Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23N—REGULATING OR CONTROLLING COMBUSTION
  • F23N1/00—Regulating fuel supply
  • F23N1/02—Regulating fuel supply conjointly with air supply
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23N—REGULATING OR CONTROLLING COMBUSTION
  • F23N5/00—Systems for controlling combustion
  • F23N5/003—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 
  • F23C3/00—Combustion apparatus characterised by the shape of the combustion chamber
  • F23C3/002—Combustion apparatus characterised by the shape of the combustion chamber the chamber having an elongated tubular form, e.g. for a radiant tube
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23D—BURNERS
  • F23D14/00—Burners for combustion of a gas, e.g. of a gas stored under pressure as a liquid
  • F23D14/12—Radiant burners
  • F23D14/126—Radiant burners cooperating with refractory wall surfaces
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23D—BURNERS
  • F23D14/00—Burners for combustion of a gas, e.g. of a gas stored under pressure as a liquid
  • F23D14/46—Details
  • F23D14/60—Devices for simultaneous control of gas and combustion air
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23N—REGULATING OR CONTROLLING COMBUSTION
  • F23N1/00—Regulating fuel supply
  • F23N1/02—Regulating fuel supply conjointly with air supply
  • F23N1/025—Regulating fuel supply conjointly with air supply using electrical or electromechanical means
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23N—REGULATING OR CONTROLLING COMBUSTION
  • F23N2221/00—Pretreatment or prehandling
  • F23N2221/10—Analysing fuel properties, e.g. density, calorific
• • 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 invention relates to an electronic control module and a method for optimum control of the combustion and safety of industrial burners with radiant tubes equipping in particular horizontal or vertical lines of continuous heat treatment of metal strips.
• Figure 1 of the drawings there is shown a schematic example of a portion of a vertical line of continuous heat treatment of a metal strip according to the state of the art. It comprises a zone Z1 for preheating the strip 2, for example by hot gas jets, a zone Z2 for heating the strip by radiant tube burners, a zone Z3 for maintaining the temperature of the strip also equipped with burners for heating. radiant tubes and Z4 and following non-detailed downstream zones used for other processing of the strip, for example its cooling.
• This line is composed of an insulated enclosure 1 in which the strip 2 penetrates on a plurality of rollers 3 ensuring its guidance in a multitude of vertical passes.
• radiant tubes 4, 5 schematically represented by rectangles.
• the number of radiant tubes - thus of burners - installed can be between 200 and 400. Each of these burners is driven individually and works in all or nothing, the radiant tubes functioning for example in mode push-pull.
• Z2 heating corresponds to the simultaneous ignition of all radiant tubes.
• P max for example equal to 60% of P max
• each of the burners of the radiant tubes of the heating zone is lit for 60% of the cycle time, typically set at 1 or 2 minutes. It will be understood that obtaining at each instant the required heating power P re quest is obtained by adjusting the operating time of each radiant tube burner during a portion of the cycle time equal to the percentage of P re quise / Pmax-
• Fig. 2 has a column of radiant tubes 4, 5 located on one side of the strip 2 which runs on rollers 3.
• the feeds / evacuation of each of the radiant tubes 4, 5 of this column are shown in this figure, the supply of oxidant, for example combustion air, is schematized by 6, the supply of liquid or gaseous fuel, for example natural gas, by 7 and the evacuation of fumes by 8. It is understood that according to the position of the fluidic connections radiant tubes on the supply / exhaust manifolds, the air or gas supply or flue gas supply pressures are different for each of the radiant tubes.
• the ignition and extinguishing of a burner can also induce pressure fluctuations on the ducts of the burners located near or in the same zone of the furnace.
• increasing the temperature of the radiant tube has the effect of reducing the excess air.
• the nature or the composition of the gas can vary, sometimes in significant proportions, for example with variations in heating value of +/- 10% compared to an average value.
• the plant can also be fed with several types of gas, for example natural gas and coke oven gas with very different density or calorific characteristics.
• the operating conditions of the burners can be extremely variable depending on the air or gas supply or exhaust gas supply pressures, the characteristics of the gas used, the operating temperatures of the radiant tube, the influence of the ignitions and extinguishing adjacent burners in the column, zone or fluid circuit.
• the values of excess air are traditionally chosen from + 10% to + 20% with respect to the stoichiometric value, so that the combustion is carried out whatever the feed conditions. air and gas and the characteristics of the gas. This additional part of combustion air does not participate in the combustion. On the contrary, the energy required for its heating is a lost energy at the expense of the efficiency of the installation. It can be seen that the equipment according to the state of the art does not make it possible to effectively control the quality of the flame according to the variations of characteristics of the gas or its feed, including during the phases of ignition and extinguishing of the flame which are significant in a plant comprising a large amount of burners operating all or nothing.
