U.S. patent application number 13/195214 was filed with the patent office on 2012-08-02 for methods and apparatus for carbon dioxide-oxygen-coal combustion.
Invention is credited to Ian Hibbitt, Andrew P. Richardson, Donald P. Satchell, JR..
Application Number | 20120192773 13/195214 |
Document ID | / |
Family ID | 45559782 |
Filed Date | 2012-08-02 |
United States Patent
Application |
20120192773 |
Kind Code |
A1 |
Satchell, JR.; Donald P. ;
et al. |
August 2, 2012 |
METHODS AND APPARATUS FOR CARBON DIOXIDE-OXYGEN-COAL COMBUSTION
Abstract
A burner and method for oxidizing solid fuels wherein the burner
has a lance having one or more nozzle feeds and one or more nozzle
outlets concentrically surrounded by a primary oxidant passage
which is concentrically surrounded by a secondary oxidant passage
wherein the primary and secondary oxidant passages communicate at
their proximal ends with a gas supply, the lance having a distal
and proximal end and the one or more nozzle feeds is in
communication with a gas supply.
Inventors: |
Satchell, JR.; Donald P.;
(Chatham, NJ) ; Richardson; Andrew P.; (Clinton,
NJ) ; Hibbitt; Ian; (Ashbourne, GB) |
Family ID: |
45559782 |
Appl. No.: |
13/195214 |
Filed: |
August 1, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61369894 |
Aug 2, 2010 |
|
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|
Current U.S.
Class: |
110/348 ;
110/347; 431/187 |
Current CPC
Class: |
F23D 1/00 20130101; Y02E
20/34 20130101; Y02E 20/344 20130101; F23C 2900/06041 20130101;
Y02E 20/32 20130101; F23L 2900/07006 20130101; F23M 5/025 20130101;
Y02E 20/322 20130101; F23L 7/007 20130101; F23C 6/045 20130101;
F22B 37/00 20130101; F23L 2900/07001 20130101 |
Class at
Publication: |
110/348 ;
431/187; 110/347 |
International
Class: |
F23L 7/00 20060101
F23L007/00; F23D 1/00 20060101 F23D001/00; F23C 9/00 20060101
F23C009/00; F23K 3/02 20060101 F23K003/02 |
Claims
1. A burner for oxidizing solid fuels comprising a lance having one
or more nozzle feeds and one or more nozzle outlets concentrically
surrounded by a primary oxidant passage which is concentrically
surrounded by a secondary oxidant passage wherein said primary and
secondary oxidant passages communicate at their proximal ends with
one or more gas supplies, said lance having a distal and proximal
end and said one or more nozzle feeds is in communication with a
gas supply.
2. The burner as claimed in claim 1 wherein said solid fuels are
selected from the group consisting of coal, coke, peat, biomass and
mixtures thereof.
3. The burner as claimed in claim 1 wherein said solid fuel is
transported via a primary oxidant stream through said primary
oxidant passages.
4. The burner as claimed in claim 3 wherein said primary oxidant
stream has a volumetric oxygen content less than 32%.
5. The burner as claimed in claim 3 wherein said primary oxidant
stream has a volumetric oxygen content less than 25%.
6. The burner as claimed in claim 3 wherein said primary oxidant
stream has a volumetric oxygen content less than 21%.
7. The burner as claimed in claim 1 wherein a secondary oxidant
stream is fed through said secondary oxidant passage.
8. The burner as claimed in claim 1 wherein said secondary oxidant
stream has a volumetric oxygen content less than 40%.
9. The burner as claimed in claim 8 wherein said secondary oxidant
stream has a volumetric oxygen content less than 30%.
10. The burner as claimed in claim 8 wherein said secondary oxidant
stream has a volumetric oxygen content less than 28%.
11. The burner as claimed in claim 1 wherein said nozzles at said
distal end of said lance is angled in a manner whereby discharge
streams from said lance do not intercept an outer wall of said
primary oxidant passage.
12. The burner as claimed in claim 3 wherein said nozzles at said
distal end of said lance are positioned to direct oxygen into a
flow path of said primary oxidant stream containing solid fuel.
