Mass spectrometric investigations on the release of inorganic species during gasification and combustion of Rhenish lignite

To reduce problems such as fouling, slagging and corrosion, which can occur during thermal utilisation of lignite, an enhanced understanding of the underlying release mechanisms for the involved Na-, K-, Cl-, and S-species is needed. Therefore basic investigations have been performed in an atmospheric tube furnace at 1400 °C under gasification and combustion like conditions in lab-scale experiments. Molecular beam mass spectrometry has been used for on-line qualitative and semi-quantitative analysis of the hot product gas. 34H2S+ has been formed during gasification experiments, while 64SO2+ has been formed during combustion experiments. 36HCl+, 58NaCl+, 39K+ (assumed to be partly a fragment of KCl) have been the main alkali and chlorine species and have been released mainly during pyrolysis phase. Linear correlation analysis has been undertaken to investigate the dependence of coal composition on the release of Na-, K-, Cl, and S-species. The correlations have been found to be similar for both gasification and combustion experiments. The release of 34H2S+ and 64SO2+ is in high negative correlation with the Ca/S ratio and in high positive correlation with the S-content of the coals. The release of 36HCl+ shows a negative correlation with the Na/S ratio and the Na/Si ratio of the lignite under investigation. The release of 58NaCl+ depends with negative correlation on the S/Cl ratio and the content of Al + Si of the investigated lignite. The experimental results have been compared with thermodynamic equilibrium calculations. The release of H2S, SO2, and NaCl could be predicted with sufficient accuracy, though the release of HCl and K-species could not satisfactorily be predicted.