THERMOCHEMICAL CONVERSION: (CO)GASIFICATION AND HYDROTHERMAL GASIFICATION - Biomass as a Sustainable Energy Source for the Future - page 324

Raw
biosyngas

Raw
biosyngas

Cyclone

Cyclone

Freeboard

Gas phase
reactions

Gas phase
reactions
Circulating
luidized bed

Fly ash and
particles

Fuel

Additional
sand

Fuel

Additional
sand

Bubbling
luidized bed

Velocity
5-10 m/s

Velocity
2-3 m/s

Inert + char

Bottom ash and
bed material

Bottom ash and
bed material

Grate

Grate

Fluidization
medium

Fluidization
medium

Raw biosyngas
Flue gases

Fuel

Additional
sand

Velocity
5-10 m/s

Velocity
5-10 m/s

Bottom ash and
bed material

Bottom ash and
bed material

Grate

Steam Air

FIGURE 10.9 Configurations of fluidized bed reactors: BFB (top left), CFB (top right), and
interconnected (indirect) fluidized beds (bottom). (Source: Adapted with permission from
Olofsson et al. (2005). © Umeå University (Sweden).)

process is well above 90%, due to the high residence time of the biomass particles and
the residual conversion when entrained to the freeboard. The tar content of the gas is in
between the tar content of the downdraft and updraft gasifiers. An example of a BFB
design is the steam-/oxygen-blown gasifier developed by IGT, now commercially
manufactured by Carbona.