U.S. patent application number 13/759582 was filed with the patent office on 2013-08-15 for hydrocarbon/oxygen industrial gas mixer with water mist.
This patent application is currently assigned to DOW TECHNOLOGY INVESTMENTS LLC. The applicant listed for this patent is Dow Technology Investments LLC. Invention is credited to Harvey E. Andresen, Laurence G. Britton, Christopher P. Christenson, Victor R. Fey, Michael L. Hutchison, Thomas J. Kling, Charles W. Lipp, John R. Mayer, Michael J. Rangitsch.
Application Number | 20130208559 13/759582 |
Document ID | / |
Family ID | 40262976 |
Filed Date | 2013-08-15 |
United States Patent
Application |
20130208559 |
Kind Code |
A1 |
Andresen; Harvey E. ; et
al. |
August 15, 2013 |
HYDROCARBON/OXYGEN INDUSTRIAL GAS MIXER WITH WATER MIST
Abstract
A hydrocarbon-containing gas is mixed with an oxygen-containing
gas in a gas mixer in the presence of a water mist. The water mist
surrounds and contacts entrained particles in either the
oxygen-containing gas stream or the hydrocarbon-containing gas
stream. The water acts to suppress and prevent ignition of the
hydrocarbon gas in the mixer by serving as a sink for heat created
by energetic collisions between such particles and structures
within the gas mixer. The water mist also acts to quench ignition
caused by such collisions. The water mist can be introduced into
the gas mixer in a number of different configurations, including
via nozzles injecting a mist into a hydrocarbon gas manifold or an
oxygen gas manifold, nozzles placed within the gas mixer adjacent
to ends of the oxygen supply pipes, and nozzles placed coaxially
within the oxygen supply pipes in the gas mixer.
Inventors: |
Andresen; Harvey E.;
(Luling, LA) ; Christenson; Christopher P.; (Lake
Jackson, TX) ; Lipp; Charles W.; (Lake Jackson,
TX) ; Mayer; John R.; (The Woodlands, TX) ;
Kling; Thomas J.; (Midland, MI) ; Fey; Victor R.;
(West Bloomfield, MI) ; Britton; Laurence G.;
(Charleston, WV) ; Rangitsch; Michael J.;
(Saginaw, MI) ; Hutchison; Michael L.; (Poca,
WV) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Dow Technology Investments LLC; |
|
|
US |
|
|
Assignee: |
DOW TECHNOLOGY INVESTMENTS
LLC
Midland
MI
|
Family ID: |
40262976 |
Appl. No.: |
13/759582 |
Filed: |
February 5, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12678274 |
Mar 15, 2010 |
8404190 |
|
|
PCT/US2008/012586 |
Nov 7, 2008 |
|
|
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13759582 |
|
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|
61007734 |
Dec 14, 2007 |
|
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Current U.S.
Class: |
366/178.1 ;
422/224 |
Current CPC
Class: |
B01J 19/26 20130101;
B01F 3/04049 20130101; B01F 5/0456 20130101; B01J 2219/00263
20130101; C07D 301/08 20130101; B01F 5/0453 20130101; B01J 12/00
20130101; B01J 4/002 20130101 |
Class at
Publication: |
366/178.1 ;
422/224 |
International
Class: |
B01J 19/26 20060101
B01J019/26 |
Claims
1. In an industrial production system for gas-phase partial
oxidation of a hydrocarbon-containing gas, a method for mixing the
hydrocarbon-containing gas with an oxygen-containing gas,
comprising the steps of: providing a gas mixer for mixing the
oxygen-containing gas with the hydrocarbon-containing gas;
introducing a water mist into the gas mixer; and mixing the
oxygen-containing gas and the hydrocarbon-containing gas in the
presence of the water mist; wherein the oxygen-containing gas is
introduced into the gas mixer through a plurality of oxygen pipes
placed within the gas mixer, and wherein the water mist is further
introduced into the gas mixer by means of a plurality of water mist
pipes having a proximal end connected to a source of water and
peripheral end having a nozzle, wherein each of the plurality of
oxygen pipes has a water mist pipe concentrically located
therein.
