How do rotary kilns prepare laterite ore for nickel smelting?

Rotary kilns are essential in the nickel processing of laterite ores because these ores contain high levels of moisture and chemically bound water, often ranging from 35 to 40 percent.1

Because laterite ores are oxides and cannot be concentrated using conventional methods, large volumes of material must be processed. Rotary kilns perform two critical functions in preparing this ore for smelting:1

• Drying: Large rotary-kiln furnaces are used to remove the moisture present in the ore.1
• Dehydration and Reduction: These kilns are also used to remove chemically bound water in the form of hydroxides. Reduction kilns, which can exceed 100 metres in length, provide the necessary retention time to prepare the ore for the subsequent reduction of nickel oxide to nickel metal in electric furnaces.1

This preparation is vital because, unlike sulfide ores, laterite ores do not produce significant reaction heat during smelting, requiring substantial external energy input to reach the high temperatures necessary for processing.12