Lithium solution precooling device suitable for lithium solution concentration device

Abstract

The utility model discloses a lithium solution precooling device suitable for a lithium solution concentration device, which comprises a tube type heat exchanger, the tube pass of the heat exchanger is a hot side stock solution with a lower inlet and an upper outlet, and the shell pass of the heat exchanger is a cold side mother solution with an upper inlet and a lower outlet; the shell pass inlet and the shell pass outlet are respectively communicated with a mother liquor feeding pipeline and a mother liquor discharging pipeline; a tube pass inlet of the heat exchanger is connected with an outlet of a forced circulation pump, an inlet of the forced circulation pump is connected with one end of an external forced circulation pipeline, and the other end of the external forced circulation pipeline is connected with a tube pass outlet of the heat exchanger; the stock solution feeding pipeline flows into the heat exchanger through an external forced circulation pipeline via a forced circulation pump; and the stock solution outlet pipeline is connected out through an external forced circulation pipeline close to the tube pass outlet side of the heat exchanger, and the pre-cooled mother solution enters a downstream OSLO crystallizer from the stock solution outlet pipeline.

Description

Technical Field

[0001] The utility model relates to a lithium solution concentrating device, in particular to a lithium solution precooling device suitable for the lithium solution concentrating device and capable of preventing frequent scaling. Background Art

[0002] Ternary lithium battery is a kind of battery that uses lithium nickel cobalt manganese oxide (LiNi x Co y Mn 1-x-y Lithium-ion batteries with O2 as the positive electrode material and carbon as the negative electrode material are widely used in the field of new energy vehicle power batteries due to their high energy density, high number of cycles, high safety, and no memory characteristics. In recent years, more and more retired waste ternary lithium batteries have been retired. Recycling waste ternary lithium batteries can significantly alleviate the resources of precious metals (nickel, cobalt, lithium, etc.) and reduce the environmental pressure caused by waste lithium batteries. At present, the "wet process" is the mainstream in the recycling of waste ternary lithium batteries. The device uses the "black powder" mainly composed of ternary battery active materials obtained by the upstream waste battery pretreatment device as raw material, and carries out acid leaching, impurity removal, precious metal separation and other processes to recover the precious metals as raw materials for ternary lithium batteries. In the wet process using sulfuric acid plus hydrogen peroxide system as the leaching agent, after acid leaching, impurity removal, nickel, cobalt and manganese precipitation, a lithium solution containing lithium sulfate ~1% and sodium sulfate ~13% will be formed. The lithium solution concentration device is an important part of the ternary lithium battery recycling operation: the temperature is reduced by a refrigeration compressor, most of the sodium sulfate is crystallized, and then the mother liquor with most of the sodium sulfate removed is transported to the MVR evaporator for evaporation and concentration to form a concentrated lithium solution containing lithium sulfate ~10%. The use of this device can greatly improve the lithium precipitation efficiency and the purity of lithium carbonate, recover most of the sodium sulfate (in the form of Glauber's salt) and fresh water, and reduce waste liquid discharge. At present, in lithium solution concentration devices, there is a common phenomenon that the heat exchange efficiency is reduced due to frequent scaling of the lithium solution precooler, and even blockage causes shutdown, which affects the reliability of the lithium solution concentration device. Summary of the invention

[0003] The utility model aims to overcome the deficiencies in the prior art and proposes a lithium solution precooling device suitable for a lithium solution concentration device to prevent frequent scaling. The device increases the heat side flow of the tube by adding an external circulation pump and an external circulation pipeline, which can significantly increase the metal wall temperature of the heat exchange tube to make it higher than the saturation temperature of sodium sulfate in the stock solution, thereby avoiding frequent scaling and greatly improving the reliability of the lithium solution concentration device.

[0004] The utility model provides a lithium solution precooling device suitable for a lithium solution concentrating device, comprising

[0005] A lithium solution precooling device suitable for a lithium solution concentration device comprises a shell-and-tube heat exchanger, adopting countercurrent heat exchange, wherein the tube side of the heat exchanger is hot side raw liquid, which enters from the bottom and exits from the top, and the shell side of the heat exchanger is cold side mother liquid, which enters from the top and exits from the bottom; the shell side inlet and the shell side outlet are respectively connected to the mother liquid feed pipeline and the mother liquid discharge pipeline;

[0006] The tube inlet of the heat exchanger is connected to the outlet of the forced circulation pump, the inlet of the forced circulation pump is connected to one end of an external forced circulation pipeline, and the other end of the external forced circulation pipeline is connected to the tube outlet of the heat exchanger; the raw liquid feed pipeline flows into the heat exchanger through the external forced circulation pipeline via the forced circulation pump; the raw liquid outlet pipeline is connected to the side of the heat exchanger tube outlet near the external forced circulation pipeline, and the pre-cooled mother liquor enters the downstream OSLO crystallizer.

