FR3104683A1 - Method of regulating a combustion installation, as well as the corresponding combustion installation - Google Patents

Abstract

Method of regulating a combustion plant, as well as corresponding combustion plant In this control process, solid fuels (C) are introduced into a combustion chamber (10) of a combustion plant, air primary (P) is introduced into a lower part (10A) of the combustion chamber to carry out primary combustion of solid fuels there, and secondary air (S) is introduced into an upper part (10B) of the combustion chamber. combustion to perform secondary combustion of gas (G) from the primary combustion. In order to control the secondary combustion carried out in this installation, the temperature of the secondary combustion is measured in the upper part of the combustion chamber by one or more optical pyrometers (60.1 to 60.5) which are arranged laterally to the combustion chamber, and the flow of the secondary air is controlled according to the measurements of the pyrometer (s). Figure for abstract: Figure 1

Description

Method for controlling a combustion plant, as well as corresponding combustion plant

The present invention relates to a method for regulating a combustion installation. It also relates to a combustion installation.

The invention relates in particular to combustion installations integrated into a boiler which transfers the heat given off by combustion to a heat transfer fluid, generally water.

Whatever the field of application of the invention, the combustion plants concerned use, as fuel, household or industrial waste, hazardous waste, biomass or similar solid materials, which, more generally, corresponds to solid fuels, in particular inhomogeneous in time and space. Thus, the solid fuels considered here typically form a flow of matter, the exact composition of which is both inhomogeneous at a given instant and liable to vary over time.

In such combustion installations, the solid fuels are introduced into a combustion chamber in order to undergo therein a combustion, called primary combustion, in the presence of air called primary air, this primary combustion leading to the fact that, on the one hand, the the non-volatile part of the solid fuels is entirely burned, except for particulate unburned matter, and, on the other hand, the volatile part of the solid fuels, released during the heating of the latter and the combustion of their non-volatile part, is partially burned. This primary combustion is carried out in a lower part of the combustion chamber and can in particular be carried out on a grid, which delimits the combustion chamber downwards and on which the solid fuels are loaded to undergo the primary combustion there, while the he primary air is admitted under the grid before crossing the latter to enter the combustion chamber and thus reach the solid fuels. So that the volatile part of the solid fuels is entirely burned according to a so-called secondary combustion, air called secondary air, consisting of air and/or recirculated fumes, is admitted into the combustion chamber, being injected into the part top of the combustion chamber by nozzles, above the grid, in one or more levels.

In practice, the secondary air is generally injected from two opposite walls of the combustion chamber. These two opposite walls can be the front and rear walls of the combustion chamber, i.e. the walls through which, respectively, the solid fuels enter the combustion chamber and the solid combustion residues leave the chamber. burning. The two opposite walls can also be left and right side walls of the combustion chamber, that is to say the walls located on either side of the grid, along the perpendicular to a direction of advance of the fuels solids in the combustion chamber from the rear wall to the front wall. In waste combustion plants, secondary air is usually injected from the front and rear walls of the combustion chamber. In biomass combustion plants, the injection of secondary air can be provided from the side walls of the combustion chamber.

Solid fuels of the waste or biomass type are characterized by high heterogeneity both in size of the solid fragments composing them, and in composition and humidity. This strong heterogeneity leads, at the same time, to a strong disparity, in time and in space, for the physico-chemical properties of combustion relating to these solid fuels, such as their calorific value, their stoichiometric air requirement, their kinetics combustion, etc., and, as a result, a strong disparity in the composition and distribution of the gases resulting from primary combustion. Thus, in the upper part of the combustion chamber where the secondary air is injected, there is a strong variation, in time and in space, of the temperature and the contents of water, carbon monoxide, carbon dioxide , nitrogen oxides and other volatile compounds from the gases resulting from primary combustion. However, unlike the primary combustion of solid fuels, which lasts several tens of minutes, secondary combustion, carried out in the gaseous phase, is rapid, namely a few tenths of a second, because it is linked to the combustion rate of volatile materials and their residence time in the combustion chamber, generally less than two seconds. In order to limit unburnt matter, combustion is then often carried out with a large excess of air compared to the stoichiometric requirement, this excess air being all the greater as the heterogeneity of the solid fuels is significant. In particular, secondary air is admitted into the combustion chamber in substantial quantities in order to "push" the secondary combustion, which leads to many disadvantages:

-By increasing the secondary air intake, the flow rate of the fumes leaving the combustion installation is increased, which requires the combustion installation to be sized accordingly and, where applicable, the entire boiler, as well as the flue gas treatment downstream of the boiler. In particular, the air present in the secondary air in excess beyond the needs necessary for secondary combustion generates a higher volume of fumes and therefore requires a larger size for the combustion chamber in order to maintain the residence time. necessary for secondary combustion. Similarly, the recirculated fumes, present in the secondary air, increase the volume of fumes, without supplying oxygen for the secondary combustion, and therefore increase the size of the combustion chamber. In any case, the increase in secondary air intake leads to an increase in electrical consumption for the secondary air supply fans and the draft fans. In addition, the admission of secondary air tends to reduce the residence time in the combustion chamber, which, on the one hand, is unfavorable to the reduction of nitrogen oxides by compounds, such as ammonia or urea, injected into the combustion chamber and, on the other hand, delays the vitrification of molten oxides, leading to fouling downstream of the combustion chamber, in particular in the boiler exchangers.

-Once admitted in excess in the combustion chamber, the secondary air will, in the absence of means of controlling its distribution in the chamber, be distributed in an uncontrolled manner, due to turbulence, recirculation, appearance of dead zones, etc. This uncontrolled distribution of the secondary air leads to poor distribution of speeds and temperatures in the upper part of the combustion chamber, resulting in a loss of "effective volume". In particular, this poor distribution leads to a loss of thermal efficiency in "too cold" regions of the combustion chamber, an accumulation of ash in "too low speed" regions, an increased risk of erosion in "too low" regions. at too high a speed”, a risk of oxide melting and the formation of sticky ashes in “too hot” regions, etc. The combustion chamber and downstream equipment must then incorporate surface protections against corrosion and erosion at high temperature, which are more extensive and more resistant.

- The formation of carbon monoxide is favored by poor distribution of secondary air in the combustion chamber, either due to excess air at low temperature, or by a local lack of oxygen. This problem is also particularly sensitive for the combustion of biomass for which the secondary air intake is generally carried out by the left and right side walls of the combustion chamber, due to the great variability, depending on the direction of advancement of solid fuels, gas flows from primary combustion.

Faced with these difficulties, several techniques have been developed so far.

One of these techniques consists in regulating the total secondary air flow according to the oxygen content in the fumes from the combustion installation. In practice, the measurement of this oxygen content is carried out in the "cold" flue gases, typically at the boiler outlet, to ensure the resistance of the measurement sensor over time. Taking into account, on the one hand, the distance between the combustion chamber and the "cold" zone where the measurement sensor is located and, on the other hand, the response time of this measurement sensor which is at least five seconds, the measurement of the oxygen content has a reaction time greater than half a minute, which significantly limits the regulation performance for the admission of the secondary air since the kinetics of the secondary combustion is much faster , as explained above. Moreover, this measurement of the oxygen content does not reflect the inhomogeneity of the gas distribution in the upper part of the combustion chamber. In addition, the measurement of the oxygen content in wet flue gases is affected by the dilution induced by the water vapor present in the flue gases, which depends on the humidity and the hydrogen content of the solid fuels. To circumvent this difficulty, the oxygen content can be measured on “dry” smoke, which requires taking and drying smoke samples before measuring the oxygen content. The reaction time is then extended to allow the implementation of this sampling and this drying, typically of the order of twenty to forty additional seconds.

