Production method of insoluble anode electrodeposited nickel

Abstract

The invention provides a production method of insoluble anode electrodeposited nickel, which comprises the following steps of: firstly, setting the pH value of catholyte before the catholyte enters a catholyte head tank to be 2.5-3.5 so as to prevent hydrogen ions from discharging on a cathode to separate out hydrogen or prevent nickel hydroxide colloid from appearing near the cathode; then the temperature of the catholyte in the catholyte head tank is 65-75 DEG C, so that the activity of Ni < 2 + > in the catholyte can be increased, the discharging step of Ni < 2 + > is accelerated, and the electrochemical polarization effect is reduced; and finally, the nickel mass concentration of the cathode liquor in the cathode diaphragm bag is not less than 55 g / L in the electrodeposition treatment, so that discharge precipitation of other metal ions at the cathode can be inhibited, and the nickel purity of the electrodeposited nickel product is finally improved.

Description

Technical Field

[0001] The present invention relates to the technical field of insoluble anode nickel electrowinning, and particularly to a production method for electrowinning nickel with an insoluble anode. Background Art

[0002] In China, the production of metallic nickel mainly adopts the soluble anode electrolysis method, that is, the nickel-containing anode plate is electrolyzed in an electrolytic cell. Nickel ions are produced at the anode, and metallic nickel is formed at the cathode. The insoluble anode electrowinning process has many advantages such as low labor intensity and simple process flow, which determines its leading position in the metallurgical industry. The transition from the traditional soluble anode electrolytic refining process to the insoluble anode electrowinning method for producing metallic nickel is the mainstream direction of technological improvement. It is of great significance to study the key parameters and systems of the nickel electrowinning and refining process.

[0003] However, in the existing insoluble anode nickel electrowinning process, metal cation impurities, hydrogen, or nickel hydroxide colloid may precipitate on the cathode, resulting in a low purity of the electrowon nickel deposited on the cathode, and thus reducing the market competitiveness of the electrowon nickel.

[0004] Therefore, there is an urgent need to develop a production method for electrowinning nickel with an insoluble anode to improve the nickel purity of the insoluble anode electrowon nickel product. Summary of the Invention

[0005] In view of this, the present application provides a production method for electrowinning nickel with an insoluble anode to solve the technical problem of the nickel purity of the electrowon nickel product produced by the existing insoluble anode nickel electrowinning process.

[0006] The object of the present invention is achieved through the following technical solutions: To achieve the above technical object, the present application adopts the following technical solutions: The present invention provides a production method for electrowinning nickel with an insoluble anode, including: S10, subjecting the cathode solution with a pH value of 2.5 - 3.5 to heat exchange treatment and then flowing it into the cathode solution elevated tank, where the temperature of the cathode solution in the cathode solution elevated tank is 65°C - 75°C; S20, overflowing the cathode solution from the cathode solution elevated tank into the cathode diaphragm bag in the nickel electrowinning cell for electrowinning treatment, finally depositing electrowon nickel on the cathode, and simultaneously depositing oxygen on the insoluble anode; wherein, the nickel mass concentration of the cathode solution in the cathode diaphragm bag is not less than 55 g / L during the electrowinning treatment.

[0007] Preferably, in step S10, the cathode solution is a nickel sulfate solution after degreasing, the pb 2+ ≤ 1 mg / L, the TOC content of the cathode solution ≤ 40 mg / L, the boric acid content of the cathode solution is 3 - 5 mg / L, and the nickel mass concentration of the cathode solution is 85 - 95 g / L.

[0008] Preferably, in step S10, low-pressure steam is introduced into the plate-frame heat exchanger to heat-exchange the cathode liquid. Preferably, in step S10, the pressure of the low-pressure steam is 0.2 - 0.5 MPa, and the temperature of the low-pressure steam is 170°C - 180°C. Preferably, in step S10, the opening of the steam electric control valve is automatically adjusted to regulate the flow rate of the low-pressure steam, so that the temperature of the cathode liquid in the cathode liquid elevated tank is 65°C - 75°C.

[0009] Preferably, in step S20, the temperature of the cathode liquid in the cathode diaphragm bag is 60°C - 70°C.

