An impurity control system and method for lithium-containing solutions in the process of extracting lithium from salt lakes

Abstract

The present invention provides an impurity control system and method for lithium-containing solutions in the process of extracting lithium from salt lakes, belonging to the technical field of lithium extraction from salt lakes. It relates to an impurity control system for lithium-containing solutions in the process of extracting lithium from salt lakes, including a desorbed water tank, a resin tower, a buffer tank, a filter, a valve array, a conductivity meter, and a transfer pump. The above can be split into Series A and Series B. Both Series A and Series B are composed of an adsorption unit and a desorption unit, and the number of resin towers and valve arrays included in the adsorption unit is different. The two series of this impurity control system for lithium-containing solutions of the present invention work simultaneously to perform continuous adsorption, desorption, backwashing and other operations. Under the balance of this adsorption mode, the impurity content in the solution in the tower is controlled and gradually reduced, and the ratio of impurities to lithium concentration is controlled at a lowest ratio applicable to the current production conditions, thereby improving the efficiency of adsorption and desorption, ensuring the output and recovery rate, and reducing the waste of old brine.

Description

Technical Field

[0001] The present invention relates to an impurity control system and method for lithium-containing solutions in the process of extracting lithium from salt lakes, and belongs to the technical field of impurity control of lithium-containing solutions. Background Art

[0002] Lithium and its compounds are widely used in the fields of electronics, metallurgy, chemical industry, medicine, energy, etc. due to their excellent properties.

[0003] Before the mid-1980s, countries around the world mainly used lithium ores as raw materials to produce lithium salts through the process of extracting lithium from ores. This method has a long history and a relatively mature process, but it has high energy consumption and will pollute the environment to a certain extent. However, with the increasing scarcity of lithium ore resources, this method has great limitations. On the other hand, the lithium resources in salt lake brines are rich in reserves, and the cost is lower than the mining of ore lithium. The use of the process of extracting lithium from brines is increasing day by day. Generally speaking, since the process of extracting lithium from salt lakes does not require a calcination process similar to that of extracting lithium from ores, the cost is much lower than that of extracting lithium from ores, and the level of impurities is particularly important for the cost.

[0004] The methods for extracting lithium from salt lake brines mainly include precipitation method, calcination leaching method, solvent extraction method, membrane separation method, ion exchange adsorption method, etc. Among them, the ion exchange adsorption method has the advantages of simple process, high recovery rate, environmental friendliness, etc. The basic principles of different methods for extracting lithium from salt lakes are similar, that is, extracting brine from salt fields, separating and controlling impurities in the brine, and further processing the final products. However, due to the different types of salt lakes and different impurity contents, the production methods are not the same. Each method uses different methods for treating impurities. Since the process of extracting lithium from brines is not yet mature, the control of impurities, whether in the early stage or during the production process, has always been a difficult point, resulting in the abandonment of the development of a part of salt lake resources in the initial selection of the industrial chain, and it is difficult to form large-scale production. Summary of the Invention

[0005] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide an impurity control system and method for lithium-containing solutions in the process of extracting lithium from salt lakes, so as to solve the problems such as the difficulty in controlling the impurity content in lithium-containing solutions, high production costs, and limitations of production processes in the existing technology.

[0006] In order to achieve the above first purpose, an impurity control system for lithium-containing solutions in the process of extracting lithium from salt lakes is provided, and the present invention is realized through the following technical solutions.

[0007] An impurity control system for lithium-containing solution in the process of extracting lithium from salt lakes, comprising 1 desorbed water tank, several resin towers, at least 2 buffer tanks, several filters, several valve arrays, at least 4 conductivity meters, and several transfer pumps. The resin towers include an adsorption resin tower, a top water resin tower, and a desorption resin tower. The impurity control system for lithium-containing solution can be split into Series A and Series B, which are composed of an adsorption unit and a desorption unit. The adsorption unit is used to adsorb lithium ions in the old brine onto the adsorbent in the adsorption resin tower, and the desorption unit is used to desorb lithium ions from the adsorbent. The number of resin towers and valve arrays included in the adsorption units of Series A and Series B is different.

