Zinc hydrometallurgy waste electrolyte natural crystallization magnesium removal method

Abstract

The invention relates to a natural crystallization magnesium removal method for a zinc hydrometallurgy waste electrolyte, and belongs to the technical field of mineral processing. The method comprises the following steps: cooling the zinc hydrometallurgy waste electrolyte to-10 to-5 DEG C by using a cooling tower in a low-temperature natural environment with the temperature of-15 DEG C or below, enabling the zinc hydrometallurgy waste electrolyte to automatically flow into a crystallization tank with a slow stirring function, enabling the bottom of the crystallization tank to flow into a centrifugal machine, separating magnesium sulfate crystals, enabling mother liquor A to automatically flow into a crystallization mother liquor transfer tank, and enabling mother liquor B to flow into a crystallization mother liquor transfer tank; returning to a zinc hydrometallurgy electrolysis system; overflowing from the upper part of the crystallization tank into a circulating tank, and replenishing the zinc hydrometallurgy waste electrolyte with the same volume as the mother liquor A into the circulating tank; circulating tank liquid is pumped into a cooling tower to be cooled and then automatically flows into a crystallization tank with a slow stirring function; the device realizes whole-process continuous feeding and discharging, prevents crystal blockage, pump valve freezing and the like, cools the zinc hydrometallurgy waste electrolyte through the cooling tower and the circulating liquid, is beneficial to circulating cooling to realize efficient magnesium removal, and is low in energy consumption, low in cost, free of wastewater and waste residue discharge, clean and environment-friendly.

Description

Technical Field

[0001] The invention relates to a method for removing magnesium by natural crystallization of waste electrolyte from hydrometallurgical zinc smelting, and belongs to the technical field of mineral processing. Background Art

[0002] Magnesium is a common impurity element in zinc concentrate and one of the main impurity ions that is difficult to purify and separate in hydrometallurgical zinc smelting. In the process of hydrometallurgical zinc smelting, after the zinc sulfide concentrate is boiled and acid-leached, magnesium enters the solution mainly in the form of sulfate. It is difficult to remove magnesium ions during the purification process, resulting in continuous circulation and enrichment of magnesium in the hydrometallurgical zinc smelting system, which brings many problems to the production processes such as electrolysis, purification, and pipeline blockage. With the gradual increase in the proportion of high-magnesium zinc concentrate, the enrichment of magnesium is becoming more and more serious.

[0003] The cyclic enrichment of magnesium in the hydrometallurgical zinc solution is a common problem in the hydrometallurgical zinc industry. Magnesium is continuously circulated and enriched in the hydrometallurgical system, and the lack of an effective open circuit brings problems such as crystallization blockage, decreased current efficiency, and increased energy consumption to normal production. Calcium sulfate close to saturation induces the crystallization of sulfates such as magnesium sulfate and zinc sulfate when it is cooled, resulting in a large amount of crystallization in tanks such as chutes, reaction tanks, and sedimentation tanks. The importance of open-circuit removal of calcium and magnesium in the hydrometallurgical zinc process has become increasingly prominent. Therefore, the increase in the concentration of calcium and magnesium ions brings many hazards to the leaching, purification, electrolysis and other processes in the hydrometallurgical zinc smelting process, and has become an important factor restricting the improvement of the main technical indicators of hydrometallurgical zinc smelting.

