U.S. patent application number 12/866393 was filed with the patent office on 2011-03-17 for low-nox gas injector.
This patent application is currently assigned to SAINT-GOBAIN GLASS FRANCE. Invention is credited to Laurent Garnier, Carlos Mazzotti De Oliveira, Patrice Rouchy, Joseph Vernaz.
Application Number | 20110061642 12/866393 |
Document ID | / |
Family ID | 40001385 |
Filed Date | 2011-03-17 |
United States Patent
Application |
20110061642 |
Kind Code |
A1 |
Rouchy; Patrice ; et
al. |
March 17, 2011 |
LOW-NOX GAS INJECTOR
Abstract
The invention relates to: a combustion process, especially for
melting glass, in which a flame is created by gaseous fuel,
characterized in that several regularly spaced peripheral
low-pressure gas jets converge on a central high-pressure gas jet;
an injector for implementing this process; a burner comprising one
or more such injectors; and a furnace comprising at least one such
burner.
Inventors: |
Rouchy; Patrice;
(Vaucresson, FR) ; Garnier; Laurent; (Saint Martin
En Bresse, FR) ; Mazzotti De Oliveira; Carlos;
(Jundiai - Sao Paulo, BR) ; Vernaz; Joseph; (Vaux
En Bugey, FR) |
Assignee: |
SAINT-GOBAIN GLASS FRANCE
COURBEVOIE
FR
SAINT-GOBAIN EMBALLAGE
Courbevoie
FR
|
Family ID: |
40001385 |
Appl. No.: |
12/866393 |
Filed: |
February 4, 2009 |
PCT Filed: |
February 4, 2009 |
PCT NO: |
PCT/FR2009/050169 |
371 Date: |
November 19, 2010 |
Current U.S.
Class: |
126/39E ;
239/589; 431/2; 431/354 |
Current CPC
Class: |
F23D 14/84 20130101;
C03B 5/235 20130101; F23D 14/22 20130101 |
Class at
Publication: |
126/39.E ; 431/2;
239/589; 431/354 |
International
Class: |
F24C 3/12 20060101
F24C003/12; F23D 14/64 20060101 F23D014/64 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 5, 2008 |
FR |
0850701 |
Claims
1. A combustion process comprising creating a flame with gaseous
fuel, wherein at least two regularly spaced peripheral low-pressure
gas jets converge on a central high-pressure gas jet.
2. The process as claimed in claim 1, wherein 70 to 90%, of the
calorific power stems from the low-pressure gas.
3. The process as claimed in claim 1, wherein the angle of
convergence of the peripheral low-pressure gas jets toward the
central high-pressure gas jet is between 4.degree. and
10.degree..
4. The process as claimed in claim 1, wherein the number of
peripheral low-pressure gas jets is between 4 and 16.
5. The process as claimed in claim 1, wherein all peripheral
low-pressure gas jets present have the same cross section, flow
route and angle of convergence toward the axis of the central
high-pressure gas jet.
6. An injector for implementing the process as claimed in claim 1,
comprising a high-pressure gas feed duct circumscribed in a coaxial
low-pressure gas feed duct, the outlet of which is completely
obstructed by a flat ring provided with holes of identical cross
section, these being regularly spaced around the axis of said feed
ducts and all converging at the same angle on said axis.
7. The injector as claimed in claim 6, wherein the cross sections
of the holes have circular perimeters.
8. A burner comprising one or more injectors as claimed in claim
6.
9. A furnace comprising at least one burner as claimed in claim
8.
10. (canceled)
11. A method of reducing the amount of NO.sub.x emitted during
combustion of fuel, comprising: generating a flame by combusting
fuel; and converging the flow of fuel from at least two
low-pressure gas jets onto the flow of fuel from a central
high-pressure gas jet.
12. The process as claimed in claim 1, wherein 75 to 85% of the
calorific power stems from the low-pressure gas.
13. The process as claimed in claim 1, wherein the angle of
convergence of the peripheral low-pressure gas jets toward the
central high-pressure gas jet is between 5.degree. and 8.
14. The process as claimed in claim 1, wherein the number of
peripheral low-pressure gas jets is between 8 and 12.
Description
[0001] The invention relates to a combustion process and a
combustion device in which fuel is fed by at least one
injector.
