EP0216677A1 - Boiler with a circulating fluidized bed - Google Patents

Boiler with a circulating fluidized bed Download PDF

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Publication number
EP0216677A1
EP0216677A1 EP86401873A EP86401873A EP0216677A1 EP 0216677 A1 EP0216677 A1 EP 0216677A1 EP 86401873 A EP86401873 A EP 86401873A EP 86401873 A EP86401873 A EP 86401873A EP 0216677 A1 EP0216677 A1 EP 0216677A1
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EP
European Patent Office
Prior art keywords
cyclone
recirculation
fluidized bed
bed boiler
boiler according
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Application number
EP86401873A
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German (de)
French (fr)
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EP0216677B1 (en
Inventor
Jean-Xavier Morin
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Areva NP SAS
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Framatome SA
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F22—STEAM GENERATION
    • F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
    • F22B31/00—Modifications of boiler construction, or of tube systems, dependent on installation of combustion apparatus; Arrangements of dispositions of combustion apparatus
    • F22B31/0007—Modifications of boiler construction, or of tube systems, dependent on installation of combustion apparatus; Arrangements of dispositions of combustion apparatus with combustion in a fluidized bed
    • F22B31/0084—Modifications of boiler construction, or of tube systems, dependent on installation of combustion apparatus; Arrangements of dispositions of combustion apparatus with combustion in a fluidized bed with recirculation of separated solids or with cooling of the bed particles outside the combustion bed
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN  A CARRIER GAS OR AIR 
    • F23C10/00—Fluidised bed combustion apparatus
    • F23C10/02—Fluidised bed combustion apparatus with means specially adapted for achieving or promoting a circulating movement of particles within the bed or for a recirculation of particles entrained from the bed
    • F23C10/04—Fluidised bed combustion apparatus with means specially adapted for achieving or promoting a circulating movement of particles within the bed or for a recirculation of particles entrained from the bed the particles being circulated to a section, e.g. a heat-exchange section or a return duct, at least partially shielded from the combustion zone, before being reintroduced into the combustion zone
    • F23C10/08—Fluidised bed combustion apparatus with means specially adapted for achieving or promoting a circulating movement of particles within the bed or for a recirculation of particles entrained from the bed the particles being circulated to a section, e.g. a heat-exchange section or a return duct, at least partially shielded from the combustion zone, before being reintroduced into the combustion zone characterised by the arrangement of separation apparatus, e.g. cyclones, for separating particles from the flue gases
    • F23C10/10—Fluidised bed combustion apparatus with means specially adapted for achieving or promoting a circulating movement of particles within the bed or for a recirculation of particles entrained from the bed the particles being circulated to a section, e.g. a heat-exchange section or a return duct, at least partially shielded from the combustion zone, before being reintroduced into the combustion zone characterised by the arrangement of separation apparatus, e.g. cyclones, for separating particles from the flue gases the separation apparatus being located outside the combustion chamber
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN  A CARRIER GAS OR AIR 
    • F23C2206/00—Fluidised bed combustion
    • F23C2206/10—Circulating fluidised bed
    • F23C2206/101—Entrained or fast fluidised bed
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN  A CARRIER GAS OR AIR 
    • F23C2206/00—Fluidised bed combustion
    • F23C2206/10—Circulating fluidised bed
    • F23C2206/103—Cooling recirculating particles

