US3429645A - Flare stack burner - Google Patents

Description

Feb. 25, 1969 R. 0. REED FLARE STACK BURNER Filed Sept. 20, 1967 IN VENTOR ROBERT D. REED A rromwsy United States Patent 3,429,645 FLARE STACK BURNER Robert D. Reed, Tulsa, Okla., assignor to John Zink Company, Tulsa, Okla., a corporation of Delaware Filed Sept. 20, 1967, Ser. No. 669,130 U.S. 431202 3 Claims Int. Cl. F23b 5/00; F23c 9/00 ABSTRACT OF THE DISCLOSURE A burner structure for smokeless combustion of gas at the upper end of a flare stack. Aspirating devices draw air thereinto which is mixed with an aspirating medium and the mixture is discharged upwardly within the body of the flared gas moving upwardly in the stack. Low pressure is developed which draws the flared gas into the mixture to promote complete combustion. The flame is projected vertically upwardly and it is not deflected by transverse wind currents.

The present invention relates to a burner assembly for the combustion of gases at significant elevations above the surrounding terrain and the invention more specifically pertains to equipment in association with a flare stack for directing air mixed with a combustion promoting medium into the flared gas adjacent the upper end of the stack to provide smokeless burning and to develop a substantially rigid vertical flame.

A flare stack burner wherein aspirating units mix air with an aspirating medium such as a gas or steam and the mixture is discharged upwardly within the stack at the high velocity which draws the flared gas into the mixture to develop turbulence promoting intermingling of the mixture with the flared gas and providing substantially complete combustion of the flared gas and the development of a vertical flame which is not susceptible to lateral deflection by average wind currents.

Other objects and features of the invention will be appreciated and become apparent to those skilled in the art to which the invention pertains and as the present disclosure proceeds and upon consideration of the following detailed description taken in conjunction with the annexed drawing wherein an embodiment of the invention is disclosed.

In the drawing:

FIG. 1 is an axial sectional view of the upper end portion of a flare stack burner embodying the invention showing the aspirating units in association with the stack.

FIG. 2 is a plan view of the stack showing some of the aspirating devices.

FIG. 3 is an enlarged sectional view of a portion of the tip structure.

A flare stack is shown at 10 which is adapted to *be erected in a substantially vertical position. The upper end portion is formed by a tubular member 11 which may be mounted on the stack sections therebelow in any suitable manner such as by means of a flange and bolt assembly as indicated at 12. The structure of the tip will be appreciated from consideration of FIG. 3 and it comprises an annular member having a relatively large central opening 14 defined by the inner edge of a web 16 having an undulating shape when viewed in section. The annular member includes a depending flange 17 having an inner diameter substantially flush with the inner surface of the tubular member 11. The depending flange 17 merges with the web 16 to provide an annular lip 21 which is convex shaped and constitutes the most elevated extremity of the burner tip. A row of discharge ports 22 is provided in the web 16 and the exit ends of the discharge ports terminate immediately below the annular lip 21. A second row 3,429,645 Patented Feb. 25, 1969 of discharge ports 23 and a third row of discharge ports 24 extend through the web 16. The exit ends of the discharge ports 23 and 24 terminate at the upper surface of the undulating web 16 and within an annular concave recess which is positioned below the annular lip 21. The axes of the ports 23 and 24 converge towards each other in proceeding upwardly and the axes of the ports 22 converge toward the axis of tubular member to provide intermingling of the flared gas escaping through these ports. The exit end of the opening 14 is below the level of the lip 21.

