EP4055325B1 - Combustion device - Google Patents

Description

The present invention relates to a combustion installation.

The invention is particularly concerned with 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 installations 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 flow of material, the exact composition of which is both inhomogeneous at a given moment and capable of varying over time.

In such combustion installations, the solid fuels are introduced into a combustion chamber to undergo 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 non-volatile part of solid fuels is burned entirely, except for unburned particulate matter, and, on the other hand, the volatile part of solid fuels, released during heating of the latter and combustion of their non-volatile part, is partially burned. This primary combustion can in particular be carried out on a grid, which delimits the combustion chamber towards the bottom and onto which the solid fuels are loaded to undergo primary combustion, while the primary air is admitted under the grid before passing through this last to enter the combustion chamber and thus reach the solid fuels. For the volatile part of solid fuels to be completely burned and thus carry out so-called secondary combustion, it is often provided that air known as secondary air, consisting of air and/or recirculated smoke, is admitted into the combustion chamber. , by being injected above the grid in one or more levels.

In all cases, all chemical and physical reactions, which will condition the composition of the combustion gases and the particles fluidized by these gases in the combustion chamber then downstream of it, 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 primary combustion takes place. In particular, the conditions of air intake primary are critical, in the sense that they influence in particular the temperature of the primary combustion and the partial pressures of the volatile compounds in the combustion gases, which affects the physical and chemical reactions of the primary combustion, as well as the entrainment particles in the combustion gases.

In combustion installations which are quite large, it is known to distribute the primary air to be admitted into the combustion chamber by several separate boxes, which are arranged and distributed under the grid. Each of these boxes is equipped, on its air inlet, with a flow adjustment member to control the primary air flow passing through the box. The adjustment members 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 adjustment members is often carried out only occasionally by an operator, for example according to the average calorific value of solid fuels, determined over a long period of time, or according to a known variation of the composition of solid fuels. In more sophisticated installations, the distribution of primary air by the boxes can be adjusted according to the infrared radiation emitted by the layer formed by 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 expensive 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 surface temperature of the entire layer of solid fuels, this partial indication being additionally disturbed by particles and dust, present vertically between the layer of solid fuels and the infrared camera.

The use of such a group of boxes under the grille presents a real interest, compared to the situation where all the primary air flow is brought under the grille in a single volume in which the air is distributed naturally before cross the gate. Indeed, by definition, such a natural distribution does not make it possible to control in space the application of the primary air under the grille, but, on the contrary, is totally dependent on the pressure loss generated by the grille and by the layer formed by solid fuels on this grid. However, the pressure loss due to this layer is generally inhomogeneous, due to the system of deposition of solid fuels on the grid, as well as the disparity relating to the kinetics of combustion of solid fuels and heterogeneities of solid fuels, both in size of their solid fragments and in composition and humidity, in particular for solid fuels of waste or biomass type. This inhomogeneity of the pressure loss at the level of the grid has the consequence of favoring the passage of primary air in the least dense zones of the layer, in other words the zones having less solid fuels and therefore theoretically requiring less primary air, to the detriment of the densest zones of the layer, in other words the zones having more solid fuels and therefore theoretically requiring more primary air. In the densest areas of the layer, primary combustion may be incomplete. At the same time, in less dense areas, primary combustion risks being pushed to excess so that the resulting ashes risk being in less quantity, or even flying away under the effect of the speed of the air passing through the grid directly above these zones. Such untimely flights of ash can affect the equipment downstream of the combustion chamber and can also lead to the destruction of the grid because the latter then finds itself deprived of the protection conferred by the thickness of the ashes against direct radiation from the primary combustion.

This being said, despite these various drawbacks, such a natural distribution of the primary air under the grille often remains implemented for practical reasons, linked to the intrinsic costs of the group of boxes described above and, above all, to the place that these boxes take under the combustion chamber and which generally induces an elevation of all the rest of the combustion installation and the corresponding boiler.

UK 2,077,892 discloses a combustion installation for solid fuels. This combustion installation has three adjacent grids, which are separated two by two by refractory walls. Primary air supplies the combustion chamber of the installation, being admitted under each of the three grilles. For this purpose, under each grid, three independent channels are provided which are delimited by watertight partitions. The primary air is, at an upstream inlet, distributed into three distinct air flows which, under the corresponding grille, flow to this grille independently of each other due to the separation carried out. through the watertight bulkheads.

The aim of the present invention is to propose a combustion installation which, without resorting to a group of boxes under the grid, improves the conditions for the admission of the primary air.

