Only bubbling fluid bed and circulating fluid bed designs were reviewed for
this report. Fixed bed and high temperature slagging gasifiers were not
reviewed at this time.
Product gases from fixed-bed versus fluidized bed gasifier configurations vary
significantly. Fixed-bed gasifiers are relatively easy to design and operate and
are best suited for small to medium-scale applications with thermal
requirements of up to a few mega watts thermal (MWt). For large scale
applications, fixed bed gasifiers may encounter problems with bridging of the
biomass feedstock and non-uniform bed temperatures. Bridging leads to
uneven gas flow, while non-uniform bed temperature may lead to hot spots
and ash deformation and slagging. Large scale applications are also
susceptible to temperature variations throughout the gasifier as a result of poor