U.S. patent application number 10/585008 was filed with the patent office on 2007-07-05 for system and method using cool hydrogen flame for destruction of vocs and odorous compounds.
Invention is credited to Dong Fei Li, Tee David Liang, Tuti Mariana Lim, Joo Hwa Tay.
Application Number | 20070154854 10/585008 |
Document ID | / |
Family ID | 34738128 |
Filed Date | 2007-07-05 |
United States Patent
Application |
20070154854 |
Kind Code |
A1 |
Liang; Tee David ; et
al. |
July 5, 2007 |
System and method using cool hydrogen flame for destruction of vocs
and odorous compounds
Abstract
A system for using cool hydrogen flame for destruction of VOCs
and odorous compounds comprises an existing exhaust system for an
industrial process or a factory. The existing exhaust system
comprises at least an exhaust duct or a chimney for exhaust gases.
The exhaust gases may comprise of odorous compounds such as DMS,
MDSO and other VOCs. The system further comprises at least one
burner nozzle for generating a configurable hydrogen surface-mixed
diffusion flame. The main by-product from this hydrogen flame is
water and free radicals. These free radicals produced during
hydrogen combustion are extremely reactive and highly oxidative in
nature especially hydroxyl radicals. As such, odorous compounds
such as VOCs, DMS and DMSO would easily be destroyed by these free
radicals produced during hydrogen combustion.
Inventors: |
Liang; Tee David;
(Singapore, SG) ; Lim; Tuti Mariana; (Singapore,
SG) ; Tay; Joo Hwa; (Singapore, SG) ; Li; Dong
Fei; (Singapore, SG) |
Correspondence
Address: |
Blakely Sokoloff Taylor & Zafman
12400 Wilshire Boulevard
7th Floor
Los Angeles
CA
90025
US
|
Family ID: |
34738128 |
Appl. No.: |
10/585008 |
Filed: |
December 13, 2004 |
PCT Filed: |
December 13, 2004 |
PCT NO: |
PCT/SG04/00408 |
371 Date: |
June 27, 2006 |
Current U.S.
Class: |
431/5 |
Current CPC
Class: |
F23L 2900/07004
20130101; F23G 7/065 20130101; F23L 2900/07005 20130101; Y02E 20/34
20130101; F23C 2900/99001 20130101; F23L 7/00 20130101; Y02E 20/342
20130101; F23D 2900/21003 20130101; Y02E 20/344 20130101; F23C
13/00 20130101; F23L 2900/07009 20130101; F23C 2900/9901
20130101 |
Class at
Publication: |
431/005 |
International
Class: |
F23G 7/08 20060101
F23G007/08 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 29, 2003 |
SG |
200307735-1 |
Claims
1. A method for using cool hydrogen flame for destruction of VOCs
and odorous compounds in an exhaust stream, comprising the steps:
a. producing a hydrogen surface-mixed diffusion flame; and b.
exposing said hydrogen surface-mixed diffusion flame to said
exhaust stream; wherein said hydrogen surface mixed diffusion flame
further produces free radicals for destroying said VOCs and odorous
compounds.
2. The method according to claim 1, wherein said hydrogen
surface-mixed diffusion flame is configurable.
3. The method according to claim 1, wherein said hydrogen
surface-mixed diffusion flame is produced by burning pure hydrogen
in pure oxygen without pre-mixing.
4. The method according to claim 3, wherein said pure oxygen is in
excess of said pure hydrogen.
5. The method according to claim 1, further comprising the step: c.
spraying a fine mist of hydrogen peroxide towards said hydrogen
surface-mixed diffusion flame and said exhaust stream.
6. The method according to claim 1, further comprising the step: d.
introducing steam into said exhaust stream.
7. The method according to claim 1, further comprising the step: e.
introducing ozone gas into said exhaust stream.
8. The method according to claim 1, further comprising the step: f.
utilizing a flame spreader for diffusing and spreading said
hydrogen surface-mixed diffusion flame.
9. The method according to claim 8, wherein said flame spreader is
made of a catalytic metal for enhancing free radical production
during hydrogen combustion.
