U.S. patent application number 12/569228 was filed with the patent office on 2011-03-31 for combustion rotation system for fuel-injection boilers.
Invention is credited to M. Ishaq Jameel.
Application Number | 20110076630 12/569228 |
Document ID | / |
Family ID | 43780788 |
Filed Date | 2011-03-31 |
United States Patent
Application |
20110076630 |
Kind Code |
A1 |
Jameel; M. Ishaq |
March 31, 2011 |
Combustion Rotation System for Fuel-Injection Boilers
Abstract
A combustion rotation system that utilizes the placement,
direction, and/or unbalanced fuel injection flow rates to the
burners in a fuel-injection power boiler, such as pulverized coal,
oil or gas fired boiler, to achieve Inboard/Outboard (I/O) rotation
of the combustion mass or other types of mixing of the combustion
mass. The over fired air ("OFA") ports may also be placed,
directed, and/or operated to contribute to the rotation of the
combustion mass. The fuel-injection combustion rotation system may
also be controlled while the boiler is operation, and controlled
automatically, through a master control system. The fuel-injection
combustion rotation system induces multiple vortex rotation of the
combustion mass, which is more efficient and effective than
attempting to rotate the entire combustion mass in a single
vortex.
Inventors: |
Jameel; M. Ishaq;
(Beaverton, OR) |
Family ID: |
43780788 |
Appl. No.: |
12/569228 |
Filed: |
September 29, 2009 |
Current U.S.
Class: |
431/181 ;
431/185 |
Current CPC
Class: |
F23N 5/003 20130101;
F23C 5/32 20130101; F23N 2241/10 20200101; F23L 9/04 20130101; F23C
5/28 20130101; F23N 1/022 20130101; F23N 2237/02 20200101 |
Class at
Publication: |
431/181 ;
431/185 |
International
Class: |
F23C 5/32 20060101
F23C005/32 |
Claims
1. A combustion rotation system in or for an industrial
fuel-injection boiler having a combustion section, comprising: a
boiler having first and second opposing walls; a plurality of
burners, each burner supported on the first or second boiler wall
and configured for injecting a mixture of fuel and air into the
boiler; wherein each burner has an associated fuel-injection flow
rate controller; and wherein flow rate controllers are set to
impart an unbalanced fuel-injection profile to induce multiple
rotational vortexes in the combustion mass inside the combustion
section of the boiler.
2. The combustion rotation system of claim 1, wherein: the burners
have locations on the first and second boiler walls; the burners
locations on the first boiler wall are directly opposing the burner
locations on the second boiler wall; the burners on each boiler
wall are arranged into inboard columns and outboard columns; the
flow rate controllers are set to induce an unbalanced
fuel-injection profile between the inboard columns and outboard
columns on the first boiler wall; the flow rate controllers are set
to induce an unbalanced fuel-injection profile between the inboard
columns and outboard columns on the second boiler wall; the flow
rate controllers are set to induce an unbalanced fuel-injection
profile between the inboard columns on the first boiler wall and
the inboard columns on the second boiler wall; and the flow rate
controllers are set to induce an unbalanced fuel-injection profile
between the outboard columns on the first boiler wall and the
outboard columns on the second boiler wall.
3. The combustion rotation system of claim 1, wherein: the burners
on each boiler wall are arranged into columns; each column of
burners has one or more over-fire air ports located above the
column of burners; each over-fire air ports has an associated flow
rate controller; and the over-fire air port flow rate controllers
are set to impart an unbalanced air injection profile consistent
with the unbalanced fuel-injection profile imparted by the
fuel-injection rate controllers to assist the burners in inducing
the multiple rotational vortexes in the combustion mass inside the
combustion section of the boiler.
4. The combustion rotation system of claim 1, wherein: the burners
have locations on the first and second boiler walls; the burners
locations on the first boiler wall are directly opposing the burner
locations on the second boiler wall; the burners on each boiler
wall are arranged into columns; the number of columns on each
boiler wall is four and the number of rotational vortexes is two,
or the number of columns on each boiler wall is six and the number
of rotational vortexes is three, or the number of columns on each
boiler wall is eight and the number of rotational vortexes is
four.
5. The combustion rotation system of claim 1, further comprising: a
plurality of sensors for measuring boiler parameters; and a master
controller for adjusting the fuel injection profile in response to
the measured boiler parameters.
6. The combustion rotation system of claim 1, further comprising: a
plurality of sensors for measuring boiler parameters; and a master
controller for activating boiler cleaning equipment in response to
the measured boiler parameters.
7. The combustion rotation system of claim 1, wherein: each burner
has an associated fuel-injection lateral location; wherein the
fuel-injection lateral locations on the first boiler wall are
laterally offset from the fuel-injection lateral locations on the
second boiler wall to assist in the inducement of the multiple
rotational vortexes in the combustion mass inside the combustion
section of the boiler.
8. The combustion rotation system of claim 1, wherein: each burner
having an associated fuel-injection direction; wherein one or more
of the fuel-injection directions are horizontally tilted to assist
in the inducement of the multiple rotational vortexes in the
combustion mass inside the combustion section of the boiler.
9. The combustion rotation system of claim 1, wherein: each burner
has an associated fuel-injection direction; wherein one or more of
the fuel-injection directions are vertically tilted to assist in
mixing of the combustion mass inside the combustion section of the
boiler.
10. The combustion rotation system of claim 1, wherein: the burners
on each boiler wall are arranged into columns; the fuel-injection
flow controllers are set to impart a vertically unbalanced fuel
injection profile along one or more of the columns to assist in
mixing of the combustion mass inside the combustion section of the
boiler.
11. A combustion rotation system in or for an industrial
fuel-injection boiler having a combustion section, comprising: a
boiler having first and second opposing walls; a plurality of
burners, each burner supported on the first or second boiler wall
and configured for injecting a mixture of fuel and air into the
boiler; wherein each burner has an associated fuel-injection
lateral location; wherein the fuel-injection lateral locations on
the first boiler wall are laterally offset from the fuel-injection
lateral locations on the second boiler wall to induce multiple
rotational vortexes in the combustion mass inside the combustion
section of the boiler.
