U.S. patent application number 12/581978 was filed with the patent office on 2011-04-21 for multi-fuel combustion system.
Invention is credited to Vinayak Barve, Timothy A. Fox, Jaap van Kampen, Ulrich Worz, Jianfan Wu.
Application Number | 20110091829 12/581978 |
Document ID | / |
Family ID | 43879566 |
Filed Date | 2011-04-21 |
United States Patent
Application |
20110091829 |
Kind Code |
A1 |
Barve; Vinayak ; et
al. |
April 21, 2011 |
MULTI-FUEL COMBUSTION SYSTEM
Abstract
The present invention explains a multi-fuel combustion system.
It consist of a combustor basket adapted to combust at least two
type of fuels. The combustor basket has got a circumferential wall
comprising a plurality of openings. The combustion system further
has a first conduit adapted to provide a first type of fuel
directly to the combustor basket, a second conduit adapted to
provide a second type of fuel directly to the combustor basket and
a third conduit adapted to inject at least one of the first type of
fuel and the second type of fuel through the openings into the
combustor basket.
Inventors: |
Barve; Vinayak; (Oviedo,
FL) ; Fox; Timothy A.; (Hamilton, CA) ; Wu;
Jianfan; (Orlando, FL) ; Worz; Ulrich;
(Laupheim, DE) ; van Kampen; Jaap; (Roermond,
NL) |
Family ID: |
43879566 |
Appl. No.: |
12/581978 |
Filed: |
October 20, 2009 |
Current U.S.
Class: |
431/352 |
Current CPC
Class: |
F23R 3/36 20130101; Y02E
20/18 20130101; F23R 3/46 20130101; F23R 3/346 20130101; F23R 3/06
20130101; F23L 7/005 20130101; F23R 2900/00002 20130101 |
Class at
Publication: |
431/352 |
International
Class: |
F23C 6/04 20060101
F23C006/04 |
Claims
1. A multi-fuel combustion system comprising: a combustor basket
adapted to combust at least two type of fuels, said combustor
basket having a circumferential wall comprising a plurality of
openings to guide a flow of air into the combustor basket; a first
conduit adapted to provide a first type of fuel directly to the
combustor basket; a second conduit adapted to provide a second type
of fuel directly to the combustor basket; and a third conduit
adapted to inject at least one of the first type of fuel and the
second type of fuel through at least one of the openings into the
combustor basket.
2. The multi-fuel combustion system according to claim 1, wherein
the wall of the combustor basket is made of a plurality of
cylindrical regions arranged to overlap each other at the
transition and extends from the upstream end to the downstream end
of the combustor basket.
3. The multi-fuel combustion system according to claim 2, wherein
the individual cylindrical region comprises an outer surface, said
outer surface is provided with a rib structure and is covered by a
perforated layer adapted to provide an air flow for cooling the
walls.
4. The multi-fuel combustion system according to claim 2, wherein
at least two of the cylindrical regions at the upstream side of the
combustor basket further comprise the plurality of openings
distributed along the circumference of the cylindrical region to
allow a compressor discharge air to flow towards a region of
combustion in the combustor basket.
5. The multi-fuel combustion system according to claims 2, wherein
at least one of the cylindrical regions at the downstream side of
the combustor basket further comprises the plurality of openings
distributed along the circumference of the cylindrical region to
allow the compressor discharge air to flow towards a region of
combustion in the combustor basket.
6. The multi-fuel combustion system according to claim 2, wherein
the individual cylindrical region comprises between 5 and 9
openings.
7. The multi-fuel combustion system according to claim 6, wherein
the individual cylindrical region comprises an odd number of
openings.
8. The multi-fuel combustion system according to claim 1, wherein
the first type of fuel is natural gas.
9. The multi-fuel combustion system according to claim 1, wherein
the second type of fuel is syngas.
