Fuel injection burner

Details Fuel injection burner Fuel injection burner

1998-12-07

2001-06-12

Vincent, Sean E (Department: 1731)

Fluid sprinkling, spraying, and diffusing

Combining of separately supplied fluids

Including whirler device to induce fluid rotation

C239S416400, C239S416500, C239S421000, C239S423000, C239S424000, C239S424500, C239S468000, C239S482000, C239S488000, C239S494000, C239S497000

Reexamination Certificate

active

06244524

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention pertains to a combustion process and a device in which the fuel supply is provided by at least one burner equipped with at least one injector.
The invention will be described specifically for use in melting glass in glass-making ovens, particularly ovens used for making float-type flat glass or ovens used to make hollow glass containers, for example, ovens that operate opposite to the type of ovens that use regenerators (energy recovery devices). However, the invention is not necessarily limited to such applications.
2. Description of the Related Art
The majority of combustion processes of the aforementioned type, particularly those used in glass-making ovens, are confronted with problems of undesirable NO
x
emissions. No
x
emissions are harmful to humans and to the environment. Indeed, NO
2
is an irritating gas that causes respiratory ailments. Additionally, in contact with the atmosphere, these gases can gradually form acid rain. Finally, they cause photochemical pollution since in combination with volatile organic compounds and solar radiation, the NO
x
gases are the basis for the formation of so-called tropospheric ozone which, in increased concentration at low altitude, becomes harmful for human beings, especially when it is very hot.
All these factors mean that the standards with respect to NO
x
emissions are becoming increasingly restrictive. Currently, because of said standards, oven manufacturers such as those that manufacture glass-making ovens are constantly concerned with limiting the maximum level of NO
x
emissions, preferably at a rate less than 500 mg/m
3
.
The parameters that influence the production of NO
x
gases are known. One such parameter is temperature; beyond 1300° C., the emission of NO
x
gases increases exponentially with excess air, since the concentration of NO
x
gases depends on the square root of that of oxygen or even the concentration of N
2
.
Many techniques have been proposed to reduce NO
x
emissions. One involves causing a reducing agent to convert the NO
x
gases to nitrogen. This reducing agent can be ammonia, but this has disadvantages including difficulties with storage and handling of such a product. It is also possible to use a natural gas as a reducing agent, but this has detrimental effects on the fuel consumption rate of the oven and increases the CO
2
emissions.
Therefore it is preferable, although not mandatory, to avoid this technique by adopting the so-called primary measures. These measures are called “primary” because one does not attempt to destroy the NO
x
gases that are already formed, as in the previously described technique. Rather, one tries to prevent their formation, for example at the flame level. Additionally, these measures are simpler to implement and, consequently, more economical. They do not have to completely substitute for the aforementioned technique but can advantageously complement it. These primary measurements in general amount to an indispensable precondition for reducing the consumption of reagents of the secondary measures.
One can categorize, in a non-limiting way, the existing measures in several categories:
A primary category consists of reducing the production of NO
x
gases via the so-called “reburning” technique by which one creates an air-deficient zone at the oven combustion chamber level. This technique has the disadvantages of increasing the temperature at the regenerator stack and of requiring a specific design of the regenerators and their stacks, especially in terms of airtightness and resistance to corrosion.
A second category consists of affecting the flame by reducing or preventing the formation of NO
x
gases at that level. To do this one can, for example, attempt to reduce the amount of excess combustion air. It is also possible to attempt to limit the temperature peaks by maintaining the 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 French patent application FR 96/08663 and international application PCT/FR/97 01244, which were filed on Jul. 11, 1996 and Jul. 9, 1997, respectively. The solution consists of a combustion process for melting glass in which the liquid fuel supply and the supply of the gas and air mixture are both brought about in such a way as to spread out periodically the liquid fuel/gas-air mixture contact and/or to increase the volume of this contact in order to reduce NO
x
emissions.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a new combustion process and device in which the fuel used is liquid, allowing one to make the flame longer and/or to reduce the temperature peaks inside the flame in order to reduce the formation of NO
x
gases.
Another object of the invention is to propose a combustion process and that are adjusted to all of the existing glass-making oven configurations. This will allow one to obtain an optimal thermal transfer, particularly by providing a flame of adequate length and of sufficiently great volume in order to enhance maximum coverage of the bath of substances which can be vitrified when melted.
In order to accomplish these and other objects, the invention provides a combustion process, particularly one used for melting glass, in which the fuel supply is provided by at least one burner equipped with at least one injector that includes a liquid fuel delivery tube which has at least one internal wall and one injection fluid delivery tube arranged concentrically with respect to the liquid fuel delivery tube. Immediately before ejecting the liquid fuel is ejected from its delivery tube, it is formed into a hollow jet that substantially takes on the shape of said internal wall. This perfectly resolves the problem presented. By creating a very specific flow of liquid fuel immediately before it goes out of its delivery tube, there results an increased amount of mechanical injection of the liquid fuel by the injection fluid at its outlet from this tube, resulting in heterogeneity of the drops of the fuel, and thereby avoiding burning occurring at too high a speed, which is a source of the formation of NO
x
gases. Consequently, for a desired flame temperature one can allow less fuel to be delivered to the intake and therefore to the flame base, which will also reduce the risk of the formation of NO
x
gases.
The method according to the invention does not necessarily substitute for the existing techniques but can, if necessary, complement them quite advantageously.
According to an advantageous characteristic of the invention, the liquid fuel is ejected at a delivery driving pressure of at least 1.2 MPa.
Whatever the particular configuration of the oven in which the process of the invention is implemented, one should ensure atomization of the liquid fuel necessary to avoid too rapid a burning rate.
In a preferred manner, the liquid fuel should be ejected at a temperature between 100 and 150° C., preferably between 120 and 135° C. Such a temperature range allows one to introduce any kind of liquid fuel that is used in traditional units, particularly in glass-making ovens, at the required viscosity immediately before it is injected from its delivery tube. This viscosity can advantageously be at least equal to 5·10
−6
m
2
/s, especially between
10
−5
and 2·10
−5 m
2
/s.
According to another characteristic of the invention, the liquid fuel is ejected at an opening angle cone of at least 10°, especially between 10° and 20°. Such values allow, independent of the geometry of the liquid fuel delivery tube and its dimensions, both the necessary systematic interference between the jet of injection fluid and the liquid fuel drops, and a dispersion of the size of these drops which is optimal, so that the resulting flame will be homogeneous in temperature over its entire length.
As for the injection fluid, one can eject it in a very advantageous manner at a flow rate of more than 40 Nm
3
/h. Obviously, the value of the injec

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