Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23N—REGULATING OR CONTROLLING COMBUSTION
  • F23N5/00—Systems for controlling combustion
  • F23N5/003—Systems for controlling combustion using detectors sensitive to combustion gas properties
  • F23N5/006—Systems for controlling combustion using detectors sensitive to combustion gas properties the detector being sensitive to oxygen
• • 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
  • F23C6/02—Combustion apparatus characterised by the combination of two or more combustion chambers or combustion zones, e.g. for staged combustion in parallel arrangement
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23N—REGULATING OR CONTROLLING COMBUSTION
  • F23N1/00—Regulating fuel supply
• • 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
  • F23N5/00—Systems for controlling combustion
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23N—REGULATING OR CONTROLLING COMBUSTION
  • F23N5/00—Systems for controlling combustion
  • F23N5/003—Systems for controlling combustion using detectors sensitive to combustion gas properties
• • 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
  • F23C2201/20—Burner staging
• • 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
  • F23C2202/20—Premixing fluegas with 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 
  • F23C2202/00—Fluegas recirculation
  • F23C2202/30—Premixing fluegas with combustion air
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23D—BURNERS
  • F23D2203/00—Gaseous fuel burners
  • F23D2203/002—Radiant burner mixing tubes
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23N—REGULATING OR CONTROLLING COMBUSTION
  • F23N2237/00—Controlling
  • F23N2237/02—Controlling two or more burners