10. The multi-fuel combustion system according to claim 1, wherein
the first conduit comprises a nozzle to supply at least one of the
first type of fuel and the second type of fuel directly to the
combustor basket for combustion, wherein the nozzle comprises a
plurality of holes positioned at, at least two different radial
distances from the center of the nozzle for enabling a fuel flow
into a region of combustion in the combustor basket.
11. The multi-fuel combustion system according to claim 1, further
comprises an exit cone at the downstream end of the combustor
basket comprising of plurality of slots aligned to the plurality of
openings associated with at least one of the cylindrical
regions.
12. The multi-fuel combustion system according to claim 1, further
comprises a flow conditioner positioned to encircle the combustor
basket and having a conical section and a cylindrical section
having plurality of holes adapted to allow the compressor discharge
air to flow towards a region of combustion in the combustor
basket.
13. The multi-fuel combustion system according to claim 1, further
comprises a cover plate coupled to the combustor basket and the
conduits, such that the combustor basket and the conduits are
attached to a casing using said cover plate.
14. The multi-fuel combustion system according to claim 1, wherein
the first conduit and the second conduit is concentrically arranged
for effective delivery of the first type of fuel and the second
type of fuel to the combustor basket.
15. The multi-fuel combustion system according to claim 1, wherein
the third conduit is adapted to inject at least one of the first
type of fuel and the second type of fuel into a compressor
discharge air that flow through at least one of the openings
associated with at least one of the cylindrical regions.
16. The multi-fuel combustion system according to claim 1, wherein
the third conduit further comprises an injector nozzle having at
least one hole to inject at least one of the first type of fuel and
the second type of fuel into a compressor discharge air that flow
through at least one of the openings associated with at least one
of the cylindrical regions.
17. A method of operating a multi-fuel combustion system comprising
a first phase and a second phase, wherein the first phase
comprises: providing ignition to a combustor basket to ignite a
first type of fuel, where the first type of fuel is supplied to the
combustor basket through a first conduit; supplying steam to the
first conduit in addition to the first type of fuel and supplying
steam to the second conduit after the ignition; and wherein the
second phase comprises: supplying a second type of fuel to the
combustor basket after ignition of the first fuel through the
second conduit, while stopping the supply of the first fuel.
18. A method of operating a multi-fuel combustion system according
to claim 17, further comprising supplying a portion of the second
type of fuel to the combustor basket through the first conduit
during the second phase.
19. A method of operating a multi-fuel combustion system according
to claim 17, wherein the first type of fuel is natural gas.
20. A method of operating a multi-fuel combustion system according
to claim 17, wherein the second type of fuel is syngas.
Description
FIELD OF INVENTION
[0001] The present invention lies in the field of combustion
turbines in particular for generating electrical energy and more
particularly, to combustor baskets employed therein.
BACKGROUND OF INVENTION
[0002] Future energy demand, scarcity of available fuels and
environmental regulations put pressure on power plant producers to
come up with solutions for safe, efficient and clean ways to
generate power. The scarcity of fuels mainly applies to oil and to
a lesser extend to natural gas. With an availability of coal in
abundance, electricity production from coal is mostly done using
steam power plants. A cleaner and more efficient option to generate
power from coals is to use them in an integrated gasification
combine cycle (IGCC). In an IGCC, coals are first gasified to yield
syngas, consisting mainly of CO (carbon monoxide) and H.sub.2
(hydrogen).
[0003] Syngas typically has a significantly lower calorific value
as compared to conventional natural gas fuels. By removing the CO
content from the syngas prior to combusting it, one also has an
effective means for CO.sub.2 (carbon-dioxide) capture. The IGCC
concept with pre-combustion CO.sub.2 capture is one of the most
cost-effective ways to produce electricity and avoid the emission
of CO.sub.2 in the future. The economical potential of the IGCC
plant with CO.sub.2 capture can increase even further when natural
gas prices rise faster than expected or with increased carbon tax
regulation.
[0004] Due to the low calorific value and high hydrogen content,
the combustion of syngas fuels requires the development of adapted
or completely new combustion systems which are able to handle the
wide range of syngas fuels, and produce little emissions and can
handle the high reactivity of the fuels.