12. The combustion rotation system of claim 11, wherein: each
burner has an associated fuel-injection flow rate controller; and
the flow rate controllers are set to impart an unbalanced
fuel-injection profile to assist in the inducement of the multiple
rotational vortexes in the combustion mass inside the combustion
section of the boiler.
13. The combustion rotation system of claim 12, wherein: each
burner having an associated fuel-injection direction; and one or
more of the fuel-injection directions are horizontally tilted to
assist in the inducement of the multiple rotational vortexes in the
combustion mass inside the combustion section of the boiler.
14. The combustion rotation system of claim 11, wherein: each
burner has an associated fuel-injection direction; one or more of
the fuel-injection directions are vertically tilted to assist in
mixing of the combustion mass inside the combustion section of the
boiler.
15. The combustion rotation system of claim 11, wherein: the
burners on each boiler wall are arranged into columns; the
fuel-injection flow controllers are set to impart a vertically
unbalanced fuel injection profile along one or more of the columns
to assist in mixing of the combustion mass inside the combustion
section of the boiler.
16. A combustion rotation system in or for an industrial
fuel-injection boiler having a combustion section, comprising: a
boiler having first and second opposing walls; a plurality of
burners, each burner supported on the first or second boiler wall
and configured for injecting a mixture of fuel and air into the
boiler; wherein each burner has an associated fuel-injection
direction; wherein the fuel-injection directions are set to induce
multiple rotational vortexes in the combustion mass inside the
combustion section of the boiler.
17. The combustion rotation system of claim 16, wherein: wherein
each burner has an associated fuel-injection lateral location;
wherein the fuel-injection lateral locations on the first boiler
wall are laterally offset from the fuel-injection lateral locations
on the second boiler wall to induce multiple rotational vortexes in
the combustion mass inside the combustion section of the
boiler.
18. The combustion rotation system of claim 16, wherein: each
burner has an associated fuel-injection flow rate controller; and
the flow rate controllers are set to impart an unbalanced
fuel-injection profile to assist in the inducement of the multiple
rotational vortexes in the combustion mass inside the combustion
section of the boiler.
19. The combustion rotation system of claim 16, wherein one or more
of the fuel-injection directions are vertically tilted to assist in
mixing of the combustion mass inside the combustion section of the
boiler.
20. The combustion rotation system of claim 16, wherein: the
burners on each boiler wall are arranged into columns; the
fuel-injection flow controllers are set to impart a vertically
unbalanced fuel injection profile along one or more of the columns
to assist in mixing of the combustion mass inside the combustion
section of the boiler.
Description
REFERENCE TO RELATED APPLICATIONS
[0001] The present invention claims priority to U.S. Provisional
Patent Application Ser. No. 61/100,949 entitled "Method and System
for Multiple Vortex Combustion Rotation in a Coal Fired Boiler"
filed 29 Sep. 2008, which is incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to industrial boilers and,
more particularly, relates to a combustion rotation system for an
industrial fuel-injection boiler in which the burners and over fire
air (OFA) ports are located, directed and operated to induce
multiple rotational vortexes in the combustion mass inside the
combustion section of the fuel-injection boiler.
BACKGROUND OF THE INVENTION
[0003] For decades, industrial fuel-injection boilers have been
operated with balanced fuel injection profiles that produce rising,
non-rotating combustion masses inside the combustion section of the
boiler. No systems are presently available for rotating or
otherwise mixing the combustion mass in conventional fuel-injection
boilers. U.S. Pat. No. 7,185,594 describes a combustion rotation
system for a chemical recovery boiler in which supplemental air is
injected into the combustion chamber to induce rotation of the
combustion mass. This approach is not amenable for use in a
fuel-injection boiler, such as a pulverized coal, oil or gas
boiler, because injection of supplemental air to induce rotation of
the combustion mass would change the air-fuel mixture in the boiler
and impart other undesirable combustion characteristics. U.S. Pat.
No. 5,809,910 describes a waste incinerator using over fire air
(OFA) ports to rotate the combustion mass to more completely
incinerate the contaminants in the waste product. This boiler is
not a fuel injection boiler and describes rotating the entire
combustion mass in a single vortex combustion rotation. Therefore,
there remains a need for a combustion rotation system suitable for
fuel-injection boilers, such as coal, oil and gas boilers.
SUMMARY OF THE INVENTION
[0004] The present invention may be implemented in a combustion
rotation system in or for an industrial fuel-injection boiler with
a combustion section, first and second opposing boiler walls, and a
plurality of burners. Each burner is supported on the first or
second boiler wall and configured for injecting a mixture of fuel
and air into the boiler. Each burner has an associated
fuel-injection flow rate controller. The flow rate controllers are
set in a coordinated manner to impart an unbalanced fuel-injection
profile to induce multiple rotational vortexes in the combustion
mass inside the combustion section of the boiler.
[0005] In addition, each column of burners typically has one or
more over-fire air ports located above the column of burners, and
each over-fire air port has an associated flow rate controller. The
over-fire air port flow rate controller may be set to impart an
unbalanced air injection profile consistent with the unbalanced
fuel-injection profile imparted by the fuel-injection rate
controllers to assist the burners in inducing the multiple
rotational vortexes in the combustion mass inside the combustion
section of the boiler.
[0006] In a typical configuration, the burner locations on the
first boiler wall are directly opposing the burner locations on the
second boiler wall and the burners on each boiler wall are arranged
into inboard columns and outboard columns. For an inboard/outboard
rotational technique, the flow rate controllers are set to induce
an unbalanced fuel-injection profile between the inboard columns
and outboard columns on the first boiler wall, an unbalanced
fuel-injection profile between the inboard columns and outboard
columns on the second boiler wall, an unbalanced fuel-injection
profile between the inboard columns on the first boiler wall and
the inboard columns on the second boiler wall, and an unbalanced
fuel-injection profile between the outboard columns on the first
boiler wall and the outboard columns on the second boiler wall.
