DETERMINATION OF ALKALI TRACES IN COAL COMBUSTION BY EXCIMER-LASER INDUCED FRAGMENTATION FLUORESCENCE

Gas phase sodium concentrations were measured in situ in the flue gas of a fluidised bed reactor using the excimer laser induced fragmentati on fluorescence (ELIF) technique. Several different coals were investi gated for a fixed set of reactor conditions at approximately 1 bar tot al pressure. Measured signals were converted to absolute concentration s using a calibration system that monitors alkali compounds under well -defined conditions. Concentrations ranging from the sub-ppb region to 25 ppb were obtained. Contrasting concentration histories were observ ed for the brown and hard coals studied