EP3830480B1 - Étalonnage d'une chaudière - Google Patents

Étalonnage d'une chaudière Download PDF

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Publication number
EP3830480B1
EP3830480B1 EP19749329.9A EP19749329A EP3830480B1 EP 3830480 B1 EP3830480 B1 EP 3830480B1 EP 19749329 A EP19749329 A EP 19749329A EP 3830480 B1 EP3830480 B1 EP 3830480B1
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Prior art keywords
burner
boiler
emissions
state
air
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EP19749329.9A
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German (de)
English (en)
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EP3830480A1 (fr
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Jeremy Miller
Mitchell Kane
Kevin RUSHBROOKE
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Spirax Sarco Ltd
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Spirax Sarco Ltd
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F22—STEAM GENERATION
    • F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
    • F22B35/00—Control systems for steam boilers
    • 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
    • F23N2237/00—Controlling
    • F23N2237/22—Controlling water injection
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N2241/00—Applications
    • F23N2241/04—Heating water

Definitions

  • the present disclosure relates to methods for calibrating a boiler having a burner to optimise efficiency.
  • Industrial boilers are used to generate steam, for example for power generation or for heat transfer (e.g. in medical sterilisation, industrial cooking and other industrial processes).
  • the burner of a typical steam boiler receives fuel (e.g. natural gas) and burns it in air to generate heat. This is known to generate emissions in a flue gas from the burner, such as oxides of nitrogen (NOx) and carbon monoxide.
  • fuel e.g. natural gas
  • NOx oxides of nitrogen
  • COx carbon monoxide
  • Stoichiometric combustion is generally not practical, and so most burners use an air-to-fuel ratio above stoichiometric ( ⁇ >1) to ensure complete combustion of the fuel.
  • thermal dilution excessive air reduces burner temperature
  • High flame temperature may cause generation of oxides of nitrogen (NOx), largely owing to nitrogen dissociating and combining with oxygen at high temperature. It is known to counteract an emissions of oxides of nitrogen (NOx) by injecting water into the burner, to reduce the flame temperature.
  • NOx oxides of nitrogen
  • US 6,289,666 discloses a power generating system which operates at high pressure and utilizes a working fluid consisting of a mixture of compressed non-flammable air components, fuel combustion products and steam.
  • the working fluid exiting the power generating system is substantially free of NOx and CO.
  • Working fluid is provided at constant pressure and temperature.
  • Combustion air is supplied by one or more stages of compression.
  • Fuel is injected at pressure as needed.
  • Inert liquid is injected at high pressure to produce working an inert mass of high specific heat diluent vapor for use for internal cooling of the combustion chamber.
  • the use of non-flammable liquid injection inhibits the formation of pollutants, increases the efficiency and available horsepower from the system, and reduces specific fuel consumption.
  • Control systems allow the independent control of the quantity, temperature and pressure of the air, fuel and non-flammable liquid introduced in the combustion chamber allowing control of the maximum temperature and average temperature within the combustion temperature as well as the temperature of the exhaust from the combustion chamber.
  • US 2018/025288 discloses an optimisation system for a power generating unit which manipulates variables to reach a goal, such as minimising NOx emissions.
  • a method of calibrating a boiler having a burner comprising: supplying fuel to the burner at a fuel supply rate and supplying combustion air to the burner at an air supply rate, so that fuel is burnt at an air-to-fuel ratio; and supplying water to the burner at a water supply rate; adjusting burner operating variables, including adjusting both the air-to-fuel ratio and the water supply rate, to define a plurality of burner states; testing operation of the boiler at the plurality of burner states; for each burner state; determining an efficiency parameter relating to an efficiency of the boiler; monitoring emissions in a flue gas downstream from the burner; comparing the emissions to one or more emissions thresholds to determine if they are excessive or acceptable; and from a set of burner states correlated to acceptable emissions, selecting an operational burner state to optimise the efficiency parameter, for operation of the boiler.
  • the method may further comprise determining a plurality of burner states that lie on an emissions boundary in a state space of burner states in which the air-to-fuel ratio and water supply rate are state variables, the emissions boundary corresponding to the one or more emissions thresholds; and wherein the operational burner state is selected from the plurality of burner states on the boundary.
  • the emissions boundary may be a compound boundary based on each of the respective thresholds.
  • One or more of the burner states on the emissions boundary may be determined by calculation. In other words, when the operational burner state is selected from the plurality of burner operating states on the boundary, one or more of those burner operating states may be determined to lie on the boundary by calculation rather than by operating the burner at each respective burner operating state.
  • the efficiency parameter may be a flue-derived boiler efficiency determined at least partly based on a monitored level of excess oxygen and/or a monitored level of carbon monoxide and/or a monitored level of carbon dioxide in the flue gas.