[0008] Preferably, the desorption units of Series A and Series B are both three-stage desorption. The desorption resin tower includes a first-stage desorption resin tower, a second-stage desorption resin tower, and a third-stage desorption resin tower. The filters include a tail brine filter, a feed top water filter, and a qualified liquid filter. The transfer pumps include an old brine transfer pump, a tail brine booster pump, and a desorption pump. The desorption pump includes a first-stage desorption pump, a second-stage desorption pump, and a third-stage desorption pump.

[0009] Preferably, the impurity control system for lithium-containing solution includes 1 desorbed water tank, 55 resin towers, 2 buffer tanks, 6 filters, 11 valve arrays, 4 conductivity meters, and several transfer pumps. Series A includes 25 resin towers and 5 valve arrays, and Series B includes 30 resin towers and 6 valve arrays.

[0010] Preferably, Series A is composed of an adsorption unit A and a desorption unit A. The adsorption unit A includes 5 groups of double-tower series-connected A adsorption groups, a tail brine filter, and a transfer pump. Each group of double-tower series-connected A adsorption groups includes 1 valve array and 2 adsorption resin towers. The desorption unit A includes 1 top water resin tower, a feed top water filter, a first-stage desorption pump, 4 first-stage desorption resin towers, a second-stage desorption pump, 3 second-stage desorption resin towers, a third-stage desorption pump, 7 third-stage desorption resin towers, a qualified liquid filter, a buffer tank, 2 conductivity meters, and a tail brine booster pump.

[0011] Preferably, Series B is composed of an adsorption unit B and a desorption unit B. The adsorption unit B includes 3 groups of double-tower series-connected B adsorption groups, 3 groups of triple-tower series-connected B adsorption groups, a tail brine filter, and a transfer pump. Each group of double-tower series-connected B adsorption groups includes 1 valve array and 2 adsorption resin towers, and each group of triple-tower series-connected B adsorption groups includes 1 valve array and 3 adsorption resin towers. The desorption unit B includes 1 top water resin tower, a feed top water filter, a first-stage desorption pump, 4 first-stage desorption resin towers, a second-stage desorption pump, 3 second-stage desorption resin towers, a third-stage desorption pump, 7 third-stage desorption resin towers, a qualified liquid filter, a buffer tank, 2 conductivity meters, and a tail brine booster pump.

[0012] Preferably, each of the 11 valve arrays is configured with an independent adsorption pipeline, the A series and the B series are each configured with a horizontal main pipeline, and the adsorption units and desorption units within the same series are jointly configured with a vertical main pipeline.

[0013] To achieve the second object, a method for controlling impurities in a lithium-containing solution during the extraction of lithium from salt lakes is provided, and the present invention is achieved through the following technical solutions.

[0014] Using the lithium-containing solution impurity control system of this embodiment to perform the operation of extracting lithium from salt lakes, ensuring that the A series and the B series simultaneously perform adsorption, desorption, tower position transformation, and backwashing operations. This lithium-containing solution impurity control method includes the following steps:

[0015] S1. Adsorption

[0016] Dilute the old brine with fresh water, and transport the diluted old brine to the adsorption unit through the old brine transfer pump for adsorption. After the adsorption is completed, the tail brine is discharged to the tail brine channel through the tail brine filter;

[0017] During this process, the old brine is adsorbed by 25 adsorption resin towers in adsorption unit A and 30 adsorption resin towers in adsorption unit B. The adsorption resin towers adsorb lithium ions and impurities;

