EP2113718A2 - Cylindrical combustion grate for a furnace with a cooling system - Google Patents

Abstract

The roller (1) has a combustible support surface mounted on a metallic hollow structure (2) forming a cylindrical cage, and a passage pipe (3) for allowing passage of cooling fluid. A series of hollow rings (6) is coaxial to an axis and is distributed on length of the roller, where each ring is provided with a fluid inlet (7) and a fluid outlet (8). Inter-ring bridges (9) connect the fluid outlet of the ring to the fluid inlet so as to form cooling fluid passage circuit wrapped around the structure.

Description

TECHNICAL FIELD OF THE INVENTION

The invention relates to a roll for a grate of combustion and / or incineration furnace, and in particular for the incineration of waste.

The invention also relates to an incineration furnace and the use of such an oven.

STATE OF THE ART

Rollers for combustion and / or incineration furnaces are well known in the prior art. Commonly, the rolls are composed of a cylindrical metal frame on which bars are arranged to form a waste support surface. Annular slots are formed to allow combustion air to pass through the roll. Rollers of this type are described in particular in the document EP 0 124 826 .

However, the bars on which the waste is placed are subjected to very severe thermal stresses because of the high temperature levels prevailing in the combustion zone and the large temperature differences between the heatings due to the radiation and the contact of the materials in combustion and cooling from the blowing of combustion air. These large thermal stresses cause expansions and contractions of the constituent material of the bars causing dimensional variations and offsets between the bars and thus making possible the passage of clinker or metal casting between the bars. In addition, the air passing through the rollers is no longer distributed properly.

Thus, the life of the bars is reduced because they must be changed regularly to avoid the disadvantages mentioned above.

In addition, the grids equipped with such rollers can only partially exploit the calorific value of the waste. Indeed, in order to limit the thermal stresses exerted on the bars, the temperature in the furnace hearth is limited so that the combustion of some waste remains incomplete.

To solve these problems, it is known to provide the rollers with a cooling device for maintaining the bars at a restricted temperature.

The document US 5,042,401 describes a roller having hollow longitudinal bars forming the outer surface of the waste support and allowing the passage of a cooling fluid. The bars are fed in parallel by means of a flow distribution device disposed at one end of said roll. However, in this case, the bars undergo significant deformations related to an "all or nothing" exposure in the furnace of the incineration furnace. In addition, because of this arrangement of the bars and the risk of deformation, the risk of blockage of the rollers by the transit areas between two adjacent rollers and / or slag falls in these transit areas are important.

The document GB 251 849 describes a roller composed of a cylindrical central tube inside which circulates a cooling fluid and around which are arranged curved bars forming rings around said central tube. However, the cooling circuit only allows a poor cooling of the surface of the bars actually in contact with the products to be incinerated and the thermal stresses applied on the bars are only slightly decreased.

In addition, the patent application FR 2908180 unpublished patent filed by the Applicant discloses rollers comprising a framework, a support surface mounted around the framework and formed by a conduit for passage of a cooling fluid forming a helical winding around the longitudinal axis of the roller. Thus, the particular shape of the passage of the cooling fluid ensures uniform cooling of the support surface. In addition, the shape of the winding serves to purge the air present in the duct during the rotation of the roller.

However, the manufacture and installation on the roll of a spiral-shaped conduit are relatively complex.

In addition, because of its helical disposition, the conduit for passage of the cooling circuit is still deformed degrading its life.

OBJECT OF THE INVENTION

The invention aims to remedy these problems by proposing a roll for an oven rack resistant to the temperature conditions prevailing in the oven, in order to limit the maintenance operations and to allow the incineration of the waste at high temperatures so as to obtain a complete combustion of waste, and whose manufacture, maintenance and assembly are simple.

• une ossature formant une cage cylindrique ;
• une surface de support du combustible, montée autour de ladite ossature et pourvue de moyens de passage du gaz comburant au travers du rouleau, ladite surface de support étant formée par au moins une surface d'un conduit permettant le passage d'un fluide de refroidissement.

Le rouleau est remarquable en ce que le conduit de passage du fluide de refroidissement comprend :

• une série d'anneaux creux, coaxiaux à l'axe A, répartis sur la longueur dudit rouleau, comprenant chacun une entrée et une sortie de fluide ; et
• des pontages raccordant la sortie de fluide d'un anneau à l'entrée de fluide de l'anneau suivant, afin de former un circuit de passage du fluide de refroidissement enroulé autour de ladite ossature.

