Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23L—SUPPLYING AIR OR NON-COMBUSTIBLE LIQUIDS OR GASES TO COMBUSTION APPARATUS IN GENERAL ; VALVES OR DAMPERS SPECIALLY ADAPTED FOR CONTROLLING AIR SUPPLY OR DRAUGHT IN COMBUSTION APPARATUS; INDUCING DRAUGHT IN COMBUSTION APPARATUS; TOPS FOR CHIMNEYS OR VENTILATING SHAFTS; TERMINALS FOR FLUES
  • F23L7/00—Supplying non-combustible liquids or gases, other than air, to the fire, e.g. oxygen, steam
  • F23L7/007—Supplying oxygen or oxygen-enriched air
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01K—STEAM ENGINE PLANTS; STEAM ACCUMULATORS; ENGINE PLANTS NOT OTHERWISE PROVIDED FOR; ENGINES USING SPECIAL WORKING FLUIDS OR CYCLES
  • F01K23/00—Plants characterised by more than one engine delivering power external to the plant, the engines being driven by different fluids
  • F01K23/02—Plants characterised by more than one engine delivering power external to the plant, the engines being driven by different fluids the engine cycles being thermally coupled
  • F01K23/06—Plants characterised by more than one engine delivering power external to the plant, the engines being driven by different fluids the engine cycles being thermally coupled combustion heat from one cycle heating the fluid in another cycle
  • F01K23/10—Plants characterised by more than one engine delivering power external to the plant, the engines being driven by different fluids the engine cycles being thermally coupled combustion heat from one cycle heating the fluid in another cycle with exhaust fluid of one cycle heating the fluid in another cycle
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01K—STEAM ENGINE PLANTS; STEAM ACCUMULATORS; ENGINE PLANTS NOT OTHERWISE PROVIDED FOR; ENGINES USING SPECIAL WORKING FLUIDS OR CYCLES
  • F01K7/00—Steam engine plants characterised by the use of specific types of engine; Plants or engines characterised by their use of special steam systems, cycles or processes; Control means specially adapted for such systems, cycles or processes; Use of withdrawn or exhaust steam for feed-water heating
  • F01K7/16—Steam engine plants characterised by the use of specific types of engine; Plants or engines characterised by their use of special steam systems, cycles or processes; Control means specially adapted for such systems, cycles or processes; Use of withdrawn or exhaust steam for feed-water heating the engines being only of turbine type
  • F01K7/22—Steam engine plants characterised by the use of specific types of engine; Plants or engines characterised by their use of special steam systems, cycles or processes; Control means specially adapted for such systems, cycles or processes; Use of withdrawn or exhaust steam for feed-water heating the engines being only of turbine type the turbines having inter-stage steam heating
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01K—STEAM ENGINE PLANTS; STEAM ACCUMULATORS; ENGINE PLANTS NOT OTHERWISE PROVIDED FOR; ENGINES USING SPECIAL WORKING FLUIDS OR CYCLES
  • F01K7/00—Steam engine plants characterised by the use of specific types of engine; Plants or engines characterised by their use of special steam systems, cycles or processes; Control means specially adapted for such systems, cycles or processes; Use of withdrawn or exhaust steam for feed-water heating
  • F01K7/34—Steam engine plants characterised by the use of specific types of engine; Plants or engines characterised by their use of special steam systems, cycles or processes; Control means specially adapted for such systems, cycles or processes; Use of withdrawn or exhaust steam for feed-water heating the engines being of extraction or non-condensing type; Use of steam for feed-water heating
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01K—STEAM ENGINE PLANTS; STEAM ACCUMULATORS; ENGINE PLANTS NOT OTHERWISE PROVIDED FOR; ENGINES USING SPECIAL WORKING FLUIDS OR CYCLES
  • F01K9/00—Plants characterised by condensers arranged or modified to co-operate with the engines
  • F01K9/02—Arrangements or modifications of condensate or air pumps
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN  A CARRIER GAS OR AIR 
  • F23C9/00—Combustion apparatus characterised by arrangements for returning combustion products or flue gases to the combustion chamber
  • F23C9/08—Combustion apparatus characterised by arrangements for returning combustion products or flue gases to the combustion chamber for reducing temperature in combustion chamber, e.g. for protecting walls of combustion chamber
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E20/00—Combustion technologies with mitigation potential
  • Y02E20/32—Direct CO2 mitigation
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E20/00—Combustion technologies with mitigation potential
  • Y02E20/34—Indirect CO2mitigation, i.e. by acting on non CO2directly related matters of the process, e.g. pre-heating or heat recovery

Definitions

• the invention relates to a power generation system comprising an oxy-fuel burner, a first heat exchanger assembly, and a rankine-cycle , wherein said rankine-cycle comprises at least one turbine expanding a working media or process fluid, down- stream said turbine at least one condenser condensing said process fluid, downstream said condenser at least one first working media pump (or feed water pump) delivering said process fluid to a higher pressure level, downstream said working media pump at least one first working media pre-heater (or feed water pre-heater) heating said process fluid by extracted process fluid or extracted working media from said turbine, and downstream said working media pre-heater said process fluid passes said first heat exchanger assembly to be boiled and superheated.