Definitions

  • the invention relates to a circulating fluidized bed boiler using the heat produced by the combustion of circulating materials.
  • Such boilers generally comprise a main body constituting an elongated fluidization chamber arranged with its vertical axis, a recirculation cyclone in communication with the upper part of the fluidization chamber, a recirculation duct or leg bringing the lower part of the cyclone into communication with the lower part of the main body, as well as one or more heat exchanger elements in which the heating and vaporization of water are ensured by thermal contact with the gases and solid materials at high temperature circulating in the boiler.
  • Combustible materials and possibly non-combustible materials in the form of solid particles are introduced at the base of the fluidization chamber and are suspended in an oxidizing gas which is generally air flowing from bottom to top in this chamber, with a speed sufficient to drive a substantial part of the solid particles up the fluidization chamber and from there into the recirculation cyclone.
  • Three main types of fluidized bed boilers are known, which differ mainly in the structure and functions of the main body constituting in particular the fluidization chamber.
  • the main body has membrane walls constituting the heat exchanger and combustion develops in this main body, within a fluidized medium circulating at a speed of the order of 5 to 6 meters /second.
  • the inner walls of the main body which constitute the exchange surfaces directly collect the heat developed by the combustion which is regulated so as to operate in the optimal temperature zone for desulphurization of the fuel, while operating with a reasonable excess of air.
  • This type of boiler has relatively satisfactory operating characteristics; these performances are however limited by the fact that the density of suspension of the solids is still low (10 to 30 kg / Nm3 of smoke), by the fact that the exchange coefficient, the value of which is generally between 50 and 80 kcal / m2h ⁇ C is limited by the presence of a layer of solid materials pressed against the exchange walls and by the fact that the pre-gasification zone of solid materials, at the base of the main body is very small, if although the nitrogen oxide emissions in the gases are relatively large due to the fact that a significant excess of air is used (of the order of 20%).
  • a second type of circulating fluidized bed boiler comprises a main body, the internal wall of which is partially coated with refractory material and partially provided with membrane walls, in its upper part.
  • An external heat exchanger is associated with the boiler and receives solid particles taken from the recirculation leg, at the outlet of the cyclone and reinjected into the main body. The removal of solids and their cooling at the level of the external exchanger ensure thermal equilibrium so as to operate in the optimum temperature zone for desulfurization of the fuel with a reasonable excess of air which is always around 20%. Fluidization velocities in the main body are somewhat higher than for the first type of boiler (6 to 8 m / s).
  • the density of materials in suspension and the heat exchange coefficient in the upper part of the main body remain roughly identical to what they were in the case of boilers of the first type.
  • the exchange coefficient reaches a value of around 300 to 350 kcal / m2 ⁇ C in the external exchanger which operates in a fluidized bed at low speed to limit the erosion of the exchanger tubes immersed in the fluidized bed .
  • a third type of boiler has a main body of small dimensions entirely coated on its internal surface with refractory material and in communication, as in other types of boilers, with a recirculating cyclone.
  • This type of boiler also includes an external exchanger, the exchange walls of which are brought into contact with particles taken from the recirculation leg, particles which are then reinjected into the main body.
  • the fluidization speed is very high (8 to 10 m / s) and the heat transfer takes place entirely outside the main circulation loop of the fluidized bed.
  • the downside of this type of boiler is that requires, as before, an additional solids circulation loop on which the external exchanger is located, which results in an increased construction cost.
  • the object of the invention is therefore to provide a circulating fluidized bed boiler using the heat produced by the combustion of circulating materials and comprising an elongated fluidization chamber with vertical axis entirely coated, on its internal surface, with a layer of refractory material, at the base of which a combustible material and possibly a non-combustible solid material are introduced in the form of particles, as well as an oxidizing gas for suspending said solid materials circulating from bottom to top in the chamber, at least a recirculation cyclone with a vertical axis, in communication with the upper part of the fluidization chamber by a conduit disposed substantially tangentially with respect to the recirculation cyclone, a solids recycling conduit bringing the lower part of the cyclone into communication recirculation with the lower part of the fluidization chamber and at least one heat exchanger element eur in which circulates water to be heated and vaporized, the external exchange surface of which comes into contact with hot gases and solid matter in circulation, a boiler which makes it possible to obtain
  • At least one heat exchanger element is placed inside the recirculation cyclone, at least in its upper part which comprises means ensuring the combustion of the gases and combustible solids circulating in this part of the cyclone .
  • the recirculation cyclone comprises, at least in its upper part, means for injecting air into the circulating fluidized bed arranged in directions substantially tangential to the cyclone.
  • Fig. 1 the entire boiler is seen comprising a main body 1 of elongated shape with a vertical axis, a recirculation cyclone of cylindro-frustoconical shape 2 and a recirculation leg 3.
  • the upper part of the main body 1 is placed in communication with the upper part of the cyclone 2, by means of a directed duct 4 tangentially with respect to cyclone 2, as can be seen in FIG. 2.
  • the components 1, 2, 3 and 4 of the boiler constitute the circulation loop of the fluidized bed.
  • the lower part of the main body 1 receives the solid materials which are introduced into the terminal chute 3a of the recirculation leg 3 through a pipe 7; these solid materials are constituted, for example, by particles of coal which constitute the fuel and particles of limestone which constitute a desulfurizing and heat-transferable material. These solid materials are received by a fluidization grid 5 placed at the lower end of the main body 1 under which opens a primary air injection pipe 8 carrying out the fluidization of the solid materials in the lower part of the main body 1 which constitutes the fluidization chamber of the boiler.
  • this lower part of the main body 1 has a square section enlarged with respect to the current rectangular section of the main body visible in FIG. 2.
  • this lower part 1a receives, in addition to the fluidization means 5, 8, the starting burner 9 of the boiler, a preheating burner 10, an ash evacuation duct 12 and thermocouples 13 allowing the determination of the temperature in this area of the boiler, for driving the pro stopped.
  • the inner surface of the main body 1 constituting the fluidization chamber is entirely coated with a refractory material 14 ensuring the protection of its external metallic envelope on which is inserted an expansion joint 15 in the lower part.
  • Thermocouples 16 pass through the wall of the main body 1 in its upper part.
  • the main body 1 also includes a safety valve 18, at its upper end connected to the duct 4 for the tangential arrival of the bed circulating in the recirculation cyclone 2.
  • the cyclone 2 has an upper part 20 entirely coated with refractory material and in communication at its upper part with a chamber 21 for evacuating the fumes which are taken via a pipe 22 internally coated with refractory, to an installation for heat recovery and dust removal of the type usually used in association with circulating bed boilers.
  • the recirculation cyclone 2 comprises, below its part 20 coated with a refractory, a part 24 of cylindrical shape, the inner wall of which carries a heat exchanger 25 in which water circulates, the whole of the inner wall of the part 24 of the cyclone constituting an exchange surface.
  • the smoke evacuation chamber 21 is placed in communication with the part 20 of the cyclone by means of a separator tube 27, the wall of which constitutes a heat exchanger wall in which water circulates.
  • the lower part 26 of cyclone 2, of frustoconical shape comprises on the greater part from its height, a membrane wall in which water circulates constituting a heat exchanger 28 and in its lower part, over a small height, a wall 29 internally covered with refractory material, this lower part being in direct communication with the leg recirculation 3 also covered with refractory material.
  • Lines 30 for introducing secondary air into the cyclone, in a direction substantially tangential with respect to the latter, are placed, both at the level of the upper part 20 and of the cylindrical upper part 24 of this cyclone.
  • Thermocouples 32 and 33 pass through the wall of the cyclone, at its part 20 and its part 24 respectively.
  • Support tabs 34 are welded to the outer surface of the frustoconical part 26 of the cyclone.
  • the lower part of the recirculation cyclone 2 is in communication with the recirculation leg 3, the shape of which is visible by referring to FIGS. 1 and 3.
  • This recirculation leg has a "J" shape which allows the formation of an airlock for the gas circulating in the lower part 1a of the fluidization chamber and thus avoiding the passage of this gas from the main body 1 to the cyclone 2, via the recirculation conduit 3.
  • the solid matter separated from the gases reaching at the bottom of the cyclone and consisting mainly of combustion ash and heat-transferable limestone particles pour into the vertical inlet part of the recirculation duct 3 and are then received on the horizontal bottom of this duct; the recirculation of these solid particles into particles is ensured by recirculation air injection nozzles 35 culation crossing the horizontal bottom of the recirculation leg 3.
  • the solid materials recirculated by the nozzles 35 inclined towards the outlet of the leg 3 rise in its vertical outlet part from which they pour into the chute 3a communicating with part 1a of the fluidization chamber.
  • Part of the solids arriving in the recirculation leg 3 can be evacuated via a pipe 36 which is connected to a circuit on which there is an external heat exchanger, a valve for controlling the solids extraction flow rate allowing adjustment of this extraction.
  • the circuit of the external exchanger closes on the recirculation leg 3 thanks to a pipe 37 for reinjection of the cooled solid materials.
  • coal and limestone in particulate form are introduced into the lower part 1a of the fluidization chamber and primary air is introduced under the grid 5 by through the conduits 8.
  • the primary air flowing from bottom to top in the fluidization chamber 1 carries the solid particles upwards from this chamber.
  • the enlarged part 1a at the base of this chamber 1 makes it possible to trap particles with large particle sizes whose narrowing of the chamber prevents entrainment towards the upper part.
  • the start-up burner 9 makes it possible to raise the temperature in the enclosure, which then allows the introduction of the fuel, which therefore undergoes prepyrolysis and gasification in zone 1a.
  • the process is carried out in a reducing regime in this zone 1a, the air introduced at the base of chamber 1 being limited to the amount of air required for fluidization.
  • This mode of operation with a secondary reaction zone at the base of the chamber 1 makes it possible in particular to reduce the discharges of nitrogen oxide in the gases and to avoid the entrainment of large fuel particles towards the upper part of the cyclone where these particles could damage the refractory lining material. These particles with a large particle size can be fractured and converted inside the zone 1a.
  • This zone 1a also has the advantage of favoring the mixing between the fuel introduced and the solid matter recirculated by the leg 3.
  • the fluidized bed arriving in the upper part of the cyclone is constituted by a mixture of gas and solids containing a high proportion of combustible materials.
  • This mixture undergoes a vortex movement upon entry of the cyclone and constitutes a vortex, which, with the combined action of the impact of the particles on the impact surface in refractory 20, considerably reduces the speed of vertical circulation of materials in the cyclone and increases the density of matter in the form of solid particles in the gases.
  • This vortex effect is increased by the staged and tangential injections of secondary air injected through the conduits 30.
  • the cooled solid materials then fall back into the recirculation duct 3 to be recycled inside the lower part 1a of the chamber 1.
  • the ash formed is periodically removed by the extraction duct 12.
  • the main characteristics of the device namely the presence of a fluidization chamber entirely coated with refractory and the arrangement of heat exchanger bodies in the recirculation cyclone and more particularly in its upper part, make it possible to obtain operation with higher solids densities and much longer gas residence times in the reaction zone, for the same height of the installations.
  • the main reaction zone being located in the upper part of the cyclone.
  • the heat exchanges in this area are greatly increased by the vortex effect, so that the heat exchange surfaces can be considerably reduced, of the order of 30%. This will have considerably reduced the size and the cost of construction of the boiler and its ancillary installations. Tangential injections in the upper part of the cyclone can reinforce these effects.
  • the upper zone 20 of the cyclone coated with refractory material makes it possible to slow down the particles in circulation and therefore to reduce the erosion of the exchange walls located below the zone 20.
  • the constructive provisions adopted allow the pressurization of the equipment which, therefore, can be used in a direct cycle die, that is to say without external exchanger.
  • the invention is not limited to the embodiment which has been described. This is how the heat exchanger elements can be arranged in a different way from that which has been described; for example, these heat exchanger elements can be strictly limited to the cylindrical upper part of the recirculation cyclone. These heat exchangers can be produced in the form of membrane walls of any type comprising means for distributing water and recovering steam.
  • the installation can be carried out in modular form, a single main body constituting the fluidization column being connected for their supply to several recirculation cyclones containing heat exchangers.
  • Recirculation cyclones can be of any known type, from the moment they allow the provision of heat exchangers on their internal wall. In particular, they can be of the counter-current type as in the embodiment which has just been described or with streams of recovered gases and particles circulating in the same direction.
  • the size of these cyclones can be arbitrary since the effects of tangential gas circulation can be controlled by means of gas injections at different stepped locations in the cyclone.
  • the boiler according to the invention can be supplied with all fuels or other materials in the form of particles, its pipe being particu smoothly flexible, thanks to the internal means or to the additional means available for adjusting the combustion and the circulation of the fluidized bed.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Fluidized-Bed Combustion And Resonant Combustion (AREA)
  • Air Supply (AREA)

Abstract

Boiler with a circulating fluidized bed, comprising a fluidization column completely lined with refractory material, a recirculation cyclone (2) and a duct (3) for recycling the solid materials. At least one heat-exchanger component (25, 26, 27) is placed in the recirculation cyclone (2). Pipe lines (30) enable air to be injected in tangential directions into the upper part of the cyclone (2) and thereby to increase the vortex effect. The combustion takes place substantially in the upper part of the cyclone (2). The fluidization column (1) comprises a widened section (1a) in its lower part.

