JP3471035B2 - Gas fuel combustion method and gas burner device therefor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion method and a burner thereof in which pollutants such as CO and NO ₂ are extremely small.

The invention is particularly applicable to gas-fired radiant burners which have a combustion surface and in which a gaseous fuel such as natural gas is combusted at or near its combustion surface. The burner was developed primarily for use in gas burner space heating systems and will be described with respect to this particular application. However, the invention is not limited to this particular field of application, but is equally applicable to other types of gas burners and other burners using a variety of different fuels.

[0003]

Gas fired burners are widely used in commercial and indoor environments for heating, including heating of spaces that regulate the temperature of interior spaces. Such burners are generally more widely used than electricity because of their low cost, efficiency, and overall flexibility. However, all types of burners are known to be sources of indoor pollutants, especially nitrogen oxides (NO _x ).

NO _x is a complex compound of nitrogen, especially N
It is a nomenclature for O, N ₂ O and N 0 ₂ . For example, NO and N ₂ O are atmospheric materials of particular interest in connection with acid rain, ozone and photochemical smog. But,
N0 _2, because of its impact on lung function, the more material of interest for medical institutions. A medical study conducted in the 1980s reported that lung function was affected by much lower amounts of NO ₂ than previously thought. As a result, in particular for regulating the emission of NO _2, has led to severe restrictions are imposed with respect to the allowable emission standards NO _X.

[0005]

In general, radiant burners with a burning surface tend to generate NO ₂ in the amount of 15 to 30 ng / Joule, and thus NO _x.
Is preferred over blue flame burners, which are believed to have no potential to reduce For such reasons, research of the NO _X gas burner is directed primarily different types of surface combustion burner.

[0006] Over the past 20 years, research for the production of gas burners with low NO _X generation amount is focused on the development of technologies to be used in conjunction with a combustion apparatus which alone or built-in second stage excess air It was As a result, many of these burners are quite complex in terms of design and operation.

For example, until recently, the best burner designs have utilized pressurized and premixed air-fuel mixtures that burn in variously shaped metal surfaces, ceramic surfaces or afterburners. All such burners utilize large amounts of excess air and high combustion loads.
As a result, a pressurizing device, an afterburner and a large combustion load are required, and the size and complexity of the gas burner are complicated and its function lacks flexibility, and the cost is high.

Furthermore, some of these burners, as compared with the more old burner has been successful in reducing the NO _X generation, still it is not possible to achieve the desired target generation amount of the NO _X it is conceivable that.

However, Australian Patent Application No. 64743/90 and corresponding US Patent Application No. 598,021 filed October 16, 1990, which the applicant assigns and incorporates herein by reference. result of recent development of the surface combustion burner as described in the specification of JP, it has become possible to generate of the NO _X containing both NO and NO ₂ to produce a very small surface combustion gas burner. This burner is
It is called the "Bowin" burner.

The present invention is a further development of the initial development work of the low NO _x burner described above. This development work is further significantly reduced emissions of NO _X, in some cases, it has been found that it is possible to completely remove all measurable NO ₂ residue. Through a series of experiments, it has been found that most burners can be modified by control methods not previously known in the art to prevent the generation of NO ₂ .

As a result of tests conducted during the development of the above-mentioned bow-in burner, the amount of nitrogen oxides generated, along with other matters, should be limited to a certain limit value of the flame temperature to prevent the generation of NO. It turned out that it was controllable. NO is then oxidized to NO ₂ , NO ₂
It is considered to be a precursor of. Therefore, it is possible to limit the generation of NO ₂ to an extremely small amount by reducing the generation of NO and suppressing the combustion temperature.

However, to date, it is not possible to completely prevent the generation of NO ₂ because at least some of the NO ₂ is formed from NO outside the burner with little or no control. there were.

[0013]

The present invention uses a simple technique applicable to most types of burners to provide NO to N
It is intended to provide a device that prevents conversion to O ₂ .

The radiant burner of particular interest to the present invention is a non-powered burner that is not of the type that supplies combustion air with a power driven fan or blower. A pressurized fuel source is used to draw in the required stoichiometric or higher amount of combustion air and supply it to the combustion surface. Traditionally, ambient air or atmosphere has been freely available for the combustion process to take place near the combustion surface. The atmosphere is typically at a relatively low temperature compared to the combustion gases.

