A frozen magnesium removal pre-cooler anti-crystallization precipitation plugging system and method

Abstract

This application relates to the field of cryogenic magnesium removal technology in hydrometallurgical zinc smelting, and discloses a system and method for preventing crystallization and blockage in a cryogenic magnesium removal precooler. The system includes a first precooler, a second precooler, a third precooler, a waste liquid circulation pump group, a mother liquor circulation pump group, and a crystallization tank group. The three precoolers are connected in parallel. The waste liquid circulation pump group is used to introduce the high-temperature waste electrolyte to be cooled into the tube side of each precooler, the mother liquor circulation pump group is used to introduce the low-temperature mother liquor into the shell side of each precooler, and the crystallization tank group is used to receive the cooled waste electrolyte after heat exchange for magnesium salt crystallization and precipitation. The parallel connection of the three precoolers can achieve a "one in use, one on standby, one soaking" operating state, which can perform online flushing and soaking of blocked precoolers without interrupting production to complete online restoration. The composite cleaning process of the precoolers is accurately adapted to the characteristics of stubborn magnesium sulfate crystals in hydrometallurgical zinc waste electrolyte, which are easy to adhere to the tube wall, resulting in good unblocking and magnesium removal effects.

Description

Technical Field

[0001] This application belongs to the field of wet zinc refining cryogenic magnesium removal technology, specifically relating to a system and method for preventing crystallization and blockage in a cryogenic magnesium removal precooler. Background Technology

[0002] In the waste electrolyte of hydrometallurgical zinc refining, magnesium mainly exists in the form of magnesium sulfate (MgSO4). The freezing magnesium removal process is a key step in controlling the circulation and enrichment of magnesium ions and ensuring the quality of electrolytic zinc products during hydrometallurgical zinc refining. Its basic principle is as follows: taking advantage of the fact that the solubility of magnesium sulfate is very sensitive to temperature changes and decreases sharply as the temperature decreases, the high-temperature waste electrolyte (temperature about 40℃, acidity about 200g / L, zinc content about 40g / L, magnesium ion content 23-27g / L) is deeply cooled by a precooler. Magnesium sulfate will preferentially reach saturation and precipitate in the form of magnesium sulfate heptahydrate (MgSO4·7H2O). Meanwhile, other soluble metal ions such as zinc and manganese in the solution can still exist stably in the solution, achieving selective separation. The solution after magnesium removal is returned to the electrolyte preparation for recycling.

[0003] Currently, conventional cryogenic magnesium removal processes typically employ three precoolers connected in series, each with a heat exchange area of ​​20 m². Each precooler contains 380 silicon carbide heat exchange tubes with an inner diameter of 19 mm and a length of 2 m. The high-temperature waste electrolyte flows sequentially through the three precoolers, gradually cooling down. The precoolers usually use silicon carbide heat exchange tubes, with the high-temperature waste electrolyte flowing inside the tubes and a low-temperature cooling medium (approximately -10°C) flowing through the tube shell. Through heat exchange, the temperature of the waste electrolyte is reduced to the temperature required for crystallization.

[0004] However, in actual operation, the aforementioned series-connected precooler group suffers from a high magnesium ion content in the waste electrolyte and a small inner diameter of the heat exchange tubes. The temperature difference between the tube-side medium temperature (40°C) and the shell-side medium temperature (-10°C) is as high as 50°C. This leads to supercooling of the inner wall of the heat exchange tubes, causing crystals to preferentially precipitate on the tube wall and gradually thicken. Furthermore, the three precoolers are arranged in series, resulting in a long total flow path and slow flow velocity of the waste electrolyte within the precooler group. This further exacerbates the crystallization on the tube wall, causing the internal fluid channels of the heat exchange tubes to become blocked by crystals. In practical applications, the heat exchange tubes of the precoolers become blocked within 5 days and cannot be used, requiring shutdown and cleaning. This seriously affects the continuity and economy of production.

[0005] Several improved solutions have been proposed to address the problem of crystallization blockage in precoolers. For example, Chinese Patent CN212854700U discloses a multi-stage cooling and circulating freezing crystallization system, which uses multiple parallel freezing heat exchangers. By switching at least two sets of freezing heat exchangers, the load on a single heat exchanger can be reduced, preventing blockage of the heat exchange tubes within both sets. Another example is a zero-emission salt separation freezing crystallization device disclosed in Chinese Patent CN217650938U, which uses two sets of heat exchangers, allowing for one to be used and one to be on standby, or both to be used simultaneously. This avoids the drawback of traditional freezing crystallizers causing system shutdowns due to freezing blockage, making it less prone to blockage. Finally, Chinese Patent CN110332842B discloses a coking circulating ammonia water self-cleaning parallel heat exchange device and its operation control method. This device uses a parallel connection of dual heat exchangers for heat exchange, sets up a standby heat exchanger, and judges the blockage situation by comparing the heat exchange volume, achieving automatic switching and cleaning.

[0006] However, the existing anti-clogging solutions for precoolers mentioned above are mainly designed for media such as industrial wastewater, chemical wastewater, and coking ammonia water. The crystal characteristics, temperature range, and heat exchange tube specifications of these media are significantly different from the characteristics of waste electrolyte in the wet zinc smelting process for removing magnesium by freezing, which has high acidity, high zinc ion, high magnesium ion, and large temperature difference. In particular, magnesium sulfate crystallizes and precipitates extremely rapidly and stubbornly under large temperature differences. Therefore, for the precooler to prevent crystallization and clogging, simply using the traditional parallel structure of heat exchangers or conventional automatic flushing methods cannot completely remove the crystals inside the tubes. The service life of the precooler is still relatively short, and it is impossible to complete online recovery without interrupting production.

[0007] Therefore, how to effectively prevent crystallization and blockage of the precooler in the cryogenic magnesium removal process, extend the continuous operation cycle of the precooler, and achieve online monitoring, automatic switching, and uninterrupted cleaning remains a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0008] To address or partially address the problems existing in related technologies, this application provides a system and method for preventing crystallization and blockage in a cryogenic magnesium removal precooler. This system can perform online flushing and soaking of the blocked precooler without interrupting production, thus achieving online recovery without the need for shutdown and disassembly. The system is simple, has a fast response, and is suitable for the characteristics of stubborn magnesium sulfate crystals in wet zinc smelting waste electrolyte that easily adhere to the pipe wall.

[0009] The first aspect of this application provides a system for preventing crystallization and blockage in a cryogenic magnesium removal precooler, comprising: First precooler, second precooler, third precooler, waste liquid circulation pump set, mother liquor circulation pump set; The first precooler, the second precooler, and the third precooler are connected in parallel. The waste liquid circulation pump set is used to introduce the high-temperature waste electrolyte to be cooled into the tube side of each precooler, and the mother liquor circulation pump set is used to introduce the low-temperature mother liquor into the shell side of each precooler. The waste liquid inlet pipe of the first precooler is connected to the waste liquid circulation pump group, and the waste liquid outlet pipe of the first precooler is connected to the waste liquid outlet pipes of the second and third precoolers in sequence. A waste liquid inlet valve is installed on the waste liquid inlet pipes of the first, second and third precoolers respectively. A precooler flushing valve with an external flushing water circuit is set between each waste liquid inlet valve and the tube inlet of the corresponding precooler. A waste liquid discharge valve is set between the precooler flushing valve and the waste liquid inlet valve. A waste liquid outlet valve is installed on the waste liquid outlet pipes of the first, second and third precoolers respectively. The mother liquor inlet pipe of the first precooler is connected to the mother liquor circulation pump group, and the mother liquor outlet pipe of the first precooler is connected to the mother liquor outlet pipes of the second and third precoolers in sequence. A mother liquor inlet valve is installed on the mother liquor inlet pipes of the first, second and third precoolers, and a mother liquor outlet valve is installed on the mother liquor outlet pipes of the first, second and third precoolers.

[0010] In one alternative, the anti-crystallization and clogging system of the refrigerated magnesium removal precooler also includes a crystallization tank group, which includes at least a first crystallization tank, a second crystallization tank, a third crystallization tank, a fourth crystallization tank, a fifth crystallization tank, a sixth crystallization tank, and a mother liquor tank. The waste liquid outlet pipe of the third precooler is connected to the feed inlets of the first and second crystallization tanks. The waste electrolyte that has been cooled after heat exchange is simultaneously discharged into the first and second crystallization tanks for magnesium salt crystallization. An automatic feed valve is installed on the feed pipes of the first, second, third, fourth, fifth, and sixth crystallization tanks. An automatic flushing valve with an external flushing water circuit is set between each automatic feed valve and the feed inlet of the corresponding crystallization tank. A first feed pump, a second feed pump, a third feed pump, and a fourth feed pump are sequentially installed between the feed inlets of the second, third, fourth, fifth, and sixth crystallization tanks and the automatic feed valves of the previous crystallization tank. An automatic discharge valve is installed below the automatic feed valves of the first and second crystallization tanks. An automatic discharge valve is installed below the automatic feed valves of the third, fourth, fifth, and sixth crystallization tanks. The first and second crystallization tanks are fed at the same time, while the third, fourth, and fifth crystallization tanks are fed at the same time in sequence. The mixture of magnesium salt crystals and uncrystallized waste liquid is transported to the downstream crystallization tank for magnesium salt crystallization. The sixth crystallization tank is fed at the last time to discharge the mixture of magnesium salt crystals and the remaining low-temperature acid liquid after crystallization. The low-temperature acid liquid is stored in the mother liquor tank as mother liquor for later use.

