Pressurized oxy-combustion power boiler and power plant and method of operating the same

Abstract

A pressurized oxy-combustion circulating fluidized bed power plant having a circulating fluidized bed boiler is provided. A combustion chamber of the boiler is in fluid communication with a separator and configured so that solids produced during combustion enter the separator. The power plant further includes an air separation unit that is in fluid communication with the combustion chamber. The air separation unit is configured to supply substantially pure oxygen to the combustion chamber at a pressure greater than 1 bar. An external heat exchanger is in fluid communication with the separator and in fluid communication with the combustion chamber. The external heat exchanger is configured so that a portion of the solids received in the separator pass through the external heat exchanger and transfer heat to a working fluid, after which the solids are returned to the combustion chamber to moderate or control the temperature in the combustion chamber.

What is claimed is: 
     
         1 . A pressurized oxy-combustion circulating fluidized bed power plant, comprising:
 a circulating fluidized bed boiler including a combustion chamber and a separator, the combustion chamber being in fluid communication with the separator and configured so that solids produced during combustion in the combustion chamber enter the separator;   an air separation unit in fluid communication with the combustion chamber, the air separation unit configured to supply substantially pure oxygen to the combustion chamber at a pressure greater than 1 bar; and   an external heat exchanger in fluid communication with the separator and in fluid communication with the combustion chamber, the external heat exchanger being configured so that a portion of the solids received in the separator pass through the external heat exchanger and transfer heat to a working fluid, after which the solids are returned to the combustion chamber to moderate a temperature of combustion in the combustion chamber.   
     
     
         2 . The pressurized oxy-combustion circulating fluidized bed power plant of  claim 1  wherein the pressure of the substantially pure oxygen supplied from the air separation unit to the combustion chamber is between 6 bar and 30 bar. 
     
     
         3 . The pressurized oxy-combustion circulating fluidized bed power plant of  claim 2  wherein the external heat exchanger comprises one or more of a fluidized bed head exchanger or a moving bed heat exchanger. 
     
     
         4 . The pressurized oxy-combustion circulating fluidized bed power plant of  claim 3 , further comprising:
 a condensing heat exchanger; and   wherein a portion of a flue gas generated during combustion in the combustion chamber is passed through the condensing heat exchanger.   
     
     
         5 . The pressurized oxy-combustion circulating fluidized bed power plant of  claim 4  wherein latent energy recovered in the condensing heat exchanger is used to supplement steam extracted from a turbine in the power plant for heating feedwater being fed to the boiler. 
     
     
         6 . The pressurized oxy-combustion circulating fluidized bed power plant of  claim 5 , wherein a portion of the flue gas exiting the condensing heat exchanger is returned to the combustion chamber to fluidize and transport solids in the combustion chamber. 
     
     
         7 . The pressurized oxy-combustion circulating fluidized bed power plant of  claim 6 , wherein a portion of the flue gas exiting the condensing heat exchanger is directed to the external heat exchanger for solids fluidization if necessary. 
     
     
         8 . A pressurized oxy-combustion circulating moving bed power plant, comprising:
 a circulating moving bed boiler including a combustion chamber and moving bed heat exchanger, the boiler being configured so that the combustion chamber is located in a tower above the moving bed heat exchanger so that solids produced during combustion in the combustion chamber flow downward into the moving bed heat exchanger; and   an air separation unit in fluid communication with the combustion chamber, the air separation unit configured to supply substantially pure oxygen to the combustion chamber at a pressure greater than 1 bar;   wherein solids that enter the moving bed heat exchanger transfer heat to a working fluid, after which the solids are returned to the combustion chamber to moderate a temperature of combustion in the combustion chamber.   
     
     
         9 . The pressurized oxy-combustion circulating moving bed power plant of  claim 8  wherein the pressure of the substantially pure oxygen supplied from the air separation unit to the combustion chamber is between 6 bar and 30 bar. 
     
     
         10 . The pressurized oxy-combustion circulating moving bed power plant of  claim 9 , further comprising:
 a condensing heat exchanger.   
     
     
         11 . The pressurized oxy-combustion circulating moving bed power plant of  claim 9 , wherein a portion of a flue gas generated during combustion in the combustion chamber is passed through the condensing heat exchanger. 
     
     
         12 . The pressurized oxy-combustion circulating moving bed power plant of  claim 11  wherein latent energy recovered in the condensing heat exchanger is used to supplement steam extracted from a turbine in the power plant for heating feedwater being fed to the boiler. 
     
     
         13 . The pressurized oxy-combustion circulating moving bed power plant of  claim 8 , wherein a portion of the flue gas exiting the condensing heat exchanger is returned to the combustion chamber to fluidize and transport solids in the combustor. 
     
     
         14 . A method of operating a pressurized oxy-combustion fluidized bed power plant, comprising:
 providing a fluidized bed boiler including a combustion chamber and a separator, the combustion chamber being in fluid communication with the separator and configured so that solids produced during combustion in the combustion chamber enter the separator;   supplying substantially pure oxygen to the combustion chamber at a pressure greater than 1 bar; and   passing a portion of the solids received in the separator through an external heat exchanger and transfer heat to a working fluid, returning the solids to the combustion chamber to moderate a temperature of combustion in the combustion chamber.   
     
     
         15 . The method of  claim 14  wherein the pressure of the substantially pure oxygen supplied to the combustion chamber is between 6 bar and 30 bar. 
     
     
         16 . The method of  claim 15  wherein the external heat exchanger comprises one or more of a fluidized bed heat exchanger or a moving bed heat exchanger. 
     
     
         17 . The method of  claim 16 , further comprising the steps of:
 providing a condensing heat exchanger; and   passing a portion of a flue gas generated during combustion in the combustion chamber through the condensing heat exchanger.   
     
     
         18 . The method of  claim 17  wherein latent energy recovered in the condensing heat exchanger supplements steam extracted from a turbine in the power plant for heating feedwater being fed to the boiler. 
     
     
         19 . The method of  claim 18 , further comprising the steps of:
 returning a portion of the flue gas exiting the condensing heat exchanger to the combustion chamber to fluidize and transport solids in the combustion chamber.   
     
     
         20 . The method of  claim 19 , wherein a portion of the flue gas exiting the condensing heat exchanger is directed to the external heat exchanger for solids fluidization if necessary.