Environmental Engineering Reference
In-Depth Information
TABLE 16.2 Typical gas cleaning options (Liu et al. 2011)
Contaminants
Low temperature
High temperature
Particulates
Bag filter, cyclone wet
scrubber, wet electrostatic
precipitator (WESP)
Cyclone, electrostatic precipitator
(ESP), bag filter, granular bed
filter, rigid barrier filter
Catalytic cracking (750-900 C) or
high-temperature (900-1200 C)
thermal cracking
Tars
Wet scrubber, WESP, filter
Alkali compounds
Removal as solid particulates
Removal as solid particulates
(<600 C), alkali getter (>800 C)
Sorbents (>300 C, e.g., ZnO)
H 2 S
Wet scrubber, activated
carbon
Sorbents (300-600 C, e.g., Na 2 CO 3 )
HCl
Wet scrubber
16.3.2.8 Summary of Gas Cleaning Various systems are available for the removal
of the major biosyngas contaminants to certain levels, which may not necessarily meet
the requirements for SOFCs. Some of these systems are commercially available, and
others are in the research and development stages. These gas cleaning techniques
have to be studied in detail to explore the application in gasifier
SOFC systems.
Table 16.2 summarizes the general cleaning possibilities considered at both high
and low temperatures.
Efforts to design suitable cleaning systems for SOFC operation with biosyngas
are still in the early stage. Presently available low-temperature cleaning systems could
be the first choice for connecting SOFCs to biomass gasifiers. However, high-
temperature gas cleaning systems are preferable, but their development is rather
complicated and requires extensive research and development.
-
16.3.3 Operational Experience with SOFCs Connected to Biomass Gasifiers
A few studies have been reported on tests with FC downstream of a biomass gasifier.
The Energy Center of the Netherlands (ECN) tested a Sulzer Hexis 1 kWe SOFC stack
downstream of a two-stage gasifier with two fuels, willow and Rofire. Rofire is a
mixture of plastics and paper waste. An electrical efficiency of 41% was observed
with willow and 36% with Rofire. The longest test was reported to last 48 h, with only
a slight degradation in the performance of the stack (Oudhuis et al., 2004). The Paul
Scherrer Institute in Switzerland reported the testing of an SOFC stack downstream of
an updraft gasifier with a ceramic filter operated at 400 C for gas cleaning. The stack
was operated for a period of 100 h with a fuel consisting of 50
60% filtered fuel gas
from the gasifier and hydrogen. The performance of this system was reported to
remain constant (Sime et al., 2002). Hofmann et al. (2009) investigated the influence
of real biosyngas with a tar level of over 10 g mn −3 on the performance of SOFCs with
Ni
-
GDC anodes and reported successful SOFC operation for 7 h. A planar SOFC
stack fueled by gas obtained by gasifying wood in the Viking gasifier has operated
-
Search WWH ::




Custom Search