U.S. patent application number 15/310557 was filed with the patent office on 2017-03-23 for flameless oxidation device, apparatus and method.
This patent application is currently assigned to DOOSAN BABCOCK LIMITED. The applicant listed for this patent is DOOSAN BABCOCK LIMITED, WS WARMEPROZESSTECHNIK GMBH. Invention is credited to Angus DUNCAN, Gerry HESSELMANN, Joachim G WUNNING.
Application Number | 20170082283 15/310557 |
Document ID | / |
Family ID | 51032682 |
Filed Date | 2017-03-23 |
United States Patent
Application |
20170082283 |
Kind Code |
A1 |
DUNCAN; Angus ; et
al. |
March 23, 2017 |
FLAMELESS OXIDATION DEVICE, APPARATUS AND METHOD
Abstract
A device for the flameless oxidation of fuel includes a
flameless oxidation burner, a first conduit to convey a fluid fuel
phase to a first outlet and a direct primary jet including the
fluid fuel phase outwardly therefrom. A second conduit is provided
to convey a jacketing gas to a second outlet. The second conduit is
disposed surrounding the first conduit so as to direct a jacketing
jet of the jacketing gas outwardly therefrom surrounding the
primary jet.
Inventors: |
DUNCAN; Angus; (Renfrew,
GB) ; HESSELMANN; Gerry; (Renfrew, GB) ;
WUNNING; Joachim G; (Renningen, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
DOOSAN BABCOCK LIMITED
WS WARMEPROZESSTECHNIK GMBH |
Crawley, Sussex
Renningen |
|
GB
DE |
|
|
Assignee: |
DOOSAN BABCOCK LIMITED
Crawley, Sussex
GB
WS WARMEPROZESSTECHNIK GMBH
Renningen
DE
|
Family ID: |
51032682 |
Appl. No.: |
15/310557 |
Filed: |
May 11, 2015 |
PCT Filed: |
May 11, 2015 |
PCT NO: |
PCT/GB2015/051371 |
371 Date: |
November 11, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F23G 2202/30 20130101;
Y02E 20/348 20130101; Y02E 20/34 20130101; Y02E 20/342 20130101;
F23D 1/005 20130101; F23L 15/02 20130101; F23C 9/08 20130101; F23G
5/0276 20130101; F23C 9/003 20130101; F23C 99/00 20130101; F23C
2900/99001 20130101; F23L 15/00 20130101 |
International
Class: |
F23C 99/00 20060101
F23C099/00; F23L 15/02 20060101 F23L015/02; F23D 1/00 20060101
F23D001/00; F23C 9/00 20060101 F23C009/00; F23C 9/08 20060101
F23C009/08 |
Foreign Application Data
Date |
Code |
Application Number |
May 13, 2014 |
GB |
1408459.4 |
Claims
1. A device for the flameless oxidation of fuel comprising: a first
conduit to convey a fluid fuel phase to a first outlet and direct a
primary jet comprising the fluid fuel phase outwardly therefrom; a
second conduit to convey a jacketing gas to a second outlet;
wherein the second conduit is disposed surroundingly about the
first conduit so as direct a jacketing jet of the jacketing gas
outwardly therefrom surroundingly about the primary jet.
2. A device in accordance with claim 1 comprising: a first inlet to
receive a supply of fuel in a fluid phase, a first outlet and a
first conduit disposed as a channel means to convey the fuel in a
fluid phase from the first inlet to the first outlet; a second
inlet to receive a supply of jacketing gas, a second outlet and a
second conduit disposed as a channel means to convey the jacketing
gas from the second inlet to the second outlet.
3. A device in accordance with claim 2 comprising: a fuel supply in
fluid communication with said first inlet; a jacketing gas supply
in fluid communication with said second inlet.
4. A device in accordance with claim 3 wherein the jacketing gas
supply comprises a supply in fluid communication with said second
inlet of one or more gases selected from: a comburant gas; an
exhaust gas; an inert gas.
5. A device in accordance with claim 3 wherein the fuel supply
comprises a supply in fluid communication with said first inlet of
pulverous coal in a carrier gas.
6. A device in accordance with claim 1 comprising an annular second
outlet surroundingly disposed concentrically around a circular
first outlet.
7. A device in accordance with any preceding claim 1 further
comprising a third conduit to convey a comburant gas to a third
outlet.
8. A device in accordance with claim 7 comprising a third conduit
disposed surroundingly about the first and second conduits so as
direct a comburant jet of the comburant gas outwardly therefrom
surroundingly about the primary and jacketing jets.
9. A device in accordance with claim 7 comprising a plurality of
third conduits arrayed surroundingly about the first and second
conduits having a corresponding plurality of third outlets
configured to produce a corresponding plurality comburant jets
projecting outwardly beyond each third outlet surroundingly about
the jacketing jet.
10. A device in accordance with claim 9 comprising concentrically
disposed: a central circular first outlet, a second annular outlet
surroundingly disposed about the first outlet, and an array of at
least two third outlets, disposed about the second outlet
11. An apparatus for the flameless oxidation of fuel comprising: a
reaction chamber having an internal reaction volume defined by one
or more chamber walls; at least one device in accordance with claim
1 extending through the wall and disposed to direct a primary jet
comprising a fluid fuel phase into the reaction volume via its
first outlet and to direct a jacketing jet comprising a jacketing
gas into the reaction volume via its second outlet surroundingly
around the primary jet.
