[0001] The present invention relates to a combustion grate for solid fuels, particularly
suitable for the combustion of municipal solid waste, refuse-derived fuel, biomasses,
fossil fuels in general, and the like.
[0002] The type of combustion grate according to the present invention is particularly suitable
in incineration ovens and particularly in the field of the waste-to-energy conversion
of the solid fuels cited above.
[0003] Every incineration plant has a region where combustion occurs. The combustible material
is usually introduced in the combustion chamber of the plant by gravity from above.
The combustion material then falls onto the combustion grate, where a "mat" of combustible
material forms. In order to produce a uniform layer of combustible material along
the grate, such grate can be inclined with respect to the horizontal direction with
a certain inclination, so as to prevent the combustion material from piling up proximate
to the region where it is introduced by gravity, producing the gravity descent of
the combustion material, which is thus distributed more evenly along the entire length
of the combustion grate.
[0004] In the chamber, the combustion of the solid combustible material occurs continuously
by spontaneous combustion. Part of the comburent (usually air) is sent to the region
below the combustion grate and, by passing through it, feeds the combustion of the
overlying material.
[0005] The combustion grates suitable for this purpose comprise a series of fire bars, elements
which are suitable to withstand the high temperatures reached on the surface of the
combustion grate. Such fire bars cover the structure of the grate and constitute the
supporting surface of the combustion material. Said supporting surface is provided
by arranging a plurality of elements side by side. In this manner it is also possible
to replace elements compromised by the thermal stress. The more superficial portion
of material of the bed, by being more exposed to the flame, bums at higher temperatures,
while the underlying layers remain at lower temperatures, making the combustion process
uneven. In order to homogenize the layer of material, improve its distribution and
make it advance, the grates are generally constituted by rows of alternately fixed
and movable fire bars, so that it is possible to optimize the combustion process of
the material.
[0006] Therefore, combustion grates are complex systems, which must meet several requirements,
including the need to allow the flow of comburent through the bed of combustible material
and to remix and redistribute continuously the material that undergoes the combustion
process.
[0007] The combustion grate reaches very high operating temperatures, and therefore it is
necessary to provide a system for cooling the elements that compose it, especially
the fire bars, which are the parts subjected to the most intense thermal stresses.
[0008] The combustion grates are in fact subject to corrosion caused by high temperatures.
In order to solve these problems, air- and water-based cooling systems have been devised.
In practice, it has been found that traditional air cooling achieves inferior results
with respect to water cooling.
[0009] The limitation of water-cooled grates is the considerable plant complexity of the
cooling systems and the fact that since there are no alternative cooling systems,
a failure of the liquid cooling system compromises the operation of the entire grate.
As regards the complexity of liquid cooling systems, it has to be considered that
the heat conveying liquid must flow through each individual fire bar and that the
entire system must therefore have appropriate connectors which are adapted to avoid
hindering the relative motion of the rows of movable fire bars with respect to the
rows of fixed fire bars. Feeding the coolant to the fire bars, when working in a particularly
hostile environment, is particularly delicate.
[0010] A combination of features as set forth in the pre-characterizing portion of the appended
claim 1 is disclosed for example in
BE 420 333.
[0011] The aim of the present invention is to provide a new type of combustion grate which
solves or at least reduces the drawbacks that affect the background art.
[0012] Within this aim, an object of the present invention is to provide a new type of combustion
grate, which while allowing to stir effectively the combustible material deposited
thereon uses a particularly simple cooling system.
[0013] Another object of the present invention is to optimize the cooling of the elements
that compose the grate, particularly the fire bars.
[0014] Another object of the present invention is to provide a new type of combustion grate
which can be liquid- and air-cooled effectively, i.e., so that the two cooling systems
are independent from each other, so as to allow operation even without one of the
two cooling fluids.
[0015] Another object of the present invention is to provide a combustion grate which is
capable of optimizing the uniformity of the combustion along the grate.
[0016] In accordance with the invention, there is provided a combustion grate for solid
combustible materials, as defined in the appended claims.
