0 25 in wide between fixed portion 18 and portion 19 seals 21 and 22 are preferably formed of a material such as teflon as flexible strips and are mounted such that each seal slides across an exterior surface of the other plenum portion i e portion 19 it will be understood that seals 21 and 22 are illustrative of seals that can be utilized with apparatus illustrated in fig1 inlet 20 of fan 11 is connected to annular passage 15 of plenum chamber 17 while the outlet of fan 11 is connected through a conduit 25 which in turn is in communication with a manifold 27 a plurality of outlets 28 29 and 30 extend from manifold 27 and are disposed in communication with the interior of kiln 10 suitable valve means such as butterfly valves 31 which may be opened and closed upon actuation of a cam member 32 are disposed in outlets 28 29 and 30 with two of such valve and cam members being illustrated in fig1 in operation kiln 10 is rotated at a conventional speed of between approximately 0 75 and 2 0 ft sec and a charge of material to be calcined such as green petroleum coke is supplied thereto to form a bed in the lower region of kiln 10 motor 12 is energized to drive fan 11 which in turn causes a flow of air.