[0011] In one optional embodiment, the waste liquid circulation pump set includes a first waste liquid circulation pump and a second waste liquid circulation pump; the inlet and outlet ends of the first waste liquid circulation pump are respectively equipped with a first waste liquid inlet electric valve and a first waste liquid outlet electric valve, and a first waste liquid pump flushing valve with an external flushing water path is provided between the inlet end of the first waste liquid circulation pump and the first waste liquid inlet electric valve; the inlet and outlet ends of the second waste liquid circulation pump are respectively equipped with a second waste liquid inlet electric valve and a second waste liquid outlet electric valve, and a second waste liquid pump flushing valve with an external flushing water path is provided between the inlet end of the second waste liquid circulation pump and the second waste liquid inlet electric valve; the inlets of the first waste liquid circulation pump and the second waste liquid circulation pump are combined into one channel and connected to the pipeline for conveying high-temperature waste electrolyte, and the outlet ends of the first waste liquid circulation pump and the second waste liquid circulation pump are combined into one channel and connected to the waste liquid inlet pipeline of the first precooler.

[0012] In one optional embodiment, the mother liquor circulation pump set includes a first mother liquor circulation pump and a second mother liquor circulation pump. The inlet and outlet ends of the first mother liquor circulation pump are respectively equipped with a first mother liquor inlet electric valve and a first mother liquor outlet electric valve, and a first mother liquor pump flushing valve with an external flushing water path is provided between the inlet end of the first mother liquor circulation pump and the first mother liquor inlet electric valve. The inlet and outlet ends of the second mother liquor circulation pump are respectively equipped with a second mother liquor inlet electric valve and a second mother liquor outlet electric valve, and a second mother liquor pump flushing valve with an external flushing water path is provided between the inlet end of the second mother liquor circulation pump and the second mother liquor inlet electric valve. The inlets of the first mother liquor circulation pump and the second mother liquor circulation pump are combined into one channel and connected to the mother liquor tank, and the outlet ends of the first mother liquor circulation pump and the second mother liquor circulation pump are combined into one channel and connected to the mother liquor inlet pipeline of the first precooler.

[0013] The second aspect of this application provides a method for preventing crystallization and blockage in a cryogenic magnesium removal precooler, employing the aforementioned system for preventing crystallization and blockage in a cryogenic magnesium removal precooler. The method includes the following steps: S1: System Start-up Control: During the non-start-up phase, there is waste liquid in the crystallizer and treated cold acid in the mother liquor tank. Start the first waste liquid circulation pump or the second waste liquid circulation pump, start the first mother liquor circulation pump or the second mother liquor circulation pump, start the material flow of waste liquid and mother liquor, start waste liquid heat exchange, and execute the start-up control to start the system. S2: Operation and monitoring of the first precooler: Open the mother liquor inlet valve, mother liquor outlet valve, waste liquid inlet valve, and waste liquid outlet valve on the first precooler, and keep the mother liquor inlet valve, mother liquor outlet valve, waste liquid inlet valve, and waste liquid outlet valve on the second and third precoolers closed. Start the first or second waste liquid circulation pump to pump the high-temperature waste electrolyte to be cooled into the tube side of the first precooler through the waste liquid inlet valve. Start the first or second mother liquor circulation pump to pump the low-temperature mother liquor into the shell side of the first precooler through the mother liquor inlet valve, so that the high-temperature waste electrolyte and the low-temperature mother liquor can exchange heat in the first precooler. Monitor the waste liquid outlet flow rate in the waste liquid outlet pipe of the first precooler in real time. When the waste liquid outlet flow rate is lower than the set value, start switching the precooler. S3: Precooler operation switching: Open the mother liquor inlet valve, mother liquor outlet valve, waste liquid inlet valve, and waste liquid outlet valve on the second precooler, and at the same time close the mother liquor inlet valve, mother liquor outlet valve, waste liquid inlet valve, and waste liquid outlet valve on the first precooler to switch to the operation of the second precooler, so that the high-temperature waste electrolyte and the low-temperature mother liquor are switched to the second precooler for heat exchange. At this time, the first precooler stops operating, and the third precooler is in standby mode. S4: Rinse and soak the first precooler: Open the waste liquid discharge valve on the waste liquid inlet pipe of the first precooler to drain the waste liquid in the tube side of the first precooler. After draining the waste liquid, close the waste liquid discharge valve on the waste liquid inlet pipe and reopen the waste liquid outlet valve on the waste liquid outlet pipe. Then open the precooler flushing valve to introduce flushing water into the tube side of the first precooler. After flushing for the set time, close the precooler flushing valve and the waste liquid outlet valve to soak the first precooler for the set time. S5: Secondary rinsing of the first precooler: After soaking, open the waste liquid discharge valve on the waste liquid inlet pipe to drain the soaking wastewater in the tube side of the first precooler. After draining the soaking wastewater, close the waste liquid discharge valve on the waste liquid inlet pipe and reopen the precooler rinsing valve. Open the waste liquid outlet valve on the waste liquid outlet pipe to introduce rinsing water into the tube side of the first precooler for secondary rinsing for the set time. S6: First precooler standby: After the second flushing is completed, close the precooler flushing valve and keep the waste liquid outlet valve on the waste liquid outlet pipe open until the flushing water in the tube side of the first precooler is drained. After draining the flushing water, close the waste liquid outlet valve on the waste liquid outlet pipe. At this time, the first precooler is cleared and enters standby mode. S7: Precooler secondary operation switch: Real-time monitoring of the waste liquid discharge flow rate in the waste liquid discharge pipe of the second precooler. When the waste liquid discharge flow rate in the waste liquid discharge pipe of the second precooler is lower than the set value, the operation is switched to the third precooler. The second precooler stops running and is flushed and soaked. The first precooler is in standby mode. S8: Precooler restart operation switch: Real-time monitoring of the waste liquid flow rate in the waste liquid outlet pipe of the third precooler. When the waste liquid flow rate in the waste liquid outlet pipe of the third precooler is lower than the set value, the system switches back to the operation of the first precooler. The third precooler stops operating and is flushed and soaked. The second precooler is in standby mode. The system switches back and forth in this manner.

[0014] In one alternative approach, step S1 specifically includes: S1.1: When starting the machine, the material flow of waste liquid and mother liquor is started. After the waste liquid heat exchange is completed, the cooled waste liquid is simultaneously discharged into the first crystallization tank and the second crystallization tank for magnesium salt crystallization. When the first crystallization tank and the second crystallization tank are feeding at timed intervals, the automatic flushing valves of the discharge port on the first crystallization tank and the second crystallization tank are opened first to flush the discharge pipe. After flushing is completed, the two automatic flushing valves of the discharge port are closed. At the same time, the automatic discharge valves on the first crystallization tank and the second crystallization tank are opened, the first discharge pump is started, the first crystallization tank and the second crystallization tank begin to discharge, and the mixture of magnesium salt crystals and uncrystallized waste liquid is transported to the third crystallization tank for magnesium salt crystallization. S1.2: After the first and second crystallization tanks have finished feeding, shut down the first feeding pump, shut down the automatic feeding valve, open the automatic discharge valve, delay opening the automatic flushing valve at the feeding port, flush the pipeline and the waste liquid inside the first feeding pump, then shut down the automatic flushing valve at the feeding port and delay closing the automatic discharge valve to discharge the flushing water and magnesium salt crystals in the pipeline. S1.3: When the third crystallizer is scheduled to discharge material, first open the automatic flushing valve at the discharge port on the third crystallizer to flush the discharge pipe. After flushing, close the automatic flushing valve at the discharge port. At the same time, open the automatic discharge valve on the third crystallizer and start the second discharge pump. The third crystallizer begins to discharge material, and the mixture of magnesium salt crystals and uncrystallized waste liquid is transported to the fourth crystallizer for magnesium salt crystallization and precipitation through the second discharge pump. Similarly, the fifth and sixth crystallizers are fed by the third and fourth discharge pumps in sequence for magnesium salt crystallization and precipitation, and are discharged in sequence. S1.4: The sixth crystallization tank is fed at regular intervals, and a mixture of magnesium salt crystals and residual low-temperature acid solution after crystallization is discharged. The mixture is centrifuged to produce low-temperature acid solution which is stored in the mother liquor tank as mother liquor, which is then used by the first or second mother liquor circulation pump. The start-up control is then completed.

[0015] In one alternative, during the operation of the precooler group, the waste liquid circulation pump is switched to operate according to the fault status or operating time of the first waste liquid circulation pump and the second waste liquid circulation pump, so as to cyclically switch the operation of the first waste liquid circulation pump and the second waste liquid circulation pump.

