U.S. patent number 3,607,120 [Application Number 04/861,714] was granted by the patent office on 1971-09-21 for gas-treating apparatus.
This patent grant is currently assigned to Midland-Ross Corporation. Invention is credited to Klaus H. Hemsath, John D. Nesbitt.
United States Patent |
3,607,120 |
Nesbitt , et al. |
September 21, 1971 |
**Please see images for:
( Certificate of Correction ) ** |
GAS-TREATING APPARATUS
Abstract
A gas-treating apparatus for causing a nonhomogeneous stream of
gases to flow through a casing and to become homogeneously mixed in
a relatively short span of time and space. A baffle extends
laterally from the inner surface of the casing partially across the
casing so that the outside streamlines of the forward flow do not
attach readily to the inner surface of the casing. The inner edge
of the baffle defines an opening which has an area and shape that
correspond with the cross-sectional area and shape of the
casing.
Inventors: |
Nesbitt; John D. (Toledo,
OH), Hemsath; Klaus H. (Sylvania, OH) |
Assignee: |
Midland-Ross Corporation
(Toledo, OH)
|
Family
ID: |
25336559 |
Appl.
No.: |
04/861,714 |
Filed: |
September 29, 1969 |
Current U.S.
Class: |
422/183; 431/5;
110/212; 431/202 |
Current CPC
Class: |
F23G
7/065 (20130101) |
Current International
Class: |
F23G
7/06 (20060101); F23g 007/06 () |
Field of
Search: |
;23/277C ;48/180
;110/8A,18A ;431/5,202 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Scovronek; Joseph
Assistant Examiner: Serwin; R. E.
Claims
We claim:
1. A gas-treating apparatus comprising: a casing, means for
conducting a first gas stream through said casing, means located
interiorly of said casing and said first gas stream for injecting
at least one gas stream curtain having a lineal lateral cross
section into the interior of said first gas stream, and a mixing
baffle means downstream from said injecting means, said baffle
means having a rim member extending laterally inward from the
surface of said casing a substantially uniform distance thereby
defining an opening in said baffle which is symmetric with the
outer cross-sectional surface of said gas stream curtain, the
downstream surface of said rim member substantially planar so as to
provide a recirculation region therebeyond.
2. A gas-treating apparatus according to claim 1 wherein said rim
member substantially blocks a peripheral area of a size of about 35
to 85 percent of the lateral cross-sectional area of said
casing.
3. A gas-treating apparatus according to claim 2 wherein said
baffle means further includes a central baffle member which
effectively blocks between about 15 to 50 percent of said
cross-sectional area of said casing and said rim member effectively
blocks between about 35 to 75 percent of said casing area forming
an elongated slot opening between the rim member and central member
of said baffle.
4. A gas-treating apparatus according to claim 3 wherein said slot
opening is located in the inner 67 percent of the outer peripheral
75 percent of said casing area.
5. A gas-treating apparatus according to claim 3 wherein said
casing is a cylindrical casing and said elongated slot opening is a
substantially continuous annular slot formed between a rim member
and a concentrically disposed hub member of said baffle.
6. A gas-treating apparatus according to claim 5 wherein the center
diameter of said annular slot is between about 0.5 and 0.8 of the
inside diameter of said cylindrical casing.
7. A gas-treating apparatus according to claim 6 wherein said
center diameter is between 0.65 and 0.75 of said inside diameter of
said casing.
8. A gas-treating apparatus according to claim 1 wherein said
baffle means defines a lineal slot having an area of between about
15 to 50 percent of the lateral cross-sectional area of said
casing.
9. A gas-treating apparatus according to claim 8 wherein the
effective area of said slot is between about 20 to 35 percent of
the lateral cross-sectional area of said casing.
10. A gas-treating apparatus according to claim 1 having a means
for injecting a plurality of said gas stream curtains, and said
baffle has an equivalent number of said slot openings each of which
is aligned with a corresponding gas stream curtain.
11. A gas-treating apparatus for homogeneously mixing in a short
span of time and space two gas streams in volumetric proportions of
above 8:1, said apparatus comprising: a casing, means for
conducting a first gas stream through said casing, means for
injecting at least one gas stream curtain into the interior of said
first gas stream, said gas stream curtain having a lineal lateral
cross section, and a mixing baffle means having at least one lineal
slot opening which is symmetric with said cross section, said
baffle means has a rim member and a hub member, said rim member has
a substantially uniform width which extends laterally inward from
the inner surface of said casing and substantially blocks a
peripheral area of a size about 35 to 75 percent of the
cross-sectional of said casing, said hub member is centrally
located with respect to said rim member and blocks an area of a
size of about 10 to 50 percent of the cross-sectional area of said
casing.
