Note: Descriptions are shown in the official language in which they were submitted.
~276~33~ ;
~URNER ESPECIALLY FOR BURNING BIOMASS
The present invention relates to a burner which is
particularly suited for burning biomass such RS wood chips ~ -
and peat, the sald burner comprising a ~ombustion chamber
whereinto the fuel is fed, an ash pit located below the
- combustion chamber, and an sutomatic feeder which is
connected to the combustion chamber by means of an inlet
shaft or equivalent arrangement. The term 'burner' here
refers to a fuel feeding and burning device which is
attached to a furnace as an auxiliary arrangement.
; In the prior art there are known separate front extension -
- furnaces which can be connected to standard central heating
furnaces. The front extension furnace comprises a
combustion chamber, a grate and an ssh pit. The front
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~ furnace is connectable to the furnace proper by means of a
- fire shaft. A fuel storage hopper is located above the
front extension furnace so that hetween the hopper and the
combustion chamber there are arranged locking means which
are used for supplying fuel into the combustion chamber. `
For primary air supply and ash removal, the combustion
chamber is provided with a hatch. For secondary air sypply,
~1 an air inlet pipe is connected to the fire shaft. The fuel
~ 25 is gasified in the front extension furnace, and the ~`-
- resulting gases are burned by means of secondary air in the
-~ furnace proper.
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The front extension furnaces are devices oF the same size
3û as the main furnace, and their purpose is to readjust for
example an oId oil furnace so that it is suitable for
burning sawdust or wood chips. The readjustment operations
are cumbersome and the front extension furnace requires a
lot of ~pace. This kind of a front extension furnace and
~ 35 main furnace combination has a high draught resistance, and
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the output regulation of the combustion process and the
said combination becomes difficult. The combination is not
easily adapted to quick changes in the fuel charge, and it
does not function with small charges. Damp wood chips or
damp sawdust cannot be used as fuel because the combustion
temperature is relatively low, and the Fuel supply into the
front extension chamber is carried out in comparatively
large and uneven batches by means of opening the locking
members.
The German Patent Publication No. 62 û43, 917 741 and
917 7~2 introduce various furnace constructions resembling
the front extension furnace and main furnace combinations;
in these furnace constructions, the combustion chamber
provided for solid fuel, and the afterburning chamber for
gases, form a uniform furnace assembly. The combustion
chamber is large, and it is provided with vertical and/or
inclined grate arrangements. The use of these arrangements
aims at achieving a high total output, which again requires
- 20 that large amounts of fuel are treated at a time. The
furnace output cannot be substantially regulated.
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- The instlllation of an automatic solid fuel feeder in- connection to the aforementioned type~ of furnace and/or
; 25 front extension furnace and main furnace combinations is
difficult, sometimes outriyht impossible. If the feeder is
managed to be connected to the furnace, the burning
effeciency often remains poor because these furnaces and/or
front extension furnaces generally have a large grate and a
combustion chamber which is too small with respect to the
grate. The flame temperature remains too low because the
flames get into immediate contact with the cold fire
surfaces and are cooled off so that complete combustion is
not possible. The feeder input heigth also tends to rise
high, particularly in bottom-heated furnaces where the fuel
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is fed in through the fuel supply hatch. In conventional
furnaces the burning of sod peat, milled peat, peat pellets
and straw pelleta i8 also difficult owing -to the large
amount of created ashes and the fact that the ashes are
sintered.
Within the class of regular burners which are suited for
solid fuels can be included for instance so-called stokers
that are primarily meant for burning wood chips, and
incineration dishes or shafts which are provided with
various fuel feeding means located on the top or on the
same level as the dish or shaft itself. The stokers,
~- incineration dishes and shafts are installed within the
- furnace combustion chamber so that they take up part of the
chamber volume. The feeding means are often spiral feeders.
The drawbacks in the aforementioned burners sre connected
with ash removal, fuel supply and power regulation. Ashes
are removed for instance from the combustion chamber of the
stoker or from the fire shaft of the burner so that they
are pushed off by the fresh fuel fed in by the feeder
spiral. The ashes are sintered, i.e. the ashes, while first
~-~ melting and subsequently cooling off, form a solid
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- substance which sticks onto the walls of the combustion
chamber or onto the shaft or the grate. The sintered ashes
- diminish the combustion space and block the air inlets in
the shaft or in the grate. While the operation of the
feeder i9 continued, part of the unburned fuel drops over
the edges of the stoker or of the fire shaft down onto the
bottom of the furnace, and thus the air supply is
obstructed, which causes the combustion process to slow
down. This causes the maintenance periods to become fairly
short, particularly at times when the fuel charge is at its
largest. The output regulation is also difficult with these
kind of burners; it is particularly difficult to arrange
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the apparatus to idle~ i.e. to function with minimum power.
