U.S. patent application number 15/981338 was filed with the patent office on 2018-11-29 for system for increasing flue gas side draft of heater assemblies using a draft booster impeller assembly.
The applicant listed for this patent is ExxonMobil Research and Engineering Company. Invention is credited to Ada M. Cardenas, Todd A. Grubb, Hyungsik Lee, Kelly T. Murphy.
Application Number | 20180340686 15/981338 |
Document ID | / |
Family ID | 64400435 |
Filed Date | 2018-11-29 |
United States Patent
Application |
20180340686 |
Kind Code |
A1 |
Lee; Hyungsik ; et
al. |
November 29, 2018 |
SYSTEM FOR INCREASING FLUE GAS SIDE DRAFT OF HEATER ASSEMBLIES
USING A DRAFT BOOSTER IMPELLER ASSEMBLY
Abstract
A system for increasing flue gas side draft in a heater or
boiler assembly is disclosed utilizing an impeller assembly to
enable an increase in firing rates beyond the ability of the
exhaust stack and to reduce the size of the low flue gas side
pressure drop heat pipe air preheaters.
Inventors: |
Lee; Hyungsik; (Houston,
TX) ; Murphy; Kelly T.; (Conroe, TX) ;
Cardenas; Ada M.; (Houston, TX) ; Grubb; Todd A.;
(Conroe, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ExxonMobil Research and Engineering Company |
Annandale |
NJ |
US |
|
|
Family ID: |
64400435 |
Appl. No.: |
15/981338 |
Filed: |
May 16, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62511501 |
May 26, 2017 |
|
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|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F23L 7/00 20130101; Y02E
20/34 20130101; F23L 17/005 20130101; F23L 15/04 20130101 |
International
Class: |
F23L 17/00 20060101
F23L017/00; F23L 15/04 20060101 F23L015/04 |
Claims
1. A system for increasing flue gas side draft in a heater
assembly, wherein the heater assembly includes a heater, an inlet
supply of combustion air, an exhaust flue gas duct and an exhaust
stack, wherein flue gas produced in the heater exits the heater
through the exhaust duct and stack, the system comprising: an
impeller assembly operatively coupled to one of the exhaust flue
gas duct and the exhaust stack, wherein operation of the impeller
assembly increases flue gas draft in the heater assembly to enable
an increase in firing rate within the heater beyond the ability of
the exhaust stack.
2. The system according to claim 1, wherein heater assembly further
includes a low flue gas side pressure drop air preheater and
associated ducting for preheating at least a portion of the
combustion air, at least a portion of the flue gas and the
combustion air are directed to the air preheater, wherein at least
a portion of the impeller assembly is located within the exhaust
flue gas duct.
3. The system according to claim 1, wherein the impeller assembly
includes a motor and an axial impeller.
4. The system according to claim 3, wherein the heater is one of a
fired heater and a boiler.
5. The system according to claim 3, wherein the impeller assembly
includes an axial impeller.
6. The system according to claim 5, wherein the axial impeller and
the motor are located within the exhaust flue gas duct.
7. The system according to claim 6, further comprising a
pressurized bearing lubrication system to enable operation in high
temperature environments.
8. The system according to clam 5, wherein the axial impeller is
located within the flue gas duct and the motor is located
externally of the exhaust flue gas duct, wherein the impeller
assembly furthers include a seal located within a wall of the
exhaust flue gas duct and a shaft passing through the seal, wherein
the axial impeller and the motor are operatively connected via the
shaft.
9. The system according to claim 5, wherein the axial impeller
includes one of a gear box or a plurality of variable vanes, such
that angle of the vanes can be adjusted.
10. The system according to claim 9, wherein adjustment of one of
the gear box or plurality of vanes can adjust the flue gas side
draft.
11. The system according to claim 1, wherein a draft created from
the impeller is less than 1.5 inch of water column of pressure
gain.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application relates and claims priority to U.S.
