A DEVICE FOR BURNING GAS FROM A PRODUCTION PLANT FOR OIL OR GAS

DISPOSITIF SERVANT A BRULER LE GAZ A LA SORTIE D'UNE INSTALLATION DE PRODUCTION DE PETROLE OU DE GAZ

English Abstract

A device for burning gas from a production plant for oil/gas comprising a
burner at the top of a flare pipe (8). The production plant is connected to
the flare pipe (8) through a low pressure collection line (1) for process gas.
One has aimed at reducing combustion of valuable production gas to a minimum.
To this end, the collection line (1) is connected to an expansion tank (2)
having a return line (4) to the production plant and, downstream relative to
the expansion tank (2), a liquid trap (6) has been disposed.

French Abstract

Dispositif servant à brûler le gaz à la sortie d'une installation de production de pétrole ou de gaz, et comportant un brûleur monté à l'extrémité supérieure d'une conduite de torchage (8). L'installation de production est reliée à la conduite de torchage (8) par l'intermédiaire d'un tuyau collecteur à basse pression (1) pour le gaz produit. On a cherché à minimiser la combustion du précieux gaz de production. A cette fin, le tuyau collecteur (1) est relié à un réservoir de détente (2) possédant un tuyau de retour (4) vers l'installation de production, et un piège à liquide (6) est monté en aval par rapport au réservoir de détente (2).

Claims

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CLAIMS
1. A device for burning gas from a production plant for
oil/gas, comprising a flare burner at the top of a
flare pipe (8), raid production plant being connected
to said flare pipe (8) through a low pressure
collection line (1) for process gas, a liquid trap (6)
being positioned between said production plant and said
flare pipe (8), characterized in that
said low pressure collection line is connected to a
tank (2) having a return line (4) to said production
plant, said liquid trap (6) being positioned between
said tank (2) and said flare pipe (8).
2. A device as sect forth in claim 1,
characterized in that said liquid trap
(6) is formed from an upwardly concave pipe bend which,
at one end thereof, is connected to a downwardly
directed pipeline portion included in a pipeline
extending between said tank (2) and said liquid trap
(6) and which, at the other end thereof, is connected
to said flare pipe (8) through the intermediary of a
flare pipe pot (7).
3. A device as set forth in claim 1,
characterized in that said liquid trap
(6) is connected to a liquid reservoir (12), to a level
controller (13) as well as to a non-return valve (17)
disposed in a connection line (16) extending between
said liquid reservoir (12) and said liquid trap (6).

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4. A device as set forth in claim 1,
characterized in that said tank (2) is
connected to a compressor (3) connected to said
production plant and adapted to establish and maintain
an underpressure within said tank (2), and that said
flare burner at the top of said flare pipe (8) is
connected to a separate fuel supply pipe (9).
5. A device as set forth in claim 2,
characterized in that said flare pipe
pot (7) internally has one or more guide/barrier plates
(18, 18') having a vertically through-going aperture
(19, 19').

Description

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WO 96/10719 PCT/N095/00175
1
A device for burning gas from a production plant for
oil or gas.
The invention relates to a device for burning gas in oil/
gas production, wherein the production plant is assigned
a burner through a low pressure collection conduit for
process gas.
Gas escaping a production plant for oil/gas constitutes
an explosion risk and is, consequently, burned before the
combustion products are released iW;:o thc~ atmos phere.
In order that sudden and unintentional discharges of gas
could be burned in the burner, the latter has to be ignited
at all times. This involves the necessity of supplying the
burner with gas continuously.
Burning gas pollutes the atmosphere and gives an increased
discharge of COZ ~ Moreover, in order to maintain the
ermanent flame, one has to burn gas that otherwise might have
been sold and it is, therefore, connected with substantial
costs to keep the burner continuously in operation with a
view to a possible future unintentional discharge of gas.
Consequently, the object of the invention has been to
provide a device for burning gas in accordance with the
introduction section, Wherein burning of valuable production
gas has been kept at a minimum level.
According to the invention, this object is realized through

CA 02201517 1999-09-09
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the provision of a device for burning gas from an
oil/gas production plant comprising a flare burner at
the top of a flare pipe connected to the production
plant through a low-pressure collection line for
process gas, a :Liquid trap being positioned between the
production plants and the flare pipe. The device is
particularly ch<~racterized in that the aforementioned
low-pressure co:Llection line is connected to a tank
which has a return line to the production plant, the
liquid trap being positioned between the tank and the
flare pipe.
A process plant to which the device according to the
invention should be assigned, is in known manner
connected to a collection line for surplus gas. This
collection line is assigned a tank (expansion tank) in
which an underpressure is maintained, a compressor
carrying surplu:~ gas from the tank and back into the
process. The tank is connected to a flare burner
through a liquid trap preventing the compressor to suck
false air.
Thus, according to an important feature of the
invention, the burner is connected to an expansion tank
through a liquid trap.
According to another important feature of the
invention, the 7_iquid trap is assigned a liquid
reservoir and a level controller adapted to influence
the liquid resex-voir in order to replace possible loss
of liquid in the' liquid trap.
Advantageously, the liquid trap may be assigned a non-
return valve adapted to prevent gas from penetrating
into said liquid reservoir.
A flare pipe pot: may be disposed downstream relative to

