FR3108388A1 - Processes for optimizing the operation of a boiler, devices and corresponding boilers - Google Patents

Abstract

Method for optimizing the operation of a boiler, devices and corresponding boilers This method comprises steps consisting in: measuring the temperature values of flue gases resulting from combustion in the boiler, these measurements being carried out by at least one temperature sensor. temperature (32) installed in the boiler, said at least one sensor being associated with at least one area of interest to be monitored; - automatically construct, by means of a monitoring system (30) associated with the boiler (4), a history of the temperature values measured for the area of interest; - identify automatically, by the monitoring system and according to the history of the temperature values and of at least one predefined limit, the occurrence of a criticality condition of the area of interest. Figure for abstract: Figure 1

Description

Methods for optimizing the operation of a boiler, devices and corresponding boilers

The present invention relates to methods for optimizing the operation of a boiler, as well as corresponding devices and boilers.

The invention is particularly applicable to the field of boilers used in household waste incinerators, although this example is not limiting and this invention can be applied to other types of boiler using fouling fuels, such as biomass .

In combustion installations, such as industrial incinerators, in particular those intended to burn fuels containing a mineral fraction, such as household waste, it is common for the boilers to become clogged or to suffer damage over time, in particular by corrosion. , or incompatibility of materials with the generated temperature levels (refractory, steel, etc.). All this leads to a reduction:

• the energy performance of the boilers, this performance being characterized by the quantity of energy produced per mass of waste;
• their availability, characterized by the mass of waste that can be treated in a given period (for example one year);
• the lifetime of the installation, characterized by the number of years before replacement of the main equipment.

It is therefore necessary, in order to maintain the expected performance, to clean the boilers, in particular to clean the surfaces of their heat exchangers. It is also necessary to operate the boiler in operating ranges where the risk of corrosion is lower and/or where there is no thermal incompatibility between the temperature and the materials used.

The replacement of corroded or affected elements generates significant downtime and maintenance costs and cleaning operations typically require stopping the installation, which induces a loss of availability of the installation and can, under certain circumstances, generate a significant economic cost for the operator. In addition, restarting the installation after a complete shutdown is likely to generate significant mechanical stresses which can cause premature wear of certain components of the installation.

As far as cleaning is concerned, certain methods can certainly be implemented when the boiler is in operation, without it being necessary to completely shut down the installation or, possibly, reduce its load. However, these cleaning methods are generally discontinuous and energy-intensive, such as cleaning by steam sweeping, which results in a loss of performance between two cleanings or during cleaning and therefore their repeated use can have a negative impact on the efficiency and on the performance of the installation, or even cause wear or premature mechanical damage to certain components of the installation, which also entails an economic cost for the operator of the installation.

Certain operating conditions also generate on certain exchangers temperature levels favorable to the deposits of oxides or very corrosive or very sticky molten salts, the effects of which are either irreversible damage to the materials and exchange surfaces, or the attachment of deposits cannot be removed by the boiler cleaning systems in service. These operating conditions will therefore affect the availability and/or the life of the installation.

There is therefore a need for methods and devices making it possible to limit the fouling of boilers and to avoid the aforementioned problems.

According to one aspect, the invention relates to a method for optimizing the operation of a combustion installation comprising a boiler, in which the method comprises steps consisting of:

- measuring flue gas temperature values resulting from combustion in the boiler, these measurements being carried out by at least one temperature sensor installed in the boiler, said at least one sensor being associated with at least one zone of interest to be monitored ;

- automatically build, by means of a monitoring system associated with the boiler, a history of the temperature values measured for the area of interest;

- automatically identify, by the monitoring system and according to the history of the temperature values and at least one predefined limit, the occurrence of a condition of criticality of the zone of interest.

According to advantageous but not mandatory aspects, such a method may incorporate one or more of the following characteristics, taken in isolation or in any technically permissible combination:

- The method comprises, following the identification of the criticality condition, a step consisting in automatically activating a cleaning system integrated into the boiler to clean the zone of interest without interrupting the operation of the combustion installation and/or to control a reagent injection system and/or to modify the operating conditions of the boiler.

- The method comprises, following the identification of the criticality condition, a step consisting in sending an alert on a man-machine interface of a user terminal coupled to the monitoring system.

- A condition of criticality is identified if the temperature or a value representative of the temperature remains within a predefined interval for a duration greater than a predefined threshold duration, the predefined interval being defined from said temperature limit value.

