U.S. patent application number 12/091650 was filed with the patent office on 2009-05-14 for process and apparatus for low-nox combustion.
This patent application is currently assigned to L'Air Liquide Societe Anonyme Pour L'Etude ET L 'Exploitation Des Procedes Georges Claude. Invention is credited to Martin Adendorff, Lothar Backes, Horst Koder.
Application Number | 20090120338 12/091650 |
Document ID | / |
Family ID | 36577452 |
Filed Date | 2009-05-14 |
United States Patent
Application |
20090120338 |
Kind Code |
A1 |
Adendorff; Martin ; et
al. |
May 14, 2009 |
Process and Apparatus for Low-NOx Combustion
Abstract
The invention relates to a process and an apparatus for low-NOx
combustion with at least one burner (5) using fuel and oxidizing
agent and/or furnace off-gases and/or carbon dioxide and/or steam.
The low-NOx combustion according to the invention can be used in
conventional melting and holding furnaces, in particular in
aluminum holding furnaces or rotary drum furnaces and glass-melting
furnaces, with the potential for considerable economies to be
made.
Inventors: |
Adendorff; Martin; (Krefeld,
DE) ; Backes; Lothar; (Duisburg, DE) ; Koder;
Horst; (Schkopau Luppenau, DE) |
Correspondence
Address: |
AIR LIQUIDE;Intellectual Property
2700 POST OAK BOULEVARD, SUITE 1800
HOUSTON
TX
77056
US
|
Assignee: |
L'Air Liquide Societe Anonyme Pour
L'Etude ET L 'Exploitation Des Procedes Georges Claude
Paris
FR
|
Family ID: |
36577452 |
Appl. No.: |
12/091650 |
Filed: |
October 28, 2005 |
PCT Filed: |
October 28, 2005 |
PCT NO: |
PCT/EP2005/011562 |
371 Date: |
August 20, 2008 |
Current U.S.
Class: |
110/345 ;
110/205; 110/344; 431/115; 431/12; 431/215 |
Current CPC
Class: |
F23L 7/007 20130101;
F23L 15/04 20130101; F23C 2900/09002 20130101; F23C 9/08 20130101;
F23L 7/005 20130101; C03B 5/235 20130101; Y02E 20/34 20130101; F23D
2900/00004 20130101 |
Class at
Publication: |
110/345 ;
431/115; 431/215; 431/12; 110/205; 110/344 |
International
Class: |
F23C 9/08 20060101
F23C009/08; F23L 7/00 20060101 F23L007/00; F23L 15/04 20060101
F23L015/04 |
Claims
1-27. (canceled)
28. A process for low-NOx combustion in a combustion chamber with
at least one burner using fuel and oxidizing agent and furnace
off-gas and/or carbon dioxide and/or steam, wherein the oxidizing
agent and the furnace off-gases and/or the carbon dioxide and/or
the steam are fed to the burner as a mixture which is produced by
means of an injector, wherein the burner is connected by means of a
pipeline: to the injector and to a heat exchanger for heating
oxidizing agent, carbon dioxide or steam, wherein the heat
exchanger is arranged in a stack which discharges the furnace
off-gases from the combustion chamber and wherein the injector is
arranged in the line.
29. The process of claim 28, wherein the injector is operated with
the oxidizing agent.
30. The process of claim 28, wherein the mixture of oxidizing agent
and furnace off-gases and/or carbon dioxide and/or steam which is
fed to the burner has an oxygen content of at least 5% by volume of
oxygen.
31. The process of claim 28, wherein the mixture of oxidizing agent
and furnace off-gases and/or carbon dioxide and/or steam which is
fed to the burner at a temperature of from 20.degree. C. to
1600.degree. C.
32. The process of claim 28, wherein the oxidizing agent used is
oxygen or an oxygen-containing medium containing at least 10% by
volume of oxygen at a pressure of from 0.2 to 40 bar and a
temperature of from -20 to 40.degree. C.
