Abstract: Solid fuels, such as contaminated biomass and solid city waste, are converted into a synthesized gas by gasification and exploitation of the energy contained in the fuels. The fuel is gasified an a co-current gasogen (1), while the cinders are separated, removed and purified after a fraction of the fuels has undergone combustion and before the fuel has been gasified. Cinder purification is made by complete combustion, while the fuel that has undergone the gasification step without being completely transformed in CO is recirculated by mixing it to fresh fuel material. The process is carried out in an apparatus comprising a vertical co-current gasogen (1) and a device for the separation and removal of cinders (16,19,5,6) as well as a scorification chamber (3) where cinders are purified from accompanying fuel material by complete combustion and are then collected in a waste tank (28).