[0017] Further characteristics and advantages of the present invention will become better
apparent from the following detailed description, given by way of nonlimiting example
and illustrated in the accompanying figures, which exemplify a possible embodiment,
wherein:
Figure 1 is a schematic sectional side view of the combustion grate, illustrating
the supporting structure and the corresponding fire bars, the movable fire bars being
in a retracted position;
Figure 2 is the same sectional side view as Figure 1, wherein the movable fire bars
of the combustion grate are in a forward position;
Figure 3 is the same side view as in Figures 1 and 2, wherein the movable fire bars
are in a full-forward position, which allows to disassemble said fire bars from the
combustion grate;
Figure 4 is a transverse sectional side view of a fire bar with which the combustion
grate according to the present invention is provided;
Figure 5 is a sectional view, taken along the horizontal plane E-E, of the fire bar
of Figure 4;
Figure 6 is a sectional view, taken along the vertical plane A-A, of the fire bar
of Figure 4;
Figure 7 is a sectional view, taken along the horizontal plane H-H, of the fire bar
of Figure 4.
[0018] With reference to the figures, a possible embodiment of the combustion grate 1 according
to the present invention comprises a supporting structure, generally designated by
the reference numeral 2, which comprises a plurality of movable and fixed supporting
elements 2a and 2b.
[0019] The movable supporting elements 2a can perform a translational motion because they
are mounted on a structure, for example of the carriage type, which is provided with
suitable movement means.
[0020] Each movable supporting element 2a is arranged laterally adjacent at least to a fixed
supporting element 2b and is restrained by the presence of the fixed supporting element
2b so as to perform a translational motion parallel thereto.
[0021] With reference to the structure shown in Figure 1, for example, it can be seen that
the repetitiveness of the modular structure of the grate entails that each movable
element 2a is flanked by two fixed elements 2b, so that the movable elements 2a are
restrained so as to perform a translational motion parallel to the two adjacent fixed
elements 2b.
[0022] According to the present invention, the supporting elements 2a and 2b are constituted
by beams. Said beams 2a, 2b may have any cross-section and can for example have a
rectangular cross-section, according to what is shown in the accompanying figures.
[0023] Again with reference to Figures 1 to 3, a fire bar, designated by the reference numeral
3, is mounted on each supporting element 2a, 2b. The fire bars 3 arranged so as to
cover the supporting elements 2a, 2b are, as mentioned, in contact with the combustible
material, by generically constituting the supporting surface of said material.
[0024] The fire bars 3 can be of the same type, both when they are mounted on the movable
supporting elements 2a and when they are mounted on the fixed supporting elements
2b. For the sake of convenience in description, the fire bars also have been designated
as movable fire bars 3a and fixed fire bars 3b, depending on whether they are fitted
respectively on a movable supporting element 2a or a fixed supporting element 2b.
[0025] Each supporting element 2a, 2b supports a plurality of fire bars arranged side-by-side,
so that the fire bars are substantially mutually parallel along a same beam.
[0026] In the combustion grate 1 according to the present invention, said supporting beams
are crossed by a fluid-based cooling system. In particular, the structure might provide
that only the fixed supporting beams 2b be crossed by the liquid cooling system.
[0027] The cooling system allows to cool the fixed fire bars 3b which are in contact with
the fixed beam 2b, since said beam is crossed by the cooling fluid, which can be constituted
for example simply by water or by other liquids. The cooling system that passes through
the beams 2b can be constituted for example simply by pipes capable of allowing heat
exchange. The cooling of the movable fire bars 3a, if only the fixed beams 2b are
cooled, occurs indirectly due to the proximity of the movable fire bars with respect
to the fixed supporting beams 2b crossed by the liquid cooling system.