[0016] In one alternative approach, the specific steps for switching the operation of the waste liquid circulation pump include: Waste liquid circulation pump operation: When starting up, open the first waste liquid inlet electric valve and the first waste liquid outlet electric valve located at the inlet and outlet of the first waste liquid circulation pump to start the first waste liquid circulation pump. The first waste liquid circulation pump pumps the high-temperature waste electrolyte to be cooled, which enters the first precooler, the second precooler, or the third precooler through the corresponding waste liquid inlet valve. Waste liquid circulation pump operation switching: When the first waste liquid circulation pump fails or runs to the set time, open the second waste liquid inlet electric valve and the second waste liquid outlet electric valve located at both ends of the second waste liquid circulation pump, and close the first waste liquid circulation pump and the first waste liquid inlet electric valve. At the same time, start the second waste liquid circulation pump and switch to pumping the high-temperature waste electrolyte to be cooled by the second waste liquid circulation pump. Cleaning waste liquid circulation pump: Keep the first waste liquid outlet electric valve open to drain the waste liquid in the first waste liquid circulation pump. Then open the first waste liquid pump flushing valve located at the water inlet of the first waste liquid circulation pump to flush the pump head of the first waste liquid circulation pump for a set time. Waste liquid circulation pump shutdown and standby: After flushing is completed, close the flushing valve of the first waste liquid pump and delay closing the electric valve of the first waste liquid outlet. At this time, the first waste liquid circulation pump is in an empty pump state and can be inspected or standby. Secondary operation switching of waste liquid circulation pump: When the second waste liquid circulation pump fails or runs to the set time, reopen the first waste liquid inlet electric valve and the first waste liquid outlet electric valve located at both ends of the first waste liquid circulation pump, and close the second waste liquid circulation pump and the second waste liquid inlet electric valve. At the same time, start the first waste liquid circulation pump and switch back to pumping the high-temperature waste electrolyte to be cooled by the first waste liquid circulation pump. Then open the flushing valve of the second waste liquid pump to clean the second waste liquid circulation pump. This cycle of switching operation is repeated.

[0017] In one alternative, during the operation of the precooler group, the mother liquor circulation pump is switched to operate based on the fault status or operating time of the first mother liquor circulation pump and the second mother liquor circulation pump, so as to cyclically switch the operation of the first mother liquor circulation pump and the second mother liquor circulation pump.

[0018] In one alternative approach, the specific steps for switching the operation of the mother liquor circulation pump include: Mother liquor circulation pump operation: When starting up, open the first mother liquor inlet electric valve and the first mother liquor outlet electric valve located at the inlet and outlet of the first mother liquor circulation pump to start the first mother liquor circulation pump. The first mother liquor circulation pump pumps the high-temperature mother electrolyte to be cooled, which enters the first precooler, the second precooler, or the third precooler through the corresponding mother liquor inlet valve. Mother liquor circulation pump operation switching: When the first mother liquor circulation pump fails or runs to the set time, open the second mother liquor inlet electric valve and the second mother liquor outlet electric valve located at both ends of the second mother liquor circulation pump, and close the first mother liquor circulation pump and the first mother liquor inlet electric valve. At the same time, start the second mother liquor circulation pump and switch to pumping the high-temperature mother electrolyte to be cooled by the second mother liquor circulation pump. Cleaning the mother liquor circulation pump: Keep the first mother liquor outlet electric valve open to drain the mother liquor in the first mother liquor circulation pump. Then open the first mother liquor pump flushing valve located at the water inlet of the first mother liquor circulation pump to flush the pump head of the first mother liquor circulation pump for a set time. Mother liquor circulation pump shutdown and standby: After rinsing is completed, close the first mother liquor pump rinsing valve and delay closing the first mother liquor outlet electric valve. At this time, the first mother liquor circulation pump is in an empty pump state and can be inspected or standby. Secondary operation switching of the mother liquor circulation pump: When the second mother liquor circulation pump fails or runs to the set time, reopen the first mother liquor inlet electric valve and the first mother liquor outlet electric valve located at both ends of the first mother liquor circulation pump, and close the second mother liquor circulation pump and the second mother liquor inlet electric valve. At the same time, start the first mother liquor circulation pump and switch back to pumping the high-temperature mother electrolyte to be cooled by the first mother liquor circulation pump. Then open the flushing valve of the second mother liquor pump to clean the second mother liquor circulation pump. This cycle of switching operation is repeated.

[0019] The beneficial effects of this application are: 1. By setting up three precoolers in parallel, each precooler can operate independently. Waste liquid flows into each precooler from the same source, allowing the three precoolers to operate independently in a "one-in-use, one-in-standby, one-in-soaking" state. When one precooler needs to be cleaned of crystal blockage after running for a certain period of time, there is no need to stop the machine. Simply close the waste liquid and mother liquor inlet and outlet valves of that precooler and switch to another parallel precooler in standby to continue operation. This allows for online flushing and soaking of the blocked precooler without interrupting production, thus completing online recovery without stopping the machine for disassembly and cleaning. This greatly extends the continuous operation cycle of the precooler group and ensures the continuity and economy of production. 2. By monitoring the waste liquid outflow rate of the precooler in real time, the degree of crystallization blockage in the tube can be accurately determined, enabling online blockage monitoring based on flow rate. This allows for timely switching before the blockage becomes severe enough to affect heat exchange efficiency, avoiding passive shutdown after the equipment is completely blocked. Compared to the existing technology that uses the heat exchange comparison method and requires the detection of multiple parameters such as temperature and flow rate, this solution only requires one flow rate parameter, making the system simple and fast-responding. 3. The precooler is designed with a composite cleaning process: first, drain the waste liquid → rinse to remove most of the loose crystals → soak to dissolve or soften stubborn crystals → rinse again to thoroughly remove them → drain the precooler for backup. This process is accurately adapted to the characteristics of stubborn magnesium sulfate crystals in wet zinc smelting waste electrolyte, which are easy to adhere to the pipe wall. It has a stronger ability to remove magnesium sulfate crystals in small diameter silicon carbide tubes, with good unblocking effect. It can restore the heat exchange capacity of the precooler to near its initial state and has a good magnesium removal effect.

[0020] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram showing the connection between the first precooler, the second precooler, the third precooler, the waste liquid circulation pump group, the mother liquor circulation pump group, and the mother liquor tank in an embodiment of the anti-crystallization and clogging system of the cryogenic magnesium removal precooler. Figure 2 This is a schematic diagram showing the connection between the third precooler, the first crystallizer, the second crystallizer, the third crystallizer, the fourth crystallizer, the fifth crystallizer, and the sixth crystallizer in an embodiment of the anti-crystallization and clogging system of the magnesium removal precooler in this application. Figure 3 This is a flowchart of a method for preventing crystallization and blockage in a cryogenic magnesium removal precooler according to one embodiment of this application.

[0023] The following are the reference numerals in the diagram: 1-First precooler, 2-Second precooler, 3-Third precooler, 4-Waste liquid inlet valve, 5-Precooler flushing valve, 6-Waste liquid discharge valve, 7-Waste liquid outlet valve, 8-Mother liquor inlet valve, 9-Mother liquor outlet valve, 10-First crystallizer, 11-Second crystallizer, 12-Third crystallizer, 13-Fourth crystallizer, 14-Fifth crystallizer, 15-Sixth crystallizer, 17-Mother liquor tank, 18-Automatic discharge valve, 19-Automatic flushing valve at discharge port, 20-First discharge pump, 21-Second discharge pump, 22-Third discharge pump, 23-Fourth discharge pump, 24- Automatic discharge valve, 25-First waste liquid circulation pump, 26-Second waste liquid circulation pump, 27-First waste liquid inlet electric valve, 28-First waste liquid outlet electric valve, 29-First waste liquid pump flushing valve, 30-Second waste liquid inlet electric valve, 31-Second waste liquid outlet electric valve, 32-Second waste liquid pump flushing valve, 33-First mother liquor circulation pump, 34-Second mother liquor circulation pump, 35-First mother liquor inlet electric valve, 36-First mother liquor outlet electric valve, 37-First mother liquor pump flushing valve, 38-Second mother liquor inlet electric valve, 39-Second mother liquor outlet electric valve, 40-Second mother liquor pump flushing valve. Detailed Implementation

[0024] The specific embodiments of this application will be further described in detail below with reference to the accompanying drawings and examples. The following examples are used to illustrate this application, but are not intended to limit the scope of this application. Similarly, the following examples are only some embodiments of this application, not all embodiments. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0025] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0026] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0027] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between components; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0028] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0029] In this application, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0030] To address the aforementioned problems, this application proposes improvements and innovations, including the following embodiments.

[0031] Example In one implementation, see Figures 1-2 The first aspect of this application provides a system for preventing crystallization and blockage in a refrigeration magnesium removal precooler, including a first precooler 1, a second precooler 2, a third precooler 3, a waste liquid circulation pump group, and a mother liquor circulation pump group; the first precooler 1, the second precooler 2, and the third precooler 3 are arranged in parallel, the waste liquid circulation pump group is used to introduce the high-temperature waste electrolyte to be cooled into the tube side of each precooler, and the mother liquor circulation pump group is used to introduce the low-temperature mother liquor into the shell side of each precooler, the low-temperature mother liquor originating from the mother liquor tank 17.

