EP1582812A1 - Incineration grate with water-cooled fixed steps - Google Patents

Abstract

The module (5) has a module cooling system formed of lower walls that are associated under combustion walls to form chambers in which cooling liquid e.g. water, circulates. Each chamber is formed between the corresponding lower wall and combustion wall. A movable part (51) pushing household waste is displaced in translation along an upper side (17) of a component (6) between retracted and deployed positions. An independent claim is also included for an installation for combustion of household waste, comprising a furnace provided with a grid constituted of several modules.

Description

The invention relates to a module intended to be associated with other modules of similar geometry to form a grate for waste incineration furnace a grid comprising a plurality of such modules, as well as a installation for the incineration of household refuse.

An installation of this type includes an oven in which is provided a grid on which are placed the garbage during their combustion.

The garbage to be incinerated is brought into the furnace, upstream of the grid, then gradually moved on the grid downstream, the grid being inclined towards the low compared to the horizontal in the direction of progression of the garbage.

Grids generally consist of a plurality of modules of analog geometry placed one after the other in a staggered manner vertically and horizontally, so that the grid looks like a succession of "tiers". Each module includes several elements forming on the one hand a fixed part, serving in particular as support for garbage during their combustion, and secondly a mobile part arranged to push garbage from the fixed part of the module under consideration to the fixed part of the adjacent module immediately downstream.

Incineration grids of this type are already known.

According to a first possible embodiment, the different parts of the module are each consisting of a simple metal plate, and the module is cooled by a circulation of air.

This mode of cooling generally gives satisfaction for furnaces of low to medium capacity: around 2.5 to 6 tonnes of garbage treated with hour for example, and a lower ICP (lower calorific value of waste) at 11 000 kJ / kg.

However, garbage PCI tends to increase, and can reach 15,000 kJ / kg.

Under these conditions, the air cooling does not allow to lower the temperature of the modules, which can reach 400 to 550 ° C or more. This results in a degradation of the modules, and therefore the grid, which results in particular in a loss of the quality of the combustion, problems of mechanical strength, and a greatly diminished life.

To overcome this problem, it is possible to limit the capacity of the ovens. However, this is not usually desired. On the contrary, we wish to more and more increase the capacity of the furnaces, up to 10 t / h, even 12 t / h.

Thus, this type of air-cooled rack has an allowable heating value. too limited, and does not meet the growing demands in terms of the capacity of treated waste and the quality of the combustion.

According to a second possible known realization, the different parts of the module each form a hollow compartment in which a liquid circulates cooling, for example water.

As a result, the cooling of a grid module is more efficient than the air cooling provided in the first known embodiment. The capacity admissible by the furnace provided with this grid is therefore more important.

However, the cooling of the module by circulation of liquid poses a number of problems, especially with regard to the mobile part.

Indeed, the routing of the coolant to and from this part requires the use of flexible and non-fixed hoses, in view of its mobility. The reciprocating movement of this part leads to a fatigue of the hoses which can cause gaps, or even the rupture of Flexible.

It is therefore necessary to monitor the condition of the hoses and, if necessary, replace defective hoses, which necessitates the temporary stopping of the furnace and proves to be extremely restrictive and expensive. However, the hoses are positioned under the grid in an area difficult to inspect (circulating air temperature 130 ° C approximately, risk of falling incandescent dusts or metals in fusion, etc.).

In an extreme case, the appearance of undetected cracks in a hose can generate coolant leaks, the moving part of the module not being sufficiently cooled down and being able to undergo degradation irreversible. In addition to the financial consequences that this implies installation, replacement of damaged modules), there are risks not negligible for operators working near the oven.

The object of the invention is to provide a grate module for a furnace for incineration of garbage that has a significant allowable capacity and is provided with a efficient cooling system and little binding.

• un premier élément comprenant une première paroi de combustion des ordures, sensiblement plane ;
• un deuxième élément comprenant une deuxième paroi de combustion des ordures s'étendant à partir de l'extrémité aval de la première paroi de combustion en étant globalement inclinée par rapport à ladite première paroi de combustion d'un angle α compris entre 15 et 45° ;
• un moyen de poussée des ordures, mobile en translation par cycles le long de la face supérieure de la première paroi, entre une position rétractée, dans laquelle l'extrémité aval du moyen de poussée est située au voisinage de l'extrémité amont de la première paroi de combustion, et une position déployée, dans laquelle l'extrémité aval du moyen de poussée est située au voisinage de l'extrémité aval de la première paroi de combustion, ledit moyen de poussée étant en position rétractée pendant au moins 70 % de la durée d'un cycle ;
• un système de refroidissement du module, ledit système de refroidissement étant formé d'au moins une paroi qui est associée sous les première et deuxième parois de combustion de sorte à former entre ladite paroi et lesdites première et deuxième parois de combustion au moins une chambre dans laquelle un liquide de refroidissement est apte à circuler.

