GRATE WITH MEANS FOR DISCHARGING OF ASH

GRILLE AVEC SYSTEME POUR DECHARGER LES CENDRES

English Abstract

Grate (1) comprises essentially concentrically set stationary and rotating
unified grate rings (6a-d, 7a-c), which alternate from the
centre outwards to the peripheral ring. Each grate ring is lower than the next
ring further in and has a larger diameter than it, when the
fuel fed from beneath to the centre of the grate flows over the grate rings
while it burns to the peripheral ring, in which the ash drops
through openings (30) arranged in it to an ashbox (5). The peripheral ring has
stationary and circumferentially oriented moving units (15,
16), which are arranged in one extreme position to cover the entire peripheral
ring and in the opposite extreme position to interlap in pairs
on top of each other and form the aforesaid openings (30) between the
interlapped pairs.

French Abstract

Une grille (1) comprend des anneaux unifiés stationnaires et des anneaux unifiés rotatifs (6a-d, 7a-c), disposés de manière sensiblement concentrique, qui alternent en allant du centre vers l'anneau périphérique. Chaque anneau de la grille est plus bas que l'anneau qui le suit en allant vers l'intérieur et a un diamètre supérieur au sien. Le combustible amené par dessous arrive au centre de la grille, puis descend en brûlant par-dessus les anneaux et aboutit à l'anneau périphérique, au niveau duquel les cendres traversent des orifices (30) creusés dans ledit anneau et tombent dans un cendrier (5). L'anneau périphérique comprend des unités stationnaires et des unités mobiles orientées circonférentiellement (15, 16) qui, dans une position extrême, sont disposées de façon à recouvrir la totalité de l'anneau périphérique et, dans la position extrême opposée, de façon à se chevaucher par paires par leurs sommets et à former lesdits orifices (30) entre les paires superposées.

Claims

CLAIMS
1. A grate, which comprises a set of substantially
concentric stationary and rotating unified grate rings,
which alternate from the centre outwards to a peripheral
grid ring and in which each grate ring is lower and has a
larger diameter than the inwardly adjacent ring, wherein
fuel fed from beneath to the centre of the grate flows over
the grate rings while it burns to the peripheral grid ring,
and wherein ash drops through openings arranged in the
peripheral ring to an ashbox characterized in that the
peripheral grid ring has pairs of stationary and
circumferentially oriented moving units, which are arranged,
in one extreme closed position, as a grid extending over the
entire surface area of the peripheral grid ring and in the
opposite extreme open position, interlapping in pairs beside
each other and forming the aforesaid openings between the
interlapped pairs.
2. A grate according to claim 1, wherein the units are
components comprising circumferentially oriented rods, in
which the rods are radially offset from each other, forming
a grid structure and that the rods of the moving units are
offset between the rods of the stationary units, so that the
moving units take a position between the stationary units,
when the units are in the interlapped open position.
3. A grate according to claim 2, wherein each unit
comprises 2 to 4 bars, the radial intervals between which
are 2 to 4 cm.
4. A grate according to any one of claims 1 to 3, wherein
there are 10 to 20 of both stationary and moving units
covering together the entire ring.

6
5. A grate according to either one of claims 1 or 2,
wherein the moving units are supported from a unified
support ring that is arranged to rotate and which is
supported in the axial and radial directions from a support
structure of the grate and to which an operating device is
connected to drive the support ring, so that the moving
units can be moved between the open and closed positions.
6. A grate according to claim 5, wherein the unified
support ring is carried both axially and radially at several
support points on bearings, over which the support ring
rolls, and wherein the bearing surface of the support ring
includes a step over part of its length, which creates a
change in the level of the moving element during the
movement.
7. A grate according to either one of claims 5 or 6,
wherein the operating device is located in an air intake
duct, so that intake air effectively cools it.

Description

CA 02282271 1999-08-27
WO 98/39601 PCT/F198/00185
Grate with means for discharging of ash.
The present invention relates to a grate, which comprises
essentially concentrically arranged stationary and rotating
grate rings, which alternate from the centre outwards to the
peripheral ring and in which each grate ring is lower than the
next one inwards and has a greater diameter than it, so that
fuel fed from underneath in the centre flows while it burns
towards the peripheral ring, where the ash drops through
io openings arranged in it into an ashbox.
A grate of the type referred to above is described in Finnish
patent No. 95964. The rotating grate rings are set slightly
eccentrically, when they also move the downwards flowing mass
radially. In addition, the grate rings rotate in opposite
directions, which improves the transport of the ash over the
grate rings. An opening has been left between the peripheral
ring of a grate of this kind and the wall, from which the ash
drops into an ashbox beneath it. The opening must be quite
wide, because the ash contains some large clinkers. As the fuel
feed is increased, the proportion of unburnt material in the
ash increases. This limits the available output of the grate,
though the grate could otherwise burn a much larger amount of
fuel.
The purpose of the invention is to create an improvement over
the case referred to above. The characteristic features of the
invention are described in the accompanying Claims. With the
aid of units according to the invention, the intermediate space
that was previously a free opening is covered with a grid
construction, in which openings can be formed if necessary. The
grate can then be loaded much more than previously, particu-
larly for short periods, with no fear of considerable quanti-
ties of unburned material flowing with the ash. Even large
lumps of clinker can be removed through the openings formed at
regular intervals between the units, though otherwise the

