A plant for refining raw materials containing organic constituents includes a reactor configured to receive raw materials; a furnace configured to receive solids and fuel from the reactor; a return conduit configured to recirculate hot solids generated in the furnace to the reactor; and a sealing device configured to separate an oxidizing atmosphere of the furnace from an atmosphere of the reactor. The sealing device includes: a downpipe disposed between the furnace and the reactor, the downpipe being configured to withdraw a stream of solids from the furnace; a rising pipe disposed near a bottom of the downpipe and branching off there from to a top, the rising pipe being configured to transport a fluidized stream of solids to the reactor; and a conveying gas supply disposed below the rising pipe, the conveying gas supply being configured to fluidize a stream of solids withdrawn from the furnace.