• the oxy-fuel burner will be provided with recirculated and compressed exhaust fluid from said oxy- fuel burner.
• the oxygen containing gas is basically pure oxygen with minor impurities generated by for example an air separation unit, which can be of conventional membrane type.
• an oxy-fuel burner is characterized by burning basically a fuel with an oxygen containing gas wherein said oxygen containing gas has significant higher oxygen content than ambient air and wherein oxygen is its main component and wherein said oxygen containing gas is preferably pure oxygen with some impurities.
• This oxygen containing gas may contain some further additives but its main component is preferably oxygen.
• the oxygen containing gas is a gas with an elevated oxygen content compared to ambient air.
• the total efficiency of a conventional power generation sys- tern with an oxy-fuel burner is significantly below the efficiency of an ordinary power generation system if the energy consumption of the air separation unit is considered.
• the efficiency is therefore to be improved to make this technology economically feasible and to have a positive effect on the environment.
• the object of enhancing the efficiency of the incipiently defined power generation system is achieved by a power generation system according to the incipiently mentioned type with the further features of the characterizing portion of claim 1. Further the object is achieved by a method of the incipi- ently mentioned type with the further features of the characterizing portion of the independent method claim. Embodiments can be found in the dependent claims.
• One essential aspect of the proposed improvement of the power generation system respectively the method according to the invention is the combination of oxy-fuel combustion principle with a boiler design separating the carbon dioxide - steam cycle from the steam - water cycle.
• This unique feature enables the operation of the exhaust fluid - i.e. a heat carrying media - at elevated pressure above atmospheric pressure. Further high efficiency is achieved by taking the recircula- tion of exhaust fluid from upstream economizers in the boiler such that as little heat as possible is moved from high temperature to a low temperature parts of the cycle.
• Said oxy-fuel burner according to the invention is basically a gas generator generating an exhaust gas respectively exhaust fluid from a fuel burned with essentially pure oxygen.
• This exhaust gas is referred to as exhaust-fluid since it might contain liquid components or parts of the fluid might condense to a liquid.
• a further beneficial efficiency improvement of the process according to the invention or an embodiment thereof is obtained by providing said turbine as a combination of at least a high pressure turbine and a low pressure turbine, wherein between these two turbines the working media or process fluid - both terms will be used to identify the closed loop fluid or medium of the steam cycle - is led through a reheater, wherein said reheater is part of said first heat exchanger assembly, so that said process fluid is reheated by said ex- haust fluid downstream said high pressure turbine and upstream said low pressure turbine.
• Another beneficial improvement of the invention is given by providing at least one adjustable valve and/or one adjustable pump - which can be a multiphase pump or might as well be a compressor - to control the flow through said recirculation line.
• a control unit controls the position of said adjustable valve or pump in the recirculation line according to a temperature measurement located preferably upstream said heat exchanger assembly.
• This control unit is designed such that it receives the measurement results from temperature measurement and sub- mits control signals to said control valve.
• the control method preferably is designed such that the valve opens further when exceeding a temperature limit is recognized. Further the valve control can be designed such that upper limits of temperature increases respectively steep temperature transients in a turbine of the power generation system are avoided.
• a mixing pre-heater is provided upstream of said at least one first working media pre-heater (or first feed water pre-heater) .
• Said mixing pre- heater mixes a third extracted process fluid (or extracted working media) from said turbine with said process fluid downstream said condenser.