Description

L'invention concerne une chaudière à lit fluidisé circulant utilisant la chaleur produite par la combustion de matières en circulation.The invention relates to a circulating fluidized bed boiler using the heat produced by the combustion of circulating materials.

De telles chaudières comportent généralement un corps principal constituant une chambre de fluidi­sation allongée disposée avec son axe vertical, un cyclone de recirculation en communication avec la partie supérieure de la chambre de fluidisation, un conduit ou jambe de recirculation mettant en communi­cation la partie inférieure du cyclone avec la partie inférieure du corps principal, ainsi qu'un ou plu­sieurs éléments d'échangeur de chaleur dans lesquels l'échauffement et la vaporisation d'eau sont assurés par contact thermique avec les gaz et matières solides a haute température circulant dans la chaudière. Les matières combustibles et éventuellement des matières non combustibles sous forme de particules solides sont introduites à la base de la chambre de fluidisation et sont mises en suspension dans un gaz oxydant qui est généralement de l'air circulant de bas en haut dans cette chambre, avec une vitesse suffisante pour en­traîner une partie substantielle des particules so­lides vers le haut de la chambre de fluidisation et de là, dans le cyclone de recirculation.Such boilers generally comprise a main body constituting an elongated fluidization chamber arranged with its vertical axis, a recirculation cyclone in communication with the upper part of the fluidization chamber, a recirculation duct or leg bringing the lower part of the cyclone into communication with the lower part of the main body, as well as one or more heat exchanger elements in which the heating and vaporization of water are ensured by thermal contact with the gases and solid materials at high temperature circulating in the boiler. Combustible materials and possibly non-combustible materials in the form of solid particles are introduced at the base of the fluidization chamber and are suspended in an oxidizing gas which is generally air flowing from bottom to top in this chamber, with a speed sufficient to drive a substantial part of the solid particles up the fluidization chamber and from there into the recirculation cyclone.

On connaît trois types principaux de chau­dières à lit fluidisé qui diffèrent principalement par la structure et les fonctions du corps principal cons­tituant en particulier la chambre de fluidisation.Three main types of fluidized bed boilers are known, which differ mainly in the structure and functions of the main body constituting in particular the fluidization chamber.

Dans un premier type de chaudière, le corps principal comporte des parois membranées constituant l'échangeur de chaleur et la combustion se développe dans ce corps principal, au sein d'un milieu fluidisé circulant à une vitesse de l'ordre de 5 à 6 mètres/­seconde. Les parois intérieures du corps principal qui constituent les surfaces d'échange recueillent direc­tement la chaleur développée par la combustion qui est réglée de façon à opérer dans la zone optimale de tem­pérature de désulfuration du combustible, tout en opé­rant avec un excès d'air raisonnable. Ce type de chau­dière présente des caractéristiques de fonctionnement relativement satisfaisantes ; ces performances sont toutefois limitées par le fait que la densité de sus­pension des solides reste encore faible (10 à 30 kg/Nm³ de fumée), par le fait que le coefficient d'é­change dont la valeur est généralement comprise entre 50 et 80 kcal/m²h·C est limité par la présence d'une couche de matières solides plaquées contre les parois d'échange et par le fait que la zone de pré-gazéifica­tion des matières solides, à la base du corps princi­pal est de très faible volume, si bien que les rejets d'oxyde de l'azote dans les gaz sont relativement im­portants du fait qu'on utilise un excès d'air signifi­catif (de l'ordre de 20 %).In a first type of boiler, the main body has membrane walls constituting the heat exchanger and combustion develops in this main body, within a fluidized medium circulating at a speed of the order of 5 to 6 meters /second. The inner walls of the main body which constitute the exchange surfaces directly collect the heat developed by the combustion which is regulated so as to operate in the optimal temperature zone for desulphurization of the fuel, while operating with a reasonable excess of air. This type of boiler has relatively satisfactory operating characteristics; these performances are however limited by the fact that the density of suspension of the solids is still low (10 to 30 kg / Nm³ of smoke), by the fact that the exchange coefficient, the value of which is generally between 50 and 80 kcal / m²h · C is limited by the presence of a layer of solid materials pressed against the exchange walls and by the fact that the pre-gasification zone of solid materials, at the base of the main body is very small, if although the nitrogen oxide emissions in the gases are relatively large due to the fact that a significant excess of air is used (of the order of 20%).

Un second type de chaudière à lit fluidisé circulant comporte un corps principal dont la paroi interne est partiellement revêtue de matière réfrac­taire et partiellement munie de parois membranées, dans sa partie supérieure. Un échangeur de chaleur externe est associé à la chaudière et reçoit des par­ticules solides prélevées sur la jambe de recircula­tion, en sortie du cyclone et réinjectées dans le corps principal. Le prélèvement de matières solides et leur refroidissement au niveau de l'échangeur externe permettent d'assurer l'équilibre thermique de façon à opérer dans la zone de température optimale de désul­furation du combustible avec un excès d'air raisonna­ble qui est toujours de l'ordre de 20 %. Les vitesses de fluidisation dans le corps principal sont un peu plus élevées que pour le premier type de chaudière (6 à 8 m/s).A second type of circulating fluidized bed boiler comprises a main body, the internal wall of which is partially coated with refractory material and partially provided with membrane walls, in its upper part. An external heat exchanger is associated with the boiler and receives solid particles taken from the recirculation leg, at the outlet of the cyclone and reinjected into the main body. The removal of solids and their cooling at the level of the external exchanger ensure thermal equilibrium so as to operate in the optimum temperature zone for desulfurization of the fuel with a reasonable excess of air which is always around 20%. Fluidization velocities in the main body are somewhat higher than for the first type of boiler (6 to 8 m / s).

Cependant, la densité des matières en su­pension et le coefficient d'échange de chaleur dans la partie supérieure du corps principal restent à peu près identiques à ce qu'elles étaient dans le cas des chaudières du premier type. En revanche, le coeffi­cient d'échange atteint une valeur d'environ 300 à 350 kcal/m²·C dans l'échangeur externe qui opère en lit fluidisé à basse vitesse pour limiter l'érosion des tubes d'échangeur immergés dans le lit fluidisé.However, the density of materials in suspension and the heat exchange coefficient in the upper part of the main body remain roughly identical to what they were in the case of boilers of the first type. On the other hand, the exchange coefficient reaches a value of around 300 to 350 kcal / m² · C in the external exchanger which operates in a fluidized bed at low speed to limit the erosion of the exchanger tubes immersed in the fluidized bed .

Une telle chaudière présente cependant l'inconvénient de nécessiter un échangeur externe et des circuits d'agents de fluidisation, d'évacuation de gaz et de prélèvement et de réinjection de solides associés à cet échangeur externe ; le circuit de pré­lèvement de solides doit comporter une vanne de contrôle des quantités prélevées. Il en résulte que la construction de telles chaudières nécessite des inves­tissements supplémentaires relativement importants.However, such a boiler has the drawback of requiring an external exchanger and circuits of fluidizing agents, gas evacuation and sampling and reinjection of solids associated with this external exchanger; the solids sampling circuit must include a valve for controlling the quantities sampled. As a result, the construction of such boilers requires relatively large additional investments.

Un troisième type de chaudière possède un corps principal de faibles dimensions entièrement re­vêtu sur sa surface interne de matière réfractaire et en communication, comme dans les autres types de chau­dières, avec un cyclone de recirculation. Ce type de chaudière comporte également un échangeur externe dont les parois d'échange sont mises en contact avec des particules prélevées dans la jambe de recirculation, particules qui sont ensuite réinjectées dans le corps principal. Dans ce type de chaudière, la vitesse de fluidisation est très élevée (8 à 10 m/s) et le trans­fert thermique s'effectue intégralement en dehors de la boucle principale de circulation du lit fluidisé. L'inconvénient de ce type de chaudière est qu'il nécessite, comme précédemment, une boucle de circula­tion de solides supplémentaires sur laquelle est situé l'échangeur externe, ce qui se traduit par un coût de construction accru. Il est également nécessaire d'in­troduire des particules de très forte granulométrie à la base du corps principal, ces particules n'étant pas mises en circulation et permettant de créer artifi­ciellement une phase dense susceptible de piéger et de convertir les particules fines de combustible qui sont réintroduites à la base du corps principal.A third type of boiler has a main body of small dimensions entirely coated on its internal surface with refractory material and in communication, as in other types of boilers, with a recirculating cyclone. This type of boiler also includes an external exchanger, the exchange walls of which are brought into contact with particles taken from the recirculation leg, particles which are then reinjected into the main body. In this type of boiler, the fluidization speed is very high (8 to 10 m / s) and the heat transfer takes place entirely outside the main circulation loop of the fluidized bed. The downside of this type of boiler is that requires, as before, an additional solids circulation loop on which the external exchanger is located, which results in an increased construction cost. It is also necessary to introduce particles of very large particle size at the base of the main body, these particles not being circulated and making it possible to artificially create a dense phase capable of trapping and converting the fine particles of fuel which are reintroduced at the base of the main body.

