liquid discharged from the concentrated water outlet end of the primary nanofiltration module into a titanium adsorption device, and adsorbing the lithium in the liquid through the titanium adsorption device; S4: inputting the adsorbed qualified liquid discharged from the titanium adsorption device into the sand filtration and ultrafiltration combined treatment device, and removing the suspended solids and colloids in the liquid and reducing the turbidity through the sand filtration and ultrafiltration combined treatment device; S5: inputting the liquid treated by the sand filtration and ultrafiltration combined treatment device into the qualified liquid reverse osmosis device, inputting the liquid discharged from the concentrated water outlet end of the qualified liquid reverse osmosis device into the boron removal resin for boron removal, and inputting the liquid discharged from the water outlet end of the boron removal resin into the lithium chloride MVR device; S6: concentrating the liquid inputted into the lithium chloride MVR device through the lithium chloride MVR device; S7: inputting the lithium chloride concentrated liquid obtained through the lithium chloride MVR device into the lithium precipitation device to react with the sodium carbonate solution, generating lithium carbonate precipitate in the solution, and separating and recovering the generated lithium carbonate precipitate from the solution through the separation and recovery device.

8. A method for comprehensive recovery of lithium, potassium and sodium resources in salt lake brine, characterized in that, The lithium, potassium and sodium resource comprehensive recovery system in the salt lake brine according to claim 4 comprises the following steps: S1: inputting the salt lake brine into an ultrafiltration device, and removing the suspended solids and colloids in the salt lake brine through the ultrafiltration device; S2: inputting the salt lake brine treated by the ultrafiltration device into a primary nanofiltration module, and removing the sulfate and carbonate in the salt lake brine through the primary nanofiltration module; S3: inputting the liquid discharged from the water outlet end of the primary nanofiltration module into a secondary nanofiltration module to remove the carbonate; S4: inputting the liquid discharged from the water outlet end of the secondary nanofiltration module into a carbon removal device to remove the bicarbonate; S5: inputting the liquid discharged from the carbon removal device into an aluminum adsorption device to adsorb the lithium in the liquid through the aluminum adsorption device; S6: inputting the adsorbed qualified liquid discharged from the aluminum adsorption device into the sand filtration and ultrafiltration combined treatment device to remove the suspended solids and colloids in the liquid and reduce the turbidity through the sand filtration and ultrafiltration combined treatment device; A part of the unqualified liquid discharged from the aluminum adsorption device is used to prepare sodium chloride through the low-temperature evaporation device and the sodium chloride hot melting device, and to prepare potassium chloride through the potassium chloride cold precipitation device; another part of the unqualified liquid discharged from the aluminum adsorption device is discharged into a tail brine nanofiltration device, the water discharged from the water outlet end of the tail brine nanofiltration device is discharged into a bipolar membrane electrodialysis device, liquid alkali is recovered at the anode of the bipolar membrane electrodialysis device, and hydrochloric acid is recovered at the cathode of the bipolar membrane electrodialysis device; the water discharged from the concentrated water outlet end of the tail brine nanofiltration device is used to prepare sodium chloride through the low-temperature evaporation device and the sodium chloride hot melting device, and to prepare potassium chloride through the potassium chloride cold precipitation device; S7: inputting the liquid treated by the sand filtration and ultrafiltration combined treatment device into the qualified liquid reverse osmosis device, and inputting the liquid discharged from the concentrated water outlet end of the qualified liquid reverse osmosis device into the boron removal resin for boron removal. S8: the liquid from the water production end of the boron-removing resin enters the lithium chloride MVR device, which concentrates the liquid entering it; S9: the lithium chloride concentrated liquid obtained by concentration of the lithium chloride MVR device enters a lithium precipitation device to react with a sodium carbonate solution, lithium carbonate precipitates are generated in the solution, and the generated lithium carbonate precipitates are separated and recovered from the solution by the separation and recovery device.

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