Fuel-burner apparatus and method for use in a furnace

The present invention provides a burner for burning a fuel in an oxidant. In accordance with the apparatus, a fuel nozzle is provided for producing a fuel jet of the fuel adapted to burn within the oxidant with the flame extending outwardly from the fuel nozzle and such that the particles of fuel become increasingly more buoyant along the length of the flame. A lower oxidant nozzle is located below the fuel nozzle for creating a lower oxidant jet of the oxidant that produces a low-pressure field below the fuel jet for downwardly spreading the fuel into the oxidant. Additionally, an upper oxidant nozzle is located above the fuel and lower oxidant nozzles for creating an upper oxidant jet of the oxidant to burn the increasingly more buoyant particles of the fuel. The velocities of the upper and lower oxidant jets can be adjusted independently of their mass flow rates to adjust the flame shape from sharp (convection dominated) to lazy (radiation dominated) without changing the stoichiometry of the flame. Additionally, the present invention provides a furnace containing such a burner for heating a melt confined between bottom and sidewalls of the furnace.

BACKGROUND OF THE INVENTION 
The present invention relates to a fuel-burner apparatus and method wherein 
a fuel is burned in an oxidant to heat a furnace heat-load, such as glass, 
ferrous and non-ferrous melts and etc. More particularly, the present 
invention relates to a fuel-burner apparatus and method involving 
globally-enhanced mixing of the oxidant and fuel. 
Furnaces used in heating thermal loads such as glass and metal melts 
typically incorporate one or more burners set within burner blocks along 
the sides of the furnace. The burner produces the required heat by burning 
a liquid fuel, such as No. 2 or No. 6 fuel oil or a gaseous fuel such as 
natural gas in an oxidant such as oxygen or oxygen-enriched air. The 
resultant flame extends over the melt and heat is transferred from the 
flame to the melt by radiation and conduction. 
Global-enhancement burners are provided in which the mixing of the oxidant 
and the fuel occurs over a large area as opposed to a localized mixing of 
the oxidant and fuel. As a result, a broad flame is produced having a 
controlled heat release pattern which can be quite uniform throughout the 
flame. An example of a global enhancement burner can be found in U.S. Pat. 
No. 4,927,357, in which a non-axisymmetric oxidant nozzle is located below 
a fuel nozzle to produce a low-pressure field of the oxidant below the 
fuel nozzle. The low-pressure field enhances aspiration of the fuel into 
the oxidant. The oxidant and fuel jets produced by the oxidant and fuel 
nozzles fan out from the burner so that the mixing between the two occurs 
over a wide area. The resultant flame produced by combustion of the fuel 
within the oxidant has quite a uniform heat distribution with the virtual 
elimination of hot spots. In some operating regimes, a long flame is 
produced in which unburned particles of fuel become increasingly more 
buoyant along the length of the flame. The disadvantage of this is that 
unburned particles of fuel at the end of the flame rise to burn outside of 
the oxidant provided directly through the burner in a controlled manner. 
This is typically observed as the flame licking up at its end. As a 
result, part of the heat released by the flame is diverted from the 
heat-load to the top or crown of the furnace. 
Another disadvantage of many prior art burners, including 
global-enhancement burners, is that it is difficult to control the mode of 
heat transfer to the melt without changing the stoichiometry of the flame. 
In this regard, certain types of melts are highly reflective of radiant 
heat. In such case, it is known that more effective heat transfer can be 
obtained with a convective-type flame. One way to achieve this is to 
increase the velocity of the oxidant jet and thereby sharpen the flame 
pattern from a lazy flame pattern. A sharp flame results in a lower degree 
of radiative and a higher degree of convective heat transfer than a lazy 
flame. However, it is difficult to control the oxidant velocity 
independently of oxidant mass flow rate without a sophisticated 
flow-control system. As such, an increase in oxidant velocity is 
accompanied by a decrease in oxidant mass flow-rate. The decreased oxidant 
mass-flow rate changes the stoichiometry of the reaction between the fuel 
and the oxidant to in turn, change the rate at which heat is released by 
the flame and may result in unburned fuel in the exhaust system of the 
furnace. 
As will be discussed, the present invention provides a burner that more 
effectively aspirates the fuel into the oxidant to prevent the more 
buoyant particles of fuel from burning outside of the oxidant. 