33. The process of claim 28, wherein the combustion is carried out
at a flame temperature of from 800.degree. C. to 2700.degree.
C.
34. The process of claim 28, wherein the burner has a burner mouth
and the velocity at which the mixture of oxidizing agent and
furnace off-gases and/or carbon dioxide and/or steam emerges at the
burner mouth is between 20 and 80 m/s.
35. The process of claim 28, wherein the burner has a burner mouth,
and wherein: a) the mixture of oxidizing agent and furnace
off-gases and/or carbon dioxide and/or steam flows out of the
burner mouth at a velocity which is 0.3 to 4 times higher than the
velocity at which the fuel flows out of the burner mouth; b) a
total momentum flux, based on the burner power, of from 1.5 to 8
N/MW is established; c) a ratio of the momentum flux densities of
the mixture of oxidizing agent and furnace off-gases and/or carbon
dioxide and/or steam to fuel is from 0.8 to 31; and d) a power
density of from 0.2 to 0.5 KW/mm.sup.2 is reached at the outlet of
the burner block (4).
36. The process of claim 28, wherein the burner comprises a fuel
tube wherein partial self-carburization of the fuel takes place in
the fuel tube through recuperative heat exchange with the mixture
of oxidizing agent and furnace off-gases and/or carbon dioxide
and/or steam.
37. The process of claim 28, wherein the injector comprises an
outflow nozzle wherein the oxidizing agent flows out of the outflow
nozzle at a velocity of from 20 to 660 m/s.
38. An apparatus for carrying out low-NOx combustion with at least
one burner, which is arranged in a burner block of a furnace wall
surrounding the combustion chamber and which is supplied with
oxidizing agent and fuel, as described in one of the preceding
claims, wherein the burner is connected by means of a line: to a
heat exchanger for heating oxidizing agent, carbon dioxide or steam
and to an injector for producing a mixture of oxidizing agent and
furnace off-gas and/or carbon dioxide and/or steam, wherein the
heat exchanger is arranged in a stack which discharges the furnace
off-gases from the combustion chamber and whereby the injector is
arranged in the pipeline.
39. The apparatus of claim 38, wherein the injector has an axially
displaceable outflow nozzle.
40. The apparatus of claim 38, wherein the heat exchanger is a
recuperator or regenerator.
41. The apparatus of claim 38, wherein the burner has at least one
connection for supplying the oxidizing-agent mixture and at least
one connection for supplying the fuel.
42. The apparatus of claim 41, wherein the fuel feed and/or
oxidizing-agent mixture feed of the burner are arranged
substantially coaxially with respect to one another.
43. The apparatus of claim 41, wherein the furnace has an off-gas
opening wherein the burner is arranged opposite the off-gas
opening.
44. The apparatus of claim 38, wherein the burner is arranged on
the off-gas side of the furnace.
45. The apparatus of claim 44, wherein the burner is arranged on
the off-gas side of the furnace in the off-gas opening or in the
stack.
46. The apparatus of claim 38, wherein the media-carrying lines
consist of a heat-resistant and corrosion-resistant NiCr or ODS
alloy.
47. The apparatus of claim 42, wherein the media-carrying lines
have a thermal insulation on the outer side and/or a thermal
protection on the inner side.
48. The apparatus of claim 47, wherein the media-carrying lines
have a thermal insulation on the outer side and/or a thermal
protection on the inner side consisting of ceramic fibres or
ceramic block.
49. The apparatus of claim 38, wherein the burner block which
includes the burner preferably has a cylindrical opening.
50. The apparatus of claim 38, wherein the burner is equipped with
a UV light receiver for flame monitoring.
51. The apparatus of claim 38, wherein said apparatus is used in a
furnace selected from aluminium holding furnaces, rotary drum
furnaces or glass-melting furnaces.
52. The process of claim 28, wherein said process is used in a
furnace selected from aluminium holding furnaces, rotary drum
furnaces or glass-melting furnaces.
Description
[0001] The invention relates to a process and an apparatus for
low-NO.sub.x combustion using fuel and oxidizing agent and/or
furnace off-gases and/or carbon dioxide and/or steam.