For this purpose, and according to a first aspect, the invention relates to a module intended to be associated with other modules of similar geometry to form a grid for incineration furnace of household waste, said module comprising:

• a first element comprising a first substantially flat waste combustion wall;
• a second element comprising a second combustion wall of the refuse extending from the downstream end of the first combustion wall being generally inclined with respect to said first combustion wall of an angle α of between 15 and 45 ° ;
• a means of thrusting the refuse, movable in translation in cycles along the upper face of the first wall, between a retracted position, in which the downstream end of the thrust means is situated in the vicinity of the upstream end of the first combustion wall, and an extended position, wherein the downstream end of the thrust means is located in the vicinity of the downstream end of the first combustion wall, said thrust means being in the retracted position for at least 70% of the duration of a cycle;
• a cooling system of the module, said cooling system being formed of at least one wall which is associated under the first and second combustion walls so as to form between said wall and said first and second combustion walls at least one chamber in which a coolant is able to circulate.

Thus, during a movement cycle, the moving part moves towards its deployed position, pushing the garbage along the first wall of combustion down to the downstream end of this first combustion wall, that is to say until the break of slope. Then the garbage falls and slips along the second combustion wall, because of its inclination, while that the moving part moves to its retracted position.

For most of its travel cycle (over 70% of duration of a cycle, or even more than 80%, or even more than 90%), the mobile part is located entirely under the adjacent module located immediately upstream, and is therefore protected and less exposed to heat.

As a result, thanks to this particular design of the module, it is not necessary to provide a cooling system specific to the part mobile by a liquid, an air cooling being sufficient, and this even for PCIs of 15,000 kJ / kg.

The invention thus makes it possible to dispense with liquid transport hoses cooling, and all the associated disadvantages.

For example, the length of the second combustion wall is included between about 50% and 150% of the length of said first wall of combustion, and is therefore relatively large compared to the total length of the module. As a result, the stroke of the moving part is relatively small. After an initial push, the garbage falls and turns naturally along the second combustion wall, and the thrust means can therefore return to its retracted position.

According to one possible embodiment, the cooling system of the module comprises a third associated wall under the first combustion wall so as to form between said first and third walls a first chamber, and a fourth associated wall under the second wall of combustion, so as to form between said second and fourth walls a second bedroom separate from the first bedroom.

For example, at least one element comprises a side wall projecting from the upper wall, the lower wall of the element being welded to the part bottom of the side wall.

A partition wall may extend inside said chamber between a port and an exit port, over substantially the entire height of the chamber and over a distance intended to guide the flow of liquid in said chamber.

For example, the exit port of the first chamber, respectively the second, is connected to the port of entry of the first chamber, respectively the second.

The second combustion wall may comprise a succession of 4 to 7 steps each comprising a substantially flat portion and parallel to the first combustion wall and a substantially flat portion and perpendicular to the first combustion wall, so as to form a staircase.

According to another characteristic, a chamber comprises a port of entry and a coolant outlet port, the port of entry comprising a duct opening into the room under and in the immediate vicinity a portion of the first or second combustion wall for be placed substantially horizontally in the oven.

The benefit of this structure is the reduction of the size of the dead zone where a bubble of air delivered via the duct may be trapped, this which could lead to a loss of cooling efficiency.

A combustion air supply system can be provided, this system having at least one air passage channel passing through the first element substantially vertically and opening on the one hand through an opening formed in the lower wall and on the other hand by a hole in the upper wall, substantially horizontal, of the first element, the channel presenting, throughout its height, a horizontal section of dimensions greater than or equal to those of the orifice, the channel widening from the face upper part of the element towards the lower wall of said element at least on a part of the height of the canal.

The channel widening downwards (continuously, in the manner of a cone by example, or discontinuously, forming degrees), its clogging by garbage is more difficult, these can fall without being blocked in the canal.

The combustion air supply system may further comprise at least one air channel passing through the second element from bottom to top, and opening through an orifice in a substantially vertical portion of the upper wall of said second element.

The holes being made in a vertical wall, and the movement of thrust of garbage tending to remove garbage from these orifices, the risk of capping is weak.

According to one possible embodiment, at least one of the elements comprises at least a first projection extending from a first side wall of said element outward, and at least one second projection extending from a second side wall of said element towards the outside, the upper face of the second projection being shifted downwards with respect to the upper face of the first projection a distance greater than the height of the first projection, so that when two substantially identical elements are associated laterally, the first projection of an element covers the second projection of the adjacent element.