Moreover, the spiral feeding system is sensitive to distur-
bances and expensive to manufacture.
The object of the presen~ invention is to achieve an improve-
ment in solid fuel burners and feeders and to reali~e a
burner, the output whereof can be regulated within a wide
range and fairly quicklyt and which burner needs regular
maintenance at remarkably longer intervals than conventional
solid fuel burners. The invention is characterized by the
novel features enlisted in the appended patent claims.
According to the above object, from a broad aspect, the
present invention provides a biomass burner for attachment
to a furnace having a combustion gas furnace opening. The
burner comprises a separate burner housing having a tubular
combustion gas discharge connected to the furnace opening.
Wall means defines an ash pit below the furnace opening. A
combustion chamber is provided over the ash pit and has a
connection at one end to the combustion gas discharge and is
further provided with an opposite combustion chamber end.
A burnable material inlet shaft is connected to the combus-
tion chamber opposite end. The combustion chamber is a fire
shaft above the ash pit and has an inclined inlet surface
extending inwardly and downwardly from one side toward the
middle of the inlet fire shaft. The inlet surface has an
upper end connected to the burnable material inlet shaft.
Support means extends into the fire shaft. The inlet surface
has a lower end extending downwardly and inwardly of the
upper end and is supported on the support means. An inclined
counter surface is also provided and has a lower end spaced
from the inlet lower end surface so as to define together
with the inlet surface an ignited material support with an
air passage opening therebetween for ash and combustion air.
Means is further provided for directing air through the air
passage opening.
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The aforementioned drawbacks are eliminated in the 801id
fuel bu~nar of th~ pr~ent inv~ntion. Th~ burner forms a
separate unit which can be combined to any existing
Furnace, psrticularly externally. The burner i~ instslled
for example in the bottom hatch of the furnace, so that the
feeder input height remsins low, preferably between 30-60
cm .
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~` In the burner, the fuel i5 burned directly and
immediately. The inlet surface ~nd the countersurface form
fire ~haft whereby ide~l conditions are created for the
rapid gasification and immediate combu~tion o~ the fuel.
`~ Fuel is added into the powerfully glowing he~p oF embers
~` or to the immediate vicinity thereof. Combustion takes
; place mainly in the vicinity of the countersurface~ so that
- e~peecially damp fuel h~s time to dry gradually and at
least partly beFore ignition. Experiments have proved thst
even biomass with a humidity content of approximately 60 ~
can be fed into tne combustion chamber, which has not been
pos~ible in the prior art furnaces or burners without
suFFoo~ting the oombustion pro:ess.
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The temper~ture of the flame is remarkably high, generally
between 600-130~C~ This leads to a high burning
efficiency. Inside the furnace itself there is left
additional space for proper afterburning brickworks, fQr
instance, so that the combustion process proceeds in a high
temperature to the very end. The Fuel supply into the
combustion chamber is sdjusted by means of the automatic
stoker connected to the inclined inlet surface, and the
amount of combustion air is regulated by means of a blower;
consequently the ratio between the fuel and the combustion
air is accurately adjusted. All furnaces can be converted
into top-heated furnaces operated on the so-called
scsttering principle. All of the fire surfacs of the
furnaces become practically useful, so that the outlet
temperature of the combustion gases is decreased and the
total efficiency of the furnaces is increased. Idling
losses are accordingly diminished, beacause the fuel
addition scattered each time into the combustion chamber of
the burner needs only to be sufficient for keeping up the
firP.
In the burner of the invention, solid fuels is burned in a
; process which is in complete control; the total efficiency
; of the furnace whereto the burner is connected can be
adjusted within a very wide range by regulating the fuel
; supply and the air flow. In conventional furnaces or in
furnaces provided with a front extension furnace, this kind
of process-scale control is not possible.
In the combustion chamber of the burner there can also be
burned materials, for example peat, with a low ash melting
point and a high ash content. At least half of the created
ashes are now left in the ash pit of the burner. Ash
` removal from the furnace is much more troublesome than ash
removal from the ash pit of the burner. Moreover, the wall
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surfaces in the furnace combustion chamber re~ain cleaner
than in other burner applications. This is an important
argument also when burning biomass other than peat.
