EP3819543A1 - Method for regulating a combustion facility, and corresponding combustion facility - Google Patents

Abstract

In this method of regulating a combustion installation (1), solid fuels (C) are introduced into a combustion chamber (10) and burn there according to a primary combustion in the presence of primary air (P) which is introduced. in the combustion chamber with a primary air flow. To control the primary combustion carried out in this installation, provision is made for the primary combustion of solid fuels to have a temperature which is measured in the combustion chamber by one or more optical pyrometers (50.1 to 50.5), which are arranged laterally to the chamber. combustion and which point the combustion gases (G) generated by the primary combustion in the immediate vicinity of the solid fuels so as to measure the radiation of both these combustion gases and the solid particles contained in these combustion gases. The primary air flow is controlled according to the measurements of the pyrometer (s).

Description

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 released by combustion to a heat transfer fluid, generally water.

Whatever the field of application of the invention, the combustion plants concerned use, as fuels, 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 material flow, 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 combustion therein, 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 burned entirely, except for particulate unburnt particles, 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, or partially burned. This primary combustion can in particular be carried out on a grate, which delimits the combustion chamber downwards and on which the solid fuels are loaded to undergo the primary combustion therein, while the primary air is admitted under the grate before passing through this last to enter the combustion chamber and thus reach the solid fuels. So that the volatile part of the solid fuels is completely burned and thus operate a so-called secondary combustion, it is often expected that the air called secondary air, consisting of air and / or recirculated fumes, is admitted into the combustion chamber , by being injected above the grid in one or more levels.

In all cases, all the chemical and physical reactions, which will condition the composition of the combustion gases and of the particles fluidized by these gases in the combustion chamber and then downstream thereof, in particular in the heat exchangers of the boiler, are initiated by primary combustion. It is therefore desirable to control as much as possible the conditions under which the primary combustion is carried out. In particular, the conditions of the primary air intake are critical, in the sense that they influence in particular the temperature. of primary combustion and on the partial pressures of volatile compounds in the flue gases, which affects the physical and chemical reactions of primary combustion, as well as the entrainment of particles in the flue gases.

Solid fuels of the waste or biomass type are characterized by a strong heterogeneity both in size of the solid fragments composing them, in composition and in humidity. This strong heterogeneity entails, at the same time, a strong disparity, in time and in space, for the physicochemical properties of combustion relating to these solid fuels, such as their calorific value, their stoichiometric need for air, their kinetics. combustion, etc., and poor physical distribution of these solid fuels in the combustion chamber, in particular on the grate of the latter. This heterogeneity often leads to the combustion being deliberately carried out with a large excess of air relative to the stoichiometric requirement, in order to limit unburnt material. This excess air is often all the greater the greater the heterogeneity of the solid fuels, in order to ensure that the primary combustion is as complete as possible. The heterogeneity of solid fuels also frequently leads to the admission of the primary air into the combustion chamber, typically through the grid of the latter, to be poorly distributed in space, due to the inhomogeneity. the pressure drop generated by the layer formed by the solid fuels on the grid. The relative inhomogeneity of this layer results in particular from the variability in the size and density of the solid fragments present in the fuels, from the system for depositing solid fuels on the grate, and from the disparity in the combustion kinetics relating to these solid fuels.

• La formation d'oxydes d'azote, par oxydation de l'azote contenu dans l'air primaire, est favorisée par une mauvaise maîtrise de l'admission de l'air primaire dans les combustibles solides, soit en raison d'un excès d'air globalement trop important, soit par un défaut local d'air primaire conduisant à une température locale trop élevée et favorisant ainsi l'oxydation de l'azote de l'air.
• Si la formation de sels fondus est inévitable, compte tenu de la température de la combustion primaire, les oxydes dont la température de fusion est comprise entre 1100 et 1400°C sont en partie fondus et en partie solides. La répartition entre matières solides et matières fondues dépend bien sûr de la composition des combustibles solides mais aussi, pour une composition donnée, de la température de la combustion primaire et donc des conditions de l'admission d'air primaire.

• Plus l'excès d'air primaire est important, plus la vitesse des gaz générés par la combustion primaire est importante, favorisant ainsi l'entraînement des particules solides et des gouttelettes liquides, qui vont participer à l'encrassement, à la corrosion et à l'érosion des équipements en aval de la chambre de combustion, notamment des échangeurs thermiques de la chaudière.
• La mauvaise répartition de l'air primaire sous la grille de la chambre de combustion affecte l'homogénéité de l'épaisseur de la couche de cendres présente sur la grille, alors que cette couche de cendres assure une protection efficace contre les rayonnements directs de la combustion primaire, pouvant générer un échauffement indésirable et, par-là, la destruction des composants de la grille. En effet, la couche protectrice de cendres, tout spécialement lorsque les combustibles solides sont de la biomasse qui, usuellement, génère moins de cendres que des déchets ménagers ou du charbon, peut rapidement disparaître d'une portion significative de la grille, du fait d'une combustion trop rapide et/ou d'envolées des cendres sous l'effet de vitesses trop importantes pour l'air primaire au niveau de cette portion de la grille. Ce dernier phénomène d'envolées est d'ailleurs accentué par le fait que si la couche de cendres disparaît ou s'amenuise localement, la portion correspondante de la grille voit sa perte de charge diminuer, engendrant au niveau de cette portion un flux d'air primaire plus important et plus rapide.
• la maîtrise insuffisante de la combustion primaire oblige à ajouter une quantité non négligeable d'air secondaire pour opérer la combustion secondaire mentionnée plus haut. Cet air secondaire est brassé avec les gaz issus de la combustion primaire afin de parfaire les réactions de combustion et d'oxyder ainsi les composés partiellement oxydés, tels que le monoxyde de carbone, les gaz de pyrolyse et, de manière plus générale, les composés organiques imbrûlés qu'ils soient gazeux ou particulaires. L'admission de l'air secondaire augmente le débit des fumées sortant de l'installation de combustion, ce qui nécessite de dimensionner en conséquence l'installation de combustion et, le cas échéant, toute la chaudière, ainsi que le traitement des fumées en aval de la chaudière. En particulier, l'air présent dans l'air secondaire en excès au-delà de la quantité stœchiométrique nécessaire à la combustion secondaire génère un volume de fumées plus élevé et donc une taille plus importante pour la chambre de combustion afin de maintenir les temps de séjour nécessaires à la combustion secondaire. De même, les fumées recirculées, présentes dans l'air secondaire, augmentent le volume de fumées, sans apporter d'oxygène pour la combustion secondaire, et donc augmentent la taille de la chambre de combustion. Dans tous les cas, l'admission d'air secondaire conduit à une augmentation de la consommation électrique pour les ventilateurs d'alimentation en air secondaire et les ventilateurs de tirage. De plus, l'admission de l'air secondaire tend à réduire le temps de séjour dans la chambre de combustion, ce qui, d'une part, est défavorable à la réduction des oxydes d'azote par des composés, tels que l'ammoniac ou l'urée, injectés dans la chambre de combustion et, d'autre part, retarde la vitrification d'oxydes fondus, conduisant à des encrassements en aval de la chambre de combustion, en particulier dans des échangeurs de la chaudière.