  • the flue-derived boiler efficiency may be determined based on the fuel supply rate; the air supply rate; a flue gas parameter selected from the group consisting of level of oxygen, level of carbon dioxide, level of carbon monoxide; and a flue gas temperature.
  • the efficiency parameter may be a boiler heat transfer efficiency determined based on the heat transfer to a working fluid of the boiler relative the heat input to the burner (i.e. a working-fluid derived boiler efficiency).
  • the boiler heat transfer efficiency may be determined by calculating the ratio of the thermal power difference of the working fluid to the sum of thermal power to the burner from air, fuel and water, and thermal power released by complete combustion of the fuel.
  • the emissions may be compared to one or more of an oxides of nitrogen (NOx) threshold; a carbon monoxide threshold; a carbon dioxide threshold; and an oxides of sulphur (SOx) threshold.
  • NOx oxides of nitrogen
  • SOx oxides of sulphur
  • the water may be liquid as supplied to the burner, whereby the water vaporises to turbulently expand and mix at the burner.
  • the boiler may be in-service in an industrial plant, the boiler having a demand state corresponding to a load on the boiler, wherein the burner operating variables are iteratively adjusted to optimise the efficiency parameter.
  • Iteratively adjusting the burner operating variables may comprise: obtaining a prediction of emissions and/or the efficiency parameter for a first burner state of the plurality, based on calibration data correlating emissions and/or the efficiency parameter respectively with the burner variables; determining observed data for emissions and/or the efficiency parameter; comparing the prediction and observed data to determine a performance error; defining a second burner state based on a model correlating emissions and/or efficiency to the burner operating variables to compensate for the performance offset.
  • the method may further comprise storing calibration data for each of the burner states at which the burner is tested, the calibration data comprising: efficiency data including the efficiency parameter; state data including: the water supply rate, the air-to-fuel ratio; and/or the fuel supply rate and the air supply rate; and emissions data relating to the emissions in the flue gas.
  • Each of the burner operating states may correspond to the same demand state of the boiler.
  • the demand state may correspond to a load serviced by the boiler, a heat transfer demand at the boiler (e.g. a thermal power input output to the working fluid, or a thermal power input to the burner), or a fuel supply rate, for example.
  • the method may comprise storing calibration data correlated to the demand state.
  • the calibration data may comprise state data for at least the selected burner operating state, the state data including: the water supply rate; the air-to-fuel ratio, and/or the fuel supply rate and the air supply rate.
  • a method of calibrating a boiler at a plurality of demand states comprising, for each demand state, calibrating the boiler by a method in accordance with the first aspect.
  • the boiler may be in a test installation remote from an industrial plant, to generate calibration data for use at an industrial plant.
  • the boiler of the test installation may not be in-service in an industrial plant, but is instead configured for generating calibration data remotely from an industrial plant.
  • the boiler may be in-service in an industrial plant.
  • the method may further comprise: determining a demand state of the boiler; selecting an operational burner state from the calibration data based on the demand state; and operating the boiler at the operational burner state.
  • a method of operating a boiler having a burner comprising: determining a demand state of the boiler; selecting an operational burner state from calibration data generated by a method in accordance with the first or second aspects, based on the demand state; and operating the burner at the operational burner state.
  • a method of operating a boiler having a burner comprising: calibrating the boiler by a method in accordance with the first or second aspects; wherein the boiler is calibrated periodically and/or in response to a stimulus selected from the group consisting of: a determination of excessive emissions in a flue gas of the boiler; a determination of a change in emissions, oxygen or carbon dioxide levels in the flue gas exceeding a respective threshold; a change in a demand state of the boiler.
  • a boiler controller configured to operate a boiler by: controlling a fuel supply rate of fuel to a burner of the boiler at a fuel valve; controlling an air supply rate of air to the burner at an air valve; controlling a water supply rate of water to the burner at a water supply valve; receiving emissions data from an emissions analyser of the boiler; wherein the controller is configured to carry out a method in accordance with any preceding claim.
  • a boiler installation comprising: a boiler having a burner; optionally an emissions analyser for monitoring emissions in a flue gas of the boiler; a fuel valve for controlling a supply of fuel to the burner; an air valve for controlling a supply of air to the burner; a water valve for controlling a supply of water to the burner; and a boiler controller in accordance with the fifth aspect.
  • a seventh aspect there is provided a computer program comprising instructions to cause a boiler controller or a boiler installation to carry out a method in accordance with any of the first to fourth aspects.
  • the invention may comprise any combination of features described herein, except such combinations as are mutually exclusive.
  • a boiler installation may be commissioned by temporarily fitting an emissions analyser in the flue and adjusting the air-to-fuel ratio to target a specified level of excess oxygen in the flue gas which is thought to correspond to complete combustion at the burner.
  • the burner may be setup for water injection to reduce the oxides of nitrogen to an acceptable level.
  • an emissions analyser may be installed in the flue and the air-to-fuel ratio may be re-adjusted to target the specified level of excess oxygen.
