U.S. patent application number 16/314879 was filed with the patent office on 2019-10-10 for metallic burner components.
This patent application is currently assigned to NOVA Chemicals (International) S.A.. The applicant listed for this patent is NOVA Chemicals (International) S.A.. Invention is credited to Leslie Wilfred Benum, Eric Clavelle, Jeffrey Crowe, Vasily Simanzhenkov.
Application Number | 20190309943 16/314879 |
Document ID | / |
Family ID | 59071033 |
Filed Date | 2019-10-10 |
![](/patent/app/20190309943/US20190309943A1-20191010-D00000.png)
![](/patent/app/20190309943/US20190309943A1-20191010-D00001.png)
![](/patent/app/20190309943/US20190309943A1-20191010-D00002.png)
![](/patent/app/20190309943/US20190309943A1-20191010-D00003.png)
United States Patent
Application |
20190309943 |
Kind Code |
A1 |
Crowe; Jeffrey ; et
al. |
October 10, 2019 |
METALLIC BURNER COMPONENTS
Abstract
The present disclosure seeks to provide a method to design a
metallic burner component for use in industrial processes such as
cracking, reforming and steam generation for which the burner
component is exposed to high furnace temperatures. The burner
component comprises a series of cooling channels and internal
baffling to direct the flow of one or more fuel and oxidant over
the portions of the burner exposed to the high furnace
temperatures. The present disclosure also provides the resulting
burner.
Inventors: |
Crowe; Jeffrey; (Calgary,
CA) ; Clavelle; Eric; (Calgary, CA) ; Benum;
Leslie Wilfred; (Red Deer, CA) ; Simanzhenkov;
Vasily; (Calgary, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NOVA Chemicals (International) S.A. |
Fribourg |
|
CH |
|
|
Assignee: |
NOVA Chemicals (International)
S.A.
Fribourg
CH
|
Family ID: |
59071033 |
Appl. No.: |
16/314879 |
Filed: |
June 1, 2017 |
PCT Filed: |
June 1, 2017 |
PCT NO: |
PCT/IB2017/053240 |
371 Date: |
January 3, 2019 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
62359748 |
Jul 8, 2016 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F23D 14/125 20130101;
F23D 14/48 20130101; F23D 14/66 20130101; F23N 1/025 20130101; F23D
14/32 20130101; F23N 2225/16 20200101; F23D 14/22 20130101; F23D
2214/00 20130101; F23D 14/78 20130101 |
International
Class: |
F23D 14/12 20060101
F23D014/12; F23D 14/22 20060101 F23D014/22; F23D 14/32 20060101
F23D014/32; F23D 14/78 20060101 F23D014/78; F23D 14/48 20060101
F23D014/48; F23N 1/02 20060101 F23N001/02 |
Claims
1. A method to determine the need for one or more of heat
conducting channels, fins, protuberances on the internal surface of
a fluid fired burner, or internal baffles, the burner operating at
temperatures of not less than 600.degree. C., comprising at least
one metal component having a thickness T and a planar uninsulated
surface directly facing (forming part of) the furnace and internal
baffles within the burner modifying the flow of one or more oxidant
and fuel and an internal having a grid of one or more heat
conducting channels, fins, or protuberances, or internal baffles,
forming part of the burner wherein one or more of oxidant and fuel
flow over said one or more heat conducting channels fins,
protuberances on the internal surface of said metal and remove heat
from the surface comprising forming a virtual or material model of
said burner and determining using one or more methods comprising
computational fluid dynamics, burner testing, pilot plant testing
and commercial trials to determine if the burner operates at
temperatures below its distortion temperature.
2. The method according to claim 1, comprising computational fluid
dynamics method comprising simulation of a burner under equilibrium
operating conditions of a furnace comprising: a. calculating the
heat flux [in W/m.sup.2 K] from the furnace through the surface of
the metal component; b. calculating the convective heat transfer
from the internal surface of the metal component to said one or
more of oxidant and fuel; c determining an equilibrium temperature
of the metal component at operating conditions of the furnace; d.
comparing the calculated equilibrium temperature of the metal
component to the distortion temperature of the metal component; e.
if the distortion temperature of the metal component is less than
20.degree. C. below the calculated equilibrium temperature of the
metal component modifying one or more of: i) modifying the heat
conducting channels, fins, protuberances dimension and density on
the internal surface of said metal component; and ii) the internal
baffles therefor modifying the velocity of gas and heat transfer
coefficient on the internal surface of said metal component; f)
reiterating steps a) through e) until the calculated temperature of
the metal component is at least 20.degree. C. lower than the
distortion temperature of the metal component.
