U.S. patent application number 12/302984 was filed with the patent office on 2009-08-20 for pellet burner.
Invention is credited to Brage Norin.
Application Number | 20090205545 12/302984 |
Document ID | / |
Family ID | 38778892 |
Filed Date | 2009-08-20 |
United States Patent
Application |
20090205545 |
Kind Code |
A1 |
Norin; Brage |
August 20, 2009 |
PELLET BURNER
Abstract
Burner for particulate fuel, above all pellets such as
bio-pellets, comprising a chute (10) having a longitudinal axis
(11), the chute having a generally horizontally oriented
longitudinal axis and having an inner wall of an essentially
cup-shapedly upwardly open cross-section shape, a feeding device
(30-34) for feeding a bed (20) of the particulate matter in and
along the chute (10), and a device (40) for supply of primary air
to the bed (20) in the chute (10), characterized in that the
primary air supply device (40) is arranged to, without contact,
direct primary air from above toward the free top-side of the bed
(20) in the chute.
Inventors: |
Norin; Brage; (Boden,
SE) |
Correspondence
Address: |
DICKSTEIN SHAPIRO LLP
1825 EYE STREET NW
Washington
DC
20006-5403
US
|
Family ID: |
38778892 |
Appl. No.: |
12/302984 |
Filed: |
May 30, 2007 |
PCT Filed: |
May 30, 2007 |
PCT NO: |
PCT/SE2007/000521 |
371 Date: |
December 1, 2008 |
Current U.S.
Class: |
110/260 ;
110/267 |
Current CPC
Class: |
Y02E 20/34 20130101;
F23L 15/04 20130101; F23L 1/00 20130101; F23B 40/06 20130101 |
Class at
Publication: |
110/260 ;
110/267 |
International
Class: |
F23C 1/00 20060101
F23C001/00; F23K 3/00 20060101 F23K003/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 30, 2006 |
SE |
0601191-0 |
Claims
1. Burner for particulate fuel, above all pellets such as
bio-pellets, comprising a chute (10) having a longitudinal axis
(11), the chute having a generally horizontally oriented
longitudinal axis and having an inner wall of an essentially
cup-shapedly upwardly open cross-section shape, a feeding device
(30-34) for feeding a bed (20) of the particulate matter in and
along the chute (10), and a device (40) for supply of primary air
to the bed (20) in the chute (10), the primary air supply device
(40) being arranged to, without contact, direct primary air from
above toward the free topside of the bed (20) in the chute,
characterized in that the supply device (40) has one or more
primary air outlet openings (410) that along a substantial portion
of the length of the chute (10) direct primary air downward close
by the inside of each one of the upper edge parts (11) of the chute
(10).
2. Burner according to claim 1, characterized in that primary air
supply device comprises one or more outlet openings (411) that
direct primary air toward the free topside of the bed in the
transversally central area of the bed.
3. Burner according to claim 1, characterized in that the primary
air supply device has one or more air outlet openings directed to
lead primary air over substantially the entire width of the free
surface of the bed along at least one longitudinal section of the
chute (10), whereby a crust (21) of combustion deposits being
established on the top surface of the bed (20) when burning the
particle bed, if the ashes vitrify.
4. Burner according to claim 1, characterized in that one or more
of said at least one primary air outlet opening of the supply
device are in the form of a slot extending along a substantial part
of the length of the chute.
5. Burner according to claim 1, characterized in that the air
outlet openings for primary air are in the form of a row of
openings extending along a substantial part of the length of the
chute.
6. Burner according to claim 1, characterized in that the supply
device has one or more openings for blowing in secondary air toward
an area above the bed (20) in the chute (10).
7. Burner according to claim 1, characterized in that the chute is
double-walled, and that primary air and possibly also secondary air
is led through a hollow space (12) in the double-wall chute to a
supply device (40) extending along the upper edge of the respective
wall of the chute (10).
8. Burner according to claim 1, characterized in that the air
supply device (14, 40) extends along the upper edge of the
respective side wall of the chute (10).
Description
[0001] The invention relates to burner of the kind that is defined
in the preamble to the appended claim 1.