Le but de l'invention est donc de proposer une chaudière à lit fluidisé circulant utilisant la chaleur produite par la combustion de matières en cir­culation et comportant une chambre de fluidisation allongée à axe vertical entièrement revêtue, sur sa surface interne, d'une couche de matériau réfractaire, à la base de laquelle on introduit une matière combus­tible et éventuellement une matière solide non combus­tible sous forme de particules, ainsi qu'un gaz oxy­dant de mise en suspension des dites matières solides circulant de bas en haut dans la chambre, au moins un cyclone de recirculation à axe vertical, en communica­tion avec la partie supérieure de la chambre de flui­disation par un conduit disposé de façon sensiblement tangentielle par rapport au cyclone de recirculation, un conduit de recyclage de matières solides mettant en communication la partie inférieure du cyclone de re­circulation avec la partie inférieure de la chambre de fluidisation et au moins un élément d'échangeur de chaleur dans lequel circule de l'eau à chauffer et à vaporiser dont la surface d'échange externe vient en contact avec des gaz et matières solides chaudes en circulation, chaudière qui permette d'obtenir de très bonnes performances de fonctionnement et dont les coûts de construction et d'entretien soient limités.The object of the invention is therefore to provide a circulating fluidized bed boiler using the heat produced by the combustion of circulating materials and comprising an elongated fluidization chamber with vertical axis entirely coated, on its internal surface, with a layer of refractory material, at the base of which a combustible material and possibly a non-combustible solid material are introduced in the form of particles, as well as an oxidizing gas for suspending said solid materials circulating from bottom to top in the chamber, at least a recirculation cyclone with a vertical axis, in communication with the upper part of the fluidization chamber by a conduit disposed substantially tangentially with respect to the recirculation cyclone, a solids recycling conduit bringing the lower part of the cyclone into communication recirculation with the lower part of the fluidization chamber and at least one heat exchanger element eur in which circulates water to be heated and vaporized, the external exchange surface of which comes into contact with hot gases and solid matter in circulation, a boiler which makes it possible to obtain very good operating performance and whose construction and maintenance costs are limited.

Dans ce but, au moins un élément d'échangeur de chaleur est placé à l'intérieur du cyclone de re­circulation, au moins dans sa partie supérieure qui comporte des moyens assurant la combustion des gaz et des solides combustibles en circulation dans cette partie du cyclone.For this purpose, at least one heat exchanger element is placed inside the recirculation cyclone, at least in its upper part which comprises means ensuring the combustion of the gases and combustible solids circulating in this part of the cyclone .

Dans un mode de réalisation préférentielle, le cyclone de recirculation comporte, au moins dans sa partie supérieure, des moyens d'injection d'air dans le lit fluidisé circulant disposés dans des directions sensiblement tangentielles par rapport au cyclone.In a preferred embodiment, the recirculation cyclone comprises, at least in its upper part, means for injecting air into the circulating fluidized bed arranged in directions substantially tangential to the cyclone.

Afin de bien faire comprendre l'invention, on va maintenant décrire, à titre d'exemple non limi­tatif, en se référant aux figures jointes en annexe, un mode de réalisation d'une chaudière à lit fluidisé circulant selon l'invention.

  • La Fig. 1 est une vue en coupe verticale, suivant A-A de la Fig. 2, d'une chaudière à lit flui­disé circulant selon l'invention ;
  • La Fig. 2 est une vue en coupe suivant B-B de la Fig. 1 ;
  • La Fig. 3 est une vue suivant F de la Fig. 1.
  • La Fig. 4 est une vue en coupe suivant C-C de la Fig. 1.
In order to clearly understand the invention, a description will now be given, by way of nonlimiting example, with reference to the appended figures, an embodiment of a circulating fluidized bed boiler according to the invention.
  • Fig. 1 is a view in vertical section, along AA in FIG. 2, of a circulating fluidized bed boiler according to the invention;
  • Fig. 2 is a sectional view along BB of FIG. 1;
  • Fig. 3 is a view along F of FIG. 1.
  • Fig. 4 is a sectional view along CC of FIG. 1.

Sur la Fig. 1, on voit l'ensemble de la chaudière comportant un corps principal 1 de forme allongée à axe vertical, un cyclone de recirculation de forme cylindro-tronconique 2 et une jambe de re­circulation 3.In Fig. 1, the entire boiler is seen comprising a main body 1 of elongated shape with a vertical axis, a recirculation cyclone of cylindro-frustoconical shape 2 and a recirculation leg 3.

La partie supérieure du corps principal 1 est mise en communication avec la partie supérieure du cyclone 2, par l'intermédiaire d'un conduit 4 dirigé de façon tangentielle par rapport au cyclone 2, comme il est visible sur la Fig. 2. La jambe de recircula­tion 3, en forme de "J", comme il est visible sur la Fig. 3, met en communication la partie inférieure du cyclone de recirculation 2 avec la partie inférieure du corps principal 1. Les composants 1, 2, 3 et 4 de la chaudière constituent la boucle de circulation du lit fluidisé.The upper part of the main body 1 is placed in communication with the upper part of the cyclone 2, by means of a directed duct 4 tangentially with respect to cyclone 2, as can be seen in FIG. 2. The recirculation leg 3, in the shape of a "J", as can be seen in FIG. 3, puts the lower part of the recirculation cyclone 2 into communication with the lower part of the main body 1. The components 1, 2, 3 and 4 of the boiler constitute the circulation loop of the fluidized bed.

La partie inférieure du corps principal 1 reçoit les matières solides qui sont introduites dans la chute terminale 3a de la jambe de recirculation 3 par une conduite 7 ; ces matières solides sont consti­tuées, par exemple, par des particules de charbon qui constituent le combustible et des particules de cal­caire qui constituent une matière désulfurante et ca­loporteuse. Ces matières solides sont reçues par une grille de fluidisation 5 placée à l'extrémité infé­rieure du corps principal 1 sous laquelle débouche une conduite 8 d'injection d'air primaire réalisant la fluidisation des matières solides dans la partie infé­rieure du corps principal 1 qui constitue la chambre de fluidisation de la chaudière.The lower part of the main body 1 receives the solid materials which are introduced into the terminal chute 3a of the recirculation leg 3 through a pipe 7; these solid materials are constituted, for example, by particles of coal which constitute the fuel and particles of limestone which constitute a desulfurizing and heat-transferable material. These solid materials are received by a fluidization grid 5 placed at the lower end of the main body 1 under which opens a primary air injection pipe 8 carrying out the fluidization of the solid materials in the lower part of the main body 1 which constitutes the fluidization chamber of the boiler.

Ainsi qu'il est visible sur les Fig. 3 et 4, cette partie inférieure du corps principal 1 présente une section carrée élargie par rapport à la section courante de forme rectangulaire du corps principal vi­sible sur la Fig. 2.As can be seen in Figs. 3 and 4, this lower part of the main body 1 has a square section enlarged with respect to the current rectangular section of the main body visible in FIG. 2.

Comme il est visible sur la Fig. 1, cette partie inférieure 1a reçoit, en plus des moyens de fluidisation 5, 8, le brûleur de démarrage 9 de la chaudière, un brûleur de préchauffage 10, un conduit d'évacuation de cendres 12 et des thermocouples 13 permettant la détermination de la température dans cette zone de la chaudière, pour la conduite du pro­ cessus.As can be seen in FIG. 1, this lower part 1a receives, in addition to the fluidization means 5, 8, the starting burner 9 of the boiler, a preheating burner 10, an ash evacuation duct 12 and thermocouples 13 allowing the determination of the temperature in this area of the boiler, for driving the pro stopped.

