Membrane distillation coupling adsorption lithium extraction device and lithium extraction method

Abstract

The invention discloses a membrane distillation coupling adsorption lithium extraction device and a lithium extraction method, and belongs to the field of low-grade brine resource development. The membrane distillation coupling adsorption lithium extraction device comprises a membrane distillation assembly and an adsorption unit, and low-grade salt lake brine is heated by photo-thermal / geothermal resources and enters the membrane distillation assembly to realize fresh water recovery and brine concentration upgrading, so that the low-grade salt lake brine enters the adsorption unit to realize efficient extraction of lithium resources. The device synchronously realizes upgrading of low-grade brine and recovery of fresh water, effectively reduces the lithium extraction period of the low-grade brine, and improves the adsorption lithium extraction performance.

Description

Technical Field

[0001] The present invention belongs to the field of development of low-grade brine resources, and particularly relates to a membrane distillation coupled adsorption lithium extraction device and a lithium extraction method. Background Art

[0002] Lithium is an ideal battery metal element. Compared with hydrogen fuel cells and sodium-ion batteries, lithium-ion battery technology is mature and has a high energy density. In the past decade, the sales volume of electric vehicles has shown a booming upward trend. Correspondingly, the global demand for lithium resources has also increased rapidly. However, the reserves of land lithium ore resources are limited, and traditional mining methods are accompanied by severe environmental costs. In contrast, liquid lithium resources such as seawater and salt lake brine have attracted much attention due to their rich reserves and wide distribution, but generally have characteristics such as low lithium concentration and many associated impurity ions.

[0003] Most of China's lithium resources are distributed in the Qinghai-Tibet region. This region has a high altitude, strong sunlight, and little precipitation, and belongs to a fragile plateau ecological area. The Qinghai-Tibet salt lake brine is a low-grade lithium resource with a low lithium ion concentration. Based on the abundant light and heat resources in the Qinghai-Tibet region, the lithium extraction technology of solar pond evaporation and crystallization is prevalent. However, the lithium extraction cycle is long, and a large amount of fresh water resources are wasted during the evaporation process. In contrast, the adsorption method has gradually become the core method for lithium extraction from salt lake brine due to its short lithium extraction cycle and high selectivity. However, the adsorption performance of lithium extraction by adsorption in low-grade brine is general. Therefore, it is very necessary to further improve the efficiency and rate of lithium extraction by the adsorption method while maintaining fresh water resources. Summary of the Invention

[0004] Aiming at the deficiencies in the prior art, the present invention proposes a membrane distillation coupled adsorption lithium extraction device and a lithium extraction method, which can simultaneously upgrade low-grade brine and recover fresh water, effectively reduce the lithium extraction cycle of low-grade brine, and improve the lithium extraction efficiency by adsorption.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A membrane distillation coupled adsorption lithium extraction device, the device includes a membrane distillation unit and an adsorption unit. The membrane distillation unit includes a pool body. A plurality of baffles are vertically arranged on both opposite side walls inside the pool body. The baffles on the two opposite side walls are staggered to form an 'S'-shaped brine flow channel. Membrane distillation grid plates are vertically arranged on the inner side of the pool wall and on both sides of each baffle perpendicular to the pool bottom. The gaps formed between the membrane distillation grid plates and the pool wall and the baffles are mutually communicated to form a fresh water flow channel; a distillation membrane is attached to the side of the membrane distillation grid plate in contact with the brine. The adsorption unit includes an adsorption cavity, and a lithium ion sieve adsorbent is arranged inside the adsorption cavity. The bottom of the brine flow channel is communicated with the bottom of the adsorption cavity through a brine delivery pipeline. A de-lithiated brine delivery pipeline is connected to the top of the adsorption cavity and is connected to a subsequent treatment operation unit.

[0007] Preferably, the baffle, the membrane distillation grid plate and the cell body are integrally connected.

[0008] The part of the membrane distillation grid plate with the distillation membrane attached is provided with a microporous array. The micropores on the microporous array communicate the brine flow channel and the fresh water flow channel. The distillation membrane is a hydrophobic microporous membrane, which only allows the gaseous water on the surface of the high-temperature brine to pass through and condenses into the normal-temperature fresh water. The hydrophobic microporous membrane is used for the transfer of gaseous water.

[0009] Inside the adsorption cavity, a primary support material, a secondary support material and a lithium ion sieve adsorbent are sequentially arranged from bottom to top, and the particle sizes of the primary support material, the secondary support material and the lithium ion sieve adsorbent decrease in sequence.