[0005] The syngas fuel composition depends on the type of gasifier
used and on whether or not the CO is separated from the fuel.
Besides syngas fuels, the combustion system might run on a second
conventional fuel for backup and start up. The ideal possibility is
to have all the different types of fuels combusted in a stable way
by one combustion system. To increase the efficiency and compensate
for the efficiency loss due to the gasifier and CO.sub.2 separation
techniques, the trend will be to increase pressure and turbine
inlet temperatures, even beyond values where currently natural gas
experience is available. With these increasing pressures and
temperatures, it becomes even more important to design a combustion
system that is able to combust the syngas and hydrogen fuel, as
danger for burner overheating and thermo acoustic excitation
typically increases with pressure and temperature.
SUMMARY OF INVENTION
[0006] In view of the foregoing, an embodiment herein includes a
multi-fuel combustion system comprising: a combustor basket adapted
to combust at least two type of fuels, said combustor basket having
a circumferential wall comprising a plurality of openings; a first
conduit adapted to provide a first type of fuel directly to the
combustor basket; a second conduit adapted to provide a second type
of fuel directly to the combustor basket; and a third conduit
adapted to inject at least one of the first type of fuel and the
second type of fuel trough the openings into the combustor
basket.
[0007] In view of the foregoing, another embodiment herein includes
a method of operating a multi-fuel combustion system comprising a
first phase and a second phase, wherein the first phase comprises:
providing ignition to a combustor basket to ignite a first type of
fuel, where the first type of fuel is supplied to the combustor
basket through a first conduit; supplying steam to the first
conduit in addition to the first type of fuel and supplying steam
to the second conduit after the ignition; and wherein the second
phase comprises: supplying a second type of fuel to the combustor
basket after ignition of the first fuel through the second conduit,
while stopping the supply of the first fuel.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] The present invention is further described hereinafter with
reference to illustrated embodiments shown in the accompanying
drawings, in which:
[0009] FIG. 1 illustrates a longitudinal cross-section of the
multi-fuel combustion system,
[0010] FIG. 2 shows fuel injector holes at the region of nozzle of
the first and the second conduits,
[0011] FIG. 3 shows the fuel injector holes of the first conduit
based on a preferred embodiment of the invention,
[0012] FIG. 4 illustrates a first embodiment of cross section of
the combustor basket taken along the plane 2-2a of FIG. 1,
[0013] FIG. 5 illustrates a second embodiment of cross section of
the combustor basket taken along the plane 2-2a of FIG. 1,
[0014] FIG. 6 illustrates a third embodiment of cross section of
the combustor basket taken along the plane 2-2a of FIG. 1,
[0015] FIG. 7 illustrates the arrangement of the wall of the
combustor basket,
[0016] FIG. 8 illustrates the rib structure of the cylindrical
region of the combustor basket, and
[0017] FIG. 9 illustrates a transition and a flow conditioner
arrangement according to an embodiment of the invention.
DETAILED DESCRIPTION OF INVENTION
[0018] In general terms, a combustion turbine comprises three
sections: a compressor section, a combustor section having a
typical combustor basket and a turbine section. Air drawn into the
compressor section is compressed. The compressed air from the
compressor section flows through the combustor section where the
temperature of the air mass is further increased after combustion
of a fuel. From the combustor section the hot pressurized gas flow
into the turbine section where the energy of the expanding gases is
transformed into rotational motion of a turbine rotor that drives
an electric generator.
[0019] The lower calorific value of the syngas fuels and the
necessity to also operate the burner on a backup fuel like natural
gas, significantly affects the design of the burners. The burner
should be able to handle large fuel mass flows and the fuel
passages consequently need to have a large capacity. A too small
capacity results in a high fuel pressure drop. Due to the large
fuel mass flow involved, a high pressure drop has a much larger
impact on the total efficiency of the engine as compared to a
typical natural gas fired engine.
