Effect of siderite in coal on reductive pyrolytic analyses

The effect of the presence of siderite (FeCO3) in coal on the atmospheric pressure–temperature programmed reduction (AP–TPR) analysis of coal is studied. Siderite is added to demineralised Maritza Iztok (lignite) and raw Nowy Wirek (high volatile bituminous) coal before analysis. Results show an extra troilite FeS peak in the AP–TPR profiles for both siderite doped coals. The mechanism of H2S capture by siderite is discussed on the base of a model reaction. Additionally, the formation of troilite from the pyrite present in the initial coal during the AP–TPR experiment was monitored by scanning electron microscopy with an energy dispersive X-ray analyser (SEM–EDX). During AP–TPR analysis the evolving H2S is captured by FeO or FeCO3 and FeS is formed. These phenomena disturb the AP–TPR profiles as well as the sulphur recovery.