United States Patent (10) Patent No.: US 7,325.400 B2 Cunningham Et Al
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USOO7325400B2 (12) United States Patent (10) Patent No.: US 7,325.400 B2 Cunningham et al. (45) Date of Patent: Feb. 5, 2008 (54) RANKINE CYCLE AND STEAM POWER 5,850,739 A 12/1998 Masnoi PLANT UTILIZING THE SAME 6,003,317. A 12/1999 Neubert 6,234,400 B1* 5/2001 Guyer ....................... 237,121 (75) Inventors: Carla I. Cunningham, Orlando, FL s: R 23: R SS MichaelA S. Briesch, Orlando, FL 6,457.95044 B1 10/2002 CooperaSSlly et al. FOREIGN PATENT DOCUMENTS (73) Assignee: Siemens Power Generation, Inc., Orlando, FL (US) DE 2 242302 3, 1974 DE 33 27 838 A1 12, 1983 (*) Notice: Subject to any disclaimer, the term of this DE 35 31 469 A1 1987 patent is extended or adjusted under 35 DE 36 16 797 A1 11, 1987 U.S.C. 154(b) by 686 days DE 195 24 216 A1 1, 1997 M YW- y yS. FR 974 116 2, 1951 GB 885643 12, 1961 JP 2002-303105 * 10/2002 (22) Filed: Jan. 9, 2004 * cited by examiner (65)65 PriorO PublicationDO Dat Primary Examiner—Hoang Nguyen US 2005/O15O227 A1 Jul. 14, 2005 (57) ABSTRACT (51) Int. Cl. FOIK I3/00 (2006.01) A steam power plant (100) implementing an improved (52) U.S. Cl. ........................................... 60/645; 60/670 Rankine cycle (55) wherein steam is injected (82, 96) (58) Field of Classification Search .................. 60/651, directly into the energy addition portion of the plant, and the 60/671, 645, 670 resulting two-phase flow is pressurized by multiphase See application file for complete search history. pumps (88.98). By relying more heavily on pump pressur ization than on a temperature difference for energy injection, (56) References Cited plant efficiency is improved over prior art designs since energy injection by pump pressurization results in less U.S. PATENT DOCUMENTS irreversibility than energy injection by temperature differ 3,314,236 A 4, 1967 Zanoni ence. Direct steam injection and multiphase pumping may 4,178,989 A * 12/1979 Takeshita et al. ............. 165/62 be used to bypass the condenser (20), to replace any one or 4,297,848 A 11/1981 Silvestri, Jr. 5,027.602 A * 7/1991 Glen et al. .................... 60/651 all of the feedwater heaters (24, 32, 34), and/or to provide 5,052,175 A 10, 1991 Brueckner et al. additional high-pressure energy addition. 5,216,899 A 6/1993 Fabris ....................... 62,324.6 5.437,157 A * 8/1995 Bronicki. 60/655 21 Claims, 7 Drawing Sheets 14 16 18 Condenser 78 U.S. Patent Feb. 5, 2008 Sheet 1 of 7 US 7,325.400 B2 FIG. 1 PRIOR ART FIG. 2 Entropy PRIOR ART FIG. 3 Entropy U.S. Patent Feb. 5, 2008 Sheet 2 of 7 US 7,325.400 B2 s 9 Induedue U.S. Patent Feb. 5, 2008 Sheet 3 of 7 US 7,325.400 B2 Number of LP FWH's Bypassed FIG. 6 U.S. Patent Feb. 5, 2008 Sheet 4 of 7 US 7,325.400 B2 5|| || | | | | | | | : Big E. 48.248.5 FNTNN | | | | FEE. 48.1 SSNH - - - BGSe Pont 27 | | E------its-N-STSN || 77 SNNN 276 || || ||NNS 47H75 SN 0.00 0.10 0.20 0.30 0.40 0.50 0.60 Quality After Mixing FIG. 8 U.S. Patent Feb. 5, 2008 Sheet 5 of 7 US 7,325.400 B2 14 16 18 aIP (WE) FW LP FIG. 9 -- P=2000 psi -- P=1500 psi -0- P=1000 psi - - - Bose Plant w/FWH's Quality After Mixing FIG. 1 O U.S. Patent Feb. 5, 2008 Sheet 6 of 7 US 7,325.400 B2 BOSeline 4 LP 4 LP 1 IP 1 HP 2 HP Al Optimized Optimized Deleted Feedwater Heoters FIC. 12 U.S. Patent Feb. 5, 2008 Sheet 7 Of 7 US 7,325.400 B2 1OO 14 16 18 12 86 82 O HP IP FW 88 FWH FWH Tonk 34 32 28 FIC. 13 US 7,325,400 B2 1. 2 RANKINE CYCLE AND STEAM POWER states 52, 54 respectively. The water is then heated to PLANT UTILIZING THE SAME Saturation temperature, boiled and typically superheated back to state 40 in boiler 12. FIELD OF THE INVENTION The rising cost of fuel and the demand for lower emis 5 Sions provide a continuing need for improvements in the This invention relates generally to the field of vapor efficiency of operation of steam power plants. cycles and more particularly to steam power plants operating on a Rankine cycle. BRIEF DESCRIPTION OF THE DRAWINGS BACKGROUND OF THE INVENTION 10 FIG. 1 is a schematic illustration of a prior art steam power plant. Basic elements of a conventional steam power plant 10 FIG. 2 is a Ts diagram for a prior art Rankine cycle steam are illustrated in schematic form in FIG.1. Aboiler 12 burns power plant. a combustible fuel to provide heat energy to convert feed FIG. 3 is a Ts diagram for an improved Rankine cycle water into saturated or superheated steam for delivery to a 15 steam power plant. high-pressure