EP2652397A2 - Four de combustion et procédé de fonctionnement - Google Patents

Four de combustion et procédé de fonctionnement

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Publication number
EP2652397A2
EP2652397A2 EP11811366.1A EP11811366A EP2652397A2 EP 2652397 A2 EP2652397 A2 EP 2652397A2 EP 11811366 A EP11811366 A EP 11811366A EP 2652397 A2 EP2652397 A2 EP 2652397A2
Authority
EP
European Patent Office
Prior art keywords
furnace
combustion
gas
control
air
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP11811366.1A
Other languages
German (de)
English (en)
Inventor
Konrad Jerzy Kuczynski
David James Adams
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Power Systems Synectics Ltd
Altrad Babcock Ltd
Original Assignee
Doosan Babcock Ltd
Power Systems Synectics Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Doosan Babcock Ltd, Power Systems Synectics Ltd filed Critical Doosan Babcock Ltd
Publication of EP2652397A2 publication Critical patent/EP2652397A2/fr
Withdrawn legal-status Critical Current

Links

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
    • F23L9/00—Passages or apertures for delivering secondary air for completing combustion of 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 
    • F23C6/00—Combustion apparatus characterised by the combination of two or more combustion chambers or combustion zones, e.g. for staged combustion
    • F23C6/04—Combustion apparatus characterised by the combination of two or more combustion chambers or combustion zones, e.g. for staged combustion in series connection
    • 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 
    • F23C6/00—Combustion apparatus characterised by the combination of two or more combustion chambers or combustion zones, e.g. for staged combustion
    • F23C6/04—Combustion apparatus characterised by the combination of two or more combustion chambers or combustion zones, e.g. for staged combustion in series connection
    • F23C6/045—Combustion apparatus characterised by the combination of two or more combustion chambers or combustion zones, e.g. for staged combustion in series connection with staged combustion in a single enclosure
    • F23C6/047—Combustion apparatus characterised by the combination of two or more combustion chambers or combustion zones, e.g. for staged combustion in series connection with staged combustion in a single enclosure with fuel supply in stages
    • 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
    • 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
    • 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
    • F23L9/00—Passages or apertures for delivering secondary air for completing combustion of fuel 
    • F23L9/04—Passages or apertures for delivering secondary air for completing combustion of fuel  by discharging the air beyond the fire, i.e. nearer the smoke outlet
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N3/00—Regulating air supply or draught
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N3/00—Regulating air supply or draught
    • F23N3/002—Regulating air supply or draught using electronic means
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N5/00—Systems for controlling combustion
    • F23N5/24—Preventing development of abnormal or undesired conditions, i.e. safety arrangements
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N5/00—Systems for controlling combustion
    • F23N5/24—Preventing development of abnormal or undesired conditions, i.e. safety arrangements
    • F23N5/242—Preventing development of abnormal or undesired conditions, i.e. safety arrangements using electronic means
    • 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 
    • F23C2201/00—Staged combustion
    • F23C2201/10—Furnace staging
    • F23C2201/101—Furnace staging in vertical direction, e.g. alternating lean and rich zones
    • 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
    • F23L2900/07003—Controlling the inert gas supply
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N5/00—Systems for controlling combustion
    • F23N5/18—Systems for controlling combustion using detectors sensitive to rate of flow of air or fuel
    • F23N2005/181—Systems for controlling combustion using detectors sensitive to rate of flow of air or fuel using detectors sensitive to rate of flow of air
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N2237/00—Controlling
    • F23N2237/16—Controlling secondary air
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N2237/00—Controlling
    • F23N2237/24—Controlling height of burner
    • F23N2237/28—Controlling height of burner oxygen as pure oxydant
    • 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 furnace and its method of operation.
  • the invention in particular relates to furnace pressure control.
  • the invention in particular relates to a control system for and a method of operation of a furnace for a thermal power plant, and in particular a furnace having a conventional and an oxyfuel fired capability, but is not limited to application in such preferred cases.
  • Control of both furnace pressure and combustion conditions is important for safe, efficient and flexible operation of a thermal power plant.
  • a conventional air fired power plant the maintenance of correct combustion conditions is normally achieved by control of the FD and ID fans. These are operated such that the total flow of combustion air into the furnace from the environment to match fuel flow is controlled by the FD fan, whilst control of furnace pressure, normally to a value slightly below ambient atmospheric pressure, is achieved by modification of the mass flow extracted by the ID fan to the environment.
  • control of furnace pressure normally to a value slightly below ambient atmospheric pressure
  • furnace pressure is important for a number of reasons including:
  • the level of pressure excursion for any particular event or disturbance within the furnace and combustion system of existing furnace designs is influenced by the level of furnace leakage and therefore mass balance caused by the ingress or egress of gas through imperfections in the air- tightness of the furnace itself. Such imperfections typically arise due to the construction of the furnace walls and seals associated with penetrations such as inspection doors and ashing facilities.
  • the level of furnace leakage also has a significant effect on the sensitivity of furnace pressure to changes in the mass flow of gas extracted from the system.