[0028] According to another aspect of the present invention, the fire bars, which may for
example have the configuration shown in Figure 4, are constituted by a main body 4,
having a lower surface 6 which is shaped conveniently for the contact of said fire
bar against the supporting beam 2. In particular, in the embodiment described by way
of example in the accompanying figures, the lower supporting surface 6 of the fire
bar has a profile which is adapted to rest against the supporting beam 2 having a
rectangular cross-section. Such lower supporting surface 6 therefore has a substantially
rectilinear portion 6c, which is adapted to rest against the upper surface 21 of the
supporting bar 2.
[0029] Two portions 6a and 6b, which are substantially perpendicular to the supporting surface
6c, by abutting against the lateral surfaces respectively 22 and 23 of said beam 2,
allow to stabilize the contact of the fire bar 3 against the beam 2. Of course, different
configurations of the cross-section of the beam 2 might be matched by different configurations
of the lower supporting surface 6 of the fire bar 3.
[0030] The external surfaces of the fire bar 3 might be substantially flat, like the upper
surface 7 and the lower end surface 8, so as to facilitate the relative translational
motion of the movable fire bars 3 with respect to the fixed fire bars that are adjacent
thereto.
[0031] The fire bars 3 can be crossed advantageously by one or more means adapted to convey
the combustion air that arrives from the region below the grate. In particular, said
air conveyance means can be constituted, for example, by one or more grooves or guides
which cross the fire bars, as shown in Figures 4 to 7. In particular, Figures 6 and
7 show that said grooves or guides 5 run across the entire length of the fire bar
3.
[0032] With reference to Figure 4, the fire bar 3 has a rear region 10 and a front region
11, where the front part of the fire bar is defined as the part that faces toward
the outside of the combustion grate, i.e., toward the combustible material. The front
part 11 of the fire bar 3 is conveniently spoon-shaped so as to contain the combustion
ash.
[0033] Moreover, the fire bars 3 can be provided with protrusions 12, 13, which are arranged
at the upper surface 7, are variously shaped and are adapted to engage corresponding
recesses 14, 15 provided at the lower end surface 8 of the adjacent fire bar. These
coupling means allow to engage each fire bar with the fire bars that are adjacent
thereto in order to vary, with their relative position, the load loss of the air that
flows through them.
[0034] With particular reference to Figure 3, the stroke limit of the movement means that
support the movable beams 2a may allow to move the movable fire bars 3a forward enough
to disengage them from the adjacent fixed fire bars 3b. This allows, if necessary,
to remove the fire bars, both the fixed ones and the movable ones, which need to be
replaced. Likewise, they can be retracted in order to allow the disassembly of the
fixed fire bars.
[0035] Operation of the combustion grate 1 according to the present invention can be illustrated
as follows.
[0036] As described up to now with reference to a preferred embodiment of the combustion
grate according to the present invention, said grate comprises rows of fire bars 3b
and 3a, which are respectively fixed and movable, since they rest on beam-shaped supporting
elements 2a and 2b, which are respectively movable and fixed. Each movable supporting
element 2a is mounted on a carriage, which allows its advancement and retraction substantially
along a straight line with respect to the fixed beam-shaped supporting element 2b,
and fixed and movable beams are alternated.
[0037] The relative movement of the fire bars allows to stir the combustion material, achieving
even distribution of said material in the various points of the grate as well as continuous
recirculation of the material that lies at the top of the bed of material with the
material that is in contact with the fire bars of the combustion grate.
[0038] The fixed supporting elements 2b are provided conveniently with a cooling system
which is adapted to convey a heat conveying fluid. The passage of the cooling fluid
within the fixed supporting elements 2b contributes to the cooling mainly by conduction
of the fixed fire bars 3b and movable fire bars 3a which rest thereon. The movable
supporting element 2a which supports the movable fire bars 3a might not be crossed
by the cooling fluid, thus simplifying considerably the cooling system and eliminating
any possible hindrance to the movement of the carriage which constitutes the movable
part of the supporting structure. In this case, when the movable fire bars 3a are
in the more retracted position shown in Figure 2, each movable fire bar 3a is substantially
laterally adjacent to an adjacent fixed beam 2b. The proximity of the movable fire
bar 3a with respect to the adjacent fixed supporting element 2b allows to also cool
said movable fire bar 3a by convection/conduction, even if each movable supporting
element 2a is not crossed by the cooling fluid.