SUMMARY OF THE INVENTION It is therefore an object of the invention to provide a non-powered radiant burner apparatus and combustion method which overcomes, or substantially alleviates, the above disadvantages of prior art burners and combustion techniques. Another object of the present invention is to produce and operate a related type of burner with low pollutant emissions and to substantially reduce and / or eliminate CO and NO ₂ emissions. .

According to the present invention, formation of pollutants is suppressed by promoting completion of the combustion reaction. The atmosphere is kept separate from the hot combustion products, reducing the production of pollutants such as CO and NO ₂ . The combustion process is controlled or regulated in a manner that at least initially separates hot combustion products and delays contact with the relatively cool atmosphere.

The mechanism by which the production of pollutants such as CO and NO ₂ by separating the relatively cool atmosphere from the hot combustion products has not been fully elucidated. The cooler atmosphere may prevent combustion reactions in which the pollutant or its precursors are normally consumed, freezing the gas composition to an undesirable state. Alternatively, the cold atmosphere may excite or accelerate unwanted reactions, resulting in the generation of such pollutants. Further, blocking the desired reaction and promoting the undesired reaction may occur simultaneously. In any case, it has been found that by separating the atmosphere and / or delaying the supply of the atmosphere to the combustion products, the emission of pollutants, in particular CO, NO ₂ , can be reduced.

The present invention is based, in part, on the idea that the combustion reaction associated with pollutants can be significantly altered by adjusting the combustion process adjacent to the combustion surface. That is, it was found that the generation of various pollutants can be significantly reduced by regulating, adjusting or controlling the atmosphere flowing in the combustion process at or near the combustion surface. In other words, it has been found that combustion phenomena can be significantly affected by process controls and devices operating or located in close proximity to the combustion surface. For example, CO and NO in the flue gas formed by performing the combustion process and operating the device within a distance of about 1 inch (25.4 mm) or less from the combustion surface.
It was found that the generation amount of ₂ can be effectively suppressed. In combination with the development of these methods and apparatus, it has been determined that the majority of combustion reactions occur and tend to complete very close to the combustion surface in the radiant burner. Laser fluorescence techniques have shown that the highest concentrations of various reactive molecules occur within a temperature range of about 830 to 870 ° C. within about 1 inch of the burning surface.

The invention is also based on the recognition that the application of control to the radiant combustion surface by means of the method and apparatus described above can be effective at the outer periphery of the combustion surface or at both ends thereof. Therefore, separating the atmosphere from the hot combustion products at and near the periphery of the combustion surface has the effect of reducing the amount of pollutants generated. The internal area of the burning surface is
It is believed that the high temperature combustion products rise upward due to their natural buoyancy and are effectively shielded from the harmful contact between the combustion products and the atmosphere or their action.

In the illustrated embodiment, it has been confirmed that the radiant burner in which the flow rate of the atmosphere is controlled according to the present invention has a smaller amount of pollutants than the burner which is the same in other respects which does not control the atmosphere. . According to the present invention, the secondary combustion air is unnecessary because the primary combustion air is supplied in a stoichiometric amount or more, that is, in an amount equal to or more than the amount required for theoretical complete combustion. This control is realized by isolating the burner in the first embodiment. More specifically, a non-powered radiant burner comprises a combustion surface contained within a sealed or closed combustion chamber that is vented to the atmosphere by natural aeration.

In a second embodiment, the radiant burner extends along the burner circumference adjacent the burner surface to limit the inflow of atmospheric air into the burner flame and / or adjacent the combustion surface. It is equipped with an air baffle or partition to control hot combustion products. The partition wall extends along a major portion of the outer circumference of the combustion surface to prevent atmospheric flow laterally from directly impinging on the combustion surface.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows a burner device having a space heater 10 suitable for indoor heating. The heater 10
1 is a gas-fired burner of the type referred to as a bow-in burner described in detail in the above mentioned Australian patent application No. 64743/90 and corresponding US patent application No. 598,021.
Is equipped with. Details of the burner 1 can be known by referring to the specification of the above patent application.

The burner 1 has an intake port and a reference numeral 3 as a whole.
The fuel mixing device indicated by reference numeral 2 as a whole is arranged so as to be able to supply the air-fuel mixture to the combustion region indicated by. More specifically, the fuel mixing device 2 comprises a fuel gas injection nozzle 12 arranged so as to be able to supply a fuel gas flow into the Venturi tube 14, which sucks and mixes the primary air content and burns it. Form a possible air-fuel mixture.
The air-fuel mixture is supplied by a Venturi tube 14 into a tubular plenum chamber 16 and distributed to a porous combustion surface 18 formed by wire mesh, sintered metal or ceramic material in a known manner. The air-fuel mixture advances through the combustion surface 18 and is burned at or near the combustion surface 18 in the combustion region 3. Combustion along the combustion surface 18 results in combustion surface 1
8 form a plurality of flames that extend from the associated holes to a height generally below the height of the combustion zone.