Additionally, a burner of the present invention allows for the velocity of 
the oxidant to be controlled independently of its mass flow rate to 
selectively produce either sharp or lazy flame patterns without affecting 
the stoichiometry of the reaction between the fuel and oxidant. As a 
result, the heat release characteristics of the flame can be adjusted from 
radiation dominated to convection dominated independently of stochiometry. 
SUMMARY OF THE INVENTION 
The present invention provides a burner for burning fuel and an oxidant. 
Fuel nozzle means are provided for producing a fuel jet of the fuel 
adapted to burn within the oxidant with an outwardly extending flame and 
such that particles of the fuel become increasingly more buoyant along the 
length of the flame. Lower oxidant nozzle means are provided below the 
fuel nozzle means for creating a lower oxidant jet of the oxidant that 
produces a low-pressure field below the fuel jet for downwardly aspirating 
the fuel into the oxidant. Upper oxidant nozzle means is located above the 
fuel and lower oxidant nozzle means for creating an upper oxidant jet to 
burn the increasingly more buoyant particles of fuel. The upper oxidant 
jet, by burning the increasingly more buoyant particles of the fuel, 
prevents the fuel from burning outside of the oxidant. This in turn more 
effectively utilizes the oxidant so that the flame does not lick up at its 
end to heat the crown of the furnace. It is to be noted that fuel is 
upwardly asperated into the upper oxidant jet due to its low pressure as 
compared with the fuel jet. However, oxidant asperation into the fuel from 
the lower oxidant jet is much more effective than that provided by the 
upper oxidant jet and thus, predominates in this function. Although not 
specifically mentioned, this is understood to be the case in the 
description and claims of the subject invention set forth hereinbelow. 
The upper and lower oxidant nozzle means can be formed in an oxidant duct 
having an open front end from which the upper and lower oxidant jets are 
discharged and an inlet spaced behind the open front end of the oxidant 
duct to receive the oxidant under pressure. A central fuel body is 
recessed within the oxidant duct and located between the open front end 
and the inlet of the oxidant duct. The central fuel body and the oxidant 
duct can have two opposed, spaced sets of top and bottom surfaces, 
separated by the central fuel body and shaped to define 
converging/diverging upper and lower nozzles through which the oxidant is 
adapted to be forced to create the upper and lower oxidant jets. The upper 
and lower nozzles have a ratio of transverse cross-sectional areas of less 
than unity such that a greater mass flow of the oxidant passes through the 
lower nozzle than the upper nozzle and thereby, the low-pressure field is 
produced in the lower oxidant jet. The fuel nozzle means can comprise a 
fuel nozzle configured to form the fuel jet. The fuel nozzle is frontally 
located on the central fuel body such that the fuel jet is discharged 
through the open front end of the oxidant duct between the upper and lower 
oxidant jets. Fuel supply means are provided for supplying the fuel under 
pressure to the fuel nozzle. 
The open front end of the oxidant duct can be horizontally flared and 
shaped such that the upper and lower oxidant jets assume a horizontally 
divergent, fan-shaped configuration upon discharge therethrough. The fuel 
nozzle can also be configured such that the fuel jet has the horizontally 
divergent, fan-shaped configuration of the upper and lower oxidant jets. 
As a result, mixing between the oxidant and the fuel occurs globally, over 
a wide area and in quite a uniform manner. 
The central fuel body can be adapted for movement toward and away from the 
open front end of the oxidant duct. In such case, the transverse 
cross-sectional areas of the upper and lower nozzles are variable, 
decreasing and increasing as the fuel body is moved away from and toward 
the front end of the oxidant duct, respectively. The upper and lower 
nozzles can also be shaped such that their transverse cross-sectional area 
ratio remains constant at any location along the oxidant duct and at any 
position of the central fuel body. Therefore, in any position of the fuel 
nozzle, the lower oxidant jet produces the low-pressure field. The oxidant 
nozzle means also can be provided with selective movement means for 
selectively moving the central fuel body to selective positions, toward 
and away from the open front end of the oxidant duct. As a result, 
selective movement of the central fuel body away from and towards the open 
front end of the oxidant duct simultaneously increases and decreases 
oxidant jet velocity in accordance with the decrease and increase of the 
transverse, cross-sectional areas of the upper and lower nozzles to 
selectively impart to the flame sharp and lazy configurations. 
