U.S. patent application number 10/459789 was filed with the patent office on 2004-09-23 for mixing process for increasing chemical reaction efficiency and reduction of byproducts.
Invention is credited to Moberg, Goran.
Application Number | 20040185402 10/459789 |
Document ID | / |
Family ID | 33551339 |
Filed Date | 2004-09-23 |
United States Patent
Application |
20040185402 |
Kind Code |
A1 |
Moberg, Goran |
September 23, 2004 |
Mixing process for increasing chemical reaction efficiency and
reduction of byproducts
Abstract
A system and method for increasing reaction and reactor
efficiency, including the steps of providing a reactor with a
plurality of reagent introduction or injection ducts,
asymmetrically positioned in a tangentially reinforcing manner at
spaced apart predetermined locations; injecting at least one
reagent; wherein the velocity of the injected reagent(s) is such
that the ratio of the reagent velocity to the reactor width is
between about 2 sec.sup.-1 to about 150 sec.sup.-1; thereby
increasing reaction and reactor efficiency and reducing the
byproducts produced thereby, via mixing and rotation of the
reaction space.
Inventors: |
Moberg, Goran; (Cary,
NC) |
Correspondence
Address: |
JINAN GLASGOW
P O BOX 28539
RALEIGH
NC
276118539
|
Family ID: |
33551339 |
Appl. No.: |
10/459789 |
Filed: |
June 12, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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10459789 |
Jun 12, 2003 |
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10391825 |
Mar 19, 2003 |
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Current U.S.
Class: |
431/9 |
Current CPC
Class: |
F23L 9/02 20130101; F23C
5/32 20130101; F23C 6/045 20130101; F23J 7/00 20130101; F23C
2201/101 20130101 |
Class at
Publication: |
431/009 |
International
Class: |
F23M 003/00 |
Claims
What is claimed is:
1. A method for increasing reaction efficiency and for reducing
byproducts formation, comprising the steps of: providing a staged
reaction system including a reactor and at least one reagent for
introduction into a reaction process, introducing the at least one
reagent to the reactor by asymmetrical injection at predetermined,
spaced apart locations; controlling the asymmetrical injection to
produce a high velocity mass flow and a turbulence resulting in
dispersion of the at least one reagent into the reaction system and
mixing of the reaction space, thereby providing increased reaction
efficiency and reduced byproducts formation in the reaction
process.
2. The method according to claim 1, further including the step of
adding additional reagents in stages, spaced apart in location and
time, at high velocity.
3. The method according to claim 1, wherein at least one reagent is
fuel.
4. The method according to claim 1, wherein at least one reagent is
secondary air.
5. The method according to claim 2, wherein the additional reagents
are introduced at a plurality of injection ducts, asymmetrically
positioned in an opposing manner;
6. The method according to claim 1, wherein two reagents, a first
reagent and a second reagent, are introduced to the system in a
sequential manner with the first reagent being introduced prior to
the second reagent.
7. The method according to claim 1, the velocity of the injected
reagent is such that the ratio of the velocity to the reactor width
is between about 2 sec.sup.-1 to about 150 sec.sup.-1; thereby
increasing combustion efficiency and furnace efficiency via swirl,
peripheral turbulence, and rotation-induce turbulence of the
reactor.
10. The method of claim 1, wherein the system has at least two
levels of injection ducts.
11. The method of claim 10, wherein the system has at least three
levels of injection ducts for injection of the at least one
reagent.
12. The method of claim 1, wherein the velocity of the injected
reagent is such that the ratio of the velocity to the reactor width
is between about 3 sec.sup.-1 to about 60 sec.sup.-1.
13. A method for increasing combustion efficiency in a reactor and
for reducing byproducts therein, comprising: providing a reactor
with a plurality of reagent injection ducts, asymmetrically
positioned in an opposing manner; injecting a first reagent through
a first stage prior to injection of a second reagent; injecting a
second reagent through the plurality of reagent injection ducts;
wherein the velocity of the injected second reagent is such that
the penetration of the injected reagents is greater than the
reactor width by at least about 1.5 widths; thereby increasing
reaction efficiency and reducing pollutants via mixing and rotation
of the reaction space.
16. The method of claim 13, wherein the system has at least two
levels of reagent introduction ducts for injection of the at least
one reagent.
17. The method of claim 16, wherein the system has at least three
levels of reagent ducts for injection of the at least one
reagent.
