At the 2025 Indonesia Mining Conference & Critical Metals Conference – Nickel-Cobalt-NEV Venue, Sun Haikuo, President of China ENFI Engineering Corporation, shared insights on the topic of “Selecting the Development Process Route for Indonesia’s Laterite Nickel Ore.”
Mainstream Technologies for Laterite Metallurgy
Utilization Routes for Laterite Nickel Ore
The high-pressure acid leaching (HPAL) process is suitable for treating limonite-type laterite nickel ore, while weathered-type laterite nickel ore is better suited for the RKEF process.
Currently, there is no economically viable and proven technology for processing medium-grade ore. More practical efforts are needed to identify reliable new technologies.
Main Metallurgical Processes for Nickel Laterite Ore
Mature Pyrometallurgical Process – RKEF
The RKEF (Rotary Kiln-Electric Furnace) process is a mature pyrometallurgical process primarily used for treating nickel laterite ore. This process involves drying and reducing the nickel laterite ore using a chain grate and a rotary kiln, followed by smelting and reduction in an electric furnace to produce crude ferronickel (FeNi) containing nickel and some iron.
Ore Characteristics: High nickel content (1.6-2.2%), low cobalt content, and high magnesium oxide content.
Recovery Rate: Nickel recovery ranges from 92% to 97%.
Mature Pyrometallurgical Treatment Process – RKEF
Advanced Hydrometallurgical Technology – HPAL
The HPAL process achieves efficient and selective leaching of nickel and cobalt under high-temperature conditions, while concentrating most impurities such as iron and aluminum in the tailings, ensuring efficient recovery of valuable metals.
Ore Characteristics: Low nickel content (0.8-1.5%), high iron content (40-50%), and low silica and magnesium oxide content.
Recovery Rate: Nickel recovery exceeds 90%, and cobalt recovery exceeds 90%.
As a mature hydrometallurgical process, HPAL is a systematic technology. During project implementation, it is necessary not only to meet the basic requirements of the process reactions but also to adopt a systematic approach to ensure extremely high standards in terms of operability, maintainability, automation, safety, economy, and environmental protection, aiming to achieve stable and efficient system operation.
Key technologies for the pressure leaching system include, but are not limited to, the following aspects:
Pressure Leaching System:Including technologies such as raw material preparation, slurry preheating, pressure leaching, flash evaporation, and off-gas treatment.
Heat Balance Technology:Such as heat recovery or cooling.
Equipment and Material Selection:Proper selection of pressure leaching equipment and materials.
Automation and Safety:Achieving a high level of automation and safety.
Operation and Maintenance System
Mature Hydrometallurgical Process – HPAL
Comparison Between RKEF and HPAL
Cost Analysis:
The cash cost of producing MHP using the HPAL process is approximately $8,000-$10,000 per mt of nickel.
The cash cost of producing FeNi using the RKEF process is approximately $9,000-$12,000 per mt of nickel.
Note: Assumes the use of a high-grade ore pricing mechanism.
Carbon Emissions
China’s Equipment Manufacturing and Process Maturity – Significantly reduces the capital expenditure for HPAL compared to earlier stages; compared to pyrometallurgical processes, hydrometallurgical processes have lower cash costs and carbon emission intensities.
Side-blown technology
Process flow for producing nickel matte from laterite nickel ore using side-blown technology
Why develop side-blown technology?
Against the backdrop of “carbon peaking and carbon neutrality” and restrictions on coal-fired power plants, the side-blown process, compared to the RKEF process, has the advantage of not relying on large power plants, with relatively lower capital expenditure and a shorter construction period.
Challenges and problems faced by traditional side-blown furnaces:
Extending the service life of the furnace lining:During the molten pool smelting process, when the temperature exceeds 1,550°C, intense reactions can cause severe corrosion of the furnace lining, significantly shortening its service life.
Improving thermal efficiency:The reduction process of iron requires a significant amount of heat. To produce nickel matte, nickel and most of the iron need to be reduced first, followed by sulfidation treatment. This process requires both a reducing atmosphere and sufficient heat.
Durability of the lance body: At high temperatures up to 1,500°C and with intense heat supply, the lance body of the side-blown furnace is prone to severe corrosion, affecting its service life.
Achieving multi-step reduction and metal separation:Producing high-quality nickel matte requires strict control of the reducing and sulfidation atmosphere to prevent over-reduction or under-reduction. In addition, intense stirring in the molten pool is not conducive to the effective separation of slag and metal. The production of iron-nickel alloy has higher requirements for operating conditions.
High requirements for ore specifications:Traditional side-blown furnaces have high requirements for ore specifications and poor adaptability, requiring the use of suitable raw ore or blended ore to achieve ideal production results.
ENFI Submerged Combustion Bath Smelting Process (SSC)
ENFI has developed an innovative side submerged combustion smelting technology (SSC). Compared to traditional side-blown furnaces, the outstanding advantage of SSC lies in its furnace structure that adopts submerged combustion and vertical cooling.
This technology, pioneered by ENFI, possesses exclusive intellectual property rights for “submerged combustion heating in the bath” and has obtained multiple invention patents. The SSC smelting process has now been successfully applied in various fields such as the recycling of secondary copper resources, secondary lead resources, and hazardous waste treatment.
On this basis, ENFI has further developed the Blowing Reduction Electric Furnace (BREF) technology suitable for the production of iron-based alloys. This technology integrates and expands upon the SSC smelting and EF smelting technologies, fully leveraging its rich technical experience.
Enhancing reaction kinetics: Using submerged lances to inject oxygen-enriched air and fuel at high speed into the molten pool promotes intense stirring of the melt. Optimizing thermodynamic conditions: Directly supplying heat to the molten pool through submerged combustion improves energy utilization efficiency.
Summary
The key to optimizing resource utilization and enhancing project benefits lies in selecting the most suitable treatment process for different types of laterite nickel ore. Currently, the high-pressure acid leaching (HPAL) process is suitable for limonite, while the Rotary Kiln-Electric Furnace (RKEF) process is more suitable for saprolite.
When producing nickel-cobalt products for the battery market, the HPAL process has a cost advantage over the RKEF and side-blowing processes due to its ability to process low-nickel, high-cobalt limonite.
If the RKEF process is used to produce nickel matte, additional facilities need to be added on the basis of FeNi/NPI production, along with increased costs for sulphidizing and desulphurizing agents. When nickel sulphate prices are not significantly higher than those of FeNi/NPI, the cost competitiveness of this process is low.
When using side-blowing technology to treat laterite nickel ore with moderate nickel-cobalt content, the production of nickel matte has investment and cost advantages over the RKEF process. However, to optimize production line operations, several key issues need to be addressed: extending the service life of furnace linings and lances, improving heat supply efficiency, and gradually achieving iron reduction and effective separation of metal and slag.
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