Method for reducing specific air consumption in a caes system

Abstract

A system and method are provided for a compressed air energy storage (CAES) system. The system and method may include compressing a process gas with a compressor train to produce a compressed process gas. The compressed process gas may be directed to a compressed gas storage unit and stored therein. The compressed process gas from the compressed gas storage unit may be released to a heat recovery unit via a feed line. The heat recovery unit may heat the compressed process gas and direct the heated compressed process gas to an expansion assembly to generate a power output. Feed water from a feed water source may be heated in the heat recovery unit to produce steam for injection into a combustion turbine assembly. The combustion turbine assembly may heat the heat recovery unit via an exhaust line.

1 . A method for reducing specific air consumption in a compressed air energy storage system, comprising:
 compressing a process gas with a compressor train to produce a compressed process gas;   directing the compressed process gas to a compressed gas storage unit and storing the compressed process gas in the compressed gas storage unit;   releasing the compressed process gas from the compressed gas storage unit to a heat recovery unit via a feed line;   heating the compressed process gas in the heat recovery unit and directing the heated compressed process gas to an expansion assembly to generate a first power output;   feeding feed water from a feed water source to the heat recovery unit and heating the feed water to produce steam;   compressing a second process gas in a compressor of a combustion turbine assembly and directing the compressed second process gas to a combustor;   combusting a fuel and the compressed second process gas from the compressor in the combustor to provide a combustion product;   expanding the combustion product in a turbine of the combustion turbine assembly to provide an exhaust product and a second power output;   directing the exhaust product to the heat recovery unit via an exhaust line to heat the heat recovery unit; and   introducing the steam from the heat recovery unit to the combustion turbine assembly to reduce the specific air consumption in the compressed air energy storage system.   
     
     
         2 . The method of  claim 1 , further comprising introducing the steam to the combustion turbine assembly upstream of the combustor. 
     
     
         3 . The method of  claim 1 , further comprising:
 receiving the exhaust product from the exhaust line in a duct burner of the heat recovery unit; and   further heating the exhaust product in the duct burner.   
     
     
         4 . The method of  claim 1 , further comprising:
 directing the compressed process gas from the compressed gas storage unit to a first recuperator of the heat recovery unit;   transferring heat from the exhaust line to the compressed process gas in the first recuperator to preheat the compressed process gas; and   directing the preheated compressed process gas to a second recuperator for further heating before directing the heated compressed process gas to the expansion assembly.   
     
     
         5 . The method of  claim 1 , further comprising expanding the heated compressed process gas from the heat recovery unit via a turbine of the expansion assembly to provide an expanded process gas and the first power output. 
     
     
         6 . The method of  claim 5 , further comprising directing the expanded process gas to the compressor of the combustion turbine assembly. 
     
     
         7 . The method of  claim 1 , wherein the steam produced by the heat recovery unit does not combine with the compressed process gas from the compressed gas storage unit.