13. The burner as claimed in claim 1 wherein said burner further
comprises a quarl.
14. The burner as claimed in claim 13 wherein said nozzles at said
distal end of said lance are arranged complimentary to said primary
and secondary oxidant streams direction through said quad.
15. The burner as claimed in claim 13 wherein said nozzles at said
distal end of said lance are angled so their projected axis
intercepts an outer edge of said burner quad.
16. The burner as claimed in claim 1 wherein said burned is adapted
for external oxidant staging.
17. A method for oxidizing solid fuels comprising feeding said fuel
and oxidant mixtures of oxygen and carbon dioxide to a burner
comprising a lance having one or more nozzle feeds and one or more
nozzle outlets concentrically surrounded by a primary oxidant
passage which is concentrically surrounded by a secondary oxidant
passage wherein said primary and secondary oxidant passages
communicate at their proximal ends with one or more gas supplies,
said lance having a distal and proximal end and said one or more
nozzle feeds is in communication with a gas supply.
18. The method as claimed in claim 17 wherein said solid fuels are
selected from the group consisting of coal, coke, peat, biomass and
mixtures thereof.
19. The method as claimed in claim 17 wherein said solid fuel is
transported via a primary oxidant stream through said primary
oxidant passages.
20. The method as claimed in claim 19 wherein said primary oxidant
stream has a volumetric oxygen content less than 32%.
21. The method as claimed in claim 19 wherein said primary oxidant
stream has a volumetric oxygen content less than 25%.
22. The method as claimed in claim 19 wherein said primary oxidant
stream has a volumetric oxygen content less than 21%.
23. The method as claimed in claim 17 wherein a secondary oxidant
stream is fed through said secondary oxidant passage.
24. The method as claimed in claim 17 wherein said secondary
oxidant stream has a volumetric oxygen content less than 40%.
25. The method as claimed in claim 24 wherein said secondary
oxidant stream has a volumetric oxygen content less than 30%.
26. The method as claimed in claim 24 wherein said secondary
oxidant stream has a volumetric oxygen content less than 28%.
27. The method as claimed in claim 17 wherein said nozzles at said
distal end of said lance is angled in a manner whereby discharge
streams from said lance do not intercept an outer wall of said
primary oxidant passage.
28. The method as claimed in claim 19 wherein said nozzles at said
distal end of said lance are positioned to direct oxygen into a
flow path of said primary oxidant stream containing solid fuel.
29. The method as claimed in claim 17 wherein said burner further
comprises a quad.
30. The method as claimed in claim 30 wherein said nozzles at said
distal end of said lance are arranged complimentary to said primary
and secondary oxidant streams direction through said quarl.
31. The method as claimed in claim 30 wherein said nozzles at said
distal end of said lance is angled so their projected axis
intercepts an outer edge of said burner quad.
32. The method as claimed in claim 17 wherein said burned is
adapted for external oxidant staging.
33. The method as claimed in claim 17 wherein said oxidant stream
issuing through said distal end of said lance is at a higher
velocity than said primary oxidant.
34. The method as claimed in claim 17 wherein said oxidant stream
issuing through said distal end of said lance is less than four
times the velocity of said primary oxidant.
35. The method as claimed in claim 17 wherein said fuel and oxidant
mixture comprises oxygen and carbon dioxide.
36. The method as claimed in 35 wherein said fuel and oxidant
mixture is formed by mixing flue gases from a combustion process
with industrially pure oxygen.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application claims priority from U.S. provisional
patent application Ser. No. 61/369,894 filed on Aug. 2, 2010.
BACKGROUND OF THE INVENTION
[0002] The invention provides for the use of a burner for carbon
dioxide-oxygen-coal combustion processes. More particularly, the
invention provides for a lance in connection with a burner to more
effectively combust a solid fuel, such as coal, with an oxidant
mixture comprising predominantly of carbon dioxide and oxygen, such
as may be formed by the addition of substantially pure oxygen with
flue gas recirculated from said combustion process.