Other techniques plan to regulate the total secondary air flow either as a function of the temperature at the outlet of the combustion chamber, typically measured by a thermocouple, or as a function of the solid fuel inlet flow, or by function of the steam production rate at the boiler outlet. In all cases, the regulation has a response time that is far too long compared to the kinetics of the secondary combustion and does not make it possible to manage the inhomogeneity of the gas distribution in the upper part of the combustion chamber.

Another technique, which can be combined with the previous ones, consists of dividing the secondary air intake into several levels of the combustion chamber and individually controlling the air flow at each level by means of flow adjustment devices. The adjustment devices thus make it possible to distribute the total secondary air flow between the different secondary air intake levels. This distribution is defined by a law determined when the installation is started up. It is either a constant percentage for each level, or a variable percentage depending on a single parameter, such as the solid fuel inlet flow rate, or the sum of the main and of secondary air sent to the combustion chamber.

All the techniques mentioned so far do not therefore make it possible to take into consideration the heterogeneity of the characteristics of the gases resulting from primary combustion. The performance of these different techniques is therefore limited in terms of their possibility of controlling or improving the homogeneity of the thermal profile in the upper part of the combustion chamber.

The object of the present invention is to propose an improved regulation of a solid fuel combustion installation, in order to control the secondary combustion carried out in this installation.

To this end, the subject of the invention is a process for regulating a combustion installation, in which solid fuels are introduced into a combustion chamber, in which primary air is introduced into a lower part of the chamber combustion chamber to effect primary combustion of solid fuels therein, and in which secondary air is introduced, with a flow rate of secondary air, into an upper part of the combustion chamber to effect secondary combustion therein of gases resulting from primary combustion. According to the invention, the secondary combustion has a temperature which is measured in the upper part of the combustion chamber by one or more optical pyrometers which are arranged laterally to the combustion chamber, and in that the secondary air flow is controlled according to the measurements of the pyrometer(s).

The invention also relates to a combustion installation, comprising a combustion chamber adapted so that solid fuels are introduced therein, a primary air intake device adapted to supply with primary air a lower part of the combustion chamber for performing primary combustion of solid fuels therein, and a secondary air intake device suitable for supplying with secondary air, according to a secondary air flow rate, an upper part of the combustion chamber for carry out a secondary combustion there of gases resulting from the primary combustion. According to the invention, this combustion installation further comprises one or more optical pyrometers, which are arranged laterally to the combustion chamber and which are suitable for measuring a temperature of the secondary combustion in the upper part of the combustion chamber, as well regulation means suitable for, from the measurements of the pyrometer or pyrometers, controlling the flow rate of secondary air from the secondary air intake device.

One of the ideas underlying the invention is to use one or more optical pyrometers, which, by definition, provide temperature measurements based on the intensity of the wavelengths emitted by a radiating body. These pyrometers are arranged laterally to the combustion chamber so as to measure a temperature of the secondary combustion, by carrying out their measurement as close as possible to the gases resulting from the primary combustion while the latter are burning in the presence of air. secondary, in order to know the intensity of the radiation of the secondary combustion. The measurements provided by the or each pyrometer are representative, in real time, of the temperature of the secondary combustion, in the sense that these measurements are instantaneous and integrate the thermal conditions on the optical path between the pyrometer and the mixture between the air secondary and the gases resulting from the primary combustion, in particular without being affected by fouling or by wall effects. The temperature thus measured by this or these pyrometers can be qualified as the radiative temperature of the secondary combustion.

The invention also provides for using this radiative temperature to control the flow of secondary air and, advantageously, the distribution of this flow of secondary air in the upper part of the combustion chamber. Indeed, without wishing to be bound by a theory, the inventors have established that this radiative temperature is an indicator close to the adiabatic temperature of the secondary combustion, that is to say the theoretical temperature for the secondary combustion to be complete. , in the sense that, like the adiabatic temperature, the radiative temperature of the secondary combustion is very sensitive to both the amount of air consumed by the secondary combustion and the amount of gas burned during the secondary combustion. Thus, for a given zone of the upper part of the combustion chamber, pointed by the or one of the pyrometers, the temperature measured by this pyrometer is an excellent indicator of the ratio between the quantity of gas actually burned and the air flow actually consumed in the area under consideration. Thanks to the invention, the secondary air flow admitted into the combustion chamber is regulated according to the temperature measurements provided by the pyrometer(s), in particular by comparison with a temperature setpoint, as explained in more detail below. . Advantageously, the invention provides for measuring the temperature of the secondary combustion in several zones of the upper part of the combustion chamber, distributed between the front and the rear of the combustion chamber, by respective pyrometers, and adjust the secondary airflow zone by zone. In all cases, the invention makes it possible to control in real time the admission of secondary air into the combustion chamber so as to provide, advantageously zone by zone, the quantity of secondary air necessary and sufficient for combustion secondary is complete, in other words so as to optimize, advantageously zone by zone, the ratio between the secondary air admitted and the quantity of gas burned. This control of secondary combustion, permitted by the invention, has many advantages, as detailed below.

It will be noted that the invention is applicable to combustion installations in the combustion chamber of which the solid fuels form either a circulating fluidized bed, or a mobile bed on a grate, this second case being explained in more detail below.

According to advantageous additional characteristics of the control method and of the combustion installation in accordance with the invention, taken in isolation or in all technically possible combinations:

- The combustion chamber is delimited downwards by a grate on which the solid fuels form a bed which is movable in a direction of advance in the lower part of the combustion chamber, the primary air being admitted under the front grate to cross the grate to enter the lower part of the combustion chamber and reach the bed of solid fuels, in which the upper part of the combustion chamber is divided into several zones, preferably at least three zones, which follow one another according to the direction of advance, each zone being associated with at least one of the pyrometers so that, for each zone, the pyrometer(s) associated with the zone measure the temperature of the secondary combustion in this zone; the secondary air is admitted into the upper part of the combustion chamber by being distributed in air jets, which are introduced below the pyrometers, by being respectively projected by nozzles arranged laterally to the combustion chamber, and which, at the level of the pyrometers, flow upwards in at least one of said zones; each jet of air is projected by the corresponding nozzle with a flow rate which is controlled according to the measurements of the pyrometer(s) associated with that or those of the said zones in which this jet of air flows.

-Each air jet mainly flows in only one of said zones, and each of said zones is associated with at least one of the air jets, which flows in this zone.

-The nozzles are distributed between several stages which are respectively located at different levels, the nozzles of each stage being located substantially in the same geometric plane which is parallel to the grid.

-The combustion chamber is delimited by a rear wall and a front wall, which are opposite to each other in the direction of advance, and the nozzles are distributed between rear nozzles, which are arranged on the rear wall , being distributed along a horizontal direction perpendicular to the direction of travel, and front nozzles, which are arranged on the front wall, being distributed along said horizontal direction.