2. The method of claim 1, wherein the oxygen-containing gas is
introduced into the gas mixer through a plurality of oxygen pipes
placed within the gas mixer, and wherein the water mist is further
introduced into the gas mixer by means of a plurality of water mist
pipes having a proximal end connected to a source of water and
peripheral end having a nozzle, wherein the water mist pipes are
positioned within the gas mixer adjacent to the oxygen pipes.
3. The method of claim 1, wherein the gas mixer includes an oxygen
gas manifold receiving a stream of oxygen-containing gas, and
wherein the introducing step comprises the step of supplying the
water mist to the oxygen gas manifold.
4. The method of claim 3, wherein the oxygen manifold is connected
to a mixing chamber by means of a plurality of oxygen pipes, the
pipes conducting oxygen-containing gas and the mist to the mixing
chamber where the hydrocarbon-containing gas is introduced into the
mixing chamber.
5. The method of claim 1, further comprising the steps of:
conducting the oxygen-containing gas into a mixing chamber of the
gas mixer in a plurality of oxygen pipes, and wherein the
introducing step comprises the steps of (1) providing a plurality
of water mist pipes having a proximal end connected to a source of
water and peripheral end having a nozzle, (2) positioning a water
mist pipe concentrically within each of the oxygen pipes, and (3)
directing water through the water mist pipes and producing the
water mist with the nozzles.
6. The method of claim 5, wherein the oxygen pipes have a distal
open end through which oxygen-containing gas flows out of the
oxygen pipes, and wherein the nozzles are located within the oxygen
pipes at a location adjacent to the distal end of the oxygen
pipes.
7. The method of claim 1, wherein the method further comprises the
step of conducting the oxygen-containing gas into a mixing chamber
of the gas mixer in a plurality of oxygen pipes, and wherein the
water mist is introduced into the gas mixer by means of a plurality
of water mist pipes having a proximal end connected to a source of
water and peripheral end having a nozzle, wherein the water mist
pipes are positioned within the mixing chamber adjacent to the
oxygen pipes.
8. In a gas mixer for an industrial production system for gas-phase
partial oxidation of a hydrocarbon-containing gas, the improvement
comprising: providing a means for producing a water mist in the gas
mixer wherein the oxygen-containing gas and the
hydrocarbon-containing gas are mixed in the gas mixer in the
presence of the water mist; wherein the gas mixer further
comprises: a plurality of oxygen pipes located within the gas
mixer, the oxygen-containing gas introduced into the gas mixer
through the plurality of oxygen pipes.
9. The improvement of claim 8, wherein the means for producing a
water mist comprises a plurality of water mist pipes having a
proximal end connected to a source of water and peripheral end
having a nozzle, wherein each of the plurality of oxygen pipes has
a water mist pipe concentrically located therein.
10. The improvement of claim 8, wherein the means for producing a
water mist comprises a plurality of water mist pipes having a
proximal end connected to a source of water and peripheral end
having a nozzle, wherein the water mist pipes are positioned within
the gas mixer adjacent to the oxygen pipes.
11. The improvement of claim 8, further comprising a processing
station recovering water from the mixed hydrocarbon and oxygen
gases.
12. The improvement of claim 8, wherein the gas mixer further
comprises an oxygen gas manifold receiving a stream of
oxygen-containing gas, and wherein the means for producing a water
mist comprises water mist producing devices producing the water
mist and supplying the water mist into the oxygen gas manifold.
13. The improvement of claim 12, further comprising a plurality of
oxygen pipes, the oxygen pipes connecting the oxygen manifold to a
mixing chamber, the pipes conducting oxygen-containing gas and the
mist from the oxygen manifold to the mixing chamber.
14. In a gas mixer for an industrial production system for
gas-phase partial oxidation of a hydrocarbon-containing gas, the
improvement comprising: providing a means for producing a water
mist in the gas mixer wherein the oxygen-containing gas and the
hydrocarbon-containing gas are mixed in the gas mixer in the
presence of the water mist; wherein the gas mixer further
comprises: a mixing chamber; and a plurality of oxygen pipes
conducting oxygen-containing gas into the mixing chamber of the gas
mixer.