3. The method according to claim 2 once a step f has been satisfied
further modifying one or more of the heat conducting channels,
fins, protuberances dimension and density, or size, location and
number of the internal baffles, while meeting the criterion of step
f) to minimize the manufacturing cost.
4. The method according to claim 3, further comprising modifying
the flow rate of oxidant and fuel to determine a safe operating
window for said burner.
5. The method according to claim 1, wherein the fuel is natural
gas.
6. The method according to claim 1, wherein the oxidant is selected
from air and mixtures of oxygen and an inert gas.
7. The method according to claim 1 wherein the burner is a wall
burner.
8. The method according to claim 1, wherein the burner is a top
downward directed burner.
9. The method according to claim 1 wherein the burner is a floor
burner.
10. A burner for a chemical reactor prepared according to claim
1.
11. A burner for a boiler prepared according to claim 1.
12. A burner for a heater prepared according to claim 1.
13. A chemical reformer having one or more burner according to
claim 10.
14. A boiler having one or more burners according to claim 11.
15. A superheater having one or more burners according to claim
12.
16. A chemical cracker having one or more burners according to
claim 10.
17. A chemical refiner having one or more burners according to
claim 10.
18. A method according to claim 1, comprising one or more of burner
testing, pilot plant testing and commercial trials comprising: a.
manufacturing one or more burner components or the burner per se
from a metal stable at temperatures 700.degree. C. to about
1350.degree. C. having for one or more of heat conducting channels,
fins, protuberances of a selected dimension and density, and one or
more internal baffles of a selected size and location; b. testing
the burner or burner components in one or more of burner testing,
pilot plant testing and commercial trials at anticipated operating
temperatures and various flow conditions of the fuel and oxidant
over said one or more of heat conducting channels, fins,
protuberances, and internal baffles to determine if the temperature
of the burner or components under the test conditions is less than
20.degree. C. below the heat distortion temperature of the metal;
c. if the temperature of the burner or components under the test
conditions is less than 20.degree. C. below the heat distortion
temperature of the metal manufacturing a new more burner components
or the burner having one or more modifications to dimensions of the
heat the conducting channels, fins, protuberances and density the
heat the conducting channels, fins, protuberances, size, location
and number of internal baffles to improve the heat transfer
properties thereof; d. repeating steps a through c until the heat
distortion temperature of the burner or components is more than
20.degree. C. below the heat distortion temperature of the metal.
Description
FIELD
[0001] The present disclosure relates to the design of metallic
components for use in burners for stationary industrial
applications in which the metal components are directly exposed to
a high temperature of not less than 600.degree. C. Such burners are
applicable in many applications including chemical process such as
cracking, reforming, refining and non chemical applications such as
heating and power generation such as super heaters.
BACKGROUND
[0002] The cracking of paraffins such as ethane to olefins such as
ethylene is energy intensive. The paraffin passes through tubes or
coils in a furnace with flue gasses heated up to about 1200.degree.
C. The internal walls of the furnace are refractory material which
radiate heat to the process coils. The walls are heated by a series
of burners in the floor or walls or both. The temperature of the
walls may reach temperature in the range from 700.degree. C. to
1350.degree. C., typically 800.degree. C. to 1200.degree. C.
[0003] Currently, parts of the burner in the interior of the
furnace are manufactured with a refractory material. This makes the
burners heavy. Additionally, the refractory or ceramic tends to be
brittle and can break during operation.
[0004] British patent 1,480,150 discloses an improvement relating
to high temperature burners in which a metallic double walled quarl
having an inner and outer surface and providing a closed chamber
surrounds the burner. A cooling medium passes through the quarl to
keep the burner at a lower temperature. The patents teaches the
cooling medium could be air being fed to the burner or exhaust
gasses from combustion. The reference teaches away from the present
disclosure as a double walled quarl is not used.
[0005] The paper Development of Ultra Compact Low NOx Burner for
Heating Furnace in the Proceedings of the 1998 International Gas
Research Conference by A. Omori of Osaka Gas Co., Ltd. pages
269-276 discloses a metal burner. The burner does not have channels
in the interior metal burner walls to pass air over the wall and
cool the burner. Further the burner is designed to provide a vortex
flow of air to the flame to increase the surface area and reducing
the flame temperature. Such a reduction in flame temperature may
not be desirable.
[0006] United States Patent application 20100021853 published Jan.
28, 2010 in the name of Bussman assigned to John Zink Company LLC.
Teaches a burner to produce low NOx emissions. In the figures the
burners are tiles (e.g. ceramic or refractory) in which a
significant amount of the burner is made of such materials. In
contrast the burners of the present disclosure comprise less than
20 wt % of ceramic or refractory, preferably no ceramic or
refractory. Additionally, is ceramic or refractory is used it is
over coated on the outside of the metal.