Definitions

• the present invention relates to a method of adjusting the supply devices of a combustion chamber assembly supplied with an oxidant and a fuel whose properties are variable. It makes it possible to take into account the possible fluctuations of these properties so as to maintain the desired combustion quality.
• Many industrial heating equipment consists of a set of separate combustion chambers fed by a common oxidizer and fuel supply device.
• a common oxidizer and fuel supply device For example, in the iron and steel industry, this is the case of furnaces for continuous lines for treating metal strips, equipped with radiant tubes.
• the oxidants or fuels used have variable properties over time.
• enriched air or depleted air or when using locally produced fuels such as coke oven gas, steelmaking gas, a gas mixture, or still alternative fuels such as bio gas or a generator gas.
• fuels such as coke oven gas, steelmaking gas, a gas mixture, or still alternative fuels such as bio gas or a generator gas.
• methods of correcting the regulation of an oven according to the properties of the fuel are many methods of correcting the regulation of an oven according to the properties of the fuel. These methods make it possible to correct the fluctuation of one of the main parameters of the fuel, for example the heating value PCI, the comburivore power, the combustion index or the Wobbe index.
• a particular method is provided by FR2712961.
• a burner is adjusted by taking a given flow rate of fuel. burns this fuel in a dedicated chamber with an air flow such that it leads to combustion in excess of air, and a total quantity reflecting the stoichiometric difference is measured in the complete combustion fumes of the fuel. This quantity is then used to determine the representative value of the combustion air flow rate regulator of the burner.
• This comburimeter device consists of a combustion tunnel, a burner and appropriate measuring means.
• This system has the disadvantage of implementing a specially constructed mini oven in which one burns an air / fuel mixture to proportions set to have an excess of air.
• This mini oven consumes fuel and must operate in excess of air.
• Combustion is carried out in this mini-oven on an operating point which may be remote from that of the installation to be regulated, for example as regards the power of the burner, the air / gas ratio, the temperature of the oven, and the containment of the flame.
• the exploitation of the results thus requires the use of mathematical correction formulas.
• This system also has the disadvantage of being dedicated exclusively to taking into account variations in fuel properties. It does not take into account the variations in oxidant properties or the combustion parameters specific to the controlled installation, namely the unburnt rate or the emission rate of NOx nitrogen oxides.
• the object of the invention is, above all, to improve the control of the combustion of a set of combustion chambers participating in a manufacturing process; in particular, the invention aims to improve the adjustment of a set of radiant tubes of a line of continuous treatment of metal strips.
• These combustion chambers are of the same nature. The power of each of them can be variable but the technologies implemented are similar. The differences between these combustion chambers have no influence on the combustion parameters that we want to control.
• one of these tubes is used in the furnace laboratory as a reference tube. It participates in heating the band as all other tubes.
• This radiant tube is of a construction similar to that of the others tubes and is solicited in a manner representative of the operation of the other tubes which participate in the heating.
• a measuring apparatus which provides information on the state of the combustion products after the tube. It is usually a gas analyzer allowing in particular to know for example the excess air and / or unburnt.
• the method of real-time and continuous adjustment of a set of combustion combustion chambers having similar characteristics supplied by the same oxidant and fuel networks is characterized in that:
• one of the speakers is used as a reference speaker
• combustion parameters are measured in the fumes at the outlet of the reference chamber,
• the regulation parameters of all the speakers are adjusted according to the combustion parameters measured at the outlet of the reference chamber, in particular according to the proportion between the oxidant and the fuel and / or the composition of the oxidizer and / or fuel.
• the combustion parameters measured in the fumes at the outlet of the reference chamber may consist of at least the oxygen concentration, and / or the carbon dioxide concentration, and / or the hydrogen concentration, and / or the concentration of nitrogen oxides and / or the rate of unburnt.
• the excess air can be determined according to the concentration of oxygen or carbon dioxide in the flue gases leaving the reference chamber.
• the air defect can be determined by the concentration of carbon monoxide, or hydrogen, or unburned, in the flue gas leaving the reference chamber.
• control parameters of all the enclosures are adjusted so as to obtain the excess air and / or the rate of unburnt targeted.
• the concentration of nitrogen oxides can be regulated by adjusting the composition of the oxidant and / or the fuel, in particular by dilution with products of combustion.
• the thermal chambers may consist of radiant tubes supplied with gas proportions different from those of the reference tube.
• the invention also relates to an installation for implementing a method as defined above, comprising a set of combustion combustion chambers having similar characteristics, fed by the same oxidant and fuel networks, characterized in that what:
• one of the speakers is used as a reference speaker
• means for measuring combustion parameters are installed on the output of the reference chamber for measuring these combustion parameters in the flue gases at the outlet,
• the thermal chambers may consist of radiant tubes, and a reference tube may be fed in a common manner with the other tubes, the regulating members being placed on supply circuits common to all the tubes.
• the radiant tubes are supplied in a manner distinct from the reference tube and have regulating means different from those of the reference tube, on different supply circuits, the regulating members of the tubes being controlled so that these tubes are fed with the same proportions of gas as the reference tube.
• the regulating members of the radiant tubes can be controlled so that these tubes are fed with proportions of gases different from those of the reference tube, in particular with a different excess of air.
• the equipment used according to the state of the art according to the invention is used as combustion chamber standard equipment similar to the others, which participates in the process and whose setting is perfectly representative of the operation of all equipment. It allows, in particular, to control parameters that depend on the operating mode of the entire installation.
• the master parameter is the excess air measured by the oxygen concentration.
• the unburnt when the oven is cold or the NOx emissions that can be regulated, for example according to the changes in the properties of the oxidant and / or fuel.
• the method according to the invention also makes it possible to regulate equipment operating in lack of air.
• the controlled parameter may be a compound representing one of the gases representative of this mode of combustion, present in large proportion in the fumes. It can be for example CO carbon monoxide.
• the reference tube is fed by fuel and fuel supply circuits equipped with regulating devices to adjust their proportion. It can also be powered by additional circuits, for example combustion fumes or oxygen.
• the analyzes carried out on the products of combustion at the outlet of the reference tube are taken into account to control the regulating elements of the supply circuits so as to reach the desired combustion quality.
• the reference tube is fed in a common way with the other tubes, that is to say when the regulating members are placed on supply circuits common to all the tubes, including the reference tube the other tubes benefit from this same setting.
• radiant tubes are supplied in a manner distinct from the reference tube, that is to say that they have regulating members on different supply circuits, these regulating members are controlled so that these tubes are fed with the same proportions of gas as the reference tube, or with a different proportion.