-The combustion chamber is delimited by left and right side walls, which are opposed to each other in a horizontal direction perpendicular to the direction of advance, and the nozzles are distributed between left nozzles, which are arranged on the left side wall, being distributed along the direction of travel, and right nozzles, which are arranged on the right side wall, being distributed along the direction of travel.

-The pyrometer(s) are separated by between one and four meters from the highest introduction of the air jets.

-All the nozzles are supplied with secondary air from a common inlet, and the flow rate of each air jet is controlled by a flow control device, which is provided on a pipe connecting the common inlet and the nozzle projecting this jet of air, and/or a flow section adjustment member, which is integrated into the nozzle projecting this jet of air.

-To measure the temperature of the secondary combustion, the or each pyrometer emits, in the upper part of the combustion chamber, at least one bichromatic laser beam and/or two laser beams which intersect substantially in the plane of a wall of the combustion chamber, on which the pyrometer is arranged.

-The combustion installation further comprises a grid which delimits the combustion chamber downwards, which is adapted to support a bed which is formed by the solid fuels and which is movable in a direction of advance in the lower part of the combustion chamber, and under which the primary air intake device opens out so that the primary air supplied by this primary air intake device enters the lower part of the combustion chamber by crossing the grille ; the upper part of the combustion chamber is divided into several zones, preferably at least three zones, which follow one another in the direction of advance, each zone being associated with at least one of the pyrometers so that, for each zone, the or the pyrometers associated with the zone measure the temperature of the secondary combustion in this zone, in which the secondary air intake device is adapted to distribute the secondary air into air jets, which are introduced below pyrometers, being respectively projected by nozzles arranged laterally to the combustion chamber, and which, at the level of the pyrometers, flow upwards in at least one of said zones, and in which the regulation means are adapted to control the flow rate with which each of the air jets is projected by the corresponding nozzle, based on the measurements of the pyrometer(s) associated with that or those of said zones in which this air jet or jets flows.

The invention will be better understood on reading the following description, given solely by way of example and made with reference to the drawings in which:

Figure 1 is a diagram of a combustion plant according to the invention;

Figure 2 is a partial schematic section along line II-II of Figure 1;

FIG. 3 is a diagram of the circled detail III in FIG. 1, illustrating an alternative embodiment of the combustion installation;

FIG. 4 is a view similar to FIG. 1, illustrating a second embodiment of a combustion installation according to the invention; And

Figure 5 is a schematic section along line VV of Figure 4.

In Figure 1 is shown a combustion plant 1 suitable for burning solid fuels C.

Solid fuels C are in particular household or industrial waste, hazardous waste, biomass, or similar solid materials, that is to say, more generally, solids exhibiting heterogeneity in size, composition and/or humidity, as mentioned in the introductory part of this document.

Combustion installation 1 typically belongs to a boiler which makes it possible to produce steam by using the heat of the fumes from the combustion installation.

The combustion installation 1 comprises a combustion chamber 10 adapted so that the solid fuels C are introduced therein and burn, in a lower part 10A of the combustion chamber, according to a primary combustion in the presence of air, called primary air P The combustion chamber 10 is designed so that, once the solid fuels C are loaded therein, these solid fuels C stay in the lower part 10A for a time necessary, typically several minutes, to carry out the primary combustion. During their primary combustion, the solid fuels C generate, in the lower part 10A of the combustion chamber 10, gases G. The combustion chamber 10 is also designed to burn, in an upper part 10B of the combustion chamber, the gases G according to a secondary combustion in the presence of air, called secondary air S, consisting of air and/or recirculated fumes.

The primary air P is admitted into the lower part 10A of the combustion chamber 10 so as to supply the primary combustion, resulting in that, in this lower part 10A of the combustion chamber, on the one hand, the part not volatile of the solid fuels C is entirely burned, except for the particulate unburnt fluidized in the gases G, and, on the other hand, the volatile part of the solid fuels, released during the heating of the latter and during the combustion of their non-volatile part , is partially burned, forming the gases G. The secondary air S is admitted into the upper part 10B of the combustion chamber 10 so as to supply the secondary combustion, resulting in that, in this upper part 10B of the chamber combustion, the gases G mix with the secondary air S, forming a mixture GS, and burn giving off fumes F. The combustion chamber 10 is designed to channel the fumes F to their exit from the combustion chamber. combustion from which these fumes escape to circulate in boiler equipment, such as heat exchangers.

The combustion chamber 10 is delimited laterally by a rear wall 11, by a front wall 12 and by two side walls 13. The solid fuels C are loaded inside the combustion chamber 10 through the rear wall 11, through an external chute 20. The solid fuels C, once burned, leave the combustion chamber 10 through the front wall 12, via an outlet 21. The side walls 13 are horizontally spaced from each other and each connect the rear 11 and front 12 walls, only one of these two side walls 13 being visible in Figure 1.

In the embodiment considered here, the combustion chamber 10 comprises a grid 14 which delimits the bottom of the combustion chamber. This grid 14 is designed to support the solid fuels C inside the combustion chamber 10 so that, as illustrated in FIG. 1, these solid fuels form a bed which is located in the lower part 10A of the combustion chamber. combustion and which rest on the grate 14, extending from the rear wall 11 to the front wall 12. At the level of the rear wall 11, the bed is fed by the external chute 20 while, at the level of the front wall 12, the bed falls into the evacuation 21. Between the rear 11 and front 12 walls, the bed of solid fuels C is movable in a direction of advancement Z in the lower part 10A of the combustion chamber 10. Thus, the direction of advancement Z extends from the rear wall 11 to the front wall 12, while being parallel to the grid 14. In practice, the grid 14 can just as well be inclined with respect to a horizontal plane, as in the figure 1, that extend in a horizontal plane. In all cases, the grid 14 has two side edges, which are opposite each other in a horizontal direction perpendicular to the direction of advancement Z and which extend respectively along the two side walls 13 of the combustion chamber 10. The arrangements of the combustion chamber 10, which drive the bed of solid fuels C along the direction of advancement Z, are not limiting of the invention: in a manner known per se, the grid 14 can be provided movable to act on the drive of the bed and/or be provided inclined to allow the gravity drive of the bed. Whatever the embodiment of the grid 14, the primary air P is admitted under the grid and this grid 14 is designed to let the primary air P cross from bottom to top to allow the latter to enter in the lower part 10A of the combustion chamber 10 and thus reach the bed of solid fuels C.

The combustion installation 1 also comprises an intake device 30 making it possible to supply the lower part 10A of the combustion chamber 10 with the primary air P. The embodiment of this intake device 30 is not limitation of the invention. In the exemplary embodiment considered here, the inlet device 30 is, at least for its downstream outlet, arranged below the grid 14. In particular, as envisaged in FIG. 1, the inlet device 30 comprises several separate boxes 31, which here are five in number and which are arranged under the grid 14, in succession in the direction of advancement Z. Each of the boxes 31 is designed to receive primary air P, from a pipe supply 32 common to the various boxes 31, and to channel the air passing through it to an outlet, specific to each box, from which the air emerges just below a corresponding region of the grid 14. The flow rate of primary air P admitted into the combustion chamber 10 by the intake device 30, in other words the total flow rate of the primary air P passing through this intake device 30, corresponds to the sum of the flow rates of air which respectively pass through the boxes 31. As indicated above, other embodiments than the boxes 31 are possible for the admission device 30.

