The effect of sample compactness on the syngas characteristics evolved from the gasification at different temperatures of wood pellets (8 mm and 12 mm) and wood chips of different compactness from the wood pellets is presented. Results show the distinct role of sample compactness on syngas and H_2 evolved from biomass fuels. An increase in reactor temperature increased the flow rate of the syngas and hydrogen. The hydrogen flow rate peaked between the first and second minutes into the gasification, which is attributed to the time it took for the sample to reach the nominal reactor temperature. The H_2/CO molar ratio showed a continuous increase at higher temperatures at decreased residence time in the reactor. At the pyrolysis-dominated regime (during the first three minutes), an increase in reactor temperature resulted in an increased H_2/CO ratio. This effect is due to the higher heating rate at higher reactor temperatures. However, at longer times into gasification the effect of reactor temperature was reversed wherein the increase in reactor temperature decreased the H_2/CO ratio. A comparison of the results from these biomass fuel samples showed that compactness decreases the overall yield of syngas, combustible gas and hydrogen. More compact samples promoted diffusion resistance to the gasifying agent penetrating the sample and increased the syngas diffusion resistance penetrating the sample on its way out of the sample. This increase in diffusion resistance decreased the syngas yield from the more compact samples. In addition, the increase in sample compactness decreased the heating rate, which in turn decreased the overall yield from pyrolysis.
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