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
  • F22—STEAM GENERATION
  • F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
  • F22B35/00—Control systems for steam boilers
  • F22B35/002—Control by recirculating flue gases
• • 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
  • F23C9/003—Combustion apparatus characterised by arrangements for returning combustion products or flue gases to the combustion chamber for pulverulent fuel
• • 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
• • 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
  • F23L15/00—Heating of air supplied for combustion
  • F23L15/04—Arrangements of recuperators
  • F23L15/045—Arrangements of recuperators using intermediate heat-transfer fluids
• • 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 
  • F23C2202/00—Fluegas recirculation
  • F23C2202/30—Premixing fluegas with combustion air
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23J—REMOVAL OR TREATMENT OF COMBUSTION PRODUCTS OR COMBUSTION RESIDUES; FLUES 
  • F23J2215/00—Preventing emissions
  • F23J2215/50—Carbon dioxide
• • 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
  • F23L2900/00—Special arrangements for supplying or treating air or oxidant for combustion; Injecting inert gas, water or steam into the combustion chamber
  • F23L2900/07001—Injecting synthetic air, i.e. a combustion supporting mixture made of pure oxygen and an inert gas, e.g. nitrogen or recycled fumes
• • 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
  • F23L2900/00—Special arrangements for supplying or treating air or oxidant for combustion; Injecting inert gas, water or steam into the combustion chamber
  • F23L2900/07006—Control of the oxygen supply
• • 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
  • F23L2900/00—Special arrangements for supplying or treating air or oxidant for combustion; Injecting inert gas, water or steam into the combustion chamber
  • F23L2900/07007—Special arrangements for supplying or treating air or oxidant for combustion; Injecting inert gas, water or steam into the combustion chamber using specific ranges of oxygen percentage
• • 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 present invention relates to a method of and a system for generating power by oxyfuel combustion.
• the invention especially relates to a flexi-burn or dual- firing combustion system, i.e., a system which can be easily switched between the modes of oxyfuel combustion and combustion with air.
• Oxyfuel combustion is one of the methods suggested for removing CO 2 from the combustion gases of a power generating boiler, such as a pulverized coal (PC) boiler or a circulating fluidized bed (CFB) boiler.
• Oxyfuel combustion is based on combusting carbonaceous fuel with substantially pure oxygen, typically of about 95% purity, so as to have carbon dioxide and water as the main components of the exhaust gas discharged from the boiler. Thereby, the carbon dioxide can be captured relatively easily, without having to separate it from a gas stream having nitrogen as its main component, such as when combusting the fuel with air.
• Generating power by oxyfuel combustion is more complicated than conventional combustion by air, because of the need of an oxygen supply, for example, a cryogenic or membrane based air separation unit (ASU), where oxygen is separated from other components of air.
• ASU cryogenic or membrane based air separation unit
• the produced exhaust gas is then ready for sequestration OfCO 2 when water is removed from the oxidant, fuel and air-leakage.
• This purification is typically done by CO 2 condensation at a low temperature under high pressure.
• CO 2 can be separated from the exhaust gas, for example, by cooling it to a relatively low temperature, while compressing it to a pressure greater than one hundred ten bar.
• an oxyfuel combustion boiler where the combustion conditions are arranged to be close to those of air- firing combustion. This can be done by recycling exhaust gas back to the furnace so as to provide an average O 2 content of the oxidant gas of, for example, about 20 to about 28%.
• Such oxyfuel combustion boilers can advantageously be built by modifying existing air- firing boilers. Due to many uncertainties related to oxyfuel combustion with the capture and storage of carbon dioxide, there is also a need for dual firing boilers, i.e., boilers which can be changed from oxyfuel combustion to air- firing, and back, as easily as possible, preferably, without any changes in the actual construction.
• a dual firing boiler With such a dual firing boiler, it is possible to have maximum power output, by using air- firing combustion, during a high load demand, such as during the summer or the day-time, and applying oxyfuel combustion with CO 2 removal in other conditions. Also, it is possible to use a dual firing boiler in an air- firing mode, for example, when the separation unit or CO 2 sequestration unit is out of order.
