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In situ alkali concentration measurements in a pressuried, fluidized-bed coal combustor by excimer laser induced fragmentation fluorescence

1996; Elsevier BV; Volume: 26; Issue: 2 Linguagem: Inglês

10.1016/s0082-0784(96)80177-9

1878-027X

F. Greger, K. T. Hartinger, P. Monkhouse, J. Wolfrum, Herbert Baumann, Bernhard Bonn,

Petroleum Processing and Analysis

Absolute concentrations of total gas-phase sodium and potassium compounds were determined in the flue gas of a fluidized bed coal combustor at 10 bar using excimer laser-induced fragmentation fluorescence (ELIF). In this in situ and on-line technique, the alkali compound molecules are photodissociated by ArF-excimer laser light at 193 nm, whereby excited Na(32P) and K(42P) atoms are formed. Fluorescence from these atoms is simultaneously detected in two separate channels at 589 nm and 768 nm, respectively. The calibration system and data evaluation procedure to convert measured signals to absolute concentrations is described. Studies on lignite and hard coal under several different combustion conditions are reported. The measured concentrations span a dynamic range of more than three orders of magnitude, with a detection limit of <0.2 ppb for Na and K. Large differences between the coals in the release of alkalis were observed. For the lignite investigated, potassium-compound concentrations up to 800 ppb and sodium-compound concentrations up to 500 ppb were determined, whereas the concentrations for the hard coal were less than 10 ppb. These large variations in alkali release reflect the very different structures of the respective coals, emphasizing the influence of mineral coal components on release and recapturing of gas-phase alkali species. It is also clear that more detailed, systematic studies are needed for a proper understanding of alkali release in PFBC.