Strontium chloride continuous crystallization device

Abstract

This invention discloses a continuous crystallization apparatus for strontium chloride, comprising a flash crystallizer and a cooling crystallizer. The flash crystallizer contains a mixing tube, into which a strontium chloride solution from the evaporation and concentration process enters the mixing tube via a feed pipe, forming a mixture with the strontium chloride mother liquor in the mixing tube. The outlet of the flash crystallizer is connected to the cooling crystallizer via a pipette pump. A cooling water jacket is installed outside the cooling crystallizer, with an inlet at the bottom and an outlet at the top. A stirrer is installed inside the cooling crystallizer, and its bottom opening is connected to a discharge pump, which delivers the crystallized strontium chloride slurry to a subsequent centrifugal separation process. This achieves a continuous crystallization process for the evaporated and concentrated strontium chloride solution.

Description

Technical Field

[0001] This invention relates to the production of strontium chloride, and in particular to a continuous crystallization apparatus for strontium chloride. Background Technology

[0002] In the production of strontium chloride, the strontium chloride solution needs to be evaporated and concentrated, then cooled and crystallized, filtered, and dried to obtain the product. Crystallization tanks are used for strontium chloride solution crystallization, which requires a considerable amount of time for cooling and crystallization. Depending on the production volume, multiple crystallization tanks are needed to meet production requirements. Furthermore, during the cooling process of the crystallization tanks, thick crystals easily form on the heat exchange surfaces, reducing heat transfer efficiency and slowing down the cooling rate. After crystallization, hot water is needed to melt the slag (strontium chloride crystals formed on the heat exchange surfaces), adversely affecting production. Using this continuous crystallizer solves the problems of high equipment investment, high power consumption, and long crystallization cycles caused by using multiple crystallization tanks. It also solves the problem of low heat exchange efficiency caused by slag buildup on the heat exchange surfaces of the crystallization tanks. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention provides a continuous crystallization apparatus for strontium chloride.

[0004] A continuous crystallization apparatus for strontium chloride includes a flash crystallizer and a cooling crystallizer. The flash crystallizer contains a mixing tube. A strontium chloride solution from an evaporation and concentration process enters the mixing tube through a feed pipe, forming a mixture with the strontium chloride mother liquor in the mixing tube. The outlet of the flash crystallizer is connected to the cooling crystallizer via a pipette pump. A cooling water jacket is installed outside the cooling crystallizer, with an inlet at the bottom and an outlet at the top. A stirrer is installed inside the cooling crystallizer. The bottom opening of the cooling crystallizer is connected to a discharge pump, which delivers the crystallized strontium chloride slurry to a subsequent centrifugal separation process.

[0005] Optionally, a V-shaped liquid distributor is formed at the top of the mixing pipe; a mother liquor circulation pump is installed outside the flash crystallizer, one end of which is connected to the flash crystallizer via a pipe, and the other end is connected to the mixing pipe via a pipe; the bottom of the flash crystallizer is conical, and a discharge port is formed at the bottom of the cone; level gauges are respectively provided in the flash crystallizer and the cooling crystallizer.

[0006] Furthermore, the flash crystallization tank includes an outer tank and an inner tank located inside the outer tank. Both the outer tank and the inner tank are under negative pressure. One flash evaporation is completed in the outer tank, and a second flash evaporation is completed in the inner tank. An external mixing pipe is provided inside the outer tank, and an internal mixing pipe is provided inside the inner tank. A conical crystallization zone is formed at the bottom of the inner tank. The internal mixing pipe passes through the crystallization zone and opens into the bottom of the outer tank, communicating with the outer tank. The external mixing pipe opens outside the outer tank and is used to receive strontium chloride solution from the evaporation and concentration process. A first opening and a second opening are opened on the portion of the external mixing pipe located inside the outer tank, with the first opening located above the second opening. A circulation pipe is provided inside the outer tank, and a circulation pump is installed on the circulation pipe. The entire circulation pipe is located within the outer tank. One end of the circulation pipe opens into the inner tank, and the other end is connected to the first opening. The second opening is connected to the internal mixing pipe through a branch pipe.