  • air-to-fuel ratio may be reduced in order to reduce thermal dilution at the flame (owing to excess air) whilst ensuring complete combustion.
  • Air-to-fuel ratio may be varied based on monitoring excess oxygen in flue gas (indicative of excess air) and/or monitoring carbon monoxide in the flue gas (indicative of incomplete combustion owing to insufficient air).
  • the oxides of nitrogen (NOx) at this first example burner state may be excessive, for example owing to high flame temperature. Accordingly, in this simple example, the excessive level of oxides of nitrogen (NOx) may be reduced by injecting water, to define a second burner state at the same air-to-fuel ratio but with a higher rate of water injection.
  • a burner state may be selected during commissioning which does not represent the highest achievable boiler efficiency.
  • Figure 1 is a plot of boiler efficiency as a function of burner operating variables of air-to-fuel ratio and water injection rate. Overlaid on the plot (in dashed lines) is a compound emissions boundary 2 which in this example reflects burner states at which at least one type of emissions is at the respective threshold.
  • the emissions boundary is a compound boundary for both a level of oxides of nitrogen (NOx) and a level of carbon monoxide (CO) in a flue gas.
  • NOx oxides of nitrogen
  • CO carbon monoxide
  • the emissions boundary 2 indicates that burner states having a lower water injection rate or a lower air-to-fuel ratio will exceed at least one of the emissions thresholds.
  • the present disclosure relates to selection of an operational burner state which represents the highest boiler efficiency that can be achieved without exceeding one or more emissions thresholds.
  • the operational burner state is shown on Figure 1 at point 4.
  • the first and second burner states as described in the example above are shown at points 6 and 8 respectively.
  • the first burner state 6 represents a higher boiler efficiency than the operational burner state 4, which may be because the absence of injected water leads to higher flame temperatures and heat transfer to the boiler and the working fluid (e.g. water to be converted to steam).
  • the second burner state 8 represents a worse boiler efficiency than the operational burner state 4, which may be because the flame temperature is so high at burner state 4 that the water injection to reduce it to acceptable levels results in excessive thermal dilution.
  • the operational burner state 4 has a higher air-to-fuel ratio and a higher water supply rate than an optimal-efficiency burner state 6 having excessive emissions.
  • Figure 1 indicates the boiler efficiencies associated with each burner state as calculated based on heat transfer to the working fluid (based on the measured thermal power input to the working fluid relative to the thermal power provided to the boiler), as will be described in the example below. This may be referred to as heat transfer efficiency in the present disclosure, or a working fluid-derived boiler efficiency.
  • boiler efficiency may be calculated based on monitoring (i) various gas levels in the flue gas (e.g. oxygen, carbon monoxide) and (ii) temperature of the flue gas.
  • the various gas levels may correlate to the completeness of the combustion, whereas the temperature of the flue gas may correlate to the amount of heat released by combustion that is not transferred to the boiler.
  • a controller may calculate or predict boiler efficiency based on flue-derived parameters, rather than direct monitoring of the thermal power input to the working fluid, as will be described in further detail below.
  • flue-derived boiler efficiency This may be referred to as flue-derived boiler efficiency in the present disclosure - which is intended to mean an indirect calculation of boiler efficiency which uses parameters (e.g. temperature and/or gas levels) from the flue, rather than direct monitoring of the change of thermal power of the working fluid.
  • burner operating variables i.e. air-to-fuel ratio and water injection rate
  • Figure 2 shows an example boiler installation 10 for conducting burner calibration testing as described in outline with respect to Figure 1 .
  • the boiler installation 10 is not in-service (i.e. for servicing a load), but is installed remote from an industrial plant, or is in a calibration or commissioning phase of an industrial plant, in order to generate calibration data for subsequent use.
  • the boiler installation 10 comprises a boiler 12 configured to receive a working fluid, and a burner 14 configured to burn fuel in the presence of air to transfer heat to the working fluid.
  • the boiler is for generating steam and has an inlet 16 for receiving liquid water and an outlet 18 for discharging steam.
  • a flue 20 extends from the burner 14 to discharge flue gas outside of the boiler 12.
  • the burner is configured to receive fuel from a fuel inlet pipe 22, to receive air from an air inlet pipe 24, and to receive water from a water injection pipe 26.
  • the boiler installation 10 further comprises a controller 50 configured to control operation of the burner 14.
  • the controller 50 comprises a non-transitory machine-readable medium 52 which in this example stores instructions for controlling the boiler installation 10, and optionally calibration data recorded at the boiler installation 10 (although in other examples such data may be stored remotely).
  • the controller 50 is coupled to control equipment throughout the boiler installation, including:
  • the controller 50 is configured to control a fuel supply rate at which fuel is supplied to the burner 14, an air flow rate at which air is supplied to the burner 14, and a water injection rate at which water is injected to the burner 14, as will be described below with respect to the example methods of boiler calibration.