[0002] In the known low-NO.sub.x combustion, the furnace off-gases,
which are sucked in by a blower, sheath the burner flame, thereby
reducing the flame temperature and consequently the thermal
emission of NO.sub.x.
[0003] However, this conventional combustion has the significant
drawback that the furnace off-gases which are recirculated in the
furnace installation are not completely mixed with the oxidizing
agent, and consequently the stipulated emission of NO.sub.x in the
off-gas can only be realized at additional cost.
[0004] High investment costs are inevitable with the known
low-NO.sub.x combustion, and costs are additionally incurred for
maintenance of the installation, in particular the highly loaded
blower and the pipelines. Moreover, external energy is required to
operate the blower.
[0005] Therefore, it is an object of the present invention to
provide a process and an apparatus which allow economical and
low-pollutant (low-NO.sub.x) combustion in conventional furnace
installations.
[0006] This object is achieved by a process having the features of
claim 1 and by an apparatus having the features of claim 13.
[0007] Advantageous refinements of the invention are given in the
subclaims. According to the invention, a mixture of oxidizing agent
and/or furnace off-gas and/or carbon dioxide and/or steam is burnt
with the fuel, which is fed to the burner separately, by means of
the burner, which is arranged in a burner block in a refractory
lining of a furnace installation.
[0008] For this purpose, the oxidizing agent is fed to an injector
at a pressure of from 0.2 to 40 bar and advantageously having been
heated from 20 to 900.degree. C. in a heat exchanger by means of
furnace off-gas. The oxidizing agent may also be fed to the
injector directly without being heated.
[0009] The oxidizing agent, which expands as it flows out of the
nozzle (which is axially displaceable in the injector at the flow
end side), generates a gas jet at a velocity of from 20 to 660 m/s,
and thereby generates a reduced pressure in the injector, the
sucking action of which sucks either furnace off-gas and/or carbon
dioxide (CO.sub.2) and/or superheated steam generated from water
through heat exchange with furnace off-gas into the jet of
oxidizing agent, and this mixture is then fed to the burner, with
temperature balancing, in a line connecting the injector to the
burner.
[0010] A conventional blowing nozzle or some other equivalent
technical means can also be used instead of the injector, which is
advantageously arranged in a stack provided for discharging the
furnace off-gases from the combustion chamber of the furnace
installation.
[0011] As an alternative to the oxidizing agent, it is possible for
fuel gas at a pressure of from 0.2 to 40 bar to be fed to the
injector. In this case, the oxidizing agent is added to the
burner.
[0012] The mixture of oxidizing agent and/or furnace off-gases
and/or carbon dioxide (CO.sub.2) and/or steam, which is fed to the
burner at a temperature of from 20.degree. C. to 1600.degree. C.,
preferably 900.degree. C., and at a velocity of from 5 to 70 m/s,
has an oxygen content of at least 5% by volume.
[0013] The burner, which is, for example, arranged set back in the
burner block, is advantageously a parallel-flow burner with two
tubes (inner tube and outer tube) arranged substantially coaxially
with respect to one another for feeding fuel and oxidizing agent
and/or furnace off-gases and/or carbon dioxide and/or steam to the
burner mouth. The fuel or the oxidizing-agent mixture may be passed
to the burner mouth through the inner tube or through the outer
tube.
[0014] The oxidizing agent used is an oxygen-containing medium with
an oxygen content of at least 10% by volume.
[0015] The fuel used may be any conventional gaseous or liquid
fuel, particularly advantageously natural gas.
[0016] The injector, which is advantageously operated with the
oxidizing agent, is equipped with an axially displaceable nozzle
for controlling the intake quantity and concentration and
temperature of the mixture fed to the burner. This eliminates the
need to supply the injector with external energy, which entails
additional costs.
[0017] The heat exchanger which is used to heat the oxygen, carbon
dioxide and the water and is advantageously arranged in the stack
that discharges the furnace off-gases from the combustion chamber
of the furnace installation is advantageously a conventional
recuperator or regenerator.