15. The improvement of claim 14, wherein the means for producing a
water mist comprises a plurality of water mist pipes having a
proximal end connected to a source of water and peripheral end
having a nozzle; wherein a water mist pipe is located coaxially
within each of the oxygen pipes; and wherein water is directing
through the water mist pipes and the water mist is produced by the
nozzles.
16. The improvement of claim 14, wherein the oxygen pipes have a
distal open end through which oxygen-containing gas flows out of
the oxygen pipes, and wherein the nozzles are located within the
oxygen pipes at a location which is adjacent to the distal end of
the oxygen pipes.
17. The improvement of claim 14, wherein the means for producing a
water mist comprises a plurality of water mist pipes having a
proximal end connected to a source of water and peripheral end
having a nozzle; and wherein the water mist pipes are positioned
within the mixing chamber adjacent to the oxygen pipes.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional application of U.S. patent
application Ser. No. 12/678,274, filed Mar. 15, 2010, which claims
priority to International Application No. PCT/US2008/012586, filed
Nov. 7, 2008, which claims priority to U.S. Provisional Patent
Application No. 61/007,734, filed Dec. 14, 2007, all of which are
hereby incorporated herein by reference in their entirety.
BACKGROUND
[0002] This invention relates generally to gas mixers used in
systems for gas-phase partial oxidation of hydrocarbon-containing
gases. An example of where this invention has utility is systems
for industrial production of ethylene oxide.
[0003] The chemical compound ethylene oxide (chemical formula
C.sub.2H.sub.4O) is an important industrial chemical used as an
intermediate in the production of ethylene glycol (the main
component of automotive antifreeze) and other chemicals. Ethylene
oxide is also used as a sterilant for foods and medical supplies.
It is a colorless flammable gas at room temperature, and can be
cooled and stored as a liquid.
[0004] Ethylene oxide first achieved industrial importance during
World War I as a precursor to both ethylene glycol and the chemical
weapon mustard gas. In 1931, Theodore Lefort, a French chemist,
discovered a means to prepare ethylene oxide directly from ethylene
and oxygen, using silver as a catalyst. Since 1940, almost all
ethylene oxide produced industrially has been made using this
method.
[0005] In current industrial processes, ethylene oxide is produced
when ethylene (CH.sub.2=CH.sub.2) and oxygen (O.sub.2) react on a
silver catalyst at 200-300.degree. C. showing large Ag
nanoparticles supported on Alumina Typically, chemical modifiers
such as chlorine are also included. Pressures used are in the
region of 1-2 MPa. The chemical equation for this reaction is:
CH.sub.2.dbd.CH.sub.2+1/2O.sub.2.fwdarw.C.sub.2H.sub.4O
[0006] In ethylene oxide production systems, a gas mixer is used to
mix the hydrocarbon and oxygen gas streams just upstream of the
reaction chamber where the silver catalyst is present. The gas
mixer is typically constructed in the form of a vessel or pipe. The
vessel includes an inlet manifold for each of the two gases. The
vessel is sometimes constructed with a main outer pipe containing
the hydrocarbon gas stream and internal concentric tubes or
"fingers" which contain the oxygen stream. Mixing occurs at the
point where the internal tubes end, where the oxygen gas flowing
out of the fingers meets the main stream of hydrocarbon gas flowing
in the outer tube. This basic design is described in U.S. Pat. No.
3,706,534.
[0007] The art has long recognized that there is a risk of ignition
of a hydrocarbon-containing gas stream (e.g., a stream of gas
containing for example ethylene mixed with other hydrocarbon gases)
at the point where it is combined with an oxygen gas in a gas
mixer. Ignition can occur when a particle (e.g. a piece of sand,
rust or pipe scale) entrained in the hydrocarbon or oxygen gas
stream strikes a metallic surface in the mixer, e.g., the wall of
the mixer, thereby producing a spark. If the spark occurs in the
hydrocarbon stream in the highly flammable zone e.g., at, or close
to, the point of mixing of the two gas streams, ignition can occur.