[0007] The beneficial effects of this invention are as follows: Its most significant feature is the realization of a continuous crystallization process for strontium chloride evaporation and concentration solution. During production, the low supersaturation prevents the tank's heat exchange surface from accumulating residue or grime, saving the need for multiple crystallization tanks, reducing operator workload, recovering some condensate, and conserving water resources. Two flash evaporations can be completed in a single flash tank, significantly increasing the crystallization rate and production efficiency. The entire flash evaporation process still uses a single circulating pump, achieving two flash evaporations with a single pump, resulting in a substantial reduction in energy consumption (approximately 40%). During flash evaporation, the circulating pipes are located inside the outer tank, reducing heat loss. The low supersaturation during both the first and second flash evaporations prevents residue or grime buildup on the tank's heat exchange surface. During crystallization, the crystals are smaller after the first crystallization, and the solution temperature decreases. When the solution mixes with the high-temperature, high-pressure concentrated strontium chloride solution, under external negative pressure, nucleation and crystallization are more likely, leading to increased crystal volume. Attached Figure Description

[0008] Figure 1 This is a structural schematic diagram of Example 1;

[0009] Figure 2 This is a schematic diagram of the structure of Example 2. Detailed Implementation

[0010] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings, so that the above and other objects, features, and advantages of the present invention will become clearer. In all the drawings, the same reference numerals indicate the same parts. The drawings are not intentionally drawn to scale; the focus is on illustrating the main points of the invention.

[0011] Example 1

[0012] See Figure 1 The strontium chloride continuous crystallization apparatus of the present invention includes a flash crystallizer 1 and a cooling crystallizer 2. The flash crystallizer 1 is equipped with a mixing pipe 4, the top of which forms a V-shaped liquid distributor. A mother liquor circulation pump 5 is installed outside the flash crystallizer 1. One end of the mother liquor circulation pump 5 is connected to the flash crystallizer 1 via a pipe, and the other end is connected to the mixing pipe 4 via a pipe. The strontium chloride solution from the evaporation and concentration process enters the mixing pipe 4 through a feed pipe, forming a mixture with the strontium chloride mother liquor in the mixing pipe 4. The bottom of the flash crystallizer 1 is conical, with a discharge port at the bottom. The discharge port is connected to the cooling crystallizer 2 via a pipette pump 3, and the strontium chloride mother liquor at the bottom of the cone is pumped into the cooling crystallizer 2 by the pipette pump 3. A cooling water jacket is installed outside the cooling crystallizer 2, with an inlet at the bottom and an outlet at the top. A stirrer is installed inside the cooling crystallizer 2. The bottom opening of the cooling crystallization tank 2 is connected to the discharge pump 6, which sends the crystallized strontium chloride slurry to the subsequent centrifugal separation process.

[0013] Strontium chloride solution is evaporated and concentrated to a concentration of 45 μmol / L at a temperature of 80°C, denoted as solution A. This solution is pumped into mixing pipe 4 via pump and valve V1, where it mixes with the circulating strontium chloride mother liquor in the inner circulation pipe 4 to form mixed strontium chloride solution B. The temperature and pressure of solution B are higher than those inside flash crystallizer 1 (the tank is under negative pressure). After solution B enters the V-shaped liquid distributor, some of the water in the solution is flash-evaporated, increasing the concentration of the solution due to water evaporation. Simultaneously, the temperature of the solution decreases to the temperature inside flash crystallizer 1 due to the heat absorbed during flash evaporation, thus causing the solution entering flash crystallizer 1 to reach a supersaturated state. Since the amount of solution A added is relatively small compared to the amount of solution B, the resulting supersaturation is low, preventing the formation of a large number of crystal nuclei, which is conducive to the growth of crystal nuclei and crystals. Part of the solution in flash crystallizer 1 enters mixing pipe 4 through pipes, circulation pump 5, and valve, where it mixes with the externally added solution A and enters the V-shaped liquid distributor together, completing one mixing, evaporation, concentration, and crystallization process. A portion of the solution and strontium chloride crystals mixed slurry is transferred from the lower part of flash crystallizer 1 to the upper part of cooling crystallizer 2 via transfer pump 3, control valve V2, and pipeline. Cooling crystallizer 2 is equipped with a chilled water jacket, with chilled water entering from the bottom and exiting from the top to complete the cooling process. An agitator is installed inside the tank to facilitate cooling and heat exchange of the slurry. A paddle agitator is used with two agitators at a speed of 20 rpm. The crystallizing slurry is continuously discharged via discharge pump 6, with the flow rate controlled by valve V3. Through level adjustment, it proceeds to the next process, completing the continuous crystallization process. Steam in flash crystallizer 1 is extracted through a vacuum generated by a secondary steam condenser and vacuum pump, and distilled water is recovered. The pressure inside flash crystallizer 1 is negative.