[0007] U.S. Pat. No. 8,220,269 issued Jul. 17, 2012 from an
application filed Sep. 30, 2008 discloses a combustor for a gas
turbine engine. There is a baffle 9 in the combustion zone. Air may
be introduced behind the baffle which helps to cool the baffle.
There is no hint or suggestion of any type of channeling on the
back of the baffle to help cool it.
[0008] The present disclosure seeks to provide a method to
calculate the required heat removal from burner surfaces directly
exposed to high furnace temperatures to keep the component below
its distortion temperature. The heat removal requirements are used
to determine the density and dimension of cooling channels and
internal baffles to direct the flow of at least one or more of the
fuel and the oxidant flow over the burner surfaces.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is a schematic drawing of a floor burner design used
for the CFD (computational fluid dynamics) or
experiment/demonstration.
[0010] FIG. 2 is a schematic drawing of a cracking furnace.
[0011] FIG. 3 is a grey scale of the burner of FIG. 1 showing the
calculated temperature distribution of the burner simulated using
CFD analysis.
SUMMARY
[0012] The present disclosure provides a method to determine the
need for one or more of heat conducting channels, fins,
protuberances on the internal surface of a fluid fired burner, or
internal baffles, the burner operating at temperatures of not less
than 600.degree. C., comprising at least one metal component having
a thickness T and a planar uninsulated surface directly facing
(forming part of) the furnace and internal baffles within the
burner modifying the flow of one or more oxidant and fuel and an
internal having a grid of one or more heat conducting channels,
fins, or protuberances, or internal baffles, forming part of the
burner wherein one or more of oxidant and fuel flow over said one
or more heat conducting channels, fins, protuberances on the
internal surface of said metal and remove heat from the surface
comprising forming a virtual or material model of said burner and
determining using one or more methods comprising computational
fluid dynamics, burner testing, pilot plant testing and commercial
trials to determine if the burner operates at temperatures below
its distortion temperature.
[0013] A further embodiment comprises a computational fluid
dynamics method comprising simulation of a burner under equilibrium
operating conditions of a furnace comprising:
[0014] a. calculating the heat flux [in W/m.sup.2 K] from the
furnace through the surface of the metal component;
[0015] b. calculating the convective heat transfer from the
internal surface of the metal component to said one or more of
oxidant and fuel;
[0016] c determining an equilibrium temperature of the metal
component at operating conditions of the furnace;
[0017] d. comparing the calculated equilibrium temperature of the
metal component to the distortion temperature of the metal
component;
[0018] e. if the distortion temperature of the metal component is
less than 20.degree. C. below the calculated equilibrium
temperature of the metal component modifying one or more of: [0019]
i) modifying the heat conducting channels, fins, protuberances
dimension and density on the internal surface of said metal
component; and [0020] ii) the internal baffles
[0021] therefor modifying the velocity of gas and heat transfer
coefficient on the internal surface of said metal component;
[0022] f) reiterating steps a) through e) until the calculated
temperature of the metal component is at least 20.degree. C. lower
than the distortion temperature of the metal component.
[0023] In a further embodiment once step f has been satisfied
further modifying one or more of the heat conducting channels,
fins, protuberances dimension and density, or size, location and
number of the internal baffles, while meeting the criterion of step
f) to minimize the manufacturing cost.
[0024] In a further embodiment further comprising modifying the
flow rate of oxidant and fuel to determine a safe operating window
for said burner.
[0025] In a further embodiment the fuel is natural gas.
[0026] In a further embodiment the oxidant is selected from air and
mixtures of oxygen and an inert gas.
[0027] In a further embodiment the burner is a wall burner.
[0028] In a further embodiment the burner is a top downward
directed burner.
[0029] In a further embodiment the burner is a floor burner.
[0030] In a further embodiment a burner for a chemical reactor is
prepared as above.
[0031] In a further embodiment a burner for a boiler is prepared as
above.
[0032] In a further embodiment a burner for a heater is prepared as
above.
[0033] A further embodiment provides a chemical reformer having one
or more burner as above.
[0034] A further embodiment provides a boiler having one or more
burners as above.
[0035] A further embodiment provides a superheater having one or
more burners as above.
[0036] A further embodiment provides a chemical cracker having one
or more burners as above.
[0037] A further embodiment provides a chemical refiner having one
or more burners as above.
