A field study on the trace metal behavior in atmospheric circulating fluidized-bed coal combustion
Trace element behavior in atmospheric circulating fluidized-bed combustion (CFBC) of Venezuelan bituminous coal was studied by determining particle size distributions in the CFBC flue gas. The size distributions of calcium, iron, aluminium, and 21 trace elements, Sc, V, Cr, Mn, Co, Ni, Zn, Ga, As, Se, Sr, Cd, Sb, Cs, Ba, La, Ce, Sm, Lu, Pb, and Th, in the size range 0.01--70{micro}m, were determined by collecting aerosols with a low-pressure impactor-cyclone sampling train from the flue gases of an 80-MW(th) CFBC boiler upstream of the electrostatic precipitator. The collected samples were analyzed gravimetrically and with instrumental neutron activation analysis (INAA), particle-induced X-ray emission analysis (PIXE), and inductively coupled plasma mass spectrometry (ICP-MS). The number size distributions of the aerosols were determined with a differential electrical mobility method in the size range 0.01--0.8 {micro}m. In the ultrafine particle mode, i.e., D{sub p} < 0.1 {micro}m, the CFBC number concentrations varied strongly during the experiments, being one to two orders of magnitude lower than those observed in pulverized coal combustion. For all of the elements studied, 75% or more were found in particles larger than 5{micro}m. None of the studied elements showed significant vaporization and subsequent chemical surface reaction or condensation in the CFBC. The Sr, Se, V, Zn, Ga, Cs, Ba, La, Sm, Lu, and Th size distributions resembled those of aluminium, suggesting their occurrence in aluminosilicate-rich particles in the fly ash. The association of the trace elements with aluminium in the fly ash particles may result from reactions of the trace elements with the aluminosilicate mineral particles inside the burning coal particles, or their initial occurrence in association with these minerals.
- OSTI ID:
- 93164
- Report Number(s):
- CONF-940711-; TRN: IM9537%%207
- Resource Relation:
- Conference: 25. international symposium on combustion, Irvine, CA (United States), 31 Jul - 5 Aug 1994; Other Information: PBD: 1994; Related Information: Is Part Of Twenty-fifth symposium (international) on combustion; PB: 1838 p.
- Country of Publication:
- United States
- Language:
- English
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