In practice, the primary air intake in excess and / or poorly distributed leads to numerous drawbacks:

• The formation of nitrogen oxides, by oxidation of the nitrogen contained in the primary air, is favored by poor control of the admission of primary air into solid fuels, either due to an excess of overall too much air, or by a local primary air defect leading to too high a local temperature and thus promoting oxidation of nitrogen in the air.
• If the formation of molten salts is inevitable, taking into account the temperature of the primary combustion, the oxides with a melting point of between 1100 and 1400 ° C are partly molten and partly solid. The distribution between solids and molten materials obviously depends on the composition of the solid fuels but also, for a given composition, the temperature of the primary combustion and therefore the conditions of the primary air intake.

• The greater the excess primary air, the greater the speed of the gases generated by the primary combustion, thus favoring the entrainment of solid particles and liquid droplets, which will participate in fouling, corrosion and erosion of equipment downstream of the combustion chamber, in particular the heat exchangers of the boiler.
• The poor distribution of the primary air under the grate of the combustion chamber affects the homogeneity of the thickness of the layer of ash present on the grate, while this layer of ash provides effective protection against direct radiation from the grate. primary combustion, which can generate unwanted heating and thereby destroy the components of the grate. Indeed, the protective layer of ash, especially when the solid fuels are biomass which usually generates less ash than household waste or coal, can quickly disappear from a significant portion of the grate, due to 'too rapid combustion and / or soaring ash under the effect of speeds too high for the primary air at this portion of the grate. This last phenomenon of soaring is moreover accentuated by the fact that if the layer of ash disappears or diminishes locally, the corresponding portion of the grid sees its pressure drop decrease, generating at the level of this portion a flow of larger and faster primary air.
• insufficient control of the primary combustion makes it necessary to add a not insignificant quantity of secondary air to operate the secondary combustion mentioned above. This secondary air is mixed with the gases resulting from the primary combustion in order to perfect the combustion reactions and thus oxidize the partially oxidized compounds, such as carbon monoxide, pyrolysis gases and, more generally, the compounds. unburnt organic, whether gaseous or particulate. Admission of secondary air increases the flow of flue gases leaving the combustion plant, which means that the combustion plant and, where applicable, the entire boiler, as well as the flue gas treatment, need to be dimensioned accordingly. downstream of the boiler. In particular, the air present in the secondary air in excess beyond the stoichiometric quantity necessary for the secondary combustion generates a higher volume of smoke and therefore a larger size for the combustion chamber in order to maintain the combustion times. stay necessary for secondary combustion. Likewise, the recirculated fumes, present in the secondary air, increase the volume of fumes, without adding oxygen for secondary combustion, and thus increase the size of the combustion chamber. In all cases, the intake of secondary air leads to an increase in power 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 for 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 exchangers of the boiler.

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

One of these techniques consists in regulating the total flow rate of the primary air as a function of the oxygen content in the fumes from the combustion installation. In practice, the measurement of this oxygen content is carried out in the “cold” fumes, typically at the boiler outlet, to ensure the resistance over time of the measurement sensor. 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 being 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 intake of the primary air. Moreover, this measurement of the oxygen content does not accurately reflect the heterogeneity of solid fuels. In addition, the measurement of the oxygen content in the 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 get around this difficulty, the oxygen content can be measured on “dry” fumes, which requires taking and drying smoke samples before measuring the oxygen content. However, the reaction time is then lengthened to allow this sampling and this drying to be carried out, typically of the order of twenty to forty additional seconds.

Another technique, which can be combined with the previous one, consists in distributing the primary air by means of several boxes, which are arranged under the grille and which are each equipped, on their air inlet, with a flow adjustment member for control the primary air flow passing through the box. The regulators thus make it possible to distribute the total flow of primary air between the respective outlets of the boxes. In practice, the adjustment of the regulating members is often carried out only occasionally by an operator, for example depending on the power. average calorific value of solid fuels, determined over a long period of time, or as a function of a known change in the composition of solid fuels. In more sophisticated installations, the distribution of the primary air by the boxes can be adjusted as a function of the infrared radiation emitted by the layer formed by the solid fuels in the combustion chamber. This infrared radiation is measured by an infrared camera installed on the ceiling of the combustion chamber. However, in addition to the costly nature of such an infrared camera and the associated image processing, this infrared camera does not provide information on the effective temperature of the primary combustion of solid fuels, but only provides a partial indication of the temperature at the surface of the solid fuels. the whole of the solid fuel layer, this partial indication being furthermore disturbed by particles and dust, present vertically between the solid fuel layer and the infrared camera. As a result, the total primary air flow is often voluntarily increased, to prevent the primary combustion from being incomplete.

WO 90/09552 proposes that the primary air flows supplying boxes distributed under a combustion grate be controlled as a function, among other things, of temperature measurements made in the combustion chamber by dedicated temperature sensors. These temperature sensors are either infrared cameras, which observe the solid fuel bed over a large area, or individual infrared detectors, which are divided into groups according to areas of the grid. In all cases, the temperature measurements made by these detectors relate to the surface of the bed of solid fuels.

EP 1,489,355 also proposes to control the primary air flow according to various measurements, including temperature measurements from two temperature sensors. The first sensor is arranged in the ceiling of the combustion chamber, pointing to the downstream end zone of the grate. The second sensor is arranged downstream of the secondary air intake and measures the temperature of the gases resulting from the secondary combustion.

Thus, the performance of the various existing techniques is limited.

The aim of the present invention is to provide improved regulation of a solid fuel combustion installation, in order to control the primary combustion carried out in this installation.

To this end, the subject of the invention is a method for regulating a combustion installation, as defined in claim 1.

The subject of the invention is also a combustion installation, as defined in claim 10.

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 primary combustion, by performing their measurement as close as possible to the solid fuels being burned in order to know the intensity of the radiation from the primary combustion, in in particular the radiation of the combustion gases at the time of their generation by the primary combustion and the radiation of the particles contained in these combustion gases. The measurements provided by the or each pyrometer are representative, in real time, of the temperature of the primary combustion, in the sense that these measurements are instantaneous and integrate the thermal conditions on the optical path between the pyrometer and the solid fuels, in particular without be affected by contamination or wall effects. The temperature thus measured by this or these pyrometers can be qualified as the radiative temperature of the primary combustion.

The invention also provides for using this radiative temperature to control the primary air flow and, advantageously, the distribution of this primary air flow in 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 primary combustion, that is to say of the theoretical temperature for the primary combustion to be complete. , in the sense that, like the adiabatic temperature, the radiative temperature of the primary combustion is very sensitive to both the quantity of air consumed by the primary combustion and the quantity of fuel burned during the primary combustion. Thus, for a given solid fuel zone, 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 solid fuels actually burned and the air flow rate effectively consumed in the zone of combustion. Thanks to the invention, the primary air flow admitted into the combustion chamber is regulated as a function of 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 primary combustion in several zones of the solid fuels, by respective pyrometers, and for adjusting the primary air flow rate zone by zone. In all cases, the invention allows to control in real time the admission of primary air into the combustion chamber so as to provide, advantageously zone by zone, the quantity of primary air necessary and sufficient for the primary combustion to be complete, in other words so as to optimizing, advantageously zone by zone, the ratio between the primary air admitted and the quantity of fuel burnt. This control of primary combustion, made possible by the invention, has many advantages, as detailed below.

The invention is applicable to combustion installations in the combustion chamber of which the solid fuels form either a fluidized bed or a moving bed on a grid. In the second case, the invention is of remarkable interest, in connection with the possibility of distributing the bed of solid fuels into several successive zones according to the direction of advance of the bed, as explained in more detail below.

Additional advantageous characteristics of the control method and of the combustion installation according to the invention are specified in the other claims.