The ignition damages the gas mixer and also requires an interrupt
of production to suppress the ignition and allow the gas mixer to
cool before recommencing production. The flammable region is
confined to the mixing zone of the two gases. The
hydrocarbon-containing gas as well as the reactor feed blend are
below the lower O.sub.2 flammability limit--i.e., too rich to
burn.
[0008] The art has devised a variety of gas mixer designs. Some of
the designs are specifically directed to reducing the risk of
ignition of hydrocarbon and oxygen gas stream. The known prior art
includes the following patent documents, in addition to the
above-cited '534 patent: U.S. Pat. No. 4,573,803; U.S. Pat. No.
3,702,619; U.S. Pat. No. 4,256,604; U.S Pat. No. 4,415,508; U.S.
Pat. No. 6,657,079; U.S. 2003/0021182; U.S. Pat. No. 3,518,284;
U.S. Pat. No. 4,390,346; U.S. Pat. No. 3,237,923; U.S. Pat. No.
3,081,818; U.S. Pat. No. 2,614,616 and U.S. Pat. No. 6,840,256.
[0009] Other prior art of interest include British patents GB
705,176 and 2,357,318; U.S. Pat. No. 5,336,791; and U.S. Pat. No.
4,393,817.
SUMMARY
[0010] In a first aspect of this disclosure, industrial production
systems for gas-phase partial oxidation of a hydrocarbon-containing
gas are disclosed which use a method for mixing the
hydrocarbon-containing gas with an oxygen-containing gas. The
method includes providing a gas mixer for mixing the
oxygen-containing gas with the hydrocarbon-containing gas,
introducing a water mist into the gas mixer, and mixing the oxygen
gas and the hydrocarbon-containing gas in the presence of the water
mist. The invention can be applied to hydrocarbon-air mixers and
hydrocarbon-enriched air mixers. Hence, the term "oxygen-containing
gas" is intended to encompass a stream of a gas containing oxygen
generally, such as for example a stream of pure or substantially
pure oxygen gas, a stream of air, or a stream of air which is
enriched with oxygen gas. In another aspect, an improvement to a
gas mixer for an industrial production system for gas-phase
oxidation of a hydrocarbon-containing gas is provided. The
improvement is providing a means for producing a water mist in the
gas mixer wherein the oxygen-containing gas and the
hydrocarbon-containing gas are mixed in the gas mixer in the
presence of the water mist. Several examples of the means for
producing the water mist are described, including atomizers
(nozzles) which inject a water mist into a hydrocarbon gas
manifold, nozzles which inject a water mist into an oxygen gas
manifold, and water pipes with mist-producing nozzles at the ends
thereof either (1) concentrically located within oxygen pipes
supplying oxygen in the gas mixer, (2) positioned along side the
oxygen pipes, or both (1) and (2).
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a schematic representation of a gas mixer for an
industrial production system for gas-phase oxidation of a
hydrocarbon-containing gas, showing a first embodiment of a means
for introducing a water mist into the gas mixer in the form of (1)
atomizers (nozzles) which inject a water mist into a hydrocarbon
gas manifold and (2) water pipes with mist-producing nozzles at the
ends thereof concentrically located within oxygen pipes supplying
oxygen to the gas mixer.
[0012] FIG. 2 is an end view of the one of the pipes carrying the
hydrocarbon-containing gas shown in FIG. 1, showing the water pipes
within the oxygen pipes and the mist provided by the atomizers and
the nozzles at the end of the water pipes.
[0013] FIG. 3 is an illustration of a second embodiment of a gas
mixer which features water pipes carrying water and nozzles at the
end thereof which produce a mist at the mixing point where oxygen
and hydrocarbon-containing gases are mixed.
[0014] FIG. 4 is an end view of the gas mixer of FIG. 3 showing the
water pipes placed both adjacent to the oxygen pipes and
concentrically within the oxygen pipes.
[0015] FIG. 5 is an illustration of a third embodiment of a gas
mixer which features atomizing nozzles injecting a water mist into
an oxygen gas manifold.