[0007] This combustion technique may be extended to boilers with
larger numbers of columns of burners. In a first illustrative
configuration, the number of columns on each boiler wall is four
and the number of rotational vortexes is two. In a second
illustrative configuration, the burners locations on the first
boiler wall are directly opposing the burner locations on the
second boiler wall. In a third second illustrative configuration,
the number of columns on each boiler wall is six and the number of
rotational vortexes is three. In a fourth illustrative
configuration, the number of columns on each boiler wall is eight
and the number of rotational vortexes is four.
[0008] In another combustion rotation technique, the fuel-injection
lateral locations on the first boiler wall are laterally offset
from the fuel-injection lateral locations on the second boiler wall
to assist in the inducement of the multiple rotational vortexes in
the combustion mass inside the combustion section of the boiler. In
addition, one or more of the fuel-injection directions may be
horizontally tilted to assist in the inducement of the multiple
rotational vortexes in the combustion mass inside the combustion
section of the boiler. As another technique, one or more of the
fuel-injection directions may be vertically tilted to assist in
mixing of the combustion mass inside the combustion section of the
boiler. As yet another technique, the fuel-injection flow
controllers may be set to impart a vertically unbalanced fuel
injection profile along one or more of the columns to assist in
mixing of the combustion mass inside the combustion section of the
boiler. These techniques may be implemented individually or in
various combinations to rotate and mix the combustion mass. A
master controller may also be used to rotate and/or mix the
combustion mass and/or actuate boiler cleaning equipment while the
boiler is in operation in response to measured boiler parameters,
such as temperature, pressure, gas analysis, and heat flux.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is a conceptual side view of a conventional
fuel-injection boiler without combustion rotation.
[0010] FIG. 2 is a conceptual side view of a conventional
fuel-injection boiler with burner ports and over fire air ("OFA")
ports imparting rotation to the combustion mass inside the
boiler.
[0011] FIG. 3 is a conceptual front view of a first boiler wall
illustrating the burner and OFA ports on one side of the
boiler.
[0012] FIG. 4 is a conceptual front view of a second boiler wall
opposing the first boiler wall illustrating the burner and OFA
ports on the opposing side of the boiler.
[0013] FIG. 5 is a conceptual perspective view of a fuel-injection
boiler illustrating opposing placement of the burner and OFA
ports.
[0014] FIG. 6 is a conceptual top view of burner ports in a first
alternative fuel-injection boiler with laterally opposing burner
ports illustrating the lateral placement and operation of the
burner ports.
[0015] FIG. 7 is a conceptual top view of burner ports in a second
alternative fuel-injection boiler with laterally opposing burner
ports illustrating the lateral placement and operation of the
burner ports.
[0016] FIG. 8 is a conceptual top view of burner ports in a third
alternative fuel-injection boiler with laterally opposing burner
ports illustrating the lateral placement and operation of the
burner ports.
[0017] FIG. 9 is a conceptual top view of burner ports in a first
alternative fuel-injection boiler with laterally offset burner
ports illustrating the lateral placement and operation of the
burner ports.
[0018] FIG. 10 is a conceptual top view of burner ports in a second
alternative fuel-injection boiler with laterally offset burner
ports illustrating the lateral placement and operation of the
burner ports.
[0019] FIG. 11 is a conceptual top view of burner ports in a third
alternative fuel-injection boiler with laterally offset burner
ports illustrating the lateral placement and operation of the
burner ports.
[0020] FIG. 12 is a conceptual front view of a boiler wall
illustrating the vertical placement of the burner and OFA ports on
one side of the boiler.
[0021] FIG. 13 is a conceptual side view of burner ports in a first
alternative fuel-injection boiler with vertically opposing burner
ports illustrating the vertical placement and operation of the
burner ports.
[0022] FIG. 14 is a conceptual side view of burner ports in a
second alternative fuel-injection boiler with vertically opposing
burner ports illustrating the vertical placement and operation of
the burner ports.
[0023] FIG. 15 is a conceptual top view of burner ports in a first
alternative fuel-injection boiler with laterally offset and
laterally directed burner ports illustrating the lateral placement,
operation and orientation of the burner ports.
[0024] FIG. 16 is a conceptual top view of burner ports in a second
alternative fuel-injection boiler with laterally offset and
laterally directed burner ports illustrating the lateral placement,
operation and orientation of the burner ports.
[0025] FIG. 17 is a conceptual top view of burner ports in a first
alternative fuel-injection boiler with laterally offset and
progressively directed burner ports illustrating the lateral
placement, operation and orientation of the burner ports.
[0026] FIG. 18 is a conceptual top view of burner ports in a second
alternative fuel-injection boiler with laterally offset and
progressively directed burner ports illustrating the lateral
placement, operation and orientation of the burner ports.
[0027] FIG. 19 is a conceptual side view of burner ports in as
alternative fuel-injection boiler with laterally opposing and
vertically directed burner ports illustrating the vertical
placement, operation and orientation of the burner ports.
[0028] FIG. 20 is a functional block diagram of a fuel-injection
burner with adjustable burner and OFA ports and a control system
for adjusting the flow and direction of the burner and OFA ports
while the boiler is in operation.
DETAILED DESCRIPTION
[0029] The present invention may be implemented in a combustion
rotation system that utilizes the placement, direction, and/or
unbalanced fuel injection flow rates to the burners in a
fuel-injection power boiler, such as pulverized coal, oil or gas
fired boiler, to achieve rotation of the combustion mass and other
types of mixing of the combustion mass. The over fired air ("OFA")
ports may also be placed, directed, and/or operated to contribute
to the rotation of the combustion mass. For example, in a typical
boiler configuration with four opposing columns of burner and OFA
ports on opposite walls of the boiler, the jets are located,
directed and/or operated to produce two counter-rotating
inboard/outboard vortices in the combustion mass. The
fuel-injection combustion rotation system may also be controlled
while the boiler is operation, and controlled automatically,
through a master control system.