Provisional Patent Application No. 62/511,501, filed on May 26,
2017, entitled "System For Increasing Flue Gas Side Draft Of Heater
Assemblies Using A Draft Booster Impeller Assembly", which is
incorporated herein specifically herein by reference in its
entirety.
BACKGROUND
Field
[0002] The presently disclosed subject matter relates to a system
for increasing flue gas side draft in a heater assembly. In
particular, the presently disclosed subject matter relates to a
system for increasing flue gas side draft in a heater assembly
utilizing a draft booster impeller assembly positioned within flue
gas ducting.
Description of Related Art
[0003] There is a desire to increase flue gas side draft in fired
heaters and boilers, which may result in increased firing rates
within the fired heaters and boilers. This has been accomplished
using various techniques.
[0004] Centrifugal induced draft fans have been applied in creating
a high level of the flue gas side draft gain in fired heaters and
boilers. One such application is illustrated in FIG. 1. A forced
draft fan 1 is used to supply ambient air to a heater 2 for
combustion. A portion of the ambient air is fed through an air
preheater assembly 3 and a portion may be fed directly to the
heater 3. The air and fuel are combusted within the heater. Flue
gas is created which exits the heater from an exhaust stack 4. The
exhaust stack 4 includes a bypass damper 5 whereby the flue gas is
directed via ducting 6 to the preheater assembly 3 whereby the warm
flue gas heats the incoming ambient air. A centrifugal draft fan 7
is utilized in connection with an air preheater 2 to pull flue gas
through the preheater before returning the same to the exhaust
stack. The pressure gain from the centrifugal induced draft fan 7
is typically large by overcoming over 4 inch of water column of
pressure drop in the air preheater and associated ducting.
Substantial design modifications are required to use the
conventional centrifugal induced draft fan for generating low level
of pressure gain. These fans are often located at ground level when
used in conjunction with an air preheater. Therefore additional
ducting is required from the exhaust stack to the ground where the
induced draft fan is located. As such, the installation of
centrifugal induced draft fans is costly due to addition of the fan
and flue gas ducting.
[0005] Others have utilized steam eductors to boost a small level
of the draft within the furnace. The use of a steam eductor 11 is
illustrated in FIG. 2. In FIG. 2, a steam eductor 11 is located
within the exhaust stack 12. The kinetic energy of the steam in the
eductor facilitates the movement of flue gas, which creates the
desired draft improvement. Steam eductors are noisy and
inefficient, which often require the use of a silencer to reduce
noise. Eductors are also costly because steam or other medium is
necessary to operate the eductor.
[0006] Axial fans have also been used to generate a low level of
draft improvement. Typical axial fans connect the fan to the motor
with belts, and often a separate cooling fan is used to cool the
bearings, both which are unreliable in high temperature
applications.
[0007] There is a need for a low cost solution to generate a low
level of draft improvement within a fired heater or boiler assembly
that overcomes the deficiencies in the prior art.
SUMMARY
[0008] In accordance with one aspect of the present invention, a
system for increasing flue gas side draft in a heater assembly is
disclosed. The assembly includes a heater, an inlet supply of
combustion air, an exhaust duct and an exhaust stack. Flue gas is
produced in the heater during the operation and exits the exhaust
duct and stack. It is contemplated that the heater can be one of a
fired heater, a boiler or other suitable assembly for generating
heat for one or more process streams in a refinery or petrochemical
processing facility. The heater assembly may further include a low
flue gas side pressure drop air preheater and associated ducting
for preheating at least a portion of the combustion air. As
illustrated in FIG. 1 of the prior art, at least portions of the
flue gas and air may be directed to the combustion air preheater to
preheat the combustion air. Alternatively, the air preheater can be
installed in the connecting duct between the fired heater and a
ground mounted stack with the bypass ducts around the air
preheater. The warmed combustion air is then fed to the heater. The
system in accordance with the presently disclosed subject matter
includes an impeller assembly coupled to the exhaust stack. The
operation of the impeller increases flue gas draft in the heater
assembly to enable an increase in firing rates beyond the ability
of the exhaust stack. In addition, it can be used to overcome the
flow resistance in the low flue gas side pressure drop air
preheaters. The impeller assembly preferably includes a motor and
one of an axial impeller having a plurality of vanes and a
centrifugal impeller having a plurality of rotating impellers.
