Flare stack

Description

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims the benefit of U.S. Provisional Patent Application Ser. No. 60/715,148 filed Sep. 9, 2005 entitled “Improved Flare Stack”.

FIELD OF THE INVENTION

The present invention relates generally to an apparatus and method for burning a vapor. More particularly, the present invention relates to an apparatus and method for burning a waste vapor, such as methane at a well site.

BACKGROUND OF THE INVENTION

Industrial operations often generate or release vapors which require disposal, for a variety of reasons. At one time, these vapors were merely vented to atmosphere and allowed to dissipate. However, it is more common, in the case of flammable vapors, for the vapors to be burnt off or incinerated in a controlled manner.

One industry where this is common is in oil and gas exploration, production, and service industries, as these operations often lead to relatively small amounts of waste vapors which must be captured or otherwise disposed of. Frequently, these waste vapors are burnt on-site using a flare stack.

As an example, in coal bed methane fracturing operations, liquid nitrogen is used to fracture coal seams. The liquid nitrogen is heated to a gaseous state and then pumped into a coal seam at high pressure. The high pressure nitrogen fractures the coal seam to provide channels which allow increased access or production of methane from the coal seams.

As part of these operations, the nitrogen is allowed to return to surface along with coal and other debris. In this case a catch tank is used to catch flow from the well and help dissipate such flow before it enters the atmosphere, thereby providing a safe way to bleed off excess pressure during and after a fracturing operation.

The well will then start to flow produced gas (e.g. methane). While the well is being evaluated, or “on-test”, and until the well is tied in to a collection system, the produced gas is usually burnt off using a flare stack. Hydrogen sulfide is not known to be associated with coal bed methane operations, and the methane is burned off to produce CO₂ and H₂O. The burning flames from open flare stacks may contribute to forest fires in certain circumstances.

Abnormal flaring operations created by emergency situations or otherwise can result in a large visible flame, considerable noise, and smoke. Normal or planned flaring operations are designed or engineered to appropriately plan for the flame size, and to control noise and smoke. Environmental regulations may require public notice of any extended planned flaring. However, to a casual observer it may not be obvious when a particular flaring operation is planned (normal) or emergency (abnormal).

Well sites are often near populated areas, and while flaring operations are generally thought to be relatively harmless, a nearby resident who observes flaring can become concerned that something bad, abnormal, or dangerous is occurring at the well site. This is particularly problematic for well servicing operations (such as coal bed methane fracturing or well testing) as these operations are normal, but do result in flaring which is not a normal occurrence at the well site.

Thus, well site operators may experience frequent phone calls or other communications from nearby residents or passers by expressing concern whenever flaring operations are underway. These misunderstandings have the potential to cause bad will or mistrust towards the oil and gas companies.

A known way of reducing the concern of neighbors is through the use of a fueled incinerator system to dispose of waste vapors. These systems use a separate fuel source to burn off the waste vapor and the flame at all times is concealed from view inside the incinerator. However, these incinerator systems are of considerable size and cost and require auxiliary equipment (such as a power supply from a generator set) and require a separate fuel supply which must be delivered to site by truck, pipeline or otherwise.

It is, therefore, desirable to provide an apparatus and method for burning waste gas at a location such as a well site which visibly conceals the flame and does not require a separate fuel source.

SUMMARY OF THE INVENTION

It is an object of the present invention to obviate or mitigate at least one disadvantage of previous flare stacks.

In a first aspect, the present invention provides a flare stack for burning a waste vapor having a chamber having a vapor inlet, an outlet, and an elongate intermediate section, the chamber having a plurality of air intakes adapted to allow air to flow into the chamber, and ignition means for igniting the vapor adapted to create a flame, wherein the flare stack is adapted to substantially visually contain the flame.

