Field study on ash behavior during circulating fluidized-bed combustion of biomass. 2. Ash deposition and alkali vapor condensation.

Fly ash deposition on heat-exchanger surfaces during fluidized-bed combustion of biomass causes operational problems such as reduced heat transfer and corrosion of superheater tubes. Ash deposition and alkali vapor condensation were studied during circulating fluidized-bed combustion of forest residue in a 35 MW co-generation plant. A 70 ± 10% amount of fly ash was deposited on the heat-exchanger surfaces in the convective back pass between soot-blowing periods. Practically all the largest ash particles (d > 10 μm) but only a small fraction of particles d 10 μm) ash particles.