For this purpose, and according to a first aspect, the invention proposes a roll for an oven rack, intended to be rotatably mounted in the hearth of said oven about an axis A longitudinal to said roll, comprising:

• a frame forming a cylindrical cage;
• a fuel support surface mounted around said framework and provided with means for passage of the oxidant gas through the roller, said support surface being formed by at least one surface of a conduit for the passage of a cooling fluid; .

The roller is remarkable in that the cooling fluid passageway comprises:

• a series of hollow rings, coaxial with the axis A, distributed over the length of said roller, each comprising an inlet and a fluid outlet; and
• bridges connecting the fluid outlet of a ring to the fluid inlet of the next ring, to form a coolant passage circuit wrapped around said framework.

Thus, the manufacture and assembly of the rollers according to the invention are relatively easy because the conduit for the passage of cooling is composed of rings simpler to make and assemble than turns.

In addition, the particular shape of the coolant passage conduit also ensures uniform cooling of the support surface of the fuel.

In addition, the annular orientation of the conduit limits dilations and contractions. Consequently, the support surface of the fuel is subjected only to slight expansions and / or contractions during the rotation of the roller and its successive exposures to the combustion chamber and, to the blowing zone of the combustion air. Thus, the dimensional variations of the passage means of the oxidizing gas are limited.

Advantageously, inter-ring bypasses are fixed to the framework.

Advantageously, the frame carries at least one longitudinal assembly plate of the fluid inlets and outlets of the rings to the bridges.

Advantageously, the bridges are U-shaped tubes.

Advantageously, the cooling fluid inlets and outlets of the rings are arranged in such a way that the cooling fluid circulates in the same direction in each of the rings.

Advantageously, the bridges extend in a plane inclined at an angle of between 0 and 90 ° relative to the plane of the rings.

In a preferred embodiment, the rings comprise a plurality of peripheral sectorial elements communicating via internal connections. Therefore, the mounting of the rings, as well as access to the interior of the roll for maintenance operations and change of elements are simple operations.

Advantageously, the connections are fixed to the frame.

The frame carries longitudinal plates for assembling the ends of the peripheral sectoral elements to the internal connections.

Advantageously, the connections are U-shaped tubes.

Advantageously, the rings consist of six sectoral elements.

According to a second aspect, the invention relates to a combustion and / or incineration furnace comprising a plurality of rollers according to the first aspect of the invention.

Finally, according to a third aspect, the invention relates to the use of a combustion furnace according to the second aspect of the invention, in which at least one roller is rotated about its longitudinal axis A in a direction z and the cooling fluid passage is fed so that the cooling fluid moves in a direction w around the framework, inverted with respect to z.

BRIEF DESCRIPTION OF THE FIGURES

• la figure 1 est une vue schématique d'un rouleau selon l'invention, en coupe longitudinale, implanté dans un four;
• la figure 2 est une vue schématique des tubes coaxiaux d'alimentation et d'évacuation du circuit de passage du fluide de refroidissement ;
• la figure 3 est une vue schématique partielle en coupe longitudinale d'un rouleau selon l'invention ;
• la figure 4 est une vue schématique d'un plaque longitudinale d'assemblage des entrées et des sorties de fluide des anneaux aux pontages ;
• la figure 5 est une vue schématique d'une plaque longitudinale d'assemblage des extrémités des éléments sectoriels périphérique aux raccords internes ;
• la figure 6 est une vue en coupe transversale d'un raccord interne ;
• la figure 7 est une vue en coupe selon le plan VII-VII de la figure 6 ;
• la figure 8 est une vue de dessus des extrémités jointives de deux éléments sectoriels périphériques ;
• la figure 9a est une vue en coupe selon le plan IX a-IX a de la figure 3 ;
• la figure 9b est une vue en coupe selon le plan IX b-IX b de la figure 3 ;
• la figure 10 est une vue en coupe selon le plan X-X de la figure 12, illustrant un raccord interne ;
• la figure 11 est une vue en coupe selon le plan XI-XI de la figure 13, illustrant un pontage ;
• la figure 12 est une vue de dessus d'une plaque longitudinale d'assemblage des extrémités des éléments sectoriels périphérique aux raccords internes ;
• la figure 13 est une vue de dessus d'une plaque longitudinale d'assemblage des entrées et des sorties de fluide des anneaux aux pontages ;
• la figure 14 est une vue schématique détaillée de la fixation des éléments sectoriels périphériques à une plaque longitudinale ;
• la figure 15 est une vue de dessus de l'extrémité d'un élément sectoriel périphérique ;
• la figure 16 est une vue en coupe selon le plan XVI-XVI de la figure 15 ; et
• la figure 17 représente le dispositif de double étanchéité tournant pour l'alimentation et l'évacuation du fluide de refroidissement ; et
• la figure 18 est une vue partielle en couple longitudinale d'un rouleau selon l'invention.