• the air-gas ratio at each instant of the ignition, operating and extinguishing phases of the burner is the result at each instant of the opening percentage of the air and gas valves, of the supply pressures of the air and gas manifolds and the actual heating value of the gas with respect to the theoretical setting value.
• the current control equipment installed according to the standards in force, for example ⁇ 746-2, and ⁇ 298, check the existence of the flame without the quality of said flame being verified. It is therefore open-loop operating modes that do not optimize combustion.
• combustion control defects concern rapid phenomena, on the scale of the operating cycle time of the burners or the opening / closing times of the gas and / or air supply valves.
• These short periods of poor control of combustion and operational safety of the burner require the implementation of rapid control devices, preferably local, closer to the controlled burner, and operating in the form of control loops closed with fast reaction times.
• Some commercial equipment includes sensors located in air and gas supplies or fumes to make corrections to the operating conditions of the burners but none allows to optimize each phase of operation of the all-or-nothing cycle and to compensate for variations in calorific value of the feed gas.
• the equipment according to the state of the art does not quickly detect a malfunction on a radiant tube, whether it is the failure of an organ or a degraded mode of operation.
• the electronic control module and the method according to the invention make it possible to optimize the combustion of the radiant tube burners, to reduce the quantities of pollutants emitted, to compensate for variations in the heating power of the feed gas, to improve the efficiency. by reducing the excess air necessary to ensure proper operation of the burner and quickly detect a malfunction on said radiant tube.
• a control module for at least one radiant tube burner the burner comprising a fuel supply valve, an oxidizer supply valve and a flue gas discharge duct
• the control module is characterized in that it comprises: a means for measuring the quality of the combustion installed in the combustion flue of said at least one burner, a fuel flow measuring member, a flow measuring member of oxidant, a means for controlling said at least one burner, acting on the opening percentages of the oxidizer and fuel supply valves of said at least one burner to adapt the oxidant flow rate / fuel flow rate ratio according to the information delivered by the combustion quality control means.
• control module comprises a means for calculating the comburivore power Va of the fuel using the data provided by the combustion quality measuring means, the fuel flow measuring member and the flow measurement member. oxidant, the value of Va calculated by the calculation means being compared with a theoretical value in order to detect a difference exceeding a predefined threshold.
• the means for controlling the quality of the combustion may be a residual oxygen sensor.
• the module may be able to control two radiant tube burners, the comburivore power Va of the fuel being calculated for each burner, in particular from the data supplied by the oxidant and fuel flow measurement devices and the information delivered by the combustion quality control means, the two Va values obtained for the two burners being compared to detect a deviation exceeding a defined threshold.
• the invention also relates to a method for controlling at least one radiant tube burner, the burner comprising a fuel supply valve, an oxidizer supply valve and a flue gas exhaust duct, the process characterized in that it consists in: controlling the operation of said at least one burner with a regulation of the opening percentage of the oxidizer and fuel supply valves of said at least one burner according to a desired oxidant / fuel ratio from the information delivered by a means of measuring the quality of the combustion installed in the combustion flue of said at least one burner, calculate a value of comburivore power Va fuel supplying said at least one burner, in particular from data provided by oxidant and fuel flow measuring devices and information delivered by the quality measuring means combustion of said at least one burner, and comparing this value Va of the comburivore power with a theoretical value in order to detect a deviation exceeding a defined threshold.
• control method also makes it possible to: control two radiant tube burners, calculate a value of the comburivore power Va of the fuel for each burner, in particular on the basis of the data supplied by the oxidant and fuel flow measurement members and the information delivered by the means of measuring the quality of the combustion of said burner, and comparing the two Va values obtained for the two burners to detect a difference exceeding a defined threshold.
• the invention thus provides a fast and efficient system for managing the operation of radiant tube burners installed in large numbers on an industrial furnace. It optimizes combustion and reduces the amount of pollutants produced while ensuring the safe operation of the burners.
• the invention provides a solution for controlling the burners even when the feed gas has variable characteristics (calorific value or supply pressure), allowing the amount of gas to be controlled according to the quantity of air to maintain Permanently the air / gas ratio required for each burner.
• FIG. 2 is a partial schematic representation in elevation of the fluid distribution manifolds to the burners according to the state of the art
• Figure 3 is a schematic representation of a radiant tube assembly according to an exemplary embodiment of the invention.
• the radiant tube burners are fed by air and gas collectors 6.