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

The idea underlying the invention is to keep a single distribution volume of the primary air under the grille, but to integrate into this volume specific aeraulic features capable of forcing the distribution of the primary air under the grid, without significantly affecting the size, in particular the vertical dimension, of this volume. The invention thus provides for subdividing the air inlet of a single box, to form primary air veins whose flow rate is individually adjustable. The invention also makes it possible to act on the aeraulics of these primary air veins, thanks to dedicated internal arrangements of the single box, in order to send these primary air veins to respective regions of the grid. These arrangements are advantageously designed to prevent the accumulation of ashes under the grill. The combustion installation according to the invention thus makes it possible to control the spatial and quantitative distribution of the primary air intake, thanks to compact and economical arrangements.

In practice, as explained in more detail later, the actuation of the flow adjustment members can be manual or controlled automatically. In the latter case, the corresponding control can advantageously be provided from measurements of the temperature of the primary combustion, carried out by pyrometers, as detailed below.

Additional advantageous characteristics 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 vue à plus grande échelle d'un encadré Il de la figure 1, illustrant une variante de la partie correspondante de l'installation de combustion ; et
• [Fig. 3] la figure 3 est une coupe schématique partielle selon la ligne III-III de la figure 1.

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 ] there figure 1 is a diagram of a combustion installation according to the invention;
• [ Fig. 2 ] there figure 2 is a larger scale view of a boxed Il of the figure 1 , illustrating a variant of the corresponding part of the combustion installation; And
• [ Fig. 3 ] there Figure 3 is a partial schematic section along line III-III of the figure 1 .

On the figure 1 is shown a combustion installation 101 adapted to burn 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 presenting heterogeneity in size, composition and/or humidity, as mentioned in the introductory part of this document.

The combustion installation 101 typically belongs to a boiler which makes it possible to produce water vapor using the heat of the fumes coming from the combustion installation.

• une paroi arrière 111, au travers de laquelle les combustibles solides C sont chargés à l'intérieur de la chambre de combustion par, par exemple, une goulotte externe 120,
• par une paroi avant 112, au travers de laquelle les combustibles solides C, une fois brûlés, sortent de la chambre de combustion via une évacuation 121, et
• par deux parois latérales 113, qui sont horizontalement distantes l'une de l'autre et qui relient chacune les parois arrière 111 et avant 112, une seule de ces deux parois latérales 113 étant visible sur la figure 1.

The combustion installation 101 comprises a combustion chamber 110 adapted so that the solid fuels C are introduced there and burn there according to primary combustion in the presence of air, called primary air P. The combustion chamber 110 is delimited laterally by:

• a rear wall 111, through which the solid fuels C are loaded inside the combustion chamber by, for example, an external chute 120,
• by a front wall 112, through which the solid fuels C, once burned, exit the combustion chamber via an evacuation 121, and
• by two side walls 113, which are horizontally spaced from each other and which each connect the rear walls 111 and front 112, only one of these two side walls 113 being visible on the figure 1 .

The combustion chamber 110 is designed to, once the solid fuels C are loaded into it, cause these solid fuels C to remain for a necessary time, typically several minutes, to carry out the primary combustion. During their primary combustion, solid fuels C generate gases which, in the immediate vicinity of solid fuels C, are referenced G on the figure 1 . The combustion chamber 110 is designed to channel these gases until they exit the combustion chamber 110 from which fumes F circulating in boiler equipment, such as heat exchangers, escape.

In the example of realization considered on the figure 1 , the combustion chamber 110 is designed to admit a secondary air S, consisting of recirculated air and/or smoke. As indicated on the figure 1 , the admission of the secondary air S into the combustion chamber 110 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 the secondary air S is referenced GS on the figure 1 and forms the fumes F at the outlet of the combustion chamber 110. In practice, the secondary air can thus be introduced in several vertical levels, as indicated on the figure 1 .

Primary combustion results in, on the one hand, the non-volatile part of the solid fuels C being completely burned, except for unburnt particulate matter fluidized in the gases G, and, on the other hand, the volatile part of the solid fuels being released. during the heating of the latter and during the combustion of their non-volatile part, or partially burned, forming the gases G. The secondary air S feeds a secondary combustion, namely the combustion of the gases G to form the gases GS, thus completely burning the volatile part of solid fuels C.

