Wet metallurgical process of laterite nickel ore
The main industrial applications of wet metallurgical treatment of laterite nickel ore currently include reduction roasting ammonia leaching method and pressurized acid leaching method.
Wet metallurgy is a metallurgical method for extracting metals in liquid media, suitable for processing certain types of metal ores, including laterite nickel ore. At present, the wet metallurgical processes commonly used in industrialization include reduction roasting ammonia leaching and pressurized acid leaching.
1.Reduction roasting+ammonia leaching process
- 1.Raw ore drying：First, dry the laterite nickel ore to remove moisture from the ore.
- 2.Reduction roasting：The dried laterite nickel ore is subjected to reduction roasting at a temperature of 600-700 ℃. This step usually needs to be carried out in a specialized furnace, such as a converter. During the roasting process, the oxides in the ore are reduced to metal oxides, such as nickel oxides.
- 3.Ammonia leaching：The roasted material is crushed and ground into powder, and then mixed with ammonia water for ammonia leaching. Ammonia leaching is the process of using ammonia water to dissolve metal ions, and nickel ions are dissolved in the complex formed by ammonia water.
- 4.Multi stage countercurrent ammonia leaching：In order to improve the extraction efficiency of nickel, multi-stage countercurrent ammonia leaching is usually used, which means that the leaching solution and fresh ammonia water flow in reverse between different levels to improve the metal recovery rate.
- 5.Sulfurization precipitation：The solution after ammonia leaching contains nickel ions and other impurity ions. By adding a sulfurizing agent, such as sulfur powder, nickel ions can combine with sulfides to form nickel sulfide precipitation.
- 6.Impurity removal：Separate the precipitated nickel sulfide from other impurities in the solution through physical or chemical methods such as solid-liquid separation.
- 7.Calcination：Finally, the precipitated nickel sulfide after impurity removal is calcined to convert it into nickel oxide. The calcination process is usually carried out in a high-temperature furnace to remove sulfur and form nickel oxide.
Technological advantages
- Applicability：This process is suitable for the treatment of laterite nickel ore with high magnesium oxide content (more than 10%) and low nickel grade (about 1%).
- Cost Benefit：Compared with other processes, the reduction roasting ammonia leaching method has better cost-effectiveness in treating low-grade ores.
- Environmentally friendly：The ammonia used in this process can be recycled and has a relatively small impact on the environment.
- Flexible operation：The process flow can be adjusted according to the properties and processing requirements of the ore, resulting in high operational flexibility.
- The reduction roasting ammonia leaching method is a wet metallurgical process suitable for treating specific types of laterite nickel ores, which has advantages such as high cost-effectiveness, environmental friendliness, and flexible operation.
2.Pressure acid leaching process
The pressurized acid leaching method is a wet metallurgical process suitable for treating low magnesium (aluminum) and high iron laterite nickel ores. This method uses dilute sulfuric acid to dissolve nickel under pressure conditions, and then purifies and recovers nickel through a series of chemical treatment steps.
- 1.Raw ore crushing： First, crush the laterite nickel ore to a certain size for subsequent processing.
- 2.Pressure acid leaching：The crushed ore reacts with dilute sulfuric acid (such as sulfuric acid or hydrochloric acid) under pressure conditions (230-260 ℃, 4-5MPa). During this process, nickel is dissolved into ionic form.
- 3.Impurity removal：The solution after acid leaching contains nickel ions and other impurity ions. By adding chemical reagents such as sodium hydroxide or ammonium hydroxide, impurities such as iron and magnesium can be precipitated, thereby purifying the nickel solution.
- 4.Hydrogen sulfide reduction neutralization：In order to reduce nickel ions to nickel metal and further neutralize acidic substances in the solution, hydrogen sulfide gas can be introduced into the solution.
- 5.Precipitation： Nickel metal in the solution after reduction and neutralization treatment precipitates in the form of nickel sulfide.
- 6.Nickel Product Extraction：After solid-liquid separation (such as filtration), the precipitated nickel sulfide can be further processed, such as drying and calcination, to obtain high-quality nickel products.
Technological advantages
- Applicability：The pressurized acid leaching method is particularly suitable for processing low magnesium (aluminum) and high iron laterite nickel ores, and has very good effects on these types of ores.
- High efficiency：Under pressurized conditions, the dissolution rate of nickel is faster and the efficiency is higher.
- High nickel recovery rate：Through precise chemical treatment steps, nickel can be effectively recovered, and the recovery rate of nickel is relatively high.
- Environmentally friendly： The acids and chemical reagents used in this process can be effectively controlled and can be recycled and reused to reduce environmental impact.
- Operation safety： Under pressurized conditions, special equipment and operating procedures are required, but at the same time, reaction conditions can be better controlled to ensure the safety of the operation.
- The pressurized acid leaching method is an efficient, environmentally friendly, and suitable wet metallurgical process for specific types of laterite nickel ores.