[0004] At present, the main magnesium removal processes at home and abroad are chemical methods: zinc sulfide concentrate acid washing and magnesium removal method, fluoride precipitation method, open circuit solution method (waste electrolyte lime neutralization treatment method), physical methods: supernatant cooling crystallization method, waste electrolyte freezing crystallization method, etc. The acid washing and magnesium removal of zinc sulfide concentrate leads to the loss of valuable metals; the fluoride precipitation magnesium removal method introduces fluoride ions and brings new problems; the open solution method for magnesium removal produces a large amount of gypsum waste slag, and a large amount of zinc is lost during the magnesium precipitation process; the supernatant cooling crystallization method uses forced cooling of the supernatant under normal operating conditions to precipitate magnesium crystals, but it carries a large amount of basic zinc sulfate and zinc sulfate, making liquid-solid separation difficult, the magnesium removal product has a low magnesium content, and a large amount of zinc loss; compared with the supernatant cooling crystallization method, the waste electrolyte freezing crystallization method has high magnesium removal efficiency and low zinc loss. No chemical reagents are added in the magnesium removal process, and no neutralization reaction is required. Sulfuric acid in the waste electrolyte is not lost, and no gypsum slag or neutralization wastewater is produced. The process is environmentally friendly and efficient, has no potential hazards and adverse effects on wet zinc smelting, and has broad application prospects, but an external refrigeration unit is required to exchange heat for the waste electrolyte and cool it to below minus 10°C. The freezing process consumes a certain amount of electricity.

[0005] Therefore, it is of great significance to further develop new technologies and process systems that are cleaner and more environmentally friendly for magnesium removal, and to achieve clean and efficient removal of magnesium from waste electrolyte of hydrometallurgical zinc smelting. Summary of the invention

[0006] In view of the problems of large amount of waste slag and high energy consumption in physical crystallization and magnesium removal of waste electrolyte from wet zinc smelting in the prior art, the present invention proposes a natural crystallization and magnesium removal method for waste electrolyte from wet zinc smelting, wherein a natural crystallization and magnesium removal device for waste electrolyte from wet zinc smelting is used to cool the waste electrolyte from wet zinc smelting to a temperature of -10 to -5°C in a low-temperature natural environment below -15°C by using a cooling tower, and the waste electrolyte from wet zinc smelting flows by gravity into a crystallization tank with slow stirring, and flows into a centrifuge at the bottom of the crystallization tank to separate magnesium sulfate crystals, and mother liquor A flows by gravity into a crystallization mother liquor transfer tank and returns to the wet zinc smelting electrolysis system; overflow from the upper part of the crystallization tank flows into a circulation tank, and a waste electrolyte from wet zinc smelting with an equal volume to that of the mother liquor A is added into the circulation tank at the same time; after the circulating tank liquid is pumped into a cooling tower for cooling, it flows by gravity into a crystallization tank with slow stirring. The present invention reduces the temperature of the waste electrolyte to the crystallization temperature through circulating cooling in a cooling tower without refrigeration energy consumption. The present invention is particularly suitable for magnesium removal in low-temperature seasons in wet zinc smelting enterprises in northern regions. The present invention has the characteristics of being clean and efficient, free of wastewater and waste residue, and having low energy consumption and low cost.

[0007] A method for removing magnesium by natural crystallization of waste electrolyte from zinc smelting by hydroprocess, using a device for removing magnesium by natural crystallization of waste electrolyte from zinc smelting by hydroprocess,

[0008] The device for natural crystallization and magnesium removal of waste electrolyte of zinc smelting by hydroprocess comprises a waste electrolyte storage tank of zinc smelting by hydroprocess, a cooling tower, a crystallization tank, a circulation tank, a centrifuge, and a crystallization mother liquor transfer tank, wherein the liquid outlet of the waste electrolyte storage tank of zinc smelting by hydroprocess is connected with the liquid inlet of the circulation tank through a first pipeline, the liquid outlet of the circulation tank is connected with the liquid inlet of the cooling tower through a second pipeline, the liquid outlet of the cooling tower is connected with the liquid inlet of the crystallization tank through a third pipeline, the overflow outlet at the top of the crystallization tank is connected with the overflow inlet of the circulation tank through a fourth pipeline, the discharge outlet at the bottom of the crystallization tank is connected with the feed inlet of the centrifuge through a fifth pipeline, a flushing port is provided at the top of the centrifuge, the solid outlet at the bottom of the centrifuge is connected with the crystallization collector through a sixth pipeline, and the liquid outlet at the bottom of the centrifuge is connected with the crystallization mother liquor transfer tank through a seventh pipeline;

