US3730673A - Vent seal - Google Patents

Abstract

A vent seal is provided for use with vent stacks, blow down lines, flare systems and the like to prevent entrainment of air into the stack which comprises a diode interposed in the stack below the top, the diode comprising spaced frustoconical concentric baffles with aligned central openings providing an obstruction to down flow of air within the stack but not retarding upward delivery of hot gas.

Description

United States Patent 1191 Straitz, III

15 1 VENT SEAL [75] Inventor: John F. Straitz, III, CheItenham, Pa.

[73] Assignee: Combustion Unlimited, Incorporated, Elkins Park, Pa.

['22,] Filed: May 12, 1971 [21] App1.No.: 142,700

[52] US. Cl ..431/278, 126/307 A, 138/44,

431/4, 431/202, 431/346 [51] Int. Cl...; ..F23d 13/20 [58] Field of Search ..431/202, 278, 283,

[56] References Cited UNITED STATES PATENTS 738,433 9 1903 Graham ..431/346 1,663,998 3/1928 Schmidt ..l38/44 x 1,976,870 10 1934 Weber ..431/346 x 1451 May 1, 1973 2,537,091 1/1951 Rodman et a1 ..431/346 X 2,781,716 2/1957 Moran ..98/58 2,506,972 5/1950 Schellentrager et a1 ..431/202 FOREIGN PATENTS OR APPLICATIONS 93,949 4/1969 France ..126/307 A Primary Examiner-William F. ODea Assistant Examiner-Peter D. Ferguson Attorney-Zachary T. Wobensmith, 2nd

571 ABSTRACT A vent seal is provided for use with vent stacks, blow down lines, flare systems and the like to prevent entrainment of air into the stack which comprises a diode interposed in the stack below the top, the diode comprising spaced frustoconicaI concentric baffles with aligned central openings providing an obstruction to downflow of air within the stack but not retarding upward delivery of hot gas 3 Claims, 6 Drawing Figures 2 Sheets-Sheet 1 77/ 7] v INVENTO/F' Patented May 1, 1973 2 Sheets-Sheet 2 INVENTOR JOHN F. STRA/TLE FIG. 4

A TTOR/VEV VENT SEAL BACKGROUND OF THE INVENTION tube or pressure drop effect.

The prior designs overlooked the phenomena best suited to prevent air from moving down the stack by imposing a discontinuity on the flow pattern so that the air current moving down the stack is turned back upon itself as well as by an upward jet action of the purge gases.

SUMMARY OF THE INVENTION In accordance with the invention a fluidic seal is provided in a vent stack, the seal having the action of .an obstruction to down flow of air within the stack together with an upward jet action of the stack or purge gases.

It is the principal object of the present invention to provide a seal system which prevents downflow of air in the stack whether by external wind conditions or contraction by cooling of hot gas in the system.

It is a further object of the present invention to provide a seal system in which fluid oscillations will be prevented.

Other objects and advantageous features of the invention will be apparent from the description and claims.

BRIEF DESCRI ITION OF THE DRAWINGS The nature and characteristic features of the invention will be more readily understood from the following description taken in connection with the accompanying drawings forming part thereof, in which:

FIG. 1 is a view partly in elevation and partly in vertical section of a flare burner with the fluidic diode of the invention incorporated'therewith;

FIG. 2 is a horizontal sectional view taken approximately on the line 2-2 of FIG. 1;

FIG. 3 is a view similar to FIG. 1 but showing a different construction of flare burners;

FIG. 4 is a top plan view of the flare burner shown in FIG. 3;

FIG. 5 is a view similar to FIG. 1 but showing a still different construction of flare burner; and

FIG. 6 is a top plan view of the flare burner shown in FIG. 5.

It should, of course, be understood that the description and drawings herein are illustrative merely and that various modifications and changes can be made in the structure disclosed without departing from the spirit of the invention.

Like numerals refer to like parts throughout the several views.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now more particularly to FIGS. 1 and 2 of the drawings a stack 10 is shown to which hot flare gas from an oil refinery or the like is delivered for combustion.

The stack 10 has an upper section 11 to which a pipe 12 extends, the pipe 12 having a discharge nozzle or tip 13 centrally disposed within the stack section 11 for the delivery of gas free from oxygen for purging.

Immediately above the section 11, a fluidic diode 15 is provided in the stack 10.

The diode 15 preferably comprises a plurality of frustoconical baffles 16, 17, 18 and 19 of metal of suitable gage, or other material,- not adversely affected by the elevated temperature of the flare gas which may.

be of the order of 400 to 700 Fahrenheit. The baffles 16, 17, 18 and 19 terminate at their peripheries at the stack 10.