The combustion installation 1 also comprises an intake device 40 making it possible to supply the upper part 10B of the combustion chamber 10 with the secondary air S.

In the embodiment considered in FIG. 1, the intake device 40 comprises secondary air projection nozzles S in the upper part 10B of the combustion chamber 10. These nozzles are distributed, at the same time, between several stages and between the rear 11 and front 12 walls of the combustion chamber 10. The aforementioned stages, which are three in number in the example of FIG. 1, are respectively located at different levels of the combustion chamber 10 , by providing that the nozzles of each of these stages are located substantially in the same geometric plane which is at least generally parallel to the grid 14, as represented schematically in FIG. 1. Thus, in the example illustrated in FIG. 1, the aforementioned nozzles consist of:

- rear lower nozzles 41.1, which belong to the lowest floor and which are arranged on the rear wall 11, being distributed in a horizontal direction perpendicular to the direction of advancement Z, only one of these nozzles 41.1 being represented in Figure 1,

-front lower nozzles 41.2, which belong to the lowest floor and which are arranged on the front wall 12, being distributed in a horizontal direction perpendicular to the direction of advancement Z, only one of these nozzles 41.2 being represented in Figure 1,

- rear intermediate nozzles 41.3, which belong to the intermediate stage and which are arranged on the rear wall 11, being distributed in a horizontal direction perpendicular to the direction of advancement Z, only one of these nozzles 41.3 being represented on the figure 1,

-front intermediate nozzles 41.4, which belong to the intermediate stage and which are arranged on the front wall 12, being distributed in a horizontal direction perpendicular to the direction of advancement Z, only one of these nozzles 41.4 being represented on the figure 1,

- rear upper nozzles 41.5, which belong to the highest floor and which are arranged on the rear wall 11, being distributed in a horizontal direction perpendicular to the direction of advancement Z, only one of these nozzles 41.5 being represented in Figure 1, and

-front upper nozzles 41.6, which belong to the highest stage and which are arranged on the front wall 12, being distributed in a horizontal direction perpendicular to the direction of advancement Z, only one of these nozzles 41.6 being represented in figure 1.

The nozzles 41.1 to 41.6 are supplied with secondary air S from an inlet 42 common to the various nozzles. In a manner not shown in Figure 1, the secondary air S is delivered under pressure to the inlet 42 by a fan or similar device. The nozzles 41.1 to 41.6 are connected to the inlet 42 by respective pipes 43.1 to 43.6, as shown in Figure 1.

Each of the nozzles 41.1 to 41.6 opens into the upper part 10B of the combustion chamber 10 and projects therein a jet of air J1 to J6, giving the latter an impulse, otherwise called momentum, which can be quantified by the product between the mass flow and the speed of the air jet at the outlet of the corresponding nozzle. Due to the staging of the nozzles 41.1 to 41.6, the air jets J1 and J2 are projected below the air jets J3 and J4, which are themselves projected below the air jets J5 and D6. Due to the distribution of the nozzles 41.1 to 41.6 between the rear 11 and front 12 walls, the air jets J1, J3 and J5 are projected from the rear wall 11 while the air jets J2, J4 and J6 are projected from the front wall 12. The nozzles 41.1 to 41.6 project the air jets J1 to J6 so that, at least in the immediate vicinity of the rear 11 and front 12 walls, these air jets J1 to J6 progress in the upper part 10B of the combustion chamber 10 away from the wall 11 or 12 from which they are projected, and this transversely to the latter, as shown schematically in Figure 1. Once introduced into the upper part 10B of the combustion chamber 10, the air jets J1 to J6 tend to flow in this upper part 10B of the combustion chamber in a segregated manner, due to the arrangement of the nozzles 41.1 and 41.6 and the impulse they give to the jets of air, as well as due to the flow of the gases G and their progressive mixing with the secondary air supplied by the air jets, channeled through the combustion chamber 10. In other words, as shown schematically in FIG. 1, after having moved away from the rear wall 11 or front wall 12 from which the air jets J1 to J6 are projected, each of these air jets mixes substantially with the gases G resulting from the primary combustion, but only mixes marginally with the other air jets. Thus, as shown in Figure 1, the secondary air S admitted into the combustion chamber 10 by the intake device 40 is distributed between:

-the air jets J5 and J6 which, above the aforementioned highest stage, flow upwards in, respectively, a rear zone and a front zone of the upper part 10B of the combustion chamber 10,

the air jets J1 and J2 which, above the aforementioned highest floor, flow upwards in a middle zone of the upper part 10B of the combustion chamber 10, and

-the air jets J3 and J4 which, above the aforementioned highest stage, flow upwards in, respectively, two intermediate zones of the upper part 10B of the combustion chamber 10, namely an intermediate zone between the rear zone and the middle zone, and an intermediate zone between the middle zone and the front zone.

As shown schematically in Figure 1, each of the pipes 43.1 to 43.6 is provided with a flow control member 44.1 to 44.6. The embodiment of these flow adjustment members 44.1 to 44.6 does not limit the invention, as long as each of these flow adjustment members makes it possible to control the flow rate of the jet of air projected by the nozzle supplied by the pipe provided with this flow control member. In practice, the flow control members 44.1 to 44.6 are valves, dampers, etc.

In all cases, each of the flow adjustment members 44.1 to 44.6 is designed to be controlled by a control unit 50 of the combustion installation 1. The control unit 50 comprises electronic and/or electromechanical components, to even to generate control signals, which are transmitted to the flow adjustment members 44.1 to 44.6 in order to individually actuate the latter to control the respective flow rates of the air jets J1 to J6. Here again, the material specificities of the control unit 50, as well as those of the connection between the latter and the flow adjustment members 44.1 to 44.6 are not limiting of the invention.

As shown in Figure 1, the combustion plant 1 further comprises optical pyrometers, five of them being visible in Figure 1. All the pyrometers are located above the highest stage of the nozzles 41.1 to 41.6 and are arranged laterally to the combustion chamber 10, each being provided on at least one of the rear wall 11, of the front wall 12 and of the side walls 13. The pyrometers make it possible to carry out temperature measurements of the upper part 10B of the combustion chamber 10, and this from the wall of the latter on which they are provided. In the embodiment considered in FIG. 1, all these pyrometers are integrated into the side walls 13: more precisely, the side wall 13 visible in FIG. 1 thus integrates five pyrometers 60.1 to 60.5. These pyrometers 60.1 to 60.5 are respectively associated with five zones Z1 to Z5 of the upper part 10B of the combustion chamber 10, which follow one another along the direction of advancement Z from the rear wall 11 to the front wall 12 of the combustion chamber 10. The pyrometer 60.1 measures a temperature of the secondary combustion in the zone Z1, the pyrometer 60.2 measures a temperature of the secondary combustion in the zone Z2 and so on, up to the pyrometer 60.5 which measures a temperature of the secondary combustion in zone Z5. The temperature measurements are taken by the pyrometers 60.1 to 60.5 as close as possible to the mixture GS between the secondary air S and the gases G resulting from the primary combustion, thus measuring the radiation of the gaseous compounds and of the solid particles present in the mixture. GS.