[0038] In a further embodiment there is provided a method as above,
comprising one or more of burner testing, pilot plant testing and
commercial trials comprising:
[0039] a. manufacturing one or more burner components or the burner
per se from a metal stable at temperatures 700.degree. C. to about
1350.degree. C. having for one or more of heat conducting channels,
fins, protuberances of a selected dimension and density, and one or
more internal baffles of a selected size and location;
[0040] b. testing the burner or burner components in one or more of
burner testing, pilot plant testing and commercial trials at
anticipated operating temperatures and various flow conditions of
the fuel and oxidant over said one or more of heat conducting
channels, fins, protuberances, and internal baffles to determine if
the temperature of the burner or components under the test
conditions is less than 20.degree. C. below the heat distortion
temperature of the metal;
[0041] c. if the temperature of the burner or components under the
test conditions is less than 20.degree. C. below the heat
distortion temperature of the metal manufacturing a new more burner
components or the burner having one or more modifications to
dimensions of the heat the conducting channels, fins, protuberances
and density the heat the conducting channels, fins, protuberances,
size, location and number of internal baffles to improve the heat
transfer properties thereof;
[0042] d. repeating steps a through c until the heat distortion
temperature of the burner or components is more than 20.degree. C.
below the heat distortion temperature of the metal.
DETAILED DESCRIPTION
[0043] Other than in the operating examples or where otherwise
indicated, all numbers or expressions referring to quantities of
ingredients, reaction conditions, etc. used in the specification
and claims are to be understood as modified in all instances by the
term "about." Accordingly, unless indicated to the contrary, the
numerical parameters set forth in the following specification and
attached claims are approximations that can vary depending upon the
properties that the present disclosure desires to obtain. At the
very least, and not as an attempt to limit the application of the
doctrine of equivalents to the scope of the claims, each numerical
parameter should at least be construed in light of the number of
reported significant digits and by applying ordinary rounding
techniques.
[0044] Notwithstanding that the numerical ranges and parameters
setting forth the broad scope of the disclosure are approximations,
the numerical values set forth in the specific examples are
reported as precisely as possible. Any numerical values, however,
inherently contain certain errors necessarily resulting from the
standard deviation found in their respective testing
measurements.
[0045] Also, it should be understood that any numerical range
recited herein is intended to include all sub-ranges subsumed
therein. For example, a range of "1 to 10" is intended to include
all sub-ranges between and including the recited minimum value of 1
and the recited maximum value of 10; that is, having a minimum
value equal to or greater than 1 and a maximum value of equal to or
less than 10. Because the disclosed numerical ranges are
continuous, they include every value between the minimum and
maximum values. Unless expressly indicated otherwise, the various
numerical ranges specified in this application are
approximations.
[0046] All compositional ranges expressed herein are limited in
total to and do not exceed 100 percent (volume percent or weight
percent) in practice. Where multiple components can be present in a
composition, the sum of the maximum amounts of each component can
exceed 100 percent, with the understanding that, and as those
skilled in the art readily understand, that the amounts of the
components actually used will conform to the maximum of 100
percent.
[0047] As used in this specification, and as it relates to the
burner material, substantially metal or substantially metallic,
metal and metallic all mean, relative to the total construction of
the burner not less than 80% of the burner is metallic and the
balance is an optional ceramic over coating on limited external
surfaces of the burner as described below. In other words, the
burner has no more than 20 wt. % of ceramic or refractory, or no
more than 10% or no more than 5%, of ceramic or refractory.
[0048] As used in this specification, cooling channels are machined
into the internal surface of the burner, the dimensions of the
cooling channels refers to the width and height of the cooling
channels. The width of the cooling channels is determined at the
base of the cooling channel. The height of the cooling channel
(ribs) refers to the height of the wall of the cooling channel
above the base of the channel. However, if walls of the cooling
channel are not perpendicular to the metal component then it refers
to the height from the outer tip of the wall to the base of the
cooling channel.
[0049] As used in this specification, fins refer to thin ribbons of
metal adhered to the inner surface of the burner, the dimensions of
the cooling fins refers to the thickness and height of the cooling
fins above the surface of the metal.
[0050] As used in this specification, protuberances refer to small
discrete surface modification to increase surface area and
turbulence at the surface.
[0051] As used in this specification, baffles refer to metal plates
internal to the burner that are used to modify the flow path and
velocity of one or more oxidant or fuel over surfaces exposed to
high furnace temperatures.
[0052] The density of the cooling channels, fins, protuberances or
combinations thereof means the number of channels fins or array of
protuberances per unit length transverse to the channels fins or
array of protuberances (e.g. 5 channels per cm.) in those areas
where the channels are present. This is distinct from the surface
area coverage of the cooling channels. For example if only half of
the internal surface of the metal component has cooling channels
fins or protuberances, the channels fins or protuberances would
have a different dimension than for channels covering the entire
surface of the metal component. The fabrication costs for these
different designs would differ so that in some embodiments the
channel, fin, protuberance or protuberance array design or
combinations thereof and surface coverage (either total or
segregated by the type of heat conductive structure) is optimized
to reduce manufacturing cost.