[0009] In accordance with the presently disclosed subject matter,
it contemplated that at least a portion of the impeller assembly is
located within one of the flue gas duct or the exhaust stack. Each
location is effective in increasing the flue side draft.
[0010] In accordance with one aspect of the presently disclosed
subject matter, the impeller assembly includes an axial impeller.
It is contemplated that both the axial impeller and the motor can
be located within the flue gas duct or the exhaust stack.
Alternatively, it is contemplated that only the axial impeller is
located within the flue gas duct or the exhaust stack. With such an
arrangement, the motor is located externally of the flue gas duct
or exhaust stack. A seal is provided, located within either the
duct wall or stack wall. A shaft connects the motor to the axial
impeller. The shaft passes through the seal to prevent the escape
of flue gas.
[0011] In accordance with one another aspect of the presently
disclosed subject matter, the impeller assembly includes a
centrifugal impeller. It is contemplated that only the centrifugal
impeller is located within the flue gas duct or the exhaust stack.
With such an arrangement, the motor is located externally of the
flue gas duct or exhaust stack. A seal is provided located within
either the duct wall or stack wall. A shaft connects the motor to
the centrifugal impeller. The shaft passes through the seal to
prevent the escape of flue gas. A self-lubrication system is
employed with a gear box to control the speed of the impeller
[0012] The accompanying drawings, which are incorporated in and
constitute part of this specification, are included to illustrate
and provide a further understanding of the disclosed subject
matter. Together with the description, the drawings serve to
explain the principles of the disclosed subject matter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a schematic view of a fired heater having an air
preheater using an induced draft fan in accordance with the prior
art;
[0014] FIG. 2 is a schematic view of a fired heater having steam
eductor in accordance with the prior art;
[0015] FIG. 3 is a schematic view of a system for increasing flue
gas side draft in a heater assembly using an axial impeller in
accordance with one aspect of the present invention;
[0016] FIG. 4 is a schematic view of a system for increasing flue
gas side draft in a heater assembly using an axial impeller in
accordance with another aspect of the present invention;
[0017] FIG. 5 is a schematic view of a system for increasing flue
gas side draft in a heater assembly using a centrifugal impeller in
accordance with yet another aspect of the present invention;
and
[0018] FIG. 6 is a schematic view of a system for increasing flue
gas side draft in a heater assembly using a centrifugal impeller in
accordance with yet another aspect of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0019] Reference will now be made in detail to the various
exemplary embodiments of the disclosed subject matter, exemplary
embodiments of which are illustrated in the accompanying drawings.
The structure and corresponding method of installation of the
disclosed subject matter will be described in conjunction with the
detailed description of the system.
[0020] Various aspects of the system for increasing flue gas side
draft in a heater assembly below 1.5 inch of water column gain will
now be described in greater detail with respect to the Figures. The
terminology heater assembly is utilized to refer to fired heaters
or boilers or other suitable heat source for heating a process
stream within a refinery or petrochemical processing facility. One
application of the presently disclosed subject matter is to create
low level of draft utilizing an axial or centrifugal fan assembly,
which can replace the existing educator and belt-driven axial fan
system. Another application is utilized in the fired heater with
heat pipe preheater disclosed in commonly assigned U.S. Provisional
Application No. 62,352099 entitled "Fired Heater With Heat Pipe
Preheater", now U.S. patent application Ser. No. 15/606,038, the
disclosure of which is incorporated herein by reference in its
entirety.