• FIG. 1 shows a schematic flow diagram of an oxy fuel power plant comprising the arrangement according to the invention and depicting the method according to the invention
• figure 2 shows a schematic flow diagram of an oxy fuel power plant comprising the arrangement according to a second embodiment of the invention and depicting the method according to the invention .
• Figure 1 - and also Figure 2 later on - is a schematic depic tion of a simplified flow diagram showing a power generation system and illustrating a method according to the invention.
• fuel F and oxygen 0 2 from an air sepa- ration unit ASU are both elevated to a higher pressure level by compressors CI, C2 , which compressors CI, C2 might be provided with not shown intercoolers before both fluids (F and 0 2 ) are injected in an oxy- fuel burner OXB at a pressure of around 20bar.
• said oxy-fuel burner OXB - which can also be considered as a gas generator - combustion takes place of said fuel F with said oxygen 0 2 generating exhaust gas hereinafter referred to as exhaust-fluid EXH.
• oxygen 0 2 or "pure oxy- gen" a gas with an elevated content of oxygen is meant, e.g. of 95% oxygen content.
• the exhaust fluid EXH - or more generally called heat carrying media - exits said oxy-fuel burner OXB and enters a first heat exchanger assembly HEA1.
• said exhaust fluid EXH Downstream said first heat exchanger assembly HEA1 said exhaust fluid EXH is divided at a division point DP into recir- culated exhaust fluid EXE stream and the remaining exhaust fluid (referred to as first part EXHl which it is diminished by recirculated exhaust fluid stream EXE, which is also called second part EXH2) being conducted through a continued exhaust fluid line EXLB .
• first part EXHl which it is diminished by recirculated exhaust fluid stream EXE, which is also called second part EXH2
• the division of fluids can be performed even inside the first heat exchanger assembly HEA1.
• the temperature of said first part EXHl of the exhaust fluid stream EXH is adjusted by controlling said flow of recirculated exhaust fluid EXE (as said also called the second part EXH2 after the branch off) to the oxy-fuel burner OXB to be mixed with the fuel F and oxygen containing gas OCG and thus cool the exhaust fluid EXH (i.e. the second part EXH2) to the right temperature to subsequently enter said heat first exchanger assembly HEA1.
• This control is done by a control unit CU controlling a compression unit PU and/or a control valve CV.
• a control valve CV Optionally only one of the compression unit PU or the valve CV can be provided.
• the compression unit PU can be a pump can as well be a multiphase pump or a compressor or fan depending on the phase of the recirculated exhaust fluid EXE.
• the pump or multiphase pump will be used for liquid content, the compressor or fan for gaseous content.
• gases will be guided through the recirculating line RCL, so a compressor or fan will be used for the compression unit PU.
• the fluid in the recirculating line RCL may be called pressurized recirculating fluid PEXE which then is delivered to the oxy-fuel burner OXB.
• said exhaust fluid EXH passes a first cooler C0L1 before it enters a feed water heat exchanger FWE (or working media heat exchanger) transferring thermal energy to said process fluid PF (also called working media) of said rankine cycle RC .
• This additional sub-cooling effect further separates carbon dioxide C0 2 from water H 2 0 of the exhaust fluid EXH.
• Said feed water heat exchanger FWE provides further the feature of separating the gaseous phase from the liquid phase so that said carbon dioxide C0 2 is divided from the water H 2 0 to be stored or to be recycled separately.
• the stream of carbon dioxide C0 2 and water H 2 0 are respectively compressed and cooled by a respective intercooled compressor assembly (which will be called CCC02 , CCH20) .
• Said first exchanger assembly HEA1 comprises several single heat exchangers designed for different temperature levels of heat exchange.
• Figure 1 shows three of these heat exchangers: a first assembly heat exchanger AH1 (or first reheater) , a second assembly heat exchanger AH2 (or second reheater) and a third assembly heat exchanger AH3 (or third reheater) .
• the first heat exchanger AH1 is also identified as reheater for the process fluid between two turbine stages.
• a fourth reheater (not shown) may optionally be present within the oxy-fuel burner OXB to pre-heat the working media PF to be provided to the third assembly heat exchanger AH3.
