FR2604241A1 - PROCESS FOR PRODUCING AN OXYGEN ENRICHED FLAME - Google Patents

Abstract

THIS PROCESS CONSISTS OF REALIZING, BY MEANS OF A PERFORATED PLATE 12 ARRANGED AT THE LEVEL OF THE FRONT PART OF THE BURNER NOZZLE, A CENTRAL FLOW OF THE GAS FUEL CIRCULATING IN A CENTRAL PASSAGE 48 OF THE PLATE, A MULTIPLICITY OF FLOWS OF AIR ENRICHED WITH OXYGEN SURROUNDING THE MAIN FLOW AND PASSING THROUGH ORIFICES 22 OF THE PLATE WHICH ARE INCLINED RADIALLY BETWEEN APPROXIMATELY 20 AND ABOUT -20 FROM THE LONGITUDINAL AXIS OF THE CENTRAL FLOW OF THE GAS FUEL, TO BE MIXED ALL THE FLOWS AND TO CARRY OUT THE COMBUSTION OF THIS MIXTURE TO OBTAIN A CLEAN FLAME, WITH REDUCED RATES OF HARMFUL SECONDARY COMBUSTION PRODUCTS. APPLICATION IN PARTICULAR TO BURNERS USED IN OVENS.

Description

Process for producing an oxygen enriched flame The present invention

  relates to methods for producing heat and more particularly to improved methods for efficient heating at a reduced cost, by direct combustion of a gaseous fuel using oxygen-enriched air streams. The prior art has made known various types of burners to achieve the most effective heating air to produce a direct heat transfer, as in a furnace, and to achieve the heating of liquids that can be contained in a boiler, in order to obtain an indirect transfer of such heat. Some of such prior art heating mechanisms used stoichiometric mixtures of different fuels, including for example

  gaseous fuels, with ambient air. However, some of these mechanisms

  burners produced flame of excessive temperature and shapes which applied a shock to the generally required refractory block, which was used as a sleeve to contain such a flame.

  to keep it in the form of an entity that can be

  outfit. Usually, an extremely durable material could not be used to form this block, given the high temperatures of such prior art structures receiving a flame. Likewise, some of such prior art burner mechanisms were relatively inefficient for the combustion of the gaseous fuel and produced excessive combustion products, especially NO and NO2.

  (sometimes referred to as NO).

  X Given the disadvantages and the disasters of burners

  In the prior art, it is an object of the present invention to provide

  which do not require the use of a refractory block.

  but instead, who are able to use a metal sleeve

  in order to avoid any contamination of the flame and therefore of the material being heated, and also to resist a rupture due to

a shock applied inadvertently.

  It is another object of the present invention to provide improved processes for obtaining oxygen enrichment levels of at least about 35% to 100%, which levels provide a more efficient flame and significantly lower levels of oxygenation products. combustion. Another object of the present invention is to provide methods

  perfected to obtain an oxygen enrichment of the

  air, and apply a "twist" to the airflow with sufficient velocity, pressure, angle of convergence or divergence, and torsion angle to form a flame for to create a reduced temperature zone inside the block, which in turn effectively reduces the shock applied to the block, while maintaining efficient combustion and substantially reducing

  the formation of combustion products.

  Another object of the present invention is also to provide improved methods for maintaining, within a burner structure, the same isotherms as those which may be present in the

  the use of ambient air, but with a reduction in

  15% of the gaseous fuel while simultaneously maintaining

reduced emissions of NO.

  The improved processes according to the present invention can be specially adapted to facilities used for the production of alumirium, which produce 35% oxygen enriched air as

  secondary product of such aluminum production. The processes

  according to the present invention may also find a particular application in the case where an extremely clean flame is required, such as for example when heating the glass and in

other similar applications.

  These goals as well as other goals of the advanced processes

  forms of the present invention will clearly be apparent, for the specialist

  list of the technique, after reading the description of the modes of

  preferred embodiments of the invention, in particular given modes of implementation.

  as examples, and the accompanying drawings.

