U.S. patent application number 12/434336 was filed with the patent office on 2009-09-10 for system and method for vaporizing a cryogenic liquid.
This patent application is currently assigned to Selas Fluid Processing Corporation. Invention is credited to Peter Falcone, Marc Rost.
Application Number | 20090227826 12/434336 |
Document ID | / |
Family ID | 36692730 |
Filed Date | 2009-09-10 |
United States Patent
Application |
20090227826 |
Kind Code |
A1 |
Rost; Marc ; et al. |
September 10, 2009 |
SYSTEM AND METHOD FOR VAPORIZING A CRYOGENIC LIQUID
Abstract
A flameless thermal oxidizer including a matrix bed containing
media and an inlet tube extending into the matrix bed and having an
outlet positioned to deliver reacting gases into the matrix bed is
disclosed. The matrix bed defines a void proximal the outlet of the
inlet tube. Also disclosed is a method of reducing pressure losses
in a flameless thermal oxidizer including the step of introducing
reacting gases from an inlet tube into a void defined by a matrix
bed.
Inventors: |
Rost; Marc; (Lansdale,
PA) ; Falcone; Peter; (Media, PA) |
Correspondence
Address: |
RATNERPRESTIA
P.O. BOX 980
VALLEY FORGE
PA
19482
US
|
Assignee: |
Selas Fluid Processing
Corporation
Blue Bell
PA
|
Family ID: |
36692730 |
Appl. No.: |
12/434336 |
Filed: |
May 1, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11037034 |
Jan 18, 2005 |
7540160 |
|
|
12434336 |
|
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Current U.S.
Class: |
588/320 ;
422/173 |
Current CPC
Class: |
Y02E 20/34 20130101;
Y02E 20/342 20130101; F23C 99/006 20130101 |
Class at
Publication: |
588/320 ;
422/173 |
International
Class: |
A62D 3/38 20070101
A62D003/38; B01J 19/00 20060101 B01J019/00 |
Claims
1. A flameless thermal oxidizer comprising: a matrix bed containing
media; and an inlet tube extending into said matrix bed and having
an outlet positioned to deliver reacting gases into said matrix
bed; said matrix bed defining a void proximal said outlet of said
inlet tube.
2. The flameless thermal oxidizer of claim 1, further comprising a
disc positioned adjacent said outlet of said inlet tube and
configured to direct reacting gases away from said inlet tube.
3. The flameless thermal oxidizer of claim 1, said void being
substantially cylindrical.
4. A method of reducing pressure losses in a flameless thermal
oxidizer comprising introducing reacting gases from an inlet tube
into a void defined by a matrix bed.
5. The method of claim 4, wherein the introducing step comprises
introducing gases from an inlet tube into a cylindrical void
defined by the matrix bed.
6. The method of claim 4 further comprising the step of directing
reacting gases away from said inlet tube by a disc positioned
adjacent the outlet of the inlet tube.
7. A flameless thermal oxidizer that is configured for reducing
pressure loss of reacting gases comprising: a matrix bed containing
media; and an inlet tube extending into said matrix bed and having
an outlet positioned to deliver reacting gases into said matrix
bed; and a disc positioned adjacent said outlet of said inlet tube
and configured to direct reacting gases away from said inlet tube;
said matrix bed defining a void proximal said outlet of said inlet
tube that is substantially devoid of media, wherein said outlet of
said inlet tube is positioned to deliver reacting gases into said
void defined in said matrix bed in order to lower pressure losses
of the reacting gases in the flameless thermal oxidizer.
8. The flameless thermal oxidizer of claim 7 said void being
substantially cylindrical.
9. The flameless thermal oxidizer of claim 8 wherein a ratio of a
diameter dimension of said substantially cylindrical void to a
depth dimension of said substantially cylindrical void is about
8:3.
10. The flameless thermal oxidizer of claim 8 wherein a ratio of a
diameter dimension of said substantially cylindrical void to a
depth dimension of said substantially cylindrical void is at least
about 8:3.
11. The flameless thermal oxidizer of claim 8 wherein a ratio of a
depth dimension of said substantially cylindrical void to a
diameter dimension of said substantially cylindrical void is at
least about 3:8.
12. The flameless thermal oxidizer of claim 7 wherein said void is
bounded by media and said outlet of said inlet tube.
13. The flameless thermal oxidizer of claim 7, said inlet tube
having an inlet for receiving a fuel and air mixture, wherein said
inlet is disposed opposite said outlet of said inlet tube and said
inlet is positioned outside of said matrix bed.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This U.S. application is a divisional patent application
claiming priority to U.S. patent application Ser. No. 11/037,034,
filed on Jan. 18, 2005, which is incorporated by reference herein
in its entirety.
FIELD OF THE INVENTION
[0002] This invention relates to a system and method for vaporizing
a cryogenic liquid and, more particularly, a system for providing
heat for cryogenic liquid vaporization.