• Said rankine cycle RC comprises a high pressure turbine HPST and a low pressure turbine LPST, which are basically designed as steam turbines, wherein said turbines respectively said rankine cycle are/is operated using preferably water as a process fluid PF .
• Said first exchanger assembly HEA1 works as the boiler of said rankine cycle RC boiling the water and superheating the steam generated to be expanded first in said high pressure turbine HPST starting from an entrance pressure level of around 15Obar .
• a full capacity first bypass station BSTl is provided upstream of said high pressure turbine HPST to allow full operation flexibility especially during start-up and shut-down. Said n
• high pressure turbine receives its steam respectively process fluid PF not from the most upstream first assembly heat exchanger AH1 but from said second assembly heat exchanger AH2 and is therefore not using the highest temperature level available from the exhaust fluid line EXL .
• process fluid PF as passed the high pressure turbine HPST it is conducted to the first assembly heat exchanger AH1 for being reheated to further downstream pass a second full capacity bypass station BST2 and to further downstream enter a low pres- sure turbine LPST to be expanded from 40bar down to around 0.045bar .
• Both turbines HPST, LPST are driving a generator GEN but can as well be used to drive a different consumer.
• first extracted process fluid stream XPF1 also called first extracted working media stream
• second extracted process fluid stream XPF2 also called second extracted working media stream
• third extracted process fluid stream XPF3 also called third extracted working media stream
• fourth extracted process fluid stream XPF4 also called fourth extracted working media stream
• the process fluid exiting said low pressure turbine LPST enters a condenser CON, where it is condensed to liquid together with said fourth extracted process fluid stream XPF4 , which is recycled into the main process fluid PF .
• Water or steam may be a preferred process fluid PF.
• feed water is also used, also in combination with devices like “feed water pump” or “feed water pre-heater” or “feed water heat exchanger” .
• feed water would be “working media” and therefore the devices "feed water pump” or “feed water pre-heater” or “feed water heat exchanger” or the like may be called more generally “working media pump” or “working media pre-heater” or “working media heat exchanger”.
• working media pump stands for example for a feed water pump but also for a condensate pump.
• said process fluid PF Downstream said condenser CON said process fluid PF enters a first feed water pump FWP1 (or first working media pump) before receiving thermal energy from said fourth extracted process fluid stream XPF4 in an intermediated heat exchanger IHE . Further downstream said process fluid PF enters a mixing pre-heater MP and is mixed with said third extracted process fluid stream XPF3 directly coming from the extraction point of said low pressure turbine LPST . Said first and second extracted process fluid streams XPF1, XPF2 and said fifth extracted process fluid stream XPF5 (also called fifth extracted working media stream) are injected into said mixing pre- heater MP, too, after they respectively were used to preheat said process fluid PF.
• said process fluid PF Downstream said mixing pre-heater MP said process fluid PF enters a second feed water pump FWP2 (or second working media pump) increasing the pressure well above 150bar before said process fluid enters downstream said feed water heat exchanger FWE . Subsequently said process fluid PF enters a preheating assembly PAS comprising a sequence of three feed water pre-heaters (or working media pre- heaters) , a first feed water pre-heater PHI (or first working media pre-heater) , a second feed water pre-heater PH2 (or se- cond working media pre-heater) , a third feed water pre-heater PH3 (or third working media pre-heater) .
• a preheating assembly PAS comprising a sequence of three feed water pre-heaters (or working media pre- heaters) , a first feed water pre-heater PHI (or first working media pre-heater) , a second feed water pre
• Said first feed water pre-heater PHI consists of a first sub- cooler SCI and a first main heat exchanger MH1.
• Said second feed water pre-heater PH2 consists of a second sub-cooler SC2 and a second main heat exchanger MH2 , wherein said first feed water pre-heater PHI receives said second ex- tracted process fluid stream XPF2 and said second feed water pre-heater PH2 receives said first extracted process fluid stream XPFl.
• the respective sub-coolers are located upstream of the main heat exchangers with regard to said process fluid PF stream.