[0014] The flash crystallizer 1 and the cooling crystallizer 2 are each equipped with a level gauge. The opening of the inlet and outlet valves is controlled by the level signal to automatically adjust the level and the amount of liquid entering and leaving the tank. The temperature of the cooling crystallizer 2 is adjusted by controlling the cooling water outlet valve V4, which is automatically controlled.

[0015] The most significant feature of this invention is that it enables a continuous crystallization process for the strontium chloride evaporation and concentration solution. Due to the low supersaturation during production, the heat exchange surface of the tank does not accumulate residue or grime, saving the need for multiple crystallization tanks, reducing the number of operators, recovering some condensate, and conserving water resources.

[0016] Example 2

[0017] This embodiment focuses on the differences from Embodiment 1, while the similarities will not be repeated.

[0018] Although the flash evaporator in Example 1 reduces the crystallization time compared to the multiple crystallizer scheme, the production efficiency is still low because the amount of strontium chloride solution entering the evaporator each time during continuous crystallization cannot be too large. On the other hand, the circulating pump needs to circulate the mother liquor multiple times to complete the flash evaporation, resulting in high energy consumption. Furthermore, in Example 1, a single-circulation, low-saturation scheme was adopted, resulting in smaller crystal grains.

[0019] In response to the above problems, such as Figure 2 As shown, a dual-cycle flash evaporator is used in this embodiment, and dual-cycle flash crystallization can be completed using only one flash evaporator.

[0020] The flash crystallization tank 1 includes an outer tank 1.1 and an inner tank 1.11 located inside the outer tank 1.1. Both the outer tank 1.1 and the inner tank 1.11 are under negative pressure, with the negative pressure in the outer tank 1.1 being greater than that in the inner tank 1.11. An external mixing pipe 1.3 is installed inside the outer tank 1.11, and an internal mixing pipe 1.10 is installed inside the inner tank.

[0021] A conical crystallization zone 1.9 is formed at the bottom of the inner tank 1.11. An inner mixing pipe 1.10 passes through the crystallization zone 1.9 and opens to the bottom of the outer tank 1.1, communicating with the outer tank 1.1. An outer mixing pipe 1.3 opens outside the outer tank 1.1 and is used to receive the strontium chloride solution from the evaporation and concentration process. A first opening 1.4 and a second opening 1.5 are formed on the portion of the outer mixing pipe 1.3 located inside the outer tank 1.1. The first opening 1.4 is above the second opening 1.5, meaning the height of the first opening 1.4 is greater than that of the second opening 1.5.

[0022] A circulation pipe 1.2 is installed inside the outer tank 1.1, and a circulation pump is installed on the circulation pipe 1.2. The entire circulation pipe 1.2 is located inside the outer tank 1.1. One end of the circulation pipe 1.2 opens into the inner tank 1.11, and the other end is connected to the first opening 1.4. The second opening 1.5 is connected to the inner mixing pipe 1.10 through the branch pipe 1.6.

[0023] During production, the strontium chloride solution from the concentration process enters the outer mixing pipe 1.3, and a portion of the strontium chloride solution enters the inner mixing pipe 1.10 through the branch pipe 1.6. The strontium chloride solution entering the outer mixing pipe 1.3 has a higher temperature and pressure. The circulation pump installed on the circulation pipe 1.2 draws the mother liquor from the inner tank 1.11. The mother liquor and the newly entered strontium chloride solution are mixed in the mixing pipe 1.3 and sprayed out through the distribution plate. Due to the negative pressure state of the outer tank 1.1, a flash evaporation is completed, and the steam is discharged from the exhaust port 1.13 of the outer tank.