• the two sets of radiant tubes are designed to have identical regulated parameters, for example an identical supply pressure, for a different operating power while maintaining the same proportion of gas, the regulated parameters of the reference tube are reproduced for the members of the supply circuits of the second set of tubes.
• the regulated parameters of the reference tube are corrected for the circuit elements of feeding the second set of tubes. This correction depends on the physical law of the measured value, for example the variation of the flow as a function of the square variation of the differential pressure.
• radiant tubes when radiant tubes are fed in a manner distinct from the reference tube, their regulating members can be controlled so that these tubes are fed with proportions of gas different from those of the reference tube, for example with a different air excess.
• the regulation of the heat demand of the reference tube can be carried out in terms of rate modulation or modulation of duration. It may be associated with that of other radiant tubes or it may be distinct.
• Fig. 1 is a schematic view of a line of continuous treatment of metal strips
• - Fig. 2 is a schematic view of a radiant tube
• - Fig. 3 represents an example of feeding a pair of radiant tubes
• FIG. 4 is a second example of feeding a set of radiant tubes.
• a furnace 1 equipped with radiant tubes 2 for heating a metal strip 3, scrolling on unrepresented rollers.
• the heating is carried out under a protective atmosphere generally composed of a mixture of nitrogen and hydrogen.
• combustion is provided in a confined combustion chamber, separated from the laboratory oven by the tube.
• FIG. 2 of the drawings one can see, schematically shown, a U-shaped radiant tube 2.
• the radiant tubes may have other shapes, for example I, P, double P or W.
• a burner 4 is located at one end of the tube 2.
• the flame 5 propagates in the tube and releases its energy towards the walls of the tube which heats the laboratory and the band. As they travel through the tube, the fumes heat up on the walls of the tube.
• a heat recovery unit not shown, for preheating the combustion air.
• the fumes in spent parts are discharged to a manifold 6, connected to a chimney.
• An analyzer 7, implanted after the exit of the tube, allows the analysis of the products of combustion.
• FIG. 3 of the drawings we can see, schematically represented, an embodiment of the fuel supply circuit and fuel of a set of U-shaped radiant tubes, including a reference tube 2r.
• the burners 4 are fed by an oxidizer supply system 8, with an FCVc control valve, and a fuel supply system 9, with an FCVf control valve.
• the automatic adjustment of the valves can be provided by a controller (not shown) which receives as input the information on the combustion parameters measured by the analyzer 7 at the output of the reference tube 2r.
• the controller provides, on outputs connected to the valve controls, setting instructions determined according to the input data.
• the furnace zone is equipped with radiant tubes 2 whose burners 4 are supplied in parallel by common oxidant and fuel networks.
• the variation in heat demand is managed by the operating times of the burners, that is to say for each burner the proportion of the opening time of its FCVc oxidizer valve and its FCVf fuel valve for a given time.
• each of the burners was previously set during commissioning for a known operating point by means of manual flow rate limiters 10.
• each of the burners was previously regulated by a singular device of limitation of flow.
• the operation of a tube chosen as a reference tube is the overall image of the operation of all the burners connected to the same supply systems.
• the setting of the FCVc and FCVf valves causes a variation in the pressure of the oxidant Pc or the fuel pressure Pf making it possible to adjust the proportion of gases to the same for all the tubes.
• the measurements made by the analyzer 7 placed at the outlet of the reference tube may for example be limited to two parameters: the oxygen content, which represents the excess of oxidant, and the proportion of unburnt, the quantity of which may lead to Excess air corrections, especially at low temperatures.
• FIG. 4 of the drawings one can see, schematically represented, an oven equipped with U-shaped radiant tubes.
• a set of four radiant tubes 2 is fed by oxidizing networks 8 and fuels 9 common to all four tubes by means of control valves FCVc and FCVf.
• a reference radiant tube 2i is fed separately with its own oxidizer supply system 8i regulated by a valve FCVci, and fuel 9i regulated by a valve FCVfi.
• the transmitters used on the reference tube 2i and the group of tubes 2 to be regulated exploit the same physical laws.
• a differential pressure transmitter can be used to measure a flow rate.
• each of the burners including that of the reference tube, was previously set for commissioning by a singular device for limiting the flow rate, in particular manual adjustment, so as to obtain the same oxidizer / fuel ratio on each burner.
• This adjustment is made under the same conditions for all the tubes, that is to say with the same quality of oxidant and fuel.
• each of the tubes may have a nominal power and / or different dimensions.
• the tubes may also be of different shapes, for example in U or W.
• the oxidant and fuel flow rates of the reference tube are adjusted to have the correct oxygen level in the flue gas according to the changes in the properties of the fuel and / or the oxidant.
• the analyzer 7 makes it possible to adjust the FCVci and FCVfi valves so as to obtain the targeted combustion quality in the reference tube.
• the corresponding operating point measured by the pressures Pci and Pfi, defines the setpoints Pc and Pf used to set the valves FCVc and FCVf.
• the fuel valve FCVf will be adjusted according to the heat demand and the oxidizer valve FCVc will be set so that the value Iva of the signal of the representative flow rate measurement of the oxidant on the group to be regulated, is defined according to the following relation:
• K is a constant
• Ivai expresses the signal of the representative measurement of the oxidant on the reference tube 2i
• Ivfi expresses the signal of the measurement representative of the fuel on the reference tube 2i
• Ivf expresses the signal of the representative measurement of the fuel on the group of tubes 2 to be regulated.
• An extension of this application is to control an installation whose composition of the oxidant is variable. This variation can be unintended, for example the composition of the air is dependent on the moisture content.
• This variation can be voluntary, for example by changing the oxygen content of the oxidizer.
• an oxygen enrichment can be achieved to increase the production of an oven, reduce fuel consumption or reduce CO2 emissions.
• Oxygen depletion can be achieved in order to modify the heat transfer, for example by lengthening the flame, or to reduce NOx emissions.
• a measurement of NOx in the flue gases of the reference tube will be used to regulate the dilution ratio of the oxidant.
• the invention makes it possible to adjust settings that may be different from that of the reference burner.
• the flame develops in a reference chamber similar to other speakers, and not in the open air.
• the combustion in an enclosure is strongly influenced by the geometry of it. This conditions the flame confinement, the nature of the gas flows, the recirculation of a part of the fumes and the temperature mapping in the enclosure. All these parameters affect the combustion, especially the flame temperature.

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• 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)
• Feeding And Controlling Fuel (AREA)

Applications Claiming Priority (2)

Publications (2)

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ID=42312642

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• 2009
  • 2009-11-30 FR FR0905752A patent/FR2953280B1/fr active Active
• 2010
  • 2010-11-26 BR BR112012013060A patent/BR112012013060A2/pt not_active IP Right Cessation
  • 2010-11-26 EP EP10790878.2A patent/EP2507551B1/de active Active
  • 2010-11-26 KR KR1020127016791A patent/KR20120106965A/ko not_active Ceased
  • 2010-11-26 US US13/512,207 patent/US20120291679A1/en not_active Abandoned
  • 2010-11-26 WO PCT/IB2010/055454 patent/WO2011064752A1/fr not_active Ceased
  • 2010-11-26 CN CN201080054052.7A patent/CN102686946B/zh active Active

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