Heat exchange system for electrolyte waste liquid treatment

Abstract

This utility model belongs to the field of metallurgy, specifically relating to a heat exchange system for treating electrolytic waste liquid. It includes a primary copper stripping tank, a vacuum evaporator, a water-cooled crystallization tank, a first filtration unit, an electrowinning tank, a cryogenic crystallization kettle, and a second filtration unit connected in sequence. The filtrate outlet of the second filtration unit is connected to the cooling medium inlet of the water-cooled crystallization tank, and the cooling medium outlet of the water-cooled crystallization tank is connected to a cryogenic crystallization raw material treatment system. This solution uses cryogenic crystallization raw material instead of circulating water to cool the evaporated liquid, reducing the temperature of the evaporated liquid to 10-25℃, significantly improving the problem of poor cooling effect of cooling water in summer. This utility model utilizes the low temperature of the cryogenic crystallization raw material, avoiding waste of the cold source, greatly reducing energy consumption in the preceding cooling stages, improving the cooling effect, and addressing the problem of high copper content in the final depurified liquid affecting the high copper content of nickel sulfate products.

Description

Technical Field

[0001] This utility model belongs to the field of metallurgy, and specifically relates to a heat exchange system for treating electrolytic waste liquid. Background Technology

[0002] In the electrolysis workshop of a copper smelting enterprise, the waste electrolyte replaced by the electrolysis process is purified to produce a cleaned final solution. Based on the principle of the difference in nickel sulfate saturation at different temperatures, the cleaned final solution is subjected to freeze crystallization and solid-liquid separation to obtain nickel sulfate and freeze crystallization stock solution.

[0003] The final purified solution is the solution obtained after the electrolyte has undergone a series of processes, including copper removal, vacuum evaporation, water-cooled crystallization, filtration, and electrodeposition for further purification. For example... Figure 1 As shown, the water-cooled crystallization process typically employs three water-cooled crystallization tanks, using jacketed refrigerant (outdoor circulating water) to continuously cool the mother liquor within the tanks. In summer, due to the higher temperature of the outdoor circulating water, the cooling effect is relatively poor, resulting in a higher outlet temperature after freezing (30-40℃). This leads to a higher copper content in the mother liquor, affecting the efficiency of subsequent electrowinning and impurity removal. It also results in a higher copper content in the subsequent nickel sulfate product, severely impacting the quality of the nickel sulfate product.

[0004] In the process of freezing and crystallizing the purified final liquid and separating the solid and liquid to produce nickel sulfate and the raw freezing crystallization solution, the purified final liquid directly enters the freezing crystallization tank. Inside the tank, an external jacket refrigerant (freezing brine) continuously cools the purified final liquid in the inner jacket to -20±2℃. The cooled final liquid is then pumped into a plate and frame filter press for filtration, resulting in solid-liquid separation and the production of nickel sulfate and the raw freezing crystallization solution. Because the temperature of the purified final liquid is between 40-50℃, cooling it to around -20℃ requires a significant amount of energy, making the refrigeration unit extremely energy-intensive. Utility Model Content

[0005] The purpose of this invention is to provide a heat exchange system for treating electrolytic waste liquid, which returns the frozen crystallization raw liquid to the water-cooled crystallization step as a cooling medium, saving energy and avoiding waste of cold source.

[0006] To achieve this objective, the technical solution adopted by this utility model is as follows: a heat exchange system for treating electrolytic waste liquid, comprising a primary copper stripping tank, a vacuum evaporator, a water-cooled crystallization tank, a first filtration unit, an electrowinning tank, a freezing crystallization kettle, and a second filtration unit connected in sequence. The filtrate outlet of the second filtration unit is connected to the cooling medium inlet of the water-cooled crystallization tank, and the cooling medium outlet of the water-cooled crystallization tank is connected to the freezing crystallization raw liquid treatment system.

[0007] The above solution uses cryogenic crystallization stock solution instead of circulating water to cool the evaporated liquid, which can reduce the temperature of the evaporated liquid to 10-25℃, greatly improving the problem of poor cooling effect of cooling water in summer. This utility model utilizes the low temperature of the cryogenic crystallization stock solution, which not only avoids the waste of the cold source of the cryogenic crystallization stock solution, but also greatly reduces the energy consumption of the preceding cooling process, improves the cooling effect, and alleviates the problem that the high copper content in the final purified liquid affects the high copper content of nickel sulfate products. Attached Figure Description

[0008] Figure 1 and Figure 2 These are two embodiments of the electrolytic waste liquid treatment system of this utility model.