BACKGROUND OF THE INVENTION
[0003] It is often necessary or desirable to vaporize a cryogenic
liquid (i.e., to bring about vaporization of a cryogenic liquid to
a vaporized state). For example, and though a wide variety of
applications exist for liquid vaporization, it is often necessary
or desirable to vaporize liquid natural gas (LNG) so that it can be
handled and distributed as a fuel source.
[0004] Many vaporization systems operate with burners in order to
produce the necessary vaporization heat. For example, evaporators
of the submerged combustion type comprise a water bath in which a
flue gas tube of a gas burner is installed as well as an exchanger
tube bundle for the vaporization of the liquefied gas. The gas
burner discharges the combustion flue gases into the water bath,
which heat the water and provide the heat for the vaporization of a
liquefied gas that flows through the tube bundle. Such vaporization
systems are provided, for example, by T-Thermal Company, a division
of Selas Fluid Processing Corporation, under the registered
trademark SUB-X.
[0005] Evaporators of this type are reliable and of compact size,
but they may become expensive to operate. For example, in order to
reduce emissions of nitrogen oxide (NOx) from such systems, a
current practice utilizes a gaseous fuel burner in combination with
water injection to reduce NOx emissions. In such systems, NOx
emissions can be reduced to approximately 30 ppmvd, corrected to 3
volume percent oxygen (dry basis).
[0006] Further reduction of NOx emissions may require post
combustion catalytic treatment. For example, a catalytic treatment
system may be located at the outlet of a submerged liquid bath.
Such treatment utilizes a portion of the burner exhaust to reheat
the gases that are exiting the liquid bath, so as to reduce the
moisture content of the gases before they enter the post combustion
catalytic system. The corresponding use of this portion of the
burner exhaust can, however, reduce the energy efficiency of the
system, since this portion of the burner gases are not used to heat
the cryogenic fluid.
[0007] Accordingly, there remains a need for an improved method and
system for cryogenic liquid vaporization.
SUMMARY OF THE INVENTION
[0008] According to one aspect of the invention, a flameless
thermal oxidizer is provided. The flameless thermal oxidizer
includes a matrix bed containing media, an inlet tube extending
into the matrix bed and having an outlet positioned to deliver
reacting gases into the matrix bed. The matrix bed defines a void
proximal the outlet of the inlet tube. In the oxidizer, a disc is
optionally positioned adjacent the outlet of the inlet tube and
configured to direct reacting gases away from the inlet tube. The
void defined in the matrix bed is optionally substantially
cylindrical.
[0009] According to another aspect, this invention provides a
method of reducing pressure losses in a flameless thermal oxidizer,
the method including introducing reacting gases from an inlet tube
into a void defined by a matrix bed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] Exemplary embodiments of the invention will be described
with reference to several embodiments selected for illustration in
the drawing, of which:
[0011] FIG. 1 is a schematic, block diagram of a vaporization
system according to one exemplary embodiment of this invention;
[0012] FIG. 2 is a schematic diagram of an embodiment of a
flameless thermal oxidizer capable of use in the vaporization
system illustrated in FIG. 1;
[0013] FIG. 3 is a schematic diagram of another embodiment of a
flameless thermal oxidizer capable of use in the vaporization
system illustrated in FIG. 1;
[0014] FIG. 4 is a perspective view of yet another embodiment of a
flameless thermal oxidizer capable of use in the vaporization
system illustrated in FIG. 1;
[0015] FIG. 5 is a perspective view of still another embodiment of
a flameless thermal oxidizer capable of use in the vaporization
system illustrated in FIG. 1;
[0016] FIG. 6A is an elevation view of another embodiment of a
vaporization system according to this invention;
[0017] FIG. 6B is a plan view of the vaporization system
illustrated in FIG. 6A;
[0018] FIG. 6C is an elevation view of the vaporization system
shown in FIG. 6A, with portions removed to reveal internal
details;
[0019] FIG. 7A is an elevation view of an embodiment of a manifold
and distributor assembly capable of use in the vaporization system
illustrated in FIG. 6A;
[0020] FIG. 7B is an end view of the manifold and distributor
assembly illustrated in FIG. 7A;
[0021] FIG. 7C is a cross-sectional, end view of the manifold and
distributor assembly illustrated in FIG. 7A;
[0022] FIG. 7D is a plan view of a portion of the manifold and
distributor assembly illustrated in FIG. 7A;
[0023] FIG. 8A is an elevation view of an embodiment of a tube
bundle assembly capable of use in the vaporization system
illustrated in FIG. 6A; and
[0024] FIG. 8B is a cross-sectional end view of the tube bundle
assembly illustrated in FIG. 8A.
DETAILED DESCRIPTION OF THE INVENTION
[0025] The invention will next be illustrated with reference to the
Figures. Such Figures are intended to be illustrative rather than
limiting and are included herewith to facilitate explanation of the
present invention. The Figures are not to scale, and are not
intended to serve as engineering drawings.