18. A method for increasing chemical reaction efficiency,
comprising: providing a reactor with a plurality of reagent
injection ducts, asymmetrically positioned in an opposing manner;
injecting at least one reagent through the ducts in stages; wherein
the velocity of the at least one reagent is such that the at least
one injected reagent rotates at least one half revolution prior to
exiting the reactor; thereby increasing reactor efficiency via
mixing and rotation of the reagents in the reactor.
21. The method of claim 18, wherein the system has at least two
levels of reagent ducts for injection of the reagents.
22. The method of claim 18, wherein the system has at least three
levels of reagent ducts for injection of the reagents.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This nonprovisional utility patent application claims the
benefit of one or more prior filed copending nonprovisional
applications; a reference to each such prior application is
identified as the relationship of the applications and application
number (series code/serial number): The present application is a
Continuation-In-Part of application Ser. No. 10/391,825, which is
incorporated herein by reference in its/their entirety.
BACKGROUND OF THE INVENTION
[0002] (1) Field of the Invention
[0003] The present invention relates generally to a system and
method for improving the efficiency of chemical reactions and for
reducing byproducts production, and, more particularly, to a system
and method for improving combustion efficiency and reduction of
nitrogen oxides (NOx).
[0004] (2) Description of the Prior Art
[0005] Increases in fuel costs have required power generation
plants seek increases in furnace efficiencies in order to reduce
power generation costs. However, NOx formation must also be
prevented to comply with environmental regulations. NOx formation
is reduced in furnaces by the process of stage combustion, which
includes administering an initial substoichiometric or suboptimal
ratio of oxygen to fuel to maintain combustion gas temperatures
below the peak NOx-producing temperature, about 2,800 degrees F.
(approximately 1540 degrees C.), followed by the addition of
secondary air, or over-fire-air (OFA), to finish the combustion
reaction. Proper mixing of secondary air and combustion gases
inside a furnace is thus important to achieve optimum combustion
and has been improved by the use of rotating over-fire-air (ROFA).
However, these existing NOx reduction systems do not optimize
combustion efficiency or furnace heat exchange efficiency.
[0006] Therefore, a need exists to improve energy efficiency of
ROFA systems without negatively affecting, or even improving the
reduction of pollutants, in particular NOx reduction.
SUMMARY
[0007] The present invention is directed to a mixing process and
system for increased chemical reaction and chemical reactor
efficiency and for improved reduction of by-products, in particular
NOx reduction.
[0008] The present invention is further directed to a system and
method for increased furnace efficiency through increased retention
time in the furnace. In a preferred embodiment, the process employs
systems and methods to improve the reaction homogeneity and
combustion zone swirling, resulting in combustion efficiency gains
and thermal flux gains with corresponding gains in reactor
efficiency.
[0009] The present invention is directed toward increasing furnace
energy efficiency via increased combustion efficiency and increased
furnace thermal flux, thereby also improving the reduction of
pollutants, in particular the reduction of NOx.
[0010] It is one aspect of the present invention to increase
chemical reaction efficiency by the asymmetrical, staged addition
of reagents at high-velocity for the induction of turbulent mixing
in the reaction mixture. Another aspect of the present invention is
to increase reactor and reaction efficiency by increasing the
residence time of the reactor and reducing laminar flow at
surfaces. Yet another aspect of the present invention is to
increase thermal flux in a reactor by increasing the residence time
of combustion gases in the reactor and decreasing the laminar flow
at heat exchange surface. In the present invention, these
parameters are improved by the induction of turbulence in the
reaction mixture and at the mixture/reactor interface.
[0011] Furthermore, the present invention increases the reaction
efficiency through the rapid, thorough mixing of the injected
secondary reagents with the reaction mixture via increased
turbulence. This rapid, thorough mixing effects a more complete
reaction of the primary reagent while reducing the secondary
reagent requirements.
[0012] These and other aspects of the present invention will become
apparent to those skilled in the art after a reading of the
following description of the preferred embodiment when considered
with the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a side view of a combustion furnace operated
according to the present invention.
[0014] FIG. 2 is a cross-sectional view of Zone A of the furnace of
FIG. 1 showing the gas swirl and deflection turbulence induced by
operation according to the present invention.
[0015] FIG. 3 is a cross-sectional view of Zone A of the furnace of
FIG. 1 showing the gas rotation induced by operation according to
the present invention.
[0016] FIG. 4 is a cross-sectional view of Zone B of the furnace
showing the turbulence induced by rotation in a non-circular
furnace.