12. A gas-treating apparatus according to claim 11 wherein said
casing is cylindrical and said elongated slot opening is a
substantially continuous annular opening located in the inner 67
percent of the outer annular 75 percent of the cross-sectional area
of said casing.
13. A fume incinerator comprising: a casing, means for conducting a
stream of fumes through said casing, a burner located interiorly of
said casing and said fume stream for producing at least one curtain
of hot gases having lineal lateral cross section, said burner
including a fuel injector and a flame stabilizer bar confronting
said injector, mixing baffle means in said casing downstream from
said burner, said baffle means having at least one opening which is
symmetric with the outside surface of said curtain, and a fume
combustion chamber downstream from said baffle means.
14. A fume incinerator according to claim 13 wherein said baffle
has a rim member which extends inwardly from the inner surface of
said casing and substantially blocks a peripheral area of a size of
about 35 to 75 percent of the lateral cross-sectional area of said
casing.
15. A fume incinerator according to claim 14 wherein said baffle
means also has a plurality of narrow slots extending outwardly from
its inner edge towards its outer edge.
16. A fume incinerator according to claim 13 wherein the downstream
side of said baffle means is protected by an insulative refractory
material.
17. A fume incinerator according to claim 14 wherein the size of
the slot area in said baffle means is between about 15 to 50
percent of the lateral cross-sectional area of said casing.
18. A fume incinerator according to claim 14 wherein said casing is
a cylindrical casing and said elongated slot is a generally
annularly shaped slot formed between a rim member and a
concentrically disposed hub member.
19. A fume incinerator according to claim 18 wherein the size of
said annular slot is between about 15 and 35 percent of the lateral
cross-sectional area of said casing and said annular slot is
located in the inner 67 percent of the outer peripheral 75 percent
of said cross-sectional area.
20. A fume incinerator according to claim 14 wherein said burner is
a ring-type burner for producing a hollow columnar curtain of
gases.
21. A fume incinerator according to claim 20 wherein said ring-type
burner has segments arranged to form substantially an equilateral
polygon in a plane perpendicular to the mass flow of fumes, said
segments each being centrally fed by a radially extending fuel line
connected to a central fuel supply hub.
22. A fume incinerator according to claim 14 wherein said baffle is
located downstream from said burner a distance equivalent to less
than one-third the mean lateral cross-sectional dimension of said
casing.
Description
BACKGROUND OF INVENTION
Up to the present time there has been an unfulfilled need for a
simple gas-treating device which is capable of homogeneously mixing
large volumes of gases in a relatively short span of time and
space. Gas mixing and treating apparatuses capable of treating
large volumes of gas are particularly useful in drying and other
heat-processing operations. Another use is in fume incinerators in
which a small quantity of gaseous fuel is burned and mixed with a
large quantity of exhaust fumes or waste gases containing a low
concentration of combustible material and sufficient oxygen to
complete combustion. The fumes are purified by being raised to a
sufficiently high reaction temperature and held at or above this
temperature until incineration is completed. The efficiency of
these devices is primarily dependent upon the ease and thoroughness
with which they are able to mix the gas streams and also on the
rate of mixing.
Gas mixing devices are quite common in burners and combustion
apparatuses, but they generally involve complex means for
dispersing one gas throughout another by means of turbulence. The
turbulence needed for the mixing is created normally be a radical
change in the velocity of a high-velocity gas stream which results
in a severe pressure drop. An example of a method which is commonly
used and which does produce a severe pressure drop is to break up a
bulk stream of gasses into a plurality of small discrete streams by
means of a grid plate or the like. Also, prior art gas-treating
devices do not perform satisfactorily when they are required to mix
a large volume of gas comprising two gas streams of low velocity
and pressure. The problem of mixing becomes more severe when the
ratio between the volumes of the two gasses is above 8:1 and
particularly when it is between about 20:1 and 500:1.
SUMMARY OF INVENTION
Generally speaking, the gas-treating apparatus of this invention
comprises a casing having means for introducing gases at one end, a
treating chamber adjacent the other end, and a baffle means located
intermediate the ends. Although the apparatus may be used to
uniformly mix a single heterogeneous stream of gases, the
embodiments shown in the drawing will be described primarily with
respect to the mixing together of two streams of different gases.