turbine 14. The steam is expanded through the FIG. 4 is the Ts diagram of FIG. 4 and including lines of turbine 14 to turn a shaft that powers an electrical generator constant enthalpy. (not shown). The steam is then directed in sequence through FIG. 5 is a schematic illustration of a steam power plant an intermediate pressure turbine 16 and a low-pressure wherein low-pressure feedwater heaters are replaced by turbine 18 where additional shaft energy is extracted. The Steam injection and multi-phase pumping. spent steam leaving the low-pressure turbine 18 is converted FIG. 6 is a chart of the plant efficiency achieved as back to water in condenser 20. A condensate pump 22 low-pressure feedwater heaters are replaced by condenser delivers water from the condenser 20 to a low-pressure bypass flow and multiphase pumping. feedwater heater 24. The feedwater heater 24 is a heat FIG. 7 is a schematic illustration of a steam power plant exchanger that adds energy to the water as a result of a 25 wherein high-pressure steam injection and multi-phase temperature difference between the water and steam sup pumping is provided downstream of the high-pressure feed plied through a low-pressure steam extraction line 26 from water heater. the low-pressure turbine 18. The heated water is collected in FIG. 8 is a chart of plant efficiency achieved with high a feedwater tank 28 which is also provided with an inter pressure feed-water heating and direct high-pressure steam mediate-pressure steam extraction connection 29. From the 30 injection. Plant efficiency is shown as a function of steam feedwater tank 28, the water is delivered by a feedwater quality after mixing. pump 30 through an intermediate pressure feedwater heater FIG. 9 is a schematic illustration of a steam power plant 32 and high-pressure feedwater heater 34, where additional wherein high-pressure steam injection and multi-phase energy is supplied via the temperature difference between pumping is provided in lieu of the high-pressure feedwater the water and steam supplied through intermediate pressure 35 heaters. Steam extraction line 36 and high-pressure steam extraction FIG. 10 is a chart of plant efficiency achieved with direct line 38 respectively. The heated feedwater is then delivered high-pressure steam injection in lieu of HP feedwater heaters back to the boiler 12 where the cycle is repeated. Plant 10 as a function of steam quality after mixing. may include many other components, systems and sub FIG. 11 is a schematic illustration of a steam power plant systems that are not illustrated in FIG. 1 but that are well 40 wherein low-pressure steam injection and multi-phase known in the art. Other known steam power plant designs pumping is provided in lieu of the low-pressure feedwater may utilize fewer or additional pressure stages for both heaters. energy extraction and feedwater heating. FIG. 12 is a chart of plant efficiency achieved by the use The powerplant 10 of FIG. 1 is a heat engine with a vapor of direct steam injection in lieu of feedwater heaters. cycle commonly referred to as a Rankine cycle. An ideal 45 FIG. 13 is a schematic illustration of a steam power plant Rankine cycle consists of four processes: isentropic expan wherein low-pressure and high-pressure steam injection and Sion through an expansion engine such as a turbine, piston, multi-phase pumping is provided. etc.; isobaric heat rejection through a condenser, isentropic compression through a pump; and isobaric heat supply DETAILED DESCRIPTION OF THE through a boiler. FIG. 2 is a typical Ts diagram illustrating 50 INVENTION the relationship of entropy and temperature for a prior art Rankine cycle 39 such as may be implemented in prior art The energy addition upstream of the boiler 12 in prior art power plant 10. The dashed line represents the vapor dome steam power plant 10 of FIG. 1 occurs primarily through the underneath which the working fluid (water for most com temperature difference (PT) generated within the feedwater mercial power plants) will exist in both the liquid and vapor 55 heaters 24, 32, 34, with a relatively smaller portion of the States simultaneously. Saturated or superheated steam enters energy being supplied by condensate pump 22 and feedwa a turbine at state 40, where it expands to the exit pressure at ter pump 30. It is well known that energy addition via a State 42. This expansion is not completely isentropic due to temperature difference will increase the enthalpy of a system the expected inefficiencies in the turbine design.