  • Figure 3 shows a first example method of boiler calibration in which the controller tests operation of the boiler of Figure 2 at a plurality of burner states.
  • a matrix of burner states are defined for testing the boiler, for example at 8 different air-to-fuel ratios (e.g. between 1.01 and 1.06) and at 8 different water injection rates (e.g. between nil and 10% of the fuel flow rate).
  • air-to-fuel ratios e.g. between 1.01 and 1.06
  • water injection rates e.g. between nil and 10% of the fuel flow rate
  • a different range of air-to-fuel ratios may be defined.
  • burner states may be defined differently, for example: iteratively to maximise an efficiency parameter, or by successively reducing the air-to-fuel ratio and raising the water injection rate to compensate for emissions.
  • one of the burner states of the matrix of burner states is determined for test operation of the boiler.
  • the burner state defines the water injection rate and the air-to-fuel ratio.
  • the air-to-fuel ratio can be varied by either adjusting the air supply rate, the fuel supply rate, or both (in this example, air supply rate is varied).
  • the controller 50 tests operation of the boiler at the determined burner state by controlling the respective flow controllers 23, 25, 27 to set the respective rates for fuel, air and water supply and operating the burner whilst monitoring various parameters for storage as calibration data over a test period, for example 30 minutes or 1 hour.
  • the boiler is out of service and is configured for testing. It is operated at a constant demand state corresponding to supply of 10 tonnes of steam per hour (2.78kg/s) at a pressure of 3bar.
  • the demand state is constant in that the load and operating conditions of the boiler - and thereby the heat transfer to the burner to the working fluid - does not vary between successive tests of the boiler at the burner states.
  • the demand state may vary owing to variation of a real load serviced by the boiler (e.g. variation in a flow rate at which steam is drawn from the boiler, or variation of the pressure at which the steam is demanded), or by virtue of variation of the operating conditions of the boiler (e.g. variation of the supply rate of feed-water to the boiler, and/or the temperature of feed-water as supplied to the boiler, and/or the amount of water in the boiler).
  • variation of a real load serviced by the boiler e.g. variation in a flow rate at which steam is drawn from the boiler, or variation of the pressure at which the steam is demanded
  • variation of the operating conditions of the boiler e.g. variation of the supply rate of feed-water to the boiler, and/or the temperature of feed-water as supplied to the boiler, and/or the amount of water in the boiler.
  • Boiler controllers conventionally control fuel supply in response to variable real loads and operating conditions.
  • a boiler controller may control fuel supply rate based on a feedback loop targeting an operational supply pressure of steam.
  • a boiler controller may further control the fuel supply rate based on the supply rate, temperature of feed-water and/or the amount of water in the boiler (which may be maintained by a separate control loop between a maximum and a minimum).
  • the demand state as described herein is related to the heat transfer demanded at the boiler, and may vary according to the same principles underlying the above-described variation of fuel supply rate.
  • the demand state may vary in dependence on downstream demand (e.g. load serviced by the boiler) and/or upstream operating conditions (e.g. the temperature and/or flow rate of feed-water, quantity of water in the boiler).
  • the demand state may be characterised (i.e. for correlation and data storage) in different ways.
  • the demand state may be specified in terms of the actual rate of heat transfer to the working fluid (i.e. the thermal power output in watts, as determined based on the thermodynamic properties of the working fluid into and out of the boiler).
  • the demand state may otherwise be specified in terms of the actual rate of heat transfer (i.e. thermal power in watts) input to the burner (e.g. the sum of the calculated thermal power released by combustion, and the thermal power of the fuel, water and air supplied to the burner).
  • the thermal power input to the burner is transferred to the working fluid at an efficiency less than unity, for example owing to power losses by conduction through the apparatus, and heat which is rejected to the flue.
  • the demand state may be specified by the fuel flow rate.
  • the calibration data may be correlated both by burner state and demand state to either permit calibration data to be generated for a plurality of burner states at each respective demand state, or to permit interpolation of results at different demand states (i.e. mapping observations from one demand state to another demand state based on predetermined relationships).
  • calibration data 350 relating to the performance of the boiler is stored, correlated to the burner state (and optionally the demand state, as mentioned above).
  • the calibration data stored for each burner state comprises the demand state, the burner state, an efficiency parameter 352 relating to the efficiency of the boiler at the burner state, and emissions data 354 relating to the emissions in the flue gas.
  • ⁇ P water is the thermal power transferred to the working fluid between the water inlet 16 and the steam outlet 18, and is calculated based on the flow rate and the temperature of the working fluid at the sensors 17, 19.
  • P input is the input power and, in this example, is calculated as the total of the thermal power of each of the fuel (i.e. not including combustion), air, water as supplied to the burner, together with the thermal power released by complete combustion of the fuel.
