The difficulty in mineral processing of carbonatic iron ore from the „Steirische Erzberg“ is the close intergrowth between the valuable mineral sideroplesite (Fe,Mg,Ca)CO3 and the gangue mineral ankerite Ca(Fe,Mg)(CO3)2. According to an investigation at the Department of Mineral Processing, liberation starts at a particle size below 1mm.
A possible solution for the separation of sideroplesite and ankerite is low-intensity magnetic separation after selective magnetizing calcination of sideroplesite.The formation of ferrite and in a lesser extent of magnetite at different degrees of calcination leads to a continuous distribution in the magnetic susceptibility of the roasted ore.
The size fraction of the iron ore suitable for the magnetizing calcination was subject to an investigation of the intergrowth characteristics of the carbonates.
Henry-Reinhardt diagrams showed that the degree of liberation of siderite does not vary very much in the size fractions 6,3mm down to 0,1mm.
Magnetic separation tests with the calcination product showed that the particle size and the degree of calcination have the most significant influence on the success of the separation. Drum rotation speed and feed rate have less effect.
A preliminary test showed that the calcination product has a certain capability for adsorption of SO2.