In the embodiment considered here, the combustion chamber 110 includes a grid 114 which delimits the bottom of the combustion chamber. This grid 114 is designed to support the solid fuels C inside the combustion chamber 110 so that, as illustrated in the figure 1 , these solid fuels form a bed which rests on the grid 114, extending from the rear wall 111 to the front wall 112. At the level of the rear wall 111, the bed is supplied with solid fuels to be burned, for example by the external chute 120, while, at the level of the front wall 112, the bed is evacuated, in particular by falling into the evacuation 121. Between the rear walls 111 and front 112, the bed of solid fuels C is movable in one direction of advancement Z in the combustion chamber 110. Thus, the direction of advancement Z extends from the rear wall 111 to the front wall 112, while being parallel to the grid 114. In practice, the grid 114 can also be inclined relative to a horizontal plane, as on the figure 1 , that extend in a horizontal plane. In all cases, the grid 114 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 113 of the combustion chamber 110. The arrangements of the combustion chamber 110, which ensure the driving of the bed of solid fuels C in the direction of advancement Z, are not limiting to the invention: in a manner known per se, the grid 114 can be provided inclined to allow the gravity drive of the bed and/or be provided movable to act on the drive of the bed, while then being driven by a movement allowing a slow movement of the solid fuels from their point of arrival on the grate, where they are not yet burned, to their point of evacuation from the grate, where they are completely burned. In the case where the grid is mobile, various drive systems are known, so that, for example, the grid rotates like a treadmill, or bars of the grid move alternately, etc.

In practice, the embodiment of the grid 114 can also be linked to the device for introducing solid fuels C into the combustion chamber. Indeed, rather than supplying the combustion chamber 110 with solid fuels through the rear wall 111 by means of the external chute 120 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 112, the introduction device then being an external, mechanical and/or pneumatic injector, which is even project the solid fuels into the combustion chamber, from the front wall to the region of the grid 114, adjacent to the rear wall 111.

Whatever the embodiment of the grille 114, the primary air P is admitted under the grille and this grille 114 is designed to allow the primary air P to pass through from bottom to top to allow the latter to enter. in the combustion chamber 110 and thus reach the solid fuel bed C.

The combustion installation 101 also comprises an admission device 130 making it possible to supply the combustion chamber 110 with the primary air P. In the example of embodiment considered here, the admission device 130 is, at least for its downstream outlet, arranged below the grid 114.

As shown on the figure 1 , the admission device 130 comprises a single box 131 having an air inlet 132 designed to be supplied with the primary air P. The air inlet 132 opens into a casing 133 of the box 131, arranged below of grid 114.

As shown schematically on the figure 1 , 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 pipe 135, which transports the primary air P and which is common to the different 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 same primary air distribution volume, which is arranged under the grille 114 and which is formed by the internal volume of the casing 133. 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 pipe 135 to the internal volume of the casing 133.

Each of the subdivisions 132.1 to 132.3 is provided with a flow 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 does not limit the invention.

In the example considered on the figure 1 , each of the flow adjustment members 134.1 to 134.3 comprises a register 136, which is arranged inside the corresponding subdivision 132.1 to 132.3 and which is designed to pivot on itself in order to adjust the flow rate of the flow stream. corresponding primary air V1 to V3. This register 136 is for example a butterfly register.

An alternative embodiment for the flow adjustment members 134.1 to 134.3 is illustrated in figure 2 . More precisely, the figure 2 shows an alternative embodiment for the flow control member 134.1, it being understood that this alternative embodiment can be applied to the other flow control members 134.2 and 134.3. In the embodiment illustrated in figure 2 , the flow adjustment member 134.1 comprises two flaps 138A and 138B, which are arranged symmetrically inside the subdivision 132.1, each being articulated relative to this subdivision. By means of their articulated movement relative to the subdivision 132.1, the flaps 138A and 138B move away from or approach one another, symmetrically with respect to one another, 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 the figure 2 . The symmetry of the arrangement and 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 loss, in particular without significantly modifying the flow speed of the stream d air V1 in subdivision 132.1. In practice, the pressure loss is all the more limited as the flaps 138A and 138B are slightly inclined, typically less than 45°, relative to the flow axis of the air stream V1 in 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 therefore makes it easier to 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 shutters 138A and 138B in movement, the flow adjustment member 134.1 comprises an actuator 139, such as a jack, which is connected to the shutters 138A and 138B in an appropriate manner, for example by rods, as illustrated schematically on the figure 2 .