La surface intérieure du corps principal 1 constituant la chambre de fluidisation est entièrement revêtue par une matière réfractaire 14 assurant la protection de son enveloppe métallique externe sur la­quelle est intercalé un joint de dilatation 15 en partie inférieure. Des thermocouples 16 traversent la paroi du corps principal 1 dans sa partie supérieure. Le corps principal 1 comporte également un clapet de sécurité 18, à son extrémité supérieure reliée au conduit 4 d'arrivée tangentielle du lit circulant dans le cyclone de recirculation 2.The inner surface of the main body 1 constituting the fluidization chamber is entirely coated with a refractory material 14 ensuring the protection of its external metallic envelope on which is inserted an expansion joint 15 in the lower part. Thermocouples 16 pass through the wall of the main body 1 in its upper part. The main body 1 also includes a safety valve 18, at its upper end connected to the duct 4 for the tangential arrival of the bed circulating in the recirculation cyclone 2.

Le cyclone 2 comporte une partie supérieure 20 entièrement revêtue de matériau réfractaire et en communication à sa partie supérieure avec une chambre 21 d'évacuation des fumées qui sont emmenées par l'in­termédiaire d'une conduite 22 revêtue intérieurement de réfractaire, vers une installation de récupération thermique et de dépoussiérage du type habituellement utilisé en association avec les chaudières à lit cir­culant.The cyclone 2 has an upper part 20 entirely coated with refractory material and in communication at its upper part with a chamber 21 for evacuating the fumes which are taken via a pipe 22 internally coated with refractory, to an installation for heat recovery and dust removal of the type usually used in association with circulating bed boilers.

Le cyclone de recirculation 2 comporte en-­dessous de sa partie 20 revêtue de réfractaire, une partie 24 de forme cylindrique dont la paroi intérieu­re porte un échangeur de chaleur 25 dans lequel circu­le de l'eau, l'ensemble de la paroi intérieure de la partie 24 du cyclone constituant une surface d'échan­ge. La chambre d'évacuation des fumées 21 est mise en communication avec la partie 20 du cyclone par l'in­termédiaire d'un tube séparateur 27 dont la paroi constitue une paroi d'échangeur de chaleur dans la­quelle circule de l'eau.The recirculation cyclone 2 comprises, below its part 20 coated with a refractory, a part 24 of cylindrical shape, the inner wall of which carries a heat exchanger 25 in which water circulates, the whole of the inner wall of the part 24 of the cyclone constituting an exchange surface. The smoke evacuation chamber 21 is placed in communication with the part 20 of the cyclone by means of a separator tube 27, the wall of which constitutes a heat exchanger wall in which water circulates.

La partie inférieure 26 du cyclone 2, de forme tronconique, comporte sur la plus grande partie de sa hauteur, une paroi membranée dans laquelle cir­cule de l'eau constituant un échangeur de chaleur 28 et dans sa partie inférieure, sur une faible hauteur, une paroi 29 recouverte intérieurement de matériau réfractaire, cette partie inférieure étant en commu­nication directe avec la jambe de recirculation 3 également recouverte de matériau réfractaire.The lower part 26 of cyclone 2, of frustoconical shape, comprises on the greater part from its height, a membrane wall in which water circulates constituting a heat exchanger 28 and in its lower part, over a small height, a wall 29 internally covered with refractory material, this lower part being in direct communication with the leg recirculation 3 also covered with refractory material.

Des conduites 30 d'introduction d'air secon­daire dans le cyclone, de direction sensiblement tan­gentielle par rapport à celui-ci sont placées, aussi bien au niveau de la partie supérieure 20 que de la partie supérieure cylindrique 24 de ce cyclone. Des thermocouples 32 et 33 traversent la paroi du cyclone, au niveau de sa partie 20 et de sa partie 24 respecti­vement. Des pattes de support 34 sont soudées sur la surface extérieure de la partie tronconique 26 du cyclone.Lines 30 for introducing secondary air into the cyclone, in a direction substantially tangential with respect to the latter, are placed, both at the level of the upper part 20 and of the cylindrical upper part 24 of this cyclone. Thermocouples 32 and 33 pass through the wall of the cyclone, at its part 20 and its part 24 respectively. Support tabs 34 are welded to the outer surface of the frustoconical part 26 of the cyclone.

La partie inférieure du cyclone de recircu­lation 2 est en communication avec la jambe de recir­culation 3 dont la forme est visible en se reportant aux figures 1 et 3. Cette jambe de recirculation a une forme de "J" qui permet la constitution d'un sas pour le gaz en circulation dans la partie inférieure 1a de la chambre de fluidisation et d'éviter ainsi le passa­ge de ce gaz du corps principal 1 au cyclone 2, par l'intermédiaire du conduit de recirculation 3. Les ma­tières solides séparées des gaz parvenant à la partie inférieure du cyclone et constituées en grande partie de cendres de combustion et de particules de calcaire caloporteuses se déversent dans la partie verticale d'entrée du conduit de recirculation 3 puis sont reçues sur le fond horizontal de ce conduit ; la re­circulation de ces matières solides en particules est assurée par des buses 35 d'injection d'air de recir­ culation traversant le fond horizontal de la jambe de recirculation 3. Les matières solides remises en cir­culation par les buses 35 inclinées vers la sortie de la jambe 3 remontent dans sa partie verticale de sor­tie à partir de laquelle elles se déversent dans la chute 3a communiquant avec la partie 1a de la chambre de fluidisation. Une partie des matières solides par­venant dans la jambe de recirculation 3 peut être évacuée par une conduite 36 qui est reliée à un cir­cuit sur lequel se trouve un échangeur de chaleur ex­terne, une vanne de contrôle du débit d'extraction de matières solides permettant le réglage de cette ex­traction. Le circuit de l'échangeur externe se referme sur la jambe de recirculation 3 grâce à une conduite 37 de réinjection des matières solides refroidies.The lower part of the recirculation cyclone 2 is in communication with the recirculation leg 3, the shape of which is visible by referring to FIGS. 1 and 3. This recirculation leg has a "J" shape which allows the formation of an airlock for the gas circulating in the lower part 1a of the fluidization chamber and thus avoiding the passage of this gas from the main body 1 to the cyclone 2, via the recirculation conduit 3. The solid matter separated from the gases reaching at the bottom of the cyclone and consisting mainly of combustion ash and heat-transferable limestone particles pour into the vertical inlet part of the recirculation duct 3 and are then received on the horizontal bottom of this duct; the recirculation of these solid particles into particles is ensured by recirculation air injection nozzles 35 culation crossing the horizontal bottom of the recirculation leg 3. The solid materials recirculated by the nozzles 35 inclined towards the outlet of the leg 3 rise in its vertical outlet part from which they pour into the chute 3a communicating with part 1a of the fluidization chamber. Part of the solids arriving in the recirculation leg 3 can be evacuated via a pipe 36 which is connected to a circuit on which there is an external heat exchanger, a valve for controlling the solids extraction flow rate allowing adjustment of this extraction. The circuit of the external exchanger closes on the recirculation leg 3 thanks to a pipe 37 for reinjection of the cooled solid materials.

Le fonctionnement de la chaudière selon l'invention qui a été décrite est le suivant : du charbon et du calcaire sous forme particulaire sont introduits dans la partie inférieure 1a de la chambre de fluidisation et de l'air primaire est introduit sous la grille 5 par l'intermédiaire des conduites 8. L'air primaire circulant de bas en haut dans la cham­bre de fluidisation 1 entraîne les particules solides vers le haut de cette chambre. La partie élargie 1a à 1a base de cette chambre 1 permet de réaliser le pié­geage des particules à forte granulométrie dont le ré­trécissement de la chambre empêche l'entraînement vers la partie supérieure.The operation of the boiler according to the invention which has been described is as follows: coal and limestone in particulate form are introduced into the lower part 1a of the fluidization chamber and primary air is introduced under the grid 5 by through the conduits 8. The primary air flowing from bottom to top in the fluidization chamber 1 carries the solid particles upwards from this chamber. The enlarged part 1a at the base of this chamber 1 makes it possible to trap particles with large particle sizes whose narrowing of the chamber prevents entrainment towards the upper part.

A la mise en route de la chaudière, le brû­leur de démarrage 9 permet d'élever la température dans l'enceinte ce qui permet ensuite l'introduction du combustible qui subit de ce fait une prépyrolyse et une gazéification dans la zone 1a. Le processus est conduit en régime réducteur dans cette zone 1a, l'air introduit à la base de la chambre 1 étant limité à la quantité d'air nécessaire pour la fluidisation.When the boiler is started, the start-up burner 9 makes it possible to raise the temperature in the enclosure, which then allows the introduction of the fuel, which therefore undergoes prepyrolysis and gasification in zone 1a. The process is carried out in a reducing regime in this zone 1a, the air introduced at the base of chamber 1 being limited to the amount of air required for fluidization.