[0010] Preferably, in step S20, the cathode is any one of nickel starting sheets, stainless steel plates, and titanium plates, and the insoluble anode is a lead alloy anode or a titanium iridium anode.

[0011] Preferably, in step S20, the cathode is hot-washed or pickled before entering the nickel electrowinning cell.

[0012] Preferably, in step S20, water at 65°C - 75°C is used for hot-washing, and H 2 SO 4 with a concentration of 400 g / L - 700 g / L is used for pickling and soaked for 30 - 120 s.

[0013] Preferably, in step S20, the flow rate of the cathode liquid flowing into the cathode diaphragm bag is maintained at 400 L / h - 600 L / h by adjusting the valve to maintain the flowmeter.

[0014] Beneficial effects: The present invention provides a production method for electrowinning nickel with an insoluble anode. First, the pH value of the cathode liquid before entering the cathode liquid elevated tank is set at 2.5 - 3.5, which can prevent hydrogen ions from discharging and precipitating hydrogen on the cathode or prevent the appearance of nickel hydroxide colloid near the cathode; then, the temperature of the cathode liquid in the cathode liquid elevated tank is 65°C - 75°C, which can increase the activity of Ni 2+ in the cathode liquid, thereby accelerating the discharge step of Ni 2+ , reducing the electrochemical polarization effect; finally, the nickel mass concentration of the cathode liquid in the cathode diaphragm bag is not less than 55 g / L during the electrowinning process, which can inhibit the discharge and precipitation of other metal ions on the cathode and ultimately improve the nickel purity of the electrowon nickel product. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a schematic flow chart of the production method for electrowinning nickel with an insoluble anode provided by an embodiment of the present application; Figure 2 is a process flow chart before nickel electrowinning refining in the production method for electrowinning nickel with an insoluble anode provided by an embodiment of the present application; Figure 3 This is the process flow diagram of the nickel electrowinning refining treatment in the production method of insoluble anode electrowinning nickel provided by the embodiments of the present application. Detailed implementation manners

[0016] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0017] Aiming at the technical problem that the nickel purity of the electrowon nickel deposited on the cathode in the insoluble anode nickel electrowinning process of the prior art is relatively low. The production method of insoluble anode electrowinning nickel provided by the present invention can effectively improve the nickel purity of the electrowon nickel product by optimizing key process parameters (such as the pH value of the cathode solution, the nickel mass concentration of the cathode solution, and the temperature of the cathode solution).

[0018] The present invention provides a production method of insoluble anode electrowinning nickel, which is applied to a 50,000-ton annual electrolytic nickel construction project; the nickel metal in the above-mentioned production method of insoluble anode electrowinning nickel is deposited and precipitated on the cathode, so as to achieve the purpose of extracting the metal. An oxygen evolution reaction occurs on the anode during the electrowinning process, and the generated acid mist is captured and absorbed and then discharged. Nickel ions in the solution are reduced and precipitated on the cathode to form the final product - electrowon nickel. The electrolysis processes of its anode and cathode are as follows: (1) On the insoluble anode, the following electrochemical reaction occurs: H 2 O - 2e → 1 / 2O 2 ↑ + 2H + , this reaction produces a large amount of oxygen and generates an equivalent amount of acid, and the acidity of the solution will increase.

[0019] (2) The purpose of nickel electrowinning is to precipitate relatively pure electrolytic nickel on the cathode without precipitating or minimizing the precipitation of hydrogen. The main reaction occurring on the cathode during electrowinning is the reduction reaction: Ni 2+ + 2e = Ni.

[0020] Please refer to Figure 1 , Figure 1 This is the schematic flow diagram of the production method of insoluble anode electrowinning nickel provided by the embodiments of the present application; wherein, the above method includes the following steps: S10, heat-exchange the cathode solution with a pH value of 2.5 - 3.5 and then flow it into the cathode solution elevated tank, and the temperature of the cathode solution in the cathode solution elevated tank is 65°C - 75°C.