A flare stack embodying the invention includes a plurality of aspirating units 31 mounted on the tubular member 11 and cooperate with the tip structure to promote combustion of the flared gas. These aspirating units are of a well known construction and an aspirating medium under pressure is supplied into each aspirating unit 31 from an associated pipe 32. The aspirating medium as it is discharged into the throat of the aspirating unit draws air thereinto the provide a mixture of air and the aspirating medium. Each aspirating unit is supported by a conduit 33 which may extend through the wall of the tubular member 11. The respective conduits 33 extend upwardly within the tubular member 11 and each conduit has an open upper end adjacent the tip structure. In the embodiment shown in the drawing there is a centrally positioned conduit 33 which extends upwardly along the axis of the tubular member. The centrally positioned conduit 33 may be of larger diameter than the other conduits and its aspirator may be of larger diameter.

The open upper end of the central conduit 33 is desirably of cylindrical shape as shown in FIG. 2. The upper end of each other conduit may be flattened as shown at 38 so that the open upper ends of these conduits are elongated as shown in FIG. 2. The major dimension of the elongated openings is in directions radially of the central opening 14. All of the conduits terminate substantially at at the level of the exit end of the central opening 14 and below the level of the annular lip 21.

The aspirating medium for the aspirator units may be methane, hydrogen or gases including air but in carrying out the invention, steam has an advantage for the aspirating medium because of the chemical potential it provides and because of its thermal energy. Steam supplied through the pipes 32 at pressures of about twenty-five pounds per square inch draws approximately fifteen cubic feet of air into each aspirating unit for each cubic foot of steam. The steam and air are homogeneously mixed within each aspirating unit and the mixture moves upwardly within the conduits 33. The mixture is discharged through the open ends of the conduits at velocities of at least two hundred feet per second. The mixture is discharged within the body of the flared gas moving upwardly within the tubular member 11. The velocity of the mixture is much greater than the velocity of the flared gas. A low pressure condition is developed within the higher velocity mixture and the flared gas is drawn into the low pressure zones. The flared gas is thoroughly mixed with steam from each conduit 33. A high state of turbulence is also developed at the upper end of the flare stack. The high velocity of the mixture escaping from the conduits 33 produces a flame in the burning of the flared gas. The flame is vertical and substantially rigid. Its upward-velocity is so great that average transverse wind currents do not deflect the flame.

A flare stack exhibiting the structural characteristics hereinabove described provides improvements in the art of smokeless burning. When steam is employed as the aspirating medium complete combustion of the flare gas is attained with less than one-half of the steam required with prior flare stack burners. There is virtually no horizontal projection of the flame and the height of the stack may be reduced providing a further reduction of cost in the combustion of flared gases.

While the invention has been described with reference to one arrangement of aspirator units in association with the upper end of a flare stack itwill be appreciated that Patent is:

1. In a flare stack burner, a vertically disposed tubular member for guiding gas upwardly therein, a tip structure at the upper end of said tubular member having a central opening for the upward escape of gas, a plurality of conduits each having a vertically disposed portion within the tubular member and an open upper end adjacent said tip structure, an aspirating unit outside said tubular member connected to each conduit, means directing an aspirating medium into each aspirating unit whereby air is drawn into the associated unit to provide a mixture of air and the aspirating medium within said conduits, and said conduits directing the mixtures upwardly through said open upper ends at velocities greater than the upwardly moving gas whereby low pressure Within the streams of said mixtures draws the gas thereinto.

2. In a flare stack burner according to claim 1 wherein one of the conduits is centrally positioned and extends along the axis of the tubular member and the other conduits are circumferentially spaced around the central conduit.

3. In a flare stack burner according to claim 1 wherein one of the conduits has a cylindrically shaped open upper end arranged coaxially of the tubluar member with the other conduits circumferentially spaced therearound, and the open upper ends of said outer conduits viewed in plan being elongated in directions radially of the axis of the tubular member.

References Cited UNITED STATES PATENTS 2,204,719 6/ 1940 Zink 431-283 XR 2,480,230 8/1949 Elster 431-202 XR 2,506,972 5/ 1950 Schellentruger et al. 431202 FREDERICK L. MATTESON, JR., Primary Examiner.

H. B. RAMEY, Assistant Examiner.

US. Cl. X.R.

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