12. An apparatus in accordance with claim 11 wherein the at least
one device comprises an oxidation device to direct a fuel jet and a
jacketing jet towards an oxidation zone in the reaction chamber,
and wherein the apparatus further comprises a comburant gas supply
conduit arranged to supply comburant to the oxidation zone and/or
an exhaust gas supply conduit arranged to supply hot recycled
exhaust gas to the oxidation zone.
13. An apparatus in accordance with claim 12 wherein the oxidation
device comprises a plurality of comburant gas supply conduits
disposed surroundingly around the first and second conduits of the
oxidation device.
14. An apparatus in accordance with claim 13 comprising a
combustion apparatus for the flameless oxidation of fuel to
generate heat in a furnace chamber.
15. A method of flameless oxidation of fuel comprising the steps
of: directing a fluid fuel phase towards a flameless oxidation zone
in a reaction chamber; causing a jacketing gas jet to be directed
towards the said oxidation zone in a manner disposed surroundingly
about the primary jet; supporting flameless oxidation of the fuel
jet in the oxidation zone at least by supplying to the oxidation
zone one or both of comburant gas and hot exhaust gas.
16. A method in accordance with claim 15 wherein the steps of
directing a fluid fuel phase towards a flameless oxidation zone and
causing a jacketing gas jet to be directed towards the said
oxidation zone are respectively performed by causing a fluid fuel
phase to be conveyed via a first conduit to a first outlet letting
into the reaction chamber, and causing a jacketing gas to be
conveyed via a second conduit to a second outlet letting into the
reaction chamber disposed surroundingly about the first outlet.
17. A method in accordance with claim 15 wherein the jacketing gas
comprises one or more gases selected from: a comburant gas; an
exhaust gas; an inert gas.
18. A method in accordance with claim 15 wherein the fluid fuel
phase is pulverous coal in a carrier gas.
Description
[0001] The invention relates to a device for the flameless
oxidation of fuel, for example comprising a flameless oxidation
burner. The invention further relates to an apparatus for the
flameless oxidation of fuel comprising one or more such devices,
for example disposed to direct such fuel into a reaction chamber
for flameless oxidation. The invention further relates to a method
of flameless oxidation of fuel and to a method of operation of such
a device or apparatus.
[0002] In the preferred case the invention relates to a device for
the flameless oxidation of particulate solid carbonaceous fuel. In
the preferred case the fuel is pulverous solid carbonaceous fuel
and for example pulverised coal, and the invention is particularly
discussed in that context. However the general principles of the
invention may be applied to other solid carbonaceous fuel such as
biomass, oil shales, petroleum, coke etc, and to other fuels
including non-solid fuels.
[0003] In particular, but not exclusively, the invention relates to
a combustion apparatus for the flameless oxidation of fuel to
generate heat in a furnace chamber, for example for use in a power
generation apparatus, and to a power generation apparatus
incorporating such a combustion apparatus.
[0004] The heating of a furnace chamber with one or more burners
designed for flameless oxidation of fuel within a reaction volume
defined by the furnace chamber is known in the art. Burners adapted
to heat a furnace chamber by means of a flameless oxidation of the
fuel have advantages in many applications over burners that form
flames. For example the distribution of generated heat over a large
area of the furnace chamber provides for safe operation with a
range of gaseous, liquid and solid fuels in hot combustion
chambers. Emissions may be reduced, and for example the formation
of nitrogen oxides may be suppressed.
[0005] Flameless oxidation is applied in many different
applications. Flame formation and corresponding peak temperatures
are suppressed by internal recirculation of host combustion
products. It should be noted that the desirable internal local
recirculation of hot exhaust gas combustion products is internal to
the furnace, not external via a fan. This `internal recirculation`
is jet induced recirculation in the furnace, or `induced
recirculation`. This may be distinguished from `external
recirculation` as recirculation of flue gases via a fan or other
positive circulation device, or `forced recirculation`.
[0006] Since there is no need for flame stability, flameless
oxidation is ideally suited for combustion of difficult fuels, even
with changing composition.
[0007] Flameless oxidation burners are known for use with solid
carbonaceous fuels such as coals. The fuel is in particulate and
for example pulverous form and is conveyed as a primary fuel jet by
means of a carrier gas. The gas carrier preferably comprises or
includes a comburant gas, which is for example combustion air.
[0008] In most cases, flameless oxidation may be achieved by
careful arrangement of free jets. Depending on boundary conditions,
fuel and combustion air can be injected premixed, combined or
delivered through separate jets.
[0009] However, tests with pulverised coal fuel in particular have
shown that ignition can occur at the borders of the fuel jet where
the fuel jet comes into contact early with hot locally recirculated
exhaust gases which can then act as a pilot flame igniting a main
flame. Pulverised coal is usually transported with a carrier gas
capable of supporting combustion, for example combustion air. This
air, in combination with a high reactivity of volatiles and high
combustion chamber temperatures typically encountered lead to the
unwanted self-ignition. This effect can be found to occur
especially for high burner capacities, highly reactive fuels (such
as hydrogen or volatiles of coal), high combustion chamber
temperatures and low jet velocities.
