Currently, there are many studies that analyze the co-gasification or co-combustion of biomass with coal in fluidized-bed reactors. Mixing these two materials takes advantage of particle segregation as a result of the differences in density, shape, and size; this phenomenon requires due attention because it can lead to reactor operation issues. Some common problems seen with biomass are gap flow, plug flow, and large bubbles that reduce mass and energy transport, thus lowering the quality of the syngas product. In this study, we found that mixing biomass palm kernel shell (PKS) with coal greatly reduces these problems. Furthermore, we propose that this technique can be applied to other biomasses than the biomass used in our study without observing fluid dynamic issues. Continuous feeding co-gasification tests were performed with PKS and sub-bituminous coal type A (sub-bA coal) in a pilot-scale fluidized-bed reactor using air as the gasifying agent.