Air-fired CO2 capture ready circulating fluidized bed heat generation with a reactor subsystem

A heat generating system operable in a non-CO2 capture mode or a CO2 capture mode, comprising:

• a combustor configured to (i) combust a fluidized bed of fossil fuel to heat a working fluid and generate flue gas, and (ii) exhaust the heated working fluid and the generated flue gas;
• and
• a preheater configured to preheat air, and having a first gas passageway for directing the exhausted flue gas to preheat the air and a second gas passageway for directing other gas with CO2 generated by combustion outside of the combustor;
• wherein the combustor is further configured to fluidize a bed of fossil fuel with the preheated air;
• wherein, in the non-CO2 capture mode, (i) the preheater receives the exhausted flue gas, but not the other gas, and (ii) the first passageway directs the received flue gas to preheat the air, thereby cooling the directed flue gas.

A method of operating a heat generating system, having a preheater for preheating air that includes a first gas passageway and a second gas passageway, comprising:

• combusting a fluidized bed of fossil fuel to heat a working fluid and generate first gas;
• when the heat generating system is only in a non-CO2 capture mode;
• directing the generated first gas via the first gas passageway to preheat the air, thereby cooling the generated first gas;
• directing the cooled first gas along a first path;
• fluidizing a bed of fossil fuel with the preheated air;
• when the heat generating system is only in a CO2 capture mode:
• combusting the generated residual solids to generate a second gas with CO2;
• directing the generated second gas via the second gas passageway to preheat the air, thereby cooling the generated second gas;
• and
• directing the cooled second gas along a second path different than the first path;
• and
• removing CO2 from the cooled second gas directed along the second path.