10 January 2025
From electric vehicle batteries to stainless steel, nickel is a metal with important applications in a variety of modern technologies. In Indonesia, Harita Nickel plays a key role in maximizing added value through a range of sustainable nickel processing methods.
In this article, we will discuss the two main nickel processing methods utilized by Harita Nickel, namely Rotary Kiln Electric Furnace (RKEF) and High-Pressure Acid Leaching (HPAL).
RKEF is a method that is often used to process high-grade nickel ore (saprolite nickel ore). It works by using intense heat to convert nickel ore into ferronickel, which can then be used in the manufacture of stainless steel.
The RKEF nickel processing process comprises several stages:
a. Separation of Nickel Ore
First, pieces of nickel ore larger than 2 cm are isolated.
b. Drying
Next, the nickel ore is dried using a rotary dryer at temperatures of 200-300 degrees Celsius. This process reduces the water content from around 40 to 20 percent.
c. Calcination
After that, the nickel ore is heated again, this time in a rotary kiln, to temperatures of 700-750 degrees Celsius, in order to remove any unnecessary elements.
d. Smelting
The heated ore is then melted in an electric furnace at a temperature of 1,600 degrees Celsius, in order to remove impurities from the ferronickel.
e. Molding
Finally, the molten ferronickel is molded into ingots and is ready to be transported for use in the steel industry.
Currently, Harita Nickel has 12 RKEF production lines, with a total capacity of up to 120,000 tons of nickel per year.
HPAL is a more complicated method and is normally used to process low-grade nickel ore, or limonite, which was previously considered to have no economic value and was therefore discarded as overburden. HPAL technology uses concentrated sulfuric acid, along with high temperatures and pressures, to extract nickel from its ore.
Below are the stages of the HPAL process:
a. Ore Washing
Limonite nickel ore is washed and separated from rocks and impurities to make slurr
b. Thickening Process
This slurry is then thickened until its solid content reaches 45 percent.
c. Leaching
Next, the slurry is piped into a pressure vessel, commonly called an Autoclave, as part of the extraction process. In this Autoclave, the slurry undergoes special treatment by mixing concentrated sulfuric acid, which is heated to temperatures of up to 250 degrees Celsius, and subjected to high pressures (50 bar) that are equivalent to pressures found on the seafloor at a depth of 500 meters. After that, all the materials are stirred by the agitator machine in the Autoclave, allowing nickel to dissolve in the acid and the other materials to settle at the bottom.
d. Separation
The liquid containing nickel is then separated from the slurry residue in seven counter current decantation (CCD) tanks.
e. Purification
After that, the Aluminum–Iron separation process (also referred to as the FeAl removal process) is carried out, before the nickel liquid is further processed to produce a mixture of nickel and cobalt known as Mixed Hydroxide Precipitate (MHP). MHP can be further refined at PT HPAL's new facility, the Nickel Sulfate and Cobalt Sulfate Plant, to produce nickel sulfate and cobalt sulfate that can be used for various technologies and products, including the raw materials for the manufacture of electric vehicle batteries.
Harita Nickel is the first company in Indonesia to successfully operate HPAL technology and produce MHP, nickel sulfate, and cobalt sulfate. Currently, Harita Nickel has six HPAL production lines with a combined capacity of 120,000 tons of nickel per year, operated by PT Halmahera Persada Lygend (PT HPL) and PT Obi Nickel Cobalt (PT ONC), each of which is responsible for three production lines.
This article has been reviewed by Deputy Head of the Technical Support Department at PT Halmahera Jaya Feronikel, Agung Aribowo; and the Technical Support Manager of PT Halmahera Persada Lygend, Dian Kristiyanto.
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