• [Fig. 1] la figure 1 est un schéma d'une installation de combustion conforme à l'invention ;
• [Fig. 2] la figure 2 est une coupe schématique partielle selon la ligne II-II de la figure 1 ;
• [Fig. 3] la figure 3 est une vue similaire à la figure 1, illustrant un autre mode de réalisation d'une installation de combustion conforme à l'invention ; et
• [Fig. 4] la figure 4 est une vue à plus grande échelle d'un encadré IV de la figure 3, illustrant une variante de la partie correspondante de l'installation de combustion.

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

• [ Fig. 1 ] the figure 1 is a diagram of a combustion installation according to the invention;
• [ Fig. 2 ] the figure 2 is a partial schematic section on line II-II of the figure 1 ;
• [ Fig. 3 ] the figure 3 is a view similar to the figure 1 , illustrating another embodiment of a combustion installation according to the invention; and
• [ Fig. 4 ] the figure 4 is a view on a larger scale of a Box IV of the figure 3 , illustrating a variant of the corresponding part of the combustion installation.

On the figure 1 is shown a combustion installation 1 suitable for burning solid fuels C.

The 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 in humidity, as mentioned in the introductory part of this document.

The combustion installation 1 typically belongs to a boiler which makes it possible to produce water vapor by using the heat of the fumes coming from the combustion installation.

• une paroi arrière 11, au travers de laquelle les combustibles solides C sont chargés à l'intérieur de la chambre de combustion par, par exemple, une goulotte externe 20,
• par une paroi avant 12, au travers de laquelle les combustibles solides C, une fois brûlés, sortent de la chambre de combustion via une évacuation 21, et
• par deux parois latérales 13, qui sont horizontalement distantes l'une de l'autre et qui relient chacune les parois arrière 11 et avant 12, une seule de ces deux parois latérales 13 étant visible sur la figure 1.

The combustion installation 1 comprises a combustion chamber 10 adapted so that the solid fuels C are introduced therein and burn there according to a primary combustion in the presence of air, called primary air P. The combustion chamber 10 is delimited laterally by:

• a rear wall 11, through which the solid fuels C are loaded inside the combustion chamber by, for example, an external chute 20,
• by a front wall 12, through which the solid fuels C, once burned, leave the combustion chamber via an outlet 21, and
• by two side walls 13, which are horizontally distant from each other and which each connect the rear 11 and front 12 walls, only one of these two side walls 13 being visible on the figure 1 .

The combustion chamber 10 is designed for, once the solid fuels C are loaded therein, to allow these solid fuels C to stay for a time necessary, typically several minutes, to carry out the primary combustion. During their primary combustion, the solid fuels C generate gases which, in the immediate vicinity of the solid fuels C, are referenced G on the figure 1 . The combustion chamber 10 is designed to channel these gases, up to their exit from the combustion chamber 10 from which escape fumes F circulating in the equipment of the boiler, such as heat exchangers.

In the exemplary embodiment considered on figure 1 , the combustion chamber 10 is provided to admit therein a secondary air S, consisting of air and / or recirculated fumes. As shown on the figure 1 , the admission of the secondary air S into the combustion chamber 10 is located vertically at a distance from the solid fuels C present in the combustion chamber, so that the aforementioned gases G are only generated by the primary combustion of the solid fuels C , without including secondary air S, while the mixture between these gases G and secondary air S is referenced GS on the figure 1 and forms the fumes F at the outlet of the combustion chamber 10. In practice, the secondary air can thus be introduced in several vertical levels, as indicated on the figure. figure 1 .

The primary combustion leads to the fact that, on the one hand, the non-volatile part of the solid fuels C is completely burned, except for unburned particles 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, that is to say partially burnt, by forming the gases G. The secondary air S supplies secondary combustion, namely the combustion of the gases G to form the gases GS, thus completely burning the volatile part of the solid fuels C.

In the embodiment considered here, the combustion chamber 10 comprises a grid 14 which delimits the bottom of the combustion chamber. This grate 14 is designed to support the solid fuels C inside the combustion chamber 10 so that, as illustrated in the figure figure 1 , these solid fuels form a bed which rests on the grid 14, extending from the rear wall 11 to the front wall 12. At the rear wall 11, the bed is supplied with solid fuels to be burned, for example by the outer chute 20, while, at the level of the front wall 12, the bed is evacuated, in particular by falling into the evacuation 21. Between the rear walls 11 and front 12, the bed of solid fuels C is movable in a direction of advance Z in the combustion chamber 10. Thus, the direction of advance Z extends from the rear wall 11 to the front wall 12, while being parallel to the grate 14. In practice, the grate 14 can also well be inclined in relation to a horizontal plane, as on the figure 1 , that extend in a horizontal plane. In all cases, the grid 14 has two side edges, which are opposite to each other in a horizontal direction perpendicular to the direction of advance Z and which respectively extend 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 in the direction of advance Z, are not restrictive of the invention: in a manner known per se, the grate 14 may be provided inclined to allow the gravity drive of the bed and / or be provided movable to act on the drive of the bed, then being driven by a movement allowing a slow displacement of the solid fuels from their point of arrival on the grate, where they are not yet burnt, to their outlet point of the grate, where they are completely burnt. In the case where the grid is movable, various drive systems are known, so that, for example, the grid turns like a conveyor belt, or the bars of the grid move alternately, etc.

In practice, the embodiment of the grid 14 can also be linked to the device for introducing the solid fuels C into the combustion chamber. Indeed, rather than supplying the combustion chamber 10 with solid fuels through the rear wall 11 by means of the external chute 20 as on the figure 1 , the solid fuels C can be introduced through another wall of the combustion chamber, in particular through the front wall 12, the introduction device then being an external, mechanical and / or pneumatic injector, which is to even to project solid fuels into the chamber combustion chamber, from the front wall to the region of the grate 14, adjoining the rear wall 11.

Whatever the embodiment of the grid 14, the primary air P is admitted under the grid and this grid 14 is designed to be passed from bottom to top by the primary air P to allow the latter to enter. in the combustion chamber 10 and thus reach the solid fuel bed C.

The combustion installation 1 also comprises an intake device 30 making it possible to supply the combustion chamber 10 with the primary air P. In the embodiment considered here, the intake device 30 is, at least for its downstream outlet, arranged below the grid 14.

As envisioned on the figure 1 , the intake device 30 comprises several separate boxes, which here are five in number, being respectively referenced 31.1, 31.2, 31.3, 31.4 and 31.5, and which are arranged under the grid 14, succeeding each other in the direction of Z advancement. Each of the boxes 31.1 to 31.5 is designed to form, from the primary air P, a primary air flow P1 to P5. To this end, each box 31.1 to 31.5 is designed to receive primary air P via an air inlet 32.1 to 32.5 from the box and to channel the air passing through it to an air outlet 33.1 to 33.5 d 'where emerges the corresponding primary air flow P1 to P5. The primary air flow rate 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 the intake device 30, corresponds to the sum of the respective flow rates of the primary air flow P1 to P5.

The air inlets 32.1 to 32.5 are designed to be supplied with the primary air P, being connected, upstream of the boxes 31.1 to 31.5, to a common supply pipe 35, carrying the primary air P.

