Device for extracting lithium salt from salt lake brine

Abstract

The utility model relates to a device for extracting lithium salt from salt lake brine. The device comprises a nanofiltration membrane and a lithium salt extraction device, wherein the nanofiltration membrane is used for carrying out nanofiltration separation on the salt lake brine to obtain nanofiltration concentrated liquor and nanofiltration filtrate; the adsorption stirring box is connected with the nanofiltration filtrate side of the nanofiltration membrane and is filled with a lithium adsorbent for adsorbing and extracting lithium from filtrate of the nanofiltration membrane to obtain a lithium adsorbent mixed solution; the filter tank is internally provided with an immersed membrane component, is connected with the adsorption stirring box, and is used for screening and filtering the lithium adsorbent mixed liquid in the adsorption stirring box to obtain lithium adsorbent concentrated liquid and produced water; the suction filtration mechanism is connected with the lithium adsorbent concentrated liquid side of the filter tank and is used for suction filtration to obtain a filter cake containing the lithium adsorbent; and the desorption mechanism is connected with the suction filtration mechanism and is used for desorbing the filter cake containing the lithium adsorbent. Compared with the prior art, the device has the advantages of improving the adsorbent efficiency, reducing the operation cost and the like.

Description

Technical Field

[0001] The utility model relates to the technical field of inorganic salt chemical industry, in particular to a device for extracting lithium salt from salt lake brine. Background Art

[0002] The concentration of lithium ions in salt lake brine is low, and it often coexists with various alkali metal and alkaline earth metal ions, especially the high content of magnesium ions. At the same time, there are trace amounts of sodium and potassium ions, which makes it difficult to separate and extract lithium from salt lake brine. The existing or under-study processes for extracting lithium from salt lake brine mainly include precipitation, solvent extraction, adsorption, calcination leaching, carbonization, salting out, etc. Each method has its own advantages and disadvantages.

[0003] The basic principle of the adsorption method is to use an adsorbent that selectively adsorbs lithium ions to adsorb lithium ions, and then elute the lithium ions to achieve the purpose of separating lithium ions from other metal ions. It is very suitable for separating and extracting lithium ions from salt lake brine with a high magnesium-lithium ratio. However, the adsorption of lithium solutions by different adsorbents is affected by temperature, pH value, calcium ions, magnesium ions, etc. At the same time, the separation of the adsorbed solution and the adsorbent by ordinary filtration has the problems of long cycle and low efficiency. Utility Model Content

[0004] The purpose of the utility model is to provide a device for extracting lithium salt from salt lake brine in order to overcome the defects of low efficiency and high operating cost of separation of adsorbent and solution in the above-mentioned prior art, thereby improving the efficiency of the adsorbent and reducing the operating cost.

[0005] The purpose of the utility model can be achieved through the following technical solutions:

[0006] A device for extracting lithium salt from salt lake brine, comprising:

[0007] A nanofiltration membrane for nanofiltration separation of salt lake brine to obtain nanofiltration concentrate and nanofiltration filtrate;

[0008] an adsorption stirring box connected to the nanofiltration filtrate side of the nanofiltration membrane, wherein the adsorption stirring box is filled with a lithium adsorbent for adsorbing and extracting lithium from the filtrate of the nanofiltration membrane to obtain a lithium adsorbent mixed solution;

[0009] A filter tank containing an immersed membrane assembly is connected to the adsorption stirring tank, and the lithium adsorbent mixed liquid in the adsorption stirring tank is screened and filtered to obtain a lithium adsorbent concentrated liquid and produced water;

[0010] A suction filtration mechanism connected to the lithium adsorbent concentrate side of the filtration tank and used for suction filtration to obtain a filter cake containing the lithium adsorbent;

[0011] A desorption mechanism is connected to the suction filtration mechanism and is used to desorb the filter cake containing the lithium adsorbent.

[0012] Furthermore, the salt lake brine is separated by nanofiltration to separate magnesium, calcium ions, etc. in the solution. These impurity ions will compete with lithium ions for adsorption positions during the lithium adsorption process, reducing the lithium adsorption efficiency. The nanofiltration membrane used has a retention rate of more than 98% for magnesium sulfate, an operating pressure of 15-35 bar, and a temperature of 20-45°C. The nanofiltration concentration multiple is controlled according to the ion concentration in the salt lake brine, generally 2-5 times. If the ion concentration in the salt lake brine is high, it can be diluted and separated by nanofiltration. After nanofiltration, magnesium, calcium and other ions are in the nanofiltration concentrate, and most of the lithium ions are in the nanofiltration filtrate. The nanofiltration filtrate enters the adsorption stirring box and mixes with the lithium adsorbent.