As shown schematically in Figure 1, the arrangement of the pyrometers 60.1 to 60.5 and, thereby, of the zones Z1 to Z5 is provided so that:

- at the level of the pyrometer 60.1, the J5 air jets projected by the rear upper nozzles 41.5 flow upwards in the zone Z1, throughout the month mainly in this zone Z1,

-at the level of the pyrometer 60.2, the air jets J3 projected by the rear intermediate nozzles 41.3 flow upwards in the zone Z2, throughout the month mainly in this zone Z2,

-at the level of the pyrometer 60.3, the jets of air J1 and J2 projected respectively by the lower rear nozzles 41.1 and by the lower front nozzles 41.2 flow upwards in the zone Z3, throughout the month mainly in this zone Z3 ,

- at the level of the pyrometer 60.4, the jets of air J4 projected by the front intermediate nozzles 41.4 flow upwards in the zone Z4, throughout the month mainly in this zone Z4, and

- at the level of the pyrometer 60.5, the jets of air J6 projected by the upper front nozzles 41.6 flow upwards in the zone Z5, throughout the month mainly in this zone Z5.

In practice, having regard to the succession of zones Z1 to Z5 along the direction of advancement Z, the pyrometers 60.1 to 60.5 are advantageously distributed over the side wall 13 along the direction of advancement Z, in particular to limit the optical path between the pyrometers and secondary combustion and to have maximum integration of the thermal radiation emitted by secondary combustion. This being so, the precise arrangement of the pyrometers 60.1 to 60.5 on the side wall 13 does not limit the invention and can in particular be determined either by experience or by observation of the state of the interior surface of the side wall. 13 during maintenance operations, either by simulation of the flows of the air jets projected by the nozzles 41.1 to 41.6, conducted using numerical fluid mechanics tools. In all cases, this precise arrangement of the pyrometers 60.1 to 60.5 aims to associate with each pyrometer a zone of upward flow, at the level of this pyrometer, of at least one of the jets projected by the nozzles of the admission device 40.

In all cases, in the vertical direction, each of the pyrometers 60.1 to 60.5 is preferably separated by between one and four meters from the highest introduction of the air jets J1 to J6, in other words separated by between one and four meters from the geometric plane to which the upper nozzles 41.5 and 41.6 belong. In this way, the relevance of the measurements carried out by the pyrometers 60.1 to 60.5 is optimized.

The type of optical pyrometers 60.1 to 60.5 does not limit the invention, since these pyrometers provide temperature measurements based on the intensity of the wavelengths emitted by a radiating body. Preferably, the pyrometers 60.1 to 60.5 are bichromatic laser pyrometers, that is to say that, for the purposes of measuring the temperature of the secondary combustion, each pyrometer emits, in the combustion chamber 10, at least one beam laser with two different wavelengths: pyrometers are thus less sensitive to dust emissions. For example, the spectral response of these pyrometers is of the order of 1 µm.

Moreover, the specificities relating to the focusing of the pyrometers 60.1 to 60.5 do not limit the invention either. This being so, a preferred embodiment is illustrated in FIG. 2 for the pyrometer 60.1, it being understood that this embodiment is applicable to the other pyrometers 60.2 to 60.5. Thus, as shown in FIG. 2, the pyrometer 60.1 is designed, for the purposes of measuring the temperature of the secondary combustion, to emit two laser beams into the upper part 10B of the combustion chamber 10, via an opening 13.1 of the side wall 13. Each of these two laser beams can be bichromatic, as indicated above. In all cases, these two laser beams intersect substantially in the plane of the side wall 13. This economical arrangement makes it possible to limit the diameter of the opening 13.1, while keeping a large divergent field of view for the pyrometer.

In all cases, the measurements of pyrometers 60.1 to 60.5 are transmitted, by any appropriate form of link, to the control unit 50 in order to be automatically processed by the latter, in particular by a computer or a similar component of the latter. . Whatever the specifics of the processing which is carried out by the control unit 50 and examples of which will be given later, the control unit 50 is advantageously designed to control:

-the flow adjustment members 44.1 and 44.2 from the temperature measurements provided by the pyrometer 60.3,

-the flow control device 44.3 from the temperature measurements provided by the pyrometer 60.2,

-the flow control device 44.4 from the temperature measurements provided by the pyrometer 60.4,

-the flow regulator 44.5 from the temperature measurements provided by the pyrometer 60.1, and

-the flow control device 44.6 from the temperature measurements provided by the pyrometer 60.5.

Aspects relating to the control of the combustion plant 1 are further described below.

In this context, it is considered that the combustion installation 1 is in normal operation, that is to say that its combustion chamber 10 is fed under normal conditions, both with the solid fuels C, the primary air P and secondary air S, and that the primary and secondary combustions take place there, as explained above. Apart from the aspects relating to the regulation of the secondary air which will be presented in detail below, the other aspects of the operation of the combustion plant 1 are well known in the art and are therefore not presented here further. .

While the combustion chamber 10 is operating under normal conditions, the pyrometers 60.1 to 60.5 continuously measure the temperature of the secondary combustion in, respectively, the zones Z1 to Z5 of the upper part 10B of the combustion chamber. The temperature measurements taken by these pyrometers 60.1 to 60.5 are sent continuously to the control unit 50 in order to be automatically processed in real time by the latter. According to a preferred embodiment for the processing carried out by the control unit 50, the latter compares in real time the temperature measurements provided by each of the pyrometers 60.1 to 60.5 with a temperature setpoint which is specific to the pyrometers considered, otherwise said which is specific to the zone associated with this pyrometer among the zones Z1 to Z5. Depending on the result of this comparison specific to each of the zones Z1 to Z5, the control unit 50 transmits in real time to the corresponding flow adjustment device(s), that is to say to that or those of the adjustment devices 44.1 to 44.6 which is or are associated with the nozzles projecting the jets of air flowing in the zone concerned at the level of the pyrometers, an actuation control so that the flow adjustment member or members act on the flow rate of the air jets, among the air jets J1 to J6, which correspond to the zone associated with the pyrometer concerned. For example, if, for zone Z2, the temperature measured by pyrometer 60.2 is 5% lower than the temperature setpoint specific to zone Z2 for more than five to ten consecutive seconds, control unit 50 activates the flow adjustment member 44.3 to increase the flow of the air jet J3 by 10%.

In practice, the temperature setpoints respectively specific to the zones Z1 to Z5 are provided beforehand to the control unit 50. These temperature setpoints can be prefixed for the combustion installation 1 or, preferably, are determined, in particular by calculation , from a reference temperature, which is common to all the zones and to which is applied a correction which is specific to the zone concerned from among the zones Z1 to Z5.

The aforementioned reference temperature is either prefixed or determined, if necessary continuously, from the oxygen content in the fumes F, this content being typically measured at the outlet of the boiler, as mentioned in the introductory part of this document. document.