According to an optional arrangement, illustrated by the figure 1 , the air inlet 132 extends substantially horizontally, 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 extension towards the top of the air inlet of the box. In addition, for aeraulic reasons which will appear later, the subdivisions 132.1 to 132.3 of the air inlet 132 are then advantageously arranged one above the other: on the figure 1 , subdivision 132.1 is arranged above subdivision 132.2 which is itself arranged above subdivision 132.3.

Whatever the specifications for producing subdivisions 132.1 to 132.3 of the air inlet 132, the casing 133 is arranged 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 advancement 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 exiting subdivisions 132.1 to 132.3, so that these primary air streams form, at the outlet of the box 131, respective primary air flows P1, P2 and P3, which are sent, below grid 114, respectively towards 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 up to regions 114.1 to 114.3 of grid 114.

It will be understood that regions 114.1 to 114.3 of the grid 114 are fixed in the combustion chamber 110, whatever the embodiment of the grid 114: thus, when the grid 114 is fixed in the combustion chamber 110, each of the regions 114.1 to 114.3 corresponds to a part of this grid, which is unchanged during the operation of the combustion installation 101; when the grid 114 is mobile, each of the regions 114.1 to 114.3 is, at each instant of operation of the combustion installation 1, occupied by a part of the grid 114, this part being able to change region during the movement of the grid 114 . On the figure 1 , region 114.1 is, among regions 114.1 to 114.3, the closest to the rear wall 111 while region 114.3 is closest to the front wall 112, this region 114.3 succeeding region 114.2 which itself succeeds region 114.1 following the direction of advancement Z. In addition, we note Z1 to Z3 of the zones of the bed of solid fuels C, which follow one another in the direction of advancement Z and which are respectively located vertically above regions 114.1 to 114.3 of the grid 114. In other words, the zone Z1 of the bed of solid fuels C rests on the region 114.1 of grid 114, zone Z2 rests on region 114.2, and zone Z3 rests on region 114.3 of grid 114. Similarly to regions 114.1 to 114.3 of grid 114, zones Z1 to Z3 of bed solid fuels C are fixed in the combustion chamber 110. It is therefore understood that, at a given moment during the operation of the combustion installation 101, each of the zones Z1 to Z3 of the bed is made up of a part of the solid fuels C and that, at a later moment in the operation of the combustion installation, each of the zones Z1 to Z3 of the bed is occupied by another part of the solid fuels C, at least partially different from the aforementioned part of these solid fuels C, of the caused by the movement of the bed in the direction of advancement Z. Thus, during their primary combustion, the solid fuels C gradually pass, in the combustion chamber 110, through the zone Z1 of the bed formed by these fuels C on the grid 114 , then through zone Z2, and finally through zone Z3 of the bed. By thus progressing through zones Z1 to Z3, 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.

In the embodiment shown in figure 1 , the aforementioned internal arrangements of the box 101 include plane deflectors 137.1 and 137.2. Each deflector 137.1, 137.2 forms an angle with the vertical of between 0 and 20°, which amounts to saying that each of the deflectors 137.1 and 137.2 extends either strictly vertically, 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 deflectors 137.1 and 137.2 presents aeraulic and practical advantages: on the one hand, deflectors 137.1 and 137.2 can thus modify the direction of the air flows inside the casing 133, passing from the substantially horizontal flow direction for the primary air streams V1 to V3 to the substantially vertical flow direction for the primary air flows P1 to P3; on the other hand, the deflectors 137.1 and 137.2 prevent the accumulation of ashes which fall on them from the grid 114. Furthermore, to act selectively on the different 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 each other. In the example considered on the figure 1 , 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 specifics of the staging of the lower ends of the deflectors 137.1 and 137.2 may deviate from what has just been described in connection with the example of the figure 1 . In practice, this staging can be optimized by prior computational fluid mechanics calculations, 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 respectively direct the latter towards the corresponding regions 114.1 to 114.3 of grid 114: in the example of figure 1 , the primary air stream V1 is deflected by the deflector 137.1, the primary air stream 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 grid 114 and, thereby, respectively associated with corresponding zones Z1 to Z3 of the bed formed by solid fuels C on grid 114.

Advantageously, 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 the solid fuels and combustion for the non-volatile part of these solid fuels, and the zone Z3 corresponds to a cooling and combustion finishing zone for the non-volatile part of the solid fuels.