[0032] The waste liquid inlet pipe of the first precooler 1 is connected to the waste liquid circulation pump group, and the waste liquid outlet pipe of the first precooler 1 is connected to the waste liquid outlet pipes of the second precooler 2 and the third precooler 3 in sequence. A waste liquid inlet valve 4 is installed on the waste liquid inlet pipes of the first precooler 1, the second precooler 2, and the third precooler 3 respectively. A precooler flushing valve 5 with an external flushing water circuit is installed between each waste liquid inlet valve 4 and the corresponding precooler tube inlet. A waste liquid discharge valve 6 is installed between the precooler flushing valve 5 and the waste liquid inlet valve 4. A waste liquid outlet valve 7 is installed on the waste liquid outlet pipes of the first precooler 1, the second precooler 2, and the third precooler 3 respectively. The mother liquor inlet pipe of precooler 1 is connected to the mother liquor circulation pump group. The mother liquor outlet pipe of the first precooler 1 is connected to the mother liquor outlet pipes of the second precooler 2 and the third precooler 3 in sequence. A mother liquor inlet valve 8 is installed on the mother liquor inlet pipes of the first precooler 1, the second precooler 2 and the third precooler 3 respectively. A mother liquor outlet valve 9 is installed on the mother liquor outlet pipes of the first precooler 1, the second precooler 2 and the third precooler 3 respectively. That is, the waste liquid and mother liquor inlet and outlet pipes of each precooler are respectively gathered into one line, and a set of valves is installed at the inlet and outlet of each precooler respectively, so that the first precooler 1, the second precooler 2 and the third precooler 3 are connected in parallel.

[0033] In this way, by setting up three precoolers in parallel, each precooler can operate independently. Waste liquid flows into each precooler from the same source, allowing the three precoolers to operate independently in a "one-in-use, one-in-standby, one-in-soaking" state. When one precooler needs to be cleaned of crystallization blockage after running for a certain period of time, there is no need to stop the machine. Simply close the waste liquid and mother liquor inlet and outlet valves of that precooler and switch to another parallel precooler in standby to continue operation. This allows for online flushing and soaking of the blocked precooler without interrupting production, thus completing online recovery without stopping the machine for disassembly and cleaning. This greatly extends the continuous operation cycle of the precooler group and ensures the continuity and economy of production. In addition, by setting flushing valves and discharge valves between the waste liquid inlet valve 4 of each precooler and the tube inlet, the waste liquid can be emptied first, and then flushing water can be introduced. This allows the flushing water to enter from the inlet and exit from the outlet, flowing in the forward direction through the tube. It can also stay in the tube to soak the tube, so that the residual crystals can be fully dissolved or softened. Thus, the tube wall crystals can be thoroughly cleaned through the flushing and soaking process, resulting in a good unblocking effect.

[0034] In some embodiments, the anti-crystallization and clogging system of the refrigeration magnesium removal precooler further includes a crystallization tank group, which includes at least a first crystallization tank 10, a second crystallization tank 11, a third crystallization tank 12, a fourth crystallization tank 13, a fifth crystallization tank 14, a sixth crystallization tank 15, and a mother liquor tank 17. The waste liquid outlet pipe of the third precooler 3 is connected to the feed port of the first crystallization tank 10 and the second crystallization tank 11, so that the waste electrolyte cooled by heat exchange is simultaneously discharged into the first crystallization tank 10 and the second crystallization tank 11 for magnesium salt crystallization and precipitation. An automatic feed valve is installed on the discharge pipe of the first crystallization tank 10, the second crystallization tank 11, the third crystallization tank 12, the fourth crystallization tank 13, the fifth crystallization tank 14, and the sixth crystallization tank 15. 18. An automatic flushing valve 19 with an external flushing water circuit is provided between each automatic feeding valve 18 and the feeding port of the corresponding crystallizer. A first feeding pump 20, a second feeding pump 21, a third feeding pump 22, and a fourth feeding pump 23 are sequentially provided between the feeding port of the second crystallizer 11, the third crystallizer 12, the fourth crystallizer 13, the fifth crystallizer 14, and the sixth crystallizer 15 and the automatic feeding valve 18 corresponding to the previous crystallizer. An automatic discharge valve 24 is provided below the automatic feeding valve 18 of the first crystallizer 10 and the second crystallizer 11. An automatic discharge valve 24 is provided below the automatic feeding valve 18 of the third crystallizer 12, the fourth crystallizer 13, the fifth crystallizer 14, and the sixth crystallizer 15. Therefore, the first crystallization tank 10 and the second crystallization tank 11 are used to simultaneously receive the waste electrolyte that has just been cooled after heat exchange. The third crystallization tank 12, the fourth crystallization tank 13, the fifth crystallization tank 14, and the sixth crystallization tank 15 are connected in series. The first crystallization tank 10 and the second crystallization tank 11 are simultaneously fed at timed intervals. The mixture of magnesium salt crystallizer and non-crystallized waste liquid is transported to the third crystallization tank 12 by the first feed pump 20 for magnesium salt crystallization and precipitation. Then, the mixture of magnesium salt crystallizer and non-crystallized waste liquid is fed at timed intervals by the second feed pump 21. Magnesium salt crystallization is carried out in the fourth crystallization tank 13, and then the mixture of magnesium salt crystals and uncrystallized waste liquid is fed at regular intervals through the third feeding pump 22 to the fifth crystallization tank 14 for magnesium salt crystallization and precipitation. Then the mixture is fed at regular intervals through the fourth feeding pump 23 to the sixth crystallization tank 15 for magnesium salt crystallization and precipitation. Then the mixture is fed at regular intervals. The mixture of magnesium salt crystals and the remaining low-temperature acid liquid after crystallization is discharged from the sixth crystallization tank 15. The low-temperature acid liquid produced is stored in the mother liquor tank 17 as mother liquor for later use.

[0035] Thus, by feeding the first crystallizer 10 and the second crystallizer 11 in parallel, a large amount of waste electrolyte that has just completed heat exchange and been cooled from the precooler group can be accepted. This effectively avoids overflow caused by insufficient capacity of a single tank and avoids the impact of excessively short residence time on crystallization. By connecting multiple crystallizers in series, a stepped cooling sequence is further formed during the crystallization process of the waste electrolyte that has completed heat exchange and been cooled. The waste electrolyte is initially cooled in the first and second crystallizers 11, and magnesium sulfate begins to precipitate, but has not yet reached extremely high supersaturation. Subsequently, it enters the third to sixth crystallizers 15 in sequence. The temperature is further reduced in each tank, and the supersaturation is always controlled within the metastable region, avoiding "explosive nucleation" that produces a large number of fine crystals. This achieves stepped cooling crystallization of the waste liquid, allowing magnesium sulfate crystals to grow slowly and uniformly on the existing seed crystals, ultimately producing large and uniform crystals with good crystallization effect, good magnesium removal effect, and easy subsequent centrifugal separation, thus improving magnesium removal efficiency and acid purity.

[0036] Meanwhile, by setting an automatic flushing valve 19 for the discharge port with an external flushing water circuit between the automatic discharge valve 18 and the discharge port of each crystallizer discharge pipe, flushing water can be introduced to flush the discharge port and pipe before discharge to clean the crystals deposited in the pipe and prevent crystals from clogging the discharge port. By setting an automatic discharge valve 24 below the automatic discharge valve 18, flushing water and crystal blockage can be discharged in a timely manner, which can effectively prevent magnesium salt crystals from depositing and clogging in the pipe and improve the reliability of the long-term operation of the system.

[0037] In some embodiments, the waste liquid circulation pump set includes a first waste liquid circulation pump 25 and a second waste liquid circulation pump 26; the inlet and outlet ends of the first waste liquid circulation pump 25 are respectively provided with a first waste liquid inlet electric valve 27 and a first waste liquid outlet electric valve 28, and a first waste liquid pump flushing valve 29 with an external flushing water path is provided between the inlet end of the first waste liquid circulation pump 25 and the first waste liquid inlet electric valve 27; the inlet and outlet ends of the second waste liquid circulation pump 26 are respectively provided with a second waste liquid inlet electric valve 30 and a second waste liquid outlet electric valve 31, and a second waste liquid pump flushing valve 32 with an external flushing water path is provided between the inlet end of the second waste liquid circulation pump 26 and the second waste liquid inlet electric valve 30; the inlets of the first waste liquid circulation pump 25 and the second waste liquid circulation pump 26 are combined into one and connected to the pipeline for conveying high-temperature waste electrolyte, and the outlet ends of the first waste liquid circulation pump 25 and the second waste liquid circulation pump 26 are combined into one and connected to the waste liquid inlet pipeline of the first precooler 1.

[0038] In this way, the first waste liquid circulation pump 25 and the second waste liquid circulation pump 26 can be used and kept on standby, with a dual-pump redundancy design. When one waste liquid circulation pump fails or needs maintenance after a set time, it can be immediately switched to the other waste liquid circulation pump, which can achieve maintenance without stopping production and eliminate the risk of a complete shutdown caused by a single pump failure. At the same time, the dead zone where waste liquid remains in the pump chamber is prone to crystallization due to temperature drop, which may cause jamming or seal damage during the next start-up. By setting the first waste liquid pump flushing valve 29 and the second waste liquid pump flushing valve 32 to introduce flushing water, the idle waste liquid circulation pump can be completely emptied and flushed clean, preventing residual waste liquid from crystallizing and clogging the pump chamber or corroding the mechanical seal.

[0039] In some embodiments, the mother liquor circulation pump set includes a first mother liquor circulation pump 33 and a second mother liquor circulation pump 34; the inlet and outlet ends of the first mother liquor circulation pump 33 are respectively provided with a first mother liquor inlet electric valve 35 and a first mother liquor outlet electric valve 36, and a first mother liquor pump flushing valve 37 with an external flushing water path is provided between the inlet end of the first mother liquor circulation pump 33 and the first mother liquor inlet electric valve 35; the inlet and outlet ends of the second mother liquor circulation pump 34 are respectively provided with a second mother liquor inlet electric valve 38 and a second mother liquor outlet electric valve 39, and a second mother liquor pump flushing valve 40 with an external flushing water path is provided between the inlet end of the second mother liquor circulation pump 34 and the second mother liquor inlet electric valve 38; the inlets of the first mother liquor circulation pump 33 and the second mother liquor circulation pump 34 are combined into one channel and connected to the mother liquor tank 17, and the outlet ends of the first mother liquor circulation pump 33 and the second mother liquor circulation pump 34 are combined into one channel and connected to the mother liquor inlet pipe of the first precooler 1.