[0013] Furthermore, the adsorption stirring box also includes:

[0014] A pH meter and a thermometer installed in the adsorption stirring box;

[0015] A heating component installed inside or on the outer wall of the adsorption stirring box;

[0016] A stirring paddle installed on the top of the adsorption stirring box;

[0017] And a first aeration component installed at the bottom of the adsorption stirring box.

[0018] Furthermore, the adsorption stirring box also includes a pH adjustment channel for adjusting the pH.

[0019] Furthermore, the heating assembly includes a heating tube, a heating rod, a heating plate, and a heater.

[0020] Furthermore, the nanofiltration filtrate and the lithium adsorbent are mixed evenly in the adsorption stirring box. The adsorption stirring box is provided with a pH meter and a thermometer, and the temperature and pH of the mixture of the nanofiltration filtrate and the lithium adsorbent can be adjusted according to the factors affecting the adsorption to improve the adsorption effect. In order to enhance the stirring and mixing effect, a stirring paddle is installed in the adsorption stirring box, and a first aeration component is provided at the bottom to enhance the stirring effect and improve the adsorption effect of the adsorbent. Furthermore, the lithium adsorbent is in powder form.

[0021] Furthermore, when desorption is selected after incineration, the type of lithium adsorbent added is selected to be a lithium adsorbent that is not affected by incineration, so that desorption after incineration is easier.

[0022] Furthermore, the lithium adsorbent may be a well-known organic or inorganic adsorbent with strong selective adsorption of lithium, preferably an aluminum salt adsorbent.

[0023] Furthermore, the submerged membrane assembly includes curtain type, column type, "U" type or seaweed type.

[0024] Furthermore, the material of the submerged membrane assembly includes polytetrafluoroethylene, polycarbonate, cellulose ester, polyvinylidene fluoride, polyvinyl chloride, polyetherimide, polypropylene, polyamide, polysulfone, polyethersulfone, polyacrylonitrile (PAN), cellulose ester, polyimide or polyetheramide, preferably polytetrafluoroethylene.

[0025] Furthermore, a second aeration component is provided at the bottom of the filter tank.

[0026] Furthermore, the first aeration component and the second aeration component include a blower aeration device and a mechanical aeration device, which can be selected according to actual needs of the device.

[0027] Furthermore, the filter pool is connected to a backwash water tank, and a water production channel flowing from the filter pool to the backwash water tank and a backwash channel flowing from the backwash water tank to the filter pool are connected between the filter pool and the backwash water tank.

[0028] Furthermore, a backwash pump is installed on the backwash channel, and a water production pump is installed on the water production channel.

[0029] Furthermore, a concentrate pump is connected between the filter tank and the filtration mechanism.

[0030] Furthermore, after the nanofiltration filtrate and the lithium adsorbent are mixed and stirred in the adsorption stirring box, the lithium adsorbent mixed liquid is transported to a filter tank equipped with an immersed membrane assembly, and the lithium adsorbent is separated and filtered to obtain produced water and adsorbent concentrate.

[0031] Furthermore, the submerged membrane assembly is placed in the filter tank, and the lithium adsorbent mixed liquid directly enters the filter tank. Under the action of the second aeration assembly, the lithium adsorbent mixed liquid is in a suspended state with uniform concentration. After screening and filtration by the submerged membrane assembly, the produced water is discharged from the filter tank through the produced water pump, and the retained lithium adsorbent concentrate is discharged from the filter tank through the concentrate pump. The lithium adsorbent concentrate is the adsorbent after lithium adsorption. Regular backwashing using the backwash water tank can reduce the contamination of the membrane in the submerged membrane assembly.

[0032] Furthermore, the pore size of the membrane is generally between 10nm and 500nm. The filtration temperature is preferably 5-50°C, and more preferably 20-40°C. The backwash pressure in the backwash channel is preferably 0.01-0.1MPa, and more preferably 0.03-0.08MPa. The backwash cycle is preferably 30-240min, and more preferably 60-150min. The backwash time is preferably 5-60s, and more preferably 20-40s.