[0039] According to what has been described earlier, the air conveyance or guiding means
5 provided inside each fire bar 3 contribute to the cooling of the fire bars. The
combustion air in fact passes through the grate in order to reach the upper region
of the grate, where the bed of combustion material is burning. The combustion air
reaches the combustion area of the material by utilizing passages which are provided
appropriately between one fire bar and the other, as shown for example in Figure 1.
However, by also being conveyed into the grooves or guides 5 for the conveyance of
the air which are provided inside each fire bar, such combustion air also performs
a cooling function, helping to reduce the temperature of the fire bars.
[0040] The possibility to convey inside the fire bars part of the air designed to feed combustion
allows to further cool the fire bars. If air cooling is associated with the water
cooling described above, if water cooling is interrupted due to breakage or to a technical
fault, the described air flow alone would still ensure a good cooling of the elements
of the combustion grate that are most intensely subjected to thermal stresses.
[0041] The described configuration for the fire bars allows to meet a further requirement,
which is constituted by control of load losses through the grate. The combustion material
arranged on the grate in fact inevitably causes resistance to the flow of combustion
air. By way of a higher load loss of the air that passes through the grate, it is
possible to better control, and therefore optimize, the distribution of the combustion
air. A high load loss of the grate when empty in fact allows to reduce the influence
that the bed of combustible material, arranged above the grate and generally uneven,
has on the distribution of the air.
[0042] The overlap of the fire bars which are mutually engaged by way of the coupling means
constituted by the protrusions 12, 13 and by the recesses 14, 15 forms a hindrance
to the flow of the air, which is consequently forced to pass through the grate only
through the regions provided specifically for this purpose between the fire bars.
The reduced cross-section provided for the flow of the combustion air entails a high
value of the load losses through the grate when empty, i.e., without considering the
load losses caused by the presence of the combustion material. Moreover, the passage
section of the air can vary depending on the position of the movable fire bar with
respect to the fixed adjacent ones. Accordingly, it is possible to change from the
outside, by modifying the stroke limit positions of the movable fire bars 3a, the
load loss imposed on the combustion air in passing through the grate. Therefore, by
controlling and, if necessary, increasing the value of the load loss associated with
the grate, it is possible to achieve a more even distribution of the combustion air
and therefore, ultimately, a more even process of combustion of the material.
[0043] It has thus been shown that the present combustion grate achieves the intended aim
and objects. In particular, a new type of combustion grate has been described which
allows to optimize the cooling of the elements, i.e., of the fire bars, of the grate
which constitute the supporting surface of the combustible material.
[0044] Moreover, the combustion grate according to the present invention achieves this aim
by means of a cooling system which is considerably simplified with respect to those
currently used in the field, leading to savings in execution, assembly and maintenance
of said combustion grate.
[0045] Moreover, the present combustion grate allows to improve the uniformity of the combustion
process along the entire grate thanks to the possibility to control load losses for
the combustion air which passes through the grate.
[0046] Numerous modifications may be performed by the person skilled in the art without
abandoning the scope of the protection of the present invention.
[0047] Therefore, the scope of the protection of the claims must not be construed as being
limited by the illustrations or by the preferred embodiments shown by way of example
in the description, but rather the claims must comprise all the characteristics of
patentable novelty that can be deduced from the present invention, including all the
characteristics that would be treated as equivalent by the person skilled in the art.
[0048] Where technical features mentioned in any claim are followed by reference signs,
those reference signs have been included for the sole purpose of increasing the intelligibility
of the claims and accordingly such reference signs do not have any limiting effect
on the interpretation of each element identified by way of example by such reference
signs.