[0040] Similarly, by setting up a mother liquor circulation pump set, the first mother liquor circulation pump 33 and the second mother liquor circulation pump 34 can be used and kept on standby, with a dual-pump redundancy design. When one mother liquor circulation pump fails or needs maintenance after a set time, it can be immediately switched to the other mother liquor circulation pump, enabling maintenance without interrupting production and eliminating the risk of a complete shutdown due to a single pump failure. At the same time, by setting up flushing valves 37 and 40 for the first mother liquor pump to allow flushing water to be introduced, the unused mother liquor circulation pump can be completely emptied and flushed clean, preventing residual mother liquor from flowing out during maintenance and causing injury to maintenance personnel.

[0041] Example 2 See Figures 1-3 Corresponding to the embodiments, the second aspect of this application provides a method for preventing crystallization and blockage in a cryogenic magnesium removal precooler, employing the aforementioned system for preventing crystallization and blockage in a cryogenic magnesium removal precooler. The method includes the following steps: S1: System Start-up Control: During the non-start-up phase, there is waste liquid in the crystallization tank and treated cold acid in the mother liquor tank 17. Start the first waste liquid circulation pump 25 or the second waste liquid circulation pump 26, and start the first mother liquor circulation pump 33 or the second mother liquor circulation pump 34 to start the material flow of waste liquid and mother liquor and begin waste liquid heat exchange. Then, execute the start-up control to start the system.

[0042] The specific steps include: S1.1: When the machine is started, the material flow of waste liquid and mother liquor is started and the waste liquid heat exchange is started. After the heat exchange is completed and the cooled waste liquid is cooled, it is simultaneously discharged into the first crystallization tank 10 and the second crystallization tank 11 for magnesium salt crystallization and precipitation. When the first crystallization tank 10 and the second crystallization tank 11 are fed at a time, the automatic flushing valve 19 of the discharge port on the first crystallization tank 10 and the second crystallization tank 11 is opened first to flush the discharge pipeline. After flushing is completed, the two automatic flushing valves 19 of the discharge port are closed. At the same time, the automatic discharge valve 18 on the first crystallization tank 10 and the second crystallization tank 11 is opened and the first discharge pump 20 is started. The first crystallization tank 10 and the second crystallization tank 11 start to discharge, and the mixture of magnesium salt crystallization and uncrystallized waste liquid is transported to the third crystallization tank 12 for magnesium salt crystallization and precipitation through the first discharge pump 20. S1.2: After the first crystallization tank 10 and the second crystallization tank 11 have finished feeding, turn off the first feeding pump 20, turn off the automatic feeding valve 18, open the automatic discharge valve 24, delay opening the automatic flushing valve 19 at the feeding port, flush the pipeline and the waste liquid inside the first feeding pump 20, then turn off the automatic flushing valve 19 at the feeding port and delay closing the automatic discharge valve 24 to discharge the flushing water and magnesium salt crystals in the pipeline. S1.3: When the third crystallization tank 12 is scheduled to discharge material, the automatic flushing valve 19 at the discharge port on the third crystallization tank 12 is first opened to flush the discharge pipe. After flushing, the automatic flushing valve 19 at the discharge port is closed. At the same time, the automatic discharge valve 18 on the third crystallization tank 12 is opened, and the second discharge pump 21 is started. The third crystallization tank 12 begins to discharge material, and the mixture of magnesium salt crystals and uncrystallized waste liquid is transported to the fourth crystallization tank 13 for magnesium salt crystallization and precipitation through the second discharge pump 21. Similarly, the fifth crystallization tank 14 and the sixth crystallization tank 15 are fed by the third discharge pump 22 and the fourth discharge pump 23 in sequence for magnesium salt crystallization and precipitation and are discharged in sequence. S1.4: The sixth crystallization tank 15 feeds material at regular intervals, discharging a mixture of magnesium salt crystals and the remaining low-temperature acid solution after crystallization. The mixture is centrifuged to produce low-temperature acid solution which is stored in the mother liquor tank 17 as mother liquor, to be extracted and used by the first mother liquor circulation pump 33 or the second mother liquor circulation pump 34. Then the start-up control is completed and the system enters normal operation.

[0043] Thus, when the system is started up by executing the start-up control, by feeding the first crystallizer 10 and the second crystallizer 11 in parallel, a large amount of waste electrolyte that has just completed heat exchange and been cooled from the precooler group can be accepted. This effectively avoids overflow caused by insufficient capacity of a single tank and avoids the effect of excessively short residence time on crystallization. By connecting multiple crystallizers in series, a stepped cooling sequence is further formed for the waste electrolyte that has completed heat exchange and been cooled during the crystallization process. The waste electrolyte is initially cooled in the first and second crystallizers 11, and magnesium sulfate begins to precipitate, but has not yet reached extremely high supersaturation. Subsequently, it enters the third to sixth crystallizers 15 in sequence. The temperature is further reduced in each tank, and the supersaturation is always controlled within the metastable region, avoiding "explosive nucleation" that produces a large number of fine crystals. This achieves stepped cooling crystallization of the waste liquid, allowing magnesium sulfate crystals to grow slowly and uniformly on the existing seed crystals, ultimately producing large and uniform crystals with good crystallization effect, good magnesium removal effect, and easy subsequent centrifugal separation, thus improving magnesium removal efficiency and acid purity.

[0044] Meanwhile, by setting an automatic flushing valve 19 for the discharge port with an external flushing water circuit between the automatic discharge valve 18 and the discharge port of each crystallizer discharge pipe, flushing water can be introduced to flush the discharge port and pipe before discharge to clean the crystals deposited in the pipe and prevent crystals from clogging the discharge port. By setting an automatic discharge valve 24 below the automatic discharge valve 18, flushing water and crystal blockage can be discharged in a timely manner, which can effectively prevent magnesium salt crystals from depositing and clogging in the pipe and improve the reliability of the long-term operation of the system.

[0045] S2: Operation and monitoring of the first precooler 1: Open the mother liquor inlet valve 8, mother liquor outlet valve 9, waste liquid inlet valve 4, and waste liquid outlet valve 7 on the first precooler 1, and keep the mother liquor inlet valve 8, mother liquor outlet valve 9, waste liquid inlet valve 4, and waste liquid outlet valve 7 on the second precooler 2 and the third precooler 3 closed. Start the first waste liquid circulation pump 25 or the second waste liquid circulation pump 26 to pump the high-temperature waste electrolyte to be cooled into the tube side of the first precooler 1 through the waste liquid inlet valve 4. Start the first mother liquor circulation pump 33 or the second mother liquor circulation pump 34. The low-temperature mother liquor is pumped into the shell side of the first precooler 1 through the mother liquor inlet valve 8, so that the high-temperature waste electrolyte and the low-temperature mother liquor exchange heat in the first precooler 1. The waste liquid discharge flow rate in the waste liquid discharge pipe of the first precooler 1 is monitored in real time. Specifically, the flow rate change can be reflected by a flow sensor or a pressure sensor. In this embodiment, it is preferable to install a flow sensor on the waste liquid discharge pipe. When the waste liquid discharge flow rate is lower than the set value, for example, when the waste liquid discharge flow rate is lower than 70% of the normal flow rate, it indicates that the tube side is seriously blocked by crystallization, and then the precooler is switched. S3: Precooler operation switching: Open the mother liquor inlet valve 8, mother liquor outlet valve 9, waste liquid inlet valve 4, and waste liquid outlet valve 7 on the second precooler 2, and at the same time close the mother liquor inlet valve 8, mother liquor outlet valve 9, waste liquid inlet valve 4, and waste liquid outlet valve 7 on the first precooler 1 to switch to the operation of the second precooler 2, so that the high-temperature waste electrolyte and the low-temperature mother liquor are switched to the second precooler 2 for heat exchange. At this time, the first precooler 1 stops operating, and the third precooler 3 is in standby mode. S4: Rinsing and soaking the first precooler 1: Open the waste liquid discharge valve 6 on the waste liquid inlet pipe of the first precooler 1 to drain the waste liquid in the tube side of the first precooler 1. Specifically, it can be discharged to the waste liquid collection tank or discharged back to the upstream waste liquid inlet end. After draining the waste liquid, close the waste liquid discharge valve 6 on the waste liquid inlet pipe and reopen the waste liquid outlet valve 7 on the waste liquid outlet pipe. Then open the precooler flushing valve 5 to introduce flushing water into the tube side of the first precooler 1. The flushing water can be industrial clean water. After the set flushing time, close the precooler flushing valve 5 and the waste liquid outlet valve 7 and soak the first precooler 1 for the set time. The flushing time is set to 10-30 minutes and the soaking time is set to 1-2 hours. The specific duration can be adjusted according to the degree of crystallization. S5: Secondary rinsing of the first precooler 1: After soaking, open the waste liquid discharge valve 6 on the waste liquid inlet pipe to drain the soaking wastewater in the tube side of the first precooler 1. After draining the soaking wastewater, close the waste liquid discharge valve 6 on the waste liquid inlet pipe and reopen the precooler rinsing valve 5. Open the waste liquid outlet valve 7 on the waste liquid outlet pipe to introduce rinsing water into the tube side of the first precooler 1 for secondary rinsing. The secondary rinsing time is set to 5-20 minutes. The specific duration is adjusted according to the degree of crystallization to ensure that the crystals on the tube wall are completely removed. S6: First precooler 1 standby: After the second flushing is completed, close the precooler flushing valve 5 and keep the waste liquid outlet valve 7 on the waste liquid outlet pipe open until the flushing water in the tube of the first precooler 1 is drained. After draining the flushing water, close the waste liquid outlet valve 7 on the waste liquid outlet pipe. At this time, the first precooler 1 has completed the cleaning and enters the standby state. At this time, the first precooler 1 has completed the cleaning and the tube is clean and free of residue. It is in the standby state and can be put back into operation at any time. S7: Switching to Secondary Operation of Precooler: Monitor the waste liquid flow rate in the waste liquid outlet pipe of the second precooler 2 in real time. When the waste liquid flow rate in the waste liquid outlet pipe of the second precooler 2 is lower than the set value, switch to the operation of the third precooler 3 in the same way. That is, open the mother liquor inlet valve 8, mother liquor outlet valve 9, waste liquid inlet valve 4, and waste liquid outlet valve 7 on the third precooler 3, and close the mother liquor inlet valve 8, mother liquor outlet valve 9, waste liquid inlet valve 4, and waste liquid outlet valve 7 on the second precooler 2 to switch to the operation of the third precooler 3, so that the high-temperature waste electrolyte and the low-temperature mother liquor are switched to the third precooler 3 for heat exchange. At this time, the second precooler 2 stops operating. Then, the rinsing, soaking and standby process of steps S4-S6 is performed on the second precooler 2 to put the first precooler 1 into standby state. S8: Precooler restart operation switch: Real-time monitoring of the waste liquid flow rate in the waste liquid outlet pipe of the third precooler 3. When the waste liquid flow rate in the waste liquid outlet pipe of the third precooler 3 is lower than the set value, the system switches back to the operation of the first precooler 1. The third precooler 3 stops operating and is flushed and soaked. The second precooler 2 is in standby mode. The system switches in this way in a cycle, that is, the three precoolers switch in a cycle in the order of "first precooler 1 → second precooler 2 → third precooler 3 → first precooler 1...".

