Regenerative preheater for two separate gas streams

A regenerative air preheater comprising:

• a heat-exchange sector plate centered on an axis and formed with a multiplicity of axially throughgoing passages;
• intake and output heating-gas hoods axially flanking the plate;
• conduit means for passing a heating gas from the intake hood through the plate to the output hood for heating the plate;
• intake and output secondary heated-gas hoods each within one of the heating-gas hoods and axially flanking the plate, the secondary hoods being axially aligned with each other and only covering a portion of the plate, whereby the heating gas can pass through the plate only around the plate portion covered by the secondary hoods;
• conduit means for passing a secondary stream of a gas to be heated from the intake secondary hood through the plate at the plate portion covered by the secondary hoods to the output secondary hood;
• drive means for rotating the secondary hoods synchronously with each other about the axis in a predetermined rotational sense, whereby the heating gas will heat regions of the plate not covered by the secondary hoods so that when same move into alignment with these heated regions the secondary gas stream will be heated;
• intake and output primary heated-gas hoods within the respective secondary hoods and axially flanking the plate, the primary hoods being axially aligned with each other and only covering a subportion of the plate portion covered by the secondary hoods, whereby the secondary gas will be heated at regions of the plate portion not covered by the primary hoods;
• conduit means for passing a primary stream of a gas to be heated from the intake primary hood through the plate subportion aligned with it to the output primary hood;
• and
• control means for displacing the primary hoods at least partially nonaxially within the respective secondary hoods and thereby varying the heat-exchange between the primary stream and the plate.