Abstract: In a system for discharging particulate material from a reactor, the material is conveyed pneumatically from a drain zone of the reactor via a first vacuum line to a gas/solids separator and solids we fed from the separator to a receiving vessel via a gas-tight line and an inlet port provided on a cover member sealingly engaged with the top of the vessel. The majority of the gas is re-cycled from the separator to the drain zone via a main vacuum return line and the remainder of gas is drawn from the separator to the receiving vessel via a further vacuum line and a gas inlet provided on the cover member. Gas is passed from the receiving vessel to the main vacuum return line via an outlet port provided on the cover member and an auxiliary vacuum return line. The cover member is mounted for movement towards and away from the receiving vessel so that successive receiving vessels can be covered by the cover member and filled with separated solids.