System and process for continuously crystallizing nickel sulfate in high-acid environment

Abstract

The invention relates to a continuous crystallization system for nickel sulfate in a high-acid environment. The continuous crystallization system comprises a condenser, a crystallizer, a thickener and a mother liquor tank, a layer of partition plate is arranged in the middle of the condenser; a liquid inlet is formed in the top of the right condenser of the partition plate, and a liquid outlet I is formed in the top of the left condenser; the liquid inlet is connected with a liquid outlet II of the crystallizer; a central circulating pipe is arranged in the crystallizer, the bottom of the central circulating pipe is open, and the top of the central circulating pipe is communicated with a feeding hole of the crystallizer; the bottom of the crystallizer is provided with a hydrometer, the lower part of one side is provided with a high-low liquid outlet, and the upper part is provided with a clear liquid outlet I; the high and low liquid outlets are connected with the thickener; a speed reduction stirrer is arranged in the thickener, and a clear liquid outlet II is formed in one side of the thickener; the bottom of the thickener is connected with the solid-liquid separation system; and the solid-liquid separation system is connected with the mother liquor tank. Meanwhile, the invention also discloses a continuous crystallization process adopting the system. According to the invention, not only is efficient and stable continuous production realized, but also the yield and quality of nickel sulfate are remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrometallurgy of non-ferrous metals, and particularly to a continuous crystallization system and process of nickel sulfate in a high-acid environment. Background Art

[0002] Nickel sulfate is an important chemical raw material and metal material, which is widely used in fields such as electroplating, battery manufacturing, and catalysts. Traditional methods for producing nickel sulfate mainly include two categories: hydrometallurgy and pyrometallurgy. Among them, the hydrometallurgy method extracts nickel from nickel-containing ores or wastes through steps such as leaching, extraction, and precipitation, and then generates nickel sulfate through chemical reactions. However, the traditional hydrometallurgy process has the following problems: (1) Low production efficiency: The traditional hydrometallurgy process mostly adopts batch operation, with a long production cycle, low output, and it is difficult to meet the needs of large-scale industrial production; (2) High energy consumption: Batch operation requires frequent heating and cooling, resulting in a large amount of energy waste. At the same time, the start-up and shutdown processes of equipment also consume additional energy; (3) Unstable product quality: During the batch operation process, the operating conditions of each batch may be different, resulting in large fluctuations in product quality and it is difficult to ensure the consistency of the quality and performance of each batch of products.

[0003] CN112807734A discloses a crystallization system and crystallization method for continuously producing nickel sulfate, which includes a crystallizer, a fine crystal eliminator, a feed pump, a heat exchanger, a discharge pump, a thickener, and a centrifuge, and can ensure that the nickel sulfate solution everywhere in the crystallizer forms a uniform supersaturation, so as to realize the preparation of nickel sulfate products with a uniform particle size distribution and a particle size of more than 800 μm. However, it is only applicable to the traditional nickel sulfate crystallization process and is not suitable for the continuous crystallization process of nickel sulfate in a high-acid environment. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a high-efficiency and low-cost continuous crystallization system of nickel sulfate in a high-acid environment.

[0005] Another technical problem to be solved by the present invention is to provide a continuous crystallization process of nickel sulfate in a high-acid environment.

[0006] To solve the above problems, a continuous nickel sulfate crystallization system in a high-acid environment according to the present invention includes a condenser, a crystallizer, a thickener, and a mother liquor tank, and is characterized in that: a partition is provided in the middle of the condenser; a liquid inlet is provided at the top of the right side of the partition of the condenser, and a liquid outlet I is provided at the top of the left side of the condenser; the liquid inlet is connected to the liquid outlet II of the crystallizer through a circulation pump via a circulation pipe; a central circulation pipe is provided in the crystallizer, the bottom of the central circulation pipe is open, and the top is communicated with the feed inlet of the crystallizer; the liquid outlet I is connected to the feed inlet through pipeline I; a hydrometer is provided at the bottom of the crystallizer, a high and low liquid outlet is provided at the lower part of one side, and a clear liquid outlet I is provided at the upper part; the high and low liquid outlet is connected to the thickener through a transfer pump via pipeline II; the clear liquid outlet I is connected to the mother liquor tank through pipeline III; a slow-speed stirrer is provided inside the thickener, and a clear liquid outlet II is provided at one side, and the clear liquid outlet II is connected to the mother liquor tank through pipeline IV; a discharge port is provided at the bottom of the thickener, and the discharge port is connected to a solid-liquid separation system through pipeline V; the solid-liquid separation system is connected to the mother liquor tank through pipeline VI; one side of the mother liquor tank is communicated with the feed inlet through a mother liquor pump via pipeline VII.