[0026] A flameless thermal oxidizer (FTO) has been coupled with a
cryogenic heat exchanger according to one aspect of this invention
to vaporize a liquid such as liquefied natural gas prior to
injection into a utility distribution system. The resulting
vaporization system minimizes oxides of nitrogen (NOx) emissions to
the environment normally associated with conventional combustion
processes. The thermal reaction of commercial fuel gas with air in
a matrix bed of porous inert media is accomplished using the
flameless thermal oxidizer. The reaction is optionally conducted in
an apparatus that is capable of establishing and maintaining a
non-planar reaction wave within the matrix bed.
[0027] Generally, and according to one exemplary embodiment, the
vaporization system includes a vessel that contains a matrix bed;
one or more feed tubes that extend into the matrix bed; a burner or
other matrix bed preheat system; connecting ductwork to a heat
exchanger (such as the Sub-X.RTM. heat exchanger provided by
T-Thermal Company of Blue Bell, Pa.); process controls; and an
exhaust outlet to the atmosphere. A non-planar reaction wave (such
as the one formed by the oxidizer shown in FIG. 3, for example) is
established by heating at least a portion of the matrix bed to the
minimum reaction temperature of a commercial fuel gas/air mixture
and feeding said mixture at controlled rates into the feed tube(s).
Upon exiting the feed tube(s), the commercial fuel gas/air mixture
is reacted in a non-planar reaction wave to produce heat and
non-toxic combustion products.
[0028] The heat generated in the non-planar reaction wave maintains
the interior surfaces of the vessel at a temperature of at least
1600 degree F. but less than 2400 degree F. during the entire
operation, which minimizes the formation of NOx emissions. The hot
exhaust gases are directed from the vessel through ductwork to a
specialized cryogenic heat exchanger submerged in a water bath.
Cryogenic liquids are directed through tubes in the interior of the
heat exchanger as the quenched exhaust gases contact the exterior
surfaces of the tubes via the water bath. The cryogenic fluid
inside the heat exchanger completes a phase change to a gaseous
product resulting from the flow of heated gases within the water
bath. Exhaust gases exit the water bath and are released to the
atmosphere via a stack.
[0029] The natural gas vaporization capacity of the system ranges
from about 150 to 200 million cubic feet per day, dependent on
operating pressure conditions. Heat release rate for the flameless
thermal oxidizer is 120 MMBtu/hr, and the emission rate of nitrogen
oxides is reduced.
[0030] The emissions of nitrogen oxides from the flameless
oxidation process are approximately 2 ppmvd (corrected to 3 volume
percent oxygen (dry basis)), which is significantly lower than the
nitrogen oxide emissions from the burner exhaust of the current
practice. The use of the flameless oxidation eliminates the need
for water injection, as well as the post combustion catalytic NOx
reduction treatment system. This elimination of the catalytic
treatment system in turn eliminates the reoccurring use of both the
catalyst and associated reducing agent (such as ammonia). Catalyst
has a limited operating lifetime and is expensive to replace. The
elimination of the reducing agent may make the system safer to
operate by eliminating the storage and handling of ammonia. The
elimination of the post catalytic treatment system along with the
necessary heat input required to reheat the exhaust gases will
increase the system energy efficiency by utilizing all of the
flameless oxidation exhaust to heat the cryogenic fluid.
[0031] Referring to the Figures generally, and according to one
aspect of this invention, a system 1, 100 is provided for
vaporizing a cryogenic liquid. To heat or vaporize fluids such as
cryogenic liquids, the system 1, 100 utilizes flameless oxidation
to provide the heat input into a submerged heat exchanger coil.
[0032] The system 1, 100 includes means for producing an exhaust
gas by flameless thermal oxidation of a fuel/air mixture. For
example, the means for producing an exhaust gas optionally includes
an oxidizer 2, 10, 40, 70, 108 having a matrix bed 29, 42, 72,112;
a fuel/air mixture inlet 4, 54 positioned to deliver the fuel/air
mixture to the matrix bed 29, 42, 72,112; and an exhaust outlet 5,
45, 78A, 78B, 114 positioned to deliver the exhaust gas from the
oxidizer 2, 10, 40, 70, 108.
[0033] The system 1, 100 also includes means for transferring heat
from the exhaust gas to the cryogenic liquid. For example, the
means for transferring heat optionally includes a vaporizer 3
having a receptacle 122 configured to hold a heat transfer medium;
a conduit 118, 144 for cryogenic liquid extending into the
receptacle; and a sparger 138 positioned to deliver exhaust gas
from the exhaust gas producing means to the receptacle 122.
[0034] The heat transferring means of the system 1, 100 is coupled
to receive the exhaust gas from the exhaust gas producing means. In
this manner, the products of reaction or oxidation in the exhaust
gas producing means are delivered to the heat transferring means.
Such heat transfer brings about vaporization of a cryogenic
liquid.
[0035] In use of system 1, 100, a fuel/air mixture is oxidized in a
flameless thermal oxidizer 2, 10, 40, 70, 108 to produce an exhaust
gas. Heat is then transferred from the exhaust gas to the cryogenic
liquid, thereby vaporizing the cryogenic liquid. The oxidizing step
optionally includes delivering fuel/air mixture into a matrix bed
29, 42, 72,112, and the transferring step optionally includes
introducing exhaust gas into a heat transfer medium such as
water.