[0010] The lithium ion sieve adsorbent is a polymer porous microsphere carrier loaded with adsorbent powder, and both the primary support material and the secondary support material are polymer porous microspheres without adsorbent.

[0011] On two opposite side walls of the cell body, a brine flow channel inlet and a brine flow channel outlet are respectively arranged. The brine flow channel outlet is communicated with a brine conveying pipeline. On the side wall of the cell body, a fresh water flow channel inlet and a fresh water flow channel outlet are respectively arranged.

[0012] The brine flow channel inlet is arranged on the side wall of the cell body at the end far from the adsorption unit, and the brine flow channel outlet is arranged on the side wall of the cell body at the end close to the adsorption unit.

[0013] Both the fresh water flow channel inlet and the fresh water flow channel outlet are arranged on the side wall of the cell body at the end far from the adsorption unit.

[0014] A lithium extraction method using the membrane distillation coupled adsorption lithium extraction device described above includes the following steps:

[0015] Step 1: Heat the low-grade brine to 60 - 80 °C by solar thermal or geothermal resources, and transport it to the brine flow channel. Utilize the hydrophobic microporous property of the distillation membrane to enable the gaseous water to pass through the distillation membrane and condense and recover in the fresh water in the fresh water flow channel, while concentrating the high-temperature brine;

[0016] Step 2: The concentrated high-temperature brine enters the adsorption unit through the brine conveying pipeline, flows through the primary support material, the secondary support material and the lithium ion sieve adsorbent in sequence to adsorb lithium ions, and the brine after lithium extraction is discharged through the de-lithiated brine conveying pipeline for subsequent treatment.

[0017] The flow rate of the brine in the brine flow channel is 100 - 150 ml / min, and the flow rate of the fresh water in the fresh water flow channel is 100 - 150 ml / min, and the temperature is 10 - 20 °C.

[0018] Compared with the prior art, the beneficial effects of the present invention are:

[0019] 1. Compared with the solar pond evaporation crystallization method, the present invention utilizes membrane distillation technology to accelerate the evaporation and concentration process of low-grade salt lake brine, significantly shortening the lithium extraction cycle, and simultaneously achieving the collection of evaporated fresh water resources.

[0020] 2. Compared with the lithium adsorption method, the present invention utilizes the rich solar thermal resources and geothermal resources in the Qinghai-Tibet region to heat up low-grade salt lake brine, and uses membrane distillation technology to concentrate the high-temperature brine, increasing the lithium ion concentration in the brine, upgrading the brine grade, and effectively improving the lithium extraction rate and efficiency of the lithium ion sieve adsorbent in the adsorption unit.

[0021] 3. The present invention is simple to operate, green and environmentally friendly, and makes full use of the rich solar thermal resources and geothermal resources in the Qinghai-Tibet region to simultaneously recover fresh water resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a three-dimensional view of the membrane distillation coupled lithium adsorption device in the present invention Figure 1 ;

[0023] Figure 2 is a three-dimensional view of the membrane distillation coupled lithium adsorption device in the present invention Figure 2 . DETAILED DESCRIPTION OF THE INVENTION

[0024] The following will clearly and completely describe the technical solutions in the present invention in conjunction with the drawings and embodiments. Obviously, the described embodiments are only a part of the embodiments of the invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0025] A membrane distillation coupled lithium adsorption device, the device includes: a membrane distillation unit 1 and an adsorption unit 2. A brine delivery pipeline 108 is connected between the membrane distillation unit 1 and the adsorption unit 2; a de-lithiated brine delivery pipeline 205 is connected after the adsorption unit 2; the membrane distillation unit 1 is composed of a brine flow channel 101, a membrane distillation grid plate 103, a distillation membrane 104, and a fresh water flow channel 102; the brine flow channel 101 of the membrane distillation unit 1 is separated into an 'S'-shaped flow channel inside the pool body by the membrane distillation grid plates 103 that alternately appear in space; the brine flow channel 101 of the membrane distillation unit 1 starts from the brine flow channel inlet 107 and ends at the brine delivery pipeline 108; the fresh water flow channel 102 of the membrane distillation unit 1 is a flow channel formed by the gaps between the membrane distillation grid plates 103 that alternately appear in space and the internal baffles 110 thereof and the gaps between the membrane distillation grid plates 103 and the pool wall; the fresh water flow channel 102 of the membrane distillation unit 1 starts from the fresh water flow channel inlet 105 and ends at the fresh water flow channel outlet 106.

