Process for retrofitting an industrial gas turbine engine for increased power and efficiency

Abstract

A process for retrofitting an industrial gas turbine engine of a power plant where an old industrial engine with a high spool has a new low spool with a low pressure turbine that drives a low pressure compressor using exhaust gas from the high pressure turbine, and where the new low pressure compressor delivers compressed air through a new compressed air line to the high pressure compressor through a new inlet added to the high pressure compressor. The old electric generator is replaced with a new generator having around twice the electrical power production. One or more stages of vanes and blades are removed from the high pressure compressor to optimally match a pressure ratio split. Closed loop cooling of one or more new stages of vanes and blades in the high pressure turbine is added and the spent cooling air is discharged into the combustor.

We claim the following: 
     
         1 . A process for retrofitting an industrial gas turbine engine of a power plant, the industrial gas turbine engine having a main compressor driven by a main turbine and an electric generator either driven by the main compressor or by a power turbine driven by the main turbine, the process comprising the steps of:
 adding a new inlet to the main compressor capable of receiving a greater air flow;   adding a low spool with a low pressure turbine driving an low pressure compressor to the main turbine such that the low pressure turbine is driven by exhaust from the main turbine;   adding a variable inlet guide vane assembly to an inlet side of the low pressure turbine;   adding a compressed air line connecting the low pressure compressor to the new inlet of the main compressor such that compressed air from the low pressure compressor flows into the main compressor; and, replacing the electric generator with a new electric generator that has around twice the electrical power production.   
     
     
         2 . The process for retrofitting an industrial gas turbine engine of a power plant of  claim 1 , and further comprising the steps of:
 removing at least one stage of rotor blades and stator vanes from the main compressor to optimally match a pressure ratio split between the low pressure compressor and the main compressor.   
     
     
         3 . The process for retrofitting an industrial gas turbine engine of a power plant of  claim 1 , and further comprising the steps of:
 removing the old electric generator from the power turbine;   adding a low pressure compressor to be driven by the power turbine;   adding a variable inlet guide vane assembly to an inlet side of the power turbine;   adding a compressed air line connecting the low pressure compressor to the new inlet of the main compressor such that compressed air from the low pressure compressor flows into the main compressor; and,   adding a new electric generator having around twice the electrical power production of the old generator to be driven by the high pressure compressor shaft.   
     
     
         4 . The process for retrofitting an industrial gas turbine engine of a power plant of  claim 3 , and further comprising the steps of:
 removing at least one stage of rotor blades and stator vanes from the main compressor to optimally match a pressure ratio split between the low pressure compressor and the main compressor.   
     
     
         5 . The process for retrofitting an industrial gas turbine engine of a power plant of  claim 3 , and further comprising the steps of:
 adding a gear box between the new electric generator and the high pressure compressor shaft.   
     
     
         6 . The process for retrofitting an industrial gas turbine engine of a power plant of  claim 1 , and further comprising the steps of:
 removing at least one stage of the stator vanes form the high pressure turbine;   installing new at least one stage of stator vanes in the high pressure turbine in which the new stator vanes have a closed loop cooling circuit;   providing a source of compressed air for cooling of the new stage of turbine stator vanes; and,   discharging spent cooling air from the new stage of turbine stator vanes into the combustor that produces the hot gas stream for the high pressure turbine.   
     
     
         7 . The process for retrofitting an industrial gas turbine engine of a power plant of  claim 6 , and further comprising the steps of:
 bleeding off cooling air from the high pressure compressor;   intercooling the cooling air;   increasing the pressure of the cooling air to a pressure slightly higher than an outlet pressure of the high pressure compressor; and,   passing the higher pressure cooling air through the closed loop cooling circuit in the new stage of turbine stator vanes.   
     
     
         8 . The process for retrofitting an industrial gas turbine engine of a power plant of  claim 6 , and further comprising the steps of:
 compressing ambient air with an external compressor to a pressure slightly higher than an outlet pressure of the high pressure compressor;   intercooling the cooling air; and,   passing the higher pressure cooling air through the closed loop cooling circuit in the new stage or stages of turbine stator vanes.   
     
     
         9 . The process for retrofitting an industrial gas turbine engine of a power plant of  claim 6 , and further comprising the steps of:
 bleeding off compressed cooling air from an outlet of the high pressure compressor;   intercooling the compressed cooling air;   increasing the pressure of the compressed cooling air to a pressure slightly higher than an outlet pressure of the high pressure compressor; and,   passing the higher pressure cooling air through the closed loop cooling circuit in the new stage of turbine stator vanes.   
     
     
         10 . The process for retrofitting an industrial gas turbine engine of a power plant of  claim 6 , and further comprising the steps of:
 bleeding off compressed cooling air from an outlet of the high pressure compressor;   increasing the pressure of the compressed cooling air to a pressure slightly higher than an outlet pressure of the high pressure compressor;   intercooling the compressed cooling air; and,   passing the higher pressure cooling air through the closed loop cooling circuit in the new stage or stages of turbine stator vanes.   
     
     
         11 . The process for retrofitting an industrial gas turbine engine of a power plant of  claim 6 , and further comprising the steps of:
 bleeding off some of the compressed air from the compressed air line between the low pressure compressor and the high pressure compressor for use as the cooling air for the new stage of turbine stator vanes; and,   cooling and compressing the cooling air to a pressure slightly higher than an outlet pressure of the high pressure compressor.   
     
     
         12 . The process for retrofitting an industrial gas turbine engine of a power plant of  claim 1 , and further comprising the steps of:
 adding a variable inlet guide vane assembly to both the main compressor and the low pressure compressor.   
     
     
         13 . A power plant with a retrofitted industrial gas turbine engine capable of producing greater power and at high efficiency, the power plant comprising:
 an old main compressor driven by a high pressure turbine with a combustor;   a new inlet for the old main compressor capable of greater compressed air flow;   re-using the old electric generator;   a low spool with a new low pressure turbine or an old power turbine driven by exhaust gas from the high pressure turbine;   a new low pressure compressor driven by the low pressure turbine;   a new compressed air line connecting the new low pressure compressor to the new inlet of the high pressure compressor; and,   a new variable inlet guide vane assembly for the new low pressure turbine or the old power turbine.   
     
     
         14 . The power plant of  claim 13 , and further comprising:
 the old main compressor is without at least one stage of stator vanes and rotor blades such that a pressure ratio is optimally matched between the main compressor and the new low pressure compressor.   
     
     
         15 . The power plant of  claim 13 , and further comprising:
 the high pressure turbine has at least one stage of new stator vanes with a closed loop cooling circuit;   a source of compressed cooling air;   a compressed air cooling circuit to deliver compressed cooling air to the closed loop cooling circuit of the stator vanes and discharge spent cooling air into the combustor.   
     
     
         16 . The power plant of  claim 15 , and further comprising:
 a new boost compressor between the source of compressed cooling air and the stage of stator vanes to increase the pressure of the cooling air; and,   a new intercooler between the source of compressed cooling air and the stage of stator vanes to cool the compressed cooling air.   
     
     
         17 . The power plant of  claim 13 , and further comprising:
 Replacing the old electric generator with a new electric generator driven by the old main compressor with the new electric generator having a greater electrical power production than the old electric generator.