This invention is to cope with users requesting the delivery of stream data, flexibly. A planar seal and at least one O-ring seal are positioned in the groove, with the O-ring seal under the planar seal. Raised formations on the support beam engage the interior of the sleeve to support the inner shell within the outer shell. Alternative constructions of the mixing zone are disclosed to provide the first and second stages having such characteristics, as well as options for both the passive and active control of the secondary combustion air. Controller may be responsive to sensors measuring the water and sulfur content of flue gas exhausted to atmosphere. The conveying system includes a single-pod conveyor 10 for conveying pods 5 one by one, a pod stacker 50 for stacking a plurality of pods 5, a stacked pod conveyor 60 for conveying the stacked pods 5, and a pod destacker 50 for destacking the stacked pods.