[0053] There is a significant amount of prior relating to cooling
of burner tips directly exposed to the furnace. In some
embodiments, this art requires some sort of "swirling" vane to
direct gas passing out of the nozzle across the surface of the
nozzle. There does not appear to be any art relating to providing a
metal component such as a planar piece or sheet exposed directly to
the furnace, without insulation (e.g. a refractory) with cooling
channels, fins, or protuberances, or combinations thereof on the
surface not exposed to the furnace (e.g. the reverse or internal
side).
[0054] As used herein planar refers to the degree of curvature of
an element. But the current disclosure is not limited by the shape
or geometry of the sides of the enclosure (e.g. box). While planar
surfaces are exemplified, embodiments where the sides of the
enclosure are curved or wavy are also envisioned.
[0055] In some embodiments the fuel is predominantly a fluid fuel,
for example a gas such as natural gas. In some embodiments the fuel
could be a liquid hydrocarbon for example a saturated C.sub.4-10
aliphatic or cyclic hydrocarbon. The fuel is not a solid
particulate such as pulverized coal.
[0056] In some embodiments the oxidant comprises gaseous oxygen,
for example air but it may also comprise mixtures of oxygen and
inert gases such as nitrogen. The mixtures may comprise up to about
60 wt. % of inert gas, for example from 60 to 40 wt. % of inert
gas.
[0057] The burners of the present disclosure comprise a chamber
upstream from the exit to the furnace through which one or more of
the oxidant and the fuel mix pass before entering the furnace. The
chamber comprises one or more metal components having one or more
faces or surfaces which are directly exposed to the furnace. The
opposite side of the metal component faces the interior of the
chamber. In accordance with the present disclosure the heat
conducting channels, fins or protuberances or combinations thereof
are provided on the inward facing side of the metal component
through which one or more of the oxidant and fuel pass removing
heat from the metal component.
[0058] However the issue is determining by calculation (e.g. CFD)
or experiments (burner testing, pilot plant trials or plant trials)
or combinations thereof the dimension and density of channels,
fins, protuberances or combinations thereof to provide the
appropriate amount of cooling so that the part does not distort or
degrade (soften or melt) under the conditions of use. In some
embodiments the temperature of the metal component should be kept
at least 20.degree. C. below the distortion or softening
temperature of the metal.
[0059] In one embodiment the first step in the present disclosure
is to make a computer model of the burner in question and
particularly the chamber and the metal component(s) which are to be
directly exposed to the furnace without an insulation covering. The
computer model may be generated by any known design software used
in CAD/CAM applications. In preparing the model as a starting point
the sides of the metal component directly exposed to the furnace
should be free of channels. The opposite side (e.g. inside the
chamber) may be free of heat conducting channels, fins, or
protuberances or combinations thereof or have heat conducting
channels, fins, protuberances or combinations thereof having a
size, density and surface coverage based on an estimate of an
experienced operator. The CAD/CAM model of the interior of the
burner should be free of baffles.
[0060] In some embodiments a starting point for the modeling may
include the following.
[0061] The longitudinal channels, if present, may have a height to
width ratio from 0.1 to 2 in some embodiments from 0.5 to 2, in
some embodiments from 0.5 to 1. The ribs may have a height from 4
to 25 mm, or from 8 to 22 mm, in some instances from 10 to 20
mm.
[0062] The fins may have dimensions and spacing comparable to the
longitudinal channels. They may have a height form about 4 to 25
mm, or from 8 to 22 mm, in some instances form 10 to 20 mm and a
thickness from 2 to 20 mm, in some embodiments from 5 to 1.5 cm and
be spaced apart 2 mm to 2 cm, in some instances from 5 mm to 1.5
cm.
[0063] The fins may have a number of cross sectional shapes, such
as rectangular, square, triangular or trapezoidal. A trapezoidal
shape may not be entirely intentional, but may arise from the
manufacturing process, for example when it is too difficult or
costly to manufacture (e.g. cast or machine) a triangular cross
section.
[0064] In some embodiments the fin may be cast as part of the metal
surface or be welded to the metal surface.
[0065] The protuberances are closed solids.