[0016] FIG. 6 is a detailed cross-section of the ends of the oxygen
pipes of FIG. 5.
DETAILED DESCRIPTION
[0017] In industrial production systems for gas-phase partial
oxidation of a hydrocarbon-containing gas, such as production of
ethylene oxide, the mixing of hydrocarbon and oxygen gases in a
safe, reliable manner is a continuing problem, particularly when
the gases to be mixed may go through a flammable zone in the mixing
process. The features of this disclosure provide improvements to a
gas mixer and method of mixing gases which minimizes the
probability of ignition. The mixing of the two gases is performed
in a water mist environment.
[0018] Several different embodiments of a gas mixer featuring
apparatus for producing the water mist environment will be
described in some detail below. These embodiments illustrate
applications suitable for ethylene oxide production in a gas mixer
featuring low shear co-axial gas mixing. However, variation from
the disclosed embodiments is of course possible and the invention
can be practiced in a high shear gas mixer, such as described in WO
2009/078899, entitled Oxygen/Hydrocarbon Rapid (High Shear) Gas
Mixer, Particularly For The Production Of Ethylene Oxide, the
entire content of which is incorporated by reference herein. In the
low shear embodiments, a water mist is injected coaxially in one
gas stream, particularly a high-purity oxygen feed, and/or
alternatively surrounding one gas stream at the point of entry into
the second gas stream, particularly the mixing of a high-purity
oxygen stream into a hydrocarbon-containing gas stream.
[0019] The purpose of the water mist environment is to reduce the
probability of ignition of the flammable gas envelope where the two
gases initially mix, or to quench an ignition should one initiate,
by introducing a sufficient quantity of small water droplets into
the gas stream at the point of the high flammability gas envelope
so as to provide enhanced mixing, wetting of the surface of any
entrained particles in either the hydrocarbon stream or the oxygen
stream, and a heat sink to transfer any heat generated from
particle impact or particle fracture while the particle is still
present in the flammable region of the flammable gas stream. In
general, the gas mixer features atomizers (water mist producing
nozzles) which are designed to produce the water droplet having a
size approximately <200 microns SMD (Sauter Mean Diameter). This
term is defined as the drop diameter that has the same surface area
to volume ratio as the entire spray. However, the droplets could be
considerably smaller, such as for example as small as 1 micron. At
elevated pressures, such as found in the gas mixers of the type of
this disclosure, the water mist may act like a dense gas which
travels with the oxygen gas into the high flammability zone and act
as an ignition suppressant. Materials for construction of the gas
mixer and the mist/fog generating devices may be stainless steel,
Monel, Inconel, or other corrosion and ignition resistant metal.
Such metals may also be used in the highest velocity zones and the
gas-distributing pipes.
[0020] One application of the invention is direct oxidation
ethylene oxide process mixers, which mix oxygen at intermediate
pressure (.about.20 bar) with recycled hydrocarbon gas containing
ethylene and other gases. Oxygen pressures run around .about.26
bar. The invention can similarly be used for other partial
oxidation processes using pure oxygen or enriched air.
[0021] The features of this disclosure redefines the
oxygen/hydrocarbon mixing process to reduce the potential for
ignition in the high flammable gas envelope that exists for some
distance downstream of the point of injection of oxygen into the
hydrocarbon-rich stream prior to complete mixing of the
oxygen-hydrocarbon stream. The invention accomplishes this by
mixing the gases in the presence of a fine water mist, and most
preferably in the presence of a droplet size of 1-15 micron SMD,
which behaves as a dense gas, to provide a heat sink to dissipate
the impact energy of entrained particles in either the hydrocarbon
or oxygen gas streams or to quench an ignition should one occur.
The invention is particularly useful for mixing oxygen into the
recycle gas containing ethylene in an ethylene oxide process.