• Said third feed water pre-heater PH3 is heated by a fifth extracted process fluid stream XPF5 extracted from said high pressure turbine HPST, wherein said process fluid PF first passes a third heat exchanger HEX3 of said third feed water pre-heater PH3 before it enters said third feed water pre- heater PH3 and downstream enters said second heat exchanger HEX2 also heated by said fifth extracted process fluid stream XPF5. Downstream said second heat exchanger HEX2 said process fluid PF enters said third assembly heat exchanger AH3. Downstream said second assembly heat exchanger AH2 said process fluid PF passes said first bypass station BST1 and further downstream enters said high pressure turbine HPST.
• rankine- cycle RC is operated with the working media (the process fluid PF) and that this working media is circulating separately from the exhaust fluid EXH .
• "Separately" means in this respect that the two media do not mix with each other.
• the rankine cycle is a closed cycle without input or output during normal operation. Particularly no exhaust fluid EXH is transferred into the rankine cycle RC as or to mix with working media of the rankine cycle RC .
• the exhaust fluid EXH and the working media PF are kept separate or unmixed.
• the ex- haust fluid EXH is also rerouted back to the oxy-fuel burner but a part of the fluid may be extracted, but not to enter the rankine cycle RC .
• the first heat exchanger assembly HEAl may have two output ports included into the first heat exchanger assembly HEA1.
• the complete recirculation via recirculation line RCL and the compression unit PU may also be incorporated into the first heat exchanger assem- bly HEA1.
• a power generation system comprising an oxy- fuel burner (OXB) , a first heat exchanger assembly (HEA1) , and a rankine-cycle (RC) ,
• rankine-cycle comprises at least one turbine (ST) expanding a process fluid (PF) , downstream said turbine (ST) at least one condenser (CON) condensing said process fluid (PF) ,
• rankine-cycle comprises downstream said condenser (CON) at least one first feed water pump (FWP) delivering said process fluid (PF) to a higher pressure level
• rankine-cycle comprises downstream said feed water pump (FWP) at least one first feed water pre- heater (PH) heating said process fluid (PF) by extracted process fluid (XPF1, XPF2) from said turbine (ST) ,
• At least one feed water heat exchanger is provided to heat up said process fluid (PF) of said rankine- cycle (RC) downstream said feed water pump (FWP) and upstream said feed water preheater (PH) by said exhaust fluid (EXH) ,
• said exhaust fluid line (EXL) is provided with a recirculation line (RCL) downstream said first heat exchanger assembly (HEA1) and upstream said feed water heat exchanger (FWE) extracting exhaust fluid (EXH) from said exhaust fluid line (EXL) , conducting extracted exhaust fluid (EXE) to a pump (PU) to increase pressure and injecting downstream said extracted exhaust fluid (EXE) into said oxy-fuel burner (OXB) .
• RCL recirculation line
• HSA1 first heat exchanger assembly
• FWE feed water heat exchanger
• PGS power generation system
• OXB oxy-fuel burner
• HAA1 first heat exchanger assembly
• RC rankine-cycle
• EXL exhaust fluid line
• RCL recir- culation line downstream said first heat exchanger assembly (HEA1) and upstream said feed water heat exchanger (FWE) extracting exhaust fluid (EXH) from said exhaust fluid line (EXL)
• Figure 1 is directed to a process for production of power via combustion by combining a fuel gas stream and an oxygen rich stream in burner (s) in a steam generating boiler.
• the resulting exhaust gas mainly consisting of C02 and steam is cooled to a desired temperature by adding a recirculated exhaust flow.
• the process is based on steam turbine technology and the configuration is similar to a reheat steam cycle seen in known applications.
• the steam generating boiler ac- cording to Figure 1 is different to a conventional boiler in that it is closed at the exhaust gas side to deliver carbon dioxide C02 produced to a compressor and that it has a large recirculation of exhaust gas.
• Water formed in the combustion is condensed before the remaining carbon dioxide C02 rich exhaust is led to a compressor and clean-up for delivery to a carbon dioxide consumer or injection in ground.
• the process separates the exhaust gas from the power cycle working media (water/steam circuit) such that turbo-machinery of known existing type can be selected and will run in an environment as designed for. By separating the exhaust from the water/steam circuit the process will also be relatively in- sensitive to soot or emissions resulting from the fuel or combustion .
• the boiler can be operated at an exhaust gas pressure of about atmospheric pressure but can also be designed to be op- erated at an exhaust gas pressure elevated above atmospheric pressure in order to save boiler size, reduce size of burners, reduce size of recirculation duct and fan and to reduce size of final carbon dioxide (C0 2 ) compressor.