[0018] S2. Desorption

[0019] Preset the various values of the conductivity meter, and perform three-stage desorption of the resin tower using the desorbing liquid in the desorbing water tank; when the measured conductivity value of the desorbing liquid is lower than the preset conductivity value, transport the desorbing liquid to the qualified liquid filter to obtain the qualified liquid, and transport the qualified liquid to the subsequent process; when the measured conductivity value of the desorbing liquid is higher than the preset conductivity value, transport the desorbing liquid in the buffer tank to the three-stage desorption resin tower through the three-stage desorption pump for continued desorption, and then enter the secondary adsorption;

[0020] When the conductivity value of the desorbing liquid is lower than the preset conductivity value, it indicates that the impurity content in the desorbing liquid has been further reduced and controlled at a relatively low level. At this time, switch the valve array to transport the desorbing liquid to the qualified liquid filter, and the qualified liquid is obtained;

[0021] When the measured conductivity value of the desorbing liquid is higher than the preset conductivity value, it indicates that the impurity content in the desorbing liquid is still relatively high, and desorption operation needs to be continued, that is, enter the secondary adsorption;

[0022] S3. Water flushing

[0023] Preset the conductivity meter and control the amount of water flushed by flow. Preset the fixed value of the amount of water flushed, transport the tail brine to the water flushing resin tower through the tail brine booster pump, and after being detected by the material water flushing filter and the conductivity meter set beside it, transport it back to the desorbing water tank to complete the recovery of the desorbing liquid;

[0024] This step controls the impurity content in the desorbing liquid, avoids the enrichment of impurities in the desorbing liquid, and at the same time ensures the recovery rate of the desorbing liquid.

[0025] S4. Backwashing

[0026] When the position of the resin bed in the resin tower may have a flow deviation, the enrichment rate of impurity ions in the resin tower is too fast, breaking the desorption balance, and the impurity content gets out of control. At this time, the resin tower needs to be backwashed to adjust the position of the resin bed.

[0027] Preferably, during the processes of adsorption, desorption, top water, and backwashing, tower position transformation is carried out. The conductivity fluctuation of the qualified liquid is measured by a conductivity meter, the homogeneous analysis of the impurity content in the qualified liquid is performed, the tower position transformation time is set, and the adsorption residence time of the adsorption resin tower in the process of step S1 is calculated to complete the tower position transformation of the adsorption units in series A and B. First, the tower position transformation time can not only ensure high adsorption efficiency but also ensure that the impurity content is controlled at a lowest level under this adsorption condition. Second, the length of the adsorption residence time also affects the content of lithium ions and impurities.

[0028] Preferably, the backwashing operation in step S4 is carried out according to the progress of the tower position transformation and the conductivity fluctuation of the conductivity meter to adjust the position of the resin bed.

[0029] Advantages of the present invention:

[0030] (1) The present invention relates to an impurity control system for lithium-containing solution in the process of extracting lithium from salt lakes. The impurity control system for lithium-containing solution includes series A and B. The two series work simultaneously to perform continuous adsorption, desorption, backwashing and other operations. Under the balance of this adsorption mode, the impurity content in the solution in the tower is controlled and gradually reduced, and the ratio of impurity to lithium concentration is controlled at a lowest ratio suitable for the current production condition, thereby improving the adsorption and desorption efficiency, ensuring the output and recovery rate, and reducing the waste of old brine.

[0031] (2) The present invention relates to a method for controlling impurities in lithium-containing solution in the process of extracting lithium from salt lakes. The control method sets the tower position transformation time through the desorption amount, water washing amount, impurity content, etc., and performs backwashing operations according to the progress of the tower position transformation and the conductivity fluctuation measurement of the conductivity meter, timely grasps the progress of lithium extraction, reduces the extension of unnecessary time, and ensures the adsorption and desorption efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] By reading the detailed description of the non-restrictive embodiments with reference to the following drawings, other features, objectives and advantages of the present invention will become more obvious:

[0033] Figure 1Process flow diagram of Series A of the present invention;

[0034] Figure 2 Process flow diagram of Series B of the present invention.

