Existence form of sodium in high sodium coals from Xinjiang and its effect on combustion process

The existence form of sodium in Xinjiang coals was studied by extraction with distilled water, ammonium acetate and hydrochloric acid step by step. The extraction liquid and the residual coal samples were analyzed using an ion chromatography and an inductively coupled plasma atomic emission spectroscopy. The influences of different forms of sodium on the combustion characteristics of the high sodium coal were evaluated by the ignition temperature, the burnout temperature and the combustion characteristic index. The results indicate that the sodium existing in the coals is mainly in the form of water-soluble sodium, while the proportions of acid-soluble sodium and insoluble sodium are smaller. The particle size and inner pore structure of coal may have great influences on the water-soluble sodium content in coal samples, while the organic sodium contained in different particle size ranges of coal remains relatively constant. The water-soluble sodium and chlorine in different coals differ from each other. The water-soluble sodium would increase the ignition temperature and burnout temperature and decrease the combustion characteristic index, while the organic sodium would have catalysis on the combustion of coal.