The air outlets 33.1 to 33.5 are arranged under the grid 14, being respectively located vertically plumb with corresponding regions 14.1 to 14.5 of the grid, which succeed one another in the direction of advance Z. Thus , each of the boxes 31.1 to 31.5 opens upwards, via its air outlet 33.1 to 33.5, on the underside of the corresponding region 14.1 to 14.5 of the grille 14 and sends its primary air flow P1 to P5 respectively to the regions 14.1 to 14.5 of the grid, as shown in the figure 1 . It will be understood that the regions 14.1 to 14.5 of the grate 14 are fixed in the combustion chamber 10, whatever the embodiment of the grate 14: thus, when the grate 14 is fixed in the combustion chamber 10, each of the regions 14.1 to 14.5 corresponds to a part of this grid, which is unchanged during the operation of the combustion plant 1; when the grid 14 is movable, each of the regions 14.1 to 14.5 is, at each instant of operation of the combustion installation 1, occupied by a part of the grate 14, this part being able to change region during the movement of the grate 14. On the figure 1 , the region 14.1 is, among the regions 14.1 to 14.5, the closest to the rear wall 11 while the region 14.5 is the closest to the front wall 12, this region 14.5 succeeding the region 14.4 which itself succeeds region 14.3 which itself succeeds region 14.2 which itself succeeds region 14.1 in the direction of advance Z.

Z1 to Z5 are denoted by zones of the solid fuel bed C, which follow one another in the direction of advance Z and which are respectively located vertically plumb with regions 14.1 to 14.5 of grid 14. In other words, zone Z1 of the solid fuel bed C rests on region 14.1 of grid 14, area Z2 rests on region 14.2, and so on, up to zone Z5 of the bed, which rests on region 14.5 of grid 14. In a similar manner to regions 14.1 to 14.5 of grid 14, zones Z1 to Z5 of the bed of solid fuels C are fixed in combustion chamber 10. It is therefore understood that, at a given moment in the operation of the combustion installation 1, each of the zones Z1 to Z5 of the bed consists of a part of the solid fuels C and that, at a later instant in the operation of the combustion installation, each of the zones Z1 to Z5 of the bed is occupied by another part of solid fuels C, at least partially different from the p Aforementioned artie of these solid fuels C, due to the displacement of the bed in the direction of advance Z. Thus, during their primary combustion, the solid fuels C progressively pass, in the combustion chamber 10, through the zone Z1 of the bed. formed by these fuels C on the grid 14, then by the zone Z2, then by the zone Z3, then by the zone Z4, and finally by the zone Z5 of the bed. By thus progressing through zones Z1 to Z5, the solid fuels C undergo the progressive effects of primary combustion, namely first their drying, then gasification for their volatile part and combustion for their non-volatile part, and finally a cooling and a combustion finish for their non-volatile part. By way of example, zone Z1 is intended to correspond to a drying zone for solid fuels C, zones Z2 and Z3 are intended to correspond to a gasification zone for the volatile part of the solid fuels and combustion for the non-volatile part of the solid fuels, and the zones Z4 and Z5 are provided to correspond to a combustion finishing zone for the non-volatile part of the solid fuels and cooling.

As shown schematically on the figure 1 , each of the air inlets 32.1 to 32.5 of the boxes 31.1 to 31.5 is provided with a flow adjustment member 34.1 to 34.5. The embodiment of these flow rate regulating members 34.1 to 34.5 is not restrictive of the invention, as long as each of these flow rate adjusting members 34.1 to 34.5 makes it possible to control the flow rate of the primary air flow P1 to P5 associated with the corresponding box. The flow rate regulators are for example valves, registers, etc.

In all cases, each of the flow rate regulating members 34.1 to 34.5 is designed to be controlled by a control unit 40 of the combustion installation 1. The control unit 40 comprises electronic and / or electromechanical components, to even to generate control signals, which are transmitted to the flow control members 34.1 to 34.5 in order to actuate the latter individually to control the respective flow rates of the primary air flows P1 to P5. Here again, the material specificities of the control unit 40, as well as those of the connection between the latter and the flow rate adjustment members 34.1 to 34.5 are not limiting of the invention.

As shown on the figure 1 , the combustion installation 1 further comprises optical pyrometers, five of them being visible on the figure 1 . All the pyrometers 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 take temperature measurements. from the wall of the combustion chamber 10, on which they are provided. In the exemplary embodiment considered in the figures, all these pyrometers are integrated into the side walls 13: more precisely, the side wall 13, visible in the figure. figure 1 , thus integrates five pyrometers 50.1 to 50.5. These pyrometers 50.1 to 50.5 are respectively associated with zones Z1 to Z5 of the bed of solid fuels C and, therefore, to regions 14.1 to 14.5 of the grid 14, so that the pyrometer 50.1 measures a temperature of the primary combustion of the fuels solids C in zone Z1, the pyrometer 50.2 measures a temperature of the primary combustion of solid fuels in zone Z2, and so on, up to pyrometer 50.5 which measures a temperature of the primary combustion of solid fuels in zone Z5 . The temperature measurements are carried out by pyrometers 50.1 to 50.5 as close as possible to the bed of solid fuels C, in particular by pointing the gases G respectively coming from zones Z1 to Z5 of the bed and thus measuring the radiation of the gaseous compounds and of the solid particles present in these G.

The precise arrangement of the pyrometers 50.1 to 50.5 on the side wall 13 is not restrictive of the invention. In practice, it is understood that the sighting axis of each pyrometer 50.1 to 50.5 is parallel or substantially parallel, that is to say parallel to within a few degrees, at the plane of the grid 14. Preferably, in particular to limit the optical path between the pyrometers and the primary combustion, in particular the G gases, and to have maximum integration of the thermal radiation emitted by the primary combustion, the pyrometers 50.1 to 50.5 are distributed over the side wall 13 in the direction of advance Z, being respectively located vertically in line with the zones Z1 to Z5 of the solid fuel bed C, as shown schematically on the figure 1 . Furthermore, in the vertical direction, each of the pyrometers 50.1 to 50.5, which are necessarily above the grid 14, is preferably located at a vertical distance from the latter, which is between half and two-thirds of the grid. distance between the grid 14 and the secondary air inlet S: in this way, the pyrometers 50.1 to 50.5 are located in the upper half of the vertical gap between the grid 14 and the secondary air inlet S, to prevent the flames generated by the primary combustion from disturbing the radiation measurements made by the pyrometers, without being in the upper third of this gap, to prevent the "cold" introduced into the combustion chamber 10 by the secondary air S does not interfere with the measurements made by the pyrometers.

Likewise, the type of optical pyrometers 50.1 to 50.5 is not limiting on the invention, since these pyrometers provide temperature measurements based on the intensity of the wavelengths emitted by a radiating body. Preferably, the pyrometers 50.1 to 50.5 are bichromatic laser pyrometers, that is to say that, for the purposes of measuring the temperature of the primary combustion, each pyrometer emits, in the combustion chamber 10, at least one beam laser with two different wavelengths: pyrometers are therefore less sensitive to dust emissions. By way of example, the spectral response of these pyrometers is of the order of 1 μm.

In addition, the specific features relating to the focusing of the pyrometers 50.1 to 50.5 are not limiting of the invention either. This being the case, a preferred embodiment is illustrated on figure 2 for the pyrometer 50.1, it being understood that this embodiment is applicable to the other pyrometers 50.2 to 50.5. So, as shown on figure 2 , the pyrometer 50.1 is designed, for the purpose of measuring the temperature of the primary combustion, to emit two laser beams into the combustion chamber 10, via an opening 13.1 of the side wall 13. Each of these two laser beams can be bichromatic, as mentioned 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 aperture 13.1, while keeping a large divergent field of view for the pyrometer.