[0033] Furthermore, the bottom of the filter tank is provided with the second aeration component, and the aeration volume is preferably 10-100 Nm 3 / h, more preferably 30-60Nm 3 / h. Bottom aeration can not only make the solution in the filter pool evenly mixed, flush the membrane surface, and reduce the pollution of the membrane surface. At the same time, aeration makes the lithium adsorbent in the filter pool always in a suspended state, and the lithium adsorbent and the salt lake brine are fully contacted again, which also improves the adsorption efficiency. The lithium adsorbent concentrate is discharged from the filter pool through the concentrate pump, and lithium salt is further extracted from the lithium adsorbent concentrate.

[0034] Furthermore, the lithium adsorbent concentrate can be vacuum filtered and dehydrated by a filtration mechanism, and vacuum filtration can achieve efficient dehydration and fine solid-liquid separation, and the concentration of recovered lithium is higher. After the filter cake is washed with water, it enters the desorption mechanism and is desorbed using a desorbent, and the desorption liquid after desorption is the recovered lithium.

[0035] Furthermore, a desorbent adding pipe for adding desorbent is connected to the top of the desorbent mechanism.

[0036] Furthermore, the desorbent includes an aqueous solution, phosphoric acid, sulfuric acid or hydrochloric acid solution, which is used to desorb lithium ions from the lithium adsorbent to separate lithium salts. The obtained lithium salts can be further purified and concentrated by nanofiltration, reverse osmosis, cross-linking, electrodialysis and other technologies to obtain high-purity and high-concentration lithium salts.

[0037] Furthermore, an incineration mechanism is connected between the suction filtration mechanism and the desorption mechanism, and the suction filtration mechanism is incinerated to obtain a filter cake containing the lithium adsorbent.

[0038] Compared with the prior art, the beneficial effects of the utility model are as follows:

[0039] (1) The device provided by the utility model can effectively separate lithium ions from other impurity ions in salt lake brine through nanofiltration, adsorption, membrane separation, suction filtration and desorption, thereby achieving effective enrichment of lithium ions with simple process and high efficiency.

[0040] (2) The device provided by the utility model uses nanofiltration to remove impurities in salt lake brine before adsorption, thereby improving the adsorption efficiency of the lithium adsorbent.

[0041] (2) The adsorption stirring box provided by the utility model has high solid-liquid mixing efficiency, and is provided with a stirring paddle and an aeration component to enhance the stirring and mixing effect; at the same time, the stirring box is provided with pH and temperature detection, and the pH value and temperature of the mixed liquid can be adjusted according to the adsorption efficiency, thereby further improving the adsorption efficiency.

[0042] (3) The device provided by the utility model uses an immersed membrane to perform solid-liquid separation on the lithium adsorbent after adsorption in the adsorption stirring box. The immersed membrane is provided with an aeration component so that the lithium adsorbent can adsorb as many lithium ions as possible, thereby improving the lithium yield.

[0043] (4) The device provided by the utility model adopts an immersed membrane, which has high solid-liquid separation efficiency, strong anti-pollution ability and low energy consumption; the immersed membrane component has a large specific surface area, the equipment is compact and occupies a small area;

[0044] (5) The device provided by the utility model adopts vacuum filtration for separation and dehydration, and vacuum filtration can achieve efficient dehydration and fine solid-liquid separation. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 This is a schematic diagram of the structure of the device for extracting lithium salt from salt lake brine shown in Example 1;

[0046] Figure 2 This is a schematic diagram of the structure of the device for extracting lithium salt from salt lake brine shown in Example 2.

[0047] Description of the markings in the figure:

[0048] 1-Nanofiltration membrane;

[0049] 2-adsorption stirring box, 21-pH meter, 22-thermometer, 23-heating component, 24-stirring paddle, 25-first aeration component, 26-pH adjustment channel, 27-lithium adsorbent channel;

[0050] 3-filtration tank, 31-submerged membrane assembly, 32-second aeration assembly, 33-concentrate pump;

[0051] 4- Filtration mechanism;

[0052] 5-desorption mechanism, 51-desorption agent adding pipe;

[0053] 6-backwash water tank, 61-water production channel, 611-water production pump, 62-backwash channel, 621-backwash pump;

[0054] 7-Incineration mechanism. DETAILED DESCRIPTION

[0055] The utility model is described in detail below in conjunction with the accompanying drawings and specific embodiments. The embodiments are implemented based on the technical solution of the utility model, and provide detailed implementation methods and specific operation processes, but the protection scope of the utility model is not limited to the following embodiments. In the following implementation methods or embodiments, if there is no special description of the functional components or structures, it indicates that they are all conventional components or conventional structures used in the field to achieve the corresponding functions.