  • This sensitivity affects control performance and tunings and changes both with the level of furnace leakage and the actual furnace pressure itself. All of these factors influence the ultimate performance of the control system
  • a combustion furnace comprises a chamber defining a combustion volume having at least one primary inlet for fuel and combustion supporting gases and at least one primary outlet for combustion product gases, which chamber is provided with one or more additional ports allowing for secondary gas flow into and/ or out of the combustion volume.
  • the invention therefore recognises that a number of benefits may be realised by the use of additional, controlled 'leakage' or re-cycling of gas into the furnace.
  • Air fired furnaces typically have a nominal uncontrolled leakage in the range of 2 to 5% of the full load combustion gas flow. This level of leakage, coupled with typical 'random' variations in heat release and dynamic response of furnaces results in the operating setpoint for furnace pressure being fixed in the range -0.5 to -LOmbarg (-0.05 to -O.l kPAg); this figure being a compromise of considerations of preventing leakage of combustion products and unburned fuel into the boiler house and minimising the effects of unnecessary in-leakage of ambient air on the combustion process and combustion control.
  • the invention therefore recognises the scope to dynamically optimise the furnace pressure setpoint, without any necessary addition of further 'controlled leakage air subject to the constraining objective of avoiding significant instances of gas leakage into the boiler house.
  • this part of the invention reduces any impact of leakage air on combustion and reduces ID fan works power
  • efforts are made in the design to reduce the level of furnace leakage because of the reduction in the efficiency of the CO2 compression and extraction process resulting from the presence of Nitrogen in the CO2 rich gas stream. This has the effect of increasing the sensitivity of furnace pressure to control actions taken by the ID fan, chimney vents and/or CO2 compressors further increasing the inherent control and stability issues demonstrated by oxyfuel pilot plants.
  • the invention therefore recognises that by the addition of controlled 'leakage' or re-cycled gas taken from outside the gas closed loop recirculation system of the oxyfuel cycle, a reduction in furnace pressure sensitivity may be achieved, reducing or eliminating the need for continuous venting of gas from the combustion system to the environment
  • the invention also recognises that, by appropriate control and adaption of the level of injection of gas into the furnace as described above, that the large and potentially damaging excursions in furnace pressure demonstrated by oxyfuel pilot plants for commonly occurring process operations may be significantly reduced.
  • the invention therefore recognises that these characteristics may be used as a basis to realise improved levels of furnace pressure control for both conventional air fired plant and oxyfuel equipped plant in both air and oxyfuel modes of operation and that a reduction in the overall level of furnace air leakage may also be achieved by the use of a control based optimisation technique.
  • the one or more additional ports may be provided in fluid communication with a supply of gas for secondary gas flow, being for example a connection to ambient environment in the case of air firing and a connection to a CO2 rich gas source in the case of an oxyfuel fired system.
  • Multiple ports may be provided in fluid communication with one or more secondary supplies of gas.
  • the furnace may be provided with at least two sets of additional ports each in fluid communication with a different supply of gas for secondary gas flow.
  • one supply may be ambient air and another supply may be a CO2 rich gas source where a CO2 rich gas source will be understood to mean a gas source with CO2 levels in excess of that of atmospheric air and in particular substantially above that of atmospheric air.
  • another supply may be a nitrogen rich gas source
  • an nitrogen rich gas source will be understood to mean a gas source with nitrogen levels above that of atmospheric air and for example a source of substantially pure nitrogen.
  • Control means are preferably provided adapted to control the secondary flow of gas through the one or more ports and for example the supply of gas to the furnace, for example in by way of dynamic response in real time to provide additional (or reduced) mass flow to the furnace in order to limit pressure excursions for events such as mill start-up, shut-down, partial or full loss of ignition etc, and in the case of a furnace adapted for transition between air firing and oxyfuel firing during transition between air and oxyfuel modes.
  • the invention in the first aspect introduces a physical modification to a conventional furnace consisting of an additional port, or ports, in the furnace wall for example connected to the environment via additional ductwork and a control device or, additionally or alternatively in the case of an oxyfuel plant, to a CO2 rich gas source via additional ductwork and a control device.
  • the invention reduces the coupling between extraction mass flow and furnace pressure by controlled admission of leakage gas into the furnace during events such as plant start-up or shut-down, the starting or stopping of mills, partial or full loss of Ignition etc.
  • the resulting reduction in furnace pressure deviations associated with such events then also allows the operating setpoint for furnace pressure control to be reduced dynamically and on a statistical basis in order to minimise the long term level of air ingress.
  • the invention provides all of the above features and operational benefits with additional benefits relating to the transition to and from air firing and oxyfuel mode and the ability to reduce the level of air ingress and nitrogen pick-up in oxyfuel mode of operation.
  • the invention might be used optionally to maintain the CO2 concentration in the furnace exit flue gas and reduce utilisation of the rich CO2 gas from the storage by mixing it with air in the mixer.
  • the total mass flow is defined by the furnace pressure excursion reduction control and the mixer is changing the proportions of the air and the rich CO2 mass flows This enables to maintain quality of flue gas produced and minimise the utilisation of rich CO2 gas from storage as an addition to all the above features associated and operational benefits.