[0018] The burner used is preferably a conventional parallel-flow
burner with at least one feed for the oxidizing agent and at least
one feed for the fuel, preferably comprising two cylindrical,
concentrically arranged tubes.
[0019] The burner design according to the invention allows the
mixture of oxidizing agent and/or furnace off-gases and/or carbon
dioxide (CO.sub.2) and/or steam to flow out of the burner mouth of
the burner at a velocity which is 0.3 to 4 times higher than the
fuel, with the result that a total momentum flux, based on the
burner power, of from 1.5 to 8 N/MW and a ratio of the momentum
flux densities of the mixture of oxidizing agent and furnace
off-gases to fuel of from 0.8 to 31 are ensured, and as a result a
power density of from 0.2 to 0.5 KW/mm.sup.2 is reached at the
outlet of the burner block.
[0020] The outlet velocity of the mixture of oxidizing agent and/or
furnace off-gases and/or carbon dioxide (CO.sub.2) and/or steam is
between 20 and 80 m/s at the burner mouth.
[0021] The burner may also be arranged on the off-gas side of the
furnace installation, preferably in the stack which discharges the
furnace off-gases from the combustion chamber of the furnace
installation, or at any other location which is suitable for its
intended use in the furnace wall surrounding the combustion chamber
of the furnace installation.
[0022] It is also possible for the injector and the heat exchanger
to be arranged in the burner. An injector/heat exchanger
arrangement of this type is advantageous if the furnace off-gas is
extracted through an annular gap around the burner mouth, as for
example in the case of rotary drum furnaces, in particular when the
burner is installed on the off-gas side of the furnace. In this
case, the mixture of oxidizing agent and/or furnace off-gas and/or
carbon dioxide and/or steam is recuperatively heated by the furnace
off-gases.
[0023] The lines which carry the oxidizing agent, the furnace
off-gas, the carbon dioxide and the steam consist of heat-resistant
and corrosion-resistant NiCr or ODS alloys and are provided with an
insulation which ensures the required thermal protection from the
inside and/or the outside and preferably ceramic fibres.
[0024] The burner block which includes the burner preferably has a
cylindrical opening.
[0025] The burner is equipped with a UV light receiver for flame
monitoring.
[0026] The mixture of oxidizing agent and/or furnace off-gas and/or
carbon dioxide and/or steam which is fed to the burner in
accordance with the invention reduces the reaction rate of the
combustion, since the reactions of the oxygen with the fuel are
impeded by the CO.sub.2 and/or H.sub.2O molecules.
[0027] The mixing of the oxidizing agent with furnace gas and/or
carbon dioxide and/or steam results in the formation of a
voluminous combustion flame with a high concentration of carbon
dioxide and steam. The greater volume of the flame compared to that
achieved with known combustion, and the higher concentration of
carbon dioxide and/or steam in the burner flame significantly
increase the gas radiation of carbon dioxide and/or steam, which
takes place in the spectral region in radiation bands, with the
result that the material to be treated can be heated by a flame
temperature which lowers the levels of NO.sub.x in the off-gas. The
radiation bands which are relevant to carbon dioxide are in the
range from 2.4 to 3 .mu.m, 4 to 4.8 .mu.m, 12.5 to 16.4 .mu.m, and
those which are relevant to steam are in the range from 1.7 to 2
.mu.m, 2.2 to 3 .mu.m and 12 to 30 .mu.m.
[0028] As a result of the high-viscosity mixture of oxidizing agent
and/or furnace off-gases and/or carbon dioxide and/or steam being
fed to the burner at a temperature of from 20.degree. C. to
1600.degree. C., preferably 900.degree. C., this mixture is mixed
in such a manner with the fuel at the burner mouth that the
combustion takes place at a flame temperature of from 800.degree.
C. to 2700.degree. C., which significantly reduces the thermal
NO.sub.x off-gas potential of the furnace installation.