• the elevated pressure may also lead to marginally better cycle performance due to less expansion of delivered fuel gas and oxygen and less compression work for delivered carbon dioxide C02, however depending on specific project pre-requisites .
• Boiler elevated exhaust pressure may also enable modularization of boiler supply to enable road transport of boiler proper where an atmospheric boiler would be constructed at site or be divided in a number of modules.
• Boiler type may be a traditional drum type boiler or a once-through (Benson) type. Steam cycle may be with or without reheat and high pressure main steam pressure below of above critical.
• a special feature of the process is the combination of oxy- fuel combustion principle with a boiler design separating the C02/steam from the steam/water cycle (and optionally by operation of the exhaust gas at elevated pressure above atmos- pheric) .
• High efficiency is achieved by taking the recirculation of exhaust from upstream economizers in the boiler such that as little heat as possible is moved from high temperature to low temperature parts of the cycle.
• Fuel gas and oxygen are supplied to a boiler where combustion takes place in burners (s) at atmospheric pressure or at increased pressure (in order to reduce size and cost) .
• a recir- culation of exhaust gas is applied to reduce the firing temperature .
• the exhaust passes a superheater, a reheat superheater and evaporator coils. Finally the exhaust is split in two
• the pressure resistant boiler casing is protected from hot gases by water cooling either combined in the shell design or by internal separate water cooled lining. Internal insulation may be applied instead of water cooling or as a complement.
• the steam generation side of the boiler may be a conventional single pressure drum type or a once through (e.g. Benson) type.
• the heat recovery section downstream the main boiler cools the exhaust stream which is not re-circulated back to the burner section. This heat recovery is anticipated to consist of heat exchange utilized for preheating of oxygen and fuel to the burners and a condenser transferring the heat to the feed water preheat section in the closed steam cycle.
• the condenser condenses only the steam in the exhaust gas resulting from the combustion of the hydrogen in the fuel, i.e. a rather small heat load.
• the rest of the exhaust gas, consisting mainly of carbon dioxide C0 2 extracted from the condenser is compressed and cleaned.
• the pressure in the condenser and thus also the C0 2 -extraction is as in the boiler minus some pressure drop, i.e. atmospheric or increased depending on design.
• High pressure (HP) steam generated and superheated in the boiler is admitted to the high pressure steam turbine and is expanded to an intermediate pressure, producing power.
• the steam is then returned to the boiler to pass a second superheat (reheat) and then forwarded to a low pressure (or inter- mediate pressure) steam turbine where it is further expanded to the near vacuum condition in the condenser producing more power .
• the condenser is preferably to be water cooled. However an air cooled condenser may be used as well. Cooling water may come from an open source or a cooling tower. Condensate collected in the condenser is pumped through a sequence of pre- heaters to the deaerator/feed water tank (i.e. the mixing pre-heater MP) .
• Feed water is taken from the deaerator (mixing pre-heater MP) and is pumped through further pre-heaters before being introduced in the boiler again.
• the pre-heaters are supplied by steam taken from steam turbine extractions or other source. Some heat for the feed water preheating is also recovered from cooling and condensing water from the exhaust stream exiting the boiler.
• the cycle may be equipped with turbine full capacity bypasses and startup vents both at high pressure and low pressure.
• turbine full capacity bypasses and startup vents both at high pressure and low pressure.
• the steam conditions may be increased.
• high pressure steam at supercritical condition 250 bars and 600 degrees would provide an increased net efficiency compared to examples given in figure above.
• a third steam turbine module would then be installed. If double reheat is introduced in a supercritical cycle even a further improvement would be possible.
• pressurizing the exhaust gas side of the boiler a significant reduction in size and hopefully in cost could be gained. This is a difference of this cycle compared to existing boilers where pressurization would require a turbine for pressure recovery when letting the exhaust to a stack. In this case there is no stack but instead a requirement to further compress. The largest cost and space saving would be gained by a pressure of about 5 to 8 bars.
• the previous configuration can be operated with exhaust flu- ids with atmospheric pressures, but possibly also with elevated pressure up to 20 bar.
• the exhaust fluid is operated with elevated pressure, for example above 5 bar or above 10 bar, particularly between 10 to 40 bar, preferably between 15 to 30 bar.