Ce mode de fonctionnement avec une zone ré­actionnelle secondaire à la base de la chambre 1 per­met en particulier de diminuer les rejets d'oxyde de l'azote dans les gaz et d'éviter l'entraînement des grosses particules de combustible vers la partie supé­rieure du cyclone où ces particules risqueraient d'en­dommager le matériau réfractaire de revêtement. Ces particules à forte granulométrie peuvent être fractu­rées et converties à l'interieur de la zone 1a. Cette zone 1a a également l'avantage de favoriser le mélange entre le combustible introduit et les matières solides remises en circulation par la jambe 3.This mode of operation with a secondary reaction zone at the base of the chamber 1 makes it possible in particular to reduce the discharges of nitrogen oxide in the gases and to avoid the entrainment of large fuel particles towards the upper part of the cyclone where these particles could damage the refractory lining material. These particles with a large particle size can be fractured and converted inside the zone 1a. This zone 1a also has the advantage of favoring the mixing between the fuel introduced and the solid matter recirculated by the leg 3.

Dans la chambre 1 on réalise, en plus de la fluidisation, une pyrolyse et une gazéification plus ou moins complète du combustible, si bien que le lit fluidisé parvenant dans la partie supérieure 20 du cy­clone est constitué par un mélange de gaz et de matiè­res solides renfermant une forte proportion de matiè­res combustibles. Ce mélange subit un mouvement tour­billonnaire dès l'entrée du cyclone et constitue un vortex, ce qui, avec l'action combinée du choc des particules sur la surface d'impact en réfractaire 20, réduit considérablement la vitesse de circulation ver­ticale des matières dans le cyclone et accroît la den­sité de matières sous forme de particules solides dans les gaz. Cet effet de vortex est accru par les injec­tions étagées et tangentielles d'air secondaire injec­té par les conduites 30. Ceci contribue à maintenir une densité élevée des particules solides dans la zone cylindrique du cyclone. L'air secondaire est injecté en quantité suffisante pour réaliser une combustion poussée des matières en circulation et pour maintenir une atmosphère nettement oxydante dans la partie supé­rieure du cyclone. Sous l'effet de la température et de l'atmosphère oxydante, on réalise la désulfuration des matières combustibles par formation de sulfate CaSo4 stable à partir du sulfure de calcium précédem­ment formé par réaction du soufre du combustible sur les particules de calcaire.In the chamber 1, in addition to the fluidization, a pyrolysis and a more or less complete gasification of the fuel are carried out, so that the fluidized bed arriving in the upper part of the cyclone is constituted by a mixture of gas and solids containing a high proportion of combustible materials. This mixture undergoes a vortex movement upon entry of the cyclone and constitutes a vortex, which, with the combined action of the impact of the particles on the impact surface in refractory 20, considerably reduces the speed of vertical circulation of materials in the cyclone and increases the density of matter in the form of solid particles in the gases. This vortex effect is increased by the staged and tangential injections of secondary air injected through the conduits 30. This contributes to maintaining a high density of solid particles in the cylindrical zone of the cyclone. Secondary air is injected in sufficient quantity to achieve a high combustion of the circulating materials and to maintain a clearly oxidizing atmosphere in the upper part of the cyclone. Under the effect of the temperature and the oxidizing atmosphere, the desulfurization of the combustible materials is carried out by formation of stable CaSo4 sulfate from the calcium sulfide previously formed by reaction of the sulfur of the fuel with the limestone particles.

On constitue donc dans la partie supérieure 20, 24 du cyclone 2 une zone réactionnelle dans la­quelle l'effet vortex augmente le temps de séjour des particules solides. La circulation des gaz et particu­les favorise d'autre part le contact et les échanges thermiques avec l'échangeur de chaleur 25 d'une façon telle que la surface d'échange balayée par un gaz à grande vitesse ne se trouve pas recouverte par une couche de solides et qu'en conséquence le coefficient d'échange de chaleur reste élevé. Les parois du tube séparateur 27 favorisant la séparation des gaz et des particules solides constituent également des surfaces d'échanges récupérant une partie de la chaleur de com­bustion. Les gaz brûlés portant en suspension des par­ticules solides fines sont entraînées, à l'intérieur du tube vertical 27, vers la chambre 21 pour consti­tuer les fumées extraites par le conduit 22. Les par­ticules solides récupérés par le cyclone retombent dans la partie tronconique 26 de ce cyclone et sont refroidies au contact des parois de l'échangeur de chaleur 28 constituant une partie de la paroi interne du tronc de cône 26.There is therefore formed in the upper part 20, 24 of the cyclone 2 a reaction zone in which the vortex effect increases the residence time of the solid particles. The circulation of gases and particles also promotes contact and heat exchanges with the heat exchanger 25 in such a way that the exchange surface swept by a gas at high speed is not covered by a layer. solids and therefore the heat exchange coefficient remains high. The walls of the separator tube 27 promoting the separation of gases and solid particles also constitute exchange surfaces recovering part of the heat of combustion. The burnt gases carrying fine solid particles in suspension are entrained, inside the vertical tube 27, towards the chamber 21 to constitute the fumes extracted by the conduit 22. The solid particles recovered by the cyclone fall back in the frustoconical part 26 of this cyclone and are cooled in contact with the walls of the heat exchanger 28 constituting a part of the internal wall of the truncated cone 26.

Les matières solides refroidies retombent alors dans le conduit de recirculation 3 pour être recyclées à l'intérieur de la partie inférieure 1a de la chambre 1. Les cendres formées sont évacuées pé­riodiquement par le conduit d'extraction 12.The cooled solid materials then fall back into the recirculation duct 3 to be recycled inside the lower part 1a of the chamber 1. The ash formed is periodically removed by the extraction duct 12.

Lorsqu'on utilise un circuit comportant un échangeur de chaleur externe, on dispose d'un moyen supplémentaire pour prélever la chaleur des matières solides recyclées.When a circuit with an external heat exchanger is used, there is an additional means for removing heat from the recycled solid materials.

On voit donc que les principales caractéris­tiques du dispositif, à savoir la présence d'une cham­bre de fluidisation entièrement revêtue de réfractaire et la disposition de corps d'échangeurs de chaleur dans le cyclone de recirculation et plus particulière­ment dans sa partie supérieure, permettent d'obtenir un fonctionnement avec des densités de matières soli­des plus élevées et des temps de séjour du gaz dans la zone réactionnelle beaucoup plus longs, pour une même hauteur des installations. Dans la chambre de fluidi­sation précédant le cyclone de recirculation, on ne réalise que la pyrolyse et la gazéification partielle du combustible, la zone principale de réaction se si­tuant dans la partie supérieure du cyclone. Les échan­ges thermiques dans cette zone sont fortement accrus par effet vortex, si bien que les surfaces d'échanges thermiques peuvent être considérablement réduites, de l'ordre de 30 %. On aura réduit ainsi considérablement l'encombrement et le coût de construction de la chau­dière et de ses installations annexes. Des injections tangentielles dans la partie supérieure du cyclone permettent de renforcer ces effets.It can therefore be seen that the main characteristics of the device, namely the presence of a fluidization chamber entirely coated with refractory and the arrangement of heat exchanger bodies in the recirculation cyclone and more particularly in its upper part, make it possible to obtain operation with higher solids densities and much longer gas residence times in the reaction zone, for the same height of the installations. In the fluidization chamber preceding the recirculation cyclone, only the pyrolysis and partial gasification of the fuel are carried out, the main reaction zone being located in the upper part of the cyclone. The heat exchanges in this area are greatly increased by the vortex effect, so that the heat exchange surfaces can be considerably reduced, of the order of 30%. This will have considerably reduced the size and the cost of construction of the boiler and its ancillary installations. Tangential injections in the upper part of the cyclone can reinforce these effects.

La zone supérieure 20 du cyclone revêtue de matière réfractaire permet de ralentir les particules en circulation et donc de diminuer l'érosion des pa­rois d'échange situées en-dessous de la zone 20.The upper zone 20 of the cyclone coated with refractory material makes it possible to slow down the particles in circulation and therefore to reduce the erosion of the exchange walls located below the zone 20.