10. A system for destruction of VOCs and odorous compounds in
exhaust gases of an exhaust system, said system comprising: at
least one burner nozzle for producing a configurable hydrogen
surface mixed diffusion flame; wherein said at least one burner
nozzle is disposed within an exhaust duct of said exhaust
system.
11. The system according to claim 10, wherein said at least one
burner nozzle is substantially in the path of the exhaust
gases.
12. The system according to claim 10, wherein the exhaust duct
comprises a chimney.
13. The system according to claim 10, wherein said system further
comprises a venturi for limiting throat of said exhaust duct.
14. The system according to claim 13, wherein said at least one
burner nozzle is substantially in a constriction of said
venturi.
15. The system according to claim 10, wherein said system further
comprises at least one spray nozzle for introducing one or a
combination of chemical agents.
16. The system according to claim 15, wherein said chemical agents
comprises hydrogen peroxide, ozone gas and steam.
17. The system according to claim 10, further comprising a flame
spreader for diffusing and spreading said configurable hydrogen
surface-mixed diffusion flame.
18. The system according to claim 17, wherein said flame spreader
is made of a catalytic metal for enhancing free radical production
during hydrogen combustion.
Description
FIELD OF THE INVENTION
[0001] The present invention relates in general to the destruction
of odorous compounds from industrial exhausts. More particularly,
the invention relates to a system and method for using cool
hydrogen flame for destruction of odorous compounds.
BACKGROUND OF THE INVENTION
[0002] Factories and industrial processes produce a variety of
exhaust gases which need to be treated before being released into
the atmosphere. Regulations and protocols require that these
exhaust gases undergo pretreatment to remove or reduce toxic
compounds present. Furthermore, with heightened awareness of
environmental conservation, releases of chemicals like the
"greenhouse gases" have also begun to be regulated.
[0003] Some compounds in certain exhaust streams contain Volatile
Organic Compounds (VOCs) and also other odorous compounds which are
often a nuisance in the work environment as well as ambient air
even at low concentrations. Such odorous compounds are often sulfur
and nitrogen containing and some examples of which are dimethyl
sulfide (DMS) and dimethyl sulfoxide (DMSO). DMS and DMSO are used
as organic solvents in the semi-conductor industry. Unfortunately,
they are difficult to treat with conventional methods, which can
also be costly.
[0004] One of the present methods used to contain and control DMS
and DMSO is by activated carbon adsorption which is also costly and
is merely transferring the pollutant from the gaseous phase into
solid form.
[0005] Other conventional methods may be simply to incinerate these
offending compounds. This conventional treatment system requires
additional space for installation of new equipment coupled to
existing exhaust systems. The costs for such additional equipment
may be quite high. Furthermore, extensive modifications to the
existing exhaust systems are usually required for such treatment to
be integrated properly.
[0006] There is thus at present a lack of and a need for a system
and method for treatment or destruction of odorous compounds with
minimal cost, use of space, and modifications to the existing
exhaust system.
SUMMARY OF THE INVENTION
[0007] The present invention seeks to provide a system and method
for using cool hydrogen flame for destruction of VOCs and odorous
compounds.
[0008] Accordingly, in one aspect, the present invention provides,
a method for using cool hydrogen flame for destruction of VOCs and
odorous compounds in an exhaust stream, comprising the steps:
producing a hydrogen surface-mixed diffusion flame; and exposing
the hydrogen surface-mixed diffusion flame to the exhaust stream;
wherein the hydrogen surface mixed diffusion flame further produces
free radicals for destroying the VOCs and odorous compounds.
[0009] In another aspect, the present invention provides, a system
for destruction of VOCs and odorous compounds in exhaust gases of
an exhaust system, the system comprising: at least one burner
nozzle for producing a configurable hydrogen surface mixed
diffusion flame; wherein the at least one burner nozzle is disposed
within an exhaust duct of the exhaust system.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] A preferred embodiment of the present invention will now be
more fully described, with reference to the drawings of which:
[0011] FIG. 1 illustrates a system in accordance with the present
invention;
[0012] FIG. 2A illustrates an alternative arrangement of FIG.1;
[0013] FIG. 2B illustrates another alternative arrangement of FIG.
1;
[0014] FIG. 3 illustrates a further alternative arrangement of FIG.