• a preferred configuration is operated with 20 bar (plus/minus 10%) .
• the pressure is significantly above atmospheric pressure. This is further explained in relation to Figure 2.
• Figure 2 shows almost all components as already explained in conjunction with Figure 1. Therefore only the differences will be discussed. All previously said still applies also for Figure 2.
• Figure 2 is designed so that the exhaust fluid is operated on elevated pressure level.
• a further control unit or the existing control unit CU is arranged to control a pressure level for said pressurized recirculating fluid (PEXE) , particularly by balancing supplied fluids and extracted fluids such that the wanted pressure level is reached.
• Said supplied fluids comprise the fluids that are provided to said oxy-fuel burner (OXB) and/or to said recirculation line (RCL) .
• Said extracted fluids comprise the fluids that are separated or extracted from said recirculation line (RCL) .
• the pressure level within the recirculation line can be set-up by controlling an amount of fuel (F) provided to said oxy-fuel burner (OXB) and/or by controlling an amount of oxygen (02) provided to said oxy-fuel burner (OXB) and/or by controlling a ratio between said first part (EXH1) of said exhaust fluid (EXH) and said second part (EXH2) and/or by controlling the outtake of C02.
• the pressure level specifically can be set by controlling valves - e.g. said control valve CV - and/or compressors and/or fans - e.g. said compression unit PU and/or an additional compression unit CU2 and/or compressors CI, C2.
• the pressure for the exhaust fluid of the oxy-fuel burner (OXB) elevated above atmospheric pressure increases exhaust fluid water gaseous phase partial pressure and thereby enable recovery of latent heat of condensation of said water, particularly at temperature level for efficient use within the rankine cycle RC .
• the working media PF when first feed water pump FWPl is guided to the feed water heat exchanger FWE to be able to use the heat of the first part EXH1 of the exhaust fluid EXH and to use also its latent heat .
• the work- ing media PF now has an increased temperature and will be provided to the mixing pre-heater MP, which has - as before - a further source from the first sub-cooler SCI and is also provided with working media via the third extracted process fluid stream XPF3 from the low pressure turbine LPST .
• the mixing pre-heater MP can provide working media via the second feed water pump FWP2 directly to the first sub-cooler SCI to be further guided to the first feed water pre-heater PHI.
• an extraction of the fourth extracted process fluid stream XPF4 from the low pressure turbine LPST may become superfluous and can be omitted. This again improves the effectiveness of the cycle.
• the first cooler COL1 may be upstream or down- stream of the feed water heat exchanger FWE, or may even be incorporated into a common vessel with the feed water heat exchanger FWE.
• the first cooler COL1 can be connected to a heat exchanger in a branch that is providing the fuel F.
• the first cooler COL1 can be connected to a heat exchanger in a branch that is providing the oxygen 0 2 to preheat the oxygen 0 2 .
• the feed water heat exchanger FWE can provide heat to the working media stream in the rankine cycle RC in various positions.
• Fuel F provided by a pipeline may already be provided at an elevated pressure level, often of about 30 bar.
• the compressor C2 may be superfluous. So the system can be simplified. Even more, possibly the pressure of the fuel F from the pipeline way need to be reduced - e.g. if the pipe- line is operated by for example 85 bar. The reduction would then preferably take place in an expander replacing the compressor C2.
• natural gas is provided a fuel F
• natural gas typically anyhow is provided pressurized so it is advantageous if also the exhaust fluid is pressurised.
• the oxygen 0 2 may even be provided in liquid form, e.g. when provided as liquid oxygen if no air separation unit ASU is used on site. A then needed regasification of the liquid oxygen can be integrated in the system such that the heat reac- tion can be utilized in the system, particularly via a further heat exchanger unit.
• the preheating operation can utilize heat from the rankine cycle RC.
• a catalyst unit for cleaning of said exhaust fluid EXH from residual content of oxygen may be provided - e.g. removing oxygen content that was not burned or removing unburned hydrocarbons -, particularly in the exhaust fluid line branch EXLB .
• the catalyst unit is operated by adding of further fuel and/or other combustible media to the first part EXH1 exhaust fluid EXH.
