A method for the experimental investigation of gas–solid reactions in a small-scale fluidized bed reactor (FBR) is presented. This methodology enables high heating rates (≈104 K/s), long timescale observation (up to several hours), operation with small fuel particles (≈100 μm), and accurate control of reaction conditions. In this study, the gasification reaction of biomass-based char particles with carbon dioxide–nitrogen gas mixtures is investigated under atmospheric pressure. On varying process temperature and feed-gas composition over a wide range, consistent results are realized (temperature is varied between 1173 and 1373 K, while the CO2 concentration is adjusted in an interval of 20% up to 80%). Carbon conversion curves and reaction rates are established from real-time gas product analysis by FTIR spectrometry through a detailed data analysis procedure. This procedure employs a particle surface-evolution model and accounts for sampling system signal attenuation. The obtained reaction rates are used to demonstrate the determination of kinetic parameters for different kinetic approaches concerning the heterogeneous CO2 gasification (Boudouard reaction). Throughout this study, a comparison of both different surface-evolution models as well as kinetic approaches with experimental results is performed for the inspection of best consistency.