[0010] It may be possible that this unwanted ignition could be
suppressed by dilution of the combustion air with cold exhaust gas,
or by substituting the carrier air with an inert gas. Neither of
these solutions is satisfactory.
[0011] It is desirable that a system and method is developed which
tends to suppress unwanted ignition and control the temperature
development in front of burners and better support flameless
oxidation, in particular for the flameless oxidation of pulverous
solid fuel, such as pulverous carbonaceous fuel such as pulverised
coal, without the need to recirculate large amounts of exhaust gas
and without the need to substitute the carrier air by an inert
gas.
[0012] In accordance with the invention in a first most general
aspect a device for the flameless oxidation of fuel comprises:
[0013] a first conduit to convey a fluid fuel phase to a first
outlet and direct a primary jet comprising the fluid fuel phase
outwardly therefrom, for example via a suitable nozzle;
[0014] a second conduit to convey a jacketing gas to a second
outlet;
[0015] wherein the second conduit is disposed surroundingly about
the first conduit so as direct a jacketing jet of the jacketing gas
outwardly therefrom surroundingly about the primary jet, for
example via a suitable nozzle.
[0016] The second conduit is disposed surroundingly about the first
conduit at least at their respective outlet ends, so that the
second outlet is disposed surroundingly about the first outlet and
is thereby disposed to direct a jacketing jet of the jacketing gas
outwardly therefrom surroundingly about the primary jet exiting the
first outlet. Conveniently however the second conduit may be
disposed surroundingly about the first conduit for at least a
substantial part of its length.
[0017] The jacketing gas is selected to be relatively less
oxidising than, and to isolate the primary jet to some extent from
early contact with, local hot recirculated exhaust gases, and is
for example selected from a comburant gas, cold recirculated FGR,
inert gas, or a mixture thereof.
[0018] More completely, the device comprises:
[0019] a first inlet to receive a supply of fuel, a first outlet
and a first conduit disposed as a channel means to convey a fluid
fuel phase from the first inlet to the first outlet;
[0020] a second inlet to receive a supply of jacketing gas, a
second outlet and a second conduit disposed as a channel means to
convey the jacketing gas from the second inlet to the second
outlet.
[0021] Although reference is made for convenience to a first and
second inlet in the singular this would be understood not only to
encompass the plural in the generality but in particular should be
understood to encompass, in the case where a supply comprising a
mixture of gases is envisaged, a combined inlet to receive a supply
comprising a mixture of a plurality of gases or plural inlets
respectively to receive a supply comprising each such gas.
[0022] More completely yet, the device comprises:
[0023] a fuel supply in fluid communication with said first
inlet;
[0024] a jacketing gas supply in fluid communication with said
second inlet and for example a comburant gas supply in fluid
communication with said second inlet and/or an exhaust gas supply
in fluid communication with said second inlet and/or an inert gas
supply in fluid communication with said second inlet.
[0025] As will be understood by the skilled person in this context,
a comburant gas comprises a gas capable when so supplied to support
oxidation of the fuel in an oxidation zone downstream of the fuel
outlet during use, an exhaust gas comprises one or more
recirculated exhaust products of such oxidation, and an inert gas
in this context comprises a gas not capable of supporting oxidation
of the fuel.
[0026] The purpose of the invention is to give better control over
unwanted flame formation. It has been found that ignition can occur
at the borders of the fuel jet where the fuel jet comes into
contact early with hot local recirculated exhaust gases. This
ignition of the fuel jet can then act as a pilot igniting a main
flame. Suppression of this effect is desirable to ensure flameless
oxidation. The use of a jacketed jet in the manner described in
accordance with the invention helps to suppress such pilot flame
formation, and hence the development of a main flame in the manner
described, in that the jacketing gas is selected to be relatively
less oxidising than, and thereby to isolate the primary jet to some
extent from excessively early contact and ignition by, hot locally
recirculated exhaust gases. The jacketing jet shields the fuel jet
from high exhaust temperatures and from the oxygen within the
reaction chamber, suppressing flame formation and tending to
encourage flameless oxidation.
[0027] This solution suppresses unwanted ignition and enables
better control of temperature development in front of a flameless
combustion device, and in particular in front of a burner, without
the need for external recirculation of large amounts of exhaust
flue gas to the burner inlet. Where it is desired to use a carrier
gas that supports combustion such as carrier air, it is not
necessary to dilute or substitute such a comburant by an inert gas.
The amount of necessary externally recirculated exhaust flue gas
can be drastically reduced or eliminated completely.
[0028] Control of the composition and mass flow of the jacketing
jet can provide an effective and inexpensive way to control the
course of combustion. Individual control of individual burners can
be effected in a much more ready manner than would be possible
using a solution that involved changes to the fuel phase
composition itself, for example by alternative solutions involving
dilution of any comburant gas in the mixture, provision of inert
gases etc.
