Sinter formation in zinc roasting

Excessive sinter formation in zinc roasters leads to defluidisation of the bed so that production time is lost in clearing the collapsed bed from the roaster in preparation for restart of the roaster process. At Exxaro's Zincor plant the roaster feed concentrate consisted of a blend of Rosh Pinah, Black mountain and an import concentrate. The possible formation of unwanted sinter material was investigated by thermochemical simulation of the roaster process using FactSage software. The mineralogical composition of the individual feed concentrate streams was quantified by QemScan analyses. This mineralogical analysis was simplified and then used as input into the FactSage simulation calculations. The thermochemical simulation results were used to aid in the process interpretation of mineralogical analyses of samples from a failed bed, as compared to an acceptable roaster product sample.