[0035] In the figure: 1 desorbed water tank, 2 adsorption resin tower, 3 top water resin tower, 4 primary desorption resin tower, 5 secondary desorption resin tower, 6 tertiary desorption resin tower, 7 buffer tank, 8 tail brine filter, 9 feed top water filter, 10 qualified liquid filter, 11 valve array, 12 conductivity meter, 13 old brine transfer pump, 14 tail brine booster pump, 15 primary desorption pump, 16 secondary desorption pump, 17 tertiary desorption pump, 18 adsorption pipeline, 19 horizontal main pipeline, 20 vertical main pipeline, 21 fresh water pipeline, 22 tail brine channel. Specific embodiments

[0036] To make the technical means, creative features, achieved purposes and functions of the present invention easy to understand, the present invention will be further described below in conjunction with specific embodiments.

[0037] Example 1

[0038] As Figure 1 and Figure 2 shown, an impurity control system for lithium-containing solution in the process of extracting lithium from salt lakes includes 1 desorbed water tank 1, several resin towers, at least 2 buffer tanks 7, several filters, several valve arrays 11, at least 4 conductivity meters 12, and several transfer pumps. In this embodiment, the number of resin towers is 55, the number of buffer tanks 7 is 2, the number of filters is 6, the number of valve arrays 11 is 11, and the number of conductivity meters 12 is 4. Among them, the 55 resin towers are further divided into adsorption resin towers 2, top water resin towers 3 and desorption resin towers according to their positions and functions in the control system.

[0039] In this embodiment, the impurity control system for lithium-containing solution is split into Series A and Series B. The two series share the desorbed water tank 1, and both series are respectively composed of an adsorption unit and a desorption unit, and the desorption unit is a three-stage desorption: the adsorption unit is used to adsorb lithium ions in the old brine onto the adsorbent in the adsorption resin tower 2, and the desorption unit is used to desorb lithium ions from the adsorbent. The difference between the two series lies in the different numbers of resin towers and valve arrays 11 included in the adsorption unit.

[0040] Specifically, the desorption resin towers include a primary desorption resin tower 4, a secondary desorption resin tower 5, and a tertiary desorption resin tower 6. According to their functions, the primary desorption resin tower 4 is a water top tower, the secondary desorption resin tower 5 is a water wash tower, and the tertiary desorption resin tower 6 is a desorption tower. The filters include a tail brine filter 8, a feed top water filter 9, and a qualified liquid filter 10. The transfer pumps include an old brine transfer pump 13, a tail brine booster pump 14, and a desorption pump. The desorption pump includes a primary desorption pump 15, a secondary desorption pump 16, and a tertiary desorption pump 17.

[0041] Specifically, 11 valve arrays 11 are configured with independent adsorption pipelines 18. Each of the two series is configured with a horizontal main pipeline 19, and the adsorption units and desorption units within the same series are jointly configured with a vertical main pipeline 20. A fresh water pipeline 21 is also connected beside the old brine transfer pump 13. The fresh water pipeline 21 is used to dilute the old brine before transporting it to the adsorption unit, on the one hand, reducing the concentration and viscosity of the old brine, and on the other hand, initially reducing the impurity concentration in the old brine. The setting of the fresh water pipeline 21 improves the adsorption effect of the adsorption resin tower 2 in the adsorption unit and increases the output of a single adsorption resin tower 2.

