Physico-chemical characterization of slag waste from coal gasification syngas plants: Effect of the gasification temperature on slag waste as construction material

The ash fusion temperature determines the suitability of coal for the entrained flow gasification/combustion process. For this purpose, Indonesian KPU coal samples and their ash and slag contents were comprehensibly characterized via X-ray fluorescence (XRF), X-ray diffraction (XRD), scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS), and inductively coupled plasma optical emission spectrometry (ICP-OES) methods. To assess their environmental impacts, leachate solutions were prepared from the discharged slag for ICP-OES analyses. The experimental data were comprehensively explained in terms of ash fusion temperatures and fluidity properties of the coal ashes. More specifically, the coal slagging behavior inside of coal gasifier/combustors necessitated optimization of the operational conditions for subsequent mild slagging. The currently used coal gasification operation temperature ranges favored mild slagging at 1200 to 1300 °C (19.9 to 20.1 bar) and incomplete slagging at 1100 to 1200 °C (19.7 to 20.4 bar), which was attributed to the insufficient gasification/combustion temperature for the coal samples under the latter gasification/combustion conditions. The metallic elemental composition analysis results via ICP-OES performed on the leachate solution therefrom excluded the possibility of secondary environmental pollution from the discharged slag.