As a result, the grid allows the lateral expansion of the elements, and only the air passages strictly necessary.

According to a second aspect, the invention relates to an oven rack incineration process comprising a plurality of modules such as than previously described. The modules are arranged so that their first combustion wall is placed substantially horizontally in the furnace and that the downstream end of the second combustion wall of a module is placed substantially in line with the upstream end of the first wall of combustion of the adjacent module located downstream, above the thrust means garbage from said adjacent module so as to form a succession of entertained.

According to one possible embodiment, a step comprises a plurality of modules substantially identical laterally associated with each other.

For example, the second chambers of the modules of a grid step are connected in series by their ports of entry and exit, at least partly, the first chambers of the modules of a tier of the grid are connected in series their ports of entry and exit, at least in part, the port of exit of the second chamber of a given module being connected to the port of entry of the first chamber of said module.

Finally, according to a third aspect, the invention relates to an installation for the incineration of household refuse, comprising at least one oven in which is provided such a grid, means of supply of household waste in the oven, upstream of the grid, means for collecting residues from incineration, downstream of the gate, and means for conveying a liquid of cooling of the modules of the grid.

• la figure 1 est une vue partielle d'une installation pour l'incinération des ordures ménagères comprenant une grille selon l'invention ;
• la figure 2 est une vue agrandie d'un module de la grille de la figure 1 ;
• la figure 3 est une vue de dessus d'un premier élément du module de la figure 2 ;
• les figures 4 et 5 sont des vues en coupe du premier élément de la figure 3, selon la ligne AA et la ligne BB, respectivement ;
• la figure 6 est une vue de dessus d'un deuxième élément du module de la figure 2 ;
• les figures 7, 8 et 9 sont des vues en coupe du deuxième élément de la figure 6, selon la ligne CC, la ligne DD et la ligne EE, respectivement ;
• les figures 10 et 11 sont des vues extérieures respectivement droite et gauche du deuxième élément de la figure 6 ;
• la figure 12 est une vue en coupe partielle, selon la ligne FF, de l'installation de la figure 1.

The other features of the invention result from the description which follows of an embodiment, description made with reference to the appended figures in which:

• Figure 1 is a partial view of an installation for the incineration of household waste comprising a grid according to the invention;
• Figure 2 is an enlarged view of a module of the grid of Figure 1;
• Figure 3 is a top view of a first element of the module of Figure 2;
• Figures 4 and 5 are sectional views of the first element of Figure 3, along the line AA and the line BB, respectively;
• Figure 6 is a top view of a second element of the module of Figure 2;
• Figures 7, 8 and 9 are sectional views of the second element of Figure 6 along the line CC, the line DD and the line EE, respectively;
• Figures 10 and 11 are outer views respectively right and left of the second element of Figure 6;
• FIG. 12 is a partial sectional view along the line FF of the installation of FIG. 1.

Referring first to Figure 1 which represents an installation for the incineration of household refuse.

The installation includes an oven 1 in which the garbage to be incinerated is fed, upstream, via feed means such as a feed hopper 2. In addition, the installation includes means for collecting residues from incineration downstream, as well as means of effluents - especially gases - from combustion.

The oven comprises a grid 3 generally inclined downwards with respect to horizontally, from upstream to downstream of the oven 1. Garbage, brought to the grid 3 upstream, are gradually incinerated and moved to Grid 3 to downstream.

The oven 1 also comprises several air distribution hoppers 4 located under the grid 3, and intended to provide the necessary air for the combustion of garbage. Means for conveying a coolant to and from from grid 3 are also provided.

The grid may have a length of 8 to 10 m, depending on its capacity, and a width of 3 to 6 m approximately.

The grid 3 comprises a plurality of modules 5 associated with each other offset vertically and horizontally, so that grid 3 is presents as a succession of "tiers". A step includes himself several substantially identical modules associated laterally with each other. others (see Figure 12). The number of bleachers can vary from 6 to 9, depending on the oven capacity 1.

We define a direction D1 corresponding to the direction of progression of the garbage, a substantially vertical direction D3, and a direction D2 orthogonal to D1 and D2. The terms "length", "upstream", "downstream" will be used for reference in direction D1, the terms "width", "transversal", "lateral" will be employees with reference to the D2 direction, and the term "height" will be used with reference to direction D3.

In the embodiment shown, the grid 3 is composed of three types of different modules: the module or modules located upstream, the module or modules located furthest downstream, and modules located in the middle. We will be interested in following the modules located in the middle of the grid 3.

A module 5 is now described with reference to FIGS. 2 to 11.