Other objects and advantages of the invention will become apparent from the following description, made with reference to the appended drawings, in which:

• the figure 1 is a schematic view of a roll according to the invention, in longitudinal section, implanted in an oven;
• the figure 2 is a schematic view of the coaxial feed tubes and evacuation of the cooling fluid passage circuit;
• the figure 3 is a partial schematic view in longitudinal section of a roller according to the invention;
• the figure 4 is a schematic view of a longitudinal assembly plate of the fluid inlets and outlets of the rings at the bypasses;
• the figure 5 is a schematic view of a longitudinal assembly plate of the ends of sectoral elements peripheral to the internal connections;
• the figure 6 is a cross-sectional view of an internal fitting;
• the figure 7 is a sectional view along plane VII-VII of the figure 6 ;
• the figure 8 is a top view of the contiguous ends of two peripheral sectorial elements;
• the figure 9a is a sectional view along the plane IX a-IX a of the figure 3 ;
• the figure 9b is a sectional view along the plane IX b-IX b of the figure 3 ;
• the figure 10 is a sectional view along plane XX of the figure 12 , illustrating an internal connection;
• the figure 11 is a sectional view according to plan XI-XI of the figure 13 , illustrating a bypass;
• the figure 12 is a top view of a longitudinal assembly plate of the ends of sectoral elements peripheral to the internal connections;
• the figure 13 is a top view of a longitudinal assembly plate of the fluid inlets and outlets of the rings at the bypasses;
• the figure 14 is a detailed schematic view of the fixation of the elements sectoral peripheral to a longitudinal plate;
• the figure 15 is a top view of the end of a peripheral sectoral element;
• the figure 16 is a sectional view according to plan XVI-XVI of the figure 15 ; and
• the figure 17 represents the rotating double seal device for the supply and discharge of the cooling fluid; and
• the figure 18 is a partial view in longitudinal torque of a roller according to the invention.

EXAMPLE OF REALIZATION

The incineration and / or waste combustion furnace, illustrated on the figure 1 , is equipped with several rollers 1 according to the invention. The rollers 1 are cascaded and driven in rotation at relatively low speeds, from 0.5 to 3 revolutions / hour approximately, around parallel horizontal axes A in order to allow the waste to advance into the furnace. In practice, the grids comprise about 6 rolls of about 1 meter 50 in diameter. The rollers follow one another in the direction of displacement of the fuel, according to a downward slope α of about 15 °.

A roll comprises a hollow metal frame 2 forming a cylindrical cage and a fuel support surface 4 mounted around said framework 2.

At each end of the frame 2, a shaft 14a, 14b protrudes outwardly of the frame 2 and is mounted in bearings 15a, 15b disposed on either side of the furnace hearth. A drive system 16 cooperates with one of the shafts 2b to drive the roller 1 in rotation. In order to ensure the rigidity of the roll 1, the frame 2 is furthermore provided with a central core 16 extending longitudinally between the two ends of said frame 2. Thus, the maximum deflection of the frame 2 is low. The frame 2 is hollow and allows the passage of an oxidizing gas through the roller 1.

Advantageously, the frame 2 may be equipped with fixed vanes, not shown, welded on the central core 16, to ensure a homogeneous distribution of the oxidant gas through the roller 1 and the attraction of waste in the transit area between the rollers 1.

The support surface of the fuel 4 comprises means allowing the passage of the oxidant gas through the roller. Thus, in operation, for the maintenance of the combustion, an oxidizing gas, such as air, is blown substantially vertically through the rollers 1 (arrow y).

According to the invention, the support surface 4 is formed by a conduit 3 allowing the passage of a cooling fluid, water for example. The duct 3 comprises a plurality of hollow rings 6, coaxial with the axis A, distributed along the length of said roll 1, each comprising an inlet 7 and an outlet 8 of fluid, and inter-rings 9, connecting in a manner sealing the fluid outlet 8 of a ring 6 at the fluid inlet 7 of the next ring 6.

The rings 6 are spaced from each other to form the orifices or annular slots for the passage of the oxidizing gas. The distance between the rings 6 can be constant or varied over the length of the roller 1. The distance between the rings 6 is chosen according to the type of waste treated by the installation and the desired oxidant gas flow rate.