[0009] The specific steps of the method are as follows:

[0010] (1) transporting the waste electrolyte of zinc smelting in the waste electrolyte storage tank of zinc smelting to the circulation tank through the first pipeline at a preset flow rate, and then transporting it to the cooling tower through the second pipeline at a preset flow rate;

[0011] (2) utilizing a low-temperature natural environment below -15°C to cool the waste electrolyte of hydrometallurgical zinc smelting in a cooling tower to a temperature of -10 to -5°C, and then flowing by gravity through a third pipeline into a crystallization tank with slow stirring at the same preset flow rate as in step (1) and crystallizing and precipitating in the crystallization tank to form a mixed underflow containing magnesium sulfate crystals at the bottom layer and mother liquor A at the upper layer;

[0012] (3) The mixed underflow containing magnesium sulfate crystals at the bottom of the crystallization tank is transported to a centrifuge through a fifth pipeline at a preset rate for centrifugal separation to obtain magnesium sulfate crystals and a crystallization mother liquor, and flushing water is added through a flushing port to flush the magnesium sulfate crystals. The flushed magnesium sulfate crystals are collected into a crystallization collector through a sixth pipeline, and the crystallization mother liquor and the flushing liquid are transported to a crystallization mother liquor transfer tank through a seventh pipeline and returned to the hydrometallurgical zinc electrolysis system;

[0013] (4) the mother liquor A in the upper layer of the crystallization tank overflows into the circulation tank through the fourth pipeline, and the waste electrolyte of zinc smelting in the waste electrolyte storage tank of zinc smelting is added to the mother liquor A in an equal volume through the first pipeline, and mixed evenly to form a circulating mother liquor. The circulating mother liquor replaces the waste electrolyte of zinc smelting in step (1) and is transported to the cooling tower through the second pipeline at a preset flow rate for cooling.

[0014] Preferably, the first pipeline is provided with an electrolyte feeding pump, a first analog valve and a first flow meter;

[0015] The second pipeline is provided with a circulating liquid feed pump, a second analog valve and a second flow meter;

[0016] The third pipeline is provided with a first flow valve;

[0017] The fourth pipeline is provided with a third flow meter;

[0018] The fifth pipeline is provided with a third analog valve and a fourth flow meter;

[0019] The seventh pipeline is provided with a second flow valve and a fifth flow meter.

[0020] Preferably, the stirring device in the crystallization tank is an axial flow propulsion stirring device, and the stirring speed is 5 to 50 r / min.

[0021] Preferably, the stirring device in the circulation tank is a radial flow mixing stirring device, and the stirring speed is 100 to 200 r / min.

[0022] Preferably, the centrifuge is a horizontal spiral concentrated acid filtering automatic centrifuge.

[0023] More preferably, the preset flow rate of the solution into the cooling tower is 50 to 300 m / s. 3 / h, the relationship between the preset flow rate of the solution into the cooling tower and the natural ambient temperature of the cooling tower is:

[0024] V = -10t–100;

[0025] Where: V is the flow rate, m 3 / h; t is the natural environment temperature, ℃.

[0026] The waste electrolyte from wet zinc smelting is adjusted according to the natural ambient temperature. The lower the natural ambient temperature, the greater the flow rate. The crystallization tank and the circulation tank have the same volume and size. The lower the natural ambient temperature, the shorter the residence time of the slurry flowing from the cooling tower into the crystallization tank.