The aforementioned correction, which is specific to each of the zones Z1 to Z5, is advantageously defined according to a temperature profile along the direction of advance Z, which can be described as an optimal profile. This temperature profile is determined taking into account:

- the thermal power introduced into the boiler, and/or

-characteristics of the solid fuels C supplying the combustion chamber, possibly measured continuously, such as their calorific value, and/or

-characteristics of the ashes resulting from the combustion of solid fuels C, such as the presence of certain oxides determined by ad hoc analyses, and/or

-temperature characteristics relating to the primary combustion of the solid fuels C, optionally measured continuously, such as an average temperature, for example calculated from images provided by an infrared camera observing the interior of the combustion chamber 10 , or else such as a temperature profile along the direction of advancement Z, for example measured by pyrometers 70 indicated in dotted lines in FIG. 1 and measuring a temperature of the primary combustion in respective zones, succeeding one another in the direction advancement Z, of the bed formed by the solid fuels on the grid 14.

The temperature profile making it possible to define the corrections specific to the zones Z1 to Z5 can thus be advantageously adapted, if necessary continuously over time, to reflect the composition of the gases G in the direction of advance Z and/or to avoid the fusion of at least certain oxides and thus avoid the formation of constructions and agglomerates of vitrified ash at the outlet of the combustion chamber, which are liable to affect the downstream equipment of the boiler, in particular heat exchangers.

Of course, other processing than that which has just been described can be implemented by the control unit 50, in particular as long as these other processing compare the measurements of the pyrometers 60.1 to 60.5 with respective temperature setpoints , which are specific to zones Z1 to Z5, in order to individually control the flow rate of the air jets J1 to J6. In all cases, it is understood that the control unit 50 and the adjustment members 44.1 to 44.6 jointly form regulation means which make it possible, from the measurements of the pyrometers 60.1 to 60.5, to regulate the respective flow rates of the jets of air J1 to J6 and, thereby, the total secondary air flow S supplied by the intake device 40 to the combustion chamber 10. The reaction time for these regulation means is very low, even almost instantaneous .

As a safety measure, in particular to prevent the flow rate of the air jets J1 to J6 from being too low or too high, the actuation of the flow adjustment members 44.1 to 44.6, controlled by the control unit 50, can be expected within a substantial but limited range of variations. The limits of this range of variations are predetermined by experience and/or by other operating parameters of the combustion installation 1, such as the tonnage of solid fuels C introduced into the combustion chamber 10, the pressure of the secondary air S in the inlet 42, the steam flow produced by the exchanger(s) of the boiler, etc. Also by way of control and safety, the reference temperature, mentioned above, can be compared with the instantaneous average of the temperature measurements provided by the pyrometers 60.1 to 60.5, weighted by the size of the zones Z1 to Z5 respectively associated with these pyrometers.

Figure 3 illustrates an optional arrangement for the nozzles 41.1 to 41.6. In Figure 3, this optional arrangement is shown being applied to the nozzle 41.1, but this optional arrangement can of course be applied to any other of the nozzles 41.2 to 41.6. According to this arrangement, the nozzle 41.1 incorporates a flow section adjusting member 47.1. In the embodiment considered in Figure 3, the flow section adjuster 47.1 comprises an insert 47.1A which is arranged in the outlet of the nozzle 41.1 in a sliding manner to vary the flow section at the outlet of the nozzle 41.1. For this purpose, the insert 47.1A and the outlet of the nozzle 41.1 have appropriate geometries, such as frustoconical geometries as in the example considered in FIG. 3. In order to cause the insert 47.1A to slide relative to the rest of the nozzle 41.1, the flow section adjustment member 47.1 comprises for example a rod 47.1B, one end of which is fixedly secured to the insert while the opposite end is driven by an actuator 47.1C. By modifying the position of the insert 47.1A under the driving effect of the actuator 47.1C, the flow section adjuster 47.1 modifies the flow rate of the air jet J1 projected by the nozzle 41.1, while maintaining the speed of this air jet, which amounts to saying that the flow rate is modified jointly with the pulse of the air jet J1.

It is understood that by providing that the actuator 47.1C is controllable by the control unit 50, the flow section adjustment member 47.1 makes it possible to control the flow rate of the air jet J1 while maintaining its speed, unlike the flow rate adjusters 44.1 to 44.6 which act jointly on the quantity and the speed of the air flowing in the corresponding pipe 43.1 to 43.6 to modify the flow rate of the air jets J1 to J6. In practice, the control of the flow rate of the air jets by such a flow section adjusting member can either be additional to that operated by the flow adjusting members 44.1 to 44.6, or completely replace that operated by the flow rate setting 44.1 to 44.6. In the latter case, this amounts to saying that the respective flow rates of the air jets J1 to J6 are exclusively controlled by the flow section adjusting members, such as the flow section adjusting member 47.1, and that the flow control members 44.1 to 44.6 are no longer useful.

Figures 4 and 5 show a combustion plant 101 corresponding to an alternative embodiment to the combustion plant 1.

Combustion plant 101 is functionally similar to combustion plant 1 and, like the latter, can be integrated into a boiler.

Combustion installations 1 and 101 differ in their secondary air intake device, their control unit and their pyrometers, which, unlike combustion installation 1, are referenced 40, 50 and 160.1 to 160.3 respectively. for the combustion installation 101. The rest of the combustion installation 101 is identical to that of the combustion installation 1, so that the corresponding elements of the combustion installation 101 will not be described here further and carry, in Figures 4 and 5, the same references as for the combustion plant 1.

The secondary air intake device 140 comprises nozzles which, individually, are functionally or even structurally similar to the nozzles of the secondary air intake device 40, but which are arranged within the combustion installation 101 differently than within the combustion installation 1. More specifically, the nozzles of the intake device 140 are distributed between left nozzles, which are arranged on the left side wall 13 of the combustion chamber 10, being distributed along the direction of advancement Z and being successively referenced 141.1, 141.2 and 141.3, and straight nozzles, which are arranged on the right side wall 13 of the combustion chamber, being distributed along the direction of advancement Z, in particular horizontal correspondence with the left nozzles 141.1, 141.2 and 141.3. In FIG. 4, only the left nozzles 141.1, 141.2 and 141.3 are visible, while in FIG. 5 only the left nozzle 141.1 and the right nozzle are visible in horizontal correspondence with this left nozzle 141.1, this right nozzle being referenced 141.4.

Similarly to the nozzles of the intake device 40, each of the nozzles of the intake device 140 is designed to project, into the upper part 10B of the combustion chamber 10, a jet of air. Thus, the secondary air S introduced into the combustion chamber 10 is distributed, by the intake device 140, into these different air jets. In FIGS. 4 and 5, the jets of air projected by the nozzles 141.1 to 141.4 are respectively referenced J1′, J2′, J3′ and J4′.

Also similarly to the nozzles of the intake device 40, the nozzles of the intake device 140 are supplied with the secondary air S from an inlet 142 common to the various nozzles, each of the latter being connected to this inlet 142 by respective pipes which are each provided with a flow control member. In the example considered in Figures 4 and 5, the pipes respectively connecting the nozzles 141.1 to 141.4 to the inlet 142 are respectively referenced 143.1 to 143.4. The flow control members which are respectively provided on these pipes 143.1 to 143.4 are respectively referenced 144.1 to 144.4.