[0036] To modify or retrofit a vaporizer of cryogenic liquid
according to one aspect of this invention, a flameless thermal
oxidizer 2, 10, 40, 70, 108 is coupled to the vaporizer 3, and the
flameless thermal oxidizer 2, 10, 40, 70, 108 is configured to
deliver exhaust gas to the vaporizer 3. The coupling step
optionally includes coupling an exhaust outlet 5, 45, 78A, 78B, 114
of the flameless oxidizer 2, 10, 40, 70, 108 to a sparger 138 of
the vaporizer 3.
[0037] To reduce NOx emissions according to another aspect of the
invention, a fuel/air mixture is oxidized using a flameless thermal
oxidizer 2, 10, 40, 70, 108, and heat from exhaust gases generated
by the oxidizing step is transferred to a cryogenic liquid. The NOx
emissions can be reduced to less than about 5 ppmvd NOx, preferably
about 4 ppmvd NOx or less, or more preferably about 2 ppmvd NOx or
less, corrected to 3 volume percent oxygen (dry basis). The
reduction of NOx emissions is optionally performed without
catalytic treatment.
[0038] According to another aspect of this invention, a flameless
thermal oxidizer 70 has a matrix bed 72 containing media, an inlet
tube 80 extending into the matrix bed 72 and having an outlet
positioned to deliver reacting gases into the matrix bed 72. The
matrix bed 72 defines a void 73 proximal the outlet of the inlet
tube 80. A disc 82 is optionally positioned adjacent the outlet of
the inlet tube 80 and configured to direct reacting gases away from
the inlet tube 80. The void 73 is optionally substantially
cylindrical.
[0039] To reduce pressure losses in a flameless thermal oxidizer,
reacting gases can therefore be introduced from an inlet tube 80
into a void 73 defined by a matrix bed 72. Also, plural exhaust
outlets 78A, 78B can be provided to exhaust reacted gases from the
oxidizer 70.
[0040] It has been discovered that this invention provides an
efficient vaporization technology with very low oxides of nitrogen
emissions (NOx) resulting from the combustion of natural gas fuel.
For example, a typical burner system may operate with up to 40
percent excess air in a LNG vaporizer as compared to approximately
175 percent excess air with a flameless thermal oxidizer. Such
excess air is beneficial in that it limits the maximum adiabatic
temperature achieved in the oxidizer to less than the Zeldovich
reaction mechanism requirements for high levels of NOx production.
Fuel consumption is unchanged when the burner and flameless thermal
oxidizer technologies are compared, but the volume of gases handled
by the equipment is significantly larger for a flameless thermal
oxidizer system according to this invention.
[0041] A LNG vaporizer burner system together with water injection
can produce NOx emissions in the range from 35 to 50 ppmvd. A LNG
vaporizer using a flameless thermal oxidizer as the heat source
according to this invention can produce NOx emissions in the range
from 2 to 4 ppmvd, though NOx emissions lower than 2 ppmvd and
greater than 4 ppmvd are contemplated as well (the foregoing NOx
emissions values being corrected to 3 volume percent oxygen on a
dry basis).
[0042] In order to reduce NOx emissions (e.g., to comply with NOx
emission regulations), burner systems typically use post-combustion
treatment processes involving a catalyst and injection of a
reducing agent chemical. These post-combustion control systems tend
to be expensive, difficult to maintain, and require periodic
shutdowns for catalyst cleaning and replacement.
[0043] Referring specifically to the embodiments selected for
illustration in the figures, FIG. 1 provides a schematic
illustration of an embodiment of a vaporization system, generally
indicated by the numeral 1, according to one aspect of this
invention. Vaporization system 1 includes a flameless thermal
oxidizer 2 that is coupled to a vaporizer 3. The flameless thermal
oxidizer 2 is configured to receive a fuel/air mixture 4 for
reaction within the flameless thermal oxidizer 2. Flameless thermal
oxidizer 2 is also configured to deliver exhaust gases 5 that are
produced as a result of the oxidation or reaction of the fuel/air
mixture 4.
[0044] The vaporizer 3 is configured to receive the exhaust gases 5
from the flameless thermal oxidizer 2. The vaporizer 3 is also
configured to receive a cryogenic liquid 6 and to deliver a
vaporized gas 7. Vaporizer 3 is also configured to deliver
emissions 8.
[0045] The hot exhaust gases 5 delivered from the flameless thermal
oxidizer 2 to the vaporizer 3 causes vaporization of the cryogenic
liquid 6 into a vaporized gas 7. Accordingly, the heat from exhaust
gases 5 provides a heat source for the vaporization of the
cryogenic liquid 6, and the exhaust gases 5 received in the
vaporizer 3 from the flameless thermal oxidizer 2 are discharged
from the vaporizer 3 in the form of emissions 8 either for further
treatment or discharge to the atmosphere.
