Abstract: A device for accurately controlled feeding of a fine-grained, free-running particulate material from a silo into a reactor vessel, in particular alumina from a day's supply silo to a break in the crust on an aluminium fused salt electrolytic cell, comprises essentially a vertical feed pipe which is situated below the silo and features upper and a lower closing flaps both of which are in the form of segments of a cylinder. The feed pipe mounted on the funnel shaped lower part of the silo features an outlet funnel which joins up with an outlet pipe.