U.S. patent number 3,840,320 [Application Number 05/245,369] was granted by the patent office on 1974-10-08 for flarestack combustion method.
Invention is credited to Denis Henry Desty, Christopher John Young.
United States Patent |
3,840,320 |
Desty , et al. |
October 8, 1974 |
**Please see images for:
( Certificate of Correction ) ** |
FLARESTACK COMBUSTION METHOD
Abstract
A burner for disposing of low pressure fuel gases with a steam
inlet adapted to direct steam (originally at high pressure) to flow
over a director surface so that entrainment of surrounding air
occurs (Coanda effect) and towards a fuel gas inlet supplying low
pressure fuel gas, the feed line for the fuel gas being an internal
passage of the director body.
Inventors: |
Desty; Denis Henry (Weybridge,
Surrey, EN), Young; Christopher John (Horton,
Buckinghamshire, EN) |
Family
ID: |
9997860 |
Appl.
No.: |
05/245,369 |
Filed: |
April 19, 1972 |
Foreign Application Priority Data
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Apr 29, 1971 [GB] |
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12068/71 |
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Current U.S.
Class: |
431/4; 431/5;
239/424; 431/202 |
Current CPC
Class: |
F23G
7/08 (20130101); F23G 7/085 (20130101) |
Current International
Class: |
F23G
7/08 (20060101); F23G 7/06 (20060101); F23j
007/00 () |
Field of
Search: |
;431/4,5,202,354
;239/416.5,423,424,505,506,571,DIG.7 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Dority, Jr.; Carroll B.
Attorney, Agent or Firm: Morgan, Finnegan, Durham &
Pine
Claims
What we claim is:
1. A method for disposing of low pressure fuel gases, comprising
the steps of:
causing said low pressure fuel gases to flow in a stream;
passing a stream of high pressure steam over a deflector surface
which comprises a surface of revolution formed by the rotation of a
quadrant of a circle and an inwardly curved continuation about the
axis of the direction of flow of said low pressure fuel gases,
whereby said stream of high pressure steam is directed in a first
direction generally perpendicular to the direction of flow of said
stream of low pressure fuel gases and is thereafter caused to flow
in the same general direction as the direction of flow of said
stream of low pressure fuel gases but angularly thereto so that
said stream of high pressure steam and said stream of low pressure
fuel gases converge,
the change in the direction of flow of said stream of high pressure
steam inducing a low pressure zone in the air surrounding said
stream of high pressure steam to thereby entrain said surrounding
air into said stream of high pressure steam, and
said steam, entrained air and fuel gases being mixed upon the
respective streams of steam and fuel gases converging together;
and
igniting and burning said mixture of steam, air and fuel gases.
2. A method as claimed in claim 1, wherein said steam is supplied
at a pressure of between 70 and 300 kN/m.sup.2.
Description
This invention relates to a burner for disposing of waste
combustible gas, and in particular it relates to the disposal of
refinery waste gases.
Refinery and chemical plant operation often requires that a vessel
is vented through pressure relief valves into a vent system running
at near atmospheric pressure. Gas from this low pressure vent
system is then disposed of by flaring from an elevated stack so as
to aid the dispersion of any oxides of sulphur that may be formed
during combustion.
Since the low pressure of the gas precludes the use of air
entrainment devices, and the possible sulphur content makes ground
level flaring in a natural draught flare impracticable, often the
only way to improve combustion and reduce the amount of smoke
formed during such emergency flaring operations is to add steam to
the flared gas, which then reacts with any carbon particles by
undergoing a water gas reaction, thus preventing smoke
formation.
It is an object of this invention to improve the method of
injecting steam.
According to the invention a burner for disposing of low pressure
fuel gas comprises a fuel gas inlet adapted to supply fuel gas
(originally at low pressure) to a combustion zone, a director body
at one end of which the fuel inlet is situated, the director body
having an external director surface and an internal passage for
conveying fuel gas to the fuel gas inlet, the burner also
comprising a steam inlet adapted to direct a stream of steam
(originally at high pressure) over the director surface towards the
fuel gas inlet the director surface being curved so as to initiate
the flow of steam and air towards the fuel gas inlet.
Suitably the steam is supplied at a pressure in the range 70
kN/m.sup.2 to 300 kN/m.sup.2.
It is known that a stream of gas will "stick" to a suitably shaped
surface and a curved surface can deflect a stream of gas and
thereby produce a low pressure zone. In the burner according to the
invention the initial portion of the director surface is shaped so
as to deflect the flow of steam and to produce a low pressure zone
into which atmospheric air flows.
Preferably the burner comprises a director tube the outer surface
of which is the director surface and the bore of which is a fuel
gas channel which terminates at the fuel inlet.
Preferably the initial portion of the director surface is the
surface of revolution formed by the rotation of a quadrant of a
circle about the longitudinal axis of the director body, the curved
section of the quadrant being tangential to the steam inlet.
Flame stabilisation can be improved by fitting a wind deflector. A
suitable deflector is disclosed in British Pat. No. 795,664.
According to another aspect of the present invention there is
provided a method for disposing of low pressure fuel gases which
method comprises inducing steam (originally at high pressure) to
flow over a director surface which is shaped so as to cause the
steam flow to initiate flow of steam and air towards a fuel inlet
which supplies fuel gas (originally at low pressure) into the flow
of steam and air.
The invention will now be described by way of example with
reference to the accompany drawing which shows a burner according
to the invention half in side view and half in cross section.
The burner shown comprises a director surface 10 which forms the
outer surface of a director tube which has a steam inlet 11 for
stream at its lower end and a secondary inlet 12 for fuel gas at
its upper end. During use the steam flows over the director surface
10 and this flow initiates flow of steam and air towards the
secondary inlet 12.
The director tube has a flat base 13 and the steam inlet 11 takes
the form of a circular slot formed between the wall of the steam
line 14 and the flat base 13 so that the steam leaves the steam
inlet 11 as a thin horizontal sheet.
The director surface 10 comprises two portions, namely a deflector
portion 15 which turns the direction of flow of the steam from the
horizontal to vertical, and the continuation of the portion 16
which maintains the flow of steam and air between the deflector
portion 15 and the fuel gas inlet 12. The purpose of this curved
continuation 16 is to allow a suitable separation between the steam
inlet 11 and the secondary inlet 12, while maintaining the skin
effect up to the secondary inlet 12.
The shape of the deflector portion 15 is most conveniently
specified as the surface of revolution formed by the rotation of a
quadrant of a circle about the longitudinal axis of the director
body, the curved section of the quadrant being tangential to the
steam inlet; as shown in the drawing the distance between the axis
of rotation and the centre of the quadrant is several times the
radius of the quadrant. The continuation portion 16 is again a
surface of revolution, but of an arc of larger radius than that of
the quadrant, thus giving rise to a tapered portion.
As the steam flows around the deflector portion 15 its direction of
flow is changed from (initially) horizontal to vertical. This
induces a low pressure zone in the surrounding air and hence it
induces movement of air as well as steam towards the secondary
inlet 12.
The fuel is conveyed to the secondary inlet by the fuel gas line 17
(which forms an annular configuration with the steam manifold 14)
and fuel which issues from the fuel line 17 meets the converging
steam of steam and air moving over surface 16.
* * * * *