Working fluid compositions for use in semi-closed Brayton cycle gas turbine power systems

Abstract

A gas mixture is provided which includes CO 2 , steam and oxygen. The gas mixture has characteristics which mimic those of air, so that an air compressor need not be modified to effectively compress the gas mixture. The gas mixture is compressed within the compressor and routed to a combustor where a fuel combusts with the oxygen of the gas mixture and produces an exhaust which is substantially entirely CO 2 and steam. This exhaust can be routed through a turbine and expanded to drive the compressor and output power. A portion of the exhaust is routed to a return duct where excess steam and CO 2 is discharged and oxygen is added to the exhaust sufficient to convert the exhaust back into the original gas mixture. Combustion based power is thus generated with removal of steam and CO 2 in an easily captured form.

1 - A gas mixture for use as an oxidizer mixture portion of a working fluid in a gas turbine combustor, the mixture comprising in combination: 
 by weight between about forty percent and about eighty percent carbon dioxide, between about ten percent and about fifty percent water and between about ten percent and about thirty percent oxygen.    
   
   
       2 - The mixture of  claim 1  wherein said mixture includes by weight between about forty percent and about fifty-five percent carbon dioxide, between about thirty percent and about fifty percent water and between about ten percent and about twenty percent oxygen.  
   
   
       3 - The mixture of  claim 2  wherein said mixture includes by weight about forty-eight percent carbon dioxide, about thirty-nine percent water and about thirteen percent oxygen.  
   
   
       4 - The mixture of  claim 1  wherein said mixture includes by weight between about fifty percent and about sixty-two percent carbon dioxide, between about twenty percent and about thirty-five percent water and between about ten percent and twenty-five percent oxygen.  
   
   
       5 - The mixture of  claim 4  wherein said mixture includes by weight about fifty-six percent carbon dioxide, about twenty-eight percent water and about sixteen percent oxygen.  
   
   
       6 - The mixture of  claim 1  wherein said mixture includes by weight between about fifty percent and about eighty percent carbon dioxide, between about ten percent and thirty percent water and between about fifteen percent and about thirty percent oxygen.  
   
   
       7 - The mixture of  claim 6  wherein said mixture includes by weight about sixty-three percent carbon dioxide, about seventeen percent water and about twenty percent oxygen.  
   
   
       8 - A gas mixture for use as an oxidizer in a combustor of an at least partially closed cycle power generation system, the gas mixture comprising in combination: 
 molecular gaseous oxygen (O 2 );    gaseous carbon dioxide (CO 2 );    water vapor (H 2 O); and    wherein a ratio of carbon dioxide to water within said gas mixture matches a ratio of carbon dioxide to water which occurs when methane (CH 4 ) combusts with gaseous molecular oxygen (O 2 ) substantially stoichiometrically.    
   
   
       9 - The mixture of  claim 8  wherein said mixture includes sufficient oxygen to cause said gas mixture to be compressible in a compressor designed to compress air without requiring compressor modification.  
   
   
       10 - The mixture of  claim 8  wherein said mixture includes by weight between about forty percent and about eighty percent carbon dioxide, between about ten percent and about fifty percent water vapor and between about ten percent and about thirty percent oxygen.  
   
   
       11 - The mixture of  claim 8  wherein said ratio of carbon dioxide to water is approximately one carbon dioxide molecule for every two water vapor molecules and about fifty-five percent of a combined weight of the carbon dioxide and the water is carbon dioxide and about forty-five percent of the combined weight of the carbon dioxide and the water is water.