The protuberance may have geometrical shape, having a relatively
large external surface that contains a relatively small volume,
such as for example tetrahedrons, pyramids, cubes, cones, a section
through a sphere (e.g. hemispherical or less), a section through an
ellipsoid, a section through a deformed ellipsoid (e.g. a tear
drop) etc. Some useful shapes for a protuberance include:
[0066] a tetrahedron (pyramid with a triangular base and 3 faces
that are equilateral triangles);
[0067] a Johnson square pyramid (pyramid with a square base and
sides which are equilateral triangles);
[0068] a pyramid with 4 isosceles triangle sides;
[0069] a pyramid with isosceles triangle sides (e.g. if t is a four
faced pyramid the base may not be a square it could be a rectangle
or a parallelogram);
[0070] a section of a sphere (e.g. a hemi sphere or less);
[0071] a section of an ellipsoid (e.g. a section through the shape
or volume formed when an ellipse is rotated through its major or
minor axis);
[0072] a section of a tear drop (e.g. a section through the shape
or volume formed when a non uniformly deformed ellipsoid is rotated
along the axis of deformation); and
[0073] a section of a parabola (e.g. section though the shape or
volume formed when a parabola is rotated about its major axis--a
deformed hemi- (or less) sphere), such as e.g. different types of
delta-wings.
[0074] The spacing and height of the protuberances is comparable to
that for fins. They may have a height form about 4 to 25 mm, or
from 8 to 22 mm, in some instances form 10 to 20 mm and a thickness
from 2 to 20 mm, in some embodiments from 5 to 15 cm and be spaced
apart 2 mm to 2 cm, in some instances from 5 mm to 1.5 cm.
[0075] The protuberances may also be cast on to the internal
surface of the metal. In some embodiments the protuberances form an
array. In some embodiments the array is symmetrical, for example
they may be in parallel rows (linear array) or with the
protuberances in adjacent rows offset by the array spacing (diamond
type array)
[0076] The channels, fins, protuberances or combinations thereof
may cover from about 15 to 100%, in some embodiments from 25 to
100%, in some embodiments from 60 to 100% of the internal surface
area of the flow path. When the ribs or channels cover less than
100% of the internal surface area of the flow path the ribs or
channels form a continuous series of parallel ribs or channels at
least on the internal surface of the portions of the burner exposed
to the cracking furnace.
[0077] In some of embodiments the burner may have baffles that span
between 50 to 100% of the burner width and reduce the flow area
adjacent to surfaces exposed to high furnace temperatures by 20 to
70%.
[0078] In some embodiments there is provided a burner wherein there
is a descending baffle depending from a region not more than 10%
forward of the forward lip of said one or more outlets for at least
a gaseous oxidant, to the forward lip of said one or more outlets
for said one or more gaseous oxidants, said baffle descending
inside the upper metal section of the burner from 50 to 90% of the
height of the front face of said burner; and extending laterally
across the inner surface of the burner from 100 to 75% of the width
of the face of said burner, said descending baffle being positioned
so that there are substantially equal openings (as used herein
substantially equal openings means a variation in height that is
less than 10%, or for example less than 5%, or less than 2%) on
each side of the descending baffle relative to the side walls of
the metal upper section and where necessary said descending baffle
having one or more circular channels there through to permit one or
more fuel supply lines to pass there through.
[0079] In a further embodiment there is provided a burner further
comprising an ascending baffle extending forward from the upper
wall of said lower metal flow passage into from 45 to 85% of the
open area in the chamber of a metal upper section.
[0080] In a further embodiment there is provided a burner wherein
said ascending baffle extending forward from the upper wall of said
lower metal flow passage is bent in its forward section up towards
the open top to provide an upwards facing ascending baffle parallel
to the inner front wall of upper section and where required the
upward extending section of said ascending baffle having one or
more circular channels there through to permit one or more fuel
supply lines to pass there through.
[0081] In a further embodiment there is provided a burner wherein
said ascending baffle extending forward from the upper wall of said
lower metal flow passage further comprises on the surface facing
the inner front wall of upper section a series of parallel
longitudinal internal ribs to direct the flow of said at least a
gaseous oxidant over the internal surface of said substantially
metallic flow passage.
[0082] And in some embodiments both the ascending and descending
baffles may be present.
[0083] The metallic walls may have a thickness from 4 to 25 mm, or
from 8 to 22 mm, in some instances from 10 to 20 mm.
[0084] In some embodiments the burner design or components thereof
may be fabricated in a size form test burner to commercial plant
size and experimentally tested using burner test facilities, pilot
plant facilities or in a plant trial. The resistance to heat
distortion of the fabricated burner are evaluated and modification
may be made to the burner to improve the resistance to distortion.
The testing of the modified burner would be an iterative process to
achieve a suitable design.