• U.S. Patent No. 6,202,574 suggests a combustion system for firing fossil fuel with substantially pure oxygen to produce exhaust gas having carbon dioxide and water as its two largest constituents. A portion of the exhaust gas is recycled to the combustion chamber and the rest of the exhaust gas is compressed and stripped to produce carbon dioxide in a liquid phase. The recycled exhaust gas and the substantially pure oxygen stream are preheated by the exhaust gas in respective gas-gas heat exchangers.
• German patent publication DE 103 56 703 Al shows an oxyfuel combustion boiler system comprising a feedwater heater and a gas-gas heat exchanger acting as an oxygen heater arranged to cool the exhaust gas downstream of a recycle gas take-off.
• An object of the present invention is to provide a new method of and a system for oxyfuel combustion.
• the present invention provides a method of generating power by oxyfuel combustion, the method comprising the steps of feeding carbonaceous fuel into a furnace, feeding oxidant gas into the furnace, wherein, in a first operating mode, the oxidant gas comprises a stream of substantially pure oxygen conveyed from an oxygen supply for combusting the fuel with the oxygen to produce exhaust gas comprising mainly carbon dioxide and water, discharging the exhaust gas from the furnace, dividing the exhaust gas into a recycling portion and an end portion, recycling the recycling portion of the furnace, and transferring heat from the end portion to the stream of substantially pure oxygen by circulating a liquid heat transfer medium, such as water, in a passage between an exhaust gas cooler and an oxygen heater.
• a liquid heat transfer medium such as water
• the present invention provides a system for generating power by oxyfuel combustion, the system comprising a furnace for combusting carbonaceous fuel, an oxygen channel for feeding the substantially pure oxygen from an oxygen supply to the furnace for combusting the fuel with the oxygen to produce exhaust gas comprising mainly carbon dioxide and water, an exhaust gas channel connected to the furnace for discharging the exhaust gas from the furnace, branch piping for dividing the exhaust gas into a recycling portion and an end portion, a gas recycling channel for feeding the recycling portion of the exhaust gas to the furnace, an exhaust gas cooler arranged in the exhaust gas channel downstream of the branch piping, and an oxygen heater arranged in the oxygen channel connected by a passage for transferring heat from the end portion to the stream of substantially pure oxygen by a circulating liquid heat transfer medium in the passage.
• the process of transferring heat from the exhaust gas to the oxidant gas improves the efficiency of the boiler and the process as a whole.
• the present invention differs from the prior art solution shown in U.S. Patent No. 6,202,574, for example, in that the pure oxygen stream is heated by low grade heat obtained from the end portion of the exhaust gas, which is to be discharged from the system, and not from the exhaust gas upstream of the take off point of the recycled gas. Thereby, the thermal efficiency of the process is improved.
• the exhaust gas cooler is at the low temperature portion of the exhaust gas channel, it may cool below the acid condensation temperature during the heat transfer. Therefore, the exhaust gas cooler is advantageously of a corrosion resistant type, such as a plastic gas cooler.
• the recycling portion of the exhaust gas comprises, often in oxyfuel combustion, a majority, typically, about 65 to about 80%, of the exhaust gas discharged from the furnace, whereby the end portion of the exhaust gas is about or less than a third of the exhaust gas stream.
• the end portion is always naturally about as large as the oxygen stream. Therefore, the arranging of the exhaust gas cooler downstream of the point dividing the recycling portion provides another advantage in that the gas flows of the end portion of the exhaust gas and the oxygen stream are as large, whereby it is relatively easy to obtain an energy balance between the two flows at advantageous temperature levels.
• the end portion of the exhaust gas is, in practice, virtually free of dust, while being located downstream of an electron dust separator (ESP) or a bag house. This provides conditions for arranging an effective and a compact heat exchanger. It also increases the safety of the system, while there is very little of igniting or explosive dust present.