[0029] The mixture of oxidizing agent and/or furnace off-gases
and/or carbon dioxide and/or steam which is fed to the burner, as
well as the burner which is used in accordance with the invention,
causes the fuel to be at least partially self-carburized in the
fuel tube of the burner and, owing to the design of the burner, in
the fuel-rich core of the burner flame. The self-carburization or
decomposition takes place in oxygen-free zones and at temperatures
of greater than 1000.degree. C. in the case of hydrocarbons, so as
to form soot. The heating of the soot particles in the burner flame
leads to continuous radiation in the range from 0.2 to 20
micrometers and therefore to cooling of the flame, so that the
NO.sub.x off-gas levels from the furnace installation are
additionally lowered.
[0030] A further advantage is the improved heating of lower layers,
e.g. in a glass melt bath, since liquid glass is semi-transparent
to wavelengths in the range from 0.3 to 4 micrometers.
[0031] The NO.sub.x off-gas levels are additionally reduced by the
use of preferably low-N.sub.2 oxidizing agent mixtures and
fuels.
[0032] The circulating furnace gases cause nitrogen oxides which
are present in the combustion chamber of the furnace installation
to be fed to the burner flame, and these nitrogen oxides are then
reduced to form nitrogen (N.sub.2) in the fuel-rich zones of the
burner flame.
[0033] The very long, soft and visible flames generated in the
combustion chamber of the furnace installation allow particularly
advantageous low-NO.sub.x combustion in aluminium holding furnaces
and rotary drum furnaces.
[0034] Moreover, the combustion according to the invention is
stable and low-noise. The noise level is 50-80 Decibels.
[0035] With the low-NO.sub.x combustion according to the
invention--unlike with the known flame-free combustion--the flame
radiation in the visible region advantageously increases the heat
transfer to the material to be treated.
[0036] The high concentration and volume of CO.sub.2/H.sub.2O
vapour in the burner flame additionally increases the gas radiation
of CO.sub.2 and/or H.sub.2O vapour, which takes place in the
spectral region in radiation bands, in such a manner as to ensure
improved heat transfer to the material to be treated, e.g. when
melting glass.
[0037] Furthermore, the turbulence and swirling during combustion,
which have a disruptive influence when dust-containing products are
introduced, are reduced.
[0038] The injector insert significantly reduces the wear and
maintenance costs for the furnace installation incurred, for
example, with a blower consisting of expensive heat-resistant
materials which has hitherto been used. Moreover, the supply of
external energy which has hitherto been required to operate the
blower is no longer necessary.
[0039] Furthermore, the thermal loading and therefore wear to the
pipe tubes is reduced, since the mixing of the oxidizing agent with
furnace off-gases and/or carbon dioxide and/or steam lowers the
temperature of the media that are to be transported.
[0040] In addition, primary energy can be saved through preheating
of the oxygen used as oxidizing agent and/or carbon dioxide and/or
steam by furnace off-gases in the heat exchanger, and as a result
the operating costs of the furnace installation can be reduced
further.
[0041] The low-NO.sub.x combustion according to the invention, with
a uniform temperature distribution at a low temperature level
(burner flame) in the combustion chamber and therefore with a
significantly reduced NO.sub.x off-gas potential can be used in any
conventional furnace installation, particularly advantageously in
aluminium holding furnaces or glass-melting furnaces.
[0042] The invention is explained in more detail below on the basis
of an exemplary embodiment illustrated in the drawing, in
which:
[0043] FIG. 1 diagrammatically depicts a furnace installation with
combustion apparatus;
[0044] FIG. 2 diagrammatically depicts a further furnace
installation with combustion apparatus;
[0045] FIG. 3 diagrammatically depicts a third furnace installation
with combustion apparatus.
[0046] The furnace installation illustrated in FIG. 1 comprises a
refractory lining 1 which surrounds a combustion chamber and has an
off-gas opening 19 and a stack 2, which discharges the furnace
off-gases, and pipeline 3 as well as a burner block 4 with a burner
5, the burner 5 being connected by a pipeline 7 to an injector 6
and to a heat exchanger 8 arranged in the stack 2.