[0020] FIG. 1 illustrates a cross-sectional view of the multi-fuel
combustion system 10 according to one embodiment of the invention.
A multi-fuel combustion system 10 comprises a combustor basket 12.
The wall 16 of the combustor basket 12 is made of multiple
cylindrical regions 14 arranged to overlap each other at the
transition and extends from an upstream end 20 to a downstream end
22 of the combustor basket. The upstream end 20 of the combustor
basket is close to the region, where the fuel conduits generally
supply the fuels for the combustion and the down stream end is the
region, where the gas after combustion flows out to of the
combustor basket to a turbine section. The combustion system 10 is
designed to combust at least two type of fuels, for example natural
gas and syngas. The types of fuels that could be used are not
restricted to natural gas and syngas and hence the combustion
system 10 could use other fuels for combustion.
[0021] FIG. 1 further shows a first conduit 24 adapted to provide a
first type of fuel, for example natural gas, directly to the
combustor basket 12 and the second conduit 26 is adapted to provide
a second type of fuel, for example syngas directly to the combustor
basket 12. Also there is at last one third conduit 25 adapted to
inject at least one of the first type of fuel and the second type
of fuel through one or multiple openings 18 into the combustor
basket 12. There could be more than one conduit to provide each
type of fuel to the combustor basket based on the design and
requirement. For example, there could be multiple third conduits 25
to supply the fuel through multiple openings 18 in the combustor
basket 12. Also based on the mode of operation of the combustor
basket 12, each of the conduits is adapted to handle a different
fuel. Even the conduits could handle multiple fuels at the same
point of time. The second conduit 26 is positioned to encircle the
first conduit 24 or concentrically arranged for effective delivery
of the fuels. The first conduit 24 is positioned coaxially, and
internally, of a larger diameter second conduit 26. Since the
diameter of the second conduit 26 is greater that the first conduit
24, the said second conduit 26 can handle low calorific value fuels
of larger volumes since large fuel mass flows is needed to achieve
a certain thermal power input.
[0022] The third conduit 25 is adapted to inject at least one of
the first type of fuel and the second type of fuel into a
compressor discharge air that flow through at least one of the
openings 18 associated with at least one of the cylindrical regions
14. The third conduit 25 has a fuel injector nozzle 27 at the end
having 1 to 5 injector holes that are aimed at an angle of 0 to
90.degree. relative to a centerline of the opening 18. The first
conduits 24 and the second conduit 26 under consideration consist
of concentric circles of circular holes at the region of nozzle 28
of the conduits which acts as injectors for the fuels. The nozzle
28 helps to inject the respective fuels directly into the combustor
basket 12 and is positioned at the upstream end 20 of the combustor
basket 12.
[0023] FIG. 2 shows explicitly these two rows of concentric holes
at the region of nozzle 28. Each circle of rows is associated to a
conduit. The inner row of holes 21 corresponds to the first conduit
24 and the outer row of holes 23 corresponds to the second conduit
26. The number of injectors in each conduit can vary, for example
between 8 to 18 holes, but is not restricted to this numbers. A
preferred embodiment having 14 injectors for both conduits is shown
in FIG. 2. The holes can be clocked relative to each other or can
be inline.
[0024] In another preferred embodiment, the holes in the region of
nozzle 28 of the first conduit 24 comprises multiple holes
positioned at, at least two different radial distances from the
center of the nozzle for injecting a fuel flow into a region of
combustion in the combustor basket 12. This nozzle design promotes
a greater amount of fuel flow towards the center of the nozzle,
which cools the nozzle in a cost effective and simple manner. Most
importantly the hole arrangement maintains the aerodynamic
performance of the nozzle. FIG. 3 shows such a nozzle 30, of such a
type used by the first conduit 24 to inject the fuel to the
combustor basket 12. The first set of holes 32 and the second set
of holes 34 are arranged at a first radial distance 31 and at a
second radial distance 33 respectively from the center 36 of the
nozzle.