[0046] Specifically, the first precooler 1, the second precooler 2, and the third precooler 3 operate in parallel and alternately. The system can flush and soak the clogged precoolers online without interrupting production. Each precooler is replaced and cleaned after running for a certain number of days, which completely solves the problem of having to stop and disassemble for cleaning every day in the existing technology. It can operate continuously for 60 to 90 days, which greatly extends the service life of the system.

[0047] Thus, on the one hand, by monitoring the waste liquid outflow of the precooler in real time, the degree of crystallization blockage in the tube can be accurately determined, enabling online monitoring of blockage based on flow rate. This allows for timely switching before the blockage becomes severe enough to affect heat exchange efficiency, avoiding passive shutdown after the equipment is completely blocked. Compared to the existing technology that uses the heat exchange comparison method and requires the detection of multiple parameters such as temperature and flow rate, this solution only requires one flow rate parameter, making the system simple and fast-responding.

[0048] On the other hand, by designing a composite cleaning process for the precooler—first draining the waste liquid → first flushing to remove most of the loose crystals → soaking to dissolve or soften stubborn crystals → second flushing to thoroughly remove them → draining the precooler for standby—this process is accurately adapted to the characteristics of stubborn magnesium sulfate crystals in wet zinc smelting waste electrolyte that easily adhere to the pipe wall. It has a stronger ability to remove magnesium sulfate crystals in small-diameter silicon carbide tubes, with good unblocking effect, and can restore the heat exchange capacity of the precooler to near its initial state, with good magnesium removal effect.

[0049] Furthermore, by connecting the three precoolers in parallel, each precooler can operate independently. Waste liquid flows into each precooler from the same source, allowing the three precoolers to operate independently in a "one-in-use, one-in-standby, one-in-soaking" state. When one precooler needs to be cleaned of crystallization blockage after operating for a certain period of time, there is no need to stop the machine. Simply close the waste liquid and mother liquor inlet and outlet valves of that precooler and switch to another parallel precooler in standby to continue operation. This allows for online flushing and soaking of the blocked precooler without interrupting production, thus achieving online recovery without stopping the machine for disassembly and cleaning. This greatly extends the continuous operation cycle of the precooler group, ensuring the continuity and economy of production.

[0050] In some embodiments, during the operation of the precooler group, the waste liquid circulation pumps are switched to operate according to the fault status or operating time of the first waste liquid circulation pump 25 and the second waste liquid circulation pump 26, so as to cyclically switch the operation of the first waste liquid circulation pump 25 and the second waste liquid circulation pump 26.

[0051] The specific steps for switching the operation of the waste liquid circulation pump include: Waste liquid circulation pump operation: When the machine is started, open the first waste liquid inlet electric valve 27 and the first waste liquid outlet electric valve 28 located at the inlet and outlet of the first waste liquid circulation pump 25 to start the first waste liquid circulation pump 25. The first waste liquid circulation pump 25 pumps the high-temperature waste electrolyte to be cooled, which enters the first precooler 1, the second precooler 2, or the third precooler 3 through the corresponding waste liquid inlet valve 4. Waste liquid circulation pump operation switching: When the first waste liquid circulation pump 25 fails or runs to the set time, open the second waste liquid inlet electric valve 30 and the second waste liquid outlet electric valve 31 located at both ends of the second waste liquid circulation pump 26, and close the first waste liquid circulation pump 25 and the first waste liquid inlet electric valve 27. At the same time, start the second waste liquid circulation pump 26 and switch to pumping the high-temperature waste electrolyte to be cooled by the second waste liquid circulation pump 26. Cleaning waste liquid circulation pump: Keep the first waste liquid outlet electric valve 28 open to drain the waste liquid in the first waste liquid circulation pump 25, and then open the first waste liquid pump flushing valve 29 located at the water inlet of the first waste liquid circulation pump 25 to flush the pump head of the first waste liquid circulation pump 25 for a set time. Waste liquid circulation pump shutdown standby: After flushing is completed, close the first waste liquid pump flushing valve 29 and delay closing the first waste liquid outlet electric valve 28. At this time, the first waste liquid circulation pump 25 is in an empty pump state and can be inspected or standby. Secondary operation switching of waste liquid circulation pump: When the second waste liquid circulation pump 26 malfunctions or runs to the set time, the first waste liquid inlet electric valve 27 and the first waste liquid outlet electric valve 28 located at both ends of the first waste liquid circulation pump 25 are reopened, and the second waste liquid circulation pump 26 and the second waste liquid inlet electric valve 30 are closed. At the same time, the first waste liquid circulation pump 25 is started, and the pumping of the high-temperature waste electrolyte to be cooled is switched back to the first waste liquid circulation pump 25. Then, the second waste liquid pump flushing valve 32 is opened to clean the second waste liquid circulation pump 26. This cycle of switching operation is repeated.

[0052] In this way, the first waste liquid circulation pump 25 and the second waste liquid circulation pump 26 can be used and kept on standby, with a dual-pump redundancy design. When one waste liquid circulation pump fails or needs maintenance after a set time, it can be immediately switched to the other waste liquid circulation pump, which can achieve maintenance without stopping production and eliminate the risk of a complete shutdown caused by a single pump failure. At the same time, the dead zone where waste liquid remains in the pump chamber is prone to crystallization due to temperature drop, which may cause jamming or seal damage during the next start-up. By setting the first waste liquid pump flushing valve 29 and the second waste liquid pump flushing valve 32 to introduce flushing water, the idle waste liquid circulation pump can be completely emptied and flushed clean, preventing residual waste liquid from crystallizing and clogging the pump chamber or corroding the mechanical seal.

[0053] In some implementations, during the operation of the precooler group, the mother liquor circulation pumps are switched to operate according to the fault status or operating time of the first mother liquor circulation pump 33 and the second mother liquor circulation pump 34, so as to cyclically switch the operation of the first mother liquor circulation pump 33 and the second mother liquor circulation pump 34.

