Note: Descriptions are shown in the official language in which they were submitted.
TITLE OF THE INVENTION
Low-Pressure Gas Burner
FIELD OF THE INVENTION
This invention relates to a burner adapted to be used on gas flare stacks and
the like.
BACKGROUND
Historically, industry directed low-pressure waste gases to low-pressure
flares or vent
stacks. Vent stacks release untreated waste gases into the environment. Low-
pressure
flares expose waste gases to an uncontained flame, allowing much of the waste
gas to
escape into the environment.
In order to prevent waste gases from polluting the environment, a pipe is
often connected
to the container or tank containing the waste gases to divert the gases to a
combustion
device. Historically, this has required compressing waste gas to allow for
combustion in
a conventional burner.
Low pressure gas, such as of 15 psig or less, which is often times 5 psig or
less, is difficult
to combust in a conventional burner. Compressing gas to achieve a higher
pressure is
time consuming and expensive.
There is a commercial demand for a way to combust low-pressure gases without
compressing the gas.
SUMMARY
In accordance with a broad aspect of the present invention, there is provided
a burner,
comprising: an outer wall configured as a venturi including a lower end, a mid
throat
section, and an upper end, the lower end being bell shaped and the upper end
further
including an upper end inner diameter; and a nozzle configured to receive and
deliver a
low-pressure gas stream, the nozzle having an opening into the lower end.
In accordance with another broad aspect of the present invention, there is
provided an
incinerator comprising: a body; an air intake at a lower section of the body
configured to
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allow air to enter the body; at least one burner, within the body in
communication with and
situated above the air intake, the at least one burner including: an outer
wall configured
as a venturi including a lower end, a mid throat section, and an upper end,
the lower end
being bell shaped and the upper end further including an upper end inner
diameter; and
a nozzle configured to receive and deliver a low-pressure gas stream, the
nozzle having
an opening into the lower end; a combustion area within the body in
communication with
and situated above the at least one burner; and a stack area of the body, in
communication with and situated above the combustion section; the incinerator
being
configured to achieve high combustion efficiency of a low-pressure waste gas
stream
It is to be understood that other aspects of the present invention will become
readily
apparent to those skilled in the art from the following detailed description,
wherein various
embodiments of the invention are shown and described by way of illustration.
As will be
realized, the invention is capable for other and different embodiments and its
several
details are capable of modification in various other respects, all without
departing from
the spirit and scope of the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
A further, detailed, description of the invention, briefly described above,
will follow by
reference to the following drawings of specific embodiments of the invention.
These
drawings depict only typical embodiments of the invention and are therefore
not to be
considered limiting of its scope. In the drawings:
Figure 1 is a cross section view of a burner;
Figure 2 is a bottom perspective view of an outer wall of a burner;
Figure 3 is a cross section view of a nozzle mounted on a partly cutaway
plenum chamber;
Figure 4 is a diagram illustrating flow of fluid through a burner in
operation;
Figure 5 is a perspective view of an incinerator wherein the burners are
arranged on a
first manifold in the shape of a ring, and a second manifold connected to and
surrounded
by the first manifold, the burners of the second manifold being arranged in a
grid;
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Figure 6 is a top perspective view of a plurality of burners arranged on a
manifold; and
Figure 7 is a bottom perspective view of a manifold with a plurality of
nozzles connected
thereto.
DESCRIPTION OF VARIOUS EMBODIMENTS
The detailed description set forth below in connection with the appended
drawings is
intended as a description of various embodiments of the present invention and
is not
intended to represent the only embodiments contemplated by the inventor. The
detailed
description includes specific details for the purpose of providing a
comprehensive
understanding of the present invention. However, it will be apparent to those
skilled in the
art that the present invention may be practiced without these specific
details.
The invention provides a burner configured to combust low-pressure gases into
substantially smokeless combustion products. The low-pressure gases can be
combusted as is, without requiring them to be compressed.
With reference to Figs 1 and 2, a burner 302 includes an outer wall 310 and a
nozzle 313.
The outer wall is configured as a venturi, including a lower end 314, a mid
throat section
316, and an upper end 318.
Nozzle 313 is configured to receive and deliver a low-pressure gas stream. The
nozzle
has an opening 315 in communication with the lower end of the outer wall. The
nozzle
may terminate in the lower end. The nozzle has a diameter D.
The upper end of outer wall 310 has length L, extending from an open tip 319
to the upper
limit of mid throat section, indicated in Figure 1 at the point of reference
number 316. The
upper limit of the mid throat section is where the taper of the mid throat
section stops. A
major portion of the upper end of outer wall 310 may have a substantially
constant inner
diameter d along its length L. In other words, the upper end may be
cylindrical and the
upper end diameter d substantially doesn't flare (increase) or taper
(decrease) towards
the tip. The substantially constant diameter along most or all of the upper
end from at or
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near throat 316 to tip 319 promotes mixing of the gas with oxygen, but also
maintains the
pressure and concentration of the gas.