[0007] Furthermore, the heat exchange medium of the heat exchanger is the raw liquid on the hot side in the tube side, and the mother liquid on the cold side in the shell side.

[0008] Furthermore, the tube flow rate of the heat exchanger is obtained by using ASPEN HTFS heat exchange simulation software, that is, the temperature distribution of the metal wall of the heat exchange tube under different tube flow rates is simulated by using ASPEN HTFS heat exchange simulation software, so as to optimize the most suitable tube flow rate.

[0009] Furthermore, through trial calculations, when the external forced circulation pipeline and the forced circulation pump increase the tube flow rate of the heat exchanger to 100,000 kg / hr, the metal tube wall temperature of the heat exchanger is 15.9-24.8°C from top to bottom; when the external forced circulation pipeline and the forced circulation pump increase the tube flow rate of the heat exchanger to 250,000 kg / hr, the metal tube wall temperature changes to 21.5-24.9°C from bottom to top.

[0010] Compared with the prior art, the beneficial effects brought by the technical solution of the utility model are:

[0011] The lithium solution precooling device described in the utility model can significantly increase the metal wall temperature of the heat exchange tube to be higher than the saturation temperature of sodium sulfate in the original solution by adding an external circulation pump and an external circulation pipeline to increase the hot side flow of the tube, thereby avoiding frequent scaling and greatly improving the reliability of the lithium solution concentration device. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a structural schematic diagram of the lithium solution precooling device.

[0013] in,

[0014] 1: Raw liquid feed pipeline; 2: Forced circulation pump; 3: Mother liquid discharge pipeline; 4: Heat exchanger; 5: Mother liquid feed pipeline; 6: Raw liquid discharge pipeline; 7: External forced circulation pipeline. DETAILED DESCRIPTION

[0015] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. The described specific embodiments are only used to explain the present invention and are not intended to limit the present invention.

[0016] Reference will now be made in detail to specific embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Although the present invention will be described in conjunction with specific embodiments, it will be understood that it is not intended to limit the present invention to the embodiments described. On the contrary, it is intended to cover the changes, modifications and equivalents included in the spirit and scope of the present invention as defined by the appended claims. It should be noted that the method steps described herein can all be implemented by any functional block or functional arrangement, and any functional block or functional arrangement can be implemented as a physical entity or a logical entity, or a combination of the two.

[0017] In the lithium solution concentration device, the sodium sulfate and lithium sulfate solution with high content (the process medium stock solution from the wet recovery of ternary lithium batteries, hereinafter referred to as the stock solution) is generally used. After freezing and crystallizing, the mother liquor after removing most of the sodium sulfate is pumped to the evaporator for evaporation and concentration to obtain a lithium-rich concentrated solution, which enters the subsequent lithium precipitation process. In order to make full use of the cold energy from the crystallizer mother liquor, a precooler is usually set up to precool the stock solution by heat exchange with the mother liquor. The typical inlet and outlet temperature values ​​of the precooler are 20 / 40℃ for the tube inlet / outlet temperature and 0 / 20℃ for the shell inlet / outlet temperature. Due to the temperature crossover between the cold side and the hot side, only countercurrent heat exchange can be used. In actual use, the heat exchanger is prone to scaling, resulting in frequent shutdowns for cleaning. This is mainly because the top wall temperature of the top tube of the heat exchanger is too low, lower than the saturation temperature of the stock solution, and crystals are precipitated and accumulated continuously.

[0018] For this purpose, the utility model has developed a lithium solution precooling device suitable for a lithium solution concentration device, such as Figure 1 As shown, it includes a shell-and-tube heat exchanger 4, and the two ends of the heat exchanger 4 respectively include a tube side inlet, a shell side inlet, a tube side outlet and a shell side outlet; the tube side inlet of the heat exchanger 4 is connected to the outlet of the forced circulation pump 2, the inlet of the forced circulation pump 2 is connected to one end of the external forced circulation pipeline 7, and the other end of the external forced circulation pipeline 7 is connected to the tube side outlet of the heat exchanger 4; the raw liquid feed pipeline 1 flows into the heat exchanger 4 through the external forced circulation pipeline 7 and the forced circulation pump 2; the raw liquid outlet pipeline 6 is connected to the tube side outlet side of the heat exchanger 4 through the external forced circulation pipeline 7, and the pre-cooled mother liquor enters the downstream OSLO crystallizer.