Similar to the pyrometers 60.1 to 60.5 of the combustion plant 1, the pyrometers 160.1 to 160.3 of the combustion plant 101 are arranged laterally to the combustion chamber 10, being located above the nozzles of the combustion device. intake 140 and being provided on the left side wall 13 of the combustion chamber. Each of these pyrometers 160.1 to 160.3 is associated with a zone Z1' to Z3' of the upper part 10B of the combustion chamber 10, the zones respectively associated with the various pyrometers being provided to follow one another in the direction of advance Z. Next considerations similar to those explained previously for the combustion plant 1, the arrangement of the pyrometers 160.1 to 160.3 and, thereby, of the zones Z1' to Z3' is provided so that, at the level of the pyrometers 160.1 to 160.3, the jets of air projected by the nozzles of the admission device 140 flow upwards in one or the other of the zones Z1' to Z3'. Thus, as shown schematically in Figures 4 and 5, the air jets J1' and J4' flow, at least mainly, in the zone Z1', the air jet J2' flows, at least mainly , in the zone Z2' and the jet of air J3' flows, at least mainly, in the zone Z3', at the level of the pyrometers 160.1 to 160.3

The control unit 150 of the combustion installation 101 is functionally, even structurally, similar to the control unit 50 of the combustion installation 1. Thus, taking into account the explanations given previously in connection with the installation of combustion 1, it is understood that the pyrometers 160.1 to 160.3 make it possible to measure the temperature of the secondary combustion in, respectively, the zones Z1' to Z3' and to supply the corresponding temperature measurements to the control unit 150 which, by automatic processing, control the individual actuation of the flow regulating members of the admission device 140, such as the flow regulating members 144.1 to 144.4, each of these flow regulating members being thus controlled according to the measurements of the pyrometer associated with the zone in which, at the level of the pyrometers, the air jet flows, the flow rate of which is controlled by this flow adjustment member.

The regulation of the combustion installation 101 is similar to that of the combustion installation 1, so that the regulation of the combustion installation 101 will not be described here in detail, referring to the considerations developed above for regulation of the combustion plant 1.

Beyond what has been described so far for the combustion installations 1 and 101, various arrangements and variants of these combustion installations and their regulation method can be envisaged:

-for a given zone of the upper part 10B of the combustion chamber 10, among the zones Z1 to Z5 or among the zones Z1' to Z3', more than one pyrometer can be provided. In particular, a pair of pyrometers can thus be associated with at least one of the zones Z1 to Z5 or Z1' to Z3', or even to each of these zones, the two pyrometers of each pair being provided respectively on the side wall 13 left and the right side wall 13, typically horizontally facing each other, as shown in dotted lines in the left part of FIG. 5. Such a pair of pyrometers makes it possible to measure the temperature of the secondary combustion in the zone concerned from each lateral side of the upper part of the combustion chamber. The measurements respectively coming from the different pyrometers for a given zone of the upper part of the combustion chamber are then averaged for the purposes of processing by the control unit 50 or 150.

- The staging of the nozzles of the secondary air supply device 40 or 140 is not limited to the examples envisaged in the figures. In particular, more or fewer stages of nozzles can be provided for the secondary air supply device 40, or even a single stage. Similarly, several stages of nozzles can be provided for the secondary air supply device 140.

-Rather than individually adjusting the respective flow rates of the air jets J1 to J6 or J1' to J4', provision may be made to regulate the flow rate of the secondary air in the inlet 42 or 142, by means of an ad hoc flow adjustment device, provided on this inlet and controlled by the control unit 50 or 150. The regulation of the combustion installation then makes it possible to adjust the total flow rate of the secondary air S passing through the secondary air intake device 40 or 140. In this case, a single pyrometer, similar to pyrometers 60.1 to 60.5 and 160.1 to 160.3, can be used. Of course, several pyrometers can also be used, their respective measurements being averaged for the needs of the processing of the control unit 50 or 150. The total flow rate of the secondary air thus regulated is then distributed between the various jets.

-The number, according to which the upper part 10B of the combustion chamber 10 is divided into zones, may differ from that envisaged for the combustion installations 1 and 101. This being said, this number is preferably at least three in order to include the extension, in the upper part 10B of the combustion chamber 10, of three main zones corresponding to the successive physico-chemical effects of the primary combustion, namely a drying zone for the solid fuels, a gasification zone for a part volatile solid fuels and combustion for a non-volatile part of the solid fuels, and a cooling and combustion finishing zone for the non-volatile part of the solid fuels.

-Similarly, the number of air jets which, at the level of the pyrometers, flow, at least mainly, in each of the zones of the upper part 10B of the combustion chamber 10, may not be limited to one, being in particular equal to two, or even more.

Whatever the specifics of the process of the combustion installation in accordance with the invention, the advantages provided by this invention, in particular compared to the current techniques mentioned in the introductory part of this document, are numerous.

Thus, as the temperature measurements made by the pyrometers are instantaneous and as close as possible to the secondary combustion, the regulation of the combustion installation can be carried out in real time, or in any case with reaction times much lower than the techniques existing. This very short reaction time is adapted to the speeds observed for complex and rapid phenomena, linked to secondary combustion.

The response time and the representativeness of the temperature measurements by the pyrometers allow high precision in the dosage of secondary air and good control of the ratio between the quantity of air consumed by secondary combustion and the quantity of gases resulting from the combustion. primary combustion, burned by the secondary combustion, and this, advantageously, in different zones of the upper part of the combustion chamber, in particular zones corresponding to the extensions of the three main zones mentioned above and corresponding to the successive physico-chemical effects of the primary combustion. The invention thus makes it possible to provide almost instantaneously and, advantageously, locally the quantity of air just necessary for the secondary combustion.

This "closer" adjustment of the quantity of secondary air induces a reduction in the overall flow of secondary air, which is favorable to a reduction in the size of the combustion installation and to its energy efficiency. In particular, the size of the upper part of the combustion chamber can be reduced, while respecting the minima for the residence time and the temperature required in this upper part of the combustion chamber.

In addition, by thus controlling the kinetics of secondary combustion, it is possible to control the formation/transformation of numerous compounds, in particular to avoid or reduce the formation of molten oxides at high temperature in the combustion chamber and, thereby, to avoid or reduce the appearance of vitrifications on the heat exchange surfaces in the equipment downstream of the combustion chamber. It is also possible to increase the efficiency of the reduction of nitrogen oxides by injecting into the combustion chamber reagents, such as ammonia or urea, whose chemical reaction is optimal in a reduced temperature range, generally between 900 and 1000°C: in fact, the temperature control in the different zones of the upper part of the combustion chamber increases the volume of this upper part in the aforementioned temperature range or makes it possible to control the flow rate of the reactants mentioned above according to the zones of the upper part of the combustion chamber. It is also possible to reduce polluting emissions, in particular those of carbon monoxide.

The “closest” adjustment of the quantity of secondary air also makes it possible to control the temperatures in the entire upper part of the combustion chamber. This improves the performance of equipment downstream of the combustion chamber, in particular the production of steam by the boiler exchangers. This also makes it possible to reduce the need for primary air in favor of secondary air, making it possible to increase the content of volatile matter, as well as to reinforce the gasification of solid fuels in the form of pyrolysis gases whose combustion produces less nitrogen oxide. The decrease in primary air in favor of secondary air is also accompanied by a decrease in the total air sent to the combustion chamber.

