Fluidized bed heat exchanger for a circulating fluidized bed boiler and a circulating fluidized bed boiler with a fluidized bed heat exchanger

A supercritical once-through circulating fluidized bed boiler having a boiler steam cycle, the supercritical once-through circulating fluidized bed boiler comprising:

• (a) a furnace for combusting solids in a circulating fluidized bed;
• (b) a particle separator for separating in an external hot circulation of the supercritical once-through circulating fluidized bed boiler;
• and
• (c) a heat exchanger arranged in a return channel of the external hot circulation, the return channel returning solids separated in the particle separator to the furnace, wherein the heat exchanger comprises:
• (i) a first heat exchange chamber and a second heat exchange chamber arranged in connection with a furnace, the first heat exchange chamber comprising a final superheater of the boiler steam cycle of the supercritical once-through circulating fluidized bed boiler and the second heat exchange chamber comprising a final reheater of the boiler steam cycle of the supercritical once-through circulating fluidized bed boiler;
• (ii) a first inlet channel for introducing hot solids from the particle separator of the external circulation of the supercritical once-through circulating fluidized bed boiler into the first heat exchange chamber, which is provided with first means for fluidizing solids;
• (iii) a second inlet channel for introducing solids into the second heat exchange chamber, which is provided with second means for fluidizing solids;
• (iv) a first discharge for removing a portion of the cooled solids from the first heat exchange chamber to a second inlet channel;
• (v) a second discharge for removing cooled solids from the second heat exchange chamber to the furnace;
• and
• (vi) an inlet for introducing hot solids from the internal circulation of the furnace directly to the second heat exchange chamber.

A supercritical once-through circulating fluidized bed boiler having (i) a furnace for combusting fuel and combustion supporting gas, and for producing hot solids and exhaust gas, and (ii) a boiler steam cycle, said supercritical once-through circulating fluidized bed boiler comprising:

• a first heat exchange chamber arranged in connection with the furnace of the supercritical once-through circulating fluidized bed boiler, the first heat exchange chamber comprising a final superheater of the boiler steam cycle of the supercritical once-through circulating fluidized bed boiler;
• second beat exchange chamber arranged in connection with the furnace of the supercritical once-through circulating fluidized bed boiler, the second heat exchange chamber comprising a final reheater of the boiler steam cycle of the supercritical once-through circulating fluidized bed boiler;
• an external circulation of the supercritical once-through circulating fluidized bed boiler, the external circulation including a particle separator for separating the hot solids and the exhaust gas from the furnace of the circulating fluidized bed boiler;
• a first inlet channel for receiving the hot solids from the particle separator of the external circulation and for introducing the hot solids into the first heat exchange chamber, which is provided with a first fluidizer for fluidizing solids;
• a second inlet channel for introducing solids into the second heat exchange chamber, which is provided with second fluidizer for fluidizing solids;
• a first discharge for removing a portion of cooled solids from the first heat exchange chamber and for feeding the portion to the second inlet channel to be introduced into the second heat exchange chamber;
• a second discharge for removing cooled solids from the second heat exchange chamber and to feeding the cooled solids from the second heat exchange chamber into the furnace of the supercritical once-through circulating fluidized bed boiler;
• and
• an inlet for introducing hot solids from an internal circulation of the furnace directly to the second heat exchange chamber, in order to assure a high heat exchange rate in the second heat exchange chamber, even at low loads.