[0025] Coming back to FIG. 1, the circumferential wall 16 of the
combustor basket 12 comprises multiple openings 18. At least two of
the cylindrical regions 14a and 14b nearer to the upstream end 20
of the combustor basket 12 further comprise multiple openings 18
distributed along the circumference of the respective cylindrical
regions. This multiple openings 18 allow a compressor discharge air
from a compressor stage to flow towards a region of combustion in
the combustor basket. At the same time, at least one of the
cylindrical region near to the downstream end 22 of the combustor
basket 10 may also comprise plurality of openings 18 distributed
along the circumference of the cylindrical region to allow the
compressor discharge air to flow towards a region of combustion in
the combustor basket 12.
[0026] FIG. 4 illustrates a first embodiment 40 of cross section of
the combustor basket 12 taken along the plane 2-2a of FIG. 1. The
number of openings in the individual cylindrical region 14 varies
between 5 and 9 based on the embodiments. FIG. 4 shows 6 numbers of
openings 18 in the circular region 14 of the combustor basket
12.
[0027] FIG. 5 illustrates a second embodiment 50 of cross section
of the combustor basket taken along the plane 2-2a of FIG. 1. FIG.
5 shows 7 numbers of openings 18 in the circular region 14 of the
combustor basket 12.
[0028] FIG. 6 illustrates a third embodiment 60 of cross section of
the combustor basket 12 taken along the plane 2-2a of FIG. 1. FIG.
6 shows 9 numbers of openings 18 in the circular region 14 of the
combustor basket 12. These openings in the combustor basket are
like scoops, especially radial scoops through which compressor
discharge air is injected in the combustor basket 12. The openings
are alternatively referred to as scoops in few places in the
description for convenience.
[0029] At a minimum, the length of the scoops is half the diameter
of the scoop. For example, FIG. 6 shows an opening 18, having a
length 43 and a diameter 41. This length is oriented to the
interior region of the combustor basket 12. This length helps to
lead the air further into the combustion region. The scoops deliver
air flow with greater penetration into the fuel stream, achieving
improved heating efficiency and more complete combustion. The
openings 18 are equally distributed along the circumference of the
cylindrical region 14. Odd numbers of openings are beneficial for
wall temperatures and helps against thermo-acoustic problems, since
they provide a rotational asymmetrical configuration. The scoops
can be circular or oval in cross-section. When the scoops are oval,
the smallest dimension of the oval shape lies in the direction of
the basket centerline. The scoops can have an angle of 0-45.degree.
relative to the radial direction, from the basket centerline and
aiming downstream when angled. In a particular layout, few or all
the scoops in a cylindrical region can have an angle of 15.degree.,
whereas few or all the scoops in another cylindrical region can
have an angle of 0.degree., i.e. aimed radial towards the center
line. In addition, the scoops can be directed against the flow of
thrust of the combustor system with an angle up to 15.degree.
relative to radial direction. In another alternate embodiment, the
downstream edges of the scoops are cut-off at an angle between
0-60.degree. relative to the centerline of the combustor basket.
This is basically to avoid damages caused by the recirculation of
hot air to the scoops.
[0030] The combustion system 10 further comprises a cover plate 29
coupled to the combustor basket 12 and the first, second and third
conduits. This enables the combustor basket and the conduits to be
attached to a casing.
[0031] FIG. 7 illustrates the arrangement 70 of the wall 16 of the
combustor basket. As mentioned, the wall 16 of the combustor basket
12 is made of a plurality of cylindrical regions 14 arranged to
overlap each other at the transition. The individual cylindrical
region 14 comprises an outer surface 72, said outer surface 72 is
provided with a rib structure 82 as shown in FIG. 8. The outer
surface 72 is covered substantially by a perforated layer 74
adapted to provide an air flow for cooling the wall 16. The wall 16
of the combustor basket 12 is cooled by convection and effusion
cooling. To increase the effectiveness of the cooling method,
so-called plate fin design as shown in FIG. 7 is used. These plate
fins consist of two liners. The inner liner, which is basically the
cylindrical region is provided with the cooling rib structure 82 in
the outer surface 72 to increase the cooling surface. The outer
liner is the perforated layer 74. When the cooling air exits the
plate fin, it serves as effusion cooling air.