  The improved processes according to the present invention, which aim to provide efficient heating at a reduced cost, are obtained by directly burning a fuel, preferably a gas, using oxygen-enriched air. Specifically, a central flow of such a gaseous fuel is produced, which extends along a longitudinal axis and is delivered at a pressure sufficient to direct the gaseous fuel in the longitudinal direction. It is planned a

  multiplicity of air flow enriched in oxygen, preferably in

  stoichiometric unit, and such flows are arranged, in section

  transverse, in a circular network around the flow of

  gaseous. Such gaseous flows are arranged to circulate by forming flows which are inclined radially at an angle of divergence or convergence ranging from +20 to -20 with respect to

  the longitudinal axis of the gaseous fuel flow.

  During the next operating phase of the processes according to the invention,

  In this case, the flows of the gaseous fuel and the oxygen enriched air are mixed. Finally, the mixture is burned to produce a maintainable flame in a flame-protecting block, such flame having a reduced-temperature zone around it, thereby providing combustion. efficient fuel and

  to maintain relatively low levels of combustion products.

  Other features and advantages of the present invention

  will emerge from the description given below with reference to the drawing

  illustrating, for example, an apparatus for carrying out the improved method according to the invention and in which: - Figure 1 is a partial cross sectional view and broken away showing in partial side elevation a burner used for the implementation of the process according to the invention, such a burner comprising a perforated plate whose perforations diverge for example at an angle A with respect to the longitudinal axis of the gas flow,

  a nozzle, a device for protecting the spark produced by a

  positive ignition, a back plate with a sealing gasket

  it separates it from the body of the nozzle, and furthermore a subassembly forming a spark ignition device disposed in the rear part of the body of the nozzle, the whole of the truncated block comprising an assembly held by means forming a frame holding the block and arranged on the front portion of such a nozzle body;

  FIG. 2 is a front view of a preferred embodiment

  a perforated plate as shown in FIG.

  an angle of torsion B given by way of illustration, the plurality of

  fices being distributed radially at a distance from each other in a network around the means for channeling the gaseous fuel, these means being located in a central position, and suitable for realizing

  stoichiometric combustion in ambient air containing 20.8% oxy-

  gene; FIG. 3 is a front view showing another form of

  making a perforated plate suitable for the implementation of cer-

  some other improved methods according to the present invention and showing the inclined and diverging orifices which have a diameter equal to half that of the orifices shown in the embodiment of FIG.

  FIG. 2, and suitable for use with air flows in

  rich in oxygen, containing 22.8% oxygen; and FIG. 4 is a front view of another embodiment of a perforated plate suitable for carrying out other improved methods according to the present invention and having inclined and diverging orifices which have an equal diameter. about a quarter

  the diameter of the orifices of the embodiment of FIG.

  coming for use with oxygen-enriched air flows,

containing about 35% oxygen.

  The improved methods according to the present invention

  identify efficient and cost-effective heating

  the use of direct combustion of fuels including

  in a preferred embodiment, and in an oxygen-enriched air flow, with varying amounts of oxygen such as

  oxygen-enriched air forms airflows containing between

  20.8% oxygen and 35% oxygen, and even

  % oxygen. Specifically, such improved methods

  forms of the invention include the initial operative step of

  a central flow of the gaseous fuel, which has a longitudinal axis

  tudinal and is delivered at a pressure sufficient to direct the gaseous fuel along this longitudinal direction. It is planned a multiplicity

  of oxygen-enriched air flows which, in cross-section, are re-

  away from one another according to a network of preferably

  the flow of gaseous fuel, said oxygen-enriched air flows being radially inclined such that they diverge or converge, at an angle of about +20 to about -20.

  relative to the longitudinal axis of the gaseous fuel flow.