• the air supply of the burner is equipped with a flow measuring member, for example a diaphragm 13 and a differential pressure sensor 12 and an electrically or pneumatically controlled opening valve 14 optionally with an opening position copying signal.
• the combustion air is heated by the fumes in a heat exchanger schematized by 10 to supply the burner 20 with hot air.
• the gas supply of the burner comprises a flow measuring member, for example a diaphragm 16 and a differential pressure sensor 15 and two electrically or pneumatically controlled opening valves 17 and 18 providing the double dam function.
• a flow measuring member for example a diaphragm 16 and a differential pressure sensor 15 and two electrically or pneumatically controlled opening valves 17 and 18 providing the double dam function.
• EN 746-2 and possibly at least one delivers a copy of open position (in the figure the valve 18) and a pressure switch 26 between the valves 17 and 18.
• the burner 20 is thus supplied with gas and air.
• the controlled opening valves 14, 17 and 18 may also be equipped with sensors or limit switches intended to confirm the position of the valves with full opening or closing.
• the burner 20 is equipped with a flame detection means 21, for example an ultraviolet type optical cell and an ignition means 22, for example an ignition electrode.
• the radiant tube is equipped with temperature sensors, for example at least one thermocouple 25 for measuring its surface temperature and a sensor 24 located on the evacuation of the moist fumes 8 of the radiant tube 4 to control the quality combustion, for example a residual oxygen sensor.
• temperature sensors for example at least one thermocouple 25 for measuring its surface temperature
• a sensor 24 located on the evacuation of the moist fumes 8 of the radiant tube 4 to control the quality combustion, for example a residual oxygen sensor.
• the combustion system is equipped with an electronic control module 23 located in the immediate vicinity of the burner, with output 23a and input 23b signals.
• the input signals according to the example shown are the positions of the controlled valves 14 and 18, the flame detection 21, the air and gas flow measurements 12 and 15, the residual oxygen in the humid fumes measured by the sensor 24 and the temperature of the tube measured by the thermocouple 25.
• the output signals are the controls of the valves 14, 17 and 18 and the ignition control 22.
• a digital link makes it possible to transmit and receive information between a centralized control / command system and the electronic control modules 23 and / or between the electronic control modules 23.
• This electronic control module provides all the functions processed by the burner control systems existing on the market according to the state of the art and as defined in the standards, in particular the functions of sequencing of the ignition, operating, burner extinguishing and safety related to each of these phases of operation. He owns also a combustion control and a failure control as detailed below.
• the proposed system regulates an amount of air which is the image of the instantaneous power to be delivered by the burner in its different operating phases, by means of the valve 14.
• Differential pressure 12 is connected to the electronic control module 23, which calculates the instantaneous flow rate of air delivered to the burner.
• the sensor 24 for measuring the residual oxygen in the flue gases is connected to the electronic control module 23, which determines the quantity of gas necessary in order to respect the required oxygen level in the humid fumes in the various phases of operation of the burner such as ignition, stabilized operation and extinguishing and regulates this flow by driving the valve 18.
• the differential pressure sensor 15 is connected to the electronic control module 23, which calculates the instantaneous flow rate of gas delivered to the burner.
• the air and gas flow rates are calculated using the formula described in ISO 5167-2 which integrates the geometrical characteristics of the primary measuring elements 13, 16, the parameters relating to the properties of the fluids and the conditions of the such as atmospheric pressure, specific pressures, temperatures and weights of the fluids which are common or individual dynamic data measured and transmitted to the electronic control module 23.
• the electronic control module 23 calculates the residual oxygen level expected in the humid fumes and adjusts the flow of gas to maintain the required oxygen level in the humid fumes.
• the invention This makes it possible to maintain the quality of the combustion regardless of the variations in the supply pressure of the gas and the air.
• the invention also proposes other functionalities such as a sequencer for testing the tightness of the gas valves controlled by the pressure switch 26 as well as protection in the event of exceeding a maximum operating temperature controlled by the thermocouple 25.
• the sensor 25 for measuring the temperature of the radiant tube 4 is connected to the electronic control module 23.
• the module 23 can thus control the stopping of the burner in the event of exceeding a maximum safety temperature reached by the radiant tube.
• the electronic control module 23 makes it possible to rapidly detect a malfunction on the radiant tube to which it is connected and to place said tube in the safety position if the dysfunction is judged to be important.
• the electronic module will issue an alert locally and / or to the centralized control / command system, keeping the radiant tube concerned in service, or stop it by placing it in the safety position.
• the electronic control module 23 exchanges information with the measuring and control devices of the air flows 12, 13, 14 and the gas flows 15, 17, 18, 26, as well as the sensor of residual oxygen 24 and the temperature sensor 25.