- The temperature limit value is defined by the melting points of the ashes, and in particular by the melting points of the salts, oxides and possibly unburnt carbonaceous substances.

- Temperature sensors are installed immediately upstream and downstream of the area of interest, and in which the representative temperature value is a difference between the temperature values measured by the sensors placed upstream and downstream.

- The temperature sensors are pyrometers.

- The monitoring system is separate from a control-command system integrated into the combustion installation.

- Said predefined limit is determined beforehand by learning.

- The area of interest is a surface of a boiler heat exchanger.

According to another aspect, the invention relates to a combustion installation, comprising a boiler, a monitoring device and at least one temperature sensor installed in the boiler and associated with at least one zone of interest to be monitored, said installation being configured to implement steps consisting of:

- measuring flue gas temperature values resulting from combustion in the boiler, these measurements being carried out by said at least one temperature sensor;

- automatically build, by means of the monitoring system, a history of the temperature values measured for the area of interest;

- automatically identify, by the monitoring system and according to the history of the temperature values and at least one predefined limit, the occurrence of a condition of criticality of the zone of interest.

The invention will be better understood and other advantages thereof will appear more clearly in the light of the description which will follow of an embodiment of a method of operating a boiler, given solely by way of example and made with reference to the accompanying drawings, in which:

FIG. 1 is a schematic representation of a combustion installation comprising a boiler and an analysis device according to embodiments of the invention;

FIG. 2 is a block diagram of a portion of the boiler of FIG. 1, with which temperature sensors are associated;

FIG. 3 is a graph showing a history of temperature values measured by a temperature sensor;

FIG. 4 is a graph showing a history of a composite value calculated from temperature values measured by a temperature sensor;

FIG. 5 is a diagram showing the implementation of a method for controlling the installation of FIG. 1 according to one embodiment;

FIG. 6 is a diagram showing the implementation of a method for defining limits generating the occurrence of a criticality condition during the implementation of the method of FIG. 1.

Figure 1 shows an installation 2 designed to burn fuels, such as a household waste incinerator.

This example is not limiting and the invention can be used for other types of installations, in particular for any industrial installation comprising a boiler intended to burn a fuel.

In some embodiments, the installation 2 comprises a boiler 4 comprising a furnace 6 including a combustion chamber 8 equipped with burners 10 and supplied by a fuel inlet duct 12.

For example, the fuels burned are waste, in particular household waste.

The structure of the combustion chamber 8 is conventional and is not described in more detail. During the combustion of combustible materials, fumes escape from chamber 8 and circulate in the direction of heat exchangers described below and arranged downstream of chamber 8.

As illustrated in Figure 1, the part of the boiler 4 located downstream of the combustion chamber comprises a vault which overhangs the furnace 6, a first part bent with respect to the vault, a lower part 14 (or foot), then a second part which goes up parallel to the first part.

The boiler 6 also comprises a heat exchange circuit 16 comprising one or more heat exchangers 18 installed inside the boiler, preferably in the second part, so as to be in contact with the flue gases.

The second part ends with an outlet opening 20 through which the fumes come out of the boiler 4.

Downstream of outlet 20, smoke filtering and pollution control systems can be installed, allowing the smoke to be cleaned before it is discharged outside installation 2 through a chimney.

The particular shape of the part of the boiler 4 located downstream of the chamber 8 allows the flue gases to be channeled towards the exchangers 18 then towards the outlet 20.

Within the meaning of the present description, the terms "upstream" and "downstream" are for example defined according to the direction of circulation of the fumes resulting from combustion during normal operation of the installation 2.

In figure 1, the arrow F1 represents the flow of fuel supplied to the boiler 4. The arrows F2, F3 and F4 successively illustrate the path of the flue gases from the chamber 8 towards the outlet 20.

In a known way, the installation 2 comprises a control-command system 22, for example produced by electronic and/or electromechanical means, which allows the operator to control the installation 2.

For example, the control-command system 22 allows the operator to remotely operate elements of the installation 2 such as pumps, valves, injectors, burners, fans, fuel conveyors, and so on, depending on the operating conditions of the installation 2.

Preferably, the installation 2 also comprises one or more auxiliary cleaning systems 24, installed in the boiler 4, and which allow the boiler 4 to be cleaned locally while the installation 2 is in operation. In other words, the auxiliary cleaning system(s) 24 are integrated into the boiler 4.