[0024] After the first flash evaporation, the solution enters the inner mixing pipe 1.10 from the bottom of the outer tank 1.11. In the inner mixing pipe 1.10, it mixes with the strontium chloride solution from the branch pipe 1.6 and is then sprayed out through the distribution plate. Because the negative pressure in the outer tank 1.1 is greater than that in the inner tank 1.11, a second flash evaporation is completed, and the steam is discharged from the outlet 1.12. The solution after the second flash evaporation re-enters the outer mixing pipe 1.3 through the circulation pipe 1.2 for another flash evaporation, and this cycle repeats. The crystallization slurry in the conical crystallization zone 1.9 is sent to the subsequent cooling crystallization tank through the discharge port 1.8 located at the bottom of the cone.

[0025] The flash tank in this embodiment can complete two flash evaporations with a single tank, greatly improving the crystallization rate and production efficiency. The entire flash evaporation process still uses a single circulation pump, achieving two flash evaporations with one pump, significantly reducing energy consumption (by about 40%). During the flash evaporation process, the circulation pipes 1.2 are all located inside the outer tank 1.1, reducing heat loss. The supersaturation is relatively small during both the first and second flash evaporations, preventing the tank's heat exchange surface from caking. During the crystallization process, the crystals are smaller after the first crystallization, and the solution temperature drops. After the solution mixes with the high-temperature and high-pressure concentrated strontium chloride solution, it is easier to nucleate and crystallize under external negative pressure, resulting in larger crystal volumes.

[0026] Many specific details have been set forth in the foregoing description to provide a thorough understanding of the present invention. However, the above description is merely a preferred embodiment of the present invention, and the present invention can be implemented in many other ways different from those described herein. Therefore, the present invention is not limited to the specific embodiments disclosed above. Furthermore, any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention, or modify them into equivalent embodiments, using the methods and techniques disclosed above, without departing from the scope of the present invention. Any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention, without departing from the content of the present invention, shall still fall within the protection scope of the present invention.

Claims

1. A continuous crystallization apparatus for strontium chloride, characterized in that, The system includes a flash crystallizer and a cooling crystallizer. The flash crystallizer contains a mixing tube into which a strontium chloride solution from the evaporation and concentration process enters the mixing tube via a feed pipe, forming a mixture with the strontium chloride mother liquor in the mixing tube. The outlet of the flash crystallizer is connected to the cooling crystallizer via a pipette pump. The cooling crystallizer is equipped with a cooling water jacket, with an inlet at the bottom and an outlet at the top. A stirrer is installed inside the cooling crystallizer, and its bottom opening is connected to a discharge pump, which delivers the crystallized strontium chloride slurry to a subsequent centrifugal separation process. Level gauges are installed in both the flash crystallizer and the cooling crystallizer. The flash crystallizer includes an outer tank and an inner tank located inside the outer tank. Both the outer and inner tanks are under negative pressure. A first flash evaporation is completed in the outer tank, and a second flash evaporation is completed in the inner tank. An external mixing pipe is provided inside the outer tank, and an internal mixing pipe is provided inside the inner tank; a conical crystallization zone is formed at the bottom of the inner tank, and the internal mixing pipe passes through the crystallization zone and opens at the bottom of the outer tank, communicating with the outer tank; the external mixing pipe opens outside the outer tank, and the external mixing pipe is used to receive strontium chloride solution from the evaporation and concentration process; a first opening and a second opening are opened on the portion of the external mixing pipe located inside the outer tank, and the first opening is located above the second opening; A circulation pipe is provided inside the outer tank, and a circulation pump is installed on the circulation pipe. The entire circulation pipe is located in the outer tank. One end of the circulation pipe opens into the inner tank, and the other end is connected to the first opening. The second opening is connected to the inner mixing pipe through a branch pipe.

2. The strontium chloride continuous crystallization apparatus according to claim 1, characterized in that, A V-shaped liquid distributor is formed at the top of the mixing tube.

3. The strontium chloride continuous crystallization apparatus according to claim 1, characterized in that, A mother liquor circulation pump is installed outside the flash crystallizer. One end of the mother liquor circulation pump is connected to the inside of the flash crystallizer through a pipe, and the other end is connected to the mixing pipe through a pipe.

4. The strontium chloride continuous crystallization apparatus according to claim 1, characterized in that, The bottom of the flash crystallizer is conical, with a discharge port formed at the bottom of the cone.

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