Module 5 comprises a fixed part, serving in particular as a support for garbage during their combustion, and a moving part arranged to push the garbage from the fixed part of the module considered towards the fixed part of the module adjacent immediately downstream.

Firstly, the fixed part of the module 5 is described.

The fixed part comprises a first element 6, substantially parallelepipedic, having an upper wall 7, a lower wall 8, an upstream wall 9, a downstream wall 10, a left lateral wall 11 and a right lateral wall 12. The first element 6 is placed in the oven 1 so that its upper wall 7 is substantially horizontal, and its side walls 11, 12 are substantially parallel to the direction D1.

The width of the first element is of the order of 25 cm, its length of the order of 50 cm, and its thickness close to 5 cm.

From the upper wall 7 protrudes, perpendicularly and downwards, a wall separation 13 extending parallel to D1 from the downstream wall 10 to the upstream wall 9, over a distance of the order of three quarters of the length of the first element 6, substantially halfway between the side walls 11, 12. first portion of the partition wall 13, extending from the downstream wall 10 about one-third of the length of the first element 6, is formed of a simple plate 14. A second portion, extending from the first portion to the upstream wall 9, is formed of two parallel plates 15a, 15b disposed opposite one another and associated by their downstream ends and upstream so as to form a channel 60 of rectangular horizontal section. The plates 15a, 15b are spaced apart by a distance of the order of 1 cm.

The upper wall 7 comprises two oblong orifices 16, of a length adjacent to 6 cm, opening into the space between the plates 15a, 15b. The width of the orifices 16 is of the order of 6 mm at the upper face 17 of the upper wall 7, the width of the channel 60 gradually increasing when we move downwards, the inner face of the orifice joining the face 18a, 18b of the plates 15a, 15b (Figure 5).

In addition, the first element 6 includes a first projection 19 extending from the right lateral wall 12 towards the outside, substantially in extension of the upper wall 7, over the entire length of said first element 6. The first projection 19 has a cross section substantially rectangular. The width of the first projection 19 is of the order of 1.5 cm. The height of the first projection, between its upper face located substantially in the same plane as the upper face 17 of the upper wall 7 of the first element 6, and its lower face 20, is of the order of 1 cm.

A second projection 21 extends from the left side wall 11 towards outside, but is not continuous over the entire length of the first element 6. From the upstream wall 9 to the downstream wall 10, one successively encounters: a first portion 21a of the second projection 21, of length close to 30% of the total length of the first element 6, an interruption of the second projection 21 (about 15% of the total length of the first element 6), a second portion 21b of the second projection 21 (about 10% of the length of the first element 6), an interruption of the second projection 21 (approximately 15% of the total length of the first element 6), a third portion 21 c of the second projection 21 (about 25% of the total length of the first element 6), and an interruption of the second projection 21.

The second projection 21 has a cross section substantially rectangular, a height of about 1 cm and a width of about 1.5 cm. The second projection 21 is shifted downward relative to the first projection 19, so that the upper face 22 of the second projection 21 is located substantially in the same plane as the lower face 20 of the first projection 18.

The walls 7, 9 to 14, 15a, 15b and the projections 19, 21 are made of a single piece of steel by molding.

The bottom wall 8 is a sheet metal plate having the general shape of a U, welded in the lower part of the first element 6 to the upstream and downstream walls 9 and 9, as well as, on the one hand, between the left side wall 11 and the plate 15a and, on the other hand, between the right side wall 12 and the plate 15b.

Thus, a first U-shaped chamber 23 is formed between the wall lower 8 and the upper walls 7, lateral 11, 12 and upstream 9, downstream 10. In in addition, the channel formed between the plates 15a and 15b is devoid of bottom (see Figure 5).

The bottom wall 8 has an inlet 24 and an outlet 25 located on either side of the plate 14. A conduit 26 is welded in each of these orifices 24, 25 so as to form an input port and an output port towards and from the first chamber 23. The conduit 26 opens into the interior of the first chamber 23 under and in the immediate vicinity of the upper wall 7, to a distance of less than 1 cm, for example 8 mm.

The fixed part also comprises a second element 27 comprising a upper wall 28, a lower wall 29, an upstream wall 30 and a wall downstream 31 substantially parallel to D2, a left side wall 32 and a wall lateral right 33 substantially parallel to D1. The width of the second element is of the order of 25 cm, its length of the order of 50 cm, and its height close 30 cm.

The upper wall 28 of the second element 27 comprises a succession of 5 steps each comprising a portion 28a substantially flat and parallel to the upper wall 7 of the first element 6 and a portion 28b substantially plane and perpendicular to the upper wall 7 of the first element 6. The wall upper 28 thus has the general shape of a staircase, inclined overall an angle α of the order of 23 °.