1. A combustion grate (1) for solid combustible materials, comprising a supporting structure
(2) adapted to support a plurality of fire bars (3), which form a surface for supporting
said combustible material, said supporting structure (2) comprising fixed supporting
elements (2b) and movable supporting elements (2a) connected to movement means, said
fixed supporting elements (2b) and said movable supporting elements (2a) being arranged
so as to be mutually alternated, said movable and fixed supporting elements (2a, 2b)
being each constituted by at least one beam-shaped element, each beam-shaped element
(2a, 2b) being capable of supporting a plurality of fire bars (3) arranged side-by-side
along its length, said combustion grate being characterized in that at least said fixed supporting element (2b) comprise fluid-based cooling means, and
the cooling of said movable fire bars (3a) occuring by convection and conduction due
to the vicinity of said movable fire bar (3a) to said fixed supporting element (2b)
when said movable fire bar (3a) is in the retracted position.
2. The combustion grate (1) according to claim 1, characterized in that said pluralities of fire bars (3) arranged on each beam-shaped element (2) are also
respectively fixed (3b) and movable (3a) with said supporting elements (2a, 2b), so
that each fixed fire bar (3b) is adjacent to at least one movable fire bar (3a).
3. The combustion grate (1) according to claim 1, characterized in that the cooling of said fixed fire bars (3b) occurs substantially due to the contact
of said fixed fire bar (3b) with said fixed supporting element (2b).
4. The combustion grate (1) according to any one of the preceding claims, characterized in that said movable supporting elements (2a) can move with respect to said fixed supporting
elements (2b) with a substantially rectilinear alternating translational motion.
5. The combustion grate according to any one of the preceding claims, characterized in that said fire bars are air-cooled by the combustion air.
6. The combustion grate according to any one of the preceding claims, characterized in that said fire bars (3) comprise air conveyance means (5).
7. The combustion grate according to claim 6, characterized in that said air conveyance means (5) cross said fire bar (3) along its entire length.
8. The combustion grate according to claim 6 or 7, characterized in that said air conveyance means (5) are constituted by grooves formed within the body of
said fire bar (3).
9. The combustion grate according to any one of the preceding claims, characterized in that said fire bars (3) further comprise coupling means which are adapted to engage each
fire bar with the fire bars that are adjacent thereto.
10. The combustion grate according to claim 9, characterized in that said coupling means comprise protrusions (12, 13) which are arranged at the upper
surface (7) of each one of said fire bars (3) and are adapted to engage corresponding
recesses (14, 15) provided at the lower end surface (8) of said fire bars.
11. The combustion grate according to any one of the preceding claims, characterized in that passage ports for the combustion air which reaches said combustion material are provided
between said fixed fire bars (3b) and said adjacent movable fire bars (3a).
12. The combustion grate according to claim 11, characterized in that the breadth of said passage ports for the combustion air can be adjusted by adjusting
the stroke of said movable fire bars (3a), thus allowing to adjust the load loss of
the air through the combustion grate.
1. Ein Verbrennungsrost (1) für feste brennbare Materialien, der eine tragende Struktur
(2) umfasst, die ausgebildet ist, um eine Vielzahl von Roststäben (3) zu tragen, welche
eine Oberfläche zum Tragen des brennbaren Materials bilden, wobei die tragende Struktur
(2) feste tragende Elemente (2b) und bewegliche tragende Elemente (2a) umfasst, die
mit Bewegungsmitteln verbunden sind, wobei die festen tragenden Elemente (2b) und
die beweglichen tragenden Elemente (2a) so angeordnet sind, dass sie einander abwechseln,
wobei die beweglichen und festen tragenden Elemente (2a, 2b) jeweils aus mindestens
einem balkenförmigen Element bestehen, wobei jedes balkenförmige Element (2a, 2b)
in der Lage ist, eine Vielzahl von Roststäben (3) zu tragen, welche nebeneinander
entlang seiner Länge angeordnet sind, wobei der Verbrennungsrost dadurch gekennzeichnet ist, dass mindestens die festen tragenden Elemente (2b) Kühlmittel auf Fluidbasis umfassen,
und wobei die Kühlung der beweglichen Roststäbe (3a) durch Konvektion und Leitung
stattfindet, aufgrund der Nähe des beweglichen Roststabs (3a) zu dem festen tragenden
Element (2b), wenn sich der bewegliche Roststab (3a) in der zurückgezogenen Position
befindet.