• the catalyst unit may particularly be connected in such way that heat of a catalyst process running in the catalyst unit is recovered for use in said rankine cycle RC and/or for preheating of fuel F or said oxygen enriched gas 0 2 . This allows to facilitate efficient use of generated heat in the cleanup process by the catalyst unit.
• the catalyst unit can be place at several positions in the exhaust fluid stream. It may be upstream or downstream of a condensation occurring in the feed water heat exchanger FEW.
• the catalyst unit may even be incorporated in the oxy-fuel boiler OXB .
• other refinery components may be incorporated in the exhaust fluid line branch EXLB or in the recirculating line RCL for gas filtration.
• the system according to Figure 2 provides improvement of performance and reduction of component sizes for the oxyfuel boiler process. This may improve the previously explained oxyfuel cycle, in which the cycle configuration is based on the boiler exhaust side operating at atmospheric pressure or slightly above atmospheric.
• the condensation of water from exhaust gas is typically not fully utilised to benefit from water condensation latent heat.
• Boiler exhaust pressure is increased to increase the tempera- ture level of water condensation in the exhaust gas water separation and thereby enable usage of the latent heat in the power cycle at beneficial temperature level .
• the feed water preheating heat exchanger sequence may then be adapted to fit with the changed recovery in the exhaust cooling, also some related changes to fuel and oxygen preheating may be made to suit the new configuration.
• the latent heat in steam phase in the exhaust gas formed by com- bustion is utilized in the power cycle, i.e. the power cycle makes use of the fuel higher heating value instead of the normal practice of only use of lower heating value (minus certain loss) .
• This may be seen as achieving boiler efficiency above 100% when referring to the normal efficiency defini- tion based on lower heating value.
• a number of other positive effects are also gained in equipment size and cost by the reduced gas volumes and increased heat convection factors resulting from increased pressure.
• the size of downstream equipment heat exchangers, water separation unit and C02 compressor, is reduced and parasitic load for the C02 compression is reduced.
• the boiler exhaust pressure may be increased to about 20 bars without any additional fuel compression.
• the feed water heat exchanger FWE may be divided in two or more sections and the mixing preheater may be integrated between sections.
• Fuel F and oxygen 02 preheating may be integrated with the FWE as part of the heat recovery to achieve a more efficient use of available exergy (energy related to temperature level) .
• the pressurization of the exhaust fluid benefits from that a fluid under higher pressure has a higher density. Furthermore, under pressure condensation starts at a higher temperature level (e.g. at 190°C when operating with 20 bar instead of 90°C when operating under atmospheric conditions) . As a secondary effect, sizes of components can be reduced due to pressurising the fluid, e.g. the size of the oxy-fuel burner OXB or the size of the feed water heat exchanger FWE . It may be preferred to set up the power generation system PGS such that temperature level at design working conditions for said second part EXH2 of said exhaust fluid EXH is at least two third (2/3) of saturation temperature measured in Celsius of boiling occurring in said first heat exchanger assembly HEA1. It is preferred to have a temperature level being particularly above 200°C.
• the recirculation line RCL may be implemented as shown.
• the recirculated ex- haust fluid EXE may even be kept internally to the first heat exchanger assembly HEA1. So no external piping may be required (particularly when even the compression unit PU is integrated within the first heat exchanger assembly HEA1) or may be limited to just exit the first heat exchanger assembly HEA1 to provide the recirculated exhaust fluid EXE to the compression unit PU and then provided to the oxy-fuel burner OXB .
• a further air supply may be present to guide air into the oxy-fuel burner OXB .
• the at least one working media heat exchanger FWE may comprise more than one element to allow a heat transfer from a hot exhaust fluid EXH - i.e. the first part EXHl - to a cooler medium.
• a first heat transfer element operates with the first part EXHl in gas phase and further heat transfer elements operate with the first part EXHl in liquid state.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Engine Equipment That Uses Special Cycles (AREA)

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• 2013
  • 2013-03-21 US US14/777,177 patent/US20160033128A1/en not_active Abandoned
• 2014
  • 2014-02-21 WO PCT/EP2014/053443 patent/WO2014146860A1/en active Application Filing
  • 2014-03-21 EP EP14713794.7A patent/EP2948648A1/de not_active Withdrawn
  • 2014-03-21 WO PCT/EP2014/055758 patent/WO2014147248A1/en active Application Filing

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