• the electronic control module 23 can thus detect a discrepancy between the information provided by one of these organs or sensors, the information provided by the other members or sensors, and the theoretical data expected. For example, this discrepancy may consist of:
• the electronic control module 23 calculates the fuel Va and compares it with the Theoretical va of the fuel.
• This theoretical Va is advantageously supplied to the module by the centralized control / command system. It can also be directly informed in the module by an operator.
• the electronic control module 23 emits an alert beyond a certain threshold of difference. When this difference reaches a second higher threshold, the radiant tube is stopped and made safe.
• the first threshold is, for example, 10% difference and the second threshold 15% difference.
• the theoretical Va value of the fuel is for example calculated according to the composition of the gas according to the following formula in which the chemical formulations of the gases are to be replaced by the content of these gases in the fuel expressed in m 3 gas per m 3 of fuel:
• Va H 2 x2.36 + COx2.38 + CH 4 x9.54 + C 2 H 4 x14.4 + C 2 H 6 x16.84 + C 3 H 6 x21 .84 + C 3 H 8 x24.37 + C 4 H 8 x 29.64 + C 4 Hi 0 x32.41 + C 5 Hi 2 x 40.87 - O 2 x 4.77
• the electronic control module 23 is placed in close proximity to the radiant tube that it controls. This allows a fast exchange of information between the electronic control module and the members placed on the radiant tube due to a reduced cable length. This solution makes it possible to control and secure radiant tube assemblies faster than they would be through a centralized control / command system.
• the proximity between the electronic control module and the radiant tube to which it is connected also facilitates the intervention of the operators during the commissioning of the equipment and during its maintenance.
• the electronic control module 23 is connected to two radiant tubes located close to each other. It can thus detect a different behavior of the two radiant tubes which can reveal a dysfunction of one of the two.
• This solution is particularly advantageous because it allows to erase the disturbances that would be related to a variation in the characteristics of the gas and / or air, these being common to both radiant tubes.
• the electronic control module 23 detects a shift between the residual oxygen content announced by the sensor 24 of one of the radiant tubes and the flow rates measured on the air and the gas of this radiant tube, this offset can be interpreted as being linked to a change in the composition of the fuel and its Va.
• the electronic control module 23 according to the invention checks whether this same offset is present on the second radiant tube. If this is the case, it is a change in the characteristics of one of the fluids. If this is not the case, it is a malfunction of an organ on the first radiant tube and an alert is given by the electronic control module.
• This analysis also makes it possible to detect the drilling of a radiant tube because it would result in an entry of the atmosphere of the furnace into the tube, if the radiant tube operates in push-pull mode (the pressure inside the tube is lower than that outside the tube), and therefore a drop in the residual oxygen content measured in the fumes.
• the electronic control module comprises in an optimized embodiment: safety functions according to the state of the art and the impositions of existing standards, controlling the operation of one or two burners with closed loop regulations of the openings of the air and gas supply valves, these loops operating at an air / gas ratio that depends on the value of the desired oxygen in the humid fumes at any point in the operating cycle (ignition, stabilized operation, extinguishing), that the burners operate in all or nothing mode or in proportional, the taking into account data on the characteristics of air and gas, including the compositions, temperatures, supply pressures and the heating value of the fuel, for the control of the air-to-gas ratio of the burner operation, the control of the air-gas ratio of the burner operation carried out in closed loop from the measurement of residual ⁇ 2 in the flue gases validated by the flow calculations, a system of Calculation of the Va of the gas to check if it is in conformity with that provided by the centralized control / command system and to trigger an alert if there is a different going

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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)
• Combustion Of Fluid Fuel (AREA)

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• 2015
  • 2015-12-17 FR FR1562629A patent/FR3045783B1/fr not_active Expired - Fee Related
• 2016
  • 2016-12-15 KR KR1020187018092A patent/KR20180094932A/ko not_active Withdrawn
  • 2016-12-15 PL PL16836201T patent/PL3390911T3/pl unknown
  • 2016-12-15 JP JP2018531331A patent/JP2018537649A/ja active Pending
  • 2016-12-15 US US16/062,963 patent/US20180372315A1/en not_active Abandoned
  • 2016-12-15 CN CN202010977203.1A patent/CN112066408A/zh active Pending
  • 2016-12-15 CN CN201680073367.3A patent/CN108463671A/zh active Pending
  • 2016-12-15 ES ES16836201T patent/ES2890881T3/es active Active
  • 2016-12-15 WO PCT/EP2016/081282 patent/WO2017103000A1/fr not_active Ceased
  • 2016-12-15 EP EP16836201.0A patent/EP3390911B1/fr active Active

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