[0042] Combined with Figure 1 , Series A includes 25 resin towers and 5 valve arrays 11, and is composed of an adsorption unit A and a desorption unit A: The adsorption unit A includes 5 groups of double-tower series-connected A adsorption groups, a tail brine filter 8, and transfer pumps. Each group of double-tower series-connected A adsorption groups includes 1 valve array 11 and 2 adsorption resin towers 2. One of the two adsorption resin towers 2 is for adsorption and the other is for protection; The desorption unit A includes 1 top water resin tower 3, a feed top water filter 9 connected between the desorption water tank 1 and the top water resin tower 3 through a pipeline, a primary desorption pump 15 connected to the desorption water tank 1, 4 series-connected primary desorption resin towers 4, a secondary desorption pump 16, 3 series-connected secondary desorption resin towers 5, a tertiary desorption pump 17, 7 series-connected tertiary desorption resin towers 6, a qualified liquid filter 10, a buffer tank 7, 2 conductivity meters 12, and a tail brine booster pump 14. The buffer tank 7 is arranged between the secondary desorption resin tower 5 and the tertiary desorption pump 17, and the 2 conductivity meters 12 are respectively arranged in front of the feed top water filter 9 and the qualified liquid filter 10.

[0043] Combined with Figure 2, Series B includes 30 resin towers and 6 valve arrays 11, which are composed of an adsorption unit B and a desorption unit B: The adsorption unit B includes 3 groups of double-tower series-connected B adsorption groups, 3 groups of triple-tower series-connected B adsorption groups, a tail brine filter 8, and a transfer pump. Each group of double-tower series-connected B adsorption groups includes 1 valve array 11 and 2 adsorption resin towers 2. Each group of triple-tower series-connected B adsorption groups includes 1 valve array 11 and 3 adsorption resin towers 2. Among the three resin towers in the triple-tower series-connected B adsorption group, two are for adsorption and one is for protection; The desorption unit B includes 1 top-water resin tower 3, a feed top-water filter 9 connected between the desorption water tank 1 and the top-water resin tower 3 through a pipeline, a primary desorption pump 15 connected to the desorption water tank 1, 4 series-connected primary desorption resin towers 4, a secondary desorption pump 16, 3 series-connected secondary desorption resin towers 5, a tertiary desorption pump 17, 7 series-connected tertiary desorption resin towers 6, a qualified liquid filter 10, a buffer tank 7, 2 conductivity meters 12, and a tail brine booster pump 14. The buffer tank 7 is arranged between the secondary desorption resin tower 5 and the tertiary desorption pump 17. The 2 conductivity meters 12 are respectively arranged in front of the feed top-water filter 9 and the qualified liquid filter 10.

[0044] Number all the resin towers in Series A and Series B, numbered as resin towers 1# - 55#.

[0045] In the adsorption units of the two series, the double-tower series-connected A adsorption groups are arranged in an arithmetic progression with the difference being the number of valve arrays. In this embodiment, there are 11 valve arrays 11. The resin tower numbers in the first group of double-tower series-connected A adsorption groups are 7# and 18#. The resin tower numbers in the second group of double-tower series-connected A adsorption groups are 8# and 19#. The resin tower numbers in the third group of double-tower series-connected A adsorption groups are 9# and 20#. The resin tower numbers in the fourth group of double-tower series-connected A adsorption groups are 10# and 21#. The resin tower numbers in the fifth group of double-tower series-connected A adsorption groups are 11# and 22#. The resin tower numbers in the first group of triple-tower series-connected B adsorption groups are 1#, 12#, and 23#. The resin tower numbers in the second group of triple-tower series-connected B adsorption groups are 2#, 13#, and 24#. The resin tower numbers in the third group of triple-tower series-connected B adsorption groups are 3#, 14#, and 25#. The resin tower numbers in the first group of double-tower series-connected B adsorption groups are 4# and 15#. The resin tower numbers in the second group of double-tower series-connected B adsorption groups are 5# and 16#. The resin tower numbers in the third group of double-tower series-connected B adsorption groups are 6# and 17#.

[0046] In two series of desorption units, the resin towers are numbered in the order of natural numbers. The 4 primary desorption resin towers 4 in desorption unit A are numbered 30#, 31#, 32#, 33#; the 3 secondary desorption resin towers 5 are numbered 40#, 41#, 42#; the 7 tertiary desorption resin towers 6 are numbered 43#, 44#, 51#, 52#, 53#, 54#, 55#. The 4 primary desorption resin towers 4 in desorption unit B are numbered 27#, 28#, 34#, 35#; the 3 secondary desorption resin towers 5 are numbered 36#, 37#, 38#; the 7 tertiary desorption resin towers 6 are numbered 39#, 45#, 46#, 47#, 48#, 49#, 50#.