L'existence d'une zone réactionnelle secon­daire de section élargie à la base de la colonne de fluidisation permet d'obtenir d'autres avantages quant à la conduite du processus.The existence of a secondary reaction zone of enlarged section at the base of the fluidization column makes it possible to obtain other advantages as regards the conduct of the process.

Les dispositions constructives adoptées per­mettent la mise en pression des équipements qui, de ce fait, peuvent être utilisés dans une filière à cycle direct c'est-à-dire sans échangeur extérieur.The constructive provisions adopted allow the pressurization of the equipment which, therefore, can be used in a direct cycle die, that is to say without external exchanger.

L'invention ne se limite pas au mode de réa­lisation qui a été décrit. C'est ainsi que les élé­ments d'échangeur de chaleur peuvent être disposés d'une façon différente de celle qui a été décrite ; par exemple, ces éléments d'échangeur de chaleur peu­vent être limités strictement à la partie supérieure cylindrique du cyclone de recirculation. Ces échan­geurs de chaleur peuvent être réalisés sous la forme de parois membranées d'un type quelconque comportant des moyens distributeurs d'eau et de récupération de vapeur.The invention is not limited to the embodiment which has been described. This is how the heat exchanger elements can be arranged in a different way from that which has been described; for example, these heat exchanger elements can be strictly limited to the cylindrical upper part of the recirculation cyclone. These heat exchangers can be produced in the form of membrane walls of any type comprising means for distributing water and recovering steam.

L'installation peut être réalisé sous forme modulaire, un seul corps principal constituant la co­lonne de fluidisation étant relié pour leur alimen­tation à plusieurs cyclones de recirculation renfer­mant des échangeurs de chaleur.The installation can be carried out in modular form, a single main body constituting the fluidization column being connected for their supply to several recirculation cyclones containing heat exchangers.

Les cyclones de recirculation peuvent être de tous types connus, à partir du moment où ils per­mettent la disposition d'échangeurs de chaleur sur leur paroi interne. En particulier, ils peuvent être de type à contre-courant comme dans le mode de réali­sation qui vient d'être décrit ou à courants de gaz et de particules récupérés circulant dans le même sens. La taille de ces cyclones peut être quelconque puisque les effets de circulation tangentielle des gaz peuvent être maîtrisés grâce à des injections de gaz à diffé­rents endroits étagés dans le cyclone.Recirculation cyclones can be of any known type, from the moment they allow the provision of heat exchangers on their internal wall. In particular, they can be of the counter-current type as in the embodiment which has just been described or with streams of recovered gases and particles circulating in the same direction. The size of these cyclones can be arbitrary since the effects of tangential gas circulation can be controlled by means of gas injections at different stepped locations in the cyclone.

Enfin, la chaudière suivant l'invention peut être alimentée en tous combustibles ou autres matières sous forme de particules, sa conduite étant particu­ lièrement souple, grâce aux moyens internes ou aux moyens annexes dont on dispose pour le réglage de la combustion et de la circulation du lit fluidisé.Finally, the boiler according to the invention can be supplied with all fuels or other materials in the form of particles, its pipe being particu smoothly flexible, thanks to the internal means or to the additional means available for adjusting the combustion and the circulation of the fluidized bed.

Claims (9)

1. Chaudière à lit fluidisé circulant utili­sant la chaleur produite par la combustion de matières en circulation et comportant une chambre de fluidisa­tion (1) allongée à axe vertical entièrement revêtue, sur sa surface interne, d'une couche de matériau ré­fractaire (14), à la base de laquelle on introduit une matière combustible et éventuellement une matière so­lide non combustible, sous forme de particules ainsi qu'un gaz oxydant de mise en suspension des matières solides circulant de bas en haut dans la chambre (1), au moins un cyclone de recirculation (2) à axe verti­cal, en communication avec la partie supérieure de la chambre de fluidisation (1) par un conduit (4) disposé de façon sensiblement tangentielle par rapport au cy­clone de recirculation (2), un conduit de recyclage (3) de matières solides mettant en communication la partie inférieure du cyclone de recirculation (2) avec la partie inférieure de la chambre de fluidisation (1) et au moins un élément d'échangeur de chaleur (25, 26, 27) dans lequel circule de l'eau à chauffer et à vapo­riser dont la surface d'échange externe vient en contact avec des gaz et matières solides chaudes en circulation, caractérisée par le fait qu'au moins un élément d'échangeur de chaleur (25, 26, 27) est placé à l'intérieur du cyclone de recirculation (2) au moins dans sa partie supérieure qui comporte des moyens (30) assurant la combustion des gaz et solides combustibles en circulation dans cette partie du cyclone (2).1. Circulating fluidized bed boiler using the heat produced by the combustion of circulating materials and comprising an elongated fluidization chamber (1) with vertical axis entirely coated, on its internal surface, with a layer of refractory material (14), at the base of which a combustible material and possibly a non-combustible solid material are introduced, in the form of particles as well as an oxidizing gas for suspending the solid materials circulating from bottom to top in the chamber (1), at least one recirculation cyclone (2) with vertical axis, in communication with the upper part of the fluidization chamber (1) by a conduit (4) disposed substantially tangentially with respect to the recirculation cyclone (2), a recycling conduit ( 3) solid matter communicating the lower part of the recirculation cyclone (2) with the lower part of the fluidization chamber (1) and at least one heat exchanger element (25, 26, 27) in which circulates water to be heated and vaporized, the external exchange surface of which comes into contact with hot gases and solid matter in circulation, characterized in that at least one element d heat exchanger (25, 26, 27) is placed inside the recirculation cyclone (2) at least in its upper part which comprises means (30) ensuring the combustion of the gases and combustible solids circulating in this part cyclone (2). 2. Chaudière à lit fluidisé suivant la re­vendication 1, caractérisée par le fait que le cyclone de recirculation (2) comporte, au moins dans sa partie supérieure (20, 24) des moyens d'injection d'air (30) dans le lit fluidisé circulant disposés dans des di­ rections sensiblement tangentielles par rapport au cy­clone (2).2. Fluidized bed boiler according to claim 1, characterized in that the recirculation cyclone (2) comprises, at least in its upper part (20, 24) means for injecting air (30) into the bed fluidized circulating arranged in di rections substantially tangential to the cyclone (2). 3.- Chaudière à lit fluidisé suivant l'une quelconque des revendications 1 et 2, caractérisé par le fait que le cyclone de recirculation (2) comporte une zone supérieure (20) où la paroi interne du cy­clone est revêtue d'une matière réfractaire, cette pa­roi située au-dessus des éléments d'échangeur de cha­leur (25, 26, 27) placés dans le cyclone subissant le choc des particules solides en circulation et assurant leur ralentissement.3.- fluidized bed boiler according to any one of claims 1 and 2, characterized in that the recirculation cyclone (2) has an upper zone (20) where the inner wall of the cyclone is coated with a refractory material , this wall located above the heat exchanger elements (25, 26, 27) placed in the cyclone undergoing the impact of the solid particles in circulation and ensuring their deceleration. 4. Chaudière à lit fluidisé suivant l'une quelconque des revendications 1, 2 et 3, caractérisée par le fait que la chambre ou colonne de fluidisation (1) comporte, dans sa partie inférieure, une zone élargie (1a) dans laquelle est introduite la matière combustible à fluidiser et l'air de fluidisation, re­liée à la partie courante de la chambre de fluidisa­tion (1), de plus faible section, par un rétrécisse­ment permettant le piégeage des particules de matières solides à forte granulométrie, la prépyrolyse et la gazéification de ces matières étant effectuées dans la zone élargie (1a).4. Fluidized bed boiler according to any one of claims 1, 2 and 3, characterized in that the fluidization chamber or column (1) comprises, in its lower part, an enlarged zone (1a) into which is introduced the combustible material to be fluidized and the fluidizing air, connected to the current part of the fluidization chamber (1), of smaller section, by a narrowing allowing the trapping of particles of solid materials with large particle size, the prepyrolysis and the gasification of these materials being carried out in the enlarged zone (1a). 5.- Chaudière à lit fluidisé suivant la re­vendication 4, caractérisée par le fait que le conduit (3) de recirculation des matières solides débouche, à son extrémité de sortie, dans la zone élargie (1a) dans laquelle est réalisé le brassage des matières so­lides recirculées et des matières solides neuves in­troduites à la base de la chambre de fluidisation (1).5.- fluidized bed boiler according to claim 4, characterized in that the conduit (3) for recirculating solid materials opens, at its outlet end, in the enlarged zone (1a) in which the mixing of the materials is carried out recirculated solids and new solids introduced at the base of the fluidization chamber (1). 6. Chaudière à lit fluidisé suivant l'une quelconque des revendications 1, 2, 3, 4 et 5, carac­térisée par le fait qu'elle comporte un tube sépara­teur (27) disposé à la partie supérieure du cyclone de recirculation (2) suivant son axe, débouchant à l'une de ses extrémités dans le cyclone et à son autre ex­trémité dans une chambre (21) d'évacuation des fumées, constitué par une paroi d'échangeur (27) dans laquelle circule de l'eau.6. Fluidized bed boiler according to any one of claims 1, 2, 3, 4 and 5, characterized in that it comprises a separator tube (27) disposed at the top of the cyclone of recirculation (2) along its axis, opening at one of its ends in the cyclone and at its other end in a chamber (21) for evacuating smoke, constituted by an exchanger wall (27) in which circulates the water. 7. Chaudière à lit fluidisé suivant l'une quelconque des revendications 1, 2, 3, 4, 5 et 6, ca­ractérisée par le fait que la paroi intérieure de la partie inférieure (26) du cyclone (2), de forme tron­conique, est constituée par une paroi d'échangeur (28).7. Fluidized bed boiler according to any one of claims 1, 2, 3, 4, 5 and 6, characterized in that the inner wall of the lower part (26) of the cyclone (2), of frustoconical shape, consists of an exchanger wall (28). 8. Chaudière à lit fluidisé suivant l'une quelconque des revendications 1 à 7, caractérisée par le fait qu'un échangeur de chaleur externe est inter­calé sur un circuit en dérivation sur le conduit de recirculation (3) des matières solides grâce à des conduites d'extraction et de réinjection de matières solides (36, 37).8. Fluidized bed boiler according to any one of claims 1 to 7, characterized in that an external heat exchanger is interposed on a bypass circuit on the recirculation pipe (3) of solid materials through pipes solids extraction and reinjection (36, 37). 9. Chaudière à lit fluidisé suivant la re­vendication 2, caractérisée par le fait que les moyens d'injection d'air (30) sont disposés de façon étagée dans la direction verticale, dans la partie supérieure du cyclone de recirculation (2).9. A fluidized bed boiler according to claim 2, characterized in that the air injection means (30) are arranged in a stepped manner in the vertical direction, in the upper part of the recirculation cyclone (2).
EP86401873A 1985-09-09 1986-08-26 Boiler with a circulating fluidized bed Expired EP0216677B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT86401873T ATE39019T1 (en) 1985-09-09 1986-08-26 BOILER WITH CIRCULATING FLUID BED.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8513355A FR2587090B1 (en) 1985-09-09 1985-09-09 CIRCULATING FLUIDIZED BED BOILER
FR8513355 1985-09-09

