A method for vacuum evaporation instead of electric evaporation for nickel removal

Abstract

The present application relates to a kind of vacuum evaporation instead of the method of electric evaporation nickel removal, which refers to the liquid after copper removal is concentrated using vacuum evaporation kettle under the condition that vacuum degree is-50~‑65KPa, temperature is 65~80℃, vacuum evaporation flow is 1.5~2.5m 3 / h, namely the vacuum evaporation liquid with specific gravity≥1.43 is obtained;The vacuum evaporation liquid is pre-cooled by plate condenser first, then is sequentially operated by refrigeration crystallization machine and belt filter, respectively, to obtain crude nickel sulfate and crystallization mother liquor, and the crystallization mother liquor is returned to electrolysis system.The present application has low power consumption, large solution processing capacity, good solution concentration effect, simple operation, safe and environmentally friendly operation environment, and the quality of crude nickel sulfate product prepared is stable.

Description

Technical Field

[0001] This invention relates to the field of metal extraction technology, and in particular to a method for removing nickel by vacuum evaporation instead of electroevaporation. Background Technology

[0002] In the copper electrolytic refining process, the electroevaporation-freeze crystallization process is generally used for nickel removal: the copper-removed liquid (generally containing less than 3 g / L of copper, 300-400 g / L of acid, and less than 40 g / L of nickel) from the copper electrolytic purification process is concentrated by electroevaporation at a temperature of 100-130℃; the evaporated liquid is then cooled by water-cooled crystallization at a temperature <45℃, and then enters a freeze crystallizer for further cooling. The frozen liquid is then vacuum filtered through a vacuum belt filter to produce crude nickel sulfate, and the filtrate (acidity 350-450 g / L) is returned to the electrolysis system. This process is technically mature and has a good nickel removal effect, but it has significant drawbacks: ① Electroevaporation (500KW) consumes approximately 10,000 KWh per day, resulting in high energy consumption; ② The processing capacity of a single electroevaporator is only 1-1.2 m³. 3 / h, low solution processing capacity; ③ poor electroevaporation concentration effect, concentration rate of about 80%. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a method for removing nickel by replacing electroevaporation with vacuum evaporation, which has low power consumption, large solution processing capacity, good solution concentration effect, simple operation, safe and environmentally friendly working environment, and stable product quality.

[0004] To address the aforementioned problems, the present invention provides a method for nickel removal by replacing electroevaporation with vacuum evaporation, characterized in that: the method involves evaporating the copper-removed liquid in a vacuum evaporator at a vacuum level of -50 to -65 kPa, a temperature of 65 to 80°C, and a vacuum evaporation flow rate of 1.5 to 2.5 m³ / h. 3 The concentration is carried out under the condition of / h to obtain a vacuum evaporation liquid with a specific gravity ≥1.43; the vacuum evaporation liquid is first pre-cooled by a plate condenser, and then sequentially processed by a freeze crystallizer and a belt filter to obtain crude nickel sulfate and crystallization mother liquor, respectively. The crystallization mother liquor is returned to the electrolysis system.

[0005] The copper-removed solution contains 320-350 g / L of H2SO4 and Cu. 2+ The content is 0.3~0.8 g / L, Ni 2+ The content is 26~33g / L.

[0006] The acid concentration of the liquid after vacuum evaporation is 550~580g / L, the nickel ion concentration is ≥46g / L, and the vacuum evaporation concentration rate is less than 65%.

[0007] The liquid after vacuum evaporation is pre-cooled to 35~50℃ by a plate condenser.

[0008] The temperature of the solution after freeze-crystallization drops below -17°C.

[0009] The mother liquor for crystallization contains 350-400 g / L of acid.

[0010] Compared with the prior art, the present invention has the following advantages: 1. By controlling the vacuum degree, temperature, solution flow rate and specific gravity of the liquid after evaporation, this invention can appropriately increase the concentration of acid and nickel in the solution after copper removal. After the solution is frozen and crystallized, the nickel removal rate reaches more than 76%, thus improving the direct recovery rate of nickel.

[0011] 2. This invention uses a vacuum evaporation kettle to adjust the inlet liquid flow rate and the post-evaporation liquid flow rate, achieving a vacuum evaporation processing capacity of 2.2 m³. 3 The process capacity is increased by 57% compared to electroevaporation. The specific gravity of the evaporated liquid is stable. By adjusting the solution temperature and ensuring that the solution temperature is within the control range, the solution concentration is increased, which provides favorable conditions for subsequent freeze crystallization operations.

[0012] 3. The process of this invention is simple, easy to operate, and reliable. Compared with the electroevaporation and freeze crystallization process, it has a large solution processing capacity and good concentration effect, making it suitable for the production of crude nickel sulfate by high acid crystallization. Simultaneously, it has low power consumption, reduced processing costs, automated process control, and reduced labor intensity. The crude nickel sulfate product obtained is of stable quality.

[0013] 4. The equipment of this invention requires little investment, has good airtightness, produces less acid mist, and creates a good on-site environment, thus having a certain environmental protection effect. Attached Figure Description

[0014] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0015] Figure 1 This is a schematic diagram of the process flow of the present invention. Detailed Implementation

[0016] This invention employs vacuum evaporation concentration technology. Under certain conditions, by controlling the vacuum degree, temperature, solution flow rate, and specific gravity of the evaporated liquid, the concentration of the copper-removed liquid is increased. The copper-removed liquid then enters a plate condenser for pre-cooling, and is processed by a freeze crystallizer and a belt filter to produce crude nickel sulfate.