In the following the invention and it~ addition~l
advantages are described in more detail with reference to
the sppended drawing, where
Figure 1 illustrates the structure of a burner according to
the invention, seen in side-view cross-section;
Figure 2 illustrates another embodiment of the burner of
the invention, also in cross-section; and
Figure 3 illustrates the burner of figure 2, shown along
the section A-A.
The burner o~ the in~ention is a separate unit which can be
connected to any furnace or other corresponding furnace
construction. In figures 1 and 2, the burner 1 is connected
to the furnace 2, preferably to its bottom hatch 3. The
connecting can be carried out either directly or by means
of a separate channel 5. The fuel bin, which is not
illustrated in the drawing, is connected to the burner 1
proper by means of the stoker 4.
The burner 1 comprises the combustion chamber 6, whereinto
the fuel is fed, and the ash pit B, which is located below
the combustion chamber. It can be understood that the
` aforementiond automatic stocker 4 also belongs to the
`~ burner. The stoker 4 is connected to the combustion chamber
; 6 by means of an inlet shaft or the like. The inlet shaft
3û may be a separate, for instance vertical and tubular
` member, located between the stoker 4 and the combustion
chamber 6, but the stoker 4 can, in certain conditions,
also be connected directly to the combustion chamber 6 as
is shown in figures 1 and 2.
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The cornbustion chamber 6 i9 formed of the fire shaft 7
- which comprises the inlet surface 71, the countersurface
72, and the slot 73 therebetween. The inlet surface 71 and
the countersurFace 72 are advantageously planar surfaces
which are inclined to opposi~e directions so that between
them they form a V-shaped fire shaft. At the bottom and at
two sides, this fire shaft 7 defines the combustion chamber
6 of the burner 1. The side walls of the burner 1 form the
end walls of the combustion chamber. The fuel stoker 4 is
connected to the combustion chamber 6 by means of the
inclined inlet surface 71, which thus serves as the inlet
shaft or part thereof.
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The stoker 4 if formed of one unit, or of several adjacent
feeding units. The stoker 4 is connected to the inclined
inlet surface 71 50 -~hat it is located vertically against
it 9 and simultaneously against the slot 73 and the
countersurface 72. The width s of the stoker 4 is roughly
equal to that of the inlet surface 71, and thus of the
whole combustion chamber 6.
The inclination ~ of the inlet surface 71, with respect to
an imaginable vertical plane B-B~ is generally between
15...45. The inclination B of the countersurface 72, with
1 25 respect to the imaginable vertical plane B-B, but slanted
in the opposite direction than the inclination ~ of the
inlet surface 72, is most advantageously between 6û...10.
The inclination ~ of the inlet surface 71 is defined
according to the fuel in question The fuel must slide
3û properly down along the inlet surface. The inclination ~ of
the countersurface 72 is also defined according to the fuel
to be used. The general principle is that the more rolling
or flowing is the nature of the employed solid fuel, the
gentler is the slope of the contersurface 72, i.e. the
larger is the angle ~. At its largest the angle ~ may be
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even 90. Either the inlet surface 71 or the countersurfsce
72, or both, can also be somewhat coarsened; this prevents
smsll-grained fuels from rolling too easily through the
slot 73 into the ash pit 8.
The bin 9 located below the fire shaft 7 and the ash pit 8
advantageously form together a unifor~ space. In the ash
pit 8 there can be installed an ash box or ash cassette 81,
- which can be removed from the ash pit 8 and emptied or
replaced when necesssry. Within the said uniform space,
there i9 arranged an air inlet opening lO, the si~e whereof
can also be adjusted, and which can be closed altogether if
desired.
It is sdvantageous to connect a fan ll or equivalent to the
uniform space located below the fire shaft 7~ By means of
this fan, in the space 8, 9, below the fire shaft, there is
crested positive pressure with respect to the combustion
chamber 6. When fueL is ignited by employing positive
; 20 pressure, the draught can be intensified and a successful
ignition ensured. Thereafter the combustion air may be
supplied Vi8 the sir inlet lO. As regards thr adjusting of
the combùstion process, particularly in case the employed
fuel is biomass with a high humidity content, it is
necesssry to keep the fan ll in operation throughout the
prosess.
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In the embodiments illustrated in the drawing, the fuel
stoker 4 is connected directly to the burner l. Now the
height hl of the inlet surface 71, measured From the slot
73 to the fùel inlet opening 41, is larger than the height
h2 f the countersurface 72, measured from the slot 73 to
~ the outlet of the burner l or to the connecting channel 5.
