A double-chain conveyor is assembled of trough sections defining a bottom plate provided with lateral guiding walls for scraper elements and intermediate guides extending along the entire length of the conveyor and guidingly engaging lateral edges of flat chain elements arranged parallel to the bottom plate of the trough. The flat chain elements are provided with oblong holes extending in the direction of the chain and linking vertically directed ring-shaped chain elements with a play which permits shifting movements of all chain elements in the longitudinal direction. Intermediate drives are provided between superposed bottom plates of the trough and drive a chain wheel engaging the flat chain elements both in the upper and in the lower flight of the conveying chain.