[0017] FIG. 5 is a cross-sectional view of Zone C of the furnace
showing the swirl, deflection, and rotation-induced turbulence
induced by operation according to the present invention.
[0018] FIG. 6 shows a schematic view of a system according to the
present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0019] In the following description, like reference characters
designate like or corresponding parts throughout the several views.
Also in the following description, it is to be understood that such
terms as "forward," "rearward," "front," "back," "right," "left,"
"upwardly," "downwardly," and the like are words of convenience and
are not to be construed as limiting terms.
[0020] Referring now to the drawings in general, the illustrations
are for the purpose of describing a preferred embodiment of the
invention and are not intended to limit the invention thereto.
Shown in FIG. 1 is a side view of a combustion furnace, generally
described as 12, equipped with an air injection system composed of
injection ports 14. As best seen in FIGS. 2 and 3, the present
invention provides for an air injection system that creates swirl
20, peripheral turbulence 24, and air column rotation 30 through
the tangential injection of secondary air into the furnace. The
present invention thus creates turbulence and improves mixing of
the overfire air with the combustion gases.
[0021] According to the present invention, a method is provided for
increasing reaction efficiency and for reducing byproducts
formation, including the steps of providing a staged reaction
system including a reactor and at least one reagent for
introduction into a reaction process, preferably one that takes
place within the reactor; introducing the at least one reagent to
the reactor by asymmetrical injection at predetermined, spaced
apart locations; controlling the asymmetrical injection to produce
a high velocity mass flow and a turbulence resulting in dispersion
of the at least one reagent into the reaction system, thereby
providing increased reaction efficiency and reduced byproducts
formation in the reaction process. Preferably, the at least one
reagent is a multiplicity of reagents, more preferably, at least a
first reagent and a second reagent wherein the first reagent is
introduced prior to the introduction of the second reagent in a
first stage and the second reagent is introduced in a second stage,
and wherein the stages are spaced apart in location and/or
time.
[0022] In one exemplary embodiment, the overfire air is injected
into the combustion gases at a velocity and orientation such that
the swirl and high turbulence generated in the combustion gases
achieve a rapid and thorough mixing of the advected gases and the
combustion gases.
[0023] As shown in FIG. 2, another embodiment according to the
present invention, injection of the overfire air into the
combustion gases is effected in a manner such that the advected air
travels across the column of combustion gases and is deflected by
the opposing wall. This forceful injection induces turbulent mixing
of the advected air and combustion gases in at least three ways: 1)
by the generation of swirl 20 in the gas column, 2) the generation
of turbulence in proximity of the opposing wall after deflection of
the advected air by the wall 24, and 3) by the turbulence caused by
the rotation of the column of combustion gases in a non-circular
furnace, shown as 26 in FIG. 4. Swirl 20 is also generated by the
rotation of the gas column, as shown in FIG. 4.
[0024] The rotation, shown as 30 in FIG. 3, is produced through the
tangential injection into the furnace of the advected ROFA air,
i.e. there is an injection port on each side of the furnace. The
injection port on the right may be, for example, toward the rear of
the furnace while the injection port on the left side may be toward
the front side of the furnace. This placement of ports results in a
"swirl" being created in the furnace much like the injection of
water in a whirlpool can create a swirl, resulting in mixing, such
as described in U.S. Pat. No. 5,809,910 issued Sep. 22, 1998 to
Svendssen. This system provides for the asymmetrical injection of
overfire air (OFA) in order to create turbulence in the furnace,
thus more thoroughly mixing the secondary air and the combustion
gases.
[0025] Turbulence generated in proximity of the opposing wall is
achieved when the advected air strikes the opposing wall before
being completely mixed into the combustion gases. That is, the
penetration of the injected secondary air is greater than the width
of the furnace and the secondary air deflects off the opposing wall
and generates turbulent flow. To achieve penetration and,
therefore, turbulence, the advected gas must have sufficient linear
momentum to penetrate the primary gas, strike the deflecting
surface, and rotate. This linear momentum is described as mass flow
for a continuous gas stream. The mass flow (m) of a fluid is
defined as follows:
m=density of fluid.times.Area.times.average fluid velocity normal
to Area
[0026] The mass flow of the advected gas must be sufficient to
traverse the column of flue gas, strike the deflecting surface, and
create turbulence. The distance from injection to deflection,
represented by the width of the flue gas chamber, dictates the
necessary mass flow required to achieve turbulence. However, since
the desired rate of added gas mass is limited, it is often
desirable to increase the velocity of the advected gas, thereby
increasing the mass flow. Thus, greater mass flow of the advected
air can be attained by increasing the velocity of the gas.