1;
[0015] FIG. 4 illustrates another implementation using a flame
spreader of FIG. 1; and
[0016] FIG. 5 illustrates a flowchart of a method in accordance
with the present invention.
DETAILED DESCRIPTION OF THE DRAWINGS
[0017] In this description, a system and method for using cool
hydrogen flame for destruction of VOCs and odorous compounds is
disclosed. In the following description, details are provided to
describe the preferred embodiment. It shall be apparent to one
skilled in the art, however that the invention may be practiced
without such details. Some of the details may not be described at
length so as not to obscure the invention.
[0018] Referring to FIG.1, a system 10 for using cool hydrogen
flame for destruction of VOCs and odorous compounds comprises an
existing exhaust system 6 for an industrial process or a factory 5.
The existing exhaust system 6 comprises at least an exhaust duct or
a chimney 8 for exhaust gases 12. The exhaust gases 12 may comprise
of odorous compounds such as DMS, DMSO and other VOCs. The system
10 further comprises at least one burner nozzle 20 for generating a
configurable hydrogen surface-mixed diffusion flame (CHSMDFs)
22.
[0019] The at least one burner nozzle 20 is situated inside the
exhaust duct or chimney 8 of the existing exhaust system 6. The
burner nozzle 20 is also situated such that the burner nozzle 20 is
substantially in the path of the exhaust gases 12.
[0020] The flame from the burner nozzle 20 can be described to be
gentle,"cool" and clean burning. The CHSMDF 22 is produced by
burning pure hydrogen in either pure oxygen or purified air with or
without oxygen enrichment. However, the hydrogen and oxygen are not
pre-mixed before being ignited. Instead, the burner nozzle 20 may
be of a tube in orifice design. That is to say, a main nozzle
ejecting oxygen gas, and a central nozzle positioned inside the
main nozzle ejecting hydrogen gas.
[0021] When the burner nozzle 20 is in operation, hydrogen gas is
being ejected with an envelope of oxygen gas surrounding it. When
this hydrogen gas is ignited, it burns only at the envelope of the
hydrogen gas and oxygen gas interface. This produces a flame
referred to as a configurable surface-mixed diffusion flame
(CHSMDF) 22. It can be described as a "cool" burning flame as its
temperature is much lower than conventional pre-mixed flames. The
burner nozzle 20 may not necessarily be limited to the tube in
orifice design and may also be a slot type burner nozzle. To ensure
complete combustion of the hydrogen gas, an excess of oxygen is
ejected from the burner nozzle 20.
[0022] The flame length and flame front of the CHSMDF 22 may be
configurable by adjusting the pressure and rate of flow of the
hydrogen and oxygen gases.
[0023] Using fire and thermal oxidation for the destruction of
odorous compounds and VOCs in exhaust streams is by no means new.
However, conventional flames using hydrocarbon and sulfur rich
fuels would produce soot and other contaminants that would also
further contaminate the exhaust gas. Furthermore, the high
temperatures produced by conventional flames may require additional
cooling systems to be installed to prevent overheating of the
existing exhaust system and the exhaust gases.
[0024] The hydrogen surface mixed diffusion flame is advantageously
"cool" enough not to require additional cooling systems and will
not substantially raise the temperature of the exhaust gases.
Experiments and tests have shown that the temperature of the
exhaust gases after exposure to the CHSMDF 22 exhibited increases
of less than 150.degree. C. The absence of soot during combustion
also significantly reduces radiative heat release by hydrogen
flames further making it a "cool" flame. The main by-product from
this hydrogen flame is water and free radicals.
[0025] These free radicals produced during hydrogen combustion,
especially the hydroxyl radicals are extremely reactive and highly
oxidative in nature and are thus extremely effective in the
oxidation of organic compounds. As such, odorous compounds such as
VOCs, DMS and DMSO would easily be destroyed by these free radicals
produced during hydrogen combustion.
[0026] Referring to FIG. 2A, an alternative arrangement to that of
FIG. 1 is shown. Instead of a single burner nozzle 20, there may be
a plurality of burner nozzles 20 producing a plurality of CHSMDF
22.
