Volatilization of the heavy metals during circulating fluidized bed combustion of forest residue
Journal Article
·
· Environmental Science and Technology
- VTT Chemical Technology, Espoo (Finland). Aerosol Technology Group
- VTT Energy, Espoo (Finland). Aerosol Technology Group
- Vattenfall Utveckling AB, Stockholm (Sweden)
- Univ. of Gent (Belgium)
Increasing interest in using biomass for energy production has created a need to establish a method for its sustainable utilization. During combustion, the inorganic incombustible species in the biomass are converted into ash. The environmental impact on the heavy metals contained in the combustion product ash depends on the speciation of the heavy metals and the size distributions of the heavy metals in the ash. Therefore, the behavior of cadmium, lead, copper, and zinc was studied experimentally during circulating fluidized bed combustion (CFBC) of Swedish forest residue. The size distributions and concentrations of the heavy metals in the fly ash particles and in the gas phase were determined by low-pressure impacts and filters upstream of the convective back pass at 830 C. Downstream of the convective back pass at T = 150 C, the size distributions were determined. The fly ash from CFBC was found to contain two separate particle classes. Fine particles consisted mainly of KCl, and coarse particles contained as major elements Ca and Si. Major fraction of all the studied heavy metals were found in the coarse fly ash particles at location 1 at 830 C; 7--26% of Pb, 24--27% of Cu, 1--8% of Cd, and less than 1% of Zn were found in the gas phase. The gas-to-particle conversion route for Cd, Pb, and Cu was found by chemical surface reaction, probably with silicates. None of the studied heavy metals were enriched in the fine particles at the inlet of the electrostatic precipitator.
- OSTI ID:
- 323815
- Journal Information:
- Environmental Science and Technology, Journal Name: Environmental Science and Technology Journal Issue: 3 Vol. 33; ISSN 0013-936X; ISSN ESTHAG
- Country of Publication:
- United States
- Language:
- English
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