The feeder design consists of a rotating disk in a cylindrical feed chamber containing a reciprocating piston. The piston seals the feed chamber after the coal is dumped into a reactor vessel so that there is no loss of gas from the reactor. These are the only moving parts in the feeder, and their rugged construction should present minimum wear problems. This feeder is designed for 1200 pounds per hour, operating at 30 rpm. The body of the feeder is 27 inches in diameter and 12 inches wide. The compact design makes it possible to use more than one feeder in parallel to get higher coal feed rates. Higher values of rotational speed could also increase the feed capacity. The drive requirement of a single unit at 30 rpm is 5.3 horsepower. The coal pump is all-steel construction using commercially-available standard parts wherever possible. The design consists of a minimum number of parts that can be easily manufactured and assembled to provide a reliable unit. A diaphragm seal in the piston head, and a combination of seal and wiper rings in the rod, provide effective sealing of the coal discharge. Seals between the outer casing and the rotating disk at the inlet and discharge openings, however, present challenging design situations requiring special solutions. Three types of wear-compensating seals of various configurations thus were conceived. These seals are being fabricated.