ABSTRACT
Sodium release in the early stages of coal combustion, under a range of temperatures and oxygen concentrations has been studied in a laboratory laminar flat flame burner. Coal particles were introduced into the flame and light from the particles and surrounding gases monitored with an optical spectrum analyser. Measurements on the atomic emission peaks in the visible light spectra obtained, allowed the comparison of sodium and potassium release from the particles under a range of conditions for fourteen UK power station grade coals of varying sodium and potassium content. Particle temperatures were also calculated from the same spectra. At 4% oxygen, minimum sodium and potassium release occurred at approximately 1600K for all the coals. Sodium and potassium release was greater at 12 and 20% oxygen than at 4% oxygen. At 20% oxygen concentration sodium release generally fell with increasing temperature. Sodium release was slightly higher at 0% oxygen than at 4%. This was thought to be due to the formation of refractory oxides in the presence of excess oxygen. There was generally little increase in coal particle temperature above the gas temperature at 4% oxygen, but at higher oxygen levels, particle temperature often exceeded gas temperature by more than 300K. There was no statistically significant correlation between sodium release and coal sodium content, sodium to ash ratio or chlorine content.