[0056] It should be noted that in the description of the present invention, the terms "upper", "lower", "inner", "outer", "front end", "rear end", "two ends", "one end", "the other end" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0057] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "provided with", "connected", etc. should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0058] Example 1

[0059] A device for extracting lithium salt from salt lake brine, such as Figure 1 As shown, including:

[0060] A nanofiltration membrane 1 for performing nanofiltration separation on salt lake brine to obtain a nanofiltration concentrate and a nanofiltration filtrate;

[0061] an adsorption stirring box 2 connected to the nanofiltration filtrate side of the nanofiltration membrane 1, wherein a lithium adsorbent is filled therein, and the filtrate of the nanofiltration membrane 1 is adsorbed and lithium is extracted to obtain a lithium adsorbent mixed solution;

[0062] A filter tank 3 containing an immersed membrane assembly 31 is connected to the adsorption stirring tank 2 to screen and filter the lithium adsorbent mixed liquid in the adsorption stirring tank 2 to obtain a lithium adsorbent concentrate and produced water;

[0063] A suction filtration mechanism 4 connected to the lithium adsorbent concentrate side of the filtration tank 3 is used to obtain a filter cake containing the lithium adsorbent by suction filtration;

[0064] The desorption mechanism 5 for desorbing the filter cake containing the lithium adsorbent is connected to the suction filtration mechanism 4 and receives the filter cake obtained by the suction filtration mechanism 4 .

[0065] In this embodiment, the salt lake brine has a lithium concentration of 65 mg / L, a magnesium concentration of 25 mg / L, and a calcium concentration of 3.2 mg / L. The salt lake brine is separated by nanofiltration to separate magnesium and calcium ions in the solution. These impurity ions will compete with lithium ions for adsorption positions during the adsorption of lithium, reducing the adsorption efficiency of lithium. After nanofiltration, magnesium, calcium and other ions are in the nanofiltration concentrate, and most of the lithium ions are in the nanofiltration filtrate. The nanofiltration filtrate enters the adsorption stirring box 2 and mixes with the lithium adsorbent. The content of calcium and magnesium in the nanofiltration filtrate is less than 0.1 mg / L.

[0066] In this embodiment, the adsorption stirring box 2 further includes:

[0067] A stirring paddle 24 installed on the top of the adsorption stirring box 2;

[0068] And a first aeration assembly 25 installed at the bottom of the adsorption stirring box 2.

[0069] In this embodiment, the nanofiltration filtrate and the lithium adsorbent are evenly mixed in the adsorption stirring box 2. To enhance the stirring and mixing effect, a stirring paddle 24 is installed in the adsorption stirring box 2, and a first aeration assembly 25 is provided at the bottom to enhance the stirring effect and improve the adsorption effect of the adsorbent.

[0070] In this embodiment, the lithium adsorbent is in powder form and is an aluminum salt adsorbent.

[0071] Preparation method of aluminum salt adsorbent: weigh 100g aluminum chloride and 27.2g lithium chloride, mix and dissolve them in a 1000mL volumetric flask for standby use. Take 500mL of lithium chloride and aluminum chloride mixed solution in an open crystallizer, control the reaction temperature to 80℃, control the stirring speed to 200r / min, control the peristaltic pump speed to adjust its drop rate to 3mL / min, and slowly add 5mol / L sodium hydroxide solution to the lithium chloride and aluminum chloride mixed solution for coprecipitation reaction. Control the end point pH to 6-7, wash with water, centrifuge, separate solid and liquid, and dry and grind the obtained solid in a 60℃ forced air oven to obtain the aluminum salt adsorbent product. The aluminum salt adsorbent prepared by this method is in a uniform powder form, and the adsorbent particle size is 250-550nm.

[0072] In this embodiment, the nanofiltration filtrate enters the adsorption stirring box 2, and the aluminum salt adsorbent is added into the adsorption stirring box 2. The mixture is evenly stirred for about 30 minutes, and the lithium in the salt lake brine is adsorbed by the aluminum salt adsorbent to form aluminum-lithium compound particles.

[0073] In this embodiment, the submerged membrane assembly 31 is of curtain type. The material of the submerged membrane assembly 31 is polytetrafluoroethylene.

[0074] In this embodiment, a second aeration assembly 32 is provided at the bottom of the filter pool 3. The filter pool 3 is connected to a backwash water tank 6, and a water production channel 61 flowing from the filter pool 3 to the backwash water tank 6 and a backwash channel 62 flowing from the backwash water tank 6 to the filter pool 3 are connected between the filter pool 3 and the backwash water tank 6. A water production pump 611 is installed on the water production channel 61, and a backwash pump 621 is installed on the backwash channel 62.