In all cases, the measurements from the pyrometers 50.1 to 50.5 are transmitted, by all appropriate forms of connection, to the control unit 40 in order to be processed automatically by the latter, in particular by a computer or a similar component of the latter. . Whatever the specifics of the treatment which is carried out by the control unit and examples of which will be given later, the control unit 40 is designed to control each of the flow rate regulators 34.1 to 34.5, as described above. , from the temperature measurements respectively provided by the pyrometers 50.1 to 50.5.

Hereinafter, aspects relating to the regulation of the combustion plant 1 are described in more detail.

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 supplied under normal conditions, at the same time, 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 primary 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 will therefore not be presented here further. .

While the combustion chamber 10 is operating under normal conditions, the pyrometers 50.1 to 50.5 continuously measure the temperature of the primary combustion of the solid fuels in, respectively, zones Z1 to Z5 of the bed. The temperature measurements made by the pyrometers 50.1 to 50.5 are sent continuously to the control unit 40 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 40, the latter compares in real time the temperature measurements provided by each of the pyrometers 50.1 to 50.5 with a temperature setpoint which is specific to the pyrometer in question, in other words which is specific to the zone associated with this pyrometer among the zones Z1 to Z5 of the bed of solid fuels. Depending on the result of this comparison specific to each of the zones Z1 to Z5, the control unit 40 transmits in real time to the corresponding flow rate control member, that is to say to that of the flow rate control members 34.1 to 34.5 which is associated with the zone concerned, an actuation command so that the flow adjustment member acts on the flow rate of the primary air flow, among the primary air flows P1 to P5, which corresponds to the zone associated with the pyrometer concerned. Through example, if, for zone Z2, the temperature measured by the pyrometer 50.2 is 5% lower than the temperature setpoint specific to zone Z2 for more than five to ten consecutive seconds, the control unit 40 actuates the device flow rate adjustment 34.2 to increase the flow rate of the primary air flow P2 by 10%.

In practice, the temperature set points respectively specific to zones Z1 to Z5 are previously supplied to the control unit 40. These temperature set points can be pre-set for the combustion installation 1 or, preferably, are determined, in particular by calculation. , from a reference temperature to which a correction is applied which is linked to the zone concerned among the zones Z1 to Z5 and which, where appropriate, is also linked to the characteristics of the solid fuels S, possibly continuously measured , such as their calorific value, humidity, etc. The aforementioned reference temperature is, for its part, either pre-fixed or determined, if necessary continuously, from the oxygen content in the flue gases F, this content being typically measured at the outlet of the boiler, as mentioned in the introductory part of this document.

Of course, other treatments than that which has just been described can be implemented by the control unit 40, in particular as long as these other treatments compare the measurements of the pyrometers 50.1 to 50.5 with temperature setpoints. respective, which are specific to zones Z1 to Z5, in order to individually control the flow rate of the primary air flows P1 to P5. In all cases, it will be understood that the control unit 40 and the flow rate regulating members 34.1 to 34.5 jointly form regulation means which make it possible, from the measurements of the pyrometers 50.1 to 50.5, to regulate the respective flow rates of the flows. primary air P1 to P5 and, thereby, the total flow rate of primary air P supplied by the intake device 30 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 primary air flows P1 to P5 from being too low or too high, the actuation of the flow rate regulators 34.1 to 34.5, controlled by the control unit 40, can be expected within a substantial but limited range of variation. The limits of this range of variation are predetermined by experience and / or by other operating parameters of the combustion plant 1, such as the tonnage of solid fuels C introduced into the combustion chamber 10, the pressure of l. 'primary air P in the supply line 35, the flow rate of steam produced by the exchanger (s) of the boiler, etc. Also for control and safety, the reference temperature, mentioned above, can be compared to the average instantaneous temperature measurements provided by pyrometers 50.1 to 50.5, weighted by the size of zones Z1 to Z5 respectively associated with these pyrometers.

On the figure 3 is shown, by way of a variant of the combustion installation 1, a combustion installation 101.

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

The combustion installation 101 comprises a combustion chamber 110 which is functionally, or even structurally, similar to the combustion chamber 10 of the combustion installation 1. Thus, the combustion chamber 110 is designed to be supplied with the solid fuels C , the primary air P and the secondary air S, in order to operate the primary combustion of the solid fuels C and the secondary combustion of the gases G, as explained in detail above for the combustion chamber 10. In particular, the chamber combustion chamber 110 comprises a rear wall 111, a front wall 112, side walls 113 and a grate 114, which are respectively similar functionally, even structurally, to the components 11 to 14 of the combustion chamber 10. In addition, the combustion chamber combustion 110 is associated with an outer chute 120 and an outlet 121, which are respectively similar functionally, or even structurally, to the outer chute 20 and the evacuation 21.

The combustion plant 101 also comprises an intake device 130 which is functionally similar to the intake device 30 of the combustion plant 1. The structure of the intake device 130 differs from that of the intake device 30.

The intake device 130 comprises a single box 131 having an air inlet 132 intended to be supplied with the primary air P. The air inlet 132 opens into a casing 133 of the box 131, arranged below. grid 114.

As shown schematically on the figure 3 , the air inlet 132 is divided into several subdivisions, which, in the example considered here, are three in number and which are respectively referenced 132.1, 132.2 and 132.3. Each of the subdivisions 132.1 to 132.3 connects a supply line 135, which carries the primary air P and which is common to the various subdivisions, to the casing 133, opening into the internal volume of this casing 133. Thus, the subdivisions 132.1 to 132.3 all open into a single and the same primary air distribution volume, which is arranged under the grille 114 and which is formed by the internal volume of the casing 133. The subdivisions 132.1 to 132.3 respectively transport primary air streams V1 , V2 and V3, which are distinct from each other. Each of these air streams V1 to V3 thus flows, in the corresponding subdivision 132.1 to 132.3, from the supply line 135 to the internal volume of the casing 133.

Each of the subdivisions 132.1 to 132.3 is provided with a flow rate adjustment member 134.1 to 134.3 making it possible to control the flow rate of the corresponding primary air stream V1 to V3. The embodiment of the flow adjustment members 134.1 to 134.3 is not restrictive of the invention.

In the example considered on figure 3 , each of the flow regulating members 134.1 to 134.5 comprises a register 136, which is arranged inside the corresponding subdivision 132.1 to 132.3 and which is provided to pivot on itself in order to regulate the flow rate of the stream. corresponding primary air V1 to V3. This register 136 is for example a butterfly register.