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WO 98/39601 PCT/FI98/00185
2
elements form a grid structure, on top of which combustion
continues, with the fine ash nevertheless dropping through.
Other advantageous embodiments of the invention and advantages
are described later concerning the example of application.
In the following, the invention is described with the aid of
the accompanying drawings, which show one grate according to
the invention.
Figure 1 shows a vertical cross-section of a combustion cham-
ber, to which a grate according to the invention has
been adapted.
Figure 2 shows a partial enlargement of the cross-section in
is Figure 1 in the area of the peripheral ring, in which
there is the new arrangement for removing ash.
Figure 3 shows an adaption arranged on the peripheral ring,
comprising stationary and moving units with the ash
openings closed; the Figure includes a partial en-
largement.
Figure 4 shows the arrangement in Figure 3 with the units
overlapped and forming ash openings; the Figure
includes a partial enlargement.
Figure 5 shows the vertical bracket in figure 2, seen from in
front.
In Figure 1, a grate 1 according to the invention is adapted to
a combustion chamber with a circular horizontal cross-section,
which in this adaptation acts as the front chamber of a boiler.
3o Grate 1 conforms to the patent publication referred to above,
except for the arrangement of the periphery. The lower part of
combustion chamber 2 is cylindrical, while the upper part is
conical. The conical upper part is connected to flue 3, which
is connected to the after combustion chamber and to a boiler
(not shown) for recovering heat from the flue gases. The jacket
4 of the combustion chamber has thermal insulation. Grate 1 is
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CA 02282271 2007-02-16
3
arranged in the lower part of combustion chamber 2. An annular
ashbox 5 surrounds grate 1. Grate 1 according to the invention
includes stationary and rotating grate sections. The stationary
grate components are grate rings 6a, 6b, 6c, and 6d, while the
rotating grate sections are correspondingly grate rings 7a, 7b,
and 7c. These are mutually arranged so that every other grate
ring is stationary, while the others rotate. The inner and
outermost grate rings 6a and 6d are stationary grate rings.
The fuel feed channel 8 is arranged to run horizontally beneath
grate 1 from the outside of the combustion chamber 2 to its
centre. Fuel, e. g. woodchips, conveyed by feed screw 9 travels
along the feed channel 8 to the centre of the grate and rises
through the feed cone 11 to the top of grate 1. There the fuel
ignites and while burning flows over the grate rings 6a-d, 7a- c.
Ash and possible burning residue move to the peripheral ring, in
which there is an arrangement according to this invention.
The enlargement in Figure 2 shows the new arrangement according
to the invention in detail. In this arrangement too, the ash
openings 30 are formed in a peripheral grid ring between
stationary grate ring 6d and the wall of the combustion chamber,
but the openings can be closed by stationary and moving units 15
and 16. The moving units are installed on arm 19, which is in
turn attached to support ring 14. This is supported vertically on
five bearings 13 from the support structure of the grate. Figure
2 shows one bearing 13 in cross-section, while Figure 5 shows it
seen from the front. Units 15 and 16 comprise circumferentially
oriented bars 15.1 and 16.1. According to Figure 2, bars 15.1 and
16.1 interlap, so that the bars 16.1 of moving unit 16 push
between the stationary bars 15.1.
Figure 3 shows the general arrangement of the units 15 and 16
that extend over the entire area of the peripheral grid ring,
with the ash openings closed. However, fine ash can flow down,
due to the grid construction

CA 02282271 1999-08-27
WO 98/39601 PCT/FI98/00185
4
of units 15 and 16. The partial enlargement shows the construc-
tion of the units in greater detail. They each comprise three
bars 15.1 and correspondingly 16.1 set at a distance to one
another. Bars 15.1 are attached to arm 18 and correspondingly
bars 16.1 are attached to arm 19. In general, each unit,15, 16
comprises 2 - 4 bars 15.1, 16.1, at a radial distance of 2 - 4
cm.
Support ring 14 is not only supported vertically, but also
io horizontally on five rollers 20, which roll along the cylindri-
cal support structure. The support ring is driven by operating
device 21, for example, a pneumatic cylinder, which is in-
stalled in air intake duct 22. In this way the operating device
remains cool.
In this example 16 pairs of units are used, but advantageously
these are 10 - 20.
The ash openings 30 are formed according to Figure 4 by using
operating device 21, by means of which support ring 14 is
turned slightly, so that the attached units 16 interlap with
the stationary units. Even large lumps of clinker will fit
through the ash openings 30 that are formed. According to
Figure 5, the rolling surface of the support ring incorporates
a step 17, which raises the units 16 when they are moved. This
improves the cleaning of the units and reduces the risk of them
j amming.
. _. ~
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Representative Drawing