Abstract: A point feeder for metering powder materials, for example aluminum oxide, to a Hall-Heroult electrolysis cell includes a vertical tube and a horizontal tube which are joined so that they form substantially an L-shaped channel with a material input at an upper end of the vertical tube and a material output at an end of the horizontal tube. The vertical tube is provided with a nozzle device which has one or more downward-facing holes which allow air to penetrate in the form of pulsed air flows to the lower part of the vertical tube and to the whole of the horizontal tube.

Abstract: A pneumatic metering device for metering powdered materials, for example in connection with feeding aluminum oxide and aluminum fluoride to an electrolysis cell for production of aluminum, includes a container in the form of a relatively long, closed channel or similar structure. A fluidizing element is fitted in the base of the channel for supply of air for fluidization of material which is located in the channel. The container is fitted with an inlet for feeding material to the container from a store in the form of a silo or similar and an outlet for metered discharge of material from the container. The area below the inlet is inactive and is not supplied with fluidizing air, whereas air is supplied intermittently to the fluidizing element which is designed to cover essentially all other parts of the base of the channel.