The gasification of a bituminous coal was performed in a dual fluidized-bed (DFB) steam gasifier at a fuel power of 90 kWth. The main aim of these tests was to prove the suitability of the DFB system for cheap low-grade coals that are often delivered with a wide range of particle sizes and ash loads. The fine fraction in particular can become entrained in the gas stream and thus be responsible for changes in the system performance and gas quality. The selected gasifier bed material was olivine, with an applied particle size of 375 μm, the steam-to-carbon ratio was 1.3 kg kgC−1, and the gasification temperature was 850 °C. In addition to standard online analysis of the main components of the product gas, impurities that included NH3, H2S, and tar were also examined.