[0085] In some embodiments the model of the metal component is then
used in a computational fluid dynamic model of the burner in
operation. Input data includes the flow rate and composition of the
oxidant and fuel, the furnace geometry, and the process duty. There
is a balance between the convective cooling of the fuel and oxidant
flowing through the burner relative to the heat release of the
combusting fuel. The convective cooling flow rate is interdependent
with the heat release rate, fuel composition and typical excess
air, which results in a wet molar concentration of oxygen between
1% and 10%. The required heat release of the burner and the flow
rate of oxidant and fuel will define the range of sizes of the
burner. This range will be further defined by the range of
velocities of oxidant and fuel velocities required for cooling. And
the maximum practical pressure drop of the fuel and oxidant as it
flows through the burner. The flow rate of fuel and oxidant can be
calculated as needed by a person of ordinary skill in the art.
[0086] The output of the simulation includes the conductive,
convective and radiative heat transfer throughout the furnace and
burner. In some embodiments the heat of combustion of the fuel is
considered as the flow rate will increase the convective heat
transfer to the fluid flowing over the channels but it will also
increase the heat and temperature in the furnace. The model should
calculate the equilibrium temperature of the furnace and the
equilibrium temperature of the metal part. The model will then
compare the equilibrium temperature of the metal part to a
predetermined temperature such as a specified temperature
differential (e.g. 10.degree. C., to 40.degree. C.) below the
softening temperature or heat distortion temperature. Potentially
the melting temperature could be used but it is too close to
failure of the part. There is no safety margin.
[0087] If the model determines the equilibrium temperature is the
required differential below the softening temperature then the
model need not be run further. If the temperature is too close to
the heat distortion temperature the dimensions, density, and
surface coverage of the channels as well as the internal baffles
are modified and the equilibrium temperature is compared to the
required temperature (e.g. the distortion temperature -20.degree.
C.). The process is reiterated for each change in the channels
dimensions, density and surface coverage until a satisfactory
equilibrium temperatures is obtained (e.g. the distortion
temperature -20.degree. C.).
[0088] In some embodiments after the appropriate equilibrium
temperature is obtained the metal surface may be further modeled to
obtain a more economic pattern for the channels and/or a more
mechanically stable pattern for the channels.
[0089] The chamber may be of any shape. In some embodiments the
chamber has at least one planar face exposed to the furnace. The
chamber maybe selected from one or more of the following shapes: an
N sided prism where N is a whole number greater that 4 (e.g. 5, 6,
7, 8) although in some instances N is an even number greater than
4. (hexagonal prism, octagonal prism etc.) The chamber may comprise
a combination of shapes a rectangular prism (N is 4) or a
triangular prism N is 3. Spheres and tubes are generally not
preferred shapes for the chamber. The chamber typically has an
inlet on one side (planar face) and an outlet on an opposite was or
a top.
[0090] In some embodiments, it is desirable to have a turbulent
flow through the chamber. In some instances there may be one or
more internal baffles within the chamber to increase turbulence of
the flow. The turbulent flow also helps with heat transfer from the
channels to the fluid flowing through the chamber.
[0091] The metallic components directly exposed to the furnace used
in the burner should be mechanically stable at temperatures from
about from about 700.degree. C. to about 1350.degree. C., or from
about 850.degree. C. to about 1200.degree. C., or from 850.degree.
C. to 1100.degree. C. The metal components may be made from any
high temperature steel such as stainless steel selected from
wrought stainless, austenitic stainless steel and HP, HT, HU, HW
and HX stainless steel, heat resistant steel, and nickel based
alloys. The coil pass may be a high strength low alloy steel
(HSLA); high strength structural steel or ultra high strength
steel. The classification and composition of such steels are known
to those skilled in the art.
[0092] In one embodiment the stainless steel, for example heat
resistant stainless steel, comprises from 13 to 50, or 20 to 50, or
from 20 to 38 weight % of chromium. The stainless steel may further
comprise from 20 to 50, or from 25 to 50, or from 25 to 48, or from
about 30 to 45 weight % of Ni. The balance of the stainless steel
may be substantially iron.
[0093] The disclosed embodiments may also be used with nickel
and/or cobalt based extreme austentic high temperature alloys
(HTAs). In some embodiments the alloys comprise a major amount of
nickel or cobalt. In some embodiments the high temperature nickel
based alloys comprise from about 50 to 70, or from about 55 to 65
weight % of Ni; from about 20 to 10 weight % of Cr; from about 20
to 10 weight % of Co; and from about 5 to 9 weight % of Fe and the
balance one or more of the trace elements noted below to bring the
composition up to 100 weight %. In some embodiments the high
temperature cobalt based alloys comprise from 40 to 65 weight % of
Co; from 15 to 20 weight % of Cr; from 20 to 13 weight % of Ni;
less than 4 weight % of Fe and the balance one or more trace
elements as set out below and up to 20 weight % of W. The sum of
the components adding up to 100 weight %.