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the liquid trap, and said pot may be provided with at
least one later<~1 guide/barrier plate preventing trap
liquid from the liquid trap from being hurled up into
the flare pipe :Leading to the burner which is located
at the uppermost. level.
Upon sudden discharge of gas, the pressure within the
expansion tank increases, whereupon liquid from the
liquid trap is hurled up into said flare pipe pot and,
thus, gives a free passage for gas to the burner.

WO 96/10719 'Z ~ p 7 PCT/N095/00175
According to a subordinate feature of the invention, the
burner is continuously driven with pilot gas, such that
a permanent pilot flame is being maintained. Thus, the
burner is assigned a pilot gas reservoir for controlled
supply of pilot gas to the burner. Such a controlled
combustion of pilot gas represents only insignificant
costs as compared with the excessive combustion of process
gas taking place at known and conventional process plants,
and which has been further accounted for introductorily.
Further objects, features and advantages of the invention
appear from the following description of an examplary
embodiment which is diagrammatically illustrated on the
attached drawings, wherein:
Figure 1 shows the process plant's collection line and
burner as well as intermediate equipment components in
sides elevational view/axial section;
Figure 2 shows in perspective the expansion tank and the
flare pipe pot and intermediate components;
Figure 3 shows a vertical cross-sectional view through
the flare pipe pot separately.
In the drawings, figure 1, reference numeral 1 denotes a
collection line for surplus gas and smaller gas discharges,
assigned a process plant not further shown.
The collection line 1 leads to an expansion tank 2 (a tank
which accommodating change of volume) operating at
underpressure and which, to this end, is connected to a
compressor 3 adapted to carry gas from the tank 2 back
into the process again through a pipeline 4.
Through a short pipeline 5, the expansion tank 2 is
connected to a liquid trap 6 which, at the downstream end
thereof, is connected to a flare pipe pot 7. The flare

WO 96110719 ~ ~ PCT/N095100175
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pipe which uppermost carries a burner known per se (not
further shown in figure 1), is generally denoted at
reference numeral 8.
In order to maintain a permanent pilot flame which is
independent on the supply of excess gas from the process
plant, the burner is supplied with fuel gas and air through
pipelines 9 and 10, respectively. The pilot burner at the
top of the flare pipe 8 is assigned a cap in order to
maintain good combustion conditions.
In order to replace possibly lost liquid trap liquid, a
liquid reservoir 12 has been disposed, the liquid trap 6
being assigned a level controller 13 which is coupled to the
liquid reservoir 12 for - upon falling liquid surface within
the liquid trap 6 - to cause the reservoir 12 to supply
thereto an amount of liquid corresponding to the one lost.
according to figure 2, the liquid reservoir 12 has been
assigned a liquid pump 14 and a venting pipe 15, a non-return
valve 17 being disposed in a connection line 16 between
liquid reservoir 12 and liquid trap 6, and adapted to prevent
gas from penetrating into the liquid reservoir 12.
In the example, in accordance with figure 3, the flare pipe
pot 7 is equipped with two internal, parallel guide/barrier
plates 18, 18', each having a through-going, central hole 19,
19'. The plates 18, 18' shall prevent liquid from being
hurled up into the flare pipe 8 leading to the burner.
During normal operation, excess gas and smaller discharges
of gas are conducted to the expansion tank 2 in order to have
the pressure reduced. The compressor 3 carries gas from the
tank 2 back into the process again through the pipeline 4. If
the discharge is so large that the pressure within the
expansion tank 2 exceeds a predetermined value given by
the liquid column in the liquid trap 6, the liquid trap
6 opens, liquid being hurled up into the flare pipe pot 7,

WO 96/10719 ~ ~ ~ ~ PCT/N095l00175
where the liquid is spread, so that gas may pass. When the
pressure within and the gas flow through the expansion tank
are reduced, liquid trap liquid from the flare pipe pot 7
will flow back into the liquid trap 6, which is formed by a
downwardly convex pipe bend (6). A possible loss of liquid
in the liquid trap 6, is replaced from the liquid reservoir
12 through the level controller 13.

Representative Drawing