US008091.369B2 (12) United States Patent (10) Patent No.: US 8,091,369 B2 Allam et al. (45) Date of Patent: Jan. 10, 2012 (54) METHOD AND APPARATUS FOR 5,724.805 A * 3/1998 Golomb et al. ................. 60.783 GENERATINGELECTRICAL POWER 6,117,916 A * 9/2000 Allam et al. .................. 51877O2 6,244,033 B1 6/2001 Wylie (75) Inventors: Rodney John Allam, Chippenham (GB); OTHER PUBLICATIONS Vincent White,O O Ashtead (GB); Julia Dillon.IllOn, D. J.C.J..et al. “OXV-CombustionXy-UompuSuon ProcessesP forIor CO2 Carotapture Elizabeth Milligan, Leatherhead (GB) From Advanced Supercritical PF and NGCC Power Plant”, presented a the 7th International Conference on Greenhouse Gas Control Tech (73) Assignee: As Produced hemicals, Inc., nologies (GHGT-7), Vancouver, Canada, Sep. 2004. entown, (US) Panesar, Ragi, et al., “Coal-Fired Advanced Supercritical Boiler / c Turbine Retrofit with CO2 Capture', presented at Greenhouse Gas (*) Notice: Subject to any disclaimer, the term of this Control Technologies: Proceedings of the 8th International Confer patent is extended or adjusted under 35 ence (Jun. 19-22, 2006, Trondheim, Norway). U.S.C. 154(b) by 851 days. * cited by examiner (21) Appl. No.: 12/171,699 Primary Examiner — Ehud Gartenberg (22) Filed: Jul. 11, 2008 Assistant Examiner — Vikansha Dwivedi e ----9 (74) Attorney, Agent, or Firm — Keith D. Gourley; Bryan C. (65) Prior Publication Data Hoke, Jr. US 201O/OOO7146A1 Jan. 14, 2010 (57) ABSTRACT (51) Int. Cl. A. superheater ina power plant that superheats steam to opera F22G 3/00 (2006.01) tion conditions exceeding an operating limit of an associated (52) U.S. Cl 60/772 122/460 steam-producing boiler. The Superheater combusts oxygen (58) Fi ld f c - - - - - ificati- - - - - -s - - - - - - - h- - - - - - - - s 6O7772 and fuel with cooled recycled combustion gas to produce a O a's ii. 1335 Bao 483. CO-rich combustion product gas stream at a fixed tempera s - - - -u. Y-1's - - - 122479 467 468 ture. The combustion gas is used as the heat transfer fluid in See application file for complete search histo s the Superheater's heat exchanger. The CO-rich flue gas pp p ry. stream allows for efficient capture of substantially pure CO. (56) References Cited The Superheater may be retrofitted to an existing power plant as a separate component, external to the boiler. The plant may U.S. PATENT DOCUMENTS thus have its electrical power output increased, while its over 4,272,953 A * 6/1981 Rice ................................ 60,774 all CO2 emissions per nit of generated power is decreased, 4,697.415 A * 10/1987 Schiffers ...................... 60/39.12 even when inexpensive, readily-available fossil fuels are used 5,361.377 A 11, 1994 Miller as the primary fuel for filing the boiler and/or the superheater. 5,526,386 A * 6/1996 Tsiklauri et al. .............. 376/.317 5,628,183 A * 5/1997 Rice ........................... 60,39.182 15 Claims, 6 Drawing Sheets 103 HP Steam Superheated HP Steam from Boiler to Turbines P Steam Superheated P Steam from Boiler O7 to Turbines 9 - Y --- Oxyfuel Mixer Burner 3 6 68 U.S. Patent Jan. 10, 2012 Sheet 1 of 6 US 8,091,369 B2 A./G. / P Stern (PRIOR ART) 40 bar PS HP Stedm O3 3: Pim l66 bar 565 C Air Flue Gas Coal HP Boiler Feed Water Condensate 2O A/G.2 22 HP Stedm to HP Steam from P Steam to IP Steam from 50 Superheater Superheater Superheater Superheater T66 bar 166 bor A0 bar 40 bar 565 °C 700 °C HP Boiler Feed Wolfer U.S. Patent US 8,091,369 B2 6l O O : 99 |9Z —(º)-,(2) 01 US 8,091,369 B2 1. 2 METHOD AND APPARATUS FOR nal to a main boiler. In accordance with the present invention, GENERATINGELECTRICAL POWER the superheater's heat transfer fluid is a CO-rich combustion product gas stream produced by burning a carbonaceous or BACKGROUND OF THE INVENTION hydrocarbon fuel in Substantially-pure oxygen, and control ling temperature within the combustion chamber by recycling The present invention relates generally to generation of part of the combustion gases. The production of the CO-rich electrical power in Stationary powerplants. More specifically, combustion product gas stream allows for capture of Substan the present invention provides a method and apparatus for tially pure CO from the net combustion product gas follow production of electrical power with improved efficiency and/ ing cooling, condensation and removal of liquid water. This or improved capture of carbon dioxide. 