[0002] Thus, the invention relates to a burner of the general kind
that comprises a chute having a generally horizontally oriented
longitudinal axis and having an inner wall that essentially has an
upwardly open cup-shaped cross-section shape, a feeding device for
feeding a bed of particulate fuel, particularly pellets in and
along the chute, the bed being burnt in the chute during
transportation along the same, and a device for supply of primary
air to the bed in the chute.
[0003] A drawback of burners previously known from practice and of
the kind in question relates to the fact that a substantial part of
the primary air is led into the bed via openings via the cup
surface of the chute carrying the bed. In this way, burning of said
pellets occurs close by the openings, and then the temperature
becomes particularly high close by said openings, so that formed
combustion deposits/ashes vitrify and get stuck against the chute
in the area near the openings. Accordingly, said vitrified deposits
of ashes become situated on the sliding surface of the pellet bed
in the chute, and block or interfere with the advancement of the
pellet bed along the chute. In that connection, the pellet bed will
encounter a greater and greater friction against the chute during
the advancement thereof. The feed-in of new pellets always finds
the easiest way and finally avoids the obstacle formed by the
pellet bed because of the increased friction mentioned above. The
feed-in of new pellets can no longer manage to press the pellet bed
forward in the chute in a controllable way. The pellets begin to
climb the obstacle formed and the entire burning is disturbed.
[0004] Therefore, an object of the invention is to provide a burner
device by means of which said drawbacks are entirely or partly
obviated.
[0005] The object is achieved by the invention.
[0006] The invention is defined in the appended independent device
claim.
[0007] Embodiments of the invention are defined in the appended
dependent claims.
[0008] In addition to primary air, also secondary air is supplied
in order to guarantee controlled burning of combustible gases
escaping from the bed. If the pellet ashes melt, a stabilizing
crust of vitrified combustion deposits/ashes will be formed on the
free top-surface layer of the bed, which is not in contact with the
chute. The friction against the chute is not increased thereby, and
fed-in new pellets can easily proceed to press the fuel bed forward
in a controlled way. Primary air should of course also be directed
toward the central parts of the free top surface of the bed in
order for the top side of the entire pellet bed should be reached
by primary air.
[0009] In the following, the invention will be described by way of
examples, reference being made to the appended drawing.
[0010] FIG. 1 shows a schematic vertical longitudinal section
through a pellet burner.
[0011] FIG. 2 shows a schematic cross section taken along the
drawing II-II in FIG. 1.
[0012] FIG. 3 shows in a section corresponding to FIG. 2, another
embodiment of the chute of the burner and devices for supply of
primary and secondary air.
[0013] FIG. 4 shows an oblique perspective view over a tested
embodiment of the burner.
[0014] FIGS. 1 and 2 show a burner for particulate fuel,
particularly pellets, above all so-called bio-pellets, which
usually consist of cellulose material, foremost waste wood that has
been transferred into the form of longitudinal sections of
compressed and extruded particle material.
[0015] The burner is shown to contain a chute 10 having a
longitudinal axis 11, the chute being oriented with the bottom
thereof essentially horizontally, in the direction of the
longitudinal axis 11. The chute has an upwardly open cup-shaped
cross section and receives a bed 20 on the upwardly facing side
thereof. The inside of the upper edge portions 11 of the chute 10
are shown generally vertical, while the lower part of the chute is
rounded and slopes inward toward the longitudinal centre plane of
the chute. A feed pipe 30 for pellets mouths in a screw conveyor 31
having a horizontal driving shaft 32 that is rotationally driven by
a motor 33. Pellets propelled by the screw 31 are driven into the
bottom region of the chute 10 at one end thereof. When the screw 31
feeds pellets through a tubular pipe part 34 extending in through
an adjacent end wall 36 of the chute 10. In this way, a bed 20 of
pellets progressing along the chute is formed in the chute 10.
Primary air is led in from above toward the free top surface of the
bed 20 in the chute 10 by means of a nozzle device 40. The nozzle
device 40 is located not to touch the particle bed 20, and to blow
primary air from above downward toward the free top surface of the
particle bed 20 in the chute 10. The outlet opening of the pipe
part 34 is well covered by pellets also on the topside.