[0003] Air-coal burners and steam boilers for electrical power
generation have been developed over many years through a process of
trial and error. Typically, the motive air that is used to
pulverize the coal is also used as the primary air in the air-coal
burners. Primary air and pulverized coal typically flow through an
annular conduit that is mesial to coaxial annular conduit for the
secondary air. A helical secondary oxidant flow patter is often
used to increase the mixing rate with the primary air-coal stream
with the secondary air stream.
[0004] In order to more cost effectively recover carbon dioxide
from coal fired power stations, electrical power utilities are
evaluating substituting a predominantly carbon dioxide-oxygen
oxidant for the traditional air oxidant. The carbon dioxide-oxygen
oxidant is formed by mixing a CO2 rich flue gas from the combustion
process with industrial oxygen, and as such may also contain water
vapor, nitrogen, and minor constituents arising from the combustion
process. However, substitution of the nitrogen diluent in the air
oxidant with carbon dioxide decreases the coal combustion flame
velocity more rapidly than the coal flammability limit and flame
temperature. If one tries to increase the carbon
dioxide-oxygen-coal flame velocity to acceptable values by
increasing the primary oxidant oxygen in carbon dioxide
concentration, then the fire hazard in the coal grinding mill also
increases. If one increases the flame velocity to acceptable values
by increasing the oxygen in carbon dioxide concentration in the
secondary oxidant stream, then excessive heat fluxes are observed
in the near burner region.
[0005] An additional trend is in the utilization of increasing
quantities of biomass mixed with coal, or even 100% biomass firing.
The biomass feed may be any organic material, including
agricultural crops and agricultural wastes and residues, wood and
wood wastes and residues, animal wastes, municipal wastes, algae
and aquatic plants. The biomass feed may be dried, chopped, ground,
or pelletized. Typical biomass feed examples include wood chips,
wood charcoal, pelletized grass, and similar materials Biomass,
particularly wet biomasses can further lead to reductions in flame
speed and more unstable combustion conditions. As such the addition
of biomass can lead combustion related problems that may not be
overcome by increasing the oxygen content of the secondary air.
[0006] The invention seeks to limit these concerns by adding an
oxidant lance to a conventional air-coal burner assembly.
SUMMARY OF THE INVENTION
[0007] The invention provides for the use of a predominantly carbon
dioxide-oxygen oxidant in place of air oxidant in a solid fuel
burner. The solid fuel herein after referred to as coal may be any
solid hydrocarbon fuel, such as various grades of coal, peat, coke,
or biomass The invention further provides for an improved coal
burner assembly which comprises an air-coal burner equipped with an
oxidant lance, thereby providing a better combustion with an
oxygen-carbon dioxide-coal mixture than an air-coal mixture.
[0008] In an embodiment of the invention, there is disclosed a
burner for combusting fuels such as coal comprising a lance having
one or more nozzle feeds and one or more nozzle outlets
concentrically surrounded by a primary oxidant passage which is
concentrically surrounded by a secondary oxidant passage wherein
said primary and secondary oxidant passages communicate at their
proximal ends with a gas supply, said lance having a distal and
proximal end and said one or more nozzle feeds is in communication
with a gas supply.
[0009] In another embodiment of the invention there is disclosed a
method for oxidizing coal comprising feeding a mixture of oxygen,
carbon dioxide and coal to a burner comprising a lance having one
or more nozzle feeds and one or more nozzle outlets concentrically
surrounded by a primary oxidant passage which is concentrically
surrounded by a secondary oxidant passage wherein said primary and
secondary oxidant passages communicate at their proximal ends with
a gas supply, said lance having a distal and proximal end and said
one or more nozzle feeds is in communication with a gas supply.
[0010] The solid fuel that can be used are selected from the group
consisting of coal, coke, peat, biomass and mixtures thereof. The
solid fuel is typically transported via a primary oxidant stream
through the primary oxidant passages. The primary oxidant stream
will have a molar oxygen concentration less than 32%, preferably
less than 25% and more preferably less than 21%.
[0011] The fuel and oxidant mixture comprises oxygen and carbon
dioxide and is typically formed by mixing flue gases from a
combustion process with industrially pure oxygen.