- the height hl of the inlet surface 71 is advantegeously
between 30-70 cm, while the height h2 of the countersurface
72 is h2 ~0,10...0,75 x hl.
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If the stoker 4 is connected, by mPans of a separate
tubular inlet channel (not illustrated in the drawing) or
equivalent to the ~uel inlet 41 and further to the
combustion chamber 6 of the burner 1, the height hl of the
inlet surface 71 may be equal to the height h~ of the
countersurface 72~ This means that the inlet shaft wall on
the side of the inlet surface 71 extends downwards after
the fuel inlet 41, and joins for instance the inlet surface
71 approximately at the height h2 of the countersurface 72
with respect to the slot 73, or in general somewhere
between hl~h2'
ûn the cross-section level, the fuel inlet 41 extends
horizontally from the top edge or similar point of the
inlet surface 71 as far as the slot 73 at the most, i.e. as
far as the imaginable vertical plane B-B. Advantageously
the ~uel inlet 41 is narrower than the plane B-B, as the
dotted lines in figure 1 show~ The top part or the
~ continuation 51 of the channel 5 forms part of the frame
: 20 construction of the burner 1. The purpose for limiting the
width of the fuel inlet 41 is to make sure that the fire
cannot extend from the combustion chamber 6 into the fuel
located in the stoker 4, and further into the storage bin.
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The stoker 4 is placed within a closed channel 42 through
which air is not normally conducted to the combustion
chamber, or vice versa. For safety reasons, it is further
possible to srrange a separate locking device either in the
fuel inlet 41 or in the vicinity thereof, which locking
device is employed for locking the inlet opening 41 or the
inlet channel.
Between the inlet surface 71 and the countersurface 72
there is located the slot 73, as was e~plained above.
Advantageously the said surfaces 71 and 72 are matched so
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that the imaginuble continuation fl of the inlet surface 71
intersects the countersurface ~2, or matches its bottom
edge. This arrangement allows the slot 73 to be more easily
adjustable. On the other hand, the Fuel grains 12 or the
like that slide along the inlet surface 71 are continuously
squeezed, under the pressure of the supplied fresh fuel,
against the countersurface 72, and consequently they canno-t
easily fall unburned into the ash pit 8 through the slot
73. Thus the width of the slot 73 can be larger than the
average diameter of the fuel grains.
In principle the stoker 4 connected to the burner 1 proper
can be a stoker of any of the conventional types, for
example a spiral stoker or an apron conveyor. The essential
point is that the stoker can be used for supplying solid
fuel~ such as wood chips or peat pellets, into the
combustion chamber 6 in a continuous, even flow of an
~- adjustable volume and roughly along the width of the inlet
~` 41, the inlet surface 71 and the slot 73. On this condition
~0 the burner functions in an ideal fashion.
An advantageous fuel stoker has been introduced for
instance in the international patent application
PCT/FI84/00059. The stoker 4 illustrated in the drawing
represents the said advantegeous type. The operation of the
fuel stoker 4 is based on the idea that two or more
supporting members 13, such as planes, bars or rails,
provided with dents or flakes ll~, move back and forth so
that the adjacent support member 13 always move to opposite
directions. The dents or flakes 14 are arrsnged, with
respect to the motional direction of the supporting members
13, in an asymmetrical fashion so that the solid fuel
located on top of the dents or flakes, which fuel is to be
transported and fed in, is more easily shifted in one
direction, i.e. in the transport direction C, than in the
-~ opposite direction.
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11
Stokers of the above described type can be used for
conveying and for feeding even exceptionally nonh~mogenous
and/or extremely light materials. Smull dents or flakes in
the support members - in accordance with the lump size and
lump distribution ~f the conveyed material - render a
surprisingly high material transfer efFiciency. By
regulating the length of the back and forth movement of the
supporting member, the transfer properties of the apparatus
can be adjusted to be optimal while the weight, porosity
etc. of the treated material change~ Power demand, compared
to the transfer and/or feeding output, is extremely
modest. The apparatus has a simple structure. By employing
this apparatus, for instance the feeding of wood chips into
the burner is carried out smoothly so that the total
efficiency of the heater, for e~ample, is improved.
Moreover, the stoker is not easily blocked, and it is well
suited for example for very large burners.