The hot combustion products indicated by arrow 4, ie,
Flue gas rises due to its natural buoyancy. The atmosphere indicated by arrow 5 is prevented by housing 6 from contacting and / or mixing flue gas 4 with the reactants. The housing 6 is
A base 7 is provided that extends from the plenum chamber 16 to the side wall 8 of the housing. The side wall 8 ends in an upper hole 9 provided for exhausting the flue gas 4 into the atmosphere.

The lower inner area of the housing 6 is a combustion surface 18
To form a combustion chamber 20 that encloses More specifically, the base 7 of the housing has a corrugated inner wall 22 of the housing.
In cooperation with the lower part of the enclosure, enclose the combustion surface 18 and the combustion zone 3 and prevent the contact of combustion products, ie flue gases, with the atmosphere. Combustion products are generated by the natural buoyancy of the combustion surface 18
From the combustion area 3 to move upward from the housing 6
Through the hole 9 and is discharged into the atmosphere. It should be understood that by the time the flue gas 4 reaches the holes 9, the combustion reaction is complete and the flue gas 4 has been cooled. The flue gas 4 can be cooled by recovering heat energy by indirect heat transfer and radiant heat transfer.

Through a series of tests, it has been found that by preventing the atmosphere 5 from contacting the hot reaction combustion products before reaching the holes 9, the formation of CO and NO ₂ can be prevented. The housing 6 is designed to facilitate cooling of the flue gas 4. At least 100% for burner 1
Premixed primary air is provided, which travels within a completely sealed enclosure, where the hot reaction combustion products do not interact with the atmosphere at all as described above. Such a construction provides the further advantage that the heater 10 can function much more efficiently than conventional types of burners. This is due to the relatively low flow rate of air flowing through the combustion chamber 20, which results in
Energy loss from the device is reduced.

It is possible to use a fairly large housing 6 in the heater 10 to completely enclose the burner 1. As a result, all the measurable N
O ₂ can be removed almost completely. The temperature of the exhaust gas / atmosphere mixture at the measuring point was about 550 ° C.

Referring to FIG. 2, a second embodiment of the present invention is shown. To indicate a modified part or structure, similar parts are designated by similar reference numbers with a prime number,
Hereinafter, this embodiment will be described. The burner 1 comprises a modified housing 6'comprising a pair of baffles or partitions 24 extending along a major portion of the outer periphery of the combustion surface 18. In this embodiment, the relatively cool atmosphere is the combustion surface 1
It is prevented from flowing laterally directly into the combustion zone 3 adjacent to 8.

The combustion zone 3 is, for example, a short distance, at least equal to the flame height, usually about 12.7 to 2 depending on the combustion load, the size of the holes in the combustion surface and other operating characteristics of the burner.
It extends above the combustion surface 18 a distance greater than about 5.4 mm (about 0.5 to 1 inch). The hot combustion products in the combustion zone 3 contain the highest concentration of reactive molecules, which according to the invention are isolated from the conditions of significant contact with the relatively cold atmosphere. It is therefore NO ₂ to provide a simpler means of shroud or baffle in the path where the atmosphere should be introduced and to provide a Labrinse type atmosphere bypass means.
It is effective in significantly suppressing the generation amount of.

The septum 24 comprises an elongated metal strip approximately 1 inch wide attached to the burner 1 in a suitable manner, such as by using screws. Partition wall 24
Is non-perforated and extends along the major portion of the outer periphery of the combustion surface 18. It is also possible to omit the wall portion 24 ', as shown by the dotted line, to provide clearance for other burner devices such as pilot ignition devices.

Each of the septums 24 is disposed in a plane parallel to the plane passing through the diametrical portion of the tubular plenum chamber 16 of the burner and is radially a distance of about 0.25 inches from the outer circumference of the burner. It is separated. Each of these partitions 24 extends from the combustion surface 18 in a direction substantially corresponding to the direction in which the flue gas flows due to its natural buoyancy. As shown in FIG. 3, the combustion surface 18 is semi-cylindrical in shape including major longitudinal edges 18a connected by arcuate edges 18b. The outer circumference of the combustion surface 18 extends along opposed pairs of longitudinal edges 18a and 18b. Combustion surface 18 is secured to burner 1 by crimp arms 26 that extend along each of the major edges of combustion surface 18. Each of the partitions 24 is about 0.3 inches, or 8
It extends beyond the crimp arm 26 and the edge 18a of the combustion surface involved by a distance equal to mm. The partition wall 24 defines the edge 18a of the combustion surface according to the dimensions of the combustion zone 3, other operating characteristics of the particular burner and the desired degree of reduction of pollutants.
Can be further extended. This extension distance can be easily set by trial and error.