  • one furnace could have two controlled leakage systems installed where a first one is connected to air source and a second one is connected to a rich in CO2 gas source. It is recognised that this optional embodiment could be used for furnace pressure excursions reduction together with the control of CO2 and N2 concentration in the furnace flue gas.
  • a method of control of furnace pressure in a combustion furnace comprising a chamber defining a combustion volume having at least one primary inlet for fuel and combustion supporting gases and at least one primary outlet for combustion product gases comprises the step of allowing secondary gas flow into and/ or out of the combustion volume via one or more additional ports in the chamber.
  • the secondary gas flow is additional to the primary control of furnace pressure effected by primary extraction mass flow.
  • the method comprises controlled admission of secondary gas into the combustion volume as a method of secondary control of furnace pressure.
  • the method comprises controlled admission of secondary gas from a secondary supply of gas, being for example ambient air in the case of air firing and a CO2 rich gas source in the case of an oxyfuel fired system.
  • a secondary supply of gas being for example ambient air in the case of air firing and a CO2 rich gas source in the case of an oxyfuel fired system.
  • the method for example comprises the supply by way of dynamic response in real time a quantity of secondary gas to provide additional control of furnace pressure for events such as mill start-up, shut-down, partial or full loss of ignition etc, and in the case of a furnace adapted for transition between air firing and oxyfuel firing during transition between air and oxyfuel modes.
  • a step of controlling primary mass flow of gases out of the combustion volume via the primary outlet in conjunction with controlling of secondary gas into the combustion volume is used as a method of control of furnace pressure, and in particular as a process control step to vary gas in-leakage in a coherent and stable fashion to produce fast, accurate responses to changes in operating conditions in response to changes in load demand.
  • the invention recognises and makes it possible to achieve a reduction in furnace pressure excursions associated with operational changes such as mill start-up and shut down, sootblowing etc.
  • the invention recognises and makes it possible to achieve a reduction in furnace pressure excursions due to transient changes in heat release.
  • the invention provides a method to reduce total uncontrolled air leakage into the furnace.
  • the invention recognises that the optimisation and adaption of furnace pressure setpoint made possible by the invention will reduce the long term, uncontrolled level of furnace air leakage thereby improving the CO2 concentration and efficiency of the CO2 compressors in an oxyfuel system.
  • the invention recognises the accompanying improvement in control of combustion conditions and flame stability for an oxyfuel system.
  • the invention potentially reduces the time taken to change from air firing to oxyfuel mode of operation by improvements in the controllability of the system for an oxyfuel plant.
  • the furnace is in the preferred embodiment of the invention adapted for oxyfuel firing, and in the preferred case having a conventional and an oxyfuel fired capability.
  • the invention provides potential benefits of improved control during plant start-up and shut down, trips, partial or full Loss of Ignition (LOI) and transition to and from conventional air firing and oxyfuel mode of operation
  • the invention may confer additional protection to the plant structure in response to severe events such as partial or full Loss of Ignition (LOI) for both conventional air fired and oxyfuel plant.
  • the invention enables the oxyfuel mode of operation to be adopted at an early point in the plant start-up cycle by the injection of CO2 rich gas from a storage facility.
  • the invention enables a reduction in the overall quantity of gas emitted during start-up from the injection of stored CO2 rich gas or a mixture of air and CO2 rich stored gas.
  • the invention recognises the improvement in operational flexibility and increased range of firing rates available for plant start-up or re-starting in oxyfuel mode.
  • the invention recognises that the large, positive excursions in furnace pressure seen at the onset of sootblowing with existing control schemes may be substantially reduced or eliminated by the use of an optional integrated control strategy for pre-adaption of the operating level of CO2 recycling from the CO2 compressors prior to planned sootblowing events.
  • the invention recognises that significant improvements in the ability to respond to rapid increases in load demand without the occurrence of large scale positive excursions in furnace pressure seen with existing control schemes are possible by the use of an appropriate operating level of CO2 recycling from the CO2.
  • significant commercial advantages may be achieved by optimising the level of CO2 recycling such that the cost of any additional recycling of CO2 is outweighed by additional payments for increased plant flexibility
  • Figure 1 a is an outline schematic process flow chart of a furnace leakage control method in accordance with an embodiment of the invention applied to a conventional air fired power plant;
  • Figure 1 b is an outline schematic process flow chart of a furnace leakage control method in accordance with an embodiment of the invention applied to an oxyfuel fired power plant;
  • Figure 2a is a process flow chart of an example of an air leakage control system for a conventional air fired power plant
  • Figure 2b is a process flow chart of an example of an air leakage control system for an oxyfuel fired power plant
  • Figure 3 is a graph showing the effect of controlled leakage mass flow on furnace pressure
  • Figure 4 is a process flow chart of an example of how to control furnace pressure setpoint
  • Figure 5 is an outline schematic of a possible furnace leakage and controlled leakage flow optimiser method to make use of the principles of the invention.
  • the operation of the Leakage Control System will ideally maintain the minimum controlled leakage flow commensurate with the attainment of satisfactory control over the key process variables.
  • the additional leakage flow should be zero (i.e. the leakage control device closed).
  • the level of controlled leakage mass flow may be increased in a manner and to an appropriate level for satisfactory control of key process variables during the transition process
