Investigations on the influence of steam on the release of sodium, potassium, chlorine, and sulphur species during high temperature gasification of coal

Basic investigations on the release of alkali metal, chlorine, and sulphur species form a crucial element in designing control measures and to develop hot gas cleaning strategies for coal gasification systems. Together with other experimental approaches a large body of useful data has already been delivered in this area, but the underlying reaction mechanisms are not yet sufficiently understood. Therefore, release experiments were done in lab-scale with six hard coals and four lignites at 1400 degrees C, 1 atm and a gas stream of He/7.5% O-2 and He/7.5% O-2 and additional steam, respectively. The molecular beam mass spectrometry technique used for hot gas analysis is well established and is able to detect and differentiate key chemical species released during the different phases of gasification. Main species detected by MBMS were Na-23(+), (H2S+)-H-34, (HCl+)-H-36, K-39(+)/(NaO+)-Na-39, (KOH+)-K-56, (NaCl+)-Na-58, (SO2+)-S-64, and (KCl+)-K-74. The release of these inorganic species occurred for the most part during devolatilisation phase and is strongly influenced by steam. Especially, the amount of alkali metal hydroxide compounds increased significantly under the influence of steam. (C) 2011 Elsevier Ltd. All rights reserved.