From the upper wall 28 protrudes, perpendicularly and downwards, a partition wall extending parallel to D1 from the downstream wall 31 towards the upstream wall 30, over a distance of the order of 85% of the length of the second element 27 substantially at half distance from the side walls 32, 33. The wall of separation is formed of two plates 34a, 34b spaced apart from one another distance close to 1 cm and associated with their upstream end.

Each of the substantially vertical portions 28b of the upper wall 28 has an orifice 35, extending over substantially the entire height of said portion 28b, of width corresponding to the spacing between the plates 34a, 34b, and opening into the space between said plates 34a, 34b (Figure 9).

The second element 27 comprises a series of first projections 36 each extending from the right side wall 33 outwards, substantially in extension of a substantially horizontal portion 28a of the upper wall 28, from the downstream end of said portion 28a to and slightly beyond the upstream end of said portion 28a.

Each of the first projections 36 has a cross section substantially rectangular and a width of the order of 1.5 cm. The height of a first projection 36, between its upper face, located substantially in the same plan that the upper face 37 of the portion 28a considered, and its face lower 38, is of the order of 1 cm.

The second element 27 further comprises a series of second projections 39 each extending from the left side wall 32 outwardly. Each second projections 39 has a cross-section substantially rectangular, a height of about 1 cm and a width of about 1.5 cm.

Each of the second projections 39 extends parallel to a portion 28a substantially horizontal of the upper wall 28, not an extension of it, but shifted downward, so that the upper face 40 of the second projection 39 is located substantially in the same plane as the lower face 38 of the first projection 36. In addition, each of the second projections 39 extends from the downstream end of said portion 28a to and slightly beyond the upstream end of said portion 28a.

The second element 27 thus has a left horizontal protrusion 39 and a right projection 36 at each of its steps, and is devoid of any protrusion vertical (parallel to the vertical portion 28b of each step).

According to a variant (FIGS. 10 and 11), the vertical portion 28b of the step lower section has a straight vertical protrusion 36 discontinuous extending towards the outside substantially in extension of the vertical portion 28b, and a left vertical protrusion 39 discontinuous extending outward, being offset upstream, so that the upstream face 41 of the right projection 36 is located substantially in the same plane as the downstream face 42 of the projection left 39.

The lower wall 29 of the second element 27 has, in section longitudinal, a shape similar to that of the upper wall (succession of horizontal portions 29a and vertical portions 29b forming the steps of a staircase). In top view, the bottom wall 29 has the general shape a U extending between the upstream 30 and downstream walls 31 and, on the one hand, between the left side wall 32 and the plate 34a and, on the other hand, between the wall right side 33 and the plate 34b. Thus, the channel formed between the plates 34a, 34b is devoid of background (see Figure 8).

A second U-shaped chamber 43 is thus formed between the wall lower 29 and the upper walls 28, lateral 32, 33 and upstream 30, downstream 31.

The bottom wall 29 includes a central zone 44 extending over the entire width of the second element 27, as well as an upstream zone 45 and a downstream zone 46 extending, over the entire width of the second element 27, since a end of the central zone towards, respectively, the upstream wall 30 and the wall downstream 31.

The walls 28, 30 to 33, 34a, 34b, the central zone 44, as well as the projections 36, 39 are made of a single piece of steel by molding, with the help of a core. The upstream zone 45 and the downstream zone 46 are sheet metal plates welded in lower part of the second element 27, between the central zone 44, the walls lateral 32, 33 and the upstream wall 30, respectively downstream 31.

The upstream zone 45 of the lower wall 29 of the second element 27 presents a inlet port 47 and an outlet port 48 located on either side of the plates 34a, 34b, in a horizontal portion of said bottom wall 29.

A conduit 26 is welded in each of these orifices 47, 48 so as to form a port of entry and an exit port to and from the second chamber 43. The conduit 26 opens into the second chamber 43 under and at immediate vicinity of the horizontal portion 28a of the upper wall 28 located the most upstream, at a distance of less than 1 cm, for example 8 mm. Thus, the air bubble created at the outlet of the conduit 26 is of reduced dimensions. Of more, it is located in the upper part of the second element 27, that is to say in its least hot part, which limits the problems related to bad cooling.

• ses parois latérales 32, 33 soient situées sensiblement dans les mêmes plans que les parois latérales 11, 12 du premier élément 6 ;
• sa paroi amont 30 soit adjacente à la paroi aval 10 du premier élément 6 ;
• et que la face supérieure 37 de la portion horizontale 28a de sa paroi supérieure 28 la plus en amont soit située immédiatement sous un rebord 50 saillant en prolongement de la paroi supérieure 7 du premier élément 6 vers l'aval.