10 results in increased power generation for a given CO2 emis Conventional methods of generation of electrical power in sion level or a reduced CO2 emission level for a given amount stationary power plants involves generation of high-pressure of power generated (e.g., per kWh). steam, and feeding of the steam to a steam turbine in which More specifically, an exemplary method for generating the steam pressure drops and the steam drives the turbine to electrical power in a power plant having a boiler producing a generate electrical power. For example, a fossil-fuel fired 15 steam stream fed to a steam turbine driving an electrical boiler may be used to produce high-pressure Superheated generator involves producing a pressurized high-pressure steam that is fed to an upstream steam turbine in a series train steam stream of steam at Steam conditions below an operating of turbines in which steam flows from higher pressure tur limit of the boiler, producing a CO-rich combustion product bines to lower pressure turbines, all of which are connected to gas stream by combustion of oxygen and fuel in an Oxyfuel a drive shaft of an electrical generator for producing electrical combustion process, the combustion product gas stream hav power. Optionally the Steam may be taken at an intermediate ing a temperature higher than a respective temperature of the pressure and superheated in the fossil fuel fired boiler before high pressure Steam stream, heating the high-pressure steam returning to the train of steam turbines for further expansion. stream from the boiler with the combustion product gas Many existing power plants include coal-fired boilers, and stream to produce a Superheated high-pressure steam stream use of coal-fired boilers is desirable in that a significant 25 of steam at Steam conditions above the operating limit of the amount of the world's fossil fuel reserves exists as coal. boiler, and feeding the Superheated high pressure steam Undesirably, CO emissions per kWh of electricity produc stream to the steam turbine to drive the steam turbine to tion from a coal-fired power station are relatively high, and generate electrical power. Optionally an intermediate pres may be more than double that from a natural gas fuelled Sure steam stream can be taken from the discharge of one of combined cycle power station. Further, CO capture efforts to 30 the steam turbines and superheated first in the steam boiler reduce undesirable CO emissions reduce the efficiency of and then in the external Superheater before returning at a power plants and lead to higher power generation costs. temperature above the operating limit of the boiler to the inlet The amount of electrical power produced is a function of of the next steam turbine. The method may further involve the temperature and pressure steam conditions of steam fed to treating at least a portion of the combustion product gas the turbines. Increased temperature and pressure of the steam 35 stream exiting the heat exchanger to capture Substantially tends to increase electrical power production, and thus overall pure CO. power production efficiency. However, the materials, etc. of Provided also is a power plant apparatus for generating turbines and boilers provide effective limits to the steam electrical power that includes a boiler configured to receive conditions for a given power plant. Although higher perfor boiler feedwater and to produce a pressurized high-pressure mance turbines and boilers may be available, the costs of such 40 steam stream of steam at Steam conditions below an operating higher performance equipment are often excessive, particu limit of the boiler, a steam superheater external to the boiler, larly for high performance boilers. Additionally, there may be a first steam turbine having a steam inlet connected to the heat other problems in using Such high-performance equipment. exchanger to receive the Superheated high pressure steam For example, for a conventional coal-fired steam boiler, there stream, the first steam turbine expanding the Superheated may be an operating limit of 600° C. at 300 bar pressure. To 45 high-pressure steam stream to create a first expanded stream obtain significantly higher temperatures and pressures may and to drive an electrical generator to generate electrical require very costly Super-alloys that are high in nickel con power, and a CO-capture system connected to the heat tent, which may result in problems from ash and slag depo exchanger to cause at least a portion of the CO-rich combus sition and corrosion. These alloys are not currently approved tion product gas stream exiting the heat exchanger to be for use in steam boilers but they can be used in heat exchang 50 conveyed to the CO-capture system, the CO-capture system ers for Superheating of steam. Accordingly, the boiler and/or being capable of treating the CO-rich combustion product turbine have operating limits that limit as a practical matter gas stream and capturing purified CO. The steam Super the amount of increased powerproduction efficiency that may heater includes a combustor configured to combust oxygen be obtained by increasing the temperature and pressure of the and fuel in an oxyfuel combustion process to produce a CO Steam.