Preferably, the flare stack further includes a pre-mix chamber associated with the vapor inlet, the pre-mix chamber having a pre-mix air inlet, the pre-mix chamber adapted to mix the vapor and air in a mixture for ignition by the ignition means. Preferably, the flare stack further includes a diffuser plate associated with the outlet. Preferably, the each of the plurality of air intakes are rotationally positioned at substantially 120 degrees to another of one of the plurality of air intakes.

Preferably, the plurality of air intakes comprise a tubular air intake. Preferably, the tubular air intake includes an elongate tubular extending between an inlet and an outlet, the inlet being substantially flush with the outer wall of the chamber and the outlet terminating in the bore of the chamber. Preferably, the outlet includes a substantially horizontal outlet face.

In a further embodiment, there is provided a flare stack where in addition or alternatively, the plurality of air intakes comprise an air intake chimney. Preferably, the air intake chimney comprises a substantially horizontal tubular extending between a first end through the chamber to a second end, and a substantially vertical tubular extending from the wall of the horizontal tubular and extending substantially vertical up a portion of the chamber. Preferably, the air intakes include a wind guard adapted to block direct access to the first end and the second end.

Preferably, the chamber is an elongate tubular. Preferably, the chamber is substantially vertical. Preferably, the chamber is constructed of stainless steel. Preferably, the chamber further comprises an inner coating, the inner coating covering at least a portion of an inner wall of the chamber, the coating adapted to resist heat generated by the flame.

Preferably, the flare stack is adapted to burn vapor at a rate of between 150,000 to 500,000 cubic feet per day. Preferably, the vapor comprises substantially methane. Preferably, the chamber is adapted to burn the vapor wherein the temperature of the chamber is substantially 1200 degrees Fahrenheit (648.89 degrees Celsius).

In a further aspect, the present invention provides a method for burning a vapor comprising the steps of allowing air to mix with the vapor to form a mixture, igniting the mixture to create a flame, providing an elongate substantially vertical tubular chamber for receiving the flame, allowing additional air into the chamber at a plurality of points proximate the flame, wherein the flame is substantially always substantially concealed from view.

Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described, by way of example only, with reference to the attached Figures, wherein:

FIG. 1 is a side view of a flare stack of the present invention in a first embodiment;

FIG. 1A is an enlarged top view of an air intake for the flare stack;

FIG. 1B is an enlarged bottom view of the air intake;

FIG. 2 is a side view of a flare stack of the present invention in a second embodiment; and

FIG. 2A is an enlarged top view of a diffuser plate.

DETAILED DESCRIPTION

Generally, the present invention provides a method and apparatus for burning waste vapor without a separate fuel source while visibly concealing the flame.

Referring generally to FIG. 1, a flare stack 10 of the present invention is shown in association with a catch tank 9, which is optional, but the catch tank 9 with the flare stack 10 are especially useful in coal bed methane operations.

A vapor inlet in the form of a pipe 6 is adapted to receive the vapor. In the preferred embodiment, a chamber 20 includes a pre-mix chamber 5 and a flame tube 1.

The pipe 6 is used to deliver vapor to the pre-mix chamber 5. A pre-mix air side intake 17 allows ambient air to enter the pre-mix chamber 5. A plurality of pre-mix chamber mounting plates 14 serve to connect the pipe 6 and the pre-mix chamber 5 while supporting the portion of the flare stack 10 above the pipe 6 and while providing a plurality of pre-mix air lower intakes 30.

The pre-mix chamber 5 extends upward and into the flame tube 1. A plurality of flame tube mounting plates 40 serve to connect the pre-mix chamber 5 and the flame tube 1 while supporting the portion of the flare stack 10 above the pre-mix chamber 5 and while providing a plurality of flame tube air lower intakes 45. The flame tube 1 includes a lower section 50 associated with the pre-mix chamber 5, an elongate central section 60, and an upper section 70.

