Environmental Engineering Reference
In-Depth Information
In a CFB gasifier, the oxidizing gas is introduced into the reactor with such a high
velocity that large amounts of solids are entrained with the product gas. The entrained
solids are separated from the gas in a cyclone and recycled back to the gasifier. The
CFB has a high CC efficiency (typically >95%), because of the recycling of the bed
material. The raw product gas generated by a CFB gasifier has a relatively high dust
content. An example of this technology is the 18 MW
th
Värnamo (Sweden) pressur-
ized gasifier (see, e.g., Ståhl and Neergaard (1998)); this gasifier was operated for
demonstration in the 1990s and restarted for a short period in 2007, but hereafter it
was mothballed.
Besides the BFB and the CFB, there are also designs of gasification installations
based on interconnected beds. These reactors make use of indirect, or allothermal, gas-
ification, in which the heat to drive the endothermic char gasification reactions is gen-
erated by a separate combustion process. An excellent overview is given by Corella
et al. (2007). A recent example is the fast internal circulating fluidized bed (FICFB)
reactor concept developed at Vienna University (Hofbauer et al., 2002; Pfeifer and
Hofbauer, 2008), which has become commercially available on the market (see
Table 10.4). This advanced gasifier type has been designed as a steam-blown BFB
in which biomass is gasified and char is carried over to an interconnected CFB com-
bustor, which provides heat for the endothermic reactions in the BFB reactor via inter-
nal transportation of hot bed material. Another process using interconnected beds is
TABLE 10.4 Some of the main fluidized bed biomass gasification demonstrations
Project/demo
Gasifier, thermal input
Product gas use
Current status
Güssing (Austria)
Interconnected
FICFB, 8MW
th
Combined heat and power
(CHP) (Pfeifer and
Hofbauer, 2008),
Demo-FT (Weber et al.,
2010) Demo-substitute
natural gas (SNG)
Running
Oberwart (Austria)
Interconnected
FICFB, 8MW
th
CHP
Running
Villach (Austria)
Interconnected
FICFB, 15 MW
th
CHP
Commissioned
Skive (Denmark)
BFB 28 MW
th,max
CHP
Running
NSE Biofuels,
Varkaus
(Finland)
CFB (Foster
Wheeler),
12 MW
th
Lime kiln, Demo-FT
Commissioned
HVC, Alkmaar
(the Netherlands)
Interconnected
MILENA, 10MW
th
SNG (Van der Meijden
et al., 2009)
Development
AMER
(the Netherlands)
CFB, 84 MW
th
Cofiring (Willeboer, 1998)
Running
Värnamo (Sweden)
Foster Wheeler,
CFB (air blown)
18 MW
th
CHP (Rensfelt and
Gardmark, 2010)
Mothballed,
after last
demo
in 2007
Search WWH ::
Custom Search