[0021] Specifically, step S10 further includes: Please refer to Figure 2 , Figure 2Process flow diagram of the process before nickel electrowinning refining in the nickel electrowinning method provided by the embodiments of the present application; specifically, the specific process of the process before nickel electrowinning refining is as follows: First, after degreasing, the nickel sulfate solution pump transports the purified catholyte to the catholyte storage tank; then, the catholyte transfer pump sends the catholyte in the catholyte storage tank to the plate heat exchanger for heating first, and then flows into the catholyte elevated tank, and enters each nickel electrowinning cell through overflow. Among them, low-pressure steam heats the catholyte in the plate heat exchanger, and the steam cools and part of it condenses into condensate and flows into the condensate tank, and the condensate pump transports the condensate in the tank to the plate washing tank.

[0022] In this step, the catholyte is nickel sulfate solution after degreasing, the pH value of the catholyte is 2.5 - 3.5, the pb of the catholyte 2+ ≤1mg / L, the TOC content (Total Organic Carbon) of the catholyte ≤40mg / L, the boric acid content of the catholyte is 3 - 5mg / L, and the nickel mass concentration of the catholyte is 85 - 95g / L. The above parameters are adjusted by the degreasing and acid preparation workshop to meet the requirements and then transported to the catholyte storage tank.

[0023] Specifically, in the catholyte of nickel electrolysis, in addition to containing H + ions, it often contains metal ions such as a small amount of copper, iron, cobalt, zinc and other harmful impurities. Although the content of these impurity ions is very low, the standard electrode potential is more positive than Ni 2+ positive Pb 2+ and other ions are preferentially reduced and precipitated before nickel ions. In order to prevent the precipitation of Pb 2+ etc., they can be removed as much as possible in the process before electrowinning, and their concentrations are controlled within a certain range. It is required that the Pb 2+ concentration ≤1mg / L.

[0024] Specifically, nickel electrolysis is carried out in a slightly acidic solution, and hydrogen ions with a standard electrode potential more positive than nickel in the solution may discharge and precipitate hydrogen on the cathode: 2H + +2e = H 2 ↑.

[0025] Under production conditions, the hydrogen evolution potential generally accounts for 0.5 - 1.0% of the current consumption. The discharge of H + consumes a large amount of electric energy, and causes the alkalinity in the electrolyte near the cathode surface to increase, and nickel hydroxide colloid appears. These colloid particles are easily adsorbed by the cathode, hindering the crystal growth of electrodeposited nickel on the cathode plate, and making the mechanical properties of electrodeposited nickel deteriorate. In order to prevent H +For the discharge, we usually adopt the method of increasing the pH value of the cathode liquid. However, the pH value of the cathode liquid cannot be increased too much, otherwise nickel hydroxide colloid will also appear. Generally, the pH value of the cathode liquid is required to be controlled between 2.5 and 3.5. If the pH value of the cathode liquid is too small, H + is easily discharged; if the pH value of the cathode liquid is too large, nickel hydroxide colloid is likely to appear.

[0026] In this step, low-pressure steam is introduced into the plate-frame heat exchanger to heat-exchange the cathode liquid; the low-pressure steam pressure is 0.2 - 0.5 MPa, and the low-pressure steam temperature is 170°C - 180°C.

[0027] Specifically, increasing the temperature of the cathode liquid can increase the activity of Ni 2+ in the cathode liquid, thereby accelerating the discharge step of Ni 2+ and reducing the electrochemical polarization effect. However, if the temperature of the cathode liquid is too high, the evaporation rate of the solution is too large, and the acid mist entrained is also too large, which affects the health of the staff and corrodes the equipment in the plant; therefore, the temperature of the cathode liquid in the cathode liquid high-level tank is 65°C - 75°C, and at this time the normal range of the cathode liquid temperature in the electrowinning cell is 60°C - 70°C.

[0028] Specifically, the temperature of the cathode liquid in the cathode liquid high-level tank can be maintained between 65°C and 75°C by automatically adjusting the opening of the steam motorized control valve to keep the measured values of temperatures TT1 and TT2. When the measured temperature value is greater than 75°C, the program logic automatically closes the motorized control valve slightly to reduce the low-pressure steam flow rate; when the measured temperature value is less than 65°C, the program logic automatically opens the motorized control valve to increase the low-pressure steam flow rate.