2. Der Verbrennungsrost (1) gemäß Anspruch 1, dadurch gekennzeichnet, dass die Vielzahlen von Roststäben (3), die auf jedem balkenförmigen Element (2) angeordnet
sind, auch mit den tragenden Elementen (2a, 2b) fest (3b) beziehungsweise beweglich
(3a) sind, so dass jeder feste Roststab (3b) an mindestens einen beweglichen Roststab
(3a) angrenzt.
3. Der Verbrennungsrost (1) gemäß Anspruch 1, dadurch gekennzeichnet, dass die Kühlung der festen Roststäbe (3b) im Wesentlichen aufgrund des Kontakts des festen
Roststabs (3b) mit dem festen tragenden Element (2b) stattfindet.
4. Der Verbrennungsrost (1) gemäß einem beliebigen der obigen Ansprüche, dadurch gekennzeichnet, dass die beweglichen tragenden Elemente (2a) sich im Bezug zu den festen tragenden Elementen
(2b) mit einer im Wesentlichen rechtwinkligen alternierenden Translationsbewegung
bewegen können.
5. Der Verbrennungsrost gemäß einem beliebigen der obigen Ansprüche, dadurch gekennzeichnet, dass die Roststäbe von der Verbrennungsluft luftgekühlt werden.
6. Der Verbrennungsrost gemäß einem beliebigen der obigen Ansprüche, dadurch gekennzeichnet, dass die Roststäbe (3) Luftfördermittel (5) umfassen.
7. Der Verbrennungsrost gemäß Anspruch 6, dadurch gekennzeichnet, dass die Luftfördermittel (5) den Roststab (3) entlang seiner gesamten Länge kreuzen.
8. Der Verbrennungsrost gemäß Anspruch 6 oder 7, dadurch gekennzeichnet, dass die Luftfördermittel (5) aus Rillen bestehen, die im Körper des Roststabs (3) geformt
sind.
9. Der Verbrennungsrost gemäß einem beliebigen der obigen Ansprüche, dadurch gekennzeichnet, dass die Roststäbe (3) weiter Kopplungsmittel umfassen, die ausgebildet sind, um jeden
Roststab mit den daran angrenzenden Roststäben zu koppeln.
10. Der Verbrennungsrost gemäß Anspruch 9, dadurch gekennzeichnet, dass die Kopplungsmittel Vorsprünge (12, 13) umfassen, die an der oberen Oberfläche (7)
jedes der Roststäbe (3) angeordnet und ausgebildet sind, um in entsprechende Vertiefungen
(14, 15) einzugreifen, welche an der unteren Endoberfläche (8) der Roststäbe bereitgestellt
sind.
11. Der Verbrennungsrost gemäß einem beliebigen der obigen Ansprüche, dadurch gekennzeichnet, dass Durchlassöffnungen für die Verbrennungsluft, die das Verbrennungsmaterial erreicht,
zwischen den festen Roststäben (3b) und den angrenzenden beweglichen Roststäben (3a)
bereitgestellt sind.
12. Der Verbrennungsrost gemäß Anspruch 11, dadurch gekennzeichnet, dass die Breite der Durchlassöffnungen für die Verbrennungsluft durch Anpassung des Hubs
der beweglichen Roststäbe (3a) angepasst werden kann, wodurch die Anlassung des Lastverlustes
der Luft durch den Verbrennungsrost ermöglicht wird.
