Method and apparatus are provided for transferring particles from an upper zone through an intermediate zone to a lower zone. A valveless conduit provides particle communication from the upper zone to the middle zone and a valved conduit provides particle communication from the middle zone to the lower zone. The transfer of particles between the zones through the conduits is regulated by varying the pressure of the middle zone, the flow rate of gas passing through the valveless conduit, and the valve in the valved conduit.