In this work, the influence of experimental setup on derived kinetic data for the heterogeneous Boudouard gasification reaction is studied. A thermogravimetric analyzer (TGA) and a small-scale fluidized bed reactor (FBR) are used. The two systems differ basically in their fuel heating rates and fuel bed configurations. The kinetic study was performed in both reactors for the same temperatures and partial pressures of CO 2 at ambient pressure using same-batch fuel samples (biomass, brown coal, and petcoke). Kinetic data are reported, and the influence of the thermal history of the fuel particle prior to the char gasification process is discussed. In general, the activation energies derived from both systems are lower for the brown coal fuels as compared to the wood char fuels. This finding may be explained by the high ash content of the brown coal fuels with multiple catalytic components in the ash. Both experimental setups used in this study agree well in their results for the carbon conversion rate and kinetic parameters for fuels with low volatile content, whereas fuels with high volatile content show different results in the two experimental setups. This may be explained by the physical and chemical structure of the fuel particle not being changed significantly during the in situ pyrolysis prior to gasification for the low volatile fuels. The char properties of the high volatile fuels may differ significantly due to system dependent different heating rates and gas atmospheres during the in situ pyrolysis prior to gasification. Hence, the observed reactivity becomes system dependent. In conclusion, the results show that knowledge of the thermal history of the fuel particle prior to the gasification process is most important for the interpretation of kinetic data as well as for the design of experiments for generation of kinetic data.

The objective of this study was to gain insight into the secondary pyrolysis of biomass based slurry under entrained flow gasification conditions. The focus was set on the types of solid products from secondary pyrolysis, their mechanism of formation, and subsequent conversion behavior. Primary chars and pyrolysis oils from wood and wheat straw were produced in a screw pyrolysis reactor. A suspension fuel (slurry) was prepared composed of primary straw char and straw pyrolysis oil. A drop tube reactor was used to study the secondary pyrolysis of the different fuels at 1200°C and 3 s residence time. The secondary pyrolysis of both chars yielded approximately 60 m% of secondary char. While the wood char reactivity was unchanged by the secondary pyrolysis, the straw char showed signs of massive deactivation, which is most likely explained by the loss of catalytic activity. The secondary pyrolysis of both pyrolysis oils yielded approximately 20 m% of secondary char and soot. Cenospheres could be identified with diameters close to the initial droplet diameter. Oil cenospheres and soot had similar chemical compositions but showed very different reactivities, which is likely to be explained by their different structures. The secondary pyrolysis of the straw based slurry showed results similar to those of the secondary pyrolysis of oil with primary char particles being embedded in the cenosphere carbon shell. Additional thermogravimetric measurements revealed possible conversion mechanisms of cenospheres from oil and slurry feed.

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