Controlling the temperatures in the upper part of the combustion chamber also avoids local temperature peaks which would be excessive and makes it possible to limit the extent of the surfaces of the combustion installation, protected by refractory linings.

Other advantages of the invention have also been mentioned previously or can be deduced from the foregoing by those skilled in the art.

Claims (11)

Method for regulating a combustion plant (1; 101),
in which solid fuels (C) are introduced into a combustion chamber (10),
in which primary air (P) is introduced into a lower part (10A) of the combustion chamber to effect primary combustion of the solid fuels therein, and
in which secondary air (S) is introduced, with a flow of secondary air, into an upper part (10B) of the combustion chamber in order to carry out secondary combustion of gas (G) resulting from the primary combustion therein,
characterized in that the secondary combustion has a temperature which is measured in the upper part (10B) of the combustion chamber (10) by one or more optical pyrometers (60.1 to 60.5; 160.1 to 160.3) which are arranged laterally to the chamber combustion, and in that the secondary air flow is controlled according to the measurements of the pyrometer(s). Process according to claim 1,
in which the combustion chamber (10) is delimited downwards by a grid (14) on which the solid fuels (C) form a bed which is movable in a direction of advance (Z) in the lower part (10A) of the combustion chamber, the primary air (P) being admitted under the grate before crossing the grate to enter the lower part of the combustion chamber and reach the bed of solid fuels,
in which the upper part (10B) of the combustion chamber is divided into several zones (Z1 to Z5; Z1' to Z3'), preferably at least three zones, which follow one another in the direction of advance (Z), each zone being associated with at least one of the pyrometers (60.1 to 60.5; 160.1 to 160.3) so that, for each zone, the pyrometer(s) associated with the zone measure the temperature of the secondary combustion in this zone,
in which the secondary air (S) is admitted into the upper part of the combustion chamber by being distributed into air jets (J1 to J6; J1' to J4'), which are introduced below the pyrometers, by being respectively projected by nozzles (41.1 to 41.6; 141.1 to 141.4) arranged laterally to the combustion chamber, and which, at the level of the pyrometers, flow upwards in at least one of the said zones, and
wherein each jet of air is projected by the corresponding nozzle with a flow rate which is controlled according to the measurements of the pyrometer(s) associated with that or those of said zones in which this jet of air flows. Process according to claim 2,
in which each jet of air (J1 to J6; J1' to J4') flows mainly in only one of said zones (Z1 to Z5; Z1' to Z3'), and
wherein each of said zones is associated with at least one of the air jets, which flows in this zone. Method according to one of claims 2 or 3, in which the nozzles (41.1 to 41.6) are distributed among several stages which are respectively located at different levels, the nozzles of each stage being located substantially in the same geometric plane which is parallel to the grid ( 14). A method according to any of claims 2 to 4,
in which the combustion chamber (10) is delimited by a rear wall (11) and a front wall (12), which are opposite to each other in the direction of advance (Z), and
wherein the nozzles (41.1 to 41.6) are distributed between rear nozzles, which are arranged on the rear wall, being distributed in a horizontal direction perpendicular to the direction of travel, and front nozzles, which are arranged on the wall front, being distributed in said horizontal direction. A method according to any of claims 2 to 4,
wherein the combustion chamber (10) is delimited by left and right side walls (13), which are opposite to each other in a horizontal direction perpendicular to the direction of advancement (Z), and
wherein the nozzles (141.1 to 141.4) are distributed between left nozzles, which are arranged on the left side wall, being distributed in the direction of travel, and right nozzles, which are arranged on the right side wall, in being distributed according to the direction of advance. A method according to any of claims 2 to 6, wherein the at least one pyrometer (60.1 to 60.5; 160.1 to 160.3) is spaced between one and four meters from the highest introduction of the air jets (J1 to J6; J1' to J4' ). A method according to any of claims 2 to 7,
wherein all the nozzles (41.1 to 41.6; 141.1 to 141.4) are supplied with secondary air from a common inlet (42; 142), and
wherein the flow rate of each air jet (J1 to J6; J1' to J4') is controlled by:
- a flow adjustment member (44.1 to 44.6; 144.1 to 144.4), which is provided on a pipe (43.1 to 43.6; 143.1 to 143.4) connecting the common inlet and the nozzle projecting this air jet, and/or
-a flow section adjustment member (47.1), which is integrated into the nozzle projecting this air jet. Method according to any of the preceding claims, in which, in order to measure the temperature of the secondary combustion, the or each pyrometer (60.1 to 60.5; 160.1 to 160.3) emits in the upper part (10B) of the combustion chamber (10):
- at least one bichromatic laser beam, and/or
-two laser beams which intersect substantially in the plane of a wall (13) of the combustion chamber, on which the pyrometer is arranged. Combustioninstallation(1;101),comprising:
- a combustion chamber (10), adapted so that solid fuels (C) are introduced therein,
-a primary air intake device (30), suitable for supplying with primary air (P) a lower part (10A) of the combustion chamber in order to carry out primary combustion of the solid fuels therein, and
-a secondary air intake device (40; 140), suitable for supplying with secondary air (S), according to a secondary air flow, an upper part (10B) of the combustion chamber to carry out a secondary combustion of gases (G) resulting from the primary combustion,
characterized in that the combustion installation further comprises:
-one or more optical pyrometers (60.1 to 60.5; 160.1 to 160.3), which are arranged laterally to the combustion chamber (10) and which are suitable for measuring a secondary combustion temperature in the upper part (10B) of the combustion chamber (10 ),And
- regulating means (44.1 to 44.6, 47.1, 50; 144.1 to 144.4, 150) suitable for, from the measurements of the pyrometer(s), controlling the secondary air flow (S) of the air intake device secondary (40; 140). Combustion installation according to claim 10,
in which the combustion installation (1; 101) further comprises a grate (14):
- which limits the combustion chamber (10) downwards,
- which is adapted to support a bed which is formed by the solid fuels (C) and which is movable in a direction of advance (Z) in the lower part (10A) of the combustion chamber, and
-under which the primary air intake device (30) opens out so that the primary air (P) supplied by this primary air intake device enters the lower part of the combustion chamber crossing the grate,
in which the upper part (10B) of the combustion chamber is divided into several zones (Z1 to Z5; Z1' to Z3'), preferably at least three zones, which follow one another in the direction of advance (Z), each zone being associated with at least one of the pyrometers (60.1 to 60.5; 160.1 to 160.3) so that, for each zone, the pyrometer(s) associated with the zone measure the temperature of the secondary combustion in this zone,
wherein the secondary air intake device (40; 140) is adapted to distribute the secondary air (S) into air jets (J1 to J6; J1' to J4'), which are introduced above below the pyrometers, being respectively projected by nozzles (41.1 to 41.6; 141.1 to 141.4) arranged laterally to the combustion chamber, and which, at the level of the pyrometers, flow upwards in at least one of the said zones, and
in which the regulating means (44.1 to 44.6, 47.1, 50; 144.1 to 144.4, 150) are adapted to control the rate with which each of the air jets is projected by the corresponding nozzle, based on the measurements of the pyrometer(s) associated with that or those of said zones in which this jet of air flows.