[0002] The invention will be more particularly described for a use
in melting glass in glass furnaces, especially furnaces for
manufacturing flat glass of the float type or furnaces for the
manufacture of hollow packaging glass, for example furnaces
operating in inversion mode, of the type using regenerators,
although it is not in any way limited to such applications.
[0003] Most combustion processes of the aforementioned type,
especially those used in glass furnaces, are faced with problems of
undesirable NO.sub.x emission in the combustion flue gas.
[0004] NO.sub.x has a deleterious effect both on human beings and
on the environment. Firstly, NO.sub.2 is an irritant gas causing
respiratory disorders. Secondly, in contact with the atmosphere,
NO.sub.x can progressively form acid rain. Finally, it causes
photochemical pollution since, in combination with volatile organic
compounds and solar radiation, NO.sub.x causes the formation of
what is called tropospheric ozone, the increase in concentration of
which at low altitude becomes harmful to human beings, especially
during hot periods.
[0005] This is why NO.sub.x emissions standards in force are
becoming increasingly stringent. Because of the very existence of
these standards, manufacturers and operators of furnaces, such as
glass furnaces, are constantly preoccupied with minimizing NO.sub.x
emissions, preferably down to a level of 800 mg per Nm.sup.3 of
flue gas for a side-fired furnace or 600 mg per Nm.sup.3 of flue
gas for an end-fired or horseshoe-flame furnace.
[0006] The parameters that influence NO.sub.x formation have
already been analyzed. These are essentially temperature, since
above 1300.degree. C. NO.sub.x emission increases exponentially,
and excess air, since the NO.sub.x concentration depends on the
square root of the oxygen concentration or the N.sub.2
concentration.
[0007] Many techniques have already been proposed to reduce
NO.sub.x emission.
[0008] A first technique consists in making a reducing agent act on
the emitted gas so that the NO.sub.x is converted to nitrogen. This
reducing agent may be ammonia, but this results in drawbacks such
as the difficulty of storing and handling such a product. It is
also possible to use a natural gas as reducing agent, but this is
to the detriment of the consumption by the furnace and it increases
CO.sub.2 emissions. The presence of reducing gases, such as carbon
monoxide, in certain parts of the furnace, such as regenerators,
may also cause accelerated corrosion of the refractories in these
zones.
[0009] It is therefore preferable, without this being obligatory,
to dispense with this technique, by adopting what are called
primary measures. These measures are so called as the aim is not to
destroy NO.sub.x already formed, as in the technique described
above, but rather to prevent its formation, for example in the
flame. These measures are furthermore simpler to implement and, as
a consequence, more economic. However, they cannot completely
substitute for the aforementioned technique, rather they
advantageously supplement it. In any case, these primary measures
constitute an indispensable prerequisite for reducing the
consumption of reactants for the secondary measures.
[0010] Without being limited thereto, it is possible to classify
the existing measures in several categories: [0011] a first
category consists in reducing NO.sub.x formation using what is
called the "reburning" technique, whereby a zone that is short of
air is created in the combustion chamber of a furnace. This
technique has the drawback of increasing the temperature in the
regenerator stacks and, as the case may be, of requiring a specific
design of the regenerators and their stacks, most particularly in
terms of sealing and corrosion resistance; [0012] a second category
consists in acting on the flame by reducing, or even preventing,
NO.sub.x formation therein. To do this, the aim may for example be
to reduce the excess combustion air. It is also possible to seek to
limit temperature peaks while maintaining flame length and to
increase the volume of the flame front in order to reduce the
average temperature within the flame. Such a solution is for
example described in U.S. Pat. No. 6,047,565 and WO 98/02386. It
consists of a combustion process for melting glass, in which the
fuel feed and the oxidizer feed both take place so as to spread the
fuel/oxidizer contact over time and/or to increase the volume of
this contact for the purpose of reducing NO.sub.x emission.
[0013] It will be recalled that an injector is dedicated to
propelling fuel, which is to be burnt with an oxidizer. Thus, the
injector may form part of a burner, the term "burner" generally
denoting the device comprising both the fuel supply and the
oxidizer supply.
