Method and system for power production with improved efficiency

Abstract

The present disclosure relates to systems and methods that provide power generation using predominantly CO 2 as a working fluid. In particular, the present disclosure provides for the use of a portion of the heat of compression from a CO 2 compressor as the additive heating necessary to increase the overall efficiency of a power production system and method.

1 . A method for heating a recirculating gas stream comprising:
 passing a gas stream G at a pressure P 1  and a temperature T 1  through a recuperative heat exchanger such that the gas stream is cooled to a temperature T 2  that is less than T 1 ;   separating the gas stream G into a first fraction G 1  and a second fraction G 2 ;   compressing the gas stream fraction G 1  to a pressure P 2  that is greater than P 1 ;   compressing the gas stream fraction G 2  to a pressure P 3  that is greater than P 1  so as to heat the gas stream fraction G 2  to a temperature T 3  that is greater than T 2 ;   withdrawing the heat from the compressed gas stream fraction G 2 ;   combining the gas stream fraction G 1  and the gas stream fraction G 2  to form a combined recirculating gas stream G C ;   pumping the recirculating gas stream G C  to a pressure P 4  that is greater than P 2  and greater than P 3 ; and   passing the recirculating gas stream G C  to the recuperative heat exchanger such that the gas stream G C  is heated by the cooling gas stream G;   wherein the heat withdrawn from the compressed gas stream fraction G 2  is added to the recirculating gas stream G C  after pumping to pressure P 4 .   
     
     
         2 . The method according to  claim 1 , wherein the temperature T 3  is about 100° C. to about 400° C. 
     
     
         3 . The method according to  claim 1 , wherein the pressure P 2  of gas stream fraction G 1  and the pressure P 3  of gas stream fraction G 2  are each separately about 40 bar (4 MPa) to about 100 bar (10 MPa). 
     
     
         4 . The method according to  claim 1 , wherein the pressure P 4  of the recirculating gas stream G C  is about 100 bar (10 MPa) to about 500 bar (50 MPa). 
     
     
         5 . The method according to  claim 1 , wherein the mass ratio of gas fraction G 1  to gas fraction G 2  based on the total mass of gas stream G is about 50:50 to about 99:1. 
     
     
         6 . The method according to  claim 1 , wherein the recirculating gas stream G C  after passing through the recuperative heat exchanger and receiving the heat from the compressed gas fraction G 2  has a temperature T 4  that is within 50° C. of T 1 . 
     
     
         7 . The method according to  claim 1 , wherein gas stream fraction G 2  is compressed with multi-stage compression with no intercooling. 
     
     
         8 . The method according to  claim 1 , wherein after withdrawing heat from gas stream fraction G 2 , the gas stream fraction G 2  is further compressed before combining with gas stream fraction G 1 . 
     
     
         9 . The method according to  claim 1 , wherein the recuperative heat exchanger comprises three heat exchangers or three heat exchange sections in series, such that heat is transferred in a first heat exchanger or heat exchange section operating in temperature range R 1 , a second heat exchanger or heat exchange section operating in temperature range R 2 , and a third heat exchanger or heat exchange section operating in temperature range R 3  with the temperature relationship of R 1 >R 2 >R 3 . 
     
     
         10 . The method according to  claim 9 , wherein the gas stream G is separated between the first heat exchanger or heat exchange section and the second heat exchanger or heat exchange section. 
     
     
         11 . The method according to  claim 9 , wherein the gas stream G is separated between the second heat exchanger or heat exchange section and the third heat exchanger or heat exchange section. 
     
     
         12 . The method according to  claim 9 , wherein the heat withdrawn from the compressed gas stream fraction G 2  is added to the recirculating gas stream G C  in one or both of the third heat exchanger or heat exchange section and the second heat exchanger or heat exchange section. 
     
     
         13 . The method according to  claim 1 , further comprising adding heat to the recirculating gas stream G C  after pumping to pressure P 4 , wherein the added heat is derived from one or both of an air separation unit and a gas turbine. 
     
     
         14 . The method according to  claim 1 , further comprising passing the heated recirculating gas stream G C  from the recuperative heat exchanger to a combustor that combusts a fuel with oxygen to form a combustion product stream. 
     
     
         15 . The method according to  claim 1 , wherein the gas stream G is a turbine exhaust stream. 
     
     
         16 . A method of generating power, the method comprising:
 combusting a fuel with oxygen in the combustor in the presence of a recycle CO 2  stream to produce a CO 2  containing combustion stream;   passing the CO 2  containing combustion stream through a turbine to expand the CO 2  containing combustion stream, generate power, and form a turbine exhaust stream;   withdrawing heat from the turbine exhaust stream;   dividing the turbine exhaust stream to form a first turbine exhaust portion and second turbine exhaust portion;   separating water from the first turbine exhaust portion to form a main recycle CO 2  stream;   compressing the main recycle CO 2  stream;   compressing the second turbine exhaust portion to form a heated, compressed second turbine exhaust portion;   withdrawing heat from the heated, compressed second turbine exhaust portion;   separating water from the cooled, compressed second turbine exhaust portion to form a secondary recycle CO 2  stream;   combining the main recycle CO 2  stream and the secondary recycle CO 2  stream to form a combined recycle CO 2  stream;   compressing the combined recycle CO 2  stream;   heating the combined recycle CO 2  stream with heat withdrawn from the turbine exhaust stream; and   further heating the combined recycle CO 2  stream with heat withdrawn from the heated, compressed second turbine exhaust portion.   
     
     
         17 - 25 . (canceled) 
     
     
         26 . A power generating system comprising:
 a combustor configured to exhaust a combustion stream;   a power production turbine configured to receive and expand the combustion stream and form a turbine exhaust stream;   a recuperative heat exchanger configured to receive the turbine exhaust stream;   a flow separator configured to separate the cooled turbine exhaust stream into a first gas stream and a second gas stream;   a first compressor configured to receive and compress the first gas stream;   a second compressor configured to receive and compress the second gas stream;   a pump configured to pressurize the first gas stream and the second gas stream in combination, the pump positioned downstream from the first compressor and the second compressor;   a first flow path through the recuperative heat exchanger configured for passage of the turbine exhaust stream;   a second flow path through the recuperative heat exchanger configured for passage of the pressurized first gas stream and second gas stream in combination;   a third flow path through the recuperative heat exchanger configured for passage of the compressed second gas stream;   wherein the first flow path and the third flow path are configured for heating the second flow path.   
     
     
         27 . The power generating system according to  claim 26 , wherein the recuperative heat exchanger comprises a series of three or more heat exchangers or a series of three or more heating sections. 
     
     
         28 . (canceled) 
     
     
         29 . The power generating system according to  claim 26 , wherein the first compressor comprises a multi-stage, intercooled compressor. 
     
     
         30 . The power generating system according to  claim 26 , wherein the second compressor comprises an adiabatic, multi-stage compressor with no intercooling between compressor stages.