The first and second elements 6, 27 are supported by H 49 crosspieces (Figure 2). The second element 27 is arranged so that:

• its side walls 32, 33 are located substantially in the same plane as the side walls 11, 12 of the first element 6;
• its upstream wall 30 is adjacent to the downstream wall 10 of the first element 6;
• and that the upper face 37 of the horizontal portion 28a of its topmost wall 28 is located immediately below a flange 50 projecting from the upper wall 7 of the first element 6 downstream.

The moving part 51 of the module 5 is now described (see FIG. 2).

The movable portion 51 comprises an upper wall 52 substantially rectangular, from which project, upstream, an upstream wall 53, a wall downstream 54 inclined relative to the horizontal of an angle β between 60 and 80 ° approximately, and side walls.

The movable part 51 is placed in the oven 1 so that its upper wall 52 is substantially horizontal, and its side walls substantially parallel at D1 and in the same planes as the side walls 11, 12 of the first element 6. In addition, the lower face of the movable part 51 cooperates with the upper face 17 of the upper wall 7 of the first element 6.

The width of the moving part 51 is of the order of 25 cm, its length of the order 60 cm, and its thickness close to 10 cm.

• une position rétractée, dans laquelle la paroi aval 54 de la partie mobile 51 est située au voisinage de la paroi amont 9 du premier élément 6 ;
• et une position déployée, dans laquelle la paroi aval 54 de la partie mobile 51 est située au voisinage de la paroi aval 10 du premier élément 6.

The movable part 51 is able to be displaced in translation along the upper face 17 of the first element 6, via a drive device 55 comprising a connecting rod fixed to the upstream wall 53 of the movable part 51, between:

• a retracted position, in which the downstream wall 54 of the movable part 51 is situated in the vicinity of the upstream wall 9 of the first element 6;
• and an extended position, in which the downstream wall 54 of the movable portion 51 is located in the vicinity of the downstream wall 10 of the first element 6.

For example, a movement cycle breaks down as follows: the part 51 is in the retracted position for at least 100 seconds, and moves to its deployed position, then from its deployed position to its position retracted for about 10 seconds.

The moving part 51 of the module 5 does not form an inner chamber, and is without a liquid cooling system, this part being simply cooled by a circulation of air.

Two adjacent modules 5 are arranged so that, on the one hand, the downstream wall 31 of the second element 27 of the upper module 5 is placed substantially at right - or slightly offset downstream - from the upstream wall 9 of the first element 6 of the lower module 5 and, on the other hand, the second element 27 of the upper module 5 is located above the moving part 51 of the module 5 inferior. The clearance j1 between the lower face of the second element 27 of the module 5 upper and the upper face 56 is of the order of 6 mm.

Referring now to Figure 12 which illustrates the lateral association of first elements 6 of a step of the grid 3.

The first elements 6 are placed so that the upper faces 17 of their upper walls 7 are located substantially in the same plane. The first projection 19 of an element 6 then cooperates with the second projection 21 of the adjacent element 6, since the lower face 20 of a first projection 19 is located substantially in the same plane as the upper face 22 of a second projection 21. A protrusion may rest on the adjacent projection. In a variant, there may be a very small vertical clearance between these two projections.

In addition, there is a clearance j2, for example of the order of 4 mm, between the end free of a projection 19, 21 and the side wall 11, 12 adjacent. This game allows the lateral expansion of the first elements 6, the projections sliding then one on the other in direction D2.

In normal operation, the skin temperature of the first element 6 is the order of 80 to 85 ° C, the dilation of each of the first elements 6 being limited to about 0.3 mm due to cooling efficiency. In case incident, the skin temperature can reach 500 ° C and the expansion 1.7 mm by first element 6. The value of j2 makes it possible to face this situation.

This structure in which the projections overlap does not, however, prevent the flow of air from bottom to top necessary for the proper combustion of garbage.

Indeed, as illustrated in FIG. 3, because of the game j2 and the discontinuity of the second projection 21, several openings 57 are formed between the wall left side 11 of a first element 6 and the free end of the first projection 19 of the first adjacent element 6 (shown in phantom), these openings allowing the passage of air.

It should be noted that the first elements 6 located at the lateral ends of a tier can have different lateral shapes (no projections for example).

Moreover, the lateral association of the second elements 27 is carried out according to the same principle, by cooperation of the first and second projections 36, 39 with lateral expansion play. Here again is planned an air passage between two of the second adjacent elements 27, perpendicular to each vertical portions 28b of the upper wall 28, between two projections 36, 39 consecutive (see the arrows shown in Figure 11).

The operation of the installation is now described.