For example, 24 cleaning systems can be configured to remove residues (such as ash containing mixtures of molten salts and oxides) deposited on internal boiler surfaces. These systems may be one or more of the following systems: steam or compressed air sweeping systems, or showers injecting water to locally create a thermal shock, or pneumatic hammers configured to generate a shock wave aimed to mechanically release residues deposited on surfaces, or blasting systems configured to inject metal balls capable of detaching residues deposited on the surface by micro-shock, or systems making it possible to inject and explode pockets of gas to locally peel off residues deposited on surfaces, or any possible combination of these systems.

The systems 24 can also include a system for injecting a reagent aimed at modifying upwards or downwards the melting temperatures of the mixtures of salts and oxides contained in the ashes to prevent the deposition and crystallization of these corrosive or sticky residues in critical areas of the boiler. An example of such injection systems is described in patent application FR-3053445-A1.

For example, the cleaning system(s) 24 are controlled by the control-command system 22.

In accordance with embodiments of the invention, the installation 2 also comprises a diagnostic system 30 comprising one or more temperature sensors 32 and an electronic control device 34 capable of using a telecommunications link 36 to exchange data with a remote computer server 38.

Preferably, the diagnostic system 30 is separate from the command and control system 22.

Each of the temperature sensors 32 is configured to measure, at a predetermined location inside the boiler 4, the temperature of the flue gases resulting from combustion.

The temperature sensors 32 are preferably placed at specific locations, in particular associated with surfaces liable to be clogged, such as the surfaces of the exchangers 18. Their position can be based on the thermal analysis of the boiler, feedback from experience on critical areas and/or by numerical calculations of the thermal profile of the boiler

Preferably, the temperature sensors 32 are pyrometers, such as infrared pyrometers, or monochromatic or bi-chromatic pyrometers.

In the example of Figure 1, five sensors 32 are illustrated: one located in the first part, and the other four located in the second part, being placed so that each pair of sensors frames one of the three exchangers 18.

It is understood, however, that this example is only given by way of illustration and that in practice, many other configurations can be adopted.

According to advantageous examples, the sensors 32 are placed so as to be able to measure the temperature immediately upstream and downstream of areas of interest, so as to then be able to calculate a temperature difference associated with such an area of interest, these areas of interest which may be surfaces liable to become clogged, such as the heat exchange surfaces of the exchangers 18.

According to examples, the control device 34 includes a processor (such as a microprocessor or a microcontroller) and a computer memory forming a computer-readable recording medium.

In one embodiment, the method of the invention is implemented by modules of executable code instructions stored in memory. The memory is, for example, an optical disc, a magneto-optical disc, a ROM memory, a RAM memory, a non-volatile memory (of EPROM technology, or EEPROM, or Flash, or NVRAM, or equivalent), or a card magnetic or optical or any other appropriate technology or combination of technologies.

Alternatively, said method is implemented by a programmable logic component such as an FPGA (Field Programmable Gate Array), or even by a specialized integrated circuit such as an ASIC (Application Specific Integrated Circuit).

In practice, the control device 34 is in communication with the sensors 32, for example by means of wired links, or a wireless link, such as a short-range radio link. The communication device 34 comprises for example a data acquisition interface.

According to examples, the telecommunications link 36 is a radio link, for example of the WiFi, or GSM, or LTE, or similar type, or a link using a local area network (LAN) or an Internet network.

The remote server 38 can be a computer server comprising a processor and one or more memories. The processor can for example be programmed to implement predefined processing on measurement data (measured by the sensors 32) received from the control device 34 and/or to store measurement data received from the control device 34.

The system 30 can also comprise a client terminal, such as a computer or a mobile communication device, for example a mobile phone or a tablet, this client terminal comprising a screen capable of displaying information by means of a human interface machine. The client terminal can be in communication with the remote server 38 and/or with the control device 32.

Generally, the system 30 is configured to implement steps consisting of:

- measure, repeatedly or continuously, temperature values of fumes resulting from combustion in the boiler 4, these measurements being carried out by at least one of the temperature sensors 32 installed in the boiler 4, said at least one sensor being associated at least one area of interest to be monitored;

- automatically constructing, by means of the monitoring system 30, a history of the temperature values measured for the zone of interest;

- automatically identify, by the monitoring system 30 and according to the history of the temperature values and at least one predefined limit, the occurrence of a condition of criticality of the zone of interest.

In what follows, by “condition of criticality”, or “critical condition”, is meant a critical condition likely to damage the zone of interest, such as a condition conducive to fouling or corrosion of the zone. of interest.