[0009] In the diagram, the thin solid arrow indicates the direction of the liquid to be treated, i.e., the main line for treating electrolytic waste liquid; the hollow arrow indicates the direction of the outdoor circulating water of the cooling medium in the water-cooled crystallization tank; the black outward arrow indicates the direction of the heat exchange of the frozen crystallization raw liquid; and the dashed line indicates the circulation of the refrigerant in the refrigeration unit of the frozen crystallization reactor. Detailed Implementation

[0010] The technical solution of this utility model will be further described in detail below with reference to the accompanying drawings.

[0011] A heat exchange system for treating electrolytic waste liquid includes a primary copper stripping tank 10, a vacuum evaporator 20, a water-cooled crystallization tank 30, a first filtration unit 40, an electrowinning tank 50, a freezing crystallization kettle 60, and a second filtration unit 70 connected in sequence. The filtrate outlet 71 of the second filtration unit is connected to the cooling medium inlet 31 of the water-cooled crystallization tank 30, and the cooling medium outlet 32 ​​of the water-cooled crystallization tank 30 is connected to the freezing crystallization raw liquid treatment system A.

[0012] A heat exchange unit 80 is provided between the electrodeposition tank 50 and the cryogenic crystallizer 60. The hot inlet 81 and hot outlet 82 of the heat exchange unit 80 are connected to the drain outlet 51 of the electrodeposition tank and the inlet 61 of the cryogenic crystallizer, respectively. The filtrate outlet 71 of the second filtration unit is connected to the cold inlet 83 of the heat exchange unit 80, and the cold outlet 84 of the heat exchange unit 80 is connected to the cryogenic crystallization stock solution treatment system A. The low-temperature cryogenic crystallization stock solution obtained from the second filtration unit 70 is divided into two parts: one part is transported to a water-cooled crystallization tank to cool the evaporated liquid, and the other part is used to pre-cool the purified final liquid obtained from the electrodeposition tank.

[0013] The heat exchange unit 80 can be a plate heat exchanger, which is a heat exchange device composed of many thin plates arranged at intervals. The thin plates are sealed around their perimeter by gaskets and pressed together by a frame and clamping screws. The four corner holes of the plates and gaskets form fluid distribution pipes and collection pipes. Hot and cold fluids flow in the flow channels on both sides of each plate, exchanging heat through the plates. In this invention, the purified final liquid obtained from the electrowinning cell 50 and the frozen crystallization stock solution obtained from the second filtration unit 70 are respectively introduced into the hot and cold fluid channels of the plate heat exchanger for heat exchange. The low temperature of the frozen crystallization stock solution is used to pre-cool the purified final liquid, reducing its temperature from about 50°C to 0-10°C, which facilitates the subsequent frozen crystallization step. The refrigeration unit in the frozen crystallization step further reduces the temperature of the purified final liquid to -20±2°C, significantly reducing the working pressure and energy consumption.

[0014] In another embodiment, a heat exchange unit 80 is provided between the electrowinning cell 50 and the cryogenic crystallizer 60. The hot flow inlet 81 and hot flow outlet 82 of the heat exchange unit 80 are connected to the drain outlet 51 of the electrowinning cell and the inlet 61 of the cryogenic crystallizer, respectively. The filtrate outlet 71 of the second filtration unit is connected to the cold flow inlet 83 of the heat exchange unit 80, and the cold flow outlet 84 of the heat exchange unit 80 is connected to the cooling medium inlet 31 of the water-cooled crystallizer 30. That is, the low-temperature cryogenic crystallization stock solution obtained from the second filtration unit 70 is first used to pre-cool the purified final liquid. After one heat exchange, the cryogenic crystallization stock solution is then transported to the water-cooled crystallizer to cool the evaporated liquid. After a second heat exchange, the cryogenic crystallization stock solution is then sent to the original cryogenic crystallization stock solution treatment system for further processing.

[0015] The water-cooled crystallization tank 30 includes a first water-cooled tank 30a, a second water-cooled tank 30b, and a third water-cooled tank 30c connected in series. The cooling medium inlets 31a and 31b of the first and second water-cooled tanks are connected to outdoor circulating water. The cooling medium inlet 31c of the third water-cooled tank is connected to the filtrate outlet 71 of the second filtration unit, and the cooling medium outlet 32c of the third water-cooled tank is connected to the frozen crystallization stock solution treatment system A. Since the cost of using frozen crystallization stock solution to cool the evaporated liquid is slightly higher than that of outdoor circulating water cooling, this scheme is adopted in summer, while outdoor circulating water can be preferred in winter.