In each of the rings 6, the cooling fluid flows in the z direction, illustrated on the Figures 9a and 9b . In addition, the bridges extend in a plane inclined at an angle between 0 and 90 ° relative to the plane of the rings. Thus, the cooling fluid passage circuit is wound around the frame 2.

In use, the rollers 1 are rotated in a direction opposite to the direction of circulation w of the cooling fluid in the circuit. Therefore, in case of coolant degassing or appearance of a bubble, it moves from ring 6 to ring 6 to the last, during the rotation of the roll 1, and then joins the evacuation of the cooling fluid.

In the illustrated embodiment, detailed on the Figures 9a and 9b , the rings are composed of six peripheral sectoral elements 10a, 10b, 10c, 10d, 10e, 10f removable communicating, in a sealed manner, via internal connections 11, or inter-element bridges, fixed to the frame 2. The sectoral elements 10a , 10b, 10c, 10d, 10e, 10f are hollow bars, made of cast iron, and bent longitudinally at an angle of about 60 °. The elements 10a, 10b, 10c, 10d, 10e, 10f have at each end of their inner face a passage 17 for the passage of the cooling fluid. The internal connections 11 are here formed of U-shaped tubing.

The frame 2 carries at least one longitudinal plate 12 for assembling the inlets 7 and the fluid outlets 8 of the rings 6 to the bridges 9, shown in FIGS. figures 4 , 11 and 13 . In the embodiment shown, the longitudinal plate 12 extends over the entire length of the roll 1 and supports all the bridges 13 of the roll. The longitudinal plate 12 furthermore makes it possible to support the ends of the rings 6 comprising the fluid inlets and outlets and to fix them in a sealed manner by the fastening means detailed thereafter.

Similarly, the frame 2 carries five longitudinal plates 13 for joining the ends of the peripheral sectoral elements 10a, 10b, 10c, 10d, 10e, 10f to the internal connections 11, shown in FIGS. figures 5 , 10 and 12 . These plates 13 extend, in the embodiment shown, over the entire length of the rollers 1 and support the internal connections 11. The plates also allow to receive and fix the ends of the sectoral elements 10a, 10b, 10c, 10d , 10e, 10f to the frame 2.

In the embodiment shown, the longitudinal plates 12 and 13 are identical and the attachment of the sectorial elements to these plates 12, 13 is performed identically. Similarly, the bridging 9 and the internal connections 11 consist of similar elements. However, the internal connections 11 extend in the plane of the ring while the bridges 9 are inclined relative thereto in order to connect two successive rings 6.

The longitudinal assembly plates 12 and 13 are fixed to the central core of the framework by means of radial rods 18. In addition, the longitudinal assembly plates 12 and 13 comprise circular openings 24 in which the ends bridging 9 or internal connections 11 are introduced. The bridging 9 or internal connectors 11 are secured to the plates 12 and 13, by a weld 19 for example.

The orifice 17, formed on the inner face of the sectorial elements 10a, 10b, 10c, 10d, 10e, 10f, is bordered by a collar 20. As shown in FIG. figure 14 , the underside of the sectoral elements 10a, 10b, 10c, 10d, 10e, 10f is positioned against the rigid plate 12, 13 and the end of the internal connectors 11 (or bridges 9) is inserted inside said flange 20 to ensure the connection between the inner connector 11 and the sectoral element 10a.

The longitudinal plates 12, 13 comprise sealed means for fastening sector elements 10a, 10b, 10c, 10d, 10e, 10f. In the example shown, the plates 12, 13 comprise two threaded orifices 23a, 23b, arranged on either side of the circular openings 24. Screws 22a, 22b inserted in housings 21a, 21b sectoral elements 10a, 10b, 10c, 10d, 10e, 10f are intended to be engaged in the threaded orifices 23a, 23b, in order to fix the sectoral elements 10a, 10b, 10c, 10d, 10e, 10f to the rigid plate 12, 13. The housings 21 a, 21 b screws 22a, 22b are formed in the solid ends of sector elements 10a, 10b, 10c, 10d, 10e, 10f so as not to put the screws 22a, 22b into direct contact with the cooling fluid, and to limit thus corrosion. The screws 22a, 22b used may in particular be hexagonal screw.

When it is desired to disassemble a portion of the cooling fluid passage circuit, especially for maintenance purposes, the screws 22a, 22b can then be removed in order to release one or more removable sectoral elements 10a, 10b, 10c, 10d, 10th, 10f. Thus, a selected portion of the circuit can be easily disassembled to access the interior of the roll or replace the most worn parts.

