Biomedical Engineering Reference
In-Depth Information
confirmed with further data, it remains to be seen if the extra energy required
for grinding is worth the improvement.
9.4.7 Pressure
Experiments by Van Swaaij et al. (2003) in their microreactor over the range
of 28
34.5 MPa 710
C,
those by Kruse et al. (2003) in a stirred tank
50 MPa, 500
C), and those by Lu et al. (2006) in a plug-flow reactor
(30
30 MPa, 625
C) showed no major effect of pressure on carbon conver-
sion or product distribution. Nor did Mettanant et al. (2009b) see much effect
in their temperature and pressure range, although they noted a clear positive
effect of pressure at 700
C.
(18
9.4.8 Reactor Type
The reactors used so far for SCWG research have been either batch or continu-
ous (flow). Depending on their type of mixing, they can be further divided as
follows:
Autoclave
Tubular steel
Stirred tank
Quartz capillary tube
Fluidized bed
A batch reactor is simple, does not require a high-pressure pump and can
be used for almost all biomass feedstock. However, its reaction processes are
not isothermal and it needs time to heat up and cool down. During heat up
many reactions occur that cause transformation of the feedstock; this does
not happen in a continuous-flow reactor.
Reactor type has an important effect on the influence of feed concen-
tration. The drop in gasification efficiency with feed concentration, noted
in tubular reactors, was not found in the stirred-tank reactor studied by
Matsumura et al. (2005). However, the reactor used was exceptionally
small (1.0 mm in diameter), so validation of this finding in a
reasonably large reactor (Matsumura and Minowa, 2004) is necessary. The
process development of SCW gasifiers is lagging laboratory research
because of engineering difficulties and the high cost of pilot plant
construction.
9.5 APPLICATION OF BIOMASS CONVERSION IN SCWG
Three major areas of application for biomass SCWG are: (1) energy conver-
sion, (2) waste remediation, and (3) chemical production.
Search WWH ::
Custom Search