[0029] In one embodiment: there are 2 cathode liquid transfer pumps, one in use and one in standby; there are 2 condensate pumps, one in use and one in standby.

[0030] S20, the cathode liquid overflows from the cathode liquid high-level tank into the cathode diaphragm bag in the nickel electrowinning cell for electrowinning treatment. Finally, electrowon nickel is precipitated on the cathode, and oxygen is precipitated on the insoluble anode; among them, the nickel mass concentration of the cathode liquid in the cathode diaphragm bag is not less than 55 g / L during the electrowinning treatment.

[0031] Specifically, step S20 further includes: Please refer to Figure 3 , Figure 3 which is the process flow diagram of the nickel electrowinning and refining treatment in the production method of insoluble anode electrowon nickel provided by the embodiment of the present application; among them, a DN25 steam outlet is set for every 5 - 6 nickel electrowinning cells in the steam pipeline; a DN40 pure water outlet is set for every 5 - 6 nickel electrowinning cells in the pure water pipeline, and multiple DN40 pure water outlets are set corresponding to the cell openings of the nickel electrowinning cells.

[0032] Specifically, the specific process of the nickel electrowinning refining treatment process is as follows: First, the catholyte that has undergone the pre-process of nickel electrowinning refining overflows from the cathode high-level tank and enters the cathode diaphragm bag of the nickel electrowinning cell, keeping the cathode liquid level always higher than the anode liquid level. This is beneficial for reducing the precipitation of metal cation impurities on the cathode. Among them, nickel electrowinning is carried out in an acidic solution, and hydrogen ions with a standard electrode potential more positive than nickel in the solution may discharge hydrogen gas on the cathode. The anodic process is mainly the process of electrolyzing water. Due to the generation of H + , the pH value of the solution has a downward trend. In order to minimize the reaction of H + on the cathode, in actual production, it is separated by a diaphragm bag and new catholyte is continuously replenished into the diaphragm bag to keep the cathode liquid level always higher than the anode liquid level. This is beneficial for reducing the precipitation of metal cation impurities on the cathode.

[0033] Second, by adjusting the valves to maintain flowmeter FG1 and valve-maintained flowmeter FG2 to maintain the flow rate of the cathode entering the cathode diaphragm bag at 400 L / h to 600 L / h, preferably 500 L / h.

[0034] Finally, after electrowinning in the cathode diaphragm bag, electrowon nickel is produced, and the anolyte flows out of the cathode diaphragm bag and overflows into the anolyte intermediate tank. The anolyte intermediate pump transports the anolyte to the anolyte storage tank first, and then the anolyte transfer pump transports the anolyte to the pre-evaporation liquid tank of Workshop 132, and finally conducts evaporation and concentration treatment on it.

[0035] In this embodiment, the cathode is any one of nickel starter sheets, stainless steel plates, and titanium plates, and the insoluble anode is a lead alloy anode or a titanium iridium anode.

[0036] Specifically, in current production practice, the difference between the nickel concentration in the catholyte and the nickel concentration in the anolyte is generally between 30 g / L and 35 g / L. Therefore, the nickel mass concentration in the catholyte is controlled between 85 g / L and 95 g / L to ensure that the nickel mass concentration in the bag is not less than 55 g / L, thereby ensuring the appearance quality of the electrowon nickel product.

[0037] Among them, keeping the difference between the nickel concentration in the catholyte and the nickel concentration in the anolyte at 30 g / L to 35 g / L can form a stable ion migration driving force. During the electrowinning process, nickel ions migrate from the anolyte to the catholyte through the diaphragm. This concentration difference ensures that nickel ions have sufficient power to move towards the cathode, enabling the electrowinning reaction to proceed continuously and stably. If the concentration difference is too small, the ion migration speed is slow, which will affect the electrowinning efficiency; if the concentration difference is too large, it may cause the nickel ion deposition speed on the cathode surface to be too fast, easily resulting in problems such as coarse crystallization and uneven surface, affecting the appearance quality of the product.