[0054] The specific steps for switching the operation of the mother liquor circulation pump include: Mother liquor circulation pump operation: When the machine is started, open the first mother liquor inlet electric valve 35 and the first mother liquor outlet electric valve 36 located at the inlet and outlet of the first mother liquor circulation pump 33 to start the first mother liquor circulation pump 33. The first mother liquor circulation pump 33 pumps the high-temperature mother electrolyte to be cooled, which enters the first precooler 1, the second precooler 2, or the third precooler 3 through the corresponding mother liquor inlet valve 8. Mother liquor circulation pump operation switching: When the first mother liquor circulation pump 33 fails or runs to the set time, open the second mother liquor inlet electric valve 38 and the second mother liquor outlet electric valve 39 located at both ends of the second mother liquor circulation pump 34, and close the first mother liquor circulation pump 33 and the first mother liquor inlet electric valve 35. At the same time, start the second mother liquor circulation pump 34 and switch to pumping the high-temperature mother electrolyte to be cooled by the second mother liquor circulation pump 34. Cleaning the mother liquor circulation pump: Keep the first mother liquor outlet electric valve 36 open to drain the mother liquor in the first mother liquor circulation pump 33. Then open the first mother liquor pump flushing valve 37 located at the water inlet of the first mother liquor circulation pump 33 to flush the pump head of the first mother liquor circulation pump 33 for a set time. Mother liquor circulation pump shutdown standby: After flushing is completed, close the flushing valve 37 of the first mother liquor pump and delay closing the electric valve 36 of the first mother liquor outlet. At this time, the first mother liquor circulation pump 33 is in an empty pump state and can be inspected or standby. Secondary operation switching of the mother liquor circulation pump: When the second mother liquor circulation pump 34 malfunctions or runs to the set time, the first mother liquor inlet electric valve 35 and the first mother liquor outlet electric valve 36 located at both ends of the first mother liquor circulation pump 33 are reopened, and the second mother liquor circulation pump 34 and the second mother liquor inlet electric valve 38 are closed. At the same time, the first mother liquor circulation pump 33 is started, and the pumping of the high-temperature mother electrolyte to be cooled is switched back to the first mother liquor circulation pump 33. Then, the second mother liquor pump flushing valve 40 is opened to clean the second mother liquor circulation pump 34. This cycle of switching is repeated.

[0055] Thus, by setting up a mother liquor circulation pump set, the first mother liquor circulation pump 33 and the second mother liquor circulation pump 34 can be used and kept on standby, with a dual-pump redundancy design. When one mother liquor circulation pump fails or needs maintenance after a set time, it can be immediately switched to the other mother liquor circulation pump, enabling maintenance without stopping production and eliminating the risk of a complete shutdown caused by a single pump failure. At the same time, by setting up flushing valves 37 and 40 for the first mother liquor pump to introduce flushing water, the unused mother liquor circulation pump can be completely emptied and flushed clean, preventing residual mother liquor from flowing out during maintenance and causing injury to maintenance personnel.

[0056] Finally, it should be noted that although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application, all of which should be included within the protection scope of this application.

Claims

1. A system for preventing crystallization and blockage in a cryogenic magnesium removal precooler, characterized in that, include: First precooler, second precooler, third precooler, waste liquid circulation pump set, mother liquor circulation pump set; The first precooler, the second precooler, and the third precooler are arranged in parallel. The waste liquid circulation pump group is used to introduce the high-temperature waste electrolyte to be cooled into the tube side of each precooler, and the mother liquor circulation pump group is used to introduce the low-temperature mother liquor into the shell side of each precooler. The waste liquid inlet pipe of the first precooler is connected to the waste liquid circulation pump group, and the waste liquid outlet pipe of the first precooler is connected to the waste liquid outlet pipes of the second and third precoolers in sequence. A waste liquid inlet valve is installed on the waste liquid inlet pipes of the first, second, and third precoolers respectively. A precooler flushing valve with an external flushing water circuit is set between each waste liquid inlet valve and the tube inlet of the corresponding precooler. A waste liquid discharge valve is set between the precooler flushing valve and the waste liquid inlet valve. A waste liquid outlet valve is installed on the waste liquid outlet pipes of the first, second, and third precoolers respectively. The mother liquor inlet pipe of the first precooler is connected to the mother liquor circulation pump group, and the mother liquor outlet pipe of the first precooler is connected to the mother liquor outlet pipes of the second and third precoolers in sequence. A mother liquor inlet valve is installed on the mother liquor inlet pipes of the first, second and third precoolers, and a mother liquor outlet valve is installed on the mother liquor outlet pipes of the first, second and third precoolers.

2. The anti-crystallization and clogging system for the cryogenic magnesium removal precooler according to claim 1, characterized in that: It also includes a crystallization tank assembly, which includes at least a first crystallization tank, a second crystallization tank, a third crystallization tank, a fourth crystallization tank, a fifth crystallization tank, a sixth crystallization tank, and a mother liquor tank; The waste liquid outlet pipe of the third precooler is connected to the feed inlets of the first and second crystallizers. The waste electrolyte cooled by heat exchange is simultaneously discharged into the first and second crystallizers for magnesium salt crystallization. An automatic feed valve is installed on the feed pipe of each of the first, second, third, fourth, fifth, and sixth crystallizers. An automatic flushing valve with an external flushing water circuit is provided between each automatic feed valve and the feed inlet of the corresponding crystallizer. A first feed pump, a second feed pump, a third feed pump, and a fourth feed pump are sequentially provided between the feed inlet of the second, third, fourth, fifth, and sixth crystallizers and the automatic feed valve corresponding to the previous crystallizer. An automatic discharge valve is provided below the automatic feed valves of the first and second crystallizers. An automatic discharge valve is provided below the automatic feed valves of the third, fourth, fifth, and sixth crystallizers. The first and second crystallization tanks simultaneously feed materials at timed intervals, while the third, fourth, and fifth crystallization tanks feed materials sequentially at timed intervals. The mixture of magnesium salt crystals and uncrystallized waste liquid is transported to the downstream crystallization tank for magnesium salt crystallization and precipitation. The sixth crystallization tank feeds materials at timed intervals last, discharging the mixture of magnesium salt crystals and the remaining low-temperature acid liquid after crystallization and precipitation. The produced low-temperature acid liquid is stored in the mother liquor tank as mother liquor for later use.

3. The anti-crystallization and clogging system for the cryogenic magnesium removal precooler according to claim 1, characterized in that: The waste liquid circulation pump set includes a first waste liquid circulation pump and a second waste liquid circulation pump. The first waste liquid circulation pump is equipped with a first waste liquid inlet electric valve and a first waste liquid outlet electric valve at its inlet and outlet ends, respectively, and a first waste liquid pump flushing valve with an external flushing water circuit is provided between the inlet end of the first waste liquid circulation pump and the first waste liquid inlet electric valve. The second waste liquid circulation pump is equipped with a second waste liquid inlet electric valve and a second waste liquid outlet electric valve at its inlet and outlet ends, respectively, and a second waste liquid pump flushing valve with an external flushing water circuit is provided between the inlet end of the second waste liquid circulation pump and the second waste liquid inlet electric valve. The inlet ends of the first waste liquid circulation pump and the second waste liquid circulation pump are combined into one line and connected to the pipeline for conveying high-temperature waste electrolyte. The outlet ends of the first waste liquid circulation pump and the second waste liquid circulation pump are combined into one line and connected to the waste liquid inlet pipeline of the first precooler.

4. The anti-crystallization and clogging system for the cryogenic magnesium removal precooler according to claim 1, characterized in that: The mother liquor circulation pump set includes a first mother liquor circulation pump and a second mother liquor circulation pump; The first mother liquor circulation pump is equipped with a first mother liquor inlet electric valve and a first mother liquor outlet electric valve at its inlet and outlet ends, respectively, and a first mother liquor pump flushing valve with an external flushing water path is provided between the inlet end of the first mother liquor circulation pump and the first mother liquor inlet electric valve. The inlet and outlet of the second mother liquor circulation pump are respectively equipped with a second mother liquor inlet electric valve and a second mother liquor outlet electric valve, and a second mother liquor pump flushing valve with an external flushing water circuit is provided between the inlet of the second mother liquor circulation pump and the second mother liquor inlet electric valve. The inlet ends of the first mother liquor circulation pump and the second mother liquor circulation pump are combined into one channel and connected to the mother liquor tank. The outlet ends of the first mother liquor circulation pump and the second mother liquor circulation pump are combined into one channel and connected to the mother liquor inlet pipe of the first precooler.

