A repeatable freeze-crystallization system

Abstract

This utility model discloses a repeated freeze-crystallization system, belonging to the field of titanium dioxide production technology. It consists of a crystallization tank, a separation chamber, and a freezing chamber, with the crystallization tank connected to the separation chamber, and the separation chamber connected to the freezing chamber. The crystallization tank includes a tank cover and a tank body from top to bottom. A solid-liquid outlet is provided at the bottom of the tank body, and a valve is installed at the solid-liquid outlet. An insulation layer is provided on the outside of the tank body, and an annular pipe is installed inside the insulation layer. Baffles are installed at equal intervals in the vertical direction on the inner wall of the tank. All components work together to achieve efficient freeze-crystallization. The crystallization tank adopts an inverted frustum-shaped main body, equipped with a detachable tank cover, baffles, and a stirring device to promote uniform mixing of materials, reduce residue, and accelerate discharge. The insulation layer and the freezing chamber form a closed loop, and a temperature detector precisely controls the temperature. The separation chamber achieves efficient solid-liquid separation through multi-stage gradient screen partitions. A liquid level monitor and linked valves maintain a stable separation environment, and a circulation port allows for material reuse. The modular design of the system enhances adaptability, allows for flexible parameter adjustment, significantly improves crystallization efficiency, product quality, and raw material utilization, combining high efficiency and practicality.

Description

Technical Field

[0001] This utility model relates to the field of titanium dioxide production technology, specifically to a repeated freeze-crystallization system. Background Technology

[0002] In the production of titanium dioxide, the sulfuric acid process is one of the most widely used traditional processes. This process involves reacting ilmenite or rutile with concentrated sulfuric acid to produce molten titanium. Besides the compounds containing the target product, titanium, the molten titanium also contains a large amount of ferrous sulfate. To obtain high-purity titanium dioxide, ferrous sulfate needs to be separated from the molten titanium, and freeze crystallization is one of the key steps in achieving this separation. Currently, the main methods for crystallizing ferrous sulfate in molten titanium are natural cooling crystallization and freeze crystallization. Natural cooling crystallization relies on the slow decrease in ambient temperature to promote the crystallization of ferrous sulfate, but this method is greatly affected by the environment and has extremely low efficiency, making it difficult to meet the needs of industrial production. Freeze crystallization, on the other hand, uses a device that artificially creates a low-temperature environment to accelerate the crystallization process. An ice-water bath is used in this low-temperature environment to freeze and crystallize ferrous sulfate from the molten titanium.

[0003] CN222400303U discloses a ferrous crystallization freezing pot for titanium dioxide production, relating to the technical field of titanium dioxide production equipment. It includes a heat exchange pot, a crystallization pot, a cooling coil, an inlet pipe, an outlet pipe, a stirrer, and a stirring motor. The crystallization pot is installed inside the heat exchange pot, with a cooling chamber between them. The cooling coil is installed inside the cooling chamber. One end of the inlet pipe and the outlet pipe are fixed inside the cooling chamber, and the other end is connected to a pump. The stirring motor is installed on top of the crystallization pot, and the stirrer is located inside the crystallization pot and connected to the power output end of the stirring motor.

[0004] CN109850954A discloses a ferrous sulfate crystallization apparatus for titanium dioxide production using the sulfuric acid process. The apparatus includes a crystallization tank, a first elevated tank connected to the top of the crystallization tank, inlet and outlet ports at the bottom of the crystallization tank, a side stirring device at the lower part of the crystallization tank, a vacuum ejector connected to the upper part of the crystallization tank, a second elevated tank connected to the top of the vacuum ejector, and an acid circulation tank connected to the bottom of the vacuum ejector via an acid pump and a heat exchanger. The acid circulation tank has an acid replenishment port, and a cooling circulation system is connected to the heat exchanger. An acid discharge port is located between the heat exchanger and the top of the vacuum ejector. This apparatus utilizes the gravity of the material combined with the hygroscopic and low saturated vapor pressure properties of concentrated sulfuric acid to create a vacuum environment, achieving ferrous sulfate crystallization without the need for steam, thus separating it from the titanium liquid.