[0029] The purpose of the invention is in particular to provide a
system for the flameless oxidation of fuel comprising one or more
devices such as above described, for example disposed to direct
such fuel into a reaction chamber for flameless oxidation. The
invention further relates to a method of flameless oxidation of
fuel and to a method of operation of such a device or system.
[0030] Accordingly, in accordance with the invention in a second
aspect an apparatus for the flameless oxidation of fuel comprises
one or more devices in accordance with the first aspect of the
invention. For example the apparatus comprises a reaction chamber
and one or more such devices disposed to direct fuel and comburant
into a reaction chamber for flameless oxidation.
[0031] More completely in accordance with the invention in the
second aspect an apparatus for the flameless oxidation of fuel
comprises:
[0032] a reaction chamber having an internal reaction volume
defined by one or more chamber walls;
[0033] at least one device in accordance with the first aspect of
the invention extending through the wall and disposed to direct a
primary jet comprising a fluid fuel phase into the reaction volume
via its first outlet and to direct a jacketing jet comprising a
jacketing gas into the reaction volume via its second outlet
surroundingly around the primary jet.
[0034] The apparatus in accordance with the second aspect of the
invention thus comprises one or more, and preferably a plurality
of, flameless oxidation devices in accordance with the first aspect
of the invention disposed in and through at least one wall
extending into a reaction chamber. The devices direct a fuel jet
and a jacketing jet in the manner above described into the reaction
chamber. Each fuel jet (and its jacketing jet) is directed towards
an oxidation zone downstream of the fuel outlet whereat in familiar
manner it is intended that substantially flameless oxidation of the
fuel will be supported in use. The reaction chamber may otherwise
be conventional, and in particular for example supplies hot exhaust
gas and/or comburant gas to the flameless oxidation zone in
familiar manner. Thus the apparatus preferably further comprises a
comburant gas supply conduit arranged to supply comburant to the
oxidation zone and/or an exhaust gas supply conduit arranged to
supply hot recycled exhaust gas to the oxidation zone. The
comburant gas supply conduit is disposed to supply comburant gas
supplied from an external source to the oxidation zone and is
preferably provided with and fluidly connected to an external
comburant gas supply source. The exhaust gas supply conduit is
disposed to supply hot recycled exhaust gas exhausted from the
reaction chamber to the oxidation zone and is preferably fluidly
connected to an exhaust gas outlet of the reaction chamber via a
recycle conduit.
[0035] A comburant gas supply conduit may comprise a part of the
device of the first aspect of the invention, for example in that
comburant gas is supplied via the second conduit of the device or
via a further conduit of the device or otherwise by the device.
Additionally or alternatively a separate comburant gas supply
conduit may be provided.
[0036] A an exhaust gas supply conduit may comprise a part of the
device of the first aspect of the invention, for example in that
comburant gas is supplied via the second conduit of the device or
via a further conduit of the device or otherwise by the device.
Additionally or alternatively a separate exhaust gas supply conduit
may be provided.
[0037] Preferably the apparatus in accordance with the second
aspect of the invention comprises a combustion apparatus for the
flameless oxidation of fuel to generate heat in a furnace chamber,
for example for use in a power generation apparatus, and more
completely in a further aspect there is provided a thermal power
generation apparatus incorporating such a combustion apparatus as
source of thermal energy.
[0038] Similarly, in accordance with the invention in a further
aspect a method of flameless oxidation of fuel comprises the steps
of:
[0039] directing a fluid fuel phase towards a flameless oxidation
zone for example in a suitable reaction chamber, and for example by
causing a fluid fuel phase to be conveyed via a first conduit to a
first outlet letting into the reaction chamber, for example via a
suitable nozzle;
[0040] causing a jacketing gas jet to be directed towards the said
oxidation zone in a manner disposed surroundingly about the primary
jet, for example by causing a jacketing gas to be conveyed via a
second conduit to a second outlet letting into the reaction
chamber, for example via a suitable nozzle, and disposed
surroundingly about the first outlet;
[0041] supporting flameless oxidation of the fuel jet in the
oxidation zone by control of conditions within the oxidation zone,
and in particular for example by control of temperature in the
oxidation zone and/or of supply of comburant gas to the oxidation
zone and and/or of levels of hot exhaust gases in the reaction zone
in familiar manner.
[0042] The general principle necessary for flameless oxidation of a
fuel phase will be familiar to the person skilled in the art, and
the invention assumes application of such principles. In general
principle, comburant for example comprising exhaust gases from
combustion from which some useful heat has been removed and/or
preheated oxidant such as combustion air, and for example a mixture
of the same, is kept at a temperature that is higher than the
ignition temperature of the fuel phase, and the mixture of exhaust
gas and combustion air is then brought together with the fuel,
forming an oxidation zone in which a substantially flameless
oxidation occurs in a reaction chamber.
[0043] The invention does not depart from these principles, but the
jacketing jet of the invention acts to suppress undesirable
ignition at the borders of the fuel jet where the fuel jet comes
into contact early with the hot gases, tending to support more
sustainable flameless oxidation.
[0044] The method of flameless oxidation of fuel for example
comprises a method of operation of a device in accordance with the
invention in the first aspect or system in accordance with the
invention in the second aspect.