An alternate embodiment for the flow regulators 134.1 to 134.3 is illustrated on figure 4 . More precisely, the figure 4 shows an alternative embodiment for the flow regulator 134.1, it being understood that this alternative embodiment can be applied to the other flow regulators 134.2 and 134.3. In the embodiment illustrated on figure 4 , the flow rate control member 134.1 comprises two flaps 138A and 138B, which are arranged symmetrically inside the subdivision 132.1, each being articulated with respect to this subdivision. By means of their articulated displacement relative to the subdivision 132.1, the flaps 138A and 138B move away from or approach one another, symmetrically with respect to each other, thus modifying the size of the flow section of Subdivision 132.1, while keeping this flow section centered on the central axis of Subdivision 132.1, as shown schematically on figure 4 . The symmetry of the arrangement and the movements of the flaps 138A and 138 makes it possible to control the flow rate of the primary air stream V1 with a low pressure drop, in particular without significantly modifying the flow speed of the stream of air. 'air V1 in subdivision 132.1. In practice, the pressure drop is all the more limited as the flaps 138A and 138B are slightly inclined, typically at less than 45 °, relative to the flow axis of the air stream V1 in the subdivision 132.1 . Thus, during variations in the primary air flow which are operated for example during load variations of the combustion installation 101, maintaining the speed of the air streams V1, V2 and V3 in the box 130 allows a lower variation in the penetration of the air streams into the box, this penetration being proportional to the quantity of movement, that is to say to the product between the flow rate and the speed, and consequently makes it possible to more easily maintain the distribution of air flows P1, P2 and P3, defined a little further on, between the different zones Z1, Z2 and Z3, also defined a little further on. In order to control the flaps 138A and 138B in movement, the flow rate adjustment member 134.1 comprises an actuator 139, such as a cylinder, which is connected to the flaps 138A and 138B in an appropriate manner, for example by connecting rods, as illustrated. schematically on the figure 4 .

According to an optional arrangement, illustrated by figure 3 , the air inlet 132 extends substantially horizontally, by causing the primary air streams V1 to V3 to flow substantially horizontally in the subdivisions 132.1 to 132.3, until thus opening into the internal volume of the casing 133 passing laterally through this casing. In other words, the casing 133 is not arranged in the vertical upward extension of the air inlet of the casing. In addition, for ventilation reasons which will appear later, the subdivisions 132.1 to 132.3 of the air inlet 132 are then arranged one above the other: on the figure 3 , the subdivision 132.1 is arranged above the subdivision 132.2 which is itself arranged above the subdivision 132.3.

Whatever the construction specifications of the subdivisions 132.1 to 132.3 of the air inlet 132, the casing 133 is fitted internally to direct the primary air streams V1 to V3, leaving the air inlet 132, towards respective regions 114.1, 114.2 and 114.3 of the grid 114, which follow one another in the direction of advance Z. In other words, the internal volume of the casing 133 is provided with arrangements which make it possible to act on the flow primary air streams V1 to V3, once out of subdivisions 132.1 to 132.3, so that these primary air streams form, at the outlet of box 131, respective primary air streams P1 ', P2' and P3 ', which are sent, below the grid 114, respectively to the regions 114.1 to 114.3 of this grid. It is understood that the air streams V1 to V3 respectively leaving the subdivisions 132.1 to 132.3 thus all penetrate into the same single volume formed by the internal volume of the casing 133, where the aforementioned aeraulic arrangements allow the interdependent flow and the guidance of the flows. primary air P1, P2 and P3 to regions 114.1 to 114.3 of the grille 114. Thus, for the combustion plant 101, these primary air flows P1 'to P3' are, jointly, functionally similar to the flows primary air P1 to P5 described above in connection with the combustion system 1.

In the embodiment shown in figure 3 , the corresponding internal arrangements of the box 101 include plane deflectors 137.1 and 137.2. Each deflector 137.1, 137.2 forms an angle of between 0 and 20 ° with the vertical, which amounts to saying that each of the deflectors 137.1 and 137.2 extends either strictly vertical, or slightly inclined relative to the vertical. The deflectors 137.1 and 137.2 are arranged inside the casing 133 in a fixed manner or in a slightly movable manner by manual adjustment. In all cases, this arrangement of the deflectors 137.1 and 137.2 has ventilation and practical advantages: on the one hand, the deflectors 137.1 and 137.2 can thus modify the direction of the air flows inside the casing 133, from the substantially horizontal flow direction for the primary air streams V1 to V3 to the substantially vertical flow direction for the primary air stream P1 'to P3'; on the other hand, the deflectors 137.1 and 137.2 prevent the accumulation of ash which falls on them from the grid 114. Furthermore, to act selectively on the various primary air streams V1 to V3, the deflectors 137.1 and 137.2 are arranged in a stepped manner: more precisely, the respective lower ends of the deflectors 137.1 and 137.2 are stepped relative to one another. In the example considered on figure 3 , the lower end of the deflector 137.1 is located, vertically, substantially at the same level as the separation between the subdivisions 132.1 and 132.2 and, horizontally, in half of the internal volume of the casing 133, facing the air inlet 132; as for the lower end of the deflector 137.2, it is located, vertically, substantially at the level of the separation between the subdivisions 132.2 and 132.3 and, horizontally, in half of the internal volume of the casing 133, opposite the air inlet 132. Of course, the specific features of the stepping of the lower ends of the deflectors 137.1 and 137.2 may differ from what has just been described in connection with the example of figure 3 . In practice, this staging can be optimized by preliminary computations of computational fluid mechanics, by considering the combustion installation 101 in a nominal operating regime. In all cases, the staging of the respective lower ends of the deflectors 137.1 and 137.2 is provided so that the deflectors 137.1 and 137.2 interact selectively on the primary air streams V1 to V3 to orient the latter respectively towards the corresponding regions 114.1 to 114.3 of grid 114: in the example of figure 3 , the primary air stream V1 is deflected by the deflector 137.1, the primary air flow V2 escapes the deflector 137.1 but is deflected by the deflector 137.2, and the air stream V3 escapes the deflectors 137.1 and 137.2.

Whatever the internal arrangements of the casing 133 making it possible to form the primary air flows P1 'and P3' from the primary air streams V1 to V3, these primary air flows P1 'to P3' are, as indicated above, respectively associated with portions 114.1 to 114.3 of the grid 114 and, thereby, respectively associated with corresponding zones Z1 ′ to Z3 ′ of the bed formed by the solid fuels C on the grid 114. Together, these zones Z1 ′ to Z3 ′ of the bed are functionally similar to the zones Z1 to Z5 described above in connection with the combustion installation 1. Advantageously, and taking into account the explanations given previously in connection with the combustion installation 1, the zone Z1 of the bed of solid fuels in the combustion installation 101 corresponds to a drying zone for the solid fuels C, the zone Z2 corresponds to a gasification zone for the volatile part of solid fuels and combustion for the non-volatile part of these solid fuels, and zone Z3 corresponds to a cooling and combustion finishing zone for the non-volatile part of the fuels solid.

In continuation of the foregoing considerations, an advantageous optional arrangement consists in providing that the subdivisions 132.1 to 132.3 of the air inlet 132 do not have the same cross section, but have cross sections whose respective sizes are different from the from each other: in the example shown on figure 3 , the subdivision 132.2 is planned with a size larger, of the order of double, than that of the section of each of the subdivisions 132.1 and 132.3, because, in nominal operating mode for the combustion plant 101, the quantity d 'primary air to be transported by subdivision 132.2, whose corresponding vein V2 is associated with zone Z2, is expected to be of the order of twice that to be transported by each of subdivisions 132.1 and 132.3, whose corresponding veins V1 and V3 are respectively associated with zones Z1 and Z3.

The combustion installation 101 also comprises a control unit 140 and three pyrometers 150.1, 150.2 and 150.3, which are respectively functionally similar, or even structurally identical, to the control unit 40 and to the pyrometers 50.1 to 50.5 of the installation of combustion 1. Thus, taking into account the explanations given previously in connection with the combustion installation 1, it is understood that the pyrometers 150.1 to 150.3 are respectively associated with the zones Z1 to Z3 of the bed of solid fuels C, by measuring the temperature of primary combustion in, respectively, zones Z1 to Z3 and by supplying the corresponding temperature measurements to the control unit 140 which, by automatic processing, controls the individual actuation of the flow rate regulators 134.1 to 134.3, each of these flow rate regulators being thus adjusted as a function of the measurements of the pyrometer associated with the zone to which the primary air stream is sent, of which the flow rate is controlled by this flow rate regulator.