As an extension of the above considerations, an advantageous optional arrangement consists of 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 each other : in the example illustrated on the figure 1 , subdivision 132.2 is provided with a larger size, of the order of double, than that of the section of each of subdivisions 132.1 and 132.3, because, in nominal operating conditions for the combustion installation 101, the quantity of The primary air to be transported by subdivision 132.2, whose corresponding vein V2 is associated with zone Z2, is planned 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.

In all cases, each of the flow adjustment members 134.1 to 134.3 is designed to be controlled by a control unit 140 of the combustion installation 101. The control unit 140 comprises electronic and/or electromechanical components, to even to generate control signals, which are transmitted to the flow adjustment members 134.1 to 134.3 with a view to individually actuating the latter to control the respective flow rates of the primary air flows P1 to P3. Here again, the material specificities of the control unit 140, as well as those of the connection between the latter and the flow adjustment members 134.1 to 134.3 are not limiting to the invention.

As shown on the figure 1 , the combustion installation 101 further comprises optical pyrometers, three of them being visible on the figure 1 . All the pyrometers are arranged laterally to the combustion chamber 110, each being provided on at least one of the rear wall 111, the front wall 112 and the side walls 113. The pyrometers make it possible to carry out temperature measurements from the wall of the combustion chamber 110, on which they are provided. In the embodiment considered in the figures, all these pyrometers are integrated into the side walls 113: more precisely, the side wall 113, visible on the figure 1 , thus integrates three pyrometers 150.1 to 150.3. These pyrometers 150.1 to 150.3 are respectively associated with the zones Z1 to Z3 of the solid fuel bed C and, thereby, to the regions 114.1 to 114.3 of the grid 114, so that the pyrometer 150.1 measures a temperature of the primary combustion of the fuels solids C in zone Z1, the pyrometer 150.2 measures a temperature of the primary combustion of solid fuels in zone Z2, and the pyrometer 150.3 measures a temperature of the primary combustion of solid fuels in zone Z3. The temperature measurements are carried out by the pyrometers 150.1 to 150.3 as close as possible to the bed of solid fuels C, in particular by pointing out the gases G respectively coming from zones Z1 to Z3 of the bed and thus measuring the radiation of gaseous compounds and solid particles present in these gases G.

The precise arrangement of the pyrometers 150.1 to 150.3 on the side wall 113 is not limiting to the invention. In practice, it is understood that the sighting axis of each pyrometer 150.1 to 150.5 is parallel or substantially parallel, that is to say parallel within a few degrees, to the plane of the grid 114. Preferably, in particular to limit the optical path between the pyrometers and the primary combustion, in particular the gases G, and to have maximum integration of the thermal radiation emitted by the primary combustion, the pyrometers 150.1 to 150.3 are distributed on the side wall 113 following the direction of advancement Z, being respectively located vertically above zones Z1 to Z3 of the solid fuel bed C, as indicated schematically on the figure 1 . Furthermore, in the vertical direction, each of the pyrometers 150.1 to 150.3, which are necessarily above the grid 114, is preferably located at a vertical distance from the latter, which is between half and two thirds of the spacing between the grid 114 and the secondary air inlet S: in this way, the pyrometers 150.1 to 150.3 are located in the upper half of the vertical spacing between the grid 114 and the secondary air inlet S, to prevent flames generated by the primary combustion from disturbing the radiation measurements carried out by the pyrometers, without however finding themselves in the upper third of this spacing, to prevent the “cold” being introduced into the combustion chamber 110 by the The secondary air S does not disturb the measurements made by the pyrometers.

Likewise, the type of optical pyrometers 150.1 to 150.3 is not limiting to the invention, since these pyrometers provide temperature measurements based on the intensity of the wavelengths emitted by a radiating body. Preferably, the pyrometers 150.1 to 150.3 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 110, at least one beam laser with two different wavelengths: the pyrometers are thus less sensitive to dust emissions. For example, the spectral response of these pyrometers is of the order of 1 µm.

Furthermore, the specificities relating to the focusing of the pyrometers 150.1 to 150.3 are also not limiting to the invention. This being said, a preferred embodiment is illustrated in the Figure 3 for the pyrometer 150.1, it being understood that this embodiment is applicable to the other pyrometers 150.2 and 150.3. Thus, as shown on the Figure 3 , the pyrometer 150.1 is designed, for the purpose of measuring the temperature of the primary combustion, to emit two laser beams in the combustion chamber 110, via an opening 113.1 of the side wall 113. 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 113. This economical arrangement makes it possible to limit the diameter of the opening 113.1, while maintaining a significant divergent field of view for the pyrometer.