It has been found that the partition wall 24 is effective in reducing the amount of NO ₂ produced. Furthermore, it is believed that the rapid inflow of relatively cool atmosphere results in an excessive decrease in flue gas temperature, which at least partially increases CO production. Thus, the septum 24 is effective in reducing the amount of contaminants.

According to the embodiments of FIGS. 2 and 3, in order to demonstrate the effect of the present invention on reducing the amount of pollutants generated, burners of various sizes with and without the partition wall 24 are used. did. Each of the partitions 24 is associated with a lowermost edge 18a of the combustion surface 18 as described above for the burner 1.
Was extended in the direction of the flue gas flow by a distance of about 7.62 mm (about 0.3 inch). Each of the burners 1 was operated with free access to the atmosphere so that the effects of the septum 24 could be compared. The results of these tests are listed in Table I below.

[0034]                                   Table I Burner input¹  Screen dimensions²   Perimeter rate³   When using a partition^Four  When the partition is not used^Four                Length x width% CO / CO₂  NO₂    CO / CO₂  NO₂    9MJ 178 x 86 54.8 0.007 3.5 0.006 3.9   17MJ 360 x 86 73.5 0.005 2.3 0.009 3.6   22MJ 490 x 86 79.6 0.005 1.5 0.010 2.1   28 MJ 490 x 102 77.4 0.004 2.3 0.007 3.1 1 megajoule / m²hr 2 mm 3 Percentage of edge or circumference of combustion surface along which partition wall extends 4 nanograms / joule The burners tested, as listed in Table I, have burner input values
Is 9 to 28 MJ / m²with various dimensions in the hr range
did. The burning surface is a nickel-based steel wire with a diameter of 0.014 inches.
3 layers firmly formed with an area of 30 × 32,
Its overall porosity was about 32%. For each burner size
And CO in the flue gas emitted under certain operating conditions.
And NO₂The amount of pollutants was measured. Uses standard techniques
CO and CO obtained by₂CO / C based on the measured value of
O₂Was calculated. NO₂The value of Bendix (Bend
ix) 8101-B nitrogen oxide analyzer or neotronic
The Neotronics Exotox 75 analyzer
Measured using.

As is apparent from the results in Table I, the partition wall 24 is extremely effective in reducing the generation of NO ₂ . The improvement result reaches the reduction effect of about 11% to 40%. This rate of reduction of pollutants is proportional to the peripheral rate of the combustion surface shielded by the partition. As a result of shielding the main part of the outer periphery of the combustion surface, the amount of NO ₂ produced was reduced by about 10%. With an increase in the ratio of the outer circumference of the combustion surface shielded by the partition walls, CO
The ratio of the amount of / CO ₂ generated also tends to decrease.

While this invention has been shown and described with respect to particular embodiments thereof, these are merely for purposes of illustration and not limitation, and to any person skilled in the art within the spirit and scope of the invention. Other variations and applications of the particular embodiments shown and described herein will be apparent. Therefore, the present invention is not limited to only the specific embodiments shown and described herein, nor is it not applicable to improvements in the art which are realized by the present invention.

[Brief description of drawings]

1 is an elevational end view in partial cross-section showing a burner device according to the invention with parts cut out or omitted for clarity. FIG.

FIG. 2 is a perspective view of a burner device according to a second embodiment of the invention with parts cut out or omitted for clarity.

3 is an elevational end view of the burner apparatus of FIG.