The elongate central section 60 has a number of air intakes which provide ambient air (or another oxygen source) to the flare stack 10 to allow burning or flaring of the vapors delivered to the flare stack 10 through the pipe 6. The air intakes may be of any suitable configuration that allows air into the flare stack 10 while visually blocking the flame from view by an observer 500 (see FIG. 2).

Referring to FIG. 1, a plurality of air intakes in the form of a “chimney type” air intake 65 having an elongate air intake tubular 72 extending between an inlet 80 and an outlet 90. A wind guard 100 may be used with the inlet 80.

Referring to FIG. 2, a plurality of air intakes in the form of a “tubular type” air intake 92 having an elongate tubular 110 extending between an inlet 120 and an outlet 130, the inlet 120 being substantially flush with the outer wall of the flame tube 1 and the outlet 130 terminating in the chamber 20. In the preferred embodiment, the outlet 130 of the tubular 110 is angled upward at a tubular angle 140 with respect to a horizontal reference. Preferably, the tubular angle 140 is substantially 45 degrees. Preferably, the flame tube 1 is substantially vertical. In the preferred embodiment, the outlet 130 has an outlet face 150, the outlet face 150 being substantially horizontal. Preferably, the tubular 110 is sufficiently shaped so that an observer 500 can not look generally horizontally into the flame tube 1 to visually observe the flame (not shown), for example the tubular 110 may be generally straight and have a length which is sufficient to accomplish the visual blocking. Preferably, successive “tubular type” air intakes 92 are spaced vertically apart by approximately 2 feet along the flame tube 1. Preferably, successive “tubular type” air intakes 92 are spaced circumferentially by approximately 120 degrees around the flame tube 1.

Referring to FIG. 1, a diffuser in the form of screens 160 may be positioned at the upper section 70 of the flame tube 1. A support member 170 may be used to position a support rod 180 to position and/or adjust the height of the screens 160.

Referring to FIG. 2, a diffuser in the form of diffuser plate 190 having a plurality of holes 192 spaced generally across the area of the diffuser plate 190. A support member 200 may be used to position the diffuser plate 190. The diffuser plate 190 may be movable about a pivot 195 in order to provide adjustment of exhaust flow from the flame tube 1, as desired. The diffuser plate 190 may be movable from a remote location through the use of linkage 210 and may be fixed in place by a lock 220. Preferably the lock 220 is a friction lock.

The flame tube 1 is made of materials that can withstand the temperatures and/or may be internally coated. The temperature of the flame tube 1 may be substantially 1200 degrees Fahrenheit (650 degrees Celsius). The flare stack may be adapted to burn vapor at a rate of between 150,000 to 500,000 cubic feet per day.

Referring generally to FIG. 1, an ignition system 7 includes an ignition fuel tank 11 and an ignition fuel hose 15 for supplying the ignition fuel, and an ignition tube 4 for igniting the vapor. The ignition system 7 may be of any commonly available commercial designs, for example those that use propane as the ignition fuel or simpler designs (not shown) that include an opening or openable cover in the flame tube 1 or the pre-mix chamber 5 where an ignition source, such as an open flame, spark, or otherwise, may be temporarily delivered to the vapor.

In operation, vapor is delivered to the flare stack 10 of the present invention through the pipe 6, for example the pipe 6 may be piped to receive returns from a well. The vapor is mixed with air from the pre-mix air lower intakes 30, the pre-mix air side intakes 17, the flame tube air lower intakes 45, the “chimney type” air intakes 65, the “tubular type” air intakes 92, or a mix thereof. However, not all of these air intakes are required for any given application. The vapor is burned in the flame tube 1 without being visible from the outside by the observer 500. The flare stack 10 of the present invention reduces visual pollution (i.e. no visible open flame) and reduces the circumstances where flare stacks may contribute to forest fires (i.e. there is no open flame).

The above-described embodiments of the present invention are intended to be examples only. Alterations, modifications and variations may be effected to the particular embodiments by those of skill in the art without departing from the scope of the invention, which is defined solely by the claims appended hereto.