The gases may be mixed in other than equal proportions, such as in
the ratios mentioned above, in which case the gas stream having the
greatest volume flows through the casing or duct and the other gas
is injected into the interior of the main gas stream so as to form
an confluent gas stream curtain in the main stream. The lateral
cross section of the gas curtain is lineal and is concentric with
or roughly parallels the inner surfaces of a cylindrical or
rectangular casing. Preferably the casing is cylindrical and the
lateral section of the curtain is annular in form. In thermal gas
treating apparatuses, such as fume incinerators, the injected gas
which produces the gas stream curtain may be a fuel gas and the
injecting means may be a ring or line burner and may have a flame
stabilizer.
Downstream from the gas stream curtain injection means is a baffle
which extends laterally across the casing from the inner surface of
the casing. In has an opening which corresponds in shape to the
lateral cross-sectional shape of the gas stream curtain and is
axially aligned therewith.
OBJECTS AND ADVANTAGES
It is a general object of this invention to produce a gas-treating
apparatus which is capable of homogeneously mixing in a relatively
short span of time and space a large bulk stream of gases flowing
under low pressure.
It is another object of this invention to produce such an apparatus
which will efficiently mix a heterogeneous gas stream without
causing a severe pressure drop.
It is still another object of this invention to produce a
gas-treating apparatus which is capable of mixing in approximately
two duct diameters not only gas streams flowing at very low
velocities, just sufficient to cause turbulence, but also gas
streams flowing at intermediate or high velocities.
It is still another object of this invention to produce a
gas-treating apparatus for efficiently raising a bulk stream of
gases to a uniform temperature.
It is yet another object of this invention to produce a simple and
efficient fume incinerator which is economical to operate and
maintain.
The above-mentioned objects and other objects and advantages and
the manner of attaining them will be apparent from the following
description of embodiments of this invention made with reference to
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an elevation view in perspective of a fume incinerator
having a relatively small diameter and adapted for operating at low
to moderate incineration temperatures. Portions of the apparatus
have been broken away to show interior and underlying details.
FIG. 2 is an enlarged plan view taken along line 2--2 of FIG. 1
with parts broken away.
FIG. 3 is an end view of a fume incinerator similar to that shown
in FIG. 2, but for operating at moderate to high incineration
temperatures and having a polygonal ring burner adapted for use in
a relatively large diameter casing.
FIG. 4 is a side view in section of the ring burner and mixing
baffle portions of the fume incinerator in FIG. 3.
FIG. 5 is a side view of a ring burner similar to that shown in
FIG. 4, but with a surrounding band-type flame stabilizer
associated with the ring burner.
FIG. 6 is an elevation view in perspective of a fume incinerator
with a rectangular duct having modular baffles.
FIGS. 7 and 8 show representative baffles for large cylindrical and
rectangular ducts respectively, each having alphabetical symbols
denoting areas and dimensions.
DETAILED DESCRIPTION OF THE DRAWINGS
The gas treating or mixing apparatus will be described primarily
with reference to a fume incinerator in which a stream of fuel is
injected directly into the interior of a stream of fumes and
ignited. The fume stream is homogeneously mixed with the burning or
burned fuel stream by baffle means and thereby is thermally treated
or incinerated in a subsequent chamber. Fumes as used herein shall
include any gaseous fluid containing oxygen and also containing an
oxidizable material in the form of a gas or finely divided droplets
or even solid particles capable of being suspended in the gaseous
fluid stream. Such fumes may be evolved from industrial processes,
chemical reactions, and the incomplete oxidation or burning of
combustible material. The ratio between the oxygen and the
combustible material in the fume may be such that the fume is near
or below the threshold of flammability at the temperature it is
introduced into the treating apparatus.
Referring to the drawings, FIGS. 1 and 6 show fume incinerators 10
and 20 comprising vertically disposed heat treating or incinerating
chambers 22 and 24 respectively. The incinerating chambers 22 and
24 need not be vertically disposed, but may be arranged
horizontally or in other attitudes. 37 HORIZONTALLY OR IN OTHER
ATTITUDES. These incinerators may be installed in or adjacent the
exhaust stack or in some other portion of a fume exhaust system
remote from the exhaust stack. The incinerating chamber 22 is
defined by a cylindrical wall, such as the base portion of an
exhaust stack, while the incinerating chamber 24 is defined by a
rectangular wall, such as a section of duct. Both chambers are
fabricated from materials which are capable of withstanding normal
incinerating temperatures of between about 1,200.degree. F. to
1,500.degree. F. A duct section sub assembly 26 or 28 containing
the fuel injecting means and a baffle means is connected in fluid
communication with the inlet end of each chamber 22 or 24 for
conveying fumes into these chambers. A blower 30 or other means
causes a stream of fume to flow through each duct and then through
the respective chamber 22 or 24 at a velocity sufficient to cause
turbulence. The Reynolds number indicating the fluid flow
conditions in these chambers may be as low as 2,300.
