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

48 Experiments
12
10
8
6
4
2
0
H_2
0 200 400 600 800 1000
Temperature (°C)
Figure 21: Reduction of Nickel based catalyst
The reactor was loaded with biomass and it started being heated up at 450°C under N2 flow, while
good fluidization of the bed material with steam was achieved. Prior to the catalyst tests the gasifier
was operated for ~2 hours to ensure stable operating conditions. In the beginning the product gas
bypassed the catalytic test rig and was driven directly in the combustion chamber until steady state
gas composition was reached. For the experiments of the iron based catalysts the temperature was
raised at 750°C with dp=0.9 mbar and after an hour at these conditions with the gas passing
through the catalyst, two tar samples were taken before and after the catalyst test rig. This procedure
was repeated for all the different operating conditions that were about to be tested. The set
point of dp=0.9 mbar and 800°C was tested twice to compare the tar measurements to the values
obtained at the same point about two hours earlier. Finally, the pressure drop reached the lowest
point dp=0.45 mbar. The effectiveness of the catalysts was tested in sulfur and chlorine containing
environment. The operating conditions at which the samples were taken are presented in the following
Table 5.
The two additional gas compositions sampling points for the nickel based catalysts were ~12500
1/h for dp=3 mbar and ~14500 1/h for dp=4 mbar.
All the calculations were made for 40mL amount of catalyst. However, after the experiments with
the iron based catalysts. A protective grid was placed on top of the catalyst amount inside the bed,
to prevent the larger particles to be blown away, but for the finer ones it was impossible to avoid it.
It is not known if the particles were blown away all at once in the beginning of the experiment or
they were linearly decreased.
Table 5: Different operating conditions of sampling points for iron based catalysts
Sampling Points Temperature (°C) Pressure Drop (mbar) Space Velocity (1/h)
1 750 0,9 6500
2 800 0,9 6500
3 860 0,9 6500
4 800 0,45 4500
5 800 1,5 8500
6 800 2 10000