5. A method for preventing crystallization and blockage in a cryogenic magnesium removal precooler, characterized in that: The method of using the anti-crystallization and clogging system for the cryogenic magnesium removal precooler according to any one of claims 1-4 includes at least the following steps: S1: System Start-up Control: During the non-start-up phase, there is waste liquid in the crystallizer and treated cold acid in the mother liquor tank. Start the first waste liquid circulation pump or the second waste liquid circulation pump, start the first mother liquor circulation pump or the second mother liquor circulation pump, start the material flow of waste liquid and mother liquor, start waste liquid heat exchange, and execute the start-up control to start the system. S2: Operation and monitoring of the first precooler: Open the mother liquor inlet valve, mother liquor outlet valve, waste liquid inlet valve, and waste liquid outlet valve on the first precooler, and keep the mother liquor inlet valve, mother liquor outlet valve, waste liquid inlet valve, and waste liquid outlet valve on the second and third precoolers closed. Start the first or second waste liquid circulation pump to pump the high-temperature waste electrolyte to be cooled into the tube side of the first precooler through the waste liquid inlet valve. Start the first or second mother liquor circulation pump to pump the low-temperature mother liquor into the shell side of the first precooler through the mother liquor inlet valve, so that the high-temperature waste electrolyte and the low-temperature mother liquor can exchange heat in the first precooler. Monitor the waste liquid outlet flow rate in the waste liquid outlet pipe of the first precooler in real time. When the waste liquid outlet flow rate is lower than the set value, start switching the precooler. S3: Precooler operation switching: Open the mother liquor inlet valve, mother liquor outlet valve, waste liquid inlet valve, and waste liquid outlet valve on the second precooler, and at the same time close the mother liquor inlet valve, mother liquor outlet valve, waste liquid inlet valve, and waste liquid outlet valve on the first precooler to switch to the operation of the second precooler, so that the high-temperature waste electrolyte and the low-temperature mother liquor are switched to the second precooler for heat exchange. At this time, the first precooler stops operating, and the third precooler is in standby mode. S4: Rinse and soak the first precooler: Open the waste liquid discharge valve on the waste liquid inlet pipe of the first precooler to drain the waste liquid in the tube side of the first precooler. After draining the waste liquid, close the waste liquid discharge valve on the waste liquid inlet pipe and reopen the waste liquid outlet valve on the waste liquid outlet pipe. Then open the precooler flushing valve to introduce flushing water into the tube side of the first precooler. After flushing for the set time, close the precooler flushing valve and the waste liquid outlet valve to soak the first precooler for the set time. S5: Secondary rinsing of the first precooler: After soaking, open the waste liquid discharge valve on the waste liquid inlet pipe to drain the soaking wastewater in the tube side of the first precooler. After draining the soaking wastewater, close the waste liquid discharge valve on the waste liquid inlet pipe and reopen the precooler rinsing valve. Open the waste liquid outlet valve on the waste liquid outlet pipe to introduce rinsing water into the tube side of the first precooler for secondary rinsing for the set time. S6: First precooler standby: After the second flushing is completed, close the precooler flushing valve and keep the waste liquid outlet valve on the waste liquid outlet pipe open until the flushing water in the tube side of the first precooler is drained. After draining the flushing water, close the waste liquid outlet valve on the waste liquid outlet pipe. At this time, the first precooler is cleared and enters standby mode. S7: Precooler secondary operation switch: Real-time monitoring of the waste liquid discharge flow rate in the waste liquid discharge pipe of the second precooler. When the waste liquid discharge flow rate in the waste liquid discharge pipe of the second precooler is lower than the set value, the operation is switched to the third precooler. The second precooler stops running and is flushed and soaked. The first precooler is in standby mode. S8: Precooler restart operation switch: Real-time monitoring of the waste liquid flow rate in the waste liquid outlet pipe of the third precooler. When the waste liquid flow rate in the waste liquid outlet pipe of the third precooler is lower than the set value, the system switches back to the operation of the first precooler. The third precooler stops operating and is flushed and soaked. The second precooler is in standby mode. The system switches back and forth in this manner.

6. The method for preventing crystallization and blockage in a cryogenic magnesium removal precooler according to claim 5, characterized in that, Step S1 specifically includes: S1.1: When starting the machine, the material flow of waste liquid and mother liquor is started. After the waste liquid heat exchange is completed, the cooled waste liquid is simultaneously discharged into the first crystallization tank and the second crystallization tank for magnesium salt crystallization. When the first crystallization tank and the second crystallization tank are feeding at timed intervals, the automatic flushing valves of the discharge port on the first crystallization tank and the second crystallization tank are opened first to flush the discharge pipe. After flushing is completed, the two automatic flushing valves of the discharge port are closed. At the same time, the automatic discharge valves on the first crystallization tank and the second crystallization tank are opened, the first discharge pump is started, the first crystallization tank and the second crystallization tank begin to discharge, and the mixture of magnesium salt crystals and uncrystallized waste liquid is transported to the third crystallization tank for magnesium salt crystallization. S1.2: After the first and second crystallization tanks have finished feeding, shut down the first feeding pump, shut down the automatic feeding valve, open the automatic discharge valve, delay opening the automatic flushing valve at the feeding port, flush the pipeline and the waste liquid inside the first feeding pump, then shut down the automatic flushing valve at the feeding port and delay closing the automatic discharge valve to discharge the flushing water and magnesium salt crystals in the pipeline. S1.3: When the third crystallizer is scheduled to discharge material, first open the automatic flushing valve at the discharge port on the third crystallizer to flush the discharge pipe. After flushing, close the automatic flushing valve at the discharge port. At the same time, open the automatic discharge valve on the third crystallizer and start the second discharge pump. The third crystallizer begins to discharge material, and the mixture of magnesium salt crystals and uncrystallized waste liquid is transported to the fourth crystallizer for magnesium salt crystallization and precipitation through the second discharge pump. Similarly, the fifth and sixth crystallizers are fed by the third and fourth discharge pumps in sequence for magnesium salt crystallization and precipitation, and are discharged in sequence. S1.4: The sixth crystallization tank is fed at regular intervals, and a mixture of magnesium salt crystals and residual low-temperature acid solution after crystallization is discharged. The mixture is centrifuged to produce low-temperature acid solution which is stored in the mother liquor tank as mother liquor, which is then used by the first or second mother liquor circulation pump. The start-up control is then completed.

7. The method for preventing crystallization and blockage in a cryogenic magnesium removal precooler according to claim 5, characterized in that: During the operation of the precooler unit, the waste liquid circulation pump is switched to operate according to the fault status or operating time of the first waste liquid circulation pump and the second waste liquid circulation pump, so as to cycle the operation of the first waste liquid circulation pump and the second waste liquid circulation pump.

8. The method for preventing crystallization and blockage in a cryogenic magnesium removal precooler according to claim 7, characterized in that, The specific steps for switching the operation of the waste liquid circulation pump include: Waste liquid circulation pump operation: When starting up, open the first waste liquid inlet electric valve and the first waste liquid outlet electric valve located at the inlet and outlet of the first waste liquid circulation pump to start the first waste liquid circulation pump. The first waste liquid circulation pump pumps the high-temperature waste electrolyte to be cooled, which enters the first precooler, the second precooler, or the third precooler through the corresponding waste liquid inlet valve. Waste liquid circulation pump operation switching: When the first waste liquid circulation pump fails or runs to the set time, open the second waste liquid inlet electric valve and the second waste liquid outlet electric valve located at both ends of the second waste liquid circulation pump, and close the first waste liquid circulation pump and the first waste liquid inlet electric valve. At the same time, start the second waste liquid circulation pump and switch to pumping the high-temperature waste electrolyte to be cooled by the second waste liquid circulation pump. Cleaning waste liquid circulation pump: Keep the first waste liquid outlet electric valve open to drain the waste liquid in the first waste liquid circulation pump. Then open the first waste liquid pump flushing valve located at the water inlet of the first waste liquid circulation pump to flush the pump head of the first waste liquid circulation pump for a set time. Waste liquid circulation pump shutdown and standby: After flushing is completed, close the flushing valve of the first waste liquid pump and delay closing the electric valve of the first waste liquid outlet. At this time, the first waste liquid circulation pump is in an empty pump state and can be inspected or standby. Secondary operation switching of waste liquid circulation pump: When the second waste liquid circulation pump fails or runs to the set time, reopen the first waste liquid inlet electric valve and the first waste liquid outlet electric valve located at both ends of the first waste liquid circulation pump, and close the second waste liquid circulation pump and the second waste liquid inlet electric valve. At the same time, start the first waste liquid circulation pump and switch back to pumping the high-temperature waste electrolyte to be cooled by the first waste liquid circulation pump. Then open the flushing valve of the second waste liquid pump to clean the second waste liquid circulation pump. This cycle of switching operation is repeated.

9. The method for preventing crystallization and blockage in a cryogenic magnesium removal precooler according to claim 5, characterized in that: During the operation of the precooler unit, the mother liquor circulation pump is switched to operate according to the fault status or operating time of the first mother liquor circulation pump and the second mother liquor circulation pump, so as to cycle through the operation of the first mother liquor circulation pump and the second mother liquor circulation pump.

10. The method for preventing crystallization and blockage in a cryogenic magnesium removal precooler according to claim 9, characterized in that, The specific steps for switching the operation of the mother liquor circulation pump include: Mother liquor circulation pump operation: When starting up, open the first mother liquor inlet electric valve and the first mother liquor outlet electric valve located at the inlet and outlet of the first mother liquor circulation pump to start the first mother liquor circulation pump. The first mother liquor circulation pump pumps the high-temperature mother electrolyte to be cooled, which enters the first precooler, the second precooler, or the third precooler through the corresponding mother liquor inlet valve. Mother liquor circulation pump operation switching: When the first mother liquor circulation pump fails or runs to the set time, open the second mother liquor inlet electric valve and the second mother liquor outlet electric valve located at both ends of the second mother liquor circulation pump, and close the first mother liquor circulation pump and the first mother liquor inlet electric valve. At the same time, start the second mother liquor circulation pump and switch to pumping the high-temperature mother electrolyte to be cooled by the second mother liquor circulation pump. Cleaning the mother liquor circulation pump: Keep the first mother liquor outlet electric valve open to drain the mother liquor in the first mother liquor circulation pump. Then open the first mother liquor pump flushing valve located at the water inlet of the first mother liquor circulation pump to flush the pump head of the first mother liquor circulation pump for a set time. Mother liquor circulation pump shutdown and standby: After rinsing is completed, close the first mother liquor pump rinsing valve and delay closing the first mother liquor outlet electric valve. At this time, the first mother liquor circulation pump is in an empty pump state and can be inspected or standby. Secondary operation switching of the mother liquor circulation pump: When the second mother liquor circulation pump fails or runs to the set time, reopen the first mother liquor inlet electric valve and the first mother liquor outlet electric valve located at both ends of the first mother liquor circulation pump, and close the second mother liquor circulation pump and the second mother liquor inlet electric valve. At the same time, start the first mother liquor circulation pump and switch back to pumping the high-temperature mother electrolyte to be cooled by the first mother liquor circulation pump. Then open the flushing valve of the second mother liquor pump to clean the second mother liquor circulation pump. This cycle of switching operation is repeated.

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