Additionally, the upper and lower oxidant nozzles can also be shaped such 
that at burner operating pressure, the oxidant follows the shape of the 
two opposed, spaces sets of top and bottom surfaces forming the upper and 
lower nozzles. The effect of this is that at a given burner operating 
pressures, the mass flow rate of oxidant remains essentially constant in 
any position of the central fuel body. Thus, sharp and lazy flame 
configurations can be selected at will without changing the stoichiometry 
of the reaction between the fuel and the oxidant. 
In another aspect of the present invention, a furnace is provided having an 
insulated enclosure and one or more burners. The insulated enclosure has 
connected top, bottom and side walls to confine a melt above and between 
the side and bottom walls of the enclosure. At least one burner is 
provided that projects into the furnace, above the melt. The burner has 
fuel nozzle means for producing a fuel jet of the fuel adapted to burn 
within the oxidant with an outwardly extending flame and such that 
particles of fuel become increasingly more buoyant along the length of the 
flame. Lower oxidant nozzle means are located below the fuel nozzle means 
for creating a lower oxidant jet that produces a low-pressure field below 
the fuel jet for downwardly aspirating the fuel into the oxidant. Upper 
oxidant nozzle means are provided above the fuel and lower oxidant nozzle 
means for creating an upper oxidant jet of the oxidant burning the 
increasingly more buoyant particles of the fuel to prevent the outwardly 
extending flame from being diverted toward the top wall of the furnace and 
away from the melt. The at least one burner can be constructed from the 
oxidant duct and fuel body described above together with the advantageous 
features thereof. 
In yet another aspect, the present invention provides a method of burning 
fuel in an oxidant. The method comprises producing a jet of the fuel 
adapted to burn within the oxidant with an outwardly extending flame and 
such that particles of the fuel become increasingly more buoyant along the 
length of the flame. A lower jet of oxidant is created below the jet of 
the fuel that produces a low-pressure field for downwardly aspirating the 
field into the oxidant. An upper jet of the oxidant is created above the 
jet of the fuel and the lower jet of the oxidant to burn the increasingly 
more buoyant particles of the fuel. 
In a further aspect, the present invention provides a method of heating a 
melt. In accordance with such method, the melt is confined within an 
insulated enclosure, having connected top, bottom, and side walls, between 
the side and bottom walls of the insulated enclosure. A fuel jet of a fuel 
is produced above the melt, adapted to burn within an oxidant with an 
outwardly extending flame and such that particles of the fuel become 
increasingly more buoyant along the length of the flame. A lower oxidant 
jet of an oxidant is created below the fuel jet and above the melt that 
produces a low-pressure field below the fuel jet for downwardly aspirating 
the fuel into the oxidant. An upper oxidant jet of the oxidant is created 
above the fuel and lower oxidant jets burning the more buoyant particles 
of the fuel and thereby preventing the outwardly extending flame from 
being diverted toward the top wall of the furnace and away from the melt.

DETAILED DESCRIPTION 
With reference to FIG. 1-3, a burner 10 in accordance with the present 
invention is illustrated in an operative condition, set within a burner 
block 12 of a furnace. Burner 10 is provided with an oxidant duct 14 
having an open front end 16 from which the upper and lower oxidant jets 
are discharged along with the flame resulting from burning fuel within the 
oxidant. Oxidant enters oxidant duct 14 under pressure through an inlet 18 
spaced behind open front end 16 thereof. A central fuel body 20 is 
recessed within oxidant duct 14 and is located between open front end 16 
and inlet 18. Central fuel body 20 and oxidant duct 14 have two opposed 
sets of spaced top and bottom surfaces, 22 and 24; 26 and 28, 
respectively, shaped to define converging/diverging upper and lower 
nozzles 30 and 32. Oxidant is forced through upper and lower nozzles 30 
and 32 by the pressure to create the upper and lower oxidant jets. 
Oxidant duct 14, at rear end 22, is provided with an axial bore 34 having 
threaded and unthreaded portions 36 and 38 for purposes that will become 
apparent. Near open front end 16 of oxidant duct 14, a pair of opposed 
tracks 40 and 42 are defined on the inside of oxidant duct 14. Central 
fuel body 20 is provided with opposed, horizontal projections 44 and 46. 
Projections 44 and 46 are designed to slide within tracks 40 and 42 to 
allow central fuel body 20 to slide in an axial direction of oxidant duct 
14, forward and backward, while being supported in position. 
