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Developing the next major nickel project in Brazil

Process

The Araguaia Nickel Project will utilise a low risk proven process technology called the Rotary Kiln Electric furnace (RKEF) to produce a high-grade ferronickel product to sell into for the stainless-steel market. Today the RKEF process is in operation in over 40 mines around the world and accounts for a significant portion of the nickel produced annually.

Ausenco Pty Ltd was commissioned by Horizonte to undertake the engineering of the process plant for the FS.

Detailed metallurgical test work has been completed on the ANP ore. This included initial lab and bench scale test work leading to a fully integrated pilot campaign which demonstrated the full RKEF flowsheet, on a representative bulk sample of 220 tonnes (wet) over a 10-day period operating 24 hours per day.

The key steps in the RKEF flowsheet are summarised below and can been seen in the video.

  • Run of Mine (ROM) ore, at an average moisture content of 34%, is first blended to meet metallurgical processing requirements, then transported to the primary crushing stage. Here the ore is sized using two stages of crushing to match the requirements of the subsequent steps. A mineral sizer with a 200 mm gap is used for primary sizing, while a mineral sizer with a 50 mm gap is used for the final stage.
  • The ore is then homogenised, partially dried and agglomerated to an average moisture content of 18% in a rotary dryer (4.5 m diameter x 40 m long) and fired with pulverized coal.
  • The dried agglomerated ore is then fed to the rotary kiln with the addition of reductant coal. In the kiln, the ore is completely dried, calcined to remove chemically-combined moisture, and the iron and nickel oxides are partially pre-reduced. Kiln dust is recycled to the process at the primary crushing stage ahead of the dryer/agglomerator.
  • Calcine from the kiln is then transferred to the electric furnace where further reduction of the nickel and some of the iron is achieved, and melting and separation of the metal and slag occurs at high temperature. Slag is tapped at a temperature of around 1,575°C, while FeNi metal is tapped at a temperature of close to 1,500°C.
  • After tapping, the melt is transferred by ladle to the refining stage. The final FeNi product containing 30% Ni is shotted with water, screened, dried and stockpiled prior to dispatch to the port on trucks where it either bagged or loaded bulk into sea containers for shipping to customers.
  • The electric furnace slag is granulated and transferred to the slag repository by truck

RKEF Process Flow Sheet for the Araguaia Nickel Project

Araguaia Process Flow
 

 

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