• ESP electron dust separator
• heat is transferred form the exhaust gas to the oxygen flow by means of a liquid transfer medium, instead of transferring the heat directly in a gas-gas heat exchanger.
• This feature provides the advantage that a leak in the exhaust gas cooler, which may occur especially when the heat exchanger is used below the acid dew point temperature, may only cause a leak of water, and not a leak of explosive oxygen, into the exhaust gas channel.
• Another advantage of transferring heat from the exhaust gas to the oxygen by means of a liquid heat transfer medium is that, in practice, it usually provides a relatively simple construction, although it appears to make the system more complicated.
• the oxygen supply typically, an air separation unit (ASU)
• ASU air separation unit
• the heat transferring distance may be quite long, and it is easier to transfer the heat such long distances in relatively small water tubes by making an additional excursion to much larger channels carrying hot exhaust gas or explosive oxygen gas.
• the method further comprises steps of transferring heat in a gas-gas heat exchanger from the exhaust gas to the recycling portion of the exhaust gas to produce a stream of heated recycling gas.
• the recycling gas stream and the stream of substantially pure oxygen may be conducted to the furnace separately, but, according to a preferred embodiment of the present invention, the stream of substantially pure oxygen is mixed with the stream of heated recycling gas in a mixer arranged to connect the gas recycling channel downstream of the gas-gas heat exchanger and the oxygen channel downstream of the oxygen heater.
• a stream of mixed gas is formed to be fed as the oxidant gas via a channel into the furnace.
• the feeding rate of the relatively pure oxygen is determined on the basis of the fuel feeding rate, so as to provide sufficiently complete combustion of the fuel.
• the oxygen feeding rate is controlled by monitoring the content of residual oxygen in the exhaust gas, which should stay at a suitable level, typically, about 3%.
• the recycling gas channel and the oxygen channel may advantageously be divided in multiple parallel lines, which are separately connected in multiple mixers, so as to form multiple streams of mixed gas, which may be used, for example, as primary and secondary oxidant gas in the furnace.
• the gas feeding rate to a boiler retrofitted from air- firing to oxycombustion is adjusted so as to maintain the original gas velocity in the furnace, whereby the oxygen content of the oxidant gas is advantageously adjusted to be near to that of air, typically, from about 18% to about 28%.
• the furnace temperature or heat flux of the retrofitted boiler shall advantageously also be maintained at about its original level to avoid, e.g., corrosion or material strength problems of the furnace walls.
• the same volume flow of exhaust gas at the same temperature carries more heat in the case of oxycombustion, than in air-firing combustion.
• the fuel feeding rate can be increased by at least 10%, and still maintain the original furnace temperature or heat flux. Thereby, an increased amount of heat is available, e.g., for steam generation and for heating of the oxidant gas.
• the first operating mode is performed alternatingly with a second operating mode, a so-called an air- firing mode, wherein the recycling portion is minimized, for example, by a damper and the oxidant gas comprises a stream of air.
• the system comprises an air intake for introducing air into the gas recycling line upstream of the gas-gas heat exchanger.
• the gas-gas heat exchanger is used in the second operating mode to transfer heat from the exhaust gas to the air stream.
• the combustion system is advantageously decoupled from the oxygen supply, and the exhaust gas comprises nitrogen, carbon dioxide and water, as its main components.
• the system is also decoupled from the carbon dioxide capturing and storage units, and the exhaust gas is released to the environment through a stack.
• One of the main ideas of the present invention is that it provides an oxyfuel combustion method which can be easily switched to air- firing combustion, and back, without any modifications in the actual construction, even on-line, without stopping the power generation during the change.
• the oxygen supply is not in use and, because the content of the exhaust gas is that in conventional combustion, the carbon dioxide of the exhaust gas is not purified and sequestered.
• the auxiliary power consumption of these processes is minimized, and the system provides a higher total efficiency than that in oxygen-combustion, at the cost of releasing carbon dioxide to the environment.
• the air- firing operating mode is advantageously used when the demand for power is especially high, for example, in the summer or during the day-time.
