Dipl. Ing. Matthias Mayerhofer Technische Universität München ...

Results and Discussion 57
er, the value of CH4 stabilized after a while, which indicated efficient steam reforming. It is probable
that the catalyst is semi- deactivated very fast but then it becomes stable and it can work long-term.
Either way the value of the methane at dp=0.9 and T=800°C is significantly lower than the value
obtained from the iron based catalysts at the same conditions.
Wet CH₄ composition Vol (%)
4,0
3,5
3,0
2,5
2,0
1,5
1,0
0,5
0,0
-0,5
14:35 14:51 15:08 15:25 15:42 15:59
-1,0
7.3 Tar Analysis
Figure 27: Change of wet gas composition of CH4 with time
The Table 9 presents the classification of tars. Class 1 one tars can’t be detected by the GC/FID.
Table 9: Classification of tars
Class 2 Class 3 Class 4 Class 5
Phenol toluene napthalene Fluoranthen
o-Kresol o-Xyl/Styr Biphenyl Pyren
m-Kresol Inden Fluoren
Anthracen
Time
Iron based catalysts:
It is expected that as the char is built up inside the gasifier during the experiment it acts as an in
situ catalyst, so as time passed the tar produced decreased. In the following
Figure 28, it is seen that as the sampling was made as the time passed there is a clear decrease in
for different higher hydrocarbon molecules. The following figure is referred to each tar class compound
that was detected by the GC/FID, an unknown compound that is likely benzene is not included
in the graph, and the total amount of unknown compounds produced by the gasifier.