  • the heat transfer efficiency (or working fluid derived boiler efficiency) may be relatively slow to settle upon change of a demand state or burner state, as the thermal mass of the boiler equipment is relatively high and so it can take a relatively long period (for example, between 30 minutes and 2 hours, for example 1 hour) to reach a steady state condition in which heating or cooling of the boiler equipment is negligible and there is a steady state thermal loss through the boiler equipment.
  • the emissions data comprises a level (e.g. a concentration, such as parts per million (ppm)) of oxides of nitrogen (NOx), a level of carbon monoxide, a level of carbon dioxide and a level of oxides of sulphur (SOx), all of which are determined by the emissions analyser 21 in the flue 20.
  • a level e.g. a concentration, such as parts per million (ppm)
  • NOx oxides of nitrogen
  • COx oxides of nitrogen
  • SOx oxides of s of sulphur
  • the emissions in the flue are directly related to the conditions at the burner, and so are relatively fast to settle after a change of demand state or burner state.
  • Emissions data for a burner state may be recorded based on a 2 minute average 5 minutes after a change to the respective burner state.
  • the calibration data is stored in a memory 52 of the controller.
  • the calibration data may be stored remotely from the boiler installation, for example in cloud storage accessible over an internet connection.
  • the controller determines whether the boiler tests are complete - in particular by determining whether the boiler has been operated at each burner state of the matrix of burner states. If not, the method returns to block 302 for a further burner state of the plurality. Otherwise, the method continues to block 308.
  • the controller 50 determines an operational burner state which is selected from a plurality of the burner states having acceptable emissions, so as to optimise efficiency with respect to the efficiency parameter.
  • the term "operational burner state" is intended to denote a burner state for continued operation of the boiler or a like boiler having a like burner.
  • the controller 50 evaluates the calibration data for each of the burner states and determines a subset having acceptable emissions. The controller then determines the burner state from the subset which has the highest efficiency.
  • the controller may interpolate one or more burner states based on a plurality of neighbouring burner states in the state space (i.e. of air-to-fuel ratio and water injection rate) in order to predict a burner state having high efficiency and acceptable emissions.
  • the controller may interpolate one or more burner states that lie on an emissions boundary in the state space of air-to-fuel ratio and water injection rate. It is thought that such burner states may include the burner state having the highest boiler efficiency, and therefore a search of burner states which is limited to those lying on the emissions boundary may be faster.
  • burner states belonging to a matrix of burner states are tested
  • other testing schemes may be conducted to generate calibration data.
  • burner states may be iteratively tested (i.e. with each successive burner state being defined based on the results of previous tests) to determine a local maximum for the respective efficiency parameter.
  • burner states along the emissions boundary may be tested (for example on or close to the boundary), for example by defining a next burner state to test based on a basic predictive model of emissions of the burner.
  • the example boiler installation 10 of Figure 2 is out of service and configured for generating calibration data only, which may be used for the control of other boiler installations having a like burner and boiler.
  • the method of Figure 3 may nevertheless be applied to an in-service boiler configured to service a load to generate calibration data for use in mapping the emissions and efficiency performance of the boiler to burner operating variables, for use in determining suitable operating burner states of the boiler (e.g. for various demand states of the boiler, or for like boilers).
  • Figure 4 shows an example method of controlling an in-service boiler of an industrial plant based on calibration data.
  • the in-service boiler is as described above with respect to Figure 2 , except that it is installed in an industrial plant to provide steam for an in-service load.
  • the in-service boiler may omit some of the sensors as described above with respect to Figure 2 .
  • emissions data is not required in order to select a suitable operational burner state for operation of the burner based on previously-determined data (as opposed to generating such data). Accordingly, the emissions analyser of Figure 2 may be omitted.
  • Such emissions analysers may only be required for initial calibration testing to determine operational burner states (i.e. to determine using testing which burner state from a plurality should be used to optimise efficiency), and may not be required to select an operational burner state based on previously-generated such calibration data.
  • the controller 50 obtains a demand state for the boiler (e.g. a current thermal power output required to the working fluid).
  • a demand state for the boiler e.g. a current thermal power output required to the working fluid.
  • the controller 50 obtains an operational burner state correlated to the demand state based on calibration data 450 generated by a method as described above.
  • Figure 5 shows a further example method of calibrating an in-service boiler based on a model which maps an efficiency parameter and emissions data to burner operating variables including the air-to-fuel ratio and the water supply rate.
  • a model may be generated based on prior operation of the boiler (e.g. during normal in-service operation, or an initial or periodic period of commissioning, including as described above with respect to the method of Figure 3 ).
  • the controller 50 obtains a first burner state for the boiler (i.e. a first set of burner operation variables), which may be a current burner state of the boiler.
  • the controller obtains predictions for emissions and an efficiency parameter based on previously-stored calibration data 550.
