ROASTING REDUCTION STUDY OF GREEK NICKELIFEROUS LATERITES

In the present work, a reduction roasting experimental study of Greek nickeliferous laterite samples with a gaseous reducing mixture – CO:N2- is presented. The effect of parameters such as temperature, ore grain size, and composition of the reducing mixture were examined. It is deduced that the reducibility of intermediate type laterite sample, where iron appears mainly in the form of goethite (α-FeOOH), is considerably higher than that of limonitic type laterite samples, where hematite (α-Fe2O3) is the predominant iron mineral phase. The degree of reduction of the limonitic type laterite samples does not exceed 50%, while it reaches 95% in the case of the intermediate-type laterite sample under the same experimental conditions. Increasing the temperature in the range 750-900°C does not considerably favor the reduction of the limonitic type laterites, whereas decrease of ore grain size of the limonitic-type ore samples and more intense reducing conditions increase the reduction. The considerably higher specific surface area values of the intermediate laterite samples diminish the effect of the ore grain size and this can be regarded as the critical parameter leading to the higher reducibility of this ore.