1. Grille de combustion (1) utilisée pour des matériaux combustibles solides, comprenant
une structure de support (2) adaptée pour supporter une pluralité de fers à barreaux
de grille (3) qui forment une surface supportant ledit matériau combustible, ladite
structure de support (2) comprenant des éléments de support fixes (2b) et des éléments
de support mobiles (2a) raccordés à des moyens de déplacement, lesdits éléments de
support fixes (2b) et lesdits éléments de support mobiles (2a) étant disposés de façon
à se trouver réciproquement alternés, lesdits éléments de support mobiles et fixes
(2a, 2b) étant chacun constitué d'au moins un élément en forme de poutre, chaque élément
en forme de poutre (2a, 2b) pouvant supporter une pluralité de fers à barreaux de
grille (3) disposés côte à côte sur sa longueur, ladite grille de combustion étant
caractérisée par le fait qu'au moins ledit élément de support fixe (2b) comprend un moyen de refroidissement
à base de fluide, et que le refroidissement desdits fers à barreaux de grille mobiles
(3a) s'effectue par convection et conduction du fait de la proximité dudit fer à barreau
de grille mobile (3a) par rapport audit élément de support fixe (2b) lorsque ledit
fer à barreaux de grille mobile (3a) est en position rétractée.
2. Grille de combustion (1) selon la revendication 1, caractérisée par le fait que ladite pluralité de fers à barreaux de grille (3) disposés sur chaque élément en
forme de poutre (2) est également respectivement fixe (3b) et mobile (3a) par rapport
auxdits éléments de support (2a, 2b), de sorte que chaque fer à barreaux de grille
fixe (3b) soit adjacent à au moins un fer à barreaux de grille mobile (3a).
3. Grille de combustion (1) selon la revendication 1, caractérisée par le fait que le refroidissement desdits fers à barreaux de grille fixes (3b) se produit essentiellement
du fait du contact dudit fer à barreaux de grille fixe (3b) avec ledit élément de
support fixe (2b).
4. Grille de combustion (1) selon l'une quelconque des revendications précédentes, caractérisée par le fait que lesdits éléments de support mobiles (2a) peuvent se déplacer par rapport auxdits
éléments de support fixes (2b) dans un mouvement de translation alternatif rectilinéaire.
5. Grille de combustion selon l'une quelconque des revendications précédentes, caractérisée par le fait que lesdits fers à barreaux de grille sont refroidis par air par l'air de combustion.
6. Grille de combustion selon l'une quelconque des revendications précédentes, caractérisée par le fait que lesdits fers à barreaux de grille (3) comprennent des moyens de circulation de l'air
(5).
7. Grille de combustion selon la revendication 6, caractérisée par le fait que lesdits moyens de circulation de l'air (5) traversent ledit fer à barreaux de grille
(3) sur toute sa longueur.
8. Grille de combustion selon les revendications 6 ou 7, caractérisée par le fait que lesdits moyens de circulation de l'air (5) sont constitués par des gorges formées
à l'intérieur du corps dudit fer à barreaux de grille (3).
9. Grille de combustion selon l'une quelconque des revendications précédentes, caractérisée par le fait que lesdits fers à barreaux de grille (3) comprennent également des moyens adaptés pour
engager chaque fer à barreaux de grille avec le fer à barreaux de grille adjacent.
10. Grille de combustion selon la revendication 9, caractérisée par le fait que lesdits éléments d'accouplement comprennent des saillies (12, 13) réparties sur la
surface supérieure (7) de chacun desdits fers à barreaux de grille (3) adaptées pour
s'engager dans les creux correspondants (14, 15) prévus sur la surface inférieure
(8) desdits fers à barreaux de grille.
11. Grille de combustion selon l'une quelconque des revendications précédentes, caractérisée par le fait que des orifices de passage pour l'air de combustion qui arrive jusqu'au matériau de
combustion sont prévus entre lesdits fers à barreaux de grille fixes (3b) et lesdits
fers à barreaux de grille mobiles (3a) adjacents.
12. Grille de combustion selon la revendication 11, caractérisée par le fait que la largeur desdits orifices de passage d'air de combustion peut être réglée en réglant
la course desdits fers à barreaux mobiles (3a), ce qui permet de régler la perte par
la charge de l'air passant à travers la grille de combustion.