U.S. patent application number 13/002695 was filed with the patent office on 2011-05-12 for improved radiant burner.
This patent application is currently assigned to Solaronics S.A.. Invention is credited to Koen Claerbout, Geert Dumortier, Valerie Olalde.
Application Number | 20110111356 13/002695 |
Document ID | / |
Family ID | 40119399 |
Filed Date | 2011-05-12 |
United States Patent
Application |
20110111356 |
Kind Code |
A1 |
Claerbout; Koen ; et
al. |
May 12, 2011 |
IMPROVED RADIANT BURNER
Abstract
A radiant burner comprises a body defining a premixing chamber
and a combustion chamber. The premixing chamber is separated from
the combustion chamber by at least one radiant burner plate (2)
which has multiple levels of burner surface. The combustion chamber
is further limited by a first radiant screen (4). The radiant
burner further comprises a second radiant screen (3) in the
combustion chamber. The second radiant screen is spaced from, but
near and parallel to the radiant burner plate(s), such that this
second radiant screen acts as an extended burner surface and also
heats up said at least one radiant burner plate when in use.
Inventors: |
Claerbout; Koen; (Gent,
BE) ; Dumortier; Geert; (Kortrijk, BE) ;
Olalde; Valerie; (Lille, FR) |
Assignee: |
Solaronics S.A.
Armentieres
FR
|
Family ID: |
40119399 |
Appl. No.: |
13/002695 |
Filed: |
July 3, 2009 |
PCT Filed: |
July 3, 2009 |
PCT NO: |
PCT/EP2009/058429 |
371 Date: |
January 5, 2011 |
Current U.S.
Class: |
431/329 |
Current CPC
Class: |
F23D 2203/103 20130101;
F23D 2203/106 20130101; F23D 2212/20 20130101; F23D 14/14 20130101;
F23D 2212/10 20130101 |
Class at
Publication: |
431/329 |
International
Class: |
F23D 14/14 20060101
F23D014/14 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 8, 2008 |
EP |
08159919.3 |
Claims
1. A radiant burner comprising a body defining a premixing chamber
and a combustion chamber, said premixing chamber being separated
from the combustion chamber by at least one radiant burner plate
which has multiple levels of burner surface, said combustion
chamber being further limited by a first radiant screen
characterised in that said radiant burner further comprises a
second radiant screen in said combustion chamber, said second
radiant screen being spaced from, but near and parallel to said at
least one radiant burner plate, such that said second radiant
screen acts as an extended burner surface and also heats up said at
least one radiant burner plate when in use.
2. A radiant burner according to claim 1, wherein said second
radiant screen is an arrangement of parallel spaced round rods or
square bars.
3. A radiant burner according to claim 1, wherein said first
radiant screen is a metal grid or an arrangement of parallel spaced
round rods or square bars.
4. A radiant burner according to claim 1, wherein said at least one
radiant burner plate is a ceramic burner plate.
5. A radiant burner according to claim 1, wherein said at least one
radiant burner plate has a height difference in between 2 levels of
burner surface of 1 to 20 mm.
6. A radiant burner according to claim 1, wherein said combustion
chamber further comprises at least one further radiant screen.
Description
TECHNICAL FIELD
[0001] The present invention relates to radiant burners comprising
a radiant burner plate and a screen.
BACKGROUND ART
[0002] Radiant burners comprising a radiant burner plate and a
screen are known e.g. from U.S. Pat. No. 4,799,879 or EP0539279.
The screen together with the radiant burner plate provides the
radiative output of the burner, which averages at levels around 50%
efficiency. In the past the radiative output of the burners has
been increased by modification of the radiant burner plate from a
radiant burner plate with rows of through holes or perforations
serving to channel the mixture of air and combustion agent from the
rear of the plate to the radiating face, to a radiant burner plate
wherein the through holes or perforations are arranged in what is
nowadays called honeycomb pattern as described in e.g. U.S. Pat.
No. 4,569,657 or U.S. Pat. No. 4,799,879. This or similar
modifications of the radiant burner plate increased the temperature
level and consequently also the radiative output of the burner. On
the other hand, these honeycomb-like patterns are creating local
overheating of the burner plate on the places where the flames are,
and also cause poor temperature uniformity and relative low average
burner surface temperature and thus lower energy efficiency. These
local high temperatures define therefore also the limitation of the
use of such through hole or perforation patterns, and also define
the limitation on the amount of radiation energy which can be
obtained with such systems.
[0003] Another way of achieving higher radiative output was
proposed in e.g. U.S. Pat. No. 3,847,536 which uses two radiative
screens above the radiant burner plate. Also this modification of
the radiant burner caused local overheating of the radiant burner
plates in the middle of the radiant burner, which urged the skilled
person to lower inputs which resulted in lower (local) temperatures
of the radiant burner plate for prolonging the life time of the
radiant burner.