[0038] Furthermore, controlling the nickel mass concentration in the catholyte between 85 g / L and 95 g / L provides an adequate source of nickel ions for the electrowinning reaction. When the nickel concentration in the catholyte is too low, the supply of nickel ions is insufficient, which will cause the current density distribution on the cathode surface to be uneven, resulting in uneven nickel deposition and defects such as pitting and holes. While too high a concentration may cause the nickel ions to deposit on the cathode surface too quickly, forming loose and porous deposits, which also affects the product appearance.

[0039] Furthermore, ensuring that the nickel mass concentration in the bag is not less than 55 g / L is to ensure that there is sufficient nickel ion concentration near the cathode. On the one hand, sufficient nickel ion concentration can enable nickel to preferentially precipitate on the cathode, inhibit the discharge and precipitation of other metal ions, and improve the product purity and appearance quality. On the other hand, it helps nickel to deposit evenly on the cathode surface, forming a smooth and dense nickel layer, and improving the appearance quality of electrowon nickel.

[0040] In this step, before entering the nickel electrowinning cell, the cathode is subjected to hot washing treatment or pickling treatment; among them, for the hot washing treatment, water at 65 °C to 75 °C is used, and for the pickling treatment, H 2 SO 4 with a concentration of 400 g / L to 700 g / L is used for soaking for 30 to 120 s. After pickling treatment, the surface is rinsed clean with hot water. The condensate pump sends the condensate water to the plate washing tank, and the steam condensate water can be recycled to achieve the purpose of energy saving.

[0041] Specifically, the hot washing treatment of the cathode before entering the nickel electrowinning cell has the following advantages: Removing oil and impurities: Hot water at 65 °C to 75 °C can effectively soften and remove the oil, dust and some water-soluble impurities on the cathode surface. The temperature of the hot water can reduce the viscosity of the oil, making it easy to detach from the cathode surface, and will not damage the cathode material due to too high a temperature.

[0042] Activating the cathode surface: Hot water at an appropriate temperature can cause a certain degree of thermal vibration of the metal lattice on the cathode surface, thereby activating the cathode surface, increasing its active sites, being conducive to the adsorption and reduction deposition of nickel ions on the cathode surface during the electrowinning process, and improving the electrowinning efficiency and the deposition quality of nickel.

[0043] Preheating the cathode: Making the cathode reach a certain temperature before entering the electrowinning cell, reducing the temperature difference between the cathode and the electrolyte in the electrowinning cell, and avoiding the rapid condensation of the components in the electrolyte on the cathode surface or the generation of local temperature unevenness due to too large a temperature difference, thereby affecting the stability of the electrowinning process and the uniformity of nickel deposition.

[0044] Specifically, the pickling treatment of the cathode before entering the nickel electrowinning cell has the following advantages: Dissolve the oxide film: There is usually a natural oxide film on the cathode surface. A sulfuric acid solution with a concentration of 400 g / L to 700 g / L can effectively dissolve this oxide film, exposing the fresh metal surface, enabling nickel ions to directly obtain electrons and be reduced and deposited on the active metal surface, improving the efficiency of the electrowinning reaction and the current efficiency, and reducing the increase in resistance and electrode polarization caused by the presence of the oxide film.

[0045] Remove metal impurities: Pickling can dissolve and remove some metal impurities attached to the cathode surface, such as iron, copper, etc. If these impurities exist on the cathode surface during the electrowinning process, they may deposit together with nickel, reducing the purity of the electrowon nickel and affecting the product quality. Removing them through pickling can improve the purity and quality of the electrowon nickel.

[0046] Microscopically roughen the surface: During pickling, the sulfuric acid solution micro-etchs the cathode surface, making the cathode surface microscopically rougher and increasing the specific surface area of the cathode. This can improve the adsorption capacity and reaction activity of the cathode to nickel ions, facilitating the uniform deposition of nickel ions on the cathode surface and improving the crystal morphology and appearance quality of the electrowon nickel.

[0047] Furthermore, during pickling treatment, the soaking time is controlled within 30 - 120 s to effectively remove the oxide film and impurities while avoiding over-pickling from corroding the cathode and affecting the performance and service life of the cathode. Different cathode materials and surface conditions may require appropriate adjustment of the pickling concentration and time.