[0047] The furnace off-gases which flow out of the combustion
chamber through the off-gas opening 19 are cooled as they flow
around the heat exchanger 8 and then flow out of the furnace
installation through the stack 2.
[0048] The gaseous oxygen, which is used as oxidizing agent at a
temperature of from -20 to 40.degree. C. and at a pressure of from
0.2 to 40 bar, flows into the heat exchanger 8 through an inlet
9.
[0049] The oxygen flowing through the heat exchanger 8, which is
designed as a recuperator or regenerator, is heated by the furnace
off-gases flowing around the heat exchanger 8 and flows through an
outlet 10 of the heat exchanger 8 into the injector 6 through an
inlet 11 at a temperature of from 20 to 900.degree. C.
[0050] The oxygen which flows out of the outflow nozzle 12 of the
injector 6 at a velocity of from 20 to 660 m/s expands, thereby
generating an oxygen jet flowing at a velocity of from 20 to 660
m/s.
[0051] The high flow velocity of the oxygen jet generates a reduced
pressure at position 13 in the injector 6, the sucking action of
which reduced pressure sucks the furnace off-gases out of the
combustion chamber through the pipeline 3 into the oxygen jet, and
in the pipeline 7, which is designed as a mixing section of length
x, they are mixed with the oxygen jet, with temperature balancing,
after which the mixture of oxygen and furnace off-gases is fed, at
a temperature of from 20 to 1600.degree. C., through a connection
14 to the burner 5, which via a further connection 15 is supplied
with natural gas as gaseous fuel.
[0052] The pipelines carrying the oxygen and the furnace off-gases
consist of a heat-resistant NiCr or ODS alloy and are provided on
the inner side with a thermal protection and/or on the outer side
with a thermal insulation, e.g. comprising ceramic fibres or
ceramic blocks.
[0053] The burner 5, which is used as a parallel-flow burner,
advantageously has an inner tube and an outer tube, with the
natural gas used as gaseous fuel flowing to the burner mouth 16
through the fuel tube 18, which is arranged as the inner tube, and
the mixture of oxygen and furnace off-gas flowing to the burner
mouth 16 through the outer tube, which accommodates fuel tube 18
and is designed as an annular gap 21, generating a long, soft and
visible burner flame 17 in the combustion chamber of the furnace
installation for heating material that is to be treated.
[0054] Partial self-carburization of the fuel takes place in the
fuel tube 18 of the burner 5 through recuperative heat exchange
with the mixture of oxidizing agent and furnace off-gases.
[0055] The burner structure according to the invention allows the
mixture of oxidizing agent and furnace off-gases to flow out of the
burner mouth 16 of the burner at a velocity which is 0.3 to 4 times
higher than the fuel, with the result that a total momentum flux,
based on the burner power, of from 1.5 to 8 N/MW and a ratio of the
momentum flux densities of the mixture of oxidizing agent and
furnace off-gases to fuel of from 0.8 to 31 are ensured, and as a
result a power density of from 0.2 to 0.5 KW/mm.sup.2 is reached at
the outlet of the burner block 4.
[0056] The mixture of oxidizing agent and furnace off-gases flows
out of the burner mouth 16 at a velocity of from 20 to 80 m/s.
[0057] The burner flame which burns the material that is to be
treated in the combustion chamber has a flame temperature of from
800.degree. C. to 2700.degree. C.
[0058] The burner block 4 which accommodates the burner 5 has a
preferably cylindrical opening.
[0059] The burner is advantageously equipped with a UV light
receiver 20 for flame monitoring.
[0060] The furnace installation which is diagrammatically depicted
in FIG. 2 is advantageously used if the furnace off-gases are
ladened with dust or other substances which are aggressive or
promote oxidation. This furnace installation comprises the
refractory lining 1, which surrounds a combustion chamber of a
furnace installation and has an off-gas opening 19, and a stack 2,
which discharges the furnace off-gas and accommodates the heat
exchanger 8, as well as the burner block 4, which contains the
burner 5 and is connected by a pipeline 7 to the injector 6 and the
heat exchanger 8.
