Study on the effects of steam on the precipitation characteristics of sodium during coal thermal conversion

Abstract

The char samples were prepared from the coal impregnated with NaCl under different steam concentrations and temperatures. The mode of occurrence of sodium and the contents of sodium in different chars with the same conversion ratio were analyzed by inductively coupled plasma mass spectrometry. The effects of steam and temperature on the migration and transformation of sodium in the coal during the thermal conversion processes were studied. The results showed that the increase of steam concentration enhanced the release of water-soluble sodium during the thermal conversion of coal and promoted the transformation of water-soluble sodium into ammonium acetate, hydrochloric acid and insoluble sodium. As a result, the release of sodium was suppressed to a certain extent. It was also observed that increasing the reaction temperature could promote the release of water-soluble sodium and promote the transformation of water-soluble sodium to the other soluble forms of sodium. The evolution of char structure was an important influence on the release of sodium. The results revealed that the degrees of char condensation increased with the steam gasification reaction. The formation of large aromatic ring structures from the condensation of the small aromatic rings played the important role in the encapsulation of sodium, which would inhibit the release of sodium.