[0048] The production method of electrowinning nickel with an insoluble anode provided by the present invention has many advantages such as low labor intensity and simple process flow. It can also guide production and improve production capacity.

[0049] In summary, different from the prior art, for the production method of electrowinning nickel with an insoluble anode provided by the present invention, first, the pH value of the cathode solution before entering the cathode liquid high-level tank is set at 2.5 - 3.5, which can prevent hydrogen ions from discharging and precipitating hydrogen on the cathode or prevent the appearance of nickel hydroxide colloid near the cathode; then, the temperature of the cathode solution in the cathode liquid high-level tank is 65 °C - 75 °C, which can increase the activity of Ni 2+ in the cathode solution, thereby accelerating the discharge step of Ni 2+ and reducing the electrochemical polarization effect; finally, the nickel mass concentration of the cathode solution in the cathode diaphragm bag is not less than 55 g / L during the electrowinning process, which can inhibit the discharge and precipitation of other metal ions on the cathode and ultimately improve the nickel purity of the electrowon nickel product.

[0050] The above are only the preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for producing insoluble anode nickel electrowinning, characterized in that: include: S10, subjecting the cathode liquid having a pH value of 2.5 to 3.5 to heat exchange treatment and then flowing into the cathode liquid high-level tank, wherein the temperature of the cathode liquid in the cathode liquid high-level tank is 65° C. to 75° C.; S20, overflowing the cathode liquid from the cathode liquid high-level tank into the cathode diaphragm bag of the nickel electrowinning cell for electrowinning treatment, and finally precipitating electrowinning nickel on the cathode, while precipitating oxygen on the insoluble anode; wherein the nickel mass concentration of the cathode liquid in the cathode diaphragm bag is not less than 55g / L during the electrowinning treatment.

2. The method for producing insoluble anode electrolytic nickel according to claim 1, characterized in that: In the step S10, the cathode liquid is a deoiled nickel sulfate solution, and the pb 2+ ≤1mg / L, the TOC content of the cathode liquid is ≤40mg / L, the boric acid content of the cathode liquid is 3-5mg / L, and the nickel mass concentration of the cathode liquid is 85-95g / L.

3. The method for producing insoluble anode electrolytic nickel according to claim 1, characterized in that: In the step S10, low-pressure steam is introduced into the plate-frame heat exchanger to perform heat exchange treatment on the cathode liquid.

4. The method for producing insoluble anode electrolytic nickel according to claim 3, characterized in that: In the step S10, the pressure of the low-pressure steam is 0.2-0.5 MPa, and the temperature of the low-pressure steam is 170° C.-180° C.

5. The method for producing insoluble anode electrolytic nickel according to claim 1, characterized in that: In the step S10, the flow rate of the low-pressure steam is adjusted by automatically adjusting the opening of the steam electric regulating valve so that the temperature of the cathode liquid in the cathode liquid high-level tank is 65° C. to 75° C.

6. The method for producing insoluble anode electrolytic nickel according to claim 1, characterized in that: In the step S20, the temperature of the cathode liquid in the cathode diaphragm bag is 60°C to 70°C.

7. The method for producing insoluble anode electrolytic nickel according to claim 1, characterized in that: In the step S20, the cathode is any one of a nickel starting plate, a stainless steel plate, and a titanium plate, and the insoluble anode is a lead alloy anode or a titanium-iridium anode.

8. The method for producing insoluble anode electrolytic nickel according to claim 1, characterized in that: In the step S20, the cathode is subjected to a scalding treatment or a pickling treatment before entering the nickel electrowinning cell.

9. The method for producing insoluble anode electrolytic nickel according to claim 1, characterized in that: In the step S20, the scalding treatment uses water at 65°C to 75°C, and the pickling treatment uses 400g / L to 700g / L H2SO4 for soaking for 30 to 120s.

10. The method for producing insoluble anode electrolytic nickel according to claim 1, characterized in that: In the step S20, the flow rate of the cathode liquid flowing into the cathode diaphragm bag is maintained at 400 L / h~600 L / h by adjusting the valve and maintaining the flow meter.

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