[0026] After the low-grade brine in the salt lake is heated by the geothermal resources or solar-thermal resources in the Qinghai-Tibet region, it enters the membrane distillation unit 1 through the brine flow channel inlet 107. The high-temperature brine passes through the brine flow channel 101. Among them, the fresh water component, driven by the temperature and pressure gradient mass transfer, passes through the distillation membrane 104 and the membrane distillation grid plate 103 and enters the fresh water flow channel 102, and then the fresh water resources are collected. At the same time, the high-temperature brine is concentrated, the lithium ion concentration in the high-temperature brine is increased, and the low-grade brine is upgraded. The adsorption unit 2 is composed of an adsorption cavity 204, a lithium ion sieve adsorbent 203, a primary support material 201, a secondary support material 202, and a de-lithiated brine delivery pipeline 205; the primary support material 201, the secondary support material 202, and the lithium ion sieve adsorbent 203 are vertically and layer by layer placed in the adsorption cavity 204 in the order of decreasing particle size; the high-temperature brine with upgraded grade enters the adsorption unit 2 through the brine delivery pipeline 108, and successively submerges the primary support material 201, the secondary support material 202, and the lithium ion sieve adsorbent 203; the lithium resources in the high-temperature brine are captured by the lithium ion sieve adsorbent 203 to realize lithium extraction; the high-temperature brine completes the lithium extraction process and becomes brine with a low lithium ion concentration; it enters the subsequent operation unit through the de-lithiated brine delivery pipeline 205. The high-temperature brine with upgraded grade by the membrane distillation unit 1 has a high lithium ion concentration. During the lithium extraction process of the lithium ion sieve adsorbent 203 in the adsorption unit 2, the high-concentration adsorbent and the high-temperature environment help to improve the adsorption efficiency and rate of the lithium ion sieve adsorbent 203.

[0027] Example 1:

[0028] A membrane distillation coupled with adsorption lithium extraction device, as Figure 1 、 Figure 2 shown, the brine flow channel inlet 107 is connected with a solar-thermal / geothermal heating system, and the low-grade salt lake brine with a lithium ion concentration lower than 0.1 g·L -1 in the Qinghai-Tibet region is heated and raised to 70 °C and then enters the membrane distillation unit 1. The 70 °C high-temperature brine passes through the brine flow channel 101 at a flow rate of 120 ml / min. Among them, the gaseous water, driven by the temperature and pressure gradient mass transfer, successively passes through the hydrophobic distillation membrane 104 and the microporous array on the membrane distillation grid plate 103 and enters the fresh water flow channel 102 with a water temperature of 15 °C and a flow rate of 120 ml / min, and then condenses into liquid water to realize the collection of fresh water resources. Along with the concentration of the high-temperature brine, the lithium ion concentration in the high-temperature brine is increased to 0.26 g·L -1 or above, and the low-grade brine is upgraded. The lithium ion concentration is up to 0.26 g·L -1The above high-temperature brine enters the adsorption unit 2 from the bottom through the brine delivery pipeline 108 at a flow rate of 120 ml / min, successively submerging the primary support material 201, the secondary support material 202, and the lithium-ion sieve adsorbent 203. Lithium ions in the high-temperature brine are captured by the lithium-ion sieve adsorbent 203 to achieve lithium extraction. During the lithium extraction and heat dissipation process of the high-temperature brine, it becomes brine with a lithium ion concentration lower than 0.001 g·L -1 and a water temperature lower than 40°C, and enters the subsequent operation unit through the de-lithiated brine delivery pipe 205 at a flow rate of 120 ml / min. That is, the initial lithium ion concentration of the low-grade brine is lower than 0.1 g·L -1 , and the lithium ion concentration in the brine passing through the membrane distillation unit 1 is increased to 0.26 g·L -1 . After adsorption by the adsorption unit 2, the concentration of lithium ions is lower than 0.001 g·L -1 .

[0029] The temperature of the brine entering the adsorption unit is 40 - 70°C, and this temperature can make the lithium extraction efficiency significantly higher than that of the conventional adsorption method.

[0030] The high-temperature brine upgraded in grade through the membrane distillation unit 1 has a high lithium ion concentration. During the lithium extraction process of the lithium-ion sieve adsorbent 203 in the adsorption unit 2, the high-concentration adsorbent and the high-temperature environment contribute to improving the adsorption efficiency and rate of the lithium-ion sieve adsorbent 203.

