A comparative evaluation of minerals and trace elements in the ashes from lignite, coal refuse, and biomass fired power plants
✍ Scribed by Smriti Singh; Lal C. Ram; Reginald E. Masto; Santosh K. Verma
- Publisher
- Elsevier Science
- Year
- 2011
- Tongue
- English
- Weight
- 507 KB
- Volume
- 87
- Category
- Article
- ISSN
- 0166-5162
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✦ Synopsis
Coal being a limited source of energy, extraction of energy from other sources like lignite, coal-refuse, and biomass is being attempted worldwide. The minerals and inorganic elements present in fuel feeds pose different technological and environmental concerns. Lignite ash, refuse ash, and biomass ash collected from Indian power plants burning lignite, coal-refuse, and mustard stalk, respectively, were analyzed for physicochemical characteristics and trace elements. The lignite ash has high SiO 2 , CaO, MgO, Al 2 O 3, and SO 3 ; the refuse ash has high SiO 2 and Fe 2 O 3 , but low SO 3 ; the biomass ash has high SiO 2 (but low Al 2 O 3 ), and high CaO, MgO, K 2 O, Na 2 O, SO 3 , and P 2 O 5 . A substantial presence of chloride (2.1%) was observed in the biomass ash. Quartz is the most abundant mineral species. Other minerals are mullite, hematite, gehlenite, anhydrite, and calcite in the lignite ash; orthoclase in the refuse ash; albite, sanidine, gehlenite, anhydrite, and calcite in the biomass ash. Ashes with high concentrations (N 100 mg/kg) of trace elements are: lignite ash (Vb Lab Mnb Crb Nib Ndb Ba b Ce, Znb Sr); refuse ash (Cr b Ceb V b Rbb Mn b Sr, Znb Ba); biomass ash (Cu b Znb Ba, Sr). Based on Earth crust normalization, Co, Ni, As, Se, Mo, Zn, Pb, U, and REEs (except Pr and Er) are enriched in the lignite ash; molybdenum, Zn, Cs, Pb, Th, U, La, Ce, and Lu in the refuse ash; and Mo, Zn, Sr, Cs, Pb, and Lu in the biomass ash. Elements As, Zn, Mo, Ni, Pb, Rb, Cr, V, Ba, Sr, and REEs are correlated with Al, indicating the possibilities of their association with aluminum silicates minerals. Similarly, barium, Cs, Th, and U are correlated with iron oxides; molybdenum and Sr may also be associated with sulfates and chlorides. Due to the alkaline nature of these ashes, the high concentrations of As and Se in the lignite ash; molybdenum in the biomass ash; and Se in the refuse ash may pose environmental concerns.