Upstream from the inlet end of each incinerating chamber, a fuel
injecting means is provided for supplying a curtain of fuel gas
directly into the interior of the fume stream so that the curtain
of fuel gas is isolated from the walls of the incinerator by a
surrounding portion of the fume stream.
The fuel-injecting means may be straight, circular, or polygonal in
form and be made of apertured or slotted tubes or tubes having a
plurality of jet nozzles provided that it is capable of producing a
curtain of fuel gas within the fume stream.
FIG. 1 shows an annular fuel injecting means 32 for producing a
hollow or tubular gas curtain stream in the interior of a fume
stream flowing through the duct. The fuel-injecting means is
concentrically mounted in the duct and has a plurality of jet
nozzles 34 directed parallel with its axis and spaced equally
around the annular manifold or distributor 36. The jet nozzles may
be placed sufficiently close together so that if the fuel from one
of them is ignited, the others will become ignited thereby. The
fuel gas may be supplied at a relatively low pressure equivalent to
about 1 inch of water column by means of a feed pipe 38 extending
through the wall of the duct and connected to the distributor. The
ratio of the volume of fuel to the volume of fume is approximately
between 1:20 and 1:500, depending upon the amount and composition
of the combustible material in the fume and on the temperature of
the incoming fume. A flame retention or stabilizing means, such as
an annular bar 39 having a T-shaped cross section, may be placed
directly in front of the jets a short distance downstream therefrom
so that an ignitable fuel-air gas stream is obtained adjacent the
downstream side of the stabilizing means. It was found that a
remarkably stable flame was obtained with the annular burner
apparatus.
The incinerator subassembly 40 shown in FIGS. 3 and 4 is similar to
subassembly 26 of FIG. 1, but is designed for moderate to
high-temperature operation, for example in about a 1,400.degree. F.
to 1,700.degree. F. range, for incinerating fumes which are
difficult to incinerate, such as fumes containing soot or
soot-forming hydrocarbons. The inside of the duct portion of
subassembly 40 preferably has protective layer 41 of insulative or
refractory material.
The fuel injecting means 42 and burner apparatus in FIGS. 3 and 4
are similar to those of FIG. 1, but are in the form of a polygon,
such as an octagon, in which eight fuel injecting segments 43 are
each centrally fed and supported by a fuel line 44, extending
radially from a common manifold 45 in its center. The flame
retention bar 46 is also octagonal.
FIG. 5 shows a wheellike fuel-injecting means 47 in which the fuel
is directed slightly outwardly against and along an adjacent
peripheral flame retention rim 48. The fuel orifices or jets may be
axially angled to produce a slightly spiraling hollow columnar
flame. In all of the annular and polygonal fuel-injecting means 32,
42, and 47 the fumes flow interiorly and exteriorly of the hollow
gas curtains or flames produced thereby.
The fuel injection means in FIG. 6 comprises a pair of fuel
distributing members 50 similar to straight line burners. The
members 50 each supply fuel to their respective modular section of
the incinerator. They are centrally disposed in their modular
sections parallel with the sidewalls thereof and directly in front
of an opening in a baffle which will be described later. A flame
stabilizing bar 54 may be provided in confronting relationship to
this fuel injecting means. On installations where the fume inlets
are small or located off center with respect to the duct section
28, a diffuser or distributor such as a perforated plate 55 may be
provided to distribute the fume stream evenly across the duct. In
this embodiment, as well as in the others, the fuel gas or flame
curtain is isolated from the walls of the duct by a surrounding
portion of fume.
In the incinerators shown, fume mixing baffles are provided on the
downstream side of the fuel injecting means adjacent the
incineration chamber inlet. Preferably the distance between the
fuel injecting means and the fume mixing baffle is less than about
one-third of the diameter of mean dimension across the duct. Each
baffle defines a central slot opening which corresponds with the
lateral cross sectional shape of the associated fuel gas stream or
flame curtain and is axially aligned therewith. The slot opening
need not be entirely open. It may be obstructed partially, such as
by a grid screen, struts 57, or the like, provided that the gas
stream parted by the obstruction becomes confluent in a short
distance downstream.
