Fixed-bed gasifiers
The different fixed-bed reactor types are often characterised
by the direction of the gasflow through the reactor ( upward,
downward or horizontal ) or by the direction of respectively
the solid flow and the gas stream ( co-current, counter-current
or cross-current ). For specific feedstocks a co-current gasifier
is used with the advantage that the tar content in the producer
gas is low. Additional gas cleaning - prior to fuelling a
prime mover - is avoided. Obviously this will reduce the investment
and operational costs.
Fluidized-bed gasifiers
In a fluidized bed gasifier air and biomass are mixed up
in a hot bed of solid material ( e.g. sand ). Due to the intense
mixing the different zones - drying, pyrolysis, oxidation,
reduction - cannot be distinguished; the temperature is uniform
throughout the bed. Contrary to fixed bed gasifiers the air-biomass
ratio can be changed, and as a result the bed temperature
can be controlled. The producer gas will always contain certain
amount of tar, which needs to be removed
Biomass gasifiers are used in the following applications
:
- Can be used for power generation / thermal application
or a combination of heat and power.
- Can be retrofitted to existing diesel genset ~ 75 - 80%
diesel savings in dual-fuel operation.
- In gas engines to work on 100% gas made.
The thermal applications
of biomass gasifiers are :
- Variety of drying applications ~ with closed loop temperature
control.
- Non-ferrous melting ~ 1100 C attainable with temperature
regulation.
- Generation of process steam, cooking processes.
- And many other applications where controlled temperature
is desired.
The fixed bed and
fluidized bed gasifiers supplied by CCPL are mainly meant
for the small and medium size. Fixed bed gasifiers are used
in case of a well-defined feedstock; fluidized beds are more
tolerant with respect to the feedstock. The simplest application
is the single production of heat ( pure Thermal Application
) for e.g. district heating, meeting process plant steam or
hot water generation requirement, or furnace/kiln/dryer heating
applications.
A further interesting
addition to the CHP will be cooling e.g. the application of
ad-or absorption coolers.
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