Gasifiers for the gasification of solid carbon-based fuels are disclosed herein. An example gasifier includes an inlet chamber for introducing fuel into the gasifier and a pyrolysis region for pyrolyzing the fuel introduced into the vessel. The pyrolysis region includes first means for admission of a pyrolysis agent. The example gasifier also includes a combustion region for incinerating pyrolysis gases originating from the pyrolysis region, where the combustion region includes second means for admission of a gasifying agent. Also, the example gasifier includes a reduction region for gasifying carbonized fuel originating from the pyrolysis region, an outlet for collecting gases originating from the reduction region, and a region for collecting and discharging ashes. In addition, the example gasifier includes active transfer means to actively transfer solid material from the pyrolysis region to the reduction region. In some examples, the active transfer means is located between the pyrolysis region and the combustion region, and the active transfer means includes a transfer chamber to prevent a direct flow of the solid material from the pyrolysis region to the reduction region, where the transfer chamber is permeable to the pyrolysis gases.