[0027] Rotation of combustion gas column in a furnace with a
non-circular cross-section causes additional turbulence formation
due to the non-circular cross-section. The rotation is achieved, as
previously described, by the use of opposing, coordinated,
tangential injection of secondary air into the combustion gas
column. Thus, rotation of the gas column in a non-circular
cross-section furnace produces rotation-induced turbulence,
especially at the furnace/gas interface.
[0028] In a system according to the present invention, a staged
system and method are provided. In one embodiment, the staged
system includes a series of reagent introduction ducts with nozzles
advecting the reagents into a moving column of reagents, wherein
the ducts are positioned in a predetermined, spaced apart manner to
create rotational flow of the combustion zone, as described in U.S.
Pat. No. 5,809,910, incorporated herein by reference in its
entirety. The reagent injection ducts are preferably arranged to
act at mutually separate levels or stages on the mutually opposing
walls of the reactor, as shown in FIGS. 1 and 2, which illustrate a
furnace of an incineration unit as the reactor and/or are displaced
laterally in pairs in relation to one another. Additionally, the
ducts may further include nozzles, which are preferably positioned
at successively increasing distances along the axis of flow of the
furnace away from the furnace, as shown in FIG. 1, such that
rotation is maintained by the co-ordinated, reinforcing, tangential
injection of high-velocity secondary air into the combustion gas
column, generally described as 50 in FIG. 5, which is considered
one of the reagents according to the present invention.
[0029] A fourth means of producing turbulence in the reactor of the
present invention is through the advection of overfire air or gases
that are cooler than the combustion gases. This cooler air produces
additional turbulence from the thermal expansion it undergoes upon
mixing with the combustion gases. That is, the advected gas expands
as it is warmed to the combustion gas temperature by the combustion
gas, thus displacing and further mixing the surrounding combustion
gas. However, in the case of combustion power plants, the advected
air should not be so cold as to reduce the temperature of the
exiting combustion gases and thus reduce heat exchange efficiency.
In these furnaces, ambient air between -20 and 100 degrees
centigrade (-4 to 212 degrees F.) can be used in the advected gas.
Preheated gas, such as from redirected combustion air, may also be
used in the advected gas. The redirected combustion air is
preferably between 100 and 500 degrees centigrade (200 and 930
degrees F.) and is preferably mixed, if needed, with the ambient
air at between 10 to 50% of the total advected gas, to provide an
advection gas with temperature of between about 40 and 460 degrees
centigrade. More preferably, the redirected combustion air is mixed
at 20-40% of the total advected gas, if needed to provide an
advection gas with temperature of between about 76 and 340 degrees
centigrade. This gas mixture is therefore warm enough not to reduce
the combustion gas temperature significantly and can also readily
participate in the combustion reaction upon mixing with the
combustion gas.
[0030] These turbulences can thus be further augmented by using
high-velocity secondary air, which is considered one of the at
least one reagents of the present invention. During testing of the
system, secondary air was injected into reactors, where, in
particular embodiments tested, the reactors were furnaces of
various sizes at velocities ranging from 60-300 m/s using booster
fans. The velocity necessary to provide sufficient mixing is
dependent upon the size of the reactor, the vertical velocity of
the combustion gasses and the configuration of the furnace.
[0031] Surprisingly, the turbulence generated was sufficient that
the entire furnace began operating as a single burner. The
increased turbulence, mixing swirl, and rotation in the furnace
resulted in improved combustion, increased efficiency of the fuel
combustion, reduction in secondary air requirements with
consequential increased retention time of the combustion gases in
the furnace, lower furnace exit gas temperatures due to better heat
exchange in the furnace, increased boiler efficiency and lower
pollutant emissions.
[0032] From the tests it was determined that the ratio of the
advected air velocity to the reactor, or in a particular embodiment
a furnace, width (v/w) needs to be between about 2 to about 150
sec.sup.-1, preferably between about 3 and 60 sec.sup.-1.
[0033] Furthermore, it was determined that the velocity of the
advected air should result in the combustion gas column rotating at
least one half-turn prior to exiting the furnace, more preferably
at least 1 turn prior to exiting the furnace. To achieve this
rotation, at least two levels of injection of at least one reagent
are required, thereby providing for at least two stages of the
system and method according to the present invention. More
preferably at least three levels of injection are used for
providing increased efficiency and for reduction of byproducts.
