Abstract
Ash formation during the bubbling fluidized bed (BFB) combustion of bark and pulp mill sludge has been studied on an industrial and bench scale. During co-firing in an industrial BFB a submicron fly ash mode was formed via condensation of volatilized K, Na, Sand Cl species at 0.05–0.3 μm.
The submicron mass mode below 0.3 μm made up 2.2–5.0% of the fly ash, while the share of the supermicron mass fraction was 93.6–97.2%. Elements depleted in the ultra fine ash were Ca, Si, Al, Mg, Fe, Mn, P and Ti. The bench-scale test showed that the ultrafine particle concentration was increased by a higher bed temperature and decreased due to sludge moisture. As, Cd, Pb and Rb were enriched in the ultrafine ash on a bench scale, while Ba, Co, Sr and V were depleted.
Cu and Zn were enriched in the ultrafine ash during the combustion of dried sludge, but not when wet sludge was fired. Micron-size ash particles composed of non-volatile species, Ca, Si, Mg, Al, P and Mn, adhered to the bed sand, presumably by surface forces, and sintering densified the ash layer.
The submicron mass mode below 0.3 μm made up 2.2–5.0% of the fly ash, while the share of the supermicron mass fraction was 93.6–97.2%. Elements depleted in the ultra fine ash were Ca, Si, Al, Mg, Fe, Mn, P and Ti. The bench-scale test showed that the ultrafine particle concentration was increased by a higher bed temperature and decreased due to sludge moisture. As, Cd, Pb and Rb were enriched in the ultrafine ash on a bench scale, while Ba, Co, Sr and V were depleted.
Cu and Zn were enriched in the ultrafine ash during the combustion of dried sludge, but not when wet sludge was fired. Micron-size ash particles composed of non-volatile species, Ca, Si, Mg, Al, P and Mn, adhered to the bed sand, presumably by surface forces, and sintering densified the ash layer.
Original language | English |
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Pages (from-to) | 433-455 |
Journal | Combustion Science and Technology |
Volume | 134 |
Issue number | 1-6 |
DOIs | |
Publication status | Published - 1998 |
MoE publication type | A1 Journal article-refereed |
Keywords
- fluidized beds