Abstract: Disclosed is apparatus for introducing particulate material, such as finely divided coal, into a vessel, such as a coal gasifier, having a gas pressure different from atmospheric pressure, comprising a gas lock chamber having at each of its feed and discharge ends an openable and closable material-holding valve below which is a movable openable and closable gas sealing valve, and means below the gas sealing valve for clearing away particulate material from the space through which the sealing valve moves from its opened position to its closed position, to insure that a tight gas seal can be achieved. Also disclosed is a gas valve having a seat radially spaced from the conduit through which material is distributed, to aid in gas sealing. Systems are also disclosed for automatically controlling the pressure in the gas lock chamber to enable it to act as a gas lock, and the operation of the various material holding and gas sealing valves, and clearing means.