[0034] Alternatively, the velocity of the injected air needs to be
such that the penetration of the injected reagent(s), which may
include air, is greater than the reactor width by at least about
1.5 reactor widths, more preferably by at least 2 reactor
widths.
[0035] The reduction in the secondary air results in a decrease in
combustion gas volume, which results in an increased residence time
of the combustion gases in the furnace and thus more time for
thermal flux to occur into the furnace water/steam conduits for a
furnace example of a reactor system and method according to the
present invention.
[0036] Additionally, the rotation of reagents in a non-circular
cross-section reactor generates turbulence at the reagent/reactor
surface interface. This turbulence reduces the laminar flow of the
combustion gases at the interface and therefore improves the
thermal flux, or heat transfer, across the interface. This effect
can be advantageously used to improve the efficiency of exothermic
and endothermic reactions. For exothermic reactions, the thermal
flux may be advantageously used to remove heat from the reaction
space, thereby reducing the reaction temperature and favoring the
exothermic reaction. For endothermic reactions, the thermal flux
may be used to add heat to the reaction space, thereby raising the
temperature of the reaction space and favoring the endothermic
reaction. The turbulence generated by the rotation also further
mixes the combustion gases and reduces laminar or parallel flow up
the reactor. Combustion reactions in prior art non-circular
reactors tend to demonstrate sidedness, that is the reactions are
on a particular side or zone of the furnace versus other sides,
resulting in non-uniform combustion within the reactor. Thus, the
present invention advantageously utilizes the non-circular nature
of the reactor's cross-section to eliminate the sidedness of the
reactor. The rotation that overcomes this sidedness is achieved by
the coordinated, reinforcing, tangential, or asymmetrical,
injection of high-velocity secondary air as a reagent into the
combustion column of the reactor.
[0037] Similarly, the vigorous mixing in the combustion area
produced by the present invention also prevents the laminar flow
and consequential lower residence time of higher inertia particles
in the reactor, such as combustible particulate, thereby allowing
them more time to burn in the reactor and further increasing the
combustion efficiency and thermal flux efficiency of the reactor,
as well as reducing the formation of byproducts, in particular
pollutants such as NOx.
[0038] Thus, the present invention utilizes the co-ordinated,
reinforcing, tangential injection of high-velocity secondary
reagents to improve the reaction efficiency and thermal flux
efficiency of reactors of various cross-sectional shapes.
[0039] A method according to the present invention for increasing
reactor efficiency includes providing a reactor with a plurality of
reagent introduction or injection ducts, asymmetrically positioned
in an opposing manner at spaced apart, predetermined locations;
injecting a first reagent such as fuel with a second reagent such
as primary air through the burners prior to the injection of
secondary air; injecting secondary air reagent through the
plurality of reagent introduction or injection ducts at a velocity
such that the ratio of the velocity to the reactor width is between
about 2 sec.sup.-1 to about 150 sec.sup.-1, preferably between
about 3 and about 60 sec.sup.-1; thereby increasing reaction
efficiency and reactor efficiency via mixing and rotation of the
reactor space, and improving the reduction of byproducts such as
pollutants.
[0040] Alternatively or additionally, the velocity of the injected
secondary reagent is such that the penetration of the secondary
reagent is greater than the reactor width by at least about 1.5
widths and/or the reagents acting within a reaction zone, which may
include combustion activity, rotates at least one half revolution
prior to exiting the reactor.
[0041] FIG. 6 shows a schematic view of a preferred system
according to the present invention, generally described as 20,
including a staged reaction system including a reactor 70, a
multiplicity of injection devices 14 for introduction of at least
one reagent into a reaction process by asymmetrical injection at
predetermined, spaced apart locations; at least 1 probe 40
installed downstream of at least one of the injectors of the
system, and a controller 62 for controlling the asymmetrical
injection to produce a high velocity mass flow and a turbulence
resulting in dispersion of the at least one reagent into the
reaction system and mixing of the reaction space; thereby providing
increased reaction efficiency and reduced byproducts formation in
the reaction process.
[0042] Certain modifications and improvements will occur to those
skilled in the art upon a reading of the foregoing description. All
modifications and improvements have been deleted herein for the
sake of conciseness and readability but are properly within the
scope of the following claims.
* * * * *