Th~ burner of the invention is operated as follows. The
2û fuel stoker 4 is advantageously provided with a regulation
means (not illustrated in the drawing) which regulates the
scattering of the fuel; the fuel is scattered through the
fuel inlet 41 in a continuous flow of a desired volume into
the fire shaft 7 and the cornbustion chamber 6. Thereafter
~he fuel slides, along the inclined inlet surface 71, to-
wards the slot 73 in a flow roughly as wide as the slct it-
~elf. The surfsces 71 and 72 direct the fuel towards the
slot 73, in the vicinity whereof the burning takes place
first, and always in the case of a small charge. According
to the size of the fuel grains 12, the inclinationsr~ and
of the inlet surface 71 and the countersurface 72 are
matched with each other so that the fuel cannot slide into
the ash pit ~ through the slot 73. The angle ~ of the coun-
tersurface 72 is so adjusted that the inclination is not so
steep that the fuel should slide directly into the slot
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73, but on the other hand most advantegeously so that the
surface 72 is not so near its horizontal position that the
fuel could not be directed towards the slot 73 by means of
the two surfaces 71 and 72.
While the fan 11 is in operation, positive pressure
prevails in the ash pit 8 and in general all over the space
8, 9 below the fire shaft; this positive pressure makes air
to ~low via the slot 73 and through the fuel layer lS into
the combustion chamber 6 and further towards the furnace 2,
thus intesifying the combustion process. This ensures good
conditions for a powerful and rapid gasification of the
fuel and for an immediate combustion of the gases. In the
course of the gasification and combustion process, the fuel
~ 15 grains 1~ become smaller and lighter9 so that the current
-- : of air also prevents them from fslling .into the ash pit 8
through the slot 73. Along the whole width of the slot 73
~: there is consequently formed an intensive5 centralized
combustion area, where fresh fuel is continiously supplied
. 20 along the inlet surface 71. A countercurrent principle
applies in the combustion process: while burning, the solid
fuel becomes smaller in volume and is shifted downwards,
~ and the major part thereof finally ends up in the ash pit
:~: 8, whereas the gaseous ingredients created in the
:: 25 combustion process are shifted upwards and burn immediately
in the combustion chamber 6, in the connecting channel 5
(in case it is used) and in the furnace 2, and develop a
remarkably high temperature, which may rise even up to
: lOOO~C.
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The power regulation of the burner of the invention can be
.~ realized in a more flexible fashion than is the case with a
conventional on/off system. Fuel is supplied, by employing
the stoker 4, in batches defined by the said stoker, into
~5 the combustion chamber 6 located between the inlet surface
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71 and the countersurface 72. With low efficiency, the fuel
layer is narrow: the combustion takes place near the slot
73 of the combustion chamber 6. The air needed in the
combustion process is blown in to the combustion chamber 6
through the slot 73 in a volume flow of a desired size. The
electric motor or other actuator of the fan 11 is
controlled by mesns of a suitable adjusting device. While
increasing the burner efficiency, the batching speed of the
stoker 4 is also increased so that the fuel layer in the
lû combustion chamber 6 grows thicker. Simultaneously the
combustion area is enlarged. This widening of the area
takes place particularly in the fuel layer 15a located near
the countersurface 72. Fuel can be added up to the point
where the combustion chsmher 6 is filled as far as the fuel
inlet 41. Thereafter the e~ficiency can be increased by
increasing the blowing efficiency of the fan 11, i.e. by
;~ increasing the volume flow o~ the supplied air.
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A li~it switch can be installed in the fuel inlet 41. This
~ 20 secures for instance that the stoker 4 does not batch in
fresh fuel when the combustion chamber 6 is full. On the
~` other hand7 by means of the limit switch the burner can
also be operated according to the on/off principle.
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Figure 1 illustrates a situation when a large amount of
fuel 15 is located in the combustion chambe~ 6. Combustion
takes place in the first fuel layer 15a near the
countersurface 72. The adjacent second fuel layer 15b is
~ pressed, owing to gravity and the supplied fresh fuel,
; 30 against the burning layer and is on the verge of igniting.
The third fuel layer lSc has slready reached a high
temperature, and the faurth layer 15d is rapidly warming
up. As a consequence of a process of this kind, the fuel 15
` is dried in layers before ignition. Thus the burner can be
used for burning damp fuels, even with a humidity content
as high as 60 ~.
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Solid fuels, particularly wood chips, are liable to
arching, i.e. in this case they tend to form recesses in
the fuel 15 located in the combustion chamber 6. This may
disturb the shiFting downwards of the fuel, and ev~n
interrupt it~ In order to prevent arching, the inlet
surface 71 of the burner~ or a part attached to this
surface, can be connected to a device which makes it
vibrate - i.e. it is set into a slight back and forth
motion. As a consequence, the fuel slides down along the
lû inlet surface 71 without disturbances.