Garbage, brought upstream of the grid 3, are at the end of a certain times arranged on the upper wall 7 of the first element 6 of the module 5 located furthest upstream, the corresponding moving part 51 being in position retracted. After a defined period of time, the moving part 51 is moved towards its deployed position, pushing the garbage downstream.

The garbage then naturally falls on the successive steps of the second element 27 to the first element 6 of the adjacent module 5. It is not therefore not necessary that the moving part 51 continues to push the garbage. Thus, while the garbage moves on the second elements 27, the different moving parts are moved to their retracted position for release the upper wall 7 of the first elements 6. The presence of the steps promotes the movement of garbage and their flipping, which is a advantage for combustion.

The quality of the combustion depends, among other things, on the quantity of air injected. This quantity varies according to the amount of garbage incinerated, the PCI, and the area of the oven 1: the oxygen requirement is medium in areas where occurs essentially a drying of the waste (evaporation of the water contained), important in areas of active combustion, and weak in end zones combustion (to have a minimum unburnt rate). The system of Air distribution must therefore adapt to different situations.

• les espaces prévus entre les saillies latérales des éléments (ouvertures 57 de la figure 3, flèches de la figure 11) ;
• le jeu j1 entre la partie mobile 51 d'un module 5 et le deuxième élément 27 du module 5 supérieur (sur toute la largeur de la grille 3). Du fait du déplacement de la partie mobile, le jeu j1 ne s'encrasse pratiquement pas ;
• les orifices 16 de la paroi supérieure 7 des premiers éléments 6 ;
• les orifices 35 ménagés dans les portions 28b sensiblement verticales de la paroi supérieure 28 des deuxièmes éléments 27.

The air required for combustion is supplied by the air distribution hoppers 4 via:

• the spaces provided between the lateral projections of the elements (openings 57 of FIG. 3, arrows of FIG. 11);
• the clearance j1 between the mobile part 51 of a module 5 and the second element 27 of the upper module 5 (over the entire width of the grid 3). Because of the displacement of the movable part, the game j1 does not clog substantially;
• the orifices 16 of the upper wall 7 of the first elements 6;
• the orifices 35 formed in the substantially vertical portions 28b of the upper wall 28 of the second elements 27.

In order to ensure good aeration, and therefore good combustion, the surface air passages to predict is of the order of 40 cm2 per module 5 (in the embodiment shown, and without taking into account the passages between modules adjacent laterally). The breakdown can be as follows: about 50% of the area provided in the second element 27, about 25% of the area provided in the first element 6, and about 25% of the area obtained via the game j1.

Thus, despite the possible fouling of the first element 6, the quality of the will remain relatively equal over time, since at least 75% of Air passages will still be operational.

The modules 5 are cooled on the one hand by air circulation (moving parts 51) and secondly by circulation of a coolant in the first and second chambers 23, 43.

The coolant may be water - or any suitable liquid - at a pressure of 2 to 10 bar, and especially 4 to 6 bar (to overcome network pressure drops and avoid spraying), and a flow from 1.5 to 5 m ³ / h per m ² of grid, in particular 3 m ³ / h per m ² of grid. The water entering the module is at a temperature between 60 and 90 ° C, for example about 80 ° C.

The water supply of the modules is done in the following way: the water is brought in middle of step and the circulation is carried out by half step. On a half step considered, the water is brought to the entrance of a second element 27 located substantially in the center of the step and passes successively in all the second elements 27 of the same half-step, until the exit of the second element 27 of the module 5 located at the lateral end of the step. The water is then brought into the input of the first element 6 of said module 5 and passes successively in all the first elements 6 of the same half-step, until the output of the first element 6 located substantially in the center of the step. The water is then evacuated.

In addition, the circulation and flow rate of the coolant are selected for allow the entrapment of the trapped air bubble at the outlet of the ducts 26 entrance to rooms 23, 43.

One of the advantages of the invention lies in the possibility of replacing a only part of the modules of a grid in service by modules such as previously described, without the change of the entire grid being necessary, which is very advantageous for the operator.