[0030] U.S. Pat. No. 7,185,594 describes a combustion rotation
system for a chemical recovery boiler in which supplemental air is
injected above the combustion chamber to induce rotation of the
combustion mass. While the injection of supplemental air into a
chemical recovery boiler does not adversely affect the combustion
process, this approach is not amenable for use in a fuel-injection
boiler because the injection of additional air into the boiler to
rotate the combustion mass would change the air-fuel mixture and
impart other undesirable combustion characteristics.
[0031] The present invention solves this problem by placing,
directing and/or controlling the air/fuel flow rate to the
combustion burners involved in the combustion process to induce
rotation of the combustion mass in the combustion section of the
boiler without adversely affecting the air-fuel mixture. The
placement, direction, and injection flow rates to the OFA ports may
also be selected or controlled to assist in combustion rotation.
The fuel-injection combustion rotation system induces multiple
vortex rotation of the combustion mass, which is more efficient and
effective than attempting to rotate the entire combustion mass in a
single vortex.
[0032] As opposed to the chemical recovery boiler, a fuel-injection
boiler, such as a pulverized coal, oil or gas fired boiler,
introduces the fuel and combustion air through the same jet or
burner. This means that one cannot just add additional air ports to
rotate the combustion mass, as taught in U.S. Pat. No. 7,185,594,
since this would result in an increase in the air/fuel ratio. This
is not desirable because increasing the air/fuel ratio will
increase the flue gas through the boiler resulting in multiple
problems inside the boiler and in the back-end air pollution
equipment. Altering the air/fuel ratio would also reduce the
efficiency of the boiler, which is typically designed to obtain a
desired air/fuel ratio prior to the injection of supplemental air
for combustion rotation.
[0033] Rather than adding supplemental air to impart combustion
rotation, the fuel-injection combustion rotation system utilizes
the setup (i.e., placement, direction and/or flow rates) of the
burners to impart combustion rotation, which is a significant
adaptation and improvement over the supplemental air approach to
imparting combustion rotation in a chemical recovery boiler. For
some boilers, this means some burners become high flow burners
while others become low flow burners. The high flow burners will
flow more fuel/air than the low flow burners. In a coal fired
boiler, the minimum amount of coal may be passed to the low flow
burners based on the minimum allowable coal flow for the supply
pipe, while the flow to the high flow burners is increased above
the conventional level. This type of unbalanced fuel injection
profile is quite the opposite of traditional practice where a lot
of trouble is taken to balance the fuel flow to each burner.
[0034] A typical wall fired pulverized coal boiler contains
multiple levels of burners on opposing walls. These burners on are
arranged above each other in vertical stacks or columns and
positioned so that there are similar columns of burners on opposite
sides of the boiler (i.e., directly across the boiler. If the outer
burners are chosen as the high flow burners, then the inner burners
will be the low flow burners to impart rotation vortexes into the
combustion mass. The opposite wall will have the opposite
arrangement with high flow going to the inboard burners and low
flow to the outboard burners. In this way the opposing jets will
not interfere with each other. The resulting flow pattern produces
two counter rotating inboard/outboard vortices. The spin is
reinforced as the flue gases flow up and past each level of the
burner and OFA jets, which are similarly operated. Even though the
burner flows are biased, the total fuel flow and air/fuel ratio per
level typically remains approximately the same as in the
conventional balanced fuel injection technique, although these
parameters may be altered and re-optimized if desired. In
particular, the total fuel flow and air/fuel ratio may be optimized
for efficiency, pollution control, or other desired characteristics
to take advantage of the higher efficiency combustion obtained with
combustion rotation.
[0035] Rotating the combustion mass significantly increases the
mixing between the air and fuel, which leads to an increase in
combustion efficiency enabling more complete combustion reducing
the amount of carbon monoxide generated in comparison to the
conventional balanced fuel injection technique. The spiraling
upward movement of the combustion mass increases the residence time
for the fuel in the combustion section of the boiler, enabling it
to burn more completely. The improved combustion results in a
greater heat release in the furnace and a reduction of un-burnt
fuel in the ash. All of these are desirable improvements.
[0036] NOx that is generated as part of combustion is considered a
major pollutant. Hence reducing NOx is highly desired. NOx forms
through two mechanisms. One is the oxidation of the N2 in the
atmosphere at high temperatures while the other is through a series
of chemical reactions that combine the N in the fuel with the O2 in
the atmosphere. In order to control the NOx production, combustion
engineers have staged the combustion. This is done by removing some
percentage of the air in the burner zone and introducing it further
in the furnace. To do this, multiple openings known as air ports
are made in the boiler wall. These ports are referred to as Over
Fired Air ("OFA") ports. Typically these air ports are lined up
vertically with the burners and are opposing OFA ports on the other
side of the boiler. In the fuel-injection combustion rotation
system, the certain OFA ports may be blocked off so that there are
high air flow to OFA ports above the high flow burners and no flow
to the OFA ports above the low flow burners.
[0037] Computation Fluid Dynamics (CFD) is widely used today to
model the complex combustion and fluid flow processes in a boiler.
The boiler shown in FIG. 5 was setup in a computer model and three
numerical simulations were made to see the effects of the firing
strategy shown in FIG. 6. The existing setup was the base case and
two other cases case 1 and case 2 were run with the firing strategy
shown in FIG. 6. Case 1 had the same air splits at every burner
level and the OFA as the base case. In case 2 the air was shifted
from the burner zone to the OFA zone in order to reduce the NOx.
The percentage changes in the firing system and the key boiler
parameters are shown below in Table 1. The primary air (1RY)
carries the coal while the secondary (2RY) air provides much of the
combustion air and is brought in through the burner as well.