[0021] A system 20 for increasing flue gas side draft in a heater
assembly in accordance with one aspect of the presently disclosed
subject matter is illustrated in FIG. 3. The system 20 includes an
impeller assembly 21 positioned within the flue gas stream within
an exhaust stack or flue gas duct 15. It is contemplated that the
impeller assembly 21 may be located in either the exhaust stack of
the heater assembly or a flue gas duct. The impeller assembly 21
includes an axial impeller 22 having a plurality of vanes. The
axial impeller 22 is operatively coupled to a motor 23 via shaft
24. In this arrangement, both the axial impeller 22 and the motor
23 are located within the flue gas stream within the exhaust stack
or flue gas duct. The motor 23 is preferably low speed below 800
rpm and high temperature motor. A bearing assembly 25 is provided
for achieving smooth rotation of the axial impeller. An external
lubricant supply system 26 is provided to supply lubricant to the
bearing assembly. The system 26 is preferably a pressurized bearing
lubrication system to enable operation in relatively high
temperature environments and enhance bearing reliability. The
impeller assembly 21 may further include an adjustment assembly 27
for adjusting the angle of the vanes of the axial impeller 22.
Adjusting the vane angle can change the draw created by the
operation of the axial impeller. Alternatively, the axial impeller
speed can be adjusted by a gear box. An access panel in the stack
or duct 15 may be provided to access the assembly 21 for
service.
[0022] In operation, the rotation of the axial impeller 22 pulls
the flue gas within the exhaust stack or flue gas duct, which
results in an increase in the flue gas side draft of heater
assembly. Unlike the centrifugal induced draft fan 7, the draft
generated from the use of the impellers is small (e.g., typically
less than 1.5 inch of water column gain). Nonetheless, this
additional small draft is sufficient for increasing the firing
rates of heaters and boilers or reducing the sizes of low pressure
drop heat pipe air preheaters. The system 20 is relatively compact
and be easily installed in the flue gas stream without major
changes or additions to the heater assembly and surrounding
equipment. Unlike the centrifugal induced draft fan 7, the system
20 is installed on an elevated structure (e.g. top of the heater)
resulting in a reduction in the length of the flue gas connecting
duct, decreasing installation costs. The system 20 provides quiet
operation and eliminates the need for silencers.
[0023] A system 30 for increasing flue gas side draft in a heater
assembly in accordance with another aspect of the presently
disclosed subject matter is illustrated in FIG. 4. Like system 20,
the system 30 utilizes an impeller assembly. It is contemplated
that the impeller assembly 31 may be located in either the exhaust
stack of the heater assembly, or a flue gas duct 15. The impeller
assembly 31 includes an axial impeller 32 having a plurality of
vanes. The axial impeller 32 is operatively coupled to a motor 33
via shaft 34. In this arrangement, only the axial impeller 32 is
located within the flue gas stream within the exhaust stack or flue
gas duct. The motor 33 is located outside of the flue gas stream
and is preferably low speed below 800 rpm. A bearing assembly 35 is
provided for achieving smooth rotation of the axial impeller. The
shaft 34 extends through a seal 36 in the wall of exhaust stack or
flue gas duct 15. The seal 36 prevents flue gas from escaping where
the shaft 34 extend through the wall. The impeller assembly 31 may
further include an adjustment assembly 37 for adjusting the angle
of the vanes of the axial impeller 32. Adjusting the vane angle can
change the draw created by the operation of the axial impeller.
Alternatively, the axial impeller speed can be adjusted by a gear
box. A bend or jog 151 in the flue gas duct 15 permits locating the
motor 33 outside of the flue gas stream. The operation of the
system 30 is similar to the system 20.