[0005] However, this existing device has several disadvantages. First, the freezing efficiency is low; heat exchange between the ice-water bath and the titanium liquid relies solely on natural convection and heat conduction, resulting in a slow heat transfer rate and a sluggish cooling process for the titanium liquid. Second, the crystal precipitation time is long; due to insufficient heat transfer efficiency, ferrous sulfate molecules require a considerable amount of time to reach a supersaturated state and form crystal nuclei to complete the crystallization process, significantly impacting experimental and production progress. Third, complete precipitation is difficult to achieve; some ferrous sulfate fails to crystallize due to insufficient temperature reduction or uneven heat transfer, resulting in resource waste. Furthermore, residual ferrous sulfate can affect the purity and quality of subsequent titanium dioxide products.

[0006] In summary, the low heat transfer efficiency, poor freezing efficiency, long crystallization time, and difficulty in complete precipitation of ferrous sulfate in traditional ferrous sulfate crystallization devices remain problems that urgently need to be solved. Utility Model Content

[0007] To address the above problems, this invention provides a repeated freeze-crystallization system. By setting up a freezer chamber outside a conventional crystallization tank, the titanium liquid is circulated and cooled for crystallization, which improves the crystallization rate of ferrous sulfate and increases the purity and titanium-iron ratio of the titanium compound in the titanium liquid.

[0008] This utility model provides a repeated freeze-crystallization system, including a crystallization tank, a separation chamber, and a freezing chamber, wherein the crystallization tank is connected to the separation chamber, and the separation chamber is connected to the freezing chamber; The crystallization tank comprises, from top to bottom, a crystallization tank cover and a tank body; The bottom of the tank is provided with a solid-liquid outlet, and a valve is provided at the solid-liquid outlet; The tank body is provided with an insulation layer on the outside, and the insulation layer is filled with an annular pipe; The inner wall of the tank is equipped with baffles at equal intervals in the vertical direction; A stirring device is vertically installed inside the crystallization tank, and the stirring device extends into the tank body from the crystallization tank cover. The separation chamber is equipped with partitions, and the number of partitions is ≥2.

[0009] Furthermore, the tank body is in the shape of an inverted frustum.

[0010] Furthermore, the crystallization tank lid is a detachable structure.

[0011] Furthermore, the crystallization tank cover and the tank body are separate structures, connected by flanges, bolts and gaskets to form the detachable structure.

[0012] Furthermore, the spoiler is a detachable structure.

[0013] Furthermore, the spoiler is fixed to the inner wall of the tank by bolts, forming the detachable structure.

[0014] Furthermore, the crystallizer cover is also equipped with a feed inlet and a temperature detector, the temperature detector being used to monitor the temperature inside the crystallizer in real time.

[0015] Furthermore, the annular tube is provided with an inlet and an outlet.

[0016] Furthermore, the spoiler is bolted to the inner wall of the tank, and the spoiler is located at 1 / 3 of the height of the tank.

[0017] Furthermore, a stirring controller is provided above the stirring device, and the stirring controller is located on the outside of the crystallization tank cover.

[0018] Furthermore, a stirring paddle is provided below the stirring device, and the stirring paddle is located inside the tank, at 1 / 4 of the height of the tank.

[0019] Furthermore, the stirring device is coaxially mounted with the crystallization tank cover, and the crystallization tank cover is coaxially mounted with the tank body.

[0020] Furthermore, the separation chamber is provided with a feed inlet, a discharge outlet, and a circulation outlet.

[0021] Furthermore, the feed inlet of the separation chamber is connected to the solid-liquid outlet of the crystallizer via a pipeline.

[0022] Furthermore, the circulation port of the separation chamber is connected to the feed port on the cover of the crystallizer, and the material is recovered from the discharge port of the separation chamber after solid-liquid separation in the separation chamber.

[0023] Furthermore, the partition is a screen structure.

[0024] Furthermore, when the number of partitions is ≥2, the mesh size of the partition screen is increased step by step, with an increase level of 50 mesh.

[0025] Furthermore, the partition is a detachable structure.

[0026] Furthermore, positioning grooves are provided on the left and right sides of the inner wall of the separation chamber, and the partition is inserted parallel to the positioning grooves to form the detachable structure.

