NOVELTY - A devolatilization apparatus comprises a source of carbonaceous fuel chunks (22) containing volatile matter; a steam boiler source of superheated steam; a receiver of devolatilized coke chunks; a receiver of steam and volatile matter; a sealable, and insulated, pressure vessel devolatilization reactor chamber (11) comprising a refuel transfer mechanism (25), a coke removal transfer mechanism (26), a steam inlet pipe with steam inlet valve (13), and a steam outlet pipe (31) with steam outlet valve (30); and a carbonaceous fuel control and actuator.    USE - A devolatilization apparatus for separating carbonaceous fuels, e.g. coal and biomass, to fuel products, a devolatilized coke product, and volatile matter products (claimed) used in railroad locomotive diesel engines; tug and barge diesel engines; open cast mine shovels, trucks, and draglines; cargo ships; farm tractor and harvester diesel engines; and long haul highway trucks.    ADVANTAGE - The apparatus achieves high yield of renewable engine fuel.    DETAILED DESCRIPTION - A devolatilization apparatus comprises:    (A) a source of carbonaceous fuel chunks (22) containing volatile matter;    (B) a steam boiler source of superheated steam at a steam boiler pressure;    (C) a receiver of devolatilized coke chunks;    (D) a receiver of steam and volatile matter at a receiver pressure less than the steam supply pressure;    (E) a sealable, and preferably insulated, pressure vessel devolatilization reactor chamber (11) comprising a refuel end, a coke removal end, a refuel transfer mechanism (25) for intermittently, and sealably, transferring a single refuel batch of carbonaceous fuel chunks, from the source of carbonaceous fuel chunks to the refuel end, coke removal transfer mechanism (26) for intermittently and sealably transferring, a single batch of devolatilized coke chunks, from the coke removal end to the receiver of devolatilized coke chunks, a steam inlet pipe with steam inlet valve (13) for transferring superheated steam, from the source of superheated steam to the coke removal end at steam boiler pressure, and a steam outlet pipe (31) with steam outlet valve (30) for transferring steam and volatile matter from the refuel end to the receiver of steam and volatile matter at receiver pressure; and    (F) a carbonaceous fuel control and actuator for operating the refuel transfer mechanism and the coke removal transfer mechanism, intermittently at refuel time intervals, so that the reactor chamber is maintained filled with batches of carbonaceous fuel chunks.    DESCRIPTION OF DRAWING(S) - The drawing is a schematic diagram of the devolatilization apparatus.    Devolatilization reactor chamber (11)    Steam inlet valve (13)    Carbonaceous fuel chunks (22)    Refuel transfer mechanism (25)    Coke removal transfer mechanism (26)    Steam outlet valve (30)    Steam outlet pipe (31)