For example, such a condition is reached when the temperature prevailing at surface level, or at a location of the boiler, exceeds a predefined temperature limit, this overshoot being likely to lead to damage to the zone of interest. .

According to examples, following the identification of the criticality condition, the system 30 can automatically activate the cleaning system 24 to clean the area of interest without interrupting the operation of the installation 2.

The actuation of the cleaning system 24 can be controlled by the system 30 via the command control system 22.

Preferably, the intensity of the cleaning carried out by the cleaning system 24 (such as the quantity of liquid or material injected, or the intensity of a mechanical action) can be dosed automatically by the system 30, according to the degree fouling identified.

As a variant, following the identification of the criticality condition, the system 30 can send an alert to a man-machine interface of the user terminal, for example so that an operator manually activates the cleaning system 24.

In embodiments, a condition of criticality is identified if the temperature or a value representative of the temperature remains within a predefined interval, also called "critical zone", for a duration greater than a predefined threshold duration, the predefined interval being defined from said temperature limit value. One or more temperature limit values can thus be defined for each critical zone. The temperature limit value(s) can be stored in the memory of the device 32 and/or of the server 38.

In general, the steps aimed at building the history and identifying the criticality condition can be implemented by the control device 34 and/or by the server 38.

In practice, the predefined temperature limit can be determined beforehand by a learning process, or by calibration. Such a process typically involves knowing one or more of the following information:

• the gas temperatures, measured continuously,
• the skin temperatures of the exchangers, known by calculation and
• the physico-chemical properties of the ashes deposited on the surfaces (the areas of interest to be monitored) to identify in particular the melting temperatures of the mixtures of salts and oxides contained in the ashes,

so as to establish a link between the nature and the quantity of the material deposited on the surface, the nature of the fuel (garbage, biomass, etc.) and the effective temperature of the fumes circulating in the said zone.

These melting temperatures and therefore the limit temperature value(s) can typically be determined in the laboratory by differential thermal analyzes and/or by thermogravimetic analyzes carried out on the basis of representative samples of ashes and deposits taken from the installation.

The temperature limit value(s) can be advantageously defined to avoid operating certain exchangers at temperatures close to the critical ash melting temperatures.

Preferably, these exchangers are then operated:

• either by operating them voluntarily at higher or lower temperatures, thanks to the cleaning actions on the upstream exchangers, or by adapting the nature and/or the frequencies of cleaning of the device 24 of the said exchanger, or by modifying the operating conditions of the boiler ( load and excess combustion air) which will modify the thermal profile in the boiler;
• or, when it is not possible to modify the operating temperatures of the exchangers, to prevent the deposition and crystallization of these residues by modifying their melting temperatures of the ashes (molten salts and/or oxides), by means of a reagent injection system.

This type of analysis, in addition to providing information on the melting points of the ashes (salts and oxides), can also provide information on the formation of unburnt matter and their nature. Indeed, this makes it possible to determine whether it is unburnt from carbonaceous unburnt, in particular long carbon chains formed at low thermal decomposition temperature, or unburnt from pyrolysis carbon formed at higher decomposition temperature. thermal.

This analysis can therefore, coupled with the temperatures recorded in the combustion zone, also give operating limits concerning combustion and in particular the air ratios recommended for optimal combustion.

In embodiments, when temperature sensors 32 are installed immediately upstream and downstream of the area of interest, the representative temperature value can be a difference between the temperature values measured by the sensors placed upstream and downstream.

According to variants, the representative temperature value can be a statistical quantity calculated from the history of the measured temperature values, such as an average, in particular a moving average, or a median, or a temperature distribution (for example , one or more percentages of a maximum or minimum value, or a quartile or decile value), or any appropriate quantity depending on the nature of the surface to be monitored.

For example, a history of the representative temperature value can be constructed and stored as a function of the measured temperature values.

The history can be built in real time, for example over several hours or days, or even longer, as the temperature values measured by the sensors 32 are received.

Thanks to the invention, it is possible to detect abnormal fouling of certain zones inside the boiler, in particular the surfaces of heat exchangers, and thus to intervene locally to clean the zone or zones concerned before they do not become clogged to the point of altering the operation of the installation 2 and of having to operate a cleaning process likely to reduce the performance of the installation.

Advantageously, this makes it possible to actuate the cleaning system 24 so as not to clean more than necessary, in particular so as not to clean surfaces which do not need to be cleaned.