[0027] The beneficial effects of the present invention are:

[0028] (1) The system of the present invention has low energy consumption, and only equipment power consumption is consumed: by utilizing the low temperature natural environment below -15°C, the cold liquid that has reached the crystallization temperature is mixed with the waste electrolyte of hydrometallurgical zinc smelting, and then the waste electrolyte temperature is circulated and cooled through a cooling tower to reduce the temperature of the waste electrolyte to the crystallization temperature. No refrigeration energy consumption is required, and 300m3 of waste electrolyte can be processed per day. 3 Taking the waste electrolyte of hydrometallurgical zinc smelting as an example, the system energy consumption can be reduced from 1000kW·h to 200kW·h compared with the refrigeration and magnesium removal by refrigeration;

[0029] (2) The process of the present invention is clean, and no waste water or waste residue is generated in the whole system: the crystallized product is mainly hydrated magnesium sulfate (content 65-70%) and hydrated zinc sulfate (content 30-35%), and the adsorbed water is less than 5%. The crystallized product is easy to enter the pyrometallurgical fuming volatilization system for treatment, and more than 90% of the zinc in the crystallized product is recovered in the form of zinc oxide powder; the waste electrolyte after magnesium removal has no sulfuric acid loss and can be directly returned to the zinc electrolysis system to reduce the energy consumption of zinc electrolysis, and the crystallization and precipitation of sulfate is more conducive to the acid balance of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a schematic diagram of the natural crystallization and magnesium removal device for waste electrolyte of hydrometallurgical zinc smelting according to the present invention. DETAILED DESCRIPTION

[0031] The present invention is further described in detail below in conjunction with specific implementation modes, but the protection scope of the present invention is not limited to the described contents.

[0032] Example 1: A method for removing magnesium from waste electrolyte of zinc smelting by natural crystallization, using a device for removing magnesium from waste electrolyte of zinc smelting by natural crystallization (see Figure 1 ),

[0033] The device for natural crystallization and magnesium removal of waste electrolyte of zinc smelting by hydroprocess comprises a waste electrolyte storage tank of zinc smelting by hydroprocess, a cooling tower, a crystallization tank, a circulation tank, a centrifuge, and a crystallization mother liquor transfer tank, wherein the liquid outlet of the waste electrolyte storage tank of zinc smelting by hydroprocess is connected with the liquid inlet of the circulation tank through a first pipeline, the liquid outlet of the circulation tank is connected with the liquid inlet of the cooling tower through a second pipeline, the liquid outlet of the cooling tower is connected with the liquid inlet of the crystallization tank through a third pipeline, the overflow outlet at the top of the crystallization tank is connected with the overflow inlet of the circulation tank through a fourth pipeline, the discharge outlet at the bottom of the crystallization tank is connected with the feed inlet of the centrifuge through a fifth pipeline, a flushing port is provided at the top of the centrifuge, the solid outlet at the bottom of the centrifuge is connected with the crystallization collector through a sixth pipeline, and the liquid outlet at the bottom of the centrifuge is connected with the crystallization mother liquor transfer tank through a seventh pipeline;

[0034] The specific steps of the method are as follows:

[0035] (1) transporting the waste electrolyte of zinc smelting in the waste electrolyte storage tank of zinc smelting to the circulation tank through the first pipeline at a preset flow rate, and then transporting it to the cooling tower through the second pipeline at a preset flow rate;

[0036] (2) utilizing a low-temperature natural environment below -15°C to cool the waste electrolyte of hydrometallurgical zinc smelting in a cooling tower to a temperature of -10 to -5°C, and then flowing through a third pipeline into a crystallization tank with slow stirring at the same preset flow rate as in step (1) and crystallizing and precipitating in the crystallization tank to form a mixed bottom flow containing magnesium sulfate crystals at the bottom layer and a mother liquor A at the upper layer; the preset flow rate of the solution flowing into the cooling tower is 50 to 300 m / s. 3 / h, the relationship between the preset flow rate of the solution into the cooling tower and the natural ambient temperature of the cooling tower is:

[0037] V = -10t–100;

[0038] Where: V is the flow rate, m 3 / h; t is the natural environment temperature, ℃;