In all cases, the measurements of the pyrometers 150.1 to 150.3 are transmitted, by all appropriate forms of connection, to the control unit 140 in order to be processed automatically by the latter, in particular by a calculator or a similar component of the latter . Whatever the specifics of the processing which is carried out by the control unit and examples of which will be given below, the control unit 140 is designed to control the flow adjustment members 134.1 to 134.3, as described above, from the temperature measurements respectively provided by the pyrometers 150.1 to 150.3.

Below, we further describe aspects relating to the regulation of the combustion installation 101.

In this context, it is considered that the combustion installation 101 is in normal operation, that is to say that its combustion chamber 110 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 combustion 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 installation 101 are well known in the art and will therefore not be presented here further. .

While the combustion chamber 110 operates under normal conditions, the pyrometers 150.1 to 150.3 continuously measure the temperature of the primary combustion of solid fuels in, respectively, zones Z1 to Z3 of the bed. The temperature measurements taken by the pyrometers 150.1 to 150.3 are sent continuously to the control unit 140 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 140, the latter compares in real time the temperature measurements provided by each of the pyrometers 150.1 to 150.3 with a temperature setpoint which is specific to the pyrometer considered, in other words which is specific to the zone associated with this pyrometer among zones Z1 to Z3 of the solid fuel bed. According to the result of this comparison specific to each of the zones Z1 to Z3, the control unit 140 transmits in real time to the adjustment member corresponding flow rate, that is to say to that of the flow adjustment members 134.1 to 134.3 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 stream, among the primary air streams V1 to V3, which forms, at the outlet of the box 131, the primary air flow P1, P2 or P3 corresponding to the zone associated with the pyrometer concerned. For 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 activates the flow adjustment member 34.2 to increase the flow rate of the primary air flow P2 by 10%.

In practice, the temperature setpoints respectively specific to zones Z1 to Z3 are previously supplied to the control unit 140. These temperature setpoints can be preset for the combustion installation 101 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 zones Z1 to Z3 and which, where applicable, is also linked to the characteristics of the solid fuels S, possibly measured continuously , such as their calorific value, humidity, etc. The aforementioned reference temperature is, for its part, either prefixed or determined, if necessary continuously, from the oxygen content in the flue gas F, this content being typically measured at the boiler outlet, 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 140, in particular as long as these other treatments compare the measurements of the pyrometers 150.1 to 150.3 with temperature instructions. respective, which are specific to zones Z1 to Z3, in order to individually control the flow rate of the primary air flows P1 to P3. In all cases, it is understood that the control unit 140 and the flow adjustment members 134.1 to 134.3 jointly form regulation means which allow, from the measurements of the pyrometers 150.1 to 150.3, to regulate the respective flow rates of the flows of primary air P1 to P3 and, thereby, the total flow rate of primary air P supplied by the admission device 130 to the combustion chamber 110. 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 P3 from being too low or too high, the actuation of the flow adjustment members 134.1 to 134.3, controlled by the control unit 140, can be expected within a substantial, but limited, range of variation. The limits of this variation range are predetermined by experience and/or other parameters operating conditions of the combustion installation 101, such as the tonnage of solid fuels C introduced into the combustion chamber 110, the pressure of the primary air P in the supply pipe 135, the flow rate of steam produced by the one or more boiler exchangers, etc. Also for control and safety purposes, the reference temperature, mentioned above, can be compared to the instantaneous average of the temperature measurements provided by the pyrometers 150.1 to 150.3, weighted by the size of the zones Z1 to Z3 respectively associated with these pyrometers.

• Pour une zone donnée du lit des combustibles solides C, 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 Z3, voire à chacune des zones Z1 à Z3, les deux pyromètres de chaque paire étant prévus sur respectivement l'une et l'autre des deux parois latérales 113, 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 114. 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 140.
• Le nombre, selon lequel le lit des combustibles solides C est réparti en zones et donc selon lequel la grille 114 est répartie en régions, peut différer de celui envisagé pour l'installation de combustion 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 101. Dans ce cas, chacun des pyromètres 150.1 à 150.3 est préférentiellement situé, au-dessus de la grille 114, à une distance verticale comprise entre 1,5 m et 5 m vis-à-vis de cette grille.

