The behaviour of coal mineral carbonates in a simulated coal flame

Abstract

The flame behaviour of the most important carbonates in European import coals has been investigated. The flame tests were performed in a laboratory facility in which the environment of a coal burner was simulated. For the tests the coal minerals were separated from the coal by float-sink separation. Electron microscopy was used to determine the size and morphology of the particles sampled from the flame. The viscosity of the particles was derived from tests of their adherence to refractory deposit plates placed in the flame. Calcite (CaCO 3) particles of 60 μm, a typical size in pulverized coal, broke up into fragments approximately ten times smaller. The time taken for complete fragmentation corresponded to the time calculated for the decomposition of the calcite. None of the ‘siderite’ samples tested showed fragmentation. Detailed analyses with TGA MS (thermogravimetry coupled with mass spectrometry) were performed to determine the actual fraction of FeCO 3 in the ‘siderite’ samples. Flame products of siderite proper had high viscosity. Siderite particles with embedded silicates had flame products of low viscosity. Ankerite (CaFe(CO 3) 2) did not fragment and the flame product was fluid.