Preliminary determination of the suitability of slags resulting from coal gasification as a pozzolanic raw material / Wstępne Określenie Przydatności Żużli Ze Zgazowania Węgla Jako Surowca Pucolanowego

Requirements for environmental protection, such as reducing emissions of CO2, NOx, and SO2 are the reason for growing interest in new technologies for coal utilization. One of the most promoted technologies is coal gasification. However, like any technology using coal, this process produces wastes - fly ash and slag. Due to the small number of coal gasification plants, these wastes are poorly understood. Therefore, before making decisions on the introduction of coal gasification technology, a waste utilization plan should be developed. This also applies to the slags formed in underground coal gasification technology. One of the options under consideration is to use these wastes as a component in mineral binders of a pozzolanic character. This paper compares the properties of two types of slags. The first slag (MI) comes from fuel gasification, and the second slag (BA) is from underground coal gasification. Slag MI can be classified as basic slag with a chemical composition similar to that of silica fly ash from coal combustion. Slag BA - because of its four times greater content of calcium oxide - belongs to a group of weakly basic slags. The main and only mineral component of slag MI is glassy phase. Slag BA forms - besides the glassy phase - crystalline phases such as mullite (3 Al2O3 · 2 SiO2), quartz (_-SiO2), anorthite (Ca(Al2Si2O8)), gehlenit (Ca2Al[(Si,Al)2O7]), wollastonite (Ca3[Si3O9]), 2CaO · SiO2, and 4 CaO · Al2O3 · Fe2O3. The results ofanalyses have shown that slag BA has better pozzolanic properties (the pozzolanic activity index is 75.1% at 90 days) than slag MI (69.9% at 90 days) The preliminary studies lead to the conclusion that these slags are characterized by very low pozzolanic activity and cannot be used as a pozzolanic material.