[0027] Furthermore, a liquid level monitor is installed on the outside of the separation chamber.

[0028] Furthermore, the liquid level monitor is connected to the valve.

[0029] Furthermore, when the liquid level in the separation chamber is higher than the upper limit, the valve is closed; when the liquid level in the separation chamber is lower than the lower limit, the valve is opened, and the opening size of the valve is adjusted according to the liquid level.

[0030] Furthermore, the freezer compartment is provided with a water outlet and a water inlet.

[0031] Furthermore, the water inlet of the freezer chamber is connected to the water outlet of the annular pipe, and the water outlet of the freezer chamber is connected to the water inlet of the annular pipe.

[0032] Furthermore, after the repeated freeze-crystallization system separates the titanium solution (mother liquor) containing ferrous sulfate, the titanium-iron ratio of the mother liquor is 0.3-0.37.

[0033] The beneficial effects of this utility model are: This invention utilizes a crystallization tank, a separation chamber, and a freezing chamber to repeatedly crystallize the mother liquor. The crystallization tank features an inverted frustum-shaped body with a solid-liquid outlet at the bottom, reducing material residue and accelerating discharge by gravity, thus improving material utilization and eliminating the need for pumping. The detachable tank cover facilitates the inspection and cleaning of internal components. The combination of a baffle plate and a stirring device forms a highly efficient mixing system. The specific placement of the baffle plate and stirring device breaks the laminar flow of the material, creating strong convection in the mother liquor. Together, they promote uniform solute distribution, preventing local oversaturation and significantly improving crystallization uniformity and crystallization rate. Simultaneously, the annular pipe of the outer insulation layer of the crystallization tank and the freezing chamber form a closed-loop circulation, enabling precise temperature control within the tank and providing a stable low-temperature environment for crystallization. Real-time monitoring by a temperature detector further ensures the consistency of crystallization conditions. In addition, the separated solid-liquid mixture is gradient separated by multiple removable baffles in the separation chamber, which can efficiently retain crystal particles of different sizes, reduce liquid phase entrainment loss, and improve product recovery rate. The use of a liquid level monitor can maintain the stability of the liquid level in the separation chamber and ensure separation efficiency. Through the coordinated design of various components, the freezing crystallization efficiency and product quality are significantly improved, while enhancing operational flexibility and system stability. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the structure of the repeated freeze-crystallization system described in this utility model; The labels in the diagram are as follows: 1. Crystallization tank; 2. Separation chamber; 3. Freezing chamber; 4. Crystallization tank cover; 5. Tank body; 6. Solid-liquid outlet; 7. Insulation layer; 8. Baffle plate; 9. Stirring device; 10. Stirring controller; 11. Baffle; 12. Liquid level monitor. Detailed Implementation

[0035] The utility model will be described in detail below with reference to the embodiments: This invention provides a repeated freezing and crystallization system, which efficiently crystallizes the mother liquor by setting up a crystallization tank, a separation chamber and a freezing chamber, and greatly improves the titanium-iron ratio of the mother liquor.

[0036] Example 1 This embodiment provides a repeatable freeze-crystallization system, including a crystallization tank 1, a separation chamber 2, and a freezing chamber 3. The crystallization tank 1 is connected to the separation chamber 2, and the separation chamber 2 is connected to the freezing chamber 3. The crystallization tank 1 comprises, from top to bottom, a crystallization tank cover 4 and a tank body 5; The bottom of the tank body 5 is provided with a solid-liquid outlet 6, and a valve is provided at the solid-liquid outlet 6; The outer side of the tank body 5 is provided with a heat insulation layer 7, and the heat insulation layer 7 is filled with an annular pipe; The inner wall of the tank 5 is equipped with baffles 8 at equal intervals in the vertical direction; A stirring device 9 is vertically installed inside the crystallization tank 1, and the stirring device 9 extends from the crystallization tank cover 4 into the tank body 5. The separation chamber 2 is equipped with partitions 11, and the number of partitions 11 is ≥2.

[0037] In this embodiment, the truncated cone shape of the tank 5 allows the material to flow out of the tank 5 by its own gravity, reducing the amount of material remaining in the tank 5.