Furthermore, beyond what has been described so far for the combustion installation 101, various arrangements and variants of this combustion installation and its regulation process can be considered:

• For a given zone of the solid fuel bed C, among zones Z1 to Z3, more than one pyrometer may be provided. In particular, a pair of pyrometers can thus be associated with at least one of the zones Z1 to Z3, or even with each of the zones Z1 to Z3, the two pyrometers of each pair being provided on respectively one and the other of the two side walls 113, typically facing horizontally from each other, which makes it possible to measure the temperature of the primary combustion in the zone concerned from each lateral side of the grid 114. The measurements coming respectively from the different pyrometers for a given bed area are then averaged for the purposes of treatment by the control unit 140.
• The number, according to which the bed of solid fuels C is distributed into zones and therefore according to which the grid 114 is distributed into regions, may differ from that envisaged for the combustion installation 101. This being said, this number is preferably at least least three in order to include the three main zones corresponding to the successive physico-chemical effects of primary combustion, namely a drying zone for solid fuels, a gasification zone for a volatile part of the solid fuels and combustion zone for a part non-volatile 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 into the combustion installation 101. In this case, each of the pyrometers 150.1 to 150.3 is preferably located, above the grid 114, at a vertical distance comprised between 1.5 m and 5 m in front of this grid.

The advantages linked to the pyrometers 150.1 to 150.3 and the automatic processing of their measurement by the control unit 140 are numerous. Indeed, 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 101 can be conducted in real time, or in any case with very short reaction times, which are adapted to the speeds observed for the complex phenomena linked to primary combustion. The response time and representativeness of the temperature measurements by the pyrometers allow great precision in the dosage of the primary air and 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, in different zones of the bed formed by solid fuels, in particular the three main zones mentioned above. Without wishing to be bound by a theory, the inventors have established that the radiative temperature, measured by the pyrometers, is an indicator close to the adiabatic temperature of the primary combustion, that is to say the theoretical temperature for the combustion primary is 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 combustion primary. This “closest” adjustment of the quantity of primary air induces a reduction in the overall flow rate 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. Adjusting the quantity of primary air “as closely as possible” also makes it possible to control temperatures throughout the lower part of the combustion chamber. This makes it possible to improve the performance of the equipment downstream of the combustion chamber, in particular the production of steam by the boiler exchangers. This also makes it possible to limit the formation, by fusion, of oxides at high temperatures, sources of deposits which affect thermal efficiency and which are difficult to remove by 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 levels of secondary air injection. The combustion installation is simplified, at least by reducing the volume between the grid and the secondary air intake, which is a source of significant savings. Controlling temperatures in the lower part of the combustion chamber also avoids local temperature peaks which would be excessive and makes it possible to use, for solid fuels with a high calorific value, traditional systems generally limited to solid fuels with a lower calorific value. calorific, such as non-water-cooled grates or standard refractory linings, particularly non-nitrided.

In variants not shown, the combustion installation 101 does not have the pyrometers 150.1 to 150.3, so that the regulation of the flow adjustment members 134.1 to 134.3 is modified accordingly, as explained below.

According to a first possibility, each flow adjustment member 134.1 to 134.3 is designed to be operated manually. In this case, a control unit similar to the control unit 40 is unnecessary. In practice, the actuation of each of the flow adjustment members 134.1 to 134.3 is then only carried out occasionally by an operator, for example depending on the average calorific value of the solid fuels C, determined over a long period of time, or based on a known variation in the composition of solid fuels.

According to another possibility, the combustion installation 101 comprises a control unit similar to the control unit 140, being able to individually actuate the flow adjustment members 134.1 to 134.3. In this case, the control carried out by this control unit on the flow adjustment members 134.1 to 134.3 can either result directly from dedicated instructions from an operator acting on an interface of the control unit, or be deduced from automatic processing which is carried out by the control unit from data supplied to it. In the latter case, the data may relate to solid fuels C, for example relating to their calorific value, their type, their composition, etc. The data supplied to the control unit can also be measurements relating to the operating conditions of the combustion chamber 110, for example images provided by an infrared camera observing the interior of the combustion chamber.

Whatever the specificities of construction and regulation of the combustion installation 101, the latter provides, particularly compared to existing combustion installations, economic and compactness advantages. Indeed, instead of using a group of several distinct boxes, the combustion installation 101 only provides the single box 131 to admit the primary air P under the grille 114, by means of the subdivision of 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 arrival of air 132 horizontally and by connecting it laterally to the casing 133, the intake device 130 is even more compact, avoiding costly elevation of the combustion chamber 110 relative to the supply pipe 135.