[0012] A secondary oxidant stream is fed through the secondary
oxidant passage and the secondary oxidant stream has a molar oxygen
concentration less than 40%, preferably less than 30% and more
preferably less than 28.
[0013] The nozzles at the distal end of the lance are angled in a
manner whereby the discharge streams from the lance do not
intercept an outer wall of the primary oxidant passage. Further,
these nozzles are positioned to direct oxygen into a flow path of
the primary oxidant stream containing solid fuel.
[0014] The burner further comprises a quad and the nozzles at the
distal end of the lance are arranged complementary to the primary
and secondary oxidant streams being directed through the quarl. In
some instances, the distal end of the lance is angled so that the
projected axis intercepts an outer edge of the burner quarl.
[0015] The burner can be adapted for external oxidant staging.
[0016] The oxidant stream that issues through the distal end of the
lance is at a higher velocity than the primary oxidant. Typically,
this velocity is less than four times the velocity of the primary
oxidant stream.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a schematic view of an air-coal burner.
[0018] FIG. 2 is a schematic A-A view of the air-coal burner of
FIG. 1.
[0019] FIG. 3 is a schematic view of an air-coal burner with
oxidant lance.
[0020] FIG. 4 is a schematic front view of an air-coal burner with
oxidant lance.
[0021] FIG. 5 is a graph showing the oxidant angle nozzle
relationships.
[0022] FIG. 6 is a schematic of the burner with an alternative
oxidant lance embodiment.
[0023] FIG. 7 is a schematic showing a nozzle for use with a lance
and burner shown in FIG. 6.
[0024] FIG. 8 is a schematic showing an alternative nozzle for use
with a lance and burner as shown in FIG. 6.
DETAILED DESCRIPTION OF THE INVENTION
[0025] FIG. 1 and FIG. 2 show an air-coal burner. The air-coal
burner is typically round in shape as seen in FIG. 2. Viewing the
air-coal burner from the side as in FIG. 1 shows a furnace wall 10
at the top and bottom which surrounds the air-coal burner. The
air-coal burner comprises a quarl 20 which surrounds the closed end
7 of the air-coal burner. There are two openings, the first being
the secondary air passage 6 which will concentrically surround the
second opening, coal and primary air passage 5.
[0026] FIG. 2 shows the air-coal burner of FIG. 1 along the A-A
axis and proffers a view of the air-coal burner from its end. The
furnace wall 10 is shown surrounding the quarl 20 which has two
openings in its middle. The first opening is the secondary air
passage 6 which concentrically surrounds the second opening, the
coal and primary air passage 5. Both these passages concentrically
surround the closed end 7 of the air-coal burner.
[0027] FIG. 3 shows the air-coal burner with oxidant lance of the
invention. This A-A sideways view shows the quarl 40 and the burner
wall 30 which in turn surround the closed end 35 of the air-coal
burner with oxidant lance. Concentrically surrounding the closed
end 35 is the primary oxidant passage 36 which is in fluid
communication with the motive fluid or coal transport gas and coal
channel 38. The secondary oxidant passage 37 is on the outside of
this primary oxidant passage 36.
[0028] The coal channel 38 and primary oxidant passage
concentrically surround the closed end 35 of the air-coal burner.
As seen in FIG. 3, the oxidant lance nozzle inlet 101 fluidly
connects to the oxidant lance feed channel 39. The outlet of the
oxidant lance nozzle extends towards the front of the air-coal
burner and is angled outwards from the inlet to the outlet of the
oxidant lance nozzle. In FIG. 3, the angle is 11.2.degree. from
center.
[0029] FIG. 4 is the front facing view of the air-coal burner with
oxidant lance of FIG. 3. The quarl 40 surrounds concentrically the
secondary oxidant passage 37 which in turn concentrically surrounds
the primary oxidant passage 36. Both these passages concentrically
surround the oxidant lance nozzle inlets (nozzle feed) and nozzle
outlets, 45 and 50 respectively. As seen in FIG. 4, both the
oxidant lance nozzle outlets 50 and nozzle feeds 45 comprise
several nozzles in concentric relation to each other. In this
instance, the nozzle yaw angle is 32.1.degree.