[Explanation of symbols]

1 Gas Burner 2 Fuel Mixer 3 Combustion Area 4 Flue Gas 5 Atmosphere 6 Housing 7 Housing Base 8 Housing Sidewall 9 Housing Upper Hole 10 Heater 12 Gas Injection Nozzle 14 Venturi 16 16 Plenum Chamber 18 Combustion Surface 20 Combustion Chamber 22 Housing Inner wall 24 of the housing

─────────────────────────────────────────────────── --Continued from the front page (56) References JP-A-2-223707 (JP, A) JP-A-59-21909 (JP, A) JP-A-58-129106 (JP, A) Actual development Sho-59- 65226 (JP, U) Actual development Sho 59-103024 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) F23D 14/02 F23D 14/12-14/18

Claims (12)

(57) [Claims] 1. A combustion surface having an outer circumference, a length extending along most of the outer circumference of the combustion surface, and a height protruding from the combustion surface in a flame floating direction, and the height is A method of burning gas fuel in a gas burner device comprising a naturally aspirated non-powered radiant burner comprising a non-perforated elongated partition which is substantially smaller than the length and includes one or more wall portions. Mixing the gas fuel with a predetermined amount of combustion air equal to or greater than a theoretical amount required for complete combustion of the gas fuel to form an air / fuel mixture; and the air / fuel mixture on the combustion surface. Carrying and combusting the air / fuel mixture in a single combustion zone adjacent to the combustion surface to form reactive molecular species within the single combustion zone; before to complete, adjacent the combustion surface
Adjacent ends of the combustion surface that are significantly smaller than the lateral width
The above-mentioned non-porous elongated partition walls projecting in the flame floating direction to a height above the edge flow from the lateral direction to the inside.
To prevent the atmosphere being crossed from crossing the burning surface.
Ri, relatively additional cold air comprising the steps of substantially restrain the generation of CO and NO ₂ in the hot combustion products within exhausted from the single combustion zone to said reactive species A combustion method characterized by suppressing. 2. The combustion method according to claim 1, wherein the height of the partition wall protruding from the combustion surface is not so high as compared with the total height of the single combustion zone. Method. 3. The combustion method of claim 1, wherein a majority of the outer circumference is equal to at least 50% of the outer circumference of the combustion surface. 4. The combustion method according to claim 1, wherein the elongated partition wall has a length of about 12.7 mm as measured in a flame floating direction.
A method of combustion having a height of (0.5 inches) to about 25.4 mm (1 inch). 5. The method of combustion of claim 1, wherein the elongated partition includes at least two wall portions, each wall portion being mounted on the burner to form the elongated partition. A combustion method characterized by blocking the flow of the atmosphere. 6. A gas-fired burner apparatus for combusting an air / fuel mixture to form reactive molecular species in a single combustion zone that, upon further reaction, form hot combustion products. a combustion surface, comprising the naturally aspirated unpowered drive radiant burner having a gas flow means for discharging combustion products obtained by the combustion from the gas burner apparatus, the gas flow means, includes imperforate bulkhead means, the imperforate bulkhead means has a length extending along the outer periphery of the combustion surface and
Significantly smaller than the adjacent lateral width of the combustion surface
It has a height above the adjacent edges of the combustion surface that projects from the combustion surface in the direction of the flame's flotation, thereby
Directly into the combustion zone from its two lateral ends.
It shuts off the turbulent atmospheric flow and also substantially completes the combustion reaction.
Prior to completion, the reactive
Qualitative contact is prevented, thereby reducing CO 2 as compared to similar burner devices which do not include the non-perforated partition means.
And a gas combustion burner device characterized in that an increase in NO ₂ is suppressed. 7. The gas combustion burner apparatus of claim 6, wherein the combustion surface has an outer circumference and the non-perforated partition means extends along a majority of the outer circumference of the combustion surface. A gas combustion burner device. 8. The gas fired burner apparatus of claim 7, wherein the non-perforated partition means extends along at least about 50% of the outer circumference of the combustion surface. . 9. The gas combustion burner apparatus of claim 7, wherein the non-perforated partition means in the flame floating direction is a distance that does not substantially exceed the height of the single combustion zone.
A gas combustion burner device characterized in that it projects from the combustion surface. 10. The gas combustion burner apparatus of claim 6, wherein the non-perforated partition means comprises at least one wall. 11. The gas fired burner apparatus of claim 10, wherein the wall extends from a lower boundary on the burner below the combustion surface to an upper boundary located above the outer circumference of the combustion surface. At least 7.62 mm
A gas combustion burner apparatus having a wall height extending a distance of (0.3 inches), and further having a wall length extending along at least about 50% of an outer circumference of the combustion surface. . 12. The gas fired burner apparatus of claim 7, wherein the solid apertured partition means comprises an elongated strip of metal having opposed first and second longitudinal edges.
A gas combustion burner apparatus in which the first longitudinal edge is secured to the burner and the second longitudinal edge is located above the outer circumference of the combustion surface.