[0047] Use the lithium-containing solution impurity control system of this embodiment to carry out the operation of extracting lithium from salt lakes, ensuring that the adsorption, desorption, tower position transformation, and backwashing operations are carried out simultaneously in series A and series B. The lithium-containing solution impurity control method includes the following steps:

[0048] S1. Adsorption

[0049] Calculated by mass fraction, dilute the old brine with fresh water accounting for 5-10% of the old brine consumption, and transport the diluted old brine to the adsorption unit through the old brine transfer pump (13). At this time, the old brine is simultaneously transported to the double-tower series A adsorption group in adsorption unit A, the double-tower series B adsorption group and the triple-tower series B adsorption group in adsorption unit B for adsorption. After the adsorption is completed, the tail brine (i.e., the old brine with greatly reduced lithium ion content) is discharged to the tail brine channel 22 through the tail brine filter 8;

[0050] S2. Desorption

[0051] Transport the desorbing liquid in the desorbing water tank 1 to the 4 series-connected primary desorption resin towers 4 through the primary desorption pump 15 for water displacement, then transport the desorbing liquid to the secondary desorption resin towers 5 through the secondary desorption pump 16 for water washing, and then transport the desorbing liquid in the buffer tank 7 to the tertiary desorption resin towers 6 through the tertiary desorption pump 17 for desorption;

[0052] During the water washing process, it is necessary to control the water washing flow rate and preset its fixed value, and set the desorption amount according to the water washing amount and the desorption amount;

[0053] During the desorption process, it is necessary to preset the conductivity value of the conductivity meter 12 beside the buffer tank 7 to ensure the progress of the three-stage desorption and effectively control the impurity content in the buffer tank 7. When the measured conductivity value of the desorbed liquid is lower than the preset conductivity value, it indicates that the impurity content in the desorbed liquid has been further reduced and controlled at a relatively low level. At this time, the valve array 11 can be switched to convey the desorbed liquid to the qualified liquid filter 10 to obtain the qualified liquid, and the qualified liquid is conveyed to the subsequent process. When the measured conductivity value of the desorbed liquid is higher than the preset conductivity value, the desorbed liquid in the buffer tank 7 is conveyed to the three-stage desorption resin tower 6 through the three-stage desorption pump 17 for further desorption, and then enters the secondary adsorption. The desorbed liquid in the buffer tank 7 displaces the brine in the resin tower to the tail brine pipe, and at the same time, the resin bed layer is rinsed for the first time to further control the impurity content in the resin tower.

[0054] S3. Water flushing

[0055] Preset the conductivity meter 12 and control the water flushing volume by flow. Preset the fixed value of the water flushing volume, convey the tail brine to the water flushing resin tower 3 through the tail brine booster pump 14, and after being detected by the feed water flushing filter 9 and the conductivity meter 12 set beside it, it is conveyed to the desorbed water tank 1 to complete the recovery of the desorbed liquid.

[0056] S4. Backwashing

[0057] When the position of the resin bed layer in the resin tower may have uneven flow, the enrichment speed of impurity ions in the resin tower is too fast, breaking the desorption balance, and the impurity content gets out of control. At this time, it is necessary to backwash the resin tower to adjust the position of the resin bed layer.

[0058] During the operation of extracting lithium from salt lakes using the impurity control system for lithium-containing solutions, that is, during the processes of adsorption, desorption, water flushing, and backwashing, tower position transformation is carried out. The conductivity meter 12 is used to measure the conductivity fluctuation of the qualified liquid, and the homogeneous analysis of the impurity content in the qualified liquid is carried out. According to the analysis results of the desorption amount and water washing amount, the tower position transformation time is set, and the adsorption residence time of the adsorption resin tower 2 in step S1 is calculated through the formula "adsorption residence time = tower position transformation time * number of series-connected towers * number of valve arrays".