TABLE-US-00001 TABLE 1 Case 1 Case 2 HI/ LO/ HI/ HI/ LO/ HI/ INPUT
Base Base LO Base Base LO Coal Flow/burner 134% 66% 205% 134% 66%
205% 1RY Air Flow/burner 134% 66% 205% 134% 66% 205% 2RY Air
Flow/burner 130% 63% 205% 92% 45% 205% OFA Flow 200% 0% 1059% 0%
RESULTS Case 1-Base Case 2-Base Gas Temp at SH exit -2% -1% CO at
SH exit -73% -33% Nox at SH exit 13% -47% C in Ash(LOI) -81% -81%
Total Heat transfer 5% 1%
In case 1 the high flow burners (HI) flowed 34% more coal than the
base case while the low flow burners (LO) flowed 34% less. The
ratio between the HI and LO flow burners was 2:1. In the case of
the OFA the total number of ports used was reduced from 8 to 4
hence doubling the flow per port. The enhanced mixing results in a
73% reduction in carbon monoxide (CO) and an 81% reduction of
unburnt carbon in the ash. However the NOx generation went up by
13%. This is due to the fact that more of the nitrogen came in
contact with the air due to the better mixing.
[0038] To offset this more of the secondary (2RY) air was move to
the OFA resulting in a 159% increase in OFA. This results in
substoicheometric conditions in the burner zone resulting in an
higher CO at the superheater exit giving a 33% reduction versus 73%
in case 1. As expected the NOx generation went down by 47% from the
base case. These results show that the superior mixing of this I/O
system allows one to hold the CO generation down while allowing one
to move more air to the OFA elevation to reduce NOx. Without this
type of aggressive mixing the CO generation will go up. This is
well known to people working with combustion.
[0039] Turning now to the drawings, in which like numerals refer to
similar elements throughout the figures, FIG. 1 is a conceptual
side view of a conventional fuel-injection boiler 10 without
combustion rotation. A Cartesian coordinate system is shown to
facilitate the description of the boiler. The "x" direction is
horizontal along the main boiler wall, which is into the page as
shown in FIG. 1. The "y" direction is vertical, and the "z"
direction is horizontal across the boiler, as shown in FIG. 1. The
boiler 10 is vertically organized with a heat exchanger section 14
on top, a combustion section 16 below the heat exchanger section,
and a bottom ash section 18 below the combustion section 16. In
generally, combustion occurs in the combustion section 16, the
combustion heat rises to heat steam generators in the heat
exchanger section 14, and the bulk of the ash falls into the bottom
ash section 16, where it is removed from the boiler. Although this
layout is simplified, it is sufficiently representative of
industrial boilers for the purpose of describing the present
invention.
[0040] The boiler 10 includes a pair of opposing boiler walls 11,
12 extending in the "x" direction that support a number of opposing
burners 20 that inject a mixture of air and fuel, such as
pulverized coal, oil or natural gas, into the combustion section of
the boiler. The boiler walls also support a number over-fire air
("OFA") ports 22 that inject air into the combustion section of the
boiler above the level of the burners. The burners 20 and OFA ports
22 on opposing sides of the boiler in a conventional boiler are
stacked in vertical columns directly across from each other. The
lower row of burners is sometimes referred to as the primary (1RY)
burners, the next level is sometimes referred to as the secondary
(2RY) burners, and the upper level is sometimes referred to as the
tertiary (3RY) burners. In a boiler with four levels of burners,
the lower pair of rows may be referred to as the primary (1RY)
burners, and the upper pair of rows may be referred to as the
secondary (2RY) burners. FIG. 1 shows one illustrative vertical
column consisting of four burners and one OFA ports on each
opposing boiler wall. Typically, there are at least four vertical
columns of burners and OFA ports on each boiler wall spaced apart
in the "x" direction. The inner columns are typically referred to
as the inboard columns, and the outer columns are typically
referred to as the outboard columns.
[0041] In the conventional fuel injection boiler, the burners and
OFA ports on the first wall 11 are positioned directly across from
a mirror-image set of burners and OFA ports on the opposing wall
12, and each burner and OFA port is directed horizontally, parallel
to the "z" direction at various vertical levels. In addition, each
opposing pair of burners is typically operated at the same
injection rate, which results in a "balanced" injection profile.
Each opposing pair of OFA ports is also operated at the same
injection rate in the balanced injection profile. This results in a
non-rotating combustion mass that travels inward toward the middle
of the boiler and upward toward the heat exchangers, as shown in
FIG. 1. The balanced fuel injection profile resulting in a
non-rotating combustion mass flow pattern has been used in
conventional fuel injection boiler for many decades.
[0042] The heat exchanger section 14 at the top of the boiler 10
has multiple wing walls also known as division panels 24 that come
off the front walls. These act like flow straighteners that tend to
destroy any rotation in the flow gas. Due to a relatively short
distance from the OFA ports 22 ports to the bottom of the wing
walls in a typical fuel-injection boiler, there is insufficient
space to stack more than one or two levels of OFA ports between the
burners and the division panels. Therefore, it is not possible to
use the OFA ports alone to impart significant rotation to the
combustion mass, as described for certain chemical recovery boilers
in U.S. Pat. No. 7,185,594.
[0043] As shown in FIG. 2, the present invention accomplishes the
objective of rotating the combustion mass in a fuel-injection
boiler by positioning, directing, and/or adjusting the flow rates
of the burners 20 to impart the rotation to the combustion mass.
The OFA ports 22 may also be positioned, directed, and/or operated
to assist in the rotation to the combustion mass. Preferably, the
burners and OFA ports are positioned, directed, and operated to
impart multiple upward spiraling vortexes into the combustion mass
as the combustion heat rises toward the heat exchangers. This
requires deviating from the "balanced" injection profile that has
been ingrained into the boiler industry for decades. A number of
techniques for rotating the combustion mass have been developed, as
described below.