[0007] The material of the crystallizer is 304 + Inco825 composite material, and its bottom is in an inward concave spherical structure.

[0008] The material of the thickener is PTFE material.

[0009] A stirring device is provided in the mother liquor tank.

[0010] The bottom opening of the central circulation pipe is in a flared shape.

[0011] A continuous nickel sulfate crystallization process using the above system in a high-acid environment includes the following steps: ⑴ In the mother liquor tank, mix the nickel-containing solution and concentrated sulfuric acid according to a volume ratio of 40:1 to 50:1, and adjust the hydrogen ion concentration and nickel ion concentration in the solution to obtain a nickel sulfate solution with a hydrogen ion concentration of 1.2 to 2.0 g / L and a nickel ion concentration of 160 to 240 g / L; ⑵ The nickel sulfate solution is directly transported into the central circulation pipe of the crystallizer through a mother liquor pump and enters the self-circulation pipeline of the crystallizer; the crystals in the crystallizer settle at the lower part, and the generated clear liquid enters the condenser through the circulation pipe driven by the circulation pump. During the liquid inlet process, the crystallizer operates in an overflow state; the clear liquid circulates and exchanges heat between the crystallizer and the condenser to obtain a supersaturated solution; at the same time, the clear liquid at a high level enters the mother liquor tank through the clear liquid outlet I; ⑶ The supersaturated solution is sent back into the crystallizer. During the process of the supersaturated solution passing through the crystal bed from bottom to top, the supersaturation is gradually eliminated, and the crystals gradually grow. While maintaining the temperature in the crystallizer stable at the crystallization target temperature, the produced crystal slurry is transferred to the thickener by a transfer pump through the high and low liquid outlets. ⑷ Under the action of the decelerating stirrer, the thickened material is slowly discharged into the solid-liquid separation system, and the produced supernatant enters the mother liquor tank through the supernatant outlet II. ⑸ After the thickened material is separated by the solid-liquid separation system, the solid is discharged, and the liquid enters the mother liquor tank.

[0012] The components of the nickel-containing solution: Ni ≥ 180 g / L, Fe ≤ 5.0 ppm, H + = 1.5 - 2.0 g / L.

[0013] The crystallization target temperature is 32 - 38 °C.

[0014] The present invention has the following advantages compared with the prior art: 1. In the present invention, a partition is provided in the middle of the condenser, which allows the solution to enter at the top right of the partition and exit at the top left, thus completing the process of cooling and temperature reduction.

[0015] 2. In the present invention, a central circulation pipe with a flared bottom opening is provided, which slows down the flow rate and is beneficial to the growth of crystals; at the same time, through the solution perturbation, the collision frequency of the crystals is increased, and the uniformity of the crystal appearance is better.

[0016] 3. The process of the present invention is simple and cost-saving. It not only realizes efficient and stable continuous production, but also significantly improves the output and quality of nickel sulfate.

[0017] ⑴ Improvement in production efficiency: After adopting the process of the present invention, the output of nickel sulfate has increased by about 20%, and the production cycle has been shortened by 30%.

[0018] ⑵ Reduction in energy consumption: Compared with the traditional batch process, the energy consumption of the present invention has been reduced by about 15%, especially in the cooling and heating links.

[0019] ⑶ Stable product quality: The proportion of the uniform particle size distribution (20 - 40 mesh) of the product reaches more than 95%, and the crystal particle size is controlled above 800 μm.

[0020] ⑷ Cost reduction: The equipment maintenance cost has been reduced by about 10%, the manual operation intensity has been significantly reduced, and the overall production cost has been reduced by about 15%. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The following further details the specific embodiments of the present invention in conjunction with the drawings.

[0022] Figure 1This is the flow chart of the present invention.

[0023] Among them: 1 - condenser; 2 - partition board; 3 - circulation pipe; 4 - crystallizer; 5 - feed inlet; 6 - central circulation pipe; 7 - concave spherical structure; 8 - hydrometer; 9 - high and low liquid outlets; 10 - thickener; 11 - speed reduction stirrer; 12 - mother liquor tank; 13 - discharge port; 14 - circulation pump; 15 - transfer pump; 16 - mother liquor pump; 17 - solid-liquid separation system. Specific embodiments

