Thermal analysis of materials based on calcium sulphate derived from various sources

The paper presents and discusses the results of raw materials investigations based on calcium sulphate derived from various origins. The aim of these investigations was the evaluation of perspectives of using flue gas desulfurization gypsum (FGDG) as a potential raw material in the fertilizer industry, in comparison with the currently applied raw materials and others (anhydrite, natural gypsum, phosphogypsum, synthetic building plaster). To preview a new potential industrial application of FGDG, the investigations were focused on thermal analysis (thermogravimetry, differential scanning calorimetry) coupled with mass spectrometry, X-ray fluorescence, Fourier transform infrared spectroscopy and inductively coupled plasma optical emission spectroscopy. The chemical composition and thermal analysis of FGD gypsums in comparison with other samples based on CaSO4 revealed their high purity with low concentration of impurities and heavy metals. Only for one FGDG sample, the concentration of mercury exceeded the acceptable limit. The FGD gypsums seem to be attractive raw materials in the fertilizer industry.