[0044] FIGS. 3 and 4 illustrate a representative layout of burners
20 and OFA ports 22 on the opposing burner walls 11, 12 in a
fuel-injection boiler, in which each column contains four burners
and one OFA port. FIG. 5 shows a perspective view of this boiler
configuration, and FIG. 6 shows a top view of this boiler
configuration. With reference to the Cartesian coordinate system,
each boiler wall 11, 12 lies in an "x-y" plane and they are spaced
apart from each other across the boiler in the "z" direction. This
representative boiler configuration includes four columns of
burners and OFA ports spaced apart in the "x" direction, in which
each column has four burners 20 and one OFA port 22. The inner
columns 40 on the first boiler wall 11 are referred to as inboard
columns, and the outer columns 42 on the first boiler wall 11 are
referred to as outboard columns. Similarly, the inner columns 44 on
the second boiler wall 12 are referred to as inboard columns, and
the outer columns 46 on the second boiler wall 12 are referred to
as outboard columns.
[0045] FIGS. 3 and 4 illustrate a basic technique for using the
burners and optionally the OFA ports to impart rotation to the
combustion mass in a conventional fuel-injection boiler without
making any physical alterations to the boiler. As is the case with
all of the combustion rotation techniques described below, this
technique can be applied to the burners alone or to the burners and
the OFA ports. In addition, the longer arrows indicate higher flow
rates throughout the injection flow diagrams. For this technique,
the flow rates to the inboard and outboard columns are adjusted
into an unbalanced injection pattern to impart rotation to the
combustion mass. For example, the flow rates to the outboard
columns 40 on the first boiler wall 11 are set to a relatively high
flow rate (indicated by bold ports), while the flow rates to the
outboard columns 44 on the second boiler wall 12 are set to a
relatively low flow rate (indicated by non-bold ports). Similarly,
the flow rates to the inboard columns 42 on the first boiler wall
11 are set to a relatively low flow rate (indicated by non-bold
ports), while the flow rates to the inboard columns 46 on the
second boiler wall 12 are set to a relatively high flow rate
(indicated by bold ports). These flow adjustments can typically be
implemented without changing the total mass flow rate through the
boiler, although the total mass flow rate may be changed if
desired.
[0046] As shown on FIGS. 3-6, this adjustment to the fuel injection
rates results in unbalanced flow injection rates between the
outboard columns 40 and the inboard columns 42 on the first boiler
wall 11. At the same time, unbalanced flow injection rates a the
outboard columns 44 and the inboard columns 46 on the second boiler
wall 12. This adjustment also results in unbalanced flow injection
rates between the outboard columns 40, 44 on opposing boiler walls,
and the inboard columns 42, 46 on opposing boiler walls. The top
view of FIG. 6 shows illustrates the unbalanced flow injection
profile 61 applied to the burners on the first boiler wall 11, and
the corresponding unbalanced flow injection profile 62 applied to
the burners on the second boiler wall 12. These injection profiles
produce two counter-rotating vortexes 63, 64 in the combustion
mass.
[0047] Referring to FIG. 5, with this arrangement the two
counter-rotating vortices 63, 64 (shown in FIG. 6) spiral upward
into the heat exchanger section 14 taking the flue gas past the
division panels 24, past what is known as the bull nose 70, and
past the pendent super heaters 26. The flue gas then passes the
heat exchanger exit 13 and continues to pass through further heat
transfer surfaces.
[0048] It should be appreciated that two vortices can be created
using high and low flow burner jet flows in a boiler with four
columns of burners as shown in FIGS. 3-6, whereas three vortices
can be created in a boiler with six columns of burners as shown in
FIG. 7 and four vortices can be created in a boiler with eight
columns of burners as shown in FIG. 8. This technique for rotating
the combustion mass by adjusting the flow rates in opposing burners
and OFA ports can typically be applied to existing boilers without
making physical modifications to the boiler. Illustrative examples
of burner and OFA port configurations with flow rates varying
horizontally are shown in FIGS. 6-8. FIGS. 9-11 illustrate
laterally offset burner placement while Illustrative examples of
burner and OFA port configurations with flow rates varying
vertically are shown in FIGS. 13-14.
[0049] More specifically, FIGS. 7 and 8 illustrate and expansion of
the flow injection modification technique for inducing rotation of
the combustion mass described with reference to FIGS. 3-6 to
boilers with larger numbers of opposing columns of burners and OFA
ports on opposite sides of the boiler. FIG. 7 is a conceptual top
view of burner ports in a second alternative fuel-injection boiler
70 with laterally opposing burner ports illustrating the lateral
placement and operation of the burner ports. The boiler 70 includes
six opposing columns of burners and OFA ports on opposite sides of
the boiler. FIG. 7 shows illustrates the unbalanced flow injection
profile 71 applied to the burners on the first boiler wall, and the
corresponding unbalanced flow injection profile 72 applied to the
burners on the second boiler wall These injection profiles produce
three counter-rotating vortexes 73, 74, and 75 in the combustion
mass.
[0050] This same technique can be expanded to a boiler with eight
columns of burners and OFA ports on opposing boiler walls. FIG. 8
is a conceptual top view of burner ports in a third alternative
fuel-injection boiler 80 with laterally opposing burner ports
illustrating the lateral placement and operation of the burner
ports. The boiler 80 includes eight opposing columns of burners and
OFA ports on opposite sides of the boiler. FIG. 8 shows illustrates
the unbalanced flow injection profile 81 applied to the burners on
the first boiler wall, and the corresponding unbalanced flow
injection profile 82 applied to the burners on the second boiler
wall These injection profiles produce four counter-rotating
vortexes 83, 84, 85 and 86 in the combustion mass.
[0051] For a new plant or a plant in which physical modifications
can be made, staggered burner placement can also be used to rotate
the combustion mass, which can reduce the number of columns of
burners required to produce the same number of vortices. For this
technique, the opposing burners and OFA are not directed directly
at each other, but are instead offset to induce mixing in the
combustion mass. The burners and OFA ports may be strategically
located horizontally (x direction), vertically (y direction), or
both horizontally and vertically in addition to varying the flow
rates (z direction). Strategic placement of burners can eliminate
the need for low flow burners and associated piping and support
structures. For example, FIG. 9 shows a dual vortex boiler
utilizing three staggered (laterally offset) columns of high flow
burners, FIG. 10 shows a triple vortex boiler utilizing four
laterally offset columns of high flow burners, and FIG. 11 shows a
quad vortex burner utilizing five laterally offset columns of high
flow burners. These laterally offset, multi-vortex design
alternatives are particularly attractive options for new boilers
that can be originally designed to rotate the combustion mass. The
staggered port profiles may be implemented with the same flow
injection rate to each column or in combination with flow rate
adjustment, horizontally tilted injection, and/or vertically tilted
injection.