In FIGS. 1, 2, and 5 the mixing baffle 58 comprises a flat circular
disc with an annular slot opening 60 formed by and between an
annular rim member 62 and a concentrically mounted circular hub
member 64. In small installations, such as where the inner diameter
of the rim member is 12 inches or less, a hub member is not
required and the rim member may block as much as 85 percent but not
less than 50 percent of the opening. In the larger installations
the rim member may block between 35 and 75 percent of the opening
and the hub member may block from 10 up to 50 percent of the
opening. The effective open area of the slot opening is preferably
between about 20 and 35 percent and suitably may be between 15
percent and 50 percent of the cross-sectional area of the
incinerating chamber inlet. The remaining 50 to 85 percent of the
opening is blocked by the baffle members 62 and 64. The relative
length of the average or center diameter of the annular slot
opening with respect to the diameter of the casing is such that D
d.sub.i +d.sub.o 1.6 D where D is the inside diameter of the casing
d.sub.i is the inside diameter of the annular slot defined by the
periphery of the hub member 64, and d.sub.o is the outside diameter
of the slot defined by the inner circumference of rim member 62.
Preferably 1.3 D D.sub.i +d.sub.o 1.5 D (see FIG. 7). The
proportions between the effective areas of the hub area A, the
annular slot area B, and the rim member area C are such that A+C/B
is between about 1 and 5.7, preferably between 1.8 and 4, also A C.
The range of the slot length/slot width (W.sub.s) ratio defined as
[.pi.(d.sub.i +d.sub.o)]/2W.sub.s is greater than 2 and preferably
between about 4 and 40. The hub member 64 may be displaced axially
upstream or downstream from the plane of the rim member 62 is a
slight distance, such as less than one-fourth of the duct diameter,
for higher or lower velocity streams respectively. Also, the baffle
may be streamlined on its input side.
The baffle means 68 shown in FIGS. 3 and 4 is the same as baffle
means 58 except that the rim member 70 and hub member 72 of baffle
68 have been segmented by radially extending slots 74 and 76
respectively. Also the downstream side of the baffle means has been
protected by a layer 78 of insulative and refractory material.
Preferably the edges of the layer 78 which define the annular slot
79 are inclined so as to provide boundary layer separation.
The rectangular incineration chamber 24 of the incinerator 20 of
FIG. 6 has a modular baffle system comprising two adjoining
modules. More or fewer modules may be used, depending upon the size
of the incinerator and the number of corresponding fuel injecting
members to be used. The incineration chamber 24 may be divided
axially by a partition 80 into two modular sections, each of which
has a baffle member 82. The baffle members have peripheral rims
which extend laterally across a portion of the sections from the
inner surfaces of the surrounding walls and partition. The rims
define generally rectangular central openings which are
confrontingly aligned with the fuel injecting members 50 located
upstream therefrom. A central baffle may be provided in a portion
of the baffle opening, but is not essential when the area and width
of the opening are small, such as 0.5 of a square foot or less than
6 inches in width. The fuel gas and fumes are directed vertically
downward towards the baffles 68. The relationships expressed above
with respect to annularly slotted baffles apply to rectangular
slotted baffles. Reference may be made to FIG. 8 wherein a
rectangular baffle, having a rim member and a central member, has
been given primed reference characters corresponding with the
reference characters on similar parts of the annularly slotted
baffle of FIG. 7.
The peripheral and central recirculation regions formed
respectively on the downstream side of the rim and hub members
preferably extend axially downstream about equal distances from the
plane of the rim member of each embodiment.
The effectiveness of the mixing may be shown by the temperature
uniformity attained at approximately two duct diameters downstream
from the baffle during a test run. In the test the entering fume
was about 375.degree. F. and the flame temperature was
approximately 2,500.degree. F., producing a temperature
nonuniformity on the order of 2,100.degree. F. temperature at 60
inches downstream from the baffle in a 36-inch diameter duct was
between 1,400.degree. F. and 1,425.degree. F., with an average of
1,413.5.degree. F. The nonuniformity of 25.degree. F. is about 1
percent of the temperature nonuniformity on the upstream side of
the baffle. This was achieved with a pressure drop on only 0.95
inch of water column.
While the principles of this invention are described above with
reference to specific embodiments, it is to be clearly understood
that this description is made only by way of example, and not as a
limitation to the scope of this invention. For example, the
teachings of this invention could be applied to a burner, makeup
air heating, industrial burners, catalytic fume-treating devices,
and the like.
* * * * *