[0059] In the adsorption unit A of series A, the tower position transformation of withdrawing a tower and replenishing a tower is completed within the same valve array.

[0060] In the adsorption unit B of series B, a tower is withdrawn within the valve array of the three-tower series-connected B adsorption group, and a tower is replenished within the valve array of the two-tower series-connected B adsorption group. The tower position transformations are separated by two valve arrays.

[0061] When the progress of the tower position transformation shows attenuation and the conductivity meter 12 fluctuates greatly, it indicates that the position of the resin bed layer in the resin tower may have uneven flow, and a backwashing operation should be carried out in a timely manner.

[0062] The foregoing has shown and described the basic principles, main features and advantages of the present invention. For a person skilled in the art, it is obvious that the present invention is not limited to the details of the above-described exemplary embodiments, and without departing from the spirit or basic characteristics of the present invention, the present invention can be implemented in other specific forms. Therefore, in any regard, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, it is intended to embrace all changes that fall within the meaning and scope of the equivalent elements of the claims within the present invention.

[0063] In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative manner of the specification is only for clarity. A person 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 a person skilled in the art.

Claims

1. A method for controlling impurities in a lithium-containing solution during the process of extracting lithium from a salt lake, characterized in that, Adopt a lithium-containing solution impurity control system, and the lithium-containing solution impurity control system includes 1 desorbed water tank (1), 55 resin towers, 2 buffer tanks (7), 6 filters, 11 valve arrays (11), 4 conductivity meters (12), and several transfer pumps; among them, the 55 resin towers are further divided into adsorption resin towers (2), top water resin towers (3), and desorption resin towers according to their positions and functions in the control system; The lithium-containing solution impurity control system can be split into Series A and Series B. The two series share the desorbed water tank (1), and both series are respectively composed of an adsorption unit and a desorption unit, and the desorption unit is a three-stage desorption; the adsorption unit is used to adsorb lithium ions in the old brine onto the adsorbent in the adsorption resin tower (2), and the desorption unit is used to desorb lithium ions from the adsorbent; the number of resin towers and the number of valve arrays (11) included in the adsorption units of Series A and Series B are different; The desorption resin tower includes a primary desorption resin tower (4), a secondary desorption resin tower (5), and a tertiary desorption resin tower (6); the primary desorption resin tower (4) is a water top tower, the secondary desorption resin tower (5) is a water wash tower, the tertiary desorption resin tower (6) is a desorption tower, the filters include a tail brine filter (8), a feed top water filter (9), and a qualified liquid filter (10), the transfer pumps include an old brine transfer pump (13), a tail brine booster pump (14), and desorption pumps, and the desorption pumps include a primary desorption pump (15), a secondary desorption pump (16), and a tertiary desorption pump (17); The 11 valve arrays (11) are configured with independent adsorption pipelines (18), each of the two series is configured with a horizontal main pipeline (19), and the adsorption units and desorption units within the same series are jointly configured with a vertical main pipeline (20). A fresh water pipeline (21) is also connected beside the old brine transfer pump (13). The fresh water pipeline (21) is used to dilute the old brine before transporting it to the adsorption unit, on the one hand, reducing the concentration and viscosity of the old brine and on the other hand playing a role in initially reducing the impurity concentration in the old brine. The setting of the fresh water pipeline (21) improves the adsorption effect of the adsorption resin tower (2) in the adsorption unit and increases the output of a single adsorption resin tower (2); Series A includes 25 resin towers and 5 valve arrays (11), and is composed of an adsorption unit A and a desorption unit A: the adsorption unit A includes 5 groups of double-tower series-connected A adsorption groups, a tail brine filter (8), and transfer pumps. Each group of double-tower