[0019] The utility model increases the tube flow rate by adding a forced circulation pump 2 and an external forced circulation pipeline 7 on the tube side, which can effectively increase the tube metal wall temperature to make it higher than the saturation temperature of the original liquid, thereby avoiding the problem of scaling caused by the precipitation of sodium sulfate crystals. Combined with the heat exchanger thermal calculation software ASPEN HTFS, the tube metal wall temperature corresponding to each tube flow rate can be accurately simulated according to actual process conditions, and then the capacity of the forced circulation pump can be determined, thereby optimizing the optimal external forced circulation flow rate.

[0020] The working process of the lithium solution precooling device is as follows:

[0021] The stock solution first enters the tube side of the heat exchanger 4 from the bottom of the heat exchanger 4 through the forced circulation pump 2 from the stock solution feed pipeline 1, and then flows into the external forced circulation pipeline 7 after being discharged from the stock solution outlet at the top of the shell and tube heat exchanger 4. After the heat exchanger 4 and the external forced circulation pipeline 7, it flows into the downstream OSLO crystallizer through the stock solution discharge pipeline 6;

[0022] After the heat exchanger 4 and the external forced circulation pipeline 7 are filled, the forced circulation pump 2 is started;

[0023] The mother liquid enters the shell side inlet at the top of the heat exchanger 4 through the mother liquid feed pipeline 5, and after heat exchange, flows out from the shell side inlet to the mother liquid discharge pipeline 3.

[0024] Conventional lithium solution precoolers have no forced circulation pumps and external forced circulation pipelines. The reasons for frequent scaling and even blockage are analyzed. The material flow data on the cold and hot sides are shown in Table 1. The heat exchanger thermal calculation software ASPEN HTFS is used to simulate the metal tube wall temperature of the shell-and-tube heat exchanger. It is found that the metal tube wall temperature gradually decreases from 21.9°C to 4.7°C from bottom to top. The wall temperature of nearly half of the length of each heat exchange tube is lower than the saturation temperature of sodium sulfate in the original solution by 14°C, causing the sodium sulfate crystals in the tube to accumulate and scale and even block the heat exchange tube.

[0025] Table 1 Typical material flow data of lithium solution precooling device

[0026]

[0027] When the heat exchanger thermal calculation software ASPEN HTFS was used to simulate the relationship between the tube side flow rate and the metal tube wall temperature of the shell-and-tube heat exchanger, it was found that the lithium solution precooling device of the lithium solution concentration device described in the utility model was used to introduce a forced circulation pump 2 and an external forced circulation pipeline 7 on the tube side, which can greatly increase the tube side flow rate. Without changing the feed temperature and flow rate on the cold and hot sides, the metal wall temperature of the heat exchange tube can be effectively increased. When the external forced circulation flow rate is changed to 100,000 kg / hr, the metal tube wall temperature becomes 15.9-24.8°C, and when the external forced circulation flow rate is further increased to 250,000 kg / hr, the metal tube wall temperature becomes 21.5-24.9°C. Using this result, according to the saturation temperature of the hot side solution, a suitable external forced circulation flow rate can be selected to keep the metal wall temperature of the heat exchange tube away from its saturation temperature, thereby avoiding the problem of frequent scaling or even blockage caused by too low metal wall temperature.

[0028] If there is no external forced circulation pipeline 7, when the tube flow rate is 2879 kg / hr, the metal wall temperature of the tube side of the heat exchanger is 4.7-21.9° C. from top to bottom. The metal wall temperature of a considerable part of the heat exchange tube is 14 degrees lower than the saturation temperature of the original sodium sulfate solution.

[0029] Although the preferred embodiments of the present invention have been described above in conjunction with the accompanying drawings, the present invention is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the purpose of the present invention and the claims, all of which belong to the scope of protection of the present invention.

Claims

1. A lithium solution precooling device suitable for a lithium solution concentration device, characterized in that: It comprises a shell-and-tube heat exchanger (4) which adopts countercurrent heat exchange. The tube side of the heat exchanger (4) is hot side raw liquid, which enters from the bottom and exits from the top. The shell side of the heat exchanger (4) is cold side mother liquid, which enters from the top and exits from the bottom. The shell side inlet and the shell side outlet are respectively connected to the mother liquid feed pipeline (5) and the mother liquid discharge pipeline (3). The pipe side inlet of the heat exchanger (4) is connected to the outlet of the forced circulation pump (2), the inlet of the forced circulation pump (2) is connected to one end of an external forced circulation pipeline (7), and the other end of the external forced circulation pipeline (7) is connected to the pipe side outlet of the heat exchanger (4); the raw liquid feed pipeline (1) flows into the heat exchanger (4) through the external forced circulation pipeline (7) and the forced circulation pump (2); the raw liquid outlet pipeline (6) is connected to the pipe side outlet side of the heat exchanger (4) through the external forced circulation pipeline (7), and the pre-cooled mother liquid enters the downstream OSLO crystallizer.

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