EFFECTS OF TEMPERATURE AND ADDITIVES ON ASH TRANSFORMATION AND MELTING OF HIGH-ALKALI-CHLORINE COAL

Abstract

The high contents of sodium and chlorine in Shaerhu coal aggravate severe slagging ash deposition and corrosion in boilers. Adding proper additives is an effective way to reduce slagging ash deposition and corrosion. Based on the experimental study, this paper investigated the effect of combustion temperature, types of additives, and its amount on the ash transformation and melting of high sodium chloride Shaerhu coal. The ash melting characteristics, elemented compositions and mineral compositions of the ash produced under different conditions were characterized. Results showed that the contents of calcium, magnesium, and sulphur in the coal ash varied slightly with the temperature increasing. Chlorine and sodium released rapidly from coal at 550–815 °C and 550–700 °C, respectively. At 1050 °C, calcium silicate was observed as the main component of the ash. The addition of different additives had no significant effect on chlorine and sodium capture. The addition of silicon species lowered the ash fusion temperatures, while the aluminum had an opposite effect. To prevent the furnace from slagging, a high aluminum additive is proposed to be adopted.