[0061] The furnace off-gases which flow out of the combustion
chamber through the off-gas opening 19 are cooled as they flow
around the heat exchanger 8, which is supplied with water, and then
flow out of the furnace installation via the stack 2.
[0062] As it flows through the heat exchanger 8, the water which is
fed to the heat exchanger 8 through the inlet 9 is evaporated
through heat exchange with the furnace off-gas flowing around the
heat exchanger 8 and then flows into the injector 6 at position 13
as superheated steam at a temperature of from 20 to 900.degree.
C.
[0063] The gaseous oxygen, which is used as oxidizing agent at a
temperature of from -20 to 40.degree. C. and a pressure of from 0.2
to 40 bar, flows into the injector 6 through the inlet 11. The
oxygen jet expanding as it flows out of the outflow nozzle 12 of
the injector 6 increases its flow velocity to 20 to 340 m/s, with
the result that a reduced pressure is generated at position 13 in
the injector 6, the sucking action of which reduced pressure sucks
the superheated steam into the oxygen jet flowing through the
injector 6 at position 13 and mixes it with the oxygen jet, with
temperature balancing, in the pipeline 7, which is designed as
mixing section of length x, and the oxygen/steam mixture flows, at
a temperature of from 20 to 1600.degree. C., through connection 14
into the burner 5, which is supplied through connection 15 with
natural gas as gaseous fuel.
[0064] The pipelines carrying the oxygen and the steam consist of a
heat-resistant and corrosion-resistant NiCr or ODS alloy and are
designed from the inside with a thermal protection or from the
outside with a thermal insulation, e.g. comprising a ceramic fibre
or ceramic block.
[0065] The burner 5, which is used as a parallel-flow burner,
advantageously has an inner tube and an outer tube, natural gas
which is used as gaseous fuel flowing to the burner mouth 16
through the fuel tube 18, which is arranged as an inner tube, and
the mixture of oxygen and steam flowing to the burner mouth 16
through the outer tube, which accommodates the fuel tube 18 and is
designed as an annular gap 21, thereby generating the long, soft
and visible burner flame 17 with a flame temperature of from
800.degree. C. to 2700.degree. C. in the combustion chamber of the
furnace installation for heating material that is to be
treated.
[0066] Partial self-carburization of the fuel takes place in the
fuel tube 18 of the burner 5 through recuperative heat exchange
with the mixture of oxidizing agent and steam.
[0067] The burner design according to the invention allows the
mixture of oxidizing agent and steam to flow out of the burner
mouth 16 of the burner at a velocity which is 0.3 to 4 times higher
than the fuel, with the result that a total momentum flux, based on
the burner power, of from 1.5 to 8 N/MW and a ratio of the momentum
flux densities of the mixture of oxidizing agent and steam to fuel
of from 0.8 to 31 are ensured, and as a result a power density of
from 0.2 to 0.5 KW/mm.sup.2 is reached at the outlet of the burner
block 4.
[0068] The mixture of oxidizing agent and steam flows out of the
burner mouth 16 at a velocity of from 20 to 80 m/s.
[0069] The burner block 4 has a preferably cylindrical opening.
[0070] The burner is equipped with a UV light receiver 20 for flame
monitoring.
[0071] The furnace installation which is diagrammatically depicted
in FIG. 3 is used if the furnace off-gases are ladened with dust or
other aggressive or oxidation-promoting substances. This furnace
installation comprises the refractory lining 1, which surrounds a
combustion chamber and has an off-gas opening 19, and the stack 2,
which is designed to discharge the furnace off-gas and contains the
heat exchanger 8, as well as the burner block 4 with burner 5,
burner 5 being connected to the injector 6 and to the heat
exchanger 8 by a pipeline 7.