  • the controller tests operation of the boiler at the first burner state and stores observed data 560 including observed emissions data and an observed efficiency parameter.
  • the controller defines a second burner state based on a comparison between the calibration data and the observed data for the first burner state. For example, the controller may determine a vector in the mapping of the calibration data to move from a point representing the observed emissions and efficiency performance to a point representing the predicted emissions and efficiency performance, and thereby determine an offset in the burner operating variables (i.e. air-to-fuel ratio and water injection rate) corresponding to the vector. For example, if the controller determines that the observed emissions are higher than predicted but the efficiency is substantially the same, then the controller may determine a vector in the mapping corresponding to marginally increasing the air-to-fuel ratio and marginally increasing the water supply rate, in order to reduce the emissions in a way that maximises efficiency.
  • the controller may determine a vector in the mapping of the mapping to move from a point representing the observed emissions and efficiency performance to a point representing the predicted emissions and efficiency performance, and thereby determine an offset in the burner operating variables (i.e. air-to-fuel ratio and water injection rate) corresponding to the vector. For example, if
  • the controller may determine that the observed emissions are lower than predicted and the efficiency is lower than predicted, and the controller may analyse the mapping of efficiency and emissions in the calibration data to determine a vector to return the performance the predicted emissions and efficiency, which may correspond to reducing the air-to-fuel ratio to maximise the efficiency without exceeding the emissions boundary.
  • the calibration data is updated based on the test operation of the boiler to re-map the emissions and efficiency performance.
  • the controller determines whether the boiler should continue to be operated at the second burner state defined at block 508, or whether a further cycle of iteratively defining a new burner state as described above with respect to blocks 502 to 508 should be repeated.
  • the criteria for continuing operation is that the differences in each of the burner operating variables between the first burner state and the second burner state should be below a predetermined threshold (e.g. 0.005 for air-to-fuel ratio, 10ml/min for water injection rate) - indicating that the burner state has settled.
  • the threshold difference for water injection may vary depending on the size of the boiler installation and the range of water injection. For example, in larger installations the minimum increment between burner states may be 50ml/min.
  • a flue-derived boiler efficiency may be calculated based on:
  • the fuel gas parameter may be used in conjunction with the fuel supply rate and the air supply rate to determine whether combustion is complete. For example, given a known quantity of fuel and air, the concentration of oxygen and carbon dioxide owing to complete combustion is readily predictable. Alternatively, a correlation between carbon monoxide levels and completeness of combustion may be used. Carbon monoxide tends to increase when combustion is incomplete. Alternatively, complete combustion may be assumed, and a fuel-derived boiler efficiency may be calculated based on the flue gas temperature and a fuel gas parameter that correlates with the air supply rate (i.e. the concentration of carbon dioxide or the concentration of oxygen). The temperature of supply air and the water supply rate may be taken into account to improve accuracy of the fuel-derived efficiency.
  • Fuel supply rate, air supply rate and water supply rate may be used to determine a thermal power into the burner.
  • the thermal power input from the fuel has two components: the thermal power of the fuel itself, and the thermal power released from complete combustion.
  • the temperature difference between the supply air and the flue gas, together with the air supply rate, may be used to deduce the thermal power rejected from the burner into the flue.
  • the thermal power transferred to the boiler can therefore be calculated as the thermal power input to the boiler, less the thermal power rejected into the flue.
  • a model for flue-derived boiler efficiency may take into account heat transfer losses at the boiler - for example by specifying a thermal power loss at the boiler, which may be constant or a function of operating temperature of the boiler.
  • a model for flue-derived boiler efficiency may approximate or ignore one or more of the above parameters.
  • an operational burner state for operation of the boiler can be found and/or selected for use.
  • the methods described herein permit an efficient burner state of a boiler to be found based on dynamic operation and/or testing of the boiler, and for a burner state to be changed dynamically in response to changes in a demand state of the boiler in operation.
  • Calibration data may be generated at a first boiler having a particular configuration (e.g. a combination of burner type and boiler type), and used for selecting an efficient operational burner state for a second boiler having a like configuration (e.g. the same combination of burner type and boiler type).
  • Initial calibration testing to determine an operational burner state for a particular demand state e.g.