In another example, the invention makes it possible to optimize the mode of operation of the cleaning system 24 and/or the operating conditions of the boiler so as to adjust the operating temperatures of the exchangers to prevent them from operating durably in a critical zone where the accumulation of ash and/or the increased risk of corrosion is proven by the analyzes carried out. It can also control the device for injecting a reagent modifying the critical temperatures as indicated above.

For example, if the cleaning system 24 comprises elements that can be actuated independently of each other to act independently on different zones of the boiler, then only the element or elements which have an effect on the surface to be cleaned are actuated, the other elements not not being actuated.

Ultimately, System 30 provides more accurate and customizable monitoring and preventative cleaning than when only facility-specific control systems are used.

Advantageously, other anomalies can be detected, such as a malfunction of a sensor 32, or a measurement error. Appropriate corrective actions can then be taken.

According to embodiments, the monitoring system 30 is separate from the control-command system integrated into the installation 2.

In practice, the control-command system 22 is generally incorporated into the installation 2 and cannot always be modified or altered by the operator, in order to guarantee its integrity and reliability.

Using a separate system 30 to collect temperature data makes it possible to overcome technical and regulatory limitations that are imposed on the control-command system 22.

FIG. 2 represents an example of a synoptic table 40 showing temperature values measured by temperature sensors 32 associated with a portion 41 of boiler 4.

The indicators associated with the temperature sensors 32 and displaying the corresponding measured values here bear the references 42-1, 42-2, 42-3, 42-4, 42-5, 42-6 and 42-7.

In addition, the temperature differences between two consecutive temperature sensors 32 (nearest neighbors to each other) can be displayed. The indicators displaying these temperature differences here bear the references 44-1, 44-2, 44-3, 44-4, 44-5 and 44-6.

Such a synoptic table can be displayed on the screen or on the man-machine interface of the client terminal.

FIG. 3 represents a graph 50 illustrating a portion of a history of temperature values measured by a sensor 32 over time, highlighting fluctuations in the temperature measured over time.

On this graph 50, given for illustrative purposes only, the temperatures are indicated on the ordinate axis and expressed in degrees Celsius, and the abscissa axis indicates the time, expressed in twelve hour increments.

The central curve 52 corresponds to an average value (moving average) of the temperatures over time. The upper and lower curves correspond, respectively, to the minimum value and to the maximum temperature value.

Threshold 54 corresponds to a predefined temperature limit. In this example, it is considered that there is an abnormal situation for the sensor 32 from which the measurements come when the average temperature (curve 52) remains below the limit value 54 for a duration greater than a predefined duration threshold (for example, one hour, this example not being limiting).

FIG. 4 represents a graph 60 illustrating a portion of a history of values of a temperature difference between the values of the temperatures measured by two sensors 32 over time.

On this graph 50, given for illustrative purposes only, temperatures are shown on the y-axis and expressed in degrees Celsius, and the x-axis shows time, expressed in arbitrary units (e.g. days) .

The central curve 62 corresponds to the temperature difference over time. Curve 64 corresponds to an average value of the temperature difference over time.

Threshold 66 corresponds to a predefined temperature limit. In this example, it is considered that there is an abnormal situation for the zone associated with the sensors 32 from which the temperature difference is calculated when the average temperature difference (curve 64) remains below the limit value 66 for a duration greater than a predefined duration threshold (for example, one hour, this example not being limiting).

FIG. 5 represents an example of implementation of a method of operation of the system 30.

The method begins at step 100, for example with the commissioning of the system 30 after the installation 2 has started.

During step 102, the sensors 32 measure the temperature of the fumes, for example at regular intervals and/or continuously, with a predefined measurement period.

During step 104, the data measured by the sensors 32 are collected by the unit 34 and, for example, are sent automatically to the server 38 via the link 36.

During step 106, the server 38 automatically calculates the temperature history, for each sensor, and/or calculates one or more statistical magnitudes representative of the collected temperatures.

Steps 102, 104 and 106 can be repeated over time and carried out continuously during the course of the process, for example as long as the installation 2 is running.

During step 108, the monitoring system automatically identifies, as a function of the history of the temperature values and/or of the history of the calculated statistical magnitude(s) and of at least one predefined limit, the occurrence of a critical condition of the area of interest.

FIG. 6 illustrates steps 200, 201 and 202 which are carried out in parallel with steps 100 to 108 and which consist in defining, or updating, the predefined limits generating the occurrence of a critical condition necessary for the triggering of the step 110.

