The nickel sulfide anode is gradually dissolved in the electrolysis process, the anode potential is 1.2V, and the precious metal elements such as gold and platinum whose standard potential is higher than the anode potential in the anode are insoluble and enter the anode mud, and iron , copper , lead , zinc, etc. which are lower than the anode potential. Dissolved into the solution, most of the sulfur enters the anode mud; the nickel ions in the solution are electrodeposited at the cathode. Therefore, the quality of the electro-nickel can be ensured by selecting the appropriate electrolyte composition and electrolysis technology conditions.
The composition of the catholyte is in addition to Ni 2 + and 
, But also contains a certain amount of Cl -, Na +, boric acid, and organic impurities. The cation has depolarization effect, the migration speed is fast, which is beneficial to reduce the cell voltage and improve the current efficiency; the sodium ion can improve the conductivity of the electrolyte, reduce the cell voltage and power consumption; boric acid is the electrolyte buffer, and the pH is stabilized. The effect of flattening the surface of the electric nickel plate. Organic matter should reduce the cathode mass, and its content should be reduced as much as possible (<1mg/L); the lower the content of impurity elements, the better the quality of nickel. Since the current efficiency of the anode and the cathode differs by 12% to 14% during electrolysis, and the purification slag removes part of the nickel liquid, in order to ensure the stability of the nickel ion concentration in the anolyte, it is necessary to replenish nickel. The chemical composition of the catholyte is listed in Table 1.
Table 1 Main chemical constituents of various raw materials for melt-casting nickel sulfide anode plates (%)
raw material name | Ni | Cu | Fe | Co | S |
Secondary nickel concentrate | 66.5 | 2.8 | 2.3 | 1.00 | 23.8 |
Anode residue | 68.1 | 3.3 | 1.5 | 0.98 | 24.5 |
Smoke | 20.9 | 2.9 | 2.1 | 0.52 | 8.1 |
Sorghum residue | 68 | 3.3 | 2.0 | 0.80 | 30.9 |
The main technical parameters of nickel anodic electrolysis of various manufacturers are listed in Table 2.
Table 2 Main parameters of nickel sulfide anode electrolyzer
factory | Jinchuan Company | Chengdu Electric Steel Factory | Chongqing Electric Metallurgical Plant |
Electrolysis temperature / °C | 65~70 | 60～65 | 65 |
Current density / A · m - 2 | 230~250 | 180~220 | 170～200 |
Slot voltage / V | 3.2 to 4.5 | 2.6~3.5 | |
Same level center distance / mm | 190 | 190 | 190~200 |
Catholyte flow rate / (L ·) (A · h) - 1 ) Anolyte flow rate / (Ml · (min · bag) - 1 ) | 0.065 380~420 | 0.08 300 | 0.085 |
Yin-anode area liquid level difference / mm | 30~50 | >20 | 50~60 |
Anode cycle / d | 9 to 10 | 9 to 10 | 6 to 9 |
Cathode cycle /d | 4~5 | 3 | 6~7 |
New liquid dosage / (m 3 · t - 1 (nickel)) | 65~70 | 60～80 |
The main equipment for nickel sulphide anodic electrorefined steel is electrolysis tank and purification device. The electrolyzer is generally a reinforced concrete structure with a lining as if it were a material. It must also be equipped with a diaphragm frame and a diaphragm bag. The main parameters of the electrolytic cell of the domestic production plant are listed in Table 3.
Table 3 Main parameters of nickel sulfide anode electrolyzer
factory | Jinchuan Company | Chengdu Electric Steel Factory | Chongqing Smelter |
Annual production capacity / t | 40000 | 5000 | 600 |
Electrolytic cell, length × width × depth / (m × m × m) | 7.34×1.15×1.48 | 5.0×1.43×1.19 | 7.60×0.70×1.20 |
Total number of slots / one | 384 | 166 | 17 |
Among them, the liquid tank | 96 | 56 | |
Slotted trough | 38 | 6 | 1 |
Electrolytic cell material | Reinforced concrete lining epoxy | Reinforced concrete lining epoxy phenolic resin | Reinforced concrete lining epoxy |
Anode, length × width × thickness / (mm × mm × mm) | 840×340×(50～55) | 750×320×(35～40) | 470×650×(25～30) |
Number of anodes per slot | 382 | 252 | 41 |
Cathode sheet, length × width (mm × mm) | 880×860 | 860×920 | 490×670 |
Number of cathodes per slot | 37 | 29 | 40 |
Same pole center distance / mm | 190 | 190 | 190~200 |
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