[0045] Preferred features of each aspect of the invention as
discussed in general principle below will accordingly be understood
to apply to all aspects by analogy.
[0046] The device, apparatus and method in accordance with the
invention operate in accordance with a principle that makes use of
a jacketing gas which is selected to be relatively less oxidising
than the hot recirculated exhaust gases typically present in a
typical flameless oxidation reaction chamber. For example, the
jacketing gas used in the method comprises, and a jacketing gas
supply in the device comprises, comburant gas, exhaust gas, or a
mixture of the two. The exhaust gas can be replaced by another
relatively inert gas.
[0047] Suitable comburant gases for use with the device, apparatus
and method in accordance with the invention are selected to support
suitable flameless oxidation conditions for flameless oxidation of
the primary jet, and will be familiar to those skilled in the art.
A typical comburant gas comprises an oxygen-containing gas, and is
for example air, simulated air, other oxygen-enriched gas including
oxygen-enriched recycled flue gas etc. The composition of any
comburant supply may be further modified for example by control of
levels of other cases and for example reduction of nitrogen etc in
familiar manner. A suitable comburant gas comprises combustion air
in familiar manner.
[0048] The device/apparatus of the invention accordingly includes
such a comburant gas supply and the method of the invention
accordingly includes a step of supplying such a comburant gas.
[0049] The device of the invention comprises a first conduit
disposed as a channel means to convey a fluid fuel phase to the
first outlet, and direct a primary jet comprising the fluid fuel
phase outwardly from the first outlet, for example via a suitable
nozzle. The first outlet is configured to direct a primary jet
comprising the fluid fuel phase outwardly from the first outlet and
is for example shaped to produce a desired primary jet shape
projecting outwardly beyond the first outlet. In a preferred case
the first outlet is so configured in that it comprises a first
nozzle shaped to direct a primary jet comprising the fluid fuel
phase outwardly from the first outlet and shaped to produce a
desired primary jet shape projecting outwardly beyond the first
outlet.
[0050] Typically a desired primary jet shape diverges as it passes
beyond the first outlet. For example a desired primary jet shape is
generally conical as it projects beyond the first outlet (wherein
conical should herein be interpreted generally as describing the
divergent surrounding nature of the jet, and not in a strict
mathematical sense as requiring a rigidly right circular cone shape
for example). In a preferred case the first outlet comprises a
first nozzle shaped to produce such a divergent and for example
generally conical primary jet. The first nozzle for example
comprises a nozzle outlet having a circular shape in a nozzle
transverse direction (transverse to a fluid fuel phase flow
direction in use) and is structured along a nozzle axial direction
(a fluid fuel phase flow direction) to produce a divergent and for
example generally conical primary jet and for example has a
diverging profile in a nozzle axial direction.
[0051] In accordance with the method of the invention, the method
in the preferred case comprises directing a primary jet having such
a shape towards the flameless oxidation zone, for example by
directing the fluid fuel phase through such a suitably configured
first outlet and for example through such a suitably configured
first nozzle.
[0052] The fluid fuel phase comprises a fuel suitable for flameless
oxidation, which may be gaseous, liquid or solid. Suitable fuels
include but are not limited to carbonaceous fuels such as fossil
fuels, biomass, waste products etc.
[0053] The fluid fuel phase may comprise a mixture of fuel with a
carrier gas, for example including comburant gas as above described
and/or other gases such as inert gases (that is to say, gases with
an inert role in the supporting of oxidation in a reaction zone).
The fuel may for example be solid carbonaceous fuel in particulate
and for example in pulverous form conveyed as a primary fuel jet by
means of such a carrier gas. The fuel is for example pulverous
coal.
[0054] Further conduit structures defining further outlets for
additional gases to modify conditions in an oxidation region, for
example including comburant gases, may be provided either as part
of the device of the first aspect of the invention or separately as
part of the apparatus of the second aspect of the invention.
[0055] Comburant gas may thus be provided as part of the mixture
comprising the fluid fuel phase and hence via the first conduit
and/or as part of the mixture comprising the jacketing gas and
hence via the second conduit.
[0056] Additionally or alternatively comburant gas may be
separately supplied via a third conduit disposed surroundingly
about the jacketing gas jet directed about the second conduit. In
this possible arrangement the jacketing jet also keeps the main
comburant away from the primary jet and from the fuel for a certain
time.
[0057] In such an embodiment the device comprises a third conduit
to convey a comburant gas to a third outlet. The third conduit may
be disposed surroundingly about the first and second conduits so as
direct a comburant jet of the comburant gas outwardly therefrom
surroundingly about the primary and jacketing jets, for example via
a suitable nozzle. Alternatively a plurality of third conduits may
be provided in the device arrayed surroundingly about the first and
second conduits and configured to produce a corresponding plurality
comburant jets projecting outwardly beyond the third outlet
surroundingly about the jacketing jet.
[0058] In such an embodiment the method additionally comprises
causing a comburant gas jet to be directed towards the said
oxidation zone in a manner disposed surroundingly about the
jacketing jet, for example by causing a comburant gas to be
conveyed via a third conduit to a third outlet letting into the
reaction chamber, for example via a suitable nozzle, and disposed
surroundingly about the second outlet.