[0022] The methods and gas mixer of this disclosure differs from
prior technology in that it introduces a fine water mist directly
and concurrently into either or both of the oxygen and hydrocarbon
streams. Ideally, the mist is formed from water droplets at or less
than 200 microns in size to wet the surface of any particles
traveling with the gas stream(s) to reduce the energy of impact of
the wet particle on mixing device wall and/or act as an ignition
suppressant. Water injection for the purpose of flame suppression
is commonly employed in a variety of applications like turbine
engines and oil well fires, however, no applications of the type
described have been found that specifically both minimize the
occurrence of ignition sources and suppress the growth of an
incipient flame.
[0023] The features of this disclosure satisfy a long-felt need in
the art in that it allows for the injection of oxygen into a
hydrocarbon-rich gas stream while minimizing the probability of
igniting the mixture. The advantage is particularly significant for
a range of application in which gas mixing occurs at elevated
pressures (e.g. 20 bar), which are commonly found in partial
oxidation processes such as ethylene oxide production.
Example 1
[0024] FIG. 1 is a schematic representation of a gas mixer
featuring a water mist environment where the hydrocarbon-containing
gas and oxygen-containing gases meet. The gas mixer 10 includes a
hydrocarbon gas manifold 12 receiving recycled gas containing
hydrocarbons such as ethylene from a source along an inlet pipe 14.
Although ethylene is the hydrocarbon gas of commercial interest in
Example 1, it is typically controlled to about 20-35% by volume
within a ballast gas such as methane or nitrogen. One or more pipes
16 are connected to the hydrocarbon gas manifold 12. Gas mixing
occurs in the pipes 16. The pipes function as mixing chambers for
the gas mixer 10. Mixed gases are collected in a second manifold
18. The gas mixer 10 features a means for producing a water mist in
the pipes 16. In particular, water supply lines 20 are provided
which supply water to atomizers 22. The atomizers 22 produce a fine
water mist. In one embodiment, the atomizers are designed to
produce water droplets of a size of about 200 microns or less.
Valves 24 are placed downstream of the atomizers 22. Tubes 26 carry
mist produced by the atomizers 22 are mounted in the hydrocarbon
gas manifold 12. Thus, a fine mist or fog is produced in the
hydrocarbon gas manifold 12, droplets being indicated at 28. The
mist created in the manifold 12 is mixed and carried into the pipes
16 and thus is present in the hydrocarbon-containing gas stream in
the pipes 16.
[0025] Oxygen is supplied to the gas mixer via an oxygen gas
manifold 36. Oxygen pipes 38, sometimes referred to in the art as
"fingers", are connected to the manifold 36. The oxygen pipes 38
are located within the hydrocarbon pipes 16. Oxygen flows into the
pipes 38 from the manifold 36 and flows out the distal open end of
the pipes 38.
[0026] The mixer 10 further includes a water manifold 30 connected
to a water source which supplies water to the proximal end of water
mist pipes 32. Each of the hydrocarbon pipes 16 has one or more
oxygen pipes 38 placed within it, and each oxygen pipe has a water
mist pipe 32 coaxially within it, as shown in FIG. 1. A nozzle 34
is placed at the distal end of the pipes 32. The nozzle 34 is
preferably a pig-tail type nozzle which produces a cone of fine
water droplets. Alternatively, the nozzle is a hollow cone pressure
swirl nozzle. The tip of the nozzle 34 is positioned either
adjacent to, or slightly inward from the distal end of the oxygen
pipe 38, as shown in FIG. 1.
[0027] In operation, hydrocarbon-containing gas enters manifold 12
where it is divided into one or more independent pipes 16. An
oxygen-containing stream, preferably pure oxygen, enters manifold
36 where the stream is divided into one or more pipes 38, smaller
than and concentric with pipes 16. Concentric pipes 38 extend some
distance down the outer pipe 16 as determined by engineering
calculations to be optimal for mixing and separation of the mixing
zone where the oxygen-containing gas mixes with the
hydrocarbon-rich gas. In addition, a water stream enters manifold
30. The manifold 30 could be positioned inside the oxygen manifold
36. The manifold 30 is connected to the proximal ends of one or
more water pipes 32. The water pipes 32 are smaller in diameter and
concentrically located within the oxygen pipe 38, which are
concentric in pipes 16. Each oxygen pipe 38 has one water pipe 32
located within it. At the end of pipes 32 are affixed atomizing
nozzles 34 designed for producing a fine water mist having a
droplet size of approximately 200 microns or less. The nozzle 34 at
the end of pipe 32 terminates approximately coincident with the end
of pipe 38 and before the end of pipe 16 so as to cause the
oxygen-containing gas to pass through a fine water mist as it mixes
with the hydrocarbon-rich gas in the pipe 16.