  As a result, the flows of oxygen-enriched air are directed

  in a plurality of paths around the fuel flow.

  zeux which occupies a central position. Such respective flows of fuel and oxygen-enriched air are mixed and burn to provide a sustainable flame having a reduced temperature area surrounding it, thereby effectively burning such gaseous fuel. and to obtain relatively low levels in

  harmful combustion products, including reduced levels of NOx.

  In certain preferred embodiments, the methods

  in accordance with the present invention allow an enrichment in oxy-

  gene up to a content of about 35% oxygen. In other preferred embodiments, pure oxygen may be used, in which case apertures having apertures whose diameter is approximately one fifth of the diameter of the orifices may be used.

  can be used with ambient air.

  Different flow pressures can be used.

  gaseous fuel, these pressures being determinable by those skilled in the art, as taught by the examples given herein, without the need for experimentation

  useless. The same applies to the required pressure of deli-

  air flows that can be used with the fuel flows.

  gaseous, as has been further indicated in the examples of the preferred embodiments and alternative embodiments

of the invention.

  The flow of gaseous fuel may preferably have a generally circular-cross sectional shape. The flows of the oxygen-enriched air surrounding the longitudinal axis of the gaseous fuel flow may be "twisted". Such a "twist" can be obtained by arranging the flows of oxygen enriched air so that they make an angle of between about 0 and 400 with respect to

  the longitudinal axis of the gaseous fuel flow. Such tor-

  In preferred embodiments, oxygen-enriched air flows may form a plurality of helical flows.

  arranged around the central flow of the gaseous fuel. The dia-

  meter in cross-section of the gaseous fuel flows and the

  respective diameters of the plurality of oxygen enriched air flows.

  gene, arranged around, can be chosen so that the combustion

  this fuel and air is essentially stoichiometric,

  in accordance with standards known to those of ordinary skill in the art and as will be indicated in the following examples of embodiments

  as well as other modes of execution.

  The respective pressures and respective diameters of the gaseous fuel flow and the multiple flows of the oxygen enriched air are selected, in preferred embodiments, so as to

  keep the isotherms essentially constant using the

  oxygen enriched air, compared to isotherms obtained in a burner apparatus using ambient air in such a burner

  to obtain the combustion of the gaseous fuel.

  Advanced methods according to the present invention can

  furthermore, radially confining the maintainable flame.

  Such radial confinement can be achieved preferably by means of

  which are free from any refractory material, in order to prevent

  of such a refractory material to contaminate the flame which can be

  and / or, through the latter, the material that is

  heated by this flame. Such radial confinement means may

  wear a metal sleeve. Likewise, in other preferred embodiments, the radial confinement can be obtained by means of a sleeve of refractory material in which the heating is indirect, and / or it is

  provided other means to reduce the element to be heated.

  In some of the preferred embodiments of the present invention,

  As shown in illustrative examples, the temperature of the flame that can be obtained can be reduced in relation to

  to combustion carried out in the ambient air.

  Referring now to the drawing and in particular to FIG. 1, the improved processes providing combustion of the gaseous fuel in oxygen enriched air can be carried out by means of the apparatus shown by way of example in the figures, although those skilled in the art may consider using other devices for

such methods.

  Figure 1 shows in partial cross-section and fragmentary side elevation, a burner generally marked 10, for carrying out the present invention. The burner

  has a perforated plate generally identified by the

  The nozzle 16 is disposed within a nozzle body 18 containing a channel portion 20 for the oxidizing gas and for transmitting the oxidant gas from an external source and

  preferably by means of an adjustable orifice valve (not re-

  present). Similarly, referring to FIG. 2, it can be seen that such an oxidizing gas passes through orifices 22 formed in the perforated plate 12, following a divergent flow corresponding to the angle of divergence A represented in FIG. to penetrate the central bore 24 of a refractory block 26. Such a refractory block 26 is supported by a block support frame 28 held by a flange 30 of the nozzle body. Such a nozzle body 18 may further include an inlet flange 31 attached to the nozzle body 18 by means of appropriate bolts 32 and sealingly applied thereto.

  against the latter by means of a gasket 34. Similarly,

  a rear plate 36 of the nozzle body is sealingly attached to the

  means of a seal 38 and bolts 40 to the nozzle body 18.