[0059] The fuel may be gaseous, liquid or solid. In the case of
solid fuel, the fuel is preferably particulate, and is for example
a pulverous material, and is delivered entrained in a carrier gas
such as above described. Suitable solid fuels include particulate
and for example a pulverised coal (which term should be considered
unless otherwise indicated herein to cover the range of materials
so described including without limitation anthracite, bituminous
coals, sub-bituminous coals and lignites), but other solid fuels
including without limitation oil shales, biomass, petroleum, coke,
comminuted solid combustible waste and the like might be
considered.
[0060] A device/apparatus in accordance with the invention
conveniently comprises a supply of a liquid fuel phase comprising a
fuel or mixture as above described. A method in accordance with the
invention conveniently comprises the step of delivery of a fuel or
mixture as above described. Such a mixture may be supplied to the
device/apparatus from a mixed supply, or components of the mixture
may be separately supplied to and caused to mix within the
device/apparatus in accordance with the invention.
[0061] The invention provides for a jacketing jet disposed
generally around the primary fuel jet to tend to shield the primary
fuel jet from high exhaust temperatures and from the oxygen in the
exhaust gases so as to tend to suppress undesirable flame
formation. The device of the invention accordingly comprises a
second conduit to convey a jacketing gas to a second outlet wherein
the second conduit is disposed surroundingly about the first
conduit so as direct a jacketing jet of the jacketing gas outwardly
therefrom surroundingly about the primary jet, for example via a
suitable nozzle.
[0062] The second outlet is configured to direct a jacketing jet
comprising a jacketing jet of the jacketing gas outwardly from the
second outlet surroundingly about the primary jet and is for
example shaped to produce a desired jacketing jet shape projecting
outwardly beyond the second outlet about the primary jet. In a
preferred case the second outlet is so configured in that it
comprises a second nozzle shaped to direct a jacketing jet of the
jacketing gas outwardly from the second outlet and shaped to
produce a desired jacketing jet shape projecting outwardly beyond
the third outlet.
[0063] The jacketing jet is suitably shaped to substantially
envelop and for example entirely surround the primary jet. In a
preferred geometry, the jacketing jet diverges outwards as it
passes beyond the second outlet, and for example forms a generally
conical jacket around the primary jet (wherein conical should
herein be interpreted generally as describing the divergent
surrounding nature of the jet, and not in a strict mathematical
sense as requiring a rigidly right circular cone shape for
example).
[0064] To effect this, a device in accordance with the invention is
provided with a second outlet comprising a nozzle configured to
produce such a jacketing jet shape, and for example shaped to tend
to direct the jacketing gas into such a jacketing jet shape as it
passes beyond the nozzle. In a preferred case the second outlet
thus comprises a second nozzle shaped to produce such a divergent
and for example generally conical jacketing jet. The second nozzle
for example comprises a nozzle outlet having an annular shape
transverse to a fluid fuel phase flow direction about the first
outlet and is structured along a fluid fuel phase flow direction to
produce a divergent and for example generally conical jacketing jet
about the primary jet. The second nozzle for example comprises a
nozzle outlet having an annular shape concentric with the primary
outlet in a nozzle transverse direction (transverse to a fluid fuel
phase flow direction in use) and is structured along a nozzle axial
direction (a fluid fuel phase flow direction) to produce a
divergent and for example generally conical jacketing jet and for
example has a diverging profile in a nozzle axial direction.
[0065] In a particular preferred case for example, a device of the
first aspect of the invention comprises an annular second outlet
surroundingly disposed concentrically around a circular primary
outlet and for example a nozzle of the second outlet comprises an
annular nozzle surroundingly disposed concentrically around a
nozzle of a first outlet.
[0066] In accordance with the method of the invention, the method
in the preferred case comprises directing a jacketing jet in such a
shape towards the flameless oxidation zone, for example by
directing the jacketing gas through such a suitably configured
second outlet and for example through such a suitably configured
second nozzle.
[0067] In a possible embodiment a third conduit is provided for a
comburant gas supply disposed to supply comburant gas surroundingly
about the jacketing jet from a third outlet. Similar preferred
features will apply by analogy. In particular in this embodiment
the third outlet is configured to direct a comburant jet comprising
comburant gas outwardly from the third outlet spaced apart from the
first and second outlets surroundingly about the jacketing jet and
is for example shaped to produce a desired comburant jet shape
projecting outwardly beyond the third outlet. Optionally plural
third conduits may be arrayed surroundingly about the first and
second outlets for example having a corresponding plurality of
third outlets configured to produce a corresponding plurality
comburant jets projecting outwardly beyond each third outlet
surroundingly about the jacketing jet.
[0068] In a preferred case the or each third outlet is so
configured in that it comprises a third nozzle shaped to direct a
comburant jet of the comburant gas outwardly from the third outlet
and shaped to produce a desired comburant jet shape projecting
outwardly beyond the third outlet. In a preferred geometry, the
comburant jet diverges outwards as it passes beyond the third
outlet, and for example forms a generally conical shape. In a
preferred case the third outlet thus comprises a third nozzle
shaped to produce such a divergent and for example generally
conical comburant jet.