Step 200 consists in defining the temperature limits imposed by the design of the boiler and the exchangers (limits of the mechanical and thermal characteristics of the materials according to the operating temperatures, identification of the zones at risk of corrosion according to the temperatures of the gases) .

Step 201 consists in restricting these temperature limits on the basis of the operating experience of the boiler and the histories carried out.

Step 202 consists in adapting these temperature limits according to the analyzes carried out on the physico-chemical properties of the ashes actually sampled on site and in particular their melting points. These limits can be reviewed by periodic analyzes of the deposits, for example during the annual or biannual shutdowns of the units.

According to examples, the steps 200, 201 and 202 are implemented by the control device 34 and/or by the remote server 38. The values of the temperature limits thus defined are stored in the memory of the control device 34 and/or in memory of the remote server 38.

During step 110, if a critical condition has been identified during step 108, then the system 30 automatically activates the cleaning system 24 (potentially including the reagent injection system) and/or sends an alert detailed on a man-machine interface of the user terminal, for example by using the link 36. This alert can either be managed by the operator himself if the latter has the competence or shared with an expert service provider in the field of corrosion and fouling of boilers to draw up an action plan within timeframes compatible with the speed of the observed phenomenon. The alert can also propose a change in the operating conditions of the boiler.

According to embodiments, if a critical condition has been identified during step 108, then the system 30 can control the reagent injection system and/or modify the operating conditions of the boiler, this in parallel or at the place of actuation of the cleaning system 24.

In general, the actions of the system 24 and/or the alerts generated are programmed beforehand in step 110 to optimize the operation of the boiler outside the critical zones and/or its cleaning and thus define an optimal level of efficiency, capacity and boiler life

This method given by way of example is not limiting and other steps can be implemented. Some of the steps described can be carried out in a different order, or even be modified, or even be omitted.

Any feature of one of the embodiments or variants described above can be implemented in the other embodiments and variants described.

Claims (11)

Method for optimizing the operation of a combustion plant (2) comprising a boiler (4), in which the method comprises steps consisting of:
- measuring (102) flue gas temperature values resulting from combustion in the boiler, these measurements being carried out by at least one temperature sensor (32) installed in the boiler, said at least one sensor being associated with at least one area of interest to monitor;
- building (104) automatically, by means of a monitoring system (30) associated with the boiler (4), a history of the temperature values measured for the zone of interest;
- identifying (108) automatically, by the monitoring system and according to the history of the temperature values and of at least one predefined limit, the occurrence of a condition of criticality of the zone of interest. A method according to claim 1, wherein the method includes, following identification of the criticality condition, a step (110) of automatically activating a cleaning system (24) integrated with the boiler to clean the area of interest without interrupting the operation of the combustion installation and/or controlling a reagent injection system (24) and/or modifying the operating conditions of the boiler. Method according to claim 1 or claim 2, in which the method comprises, following the identification of the criticality condition, a step consisting in sending an alert (110) on a man-machine interface of a user terminal coupled to the system monitoring. A method as claimed in any preceding claim, wherein a criticality condition is identified (108) if the temperature or a value representative of the temperature remains within a predefined interval for a time longer than a predefined threshold time, the interval predefined being defined from said temperature limit value. Process according to one of the preceding claims, in which the temperature limit value is defined by the melting points of the ashes (202), and in particular by the melting points of the salts, oxides and possibly unburnt carbonaceous substances. A method according to claim 4, wherein temperature sensors (32) are installed immediately upstream and downstream of the area of interest, and wherein the temperature representative value is a difference between the temperature values measured by the sensors placed upstream and downstream. A method according to any preceding claim, wherein the temperature sensors (32) are pyrometers. Method according to any one of the preceding claims, in which the monitoring system (30) is separate from a control-command system (22) integrated into the combustion installation. A method according to any preceding claim, wherein said predefined limit is determined beforehand by learning. A method according to any preceding claim, wherein the area of interest (18) is a surface of a boiler heat exchanger (16). Combustion installation (2), comprising a boiler (4), a monitoring device (30) and at least one temperature sensor (32) installed in the boiler and associated with at least one zone of interest to be monitored (18) , said installation being configured to implement steps consisting of:
- measuring (102) flue gas temperature values resulting from combustion in the boiler, these measurements being carried out by said at least one temperature sensor;
- building (106) automatically, by means of the monitoring system, a history of the temperature values measured for the area of interest;
- identifying (108) automatically, by the monitoring system and according to the history of the temperature values and of at least one predefined limit, the occurrence of a condition of criticality of the zone of interest.