Modes of occurrence of sodium in coals

The occurrence of sodium in coals is relevant closely to boiler tube fouling problem and erosion of gas turbine in PFBC. Here the modes of occurrence of sodium in coals were investigated by using sequential extraction procedures with distilled water, 1mol/ L ammonium acetate and 1mol/L hydrochloric acid in turn. The sequential extraction tests were carried out with 10 samples of coal in different ranks and particle sizes. Petrographic and proximate analyses were also proceeded at the same time. The results showed that the amount of total and insoluble sodium increased with the rank. More ammonium acetate -soluble sodium was found in rich initinite coals, and more water - soluble sodium in rich vitrinite coals. The amount of total and water - soluble sodium generally decreased as the particle size increased. The mole ratio of water - soluble sodium to chloride in coals differed from NaCl crystal which suggested that water - soluble sodium and chloring occurred independently in coals instead of NaCl molecules.