[0069] In a particular preferred case for example, a device of the
first aspect of the invention comprises concentrically disposed a
central circular first outlet and for example first nozzle, a
second annular outlet and for example annular nozzle surroundingly
disposed about the first, and an array of at least two third
outlets, and for example third nozzles, disposed about the second
outlet.
[0070] In a preferred embodiment, the device of the first aspect of
the invention comprises an elongate structure having first and
second (and where applicable further) inlets at or towards an inlet
end, and first and second (and where applicable further) conduits
extending to outlets at or towards an outlet end. The device is for
example an elongate burner.
[0071] A system of the second aspect of the invention preferably
comprises plural such burners for plural burner firing.
[0072] In accordance with the foregoing discussion, comburant gas
to support flameless oxidation in the oxidation zone may be
supplied for example as part of the jacketing gas supply and/or as
a carrier gas for the fuel phase. Additionally or alternatively,
comburant gas may be supplied by one or more additional comburant
gas supplies letting into the reaction volume. Thus, in a preferred
embodiment, an apparatus in accordance with the second aspect of
the invention further comprises at least one additional comburant
gas supply device comprising a conduit defining a fluid channel to
convey a comburant gas to a comburant gas outlet and direct a jet
of comburant gas outwardly therefrom, the additional comburant gas
supply device extending through the wall of the chamber and
disposed to direct a comburant gas supply into the reaction volume
via a comburant outlet. The comburant outlet is for example
disposed generally in the vicinity of and suitably laterally spaced
from the first and second outlets of the flameless oxidation
device. In a typical arrangement, a flameless oxidation device in
accordance with the first aspect of the invention may be provided
with a plurality of such additional comburant supply devices
disposed suitably around it.
[0073] A typical comburant gas such as combustion air may be
preheated prior to injection into a reaction chamber/combination
into a fuel phase as the case may be. To preheat the combustion
air, exhaust gases from combustion, from which useful heat has
already been removed, may typically be used. Additionally or
alternatively it would be possible to use waste heat from other
processes for preheating the comburant.
[0074] An apparatus to put this principle into practice in
conjunction with a device of the invention may therefore include a
suitable comburant preheater, for example disposed to preheat
comburant such as combustion air by transfer of recovered heat from
exhaust gases from combustion, and a method may include a step of
preheating comburant gas such as combustion air by transfer of
recovered heat from exhaust gases from combustion.
[0075] A typical comburant gas such as combustion air may be mixed
with exhaust gases from combustion prior to injection into a
reaction chamber/combination into a fuel phase as the case may be.
An apparatus to put this principle into practice in conjunction
with a device of the invention may therefore include a suitable
exhaust gas recirculation system disposed to mix comburant such as
combustion air with exhaust gases from combustion, and a method may
include a step of mixing comburant gas such as combustion air with
exhaust gases from combustion prior to injection into a reaction
chamber/combination into a fuel phase as the case may be.
[0076] It is a particular advantage of the invention that control
of oxidation conditions can be effected in individual devices by
means of control of the jacketed jet mass flow, composition and
temperature. Accordingly, in accordance with the preferred
embodiment, a device of the invention comprises means to control
the mass flow of and/or means to control the composition of and/or
means to control the temperature of the jacketing gas supply. By
analogy the method of invention comprises supplying jacketing gas
with a controlled and varied mass flow and/or composition and/or
temperature to control and vary oxidation conditions.
[0077] In a preferred case, the mass flow is controlled so that the
velocity of the jacketing jet is similar to or lower than the
velocity of the fuel jet.
[0078] An embodiment of the present invention will now be
described, by way of example only, with reference to the
accompanying drawings, in which:
[0079] FIG. 1 is a sectional side view of a prior art flameless
oxidation burner to which the principles according to the invention
could be applied, and illustrates the problem arising in particular
with pulverised coal firing;
[0080] FIG. 2 is sectional side view of a flameless oxidation
burner in accordance with an embodiment of the first aspect of the
invention;
[0081] FIG. 3 is a partial section of a flameless oxidation chamber
in accordance with a second aspect of the invention incorporating
such a flameless oxidation burner and with a simple schematic
representation of a possible fuel and gas supply system.
[0082] The simple schematic system shown in FIG. 1 shows a typical
flameless oxidation system that includes a central fuel jet supply
conduit to supply a fuel jet 1, which may contain oxygen and for
example carrier combustion air, and spaced further supply conduits
to deliver additional jets 3 which supply additional combustion air
or air plus recycled flue gas to the combustion zone. Also in
familiar manner, hot recirculated exhaust gas 2 is introduced in
advance of an intended flameless reaction zone. The combustion air
or air plus recycled flue gas is typically preheated and the
induced exhaust gas maintains temperature in a reaction zone in the
reaction chamber above the desired ignition temperature of the fuel
phase and may additionally provide some further oxygen to support
oxidation of the fuel.
[0083] The condition illustrated in FIG. 1 is the condition that
the invention seeks to suppress, in which ignition can occur at the
borders of the fuel jet in advance of the intended flameless
reaction zone which can then cause ignition of a main flame instead
of a flameless oxidation in the intended flameless reaction zone.