[0039] (3) The mixed underflow containing magnesium sulfate crystals at the bottom of the crystallization tank is transported to a centrifuge through a fifth pipeline at a preset rate for centrifugal separation to obtain magnesium sulfate crystals and a crystallization mother liquor, and flushing water is added through a flushing port to flush the magnesium sulfate crystals. The flushed magnesium sulfate crystals are collected into a crystallization collector through a sixth pipeline, and the crystallization mother liquor and the flushing liquid are transported to a crystallization mother liquor transfer tank through a seventh pipeline and returned to the hydrometallurgical zinc electrolysis system;

[0040] (4) the mother liquor A in the upper layer of the crystallization tank overflows into the circulation tank through the fourth pipeline, and the waste electrolyte of zinc smelting in the waste electrolyte storage tank of zinc smelting is added to the mother liquor A in equal volume through the first pipeline, and mixed evenly to form a circulating mother liquor, and the circulating mother liquor replaces the waste electrolyte of zinc smelting in step (1) and is transported to the cooling tower through the second pipeline at a preset flow rate for cooling;

[0041] The waste electrolyte from wet zinc smelting is adjusted according to the natural ambient temperature. The lower the natural ambient temperature, the greater the flow rate. The crystallization tank and the circulation tank have the same volume and size. The lower the natural ambient temperature, the shorter the residence time of the slurry flowing from the cooling tower into the crystallization tank.

[0042] Example 2: The natural crystallization and magnesium removal device for waste electrolyte of hydrometallurgical zinc smelting in this example is basically the same as that in Example 1, except that:

[0043] The first pipeline is provided with an electrolyte feed pump, a first analog valve and a first flow meter; the rate and flow rate of the hydrometallurgical zinc smelting waste electrolyte in the hydrometallurgical zinc smelting waste electrolyte storage tank flowing to the circulation tank are controlled by the electrolyte feed pump, the first analog valve and the first flow meter;

[0044] The second pipeline is provided with a circulating liquid feed pump, a second analog valve and a second flow meter; the rate and flow rate of the solution in the circulation tank flowing to the cooling tower are controlled by the circulating liquid feed pump, the second analog valve and the second flow meter to achieve a preset flow rate;

[0045] The third pipeline is provided with a first flow valve; by adjusting the first flow valve, the solution cooled to a temperature of -10 to -5°C in the cooling tower is controlled to flow into the crystallization tank at a preset flow rate;

[0046] The fourth pipeline is provided with a third flow meter; the third flow meter records the flow rate of the mother liquid A in the upper layer of the crystallization tank overflowing into the circulation tank;

[0047] The fifth pipeline is provided with a third analog valve and a fourth flow meter; the third analog valve and the fourth flow meter are used to control the mixed underflow containing magnesium sulfate crystals at the bottom of the crystallization tank to be sent to the centrifuge at a preset rate for centrifugal separation;

[0048] The seventh pipeline is provided with a second flow valve and a fifth flow meter; the second flow valve and the fifth flow meter are used to control the crystallization mother liquor and the flushing liquid to be transported to the crystallization mother liquor transfer tank according to the amount;

[0049] The stirring device in the crystallization tank is an axial flow propulsion stirring device, and the stirring speed is 5 to 50 r / min;

[0050] The stirring device in the circulation tank is a radial flow mixing stirring device, and the stirring speed is 100-200r / min;

[0051] The centrifuge is a horizontal spiral concentrated acid filtering automatic centrifuge;

[0052] By installing pumps, valves and flow meters on the pipeline, continuous material inflow and outflow can be achieved throughout the entire process to prevent crystallization blockage and pump valve freezing.