The upper end may further include an upper end length to upper end inner
diameter ratio
L:d within the range of 12:1 and 14:1. During development of the invention, it
was
observed that the ratios described herein, including ratio L:d and other
ratios described
below, yielded improved combustion efficiency over constructions outside the
ratio
ranges.
The flame patterns known to result in high combustion efficiency occurred
within the
ranges indicated. The measured combustion efficiency was high and with no
visible black
smoke exiting the incinerator within which the burners were operating.
The lower end is bell shaped and, as such, has a larger diameter at its mouth
311 than
at the mid throat section. The lower end may have a tapering section 322 and a
wall 324
defining the mouth.
The lower end's mouth has a mouth inner diameter d'. The mid throat section's
diameter
is substantially the same as diameter d. A mouth inner diameter to upper end
inner
diameter ratio d':d may be within the range of 1.6:1 and 2:1. Burners
configured within
this range were found to operate with high combustion efficiency. In
particular, the
measured combustion efficiency was high, with no visible black smoke observed
passing
out of the incinerator.
Wall 324 at mouth has a variable shape. That is, wall 324 may have a
substantially
constant diameter d', as illustrated in Figs 1 and 2. Alternately, wall 324
may flare adjacent
the mouth. That is, the lower end's diameter may continuously increase,
beginning where
the mid throat section transitions to the lower end, and terminating at the
mouth. In the
illustrated embodiment, wall 324 has a length where the diameter is
substantially
consistent and then the lower end tapers toward the throat.
With reference to Fig 3, nozzle 313 for the low pressure burner is often
installed on a
manifold 500. In such an embodiment, the nozzles are installed on a manifold
wall 501,
such as by threading or welding into ports on the manifold wall.
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The nozzle may have a substantially consistent inner diameter D along its
length. The
nozzle may include a nozzle height H measured from its inboard, receiving end
326 to
the nozzle's opening 315. In one embodiment, the nozzle has a nozzle height to
inner
nozzle diameter ratio H:D within the range of 7:1 to 9:1.
During testing with a nozzle configured such that the ratio H:D is within the
range of 7:1
to 9:1, it was found that gas even at low pressures of 5 psig or less and in
unprocessed
conditions, such as not completely dehydrated, flowed reliably through the
nozzle. The
nozzle with this configuration offers a desirable velocity profile with low
pressure gas and
acts like a capillary to draw gas along it. However, at the same time
condensation, if it
does occur, tends not to occlude the inner diameter. Also, the burner with
this nozzle
construction produced a flame with high combustion efficiency based on
analysis of the
resulting combustion products.
The nozzle's receiving end 326 is where the nozzle receives gas and the
nozzle's opening
315 is where the nozzle delivers gas into the outer wall's lower end 324. The
opening
may be positioned with various degrees of penetration into the lower end 314,
including
right at the mouth of the outer wall. In other words, the nozzle's opening 315
may be in
substantially the same plane as the lower limit of the outer wall or the
opening 315 may
protrude further into the lower end 314 towards throat 316. In one embodiment,
opening
315 extends into the lower end but is positioned at the transition where wall
324 begins
to taper toward throat. In particular, opening 315 may be positioned at about
the depth
where diameter of lower end 314 begins to taper.
With reference to Fig 2, the lower end may be connectable to the nozzle, for
example by
way of a cross piece 312. The nozzle and the cross piece may be connected by
threading,
including engagement between a thread on nozzle and a threaded opening 320 on
the
cross piece. Such threading allows an operator to replace a damaged outer
wall, or
substitute the outer wall for another outer wall selected for different
conditions or gases.
The lower end and the mid throat section may have a smoother surface relative
to the
inner surface of the upper end. In one embodiment, the lower end and mid
throat section
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may be treated in a first manner or have a first material selection, and the
upper end
treated in a second manner or have a second material selection, such that the
lower end
and mid throat section are smoother, and therefore have a lower Reynold's
Number,
relative to the upper end. Such treatments may include polishing, coating or
sanding the
inner facing surfaces of lower end 314and mid throat section 316. For example,
the inner
surfaces of lower end 314 and throat section 316 may be polished while the
inner surface
of upper end 318 is not polished and therefore is rougher than the lower end
and the
throat. The relatively rougher inner surface may be between the throat 316 and
tip 319
but in the illustrated embodiment the relatively rougher inner surface extends
between tip
319 and a point, such as point 317, spaced a small distance from the throat.