[0017] like Figure 1 As shown, a method for nickel removal using vacuum evaporation instead of electroevaporation is described. This method involves evaporating the copper-removed solution in a vacuum evaporator at a vacuum level of -50 to -65 kPa, a temperature of 65 to 80°C, and a flow rate of 1.5 to 2.5 m³ / h. 3Concentration is carried out under conditions of / h, resulting in a vacuum-evaporated liquid with a specific gravity ≥1.43. The acid concentration of the vacuum-evaporated liquid is 550~580g / L, the nickel ion concentration is ≥46g / L, and the volume of the liquid is reduced after evaporation, with a vacuum evaporation concentration rate of less than 65%.

[0018] After vacuum evaporation, the liquid is first pre-cooled to 35~50℃ by a plate condenser. After pre-cooling, the liquid is then passed through a freeze crystallizer to lower the solution temperature to below -17℃, resulting in a solid-liquid mixture. A belt filter separates the crystalline nickel sulfate from the solid-liquid mixture, yielding crude nickel sulfate and a crystallization mother liquor containing 350~400g / L of acid. The crystallization mother liquor is returned to the electrolysis system.

[0019] Among them: the H2SO4 content in the copper removal solution is 320~350 g / L, Cu 2+ The content is 0.3~0.8 g / L, Ni 2+ The content is 26~33g / L.

[0020] In this invention, the vacuum evaporator refers to the vacuum autoclave provided by Shandong Xintaixin Intelligent Equipment Co., Ltd., or the autoclave evaporator provided by Hefei Xiaoniu Light Industry Machinery Co., Ltd.

[0021] Example 1 18m 3 After copper removal, the liquid is passed into a vacuum evaporator for concentration. The technical conditions are: vacuum evaporation temperature 72.7℃, vacuum degree -58.2KPa, and flow rate 2.2m³ / h. 3 / h, specific gravity of the liquid after evaporation is 1.44, and the volume of the liquid after evaporation is 11m³. 3 .

[0022] The impurity element content of the copper-removed liquid and the evaporated liquid is shown in Table 1.

[0023] Table 1. Impurity element content in the copper-removed liquid and the evaporated liquid (unit: g / L) After evaporation, the liquid is cooled to 40°C by a plate condenser and then cooled by a freeze crystallizer. After the freeze crystallization operation is completed, solid-liquid separation is performed by a belt filter to produce crude nickel sulfate and crystallization mother liquor. The impurity element content of the crystallization mother liquor is shown in Table 2. The vacuum evaporation concentration rate is 61% and the nickel removal rate is 76.3% according to calculation.

[0024] Table 2. Impurity element content in crystallization mother liquor (unit: g / L) Example 2 18m 3 After copper removal, the liquid is passed into a vacuum evaporator for concentration. The technical conditions are: vacuum evaporation temperature 72℃, vacuum degree -57.8KPa, and flow rate 2.3m³ / h. 3 / h, specific gravity of the liquid after evaporation is 1.44, and the volume of the liquid after evaporation is 10m³. 3 .

[0025] The impurity element content of the copper-free liquid and the evaporation liquid is shown in Table 3.

[0026] Table 3. Impurity element content in the copper-removed liquid and the evaporated liquid (unit: g / L) After evaporation, the liquid is cooled to 40°C by a plate condenser, and then cooled by a freeze crystallizer. After the freeze crystallization operation is completed, solid-liquid separation is performed by a belt filter to produce crude nickel sulfate and crystallization mother liquor. The impurity element content of the crystallization mother liquor is shown in Table 4. The vacuum evaporation concentration rate is 56% and the nickel removal rate is 78% according to the calculation.

[0027] Table 4. Impurity element content in crystallization mother liquor (unit: g / L)

Claims

1. A method for removing nickel using vacuum evaporation instead of electroevaporation, characterized in that: This method refers to evaporating the copper-free solution in a vacuum evaporator at a vacuum level of -50 to -65 kPa, a temperature of 65 to 80°C, and a vacuum evaporation flow rate of 1.5 to 2.5 m³ / h. 3 The concentration is carried out under the condition of / h to obtain a vacuum evaporation liquid with a specific gravity ≥1.43; the vacuum evaporation liquid is first pre-cooled by a plate condenser, and then sequentially processed by a freeze crystallizer and a belt filter to obtain crude nickel sulfate and crystallization mother liquor, respectively. The crystallization mother liquor is returned to the electrolysis system.

2. The method for removing nickel by vacuum evaporation instead of electroevaporation as described in claim 1, characterized in that: The copper-removed solution contains 320-350 g / L of H2SO4 and Cu. 2+ The content is 0.3~0.8 g / L, Ni 2+ The content is 26~33g / L.

3. The method for removing nickel by vacuum evaporation instead of electroevaporation as described in claim 1, characterized in that: The acid concentration of the liquid after vacuum evaporation is 550~580g / L, the nickel ion concentration is ≥46g / L, and the vacuum evaporation concentration rate is less than 65%.

4. The method for removing nickel by vacuum evaporation instead of electroevaporation as described in claim 1, characterized in that: The liquid after vacuum evaporation is pre-cooled to 35~50℃ by a plate condenser.

5. The method for removing nickel by vacuum evaporation instead of electroevaporation as described in claim 1, characterized in that: The temperature of the solution after freeze-crystallization drops below -17°C.

6. The method for removing nickel by vacuum evaporation instead of electroevaporation as described in claim 1, characterized in that: The mother liquor for crystallization contains 350-400 g / L of acid.

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