[0032] The multi-fuel combustion system 10 further comprises a flow
conditioner 45 positioned to encircle the combustor basket 12 and
having a conical section 46 and a cylindrical section 47 having
plurality of holes 48 adapted to allow the compressor discharge air
to flow towards a region of combustion in the combustor basket 12.
The flow conditioner 45 is used to achieve the pressure drop
required for cooling and to provide a uniform air flow towards the
region of combustion in the combustor basket 12. Holes 48 in both
the cylindrical section 47 and the conical section 46 are used as
flow passage for air.
[0033] In addition, as shown in FIG. 9, a gap 92 exists between the
transition 94 and the end 96 of the conical section 46 of the flow
conditioner 45. The flow conditioner 45 slightly overlaps the
transition 94. In this way thermal expansion does not affect the
flow area of the gap 92. The conical section 46 and a cylindrical
section 47 is connected together by a flange or could be welded
together.
[0034] The multi-fuel combustion system 1 of FIG. 1 further
comprises an exit cone 35 at the downstream end 22 of the combustor
basket 12 having multiple slots 37 aligned to the plurality of
openings 18 associated with at least one of the cylindrical regions
14. This exit cone 35 is intended to improve the mixing between the
hot combustion gasses and the cold air flow coming out of a
spring-clip passage 39. The improved mixing between these flows
lead to better CO emissions. The exit cone slots 37 aligned with
the scoops 18 prevent overheating of the exit cone 35.
[0035] The method of operating the multi-fuel combustion system 10
is now described. The operation could be divided into two main
phases a first phase and a second phase. During the first phase an
ignition is provided to a combustor basket by an ignition coil to
ignite a first type of fuel, for example natural gas supplied to
the combustor basket 12 through the first conduit 24. The method
also involves supplying steam to the first conduit 24 in addition
to the first type of fuel and supplying steam to the second conduit
26 after the ignition. Steam is provided to the second conduit 26
at a time earlier than the steam provided to the first conduit 24.
The method further involves supplying a medium, for example an
inert gas, nitrogen, steam or seal air to the second conduit 26
during the first phase for stabilizing the combustion system 10 for
any pressure difference in the combustor basket 12. In a typical
industrial arrangement the combustion system or the turbine
comprises a plurality of combustor baskets, and while in operation
there could be pressure differences that could be built up between
these combustor baskets. The supply of the medium also takes care
of this pressure difference in the combustor basket due to this
type of arrangement. The supply of the medium in the second conduit
26 is shut off once the steam supply is stabilized in the first
conduit 24 and the second conduit 26 during the first stage of
operation.
[0036] In the second phase of operation, a second type of fuel for
example syngas is supplied to the combustor basket through the
second conduit 26, while stopping the supply of the first fuel. The
method further comprises supplying a portion of the second type of
fuel to the combustor basket 12 through the first conduit 24 during
the second phase. The steam is continuously supplied in the first
conduit 24 from the first phase until the beginning of supplying
the portion of the second type of fuel through the first conduit 24
during the second phase. Also the third conduit 25 may also be used
to supply any one of the first or second type of fuel for enabling
an effective and more complete combustion by introducing the said
fuels through the openings 18 if required. This further helps in
reducing NOx emissions.
[0037] Although the invention has been described with reference to
specific embodiments, this description is not meant to be construed
in a limiting sense. Various modifications of the disclosed
embodiments, as well as alternate embodiments of the invention,
will become apparent to persons skilled in the art upon reference
to the description of the invention. It is therefore contemplated
that such modifications can be made without departing from the
embodiments of the present invention as defined.
* * * * *