Central fuel body 20 has an inner bore 48 within which a tube-like vacuum 
jacket 50 projects at one end thereof. Vacuum jacket 50, in turn, encloses 
a fuel line 52 which passes through an opening 54 of vacuum jacket 50. 
Vacuum jacket 40, as may be appreciated, prevents heating or cooling of 
the fuel by conduction. A fuel nozzle 56 is frontally located on central 
fuel body 16 and in communication with fuel line 52. Fuel under pressure 
is supplied to nozzle 56 through fuel line 52 such that a fuel jet is 
discharged through open front end 16 of oxidant duct 14, between the upper 
and lower oxidant jets. 
Vacuum jacket 50 is sheathed by a sheath 58 having an unthreaded section 
60, passing through axial bore 34 of oxidant duct 14, and a threaded 
section 62. A packing nut 64 having narrow and wide threaded portions 66 
and 68 is threadably engaged, at narrow threaded portion 66, within 
threaded portion 36 of axial bore 34. Packing nut 64 is tightened within 
threaded portion 36 of axial bore 34 to bear against a teflon packing 68 
that seals oxidant duct 14 at the entry of sheath 58. An adjustment nut 70 
is threaded onto threaded section 62 of sheath 58. Adjustment nut 58 is 
retained by a lock nut 72 threaded onto wide threaded portion 68 of 
packing nut 64 so that rotation of adjustment nut 70 acts on sheath 58 and 
thus, vacuum jacket 40, to move central fuel body 20 in either a forward 
or backward direction. The action of adjustment nut 70 is frozen by 
tightening lock nut 72 on packing nut 64. Fuel line 52 projects from the 
other end of vacuum jacketing 50 and is connected to a pipe fitting 73 
which is configured to be connected to a pressurized fuel source. 
The upper and lower nozzles 30 and 32 or more exactly, the two opposed sets 
of top and bottom surfaces 22, 24; and 26, 28 of oxidant duct 14 and 
central fuel body 20 are very specially shaped. At any location of oxidant 
duct 14 and at any position of central fuel body 20, the ratio of 
transverse, cross-sectional areas between upper and lower nozzles 30 and 
32 will be less than unity and will also remain the same. The result of 
this is that a greater mass flow rate of oxidant will be discharged from 
lower nozzle 32 than upper nozzle 30 and the the lower oxidant jet will 
produce a low-pressure field beneath the fuel jet which will downwardly 
aspirate the fuel jet into the oxidant jet to produce complete mixing 
between the two. The upper fuel jet, having a lower mass flow rate, does 
not have the same influence on the fuel jet. As stated previously, 
unburned fuel particles travel along the length of the flame and tend to 
become more buoyant as they are heated. The buoyancy of such unburned fuel 
particles causes the flame to lick up because fuel particles are either 
not burnt or are burned in airborne oxygen. The upper oxidant jet burns 
the more buoyant particles of fuel to prevent the flame from licking up at 
the end, and therefore wasting the heat value of this part of the fuel. 
With reference now to FIG. 4. open front end 16 of oxidant duct 14 is 
horizontally and outwardly flared and specifically shaped such that the 
upper and lower oxidant jets will be of a horizontally divergent fan 
shaped configuration. Additionally, the upper and lower nozzles 30 and 32 
are also of rectangular transverse cross-section such that divergence of 
the upper and lower oxidant jets in the vertical direction is minimized. 
Fuel nozzle 56 is designed such that the fuel jet issuing therefrom has 
the same configuration as the oxidant jets. In this regard, for liquid 
fuels fuel nozzle 56 can be a nozzle 500033 manufactured by Spraying 
Systems Co. of Wheaton, Ill. 60188. The end result of the oxidant and fuel 
nozzle design is that the fuel mixes with the oxidant over a wide area and 
thus, burner 10 can be said to be a global enhancement burner. As can be 
appreciated, fuel nozzle 56 could be designed for gaseous fuels. 
As central fuel body 20 is moved rearwardly, away from open front end 16 of 
oxidant duct 14, the transverse cross-sectional areas of upper and lower 
nozzles 30 and 32 will simultaneously decrease. The decrease in areas will 
increase the velocities of the upper and lower oxidant jets. When central 
fuel body 20 is moved in a forward direction, toward open front end 16 of 
oxidant duct 14, the reverse action will take place, that is velocities of 
the upper and lower oxidant jets will decrease. Thus, adjustment of 
adjustment nut 70 will control the velocity of the upper and lower oxidant 
jets and thus will allow the flame configuration to be selected as either 
a sharp flame configuration (at increased oxidant jet velocity) or a lazy 
flame configuration (at reduced oxidant jet velocities). 