[0075] In this embodiment, a concentrate pump 33 is connected between the filter tank 3 and the filtration mechanism 4 .

[0076] In this embodiment, after the nanofiltration filtrate and the lithium adsorbent are mixed and stirred in the adsorption stirring box 2, the lithium adsorbent mixed liquid is transported to the filter tank 3 equipped with the submerged membrane assembly 31, and the lithium adsorbent is separated and filtered to obtain produced water and adsorbent concentrate.

[0077] In this embodiment, the submerged membrane assembly 31 is placed in the filter pool 3, and the lithium adsorbent mixed liquid directly enters the filter pool 3. Under the action of the second aeration assembly 32, the lithium adsorbent mixed liquid is in a suspended state with uniform concentration. After screening and filtration by the submerged membrane assembly 31, the produced water is discharged from the filter pool through the produced water pump 611, and the retained lithium adsorbent concentrate is discharged from the filter pool 3 through the concentrate pump 33. The lithium adsorbent concentrate is the adsorbent after lithium adsorption. Regular backwashing using the backwash water tank 6 can reduce the contamination of the membrane in the submerged membrane assembly 31.

[0078] In this embodiment, the pore size of the membrane is between 50-100 nm, and the filtration temperature is 20° C. The backwash pressure in the backwash channel 62 is 0.05 MPa, the backwash cycle is 120 min, and the backwash time is 30 s.

[0079] In this embodiment, the bottom of the filter tank 3 is provided with the second aeration component 32, and the aeration volume of the second aeration component 32 is 30 Nm 3 / h. Bottom aeration can not only make the solution in the filter pool 3 mixed evenly, flush the membrane surface, and reduce the pollution of the membrane surface. At the same time, aeration makes the lithium adsorbent in the filter pool 3 always in a suspended state, and the lithium adsorbent and the salt lake brine are fully contacted again, which also improves the adsorption efficiency. The lithium adsorbent concentrate is discharged from the filter pool 3 through the concentrate pump 33, and lithium salt is further extracted from the lithium adsorbent concentrate.

[0080] In this embodiment, the first aeration component 25 and the second aeration component 32 are blower aeration devices, which are commercially available products.

[0081] In this embodiment, the lithium adsorbent concentrate can be vacuum filtered and dehydrated by the filtration mechanism 4. The vacuum filtration can achieve efficient dehydration and fine solid-liquid separation, and the concentration of recovered lithium is higher. After the filter cake is washed with water, it enters the desorption mechanism 5 and is desorbed using a desorbent. The desorption liquid after desorption is the recovered lithium.

[0082] In this embodiment, the top of the desorption mechanism 5 is connected with a desorbent adding pipe 51 for adding desorbent.

[0083] In this embodiment, the desorbent is an aqueous solution.

[0084] In this embodiment, an incineration mechanism 7 is connected between the suction filtration mechanism 4 and the desorption mechanism 5 to incinerate the suction filtration mechanism 4 to obtain a filter cake containing the lithium adsorbent.

[0085] Salt lake brine, lithium concentration 65mg / L, magnesium concentration 25mg / L, calcium concentration 3.2mg / L. After nanofiltration separation and filtration, the content of calcium and magnesium in the nanofiltration filtrate is less than 0.1mg / L. The nanofiltration filtrate enters the adsorption stirring box 2, and the aluminum salt adsorbent is added to the adsorption stirring box 2. The mixture is evenly stirred for about 30 minutes. The lithium in the salt lake brine is adsorbed by the aluminum salt adsorbent to form aluminum-lithium compound particles. After filtration by the submerged membrane assembly 31, the filtration temperature is 20°C, the aeration volume is 30Nm3 / h, and the produced water is discharged by the suction action of the water production pump 611. A lithium-containing lithium adsorbent concentrate is obtained. After the concentrate is vacuum filtered, the filter cake is incinerated, and water is used for leaching. After filtration, a lithium solution is obtained, and the lithium recovery rate is 90%.