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  • General Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Regulation And Control Of Combustion (AREA)
  • Control Of Steam Boilers And Waste-Gas Boilers (AREA)

Claims (17)

  1. Procédé d'étalonnage d'une chaudière (12) comportant un brûleur (14) comprenant :
    la fourniture du combustible au brûleur (14) à un débit d'alimentation en combustible et la fourniture d'air de combustion au brûleur (14) à un débit d'alimentation en air, de sorte que le combustible soit brûlé à un rapport air/combustible ; et
    la fourniture d'eau au brûleur (14) à un débit d'alimentation en eau ;
    l'ajustement des variables de fonctionnement du brûleur, comprenant l'ajustement du rapport air-combustible et du débit d'alimentation en eau, pour définir une pluralité d'états du brûleur ;
    le test du fonctionnement de la chaudière (12) selon la pluralité d'états du brûleur ;
    pour chaque état du brûleur :
    la détermination d'un paramètre d'efficacité (352) relatif à un rendement de la chaudière (12) ;
    la surveillance des émissions dans un gaz de combustion en aval du brûleur (14) ;
    la comparaison des émissions à un ou plusieurs seuils d'émissions pour déterminer si elles sont excessives ou acceptables ;
    à partir d'un ensemble d'états du brûleur corrélés à des émissions acceptables, la sélection d'un état opérationnel du brûleur (4) afin d'optimiser le paramètre d'efficacité (352), pour le fonctionnement de la chaudière (12).
  2. Procédé selon la revendication 1, l'ajustement des variables de fonctionnement du brûleur (14) comprenant la réduction successive du rapport air/combustible tout en augmentant le débit d'alimentation en eau pour contrer une augmentation des émissions.
  3. Procédé selon l'une quelconque des revendications précédentes, comprenant en outre la détermination d'une pluralité d'états du brûleur qui se situent sur une frontière d'émissions dans un espace d'états du brûleur dans lequel le rapport air-combustible et le débit d'alimentation en eau sont des variables d'état, la frontière d'émissions correspondant au ou aux seuils d'émissions ; et l'état opérationnel du brûleur (4) étant sélectionné parmi la pluralité d'états du brûleur sur la frontière, éventuellement un ou plusieurs des états du brûleur sur la frontière d'émissions étant déterminés par calcul.
  4. Procédé selon n'importe quelle revendication précédente, le paramètre d'efficacité (352) étant un rendement de la chaudière (12) dérivée des fumées déterminée au moins en partie sur la base d'un niveau surveillé d'excès d'oxygène et/ou d'un niveau surveillé de monoxyde de carbone et/ou d'un niveau surveillé de dioxyde de carbone dans les fumées et/ou le paramètre d'efficacité (352) étant un rendement de transfert de chaleur de la chaudière (12) déterminée sur la base du transfert de chaleur vers un fluide de travail de la chaudière (12) par rapport à l'apport de chaleur vers le brûleur (14).
  5. Procédé selon l'une quelconque des revendications précédentes, les émissions étant comparées à un ou plusieurs des éléments suivants :
    un seuil d'oxydes d'azote (NOx) ;
    un seuil de monoxyde de carbone ;
    un seuil de dioxyde de carbone ; et
    un seuil d'oxydes de soufre (SOx).
  6. Procédé selon l'une quelconque des revendications précédentes, l'eau étant liquide telle qu'elle étant fournie au brûleur (14), l'eau se vaporisant pour se dilater et se mélanger de manière turbulente au niveau du brûleur (14).
  7. Procédé selon n'importe quelle revendication précédente, la chaudière (12) étant en service dans une installation industrielle, la chaudière (12) ayant un état de demande correspondant à une charge sur la chaudière (12), les variables de fonctionnement du brûleur (14) étant ajustées de manière itérative pour optimiser le paramètre d'efficacité (352),
    l'ajustement itératif facultatif des variables de fonctionnement du brûleur (14) comprenant :
    l'obtention d'une prédiction des émissions et/ou du paramètre d'efficacité (352) pour un premier état de brûleur de la pluralité, sur la base de données d'étalonnage (350) corrélant les émissions et/ou le paramètre d'efficacité (352) respectivement avec les variables du brûleur ;
    la détermination des données observées (560) pour les émissions et/ou le paramètre d'efficacité (352) ;
    la comparaison des données prédites et observées (560) pour déterminer une erreur de performance ;
    la définition d'un second état du brûleur (8) sur la base d'un modèle corrélant les émissions et/ou le rendement aux variables de fonctionnement du brûleur afin de compenser l'écart de performance.
  8. Procédé selon l'une quelconque des revendications précédentes, comprenant en outre le stockage de données d'étalonnage (350) pour chacun des états du brûleur auxquels le brûleur (14) est testé, les données d'étalonnage (350) comprenant :
    des données d'efficacité (354) comprenant le paramètre d'efficacité (352) ;
    des données d'état (354) comprenant :
    le débit d'alimentation en eau ;
    le rapport air/combustible ; et/ou le débit d'alimentation en combustible et le débit d'alimentation en air les données d'émission (354) relatives aux émissions dans les gaz de combustion.
  9. Procédé selon l'une quelconque des revendications précédentes, chacun des états de fonctionnement du brûleur correspondant au même état de demande de la chaudière (12).