[0046] FIG. 2 illustrates an exemplary embodiment of a flameless
matrix bed reactor, generally designated by the numeral 10, which
can be used in the vaporization system 1 illustrated in FIG. 1 as a
component of the flameless thermal oxidizer 2.
[0047] Referring to FIG. 2, there is shown a schematic of the
internal temperature zones in a flameless matrix bed reactor 10
that contains a planar reaction wave 22. Additional details of the
flameless matrix bed reactor 10 can be found in U.S. Pat. No.
6,015,540, which is incorporated herein by reference in its
entirety.
[0048] The flameless reactor 10 includes a vessel 25, having a
matrix bed of porous inert media 29. The vessel is lined with a
refractory material. Prior to the planar reaction wave, there is
typically a cool zone 27 that has a temperature below the uniform
reaction temperature. After the planar reaction wave 22, there will
be a hot region 26 that is typically at least above 1200 degree F.
By using temperature sensors 20, the planar reaction wave 22 may be
located within the matrix and moved to a desired point by
controlling the output end of a process controller 28.
[0049] While this planar reaction wave temperature profile is
effective for oxidation, corrosive products or reactants (such as
acid gases or their pre-cursors) can tend to condense in the cool
zone 27 on the interior surfaces 23 of the vessel 25. This
condensation can occur when the corrosive products or reactants
migrate through the lining of refractory material 24 adjacent to
the interior surfaces 23 of the vessel 25. Additionally, if the
vessel is constructed of heat resistant metal alloys, and there is
no internal lining of refractory material, corrosive products or
reactants can still condense on the interior surfaces of the vessel
in the cool zone 27. This condensation in turn can lead to
corrosion of the interior surfaces of the vessel. Consequently, the
life of the vessel can be reduced and/or more expensive materials
of construction may be needed to improve corrosion resistance
[0050] FIG. 3 shows another embodiment of a flameless matrix bed
reactor 40, which can be used to oxidize one or more chemicals.
Additional details of the flameless matrix bed reactor 40 can be
found in U.S. Pat. No. 6,015,540.
[0051] Referring to FIG. 3, a flameless matrix bed reactor,
generally designated by the numeral 40, is capable of use in the
vaporization system 1 illustrated in FIG. 1 as a component of the
flameless thermal oxidizer 2.
[0052] As shown in FIG. 3, the flameless matrix bed reactor
includes a vessel 41, containing a matrix bed 42 of porous inert
media; a vessel refractory lining 63, located adjacent to the
vessel interior surfaces 64; a feed tube 43 for receiving a
reactable process stream 44, where a portion of the feed tube 43
that passes through the vessel is insulated with a refractory
lining 62; an exhaust outlet 45 for removing reacted process stream
46; and a void space 47 located above the matrix bed 42. The matrix
bed 42 is heated by introducing a heated medium (flue gases
generated by a conventional fuel gas burner) 48, such as air,
through a heating inlet 49. The reactable process stream is formed
by combining in a mixing device 50 a fume stream 51 containing an
oxidizable material, an optional oxidizing agent stream 52 (such as
air or oxygen), and an optional supplementary fuel gas stream
53.
[0053] After the reactable process stream is formed, it is fed into
a feed inlet 54 of the feed tube 43. The reactable process stream
is then directed to the exit 55 of the feed tube 43. A non-planar
reaction wave 56 is established in the matrix bed located in a
region approximately around the exit 55 of the feed tube 43 and the
bottom 57 of the vessel. The reactable process stream 44 is reacted
(in this embodiment oxidized) in the non-planar reaction wave 56 to
produce the reacted process stream 46. The reacted process stream
46 is directed through the matrix bed 42, through the void space
47, and out the exhaust outlet 45.
[0054] The exhaust outlet 45 is positioned so that the reacted
process stream 46 prior to exiting the vessel 41 flows
countercurrent to the flow direction in the feed tube 43. The
exhaust outlet 45 may be connected to either the void space 47 or
matrix bed 42. However, it is preferred that the exhaust outlet be
connected to the void space 47. Temperature sensors 58 may be used
for monitoring the temperature in the flameless matrix bed reactor
40. A process controller 59 may be used for accepting input from
the temperature sensors 58 and, in response thereto, controlling
the flow rate of the reactable process stream 44, the fume stream
51, the optional oxidizing agent stream 52, the optional
supplementary fuel gas stream 53, and/or the heated medium 48
(e.g., flue gases generated by a conventional fuel gas burner).
[0055] FIG. 4 shows a schematic, perspective view of a flameless
thermal oxidizer, generally indicated by the numeral 70, that can
be used as a component of the flameless thermal oxidizer 2 of the
vaporization system 1 illustrated in FIG. 1. Flameless thermal
oxidizer 70 includes a matrix bed 72 that extends upwardly to a top
surface 74. The top surface 74 of the matrix bed 72 at least
partially defines an oxidizer head space 76.
[0056] Dual, opposed exhaust ducts 78A and 78B are positioned to
exhaust reacted gases from the oxidizer head space 76.