• the air- firing mode may be temporarily used, e.g., based on varying economical conditions, or when the oxygen supply or carbon dioxide capturing and storage systems are, for some reason, not available.
• the method advantageously comprises, in the second operating mode, a step of transferring heat from the exhaust gas to the stream of air by circulating a liquid heat transfer medium in a passage between an exhaust gas cooler and an air heater.
• a liquid heat transfer medium in a passage between an exhaust gas cooler and an air heater.
• FIG. 1 is a schematic diagram of an oxy-fuel combusting power plant in accordance with the present invention.
• FIG. 1 shows a schematic diagram of a power plant 10 in accordance with a preferred embodiment of the present invention.
• the power plant 10 comprises a boiler 12, which may be, for example, a pulverized coal (PC) boiler or a circulating fluidized bed (CFB) boiler.
• the furnace 14 of the boiler comprises conventional fuel feeding means 16, means for feeding oxidant gas 18 into the furnace, and an exhaust gas channel 20 for discharging exhaust gas produced by combusting the fuel with the oxygen of the oxidant gas.
• the details and type of some elements of the boiler 12, such as the fuel feeding means 16 and oxidant gas feeding means 18, depend, naturally, on the type of boiler. Such details, for example, as burners, coal mills, means for separately feeding primary and secondary inlet gas, are, however, not important for the present invention, and are, thus, not shown in FIG. 1.
• the oxidant gas is preferably a mixture of substantially pure oxygen, produced from an air stream 22 in an air separation unit (ASU) 24, and a portion of the exhaust gas, which is recycled via an exhaust gas recycling channel 26.
• the exhaust gas recycling channel 26 advantageously comprises a flow controller, such as a controllable fan 28 and/or a damper 30, for controlling the exhaust gas recycling rate.
• the recycling rate of the exhaust gas is advantageously adjusted such that the average O 2 content of the oxidant gas is close to that of air, preferably, from about 18% to about 28%.
• the furnace 14 usually comprises evaporation surfaces, not shown in FIG. 1, and the exhaust gas channel 20 further comprises heat exchanger surfaces 32, 34, for example, superheaters and economizers.
• FIG. 1 shows only two heat exchanger surfaces 32, 34, but, in practice, the exhaust gas channel 20 usually comprises multiple superheating, reheating and economizer surfaces for recovering heat from the exhaust gas.
• a gas-gas heat exchanger 36 usually, a regenerative heat exchanger, for transferring heat from the exhaust gas directly to the recycling portion of the exhaust gas.
• the exhaust gas channel 20 usually comprises conventional units for cleaning the exhaust gas from particles and gaseous pollutants, which are, in FIG. 1, schematically represented only by a dust separator 38.
• the dust separator 38 and possible other gas cleaning units are advantageously arranged upstream of the branch point 40 of the exhaust gas recycling channel 26.
• the exhaust gas stream is divided into a recycling portion, conveyed through the recycling gas channel 26 back to the furnace 14 and an end portion, which is conveyed through the end portion 42 of the exhaust gas channel 20 for final processing.
• the end portion 42 of the exhaust gas channel 20 is equipped with a device, schematically represented by a carbon dioxide capturing unit 44, for cooling, cleaning and compressing carbon dioxide.
• the unit 44 usually comprises a dryer for completely drying all water from the exhaust gas, and a separator for separating a stream of non-condensable gas, such as oxygen 50, and possibly other impurities, from the carbon dioxide.
• a stream of carbon dioxide 46 is typically captured in a liquid or supercritical state, at a pressure of, for example, about one hundred ten bar, so that it can be transported for further use or to be stored in a suitable place.
• FIG. 1 shows, separately, a condensing gas cooler 48, located upstream of the carbon dioxide capturing unit 44, for initially removing water from the exhaust gas.
• the end portion 42 of the exhaust gas channel 20 is, according to the present invention, equipped with a gas cooler 52, which is connected by a liquid heat transfer medium circulation to an oxygen heater 54 arranged in an oxygen channel 56 downstream of the oxygen supply 24.