The baffles 16, 17, 18 and 19 preferably have axially aligned central openings 21, 22, 23 and 24 of increasing ascending areas.

In the specific embodiment illustrated fourbaffles 16, 17, 18 and 19 are shown, these having been found to be effective. With a reduced number of baffles, say three, a tendency of the oxygen level to increase to objectionable levels was noted.

Above the diode 15 the flare burner 25 is provided and may include within the stack 10 and below the inwardly flanged terminus 26 of the stack 10, a ceramic or other refractory liner 27. i t

, A steam pipe 28 with a discharge nozzle 29 may be provided centrally disposed within the liner 27 for impelling the flare gases for discharge. i

If desired, also, externally disposed nozzles 30 for supplying steam or air, may be provided. by

The effect of wind flow around the top of the stack is to produce a high pressure zone upstream of thestack l0 and a low pressure zone downstream of the stack 10 and this may result in a circulation of air down the interior of the stack. As the air progresses down the stack along the wall it is stopped by the uppermost baffle 19 and turned back on itself. Any air at the center or at the central opening 24 is impelled upwardly not by a discontinuity of flow but by the jet action of the gas passing upwardly through the opening 24. The jet action occurs because the cross-sectional area at the opening 24 is reduced. so that the velocity of the gas passing therethrough is increased.

There may be some air leakage downwardly at the edge of opening 24 and this, upon downward movement, encounters the baffle .18 where the action is.

similar to that previously described. The baffles 17 and 16 also have a similar action.

It will be noted that the fluidic seal, by reason of its having a higher pressure drop in the reverse direction, i.e. downwardly, prevents air flow being pulled down in the stack 10 due to contraction of the gas in the system therebelow.

The fluidic seal also tends to prevent flow oscillation by reason of its higher pressure in the reverse direction.

Referring now to FIGS. 3 and 4, in the embodiment of the invention there illustrated, the stack 10 may have the diode 15 therein as before with the upper section 1 l thereabove having a refractory lining 27.

A steam delivery pipe 28 and nozzle 29 can also be provided and exteriorly of the stack 10 and, extending above the flame retention ring 26, air or steam delivery jets 30.

A pilot and igniter 35 is preferably also provided which has a combustible gas supply pipe 36 connected through a pilot inspirator 37 to provide the proper gasair mixture for combustion at the ingniter 35.

Referring now to FIGS. 5 and 6, in the embodiment of the invention there illustrated, the stack may have diode therein as before with the upper section 11 thereabove having a refractory lining 27.

A plurality of pilots and igniters 35a are provided at the top of the stack section 11 and surrounded by a cylindrical wind shield 38. The pilots and igniters 35a are supplied with combustible gas-air mixture from a gas supply pipe 36 through an inspirator 37.

The action of the diode 15 with respect to air externally at the top of the stack section 11 is the same as that previously described.

I claim:

1. The combination comprising a vertical tubular flare stack,

said stack having a burner at its upper discharge end for combustion beyond said discharge end of flare gas supplied to the lower end of said stack, pilot means for ignition of said flare gas at said burner, and means in said stack for preventing downflow in said stack due to external wind or to contraction of gas therebelow, said means comprising a fluidic diode in spaced relation from the terminus of the discharge section permitting flow for discharge with increase of velocity and obstructing return flow in the stack, frustoconical said fluidic diode being closed from fluid access except for a single fluid inlet opening and a single fluid outlet opening and comprising a plurality of axially aligned frustoconical baffles with aligned central openings. 2. A fluidic seal as defined in claim 1 in which said openings are of increasing diameter from bottom to top. 3. A fluidic seal as defined in claim 1 in which said baffles are in a stacked arrangement within said stack.

Claims (3)

1. The combination comprising a vertical tubular flare stack, said stack having a burner at its upper discharge end for combustion beyond said discharge end of flare gas supplied to the lower end of said stack, pilot means for ignition of said flare gas at said burner, and means in said stack for preventing downflow in said stack due to external wind or to contraction of gas therebelow, said means comprising a fluidic diode in spaced relation from the terminus of the discharge section permitting flow for discharge with increase of velocity and obstructing return flow in the stack, frustoconical said fluidic diode being closed from fluid access except for a single fluid inlet opening and a single fluid outlet opening and comprising a plurality of axially aligned frustoconical baffles with aligned central openings.

2. A fluidic seal as defined in claim 1 in which said openings are of increasing diameter from bottom to top.

3. A fluidic seal as defined in claim 1 in which said baffles are in a stacked arrangement within said stack.

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