[0052] FIG. 9 is a conceptual top view of burner ports in a first
alternative fuel-injection boiler 90 with laterally offset burner
ports illustrating the lateral placement and operation of the
burner ports. In the simplest configuration, the first boiler wall
includes one column 91 of burner and OFA ports and the opposing
boiler wall includes two columns 92 of burner and OFA ports. The
column 91 is located laterally (x direction) between the columns
92. This staggered port profile produces two counter-rotating
vortexes 93, 94 using only three columns of injection ports. The
staggered port profile may be implemented with the same flow
injection rate to each column, as shown in FIG. 8, or in
combination with flow rate adjustment. For example, the injection
flows rates could be adjusted so that the flow rate to column 91 is
greater than the flow rates to columns 92, or vice versa.
[0053] This same technique can be expanded to a boiler with any
number of columns of burners and OFA ports on opposing boiler
walls. FIG. 10 is a conceptual top view of burner ports in a second
alternative fuel-injection boiler 100 with laterally offset burner
ports illustrating the lateral placement and operation of the
burner ports. The first boiler wall includes two columns 101 of
burner and OFA ports and the opposing boiler wall includes two
columns 102 of burner and OFA ports. The columns 101 are laterally
(x direction) offset from the columns 102. This staggered port
profile produces three counter-rotating vortexes 103, 104, and
105.
[0054] FIG. 11 is a conceptual top view of burner ports in a third
alternative fuel-injection boiler 110 with laterally offset burner
ports illustrating the lateral placement and operation of the
burner ports. The first boiler wall includes two columns 111 of
burner and OFA ports and the opposing boiler wall includes three
columns 112 of burner and OFA ports. The columns 111 are laterally
(x direction) offset from the columns 112. This staggered port
profile produces four counter-rotating vortexes 113-116. Those
skilled in the art will appreciate that this technique can be
readily expanded to boilers with larger numbers of laterally offset
columns of burners and optional OFA ports.
[0055] FIG. 12 is a conceptual front view of a boiler wall 120
illustrating the vertical placement of the burner and OFA ports on
one side of the boiler. All of the techniques described in this
specification can be applied to boilers with fuel-injection burners
and any number of OFA ports, including boilers with no OFA ports.
The same combustion techniques can also be applied to only the
burner ports or to both the burner and OFA ports in a boiler with
burners and OFA ports. FIGS. 1-6 show a boiler in which each column
includes four burners and one OFA port. FIG. 12 expands this
concept to a boiler in which each column includes four burners and
three OFA ports. Configuring the boiler with multiple columns of
burners, each with multiple staked OFA ports, increases the ability
to adjust the flow rates through the burners and OFA ports
vertically (in the y direction) as well as horizontally (in the x
direction) to impart desired mixing in the combustion mass. The
flow rates through the burners and OFA (the force in the z
direction) may be varied from burner to burner and OFA port to OFA
port vertically (in the y direction) to impart desired mixing in
the combustion mass as an alternative or in addition to varying the
flow rates from burner to burner and OFA port to OFA port
horizontally (in the x direction).
[0056] FIG. 13 is a conceptual side view of burner ports in a first
alternative fuel-injection boiler 130 with vertically opposing
burner ports illustrating the vertical placement and operation of
the burner ports. A first vertical flow injection profile 131 is
applied to the burners and OFA ports on the first boiler wall, and
second vertical flow injection profile 132 is applied to the
burners and OFA ports on the opposing boiler wall. FIG. 14 shows a
second alternative fuel-injection boiler 140 a different vertical
flow rate injection profile. A first vertical flow injection
profile 141 is applied to the burners and OFA ports on the first
boiler wall, and second vertical flow injection profile 142 is
applied to the burners and OFA ports on the opposing boiler wall.
Those skilled in the art will appreciate that this technique can be
readily expanded to boilers with larger numbers of burners and
optional OFA ports in each column, and to apply different vertical
injection flow rate profiles as matters of design choice.
[0057] In addition to the techniques described above, one or more
of the burners and OFA jets may be injected into the boiler at a
vertically and/or horizontally tilted angle to impart desired
mixing in the combustion mass. Angling the burners can be
implemented in combination with staggered columns and/or flow rate
adjustment to further induce mixing of the combustion mass.
Examples of burner and OFA jets that are tilted horizontally (in
the x-z plane) are shown in FIGS. 15 and 16. FIG. 15 is a
conceptual top view of burner ports in a first alternative
fuel-injection boiler 150 with laterally offset and laterally
directed burner ports illustrating the lateral placement, operation
and orientation of the burner ports. In the simplest configuration,
the first boiler wall includes one column 151 of burner and OFA
ports and the opposing boiler wall includes two columns 152 of
burner and OFA ports. The column 151 is located laterally (x
direction) between the columns 152. In addition, the column 151 is
directed horizontally (z direction), while the columns 152 on the
opposite side of the boiler are horizontally tilted to assist on
combustion rotation. FIG. 16 shows this technique expanded to an
alternative boiler 160 with two columns 161 on the first boiler
wall and two columns 162 in the opposing boiler wall. Further, if
the injection stream has an asymmetrical shape, such as a fan
profile, the angle of the fan profile also can be rotated along the
axis of injection by rotating the jet nozzle about the axis of
injection, as represented by the rotational injection patterns 163
and 164 shown in FIG. 16. Those skilled in the art will appreciate
that these techniques can be readily expanded to boilers with
larger numbers of burners and optional OFA ports in each column,
and to apply different horizontal injection flow direction profiles
as matters of design choice.