This problem is particularly encountered in the use of pulverised
coal as fuel, when transported by carrier air, where the oxygen in
the carrier air in combination with the high reactivity of
volatiles and the high combustion chamber temperatures can lead to
unwanted self-ignition, but the problem is not limited to such
fuel, and nor is the solution offered by the invention so
limited.
[0084] As illustrated in FIG. 1, the effect of early contact with
the hot recirculated exhaust gas 2 in advance of a intended
flameless reaction zone can be to cause undesirable initial
ignition of flames 4 at the border of the fuel jet (and in the
particular case at the border of the fuel/combustion air jet).
These flames 4 may then ignite a main flame 5 producing unwanted
flame combustion of the fuel instead of the desired flameless
oxidation.
[0085] FIG. 2 illustrates a comparable situation where the primary
fuel jet has been modified in accordance with the principles of the
invention. Again a simple schematic is shown including a primary
fuel jet 1 which may contain oxygen such as carrier air, and is for
example pulverised coal entrained in a suitable carrier gas such as
carrier combustion air, and optional additional conduits deliver
secondary additional jets 3 to supply for example combustion air or
air plus recycled flue gas. The combustion air or air plus recycled
flue gas is typically preheated and the internally recirculated
exhaust gas 2 again maintains temperature in a reaction zone in the
reaction chamber above the desired ignition temperature of the fuel
phase and may additionally provide some further oxygen to support
oxidation of the fuel.
[0086] In this case, an additional annular conduit surrounds the
central conduit which supplies the fuel/air jet 1, and this
supplies a jacketing jet 6 containing air, exhaust or a mixture of
both (optionally with additionally or substitutionally provided
other oxidatively inert gas), shielding the fuel/air jet from high
exhaust temperatures and from the oxygen in the secondary air jets
and in the exhaust gas, and thus suppressing flame formation at the
border of the fuel/air jet.
[0087] Suppression of such initial flame formation at the border of
the fuel/air jet controls oxidation conditions more effectively,
prevents ignition of a main flame as illustrated in FIG. 1, and
instead supports flameless oxidation in the flameless oxidation
region 7.
[0088] FIG. 3 is a partial section of a flameless oxidation chamber
in accordance with a second aspect of the invention incorporating
such a flameless oxidation burner and with a simple schematic
representation of a possible fuel and gas supply system.
[0089] A chamber wall 12 (shown as partial section of one side
only) defines a reaction volume generally designated 13. A single
burner 11 in accordance with the embodiment of FIG. 2 is shown let
into the wall. A single burner is shown for simplicity. In a
practical system multiple burners will usually be provided. The
burner is structured in general as shown in FIG. 2 to deliver a
central jet comprising fuel which may be entrained in a suitable
carrier gas such as carrier combustion air jacketed by the
jacketing jet, and optional secondary additional jets 3 to supply
for example additional combustion air or air plus recycled flue gas
to a flameless reaction zone generally designated 14. A hot
recirculated exhaust gas conduit 2 supplies exhaust gas from an
exhaust outlet of the chamber (omitted for clarity) in advance of
the intended flameless reaction zone in familiar manner to control
conditions and encourage flameless oxidation.
[0090] The system is distinctly characterised by the provision of a
jacketing jet about the fuel jet. The jacketing gas of the
jacketing jet is selected to be relatively less oxidising than, and
to isolate the primary jet to some extent from early contact with,
these hot recirculated exhaust gases, and is for example selected
from a comburant gas, cold recirculated FGR, inert gas, or a
mixture thereof. A simple schematic of a fuel and gas supply
arrangement to effect this is provided in FIG. 3.
[0091] A source of fuel 22 which is for example in the preferred
pulverised coal embodiment of the invention a coal pulveriser or
silo supplies fuel which is for example pulverised coal entrained
in carrier air via a supply conduit 24 to the central conduit of
the burner of FIG. 2 and thus supplies the primary fuel jet 1.
[0092] The schematic representation also provides for completeness
a source of cold recycled flue gas 17 supplied by the recycle
conduit 18 from a flue outlet (omitted for clarity), a secondary
comburant supply 16 which supplies comburant gas for example
combustion air, and a source of oxidatively inert gas 15.
[0093] A jacketing gas supply control system 32 is in fluid
communication with the sources 15, 16 and 17 and includes at least
a selective flow control system whereby a jacketing gas comprising
air, exhaust or a mixture of both optionally with additionally or
substitutionally provided other oxidatively inert gas, is supplied
via the supply conduit 34 to the annular conduit of the burner of
FIG. 2 and thus supplies the jacketing jet 6.
[0094] A secondary comburant gas supply control system 42 is in
fluid communication with the sources 16 and 17 and includes at
least a selective flow control system whereby a comburant gas
comprising air, exhaust or a mixture of both is supplied via the
supply conduit 44 to the optional additional conduits of the burner
of FIG. 2 and thus supplies the additional jets 3. A heater 43 may
preheat the comburant gas to further control conditions at the
flameless reaction zone and encourage flameless oxidation.
* * * * *