[0024] As Figure 1 shown, a continuous nickel sulfate crystallization system in a high-acid environment includes a condenser 1, a crystallizer 4, a thickener 10, and a mother liquor tank 12. A partition board 2 is provided in the middle of the condenser 1; a liquid inlet is provided at the top of the right side of the partition board 2 in the condenser 1, and a liquid outlet I is provided at the top of the left side of the condenser 1, so that the solution enters from the top of the right side of the partition board 2 and exits from the top of the left side of the partition board 2, that is, the process of cooling and temperature reduction is completed. The liquid inlet is connected to the liquid outlet II of the crystallizer 4 through a circulation pump 14 via a circulation pipe 3; a central circulation pipe 6 is provided in the crystallizer 4, the bottom of the central circulation pipe 6 is open, and the top is communicated with the feed inlet 5 of the crystallizer 4; the liquid outlet I is connected to the feed inlet 5 through a pipeline I; a hydrometer 8 for detecting the specific gravity of the solution is provided at the bottom of the crystallizer 4, high and low liquid outlets 9 for discharging crystals of different specific gravities are provided at the lower part of one side, and a clear liquid outlet I is provided at the upper part; the high and low liquid outlets 9 are connected to the thickener 10 through a transfer pump 15 via a pipeline II; the clear liquid outlet I is connected to the mother liquor tank 12 through a pipeline III; a speed reduction stirrer 11 is provided inside the thickener 10, a clear liquid outlet II is provided at one side, and the clear liquid outlet II is connected to the mother liquor tank 12 through a pipeline IV; a discharge port 13 is provided at the bottom of the thickener 10, and the discharge port 13 is connected to the solid-liquid separation system 17 through a pipeline V; the solid-liquid separation system 17 is connected to the mother liquor tank 12 through a pipeline VI; one side of the mother liquor tank 12 is communicated with the feed inlet 5 through a mother liquor pump 16 via a pipeline VII.

[0025] Among them: The material of the crystallizer 4 is 304 + Inco825 composite material, and its bottom is in a concave spherical structure 7.

[0026] The material of the thickener 10 is PTFE material.

[0027] A stirring device is provided inside the mother liquor tank 12.

[0028] The bottom opening of the central circulation pipe 6 is in a flared shape, which is used to slow down the flow rate and is beneficial to the growth of crystals.

[0029] In the present invention, the crystal growth in the crystallizer 4 mainly relies on the solution disturbance effect in the central circulation pipe 6.

[0030] Through the action of the circulation pump 14, a liquid level difference appears in the clarified liquid generated in the crystallizer. A part of the clarified liquid is forced to circulate and exchange heat between the crystallizer 4 and the condenser 1, so as to obtain a supersaturated solution, and the other part of the clarified liquid enters the mother liquor tank 12 for cyclic operation.

[0031] A continuous crystallization process of nickel sulfate in a high-acid environment includes the following steps: ⑴ Mix the nickel-containing solution and concentrated sulfuric acid in the mother liquor tank 12 at a volume ratio of 40:1 to 50:1, and adjust the hydrogen ion concentration and nickel ion concentration in the solution to obtain a nickel sulfate solution with a hydrogen ion concentration of 1.2 to 2.0 g / L and a nickel ion concentration of 160 to 240 g / L.

[0032] Among them: the components of the nickel-containing solution: Ni≥180 g / L, Fe≤5.0 ppm, H + =1.5 to 2.0 g / L.

[0033] ⑵ The nickel sulfate solution is directly transported into the central circulation pipe 6 of the crystallizer 4 through the mother liquor pump 16 and enters the self-circulation pipeline of the crystallizer 4; the crystals in the crystallizer 4 settle at the lower part, and the clarified liquid generated is driven by the circulation pump 14 to enter the condenser 1 through the circulation pipe 3. During the liquid inlet process, the crystallizer 4 operates in an overflow state; the clarified liquid circulates and exchanges heat between the crystallizer 4 and the condenser 1 to obtain a supersaturated solution; at the same time, the clarified liquid at a high position enters the mother liquor tank 12 through the clarified liquid outlet Ⅰ.

[0034] ⑶ The supersaturated solution is sent back into the crystallizer 4. During the process of the supersaturated solution passing through the crystal bed layer from bottom to top, the supersaturation is gradually eliminated, the crystals gradually grow, and while keeping the temperature in the crystallizer 4 stable at the crystallization target temperature, the crystallization target temperature is 32 to 38 °C. The produced crystal slurry is transferred to the thickener 10 by the transfer pump 15 through the high and low liquid outlet 9.

[0035] ⑷ Under the action of the speed reduction stirrer 11, the thickened material is slowly discharged into the solid-liquid separation system 17, and the produced supernatant enters the mother liquor tank 12 through the clarified liquid outlet Ⅱ.

[0036] ⑸ After the thickened material is separated by the solid-liquid separation system 17, the solid is discharged, and the liquid enters the mother liquor tank 12.