[0030] In Table 1 below, the differences between an air-coal burner
using air versus an air-coal burner using a mixture of carbon
dioxide and oxygen are shown.
TABLE-US-00001 TABLE 1 Comparison of Air-Coal Burner versus
CO.sub.2--O.sub.2-Coal Burner Parameter Air CO.sub.2--O.sub.2
Overall Burner Properties Primary & Secondary Oxidant O.sub.2
(vol. % O.sub.2) 21% 28% Secondary air channel diameter (mm) 142
142 Primary & Secondary Oxidant (l/sec) 157 157 Coal Transport
Gas O.sub.2 Concentration (mol/%) 21% 21% Gas flow rate (l/sec) 25
25 Gas velocity (M/sec) 13 13 Oxidant Lance Gas O.sub.2
Concentration (mol/%) 40% Gas flow rate (l/sec) 28 Lance feed gas
velocity (l/sec) 13 Nozzle velocity (m/sec) 39 Primary Oxidant
(Mixed Oxidant Lance and Coal Transport Gases) O.sub.2
Concentration (mol/%) 21% 31% Gas flow rate (l/sec) 25 53 Gas
velocity (M/sec) 13 13 Secondary Oxidant O.sub.2 Concentration
(mol/%) 21% 26% Gas flow rate (l/sec) 132 104 Gas velocity (M/sec)
20 20
[0031] FIG. 5 is a graph showing the oxidant nozzle angle
relationships. This graph plots the central angle between the
nozzle inlet and outlet versus the oxidant nozzle yaw angle for
four separate parameters. The parameters were determined by the
ratio of primary oxidant inside diameter divided by the inside
diameter of the oxidant lance. As seen from FIGS. 3 and 4, the
nozzle yaw angle is 32.1.degree. and the nozzle pitch angle is
11.2.degree. for the example having a parameter of 1.57.
[0032] The overall oxygen in carbon dioxide concentration was set
at about 28 molar percent to yield roughly equivalent adiabatic
flame temperatures for the air and carbon dioxide-oxygen oxidants.
The burner outside diameter was held constant so that the carbon
dioxide-oxygen burner can use the air burner mounting system. The
overall oxidant flow rate was held constant which would result in
an approximate 30% increase in thermal output. Similar techniques
could be used for the less demanding constant thermal output basis.
The coal transport gas oxygen in carbon dioxide content was set at
21 molar percent which would decrease the coal grinding mill fire
hazard concern at higher oxygen concentrations.
[0033] The addition of oxidant lance oxidant increased the primary
oxidant oxygen in carbon dioxide content to 31 molar percent in
order to roughly match the air-coal flame velocity. Sixteen oxidant
lance nozzles as noted in FIG. 4 with gas velocities about three
times the transport gas-coal and mixed primary oxidant-coal
velocities were provided with an elevation angle of about 11
degrees and yaw angle of 32 degrees relative to the transport
gas-pulverized coal stream to ensure rapid mixing with the motive
gas-coal. The primary oxidant then, with the optimum concentration
for flame stability is fed to the quad.
[0034] In the above embodiment of the invention a primary oxidant
was thus provided by the enrichment of the coal transport gas with
a lanced oxidant to a higher level of oxygen within the discharge
end of the burner and, as such, delivering a ready mixed oxygen
concentration suitable for a stable combustion into the burner
quarl.
[0035] In a further embodiment of this invention the lance nozzles
75 are located so as to inject an oxidant directly into the burner
combustion space 93 within the burner quarl 60, as shown in FIG. 6.
For purposes of representation, the numbering scheme in FIG. 6 is
also employed in FIG. 7 and FIG. 8. By introducing the lance
oxidant 75A external to the primary oxidant passage referred to in
the above embodiment, concerns about elevated oxygen concentrations
within a fuel containing line are alleviated. In such an embodiment
as concerns over high oxidant levels are reduced industrially pure
oxygen may be delivered through the lance 70 as opposed to a mixed
or diluted gas. This has the advantage of reducing the size of the
equipment and avoiding a gas mixing device and control thereof.