• the heat transfer medium usually water, is, preferably, circulated by a pump 58 in a tubing 60 extending between the gas cooler 52 and the oxygen heater 54, which are usually, in practice, located at distant portions of the power plant 10.
• the oxygen channel 56 may be connected directly to the furnace 14, but, according to a preferred embodiment of the present invention, the oxygen channel 56 and the exhaust gas recycling channel 26 are both connected to a mixer 62, and a stream of mixed gas is lead as the oxidant gas to the furnace through the oxidant gas feeding means 18. This system makes it possible to separately control the temperature, flow rate and oxygen content of the oxidant gas.
• the system also comprises an air intake 64 for feeding air to the furnace.
• the air stream is, preferably, introduced into the exhaust gas recycling channel 26 upstream of the gas-gas heat exchanger 36, whereby it is possible to transfer heat directly form the exhaust gas to the stream of air.
• the purpose of the air intake 64 is to enable switching from oxyfuel combustion to air- firing combustion.
• the exhaust gas comprises, in the air- firing mode, carbon dioxide and water mixed with a large amount of nitrogen, whereby, it is not possible to easily capture the carbon dioxide from the exhaust gas, which is, thus, in this case, released to the environment through a stack 66.
• the heating of air in the gas-gas heat exchanger 36 is usually not sufficient, but more heat is advantageously transferred to the air stream by an air heater 68.
• the air heater 68 is also advantageous in order to increase the inlet temperature of the air in the gas-gas heat exchanger 36, so as to avoid flue gas condensation and related problems on the heat exchanger surfaces.
• the air heater 68 is preferably connected to the exhaust gas cooler 52, which is also used in the oxycombustion mode, by means of heat transfer medium circulation.
• the tubing 60 used for water circulation in the oxycombustion is in the air- firing combustion mode connected to a side tubing 70, a so-called air heating arm, including a circulation pump 72.
• a circulation pump 72 By opening a valve 74 in the air heating arm, and closing a valve 76 in the main tubing, in the so-called oxygen heating arm, the heat transfer medium can be switched to circulate through the air heater 68 instead of the oxygen heater 54.
• the water circulation pump is arranged in the common portion of the water tubing 60, it is, in the above-described case, sufficient to have only one circulation pump.
• the circulation rate of the heat transfer medium is advantageously lower in the oxycombustion mode than that in the air- firing mode.
• a parallel channel portion 78 parallel to the end portion of the exhaust gas channel 42, is arranged a parallel channel portion 78.
• the portion of the flue gas flowing through the parallel channel portion 78 can be varied by a damper 80 to be, for example, between about 0% and about 75%.
• the parallel channel portion comprises another exhaust gas cooler 82, which is in the air- firing mode connected in parallel to the exhaust gas cooler 52.
• heat is transferred in the oxycombustion mode from the exhaust gas cooler 52 to the oxygen heater 54, and, in the air- firing combustion mode, from two exhaust gas coolers 52, 82 to the air heater 68.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Air Supply (AREA)
• Combustion Of Fluid Fuel (AREA)
• Chimneys And Flues (AREA)

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Citations (6)

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• 2008
  • 2008-05-30 US US12/130,474 patent/US20090293782A1/en not_active Abandoned
• 2009
  • 2009-05-15 EP EP09754019A patent/EP2318757A2/en not_active Withdrawn
  • 2009-05-15 AU AU2009253043A patent/AU2009253043A1/en not_active Abandoned
  • 2009-05-15 JP JP2011511041A patent/JP2011523012A/ja not_active Abandoned
  • 2009-05-15 KR KR1020107029369A patent/KR20110022634A/ko not_active Application Discontinuation
  • 2009-05-15 CN CN2009801212029A patent/CN102047039A/zh active Pending
  • 2009-05-15 WO PCT/FI2009/050402 patent/WO2009144366A2/en active Application Filing
• 2010
  • 2010-11-17 ZA ZA2010/08226A patent/ZA201008226B/en unknown

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