[0072] The exhaust gases which flow out of the combustion chamber
through the off-gas opening 19 are cooled as they flow around the
heat exchanger 8, which is supplied with carbon dioxide, and then
flow out of the furnace installation through the stack 2.
[0073] Liquid or preferably gaseous carbon dioxide which is
supplied through the inlet 9 of the heat exchanger 8 is heated to
20.degree. C. to 900.degree. C. through heat exchange with the
furnace off-gas flowing around the heat exchanger 8 and flows
through the outlet 10 into the injector 6 at position 13.
[0074] The gaseous oxygen, which is used as oxidizing agent at a
temperature of from -20 to 40.degree. C. and a pressure of from 0.2
to 40 bar, is fed to the injector 6 through the inlet 11. The
oxygen flowing through the injector 6 expands as it flows out of
the outflow nozzle 12 of the injector, so that its flow velocity is
increased to from 20 to 340 m/s, with the result that a reduced
pressure is generated in the injector 6 at position 13, the sucking
action of which reduced pressure sucks the carbon dioxide into the
oxygen jet, with the carbon dioxide being mixed with the oxygen
jet, with temperature balancing, in the pipeline 7, which is
designed as a mixing section with a length x, and then the mixture
of oxygen and carbon dioxide flows, at a temperature of from 20 to
1600.degree. C., through connection 14 into the burner 5, which is
supplied via a further connection 15 with natural gas as gaseous
fuel.
[0075] The pipelines carrying the oxygen and the carbon dioxide
consist of a heat-resistant and corrosion-resistant NiCr or ODS
alloy and are provided on the inner side with a thermal protection
and/or on the outer side with a thermal insulation, e.g. comprising
ceramic fibres.
[0076] The burner 5, which is used as a parallel-flow burner,
advantageously has an inner tube and an outer tube, with natural
gas used as gaseous fuel being fed to the burner mouth 16 through
the fuel tube 18, which is arranged as the inner tube, and the
mixture of oxygen and carbon dioxide being fed to the burner mouth
16 through the outer tube, which accommodates the fuel tube 18 and
is designed as an annular gap 21, producing a long, soft and
visible burner flame 17 with a flame temperature of from
800-2700.degree. C. in the combustion chamber of the furnace
installation for heating material that is to be treated.
[0077] Partial self-carburization of the fuel takes place in the
fuel tube 18 of the burner 5 through recuperative heat exchange
with the mixture of oxidizing agent and carbon dioxide.
[0078] The burner design according to the invention allows the
mixture of oxidizing agent and carbon dioxide to flow out of the
burner mouth 16 of the burner at a velocity which is 0.3 to 4 times
higher than the fuel, with the result that a total momentum flux,
based on the burner power, of from 1.5 to 8 N/MW and a ratio of the
momentum flux densities of the mixture of oxidizing agent and
carbon dioxide to fuel of from 0.8 to 31 are ensured, and as a
result a power density of from 0.2 to 0.5 KW/mm.sup.2 is reached at
the outlet of the burner block 4.
[0079] The mixture of oxidizing agent and carbon dioxide flows out
of the burner mouth 16 at a velocity of from 20 to 80 m/s.
[0080] The burner block 4 has a preferably cylindrical opening.
[0081] The burner is equipped with a UV light receiver 20 for flame
monitoring.
LIST OF DESIGNATIONS
[0082] 1 Refractory lining [0083] 2 Stack (furnace off-gas) [0084]
3 Pipeline (furnace off-gas) [0085] 4 Burner block [0086] 5 Burner
[0087] 6 Injector [0088] 7 Pipeline [0089] 8 Heat exchanger [0090]
9 Inlet (8) [0091] 10 Outlet (8) [0092] 11 Inlet (6) [0093] 12
Outflow nozzle (6) [0094] 13 Position (6) [0095] 14 Connection (5)
[0096] 15 Connection (5) [0097] 16 Burner mouth [0098] 17 Burner
flame [0099] 18 Fuel tube [0100] 19 Off-gas opening [0101] 20 UV
light receiver [0102] 21 Annular gap
* * * * *