Such nozzles 75 may be located on the closed end of the lance 70 or
in the sides of a protruding lance or in a combination of both, as
shown by example in FIGS. 7 and 8. The nozzles 75 are located and
angled outwards such that the lance oxidant 75A has a trajectory 90
to intercept with the expanding fuel laden transport oxidant 80
within the burner quarl 60. By positioning the intercept to be
within the burner quad 60 proximal the desired location of the
flame root 92, the local combination of the lance oxidant 75A and
transport oxidant 80 creates a primary oxidant 94 with conditions
conducive for flame stabilization.
[0036] The flow patterns of the expanding oxidant streams (75A, 80
and 85) and the region for stabilization of the flame root 91 may
be determined by CFD modeling or by visual observation. A further
method for determining the angle of the lance oxidant nozzles 75 is
for them to be angled in a divergent manner towards the outer lip
or edge 65 of the burner quarl 60. The nozzles 75 may further be
angled to induce a swirling motion complimentary to the swirling
motion in combustion space 93 of any of the transport and secondary
streams 80 and 85. In order to direct the lance oxidant jets 75A
into and mix with the fuel laden transport oxidant stream it is
advantageous to operate the lance oxidant nozzles 75 at a greater
velocity than the transport oxidant stream 80. By orienting the
lance oxidant nozzles 75 in such a divergent manner and by
operation at velocities greater than that of the transport oxidant
stream the fluid recirculation patterns 100 important for a stable
combustion process in such a burner are reinforced.
[0037] As exemplified in Tables 2a and 2b a central lance
delivering relatively modest quantities of pure oxygen can deliver
significant increases in the oxygen concentration when mixed with
the transport oxidant. In these cases the secondary oxidant oxygen
content has been maintained at a constant level of 26 mol. % which
has resulted in a variation in the overall oxygen content, however
the secondary oxidant oxygen content can be raised or lowered
slightly to maintain an overall or global desired oxygen
concentration. In these cases the lance oxidant nozzles are
operated at a velocity of 45 m/s or approximately 3.5 times the
velocity of the transport oxidant
TABLE-US-00002 TABLE 2a Effect of Lance Oxidant flow on Combined
Transport and Lance Stream (Primary) Composition and Global Oxygen
Enrichment. Transport Lance Primary Secondary Global Case 1 O2
Concentration 21 100 26.9 26 26.1 (mol. %) Volumetric Flow 25 2.0
27.0 130.0 157.0 (l/s) Contained Oxygen 5.25 2.0 7.3 33.8 41.1 Flow
(l/s) Case 2 O2 Concentration 21 100 31.9 26 27.1 (mol. %)
Volumetric Flow 25 4.0 29.0 128.0 157.0 (l/s) Contained Oxygen 5.25
4.0 9.3 33.3 42.5 Flow (l/s) Case 3 O2 Concentration 21 100 40.2 26
29.0 (mol. %) Volumetric Flow 25 8.0 33.0 124.0 157.0 (l/s)
Contained Oxygen 5.25 8.0 13.3 32.2 45.5 Flow (l/s) Secondary
Stream composition kept at constant oxygen content of 26%, overall
flowrate maintained at 157 l/s and nozzle velocity of 45 m/s.
TABLE-US-00003 TABLE 2b Nozzle Configuration for Cases in Table 2a
Case 1 Case 2 Case 3 Nozzle Diameter (mm) 1.54 2.17 3.07 Primary
Oxidant Concentration (mol. %] 26.9 31.9 40.2 Global Oxidant
Concentration (mol. %) 26.1 27.1 29.0 Each case has 24 nozzles to
distribute oxygen.
[0038] While this invention has been described with respect to
particular embodiments thereof, it is apparent that numerous other
forms and modifications of the invention will be obvious to those
skilled in the art. The appended claims in this invention generally
should be construed to cover all such obvious forms and
modifications which are within the true spirit and scope of the
invention.
* * * * *