[0031] In addition, it should be understood that although this specification is described according to the embodiments, not each embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A membrane distillation coupled adsorption device for lithium extraction, characterized in that: It includes a membrane distillation unit (1) and an adsorption unit (2). The membrane distillation unit (1) includes a pool body (109). A number of baffles (110) are vertically arranged on two opposite side walls inside the pool body (109). The baffles (110) on the two opposite side walls are staggered to form an 'S'-shaped brine flow channel (101). Membrane distillation grid plates (103) are vertically arranged on the inner side of the pool wall and on both sides of each baffle (110) perpendicular to the pool bottom. The voids formed between the membrane distillation grid plates (103) and the pool wall and the baffle (110) respectively communicate with each other to form a fresh water flow channel (102); A distillation membrane (104) is attached to the side of the membrane distillation grid plate (103) in contact with the brine; The adsorption unit (2) includes an adsorption cavity (204). A lithium ion sieve adsorbent (203) is arranged inside the adsorption cavity (204). The brine flow channel (101) is communicated with the bottom of the adsorption cavity (204) through a brine delivery pipeline (108). A de-lithiated brine delivery pipeline (205) is connected and arranged at the top of the adsorption cavity (204).

2. The membrane distillation coupled adsorption lithium extraction device according to claim 1, wherein: The part of the membrane distillation grid plate (103) where the distillation membrane (104) is attached is provided with a microporous array. The micropores on the microporous array communicate the brine flow channel (101) and the fresh water flow channel (102). The distillation membrane (104) is a hydrophobic microporous membrane.

3. The lithium extraction device by membrane distillation coupling adsorption according to claim 1, wherein: Inside the adsorption cavity (204), a primary support material (201), a secondary support material (202), and a lithium ion sieve adsorbent (203) are arranged in sequence from bottom to top. The particle sizes of the primary support material (201), the secondary support material (202), and the lithium ion sieve adsorbent (203) decrease in sequence.

4. The lithium extraction device by membrane distillation coupled with adsorption according to claim 3, characterized in that: The lithium ion sieve adsorbent (203) is a polymer porous microsphere loaded with adsorbent powder. Both the primary support material (201) and the secondary support material (202) are polymer porous microspheres without adsorbent.

5. The membrane distillation coupled adsorption lithium extraction device according to claim 1, wherein: On two opposite side walls of the pool body (109), a brine flow channel inlet (107) and a brine flow channel outlet are respectively arranged. The brine flow channel outlet is communicated with the brine delivery pipeline (108).

6. The lithium extraction device by membrane distillation coupling adsorption according to claim 1, wherein: On the side wall of the pool body (109), a fresh water flow channel inlet (105) and a fresh water flow channel outlet (106) are respectively arranged.

7. The membrane distillation coupled adsorption lithium extraction device according to claim 5, characterized in that: The brine flow channel inlet (107) is arranged on the side wall of the pool body (109) at the end far from the adsorption unit (2). The brine flow channel outlet is arranged on the side wall of the pool body (109) at the end close to the adsorption unit (2).

8. A membrane distillation coupled adsorption lithium extraction device according to claim 6, characterized in that: Both the fresh water flow channel inlet (105) and the fresh water flow channel outlet (106) are arranged on the side wall of the pool body (109) at the end far from the adsorption unit (2).

9. A lithium extraction method using the membrane distillation coupled with adsorption lithium extraction device according to any one of claims 1-8, characterized in that, It includes the following steps: Step 1: Heat the brine to 60 - 80 °C by solar thermal or geothermal resources and transport it to the brine flow channel (101). The gaseous water therein enters the fresh water flow channel (102) through the distillation membrane (104) for condensation and recovery, and at the same time, the high-temperature brine is concentrated; Step 2: The concentrated high-temperature brine enters the adsorption unit (2) through the brine delivery pipeline (108), and the lithium ions are adsorbed by the lithium ion sieve adsorbent (203). The brine after lithium extraction is discharged through the de-lithiated brine delivery pipeline (205).

10. The lithium extraction method according to claim 9, characterized in that: The brine flow rate in the brine flow channel (101) is 100 - 150 ml / min, the fresh water flow rate in the fresh water flow channel (102) is 100 - 150 ml / min, and the temperature is 10 - 20 °C.

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