[0004] However, still further enhanced efficiency of the radiant
burners is desired.
DISCLOSURE OF INVENTION
[0005] An aspect of the claimed invention provides a radiant burner
which comprises a body defining a premixing chamber and a
combustion chamber. The premixing chamber is separated from the
combustion chamber by at least one radiant burner plate which has
multiple levels of burner surface. The combustion chamber is
further limited by a first radiant screen. The radiant burner
further comprises a second radiant screen in the combustion
chamber. The second radiant screen is spaced from, but near and
parallel to the radiant burner plate(s), such that this second
radiant screen acts as an extended burner surface and also heats up
said at least one radiant burner plates by back radiation when in
use. In a preferred embodiment, the second radiant screen is an
arrangement of parallel spaced round rods or square bars. In a
preferred embodiment, first and second radiant screens are produced
from highly heat resistant materials such as ceramics, especially
aluminium or zirconium oxide, aluminium titanate, silicon oxide,
corundum or mullite, silicon carbide, silicon nitride or metal
infiltrated ceramics, such as silicon-infiltrated silicon carbide.
Alternatively, the radiant screens can also be fabricated from
heat-resistant materials of other nature such as e.g. materials
which contain more than 50% by weight of a metal silicide, such as
molybdenum disilicide (MoSi.sub.2) or tungsten disilicide
(WSi.sub.2). In another preferred embodiment, the radiant screens
are fabricated from highly heat resistant steel grades, such as
high level stainless steel grades like Kanthal APM or APMT,
different grades of FeCrAl alloy designed for high temperature
corrosion, Chrome/Nickel steel grades like Avesta 253 MA, 153 MA,
Inconel 601, Incoloy 800HT, Incoloy MA956.
[0006] The radiant burner plate is preferably made of a ceramic
material with high temperature resistance, and excellent mechanical
and thermodynamic properties such as e.g. cordierite or zirconia;
partially stabilised zirconia (PSZ), alumina, silicon carbides or
other high level technical ceramics. Height difference in between
two levels of burner surface of the radiant burner plate is
preferably from 1 to 20 mm. More preferably, from 1 to 10 mm. Even
more preferably, from 2 to 7 mm. Most preferably 5 mm.
[0007] The radiant burner plate has multiple levels of burner
surfaces. In a preferred embodiment, these multiple levels are
arranged in rows and are alternating per one row of through
holes/perforations on the radiant burner plate. An example of such
burner plate can be found in FIG. 1, or alternatives in FIGS. 2 and
3. These types of burner plates, as such, provide less emissivity
compared to ceramic tiles with honeycomb or similar perforation
patterns. This is due to the multiple level burner surface, wherein
the lower levels of the burner surface of the radiant burner plates
provide a higher radiative output because the sides of the rows
also heat up and provide an additional radiative output, but the
highest level of burner surface does not have such additional
radiative output. So the overall radiative output, and therefore
also the energy efficiency, of such multilevel radiant burner plate
as such, is lower than honeycomb-like perforations in the radiant
burner plate.
[0008] However, although radiant burner plates are used which as
such have a lower radiative output, it was surprisingly observed
that by the use of such a second radiant screen near the radiant
burner plates, the radiative output of the radiant burner plates
can be increased without leading to local overheating of the burner
plates, as this would result in early failure of the radiant burner
plates. This might be explained, without pretending to be
scientifically correct, by the fact that the back radiation of the
second radiant screen on the radiant multilevel burner plates is
the highest on the highest level of the burner surface as this is
closest to the second radiant screen. This highest level thereby
also heats up more than the lower levels of the burner surface,
which are at a bigger distance from this second radiant screen. As
these lower levels in the burner surface of the radiant burner
plates were already at higher temperatures by the effect of the
flames heating up the surface surrounding the cavity wherein the
perforations open, the overall effect of the present invention is
that the different levels in the burner surface of the radiant
burner plates are at the same temperature when in use. Stated
otherwise, a greater temperature uniformity of the burner surface
of the radiant burner plate is attained. The person skilled in the
art will understand that this greater temperature uniformity
combined with the plurality of radiant screens results in a
significant higher energy efficiency of the complete radiant
burner. In a preferred embodiment, the distance between the second
radiant screen and the highest level of burner surface of the at
least one radiant burner plates is between 3 and 50 mm. More
preferably, the distance between the second radiant screen and
highest level of the radiant burner plate is between 5 and 30 mm,
even more preferably between 10 and 25 mm, most preferably between
15 and 20 mm. In a preferred embodiment, the second radiant screen
is positioned such that the second radiant screen follows the
direction of the rows of the highest level of burner surface of the
radiant burner plate.
