Lab scale drop tube furnace reactors with conditions similar to large-scale gasification reactors are able to generate applicable reaction-kinetic expressions for reactor simulation and dimensioning. In the present work, a method is introduced to determine reaction kinetic parameters from integral drop tube furnace experiments. A one-dimensional model of the gasification process was developed incorporating the influence of reaction gas composition, char particle structure change, pore diffusion and gas phase reaction. Suitable kinetic parameters were determined by fitting the gasification model to experimental data. Gasification experiments with gas mixtures of steam, carbon dioxide, carbon monoxide and hydrogen were carried out in an isothermal pressurized drop tube furnace reactor at 6 bar total pressure and temperatures of 900-1100 degrees C. It was shown that the determined kinetic expressions fit the experimental data. The best fit to the experiments was achieved by application of a Langmuir-Hinshelwood type rate expression with respect to product gas inhibition. Integrating a pore diffusion model did not improve the fitting quality.