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EP0216677A1 true EP0216677A1 (en) 1987-04-01
EP0216677B1 EP0216677B1 (en) 1988-11-30

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US (1) US4683840A (en)
EP (1) EP0216677B1 (en)
AT (1) ATE39019T1 (en)
BR (1) BR8604281A (en)
DE (1) DE3661332D1 (en)
FR (1) FR2587090B1 (en)
ZA (1) ZA866811B (en)

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EP0247798A2 (en) * 1986-05-29 1987-12-02 Donlee Technologies Inc. Fluidised bed reactor and method of operating such a reactor
EP0413612A3 (en) * 1989-08-18 1991-07-31 Foster Wheeler Energy Corporation Fluidized bed steam generating system including a steam cooled cyclone separator
EP0497528A1 (en) * 1991-01-31 1992-08-05 Foster Wheeler Energy Corporation Steam generating system utilizing separate fluid flow circuitry between the furnace section and the separating section
WO1994021964A1 (en) * 1993-03-15 1994-09-29 Buehler Ag Fluidized bed
EP0851173A3 (en) * 1996-12-30 1999-07-28 Combustion Engineering, Inc. A method of controlling nitrous oxide in circulating fluidized bed steam generators
CN1304783C (en) * 2001-12-22 2007-03-14 浙江大学 Wind control type material outside circulating device of circulating fluid bed boiler

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US5343830A (en) * 1993-03-25 1994-09-06 The Babcock & Wilcox Company Circulating fluidized bed reactor with internal primary particle separation and return
US5375409A (en) * 1993-10-08 1994-12-27 Ahlstrom Pyropower, Inc. Pressurized fluidized bed combined gas turbine and steam turbine power plant with steam injection
US5363812A (en) * 1994-02-18 1994-11-15 The Babcock & Wilcox Company Method and apparatus for controlling the bed temperature in a circulating fluidized bed reactor
US6095095A (en) * 1998-12-07 2000-08-01 The Bacock & Wilcox Company Circulating fluidized bed reactor with floored internal primary particle separator
US7047894B2 (en) * 1999-11-02 2006-05-23 Consolidated Engineering Company, Inc. Method and apparatus for combustion of residual carbon in fly ash
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FR2802287B1 (en) * 1999-12-14 2002-01-11 Abb Alstom Power Comb METHOD FOR IMPROVING COMBUSTION IN A CIRCULATING FLUIDIZED BED SYSTEM AND CORRESPONDING SYSTEM
FR2871554A1 (en) * 2004-06-11 2005-12-16 Alstom Technology Ltd METHOD FOR THE ENERGY CONVERSION OF SOLID FUELS MINIMIZING OXYGEN CONSUMPTION
US7287477B2 (en) * 2004-10-13 2007-10-30 Foster Wheeler Energy Corporation Cyclone bypass for a circulating fluidized bed reactor
US8960107B2 (en) * 2005-06-17 2015-02-24 The SEFA Group Inc. Apparatus for turbulent combustion of fly ash
EE00758U1 (en) * 2005-12-30 2008-07-15 Obschestvo S Ogranichenoy Otvetstvenostyu ''polytechenergo'' Whirlwind
US20110036280A1 (en) * 2009-08-12 2011-02-17 Bruce Toase Waste processing system
US9617087B2 (en) * 2010-10-28 2017-04-11 General Electric Technology Gmbh Control valve and control valve system for controlling solids flow, methods of manufacture thereof and articles comprising the same
US9557115B2 (en) 2010-10-28 2017-01-31 General Electric Technology Gmbh Orifice plate for controlling solids flow, methods of use thereof and articles comprising the same
JP6099263B2 (en) * 2013-05-31 2017-03-22 株式会社タクマ Circulating fluidized bed boiler
CN106287685B (en) * 2016-08-22 2018-12-07 海伦市利民节能锅炉制造有限公司 Small-sized biomass shaped fuel Circulating Fluidized Bed Hot Water Boiler
CN108050527A (en) * 2018-01-18 2018-05-18 淮安中科环保电力有限公司 Flue gas separation method and cannula type cyclone separator based on cyclone separator

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EP0247798A2 (en) * 1986-05-29 1987-12-02 Donlee Technologies Inc. Fluidised bed reactor and method of operating such a reactor
EP0247798A3 (en) * 1986-05-29 1988-09-28 Donlee Technologies Inc. Fluidised bed reactor and method of operating such a reactor
EP0413612A3 (en) * 1989-08-18 1991-07-31 Foster Wheeler Energy Corporation Fluidized bed steam generating system including a steam cooled cyclone separator
EP0497528A1 (en) * 1991-01-31 1992-08-05 Foster Wheeler Energy Corporation Steam generating system utilizing separate fluid flow circuitry between the furnace section and the separating section
WO1994021964A1 (en) * 1993-03-15 1994-09-29 Buehler Ag Fluidized bed
EP0851173A3 (en) * 1996-12-30 1999-07-28 Combustion Engineering, Inc. A method of controlling nitrous oxide in circulating fluidized bed steam generators
CN1304783C (en) * 2001-12-22 2007-03-14 浙江大学 Wind control type material outside circulating device of circulating fluid bed boiler

Also Published As

Publication number Publication date
BR8604281A (en) 1987-05-05
EP0216677B1 (en) 1988-11-30
FR2587090B1 (en) 1987-12-04
US4683840A (en) 1987-08-04
FR2587090A1 (en) 1987-03-13
ATE39019T1 (en) 1988-12-15
ZA866811B (en) 1987-04-29
DE3661332D1 (en) 1989-01-05

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