Triple valve airlock-feeder

An airlock-feeder for a coal pulverizing system which includes a raw coal bunker, a pulverizer, and a vertically extending coal duct forming a raw coal flow path from the raw coal bunker to the pulverizer. The airlock-feeder comprises upper, middle and lower, vertically separated valves disposed in the raw coal flow path. Each valve has a seal member, a disc pivotally mounted at a centerline, and a pneumatic actuator. At least one or two of the valves are closed at any given time thereby providing a positive air-tight seal.