[0053] Example 3: The natural crystallization and magnesium removal device for waste electrolyte of hydrometallurgical zinc smelting in this example is basically the same as that in Example 2, except that:

[0054] The material of the waste electrolyte storage tank and crystallization mother liquor transfer tank of hydrometallurgy is preferably glass fiber reinforced plastic, with a volume of 50m 3 The top of the upper part is provided with a liquid inlet, and the lower side is provided with a liquid outlet; the cooling tower is preferably air-cooled, and the processing scale is 3000m 3 / h; the crystallization tank is preferably made of HDPE, with a capacity of 30m 3 , with a diameter of 2.8m and a height of 4.8m. It has a liquid inlet at the top, an overflow outlet at the upper side, and a liquid outlet at the bottom. A stirring device is provided in the crystallization tank, which adopts a worm gear reducer. The material of the stirring paddle is preferably 2205 duplex stainless steel. The stirring paddle is an axial flow propulsion stirring paddle. The power of the stirring motor is 30KW, and the frequency conversion adjustment stirring speed range is 5-50r / min. The material of the circulation tank is preferably HDPE, with a volume of 30m 3 , with a diameter of 2.8m and a height of 4.8m. It has a liquid inlet at the top, an overflow inlet at the upper side, and a liquid outlet at the bottom. A stirring device is provided in the circulation tank, which adopts a worm gear reducer. The material of the stirring paddle is preferably 2205 duplex stainless steel. The stirring paddle is preferably a radial flow type mixing stirring. The power of the stirring motor is 50KW, and the frequency conversion adjustment stirring speed range is 100-200r / min.

[0055] The centrifuge is preferably a horizontal spiral concentrated acid filtration automatic centrifuge with a processing capacity range of 10 to 50 m 3 / h; the machine body material is preferably 316L, the material of the part in contact with the solution is preferably 2205 duplex stainless steel, and the filter screen material is preferably 2507 duplex stainless steel;

[0056] The waste electrolyte of hydrometallurgical zinc smelting in the waste electrolyte storage tank is fed through the electrolyte feed pump and the first analog valve (the electric valve can control the flow rate of 10 to 150m 3 / h) and the first flowmeter controls the preset flow rate into the circulation tank, and the solution in the circulation tank passes through the circulating liquid feed pump and the second analog valve (the electric valve can control the flow rate of 50-300m 3 / h) and the second flowmeter controls the preset flow rate to enter the cooling tower. The solution cooled to a temperature of -10 to -5°C in the cooling tower is controlled by the first flow valve to flow by gravity into the crystallization tank under the slow stirring of the axial flow propulsion stirring to crystallize magnesium sulfate. The overflow mother liquor A from the upper part of the crystallization tank flows by gravity to the circulation tank through the high head difference and the third flowmeter. The mixed underflow containing magnesium sulfate crystals at the bottom of the crystallization tank flows through the third analog valve (the electric valve can control the flow rate of 10 to 50m 3The magnesium sulfate crystals separated by the centrifuge are collected into a crystal collector through a sixth pipeline for storage and waiting for treatment. The mother liquor separated by the centrifuge flows into a crystal mother liquor transfer tank through a second flow valve and a fifth flow meter, and then returns to the hydrometallurgical zinc electrolysis system.

[0057] The specific implementation modes of the present invention are described in detail above, but the present invention is not limited to the above implementation modes, and various changes can be made within the knowledge scope of ordinary technicians in this field without departing from the purpose of the present invention.