[0028] As noted above, in addition to the water mist injected into
the oxygen stream, water is introduced into the hydrocarbon
manifold 12 through one or more atomizing nozzles 22 such that a
fine water mist mixes with the hydrocarbon stream. Particles
traveling with either gas stream are wetted by the mist, reducing
the impact energy of the particle if it were to strike a surface of
either pipe 16 or pipe 38. The mist also enhances heat transfer
away from the particle and quenches an ignition, if one should
occur. The oxygen/water/hydrocarbon-containing gas mixture is
re-gathered in manifold 18 for transfer to downstream water removal
processing station, prior to entering a reactor located further
downstream.
[0029] FIG. 2 is an end view of the one of the pipes 16 carrying
the hydrocarbon-containing gas shown in FIG. 1 with mist (indicated
by droplets 28A) present in the hydrocarbon-containing gas stream.
The Figure also shows the water pipes 32 coaxially located within
the oxygen pipes 38 and the mist 28B provided by the nozzles 34
located at the end of the water pipes 32. While in FIG. 2 there are
three oxygen pipes per hydrocarbon pipe 16, this may of course
vary, e.g., depending on the size and number of hydrocarbon pipes
16 in the gas mixer.
[0030] The downstream water removal processing station may use a
pressure vessel column to coalesce water out of the mixed gas
stream. For example, this vessel could be an integral part of the
CO.sub.2 removal column, which is nearby in a typical processing
scheme. The recovered water may be filtered to remove particulate
matter and recycled back into the water supplies of FIG. 1.
[0031] The nozzles 34, like the atomizers 22 of FIG. 1, are also
designed to produce a droplet size of approximately 200 microns or
less SMD. In one possible embodiment, the nozzles 34 and/or 22 are
designed to produce water droplets of a size of 1-20 microns SMD,
whereby a micron-sized droplet mist is produced.
[0032] In a variation to the embodiment of FIG. 1, the water pipes
32 are positioned in the pipes 16 but not within the oxygen pipes.
Rather, the water pipes are positioned adjacent to the oxygen pipes
38 such that the nozzles 34 at the end of the water pipes 32 direct
a water mist into the mixing zone where oxygen gas is mixed with
the hydrocarbon-containing gas in the pipes 16.
Example 2
[0033] FIG. 3 is a schematic illustration of a second example of a
gas mixer incorporating the water mist features of this
invention.
[0034] In this embodiment the hydrocarbon-rich gas is supplied from
a manifold to a single vessel or pipe 16 which functions as a
mixing chamber for the gas mixer 10. In this embodiment, the
hydrocarbon-containing gas is not separated into multiple parallel
pipes such as pipes 16 in the previous embodiment, but rather flows
around one or more oxygen-carrying pipes 38 positioned within the
vessel 16. As in Example 1, oxygen-containing gas, preferably high
purity oxygen, enters manifold 36 where the stream of gas is
divided into one or more pipes 38. The oxygen pipes have a distal
open end through which oxygen gas flows out of the oxygen pipes
38.
[0035] The gas mixer 10 features a means for producing a water mist
in the pipe or vessel 16. In particular, water enters manifold 30A
where it is divided into pipes 32A. The pipes 32A have a nozzle 34
at the end thereof for producing a water mist having a droplet size
smaller than about 200 microns SMD. Water also enters a water
manifold 30B where it is divided into multiple water mist pipes
32B, which are smaller than and concentrically located in the
oxygen pipes 38. At the end of pipes 32B are affixed atomizing
nozzles 34 capable of producing a fine water mist having droplet
sizes smaller than about 200 microns. The nozzles 34 at the end of
pipes 32B terminate coincident with the end of pipe 38 so as to
cause the oxygen-containing gas to pass through a fine water mist
as it mixes with the hydrocarbon-rich gas. The water pipes 32A are
closely adjacent and parallel to oxygen pipes 38 and interspersed
between pipes 38 in a pattern such as shown in FIG. 4. One water
mist generating pipe 32A is provided for every three or four oxygen
injection pipes 38.