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 in detail here, referring to the considerations developed above for regulation of the combustion system 1.

Whatever the specific construction and regulation features of the combustion installation 101, the latter can provide, in particular compared to the combustion installation 1, economic and compact advantages. Indeed, instead of using the multiple separate boxes 31.1 to 31.5, the combustion installation 101 provides only the single box 131 to admit the primary air P under the grid 114, by subdividing its air inlet. 132 and the presence of internal aeraulic arrangements of its casing 133, such as the deflectors 137.1 and 137.2, while controlling the spatial and quantitative distribution of the air admitted into the combustion chamber 110. In addition, by arranging the inlet 132 horizontally and by connecting it laterally to the casing 133, the intake device 130 is even more compact, avoiding costly raising of the combustion chamber 110 relative to the supply line 135. D other advantages are deductible from the foregoing by those skilled in the art.

• Pour une zone donnée du lit des combustibles solides C, parmi les zones Z1 à Z5 ou parmi les zones Z1' à Z3', plus d'un pyromètre peut être prévu. En particulier, une paire de pyromètres peut ainsi être associée à au moins l'une des zones Z1 à Z5 ou Z1' à Z3', voire à chacune des zones Z1 à Z5 ou Z1' à Z3', les deux pyromètres de chaque paire étant prévus sur respectivement l'une et l'autre des deux parois latérales 13, typiquement en regard horizontal l'un de l'autre, ce qui permet de mesurer la température de la combustion primaire dans la zone concernée depuis chaque côté latéral de la grille 14. Les mesures provenant respectivement des différents pyromètres pour une zone du lit donnée sont alors moyennées pour les besoins du traitement par l'unité de commande 40 ou 140.
• Plutôt que d'ajuster individuellement les débits respectifs des flux d'air primaire P1 à P5 ou P1' à P3', il peut être prévu de réguler le débit de l'air primaire dans la conduite d'alimentation 35 ou 135, au moyen d'un organe de réglage de débit ad hoc, prévu sur cette conduite d'alimentation et commandé par l'unité de commande 40 ou 140. La régulation de l'installation de combustion permet alors d'ajuster le débit total de l'air primaire P transitant par le dispositif d'admission 30 ou 130. Dans ce cas, un unique pyromètre, similaire aux pyromètres 50.1 à 50.5 et 150.1 à 150.3, peut être utilisé. Bien entendu, plusieurs pyromètres peuvent aussi être utilisés, leur mesure respective étant moyennée pour les besoins du traitement de l'unité de commande 40 ou 140. Le débit total de l'air primaire ainsi régulé est ensuite réparti dans les différentes zones par les organes de réglages de débit 34.1 à 34.5 ou 134.1 à 134.3.

• Le nombre, selon lequel le lit des combustibles solides C est réparti en zones et donc selon lequel la grille 14 ou 114 est répartie en régions, peut différer de celui envisagé pour les installations de combustion 1 et 101. Ceci étant, ce nombre est préférentiellement d'au moins trois afin d'inclure les trois principales zones correspondant aux effets physico-chimiques successifs de la combustion primaire, à savoir une zone de séchage pour les combustibles solides, une zone de gazéification pour une partie volatile des combustibles solides et de combustion pour une partie non volatile des combustibles solides, et une zone de refroidissement et de finition de combustion pour la partie non volatile des combustibles solides.
• Il peut être envisagé de supprimer l'admission de l'air secondaire S dans l'installation de combustion 1 ou 101. Dans ce cas, chacun des pyromètres 50.1 à 50.5 ou 150.1 à 150.3 est préférentiellement situé, au-dessus de la grille 14 ou 114, à une distance verticale comprise entre 1,5 m et 5 m vis-à-vis de cette grille.

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

• For a given zone of the bed of solid fuels C, among zones Z1 to Z5 or among 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 with each of the zones Z1 to Z5 or Z1 'to Z3', the two pyrometers of each pair being provided on respectively one and the other of the two side walls 13, typically facing each other horizontally, which makes it possible to measure the temperature of the primary combustion in the zone concerned from each lateral side of the grid 14. The measurements respectively coming from the various pyrometers for a given zone of the bed are then averaged for the needs of the treatment by the control unit 40 or 140.
• Rather than individually adjusting the respective flow rates of the primary air flows P1 to P5 or P1 'to P3', provision can be made to regulate the flow of the primary air in the supply duct 35 or 135, by means of an ad hoc flow rate regulator, provided on this supply line and controlled by the control unit 40 or 140. The regulation of the combustion installation then makes it possible to adjust the total air flow rate primary P passing through the admission device 30 or 130. In this case, a single pyrometer, similar to pyrometers 50.1 to 50.5 and 150.1 to 150.3, can be used. Of course, several pyrometers can also be used, their respective measurement being averaged for the needs of the treatment of the control unit 40 or 140. The total flow rate of the primary air thus regulated is then distributed in the various zones by the components. flow settings 34.1 to 34.5 or 134.1 to 134.3.

• The number, according to which the bed of solid fuels C is distributed into zones and therefore according to which the grid 14 or 114 is distributed into regions, may differ from that envisaged for combustion plants 1 and 101. This being the case, this number is preferably at least three in order to include the three main zones corresponding to the successive physicochemical effects of primary combustion, namely a drying zone for solid fuels, a gasification zone for a volatile part of 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.
• It may be considered to eliminate the admission of the secondary air S in the combustion installation 1 or 101. In this case, each of the pyrometers 50.1 to 50.5 or 150.1 to 150.3 is preferably located, above the grid 14. or 114, at a vertical distance of between 1.5 m and 5 m vis-à-vis this grid.

Whatever the specific features of the process and 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 primary 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 the complex phenomena linked to primary combustion.

The response time and the representativeness of the temperature measurements by the pyrometers allow a high precision of the primary air dosage and a good control of the ratio between the quantity of air consumed by the primary combustion and the quantity of solid fuels burned by primary combustion, and this, advantageously, in different zones of the bed formed by the solid fuels, in particular the three main zones mentioned above. The invention thus makes it possible to supply almost instantaneously and, advantageously, locally the quantity of air just necessary for the primary combustion.

This adjustment "as closely as possible" to the quantity of primary air induces a reduction in the overall flow of primary air, which is favorable to a reduction in the size of the combustion installation, to its energy efficiency and to a reduction. pollutant emissions. Indeed, by controlling the kinetics of primary combustion, it is possible to control the formation / transformation of numerous pollutants, such as carbon monoxide, nitrogen oxides and gaseous organic compounds.

Adjusting the quantity of primary air “as closely as possible” also makes it possible to control the temperatures throughout the lower part of the combustion chamber. This improves the performance of equipment downstream of the combustion chamber, in particular the production of steam by the exchangers of the boiler. This also makes it possible to limit the formation, by melting, of oxides at high temperature, sources of deposits which affect the thermal efficiency and which are difficult to remove by the usual cleaning techniques. This also makes it possible to considerably reduce, or even eliminate, the need for secondary air and / or to reduce the number of vertical secondary air injection levels. The combustion installation is thereby simplified, at least by reducing the volume between the grille and the secondary air intake, which is a source of significant savings.