[0094] In some embodiments the steel may further comprise a number
of trace elements including at least 0.2 weight %, up to 3 weight
%, or for example 1.0 weight %, up to 2.5 weight %, or not more
than 2 weight % of manganese; from 0.3 to 2, or for example 0.8 to
1.6, or for example less than 1.9 weight % of Si; less than 3, or
less than 2 weight % of titanium, niobium (for example less than
2.0, or less than 1.5 weight % of niobium) and all other trace
metals; and carbon in an amount of less than 2.0 weight %. The
trace elements are present in amounts so that the composition of
the steel totals 100 weight %
[0095] The burners as described above may be mounted in the wall of
the furnace, could be floor mounted or ceiling mounted (e.g. as in
a reformer). The refractory lining in the wall, floor or ceiling,
as the case may be, has an opening through which the burner fits
and then a refractory and cement are used to close the opening
through which the burner was fitted. The burner is also attached to
the external supports (frame) for the furnace and the external
ducts to supply oxidant, for example air, to the burner. Also the
fuel supply lines are connected to the fuel supply, for example,
natural gas.
[0096] The metallic burners also comprise ancillary equipment such
as pilot lights, and the fuel feed there for joining members for
duct works and any mechanical oxidant flow controllers as well as
instrumentation.
[0097] The present disclosure is illustrated by the following
demonstration.
Demonstration
[0098] One embodiment of the present disclosure will now be
demonstrated with reference to FIGS. 1, 2 and 3. FIG. 2 shows a
simple schematic of Foster-Wheeler pyrolysis furnace such as used
for cracking ethane to ethylene. In a cracker such as the ethylene
cracker shown in FIG. 2, the feed stock 201 (a mixture of ethane
and steam) enters a coil 202 passing through the exhaust portion of
the 203 typically referred to as the convection section of the
furnace. The feed is pre-heated in the convection section to a
controlled and specific temperature. In some embodiments, steam is
also heated in the convection section in a separate coil 207. In
some embodiments, boiler feed water is also heated in the
convection section in a separate coil 206. The coil 202 with the
feed stock 201 passes through the radiant section 204 of the
furnace before it exits 205 at which point it may be rapidly
quenched to a lower temperature. The coil 202 passes through the
radiant section of the furnace 204 it is exposed to the heat
generated by the burners 208. The furnace shown in FIG. 2 displays
a cracking furnace configuration with two radiant sections with the
coil passing through both radiant sections. There are numerous
other configurations including a furnace with a single radiant
section.
[0099] Computational fluid dynamics (CFD) has been used previously
to model the operation of the radiant section of a NOVA Chemicals
ethane cracker. In some embodiments the operation of this section
of this particular pyrolysis furnace has pre-heated combustion air
at 215.degree. C. air and fuel composed of a mixture of 60% molar
fraction hydrogen and 40% molar fraction natural gas at a
pre-heated temperature of 130.degree. C. The burners within the
furnace are commercially available low-NOX burners constructed of
refractory typically used in high temperature furnaces. The single
burner heat release rate is approximately 5 MMBtu/hr (1.5 MW) with
the flue gas wet oxygen molar concentration at 2%. Real plant data
and CFD model results have been compared including but not limited
to the surface temperature of the process coils, surface
temperature of the refractory burners, flue gas exit temperature
and process coil heat transfer rates. A comparison of the modeled
vs. plant operating measurements was found to be sufficiently close
(within 10%) such that it could be used for the prediction of plant
performance in a practical manner.
[0100] This validation work was used to define model requirements
and settings by the inventors to predict the performance of a
burner designed using metal as a material of construction instead
of refractory material in accordance with the present disclosure.
FIG. 2 shows a profile view of a Foster-Wheeler style pyrolysis
furnace with the radiant section 204 and the locations of burners
208. FIG. 3 shows the surface temperature as predicted by CFD of a
burner (such as shown in FIG. 1) designed in accordance with this
patent and operating at conditions equal to described in the
paragraph above. The temperature scale has a range selected to show
temperatures between 500.degree. C. and 1000.degree. C.
Temperatures below or above this range are shown at the extremes of
the scale. FIG. 3 shows that for this example burner the surface
temperature is no higher than 900.degree. C. which is below the
distortion temperature of metals that would be used for burner
construction. This shows that there is a balance of heat transfer
between the firing rate of the burner and the internal cooling rate
induced by the combustion air and the design of the metal
burner.
* * * * *