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

Claims (11)

1. A combustion facility (101) including:

   - a combustion chamber (110), adapted so that solid fuels (C) are introduced thereinto and burn thereinto according to a primary combustion in the presence of primary air (P),

   - an intake device (130), adapted to supply the combustion chamber with primary air, and

   - a grid (114), which downwardly delimits the combustion chamber and which is adapted to support a bed which is formed by the solid fuels (C) and which is movable along a direction of advance (Z) into the combustion chamber, the intake device opening under this grid so that primary air provided by the intake device enters the combustion chamber by passing through the grid, the intake device (130) including a single box (131) which:

   - has an air inlet (132) distributed into several subdivisions (132.1-132.3) which are provided so that primary air (P) flows thereinto as distinct primary air streams (V1-V3), each subdivision being provided with a flowrate adjustment member (134.1-134.3) adapted to control flowrate of the primary air stream flowing in this subdivision, and

   - comprises a casing (133) the inner volume of which forms, under the grid (114), a single distribution volume of the primary air, into which the subdivisions (132.1-132.3) open, the inner volume of the casing being provided with inner aeraulic arrangements (137.1, 137.2) designed to act on the flow of the air streams (V1-V3), once they have exited the subdivisions, so as to direct these primary air streams towards respective regions (114.1-114.3) of the grid, which succeed along the direction of advance (Z).
2. The combustion facility according to claim 1, wherein the air inlet (132) extends substantially horizontally so as to make the primary air steams (V1-V3) flow substantially horizontally in the subdivisions (132.1-132.3).
3. The combustion facility according to claim 2, wherein the subdivisions (132.1-132.3) are arranged above each other, and wherein the inner aeraulic arrangements of the box (131) include planar deflectors (137.1, 137.2), which form an angle of 0 to 20° with the vertical and the respective lower ends of which are stepped relative to each other so that the deflectors selectively interact on the primary air streams to respectively orient the latter towards the corresponding regions (114.1-114.3) of the grid (114).
4. The combustion facility according to any of the preceding claims, wherein the regions (114.1-114.3) of the grid (114) are at least three in number and respectively support zones (Z1-Z3) of the bed of the solid fuels (S), which include:

   - a zone for drying the solid fuels (C),

   - a zone for gasifying a volatile part of the solid fuels and for combusting a non-volatile part of the solid fuels, and

   - a zone for cooling and finishing combustion of the non-volatile part of the solid fuels.
5. The combustion facility according to any of the preceding claims, wherein the subdivisions (132.1-132.3) have transverse cross-sections the respective sizes of which are different from each other.
6. The combustion facility according to any of the preceding claims, wherein each flowrate adjustment member (134.1-134.3) includes a damper (136), especially a butterfly damper.
7. The combustion facility according to any of claims 1 to 5, wherein each flowrate adjustment member (134.1-134.3) includes shutters (138A, 138B), which are symmetrically arranged inside the corresponding subdivision (132.1-132.3) and which are movable inside the corresponding subdivision (132.1-132.3) by moving away from or coming closer to each other, symmetrically towards each other, by modifying the size of the flow cross-section of this subdivision while maintaining this flow cross-section centred in this subdivision.
8. The combustion facility according to claim 7, wherein the shutters (138A, 138B) are tilted by less than 45° relative to the flow of the air stream (V1) in the corresponding subdivision (132.1-132.3).
9. The combustion facility according to any of the preceding claims, wherein each flowrate adjustment member (134.1-134.3) is manually actuatable.
10. The combustion facility according to any of claims 1 to 8, wherein the combustion facility (101) further includes a control unit, which is adapted to individually actuate the flowrate adjustment member (134.1-134.3) either as a function of dedicated instructions from an operator, or from data relating to the solid fuels (C) or from measurements relating to operating conditions of the combustion chamber (110).
11. The combustion facility according to any of claims 1 to 8,

    wherein the combustion facility (101) further includes optical pyrometers (150.1-150.3); each of the regions (114.1-114.3) of the grid (114) being associated with at least one of the pyrometers so that, for each region, the pyrometer(s) associated with the region are adapted to measure temperature of the primary combustion of a zone (Z1-Z3) of the bed of the solid fuels (C) supported by this region of the grid, and

    wherein each flowrate adjustment member (134.1-134.3) is adapted to control flowrate of the corresponding primary air stream (V1-V3) from the measurements of the pyrometer(s) associated with the region towards which this air stream is directed by the inner aeraulic arrangements (137.1, 137.2) of the box (131).

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