A fluidized bed combustion system and process is disclosed, in which full load stoichiometry is maintained at lower loads. The system and process includes an enclosure and a partition disposed in the enclosure to define a furnace section and an overfire air plenum section. A bed of combustible particulate material is formed in the furnace section and air is passed into the bed in quantities sufficient to fluidize the material and insufficient to completely combust the material. Overfire air is p...

A fluidized bed gas-solids contact reactor, which utilizes at least one capped concentric dual-sided riser-downcomer unit having a central inner riser passageway and a concentric outer downcomer passageway. The riser-downcomer unit is usually located above the fluidized bed, and is adapted for directing the downflowing solids back into the fluidized bed for recycle. The reactor unit inner and outer passageway surfaces include a heat exchange panel having inner and outer channels each containing ...