  10. Procédé selon la revendication 9, comprenant en outre le stockage de données d'étalonnage (350) corrélées à l'état de demande, les données d'étalonnage (350) comprenant des données d'état (354) pour au moins l'état de fonctionnement du brûleur sélectionné, les données d'état (354) comprenant :
    le débit d'alimentation en eau ;
    le rapport air-combustible ; et/ou le débit d'alimentation en combustible et le débit d'alimentation en air ;
    et éventuellement l'étalonnage de la chaudière (12) à une pluralité d'états de demande.
  11. Procédé selon l'une quelconque des revendications 8 à 10, la chaudière (12) se trouvant dans une installation d'essai éloignée d'une installation industrielle, pour générer des données d'étalonnage (350) destinées à être utilisées dans une installation industrielle ou la chaudière (12) étant en service dans une installation industrielle, le procédé comprenant en outre :
    la détermination d'un état de demande de la chaudière (12) ;
    la sélection d'un état opérationnel du brûleur (4) à partir des données d'étalonnage (350) sur la base de l'état de la demande ; et
    le fonctionnement de la chaudière (12) à l'état opérationnel du brûleur (4).
  12. Procédé de fonctionnement d'une chaudière (12) comportant un brûleur (14), comprenant :
    la détermination d'un état de demande de la chaudière (12) ;
    la sélection d'un état opérationnel du brûleur (4) à partir de données d'étalonnage (350) générées par un procédé selon la revendication 10, sur la base de l'état de la demande ;
    le fonctionnement du brûleur (14) à l'état opérationnel du brûleur (4).
  13. Procédé de fonctionnement d'une chaudière (12) comportant un brûleur (14), comprenant :
    l'étalonnage de la chaudière (12) par un procédé conforme à l'une quelconque des revendications 1 à 12 ;
    la chaudière (12) étant étalonnée périodiquement et/ou en réponse à un stimulus choisi dans le groupe comprenant :
    une détermination d'émissions excessives dans un gaz de combustion de la chaudière (12) ;
    une détermination d'un changement dans les émissions, les niveaux d'oxygène ou de dioxyde de carbone dans les gaz de combustion dépassant un seuil respectif ;
    un changement dans l'état de la demande de la chaudière (12) .
  14. Dispositif de commande (50) de chaudière (12) configuré pour faire fonctionner une chaudière (12) par :
    la commande d'un débit d'alimentation en combustible d'un brûleur (14) de la chaudière (12) au niveau d'une vanne de combustible ;
    la commande d'un débit d'alimentation en air du brûleur (14) au niveau d'une vanne d'air ;
    la commande d'un débit d'alimentation en eau du brûleur (14) au niveau d'une vanne d'alimentation en eau ;
    la réception de données d'émissions (354) en provenance d'un analyseur d'émissions (21) de la chaudière (12) ;
    le dispositif de commande (50) étant configuré pour mettre en œuvre un procédé selon l'une quelconque des revendications précédentes.
  15. Installation de chaudière (10) comprenant :
    une chaudière (12) comportant un brûleur (14) ;
    un analyseur d'émissions (21) pour surveiller les émissions dans les gaz de combustion de la chaudière (12) ;
    une vanne de combustible pour commander l'alimentation en combustible du brûleur (14)
    une vanne d'air pour commander l'alimentation en air du brûleur (14)
    une vanne d'eau pour commander l'alimentation en eau du brûleur (14) ; et
    un dispositif de commande (50) de chaudière (12) selon la revendication 14.
  16. Programme informatique comprenant des instructions pour amener un dispositif de commande (50) de chaudière (12) ou une installation de chaudière (10) à mettre en œuvre un procédé selon l'une quelconque des revendications 1 à 11.
  17. Support non transitoire lisible par ordinateur stockant un programme informatique selon la revendication 16.
EP19749329.9A 2018-08-03 2019-08-01 Étalonnage d'une chaudière Active EP3830480B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB1812677.1A GB2576044B (en) 2018-08-03 2018-08-03 Calibration of a boiler
PCT/EP2019/070793 WO2020025758A1 (fr) 2018-08-03 2019-08-01 Étalonnage d'une chaudière

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EP3830480B1 true EP3830480B1 (fr) 2024-01-17

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GB2573135B (en) * 2018-04-25 2022-07-06 Crowcon Detection Instr Ltd A portable flue gas analyser
CN112859780B (zh) * 2021-01-07 2022-06-28 西安西热锅炉环保工程有限公司 一种基于云数据、云计算的火电厂智慧燃烧控制方法
CN113654080B (zh) * 2021-07-30 2024-04-16 新奥数能科技有限公司 燃气锅炉中燃烧器的开关机状态确定方法和装置

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US6289666B1 (en) * 1992-10-27 2001-09-18 Ginter Vast Corporation High efficiency low pollution hybrid Brayton cycle combustor
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GB2576044B (en) 2021-05-26
GB2576044A (en) 2020-02-05
EP3830480A1 (fr) 2021-06-09
GB201812677D0 (en) 2018-09-19

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