Specifically, reacted gases that enter the oxidizer head space 76
from the matrix bed 72 are delivered from the flameless thermal
oxidizer 70 via exhaust ducts 78A and 78B. The provision of dual,
opposed exhaust ducts such as ducts 78A and 78B has been discovered
to reduce the pressure losses encountered by the flameless thermal
oxidizer 70.
[0057] Flameless thermal oxidizer 70 also includes a premixed gas
dip tube 80 that extends downwardly into the matrix bed 72 in order
to deliver a premix of gas into the matrix bed 72 at a location
below the top surface 74 of the matrix bed 72. The dip tube 80 has
a dip tube outlet diverter disc 82 positioned adjacent the outlet
of the premixed gas dip tube 80. The disc 82 helps to divert
reaction gases away from the wall of the dip tube.
[0058] Referring now to FIG. 5, a modification to the flameless
thermal oxidizer 70 illustrated in FIG. 4 is shown. Specifically,
as illustrated in FIG. 5, the flameless thermal oxidizer 70 is
provided with a modification to its matrix bed 72 in order to
improve the performance of the flameless thermal oxidizer 70. A
void is created in the ceramic media bed or matrix bed 72 just
beneath the dip tube outlet SO that gases can flow with less
restriction into the matrix bed 72 to lower pressure losses in the
flameless thermal oxidizer 70. The void is provided in the form of
a cylindrical voidage 73. In one exemplary embodiment, the voidage
73 has a diameter of about 8 feet (corresponding roughly to the
diameter of the dip tube outlet diverter disc 82) and a depth of
about 3 feet.
[0059] While the embodiment of the voidage 73 illustrated in FIG. 5
is substantially cylindrical in shape, it is contemplated that the
voidage may have a wide variety of geometric shapes (e.g.,
spherical or semi spherical, elliptical, rectangular, or other
geometric configurations).
[0060] Referring now to FIGS. 6A and 6B, another embodiment of a
vaporization system, generally indicated by the numeral 100, is
illustrated. Vaporization system 100 includes a blower 102
configured to urge air into the vaporization system 100. Downstream
from the blower 102 is a start-up burner 104 used during start-up
of the vaporizer system 100 to preheat the matrix bed (described
later). Also downstream from the blower 102 is a fuel-air mixer 106
configured to mix fuel with the air introduced by the blower
102.
[0061] The vaporization system 100 also includes a flameless
thermal oxidizer vessel 108 configured to receive the fuel-air mix
provided by the fuel-air mixer 106. The flameless thermal oxidizer
vessel 108 generates the heat that is used to vaporize liquid in
the vaporization system 100. Specifically, hot gas is delivered
from the flameless thermal oxidizer vessel 108 via a hot gas duct
114.
[0062] From hot gas duct 114, hot gas is introduced into an SCV
tank 122. Gases are then delivered from the SCV tank 122 by means
of an exhaust separator 124 and an exhaust stack 126.
[0063] FIG. 6C is another elevation view of the vaporization system
100, with wall portions removed to reveal internal details of the
flameless thermal oxidizer vessel 108 and the SCV tank 122. The
illustration in FIG. 6C also indicates the flow pattern of flue
gases, indicated by arrows, in the flameless thermal oxidation
vessel 108.
[0064] The flameless thermal oxidation vessel 108 includes a dip
tube 110 that extends downwardly into a ceramic packing 112. A mix
of fuel and air is delivered through the dip tube 110 into the
ceramic packing 112 for oxidation or reaction within the ceramic
packing 112. The flue gases resulting from the reaction oxidation
of the mixture of fuel and air travels upwardly through the ceramic
packing 112 into a space above the ceramic packing 112 within the
flameless thermal oxidation vessel 108, as indicated by the arrows
in FIG. 6C. The flue gases are then urged outwardly from the
flameless thermal oxidation vessel 108 and into the hot gas duct
114 for delivery to the SCV tank 122. The hot gas duct 114 is
preferably insulated in order to reduce loss of heat from the flue
gases.
[0065] The SCV tank 122 is at least partially filled with a heat
transfer medium such as water or other suitable medium. In
operation, hot flue gases from the flameless thermal oxidizer
vessel 108 are introduced into the heat transfer medium such that
it bubbles through the heat transfer medium, heats the heat
transfer medium, and brings about heat transfer from the heat
transfer medium to cryogenic liquid flowing through a tubing bundle
situated in the heat transfer medium.
[0066] More specifically, the SCV tank 122 includes a manifold and
distributor system such as assembly 116 connected to receive hot
flue gases from the hot gas duct 114. Details of the manifold and
distributor assembly will be described later with reference to
FIGS. 7A-7D. The SCV tank 122 also includes a tube bundle 118
through which cryogenic liquid is circulated for vaporization.
Further details of the tube bundle 118 will be described later with
reference to FIGS. 8A and 8B. Liquid natural gas inlet and natural
gas outlet manifolds are provided in the SCV tank 122 as indicated
by numeral 120. It is by means of the inlet and outlet manifolds
120 that liquid natural gas is introduced into the tube bundle and
the resulting natural gas is discharged from the tube bundle.