Controlling the temperatures in the lower part of the combustion chamber also avoids excessive local temperature peaks and allows the use, for solid fuels with high calorific value, traditional systems generally limited to solid fuels with lower power. calorific, such as uncooled water grids or standard refractory linings, especially non-nitrided.

Other advantages of the invention have also been mentioned previously or are deductible from the foregoing by those skilled in the art.

Claims (13)

Method of regulating a combustion plant (1; 101), in which solid fuels (C) are introduced into a combustion chamber (10; 110) and burn there according to primary combustion in the presence of primary air (P ) which is introduced into the combustion chamber with a primary air flow, characterized in that the primary combustion of solid fuels (C) has a temperature which is measured in the combustion chamber (10; 110) by one or more optical pyrometers (50.1 to 50.5; 150.1 to 150.3), which are arranged laterally to the combustion chamber and which point the combustion gases (G) generated by the primary combustion in the immediate vicinity of the solid fuels so as to measure the radiation of both these combustion gases and the solid particles contained in these combustion gases, and in that the primary air flow is controlled as a function of the measurements of the pyrometer (s). Process according to Claim 1,
in which the combustion chamber (10; 110) is delimited downwards by a grate (14; 114) on which the solid fuels (C) form a bed which is movable in a direction of advance (Z) in the chamber combustion, and
in which the primary air (P) is admitted under the grate, with the primary air flow, before passing through the grate to enter the combustion chamber and reach the bed of solid fuels. A method according to claim 2, wherein each pyrometer (50.1 to 50.5; 150.1 to 150.3) has an axis of sight which is substantially parallel to the plane of the grid (14; 114). Process according to claim 2 or 3,
in which the bed of solid fuels (C) is divided into several zones (Z1 to Z5; Z1 'to Z3') which follow one another in the direction of advance (Z),
in which each of the zones is associated with at least one of the pyrometers (50.1 to 50.5; 150.1 to 150.3) so that, for each zone, the pyrometer (s) associated with the zone measure the temperature of the primary combustion of solid fuels in this zone, and
in which the primary air (P) is admitted under the grille (14; 114) being distributed in primary air flows (P1 to P5; P1 'to P3') which are respectively associated with the zones so that, for each zone, the primary air flow associated with the zone is sent to this zone with a flow rate which is controlled as a function of the measurements of the pyrometer (s) associated with this zone. A method according to claim 4, wherein the zones (Z1 to Z5; Z1 'to Z3') are at least three in number and include: - a drying zone for solid fuels (C), - a gasification zone for a volatile part of the solid fuels and combustion zone 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. Process according to one of Claims 4 or 5,
in which the primary air (P) is admitted under the grille (14) being distributed by separate boxes (31.1 to 31.5) which are respectively associated with the zones (Z1 to Z5) so that, for each zone, the flow primary air (P1 to P5) associated with the zone is formed at an air outlet (33.1 to 33.5) of the box associated with this zone while an air inlet (32.1 to 32.5) of the box associated with the zone is fitted with a flow rate adjustment device (34.1 to 34.5), controlled according to the measurements of the pyrometer (s) (50.1 to 50.5) associated with this zone. Method according to one of Claims 4 or 5, in which the primary air (P) is admitted under the grille (114) by a single box (131) which: - has an air inlet (132) divided into several subdivisions (132.1 to 132.3), which are respectively associated with the zones (Z1 'to Z3') and in which flow the respective primary air streams (V1 to V3 ) separate, each subdivision being provided with a flow rate regulator (134.1 to 134.3), controlled according to the measurements of the pyrometer (s) (150.1 to 150.3) associated with the corresponding zone, and - comprises a casing (133) whose internal volume forms, under the grille (114), a single primary air distribution volume, into which the subdivisions (132.1 to 132.3) open, the internal volume of the casing being provided with '' internal aeraulic arrangements (137.1, 137.2) designed to act on the flow of the air streams (V1 to V3), once out of the subdivisions, so as to direct these primary air streams towards the grille (114) to respectively form the primary air streams (P1 'to P3'). Process according to any one of claims 2 to 7,
in which secondary air (S) is admitted into the combustion chamber (10; 110) above the grate (14; 114) to effect secondary combustion of the combustion gases (G) generated by the primary combustion solid fuels (C), and
in which the pyrometer (s) (50.1 to 50.5; 150.1 to 150.3) are located at a vertical distance from the grille, which is between half and two-thirds of the distance between the grille and the air inlet secondary. A method as claimed in any one of the preceding claims, wherein, in order to measure the temperature of the primary combustion of solid fuels (C), the or each pyrometer (50.1 to 50.5; 150.1 to 150.3) emits at least one bichromatic laser beam in the combustion chamber (10; 110). A method according to any preceding claim, wherein, to measure the temperature of the primary combustion of solid fuels (C), the or each pyrometer (50.1 to 50.5; 150.1 to 150.3) emits into the combustion chamber (10; 110) two laser beams which intersect substantially in the plane of a wall (13) of the combustion chamber, on which the pyrometer is provided. Combustion installation (1; 101), comprising: - a combustion chamber (10; 110), adapted so that solid fuels (C) are introduced therein and burn there according to a primary combustion in the presence of primary air (P), and - an intake device (30; 130), adapted to supply the combustion chamber with the primary air according to a primary air flow, characterized in that the combustion installation further comprises: - one or more optical pyrometers (50.1 to 50.5; 150.1 to 150.3), which are arranged laterally to the combustion chamber (10; 110) and which are suitable for measuring a temperature of the primary combustion in the combustion chamber, by pointing combustion gases (G) generated by the primary combustion in the immediate vicinity of the solid fuels so as to measure the radiation of both these combustion gases and of the solid particles contained in these combustion gases, and - regulation means (34.1 to 34.5, 40; 134.1 to 134.3, 140) adapted to, from the measurements of the pyrometer (s), control the primary air flow of the intake device (30; 130). Combustion plant according to Claim 11,
in which the combustion installation (1; 101) further comprises a grate (14; 114): - which delimits the combustion chamber downwards (10; 110), - which is adapted to support a bed which is formed by solid fuels (C) and which is movable in a direction of advance (Z) in the combustion chamber, and - under which the intake device (30; 130) opens so that the primary air (P) supplied by the intake device according to the primary air flow enters the combustion chamber by passing through the grid, wherein the intake device (30; 130) is adapted both to distribute the primary air into primary air streams (P1 to P5; P1 'to P3'), and to send these streams to 'primary air respectively to associated regions (14.1 to 14.5; 114.1 to 114.3) of the grid, which follow one another in the direction of advance (Z), and
in which the regulating means (34.1 to 34.5, 40; 134.1 to 134.3, 140) are adapted to control the flow rate of each of the primary air flows (P1 to P5; P1 'to P3') from the measurements of the or pyrometers (50.1 to 50.5; 150.1 to 150.3) measuring the primary combustion temperature of a zone (Z1 to Z5; Z1 'to Z3') of the bed, which is supported by the region of the grate, towards which the device d The intake sends the primary air flow. Combustion plant according to Claim 12,
in which the combustion chamber (10; 110) is provided to admit therein secondary air above the grate (14; 114) for carrying out a secondary combustion of the combustion gases (G) generated by the primary combustion of the solid fuels (C), and
in which the pyrometer (s) (50.1 to 50.5; 150.1 to 150.3) are located at a vertical distance from the grille, which is between half and two-thirds of the distance between the grille and the air inlet secondary.

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