  On the rear plate 36 is installed a set 42 forming

  ignition spark ignition. You can also have a glass of observation

  44 to look inside the nozzle 16. Similarly, there may be a hollow plug of duct 46 allowing access to the body of

nozzle 18.

  Referring now to Figure 2, which represents a view

  front view of the embodiment of the perforated plate 12 as

  shown in Figure 1, which is intended to be used with ambient air, there is shown a "twist" angle B of the various orifices 22. Such orifices 22 are arranged radially spaced in a network around a central duct 48 of the gaseous fuel. The surface of the perforated plate 12 may preferably be flat, as shown,

  although it may be possible to envisage other provisions.

  FIG. 3 shows one embodiment of a plate

  112 suitable for the implementation of certain other modes of

  of the improved processes according to the present invention, this

  plate having orifices 122 having an approximately equal diameter

  at half the diameter of the orifices shown in the form of

  Figure 2 and suitable for use with

  air enriched with more than 2% oxygen. There is shown a central conduit 148 for conveying the gaseous fuel. Preferably, the surface of the plate is flat, while the orifices 122 diverge analogously at an angle A and provide a "twist" at an angle B. Similarly, Figure 4 shows a front view of a another embodiment of a perforated plate 212 suitable for the implementation of another embodiment of the improved processes according to

  to the present invention. The perforated plate 212 comprises, analogously

  a central conduit 248 for conveying the gaseous fuel and comprises

  in addition inclined and diverging apertures 222 whose diameter is appro-

  approximately equal to a quarter of the diameter of the orifices provided in the form

  embodiment of Fig 2 for ambient air. Such a form of realization

  The perforated plate 212 of FIG. 4 is suitable for its use.

  with a flow of air enriched with about 35% oxygen.

  As shown in Example 1 at the end of the

  description, six different locations of temperature

  in the examples described hereinafter by way of example of the embodiments of the methods according to the present invention, these locations being denoted respectively by T1, T2, T3, T4, T5 and T6. These locations for measuring the temperature are identified as follows:

  T1 - On the outer upper surface of the refractory block 26, close to

  mite of the output end which is located vis-à-vis the flange; T2 - Near T1 on the lateral / upper outer surface of the

  refractory block 26 and with an offset of about 45 degrees with respect to

  vertical port; T3 - On the outer surface of the refractory block 26 near T and with a shift of about 90 degrees from the vertical;

  T4 - Inside a recess to a height of about 0.63 cen-

  timers, in the front face of the refractory block 26, at the upper central portion of this face;

  T5- Inside a recess at a height of about 0.63 centimeters

  meters in the front face of the refractory block 26, in the lower central part of this face; and T6

  T6 - On the inner side surface of the refractory block 26 near

  mite of the output end, which is located vis-à-vis the flange 30.

  Examples of work of different modes of execution have been

  of the improved processes according to the present invention, which are presented in column form in Examples I and II, indicated in

the end of the description.

  In the preferred embodiments, the burner 10 may be a

  3.80 cm burner, a 5.08 cm burner, a 4.62 cm burner, a burner

  10.16 cm, a burner 13.24 cm or a burner of another size.

  The material used for the refractory block 26 may consist of

  ceramic fusible material having a high temperature resistance capability and / or other materials. When using a ceramic block 26, the initial diameter of the central bore 24 can vary between 13.80 cm and 13.97 cm for burners having sizes included

  respectively between 3.80 cm and 10.16 cm. Such a refractory block can pos-

  seduce a length between at least 23.5 cm and 33.02 cm. These dimensions

  as well as other dimensions.are not critical and can be

change appropriately.