The upper and lower nozzles 30 and 32 are also specially shaped such that 
at a given pressure, the mass flow rates of the upper and lower oxidant 
jets will remain substantially constant at any position of central fuel 
body 20. It has been found that using pure oxygen as an oxidant and No. 2 
fuel oil as fuel, at pressures up to 10 psig, there was at most about a 1% 
to 3% difference in the mass flow rate of the oxidant passing through 
burner 10 as central fuel body 20 was successively moved from a position 
in which the points of inflection of the curves of the central fuel body 
and the oxidant duct were lined up, to successive forward movements of 
central fuel body 20, 3 mm. and 6 mm. 
It is also to be noted that the shape of upper and lower nozzles 30 and 32 
results in a quiet operation of burner 10. At 100% firing, that is a full 
110 kW rated output of burner 10, a noise level of 88.7 dba was measured 
directly in front of burner 10 which increased to 89.9 dba at 30.degree. 
off the center line of burner 10, to 90.2 dba at 60.degree. off center 
line of burner 10, to 92.2 dba at 90.degree. off center line of burner 10. 
Prior art burners of equivalent output would be expected to generate a 
noise level of from anywhere of 100 dba to about 110 dba. 
The advantages inherent in the operation of burner 10, such as have been 
discussed above, arise from the fact that the oxidant tends to follow the 
curvatures of surfaces 22, 24, 26, and 28 without separation at the 
operating pressure range of burner 10 (2 to 10 psig). Among other 
important advantages arising from such smooth flow is that the flame is 
stabilized with high turn-up and turn-down ratios. In other words, burner 
10 produces a stable flame over wide mass flow ratios of oxidant and fuel, 
and therefore under wide ranges of heat output. Furthermore, the pressure 
drop at the oxidant is low and therefore, there is no need to compress 
oxygen by the use of oxygen compressors with the use of burner 10. 
With reference to FIGS. 5 and 6, oxidant duct 14 and central fuel body 16 
are machined so that the ratio between the transverse cross-sectional 
areas of upper and lower oxidant nozzle was 1:2. The exact machining 
specification is as follows: 
______________________________________ 
OXIDANT DUCT MACHINING COORDINATES 
xm yobm yotm xm yobm yotm 
______________________________________ 
(mm) (mm) (mm) (mm) (mm) (mm) 
______________________________________ 
-24 0 0 51 9.846 4.923 
0 0 0 52 9.819 4.910 
1 .021 .011 53 9.786 4.893 
2 .047 .024 54 9.745 4.873 
3 .081 .040 55 9.695 4.847 
4 .122 .061 56 9.633 4.817 
5 .172 .086 57 9.560 4.780 
6 .233 .117 58 9.471 4.736 
7 .307 .154 59 9.367 4.684 
8 .395 .120 60 9.246 4.623 
9 .499 .250 61 9.105 4.552 
10 .621 .311 62 8.943 4.471 
11 .762 .381 63 8.759 4.380 
12 .924 .462 64 8.553 4.276 
13 1.108 .554 65 8.322 4.161 
14 1.314 .657 66 8.069 4.034 
15 1.544 .772 67 7.792 3.896 
16 1.798 .899 68 7.492 3.746 
17 2.075 1.038 69 7.171 3.585 
18 2.375 1.188 70 6.830 3.415 
19 2.696 1.348 71 6.473 3.236 
20 3.037 1.518 72 6.101 3.051 
21 3.394 1.697 73 5.718 2.859 
22 3.766 1.883 74 5.328 2.664 
23 4.149 2.074 75 4.933 2.467 
24 4.539 2.270 76 4.539 2.270 
25 4.933 2.467 77 4.149 2.074 
26 5.328 2.664 78 3.766 1.883 
27 5.718 2.859 79 3.394 1.697 
28 6.101 3.051 80 3.037 1.518 
29 6.473 3.236 81 2.696 1.348 
30 6.830 3.415 82 2.375 1.188 
31 7.171 3.585 83 2.075 1.038 
32 7.492 3.746 84 1.798 .899 
33 7.792 3.896 85 1.554 .772 
34 8.069 4.034 86 1.314 .657 
35 8.322 4.161 87 1.108 .554 
36 8.553 4.276 88 .924 .462 
37 8.759 4.380 89 .762 .381 
38 8.943 4.471 90 .621 .311 
39 9.105 4.552 91 .499 .250 
40 9.246 4.623 92 .395 .198 
41 9.367 4.684 93 .307 .154 
42 9.471 4.736 94 .233 .117 