[0014] The fuel is a liquid of the fuel oil type or is a gaseous
fuel, such as natural gas. Certain injectors, as described in FR 2
834 774 for example, combine at least one liquid fuel supply with a
gaseous fuel supply.
[0015] Moreover, it is known that gaseous fuels produce more
NO.sub.x than fuel oil.
[0016] The object of the invention is to devise a combustion
process employing only gaseous fuel but producing only relatively
small amounts of NO.sub.x.
[0017] This objective is achieved by the invention, one subject of
which is a combustion process, especially for melting glass, in
which a flame is created by gaseous fuel, characterized in that
several regularly spaced peripheral low-pressure gas jets converge
on a central high-pressure gas jet.
[0018] The central high-pressure gas jet determines the flame
length, whereas the overall (low-pressure and high-pressure) gas
flow rate determines the power of the flame. The process of the
invention makes it possible to maintain a constant flame length,
while modifying the power, and vice versa.
[0019] The peripheral converging low-pressure gas jets delay flame
spread.
[0020] Therefore, the number of adjustment options is increased,
especially with shortening of the flame and reduction in NO.sub.x
emission.
[0021] According to preferred features of the process of the
invention: [0022] 70 to 90%, preferably 75 to 85%, of the calorific
power stems from the low-pressure gas; [0023] the angle of
convergence of the peripheral low-pressure gas jets toward the
central high-pressure gas jet is between 4.degree. and 10.degree.,
preferably between 5.degree. and 8.degree.; [0024] the number of
peripheral low-pressure gas jets is between 4 and 16, preferably
between 8 and 12; [0025] all the peripheral low-pressure gas jets
have the same characteristics: cross section, flow rate and angle
of convergence toward the axis of the central high-pressure gas
jet.
[0026] Another subject of the invention is an injector for
implementing a process according to the invention, characterized in
that it comprises a high-pressure gas feed duct circumscribed in a
coaxial low-pressure gas feed duct, the outlet of which is
completely obstructed by a flat ring provided with holes of
identical cross section, these being regularly spaced around the
axis of said feed ducts and all converging at the same angle on
said axis.
[0027] Preferably, the cross sections of the holes--i.e. in planes
perpendicular to the axis of the holes--have circular
perimeters.
[0028] Other subjects of the invention are: [0029] a burner
comprising one or more injectors as described above; [0030] a
furnace, especially an end-fired furnace or a side-fired furnace,
comprising at least one such burner; and [0031] the application of
the process, the injector, the burner or the furnace of the
invention for limiting NO.sub.x emissions.
[0032] The invention will now be illustrated by the following
example, with reference to the appended drawings in which:
[0033] FIG. 1 is a front view of a flat ring forming part of an
injector of the invention; and
[0034] FIG. 2 is a sectional view of this flat ring.
[0035] The flat ring 1 has ten holes 2 regularly spaced around the
axis 3.
[0036] The circular holes 2 converge at an angle of 6.degree.
toward the axis 3.
[0037] Moreover, the flat ring 1 has a central hole intended to
receive the central high-pressure gas jet, whereas the peripheral
low-pressure gas jets pass through the converging holes 2.
[0038] Trials were carried out in a 44 m.sup.2 end-fired
furnace.
[0039] The furnace was worked in a first phase with an injector
alternately in the right part and left part of the furnace.
[0040] This was a dual gas momentum injector differing from that of
the invention only by the absence of individual converging
low-pressure jets.
[0041] In this example, the injector was in a central position
beneath a stream of air and directed upwardly at an angle of
5.degree., the stream of air being directed downwardly at an angle
of 22.degree.. The injector was inclined at 3.degree. of azimuth
toward the internal central axis of the furnace.
[0042] The values are given at 8% O.sub.2 and 5000 ppm CO.
[0043] The power of the injector was kept constant at 8000 kW.
[0044] The NO.sub.x emission was 687 mg/Nm.sup.3 for a specific
momentum I.sub.sp (defined as the ratio of the total momentum of
the fuel jet to the calorific power) of 4 N/MW.
[0045] The injector was then modified in accordance with the
invention, by the use of the flat ring of FIGS. 1 and 2.
[0046] With a specific momentum of 4 N/MW, the NO.sub.x emission
dropped to 587 mg/Nm.sup.3.
* * * * *