[0086] Example 2

[0087] A device for extracting lithium salt from salt lake brine, such as Figure 2 As shown, including:

[0088] A nanofiltration membrane 1 for performing nanofiltration separation on salt lake brine to obtain a nanofiltration concentrate and a nanofiltration filtrate;

[0089] an adsorption stirring box 2 connected to the nanofiltration filtrate side of the nanofiltration membrane 1, wherein a lithium adsorbent is filled therein, and the filtrate of the nanofiltration membrane 1 is adsorbed and lithium is extracted to obtain a lithium adsorbent mixed solution;

[0090] A filter tank 3 containing an immersed membrane assembly 31 is connected to the adsorption stirring tank 2 to screen and filter the lithium adsorbent mixed liquid in the adsorption stirring tank 2 to obtain a lithium adsorbent concentrate and produced water;

[0091] A suction filtration mechanism 4 connected to the lithium adsorbent concentrate side of the filtration tank 3 is used to obtain a filter cake containing the lithium adsorbent by suction filtration;

[0092] The desorption mechanism 5 for desorbing the filter cake containing the lithium adsorbent is connected to the suction filtration mechanism 4 and receives the filter cake obtained by the suction filtration mechanism 4 .

[0093] In this embodiment, the salt lake brine has a lithium concentration of 535 mg / L, a magnesium concentration of 215 mg / L, and a calcium concentration of 28 mg / L. The salt lake brine is separated by nanofiltration to separate magnesium and calcium ions in the solution. These impurity ions will compete with lithium ions for adsorption positions during the adsorption of lithium, reducing the adsorption efficiency of lithium. After nanofiltration, magnesium, calcium and other ions are in the nanofiltration concentrate, and most of the lithium ions are in the nanofiltration filtrate. The nanofiltration filtrate enters the adsorption stirring box 2 and mixes with the lithium adsorbent. The content of calcium and magnesium in the nanofiltration filtrate is less than 0.1 mg / L.

[0094] In this embodiment, the adsorption stirring box 2 further includes:

[0095] A pH meter 21 and a thermometer 22 installed in the adsorption stirring box 2;

[0096] A heating component 23 installed inside or on the outer wall of the adsorption stirring box 2;

[0097] A stirring paddle 24 installed on the top of the adsorption stirring box 2;

[0098] And a first aeration assembly 25 installed at the bottom of the adsorption stirring box 2.

[0099] In this embodiment, the adsorption stirring box 2 further includes a pH adjustment channel 26 for adjusting pH.

[0100] In this embodiment, the nanofiltration filtrate and the lithium adsorbent are mixed evenly in the adsorption stirring box 2. The adsorption stirring box 2 is provided with a pH meter and a thermometer, and the temperature and pH of the nanofiltration filtrate and the lithium adsorbent mixed solution can be adjusted according to the factors affecting the adsorption to improve the adsorption effect. In order to enhance the stirring and mixing effect, a stirring paddle 24 is installed in the adsorption stirring box 2, and a first aeration component 25 is provided at the bottom to enhance the stirring effect and improve the adsorption effect of the adsorbent.

[0101] In this embodiment, the heating component 23 is a heating tube.

[0102] In this embodiment, the lithium adsorbent is in powder form and is an aluminum salt adsorbent.

[0103] Preparation method of aluminum salt adsorbent: weigh 100g aluminum chloride and 27.2g lithium chloride, mix and dissolve them in a 1000mL volumetric flask for standby use. Take 500mL of lithium chloride and aluminum chloride mixed solution in an open crystallizer, control the reaction temperature to 80℃, control the stirring speed to 200r / min, control the peristaltic pump speed to adjust its drop rate to 3mL / min, and slowly add 5mol / L sodium hydroxide solution to the lithium chloride and aluminum chloride mixed solution for coprecipitation reaction. Control the end point pH to 6-7, wash with water, centrifuge, separate solid and liquid, and dry and grind the obtained solid in a 60℃ forced air oven to obtain the aluminum salt adsorbent product. The aluminum salt adsorbent prepared by this method is in a uniform powder form, and the adsorbent particle size is 250-550nm.

[0104] In this embodiment, the nanofiltration filtrate enters the adsorption stirring box 2, and the aluminum salt adsorbent is added into the adsorption stirring box 2. The mixture is evenly stirred for about 30 minutes, and the lithium in the salt lake brine is adsorbed by the aluminum salt adsorbent to form aluminum-lithium compound particles.

[0105] In this embodiment, the submerged membrane assembly 31 is of curtain type. The material of the submerged membrane assembly 31 is polytetrafluoroethylene.

[0106] In this embodiment, a second aeration assembly 32 is provided at the bottom of the filter pool 3. The filter pool 3 is connected to a backwash water tank 6, and a water production channel 61 flowing from the filter pool 3 to the backwash water tank 6 and a backwash channel 62 flowing from the backwash water tank 6 to the filter pool 3 are connected between the filter pool 3 and the backwash water tank 6. A water production pump 611 is installed on the water production channel 61, and a backwash pump 621 is installed on the backwash channel 62.