  Those skilled in the art will readily understand, on reading

  the description above, the basic characteristics and

  new advanced processes according to the present invention. he

  It will be readily apparent from the evidence that many modifications and changes

  ments can be made in the implementation of

  born according to the present invention as indicated above, without departing from the scope of the invention. This is why the preferred execution modes, indicated above, as well as the variants of execution of the

  The present invention is in no way limiting in nature.

EXAMPLE I

  Flame tests with a 5 "KINEMAX bursor (I) using Ud / natural

  (1) registered trademark of Maxon Corporation; Muncie, Indiaridna.

  Pressure Volume Pressure Too Short of Orifice Temp. Length Diameter Color Gas Gas Duration of Exhaust Gas Exhaust Block Stage of Exhaust Pressure M3 / A (x03 Pa) (xlO3Pa ) 02 in 02 in t1 T2 3 T t6 flame flame flame flame combustion m / ha a12 3 4 5 6 visible (in mn) the body the furnace (C) (C) (C) (C) C) (C) ( C) meters (in meters

  16.99 23.70 5.08 20.8 2 _ 0.36 0.15 blue -

  28.32 20.32 13.55 35 2 _ _ 0.91+ 0.10 white -

  28.32 76.19 12.19 20.8 - 36.7 50.55 44.44 183.89 177.22 312.77 1704 0.36 0.15 blue 15 28.32 25.40 13.55 35 - 55 , 55 70.55 73.33 264.44 25 410 1454 0.61 0.15 white 15

_ _. __ _-. __ _ _

  28.32 76.19 12.19 20.8 - 49 72.22 66.67 205 190.56 331.11 732.22 0.36 0, 15 blue 30 28.32 25.40 13.55 35 - 111 , 11 118.89 130.56 291.66 249 407.22 1454 1.07 0.15 white 30 28.32 76.19 12.19 20.8 - 59.44 86.07 85 216.67 199 339, 44 1732.22 0.36 0.15 blue 60 to 28.32 22.01 13.55 35 - 119.44 127, 78 140.56 297.78 252.22 404 1454 1.07 0.15 white 60 16 , 99 27.09 5.08 20.8 74 112.2 116 340 47.7 593 704 0.61 0.13 blue 10 16.99 13.55 5.08 35 - 127 132.78 147.8 300 263 , 3,401.67 1482 0.76 0.15 white 10, 66 3.39 0.68 20.8 92.22 137.2 155.56 384.44 368.8c 690.56 1621 0.46 0.10 blue 15, 66 5, 08 0.68 35 131.67 145.5 159.44 307.22 292.7 435.56 732.22 0.03 0.10 white 15 blue / r 2.83 1.69 0 , 34 35 142.22 154.4 170 317.78 317.2 447.78 760 0, 46 0.10 blnc5 0.71 0.34 O35 _ 149 160 171 | 282 283 399 1760 0.15 0.03 10white t blue / 1 0.71 T 0.34 0 35 - 149 160 171 282 Z83 399 1760 0.15 0, 03 tray 1

EXAMPLE II

  Comparison between ambient air and 02 enriched air in the case of the use of the 13.25 cm KINEMAX burner, "G" series (Oven 02-2%) MRV Volume of the Pressure Pressure Percentage - MRV Volume of the Pressure Pressure Forcen - 03P g gas from the air of gas MRV gas from the air of the gas stage of 0 0 3 x qO3P 3 in the 2 (m33 year / lh 2de (m3 / h) (xiO3Pa) (x103Pa ) corns u (m3 / h) (xiO3Pa) (x103Pa) danrs dule Tube Body Body Tube

burner _ burner H.G.

