Air-fired CO2 capture ready circulating fluidized bed steam generators

A steam generating system capable of being operated in either an air fired mode or in an O2 firing mode comprising:

• a fossil fuel combustor configured so as to be operative to (i) effect the fluidization of fossil fuel to thereby create a fluidized bed therefrom, (ii) to combust the fossil fuel for purposes of heating a first working fluid therewith and for generating a hot flue gas and hot solids entrained in the hot flue gas from such combustion of the fossil fuel, and (iii) to thereafter effect the exhausting of both such heated first working fluid and such generated hot flue gas;
• an air preheater configured so as to be operative to receive such generated hot flue gas from said fossil fuel combustor;
• a first blower configured so as to be operative to (i) cause air to flow to said air preheater when said steam generating system is being operated in the air fired mode and (ii) to cause both O2 and recycled flue gas to flow to said air preheater when said steam generating system is being operated in the O2 firing mode;
• wherein, when said steam generating system is being operated in the air fired mode, said air preheater is operative to effect the transfer of heat from the flue gas received thereby to the air that is caused to flow to said air preheater in order to thereby effect the preheating of such air and to effect a cooling of such flue gas therewith, and with such preheated air thereafter being made to flow from said air preheater to said fossil fuel combustor in order to thereby effect the fluidization of the fossil fuel therewith;
• and
• wherein, when said steam generating system is being operated in the O2 firing mode, said air preheater is operative to effect the transfer of heat from the flue gas received thereby to the O2 and the recycled flue gas that are both caused to flow to said air preheater in order to thereby effect a preheating of both such O2 and such recycled flue gas therewith and to effect a cooling of such flue gas therewith, and with both such preheated O2 and recycled flue gas thereafter being made to flow from said air preheater to said fossil fuel combustor in order to thereby effect the fluidization of the fossil fuel therewith;
• a separator configured so as to be operative to effect the separation therewith of such entrained hot solids from such exhausted flue gas, wherein such exhausted flue gas that is received by said air preheater from the separator, is such exhausted flue gas that has been subjected to separation in said separator;
• a heat exchanger configured, when said steam generating system is being operated in the O2 firing mode, so as to be operative to (i) receive both such hot solids and a second working fluid, (ii) effect a transfer of heat from such hot solids received thereby to such second working fluid received thereby in order to thereby effect a cooling therewith of such the hot solids and in order to thereby effect a heating of such second working fluid, and (iii) effect the exhausting of such heated first working fluid;
• a second blower configured so as to be operative to cause such recycled flue gas to flow to said heat exchanger when said steam generating system is being operated in the O2 firing mode;
• wherein, when said steam generating system is being operated in the O2 firing mode, such recycled flue gas is caused to flow to said heat exchanger for purposes of thereby both fluidizing and causing such cooled solids to flow from said heat exchanger to said fossil fuel combustor;
• a second heat exchanger configured so as to be operative to receive such separated hot solids and to effect the transfer of heat from such hot solids received thereby in order to thereby effect the cooling of such received hot solids;
• wherein, when said steam generating system is being operated in the air fired mode, said second blower is not employed;
• and
• wherein, when said steam generating system is being operated in the O2 firing mode, said second blower is further configured so as to be operative to cause such recycled flue gas to flow to said second heat exchanger in order thereby both to effect a fluidization therewith and to cause such cooled solids to flow from said second heat exchanger to said fossil fuel combustor.

A method of generating steam either in an air fired mode or an O2 firing mode comprising the steps of:

• effecting the fluidization of fossil fuel to create a fluidized bed therefrom;
• effecting the combustion of such fossil fuel in order to effect both the heating therewith of a first working fluid and the generation of flue gas;
• effecting the transfer of heat from such generated flue gas (i) to air in order to thereby effect both a preheating of such air and a cooling of such generated flue gas, when operating in the air fired mode, or (ii) to both O2 and recycled flue gas in order to thereby effect a preheating of both such O2 and such recycled flue gas and a cooling of such generated flue gas, when operating in the O2 firing mode;
• and
• effecting a fluidization of such fossil fuel with (i) such preheated air, when operating in the air fired mode, or (ii) with both such preheated O2 and such recycled flue gas, when operating in the O2 firing mode;
• and
• effecting the transfer of heat from other separated hot solids to a third working fluid in order to thereby effect the cooling therewith of such other separated hot solids;
• effecting the cooling of such cooled other solids with (i) air, when operating in the air fired mode, or (ii) recycled flue gas, when operating in the O2 firing mode;
• and
• effecting the combustion of such fluidized other solids in order to thereby effect therewith both the heating of such first working fluid and the generation of flue gas.

The method as claimed in 8, wherein such working fluid is a first working fluid, the combusting of such fossil fuel also generates residual hot solids that become entrained in such generated flue gas, and said method further comprises the steps of:

• effecting the separation of such entrained hot solids from such generated flue gas, wherein such generated flue gas that effects the transfer of such heat therefrom comprises separated flue gas;
• effecting the transfer of heat from such separated hot solids to a second working fluid in order to thereby effect a cooling therewith of such separated hot solids;
• effecting the fluidization of such cooled solids with air, when operating in the air fired mode, or with recycled flue gas, when operating in the O2 firing mode;
• and
• effecting the combustion of such fluidized cooled solids in order to thereby both heat such first working fluid and generate such flue gas.