  • the Leakage Control System may adjust the level of controlled leakage in a manner appropriate to provide the best control of Furnace Pressure and associated combustion variables commensurate with any limiting factors such as any contractual maximum permitted level of air ingress to the system
  • the Leakage Control System will control the Leakage Control damper to minimise excursions in furnace pressure and therefore uncontrolled air leakage and Works Power.
  • the system may be used to limit large scale negative going pressure excursions caused by partial or full LOI, thereby providing additional protection to the structure of the furnace and ductwork system.
  • An arrangement for the admission of control leakage flow may include the following options in any combination: i) admission via a simple orifice with or without an isolating damper
  • the sensitivity Pressure to changes in total leakage flow has the form:- where the total leakage flow m fl is the sum of the uncontrolled casing leakage flow m fl and the controlled leakage flow m c ml .
  • modification of the controlled leakage flow with fuel flow to provide a constant sensitivity ⁇ according to:- may provide improved control for transitions over a wide range of firing levels by maintaining a more constant pressure sensitivity.
  • Modification of the controlled leakage flow may be applied to both conventional air fired power plant and to oxyfuel power plant and allows the required sensitivity to be achieved at minimum leakage flow.
  • controlled leakage flow may be achieved by direct use of equation 2 or similar calculations or by the use of functional look-up tables within the control system software determined either from equation 2 (or similar derivations) or by results from plant tests.
  • the level of controlled air admission may be limited to a maximum contractual value for overall air leakage.
  • the system provides for such injection from storage via suitable storage and injection means.
  • the system provides the ability to select any mixture of air and CO2 rich gas injected into the furnace.
  • the invention recognises that the ability to select any mixture of gas enables the optimum operational and cost strategy to be adopted for any particular set of circumstances.
  • control concept may encompass alternative simple forms of modification of gas injection based on the opening of the damper to a pre-determined position or by the use of a fixed orifice.
  • control concept may encompass the use of pressure control as a method for the achievement of the required level of injection flow.
  • control concept may encompass the use of flow control as a method for the achievement of the required level of injection flow.
  • injection of CO2 may (discretionally) be permitted for instances where the Furnace Pressure is below ambient atmospheric pressure.
  • the Mixer control unit or a similar manifestation of the concept may permit the exhausting of furnace gas where provisions for such safe exhausting are in place.
  • the invention recognises that by control of the level of additional gas flow during negative going excursions in furnace pressure and by control of the venting of additional gas flow when furnace pressure rises above ambient atmospheric pressure a reduction in furnace pressure excursions may be achieved. This may be seen with reference to Figure 3.
  • the use of a maintained level of injected flow about which level the instantaneous injected flow is varied may be used to further reduce short term excursions in furnace pressure.
  • Such use of a maintained gas flow permits a further reduction in the set operating furnace pressure by means of the reduction in transient excursions.
  • the dynamic and statistical minimisation of operating furnace pressure setpoint is subject to the need to maintain any short term egress of hot gas from the furnace within permitted levels.
  • Figure 4 is a schematic of a method to control furnace pressure setpoint.
  • the furnace operates at a sub-atmospheric pressure in order to minimise the leakage of hot gas into the boiler house.
  • Typical control systems operate with a fixed setpoint value, usually determined by the plant operator and usually in the range -0.5 to -1 .0 mbarg (- 0.05 to - 0.10 kPag); the actual value generally being set at a conservative negative pressure value to limit the number and level of positive pressure excursions in worst case transients.
  • the chosen setting depends on the performance of the furnace pressure control loop, the pressure sensitivity of the plant (as described above), the level of firing changes and on the level of short term fluctuations in furnace pressure due to 'random' changes in heat release within the furnace.
  • the long term average mass flow of leakage air into the furnace is:-
  • ⁇ is a pressure offset reflecting the vertical distribution of leakage and pressure within the furnace relative to the furnace pressure measurement point and is the inflexion point in Fig 3. If, for example, the main point of leakage is at the bottom of the furnace ⁇ will have a (small) positive value reflecting the fact that the pressure in the bottom of the furnace is greater than that at the measurement point due to the buoyancy of hot gas above the burners.
  • the long term average mass flow of combustion gas discharged into the Boiler house for positive furnace pressure is:-
  • the furnace should be operated such the both the long and short term average discharge is within an acceptable limit determined by either the plant owner or applicable statute giving:- 0 ⁇ E(m gas ) ⁇ Limit l ....(6) ⁇ m gas ⁇ Limit 2 ....(7) and that
  • the furnace pressure setpoint optimiser may be used either in conjunction with the leakage control scheme or as a stand-alone system.
  • the setpoint optimiser may enable a reduction in the level of in-leakage to the furnace
  • the use of the setpoint optimiser in conjunction with the controlled admission of leakage gas may permit a further reduction in the level of air in-leakage to the furnace by virtue of the reduction in furnace pressure variability associated with the presence of the controlled leakage mass flow.
  • the invention recognises that by varying the level of controlled injection mass flow it is possible to modify the level of uncontrolled leakage by optimisation of the furnace pressure setpoint.
  • the invention recognises that by the above process it is possible to maintain an optimum level of controlled injection mass flow in order to maintain a required level of air leakage mass flow (see Figure 5).