  Driver 5.66 3.39 0.01 20.8 Driver 5.66 3.39 0.01 35 0.34 Minimum 14.16 3.39 0.03 20.8 Minimum 22.65 3.39 0.34 35 0.7

  1 39.64 2.27 0.10 20.8 1 67.96 2.71 2.03 35 1.37

  2 53.80 5.08 0.24 20.8 2 107.60 5.08 6.10 35 4.19

  3 79.29 10.50 4.74 20.8 3 138.75 10.50 11.51 35 6.89

  4,113.27 21 5.42 20.8 4 172.73 21 17.95 35 10.34

  138.75 32.17 11.51 20.8 5 226.54 32.17 28.78 35 15.86

  6 164.24 44.02 16.25 20.8 6 263.35 44.02 33.86 35 22.06

  7 181.23 54.18 20.66 20.8 7 294.50 54.18 40.64 35 28.96

  8,202.47 67.73 24.03 20.8 8 328.48 67.73 50.80 35 35.16

  9,217.19 77.89 26.08 20.8 9,351.13 77.89 74.50 35 41.37

  226.54 84.66 27.43 20.8 10 368.12 84.66 84.66 35 46.88.

  Maximum235.03 91.43 28.78 20.8 Maximum 382.28 89.40 89_40 35 55.16 Maximum 235.03. 91.43 28.78 20.8 Maximum 382.28 89.40 89.40 35 55.16

Claims (14)

  A method for providing efficient and low cost heating using direct combustion of a gaseous fuel, characterized in that it includes the operating steps of: providing a central flow of the gaseous fuel,   along a longitudinal axis and delivered at a pressure sufficient to   managing the gaseous fuel in a longitudinal direction; - provide a multiplicity of air flows enriched with oxygen,   arranged in cross-section along a circular network around the   gaseous fuel, and inclined radially at a   taken between about +20 and about -20 relative to the longitudinal axis   the flow of the gaseous fuel, so that said   oxygen-enriched air is initially directed at a   pathways around the central flow of the gaseous fuel; mixing the flow of the gaseous fuel with the oxygen-enriched air; and   - to burn such a mixture to obtain a flame put in -   form, which can be maintained and has a reduced temperature zone   around it, in order to obtain an efficient combustion of such   gaseous and to obtain reduced levels of combustion products harmful during combustion.   2. Method according to claim 1, characterized in that the   percentage of oxygen enrichment of the air flow rises than about 35%.   3. Method according to claim 1, characterized in that the   oxygen enrichment of the airflow is such that it is a flow of pure oxygen.   4. Process according to claim 1, characterized in that the   gaseous fuel is generally circular in cross section. versale.   5. Method according to claim 1, characterized in that it further comprises applying a torsion to oxygen enriched air flows around the longitudinal axis of the flow of the gaseous fuel. 6. Method according to claim 5, characterized in that said 13 2604241   torsion operation consists in disposing oxygen enriched air flows so that they make an angle of about 0-40 with respect to   the longitudinal axis of flow of the gaseous fuel.   7. A process according to claim 5, characterized in that such twisted flows of oxygen enriched air form a plurality of spiral flows disposed around the central flow of the gaseous fuel. Method according to claim 1, characterized in that the cross-sectional diameter of the central flow of the gaseous fuel and the respective diameters of the oxygen-enriched air flows, which are arranged around the central flow, are selected ,   for a selected pressure, so as to obtain an essential combustion   stoichiometrically of said flows.   9. Process according to claim 1, characterized in that the   respective pressures and the respective diameters of the flow of the com-   gaseous fuel and the multiplicity of oxygen enriched air flows are chosen so as to maintain substantially constant isotherms with respect to the combustion with the gaseous fuel in the ambient air.   10. Process according to claim 1, characterized in that it   furthermore is to radially confine the flame that can be maintained.   11. The method of claim 10, characterized in that the   said radial confinement is obtained using means not including any refractory material, so as to prevent particles of such material   to contaminate the flame that can be maintained.   12. Process according to claim 11, characterized in that the   said radial confinement means comprise a metal sleeve.   13. The method of claim 11, characterized in that such a radial confinement is obtained by means of a sleeve (26) made in one refractory material.   14. The method of claim 1, characterized in that the temperature of the flame that can be maintained is reduced in relation to   to combustion carried out with the ambient air.