[0027] Referring to FIG. 2B, an alternative arrangement is shown
whereby the throat of the chimney 8 is substantially reduced by the
introduction of a venturi 40 into the throat of the chimney 8. This
reduces the area of the throat of the chimney 8 such that a CHSMDF
22 with a relatively small flame front is still able to produce
enough radicals to destroy the odorous compounds in the exhaust
gases 12. There may be a change in pressure due to the reduction in
area caused by the venturi 40, but may be negligible depending on
the flow of the exhaust gases 12.
[0028] Referring to FIG.3, yet another alternative arrangement is
shown, where a reaction chamber 45 may be installed in line with
the ducts or pipes leading into the chimney 8. The reaction chamber
45 comprises a chamber 42 for housing a plurality of burner nozzles
20. The plurality of burner nozzles 20 are arranged such that the
plurality of CHSMDF 22 produced is in the path of the exhaust gases
12 as they pass through the ducts.
[0029] The arrangements of the burner nozzles 20 disclosed are for
create more CHSMDF 22 or for attempting to expose more of the
CHSMDF 22 to the exhaust gases 12. The arrangements also serve to
create more free radicals for the destruction of the odorous
compounds. Referring to FIG. 4, another implementation is shown
using a flame spreader 50 to spread the CHSMDF 22 for maximum
exposure across the throat of the chimney 8. The flame spreader 50
is essentially a wire mesh for diffusing and spreading the CHSMDF
22 from the burner nozzle 20. In addition, the flame spreader may
be made from a metal that exhibits catalytic properties that
enhance the production of free radicals during the combustion of
hydrogen. Some non-limiting examples of these metals are manganese
and palladium. Flames may also be shaped by various burner/nozzle
designs such as the use of a swirl burner, or other aerodynamic
enhancements.
[0030] Referring to FIG. 5, the method 500 in accordance with the
present invention starts with the step of producing 510 a
configurable hydrogen surface mixed diffusion flame 22. Next, the
step of exposing 515 said configurable hydrogen surface mixed
diffusion flame 22 to the exhaust stream which may comprise of
odorous compounds. The free radicals produced by the CHSMDF 22 will
then destroy these odorous compounds.
[0031] The production of free radicals by hydrogen combustion which
is important to the present invention can further be enhanced by
addition of certain predetermined chemical agents or modifiers.
Examples of such chemical agents are ozone gas and hydrogen
peroxide. The apparatus 10 of the present invention can further
comprise a plurality of gas nozzles and a plurality of spray
nozzles for the introduction of ozone gas or hydrogen peroxide into
the chimney 8 to enhance the production of free radicals. The
method 500 can also further comprise additional steps of
introducing or spraying ozone gas or hydrogen peroxide into the
chimney 8.
[0032] Hydrogen peroxide may be introduced into the exhaust duct or
chimney 8 in the form of fine mists by at least one spray nozzle.
The spray nozzle is preferably located near the burner nozzles 20.
The spray nozzles could also be arranged such that the spray
nozzles are co-axial to the burner nozzles 20. The fine mist of
hydrogen peroxide directed into the exhaust duct or chimney 8
results in more free radicals being formed as the hydrogen peroxide
dissociates due to the heat generated by the CHSMDF 22. Any water
formed as a result of the dissociation of the hydrogen peroxide is
converted into steam by the CHSMDF 22 and exits the exhaust duct or
chimney together with the exhaust gases 12. Correspondingly, the
method 500 in accordance with the present invention further
comprises an additional step of spraying a fine mist of hydrogen
peroxide into the exhaust duct or chimney. This spraying of fine
mist of hydrogen peroxide occurs simultaneously with the providing
of the CHSMDF 22.
[0033] The introduction of steam into the chimney 8 may also
further assist in the destruction of the odorous compounds. Steam
may also be introduced into the chimney 8 by way of the spray
nozzle, but may be situated away from the burner nozzles 20.
[0034] Furthermore, the use of the flame spreader 50 having
catalytic properties will also aid in the enhanced production of
free radicals and enhance the effectiveness of the method 500.
[0035] It will be appreciated that various modifications and
improvements can be made by a person skilled in the art without
departing from the scope of the present invention.
* * * * *