[0016] The bed 20 is set on fire near the wall 36 and moves under
the impact of the screw conveyor 31 towards the right in FIG. 1,
that is away from the wall 36, while burning, the cross-section
area of the bed decreasing. The length of the chute 10 is suitably
selected so that in normal operating conditions, the particle bed
is essentially entirely consumed when it reaches the end of the
chute 10, so that combustion deposits then can fall down from the
chute in order to be taken care of in a way conventional per
se.
[0017] FIGS. 1 and 2 should be interpreted so that the surface of
the chute carrying the bed 20 is smooth and continuous and allows
the bed 20 to slide along the chute in a well-controlled way.
[0018] Preferably, in that connection, the chute 10 has an
essentially constant cross-section along the length thereof. Since
the cross-section area of the bed decreases in the displacement
direction of the bed, the side walls of the chute can be given a
decreasing height in the direction away from the inlet end 36 of
the chute, such as is outlined in FIG. 1.
[0019] The device 40 for supply of primary air suitably has a
nozzle device 41 that leads in the primary air from above downward
toward the bed 20 along a substantial longitudinal section of the
bed 20. Therein, the device 40 may hold a nozzle device 42 for
introduction of secondary air toward the area above the bed 40, for
burning of combustible gases escaping from the bed. The nozzle
device 42 may also be arranged to introduce air along a substantial
part of the length of the bed and chute. As is seen in FIG. 2, the
device 41 may comprise one or more nozzles 410 that direct air
downward toward the free top surface of the bed 20 near the upper
edge portion 11 of the chute. Furthermore, the device 41 may
contain one or more additional nozzles 411 that blow in primary air
over the central parts of the free top surface of the bed such as
viewed in the cross section according to FIG. 2, the nozzles 411
suitably also being arranged to supply primary air along a
substantial longitudinal section of the chute 10. The openings 410
(or the corresponding slot) lead in a part of the primary air close
by the inside of the respective wall of the chute above the bed. In
this way, it is also attained that coke and soot deposited on the
exposed insides of the chute are burnt away.
[0020] At each side of the chute, it may be enough with one nozzle
410 if this is in the form of an elongate slot along the chute.
Furthermore, it may be enough with a single nozzle 411 and 42,
respectively, if the same are in the form of a slot. In other
embodiments, said slots may be replaced by a respective row of
spaced-apart nozzles. The primary air may naturally be supplied via
a single slot or row of nozzles, if the same are formed to produce
a flow pattern of a desired character. Such as is indicated in FIG.
2, it is desirable that the primary air is introduced toward the
top surface of the bed 20 in such a way that a crust 21 of
combustion deposits is imparted to the free top surface of the bed
20. The crust 21 lets through combustion gas from the bed 20, but
blocks small particles released by the pellets of the bed 20 from
escaping upward from the bed 20. The crust 21 principally consists
of vitrified ashes.
[0021] FIG. 3 illustrates a variant in which the chute 10 is made
double-walled, and primary and secondary air is introduced into the
space 12 in the wall of the chute 10 and is led out to the upper
end portion 14 of the wall provided with nozzle openings that
afford primary and secondary air flows in the patterns accounted
for in connection with FIG. 2.
[0022] The double-wall structure, and accordingly also the hollow
space 12, also extends along each one of the upper edges of the
chute such as is shown in FIG. 3, a row of nozzles 41 being
directed downward vertically close by the inside of the side wall
11 of the chute 10, and a row of nozzles 411 being directed toward
the centre area of the top surface of the bed 20. Furthermore,
there is a row of nozzles 42 directed generally horizontally in
over the area above the bed 20 to supply secondary air for final
burning of combustible gases escaping from the bed. The row of
nozzles 42 may be terminated at a distance from the downstream end
of the chute 10, such as also is seen in FIG. 4. In FIG. 4, a duct
140 is shown along the upper edge of the respective side wall 11 of
the chute 10 along the length of the chute, the duct sections 140
being fed with air in one end, preferably from the end closest to
the wall 36 and being closed in the other end located at the
downstream end of the chute 10. Said ducts are shown to have the
centre thereof in a vertical plane tangent to the inside of the
side-wall part 11 of the chute.
[0023] In FIG. 4, it can be seen that one of the duct sections 140
has a row of nozzles 42 as well as rows of nozzles 410 and 411,
respectively. In FIG. 4, it can also be seen that the walls of the
chute 10 have a decreasing height in the direction away from the
wall 36.
* * * * *