[0009] The first radiant screen is preferably a metal grid. In
another preferred embodiment, the first radiant screen is an
arrangement of parallel spaced round rods or square bars. More
preferably, the first and second radiant screens are made of an
arrangement of parallel spaced round rods or square bars. In a
further preferred embodiment, the first and second radiant screens
are arranged in the same direction. In an alternative preferred
embodiment, the first and second radiant screens are arranged in
shifted angles with respect to one another. More preferably, the
first and second radiant screens are at a 90.degree. angle.
[0010] A further observed advantage of the present invention is a
lower level of emissions of byproducts of combustion, such as
Nitrogen Oxides or Carbon Monoxide, which is probably due to the
second radiant screen which acts as an extended burner surface and
provides a more complete combustion of the gas-air mixture.
[0011] Another aspect of the claimed invention provides a radiant
burner with at least one further radiant screen in the combustion
chamber.
BRIEF DESCRIPTION OF FIGURES IN THE DRAWINGS
[0012] Example embodiments of the invention are described
hereinafter with reference to the accompanying drawings in
which
[0013] FIGS. 1 to 3 show a cross section of example embodiments of
radiant burner plates used in the present invention.
[0014] FIG. 4 shows an example embodiment of the present invention,
with cut out for better view of the build up of the radiant
burner.
[0015] FIG. 5 shows a side view of the example radiant burner of
FIG. 4, also with cut out for better view of the build up of the
radiant burner.
[0016] FIG. 6 shows an alternative example embodiment of the
present invention.
[0017] FIG. 7 shows a side view of the example radiant burner of
FIG. 6.
MODE(S) FOR CARRYING OUT THE INVENTION
[0018] Example embodiments of the present invention will now be
described with reference to FIGS. 1 to 7.
[0019] FIGS. 1 to 3 show cross sections of example embodiments of
radiant burner plates which might be used in the present invention.
FIG. 1 shows two levels of burner surface of the radiant burner
plate 2, FIGS. 2 and 3 show three levels of burner surface, in two
alternative forms.
[0020] FIGS. 4 and 5 show an example embodiment of the present
invention. The first radiant screen 4 is a highly heat resisting
metal grid fabricated from highly heat resistant steel grades, such
as high level stainless steel grades like Kanthal APM or APMT,
different grades of FeCrAl alloy designed for high temperature
corrosion, Chrome/Nickel steel grades like Avesta 253 MA, 153 MA,
Inconel 601, Incoloy 800HT, Incoloy MA956. The second radiant
screen 3 is made of a highly heat resisting ceramic material, in
this example aluminium or zirconium oxide, aluminium titanate,
silicon oxide, corundum or mullite, silicon carbide, silicon
nitride or metal infiltrated ceramics, such as silicon-infiltrated
silicon carbide with a silicon infiltration grade of 5 to 50% or
even more. Alternatively, the radiant screens can also be
fabricated from heat-resistant materials of other nature such as
e.g. materials which contain more than 50% by weight of a metal
silicide, such as molybdenum disilicide (MoSi.sub.2) or tungsten
disilicide (WSi.sub.2). The radiant burner plate 2 is made of a two
level burner surface, ceramic tile made of cordorite or alternate
thermodynamically suited ceramics as mentioned above.
[0021] FIGS. 6 and 7 show an alternative example embodiment of the
present invention. The first and second radiant screens are made of
highly heat resisting material, in this example a ceramic like
aluminium or zirconium oxide, aluminium titanate, silicon oxide,
corundum or mullite, silicon carbide, silicon nitride or metal
infiltrated ceramics, such as silicon-infiltrated silicon carbide
with a silicon infiltration grade of 5 to 50% or even more.
Alternatively, the radiant screens can also be fabricated from
heat-resistant materials of other nature such as e.g. materials
which contain more than 50% by weight of a metal silicide, such as
molybdenum disilicide (MoSi.sub.2) or tungsten disilicide
(WSi.sub.2). In this example this first and second radiant screens
are arranged in directions which are 90.degree. with respect to one
another. The radiant burner plate 2 is made of a two level burner
surface, ceramic tile made of cordierite.
[0022] Thus there has been described a new radiant burner 1
possessing great flexibility of use and which is capable of
reaching temperatures of about 1300.degree. C. with a considerable
radiation factor increase of about 10% compared to existing
technology.
[0023] Because of their possible use at very high temperatures e.g.
1300.degree. C. and higher, their high energy efficiency and their
long service life, the radiant burner of the present invention are
particularly suitable for drying web materials at high web speeds.
One preferred area of application is the drying of moving paper
webs.
[0024] The new improved radiant burner comprises a body defining a
premixing chamber and a combustion chamber. The premixing chamber
is separated from the combustion chamber by at least one radiant
burner plate which has multiple levels of burner surface. The
combustion chamber is further limited by a first radiant screen.
The radiant burner further comprises a second radiant screen in the
combustion chamber.
[0025] The second radiant screen is spaced from, but near the
radiant burner plate(s), such that this second radiant screen acts
as an extended burner surface and also heats up said at least one
radiant burner plate when in use.
* * * * *