[0016] In summer, the outdoor circulating water temperature is generally 35-40℃. After evaporation, the liquid temperature drops from about 70℃ to about 50℃ after passing through the first water cooling tank. Then, it is cooled down to 30-40℃ by the circulating water in the second water cooling tank. If the third water cooling tank continues to use outdoor circulating water as the cooling medium, there will be no cooling effect. However, if the frozen crystallization stock solution, which is at a lower temperature and is already prepared to be transported to the next step, is used as the cooling medium in the third water cooling tank, the temperature of the evaporated liquid can be reduced to 10-20℃ in a short time, resulting in a better cooling effect.

[0017] In existing technologies, the electrolyte, after undergoing a copper removal and vacuum evaporation process, needs to pass through three water-cooling tanks sequentially. The outer jackets of these three water-cooled crystallization tanks are filled with a cooling medium, typically outdoor circulating water. During hot summer months, the outdoor circulating water's cooling effect is poor, and the temperature of the evaporated liquid after cooling in the three water-cooled crystallization tanks remains at 30-40°C. However, the temperature of the initial heat exchange freezing crystallization stock solution, which exchanges heat with the final impurity removal liquid, is relatively low. Using it as a cooling medium instead of the cooling medium in the water-cooled crystallization tanks to cool the evaporated liquid there is far superior to the cooling effect of outdoor circulating water. It can reduce the temperature of the evaporated liquid to 10-25°C, resulting in significantly better water-cooled crystallization. This greatly reduces the copper content in the crystallization mother liquor and the impurity-removed liquid obtained after electrodeposition, which is more conducive to subsequent nickel sulfate preparation and also improves the situation where the nickel sulfate product has a high copper content.

[0018] In practice, since the final temperature of the purified liquid is between 40 and 50°C, based on a daily volume of 100 m³ of purified liquid, reducing the temperature by 40°C can save energy of 40 * 2.68 J / (g * ℃) * 100 * 1.25 * 1000000 * 0.000278 = 3725.2 kWh, resulting in an annual electricity saving of 3725.2 * 365 = 1359698 kWh and a cost saving of 1359698 * 0.6 = 815,800 yuan.

Claims

1. A heat exchange system for electrolytic spent solution treatment, characterized by: The system includes a copper stripping tank (10), a vacuum evaporator (20), a water-cooled crystallization tank (30), a first filtration unit (40), an electrowinning tank (50), a freeze crystallization vessel (60), and a second filtration unit (70) connected in sequence. The filtrate outlet (71) of the second filtration unit is connected to the cooling medium inlet (31) of the water-cooled crystallization tank (30), and the cooling medium outlet (32) of the water-cooled crystallization tank (30) is connected to the freeze crystallization raw material treatment system (A).

2. The heat exchange system for electrolytic spent solution treatment according to claim 1, characterized in that: A heat exchange unit (80) is provided between the electrowinning cell (50) and the freeze crystallizer (60). The heat inlet (81) and heat outlet (82) of the heat exchange unit (80) are connected to the drain outlet (51) of the electrowinning cell and the inlet outlet (61) of the freeze crystallizer, respectively. The filtrate outlet (71) of the second filtration unit is connected to the cold inlet (83) of the heat exchange unit (80). The cold outlet (84) of the heat exchange unit (80) is connected to the freeze crystallization raw material treatment system (A).

3. The heat exchange system for electrolytic spent solution treatment according to claim 1, characterized in that: A heat exchange unit (80) is provided between the electrowinning cell (50) and the freeze crystallizer (60). The heat inlet (81) and heat outlet (82) of the heat exchange unit (80) are connected to the drain outlet (51) of the electrowinning cell and the inlet (61) of the freeze crystallizer, respectively. The filtrate outlet (71) of the second filtration unit is connected to the cold inlet (83) of the heat exchange unit (80), and the cold outlet (84) of the heat exchange unit (80) is connected to the cooling medium inlet (31) of the water-cooled crystallizer (30).

4. The heat exchange system for electrolytic spent solution treatment according to claim 1, characterized in that: The water-cooled crystallization tank (30) includes a first water-cooled tank (30a), a second water-cooled tank (30b), and a third water-cooled tank (30c) connected in series. The cooling medium inlets (31a, 31b) of the first and second water-cooled tanks are connected to outdoor circulating water. The cooling medium inlet (31c) of the third water-cooled tank is connected to the filtrate outlet (71) of the second filtration unit. The cooling medium outlet (32c) of the third water-cooled tank is connected to the frozen crystallization raw material treatment system (A).

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