[0038] In this embodiment, the tank body 5 is in the shape of an inverted frustum cone, and the crystallization tank cover 4 is a detachable structure. The crystallization tank cover 4 and the tank body 5 are separate structures, connected by flanges, bolts and gaskets to form the detachable structure. The baffle 8 is a detachable structure, fixed to the inner wall of the tank body 5 by bolts to form the detachable structure. The detachable structure of the crystallization tank cover 4 and the baffle 8 facilitates the installation, maintenance and cleaning of the crystallization tank 1, the stirring device 9 and the baffle 8.

[0039] The crystallizer cover 4 is also equipped with a feed inlet and a temperature detector, which is used to monitor the temperature inside the crystallizer 1 in real time.

[0040] The annular tube is equipped with an inlet and an outlet. The structure of the annular tube allows the heat-insulating medium to be evenly surrounded on the outside of the tank 5, forming a stable temperature field, reducing temperature fluctuations inside the tank, and providing a constant low-temperature environment for the crystallization process, which is beneficial to improving the crystallization rate and the purity of the crystallized product.

[0041] The baffle plate 8 is bolted to the inner wall of the tank 5. The baffle plate 8 is located at 1 / 3 of the height of the tank 5. The baffle plate 8 can change the flow path of the material in the crystallization tank 1, so that the material can have more full contact with the stirring device 9, enhance the stirring effect, and thus improve the uniformity and crystallization rate of crystallization.

[0042] A stirring controller 10 is provided above the stirring device 9, and the stirring controller 10 is located outside the crystallization tank cover 4.

[0043] A stirring paddle is provided below the stirring device 9. The stirring paddle is located inside the tank 5, at 1 / 4 of the height of the tank 5.

[0044] The stirring device 9 is coaxially mounted with the crystallization tank cover 4, and the crystallization tank cover 4 is coaxially mounted with the tank body 5.

[0045] The separation chamber 2 is equipped with a feed inlet, a discharge outlet, and a circulation outlet.

[0046] The feed inlet of the separation chamber 2 is connected to the solid-liquid outlet 6 of the crystallization tank 1 via a pipeline.

[0047] The circulation port of the separation chamber 2 is connected to the inlet on the cover of the crystallizer 4. After solid-liquid separation in the separation chamber 2, the material is recovered from the outlet of the separation chamber 2.

[0048] The partition 11 is a screen structure; The number of partitions 11 is 3, and the mesh size of the partitions 11 increases step by step, with an increase of 50 mesh. The mesh structure of the partitions 11 realizes solid-liquid separation, and the design of increasing mesh size by 50 meshes step by step can classify and screen crystalline particles of different sizes, thereby improving the separation accuracy. The partition 11 is a detachable structure. Positioning grooves are provided on the left and right sides of the inner wall of the separation chamber 2. The partition 11 is inserted into the positioning grooves in parallel to form the detachable structure.

[0049] A liquid level monitor 12 is installed on the outside of the separation chamber 2; The liquid level monitor 12 is connected to the valve. When the liquid level in the separation chamber 2 is higher than the upper limit, the valve is closed; when the liquid level in the separation chamber 2 is lower than the lower limit, the valve is opened. At the same time, the opening size of the valve is adjusted according to the liquid level. The liquid level monitor 12 can accurately control the amount and speed of material conveyed from the crystallizer 1 to the separation chamber 2. It works in conjunction with the liquid level monitor 12 in the separation chamber 2 to achieve linkage control, preventing the separation chamber 2 from overflowing due to excessive feeding or affecting the separation efficiency due to insufficient feeding, and ensuring the stable operation of the system.

[0050] The freezer compartment 3 is provided with a water outlet and a water inlet. The water inlet of the freezer compartment 3 is connected to the water outlet of the annular pipe, and the water outlet of the freezer compartment 3 is connected to the water inlet of the annular pipe.