Advantageously the vibrating device is realised so that the
top edge of the inlet surface 72 is attached flexibly to
the frame of the burner 1. Below the inlet surface 71 there
is arranged one or more wobblers 16, which ara rotated by
means of an axis, using a suitable actuator such as an
electric motor, either throughout the whole combustion
process or every once in a while. While rotating, the
wobbler 16 affects the inlet surface 71 and sets it into a
slight back and forth motion. In a similar fashion the
countersurface 72 can be arranged to move, either alone or
together with the inlet surface 71.
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The preferred embodiment of the burner of the invention
illustrated in figure 1 is mainly suited for burners with a
low efficiency, i.e. below 20 kW. With high-efficiency
burners, it is advantageous that a separate ash remover is
installed in the slot 73 between the inlet surface 71 and
the countersurface 72. On the other hsnd, the ash remover
30 i9 needed in low-efficiency burners as well, if for
instanca the fuel to be burned is biomass with a high ash
content, such as milled peat or sod peat or peat and straw
pellets~
~5 The ash remover 17 i9 advantageously a bar-like member or a
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hollow tubular member, as is apparent for example from
figures 2 and 3. The ash remover 17 is provided with
brackets lB, arranged at regular intervals therein. The ash
remover 17 extends, parallel to the slot 73, through the
fire shaft 7 and the combustion chamber 6. The ash remover
17 can be moved either axially, or transversally back and
forth, i.e. it can be either vibrated or rotated around its
axis 19, either in one direction or in changing
directions. At the end of the axis 19 there is attached for
instance a rotor wheel 20, which is connected, by means of
belt gearing 21, to an actuator such as an electric motor.
The ash remover 17 helps to keep the slot 73 open along the
whole width thereof, which ensures an even combustion of
the fuel. The brackets 18 provided in the ash remover 17
~ 15 prevent the sshes from sintering, and improve their
- crushing.
If the ash remover 17 is formed of a tubular member, it can
be provided with effective cooling. The ash remover 17 is
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connected to a cooling agent source, for instance to an air
or liquid supply (water, oil). The pressurized cooling
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agent circulates inside the tubular ash remover and cools
it. With this procedure, the strong heat created in the
`~ slot 73 during the combustion process does not wear the ash
~ ~ 25 remover out too quickly, but it is much more durable in
- use.
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The tubular ash remover 17 is advantageously placed on the
imaginable continuation a of the inlet surface 71. The slot
73 proper thus remains between the ash remover 17 and the
counter~urface 72. The size of this slot is defined, in the
same fashion as before, according to the type and grain
size of the fuel in question.
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In order to maintain the temperature in the combustion
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chamber 6 as high as possible, which is profitsble for the
combustion process9 the burner 1 and its possible
connecting channel 5 are provided with a heat insulating
layer 23.
In the connecting channel 5 there can be arranged secondary
air channels 24, which secure a sufficient air supply
particularly for large burners. The connecting channel 5
can be continued to the inside of the furnace 2 in the form
of a so-called afterburning channel 25. The secondary air
channels 24 and the afterburning channel 25 maintain the
gas combustion temperature high and improve the mixing and
complete burning of the gases.
The combustion chamber 6, and particularly the inlet
~ surface 71 and the countersurface 72 of the fire shaft 7,
;~ as well as the connecting channel 5, are made of a highly
heat-resistant material such as iron, or partly for
instance of ceramic materials. All inner parts of the
burner 1, and particularly the inlet surface 71 and the
countersurface 72, as well as the ash remover 17, can be
arranged to be replaceable elements. This is important with
respect to the maintenance, because none of the currently
known materials can long resist the high temperatures
created during the combustion process of the burner.
.
Th efficiency of the burners of the invention is above all
defined on the basis of the width s of the fire shaft 7.
According to a rough estimate, the burner efficiency may
rise up to 0,5 MW when s = 5û cm, and UF3 to 1,5 MW when s -
150 cm. In the above described burners, the diameter of
the tubular ash remover 17 is for instancP roughly 10 cm,
and that of the slot 73 is for instance 5 cm. The height hl
of the inlet surface 71 is for example 6û cm, when the
height h2 f the countersurface 72 is for example between
2û-40 cm. The above mentioned efficiency readings and
measures are only advisory. The invention must not by any
way be limited to them only.
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