Claims

1. A method for removing magnesium from waste electrolyte of hydrometallurgical zinc smelting by natural crystallization, characterized in that: The device for natural crystallization and magnesium removal of waste electrolyte from hydrometallurgical zinc smelting is used. The device for natural crystallization and magnesium removal of waste electrolyte of zinc smelting by hydroprocess comprises a waste electrolyte storage tank of zinc smelting by hydroprocess, a cooling tower, a crystallization tank, a circulation tank, a centrifuge, and a crystallization mother liquor transfer tank, wherein the liquid outlet of the waste electrolyte storage tank of zinc smelting by hydroprocess is connected with the liquid inlet of the circulation tank through a first pipeline, the liquid outlet of the circulation tank is connected with the liquid inlet of the cooling tower through a second pipeline, the liquid outlet of the cooling tower is connected with the liquid inlet of the crystallization tank through a third pipeline, the overflow outlet at the top of the crystallization tank is connected with the overflow inlet of the circulation tank through a fourth pipeline, the discharge outlet at the bottom of the crystallization tank is connected with the feed inlet of the centrifuge through a fifth pipeline, a flushing port is provided at the top of the centrifuge, the solid outlet at the bottom of the centrifuge is connected with the crystallization collector through a sixth pipeline, and the liquid outlet at the bottom of the centrifuge is connected with the crystallization mother liquor transfer tank through a seventh pipeline; The specific steps of the method are as follows: (1) transporting the waste electrolyte of zinc smelting in the waste electrolyte storage tank of zinc smelting to the circulation tank through the first pipeline at a preset flow rate, and then transporting it to the cooling tower through the second pipeline at a preset flow rate; (2) utilizing a low-temperature natural environment below -15°C to cool the waste electrolyte of hydrometallurgical zinc smelting in a cooling tower to a temperature of -10 to -5°C, and then flowing by gravity through a third pipeline into a crystallization tank with slow stirring at the same preset flow rate as in step (1) and crystallizing and precipitating in the crystallization tank to form a mixed underflow containing magnesium sulfate crystals at the bottom layer and mother liquor A at the upper layer; (3) The mixed underflow containing magnesium sulfate crystals at the bottom of the crystallization tank is transported to a centrifuge through a fifth pipeline at a preset rate for centrifugal separation to obtain magnesium sulfate crystals and a crystallization mother liquor, and flushing water is added through a flushing port to flush the magnesium sulfate crystals. The flushed magnesium sulfate crystals are collected into a crystallization collector through a sixth pipeline, and the crystallization mother liquor and the flushing liquid are transported to a crystallization mother liquor transfer tank through a seventh pipeline and returned to the hydrometallurgical zinc electrolysis system; (4) the mother liquor A in the upper layer of the crystallization tank overflows into the circulation tank through the fourth pipeline, and the waste electrolyte of zinc smelting in the waste electrolyte storage tank of zinc smelting is added to the mother liquor A in an equal volume through the first pipeline, and mixed evenly to form a circulating mother liquor. The circulating mother liquor replaces the waste electrolyte of zinc smelting in step (1) and is transported to the cooling tower through the second pipeline at a preset flow rate for cooling.

2. The method for removing magnesium by natural crystallization of waste electrolyte from hydrometallurgical zinc smelting according to claim 1, characterized in that: The first pipeline is provided with an electrolyte feeding pump, a first analog valve and a first flow meter; The second pipeline is provided with a circulating liquid feed pump, a second analog valve and a second flow meter; The third pipeline is provided with a first flow valve; A third flow meter is arranged on the fourth pipeline; The fifth pipeline is provided with a third analog valve and a fourth flow meter; The seventh pipeline is provided with a second flow valve and a fifth flow meter.

3. The method for removing magnesium by natural crystallization of waste electrolyte from zinc hydrometallurgy according to claim 1 or 2, characterized in that: The stirring device in the crystallization tank is an axial flow propulsion stirring device, and the stirring speed is 5-50r / min.

4. The method for removing magnesium by natural crystallization of waste electrolyte from hydrozinc smelting according to claim 1, characterized in that: The stirring device in the circulation tank is a radial flow mixing stirring device, and the stirring speed is 100-200r / min.

5. The method for removing magnesium by natural crystallization of waste electrolyte from hydrometallurgical zinc smelting according to claim 1, characterized in that: The centrifuge is a horizontal spiral concentrated acid filtering automatic centrifuge.

6. The method for removing magnesium from waste electrolyte of zinc hydrometallurgy by natural crystallization according to claim 1, characterized in that: The preset flow rate of the solution into the cooling tower is 50~300m 3 / h, the relationship between the preset flow rate of the solution into the cooling tower and the natural ambient temperature of the cooling tower is: V = -10t–100; Where: V is the flow rate, m 3 / h; t is the natural environment temperature, ℃.

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