[0067] Referring now to FIGS. 7A through 7D, details of an
embodiment of a manifold and distributor assembly are illustrated.
The manifold and distributor assembly, such as assembly 116, is
configured to receive hot gases from the hot gas duct 114 and to
deliver those hot gases into the heat transfer medium (e.g., water)
in the SCV tank 122. More specifically, the manifold and
distributor assembly 116 receives a stream of heated gas and
divides that gas for substantially even distribution into the SCV
tank to encourage heat transfer between the hot gases, the heat
transfer medium, and ultimately the cryogenic liquid such as liquid
natural gas circulating within the tube bundle 118.
[0068] Referring specifically to FIG. 7A, the manifold and
distributor assembly 116 includes a shell 128 that is substantially
cylindrical in shape, though other cross-sectional shapes are
contemplated as well. Shell 128 is coupled to the hot gas duct 114
by means of a flange 130. The opposite end of the shell 128 is
capped by a plate 132. Plural lifting lugs 134 are provided along a
top surface of the shell 128 in order to facilitate the handling of
the shell 128 during assembly, disassembly, modification and/or
maintenance. Plural supports 136 are provided to support the shell
128 against a foundation of the SCV tank 122 (not shown).
[0069] In order to facilitate the distribution of hot gases from
within the shell 128 to the heat transfer medium, the manifold and
distributor assembly 116 is provided with plural spargers 138. Each
sparger 138 extends outwardly from the shell 128 and is connected
to the shell 128 in order to receive hot gases from the shell 128
and to deliver the hot gases to the heat transfer medium within the
SCV tank 122.
[0070] Referring to FIG. 7B, which provides an end view of the
manifold and distributor assembly 116, the relationship between the
sparger 138 and the shell 128 of the manifold and distributor
assembly 116 can be seen. Specifically, each sparger 138 extends
outwardly from a lower portion of the shell 128 at an angle
substantially transverse to the axis of the shell 128.
[0071] Referring to FIG. 7C, which provides a cross-sectional end
view of the manifold and distributor assembly 116, each sparger 138
is provided with a closed end 140 and a plurality of openings 142
(generally positioned along its upper surface) to permit the flow
of hot gases from within the sparger 138 to the heat transfer
medium in the SCV tank 122.
[0072] FIG. 7D provides a plan view of a portion of a sparger 138.
Each sparger 138 includes plural rows of openings 142 (two such row
shown in FIG. 7D). By means of openings 142, hot gas flows from
within each sparger 138 and into the heat transfer medium in the
SCV tank 122.
[0073] While a specific embodiment of a manifold and distributor
assembly 116 is shown in the Figures for purposes of illustration,
a wide variety of configurations can be used in order to deliver
hot gases to a heat transfer medium. Depending on a particular
application or size constraints for a vaporization system, the
manifold and distributor assembly can have a wide variety of
shapes, sizes, and configurations. Preferably, however, the
assembly will be configured to distribute hot gases substantially
evenly into heat transfer medium so that heat can be substantially
evenly distributed for the vaporization of cryogenic liquid.
[0074] Referring now to FIGS. 8A and 8B, an exemplary embodiment of
a tube bundle configured for use in the SCV tank 122 is
illustrated. The tube bundle 144 illustrated in FIG. 8A includes
four (4) tubes, each extending from an inlet 146 for liquid natural
gas (or other cryogenic liquid) to an outlet 148 for vaporized
natural gas (or other gas). The inlet 146 and outlet 148 of tube
bundle 144 correspond to the inlet and outlet manifolds 120
illustrated in FIG. 6C.
[0075] As illustrated in FIG. 8B, which provides a cross-sectional
end view of tube bundle 144 (with the tubes removed for
clarification), the inlet 146 and outlet 148 are provided with a
plurality of openings for connection to tube bundles such as tube
bundle 144. Accordingly, a plurality of tube bundles 144 are
positioned next to each other and are connected for fluid flow
communication with the inlet 146 and outlet 148 in order to provide
a dense population of flow passages through which a cryogenic fluid
can be passed for vaporization. For example, inlet 146 and outlet
148 can accommodate up to fifteen (15) or more tube bundles 144,
each tube bundle 144 including four (4) tubes. In such an
embodiment, the tube bundle assembly will provide sixty (60) tubes
for the flow of cryogenic liquid such as liquid natural gas (LNG).
Each tube bundle 144 can also have fewer or more than four tubes,
and the tube bundle assembly can have fewer or more than fifteen
(15) rows of tube bundles.
EXAMPLE
[0076] According to one aspect of this invention, a flameless
thermal oxidizer can be modified to create a cylindrical void at
the diptube outlet. Also, a flat disc can be added to the end of
the diptube to direct reacting gases away from the diptube walls.
These modifications were run on a CFD model and resulted in a
significant reduction in pressure losses and also changed the shape
of the reaction wave to force improved containment of the reaction
gases within the ceramic media bed.