43 9.560 4.780 95 .172 .086 
44 9.633 4.817 96 .122 .061 
45 9.595 4.847 97 .081 .040 
46 9.745 4.873 98 .047 .024 
47 9.786 4.893 99 .021 .011 
48 9.819 4.910 100 0 0 
49 9.846 4.923 
50 9.867 4.933 
______________________________________ 
______________________________________ 
CENTRAL FUEL BODY MACHINING COORDINATES 
xm yfbm yftm xm yfbm yftm 
(mm) (mm) (mm) (mm) (mm) (mm) 
______________________________________ 
0 0 0 17 -8.654 
-4.327 
1 -.227 -.113 18 -8.88- 
-4.440 
2 -.520 -.260 19 -9.055 
-4.527 
3 -.884 -.442 20 -9.180 
-4.590 
4 -1.325 -.663 21 -9.271 
-4.635 
5 -1.838 -.919 22 -9.332 
-4.666 
6 -2.415 -1.208 23 -9.373 
-4.687 
7 -3.058 -1.529 24 -9.399 
-4.700 
8 -3.798 -1.899 25 -9.417 
-4.708 
9 -4.440 -2.220 26 -9.426 
-4.713 
10 -5.083 -2.541 27 -9.433 
-4.716 
11 -5.822 -2.911 28 -9.436 
-4.718 
12 -6.465 -3.233 29 -9.438 
-4.719 
13 -7.043 -3.521 30 -9.439 
-4.720 
14 -7.555 -3.778 31 -9.440 
-4.720 
15 -7.996 - 3.998 84 -9.440 
-4.720 
______________________________________ 
For both oxidant duct 14 and central fuel body 12, "bm" denotes bottom 
machining coordinates, while "tm" denotes top machining coordinates. 
As may be appreciated, a great deal of heat is generated by burner 10, 
which is conducted within oxidant duct 14. This heat is carried away by 
cooling water flowing through a water jacket 74 surrounding oxidant duct 
14. Water jacket has inlet and outlets 76 and 78 formed by appropriate 
fittings for cooling water to enter and leave water jacket 74 after 
circulating around oxidant duct 14. Burner 10 is mounted within burner 
block 12 by a clamp 80 connected to burner block 12 and clamped about 
water jacket 74. 
With reference to FIGS. 7 and 8, burner 10 is shown to be emitting a sharp 
flame 81 and a lazy flame 82 both of which are horizontally divergent and 
fan-shaped. As can be seen in FIG. 9, burner 10 projects sharp flame 81 
into an insulated enclosure 82 of a furnace 84. Insulated enclosure 82 has 
bottom, side and top walls 85, 86, 88 and 90. A melt 92 is confined 
between bottom wall 85 and sidewalls 86 and 88, below burner 10. As is 
apparent from this illustration, sharp flame 81 has very little vertical 
divergence and does not lick up at the end to heat top wall 90 of 
insulated enclosure 82. Although burner 10 is set in burner block 12 in a 
downward angle, this is peculiar to the illustrated furnace and as would 
be known, burner 10 could be used in a level orientation. Although not 
illustrated, but as would be well known in the art, furnace 84 would have 
an inlet for the raw material for the melt and an outlet for the melt. 
Moreover, a chimney would also be provided to discharge the combustion 
products of the burned fuel. 
It is to be noted that many individual features of burner 10 are 
advantageous and could be incorporated into a burner design without use of 
other features of burner 10 in such design. For instance, a burner could 
be constructed with an upper oxidant nozzle to produce an oxidant jet to 
burn more buoyant particles of fuel and a lower oxidant nozzle to produce 
a low pressure oxidant jet below the fuel jet. In such case, the burner 
would not have to constructed to incorporate each and every feature shown 
in FIG. 10. As another possible embodiment, a burner could incorporate the 
structure of the preferred embodiment with a fixed central fuel body 
preset to burn fuel within an oxidant with either a sharp or a lazy flame. 
While a preferred embodiment of the present invention has been shown and 
described in detail here and above, as will occur to those skilled in the 
art, numerous omissions, changes, and additions may be made without 
departing from the spirit and scope of the invention.