[0036] Particles traveling with either gas stream are wetted by a
mist, reducing the impact energy of the particle if it were to
strike a surface of either pipe 32, 38 or vessel 16. The
oxygen/water/hydrocarbon-containing gas mixture is transferred to
downstream water removal equipment, prior to entering a reactor
located further downstream. The use of multiple water atomizers in
this embodiment improves operating reliability of the system.
Example 3
[0037] A third embodiment of this invention is shown in FIG. 5. In
this embodiment, oxygen gas is supplied to an oxygen gas manifold
36. Hydrocarbon-containing gas is supplied via an inlet 14 to a
pipe 16 which functions as a mixing chamber in the gas mixer.
[0038] The gas mixer 10 features a means for producing a water mist
in the pipe 16. In this embodiment a fine water mist, preferably
with a droplet size at or below about 200 microns, is generated in
the oxygen manifold 36 by a series of two or more atomizing nozzles
22 connected to a water supply 20. The nozzles 22 are arranged
around the circumference of the manifold 36 and inject a water mist
into the manifold 36. Valves 24 and pipe segments 26 connect the
nozzles 22 to the manifold 36. Oxygen enters the misty environment
of manifold 36 where the wet oxygen-water mist is divided into one
or more parallel oxygen pipes 38.
[0039] Hydrocarbon-rich gas enters the gas mixer 10 from the side
inlet 14 and flows into the vessel 16 in a direction parallel to
pipes 38. Flow straighteners 62 may be provided to provide axial
flow of the hydrocarbon-containing gas. Properly designed, these
serve to equalize the flow distribution of the cycle gas across the
cross-section of the pipe 16. Supports 60 are provided to support
the oxygen pipes 38 and prevent vibration of the pipes 38. The wet
oxygen gas exits the distal open end of pipes 38 and mixes with the
hydrocarbon-rich gas. Particles traveling with either gas stream
are wetted by the mist, reducing the impact energy of the particle
if it were to strike a surface of either the outer containment pipe
16 or oxygen pipes 38. The mist also enhances heat transfer away
from the particle and quenches an ignition, if one should occur.
The length of pipes 38 is determined to minimize residence time and
reduce flow eddies. The distal end 64 of one of the oxygen pipes 38
is shown isolated and in cross-section in FIG. 6. The pipe 38
ejects an oxygen/water mist in a jet mixing zone 66 where the
oxygen gas is mixed with hydrocarbon-containing gas flowing over
the outer peripheral surface of the pipe 38.
[0040] Nozzles 22 are preferably designed to produce droplets
having a size at or below approximately 200 microns SMD.
[0041] Suitable nozzles for the design of Examples 1-3 are pig-tail
type nozzles, commercially available from BETE Fog Nozzle, Inc.,
Greenfield, Mass., or Spraying Systems Co., Wheaton Ill. Other
nozzles may be used, including spiral pintle, hollow cone pressure
swirl, and ultrasonic atomizing nozzles.
[0042] In one embodiment, the temperature of the water used to
produce the water mist is at ambient temperature. In an alternative
embodiment, the water is heated above ambient. For example, the
water is heated to the temperature of the hydrocarbon-containing
gas stream. In an EO production scenario, the temperature of the
hydrocarbon recycle gas stream is typically between about 35-40
degrees C. and 65-70 degrees C. The water that is supplied to the
spray nozzles can be either at ambient temperature, or water which
has been heated to a temperature of between 35 and 70 degrees
C.
[0043] While presently preferred embodiments have been described
with particularity, variation from the specifics of the disclosed
embodiments may be made without departure from the scope of the
invention. All questions concerning scope of the invention are to
be determined by reference to the appended claims.
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