[0077] The flameless thermal oxidizer was setup in the CFD model
with a 60 inch ID by 20 foot long diptube. The ceramic media was
simulated as 1 inch saddles, such as those used in commercial
applications, packed to a depth of 16 feet. The diptube was
simulated as being immersed 8 feet into the ceramic media bed. Two
rectangular exhaust ducts were simulated to be used to convey flue
gases from the surface of the ceramic media bed. The ducts were
simulated to be installed 180 degrees apart in the headspace above
the ceramic media bed. Dimensions for the ducts were simulated to
be 2.5 feet high by 15 feet wide by 10 feet in length. The outlet
of the diptube was simulated to be fitted with an 8 foot diameter
disc to divert reaction gases away from the diptube wall. A void
was simulated to be created in the ceramic media bed directly
beneath the diptube outlet so that gases could flow with less
restriction in an attempt to lower pressure losses in the flameless
thermal oxidizer. The void was simulated to be a cylindrical volume
8 feet in diameter and 3 feet in height.
[0078] The LNG vaporizer was simulated to exert a 60 inch water
column back pressure on the heat source due to pressure losses in
the heat exchanger tube bundle and water bath. Addition of the disc
to the diptube outlet and the void constructed in the ceramic
medial bed significantly reduced the pressure losses in the
flameless thermal oxidizer. The reduction in pressure losses was
simulated to be approximately 45 inches WC, yielding a total
pressure loss across the flameless thermal oxidizer of only 17
inches WC.
[0079] According to the simulation, the velocity of the premixed
gases traveling down the diptube is approximately 50 feet per
second. The total mass flow rate is approximately 4400 lbs/min
yielding a heat release of 122 MMBtu/hr HHV. Combustion air is
supplied at the rate of 4311 lbs./min and fuel gas at the rate of
86.26 lbs/min and, according to the simulation, the composition of
the flue gases in volume percent is as follows:
TABLE-US-00001 Component Volume Percent Oxygen 13.38 Nitrogen 76.54
Carbon Dioxide 3.32 Water Vapor 6.77
[0080] The gas velocity profile has been discovered to be
significantly different in the ceramic bed with the optional
cylindrical voidage beneath the diptube outlet, which contributes
to a significant reduction in static pressure losses. Specifically,
the temperature profile within the flameless thermal oxidizer after
having installed the diptube exit disc and the voidage beneath the
diptube differs from that of a flameless thermal oxidizer having
ceramic media packing at the diptube discharge point and no disc
attached to the diptube outlet. Also, it has been discovered that
less carbon monoxide is present in the headspace above the ceramic
media surface as compared to the unmodified oxidizer model.
Although carbon monoxide burnout is achieved prior to the exhaust
ducts in both designs, this feature is an improvement and lends
more operational flexibility to the process.
[0081] The CFD modeling results for a flameless thermal oxidizer
with a diverter disc mounted on the discharge of the diptube and a
cylindrical voidage located beneath the diptube discharge have
indicated a significant reduction in static pressure losses across
the oxidizer. This improvement benefits the operating economics for
the flameless thermal oxidizer in the LNG vaporizer application.
Pressure losses across the flameless oxidizer now amount to only 17
inches WC.
[0082] Assuming that the pressure loss across the LNG vaporizer
heat exchanger is not impacted by the flameless thermal oxidizer
flue gas flow rate, then the total system pressure loss has been
reduced from 122 inches WC to 77 inches WC. This represents a 37
percent reduction in pressure losses with the flameless thermal
oxidizer modifications presented here. The pressure loss reduction
across the flameless thermal oxidizer alone is a significant 72.6
percent with the modified design.
[0083] The temperature profile indicates that the reaction wave is
better confined to the ceramic media bed with the modified design.
While it has been generally considered acceptable for there to be
some cold gas breakout into the headspace without a loss in
performance, the reaction wave should remain within the ceramic
media bed in order to increase the robustness of the flameless
thermal oxidizer and reduce any perception of loss in performance
associated with cold gas breakout.
[0084] Although the invention is illustrated and described herein
with reference to specific embodiments, the invention is not
intended to be limited to the details shown. Rather, various
modifications may be made in the details within the scope and range
of equivalents of the claims and without departing from the
invention.
[0085] For example, the specific structures of the vaporizer and
the flameless thermal oxidizer are not critical to the invention
and may be modified within the scope of this invention. A wide
variety of heat sources and heat exchangers can be utilized
according to aspects of this invention. Similarly, the orientation
of a heat exchanger (such as a vaporizer) with respect to the heat
source (such as a flameless thermal oxidizer) can be modified to
meet specific operating parameters.
[0086] While preferred embodiments of the invention have been shown
and described herein, it will be understood that such embodiments
are provided by way of example only. Numerous variations, changes
and substitutions will occur to those skilled in the art without
departing from the spirit of the invention. Accordingly, it is
intended that the appended claims cover all such variations as fall
within the spirit and scope of the invention.
[0087] What is claimed:
* * * * *