In the non-ferrous metal smelting industry, nickel is an indispensable strategic resource. However, during the pyrometallurgical process, a large amount of nickel smelting slag is produced, which still contains considerable amounts of valuable metals such as nickel and cobalt. How can these be recovered in an economical, efficient, and environmentally friendly way?
Hydrometallurgical technology, with its advantages of high recovery rate, low energy consumption, and environmental friendliness, has become the preferred process for recovering nickel from smelting slag. The main process flow of wet nickel recovery includes: acid leaching → filtration → purification → electrolysis.
The core of wet recovery lies in the purification and concentration stages, where the choice of extraction equipment directly determines the overall efficiency and success of the process. The CWL-M centrifugal extractor, independently developed by Zhengzhou Tiei Extraction Technology Co., Ltd., is a new, efficient, and energy-saving extraction and separation equipment. It offers advantages such as short stage residence time, rapid phase separation, high extraction efficiency, and reduced solvent recovery and regeneration costs, and is widely used in nickel extraction applications.
CWL-M Centrifugal Extractor
- High-Efficiency Recovery: Featuring high mass transfer efficiency, with single-stage extraction efficiency exceeding 95%, the total nickel recovery rate can reach over 99.5%.
- Superior Separation: Powerful centrifugal demulsification ensures clear phase separation and extremely low organic phase entrainment loss.
- Economic and Energy-Saving: Low equipment holdup significantly reduces the consumption of costly extractants and overall operating costs.
- Environmentally Friendly and Safe: Fully enclosed operation eliminates unorganized VOC emissions, ensuring a clean and safe working environment.
Process Flow of Wet Recovery of Nickel from Smelting Slag
1.Pretreatment and Leaching
The nickel smelting slag is first crushed and ground to increase its specific surface area. Then, an acidic leaching agent (such as sulfuric acid) is used under specific conditions to dissolve valuable metals like nickel and cobalt from the slag into ionic form (Ni²⁺), producing a leach solution.
2. Purification and Impurity Removal
The leach solution is complex and contains various impurity ions such as iron, aluminum, copper, zinc, and magnesium. Through neutralization and precipitation, most of the easily hydrolyzed impurities like iron and aluminum are removed in advance, creating favorable conditions for subsequent efficient extraction.
3.Solvent Extraction and Purification: This is the key step for separating and enriching nickel.
Extraction: A specific extractant with selective complexation ability for nickel ions is used. When the nickel-containing leach solution (aqueous phase) and the extractant (organic phase) are thoroughly mixed and contacted in a centrifugal extractor, nickel ions transfer from the aqueous phase into the organic phase, while most residual impurities remain in the aqueous phase — achieving the separation of nickel from impurities.
Stripping: The nickel-loaded organic phase is then mixed again in the centrifugal extractor with a stripping agent (typically a more dilute sulfuric acid solution). Under stripping conditions, nickel ions are “stripped” from the organic phase back into the aqueous phase, resulting in a high-purity, high-concentration nickel sulfate solution. The organic phase is regenerated and can be recycled for reuse.
4.Subsequent Processing
The purified nickel sulfate solution obtained from the stripping step can be directly used for electrolytic nickel production or crystallized into nickel sulfate crystals, which serve as raw materials for high-end products such as battery materials.
Application Case
A large smelting enterprise adopted the Tiei Extraction CWL-M centrifugal extractor to treat nickel smelting slag leach solution. As a result, the total nickel recovery rate increased from the original 92% to 99.2%, while organic phase losses were reduced by 60%. The savings in reagent costs alone amounted to several million RMB per year, and the resulting nickel sulfate product met battery-grade purity standards, delivering outstanding economic benefits.
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