[0051] This embodiment also provides a crystallization method for the aforementioned repeated freeze-crystallization system, comprising the following steps: Open the freezer compartment 3, and cooling circulating water is supplied through the outlet of the freezer compartment 3 into the inlet of the annular pipe in the insulation layer 7 located on the outside of the crystallizer 1, and then returns to the inlet of the freezer compartment 3 through the outlet of the annular pipe, thus achieving circulation. When the temperature detector on the crystallizer cover 4 shows that the temperature inside the tank is 0°C, The mother liquor is introduced through the inlet on the crystallization tank cover 4 of the crystallization tank 1. At the same time, the stirring controller 10 above the stirring device 9 is turned on to control the stirring paddle to stir the mother liquor. The mother liquor crystallizes rapidly under the action of the stirring paddle and the baffle 8. After 10 minutes, the valve at the solid-liquid outlet 6 of the crystallization tank 1 is opened. The mother liquor flows into the inlet of the separation chamber 2 according to its own gravity. It flows through the baffle 11 to separate the solid crystals and titanium liquid. The titanium liquid filtered by the baffle 11 returns to the inlet on the crystallization tank cover 4 of the crystallization tank 1 through the circulation port of the separation chamber 2. After circulating 3 times, it is recovered from the outlet of the separation chamber 2. During the circulation process, the liquid level of the separation chamber 2 is monitored by the liquid level monitor 12. The crystals on the partition 11 are recycled after the partition 11 is disassembled. The number of partitions 11 is 3, with mesh sizes of 30, 80, and 130 mesh respectively.

[0052] In this embodiment, after the repeated freeze-crystallization system separates the titanium solution (mother liquor) containing ferrous sulfate, the titanium-iron ratio of the mother liquor is 0.37.

[0053] As can be seen from the above, the repetitive freezing and crystallization system described in this utility model has a wide range of applications, low cost, and a very high market prospect.

[0054] The above description is merely a preferred embodiment of the present utility model and is not intended to limit the present utility model in any other way. Any modifications or equivalent changes made based on the technical essence of the present utility model shall still fall within the scope of protection claimed by the present utility model.

Claims

1. A repetitive freeze crystallization system characterized by, It includes a crystallization tank (1), a separation chamber (2) and a freezing chamber (3), wherein the crystallization tank (1) is connected to the separation chamber (2) and the separation chamber (2) is connected to the freezing chamber (3); The crystallization tank (1) includes a crystallization tank cover (4) and a tank body (5) from top to bottom; The bottom of the tank (5) is provided with a solid-liquid outlet (6), and a valve is provided at the solid-liquid outlet (6); The tank body (5) is provided with an insulation layer (7) on the outside, and the insulation layer (7) is filled with an annular pipe; The inner wall of the tank (5) is equipped with baffles (8) at equal intervals in the vertical direction. A stirring device (9) is vertically installed inside the crystallization tank (1), and the stirring device (9) extends into the tank body (5) from the crystallization tank cover (4); The separation chamber (2) is equipped with partitions (11), and the number of partitions (11) is ≥2.

2. The repetitive freeze crystallization system of claim 1, wherein, The crystallizer cover (4) is also provided with a feed inlet and a temperature detector, which is used to monitor the temperature inside the crystallizer (1) in real time.

3. The repetitive freeze - crystallization system of claim 1, wherein, A stirring controller (10) is provided above the stirring device (9), and the stirring controller (10) is located outside the crystallizer cover (4).

4. The repetitive freeze - crystallization system of claim 1, wherein, The stirring device (9) is coaxially installed with the crystallization tank cover (4), and the crystallization tank cover (4) is coaxially installed with the tank body (5).

5. The repetitive freeze - crystallization system of claim 1, wherein, The separation chamber (2) is equipped with a feed inlet, a discharge outlet and a circulation outlet.

6. The repetitive freeze - crystallization system of claim 1, wherein, The circulation port of the separation chamber (2) is connected to the inlet on the cover (4) of the crystallizer. After solid-liquid separation in the separation chamber (2), the material is recycled from the outlet of the separation chamber (2).

7. The repetitive freeze crystallization system of claim 1, wherein, The partition (11) is a detachable structure.

8. The repetitive freeze - crystallization system of claim 1, wherein, A liquid level monitor (12) is installed on the outside of the separation chamber (2).

9. The repeated freeze-crystallization system according to claim 8, characterized in that, The level monitor (12) is connected to the valve.

10. The repetitive freeze - crystallization system of claim 1, wherein, The freezer compartment (3) is equipped with a water outlet and a water inlet.

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