A variable orifice valve for balancing the flow of particulate coal in an air stream relative to other parallel conduits. The valve comprises a section of conduit which changes in area along its flow axis and a variable position valve element mounted within the conduit section. The valve element has a shape which proximates that of the conduit section and is movable axially to vary the annular area of the flow path around the valve element. There is no valve seat and, therefore, the valve is always open to some degree.