Claims (15)

Module intended to be associated with other modules (5) of similar geometry to form a grid (3) for furnace (1) incineration of household waste, said module (5) comprising: a first element (6) comprising an upper wall (7) forming a first substantially flat waste combustion wall; a second element (27) comprising an upper wall (28) forming a second combustion wall of the refuse extending from the downstream end of the first combustion wall being generally inclined with respect to said first combustion wall of an angle (α) of between 15 and 45 °; a refuse thrusting means (51) movable in cycles along the upper face (17) of the first wall (7) between a retracted position, in which the downstream end of the thrust means (51) is located in the vicinity of the upstream end of the first combustion wall, and an extended position, in which the downstream end of the thrust means (51) is situated in the vicinity of the downstream end of the first combustion wall, said thrust means (51) being in the retracted position for at least 70% of the duration of a cycle; a cooling system of the module (5), said cooling system being formed of at least one bottom wall (8, 29) which is associated under the first and second combustion walls (7, 28) so as to form between said wall and said first and second combustion walls at least one chamber (23, 43) in which a coolant is able to circulate. Module according to claim 1, characterized in that the cooling system of the module (5) comprises a third wall (8) associated under the first combustion wall (7) so as to form between said first and third walls a first chamber ( 23), and a fourth wall (29) associated under the second combustion wall (28), so as to form between said second and fourth walls a second chamber (43) separate from the first chamber (23). Module according to claim 1 or 2, characterized in that at least one element (6, 27) comprises a side wall projecting from the upper wall (7, 28), the lower wall (8, 29) of the element being welded to the lower part of the side wall. Module according to one of Claims 1 to 3, characterized in that at least one chamber (23, 43) comprises an input port (24, 47, 26) and an output port (25, 48, 26). ) coolant. Module according to claim 4, characterized in that a separating wall (13, 14, 15a, 15b, 34a, 34b) extends inside said chamber (23, 43) between the input ports and outlet, over substantially the entire height of the chamber and a distance to guide the flow of liquid in said chamber. Module according to claim 4 or 5, characterized in that the output port (25, 48, 26) of the first chamber (23), respectively the second (43), is connected to the input port (24, 47, 26) of the first chamber (23), respectively the second (43). Module according to any one of claims 1 to 5, characterized in that the second combustion wall (28) comprises a succession of 4 to 7 steps each comprising a portion (28a) substantially flat and parallel to the first combustion wall ( 7) and a portion (28b) substantially flat and perpendicular to the first combustion wall, so as to form a staircase. Module according to any one of claims 4 to 7, characterized in that the input port comprises a conduit (26) opening into the chamber (23, 43) under and in the immediate vicinity of a portion of the first or second combustion wall (7, 28a) intended to be placed substantially horizontally in the oven (1). Module according to any one of claims 1 to 8, characterized in that it comprises a combustion air supply system comprising at least one air passage channel (60) passing through the first element (6) substantially vertically and opening on the one hand by an opening in the lower wall (8) and on the other hand by an orifice (16) formed in the substantially horizontal upper wall (7) of the first element (6), the channel (60) having, over its entire height, a horizontal section of dimensions greater than or equal to those of the orifice (16), the channel widening from the upper face (17) of the element (6) towards the wall lower (8) of said element (6) at least over part of the height of the channel (60). Module according to claims 7 and 9, characterized in that the combustion air supply system comprises at least one air passage channel passing through the second element (27) from bottom to top, said channel opening through an orifice (35) formed in a substantially vertical portion (28b) of the upper wall (28) of said second member (27). Module according to any one of claims 1 to 10, characterized in that at least one of the elements (6, 27) comprises at least a first projection (19, 36) extending from a first side wall (12). 33) of said member outwardly, and at least one second projection (21,39) extending from a second side wall (11,32) of said member outwardly, the upper face (22,40) of the second projection (21, 39) being offset downwardly from the upper face of the first projection (19, 36) by a distance greater than the height of the first projection (19, 36), so that, when two substantially identical elements are associated laterally, the first projection of an element covers the second projection of the adjacent element. Grid for household waste incineration furnace, characterized in that it comprises a plurality of modules (5) according to any one of claims 1 to 11, said modules (5) being arranged so that their first combustion wall (7) is placed substantially horizontally in the furnace and that the downstream end of the second combustion wall (27) of a module (5) is placed substantially in line with the upstream end of the first combustion wall of the module (5) adjacent downstream, above the thrust means (51) of the garbage of said module (5) adjacent, so as to form a succession of steps. Grid according to claim 12, characterized in that a step comprises a plurality of substantially identical modules (5) associated laterally with each other. Grid according to claims 2, 4 and 12, characterized in that the second chambers (43) of the modules (5) of a step of the gate (3) are connected in series by their input and output ports, at the least partially, the first chambers (23) of the modules (5) of a step of the grid (3) are connected in series by their input and output ports, at least in part, the output port (48). , 26) of the second chamber (43) of a given module (5) being connected to the input port (24, 26) of the first chamber (23) of said module (5). Installation for the incineration of household waste, comprising at least an oven (1) in which is provided a grid (3) according to one of Claims 12 to 14, supply means (2) for household refuse in the furnace, upstream of the grid (3), means for collecting the residues incineration, downstream of the grid (3), and means for conveying a coolant of the modules (5) of the grid (3).

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