Claims

1. A continuous nickel sulfate crystallization system in a high-acid environment, comprising a condenser (1), a crystallizer (4), a thickener (10) and a mother liquor tank (12), characterized in that: A partition plate (2) is provided in the middle of the condenser (1); a liquid inlet is provided at the top of the right side condenser (1) of the partition plate (2), and a liquid outlet I is provided at the top of the left side condenser (1); the liquid inlet is connected to the liquid outlet II of the crystallizer (4) through a circulation pump (14) via a circulation pipe (3); a central circulation pipe (6) is provided in the crystallizer (4), the bottom of the central circulation pipe (6) is open, and the top communicates with the feed inlet (5) of the crystallizer (4); the liquid outlet I is connected to the feed inlet (5) via pipeline I; a specific gravity meter (8) is provided at the bottom of the crystallizer (4), a high and low liquid outlet (9) is provided at the lower part of one side, and a clear liquid outlet I is provided at the upper part; the high and low liquid outlet (9) is connected to the thickener (10) through a transfer pump (15) via pipeline II; the clear liquid outlet I is connected to the mother liquid tank (12) via pipeline III; a slow speed stirrer (11) is provided inside the thickener (10), a clear liquid outlet II is provided at one side, and the clear liquid outlet II is connected to the mother liquid tank (12) via pipeline IV; a discharge port (13) is provided at the bottom of the thickener (10), and the discharge port (13) is connected to a solid-liquid separation system (17) via pipeline V; the solid-liquid separation system (17) is connected to the mother liquid tank (12) via pipeline VI; one side of the mother liquid tank (12) communicates with the feed inlet (5) through a mother liquid pump (16) via pipeline VII.

2. The continuous nickel sulfate crystallization system in a highly acidic environment according to claim 1, characterized in that: The crystallizer (4) is made of 304 + Inco825 composite material, and its bottom has an inner concave spherical structure (7).

3. The continuous nickel sulfate crystallization system in a high-acid environment according to claim 1, characterized in that: The thickener (10) is made of PTFE material.

4. The continuous nickel sulfate crystallization system in a highly acidic environment according to claim 1, characterized in that: A stirring device is provided inside the mother liquid tank (12).

5. A continuous nickel sulfate crystallization system in a high-acid environment according to claim 1, characterized in that: The bottom opening of the central circulation pipe (6) is in a flared shape.

6. A continuous crystallization process of nickel sulfate in a high-acid environment using the system according to any one of claims 1 to 5, comprising the following steps: ⑴ Mix a nickel-containing solution and concentrated sulfuric acid in the mother liquid tank (12) at a volume ratio of 40:1 to 50:1, and adjust the hydrogen ion concentration and nickel ion concentration in the solution to obtain a nickel sulfate solution with a hydrogen ion concentration of 1.2 to 2.0 g / L and a nickel ion concentration of 160 to 240 g / L. ⑵ The nickel sulfate solution is directly transported into the central circulation pipe (6) of the crystallizer (4) through the mother liquid pump (16) and enters the self-circulation pipeline of the crystallizer (4); the crystals in the crystallizer (4) settle at the lower part, and the generated clear liquid enters the condenser (1) through the circulation pipe (3) driven by the circulation pump (14). During the liquid inlet process, the crystallizer (4) operates in an overflow state; the clear liquid circulates and exchanges heat between the crystallizer (4) and the condenser (1) to obtain a supersaturated solution; at the same time, the clear liquid at a high level enters the mother liquid tank (12) from the clear liquid outlet I. ⑶ The supersaturated solution is sent back into the crystallizer (4). During the process of the supersaturated solution passing through the crystal bed layer from bottom to top, the supersaturation is gradually eliminated, the crystals gradually grow, and while keeping the temperature in the crystallizer (4) stable at the crystallization target temperature, the produced crystal slurry is transferred to the thickener (10) by the transfer pump (15) through the high and low liquid outlet (9). ⑷ Under the action of the deceleration stirrer (11), the thickened material is slowly discharged into the solid-liquid separation system (17), and the supernatant liquid generated enters the mother liquor tank (12) through the supernatant liquid outlet II; ⑸ After the thickened material is separated by the solid-liquid separation system (17), the solid is discharged, and the liquid enters the mother liquor tank (12).

7. A continuous crystallization process of nickel sulfate in a high-acid environment according to claim 6, characterized in that: The components of the nickel-containing solution: Ni ≥ 180 g / L, Fe ≤ 5.0 ppm, H + = 1.5 - 2.0 g / L.

8. A continuous crystallization process of nickel sulfate in a high-acid environment according to claim 6, characterized in that: The crystallization target temperature is 32-38 °C.

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