[0058] As another design option, the angle of burner and/or OFA
injection can be varied from port-to-port in the vertical direction
as shown in FIG. 17. FIG. 17 is a conceptual top view of burner
ports in a first alternative fuel-injection boiler 170 with
laterally offset and progressively directed burner ports
illustrating the lateral placement, operation and orientation of
the burner ports. In this example, the first boiler wall includes
two columns 171, 173 of the burners and/or OFA ports. Each column
includes ports at four vertical (y direction) levels. L1-L4. The
injection direction is directly across the boiler (z direction) at
L1, and the injection direction at each successive level L3-L4 is
progressively tilted horizontally (x direction) from the
cross-boiler direction. A similar, complementary progressive offset
injection profile is applied by the columns 173, 174 on the
opposite side of the boiler. This technique can be applied to
boilers with any number of columns of burners and OFA ports, and
can be combined with any of the other combustion rotation
techniques. For example, FIG. 18 illustrates the combination of the
complementary progressive offset injection profile of FIG. 17 with
an unbalanced vertical flow rate injection profile in a boiler 180
with columns 181-184.
[0059] As an alternative to, or addition to, the combustion
rotation techniques described above, the burner and OFA jets may
also be tilted or angled vertically (in the y-z plane) as shown in
FIG. 19. FIG. 19 illustrates the vertical injection tilt technique
in combination with an unbalanced vertical flow rate injection
profile in a boiler 190 with injection profiles 191-192.
[0060] Those skilled in the art will appreciate that the basic
concept of adjusting the burner flow rates, positions, injection
angles, and nozzle rotation to rotate and otherwise mix the
combustion mass may be implemented with a range of different
specific burner and OFA port configurations. Those conceptual
examples shown in the figures are merely illustrative. In general,
the equipment required to implement these combustion rotation
techniques include an air/fuel mixture and fuel injection flow rate
controller for each burner to be controlled with flow rate
adjustment, a fuel injection flow rate controller for each OFA port
to be controlled with flow rate adjustment, jet nozzle rotating
equipment for each burner and OFA port to be rotated, and jet
pointing equipment for each burner and OFA port to be directionally
controlled. Jet nozzles may be rotated with motor driven gear
assemblies. The jet pointing equipment may include mounting
structures for supporting the burner or OFA jet in a desired
orientation. Directional nozzles may also be use to direct burner
or OFA jets in desired directions. The directional nozzles may be
rotated with motor driven gear assemblies to change the pointing
directions of the jets. In general, the mounting structures and
nozzles may be fixed, in which case they are physically changed to
make adjustments, or these structures may be manually adjustable or
motorized for remotely controlled adjustment while the boiler is in
operation.
[0061] In addition, all of the injection parameters illustrated
above can be changed from burner to burner and OFA port to OFA port
as desired to impart mixing and rotation to the combustion mass.
For example, the positions, flow rates, and angles of injection for
the burners and the OFA ports can selected as design considerations
for a new plant. In addition, most of these parameters can be
changed for an existing plant, in some cases requiring equipment
upgrades such as jet pointing equipment. Once control equipment is
in place for some or all of these parameters, some or all of the
parameters can be changed while the boiler is on operation, for
example by turning burner and OFA jets on and off, adjusting the
flow rates, and adjusting injection angles. One or more of these
parameters can also be changed continually or continuously
(modulated) in accordance with predefined patterns, measured
performance characteristics, and/or feedback signals.
[0062] The fuel mixture supplied to the burners and boiler cleaning
equipment, such as water canons and sootblowers, can also be
controlled in accordance with predefined patterns, measured
performance characteristics, and/or feedback signals. As shown in
FIG. 20, the burners, OFA ports, fuel mixture and cleaning
equipment can all be controlled based on sensor data obtained in
real time to meet or optimize desired operating characteristics.
The sensor data typically includes the boiler's thermal output,
temperatures, pressures, gas content, ash content, pollution
emissions, and heat flux. The boiler can be controlled to optimize
the thermal output while meeting pollution emission thresholds, for
example NOx emission limits, and minimizing unburned carbon in the
ash.
[0063] More specifically, FIG. 20 illustrates a fuel-injection
boiler system 200 for a fuel-injection boiler 202. The system 200
includes sensors 204 that monitor boiler operating parameters, such
as temperature, pressure, gas analysis, and heat flux. These
parameters are fed to a master controller 206, which analyzes the
performance of the boiler based on the measured parameters,
predicts changed to the performance in response to changes in the
burner and optionally the OFA injection profile, and the implements
changes in the injection profile to optimize the performance of the
boiler. The master controller 206 can be programmed to optimize the
performance of the boiler while meeting pollution emission
thresholds. In particular, the master controller 206 is configured
to control burner one or more of the rotation and direction
controllers 208, burner flow rate controllers 210, and fuel/air
mixture controllers 212. For the OFA ports, the master controller
206 may also be configured to control one or more of the OFA
rotation and direction controllers 214 and the OFA flow rate
controllers 216. The master controller 206 may also determine from
the measured parameters when the boiler is in need of cleaning and
activate controlled boiler cleaning systems, such as sootblowers
and water canons. In response to the measured parameters, the
master controller 206 may control the cleaning of particular
portions of the boiler, implement general boiler cleaning, and
adjust regularly scheduled maintenance regimens. Those skilled in
the art will understand that all or a portion of the equipment
shown in FIG. 8 may be implemented as a matter of design choice in
different plants. In an existing plant, for example, a strategic
subset of the burners may be retrofitted with directional jets or
nozzle rotation equipment, as desired. New plants will benefit
greatly by strategically positioning the jets in laterally offset
configurations during original plan construction and installing
some or all of the automated combustion rotation and mixing
equipment shown in FIG. 8 to provide the plant operators with rich
sets of control options for optimizing the operation of the plant
to achieve desired performance characteristics considering at least
plant efficiency, pollution production, and cleaning regimens.
* * * * *