Landscapes

  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Regulation And Control Of Combustion (AREA)
  • Furnace Details (AREA)
  • Incineration Of Waste (AREA)

Abstract

La présente invention concerne un four de combustion et son procédé de fonctionnement. Le four comprend une chambre définissant un volume de combustion ayant au moins une entrée primaire pour un combustible et des gaz soutenant la combustion et au moins une sortie primaire pour les gaz de produit de combustion, ladite chambre étant pourvue d'un ou plusieurs orifices additionnels, par exemple en communication fluidique avec une alimentation de gaz pour un écoulement de gaz secondaire, permettant un écoulement de gaz secondaire dans et/ou hors du volume de combustion.
EP11811366.1A 2010-12-17 2011-12-16 Four de combustion et procédé de fonctionnement Withdrawn EP2652397A2 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GBGB1021480.7A GB201021480D0 (en) 2010-12-17 2010-12-17 Control system and method for power plant
PCT/GB2011/052499 WO2012080748A2 (fr) 2010-12-17 2011-12-16 Four de combustion et procédé de fonctionnement

Publications (1)

Publication Number Publication Date
EP2652397A2 true EP2652397A2 (fr) 2013-10-23

Family

ID=43598590

Family Applications (1)

Application Number Title Priority Date Filing Date
EP11811366.1A Withdrawn EP2652397A2 (fr) 2010-12-17 2011-12-16 Four de combustion et procédé de fonctionnement

Country Status (6)

Country Link
US (1) US20140057215A1 (fr)
EP (1) EP2652397A2 (fr)
KR (1) KR20140021991A (fr)
CA (1) CA2854043A1 (fr)
GB (1) GB201021480D0 (fr)
WO (1) WO2012080748A2 (fr)

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GB201021480D0 (en) 2011-02-02
CA2854043A1 (fr) 2012-06-21
WO2012080748A3 (fr) 2013-04-11
WO2012080748A2 (fr) 2012-06-21
KR20140021991A (ko) 2014-02-21
US20140057215A1 (en) 2014-02-27

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