The present invention relates to a system and process for gasifying feedstock such as carbonaceous materials. The invention includes partial combustion of dry solids and pyrolysis of carbonaceous material slurry in two separate reactor sections and produce mixture products comprising synthesis gas. The invention employs one or more catalytic or sorbent bed for removing tar from the synthesis gas. The inventive system and process allow a gasification to be carried out under higher slurry feeding rate and lower temperature with the provision to manage the tar being produced, therefore to increase the conversion efficiency of the overall gasification.