| dc.description |
A novel study on biomass-air gasification using a horizontal entrained-flow
gasifier and catalytic processing of the product gas has been conducted. The study
was designed to investigate the effect of catalyst loading on the product gas. The use
of a horizontal entrained-flow gasifier reactor was used to assess the effect of the
gasifier reactor orientation on the gasification process. Both experimental and
computational fluid dynamics (CFD) approaches were employed. The gasification
tests were conducted at 800 oC and equivalence ratio of 0.23 while the product gas
was catalysed at 350-400 oC and a gas hourly space velocity (GHSV) of 8000 h
-1
.
Preparation and characterisation of wood powder and catalysts were performed using
classical methods. Moreover, the syngas and tar composition were analysed using a
gas chromatograph (GC) and GC-mass spectrometer (GC-MS) respectively.
The research findings showed that maximum fuel conversion and cold gas
efficiency using a horizontal entrained-flow gasifier were 99 % and 70 %
respectively. The gasifier length can also be reduced from the common 1000-2000
mm to 500 mm. The catalysis study showed that pumice and kaolin have limited
catalytic effect on the product gas. However, doping with CeO2, ZrO2, CuO and NiO
improved the syngas heating value, coking resistance and tar conversion. A notable
increase in syngas LHV was achieved using ceria doped pumice (8.97 MJ/Nm3
) and
copper doped pumice (8.66 MJ/Nm3
) compared to 6.67 MJ/Nm3
of non-catalytic test.
For the tested catalysts, CeO2 doped pumice exhibited highest coking resistance.
Furthermore, catalytic tar conversion was mainly through cracking and partial
oxidation reactions. The lowest tar yield was found to be 3.55 g/Nm3
using kaolinceria-zirconia
catalyst compared to 14.92 g/Nm
3
of non-catalytic gasification. Tar
reduction using untreated pumice was through adsorption and ranged 4-6 g/Nm3
.
In general, the results of this study suggest that there exist a sensitivity to the
gasifier orientation on the overall gasification process. It has also shown that metal
oxides have both beneficial and detrimental effects of syngas composition. Although
syngas heating value increased with increasing catalyst loading, H2 showed a
decreasing trend highlighting that further catalyst modification is required.
Furthermore, pumice and kaolin can be utilised as catalyst support in the gasification
technology. However, further experimental investigation on doping various catalytic
metals and testing at different operating conditions are hereby proposed. |
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