[0024] A system 40 for increasing flue gas side draft in a heater
assembly in accordance with one aspect of the presently disclosed
subject matter is illustrated in FIGS. 5 and 6. The system 40
includes an impeller assembly 41 positioned within the flue gas
stream within an exhaust stack or flue gas duct 15. It is
contemplated that the impeller assembly 41 may be located in either
the exhaust stack of the heater assembly or a flue gas duct. The
impeller assembly 41 includes a centrifugal impeller. The
centrifugal impeller 41 is operatively coupled to a motor 43 via
shaft 44. In this arrangement, the centrifugal impeller 41 is
located within the flue gas stream within the exhaust stack or flue
gas duct. The motor 43 is located outside of the flue gas stream.
The presently disclosed subject matter, however, is not intended to
be limited to such an arrangement, rather, it is contemplated that
both the impeller 41 and the motor 43 may be located within the
stream similar to the embodiment illustrated in FIG. 3. A bearing
assembly 45 is provided to support and provide smooth rotation of
the centrifugal impeller. The shaft 44 extends through a seal 46 in
the wall of exhaust stack or by-pass duct 15. The seal 46 prevents
flue gas from escaping where the shaft 44 extend through the wall.
The system 40 is preferably located in a bend or jog 151 in the
exhaust stack or flue gas duct 15 to permit locating the motor 43
outside of the flue gas stream. A sharp bend or jog is illustrated
in FIG. 5. A more gradual bend is illustrated in FIG. 6.
[0025] Like the impeller assembly 21 and 31, the draft generated
from the use of the centrifugal impeller is small (e.g., typically
less than 1 inch H.sub.2O). Unlike the induced draft fan 7, the
system 40 is installed on an elevated structure (e.g. top of the
heater) resulting in a reduction in the length of the flue gas
connecting duct to decrease installation costs. The system 40
utilizes a self-lubrication system with a gear box to control the
speed of the impeller. The system 40 provides quiet operation and
eliminates the need for silencers. Nonetheless, this additional
small draft is sufficient to enable an increase in firing rates
beyond the ability of the exhaust stack in fired heaters and
boilers or to reduce the size of the low flue gas side pressure
drop heat pipe air preheaters.
Additional Embodiments
[0026] Additionally or alternately, the invention can include one
or more of the following embodiments.
[0027] Embodiment 1. A system for increasing flue gas side draft in
a heater assembly is disclosed. The heater assembly includes a
heater, an inlet supply of combustion air, an exhaust duct and an
exhaust stack. Flue gas that is produced in the heater exits the
heater through the exhaust duct and stack. The system includes an
impeller assembly operatively coupled to the exhaust duct or stack,
wherein operation of the impeller increases flue gas draft in the
heater assembly to enable an increase in firing rates beyond the
ability of the exhaust stack.
[0028] Embodiment 2. The system according to Embodiment 1, wherein
heater assembly further includes a low flue gas side pressure drop
air preheater for preheating at least a portion of the combustion
air fed to the inlet supply and a flue gas duct operatively
connecting to the exhaust stack to the combustion air preheater. At
least a portion of the flue gas is diverted from exhaust stack to
the combustion air preheater to preheat at least a portion of the
combustion air before returning the flue gas to the exhaust stack.
In accordance with this Embodiment, at least a portion of the
impeller assembly is located within the flue gas duct.
[0029] Embodiment 3. The system according to anyone of the
preceding embodiments, wherein the impeller assembly includes a
motor and one of an axial impeller and a centrifugal impeller.
[0030] Embodiment 4. The system according to anyone of the
preceding embodiments, wherein the impeller assembly includes an
axial impeller.
[0031] Embodiment 5. The system according to anyone of Embodiments
3 or 4, wherein the axial impeller and the motor are located within
the flue gas duct. A pressurized bearing lubrication system is
employed to enable operation in high temperature environments.
[0032] Embodiment 6. The system according to anyone of Embodiments
3 or 4 wherein the axial impeller is located within the flue gas
duct and the motor is located externally of the flue gas duct,
wherein the impeller assembly furthers include a seal located
within a wall of the duct and a shaft passing through the seal,
wherein the axial impeller and the motor are operatively connected
via the shaft.