[0107] In this embodiment, a concentrate pump 33 is connected between the filter tank 3 and the filtration mechanism 4 .

[0108] In this embodiment, after the nanofiltration filtrate and the lithium adsorbent are mixed and stirred in the adsorption stirring box 2, the lithium adsorbent mixed liquid is transported to the filter tank 3 equipped with the submerged membrane assembly 31, and the lithium adsorbent is separated and filtered to obtain produced water and adsorbent concentrate.

[0109] In this embodiment, the submerged membrane assembly 31 is placed in the filter pool 3, and the lithium adsorbent mixed liquid directly enters the filter pool 3. Under the action of the second aeration assembly 32, the lithium adsorbent mixed liquid is in a suspended state with uniform concentration. After screening and filtration by the submerged membrane assembly 31, the produced water is discharged from the filter pool through the produced water pump 611, and the retained lithium adsorbent concentrate is discharged from the filter pool 3 through the concentrate pump 33. The lithium adsorbent concentrate is the adsorbent after lithium adsorption. Regular backwashing using the backwash water tank 6 can reduce the contamination of the membrane in the submerged membrane assembly 31.

[0110] In this embodiment, the pore size of the membrane is between 50-100 nm, and the filtration temperature is 20° C. The backwash pressure in the backwash channel 62 is 0.05 MPa, the backwash cycle is 120 min, and the backwash time is 30 s.

[0111] In this embodiment, the bottom of the filter tank 3 is provided with the second aeration component 32, and the aeration volume of the second aeration component 32 is 50 Nm 3 / h. Bottom aeration can not only make the solution in the filter pool 3 mixed evenly, flush the membrane surface, and reduce the pollution of the membrane surface. At the same time, aeration makes the lithium adsorbent in the filter pool 3 always in a suspended state, and the lithium adsorbent and the salt lake brine are fully contacted again, which also improves the adsorption efficiency. The lithium adsorbent concentrate is discharged from the filter pool 3 through the concentrate pump 33, and lithium salt is further extracted from the lithium adsorbent concentrate.

[0112] In this embodiment, the first aeration component 25 and the second aeration component 32 are blower aeration devices, which are commercially available products.

[0113] In this embodiment, the lithium adsorbent concentrate can be vacuum filtered and dehydrated by the filtration mechanism 4. The vacuum filtration can achieve efficient dehydration and fine solid-liquid separation, and the concentration of recovered lithium is higher. After the filter cake is washed with water, it enters the desorption mechanism 5 and is desorbed using a desorbent. The desorption liquid after desorption is the recovered lithium.

[0114] In this embodiment, the top of the desorption mechanism 5 is connected with a desorbent adding pipe 51 for adding desorbent.

[0115] In this embodiment, the desorbent is an aqueous solution.

[0116] In this embodiment, an incineration mechanism 7 is connected between the suction filtration mechanism 4 and the desorption mechanism 5 to incinerate the suction filtration mechanism 4 to obtain a filter cake containing the lithium adsorbent.

[0117] In this embodiment, in addition to adding lithium adsorbent to the nanofiltration filtrate, in order to increase the adsorption efficiency of the lithium adsorbent, the pH in the adsorption stirring box 2 is controlled to be 7-8 and the temperature is about 55°C. After filtration by the submerged membrane assembly 31, the pore size of the membrane is 100nm, and the aeration volume is 50Nm 3 / h, the produced water is discharged through the suction action of the produced water pump 611. After running for 2 hours, backwash for 1 minute. A lithium adsorbent concentrate containing lithium is obtained. After the lithium adsorbent concentrate is vacuum filtered, the filter cake is desorbed using a desorbent to obtain a desorbent containing lithium, and the lithium recovery rate is 95%.

[0118] Example 3

[0119] Compared with Example 1, most of them are the same, except for the salt lake brine, the lithium concentration is 235 mg / L, the magnesium concentration is 123 mg / L, and the calcium concentration is 5 mg / L. After nanofiltration separation and filtration, the content of calcium and magnesium in the nanofiltration filtrate is less than 0.1 mg / L, and the nanofiltration filtrate enters the adsorption stirring box 2. Aluminum salt adsorbent is added, mixed and stirred evenly, and filtered through the submerged membrane assembly 31, the pore size of the membrane is 100 nm, the filtration temperature is 40 ° C, and the aeration volume is 60 Nm 3 / h, the produced water is discharged through the suction action of the produced water pump 611. A lithium adsorbent concentrate containing lithium is obtained, and the concentrate is vacuum filtered to obtain a filter cake containing lithium. The filter cake is desorbed using a desorbent, and the desorbed liquid is concentrated by reverse osmosis to obtain a lithium solution with a high concentration, and the lithium recovery rate is 93%.