In one embodiment, the outer wall of the burner may have a multipart
construction for
example where an upper end portion 318 is secured as by threading or welding
to the
throat 316. This construction facilitates the selection of different surface
roughness noted
above. This construction may create an annular seam on the inner surface of
upper end,
illustrated at point 317. While the seam may be substantially flush, it may
create a
discontinuity such as the illustrated step in Figure 1, which is close to the
throat in the
upper end. This step may be close to where the mid throat section transitions
into the
upper end. Since it is desirable to maintain the diameter d of the upper end
substantially
constant without flaring or tapering, any discontinuity should be small such
that the
diameter does not vary much across point 317. Regardless, after the annular
discontinuity, if any, the diameter d of a major portion of the upper end from
point 317 to
the tip remains substantially constant without flaring or tapering.
The burner may be constructed of stainless steel, thereby protecting against
damage by
corrosive gases and high temperatures encountered during combustion.
With reference to Fig 4, outer wall 314 including the lower end and the mid
throat section
act as a venturi to draw air into the lower end. This allows air to mix with
gas from the
low-pressure gas stream, thereby: creating a fluid mixture of gas and air,
increasing the
velocity, and decreasing the pressure of the fluid passing through the upper
end of the
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burner, and directing the fluid mixture up through the throat and out of the
tip. The fluid
mixture is ignited after it exits the tip 319 of the upper end.
The smooth interior of the lower end and mid throat section reduces
turbulence, thereby
facilitating laminar flow and increasing velocity, of fluid passing
therethrough. The rough
interior of the upper end, has a higher Reynolds Number than the lower end and
mid
throat, increases turbulence, thereby promoting mixing, of fluid passing
therethrough; and
causing the flame to burn at an ideal height above the tip.
If there is a discontinuity such as a step at point 317, an eddy is created,
thereby further
slowing the velocity and mixing the fluid.
Gases at low pressure are challenging to combust efficiently. Higher calorific
values
makes it difficult to induce sufficient oxygen. Lower calorific value gases
may require fuel
to supplement the combustion process. Where the low-pressure waste gas stream
may
have a low hydrocarbon content, the nozzle may be in communication with an
additional
fuel supply. Additional fuel facilitates combustion of low-pressure waste gas
that has a
low hydrocarbon content.
With reference to Fig 5, an incinerator may be configured with the above
described burner
to achieve high combustion efficiency of a low-pressure waste gas stream. In
one
embodiment, the incinerator comprises a body 100, including a lower section
200, a
combustion area 300 above the lower section, and a stack area 400 above the
combustion area. The body may be formed as an upwardly extending cylinder. The
pressure of the low-pressure waste gas stream may be between 0.1 and 15 psig,
or less
than 5 psig such as between 1 and 3 ounces/in2.
The lower section includes an air intake 210 to allow air to enter the body.
The combustion area within the body is in communication with at least one
burner, for
example, one of the burner embodiments described above. The combustion area is
configured to allow hydrocarbons in the low-pressure waste gas stream to burn
in the
presence of oxygen to reduce hydrocarbons into substantially smokeless
combustion
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byproducts. Such by-products may include carbon dioxide, water vapor and
thermal
energy.
The combustion area may further include a manifold 500 with the at least one
burner
installed thereon. With reference to Fig 3, the nozzle may be connected to the
manifold,
for example by threading, with receiving end 326 in communication with the
manifold
internal chamber. The burner, including the height H of the nozzle and the
length L of the
outer wall may extend vertically upwardly from the manifold, parallel with the
long axis
from lower section 200 and up through stack 400.
With reference to Fig 6, the manifold may be configured as a ladder, including
two side
members 502 and at least one cross member 504 extending therebetween. In the
illustrated embodiment, there is a plurality of cross members. The burners may
be
arranged on the manifold in a grid pattern. The burners may be arranged such
that the
burners are substantially evenly spaced apart. In such an embodiment, with
reference to
Fig 7, the manifold acts as a plenum chamber, thereby providing each burner a
substantially similar volume of gas, even as the low-pressure waste gas stream
surges
and wanes.
The stack area is in communication with and situated above the combustion
section, and
is configured to provide additional room, and thereby residence time, for
hydrocarbons to
reduce into substantially smokeless combustion byproducts.
The previous description of the disclosed embodiments is provided to enable
any person
skilled in the art to make or use the present invention. Various modifications
to those
embodiments will be readily apparent to those skilled in the art, and the
generic principles
defined herein may be applied to other embodiments without departing from the
spirit or
scope of the invention. Thus, the present invention is not intended to be
limited to the
embodiments shown herein, but is to be accorded the full scope consistent with
the
claims, wherein reference to an element in the singular, such as by use of the
article "a"
or "an" is not intended to mean "one and only one" unless specifically so
stated, but rather
"one or more". All structural and functional equivalents to the elements of
the various
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embodiments described throughout the disclosure that are known or later come
to be
known to those of ordinary skill in the art are intended to be encompassed by
the elements
of the claims. Moreover, nothing disclosed herein is intended to be dedicated
to the public
regardless of whether such disclosure is explicitly recited in the claims.
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