In order to guarantee the tightness of the fastening, a seal 25 is housed in a groove formed in the plate 12, 13, coming opposite the flange 20 of the sectoral element 10a, 10b, 10c, 10d, 10th, 10f. The seal 25 may in particular be made of modified polytetrafluoroethylene.

The two ends of the removable sector elements 10a, 10b, 10c, 10d, 10e, 10f are separated by a small gap allowing longitudinal expansion of said sectoral elements 10a, 10b, 10c, 10d, 10e, 10f.

The cooling fluid is introduced and evacuated inside the framework 2 via a coaxial feed tube 26 and a discharge tube 27, of axis A, represented on the figure 2 . Preferably, the supply and discharge tubes 26 are introduced into the framework by the end of the roll 1, opposite to the drive system 16. At the upstream end of the roll 1, shown in FIG. figure 9a , the fluid inlet 7 of the first ring 6 is connected to the supply tube 26 in fluid via a connection tube 28. Similarly, at the downstream end of the roll 1, shown in FIG. figure 9b , the fluid outlet of the last ring 6 is connected to the discharge tube 27 of the fluid via a connecting tube 29.

On the outside of the roll 1, the feed and discharge tubes 27 are connected to a rotating joint system 30, shown in FIG. figure 14 by means of a flange / flange assembly provided with an O-ring. The rotary joint is connected, on the one hand, to a fluid supply network 35 via a conduit 36 provided with a valve 37 and, on the other hand, with an evacuation network 32 via a conduit 33 provided with a valve 34.

The invention is described in the foregoing by way of example. It is understood that the skilled person is able to achieve different embodiments of the invention without departing from the scope of the invention.

Claims (13)

Roller (1) for oven rack, to be rotatably mounted in the hearth of said oven about an axis A longitudinal to said roll (1), comprising: - a frame (2) forming a cylindrical cage; a fuel support surface (4) mounted around said framework and provided with means (5) for passing the oxidant gas through the roller, said support surface being formed by at least one surface of a conduit (3) allowing the passage of a cooling fluid; said roller (1) being characterized in that said cooling fluid passage (3) comprises: - a series of rings (6) hollow, coaxial with the axis A, distributed over the length of said roller (1), each comprising an inlet (7) and a fluid outlet (8); and - bridges (9) connecting the fluid outlet (8) of a ring (6) to the fluid inlet (7) of the next ring, to form a cooling fluid passage circuit wrapped around said frame (2). Roller (1) for an oven rack according to claim 1, wherein the inter-ring bridges (9) are fixed to the frame (2). Roller (1) for an oven rack according to claim 1 or 2, wherein the frame (2) carries at least one longitudinal plate (12) for connecting the inlets (7) and the fluid outlets (8) of the rings. (6) at the bypasses (9). Roller (1) for oven rack according to one of claims 1 to 3, wherein the bridges (9) are U-shaped tubes. Roller (1) for an oven rack according to one of Claims 1 to 4, in which the coolant entrances (7) and the coolant outlets (8) of the rings are arranged in such a way that the coolant circulates in a same meaning in each of the rings. Roller (1) for an oven rack according to claim 5, wherein the bridges (9) extend in a plane inclined at an angle of between 0 and 90 ° with respect to the plane of the rings (6). Roller (1) for oven rack according to one of claims 1 to 6, wherein the rings (8) comprise a plurality of peripheral sectorial elements (10a, 10b, 10c, 10d, 10e, 10f) communicating via connectors internal (11). Roller (1) for oven rack according to claim 7, wherein the connections (11) are fixed to the frame (2). Roller (1) for oven rack according to claim 7 or 8, wherein the frame (2) carries longitudinal plates (13) for joining the ends of the peripheral sectoral elements (10a, 10b, 10c, 10d, 10e, 10f) to the internal connections (11). Roller (1) for oven rack according to one of claims 7 to 9, wherein the connectors (11) are U-shaped tubes. Roller (1) for oven rack according to one of claims 6 and 7, wherein the rings (8) consist of six sectorial elements (10a, 10b, 10c, 10d, 10e, 10f). Combustion and / or incineration furnace comprising a plurality of rollers (1) according to one of Claims 1 to 11. Use of a combustion furnace according to Claim 12, in which at least one roller (1) is rotated about its longitudinal axis A in a z-direction and the cooling fluid passage (3) is supplied with so that the cooling fluid moves in a direction w around the frame (2) inverted with respect to z.

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