[0120] Comparative Example 1

[0121] Compared with Example 1, most of the aspects are the same, except that the salt lake brine directly enters the adsorption stirring box 2 for adsorption without nanofiltration separation, and the recovery rate of lithium is only 80%.

[0122] Comparative Example 2

[0123] Compared with Example 2, most of them are the same, except that the submerged membrane assembly 31 in the filter tank 3 is replaced by a ceramic membrane. The lithium recovery rate is only 83%, and the energy consumption of the whole process is increased by 60%.

[0124] Comparative Example 3

[0125] Compared with Example 3, most of the contents are the same, except that the salt lake brine is directly introduced into the adsorption stirring box 2 for adsorption without nanofiltration separation, and the recovery rate of lithium is only 75%.

[0126] The above description of the embodiments is to facilitate the understanding and use of the utility model by those skilled in the art. It is obvious that those familiar with the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the utility model is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the utility model without departing from the scope of the utility model should be within the scope of protection of the utility model.

Claims

1. A device for extracting lithium salt from salt lake brine, characterized in that: include: A nanofiltration membrane (1) is used to perform nanofiltration separation on salt lake brine to obtain a nanofiltration concentrate and a nanofiltration filtrate; an adsorption stirring box (2) connected to the nanofiltration filtrate side of the nanofiltration membrane (1), wherein the box is filled with a lithium adsorbent for adsorbing and extracting lithium from the filtrate of the nanofiltration membrane (1) to obtain a lithium adsorbent mixed solution; A filter tank (3) containing an immersed membrane assembly (31) is connected to the adsorption stirring tank (2) to screen and filter the lithium adsorbent mixed liquid in the adsorption stirring tank (2) to obtain a lithium adsorbent concentrated liquid and produced water; A filtration mechanism (4) connected to the lithium adsorbent concentrate side of the filtration tank (3) and filtering to obtain a filter cake containing the lithium adsorbent; A desorption mechanism (5) is connected to the suction filtration mechanism (4) and is used to desorb the filter cake containing the lithium adsorbent.

2. The device for extracting lithium salt from salt lake brine according to claim 1, characterized in that: The adsorption stirring box (2) further comprises: A pH meter (21) and a thermometer (22) installed in the adsorption stirring box (2); A heating component (23) installed inside or on the outer wall of the adsorption stirring box (2); A stirring paddle (24) installed on the top of the adsorption stirring box (2); And a first aeration component (25) installed at the bottom of the adsorption stirring box (2).

3. The device for extracting lithium salt from salt lake brine according to claim 1, characterized in that: The adsorption stirring box (2) further comprises a pH adjustment channel (26) for adjusting pH and a lithium adsorbent channel (27) for introducing a lithium adsorbent.

4. The device for extracting lithium salt from salt lake brine according to claim 1, characterized in that: The submerged membrane assembly (31) includes curtain type, column type, "U" type or seaweed type.

5. The device for extracting lithium salt from salt lake brine according to claim 1, characterized in that: A second aeration assembly (32) is provided at the bottom of the filter tank (3).

6. The device for extracting lithium salt from salt lake brine according to claim 1, characterized in that: The filter pool (3) is connected to a backwash water tank (6), and a water production channel (61) flowing from the filter pool (3) to the backwash water tank (6) and a backwash channel (62) flowing from the backwash water tank (6) to the filter pool (3) are connected between the filter pool (3) and the backwash water tank (6).

7. The device for extracting lithium salt from salt lake brine according to claim 6, characterized in that: A water production pump (611) is installed on the water production channel (61), and a backwash pump (621) is installed on the backwash channel (62).

8. The device for extracting lithium salt from salt lake brine according to claim 1, characterized in that: A concentrate pump (33) is connected between the filter tank (3) and the suction filtration mechanism (4).

9. The device for extracting lithium salt from salt lake brine according to claim 1, characterized in that: The top of the desorption mechanism (5) is connected to a desorbent adding pipe (51) for adding desorbent.

10. The device for extracting lithium salt from salt lake brine according to claim 1, characterized in that: An incineration mechanism (7) for incinerating the filter cake containing the lithium adsorbent obtained by the incineration mechanism (4) is also connected between the incineration mechanism (4) and the desorption mechanism (5).

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