[0033] Embodiment 7. The system according to anyone of Embodiments
3, 4, 5 or 6, wherein the axial impeller includes a gear box or a
plurality of variable vanes, such that angle of the vanes can be
adjusted.
[0034] Embodiment 8. The system according to Embodiment 7, wherein
adjustment of a gear box or the plurality of vanes can adjust the
flue gas side draft.
[0035] Embodiment 9. The system according to anyone of Embodiments
1, 2 or 3, wherein the impeller assembly includes a centrifugal
impeller.
[0036] Embodiment 10. The system according to anyone of Embodiments
1, 2, 3 or 9, wherein the centrifugal impeller is located within
the flue gas duct and the motor is located externally of the duct,
wherein the impeller assembly furthers include a seal located
within a wall of the duct and a shaft passing through the seal,
wherein the centrifugal impeller and the motor are operatively
connected via the shaft.
[0037] Embodiment 11. The system according to Embodiment 1, wherein
the impeller assembly is located within the flue gas duct or
stack.
[0038] Embodiment 12. The system according to anyone of Embodiments
1 or 11, wherein the impeller assembly includes a motor and one of
an axial impeller.
[0039] Embodiment 13. The system according to anyone of Embodiments
1, 11, or 12, wherein the axial impeller is located within the
exhaust stack or flue gas duct and the motor is located externally
of the exhaust stack or the flue gas duct, wherein the impeller
assembly furthers include a seal located within a wall of the
exhaust stack or the duct and a shaft passing through the seal,
wherein the axial impeller and the motor are operatively connected
via the shaft.
[0040] Embodiment 14. The system according to anyone of Embodiments
1, 11, 12 or 13, wherein the axial impeller includes a gear box or
a plurality of variable vanes, such that angle of the vanes can be
adjusted.
[0041] Embodiment 15. The system according to Embodiment 14,
wherein adjustment of a gear box or the plurality of vanes can
adjust the flue gas side draft.
[0042] Embodiment 16. The system according to anyone of the
preceding Embodiments, wherein the heater is one of a fired heater
and a boiler.
[0043] While the disclosed subject matter is described herein in
terms of certain preferred embodiments, those skilled in the art
will recognize that various modifications and improvements can be
made to the disclosed subject matter without departing from the
scope thereof. Moreover, although individual features of one
embodiment of the disclosed subject matter can be discussed herein
or shown in the drawings of the one embodiment and not in other
embodiments, it should be apparent that individual features of one
embodiment can be combined with one or more features of another
embodiment or features from a plurality of embodiments.
[0044] In addition to the specific embodiments claimed below, the
disclosed subject matter is also directed to other embodiments
having any other possible combination of the dependent features
claimed below and those disclosed above. As such, the particular
features presented in the dependent claims and disclosed above can
be combined with each other in other manners within the scope of
the disclosed subject matter such that the disclosed subject matter
should be recognized as also specifically directed to other
embodiments having any other possible combinations. Thus, the
foregoing description of specific embodiments of the disclosed
subject matter has been presented for purposes of illustration and
description. It is not intended to be exhaustive or to limit the
disclosed subject matter to those embodiments disclosed. It is
contemplated that the presently disclosed subject matter may be
utilized in the fired heater with heat pipe preheater disclosed in
commonly assigned U.S. Provisional Application No. 62,352099
entitled "Fired Heater With Heat Pipe Preheater", the disclosure of
which is incorporated herein by reference in its entirety.
[0045] It will be apparent to those skilled in the art that various
modifications and variations can be made in the method and system
of the disclosed subject matter without departing from the spirit
or scope of the disclosed subject matter. Thus, it is intended that
the disclosed subject matter include modifications and variations
that are within the scope of the appended claims and their
equivalents.
* * * * *