NOVELTY - The reactor has an intermediate char gasification chamber (9) comprising an inlet (9a) for receiving particles from a primary char gasification chamber (5). An inlet (9b) for a fluidizing gas e.g. gas containing oxygen/water, is provided in a lower part of the reactor. An outlet (9c) is used for carrying produced gas particles from an upper part of the intermediate chamber whose outlet opens into a conduit (8) having an outlet to a lower part of a reaction chamber (1). The outlet provides fluidizing gas to the reaction chamber.    USE - Circulating fluidized bed (CFB) reactor for thermal processing of added carbonaceous material such as cereal straw, rice straw, grain cleaning waste streams, residues from crops such as sugar cane, sorghum, beets, maize, potato, nuts, tea, cotton, wine, olive and oil palms, Algae e.g. sea weed, energy crop such as Miscantus, residues from short rotation forest crops based on fast growing wood e.g. Willow and poplar, crops with an elevated content of salt, residues from meat production industry such as meat and bone meal, animal manure such as dewatered manure slurry, municipal and industrial organic waste such as organic fractions derived from streams, sewage sludge, energy containing residues such as fiber and lignin products from processing wood and raw organic products (all claimed). Can also be used for manufacturing a combustible product gas.    ADVANTAGE - The reactor can maximize gas and particle retention time in the intermediate char reaction chamber and use higher steam to air ratio in the gasification agent added to the intermediate chamber so as to provide better extent of endothermic, steam-based char decomposition reactions and reduced tendency for increased temperature in the intermediate chamber.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for a method for manufacturing a product gas.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of a CFB reactor.    Reaction chamber (1)    Primary char gasification chamber (5)    Conduit (8)    Intermediate char gasification chamber (9)    Inlets (9a, 9b)    Outlet (9c)