series-connected A adsorption groups includes 1 valve array (11) and 2 adsorption resin towers (2), one for adsorption and the other for protection; The desorption unit A includes 1 top water resin tower (3), a feed top water filter (9) connected between the desorbed water tank (1) and the top water resin tower (3) through a pipeline, a primary desorption pump (15) connected to the desorbed water tank (1), 4 primary desorption resin towers (4), a secondary desorption pump (16), 3 secondary desorption resin towers (5), a tertiary desorption pump (17), 7 tertiary desorption resin towers (6), a qualified liquid filter (10), a buffer tank (7) arranged between the secondary desorption resin tower (5) and the tertiary desorption pump (17), 2 conductivity meters (12) respectively arranged in front of the feed top water filter (9) and the qualified liquid filter (10), and a tail brine booster pump (14); Series B includes 30 resin towers and 6 valve arrays (11), and is composed of an adsorption unit B and a desorption unit B: The adsorption unit B includes 3 groups of double - tower series B adsorption groups, 3 groups of triple - tower series B adsorption groups, a tail brine filter (8), and a transfer pump. Each group of double - tower series B adsorption groups includes 1 valve array (11) and 2 adsorption resin towers (2), and each group of triple - tower series B adsorption groups includes 1 valve array (11) and 3 adsorption resin towers (2); The desorption unit B includes 1 top water resin tower (3), a feed top water filter (9), a primary desorption pump (15), 4 primary desorption resin towers (4), a secondary desorption pump (16), 3 secondary desorption resin towers (5), a tertiary desorption pump (17), 7 tertiary desorption resin towers (6), a qualified liquid filter (10), a buffer tank (7) arranged between the secondary desorption resin tower (5) and the tertiary desorption pump (17), 2 conductivity meters (12) respectively arranged in front of the feed top water filter (9) and the qualified liquid filter (10), and a tail brine booster pump (14); The method includes the following steps: S1. Adsorption Dilute the old brine with fresh water, and transport the diluted old brine to the adsorption unit for adsorption through the old brine transfer pump (13). After the adsorption ends, the tail brine is discharged to the tail brine channel (22) through the tail brine filter (8); S2. Desorption Preset the values of the conductivity meter (12) in advance, and perform three - stage desorption on the resin tower using the desorbing liquid in the desorbed water tank (1); when the measured conductivity value of the desorbing liquid is lower than the preset conductivity value, transport the desorbing liquid to the qualified liquid filter (10) to obtain the qualified liquid, and transport the qualified liquid to the subsequent process; when the measured conductivity value of the desorbing liquid is higher than the preset conductivity value, transport the desorbing liquid in the buffer tank (7) to the tertiary desorption resin tower (6) through the tertiary desorption pump (17) for continuous desorption, and then enter the secondary adsorption; S3. Top water Preset the conductivity meter (12) and control the top water volume by flow. Preset the fixed value of the top water volume, transport the tail brine to the top water resin tower (3) through the tail brine booster pump (14), and after being detected by the feed top water filter (9) and the conductivity meter (12) arranged beside it, transport it back to the desorbed water tank (1) to complete the recovery of the desorbing liquid; S4. Backwashing When there may be a deviation in the position of the resin bed in the resin tower, the enrichment rate of impurity ions in the resin tower is too fast, breaking the desorption equilibrium, and the impurity content gets out of control. At this time, the resin tower needs to be backflushed to adjust the position of the resin bed; the backflushing operation is carried out according to the progress of the tower position change and the conductance fluctuation of the conductivity meter (12) to adjust the position of the resin bed; During the processes of adsorption, desorption, top water, and backflushing, the tower position is changed. The conductivity meter (12) is used to measure the conductance fluctuation of the qualified liquid, and the homogeneous analysis of the impurity content in the qualified liquid is carried out. The tower position change time is set, and the adsorption residence time of the adsorption resin tower (2) in the process of step S1 is calculated to complete the tower position change of the adsorption units in series A and series B.

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